JPS6223420A - Treatment of combustion exhaust gas - Google Patents

Abstract

PURPOSE:To reduce the load in the treatment of waste water by reducing the discharge amount of waste gas washing waste water, by separately discharging the waste gas washing waste water from a quenching part and the condensed water from a cooling/ humidity reducing part. CONSTITUTION:Combustion exhaust gaas G11 containing HCl, SOx and heavy metals generated by the incineration of waste is introduced into a quenching part 12 from an inlet 11 to be quenched by the cooling liquid 13 recirculated and sprayed by a pump 14 and, at the same time, a part of the substance contained in the gas is absorbed and removed and the remainder is absorbed and washed by an alkaline absorbing solution 16 in an absorbing part 15. Subsequently, the exhaust gas is guided to a cooling/humidity reducing part 19 through a mist separator 18 and cooled and reduced in humidity by cooling water 22 cooled by a cooler 20 and recirculated by a pump 21 to be discharged from the tower top 24 through a mist separator 23. The alkaline absorbing liquid 16 corresponding to a replenished amount is flooded to the quenching part 12 and a part of the cooling liquid 13 is discharged to the outside as waste gas washing waste water L11. A predetermined amount is taken out from cooling water 22 of which the amount was increased by the condensation of moisture in exhaust gas in the cooling/humidity reducing part 19 to be discharged as condensed water L12.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for treating combustion exhaust gas generated during the incineration of waste.

Conventional technology Combustion exhaust gas generated from waste incineration, etc. is HC1.

Since it contains harmful gases such as SOx and harmful substances such as soot and dust, it has conventionally been cleaned using a smoke cleaning device as shown in FIG. 3 before being released into the atmosphere. That is, the third
In the smoke cleaning device shown in the figure, combustion exhaust gas (G,) is introduced from the inlet (1) to the lower quenching section (2), and the cooling liquid (3
) is circulated and sprayed to rapidly cool the exhaust gas, while at the same time absorbing and removing a part of the substances contained in the exhaust gas, a part of the cooling liquid (3) is taken out to the outside as smoke washing drainage (Ll), and then the exhaust gas is passed through the upper absorption After passing through part (4) and absorbing and cleaning harmful gases, dust, etc. with the circulating alkaline absorption liquid (5), it is released into the atmosphere from the top part (7) and circulated.
The absorption liquid (5) is newly replenished with a predetermined amount of alkaline aqueous solution (6), and a part of it overflows to the quenching section (5) and becomes the cooling liquid (
3). (8) and (9) are circulation pumps.

Problems to be Solved by the Invention In the above conventional method, the released gas (G2) is relatively high temperature and contains a large amount of moisture, so when it is released into the atmosphere, white smoke is likely to be generated due to condensation of water vapor. . In order to prevent the generation of white smoke, the 7μ potassium absorption liquid circulating within the absorption section is cooled by a cooler α1 to condense the moisture in the exhaust gas and dehumidify it. However, the condensed water gets mixed into the alkaline absorption liquid, and the amount of waste water that must be discharged outside as smoke washing water eventually increases. In particular, recently, cooling systems for alkaline absorption liquids have been developed, in order to prevent the generation of white smoke from the cooling system, instead of the conventional method of directly contacting the absorption liquid with air, methods are used that cool the absorption liquid indirectly using double pipes, etc. Since this is adopted, all the water that was released outside the υ system due to direct contact with air remains in the absorbing liquid, further increasing the amount of water discharged. For these reasons, the burden of wastewater treatment for the purpose of removing salts, SS, harmful heavy metals, etc. contained in smoke washing wastewater increases.

The present invention aims at increasing the amount of smoke washing water and the accompanying wastewater treatment by cooling the flue gas at the same time as cleaning the flue gas in the conventional method, as described above, when treating combustion flue gas generated from waste incineration, etc. The purpose is to provide a method for treating combustion exhaust gas that can solve the problem of increased burden on people.

Means for Solving the Problems In order to solve the above problems, the combustion exhaust gas treatment method of the present invention includes a quenching section that rapidly cools the combustion exhaust gas with a cooling liquid;
The smoke is treated by a smoke cleaning device consisting of an absorption section that absorbs and cleans with an alkaline absorption liquid and a cooling and dehumidifying section that condenses water, and the smoke cleaning wastewater is collected from the quenching section and the condensed water is collected from the cooling and dehumidifying section, respectively. It is characterized by being discharged.

That is, the present invention absorbs some of the substances containing HCl, SOx, heavy metals, etc. contained in the combustion exhaust gas generated during waste incineration, etc., and then absorbs and cleans it with an alkaline absorption liquid, and then further heats it to around 50°C. It is cooled, dehumidified, and released into the atmosphere. During this period, a predetermined amount of alkaline aqueous solution is replenished into the circulating alkaline absorbent, and at the same time, an amount equivalent to the replenished alkaline aqueous solution is taken out as a coolant for quenching the exhaust gas, and the quenching coolant also contains Fresh water is added as necessary, and a portion of the coolant is discharged to the outside as smoke washing wastewater, and the condensed water generated by cooling and dehumidification is discharged to the outside separately from the smoke washing wastewater. be.

