U.S. patent application number 11/178277 was filed with the patent office on 2007-01-18 for gasification furnace.
Invention is credited to Tatsuya Hasegawa, Hiroshi Hashimoto, Fumiaki Morozumi, Shinji Sekikawa.
Application Number | 20070012230 11/178277 |
Document ID | / |
Family ID | 37660501 |
Filed Date | 2007-01-18 |
United States Patent
Application |
20070012230 |
Kind Code |
A1 |
Hashimoto; Hiroshi ; et
al. |
January 18, 2007 |
Gasification furnace
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.
Inventors: |
Hashimoto; Hiroshi; (Tokyo,
JP) ; Sekikawa; Shinji; (Tokyo, JP) ;
Hasegawa; Tatsuya; (Tokyo, JP) ; Morozumi;
Fumiaki; (Tokyo, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
37660501 |
Appl. No.: |
11/178277 |
Filed: |
July 12, 2005 |
Current U.S.
Class: |
110/230 ;
110/342 |
Current CPC
Class: |
F23G 5/30 20130101; F23G
2201/303 20130101; F23G 5/027 20130101; C10B 49/22 20130101; F23G
5/16 20130101 |
Class at
Publication: |
110/230 ;
110/342 |
International
Class: |
F23G 5/00 20060101
F23G005/00; F23G 7/00 20060101 F23G007/00 |
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 gasification chamber and said combustion chamber have
furnace bottoms adjacent to said opening of said partition wall,
respectively, 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 gasification chamber and said combustion chamber have
furnace bottoms adjacent to said opening of said partition wall,
respectively, wherein said furnace bottom of said gasification
chamber is located lower than said furnace bottom of said
combustion chamber.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] 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.
[0003] 2. Description of the Related Art
[0004] 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.
[0005] 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
[0006] 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.
[0007] 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.
[0008] 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.
[0009] 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.
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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.
[0015] 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.
[0016] 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.
[0017] 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.
[0018] 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.
[0019] 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.
[0020] 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
[0021] FIG. 1 is a cross-sectional side view showing a conventional
gasification furnace;
[0022] FIG. 2A is a cross-sectional plan view showing a
gasification furnace according to a first embodiment of the present
invention;
[0023] FIG. 2B is an enlarged view of FIG. 2A;
[0024] FIG. 3 is a cross-sectional front view of the gasification
furnace shown in FIG. 2A;
[0025] FIG. 4 is a cross-sectional side view of the gasification
furnace shown in FIG. 2A;
[0026] FIG. 5 is a cross-sectional front view showing a
gasification furnace according to a second embodiment of the
present invention;
[0027] 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;
[0028] FIG. 7 is a cross-sectional front view showing a
gasification furnace according to a third embodiment of the present
invention;
[0029] FIG. 8 is a cross-sectional plan view showing a gasification
furnace according to a fourth embodiment of the present
invention;
[0030] FIG. 9 is a cross-sectional front view of the gasification
furnace shown in FIG. 8;
[0031] FIG. 10 is a partially cutaway perspective view showing a
gasification furnace according to a fifth embodiment of the present
invention;
[0032] FIG. 11 is a cross-sectional plan view of the gasification
furnace shown in FIG. 10;
[0033] FIG. 12 is a cross-sectional side view of the gasification
furnace shown in FIG. 10; and
[0034] FIG. 13 is a cross-sectional front view of the gasification
furnace shown in FIG. 10.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0035] 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.
[0036] 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).
[0037] 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 17a
made of a refractory material which is exposed to the interior of
the combustion chamber 2, an intermediate wall 17b made of a heat
insulating material, and an outer wall 17c 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 17a 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 17a is determined in a range of 100 to
150 mm. For example, the inner wall 17a has a thickness of 125 mm.
The inner wall 17a having a thickness in such a range is suitable
in consideration of strength and cost effectiveness. Nevertheless,
the inner wall 17a may be designed so as to be thicker or thinner
than this range. The inner wall 17a 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 17a is determined so that the inner wall 17a has
sufficient resistance to a hightemperature and abrasion.
