Biomass gasification system

A biomass gasification system for producing aqueous or water gases after biomass has been carbonized is disclosed. Temperatures of a thermal decomposition and gasification furnace can be quickly and uniformly stabilized with smaller thermal loss. Reaction residuals after thermal decomposition and gasification are prevented from adhering on the inner surface of the system. The biomass gasification system comprises: a main body, a first cylindrical member, a first cut-out member, a first cylinder accommodating therein a first screw conveyor, a second cylindrical member, a second cut-out member, a second cylinder accommodating therein a second screw conveyor. The first cylinder is so constructed that it penetrates the main body, the first cylindrical member and the first cut-out member in an axial direction. The first screw conveyor, the second screw conveyor and the second cut-out member have a plurality of gasifying agent ports, respectively.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority of PCT Patent Application No. PCT/JP2015/085309, filed on Dec. 17, 2015 for “Biomass Gasification System,” which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a biomass gasification system for producing aqueous gasses after carbonizing of biomass.

BACKGROUND OF INVENTION

In recent years, while attention has strongly been paid to utilization of recycling or renewable energy, especially, attention has been paid to or focused on utilization of biomass energy as one of recycling or renewable energy.

There exist various forms in utilization of biomass energy. As one of such forms, such system as producing aqueous gasses from biomass, then for generating electric powers and further for providing heat has been proposed.

For producing aqueous gasses from biomass, first of all, carbonization of biomass is necessary. For example, a carbonizing furnace which comprises a cylindrical body and an inner cylindrical member accommodated therein is disclosed in, for example, Patent Document 1.

For producing aqueous gasses from the carbonized biomass, steps of thermal decomposition and gasification are necessary. For example, in Patent Document 2, there is disclosed a thermal decomposition gasification apparatus which is formed by an outer cylindrical member, an inner cylindrical member, a turn-table and heat-storage projection members.

As explained above, in the course of producing aqueous gasses from biomass, largely divided, two steps are needed, one for carbonization of biomass and second for thermal decomposition and gasification of the carbonized biomass. In the prior art, these steps have been performed separately by the above mentioned separate apparatuses.

However, since such conventional system requires two separate apparatuses, one for carbonization of biomass and the other for thermal decomposition and gasification of the carbonized biomass, there inevitably occurs large thermal loss. Further, it takes a considerable long time until the temperature of furnace for thermal decomposition and gasification is stabilized where the heat generated in the step of carbonizing biomass is utilized for the thermal decomposition and gasification. Furthermore, in the conventional system, it has been difficult to achieve evenness or uniformity of temperature distribution of thermal decomposition and gasification furnace.

Further, it has been desired to provide a technique for preventing the reaction residuals from adhering on the inners of the apparatus after the thermal decomposition and gasification of the carbonized biomass.

PRIOR ART DOCUMENTS

Patent Documents

Patent Document 1: Japanese Patent Laid-Open Publication No 2009-270050

SUMMARY OF INVENTION

Problems to be Solved by Invention

The present invention has been provided with the above matters in the prior art being taken into consideration. One object of the present invention is to provide a biomass gasification system, in which the temperature of thermal decomposition and gasification furnace can be quickly and uniformly stabilized with smaller thermal loss. Another object of the present invention is to provide a biomass gasification system in which adherence of residuals on inner parts after the thermal decomposition and gasification of carbonized biomass is effectively prevented from occurring.

