WO2008091086A1

WO2008091086A1 - Gas generating method and it's apparatus using food waste

Info

Publication number: WO2008091086A1
Application number: PCT/KR2008/000373
Authority: WO
Inventors: Gab-Jong Park; Seung-Hyun Yang; Hak-Hyun Joe; Jae-Il Park
Original assignee: Gab-Jong Park; Seung-Hyun Yang; Hak-Hyun Joe; Jae-Il Park
Priority date: 2007-01-22
Filing date: 2008-01-21
Publication date: 2008-07-31
Also published as: KR100718865B1

Abstract

Disclosed herein is a gas generation method and apparatus, comprising obtaining solid feedstock for production of gas from food waste, producing the maximum amount of heat from the minimum amount of a heat source using the resulting solid feedstock, and using the thus- produced heat as a heat source necessary for the food waste treatment. More specifically, there is provided a gas generation method and apparatus configured to achieve generating high-temperature heat from solid feedstock (dried materials for production of gas) including food waste and recycling the thus-produced heat to dry water from the food waste, and using the residual heat as a heat source for heating of other facilities or for other industrial applications.

Description

GAS GENERATING METHOD AND IT S APPARATUS USING

FOOD WASTE

Technical Field

[1] The present invention relates to a gas generation method and apparatus, comprising obtaining solid feedstock for production of gas from food waste, producing the maximum amount of heat from the minimum amount of a heat source using the resulting solid feedstock, and using the thus-produced heat as a heat source necessary for the food waste treatment. Background Art

[2] Conventional disposal of food waste has been usually carried out by incineration of food waste in incineration facilities. However, such a traditional method involving incineration of food waste having a high water content of 70 to 80% suffers from problems such as a need for large amounts of evaporation heat for evaporation of water similar to where it is desired to use food waste as animal feed, and therefore consequent difficulty to find a heat source of evaporation heat, thus resulting in an apparent lack of economic rationality. Disclosure of Invention Technical Problem

[3] Therefore, the present invention has been made in view of the above problems and in compliance with a strong need for fundamental improvement in treatment of food waste, and it is an object of the present invention to provide a method for treatment of food waste which is capable of fundamentally preventing the risk of environmental contamination while using food waste taking advantage of the inherent nature thereof. Technical Solution

[4] The present invention is aimed to provide a method and apparatus for generation of useful gas, comprising obtaining combustible solid feedstock using food waste, producing the maximum amount of heat from the minimum amount of a heat source using the resulting solid feedstock, and using the thus-produced heat as evaporation heat necessary for evaporation of water in food waste.

[5] In accordance with an aspect of the present invention, the above and other objects can be accomplished by the provision of a gas generation method and apparatus configured to achieve generating high-temperature heat from solid feedstock (dried materials for production of gas) including food waste and recycling the thus-produced heat to dry water from the food waste, and using the residual heat as a heat source for heating of other facilities or for other industrial applications. Advantageous Effects

[6] As will be specifically illustrated hereinafter, the present invention provides a food waste treatment method whereby solid feedstock is obtained using food waste, mixed gas and water gas are produced using the resulting solid feedstock, and the thus- produced heat can be reused for desired applications.

[7] Further, the present invention is capable of fundamentally preventing environmental contamination which may occur due to waste water of food waste, via dehydration or no discharge of waste water contained in food waste. Brief Description of the Drawings

[8] FIG. 1 shows a process flow chart illustrating one embodiment of the present invention;

[9] FIG. 2 shows an overall block diagram of the present invention;

[10] FIG. 3 shows a perspective view illustrating a feedstock supply apparatus of the present invention; and

[11] FIG. 4 shows a partial cross-sectional view illustrating a discharge configuration of a second gas generator in accordance with the present invention.

