JPH10325534A - Fly ash treatment method in waste gas in waste treatment equipment - Google Patents

Abstract

(57) [Summary] [PROBLEMS] In a waste treatment apparatus for converting combustion ash generated by burning waste into molten slag, and cooling and solidifying the molten slag for recovery, the waste ash is removed from the waste treatment apparatus to outside the system. Provided is a method for treating fly ash in exhaust gas in a waste treatment device that can significantly reduce the amount of dioxins contained in discharged fly ash. SOLUTION: In a waste treatment apparatus in which waste is burned in a combustion furnace, generated combustion ash is converted into a molten slag in a melting furnace, cooled, solidified and collected, the melting furnace discharged from the melting furnace The exhaust gas is mixed with the combustion furnace exhaust gas discharged from the combustion furnace to form a mixed exhaust gas, and after a desalinating agent is injected into the mixed exhaust gas, the mixed gas is supplied to a first dust collector to collect fly ash, The collected fly ash is supplied to a heating device for heat treatment, and the heated fly ash is supplied to a cooling device for rapid cooling.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating fly ash in exhaust gas in a waste treatment apparatus for combusting waste, converting the generated combustion ash into molten slag, and cooling and solidifying the molten slag for recovery. More particularly, the present invention relates to a method for treating fly ash in exhaust gas in a waste treatment apparatus for reducing the amount of dioxin contained in fly ash of combustion furnace exhaust gas and melting furnace exhaust gas.

[0002]

2. Description of the Related Art Conventionally, waste containing combustibles such as municipal waste has been disposed of by landfill disposal after being burned in a combustion furnace to reduce its volume. However, in a waste treatment apparatus having such a combustion furnace, heavy metals are contained in the combustion ash generated in the combustion furnace, and a treatment for preventing these heavy metals from being eluted in the landfill. You need to
In addition, it is necessary to handle the ash carefully so that the ash does not scatter during transportation and become a source of pollution. In addition, the incinerated ash has a low density and is bulky, so that there is a problem that the volume cannot be significantly reduced. Was.

[0003] Therefore, in recent years, a waste treatment apparatus that burns waste, converts the generated combustion ash into molten slag, cools and solidifies the molten slag, and collects it has been receiving attention. As a waste treatment apparatus of this kind, a combustion / melting method including a combustion furnace for burning waste and a melting furnace for melting combustion ash generated in the combustion furnace,
There is known a thermal decomposition / combustion melting method in which a pyrolysis product generated by thermally decomposing waste is supplied to a combustion melting furnace, subjected to combustion treatment, and the generated combustion ash is converted into molten slag.

[0004]

However, in these waste treatment apparatuses, the treatment of the generated combustion ash has been improved by making it into molten slag, but fly ash discharged along with the exhaust gas has been improved. However, there is a problem that the processing is still insufficient. That is, in the case of the combustion / melting method in which the combustion furnace and the melting furnace are provided in parallel, the combustion furnace exhaust gas discharged from the combustion furnace and the melting furnace exhaust gas discharged from the melting furnace are mixed, and the mixed exhaust gas is subjected to desalination or the like. After injecting chemicals such as slaked lime, calcium carbonate, and sodium bicarbonate for desulfurization, it is supplied to a dust collector to collect fly ash in the mixed exhaust gas. In one of the pyrolysis / combustion melting methods,
After injecting a desalinating agent into the exhaust gas discharged from the combustion melting furnace, it is supplied to a dust collector to collect fly ash.

However, a large amount of dioxin is contained in the fly ash, and dioxin normally discharged from such a waste disposal device is discharged out of the system in the exhaust gas and fly ash. Most are emitted in fly ash. According to the findings of the present inventors, dioxin generated from 100 tons of waste is usually about 8600 μg, of which about 8000 μg is contained in fly ash and discharged.

[0006] Therefore, it is an urgent task to reduce the amount of dioxin contained and discharged in such fly ash. The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to convert combustion ash generated by burning waste into molten slag and cool the molten slag. A method for treating fly ash in flue gas in a waste treatment apparatus that can significantly reduce the amount of dioxin contained in fly ash discharged from the waste treatment apparatus to the outside in a waste treatment apparatus that is solidified and recovered. It is to provide.

[0007]

The method for treating fly ash in exhaust gas in the waste treatment apparatus according to the present invention is as follows.

