US20070012230A1

US20070012230A1 - Gasification furnace

Info

Publication number: US20070012230A1
Application number: US11/178,277
Authority: US
Inventors: Hiroshi Hashimoto; Shinji Sekikawa; Tatsuya Hasegawa; Fumiaki Morozumi
Original assignee: Individual
Current assignee: Ebara Corp
Priority date: 2005-07-12
Filing date: 2005-07-12
Publication date: 2007-01-18

Abstract

A gasification furnace has a gasification chamber for pyrolyzing a raw material in a fluidized medium being fluidized therein to produce a pyrolysis gas and a pyrolysis residue. The gasification furnace also has a combustion chamber for receiving the pyrolysis residue together with the fluidized medium, combusting the pyrolysis residue in the fluidized medium being fluidized therein to heat the fluidized medium, and returning the fluidized medium to the gasification chamber. The gasification furnace includes a partition wall for separating the gasification chamber and the combustion chamber from each other. The partition wall includes a first steel plate having a cooling structure to prevent the pyrolysis gas from flowing between the gasification chamber and the combustion chamber. The gasification furnace allows a general material to be used for components therein and have a long repair period.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a gasification furnace, and more particularly to a fluidized-bed gasification furnace suitable for producing a gas from a raw material such as various wastes and solid fuel.
2. Description of the Related Art
There have heretofore been known fluidized-bed gasification furnaces for producing a gas from solid fuel such as coal or organic wastes. Such fluidized-bed gasification furnaces include an integrated gasification furnace 910 as shown in FIG. 1. The integrated gasification furnace 910 has an integrated structure including a gasification chamber 901, a char combustion chamber 902, and a partition wall 915 to separate the gasification chamber 901 and the char combustion chamber 902 from each other. The integrated gasification furnace 910 includes a fluidized medium C circulating between the gasification chamber 901 and the char combustion chamber 902. The fluidized medium C is introduced together with char H from the gasification chamber 901 to the char combustion chamber 902. The fluidized medium C is heated in the char combustion chamber 902 by combustion of the char H. Then, the heated fluidized medium C is introduced from the char combustion chamber 902 to the gasification chamber 901. The partition wall 915 has a structure to prevent a pyrolysis gas from flowing between the gasification chamber 901 and the combustion chamber 902.
However, since the partition wall 915 is located in the gasification furnace 910, the partition wall 915 has a temperature higher than a temperature of a circumferential furnace wall 917, which separates the interior of the gasification furnace 910 from the exterior of the gasification furnace 910. Accordingly, in a case where the partition wall 915 is made of steel, it is necessary to select an expensive material for the partition wall 915 to maintain the strength at a high temperature. Further, in a case where the partition wall 915 is made of ceramics or brick, the partition wall 915 is likely to be cracked because of its brittleness. Thus, the partition wall 915 has a shorter life than the circumferential furnace wall 917. Accordingly, the gasification furnace 910 tends to have a shorter repair period.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above drawbacks. It is, therefore, a first object of the present invention to provide a gasification furnace which allows a general material to be used for components therein and have a long repair period.
According to an aspect of the present invention, there is provided a gasification furnace which allows a general material to be used for components therein and have a long repair period. The gasification furnace has a gasification chamber for pyrolyzing a raw material in a fluidized medium being fluidized therein to produce a pyrolysis gas and a pyrolysis residue. The gasification furnace also has a combustion chamber for receiving the pyrolysis residue together with the fluidized medium, combusting the pyrolysis residue in the fluidized medium being fluidized therein to heat the fluidized medium, and returning the fluidized medium to the gasification chamber. The gasification furnace includes a partition wall for separating the gasification chamber and the combustion chamber from each other. The partition wall includes a first steel plate having a cooling structure to prevent the pyrolysis gas from flowing between the gasification chamber and the combustion chamber.
The partition wall may include a refractory material covering the first steel plate. It is desirable that the partition wall includes a heat insulating material covering the first steel plate and a refractory material covering the heat insulating material.
A combustion gas can be produced in the combustion chamber 2. The partition wall can prevent the combustion gas from flowing between the gasification chamber and the combustion chamber. Thus, the gasification furnace can be a separation-type gasification furnace, which separately produces a combustible gas and a combustion gas.
The heated fluidized medium in the combustion chamber is returned to the gasification chamber. In this case, the fluidized medium may be returned directly to the gasification chamber or via another chamber to the gasification chamber. In any case, the fluidized medium is returned to the gasification chamber in a heated state.
As described above, the partition wall has a structure to prevent the pyrolysis gas from flowing between the gasification chamber and the combustion chamber. For example, a gas produced in one of the chambers may be extracted, controlled, and supplied to the other of the chambers. Particularly, it is desirable to extract such a gas at a location other than the partition wall. For example, a gas may be extracted through a path connected to the partition wall and supplied to the other of the chambers. Such an arrangement is included in a partition wall having a structure to prevent the pyrolysis gas from flowing between the gasification chamber and the combustion chamber.
The gasification chamber and the combustion chamber are configured so that gases are prevented from flowing between the gasification chamber and the combustion chamber. Accordingly, gases in the respective chambers can be separated from each other without being mixed with each other. Since the gasification chamber and the combustion chamber are separated by the partition wall including a first steel plate having the cooling structure, a lifetime of the partition wall can be prolonged.
The cooling structure may be operable to cool the first steel plate by a cooling fluid. The cooling fluid may comprise water or air. The cooling structure preferably includes at least one of water pipe membranes, air pipe membranes, a water-cooled jacket, and an air-cooled jacket.
The gasification furnace may have a circumferential furnace wall for separating internal gases in the gasification chamber and the combustion chamber from an exterior of the gasification furnace. The circumferential furnace wall may include a second steel plate and a refractory material covering an inner surface of the second steel plate. In this case, the cooling structure may be operable to cool the first steel plate by a cooling fluid. The gasification furnace may include a temperature controller operable to control a temperature of the cooling fluid so that a temperature of the partition wall is substantially equal to a temperature of the circumferential furnace wall.
Thus, the temperature of the partition wall is made substantially equal to the temperature of the circumferential furnace wall. Accordingly, the first steel plate and the second steel plate cause substantially the same thermal expansion. Therefore, the circumferential furnace wall and the partition wall can be made of the same material. Particularly, it is desirable that the tempareture of the first steel plate and the temperature of the second steel plate are controlled so as to be equal to each other.
The partition wall may have an opening through which the fluidized medium flows between the gasification chamber and the combustion chamber. In this case, the gasification chamber and the combustion chamber have furnace bottoms adjacent to the opening of the partition wall, respectively. It is desirable that the furnace bottom downstream of a flow of the fluidized medium is located lower than the furnace bottom upstream of the flow of the fluidized medium.
Specifically, the partition wall may have an opening through which the fluidized medium flows from the gasification chamber into the combustion chamber. In this case, the gasification chamber and the combustion chamber have furnace bottoms adjacent to the opening of the partition wall, respectively. It is desirable that the furnace bottom of the combustion chamber is located lower than the furnace bottom of the gasification chamber.
Alternatively, the partition wall may have an opening through which the fluidized medium flows from the combustion chamber into the gasification chamber. In this case, the gasification chamber and the combustion chamber have furnace bottoms adjacent to the opening of the partition wall respectively. It is desirable the furnace bottom of the gasification chamber is located lower than the furnace bottom of the combustion chamber.
Thus, the furnace bottom downstream of a flow of the fluidized medium is located lower than the furnace bottom upstream of the flow of the fluidized medium. Accordingly, the flow of the fluidized medium is promoted by a height difference of the furnace bottoms.
The above and other objects, features, and advantages of the present invention will be apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional side view showing a conventional gasification furnace;
FIG. 2A is a cross-sectional plan view showing a gasification furnace according to a first embodiment of the present invention;
FIG. 2B is an enlarged view of FIG. 2A;
FIG. 3 is a cross-sectional front view of the gasification furnace shown in FIG. 2A;
FIG. 4 is a cross-sectional side view of the gasification furnace shown in FIG. 2A;
FIG. 5 is a cross-sectional front view showing a gasification furnace according to a second embodiment of the present invention;
FIG. 6 is a cross-sectional front view partially showing a variation of the gasification furnace according to the second embodiment of the present invention;
FIG. 7 is a cross-sectional front view showing a gasification furnace according to a third embodiment of the present invention;
FIG. 8 is a cross-sectional plan view showing a gasification furnace according to a fourth embodiment of the present invention;
FIG. 9 is a cross-sectional front view of the gasification furnace shown in FIG. 8;
FIG. 10 is a partially cutaway perspective view showing a gasification furnace according to a fifth embodiment of the present invention;
FIG. 11 is a cross-sectional plan view of the gasification furnace shown in FIG. 10;
FIG. 12 is a cross-sectional side view of the gasification furnace shown in FIG. 10; and
FIG. 13 is a cross-sectional front view of the gasification furnace shown in FIG. 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A gasification furnace according to embodiments of the present invention will be described below with reference to FIGS. 2A through 13. Like or corresponding parts are denoted by like or corresponding reference numerals throughout drawings, and will not be described below repetitively.
FIG. 2A is a cross-sectional plan view showing an integrated gasification furnace 100 as a fluidized-bed gasification furnace according to a first embodiment of the present invention. As shown in FIG. 2A, the integrated gasification furnace 100 has a gasification chamber 1 for pyrolyzing a raw material such as various wastes or solid fuel and a char combustion chamber 2 for combusting char to heat a fluidized medium therein. The gasification chamber 1 and the char combustion chamber 2 are separated from each other by a partition wall 15. Dense beds including a fluidized medium are formed on furnace bottoms of the gasification chamber 1 and the char combustion chamber 2, respectively. The fluidized beds are fluidized by a diffuser (not shown).
As shown in FIG. 2A, the combustion chamber 2 is separated from the exterior of the furnace by a circumferential furnace wall 17. The circumferential furnace wall 17 includes an inner wall 17 a made of a refractory material which is exposed to the interior of the combustion chamber 2, an intermediate wall 17 b made of a heat insulating material, and an outer wall 17 c made of steel. Since the innermost surface of the circumferential furnace wall 17 is brought into direct contact with a combustion gas having a high temperature, the inner wall 17 a is made of a refractory material. For example, a castable (silica-alumina), which has a high strength and a high density, is used as the refractory material. The thickness of the inner wall 17 a is determined in a range of 100 to 150 mm. For example, the inner wall 17 a has a thickness of 125 mm. The inner wall 17 a having a thickness in such a range is suitable in consideration of strength and cost effectiveness. Nevertheless, the inner wall 17 a may be designed so as to be thicker or thinner than this range. The inner wall 17 a serves to provide resistance to a high temperature inside of the furnace and resistance to abrasion due to a flow of a gas in the furnace. Accordingly, the thickness of the inner wall 17 a is determined so that the inner wall 17 a has sufficient resistance to a hightemperature and abrasion.
