WO2005033250A2

WO2005033250A2 - Gasification method and apparatus

Info

Publication number: WO2005033250A2
Application number: PCT/JP2004/014881
Authority: WO
Inventors: Norihisa Miyoshi; Seiichiro Toyoda; Yuki Iwadate
Original assignee: Ebara Corporation
Priority date: 2003-10-02
Filing date: 2004-10-01
Publication date: 2005-04-14
Also published as: JP2007507555A; JP4589311B2; WO2005033250A3

Abstract

A gasification method is used for gasifying a raw material such as biomass to produce a combustible gas at high efficiency and low cost. In the gasification method, a raw material is pretreated in a pretreating process, and the pretreated raw material is gasified in a gasification chamber to produce a combustible gas and residue. The pyrolysis residue produced in the gasification chamber (4-1) is combusted in a combustion chamber (4-2) to generate a combustion gas (107), and the generated combustion gas is supplied to the pretreating process to separate part of a volatile component from the raw material.

Description

DESCRIPTION GASIFICATION METHOD AND APPARATUS

Technical Field The present invention relates to a gasification method and apparatus for gasifying a raw material such as biomass to produce a combustible gas at high efficiency and low cost.

Background Art There has been a demand for producing a combustible gas having a high utility value by gasifying a raw material such as biomass at high efficiency and low cost . Further, in order to recover energy from a material having a low heating value such as biomass at high efficiency, it is important to increase a heating value of the material by lowering a water content of the material through a drying process of the material having a low heating value. A raw material drying apparatus used in the drying process requires a large quantity of heat, and conventionally, such drying apparatus in which a fossil fuel such as heavy oil or kerosene is combusted and water contained in the material having a low heating value is evaporated by heat of combustion is most popular. The process for drying a material having a low heating value by combusting a fossil fuel requires high operating cost, and causes a problem of global warming or the like owing to discharge of carbon dioxide (C0₂) generated by combustion of the fossil fuel such as heavy oil or kerosene.

Disclosure of Invention The present invention has been made in view of the above problems. It is therefore an object of the present invention to provide a gasification method and apparatus for producing a combustible gas from a material such as biomass at high efficiency and low cost. In order to achieve the above object, according to a first aspect of the present invention, there is provided a gasification method comprising the steps of: pretreating a raw material; gasifying the pretreated raw material in a gasification chamber to produce a combustible gas and residue; combusting the residue in a combustion chamber to generate a combustion gas; and supplying the combustion gas to the pretreating step to separate part of a volatile component from the raw material. Since the raw material such as biomass is supplied to the gasification step after being pretreated, and the raw material whose heating value has been increased is gasified, a combustible gas (generated gas) can be obtained at high efficiency. Further, after harmful volatile elements are removed from the raw material by pretreatment of the raw material, the raw material is delivered to the gasification step, and hence a product gas (combustible gas) is prevented from being mixed with harmful substances. For example, the harmful substances removed by the pretreatment step include arsenic. In a preferred aspect of the present invention,- the- gasification method further comprises cooling a gaseous material discharged from the pretreating step to recover an arsenic compound and/or a pyroligneous acid component. In order to achieve the above object, according to a second aspect of the present invention, there is provided a gasification method comprising: drying a raw material in a drying apparatus; gasifying the dried raw material in a gasification chamber to produce a combustible gas and residue; combusting the residue in a combustion chamber to generate a combustion gas; and supplying the combustion gas to the drying apparatus to dry the raw material. By supplying the raw material having a low heating value which has been dried in the raw material drying apparatus to the gasification chamber, water contained in the raw material having a low heating value is evaporated, and most of hydrogen component becomes a generated gas as volatile component and is discharged from the gasification chamber. Therefore, the combustion gas discharged from the combustion chamber has a drying capability equivalent to a drying gas which is obtained by diluting a gas generated by combustion of higher hydrogen-containing fuel with a large amount of air. Thus, a raw material having a low heating value such as biomass, municipal solid waste or organic sludge can be efficiently dried because the combustion gas serving as the drying gas discharged from the combustion chamber is supplied to the raw material drying apparatus. Further, in the case where the raw material having a high water content is gasified in a gasification furnace, even if a fluidized-bed gasification furnace having a combustion chamber which is thermally efficient in producing a combustible gas (e.g. an internally circulating fluidized-bed gasification furnace) , cold gas efficiency is lowered. Specifically, ■ the ratio of the raw material- combusted increases, and the amount of the combustion gas from unit raw material discharged from the combustion chamber increases, thus increasing a drying capability of the raw material drying apparatus. As a result, the water content of the raw material to be supplied to the gasification chamber can be stabilized at all times, and the amount of the generated gas from unit raw material can be stabilized. Further, by utilizing sensible heat of the combustion gas to dry the raw material having a low heating value, the cold gas efficiency can be increased, and not only the energy recovery efficiency can be increased but also the equipment cost for installation can be reduced because heat recovery and power recovery by the use of a boiler are not required.

Thus, energy can be recovered at high efficiency and low cost . In a preferred aspect of the present invention, the gasification method further comprises cooling a gaseous material discharged from the drying apparatus to recover an essential oil component and/or a pyroligneous acid component. Since the biomass material contains an essential oil component and a pyroligneous acid component, the essential oil component and the pyroligneous acid component in the biomass material can be selectively transferred into the combustion gas by adjusting the temperature of the combustion gas appropriately when the combustion gas serving as a drying gas is introduced into the raw material drying apparatus for drying the biomass material. The transferred essential oil component and pyroligneous acid component can be easily condensed and recovered by cooling the combustion gas which has served to dry the raw material. In a preferred aspect of the present invention, the gasification method further comprises recovering heat from the combustion gas discharged from the combustion chamber and then supplying the combustion gas to the drying apparatus . In a preferred aspect of the present invention, the gasification chamber and the combustion chamber are provided in a fluidized-bed gasification furnace so as to allow a bed material to circulate between the gasification chamber and the combustion chamber. In a preferred aspect of the present invention, the gasification method further comprises at least one bed material settling chamber for allowing the bed material to descend and delivering the bed material to at least one of said gasification chamber and said combustion chamber. In order to achieve the above subject, according to a third aspect of the present invention, there is provided a gasification apparatus comprising: a pretreating chamber configured to pretreat a raw material; a gasification chamber configured to gasify the pretreated raw material to produce a combustible gas and residue; and a combustion chamber configured to combust the residue to generate a combustion gas; wherein part of a volatile component is separated from the raw material by supplying the combustion gas from said combustion chamber to the pretreating chamber. As described above, with this arrangement, a raw material having a low calorific value is dried and pretreated, and then supplied to the pyrolysis and gasification process, and hence a generated gas can be obtained at high efficiency and harmful substances are not mixed into the generated gas. Further, since heat generated by combustion of the pyrolysis reside is supplied by a bed material moving from the combustion chamber to the pretreating chamber and a combustible gas supplied to the pretreating chamber, the heat of combustion can be efficiently utilized for drying and pretreatment. In order to achieve the above subject, according to a fourth aspect of the present invention, there is provided a gasification -apparatus comprising: a drying appa-ra-t-us configured to dry a raw material; a gasification chamber configured to gasify the dried raw material to produce a combustible ^' gas and residue; and a combustion chamber configured to combust the residue to generate a combustion gas, wherein the raw material is dried and pretreated in the drying apparatus by supplying the combustion gas from said combustion chamber to said drying apparatus. As described above, the combustion gas combusted in the combustion chamber of the internal circulating fluidized-bed gasification furnace has a drying capability equivalent to a drying gas which is obtained by diluting a gas generated by combustion of higher hydrogen-containing fuel such as kerosene with a large amount of air. Thus, the raw material having a lowheatingvalue canbe efficientlydriedby supplying the combustion gas serving as a drying gas to the raw material drying apparatus after recovering heat from the combustion gas. Further, in the internal circulating fluidized-bed gasification furnace, as described above, the ratio of the raw material combusted increases, and the amount of the combustion gas discharged from the combustion chamber increases, thus increasing a drying capability of the raw material drying apparatus. As a result, the water content of the raw material to be supplied to the gasification chamber can be stabilized at all times, and the amount of the generated gas from unit raw material can be stabilized. Further, by utilizing sensible heat of the combustion gas to dry the raw material having a low heating value, the cold gas efficiency can be increased, and not only the energy recovery efficiency can be increased but also the equipment cost for installation can be reduced because heat recovery and power recovery by the use of a boiler are not required.

