JP2011026489A - Pyrolysis furnace in circulating fluidized bed gasification system and temperature control system of gasification furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gasification reacting furnace reducing the amount used of expensive porous fine particles and controlling temperatures of a fuel pyrolysis furnace and a gasification furnace with a convenient method. <P>SOLUTION: The circulating fluidized bed gasification reaction furnace, in which raw material is gasified in the fluidized bed gasification furnace, produced char and a fluidizing medium are introduced into a fluidized bed combustion furnace of a subsequent step to combust an uncombusted content and the reheated fluidized medium is circulated in the reaction furnace, includes a pyrolysis furnace having a tar absorption furnace and the fuel pyrolysis furnace on the upper and lower sides respectively on the precedent step of the fluidized bed gasification furnace, wherein a fluidizing medium containing uncombusted char taken out of the fuel pyrolysis furnace of the lower stage and a fluidizing medium, to which the tar is adsorbed, taken out of the tar absorption furnace of the upper stage are circulated respectively independently and, further, at least one side of respective fluidizing media which are separated from a cyclone of the subsequent step of the fluidized bed combustion furnace and have higher temperatures, is distributed and supplied to the pyrolysis furnace and the fluidizing bed gasification furnace so as to control the temperatures of the pyrolysis furnace and the fluidized bed gasification furnace. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a gasification reactor for extracting combustible gas from fuel, and more particularly to a thermal decomposition furnace and a temperature control system for a gasification furnace in a circulating fluidized bed gasification reactor.

Conventionally, a gasification system has been developed that uses solid fuels of hydrocarbon resources such as coal, biomass, garbage, sewage sludge, etc., and uses the generated gas as a combustible gas and heat source to effectively use organic resources. Has been.
As one of the gasification systems, the reaction furnace is separated into a fluidized bed gasification furnace and a fluidized bed combustion furnace, a solid fuel of hydrocarbon resources is supplied to the fluidized bed gasification furnace, gasified with steam, and generated There is known one using a circulating fluidized bed in which the unburned portion (char) and the fluidized medium are burned in a fluidized bed combustion furnace and the heated fluidized medium is returned to the gasification furnace (Patent Document 1).
The gasification reaction furnace is an external circulation system, but there is an internal circulation system such as the reaction furnace described in Patent Document 2, in which particulate slag is used as a fluid medium. As a result, the tar contained in the gas generated in the gasification furnace is reformed to generate a combustible gas with a small amount of tar, and the deteriorated slag is introduced into the combustion furnace together with unburned char and reactivated. , Returned to the gasifier.
In the circulating fluidized bed gasification system having these fluidized bed gasification furnace and fluidized bed combustion furnace, the gasification gas and the combustion gas can be separately taken out from the respective furnaces, and the high calorie does not contain an inert gas. Gas can be produced.

Furthermore, various proposals have been made for the circulating fluidized bed gasification furnace of the gasification system.
For example, in Patent Document 3, a circulating fluidized bed gasification furnace is introduced by introducing a chamber in which organic raw materials are supplied and generating pyrolysis gas containing tar by a pyrolysis reaction, and a pyrolysis residue generated by the pyrolysis reaction. There has been proposed a gasification apparatus that enhances the production of high-quality gasification gas by dividing it into a chamber for generating gasification gas.
Further, Patent Document 4 is based on the proposal of the present inventors, but by providing an alkali absorption furnace independently in the preceding stage of the fluidized bed gasification furnace, tar is adsorbed on the char in the alkali absorption furnace. The gasification efficiency of char can be improved, and the effect of inhibiting the gasification of char can be avoided.
Further, Patent Document 5 proposes a gasification apparatus in which a fluidized bed gasification furnace is constituted by a plurality of gasification apparatuses, and the generated gas is taken out separately.

