The dust collector must adopt a structure that does not leak gas, and it should be maintained frequently and regularly overhauled to avoid leakage of toxic gases and safety accidents.
1. Inlet dust concentration The inlet dust concentration is usually expressed as the standard volume dust mass. Consider the following when considering the inlet dust concentration and the design of the bag filter.
(1) Equipment resistance and cleaning cycle. The inlet dust concentration increases, and the resistance of the equipment increases with the same filter area. In order to maintain certain equipment resistance, the cleaning period is also shortened accordingly.
(2) Abrasives on the filter and the box. In the high concentration conditions where the dust has strong wear, the amount of wear is proportional to the dust concentration, and there should be diversion and wear resistant treatment techniques at the inlet of the dust collector, such as sintering dust, alumina powder, silica sand powder, etc.;
(3) Pre-dust collector and filter wind speed. In the case of high inlet dust concentration, a lower filter wind speed should be designed and the pre-filter should be designed. However, if the design has a primary settlement function, the pre-dust collector can be eliminated.
(4) Ash discharging device. Ash discharge capacity is based on the ability to discharge all the collected dust as the standard, and the amount of discharged dust is equal to the product of the difference between inlet and outlet dust concentration and the processing air volume. The capacity of the multi-stage ash discharge device should be designed to be larger than the first-level row. Ash ability prevails.
2. Export dust concentration The export dust concentration must be lower than the specified value of the environmental protection regulations and national health standards. The dust concentration at the outlet of the bag filter varies depending on the structure of the filter, the type of filter material, and the nature of the dust. It is generally between 1 and 50 mg/m3. In the case of lead, cadmium and other harmful substances, the export concentration is required to be particularly low. Different bag filter structures and filter materials are selected according to different uses and process characteristics during design.
3. Dust nature The nature of dust has a great influence on the design of bag filter. For some special properties of dust, effective measures must be taken according to design experience.
(1) Adhesion and cohesion. Adhesion and cohesive dust enter the bag filter, the dust will become larger when the dust agglomerates, and the dust accumulated on the surface of the filter bag can continue to condense during the process of shaking off. The amount of dust is also related to the adhesion and cohesion of the dust. Therefore, dust with very high adhesion and cohesion at the time of design, or almost no adhesion or cohesive dust, must be treated differently according to the design experience based on the type and application of the dust.
(2) Particle size. The main effect of particle size distribution on the bag filter is resistance loss and wear. Fine dust has a greater impact on pressure loss, and coarse dust plays a decisive role in wear, but only the particles with high dust concentration and hardness at the inlet have a relatively large impact.
Cross-sectional area of the bag * Filtration wind speed * 60 = Air flow per hour (m3/h) The fabric air volume of the bag filter refers to the volume of gas that the dust removal device can purify per unit time. The air flow rate of the bag filter is one of the most important factors in the design of the bag filter.
Design principle: When designing the bag filter according to the air volume, it is generally not allowed to operate the filter in excess of the specified air volume. Otherwise, the filter bag of the dust filter is easily blocked, the service life is shortened, the pressure loss is greatly increased, and the dust removal efficiency and dust removal effect are also improved. To be greatly reduced. However, the amount of air used for dust treatment cannot be too large. Otherwise, the investment and floor area of the dust collector of the dust collector will increase, and resources will be wasted and energy will not be saved. Reasonable choice of processing air volume is often determined based on process conditions and experience. From this it can be seen that not a simple formula or a fixed value can be used when considering the wind. Turn to the left | Turn to the right Bag filter treatment Wind refers to the amount of gas that can be purified by the dust collector per unit of time. It is one of the most important factors in the design of a bag filter. The bag filter has a set processing air volume range. In general, the dust collector cannot be operated when the designed air volume exceeds the set air volume range. If the air volume is too large, the filter material is clogged, and the pressure and pressure loss of the dust collector increase greatly, resulting in dust removal. The efficiency of the device declines. Below the design air volume, it is necessary to increase equipment investment and floor space accordingly. Calculating a reasonable processing air volume is of great significance for the stable operation of the dust collector and the dust removal effect. The unit for calculating air volume with the bag filter is usually expressed in m3/min or m3/h, but attention should be paid to the location and the temperature of the flue gas. The moisture content in the high-temperature gas is more, so the air volume is expressed in terms of the amount of humid air. The moisture is expressed as a volume fraction. If the temperature of the flue gas has been determined, the gas is cooled by the dilution method. When calculating the air volume, the amount of diluted air must be taken into account. When the filter area required for the bag filter is calculated, the filtration speed is the actual filtered air velocity. The air volume design value should be increased by 5%-10% on the basis of the normal air volume to ensure that the process adjustment will increase the air volume and the bag filter can continue to be used stably. However, it should be noted that the insurance coefficient should not be too large or it will increase. Investment and operating costs.