SYSTEM AND PROCESS FOR CONVERTING PLASTIC WASTE TO OIL

PRODUCTS

CROSS-REFERENCE TO RELATED APPLICATIONS

[1] This application claims the benefit of US provisional patent application 62/419,819, filed November 9, 2016, the contents of which are incorporated herein by reference in their entirety.

FIELD

[2] The specification relates generally to conversion of plastic waste. BACKGROUND OF THE DISCLOSURE [3] Plastic waste is a major environmental problem that exist in millions of metric tonnes around the globe. With nearly 288 million tonnes of plastic production per annum, plastic waste develop large landfilling problem and has environmental impact (R. Tguado, 2014). Chemical recycling includes a chemical reaction called pyrolysis which includes cracking of chemical bonds of thermoplastic polymers to hydrocarbon gaseous and liquid products. (Vasudeo, 2016) The energy consumption required for the pyrolysis reaction is high due to elevated temperatures in range of 430-550 C. (G.Grause, 201 1 ) and 30 - 45 minutes reaction residence time. The amount of energy estimated for pyrolysis reaction is around 1047 KJ/kg which can be achieved by thermal plasma with more energy efficiency at a lower cost. Thermal plasma consumes electric energy to product high efficiency heat and shows much higher temperatures than required by pyrolysis, gasification or other industrial heat consuming applications. Also, thermal plasma is more environmental field since it relies on conversion of electrical energy to heat rather than burning natural gas or fuels for a heat source. Since reactors can operate in a time range of 20 - 25 years, thermal plasma is a more sustainable, cost effective and environmental friendly replacement in comparison with traditional heating methods such as industrial furnaces. SUMMARY OF THE DISCLOSURE

[4] In one aspect, a process is provided for converting thermoplastic waste into hydrocarbon gaseous and liquid products. The process includes:

placing in a reactor an amount of thermoplastic to be converted;

depressurizing the reactor to remove air;

filling the reactor with an inert gas;

subjecting the amount of thermoplastic to a thermal plasma arc source operating at a select temperature profile for a preselected residence time to produce a gaseous product;

directing the gaseous product through at least one condenser; and

collecting a liquid fraction condensed from the gaseous product in the at least one condenser.

[5] In another aspect, a process is provided for converting thermoplastic waste into hydrocarbon gaseous and liquid products. The process includes:

receiving a feedstock of thermoplastic to be converted;

granulating the feedstock to reduce the thermoplastic to a preselected granule size;

delivering the granulated feedstock to a preheat unit and preheating the granulated feedstock based on a preselected preheat temperature profile;

delivering the preheated granulated feedstock into a reactor and subjecting the feedstock to pyrolysis based on a preselected pyrolysis temperature profile for a preselected residence time to produce a gaseous product;

directing the gaseous product through at least one condenser; and

collecting a liquid fraction condensed from the gaseous product in the at least one condenser. BRIEF DESCRIPTIONS OF THE DRAWINGS

[6] For a better understanding of the embodiments described herein and to show more clearly how they may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which: [7] Figure 2-1 is a schematic diagram illustrating the thermoplastic polymer to pyrolysis oil expected end-products (A. Onwudili, 2009);

[8] Figure 2-2A is a simplified sectional view of a plasma fixed bed reactor (L. Tang, 2013);

[9] Figure 2-2B is a simplified sectional view of a moving bed reactor design (L. Tang, 2013);

[10] Figure 2-3 is a bar graph illustrating the annual plastic waste deposition (Jambeck,

2015) ;

[11] Figure 2-4 is a diagram illustrating branched and unbranched polymers (university,

2016) ; [12] Figure 2-5 is a graph showing the three stages of PETE by thermal analysis (Wunderlich B., 2005);

[13] Figure 2-6A and Figure 2-6B are simplified schematic illustrations of nontransferable and transferable arc generators (L. Tang, 2013);

[14] Figure 2-7 is a schematic diagram of a RF plasma system with inductive coil. (L. Tang, 2013);

[15] Figure 2-8 is a schematic diagram of a microwave plasma torch (L. Tang, 2013);

[16] Figure 3-1 is a flow chart illustrating a research methodology for thermal plasma circuit design;

[17] Figure 4-1 is a graph illustrating thermal cracking at 350°C and 400°C of a thermoplastic waste mixture (Kyong-Hwan Lee, 2007); [18] Figure 4-2 is a bar graph showing product yields in wt% of individual plastics and obtained at 5 C/min, maximum temperature 500°C (Paul T. Williams, 2006);

[19] Figure 4-3 is a graph showing the relationship between the decomposition temperature and the dissociation energy (Jose Aguado, 1999);

[20] Figure 4-4 shows the general mechanism for the thermal degradation of addition polymers (Jose Aguado, 1999);

[21] Figure 4-5 is a graph showing a thermogravimetric analysis of HDPE and LDPE in a nitrogen atmosphere (D.P, 1999);

[22] Figure 4-6 is a graph of a GC analysis of the oils obtained by LDPE cracking at 420°C, 90 min (Jose Aguado, 1999);

[23] Figure 4-7 is a graph showing a thermogravimetric analysis of PP in a nitrogen atmosphere (D.P, 1999);

[24] Figure 4-8 is a graph showing a TG analysis of PS in a nitrogen atmosphere (Jose Aguado, 1999);

[25] Figure 4-9 is a graph showing the degree of dehydrochlorination of PVC at 150°C as a function of time (Jose Aguado, 1999);

[26] Figure 5-1 shows non transferred direct current thermal plasma mechanical and electrical components;

[27] Figure 5-2 is a perspective image of a direct current thermal plasma jet;

[28] Figure 5-3 is a perspective image of a direct current thermal plasma jet in a vacuum chamber;

[29] Figure 5-4 is a side view of a direct plasma generation over a ceramic nozzle;

[30] Figure 5-5 is a side view of a direct thermal plasma temperature 890°C using K- type thermocouple;

[31] Figure 5-6 is a circuit diagram of the direct current thermal plasma circuit; [32] Figure 5-7A is a circuit diagram of the half wave rectifier using a diode for AC power supply;

[33] Figure 5-7B is a graph showing output from the half-wave rectifier;

[34] Figure 6-1 is a schematic diagram of a pyrolysis experimental setup;

[35] Figure 6-2 is a perspective view of a vacuum chamber with non-transferred DC thermal plasma circuit and metal electrodes;

[36] Figure 6-3 is a side view showing DC thermal plasma emissions on a 15 g LDPE sample;

[37] Figure 6-4 is a perspective view showing the thermal plasma emission through a direct current ceramic nozzle setup;

[38] Figure 6-5 is a plan view showing a molten 15g LDPE sample at 230°C of thermal plasma heating;

[39] Figure 6-6 is a perspective view showing that the LDPE plasma sample starts to reduce in size and melt under direct current thermal plasma;

[40] Figure 6-7 is a perspective view showing a thermoplastic conversion using a laboratory electric heater;

[41] Figure 6-8 is a perspective view showing releasing gaseous products through a condensation system;

[42] Figure 7-1 is a graph showing temperature profiles in degrees Celsius of thermal plasma and thermal cracking heater;

[43] Figure 7-2 is a view of a condensed oil sample on the reactor lid from a 15 g LDPE thermoplastic in a pyrolysis reaction at 540°C and 30 minutes;

[44] Figure 7-3 is a perspective view of an oil sample collected from 15g LDPE under 540°C and 30 minutes in pyrolysis (nitrogen) conditions;

[45] Figure 7-4 is a graph showing the gas chromatography results of an oil sample collected from 15 g of LDPE using headspace GC with FID; [46] Figure 7-5 is a graph showing the GC analysis with FID identifying C 10, C 16 and C 34 for an oil sample;

[47] Figure 7-6 is a perspective view oshowingthe ignition test of hydrocarbon gases from pyrolysis reaction;

[48] Figure 7-7 is a plan view of a 15 g LDPE sample (reactant) for a pyrolysis reaction;

[49] Figure 7-8 is a plan view of a tar sample collected from 15 grams of LDPE in a pyrolysis reaction;

[50] Figure 7-9 is a perspective view of the 7 mL pyrolysis oil calculated from 15g of LDPE in a pyrolysis reaction;

[51] Figure 8-1 block flow diagram of the structure of a chemical engineering project (Roberth, Perry, 2008);

[52] Figure 8-2 is process flow diagram for processing plastic waste;

[53] Figure 8-3 is a process flow diagram of a 10 metric tonne per hour thermoplastic pyrolysis plant;

[54] Figure 8-4 is a bar graph showing the energy consumption in major process units in a thermoplastic-to-oil facility;

[55] Figure 8-5 shows a computer display with an S1 inlet stream specification;

[56] Figure 8-6 shows a computer display with the material properties -including polymers in the process system material stream;

[57] Figure 8-7 shows a computer display with the thermoplastic components added to chemical properties in Aspen HYSYS®;

[58] Figure 8-8 shows a computer display with a selection of Stream Classes for PSD simulation;

[59] Figure 8-9 shows a computer display with input components of reactants and products; [60] Figure 8-10 shows a computer display with the expected petroleum products from pyrolysis reactions;

[61] Figure 8-1 1 shows a computer display with pyrolysis reactor specifications;

[62] Figure 8-12 shows a computer display with stop criteria and operation times for a pyrolysis reactor;

[63] Figure 8-13 is a schematic diagram showing a plastic granulator energy simulation;

[64] Figure 8-14 shows a computer display with the specifications of a plastic solid granulator;

[65] Figure 8-15 is a schematic diagram showing a thermoplastic preheater from 30 to 250°C; and

[66] Figure 8-16 shows two block diagrams of two selected process systems for LCA. DETAILED DESCRIPTION

[67] In the present disclosure, following is a list of abbreviations and acronyms used:

[68] A Plasma Area

[69] AC Alternating Current

[70] BFB Bubbling Fluidized Bed

[71] C Reaction Conversion

[72] CFB Circulating Fluidized Bed

[73] DC Direct Current

[74] EPS Expanded Polystyrene

[75] FID Flame Ionization Detector

[76] FTIR Fourier Transform Infrared Spectroscopy

[77] GC Gas Chromatography [78] H SI unit of inductance

[79] HC Hydrocarbon Element

[80] HDPE High Density Polyethylene

[81] KTA Kilo tonne per annum

[82] LCA Life Cycle Assessment

[83] LDPE Low Density Polyethylene

[84] LPG Liquefied Petroleum Gas

[85] m Total Plasma gas mass flow

[86] MPW Municipal Plastic Waste

[87] n Reaction Order

[88] PE Polyethylene

[89] PBD Process Block Diagram

[90] PFD Process Flow Diagram

[91] PP Polypropylene

[92] PS Polystyrene

[93] PSD Particle Size Diameter

[94] PVC Poly Vinyl Chloride

[95] r Radial Position

[96] R Channel Radius

[97] RF Radio Frequency

[98] TGA Thermogravimetric Analysis

[99] W Weight

[100] wt Weight Percentage [101] In the present disclosure, following is a list of identifiers of properties used:

[102] Ao Reaction Rate Exponential Factor

[103] Ea Reaction Activation Energy

[104] h Enthalpy of Plasma Jet

[105] h _ave Specific Enthalpy Flow

[106] Mn Number Average Molecular weight

[107] Mw Mass Average Molecular weight

[108] ni Ion Atom Density

[109] nn Neutral Atom Density

[110] p Density Of Plasma Jet

[111] pF Pico Farad (10-12 Farad)

[112] 750 Temperature at which 50% mass loss of initial reactant occurs

[113] T _ave AveragePlasmaTemperature

[114] 7c Crystallization Temperature

[115] Tg Polymer Glass Temperature

[116] Tm Melting Temperature

[117] TP Composition Temperature

[118] Ui Ionization Energy

[119] Wo Mass of Product Oil

[120] Wi Initial Mass Sample

[1211 W∞ Final residual mass [122] t residence time

[123] For simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the Figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the embodiments described herein. Also, the description is not to be considered as limiting the scope of the embodiments described herein.

[124] Various terms used throughout the present description may be read and understood as follows, unless the context indicates otherwise: "or" as used throughout is inclusive, as though written "and/or"; singular articles and pronouns as used throughout include their plural forms, and vice versa; similarly, gendered pronouns include their counterpart pronouns so that pronouns should not be understood as limiting anything described herein to use, implementation, performance, etc. by a single gender; "exemplary" should be understood as "illustrative" or "exemplifying" and not necessarily as "preferred" over other embodiments. Further definitions for terms may be set out herein; these may apply to prior and subsequent instances of those terms, as will be understood from a reading of the present description.

[125] Any module, unit, component, server, computer, terminal, engine or device exemplified herein that executes instructions may include or otherwise have access to computer readable media such as storage media, computer storage media, or data storage devices (removable and/or non-removable) such as, for example, magnetic disks, optical disks, or tape. Computer storage media may include volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information, such as computer readable instructions, data structures, program modules, or other data. Examples of computer storage media include RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by an application, module, or both. Any such computer storage media may be part of the device or accessible or connectable thereto. Further, unless the context clearly indicates otherwise, any processor or controller set out herein may be implemented as a singular processor or as a plurality of processors. The plurality of processors may be arrayed or distributed, and any processing function referred to herein may be carried out by one or by a plurality of processors, even though a single processor may be exemplified. Any method, application or module herein described may be implemented using computer readable/executable instructions that may be stored or otherwise held by such computer readable media and executed by the one or more processors.

1. Problem Definition

[126] The heat energy needed for the pyrolysis reaction of thermoplastics in absence of oxygen limits its implementation on industrial scale due to high operating cost and very high temperature profiles. Thermal plasma technology high performance and efficiency used in pyrolysis reaction can reduce energy consumption and provide a cleaner energy alternative that delivers high thermal energy using the Plasma circuit that can be used in pyrolysis reaction. The thermal plasma circuit is built and used in the experimental setup and tested in nitrogen conditions closed system conditions.

