Pulse bag filter with its advantages of large air volume, small system resistance, thorough dedusting, partial desulphurization and defluorination function, and high dust removal efficiency, has been widely used by users and has been widely used in the dust removal market. 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.
1. analysis of the causes of condensation
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
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.
Second, the cause of condensation caused by pulse bag filter
1, there is a leakage of dust collector
Due to the phenomenon of air leakage in 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 reduced, water in the air is analyzed, and condensation occurs. The
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 poor sealing of the discharge device. The leakage of the non-standard pipe during the installation process results in the leakage of air. 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. Because 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 smoke temperature is too low
Condensation can also occur when the temperature of the fumes processed by the precipitator approaches or drops below the dew point temperature.
4, pulse injection gas temperature 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. 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, and the air bubbles in the filter bag are blocked, resulting in the dust collector not working properly.
5, dust collector shell has no heat insulation measures or poor results
The shell of the dust collector generally adopts a steel plate structure, and the thermal conductivity coefficient of the steel plate is large. When the temperature of the outside air forms a large temperature difference with the temperature of the flue gas inside the dust collector, condensation occurs on the shell of the dust collector. 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 condensation phenomenon
1, reduce the dust leakage of the dust collector
(1) In the process of production and installation of the dust collector, the JC/T532 welding standard must be strictly performed for welding, and the phenomenon of less welding and missing welding of the dust collector should be avoided. The
(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
The leakage rate of a pulse bag filter should be controlled within the ≤3% range.
2. Strictly control the water spray volume of humidifying tower
When the cooling device of the cement dry-line kiln adopts a humidifying tower, the water spray volume cannot be increased in pursuit of the cooling effect, and the water spray volume of the humidifying tower must be strictly controlled under the condition that the inlet temperature of the dust collector is ensured. 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, stable smoke temperature in a smaller range
When the temperature of the treated flue gas is high, cooling measures such as reducing the operating temperature and releasing the cold air shall be adopted immediately; when the temperature of the flue gas is low, measures for increasing the temperature such as increasing the operating temperature shall be taken immediately. 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. Reduce the temperature difference and desiccant treatment between the pulse jet gas and the dust inside the dust collector
At present, the commonly used gas supply routes for domestic compressed gas are mainly: compressed air – gas storage tank – triple gas supply – air bag – 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. The
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. The temperature difference between the pulsed gas and the dust 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, strengthen the dust collector heat insulation measures
The shell of the dust collector must be insulated and insulated. The insulation of the dust collector generally adopts rock wool, aluminum silicate board, pearl swelling rock and other thermal insulation materials with low thermal conductivity, good thermal insulation performance, low water absorption, and good heat resistance. The thermal conductivity of the material is generally not more than 0.23W/m. K. The thickness of the insulation material shall 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”.
Fourth, summary
In short, there are many causes of condensation in the pulse bag filter. We must comprehensively study the causes of the condensation of the dust collector, fully recognize the danger caused by the condensation to the dust collector, and effectively adopt effective insulation and defense measures in an effort to remove the dust collector. The condensation phenomenon is controlled in the lowest range, enabling the pulse bag filter to operate in a long-term and stable manner.