Process for the conversion of plastic material to fuels

FIELD OF THE INVENTION

The present invention relates to a process for the conversion of plastic material to fuels by using thermal cracking and fractional distillation.

BACKGROUND OF THE INVENTION

The production and consumption of plastics has increased dramatically leading to serious environmental problems due to waste plastic across the globe. Waste plastics, also known as refuse plastics, dead plastic or end-of-life plastics obtained from industrial wastes, are extremely harmful to the environment. Processes for the conversion of waste plastic into fuels will not only eliminate the refuse which is harmful to the environment, but also decrease the dependence on fossil fuels. However, processes such as incineration and gasification are not preferred, as toxic gases such as dioxins are produced during the conversion.

Pyrolysis is one of the approaches for the conversion of plastic into hydrocarbon fuels. The results from the pyrolysis process are found to be better than the other alternate methods such as incineration and gasification. However, the type of plastic used as raw material impacts the rate of conversion to fuels. Also, pyrolysis is a complex process associated with low conversion efficiencies, low energy efficiencies, high capital investments, running cost and posing undesirable environmental issues. To overcome the aforementioned problems, new technologies are being developed that will enable the production of value-added materials from plastic material.

Several patents and scientific publications disclose de-polymerization of plastic, wherein said plastic is converted into valuable fuels and energy.

DE19724144C1 discloses a process for converting waste plastic to solid, liquid and gaseous hydrocarbons, wherein the process is carried out in a cylindrical de -polymerization reactor which is designed as a vacuum vessel, with one or more heating bodies arranged axially. Vacuum is created at the lower part of the vessel, and the vaporized product is withdrawn from the top of the reactor, and fed to a distillation column for the separation of gaseous, liquid and solid hydrocarbons.

US20130274535A1 discloses a process, wherein the plastic waste is ground and fed along with a heavy oil fraction into a dehalogenation reactor. The mixture retained in the dehalogenation reactor chamber is forwarded to the de -polymerization reactor, where the temperature is maintained between 480°C and 600°C, and the hydrocarbon gas mixture is extracted and separated into fractions.

US9920255B1 discloses a method and an apparatus for the de-polymerization of waste plastic, in particular, pre- or post- consumer plastics wastes, by means of heating and thermal cracking. The plastic materials are melted and degassed before being passed on to a de-polymerization reactor comprising a heating device. The vapors released are extracted via an extraction line at the head of the reactor and supplied to a downstream separation column. In the separation column, the product mixture is further separated into products.

Jerzy Walendziewski et al. (Catalysis Today 65 (2001): 323-330) and Bidhya Kunwar et al. (Energy 111 (2016): 884-892) disclose the conversion of waste samples of polyethylene and polystyrene to fuels by subjecting them to thermal cracking or catalytic cracking. The products obtained from this process are gasoline and diesel fuel.

Existing prior art processes for de -polymerization of plastic are associated with problems such as low conversion efficiencies, inefficient heat transfer, incorporation of multiple steps, issues associated with environment and sustainability, thus increasing the overall costs.

In view of the above, there exists a need to develop a process that can overcome the aforementioned problems. To overcome the aforementioned problems, the inventor of the present invention has developed a thermal de-polymerization process wherein an in-line horizontal fractional distillation column is used to produce refuse-derived oils such as petrol, diesel and kerosene, from plastic material rendering efficient material management and reduced power consumption system. OBJECT OF THE INVENTION

The primary object of the present invention is to develop a cost-effective and ecofriendly process for efficient conversion of plastic material to fuels.

Another object of the present invention is to develop an efficient process for thermal de- polymerization of plastic material for the production of fuels.

Still another object of the present invention is to develop a single-step de -polymerization reaction for the conversion of plastic material to fuels.

SUMMARY OF THE INVENTION The present invention provides a process for the conversion of plastic material into fuels through a single-step reaction process. The said process involves thermal cracking and de -polymerization which are carried out by loading the plastic material into a de-polymerization reactor. The de polymerization reactor consists of a special heating system comprising a multi-stage temperature controller, and is operated between room temperature and 550°C. The gases from the melt plastic of the de-polymerization reactor flow into an in-line horizontal fractional distillation column to produce fuels such as petrol, diesel, kerosene and other natural gas products.

BRIEF DESCRIPTION OF THE DRAWINGS

The summary of the present invention, as well as the detailed description, is better understood when read in conjunction with the accompanying drawings that illustrate one or more possible embodiments of the present invention, of which:

Figure 1 illustrates the schematic representation depicting the flow of pre-processing plastic material and conversion of plastic material to fuels.

