JP4918833B2 - Waste melting furnace and waste melting furnace operating method - Google Patents

Description

  The present invention relates to a waste melting furnace for thermally decomposing waste to melt residues, and an operation method thereof.

As a technique for treating waste, there is a gasification melting process in which waste such as municipal waste and shredder dust is pyrolyzed to generate a combustible gas, and the pyrolysis residue is melted and discharged as slag.
This treatment method has the advantage that the combustion heat can be recovered by gasifying the waste, and the final disposal amount such as landfill disposal can be reduced by melting the residue.
There are several types of melting furnaces for performing such treatment, and one of them is a shaft type waste gasification melting furnace.
In this shaft-type waste gasification and melting furnace, for example, coke deposited at the bottom of the furnace is burned, waste is put on this high-temperature coke, pyrolyzed and gasified, and then the pyrolysis residue is removed. It is a furnace of a system that performs a process of melting into slag (see Patent Document 1).

  In such a shaft-type waste gasification and melting furnace, the functions of the furnace body are roughly divided into three in the vertical direction. That is, a high-temperature combustion zone in which coke is deposited at the bottom of the furnace is provided, a waste accumulation layer is provided on the high-temperature combustion zone, and a free board portion having a large space is provided above the furnace body.

  And in each said part, oxygen-containing gas blowing is performed. A main tuyere is provided in the high-temperature combustion zone, and oxygen-enriched air is blown into the coke deposited and burned to melt the pyrolysis residue of the waste. In addition, the waste accumulation layer is provided with a sub tuyere, and air is blown in to thermally burn the waste deposited and partly burned and slowly flow the waste. In addition, the freeboard part is provided with a three-stage tuyere, and air is blown into the pyrolyzed gas (combustible gas) generated by pyrolyzing the waste to partially burn and maintain the interior at a predetermined temperature. .

  As described above, the shaft-type waste gasification and melting furnace is a facility for performing pyrolytic gasification and melting treatment of waste in one furnace. The input waste is pyrolyzed and separated into gas and residue. The gas contains a large amount of flammable gas and is burned in a secondary combustion furnace. After heat is recovered by a boiler or economizer, relatively coarse dust is removed by a cyclone, cooled by a temperature reducing device, and harmful gas is removed by a dust collector. Is dedusted and diffused. In addition, the pyrolysis residue moves downward in the furnace, is melted in the coke high-temperature combustion zone at the lower part of the furnace, and is discharged as slag and metal.

  Until the gas generated in the gasification and melting furnace reaches the dust collector via the secondary combustion furnace, boiler, cyclone, and temperature reducing device, relatively coarse particles of the gas fall into each device. To do. For this reason, dust (referred to as fall ash) that has fallen into each device arranged between the gasification melting furnace and the dust collector is extracted, and the extracted fall ash is disposed of in landfill.

Incidentally, in response to a request to reduce the amount of landfill disposal to reduce the load on the landfill disposal site, it has been attempted to blow and melt the generated dust from the tuyere of the gasification melting furnace to form slag (Patent Document 2). reference).
In Patent Document 2, dust scattered from the gasification melting furnace is collected by a dust remover such as a cyclone, and the collected dust is blown into the furnace from the tuyere.
Japanese Patent Laid-Open No. 9-60830 JP-A-8-285250

In the dust treatment method of Patent Document 2, dust scattered from the top of the gasification melting furnace is collected by a dust remover such as a cyclone provided in the exhaust gas pipe, and the collected dust is temporarily stored in a hopper. It is cut out and blown into the furnace from the tuyere.
However, dust has large particle size dust and large lump of dust, and even if it is closed in the tuyere or blown into the furnace, it does not melt in a short time and stays at the tuyere tip to inhibit gas flow There is a problem that the situation inside the furnace may be worsened.

  The present invention has been made to solve the above-described problems, and dust generated from a waste melting furnace is blown from the tuyere without closing the tuyere or deteriorating the condition in the furnace. An object of the present invention is to provide a waste melting furnace capable of being melted and an operation method thereof.

(1) In the waste melting furnace according to the present invention, a high-temperature combustion zone is formed in the lower part of the furnace, and a waste layer is formed above the high-temperature combustion zone. A waste melting furnace,
A tuyere that blows oxygen-containing gas into the high-temperature combustion zone, and an airflow separator that receives supply of dust discharged and recovered from the waste melting furnace and classifies the dust into fine dust and coarse dust, A device for blowing fine dust from the tuyere, and a device for charging coarse dust into the furnace from the top or side of the waste melting furnace. The classification is performed by an air flow having a flow rate comparable to or higher than the gas flow rate in the furnace .

