Thermodynamics of Refractories for Black Liquor Gasification
FactSage® thermodynamic software was used to analyze the phases present in black liquor and to predict the interaction of black liquor with different refractory compounds. Black liquor is a water solution of the non-cellulose portion of wood (mainly lignin) and spent pulping chemicals (Na 2CO3, K2CO3, and Na2S). Modeling included prediction of phases formed under operating conditions of a high temperature black liquor gasification (BLG) process used in the pulp and paper industry. At the operating temperature of the BLG, it was predicted that the water would evaporate from the black liquor and that the organic portion of black liquor would combust, leaving a black liquor smelt composed of sodium carbonate (70-75%), potassium carbonate (2-5%), and sodium sulfide (20-25%). Exposure of aluminosilicates to this smelt leads to significant corrosion due to formation of expansive phases and, subsequently, cracking and spalling. Oxides such as ZrO2, CeO2, La2O3, Y 2O3, Li2O, MgO and CaO are resistant to black liquor smelt but non-oxides such as SiC and Si3N4 are oxidized and dissolved by the smelt. Other candidates such as MgAl 2O4 and BaAl2O4 are resistant to sodium carbonate but not to potassium carbonate. LiAlO2 shows stability against both sodium carbonate and potassium carbonate. Candidate materials selected on the basis of the thermodynamic calculations are being tested by sessile drop test for corrosion resistance to molten black liquor smelt.
W. Fahrenholtz et al., "Thermodynamics of Refractories for Black Liquor Gasification," Ceramic Transactions, American Ceramic Society, Jan 2005.
Materials Science and Engineering
Keywords and Phrases
Black Coatings; Black Liquor Gasification (BLG); Expansive Phases; Gasifiers; High Temperature Effects; Liquor Smelt; Thermal Expansion; Computer software; Oxidation; Refractory materials; Thermodynamics
Article - Journal
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