Advantages of metal filter bags in the field of high temperature flue gas dust removal

With the rapid development of the heavy chemical industry, the pollution problem has become increasingly prominent, and the emission control of soot particle pollutants has become more and more important. In terms of high-temperature flue gas dust removal, the metal fiber felt filter bag is characterized by its high temperature resistance, flameproof and explosion-proof, stable filtration accuracy, With the advantages of low emission concentration and environmental friendliness, it can be used in high-temperature flue gas dust removal industries such as coal-fired boilers in power plants, oil and gas separation, gas purification, calcium carbide furnaces, cement manufacturing, chemical catalyst recovery, garbage incineration, and electric furnace steelmaking.

High-temperature flue gas is the main air pollutant in heavy chemical industry, and soot-like particulate matter should be one of the main control objects. From July 1, 2014, according to the latest standards, the emission concentration of particulate matter in key areas is controlled below 20mg/m3. At present, in the dust removal of boiler flue gas, bag filter has been widely used due to the advantages of high dust removal efficiency, low investment cost and low emission concentration, but there are also problems such as bag sticking, bag breaking, bag burning, etc. The filter material in the bag filter puts forward higher requirements. In this case, the metal fiber felt filter bag came into being.

Advantages:

2.1 High temperature resistance

The metal fiber felt can be used for direct filtration at high temperature, without the need for a complex cooling process, thus reducing energy consumption and recycling waste heat; at the same time, it can protect downstream equipment and enable single-phase separation of downstream products, which solves the problem of chemical production. There are many problems that cannot be separated and have to increase the process chain. For example, in the application of calcium carbide furnace, the tar will be vaporized at above 260 ℃, and the metal fiber felt will not block the filter material during high temperature filtration. Another example is that it is used in the precious metal recycling industry. Some precious metals are gaseous at high temperature. If the temperature is lowered, the precipitation cannot be effectively separated from the dust. At present, the high temperature filter materials such as PTFE and aramid on the market can withstand a temperature of up to 260 °C, and with the fluctuation of temperature, the properties will change greatly. There are many kinds of metal fiber materials, such as 316L, 310S, Hastelloy, iron-chromium-aluminum alloy, etc. Depending on the material, the temperature resistance can reach up to 1000°C.

2.2 Flameproof and explosion-proof

In recent years, dust explosion accidents have occurred frequently in some industries, causing great harm to people's lives and property safety. There are many reasons for these accidents, but they are all related to the failure to set up a reasonable dust collector or dust collector filter material. If pure metal filter material is used, the occurrence of such accidents can be effectively reduced.

2.3 The filtration precision is stable

When the bag filter works at high temperature, the hole diameter of the bag will increase due to the thermal expansion effect, while the metal material is stable within the allowable temperature range. At present, the most commonly used cloth bags that can meet the emission standards are PPS membrane filter materials and PTFE filter materials. In the case of pressure, the bubble point of the flexible cloth bag is lower than that of the metal fiber felt, indicating that the bubbles are more likely to emerge from the bag hole. Therefore, in actual use, the pore size of the cloth bag is affected by the dual effects of temperature and pressure, the pore size will increase, and the filtration accuracy will be affected. The metal fiber felt filter material does not have this problem.

2.4 Low emission concentration

VDI test is an international standard for bag filter filter material testing. According to the technical requirements of bag filter (GB/T 6719 - 2009): firstly carry out 30 times of constant pressure (1000Pa) injection process, test and calculate the initial dust removal efficiency, outlet dust concentration and residual pressure drop of the filter material; then carry out 1 10,000 times of aging injection process; then 10 times of constant pressure injection and recovery process; finally, 30 times of constant pressure injection process to obtain various data of the aged filter material, the results can be seen that the discharge of metal fiber felt Concentrations can approach "zero emissions". Adjusting the emission concentration can be achieved by adjusting the structure.

2.5 Environmentally friendly

At present, most of the expired cloth bags have not been properly disposed of, and almost all of them are disposed of as garbage, or incinerated or buried. However, after its incineration, it will produce toxic and harmful gases such as HF and a large amount of dust, causing secondary air pollution; the biodegradability of synthetic chemical fibers is poor, and the permeate from landfills will cause groundwater and surface water pollution. Can't be reused for hundreds of years. The metal fiber filter bag is a pure metal product, which can be recycled and will not have a bad impact on the environment.

In conclusion:

Compared with the existing filter materials, the metal fiber felt filter bag has excellent properties such as high temperature resistance, good air permeability, low pressure loss, corrosion resistance, easy processing and forming, and will be more and more widely used in coal-fired boilers in power plants, Oilfield oil and gas separation, gas purification, calcium carbide furnace, cement manufacturing, chemical catalyst recovery, waste incineration, electric furnace steelmaking and other high temperature flue gas dust removal industries.