Technical Field
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The present invention relates to a slagging combustion
furnace and a gasification and slagging combustion system for
being supplied with a gas produced in a gasification furnace or
the like and containing ash and unburned carbon, and combusting
the supplied gas at a high temperature to melt the ash into molten
slag.
Background Art
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There has been a demand for incinerating wastes including
municipal wastes, industrial wastes, medical wastes, shredder
dust, waste tires, and the like to reduce the volume of the wastes,
and effectively utilizing heat of incineration of the wastes.
Because incineration ash of the wastes normally contains harmful
heavymetals, in order to discard the incineration ash in a landfill
site, it is necessary to take some measures for solidifying heavy
metal components. Further, there has been a demand for downsizing
an overall waste treatment system. In order to solve the above
problems, a gasification and melting furnace (gasification and
slagging combustion system) which can recover various metals,
melt ash to produce molten slag and recover the produced molten
slag, and recover energy in the form of heat, electric power or
the like has come into the limelight as a waste treatment system.
The gasification and slagging combustion system is not a simple
incineration treatment, but is a combination of pyrolysis
gasification and high-temperature combustion, and is capable of
performing material recycling.
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FIG. 1 is a schematic view showing a conventional
gasification andslagging combustion system whichisa combination
of a fluidized-bed gasification furnace and a swirling-type
slagging combustion furnace. As shown in FIG. 1, the gasification
and slagging combustion system comprises a fluidized-bed
gasification furnace 1 and a swirling-type slagging combustion
furnace 10. In the gasification and slagging combustion system
shown in FIG. 1, wastes are supplied to a fluidized bed 2 and
gasified to produce a combustible gas containing unburned carbon
and ash and having a temperature of about 500°C to about 600°C
in the gasification furnace 1, and the produced combustible gas
is introduced into the slagging combustion furnace 10 and
combusted by a secondary air at a high temperature under a low
air ratio of about 1.3 to about 1.5 to increase a temperature
of the interior of the furnace to a melting point of ash or higher
(for example, 1300°C or higher, preferably about 1350°C) in the
swirling-type slagging combustion furnace 10. In this
high-temperature condition, ash is collected on a wall surface
of the furnace, and a flow of molten slag is formed. The molten
slag is discharged through a slag discharge port 17 to the outside
of the furnace. Then, the discharged molten slag is brought into
contact with slag cooling water to form water-quenched slag.
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On the other hand, a high-temperature combustion gas
generated in the process in which ash content is melted to form
molten slag is introduced into a waste heat boiler, a heat exchanger
or the like in which thermal energy is recovered. In such
gasification and slagging combustion system, the structure of
the slagging combustion furnace affects melting state of ash and
stable operation of the slagging combustion furnace, and hence
it has been considered that the structure of the slagging
combustion furnace is technically important for the overall
gasification and slagging combustion system.
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FIG. 2 is a schematic view of the conventional slagging
combustion furnace. As shown in FIG. 2, reference numeral 10
represents the slagging combustion furnace 10, and the slagging
combustion furnace 10 comprises a primary combustion chamber 11,
a secondary combustion chamber 12, and a tertiary combustion
chamber 13. A passage which is formed within the slagging
combustion furnace and allows a combustion gas 16 to pass
therethrough comprises a substantially V-shaped passage as shown
by the arrow, and a slag discharge port 17 is formed at the lowermost
position of the V-shaped passage.
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A produced gas 14 produced by gasification in the
gasification furnace 1 (see FIG. 1) and containing unburned carbon
and ash, or a mixed gas of the produced gas 14 and combustion
gas is introduced into the upper part of the primary combustion
chamber 11 in a direction tangential to an inner wall surface
of the slagging combustion furnace 10. Combustion air 15 is also
introduced into the primary combustion chamber 11 in a direction
tangential to the inner wall surface of the slagging combustion
furnace 10. Thus, the produced gas 14 or the mixed gas of the
produced gas 14 and the combustion gas is mixed with the combustion
air 15, and is combusted while forming a swirling flow of the
gas, and moves to the secondary combustion chamber 12 and is
combusted at a high temperature of 1200 to 1400°C, preferably
about 1350°C in the secondary combustion chamber 12 and then the
tertiary combustion chamber 13. Then, exhaust gas 16' is
discharged from the tertiary combustion chamber 13, and is then
introduced into a waste heat boiler or the like (not shown in
the drawing) . In FIG. 2, reference numerals 18 and 19 represent
an auxiliary burner, respectively. In the above example, both
of the produced gas 14 and the combustion air 15 are introduced
in the direction tangential to the inner wall surface of the furnace.
However, one of the produced gas 14 and the combustion air 15
may be introduced in a direction tangential to the inner wall
surface of the furnace to thus generate a swirling flow of the
gas, and the other of the produced gas 14 and the combustion air
15 may be blown into the formed swirling flow, thereby combusting
while having mixed with each other.
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As described above, the produced gas 14 containing unburned
carbon and ash and the combustion air 15 introduced into the upper
part of the primary combustion chamber 11 are mixed with each
other while forming a swirling flow of the gas in the primary
combustion chamber 11, and the produced gas 14 is combusted in
the primary combustion chamber 11, and then moves to the secondary
combustion chamber 12 and the tertiary combustion chamber 13.
Ash is collected on the inner wall surface of the furnace due
to the swirling flow in the furnace, and is melted at a high
temperature to form molten slag 20. The molten slag flows
downwardly on the furnace bottom, and falls down from the slag
discharge port 17 through a slag discharge chute 30 to the outside
of the furnace. Then, the discharged molten slag 20 is brought
into contact with slag cooling water (not shown in the drawing)
to form water-quenched slag, and the granulated slag is recovered.
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FIG. 3 is a view showing the furnace bottom having the slag
discharge port of the slagging combustion furnace in an example.
As shown in FIG. 3, the molten slag 20 flowing downwardly on the
wall surface of the slagging combustion furnace 10 is collected
at the furnace bottom, and falls down along an inner wall surface
17a of the slag discharge port 17. Thus, the inner wall surface
17a of the slag discharge port 17 is concentratedly exposed to
the molten slag 20 having a high temperature to cause damage of
the inner wall surface 17a due to melting. When such melting
damage progresses, it is necessary to replace the inner wall of
the slag discharge port 17 with a new one. Further, the slag
discharge port 17 is a boundary between the high-temperature
secondary and tertiary combustion chambers 12 and 13, and the
low-temperature slag discharge chute 30 (the slag discharge chute
30 is cooled to a low temperature because slag cooling water is
in the lower part of the slag discharge chute 30), and hence
refractory material is subjected to severe conditions because
of the formation of temperature gradient and is liable to be damaged
or broken. However, because the inner wall of the slag discharge
port 17 is integrally formed with the inner wall of the slagging
combustion furnace 10, the replacement work of the inner wall
of the slag discharge port 17 is not easy and is troublesome.
