As a spray absorption equipment has been used in exhaust gas purification. It develops the concept of vulcanized bed into the vapor transfer equipment, which makes the filler in the spray tower in a fluidized state, thus making the mass transfer process can be strengthened. His characteristics are: high air speed, processing capacity, light weight of the tower, relatively uniform distribution of vapor, not easily blocked by solid and viscous materials. Especially because of the strong turbulence in the tower, the mass and energy transfer can be strengthened, so it can reduce the diameter of the tower and reduce the height of the tower. The tower handles a large amount of air, air speed of 1.5 to 6.0m/s, spray density 20 to 110m3/(m2.h), pressure loss of 1500 to 3800Pa, The defog removal device of the washing tower adopts the spinner defog device, which uses the action of centrifugal force to remove the mist by making the gas produce rotating motion through the tower plate, and its defog efficiency can reach 98%-99%, and the structure is simple pressure drop is small.

For a variety of corrosive gas purification treatment effect, can effectively remove hydrogen chloride gas (HCl), hydrogen fluoride gas (HF), ammonia gas (NH3), sulfuric acid mist (H2SO4), chromic acid mist (CrO3), cyanide gas (HCN), alkali vapor (NaOH), hydrogen sulfide gas (H2S), Fulmarin (HCHO) and other water-soluble gases. Washing tower purification efficiency is high, simple operation and management, long service life. The acid-base exhaust emissions after purification treatment meet the national emission standards.

(1) Chromium-containing exhaust gases
should be filtration recovery pretreatment and wet spray depth treatment combined. The use of mesh format chromic acid mist recovery device can initially recover 60%-80% of the chromic acid in the exhaust gas, taking into account the emission standards, follow-up also need to cooperate with spray absorption purification. The highly toxic hexavalent chromium can

be reduced to the less toxic trivalent chromium by means of sulphate solution: H2CrO7-3Na2SO3-3H2SO4→Cr2(SO4)3-3NaSO4-4H2O

(2) Nitrogen oxide (NOX)

Nitric acid solution has strong oxidation and instability, its oxide form is diverse, its purification needs to be combined with the role of its reducing agent, its reaction to produce a stable N2.
2NO-O2→2NO2

2Na2S2O3-NO2-2 NaOH→2N2-4 Na2SO4-2H2O

(3) Treatment of acid-alkaline
exhaust gasEs Because of the solubility of such exhaust gases, easy to be absorbed by water, so such exhaust gases can achieve good removal effect by absorption method. Acid exhaust gas is absorbed by lye, and alkaline gas is absorbed by acid. For example: sulfuric acid exhaust gas can be used in sodium hydroxide solution or ammonia water for neutralization and absorption treatment, ammonia-containing exhaust gas can be directly absorbed by water to produce ammonia. The reactions

are as follows: H2SO4 plus 2NaOH→Na2SO4 plus 2H2O

NH3 plus H2O→NH3 H2O

(4) Treatment
of cyanide-containing exhaust gas There are two methods of adding anti-fog agent or using absorption method. However, due to the use of anti-fog agents, may affect washability and affect the subsequent process resulting in poor plating effect and not much use. Since hydrogen cyanide can be absorbed by a variety of substances, the current common practice is to use wet method to absorb cyanide-containing exhaust gas. Cyanide exhaust gas can be absorbed by 1.5% sodium hydroxide and sodium hypochlorite solution. When using sodium hypochlorite water solution as an absorption solution, the application of sodium hydroxide regulation absorbent PH to maintain a weak alkaline state, with the general spray tower absorption, purification efficiency of more than 90%, after treatment to produce nitrogen, carbon dioxide and sodium chloride. The reaction equation is

as follows: 2NaClO-CN→ CO2-N2-2NaCl

(5) Fluorinated exhaust gases
Can be absorbed (wet) and adsorption (dry). Adsorption method for physical adsorption, general adsorption agent is not easy to absorb HF, and adsorbent high price, easy saturation, high operating costs, less market application.
Absorption method is the use of alkaline solution as an absorbent, through gas contact, mass transfer reaction to absorb fluoride. The control of certain conditions for customs clearance can also produce an economical by-product fluorosilic acid (ice crystal). The main principles are based on the water-soluble properties of hydrogen fluoride, and the second is based on the principle of acid-base neutralization. The advantages of absorption method are small purification equipment, stable purification efficiency, low investment and operating costs, commonly used Ca (OH) 2 absorption HF.
2HF+ Ca（OH）2→CaF2＋H2O