Note: Descriptions are shown in the official language in which they were submitted.
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1
DESCRIPTION
SLAGGING COMBUSTION FURNACE
Technical Field
The present invention relates to a waste treatment
system for treating wastes including municipal wastes,
industrial wastes, biomass wastes, medical wastes, automobile
wastes such as waste tires or shredder dust, and the like,
and more particularly to a slagging combustion furnace and a
method of supplying gas for combustion in the slagging
combustion furnace in a gasification and slagging combustion
system in which the above wastes are gasified to produce
combustible gas in a gasification furnace, and the produced
combustible gas is combusted or gasified together with
unburned carbon accompanied by the produced combustible gas
to generate ash or molten slag in a swirling-type slagging
combustion furnace.
Background Art
FIG. 1 of the accompanying drawings schematically
shows essential elements of a conventional gasification and
slagging combustion system having a waste heat boiler. As
shown in FIG. 1, the conventional gasification and slagging
combustion system comprises a waste supply device 1, a
fluidized-bed gasification furnace 2, and a swirling-type
slagging combustion furnace 3 having a primary combustion
chamber 4, a secondary combustion chamber 5, and a tertiary
combustion chamber 6. The gasification and slagging
combustion system further comprises a waste heat boiler 7, an
economizer 8, a bag filter 9, an exhaust gas reheater 10, a
catalytic reaction tower 11, and a stack 12.
The conventional gasification and slagging
combustion system shown in FIG. 1 operates as follows:
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Wastes a supplied from the waste supply device 1 into the
fluidized-bed gasification furnace 2 are pyrolyzed and
gasified to produce combustible gas b in a fluidized bed
where a fluidized medium c (such as sand) is fluidized by
fluidizing air g introduced from a bottom of the fluidized-
bed gasification furnace 2. The gas b produced in the
fluidized-bed gasification furnace 2 is introduced into the
swirling-type slagging combustion furnace 3. In the
swirling-type slagging combustion furnace 3, the produced gas
b is mixed with gas f for combustion in the primary
combustion chamber 4 and combusted at a high temperature of
about 1350°C in the secondary combustion chamber 5 to combust
char contained in the produced gas b, thus melting ash
contained in the char. The produced gas b is further mixed
with gas f for combustion in the tertiary combustion chamber
6 and combusted therein to generate exhaust gas e. The
exhaust gas a having a high temperature of about 1350°C is
then introduced into the waste heat boiler 7. Incombustibles
d which are contained in the wastes a and are not gasified
are discharged from the lower part of the fluidized bed in
the fluidized-bed gasification furnace 2 to the outside. The
ash melted in the swirling-type slagging combustion furnace 3
is discharged as molten slag h from the swirling-type
slagging combustion furnace 3 to the outside.
The high-temperature exhaust gas a passes
successively through the waste heat boiler 7 and the
economizer 8, and thus is cooled to a temperature of about
160°C. The cooled exhaust gas a is introduced into the bag
filter 9 where dust such as fly ash contained in the exhaust
gas a is removed. Then, the exhaust gas a is preheated to a
temperature (200°C to 210°C) enough to cause a catalytic
reaction. NOx and SOx contained in the exhaust gas a are
removed through a reaction with ammonia in the catalytic
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reaction tower 11, and then the exhaust gas a is discharged
from the stack 12 into the atmosphere. On the other hand,
steam produced in the waste heat boiler 7 is supplied to a
steam turbine ( not shown ) coupled to a generator to generate
electric power. The generated electric power is used for
operating various equipment in the gasification and slagging
combustion system to save energy and also to reduce the
running cost.
As shown in FIGS. 2A and 2B of the accompanying
drawings, the produced gas b from the fluidized-bed
gasification furnace 2 is introduced into the primary
combustion chamber 4 of the swirling-type slagging combustion
furnace 3 in a direction tangential to an inner wall surface
thereof from a high-temperature duct 21 connected to a gas
inlet port 20 defined in an upper portion of the inner wall
surface of the primary combustion chamber 4, thus generating
a swirling flow of the gas in the primary combustion chamber
4. The gas f for combustion is supplied to the produced gas
b in the primary combustion chamber 4 at a certain angle to
the swirling flow of the produced gas b from a plurality of
(eight in FIGS. 2A and 2B) gas supply nozzles 22 which are
mounted on the side wall of the primary combustion chamber 4
and are open at the inner wall surface of the primary
combustion chamber 4 downstream of the gas inlet port 20.
Thus, the produced gas b is mixed with the gas f for
combustion, and combusted at a high temperature in the
secondary combustion chamber 5 and the tertiary combustion
chamber 6. The primary combustion chamber 4 has a burner 23
mounted on its top wall for assisting the combustion of the
produced gas b in the primary combustion chamber 4.
