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Asymmetric composite tubular membranes were prepared with SiC as the support body and mullite as the membrane layer. The asymmetric mullite/SiC composite filter tube membranes were characterized by different analytic techniques. The mullite membrane was prepared as a layer on the SiC support with a thickness of about 175 μm, pore size of about 1-10 μm and porosity of 9.9%. The SiC support tube had a pore size of about 20-150 μm and porosity of 19.0%. After 360 days of high-temperature flue gas filtration, the most available pore size of the mullite/SiC composite filter tube membrane reduces from 45.2 to 36.4 μm (the reduction rate of about 19.4%). Analysis of the dust collected by back-blowing revealed that the dust particle size range was between 0.1-100 μm and about 50%of the dust particles were below 2.5 μm in size. The average capture rate of dust can reach 98.4%, indicating that the asymmetric mullite/SiC composite filter tube membrane has excellent filtration performance for the dust below PM2.5 in the high-temperature complex flue gas.

Porous ceramic fiber membranes with high gas permeance have shown great potential for the treatment of dust-laden gas. However, a major challenge is posed by the micro or nano-sized solid particles which can easily block the pore channels of the fiber membranes due to the larger surface pore size. Therefore, in this work, a novel method was proposed for the in-situ growth of mullite whiskers around the surface of the mullite fibers. This method aimed to decorate the pore channels of the fiber membranes by using a layer-by-layer construction strategy. For this purpose, a dry-pressing technique was employed to prepare a "green" mullite fiber support. It was followed by the preparation of another "green" fiber layer with the addition of catalysts on this support. After the co-sintering process, hierarchical mullite whiskers with gradient pore structures were produced. The in-situ growth of mullite whiskers around the fibers decorated the pore structure. As a result, it helped in effectively capturing the solid particles in the dust-laden gas. Additionally, the co-sintering process significantly reduced the sintering consumption and fabrication period. Moreover, a detailed investigation was carried out on the construction parameters including the sintering system atmospheres, Si–Al sol addition content, AlF 3 concentration, mechanism of whisker growth and stability. The findings showed that hierarchical mullite whisker/fiber membranes obtained from the proposed method had a mean pore size of 2.7 μm and gas permeance of ∼106 m3 m−2 h−1·kPa−1. The Darcy's permeability coefficient of the membranes was also higher than the membranes prepared from existing methods. Moreover, the optimized membrane showed 99.9% rejection of the solid particles in the dust-laden gas, including micron-size (2.5 μm) and nano-size (300 nm) solid particles. This work provides a novel method for the fabrication of hierarchical mullite whiskers with gradient pore structures having the capability to filter industrial dust-laden gas. [Display omitted] • Hierarchical mullite whisker/fiber membranes were produced by using co-sintering technique. • The in-situ grown whiskers decorated the mullite fiber supports with gradient pore structures. • The membrane exhibited high Darcy permeance compared with the literature. • The membrane showed above 99.9% rejection towards PM0.3 and PM2.5 nanoparticles. [ABSTRACT FROM AUTHOR]

Abstract: Monodispersed W/O emulsions were prepared by using submerged membrane emulsification apparatus with a mullite ceramic membrane. Kerosene was used as the continuous phase and water was used as the dispersed phase. The effects of stirring speed and transmembrane pressure on droplet size and dispersed flux were studied. The droplet size of the emulsions decreased with increased stirring speed but increased with increasing transmembrane pressure. The flux of the dispersed phase was proportional to transmembrane pressure, decreased with increasing stirring speed at a low transmembrane pressure and increased slightly at a high transmembrane pressure. The effect of pre-soaking time on the emulsification result was also investigated. [Copyright &y& Elsevier]