[12] *List of reference numerals*

[13] 100: feedstock supply apparatus 200: first gas generator

[14] 300: second gas generator 400: high-temperature heat intensifier

[15] 101: storage hopper 102: transfer conveyor

[16] 103: solid feedstock delivery passage 110: inlet pipe

[17] 111: guide plate 120: push rod

[18] 121: opening and closing plate 130: first guide bar

[19] 131: engaging plate 140: second guide bar

[20] 150: engaging unit 151: actuation lever

[21] 152: elastic member 153: sensing unit

[22] 153a: sensing pin 160: support lever

[23] 161: rotation lever 170: power transmission means

[24] 180: screw axis 181: actuation unit

[25] 210: combustion chamber 211: barrier wall

[26] 220: first gas -generating chamber 230: discharge passage

[27] 240: chain conveyor 241: kiln bricks

[28] 250: feed screw 260: steam-generating chamber

[29] 261: water-supply pipe 262: steam exhaust pipe

[30] 270: blast pipe 280: steam injection pipe

[31] 310: second gas generation 320: communication passage

[32] 330: driving means 331: upper damper [33] 332: lower damper 333: actuation lever

[34] 334: rack 335: pinion gear

[35] 360: sensing switch 370: steam injection pipe

[36] 380: power transmission means

[37]

[38] Fig. 1:

[39] Fl: Collected food waste ; F2: Mill grinder ; F3: Screener ; F4: Food waste storage tank ; F5: Mixing tank ; F6: sawdust storage tank ; F7: Ground rice straw storage tank ; F8: Rice hull storage tank ; F9: Wheat flour paste storage tank ; FlO: Kneader ; Fl 1: First dryer ; F12: Mixed (semi-aqueous) gas generator ; F13: Second dryer ; F14: Storage of dried feedstock ; F15: Molding machine for molding solid feedstock ; Fl 6: Water gas generator ; F 17: Gas ignition heat intensifier ; Fl 8: Apparatus for exchange of high-temperature heat with low-temperature heat ; F 19: Collection facility for discharged air and steam

[40] DDDD: Discharge to atmosphere

[41]

Best Mode for Carrying Out the Invention

[42] Hereinafter, the configuration of the present invention will be outlined from the first step of external collection of food waste to the final step of generating high- temperature gas which will be reused as a heat source for purpose of the present invention.

[43] Within this present disclosure the term "feedstock" may be used interchangeably with the term "raw material" or the term "material"

[44] Generally, recycling of household and restaurant food waste involves grinding of the collected food waste using a mill grinder, separating foreign materials from the ground food waste using a screener, and combining the screened food waste in a storage tank prior to use. In this connection, food waste typically has a water content of about 70 to 80%.

[45] According to the present invention, the above-stored food waste and other additive materials are mixed to obtain a solid fuel which may be used as a gas -generating fuel. Specifically, solid feedstock is provided by kneading 70 to 85% by weight of food waste, 8 to 17% by weight of sawdust, 3 to 5% by weight of rice straw, 3 to 5% by weight of rice hulls and 1 to 3% by weight of wheat flour paste in a mixing tank, transferring the kneaded materials to a first drier which is provided in the form of a conveyor-type multistage tray or a mesh dryer, passing solid kneaded materials including food waste through a heated compartment of the drier having an internal temperature of 11O⁰C to 15O⁰C to result in a water content of less than 50%, and then forming the first-dried materials into egg-shaped or briquette- shaped molded materials in a molding machine.

[46] The thus-molded solid feedstock is subjected to second drying with heated air of

11O⁰C to 15O⁰C in a second dryer to result in a water content of less than 40%, and the second-dried solid molded material is then introduced into a continuous gas generator where charge and discharge processes of materials are automatically performed.

[47] For convenient illustration of the present invention, the gas generator may be divided into main parts of a feedstock supply part, a combustion part, a mixed gas- generating part and a water gas-generating part. First, the solid molded materials introduced into the gas generator are supplied via the feedstock supply part to a combustion chamber, followed by ignition and combustion with air blasting. Then, the feedstock which was brought into a red-hot carbon state by combustion is transferred to a mixed-gas generator while being maintained at a temperature of about 700⁰C to 900⁰C.