Thus, energy can be recovered at high efficiency and low cost . In a preferred aspect of the present invention, the gasification method further comprises a cooling apparatus configured to cool a gaseous material discharged from the drying apparatus to recover an essential oil component and/or a pyroligneous acid component. Biomass material which is one of raw materials having a low heating value contains an essential oil component and a pyroligneous acid component. Since the essential oil component and the pyroligneous acid component in the biomass material can be transferred into the gases for drying in the drying process, the transferred essential oil component and pyroligneous acid component can be easily condensed and recovered by cooling the combustion gas which has been used to dry the raw material. The recovered essential oil component and pyroligneous acid component can be sold at a relatively high price, and hence significant improvement in profitability of an undertaking for recovering a product gas and energy from biomass resources can be expected. Brief Description of Drawings FIG. 1 is a block diagram showing a basic concept of a gasification method and apparatus according to the present invention; FIG.2 is a block diagram showing a gasification method and apparatus according to a first embodiment of the present invention; FIG.3 is a block diagram showing a gasification method and apparatus according to a second embodiment of the present invention; FIG. 4 is a block diagram showing a gasification method and apparatus according to a third embodiment of the present invention; and FIGS. 5A and 5B are horizontal cross-sectional views schematically showing the layout of the respective chambers in the gasification furnace shown in FIG. 4.

Best Mode for Carrying Out the Invention Abasic concept and embodiments of the present invention will be described below with reference to FIGS. 1 through 5. Like or corresponding parts are denoted by like or corresponding reference numerals throughout drawings andwill not be described below repetitively. FIG. 1 is a block diagram showing a basic concept of a gasification method and apparatus according to the present invention. As shown in FIG. 1, a raw material 100 is dried andpretreated in a device for a drying and pretreating process DP. In the present invention, pretreating means that a raw material is treated with heat for removing harmful compounds such as arsenic compounds before supplying the raw material to a gasification chamber under low temperature. The dried and pretreatedmaterial is supplied to a device for a pyrolysis and gasification process GP, and is pyrolyzed and gasified in the pyrolysis and gasification process GP to produce a generated gas (combustible gas) 101. A pyrolysis residue (mainly containing carbon) generated in the pyrolysis and gasification process GP is supplied to a device for a pyrolysis residue combustion process CP, and is combusted in the pyrolysis residue combustion process CP to generate a combustion gas 107. Since the raw material 100 having a low heating value such as biomass, municipal solidwaste or organic sludge is supplied to the pyrolysis and gasification process GP after being dried and pretreated, and the raw material 100 whose heating value has been increased is pyrolyzed and gasified, a combustible gas (generated gas) can be obtained at high efficiency. Further, after harmful volatile elements such as arsenic, mercury, halogen are removed from the raw material by pretreatment of the raw material, the raw material is delivered to the device for the pyrolysis and gasification process GP, andhence aproduct gas (generated gas) isprevented from being mixed with harmful substances such as arsenic compounds like arsenious acid. For example, the harmful substances removedby thepretreatment, heatingby introducing a combustion gas of high temperature, include arsenic. In the case where a raw material is composed of wood such as construction scrap materials which is coated with arsenic compound such as CCA (Copper chrome arsenic) for the purpose of antisepsis or termite resistance, arsenic is volatilized in the pyrolysis and gasification process GP to cause arsenic to be dispersed into the generated gas (product gas) . Thus, arsenic is mixed into the product gas . Since arsenic compound, particularly arsenious acid is virulently poisonous, it is necessary to prevent arsenic compound from being mixed into the product gas regardless of a use of the product gas because it wouldbe relativelymore difficult to alter themixedproduct gas to a harmless product gas because of a technical difficulty as well as cost demerit. According to the present invention, since sensible heat of the combustion gas generated in the pyrolysis residue combustion process CP is used for heat required for the drying and pretreating process DP, part of the heating value of the raw material is used for drying the raw material without using an external fossil fuel such as heavy oil or coal, or the like, and hence the energy efficiency can be increased in manufacturing the product gas. A gas 115 generated in the drying and pretreating process DP is cooled in a cooling process 15, and hence an essential oil component and/or a pyroligneous acid component and/or harmful substances 111 such as arsenic are recovered. Then, the combustion gas is discharged to the outside of the system as an exhaust gas 112. In FIG. 1, although a drying process and a pretreating process are integrated as a single drying and pretreating process, the drying process and the pretreating process may be separated from each other as described later on. The drying of the raw material is carried out at a temperature of 100 to 280 °C, preferably 120 to 150 °C . The reason is that the temperature of 100 °C or higher is required to evaporate water in the raw material, and the higher the drying temperature is, the shorter the drying time is, but the temperature exceeding 280 °C causes pyrolysis of the raw material, and hence the drying temperature should be lower than 280 °C . Further, the essential oil component and the pyroligneous acid component are volatilized in the drying process, and in order to extract these components selectively, the drying process should be carried out at a temperature of about 150 °C or lower. The pretreating process should be carried out at a temperature of 135 to 280 °C, preferably 150 to 200 °C to recover arsenic from construction scrap materials or the like treated by CCA. The volatilization temperature of arsenic is 135 °C or higher, but the temperature exceeding 280 °C causes pyrolysis of the raw material, and hence the pretreating process should be carried out at a temperature of 135 to 280 °C . Since emission of arsenic occurs at a temperature of 150 to 200 °C remarkably, this temperature range is more preferable. The drying process and the pretreating process can be carried out in the same raw material drying apparatus, and the drying process and the pretreating process can also be carriedout separatelyby adjusting the operating temperature, as described above. By performing the drying process and the pretreating process independently, it is possible to prevent harmful volatile components from being mixed into the essential oil component and the pyroligneous acid component. Particularly, in the case where the raw material is composed of construction scrap materials treated by CCA, pyroligneous acid can be recovered by the drying process carried out at a lower temperature of 120 to 150 °C, and arsenic canbe recovered by volatilizing arsenic at a higher temperature of 150 to 200 °C. The raw material which has been dried and pretreated in the drying and pretreating process DP is delivered to the pyrolysis and gasification process GP where the raw material is pyrolyzed and gasified. The pyrolysis and gasification process GP should be carried out at a temperature of 350 to 900 °C. The raw material is decomposed into a generated gas (combustible gas) containing hydrogen, carbon monoxide, hydrocarbon gas such as methane whose carbon number is 3 or less, and tar content composed of hydrocarbon whose carbon number is 4 or more, a pyrolysis residue (called also char) composed mainly of fixed carbon in the raw material, and ash. The generated gas 101 is discharged from an outlet of the furnace, and is delivered to a device for a gas reforming process 6. In the gas reforming process 6, the generated gas