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Alternatively, it may be considered that the inner wall
of the slag discharge port 17 is formed by refractory material
which is resistant to a thermal wear and a high temperature as
preventive measures against a thermal wear and a thermal damage.
However, because the inner wall of the slag discharge port 17
is integrally formedwith the inner wall of the slagging combustion
furnace 10, it has been difficult to form only the inner wall
of the slag discharge port 17 by refractory material which is
resistant to a thermal wear and a high temperature. Further,
since the refractory material which is resistant to a thermal
wear and a high temperature is expensive, it is uneconomical to
form the entire inner wall of the slagging combustion furnace
10 by the refractory material which is resistant to a thermal
wear and a high temperature.
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Further, in order to reduce the amount of thermal wear,
water tubes may be provided on the inner wall of the slag discharge
port 17. However, in this case, the inner wall surface 17a of
the slag discharge port 17 is cooled excessively, and hence the
molten slag 20 is adhered to the inner wall surface 17a and
solidified thereon to form aggregated slag 21 as shown in FIG.
3. In the worst case, the slag discharge port 17 is clogged with
the aggregated slag. Further, in this case, if the refractory
material is not dried and burned, the refractory material does
not display its innate strength. Therefore, when the refractory
material is cooled excessively by the water tubes, the refractory
material is liable to be damaged or broken due to a shortage of
strength.
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FIG. 4 is a second view showing the slag discharge port
of the slagging combustion furnace 10 in another example. As
shown in FIG. 4, the inner wall of the slag discharge port 17
has the same height in an entire circumference thereof.
Specifically, the height h1 of the inner wall at the upstream
side of the flow of the combustion gas 16 is equal to the height
h2 of the inner wall at the downstream side of the flow of the
combustion gas 16 (h1=h2). That is, the upper end of the slag
discharge port 17 is located at the same level, and the upper
surface 17b of the furnace bottom at an outer circumferential
portion around the slag discharge port 17 is inclined downwardly
toward the slag discharge port 17. Therefore, the combustion
gas 16 which flows at the upstream side of the slag discharge
port 17 along the upper surface 17b at the outer circumferential
portion around the slag discharge port 17 collides with the inner
wall surface 17a of the slag discharge port 17 to thus generate
a turbulent flow of the gas in the slag discharge port 17. This
turbulent flow has a bad influence on discharge conditions of
the molten slag discharged through the slag discharge port 17.
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As one of attendant problems, the molten slag 20 is adhered
to the inner wall surface 17a of the slag discharge port 17 and
solidified thereon to form aggregated slag 21 (see FIG. 3). In
the worst case, the slag discharge port 17 is clogged with the
aggregated slag, or the combustion gas 16 containing harmful
components is discharged through the slag discharge port 17 to
the outside of the slagging combustion furnace, thus contaminating
slag cooling water.
Disclosure of Invention
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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 and a gasification and
slagging combustion system which allows an inner wall of a slag
discharge port to be replaced easily with a new one if the inner
wall of the slag discharge port is damaged by melting, allows
the inner wall of the slag discharge port to be less susceptible
to a thermal wear or a breakage, and can prevent molten slag from
being adhered to the inner wall of the slag discharge port or
being solidified thereon due to an excessive cooling of the slag
discharge port.
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Another object of the present invention is to provide a
slagging combustion furnace and a gasification and slagging
combustion system in which a turbulent flow of the gas is not
generated in the slag discharge port of the slagging combustion
furnace and discharge conditions of the molten slag are not
affected.
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Still another object of the present invention is to provide
a slagging combustion furnace and a gasification and slagging
combustion system which allows adhesion or solidification of the
molten slag at the slag discharge port to be detected, can prevent
the slag discharge port from being clogged, or can dissolve
clogging of the slag discharge port.
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In order to achieve the above obj ect of the present invention,
according to an aspect of the present invention, there is provided
a slagging combustion furnace comprising: a combustion chamber
for combusting a combustible gas containing ash and melting the
ash; and a slag discharge port for discharging molten slag produced
by melting the ash; wherein the slag discharge port is formed
by refractory material which is replaceable.
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With the above arrangement, because a slag discharge port
is formed by a replaceable slag discharge port block which is
a distinct member different from a furnace wall of a slagging
combustion furnace, the slag discharge port block can be produced
in advance using refractory material having a high resistance
to a thermal wear and a high temperature through a predetermined
manufacturing process (for example, a forming process and a drying
process) in a plant. Thus, the newly produced slag discharge
port block is carried into the site where the slagging combustion
furnace is placed, and the slag discharge port block which has
been damaged by melting or broken for some cause can be easily
replaced with the newly produced slag discharge port block.
Further, since the slag discharge port block is composed of
refractory material (for example, high chromium refractory
material) which is resistant to a thermal wear and a high
temperature, the wall of the slag discharge port can be prevented
from thermal wear or breakage. Further, since the portion around
the slag discharge port is formed by the slag discharge port block,
the slag discharge port is not cooled excessively because the
refractory material is not required to be cooled or slight cooling
of the refractory material is sufficient by water tubes, unlike
a conventional discharge port, thus preventing molten slag from
being adhered to the inner wall of the slag discharge port or
being solidified thereon.
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According to one aspect of the present invention, the slag
discharge port comprises an opening formed at a central portion
of a slag discharge port block, and at least one slag discharge
groove extending from an outer peripheral portion of the slag
discharge port block at the upstream side of a flow of combustion
gas to the slag discharge port is formed in an upper surface of
the slag discharge port block.
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With the above arrangement, because a slag discharge groove
extending from an outer periphery of the slag discharge port block
at an upstream side of a combustion gas passage to the slag discharge
port is formed in an upper surface of the slag discharge port
block, molten slag flowing downwardly on the inner wall surface
of the slagging combustion furnace flows through the slag
discharge groove into the slag discharge port, and falls down
through the slag discharge port. Thus, the discharge position
of the molten slag is fixed. Further, since the molten slag flows
concentratedly, even if the scale of system or operational
condition of the system is such that the amount of slag to be
generated is small, the molten slag is less susceptible to being
cooled. Thus, the molten slag is prevented from being adhered
to the surface of the slag discharge port block or being solidified
thereon.
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According to one aspect of the present invention, the upper
surface of the slag discharge port block is a slant surface which
is inclined downwardly toward the slag discharge port, and an
upper end of an outer wall forming the slag discharge port at
the upstream side of the flow of the combustion gas is higher
than an upper end of the inner wall forming the slag discharge
port at the downstream side of the flow of the combustion gas.
