JPH11248121A - Municipal refuse incinerator and its operation method - Google Patents

Abstract

(57) [Abstract] [Problem] To stabilize the operation of the refuse incinerator 1 and simplify the exhaust gas treatment of the ash melting furnace. SOLUTION: This is a municipal incinerator having a refuse incinerator 1 and an ash melting furnace 19 for melting and processing incineration ash and fly ash discharged from the refuse incinerator 1, and a part of the exhaust gas from the refuse incinerator. And the waste gas from the ash melting furnace are merged into one
The air whose oxygen concentration is increased by an oxygen concentrator is used as secondary air of the refuse incinerator 1 while being used as secondary air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a municipal solid waste incinerator having an ash melting furnace, and more particularly to a municipal solid waste incinerator for treating high-calorie municipal solid waste and an operating method thereof.

[0002]

2. Description of the Related Art Various wastes such as municipal solid waste and sewage sludge have been incinerated in an incineration facility, and the resulting incinerated ash and dust have conventionally been disposed of in landfills. However, due to the problem of depletion of landfill sites and the problem of groundwater contamination due to elution of harmful heavy metals, the necessity for weight reduction, volume reduction, and detoxification by melting is increasing.

[0003] Under such a background, a melting treatment method using a residual carbon in ash, coke, kerosene, and electric power as a heat source has been proposed.
Actual processing is performed in part. Among them, there are a plasma arc heating method and a resistance heating method as a melting furnace using electric power as a heat source.

The resistance heating type ash melting furnace has a counter electrode disposed in a melting slag and heats and melts the ash by electric resistance heat (Joule heat) caused by direct current or alternating current.
It is characterized by 1) high thermal efficiency, 2) little generated gas, 3) no flicker due to no arc generation, and 4) separate slag that separates molten slag and molten metal.

FIG. 2 shows a flow sheet of a municipal solid waste incinerator having an ash melting furnace. In FIG. 2, 1 is an incinerator, 2
1 is a generator, 19 is a DC electric resistance type ash melting furnace, together with its auxiliary equipment, incineration facilities, power generation facilities,
It constitutes an ash melting facility. The incinerator 1 is illustrated as a stoker-type incinerator.

[0006] Among the incineration facilities, 22 is a garbage pit, which stores the received garbage and sequentially puts it into the incinerator 1 for incineration. The generated exhaust gas is discharged from a chimney 6 via a boiler 2, a gas cooler 3, a bag filter 4, and an induced blower 5. Dust (fly ash) in the exhaust gas is removed by the bag filter 4 and the collected soot is stored in a soot storage tank 8 by a soot transfer conveyor 7. In addition, incineration ash generated in the incineration process,
The boiler ash and the like are collected in a dry ash removal device 9 and guided to a magnetic separator 11 and a vibrating sieve 12 by an ash transfer conveyor 10 to remove iron 13 and bulky materials 14 and then to an ash transfer conveyor 15.
And stored in the incineration ash storage tank 16.

[0007] In the power generation facility 20, heat generated by the incineration process is recovered by the boiler 2, converted into power by a cycle composed of the boiler 2, turbine, condenser, and condensate tank, and further converted into power by the generator 21. Converting. The generator 21 is operated in parallel with an external power system, and the electric power is supplied to the incinerator 1 or the melting furnace 19.
Power is supplied to

In the ash melting facility, ash is cut out from the dust storage tank 8 and the incinerated ash storage tank 16 and supplied to an ash melting furnace 19 via an ash hopper 18 by an ash supply conveyor 17. The ash is melted in an ash melting furnace 19 to become a molten sludge 23, which is cooled and stored in a sludge storage tank 24. 25 is a metal storage tank. Since the exhaust gas discharged from the ash melting furnace 19 contains CO gas, the exhaust gas is treated by the CO gas combustor 26, and then the dust collector 4a such as a bag filter is used.
The air is discharged from the chimney 6 through the induction blower 5a. In addition,
The exhaust gas of the ash melting furnace 19 may be used as the secondary combustion gas of the refuse incinerator 1 without passing through the CO gas combustor 22.