101 is partially combusted to raise the temperature of the generated gas 101 or the generated gas 101 reacts with steam (reforming reaction) or the generated gas 101 reacts under presence of catalyst (including typical metals, typical metal oxides, or their mixtures, such as zeolite, silica-alumina or limestone or catalysts complising at least one of metals (Rh, Ru, Ni, Pd, Pt, Co, Mo, Ir, Re, Fe, Na, K) or oxides of these metals, such as Ni/Al203) to reduce the molecular weight of high molecular compound in the generated gas 101 and to generate hydrogen by reaction with steam. The reformed gas is supplied to a heat recovery process 7 where the temperature of the reformed gas is lowered, and the reformed gas is then delivered to a gas-cleaning and dust-removing process 8 where the reformed gas is cleaned to remove dust therefrom. Thereafter, the cleaned reformed gas is purified in a device for a gas purifying process 9 to produce a product gas 106 by removing chlorine compound and/or sulfur compound. Then, the product gas 106 is discharged to the outside of the system and supplied to a predetermined location (facility, container etc.). The pyrolysis residue generated in the pyrolysis and gasification process GP is delivered to the device for pyrolysis residue combustion process CP, and is combusted by reaction with a gas containing oxygen such as air (including preheated air, air containing the combusted exhaust gas) . A high-temperature combustion gas 107 generated by combustion of the pyrolysis residue is delivered to a device for a heat recovery process 11 where the temperature of the combustion gas 107 is lowered from the range of 400-1000°C to the range of 150-500°C, and the combustion gas 107 is then delivered to a dust-removing process 12. In the dust-removing process 12, ash and dust are removed from the combustion gas 107. Then, the combustion gas 107 passes through a dechlorination process 13 and a denitration process 14, and hence hydrogen chloride and nitrogen oxide are removed from the combustion gas 107. In this manner, the combustion gas 107 becomes clean, and at least part of the clean combustion gas is supplied to the drying and pretreating process DP, and is used as a heat source required for the drying and pretreatment of the raw material . Next, embodiments of the present invention in which the basic concept of the present invention shown in FIG. 1 is embodied will be described with reference to FIGS. 2 through 5. FIG. 2 is a block diagram showing a gasification apparatus according to a first embodiment of the present invention. As shown in FIG. 2, the gasification apparatus comprises a raw material drying apparatus 1, a raw material hopper 2 disposed at a lower end of the raw material drying apparatus 1, a raw material supplying apparatus 3 disposed at a lower end of the raw material hopper 2, and an internally circulating fluidized-bed gasification furnace 4. The internal circulating fluidized-bed gasification furnace comprises a gasification chamber 4-1 and a combustion chamber 4-2 which are provided in a single furnace. A raw material 100 having a low heating value such as biomass supplied to the raw material drying apparatus 1 is dried by a combustion gas discharged from the combustion chamber 4-2 of the internal circulating fluidized-bed gasification furnace 4 (described in detail later on) . The dried raw material 100 is supplied to the raw material hopper 2, and is pushed into a material inlet of the raw material supplying apparatus 3 by a pusher 5. Then, the dried raw material 100 is supplied to the gasification chamber 4-1 of the internal circulating fluidized-bed gasification furnace 4 by the raw material supplying apparatus 3. A fluidized bed 4-lb in which a bed material is fluidized is formed in the gasification chamber 4-1, and a fluidized bed 4-2b in which a bed material is fluidized is formed in the combustion chamber 4-2. The raw material 100 supplied to upper part (upper part of an interface of a dense fluidized bed) of the fluidized bed 4-lb of the gasification chamber 4-1 by the raw material supplying apparatus 3 is pyrolyzed and gasified in the fluidized bed 4-lb to produce a generated gas (combustible gas) 101 and a pyrolysis residue such as char. The generated gas 101 passes through a freeboard 4-la, and is then delivered to a gas reformer of a gas reforming process 6. The generated gas 101 which has been reformed in the gas reforming process 6 is delivered to a heat recovery process 7. In the heat recovery process 7, heat recovery is carried out to produce steam 102 by a waste heat boiler (not shown) and to obtain preheated air 103 by an air preheater (not shown) , and hence the temperature of the generated gas 101 is lowered from the range of 800-1200°C to the range of 200-500°C. The generated gas 101 whose temperature has been lowered is delivered to a gas-cleaning and dust-removing process 8. In the gas-cleaning and dust-removing process 8, the generated gas 101 is cleaned by water injection, and waste water 104 and ash 105 are removed from the generated gas 101. Then, the cleaned generated gas 101 is purified in a gas purifyingprocess 9 to produce a product gas 106. The fluidized bed 4-lb of the gasification chamber 4-1 communicates with the fluidized bed 4-2b of the combustion chamber 4-2 through an opening formed below a lower end of a partition wall 4-3. Thus, the bedmaterial and the pyrolysis residue such as char move from the fluidized bed 4-lb of the gasification chamber 4-1 into the fluidized bed 4-2b of the combustion chamber 4-2. The char and the like are combusted in the combustion chamber 4-2 to produce a combustion gas 107, and the produced combustion gas 107 passes through a freeboard 4-2a and is then delivered to a heat recovery process 11. In the heat recovery process 11, heat recovery is carried out to produce steam 108 by a waste heat boiler (not shown) and to obtain preheated air 109 by an air preheater (not shown) , and hence the temperature of the combustion gas 107 is lowered from the range of 400-1000°C to the range of 150-500°C. The combustion gas 107 whose temperature has been lowered is delivered to a device for a dust-removing process 12. In the dust-removing process 12, a fly ash 110 is removed from the combustion gas 107. Then, the combustion gas 107 passes

