Achieving profitably, operationally, and environmentally compromise flow-sheet designs by a single-criterion optimization



Compromise designs that can be achieved to a certain extent in process flow-sheet optimization not only by multicriteria but also by single-criterion optimization are described. A well-balanced compromise between the profitability, operational, and environmental efficiencies can be achieved using a suitable economic criterion. From the financial point of view, the net present value (NPV) is the correct criterion for selection from among mutually exclusive solutions and, hence, for evaluating different designs in process optimization. Other criteria are also often used in engineering practice. It is shown that optimal designs obtained using different economic objectives vary not only in their investment and other financial indicators, but also in operational efficiencies and environmental indicators. Operationally more efficient and environmentally less harmful solutions can be obtained at lower profitability, by increasing the invested funds. The net present value generates the best compromise between these objectives, as illustrated by three flow-sheet synthesis problems. © 2011 American Institute of Chemical Engineers AIChE J, 2012