With the continuous acceleration of industrial progress, high-temperature flue gas dust emitted by industrial production has also had an impact on the environment. In order to reduce the emission of harmful dust, it is necessary to adopt “high-temperature gas dust removal technology”.
High-temperature gas dust removal technology refers to the flue gas-solid separation technology for gas purification under high-temperature conditions (>260 ℃). The purified gas can be directly heat exchanged, effectively utilizing the physical sensible heat and chemical latent heat in the gas, and utilizing energy with maximum efficiency. Therefore, it has become an important research topic in high-temperature industries and filtration industries such as electricity and energy.
At present, one of the key technologies for high-temperature gas filtration is porous ceramic materials for high-temperature filtration, which is also the most commonly used filter material in high-temperature flue gas filtration at present-this is because ceramic materials are corrosion-resistant, wear-resistant, chemically stable, and have high filtration accuracy under high-temperature conditions. These advantages enable it to withstand harsh industrial conditions and gradually become one of the important high-temperature gas filtration materials.
Why choose silicon carbide? Ceramic membrane filter materials for high-temperature flue gas dust removal are mainly composed of two parts, namely, ceramic membrane and support body, which play the following roles:
(1) Ceramic membrane: The ceramic membrane is very thin and attached to the outer surface of the support body, with a thickness of only 100~200μm. It plays a decisive role in the filtration accuracy of high-temperature dusty flue gas. In addition to having high porosity and mechanical strength, it also needs to have good bonding strength with the support body and a matching thermal expansion coefficient to prevent the ceramic membrane from cracking or even peeling during use.
(2) Support body: The support body can provide reliable mechanical strength for the ceramic membrane, and can withstand multiple high-pressure backwashing “cleaning” without breaking. At the same time, it also needs to withstand the corrosion of acid and alkaline environments in high-temperature flue gas. In addition, as an important part of the ceramic filter material, the support body needs to have a larger pore size and higher porosity, and at the same time have a narrow pore size distribution to reduce the filtration pressure drop.
Currently, the ceramic filter materials that have been reported and developed can be divided into: oxide porous ceramics and non-oxide ceramics. However, oxide porous ceramic materials (alumina, cordierite, mullite, etc.) have more or less some shortcomings when dealing with harsh industrial environments, such as the high thermal expansion coefficient of alumina ceramics resulting in poor thermal shock resistance, and the poor mechanical properties and corrosion resistance of cordierite ceramics.
Taking into account the physical properties such as thermal conductivity, thermal expansion, high-temperature strength, and creep resistance, SiC has better high-temperature application advantages compared with other ceramic materials such as Si3N4 and Al2O3. Therefore, silicon carbide porous ceramics are considered to be the most promising material in high-temperature filtration applications.