The structure shown in FIGS. 2A and 2B is
disadvantageous in that, as shown in FIGS. 3A and 3B, a
clinker K, which is made from the melted ash, is adhered (or
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attached) to and deposited on the inner wall surface of the
primary combustion chamber 4 in the vicinity of the gas
supply nozzles 22, where the gas is in the state within a
transitional temperature range, which is uncertain range,
between melting and solidifying of solid material
constituting the ash in the gas.
More specifically, molten slag is produced at a
temperature of 1300°C, preferably around 1350°C for the
quality of slag.
If the combustible gas containing lots of solid
material exists around this nozzle 22 in the space which is
within the transitional temperature between melting and
solidifying of solid material constituting the ash in the
gas. In the transitional temperature, a part of the ash in
the gas is in a melting state, and a part of the ash remains
in a solid state. Because the ambient temperature of the
solid material is lower than the start temperature of slag
formation, for example, 1300°C and higher than the start
temperature of slag fusion, for example, 1000°C, the melting
state and the solid state of the material occur, and the
material becomes highly viscous. Therefore, such material is
liable to be adhered or attached to the inner wall surface.
That is a reason of the making formation of the clinker-like
material around the nozzle.
In order to prevent the clinker-like material from
being formed, it is ideal that there is no gas at the
transition temperature range. However, actually, the gas
introduced from the gasification furnace and having a
temperature of around 650°C up to 800°C should inevitably
pass through the transitional temperature range because the
gas reaches an available melting temperature of slag over
1300°C. Thus, the existence of the transitional temperature
range has a great effect on clogging of the gas supply
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nozzles 22 or the primary combustion chamber 4. When the gas
supply nozzles 22 or the primary combustion chamber 4 is
clogged, the gasification and slagging combustion system
fails to operate normally.
5
Disclosure of Invention
The present invention has been made in view of the
above drawbacks. It is therefore an object of the present
invention to provide a slagging combustion furnace for use in
a gasification and slagging combustion system which can
prevent a clinker from being adhered to an inner wall surface
of the slagging combustion furnace for thereby preventing
supply nozzles for supplying gas for combustion such as
combustion air and a primary combustion chamber from being
clogged, and allows the gasification and slagging combustion
system to operate continuously stably.
Another object of the present invention is to
provide a method of supplying gas for combustion into such
slagging combustion furnace.
In order to achieve the above object of the
present invention, according to an aspect of the present
invention, there is provided a slagging combustion furnace
comprising: a side wall and a top wall; a gas inlet port
formed in an upper portion of the side wall for introducing
combustible gas to produce a swirling flow of the combustible
gas; and a plurality of gas supply nozzles, which are open at
an inner surface of the side wall and an inner surface of the
top wall, for supplying gas for combustion; wherein the gas
for combustion is blown from the gas supply nozzles into the
swirling flow of the combustible gas.
According to the present invention, the gas for
combustion is blown from the gas supply nozzles which are
open at the inner surface of the side wall and the inner
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surface of the top wall, into the produced combustible gas to
mix the gas for combustion well with the produced gas for
thereby increasing the temperature of the gas quickly and
minimizing the time of the gas which passes through the
transitional temperature range, i.e., allowing the gas to
pass through such transitional temperature range as quickly
as possible, and minimizing the space, in the slagging
combustion furnace, where the atmosphere is within the
transitional temperature range, i.e., making such space as
small as possible. With this specific arrangement of the
present invention, the surface area of adhesion or attachment
of clinker to the inner wall of the slagging combustion
furnace is minimized, resulting in the prevention of adhesion
or attachment to the inner wall surface of the slagging
combustion furnace. As a result, a clinker is prevented from
being adhered (or attached) to the inner wall surface of the
slagging combustion furnace.
According to another aspect of the present
invention, there is provided a slagging combustion furnace
comprising: a side wall and a top wall; a gas inlet port
formed in an upper portion of the side wall for introducing
combustible gas to produce a swirling flow of the combustible
gas; and a gas supply nozzle, which is open at an inner
surface of the side wall near the gas inlet port, for
supplying the combustible gas; wherein the gas for combustion
is blown from the gas supply nozzle into the combustible gas
introduced from the gas inlet port.
