Electroplating waste gas treatment technology and existing problems and countermeasures

Electroplating companies produce a wide variety of pollutants, including heavy metals and various hazardous chemicals, as well as many toxic waste gases. If these waste gases are not treated, they will pollute humans and the ring. According to my years of experience in the electroplating process design, we put forward a number of recommendations and measures of electroplating waste gas treatment, waste gas treatment for the electroplating industry to provide technical reference, and protect the ecological environment, air pollution control is of great significance.

1 electroplating exhaust concept

1.1 Electroplating waste gas types

According to the "Electroplating Pollutant Emission Standard" GB21900-2008, the types of electroplating exhaust gas mainly include hydrogen chloride, chromic acid mist, sulfuric acid mist, nitrogen oxides, hydrogen cyanide and fluoride. In addition, there are some dust-containing gases, organic waste gases, and alkalis.

1.2 The harm of electroplating waste gas

According to the monitoring of electroplating exhaust gas, it is not difficult to find that these exhaust gases are extremely harmful to the human body. To properly control these exhaust gases, it is necessary to analyze the environmental hazards of electroplating exhaust gases.

1 The harm to the human body is mainly manifested in the harm to the human respiratory tract, eyes and skin. Some electroplating exhaust gases are colorless and odorless, causing long-term chronic damage to the respiratory tract. After gradually accumulating, the content exceeds the limit, which may lead to bronchitis and bronchial asthma. Lung cancer, liver cancer and other diseases. The hydrogen chloride, acid-base mist, etc. emitted by the electroplating process may cause irritation to human eyes and skin, and may cause symptoms such as pink eye and dermatitis.

2 The harm to plants and buildings, the sulfur dioxide and nitrogen oxides emitted by the electroplating process are harmful to the growth of plants in the air, and even kill plants. If acid rain is formed, it will cause corrosion, embroidering, etc. to the building.

In addition to the above hazards, during the electroplating process, the resulting electroplating waste will harm the electroplated products. Mainly because in the electric trace workshop, too much acid-base fog, dust, etc., will have different effects on the electrical trace equipment in the workshop and the purity of the plating materials.

2 treatment method of electroplating waste gas

According to the "Electroplating Pollutant Emission Standards" (GB21900-2008), local gas collection systems must be installed on the plating hook process and facilities, and centralized purification and treatment must be carried out to discharge the exhaust pipe to the atmosphere. Therefore, the electroplating exhaust gas can be treated in three ways, namely, reducing the electroplating exhaust gas at the source, installing the exhaust system, and installing the electroplating exhaust gas purifying device.

2.1 source reduces electroplating exhaust

By changing the process flow of the electroplating industry production, or using non-toxic materials, the purpose of zero discharge of toxic and harmful exhaust gas can be achieved in the electroplating production process.

1 In the electroplating process, when cleaning the plating parts, it is called alkali washing, acid washing and de-embedding. Therefore, adding acid mist and alkali mist inhibitor in the cleaning solution can effectively reduce acid mist and alkali mist. Emissions. 2 inhibition of chromium fog, can use low temperature equipment or low temperature process, while adding less sold perfluoroalkyl ether sulfonate in the plating solution, and pay attention to the configuration method and ratio of perfluoroether ether sulfonate, Effectively suppress the generation of chromium fog. In addition, the surface of the plated inscription can be covered with a hollow ball of polyethylene or polyvinyl chloride, which can also effectively suppress the release of chromium mist. 3 inhibition of nitrogen oxides, inhibition of nitrogen oxide emissions in the electroplating process , can be used in the plating process without nitric acid, such as aluminum plating, using sulfuric acid and phosphoric acid, and then adding a small amount of additives, can be used for aluminum parts polishing. On the other hand, the chemical oxidation method and the chemical reduction method are used to oxidize nitrous acid to nitric acid or to reduce the nitrogen oxide gas to a non-toxic inert gas.

2.2 Installation of exhaust system and purification system

Considering the treatment of electroplating exhaust gas, the exhaust gas system can be installed to transport the polluted exhaust gas to the gas purification system to achieve the purpose of removing toxic and harmful gases. It can be seen that the installation of the exhaust system and the purification system is a unified whole.

2.2.1 Installation of exhaust system

According to the characteristics of electroplating exhaust emission, the production conditions of the factory floor are limited, and the harmful exhaust gas discharge mode adopts different exhaust systems. For example, in the workshop, it is generally because the source of the sputum is not fixed, the discharge point is large, and other factors, and the local exhaust method is adopted. The gas in the local exhaust mode is monitored. If the emission standard is reached, it can be directly discharged into the atmosphere. If it exceeds the emission standard, the exhaust gas needs to be passed to the purification system, and the exhaust gas is directly collected at the point of harmful waste discharge. Discharged to the outside through the ventilation system. In order to ensure the air pressure balance in the workshop, mechanical ventilation is also required to keep the indoor air quality in line with the standard.

2.2.2 exhaust gas purification system

In the treatment of acid waste gas, the main method for purifying the acid waste gas is to spray the acid waste gas with the third-grade alkali liquid, and then discharge the chimney. For example, the lye configured to treat typical acids to the exhaust gas is shown in Table 1. When the acid waste gas is absorbed by the method, a sealing cover is installed on the vacuum pumping pump to discharge the gas in the workshop into the spray tower equipped with the packing. The efficiency of the process for removing acid waste gas can reach more than 90%.

3 Electroplating waste gas treatment technology problems and solutions

3.1 Electroplating waste gas treatment technology has problems

The electroplating industry is a heavily polluting production industry, not only exhaust gas pollution, but also other such as water pollution, sludge pollution, noise pollution, etc. The treatment of these pollutants must be considered comprehensively and processed in order to achieve the removal effect. It is also because of the high pollution and high energy consumption of the electroplating industry. There are still some blind spots in the treatment of exhaust gas. For example, when the exhaust gas is collected, the exhaust gas collection in the workshop is incomplete. At present, many exhaust gas collection devices are installed only at the exhaust gas release. That is, point installation; in addition, since there are many types of exhaust gas and treatment methods are different, it is impossible to remove all exhaust gases at the time of processing. These are all problems that need to be solved in the current electroplating industry.

3.2 Electroplating waste gas treatment technology solutions

According to the problems existing in the treatment technology of electroplating exhaust gas, the corresponding countermeasures are proposed. First, the point collection in the workshop can be changed into the combination of point collection and surface collection, that is, the collection of pollution exhaust gas collection devices for key pollutant discharges. Surface collection is also provided for the entire workshop to ensure that the concentration of pollutants in the air of the workshop does not exceed the limit; secondly, the characteristics of the spray liquids such as acid-alkaline waste gas, chromium mist, cyanide and nitrogen oxides can be combined to prepare a A kind of absorption liquid that can absorb all the exhaust gases at the same time, or study a comprehensive absorption process to ensure that all the exhaust gas in the electroplating production is absorbed and purified.

4 Conclusion

In the electroplating industry, the “three wastes” emissions are very serious. To reduce the emissions of “three wastes”, on the one hand, we must reduce the emission of pollutants from the source, the brewing process, and the electroplating production of technical rice from the first step of industrial production; The pollutants to be discharged should be purified, and the waste gas treatment technology should be determined by studying and analyzing the nature of the pollutants.