Influence of coal power plant exhaust gas on the structure and performance of ceramic nanostructured gas separation membranes. (December 2015) - Eiberger, Jan
Highlights: Testing of CO2 selective ceramic membranes in direct contact with real flue gas. Membrane plugging due to deposition of fly ash and gypsum. Degradation of interlayers by water condensation and crystallite formation. Reduced degradation in the case of SiO2 based membrane layers. Pre-treatment of the flue gas (partial drying) required for membrane operation. Abstract: In this work, we investigate the effect of coal power plant exhaust gas on amino-modified mesoporous ceramic membranes. The testing of ceramic membranes in the flue gas of coal-fired power plants represents a new approach, as testing under simulated flue gas conditions has already been undertaken, but not yet during direct exposure to exhaust gas. Flue gas exposure trials were carried out at a lignite-fueled power plant and a hard-coal-fueled power plant. Most experiments were conducted using a test rig designed to bring planar membrane samples in direct contact with unconditioned flue gas in the exhaust gas channel. Another test rig was designed to test membrane modules with pre-treated flue gas. The tested membranes had an asymmetrical structure consisting of a macroporous α-Al2 O3 support coated with a mesoporous γ-Al2 O3 or 8YSZ interlayer. The microporous functional top layer was made of amino-functionalized silica. The tests revealed different degradation mechanisms such as gypsum/fly ash deposition on the membrane surface, pore blocking by water condensation, chemical reactions and phase transformation. A detailed analysis was carried out to evaluate their impact on the membrane in order to assess membrane stability under real conditions. The suitability of these membranes for this application is critically discussed and an improved mode of membrane operation is proposed.