Fabrication of robust SiC ceramic membrane filter with optimized flap for industrial coal-fired flue gas filtration

Abstract

Silicon carbide (SiC) filter candles are particularly suitable for the purification of industrial coal-fired flue at high temperatures. However, the filters are prone to break due to the lack of bending strength, especially at the filter flap, which limits its application field and service life. In this work, the SiC filter candles with optimized flap for the removal of fly ash from the industrial coal-fired flue gas were presented. The bimodal particle size distribution of SiC powders were employed to prepare the SiC filter flap to increase the number of neck connections among the SiC particles. The bending strength of filter flap was enhanced from 18.0 MPa to 37.0 MPa while the gas permeability did not exhibit obvious decline. Besides, the SiC filter candles presented a good thermal shock resistance due to the similar coefficient of thermal expansion of SiC filter flap (5.6 × 10−6 /K, 300–450 °C) and pipe body (5.0 × 10−6 /K, 300–450 °C). When the dust-containing flue gas with high temperature (300–450 °C) passed through the SiC membrane filtration equipment, dust was removed efficiently, and downstream equipment were protected from blocking and fouling. When the surface velocity of flue gas was set at 0.8 m/min and the back flushing pressure was set at 0.6 MPa, the pressure drop was fairly stable with minor fluctuation from 2420 Pa to 2700 Pa. Meanwhile, the outlet dust concentration and filtration efficiency of coal-fired flue gas were below 5.0 mg/m3 and above 99.98 %, respectively. This work provided a robust and high-efficiency SiC filter for the purification of industrial flue gas containing submicron-sized solid particles.