Synthesis of evaporation systems using minimum utility insights

Abstract: "An evaporation system is a network of evaporators and heat exchangers which integrates an evaporation task with existing hot and cold process streams. This paper presents a systematic procedure for synthesizing evaporation systems which feature minimum utility use. A first result in this paper shows that if a minimum utility N + 1 - effect system does not contain the minimum utility N-effect system, it can be only marginally better. Given the feed and product temperatures, as well as the temperatures of the process streams, we use this insight to select the effect temperatures sequentially using a simple graphical procedure. A second set of results aids in the selection of the two most energy-efficient flowpatterns from among the N! possible in an N-effect system. A third set of results shows where to introduce evaporator bypass. An algorithm is also presented which results in an evaporation system with equal effect areas.We apply the proposed procedure to the design of a triple-effect evaporation system integrated with two process streams. The resulting minimum utility flowsheet requires 17 percent less steam than a more conventional triple-effect system design."