The bag filter mainly uses the filter material (fabric or felt) to filter the dusty gas to achieve the purpose of dust removal. The filtration process is divided into two stages. First, the dust-containing gas passes through the cleaned filter material. At this time, the filtration is mainly caused by the retention of the filter fiber. Secondly, when the retained dust is continuously increased, a part of the dust is embedded in the interior of the filter material, and a part of the dust covers the surface of the filter material to form a dust layer. At this time, the dust layer is mainly used to filter the dust-containing gas. After the dust-containing gas enters the dust collector, the airflow speed decreases, and the larger particles in the smoke directly precipitate to the ash bucket, and the remaining dust particles are filtered from the outside to the inside through the filter bag, and the cleaned smoke is discharged from the inside of the filter bag, and the fly ash is blocked. On the outside of the filter bag. As the accumulation of ash accumulates, the pressure difference between the inside and outside of the dust filter bag gradually increases. When the pressure difference reaches the set value, the pulse valve diaphragm automatically opens, the pulsed air is sprayed into the filter bag through the nozzle, and the filter bag is expanded, thereby The dust adhering to the filter bag falls off to achieve the effect of dust removal.
The structure of the bag filter:
The internal structure of the bag filter is mainly composed of an upper box, a middle box, a lower box (ash hopper), a cleaning system and a ash discharging mechanism. The bag filter is mainly composed of four major systems, namely the cleaning system, the control system, the inspection system, the safety protection system (including the boiler ignition and oil injection, the low-load operation, the fuel injection, the pre-coating ash system, the protection filter When the smoke temperature exceeds the set value, the emergency water spray system is activated to reduce the temperature of the smoke and protect the filter bag. The cleaning system is the digestive organ of the bag filter, and the operation effect of the bag filter depends largely on the bag. In the cleaning mechanism and its control system.
Type of bag filter:
Bag dust collector equipment mainly includes pulse jet bag filter, air box pulse bag filter, mechanical backwash bag filter, mechanical vibrating bag filter and other equipment. Pulse jet bag filter working principle
Working principle of air box pulse bag filter:
As the dust-containing gas passes through the filter bag, the dust layer on the filter bag is continuously thickened as the filtration time is extended, and the filter bag resistance is increased. For normal work, the resistance should be controlled within a certain range (140--170 mm). Water column), when the resistance of the equipment rises to the set value, the cleaning device starts to clean. When the dust is cleaned, each control valve is sequentially triggered by the pulse controller to open the pulse valve. First, a compartment chamber poppet valve is closed, the filtered airflow is cut off, and then the electromagnetic pulse valve is opened. The compressed air expands rapidly in the upper tank body in a very short time, and flows into the filter bag, causing the filter bag to expand and deform to generate vibration, and in the reverse airflow. Under the action of the scouring, the dust adhering to the outer surface of the filter bag is peeled off and falls into the hopper. After the cleaning is completed, the electromagnetic pulse valve is closed, the poppet valve is opened, and the chamber is restored to the filtered state. The cleaning chambers are sequentially performed, starting from the first chamber cleaning to the next cleaning, starting with a cleaning cycle. The dust that has been intercepted by the filtration and cleaning work falls into the ash hopper, and is discharged by the ash discharge device of the ash hopper. Thereby, the dust accumulated on the filter bag is periodically pulsed and cleaned, so that the purge gas passes normally, and the dust removal system is operated.
Working principle of mechanical backflush bag dust collector:
The dust-containing airflow enters the upper space of the filter chamber tangentially, and the large particles and the condensed dust particles are swirled down the hopper according to the centrifugal force, and the small particles of dust are dispersed in the gap between the filter chamber bags, thereby being retained by the dust filter bag. The purified air is collected in the clean room through the dust bag and through the filter bag guide on the flower plate, and is taken in by the fan and discharged into the atmosphere. As the filtration progresses, the resistance gradually increases. When the upper limit of the anti-blow control resistance is reached, the differential pressure transmitter sends a signal to automatically activate the anti-drying mechanism; the back airflow with sufficient momentum is blown into the filter bag by the rotary wall nozzle. The mouth blocks the filtered airflow and changes the pressure working condition in the bag, causing the filter bag to substantially vibrate, shake off the dust, and the spiral arm splits one by one. When the filter bag resistance drops to the lower limit, the anti-drying mechanism automatically stops working.
Mechanical vibrating bag filter working principle:
Mechanical vibrating bag filter is a dust removing device for collecting solid particles in dusty gas by using a bag filter element made of fiber braid. The principle of action is that the dust powder contacts the fiber due to inertia when passing through the filter cloth fiber. While being intercepted, the dust collected on the filter bag is periodically removed by the cleaning device and dropped into the ash hopper, and then discharged through the ash discharging system. The dusty flue gas enters the inlet chamber from the upper part of the mechanical vibrating bag filter. Some coarse particles fall into the ash bin due to inertia, and the other dusty flue gas enters the inlet chamber through each intake branch pipe, and evenly passes through the upper flower plate. Infiltrated into the filter bag, a large amount of dust stays in the filter bag, and some of the dust directly falls through the lower plate into the ash hopper. The purified gas enters the atmosphere through an exhaust valve. When the dust layer attached to the inner surface of the filter bag is thickened to a certain extent, the running resistance of the dust collector is increased to a certain value, and the anti-hair dryer is controlled by the microcomputer to perform the two-state chamber cleaning process, and the air is blown to change the pressure inside and outside the filter bag. Poor, the filter bag is expanded to shrink to remove the dust layer attached to the inner surface of the filter bag, so that the dust collector returns to normal operation, and the dropped dust enters the screw conveyor through the ash discharge valve to achieve the purpose of recycling the material.
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