[127] The project utilizes a direct current thermal plasma torch at elevated temperatures above 550C to heat thermoplastic mixtures of LDPE, HDPE, PS, PP or PETE in an oxygen starved environment using pure nitrogen 99.99% in a pyrolysis reaction releasing hydrocarbon products in form of gas or liquid, waxes and tar. Analytical results aim to calculate the product yield and energy efficiency using electric heaters against thermal plasma torch. The solution approach is to develop a closed system vessel with a thermoplastic mixture and nitrogen gas environment (absence of oxygen) allowing calculating the performance of the reaction and product yields with electric heaters against the plasma torches in a laboratory scale. Also, the electric circuit of the thermal plasma torch including the limitations and performance criteria in the plasma circuit as well as the temperature profile. The electrical consumption of the thermal plasma system is 270 W converting alternative current power supply to a 9000V, 30 mA 270 W power. [128] An objective is to provide an alternative system that utilizes thermal plasma torch in the pyrolysis reaction converting thermoplastics to oil products replacing the use of other thermal equipment with thermal plasma torch. The thermal plasma should reduce energy consumptions, more energy efficiency that other heating methods. In our project there are two experimental setups. Experiment 1 will include 1056 W electric heater that will heat the closed system including the thermoplastic mixture. Experiment 2 will include direct current thermal plasma torch which will be used instead of other heating methods. A temperature profile for both experiments as well as product yields and energy efficiency will be calculated. The final objective is to assess the performance of a direct current thermal plasma arc setup to be used in the thermoplastic pyrolysis conversion reaction and calculate the product yield of pyrolysis oil as well as gas chromatography results to investigate the existing chemical composition of hydrocarbon liquids.

[129] The research scope is to design and evaluate the performance of a Direct current thermal plasma torch that can convert thermoplastic waste to oil products with a reaction residence time of 30 minutes in a closed system reactor vessel (1 Litre) on a 15 g thermoplastic sample to be converted to oil products ranging from hydrocarbon gas, liquid, waxes and tar. The experiments are carried in pure nitrogen conditions to avoid oxidation reactions. A 220V, 4.8 A electric heater is used to compare performance with DC thermal plasma setup and oil samples are analyzed by GC chromatography to identify the chemical composition of pyrolysis oil. The energy consumptions are calculated for major process units for a pyrolysis chemical plant.

[130] Plastics are inexpensive, easy to mold and lightweight. Plastic properties has many advantages which makes them very promising for commercial applications. However, the problem of recycling still is a major challenge. There are both technological and economic issues that restrain the progress in this field. A slower development within the field of recycling creates a serious problem were 100 of millions of metric tonnes of used polymeric materials are discarded every year around the globe (Nations, 2009). It leads to ecological and consequently social problems. Waste deposition in landfills becomes increasingly unattractive because of its low sustainability, increasing cost, and decreasing available space. Most common types of thermoplastics such as polyolefins (HDPE, LDPE, LLDPE, PP) and poly-aromatics (PS, EPS) can be easily separated from MSW using commercially available density-based separation methods (G.Dodbiba, 2002). While recycling of plastics will solve this problem, it will also be economically beneficial as the market price of waste plastics as starting materials is at present particularly low. The different pathways for plastic recycling (Igor A. Ignatyev, June 2014) explained in waste plastic recycling techniques section.

[131] This project aims to design and implement a process system for thermoplastic waste conversion through pyrolysis to selected oil products utilizing heated plasma arc Technology as a heating source instead of traditional heating mechanisms at a more economical energy cost instead of using traditional fossil fuel heaters (e.g. gas furnaces) in the thermal cracking process of thermoplastic waste to oil products at the pyrolysis reactor stage. Aspen HYSYS V8.8 simulations will be used and supported by experimental setup and laboratory results.

[132] The research thesis focuses on five main types of thermoplastics which are LDPE, HDPE, PS, PP and PETE with plastic compositions that match realistic statistics of MPW in Ontario and Canada. The system rejects non-plastic components as well as thermosetting plastics. The main process stages for large scale chemical plants are granulation, preheating, pyrolysis reactor, condensation (heat recovery) and storage.

[133] Also, the pyrolysis reactor is evaluated by using Fired gas furnace in simulation and electric heaters in experimental results in comparison with heated plasma at the University of Ontario Institute of Technology (UOIT) - Energy Safety and Control Lab. A novel pyrolysis reactor and experimental setup analyzes pyrolysis reaction performance and energy consumption with and without Direct (DC). The laboratory equipment used in our experiment is nitrogen pressurized gas cylinder (4.5 Nm3), 1056 W electric heater, closed system reactors, Pyrex glass condensation system, mass scale, which will be elaborated further in this disclosure. [134] The experimental setup carries the thermoplastic pyrolysis reaction using electric heater in experiment 1 and heated plasma source in experiment 2. The results in terms of energy consumption, efficiency and final products are analyzed. A K-type thermocouple is used to create a temperature profile in all the experimental setups. [135] The thermal plasma electric circuit is explained in this report and temperature profile is developed to compare the thermal plasma performance in the pyrolysis reactions.

2. Description of Recycling methods and technologies

2.1 . Waste Plastics Recycling Methods

[136] There are two main types of plastic polymers: Thermoplastics and Thermosetting polymers.

[137] Thermoplastics can repeatedly soften and melt if enough heat is applied and hardened on cooling and their melting points range from 120 - 240C -Biron. 2007/. Examples are polyethylene, polystyrene, polyethylene tetraphalate, polystyrene and polyvinyl chloride, among others. In this project we will mainly focus on five types of thermoplastics including LDPE, HDPE, PS, PP, and PETE. However, the pyrolysis process can accept any type of thermoplastics as feedstock. (Igor A. Ignatyev, June 2014) [138] Thermosetting can melt and take shape only once. They are not suitable for repeated heat treatments. Therefore, after they have solidified, they stay solid. Examples are phenol formaldehyde and urea formaldehyde. (YB Sonawane, 2009) Thermosetting plastics are considered as rejected materials in our chemical process system due to decomposition and inability to convert to any useful products. Below are possible routes of plastic recycling.

2.1 .1 . Mechanical Recycling [139] Primary mechanical recycling is the direct reuse of uncontaminated discarded before reintegration of a used material into a new product, the process involves shredding, crushing or milling. This step is vital as it makes the material more homogeneous and easier to blend with additives and other polymers for further processing. It is also known as closed loop recycling. The best-known methods of this type of processing of mechanical recycling are injection molding, extrusion, rotational molding, and heat pressing. Therefore, only thermoplastic polymers, such as LDPE, HDPE, PP, PE, PETE, and PVC, can normally be mechanically recycled. (Igor A. Ignatyev, June 2014) [140] This method is applicable for uniform and uncontaminated thermoplastic waste while the main problems associated with primary recycling are degradation of the material resulting in a loss of properties as appearance, mechanical strength, chemical resistance, and processability. (Roy, 2006) Contamination highly affects the primary mechanical recycling process and causes quality degradation.

2.1 .2. Secondary Mechanical Recycling

[141] This type of recycling involves modification of the material/product without the use of chemical processes. Purity grade of polymers maybe not known therefore could be recycled in secondary mechanical recycling loop which involves separation and purification. The polymer is not changed during the secondary recycling but its molecular weight falls due to chain scissions, which occur in the presence of water and trace amounts of acids. This may result in the reduction of mechanical properties. Another reason for the drop in mechanical properties after recycling is the contamination of the main polymer (matrix) with other polymers, (i.e., their blends have mechanical properties that are inferior to those of the pure constituents. (Igor A. Ignatyev, June 2014). Another approach to secondary recycling reprocessing is melt homogenization using specialized equipment, use of ground plastics waste as a filler, and separation into single homogeneous fractions for further processing, such as partial substitution of virgin resins and blending with other thermoplastics using suitable equipment. (Roy, 2006)

[142] An example are PETE impurities in PVC, in which solid PETE lumps form in the PVC-phase. This leads to significantly downgraded properties and consequently less- valuable end products.

2.1.3. Chemical Or Tertiary Recycling

[143] Chemical Recycling is a type of polymer recycling in which a polymer chains are converted to smaller molecules through chemical process. Examples of such processes are hydrolysis, pyrolysis, hydrocracking and Gasification. Typical conversion feedstock are in liquid/molten state used for production of fuels, new polymers, and other chemicals. (Biron, 2007). Feedstock recycling is a type of polymer recycling in which polymer chains are converted to smaller molecules through chemical processes. Examples of such processes are hydrolysis, pyrolysis, hydrocracking, and gasification. Typical conversion products are liquids and gases, which can be used as feedstock for the production of fuels, new polymers, and other Chemicals. A major part of a polymer cracking process is pyrolysis in a fluidized bed reactor. It leads to formation of a fluid fraction (wax). This fraction is then transferred to thermocatalytic and catalytic crackers of a refinery for further reprocessing. (Igor A. Ignatyev, June 2014)

[144] Preparation for cracking includes grinding, removal of metals, and other coarse components in large scale production plants and not necessary in small scale or laboratory setups. Then, the plastic waste is fed into a fluidized bed pyrolysis reactor at a temperature of 500C for cracking. Dust is removed from the gas phase by a cyclone. Subsequently, HCI, which is generated by pyrolysis of chlorine-containing polymers such as PVC, is quenched over a CaO (Calcium Oxide) bed. (Igor A. Ignatyev, June 2014). It is recommended to treat PVC by removal of Chlorine ions before allowing the molten PVC liquid to enter the Pyrolysis Reactor. This could occur in a gas-liquid fluidized bed reactor (A. Lopez, 2011 ) at 280-320 C, where Chlorine ions is converted to HCI and separated from the molten polymer. This step is carried out before treatment of PVC in a Pyrolysis reactor. (G. Yuan, 2014) Thus, it is recommended to avoid simulation and experimentations on PVC (polyvinyl chloride) since it uses further treatment of chlorine removal at 280-320 C to avoid contamination in the pyrolysis reactor. [145] In a pyrolysis reactor gas and liquid phase are produced. The latter is cooled to isolate its condensable part using condensers and coolers. The condensate (wax) is further processed in a refinery. The non-condensable fraction (C1-C4) is pressurized, heated, and stored in Pressurized gaseous vessels or transported as petroleum gas. The excess is used for heat generation and implemented to optimize the process design. Certain environmental impacts (e.g., emission of dioxins) and intensive energy consumption explain why feedstock recycling is mostly limited to small-scale pilot projects. Through our plasma arc technology pyrolysis reactor, energy consumption is evaluated and compared with using electric heaters. Expected products are Gasoline, diesel, and kerosene-range chemicals are expected to be produced at a maximum oil yield of 87.5 %. (Igor A. Ignatyev, June 2014). Char is also expected to be an undesired by-product as seen in the schematic image in Figure 2-1.

[146] Different reaction kinetic models have been developed in academic publications to model the simultaneous pyrolysis reactions which is a challenging task to achieve. Reactors can be modelled using stoichiometric model, Yield model, equilibrium model, continuous stirred (CSTR) model, Plug flow model, or Batch reactor. (Don W. Green, 2008). In our simulation, yield reactors are used and pyrolysis energy reactor energy consumption required per kg is required experimental results.

2.2 Thermal Plasma Reactor

[147] As a proposed solution, a Plasma Arc Pyrolysis reactor is proposed and evaluated that converts thermoplastic waste to oil products (LDPE, HDPE, PP, PS and PETE) at 450- 550 C and atmospheric pressure in inert conditions (N2 gas environment). Below are proposed solutions for different designs of a plasma arcs used in gasification reactors. According to the following reactors setup technologies were carried out for a pyrolysis reactions of waste plastics. (L Tang, 2013)

• Cyclonic Reactor

• Circulating fluidized bed (CFB) · Bubbling fluidized bed (BFB)

• Twin screw reactor

• Stirred Reactor

• Ablative reactor

• Vacuum and plasma reactors. · Spouted bed

• Rotating cone

[148] Possible illustrated thermal plasma designs in reactors are described below:

2.2.1 Thermal Plasma Torch Fixed/Moving Bed Reactor

[149] A plasma fixed/moving bed reactor, as shown in Figures 2-2A and 2-2B are simple types of plasma reactor, namely a plasma moving bed reactor (Figure 2-2A) and a plasma fixed bed reactor (Figure 2-2B), which have a bed of plastic waste particles with a feeding unit, shredder or granulator, an ash removal unit and a gas exit. For a plasma fixed bed reactor, the waste is put in the center of the reactor while for plasma moving bed reactor, the waste enters the reactor through a point at the top or the side of the reactor and, after contact with the ionized gas, the metals and ash form a liquid pool at the bottom of the reactor. After, the thermoplastic waste is pyrolyzed, and the gaseous products rises, and exits at the top of the reactor to condensation systems. Condensed liquids are analyzed using analytical equipment such as gas chromatography or FTIR (Fourier transform infrared spectroscopy). The following GC chromatography methods are used:

• Headspace analysis to a gas chromatography with a FID (Flame ionization detection) - determination of C6 - C10 Analysis · Gas chromatography with solvent and separated using FID (Flame ionization detection).

[150] There are two approaches to the current design of the plasma fixed and moving bed plasma reactors, whether the plasma jet is located outside or immersed inside. In the first approach, promoted by Westinghouse and Hitachi, a non-transferred torch is located outside of the reactor. The hot gas then flows from the torch into the waste reactor to melt and gasify the thermoplastic mixture as we can see in Figures 2-2A and 2-2B. The second approach is an in-situ torch, the plasma torch is immersed inside the reactor itself. This torch can either be a non-transferred torch or a transfer torch (L Tang, 2013). Plasma fixed bed and moving reactors are simple to construct and have been commonly used in pilot plant with continuous waste feed mode or batch mode. Their advantages include better heat transfer to feedstock and waste continual contacting with plasma, resulting in more complete waste conversion.