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With the above arrangement, because the upper surface of
the slag discharge port block is formed into a slant surface which
is inclined downwardly toward the slag discharge port, and the
height of the inner wall of the slag discharge port at the upstream
side of a flow of the combustion gas is higher than the height
of the inner wall of the slag discharge port at the downstream
side of the flow of the combustion gas, the combustion gas which
has flowed into the upper surface of the slag discharge port block
at the upstream side of the flow of the combustion gas passes
through a location above the slag discharge port, and flows along
the upper surface of the slag discharge port at the downstream
side of the slag discharge port. Thus, since the combustion gas
does not collide with the inner wall surface of the slag discharge
port, the combustion gas can be prevented from flowing into the
slag discharge port. Further, the gas flownear the slag discharge
port is smoothed, and hence a fall position of the discharged
molten slag is not deviated. If this deviation is large, the
slag is attached to the inner surface of the slag discharge chute.
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According to one aspect of the present invention, the upper
surface of the slag discharge port block is a slant surface which
is inclined downwardly toward an outer circumferential portion
of the slag discharge port block.
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Because the upper surface of the slag discharge port block
is formed into a slant surface which is inclined downwardly toward
the outer periphery of the slag discharge port block, the
combustion gas which has flowed into the upper surface of the
slag discharge port block at the upstream side of the flow of
the combustion gas moves toward the slag discharge port in an
upward flow. Thus, the combustion gas is prevented from flowing
into the slag discharge port. Further, because the upper surface
of the slag discharge port block is formed into the slant surface
which is inclined downwardly toward the outer periphery of the
slag discharge port block, molten slag attached to the upper
surface is entirely collected at the outer circumferential portion,
and molten slag flowing downwardly on the inner wall surface of
the slagging combustion furnace is collected at the outer
circumferential portion of the slag discharge port block. Then,
the molten slag flows through the slag discharge groove into the
slag discharge port, and falls down through the slag discharge
port. Thus, the molten slag is prevented from being adhered to
the surface of the slag discharge port block or being solidified
thereon.
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According to one aspect of the present invention, the slag
discharge port block comprises a plurality of block pieces.
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With the above arrangement, since the slag discharge port
block is composedof apluralityofblockpieces, the slag discharge
port block can be easily produced and can be easily transported.
Further, even if the slag discharge port block is damaged or broken,
only the block piece which has been damaged or broken can be replaced.
Thus, the replacement of the block piece is facilitated.
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According to the present invention, there is provided a
gasification and slagging combustion system, comprising: a
gasification furnace for gasifyingwastes to produce a combustible
gas containing the ash and the unburned carbon; and a slagging
combustion furnace for combusting the combustible gas containing
ash and unburned carbon and melting the ash; the slagging
combustion furnace comprising any one of the above slagging
combustion furnaces.
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As described above, as a slagging combustion furnace of
a gasification and slagging combustion system, by using any of
the above slagging combustion furnaces, the slagging combustion
furnace which exhibits the above features and good operational
efficiency can be constructed.
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Further, in order to solve the above problems, according
to another aspect of the present invention, there is provided
a slagging combustion furnace comprising: a combustion chamber
for combusting a combustible gas containing ash and melting the
ash; and a slag discharge port for discharging molten slag produced
by melting the ash; wherein the height of an inner wall forming
the slag discharge port is higher at the upstream side of a flow
of combustion gas than at the downstream side of the flow of the
combustion gas.
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With the above arrangement, because the height of the inner
wall of the slag discharge port at the upstream side of the flow
of the combustion gas is higher than the height of the inner wall
of the slag discharge port at the downstream side of the flow
of the combustion gas, the combustion gas which has flowed along
the upper surface at the upstream side of the slag discharge port
passes through a location above the slag discharge port, and
reaches the upper surface at the downstream side of the slag
discharge port. Thus, since the combustion gas flows smoothly
without causing the combustion gas to collide with the inner wall
of the slag discharge port and without generating a turbulent
flow at the location near the slag discharge port, unlike the
conventional, the flow of the combustion gas does not affect
adversely the discharge state of the molten slag. Because the
combustion gas passes through a location above the slag discharge
port, and a flow direction of the combustion gas is changed by
the upper surface at the downstream side of the slag discharge
port, the amount of the combustion gas flowing into the slag
discharge port can be greatly reduced.
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According to one aspect of the present invention, an upper
surface at an outer circumferential portion around the slag
discharge port is a slant surface inclined upwardly toward the
slag discharge port, and at least one slag discharge groove
extending to the slag discharge port is formed in the slant surface
at the upstream side of the flow of the combustion gas.
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With the above arrangement, because the upper surface at
an outer circumferential portion around the slag discharge port
is formed into a slant surface which is inclined upwardly toward
the slag discharge port, and the height of the inner wall of the
slag discharge port and the inclination angle of the slant surface
at the upstream side of the flow of the combustion gas are set
such that the combustion gas flowing along the slant surface at
the upstream side reaches the slant surface at the downstream
side, the combustion gas which has flowed into the upper surface
at the upstream side of the slag discharge port passes though
a location above the slag discharge port, and reaches the upper
surface at the downstream side of the slag discharge port. Thus,
since the combustion gas flows smoothly without causing the
combustion gas to collide with the inner wall of the slag discharge
port and without generating a turbulent flow at the location near
the slag discharge port, the flow of the combustion gas does not
affect adversely the discharge state of the molten slag.
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Because the upper surface at an outer circumferential
portion around the slag discharge port is formed into a slant
surface which is inclined upwardly toward the slag discharge port,
the combustion gas which has flowed into the upper surface at
the upstream side of the slag discharge port moves toward the
slag discharge port in an upward flow. Thus, the combustion gas
is prevented from flowing into the slag discharge port.
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Because a slag discharge groove extending from a slant
surface at the upstream side of the combustion gas passage to
the slag discharge port is formed in the upper surface at an outer
circumferential portion around the slag discharge port, molten
slag flowing downwardly on the inner wall of the slagging
combustion furnace flows through the slag discharge groove into
the slag discharge port. Thus, the discharge position of the
molten slag is fixed. Because molten slag flows concentratedly
through a slag discharge groove, even if the scale of system or
operational condition of the system is such that the amount of
slag to be generated is small, the molten slag is less susceptible
to being cooled. Thus, the molten slag is prevented from being
adhered to the surface of the radially outer portion of the slag
discharge port or being solidified thereon.
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According to one aspect of the present invention, there
is provided a waste treatment method comprising: gasifying wastes
to produce a combustible gas containing ash in a fluidized-bed
furnace; combusting the combustible gas and melting the ash to
form molten slag in a slagging combustion furnace, the slagging
combustion furnace comprising a primary combustion chamber, a
secondary combustion chamber and a tertiary combustion chamber;
trapping the molten slag on an inner wall surface of the primary
combustion chamber and flowing the trapped molten slag downwardly
into the secondary combustion chamber; flowing the molten slag
on the inner wall surface of the secondary combustion chamber
and discharging the molten slag through a slag discharge groove
formed in a slag discharge port block to a slag discharge port
formed in the slag discharge port block, the slag discharge port
block being disposed at a lowermost part of the secondary
combustion chamber, the slag discharge groove being formed at
the primary combustion chamber side; trapping molten slag on an
inner wall surface of the tertiary combustion chamber from
combustion gas introduced into the tertiary combustion chamber,
and then discharging the trapped molten slag through the slag
discharge groove to the slag discharge port block; and supplying
the molten slag discharged from the slag discharge groove to a
water quenching trough and cooling the discharged molten slag
in the water quenching trough.