■ • through a device for a dechlorination process 13 and a device for a denitration process 14, and hence dechlorination and denitration are carried out. The combustion gas 107 which has passed through the denitration process 14 is supplied to the raw material drying apparatus 1 as a gas for drying the raw material. It should be noted that the gas reforming process 6, the heat recovery process 7, the gas-cleaning and dust-removing process 8, and the gas purifying process 9 may be omitted depending on properties or application of the generated gas 101. For example, in the case where the generated gas produced in the gasification chamber is used as a fuel gas for a boiler, a cement kiln furnace for firing cement, a limestone kiln furnace for firing limestone (also called lime-kiln) in a paper aking process, or the like, the generated gas is supplied to the boiler or the firing furnace after the dust-removing treatment without providing the gas reforming process 6, the heat recovery process 7, or the gas purifying process 9. Similarly, the heat recovery process 11, the dust-removing process 12, the dechlorination process 13, and the denitration process 14 may be omitted depending on properties of the combustion gas 107. For example, if the raw material does not contain chlorine, the dechlorination process 13 is not necessary. The raw material drying apparatus 1 is such a vertical type drying apparatus that a gas for drying the raw material (drying gas) is supplied from the lower end portion of the raw material drying apparatus 1 into the raw material drying apparatus 1 to dry the raw material while the gas for drying (drying gas) is descending, and is then discharged from the upper end of the raw material drying apparatus 1. After the combustion gas 107 supplied to the raw material drying apparatus 1 as a gas for drying the raw material (drying gas) contributes to drying of the raw material 100, the combustion gas 107 is delivered to a cooling process- 15 where an essential oil component and/or a pyroligneous acid component contained in the combustion gas (drying gas) 107 is condensed and recovered. Then, the essential oil component and/or the pyroligneous acid component is removed, and the combustion gas is discharged to the outside of the system as an exhaust gas 112. The bedmaterial 113 moves into the fluidized bed 4-2b, and is discharged from the bottom portion of the fluidized bed 4-2b, and is then supplied into the raw material supplying apparatus 3 through a bedmaterial circulation means 16. The raw material supplying apparatus 3 has such a structure that a screw 3-2 is rotatably provided in a casing 3-1, and the casing 3-1 is disposed in an inclined state at a predetermined inclined angle so that the downstream side of the casing 3-1 is located at a- higher position. With this structure, a high material seal function can be obtained by the raw material and the bed material 113 which are fully charged into the casing 3-1. On the other hand, the raw material supplying apparatus 3 can be installed in the state of not being inclined state if a material seal function is obtained enough to operate the systemwithout any trouble due to lack of the seal function. As described above, by supplying the raw material 100 having a low heating value such as biomass which has been dried in the rawmaterial drying apparatus 1 to the gasification chamber 4-1, water contained in the raw material 100 is evaporated, and most of hydrogen component becomes the generated gas 101 as volatile component and is discharged from the gasification chamber 4-1. Therefore, the combustion gas 107 discharged from the combustion chamber 4-2 hardly contains water, and has a drying capability equivalent to a drying gas which is obtained by diluting a gas generated by combustion of higher hydrogen-containing fuel such as kerosene with a large amount of air. Thus-, a raw material having a low heating value such as biomass, municipal solid wastes or organic sludge can be efficiently dried by supplying the combustion gas 107 which has been subjected to a heat recovery treatment in the heat recovery process 11, a dust-removing treatment in the dust-removing process 12, a dechlorination treatment in the dechlorination process 13, and a denitration treatment in the denitration process 14. Therefore, the product gas 106 can be recovered at high efficiency and low cost from the raw material 100 having a low heating value . The energy may also be recovered from the raw material 100. Further, in the case where the raw material 100 having a high water content is gasified in the internal circulating fluidized-bed gasification furnace 4, cold gas efficiency is lowered. Specifically, the ratio of the raw material 100 combusted increases, and the amount of the combustion gas 107 discharged from the combustion chamber 4-2 increases, thus increasing a drying capability of the rawmaterial drying apparatus 1. As a result, the water content of the rawmaterial

100 to be supplied to the gasification chamber 4-1 can be stabilized at all times, and the amount of the generated gas

101 from unit raw material can be stabilized. Further, since the biomass material 100 contains the essential oil component and the pyroligneous acid component, the essential oil component and the pyroligneous acid component in the biomass material can be selectively extracted into the combustion gas by adjusting the temperature of the combustion gas 107 appropriately when the combustion gas is introduced into the raw material drying apparatus 1 to dry the biomass material. The extracted essential oil component and pyroligneous acid component is cooled by introducing the combustion gas into the cooling process 15, whereby the essential oil component and the pyroligneous acid component can be easily condensed and recovered. The recovered essential oil component and pyroligneous acid component 111 can be sold at a relatively high price, and hence significant improvement in profitability of an undertaking for recovering a product gas and energy frombiomass resources canbe expected. Further, by utilizing sensible heat of the combustion gas 107 to dry the raw material 100 having a low heating value, not only the cold gas efficiency can be increased and the energy recovery efficiency can be increased, but also the equipment cost for installation can be reduced because heat recovery and power recovery by the use of a boiler are not required. Thus, the energy recovery apparatus which can recover energy at high efficiency and low cost can be constructed. Next, a gasification method and apparatus according to a second embodiment of the present invention will be described below with reference to FIG. 3. The gasification apparatus according to the second embodiment shown in FIG .3 is different from the gasification apparatus according to the first embodiment shown in FIG.2 in that although the vertical type raw material drying apparatus 1 is disposed above the raw material hopper 2 and the dried raw material 100 is supplied directly to the raw material hopper 2 in the first embodiment shown in FIG. 2, a kiln-type raw material drying apparatus 20 is disposed at the location spaced from the raw material hopper 2 according to the second embodiment shown in FIG. 3. Then, in the second embodiment shown in FIG. 3, the raw material 100 is supplied from a raw material supply port 20a provided at an upper portion of an end of the raw material drying apparatus 20, and the dried raw material 100'^' is discharged from a raw material discharge port 20b provided at a lower portion of the other end of the raw material drying appara-tus 20. The combustion gas 107 serving as a gas for drying (drying gas) is supplied from one end of the raw material drying apparatus 20 located at a downstream side of the rawmaterial drying apparatus 20, and is then discharged from the other end of the raw material drying apparatus 20 located at an upstream side of the raw material drying apparatus 20. Specifically, the combustion gas 107 supplied from the combustion chamber 4-2 of the internal circulating fluidized-bed gasification furnace 4 passes through the heat recovery process 11, the dust-removing process 12, the dechlorination process 13 and the denitration process 14, and is then supplied to the end of the raw material drying apparatus 20 located at the downstream side of the rawmaterial drying apparatus 20. The combustion gas 107 introduced into the raw material drying apparatus 20 flows in a direction opposite to a moving direction of the raw material 100 to dry the rawmaterial 100. Thereafter, the combustion gas 107 is discharged from the other end of the raw material drying apparatus 20 located at the upstream side of the raw material drying apparatus 20, and is then supplied to the coolingprocess 15. The dried rawmaterial 100' is supplied to the rawmaterial hopper 2 by a feeding device (not shown) . Other structure of the gasification apparatus shown in FIG. 3 is the same as that of the gasification apparatus shown in FIG. 2, and has the same operation and effect as the gasification apparatus shown in FIG. 2. FIG. 4 is a block diagram showing a gasification method and apparatus according to a third embodiment of the present invention. As shown in FIG. 4, a drying and pretreating chamber 4-4 for performing a drying and pretreating process is incorporated in the internal circulating fluidized-bed gasification furnace 4 comprising a single integral furnace for performing the pyrolysis and gasification process and the pyrolysis residue combustion process according to the first and second embodiments of the present invention. As shown in FIG. 4, the gasification furnace comprises a fluidized-bed furnace having a dense fluidized bed of a bed material which is partitioned by three partition walls A, B and C so as to form a drying and pretreating chamber 4-4, a gasification chamber 4-1, and a combustion chamber 4-2. These three chambers 4-1, 4-2 and 4-4 are fully partitioned from the upper part of the fluidized bed to the top of the furnace by the three partition walls A, B and C. Here, the upper part of the fluidized bed is defined as a portion located upward from a surface of a bed which forms the dense fluidizedbed. Specifically, these three partition walls A, B and C have respective openings located near a distributor plate 4-6 of the furnace bottom and located in the dense fluidized bed so as to allow the bed material to move between the adjacent chambers, and are constructed such that there is no communication between the adjacent chambers except for such openings. The bed material for forming the fluidized bed, the raw material and the pyrolysis residue move from one chamber to another adjacent chamber through the opening. In the present embodiment, the bedmaterial 113 and the dried and pretreated raw material move from the drying and pretreating chamber 4-4 to the gasification chamber 4-1, the bed material 113 and the pyrolysis residue move from the gasification chamber 4-1 to the combustion chamber 4-2, and the bed material 113 moves from the combustion chamber 4-2 to the drying and pretreating chamber 4-4 and the gasification chamber 4-1. With this arrangement, the bed material 113 having a high temperature by combustion of the pyrolysis residue in the combustion chamber 4-2 is supplied to the drying and pretreating chamber 4-4 and the gasification chamber 4-1, whereby heat required for the drying and pretreating process and the gasification process can be transferred by the bed material 113. In order to move the bedmaterial 113 (and the raw material, the pyrolysis residue) through the opening formed at the lower portion of the partition wall, a fluidizing state of the bed material on both sides of the opening of the partition wall, more specifically, a superficial velocity of fluidizing gas is differentiated onboth sides of the opening of the partition wall. That is, the fluidizing state of the bed material at the downstream side of the opening is made relatively stronger than the fluidizing state of the bed material at the upstream side of the opening. With this arrangement, the density difference between the fluidized beds on both sides of the opening of the partition wall is produced (the fluidized bed at the upstream side is denser than the fluidized bed at the downstream side) and the flow velocity at the downstream side is higher than the flowvelocity at the upstream side, and hence the bed material moves by an inducing effect. The moving amount of the bed material can be controlled by the difference of the fluidizing state of the bed material on both sides of the opening, i.e. the difference of the superficial velocities of fluidizing gas. Further, at least one of low partition walls D, E and

