JPH0776607B2 - Waste melting furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a high temperature hearth formed of a lumpy carbonaceous combustible substance, and municipal waste, sewage sludge, various industrial wastes, or dehydration, drying and incineration of the same. The present invention relates to a waste melting furnace that melts an intermediate processed material obtained by crushing, crushing, etc., and recovers incombustibles as slag.

[Prior Art] In a typical waste melting furnace, coke is added as a lumpy carbon-based combustible substance as shown in, for example, JP-A-55-82212 and JP-A-55-114382. Waste such as municipal waste is loaded from the top of the vertical shaft furnace,
The dry zone, carbonization gasification zone, and combustion / melting zone in the furnace are sequentially lowered. On the other hand, an oxygen-containing gas or oxygen-enriched gas is blown into the furnace from the tuyere, and the carbonaceous matter produced by coke and pyrolysis is burned at a high temperature in the high-temperature hearth, and the combustion heat produces molten slag that melts slag. Is generated.

At this time, in order to reduce the viscosity of the slag, limestone or silica stone as a basicity adjusting agent is charged from the furnace top together with the waste. The high-temperature combustion exhaust gas rises as a counter flow in the waste packed bed in the shaft, thermally decomposes the waste, and the organic matter in the waste is discharged as combustible gas and recovered as combustion heat.

The following is described in Japanese Examined Patent Publication No. 63-49128. This is because a waste charging cylinder is provided at the center of the top of the shaft furnace, the lower end is buried in the coke filling area, a coke charging inlet is arranged around the waste charging cylinder, and an exhaust pipe is further arranged around it. It is set up. Then, the waste is charged in the center and the coke is separately charged so as to cover the periphery, and dust blowing from the waste filling area due to exhaust gas is prevented by the coke suppressing action.

Furthermore, the present inventors previously disclosed that, in Japanese Patent Application No. 1-137160, which is an improvement over these prior arts, a lumpy carbon-based combustible substance is evenly distributed and filled in a hollow cone furnace without producing a space. ,
We have filed an application for a waste melting furnace in which waste, lump carbonaceous combustible substance, and basicity adjusting agent are charged from a charging cylinder whose tip is buried in a lump carbonaceous combustible substance filling area.

[Problems to be Solved by the Invention] However, JP-A-55-82212 and JP-A-55-11438
The device disclosed in Japanese Patent Publication No. 2 has to be supplied with a large amount of oxygen-containing gas in order to stably maintain the melting treatment of waste, and there is room for improvement in stabilization of the furnace condition and running cost.

Further, in Japanese Patent Publication No. 63-49128, since the massive carbonaceous combustible substance to be filled is distributed at the angle of repose in the furnace, the ventilation pressure loss of the peripheral wall portion having a low filling height is small, and the radial direction in the furnace is small. Drift occurs. The charged massive carbonaceous combustible material tends to have coarse particles distributed on the peripheral wall and fine particles distributed in the center, and the coarse particle portion has a smaller ventilation pressure loss than the fine particle portion, further promoting uneven flow in the furnace. It

This is because the lumpy carbonaceous combustibles charged into the furnace flow in while rolling over the lumpy carbonaceous combustibles that were previously charged and were in a rest position.The coarser particles roll better and reach the lower part of the peripheral wall. To do. This is a phenomenon caused by having a space in the furnace.

As a result of the uneven flow, there is a non-uniform peripheral flow with a large amount of gas flow in the periphery and a small amount of gas flow in the center.In the central part of the furnace, heat transfer to the waste and massive carbonaceous combustibles is insufficient, There are disadvantages that the thermal efficiency decreases, the exhaust gas temperature rises in the peripheral area, the superficial velocity increases, and the amount of dust entrained in the exhaust gas increases.

In addition, since waste is charged, the bulk carbon-based combustible material is not supplied to the waste charging cylinder located in the center of the furnace body, so the bulk carbon-based combustible material is supplied to the center of the high-temperature hearth. In some cases, the bed height of the lumpy carbonaceous combustible material cannot be maintained, the calorific value necessary for melting is insufficient, and stable continuous operation becomes difficult.