Figure 2 illustrates the flow diagram of the inventive process according to the embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

Various embodiments will now be described to provide an overall understanding of the principles, structure, function, manufacture, and use of the processes and apparatus disclosed herein. Those of ordinary skill in the art will understand that the features described or illustrated in connection with one example embodiment can be combined with the features of other example embodiments without generalization from the present disclosure.

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate the embodiments of the present invention, and together with the description, serve to explain the principles of the invention.

The present invention is related to a single-step reaction process for the conversion of plastic material into fuels through de -polymerization.

The said plastic material is particularly plastic material which may include, but not limited to polyethylene (PE), polypropylene (PP), low-density polyethylene (LDPE), high-density polyethylene (HDPE), light distillates (LD), heavy distillates (HD), light petroleum distillates (LDP), heavy petroleum distillates (HDP) and the like, or the mixture of one or more kinds of plastic waste.

The said fuels may include, but is not limited to synthetic diesel, synthetic aviation fuel, synthetic petrol, petro gas, petroleum coke, and the like. According to an embodiment of the present invention, the pre-processing of plastic material comprises procuring plastic from different sources and loading the same into a plastic shredding machine, wherein the plastic material is ground into powder form or chips, and manually fed into the reactor kiln 2.

According to an embodiment of the present invention, the de -polymerization is carried out in a de- polymerization reactor which is a column thermal cracking reactor wherein the said loaded plastic offers resistance to the gas and breaks down long chain hydrocarbons into small chain hydrocarbons. Melting and gasification of the said plastic material is performed in the same reactor kiln 2 wherein the de -polymerization takes place, and is therefore considered as a single-step reaction process.

The de-polymerization reactor utilizes a special heating system with multi-stage heating ability wherein the temperatures are controlled and regulated with the help of proportional-integral- derivative (PID) controllers. Temperature probes are mounted on the reactor kiln 2, the hot condenser 8 and the cold condenser 11 , to enable monitoring the temperature.

The single-step reaction process for the conversion of plastic material to fuels comprises the steps of: a) a de-polymerization process wherein, the said plastic material is loaded along with additives in the de -polymerization reactor equipped with a special heating system wherein de -polymerization takes place at a temperature of 90°C to 550°C under atmospheric pressure for 18 to 28 hours, the said de -polymerization process further comprises: i) a humidity removing process, wherein the reactor kiln 2 is heated to remove the moisture of the said plastic material at a temperature of 90°C to 140°C; ii) a self-purging process for the removal of oxygen from the reactor kiln 2, wherein this purging activity is performed in the reactor kiln 2 at 140°C to 220°C, using a temperature controller; iii) a plastic material melting process, wherein the melting of the plastic material is obtained at a temperature of 220°C to 290°C; iv) a gasification process, wherein the said plastic melt solution is heated to effect gasification of the said material at a temperature of 290°C to 320°C, at which stage the temperature of the reactor kiln 2 is raised to 350°C and maintained at this temperature for a duration of 3 hours. Due to this heat transformation, the plastic material slowly melts into a liquid form. The temperature is then slowly increased from 350°C to 400°C in a phased manner and is maintained for 8 hours; and v) a pet coke forming process, wherein the byproduct of pet coke is obtained at a temperature of 400°C to 440°C and the temperature is subsequently raised to a range of 480°C to 550°C which is maintained for 4 hours, and the plastic melt transforms into a gaseous form, which condenses to form the liquid fuels. The hot gases generated during the pet coke forming process, rise up to the raiser column 4 and travel through the transfer pipe 7 and enter the hot condenser 8 while the heavier asphalts will not travel in the column baffle due to resistance in the column. The hot condenser 8 comprises a honeycomb arrangement, and due to the resistance offered by the honeycomb arrangement, a sudden drop in the temperature and pressure of the hot gases is experienced. Due to the sudden expansion of the gases, the heavier gases condense into a liquid. The heavy liquid such as diesel is collected from the bottom half of the condenser 8 in a storage tank 20 while the lighter gases travel further in the honeycomb condenser 8 and condensate such as kerosene is collected in another storage tank 21. The lightest gases travel further in the honey comb condenser which is surrounded by a water jacket to bring the temperature down to 18°C. This water jacket acts as a heat exchanger. The condensate such as petrol generated from this step is collected in another storage tank 22.