According to the present invention, the gas for
combustion is blown from the gas supply nozzle which is open
at the inner surface of the side wall near the gas inlet port
for supplying the produced gas to mix the gas for combustion
well with the produced gas for thereby increasing the
temperature of the gas quickly and minimizing the time of the
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gas which passes through the transitional temperature range,
i.e., allowing the gas to pass through such transitional
temperature range as quickly as possible, and minimizing the
space, in the slagging combustion furnace, where the
atmosphere is within the transitional temperature range,
i.e., making such space as small as possible. With this
specific arrangement of the present invention, the surface
area of adhesion or attachment of clinker to the inner wall
of the slagging combustion furnace is minimized, resulting in
the prevention of adhesion or attachment to the inner wall
surface of the slagging combustion furnace. As a result, a
clinker is prevented from being adhered or attached to the
inner wall surface of the slagging combustion furnace.
According to a preferred aspect of the present
invention, the gas supply nozzle forms a swirling flow of the
gas for combustion.
Because the gas for combustion is introduced from
the gas supply nozzle as a swirling flow into the produced
gas, the gas for combustion is mixed well with the produced
gas for thereby increasing the temperature of the gas quickly
and minimizing the time of the gas which passes through the
transitional temperature range, i.e., allowing the gas to
pass through such transitional temperature range as quickly
as possible, and minimizing the space, in the slagging
combustion furnace, where the atmosphere is within the
transitional temperature range, i.e., making such space as
small as possible. With this specific arrangement of the
present invention, the surface area of adhesion or attachment
of clinker to the inner wall of the slagging combustion
furnace is minimized, resulting in the prevention of adhesion
or attachment to the inner wall surface of the slagging
combustion furnace. As a result, a clinker is further
prevented from being adhered to the inner wall surface of the
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slagging combustion furnace.
According to another aspect of the present
invention, there is provided a slagging combustion furnace
comprising: a side wall and a top wall; a gas inlet port
formed in the side wall for introducing combustible gas; and
a gas supply nozzle, which is open at an inner surface of the
side wall near the gas inlet, for supplying the combustible
gas; wherein the gas for combustion is blown from the gas
supply nozzle into the combustible gas introduced from the
gas inlet port.
According to another aspect of the present
invention, there is provided a method of supplying gas for
combustion into a slagging combustion furnace, the method
comprising: introducing combustible gas from a gas inlet port
formed in an upper portion of a side wall of the slagging
combustion furnace to produce a swirling flow of the
combustible gas; and introducing gas for combustion from a
plurality of gas supply nozzles which are open at an inner
surface of the side wall and an inner surface of a top wall,
into the swirling flow of the combustible gas.
According to the present invention, because the
gas for combustion is introduced from the gas supply nozzles
which are open at the inner surface of the side wall and the
inner surface of the top wall of the slagging combustion
furnace, into the swirling flow of the produced gas, a
clinker is prevented from being adhered to the side and top
walls of the slagging combustion furnace.
According to a preferred aspect of the present
invention, a method of supplying gas for combustion into a
slagging combustion furnace further comprises introducing gas
for combustion from a gas supply nozzle which is.open at an
inner surface of the side wall near the gas inlet port, into
the combustible gas.
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According to the present invention, because the
gas for combustion is introduced from the gas supply nozzle
which is open at the inner surface of the side wall near the
gas inlet port, into the produced gas, a clinker is further
prevented from being adhered to the side and top walls of the
primary combustion chamber of the slagging combustion
furnace.
According to another aspect of the present
invention, there is provided a method of supplying gas into a
slagging combustion furnace comprising a primary combustion
chamber, a secondary combustion chamber coupled to the
primary combustion chamber, and a tertiary combustion chamber
coupled to the secondary combustion chamber, the method
comprising: introducing combustible gas produced at an air
ratio ranging from 0.2 to 0.3 from a gas inlet port formed in
an upper portion of a side wall of the primary combustion
chamber; and adjusting the amount of gas for combustion
introduced respectively into the primary combustion chamber,
the secondary combustion chamber, and the tertiary combustion
chamber such that the air ratio in an upper portion of the
primary combustion chamber is approximately 1Ø
According to a preferred aspect of the present
invention, the tertiary combustion chamber is adjusted such
that the air ratios in the secondary and tertiary combustion
chambers increase from 1.0 to 1.5.