Means to Solve the Problems

According to an aspect of the invention, there is provided a biomass gasification system for producing aqueous gases after biomass is carbonized, the biomass gasification system comprising: a main body of a cylindrical form; a first cylindrical member which is accommodated in said main body and which has thermal storage characteristics; a first cut-out member of a substantially disk shape, which is arranged under said first cylindrical member; a first cylinder which penetrates in an axial direction said main body, said first cylindrical member and said first cut-out member; a first screw conveyor which is coaxially arranged within said first cylinder and which has a first shaft portion and a first blade portion spirally extending on the periphery of said first shaft portion; a second cylindrical member which is arranged below said first screw conveyor and which has thermal storage characteristics; a second cut-out member of a substantially disk shape, which is disposed under said second cylindrical member; a second cylinder which communicates with said first cylinder at a side wall of said first cylinder; and a second screw conveyor which is coaxially arranged within said second cylinder and which has a second shaft portion and a second blade portion spirally extending on the periphery of said second shaft portion; said first screw conveyor having a first gasifying agent inlet at one end of said first shaft portion; a plurality of first gasifying agent ports on a periphery of said first shaft portion; and a first gasifying agent passage in said first shaft portion which communicates said first gasifying agent inlet with said first gasifying agent ports; said second screw conveyor having a second gasifying agent inlet at one end of said second shaft portion; a plurality of second gasifying agent ports on a periphery of said second shaft portion; and a second gasifying agent passage in said second shaft portion which communicates said second gasifying agent inlet with said second gasifying agent ports; and said second cylindrical member having an internal space communicating with said first gasifying agent passage and a plurality of third gasifying agent ports at its periphery.

In the biomass gasification system of the instant invention, the first gasifying agent port is disposed near the upper first blade portion among opposing upper and lower first blade portions.

In the biomass gasification system of the instant invention, an additional first gasifying agent port may be provided at an under surface of said first blade portion.

In the biomass gasification system of the instant invention, the second blade portion is a ribbon type blade.

In the biomass gasification system of the instant invention, the first blade portion may be arranged at plural portions on said first shaft portion with a predetermined space being provided therebetween.

Effects Achieved by Invention

The biomass gasification system according to the invention wherein aqueous gasses are produced after carbonization of biomass makes it possible to quickly and uniformly stabilize the temperature of he thermal decomposition and gasification furnace with smaller thermal loss. The biomass gasification system according to the invention also makes it possible to effectively prevent residuals after thermal decomposition and gasification adhering on inner parts.

EMBODIMENT OF INVENTION

Now, some preferred embodiments of the invention will be explained hereunder with reference to the accompanying drawings.

Firstly, construction for obtaining a carbide by carbonizing a organic waste will be explained.

FIG. 1is a partial-sectional diagram which shows a biomass gasification system100of the first embodiment according to the invention.FIG. 2is a perspective diagram which shows a first cylindrical member114and a first cut-out member115of the first embodiment of the invention.

The biomass gasification system includes a main body110, the first cylindrical member114and the first cut-out member115.

The main body110of the biomass gasification system100is perpendicularly supported by a supporting member180. The shape of the main body110is not limitative but a tubular shape is preferable. Tubular means here that the cross-section shape is approximately tubular.

The height or dimension of the main body110is not limitative, and is may be arbitrarily selected depending on the amount of organic wastes to be processed or the amount of carbide to be produced. Material forming the main body110is not limited to specific one within the prior art materials. For example, stainless may well be selected.

Provided to the main body110are an organic waste inlet port150for organic wastes, a first air inlet port152, a second air inlet port154, an air exhaust port141, an outlet port156and a burner (now shown in the drawings).

The organic wastes are introduced in the main body110through the organic waste inlet port150. As shown inFIG. 1, the organic waste inlet port150may be formed by a tubular member111. For the purpose of stably introducing the organic wastes into the inner chamber of the main body110, for example, a belt-conveyor may be arranged within the tubular member111.

The organic wastes (biomass) are wastes which include carbon. More specifically, the organic wastes include food wastes, construction wastes, shredder dusts, livestock wastes, sustainable harvested woods, pruned branches, paper dusts, bamboos, wood or grass wastes, sludge, rice straws, and household general or non-industrial wastes. It is desirable that water percentages of the organic wastes have been adjusted in advance by such means as a dryer for enhancing the efficiency of carbonization and yield of carbides.

Air used when the organic wastes are burned is supplied to the inner chamber of the main body110through the first air inlet port152and the second air inlet port154. The port size or shape of the first and second air inlet ports152and154are not limitative. The first air inlet port152and second air inlet port154may be constituted by a tubular member112and a tubular member113, respectively, and they are provided with fans for blowing air into the main body110.

Thermal decomposition gases (mixed gases) generated when the organic wastes are burned are exhausted outside the main body110after secondary combustion, through the air exhaust port141which is arranged near the upper end position of the main body110. Heat obtained through the secondary combustion is used as heat source for heating a first cylinder126and it is also used, for example, for generating steam after it is supplied to a superheated vapor generating device.