Further, the lighter gases escaping from the cold condenser 11 are vented out through a pipe to a dual fuel generator. The fuels emanating from the hot and cold condensers are filled in the preliminary tanks from where they are transferred to a storage tank (20, 21 and 22) and preserved for further processing. The collected fuels in the storage tanks are treated with chemicals and stirred for 4 hours. Stirring helps in clogging the asphalts which become heavier and settle down in the tank. After stirring, a vibration motor is operated for 0.5 - 1 hour which helps in further clogging of asphalts. The fuels is then collected in a storage tank (20, 21 and 22) and subjected to a multi-stage filtration system comprising of cloth filters. Subsequently, the filtered oils are collected in designated barrels or tanks.

Referring to Figure 1 , the pre-processing of plastic material is achieved through a series of steps shown in plastic pre-processing section wherein, the plastic materials of different grades, procured from different sources are collected and sorted; which are conveyed to a washing machine to remove contaminants such as dust, sand, oil etc. and the washed material is placed in a microwave tunnel heating system to convert into plastic blocks and then passed through a hydraulic press to release the water from the plastic blocks; which are conveyed to a plastic shredding machine wherein the large plastic materials are broken into smaller plastic pieces; the said small pieces of plastic blocks are loaded into the de -polymerization plant comprising of a reactor kiln 2, a plurality of condensers, and a plurality of storage tanks. Figure 2, shows a schematic representation of the de-polymerization plant wherein the inventive process according to the embodiments of the present invention is carried out. The said de polymerization plant comprises of a control panel 1 , a plurality of heating systems in a reactor kiln 2, wherein proportional-integral-derivative (PID) controllers control the temperatures, a circuit breaker 18, and a power pole 19. The plastic blocks are loaded in the said reactor kiln 2 and are held in a vacuum tight condition by sealing with an end cap 3. A raiser column 4 is attached on top of the reactor kiln 2. The other end of the raiser column 4 comprises an end flange 6 and a unique passage system which is connected to the hot condenser 8 through a transfer pipe 7. The said system also comprises pressure gauges 5 and 9 and pressure relief valves 13 and 14 to enable operation of the process at atmospheric pressure. The said hot condenser 8 is connected to a cold condenser 11 through a connecting pipe 10.

The de -polymerization plant utilized for the execution of the process of the present invention also comprises a header 15 which is connected to the said control panel 1 through a connecting pipe 16 which carries the remaining heavy oil and is added to the plastic melt as an additive for heat absorption in the reactor kiln 2. A compressor 12 positioned above the said cold condenser 11 is used to increase the pressure of gas present in the said cold condenser 11 thus reducing the volume and enabling the collection of the condensate oil obtained from the said hot condenser 8 and the said cold condenser 11. The said de-polymerization plant also comprises three storage tanks 20, 21, and 22, to hold the various fractions of the fuels generated during the conversion process and pipe coupling 29. The said storage tanks 20, 21 , and 22 are connected in parallel to the outlet pipes 23, 24, and 25 respectively, which further comprise flow regulating valves 26, 27, and 28, and taps 30, 31, and 32.

The said de-polymerization plant is placed on a support frame 17.

The said reactor kiln 2 further comprises a raw material holding space wherein the said pre- processed plastic blocks are loaded.

The said raiser column 4 of the de -polymerization plant further comprises a unique passage system offering resistance to the pathway of the hot gases generated from the reactor kiln 2.

The said transfer pipe 7 facilitates the flow of hot vaporized gases formed in the reactor kiln 2 to the hot condenser 8. The said additive used for heat absorption in the reactor kiln 2 are crude oil, synthetic oil, synthetic sludge or synthetic heavy oil, which are recovered from the de -polymerization plant, after distillation.

The said additive may also a lava ash is added for improving heat absorption and reducing asphalts. The additives are added in the ratio of 1 : 10.

The reactor kiln 2 is maintained in an air-tight vacuum condition using an end cap 3. This may alternately be attained by using fasteners, and also the parting plane may be closed with a sealant.

The reactor kiln 2 comprises a heating system consisting of an electric power system which is positioned horizontally to cover the entire surface area of the reactor kiln 2. The heat may be infused by any method known to one skilled in the art such as radiant heating, infra-red heating, electromagnetic heating, microwave heating, or other heating techniques, which includes direct heating or indirect heating. The radiant heat dissipating from the heating element is absorbed by the reactor kiln 2.

The hot condenser 8 comprises a honeycomb arrangement, due to which a sudden drop in the temperature and pressure of the hot gases is experienced and the heavier gases condense into a liquid.

