Study Of Preparation And Properties Of SiC Composite Porous Ceramics For High Temperature Dust Removal

A high-temperature dust removal system is a key subsystem of cleaning coal technology, such as IGCC and SCGP. The porous ceramic candle filter is one of the core components of the high-temperature dust removal system, there are two usual structure (simple homogeneous and asymmetrical). The life, filtering efficiency, and filtering precision of a high-temperature filtration system are determined by the mechanical property and pore structures of porous ceramic candle filters.In this study, SiO2, mullite, cordierite-bonded porous SiC composite ceramics were prepared, respectively. The aim of this thesis is to fabricate silicon carbide (SiC) porous ceramic supports with high strength and high porosity and available coating technique for filter membrane. The influences of SiC particle diameters, green body molding pressures, sintering temperatures, and the addition of pore former(graphite) on oxidation of SiC, the phase composition(XRD), microstructure(FESEM), and pore size distribution(mercury porosimetry) of SiC porous ceramic supports has been systematically studied. The relationship of flexural strength (three-point bending test) and porosity (the Achimedes method) has been also deeply analyzed, and the preparation technology, which can simultaneously improve the flexural strength and porosity of SiC porous ceramic, has been found out. The results showed that mullite-cordierite bonded porous SiC composite ceramic with the flexural strength41.29MPa, porosity42.11%, can be obtained using the preparation technology parameters of SiC particle diameter23μm,30wt%graphite addition, and sintering temperature1400℃(3h).The filter including a fiber transition layer was designed to lie between the support and the filtration membrane. It is available that using the pre-processing fiber slurry and appropriate membrance slurry to coat the filter homogeneously and intactly by air spary technique. Supports were fabricatied by dry pressing with pre-sintering process (1000-1200℃). Coating the fiber slurry composed of mullite fibers, aluminosilicate fibers and ceramics additions on the surface of supports by air spary technique. Filtration membrace slurry was spayed on the supports with dired fiber transition layer. After dried, the porous SiC composite materials were successly prepared sintering on fixed temperature. The membrane fabricated process, by air spary technique, which was able to keep the filtration membrane intact and homogeneous, the thickness of the fiber transition layer and filtration membrane is controllable, it also have a positive influnce on lower the cost and increase the efficiency. Simultaneously, energy consumption decrease by the pre-sintering process, and the support, fiber transition layer, filtration membrance were combined tightly due to the addition of bonder to fiber slurry.