[0008] In a waste treatment apparatus in which waste is burned in a combustion furnace, and the generated combustion ash is formed into a molten slag in a melting furnace, cooled, solidified, and recovered, the melting furnace exhaust gas discharged from the melting furnace Is mixed with the combustion furnace exhaust gas discharged from the combustion furnace to form a mixed exhaust gas, and after injecting a desalinating agent into the mixed exhaust gas, the mixture is supplied to the first dust collector,
This is a method in which the collected fly ash is supplied to a heating device for heat treatment, and the heated fly ash is supplied to a cooling device for rapid cooling. The fly ash in the exhaust gas is collected and heated. The catalytic action of metals in the ash to remove the chlorine from the dioxin and cut off the oxygen bridges to cause a chemical reaction to decompose dioxin, and by rapid cooling,
Because it prevents re-synthesis of dioxin during cooling,
The amount of dioxin contained in the discharged fly ash can be significantly reduced.

Before mixing the melting furnace exhaust gas with the combustion furnace exhaust gas, the combustion furnace exhaust gas is supplied to a second dust collector, and the collected fly ash is supplied to the melting furnace. The melting furnace exhaust gas discharged from the melting furnace is supplied to a third dust collector, and then the melting furnace exhaust gas is mixed with the combustion furnace exhaust gas to form a mixed gas, and a desalinating agent is injected into the mixed gas. After that, it is a method of supplying to the first dust collecting device, increasing the amount of the molten slag, reducing the load on the first dust collecting device, the heating device and the cooling device, and flying ash that goes out of the system. Reduce the amount of

[0010] A waste treatment apparatus that supplies a pyrolysis product generated by heating and thermally decomposing waste to a combustion and melting furnace for combustion treatment, and converts the generated combustion ash into a molten slag, which is cooled, solidified, and recovered. In, after injecting a desalinating agent into the melting furnace exhaust gas discharged from the combustion melting furnace, it is supplied to the first dust collector, the collected fly ash is supplied to the heating device and subjected to heat treatment, This is a method of supplying the heat-treated fly ash to a cooling device for rapid cooling, which decomposes dioxin and prevents re-synthesis of dioxin during cooling. The amount can be greatly reduced. You.

[0011] The melting furnace exhaust gas discharged from the combustion melting furnace is supplied to a second dust collector, and the collected fly ash is supplied to the heating device and discharged from the second dust collector. This is a method in which a desalinating agent is injected into the exhaust gas to be discharged and then supplied to the first dust collector, and the amount of the molten slag is increased to increase the burden on the first dust collector, the heating device, and the cooling device. And the amount of fly ash that goes out of the system is reduced.

[0012] A method of heating the fly ash collected by the first dust collector to 400 ° C to 600 ° C by the heating device, wherein the fly ash temperature is maintained within a temperature range that promotes the decomposition of dioxin. Can be.

[0013] The heated fly ash is heated to 100 ° C to 20 ° C.
This is a method of rapidly cooling to within 0 ° C., and it is possible to lower the fly ash temperature within a temperature range where re-synthesis of dioxin can be prevented.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for treating fly ash in exhaust gas in a waste treatment apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram of a waste treatment apparatus for implementing a method for treating fly ash in exhaust gas in the waste treatment apparatus according to the present invention. Waste a is the combustion furnace 1
And is subjected to combustion processing to generate exhaust gas G1 and combustion ash b.

The combustion furnace exhaust gas G1 is a relatively high-temperature combustion gas containing fly ash F1, and the combustion furnace exhaust gas G1 is supplied to a waste heat boiler 3 where heat is recovered. Then, the combustion furnace exhaust gas G1 whose heat has been recovered and has become relatively low temperature is obtained.
Is supplied to a second dust collector 8 composed of a bag filter or the like, and most fly ash F1 in the combustion furnace exhaust gas G1 is collected.

On the other hand, the combustion ash b generated in the combustion furnace 1 and the fly ash F1 collected in the second dust collector 8 are both melted in the melting furnace 2.
And becomes a high-temperature melting furnace exhaust gas G2 containing molten slag c and molten fly ash. The molten slag c is cooled by the cooler 4 and collected as solidified slag d. The molten furnace exhaust gas G2 is supplied to the third dust collector 9, where a part of the molten furnace exhaust gas G2 is collected. Of molten fly ash F2 is collected.

