The main technical parameters for selecting a bag filter are air volume, gas temperature, dust concentration and humidity, and dust characteristics. According to the high values of air volume, gas temperature, and dust concentration in the system process design, based on the principle of slightly smaller values than those in the technical performance table, the corresponding dust collector model is the selected dust collector model. The filter material is determined based on the inlet concentration, gas temperature, humidity, and dust characteristics.
Due to its small size, bag filters often use 1 "right angle valves for their spray valves, with a spray pressure between 0.40 and 0.60MPa. Unlike ordinary dust collectors that use 2.5-3" straight through spray valves with a spray pressure of 0.15 to 0.25MPa. The transportation methods for raw materials include belt conveyors, screw conveyors, bucket elevators, and so on. The belt conveyor belongs to the open conveying method, and a single or double layer closed cover can be installed on top of the exhaust hood at the feeding point. Spiral conveying and bucket elevator belong to closed conveying methods. If the volume is small and the seal is firm, it generally does not produce dust; For large bucket elevators, strong dust will be generated at the material location, and a ventilation hood can be installed above the feeding point of the bucket elevator. The bag filter here can be divided into treatment areas for dust removal according to the layout of the factory area or different dust properties. Bag dust collectors can also be used to directly collect dust and discharge it onto the belt at the conveyor belt transportation site.
Bag filter dry pre decomposition kiln is a commonly used new and renovated kiln type in China. Due to the high flue gas temperature of 360-420 ℃ and exhaust dust concentration of 30-100g/m3, fiberglass bag filter should be selected with an economic value of 0.8-1.0m/min for filtration wind speed. The high allowable working temperature of the dust collector is 260 ℃. The flue gas temperature is cooled to around 220 ℃ before being sent to the dust collector. Cooling measures include natural/forced convection flue gas cooler, air duct heat dissipation, and cold air valve adjustment. Although the dust collector is under high temperature conditions, in poorly ventilated flue gas stagnant areas, some parts of the outer wall may still be below the dew point, so insulation measures are still needed. There are many domestic boilers with waste heat power generation and dry hollow kilns that use waste heat power generation. The flue gas temperature is generally stable at 200-240 ℃, with a dew point of around 35 ℃. Fiberglass bag dust collectors can be directly used, and the flue gas does not need to be cooled, but insulation measures need to be taken.
The operation of bag filter can be divided into trial operation and daily operation. During the trial operation, check the individual components of the system, perform adaptive operation, and conduct component performance tests. In daily operation, checks should still be conducted, especially for the performance of bag filters. Attention should be paid to the impact of changes in the load of the main equipment on the performance of the dust collector. After the machine is started, close attention should be paid to the working condition of the bag filter.
Condensation is a common phenomenon in bag filters, which means that when the humidity of the air reaches a certain level, moisture will precipitate at a specific pressure and temperature.
After analysis by our technical personnel, the main reasons for condensation in bag filters are as follows:
Dust collectors have the phenomenon of air leakage. We all know that the internal temperature of dust collectors is very high during operation, and if the machine leaks air, it will enter a part of the external air inside. Cold air will condense when it encounters hot air due to physical changes.
The humidity in the smoke exceeds the standard. When the dust collector is sucking up dust, due to the humid local air or the high moisture content in the smoke, condensation will occur when these smoke particles are sucked into the vacuum cleaner. This situation is generally more likely to occur in cement manufacturing plants.
Thirdly, when the bag filter sprays gas, the temperature is too low. The dust collector uses compressed air to achieve the goal of pulse blowing and cleaning dust. When the air is compressed, the internal pressure will change accordingly, which is not very obvious in summer. If it is in winter due to pressure changes, the internal temperature will change significantly, leading to a decrease in the temperature of the sprayed gas and the phenomenon of condensation.
Fourthly, if the shell of the bag filter itself is not insulated or has poor protective measures, condensation may occur due to the temperature difference between the inside and outside.
