A complete CFD model for the char burning stage of chemical recovery from black liquor is presented. Chemical recovery from black liquor is characterized by the occurrence of multiple, simultaneous reactions occurring in dynamic flow conditions. Rate equations for the different chemical reactions are incorporated into a multiphase CFD code MFIX. Rate equations for sulfate reduction by carbon, gasification of carbon by CO2 and H2O, and, COS and H2S formation, are incorporated into MFIX, to simulate the chemical kinetics occurring in the char burning stage. Oxidation of carbon and Na 2S by O2 are also included.;Pyrolysis of black liquor char in the presence of N2, gasification in the presence of CO2 and H2O were simulated. Results for pyrolysis and gasification, and variation with respect to temperature are presented. Two different models for sulfate reduction are compared with each other and with published experimental results. Competitive consumption of carbon by sodium sulfate and gasification reactions is studied and the effects of temperature, and heating rates of solids are discussed.
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