JPH06170162A - Method for collecting harmful metal in exhaust gas and treatment of collected ash - Google Patents

Abstract

PURPOSE:To efficiently collect harmful metal from exhaust gas by adding at least one kind selected from among slaked lime, calcium carbonate and calcium oxide, a reaction auxiliary and calcium silicate to exhaust gas discharged from an incinerator and collecting harmful metal together with the said additives by a bag filter device. CONSTITUTION:In a method for collecting harmful metal in exhaust gas discharged from an incinerator, harmful metal (i.e., cadmium, lead and mercury) is collected together with the following additives by a bag filter device 5 by adding at least one kind selected from among slaked lime, calcium carbonate and calcium oxide to exhaust gas G1 in a duct 1 thereof from a feeder 2, adding a reaction auxiliary (e.g. a mixture of diatomaceous earth and perlite) from a feeder 3 and adding calcium silicate from a feeder 4. Collected ashes W1 recovered by such a way is humidified by a humidifier 6 and thereafter molded into a pellet shape or a briquette shape by a molding device 7. The molded form is dried by a drier 8. As a result, harmful metal is efficiently collected from exhaust gas of an incineration facility.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a treatment method for collecting harmful metals from exhaust gas from municipal waste incinerators, industrial waste incinerators, and other incinerators that generate harmful metals, and the collected harmful metals. The present invention relates to a method of immobilizing.

[0002]

2. Description of the Related Art Conventionally, harmful metals (including metal oxides, chlorides, sulfates and other metal salts) in exhaust gas generated from incinerators are cyclones, electrostatic precipitators, bag filters, wet cleaning equipment. It was collected by means such as cement, stabilized by cement solidification, melt solidification, etc., and then landfilled.

[0003]

However, in the above method, harmful metals cannot be effectively collected, and the stabilization treatment is complicated. Therefore, the present invention is intended to solve the above problems and provide a method for efficiently collecting harmful metals in exhaust gas and a method for easily stabilizing the collected harmful metals.

[0004]

The present invention provides (1) a method for collecting harmful metals in exhaust gas from an incinerator, wherein at least one of slaked lime, calcium carbonate and calcium oxide is contained in the exhaust gas. , A reaction aid, and calcium silicate are added, and a harmful metal is collected together with the additive with a bag filter device, and (2) a harmful metal is collected from an incinerator. In the method for treating harmful metals in exhaust gas, slaked lime, at least one of calcium carbonate and calcium oxide, a reaction aid, and calcium silicate are added to the exhaust gas, and harmful together with the additive in a bag filter device. A harmful metal characterized by collecting metal, humidifying an additive containing a harmful metal discharged from the bag filter device, forming into pellets or briquettes, and drying. It is a processing method.

[0005]

According to the present invention, at least one of slaked lime, calcium carbonate and calcium oxide, a reaction aid, and calcium silicate are added to the exhaust gas to fix harmful metals, and at the same time, a bag filter device By collecting harmful metals, collection efficiency can be increased, and
By humidifying the collected ash, it can be easily solidified, and can be molded into pellets or briquettes without using cement or the like, and dried to obtain a molded body that does not easily elute. It can now be used as it is for landfills. As the reaction aid, diatomaceous earth or powder containing diatomaceous earth as a main component can be used, and perlite or the like can be used together.

FIG. 1 is a conceptual diagram for explaining the method of the present invention. G ₁ is a raw gas before treatment discharged from the incinerator, and contains acidic gases such as HCl, SO _x and HF in addition to harmful metals. The exhaust gas duct 1 is provided with a slaked lime supply device 2, a reaction auxiliary agent supply device 3 and a calcium silicate powder supply device 4, and a treating agent is sequentially injected so that the slaked lime absorbs an acidic gas in the exhaust gas duct 1 to obtain calcium silicate. After adsorbing harmful metals to the bag filter, the bag filter device 5 collects them, forms the additive layer on the surface of the back filter, and further absorbs and adsorbs acidic gas and harmful metals in the layer to purify them. The exhaust gas is emitted as G ₂ . next,
Collection ash W containing the above-mentioned additive collected in the bag filter 5
Are humidified by a humidifying device 6, molded into pellets or briquettes by a solidifying device 7, moisture is removed as necessary by a drying device 8, and the dried and solidified molded body W ₂ is carried out of the system, It is provided for landfills.