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According to the present invention, because a slag discharge
groove is formed only at the primary combustion chamber side,
the molten slag is concentratedly discharged through the slag
discharge groove and part of combustion gas flows through the
slag discharge groove to prevent the slag from being cooled.
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According to another aspect of the present invention, there
is provided a waste treatment method comprising: gasifying wastes
to produce a combustible gas containing ash in a fluidized-bed
furnace; combusting the combustible gas and melting the ash to
form molten slag in a slagging combustion furnace, the slagging
combustion furnace comprising a primary combustion chamber, a
secondary combustion chamber and a tertiary combustion chamber;
trapping the molten slag on a wall surface of the primary combustion
chamber and flowing the trapped molten slag downwardly into the
secondary combustion chamber; flowing the molten slag on the wall
surface of the secondary combustion chamber to a slag discharge
groove and discharging the molten slag through the slag discharge
groove, a slag discharge port block disposed at a lowermost part
of the secondary combustion chamber having a slag discharge groove
at the primary combustion chamber side; trapping molten slag on
a wall surface of the tertiary combustion chamber from combustion
gas introduced into the tertiary combustion chamber, and then
discharging the trapped molten slag through the slag discharge
groove to the slag discharge port; cooling and solidifying the
molten slag discharged from the slag discharge groove; and drawing
steam generated by the cooling and solidifying of the molten slag
and combustion gas through the slag discharge port of the secondary
combustion chamber to form a mixed gas, and introducing the mixed
gas to the tertiary combustion chamber.
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According to the present invention, because the combustion
gas is drawn through the slag discharge port together with steam
generated by cooling of slag and solidification of the slag, the
slag discharge port and a portion around the slag discharge port
can be prevented from being cooled by the steam, and can be kept
at a high temperature.
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According to one aspect of the present invention, there
is provided a waste treatment method comprising: gasifying wastes
to produce a combustible gas containing ash in a fluidized-bed
furnace; combusting the combustible gas and melting the ash to
form molten slag in a slagging combustion furnace, the slagging
combustion furnace comprising a primary combustion chamber, a
secondary combustion chamber and a tertiary combustion chamber;
trapping the molten slag on a wall surface of the primary combustion
chamber and flowing the trapped molten slag downwardly into the
secondary combustion chamber; flowing the molten slag on the wall
surface of the secondary combustion chamber to a slag discharge
groove and discharging the molten slag through the slag discharge
groove, a slag discharge port block disposed at a lowermost part
of the secondary combustion chamber having the slag discharge
groove at the primary combustion chamber side; trapping molten
slag on a wall surface of the tertiary combustion chamber from
combustion gas introduced into the tertiary combustion chamber,
and then flowing the molten slag on the wall surface of the tertiary
combustion chamber to the slag discharge port block and
discharging the molten slag through the slag discharge groove;
cooling the molten slag discharged through the slag discharge
groove in a slag discharge chute; and detecting a pressure
differential between an interior of the secondary combustion
chamber and an interior of the slag discharge chute; wherein when
the pressure differential exceeds a set value, a secondary
combustion chamber burner provided at the secondary combustion
chamber is operated to heat a portion around the slag discharge
port.
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According to the present invention, a pressure differential
between the interior of the slag discharge chute and the interior
of the secondary combustion chamber is detected, and if the
pressure differential exceeds a set value, then an inclination
of clogging of the slag discharge port by attachment of slag and
solidification of the slag is judged, and the slag discharge port
and a portion around the slag discharge port are heated by a
secondary combustion chamber burner to prevent the slag discharge
port from being clogged.
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According to one aspect of the present invention, there
is provided a waste treatment apparatus comprising: a
fluidized-bed furnace for gasifying wastes to produce a
combustible gas containing ash; a slagging combustion furnace
for combusting the combustible gas and melting the ash to form
molten slag, the slagging combustion furnace comprising a primary
combustion chamber, a secondary combustion chamber, a tertiary
combustion chamber, and a slag discharge port block at a lowermost
part of the secondary chamber and having a slag discharge groove
at the primary combustion chamber side; wherein the molten slag
is trapped on a wall surface of the primary combustion chamber
and the trapped molten slag flows downwardly into the secondary
combustion chamber, the molten slag flows on the wall surface
of the secondary combustion chamber to the slag discharge groove
and the molten slag is discharged from the slag discharge groove,
molten slag is trapped on a wall surface of the tertiary combustion
chamber from combustion gas introduced into the tertiary
combustion chamber, and then the trapped molten slag flows
downwardly to the slag discharge port block and is discharged
from the slag discharge groove; a slag discharge chute disposed
below the slag discharge port block for cooling the molten slag
discharged from the slag discharge groove; and a pressure
instrument for detecting a pressure differential between an
interior of the secondary combustion chamber and an interior of
the slag discharge chute; wherein when the pressure differential
between the interior of the secondary combustion chamber and the
interior of the slag discharge chute exceeds a set value, a
secondary combustion chamber burner provided at the secondary
combustion chamber is operated to heat a portion around the slag
discharge port.
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According to the present invention, a pressure differential
between the interior of the slag discharge chute and the interior
of the secondary combustion chamber is detected, and if the
pressure differential exceeds a set value, then an inclination
of clogging of the slag discharge port by attachment of slag and
solidification of the slag is judged, and the slag discharge port
and a portion around the slag discharge port are heated by a
secondary combustion chamber burner to prevent the slag discharge
port from being clogged.
