JP3866832B2 - Method for treating fly ash in exhaust gas in waste treatment equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for treating fly ash in an exhaust gas in a waste treatment apparatus for burning and treating waste, converting the generated combustion ash into molten slag, and cooling and solidifying the molten slag, and more specifically, a combustion furnace The present invention relates to a method for treating fly ash in exhaust gas in a waste treatment apparatus that reduces the amount of dioxin contained in the fly ash of exhaust gas and melting furnace exhaust gas.
[0002]
[Prior art]
Conventionally, waste including combustibles such as municipal waste is disposed of in landfill after being burned in a combustion furnace and reduced in volume. However, in a waste treatment apparatus having such a combustion furnace, heavy metals are contained in the combustion ash produced in the combustion furnace, and a treatment for preventing these heavy metals from being eluted at the landfill site. In addition, it must be handled carefully so that combustion ash is not scattered during transportation and becomes a source of pollution. There was a problem that it was impossible.
[0003]
For this reason, recently, a waste treatment apparatus that performs combustion treatment of waste, converts the generated combustion ash into molten slag, cools and solidifies the molten slag, and has been attracting attention. This kind of waste treatment equipment is a combustion / melting system consisting of a combustion furnace that burns waste and a melting furnace that melts the combustion ash produced in this combustion furnace, and is generated by pyrolyzing waste There is known a pyrolysis / combustion melting method in which the pyrolysis product thus produced is supplied to a combustion melting furnace, subjected to combustion treatment, and the generated combustion ash is converted into molten slag.
[0004]
[Problems to be solved by the invention]
However, in these waste treatment apparatuses, the treatment of the generated combustion ash is improved by making it into molten slag, but the treatment is still insufficient for the fly ash discharged accompanying the exhaust gas. There is a problem.
That is, in the case of a combustion / melting method in which a combustion furnace and a melting furnace are provided, 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 In order to desulfurize, chemicals such as slaked lime, calcium carbonate, and sodium bicarbonate are injected, and then supplied to a dust collector to collect fly ash in the mixed exhaust gas. In one thermal decomposition / combustion melting system, a desalting agent is injected into the exhaust gas discharged from the combustion melting furnace and then supplied to a dust collector to collect fly ash.
[0005]
However, this fly ash contains a large amount of dioxin, and usually dioxin discharged from such waste treatment equipment is included in exhaust gas and fly ash and discharged outside the system. It is contained in ash and discharged.
According to the knowledge of the present inventors, dioxin generated from 100 tons of waste is usually about 8600 μg, of which about 8000 μg is contained in the fly ash and discharged.
[0006]
Therefore, it is an urgent task to reduce dioxins contained and discharged in the fly ash.
The present invention has been made to solve the conventional problems as described above, and its purpose is to convert the combustion ash generated by the combustion treatment of the waste into molten slag and cool the molten slag. Waste ash treatment method for waste ash in waste treatment equipment that can significantly reduce the amount of dioxins contained in fly ash discharged from the waste treatment equipment to the outside of the waste treatment equipment that is solidified and recovered Is to provide.
[0007]
[Means for Solving the Problems]
The fly ash treatment method in the exhaust gas in the waste treatment apparatus according to the present invention is the following method.
[0008]
(1) In a waste treatment apparatus in which waste is combusted in a combustion furnace, and the generated combustion ash is melted slag in a melting furnace, cooled and 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 a desalting agent is injected into the mixed exhaust gas, which is then supplied to the first dust collector to collect the collected fly ash. A method of supplying heat to a heating device, heat-treating, supplying the heat-treated fly ash to a cooling device, and rapidly cooling the metal in the ash for collecting and heat-treating fly ash in the exhaust gas Deoxins are decomposed by causing a chemical reaction that removes chlorine or breaks oxygen bridges by catalytic action such as dioxins, and by rapid cooling, resynthesis of dioxins during cooling is prevented, so it is discharged Contained in fly ash The amount of ioxin can be greatly reduced.
[0009]
{Circle around (2)} Before mixing the melting furnace exhaust gas with the combustion furnace exhaust gas, supplying the combustion furnace exhaust gas to a second dust collector, supplying the collected fly ash 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 desalting agent is injected into the mixed gas. Is then supplied to the first dust collector, and the amount of molten slag is increased to lighten the burden on the first dust collector, heating device and cooling device, and fly ash coming out of the system Reduce the amount of
[0010]
(3) Waste treatment equipment that heats and pyrolyzes waste to supply pyrolysis products to a combustion melting furnace for combustion treatment, and converts the produced combustion ash into molten slag to cool, solidify and recover In, after injecting a desalting agent into the melting furnace exhaust gas discharged from the combustion melting furnace, supply to the first dust collector, supply the collected fly ash to the heating device, heat treatment, This is a method of rapidly cooling the heat-treated fly ash by supplying it to a cooling device, which decomposes dioxins and prevents re-synthesis of dioxins during cooling, so that dioxins contained in the discharged fly ash The amount can be greatly reduced. The
[0011]
(4) 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. Injecting a desalting agent into the exhaust gas to be discharged and then supplying it to the first dust collector, increasing the amount of molten slag, and burdening the first dust collector, heating device and cooling device And reduce the amount of fly ash out of the system.