The intermediate wall 17 b is made of a heat insulating material in order to prevent internal heat from being transferred to the exterior of the furnace and to decrease the temperature of a steel plate of the outer wall 17 c, which will be described later, to be lower than its heat resistant temperature (for safety of an operator). For example, a lightweight castable (silica-alumina) is used as the heat insulating material. The thickness of the intermediate wall 17 b is determined in consideration of the design temperature of steel and the temperature in the furnace. Further, the thickness of the intermediate wall 17 b depends upon the heat conductivity of the heat insulating material. For example, the thickness of the intermediate wall 17 b is determined in a range of 50 to 125 mm. The intermediate wall made of a heat insulating material can prevent the temperature of a gas from being lowered at a freeboard, which is located above the fluidized bed.
The outer wall 17 c is made of a steel plate (e.g., SS400 (JIS)) in order to protect the inner wall 17 a and the intermediate wall 17 b. The outer wall 17 c also serves to maintain sealing and strength of the furnace.
FIG. 2B is an enlarged cross-sectional view showing the circumferential furnace wall 17 with a temperature gradient. When the interior of the combustion chamber has a temperature of 800° C., an interface between the inner wall 17 a and the intermediate wall 17 b has a temperature of about 600° C., and the outer wall 17 c has a temperature of about 100° C. The outer wall 17 c hardly has a temperature difference between an inner surface and an outer surface thereof because the outer wall 17 c is made of a steel plate having a high heat conductivity.
The gasification chamber 1 includes a circumferential furnace wall having the same structure as the circumferential furnace wall 17 of the combustion chamber 2. The gasification chamber 1 has a temperature near about 700° C., which is lower than the temperature of the combustion chamber 2 (800° C.). Accordingly, the circumferential furnace wall of the gasification chamber 1 can be thinner than the circumferential furnace wall 17 of the combustion chamber 2. Tar contained in a gas produced in the gasification chamber 1 is generally considered to be condensed at about 400° C. Accordingly, it is desirable that the temperature of the freeboard is maintained at 500° C. or more.
The gasification chamber 1 and the combustion chamber 2 are partitioned by the partition wall 15. As shown in FIG. 2A, the partition wall 15 includes a membrane structure 15 c as a first steel plate located at a central portion in a thickness direction thereof. The membrane structure 15 c has a plurality of water pipes 15 e extending in a vertical direction and membranes (fins) 15 d of boiler steel plates connecting adjacent water pipes 15 e. Each membrane 15 d is in the form of a flat plate. The membranes 15 d are welded to the water pipes 15 e like fins of a frog.
Walls 15 b made of a heat insulating material are disposed on both sides of the membrane structure 15 c in the thickness direction. Further, walls 15 a made of a refractory material are disposed on both sides of the walls 15 b in the thickness direction. When the membrane structure 15 c has a temperature of 100° C., interfaces between the heat insulating material walls 15 b and the refractory material walls 15 a have a temperature of about 600° C. A surface of the refractory material wall 15 a facing the interior of the combustion chamber 2 has a temperature of about 800° C. A surface of the refractory material wall 15 a facing the interior of the gasification chamber 1 has a temperature of about 700° C.
The integrated gasification furnace 100 has a first temperature sensor 211 for detecting a temperature of the membrane 15 d and a second temperature sensor 212 for detecting a temperature of the outer wall 17 c.
The membrane structure 15 c will be described with reference to FIG. 3. FIG. 3 is a cross-sectional front view taken along line III-III of FIG. 2A. Each of the water pipes 15 e extending in the vertical direction is connected to a lower header 15 g at a lower end thereof and to an upper header 15 f at an upper end thereof. Water W for cooling is introduced from the lower header 15 g into the water pipes 15 e. The water W passes through the water pipes 15 e and flows out of the upper header 15 f. At that time, the water W removes heat from the water pipes 15 e and the membranes 15 d. When the water pipes 15 e are arranged at small intervals so that the membranes 15 d have small widths, the water pipes 15 e and the membranes 15 d have substantially the same temperature, e.g., 100° C., because the steel plate has a high heat conductivity.
The integrated gasification furnace 100 includes a control valve 214 provided at an inlet of the lower header 15 g and a temperature controller 213 operable to control opening and closing of the control valve 214. Signals from the first temperature sensor 211 and the second temperature sensor 211 are inputted into the temperature controller 213, which controls opening and closing of the control valve 214 based on the signals to thereby control the amount of water W so that the temperature of the membrane structure 15 c is substantially equal to the temperature of the outer wall 17 c. Materials and thicknesses of the inner wall 17 a and the intermediate wall 17 b are designed based on a normal external temperature and internal temperatures (of the combustion chamber and the gasification chamber) so that the temperature of the outer wall 17 c is in a range of 70 to 100° C. Accordingly, the temperature of the membrane structure 15 c is also controlled so as to be approximately in a range of 70 to 100° C. Because the outer wall 17 c is made of a steel plate having a high heat conductivity, the outer wall hardly has a temperature difference between inner and outer surfaces thereof.
Thus, the temperature of the partition wall 15 can be made equal to the temperature of the circumferential furnace wall 17. Accordingly, the durability of the partition wall 15 can be improved. Further, since the partition wall 15 and the circumferential furnace wall 17 have substantially the same temperature, the partition wall 15 and the circumferential furnace wall 17 can be made of the same material. It is desirable that the membrane structure 15 c and the outer wall 17 c have substantially the same temperature. Even if the membrane structure 15 c and the outer wall 17 c have different temperatures, it is desirable that a temperature difference between the membrane structure 15 c and the outer wall 17 c is not more than 60° C.
In the illustrated example, the temperature of the membrane structure 15 c is detected by the first temperature sensor 211. Instead, temperature sensors may be provided for detecting temperatures of the water W at the inlet of the lower header 15 g and an outlet of the upper header 15 f. In this case, an average of the detected temperatures, i.e., an average of an inlet temperature and an outlet temperature of the water W flowing through the water pipes 15 e, may be regarded as the temperature of the membrane structure 15 c for use in the control. If a temperature difference between the inlet temperature and the outlet temperature of the water W is considerably large, the amount of water W to be circulated may be increased to reduce the temperature difference. The amount of water W to be circulated is determined in consideration of the fact that it also depends upon the temperature of the water W.
When the membrane structure 15 c is set to have a temperature over 100° C., evaporation of water W can be utilized. In this case, the temperature of the membrane structure 15 c can be controlled by adjustment of a pressure of the water W.
Further, a heating medium having an evaporation temperature lower than 100° C. at 1 atmosphere can be used instead of the water to maintain the membrane structure 15 c from an inlet of the heating medium to an outlet of the heating medium at a constant temperature.
In the case where water is used as a cooling medium for the membrane structure 15 c, the water heated in the membrane structure 15 c may be introduced into a waste heat boiler, which performs heat exchange between the water and the combustion gas discharged from the combustion chamber 2. In this case, the water is heated in the waste heat boiler to produce steam. The produced steam may be supplied as a fluidizing gas to the gasification chamber 1 to thereby utilize heat efficiently in the gasification furnace 100.
Not only liquid such as water but also gas may be used as a cooling medium for the membrane structure 15 c. Particularly, air is suitable for the cooling medium for the membrane structure 15 c. In a case where air is used as a cooling medium for the membrane structure 15 c, the air heated in the membrane structure 15 c may be supplied as a fluidizing gas to the combustion chamber 2 to thereby utilize heat efficiently in the gasification furnace 100. Alternatively, the air heated in the membrane structure 15 c may be introduced into a waste heat boiler, which performs heat exchange between the air and the combustion gas discharged from the combustion chamber 2. In this case, the air heated by the waste heat boiler may be supplied as a fluidizing gas to the combustion chamber 2 to thereby utilize heat efficiently in the gasification furnace 100. When a gas is used as the cooling medium for the membrane structure 15 c, the membrane structure 15 c should have a structure suitable for the gas. For example, a cross section of the membrane structure 15 c is increased as compared to the length of passages in the membrane structure 15 c, or fins are provided in passages for the gas.
As shown in FIG. 3, the partition wall 15 has an opening 25 as a communication hole located at a lower portion thereof. Water pipes 15 e are provided around a portion at which the opening 25 is formed in the partition wall 15. Thus, the opening 25 is surrounded by the water pipes 15 e. These water pipes 15 e are also covered by a heat insulating material and a refractory material.
A furnace bottom 201 is provided at a bottom of the furnace so as to support the entire furnace. The furnace bottom 201 is made of a refractory material. This refractory material may be the same as the refractory material for the inner wall 17 a. It is desirable that the refractory material has a higher pressure resistance (a greater bearing capacity). The lower header 15 g is embedded in the furnace bottom 201.
Further details of the structure of the gasification furnace 100 will be described with reference to FIG. 4. FIG. 4 is a cross-sectional side view taken along line IV-IV of FIG. 2A. As shown in FIG. 4, the gasification chamber 1 and the combustion chamber 2 are communicated with each other via the opening 25 located at the lower portion of the partition wall 15. The opening 25 serves to allow the fluidized medium to pass therethrough. A valuable gas produced in the gasification chamber 1 and a combustion gas produced in the combustion chamber 2 hardly pass through the opening 25. This function is obtained by the fact that the gasification furnace 100 is designed so that the opening 25 is always positioned below upper surfaces of the fluidized beds including the fluidized medium in both chambers during operation of the gasification furnace 100. Thus, the gasification furnace 100 serves as a separation-type gasification furnace, which separately produces a valuable gas and a combustion gas. The fluidized medium is fluidized by a fluidizing gas ejected from a diffuser (not shown in FIG. 4) provided in the furnace bottom 201.
In FIGS. 2A, 2B, 3, and 4, the gasification furnace 100 is illustrated as being schematized for the purpose of explanation of the partition wall 15. Practically, in addition to the opening 25 to flow the fluidized medium from the combustion chamber 2 to the gasification chamber 1, the fluidized-bed gasification furnace has an additional opening (not shown) to return the fluidized medium of sand from the gasification chamber 1 to the combustion chamber 2. In this manner, the fluidized medium of sand is circulated between the gasification chamber 1 and the combustion chamber 2.
FIG. 5 is a cross-sectional front view showing an integrated gasification furnace 101 as a fluidized-bed gasification furnace according to a second embodiment of the present invention. The integrated gasification furnace 101 includes a gasification chamber 1 for pyrolysis (i.e., gasification), a char combustion chamber 2 for char combustion, and a heat recovery chamber 3 for heat recovery. The integrated gasification furnace 101 has a furnace body in the form of a cylinder or a parallelepiped. The gasification chamber 1, the char combustion chamber 2, and the heat recovery chamber 3 are housed in the furnace body and separated from each other by partition walls 11, 12, 13, and 15. Dense beds including a fluidized medium are formed on bottoms of the gasification chamber 1, the char combustion chamber 2, and the heat recovery chamber 3, respectively. Diffusers are provided on furnace bottoms of the respective chambers 1, 2, and 3 to eject fluidizing gases into the fluidized medium. The fluidized medium of the fluidized beds in the respective chambers, i.e., the fluidized bed of the gasification chamber 1, the fluidized bed of the char combustion chamber 2, and the fluidized bed of the heat recovery chamber 3, is thus fluidized by the diffusers.
