KR19980064066A - Melting furnace exhaust gas treatment method and apparatus - Google Patents

Abstract

The present invention is to increase the concentration of the non-ferrous heavy metals contained in the exhaust when exhausted from the exhaust gas discharged from the smelting furnace. It is a method of adding and removing.

Description

Method and apparatus for treating furnace exhaust gas

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the treatment of exhaust gas discharged from a melting furnace, and more particularly to an exhaust gas treatment method and apparatus for removing dust and acid gases in exhaust gas discharged from a melting furnace for melting incineration ash.

2 shows an apparatus for treating exhaust gas discharged from a conventional melting furnace. In FIG. 2, in the melting furnace 1, the incineration ash is melted, and the exhaust gas 6 containing the dust is discharged. After the exhaust gas 6 is cooled in the gas cooling chamber 2 or the like, powder 8 of slaked lime is blown into the exhaust gas in order to react with acidic gas in the exhaust gas. And dust collector 3, such as a bag filter and an electrostatic precipitator, collects the molten fly ash 10a in exhaust gas. The molten fly ash 10a contains the dust generated in the melting furnace 1 and the powder 8 of slaked lime.

Since the incineration ashes incinerated urban dust or urban waste contain nonferrous heavy metals such as Pb and Zn, the non-ferrous heavy metals are contained in the exhaust of the exhaust gas 6 discharged from the melting furnace 1. In addition, the molten fly ash 10a collected by the dust collector 3 also contains a non-ferrous heavy metal due to dust.

Therefore, when this molten fly ash is treated as a waste, it is necessary to perform a chemical treatment for preventing the dissolution of heavy metals, for example, chelating agent treatment.

In addition, the molten fly ash contained in the exhaust gas of the melting furnace has a high concentration of heavy metals compared to the incineration fly ash contained in the exhaust gas of the incinerator, which requires a large amount of chemicals and a huge treatment cost.

On the other hand, when the molten fly ash is used as a nonferrous metal raw material, since the slaked lime is contained, the concentration of heavy metals in the molten fly ash is lowered and it cannot be used as a nonferrous metal raw material. For example, if Pb and Zn contained in urban dust are representative, the lowest concentrations for recovering valuable minerals are 3.0% and 2.5%, respectively. However, the concentrations of Pb and Zn in the molten fly ash are lower than this because they contain hydrated lime, which may not be recovered as an organic substance even if the extraction process by acid or water washing or concentration of high temperature volatilization is performed. In the case of incineration of municipal waste in incinerators, the concentration of non-ferrous heavy metals in the incineration fly ash contained in the exhaust gas is not worth recovering at all.

1 is an overall configuration diagram showing an embodiment of an apparatus for treating exhaust gas discharged from a melting furnace of the present invention;

2 is an overall configuration diagram of an apparatus for treating exhaust gas discharged from a conventional melting furnace.

※ Explanation of symbols for main parts of drawing

1: melting furnace 2: gas cooling device

3: bag filter as front dust collector

5: ash 6: exhaust gas

7: melted melt 8: powder alkaline chemicals

9: process gas 10: recovered powder alkaline chemicals

11: cooling air

The present invention solves the problems of the prior art, and provides a method and apparatus for treating exhaust gas in a melting furnace that can obtain refinable dust as a nonferrous metal raw material without undergoing a special concentration process and using no special chemicals. Let's make it a task.

In the first aspect of the present invention, a method of treating the exhaust gas discharged from the smelting furnace is contained in the exhaust gas, and the step of removing the dust containing the non-ferrous heavy metal by the first dust collecting device and the exhaust gas from which the dust is removed. And a step of adding an alkaline agent to remove the acidic gas which is to be used, and a step of removing the alkaline agent that is substantially free of non-ferrous heavy metals.

In the present invention, the dust collected by the first dust collecting device preferably contains 3.0 wt% or more of Pb or 2.5 wt% or more of Zn.

Moreover, it is preferable that the said alkaline chemical | medical agent to add is powder, and the said powder is removed by a 2nd dust collector.

It is also preferable that the first dust collecting device or the second dust collecting device is a bag filter or an electric dust collector.

It is also preferred that the alkaline agent contains hydrated lime or lime.

