JP4918834B2 - 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.

  Dust collected by a dust collector (hereinafter referred to as dust collection ash) (in this specification, the case where both falling ash and dust collection ash are included is simply called dust) because it contains heavy metals derived from waste. It has been treated to prevent elution with heavy metal stabilizers and landfilled with fallen ash.

However, heavy metal elution prevention treatment is expensive, and there is also a demand for reducing the amount of landfill disposal to reduce the load on the landfill disposal site.
Therefore, in response to such a problem that heavy metal elution prevention treatment costs are required and a request to reduce the amount of landfill disposal, it has been attempted to blow and melt the generated dust from the tuyeres of the gasification melting furnace to make slag. Yes. (See Patent Document 2 and Patent Document 3)

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. Also, in Patent Document 3, when dust (falling ash and dust collection ash) is blown from the tuyere, a basicity adjusting agent such as lime powder is added to adjust the basicity of the dust (CaO / SiO ₂ weight ratio). However, the fluidity of the melt formed at the tip of the tuyere is maintained and is smoothly discharged without being retained.
Japanese Patent Laid-Open No. 9-60830 JP-A-8-285250 Japanese Patent Laid-Open No. 11-101430

  According to the dust treatment method of Patent Document 2, coarse dust out of dust scattered from the gasification melting furnace can be collected and melted, but fine dust collected by a filtration dust collector such as a bag filter. Cannot cope with the problem that the heavy metal elution prevention processing cost is required, and a sufficient solution to the request to reduce the amount of landfill disposal cannot be expected.

In the dust processing method of Patent Document 3, since the property and amount of dust vary depending on the type and amount of waste, it is necessary to adjust the basicity accordingly, and there is a problem that operation management becomes complicated.
In addition, there is a limit to adjusting the fluidity of the melt formed at the tuyere where dust is blown, only by adjusting the basicity, and there is a problem when gasifying and melting waste that generates a large amount of dust. Occurs. That is, increasing the amount of dust blown reduces the temperature around the tuyere, so that the condition of the high-temperature combustion zone is maintained normally, the oxygen concentration of the oxygen-enriched air blown into the tuyere is increased, or the amount of blown air Need to increase. In this case, the consumption of coke also increases, so that the amount of coke used increases and the operating cost increases.

  The present invention has been made to solve the above-described problems, and allows dust generated from a waste melting furnace to be blown and melted from a tuyere without increasing the amount of coke used, thereby preventing heavy metal elution. The purpose is to provide a waste melting furnace that can reduce the amount of dust required and reduce the amount of landfill disposal and its operation method.

(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,
Tuyere that blows oxygen-containing gas into the high-temperature combustion zone;
The supply of dust and carbon material discharged and recovered from the waste melting furnace is supplied to a ventilation pipe communicating with the tuyere and a mixture of the dust and the carbon material from the tuyere. A dust / carbon material supply device that blows
A carbon material supply device for supplying a carbon material to the dust / carbon material supply device;
And a carbon material supply amount control device for adjusting the carbon material amount supplied to the dust-carbon material supply unit from the carbon material supply device,
The carbon material supply amount control device includes means for measuring the blowing pressure and / or the blowing amount of oxygen-containing gas blown from the tuyere, and based on the measured blowing pressure and / or blowing amount, In the case of an increase and / or a decrease in the amount of blown air, the carbon material supply amount is controlled to increase .

(2) In the method of operating a waste melting furnace according to the present invention, a high-temperature combustion zone is formed at the bottom of the furnace, a waste layer is formed above the high-temperature combustion zone, and an oxygen-containing gas is blown into the high-temperature combustion zone A waste melting furnace operating method having a tuyere and thermally decomposing charged waste and melting the residue,
The mixture of dust and carbon material discharged and recovered from the waste melting furnace is blown from the tuyere with a dust / carbon material supply device, and the supply amount of the carbon material supplied to the dust / carbon material supply device is Control based on the measured value of the blowing pressure and / or the blowing rate of the oxygen-containing gas blown from the mouth, and control to increase the supply amount of the carbon material when the blowing pressure increases and / or the blowing rate decreases It is characterized by.

In the 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 waste that is thermally decomposed and melts the residue. A melting furnace,
A tuyere that blows oxygen-containing gas into the high-temperature combustion zone, and a dust and carbon material supplied from the waste melting furnace and collected, and a mixture of the dust and the carbon material is supplied to a ventilation pipe that communicates with the tuyere and the blown dust carbon material feeder a mixture of the dust and carbon material from the tuyere, and the carbon material supply unit for supplying carbon material to the dust-carbon material supply unit, from the carbon material supply device A carbon material supply amount control device for adjusting the amount of carbon material supplied to the dust / carbon material supply device;
The carbon material supply amount control device includes means for measuring the blowing pressure and / or the blowing amount of oxygen-containing gas blown from the tuyere, and based on the measured blowing pressure and / or blowing amount, Control was made to increase the carbon material supply in the case of an increase and / or a decrease in the amount of blown air, so that fluctuations in the furnace conditions can be grasped and combustion and melting conditions in the high-temperature combustion zone can be operated stably. As a result, even if a lot of dust is blown, there is no need to increase the oxygen concentration of the oxygen-containing gas blown into the tuyere or to increase the blowing volume, and as a result, waste gasification and melting without increasing the amount of coke used. Dust generated from the furnace can be melted. Furthermore, the amount of dust that requires heavy metal elution prevention treatment can be reduced, and the amount of dust to be landfilled can be reduced.