The organic wastes thrown in or introduced in the main body110are ignited by a burner (not shown). Such burner may be arranged at any desired position of the main body110as far as it is capable of igniting the organic wastes, and it is preferably positioned lower than the organic waste inlet port115.

The biomass gasification system100according to the present invention is provided, within the main body110, with a first cylindrical member114having heat storage characteristics. As shown inFIG. 2, the first cylindrical member114has an axis bore denoted by a reference numeral200. The first cylindrical member114functions as so called a hot-bulb when the organic wastes are carbonized in the main body110. The first cylindrical member114operates to promote carbonization of the organic wastes by applying radiant heat to the carbides therearound. The first cylindrical member114may be provided with any heating device for heating the member114itself. However, it is preferable that the first cylindrical member114is heated by the heat generated when the organic wastes are burning and the heat generated under the secondary combustion of the thermal decomposition gases.

In accordance with the rotation of the first cylindrical member114, the peripheral portion thereof is uniformly heated, thereby enhancing the efficiency of carbonization and improving the purity of carbides. The mechanism for rotating the first cylindrical member114is not limitative. For example, a shaft extending from the bottom surface of the first cylindrical member114may be rotated by prior art techniques.

Under the cylindrical member114, as shown inFIG. 2, there is integrally provided a cut-out or flange member115of a disc shape, which has the bore200. The first cut-out member115functions to receive carbides produced in the main body110in operation. The first cut-out member115is so arranged that a gap is provided between the periphery thereof and the inner surface of the main body110. In accordance with the rotation of the first cut-out member115, the carbides received thereon efficiently drops through the gap between the periphery of the first cut-out member and the inner surface of the main body110. Mass of carbides can be broken at the gap. The first cut-out member115may be integrally formed with the first cylindrical member114so that it rotates together with the cylindrical member114. The first cut-out member115may be separately formed from the first cylindrical member114. In this case, the first cut-out member115may be rotated independently.

The carbides dropped from the cut-out member115are discharged out the main body110through the outlet port156and, then, are forwarded into a second cylinder118through a throw-in inlet port161. For the purpose of effectively exhausting the carbides from the outlet port156, a scraper member (not shown) for raking the carbides may well be provided under the first cut-out member115, which rotates together with the first cut-out member115.

The inner chamber of the main body110can generally be divided into a burning area130A, a carbonizing area130B, a refining area130C and an extinguishing area130D. The burning area130A generally covers a zone between a ceiling surface of the main body110and a position of the first air inlet port152. The carbonizing area130B generally covers a zone between the position of the first air inlet port152and an upper portion of the first cylindrical member114. The refining area130C generally covers a zone between the upper portion of the first cylindrical member114and a middle position of the first cylindrical member114. The extinguishing area130D generally covers a zone between the middle position of the first cylindrical member114and a position of the bottom surface of the first cylindrical member114.

The burning area130A functions to store thereat the thermal decomposition gases (mixed gases) including hydrogen (H), carbon monoxide (CO), carbon dioxide (CO2), sulfur (S), nitrogen (N) and so on which are generated when the organic wastes burns, and the burning area130A also functions to secondarily burn the thermal decomposition gases thereat. For appropriately constituting the burning area130A in the main body110, it is desirable that the first air inlet port152be arranged at a position lower than the upper end of the main body110.

At the carbonizing area130B, the organic wastes introduced in the main body110through the organic waste inlet port150are burned with contact of the combustion gas and carbonized. As the result of the burning and carbonizing of the organic wastes here, solid content having much carbides and thermal decomposition gas are produced.

At the refining area130C, radiant heat generated from the first cylindrical member114which is heated by the heat generated when the organic wastes burn and the heat resulted from the secondary combustion of the thermal decomposition gases is applied to the carbides moving from the carbonizing area130B and, in consequence, impurities are removed from the carbides by burning of the thermal decomposition gases existing in the carbides. Further, at the refining area130C, carbonization is promoted or advanced under the condition where the carbides are kept at a high temperature while air is being supplied. For adequately forming the refining area130C in the main body110, it is desirable that the second air inlet port154be positioned between the uppermost surface and the middle portion of the first cylindrical member114.