Fig. 1 shows an example of a smoke scrubbing device used in the present invention, and is an example of a one-tower structure with an exhaust gas quenching section at the bottom, an absorption section at the middle, and a cooling and dehumidifying section at the top. . FIG. 2 also shows an example of a pond in a smoke scrubbing device used in the present invention, in which the cooling and dehumidifying section of the smoke scrubbing device shown in FIG. In the smoke cleaning device shown in Fig. 1 and Fig. 2, combustion exhaust gas (G,,) is transferred from the inlet a°C to the quenching section @
The cooling liquid a3 is circulated and sprayed by the circulation pump Q4) to be rapidly cooled, and at the same time, a part of the substances contained in the exhaust gas is absorbed and removed, and then passed through the absorption section (to) and circulated by the circulation pump αη. The contained substances are absorbed and washed with an alkaline absorption liquid of 0.0, and then guided through the mist separator (to) to the cooling and dehumidifying section (19), where it is cooled by the cooler (1),
It is then cooled and dehumidified with the cooling water (A) that is circulated through the circulation bonder Q1), and is then released to the outside as discharged gas (G, 2) from the top of the tower (C) through a mist separator. .

During this time, in the absorption section 05, the alkaline absorption liquid (
le9 is replenished with a predetermined amount of alkaline aqueous solution), and at the same time an alkaline absorbing liquid αQ in an amount approximately equivalent to the supplied alkaline aqueous solution overflows into the quenching part@
5a) and mixes into the coolant α frame, and furthermore, a part of the circulating coolant μs is discharged to the outside as smoke washing water (L, , ). In addition, at the cooling and dehumidifying section α flaw, the amount of cooling water increases due to moisture in the exhaust gas condensed by cooling.
Continuously discharge a predetermined amount of condensed water (L, 2) from a) to the outside.

In the present invention, in the washing treatment of combustion exhaust gas, so-called smoke washing waste water and condensed water are discharged to the outside separately, so the amount of smoke washing waste water discharged is at least the amount of condensed water discharged compared to the conventional method. This can significantly reduce the burden of subsequent wastewater treatment. In addition, the exhaust gas entering the cooling and dehumidifying section passes through the absorption section and the contained substances are sufficiently removed, so the amount of salts, heavy metals, etc. contained in the condensed water is small.
Therefore, even if wastewater is to be treated, a light treatment separate from the treatment of the smoke washing waste water is sufficient, and depending on the case, the wastewater can be reused or discharged as is.

Example combustion exhaust gas generated during incineration of waste (exhaust gas ff18
The QOOON door/H) was smoke-cleaned by the method of the present invention using the smoke-cleaning device shown in FIG. First, it is rapidly cooled in the quenching section, and then in the absorption section, it is quenched with an alkaline absorption liquid, HCl, SO.
Harmful substances such as x were absorbed and removed to form a moisture-saturated gas at about 70°C, which was further cooled to 50°C in a cooling and dehumidifying section to dehumidify it, and then released into the atmosphere as a discharged gas. During this period, approximately 50 m/day of smoke cleaning wastewater with a total salt concentration of approximately 15% was discharged from the quenching section, and condensed water with a total salt concentration of approximately 0.3% was discharged from the cooling and dehumidifying section.
Excreted 50-7 days. This condensed water can be reused as it is as industrial water such as equipment washing water, and the amount of wastewater that requires wastewater treatment is only 50 m'/day of smoke washing wastewater.

On the other hand, as a comparative example, the same combustion exhaust gas as that treated in the above example was treated with smoke cleaning using the conventional method of simultaneously performing absorption cleaning and cooling to reduce rodents using the smoke cleaning device shown in Fig. 3. The gas at 50°C was released into the atmosphere in the same manner as in the example. In this case, about 200 m of smoke washing drainage with a total salt concentration of about 3.5%! 7 days, but this wastewater had to be treated as full ffi wastewater.

Effects of the Invention As described above, when cleaning the combustion exhaust gas generated during waste incineration, the combustion exhaust gas is rapidly cooled, then absorbed and cleaned with an alkaline absorption liquid, and then cooled and dehumidified. , the treated wastewater is separated into a relatively small amount of smoke washing wastewater from the quenching section that requires wastewater treatment, and condensed water from the cooling condensation section, which can be discharged directly into a trench or reused as industrial water. Compared to the conventional treatment method that simultaneously performs absorption and cooling dehumidification, this method can significantly reduce the amount of smoke washing wastewater that requires wastewater treatment, reducing the burden of wastewater treatment. In addition, condensed water has a low concentration of salts, etc., so even if water treatment is carried out, simple treatment is sufficient, and as mentioned above, it is also possible to discharge or reuse it. It has exceptional effects such as:

[Brief explanation of the drawing]

FIG. 1 is a general configuration diagram showing an example of a smoke cleaning device used in the present invention, and FIG. 2 is a schematic #r configuration diagram showing an example of a smoke cleaning device used in the present invention.
... Combustion exhaust gas, (G, 2) ... Released gas, (L,,
)...Smoke washing drainage, (L12)...Condensed water, (2)・
...Quick cooling section, α1...Cooling liquid, αe...Absorption section, 4...Alkaline absorption liquid, αS...Cooling dehumidification section, (1
)...cooler, (a)...cooling water, (7)...alkaline aqueous solution, a force, α force, 4υ...circulation pump, (
To), (a)...Mist Sepanuta

Claims (1)

[Claims] 1. Combustion exhaust gas is treated by a smoke cleaning device consisting of a quenching section that rapidly cools with a cooling liquid, an absorption section that absorbs and cleans with an alkaline absorption liquid, and a cooling and dehumidifying section that condenses moisture, and the smoke washing wastewater is discharged from the quenching section. A combustion exhaust gas treatment method characterized by separately discharging condensed water from each cooling and dehumidifying section.