2.2.2 Pyrolvsis Reactor Design and Operation

[151] As mentioned above, plasma temperatures can reach very high, e.g. up to 1200C, delivering high reaction temperatures which was used previously in incineration. Our project job scope is to convert thermoplastic waste products separated from municipal plastic waste to oil products by utilizing arc plasma energy the pyrolysis reaction. There is a large fraction of electrons, ions and excited molecules together with the high energy radiation. When carbonaceous particles are injected into a plasma, they are heated very rapidly by the plasma releasing volatile matter giving rise to hydrogen, and light hydrocarbons such as methane, ethane and heavier components such as cyclohexane depending on the operating conditions of the reactor. (L Tang, 2013) The pyrolysis reactor has the following design and operating conditions:

Main Process Design Features

Feed

Thermoplastic Waste (LDPE,HDPE,PP,PS,PETE)

LDPE: 0.20 |HDPE: 0.20 |PETE

Mass Fraction used in Large scale Simulation

PS: 0.10 IPP : 0.10

Process Pyrolysis (N2)

Main Equipment Batch Reactor (BR)

Special Features

DC Arc Plasma Gasifier

Main Product Hydrocarbon Oil, Gas, Wax Operating Pressure - 0.95 bar Operating Temperature 480 - 540 C

BR ( Batch Reactor) (Roberth. Perry,

Reactor Classification

2008)

Reactor Atmosphere N2 gas 99.999% Catalyst

No Catalyst added

Reaction residence time

30 minutes 2.2.2.1 Expected End-Products

[152] Undesired Reactions in a thermal plasma pyrolysis is partial thermal oxidation reaction, which results in a high proportion of gaseous products (carbon dioxide, water, carbon monoxide, hydrogen and gaseous hydrocarbons), small quantities of char (solid product), and ash. This is prevented by using an inert gas such as nitrogen in a closed pyrolysis reactor. Nitrogen gas prevents oxidation and undesired reactions. This type of partial oxidation reaction is undesired and should be avoided or minimized to maximize the yield of useful hydrocarbons. (L Tang, 2013)

2.3 Global and Municipal Plastic Waste Statistics

[153] Municipal plastic waste is collected by municipalities that covers waste from households, including bulky waste, commerce and trade waste, office buildings, used electronics, institutions as well as construction and demolition waste. In Ontario, The Environmental Protection Act (EPA) (1990) regulates the residential waste management and recycling services which are mandated under the Recycling and composting of municipal Waste regulation. (Giroux, 2014) The global plastic waste production is estimated around 250 million tonnes which show the huge potential of thermoplastic waste to oil conversion (Jambeck, 2015) on in a pyrolysis reaction. Figure 2-3 shows a graph of plastics waste statistics generated globally.

[154] The graph in Figure 2-3 shows the huge potential for chemical recycling of thermoplastic waste to pure oil products with a global production of more than 270 million metric tonnes of deposited plastic waste. Plastic wastes have also showed an exponential growth over the last 60 years with an increase of nearly 20 times from 5 million tons in 1950 to nearly 100 million tons. (M.Syamsiro, 2014) 2.4 Chemical and Physical Properties of Plastic Mixture

[155] As our feed system will involve a mixture of thermoplastic waste, it is vital to investigate thermoplastic waste melting properties in order to utilize such information in the conceptual design stage. Plastics unlike other elements could decompose before its melting point, therefore thermoplastics properties are to be studied and experimented throughout the project. Important thermoplastics that will be converted to oil products are LDPE, HDPE, PS, PP, and PETE. Below are some physical properties of virgin thermoplastics gathered from (Biron, 2007)

Specific heat

0.55 0.55 0.46 0.32 0.31

(cal/g C) 0.55

2.3012 2.3012 1 .92464 1 .3388 1 .29704

KJ/Kg C 2.3012

[156] These properties are used in calculating the heat duty required to raise a thermoplastic mixture to pyrolysis temperatures in absence of oxygen. All operations in a pyrolysis plant need to be below glass temperatures to avoid the plastic glass state which is brittle and can destroy rotating equipment such as pumps.

[157] The oil products expected to be produced are categorized and illustrated as below:

[158] The molecular structure of LDPE and HDPE which shows branched and unbranched polymers is shown in Figure 2-4. [159] In pyrolysis reactions, in pyrolysis process, cross linked polymer will crack rather than melt or evaporate. The heat supplied in a pyrolysis reaction will break the intermolecular bonds in the polymer structure into shorter petroleum range compounds such as LPG, gasoline, diesel and heavy oil.

[160] Three stages of a heated polymer are represented in Figure 2-5 and include glass transition, melting and decomposition as temperature increases. As mentioned in Figure 2-5, as the temperature increases, the thermoplastic start with glass transition phase followed by cold crystallization and melting. For PETE as shown in Figure 2-5 after 530 K the plastic changes to a molten plastic, and start decomposing at Tp around 680 K (406.85 C).

2.5 Thermal Cracking Properties of Thermoplastic waste mixtures [161] It was mentioned above that our thermoplastic mixture is composed mainly of HDPE, LDPE, PP, PETE, PVC and PS. These polymer structures account for above 70% in waste plastics globally (D.P, 1999). It is also to be noted that in pyrolysis mixed plastics are more complex that pure plastics and thus plastic waste mixture in pyrolysis reactions behave differently than pure plastics under the same conditions due to changes in chemical and physical properties of different plastic waste interaction in a mixture. (Vasile, 2001 ). Thus the quality of oil products is affected depending on the plastic waste mixture composition. The plastic type had an influence on the yield, molecular weight distribution and product distribution as a function of the reaction residence time. (Kyong- Hwan Lee, 2007). One of the primary tools of thermal cracking experimental equipment is the TGA for reactants at a continuous heating rate (for e.g. 5 C/min, 10 C/min) in order to measure mass loss per minute from which reaction conversion can be determined.

2.5.1 Experimental Techniques in Pyrolysis Reactions

[162] The following analytical equipment are used to analyze the performance and temperature and mass profile of the thermoplastic mixture in pyrolysis reaction.

2.5.1 .1 TGA (Thermogravimetric analysis)

[163] TGA (Thermogravimetric analysis) is an experimental analysis technique in which changes in physical and chemical properties of materials are measured as a function of increasing temperature under a constant heating rate. Through TGA, the physical and chemical properties of the pyrolysis chemical reaction can be investigated. TGA can provide useful parameters for our pyrolysis reaction including second-order phase transitions, vaporization, and the chemical phenomena, decomposition and solid-gas reactions. 2.5.1 .2 TGA T50 results of different plastic mixtures

[164] TGA T50 results of different plastic mixtures refers to the degradation temperature at which weight loss of reactants amounts to 50%, or in other words the temperature at which 50% of a reactant is changed to a product. The following T50 TGA is expected from the following thermoplastic types: (Kyong-Hwan Lee, 2007)

• Polystyrene T50: 440 C

• Polypropylene T50: 455 C

• Polyethylene T50: 480 C [165] Thus the order of degradation temperature of waste thermoplastic mixture was PS < PP < HDPE < LDPE Among pure reactants, PS with polycyclic structure degrades at lowest temperature, while PP in polyolefinic polymers was degraded at lower temperature than PE. From the results it can be expected that plastic mixture of different compositions will result in different production characteristics. (Kyong-Hwan Lee, 2007)

2.5.2 GC-MS (Gas Chromatography - Mass Chromatography) Spectroscopy

[166] The liquid and gas samples from pyrolysis reactions are analyzed via GC-MS ((Gas Chromatography - Mass Chromatography) Spectroscopy) to determine hydrocarbon chain distribution in terms of paraffins, olefins, and aromatics. (J.Zeaiter, 2014). The gas chromatographer also determine the physical structure of the liquid or gas sample depending on retention times utilizing computer matching databases. (Urionabarrenchea, 2012).

2.6 Plasma Engineering [167] Advancement in thermal plasma torches have resulted that this technology is becoming a viable solution for chemical processes. The main advantages of plasma are its ability to control process chemistry and to build small footprint reactors due to its high energy density and reactivity of the free radicals that are produced. (L.Rao, 2013). Both transferred and non-transferred plasma torches can be used as a source of heat. Industrial plasmas can be classified as thermal plasmas and non-thermal plasmas.

[168] Thermal plasma is typically established between any two current conducting electrodes separated by an insulator. A plasma forming gas is blown between the two conducting electrodes resulting in a high temperature plasma plume. A plasma torch generates and maintains an electrically conducting gas column between the two electrodes: a cathode (negative electrode) and an anode (positive electrode) (D.Harbec, 2004).

[169] This plasma setup is termed as non-transferred (NT) plasma torches. The DC Power Plasma works with any oxygen free inert gas, such as argon, nitrogen, helium and/or a mixture of the above gases, as the plasma forming gas. (L.Rao, 2013) This plasma setup is very suitable since our gas medium needed in the pyrolysis reaction is high purity nitrogen.

[170] The main advantages of thermal plasma offer to treatment processes are the following: · Rapid heating and reactor start-up. ( This is also supported by our temperature profiles as DC arc plasma reached 850C in less than one second)

• High heat and reactant transfer rates.

• Smaller installation size for a given waste throughput

• Melting of high temperature materials · Using of electricity as an energy source

• Control of the processing environment through power supply. • More options for the process chemistry since the heating rate can be easily controlled through electrical output in watts.

• Higher sustainability since eliminating the usage of fossil fuels.

• Higher process controllability and smaller installation size. [171] A non-transferred arc plasma torch provides a plasma flow for treating the waste. The following formulas are shown below: (J.Heberlein, 2008). Specific enthalpy equation requires density, velocity and enthalpy as functions of the radial position r, R is the channel radius and rh is the total plasma gas flow rate.

2π f pv hrdr

h = -^- rh

[172] The average enthalpy can also be determined from an energy balance of the torch using the following equation. Were Q , _oss I = the heat lost from the plasma torch.

™ ve = I * V - Q _loss

[173] The average velocity can also be calculated from the following equation:

rh [174] m = mass of ions, l= plasma density, T _a ve = Average Plasma temperature, and A = Plasma Area.

2.6.1 Categorization of Thermal Plasma Systems

[175] As more efficient and reliable torches for thermal plasma generation which acts as an alternative clean energy source of heat, have become available in recent years due to the development of the technology and the utilization of plasma energy as an alternative energy source for pyrolysis/gasification. The technology main advantages involves delivering extremely high reaction temperatures up to 3000C (L Tang, 2013). Tdded to that, an ultra-fast reaction velocity compared to traditional pyrolysis gasification technology with great potential in plastic waste treatment. (L Tang, 2013). Since this is the chosen method and focus for our Project, our design will involve focusing on development of Plasma Arc (DC) and (RF) and its implementation on reactor design that converts thermoplastic waste mixture to oil products utilizing the highly efficient and reliable Plasma arc technology that converts thermoplastic waste to pure petroleum gas (ethane and methane) mainly and pure oil products which are illustrated in the figures. (Im Jun Cho, 2015). It was also reported that oxygen in the reactor reduces the yield of hydrocarbon gases and increases ash/tar which is the undesired product of pyrolysis and should be minimized to negligible amounts. (Im Jun Cho, 2015)

[176] Plasma pyrolysis system designs have been researched for more than half a century, which has resulted in the availability of several designs at the small and large scales. Below are useful parameters for different parts of the pyrolysis process.

2.6.1 .1 Plasma Arc Types

[177] Plasma thermal generation can be achieved using a direct current (DC), an alternating current (AC) electrical charge, an RF (i.e. radio frequency) induction or a microwave discharge (MW) explained below. (L Tang, 2013). In our project we are focusing on DC (direct current) and RF (Radio frequency) plasma arc technology and its performance in the pyrolysis reaction which has operating temperatures in range of 450 - 600C. (Vasudeo, 2016)

2.6.1 .2 Reactor Design Types

[178] Plasma fixed or moving bed reactor system, plasma entrained-flow bed system, spout reactor system and spout-fluid reactor system designs. The reactor design parameters will be feedstock volumetric flow rate, residence time, and end products to determine batch or continuous process system. (Don W. Green, 2008) (L Tang, 2013) The different reactor designs illustrate techniques of heat transfer, heating duty and residence time.

2.6.1.3 Plasma Working Gas Method

[179] N2 plasma system, Argon plasma system, H2 plasma system, mixed gas plasma system, water steam plasma system, are inert gases and can be used as a medium of heat transportation to the liquid feedstock. (Igor A. Ignatyev, June 2014) Since Pyrolysis reaction occur in inert gas, high purity 99.99% N2 gas is used in our experimental results. Nitrogen is also the most available and cheap inert gas thus is used in our project.

2.6.1.4 Thermal plasma pyrolysis systems

[180] Thermal plasma pyrolysis systems should be properly designed for energy efficient and cost-effective operations. The basic component of a thermal plasma pyrolysis is the plasma generator (torch). The torch is the source of thermal energy aimed at the reactants and can be generated by various methods discussed below, including: DC/AC electric discharges or transient arcs, RF and microwave discharges at near-atmospheric pressure, and laser-induced plasmas. (L Tang, 2013) Below are different Types of Plasma Arc Technologies. (L Tang, 2013). The Plasma source delivers sufficient heat (Heat duty, KW) that is used for the pyrolysis reaction with a specific residence time specified between 30 - 45 minutes without catalyst.

2.6.1.4.1 DC (Direct Current) arc discharge [181] DC arc discharge provides a high energy density and high temperature region between two electrodes and, in the presence of a sufficiently high gas flow, the plasma extends beyond one of the electrodes in the form of a plasma jet. The arc plasma generators can be divided into non-transferred arc torch and transferred arc torch as shown schematically in Figures 2-6A and 2-6B respectively. DC plasma arc can reach up to 1300 C (L Tang, 2013). At our Laboratory experimentation using simple DC Arc Plasma generates 800C in less than 1 second which is than the required temperature for pyrolysis reaction. Please refer to experimental results for details.