In place of the stoker-type incinerator 1, a fluidized-bed incinerator shown in FIG. 3 may be used. In a fluidized bed incinerator, a fluidized bed is formed by fluidizing air. In the high-temperature fluidized medium, refuse is dried and burned, and is composed of an air diffuser, an incombustibles extraction device, an incombustibles separator, a fluidized media circulation device, and the like.

The refuse pretreated by crushing or the like in a flowable state is supplied to the upper space of the fluidized bed which is red hot by the combustion heat of the refuse, and the inside and a part of the fluidized bed are burned in the freeboard. To keep the fluidized bed stable,
It is necessary to keep the temperature of the fluidized bed in an appropriate range with the supply of the appropriate amount of air.However, the temperature of the fluidized bed tends to decrease for low-quality waste, and the temperature of the fluidized bed rises excessively for high-quality waste. There is a concern that partial melting may occur. Therefore,
Temperature control is performed by adjusting the amount of air, the air temperature, the layer thickness, the amount of water sprayed in the furnace, or by performing auxiliary combustion. The temperature in the fluidized bed is set to 500 to 700 ° C. It is desirable to maintain the temperature at 900 ° C. or higher in the free board for 2 to 4 seconds from the viewpoint of decomposing and removing dioxin.

The fluidizing air is supplied from the lower part of the fluidized bed as primary air, and secondary air is blown into the free board to complete the combustion of the combustible gas. The flow air amount and pressure vary depending on the furnace type, but are usually 700 to 150 per furnace floor area.
0m3 [normal] / m2h, wind pressure is 1500-2500
About mmAq is selected. Fluid media is required to have an appropriate particle size distribution and heat and abrasion resistance.
Silica sand of about 2 mm is used. The fluid medium withdrawn from the bottom of the furnace together with the incombustible material is returned to the furnace again after mechanically removing the incombustible material, and the thickness of the fluidized bed is substantially maintained by being recycled.

[0012]

Generally, municipal solid waste is 1
It has a calorific value of 800 to 2000 kcal / kg. However, in the case of plastic waste in municipal waste, industrial waste, and RDF produced from municipal waste, it is 4,000 to 4,000.
Some have a calorific value of 5000 kcal / kg. When such a high heat generation amount of refuse is burned in a stoker type or a fluidized bed incinerator, primary combustion is actively performed, so that the temperature on the stoker and in the fluidized bed is excessively increased. As a result, the secondary combustion becomes inactive, the temperature of the secondary combustion chamber decreases, and the decomposition and removal of dioxin are not performed sufficiently. In particular, in the fluidized bed incinerator, as described above, if the temperature in the fluidized bed rises excessively, there is a concern that partial melting may occur, and it is necessary to spray water in the furnace.

The present invention has been devised in view of the above-mentioned problems. In a refuse incinerator for incinerating refuse having a high calorific value, exhaust gas having a low oxygen concentration is used as primary air for a refuse incinerator. The use of air with an increased oxygen concentration as the secondary air lowers the temperature of the primary combustion of the garbage incinerator and raises the temperature of the secondary combustion, making process control easy and dioxin decomposition and removal. An object of the present invention is to provide an efficient municipal solid waste incinerator and an operation method thereof.

[0014]

To achieve the above object, the municipal waste incinerator according to the first aspect of the present invention melts incinerators and incinerated ash and fly ash discharged from the incinerators. An incinerator for municipal solid waste having an ash melting furnace, wherein a part of the exhaust gas from the refuse incinerator and the exhaust gas from the ash melting furnace are combined and used as primary air for the refuse incinerator, and the oxygen is concentrated by an oxygen concentrator. The air whose concentration has been increased is used as secondary air of a refuse incinerator.