According to the present invention, the air ratio
in the upper portion of the primary combustion chamber is
approximately 1.0, and hence the temperature in the primary
combustion chamber near the gas inlet port for introducing
the produced gas is maintained at a high value of about
1300°C, thus minimizing the time of the gas which passes
through the transitional temperature range, i.e., allowing
the gas to pass through such transitional temperature range
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as quickly as possible, and minimizing the space, in the
slagging combustion furnace, where the atmosphere is within
the transitional temperature range, i.e., making such space
as small as possible. With this specific arrangement of the
5 present invention, the surface area of adhesion or attachment
of clinker to the inner wall of the slagging combustion
furnace is minimized, resulting in the prevention of adhesion
or attachment to the inner wall surface of the slagging
combustion furnace. If the air ratio were greater than 1.0,
10 the temperature in the primary combustion chamber is lowered,
thus tending to approach to the temperature range in which a
clinker is adhered to the inner wall surface of the primary
combustion chamber. Further, the amount of gas for
combustion is adjusted such that the air ratios in the
secondary and tertiary combustion chambers increase
progressively from 1.0 to 1.5, and hence the produced gas and
unburned materials such as char contained therein are
completely combusted, and the temperature in the slagging
combustion furnace is kept at a high value for thereby
increasing the percentage of slagging.
According to still another aspect of the present
invention, there is provided a gasification and slagging
combustion system comprising: a fluidized-bed gasification
furnace for gasifying wastes to produce combustible gas; and
a slagging combustion furnace for combusting the combustible
gas and melting ash contained in the combustible gas to
generate molten slag; the slagging combustion furnace
comprising: a side wall and a top wall; a gas inlet port
formed in an upper portion of the side wall fox introducing
combustible gas to produce a swirling flow of the combustible
gas; and a plurality of gas supply nozzles, which are open at
an inner surface of the side wall and an inner surface of the
top wall, for supplying gas for combustion; wherein the gas
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for combustion is blown from the gas supply nozzles into the
swirling flow of the combustible gas.
According to still another aspect of the present
invention, there is provided a gasification and slagging
combustion system comprising: a fluidized-bed gasification
furnace for gasifying wastes to produce combustible gas; and
a slagging combustion furnace for combusting the combustible
gas and melting ash contained in the combustible gas to
generate molten slag; the slagging combustion furnace
comprising: a side wall and a top wall; a gas inlet port
formed in an upper portion of the side wall for introducing
combustible gas to produce a swirling flow of the combustible
gas; and a gas supply nozzle, which is open at an inner
surface of the side wall near the gas inlet port, for
supplying gas for combustion; wherein the gas for combustion
is blown from the gas supply nozzle into the combustible gas
introduced from the gas inlet port.
The above and other objects, features, and
advantages of the present invention will become 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 Drawings
FIG. 1 is a schematic diagram of essential
elements of a conventional gasification and slagging
combustion system having a waste heat boiler;
FIG. 2A is a side elevational view of a slagging
combustion furnace in the conventional gasification and
slagging combustion system;
FIG. 2B is a plan view of a primary combustion
chamber of the slagging combustion furnace shown in FIG. 2A;
FIG. 3A is a cross-sectional view taken along line
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A-A of FIG. 3B;
FIG. 3B is a plan view showing how a clinker
is
adhered to and deposited on an inner wall surface
of the
primary combustion chamber of the slagging combustion
furnace
shown in FIG. 2A;
FIG. 4A is a side elevational view of a slagging
combustion furnace in a gasification and slagging combustion
system according to an embodiment of the present
invention;
FIG. 4B is a plan view of a primary combustion
chamber of the slagging combustion furnace shown FIG. 4A;
in
FIG. 5A is a side elevational view of a slagging
combustion furnace in a gasification and slagging combustion
system according to another embodiment of the present
invention;
FIG. 5B is a plan view of a primary combustion
chamber of the slagging combustion furnace shown FIG. 5A;
in
FIG. 6A is a side elevational view of a slagging
combustion furnace in a gasification and slagging combustion
system according to still another embodiment of
the present
invention;
FIG. 6B is a plan view of a primary combustion
chamber of the slagging combustion furnace shown FIG. 6A;
in
FIG. 7A is a side elevational view of a slagging
combustion furnace in a gasification and slagging combustion
system according to still another embodiment of
the present
invention;
FIG. 7B is a plan view of a primary combustion
chamber of the slagging combustion furnace shown FIG. 7A;
in
FIG. 8 is a view showing a gas supply nozzle for
supplying. gas for combustion used in the slagging combustion
furnace according to the present invention;
FIG. 9A is a side elevational view, partly in
cross section, of a swirler of the gas supply nozzle
shown in
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FIG. 8;
FIG. 9B is a front elevational view of the swirler
shown in FIG. 9A;
FIG. 10A is a side elevational view of a system
for introducing gas for combustion into combustion chambers
of the slagging combustion furnace according to the present
invention; and
FIG. lOB is a cross-sectional view taken along
line A-A of FIG. 10A.
