JPH0312282A - Concentration treatment of exhauste gas scrubbing waste water - Google Patents

Abstract

PURPOSE:To eliminate not only the new consumption of heat energy but also the generation of trouble such as the breakage of the pipe of a heating boiler or the inseparableness of a precipitated crystal by generating steam in No.1 evaporation boiler using high temp. air generated by utilizing the combustion gas of an incinerator and concentrating the exhaust gas scrubbing waste water in No.2 evaporation boiler using said generated steam. CONSTITUTION:The air receiving the heating of the combustion gas to become high temp. in an air heater 3 is introduced into the heating vessel 10 of No.1 evaporation boiler of a double utility evaporation concentrator through a line 9. The steam generated in No.1 evaporation boiler 10 is introduced into the heating vessel 15 of No.2 evaporation boiler 14 and the exhaust gas scrubbing waste water sent from an exhaust gas scrubbing apparatus 6 through a line 16 is heated and conc. herein and dissolved salts and heavy metals are precipitated, settled and conc. to be drawn out to a centrifugal separator 25 while the separated crystal is discharged out of the system and the filtrate is returned to No.2 evaporation boiler 14 through a line 26 to be recirculated. The steam introduced into the heating vessel 15 is used as the heat source in the heating and concn. of waste water and subsequently returned to No.1 evaporation boiler 10 through a line 17 to be recirculated.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method for concentrating smoke washing waste liquid.

Conventional technology and its problems In recent years, with the improvement of living standards, the types of municipal waste have become increasingly composed of polymer compounds, synthetic fibers, etc., and as a result, the combustion gas during incineration contains acidic gases such as HO2 and S02. The amount of gas generated is gradually increasing.Therefore, cleaning of the combustion gas with NaOH liquid is unavoidable to prevent pollution, so a large amount of HaCρ, Na2304 is contained in the smoke cleaning waste liquid.
It cannot be disposed of as it is because it contains salts such as, and other nail-damaging heavy metals such as Pb, Hg, and As.

Therefore, it is necessary to heat and condense the smoke washing waste liquid to evaporate the water content and crystallize and separate the salts and mine metals contained therein.

Heating and concentrating the smoke washing waste liquid can be easily done by applying the usual heating and concentrating means of steam heating using an evaporator equipped with a multi-tube heater, but this method uses steam as the heating source. Therefore, it requires the installation and installation of a boiler, and it also consumes fuel, which is not a good idea.

In this case, as a measure to conserve energy, it may be possible to use high-temperature combustion gas generated by garbage incineration instead of steam, but this indirect heating method of high-temperature gas may result in a high concentration of slurry, which may cause damage to the inner wall of the heater pipe. If the inside of the tube is partially blocked due to the adhesion of precipitated crystals, the tube surface temperature may rise to near the high temperature gas temperature, causing distortion such as bending in the tube, or reducing the allowable stress due to embrittlement. This creates a risk of problems such as pipe breakage.

The problems of the indirect heating method of high-temperature gas can be solved, for example, by adopting a direct heating method in which high-temperature gas is directly introduced into the liquid to be treated (for example, see Japanese Patent Publication No. 54-12262). Due to intense gas-liquid contact stirring, crystals collide and fracture, and the generation of micronuclei is unavoidable.The presence of these micronuclei inhibits crystal growth, resulting in the formation of microcrystals with poor separability. This causes the problem that crystal separation becomes difficult.

The present invention has been made with the aim of eliminating such conventional problems.

Means for Solving the Problems The present invention provides a method for concentrating smoke washing waste discharged from a waste incineration facility, in which the precipitated crystals are separated while continuously concentrating the smoke washing waste fluid, which is incinerated from the above-mentioned facility. High-temperature air generated by heat exchange between gas and air is guided to the heating can of the No. 1 evaporator of the dual-effect evaporation concentrator and used as a heat source for steam generation in the evaporator. The generated steam is led to the heating can of the No. 2 evaporator and used as a heat source for heating and concentrating the smoke washing waste liquid in the evaporator, and the drain generated in the No. 2 heating can is returned to the No. 1 evaporator for circulation. The present invention relates to a method for concentrating smoke washing waste liquid, which is characterized by the following.

EXAMPLE Below, one implementation situation of the treatment method of the present invention will be explained based on the attached drawings.

Combustion gas generated in the incinerator (1) of the incineration facility is introduced into the air heater (3) through the line (2), and then into the air heater (3) through the line (4).
After being used as a heating source for the air introduced from the line (5), the air is introduced from the line (5) to the wet smoke scrubber (6), and then the air is
After being washed with NaOH solution supplied from 7), it is discharged into the atmosphere through line (8).

The air heated to high temperature by the combustion gas in the air heater (3) is introduced into the heating can (11) of the No. 1 evaporator (10) of the double-effect evaporative concentrator through the line (9). be done.

