JPH0152654B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a waste incinerator that burns solid combustible material containing a large amount of ash and recovers the ash as slag. More specifically, the present invention applies to so-called garbage such as waste mainly consisting of solid combustibles, such as general waste such as sewage sludge, or industrial waste such as low-concentration contaminated material such as clothes contaminated with radioactivity. This invention relates to a waste incineration method in which the ash is converted into slag and recovered as a stable product.

(Prior Art) Incineration is one of the promising methods for treating waste containing solid combustibles, such as sewage sludge. Incineration is also advantageous as a method for treating waste from nuclear power plants, the handling of which has become a problem in recent years, ie, low-concentration contaminated materials such as clothes that are slightly contaminated with radioactivity. However, since these wastes contain a large amount of ash, a large amount of fly ash is generated when incinerated. This fly ash has to be caught and removed because it may adhere to the boiler heat transfer and interfere with heat conduction or cause air pollution. Furthermore, if the ash is taken out in a dry state, it has no other useful use, so it has to be thrown away, but as the amount increases year by year, there is a new problem in that it is difficult to find a place to dump it. However, if this ash is melted and turned into slag, almost no hexavalent chromium will be leached out, and it can be safely reused as aggregate for cement, heat insulating material, etc.

Therefore, it has been desired to burn these wastes and melt and extract the ash. by the way,
Since such waste is generally irregular in shape and poses a problem in handling and combustion, it is necessary to tear or crush it into pieces suitable for combustion prior to combustion, which tends to increase the size of combustion equipment. It was hot. For this reason, fluidized bed incinerators have recently attracted attention because of their advantages in many aspects, such as miniaturization of the device and reduction in equipment. According to this fluidized bed incinerator, waste can be input as is, and the auxiliary fuel can be washed and dried while being burned. However, since combustion in this fluidized bed is suppressed to 800 to 900°C, the ash does not dissolve as it is, but is scattered as fly ash or taken out from the dawcomer as dry ash. Therefore, it has been conventionally considered to melt the dried ash again into slag using an electric furnace, coke oven, microwave, or the like.

(Problems to be Solved by the Invention) However, according to this conventional method, in order to turn waste into slag, the dried ash discharged after fluidized combustion must be reheated and melted in an electric furnace, etc. However, it has the disadvantage of consuming a large amount of energy and increasing costs.

Therefore, an object of the present invention is to provide a waste combustion method that can turn waste into slag without using extra fuel.

Structure of the Invention (Means for Solving the Problems) In order to achieve the above object, the waste incineration method of the present invention partially incinerates the waste in a fluidized bed incinerator using most of the combustion air. Combustion gas including unresolved gas discharged from the fluidized bed incinerator is supplied as primary air to the slag tap type cyclone combustion furnace, while the ash and unburned waste that overflowed the fluidized bed incinerator are used as granular fuel to feed the slag tap. In the slug tap type cyclone combustion furnace, the particulate fuel is placed in a swirling flow of primary air with the remainder of the combustion air added as secondary air, and is combusted in space, using fuel other than waste. The ash contained in the fluidized waste is recovered as molten slag.

(Example) Hereinafter, the present invention will be described in detail based on an example of a waste incineration system shown in the drawings.

The waste incineration system shown is a fluidized bed incinerator 1.
and a slag tap type cyclone incinerator (hereinafter sometimes abbreviated as slag tap furnace) 2,
In the fluidized bed incinerator 1 in the first stage, most of the combustion air necessary for complete combustion of the waste 3 is used for incomplete combustion, while the residue 3a generated by the slag tap type cyclone combustion furnace 2 in the next stage is used as fuel. Secondary combustion is performed using the remaining combustion air and the combustion gas including unresolved gas discharged from the fluidized bed incinerator 1,
As a whole, the waste 3 is completely combusted using combustion air at an appropriate air ratio, and its ash 3b is melted and recovered as slag.

The fluidized bed incinerator 1 burns the silica sand and waste 3 while fluidizing them using combustion air supplied from a blower 17, and employs a known fluidized bed incinerator. The waste 3 is introduced into the fluidized bed incinerator 1 from a waste hopper 5 equipped with a screw feeder 4 at the bottom of the tank, either as it is or in an amorphous state divided into several pieces. On the other hand, the fuel residue 3a is taken out using the downcomer 6.
It is carried out after. The combustion residue 3a overflowing into the downcomer 6 is a residue mainly composed of carbon with combustible components remaining due to incomplete combustion, and has lost most of its moisture and is in the form of finely crumbled pieces or granules.
In the figure, reference numeral 7 indicates a hopper for temporarily storing the ash and fuel 3a that have overflowed the fluidized bed incinerator 1, and 8 indicates a hopper suitable for burning the above-mentioned ash and fuel 3a in the slag tap type cyclone incinerator 2. This is a pulverizer that grinds into fine particles of about 100μm.

In the slug tap type cyclone combustion furnace 2, solid fuel is placed on a swirling flow of combustion air, separated into coarse particles and fine particles by centrifugal action, and the fine solid fuel is combusted in the air, while the coarse solid fuel is transferred to the inner wall of the furnace body. The aim is to collect the ash in a molten state by attaching it to the ash and burning it under the load of a high-fire furnace. This slag tap type cyclone combustion furnace 2 can be implemented by adopting either a known horizontal slag tap furnace or a vertical slag tap furnace, but a vertical slag tap furnace, especially a slag separation chamber that allows the exhaust gas to flow out from the slag tap opening together with the molten slag, can be used. It is most preferable to employ a type of slag tap furnace. This slag tatsu furnace 2
is a cyclone burner 10 that forms a swirling flame.
It consists of a furnace body 11 that traps ash by forming a molten slag film on the lining wall, a slag separation chamber 12 and a slag cooling tank 13 connected directly below the furnace body 11, and exhaust gas from the slag tap port 14. The molten slag is discharged and extracted into the side flue 15 in the slag separation chamber 12, where it is separated from the molten slag. Combustion gas from the fluidized bed incinerator 1 is supplied to the slag tap furnace 2 as primary air through a flue 9, and a part of the combustion air supplied to the fluidized bed incinerator 1 is extracted and used as secondary air. It is supplied as. In addition, the ash and combustion residue 3a discharged from the fluidized bed incinerator 1 are discharged from the crusher 8.
It is pulverized into fine particles of about 100 μm and supplied to the cyclone burner 10. This cyclone burner 10
The fuel residue 3a, etc., is supplied to the fuel tank by pneumatic transportation.
Incidentally, the exhaust gas from this slag tap furnace 2 is passed through the heat exchanger 1.
After exchanging heat with combustion air at step 6, it is released into the atmosphere.

