Analysis and solution of condensation phenomenon in pulse bag filter
The pulse bag filter is widely used by the users due to its advantages of large air volume, small system resistance, complete cleaning, partial desulfurization and defluorination, and high dust removal efficiency. However, many dedusters have more or less dew condensation during use. If it is not properly solved, the corrosion of the dust collector will be intensified, the filter bag will be hydrolyzed, and the service life of the dust filter will be shortened. In severe cases, dust can be stuck on the surface of the filter bag to plug the pores of the filter bag, causing the resistance of the filter to increase sharply until Can not run.
First, the cause of condensation Analysis of the so-called condensation, in layman's terms, refers to the phenomenon of saturated moisture containing moist air at a certain pressure and temperature. The temperature at which moisture is extracted is called the dew point.
The higher the gas pressure in the saturated state, the lower the dew point. The higher the moisture content in the air, the higher the dew point temperature. When the moisture content in the air is constant and the moisture-containing air temperature is lower than the dew point temperature, moisture will be formed in the supersaturated air, which will cause condensation; when the air temperature is higher than the dew point, no moisture will be precipitated. No condensation will occur. In addition, if the smoke contains SO2 components, the more SO2 content, the higher the dew point of the flue gas.
II. Causes of condensation caused by the pulse bag filter 1. The air leakage phenomenon of the dust collector Due to the air leakage phenomenon of the dust collector, a large amount of cold air from the outside is sucked into the dust filter, which causes the air temperature of the dust filter to drastically drop, and the air Water is analyzed and condensation occurs.
There are many reasons for the air leakage of the dust collector. There is a leakage welding phenomenon during the process of installation and installation of the dust collector. The air leakage is caused by the evacuation of the unloading device. There is a leakage of the non-standard pipe during the installation. There is a loose seal between the dust collector and the non-standard pipe flange, causing air leakage and so on.
2. When the moisture content in the flue gas is too high When the moisture content in the treated flue gas is too high, supersaturated water is analyzed and condensation occurs. This phenomenon is particularly prominent on the kiln-end dust collector of the cement dry-process line. Because the flue gas of the cement-dry-line kiln is generally cooled and tempered using a humidification tower, when the amount of water sprayed is too large, the flue gas is generated. Moisture condensation occurs when moisture is supersaturated.
3, flue gas temperature is too low When the temperature of the flue gas treated by the dust collector is close to or lower than the dew point temperature, condensation may also occur.
4. Pulse jet gas temperature too low The dust filter used in the pulse jet cleaning process is compressed air, and the compressed air itself is a saturated air with a relative humidity of 100%. Since the atmospheric pressure is greater than atmospheric pressure, the dew point converted to atmospheric pressure is lower than the ambient dew point and there is a tendency to dew condensation. When the temperature of the compressed air is not much different from the temperature of the flue gas inside the dust collector, condensation does not generally occur. However, in the winter, especially in northern China, when the winter temperature is usually at minus ten or dozens of degrees, the pulsed compressed air and the flue gas temperature inside the dust collector are too different. When the compressed air is instantaneously injected into the filter bag, The temperature also drastically decreases, and usually a high-speed airflow that condenses mist is sprayed in a white mist, and the temperature is lower within a certain distance below the nozzle to form a low-temperature zone. Since the compressed air in the nozzle is saturated air, the drop in temperature after the gas is ejected causes the water in the area to be analyzed and cause condensation. The condensation at this time is mainly concentrated on the surface of the injected filter bag. The dust adhering to the surface of the filter bag is absorbed by the condensed moisture, resulting in adhesion and blocking of the pores of the filter bag, resulting in the dust collector not working properly.
5. The dust collector shell has no heat insulation and insulation measures or the effect is not good. The shell of the dust collector generally adopts a steel plate structure, and the thermal conductivity of the steel plate is very large. When the temperature of the outside air forms a large temperature difference with the temperature of the flue gas inside the dust collector. At that time, dew condensation occurs on the dust collector housing. If the shell of the precipitator does not adopt thermal insulation measures, or although measures for thermal insulation are taken, the condensation of the precipitator is inevitable when the effect is not good.
Third, the pulse bag filter dust collector solution phenomenon 1, to reduce the dust collector leakage phenomenon (1) dust collector in the production and installation process, we must strictly implement the JC/T532 welding standard welding, eliminate dust collector less welding, leakage Welding phenomenon.
(2) The discharge port of the precipitator should be equipped with an air lock device with good sealing performance. At present, it is mainly based on pneumatic or electric lock valves. When necessary, two-stage wind locks can be used.
The leakage rate of a pulse bag filter should be controlled within ≤ 3%.
2. Strictly control the water spray volume of the humidification tower When the cooling device of the cement dry-line kiln adopts a humidification tower, it cannot unilaterally pursue the cooling effect and increase the amount of water spray. It must be strict under the condition of ensuring the inlet temperature of the dust collector. Control the spray volume of the humidified tower. The humidification tower uses high-quality spray guns as much as possible to make the sprayed water fine and uniform, and achieve the best cooling and quenching effect with the least amount of water.
3, the stability of the flue gas temperature in a relatively small range When the treatment of flue gas temperature is too high, it must immediately take to reduce the operating temperature, let cool air and other cooling measures; when the flue gas temperature is low, it is necessary to immediately increase the operating temperature and other warming Measures. The flue gas temperature can be stabilized within the specified range to ensure the normal and stable operation of the dust collector and reduce the condensation phenomenon.
4. Reducing the temperature difference between the pulse jet gas and the internal flue gas of the dust collector and the dehumidification process The common gas supply routes for the current domestic compressed gas are mainly: Compressed air—Air storage tank—Triple air supply—Airbag— - Pulse valve. This type of gas supply has the advantages of low investment and simple equipment. However, when the outside air temperature is too low, the compressed gas is not sufficiently processed and the condensation is easy.
When the outside air temperature is too low and the air compressor station is far away, the air supply route can be: compressed air - air tank - air source triple unit - air dryer - air heater - air bag (gas Package laying insulation material) - pulse valve. This kind of gas supply method is fully and thoroughly dehumidified, and the temperature difference between the pulsed injection gas and the flue gas inside the dust collector is small, and condensation does not easily occur. When the air compressor station is not far away and the air filter in the air source triplet can meet the dehumidification requirement, it is sufficient to pay attention to placing the air filter close to the air bag. Therefore, the air dryer can be omitted. When the temperature is too low, gas pipelines, air bags, and pulse valves must all adopt insulation measures to prevent the condensation of compressed air and dew condensation.
5, to strengthen the dust collector heat insulation measures The dust collector shell must take the heat insulation measures, the dust collector heat preservation generally uses the rock wool, the aluminum silicate board, the pearl expands the rock and so on the thermal conductivity coefficient is low, the heat insulation performance is good, the water absorption rate is low , good heat-resistant insulation material. The thermal conductivity of the material is generally not more than 0.23W/m. K. The thickness of the insulation material should be determined according to the geographic location, the local minimum temperature, and the average annual temperature, which can be calculated and determined according to the calculation formula of the “control unit heat loss methodâ€.
IV. Summary In conclusion, there are many causes of condensation caused by the pulse bag filter. We must comprehensively study the causes of the condensation of the dust collector, fully recognize the harmful effects of condensation on the dust collector, and effectively adopt effective insulation and defense measures. The condensation phenomenon of the dust collector is controlled in the lowest range, so that the pulse bag filter can be operated in a long-term and stable manner.
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