The method of operating a municipal solid waste incinerator according to the second aspect of the present invention is directed to a municipal solid waste having an incinerator and an ash melting furnace for melting and processing incinerated ash and fly ash discharged from the incinerator. This is a method of operating an incinerator, in which 20 to 30% of exhaust gas from a refuse incinerator is extracted, and exhaust gas from an ash melting furnace is added to use as primary air for the refuse incinerator. Is used as secondary air of a refuse incinerator.

Next, the operation of the present invention will be described. In the case of incineration of refuse, in primary combustion such as on a stoker or in a fluidized bed, the temperature is maintained at a low temperature of 500 to 750 ° C. to extend the residence time of the refuse. In secondary combustion, dioxin is decomposed and removed. Therefore, it is desirable that the exhaust gas stay at a high temperature of 900 ° C. or higher for 2 to 4 seconds. In the present invention, attention is paid to the fact that the oxygen concentration in the exhaust gas of a refuse incinerator is as low as 11 to 12%. The secondary combustion temperature can be increased by lowering the secondary combustion temperature and using air having an increased oxygen concentration of 30 to 40% as the secondary air. In addition, the amount of exhaust gas discharged from the ash melting furnace is extremely small compared to the exhaust gas discharged from the refuse incinerator, and the amount of fine dust contained in the exhaust gas is extremely large. Processing at a high cost is wasteful. Therefore, 20 to 3 of exhaust gas from refuse incinerator
By extracting 0% and adding the exhaust gas of the ash melting furnace to the primary air of the refuse incinerator, it is possible to effectively use the exhaust gas collector of the refuse incinerator.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a flow sheet of the municipal solid waste incinerator of the present invention. In the figure, reference numeral 1 denotes an incinerator. The type of the incinerator 1 may be a stoker type or a rotary furnace type, but the fluidized bed type shown in FIG. 3 is most suitable for the present invention. Reference numeral 2 denotes a boiler, which recovers thermal energy from the high-temperature exhaust gas 29 from the incinerator 1. Reference numeral 3 denotes a gas cooler that lowers the temperature of the exhaust gas 29 to a temperature suitable for the dust collector 4 such as a bag filter provided downstream. A heater 31 raises the temperature of the exhaust gas 29 to a temperature suitable for the NOx removal catalyst tower 32 provided downstream. 6 is a chimney. 19 is a DC electric resistance type ash melting furnace. 33 is a wet type exhaust gas treatment device. The type of the wet exhaust gas treatment device 33 is, for example, as disclosed in Japanese Patent Application No. 8-142631, in which the absorbent is sprayed down from the upper portion of the absorption tower, and the exhaust gas is caused to flow in from the lower portion of the tower, and from the upper portion of the tower. It may be a form that discharges and absorbs the dust in the exhaust gas into the absorbing liquid.
996, and a combination of a bubbling tank and a jet scrubber as shown in FIG.
Reference numeral 30 denotes an oxygen concentrator, which treats air (oxygen concentration 21%) to increase the oxygen concentration to 30 to 40%. As the type of the oxygen concentrator, one using a semipermeable membrane is widely used.

Next, the operation of the present embodiment will be described. Municipal waste, RDF, industrial waste, and the like 39 having a high calorific value are put into the incinerator 1 and incinerated. Incineration ash 37 as incineration residue
Is discharged from below, and the high-temperature exhaust gas 29 is discharged from above. The exhaust gas 29 passes through the boiler 2 and the gas cooler 3,
The heat energy is collected and sent to the dust collector 4 where the exhaust gas 2
The dust in 9 is removed. Exhaust gas 29 leaving the dust collector 4
Is discharged from the chimney 6 to the outside via the heater 31 and the catalyst tower 32.

20 to 30% of the exhaust gas 29 sent from the dust collector 4 to the heater 31 is extracted for circulation. Incinerator 1
Ash 37 from the boiler 2, fly ash 38 from the boiler 2, the gas cooler 3, and the dust collector 4 are sent to the DC resistance ash melting furnace 19 and melted. The exhaust gas 35 from the ash melting furnace 19 is
Although the flow rate is extremely small as compared with the exhaust gas 29 from the incinerator 1, it contains high-concentration (150 to 200 g / m3) dust. Exhaust gas 35 is extracted from the exhaust gas 3 after most of the dust is removed by the wet exhaust gas treatment device 33.
4 and is sent as primary air 36 of the incinerator 1.
The oxygen concentration in the primary air 36 is 11 to 12%. The air 40 whose oxygen concentration has been increased to 30 to 40% by the oxygen concentrator 30 is sent to the incinerator 1 as secondary air.