Finally, the extinguishing area130D is a zone for extinguishing the carbides moving from the refining area130C with blocked air.

Now, the construction for producing aqueous gases by the thermal decomposition and gasification of the carbides will be explained hereunder.

FIG. 1is a partially sectioned diagram of the biomass gasification system100of the first embodiment according to the present invention.FIG. 3is a front view of a first screw conveyor122of the first embodiment of the invention andFIG. 4is a sectional view thereof.FIG. 5is a perspective view of the second cylindrical member123and the second cut-out member124of the first embodiment of the invention andFIG. 6is a sectional view thereof.FIG. 7is a sectional view of the second cylindrical member123and the second cut-out member124of the second embodiment of the present invention.FIG. 8is a front view of the second screw conveyor120of the first embodiment of the invention andFIG. 9is a sectional view thereof.

The biomass gasification system100comprises the first cylinder126, the first screw conveyor122which is rotatable within the first cylinder126, the second cylindrical member123, the second cut-out member124, the second cylinder118, and the second screw conveyor120which is rotatable within the second cylinder118.

The first cylinder126is constituted in the form of tubular and it is so arranged that it penetrates axially through the main body110, the first cylindrical member114and further the first cut-out member115. As the first cylinder126is arranged as above so as to function as the thermal decomposition and gasification furnace, the first cylinder126is heated rapidly and uniformly by the heat generated when the organic wastes burn in the main body110and the heat obtained by the secondary combustion of the thermal decomposition gases. The first cylindrical member126is heated directly with smaller amount of heat loss owing to the heat generated when the organic wastes burn in the main body110and the heat resulted from the secondary burning of the thermal combustion gases. Furthermore, as the first cylinder126is arranged as above so as to function as the thermal decomposition and gasification furnace, the first cylindrical member114functions as so-called hot-bulb when the organic wastes are burned in the main body110, the first cylindrical member114applies radiant heat to the carbides existing therearound whereby carbonization of the organic wastes is advanced. Furthermore, the first cylindrical member114heats the first cylinder126functioning as thermal decomposition and gasification furnace and it functions to heating and temperature keeping member for heating the first cylinder126and keeping its temperature.

The uppermost end of the first cylinder126is closed, while the lowermost end thereof is open with an outlet port163being provided thereat. From the outlet port163, aqueous gases and reaction residue ash contents are output, which are produced when the carbides are thermal decomposed and gasified in the first cylinder126.

The first screw conveyor (reaction stirring screw conveyor)122is axially arranged within the first cylinder126.

As clearly illustrated inFIG. 3, the first screw conveyor122comprises a first shaft portion300and a first fin or blade portion301which is spirally extending around the first shaft portion300. The carbides, which introduced in the first cylinder126through the communication port between the second cylinder118and the first cylinder126, move to the direction of the second cylindrical member123within the first cylinder126in accordance with the rotation of the first screw conveyor122. Here, as the first screw conveyor122rotates within the first cylinder126, the first blade301thereon functions to stir the carbides and the reaction residuals and, in consequence, such carbides and the reaction residuals do not adhere on the inner wall of the first cylinder126. Provided to the first shaft portion300are a plurality of first gasifying agent ports190for applying agents to the carbides while the carbides are moving in the first cylinder126. Number of the first gasifying agent ports190on the first shaft portion300is not limitative, but for the purpose of sufficiently supplying the gasifying agents to the carbides moving within the first cylinder126, it is preferable that a plurality of the first gasifying agent ports190be arranged with an appropriate space being provided between the adjacent gasifying agent ports190. The position where the first gasifying agent ports190are provided on the shaft portion300is not limitative. Carbides moves within the first cylinder126in such manner that, in accordance with the rotation of the first screw conveyor122, carbides are rubbed against the inner wall of the first cylinder126, and the carbides moves while they slide on an upper surface of the first blade301. With these moving actions of the carbides within the first cylinder122being taken into consideration, it is desirable that, as denoted with a reference numeral302inFIG. 3, the first gasifying agent port190be positioned near the upper blade portion between the two opposing upper and lower blades.