[48] Air and high-temperature steam are supplied to the red-hot feedstock material transferred to the mixed gas -generating part to thereby generate mixed gas. The residual red-hot carbon components, which passed through the mixed gas -generating part, are then transferred to a water gas-generating part equipped with air barrier means, and a given amount of high-temperature steam is injected into the feedstock material in the form of red-hot carbon being maintained at a temperature of 600⁰C to 800⁰C, thereby resulting in generation of water gas.

[49] The resulting mixed gas and water gas are transferred to a gas ignition heat in- tensifier to thereby obtain enhanced high-temperature heat which is then transferred to a heat exchange apparatus that transfers heat energy from one medium having a high temperature to another medium having a low temperature. Thereafter, heat energy converted into low-temperature heat can be used as an energy source necessary for pre- treatment processes including first and second drying processes of food waste as well as for other energy-consuming facilities. Therefore, the present invention provides a method and apparatus for generation of high-temperature heat using food waste.

[50] Although the preferred embodiments of the present invention have been disclosed with reference to the accompanying drawings, the present invention may be embodied in different forms and should not be misconstrued as being limited to the embodiments set forth herein, and those skilled in the art will appreciate that various modifications, additions and substitutions are possible without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Therefore, it should be understood that the embodiments disclosed herein are provided only for illustrating the present invention and should not be construed as limiting the scope and spirit of the present invention. Mode for the Invention

[51] Hereinafter, the present invention will be illustrated in more detail with reference to preferred embodiments and the accompanying drawings.

[52] FIG. 1 shows a detailed process flow chart illustrating one embodiment of the present invention, including individual processes until generation of mixed gas and water gas via use of food waste, specifically collection of food waste, mixing of raw materials and additives, preparation of solid feedstock, generation of mixed gas and water gas using the solid feedstock, transfer of the resulting gases to the gas ignition heat intensifier, and conversion of high-temperature heat into low-temperature heat. FIG. 2 shows an overall block diagram of the present invention. FIG. 3 shows a perspective view illustrating a feeding device. FIG. 4 shows a partial cross-sectional view illustrating a discharge configuration of a second gas generator in accordance with the present invention.

[53] Referring to FIG. 1, food waste (Fl) collected from external sources is transferred and ground in a mill grinder (F2), the ground food waste is screened in a screener (F3) to remove foreign materials, the screened food waste alone is stored in a storage tank (F4), and the stored food waste is then mixed with other additive materials to obtain solid feedstock. For this purpose, given amounts of materials from a screened food waste storage tank (F4), a sawdust storage tank (F6), a ground rice straw storage tank (F7), a rice hull storage tank (F8) and a wheat flour paste storage tank (F9) are discharged and mixed in a mixing tank (F5) in the following mixing ratio.

[54] Mixing ratio of raw materials to obtain solid feedstock (% by weight)

[55] Food waste (F4): 70% to 85%

[56] Sawdust (F6): 8% to 17%

[57] Ground rice straw (F7): 3% to 5%

[58] Rice hulls (F8): 3% to 5%

[59] Wheat flour paste (F9): 1 % to 3%

[60] Total: 100%

[61]

[62] Many trials and errors were made with varying mixing ratios of raw materials until desired solid feedstock of the present invention was obtained which can be used as a gas-generating material. As a result, the present inventors discovered that the solid feedstock resulting from the above-specified mixing ratio of raw materials is capable of generating useful gas in a gas generator for treatment of food waste. The present invention has been completed based on these findings.

[63] Among the raw materials to obtain the above-mentioned solid feedstock, the basic material food waste (F4) contains about 70 to 80% of water, about 6 to 8% of oil components (animal and vegetable oil including meat, fish, and cereal oil), about 9 to 15% of fiber components, and about 5 to 7% of nutrients of various foods. Therefore, the present invention is intended to prepare a gas -generating feedstock material using the oil components contained in food waste.

