Design of Sustainable Processes: Systematic Generation & Evaluation of Alternatives
Ana I. C. S. G. Carvalho1, Rafiqul Gani2, and Henrique A. S. Matos1. (1) Chemical Engeneering, Instituto Superior Técnico, Av Ruy Luís Gomes nº2, 5ºB, Amadora, 2700, Portugal, (2) Chemical Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
Chemical processes have are facing increased competition because of the supply of the raw materials and utilities they use. To be still competitive they need to improve their processes with respect to waste, environmental, safety and cost. Therefore, it is necessary to generate new alternatives that make the process more sustainable as well as adapt to the future needs. The objective of this paper is to present a new generic and systematic methodology for identifying and evaluating the potential the design (retrofit) alternatives of chemical processes operating in batch or continuous modes. This methodology uses three general indices to measure parameters in a specific chemical process that allow the identification of operational difficulties or process sensitivities and through their analysis, opportunities for targeted improvements. These indices are: the indicators, which give us general information about the costs, benefits and accumulation problems present across the process; the sustainability metrics, which evaluate the impact of the process on its surroundings (environmental, social and economic impact); and the safety indices, which measure the inherent safety of the process. The indicators are used as improvement targets, and the other two groups of indices are used as performance criteria to define the best alternative.A new software (Sustain Pro) has been developed to calculate the indicators, the sustainability metrics as well as the safety indices of a given process. Using data from plant data or from results of a simulation of the process, it is possible to make an easy analysis of the process. The critical points of the process are pointed out by the indicators and the impact of the process to its surroundings is also showed by the sustainability metrics and the safety indices. This software decreases the time spent in generating and evaluating alternatives by concentrating on the calculations that lead to identifying the most promising alternatives. Also the Sustain Pro integrates different tools by providing efficient data transfer between them. It also extends the application of this methodology to any processes, with multiple reactors, and large and/or complex flowsheets. The methodology is also being extended to handle batch operations with the creation of new set of indicators, but using the same approach for the continuous process operations. The main features of the indicator based method has been highlighted through different case studies, for example, the well known HDA process, the process from the Eastman Kodak challenge problem and a more complex process, the production of Methyl Tertiary Butyl Ether (MTBE). In this presentation, new case studies will be presented highlighting also the advantages of using computer-aided tools (Sustain Pro). Through these case studies, the main features of the algorithm, such as the determination of the indicators, and the generation of targeted retrofit alternatives, which will improve the process, will be illustrated making these processes more competitive and sustainable.