JPH0520645B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention. In a high-temperature hearth formed of lumpy carbon-based combustible materials, municipal waste, sewage sludge, various industrial wastes, or intermediate products obtained by dehydrating, drying, incinerating, or crushing them are melted, This invention relates to a waste melting furnace that recovers noncombustible materials as slag.

[Conventional technology]

In a typical waste melting furnace, waste such as municipal waste to which coke has been added as a lumpy carbon-based combustible material is charged from the top of a vertical shaft furnace, and is passed through the drying zone, carbonization gasification zone, and It descends sequentially through the combustion melting zone. On the other hand, oxygen-containing gas or oxygen-enriched gas is blown into the furnace through the tuyeres, and coke and carbonaceous matter produced by thermal decomposition are burned at high temperatures in the high-temperature hearth, and the heat of combustion burns out non-combustible materials. The melt turns into slag and slag is generated.

At this time, in order to reduce the viscosity of the slag, limestone or silica stone is charged from the top of the furnace together with the waste as a basicity regulator. The high-temperature combustion exhaust gas rises as a countercurrent through the waste-filled bed in the shaft, thermally decomposing the waste, and organic matter in the waste is discharged as combustible gas, which is recovered as combustion heat.

In addition, the following was announced in Special Publication No. 63-49128. In this method, a waste charging tube is installed in the center of the top of the shaft furnace, the lower end is buried in the coke filling area, a coke charging port is placed around the waste charging tube, and an exhaust pipe is placed around the waste charging tube. It has been set up. Waste is placed in the center and coke is charged separately to cover the periphery, in order to prevent dust blowing up from the waste filling area due to exhaust gas by the suppressing action of the coke.

[Problem to be solved by the invention]

However, since the bulk carbon-based combustible material to be filled is distributed within the furnace at an angle of repose, the ventilation pressure loss at the peripheral wall portion where the filling height is low is small, and drifting occurs in the radial direction within the furnace. The charged lumpy carbon-based combustible material tends to have coarse grains distributed in the peripheral wall and fine grains in the center, and the coarse grained part has a smaller ventilation pressure loss than the fine grained part, and uneven flow in the furnace is often promoted. be done.

This is because the lumpy carbon-based combustible material charged into the furnace
This is because the particles flow while rolling over the previously charged and resting block of carbon-based combustible material, and the coarser the particles, the better they roll and reach the lower part of the peripheral wall. This is a phenomenon that occurs due to the presence of space within the furnace.

As a result of the uneven flow, the peripheral flow becomes an uneven flow with more gas flow in the periphery and less gas flow in the center, which reduces heat exchange between waste and carbon-based combustible materials in the center of the furnace, reducing the thermal efficiency of the furnace. However, there are disadvantages in that the exhaust gas temperature rises in the peripheral area, the superficial velocity increases, and the amount of entrained dust in the exhaust gas increases.

Furthermore, since carbon-based combustible materials are not supplied to the waste charging tube placed in the center of the furnace body for charging waste, it is difficult for carbon-based combustible materials to be supplied to the center of the high-temperature hearth. , the bed height of the carbon-based combustible material cannot be maintained, and the amount of heat required for melting may be insufficient, making stable continuous operation difficult.

To compensate for this drawback, increase the fuel ratio,
This would force them to increase the oxygen enrichment rate or engage in uneconomical operations.

It is an object of the present invention to provide a waste melting furnace that suppresses the occurrence of undesirable drift in the furnace and eliminates the disadvantage of insufficient heat generation in the high-temperature hearth.

[Means to solve the problem]

In order to solve this problem, the waste melting furnace of the present invention connects a hollow cone with an enlarged upper part above a shaft part provided with a tuyere and a tap. Next, a filling area of the lumpy carbon-based combustible material is formed in the hollow cone, and a charging tube for charging the waste and the lumpy carbon-based combustible material from above the high-temperature hearth formed in the center of the shaft part is inserted into the filling area. It will be buried in the Then, a plurality of bulk carbon-based combustible material charging ports and a plurality of exhaust gas pipes are connected to the upper part of the hollow cone. The inner surface of the upper part of the hollow cone was formed at an angle equal to or greater than the angle of repose of the bulk carbon-based combustible material.

[Effect]

A lump of carbon-based combustible material (hereinafter referred to as carbon-based combustible material) is filled into a carbon-based combustible material charging port and charged into a carbon-based combustible material filling area without emptying.
When the carbon-based combustible material flows into the filling area, it gradually descends to the upper part of the hollow cone below the charging port. At this time, since the inner surface of the upper part of the hollow cone is formed at an angle equal to or greater than the angle of repose of the carbon-based combustible material, no space is created in the furnace. Therefore, the carbon-based combustible material flows in and is filled without rolling. Therefore, the particles are distributed uniformly in the furnace, no particle size segregation occurs, and the ventilation pressure loss is uniform.
No uneven flow of combustion exhaust gas occurs.