(2) In addition, in the apparatus described in (1) above, the airflow separation device recovers the fall ash from at least one of the secondary combustion furnace, the boiler, the cyclone, and the temperature reducing device connected to the waste melting furnace. It is characterized by having a device for supplying to the device.

(3) Further, in the method of operating a waste melting furnace according to the present invention, a high-temperature combustion zone is formed in the lower part of the furnace, a waste layer is formed above the high-temperature combustion zone, and an oxygen-containing gas is formed in the high-temperature combustion zone. A waste melting furnace that has a tuyere to blow in, thermally decomposes the input waste and melts the residue,
A dust collecting step for collecting the dust discharged from the waste melting furnace, a classification step for classifying the dust collected in the dust collecting step into fine dust and coarse dust, and fine dust from the tuyere And a dust melting step for charging and melting coarse dust from the top or side of the waste melting furnace into the furnace, and the classification step is the same as the gas flow rate in the gasification melting furnace. It is characterized in that airflow classification is performed by an airflow having a flow velocity of about or higher .

(4) In the above (3), the dust recovery step recovers the fallen ash from at least one of the secondary combustion furnace, boiler, cyclone, and temperature reducing device connected to the waste melting furnace. Including the step of performing.

In the present invention, blowing a classifying device for classifying the dust to fine dust and coarse dust is supplied with dust recovered is discharged from the waste melting furnace, the granules dust from the tuyere device And a device for charging coarse dust into the furnace from the top or side of the waste melting furnace, without closing the tuyere with the dust or deteriorating the in-furnace situation. It can be blown and melted from the tuyere.
In addition, as a classification device for classifying into fine ash and coarse ash, coarse particle dust is separated by using an air flow separation device that classifies with an air flow having a flow rate equal to or higher than the gas flow velocity in the gasification melting furnace. Even if it is fed as it is from the top or side of the waste melting furnace, it settles sufficiently with respect to the gas flow in the furnace at the top of the waste melting furnace, so it can be easily melted without splashing outside the furnace. .

FIG. 1 is an explanatory diagram of a waste gasification melting furnace according to an embodiment of the present invention.
As described above, the gasification melting furnace 1 deposits coke at the bottom of the furnace, blows oxygen-enriched air into the coke layer, and burns it to form a high-temperature combustion zone. Waste is introduced and thermally decomposed to melt the residue.

Such a gasification melting furnace 1 has the following structure.
The overall shape is a bowl-shaped and cylindrical shape, with the upper part being expanded in diameter. The upper diameter-enlarged portion is a free board portion 3. A waste material inlet 5 is provided at the upper end of the furnace, and in the vicinity of the waste material inlet 5 there is a secondary material conveyor 7 that conveys coke and molten slag property modifier limestone to the inlet. is set up.
A gas outlet 9 is provided near the upper end of the furnace, and a molten slag outlet 11 is provided at the lower part of the furnace.

A main tuyere 13 for blowing air for burning coke or oxygen-enriched air is provided at a position where a high-temperature combustion zone is formed in the lower part of the furnace. A blower pipe 15 is connected to the main tuyere, and a blower 17 that blows air or oxygen-enriched air to the main tuyere 13 is connected to the blower pipe 15.
A sub tuyere 19 is provided at the position of the waste existing above the high-temperature combustion zone for blowing air for fluidizing the input waste. The freeboard unit 3 is provided with a three-stage tuyere 21 for blowing air for partially combusting pyrolysis gas (combustible gas) generated in the lower part of the furnace.

  A secondary combustion furnace 23 for burning the combustible gas discharged from the gasification melting furnace 1 is installed on the downstream side of the gas outlet 9, and a boiler 25, which is a heat recovery device, is installed on the downstream side of the secondary combustion furnace 23. is set up. Further, an economizer 27, which is also a heat recovery device, is installed on the downstream side of the boiler 25, and a cyclone 28 for removing relatively coarse dust in the exhaust gas is installed on the downstream side of the economizer 27. Is provided with a temperature-decreasing tower 29 which is a gas cooler for cooling the heat-recovered exhaust gas to a temperature suitable for exhaust gas purification treatment. Further, a bag filter 31 is installed on the downstream side of the temperature reducing tower 29.

