A single ASPEN model has been developed that encompasses the Gasifier Quench (Section 1100), Gas Cooling (Section 1300), Shift Conversion (Section 1200), and Gas Liquor Separation (Section 1800). This model is based on the process descriptions given in Sections 6.7, 6.8, 6.9 and 6.13 of the Great Plains Project Management Plan and Lummus Schematic Process Flow Diagrams, Dwg. No. SK-7102-201A-2, SK-7102-1D-2, SK-7102-1D-2, and SK-7102-1H-2. The model is primarily a flowsheet simulation that will calculate the material and energy balances and equipment duties for a given set of process conditions. The model is unable to predict fully changes in process conditions that would result from load changes on equipment of fixed sizes, such as a rating model would. The model can be used to simulate the steady-state operation of the plant at or near design conditions, or to design other similar processes. The model also can be used in optimization studies on operating conditions, particularly in the shift conversion area. Because of the limited amount of process information that was available, several major process assumptions had to be made in the development of the flowsheet model. The model developed is robust and no convergence problems were encountered. Varied in the case studies were the temperature approach to equilibrium in the shift reactor and the quantity of gas being shifted. The results are as expected, the lower the equilibrium approach temperature and the more gas being sent to the shift reactor, the lower the carbon monoxide-to-hydrogen ratio obtained. The converse is true for higher approach temperatures and less gas being shifted. 55 references, 5 figures, 9 tables.