To compensate for this drawback, the fuel ratio is increased, the oxygen enrichment ratio is increased, and uneconomical operation is forced.

Further, in Japanese Patent Application No. 1-137160, a shaft portion provided with tuyere and tap holes (hollow cones with D / H ≦ 1 and D / d ≦ 1.5. D,
(d = diameter of cone, H = height of cone) and an enlarged hollow cone with its upper part formed at the repose angle of the massive carbonaceous combustible substance or above the repose angle. It was found that there is a case where a convex cone surface with a large bending angle is formed at the joint of and the gravity drop of the surrounding massive carbonaceous combustible material is not stable, which also disturbs the furnace condition. In addition, when the treatment scale becomes large, it is necessary to increase the inner diameter of the tuyeres at the tip and the charging cylinder. The consumption amount of the lumpy carbonaceous combustible substances in the surroundings increases with respect to the processing amount, and the fuel ratio becomes high, which is uneconomical. Conversely, if the diameter of the charging cylinder is increased, the amount of lumpy carbonaceous combustible substances supplied from the charging pipe to the high-temperature hearth can be increased, but the amount of combustion of the lumpy carbonaceous combustible substances distributed around the charging cylinder is increased. Decrease, and the ash content distributed around the inside of the charging cylinder,
The slag formation of incombustibles is not stable, it becomes difficult to melt and drip, and the peripheral gas flow path is not secured stably, and the furnace condition becomes unstable.

On the other hand, the number of stages of tuyere may be 1 to 2 when the treatment scale is small, but as the treatment scale becomes larger and the furnace diameter is expanded with the shaft shape unchanged, the reaching distance of oxygen from the tuyere However, it becomes difficult to uniformly burn the massive carbonaceous combustible material supplied to the charging cylinder to the center of the lower part of the furnace.

Some of the waste is lighter than the bulk specific gravity of the bulk carbonaceous combustible material (for example, shredder dust, separated trash, etc.). When melting these, if the lower end level of the charging cylinder is too high, the charging cylinder The ratio of the amount of lumpy carbonaceous combustibles falling around the waste filling area in the lower part may be higher, and the amount of lumpy carbonaceous combustibles may be consumed more than the calorific value necessary for the melting process.

The object of the present invention is to suppress the generation of an undesired uneven flow in the furnace, to solve the inconvenience that the calorific value is insufficient in the high-temperature hearth, and to increase the diameter of the furnace so that the flammable carbonaceous combustible It is intended to provide a waste melting furnace with a high thermal efficiency, in which a material is burned in a uniform cross section and the amount of lumpy carbonaceous combustible material in the vicinity is burned down.

[Means for Solving the Problem] In order to solve the problem, in the waste melting furnace of the present invention, one or more stages of tuyeres and tap holes are provided in the lower part of the hollow cone whose upper part is enlarged. The filling area is formed by forming a filling area for the lumpy carbonaceous combustible substance in the body, and charging the waste and the lumpy carbonaceous combustible material from above the high temperature hearth formed in the center of the lower part of the hollow cone. It is buried in and installed. Further, the inner diameter of the charging cylinder is set to 0.7 to 1.3 times the inner diameter of the uppermost tuyere tip end furnace, and a plurality of massive carbonaceous combustible substance charging ports and a plurality of exhaust gas pipes are connected to the upper part of the hollow cone. . The inner surfaces of the upper and lower parts of the hollow cone are formed at an angle of repose or more of the massive carbonaceous combustible material, and the gap δ between the lower end of the charging cylinder and the inner surface of the hollow cone.
Was set to 4 times or more of the average particle size of the lumpy carbon-based combustible material.

