Generic Modelling of Integrated Material Flows and Energy Systems

Doctoral thesis, 1993

This dissertation describes MIMES, a nonlinear model for the optimization of linked material and energy flow systems. The model is generic, intended for systems that can be described by material and energy balances. MIMES offers an improvement to the existing energy systems engineering models on which it is based, by its inclusion of material flows and the joint optimization of both energy and material flows. The technical modelling procedure is presented with a description of the four stages of the model: the graphic description by REMS flow diagrams, the descriptions of processes by DEVICES, the mathematical representation and, finally, the optimization. The procedure for specifying control and communication between system parts receives special attention. The purpose of the model is to provide a tool to assist decisions about systems with complex and nested material and energy flows. Issues suitable for analysis by the model range from energy conservation in industrial plants, specific industries or industrial subsectors to municipal waste management and to fuel and material life cycle analysis. This dissertation presents applications to two of these issues, municipal solid waste management and energy conservation in industrial plants. In the waste management systems applications, MIMES is used for broad technical analysis for the purpose of evaluating strategies for future development. Present-day waste management organizations confront a broad range of concerns, including strategies for source separation and recycling, new technical options for waste processing, sales to the energy and material market, and options for reducing pollutants and emissions resulting from the system. MIMES, referred to as MIMES/WASTE in this application, is a tool to assist decisions in these areas. MIMES/WASTE is more comprehensive than earlier models. The joint optimization of energy and materials, the integration of emissions control and the detailed description of waste streams are the main improvements. The application of the model for industrial systems is demonstrated for a paper production line in a paper mill. The example shows how the model can be used for joint analysis of energy and water conservation, substitution of energy carriers, and utilization of waste heat outside the system. The latter is demonstrated for the option of selling low-temperature water to the district heating utility.