For example, each of the diffusers includes a porous plate disposed on the furnace bottom. The porous plate is divided into a plurality of compartments separated along a width direction. In order to change superficial velocities at local regions in the respective chambers, the diffusers are configured to change flow velocities of fluidizing gases to be ejected from the respective compartments through the porous plate. Thus, superficial velocities are relatively different from region to region in the chamber. Accordingly, fluidization states are also different from region to region in the chamber. As a result, an internal circulating flow is formed in the chamber. Further, since fluidization states are different from region to region in the chamber, the internal circulating flow promotes to mix the fluidized medium in the chamber. In FIG. 5, hatched arrows show fluidizing gases to be ejected. The sizes of the hatched arrows represent flow velocities of the fluidizing gases. For example, a thicker arrow at a location 2 b represents a flow velocity higher than a flow velocity represented by a thinner arrow at a location 2 a.
The gasification chamber 1 and the char combustion chamber 2 are partitioned by the partition walls 11 and 15. The char combustion chamber 2 and the beat recovery chamber 3 are partitioned by the partition wall 12. The gasification chamber 1 and the heat recovery chamber 3 are partitioned by the partition wall 13. FIG. 5 is an expansion plan of the gasification furnace 101. Accordingly, the partition wall 11 is illustrated as not being provided between the gasification chamber 1 and the char combustion chamber 2, and the partition wall 13 is illustrated as not being provided between the gasification chamber 1 and the heat recovery chamber 3. Specifically, the respective chambers are not formed as separate furnaces in the integrated gasification furnace 101. Thus, the respective chambers are integrally formed as a single furnace.
As with the first embodiment, the partition wall 15 includes a membrane structure 15 c (not shown), heat insulating material walls 15 b, and refractory material walls 15 a. The walls 15 b and 15 a interpose the membrane structure 15 c therebetween. The circumferential furnace wall 17 (not shown in FIG. 5) includes an inner wall made of a refractory material, an intermediate wall made of a heat insulating material, and an outer wall made of steel, as with the first embodiment. The gasification furnace 101 has sensors (not shown) for detecting temperatures of the membrane structure 15 c and the outer wall of the circumferential furnace wall 17, and a temperature controller (not shown) for controlling temperatures based on the detected temperature.
The char combustion chamber 2 has a furnace bottom 51 near the partition wall 15 adjacent to the gasification chamber 1. The gasification chamber 1 has a furnace bottom 32 near the partition wall 15 adjacent to the char combustion chamber 2. The furnace bottom 51 of the char combustion chamber 2 and the furnace bottom 32 of the gasification chamber 1 are formed in a stepped manner so that the furnace bottom 51 is located higher than the furnace bottom 32. The furnace bottom 51 and the furnace bottom 32 are disposed so as to interpose therebetween an opening 25 of the partition wall 15, which serves as a communication hole. A weak fluidizing region 2 a is formed on the furnace bottom 51 by a fluidizing gas ejected at a low flow velocity. An intense fluidizing region 1 b is formed on the furnace bottom 32 by a fluidizing gas ejected at a high flow velocity.
Similarly, the char combustion chamber 2 has a furnace bottom 52 near the partition wall 11 adjacent to the gasification chamber 1. The gasification chamber 1 has a furnace bottom 31 near the partition wall 11 adjacent to the char combustion chamber 2. The furnace bottom 52 of the char combustion chamber 2 and the furnace bottom 31 of the gasification chamber 1 are formed in a stepped manner so that the furnace bottom 52 is located lower than the furnace bottom 31. The furnace bottom 52 and the furnace bottom 31 are disposed so as to interpose therebetween an opening 21 of the partition wall 11, which will be described later. An intense fluidizing region 2 b is formed on the furnace bottom 52 by a fluidizing gas ejected at a high flow velocity. A weak fluidizing region 1 a is formed on the furnace bottom 31 by a fluidizing gas ejected at a low flow velocity.
Here, the fluidized bed and the interface thereof will be described. The fluidized bed includes a dense bed located at a lower portion thereof in a vertical direction and a splash zone located above the dense bed in the vertical direction. The dense bed densely contains a fluidized medium (e.g., silica sand), which is fluidized by a fluidizing gas. The splash zone contains the fluidized medium and a large amount of gas. The fluidized medium is vigorously splashed in the splash zone. A freeboard is located above the fluidized bed, i.e., above the splash zone. The freeboard hardly contains the fluidized medium. The freeboard mainly contains a gas. An interface of the fluidized bed means the splash zone having a certain thickness. An interface may be regarded as an imaginary plane located at an intermediate location between an upper surface of the splash zone and a lower surface of the splash zone (an upper surface of the dense bed).
When chambers are partitioned by a partition wall so that a gas does not flow vertically above an interface of a fluidized bed, it is desirable that the gas does not flow above an upper surface of a dense bed, which is located at a position lower than the interface.
The partition wall 11 between the gasification chamber 1 and the char combustion chamber 2 extends almost entirely from a ceiling 19 of the furnace to the furnace bottom (the porous plate of the diffuser). The partition wall 11 has a lower end which is not brought into contact with the furnace bottom. Thus, the partition wall 11 has an opening 21 near the furnace bottom. An upper end of the opening 21 is not located above an interface of the fluidized bed in the gasification chamber 1 or an interface of the fluidized bed in the char combustion chamber 2. Preferably, the upper end of the opening 21 is not located above an upper surface of the dense bed in the gasification chamber 1 or an upper surface of the dense bed in the char combustion chamber 2. In other words, it is desirable that the opening 21 is always located in the dense beds. Specifically, the gasification chamber 1 and the char combustion chamber 2 are partitioned by the partition wall 11 so that a gas does not flow between the gasification chamber 1 and the char combustion chamber 2 in at least the freeboards, preferably above the interfaces of the fluidized beds, more preferably above the upper surfaces of the dense beds.
Thus, a gas does not flow between the gasification chamber 1 and the char combustion chamber 2. This means that a pyrolysis gas does not flow substantially over the partition wall 11 between the gasification chamber 1 and the char combustion chamber 2. A gas produced in one of the chambers may be intentionally discharged through a path (not shown) provided at a location other than the partition wall 11, controlled, and supplied to the other of the chambers. For example, a combustible gas in the gasification chamber 1 may be withdrawn as auxiliary fuel for the char combustion chamber 2 and combusted when a high temperature is not sufficiently maintained in the char combustion chamber 2 due to lack of char.
Further, the partition wall 12 between the char combustion chamber 2 and the heat recovery chamber 3 has an upper end located near the interfaces, i.e., above the upper surfaces of the dense beds but below upper surfaces of the splash zones. The partition wall 12 has a lower end located near the furnace bottom. The lower end of the partition wall 12 is not brought into contact with the furnace bottom. The partition wall 12 has an opening 22 near the furnace bottom. An upper end of the opening 22 is not located above upper surfaces of the dense beds. In other words, only the fluidized beds are partitioned between the char combustion chamber 2 and the heat recovery chamber 3 by the partition wall 12. The partition wall 12 has the opening 22 near a surface of the furnace bottom of the heat recovery chamber 3. The fluidized medium in the char combustion chamber 2 flows above the partition wall 12 into the heat recovery chamber 2 and returns to the char combustion chamber 2 through the opening 22 of the partition wall 12 near the surface of the furnace bottom of the heat recovery chamber 3. Thus, a circulating flow is formed in the furnace.
The partition wall 13 between the gasification chamber 1 and the heat recovery chamber 3 extends entirely from the furnace bottom to the ceiling 19 of the furnace. The partition wall 15 between the char combustion chamber 2 and the gasification chamber 1 is the same as the partition wall 11. Specifically, the partition wall 15 extends almost entirely from the ceiling 19 of the furnace to the furnace bottom. The partition wall 15 has a lower end which is not brought into contact with the furnace bottom. Thus, the partition wall 15 has the opening 25 near the furnace bottom. An upper end of the opening 25 is located below the upper surfaces of the dense beds. Specifically, an upper end of the opening 25 is not located above an interface of the fluidized bed in the gasification chamber 1 or an interface of the fluidized bed in the char combustion chamber 2. Preferably, the upper end of the opening 25 is not located above an upper surface of the dense bed in the gasification chamber 1 or an upper surface of the dense bed in the char combustion chamber 2. In other words, it is desirable that the opening 25 is always located in the dense beds. Specifically, the gasification chamber 1 and the char combustion chamber 2 are partitioned by the partition wall 15 so that a gas does not flow between the gasification chamber 1 and the char combustion chamber 2 in at least the freeboards, preferably above the interfaces of the fluidized beds, more preferably above the upper surfaces of the dense beds.
As shown in FIG. 5, wastes or solid fuel A is introduced into the gasification chamber 1. The wastes or solid fuel A receives heat from a fluidized medium C1, so that the wastes or solid fuel A is pyrolyzed and gasified. Typically, the wastes or solid fuel A is not combusted in the gasification chamber 1 but is subjected to carbonization. Remaining dry distillation char H flows through the opening 21 located at the lower portion of the partition wall 11 into the char combustion chamber 2 together with the fluidized medium C1. Thus, the char H introduced from the gasification chamber 1 is combusted in the char combustion chamber 2 to heat a fluidized medium C2. The fluidized medium C2 heated by combustion heat of the char H in the char combustion chamber 2 flows over the upper end of the partition wall 12 into the heat recovery chamber 3 as needed. Then, heat is removed from the fluidized medium C2 by a submerged heat transfer pipe 41, which is located at a position lower than the interface of the fluidized bed in the heat recovery chamber 3, to cool the fluidized medium C2. Thereafter, the fluidized medium C2 flows through the opening 22 of the partition wall 12 into the char combustion chamber 2.
The heat recovery chamber 3 is not necessarily required for an integrated gasification furnace (gas supply apparatus) according to the present invention. Specifically, the heat recovery chamber 3 to remove heat from the fluidized medium may be eliminated if the amount of char H mainly containing carbon that remains after volatile components have mainly been gasified in the gasification chamber 1 is approximately equal to the amount of char required to heat the fluidized medium C2 in the char combustion chamber 2. Further, if the amount of char H is larger than the amount of char required to heat the fluidized medium C2, the temperature of the fluidized bed in the gasification chamber 1 is increased so as to promote the gasification of char. As a result, the amount of heat of gasification reaction is increased so as to decrease the amount of char H. Thus, the amount of char is balanced.
The gasification furnace 101 having the heat recovery chamber 3 as shown in FIG. 5 can cope with a wide variety of wastes or fuel from coal, which produces a large amount of char, to municipal wastes, which hardly produce char. Specifically, whichever wastes or fuel is supplied to the gasification furnace 101, the fluidized medium can be maintained at a proper temperature by properly adjusting the amount of heat recovery in the heat recovery chamber 3 and properly adjusting the combustion temperature in the char combustion chamber 2.
The fluidized medium C2 heated in the char combustion chamber 2 is induced from a flow of a slow fluidizing gas on the furnace bottom 51 to a flow of a fast fluidizing gas on the furnace bottom 32 while it is circulated and fluidized. Thus, the fluidized medium C2 flows through the opening 25 located at a lower portion of the partition wall 15 into the gasification chamber 1. This flow is promoted because the furnace bottom 51 is located at a position higher than the furnace bottom 32. At that time, a circulating flow is also formed above the furnace bottom 51. Char is also combusted above the furnace bottom 51. The furnace bottom 51 is formed as a portion of the char combustion chamber 2. A space above the furnace bottom 51 is a portion of the char combustion chamber 2. Thus, the heated fluidized medium is moved directly from the char combustion chamber 2 to the gasification chamber 1.
Fluidization of the fluidized medium and movement of the fluidized medium between the respective chambers will be described below.
The gasification chamber 1 includes an intense fluidizing region 1 b near the partition wall 15 between the gasification chamber 1 and the char combustion chamber 2. The intense fluidizing region 1 b maintains a fluidization state stronger than that in the char combustion chamber 2. It is desirable to change superficial velocities of fluidizing gases G1 and G2 from place to place as to promote to mix and diffuse the introduced fuel and the fluidized medium. For example, as shown in FIG. 5, a weak fluidizing region 1 a is produced in addition to the intense fluidizing region 1 b so as to form a circulating flow in the gasification chamber 1.