[64] Addition of sawdust (F6) during the preparation of gas-producing feedstock material facilitates drying of the food material, because oil components are absorbed by sawdust while water alone is separated during performance of a drying process based on the boiling point difference using heated hot air of about 11O⁰C to 15O⁰C under the condition that water and various oil components contained in the food waste were absorbed by the sawdust component. Particularly, various oil components incorporated into the sawdust, and various fiber components and nutrients in the food waste are combined into carbon carbides as solid feedstock.

[65] Further, addition of the ground rice straw (F7), when the raw materials are ignited and burned in a dried state, helps rapid elevation to high-temperature heat, and provides high temperature -retaining effects which maintain a high-temperature red hot state during transfer of the materials to a gas generator.

[66] Further, the rice hulls (F8) are added to enhance gas -generating effects. Rice hulls usually exhibit poor absorption of moisture or oil. However, when the milled rice hulls are added, rice hull particles are split into 1/3 to 1/5 the size of original particles and absorb some of moisture and oil, and are combined into solid feedstock materials. When gas -generating feedstock is ignited and burned, thus resulting in aggregation into carbon carbides, a volume of the feedstock is reduced to a compact form having 1/3 the volume size of the initial solid feedstock. Rice hull particles uniformly distributed throughout the reduced solid feedstock are carbonized while maintaining a volume of rice hull, thus resulting in formation of void volumes, so water vapor molecules are allowed to easily pass through the void volumes which were occupied by rice hulls, thereby improving gas -generating effects.

[67] Addition of wheat flour paste (F9) provides adhesive effects when solid feedstock is formed into an egg shape or the like.

[68] Food waste, sawdust, rice straw, rice hulls and wheat flour paste in accordance with the present invention are mixed in a mixing kneader (FlO), and the resulting mixture is then dried to a water content of less than 50% in a first drier (Fl 1) at a temperature of HO⁰C tO 15O⁰C.

[69] Finally, molding and drying processes are carried out. For this purpose, gas- generating feedstock dried in the first drier is molded into an egg- or briquette-shape in a molding machine (F12), and the resulting gas -generating molded materials are then dried to a water content of less than 40% in a second drier (F 13).

[70] The thus-prepared gas -generating molded materials are introduced into a gas generator such that mixed gas and water gas can be produced, and the remaining materials are transferred to a storage tank (F 14).

[71] FIG. 2 depicts a gas generator in accordance with the present invention. Hereinafter, the gas generator will be specifically described with reference to FIG. 2.

[72] The gas generator of the present invention may be broadly divided into a feedstock supply apparatus 100 for supply of solid feedstock, a first gas generator 200 for combustion of the feedstock and production of mixed gas, and a second gas generator 300 for production of water gas under low-oxygen concentration conditions.

[73] The feedstock supply apparatus 100 includes a storage hopper 101 for temporary storage of the dried solid feedstock such that charge and discharge of a given amount of the gas -generating solid feedstock are automatically performed, a transfer conveyor 102 for a constant supply of the waiting solid feedstock, and input means IOOA for automatic charge of the transferred solid feedstock via a delivery passage 103 into a combustion chamber 210 which will be described hereinafter.

[74] FIG. 3 depicts the input means IOOA, which is fitted into an inlet pipe 110 being in communication with a delivery passage 103 and formed in horizontal communication with a combustion chamber 210, and is provided with a push rod 120 such that the input means IOOA is guided toward guide plates 111 formed at both sides in the rear. Engaging plates 131, which are allowed to move forward and backward along first guide bars 130 installed outside the guide plates 111, are connected with the push rod 120 to achieve forward and backward movement of the push rod 120 therewith.