Advantageously, the process of the present invention is eco-friendly and effectively reduces the toxic pollutants that damage the environment. The process of the present invention is equally effective for the conversion of plastic to fuels. Another advantage is that addition of an additive derived from the plastic material results in improved heat absorption. Further advantage is that the process of the present invention is energy efficient, wherein the power consumption to convert 1 kg of plastic into fuels is 1000 watts i.e., , it takes 1 unit of power.

The process of the present invention is further explained through examples. Example 1:

Plastic powder obtained from plastic chair industry or granules obtained from recycling industries comprising of polyethylene, polypropylene, high-density polymer (HDP), low-density polymer (LDP) and mixtures thereof, and weighing approximately 300 kg., is fed into a plastic washing machine to remove sand, oil etc. The washed plastic material is placed in a microwave tunnel heating system to convert into plastic blocks and passed through a hydraulic press to release the water from the plastic blocks. The washed plastic blocks are fed into a de -polymerization reactor kiln 2 using a 2-stage programmed heating. The said plastic blocks are then de-polymerized in the reactor kiln 2 at a temperature range of 300°C to 480°C under atmospheric pressure (> 4 psi) for 24 hours. The vaporous products are extracted from the reactor kiln 2 through an extraction line via the raiser column 4. The required heat energy for triggering the endothermic cracking reaction is obtained from the mixture of plastics melt/heavy oil introduced into the reactor kiln 2. The vaporous product mixture extracted via the extraction line at the raiser column 4 of the reactor is supplied to a downstream horizontal distillation column comprising of hot condenser 8 and cold condenser 11 systems following which the product mixture is separated into three product lines. The product mixture is separated into gas (C4), petrol (CH), diesel (C14), pet coke, a naphtha- containing product as well as products similar to gas oil. The conversion efficiency of this process is 52%.

Example 2:

Plastic powder obtained from plastic chair industry or granules obtained from recycling industries comprising of polyethylene, polypropylene, high-density polymer (HDP), low-density polymer (LDP) and mixtures thereof, and weighing approximately 300 kg., is fed into a plastic washing machine to remove sand, oil etc. The washed plastic material is placed in a microwave tunnel heating system to convert into plastic blocks and passed through a hydraulic press to release the water from the plastic blocks. The washed plastic blocks are fed into the de -polymerization reactor kiln 2 using a 4-stage programmed heating. The said plastic blocks are then de-polymerized in the reactor kiln 2 at a temperature range of 240°C to 400°C under atmospheric pressure (> 4 psi) for 21.5 hours. The vaporous products are extracted from the reactor kiln 2 through an extraction line via the raiser column 4. The required heat energy for triggering the endothermic cracking reaction is obtained from the mixture of plastics melt/heavy oil introduced into the reactor kiln 2.

The vaporous product mixture extracted via the extraction line at the raiser column 4 of the reactor is supplied to a downstream horizontal distillation column comprising of hot condenser 8 cold condenser 11 systems following which the product mixture is separated into three product lines. The product mixture is separated into gas (C4), petrol (Cg), Kerosene (C10), diesel (C _M ), pet coke, a naphtha-containing product as well as products similar to gas oil. The conversion efficiency of this process is 70%.

Example 3:

Plastic powder obtained from plastic chair industry or granules obtained from recycling industries comprising of polyethylene, polypropylene, high-density polymer (HDP), low-density polymer (LDP) and mixtures thereof, and weighing approximately 300 kg., is fed into a plastic washing machine to remove sand, oil etc. The washed plastic material is placed in a microwave tunnel heating system to convert into plastic blocks and passed through a hydraulic press to release the water from the plastic blocks. The washed plastic blocks are fed into the de -polymerization reactor kiln 2 using a 5 -stage programmed heating. The said plastic blocks are then de-polymerized in the reactor kiln 2 at a temperature range of 220°C to 480°C under atmospheric pressure (> 4 psi) for 20 hours. The vaporous products are extracted from the reactor kiln 2 through an extraction line via the raiser column 4. The required heat energy for triggering the endothermic cracking reaction is obtained from the mixture of plastics melt/heavy oil introduced into the reactor kiln 2.

The vaporous product mixture extracted via the extraction line at the raiser column 4 of the reactor is supplied to a downstream horizontal distillation column comprising of hot condenser 8 and cold condenser 11 systems following which the product mixture is separated into three product lines. The product mixture is separated into gas (C4), petrol (Cg), kerosene (C10), diesel (CM), pet coke and a naphtha-containing product as well as products similar to gas oil. The conversion efficiency of this process is 85%.