Development of Heat-Integrated Evaporation and Crystallization Networks for Ternary Wastewater Systems. 2. Interception Task Identification for the Separation and Allocation Network

This work introduces the problem of simultaneous allocation and recovery via crystallization and evaporation for ternary wastewater systems and is a continuation of work proposed in part 1. The problem at hand is solved within the framework of mass integration. Different sources and sinks are identified. Varying sink inlet flow and composition constraints necessitate the use of the path equations for global tracking of all species of interest. Constraint propagation is invoked to determine bounds on allowable sink flow-rate and composition constraints. A two-step solution procedure is proposed to solve the problem. The first step consists of interception task identification for a given stream in the process. This is useful because it enables elimination of infeasible nodes prior to detailed design, thus leading to computational efficiency. The second step consists of the design of a separation network for an identified separation task. This step has been previously described in part 1. Part 2 couples the separation task via evaporation and crystallization to the allocation requirements of various sinks. A case study dealing with the ammonium nitrate manufacturing process is included to demonstrate the broad applicability and value of this work.