In the secondary combustion furnace 23, the boiler 25, the economizer 27, the cyclone 28, and the temperature reducing tower 29, coarse dust in the exhaust gas from the gasification melting furnace falls and is extracted as fall ash. And the fall ash conveyance conveyor 33 for collecting and conveying the fall ash extracted from each apparatus is installed.
Further, a sieving device 35 is provided as a classification device that receives the supply of the falling ash from the falling ash conveyor 33 and classifies the ash into fine ash and coarse ash. In addition, although the fall ash conveyance conveyor 33 and the sieve apparatus 35 are connected by the conveyance conveyor, this conveyance conveyor is abbreviate | omitting illustration.

Below the sieving device 35, a fine ash storage tank 37 for storing fine ash sieved by the sieving device 35 is provided. The fine-grained ash storage tank 37 is provided with a rotary valve 39 for cutting out the fine-grained ash from the fine-grained ash storage tank 37, and the cut-out fine ash is oxygenated to the main tuyere 13 via the chute 41 and the gate valve 43. It is supplied to the blower pipe 15 for supplying the contained gas.
A coarse ash conveying conveyor 45 is provided that receives the coarse ash on the sieve from the sieving device 35 and conveys the coarse ash on the top of the gasification melting furnace.

The waste gasification and melting treatment in the waste gasification and melting furnace configured as described above is performed as follows.
Waste such as municipal waste, industrial waste or waste incineration residue, coke and limestone are weighed and put into the gasification melting furnace 1. Among the components charged into the gasification melting furnace 1, coke is deposited at the bottom of the furnace, and air or oxygen-enriched air (hereinafter referred to as oxygen-containing gas) is blown into the main tuyere 13.
Coke is combusted by blowing the oxygen-containing gas, and a high-temperature combustion zone is formed. The thrown-in waste stays in the upper part of the high-temperature combustion zone while flowing by the air blown from the sub tuyere 19 to form a fluidized layer. Waste is preheated while it is fluidized and is pyrolyzed to generate flammable gases.

The thermal decomposition residue of the waste is melted in the high temperature combustion zone and extracted from the molten slag outlet 11 at the bottom of the furnace.
On the other hand, the combustible gas generated by the thermal decomposition of the waste is partly combusted when air is blown from the three-stage tuyere 21 in the free board portion 3 and is discharged from the gas outlet 9.
The gas discharged from the gas outlet 9 is blown into the secondary combustion air in the secondary combustion furnace 23 and burned, and then sent to the boiler 25 and the economizer 27 for heat recovery. The heat-recovered exhaust gas is subjected to cyclone 28 to remove relatively coarse dust in the exhaust gas, and further sprayed with water in a temperature reducing tower 29 to be cooled to about 200 ° C. or less.
Next, harmful substance removing agents such as activated carbon for adsorbing and removing slaked lime powder and dioxins for removing hydrogen chloride are blown into the exhaust gas, and sent to the bag filter 31 for dust collection. The dust collection ash collected by the bag filter 31 is sent to a fly ash treatment apparatus, subjected to heavy metal elution prevention treatment, and disposed of in landfill.

Since the fall ash falls before the gas discharged from the gasification melting furnace 1 reaches the bag filter 31, the secondary combustion furnace 23, the boiler 25, the economizer 27, the cyclone 28, and the temperature reducing tower 29 Dropped ash is extracted and collected and transported to the fallen ash transport conveyor 33. Dropped ash is transported from the falling ash transport conveyor 33 to the sieving device 35 by a transport conveyor (not shown) and sieved.
Then, the coarse ash on the sieve is conveyed by the coarse ash conveying conveyor 45, and the coarse ash is put into the gasification melting furnace 1 as it is from the top of the furnace, and is melted together with the pyrolysis residue of the waste to form slag. . Coarse ash has a relatively large particle size even if it is fed directly from the top of the furnace, so it hardly scatters outside the furnace and is melt-processed.

  Fine ash under the sieve is stored in the fine ash storage tank 37, a predetermined amount is cut out by the rotary valve 39, supplied into the blower pipe 15 through the chute 41 and the gate valve 43, and from the main tuyere 13. Blow into the hot combustion zone. When fine ash is blown from the main tuyere into the high-temperature combustion zone, the fine ash is heated and melted in a short time while passing through the combustion space (raceway) at the tip of the main tuyere, and flows down to the bottom of the furnace, resulting in pyrolysis residue. Together with the molten material.

  As described above, the fall ash is separated into the coarse ash and the fine ash by the sieving device 35, and only the fine ash is blown from the main tuyere, so that the main tuyere may be blocked by the fall ash. In addition, it is possible to prevent deterioration in the furnace due to poor melting at the main tuyere. Further, since the coarse ash is also charged from the top of the furnace and melted, the total amount of fallen ash can be melted to form slag, and the amount of landfill disposal can be reduced.

