JPH10281442A - Method for melting and solidifying dust combustion fly ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for melting and solidifying dust combustion fly ash in which discharging of acid gas can be restricted and cost required for processing the fly ash can be reduced. SOLUTION: Slaked lime of high specific-surface ratio of 35 m<2> /g or more is added to upstream side of a dust collecting machine 4 in a discharged gas processing system of a dust incinerator, gathered ash is collected by a dust collecting machine together with reaction products generated through reaction between slaked lime and acid gas such as HCl, SOx, etc., contained in discharged gas, the fly ash is supplied by gas transferring operation into flame of high temperature of an oxygen burner using combustion assisting gas of oxygen concentration of 90% or more and melted, thereafter they are cooled and solidified.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for melting and reducing the volume of ash collected from exhaust gas discharged from an incinerator for incinerating waste such as municipal solid waste, sewage treatment sludge and industrial waste by a melting furnace.
The present invention relates to a method for stabilizing refuse incineration dust ash by melting and solidifying.

[0002]

2. Description of the Related Art When waste such as municipal solid waste, sewage sludge, and industrial waste is incinerated in an incinerator, HC is contained in the exhaust gas.
Since acidic gases such as l and SOx are generated, slaked lime powder is conventionally blown into a flue to remove CaO, which is a reaction product, by a bag filter.
No harmful acid gases are emitted. However, since the reaction with the acid gas component basically occurs on the surface of slaked lime, the reaction efficiency is poor in JIS special No. slaked lime (produced by reacting thick quick lime with water), which has been conventionally used, Therefore, it was necessary to put a large amount of slaked lime. In addition, the burden on the bag filter is increased, and the amount of dust collection ash becomes extremely large.

Further, the dust collected by the bag filter has a high melting point, and it is difficult to completely melt the dust collected by the conventional arc furnace because the temperature near the electrode is high and the temperature around the electrode is low in the conventional melting. In addition, since a large amount of dust is generated, there is a problem that the heat energy required for melting is high. Therefore, development of a more efficient melting method has been awaited.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for melting and solidifying refuse incineration collected ash which can reduce the emission of acid gas and reduce the cost for treating refuse incineration collected ash. Things.

[0005]

For this purpose, the method for melting and solidifying garbage incineration dust and ash according to the present invention employs a high specific surface area slaked lime having a specific surface area of 35 m ² / g or more upstream of a dust collector in an exhaust gas treatment system of a refuse incinerator. The dust is collected by the dust collector together with a reaction product of the slaked lime and acid gases such as HCl and SOx in the exhaust gas, and is collected in a high-temperature flame of an oxygen burner using a supporting gas having an oxygen concentration of 90% or more. The dust collected ash is supplied by gas transport, melted, and then cooled and solidified. Further, the present invention is characterized in that in the above-mentioned method of melting and solidifying refuse incineration dust ash, a bag filter is used in a dust collector, and slaked lime having a high specific surface area is produced by dissolving quick lime as a raw material in alcohol or amines and then depositing. And

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an overall flow of a facility for incinerating general combustible waste 8. In this facility, the exhaust gas discharged from the grate incinerator 1 passes through a steam boiler 2 for effectively using the waste heat, and then cooled, a tower 3, a bag filter 4,
The exhaust gas passes through the exhaust gas heater 5, the catalytic denitration tower 6, and is discharged from the chimney 7 into the atmosphere. Then, incineration ash 9 is taken out from the incinerator 1 and the boiler 2, and incineration fly ash 10 discharged together with the exhaust gas is taken out from the cooling tower 3.

An air passage 11 is provided upstream of the bag filter 4 for blowing powdery high specific surface area slaked lime. The air is supplied from the blower 12 to the air passage 11 and the air is passed through the cut-out device 13. The slaked lime having a high specific surface area stored in the silo 16 is supplied to the ventilation passage 11. Then, HCl in the exhaust gas after passing through the bag filter 4
Is measured by an HCl measuring device 14, and the measuring device 14
The feed amount control device 15 feedback-controls the blower 12 in accordance with the signal of (1), and the HCl concentration of the exhaust gas after passing through the bag filter 4 is always set to H in the cut amount control device 15.
It is set to be below the Cl control concentration.

Reference numeral 17 denotes incinerated fly ash 1 discharged from the cooling tower 3
This is a silo for storing dust ash discharged from the bag filter 0 and the bag filter 4. Reference numeral 18 denotes an oxygen burner type melting furnace.
An oxygen burner 19 is provided downward on the upper wall of the furnace body, and a molten slag 20 is stored at the bottom of the furnace. The oxygen burner 19 is provided with a fuel supply nozzle, a supporting oxygen supply nozzle, and an ash supply nozzle concentrically. The dust ash stored in the silo 17 passes through a cutting device 21 from a compressor 22 to a dehumidifier. Dry air is pumped through 23 so that the gas is transported to the oxygen burner 19.

24 is a zeolite adsorbent (molecular sieve)
A gas purifying apparatus that purifies high oxygen gas having an oxygen concentration of 90% or more by repeatedly compressing and expanding air (an oxygen producing apparatus according to this method is referred to as PSA).
The high oxygen gas is supplied as a supporting gas to the oxygen burner 19, and fuel such as kerosene is sent by the pump 25 and burned by the oxygen burner 19 to form a high-temperature (2000 ° C. or higher) flame. The dust is melted by blowing dust ash into the flame, and the molten slag 20 is stored at the bottom of the furnace. The slag is dropped into a water tank 27 from a flow outlet 26 provided on one side wall to be rapidly cooled and solidified. And crushed into granules to stabilize and reduce the volume. Reference numeral 28 denotes a conveyor provided to scoop out the crushed solid slag 29 in the water tank 27.

