The chemical recovery cycle, a key component of a kraft pulp mill. produces energy and regenerates the active pulping chemicals, NaOH and Na2S, from the spent pulping liquor (called black liquor). The development of gasification-based recovery technology requires information on the rates of several interrelated chemical reactions, most importantly the gasification of carbon and sulfur in the char. The sulfur emission rate during steam gasification of black liquor char was studied as a function of temperature (60-700 degrees C) and H2O and H-2 concentrations. The major sulfur-containing gas generated is H2S. Analyses of the experimental results obtained with a thermobalance system indicate that the H2S concentration in a 0.5 mm high char bed is at thermodynamic equilibrium. Therefore, the rate of H2S production is influenced by thermodynamics, the carbon gasification rate, gasification product distribution, and the mass transfer coefficient between the char bed and the surrounding gas phase. Based on thermodynamics, gasification kinetics, and a material balance, a simple expression for the H2S emission rate is derived. Good agreement is obtained between the measured and predicted rates.