ABSTRACT
Dehydration and deep chilling operations are important activities of the chemical and food processing industries. The objective of dehydration is the removal of water up to a certain level such that the microbial spoilage is minimized. On the other hand,
the main effort of chilling food products is to ensure that they have reached certain low temperature thermodynamic conditions in order to prevent the development of pathogenic bacteria that contaminates them. The increasing concern for meeting product quality specifications and conserving energy, the need for a thorough understanding of drying and chilling processes, and the problems related to the design and operation of their related equipment should be emphasized. The process design or synthesis problem typically involves determination and evaluation of the process flowsheet structure, corresponding construction characteristics, and operation conditions when a nominal production level is given for all products processed in the plant. The objective is to minimize the total annual cost (or similarly to maximize the profit) resulting from the construction of a new plant or the operation of an existing one by adding new production lines under structural and varying operating constraints. In most cases, determination of the flowsheet structure refers to the solution of a complex combinatorial mixed integer nonlinear programming (MINLP) problem. This involves numerous continuous and integer decision variables, a large number of space variables, and constraints. In this chapter, the main effort is to examine and analyze two typical real life industrial case studies, namely design of multiproduct conveyor-belt dryers and tray tunnels for deep chilling. In both cases, optimum flowsheet configurations are sought and verified by effective mathematical formulations and modeling approaches of design and optimization strategies and techniques.
