Synthesis of Flexible Batch Water Networks Using Dynamic Programming

Water conservation is becoming increasingly important due to increasing demand and stringent environmental legislations. This work proposes a dynamic programming (DP) method for the design of water-using networks in flexible batch plants. The proposed methodology is described as follows. First, based on the inlet concentration of each operation, all of the operations could be assigned to the specific stages. Second, the water requirement of water-using units in each stage is satisfied by either freshwater or reusable water from other operations, with no option for dilution. The state of stored water is then determined. The target of freshwater consumption is thus obtained after water requirements of all of the operations have been determined. Three examples from the literature are considered. Example 1 is treated as a fixed-quantity problem. Example 2 is a hybrid batch water system comprising fixed-mass load and fixed-quantity operations. Example 3 refers to a water system with multiple contaminants. The results obtained in this work are comparable to those obtained from the published literature, implying that the proposed approach is applicable to redesigning the schedule of water operations in batch plants.