METHOD AND APPARATUS FOR PRODUCING FUEL GAS FROM BIOMASS

FIELD OF THE INVENTION

The present invention relates to biomass conversion into energy. More particular, the present invention relates to an apparatus and a method for producing fuel gas as a source of energy (e.g., generation of electricity).

BACKGROUND OF THE INVENTION

Biomass resources can be used as bioenergy. Biomass in general is the biodegradable fraction of products, waste and residues from agriculture (including vegetal and animal substances), forestry and related industries, as well as the biodegradable fraction of industrial and municipal waste. Usage of biomass resources is developed in three ways: biomass for heating purposes (bio-heating); biomass for electricity production (bio-electricity); and biomass for transport fuels (transportation biofuels).

As mentioned herein before, many types of biomass are available for conversion into energy. The efficiency of converting biomass into energy is determined by specific characteristics of the applied biomass technology. The profitability of the applied technology is strongly determined by the amount of the biomass available. One of the problems associated with biomass usage is the relatively high cost of biomass transportation that reduces the profitability.

At present, the following technologies are developed and applied for biomass conversion into electric power:

1) Firing in boilers (fluid beds) with generation of steam and its utilization in Rankin cycle; application of this method is limited by the necessity of gathering big amounts of biomass.

2) Gasification of biomass and further firing of the gases in gas turbines or engines; low calorific value of the generated fuel gases seriously limits its efficiency.

3) Pyrolysis of biomass. This method, if successful, provides liquid or gaseous fuels with high calorific value for power generation and seems to be especially convenient for small power units (~ 0.5 MW) destined for in-situ heat generation. Many types of biomass are available to be converted into energy. The efficiency of converting biomass into energy is determined by specific characteristics of the applied biomass technology. The profitability of the applied technology is strongly determined by the amount of the biomass available. One of the problems associated with biomass usage is the relatively high cost of biomass transportation that reduces the profitability.

The available solutions that are brought herein as references as well as other solutions fail to provide an efficient pyrolytic reactor (pyrolyzer) for biomass conversion into energy. Most of those solutions do not deal with in situ reactors and therefore, do not solve the high costs of biomass transportation involved in biomass-to-energy conversion.

The inventors of the present invention disclosed in PCT application published as WO 2006/103668 a method and apparatus performing high temperature fast pyrolysis of dry biomass. The invention discloses high yield of gases with medium caloric value and low tar content. An electric current is passed through a mixture of biomass mixed with conductive particles in a stirred bed inside the reactor. The current provides the intensive direct heating of the biomass in the pyrolytic reactor it is needed to provide a biomass power generation system that has high thermal efficiency and power generation efficiency, and that is capable of stably generating power by pyrolysis and gasification.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an apparatus and a method of converting biomass raw material directly to fuel gas using an improved apparatus.

It is another object of the present invention to provide an apparatus and a method for biomass conversion to fuel gas that is both effective and economical. It is another object of the present invention to provide an apparatus and a method for conversion of dry solid waste biomass to fuel gas.

It is another object of the present invention to provide an apparatus and a method for conversion of a group of biomasses such as olive waste (husks), wood, forest and agricultural residues such as bagasse, coconut shell, corn stalks, wheat straw, rice husk and rice straw, dried sludge from water treatments to fuel gas.

It is another object of the present invention to provide a pyrolytic reactor for biomass processing comprising a vertical cylindrical body having an input in an upper portion and an output in a bottom portion; a revolving mixer provided within said vertical cylindrical body, wherein said revolving mixer is capable of rotating in an upwardly direction; conductive particles provided within said vertical cylindrical body; electricity supply connected to the pyrolytic reactor so as to pass current through said conductive particles; whereby the biomass is inserted into the reactor through said input and discharged through said output. It is another object of the present invention to provide a pyrolytic reactor for biomass processing comprising a screw type.

It is another object of the present invention to provide a pyrolytic reactor for biomass processing comprising a motor attached to a revolving mixer capable of rotating the mixer.

It is another object of the present invention to provide a pyrolytic reactor for biomass processing comprising bearing and ceramic isolation for efficient rotation of the revolving mixer.

It is another object of the present invention to provide a pyrolytic reactor for biomass processing comprising conductive particles are that is a coke.