JP 2005-41959 A JP 2005-68297 A JP 2008-156552 A JP 2008-303377 A JP 2009-40887 A Japanese Patent Application No. 2009-37625

The present inventors further examined the gasification method and apparatus using the circulating fluidized bed gasification reactor, and when a tar adsorbing substance such as alumina, limestone, or zeolite was added as a fluid medium, the tar was Although there is an advantage that it can be adsorbed efficiently, in particular, when porous particles such as porous alumina are used as the tar adsorbing substance, although tar can be adsorbed more efficiently, it is more than the conventional sand used as a fluid medium. However, it is necessary to reduce the amount of use as much as possible.
Further, since porous particles and ash particles coexist in the furnace, the porous particles are also extracted together when the ash is extracted from the lower part of the furnace at regular intervals.
Furthermore, it is necessary to reduce the cost (reforming furnace, scrubber, etc.) required for tar treatment at the latter stage of the furnace.

As a result of intensive studies to achieve the above-mentioned problems, the present inventors have provided a fuel pyrolysis furnace having a two-stage furnace structure with a tar absorption furnace in the upper stage in the front stage of the gasification furnace and a lower stage fuel. Obtained the knowledge that the fluid medium containing unburned char taken out from the pyrolysis furnace and the fluid medium adsorbed with the tar taken out from the upper tar absorption furnace can be solved by independently circulating the patent. An application has been filed (Patent Document 6).
Patent Document 3 describes that the fluid medium returned from the combustion furnace is distributed to both the preceding pyrolysis chamber and the gasification chamber, and Patent Document 5 describes a plurality of gases. In the apparatus in which the gasifiers are connected in multiple stages in the vertical direction, it is described that the fluidized medium is distributed to each gasifier, both of which are a fluid medium containing unburned char and a fluid medium in which tar is adsorbed Are not circulated independently.

By the way, the thermal decomposition of the fuel is sufficiently possible even at a low temperature of, for example, about 600 ° C. However, the gasification rate of char becomes higher at higher temperatures, for example, 700 ° C. and 800 ° C. The more the amount of combustible gas obtained from the char particles in the same residence time in the gasification furnace is increased. However, for this purpose, it is necessary to raise the temperature of the gasification furnace as compared with the pyrolysis furnace. For example, a method of producing high-temperature steam at 800 ° C. and supplying it to the gasification furnace can be considered, but the production cost is low. As a result, system efficiency is reduced.
Further, since the pyrolysis and gasification reactions are endothermic reactions, there is also a problem that the particle temperature of the fluidized medium decreases in the furnace.

  However, in the earlier patent application, although the tar generated from the lower stage of the pyrolysis furnace is adsorbed to the tar adsorbing substance and combustible gas is produced in the gasification furnace, there is an advantage that the total amount of generated gas is higher. In the same manner as described in Patent Document 3, the high temperature particles separated by the cyclones at the respective combustion furnace outlets are sent to the respective pyrolysis furnaces. Was found to require further improvement.

  The present invention solves such problems in the prior art, reduces the usage amount of expensive tar-adsorbing substances without mixing with ash particles as much as possible, and further uses a simple method to An object of the present invention is to provide a gasification system capable of controlling the temperatures of the respective furnaces above and below the gasification furnace.

  As a result of intensive studies to achieve the above object, the inventors of the present invention have been separated from the cyclone provided in the subsequent stage of each combustion furnace in the circulating fluidized bed gasification reactor of the previous patent application and brought to a high temperature. It was found that the temperature of the pyrolysis furnace and the gasification furnace can be controlled by distributing the fluidized medium to each of the pyrolysis furnace and the gasification furnace.

