Pulse bag filter dew condensation phenomenon:
The so-called condensation, in layman’s terms, refers to the phenomenon that saturated air is precipitated with moist air under 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.
Causes of condensation in pulse bag filter
1. There is a phenomenon of air leakage in 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 collector, so that the local air temperature of the dust collector is drastically decreased, water in the air 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 leakage of the air leakage is caused by the loosing of the unloader. There is a leakage of the non-standard pipeline during the installation process. There is a loose seal between the dust collector and the non-standard pipe flange, causing air leakage and so on.
2. 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. As the flue gas of the cement-dry-line kiln is generally cooled and tempered using a humidification tower, the amount of water sprayed is too large, resulting in smoke Moisture condensation occurs when moisture is supersaturated.
3. The temperature of the flue gas is too low: When the temperature of the flue gas processed by the dust collector is close to or lower than the dew point temperature, condensation will also occur.
4. The temperature of the pulse jet gas is too low: the dust collector uses compressed air during the pulse jet cleaning process, and the compressed air itself is 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. 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 the pores of the filter bag are blocked, resulting in malfunction of the filter. .
5, the dust collector shell has no heat insulation measures or effect is not good: the shell of the dust collector generally adopts steel plate structure, and the thermal conductivity coefficient of the steel plate is very large, when the temperature of the outside air and the temperature of the flue gas inside the dust collector form a large temperature When it is bad, 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.
Solution to the phenomenon of condensation in pulse bag filter
1. Reduce the air leakage phenomenon of the dust collector: (1) During the process of production and installation, the dust collector must strictly implement the JC/T532 welding standard for welding, and eliminate the phenomenon of less welding and missing welding of the dust collector. (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 humidifying tower: When the cooling device of the cement dry-line kiln adopts a humidifying tower, it can not unilaterally pursue the cooling effect and increase the amount of water spray, and must ensure the inlet temperature of the dust collector. Strictly control the water spray volume of the humidification tower. The humidifying 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 smaller range: When the temperature of the treated flue gas is high, it is necessary to immediately take measures to reduce the temperature of the operating temperature, put the cold air; when the flue gas temperature is low, it must be taken to improve the operating temperature, etc. Warming measures. The flue gas temperature can be stabilized within the specified range, ensuring the normal and stable operation of the dust collector and reducing the condensation phenomenon.
4. Reducing the temperature difference between the pulse jet gas and the internal flue gas of the dust collector and the de-wetting treatment: The current commonly used gas supply routes for the domestic compressed gas are mainly: compressed air – gas tank – gas source triple unit – air bag – Electromagnetic 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 dew 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, thus eliminating the need for an air dryer. When the temperature is too low, gas pipelines, air bags, and pulse valves must all adopt insulation measures to prevent condensation of compressed air and condensation from the dust collector.
5, to strengthen the dust collector insulation measures: the dust collector shell must take measures to insulation, dust collector insulation generally use rock wool, aluminum silicate board, pearl expansion rock and other thermal conductivity is low, good thermal insulation, water absorption Low, good thermal 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 “control unit heat loss method”.