The char combustion chamber 2 includes a weak fluidizing region 2 a at a central area and intense fluidizing regions 2 b at peripheral areas. The fluidized medium and char form an internal circulating flow in the char combustion chamber 2. It is desirable that the intense fluidizing regions in the gasification chamber 1 and the char combustion chamber 2 have a fluidizing velocity of 5 Umf or more. It is desirable that the weak fluidizing regions in the gasification chamber 1 and the char combustion chamber 2 have a fluidizing velocity of 5 Umf or less. The flow velocities of the weak fluidizing regions and the intense fluidizing regions may exceed these ranges as long as the weak fluidizing regions and the intense fluidizing regions have fluidizing velocities that are clearly different from each other. It is desirable that an intense fluidizing region 2 b is located at an area in the char combustion chamber 2 adjacent to the heat recovery chamber 3. Further, it is desirable that the furnace bottom has a gradient that decreases from the weak fluidizing regions to the intense fluidizing regions. The unit Umf is defined as 1 Umf is equal to a minimum fluidizing velocity (a velocity at which fluidization is started). Specifically, 5 Umf is equal to 5 times a minimum fluidizing velocity.
Thus, the fluidization state near the partition wall 12 in the char combustion chamber 2 is maintained so as to be stronger than the fluidization state near the partition wall 12 in the heat recovery chamber 3. Accordingly, the fluidized medium flows over an upper end of the partition wall 12, which is located near the interfaces of the fluidized beds, from the char combustion chamber 2 into the heat recovery chamber 3. The fluidized medium in the heat recovery chamber 3 is moved downward (toward to the furnace bottom) due to a relatively weak fluidization state, i.e., a high density state, in the heat recovery chamber 3. Then, the fluidized medium flows under a lower end of the partition wall 12 (through the opening 22), which is located near the furnace bottom of the heat recovery chamber 3. Thus, the fluidized medium is moved from the heat recovery chamber 3 to the char combustion chamber 2.
The furnace bottom of the heat recovery chamber 3 is located at a position higher than the furnace bottom of the char combustion chamber 2. Particularly, the furnace bottom surfaces adjacent to the partition wall 12 have different heights. Accordingly, the fluidized medium can smoothly flow from the heat recovery chamber 3 through the opening 22 into the char combustion chamber 2. The flow of the fluidized medium may not be promoted by the height difference because the fluidized medium in the heat recovery chamber 3 adjusts fluidization or stopping the fluidization.
Similarly, the fluidization state near the partition wall 11 in the char combustion chamber 2 is maintained so as to be stronger than the fluidization state near the partition wall 11 in the gasification chamber 1. Accordingly, the fluidized medium flows through the opening 21 of the partition wall 11, which is located below the interfaces of the fluidized beds, preferably at a position lower than the upper surfaces of the dense beds (i.e., under the dense beds). The flow of the fluidized medium is promoted because the furnace bottom 52 of the char combustion chamber 2 is located at a position lower than the furnace bottom 31 of the gasification chamber 1.
The heat recovery chamber 3 is entirely fluidized and maintained so as to be in a fluidization state equal to or weaker than that of the char combustion chamber 2 adjacent to the heat recovery chamber 3. Accordingly, the superficial velocity of the fluidizing gas in the heat recovery chamber 3 is controlled so as to be in a range of 0 to 3 Umf. The fluidized medium forms a descending fluidized bed while it is gently fluidized. Here, 0 Umf is defined as a state in which the fluidizing gas is stopped. In such a state, heat recovery can be minimized in the heat recovery chamber 3. Specifically, the amount of heat recovery can be controlled within a range from a maximum value to a minimum value by changing the fluidization state of the fluidized medium in the heat recovery chamber 3. Further, fluidization may be started or stopped in the entire heat recovery chamber 3, or the strength of the fluidization may be adjusted in the entire heat recovery chamber 3. Alternatively, fluidization may be stopped at some regions while other regions are in a fluidization state. The strength of the fluidization state may be adjusted at some regions.
Relatively large incombustible D contained in wastes or fuel A is discharged together with a fluidized medium C3 through an incombustible discharge port 33, which is provided in the furnace bottom of the gasification chamber 1 near the partition wall 15. The furnace bottoms of the respective chambers may have horizontal surfaces. Alternatively, the furnace bottoms of the respective chambers may have inclined surfaces according to flows of the fluidized medium near the furnace bottoms in order to prevent stagnation of the flows of the fluidized medium. The incombustible discharge port 33 may be provided in the furnace bottom of the char combustion chamber 2 or the heat recovery chamber 3 as well as in the furnace bottom of the gasification chamber 1.
In a conventional fluidized-bed gasification furnace, relatively large incombustible contained in wastes or fuel is discharged through an incombustible discharge port provided in the furnace bottom, which is not necessarily near the partition wall. Fluidization is inhibited around the incombustible discharge port because a fluidizing gas is unlikely to be supplied around the incombustible discharge port. In the present embodiment, a step is provided near the communication hole. Thus, as shown in FIG. 5, the incombustible discharge port 33 can have a vertical wall of the step to facilitate discharge of the incombustible. Accordingly, the fluidization is not prevented by the incombustible discharge port 33.
It is desirable that a portion of a produced gas B is pressurized and recycled as the fluidizing gas G1 in the gasification chamber 1. Thus, the gasification chamber 1 discharges only a gas produced from the fuel. Accordingly, a high quality gas can be obtained. Specifically, since the gas produced by pyrolysis and gasification in the gasification chamber 1 is not diluted with other gas components, the gas can have a high heating value and a high concentration. If the produced gas B cannot be used as the fluidizing gas G1 in the gasification chamber 1, it is desirable to use a gas containing oxygen as little as possible (non-oxygen gas), such as steam, carbon dioxide (CO₂), or a combustion gas E discharged from the char combustion chamber 2. If the bed temperature of the fluidized medium is lowered by an endothermic reaction of the gasification, a combustible gas having a temperature higher than the pyrolysis temperature may be supplied as needed. Alternatively, oxygen or a gas containing oxygen (e.g., air) may be supplied instead of non-oxygen gas to combust a portion of the produced gas B. The fluidizing gas G2 supplied into the char combustion chamber 2 comprises a gas containing oxygen required for char combustion, such as air or a gas mixture of oxygen and steam. When the fuel A has a low heating value (calorie), it is desirable to increase the amount of oxygen. For example, oxygen per se is supplied. Further, the fluidizing gas supplied into the heat recovery chamber 3 comprises air, steam, or the combustion gas E.
Portions above the upper surfaces of the fluidized beds of the gasification chamber 1 and the char combustion chamber 2 (upper surfaces of the splash zones), i.e., the freeboards, are completely partitioned by the partition walls 11 and 15. In other words, portions above the upper surfaces of the dense beds, i.e., the splash zones and the freeboards are completely partitioned by the partition walls 11 and 15. Accordingly, even if pressures of the freeboards of the char combustion chamber 2 and the gasification chamber 1 are unbalanced to some extent, the unbalanced pressures can be absorbed by changing a positional difference between the interfaces of the fluidized beds or a positional difference between the upper surfaces of the dense beds, i.e., a difference of the bed heights. Specifically, since the gasification chamber 1 and the char combustion chamber 2 are separated by the partition walls 11 and 15, even if pressures are varied in the respective chambers, the pressure difference can be absorbed by a difference of the bed heights. The pressure difference can be absorbed until either one of the beds is lowered to upper ends of the openings 21 and 25. Accordingly, a maximum pressure difference between the freeboards of the char combustion chamber 2 and the gasification chamber 1 that can be absorbed by a difference of the bed heights is approximately equal to a head difference between heads of the fluidized beds of the gasification chamber 1 and the char combustion chamber 2 from the upper ends of the lower openings 21 and 25 of the partition walls 11 and 15.
FIG. 6 is a cross-sectional front view partially showing a variation of the gasification furnace according to the second embodiment of the present invention. In the foregoing description, the furnace bottoms upstream and downstream of the openings 21 and 25 have different heights to smoothen the flow of the fluidized medium. A settling chamber may be provided near one of the opening 21 and the opening 25. For example, a char combustion settling chamber 4 is provided above the furnace bottom 51 near the opening 25 in the char combustion chamber 2. A partition wall 14 is provided between the char combustion settling chamber 4 and the char combustion chamber 2. In order to define the char combustion settling chamber 4 in the char combustion chamber 2, an upper end of the partition wall 14 is located near the interface of the fluidized bed, and a lower end of the partition wall 14 is connected to the furnace bottom. A relationship between the upper end of the partition wall 14 and the fluidized bed is the same as the relationship between the partition wall 12 (see FIG. 5) and the fluidized bed. Specifically, the char combustion chamber 2 and the char combustion settling chamber 4 are partitioned by the partition wall 14. The partition wall 14 has an upper end located near the interfaces, i.e., above the upper surfaces of the dense beds but below upper surfaces of the splash zones. The fluidized medium in the char combustion chamber 2 flows above the partition wall 14 into the char combustion settling chamber 4. The partition wall 14 can promote circulation of the fluidized medium.
A fluidization state near the partition wall 14 in the char combustion chamber 2 is maintained so as to be stronger than a fluidization state near the partition wall 14 in the char combustion settling chamber 4. Thus, the fluidized medium flows over the upper end of the partition wall 14, which is located near the interface of the fluidized bed, from the char combustion chamber 2 into the char combustion settling chamber 4. The fluidized medium in the char combustion settling chamber 4 is moved downward (toward to the furnace bottom) due to a relatively weak fluidization state, i.e., a high density state, in the char combustion settling chamber 4. Then, the fluidized medium flows under a lower end of the partition wall 15 (through the opening 25), which is located near the furnace bottom 51 of the char combustion settling chamber 4. Thus, the fluidized medium is moved from the char combustion settling chamber 4 into the gasification chamber 1. A fluidization state near the partition wall 15 in the gasification chamber 1 is maintained so as to be stronger than a fluidization state near the partition wall 15 in the char combustion settling chamber 4. Accordingly, movement of the fluidized medium from the char combustion settling chamber 4 and the gasification chamber 1 is promoted by an induction effect.
It is desirable that the furnace bottom 51 of the char combustion settling chamber 4 is located higher than the furnace bottom 32 of the gasification chamber 1.
In FIGS. 5 and 6, the partition wall 15 is illustrated as having a membrane structure. It is desirable that the other partition walls 11, 12, 13, and 14 also have a membrane structure. In such a case, the partition walls can be made of the same material as the circumferential furnace wall, and lifetimes of the partition walls can be prolonged as with the circumferential furnace wall. Further, when a membrane structure is covered with a refractory material and a heat insulating material, heat is prevented from being wastefully removed from the gasification chamber 1 and the combustion chamber 2. Thus, combustion heat can sufficiently be utilized for the gasification. Accordingly, the efficiency of the gasification furnace can be enhanced.
In the integrated gasification furnace 101 described above, three chambers, i.e., a gasification chamber, a char combustion chamber, and a heat recovery chamber, are provided in one fluidized-bed furnace while the chambers are separated by the partition walls. The char combustion chamber and the gasification chamber are disposed adjacent to each other. The char combustion chamber 2 and the heat recovery chamber 3 are provided adjacent to each other. The integrated gasification furnace 101 is operable to circulate a large amount of fluidized medium between the char combustion chamber 2 and the gasification chamber 1. Accordingly, the amount of heat required for the gasification can be met only by sensible heat of the supplied fluidized medium.