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 charging port 5 is provided at the upper end of the furnace. In the vicinity of the waste charging port 5, a coke charging port 7 for charging coke and limestone as a molten slag property adjusting agent are charged. A limestone entrance 8 is provided.
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 13, and a blower 17 (see FIG. 2 described later) for blowing 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. The bag filter 31 collects dust ash. The extracted fall ash and a part of the collected dust ash are input to the dust / carbon material supply device 33. Carbon material is mixed with the fall ash and dust collection ash charged into the dust / carbon material supply device 33 and blown into the gasification melting furnace 1 through the main tuyere 13.
The carbon material is, for example, a powder obtained by dry distillation of pulverized coal, pulverized coal, powdered coke, building waste material, RDF, and the like, and is a powdery material having a carbon weight ratio of 50% or more and low ash content.

The reason why the carbon material is mixed with the falling ash and dust collection ash will be described below.
When only dust is blown from the main tuyere 13 and melting is attempted at the tip of the main tuyere, particularly when the amount of dust supply is large, a large amount of heat is required for melting the dust. For this reason, the temperature decreases and the high-viscosity melt accumulates and stays in the combustion space (raceway) behind the main tuyere, which inhibits the gas flow at the main tuyere. In particular, the dust ash contains slaked lime powder blown to remove hydrogen chloride before the bag filter, and therefore has a high basicity of 1.5 or higher and a high melting point. Therefore, the conventional tuyere blowing method is difficult to melt and has poor fluidity, and the dust ash melting process is limited.
Therefore, by blowing carbon material from the main tuyere 13 together with dust, the carbon material is burned in the raceway to prevent the temperature of the main tuyere tip from decreasing, and the temperature of the main tuyere tip is set to a temperature suitable for melting the dust collection ash. Therefore, the molten material is prevented from staying and smoothly discharged, so that the gas flow at the main tuyere tip is not hindered.

  By blowing the carbon material from the main tuyere 13 together with dust in this way, the combustion and melting conditions of the high-temperature combustion zone can be stably operated, so the oxygen concentration of the oxygen-containing gas blown into the tuyere even if much dust is blown As a result, the dust generated from the waste gasification melting furnace can be melted without increasing the amount of coke used.

FIG. 2 shows details of an apparatus for blowing dust and carbon material into the gasification melting furnace 1. As shown in FIG. 2, this apparatus includes a dust / carbon material supply device 33, a dust / carbon material, and a dust / carbon material supply device 33. A carbon material supply device 35 that supplies carbon material to the material supply device 33 and a carbon material supply amount control device 37 that adjusts the amount of carbon material supplied from the carbon material supply device 35 to the dust / carbon material supply device 33. Yes.
The dust / carbon material supply device 33 includes a dust storage tank 38 that stores fall ash and dust collection ash, a rotary valve 39 that cuts out dust from the dust storage tank 38, and a chute 41 that supplies the cut dust to the blower pipe 15. And a gate valve 43 provided on the chute 41.

The carbon material supply amount control device 37 includes a blow pressure gauge 45 that measures the blow pressure of the oxygen-containing gas that is provided in the blow pipe 15 and is blown into the main tuyere, and a blow flow meter 47 that measures the blow quantity. The amount of carbon material supplied from the carbon material supply device 35 to the dust / carbon material supply device 33 is adjusted based on the measurement values of the air pressure gauge 45 and the air flow meter 47.
The carbon material supply amount control device 37 may adjust the carbon material amount based on the measured values of both the blowing pressure gauge 45 and the blowing flow meter 47, or the carbon material based on one of the measured values. The amount may be adjusted.
Further, the adjustment of the carbon material amount by the carbon material supply amount control device 37 may be performed independently for each main tuyere, or the air pressure gauge 45 and the air flow meter provided in one air pipe 15. Control on all main tuyere may be performed based on the 47 measured values. Further, a blower pressure gauge 45 and a blower flow meter 47 are provided in a blower pipe (not shown) on the upstream side before branching to the blower pipe 15 communicating with each main tuyere 13, and based on these measured values, all the main feathers are provided. You may make it perform control with respect to a mouth.

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 hot air of air or oxygen-enriched air (hereinafter referred to as oxygen-containing gas) is blown into the main tuyere 13 here.
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.

  Since the fall ash falls before the gas discharged from the gasification melting furnace 1 reaches the bag filter 31, it falls from the secondary combustion furnace 23, the boiler 25, the economizer 27, the cyclone 28 and the temperature reducing tower 29. The ash is extracted and stored in a storage tank (not shown). A part of the collected ash collected from the fall ash and the bag filter 31 is conveyed to the dust / carbon material supply device 33 by a belt conveyor or an air conveyance device, and mixed with the carbon material supplied from the carbon material supply device 35. To do. A predetermined amount of a mixture of dust and carbon material is cut out by a rotary valve 39 and supplied to a blower pipe 15 for supplying an oxygen-containing gas to a main tuyere 13 via a chute 41 and a gate valve 43, and high temperature combustion is performed from the main tuyere 13. Blow into the obi.