A predetermined amount of water is circulated between the No. 1 evaporator (10) and the heating can (11), and the high-temperature air is heated in the heating can (11).
Line (12) used as a heating source for the above circulating water
released into the atmosphere through

Since high-temperature air is used as a heating source in the heating can (11), it is preferable that the heating heat transfer area on the high-temperature air side is expanded. A heating can of the Erofin heater type can be used.

Steam is generated in the No. 1 evaporator (10) by heating with high-temperature air. The high-temperature air used as a heat source for steam generation is obtained by using combustion gas, ie, waste heat, from the incinerator (1), and serves as a measure for energy conservation.

The steam generated in the No. 1 evaporator (10) is transferred to the line (13)
It is then introduced into the heating can (15) of the No. 2 evaporator (14).

The No. 2 evaporator (14) is connected to the line (16) from the smoke scrubber (6).
) is heated and concentrated to remove dissolved salts (NaCΩ, Na2SO4, etc.) and landmine metals (P
b, Hg, As, etc.).
The steam from the No. 1 evaporator (10) introduced into the heating can (15) is used as a heat source for heating and concentrating the waste liquid, and then passes through the line (17) in the form of a drain to the No. 1 evaporator (10). ) and circulated. A line (18) is connected to this line (17) for appropriately compensating for the amount of water lost due to leakage or the like.

The steam generated in the No. 2 evaporator (14) is transferred to the line (19)
is led to the barometric capacitor (20) through
While being condensed by the cooling water introduced from the line (21), it is discharged from the system through the line (22), while non-condensable gas is discharged from the top of the condenser (20) through the line (23).
), and the inside of the No. 2 evaporator (14) is maintained at a predetermined degree of reduced pressure by these discharges.

From the bottom of the No. 2 evaporator (14), a predetermined amount of the precipitated and concentrated slurry is passed through the line (24) to the centrifugal square device (25).
), the separated crystals are discharged outside the system, and the p liquid is returned to the No. 2 evaporator (14) through the line (26) and circulated.

Since steam is used as the heating source in the No. 2 evaporator (14), smooth concentration operation is possible in the same way as a standard concentration crystallizer using steam heating, and there is no possibility of tube breakage that occurs when high-temperature gas is used. You can eliminate such troubles. Furthermore, since it is an indirect heating method using steam, there is no negative effect on the crystal growth surface as seen in direct heating methods using high-temperature gas.
Crystal separation can be easily carried out by applying conventional methods.

In order to further clarify the features of the present invention, examples of the present invention will be described below using numerical values.

300 that generated combustion gas from an incinerator as a heating source
℃ high temperature air 1380ONrri'/h heat transfer area 20
Introduced into 0ni' Erofin Heater No. 1 heating can,
1350 kg of steam at 98°C by heating water
We were able to generate h.

This steam is mixed with NaCJ27.0%, Na25Oa3.0
1300 kg/h of smoke washing waste liquid containing
Evaporated 60kg/h, NaC, f2 approx. 63.5%, N
143 kg/h of mixed crystals containing about 27.2% of a2 SO4 were recovered.

Effects According to the present invention, high-temperature air is generated using combustion gas from an incinerator, and steam is generated in the No. 1 evaporator of a dual-effect evaporative concentrator using this high-temperature air. Since we have adopted a structure that uses steam to condense the smoke washing waste liquid in the No. 2 evaporator, this kind of smoke washing waste liquid can be concentrated without consuming additional thermal energy, and in addition, the pipes of the heating can It has the feature that it can be carried out without problems such as breakage or inability to separate precipitated crystals.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram showing one implementation situation of the present invention. In the figure, (1) is the incinerator, (2) is the line, (3) is the air heater, (4) is the line, (5) is the line, and (6) is the line.
) is a wet smoke cleaning device, (7) is a line, (8) is a line,
(9) is the line, (10) is the No. 1 evaporator, (11) is the heating can, (12) is the line, (13) is the line, (1
4) is the No. 2 evaporator, (15) is its heating can, (16) is the line, (17) is the line, (18) is the line, (19)
) is a line, (20) is a condenser, (21) is a line, (22) is a line, (23) is a line, (24) is a line, (25) is a centrifugal separator, and (26) is a line. (that's all)

Claims (1)

[Claims] (1) In the process of concentrating smoke washing waste fluid from waste incineration facilities, which continuously concentrates and separates precipitated crystals, generated by heat exchange between combustion gas from the above facility and air. The high-temperature air is led to the heating can of the No. 1 evaporator of the dual-effect evaporation concentrator and used as a heat source for steam generation in the evaporator, and the steam generated in the No. 1 evaporator is transferred to the No. 2 evaporator. The smoke washing waste liquid is introduced into a heating can and used as a heat source for heating and concentrating the smoke washing waste liquid in the evaporator, and the drain generated in the No. 2 heating can is circulated back to the No. 1 evaporator. Concentration processing method.