[182] The Arc Plasma Generators can be divided into non-transferred and transferred arc torch. In non-transferred torch, the two electrodes don't participate, in the processing and have only a function of plasma generation. In a transferred arc reactor, the substance to be processed is placed in an electrically grounded metallic vessel and acts as the anode, hence this method is suitable only for reacting material which is electrically conductive. (L Tang, 2013) [183] The average lifetime of electrodes ranges between 200 and 500 hours of operation under oxidative conditions. Normal power levels up to 1 .5 MW. Scale-up is possible to 6 MW (Plasma Technology Research Centre, 201 1 ). The majority of thermal plasma processes developed to date have used DC plasma generators due to the stable arcs that they can generate, however this type of plasma generation is comparable and includes narrow pathways for gaseous materials. (L Tang, 2013)

2.6.4.2 RF (Radio Frequency) Plasma system

[184] A radio frequency plasma system (an example of which is illustrated in Figure 2-7) employs RF plasma torches that utilize inductive or capacitive coupling to transfer electromagnetic energy from the RF power source to the plasma working gas. The advantages of this plasma system includes compact design, extraordinarily high input energy per unit volume, ability of the RF plasma reactor to handle any chemical owing to the absence of metal electrodes and a very long lifetime. RF plasma generators are commonly available at power levels of 100 kW and can be scaled to 1 MW range. (L Tang, 2013). RF frequencies are usually in range of 10 MHz to 16MHz. It is to be mentioned that RF plasma systems often utilize oscillator electronics which have inherently low efficiencies. The RF Plasma experimental setup requires vacuum environment to work efficiently. (L Tang, 2013). The RF Plasma source used in the lab for the pyrolysis experiments is 13.56 MHz which is a standard plasma generation frequency for RF Plasma. (L Tang, 2013)

2.6.4.3 Microwave Plasma System

[185] Microwave plasma systems are plasma systems that are created by the injection of microwave power (i.e. electromagnetic radiation in the frequency range of 300 MHz - 10 GHz, typically 2.45 GHz; can in principle be called "microwave induced plasmas". An example of this is shown in Figure 2-8. Microwave plasma operating pressure ranges from 0.1 Pa to 10 Pa, In terms of power between a few Watts and several hundreds of kWatts, sustained in both noble gases and molecular gases. (L Tang, 2013)

[186] Thermal Plasma are partially or strongly ionized gases, usually created by electric arcs at atmospheric pressure. In fact, thermal plasmas can be generated by many methods such as DC ( direct current ) electrical discharges at current intensities higher than a few A and up to 10 ⁵ A either transferred arcs, or non-transferred plasma torches, AC or transient arcs, pulsed arcs, RF and microwave discharges at near atmospheric pressure. (Gleizes, 2005)

[187] In thermal plasmas the electrons are mainly responsible for inelastic collisions such as ionization, recombination, excitation, attachment and detachment.: [188] The electron temperature is equation to the ion temperature producing a plasma temperature (Tpiasma) in range of 10 ⁶ - 10 ⁸ . The factors below are used in a plasma arc system design: • Ability to use not only inert active gases such as N2, Air, CO2 used as carrier plasma gases.

• Sufficient long electrode life (typical 20 - 10,000 hour).

• Ability to control gas enthalpy or heat transferred to the treated material. · Energy efficiency and impulse power of the Thermal plasma circuit.

• The high specific heat flux at the cathode makes it a beneficial component to select properly despite the higher losses at the anode. The choice of cathode is determined by the plasma forming gas and the specific enthalpy and should withstand the highest number of hours to reduce maintenance work and increase operations reliability.

2.6.2 Industrial Thermal Plasma systems

2.6.2.1 Westinghouse Plasma Corporation (WPC)

[189] The Westinghouse plasma gasification technology has been in operation globally for the past 10 years leading to successfully processed multiple feed stocks including municipal solid waste, auto shredder residue, sewage sludge and a variety of caustic hazardous materials. The Westinghouse plasma gasification technology has three reference plants and two commercial plants and illustrated below are the major process units and technologies used in Westinghouse gasification plants.

[190] A typical facility includes at least one continuously operating pyrolysis reactor. Within the reactor the charge material exposed to very high temperature profile which exits the top of the reactor through two outlets. As stated below, here are the main process units at Westinghouse Thermal Plasma Pyrolysis Large Scale Treatment Facility: • Feed system: Received recyclable thermoplastic waste as Feedstock to be processed, this stage involves feed elevator, hopper, shredder and screw conveyer of feedstock waste to prevent malfunction.

• Particulate recycle system: Unprocessed feedstock after gasification is recycled by transferring un-gasified plastic waste to the Feedstock system.

• Plasma gasification system: A slag removal system is installed before the reactor.

Plasma torches in a plasma gasifier (reactor) provide thermal energy raising the Temperature to cracking Temperatures producing syngas from thermoplastic waste.

• Boiler: Produces LP, MP, and HP Steam which delivers the required steam for steam turbine generator.

• Gas clean-up system: A system in plasma gasification processes aims to remove .

• Thermal oxidizer: An air pollution control unit that decomposes hazardous gases at a high temperature and releases them into the atmosphere. (Process Engineering, 2014)

• Steam turbine generator: Extracts thermal energy from pressurized steam through rotating shafts.

2.7 Conclusion

[191] In chapter 2, the main thermoplastic types are identified and the operating conditions for thermoplastic pyrolysis reactions are collected. Five main types of thermoplastics that form more than 90 wt% are LDPE, HDPE, PS, PP and PETE. The optimum operation temperatures are 430-550C, reaction residence of 30 - 45 minutes. The main products from pyrolysis reaction are hydrocarbon gases, liquids, wax and tar. A condition of pyrolysis reactions is absence of oxygen and the most commonly used inert gas is nitrogen since it is abundant and economical. [192] Existence of PVC in thermoplastic feed stock causes negative effects due to formation of HCI which is toxic, has a high reactivity with water, causes damage to metal structures. To address this, pretreatment at 320C of PVC feed stock can be used to remove chlorine ions. A CaO catalyst bed can be used to remove chlorine ions at 320C for any thermoplastics that have CI ions in their chemical structure.

[193] The heat duty required for pyrolysis can be calculated from specific and latent heat capacity of individual plastics depending on the feed stock composition used in the pyrolysis reactor. The average heat duty required is 1047 KJ/kg which is used in the thermal plasma heat calculations. [194] Thermal plasma can be used in thermoplastic pyrolysis reaction using DC, RF or MW thermal plasma can be used and requires vacuum conditions to operate effectively. Thermal plasma achieves better heat performance, and can be used for pyrolysis reactions 430-550C temperature profile and temperature can be controlled through current thus providing better control characteristics, more sustainable technology and no harmful gaseous emissions.

[195] After the reaction residence time, gaseous products are condensed through a condensation system for collection of hydrocarbon liquids and wax. Tar is reduced by ensuring inert conditions to inhibit oxidation or combustion of thermoplastics.

3. Methodology

3.1 Introduction

[196] In order to convert thermoplastics to hydrocarbon gaseous and liquid products in a pyrolysis (oxygen starved environment) reactor, a 1 L closed system reactor of stainless steel 301 L is set as the experimental apparatus. In order to compare the effectiveness of the DC thermal plasma setup, a 220 V 4.8 A electric heater that raises the temperature of a laboratory reactor to 550C is used. The closed system reactor uses compressed gas (N2) to ensure pyrolysis environment. A stop watch is used for time monitoring and a K- Type thermocouple is inserted inside the reactor few centimeters away from the thermoplastic sample to monitor the temperature in Celsius scale per minute.

[197] An initial sample of 15 grams of thermoplastic sheets are placed at the plastic holder and the reactor is filled with pure nitrogen gas through a compressed nitrogen cylinder and a regulator. The process of nitrogen filling is repeated three times through inlet/outlet valves using a vacuum pump that removes all air from the reactor vessel, then nitrogen gas is pumped inside the reactor till pressure reaches 1 bar. The step of placing the sample in the reactor may more broadly be referred to as placing in a reactor an amount of thermoplastic to be converted. The step of using the vacuum pump to remove air from the reactor may more broadly be referred to as depressurizing the reactor to remove air. The step of nitrogen filling may more broadly be referred to as filling the reactor with an inert gas.

[198] The chosen reaction residence time is 30 minutes for both experiments (Experiment 1 : Using electric heater Experiment 2 using: DC Thermal Plasma arc source). After the reaction is carried out for the residence time K, the heating source is switched off and the gaseous products escape the reactor system into a condensation system through a ball valve. The liquid sample is collected and weighted. The step of maintaining the reaction for the 30 minute residence time may more broadly be referred to as subjecting the amount of thermoplastic to a thermal plasma arc source operating at a select temperature profile for a preselected residence time to produce a gaseous product. It will be understood that the residence time may be longer or shorter than the 30 minutes used in the present disclosure. The step of the gaseous products escaping the reactor system into a condensation system through a ball valve may more broadly be referred to as directing the gaseous product through at least one condenser. The step of collecting and weighing the liquid sample may more broadly be referred to as collecting a liquid fraction condensed from the gaseous product in the at least one condenser.

[199] The process steps may alternatively be identified as follows: receiving a feedstock of thermoplastic to be converted; granulating the feedstock to reduce the thermoplastic to a preselected granule size (or otherwise size-reducing the feedstock to reduce the thermoplastic to a preselected particle size);

delivering the granulated feedstock to a preheat unit and preheating the granulated feedstock based on a preselected preheat temperature profile;

delivering the preheated granulated feedstock into a reactor and subjecting the feedstock to pyrolysis based on a preselected pyrolysis temperature profile for a preselected residence time to produce a gaseous product;

directing the gaseous product through at least one condenser; and

collecting a liquid fraction condensed from the gaseous product in the at least one condenser.

[200] In general, while granulating may be the preferred way to reduce the particle size of the thermoplastic, other ways may be used.

[201] The liquid product yield is calculated through the following equation:

W∞

Product conversion yield =

W∞

[202] The initial thermoplastic sample is weighted using a mass scale, the hydrocarbon liquid yield produced and the product yield is calculated for the thermoplastic initial sample. The initial plastic sample is chosen to be 15g for different types of thermoplastics including LDPE, HDPE, PS, PP and PETE.

[203] The hydrocarbon liquid sample is then analyzed using a headspace gas chromatography analysis -with an FID (Flame Ionization Detector). The gas chromatography identifies the composition of the oil depending on the retention time which is matched to a retention time hydrocarbon identification table and the carbon number of the hydrocarbon is identified.

[204] The same process is repeated for any thermoplastic sample collected from both experiments either electric heater or Direct current thermal plasma heating source. The K- type thermocouple measures the temperature profile of the heating source of both experiments. The temperature profile with the gas chromatography and product yield results can assess the performance of direct current thermal plasma arcs to replace traditional industrial heating methods that is required for large scale production pyrolysis reactors. The control experiment is to ensure same sample size is used for the initial thermoplastic used in both experiments. The 1 Litre closed system reactor uses a vacuum pump to depressurize the closed vessel system, and pure nitrogen gas fills the reactor. The process is repeated three times to ensure that the reactor vessel is completely filled with nitrogen before switching on the thermal plasma system. The data is recorded and the thermal plasma system is assessed in terms of thermal efficiency, conversion rate. The oil products are analyzed using the Gas chromatography results thus showing the chemical composition of the produced oil and thus the thermoplastic mixture composition can be adapted to lead to a specific oil mixture composition such as gasoline or diesel.

[205] Figure 3-1 is a thermal plasma circuit design flow chart.

3.2 Research Methodology Phases

[206] The study was conducted into three phases which are discussed below:

[207] Phase 1 : Collection of operating conditions, reaction engineering, process operation related to thermoplastic pyrolysis to oil products. This phase also involves calculating the energy duty required for thermoplastics to convert to oil in inert conditions. Also, the reaction residence time required and the various types of thermoplastics that can be converted to oil products.

[208] Phase 2: This phase aims to integrate direct current thermal plasma to be utilized in pyrolysis reactor. The circuit is designed to achieve the required heat duty in an experimental scale and to be able to work under the pyrolysis reaction conditions in inert environments and achieve the required high temperatures for 30 minutes. This stage involves carrying thermal plasma experiments in a vacuum vessel without a plasma sample.

[209] Phase 3: This phase involves quantitative measurements including temperature profiles of thermal plasma during operation in a 1 Litre vessel. Also, hydrocarbon liquid products are analyzed using an FID Gas Chromatography and product yield is calculated. Life cycle cost analysis for usage of thermal plasma against other heating methods are investigated.

3.3 Conclusion

[210] Three phases are chosen for methodology, starting with detailed study of the process conditions, heat duty and applicable pressures and temperatures needed for successful conversion of thermoplastics to oil. Phase 2 includes designed the thermal plasma circuit to comply with HSE standards and achieve required heat duty needed for the pyrolysis reaction. Phase 3 will follow chart in Figure 3-1 to ensure direct current thermal plasma performance in the pyrolysis reaction. Phase 3 aims to design a thermal plasma circuit that can achieve controllable high temperature, operate in nitrogen environment and vacuum pressure. Hydrocarbon products are analyzed using gas chromatography and product yields are calculated. [211] The flow chart of the thermal plasma system methodology ensures in initial design stages that the direct current thermal plasma can achieve the required heat duty and temperature profile. The thermal plasma circuit is designed to comply with operating temperature and pressure required for the targeted residence time of 30 minutes. The circuit is designed to achieve controllable temperature through current input thus inhibiting runaway reactions. The plasma circuit is modified and a different plasma method is used in case conditions are not achieved. [212] The plasma circuit is tested in vacuum conditions to ensure safe operations and a closed system vessel is used. After successful pressure testing, a 15g sample is used in the thermal plasma circuit.

