The principle of pulse jet bag filter dust removal system
The dust removal methods of the bag filter mainly include: ①mechanical dust removal; ②pulse dust removal; ③reverse blowing dust removal; ④combined dust removal, etc.
The principle of dust removal system. Pulse dust removal uses compressed air to spray into the filter bag at a high speed in a very short time (usually no more than 0.3s), and at the same time induces several times the air to form a shock wave, which makes the filter bag produce sharp After expansion and vibration, the filter bag collapses. This process of expanding and deflating causes the dust on the surface of the filter bag to fall off. The injection system is composed of pulse controller, solenoid valve, injection pipe, etc. The pulse controller controls the solenoid valve to turn on and off instantly to form a pulsed airflow.
From the perspective of the cleaning process, the amount of dust shedding is related to the degree of "swelling" and "deflation" of the filter bag. This process is determined by the amount of compressed air sprayed into the filter bag, air pressure, interval, and time, which are composed of a comprehensive effect. The concept of so-called cleaning intensity. The interval is the pulse period, that is, the time interval between two adjacent openings of the same solenoid valve (usually 3 to 180s), which determines the frequency of dust removal. The time is the pulse width, that is, the time for the solenoid valve diaphragm to open (usually 0.03 ~ 0.3s), which determines the amount of dust removal. Both parameters are continuously adjustable and determined by the pulse controller.
The formation of the dust layer is related to the filtration speed. When the filtration speed is high, the formation of the dust layer is faster; when the filtration speed is low, the formation of the dust layer is slow. The adhesion of dust on the filter material is very strong, which can reach 1000-4200 times the weight of the particles. After cleaning, the dust layer will continue to exist. However, if the cleaning intensity is too high, it will destroy the dust layer, cause the "leakage" of the dust layer, reduce the dust trapping effect, and directly manifest as the intermittent dust emission of the bag filter.
The pressure of pulse cleaning is divided into high pressure and low pressure. The high pressure is generally 0.5～0.7MPa, and the low pressure is generally about 0.1MPa. High-pressure ash removal induces a large amount of air and high energy consumption; low-pressure ash removal saves compressed air consumption, has small pressure loss, large nozzle diameter, low energy consumption, and is suitable for filter materials with relatively low bending resistance. In terms of the cleaning effect, there is not much difference between the two. This division is not. With people’s further understanding of the dust removal mechanism, the selection of air source pressure and air volume for dust removal will be more reasonable, and the configuration of the dust removal system can be flexibly controlled to extend the service life of the filter material.
The electromagnetic pulse valve is a key component of the pulse bag filter for dust removal, and its normal operation directly affects the dust removal effect and continuous working ability of the pulse bag filter. The electromagnetic pulse valve is installed at the outlet of the air distribution box of the dust collector. When the filter bag does not need to be cleaned, the electromagnetic pulse valve is closed to seal the compressed gas in the air distribution box; when the filter bag needs to be cleaned, the dust is removed The control system sends out an electric pulse signal, the pulse valve opens instantly, and the compressed gas is released from the gas distribution box and sent into the bag opening of the filter bag through the nozzle of the blowing pipe. The high-speed airflow from the nozzle is mixed with the secondary airflow ejected by it. The high-pressure air mass in the filter bag moves from the mouth of the bag to the bottom of the bag, strongly impacts the side wall of the filter bag, and causes it to expand outwardly. The dust layer deposited on the surface of the filter bag is destroyed and falls off. The dust filtering function of the bag is restored. Therefore, whether the pulse bag filter can run for a long time, the function of the electromagnetic pulse valve is very important.