An ASPEN model has been developed of the Methanation Section, Section 1700, of the Great Plains Gasification Plant. The basis for this model is the process description given in section 6.12 of the Great Plains Project Management Plan and the Lummus Methanation Schematic Process Flow Diagram, Dwg. No. SK D-7102-IF-2. The ASPEN model that has been developed can handle the full list of process chemical components that are present in other sections of the plant; however, only the following components are assumed present in the section feed: hydrogen, nitrogen, ammonia, carbon dioxide, carbon monoxide, methane, and water. The model is primarily a flowsheet simulation which will give 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 predict. The model can be used to simulate the steady-state operation of the plant at or near design conditions or can be used to design other methanation plants. The model also can be used in optimization studies of operating conditions. 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. No catalyst specification, nor reactor size, nor kinetic data was available for the specific catalyst used at Great Plains. Among the most significant assumptions made were the outlet temperatures for the three stages of reaction and the approaches of the reactions to equilibrium. 47 references.