The use of dust filter bag in high temperature flue gas

I. Water mist cooling In order to avoid the sudden rise of flue gas temperature due to air preheater jamming or other flue gas combustion failures, which affects the service life of filter bags, measures should be taken to cool down and spray water mist before the inlet of the dust collector. This measure is to set up a group of atomizing nozzles for cooling in the flue before the baffle of the dust collector, and the connecting pipes of the nozzles are connected to the pressure water source through the automatically controlled solenoid valve. Under normal circumstances, the solenoid valve is closed. When an abnormal working condition occurs (the temperature of the smoke exceeds the temperature that the filter bag can withstand), the solenoid valve is automatically opened, and the pressure water is sprayed through the nozzle and atomized, and mixed with the flue gas to vaporize and reduce the heat absorption. The smoke temperature plays the role of protecting the filter bag.

 Here are a few things to keep in mind when using this protection:

1. The position of the nozzle should be as far away from the bag filter as possible, because generally the smoke velocity is relatively high, and the atomized water droplets and the flue gas should be fully mixed to vaporize and absorb heat (generally it takes a few seconds to fully vaporize) , in order to achieve the cooling effect. Otherwise, it is easy to cause condensation and corrosion in local areas.

2. If mechanical atomization is used, the selection of nozzles and the selection of water source parameters requires that the diameter of water droplets after water atomization can be less than 3005m and can reach about 505m. In addition, the water quality should be good and free of impurities, otherwise, install a filter, and let a small amount of air continuously enter when not spraying water to prevent the nozzle from being blocked.

3. If gas-phase atomization is used, the particle diameter of water atomization and the problem of nozzle blocking prevention are relatively easy to solve, but in particular, it is necessary to avoid the occurrence of pressure water pouring into the compressed air system.

4. After the flue gas is sprayed with water, the particles of the water mist will settle with the dust particles in the flue gas before being vaporized, or stick to the inner wall of the flue.

II. The pre-dusting of the bag filter requires fuel when the unit is started and the low-load stable combustion Including ash storage tank, silo roof dust collector, feeder, ash suction fan, etc.

III. The main reason for the prevention of paste bags is the drilling of water or oil in the powder layer of the filter bag. In order to avoid the formation of paste bags, a powder spraying device is installed in the front of the dust collector to spray oxidation before the flue gas enters the dust collector. The calcium powder, mixed with the soot, enters the dust collector, wraps the fine dust in the soot and the moisture in the soot, and plays the role of desulfurization and dechlorination at the same time. If the boiler explodes and the moisture content in the smoke exceeds, the dust collector PLC will control the bypass operation of the dust collector; when the smoke temperature is too low during operation, the bypass will be opened. Clean the dust after the dust collector is out of service.