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

From the central waste charging tube, waste and part of the carbon-based combustible material are charged alternately or mixed to form a waste filling area. Therefore, the necessary carbon-based combustibles are supplied to the high-temperature hearth, and there is no shortage of calorific value.

〔Example〕

Hereinafter, the features of the present invention will be specifically explained using examples with reference to the drawings.

FIG. 1 shows a 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, this is an example of a case where there is a large amount of ash and non-combustible content, such as incineration ash of municipal waste or sewage sludge.

This waste melting furnace 1 has a high-temperature hearth 12 filled with a lumpy carbon-based combustible material B (hereinafter an example using coke) in a shaft part 11, and above the hearth 12, an enlarged upper part with an inclination angle of 60 degrees is formed. The hollow cones 15 are connected to form a region 13 filled with waste A, coke B and limestone C, and a region 14 filled with coke. The inside of the melting furnace is filled with these filling regions 13 and 14 and has no space.

The diameter of the coke filling area 14 is expanded to three times the diameter of the tuyere cross section so as to reduce the superficial velocity of the combustion ash gas, and a 50 degree slope is formed around the upper peripheral wall 16 of the coke filling area 14. Four exhaust gas pipes 17 with
are installed at equal intervals. The combustion exhaust gas E is transferred from the exhaust gas pipe 17 to a secondary combustion chamber 2, an air preheater 3,
The gas is discharged through a gas cooler 4, a dust collector 5, a smoke scrubber 6, an induced blower 7, and a chimney 8.

The above-mentioned inclination angle and dimensional ratio are for the case where a medium lump of blast furnace coke is used, and are preferably changed depending on the lump carbon diameter combustible material used, such as petroleum coke, pit coke, electrode scrap, etc.

Four lumpy carbon-based combustible material charging ports 18 (hereinafter referred to as coke charging ports) are provided in the upper part of the hollow cone 15. The upper inner surface of the hollow cone 15 is
It is formed at an angle of 45 degrees, which is greater than the angle of repose of coke, and is connected to the charging port 18.

A charging tube 19 for charging waste A, coke B, and limestone C is arranged in the center of the furnace, and the charging tube 1
The lower end of 9 is buried in a coke filling region 14 . Waste A and coke B are discharged from the charging cylinder 19.
30 to 70 percent of the raw materials are charged in layers or mixed. At this time, limestone C is charged from the charging tube together with the waste. A plurality of optimal combinations of the number of exhaust gas pipes 17 and coke charging ports 18 are selected depending on the scale of the waste melting furnace and the equipment layout conditions around the furnace.

In addition, preheated oxygen-containing gas (hereinafter referred to as blown air D) is supplied to the shaft portion 11 from a forced air blower 9 through an air preheater 3 so as to burn the coke in the furnace and form a grate with a high temperature atmosphere. Eight lower air blowing tuyeres 20 are used to blow in air, and eight
The upper air blowing tuyere 21 of the book is symmetrically arranged in the middle of the lower air blowing tuyere 20. The tuyere 20, 21 may be configured in one stage instead of two stages, upper and lower.

Further, at the bottom of the lower furnace of the shaft part 11, there is provided an outlet 22 for discharging molten slag in which the ash of waste, incombustible materials, coke, and limestone are melted and mixed at high temperature and the basicity has been adjusted. .

Waste A descends inside the charging tube 19 and enters the filling area 13.
begins to form. In this process, 500 to 800 mm of waste is deposited in the charging tube 19, and the combustion exhaust gas temperature is maintained at approximately 250°C. In this state, the waste reaches 700 to 1000°C at the center of the lower level of the charging tube. There is.
By the time they reach the high-temperature hearth 12, the ash and non-combustibles rapidly soften, melt, melt, and drip through the gaps in the coke grate due to the radiant heat from the red-hot coke and the high-temperature combustion exhaust gas from coke combustion. start.

The coke charged from the coke charging port 18 forms a coke filling area 14, where it exchanges heat with the combustion exhaust gas discharged into the exhaust gas pipe 17 while descending, and the coke gradually increases its temperature and is blown into the upper stage. When reaching the air blowing tuyere, a portion of the CO gas in the flue gas rising from below is preferentially combusted, and the resulting heat is used to further heat the CO gas to a higher temperature. In this region, the ash and non-combustible components have started to soften and melt as described above, making it relatively difficult for the rising gas to pass through. A ring-shaped coke layer is formed on the peripheral wall side, and rising gas passes through this portion with good air permeability.
At this time, the flow velocity of the rising gas is maintained uniform in the circumferential direction, and the flow velocity is increased.
Heat transfer is promoted at the boundary between the filled regions 13 and 14.

Furthermore, in the high-temperature hearth 12, the coke bed is maintained by the coke supplied into the central charging cylinder, and the high-temperature coke grate is stably maintained by the preheated air blown from the lower air blowing tuyere 20. maintained.

