CAPITAL-COST TARGETS FOR MASS-EXCHANGE NETWORKS - A SPECIAL CASE - WATER MINIMIZATION

Pinch analysis has been applied to mass exchange network synthesis. Un til now, minimum utility targets have existed, but not capital cost ta rgets. Previous work minimised the number of units in a network, but t his paper shows that this does not necessarily minimise the capital co st. This paper focuses on the special case of water minimisation. It c onsiders a simple example involving a network of absorption columns wh ich use water to remove sulphur dioxide from a set of gas streams. The paper describes the first known method for targeting the minimum numb er; of trays in the network, based on a specified 'minimum composition difference'. This is then translated into a capital cost target. An i nteractive design method is presented which allows the targets to be a pproached to within 5%. The example is then extended to demonstrate ho w the targets can be used to trade off capital and operating costs in order to optimise the network before design. A further extension deals with multiple water sources. This work may be extended to other absor bents and generalised to other mass exchange networks. (C) 1997 Elsevi er Science Ltd.