During this period we have revised the Bigas computer program by refining the solid phase mass balance subroutine, SPMBL. The factor which dominates the temperatures in the combustor was discovered. The unsteady-state heat transfer for the solid phase energy balance subroutine, XIMPL, has been tested under two different operating conditions. The oxygen breakthrough problem of the Bigas Gasifier has been analyzed by bypassing 10% of oxygen and 10% of the purging gas which normally fed to the combustor and injecting them into the reducer. The Carbon Conversion measured experimentally was compared to the simulated results based on various mechanisms. The phase plane analysis and stability study of the combustor was continuously studied during this period using the simplified one stage model. The input data used for the latter study were similar to that adopted by Mountain Fuel Project. 13 figures, 3 tables.