Then, the combustion furnace exhaust gas G1 discharged from the second dust collector 8 and the melting furnace exhaust gas G2 discharged from the third dust collector 9 are mixed to form a mixed exhaust gas G3. A chemical n such as slaked lime, calcium carbonate, or sodium bicarbonate is injected into the mixed exhaust gas G3 for desalination and desulfurization, and then supplied to the first dust collector 5, where the mixed gas is mixed. Fly ash F3, which is a mixture of fly ash F1 'and molten fly ash F2' from combustion furnace exhaust gas G1 remaining in exhaust gas G3, is collected, and clean mixed gas G3 'is collected by induction blower 10.
Through the chimney 11 to the atmosphere.

The collected fly ash F3 (= F1 '+ F
2 ′) and the molten fly ash F2 collected by the third dust collecting device 9 are heated by the heating device 6. This heating device 6
Specifically, for example, as shown in FIG. 2, a heater 81 as a heating means is provided around a rotary drum 80 having an inlet hood 82 and an outlet hood 83 at the front and rear. This heating means may use a gas or oil flame burner in addition to the heater. Further, an inert gas e such as nitrogen is supplied into the rotating drum 80 from the line L1, and the inside of the heating device 6 is maintained in a low oxygen atmosphere.

In the heating device 6, the fly ash F3 is supplied into the rotary drum 80 by the fixed-quantity supply device 84, and is heated by the heater 81 to about 450 ° C., preferably 400 ° C. to 6 ° C.
Heating in a low oxygen atmosphere within the range of 00 ° C. for 1 minute to 1 minute
By performing the treatment maintained for 0 minutes, the catalytic action of metals and the like contained in the fly ash F3 removes chlorine from dioxin and causes a reaction to cut off oxygen bridges, and is included in the fly ash F3. Decomposes dioxins that are present.
Therefore, the amount of dioxin contained in the fly ash F3 is significantly reduced.

The fly ash F3 ', which has been subjected to the heat treatment in this heating device 6 to decompose the dioxin, is rapidly cooled, and the temperature of the cooled fly ash F3 "is 100.degree.
C., preferably 150 ° C. or less, to prevent re-synthesis of dioxin. FIG. 3 is a system diagram of a waste treatment apparatus showing another embodiment of the method for treating fly ash in exhaust gas in the waste treatment apparatus according to the present invention.

In FIG. 3, the waste a is supplied to a pyrolysis reactor 24 and heated to become a carbonization gas G4 and a pyrolysis residue f.
In 2 flammable components g and non-flammable components j are separated. Then, the dry distillation gas G4 and the combustible component g are supplied to the combustion melting furnace 25, where they are burned in a high temperature range of about 1,300 ° C. to become high temperature exhaust gas G5 and molten slag c.

The molten slag c is cooled by the cooler 4 and recovered as solidified slag d.
Is recovered by the waste heat boiler 3, and fly ash (melted fly ash) F5 is collected by the second dust collector 8. A part F51 of the collected fly ash F5 is supplied to the heating device 6 for decomposing dioxin, and most of the other fly ash F52 is supplied to the combustion melting furnace 25 again.

The exhaust gas G6 that has passed through the second dust collector 8 is injected with a chemical n for desalination and desulfurization.
And the remaining fly ash (melted fly ash) F6 contained in the exhaust gas G6 is collected and turned into a low-temperature clean exhaust gas G7 via the induction blower 10 and the chimney 11
Emitted from the atmosphere. The fly ash F6 collected by the first dust collecting device 5 is supplied to the heating device 6 together with a part F51 of the fly ash F5 collected by the second dust collecting device 8. The heating device 6 performs the same operation as the heating device 6 in the system diagram shown in FIG. 1, and the fly ash F51 ′, F6 ′ that has been heat-treated here is the same as the system diagram shown in FIG. The cooling process is performed by the cooling device 7 that performs the same operation as the cooling device 7 in.

Therefore, the dioxin contained in the fly ash F51, F6 is thermally decomposed and re-synthesis is prevented, so that the fly ash F5 discharged from the waste disposal system.
Dioxin in 1 "and F6" can be significantly reduced. According to the method for treating fly ash in exhaust gas in such a waste treatment apparatus, fly ash F3, F51 + F in exhaust gas is used.
Catalytic action of metals in the ash for collecting and heat-treating 6 to cause a chemical reaction that removes chlorine from diokin and cut oxygen bridges, decompose dioxin, and rapidly cool. Prevents the resynthesis of dioxin during cooling, so that fly ash F
The amount of dioxin contained in 3 ″, F51 ″ + F6 ″ can be greatly reduced.