With reference toFIG. 3, the details of the position where the first gasifying agent port190on the shaft portion300will be explained. It is preferable that the first gasifying agent port190be arranged at the position near the upper first blade portion301U between the two opposing upper and lower blades301U and301L. That is, the position designated by a reference numeral302A is preferable. By positioning the first gasifying agent ports190on the shaft portion300as above, clogging in the first gasifying agent ports190by the carbides moving within the first cylinder126can be effectively prevented from occurring.

As shown inFIG. 4, the first screw conveyor122has at its uppermost end a first gasifying agent inlet400through which a gasifying agent is introduced into the first screw conveyor122. The first screw conveyor122has therein a first gasifying agent passage402. The first gasifying agent input in the first gasifying agent inlet400moves to the first gasifying agent port190through the first gasifying agent passage402. The first screw conveyor122has at its lowermost end an open outlet401. Through this open outlet401, the first gasifying agent passage402communicates with the inner of the second cylindrical member123which is arranged under the first screw conveyor122. The diameter of the first gasifying agent passage402is not limitative, and is may well be selected depending on the amount of gasifying agent supplied to the amount of carbides moving within the first cylinder126or the amount of gasifying agent needed to be forwarded to the inner of the second cylindrical member123.

The dimension (diameter) or size of the first screw conveyor122is not limitative. With the thermal expansion of various elements being taken into consideration, the dimension of the first screw conveyor122should be designed to provide a gap between the periphery of the first screw conveyor122and the inner surface of the first cylinder126. The material constituting the first screw conveyor122is not limitative. The first screw conveyor122may well be formed by, for example, SUS310S stainless steel among various prior art materials.

At the lower portion of the first screw conveyor122, there is provided the second cylindrical member (stagnation reaction cylinder)123which has thermal storage characteristics. The second cylindrical member123is of a substantially column shape and it makes the sectional area defined by the first cylinder123small here so that the carbides tend to stagnate here when they pass at the side of the second cylindrical member123. The second cylindrical member123functions as a so-called hot-bulb when carbides are subjected to thermal decomposition and gasification within the first cylinder126. The second cylindrical member123further functions to promote or advance the thermal decomposition and gasification by applying radiant heat to the carbides stagnating and existing therearound. Although the second cylindrical member123may have a heating device for heating itself, it is preferable that the second cylindrical member123be heated by the heat generated when the organic, wastes burn in the main body110and the heat obtained through the secondary combustion of the thermal decomposition gases.

The second cylindrical member123is adapted to rotate as an axis of a vertical line passing through the bottom surface and ceiling surface of the second cylindrical member123. In accordance with the rotation of the second cylindrical member123, the periphery of this second cylindrical member123is uniformly heated whereby the efficiency of thermal decomposition and gasification of the carbides is highly enhanced or improved. The second cylindrical member123may be integrally connected to the first screw conveyor122and then it may be rotated together with the first screw conveyor123. Otherwise, the second cylindrical member123may be rotated independently from the first screw conveyor122.

As shown inFIG. 5, at the upper surface of the second cylindrical member123, there is provided an opening500corresponding to the open outlet (FIG. 4) of the first screw conveyor122. In the peripheral side portion of the second cylindrical member123, there are provided a plurality of third gasifying agent ports192for supplying gasifying agents to the carbides existing therearound. Number of the third gasifying agent ports192and locations where they are arranged on the second cylindrical member123are not limitative. However, for the purpose of sufficiently supplying the gasifying agents to the carbides existing therearound, it is desirable that a plurality of ports192are provided all around the periphery of the second cylindrical member123.

As shown inFIG. 6, the second cylindrical member123has an internal space600communicating with the first gasifying agent passage402(FIG. 4) through the open outlet401(also inFIG. 4) and the opening500. The gasifying agents introduced through the first gasifying agent inlet400and then forwarded to the internal space600through the first gasifying agent passage402are supplied to the carbides existing around the second cylindrical member123, through the third gasifying agent ports192.

Under the second cylindrical member123, there is provided the second cut-out member124which is of a substantial disk shape and which is rotatable. The second cut-out member124functions to receive ash contents (reaction residuals) produced when the carbides are subjected to the thermal decomposition and gasification within the first cylinder126. The second cut-out member124is so arranged in the first cylinder126that a gap is provided between the periphery thereof and the inner surface of the first cylinder126. The rotation of the second cut-out member124makes it easy that the ash contents drop between the gap defined by the periphery of this cut-out member124and the inner surface of the first cylinder126.