The sieve of the sieving device 35 is preferably a sieve that is sieved so that the coarse ash on the sieve is not larger than the particle size so that it does not easily scatter out of the furnace even if it is fed directly from the top of the furnace. That is, it is preferable to determine the sieve so that dust having a particle size or larger that can sufficiently settle with respect to the gas flow in the furnace at the upper part of the gasification melting furnace is used as the sieve. For example, a sieve having a size of about 5 to 10 mm is preferred as the sieve of the sieving device 35, since the coarse ash on the sieve is not easily scattered from the furnace top even if it is directly fed from the furnace top.
Moreover, although the format of the sieving device 35 is not ask | required, it is preferable to use a vibration sieve.

A part of the collected ash collected by the bag filter 31 may be conveyed to the sieving device 35 and melted together with the falling ash.
The heavy metals contained in the dust collection ash by melting a part of the dust collection ash are contained in a non-eluting form in the slag produced by the melt treatment. Therefore, it is possible to reduce the amount of dust collection ash that is subjected to heavy metal elution prevention treatment and landfilled.
In addition, it is preferable to operate according to said process to melt-process 20-25% of the dust collection ash collect | recovered with the bag filter.

Moreover, as a classification apparatus which classifies fall ash into a fine ash and a coarse ash, not only a sieve apparatus but other classification apparatuses, such as an airflow separator, a cyclone, and a centrifugal separator, can be used. In the airflow separation device, the fall ash is classified into fine ash that is transported into the airflow and coarse ash that settles without being transported by the airflow at a predetermined flow velocity. Fine ash is collected by a bag filter or the like and stored in the fine ash storage tank 37 so that the coarse ash is charged into the furnace. Even if the coarse ash is charged as it is from the top of the furnace by classifying it with an air flow at the same or higher flow rate than the gas flow rate in the gasification melting furnace, Falling ash having a particle size that can settle sufficiently and does not easily fly out of the furnace can be classified so as to be coarse ash.
In the cyclone, coarse ash settles and is separated and classified.

  Moreover, in addition to charging coarse ash from the top of the gasification melting furnace, it may be charged by providing a charging port on the side of the furnace, or may be charged from both. Alternatively, coarse ash may be transported to a waste pit for storing waste and charged into a gasification melting furnace together with the waste.

It is explanatory drawing of the waste gasification melting furnace which concerns on one embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gasification melting furnace 5 Waste inlet 9 Gas outlet 13 Main tuyere 23 Secondary combustion furnace 25 Boiler 29 Temperature-reducing tower 33 Falling ash conveyance conveyor 35 Sieve apparatus 37 Fine grain ash storage tank 45 Coarse ash conveyance conveyor

Claims (4)

A waste melting furnace in which a high-temperature combustion zone is formed at the bottom of the furnace and a waste layer is formed above the high-temperature combustion zone, and the waste that has been charged is thermally decomposed and the residue is melted,
A tuyere that blows oxygen-containing gas into the high-temperature combustion zone, and an airflow separator that receives supply of dust discharged and recovered from the waste melting furnace and classifies the dust into fine dust and coarse dust, A device for blowing fine dust from the tuyere, and a device for charging coarse dust into the furnace from the top or side of the waste melting furnace. A waste melting furnace characterized by classification with an air flow having a flow rate comparable to or higher than the gas flow rate in the furnace. 2. A device for recovering fall ash from at least one of a secondary combustion furnace, a boiler, a cyclone, and a temperature reducing device connected to a waste melting furnace and supplying the ash to an airflow separation device. The waste melting furnace described in 1. A high-temperature combustion zone is formed in the lower part of the furnace, a waste layer is formed above the high-temperature combustion zone, and there is a tuyere that blows oxygen-containing gas into the high-temperature combustion zone. A method of operating a waste melting furnace for melting residues,
A dust collecting step for collecting the dust discharged from the waste melting furnace, a classification step for classifying the dust collected in the dust collecting step into fine dust and coarse dust, and fine dust from the tuyere And a dust melting step for charging and melting coarse dust from the top or side of the waste melting furnace into the furnace, and the classification step is the same as the gas flow rate in the gasification melting furnace. A method for operating a waste melting furnace, characterized in that air classification is performed by an air flow having a flow velocity of about or higher . The dust recovery step includes a step of recovering fall ash from at least one of a secondary combustion furnace, a boiler, a cyclone, and a temperature reducing device connected to the waste melting furnace. Waste melting furnace operation method.

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