Brief Description of Drawings
-
- FIG. 1 is a schematic view showing a conventional
gasification and slagging combustion system;
- FIG. 2 is a schematic view of the conventional slagging
combustion furnace;
- FIG. 3 is a view showing a slag discharge port and its vicinity
of a slagging combustion furnace in an example;
- FIG. 4 is a view showing a slag discharge port and its vicinity
of a slagging combustion furnace in another example;
- FIG. 5 is a view showing a slag discharge port and its vicinity
of a slagging combustion furnace according to the present
invention;
- FIGS. 6A through 6C are views showing a slag discharge port
block, and FIG. 6A is a cross-sectional view (taken along line
VIA-VIA of FIG. 6B), FIG. 6B is a plan view, and FIG. 6C is a
cross-sectional view (taken along line VIC-VIC of FIG. 6B);
- FIG. 7 is a view showing a slag discharge port block of
a slagging combustion furnace according to an example of the
present invention;
- FIG. 8 is a view showing a slag discharge port and its vicinity
of a slagging combustion furnace according to the present
invention;
- FIG. 9A is a cross-sectional view of a slag discharge port
block shown in FIG. 8 (a cross-sectional view taken along line
IXA-IXA of FIG. 9B), and FIG. 9B is a plan view of the slag discharge
port block shown in FIG. 8;
- FIG. 10 is a view showing a slag discharge port of a slagging
combustion furnace according to another embodiment of the present
invention;
- FIG. 11 is an enlarged cross-sectional view showing an
essential part of FIG. 10;
- FIG. 12 is a view showing a slag discharge port of a slagging
combustion furnace according to another embodiment of the present
invention;
- FIG. 13A is a cross-sectional view showing the slag discharge
port, and FIG. 13B is a plan view;
- FIG. 14 is a view showing a slagging combustion furnace
according to still another embodiment of the present invention;
- FIGS. 15A through 15C are views showing the slag discharge
port block, and FIG. 15A is a perspective view of the slag discharge
port block, FIG. 15B is a cross-sectional view taken along line
XVB-XVB of FIG. 15A, and FIG. 15C is a cross-sectional view taken
along line XVC-XVC of FIG. 15A;
- FIG. 16 is an enlarged cross-sectional view showing an
essential part of FIG. 14;
- FIGS. 17A and 17B are cross-sectional views showing the
manner in which molten slag flows through the slag discharge port;
and
- FIG. 18 is a view showing a slagging combustion furnace
according to still another embodiment of the present invention.
-
Best Mode for Carrying Out the Invention
-
Embodiments of the present inventionwill be described below
with reference to the drawings.
-
FIG. 5 is a view showing a slag discharge port and its vicinity
of a slagging combustion furnace according to the present
invention. As shown in FIG. 5, a slag discharge port block 22
is provided at the furnace bottom between the secondary combustion
chamber 12 and the tertiary combustion chamber 13 in the slagging
combustion furnace 10. Reference numeral 23 represents water
tubes 23 provided under the slag discharge port block 22.
-
FIGS. 6A through 6C show the slag discharge port block 22,
and FIG. 6A is a cross-sectional view (taken along line VIA-VIA
of FIG. 6B), FIG. 6B is a plan view, and FIG. 6C is a cross-sectional
view (taken along line VIC-VIC of FIG. 6B). The slag discharge
port block 22 is made of refractory material which is resistant
to a thermal wear and a high temperature. For example, the
refractory material comprises a high chromium refractory material
containing chromium of 60% ormore. The slag discharge port block
22 has a slag discharge port 17 at the central portion thereof.
The upper surface 22a of the slag discharge port block 22 is formed
into a slant surface which is inclined downwardly toward the slag
discharge port 17, and an inner circumferential surface 22c
constituting an inner wall surface of the slag discharge port
17 is formed into a vertical surface.
-
In the inner circumferential surface 22c of the slag
discharge port block 22 constituting the inner wall surface of
the slag discharge port 17, the height h1 at the upstream side
(the arrow C side) of a flow of the combustion gas 16 is higher
than the height h2 at the downstream side (the arrow D side) of
the flow of the combustion gas 16 (h1>h2). The slag discharge
port block 22 has a slag discharge groove 22d formed in the upper
surface 22a such that the slag discharge groove 22d extends from
the outer periphery at the upstream side of the flow of the
combustion gas 16 to the slag discharge port 17. The width of
the slag discharge groove 22d is wider at the outer circumferential
side than at the slag discharge port 17 side, and the slag discharge
groove 22d has a substantially semicircular cross section.
-
In the case where the slag discharge port block 22 having
the above structure is provided at the opening portion formed
at the furnace bottom between the secondary combustion chamber
12 and the tertiary combustion chamber 13, the combustion gas
16 flowing from the secondary combustion chamber 12 to the tertiary
combustion chamber 13 flows into the upper surface 22a of the
slag discharge port block 22 from the upstream side (the arrow
C side) of the slag discharge port, and flows through a location
above the slag discharge port 17 to the downstream side (the arrow
D side) of the slag discharge port. As described above, in the
inner circumferential surface 22c, the height h1 at the upstream
side is higher than the height h2 at the downstream side (h1>h2).
Therefore, as shown in FIG. 6A, an inclination angle of the upper
surface 22a at the upstream side is set such that the combustion
gas 16 which has passed through the location above the slag
discharge port 17 does not collide with the inner circumferential
surface 22c, and hence the combustion gas 16 flows along the upper
surface 22a at the downstream side into the tertiary combustion
chamber 13. Therefore, the combustion gas 16 is prevented from
being flowing into the slag discharge port 17.
-
Because the slag discharge port block 22 is composed of
a distinct member different from the furnace wall of the slagging
combustion furnace, the slag discharge port block 22 is not cooled
excessively by the water tubes 23, and thus the molten slag 20
is not adhered to the slag discharge port block and is not solidified
thereon due to an excessive cooling. Further, since the slag
discharge groove 22d extending from the outer periphery at the
upstream side to the slag discharge port 17 is formed in the upper
surface 22a of the slag discharge port block 22, the molten slag
20 flowing downwardly on the inner wall surface of the slagging
combustion furnace 10 collects in the slag discharge groove 22d,
and then flows into the slag discharge port 17. Thus, the molten
slag 20 is prevented from being adhered to the surface of the
slag discharge port block 22 and being solidified thereon. The
number of the slag discharge grooves 22d may be one or plural.
-
The length of the inner circumferential surface 22c of the
slag discharge port block 22 constituting the inner wall surface
of the slag discharge port 17 is preferably short in view of
preventing the molten slag 20 from being adhered thereto or
solidified thereon. For example, as shown in FIG. 7, the height
h of the slag discharge port block 22 should be short.
-
FIG. 8 is a view showing a slag discharge port and its vicinity
of a slagging combustion furnace according to the present
invention. FIG. 9A is a cross-sectional view of the slag discharge
port block (cross-sectional view taken along line IXA-IXA of FIG.
9B), and FIG. 9B is a plan view of the slag discharge port block
22 shown in FIG. 8. As shown in FIGS. 9A and 9B, the slag discharge
port block 22 has an upper surface 22a which is a slant surface
inclined downwardly toward the outer circumferential portion
thereof. A slag discharge groove 22d extending from an outer
periphery at the upstream side of a flow of the combustion gas
to the slag discharge port 17 is formed in the upper surface 22a.