F having substantially the same height as the surface of the dense fluidized bed from the furnace bottom should be provided in at least one of the drying and pretreating chamber 4-4, the gasification chamber 4-1, and the combustion chamber 4-2. These lowpartition walls are provided at the location upstream of the opening of the partition wall communicating with the downstream chamber in the flow direction of the bedmaterial, whereby regions enclosed by the partition walls A, B, C and the low partition walls D, E, F are formed. In such region enclosed by the two types of the partition walls, for example, the partition walls B and E, the bed material flows from a region other than such region in the chamber (for example, region other than such region enclosed by the partition walls

B and E in the gasification chamber 4-1) into such region enclosed by the two types of the partition walls (for example, the partition walls B and E) beyond the low partition wall (for example, the partition wall E) . Then, the bed material moves through the opening formed at the lower portion of the partition wall (for example, the partition wall B) into the adjacent chamber (for example, the combustion chamber 4-2) . Specifically, the region enclosed by the two types of the partition walls (for example, the partition walls B and E) has a function for allowing the bed material to descend and delivering the bed material to the adjacent chamber, and is referred to as a bedmaterial settling chamber. For example, a bed material settling chamber 4-5 is formed by the partition walls B and E. In the fluidized bed settling chamber, a relativelyweak fluidizing state of the bedmaterial is formed. In the case where the low partition wall is provided to form the fluidized bed settling chamber, the bed material which flows into the bed material settling chamber is accumulated in the bed material settling chamber due to the weak fluidization in the bedmaterial settling chamber . By setting the height of the low partition wall properly, it is possible to form a fluidized bed having a height higher than a main fluidized bed portion (portion other than the fluidized bed settling chamber) of the gasification chamber 4-1, the combustion chamber 4-2 , and the drying andpretreating chamber 4-4. By making the height of the fluidized bed in the bed material settling chamber higher than the fluidized bed in other regions, it is possible to increase the circulation amount of the bedmaterial. That is, the circulation amount of- the bed material can be controlled- by the -height of the fluidized bed in the bed material settling chamber . Further, since a relatively weak fluidizing state of the bed material is formed in the bedmaterial settling chamber, the fluidized bed in the bed material settling chamber has a higher density than the fluidized bed in other regions . Since a high density fluidizedbed canbe formed in the bedmaterial settling chamber, the circulation amount of the bed material can be controlled. Further, the high density bed in the bed material settling chamber has an excellent gas sealing function for preventing the gas to flow from the adjacent chamber (downstream side in the flow direction of the bedmaterial) into the bedmaterial settling chamber. As described above, the combustion gas supplied from the combustion chamber 4-2 should be used as a fluidizing gas in the drying and pretreating chamber 4-4, and sensible heat of the combustion gas should be used for drying and pretreating the raw material . A gas such as steam containing no oxygen, or a gas having oxygen content of 0-5%, preferably 0-3%, for example, a combustion exhaust gas should be used. If a gas containing oxygen is supplied to the gasification chamber 4-1, the generated gas (combustible gas) produced by pyrolysis is combusted, and hence it is not desirable that part of combustible gas components in the generated gas are consumed. An oxygen-containing gas such as air or oxygen-enriched air should be supplied to the combustion chamber 4-2. FIGS. 5A and 5B are horizontal cross-sectional views schematically showing the layout of the respective chambers in the gasification furnace shown in FIG. 4. The interior of the rectangular gasification furnace is divided into the drying and pretreating chamber 4-4, the gasification chamber 4-1, and the combustion chamber 4-2 by the partition walls A, B, C-l and C-2. Two bed material settling chambers 4-5A, 4-5B partitioned by low partition walls F-l, F-2 are provided in the combustion chamber 4-2. The partition walls A, B, C-l and C-2 extend from the furnace bottom to the furnace top, and have openings in the vicinity of the furnace bottom for allowing the bedmaterial, the rawmaterial and the pyrolysis residue to move between the adjacent chambers. The drying and pretreating chamber 4-4 and the gasification chamber 4-1 are partitioned by the partition walls so that the drying and pretreating chamber 4-4 and the gasification chamber 4-1 are independent from any of the chambers, except for the openings provided near the furnace bottomportion for allowing the bedmaterial to pass therethrough. Since the opening for allowing the bed material to pass therethrough is provided near the furnace bottom in the dense fluidized bed, the bed material, the raw material and the pyrolysis residue can move to the adjacent chamber through the opening. However, gases produced in the drying and pretreating chamber 4-4, the gasification chamber 4-1, and the combustion chamber 4-2, i.e. a dried and pretreated gas, a generated gas (combustible gas) and a combustion gas can be independently discharged from the respective discharge ports formed on the upper parts of the furnace without moving to the adjacent chamber. Specifically, the gases produced in the respective chambers can be taken out from the respective chambers without being mixed with each other. The two low partition walls F-l, F-2 are provided in the combustion chamber 4-2 so that the bed material settling chamber 4-5A enclosed by the partition walls F-l and C-l and the bedmaterial settling chamber 4-5B enclosed by the partition walls F-2 and C-2 are formed. Next, the fluidizing gas supplied to the fluidized bed and the movement (flow) of the bed material (including the raw material and the pyrolysis residue which move together with the- bed- material) will be described below.- Hatched regions in FIGS .5A and 5B are in a relatively weak fluidizing state compared with unhatched regions located adjacent to the hatched regions. The weak fluidizing state of the bed material in the regions is formed by supplying such regions with a fluidizing gas having a smaller superficial velocity than the superficial velocity of a fluidizing gas supplied to the adjacent regions. For example, the superficial velocity of the fluidizing gas supplied to the left region is relatively smaller than the superficial velocity of the fluidizing gas supplied to the right region in the combustion chamber 4-2 so that the fluidizing state is weak in the left region and strong in the right region in FIGS .5A and 5B . If the fluidizing regions having different fluidizing speeds coexist in the single chamber, a flow of the bed material is created such that the bed material descends in the weak fluidizing region (the left region in the combustion chamber 4-2) , and the bed material ascends in the strong fluidizing region (the right region in the combustion chamber 4-2 ) . This flow of the bed material is referred to as "revolving flow". By forming the revolving flow of the bed material in the gasification chamber 4-1 or the combustion chamber 4-2, the raw aterial and the pyrolysis residue can be uniformly dispersed in the fluidized bed, and the pyrolysis and gasification reaction (in the gasification chamber 4-1) and the combustion reaction (in the combustion chamber 4-2) can take place sufficiently. The movement of the bed material between the adjacent chambers divided by the partition wall takes place by the pressure difference on both sides of the opening of the partition wall. Specifically, the bed material moves from a high pressure side to a low pressure side. The pressure of a region is defined as the product of a density of the fluidized bed of the region, a height of the fluidized bed of the region, and an acceleration of gravity. Hence, the moving amount of the bedmaterial canbe controlled or adjusted (or changed) by changing or differentiating the densities of the fluidized bed or the height of the fluidized bed of a plurality of region. For example, the movement of the bed material from the gasification chamber 4-1 to the combustion chamber 4-2 through the opening of the partition wall B between the gasification chamber 4-1 and the combustion chamber 4-2 takes place as follows: The fluidizing state of the bed material at the locations near the opening of the partition wall B on both sides of the partition wall B are such that the fluidizing state in the gasification chamber 4-1 is weak and the fluidizing state in the combustion chamber 4-2 is strong. Thus, the descending flow of the bed material is formed in the gasification chamber 4-1 and the ascending flow of the bed material is formed in the combustion chamber 4-2. Further, if the superficial velocities of the fluidizing gases are different from each other, the densities of the fluidized beds are different fromeach other . Specifically, the density of the fluidized bed in the weak fluidizing region (region where the superficial velocity is relatively low, the gasification chamber side) is higher than the density of the fluidized bed in the strong fluidizing region (region where the superficial velocity is relatively high, the combustion chamber side) . That is, the densities of the fluidized beds on both sides of the opening of the partition wall are different from each other . The bed material moves from the