Further, the aforementioned integrated gasification furnace can seal between the char combustion gas E and the produced gas B almost completely. Accordingly, a pressure balance between the gasification chamber 1 and the char combustion chamber 2 can satisfactorily be controlled so that the combustion gas E and the produced gas B are not mixed with each other. Thus, properties of the produced gas B are not degraded.
The fluidized medium C1 as a heating medium and the char H flow from the gasification chamber 1 into the char combustion chamber 2. The same amount of fluidized medium C2 as the fluidized medium C1 and the char H returns from the char combustion chamber 2 into the gasification chamber 1. Accordingly, mass balance can be achieved spontaneously. It is not necessary to mechanically transport the fluidized medium from the char combustion chamber 2 to the gasification chamber 1 by a conveyer or the like. Further, it is possible to eliminate problems including difficulty in handling particles having high temperatures and a large amount of sensible heat loss.
Operation of the aforementioned integrated gasification furnace 101 will be described below. Wastes or fuel A is supplied into the gasification chamber 1 in the integrated gasification furnace 101. The wastes or fuel A is pyrolyzed into a combustible gas B, char H, and ash contents F. It is desirable that the wastes or fuel A comprises organic wastes or fuel having a high heating value, such as waste plastics, tire wastes, automobile shredder dust, ligneous wastes, municipal solid wastes, RDF, coal, heavy oil, and tar.
Thus, the char H is produced by the pyrolysis in the gasification chamber 1. Char that has a large particle diameter and do not follow the combustible gas B is moved to the char combustion chamber 2 together with the fluidized medium C1. In the char combustion chamber 2, the char H is completely combusted by using oxygen gas such as oxygen-rich air or oxygen as a fluidizing gas G2 (see FIG. 5). A portion of heat produced by the combustion of the char H is supplied into the gasification chamber 1 as sensible heat of the fluidized medium C2, which is circulated and returned into the gasification chamber 1, and used as heat required for the pyrolysis in the gasification chamber 1.
According to this method, the combustible gas (produced gas) B produced by the pyrolysis of the wastes or solid fuel A in the gasification chamber 1 and the combustion gas E produced by the combustion of the char H in the char combustion chamber 2 are not mixed with each other. Therefore, the produced gas B can have a high calorie and is suitable for liquid fuel synthesis.
Particularly, when the fluidizing gas G1 in the gasification chamber 1 contains no air or oxygen gas, heat produced by the combustion of the char H in the char combustion chamber 2 is supplied as sensible heat of the fluidized medium into the gasification chamber 1 to provide the entire amount of heat required for the pyrolysis. In such a case, a produced gas having a high calorie and a considerably low concentration of combustion gas components such as CO₂, H₂O, and N₂can be obtained without necessity of partial combustion in the gasification chamber 1.
FIG. 7 is a cross-sectional front view showing a gasification furnace 102 according to a third embodiment of the present invention. FIG. 7 shows a structure of a gasification chamber 1 and a char combustion chamber 2 and movement of a fluidized medium.
The gasification furnace 102 in the present embodiment has substantially the same structure as the gasification furnace in the second embodiment. In addition to the structure of the second embodiment, the gasification furnace 102 includes a steam supply port 35 a for supplying steam from a furnace bottom near a communication hole 25, through which the fluidized medium flows from the char combustion chamber 2 into the gasification chamber 1. The steam supply port 35 a is located downstream of the communication hole 25 (in the gasification chamber 1). Similarly, the gasification furnace 102 includes a steam supply port 35 b for supplying steam from a furnace bottom near a communication hole 21, through which the fluidized medium flows from the gasification chamber 1 into the char combustion chamber 2. The steam supply port 35 b is located downstream of the communication hole 21 (in the char combustion chamber 2).
The flow of the fluidized medium from the char combustion chamber 2 into the gasification chamber 1 is promoted by a height difference of the furnace bottoms. A gas in the char combustion chamber 2 may flow into the gasification chamber 1 together with the fluidized medium flowing through the communication hole 25. In this case, a combustible gas in the gasification chamber 1 may be combusted by oxygen contained in the gas flowing from the char combustion chamber 2. Accordingly, the calorie of the combustible gas recovered from the gasification chamber 1 may be lowered.
In the present embodiment, steam is supplied from the steam supply port 35 a provided on the furnace bottom of the gasification chamber 1 near the communication hole 25, through which the fluidized medium flows from the char combustion chamber 2 into the gasification chamber 1, to thereby prevent a gas from flowing from the char combustion chamber 2 into the gasification chamber 1. Further, a portion of the combustible gas to be recovered from the gasification chamber 1 is prevented from being combusted in the gasification chamber 1.
The flow of the fluidized medium from the gasification chamber 1 into the char combustion chamber 2 is promoted by a height difference of the furnace bottoms. The combustible gas and char, which is a combustible pyrolysis residue of a raw material supplied into the gasification chamber 1, in the gasification chamber 1 may flow into the combustion chamber 2 together with the fluidized medium flowing through the communication hole 21. In this case, the concentration of combustibles is increased near a downstream portion of the communication hole 21 to cause local superheat and local high temperature. If the local high temperature exceeds a melting temperature of the ash contents in the char, melted substances (liquid substances) of ash contents in the char problematically inhibit the fluidization.
In the present embodiment, steam is supplied from the steam supply port 35 b provided on the furnace bottom of the char combustion chamber 2 near the communication hole 21, through which the fluidized medium flows from the gasification chamber 1 into the char combustion chamber 2, to thereby prevent a gas (combustible gas) from flowing from the gasification chamber 1 into the char combustion chamber 2. Further, the density of combustibles can be lowered near a downstream portion of the communication hole 21. Thus, local superheat and local high temperature are prevented near the downstream portion of the communication hole 21. Further, the supply of the steam can diffuse the fluidized medium and the char (or ash contents) having increased temperatures due to char combustion near the downstream portion of the communication hole 21. Accordingly, inhibition of the fluidization which would be caused by melting ash at a local high temperature can be prevented.
In the present embodiment, the partition wall 15 having the communication hole 25 has a cooling structure including a membrane structure as with the second embodiment. The partition walls 11 and 13 also have a cooling structure including a membrane structure as with the second embodiment. Further, it is desirable that the partition walls 14 in the fluidized beds have a cooling structure including a membrane structure as with the second embodiment.
In the present embodiment, as shown in FIG. 7, a heat recovery chamber is not provided in the gasification furnace 102, but a submerged heat transfer pipe 41 is provided adjacent to the partition wall 15 in the char combustion chamber 2. The submerged heat transfer pipe 41 serves to recover heat of excessively combusted char (with respect to the amount of combusted char required for heating the fluidized medium). With this arrangement, the entire gasification furnace 102 can be simplified as compared to a gasification furnace having a heat recovery chamber.
In the present embodiment, the partition walls 14 in the fluidized beds may be eliminated to simplify the gasification furnace 102.
FIG. 8 is a cross-sectional plan view showing an integrated gasification furnace 103 according to a fourth embodiment of the present invention, and FIG. 9 is a cross-sectional front view of the gasification furnace 103 shown in FIG. 8. FIG. 8 is a cross-sectional view taken along line VIII-VIII of FIG. 9, and FIG. 9 is a cross-sectional view taken along line IX-IX of FIG. 8. As shown in FIG. 8, the gasification furnace 103 has a rectangular circumferential furnace wall 17. The interior of the circumferential furnace wall 17 is divided into a gasification chamber 1 and a char combustion chamber 2 by partition walls 11, 15, and 16. The partition walls 11, 15, and 16 are formed continuously as shown in FIG. 8. The partition wall 11 has an opening through which a fluidized medium flows from the gasification chamber 1 into the char combustion chamber 2. The partition wall 15 has an opening through which the fluidized medium flows from the char combustion chamber 2 into the gasification chamber 1. The partition wall 16 connects the partition wall 11 and the partition wall 15 to each other.
As shown in FIG. 8, the gasification furnace 103 has a central furnace bottom which is located at a position lower than other furnace bottoms. The central furnace bottom extends from one side of the circumferential furnace wall 17 to another side of the circumferential furnace wall 17 along a direction Y across a furnace body surrounded by the circumferential furnace wall 17. As shown in FIG. 9, the central furnace bottom is formed by a diffusion plate having a ridge 53. The ridge 53 of the central furnace bottom has an edge line extending along the direction Y. A weak fluidizing region is formed above the furnace bottom around the edge line of the central furnace bottom. Intense fluidizing regions are formed above the furnace bottom on both sides of the edge line, i.e., above base portions of the central furnace bottom. A space above the central furnace bottom is partitioned by the partition wall 16 extending from the furnace bottom to a ceiling 19 of the furnace. The partition wall 16, which is formed integrally with the partition walls 11 and 15, is arranged in parallel to a direction X, which is perpendicular to the direction Y. The central furnace bottom has gentle slopes from the edge line to the base portions.
The partition walls 15, 16, and 11 have a cooling structure including a membrane structure, as with the first, second, and third embodiments.
The central furnace bottom in the char combustion chamber 2, which is divided by the partition wall 16, includes a top portion 53 for a weak fluidizing region 2 a and base portions 52 and 54 for intense fluidizing regions 2 b which are adjacent to the top portion 53 (see FIG. 9). Similarly, the central furnace bottom in the gasification chamber 1 includes a top portion (edge line portion) 35 for a weak fluidizing region 1 a and base portions 32 and 34 for intense fluidizing regions 2 b which are adjacent to the top portion 35. The top portion 35 and the base portions 32 and 34 are not illustrated in FIG. 9 because of the partition wall 16.
The gasification furnace 103 has furnace bottoms 51 and 31 located on both sides of the central furnace bottom in the direction X at positions higher than the central furnace bottom. Weak fluidizing regions are formed on the furnace bottoms 51 and 31. The furnace bottoms 51 and 31 may be formed by a diffusion plate. Alternatively, the furnace bottoms 51 and 31 may have a plurality of ejecting nozzles disposed at proper intervals thereon. The ejecting nozzles are connected to a fluidizing gas pipe provided within a thick partition wall. The furnace bottom 51 is located in the combustion chamber 2. The furnace bottom 31 is located in the gasification chamber 1.
The furnace bottom 51 located below the partition wall 15 has an opening 125 as a communication hole interconnecting the combustion chamber 2 and the gasification chamber 1. This arrangement is included in an embodiment in which a partition wall has a communication hole at a lower portion thereof. The furnace bottom 32 in the gasification chamber 1, which is separated from the furnace bottom 51 by the partition wall 15, is located at a position lower than the furnace bottom 51 in the combustion chamber 2.
The furnace bottom 31 located below the partition wall 11 has an opening 121 as a communication hole interconnecting the gasification chamber 1 and the combustion chamber 2. This arrangement is included in an embodiment in which a partition wall has a communication hole at a lower portion thereof. As shown in FIG. 9, the furnace bottom 52 in the combustion chamber 2, which is separated from the furnace bottom 31 by the partition wall 11, is located at a position lower than the furnace bottom 31 in the gasification chamber 1.
As shown in FIG. 8, the gasification chamber 1 has a gas outlet 61 provided on the circumferential furnace wall 17 for discharging a produced gas. As shown in FIG. 9, the char combustion chamber 2 has a gas outlet 62 provided on the circumferential furnace wall 17 for discharging a combustion gas.
