How to determine the type of industrial dust

In recent years, the government has issued new emission standards for various production industries, and has stricter requirements for the dust content in exhaust gases. In order to adapt to higher emission standards, improve dust removal efficiency, and reduce production costs, it is particularly important to appropriately select dust removal methods to ensure the dust removal effect and the economics of dust removal for different types of dust.

1. Dust classification and composition analysis

The classification basis for industrial dust is different. It can be classified according to the composition, particle size, shape and physical and chemical properties of the material. According to the dust production industry, this article divides industrial dust into cement industry dust, coal-fired power generation industry dust, steel industry dust, wood industry dust, non-ferrous metal industry dust and other types of dust.

1.1 Cement Industry Dust

At present, thermal power generation, cement, and steel are relatively serious industries in China for dust pollution. Cement dust mainly consists of SiO2, Al2O3, Fe2O3, CaO, MgO and K2O.

Only part of the dust generated in the mining phase of cement dust can settle naturally. In other phases, 85% of the dust particle size is 0 to 10 μm, and dust removal must be performed. Because SiO2 is the most important component, the SiO2 specific resistance should be considered when choosing the dust removal process, the adhesion is stronger, and the angle of repose is larger.

1.2 Coal dust generated by power generation industry

The coal-fired power generation industry's production processes include coal transportation systems, combustion systems, thermal systems, chemical water treatment systems, ash removal systems, and electrical systems. In the process of coal transportation and combustion process, a large amount of smoke dust will be generated. During the production process of coal-fired power plants, there will also be a lot of dust, mainly coal dust, limestone dust, gypsum dust and haze.

Because the dust is dominated by pulverized coal and whisky, the flammability and explosiveness of pulverized coal must be taken into consideration when dust is removed. At the same time, the specific resistance of the dust must be taken into account. Therefore, the dust removal method must be properly selected in different production stages. At present, 95% of the domestic coal-fired flue gas is treated as electrostatic precipitators, but as the emission standards increase, it is gradually replaced by the method of integrating the electric bags.

1.3 Iron and steel industry dust

Iron and steel enterprises have a long production process. Since mining and refining are the main dust production stages, this paper only analyzes the dust components produced in the two processes of mining and refining. The dust characteristics produced during the mining phase are mainly TFe and SiO2, and most of them have a mass particle size distribution of more than 40 μm. At the refining stage, the components of the dust in the flue gas mainly contain TFe/CaO/MgO/SiO2. Most of the mass distribution in the blast furnace is more than 40μm, and the mass diameter in the mine is mainly distributed in the range of 30μm-40μm.

1.4 Wood Industry and Non-ferrous Metal Industry Dust

Wood dust is particles floating in the air produced during wood processing. According to the particle size, wood dust can be divided into large particle size and small particle size. Large particle size dust refers to dust particles with particle size greater than 10 μm, and small particle size dust refers to dust particles with particle size less than 10 μm. Large particle dust can be removed by mechanical dust removal. Small particle dust has the characteristics of large angle of repose, high specific resistance, and large explosion limit. Therefore, bag dust removal is generally used.

In the non-ferrous metals industry, the main source of dust is in the flue gas during the smelting process and in the mining process, among which the smelting process is particularly serious. The smoke produced in the smelting process is mainly composed of oxides and sulfur-nitrogen oxides of various high-temperature volatile metals. Because the flue gas produced by smelting contains metal oxides, and the temperature of the metal oxides is high, dust should be avoided when the dust is removed.

Therefore, the correct judgment of the type of industrial dust is the primary prerequisite for a reasonable choice of dust removal equipment.