gasification chamber 4-1 having a higher density fluidized bed to the combustion chamber 4-2 having a lower density fluidized bed. By providing the regions having different fluidizing state on both sides of the opening of the partition wall, the bed material -can move from the chamber having a weak fluidizing region to the chamber having a strong fluidizing region. Further, if the superficial velocity in the weak fluidizing region in the gasification chamber side is made lower, the viscosity of the fluidized bed becomes larger, and the moving amount of the bed material decreases. By utilizing change of the viscosity of the fluidized bed, the moving amount of the bed material can be also changed. This specific arrangement exists in the locations where there are movement of the bed material and the raw material from the drying and pretreating chamber 4-4 to the gasification chamber 4-1 (hatched arrow a-1), movement of the bed material and the pyrolysis residue from the gasification chamber 4-1 to the combustion chamber 4-2 (hatched arrow b-1), movement of the bed material from the bed material settling chambers 4-5A, 4-5B to the gasification chamber 4-1 (hatched arrows c-l and c-2) , and movement of the bed material from the bed material settling chambers 4-5A, 4-5B to the drying and pretreating chamber 4-4 (hatched arrows c-3 and c-4) . In these locations, although the movement of the bed material takes place, it is desirable that a gas produced in each chamber does not move to the adjacent chamber (gases are not mixed with each other) . Thus, the movement of the bed material should be performed using the opening of the partition wall . The moving amount of the bed material which passes through the opening of the partition wall can be changed depending on magnitude of the difference of the fluidizing state on both sides of the opening of the partition wall between the adj acent chambers . That is, as the difference between the fluidizing state of the bed material at the upstream side of the opening and the fluidizing state of the bed material at the downstream side of the opening is larger, the moving amount of the bedmaterial is larger. Specifically, if the superficial velocity at the upstream -side is made lower, or the superficial velocity at the downstream side is made higher, or the superficial velocity at the upstream side is made lower and the superficial velocity at the downstream side is made higher, then the moving amount of the bed material is made larger. For example, the movement of the bed material from the combustion chamber 4-2 to the bed material settling chamber 4-5A beyond the low partition wall F-l between the combustion chamber 4-2 and the bed material settling chamber 4-5A takes place as follows: The fluidizing state of the bed material on both sides of the partition wall F-l is such that the fluidizing state of the bed material is relatively strong at the combustion chamber side and relatively weak at the bedmaterial settling chamber side. Thus, the ascending flow of the bedmaterial is formed at the combustion chamber side, and the descending flow of the bed material is formed at the bed material settling chamber side. In the ascending flow of the bed material at the combustion chamber side, the bed material flies out by burst of bubbles in the vicinity of the surface of the dense fluidized bed. Part of the bed material which has flied out over the fluidized bed jumps over the partitionwall F-l and enters the bedmaterial settling chamber 4-5A. The amount of the bed material which jumps in the bed material settling chamber 4-5A depends on the relationship between the height of the fluidized bed in the combustion chamber 4-2 and the height of the partition wall F-l, and the fluidizing state of the bed material near the partition wall F-l at the combustion chamber side, i.e. the velocity of the fluidizing gas . If the height of the fluidized bed at the combustion chamber side is much lower than the height of the partition wall F-l, even if the superficial velocity of the fluidizing gas is made higher at the location near the partition wall in the combustion chamber 4-2, the amount -of the bed- material which jumps over- the partition wall is small. If the height of the fluidized bed in the combustion chamber 4-2 is close to the height of the partition wall F-l and slightly lower than the height of the partition wall F-l, then a large amount of the bed material which has jumped out over the fluidized bed in the combustion chamber 4-2 jumps over the partition wall F-l and moves to the bed material settling chamber 4-5A. As the superficial velocity of the fluidizing gas is higher, the amount of the bedmaterial which jumps out over the fluidized bed is larger. Thus, the moving amount of the bed material can be changed by changing the superficial velocity near the partition wall F-l in the combustion chamber 4-2. Further, if the height of the fluidized bed in the combustion chamber 4-2 is higher than the height of the partition wall F-l, the bedmaterial flows from the combustion chamber 4-2 to the bed material settling chamber 4-5A beyond the partition wall F-l . In this case, the bed material moves from the combustion chamber 4-2 to the bed material settling chamber 4-5A until both heights of the fluidized beds in the combustion chamber 4-2 and the bed material settling chamber 4-5A become the same height at the location higher than the partition wall F-l, or the height of the fluidized bed in the combustion chamber becomes equal to the height of the partition wall F-l, irrespective of the fluidizing state of the bedmaterial. The partition wall F-l has no opening, and hence the movement of the bed material between the adjacent chambers does not take place in the dense fluidized bed from the furnace bottom to the upper end of the partition wall. In the gasification chamber shown in FIG. 5A, the bed material is supplied to both of the drying and pretreating chamber 4-4 and the gasification chamber 4-1 from the two bed material settling chambers 4-5A, 4-5B. In the gasification furnace shown in FIG. 5B, the bed material- is supplied from the bed material settling chamber 4-5B to the drying and pretreating chamber 4-4, and the bed material is supplied from the bed material settling chamber 4-5A to the gasification chamber 4-1. As described above, the bed material can move at the location of each of the partition walls, and the circulation of the bedmaterial and the circulating amount (moving amount) of the bed material can be controlled in the following manner in the gasification furnace shown in FIGS. 5A and 5B. In the case of the gasification furnace shown in FIG. 5A, the rawmaterial is supplied to the drying and pretreating chamber 4-4. The supplied rawmaterial is swallowed into the fluidized bed by the revolving flow of the bed material in which the bed material descends in the central hatched portion of the drying and pretreating chamber 4-4 and ascends in the upper and lower unhatched portions of the drying and pretreating chamber 4-4 in FIG. 5A, and then the rawmaterial is uniformlydispersed. The rawmaterial is heatedby sensible heat held by the bed material which is supplied from the bed material settling chambers 4-5A, 4-5B to the drying and pretreating chamber 4-4 and sensible heat of the combustion gas serving as a fluidizing gas, and hence the raw material is dried and pretreated, thus separating a gas generated by the drying andpretreatment and other solid atters . Amixture of the gas for drying and pretreatment and the gas generated from the raw material by the drying and pretreatment is discharged from the discharge port provided at the furnace top, and is delivered to the cooling apparatus in which an essential oil component and/or a pyroligneous acid component and/or harmful substances such as arsenic are recovered. Then, the exhaust gas is discharged to the outside of the system. The solidmatters other than the gas components move together with the bedmaterial from the drying and pretrea-ting chamber 4-4 to the gasification chamber 4-1 through the opening of the partition wall A as shown by the hatched arrow a-1. The solid matters which have moved to the gasification chamber 4-1 are uniformly dispersed by the revolving flow of the bed material in which the bed material descends in the region from the central part of the gasification chamber 4-1 to the partition wall B and ascends in the peripheral portion surrounding such region, and are pyrolyzed and gasified by sensible heat of the bed material supplied from the bed aterial settling chambers 4-5A, 4-5B, thus separating a generated gas produced by pyrolysis and gasification and a pyrolysis residue composed mainly of fixed carbon in the raw material . The generated gas produced in the gasification chamber 4-1 is discharged from the discharge port provided at the furnace top, and is reformed in the reforming process, and then becomes a product gas after the heat recoveryprocess, the cleaning process, the dust-removing process, and the purifying process. The pyrolysis residue generated in the gasification chamber 4-1 moves together with the bed material from the gasification chamber 4-1 to the combustion chamber 4-2 through the opening of the partition wall B as shown by the hatched arrow b-1. The pyrolysis residue which has moved to the combustion chamber 4-2 is combusted by oxygen supplied to the combustion chamber 4-2, and hence the bed material is heated by heat of combustion of the pyrolysis residue. The combustion gas generated by combustion of the pyrolysis residue is discharged from the discharge port provided at the furnace top, and then the combustion gas is treated by the heat recovery process, the dust-removing process, the dechlorination process and the denitration process . Thereafter, part of the combustion gas is supplied to the drying and pretreating chamber 4-4