The present invention has been completed based on these findings, and according to the present invention, the following inventions are provided.
[1] The raw material is gasified in the fluidized bed gasification furnace into which the fluidized medium is introduced, and the char and fluidized medium generated during the gasification are introduced into the subsequent fluidized bed combustion furnace to burn the unburned portion. A circulating fluidized bed gasification reactor configured to circulate the reheated fluid medium in the reactor,
In front of the fluidized bed gasification furnace, a two-stage furnace pyrolysis furnace equipped with a tar absorption furnace and a fuel pyrolysis furnace is provided, and contains unburned char taken out from the lower fuel pyrolysis furnace. Circulating the fluid medium and the fluid medium adsorbed with the tar taken out from the upper tar absorption furnace are independently circulated,
Furthermore, by distributing and supplying at least one of each of the fluidized media separated from a cyclone provided at the latter stage of the fluidized bed combustion furnace to the pyrolysis furnace and the fluidized bed gasification furnace. A circulating fluidized bed gasification system characterized by controlling the temperatures of a pyrolysis furnace and a fluidized bed gasification furnace.
[2] The circulating fluidized-bed gasification system according to [1], wherein a downcomer provided at the lower stage of the cyclone is bifurcated as the means for distributing and supplying.
[3] The circulating fluidized bed gas according to the above [2], wherein the amount of the high-temperature fluidized medium introduced into each furnace is varied by making a difference in the cross-sectional area of the downcomer after the branching. System.
[4] The circulating fluidized bed gasification system according to [2] or [3], wherein a cross-sectional area of the downcomer after branching is variable.
[5] The circulating fluidized-bed gasification system according to any one of [1] to [4], wherein the branched downcomer is connected to the furnace at an upper part or a side of the furnace, and the material is sealed.
[6] The circulating fluidized bed gasification system according to the above [1] to [5], wherein the downcomer on the fluidized bed gasification furnace side is connected to the communication path between the pyrolysis furnace and the gasification furnace and material sealing is performed.
[7] The circulating fluidized bed gasification system according to any one of [1] to [6], wherein a heat exchanger is installed below the downcomer on the fuel pyrolysis furnace side.
[8] The circulating fluidized bed gasification system according to any one of [1] to [7], wherein a multicyclone or a multistage cyclone is used as the temperature control means, and the introduction amount of the high-temperature fluidized medium into each furnace is controlled.
[9] The above-mentioned upper tar absorption furnace uses a tar adsorbing substance as a fluid medium, and adsorbs the tar generated in the lower fuel pyrolysis furnace to the fluid medium. The circulating fluidized bed gasification system of [1] to [8].
[10] The circulating fluidized bed gasification system according to any one of [1] to [9] above, wherein the lower fuel pyrolysis furnace uses dredged sand as a fluidized medium.
[11] Pyrolysis gas generated by pyrolysis of volatile matter and tar reforming in the fuel pyrolysis furnace, gasification gas generated by char and / or coke gasification in the fluidized bed gasification furnace, and The circulating fluidized bed gasification system according to any one of the above [1] to [10], comprising means for independently taking out combustion gases generated by combustion of char residue and / or coke residue in a fluidized bed combustion furnace .
[12] The circulating fluidized bed gasification system according to any one of [1] to [11], wherein the fuel pyrolysis furnace has an alkali absorption function.

According to the present invention, the fluidized bed gasification furnace is heated to a high temperature by distributing and supplying at least one of the high temperature fluidized media from the char residue combustion furnace and the coke residue combustion furnace to the pyrolysis furnace and the fluidized bed gasification furnace. In particular, by increasing the amount of the high-temperature fluidized medium sent to the fluidized bed gasifier side more than the amount sent to the pyrolysis furnace, the fluidized bed gasifier temperature is higher than the temperature of the pyrolysis furnace. Can be easily increased.
Further, in the present invention, by making the cross-sectional area of the downcomer variable or adopting a multi-cyclone or multi-stage cyclone, even when conditions such as fuel and furnace temperature are different, the high-temperature fluidized medium to be put in each furnace The amount can be adjusted easily and can be adjusted to the optimum reaction temperature for each furnace.

The figure which shows typically 1st Embodiment of the gasification apparatus of this invention. Cold gas when the pyrolysis furnace and gasification furnace temperatures (each two-stage furnace) are gasified under the same conditions and when the gasification furnace temperature is higher than the pyrolysis temperature (the upper and lower temperatures are the same) The figure which shows the result of having compared efficiency. The figure which shows typically another embodiment of the gasification apparatus of this invention. The figure which shows typically another embodiment of the gasification apparatus of this invention. The figure which shows typically another embodiment of the gasification apparatus of this invention. The figure which shows typically another embodiment of the gasification apparatus of this invention. The figure which shows typically another embodiment of the gasification apparatus of this invention.

Embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to these embodiments.
FIG. 1 is a diagram schematically showing a first embodiment of a circulating fluidized bed gasification reactor according to the present invention, comprising a pyrolysis furnace having a two-stage furnace structure having a tar absorption furnace in the upper stage, A char gasification furnace and a char residue combustion furnace are connected to the lower stage of the fuel pyrolysis furnace in this order as independent types, respectively, and a coke gasification furnace and a coke residue combustion are connected to the rear stage of the upper tar absorption furnace. The furnaces are connected in this order as independent types.
Further, a cyclone is provided at the rear stage of the char residue combustion furnace, and the downcomer (shown by a dotted line) at the lower stage is bifurcated. The high temperature fluid medium from the char residue combustion furnace is supplied to the fuel pyrolysis furnace and the char gas. It can be distributed and supplied to the reactor.
Similarly, a cyclone is also provided at the rear stage of the coke residue combustion furnace, and the downcomer (shown by a dotted line) at the lower stage is bifurcated. In addition, each can be distributed and supplied.
In the present invention, the fuel pyrolysis furnace is a furnace having an alkali absorption function as described in Patent Document 3, and the gasification catalyst is prepared by actively adsorbing the alkali in the volatile gas to the char. Needless to say, the gasification efficiency of char can be improved.

Porous particles such as porous alumina are preferably used in order to efficiently absorb tar generated from the raw material, but have the disadvantage of being expensive.
In the circulating fluidized bed gasification reactor according to the present invention, a fuel pyrolysis furnace having a two-stage furnace structure in which a tar absorption furnace is provided in the upper stage is provided upstream of the fluidized bed gasification furnace. A fluid medium with good tar adsorption efficiency such as porous particles is used, and the fluid medium introduced into the lower fuel pyrolysis furnace is mainly composed of inexpensive dredged sand that is generally used. By using a thing, it becomes possible to minimize the usage-amount of an expensive fluidized medium.
In addition, since the char residue combustion furnace and the coke residue combustion furnace are separated, fluid media such as porous fine particles circulating in the upper tar absorption furnace should not be mixed with the ash particles generated in the char residue combustion furnace. it can.

Hereinafter, the gasification of the raw material will be described using an example in which porous particles such as porous alumina are used for the fluid medium of the upper tar absorption furnace and dredged sand is used for the fluid medium of the lower fuel cracking furnace. I will explain it.
A hydrocarbon-based solid fuel such as biomass, garbage, sewage sludge, and coal is supplied to the lower fuel pyrolysis furnace, and CO ₂ gas in which a part of the generated combustion gas is circulated from the lower part, or An inert gas such as N ₂ or Ar is introduced as a flowing gas, and the hydrocarbon solid fuel supplied to the fuel cracking furnace is pyrolyzed.
The tar generated simultaneously with the generated pyrolysis gas flows to the upper tar absorption furnace. The tar is adsorbed by the porous particles in the tar absorption furnace, and a part thereof is reformed to gas. The pyrolysis gas containing no tar can be taken out from the pyrolysis gas take-out means provided at the top.

The extracted pyrolysis gas is a kind of combustible gas, and is used for power generation by a fuel cell or a gas engine, liquid fuel, and the like.
In the present invention, the raw material for gasification is not limited to the hydrocarbon-based solid fuel as described above, and a liquid fuel that easily generates tar can also be used.
In the lower fuel pyrolysis furnace, the pyrolyzed char and cinnabar are sent to the next char gasification furnace.
On the other hand, the porous particles adsorbing the upper tar are sent to the upper coke gasification furnace.