[Operation] A lumpy carbon-based combustible substance (hereinafter referred to as carbon-based combustible substance) is filled in the carbon-based combustible substance inlet, and is charged into the carbon-based combustible substance filling area without being emptied. When the carbon-based combustible material flows into the filling area, the carbon-based combustible material is gradually lowered above the hollow cone under the charging port. At this time, since the inner surface of the lower part of the hollow cone is formed at an angle greater than the repose angle of the carbonaceous combustible material, no space is created in the furnace. In Japanese Patent Publication No. 63-49128 mentioned above, the bulk carbonaceous combustible substance to be filled is distributed at the angle of repose, whereas the angle of the upper surface is about 20 °, so a space is created in the furnace and it is charged afterwards. The carbonaceous combustible substance that flows in is flowing while rolling on the massive carbonaceous combustible substance at the rest position. On the other hand, in the present invention, the carbon-based combustible material is inflow-filled without rolling.
Therefore, it is evenly distributed in the furnace, particle size segregation does not occur, ventilation pressure loss becomes uniform, and uneven flow of combustion exhaust gas does not occur. Furthermore,
As in the case of Japanese Patent Application No. 1-137160, since a convex pyramid surface with a large bending angle is not formed at the joint between the shaft and the hollow cone, the inflow and descent of the carbon-based combustible material can be easily performed by gravity. Be seen.

Since the lower end of the exhaust gas pipe comes into contact with the slope of the carbon-based combustible material at the rest position, the filling height is kept constant. Therefore, the pressure loss of the exhaust gas is also kept constant.

From the central charging cylinder, the waste and a part of the carbon-based combustible material are alternately charged or mixed to form a waste filling area. At this time, the inner diameter of the furnace at the tip of the uppermost tuyere is 0.7 to
By using a charging cylinder with an inner diameter of 1.3 times, the waste and carbon-based combustibles from the charging cylinder and the carbon-based combustibles from the surroundings flow in in a well-balanced manner to maintain the high-temperature hearth and secure the peripheral gas flow path. As a result, the furnace conditions stabilize. For this reason, the necessary carbon-based combustibles are supplied to the high-temperature hearth, and the calorific value does not become insufficient.

In the melting furnace of JP-B-63-49128, the inner diameter of the waste charging cylinder in the center is not specified, but it is estimated from the drawing that the inner diameter of the bottom of the narrowest hollow cone is at most 0.5
This is about twice, and the inner diameter of the charging cylinder is too narrow, and the balance between the waste and the carbon-based combustible material is poor, and a large amount of carbon-based combustible material is used.

When treating waste with a low bulk specific gravity, make the gap δ between the lower end of the charging cylinder and the inner surface of the hollow cone 4 times or more the particle size of the carbon-based combustible material, and inflow and fall amount of the surrounding carbon-based combustible material. By appropriately suppressing the above, the heat generation amount of the surrounding carbon-based combustible material necessary for the melting process is appropriately maintained, the combustion consumption amount of the carbon-based combustible material is suppressed, and the thermal efficiency is increased.

Regarding the gap δ between the lower end of this charging cylinder and the inner surface of the hollow cone,
There is no description in the above-mentioned Japanese Examined Patent Publication No. 63-49128, and it is merely set within the range of the vertical cylindrical portion far from the cone portion of the furnace body in the drawing, and the range of the hollow cone The melting furnace of the present invention in which the gap between the lower end of the charging cylinder and the inner surface of the hollow cone is specified in relation to the particle size of the carbon-based combustible material with the above-mentioned purpose is extremely superior to known furnaces. is there.

[Examples] The features of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a longitudinal sectional view of a waste melting furnace 1 and a waste melting treatment system according to a first embodiment of the present invention. For example, it is an example of the case where there is a large amount of ash and incombustibles such as incinerated ash of municipal waste and sewage sludge.

This waste melting furnace 1 has a high-temperature hearth 12 in which an agglomerated carbon-based combustible material B (hereinafter, an example using coke) is filled in a hollow cone lower part 11 with an inclined angle of 65 degrees, the upper part of which is expanded. A hollow cone upper part 15 having an enlarged upper part with an inclination angle of 68 degrees is connected to the upper part to fill a waste A, coke B and limestone C filling area 13
And constitutes a coke filling area 14. The inside of the melting furnace is filled with these filling areas 13 and 14 and has no space. The lower part 11 of the hollow cone and the upper part 15 of the hollow cone may have the same inclination angle, and the lower part 11 of the hollow cone is a hollow cone with D / H> 1 and / or D / d> 1.5. It does not matter as long as the conditions are satisfied.