-as a drying and • pretreating heat source. The -heated -bed material moves to the bed material settling chambers 4-5A, 4-5B beyond the partition walls F-l and F-2 as shown by the unhatched arrows f-l and f-2. Part of the bed material which has moved to the bed material settling chambers 4-5A, 4-5B moves from the bed material settling chambers 4-5A, 4-5B to the gasification chamber 4-1 through the openings of the partition walls C-l and C-2 as shown by the hatched arrows c-l and c-2, and the reminder of the bed material moves from the bed material settling chambers 4-5A, 4-5B to the drying and pretreating chamber 4-4 through other openings of the partition walls C-l and C-2 as shown by the hatched arrows c-3 and c-4. In summary, in the case of the gasification furnace shown in FIG. 5A, the bed material is circulated in the following circulation route: the drying and pretreating chamber 4-4 → the gasification chamber 4-1 → the combustion chamber 4-2 → the fluidizedbed settling chambers 4-5A, 4-5B→ the drying and pretreating chamber 4-4 → the gasification chamber 4-1. That is, the bedmaterial flows in the order of the pretreating chamber 4-4, the drying and pretreating chamber 4-1, the combustion chamber 4-2, the fluidized bed settling chambers 4-5A, 4-5B, the drying and pretreating chamber 4-4 and the gasification chamber 4-1. The circulating amount of the bed material in this circulation can be changed freely not by changing the respective velocities in the partition wall portions for partitioning the adjacent chambers but by changing the flowvelocity in the bedmaterial settling chamber 4-5A or 4-5B. Because reactions take place in the drying and pretreating chamber 4-4, the gasification chamber 4-1, and the combustion chamber 4-2, respectively, the amount of the gas supplied to such chambers, i.e. the amount of the fluidizing gas should not be changed from a viewpoint of reaction which is desirably performed under the constant condition,- if the kind and amount of the raw material is not changed. If the supply amount of the rawmaterial is changed, it is desirable that the amount of the fluidizing gas (reaction gas) supplied to these chambers is changed relatively depending on change of the supply amount of the raw material. Specifically, the amount of the fluidizing gas supplied to the drying and pretreating chamber 4-4, the gasification chamber 4-1, and the combustion chamber 4-2 is changed according to the kind and supply amount of the rawmaterial, but should not be changed for the circulation of the bed material. In the case where the superficial velocity is under a certain constant condition in the chambers except for the bedmaterial settling chambers 4-5A, 4-5B, if the superficial velocity is made lower in the bed material settling chamber 4-5A, 4-5B, the amount of the bed material moving from the bed material settling chambers 4-5A, 4-5B to the drying and pretreating chamber 4-4 or the gasification chamber 4-1 increases because the difference of the superficial velocities between the bed material settling chamber 4-5A, 4-5B, and the drying and pretreating chamber 4-4 or the gasification chamber 4-1 divided by the partition walls C-l and C-2 is larger. Adversely, if the superficial velocity is made higher in the bed material settling chamber 4-5A, 4-5B, the amount of the bed material moving from the bed material settling chambers 4-5A, 4-5B to the drying and pretreating chamber 4-4 or the gasification chamber 4-1 decreases because the difference of the superficial velocity between the bed material settling chamber 4-5A, 4-5B, and the drying and pretreating chamber 4-4 or the gasification chamber 4-1 divided by the partition walls C-l and C-2 is smaller. If the amount of the bed material flowing into the drying and pretreating chamber 4-4 or the gasification chamber 4-1 is changed, the height of- the fluidized bed in the drying and pretreating chamber 4-4 or the gasification chamber 4-1 is changed. As described above, since the moving amount of the bed material depends on the height of the fluidized bed, as the amount of the bed material flowing from the bed material settling chambers 4-5A, 4-5B into the gasification chamber 4-1 becomes larger, the height of the fluidized bed in the gasification chamber 4-1 becomes higher, and hence the moving amount of the bed material flowing from the gasification chamber 4-1 to the combustion chamber 4-2 becomes larger. As the amount of the bed material flowing into the combustion chamber 4-2 becomes larger, the height of the fluidized bed in the combustion chamber 4-2 becomes higher, and hence the amount of the bedmaterial flowing from the combustion chamber 4-2 to the bed material settling chambers 4-5A, 4-5B becomes larger. In this manner, the circulating amount of the bed material into all the chambers can be controlled only by changing the superficial velocity in the bedmaterial settling chamber 4-5A or 4-5B. In the case of the gasification furnace shown in FIG. 5B, the rawmaterial is supplied to the drying and pretreating chamber 4-4. The supplied rawmaterial is swallowed into the fluidized bed by the revolving flow of the bed material in which the bed material descends at the partition wall side (the side of the partition wall A) of the drying andpretreating chamber 4-4 and ascends at the partition wall side (the side of the partitionwall C-2) of the drying andpretreating chamber 4-4, and then the raw material is uniformly dispersed. The rawmaterial is heatedby sensible heat heldby the bedmaterial which is supplied from the bedmaterial settling chamber 4-5B to the drying and pretreating chamber 4-4 and sensible heat of the combustion gas serving as a fluidizing gas, and hence the raw material is dried and pretreated, thus separating a gas generated by the drying and pretreatment and other solid matters. A mixture of the gas for drying and pretreatment and the gas generated from the raw material by the drying and pretreatment is discharged from the discharge port provided at the furnace top, and is delivered to the cooling apparatus in which an essential oil component and/or a pyroligneous acid component and/or harmful substances such as arsenic are recovered. Then, the exhaust gas is discharged to the outside of the system. The solid matters other than the gas components move together with the bed material from the drying and pretreating chamber 4-4 to the gasification chamber 4-1 through the opening of the partition wall A as shown by the hatched arrow a-1. The solid matters which have moved to the gasification chamber 4-1 are uniformly dispersed by the circulating flow of the bed material in which the bed material descends in the central part of the gasification chamber 4-1 and ascends at the upper and lower partition wall sides (the side of the partition wall A and the side of the partition wall C-l) of the gasification chamber 4-1, and are pyrolyzed and gasified by sensible heat of the bed material supplied from the bed material settling chamber 4-5A, thus separating a generated gas produced by pyrolysis and gasification and a pyrolysis residue composed mainly of fixed carbon in the raw material. The generated gas produced in the gasification chamber 4-1 is discharged from the discharge port provided at the furnace top, and is reformed in the reforming process, and then becomes a product gas after the heat recovery process, the cleaning process, the dust-removingprocess, and thepurifyingprocess . The pyrolysis residue generated in the gasification chamber 4-1 moves together with the bedmaterial from the gasification chamber 4-1 to the combustion chamber 4-2 through the opening of the partition wall B as shown by the hatched arrow b-1. The pyrolysis residue which has moved to the combustion- chamber 4-2 is combusted by oxygen supplied to the combustion chamber 4-2, and hence the bed material is heated by heat of combustion of the pyrolysis residue. The combustion gas generated by combustion of the pyrolysis residue is discharged from the discharge port provided at the furnace top, and then the combustion gas is treated by the heat recovery process, the dust-removing process, the dechlorination process and the denitration process. Thereafter, part of the combustion gas is supplied to the drying and pretreating chamber 4-4 as a drying and pretreating heat source. The bed material heated in the combustion chamber 4-2 moves to the bedmaterial settling chambers 4-5A, 4-5B beyond the partition walls F-l and F-2 as shown by the unhatched arrows f-l and f-2. The bed material which has moved to the bed material settling chamber 4-5A moves from the bed material settling chamber 4-5A to the gasification chamber 4-1 through the opening of the partition wall C-l as shown by the hatched arrow c-l, and the bed material which has moved to the bed material settling chamber 4-5B moves from the bed material settling chamber 4-5B to the drying and pretreating chamber 4-4 through the opening of the partition wall C-2 as shown by the hatched arrow c-3. In summary, in the case of the gasification furnace shown in FIG. 5B, the bed material is circulated in the following circulation route: the drying and pretreating chamber 4-4 → the gasification chamber 4-1 —> the combustion chamber 4-2 -→ the fluidized bed settling chambers 4-5A, 4-5B → the drying and pretreating chamber 4-4 and the gasification chamber 4-1. That is, the bed material flows in the order of the drying and pretreating chamber 4-4, the gasification chamber 4-1, the combustion chamber 4-2, the fluidized bed settling chambers 4-5A, 4-5B, the drying and pretreating chamber 4-4 and the gasification chamber 4-1. The circulating- amount of the bedmaterial in this circulation canbe controlled in the same manner as the gasification furnace shown in FIG. 5A. Although certain preferred embodiments of the present invention have been shown and described in detail, it should be understood that various changes and modifications may be made therein without departing from the scope of the appended claims. Industrial Applicability The present invention is applicable to a gasification method and apparatus for gasifying a raw material such as biomass to produce a combustible gas at high efficiency and low cost.