[0038] The intermediate wall 17b 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 17c, 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 17b is determined in consideration of the design
temperature of steel and the temperature in the furnace. Further,
the thickness of the intermediate wall 17b depends upon the heat
conductivity of the heat insulating material. For example, the
thickness of the intermediate wall 17b 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.
[0039] The outer wall 17c is made of a steel plate (e.g., SS400
(JIS)) in order to protect the inner wall 17a and the intermediate
wall 17b. The outer wall 17c also serves to maintain sealing and
strength of the furnace.
[0040] 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.degree. C., an interface between the inner wall 17a and the
intermediate wall 17b has a temperature of about 600.degree. C.,
and the outer wall 17c has a temperature of about 100.degree. C.
The outer wall 17c hardly has a temperature difference between an
inner surface and an outer surface thereof because the outer wall
17c is made of a steel plate having a high heat conductivity.
[0041] 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.degree. C., which is
lower than the temperature of the combustion chamber 2 (800.degree.
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.degree. C. Accordingly, it is desirable
that the temperature of the freeboard is maintained at 500.degree.
C. or more.
[0042] 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 15c as a first
steel plate located at a central portion in a thickness direction
thereof. The membrane structure 15c has a plurality of water pipes
15e extending in a vertical direction and membranes (fins) 15d of
boiler steel plates connecting adjacent water pipes 15e. Each
membrane 15d is in the form of a flat plate. The membranes 15d are
welded to the water pipes 15e like fins of a frog.
[0043] Walls 15b made of a heat insulating material are disposed on
both sides of the membrane structure 15c in the thickness
direction. Further, walls 15a made of a refractory material are
disposed on both sides of the walls 15b in the thickness direction.
When the membrane structure 15c has a temperature of 100.degree.
C., interfaces between the heat insulating material walls 15b and
the refractory material walls 15a have a temperature of about
600.degree. C. A surface of the refractory material wall 15a facing
the interior of the combustion chamber 2 has a temperature of about
800.degree. C. A surface of the refractory material wall 15a facing
the interior of the gasification chamber 1 has a temperature of
about 700.degree. C.
[0044] The integrated gasification furnace 100 has a first
temperature sensor 211 for detecting a temperature of the membrane
15d and a second temperature sensor 212 for detecting a temperature
of the outer wall 17c.
[0045] The membrane structure 15c 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 15e extending in the
vertical direction is connected to a lower header 15g at a lower
end thereof and to an upper header 15f at an upper end thereof.
Water W for cooling is introduced from the lower header 15g into
the water pipes 15e. The water W passes through the water pipes 15e
and flows out of the upper header 15f. At that time, the water W
removes heat from the water pipes 15e and the membranes 15d. When
the water pipes 15e are arranged at small intervals so that the
membranes 15d have small widths, the water pipes 15e and the
membranes 15d have substantially the same temperature, e.g.,
100.degree. C., because the steel plate has a high heat
conductivity.
[0046] The integrated gasification furnace 100 includes a control
valve 214 provided at an inlet of the lower header 15g 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
15c is substantially equal to the temperature of the outer wall
17c. Materials and thicknesses of the inner wall 17a and the
intermediate wall 17b 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 17c is in a range of 70 to 100.degree. C. Accordingly, the
temperature of the membrane structure 15c is also controlled so as
to be approximately in a range of 70 to 100.degree. C. Because the
outer wall 17c 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.
[0047] 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 15c and the outer wall 17c have substantially
the same temperature. Even if the membrane structure 15c and the
outer wall 17c have different temperatures, it is desirable that a
temperature difference between the membrane structure 15c and the
outer wall 17c is not more than 60.degree. C.
[0048] In the illustrated example, the temperature of the membrane
structure 15c 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 15g
and an outlet of the upper header 15f. 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 15e, may be regarded as the temperature of the membrane
structure 15c 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.