[75] An actuation lever 151 having actuation pins 15 Ia, 15 Ib at both sides thereof is connected to the rear of an engaging unit 150 adapted to move forward and backward along another second guide bar 140 disposed outside one side of the first guide bar 130. One side end of a rotation lever 161 pivotally mounted to a support lever 160 which is separately supported is disposed between the actuation pins 15 Ia, 15 Ib of the actuation lever 151, whereas the other side end of the rotation lever 161 is connected in engagement with a plate 121 opening and closing the delivery passage 103, such that the push rod 120 and the opening/closing plate 121 move forward and backward in the opposite direction to each other when the actuation lever 151 moves forward and backward.

[76] Further, a sensing unit 153 is axially fitted to the engaging unit 150 and is connected to the engaging plate 131 while having an elastic member 152. The sensing unit 153 is further provided with a sensing pin 153a adapted to actuate a sensing switch (Sl) which is installed to control at a predetermined position.

[77] Outside the second guide bar 140 is further provided with an actuation unit 181 which is screw-connected to move forward and backward in response to the rotation of a screw axis 180 provided to be rotated by power transmission means 170 through driving of a motor (M). The actuation unit 181 is further provided with a sensing pin 181a for actuating sensing switches S2,S2' provided at a given operation distance on opposite sides thereof.

[78] Referring to FIG. 2, a first gas generator 200, which carries out combustion of raw materials introduced by the feedstock supply apparatus 100 and a gas -generating process to thereby produce mixed gas, will be described in detail. The first gas generator 200 includes a combustion chamber 210, the upper part of which being formed in communication with the inlet pipe 110, and a first gas -generating chamber 220 having an open-bottom, provided at one side of the combustion chamber 210 and partitioned by provision of a barrier wall 211. Beneath the combustion chamber 210, a chain conveyor 240, which is installed to support and transfer the burning materials, is provided with kiln bricks 241 continuously arranged at regular intervals to perform combustion of materials as a function of the kiln.

[79] At one side of the chain conveyor 240 is formed a discharge passage 230 for discharging the feedstock escaped from the chain conveyor 240. Further, below the chain conveyor 240 is axially installed a feed screw 250, such that carbides falling to the ground below the chain conveyor 240 can be discharged to the discharge passage 230.

[80] The outer circumference of the combustion chamber 210 is provided with a steam- generating chamber 260 to generate high-temperature steam by combustion heat. The steam-generating chamber 260 includes a water-supply pipe 261 and a steam exhaust pipe 262, whereas the combustion chamber 210 and the first gas-generating chamber 220 include exhaust pipes 212,221 for emission of heat to the outside and discharge of mixed gas, respectively.

[81] A blast pipe 270 is further provided such that air blasting can be made on the kiln bricks 241 of the combustion chamber 210. Further, a steam injection pipe 280 is provided to inject high-temperature steam exiting the steam exhaust pipe 262 into materials being combusted in the first gas-generating chamber 220.

[82] Referring to the second gas generator 300, a second gas-generating chamber 310 has a hopper shape and receives red-hot carbon materials, the upper part of which is provided with a communication passage 320 being connected in communication with the discharge passage 230. Upper and lower parts of the communication passage 320 are each provided with upper and lower dampers 331,332 having opening and closing functions, which are operated in the opposite direction by driving means 330.

[83] The driving means 330 is provided with a pinion gear 335 which is axially and engageably installed between a rack 334 being connected to the upper damper 331 at the end of the actuation lever 333 screw-fitted to the screw axis 332 being rotated by the power transmission means 331 via driving of a motor to thereby move forward/ backward in accordance with the rotation direction of the screw axis 332, and a rack 336 being connected to the lower damper 332, such that the upper and lower dampers 331,332 are moved forward/backward in the opposite direction to each other in accordance with the rotation direction of the pinion gear 335. The actuation unit 333 is further provided with a sensing pin 333a which actuates sensing switches 360,360' provided at an operation distance on opposite sides thereof.