Best Mode for Carrying Out the Invention
A slagging combustion furnace according to
embodiments of the present invention will be described below
with reference to the drawings. FIGS. 4A and 4B through 10A
and 10B show slagging combustion furnaces in a gasification
and slagging combustion system according to various
embodiments of the present invention. Those parts of the
slagging combustion furnaces shown in FIGS. 4A and 4B through
10A and 10B which are identical to those of the conventional
slagging combustion furnace shown in FIGS. 2A and 2B are
denoted by identical. reference numerals, and will not be
described in detail below.
FIGS. 4A and 4B show a slagging combustion furnace
in a gasification and slagging combustion system according to
an embodiment of the present invention. As shown in FIGS. 4A
and 4B, the slagging combustion furnace comprises a swirling-
type slagging combustion furnace 3 having a primary
combustion chamber 4, a secondary combustion chamber 5, and a
tertiary combustion chamber 6.
The swirling-type slagging combustion furnace 3
has a high-temperature duct 21 connected to a gas inlet port
2 0 def fined in an upper portion of the inner wall surface of
the primary combustion chamber 4. The high-temperature duct
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21 serves to introduce the produced gas b supplied from the
fluidized-bed gasification furnace 2 (see FIG. 1).
Simultaneously, supplying a gas for combustion into the flow
of the produced gas b is performed in a direction so as to be
substantially along the flow of the produced gas b at the
introductory part of the produced gas b in the slagging
combustion furnace 3. That is, the gas for combustion is
introduced into the flow of the produced gas b so as to flow
in the identical direction or in substantially the same
direction as the produced gas b. The swirling-type slagging
combustion furnace 3 also has a plurality of (six in FIGS. 4A
and 4B) gas supply nozzles 24 which are mounted on the top
wall of the primary combustion chamber 4 and are open at the
inner wall surface of the primary combustion chamber 4, and a
plurality of (four in FIGS. 4A and 4B) gas supply nozzles 25
which are mounted on the side wall of the primary combustion
chamber 4 and are open at the inner wall surface of the
primary combustion chamber 4 near the gas inlet port 20.
The gas supply nozzles for supplying gas for
combustion are disposed at the introduction part of the
produced gas b supplied from the gasification furnace in the
slagging combustion furnace. The amount of the gas for
combustion supplied from the gas supply nozzles is such an
amount that the supplied produced gas is substantially
completely combusted ( in case of air, the air ratio is 1. 0 ) ,
and hence combustion of the produced gas caused by supply of
the gas for combustion raises rapidly the ambient temperature
of the introduction part in the slagging combustion furnace
to 1350°C. Therefore, the number of the gas supply nozzles
is different depending on the size of the system and is not
so important, and may be one or two or more.
In the swirling-type slagging combustion furnace 3
having the above structure, the produced gas b is introduced
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from the high-temperature duct 21 through the gas inlet port
into the primary combustion chamber 4 to generate a
swirling flow of the produced gas b therein. At the same
time, gas f fox combustion comprising air, oxygen-enriched
5 air, or oxygen is introduced from the gas supply nozzles 24
whose tip ends are open at the inner wall surface of the top
wall, into the swirling flow in a direction perpendicular to
the swirling flow of the produced gas b. Further, gas f for
combustion is introduced from the gas supply nozzles 25 whose
10 tip ends are open at the inner wall surface of the side wall,
into the swirling flow of the produced gas b at a certain
angle to the swirling flow. Since the gas f for combustion
is introduced from the gas supply nozzles 24 and 25 on the
top and side walls of the primary combustion chamber 4, it is
15 well mixed with the produced gas b, thus allowing the
produced gas b to be combusted quickly and achieving
temperature rise quickly, and minimizing the time of the gas
which passes through the transitional temperature range,
i.e., allowing the gas to pass through such transitional
20 temperature range as quickly as possible, and minimizing the
space, in the slagging combustion furnace, where the
atmosphere is within the transitional temperature range,
i.e., making such space as small as possible. With this
specific arrangement of the present invention, the surface
area of adhesion or attachment of clinker to the inner wall
of the slagging combustion furnace is minimized, resulting in
the prevention of adhesion or attachment to the inner wall
surface of the primary combustion chamber 4 and furthermore
the inner wall surface toward the outlet where the melted ash
(i.e. slag) is discharged.