The diameter of the upper part of the coke filling area 14 is increased to 5 times the diameter of the cross section of the tuyere 20 so that the superficial velocity of the combustion exhaust gas is reduced, and the diameter of the upper part of the coke filling area 14 around the upper peripheral wall 16 is 65 Four exhaust gas pipes 17 each having a degree of inclination are attached at equal intervals. The combustion exhaust gas E is supplied from the exhaust gas pipe 17 to the secondary combustion chamber 2,
Air preheater 3, gas cooler 4, dust collector 5, smoke washing device 6,
It is discharged through the induction blower 7 and the chimney 8.

The above-mentioned inclination angle and dimensional ratio are in the case of using a medium lump of blast furnace coke, and are preferably changed depending on the lumpy carbonaceous combustible substance used, for example, petroleum coke, pitch coke, electrode scrap, and the like.

On the upper part 15 of the hollow cone, a carbon-based combustible material charging port 18
There are four locations (hereinafter referred to as coke charging ports). The inner surface of the upper part of the hollow cone upper part 15 is formed at an angle of 45 degrees, which is equal to or greater than the repose angle of coke, and is connected to the coke charging port 18.

Charging cylinder 19 for charging waste A, coke B and limestone C 19
Is arranged in the center of the furnace, and the inner diameter of the charging cylinder 19 is the tuyere of the upper stage.
21 0.7 to 1.3 times the inner diameter of the furnace at the tip, preferably 0.9 to 1.1
Doubled, the lower end of the charging cylinder 19 is embedded in the coke filling area 14, and the gap δ with the inner surface of the upper part 15 of the hollow cone is 8 times the average particle diameter of coke. From the charging cylinder 19, 40 to 80% of the waste A and the coke B are charged in layers or mixed. At this time, the limestone C is charged together with the waste from the charging cylinder 19.

As for the number of exhaust gas pipes 17 and coke inlets 18, an optimum combination of a plurality of exhaust gas pipes 17 and coke inlets 18 is selected depending on the scale of the waste melting furnace and the conditions of peripheral equipment layout.

In the lower part 11 of the hollow cone, a preheated oxygen-containing gas (hereinafter referred to as blast air) is passed from the forced air blower 9 through the air preheater 3 so that the coke in the furnace is burned to form a grate of high temperature atmosphere. D) Four lower stage blown air blowing tuyere 20 and the coke distributed around the inside of the charging cylinder are burned to widen the melting range of ash and incombustibles to increase the processing capacity and preheat the peripheral coke. However, for the purpose of expanding the high temperature atmosphere, eight upper blast air blowing tuyeres 21 are symmetrically arranged between the lower blast air blowing tuyeres 20. When the treatment scale is small, it does not matter if the tuyeres 20 and 21 are constructed in one stage instead of two stages, and when the treatment scale becomes large,
You may comprise in three or more steps.

The number of tuyeres 20 and 21 may be set in various combinations depending on the inclination angle of the inner surface of the lower part 11 of the hollow cone, the selection of the inner diameter of the tuyeres 20 and 21 at the tip, and the conditions of the surrounding equipment layout. It is also possible to provide the tuyere 21 on the upper part 15 of the hollow cone. Further, the tips of the tuyere 20 and 21 serve as water-cooled tuyere to suppress the tuyere blockage caused by the slag flowing inward from the inner surface of the hollow cone lower portion 11 and flowing down the inner wall surface, and to prevent the coke supplied to the charging cylinder. It can also be actively burned.

Further, at the bottom of the hollow cone lower part 11, there is provided a tap hole 22 for discharging the ash, incombustibles, coke, and limestone ash of the waste, which are mixed and mixed at high temperature to discharge the molten slag whose basicity is adjusted. ing. As for the tap hole 22, a plurality of the same shape are provided at equal intervals, only one is used during operation, and it is also possible to rotate the hollow cone lower part 11 and attach it alternately when restarting after the furnace is stopped. Is.