[0025]

As is clear from the above description, according to the method for treating fly ash in exhaust gas in the waste treatment apparatus according to the present invention, the combustion ash generated by burning waste is converted into molten slag. In a waste treatment apparatus in which this molten slag was cooled and solidified slag was collected, at least fly ash containing molten fly ash discharged from a melting furnace or a combustion melting furnace was heat-treated to thermally decompose dioxin. rear,
Since it is configured so as to prevent rapid re-synthesis of dioxin by rapid cooling, the amount of dioxin contained in fly ash discharged from the waste treatment device to the outside of the system can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a system diagram of an exhaust gas treatment device showing a method for treating fly ash in exhaust gas in a waste treatment device according to the present invention.

FIG. 2 is a sectional view of one embodiment of the heating device shown in FIG.

FIG. 3 is a system diagram of a waste treatment apparatus showing a method for treating fly ash in exhaust gas in another waste treatment apparatus according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Combustion furnace 2 ... Melting furnace 3 ... Waste heat boiler 4 ... Cooler 5 ... 1st dust collection device 6 ... Heating device 7 ... Cooling device 8 ... 2nd dust collection device 9 ... 3rd dust collection device 10 ... Induction blower 11 ... Chimney 22 ... Separator 24 ... Pyrolysis reactor 25 ... Combustion melting furnace 80 ... Rotary drum 81 ... Heater 82 ... Inlet hood 83 ... Outlet hood 84 ... Quantitative feeder

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F23J 15/08 F23J 15/00 L 15/00 Z

Claims (6)

[Claims] 1. A waste treatment apparatus in which waste is burned in a combustion furnace, and the generated combustion ash is converted into a molten slag in a melting furnace, cooled, solidified, and recovered. The furnace flue gas is mixed with the combustion furnace flue gas discharged from the combustion furnace to form a mixed flue gas, and a desalinating agent is injected into the mixed flue gas, and then supplied to the first dust collector to collect the collected flue gas. A method for treating fly ash in exhaust gas in a waste treatment device, wherein the ash is supplied to a heating device for heat treatment, and the heat-treated fly ash is supplied to a cooling device for rapid cooling. 2. Before mixing the melting furnace exhaust gas with the combustion furnace exhaust gas, the combustion furnace exhaust gas is supplied to a second dust collector, and the collected fly ash is supplied to the melting furnace. The melting furnace exhaust gas discharged from the melting furnace
After that, the melting furnace exhaust gas is mixed with the combustion furnace exhaust gas to form a mixed gas, a desalinating agent is injected into the mixed gas, and then supplied to the first dust collecting device. A method for treating fly ash in exhaust gas in the waste treatment apparatus according to claim 1. 3. A waste which is obtained by heating and thermally decomposing a waste, supplying a pyrolysis product generated to the combustion and melting furnace to perform a combustion treatment, and converting the generated combustion ash into a molten slag to be cooled and solidified for recovery. In the processing apparatus, after injecting a desalinating agent into the melting furnace exhaust gas discharged from the combustion melting furnace, the desalting agent is supplied to the first dust collector, and the collected fly ash is supplied to the heating device to perform the heat treatment. A method for treating fly ash in exhaust gas in a waste treatment device, wherein the heat-treated fly ash is supplied to a cooling device and rapidly cooled. 4. The exhaust gas of the melting furnace discharged from the combustion melting furnace is supplied to a second dust collector, and the collected fly ash is supplied to the heating device, and the second dust collector is provided. 4. The method for treating fly ash in exhaust gas in a waste treatment apparatus according to claim 3, wherein a desalinating agent is injected into the exhaust gas discharged from the apparatus, and then supplied to the first dust collector. 5. The waste gas in a waste treatment device according to claim 1, wherein the fly ash collected by the first dust collector is heated to 400 ° C. to 600 ° C. by the heating device. Fly ash treatment method. 6. The heated fly ash is heated to 100 ° C. to 200 ° C.
The cooling device according to any one of claims 1 to 5, wherein the cooling device rapidly cools the temperature within the range of ° C.