Analysis of bag-type dust collector running resistance, dust removal efficiency is low.Date: 2019-06-19 Views:
Whether the design of bag filter is reasonable and whether the operation is normal or not is mainly manifested in the service life of filter bag and the resistance of equipment operation. The breakage of filter bag is related to the high resistance of equipment operation. When the dusty gas enters the dust collector, the dust layer will be formed on the surface of the filter bag due to the effects of screen filtration, collision, retention, diffusion, static electricity and so on.
With the accumulation of dust on the surface of the filter bag, the efficiency and resistance of the bag dust collector also increase correspondingly. The high resistance of the dust collector will reduce the air volume of the dust removal system, and the dust removal efficiency will also be greatly reduced. Therefore, in the operation of the dust collector, we should pay more attention to whether the resistance of the dust collector is on the high side.
The operation resistance of dust collector is caused by three parts: filter bag, body and dust adsorbed on filter bag. The difference of structure design, filter material, filtration wind speed, gas dust concentration, dust particle size, gas humidity and other factors have great influence on the operation resistance of bag dust collector.
(1) whether the structural design is reasonable or not
In addition, the positive pressure gas blowing back when cleaning ash is also one of the reasons for the high operation resistance of bag dust remover. Frequent injection of positive pressure gas into the bag chamber is bound to increase the operation resistance of the equipment. Therefore, when the dust concentration is too high, the material leveling device should be added in the inlet duct and ash bucket to carry out pre-dust collection treatment in order to reduce the filter bag load of bag dust collector and reduce the resistance of the equipment.
(3) Dust particle size
The main influence of dust particles on bag dust collector is pressure loss and equipment wear. The biggest pressure loss is fine dust, which can block the filtration gap, reduce the permeability of filter media and increase the resistance. It is generally believed that needle-like crystal particles and sheet particles are easy to block filter bags, reduce dust removal efficiency and increase operation resistance. For fine particles of dusty gas, such as cement kiln tail, slag grinding system and so on, film-coated filter bags should be used.
The gas usually contains a small amount of water vapor. When the relative humidity is between 30%and 80%, it is in the general state, and it is in a high humidity state when the gas exceeds the range. When the gas in the bag-type dust collector is in a high humidity state, condensation occurs under the action of external cold air, resulting in dust binding and blocking the filter bag, resulting in the reduction of the dust collection function of filter material, difficulty in dust removal, and the equipment pressure increases. For condensation, the filter material with smooth surface shall be selected as much as possible, such as film-coated filter material. In addition, thermal insulation of the equipment and increasing the inlet temperature of dust-containing gas can reduce the negative effect of cold air and prevent condensation.
(5) Air permeability of filter media
In general, the pressure loss of clean filter cloth is relatively small and the air permeability is high. in work, the small pressure loss means that its pores are relatively large, dust is easy to penetrate, and the non-trapping property of dust is relatively low in general. In addition, the pressure loss of dust layer on the surface of filter bag is one of the factors that affect the pressure loss of filter bag, which is related to whether the pores of filter cloth are clogged or not, so it is required that the pores of filter cloth are not easy to be blocked, the dust collection rate is high, the pressure loss is small, the ash cleaning performance is good, and the service life is long.
(6) filter bag filtration wind speed
Filtration wind speed is an important parameter of bag dust collector. When the ash cleaning mode, filter material and smoke and dust characteristics are different, the designed filtration wind speed should also be different, so the filtration resistance is also different.
For the dust in cement industry, when collecting cement, because the dust humidity is small and the viscosity is relatively small, pulse bag dust collector is often used, and the filtration wind speed is generally 0.8 × 1.0 m ·min. For drying dust removal or cement rotary kiln tail gas dust removal, because the smoke dust moisture is relatively high, the dust humidity is relatively large, when the glass fiber bag reverse blowing bag dust collector is used, the filtration wind speed is generally controlled between 0.3~0.5m/min, when the long bag pulse bag dust collector is used, the filtration wind speed is generally controlled between 0.7~0.9m/min; for the preparation of pulverized coal in cement and metallurgical industry, the filtration wind speed is generally controlled between 0.7~0.9m/min; for the preparation of pulverized coal in cement and metallurgical industry, the filtration wind speed is generally controlled between the two groups.
When the ash cleaning efficiency of the dust collector is not high, the operation resistance will be increased directly due to the attachment of too much dust on the surface of the filter bag. Therefore, improving the ash cleaning efficiency of dust collector is also one of the guarantee measures to reduce the resistance of equipment.
When the filter bag is too long, it may also make the ash cleaning near the bottom of the filter bag inefficient because of the insufficient injection strength or gas volume. The spacing between nozzle and board, the size of nozzle, the length of filter bag and the type of pulse valve can reduce the low ash cleaning efficiency and high operation resistance caused by injection system.
The positive pressure of the system and the ash removal of the air leakage pulse pipeline system of the equipment system are high pressure gas, which is in the positive pressure state. In order to achieve the effect of ash cleaning, the compressed air injected by the pulse valve must reach a certain amount, which is generally more than 2 times of the internal volume of the ash filter bag.
under the working condition, the equipment box is a negative pressure, when an excessive positive pressure air flow is injected into the equipment, the resistance value of the front and rear resistance of the equipment is increased, and the effect is equivalent to the air leakage of the equipment; therefore, the blowing pressure and the blowing time are reasonably selected, so that the service life of the filter bag can be prolonged, And the operation resistance of the bag-type dust collector is reduced by a certain positive effect, and the situation is particularly shown when the number of the equipment box chambers is small. In the actual production operation, in order to pursue the ash cleaning effect, some manufacturers blindly improve the ash cleaning pressure or prolong the blowing time, which is not possible.
If the ash cleaning pressure is too high, it will accelerate the damage of the filter bag and affect the running resistance at the same time. However, prolonging the injection time has little positive effect on the ash cleaning except by injecting more positive pressure gas and increasing the running resistance of the equipment.
(9) Reliability of the supporting piece
Scientific and reasonable structural design and parameter determination, fitting selection is an important part of the stable operation of the bag-type dust collector, and the operation of the equipment is reasonable and correct, and the effective management and maintenance is the guarantee of the stable operation of the bag-type dust collector.