In the processing of non-ferrous metals such as copper, titanium, single crystal silicon, etc., in order to make the surface of the product smooth, and in the processing of aluminum oxide colored frosted profiles, in order to form a special frosted surface and remove the oxide layer on the metal surface, a mixed acid of 10%~35% HNO3 and other acids is usually used for surface treatment. During the acid washing process, due to the intense reaction between the metal and metal oxide with the acid, a large amount of NOX is generated, with a concentration of 200~350mg/m ³. Nitrogen oxides include N2O, NO, NO2, N2O4, and N2O5, collectively referred to as nitrogen oxides, represented by NOX. The NOX generated during acid washing is mainly NO and NO2. If not treated and directly discharged into the atmosphere, it will cause serious harm to the surrounding environment, human health, and other animals and plants.

1、 Common governance methods

The commonly used treatment method for NOX is absorption. Catalytic reduction method and adsorption method:

The absorption method uses alkaline solutions such as NH3H2O, NaOH, Ca (OH) 2, Na2CO3, etc. as absorbents to remove NOX by reacting alkali with NOX to generate nitrate or smoke nitrate. The reaction equation is as follows:

2OH-+NO+NO2→NO3-+H2O

2、 Process flow

The nitric acid yellow smoke treatment and purification equipment uses sodium hydroxide solution as the absorption and neutralization solution. The exhaust gas is pressed into the purification tower by a fan, forming a pressure chamber in the inner cylinder, and then distributed to each bubble tube through the pressure chamber. The exhaust gas enters the absorption and neutralization liquid in the storage tank through the bubble tube to generate bubbles, and then the bubbles pass through the packing layer, allowing the gas-liquid to fully contact again. The absorbed exhaust gas continues to flow upward and reacts with the absorption and neutralization liquid sprayed from the spray pipe. The standard gas after neutralization reaction is dehazed by the demister device and then discharged into the atmosphere.

3、 Structure and Characteristics

The tower body of this purification equipment is a cylindrical tower body wrapped with fiberglass as a whole, without segmented connecting flanges. The specific structure consists of a pressure chamber, a liquid storage tank, packing, a spray device, a foam removal device, etc. The structure of this purification tower:

(1) Adopting the saturated contact of exhaust gas directly entering water, the chemical reaction is complete, and the purification efficiency is high; (2) Adopting a new type of filler with a large specific surface area, high porosity, and uniform arrangement; (3) Adopting two absorption processes of spraying and bubbling, the absorption is sufficient and the purification effect is good.

This tower can be equipped with a control system consisting of gas online analyzer, pH control meter, differential pressure transmitter, liquid level control meter, solenoid valve, and control cabinet, and is equipped with fault alarm, which facilitates operation, management, and maintenance.

4、 Technical parameters and selection

Due to different technical parameters such as gas concentration and temperature, this treatment equipment should be designed and selected according to actual conditions. Our company has a specialized design program that can design specific technical parameters that meet the standards according to the actual situation.

The design conditions that users need to provide include:

1. Provide a usable site for equipment operation;

2. Provide the amount and concentration of exhaust gas, temperature, and the standards required for treatment;

3. Provide whether the control mode is manual or automatic, and the degree of control achieved;

4. Provide us with the equipment and supporting facilities, pipelines, and accessories that we need to supply.