It is another object of the present invention to provide a pyrolytic reactor for biomass processing comprising a coaxial heating chamber surrounding the vertical cylindrical body wherein an input pipe of hot gases and an output pipe of gases are provided to and from coaxial heating chamber. It is another object of the present invention to provide a pyrolytic reactor for biomass processing comprising electricity supply that is connected to the revolving mixer in one side and to said vertical cylindrical body in a second side.

It is another object of the present invention to provide a pyrolytic reactor for biomass processing further comprising a gasifier positioned beneath the reactor capable of receiving the biomass exiting the output.

It is another object of the present invention to provide a pyrolytic reactor for biomass processing further comprising a gasifier comprises an internal receiving pipe capable of receiving the biomass exiting output and a gasification zone through which the biomass is downwardly passing. It is another object of the present invention to provide a pyrolytic reactor for biomass processing further comprising a gasifier comprising at least one air blower supplying hot air to the gasification zone.

It is another object of the present invention to provide a pyrolytic reactor for biomass processing further comprising a gasifier comprising gasification zone that is provided with conical inserts capable of controlling the flow of biomass.

It is another object of the present invention to provide a pyrolytic reactor for biomass processing further comprising a gasifier provided with an output allowing hot gasses to be released.

It is another object of the present invention to provide a method for producing fuel gases from biomass using a two-stage reaction apparatus

comprising: providing a vertical reactor having an input in an upper portion and an output in a bottom portion that comprises a revolving mixer; connecting electricity supply to said vertical reactor; providing conductive particles within said vertical reactor; passing the biomass through said vertical reactor from said input to said output; passing current from said electricity supply to said vertical reactor.

It is another object of the present invention to provide a method for producing fuel gases from biomass using a two-stage reaction apparatus further comprising: providing a gasifier beneath said vertical reactor so as to allow the biomass from the reactor to enter the gasifier; heating said biomass with hot air; discharging the processed biomass.

BRIEF DESCRIPTION OF THE DRAWING

In order to better understand the present invention and appreciate its practical applications, the following Figures are attached and references herein. Like components are denoted by like reference numerals.

It should be noted that the figures are given as examples and preferred embodiments only and in no way limit the scope of the present invention as defined in the appending Description and Claims.

Figure 1 illustrates a cross sectional side view of a pyrolytic reactor in accordance with a preferred embodiment of the present invention.

Figure 2 illustrates a cross sectional side view of a downdraft gasifier in accordance with a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION AND FIGURES

The method for converting biomass to available energy described in the present invention is based on fast and intensive heating of biomass within a specially designed two-stage reaction apparatus. The fast heating is achieved by mixing the biomass with conductive solid particles through which an electric current is passed as elaborated in WO/2006/ 103668 by the inventors of the present invention. It was revealed that the passing an electric current through a mixture of conductive and non-conductive particles allows fast heating this bed. When adding to this heated bed of particles of dry biomass, the electric heating goes on and an efficient pyrolysis is obtained.

In practicing the reactor disclosed previously by the inventors, it was shown that an improved and efficient reactor can achieve better results. The inventors of the present invention invented a method of converting biomass raw material directly to fuel gas and an improved apparatus for reducing self power consumption, effectiveness increase conversion process and reduction tar content in produced gases. A vertical two-stage reaction apparatus was developed that comprises a first stage of pyrolysis process and a second stage that comprises a downdraft gasifier for partial oxidation of pyrolysis products. For intensification process of biomass heating, which is provided by passing an electric current through mixture of biomass (non-conductive particles) with conductive particles (coke), it is necessary to provide the following conditions: 1) The mixture of conducting (coke) and non-conducting (biomass) particles must be conductive, for this purpose, according to the percolation theory, it is necessary to provide certain necessary ratio between conductive (coke) and non- conductive (biomass) particles in mixture so that the percent of conductive particles always would be more some critical parameter. At any critical value will take place percolating transfer being geometrical analogue of metal - isolator transfer.

2) The distance between the electrodes should be sufficient to provide the necessary heating.

