Slag Formation and Corrosion of SiC-refractories in Biomass Gasification Reactors
CNRS, CEMHTI UPR3079 and University of Orléans, 45071 Orléans Cedex 2/France
Revision 29.01.2014, 17.02.2014
Volume 6, Issue 2, Pages 84 - 88
During the gasification of biomass, inorganic species are produced and constitute an important obstacle in this process. Inorganics are the mineral elements and compounds present in biomass apart from the main gas (CO, H2, CO2, H2O, CH4) and organic species. They play an important role on the gas phase pollution and on the corrosion of the refractory structure. The objective of this study is the understanding of the corrosion of the refractory lining by the liquid ashes (slag). The walls are externally cooled to reach a low temperature at the interface with the solid ash layer. The ashes condensate and solidify on the refractory wall. This ash layer plays the role of a thermal insulating lining to minimize the heat losses and to protect the refractory layer against all external attacks. The chosen material is a silicon carbide containing ramming paste to ensure the higher conductivity. Lab tests show a limited corrosion of the SiC ramming paste. Oxidation of silicon carbide grains by iron oxide from liquid ashes is observed. The silica quantity is higher in the liquid ashes in contact with silicon carbide grains, which leads to an increase in liquid viscosity. The refractory wall is also protected by three effects: • The highly viscous layer of ashes, which limits the slag penetration into the porosity of the ramming paste. • The low temperature of the wall, which solidifies the liquid ashes. • The no wettability of the carbon, which minimizes the slag/refractory lining interactions.
SiC refractories, biomass, gasification, miscanthus ash, corrosion
 Jinsong, Z.; et al.: Biomass-oxygen gasification in a high-temperature entrained-flow gasifier. Biotechnol. Adv. 25 (2005)  606–611  Froment, K.; et al.: Thermodynamic equilibrium calculations of the volatilization and condensation of inorganics during wood gasification, Fuel 107 (2013) 269–281  Ferbe, M.K.; et al.: Characterization of corrosion mechanism occurring in a sintered SiC exposed to basic coal slags, J. Amer. Ceram. Soc. 68 (1985)  191–197  McKee, D.W.; Chatterji, D.: Corrosion of silicon carbide in gases and alkaline slags. J. Amer. Cer am. Soc. 59 (1976)  910  Poirier, J.; et al.: Analysis and interpretation of refractories microstructures in studies of corrosion mechanisms by liquid oxides. J. Europ. Cer am. Soc. 28 (2008)  1557–1568  Zevenhoven-Onderwater, M.; et al.: The ash chem istry in fluidised bed gasification of biomass fuels. Part I: Predicting the chemistry of melting ashes and ash-bed material interaction. Fuel 80 (2001)  1489–1502  Zevenhoven-Onderwater, M.; et al.: The ash chem istry in fluidised bed gasification of biomass fuels. Part II: Ash behaviour prediction versus bench scale agglomeration tests. Fuel 80 (2001)  1503–1512  Froment, K.; et al.: Inorganic species behaviour in thermochemical processes for energy biomass valorisation. Oil Gas Sci. Technol. 68 (2013)  725–739  Bale, C.W.; et al.: FactSage thermochemical soft ware and databases – recent developments. Calphad-Computer Coupling of Phase Diagrams and Thermochemistry 33 (2009)  295–311  Berjonneau, J.; et al.: Determination of the liquidus temperature of ashes from the biomass gazification for fuel production by thermodynamical and experimental approaches. Energy & Fuels 23 (2009) 6231–6241  Urbain, G.: Viscosity estimation of slags. Steel
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