How to Use Nomex Filter Bag
As for the use method of Nomex filter bag, we all know that the filter bag has high dust removal efficiency, can be used to capture dust above 0.3nm, and can purify the dusty gas to 15mg / m3 or below; It can also be used to capture the dust that is difficult to recover by the electrostatic precipitator, especially suitable for capturing fine and dry dust. The collected dry dust is easy to dispose of and recycle; The bag filter has high safety when collecting dusty gas with explosion risk or spark.
The high dust removal efficiency of the Nomex filter bag is closely related to the dust removal bag. The correct use of a Nomex filter bag can maintain high dust removal efficiency for a long time. How can you correctly use a dust removal bag?
First of all, it is important to install the dust removal bag correctly and carefully.
1. Installation mode of the external filter bag ① the bag mouth and perforated plate shall be sealed and fixed reliably. ② The Nomex filter bag is suspended vertically under the perforated plate. ③ Adjacent Nomex filter bags shall not collide with each other. ④ The Nomex filter bag shall be correctly matched with the frame, and the frame shall be straight without burrs.
2. Installation method of internal filter bag ① the upper end of the bag is equipped with a bag cap and hung on the cross beam of the dust collector through the hanging device, and the lower end is reliably sealed and fixed with the lower bag. ② The tension of the Nomex filter bag shall be adjusted to reach the specified value during the installation of the Nomex filter bag so that the Nomex filter bag will not loosen and fall off during filtration and back blowing, and it shall be adjusted again after weeks and months of use. ③ All accessories (anti deflating ring) in the Nomex filter bag shall be matched correctly, and all accessories shall be free of burr or fracture. Secondly, reliable and effective ash cleaning is required. During the use of the Nomex filter bag, the ash in the dust-facing area gradually increases, and the pressure difference increases. The dust shall be isolated through effective ash cleaning to keep the pressure difference inside and outside the Nomex filter bag within the set range. Then, it is necessary to prevent sudden abnormal conditions. When the bag filter is running, it shall prevent sudden abnormal conditions, such as sudden increase of gas temperature, entry of corrosive gas, or sudden decrease of gas temperature below the dew point, which are damaged by factors such as temperature, humidity, chemical corrosivity, mechanical wear or impact exceeding the tolerance of the bag## After that, keep up with the maintenance of the equipment. If the bag is damaged, it shall be found and replaced in time. The differential pressure change of the bag filter shall be observed frequently. If the ash cleaning fault occurs, it shall be eliminated in time. Whether the ash cleaning system works normally. If the process conditions of the dust removal system change, the ash cleaning cycle or the working system of the bag filter shall be adjusted in time.
Methods to improve the service life of Nomex filter bags:
1. New and old Nomex filter bags shall not be mixed to avoid different damage times affecting the normal operation of dust removal equipment.
2. Aging of Nomex filter bags. If it is mainly caused by the following reasons, it is necessary to investigate the causes, take elimination measures and replace the dust removal filter bag. ① Hardening and shrinkage due to abnormally high temperature; ② Reaction due to vapor contact with acid, alkali, or organic solvent; ③ React with water.
3. The filter cloth should not be hung too loose or too tight. If it is too loose, it is easy to accumulate dust, and if it is too tight, it is easy to be damaged.
4. The replaced Nomex filter bag shall be blown out with compressed air first, and then checked for holes. If any holes are repaired, they shall be reserved for replacement. If the Nomex filter bag is pasted by dust, wash it with water and leave it for replacement after drying.
5. Blockage of Nomex filter bag. When the Nomex filter bag is blocked, the resistance increases, which can be shown by the increase of the reading of the differential pressure gauge. Nomex filter bag blockage is the main cause of Nomex filter bag wear, perforation, and falling off. Check and repair the causes of dust removal bag blockage according to the table below. Generally, the following measures shall be taken: ① temporarily strengthen ash cleaning to eliminate the blockage of Nomex filter bags; ② Replace the Nomex filter bag partially or completely; ③ Adjust installation and operating conditions.
The protection measures of the Nomex filter bag mainly include the following:
1. Prevent the dust bag of bag filter from being damaged by oil mist
For example, when the coal-fired boiler industry starts the bag filter and reduces the load to operate the bag filter, fuel oil will be put in. At this time, there is a large amount of oil mist in the flue gas of the bag filter, which will directly endanger the service life of the bag, so preventive measures need to be taken. The dust-containing flue gas condition of the bag filter is slightly different under the two conditions. When the bag filter unit is started, it mainly depends on fuel oil's ignition and temperature rise. Under the load reduction operation condition of the bag filter, the fuel oil is used as combustion support, and the oil mist content in the dusty flue gas of the bag filter is relatively small. Moreover, due to the high temperature of the flue gas, dust removal equipment, and pipeline of the bag filter, the damage to the bag of the bag filter is relatively light. Therefore, water repellent, oil proof, and dust bag or film-coated dust bag shall be used
2. Prevention and measures of high-temperature flue gas harm to bag filter
When the temperature of the dust-containing flue gas of the bag filter is higher than the temperature that the bag hand can bear, cooling measures shall be taken for the flue gas of the bag filter. There are two specific cooling measures:
Cooling by cold air: an automatic control valve for low-temperature air (generally atmosphere) is set on the flue in front of the inlet baffle door of the bag filter. Under normal conditions, the valve is closed. In case of abnormal working conditions (the smoke temperature of the bag filter exceeds the temperature that the bag can bear), the door will automatically open and cool the air to protect the bag. In this method, it should be noted that the position of the cold air into the bag dust collector should be as far away from the bag dust collector as possible, because the general smoke speed is relatively high, and the cooling effect can be achieved only by fully mixing the cold and hot air in the bag dust collector.
Spray mist cooling: a group of atomizing nozzles for cooling are set in the inlet valve flue of the bag filter. The nozzle's connecting pipe is connected with the pressure water source through an automatically controlled solenoid valve. When the dust-containing flue gas of the bag filter is higher than the temperature that the bag can bear, the solenoid valve will open automatically, and the nozzle will spray water mist to absorb the heat of flue gas. If this measure is adopted, it should be noted that the farther the nozzle is from the bag dust collector, the better. Because the smoke speed of the bag dust collector is relatively high, the atomized water droplets of the bag dust collector should be fully mixed with the flue gas to vaporize and absorb heat to achieve the cooling effect of the bag dust collector.
Waste heat utilization: flue gas is the main way for general energy-consuming equipment to waste energy. It is to convert the heat carried by the flue gas in the bag-type dust collector into usable heat in some way. Waste heat utilization is to install the heat pipe waste heat recovery device in the flue of the bag type dust collector, recover the waste heat of the flue gas, and heat it into the air. The heat pipe waste heat recovery device is suitable for large-scale industrial kilns. The equipment has the advantages of convenient installation, safety and reliability, long service life, and energy saving
3. Preventive measures against the harm of low-temperature flue gas of bag filter
When the temperature of the dust-containing flue gas of the bag-type dust collector is low, the flue gas may be bedewed. In some bag-type dust collectors at the kiln tail with dry cement, the excessive content of flue gas and the excessive saturated water will produce dewing after analysis. At this time, reduce the amount of water spray or increase the drying system to minimize the occurrence of dewing. It is necessary to take measures to raise the temperature of flue gas and heat preservation of the bag filter. When the bag-type dust collector is in daily use, ensure that the dust-containing flue gas of the bag-type dust collector is more than 20 ℃ higher than the dew point