The char gasification furnace and the coke gasification furnace are in a two-stage fluidized bed having the respective furnaces in the lower stage and the upper stage, and the char and coke introduced into each furnace are combined with the gasifying agent introduced from the lower part. It is gasified by the gasification reaction. As the gasifying agent, water vapor, oxygen, air, or the like is used. The gasification gas produced by reacting with the gasifying agent is taken out from the upper part of the coke gasification furnace.
The extracted gasification gas is a combustible gas, and is used for power generation by a fuel cell or a gas engine, liquid fuel, or the like.

The apparatus shown in FIG. 1 is configured to be a two-stage gasification furnace in which a char gasification furnace and a coke gasification furnace are provided in the lower stage and the upper stage, respectively, and the generated gasification gas is taken out from the upper stage coke gasification furnace. However, these gasification furnaces are respectively separate gasification furnaces, the gasifying agent is introduced from the lower part of each gasification furnace, and the generated gasification gas is taken out at the upper part. It can also be configured to be taken out from.
Further, in the apparatus shown in FIG. 1, the pyrolysis gas taken out from the upper part of the tar absorption furnace and the gasification gas taken out from the upper part of the coke gasification furnace are taken out separately, but the pyrolysis gas and the gasification gas are taken out. They may be used after being merged after each furnace outlet, and when used as a heat source, a heat exchanger can be attached before or after the merge.
The residue char in the char gasification furnace and the residue coke in the coke gasification furnace are respectively introduced into the next residue char combustion furnace and residue coke combustion furnace, which are separately provided.

Both the residue char combustion furnace and the residue coke combustion furnace are fluidized beds, and ensure a residence time during which the residue char and residue coke can be completely combusted. In each combustion furnace, the introduced residue char and residue coke are burned together with air or oxygen introduced from the lower part of each combustion furnace, and the combustion gas is extracted from the extraction means provided in the upper part of each furnace by a cyclone. It is taken out.
The combustion gas taken out from each combustion furnace is mainly used as a heat source, and as described above, a part of the combustion gas can be recycled to the fuel pyrolysis furnace. It can also be used as a preheating source for air or steam introduced into the gasification furnace or each combustion furnace.

Note that the char concentration is closely related to the reaction (especially shift reaction) occurring in the gasification furnace, and if the heat balance is within the range, a part of the unburned char is recirculated, By controlling the char concentration in the gasification furnace to a concentration suitable for the reaction, for example, the H ₂ / CO ratio at the time of gasification can be controlled, and the use for liquid fuel is advantageous.
Furthermore, if the heat balance cannot be established with only the combustion heat obtained from the residue char and residue coke, the heat balance is maintained by supplying a predetermined amount of pyrolysis gas and gasification gas to each combustion furnace and burning them. It is also possible to do.

On the other hand, the cinnabar sand, which has been reheated in the char residue combustion furnace and heated to a high temperature, is returned to the fuel pyrolysis furnace and the char gasification furnace again from the downcomer branched into two branches under the cyclone.
Similarly, the porous particles which are reheated in the coke residue combustion furnace and become high temperature are returned to the tar absorption furnace and the coke gasification furnace from the downcomer branched into two branches at the lower part of the cyclone.
In addition, as shown in FIG. 1, for example, heat exchangers are respectively attached to the downcomer on the upper tar absorption furnace side and the downcomer on the lower fuel pyrolysis furnace side to lower the temperature of the fluidized medium to a predetermined temperature. Thus, steam and air can be preheated using the extracted heat.

  A fuel pyrolysis furnace and a char gasification furnace, a char gasification furnace and a residue char combustion furnace, a tar absorption furnace and a coke gasification furnace, or a communication path connecting each of the coke gasification furnace and the residue coke combustion furnace is a loop seal, L-shaped Any type of material can be used as long as it can seal materials such as a valve and a moving layer.

  As described above, in the gasification reactor shown in FIG. 1, the flow of the fluid medium made of cinnabar and the solid fuel is as follows: fuel pyrolysis furnace → communication passage → char gasification furnace → communication passage → char residue combustion furnace → cyclone → down Comer → fuel pyrolysis furnace and char gasification furnace, while the flow of fluid medium consisting of porous particles is tar absorption furnace → communication path → coke gasification furnace → communication path → coke residue combustion furnace → cyclone → downcomer → tar It becomes an absorption furnace and a coke gasification furnace.