FIGS. 5A and 5B show a slagging combustion furnace
in a gasification and slagging combustion system according to
another embodiment of the present invention. The slagging
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combustion furnace shown in FIGS. 5A and 5B differs from the
slagging combustion furnace shown in FIGS. 4A and 4B in that
it additionally has a vertical array of (three in FIGS. 5A
and 5B) gas supply nozzles 26 which are mounted on the side
wall of the primary combustion chamber 4 and are open at the
inner wall surface of the primary combustion chamber 4 on one
side of the gas inlet port 20 in the vicinity of the gas
inlet port 20. The gas supply nozzles 26 serve to introduce
gas f for combustion comprising air, oxygen-enriched air, or
oxygen so as to be across the gas inlet port 20. In the case
where the produced gas b has a low calorific value, as the
content of NZ which is not related to the combustion is low,
the gas f for combustion supplied from the gas supply nozzles
26 allows the produced gas b to be combusted efficiently for
thereby achieving high temperature quickly. In addition to
the advantages offered by the slagging combustion furnace
shown in FIGS. 4A and 4B, the slagging combustion furnace
shown in FIGS. 5A and 5B also offers the advantage that it is
capable of preventing a clinker from being adhered to the
vicinity of the gas inlet port 20.
FIGS. 6A and 6B show a slagging combustion furnace
in a gasification and slagging combustion system according to
still another embodiment of the present invention. The
slagging combustion furnace shown in FIGS. 6A and 6B differs
from the slagging combustion furnace shown in FIGS. 5A and 5B
in that it additionally has two vertical arrays of (six in
FIGS. 6A and 6B) gas supply nozzles 26 and 27 which are
mounted on the side wall of the primary combustion chamber 4
and are open at the inner wall surface of the primary
combustion chamber 4 on both sides of the gas inlet port 20
in the vicinity of the gas inlet port 20. The gas supply
nozzles 26 serve to introduce the gas f for combustion
comprising air, oxygen-enriched air, or oxygen so as to be
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across the gas inlet port 20, and the gas supply nozzles 27
serve to introduce the gas f for combustion at a certain
angle to the swirling flow of the produced gas b. In
addition to the advantages offered by the slagging combustion
furnace shown in FIGS. 5A and 5B, the slagging combustion
furnace shown in FIGS. 6A and 6B also offers the advantage
that it is capable of effectively preventing a clinker from
being attached to the inner wall surface of the primary
combustion chamber 4 in the vicinity of the gas inlet port
20.
FIGS. 7A and 7B show a slagging combustion furnace
in a gasification and slagging combustion system according to
still another embodiment of the present invention. The
slagging combustion furnace shown in FIGS. 7A and 7B differs
from the slagging combustion furnace shown in FIGS. 6A and 6B
in that the gas supply nozzles 27 have tip ends 27a bent so
as to cause the gas f for combustion introduced therefrom to
flow in substantially the same direction as the produced gas
b introduced from the gas inlet port 20. In addition to the
advantages offered by the slagging combustion furnace shown
in FIGS. 6A and 6B, the slagging combustion furnace shown in
FIGS. 7A and 7B also offers the advantage that it is capable
of more effectively preventing a clinker from being adhered
to the inner wall surface of the primary combustion chamber 4
in the vicinity of the gas inlet port 20.
FIGS. 8, 9A and 9B show one of the gas supply
nozzles 25 which supply gas for combustion and are identical
to each other. As shown in FIG. 8, the gas supply nozzle 25
has an outer tube 25a, an inner tube 25c disposed in the
outer tube 25a, and a swirler 25b attached to a distal end of
the inner tube 25c. An outlet tube 25e is connected to the
swirler 25d and disposed in the outer tube 25a which is open
at the inner wall surface of the primary combustion chamber
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4. A gas inlet tube 25g for introducing the gas f for
combustion is connected to the outer tube 25a, and the outer
tube 25a has a rear end closed by a lid 25b remotely from the
primary combustion chamber 4.
As shown in FIGS. 9A and 9B, the swirler 25d
comprises a boss 25d-3 fixed to the tip end of the inner tube
25c, a ring plate 25d-1 disposed around the boss 25d-3, and a
plurality of swirling vanes 25d-2 disposed between and joined
to the boss 25d-3 and the ring plate 25d-1 for producing a
swirling flow of the gas for combustion.
The gas supply nozzle 25 operates as follows: The
gas f for combustion introduced from the gas inlet tube 25g
passes through the gap between the outer tube 25a and the
inner tube 25c to the swirler 25d, and is turned by the
swirling vanes 25d-2 into a helical swirling flow. Then, the
gas f for combustion is introduced in the swirling flow
through the outlet tube 25e into the primary combustion
chamber 4.
Since the gas f for combustion is introduced as a
swirling flow from the gas supply nozzle 25 into the primary
combustion chamber 4, the gas f for combustion is well mixed
with the produced gas b, thus allowing the produced gas b to
be combusted quickly and achieving temperature rise quickly..
Consequently, the temperature range in which a clinker is
adhered to the inner wall surface of the primary combustion
chamber 4 is minimized. Each of the gas supply nozzles 24,
26 and 27 described above should preferably be of a structure
identical or similar to the gas supply nozzle 25 shown in
FIGS. 8, 9A and 9B.
