JPH04302909A - Method and apparatus for treating waste - Google Patents

Abstract

PURPOSE:To stabilize the melting operation by decreasing the quantity by changing the charge put onto a coke bed into thermally decomposed gas using a rotary kiln and then preheating, to prevent thermal decomposition residue from sticking to the internal wall of rotary kiln on the furnace rear side, and to prevent iron oxide from being present in slag when waste is melted by thermal decomposition. CONSTITUTION:The waste and lime stone and coke, if necessary, are supplied into a rotary kiln 1 to thermally decompose the waste in the rotary kiln 1 by suppressed combustion. In a coke bed fusion furnace 2 connected to the furnace rear side of rotary kiln 1, the thermal decomposition residue discharged from the rotary kiln 1 is melted to be harmless.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention applies to hydrocarbon-based combustible materials such as paper, fibers, trash, trees and plants, plastics, rubber, and leather, and non-combustible materials such as glass, metal, earth and sand, concrete, and ceramics. The present invention relates to a waste treatment method and apparatus for treating waste consisting of materials by thermal decomposition.

0002

[Prior Art] Conventionally, as waste treatment methods, (1)
As disclosed in Japanese Patent Publication No. 63-57682, a thermal decomposition section for depositing waste is provided in the upper part of the furnace, and a sludge melting section is provided in the lower part of the furnace for slag-melting noncombustible materials. , a tar removal device for removing tar from the pyrolysis gas is provided in the upper part of the pyrolysis section, the tar from the tar removal device is supplied to the pyrolysis section of the furnace, and a tar removal device is provided in the lower part of the pyrolysis section in the furnace. (2) As shown in FIG.
Waste is supplied to a rotary kiln 1 equipped with a burner on the front side of the furnace, and the waste is thermally decomposed to generate flammable gas, which is burned in a re-combustion chamber connected to the bottom of the furnace.
After the thermal decomposition residue discharged from the rotary kiln 1 is incinerated in the post-combustion stoker furnace 8 provided at the lower part of the re-combustion chamber, the generated incinerated ash is water-cooled in the water-cooling tank 25 to form water-cooled incinerated ash. A method is known in which the water-cooled incinerated ash is conveyed out by a conveyor, further melted at a high temperature in an electric furnace 26, and rapidly cooled in a granulated water tank 28 to be taken out as granular slag.

0003

[Problem to be Solved by the Invention] In the case of the waste treatment method (1) above, since the gas flow in the furnace and the waste flow are countercurrent, the discharge temperature of the pyrolysis residue cannot be controlled. Therefore, there is a drawback that the discharge temperature of the pyrolysis residue fluctuates due to changes in the properties of the waste, and the furnace conditions of the coke bed melting furnace installed below the pyrolysis section change. In addition, since the top of the coke bed melting furnace is connected to the gas introduction part of the pyrolysis section, changes in ventilation pressure loss in the pyrolysis section fluctuate the pressure at the top of the coke bed melting furnace, which controls the air blowing to the coke bed. In addition, pressure fluctuations affect the molten slag extraction equipment, and in the case of a water seal type gas seal, the depth of the water seal changes, reducing safety and complicating operation management. . In addition, in the case of the waste treatment method (2) above, the pyrolysis product gas is subjected to secondary combustion on the bottom side of the rotary kiln 1, and the pyrolysis residue is post-combusted, so the bottom side of the rotary kiln 1 is The disadvantage is that the interior is locally overheated due to radiant heating from the afterburning chamber and the afterburning stoker furnace 8, and as a result, pyrolysis residues fuse to the inner wall on the discharge side of the rotary kiln 1, causing coating trouble. There is. Furthermore, as the waste is heated and melted in the oxidizing atmosphere in the melting furnace, some iron is present in the slag as iron oxide, which causes the slag to turn black and become brittle, so the slag can be recycled as a resource. It is disadvantageous to use it.

0004

[Means for Solving the Problems] The present invention uses a coke bed melting furnace to melt the pyrolysis residue in a reducing atmosphere, thereby completely melting the entire pyrolysis residue at a high temperature and removing iron oxide. Prevents it from being caught in the slag. In addition, by connecting a coke bed melting furnace near the outlet side of the rotary kiln without connecting a post-combustion stoker furnace or secondary combustion furnace, the temperature at the bottom side of the rotary kiln can be easily controlled. Prevents thermal decomposition residue from fusing to the inner wall at the bottom of the furnace.