[0012]
(5) A method of heating fly ash collected by the first dust collector with the heating device to 400 ° C. to 600 ° C., and maintaining the fly ash temperature within a temperature range that promotes the decomposition of dioxins. Can do.
[0013]
(6) A method of rapidly cooling the heated fly ash within a range of 100 ° C. to 200 ° C., and the fly ash temperature can be lowered within a temperature range in which dioxin resynthesis can be prevented.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments 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 carrying out the fly ash treatment method in exhaust gas in the waste treatment apparatus according to the present invention. The waste a is put into the combustion furnace 1 and burned to generate exhaust gas G1 and combustion ash b.
[0015]
This combustion furnace exhaust gas G1 is a relatively high-temperature combustion gas containing fly ash F1, and this combustion furnace exhaust gas G1 is supplied to the waste heat boiler 3 where it is recovered by heat. The combustion furnace exhaust gas G1 recovered by heat and having a relatively low temperature is supplied to the second dust collector 8 composed of a bag filter or the like, and most of the fly ash F1 in the combustion furnace exhaust gas G1 is collected. The
[0016]
On the other hand, the combustion ash b generated in the combustion furnace 1 and the fly ash F1 collected by the second dust collector 8 are both supplied to the melting furnace 2 and melted at a high temperature containing the molten slag c and the molten fly ash. It becomes furnace exhaust gas G2. The molten slag c is cooled by the cooler 4 and recovered as solidified slag d, but the melting furnace exhaust gas G2 is supplied to the third dust collector 9, where a part of the melting furnace exhaust gas G2 is provided. The molten fly ash F2 is collected.
[0017]
And the combustion furnace exhaust gas G1 discharged | emitted from the 2nd dust collector 8 and the melting furnace exhaust gas G2 discharged | emitted from the 3rd dust collector 9 are mixed, and it becomes mixed exhaust gas G3. This mixed exhaust gas G3 is injected with a chemical n such as slaked lime, calcium carbonate, or baking soda for demineralization or desulfurization, and then supplied to the first dust collector 5, where it is mixed in the first dust collector 5. The fly ash F3 mixed with the fly ash F1 ′ and the molten fly ash F2 ′ from the combustion furnace exhaust gas G1 remaining in the exhaust gas G3 is collected, and the clean mixed gas G3 ′ passes from the chimney 11 via the induction fan 10. Released into the atmosphere.
[0018]
The collected fly ash F3 (= F1 ′ + F2 ′) and the molten fly ash F2 collected by the third dust collector 9 are heated by the heating device 6. Specifically, for example, as shown in FIG. 2, the heating device 6 is formed by disposing a heater 81 as a heating unit 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 rotary drum 80 from the line L1, and the inside of the heating device 6 is maintained in a low oxygen atmosphere.
[0019]
In the heating device 6, the fly ash F3 is supplied into the rotary drum 80 by the quantitative feeder 84 and heated by the heater 81 in a low oxygen atmosphere at a temperature of about 450 ° C., preferably 400 ° C. to 600 ° C. Then, by carrying out a treatment that is maintained for 1 to 10 minutes, the catalytic action of the metals contained in the fly ash F3 can cause the reaction of removing chlorine from dioxins or breaking the oxygen bridge. Decomposes dioxins contained in fly ash F3. Therefore, the amount of dioxins contained in the fly ash F3 is greatly reduced.
[0020]
The fly ash F3 ′, which is heat-treated by the heating device 6 and decomposed dioxin, is rapidly cooled, and the temperature of the fly ash F3 ″ after cooling is 100 ° C. to 200 ° C., preferably 150 ° C. or less. The re-synthesis of dioxins is prevented by rapidly cooling to
FIG. 3 is a system diagram of the 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.
[0021]
In FIG. 3, the waste a is supplied to the pyrolysis reactor 24 and heated to become a dry distillation gas G4 and a pyrolysis residue f. The pyrolysis residue f is separated into combustible components in the separator 22. g and non-combustible component j. Then, the dry distillation gas G4 and the combustible component g are supplied to the combustion melting furnace 25 and are combusted in a high temperature range of about 1,300 ° C. to become high temperature exhaust gas G5 and molten slag c.
[0022]
The molten slag c is cooled by the cooler 4 and recovered as solidified slag d. One high-temperature exhaust gas G5 is recovered by the waste heat boiler 3 and is then fly ash (molten fly ash) by the second dust collector 8. ) F5 is collected. A part F 51 of the collected fly ash F 5 is supplied to the heating device 6 for dioxin decomposition, and most of the other fly ash F 52 is supplied again to the combustion melting furnace 25.
[0023]
The exhaust gas G6 that has passed through the second dust collector 8 is injected with the chemical n for desalting and desulfurization, supplied to the first dust collector 5, and the remaining exhaust gas G6 contains the remaining amount. Fly ash (molten fly ash) F6 is collected and becomes low-temperature clean exhaust gas G7, which is released from the chimney 11 to the atmosphere via the induction fan 10.