-
Since the upper surface 22a of the slag discharge port block
22 is formed into the slant surface which is inclined downwardly
toward the outer periphery of the slag discharge port block 22,
molten slag attached to the upper surface 22a is entirely collected
at the outer circumferential portion of the slag discharge port
block 22. Then, the collected molten slag flows together with
molten slag 20 flowing on the inner wall surface of the secondary
combustion chamber 12 and the tertiary combustion chamber 13 of
the slagging combustion furnace 10 into the connecting portion
between the inner wall surface of the slagging combustion furnace
10 and the outer circumferential surface of the slag discharge
port block 22. Thereafter, the molten slag 20 flows through the
slag discharge groove 22d into the slag discharge port 17, and
falls down through the slag discharge port 17. Thus, the molten
slag 20 is prevented from being adhered to the surface of the
slag discharge port block 22 and being solidified thereon. The
number of the slag discharge grooves 22d may be one or plural.
-
On the other hand, the combustion gas 16 which has flowed
into the upper surface 22a at the upstream side of the slag discharge
port block 22 moves toward the slag discharge port 17 in an upward
flow (see FIG. 9A). Thus, the combustion gas 16 flows through
a location above the slag discharge port 17, and hence the
combustion gas 16 is prevented from flowing into the slag discharge
port 17. Further, because the upper surface of the slag discharge
port block is formed into a slant surface which is inclined
downwardly toward the outer periphery of the slag discharge port
block, molten slag attached to the upper surface is entirely
collected at the outer circumferential portion of the slag
discharge port block, and molten slag flowing downwardly on the
inner wall surface of the slagging combustion furnace is collected
at the outer circumferential portion of the slag discharge port
block. Then, the molten slag flows through the slag discharge
groove 22d into the slag discharge port 17, and falls down through
the slag discharge port 17. Thus, the molten slag is prevented
from being adhered to the surface of the slag discharge port block
and being solidified thereon.
-
Further, the slag discharge port block 22 is produced in
advance from refractory material through a forming process and
a drying process as a precast block in a plant. Thus, it is possible
to employ refractory material (for example, high chromium
refractory material containing chromium of 60% or more) which
is resistant to a thermal wear and a high temperature. Further,
if the slag discharge port block 22 comprises a plurality of block
pieces, which have been produced through the above forming process
and drying process, then production of the block pieces, and
transportation of the block pieces are facilitated, and only
damaged or broken block pieces can be replaced. Although the
slag discharge port block 22 comprises a circular disk in the
above embodiment, the slag discharge port block 22 may comprise
an elliptical disk or a rectangular parallelepiped so as to fit
the structure of the slagging combustion furnace 10.
-
FIG. 10 is a view showing a slag discharge port of a slagging
combustion furnace according to another embodiment of the present
invention. As shown in FIG. 10, a slag discharge port 17 is
provided at the furnace bottom between the secondary combustion
chamber 12 and the tertiary combustion chamber 13 of the slagging
combustion furnace 10 . The upper surface 17b of the furnace bottom
at an outer circumferential portion around the slag discharge
port 17 is formed into a slant surfacewhich is inclined downwardly
toward the slag discharge port 17, and the height h1 of the inner
wall surface of the slag discharge port 17 at the upstream side
of a flow of the combustion gas 16 is higher than the height h2
of the inner wall surface of the slag discharge port 17 at the
downstream side of the flow of the combustion gas 16 (h1>h2).
-
FIG. 11 is an enlarged view showing an essential part of
FIG. 10. As shown in FIG. 11, an inclination angle α of the upper
surface 17b at the upstream side of the flow of the combustion
gas 16, the height h1 of the innerwall surface of the slag discharge
port 17 at the upstream side of the flow of the combustion gas
16, and the height h2 at the downstream side of the flow of the
combustion gas 16 are set such that the combustion gas 16 flowing
on the upper surface 17b at the upstream side of the slag discharge
port 17 passes through a location above the slag discharge port
17, and reaches the upper surface 17b at the downstream side of
the slag discharge port 17.
-
Because the inclination angle α of the upper surface 17b
at the upstream side of the slag discharge port 17, the height
h1 of the inner wall surface of the slag discharge port 17 at
the upstream side, and the height h2 at the downstream side are
set in the above-described manner, the combustion gas 16 which
has flowed into the upper surface 17b at the upstream side of
the slag discharge port 17 passes though a location above the
slag discharge port 17 in a smooth stream without generating a
turbulent flow at the location near the slag discharge port 17.
Therefore, the flow of the combustion gas 16 does not affect
adversely the discharge state of the molten slag 20 flowing into
the slag discharge port 17. Further, the combustion gas 16 can
be prevented from being discharged through the slag discharge
port 17 to the outside of the furnace.
-
FIG. 12 is a view showing a slag discharge port and its
vicinity of a slagging combustion furnace according to the present
invention. FIG. 13A is a cross-sectional view showing the slag
discharge port shown in FIG. 12, and FIG. 13B is a plan view showing
the slag discharge port shown in FIG. 12. The upper surface 17b
of the furnace bottom at an outer circumferential portion around
the slag discharge port 17 is formed into a slant surface which
is inclined upwardly toward the slag discharge port 17. A slag
discharge groove 17d extending from an outer periphery at the
upstream side of a flow of the combustion gas to the slag discharge
port 17 is formed in the upper surface 17b.
-
As described above, since the upper surface 17b at the
radially outer side of the slag discharge port 17 is formed into
the slant surface which is inclined upwardly toward the slag
discharge port 17, the combustion gas 16 which has flowed into
the upper surface 17b at the upstream side of the slag discharge
port 17 moves toward the slag discharge port 17 in an upward flow
as shown in FIG. 13A. Thus, the combustion gas 16 flows through
a location above the slag discharge port 17, and hence the
combustion gas 16 is prevented from flowing into the slag discharge
port 17. Further, because the upper surface 17b at the outer
circumferential portion around slag discharge port 17 is formed
into the slant surface which is inclined upwardly toward the slag
discharge port 17, molten slag 20 attached to the upper surface
is entirely collected at the radially outer side of the slag
discharge port 17, and molten slag flowing downwardly on the inner
wall surface of the slagging combustion furnace is collected at
the radially outer side of the slag discharge port 17. Thus,
the molten slag 20 is prevented from being adhered to the upper
surface 17b and being solidified thereon.
-
Further, in the case where a gasification and slagging
combustion system according to the present invention comprises
a gasification furnace for gasifying wastes to produce a gas
containing ash and unburned carbon, and the slagging combustion
furnace having the above structure, the gasification furnace may
comprise an internal circulating fluidized-bed gasification
furnace, an external circulating fluidized-bed gasification
furnace, a kiln furnace, or the like.
-
Although the swirling-type slagging combustion furnace has
been described as a slagging combustion furnace, in the case where
the present invention is characterized by the height of the slag
discharge port and/or the inclination angle of the upper surface
around the slag discharge port to prevent clogging of the slag
discharge port of the slagging combustion furnace, the slagging
combustion furnace is not limited to the swirling-type slagging
combustion furnace, and may be any type of slagging combustion
furnace.