According to a second aspect of the present invention, there is provided a first dust collecting device for removing dust contained in the melting furnace and the exhaust gas discharged from the melting furnace, and also containing non-ferrous heavy metals, and for removing the acidic gas contained in the exhaust gas from which the dust has been removed. A supply apparatus for adding an alkaline chemical agent made of powder and a second dust collecting device for removing the alkaline chemical agent substantially free of non-ferrous heavy metal are provided.

In the present invention, it is preferable that the first dust collecting device is a bag filter having a robe made of heat resistant engineering plastic, metal or ceramic.

In the present invention, since the dust in the exhaust gas is removed by the dust collector before adding the alkaline chemical agent, the concentration of the nonferrous metal contained in the dust can be increased, and the dust itself can be effectively reused as a nonferrous metal raw material. Can be.

In addition, since the acidic gas in the exhaust gas is removed after the dust is removed, the recovered alkaline chemicals do not contain heavy metals, and no special intermediate treatment for heavy metals is necessary.

(Example)

The structural diagram of the waste gas processing apparatus discharged | emitted from the melting furnace of this invention is shown in FIG. In Fig. 1, 1 is a melting furnace, 2 is a gas cooling device, 3 is a dust collecting device at the front end, and 4 is a dust collecting device at the rear end.

The melting furnace 1 is capable of reducing the volume by melting a small specific gravity of ash or the like. Typically, the incineration ash of an incinerator, the incineration fly ash contained in the exhaust gas of an incinerator, etc. are processed. In FIG. 1, the ash 5 is introduced into the melting furnace 1 through the supply hole, and is subsequently melted inside the melting furnace 1 by being heated by a heat source. As a heat source, it is electric power, for example, and a plasma type melting furnace can be used. There is also a method of burning incomplete combustion gas generated in an incinerator. The melt inside the melting furnace 1 is discharged, for example, from an outlet not shown, and then solidified by cooling. The volume of this solid is decreasing compared with the volume of the ash supplied.

The exhaust gas 6 discharged from the melting furnace 1 is cooled to a temperature introduced into the dust collector 3 by the gas cooling device 2. The exhaust gas 6 is preferably cooled to 150 ° C to 550 ° C. In one embodiment it is preferable to cool to 160 ℃ ~ 230 ℃, in another embodiment it is preferable to cool to 400 ℃ ~ 550 ℃.

Hereinafter, the matters common to all the embodiments will be described.

The dust collecting apparatus 3 removes the dust 7 contained in exhaust gas. As the dust collector 3, a bag filter or an electrostatic precipitator is preferable, and a bag filter is more preferable. The dust 7 contains a large amount of nonferrous heavy metals, and the collected dust 7 is stored by the dust storage facility and sent to a facility for proper refining. The dust collected by the dust collector 3 preferably contains 3.0 wt% or more of Pb or 2.5 wt% or more of Zn. It is more preferable that the dust contains 4.0 wt% or more of Pb or 3.5 wt% or more of Zn, and more preferably 5.0 wt% or more of Pb or 4.0 wt% or more of Zn.

Thereafter, the acidic gas contained in the exhaust gas from which the dust has been removed is removed again. First, an alkaline chemical agent 8, preferably an alkaline chemical agent in powder form is added to the exhaust gas. For example, commercially available feeders such as powder can be used. And this alkaline chemical is removed. When an alkaline chemical agent is powder, it is preferable to remove this powder by the dust collector 4. As the dust collector 4, a bag filter and an electric dust collector can be used suitably.

Since the powder 10 recovered by the dust collector 4 does not contain heavy metals, it can be reused without any special treatment. For example, when alkaline calcium compounds such as slaked lime (main component is Ca (OH) ₂ ) and lime (main component is CaO) are added as powders, the recovered powder can be reused as a cement raw material.

The exhaust gas 9 discharged from the dust collector 4 at the rear stage is discharged through a manned blower or other acidic gas removal device.

Hereinafter, an embodiment in which the gas cooling device 2 cools the exhaust gas 6 to 400 ° C to 550 ° C will be described. In such a case, it is preferable that the dust collector 3 is a bag filter having a lopo made of heat resistant engineering plastic, metal or ceramic. This is because the lofo made of these materials has sufficient mechanical strength, durability and the like even when the temperature of the exhaust gas 6 is 400 ° C to 550 ° C, preferably 400 ° C to 500 ° C. As a metal loaf, net stainless steel is used, for example. Porous alumina is used as a ceramic ropo, for example. When the temperature of the exhaust gas is such a high temperature, the dust collector becomes compact.

