Hot gas cleaning is one of the key technological barriers remaining in the development of advanced coal-fired power plant combustion cycles. Despite research and development over the last two decades, the problems of hot gas cleaning have yet to be resolved. Recent analysis suggests that the metallic candle filter is one of the most promising approaches to hot gas cleaning for advanced coal conversion technologies. A unique spherical powder processing and sintering technique is being developed to fabricate metallic filters having uniform, closely controlled porosity. A Ni-based superalloy, Haynes 214, was selected for initial trials of this processing technique based on its reported ability for stable alumina scale formation and retention of useful strength beyond the 850°C requirement of advanced power applications. High pressure gas atomized powder samples of Haynes 214-alloy were tap densified and sintered to densities ranging from 64% to 74% and ambient temperature transverse rupture strengths Tom 272 MPa to 613 MPa, respectively. Microstructural analysis revealed the sintering conditions necessary to produce open permeable pore networks and sufficient interparticle bonding. Permeability measurements indicated that the initial filter flow characteristics of the sintered samples equaled the levels of high performance Sic filters. The corrosion resistance of these filter samples and a complete collection of alloy alternatives remain to be evaluated under simulated gaseous combustion environments to determine the suitability of this filter structure and to allow improved alloy selection.
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