-
FIG. 14 is a view showing a slagging combustion furnace
according to another embodiment of the present invention. A slag
discharge port block 32 is disposed at the lowermost position
of the secondary combustion chamber, and a slag discharge groove
32d is formed in the slag discharge port block 32 only at the
primary combustion chamber 11 side. FIGS. 15A through 15C show
the slag discharge port block, and FIG. 15A is a perspective view
of the slag discharge port, FIG. 15B is a cross-sectional view
taken along line XVB-XVB of FIG. 15A, and FIG. 15C is a
cross-sectional view taken along line XVC-XVC of FIG. 15A. As
shown in FIGS. 15A through 15C, the slag discharge port block
32 has the slag discharge groove 32d which faces the primary
combustion chamber 11. The slag discharge port block 32 is
disposed at the bottomportion of the secondary combustion chamber
12 which is an end portion of the primary combustion chamber 11.
-
With this arrangement, as shown in FIG. 15A, molten slag
20 which has flowed on the inner wall surface of the slagging
combustion furnace 10 is collected at the location around the
slag discharge port block 32, and then is discharged from the
slag discharge groove 32d. Because the discharge of molten slag
is concentratedly carried out by the slag discharge groove 32d,
the molten slag is prevented from being cooled. Further, since
the slag discharge groove 32d is formed at the upstream side (the
primary combustion chamber side) of a flow of the combustion gas
16, part of the combustion gas 16 flows through the slag discharge
groove 32d, thus keeping the molten slag 20 at a high temperature.
-
FIG. 16 is a view showing a detailed structure of the
embodiment. FIGS. 17A and 17B are cross-sectional views showing
the manner in which molten slag flows through the slag discharge
port. As shown in FIGS. 14 and 16, a line 40 is provided to connect
a slag discharge chute 30 and the tertiary combustion chamber
13, and a dust collector 41 and a fan 42 are provided in the line
40. The slag discharge chute 30 constitutes a'water quenching
trough which cools molten slag 20 discharged through the slag
discharge port by slag cooling water to form water-quenched slag.
With the above arrangement, steam generated by cooling of molten
slag and solidification of the slag is drawn from the slag discharge
chute 30 by the fan 42, and the combustion gas 16 which has passed
through the slag discharge port 17 is drawn by the fan 42, thus
forming a mixed gas. The mixed gas is fed to the tertiary
combustion chamber 13. With this arrangement, the molten slag
can be smoothly discharged through the slag discharge port 17
to the slag discharge chute 30 and then a water reservoir 43 as
shown in FIGS. 16 and 17A.
-
The supply position of the mixed gas which is drawn from
the slag discharge chute and is supplied to the slagging combustion
furnace 10 is not limited to the tertiary combustion chamber 13.
Specifically, the line 40 can be constructed such that the line
40 connects the slag discharge chute and at least one of a duct
connecting the gasification furnace and the slagging combustion
furnace, the primary combustion chamber, the secondary combustion
chamber, the tertiary combustion chamber, and a flue provided
upstream of a waste heat boiler. In this case, the dust collector
41 and the fan 42 are provided in the line 40, and a warm-up device
may be further provided. With this arrangement, the slag
discharge port 17 can be prevented from clogging and the molten
slag can be smoothly discharged through the slag discharge port
17 to the slag discharge chute 30 and then the water reservoir
43 as shown in FIGS. 16 and 17A. With this arrangement, even
if the mixed gas contains unburned carbon and the like, such
unburned carbon and the like can be combusted and treated, and
hence the mixed gas can be properly treated. In the case where
the warm-up device is provided in the line 40, it is desirable
that the mixed gas is warmed up to a temperature of about 200°C
or higher, preferably about 300°C or higher so as not to cause
a remarkable temperature drop in the slagging combustion furnace,
even if the mixed gas is supplied to the slagging combustion
furnace.
-
Even if the above arrangement is employed, when the system
is operated for a long period of time, as shown in FIG. 14, even
if the molten slag is prevented frombeing rapidly cooled locally,
the molten slag is attached to the slag discharge port and its
vicinity of the slag discharge block 32 or the like to form
aggregated slag 21, and thus the slag discharge port 17 may be
clogged with the slag (see FIG. 17B). If this clogging of the
slag discharge port occurs, the molten slag cannot be discharged
through the slag discharge port. Further, when the system is
operated for a long period of time, even if the slag discharge
function is not completely lost, the slag discharge port tends
to be clogged with the slag adhesion and solidification. Thus,
it is important to avoid an inclination of clogging of the slag
discharge port because if there is an indication of decreasing
an opening area of the slag discharge port, the clogging of the
slag discharge port rapidly progresses due to the following
vicious circle. Specifically, the vicious circle is as follows:
As the opening area of the slag discharge port is reduced, draft
resistance (pressure loss) of the combustion gas 16 which passes
through the slag discharge port is increased. Thus, the amount
of combustion gas to be drawn is lowered, it is difficult to keep
the molten slag at a high temperature, and hence the opening area
of the slag discharge port is further reduced. Therefore, an
inclination of clogging of the slag discharge port has to be avoided.
Thus, it is extremely important to prevent the above problems
from occurring for the purpose of ensuring the slag discharge
function for discharging molten slag smoothly through the slag
discharge port.
-
In order to achieve the above object, in an embodiment shown
in FIG. 18, the pressure differential between the interior of
the slag discharge chute 30 and the interior of the secondary
combustion chamber 12 is detected by the pressure instrument 45,
and if the pressure differential exceeds a set value, an
inclination of clogging of the slag discharge port is judged,
and the slag discharge port and a portion around the slag discharge
port are heated by a secondary combustion chamber burner 46. For
example, a signal indicative of a pressure differential measured
by the pressure instrument 45 is sent to a controller (not shown)
through a first signal transmitting means. The controller judges
whether the pressure differential is equal to or larger than a
set value, and if the pressure differential is equal to or larger
than the set value, then the controller sends a starting signal
for starting the secondary combustion chamber burner 46 to the
secondary combustion chamber burner 46 through a second signal
transmitting means. This arrangement can prevent the slag
discharge port and a portion around the slag discharge port from
being clogged.
-
According to the present invention, the following excellent
effects can be obtained.
- (1) Because a slag discharge port is formed by a replaceable
slag discharge port block which is a distinct member different
from a furnace wall, the slag discharge port block can be produced
in advance using refractory material having a high resistance
to a thermal wear and a high temperature through a predetermined
manufacturing process (for example, a forming process and a drying
process) in a plant. Thus, the newly produced slag discharge
port block is carried into the site where the slagging combustion
furnace is placed, and the slag discharge port block which has
been damaged by melting or broken for some cause can be easily
replaced with the newly produced slag discharge port block.
Further, since the slag discharge port block is composed of
refractory material (for example, high chromium refractory
material) which is resistant to a thermal wear and a high
temperature, the inner wall of the slag discharge port can be
prevented from being damaged by melting or being broken. Further,
since the slag discharge port is formed by the slag discharge
port block, the slag discharge port is not cooled excessively
by water tubes, unlike a conventional discharge port, thus
preventing molten slag from being adhered or being solidified.