In each of the above embodiments, the swirling-
type slagging combustion furnace 3 is of a substantially U-
shaped configuration in which the primary combustion chamber
4, the secondary combustion chamber 5, and the tertiary
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combustion chamber 6 are successively arranged. However, the
swirling-type slagging combustion furnace according to the
present invention is not limited to the illustrated
structure, but may be of any structure capable of introducing
produced combustible gas from a gas inlet port in a side wall
thereof and generating a swirling flow of the produced
combustible gas.
FIGS. 10A and 10B show a system for introducing
gas for combustion into the combustion chamber of the
slagging combustion furnace according to the present
invention. FIG. 10A is a side cross-sectional view of the
slagging combustion furnace, and FIG. 10B is a cross-
sectional view taken along line A-A. As shown in FIG. 10A,
the system includes a blower 30 for supplying gas f (mainly
air) for combustion, a damper 31 connected to the blower 30,
and flow control valves 32, 33, 34 and 35 connected to the
damper 31 for supplying the gas f for combustion to the gas
inlet port 20, the primary combustion chamber 4 coupled to
the gas inlet port 20, the secondary combustion chamber 5
coupled to the primary combustion chamber 4, and the tertiary
combustion chamber 6 coupled to the secondary combustion
chamber 5.
As shown in FIG. 10B, the produced gas b flows
through the high-temperature duct 21 and is introduced from
the gas inlet port 20 at a speed of 15 m/s to 25 m/s,
preferably 18 m/s to 20 m/s into the primary combustion
chamber 4, and the gas f for combustion is introduced from
the gas supply nozzles 26 and 27 into the gas inlet port 20,
thereby forming flames 39 in the primary combustion chamber 4
of the swirling-type slagging combustion furnace 3. The gas
f for combustion is blown such that the air ratio A~R in the
upper portion of the primary combustion chamber 4 is in the
range of 0.8 to 1.1, preferably 0.9 to 1Ø The air ratio is
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defined as the ratio of the amount of supplied air to the
amount of air, which is set to 1.0, required to completely
convert combustibles in the wastes into HZO and C02 by way of
combustion.
5 With the gas f for combustion thus introduced, the
temperature in the primary combustion chamber 4 including the
area near the gas inlet port 20 can be maintained at a high
value of about 1300°C or higher, thus minimizing the time of
the gas which passes through the transitional temperature
10 range, i.e., allowing the gas to pass through such
transitional temperature range as quickly as possible, and
minimizing the space, in the slagging combustion furnace,
where the atmosphere is within the transitional temperature
range, i.e., making such space as small as possible. With
15 this specific arrangement of the present invention, the
surface area of adhesion or attachment of clinker to the
inner wall of the slagging combustion furnace is minimized,
resulting in the prevention of adhesion or attachment to the
inner wall surface of the slagging combustion furnace. If
20 the air ratio were greater than 1.0, the amount of air which
does not contribute to combustion would increase, and the
cooling effect caused by air would also increase, thus
lowering the temperature in the primary combustion chamber 4
and tending to expand the temperature range in which a
clinker is adhered to the inner wall surface of the primary
combustion chamber 4.
The air ratio A~R is increased successively in the
secondary combustion chamber 5 and the tertiary combustion
chamber 6. Specifically, the air ratio A~R in the secondary
combustion chamber 5 is set to a value ranging from 0.9 to
1.3, preferably from 1.0 to 1.2, and the air ratio A~R in the
tertiary combustion chamber 6 is set to a value ranging from
1.2 to 1.7, preferably from 1.3 to 1.5. When the air ratio
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A~R is set to a value ranging from 0.9 to 1.3, preferably
from 1.0 to 1.2 until the molten slag h is discharged from a
slag outlet port 40, the temperature in the secondary
combustion chamber 5 up to the slag outlet port 40 is
maintained at a maximum level, thus allowing the molten slag
h to be discharged downwardly stably. In consideration of
discharge of the exhaust gas to the outside of the stack,
adding the gas for combustion in the high temperature is
effective to combust a small amount of unburned CO (carbon
monoxide) in almost all combusted gas in the slagging
combustion furnace. Thus, the air ratio is set to a value
ranging from 1.2 to 1.7, preferably from 1.3 to 1.5, while
keeping the slagging combustion furnace at a high
temperature. That is, the air ratio A~R in the tertiary
combustion chamber 6 is set to a large value ranging from 1.3
to 1.5, whereby unburned CO is effectively combusted, and
pyrolyzed gas and char are completely combusted without lack
of air for combustion, even if the wastes are fluctuated in
the supplied amount or quality.
