China's shaft kiln plant production license and no production license has nearly 10,000, the annual output of cement accounts for China's annual output of more than 80% of the total amount of cement. In 1998 China's total output of 530 million tons of cement, shaft kiln plant output of about 420 million tons and above. If the shaft kiln dust emissions by 4% of shaft kiln production, the annual total emissions of shaft kiln dust as high as 16 million tons. According to incomplete statistics, shaft kiln dust emissions reached less than 2% of the standard. Although the State Economic and Trade Commission has decided to phase out over 3,500 shaft kilns less than 2.2 meters in diameter in 1997 and all shaft kilns with an annual output of less than 44,000 tons in 2000 will be phased out, there are still a considerable number of shaft kilns not included in the phase-out list. According to the requirements of the local environmental protection department, the factory also has to go through the deadline for compliance with the standards, otherwise the plant will be ordered to stop production and shut down. In the face of this grim situation, manufacturers are anxious, so it is urgent to provide the existing shaft kiln plant with high performance, high efficiency, low cost, long-term safe operation of the dust removal equipment.
Status of shaft kiln dust removal technology
Since the nature of shaft kiln flue gas and dust depends on the operating method of the shaft kiln, the nature of the feedstock and fuel and the process conditions, and the range of variation is large and fast, great difficulties are encountered in dust management. With the increasingly stringent emission standards set by the state and the enhancement of urban and rural people's awareness of environmental protection, the dust-settling chamber of the shaft kiln no longer adopts the settlement chamber with simple structure, investment saving and dust removal efficiency less than 50%, prompting many scientific research and design institutes and environmental protection product manufacturers Research and development of new efficient, inexpensive dust removal device. This is the main reason that various types of water precipitators on a shaft kiln have mushroomed in recent years. Of course, with the mud received can be fed into the pre-water into the ball system biaxial mixer to solve the problem of secondary pollution.
Water Dusting Facilities have the advantages of simpler construction and less investment than bag filters and electrostatic precipitators. However, according to the test results of manufacturers with water dust removal facilities, the concentration of dust emission is unstable and it is difficult to maintain the emission concentration for a long period of time per standard cubic meter Less than 150 milligrams, to achieve the emission concentration of less than 100 milligrams per standard cubic meter more difficult. In addition, the fatal weakness of water dust is dust can not smoke. Such as Tongchuan in Shaanxi Province kiln plant burned higher sulfur content of bituminous coal, and some plants equipped with different forms of water dust removal device, although the dust emissions have been controlled, but still discharged from the chimney yellow smoke, according to the analysis of discharge Of the yellow smoke is not gas, but the combustion of volatile coal combustion generated particle size less than 5 microns of smoke, in essence, or belong to the category of dust. These tiny fumes, using spray or spray water dust can not do anything. Therefore, Tongchuan water purification facilities, manufacturers have switched to bag dust or electric dust trend.
Since water dusting is difficult to achieve the desired effect of shaft kiln dust removal, it is inevitable to use the technology of mature bag dust or electric dust removal. Take the bag filter as an example, due to the structure of the body, cleaning methods and the improvement of the valve, the technological progress of the filter media, the filter bag and the cleaning control system, and the application of the auxiliary cleaning technology, the technology of the bag dust remover More mature and perfect. In particular bag filter dust resistance from the restrictions, but also for shaft kiln dust. However, the larger the bag filter resistance, generally an average of more than 1200 Pa, by the shaft kiln natural exhaust is unlikely, so the need for a separate configuration exhaust fan, such as diameter 2.8 × 10 m shaft kiln, air volume 55,000 cubic meters per hour M considered, the main exhaust fan blower with the required power of about 80 kilowatts or more, another filter bag filter area greater than 1800 square meters, if the commonly used glass fiber filter at 23 yuan / square meter, two years for a Bag, you need more than 4 million, but also requires a relatively stable operation of the shaft kiln, especially for the operating temperature, because the temperature is too high, easy to burn bags, the temperature is too low, easy paste bag. Bag filter because of the above shortcomings, and an investment is not low, making it widely promoted in the shaft kiln is limited, especially in northern coal-fired shaft kiln bag dust collector with more careful.
Shaft kiln using ESP and bag filter, there are many failed lessons. In addition to the resistance of the dust than the resistance, but also by the shaft operating conditions, but in general, the operating conditions are not as high as the bag filter, and can use the chimney of the natural pressure of natural exhaust ventilation. As long as the effective solution to the pole over-temperature deformation and corrosion problems, the use of electrostatic precipitator shaft kiln is more reliable, although a larger investment, but at least with the bag filter flat.
Progress of shaft kiln electric precipitator technology
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