JPH03224618A - How to suppress dioxin generation - Google Patents

Abstract

PURPOSE:To prevent the generation of dioxine by neutralizing HCl concerned in the generation of dioxine with an alkaline compd. at 900-300 deg.C into KCl or NaCl ready to be post-treated. CONSTITUTION:One or 2 kinds of alkaline compds. selected from a group consisting of KOH, K2CO3, KHCO3, NaOH, Na2CO3 and NaHCO3 are supplied from a feeder 7 into a waste gas discharge passage 6 from an incinerator at 900-300 deg.C to neutralize HCl contained in the waste gas and involving the generation of dioxine into KCl or NaCl as a stable compd. Consequently, the generation of dioxine is prevented, and the waste gas free of dioxine is discharged into the atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for suppressing the generation of dioxins accompanying the incineration of municipal waste, industrial waste, etc. or the treatment of exhaust gas thereof.

[Prior art and its problems] Dioxins emitted from garbage incinerators, etc., have many unknown points about their formation process, but they are generated in the presence of HCl in a low temperature region of less than 300 degrees Celsius downstream of the incinerator, and are produced in the presence of ash. It has been found that the amount generated increases with the presence of Although dioxins are only contained in trace amounts in exhaust gas, they are extremely toxic to the human body even in trace amounts, and are particularly carcinogenic.Dioxins have recently come under the spotlight as a new pollution problem caused by waste incinerator exhaust gas. It is being done.

In the conventional exhaust gas treatment method, the flow is shown in Figure 2. The exhaust gas generated in the waste incinerator (1) is discharged from the top outlet, and after being removed by the electrostatic precipitator (2), it is sent to the exhaust gas cleaning treatment equipment. A wet cleaning treatment is performed at Fl<3), and the treated exhaust gas is dissipated into the atmosphere from the chimney (5) by an induction fan (4). However, in this exhaust gas treatment flow, dioxins can hardly be absorbed and removed by wet cleaning treatment.
Currently, it is released into the atmosphere as is.

In view of the above-mentioned circumstances, it is an object of the present invention to provide a method for suppressing the generation of dioxins accompanying the incineration of municipal waste, industrial waste, etc. or the treatment of their exhaust gas.

[Means for Solving Problems] In order to achieve the above object, the method for suppressing the generation of dioxin according to the present invention injects KOH, niCO* into a temperature range of 900 to 300°C in the exhaust gas discharge path from the incinerator.
, KHCO, , Na0HSNa, Co3 and Na
1 alkaline compound selected from the group consisting of HCOi
The method is characterized in that a species or two or more species are supplied to neutralize HCl contained in the exhaust gas and involved in the production of dioxin to produce a stable compound K C/ or NaC/.

In the above, KOH, 2 CO3, K2CO3, K
HCO3, NaOH, Na2CO3 and NaHCOl
The supply temperature range of the alkaline compound selected from the group consisting of is preferably 700 to 400°C.

The reason for this is that when the temperature exceeds 700°C, Na25O1, K
Sulfates such as 2SO4 may melt and adhere to the surface of boiler tubes, causing corrosion of the tubes or reducing the heat transfer rate. This is because there is a possibility that this may occur. For example, the reaction between the alkaline compound and HCl is as follows.

KOH+HC1→KCl+H2O NaOH+HCl−NaC/+H20 2 CO3+2HCl →2 K C/ + H20+ CO2Na2CO3+
2HCl →2 N a Cl +H20+CO2KHCO,+H
Cl → KCl + H20 + C02 Na HCO3+ HCl → NaC/+H20 + CO
90, which is a temperature range higher than that where dioxins are generated.
At 0-300℃.

A stable compound KCl or NaC/ is produced.

As a result, the generation of dioxin is prevented, and exhaust gas containing no dioxin is released into the atmosphere.

[Example] Next, the present invention will be specifically explained with reference to the illustrated example.

FIG. 1 shows the flow of the method for suppressing dioxin generation according to the present invention. In the same figure, the exhaust gas discharged from the top outlet of the waste incinerator (1) is connected to the supply device (7) in the exhaust gas discharge path (6) connecting the top outlet of the incinerator (1) and the electrostatic precipitator (2). ) by KOH, to 2 CO3,
KHCO3, Na OHSN a 2 CO] and N
One or more alkaline compounds selected from the group consisting of aHCO are supplied. The alkaline compound is supplied in powder form by spraying it using a supply device (7) consisting of a blower, or by spraying it as an aqueous solution using a supply device (7) consisting of a pump. Then, the exhaust gas is removed by an electrostatic precipitator (2).

After that, the exhaust gas is cleaned in a cleaning treatment device (3),
The treated exhaust gas is dissipated into the atmosphere from the chimney (5) by the induced fan (4).

As the electrostatic precipitator (2), a high temperature type is preferable.

The reason is that when the temperature inside the electrostatic precipitator (2) is low, S02 becomes 803. This is because there is a risk that the electrostatic precipitator (2) will be corroded by SO3.

In this exhaust gas treatment flow, HCl, a substance involved in the generation of dioxin, is converted to 99% by alkaline compounds.
KCl or NaC/, which is a stable compound that is neutralized in the temperature range of 00 to 300°C and is easily post-treated, is produced. As a result, the generation of dioxin is prevented, and exhaust gas containing no dioxin is released into the atmosphere.

Furthermore, almost no dioxins were detected in the high-temperature garbage incinerator or in the exhaust gas exhaust path between the incinerator and the electrostatic precipitator. When the alkaline compound is not supplied, dioxins begin to be produced at a temperature around 300° C., and rapidly increase at lower temperatures. In particular, the production of dioxin is remarkable in the electrostatic precipitator, where the temperature is below 300°C, and it is thought that the electrostatic precipitator is a hotbed for the production of dioxin.

[Effects of the Invention] According to the method for suppressing dioxin generation of the present invention, HCl, which is thought to be involved in the generation of dioxin, is neutralized with an alkaline compound at a temperature range of 900 to 300°C, and HCl is easily post-treated. C/ or NaC/ can be produced.

As a result, it is possible to prevent the generation of dioxin and to release exhaust gas that does not contain dioxin into the atmosphere.

[Brief explanation of drawings]

FIG. 1 is a flow sheet for exhaust gas treatment showing an embodiment of the present invention, and FIG. 2 is a flow sheet for conventional exhaust gas treatment. (+) ...garbage incinerator,

Claims (1)

[Claims] KOH, K_2CO_3, KHCO_3, N
One or more alkaline compounds selected from the group consisting of aOH, Na_2CO_3, and NaHCO_3 are supplied to neutralize HCl, which is contained in exhaust gas and participates in the production of dioxin, to produce stable compounds such as KCl or N.
A method for suppressing dioxin generation, the method comprising generating aCl.