4. Pyrolysis Reactions Process Analysis

4.1 Thermal Cracking Optimum Temperatures

[213] In order to get good design temperatures for our thermal cracking process, analyzing thermoplastic waste mixture thermal cracking is a beneficial step to recommend an optimum design temperature. Several thermal cracking experimentations have been investigated (Kyong-Hwan Lee, 2007). In comparison between 350C and 400C, thermal cracking at 400C showed better product yields which can be shown below in Figures 4-1 . (Kyong-Hwan Lee, 2007)

4.2 Activation Energy and reaction kinetics measurements for Polymers

Polystyrene: The activation energy of polystyrene consumed in pyrolysis reactions range from 164 to 249 KJ mol-1 . (Seung-Soo-Kim, 2004) Propylene: The activation energy of Propylene ranges from 208 to 288 KJ mol-1 (Seung- Soo-Kim, 2004)

[214] The Table below illustrates the kinetic parameters of selected thermoplastics mixtures

Material E _a (KJmol-1) References

Low Density Polyethylene (LDPE) 259.70 (J.Encinara, 2008) Polystyrene (PS) 164-249 (N.Wang, 2013)

Polypropylene (PP) 208 - 288 (N.Wang, 2013)

Polyethylene Tetraphalate (PETE) 235.7 (J.Encinara, 2008)

High Density Polyethylene (HDPE) 147.25 (S.M.AI-salem, 2010)

4.2.1 . Reaction Rate Calculation Models

4.2.1 .1 . Temperature Independent Reaction Rate Equation (Simplified Model)

[215] This section investigates the reaction kinetics related to pyrolysis of thermoplastic waste mixtures. The methods elaborated will help us in the design stage to final the rate of products over rate of reactants. The following rate of reaction definitions are all interrelated and all intensive rather than extensive measures. (Levenspiel, 1999). The following is a basic explanation of reaction rate in terms of component i. The rate of change in numbers of moles of this component due to the reaction rate dNi/dt, then the rate of reaction in its various forms is defined as follows:

[216] Based on unit Volume of reacting fluid:

1 dNi moles of i formed

(Levenspiel, 1999)

[217] It will be noted that the reaction rate varies from a reaction to other which decides the type of the reactor to be chosen either Batch reactor, Semi-batch reactor, continuous - stirred Tank reactor or a plug flow reactor (PFR) (Sinnott, 2005). The method explained above is a very simple method to determine the rate of reaction from moles of products formed per unit time.

[218] The following conversion X equation is defined as follows: w ₀ - w∞

X = Mass Conversion, Wo = Mass of oil product, Wi = initial mass sample, and W∞ = Final Mass sample.

4.2.1.2. Reaction kinetics of Pyrolysis reactions

[219] Following this kinetic study (Paul T.Williams, 2006), a pyrolysis pressure reactor at an initial nitrogen pressure of 0.2MPa generating a maximum of 10MPa pressure at elevated pyrolysis temperature of 500C. The following table shown below, shows the reaction simulated mass fractions of different thermoplastics by weight proportions.

[220] Below is a Table explaining the pyrolysis product yields of plastic wastes produced from the mixture mentioned above: Pyrolysis (Nitrogen) 48.7 3.7 34.6

[221] The results showed that existence of paper and dirt in the feed sample (reactant) also reduces the Oil and Hydrocarbon Gas and produces a very high percentage of residue/tar is produced. Therefore, it is vital to ensure that all the mixture plastic mixture is free from paper or dirt to ensure the profitability and high product yield of oil and hydrocarbon. Thermoplastics can be separated easily from MSW using commercially available density-based separation methods. (G.Dodbiba, 2002)

[222] It was also noted that oil products produced from pyrolysis had a high concentration of alkanes and single aromatic compounds which will be investigated in experimentation. (Paul T.Williams, 2006) Product yields from individual plastics pyrolysis are shown in Figure 4-2.

4.2.2. Achieving heavy oils or gaseous oil products at different operating conditions

[223] Referring to (Kastner H. and Kaminsky, 1995), thermal cracking of polyethylene in a fixed bed reactor over temperature ranges less than 550C, high yields of useful products such as heavy, liquid oil were achieved. Changing the reaction temperatures to above 550C yields more gaseous products and aromatics due to more secondary reactions of aromatics above that temperature. (Kastner H. and Kaminsky, 1995) (Prakash K, 1997). Another reaction kinetic study, according to (S.M.AI-salem, 2010), the following is a calorific Value of some major plastics compared with common fuels.

Polystyrene(PS) 41 .90

Kerosene 46.50

Gas Oil 45.20

Heavy Oil 42.50

Petroleum 42.5

[224] Another study showed the reaction kinetics of pyrolysis reactions, the following two equations calculate the activation energies of cracking reactions and mass conversion with time in the reaction. The equation below can be used to develop reaction rate.

dW

= k x W ⁿ (N. Miskolxzi, 2012)

dt

dW

Reactant mass loss per unit time

dt

[225] n is the reaction order n = 1 for pyrolysis, W = Initial Weight of Sample, Ao exponential factor, c = conversion factor

Wo

c =

W

[226] Activation energies were calculated by using the Arrhenius equation.

Ea

fc = _4o exp(-— ) [227] According to experimental trials and publication (N.Miskolczi, 2012), below are values of k. reaction Rate has units of mol dm ^"3 s ^~1 .

4.2.3. Reaction Products and Temperature Profiles of Thermoplastics

[228] According to one of the main handbooks in Plastic Recycling, (Jose Aguado, 1999) there are four Main Product fractions expected from recovering of plastic feedstock recycling through pyrolysis (i.e. thermal degradation in inert conditions) which are gases, oils, solid waxes and a solid residue. As the Temperature is increased, the amount of gases, the fraction of gases also increases and the solid residue appears as a solid char due to the enhancement of hydrocarbon coking reactions. There are three different decomposition pathways for pyrolysis of plastic feedstock recycling:

• Random scission at any point in the polymer backbone leading to the formation of smaller polymeric fragments as primary products. · End-chain scission, where a small molecule and a long-chain polymeric fragment are formed.

• Abstraction of functional substituents to form small molecules.

[229] The most common pathways occur simultaneously. For PE polyethylene and PP polypropylene thermal degradation occur by both random and end-chain scissions. In the case of PVC, however, the predominant mechanism of the first step is the removal of HCI to avoid chloride ions during pyrolysis which change the PH and damage the reactor vessel followed by normal pyrolysis reaction similar to other thermoplastics. (D.P, 1999).

[230] Polymer thermal decomposition is an endothermic process that involves the dissociation of the C-C bond thus breaking down the polymer into useful oil products. Figure 4-3 is a direct relationship between the dissociation energy and the decomposition temperature for different polymers.

[231] Figure 4-4 shows the pyrolysis reactions that occur in thermoplastic polymer cracking.

[232] As shown in Figure 4-4, the following reactions occur in thermoplastic pyrolysis of polymers (Jose Aguado, 1999)

• Initiation, involving the scission of the first bonds in the chain yielding two radicals, which may occur at random or end-chain positions.

• Depropagation, including the release of olefinic monomeric fragments from primary radicals. · Hydrogen chain transfer reactions, which may occur as intermolecular or intramolecular processes.

• P-Cleavage of secondary radicals to yield an end-chain olefinic group and a primary radical.

• Formation of branches by the interaction between two secondary radicals or between a secondary and a primary radical.

• Termination, which takes place either in a bimolecular mode, involving the coupling of two primary radicals, or by disproportionation of the primary macro radicals.

4.3. Thermal conversion of Individual and Mixture Plastics [233] This section discusses in details aspects of the thermal conversion of individual polymers which are the main components of plastic waste stream such as polyethylene, polystyrene, PVC, and PETE. This session focuses on the mechanistic and kinetic factors as well as type of products derived from thermal decomposition of each individual polymer.

4.3.1 . Polyethylene

[234] Polyethylene is the major polymer present in plastic wastes. Both low density and high density polyethylene are found in large quantities in plastic residues. HDPE is a highly linear polymer, whereas LDPE possesses a certain degree of branching. (D.P, 1999) HDPE exhibits a higher crystallinity and a higher crystalline melting point than LDPE, due to linear chains of LDPE can be more closely packed the polyolefin are completely volatilized at temperatures below 500 C which can also be noticed in Figure 4-5.

[235] Referring to Figure 4-6, it can be seen that optimum operating conditions for HDPE is around 447 C and for LDPE around 417 C. The main products observed in the gaseous effluent from the pyrolysis reactor were methane, ethane, ethylene, propane, propylene, acetylene, butane, butene, pentane, benzene, toluene, xylene and styrene. At the lowest temperatures investigated (450 and 550 C), significant amounts of tars and waxes were detected in addition to gaseous products. It was observed that the more branched polyethylene yielded more aromatic compounds. (Jose Aguado, 1999) therefore, LDPE yield more aromatic compounds than other unbranched polymers.

4.3.2. Polypropylene

[236] Polypropylene is a polyolefin found in high concentrations in the plastic waste stream. Compared to PE, the backbone of the PP molecule is characterized by the presence of a side methyl group at every second carbon. Random chain scission of polypropylene produces both primary and secondary radicals. Subsequently, tertiary radicals are formed by intramolecular radical transfer reactions. This fact implies that half of the carbons in a PP chain are tertiary carbons and so, as a consequence of their higher reactivity, PP is thermally degraded at a faster rate than PE which can be noticed in Figure 4-7 below, which shows that pyrolysis occurs at much lower temperatures than PE. The optimum operating temperature for a PP Polymer pyrolysis reactor is 407 C.

4.3.3. Polystyrene

[237] Polystyrene plastics constitute a significant part of industrial and household wastes. As in the case of polypropylene, half of the carbons in the polystyrene chain are tertiary due to the presence of side benzylic groups. (Jose Aguado, 1999) Therefore, thermal PS pyrolysis also occurs at relatively low temperatures in range of 350C using a GC and TG analysis with higher intensity at 420 C (Figure 4-8). It is also to be noted that the major product obtained is the starting monomer. This fact is valid for both low and high temperature degradation. Therefore, PS is one of the few polymers that can be thermally depolymerized. Main stable products reported were Toluene, ethylbenzene, cumene, tri- phenyl benzene, a-methyl-styrene, diphenyl-propane and diphenyl butane. (Jose Aguado, 1999)

4.3.4. Polyvinyl Chloride

[238] Polyvinyl chloride is a polymer with a wide range of commercial applications. However, its use has been the subject of great controversy in recent years due to its high chlorine content. (D.P, 1999) Approximately 56 wt% of the polymer is HCI, which is released at relatively low temperatures, creating toxic and corrosive conditions such Cl- ions need to be separated before pyrolysis reaction.

[239] HCI can be removed at low temperature in range of 200-360 C thermal decomposition of PVC is recommended in a two-step process. Step 1 , dehydrochlorination of the polymer to form a polyene macromolecular structure followed by cracking and decomposition of the polyene at elevated temperatures above 375 C (see Figure 4-9).

4.3.5. Polyethylene Tetraphalate PETE

[240] Pyrolysis experiments in Inert gases showed show a peak around 420C whereas 82% of the initial mass is volatilized up to 500C. The products released were a complex mixture composed mainly of acetaldehyde, benzoic acid, ethyl-benzoate and vinyl- benzoate. (Jose Aguado, 1999). Williams and Williams have investigated PETE pyrolysis up to 700 C in a fixed bed reactor, three fractions being collected: gases, oil and char. Gases and oil accounted for about 80% of the starting polymer mass. The gases were mainly carbon dioxide, due to the presence of oxygen in the PET macromolecules, although minor amounts of methane and ethylene were also detected. (Williams, 1997)

4.3.6. Thermal Conversion Of Mixture Plastics

[241] In this section, Conversion of complex Thermoplastic waste mixtures of several types of plastic, which is the case when processing real municipal plastic wastes are discussed. (Jose Aguado, 1999) This section will highlight technical factors such as descriptions of reactors and processes, pretreatments for mixed plastic wastes as well as possible interactions which may occur when several plastics are simultaneously degraded. Pyrolysis of thermoplastic mixtures yield different results in comparison with individual plastics due to polymer chain interaction.

4.3.6.1. Activation Energy Measurements for Plastic Mixtures [242] Activation Energies are a vital measurement for reaction kinetics of molten plastic waste to pure oil products. Below are the activation energy and Arrhenius exponential factors of different types of polymers. (J.F.Gonzalez, 2008) These values can be calculated to find the estimated energy needed to achieve pyrolysis reaction either in process simulation or expected heat duty and rate of reaction needed.

Plastic Type Ea (KJ mor ¹ ) Ko, s- ¹

Polystyrene (PS) 136.64 1.61 x 108

Low Density polyethylene (LDPE ) 118.31 6.97 x 108

Polyethylene Tetraphalate (PETE) 161.23 3.85 x 109

Polypropylene (PP) 169.35 1.06x 1010

Recycled Plastics (RP) 210.35 3.5x1012

5. Proposed Thermal Plasma System

[243] Plasma is a quasi-neutral ionized gas assumed to be in thermal equilibrium, using the following equation known as Saha-Langmuir equation that relates the ionization state of an element to temperature and pressure. The equation can be used to estimate the amount of ionization is to be expected in a gas, assuming thermal equilibrium.

3

— = 2.4 * 10 ²¹ *— * e κτ' [244] rii and n _n are the ion and neutral atom density respectively. T is the gas temperature in degree kelvin

[245] K Boltzmann constant

[246] Ui ionization energy required to strip one electron from an atom [247] Another equation that is used that compute average energy density, using Maxwellian distribution:

Eavg = ½ KT per degree freedom U ² = Kinetic energy of the particles

F (u) = Number of particles per m ³ with velocity between U and U + du M = average mass of particles

Added to that, thermal motions generate pressure thus the following equation relates pressure and temperature:

P = n ^* KT

P = Particle pressure n = Particle Density

K = Boltzmann Constant T = absolute Temperature [248] Figure 5-1 is a diagram categorization of mechanical and electrical components needed for the thermal plasma circuit implementation in pyrolysis reactors.