According to the apparatus shown in FIG. 1, since the pyrolysis furnace has a two-stage furnace structure having a tar absorption furnace in the upper stage and a fuel pyrolysis furnace in the lower stage, the tar adsorption efficiency of expensive porous particles and the like is good. By supplying a simple fluid medium such as porous alumina only to the upper tar absorption furnace, there is an advantage that the amount of use can be minimized.
In addition, the fluidized medium is separately circulated in a system consisting of a lower fuel pyrolysis furnace, a char gasification furnace and a residue char combustion furnace, and a system consisting of a tar absorption furnace, a coke gasification furnace and a residue coke combustion furnace. Therefore, porous particles and ash particles can be prevented from being mixed.
Furthermore, the dredged sand and porous particles that have been reheated in each combustion furnace and heated to high temperatures are separated from the downcomers that are bifurcated into the lower part of the cyclone, and the upper and lower pyrolysis furnaces (fuel pyrolysis furnace and tar absorption furnace). In addition to being supplied to upper and lower fluidized bed gas furnaces (char gasification furnace and coke gasification furnace), the fluidized bed gasification furnace can be easily heated to a high temperature.

In particular, the amount of high-temperature particles sent to the gasification furnace is increased by making the downcomer at the lower part of the cyclone downstream of each combustion furnace into two and making the cross-sectional area of the gasification furnace larger than that of the pyrolysis furnace. Therefore, the temperature of the fluidized bed gasification furnace can be made higher than the temperature of the pyrolysis furnace. By this method, it is possible to control the optimum reaction temperature in each furnace including the upper and lower sides.
In addition, the size of the cross-sectional area of each downcomer can be easily adjusted with a valve, etc., so even when conditions such as fuel and furnace temperature are different, the amount of high-temperature fluid medium to be placed in each furnace can be easily adjusted. it can.
Furthermore, other methods for controlling the amount of high-temperature particles include multicyclones and multistage cyclones.

In the fluidized bed basic experiment, when the pyrolysis furnace and gasifier temperature (each two-stage furnace) are gasified under the same conditions and when the gasifier temperature is higher than the pyrolysis temperature (the upper and lower temperatures are respectively The result of comparing the cold gas efficiency with the same) is shown in FIG.
Although this condition is only an example, the cold gas efficiency is significantly improved when the gasifier temperature is increased. In addition, since the amount of H ₂ and CO produced increases, it can be said that it is a more effective method when, for example, liquid fuel such as DME or methanol is produced from the produced combustible gas.

FIGS. 3 to 5 are diagrams schematically showing another embodiment of the gasification reactor according to the present invention, and the apparatus shown in FIG. 3 is connected to a downcomer to a coke gasification furnace and a char gasification furnace. Are provided in the communication path between the fuel pyrolysis furnace and the fluidized bed gasification furnace, and a downcomer connection to the tar absorption furnace is provided in the upper part of the furnace.
There is something.
The apparatus shown in FIG. 4 has a downcomer connection to the coke gasification furnace provided in the upper part of the furnace.
Further, the apparatus shown in FIG. 5 is provided with a downcomer connection to the coke gasification furnace and the char gasification furnace in the communication passages of the fuel pyrolysis furnace and the fluidized bed gasification furnace, respectively.
Without being limited to these examples, in the circulating fluidized bed gasification system of the present invention, the downcomer connection part is made of a material seal such as the upper and side surfaces of the furnace, the communication path between the pyrolysis furnace and the gasification furnace, and the gas flows. Various changes are possible without backflow.
The communication path may be any type as long as material seal such as a loop seal, an L-shaped valve, and a moving layer can be sealed.