As described above, since the primary air having a low oxygen concentration is used in the incinerator 1, a fluidized bed incinerator is used as the incinerator 1 to incinerate high calorific value municipal waste. Even if the large amount of primary air required to maintain the fluidity of the fluidized bed is used, there is no possibility that the temperature in the fluidized bed will rise excessively, and the residence time of the refuse in the fluidized bed will be sufficient. Can be kept.

Since the air having a high oxygen concentration is used as the secondary air of the incinerator 1, a small amount of air is required.
While maintaining a high temperature of 0 ° C. or higher, the residence time of the exhaust gas can be maintained for 2 to 4 seconds. The ash melting furnace 19
Exhaust gas from the incinerator 1 is not directly discharged to the outside.
Since it is used as the secondary air, the CO gas combustor 26 shown in FIG. 2 is not required, and the dust in the exhaust gas 35 does not need to be completely removed.

The present invention is not limited to the embodiment described above, and various modifications can be made without departing from the gist of the invention. For example, the wet exhaust gas treatment device 33
May be omitted.

[0023]

As described above, the municipal solid waste incinerator and the method of operating the same according to the present invention combine the part of the exhaust gas from the refuse incinerator with the exhaust gas from the ash melting furnace to form primary air in the refuse incinerator. In addition, the air having an increased oxygen concentration is used as the secondary air of the refuse incinerator, so that the following excellent effects are obtained. (1) By keeping the primary combustion temperature of the refuse low, the residence time can be sufficiently maintained and a good combustion state can be secured. (2) Since the temperature of the secondary combustion can be made sufficiently high and the residence time can be made sufficient, the decomposition and removal of dioxin can be sufficiently performed. (3) The treatment of exhaust gas from an ash melting furnace with a high dust concentration can be omitted or simplified.

[Brief description of the drawings]

FIG. 1 is a flow sheet of the municipal solid waste incinerator of the present invention.

FIG. 2 is a flow sheet of the conventional municipal solid waste incinerator.

FIG. 3 is a sectional view of a fluidized bed incinerator.

FIG. 4 is a flow sheet of the wet exhaust gas treatment device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Waste incinerator 2 Boiler 4 Dust collector 19 Ash melting furnace 30 Oxygen concentrator

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hideki Iwata 2-1-1 Toyosu, Koto-ku, Tokyo Ishikawajima Harima Heavy Industries Co., Ltd. Tokyo 1st Factory (72) Inventor Toshiyuki Suzuki 2-1-1 Toyosu, Koto-ku, Tokyo No. 1 Ishikawajima Harima Heavy Industries Co., Ltd. Tokyo 1st factory

Claims (2)

[Claims] Claims 1. An municipal incinerator having a refuse incinerator and an ash melting furnace for melting and processing incineration ash and fly ash discharged from the refuse incinerator. Municipal waste incineration characterized by combining exhaust gas from the melting furnace and using it as primary air for waste incinerators, and using air whose oxygen concentration has been increased by an oxygen concentrator as secondary air for waste incinerators apparatus. 2. A method of operating a municipal solid waste incinerator having a refuse incinerator and an ash melting furnace for melting and processing incinerated ash and fly ash discharged from the refuse incinerator, wherein the refuse incinerator has an exhaust gas of 20%. ３０30% is extracted, and the exhaust gas of the ash melting furnace is added to use as the primary air of the refuse incinerator, and the air whose oxygen concentration is increased to 30-40% by the oxygen concentrator is used for the secondary of the refuse incinerator. A method for operating a refuse incinerator characterized by using it as air.