The fly ash F6 collected by the first dust collector 5 is supplied to the heating device 6 together with a part F51 of the fly ash F5 collected by the second dust collector 8. This 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 'and F6' heat-treated here are the system diagram shown in FIG. The cooling device 7 performs the same cooling operation as the cooling device 7 in FIG.
[0024]
Accordingly, the dioxins contained in the fly ash F51, F6 are thermally decomposed and resynthesis is prevented, so that the dioxins in the fly ash F51 ", F6" discharged from the waste treatment system are greatly reduced. be able to.
According to the method for treating fly ash in the exhaust gas in such a waste treatment device, the chlorine of the dioquine is removed by the catalytic action of metals in the ash for collecting and heat-treating the fly ash F3, F51 + F6 in the exhaust gas. Or by causing a chemical reaction that breaks oxygen bridges to decompose dioxins, and by rapid cooling, resynthesis of dioxins during cooling is prevented, so discharged fly ash F3 ″, F51 ″ + F6 The amount of dioxin contained in "can be greatly reduced.
[0025]
【The invention's effect】
As is clear from the above description, according to the fly ash treatment method in the exhaust gas in the waste treatment apparatus according to the present invention, the combustion ash generated by the combustion treatment of the waste is made into molten slag, and this molten slag is cooled. In the waste treatment equipment that is recovered as solidified slag, at least the fly ash containing molten fly ash discharged from the melting furnace or combustion melting furnace is heat-treated to thermally decompose dioxins, and then rapidly cooled. Therefore, the amount of dioxin contained in the fly ash discharged out of the system from the waste treatment apparatus can be greatly reduced.
[Brief description of the drawings]
FIG. 1 is a system diagram of an exhaust treatment apparatus showing a method for treating fly ash in exhaust gas in a waste treatment apparatus according to the present invention.
FIG. 2 is a cross-sectional view of an embodiment of the heating device shown in FIG.
FIG. 3 is a system diagram of the waste treatment apparatus showing a method for treating fly ash in exhaust gas in another waste treatment apparatus according to the present invention.
DESCRIPTION OF SYMBOLS 1 ... Combustion furnace 2 ... Melting furnace 3 ... Waste heat boiler 4 ... Cooler 5 ... 1st dust collector 6 ... Heating device 7 ... Cooling device 8 ... 2nd dust collector 9 ... 3rd dust collector 10 Induction blower 11 ... Chimney 22 ... Separation device 24 ... Pyrolysis reactor 25 ... Combustion melting furnace 80 ... Rotary drum 81 ... Heater 82 ... Inlet hood 83 ... Outlet hood 84 ... Fixed quantity feeder

Claims (4)

Combustion waste gas is burned in a combustion furnace, the generated combustion ash is made into molten slag in a melting furnace, cooled and solidified and recovered, and the melting furnace exhaust gas discharged from the melting furnace is discharged from the combustion furnace. In the waste treatment apparatus supplied to the first dust collector, after mixing the molten furnace exhaust gas into the mixed exhaust gas, before mixing the melting furnace exhaust gas with the combustion furnace exhaust gas The combustion furnace exhaust gas is supplied to the second dust collector, the collected fly ash is supplied to the melting furnace, and the melting furnace exhaust gas discharged from the melting furnace is supplied to the third dust collector. Then, the melting furnace gas is mixed with the combustion furnace exhaust gas to form a mixed gas, a desalting agent is injected into the mixed gas, and then supplied to the first dust collector. and fly ash that is collected by the dust collecting apparatus, Fei trapped in the third dust collector A heating device supplied with heat treatment, rapid cooling by supplying fly ash which is heat treatment in the cooling device, fly ash treatment method in the exhaust gas in the waste disposal apparatus. Pyrolysis products generated by heating and pyrolyzing waste are supplied to the combustion melting furnace for combustion treatment, and the generated combustion ash is cooled and solidified in the melting furnace to be recovered and recovered. In a waste treatment apparatus for supplying a first dust collector after desalting agent is injected into a melting furnace exhaust gas discharged from the furnace, the melting furnace exhaust gas discharged from the combustion melting furnace is secondly collected. A part of the fly ash collected by the second dust collector is supplied to the heating device, and the other part is supplied to the combustion melting furnace, and is discharged from the second dust collector. The desalting agent is injected into the exhaust gas, and then supplied to the first dust collector. The fly ash collected by the first dust collector and collected by the second dust collector. A portion of the fly ash is supplied to the heating device for heat treatment, and the heat-treated fly ash is supplied to the cooling device for rapid cooling. , Fly ash treatment method in the exhaust gas in the waste disposal apparatus. The fly ash treatment method in exhaust gas in the waste treatment apparatus according to claim 1 or 2, wherein the fly ash supplied to the heating device is heated to 400 ° C to 600 ° C. The method for treating fly ash in exhaust gas in a waste treatment apparatus according to claim 1, 2 or 3, wherein the heated fly ash is rapidly cooled within a range of 100C to 200C.

Images