[249] As seen in Figure 5-2, a 270 W Thermal plasma operating in vacuum pressure of - 0.95 bar using non-transferred direct current with ceramic nozzle setup to stand high temperature emission of plasma ions.

[250] The plasma temperature reaches in a fraction of a second 890 C which is a much higher temperature than the required operation temperatures of thermoplastic to oil pyrolysis reactions.

[251] Figure 5-3 shows a direct current thermal plasma jet in vacuum chamber. Figure 5- 4 is a direct plasma generation over a ceramic nozzle. Figure 5-5 shows a direct thermal plasma temperature 890 C using K-Type thermocouple.

[252] The plasma emission is used to be directed over a thermoplastic holder of 15 g of LDPE in nitrogen atmosphere at vacuum pressure of - 0.95 bar. The plasma emission is allowed to work for thermoplastic pyrolysis reaction time of 30 minutes and switched off before gaseous products are released to the condensation system.

[253] In the designed experiment direct current non-transferred circuit of 9000 V, 30 mA current at frequency 60Hz. The circuit includes capacitors, Ceramic plates, Diode, and resistors. The Input power source of the thermal plasma circuit is AC (alternating current) and the output impulse power is DC as shown in Figure 5-6.

5.1.1. Capacitors calculations

[254] C=1500PF

[255] Vc =3KV [256] V _T =9KV

[257] CTOTAL=1000PF

[258] Rc =1 Q [259] L=1000nH

[260] As shown below, C stands for capacitors, each of which has 1500 PF in two loops connected in parallel to a diode that restricts the current to pass to the capacitors which store the electric energy, [261] As seen above, the thermal plasma circuit, has three capacitors in series each capacitor with 1500 PF, Pico Farad.

1 1

J_ ₊ J_ ₊ J_

^2 ^3

[262] Thus total capacitance in the parallel loops is 1000pF or 1 nF.

5.1.2. Half Wave Rectifier

[263] With reference to Figure 5-7A, the function of the diode is to convert the alternating current to direct current for thermal plasma generation creating a half wave rectifier as shown. A half cycle is used to charge the capacitors, and in the response time of absence of current (see Figure 5-7B), the capacitors release the charge load at the electrodes generating a thermal plasma torch at vacuum operating pressure - 0.95 bar.

[264] The equations used to calculate the total voltage, current and other correlations are shown below:

1 —dq d ² q

V _T = q(t) + Rc

Total dt dt ²

[265] Thermal plasma pulse power can be calculated as max x V, max [266] Thus impulse power for plasma generation is calculated as below: Impulse power used Pi mpulse- 270 W.

5.2. Conclusion

[267] The thermal plasma circuit includes a diode that converts AC power supply to half wave rectifier and total capacitance in the circuit is 1 nF. A half wave rectifier is created, in presence of current half cycle, the capacitors are charged, while in absence of current, the charge is released and thermal plasma discharge is created. A K-type thermocouple shows 625.6 C as an initial temperature and maximum temperature of 890 C is achieved.

6. Thermoplastic Reaction Experiment

[268] The laboratory experimental setup aims to convert thermoplastic waste to oil products in nitrogen conditions at atmospheric and vacuum pressures since thermal plasma operates best at vacuum pressures. Sophisticated laboratory equipment were purchased and the following experimental setup were developed aiming to convert single thermoplastics as well as mixture components of LDPE, HDPE, PETE, PP and PS materials. Figure 6-1 is a schematic diagram of an example of an experimental setup.

6.1. Equipment Overview Equipment used is described below:

6.1.1. Pure Nitrogen Gas Cylinder [269] An Air Liquide™ compressed Pure nitrogen cylinder (4.5 Nm3 99.99% pure nitrogen) is purchased for pyrolysis and thermal plasma operations. The nitrogen cylinder emits pure nitrogen gas through a regulator emiting nitrogen at 2 bar inside the closed vessel operated by V-2. All other valves should be closed and V-2 opened before allowing nitrogen gas to flow to reactor. The vessel is filled with nitrogen till pressure increases from -0.95 bar to 1 bar. The process is repeated 3 times (vacuum - nitrogen filling) till the vessel is made sure to be mostly nitrogen. It is to be noted that vacuum pump and nitrogen filling is operated separately to avoid gas leaking.

6.1.2. Condensation System Operations

[270] After the reaction residence time of 30 minutes, the gaseous products are expected to be hydrocarbon gases and liquids. The thermal plasma system is switched off, and valve V-3 is opened to allow gaseous products to pass through the condensation system. The condensation system runs tap water at 25C in a continuous cycle. Condensation system only operates after the reaction residence time is achieved for 30 minutes. The heating source is switched off, pressure is changed to atmospheric and gaseous products are allowed to condense through the condensation system. The gaseous hydrocarbons condense to light oil, diesel and wax into the oil collector.

6.1.3. K-Type Thermocouple

[271] A K-Type thermocouple is inserted inside the closed vessel attached to the heating source to get a temperature / time profile. The thermocouple has an initial temperature of 23.5C before starting the experiment., the temperature profile is measured per minutes of 30 minutes and the performance is compared with the thermal plasma experiment.

6.1.4. DC Thermal Plasma and Electric Heater heating sources [272] In experiment 1 , a ceramic electric heater is used as a heating source for the thermoplastic pyrolysis reaction, while in experiment 2, thermal plasma is used as the heating source on a 15 g LDPE sample and a temperature profile as well as hydrocarbon products are collected and analyzed. In experiment 2, the electric heater is used without the thermal plasma setup.

[273] Both experiments are carried out in the same closed system to ensure similar parameters. Temperature profiles are recorded as well as electric consumption and product yields.

6.2. Experimental Setup

6.2.1 . Thermal Plasma Experiment

[274] The direct current thermal plasma circuit was tested in a vacuum chamber for 30 minutes including a k-type thermocouple to measure plasma temperature on a 15 g plastic sample. The pyrolysis reactor vessel is a 1 L stainless steel vacuum chamber. The setup is shown in Figure 6-2.

[275] As shown above, a thermal vacuum chamber (1 L) is used to demonstrate a non- transferred DC thermal plasma source that releases heat on a plastic holder. The system operates in vacuum till reaction residence time is achieved.

[276] Figure 6-3 shows DC thermal Plasma emissions on a 15g LDPE sample. The thermal plasma arc is switched on, on a 15g thermoplastic sample for a reaction residence time 30 minutes and the temperature profile is recorded. After 30 minutes, the gaseous products are allowed to escape out of the reactor and into the condensation system. Figure 6-4 shows thermal plasma emission through direct current ceramic nozzle setup.

[277] At around 230 C, as shown in Figure 6-5, the thermoplastics start to change to a molten state before reaching pyrolysis temperatures. [278] As seen in Figure 6-6, the direct current thermal plasma emission melts the LDPE plastic sample and reduces in size after few seconds, to check the temperature profile please refer to results section.

6.3. Thermoplastic pyrolysis using an electric ceramic heater

[279] In order to compare the performance of the direct current thermal plasma, the pyrolysis experiment is carried out using a laboratory Cole Parmer™ electric heater consuming electrical energy 1058 W and can reach up to 550 C as shown in Figure 6-7. [280] After the reaction residence time, the gaseous products are allowed to escape at atmospheric pressure through a condensation system thus condensing liquid hydrocarbons and waxes. Figure 6-8 shows the release of gaseous products through a condensation system.

6.4. Laboratory Health, safety and Environmental Regulations

6.4.1. Compressed Nitrogen Gas Handling

[281] The use of compressed gases should protect the users and can be achieved by safe storage, proper gas handing and operations, and taking the necessary precautions when dealing with pressurized cylinders, and usage of appropriate cylinder regulators. (O.Karl, 2006). Complying with OSHA standards 29 CFR 1910.1200. (PraxAir, August 2013)

[282] The expected potential health effects, are as follows:

6.4.1.1. Effect of a Single Acute Over exposure [283] Inhalation: Asphyxiant. Effects are due to lack of oxygen. Moderate concentrations may cause headache, dizziness, excitation, vomiting and at maximum exposure could cause death due to suffocation. [284] Skin Contact: No harm expected.

[285] Eye contact: No harm expected.

[286] Effects of Repeated(Chronic) over exposure: No harm expected.

6.4.1.2. First Aid measures

[287] Inhalation: Remove to fresh Air. If not breathing give artificial respiration. If breathing is difficult, qualified person may give oxygen.

[288] Skin Contact: An unlikely route of exposure. This product is a gas at normal temperature and pressure. [289] Eye Contact: An unlikely route of exposure. This product is a gas at normal temperature and pressure. (PraxAir, August 2013)

6.4.2. Thermal Plasma Handling

[290] Thermal plasma can achieve very high temperatures and special precautions need to be taken for safety and health standards. (O.P.Solonenko, 2003) Thermal plasma temperatures can reach up to 5000 C and the chosen high temperature limit for the experiment is 1000 C. Measurements taken in case of higher temperature detected using K-Type thermocouple:

• Switching off main power supply. • Pressure Test before switching on the thermal plasma system to prevent leaks during operations.

• Ensure pressure is below atmospheric for optimum plasma operations.

6.5. Conclusion

[291] A closed system vacuum chamber that operates under - 0.95 bar using nitrogen gas to achieve inert conditions required by pyrolysis reaction. A 270 W direct current non- transferred thermal plasma is compared to a 1056 W electric heater in pyrolysis reaction of a 15 g LDPE and a 30 minute reaction time. A k-type thermocouple is used to measure the temperature per minute of the two heating source systems while the gaseous products are passed through a condensation system after the reaction time. The collected samples are used to calculate product yields and pyrolysis oil is analyzed using flame ionized detector gas chromatography.

7. Experimental Results

7.1 Temperature Profiles

[292] Figure 7-1 shows temperature profiles which were recorded using the K-Type thermocouple for the Direct Current thermal plasma system (30 mA, 9000 V, 270 W) in comparison to a laboratory electric heater that uses (4.8A, 220 V, 1056 W). As seen in Figure 7-1 , the direct current thermal plasma has a higher and better temperature performance on the 15 g thermoplastic sample and can be easily controlled by the input current to the plasma circuit. It can also be noted that the DC thermal plasma with 240 W can achieve higher temperatures than needed by the pyrolysis and can achieve up to 860 C. [293] Below are the computed temperature profiles computed per minute:

7.2. Gas Chromatography Results

[294] The gaseous products from the pyrolysis experiment pass through a condensation system and the volatile oil sample is collected and analyzed using Gas chromatography. Figure 7-2 shows the oil sample collected from a 15g sample of LDPE.

[295] In order to collect the maximum amount of liquid oil products from the plastic sample, after 20 minutes, the gaseous products are allowed to enter a closed condensation system and the liquid products are collected in a flask as shown in Figure 7- 3. The gaseous products are allowed to condense at 25C using potable cooling water.

7.2.1. Headspace Gas Chromatography analysis -with an FID (Flame ionization detector)

[296] The oil sample was analyzed using a headspace gas chromatography using methanol flame ionization detector. The oil sample showed the existence of the following hydrocarbon compounds:

• 1 ,4, dichlorobenzene • N-butyl benzene

• Undecane (Sur)

[297] In Figure 7-4, a different GC method with FID, shows the existence of the following hydrocarbon compounds:

• C10 (decane)

• C16

• C34

[298] In Figure 7-5, GC Analysis with FID shows the existence of C10, C16 and C34 compounds in the pyrolysis oil which shows heavy hydrocarbon compounds existence in the oil sample collected from the pyrolysis experiment.

[299] The analysis of the pyrolysis oil is shown in the following table:

Parameter Result

1 ,4-dichlorobenzene-d4 (Surr) 87.9

Benzene 0.008

Ethylbenzene 0.041

F1 (C6-C10) -Less BTEX 61 .8

F1 (C6-C10) Incl. BTEX 62.4 p-Xylene 0.098 o-Xylene 0.183

Toluene 0.271

Total Xylenes 0.281 undecane (Surr) 134 F2 (C10-C16) 2340

F3 (C16-C34) 685 g/g

F4 (C34-C50) <10 g/g

[300] The data displayed in and shows existence of 1 -4 dichlorobenzene in small quantity, minor percentages of benzene, ethylbenzene. In terms of hydrocarbon analysis (C10-C16) shows the highest concentration of 2340 μg g, followed by existence of C16- C34 and small traces of heavier hydrocarbon content of C34-C50.

7.3. Pyrolysis Gas Ignition Test

[301] The pyrolysis hydrocarbon gases that was emitted in the reaction (C1 - C4) was tested for ignition to ensure existence of methane or petroleum gases. The ignition test was using an ignition sparker and showed ignition capability thus showing the existence of flammable components as shown in the Figure 7-6.

7.3.1 Product Yield Results

[302] As mentioned earlier, the expected products from a thermoplastic pyrolysis reactions are hydrocarbon gases, oil, wax and tar. Existence of pure nitrogen gas reduces the tar which is an undesired product in our reaction. The product yield results use the following equation to calculate yield in terms of mass:

X =

W ₀ - W∞ [303] X = Mass Conversion, Wo = Mass of product oil, Wi = initial mass sample, W+ = final mass sample.

[304] The initial thermoplastic sample weight, Wo is measured using a mass scale and placed inside the reactor. The final tar and wax sample is measured which is W∞ and considered undesired product. The conversion X is the successful conversion of thermoplastic waste to oil products which is the desired product. Below are the results from a 15g LDPE sample.

Material Weight (g)

LDPE (Reactant) 15g Pyrolysis Oil Volume

7ml_ ( 8.54 g )

Density 1.22g/cm3

X ( Conversion Rate) 0.569 ( 56.9%)

[305] Figure 7-7 shows the products obtained from thermoplastic conversion of LDPE in a 30 minutes pyrolysis reaction under 550 C.

