Discussion on the Treatment of Electroplating Waste Gas


Time:

2020-07-11

Electroplating is an essential basic process industry in the national economy. In recent years, with the rapid development of the economy, the field of electroplating processing has continued to increase, and the influence of the electroplating industry is gradually expanding.

Discussion on the Treatment of Electroplating Waste Gas
Electroplating is an essential basic process industry in the national economy. In recent years, with the rapid development of the economy, the field of electroplating processing has continued to increase, and the influence of the electroplating industry is gradually expanding. In this situation, the treatment of waste gas, wastewater, and slag generated by electroplating is receiving increasing attention. Without a doubt, reasonable control and treatment will be of great significance for protecting the ecological environment and controlling air pollution.
This article will further introduce the types and main treatment methods of electroplating waste gas:
1、 Types of electroplating waste gas
There are many types of electroplating, in addition to the four conventional plating types of zinc plating, copper plating, nickel plating, and chromium plating, there are also widely used zinc nickel, zinc cobalt, zinc iron alloy electroplating, copper zinc, copper tin, copper zinc tin imitation gold electroplating, nickel zinc, nickel tin black coating electroplating, as well as gold plating, silver plating, tin plating, and even a small amount of rare precious metals such as ruthenium and rhodium that exist to meet the special needs of certain products in the IT and electronic industries Plating of palladium, indium, etc. At the same time, there will also be surface treatment processes such as metal oxidation, phosphating, and passivation. At present, there are still a few plating species that cannot eliminate cyanide in the short term, so cyanide containing electroplating still exists in certain special product electroplating. Especially with the increase of surface treatment before plating and the amount of acid and alkali used during stripping, a large amount of waste gas is inevitably generated during the electroplating production process. This mainly includes metal dust, acid alkali waste gas, organic waste gas, chromic acid mist, and various types of waste gases emitted by heating electroplating bath solutions, including ammonia containing waste gas, cyanide containing waste gas, etc.
2、 Treatment methods for electroplating waste gas
According to the "Emission Standards for Electroplating Pollutants" (GB21900-2008), electroplating processes and facilities must install local gas collection systems and undergo centralized purification treatment in order to be uniformly discharged into the atmosphere from the exhaust funnel. From this, electroplating waste gas can be treated in three ways: reducing electroplating waste gas at the source, installing exhaust systems, and installing electroplating waste gas purification equipment.
1. Reduce the generation of exhaust gas from the source
(1) In the process of alkaline cleaning for oil removal, acid cleaning for rust removal, or scale removal before electroplating, alkali mist inhibitors and acid mist inhibitors can be added to the solution respectively, thereby greatly reducing the overflow of alkali mist and acid mist. At the same time, a narrow and movable wind deflector can be added on both sides of the groove of each electroplating tank. In addition to covering the anode hook, anode plate, and heater to make the tank surface appear clean, it can also enhance the ventilation effect of the tank edge due to the reduction of the visible tank liquid area, thereby reducing the pollution of waste gas to the workshop environment.
(2) When removing the oxide scale on steel parts, shot peening process can be used instead of partial chemical pickling or acid free pickling process, which can greatly reduce the generation of acidic waste gas at the source.
(3) For copper parts, when cleaning with mixed acid (sulfuric acid and nitric acid) or stripping with nitric acid, the production of nitrogen oxides can be suppressed and reduced by adding a small amount of urea. It is not recommended to simply use nitric acid pickling and stripping.
(4) Adding a small amount of F-53 (perfluoroalkyl ether sulfonate) to the chrome plating bath can suppress the generation of chromic acid mist. If there are polyethylene or polyvinyl chloride hollow plastic balls floating on the liquid surface in the chrome plating tank, the fog suppression effect will be better.
2. Install exhaust and purification systems
The treatment of electroplating waste gas can be achieved by installing an exhaust system to transport the contaminated waste gas to a gas purification system, in order to remove toxic and harmful gases. It can be seen that the installation of exhaust and purification systems is a unified whole.
The area of an electroplating factory is generally large and belongs to the same production process. The staff are distributed throughout the room. In order to maintain a certain negative pressure indoors, fully ventilated mechanical air supply should be used. The sources of pollutants are all electroplating tanks, and during the working process, pollutants will be directly released from the electroplating tanks. Therefore, it is only necessary to locally exhaust each electroplating tank, and then treat it according to the regulations. After reaching the standard, it can be discharged to the outdoor. In order to evenly exhaust and reduce the resistance of the ventilation and exhaust system, the bends and three-way connections of the air duct should be designed along the airflow direction. To adjust the reasonable air volume, adjustable dampers can also be installed in the air duct.
In the treatment of acidic waste gas, the main method of purifying acidic waste gas is to spray the acidic waste gas with a three-level alkaline solution, and then discharge it through a chimney. When using this method to absorb acidic waste gas, a sealed cover is installed on the vacuum pump to discharge the gas in the workshop into a spray tower equipped with fillers. The efficiency of removing acidic waste gas by this process can reach over 90%.
3、 Conclusion
To reduce the emissions of the "three wastes" in the electroplating industry, especially the exhaust gas, on the one hand, it is necessary to improve the process flow and electroplating production technology from the source, and reduce the emissions of pollutants from the first step of industrial production; On the other hand, it is also necessary to purify the pollutants emitted. By studying and analyzing the properties of the pollutants, various methods such as chemistry, physics, and biology are used to remove the pollutants, ultimately meeting the pollutant discharge standards and ensuring that the environment is not polluted.