Microstructural determination in some SiC based hot gas filter materials

Abstract

Insufficient reliability of hot gas filter materials is among the main obstacles to the replacement of traditional power generation processes with advanced, more efficient coal or biomass based routes. Knowledge of the effects of water vapour and thermal transients on microstructure and its relation to the mechanical properties of filter materials is important for understanding the material degradation process in complex operating environments, for lifetime prediction and for further materials development. In the present study, the microstructure of two advanced, commercially available SiC based clay bonded filters was characterised by scanning electron microscopy (SEM) and a quantitative X-ray diffraction (XRD) method. Porosity, density and thermal expansion coefficient of the materials were determined. The quantitative XRD method specially developed for the materials studied is described in detail. Apparent densities and coefficients of thermal expansion calculated from the determined phase compositions of the two filters were in agreement with measured values.

Mini-Review on Hot Gas Filtration in Biomass Gasification: Focusing on Ceramic Filter Candles

“…47 In summary, on the one hand, there has been significant improvement in the performance of ceramic candle filters but with significant scope remaining for further improvement to achieve a better stability and durability at the ultrahigh temperature over 800 °C. On the other hand, there are certain fundamental limitations to improvement owing to the intrinsic material properties of ceramic filters and biomass ashes; for instance, microstructural changes and the degradation of ceramic candles due to an exposure to HT water vapor environments, 87 the infiltration and slag formation actuated by the melting point decrease due to alkali-rich ashes, 85,86 and the noticeable increase in the adhesive force of calcium-rich ashes over 800 °C, especially under a CO 2 -containing condition. 88 As a result, it should be also clear that alternate routes involving medium-temperature operating conditions (<500 °C) and process-related changes should be explored to develop a more reliable and efficient hot gas cleaning technology.…”

Effects of pore size on electrical and thermal properties of porous SiC ceramics

“…Owing to their unique combination of properties, such as excellent heat resistance, good mechanical properties, tunable thermal and electrical conductivities, excellent thermal shock and corrosion resistance, and high permeability, [1][2][3][4][5][6][7][8][9][10] porous SiC ceramics have been considered as one of the most promising filter materials for molten-metal filtration, particulate filtration, hot gas filtration, and wastewater filtration. [11][12][13] They are also good candidates for use as thermal insulators, catalyst supports, gas diffusers, sandwich materials for dual-coolant lead-lithium blankets, thermoelectric energy converters, and energy materials for other advanced applications. [14][15][16][17][18][19] The performance of porous SiC ceramics in different application fields largely depends on their microstructure, porosity, pore size, thermal conductivity, electrical conductivity, mechanical strength, and permeability prop-erties.…”

Investigations on Material and Mechanical Properties, Air‐Permeation Behavior and Filtration Performance of Mullite‐Bonded Porous SiC Ceramics

“…Porous SiC ceramics are used as refractories, thermal insulating materials, gas burner media, bio-implants, catalyst support structures, catalytic membrane reactors, hot gas, and molten metal filters, etc. [1][2][3][4][5][6][7][8] SiC ceramics have a low density, high hardness, high thermal conductivity, low coefficient of thermal expansion (CTE), proven abilities to withstand high temperatures, mechanical and chemical stresses in challenging conditions which make them suitable as candidate materials for such applications. Different methods of manufacturing porous SiC ceramics were nicely discussed in two reviews of published literature.…”