Cooling air 11 is introduced into the introduction hole with respect to the exhaust gas discharged from the dust collector 3, and the exhaust gas is cooled. Preferably, the exhaust gas is cooled to 160 ° C to 230 ° C. As a result, no special heat resistance is required for the dust collector 4 in the rear stage, and the cost can be reduced.

Alternatively, a gas cooling device may be used instead of introducing the cooling air 11 into the inlet hole. In the case where the temperature of the exhaust gas 6 is cooled to around 200 ° C. in the gas cooling device 2, it is not necessary to provide an introduction hole.

Hereinafter, an Example demonstrates this invention. However, this invention is not limited to the following Example.

In the embodiment, an apparatus for treating exhaust gas discharged from the melting furnace of the present invention of FIG. 1 was used. Moreover, as a comparative example, the waste gas processing apparatus discharged | emitted from the conventional melting furnace of FIG. 2 was used. In the Example and the comparative example, only the presence or absence of the bag filter 4 of the rear end was used, and the other thing used the same thing. In addition, neither the Example nor the comparative example introduces the cooling air 11.

As the melting furnace 1, a plasma type melting furnace (equipment output 150 kW, maximum throughput 150 kg / h) was used.

As ash 5, the incineration ash after burning municipal waste in an incinerator was supplied to the melting furnace 1 at 100 kg / hr. The components of this incineration ash are as shown in Table 1.

ingredient Concentration (% by weight) SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ CaOMgONa ₂ OK ₂ OZnPbCu 567.83.2140.711.30.290.290.20.43

Further, electric power was supplied to the melting furnace and arc discharged in air to generate a high temperature plasma gas flow of 10000 K or more. The incineration ash was melted by the plasma gas flow at a furnace temperature of 1400 ° C.

In the gas cooling apparatus 2, the exhaust gas 6 was cooled to about 200 degreeC with cooling air.

As the dust collector 3 at the front end, a bag filter of a heat resistant ropo having a heat resistance temperature of 550 ° C. was used. On the other hand, a bag filter having a heat resistance temperature of 250 ° C. was used as the dust collector 4 in the rear stage.

As an alkaline chemical, powdered special lime was added at 300 g / h.

The results are shown in Table 2.

Example Comparative example Pb (wt%) Zn (wt%) 4.83.5 2.21.9

In the Example of Table 1, the density | concentration in the molten fly ash 7 collected by with the dust collector 3 of the front end of FIG. 1 is shown. In the comparative example, the concentration of 10a in the molten fly ash collected by the dust collector 3 of FIG. 2 is shown.

In the present invention, the Pb and Zn concentrations in the molten fly ash are remarkably improved and can be reused.

As described above, according to the present invention, molten fly ash that has been disposed of in the final disposal site by chemical treatment can be reused.

Claims (7)

In the method for treating the exhaust gas discharged from the melting furnace, Removing the dust contained in the exhaust gas and containing the non-ferrous heavy metal by the first dust collecting device, Adding an alkaline chemical to remove the acidic gas contained in the exhaust gas from which the dust has been removed; And a step of removing the alkaline chemicals substantially free of non-ferrous heavy metals. The method of claim 1, The dust collected by the said first dust collector contains 3.0 wt% or more of Pb or 2.5 wt% or more of Zn. The method according to claim 1 or 2, The alkaline chemical agent to add is powder, The processing method of the melting furnace exhaust gas which removes the said powder by a 2nd dust collector. The method of claim 3, The first dust collector or the second dust collector is a bag filter or an electrostatic precipitator, characterized in that the furnace exhaust gas treatment method. The method according to any one of claims 1 to 4, A method for treating a furnace exhaust gas in which the alkaline chemicals contain hydrated lime or lime. With melting furnace, A first dust collecting device which is contained in the exhaust gas discharged from the melting furnace and removes dust containing non-ferrous heavy metals; A feeder for adding an alkaline chemical agent in powder to remove the acidic gas contained in the exhaust gas from which the dust is removed; And a second dust collecting device for removing the alkaline chemicals substantially free of non-ferrous heavy metals. The method of claim 6, An apparatus for treating smelter exhaust gas, wherein the first dust collector is a bag filter having a lopo made of heat resistant engineering plastic, metal, or ceramic.