[0049] When the membrane structure 15c is set to have a temperature
over 100.degree. C., evaporation of water W can be utilized. In
this case, the temperature of the membrane structure 15c can be
controlled by adjustment of a pressure of the water W.
[0050] Further, a heating medium having an evaporation temperature
lower than 100.degree. C. at 1 atmosphere can be used instead of
the water to maintain the membrane structure 15c from an inlet of
the heating medium to an outlet of the heating medium at a constant
temperature.
[0051] In the case where water is used as a cooling medium for the
membrane structure 15c, the water heated in the membrane structure
15c 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.
[0052] Not only liquid such as water but also gas may be used as a
cooling medium for the membrane structure 15c. Particularly, air is
suitable for the cooling medium for the membrane structure 15c. In
a case where air is used as a cooling medium for the membrane
structure 15c, the air heated in the membrane structure 15c 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 15c 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 15c, the membrane structure 15c should have a
structure suitable for the gas. For example, a cross section of the
membrane structure 15c is increased as compared to the length of
passages in the membrane structure 15c, or fins are provided in
passages for the gas.
[0053] 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 15e 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 15e. These water pipes 15e are also covered by a
heat insulating material and a refractory material.
[0054] 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 17a. It is desirable
that the refractory material has a higher pressure resistance (a
greater bearing capacity). The lower header 15g is embedded in the
furnace bottom 201.
[0055] 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.
[0056] 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.
[0057] 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.
[0058] 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
2b represents a flow velocity higher than a flow velocity
represented by a thinner arrow at a location 2a.
[0059] 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.
[0060] As with the first embodiment, the partition wall 15 includes
a membrane structure 15c (not shown), heat insulating material
walls 15b, and refractory material walls 15a. The walls 15b and 15a
interpose the membrane structure 15c 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
15c and the outer wall of the circumferential furnace wall 17, and
a temperature controller (not shown) for controlling temperatures
based on the detected temperature.
[0061] 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 2a is formed on the furnace bottom 51 by a
fluidizing gas ejected at a low flow velocity. An intense
fluidizing region 1b is formed on the furnace bottom 32 by a
fluidizing gas ejected at a high flow velocity.
[0062] 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 2b is formed on the furnace bottom 52 by a
fluidizing gas ejected at a high flow velocity. A weak fluidizing
region 1a is formed on the furnace bottom 31 by a fluidizing gas
ejected at a low flow velocity.
[0063] 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).
[0064] 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.
[0065] 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.
[0066] 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.
[0067] 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.
[0068] 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.
[0069] 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.
[0070] 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.
[0071] 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.
[0072] 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.
[0073] Fluidization of the fluidized medium and movement of the
fluidized medium between the respective chambers will be described
below.
[0074] The gasification chamber 1 includes an intense fluidizing
region 1b near the partition wall 15 between the gasification
chamber 1 and the char combustion chamber 2. The intense fluidizing
region 1b 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
1a is produced in addition to the intense fluidizing region 1b so
as to form a circulating flow in the gasification chamber 1.
[0075] The char combustion chamber 2 includes a weak fluidizing
region 2a at a central area and intense fluidizing regions 2b 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 2b 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.
[0076] 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.
[0077] 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.
[0078] 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.
[0079] 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.
[0080] 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.
[0081] 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.
[0082] 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 (CO.sub.2), 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.
[0083] 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.
[0084] 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.
[0085] 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.
[0086] 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.
[0087] 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.
[0088] 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.
[0089] 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.
[0090] 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.
[0091] 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.
[0092] 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.
[0093] 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.
[0094] 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 CO.sub.2, H.sub.2O, and N.sub.2 can be obtained
without necessity of partial combustion in the gasification chamber
1.
[0095] 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.
[0096] 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 35a 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 35a is located downstream of the
communication hole 25 (in the gasification chamber 1). Similarly,
the gasification furnace 102 includes a steam supply port 35b 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
35b is located downstream of the communication hole 21 (in the char
combustion chamber 2).