By progressively increasing the air ratio A~R in
the slagging combustion furnace 3 successively through the
primary combustion chamber 4, the secondary combustion
chamber 5, and the tertiary combustion chamber 6 from A~R=1.3
to A~R=1.5, the gas f for combustion is supplied in an
excessive amount to absorb variations in the supplied amount
of wastes and minimize any reduction in the temperature in
the slagging combustion furnace 3. Therefore, the produced
gas b and unburned materials such as char contained therein
can be completely combusted, and the temperature in the
slagging combustion furnace 3 can be kept at a high level for
thereby increasing the percentage of slagging.
As shown in FIG. 10A, thermometers 36, 37 and 38
are mounted on the top wall of the primary combustion chamber
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4, the wall of the secondary combustion chamber 5, and the
wall of the tertiary combustion chamber 6, respectively, for
measuring the temperatures in these combustion chambers.
Each of the thermometers 36, 37 and 38 may comprise a
thermocouple or a radiation thermometer. The temperatures in
the combustion chambers may alternatively be calculated from
the temperature of the exhaust gas discharged from the
slagging combustion furnace 3 using the amount of recovered
heat and the amount of cooling air that is used. The above
ranges of the air ratio can be controlled using the
temperatures thus measured or calculated.
According to the present invention, the following
excellent effects can be obtained.
1) The gas for combustion is blown from the gas
supply nozzles which are open at the inner surface of the
side wall and the inner surface of the top wall, into the
produced combustible gas to mix the gas for combustion well
with the produced gas for thereby increasing the temperature
of the gas quickly and minimizing the temperature range in
which a clinker is adhered (or attached) to the inner wall
surface of primary combustion chamber of the slagging
combustion furnace. As a result, a clinker is prevented from
being adhered or attached to the inner wall surface of the
slagging combustion furnace. Consequently, the gasification
and slagging combustion system can be stably operated
continuously.
2) The gas for combustion is blown from the gas
supply nozzle which is open at the inner surface of the side
wall near the gas inlet port for supplying the produced gas
to mix the gas for combustion well with the produced gas for
thereby increasing the temperature of the gas quickly and
minimizing the temperature range in which a clinker is
adhered or attached to the inner wall surface of the slagging
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combustion furnace. As a result, a clinker is prevented from
being adhered or attached to the inner wall surface of the
slagging combustion furnace. Consequently, the gasification
and slagging combustion system can be stably operated
continuously.
3) Because the gas for combustion is introduced
from the gas supply nozzle as a swirling flow into the
produced gas, the gas for combustion is mixed well with the
produced gas for thereby increasing the temperature of the
ZO gas quickly and minimizing the temperature range in which a
clinker is adhered to the inner wall surface of the slagging
combustion furnace. As a result, a clinker is further
prevented from being adhered to the inner wall surface of the
slagging combustion furnace.
4) Because the gas for combustion is introduced
from the gas supply nozzles which are open at the inner
surface of the side wall and the inner surface of the top
wall of the slagging combustion furnace, into the swirling
flow of the produced gas, a clinker is prevented from being
adhered to the side and top walls of the slagging combustion
furnace.
5) Because the gas for combustion is introduced
from the gas supply nozzle which is open at the inner surface
of the side wall near the gas inlet port, into the produced
gas, a clinker is further prevented from being adhered to the
side and top walls of the slagging combustion furnace.
6) The air ratio in the upper portion of the
primary combustion chamber is approximately 1.0, and hence
the temperature in the primary combustion chamber near the
gas inlet port for introducing the produced~gas is maintained
at a high value of about 1300°C, thus minimizing the
temperature range in which a clinker is adhered or attached
to the inner wall surface of the primary combustion chamber.
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Further, the amount of gas for combustion is adjusted such
that the air ratios in the secondary and tertiary combustion
chambers increase progressively from 1.0 to 1.5, and hence
the produced gas and unburned materials such as char
contained therein are completely combusted, and the
temperature in the slagging combustion furnace is kept at a
high value for thereby increasing the percentage of slagging.
Although certain preferred embodiments of the
present invention have been shown and described in detail, it
should be understood that various changes and modifications
may be made therein without departing from the scope of the
appended claims.
Industrial Applicability
The present invention is applicable to a slagging
combustion furnace in a gasification and slagging combustion
system in which wastes including municipal wastes, industrial
wastes, biomass wastes, medical wastes, automobile wastes
such as waste tires or shredder dust, and the like are
gasified to produce combustible gas in a gasification
furnace, and the produced combustible gas is combusted or
gasified together with unburned carbon accompanied by the
combustible gas to generate ash or molten slag in a swirling-
type slagging combustion furnace.
