The application of dust removal technology of dryer waste gas is summarized

The waste gas treatment of dryer is the difficulty of dust removal technology. This paper introduces several kinds of dust removal technology of dryer waste gas.

The exhaust gas of dryer has large air volume, high dust concentration, large moisture, high dew point, easy condensation, high emission point and wide pollution range, which are the difficulties of dust removal technology. The tail gas of the dryer is related to the process conditions of each factory. Some enterprises are used for drying materials at many places. The production changes greatly, the start-up and shutdown are frequent, and the fluctuation range is large. Moreover, when coal is used as the drying heat source, the sulfur oxide in the waste gas has corrosive effect on metal structure parts, which brings certain difficulties to the selection of dust remover.

Cyclone dust removal technology

Cyclone dust removal technology has the characteristics of low equipment cost, high temperature gas treatment, easy operation and suitable for gas with high dust concentration. Its working principle is that under the action of the fan, the dust laden air flow enters into the volute of the dust collector at a high speed from the inlet, and makes a spiral rotation movement from top to bottom. Under the action of centrifugal force, the dust particles are thrown to the outer wall, and rotate downward along the wall surface. With the contraction of the cone, it turns to the axis center and returns under the resistance of the lower part. It rotates from bottom to top along the axis and is discharged through the core tube Out. Driven by gravity and downward moving air flow, the dust particles on the outer wall fall into the ash hopper along the wall to achieve the purpose of dust removal. Because the cyclone dust collector relies on the inertia separation of dust particles, the dust removal efficiency is directly proportional to the particle size, and the dust removal effect is good when the particle size is large; the dust removal effect is poor due to the small particle size. Generally, the dust removal efficiency is 70% - 90% when the dust is more than 20 microns.

Bag dust removal technology

It is generally acknowledged that the bag filter is stable, efficient, easy to maintain and reliable in operation. It can remove dust as high as 99% for particles containing 0.1 μ m dust. It is unnecessary to consider the problem of excessive emission concentration when using bag filter for dust removal of dryer exhaust gas. The anti condensation glass fiber bag filter of dryer is an ideal dust removal and purification equipment at present. The equipment is controlled by microcomputer, back blowing in different rooms, cleaning dust regularly, and equipped with temperature detection display and over temperature alarm device. Cw300-fca anti condensation glass fiber filter bag is adopted, which can effectively prevent the filter bag from condensation and will not burn the filter bag. The two-stage dust removal process of the slag dryer with a diameter of 3 × 24m in Hebei Taihang Group Co., Ltd. is changed into a first-class lfef7 × 358-hsy / h anti condensation bag filter. According to the environmental protection department, the waste gas volume is 42621 standard cubic meters per hour, the dust concentration at the inlet is 69620 mg per standard cubic meter, and the dust concentration at the outlet is 147 mg per standard cubic meter, which meets the national emission standard. Not only the output is increased, but also the dry materials are recovered. The annual economic benefit is more than 700000 yuan and obvious social benefit is received. However, bag filter has the disadvantages of large area and high investment. With the development of filter bag covering technology, this shortcoming will be overcome and used more widely.

High voltage electrostatic precipitator technology

High voltage electrostatic precipitation technology is to change 50 Hz, 220 V alternating current into more than 100 kW direct current and add it to corona electrode (cathode) to form uneven high-voltage electric field, which can ionize the gas and produce a large number of negative ions and electrons, so that the gas dust entering the electric field is charged. Under the action of electric field force, the charged dust tends to the opposite electrode. Generally, the anode is the dust collector, which falls into the ash hopper row by rapping The purification process is completed. High voltage electrostatic precipitator with high efficiency and low resistance can be widely used in building materials, metallurgy, chemical industry and other industries. It can deal with dust with high concentration. The dust removal effect is more obvious for 0.01 micron fine or high specific resistance dust. The series of products can meet the drying equipment of different air volume and match flexibly, which is suitable for dust control of exhaust gas characteristics of dryer.

Wet dedusting technology

The wet dust removal technology is that the dust containing gas is sent to the lower part of the dust removal tower by the induced draft fan through the air duct. Because the cross section becomes larger, the flow rate decreases, and the coarse dust first settles in the air flow. The finer dust rises with the air flow, and the water droplets and dust air flow move in reverse direction. The dust is wetted and its weight increases continuously. Under the action of gravity, it overcomes the lifting force of the air flow and drops into slurry water The lower pipe enters the sedimentation tank to achieve the purpose of dust removal. The slurry water is generally changed into clear water after 2-3 stage circulating sedimentation, and is pumped into the dust removal tower for recycling, which does not cause secondary pollution. The positive pressure operation of the dust removal technology is generally used for the drying of clay and drying of various materials (raw materials). The recycled materials are easy to mix up and can not be used, and the wind blades are greatly worn. The wet dedusting technology is used in the clay dryer with a diameter of 2.2 × 12m in Suzhou cement plant. The emission concentration is 132 mg / standard cubic meter, which meets the national emission standard. The sedimentation tank is cleaned once a year, and the wet soil is stored in the air for production raw materials. The system has the advantages of high dust collection efficiency, low resistance, no secondary pollution, flexible process, reliable operation, low power consumption, low investment, no condensation, strong adaptability and good economic and social benefits.

Gravity sedimentation + high voltage electrostatic precipitation technology

The dust removal process is composed of a settling chamber and a high-voltage electrostatic precipitator. The dust containing waste gas is sent to the settling chamber by the induced draft fan at high speed through the air duct and collides with the wall. The air flow direction changes so that the wind speed decreases rapidly. The particle dust settles and is discharged through the conveying equipment. The fine dust enters the electric field of the high-voltage electrostatic precipitator with the air flow. It is charged under the continuous bombardment of ions and flies to the dust collector to be collected and discharged, The purified gas is discharged into the atmosphere by the air duct. In the two-stage dust removal process, the primary settling chamber collects the dust with a size of more than 40 microns, which reduces the dust concentration in the gas, and is conducive to improving the dust removal efficiency of the high-voltage electrostatic precipitator. The wind speed can be larger and the equipment can be smaller, which can effectively reduce the investment. In the dust removal process of clay dryer with a diameter of 2.2 × 12 meters in Lanxi cement plant, Zhejiang Province, the dust containing waste gas is sent from the tail cover of the dryer to the square settling chamber made of steel plate by the induced draft fan through the air duct, and the waste gas is discharged into the high-voltage electrostatic precipitator after settling and then discharged into the atmosphere after purification. The induced draft fan and settling chamber are installed indoors, and the electrostatic precipitator is installed outdoors. The dust removal system operates normally and has been used for many years without condensation. According to the environmental protection department, the emission concentration is 48 mg per standard cubic meter, which is lower than the national emission standard.

Cyclone + high voltage electrostatic precipitator technology

The dust removal technology is that the dust containing waste gas of the dryer enters the front stage high-efficiency cyclone dust collector through the air duct for pre dust removal. The dust is discharged from the ash hopper through the ash discharge equipment, and the dust concentration in the air flow is reduced, and then it enters the secondary dust removal of the high-voltage electrostatic precipitator. The purified gas is discharged into the atmosphere by the air outlet fan, so that the dust removal efficiency is improved, the process is flexible, safe and reliable.

The application of dust removal technology of dryer waste gas not only protects the environment, reduces the labor intensity, but also improves the output per hour and reduces the expenditure of sewage charges. The recovered dust is a good raw material for cement production and has significant economic, social and environmental benefits.