The filling height in the furnace in this example is approximately 1.8 m, the ventilation pressure loss of the packed bed is 200 to 300 mm water column, and the gas ejected from the tap has a flame length of 150 to 200 mm when released to the atmosphere. is burned.

In addition, the blow air D is supplied to the upper air blowing tuyere 21.
Injection of 10 to 20 percent of the amount of molten metal was effective in lowering the coke-fuel ratio, raised the temperature of the molten slag, and produced stable tapped slag.

FIG. 2 shows a second embodiment. In the waste melting furnace 1 of this embodiment, exhaust gas may also be discharged from the charging tube 19. Further, each exhaust gas pipe 17 may be provided with an exhaust gas flow rate control valve 26, respectively.
Further, the charging cylinder 19 also has a charging cylinder exhaust gas flow rate control valve 25.
may be installed.

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

Flow control valves 25 and 2 are installed in the middle of each exhaust gas flow path.
By providing 6, the type, nature,
The flow rate of exhaust gas inside the charging tube 19 can be varied according to the bulk specific gravity, moisture, etc., which promotes drying, preheating, carbonization, etc. of waste, and further increases the thermal efficiency of the furnace. The filling height can be adjusted to keep the ventilation pressure drop low and the exhaust gas temperature between 250 and 400°C, and it is also possible to control the superficial velocity to reduce dust scattering.

Maintaining the lower end level of the charging tube 19 at a temperature of approximately 700 to 1000°C above the high-temperature hearth 12 stabilizes the descent of the waste and suppresses the charging pressure of the surrounding lumpy carbon-based combustible material. , aggressive descent can be suppressed. Therefore, if the charging tube is varied up and down to achieve the above-mentioned temperature conditions in accordance with the operating conditions, it becomes possible to form an optimal heat pattern in the furnace with a reduced fuel ratio.

Furthermore, by moving the charging tube 19 up and down, the amount of descending peripheral coke can be controlled, which has the effect of accelerating the descent of central waste, and is effective in increasing the throughput and reducing the fuel ratio. Occasionally, when there are signs that the furnace condition is deteriorating, it has the advantage that it can be moved up and down at a higher level and used as a means to forcibly feed peripheral coke to the lower part of the furnace.

FIG. 3 shows the third embodiment in yet another state. This has four coke charging ports 18 and four
This is an embodiment in which the arrangement of the exhaust gas pipe 17 is reversed. This increases the degree of freedom in device layout.

〔Effect of the invention〕

As explained above, according to the present invention, the lumpy carbon-based combustible material is uniformly distributed within the furnace without creating any space, and no drift occurs. In addition, the combustion exhaust gas flows uniformly, ensuring a uniform high-temperature hearth of the lumpy carbon-based combustible material, and improving thermal efficiency. Furthermore, since the pressure loss of the exhaust gas can be maintained constant, there is little variation in the amount of gas ejected from the tap, the oxygen-containing gas blowing pressure can be reduced to less than 1000 mm of water column, and the pressure fluctuation in the furnace is small, so the molten slag can be continuously You can get hot water stably. Therefore, since a lack of calorific value is not caused, a high temperature hearth can be uniformly maintained without increasing the fuel ratio, and stable operation can be achieved.

[Brief explanation of the drawing]

1 to 3 show embodiments of the present invention, and the first
The figures are diagrams showing a cross section of the waste melting furnace and the processing system of the first embodiment, FIG. 2 is a diagram showing the second embodiment, and FIG. 3 is a diagram showing the third embodiment. A...Waste, B...Coke, C...Limestone, D...Blow air, E...Combustion exhaust gas, 1...
Waste melting furnace, 2... Secondary combustion chamber, 3... Air preheater, 4... Gas cooler, 5... Dust collector, 6...
Smoke cleaning device, 7... induced blower, 8... chimney, 9...
... Forced blower, 11... Shaft part, 12...
...High-temperature hearth, 13...Waste, coke, limestone filling area, 14...Coke filling area, 15...
Hollow cone, 16... Upper peripheral wall, 17... Exhaust gas pipe, 18... Coke charging port, 19... Charging tube,
20, 21...Air blowing tuyere, 22...
Tap water outlet, 23...drive device, 24...expansion joint,
25, 26...Exhaust gas flow rate control valve.

Claims (1)

[Claims] 1. A shaft portion provided with a tuyere and a spout is connected to a hollow cone whose upper part is enlarged, and a region filled with a lumpy carbon-based combustible material is formed within the hollow cone,
A charging tube into which waste and bulk carbon-based combustible materials are charged from above the high-temperature hearth formed in the center of the shaft is buried in the filling area, and a plurality of carbon blocks are placed in the upper part of the hollow cone. A waste melting furnace, characterized in that a system combustible material charging port is connected to a plurality of exhaust gas pipes, and the inner surface of the upper part of the hollow cone is formed at an angle of repose at or above the angle of repose of a lumpy carbon-based combustible material.