11 Tips Help To Improve Your Bag Filter

Bag filter can not only remove particulate matter from industrial waste gas, reduce exhaust emissions and treatment costs, but also capture valuable dust such as precious metal dust and mineral dust, thereby achieving effective utilization of resources.

As a commonly used dust filtering device, the dust removal effect of bag filters directly affects whether production is qualified and whether it can meet environmental protection requirements. In this article, we will discuss 11 tips to improve the effectiveness of bag filters.

1. Selection of Filter Bags

Filter bags should be made of wear-resistant and high-temperature resistant materials, such as fiberglass cloth/felt, NOMEX, needle felt, P84 needle felt, etc. Suitable materials and specifications should be selected based on the nature and concentration of dust.

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Generally, for dust containing gases with low water content and no acidity, they can be selected according to their temperature. At room temperature or ≤ 130 ℃, 500-550g/㎡ polyester needle felt is commonly used At 250 ℃, use 800g/㎡ glass fiber needle felt.

When the moisture content is high and the dust concentration is high, it is advisable to choose waterproof, oil resistant filter materials or membrane covered filter materials.

When the dusty gas contains acid, alkali, and the temperature is ≤ 190 ℃, Laitong needle felt is often used; When the gas temperature is ≤ 240 ℃ and the requirements for acid and alkaline resistance are not high, P84 is often chosen.

When the dusty gas is a flammable and explosive gas, anti-static polyester needle felt should be used; When the dusty gas contains both a certain amount of moisture and is a flammable and explosive gas, waterproof, oil resistant, and electrostatic discharge polyester needle felt should be used.

2. Quality of Filter Bags

As the most critical accessory of a bag filter, the performance and quality of the filter bag largely determine the dust removal effect, work efficiency, and service life of the bag filter. Poor quality filter bags are prone to problems such as damage and burning during production, so users should pay more attention when choosing.

3. Temperature Control

Generally, the temperature that a filter bag can withstand does not exceed 200 ℃, so the inlet temperature of the treatment facility should be controlled below 200 ℃. When the flue gas passing through the long flue pipe reaches the dust collector box, the temperature can be reduced to below 200 ℃. In special circumstances, water cooling can be carried out and a cooler can be installed at the main flue pipe.

4. Selection of Fans

Induced draft fans have better performance than forced draft fans.

5. Ash Cleaning Method

Mechanical dust removal is more convenient and clean than manual dust removal, but the cost of mechanical dust removal is high. Currently, pulse dust removal is mostly used.

There are three main cleaning methods for bag filters, namely pulse back blowing method, reverse airflow back blowing method, and mechanical vibration method. The pulse back blowing bag filter is currently the most widely used dust removal device in the world due to its adjustable pulse back blowing intensity and frequency, and good dust removal effect.

Adjust the air pressure of the gas source to ensure that the high-pressure pulse airflow formed by the pulse valve can effectively clean the ash. Use a large caliber air bag and a large volume pressure stabilizing tank to increase the air replenishment speed and improve the cleaning effect.

6. Air leakage and Resistance

The theoretical calculation shows that the dust removal efficiency of the bag filter reaches 99%, but it cannot be achieved in actual measurement. The main reason is the influence of air leakage and resistance. The lower the air leakage rate, the better the dust removal effect; Resistance has a certain impact on the dust removal effect. Regularly emptying the filter bag to reduce resistance can improve the dust removal effect.

7. Dust Collection Hood layout

The dust collection hood should be as close as possible to the furnace head to make it easier for dust to enter the hood, increase the dust collection amount, and reduce unorganized emission pollution.

8. Equipment Maintenance

Instrument equipment and cloth bags are prone to damage and should be repaired and replaced in a timely manner. Regularly inspect the purification chamber and filter bag, and also check for dust accumulation, water vapor, or rust spots based on abnormal fluctuations in the differential pressure in the chamber. Once the above situation occurs, it indicates that the filter bag is damaged or the operating conditions are incorrect.

Regularly inspect, clean, and replace the filter bags of the bag filter to maintain the equipment in good operating condition.

9. Filtering Speed

The filtration rate should be determined based on the nature of the smoke or dust, application situation, dust particle size, viscosity, gas temperature, water content, etc.

When the dust particle size is fine, the temperature and humidity are high, the concentration is high, and the viscosity is high, it is easy to choose a low value. Conversely, a high value can be chosen, but generally it should not exceed 1.5m/min. For dust with large particle size, room temperature, dry, non viscous, and extremely low concentration, 1.5-2m/min can be selected.

10. Filter Area

The larger the filtration area, the higher the dust removal efficiency, but the corresponding increase in cost. Therefore, the air volume should be calculated in advance and the corresponding dust collector model should be selected.

11. Secondary Dust Removal

A settling chamber is installed in front of the dust collector box to form a secondary dust removal system. Dusty gas flows slowly in the settling chamber, and the dust particles are separated by their own gravity, which can remove a portion of the large particle dust, lower the temperature, and reduce the pressure of the dust collector.

In order to improve the dust removal efficiency of the settling chamber, some vertical baffles are installed indoors, while others use louvers instead of baffles for better results. Some even change the vertical baffles to “herringbone” shaped baffles, causing small vortices in the airflow. The dust is separated from the gas by centrifugal force and touches the wall and baffle, causing the dust to settle.

Currently, dust collectors have become essential equipment for dust prevention in production, and bag filters are one of the widely used products. Understanding the factors that affect the dust removal efficiency of dust collectors and understanding the measures to improve the effectiveness are crucial for the clean and efficient production of the entire production line.