Claims

1. A gasification method comprising the steps of: pretreating a raw material; gasifying the pretreated rawmaterial in a gasification chamber to produce a combustible gas and residue; combusting the residue in a combustion chamber to generate a combustion gas; and supplying the combustion gas to said pretreating step to separate part of a volatile component from the rawmaterial .

2. A gasification method according to claim 1, further comprising cooling a gaseous material discharged from said pretreating step to recover an arsenic compound and/or a pyroligneous acid component.

3. A gasification method according to claim 1, wherein said gasification chamber and said combustion chamber are provided in a fluidized-bed gasification furnace so as to allow a bed material to circulate between said gasification chamber and said combustion chamber.

4. A gasification method according to claim 3, wherein said pretreating step is carried out in a pretreating chamber, and saidpretreating chamber is provided in said fluidized-bed gasification furnace.

5. A gasification method according to claim 3 or 4, further comprising at least one bed aterial settling chamber for allowing the bed material to descend and delivering the bed material to at least one of said gasification chamber and said combustion chamber.

6. A gasification method according to claim 1, wherein the raw material comprises biomass.

7. A gasification method comprising: drying a raw material in a drying apparatus; gasifying the dried raw material in a gasification chamber to produce a combustible gas and residue; combusting the residue in a combustion chamber to generate a combustion gas; and supplying the combustion gas to said drying apparatus to dry the raw material.

8. A gasification method according to claim 7, further comprising cooling a gaseous material discharged from said drying apparatus to recover an essential oil component and/or a pyroligneous acid component.

9. A gasification method according to claim 7, further comprising: recoveringheat from the combustion gas discharged from said combustion chamber and then supplying the combustion gas to said drying apparatus.

10. Agasificationmethod according to claim7, wherein said gasification chamber and said combustion chamber are provided in a fluidized-bed gasification furnace so as to allow a bed material to circulate between said gasification chamber and said combustion chamber.

11. A gasification method according to claim 10, further comprising at least one bedmaterial settling chamber for allowing the bed material to descend and delivering the bed material to at least one of said gasification chamber and said combustion chamber.

12. A gasification method according to claim 7, wherein the raw material comprises biomass.

13. A gasification apparatus comprising: a pretreating chamber configured to pretreat a raw material; a gasification chamber configured to gasify the pretreated raw material to produce a combustible gas and residue; and a combustion chamber configured to combust the residue to generate a combustion gas; wherein part of a volatile component is separated from the raw material by supplying the combustion gas from said combustion chamber to said pretreating chamber.

14. A gasification apparatus according to claim 13, further comprising a cooling apparatus configured to cool a gaseous material discharged from said pretreating chamber to recover an arsenic compound and/or a ptroligneous acid component.

15. A gasification apparatus according to claim 13, wherein said gasification chamber and said combustion chamber are provided in a fluidized-bed gasification furnace so as to allow a bedmaterial to circulate between said gasification chamber and said combustion chamber.

16. A gasification apparatus according to claim 15, wherein said pretreating chamber is provided in said fluidized-bed gasification furnace.

17. A gasification apparatus according to claim 15 or

16, further comprising at least one bed material settling chamber for allowing the bedmaterial to descend and delivering the bed material to at least one of said gasification chamber and said combustion chamber.

18. A gasification apparatus comprising: a drying apparatus configured to dry a raw material; a gasification chamber configured to gasify the dried raw material to produce a combustible gas and residue; and a combustion chamber configured to combust the residue to generate a combustion gas; wherein the raw material is dried in said drying apparatus by supplying the combustion gas from said combustion chamber to said drying apparatus.

19. A gasification apparatus according to claim 18, further comprising a cooling apparatus configured to cool a gaseous material discharged from said drying apparatus to recover an essential oil component and/or a pyroligneous acid component .

20. A gasification apparatus according to claim 18, further comprising: a heat recovery device configured to recover heat from the combustion gas discharged from said combustion chamber, wherein the combustion gas discharged from said heat recovery device is supplied to said drying apparatus.

21. A gasification method according to claim 18, wherein said gasification chamber and said combustion chamber are provided in a fluidized-bed gasification furnace so as to allow a bed material to circulate between said gasification chamber and said combustion chamber.

22. A gasification method according to claim 21, further comprising at least one bed aterial settling chamber for allowing the bed material to descend and delivering the bed material to at least one of said gasification chamber and said combustion chamber.

23. A gasification apparatus according to claim 18, wherein the raw material comprises biomass.