The ash contents dropped down from the second cut-out member124are output outside the first cylinder126through the outlet port163. For the purpose of effectively outputting the ash contents through the output port163, for example, a scraper member (not shown) which rotates together with the second cut-out member163may well be provided under the second cut-out member163.

The second cut-out member124may be formed in a solid state as shown inFIG. 6or may be formed to have an internal space700as shown inFIG. 7. In the latter case, by communicating the internal space700with the internal space600, the amount of, the first gasifying agents introduced through the first gasifying inlet400can be increased.

Referring back toFIG. 1, the second cylinder (carbide conveying cylinder)118may be formed in a tubular shape. One end of the second cylinder118communicates with the first cylinder126near the upper end of the first cylinder126. Near the other end of the second cylinder118, there is provided the throw-in inlet port161through which the carbides output from the outlet port156are introduced into the second cylinder118.

The second screw conveyor (crusher screw conveyor)120is arranged coaxially within the second cylinder118.

As shown inFIG. 8, the second screw conveyor (crusher screw conveyor)120comprises a second shaft portion800and a second fin or blade portion801spirally extending around the second shaft portion800. In accordance with rotation of the second screw conveyor120, the carbides introduced through the inlet port161are forwarded within the second cylinder118toward the connection point between this second cylinder118and the first cylinder126. Here, as the rotation of the second screw conveyor120functions to rake the carbides and the reaction residuals by its blade portion801, the carbides and the reaction residuals are prevented from adhering on the inner surface of the second cylinder118. On the periphery of the second shaft portion800, there are provided a plurality of second gasifying agent ports191for supplying gasifying agents to the carbides moving within the second cylinder118. Again number of the second gasifying agent ports191is not limitative. For the purpose of sufficiently supplying the gasifying agents to the carbides moving in the second cylinder118, it is desirable that a plurality of ports191be arranged with an appropriate space being provided between adjacent ports191. Positions where the gasifying agent ports191on the shaft portion800are arranged are not limitative and may be selected arbitrarily with design choice.

For assisting more effective thermal decomposition and gasification of the carbides in the first cylinder126to follow, it is desirable that surface areas of the carbides be large in advance by the crushing in the second cylinder118. For this purpose, it is desirable that the second screw conveyor120forward the carbides thrown in through the throw-in inlet port161toward the connection point while the carbides being crushed by the second screw conveyor120. To this end, the second blade portion801is preferably a ribbon type screw. The second blade portion801is supported by a plurality of supporting members802. The dimension, shape and constituting material are not limitative and they may well be selected depending on the degree of crushing needed and the strength or rigidity needed.

As shown inFIG. 9, the second screw conveyor120has at its one end a second gasifying agent inlet port900for introducing gasifying agents within the second screw conveyor120. The second screw conveyor120has therein a second gasifying agent passage902for forwarding the gasifying agents introduced through the second gasifying agent inlet port900to the second gasifying agent ports191. The diameter of the second gasifying agent passage902is not limitative and it may be selected arbitrarily depending on the amount of the gasification agents supplied to the carbides moving within the second cylinder118. The other end of the second screw conveyor120may well be open with an open port901.

Now, the actual operation of the biomass gasification system100of one preferred embodiment according to the present invention will be explained.

The biomass gasification system100of the present invention operates in accordance with the following sequential steps:(1) Step for introducing organic wastes;(2) Step for burning and carbonizing the organic wastes;(3) Step for extinguishing the carbonized organic wastes;(4) Step for discharging the extinguished carbides;(5) Step for throwing-in the discharged carbides;(6) Step for crushing the thrown-in carbides;(7) Step for thermal decomposing and gasifying the crushed carbides;(8) Step for exhausting the produced aqueous gases and reaction residuals.

Hereunder, respective steps (1) through (8) will be explained.

(1) Step for Introducing Organic Wastes

Organic wastes are thrown-in in the main body110through the organic waste inlet port150by prior art techniques.