[0097] 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.
[0098] In the present embodiment, steam is supplied from the steam
supply port 35a 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.
[0099] 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.
[0100] In the present embodiment, steam is supplied from the steam
supply port 35b 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.
[0101] 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.
[0102] 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.
[0103] In the present embodiment, the partition walls 14 in the
fluidized beds may be eliminated to simplify the gasification
furnace 102.
[0104] 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.
[0105] 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.
[0106] The partition walls 15, 16, and 11 have a cooling structure
including a membrane structure, as with the first, second, and
third embodiments.
[0107] 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 2a and base portions 52 and 54 for
intense fluidizing regions 2b 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 1a and base portions 32 and 34 for
intense fluidizing regions 2b 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.
[0108] 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.
[0109] 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.
[0110] 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.
[0111] 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.
[0112] 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.
[0113] 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.
[0114] 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.
[0115] 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.
[0116] 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.
[0117] 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.
[0118] The flow of the fluidized medium can be smoothened and
smoothly circulated even without a char combustion settling
chamber.
[0119] 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.
[0120] 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.
[0121] 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.
[0122] 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.
[0123] 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.
[0124] 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.
[0125] 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.
[0126] 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.
[0127] 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.
[0128] 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.
[0129] 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.
[0130] 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.
[0131] 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.
[0132] As shown in FIG. 11, the furnace bottom of the char
combustion chamber 2 is rectangular in the plan view. An intense
fluidizing region 2b is formed on the furnace bottom 52 adjacent to
the partition wall 11. A weak fluidizing region 2a 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
2a are formed on the furnace bottoms 511 and 512 in the settling
chamber.
[0133] The furnace bottom of the gasification chamber 1 is
rectangular in the plan view. Intense fluidizing regions 1b are
formed on the furnace bottoms 321 and 322 adjacent to the partition
walls 151 and 152. A weak fluidizing region 1a is formed on a
central portion 31 of the gasification chamber 1 away from the
partition walls 151 and 152, which face each other.
[0134] 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.
[0135] 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.
[0136] 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 2b into which a fluidizing gas is strongly
ejected is formed on the furnace bottom 52. A weak fluidizing
region 1a into which a fluidizing gas is weakly ejected is formed
on the furnace bottom 31.
[0137] 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.
[0138] Further, an incombustible withdrawing port 33a 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 33a 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 33a is connected via an incombustible introduction
passage 33b to an incombustible discharge port 33 for discharging
the incombustibles to the exterior of the furnace.
[0139] 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 33b, 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.
[0140] 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.
[0141] 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.
[0142] 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.
[0143] In the present embodiment, the furnace bottom of the
combustion chamber 2 has a slope directed downward toward the
incombustible withdrawing port 33a so as to improve the capability
of discharging incombustibles.
[0144] 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.
[0145] The furnace bottom 31 of the gasification chamber 1 on which
a weak fluidizing region 2a 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.
[0146] 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.
[0147] 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.
[0148] 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.
[0149] 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.
[0150] 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.
[0151] The furnace bottoms 511, 512 and the furnace bottoms 321,
322 interpose the opening 251, 252 therebetween. As described
above, weak fluidizing regions 2a into which slow fluidizing gases
are ejected are formed on the furnace bottoms 511 and 512. Further,
intense fluidizing regions 1b into which fast fluidizing gases are
ejected are formed on the furnace bottoms 321 and 322.
[0152] 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.
[0153] 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+H.sub.2O.rarw..fwdarw.CO.sub.2+H.sub.2).
[0154] The aforementioned embodiments of the gasification furnace
with furnace bottoms having height differences are summarized as
follows.
[0155] (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.
[0156] 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.
[0157] 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.
[0158] (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.
[0159] 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.
[0160] (3) The first fluidized bed and the second fluidized bed may
comprise a circulating fluidized bed in the fluidized-bed
system.
[0161] 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.
[0162] (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).
[0163] 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.
[0164] 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.
[0165] 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.
[0166] 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.
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