[0005]

Embodiment FIGS. 1 to 5 show an embodiment of the present invention, in which an ignition burner 8 and a supply air nozzle 7 for suppressed combustion are provided on the front side of a rotary kiln 1. A vertical coke bed melting furnace 2 is provided at the bottom of the fixed hood on the bottom side of the rotary kiln 1.
The upper part of a high temperature holding furnace 5 having a heating torch 13 is connected to the slag outlet 4 provided at the bottom of the coke bed melting furnace 2, and the lower end opening of the high temperature holding furnace 5 is connected to the top of the furnace. is disposed underwater in a granulated cooling tank 6 having a rake-type residue scraping and discharging device 14, and an annular air supply pipe 11 surrounding the coke bed melting furnace 2 is provided at the bottom of the coke bed melting furnace 2. 11 and coke bed melting furnace 2
It is connected to the lower part of the air supply pipe 12 via a plurality of air pipes 12. Further, a charging port 10 for charging coke and the like is provided at the top of the coke bed melting furnace 2.

A nozzle 9 for discharging flammable gas is provided on the upper part of the fixed hood on the bottom side of the rotary kiln 1, and the nozzle 9 is connected to the exhaust gas inlet of a cyclone 15 through a pipe, and the exhaust gas of the cyclone 15 is The outlet is connected via a pipe to the exhaust gas inlet of a secondary combustion furnace 16, and the secondary combustion furnace 16 is connected to a boiler 17 for operating a turbine 18, and the exhaust gas outlet of the boiler 17 is connected to the electrostatic precipitator 1.
The exhaust gas outlet of the electrostatic precipitator 19 is connected to the exhaust gas inlet of the smoke cleaning device 21, and the exhaust gas outlet of the smoke cleaning device 21 is connected to the exhaust gas inlet of the white smoke preventer 23 via the induction blower 22. The exhaust gas outlet of the white smoke preventer 23 is connected to the chimney 24. Further, the exhaust gas outlet of the electrostatic precipitator 19 is branched through a pipe and a blower 20 and connected to an air supply nozzle 7 provided in front of the rotary kiln 1.

In the apparatus of the embodiment described above, the waste to be treated is charged into the rotary kiln 1 by a charging device 3 together with limestone or limestone and coke. The charged waste is suppressed and combusted by the oxygen contained in the gas blown from the air supply nozzle 7. In other words, part of the combustible components such as hydrocarbons contained in the waste is combusted near the kiln inlet, and at the same time the temperature rises due to the heat of combustion, and the remaining hydrocarbons are pyrolyzed and gasified in a reducing atmosphere. . Incombustible matter, ash, etc. that are not thermally decomposed at this time become thermal decomposition residues, which are filled in the upper part of the packed bed of the coke bed melting furnace 2 together with limestone or limestone and coke while maintaining a high thermal decomposition temperature. In addition, when coke is not supplied to the rotary kiln 1 or when the coke supplied to the rotary kiln 1 is insufficient, the insufficient amount of coke is charged from the charging port 10 and is filled into the upper part of the packed bed of the coke bed melting furnace 2. Ru.

Air and oxygen supplied to the annular air supply pipe 11 are passed through the air supply pipe 12 to the coke bed melting furnace 2.
is fed to the tuyere at the bottom of the The oxygen in this supply gas is
The coke at the bottom of the packed bed is burned to form a high-temperature coke bed, and at the same time, limestone and pyrolysis residues present in the packed bed above the scorching coke bed are heated in a reducing atmosphere and turned into molten slag. The molten slag flows down through gaps in the red-hot coke bed and is discharged from a slag outlet 4 provided at the lower part of the coke bed melting furnace 2. The extracted molten slag is passed through a high temperature holding furnace 5 kept at a high temperature by a heating torch 13, etc.
The molten slag is stably slaged while preventing a drop in fluidity due to a drop in temperature. The discharged molten slag falls into a granulated water cooling tank 6 provided at the lower part of the high-temperature holding furnace 5, where it is crushed and rapidly cooled to become a slag slag. The water slag is discharged by a rake-type residue scraping and discharging device 14. Further, the water vapor generated in the lower part of the high temperature holding furnace 5 is discharged to the secondary combustion furnace via the gas discharge nozzle B.