[306] After the reactant is placed, a vacuum pump is used to reduce pressure to -0.95 bar and nitrogen gas is pressurized inside the vessel, the process is repeated multiple times to ensure inert conditions (N2 gas) for the pyrolysis reaction. Samples were collected of hydrocarbon oil, wax and tar as shown Figure 7-8. With reference to Figure 7-9, 7 ml_ pyrolysis oil calculated from 15g of LDPE in a pyrolysis reaction.

7.4. Conclusion

[307] A 240 W direct current thermal plasma circuit showed higher temperature performance against 1056 W electric heater and achieved more than pyrolysis temperatures needed 550C on a 15 g LDPE thermoplastic sample. 15 mL were produced from a 15g LDPE thermoplastic sample under vacuum pressure of -0.95 bar, operating temperature of 550 C and reaction residence time of 30 minutes. The pyrolysis oil produced were analyzed using a FID gas chromatography that showed existence of ethylbenzene and decane.

[308] Toluene and Xylene chemical components were also found in the pyrolysis oil produced.

[309] Product Yield achieved using the mentioned conditions are 60 wt% to pure oil products. Hydrocarbon gases released were tested for ignition and showed high ignition characteristics. Tar is reduced by ensuring reaction occurs in nitrogen conditions through the usage of nitrogen pressurized gas.

8. Large Scale Plastic to Oil Pyrolysis Process Design

[310] Development of a new chemical plant or process from concept evaluation to profitable reality is often an enormously complex problem. A plant-design project moves to completion through a series of engineering stages such as is shown in the following:

1. Inception

2. Preliminary evaluation of economics and market 3. Development of data necessary for final design

4. Final economic evaluation

5. Detailed engineering design

6. Procurement

7. Erection 8. Startup and trial runs 8. Production

8.1. Conceptual and Preliminary Plant Design

[311] Constraints of a design such as those that arise from physical laws, and thermodynamics of the feed or reactants. Within this boundary there will be a number of plausible designs bounded by the other constraints, the internal constraints, over which the designer has some control such as, choice of process, choice of process conditions, materials, and equipment. [312] Economic considerations are obviously a major constraint on any engineering design, since plants must make a profit. (Sinnott, 2005). During the conceptual design phase, the target of the project may be defined and an optimum process is designed based on this information. The following points need to be achieved during the conceptual design stage: ^■ Mass and energy balances

^■ Process simulation (e.g. with Aspen Plus®)

^■ Process selection

^■ Evaluation and comparison of design options

^■ Plant layout - The design work required in a chemical engineering plant can be divided into two phases:

Phase 1 : Process Design

[313] This covers the steps including initial selection of the process to be used, through Process Flowsheets, reaction path selection, specification, and chemical engineering design equipment. This follows by Process Flow diagram and Piping and Instrumentation (P&ID) Diagram. Phase 2: Plant Design

[314] Detailed mechanical design of equipment including the detailed mechanical design of equipment, structural, civil, and electrical design; and the specification and design of the ancillary services. As seen Figure 8-1 is the detailed structure of a chemical engineering project.

8.2. Plastic to Oil Conceptual Design Engineering Project

[315] Plant Design Basis: Processing Thermoplastic waste feed at 10 tonnes/ hour to pure oil products including LPG, gasoline, diesel, wax and tar production. The expected annual production for this plant is 87.6 KTA (Kilo tonne per annum). The following are the major process steps in the thermoplastic to oil plants.

8.2.1. Municipal Plastic Waste Granulation

[316] The pyrolysis chemical plant aims to convert thermoplastic feed from Municipal waste of Ontario through a series of chemical and physical processes to oil products. A unit that can be used in large scale pyrolysis plants is the granulation process chosen to be Unit 1. It includes mechanical equipment for granulation that reduce the size of solid plastic waste in order to increase the heat transfer surface area and heat transfer properties during preheating stage. Particle size diameter is a parameter in granulators. The PSD chosen is set to be 6-8 mm.

8.2.2. Thermoplastic Preheating to Molten Plastic [317] This unit receives granulated thermoplastic waste in agitated tanks were Preheating is applied to molten solid thermoplastic waste mixture to liquid state. The feed temperature to this system is around 30C and the exit temperature is 250C to ensure that all the thermoplastic waste is in liquid state. This Unit prepares the thermoplastic waste for thermal cracking to oil products and prevents agglomeration of solid plastics inside the pyrolysis reactor. (Sinnott, 2005)

8.2.3. Pyrolysis of Molten Thermoplastic waste to Oil Products

[318] This stage involves Thermal cracking or pyrolysis at elevated Temperatures of up to 450 C - 540 C in inert conditions. The optimum Temperature is determined the feed stock thermoplastic composition. The chosen residence time of the pyrolysis reactor is 30 minutes and gaseous products are allowed to enter a condensation system and gaseous products condense to hydrocarbon liquids.

8.2.4. Wax and Tar Removal

[319] Removal of Wax, tar and solids from the system to avoid clogging and poor heat transfer since plastics are poor conductors of heat. Therefore, ash, tar and wax need to be removed continuously from the pyrolysis reactor system which is removed from the bottom of the reactor using valves.

8.2.5. Light Oil and heavy Separation Units

[320] This stage involves separation of oil products, coke and tar removal, condensers, vessels and separation tanks. The condensation system reduces temperatures using flash separators to condense gaseous products from 550C to 30C and can be used as an energy recovery to heat cold streams.

8.2.6. Storage of hydrocarbon fuels

[321] This unit includes storage tanks that store End-Product hydrocarbon fuels at atmospheric pressure that ensures safe storage at atmospheric temperature for a storage capacity for 15-30 days depending.

8.2.7. Design Factor (Design Margins)

[322] Experienced designers include a degree of over-design known as a "design factor, design margin, or safety factor, to ensure that the design that is built meets product specifications and operates safely. Design factors are also applied in process design to give some tolerance in the design. For example, the process stream average flows calculated from material balances are usually increased by a factor, typically 10%, to give some flexibility in process operation. This factor will set the maximum flows for equipment, instrumentation, and piping design. Design factors can be mentioned in drawings, calculation sheets, and manuals.

8.3. Process Block Diagram (PBD) and Process Flow diagram (PFD)

[323] A block diagram is the simplest form of presentation. Each block can represent a single piece of equipment or a complete stage of a process. It shows the principle stages of a process including separators, reactors, vessels, heat exchangers, vessels and tanks. The process block diagram shows limited information including design temperature and pressures, equipment, line number, Mass and volumetric flow rates and the medium in the chemical equipment. Below is information to be included (Sinnott, 2005) :

^■ Stream composition m/mtotal, and flow rate of each individual component in kg/hr.

^■ Total stream flow rate, kg/hr ■ Stream temperature, degrees Celsius preferred

^■ Nominal operating pressure

^■ Stream enthalpy, kJ/hr.

[324] Figure 8-2 is a process block diagram Following the chemical engineering standards were every block represent a stage in a process system:

8.4. Process Flow Diagram

[325] Figure 8-3 process flow diagram specifies the major process units needed for a 10 metric tonnes per hour feed stock mass flow rate operating temperatures and pressures as well as equipment sizing and design capacities.

[326] The following are the mass and energy balance as well as diagram key.

LDPE 0.2 0.2 0.2

HDPE 0.2 0.2 0.2

PS 0.1 0.1 0.1

PP 0.1 0.1 0.1

PETE 0.4 0.4 0.4

Products

Petroleum Gas

0.08

(Methane)

Gasoline

0.92

(Cyclohexane)

Diesel ( decane) 1.0

Tax/Wax - -

8.5. Mass and Energy Balance Calculations

8.5.1. Basis of Calculation

[327] In our Basis of Calculation and based on the statistical values of common thermoplastic waste materials in Ontario, here are the Following Mass Compositions of Streams which is expected to be our feed stream for MPW (municipal plastic waste) in Ontario: [328] Stream Number: S1

[329] Mass Fraction: LDPE: 0.2 HDPE: 0.2 PETE: 0.4 PS: 0.1 PP: 0.1

[330] Mass Flow rate = 10,000kg/hr (87,660 Tonne per Annum, 87.6 KTA), T=25C P = 1 atm [331] Mass Flow rate (10 tonne/hr)

[332] Molecular Mass Mw (T) of Mixture = (mLDPE ^* MLDPE) +( mHDPE ^* MHDPE) +(mPETE ^* MPETE)+(mPP ^* MPP) )+(mPS ^* MPS) (S.Mostafa Ghasian, 2008)

[333] Referring to, the molecular masses Mw are: (Biron, 2007) [334] MLDPE = 28.06376 g/mol [335] MHDPE= 28.05376 g/mol [336] MPETE =192.1711 g/mol [337] MPP =42.08 g/mol [338] MPS = 104.1 g/mol

[339] The Granulator aims to reduce the PSD of Thermoplastic waste to 6-8 mm. Thus we are required to find the heat duty of granulators using Aspen one software and compare it with our manual results.

8.5.1.1. Electrical Duty of Mechanical Granulation Stage

[340] For a 10,000kg/hr which is equivalent to 22,046 Ib/hr Typically, the horsepower (HP) for common plastic grinders is 250 HP for 13,500 Ib/hr.

[341] Therefore, at a rate of 10,000kg/hr the expected Horse power (HP) of the equipment needed is 409HP. Therefore, required power at a rate of 10,000kg/hr is 305 KW. 8.5.1.2. Heat Duty Calculations for raising temperature of S2 from 30C degrees to 250 C

[342] Referring to the Process Plow diagram and simulation, and to (Wunderlich M. V., 1990) we can find the Cp, specific heat capacity of Polymers thus determining the Heat Duty required for raising the temperature of our mixture from 30 C degrees to 250 C.

[343] Specific Heat Capacity of LLDPE, HDPE and PETE In (Biron, 2007), p.238 the thermal properties of LDPE, HDPE is illustrated

[344] Specific Heat Capacity (cal/g.C) LDPE = 0.55 cal /g.C, HDPE = 0.55 cal /g.C. On page 424 it I illustrated that the Specific Heat Capacity (cal/g.C) PET = 0.31 cal /g.C

[345] Specific Heat Capacity of Thermoplastic Mixture

[346] q LLPE = (2302.74) (0.2) (10,000kg/h) (90) = 414.493 MJ/h = 115.14 KW [347] q HDPE = (2302.74) (0.35) (10,000kg/hr) (90) = 725.353 MJ/h = 201.49 KW

[348] q PET = (1297.9) (0.45) (10,000kg/h) (90) = 525.649 MJ/H = 151.57 KW

[349] Total Heat Duty (Q) for raising the temperature from 30C to 120C of 10,000kg.hr Granulated polymer mixture = 115.14KW + 201 .49 KW + 151.57 KW = 468.2 KW with 2,000kg/hr (21 KW) = 489.2 KW

8.5.1.3. Thermal Cracking Reactions Mass and Energy Balance

[350] Ea Activation Energy Needed for the Reaction

[351] (Assuming First Order Reaction, and calculating using Arrhenius equation of order (Elham KhaghanikavkanM & Farid, 2010)) In the thermal cracker we will calculate the reaction enthalpies, for thermally cracking a thermoplastic mixture to oil products through Pyrolysis reactions. Polyethylene has a molecular formula of - (CH2-CH2) _n and several kinetic studies have been done in order to determine heat of reaction of pyrolysis of polyethylene to various oil products. (Gan, 2007) [352] Using the Kinetic Reaction Equation for range of Pyrolysis at 450 C to 550 C.

— Ea

K = Ko exp (— )

[353] Polyethylene Enthalpy calculations Ea = 376KJ/mol, K0 = 3.2E24 (1/sec), (Ceamanos, Jet, al, 2000) [354] (Rate coefficient at 450C ) K = 2.184068 sec ^"1

[355] The energy to be supplied per kg of thermoplastic is around 1047 KJ/kg. Therefore, Heat Duty needed (Gao, 2010):

Q pyrolysis reaction = (10,000kg/hr) (1047kJ/kg)/ (3600s) = 2908.33 KW [356] Figure 8-4 shows the energy consumption in major process units in a thermoplastic-to-oil facility.

8.6. Aspen HYSYS Simulation and Justification

[357] Using Aspen ONE® Version 8.8 for simulation of Thermoplastic waste Mixture to oil products in a pyrolysis reaction at atmospheric pressure (1 atm ) and Temperature conditions ranging from 380C to 540C. Reaction residence time are also to be included in our settings.

[358] Stream S1 (Inlet Stream) with reference to Figure 8-5 [359] T = 30C, P = 3 Bar, Stream Number: S1 , Mass Flow rate: 10,000Kg/hr (10 tonnes/hour)

[360] S1 Stream Mass Fraction Composition LDPE: 0.2 HDPE: 0.2 PETE: 0.4 PS: 0.1 PP: 0.1

[361] Adding thermoplastic components such as polyethylene LLDPE and HDPE, Polyethylene-Tetraphalate, Polystyrene and polypropylene in the Chemical Properties is illustrated in Figures 8-6 and 8-7.

[362] Stream Class is a useful feature in Aspen HYSYS in which the stream is classified as Conventional (dissolved) Liquids or solids, non-conventional (non-dissolved) solids were PSD (particle size diameter) for non-conventional solids need to be specified, illustrated in Figure 8-8.

[363] Figure 8-9 shows input components of reactants and products. [364] Figure 8-10 shows expected Petroleum Products from pyrolysis Reactions.

[365] Propane, C3H8, represents LPG, Liquefied petroleum gas. N-DODECANE CH3 (CH2) 10CH3, represents hydrocarbon diesel. While, Cyclohexane, C6H12, represents hydrocarbon gasoline.