Operation of the gasification furnace 103 in the fourth embodiment will be described. A fluidized medium C2 is heated in the char combustion chamber 2. The fluidized medium C2 in a flow of a slow fluidizing gas on the furnace bottom 51 is induced to flow through the opening 125 into the gasification chamber 1 by a flow of a fast fluidizing gas on the furnace bottom 32 while the fluidized medium C2 is fluidized by a circulating flow. This flow of the fluidized medium C2 is promoted by the fact that the furnace bottom 51 is located higher than the furnace bottom 32. At that time, a circulating flow is also formed on the furnace bottom 51. Char is also combusted on the furnace bottom 51. Further, the furnace bottom 51 is a portion of the char combustion chamber 2, and a space above the furnace bottom 51 is also a portion of the char combustion chamber 2. Thus, the heated fluidized medium flows directly from the char combustion chamber 2 into the gasification chamber 1.
Similarly, wastes or fuel is gasified in the gasification chamber 1 to produce char H and a gas. A fluidized medium C1 containing the char H in a flow of a slow fluidizing gas on the furnace bottom 31 is induced to flow through the opening 121 into the char combustion chamber 2 by a flow of a fast fluidizing gas on the furnace bottom 52 while the fluidized medium C1 is fluidized by a circulating flow. This flow of the fluidized medium C1 is promoted by the fact that the furnace bottom 52 is located lower than the furnace bottom 31. A circulating flow is also formed above the furnace bottom 31. Gasification is also performed above the furnace bottom 31. Further, the furnace bottom 31 is a portion of the gasification chamber 1, and a space above the furnace bottom 31 is also a portion of the gasification chamber 1. Thus, the fluidized medium flows directly from the gasification chamber 1 into the char combustion chamber 2.
The gas produced in the gasification chamber 1 is discharged from the gas outlet 61. The combustion gas produced in the char combustion chamber 2 is discharged from the gas outlet 61.
As described above, according to the present embodiment of the present invention, the furnace bottom downstream of the flow of the fluidized medium flowing through the communication hole between the gasification chamber 1 and the char combustion chamber 2 is located lower than the furnace bottom upstream of the flow of the fluidized medium. Accordingly, the flow of the fluidized medium is smoothened and promoted. Thus, the amount of fluidized medium moving (circulating) through the communication hole can be increased per opening area.
In the above embodiments, the furnace bottoms have steps like stairs to provide height differences. Such furnace bottoms having steps are simple in structure and can readily be produced. Nevertheless, the furnace bottoms may have slopes to provide height differences. Particularly, it is desirable that a furnace bottom located at a higher position has a slope toward a communication hole.
In the above embodiments, each of the gasification chamber and the char combustion chamber comprises a fluidized bed having a circulating flow of bed materials. However, each of the gasification chamber and the char combustion chamber may comprise a fluidized bed uniformly bubbling, i.e., a fluidized bed having no circulating flow of bed materials. In this case, when furnace bottoms have height differences, a flow of a fluidized medium is promoted from a higher furnace bottom to a lower furnace bottom and thus smoothened.
The flow of the fluidized medium can be smoothened and smoothly circulated even without a char combustion settling chamber.
In the present embodiment, the partition walls 15, 16, and 11 have a cooling structure including a membrane structure. Accordingly, lifetimes of the partition walls 15, 16, and 11 can be prolonged. Further, when a membrane structure is covered with a refractory material and a heat insulating material, heat is prevented from being wastefully removed from the gasification chamber 1 and the combustion chamber 2. Accordingly, a lifetime of the gasification furnace can be prolonged, and the efficiency of the gasification furnace can be enhanced.
FIG. 10 is a partially cutaway perspective view showing an integrated gasification furnace 104 according to a fifth embodiment of the present invention. FIG. 10 is illustrated as being schematized. In FIG. 10, a refractory material or fluidized beds are not illustrated for simplification. The gasification furnace 104 has a gasification chamber 1 and a char combustion chamber 2. The gasification furnace 104 has a furnace body in the form of a rectangular shape (parallelepiped). Specifically, a circumferential furnace wall 17 having side surfaces of the furnace body are approximately rectangular. The entire furnace body is formed as a parallelepiped. With a rectangular furnace body or a parallelepiped furnace body, the furnace can be designed flexibly. For example, when the length of the char combustion chamber 2 is changed in a direction X or Y while the size of the gasification chamber 1 (the area and shape of the gasification chamber 1) is fixed, only an area of the char combustion chamber 2 can be changed as desired. In other words, an optimal size of the furnace can readily be determined according to properties of a raw material (e.g., concentration of fixed carbon). When a circumferential furnace wall is cylindrical, the size of the furnace is determined by a diameter of the outer wall. Accordingly, if the size of either one of chambers is changed, the size of the other chamber is also changed.
In FIG. 10, a rectangular coordinate system XYZ has a horizontal plane XY and a vertical axis Z. The axis Y faces a front face of the furnace. The gasification furnace 104 is arranged symmetrically with respect to the axis Y.
The gasification chamber 1 and the char combustion chamber 2 are partitioned by partition walls 11, 151, and 152. Dense fluidized beds including a fluidized medium are formed on furnace bottoms of the gasification chamber 1 and the char combustion chamber 2. The fluidized beds in the respective chambers are the same as those in the above embodiments and will not be described repetitively.
As with the aforementioned embodiments, each of the front partition wall 11 and the side partition walls 151 and 152 has a membrane structure, heat insulating material walls, and refractory material walls. The membrane structure is interposed between the heat insulating material walls and the refractory material walls. Details of the partition walls are not illustrated in FIG. 10. As with the aforementioned embodiments, the circumferential furnace wall 17 has an inner wall made of a refractory material, an intermediate wall made of a heat insulating material, and an outer wall made of steel.
As with the aforementioned embodiments, the gasification furnace 104 includes sensors (not shown) for detecting temperatures of the membrane structure and the outer wall and a temperature controller for controlling temperatures based on the detected temperatures.
The side partition walls 151 and 152 extend vertically from the furnace bottoms and bend diagonally upward in a freeboard. The side partition walls 151 and 152 are connected to the circumferential furnace wall 17. In other words, water pipes of membrane structures in the partition walls 151 and 152 do not extend to a ceiling but penetrate the outer wall at an intermediate portion of the furnace. As a result, the water pipes in the side partition walls 151 and 152 do not extend to the ceiling but penetrate the outer wall at the intermediate portion of the furnace.
Thus, the gasification chamber 1 has a space widened in the freeboard near a gas outlet 61. Accordingly, the superficial velocity of the produced gas can be reduced before the produced gas is discharged from the gas outlet 61. Thus, unburnt components are prevented from scattering.
The front partition wall 11 extends from the furnace bottom to the ceiling. The front partition wall 11 is illustrated as being broken so that the structure of the gasification chamber 1 can be seen. The three partition walls 11, 151, and 152 are disposed in the form of a hook within the fluidized bed and the freeboard, which is near the fluidized bed (above the fluidized bed), in the furnace surrounded by the rectangular circumferential furnace wall 17. The partition wall 11 is disposed at an upper portion of the freeboard (near the ceiling). The partition wall 11 separates the gasification chamber 1 and the combustion chamber 2 from each other.
As with other embodiments, the partition wall 151 has an opening 251 formed at a lower portion thereof, and the partition wall 152 has an opening 252 formed at a lower portion thereof. Further, the partition wall 11 has an opening 21 formed at a lower portion thereof.
In the fifth embodiment, the furnace bottoms downstream and upstream of the openings 21, 251, and 252 have height differences to smoothen the flow of the fluidized medium, as with the variation of the second embodiment shown in FIG. 6. The gasification furnace 104 has char combustion settling chambers provided adjacent to the openings 251 and 252 on the furnace bottoms 511 and 512 in the char combustion chamber 2.
The partition walls 141 and 142 are provided between the char combustion settling chambers and the char combustion chamber 2. The partition walls (baffle plates) 141 and 142 may have a cooling structure including a membrane as with the partition walls 11, 151, and 152. In such a case, when the gasification furnace 104 is made large in size, the partition walls 141 and 142 can have a high temperature strength as with the partition walls 11, 151, and 152. Other structures and functions of the partition walls 141 and 142 are the same as the partition wall 14 described above and will not be described repetitively. With the partition walls 141 and 142, the circulation of the fluidized medium can be promoted.
FIG. 11 is a cross-sectional plan view taken along line XI-XI of FIG. 10. FIG. 12 is a cross-sectional side view taken along line XII-XII of FIG. 11. The integrated gasification furnace 104 will be described in detail with reference to FIGS. 11 through 12. In FIGS. 12 and 13, an upper portion of the gasification furnace 104 is not illustrated.
As shown in FIG. 11, the furnace bottom of the char combustion chamber 2 is rectangular in the plan view. An intense fluidizing region 2 b is formed on the furnace bottom 52 adjacent to the partition wall 11. A weak fluidizing region 2 a is formed on the furnace bottom 53 away from the partition wall 11, i.e., near the circumferential furnace wall 17. Further, weak fluidizing regions 2 a are formed on the furnace bottoms 511 and 512 in the settling chamber.
The furnace bottom of the gasification chamber 1 is rectangular in the plan view. Intense fluidizing regions 1 b are formed on the furnace bottoms 321 and 322 adjacent to the partition walls 151 and 152. A weak fluidizing region 1 a is formed on a central portion 31 of the gasification chamber 1 away from the partition walls 151 and 152, which face each other.
The flow of the fluidized medium in the furnace bottom structure will be described below with reference to FIG. 11. The flow of the fluidized medium is promoted by a stepped structure of the furnace bottoms. When fluidization states near the partition walls are maintained so as to be stronger or weaker, the fluidized medium is fluidized and circulated between the chambers.
The fluidized medium heated in the char combustion chamber 2 flows over the partition walls 141 and 142 into the settling chamber. The fluidized medium flows through the openings 251 and 252 of the partition walls 151 and 152 into the gasification chamber 1. The fluidized medium is used to heat fuel in the gasification chamber 1. Then, the fluidized medium returns through the opening 21 of the partition wall 11 into the char combustion chamber 2.
As shown in FIG. 12, the furnace bottom 52 of the char combustion chamber 2 near the partition wall 11 is formed in a stepped manner so as to be lower than the furnace bottom 31 of the gasification chamber 1 near the partition wall 11. The furnace bottom 52 and the furnace bottom 31 are disposed with the opening 21 interposed therebetween. As described above, an intense fluidizing region 2 b into which a fluidizing gas is strongly ejected is formed on the furnace bottom 52. A weak fluidizing region 1 a into which a fluidizing gas is weakly ejected is formed on the furnace bottom 31.
The partition wall 11 has a portion DF projecting toward the freeboard at an intermediate portion of the furnace. The portion DF serves as a deflector for promoting an internal circulating flow. The deflector DF is made of a refractory material.
Further, an incombustible withdrawing port 33 a is formed below the partition wall 11, i.e., below the opening 21. In the present embodiment, incombustibles are discharged from the furnace bottom of the char combustion chamber 2. The incombustible withdrawing port 33 a is located at a stepped portion between the furnace bottom 31 of the gasification chamber 1 and the furnace bottom 52 of the char combustion chamber 2. The incombustible withdrawing port 33 a is connected via an incombustible introduction passage 33 b to an incombustible discharge port 33 for discharging the incombustibles to the exterior of the furnace.
An edge surface of the furnace bottom 31 of the gasification chamber 1, which is an extended surface of the partition wall 11, and an edge surface of the furnace bottom 52 of the combustion chamber 2, which is an inner surface of the incombustible introduction passage 33 b, are located on the same plane extending vertically. With such an arrangement, as seen in the cross-sectional plan view (FIG. 11), diffusion ranges of the fluidizing gases are continuously formed so as not to cause poor fluidization.
