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Introduction to purification scrubber equipment

Views:5     Author:Xicheng Ep Ltd     Publish Time: 2021-09-12      Origin:Xicheng Ep Ltd

As a spray absorption device, it has been used in exhaust gas purification. It develops the concept of fluidized bed into vapor-liquid mass transfer equipment so that the filler in the spray tower is in a fluidized state so that the mass transfer process can be enhanced. Its characteristics are high gas velocity, large processing capacity, the lightweight of the tower, relatively uniform vapor-liquid distribution, and not easy to be blocked by solid and viscous materials. In particular, due to the strong turbulence in the tower, the mass, and energy transfer are strengthened, so that the tower diameter and the tower height can be greatly reduced. The tower handles a large amount of air, the air velocity of the empty tower is 1.5-6.0m/s, the spray density is 20-110m3/(m2·h), and the pressure loss is 1500-3800Pa. The demister of the scrubber adopts a cyclone demister. , By making the gas pass through the tray to generate a rotating motion, and use the centrifugal force to remove the mist, the defogging efficiency can reach 98%-99%, and the structure is simple and the pressure drop is small.


Corresponding processing gas


The purification treatment effect for various corrosive gases is obvious, and it can effectively remove hydrogen chloride gas (HCl), hydrogen fluoride gas (HF), ammonia (NH3), sulfuric acid mist (H2SO4), chromic acid mist (CrO3), hydrogen cyanide gas ( HCN), alkali vapor (NaOH), hydrogen sulfide gas (H2S), formalin (HCHO) and other water-soluble gases. The scrubber tower has high purification efficiency, simple operation and management, and long service life. The acid-base waste gas after purification treatment meets the national emission standards.

Exhaust gas scrubber system


① Exhaust gas containing chromium

It is necessary to adopt a combination of filtration recovery pretreatment and wet spray advanced treatment. The grid-type chromic acid mist recovery device can initially recover 60%-80% of the chromic acid in the exhaust gas. Considering the emission of up to the standard, the subsequent spray absorption and purification are required. The highly toxic hexavalent chromium can be reduced to the less toxic trivalent chromium through the sulfurous acid solution:

       H2CrO7+3Na2SO3+3H2SO4→Cr2(SO4)3+3NaSO4+4H2O


② Nitrogen oxide (NOX)

Nitric acid solution is highly oxidizing and unstable, and its oxide forms are diverse. Its purification needs to be combined with the effect of its reducing agent to react it to produce stable N2.

       2NO+O2→2NO2

       2Na2S2O3+NO2+2 NaOH→2N2↑+4 Na2SO4+2H2O


③ Treatment of acid and alkaline waste gas

Because this kind of waste gas has good water solubility and is easily absorbed by water, the absorption method of this kind of waste gas can achieve a good removal effect. Acid waste gas is absorbed by lye, and alkaline gas is absorbed by acid. For example, sulfuric acid waste gas can be neutralized and absorbed by sodium hydroxide solution or ammonia water, and ammonia-containing waste gas can be directly absorbed by water to generate ammonia water. The reaction formula is as follows:

       H2SO4+2NaOH→Na2SO4+2H2O

       NH3+H2O→NH3·H2O


④ Treatment of cyanide-containing waste gas

There are two methods of adding mist suppressant or using the absorption method. However, the use of fog inhibitors, may affect the washing performance and affect the subsequent process, resulting in a poor electroplating effect and not much use. Since hydrogen cyanide can be absorbed by a variety of substances, the currently common practice is to use wet methods to absorb cyanide-containing waste gas. Cyanide waste gas can be absorbed by 1.5% sodium hydroxide and sodium hypochlorite solution. When sodium hypochlorite aqueous solution is used as the absorption liquid, sodium hydroxide is used to adjust the pH of the absorption liquid to maintain a weak alkaline state, and the general spray tower is used for absorption. The purification efficiency can reach more than 90%. The products after treatment are nitrogen, carbon dioxide and sodium chloride. The reaction equation is as follows:

       2NaClO+CN→CO2+N2+2NaCl


⑤ Fluorine-containing waste gas

Both absorption methods (wet type) and adsorption methods (dry type) can be used. The adsorption method is physical adsorption. The general adsorbents are not easy to adsorb HF well, and the adsorbents are expensive, easy to saturate, and have high operating costs, so they are less widely used in the market.

The absorption method uses an alkaline solution as an absorbent to absorb fluoride through gas-liquid contact and mass transfer reaction. Under certain conditions of customs clearance, fluorosilicic acid (cryolite), a by-product with economic benefits, can also be generated. The main principle is based on the water-soluble property of hydrogen fluoride, and the second is based on the principle of acid-base neutralization. The advantages of the absorption method are that the purification equipment is small in size, the purification efficiency is stable, and the investment and operating costs are low. Ca(OH) 2 is commonly used to absorb HF.

       2HF+ Ca(OH)2→CaF2+H2O


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