The waste A descends in the charging cylinder 19 and forms the filling area 13. In this process waste A, coke B, limestone C
Is deposited in the charging cylinder 19 for 500 to 800 mm and the combustion exhaust gas temperature is maintained at about 250 to 300 ° C. In this state, the waste reaches 700 to 1000 ° C in the lower center of the charging cylinder, and by the time it reaches the high-temperature hearth 12, radiant heat from the red-hot coke and high-temperature combustion exhaust gas from the combustion of the coke cause ash and non-combustible components. Rapidly softens, melts, melts, and drip the voids in the coke grate.

The coke charged from the coke charging port 18 forms a coke filling area 14, where heat exchange is performed while descending with the combustion exhaust gas discharged to the exhaust gas pipe 17, and the temperature of the coke is gradually raised and the upper stage air is blown. When reaching the air blowing tuyere 21, a part of the CO gas in the combustion exhaust gas rising from below is preferentially burned, and the obtained heat heats it to a higher temperature and part of the blown oxygen. Burns the coke distributed around the inside of the charging cylinder. At this part, as described above, softening and melting of ash and incombustibles have started, and it is in a situation that rising gas is relatively difficult to pass through, but a ring-shaped coke layer is formed on the peripheral wall side. Therefore, the rising gas comes to pass through this portion having good air permeability. At this time, since the rising gas maintains a uniform flow in the circumferential direction and the flow velocity is increased, heat transfer is promoted at the boundary below the filling regions 13 and 14.

Furthermore, in the high-temperature hearth 12, the preheated air blown from the lower stage blowing air tuyere 20 also uniformly burns the center coke of the coke supplied into the charging cylinder, thus stabilizing the high-temperature coke grate. Maintained.

The filling height in the furnace of this example is about 2.5 m, the ventilation pressure loss of the packed bed is 100 to 200 mm water column, and the gas ejected from the tap hole is burned with a flame length of 200 to 250 mm in a state of being released to the atmosphere. To be done.

In addition, 40-70 of the blast air D is blown into the upper stage blown air tuyere 21.
Blow-in amount was effective in lowering the coke fuel ratio, and the molten slag was heated to a high temperature, and stable tapping slag was obtained.

FIG. 2 shows a second embodiment. In the waste melting furnace 1 of the present embodiment, a granular material (a lump obtained by sieving a mixture of a lump and a powder such as municipal waste incineration ash, or a powder such as sewage sludge incineration ash or dust ash) is used. When the waste is granulated by pretreatment (melting process), etc., when the packed bed of the waste is permeable, the exhaust gas is positively discharged to the extent that dust is not scattered from the charging cylinder 19 too. It can be discharged to promote preheating of the granular material and further improve the thermal efficiency. Also, each exhaust gas pipe
An exhaust gas flow rate control valve 26 for an exhaust gas pipe may be installed in each of the 17 parts. Furthermore, the charging cylinder 19 may be provided with a charging cylinder exhaust gas flow rate control valve 25. As described above, by providing the flow rate control valves 25 and 26 in the respective exhaust gas flow paths, the exhaust gas flow rate in the charging cylinder 19 can be varied according to the type, property, bulk specific gravity, water content, etc. of the waste. It becomes possible, drying of waste, preheating, dry distillation gasification, etc. are promoted, and the thermal efficiency of the furnace is further increased,
Vent pressure loss in the charging cylinder 19 is kept low, and exhaust gas temperature is 200 to 4
It can be adjusted to maintain around 00 ° C, and further, it becomes possible to control the superficial velocity with less dust scattering.

Further, the charging cylinder 19 may be configured to move up and down while performing gas sealing with the expansion joint 24 using the drive device 23.

The lower end level of the charging cylinder 19 is set to be 4 times or more, preferably about 8 times, the coke particle size so that the clearance between the charging cylinder 19 and the inner surface of the hollow cone upper portion 15 is maintained to be higher than the high temperature hearth 12. In this way, the temperature distribution can be made uniform, the drop of waste can be stabilized, the coke filling pressure in the surrounding area can be suppressed, and the positive effect can be suppressed. Therefore, if the charging cylinder is changed up and down according to the operating conditions as described above, it is possible to form an optimum heat pattern in the furnace with a reduced fuel ratio.