6 and 7 are diagrams schematically showing still another embodiment of the gasification reactor of the present invention, in which the apparatus shown in FIG. The apparatus shown in FIG. 7 distributes and supplies the high-temperature fluid medium from the coke residue fuel furnace to the tar absorption furnace and the coke gasification furnace. It is what you do.
As shown in FIGS. 6 and 7, the circulating fluidized bed gasification system of the present invention can branch only one of the downcomers into two branches depending on the gas generation amount condition.
Further, FIGS. 1 and 3 to 7 are all conceptual views of the apparatus, and each furnace is not only a completely separated type as shown in the figure, but also a part or all of these furnaces are integrated. It is also possible to do.

  The circulating fluidized bed gasification system of the present invention is applied to use of unused hydrocarbon resources such as biomass, garbage, sewage sludge, for example, hybrid gasification (cogasification) with coal or biomass, or It can also be applied to hybrid gasification of solid fuel and liquid fuel.

Claims (12)

The raw material is gasified in the fluidized bed gasification furnace into which the fluidized medium is introduced, and the char and fluidized medium generated during the gasification are introduced into the subsequent fluidized bed combustion furnace to burn the unburned components and reheat. A circulating fluidized bed gasification reactor configured such that the fluidized medium circulated in the reactor,
In front of the fluidized bed gasification furnace, a two-stage furnace pyrolysis furnace equipped with a tar absorption furnace and a fuel pyrolysis furnace is provided, and contains unburned char taken out from the lower fuel pyrolysis furnace. Circulating the fluid medium and the fluid medium adsorbed with the tar taken out from the upper tar absorption furnace are independently circulated.
Furthermore, by distributing and supplying at least one of each of the fluidized media separated from a cyclone provided at the latter stage of the fluidized bed combustion furnace to the pyrolysis furnace and the fluidized bed gasification furnace. A circulating fluidized bed gasification system characterized by controlling the temperatures of a pyrolysis furnace and a fluidized bed gasification furnace.   The circulating fluidized bed gasification system according to claim 1, wherein a downcomer provided at a lower stage of the cyclone is bifurcated as the distribution and supply means.   The circulating fluidized bed gasification system according to claim 2, wherein the amount of the high-temperature fluidized medium introduced into each furnace is varied by making a difference in the cross-sectional area of the downcomer after the branching.   The circulating fluidized bed gasification system according to claim 2 or 3, wherein the cross-sectional area of the branched downcomer is variable.   The circulating fluidized bed gasification system according to any one of claims 1 to 4, wherein a connecting portion of the branched downcomer to the furnace is formed on the top or side of the furnace and material sealed. .   The circulating fluidized bed gasification system according to any one of claims 1 to 5, wherein a downcomer on the fluidized bed gasification furnace side is connected to a communication path between the pyrolysis furnace and the gasification furnace and material sealing is performed. .   The circulating fluidized bed gasification system according to any one of claims 1 to 6, wherein a heat exchanger is installed in a lower part of the downcomer on the fuel pyrolysis furnace side.   The circulating fluidized bed gasification system according to any one of claims 1 to 7, wherein a multi-cyclone or a multi-stage cyclone is used as the temperature control means, and an introduction amount of the high-temperature fluidized medium into each furnace is controlled. .   The upper tar absorption furnace uses a tar adsorbing substance as a fluid medium, and adsorbs the tar generated in the lower fuel pyrolysis furnace to the fluid medium. The circulating fluidized bed gasification system according to claim 8.   The circulating fluidized bed gasification system according to any one of claims 1 to 9, wherein the lower fuel pyrolysis furnace uses dredged sand as a fluidized medium.   Pyrolysis gas produced by pyrolysis of volatile matter and tar reforming in the fuel pyrolysis furnace, gasification gas produced by gasification of char and / or coke in the fluidized bed gasification furnace, and fluidized bed combustion The circulating fluidized bed gasification according to any one of claims 1 to 10, further comprising means for independently taking out combustion gases generated by combustion of char residue and / or coke residue in a furnace. system. The circulating fluidized bed gasification system according to any one of claims 1 to 11, wherein the fuel pyrolysis furnace has an alkali absorption function.

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