[84] The lower part of the gas-generating chamber 310, as shown in FIG. 2 and FIG. 4, is provided with a feed screw 340 axially installed to be rotated by power transmission means 380 via driving of a motor. Further, one side of the gas-generating chamber 310 is provided with an elongated discharge pipe 350, such that the exiting carbides are densely aggregated and slowly discharged to the outside. The upper part of the gas- generating chamber 310 is provided with an exhaust pipe 311 for discharging water gas, the water gas exiting the exhaust pipe 311 being transferred to a heat intensifier 400, and a steam injection pipe 370 for injecting high-temperature steam into stacked materials in a red hot state and flowing into the gas-generating chamber 310.

[85] Hereinafter, the operation of the apparatus in accordance with the present invention as configured above will be specifically described.

[86] A continuous supply of the solid feedstock contained in the storage hopper 101 is periodically made by the feedstock supply apparatus 100 via the inlet pipe 110 of the first gas generator 200. A given amount of the solid feedstock charged into the combustion chamber 210 is flowed into the kiln bricks 241 on the chain conveyor 240 located below the chamber 210 and then ignited by a separate ignition device. At the same time, sufficient ignition is achieved as air blasting to an ignition part is performed via the blast pipe 270. As a result, water of the steam-generating chamber 260 formed along the circumference of the combustion chamber 210 is warmed by high- temperature heat to thereby result in production of high-temperature steam. Then, the resulting high-temperature steam is discharged through the steam exhaust pipe 262, and the high-temperature heat is transferred to the gas ignition heat intensifier 400 through the exhaust pipe 212 along the supply line.

[87] The solid feedstock which was brought into a red-hot carbon state by the combustion process is slowly introduced at a given low rotation speed into the first gas-generating chamber 220, and the combustion chamber 210 is ready to receive the solid feedstock as much as the amount of solid feedstock charged to the first gas- generating chamber. When high-temperature steam supplied from the steam-generating chamber 260 is periodically injected via the steam injection pipe 280 into the solid feedstock in the red-hot carbon state flowing into and slowly passing through the first gas-generating chamber 220, high-temperature steam contacts and reacts with red-hot solid feedstock having a temperature of about 700⁰C to 900⁰C to thereby produce semi- aqueous mixed gas containing high-temperature heat. The resulting mixed gas is then transferred to the gas ignition heat intensifier 400 through the exhaust pipe 221 along the supply line.

[88] When weight and components of gas entrapped in the first gas-generating chamber

220 were analyzed by a gas meter and gas chromatography, the entrapped gas was found to consist of 22 to 28% of carbon monoxide, 3 to 6% of carbon dioxide, 24 to 32% of hydrogen, 3 to 10% of methane and the balance of nitrogen and oxygen, thus confirming formation of the mixed gas.

[89] The solid feedstock exiting from the first gas-generating chamber 220 by operation of the chain conveyor 240 is introduced through the discharge passage 230 into the second gas generator 300. First, the upper damper 331 provided in the communication passage 320 which is an inlet is closed, so the solid feedstock is on standby. When the upper damper 331 is opened by the operation of the driving means 330, the lower damper 332, which was in the open state, is simultaneously closed, so a proper amount of the solid feedstock is transferred to the lower damper 332. Then, the upper damper 331 is closed again and the lower damper 332 is opened, so the solid feedstock located in the lower damper 332 is introduced into the second gas-generating chamber 310. Through the continuous process as described above, inflow of the solid feedstock is periodically made at regular intervals.

[90] Under low-oxygen concentration conditions where inflow of external air is blocked to some extent, the red-hot carbon state of the solid feedstock material introduced into the second gas -generating chamber 310 contacts with high-temperature steam supplied via the steam injection pipe 370 connected to a line of the steam exhaust pipe 262, thus resulting in generation of water gas. The resulting water gas is delivered to the gas ignition heat intensifier 400 via the feed line 311. The lower part of the second gas- generating chamber 310 is provided with a feed screw 340 which serves to discharge the downward-moving burnt carbides to the outside via the discharge pipe 350. Since the discharge pipe 350 is made in the form of an elongated tube, the exiting carbides are densely aggregated and slowly discharged to the outside, so the inflow of external air through the discharge pipe is blocked.