On the other hand, the flammable gas generated in the rotary kiln 1 and the combustible gas generated in the coke bed melting furnace 2 and rising to the top of the furnace are mixed in a fixed hood on the bottom side of the rotary kiln, and then passed through the nozzle. After entering the cyclone 15 through the cyclone 9 and removing the contained char and dust, it is introduced into the secondary combustion furnace 16. The combustible gas introduced into the secondary combustion furnace is combusted by the combustion air blown in, and the temperature is 800°C or higher and the CO concentration is 50ppm (O2 = 12%) or lower.
Obtain high-temperature exhaust gas with an O2 concentration of 6% or more. The high-temperature exhaust gas is allowed to remain in the secondary combustion furnace for more than 2 seconds, and at the same time,
By blowing in NH3 (ammonia) and mixing, a denitrification reaction is caused. These high temperature exhaust gases enter the connected boiler 17 and are cooled. At this time, the steam obtained by the boiler drives the turbine 18 to obtain electric power. Exhaust gas leaving the boiler 17 enters an electrostatic precipitator 19 with high dust removal efficiency to remove dust, and then is introduced into a connected wet smoke cleaning device 21 and a connected exhaust gas circulation blower 20. The exhaust gas that has entered the wet smoke cleaning device 21 is cleaned with an alkaline aqueous solution to remove HCl and SOX.
After removing acidic gases such as mercury, heavy metals such as mercury, and soot and dust not removed by the dust collector, the pressure is increased by the induction blower 22, the temperature is raised by the white smoke preventer 23, and the air is discharged from the chimney 24. . The gas introduced into the exhaust gas circulation fan 20 is blown into the rotary kiln 1 through the nozzle 7 and is used for suppressed combustion.

0010

According to the present invention, waste and limestone, or waste, limestone, and coke, which are charged to the coke bed melting furnace 2, are heated in advance in the rotary kiln, and at the same time, the waste The amount of limestone is reduced to a residue consisting mainly of non-combustible components by evaporation of water and gasification of most of the combustible components, and limestone is calcined and decomposed in the high-temperature section of the rotary kiln, so it cannot be melted in the coke bed melting furnace 2. The amount of heat required for the temperature raising process can be reduced compared to when waste is directly charged into a coke bed melting furnace at room temperature, reducing coke consumption and at the same time ensuring stable operation of the melting furnace. can. Waste and limestone or waste and limestone and coke are supplied into the rotary kiln 1, and the waste is thermally decomposed by suppressed combustion in a reducing atmosphere, and then connected to the fixed hood on the bottom side of the rotary kiln 1. Since the thermal decomposition residue discharged from the rotary kiln 1 is melted in the reducing atmosphere in the coke bed melting furnace 2, iron oxide is prevented from being interposed in the slag discharged from the coke bed melting furnace 2. In addition, the rotary kiln 1 has a fixed hood on the bottom side, and a post-combustion stoker furnace and 2
By connecting the top of the vertical coke bed melting furnace 2 without connecting the secondary combustion furnace, the temperature on the outlet side of the rotary kiln 1 can be easily controlled.
It is possible to prevent thermal decomposition residue from being fused to the inner wall on the exit side of the reactor. Further, since the gas in the coke bed melting furnace 2 is discharged without affecting the inside of the rotary kiln 1, the temperatures of the rotary kiln 1 and the coke bed melting furnace 2 can be easily controlled.

[Brief explanation of the drawing]

FIG. 1 is a partially longitudinal side view of a waste treatment device.

FIG. 2 is a longitudinal sectional side view showing the waste supply side of the waste treatment apparatus shown in FIG. 1;

3 is a longitudinal sectional side view showing the vicinity of a coke bed melting furnace and a high temperature heating tank in the waste treatment apparatus shown in FIG. 1. FIG.

4 is a side view showing a portion between a cyclone and an electrostatic precipitator in the waste treatment apparatus shown in FIG. 1. FIG.

5 is a longitudinal sectional side view showing a portion between an electrostatic precipitator and a chimney in the waste treatment apparatus shown in FIG. 1. FIG.

FIG. 6 is a longitudinal side view showing an example of a conventional waste treatment device.

[Explanation of symbols]

1 Rotary kiln 2 Coke bed melting furnace 3 Charging device 4 Slag outlet 5 High temperature holding furnace 6. Granulated water cooling tank 7 Air supply nozzle 9 Nozzle 10 Loading inlet 11 Annular air supply pipe 12 Air pipe 13 Heating torch 14 Rake type residue scraping discharge device 15 Cyclone 16 Secondary combustion furnace 17 Boiler 18 Turbine 19 Electrostatic precipitator 20 Exhaust gas circulation fan 21 Smoke cleaning device 22 Induced blower 23 White smoke preventer 24 Chimney

Claims (2)

[Claims] 1. Supplying waste and limestone or waste, limestone and coke into a rotary kiln 1, and pyrolyzing the waste in the rotary kiln 1 by suppressed combustion,
A waste treatment method in which the pyrolysis residue discharged from the rotary kiln 1 is melted and rendered harmless in a coke bed melting furnace 2 connected to the lower part of the fixed hood on the bottom side of the rotary kiln 1. 2. A feeding device 3 for feeding waste and limestone or waste, limestone and coke is provided on the front side of the rotary kiln 1, and a vertical coke feeder is provided at the bottom of a fixed hood on the bottom side of the rotary kiln 1. The top of the bed melting furnace 2 is connected, and the upper part of the high temperature holding furnace 5 is connected to the lower discharge port 4 of the coke bed melting furnace 2. Waste treatment equipment located in.