The fraction of carbon in char converted by steam gasification in a transport gasifier such as that being developed by Kellogg Brown and Root (KBR) was kinetically modeled. Char removed during the operation of a transport gasifier was collected, and the rate was determined using thermogravimetric analysis. Tests were performed in a simulated gasification environment containing a mixture of H2O, CO, CO2, H-2, and N-2. The steam gasification reaction rate for a North Dakota lignite at 815-950 degreesC can be estimated as dX/dt = 1.4 X 10(7) X e((-2.0 X 104lT)) X P-H2O(0.63) P-Total(-0.70) X [CO/(CO + CO2)](-1.91). This rate law was used to predict the fraction of carbon steam gasified per minute based on steam concentration. (C) 2004 Elsevier Ltd. All rights reserved.