(2) Step for Burning and Carbonizing the Organic Wastes

Organic wastes introduced or thrown-in into the main body110are burned and carbonized at the carbonizing area130B. More specifically, the organic wastes are ignited by, for example, a burner and are burned with air being supplied in the main body110from the first air inlet port152. As a result of sufficient burning of the organic wastes in the main body110, there are produced solid contents having much carbides and thermal decomposition gases. The solid contents having much carbides are forwarded to the refining area130C while the thermal decomposition gases are forwarded to the burning area130A and subjected to the secondary combustion thereat. The heat obtained through the secondary combustion contributes to heat the first cylindrical member114and also contributes to heat rapidly and uniformly the first cylinder126with small heat loss. Because, in the solid contents moved to the refining area130C which have much carbides, there are thermal decomposition gases, if they are extinguished as they are, impurities involved in the carbides become great or large and yields of carbides are likely to be low. To cope with these problems, in this refining step, by applying radiant heat to the solid contents having much carbides from the first cylindrical member114while sufficient air is being supplied through the second air inlet154, burning of thermal decomposition gases existing in the solid contents having much carbides is promoted or advanced and, therefore, carbonization is efficiently promoted. In this way, the thermal decomposition gases existing in the solid contents having much carbides are efficiently removed therefrom. According to the rotation of the first cylindrical member114, the periphery of the first cylindrical member114is uniformly heated and, in consequence, carbonization is uniformly performed. In this refining step, it is preferable that temperatures around the organic waste inlet port150and the burning area130A be kept at 800° C. to 1000° C. and the temperature at the refining area130C be kept at in the order of 600° C. to 800° C. If retention time of the thermal decomposition gases in the burning area130A is longer than 2 seconds, generation of dioxin is effectively reduced.

(3) Step for Extinguishing the Carbonized Organic Wastes

The carbides resulted from sufficient carbonization of the solid contents having much carbides at the previous refining area130C then move to the extinguishing area130D. Because this extinguishing area130C is a low-oxygen atmosphere, the carbides moved to this extinguishing area130C are extinguished here.

(4) Step for Discharging the Extinguished Carbides

The carbides extinguished at the previous extinguished area130D drop down through the gap between the periphery of the first cut-out member115and the inner surface of the main body110and, then, they are discharged out main body110through the outlet port156.

(5) Step for Throwing-in the Discharged Carbides

The carbides exhausted out the main body110through the outlet port156in the previous step are then introduced in the second cylinder118though the throw-in inlet port161. Here, means for transporting the carbides from the outlet port156to the throw-in inlet port161are not limitative and, such as a packet conveyor in the prior art techniques can well be used.

(6) Step for Crushing the Thrown-in Carbides

The carbides introduced in the second cylinder118through the throw-in inlet port161are moved toward the connecting portion of the first cylinder126due to the compelling force by rotation of the second screw conveyor120. It is preferable that the thrown-in carbides be subjected to crushing action within the second screw conveyor120while they are being moved to the connecting portion within the conveyor120. Further, it is desirable that aqueous gasification reaction and water gas shift reaction, which are explained hereinafter, advance in the carbides introduced in the second cylinder118while the carbides are being moved to the connecting portion. Here, as the second cylinder118is communicated with the first cylinder126, the inner space of the second cylinder118is kept at a high temperature as is in the same the first cylinder126. Vapor as a gasifying agent is introduced in the second screw conveyor120through a second gasifying agent inlet900, then moves in a second gasifying agent passage902, then jets out through a plurality of second gasifying ports191, whereby the gasifying agent is supplied to the carbides moving within the second cylinder118.

