Current techniques to remove the particulates from hot gases derived from combustion or gasification of coal include the use of porous, rigid, ceramic filter elements intended to remove all particles 1 µm in diameter and larger, and to maintain permeability for extended filtration service by use of gas backflushing. Unfortunately, the use of ceramic filters has limitations, owing primarily to their inherent brittleness, long-term microstructural instabilities at operating temperatures, and poor thermal fatigue resistance. Metal filters of high-temperature corrosion-resistant alloys can offer enhanced thermal and mechanical shock resistance, and high strength—sufficient for filter assembly and operation in high frequency, high-pressure pulsing modes. In addition, alloy filters processed from high-quality spherical powders of a controlled size can utilize unique designs, be processed by many innovative methods, and joined by welding to facilitate filtration system assembly to allow novel filtration system configurations. The objectives of this study are to design and develop metallic filters having uniform, closely controlled porosity, using a unique spherical powder processing and sintering technique. The corrosion resistance of the filter materials (such as Haynes 214, Kanthal AF, and Krupp 602CA) will be evaluated under simulated PFBC/IGCC gaseous environments to determine the optimum alloy composition and filter structure. Corrosion tests also provide a means to estimate the service life of experimental filter materials, when subjected to either normal or abnormal PFBC/IGCC plant operating conditions. Metallic filters are expected to offer the benefits of non-brittle mechanical behavior and improved resistance to thermal fatigue compared to ceramic filter elements, thus improving filter reliability. Moreover, the binder-assisted powder processing and sintering techniques developed from this study will permit additional filter design capability (e.g., highly controlled filter porosity/permeability with greatly enhanced processing simplification), thus enabling more efficient and effective filtration.
Project Leader(s): Iver Anderson Principal Investigators: Iver Anderson