When the charging cylinder 19 is moved up and down, the amount of peripheral coke falling can be regulated, which has the effect of facilitating the lowering of central waste, effectively increasing the throughput and reducing the fuel ratio. At times, if there is a sign that the condition of the furnace deteriorates due to the treated material, it has the advantage that it can be used as a means of forcibly supplying the peripheral coke to the lower part of the furnace by moving it up and down at a higher level.

FIG. 3 shows a third embodiment of yet another aspect.
It has four coke inlets 18 and four exhaust pipes 17
It is an embodiment in which the arrangement is reversed. By doing so, the degree of freedom in the device layout is increased.

In the first to third embodiments described above, the coke B is sieved so that the one having a large particle size is charged into the charging cylinder 19 and the one having a small particle size is charged into the coke charging port 18. You may change it.

[Effect of the Invention] As described above, in the present invention, the lumpy carbon-based combustible substance is uniformly distributed without forming a space in the furnace and does not cause a drift. In addition, the combustion exhaust gas becomes a uniform flow, and even if the furnace diameter is expanded, uniform combustion is ensured within the horizontal cross section of the high-temperature hearth of the lumpy carbonaceous combustible material, and the combustion consumption of the surrounding lumpy carbonaceous combustible material is suppressed and thermal efficiency is improved. Is improved. Furthermore, since the pressure loss of the exhaust gas can be maintained constant, there is little fluctuation in the amount of gas ejected from the tap hole, and the oxygen-containing gas injection source pressure is also 1000 mm.
Since it can be reduced to below the water column and the pressure fluctuation in the furnace is small, molten slag can be continuously and stably discharged. Therefore, since the calorific value is not insufficient, the high-temperature hearth can be uniformly secured without increasing the fuel ratio, and stable operation can be achieved.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention, and FIG.
2 is a drawing showing a longitudinal section of a waste melting furnace and a treatment system of the embodiment, FIG. 2 is a drawing showing a second embodiment, and FIG. 3 is a drawing showing a third embodiment. A: waste, B: coke, C: limestone, D:
Blower air, E ... Combustion exhaust gas, δ ... Gap, 1 ... Waste melting furnace, 2 ... Secondary combustion chamber, 3 ... Air preheater, 4 ...
… Gas cooler, 5 …… Dust collector, 6 …… Smoke washing device, 7 ……
Induction blower, 8 ... Chimney, 9 ... Push-in blower, 11 ...
… Lower hollow cone, 12 …… High temperature hearth, 13 …… Waste, coke, limestone filling area, 14 …… Coke filling area, 15…
… Upper hollow cone, 16 …… Upper peripheral wall, 17 …… Exhaust gas pipe, 18
…… Coke charging port, 19 …… charging cylinder, 20, 21 …… blowing air blowing tuyere, 22 …… tapping port, 23 …… drive device, 24…
… Expansion joint, 25,26 …… Exhaust gas flow control valve.

Claims (1)

[Claims] 1. A tuyere and tap hole at one or more stages are provided in the lower part of the hollow cone whose upper part is enlarged to form a filling region of a lumpy carbonaceous combustible substance in the hollow cone, and in the center of the lower part of the hollow cone. A charging cylinder for charging waste and massive carbonaceous combustible material from above the high-temperature hearth to be formed is provided by being embedded in the filling zone, and the inner diameter of the charging cylinder is the innermost surface of the uppermost tuyere tip With a diameter of 0.7 to 1.3 times, a plurality of massive carbonaceous combustible substance inlets and a plurality of exhaust gas pipes are connected to the upper part of the hollow cone, and the inner surfaces of the upper and lower parts of the hollow cone have a repose angle of the massive carbonaceous combustible substance. A waste melting furnace, which is formed at the above angle and the gap δ between the lower end of the charging cylinder and the inner surface of the hollow cone is set to 4 times or more of the average particle diameter of the massive carbonaceous combustible material.