The high specific surface area slaked lime to be added upstream of the bag filter 4 is produced by dissolving quick lime as a raw material in a mixed solvent of an amine such as alcohol or monoethanolamine and water and then precipitating the same. It has a specific surface area of 35 m ² / g or more, twice or more that of conventionally used lime slaked lime, and has a bulky specific gravity of about 0.36.

Table 1 shows the effects of the use of this high specific surface area slaked lime and the JIS special slaked lime on the melting of the dust ash.

[Table 1] In addition, in Table 1, the slaked lime usage rate was compared with the addition amount when the HCl concentration of the exhaust gas was 35 ppm (O ₂ = 12% conversion). The definition of the melting point and pour point and the measuring method are based on DIN-51730 (German standard) concerning the ash melting property test.

As shown in Table 1, by using slaked lime having a high specific surface area, the usage rate of slaked lime is reduced by half, and the amount of dust collection ash is reduced accordingly. For this reason, the melting equipment cost and the heat energy cost required for melting are also reduced. Further, since the amount of CaO is reduced, the melting temperature is lowered, the required heat energy can be further reduced, and the life of the refractory constituting the melting furnace is extended, so that the repair cost can be reduced.

[0013] The slaked lime having a high specific surface area produced by the above method has a small particle size, is uniform and smooth, and has a very good fluidity. Therefore, even if gas is transported to a burner, it may become clogged in pipes and nozzles. Maintenance is also easy because troubles do not easily occur.

Unreacted slaked lime: Ca (OH) ₂
Is unstable at high temperature, and CaO and H ₂ O
Decompose into CaO has a melting point of about 2570 ° C. and a boiling point of 2850.
° C, the slag enters the slag and becomes a slag having a high pour point with a high ratio of CaO to SiO ₂ and Al ₂ O ₃ ,
When the temperature falls slightly below the pour point, the fluidity deteriorates, making it difficult to discharge from the furnace. In this respect, in the present invention, since the amount of unreacted slaked lime can be reduced, the pour point of the slag is lowered, and the dischargeability from the furnace is easily maintained.

The flame of the oxygen burner is at 2000 ° C. or higher, and all of the collected ash passes through the high temperature region.
The temperature is raised to 00 ° C. or higher to melt. The stable compound CaCl _{2 has} a boiling point of a little over 1600 ° C. and evaporates in less than 1/10 second after passing through the burner flame. Therefore, the Ca content in the molten slag accumulated in the melting furnace is reduced to the Ca content in the ash. Lower. As a result, the melting point and pour point of the slag decrease, and the dust ash is melted and discharged easily.

[0016]

[Table 2] Table 2 shows the slag composition melted by the oxygen burner and the slag composition melted by the arc furnace. CaCl ₂ in the collected ash is CaCl ₂ .nH combined with water of crystallization.
It exists in the form of ₂ O. When it stays for a long time at 1550 ° C. or less as in the case of melting in an arc furnace, this CaCl _2.
nH ₂ O is decomposed into, for example, CaCl ₂ .6H ₂ O → CaO + 2HCl + 5H ₂ O. Since the CaO enters the molten slag, the CaO content of the slag does not decrease, and as a result, the melting point becomes high in the arc furnace melting, and the melting becomes difficult.

As shown in FIG. 1, an exhaust gas outlet 30 is formed in the upper portion of the side wall of the melting furnace 18. 3
1 is an exhaust gas cooling device, and the cooling device 31 sprays cooling water in the form of a mist, thereby filtering the exhaust gas into a bag filter 32.
(For example, an exhaust gas of 1500 ° C. is cooled to 150 ° C.) to cause molten fly ash to precipitate from the exhaust gas, and the molten fly ash is collected by the bag filter 32. The exhaust gas discharged from the bag filter 32 merges with the exhaust gas discharged from the bag filter 4, and is discharged to the chimney 7 through the exhaust gas heater 5 and the catalytic denitration tower 6.

[0018]

As described above, in the method for melting and solidifying the refuse incineration collected ash of the present invention, the waste gas from the refuse incinerator is neutralized by adding slaked lime having a high specific surface area to the exhaust gas, and the reaction product is collected by the dust collector together with the collected ash. Since the collected ash is collected and melted by an oxygen burner using a supporting gas having an oxygen concentration of 90% or more, the heat energy required for melting can be reduced, and the operation cost and equipment cost are also reduced. . Further, since the amount of generated dust ash to be melted is reduced, there is a beneficial effect that costs can be further reduced.

[Brief description of the drawings]

FIG. 1 is a flow chart of an entire facility for implementing a method for melting and solidifying refuse incineration collected ash according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Grate incinerator 3 Cooling tower 4 Bag filter 14 Measuring device 15 Cut-out amount control device 16 Silo 17 Silo 18 Melting furnace 19 Oxygen burner 20 Melting slag 27 Water tank 29 Solid slag

Claims (2)

[Claims] 1. A high specific surface area slaked lime having a specific surface area of 35 m ² / g or more is added upstream of a dust collector in an exhaust gas treatment system of a refuse incinerator, and the slaked lime and HCl in exhaust gas are added by the dust collector.
Collect dust ash together with the reactant with acid gas such as SOx,
Melting of refuse incineration ash, characterized in that the ash is supplied by gas transport and melted in a high-temperature flame of an oxygen burner using a supporting gas having an oxygen concentration of 90% or more, and then cooled and solidified. Solidification method. 2. A slaked lime having a high specific surface area is produced by dissolving quicklime as a raw material in an alcohol or an amine and then depositing the slaked lime using a bag filter in a dust collector.
3. The method for melting and solidifying the incinerated dust collection ash according to the above.