(7) Step for Thermal Decomposing and Gasifying the Crushed Carbides

The carbides reached the inner space of the first cylinder126due to the rotation of the second screw conveyor120moves within the first cylinder126toward the second cylindrical member123due to the ration of the first screw conveyor122and, during this movement, water gas reaction (C+H2O→CO+H2−28.36 kcal/mol) and water gas shift reaction (CO+H2O→CO2+H2+9.85 kcal/mol) continuously progress or advance. At this time, as the carbides move due to rotation of the first screw conveyor122while they are being rubbed against the inner wall of the first cylinder126, the carbides are directly heated by the first cylinder126and thus the thermal decomposition and gasification of the carbides are promoted. Here, the first cylinder126is heated by the heat generated when the organic wastes burn within the main body110and the heat obtained by the secondary combustion of the thermal decomposition gases. As the carbides move on an upper surface of a first blade portion301as if they slide thereon in accordance with the rotation of the first screw conveyor122, the carbides are directly heated by the first blade portion301whereby the thermal decomposition and gasification thereof are effectively promoted or advanced. Here, the first blade portion301is also heated by the heat generated when the organic wastes burn within the main body110, the heat obtained by the secondary combustion of the thermal decomposition gases and further the radiant heat generated from the first cylinder126. Vapor as a gasifying agent is introduced within the first screw conveyor122through a first gasifying agent inlet400, then moves in a first gasifying agent passage402, and finally is jetted out through a plurality of first gasifying agent ports190, whereby vapor is supplied to the carbides moving within the first cylinder126. As a result, thermal decomposition gases (water or aqueous gases) which include as contents hydrogen (H), carbon monoxide (CO and carbon dioxide (CO2) are produced. Generally, at low temperatures (750° C. to 800° C.), as water gas shift reaction of exothermic reaction is promoted and hydrogen of low calorie is produced while carbon monoxide of high calorie is consumed, thermal decomposition gases of rich in hydrogen and of lower calorific values per unit volume are produced. To the contrary, in general, at high temperatures (900° C. to 950° C.), thermal decomposition gases of rich in carbon monoxide are produced. Furthermore, the ratio of H2/CO in the thermal decomposition gases becomes higher in proportion to increase of amount of the supply of vapor as the gasifying agent. Thermal decomposition and gasification of the carbides reached near the second cylindrical member123is further advanced by radiant heat generated by the second cylindrical member123and vapor jetted out through a plurality of third gasifying agent ports192. Due to the rotation of the second cylindrical member123, the periphery of this second cylindrical member123is uniformly or evenly heated, whereby the necessary thermal decomposition and gasification action is enhanced.

(8) Step for Exhausting the Produced Aqueous Gases and Reaction Residuals

The water or aqueous gases produced by the thermal decomposition and gasification of the carbides within the first cylinder126are derived from the outlet port163. Ash contents (reaction residuals) generated after the thermal decomposition and gasification of the carbide within the first cylinder126drop down the gap defined by the periphery of the second cut-out member124and the inner surface of the first cylinder126and they are exhausted out the first cylinder126through the same outlet port163. The resulted aqueous gases of gas and the reaction residuals of solid may well be separated by, for example, a cyclone.

Finally, with reference toFIG. 10, the first screw conveyor122of another embodiment according to the present invention will be explained hereunder.

FIG. 10is a front view of the first screw conveyor122of another embodiment of the instant invention. As shown therein, a plurality of first blade portions301are arranged at plural positions on the first shaft portion300axially scattered thereon. By so arranging the first blade portions301on the common shaft portion300, the carbides move more quickly at the areas where the first blade portions are not provided. For this reason, time of movement of the carbides within the first cylinder126, that is, time of thermal decomposition and gasification of the carbides therein can be adequately adjusted. At the positions where the first blade portions301are disposed, the carbides are subjected to the thermal decomposition and gasification while they are being rubbed against the inner wall of the first cylinder126. If a plurality of first screw conveyors122in which the positions of the blade portions are different from one another and they are periodically exchanged, specific concentration on the inner surface of the first cylinder126where the rubbing action of the carbides against the inner wall of the first cylinder126occurs during thermal decomposition and gasification is prevented from occurring, thereby making it possible to achieve the long life of the first cylinder126.

It should be noted that, although the preferred embodiments of the present invention have been explained hereinabove with reference to the appended drawings, various modifications and changes can be made without departing from the spirit and scope of the invention.

For example, the first gasifying agent port190may well be provided under (on rear side of) the first blade portion301. Because the carbide move within the first cylinder126in such manner that they move while they are being rubbed against the inner wall of the first cylinder126and slide on the upper surface of the first blade portion301, provision of the first gasifying agent ports190on the lower surface (rear side) of the first blade portion301makes it possible to effectively prevent clogging of carbides in the first gasifying agent ports190from occurring.