  The in-furnace situation of the gasification melting furnace 1 varies depending on the type and amount of waste processed in the gasification melting furnace. A control method for smoothly blowing and melting dust from the main tuyere 13 in response to such fluctuations in the furnace situation will be described below.

When the situation inside the furnace fluctuates, the gas flow in the high-temperature combustion zone fluctuates, so that it is possible to grasp the fluctuation of the situation inside the furnace by detecting this.
When the gas flow at the tip of the tuyere fluctuates due to fluctuations in the melting state, such as stagnation of the melt, the blowing pressure and blowing amount of the oxygen-containing gas blown from the tuyere changes. The blowing pressure and the blowing amount are measured by the blowing pressure gauge 45 and the blowing flow meter 47, and when the measurement value signal is input to the carbon material supply amount control device 37, the carbon material supply amount control device 37 A signal for adjusting the carbon material supply amount to an appropriate amount is sent to the carbon material supply device 35 based on the pressure measurement value or the air flow measurement value.

  When the melting state in the high-temperature combustion zone is poor and the gas flow at the tip of the tuyere is hindered, the blowing pressure of the oxygen-containing gas blown from the tuyere increases and the blowing rate decreases. For this situation, the amount of carbon material supply is increased to increase the combustion of the carbon material at the tuyere and raise the temperature to make the melting situation appropriate.

  It should be noted that the change in the in-furnace situation is measured by measuring a change in the balance of the amount of oxygen-containing gas blown to the plurality of main tuyere 13 and detected based on this balance change to adjust the carbon material supply amount You may do it.

The dust blown from the main tuyere 13 to the high-temperature combustion zone is melted and extracted from the molten slag discharge port 11 at the bottom of the furnace together with the molten pyrolysis residue.
By blowing a part of the dust collection ash from the main tuyere 13, the ash content and part of the heavy metals contained in the dust collection ash are contained in a non-eluting form in the slag produced by the melting 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.

In addition, by increasing the amount of carbon material relative to the amount of dust blown into the main tuyere 13, the carbon material can be used as an alternative to coke burned in the high-temperature combustion zone, and the amount of coke used can be reduced. By using a carbon material that is cheaper than coke, the operating cost of the gasification melting furnace can be reduced.
Fig. 3 is a graph showing the relationship between the weight ratio (C / D ratio) of carbon in the carbon material and dust (C / D ratio) and the coke usage ratio compared to when no dust and carbon material are blown. The horizontal axis indicates the C / D ratio (%), and the vertical axis indicates the coke usage ratio (%).

  As shown in Fig. 3, when dust is blown without blowing carbon material, the coke usage ratio increases by 3%, but by blowing carbon material so that the C / D ratio is 5%, coke usage is increased. Can be eliminated. Furthermore, if the amount of carbon material blown is increased so as to increase the C / D ratio, the amount of coke used can be reduced. For example, if the C / D ratio is 30%, the coke usage can be reduced by 10%, and if the C / D ratio is 40%, the coke usage can be reduced by 14%.

It is explanatory drawing of the waste gasification melting furnace which concerns on one embodiment of this invention. It is explanatory drawing explaining a part of FIG. 1 in detail. It is a graph which shows the relationship between the carbon ratio in a carbon material, and the weight ratio (C / D ratio) of dust, and the coke usage-amount ratio compared with the time when dust and a carbon material are not blown.

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 reduction tower 33 Dust and carbon material supply apparatus 35 Carbon material supply apparatus 37 Carbon material supply amount control apparatus

Claims (2)

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,
Tuyere that blows oxygen-containing gas into the high-temperature combustion zone;
The supply of dust and carbon material discharged and recovered from the waste melting furnace is supplied to a ventilation pipe communicating with the tuyere and a mixture of the dust and the carbon material from the tuyere. A dust / carbon material supply device that blows
A carbon material supply device for supplying a carbon material to the dust / carbon material supply device;
And a carbon material supply amount control device for adjusting the carbon material amount supplied to the dust-carbon material supply unit from the carbon material supply device,
The carbon material supply amount control device includes means for measuring the blowing pressure and / or the blowing amount of oxygen-containing gas blown from the tuyere, and based on the measured blowing pressure and / or blowing amount, A waste melting furnace characterized by controlling the carbon material supply amount to increase in the case of an increase and / or a decrease in the blowing rate . 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,
The mixture of dust and carbon material discharged and recovered from the waste melting furnace is blown from the tuyere with a dust / carbon material supply device, and the supply amount of the carbon material supplied to the dust / carbon material supply device is Control based on the measured value of the blowing pressure and / or the blowing rate of the oxygen-containing gas blown from the mouth, and control to increase the supply amount of the carbon material when the blowing pressure increases and / or the blowing rate decreases A method for operating a waste melting furnace.

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