[91] When weight and components of gas entrapped in the second gas -generating chamber for production of water gas from red-hot carbon materials under blocking of air inflow at a temperature of 600⁰C to 800⁰C were analyzed by a gas meter and gas chromatography, the entrapped gas was found to consist of 40 to 48% of hydrogen, 32 to 40% of carbon monoxide, 4 to 8% of carbon dioxide, 1 to 3% of methane and the balance of nitrogen, thus confirming formation of the water gas primarily containing hydrogen, carbon monoxide and methane.

[92] Therefore, the present invention provides a method and apparatus for generation of high-temperature heat using food waste. Specifically, mixed gas and water gas are generated in a gas generation apparatus using high-temperature heat produced from solid feedstock (dried materials for production of gas) including food waste, and the thus-produced heat can be recycled to a pretreatment process, e.g. drying of water from the food waste. The residual heat can also be used as a heat source for heating of other facilities or for other industrial applications including plastic greenhouses. The present invention has been completed based on these findings.

[93] As discussed hereinbefore, the apparatus of the present invention is broadly comprised of the feedstock supply apparatus 100, the first gas generator 200 for generation of mixed gas, and the second gas generator 300 for generation of water gas. Therefore, production of mixed gas and production of water gas may be carried out alone or in combination. The thus -generated gases are supplied to the heat intensifier 400 where heat temperature is increased to a high temperature range of 1000⁰C to HOO⁰C by the action of high-temperature gas. Alternatively, for dilution and exchange with external air, the thus-generated high-temperature heat is exchanged with low- temperature heat of 11O⁰C to 13O⁰C, so it is possible to sufficiently dry about 70 to 80% of a water content in food waste by using self-generating heat. Further, it is expected that more than 40% of a heat source is in excess, after the produced heat is used for the treatment of food waste. Therefore, the residual heat can be reused for heating of plastic greenhouses or industrial facilities or for other applications as desired.

[94] In addition, the present invention is capable of fundamentally preventing environmental contamination arising from waste water of food waste, because there is no discharge of waste water which has been a significant problem associated with treatment of food waste.

[95] Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Industrial Applicability

[96] The present invention is industrially advantageous by providing a preparation method of a recyclable heat source, which comprises obtaining combustible solid feedstock using food waste, producing the maximum amount of heat from the minimum amount of a heat source using the resulting solid feedstock, and using the thus-produced heat for treatment of the food waste and as an energy source for other applications.

Claims

[1] A method for generation of gas using food waste, comprising: collecting and grinding food waste, screening the ground food waste to separate foreign materials and storing the screened food waste; mixing and kneading the food waste with ground rice straw, sawdust, rice hulls and wheat flour paste to obtain kneaded solid feedstock for generation of gas; drying the gas -generating solid feedstock in hot air of 11O⁰C to 15O⁰C to a water content of less than 50% (first drying); molding the first dried feedstock into solid feedstock having a given size in a molding machine, and drying the molded solid feedstock in hot air of 11O⁰C to 15O⁰C (second drying); introducing the second dried solid feedstock into a gas generator, and igniting and burning the solid feedstock under control of air inspiration to bring the solid feedstock into a red-hot state; transferring the red-hot solid feedstock with completion of combustion of volatile components in the solid feedstock to a mixed-gas generator at a temperature of 700 to 900⁰C to thereby generate mixed gas under control of steam and air amounts; transferring the red-hot solid feedstock from the mixed-gas generator to a water- gas generator at a temperature of 600 to 800⁰C, followed by controlled injection of steam under exclusion of air to generate water gas; and using the mixed gas or water gas generated from the mixed-gas generator or the water-gas generator as a heat source for drying of food waste.