- (2) Because a slag discharge groove extending from an outer
periphery of the slag discharge port block at an upstream side
of a combustion gas passage to the slag discharge port is formed
in an upper surface of the slag discharge port block, molten slag
flowing downwardly on the inner wall surface of the slagging
combustion furnace flows through the slag discharge groove into
the slag discharge port, and falls down through the slag discharge
port. Thus, the discharge position of the molten slag is fixed.
Further, since the molten slag flows concentratedly, even if the
scale of system or operational condition of the system is such
that the amount of slag to be generated is small, the molten slag
is less susceptible to being cooled. Thus, the molten slag is
prevented from being adhered to the surface of the slag discharge
port block or being solidified thereon.
- (3) Because the upper surface of the slag discharge port
block is formed into a slant surface which is inclined downwardly
toward the slag discharge port, and the height of the inner wall
of the slag discharge port at the upstream side of a flow of the
combustion gas is higher than the height of the inner wall of
the slag discharge port at the downstream side of the flow of
the combustion gas, the combustion gas which has flowed into the
upper surface of the slag discharge port block at the upstream
side of the flow of the combustion gas passes through a location
above the slag discharge port, and flows along the upper surface
of the slag discharge port at the downstream side of the slag
discharge port. Thus, since the combustion gas does not collide
with the inner wall surface of the slag discharge port, the
combustion gas can be prevented from flowing into the slag
discharge port. Further, the gas stream near the slag discharge
port is smoothed, and hence a fall position of the discharged
molten slag is not deviated.
- (4) Because the upper surface of the slag discharge port
block is formed into a slant surface which is inclined downwardly
toward the outer periphery of the slag discharge port block, the
combustion gas which has flowed into the upper surface of the
slag discharge port block at the upstream side of the flow of
the combustion gas moves toward the slag discharge port in an
upward flow. Thus, the combustion gas is prevented from flowing
into the slag discharge port. Further, because the upper surface
of the slag discharge port block is formed into the slant surface
which is inclined downwardly toward the outer periphery of the
slag discharge port block, molten slag attached to the upper
surface is entirely collected at the outer circumferential portion
of the slag discharge port block, and molten slag flowing
downwardly on the inner wall surface of the slagging combustion
furnace is collected at the outer circumferential portion of the
slag discharge port block. Then, the molten slag flows through
the slag discharge groove into the slag discharge port. Thus,
the molten slag is prevented from being adhered to the surface
of the slag discharge port block or being solidified thereon.
- (5) Since the slag discharge port block is composed of a
plurality of block pieces, the slag discharge port block can be
easily produced and can be easily transported. Further, even
if the slag discharge port block is damaged or broken, only the
block piece which has been damaged or broken can be replaced.
Thus, the replacement of the block piece is facilitated.
- (6) As a slagging combustion furnace of a gasification and
slagging combustion system, by using any of the above slagging
combustion furnaces, the slagging combustion furnace which
exhibits the above features can be constructed.
- (7) Because the height of the inner wall of the slag discharge
port at the upstream side of the flow of the combustion gas is
higher than the height of the inner wall of the slag discharge
port at the downstream side of the flow of the combustion gas,
the combustion gas which has flowed along the upper surface at
the upstream side of the slag discharge port passes through a
location above the slag discharge port, and reaches the upper
surface at the downstream side of the slag discharge port. Thus,
since the combustion gas flows smoothly without causing the
combustion gas to collide with the inner wall of the slag discharge
port and without generating a turbulent flow at the location near
the slag discharge port, the flow of the combustion gas does not
affect adversely the discharge state of the molten slag.
- (8) Because the combustion gas passes through a location
above the slag discharge port, and a flow direction of the
combustion gas is changed by the upper surface at the downstream
side of the slag discharge port, the amount of the combustion
gas flowing into the slag discharge port can be greatly reduced.
- (9) Because the upper surface at an outer circumferential
portion around the slag discharge port is formed into a slant
surface which is inclined upwardly toward the slag discharge port,
and the height of the inner wall of the slag discharge port and
the inclination angle of the slant surface at the upstream side
of the flow of the combustion gas are set such that the combustion
gas flowing along the slant surface at the upstream side reaches
the slant surface at the downstream side, the combustion gas which
has flowed into the upper surface at the upstream side of the
slag discharge port passes through a location above the slag
discharge port, and reaches the upper surface at the downstream
side of the slag discharge port without causing the combustion
gas to collide with the inner wall of the slag discharge port
and without generating a turbulent flow at the location near the
slag discharge port, the combustion gas flow smoothly and the
flow of the combustion gas does not affect adversely the discharge
state of the molten slag.
- (10) Because the upper surface at an outer circumferential
portion around the slag discharge port is formed into a slant
surface which is inclined upwardly toward the slag discharge port,
the combustion gas which has flowed into the upper surface at
the upstream side of the slag discharge port moves toward the
slag discharge port in an upward flow. Thus, the combustion gas
is prevented from flowing into the slag discharge port.
- (11) Because a slag discharge groove extending from a slant
surface at the upstream side of the flow of the combustion gas
to the slag discharge port is formed in the upper surface at an
outer circumferential portion around the slag discharge port,
molten slag flowing downwardly on the inner wall of the slagging
combustion furnace flows through the slag discharge groove into
the slag discharge port. Thus, the discharge position of the
molten slag is fixed.
- (12) Because molten slag flows concentratedly through a
slag discharge groove, even if the scale of system or operational
condition of the system is such that the amount of slag to be
generated is small, the molten slag is less susceptible to being
cooled. Thus, the molten slag is prevented from being adhered
to the surface of the radially outer portion of the slag discharge
port or being solidified thereon.
- (13) Because a slag discharge groove is formed only at the
primary combustion chamber side, the slag is concentratedly
discharged through the slag discharge groove to prevent the molten
slag from being cooled.
- (14) Because the combustion gas which has passed through
the slag discharge port is drawn together with steam generated
by cooling of slag and solidification of the slag, the slag
discharge port and a portion around the slag discharge port can
be prevented from being cooled by the steam, and can be kept at
a high temperature.
- (15) A pressure differential between the interior of the
slag discharge chute and the interior of the secondary combustion
chamber is detected, and if the pressure differential exceeds
a set value, then an inclination of clogging of the slag discharge
port by attachment of slag and solidification of the slag is judged,
and the slag discharge port and a portion around the slag discharge
port are heatedby a secondary combustion chamber burner to prevent
the slag discharge port from being clogged.
-
Industrial Applicability
-
The present invention is applicable to a slagging combustion
furnace and a gasification and slagging combustion system for
being supplied with a gas produced in a gasification furnace or
the like and containing ash and unburned carbon, and combusting
the supplied gas at a high temperature to melt ash into molten
slag.