| Membrane separation technology has been widely used in energy, environmental protection, petrochemical, food and other fields, and has the advantages of high strength, high temperature resistance, good chemical stability, long service life, easy regeneration and separation efficiency higher of porous ceramic filtration membrane is the most significant. As the core component of the high efficiency cross flow filter, it has broad application prospects in high temperature, corrosion resistance and other harsh environments. Ceramic membrane structure design and optimization is the premise of its application, the key is how to achieve a good balance between high permeability flux and separation accuracy. The asymmetric membrane structure design is an effective method to solve the problem, asymmetric membrane by supporting body, transition layer and microporous membrane composition, high porosity and large aperture of the supporting body with low fluid resistance and meet the high permeability, and give the membranous layers of mechanical support; fine particles composed of surface film layer of small aperture, small thickness, with better separation accuracy; the support of large particle size difference and the film by transition layer structure be regulated. This paper mainly studies the porous ceramic support and film preparation method, microstructure, geometric size, permeability and mechanical strength, to provide theoretical guidance and experimental support for the development and application of porous SiC ceramic membrane.In the first place, the method of preparing porous silicon carbide ceramic support by compression molding and low temperature sintering was studied. The porous silicon carbide ceramic body was prepared by using 34 μm silicon carbide particles, adding 12% low temperature binder and 1.5% dextrin solution, using the molding method, adjusting the forming pressure and sintering temperature. In the preparation of porous silicon carbide ceramics, sintered at 850℃, 870℃, 900℃ and 950℃, with the increase of sintering temperature, gas permeability by 322.66 m3/m2·h·kPa to 361.82 m3/m2·h·kPa, after and reduced to 308.24 m3/m2·h·kPa, and the open porosity rate of gas permeability effect is more remarkable. Dead end filtration method show that with porous SiC ceramic filter thickness by 2.3 mm to 7.5 mm process water permeation flux decreased linearly; in a certain thickness, with increase of open porosity, water permeation flux increased rapidly; in 50 MPa forming, 870℃ when firing prepared open porosity was 38.4%, the compressive strength 83.2 MPa, gas permeability is 361.82 m3/m2·h·kPa porous SiC ceramic supporting body.Secondly, stabilized silicon carbide ceramic slurry prepared by adding dispersing agent and anti foaming agent. Pure CMC solution viscosity and CMC increase exponentially, the solution of static for 60 h process, viscosity increased, then decreased gradually; after the addition of different particle size of the SiC, the viscosity of the fluid and solid content is an index of the relationship; solid content at the same time, CMC content is high, suspension stability is better; CMC is the same, with the increase of the solid content, the suspending stability of raise. The sedimentation experiment indicates that the prefabricated slurry 0.5% CMC, 55% solid content, static stability of suspension in 2 h of 100%, static stability of suspension in 5 h of 98%.Finally, the film prepared by dip-coating method for porous ceramic tube outer surface, the maximum pore size of 65 μm, Φ60 mm. With the viscosity and solid content is increased, the pulling of preparing SiC coating thickness increased; and pulling rate by 1 mm/min to 1000 mm/min, SiC coating, the thickness decreased. When the thickness of the film is increased from 176 μm to 804 μm, the gas permeability is reduced from 302 m3/m2·h·kPa to 235 m3/m2·h·kPa, and the thickness and gas permeability is linear. |
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