Catalytic Combustion Of Sulphur-bearing Gasified Biomass

The main advantages of catalytic combustion are ultra-low emissions of nitrogenoxides （NOX）, carbon monoxide （CO） and unburned hydrocarbons （UHC）, also to stabilisecombustion of low heating value gas at relatively low temperatures. Catalytic combustion isone of the most promising processes to produce environmentally clean energy. However,the utilization is prevented by the complexity of the composition for the gasified biomasswhich contains certain amount of impurities such as sulfur..Nowadays the research ofcatalytic combustion focuses on how to prepare the catalysts which can stabilise theignition and combustion also have a certain resistancefor S poisoning.The influence of sulphur on catalytic combustion of gasified biomass for gas turbineapplications has been studied over precious metal and metal oxide based catalysts, namelyPd/LaAl₁₉₁₉O₁₉9, Pt/LaAl₁₉₁₉O₁₉9, Pt/La_0.5Ba_0.5Mn_0.5Fe_0.5Al₁₉₁₉O₁₉9,La_0.5Ba_0.5Mn_0.5Fe_0.5Al₁₉₁₉O₁₉9.The samples were washcoated on cordierite monoliths and characterized by means of XRD,BET. Besides they were tested in a bench scale reactor with a synthetic low-heating valuefuel mixed with air. The fuel gas, that resembles the gas from air-blown fluidised bedgasification of biomass, was composed of H₂, CO, CH₄, N2and O2. Also50ppm hydrogensulphide were added to the fuel gas. Combined the characterization results of XPS, SEMand FTIR after the activity tests, a preliminary analysis of the mechanism for the sulfurpoisoning of the catalysts were deduced.It was found that percursosr obtained after calcination at₁₉200℃still maintain arelatively high surface area, indicating that the catalyst has a strong stability andcapabilities for resistance to high temperature sintering, besides XRD analysis showed thatthe percursosr were aclcined at₁₉200℃for4hours leads to the formation of a finalmonophasic materials. After loading for the precious metals a weak diffraction peaks of Ptand PdO appearanced. The results also show a excellent catalytic activity whichsignificantly reducing the ignition temperature of combustible ingredients, besides allsamples were deactivated to some extent by addition of sulphur, although poisoning of thecatalytic combustion for each fuel component varied depending both on the active phase and on the support and generally was reversible. The palladium catalyst was severelydeactivated for combustion of methane, although activity for carbon monoxide andhydrogen was almost maintained. Platinum catalysts were more severely poisoned forcarbon monoxide and hydrogen, but not for methane. Metal oxide catalysts were severelydeactivated for all fuel components, especially for carbon monoxide, The samplescharacterised by ICP,SEM+EDX, XPS showed that the poisoning processes mainly throughthe formation of sulfate which deposition on the surface composition, then covered theactive site which turn into a blunt surface sulfate, resulting a decrease in catalytic activity.