Flue gas treatment in waste aluminum smelting process

[China Aluminum Network] China's renewable aluminum industry has developed rapidly in recent years. Both in terms of output and production scale, it ranks first among renewable non-ferrous metals and has occupied an important position in the aluminum industry in China. However, incongruous with the rapidly developing renewable aluminum industry is the poor environmental awareness of the industry. Environmental protection work is very backward and has seriously affected the development of this area.

As the state attaches great importance to environmental protection work, relevant departments continue to strengthen the management of the recycled aluminum industry environment, and some heavily recyclable aluminum companies will be eliminated. It can be asserted that in the future, the competition in the recycled aluminum industry will be a competition in the environment, and environmental issues will not be solved. Enterprises will be unable to survive. We should have a clear understanding of this.

Judging from the present environmental status of China's regenerated aluminum industrial enterprises, the main pollutant that causes pollution to the environment is exhaust gas. Therefore, this article will introduce the source, main components and processing technology of waste gas in the recycled aluminum industry, and according to the characteristics of China's recycled aluminum industry, recommend a more applicable environmental protection process for the reference of recycled aluminum enterprises in the construction of environmental protection. .

First, the source of flue gas pollutants China's waste aluminum recycling mainly uses pyrometallurgical melting, the process of generating waste gas and potentially affecting the environment is mainly smelting process. In the smelting process, the main fuels used are coal, coke, heavy oil, diesel oil, coal gas, natural gas, etc. After the fuel is burned, the exhaust gas contains a lot of soot and sulfur, carbon, phosphorus and nitrogen oxides and other gases. After the charge (aluminum scrap) is heated, the oil of the waste itself and the combustibles contained will burn, and a large amount of oxides containing sulfur, carbon and nitrogen will also be produced. In the smelting process, in order to reduce the damage and increase the recovery rate of aluminum, To ensure the quality of aluminum alloys, a certain amount of covering agents, refining agents, and degassing agents are added. These additives react with various impurities in the aluminum melt to generate a large amount of exhaust gas and smoke. These exhaust gases and smoke contain various substances. Metal oxides and non-metal oxides, as well as potentially hazardous substances, may cause environmental pollution.

Second, the classification and composition of recycled aluminum fumes Classification of Waste Gas from the Recycled Aluminum Industry According to the provisions of the environmental protection department, the waste gas generated by the industrial sector can be divided into two categories: particulate-containing exhaust gas and gaseous pollutant-laden exhaust gas. Due to the complexity of raw materials in the recycled aluminum industry, both of the above two types of exhaust gas exist in the production process, both particulate-containing exhaust gas and gaseous pollutant-containing exhaust gas. Therefore, while treating the exhaust gas, it is necessary to comprehensively consider dust and harmful substances in the exhaust gas. The effect of gas on the environment.

2. The main components of waste gas are due to different sources of raw materials for recycling aluminum industry, different types of waste materials, different levels of pollution, different fuels used, different additive components, and different smelting technologies used. Therefore, pollutants in exhaust gas are also different. Different, summed up can be the following:

(1) Particulate wastes are mainly metal oxides and non-metal oxides produced during the smelting process, such as oxides and chlorides of Mg, Zn, Ca, Al, Fe, Na, Mg, K, and a large amount of carbon. Grain ash, etc., constitute the dust we often talk about.

(2) Main components of gaseous pollutant exhaust gas The regenerated aluminum industry may have the following gaseous pollutant exhaust gases: CO, CO2, NOX, SO2, HCl, HF, hydrocarbons, and volatile metal oxides or volatile metals. There will be chlorine, etc. Of course, not all ingredients are harmful, but most of them will have a great impact on the environment, and some may endanger the lives of workers.

III. Control of soot dust Control of fume dust First, the dust in the flue gas is collected to a greater extent, so that the harmful gases are converted into harmless and stable substances, reaching the national emission standards. The management of the environment must first be controlled from the source. For recycled aluminum, it is necessary to strengthen the pretreatment and classification of wastes, make comprehensive use of various wastes as much as possible, and reduce the amount of pollutants generated; second, try to use pollution-free Additives; third is to improve the smelting technology to reduce the amount of waste generated. The commonly used smoke treatment technology is as follows:

1. Dust collection room The dust collection room is a relatively simple method in the dust collection equipment. The principle is that when the velocity of the fluid suddenly decreases, the particles settle due to their own gravity. The flue gas produced from recycled aluminum flows in the flue at a certain speed. When the space of the flue gas suddenly increases, the velocity of the air flow also suddenly slows down. As the velocity of the particles decreases, the particles are deposited under the action of their own gravity. There are many kinds of dust chambers, as shown in the figure.

The simpler method is to use bricks. If some baffles are made in the dust collection chamber, the dust collection effect of the particles can be improved, but in general, the collection efficiency of the dust collection chamber is not good.

2. Cyclone dust collector

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