[2] The method according to claim 1, wherein the kneaded gas-generating solid feedstock is a mixture of 70 to 85% by weight of food waste, 8 to 17% by weight of sawdust, 3 to 5% by weight of ground rice straw, 3 to 5% by weight of rice hulls and 1 to 3% by weight of wheat flour paste.

[3] A gas generator, comprising: a feedstock supply apparatus including a storage hopper for temporary storage of solid feedstock, and input means for automatic charge of the solid feedstock into a combustion chamber; a first gas generator for combustion of the feedstock introduced by the feedstock supply apparatus and production of mixed gas; and a second gas generator for production of water gas from the solid feedstock passed through the first gas generator under low-oxygen concentration conditions, wherein the resulting mixed gas and water gas are transferred to a heat intensifier via a supply line.

[4] The gas generator according to claim 3, wherein the input means of the feedstock supply apparatus is fitted into an inlet pipe, and includes a push rod such that it is guided toward guide plates formed at both sides in the rear, and engaging plates connected to the push rod and allowed to move forward and backward along first guide bars installed outside the guide plates; an actuation lever having actuation pins at both sides thereof is connected to the rear of an engaging unit adapted to move forward and backward along another second guide bar disposed outside one side of the first guide bar, and one side end of a rotation lever pivotally mounted to a support lever being separately supported is disposed between two actuation pins of the actuation lever whereas the other side end of the rotation lever is connected in engagement with a plate opening and closing the delivery passage; a sensing unit is axially fitted to the engaging unit and is connected to the engaging plate while having an elastic member, the sensing unit including a sensing switch (Sl) having a sensing pin adapted to control at a given position; and an actuation unit is outside the second guide bar and is screw-connected to move forward and backward within the predetermined range in response to the rotation of a screw axis provided to be rotated by power transmission means through driving of a motor (M).

[5] The gas generator according to claim 3, wherein the first gas generator comprises: a combustion chamber, the upper part of which being formed in communication with the inlet pipe, and a first gas-generating chamber having an open-bottom, provided at one side of the combustion chamber and partitioned by provision of a barrier wall; a chain conveyor located beneath the combustion chamber and having kiln bricks; a discharge passage for discharging the feedstock and formed at one side of the chain conveyor, and a feed screw axially installed below the chain conveyor, such that carbides falling to the ground below the chain conveyor are discharged to the discharge passage; a steam-generating chamber for generating high-temperature steam by combustion heat and formed on the outer circumference of the combustion chamber; a water-supply pipe and a steam exhaust pipe formed in the steam-generating chamber; exhaust pipes for emission of heat to the outside and discharge of mixed gas, and formed in the combustion chamber and the first gas -generating chamber, respectively; a blast pipe for air blasting to the kiln bricks of the combustion chamber; and a steam injection pipe for injection of high-temperature steam exiting the steam exhaust pipe into materials being combusted in the first gas-generating chamber.

[6] The gas generator according to claim 3, wherein the second gas generator is configured such that: a second gas-generating chamber receives red-hot carbon materials, the upper part of which being provided with a communication passage being connected in communication with the discharge passage, and upper and lower parts of the communication passage are each provided with upper and lower dampers having opening and closing functions, which are operated in the opposite direction by driving means; and the lower part of the gas-generating chamber is provided with a feed screw axially installed to be rotated by power transmission means via driving of a motor, one side of the gas -generating chamber is provided with an elongated discharge pipe, and the upper part of the gas-generating chamber is provided with an exhaust pipe for discharging gas, and the inside of the gas -generating chamber is provided with a steam injection pipe for injecting high-temperature steam and connected to a steam exhaust line.

[7] The gas generator according to claim 6, wherein the driving means is provided with a pinion gear which is axially and engageably installed between a rack being connected to the upper damper at the end of the actuation lever screw- fitted to the screw axis being rotated by the power transmission means via driving of a motor to thereby move forward/backward within the operation distance in accordance with the rotation direction of the screw axis, and a rack being connected to the lower damper.