The rapidly industrial development causes a considerable increase of water requirement in process plants. For that reason, water minimization has received more and more attention in the past decades and becomes a popular research topic. The efficiency of water utilization can be improved with a proper conservation strategy which not only reduces the operating cost but also lowers the environmental impact. Up to now, most of works on water minimization are concerned with continuous processes (Bagajewicz, 2000; Yoo et al., 2007), whereas the works for batch processes are rather less because of the fact that water usually constitutes a small part of the operating cost in batch operations. However, from the aspect of environmental protection and resource saving, water integration is still important and necessary to be considered in batch processes.

Batch processes are practically common in various industrial sectors, such as the production of food, pharmaceuticals and agrochemicals, etc. In this work, a general mathematical formulation is developed for the design of water-using network in batch plants, which is capable to deal with the cases of multiple contaminants and multiple storage tanks. For modelling the design problem, a set of superstructures are proposed to incorporate all possible connections in the batch water-reuse system, where a number of water-using tasks are proceeded and a number of storage tanks are placed for temporary storage to enhance the opportunities of water reuse/recycle. Besides the exploration of ultimate water recovery, the forbidden matches between specific water-using tasks in terms of water reuse are further taken into consideration as the practical restraint and an effective technique is presented to meet this special request. Representative examples from literature (Majozi 2005a, 2005b, 2006) are provided to demonstrate the adequacy of presented formulation.

References

1. Bagajewicz, M. A Review of Recent Design Procedures for Water Networks in Refineries and Process Plants. Comput. Chem. Eng. 2000, 24, 2093-2113.

2. Yoo C.K., Lee T.Y., Kim J., Moon I., Jung J.H., Han C., Oh J.M. and Lee I.B. Integrated Water Resource Management through Water Reuse Network Design for Clean Production Technology: State of the Art. Korean J. Chem. Eng. 2007, 24, 567-576.

3. Majozi, T. Wastewater Minimisation Using Central Reusable Water Storage in Batch Plants. Comput. Chem. Eng. 2005a, 29, 1631-1646.

4. Majozi, T. An Effective Technique for Wastewater Minimisation in Batch Processes. J. Clean. Prod. 2005b, 13, 1374-1380.

5. Majozi, T. Storage Design for Maximum Wastewater Reuse in Multipurpose Batch Plants. Ind. Eng. Chem. Res. 2006, 45, 5936-5943.