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Treatment method of acid mist waste gas

Views: 14     Author: Xicheng Ep Ltd     Publish Time: 2022-06-18      Origin: Xicheng Ep Ltd

The treatment method of acid mist waste gas adopts chemical method to treat waste gas. The packed tower is used as a purification device. The packed tower feeds the waste gas from the top to the bottom of the absorbing liquid, so that the gas and the absorbing liquid can be fully contacted, and the purification efficiency is also very high. The alkaline solution is used as the absorbent, and the principle of acid-base neutralization is used to achieve the purpose of purifying the exhaust gas, and at the same time, the exhaust gas can be cooled. At the same time, it is also necessary to carry out anti-corrosion treatment on the pipeline and the gas collecting hood. In this design, the fan is placed behind the purification system to avoid corrosion of the fan.

The nature of acid mist

Acid mist (acid mist) generally refers to mist-like acidic substances. The particles of acid mist in the air are very small, which can be said to be smaller than the particles of water mist, and the humidity is higher than that of smoke. Its particle size is 0.1~10чm, which is a substance between flue gas and water mist, and its corrosiveness is strong. Acid mist contains sulfuric acid, nitric acid, hydrochloric acid, formic acid and acetic acid, etc.

The cause of acid mist: After the surface of the acid liquid evaporates, the acid molecules enter the air, and then form droplets with the moisture in the air; or the chemical reaction occurs in the acid solution to form bubbles that float to the page and explode, bringing the liquid out.

liquid absorption

Liquid absorption methods generally include water washing and lye neutralization. Absorbents commonly used for lye absorption include aqueous solutions of 10% Na2CO3, 4% to 6% NaOH and NH3. The purification treatment equipment used in it mainly includes washing towers, foam towers, packed towers, inclined orifice plate towers, etc. The main principle of purifying waste gas is to make the gas and liquid fully contact, and then the acid-base neutralization reaction occurs, so that the acidic substances are removed.

The advantages of the liquid absorption method are lower equipment investment and simpler process. However, its disadvantages are that it consumes a lot of energy and water, and has high operating costs; and it is easy to cause secondary pollution; secondly, it is easy to freeze in winter because the temperature is too low, causing the equipment to fail to operate normally; finally, because the nitric acid mist contains insoluble Therefore, the purification efficiency of nitric acid mist by liquid absorption method is often relatively low.

After the exhausted acid gas and acid mist are absorbed by the gas collecting hood, the exhaust gas is induced by the fan to cause evolution treatment in the acid mist absorption tower. The principle of the purification equipment is to make the alkaline substances fully contact with the exhaust gas, and the acid-base neutralization reaction occurs, so as to achieve the purpose of removing the acidic substances, so that the discharged exhaust gas can meet the emission standards.

Packed tower scrubber

packed tower scrubber

The column is filled with a suitable height of packing to increase the contact surface between the two fluids. For example, when applied to gas absorption, the liquid enters from the upper part of the tower through the distributor and descends along the packing surface. The gas flows upstream from the lower part of the tower through the pores of the packing, and interacts with the liquid in close contact. The structure is relatively simple, and the maintenance is relatively convenient. Packed towers have the advantages of large production capacity, high separation efficiency, small pressure drop, small liquid holdup, and large operating flexibility. The column internals mainly include the following parts: liquid distribution device, packing pressing device, packing support device, liquid collection and redistribution and feeding and discharging device, gas feeding and distribution device, etc. In recent years, a lot of research has been carried out and breakthroughs have been made. The maximum diameter of the currently used large-scale fillers can reach 14-20m.

Parameter selection of washing tower packing

PP polyhedral ball packing

Basic requirements for fillers: large specific surface area, high porosity, and materials for making fillers should ensure sufficient mechanical strength, not easily broken, light in weight, corrosion-resistant, and cheap and easy to obtain.

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