When an incombustible withdrawing port is provided so that incombustibles are discharged from the furnace bottom of the combustion chamber 2 as in the present embodiment, the incombustibles may be entangled with the opening extending from the gasification chamber 1 to the combustion chamber 2 so as to clog the opening. Further, oxidized metals may be discharged. However, unburnt char or tar attached to the incombustibles or contained in the fluidized medium can be cleaned up by combustion. Accordingly, troubles in a withdrawing system can be reduced.
On the contrary, an incombustible withdrawing port may be provided so that incombustibles are discharged from the furnace bottom of the gasification chamber 1. In such a case, unburnt char or tar is discharged together with the incombustibles. Accordingly, ignition in the withdrawing system and dirt of the incombustibles are problematic. However, since metals can be withdrawn without being oxidized, such an arrangement is suitable for recycling. Further, since incombustibles are withdrawn from a side into which a raw material is supplied, there can be reduced fear that the incombustibles clog the opening.
It is desirable to determine whether an incombustible discharge port is provided on the furnace bottom of the combustion chamber or on the furnace bottom of the gasification chamber based on a method of reusing discharged incombustibles, and composition and shapes of the incombustibles.
In the present embodiment, the furnace bottom of the combustion chamber 2 has a slope directed downward toward the incombustible withdrawing port 33 a so as to improve the capability of discharging incombustibles.
Air for fluidization of the fluidized medium and combustion is ejected from the furnace bottoms 52 and 53 of the combustion chamber 2. A steam ejection port 202 for ejecting steam ST is provided in the combustion chamber 2 near the opening 21, through which the fluidized medium flows from the gasification chamber 1 into the combustion chamber 2. Alternatively, a steam ejection port may be formed in a diffusion plate for ejecting air. With such an arrangement, it is possible to prevent air from leaking through the opening 21 into the gasification chamber 1. Thus, it is possible to prevent a produced gas from being combusted by leaking air.
The furnace bottom 31 of the gasification chamber 1 on which a weak fluidizing region 2 a is formed has a slope directed downward toward the opening 21 from the gasification chamber 1 to the combustion chamber 2. Such a slope promotes the movement of the fluidized medium.
A raw material supply port 63 is provided about 1 m to about 2 m above an interface of the fluidized bed in the gasification chamber 1. Even if the pressure near the interface of the fluidized bed becomes positive with respect to an atmospheric pressure due to variation of the amount of fluidizing gas or variation of the amount of supplied raw material A, a gas in the furnace is prevented from flowing back through the raw material supply port 63.
Furthermore, the furnace is usually operated so that the freeboard has a negative pressure (about −5 kPa) with respect to the atmospheric pressure. The pressure of a space from the bottom surface to the interface of the fluidized bed becomes a positive pressure due to pressure loss of the fluidized bed. Further, bubbles of the fluidizing gas are developed within the fluidized bed. When the bubbles are burst on the surface of the fluidized bed, the pressure is abruptly changed (increased). When a pressure increase is produced near the raw material supply port 63, a gas having a high temperature or a combustible gas in the furnace may flow back to a side of the raw material to cause explosion or combustion. It is possible to prevent such explosion and combustion by providing the raw material supply port 63 at a position higher than the surface of the fluidized bed. Particularly, it is desirable that the raw material supply port 63 is provided about 1 m to about 2 m above an interface of the fluidized bed in the gasification chamber 1.
An auxiliary fuel supply port (not shown) may be provided in the combustion chamber 2 for supplying auxiliary fuel when the furnace is started or the temperature of the fluidized bed is lowered.
As shown in FIG. 12, the combustion chamber 2 has a water supply port for supplying water W. A water supply nozzle is inserted through the water supply port from the outer wall of the combustion chamber 2 into the interior of the furnace. With such an arrangement, when the temperature of the fluidized bed is exessively increased by variation of properties of the raw material or changes of operation, water can be supplied directly to the fluidized bed without a heat recovery chamber. Accordingly, the temperature of the fluidized bed can be reduced. Further, a water spray device (not shown) is provided on the ceiling of the combustion chamber 2. When the temperature of the exhaust gas should be reduced, water is sprayed from the water spray device.
FIG. 13 is a cross-sectional front view taken along line XIII-XIII of FIG. 11. As shown in FIG. 13, the furnace bottoms 511 and 512 of the char combustion settling chambers near the partition walls 151 and 152 are located higher than the furnace bottoms 321 and 322 of the gasification chamber 1 near the partition walls 151 and 152. In the present embodiment, each of the char combustion settling chambers has a slope directed downward toward the gasification chamber 1 to provide height differences. However, the furnace bottoms may be in a stepped form.
The furnace bottoms 511, 512 and the furnace bottoms 321, 322 interpose the opening 251, 252 therebetween. As described above, weak fluidizing regions 2 a into which slow fluidizing gases are ejected are formed on the furnace bottoms 511 and 512. Further, intense fluidizing regions 1 b into which fast fluidizing gases are ejected are formed on the furnace bottoms 321 and 322.
As with the partition wall 11, each of the partition walls 151 and 152 has a portion DF projecting toward the freeboard at an intermediate portion of the furnace. The portions DF serve as deflectors for promoting an internal circulating flow in the gasification chamber 1. The deflectors DF are made of a refractory material. Downward slopes are formed from the char combustion settling chambers in the combustion chamber 2 toward the gasification chamber 1 so as to promote the movement of the fluidized medium. These slopes may be in a stepped form.
A nozzle (not shown) for supplying secondary air is provided at the freeboard of the combustion chamber 2 shown in FIG. 12. When a large amount of unburnt components scatters from the fluidized bed, secondary air is supplied to combust the unburnt components at the freeboard. The fluidized medium can be heated by radiation heat of the combustion. Further, a nozzle (not shown) for supplying steam may be provided at the freeboard of the gasification chamber 1. In this case, steam is supplied in addition to steam introduced as a fluidizing gas from the furnace bottom to promote a gasification reaction or shift reaction (CO+H₂O←→CO₂+H₂).
The aforementioned embodiments of the gasification furnace with furnace bottoms having height differences are summarized as follows.
(1) For example, as shown in FIG. 5, a fluidized medium is fluidized in a fluidized-bed system. The gasification furnace has a first chamber 1 including a first fluidized bed having a first interface and a second chamber 2 including a second fluidized bed having a second interface. The first chamber 1 and the second chamber 2 are partitioned by the partition wall 15 so that a gas does not flow vertically above the interfaces of the fluidized beds in the chambers. The partition wall 15 has a communication hole 25 formed at a lower portion thereof, which interconnects the first chamber 1 and the second chamber 2 to each other. The height of an upper end of the communication hole 25 is lower than the heights of the first interface and the second interface. The fluidized medium flows through the communication hole 25 from the second chamber 2 into the first chamber 1. The partition wall 15 is disposed between a first furnace bottom of the first chamber 1 and a second furnace bottom of the second chamber 2. The first furnace bottom of the first chamber 1 is located lower than the second furnace bottom of the second chamber 2.
Typically, two or more holes are formed as the communication hole (a first communication hole and a second communication hole). The fluidized medium is moved through one of the communication holes (first communication hole 25) from the second chamber 2 into the first chamber 1. The fluidized medium is moved through another of the communication holes (second communication hole 21) from the first chamber 1 into the second chamber 2. The furnace bottoms on both sides of the partition wall 15 having the communication hole (first communication hole) through which the fluidized medium flows from the second chamber 2 into the first chamber 1 have different heights so that the furnace bottom of the first chamber 1 is located lower than the furnace bottom of the second chamber 2.
With such an arrangement, since the furnace bottoms on both sides of the partition wall have different heights so that the furnace bottom of the first chamber 1 is located lower than the furnace bottom of the second chamber 2, the movement of the fluidized medium from the second chamber 2 into the first chamber 1 can be promoted.
(2) It is desirable that the fluidized medium is moved directly from the second chamber 2 into the first chamber 1 through the communication hole 25 formed at a lower portion of the partition wall 15 in the fluidized-bed system.
For example, direct movement of the fluidized medium means that when the second chamber comprises a char combustion chamber, the fluidized medium is moved directly from a portion of the char combustion chamber at which combustion is performed, without passing through a char combustion settling chamber in which combustion is not required to be performed. Since the furnace bottom of the first chamber 1 is located lower than the furnace bottom of the second chamber 2, the fluidized medium can smoothly be moved without a char combustion settling chamber.
(3) The first fluidized bed and the second fluidized bed may comprise a circulating fluidized bed in the fluidized-bed system.
In such a case, the fluidized medium is circulated in the circulating fluidized bed. Accordingly, when wastes or fuel is processed in the fluidized bed, the fluidized medium is likely to be brought into uniform contact with the wastes or fuel. Thus, the process efficiency can be enhanced. The fluidized medium is moved not only by vertical diffusion but also by horizontal diffusion. Accordingly, the fluidized medium is promoted to be mixed and circulated. Particularly, a circulating fluidized bed is formed in a space adjacent to the partition wall in the second chamber 2.
(4) Further, as shown in FIG. 5, a fluidized medium having a high temperature is fluidized in a gasification chamber 1 to form a fluidized bed having a first interface therein. Wastes or fuel A is gasified in the fluidized bed of the gasification chamber to produce a produced gas B. A fluidized medium having a high temperature is fluidized in a char combustion chamber 2 to form a fluidized bed having a second interface therein. Char H produced by gasification in the gasification chamber 1 is combusted in the fluidized bed of the char combustion chamber 2 to heat the fluidized medium. The gasification chamber 1 and the char combustion chamber 2 are partitioned by a partition wall 15 (or 11) so that a gas does not flow vertically above the interfaces of the fluidized beds in the respective chambers. The partition wall 15 (or 11) has a communication hole formed at a lower portion thereof, which interconnects the gasification chamber 1 and the char combustion chamber 2 to each other. The height of an upper end of the communication hole 25 (or 21) is lower than the heights of the first interface and the second interface. The fluidized medium flows through the communication hole 25 (or 21) from the char combustion chamber 2 into the gasification chamber 1 or from the gasification chamber 1 into the char combustion chamber 2. The partition wall 15 (or 11) is disposed between a first furnace bottom of the gasification chamber 1 and a second furnace bottom of the char combustion chamber 2. The furnace bottom 32 (or 52) downstream of the fluidized medium is located lower than the furnace bottom 51 (or 31) upstream of the fluidized medium. Circulating fluidized beds are formed within a space in the char combustion chamber 2 adjacent to the partition wall 15 (or 11) and within a space in the gasification chamber 1 adjacent to the partition wall 15 (or 11).
Typically, the fluidized medium may be moved through a communication hole from the char combustion chamber 2 into the gasification chamber 1 while the fluidized medium is moved through another communication hole from the gasification chamber 1 into the char combustion chamber 2.
Typically, the fluidized medium flowing from the char combustion chamber 2 into the gasification chamber 1 comprises a fluidized medium heated in the char combustion chamber 2. Further, the fluidized medium flowing from the gasification chamber 1 into the char combustion chamber 2 comprises a fluidized medium including char produced in the gasification chamber 1.
As described above, according to the present invention, the gasification chamber and the combustion chamber are configured so that no pyrolysis gas substantially flows between the gasification chamber and the combustion chamber. Thus, the gasification chamber and the combustion chamber are separated from each other so that gases are not mixed with each other. Further, the gasification chamber and the combustion chamber are partitioned by a partition wall having a first steel plate including a cooling structure. Accordingly, a lifetime of the partition wall can be prolonged in the gasification furnace.
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.

