Simultaneous process and molecular design/selection through property integration
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The overall purpose of this work is to develop systematic methodology for the simultaneous design and selection of processes and molecules (materials). A propertybased approach is used to develop an interface between process and molecular design/selection. In particular, we focus on the problem of designing/selecting materials that are used in the context of a recycle/reuse system of process streams and for energy applications. Fresh and recycled resources (e.g., process streams, biomass, solvents, etc.) are integrated with the process to satisfy property-based constraints for the process units and to optimize the usage of the resources and the design of the process. For molecular design, property operators for mixing streams and group contribution methods (GCM) are used to consistently represent process sources, sinks, and different functional groups on the same property-base. For material selection, property based criteria (e.g., heat rate, high heating value, etc.) are used to bridge the process with material. This consistent representation enables the definition of the optimization problem formulation for product design while taking into consideration the recycle/reuse of process streams. In particular, this dissertation addresses four integrated topics. First, a new graphical approach for material targeting and substitution is presented. This graphical approach offers initial solutions and valuable insights that can be effectively used for conceptual design and for initializing mathematical programming techniques. Second, a mathematical optimization approach is developed along with a decomposition-based global solution procedure for material targeting and substitution using property integration. Third, an implementation approach is developed to synthesize the details of a recycle/reuse process network design based on the targets identified through the graphical and/or the mathematical approaches. Finally, property integration techniques are extended to a broader scope which deals with the lifecycle analysis of biomass utilization for energy generation. A generic model is developed to optimize the types and quantities of the feedstocks used to optimize power generation with biomass-fossil fuel co-fed system. Important issues of biomass growth, harvesting, transportation, processing, and disposal are included. Property-based tracking and constraints are included in the analysis. Also, the issues associated with greenhouse gas (GHG) emissions are incorporated in the analysis. Case studies are solved throughout the dissertation to demonstrate the applicability of the developed procedures.