The Scientific Design Company contracted with the United States Department of Energy through its Morgantown Energy Technology Center to develop a steady-state simulation model of the Great Plains Coal Gasification plant. This plant produces substitute natural gas from North Dakota lignite. The model was to be developed using the ASPEN (Advanced System for Process Engineering) simulation program. The project was divided into the following tasks: (1) Development of a simplified overall model of the process to be used for a sensitivity analysis to guide the development of more rigorous section models. (2) Review and evaluation of existing rigorous moving-bed gasifier models leading to a recommendation of one to be used to model the Great Plains gasifiers. Adaption and incorporation of this model into ASPEN. (3) Review of the accuracy and completeness of the physical properties data and models provided by ASPEN that are required to characterize the Great Plains plant. Rectification of inaccurate or incomplete data. (4) Development of rigorous ASPEN models for critical unit operations and sections of the plant. (5) Evaluation of the accuracy of the ASPEN Cost Estimation and Evaluation System and upgrading where feasible. Development of a preliminary cost estimate for the Great Plains plant. (6) Validation of the simulation models developed in the course of this project. Determination of model sensitivity to variations of technical and economic parameters. (7) Documentation of all work performed in the course of this project. Essentially all of these tasks were completed successfully. 34 figs.