8.6.1. Pyrolysis Reactor operating Conditions

[366] In Reactor specifications, as shown in Figure 8-1 1 , constant reaction temperature is set at 500C and reaction pressure set at 2 bar with no catalyst loading. [367] Reactor settings shown in Figure 8-12, including Stop Criteria, Mass Fraction of reactants to be 0.99, while operating times was set to be 1 hour as a batch reactor.

[368] This unit receives thermoplastic waste solids and granulates them to small granules between 6 - 8 mm hole diameter size. It is beneficial to ensure that thermoplastic particles are small in size in order to increase surface area for effective heat transfer to enable the thermoplastic mixture to change to a liquid/molten state. (Sinnott, 2005) It is useful to specify mass fractions in automated or manual mode (e.g., GGS, RRSB) or enter dispersion parameters derived from experimental data). (Reimers, 2013)

[369] Figure 8-13 is an image from a plastic granulator energy simulation.

[370] Figure 8-14 shows specifications of the plastic solid granulator. [371] Figure 8-15 shows a thermoplastic preheater from 30 to 250C.

[372] Using Aspen HYSYS Software Simulation, Q (heat energy) required to convert thermoplastic mixture from solid to liquid at 10,000kg/hr Mass Fraction: LDPE 0.2 | HDPE 0.35| PET 0.45

Q = 501.988 KW [373] The difference between Manual Calculations and Simulation results is 7.21 % using high pressure Steam as heating utility. 8.7. Economic Analysis

[374] In this chapter and through our economic calculations, we will adapt based on the Canadian Market prices (CA $) for utilities, capital and operating costs. Based on economic analysis we can calculate pricing for capital equipment, operating costs and compare prices for different operating routes. It is to be noted that economic evaluation is useful during the development stage of a process design to access its profitability. (Timmerhaus, 2002) It is during the preliminary evaluation associated with Laboratory scale experiments and research samples of final products. As soon as the final product design is complete, economic evaluation shall be done. The economic analysis is to be carried out on the Mass and Heat Balance sheet, and the finalized conceptual design of the process system. (Timmerhaus, 2002)

8.7.1 . optimum Design and Optimum economic design

[375] As mentioned earlier in this report, there are several alternative methods which can be used for any given process or operation. For example, formaldehyde can be products by catalytic dehydrogenation of methanol, by controlled oxidation of natural gas, or by direct reaction between CO and H2 under special conditions of catalyst, temperature and pressure. (Timmerhaus, 2002) It is the responsibility of the chemical engineer to choose the best process and to incorporate into his design the equipment and methods that will give the best results. In our report we will aim for the optimum engineering design to achieve the optimum operating and economic design. (Timmerhaus, 2002)

[376] Optimum economic design is achieved if there are two or more methods for obtaining exactly equivalent final results, the preferred method would be the one involving the least total cost. This is the basic definition of an optimum economic design. (Timmerhaus, 2002) 8.7.2. Capital Investments

[377] Before an industrial plant is put into operation, a large amount of money must be supplied to purchase or install the necessary machinery and equipment. The capital needed to supply the necessary manufacturing and plant facilities is called a fixed capital investment while that necessary for the operation of the plant is termed the working capital.

Total Capital Investment = Fixed Capital Investment + Operating Capital Investment

[378] Below are the sub-categories of fixed and operating capital investments.

[379] Breakdown of fixed Capital Investment items for a chemical plant (Timmerhaus, 2002)

[380] Direct Costs a) Purchased Equipment b) Purchased equipment Installation c) Instrumentation and controls d) Piping e) Electrical equipment and materials f) Buildings (including services) g) Yard Improvements h) Service Facilities i) Land [381] Indirect Costs a) Engineering and supervision b) Construction Expenses c) Contractor's fee d) Contingency

8.7.2.1. Marshal and Stevens's equipment-cost index

[382] The Marshal and Stevens equipment cost index is divided into two categories, the all industry equipment index and the process industry index. (Timmerhaus, 2002)

[383] The Model uses the Following equation to calculate present cost Present Cost =

index value at present time

x original cost (Timmerhaus, 2002)

index value at time original cost was obtained

[384] The Marshall and Stevens equipment cost index takes into consideration the cost of machinery and major equipment plus costs for installation, fixtures, tools office furniture and other minor equipment. Below is the list of equipment based on our process system design where capital and operating costs are calculated. The table is organized into direct and indirect costs statistics on a chemical plant.

Component Range % Median %

Direct Costs Purchased Equipment 20 - - 40 32%

Purchased-Equipment Installation 7.3 - 26.0 12.5%

Instrumentation and Control (installed) 2.5 - 7.0 4.3%

Piping (installed) 3.5 - 15 9.3%

Electrical (installed) 2.5 - 9.0 5.8%

Buildings (including services) 6.0 - 20 11 .5%

Yard Improvements 1 .5 - 5.0 3.2%

Service Facilities (Installed) 8.1 - 35 18.3%

Land 1 .0- 2.0 1.5%

Indirect Costs

Engineering and Supervision 4.0 - 21 13.0

Contruction expense 4.8 - 22.0 14.5

Contractors Fee 1 .5 - 5.0 3.0

Contingency 6.0 - 18.0 12.3

[385] It is often necessary to estimate the cost of a piece of equipment when no cost of data is available for a particular size or operational capacity involved. Good results can be obtained using the logarithmic relationship known as the six-tenths factor rule. (Timmerhaus, 2002)

[386] According to this rule if the cost of a given unit at one capacity is known, the cost of a similar unit with X times the capacity if the first is approximately (X) ^{0 6} times the initial cost.

„ _r „ _r . .capacity o f equip. a

Cost of equipment, a = Cost of equipment b ( )

capacity of equip.b [387] A more detailed and accurate exponent for equipment cost vs. capacity can be seen in (Timmerhaus, 2002)

8.7.2.2. Estimation of Fixed Capital Investment based on plant Capacity

[388] This method is known as seven-tenths rule for process Plants. (Don W. Green, 2008) The Formula is as follows:

Cost of Plant B = Cost of Plant A ( ^avacity ° ^{f Plant B} ) ⁰ - ⁷

capacity of Plant A

[389] This method will be our main method for equipment cost estimation in order to develop a reliable equipment cost analysis for pyrolysis of thermoplastic waste to oil products. It is also crucial to include the Marshal and Stevens equipment cost index to update the purchase cost of the equipment/asset. (Timmerhaus, 2002). Pg.108-109

8.7.3. Thermoplastic to Oil Chemical Economic Analysis

[390] As discussed in mass and energy balance, our mass flow rates are 87,660 Tonne per Annum, 87.6 KTA of thermoplastic waste.

[391] Therefore the expected Fixed Capital Cost based on choosing process industry for a solid-fluid processing plant. (Timmerhaus, 2002). Also CEPCI Index for Nov. 2015 is available (CEPCI, 2015) in order to update prices to 2016 Cost Index using Marshall and Stevens method

8.7.3.1. Purchased equipment estimate [392] The cost of purchased equipment is the basis of several predesign methods for estimating capital investment prices and can be divided conveniently into groups as follows: ^■ Processing equipment

^■ Raw-Materials handling and storage equipment

^■ Finished Products handling and storage equipment

[393] Referring to example in (Don W. Green, 2008) a 620.9 kg/hr of Product X has an initial investment of the following: ^■ Fixed Capital Investment = $80,000

Land = $25,000

Working Capital = $120,000

Scaling up for our 10,000Kg/hr Project we get the following results using cost estimation equations.

[394] Therefore a 10 metric tonne per hour pyrolysis plant in 2015 acording to Chemical engineering cost Index scale up Fixed Capital investment is $ 6,723,608.0667

8.8. Life cycle Assessment [395] Life cycle assessment is a technique used to assess environmental impacts associated with all the stages of product's life cycle including raw materials, materials processing, manufacturing, production and packaging. A vital criterion for life cycle assessment is also assessing alternatives of pyrolysis oil production. (J.F.Peters, 2015) The goal of the LCA is also to estimate and compare the environmental impacts that can be avoided by implementing pyrolysis oil production. The LCA compares plastic to oil pyrolysis plant in comparison with a crude oil refinery. The following assumptions are made in the block diagram comparison: ■ For both scenarios, transportation of waste is ignored by assuming that both the plants were in same distance and transportation has a relatively small contribution of environmental burden in the overall waste life cycle. (Zaman, 2013)

^■ Municipal solid waste has the block diagram shown in Figure 8-16 and syngas is used in electricity production. (C.Young, 2010) [396] Below are the LCA details for the chosen two recycling chemical plants:

[397] Carbon dioxide emissions are also much lower in pyrolysis in comparable with combustion or other waste treatment methods. (J. T.Conesa, 2008). CO2 emissions of plastics such as PVC or polyester for pyrolysis compared to combustion. [398] As seen below, pyrolysis reactions emit much lower carbon dioxide emissions in comparable with combustion.

8.9. Conclusion

[399] Large scale Plastic to Oil production plants include major process units starting with granulation, preheating, pyrolysis reaction, Light and heavy oil separation units, wax removal units. Aspen HYSYS simulation shows highest energy consumption in the pyrolysis reactor 125.8 MW for 87.6 KTA Plastic to Oil pyrolysis plant. Implementation of thermal plasma in pyrolysis reactions can significantly reduce the energy consumption. Pyrolysis oils include light and heavy components which need to be separated using flash separators. Tar is reduced by ensuring nitrogen conditions. The Carbon dioxide emissions are much lower for pyrolysis in comparison with combustion methods. [400] In terms of capital investment, pyrolysis has nearly 8% more capital investment that gasification chemical plants. However, pyrolysis produces liquid products in comparison with only syngas production for gasification chemical plants. Pyrolysis oil has higher selling value than syngas and can be used for transport or combustion engines unlike syngas is mainly used for electricity production.

9. Conclusion and Future Work

9.1. Conclusion

[401] A direct current thermal plasma circuit was used in thermoplastic to oil products pyrolysis reaction with chosen residence time of 30 minutes and operating temperature of 550C. A 7ml_ was collected from a 15-gram thermoplastic sample and results showed existence of n-butyl benzene, undecane and other hydrocarbon mixtures, the yield conversion achieved in a 1 L pyrolysis reactor under - 0.95 bar was nearly 60 wt% to hydrocarbon pyrolysis oil, the hydrocarbon gases were tested for flammability and wax and tar was collected. It was also shown that existence of oxygen increases tar production.

[402] The direct current thermal plasma showed better temperature profile using a K-type thermocouple in comparison with a 220 V, 4.8 A, 1056 W on a 15 gram LDPE sample, the residence time for both reactions were chosen to be 30 minutes, thermal plasma showed faster gaseous products and lower content of unreacted thermoplastics and achieve same product yields of pyrolysis oil showing benzene and butyl benzene as major products with minor quantities of undecane. Hydrocarbon gases were tested for ignition and showed high flammability and can be used for combustion purposes.

[403] The direct current thermal plasma is a reliable source of thermal energy and can be scaled up for usage in large scale pyrolysis reactors under operating conditions -0.95 bar and 550C. The direct current thermal plasma used was 30mA and 9000 V thus consuming 270 W. Pure nitrogen 99.99% should be used to prevent oxidation or unwanted reactions to occur during pyrolysis. Gaseous products are only allowed to condense after the mentioned residence time of 30 minutes which allow hydrocarbon liquids and waxes to condense which is later collected and weighted to calculate product yield.

[404] To conclude, the direct current thermal plasma system operates at vacuum pressure at 60 Hz and achieves better temperature profile in comparison with other heating methods, thermoplastic sample shows thermal cracking at a faster rate than other heating methods, gaseous products are allowed to condense and hydrocarbon pyrolysis oil weight 59 wt% while tar is reduced by providing an oxygen-free environment.

9.2. Future Work

[405] The same experimental setup can be used on a variety of thermoplastics, where the chemical compositions of oil products are identified, followed by categorizing thermoplastics that produce heavy oils and others that produce light oil products. If diesel is the desired final product, specific thermoplastics can be selected to achieve diesel liquid products. Added to that, the ignition properties of the pyrolysis oil are to be studied for LDPE, HDPE, PS, PP and PETE since they form more than 90 wt% of pyrolysis oil.

[406] In order to improve reaction kinetics, HZSM-5 and HUSY catalysts may possibly be used to reduce residence time and operating temperatures as well as their performance with thermal plasma torches. RF thermal plasma at 13.56 MHz frequency may be used with individual thermoplastics and thermoplastic mixtures to confirm its benefit.

9.3. Contribution

[407] This work illustrates the integration of direct current controllable thermal plasma circuit to be used in thermoplastic to oil conversion reactions. While pyrolysis reactions consume large amount of thermal energy (e.g. around 1047 KJ/Kg in a 30 minute reaction residence time), the thermal plasma can achieve such heat energy at a much lower power consumption to traditional electric heaters at a much higher efficiency. Also, thermal plasma temperature can be easily controlled which is beneficial in achieving desired products in thermoplastic to oil conversion reactions. Thermal plasma also works excellent in inert conditions in nitrogen gas and can be used in large scale pyrolysis chemical plants. In the experimental setup, a 270 W Direct current thermal plasma were used against a 1056 W electric heater on a 15 g LDPE sample and pyrolysis oil were collected with a product yield of 59 wt%. The pyrolysis oil sample shows butyl-benzene as a major product and existence of small traces of decane - diesel range fuel. The direct current thermal plasma system can be scale up and can drive thermoplastic to oil chemical recycling and achieve the required high thermal energy consumption in large scale pyrolysis reactors. The direct current thermal plasma jets are much more efficient to be used in pyrolysis reactors and have shown much higher temperature profiles and have lower electrical consumption than traditional electric heaters or other traditional industrial heating systems such as industrial furnaces and thermal cracking units.

[408] Persons skilled in the art will appreciate that there are yet more alternative implementations and modifications possible, and that the above examples are only illustrations of one or more implementations. The scope, therefore, is only to be limited by the claims appended hereto.

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