Claims

1. A gasification furnace comprising:

a gasification chamber for pyrolyzing a raw material in a fluidized medium being fluidized therein to produce a pyrolysis gas and a pyrolysis residue;

a combustion chamber for receiving the pyrolysis residue together with the fluidized medium, combusting the pyrolysis residue in the fluidized medium being fluidized therein to heat the fluidized medium, and returning the fluidized medium to said gasification chamber; and

a partition wall for separating said gasification chamber and said combustion chamber from each other, said partition wall including a first steel plate having a cooling structure to prevent the pyrolysis gas from flowing between said gasification chamber and said combustion chamber.

2. The gasification furnace as recited in claim 1, wherein said cooling structure is operable to cool said first steel plate by a cooling fluid.

3. The gasification furnace as recited in claim 1, further comprising:

a circumferential furnace wall for separating internal gases in said gasification chamber and said combustion chamber from an exterior of said gasification furnace, said circumferential furnace wall including a second steel plate and a refractory material covering an inner surface of said second steel plate.

4. The gasification furnace as recited in claim 3, wherein said cooling structure is operable to cool said first steel plate by a cooling fluid,

wherein said gasification furnace comprises a temperature controller operable to control a temperature of the cooling fluid so that a temperature of said partition wall is substantially equal to a temperature of said circumferential furnace wall.

5. The gasification furnace as recited in claim 1, wherein said partition wall has an opening through which the fluidized medium flows between said gasification chamber and said combustion chamber,

wherein said gasification chamber and said combustion chamber have furnace bottoms adjacent to said opening of said partition wall, respectively,

wherein said furnace bottom downstream of a flow of the fluidized medium is located lower than said furnace bottom upstream of the flow of the fluidized medium.

6. The gasification furnace as recited in claim 1, wherein said partition wall has an opening through which the fluidized medium flows from said gasification chamber into said combustion chamber,

wherein said furnace bottom of said combustion chamber is located lower than said furnace bottom of said gasification chamber.

7. The gasification furnace as recited in claim 1, wherein said partition wall has an opening through which the fluidized medium flows from said combustion chamber into said gasification chamber,

wherein said furnace bottom of said gasification chamber is located lower than said furnace bottom of said combustion chamber.