Development of heat-integrated evaporation and crystallization networks for ternary wastewater systems. 1. Design of the separation system

This paper considers the optimal design of an evaporation and crystallizati on network for separation of a ternary wastewater stream with two salts and is the first part in a two part series on evaporation and crystallization networks. A crystallization and evaporation design is compared with previou s work on condensation within the framework of a heat-induced separation ne twork design. Detailed mathematical expressions are listed for complete mat erial and energy balances, pinch equations, and unit sizing and cost of the evaporation and crystallization network. Some generic structures are propo sed for heat integration of a typical evaporation and crystallization netwo rk. Several graphical insights are listed that allow one to use the represe ntation of evaporation and crystallization operations on a ternary triangul ar composition diagram and to avoid mathematical complexity. Graphical insi ghts enable reduction of the search space and allow solution of the problem in a computationally efficient manner. A graphical solution strategy and a lgorithm are described to converge to the optimal design. The solution algo rithm requires the identification and bounding of certain critical design v ariables. A case study is solved to demonstrate the broad applicability and value of the proposed approach.