This report presents process analysis of the Process Demonstration Unit (PDU) operations and is a continuation of the process analysis work performed in FY-1980 through 1983 and reported in Process Analysis Topical Report FE-19122-45. Included herein is work performed on PDU process data collected in FY-1984 and FY-1985, covering the following: gasification; ash agglomeration; fines carryover, recycle and consumption; description of temperature and concentration profiles in the fluidized-bed gasifier; development of a mechanistic gasifier model to predict PDU performance; development of a jet temperature model to predict maximum jet temperature; and multiple jet scoping studies. Data collected during the mechanistic test series enabled an in-depth understanding of the PDU behavior, development of dimensionless equations to represent temperature and steam concentrations, and the development of a mechanistic gasifier model and a jet temperature model. Both these models are required to address the effect of various operating parameters on PDU performance and operability. 10 refs., 71 figs., 34 tabs.