The bag filter is a dry filter. It is suitable for trapping fine, dry and non-fibrous dust. The filter bag is made of textile filter cloth or non-textile felt. The filter function of the fibre fabric is used to filter the dust-containing gas. When the dust-containing gas enters the bag filter, the dust with large particle size and large specific gravity settles down and falls into the dust hopper. When the gas containing smaller dust passes through the filter material, the dust is powdered. Dust is trapped to purify the gas.
Working principle:
The filter type dust collector is a device which can separate gas and solid by blocking and trapping dust particles in the air stream when the dust-containing gas holes pass through the filter layer.
The filter type dust collector includes bag filter and granular layer dust collector. The former usually uses the filter bag made of organic or inorganic fiber fabric as the filter layer, while the latter mostly uses different particle sizes, such as quartz sand, River sand, ceramsite, slag and so on. With the powder repeatedly attached to the outside surface of the filter bag, the powder layer continues to thicken, and the resistance value of the bag dust collector also increases; when the pulse valve diaphragm gives instructions, the pulse valve opens when the left and right submergence occurs, the compressed air in the high-pressure air bag opens, and if there is no dust or to a certain extent, the mechanical dust cleaning work will stop. Work.
Product structure:
The main structure of bag filter is composed of upper box, middle box, lower box (ash bucket), ash cleaning system and ash removal mechanism.
In addition to the correct selection of filter bag material, the cleaning system plays a decisive role in the performance of bag filter. Therefore, the method of cleaning dust is one of the characteristics of bag filter, and it is also an important part in the operation of bag filter.
Structure type:
1. According to the shape of filter bags, they are divided into flat bags (trapezoidal and flat) and round bags (cylindrical).
2. According to the way of air in and out, it can be divided into two types: downwind, upwind, downwind and direct current (limited to flat flat bags).
3. According to the way of bag filtration, it can be divided into external filter and internal filter.
The fibers used for filter materials are cotton, wool, synthetic and glass fibers. The filter materials woven from different fibers have different properties. The commonly used filter material is 208 or 901 polyester velvet cloth, the use temperature generally does not exceed 120 C, the use temperature of glass fiber filter bags treated with silicone tunnel resin generally does not exceed 250 C, cotton wool fabric is generally suitable for non-corrosive; the temperature is below 80-90 C, dust-containing gas.
Product advantages:
(1) Dust removal efficiency is high, generally more than 99%. The dust concentration at the outlet of the dust collector is within tens of mg/m3, which has a high classification efficiency for sub-micron particles.
(2) The range of air handling capacity is wide, small only 1 minute m3, large up to tens of thousands of m3 in one minute. It can be used for dust removal of flue gas from industrial furnaces and kilns to reduce the emission of atmospheric pollutants.
_The structure is simple and easy to maintain and operate.
(4) On the premise of ensuring the same high dust removal efficiency, the cost is lower than that of the electrostatic precipitator.
_When glass fiber, PTFE, P84 and other high temperature resistant filters are used, they can be operated at high temperature above 200 C.
(5) It is insensitive to the characteristics of dust and is not affected by dust and resistance.
Product Maintenance:
1. Always check the action of control valve, pulse valve and timer.
The failure of rubber diaphragm of pulse valve is a common fault of bag filter, which directly affects the cleaning effect. The equipment belongs to the external filter type, with the framework inside the bag. It is necessary to check whether the parts of the fixed filter bag are relaxed and the tension of the filter bag is appropriate. Whether the support frame is smooth to prevent wear and tear of the filter bag. Compressed air is used for ash cleaning. Therefore, it is required to remove oil mist and water droplets, and the oil-water separator must be cleaned regularly in order to prevent the failure of the motion mechanism and the clogging of the filter bag.
2. Whether the treatment air volume and the pressure and temperature at each test point are in accordance with the design.
3. Installation of filter bags, whether bags drop, loosen, wear and tear occur after use, can be judged by visual measurement of chimney discharge after commissioning.
4. Prevention of condensation
In use, it is necessary to prevent gas from cooling below dew point in bag chamber, especially when using bag filter under negative pressure. Because of the air leaking into the outer shell, the air temperature in the bag chamber is lower than dew point, and the filter bag will be damp. The dust is not loose, but sticky to the filter bag. The fabric hole is blocked, resulting in dust removal failure, so that the pressure drop of the dust collector is too large to continue to operate, and some of the bags can not be cleaned.
In order to prevent condensation, it is necessary to keep the temperature of gas in the dust collector and its system higher than that of dew point 25-35 C (such as dew point temperature of kiln grinder 58 C, operation temperature should be above 90 C), so as to ensure the good use of filter bags.
Market status:
There is a huge demand for bag filter in our country, and the filter material, especially the high temperature resistant fiber filter material, has broad market prospects. China's "Twelfth Five-Year Plan" puts forward higher demand for environmental protection. Water, gas, sound and slag will be more used as filter materials. The market prospect of filter materials industry is promising. In the field of smoke and dust control, bag dust removal is more and more widely used at home and abroad, accounting for 80% of the dust removal equipment because of its high efficiency, no secondary pollution and easy recovery of dry materials. Iron and steel industry is one of the main sources of atmospheric pollution. China's steel output has exceeded 300 million tons. According to the application of bag dust removal in Baosteel, 2100 is needed.
