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DESIGNING ENVIRONMENTALLY FRIENDLY CHEMICAL PROCESSES WITH FUGITIVE AND OPEN EMISSIONS
Citation:
Smith*, R L., T. M. Mata, D M. Young*, H C. Cabezas*, AND C. V. Costa. DESIGNING ENVIRONMENTALLY FRIENDLY CHEMICAL PROCESSES WITH FUGITIVE AND OPEN EMISSIONS. Huisingh, D. (ed.), JOURNAL OF CLEANER PRODUCTION. Elsevier Online, New York, NY, 12(2):125-129, (2004).
Description:
Designing a chemical process normally includes aspects of economic and environmental disciplines. In this work we describe methods to quickly and easily evaluate the economics and potential environmental impacts of a process, with the hydrodealkylation of toluene as an example. The process economics of such a design have been described by Douglas (1988), and therefore our focus is on combining process economics with environmental costs and impacts.
To evaluate the potential environmental impacts of a process, the work of Young and Cabezas (1999) on the Waste Reduction (WAR) algorithm is extended to include both open and fugitive emissions. The WAR algorithm uses a database of potential environmental impacts (including toxicity, acid rain, global warming, etc.) for 1600+ chemicals to evaluate streams that cross the system boundaries. While certain exit streams are known sources of waste, other sources come from leaks through valves, flanges, etc. This work studies the tradeoffs between economics and emissions, and also the environmental importance of fugitive versus open emissions.
Results of the study show the costs associated with environmental emissions due to material losses and waste handling. Thus, the economics of environmentally friendly processes benefit from waste minimization. Depending on the process design either fugitive or open emissions can dominate the potential environmental impacts. Design alternatives are considered and evaluations of the economics and potential environmental impacts are presented. The results show that tradeoffs can exist between eliminating open emissions and creating additional fugitive emissions. Exploration of individual impact categories indicates where tradeoffs exist between impacts, and from this analysis one can see where attention should be focused.
Fugitive or open emissions can dominate the potential environmental impacts of a chemical process. In this work the design and simulation calculations of a process provide an opportunity to visualize relationships between economic potentials and potential environmental impacts. The analysis of the economic and environmental effects of process alternatives are completed quickly and easily using order of magnitude costing techniques and the Waste Reduction (WAR) algorithm for environmental evaluation. In the example studied, the hydrodealkylation of tolune, both the economic and environmental results point towards the alternative of recycling diphenyl to extinction, which is a form of pollution prevention by source reduction. As open emissions are eliminated, the importance of fugitive emissions is shown to increase. Finally, results show where economic optimum and minimal environmental impact designs occur, and therefore one can see tradeoffs between these designs.