Reference is made to Figure 1 illustrating a side view of a pyrolytic reactor in accordance with a preferred embodiment of the present invention. A vertical pyrolytic apparatus comprises a vertical cylindrical body 1 , inside which a vertical revolving mixer, for example a revolving screw 2 is provided for mixing the materials. It is further provided with an input 3 that also grind the biomass that is inserted into said cylindrical body. A source of electrical power 4 is provided so as to provide electricity to the system as well as a motor 5 of a screw 2. In order to allow efficient rotation of the screw 2, bearing 6, a ceramic isolation flange 7, a pad ring 8, a stuffing-box 9, a ceramic isolation ring 10 are provided. A coaxial heating chamber 11 is surrounding cylindrical body 1 wherein an input branch pipe 12 of hot gases (from a gasifier) and an output branch pipe 13 of gases are provided to and from coaxial heating chamber 1 1. An output 14 of pyrolysis products is provided downstream.

The raw material travels downstream through cylindrical body 1 by gravitational force (according to the arrow on the left side of the screw). Screw 2 rotates in an upwardly direction through the processed raw biomass (according to the arrow shown in the right side of the screw) and provides intensive mixing and reverse feeding of coke (received as a result of biomass conversion). The use of a vertical cylindrical body allows full utility of the volume of the reactor in oppose to the reactor described in WO 2006/103668 in which the reactor is only partially full. The intensive mixing of the biomass allows more uniform biomass and particles mixture to be formed. Moreover, screw 2 is designed to be thin enough so that to allow a significant distance between the end of the screw's diameter and the cylindrical body's diameter. This feature facilitates the heating quality of the biomass to be significantly higher than the heating of the biomass in the horizontal reactor described in the PCT publication.

At least one system for raw material feeding 7 is provided on top of cylindrical body 1 and at least one solids discharge system 14 is provided in the bottom part of the body.

Since the biomass is mixed with conductive particles, it should be noted that the circuit is closed by the electro-conductive particles (coke).

The primary pyrolysis products (fuel gas mixture, pyrolysis liquid (tar) and coke) that emerge from the first reactor through outlet 10 enter into a second stage - gasifier reactor. In this stage, cleaning of the produced gases by partial oxidation is achieved. Reference is now made to Figure 2 illustrating a side view of a gasifier in accordance with a preferred embodiment of the present invention. A down flow gasifier comprises an input 101 of pyrolysis products that travels from the pyrolytic reactor. The gasifier comprises an internal cylindrical pipe 102 at the upper side of the gasifier through which the biomass is entering a vertical cylindrical body 105 of the gasifier. Hot air (or steam) supply system 103 having air blower 104 supplies hot air to the gasifier into an oxidation chamber 106 while the hot gases are released from the system through an output 108. Gasification takes place within a gasification zone 107 while the down flow of the biomass is controlled by conical inserts 109. At the bottom portion of the gasification zone, the processed biomass, which is now solid rest (ash), is released through output 110.

Products of gasification are separated into two flows. One flow composed of gases (volatile) that can be inserted into a cyclone, then in a coaxial heating chamber of a pyrolytic reactor and further in system of heat recovery of gases. Air heated in recuperation system is separated and directed both to a gasifier and into a dryer for removal of moisture from initial biomass. The refrigerated and cleaned flue gases enter in a gas engine. The second flow - coke and ash (solid carbonaceous residues) is directed in a retention tank for further possible uses.

Other objects of the invention are attained by the provision of a power generation system comprising a gas-fueled power generator; two-stage reaction

apparatus for producing a fuel gas from biomass, operatively connected to supply fuel gas to the power generator; and means for controlling the flow of fuel gas from the reaction apparatus to the generator, the reaction apparatus being constructed for effecting fuel gas-producing process herein described. Normally, the system will include electronic data processing means for controlling the steps of the process and programmed to monitor gas phase products.

An apparatus similar to the reactor shown in the figures was built and tested to show feasibility.

It should be mentioned that any type of biomass can be used and converted into energy using the method of the present invention. The apparatus of the present invention is especially designed for olive oil production waste; however, any other type of biomass is covered by the scope of the present invention.

It should be clear that the description of the embodiments and attached Figures set forth in this specification serves only for a better understanding of the invention, without limiting its scope as covered by the following Claims. It should also be clear that a person skilled in the art, after reading the present specification can make adjustments or amendments to the attached Figures and above described embodiments that would still be covered by the following Claims.