Development of water recycle networks for a discontinuous manufacturing system.

摘要

Wastewater should be reduced to improve sustainability of future production systems. In particular, wastewater generated from food and biological processing draws our attention because it contains processing materials that are major pollutants and must be reclaimed. Development of a water recycle network system is an ideal approach to reduce wastewater significantly and economically. Because wastewater is generated discontinuously, it is necessary to develop the network by introducing wastewater storage and separation equipment into the production system.;Identification of a good network structure for discontinuous processes is difficult when evolution schemes for a minimum-scale network are considered. We propose development of a basic form of water recycle network. Effectiveness of the basic form is validated through modifications of its structure and operation design conditions. Under variable production operations, wastewater-processing equipment must allow feasible water recycles. Optimal capacities of tanks and separators are analyzed based on a statistical approach to network cost variations that are caused from processing changes, storage tank initialization, and scale up on the number of batch processes.;To validate feasibility of water recycle at actual systems, we consider rules of water stream division, with which water demands of actual batch operations can be satisfied. As a more general approach, we also studied time interval effects on water recycle design and operations. Analyzing the time effects, we developed rules for time interval determination that would be efficient to handle wastewater problems of practical systems. Our methodology of network design and validation is developed mainly to solve wastewater problems, but we think that it can be applied to solving general network design problems of discontinuous or batch processes.