According to the waste incineration system configured as above, irregularly shaped waste is fed from the waste hopper 5 into the fluidized bed incinerator 1 by the screw feeder 4 either as it is or after being cut into several pieces. It burns while flowing together with the silica sand in the combustion chamber. At this time, fluidized combustion is carried out under combustion air that is the majority of the amount actually required to completely burn the waste, preferably 60 to 90% of the theoretical air amount, and most preferably about 70 to 80%. This results in incomplete combustion, which is kept at a relatively low temperature of around 900℃. Therefore, the waste 3 becomes a combustible residue 3a mainly composed of carbon with combustible content remaining, loses most of its moisture, becomes finely crumbled pieces or granules, and sequentially overflows into the downcomer 6. This fuel residue 3a, etc. is temporarily stored in the hopper 7, and then processed in the crusher 8.
It is crushed into fine particles of about 100 μm and is used as fuel suitable for combustion in the slag tap furnace 2. Then, this particulate fuel/residue (hereinafter referred to as particulate fuel) 3a is transported to the slug tap furnace 2 by means of transport (not shown), such as a screw conveyor, and is injected into the cyclone burner 10 by pneumatic transport.

On the other hand, combustible combustion gas containing CO, H ₂ , CO ₂ , H ₂ O, N ₂ and the like is discharged from the fluidized bed incinerator 1 due to incomplete combustion. This combustion gas is supplied as primary air to the slag tap furnace 2 through the flue 9, and is swirled into the furnace from the cyclone burner 10 together with the fine particles 3a and secondary air. The fine particles 3a mixed in the swirling flow formed by the combustion gas supplied from the fluidized bed incinerator 1 and the remaining combustion air are spatially combusted in the swirling flow of particles with relatively small particle sizes. Particles with a relatively large size are scattered toward the furnace inner wall surface due to the violently accelerated swirling action of the swirling vortex flow, are captured by the molten slag film attached to the wall surface, and are then burned under a high furnace load. Therefore, the particulate fuel residue 3a adhering to the slag film on the row wall becomes ash through high-load combustion, then melts and gradually flows down. Further, the particulate fuel residue 3a that has been burned in space also melts while falling on the swirling flow, or is captured by the slag film and melted. The molten slag 3v flows down from the slag tap port 14 to the slag cooling tank 13, is cooled and solidified therein, and is then taken out.
Incidentally, the ash gas is released into the atmosphere after preheating the combustion air in the heat exchanger 16 and recovering heat.

Here, the remaining combustion air supplied to the slag tap furnace 2 as secondary air is 50% to 50% of the theoretical air amount.
It is about 30%. Therefore, the combustion air used in the entire waste incineration system is maintained at an air ratio of about 1.1, which is about 10% excess than the theoretical air amount. Note that oxygen-enriched air of 21 to 30% _O2 may be used as combustion air.

In addition, in this waste incineration system, the combustion air necessary to completely burn the waste is distributed between the fluidized bed incinerator 1 and the slag tap furnace 2 for partial combustion, and in the slag tap furnace 2 in the next stage. Since the waste itself to be incinerated is used as fuel,
Auxiliary fuel and slag tap furnace 2 for heating fluidized sand
Other than the fuel used in the pilot burner, no extra fuel other than the waste is used to burn the waste or melt its ash.

Effects of the Invention As is clear from the above explanation, the waste incineration method of the present invention distributes the combustion air necessary for complete combustion of waste to a fluidized bed incinerator and a slag tap type cyclone incinerator. During the fluidized combustion in the first stage, most of the combustion air is used to incompletely burn the waste to obtain combustion gas containing unburned gas and fine particulate residue in which combustible matter remains. In the stage slag tap furnace, the residual combustion air and the combustion gas are used as fuel for high-load secondary combustion, so the waste can be combusted without using excess fuel other than the waste. Moreover, the ash therein can be melted and recovered as slag.

[Brief explanation of drawings]

The drawing is a principle diagram of a waste incineration system showing an embodiment of a system for carrying out the waste incineration method of the present invention. DESCRIPTION OF SYMBOLS 1... Fluidized bed incinerator, 2... Slag tap type cyclone combustion furnace, 3... Waste, 3a... Particulate combustion residue, 3b... Slag, 8... Pulverizer, 9... Flue.

Claims (1)

[Claims] 1 The waste is partially combusted in a fluidized bed incinerator using most of the combustion air, and the combustion gas containing unburned gas discharged from the fluidized bed incinerator is supplied as primary air to the slug tap cyclone combustion furnace, while the above-mentioned The ash and unburned waste that overflowed the fluidized bed incinerator are made into granular fuel and supplied to the slug tap type cyclone incinerator, where the pulverized fuel is used as primary air and the remainder of the combustion air is converted into secondary air. A waste incineration method characterized by spatial combustion in a swirling flow added as air and recovering the ash content as dissolved slag.