How to choose a dust collector in a cement plant?

  In the cement industry, the finished and semi-finished products mainly exist in the form of powder and are accompanied by the calcination process, so the dust emission causes great pollution to the atmosphere. Fine particles, sulfides, and nitrogen oxides produced in cement production are all factors that form PM2.5. It can be said that the cement industry is one of the major producers of by-product PM2.5.

  The main pollution sources of the cement industry affecting the atmosphere are dust and waste gas. Dust is mainly due to the waste gas emission or escape from the raw fuel and cement product storage and transportation, material crushing, drying, grinding, calcining and other processes in the cement production process. Among them, the dust emissions from the grinding and calcination of raw materials and fuels are the most serious, accounting for more than 70% of the total dust emissions from cement plants. The waste gas (including SO2, NOx, CO2, HF, etc.) that the cement industry has an impact on the atmospheric environment, in which SO2 is produced by the combustion of sulfur-containing fuel in the firing system; CO2 is produced by the decomposition of CaCO3 and coal combustion in cement production. ; NOx is produced by N2 in the air under high temperature aerobic combustion conditions. According to the total annual cement production in my country, the amount of dust and waste gas emitted to the atmosphere due to cement production in China are: about 13.3 million tons of various types of dust; in terms of exhaust gas emissions, about 200 million tons of CO2 are emitted into the atmosphere each year ; SO2 emissions about 1 million tons; NOX emissions 1.3 ~ 1.6 × 106 cubic meters.

  The control of dust emissions in the cement industry is mainly through the filtration of dust collectors. According to the GB4915-2004 standard, from January 1, 2005, the dust emission concentration of new, renovated and expanded cement production lines should reach: the dust emission concentration of crushers, mills, packaging machines and other ventilation equipment is below 30mg/m3; kiln, The emission concentration of thermal equipment such as dryers and grate coolers is below 50mg/m3; from January 1, 2010, the dust emission concentration of all production equipment in the existing production line shall comply with the above emission requirements. The standard was revised in 2011. Emissions of particulate matter are more stringent. The bag filter is the most efficient dust removal method, and it is also the most rapidly developed dust removal method in recent years. The bag filter has high dust removal efficiency and can filter sub-micron dust particles. The progress of bag dust removal technology provides an effective technical means for the control of PM2.5 dust emission in the cement industry.

  Experiments show that the change of dust particle size distribution has little effect on the resistance of the bag filter. Under stable conditions, when other conditions are the same, the coarse dust retained on the filter bag is less than the fine dust, and the penetration rate of the coarse dust is not as high as that of the fine dust. Cement industry dust particles range in size from submicron dust to millimeter-sized particles that are easy to settle. For electrostatic precipitators, the particle size distribution of dust and the specific resistance of dust will affect its dust removal efficiency. In addition, the operation of electrostatic precipitator also has many uncertain factors, such as: poor operation of high and low pressure control design, unreasonable operation mode of rapping cleaning device, etc. Although the electrostatic precipitator has high dust removal efficiency under normal operating conditions, for ultra-fine particulate matter, up to 15% of the particulate matter will still be discharged into the atmosphere. The cement industry will gradually be included in the ranks of elimination. The bag filter uses the mechanical blocking and filtering mechanism, which integrates the comprehensive effects of various forces such as gravity, sieving, inertial collision, adsorption effect and diffusion effect. filter performance.

  The key to the use of the bag filter is cleaning, and the cleaning effect largely determines the success or failure of the bag filter and the entire system. The pulse bag filter characterized by strong cleaning has become the first choice. The new generation of pulse bag dust removal technology completely overcomes the shortcomings of traditional pulse dust removal. It has the advantages of low air pressure, reliable operation and small maintenance workload, which eliminates the common phenomenon of excessive resistance in weak dust cleaning bag filter. The dust removal efficiency of the bag filter has been further improved.