[0007]

【Example】

(Example 1) Exhaust gas from an MSW incinerator was treated by the apparatus shown in FIG. HCl in the exhaust gas is 500 ppm, SO
_X is 100 pmm, dust is 3.0 g / Nm ³ , Cd is 0.8 mg / Nm ³ as a harmful metal, and Pb is 31.6.
mg / Nm ^3, and the Hg containing 0.32 mg / Nm ^3, the amount of exhaust gas was 20000Nm ³ -Dry / hr. Additives are 60 kg / hr of slaked lime powder and 15k of reaction aid (diatomaceous earth / perlite weight ratio = 9/1).
g / hr, and calcium silicate powder (SiO ₂ / CaO
(Weight ratio of 1/1) was injected from each of the supply devices at 6 kg / hr.

As a result, in the exhaust gas after the treatment, HCl
Is 10 ppm or less, SO _X is 5 pmm or less, soot and dust is 1 mg / Nm ³ or less, Cd is 0.01 mg / Nm ³ or less, Pb is 0.01 mg / Nm ³ or less, and Hg is 0.05.
It could be purified to less than mg / Nm ³ . The amount of ash (including slaked lime, reaction aid and calcium silicate) collected by the bag filter was about 141 kg / hr. Moisture of 40 kg / hr was added to the collected ash to humidify it, and thereafter, it was solidified by a briquette machine, evaporated with a drying device at a drying rate of 20 kg / hr, and then discharged outside the system.

(Comparative Example) Among the conditions of Example 1, when the supply of calcium silicate was omitted, the treated exhaust gas contained 10 ppm of HCl, 5 ppm of SO _X , 1 mg / Nm ^{3 of} dust and Cd of 0. 0.03 mg / Nm ³ , Pb
There 0.02mg / Nm ^3, Hg is 0.08mg / Nm ³
It was contained, and the collected ash was about 135 kg / hr. Moisture 40 kg / hr was added to the collected ash to humidify it.
After that, I tried to solidify with a briquette machine, but could not solidify well.

Example 2 Exhaust gas from an industrial waste incinerator was treated by the apparatus shown in FIG. HCl in the exhaust gas is 10
00ppm, SO _x 20pmm, Dust 10g /
Nm ^3, Cd and 0.2 mg / Nm ³ as toxic metals, P
b of 50 mg / Nm ³ and Hg of 0 mg / Nm ³ ,
The amount of exhaust gas was 15000 Nm ³ -Dry / hr.
As additives, slaked lime powder 65 kg / hr, reaction aid (diatomaceous earth / perlite weight ratio = 8/2) 6 k
g / hr and calcium silicate powder (SiO ₂ / CaO weight ratio = 1/1) were sprayed from respective feeders at 6 kg / hr.

As a result, the treated exhaust gas contains 2% HCl.
0ppm or less, SO _X is 1pm or less, soot and dust 5m
g / Nm ³ or less, Cd 0.01 mg / Nm ³ or less, P
b could be purified to 0.01 mg / Nm ³ or less. The ash collected by the bag filter is about 227 kg / hr
Met. A moisture content of 70 kg / hr was added to the collected ash to humidify it, then solidified by a pellet machine, and the moisture content was evaporated at a drying rate of 35 kg / hr in a drying device, and then it could be discharged to the outside of the system.

[0012]

EFFECTS OF THE INVENTION By adopting the above-mentioned constitution, the present invention can effectively remove harmful metals and acid gases from exhaust gas discharged from municipal waste incinerators, industrial waste incinerators and the like. In addition, the collected harmful metals can be easily solidified and can be supplied as a harmless landfill material.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a method for treating exhaust gas from an incinerator which is an embodiment of the present invention.

Claims (2)

[Claims] 1. A method for collecting harmful metals in exhaust gas from an incinerator, wherein slaked lime, at least one of calcium carbonate and calcium oxide, a reaction aid, and calcium silicate are added to the exhaust gas. A method for collecting a harmful metal, wherein a bag filter device collects the harmful metal together with the additive. 2. A method for treating harmful metals in exhaust gas collected from an incinerator, wherein the exhaust gas contains at least one of slaked lime, calcium carbonate and calcium oxide, a reaction aid,
Also, calcium silicate is added, a harmful metal is collected together with the additive in a bag filter device, and the additive containing the harmful metal discharged from the bag filter device is humidified to form a pellet or briquette. And a method of treating harmful metals, characterized by drying.