Abstract
The coal chemical industry’s high-water consumption has become the bottleneck for its sustainable development. Therefore, the efficient utilization of water and minimization of wastewater discharge is required. The stringent environmental regulations, as well as the escalating cost of freshwater and wastewater treatment has motivated the process and manufacturing industries to have emphasis on fresh water and waste minimization in their daily operations. In particular, optimal design and retrofit of industrial water systems provide a systematic approach for freshwater conservation. Conventional water system optimization often only considers flowrate of fresh water, but ignores flowrates of desalted water, steam and condensate water. The relationship between those types of water is lack of analysis. The minimum freshwater flowrate for the whole water system cannot be determined in one step via the conventional water system optimization model. In order to overcome such a limitation, this paper proposed a general model of a water-using process including more water types, and presented a general superstructure of water system optimization for a coal- based chemical complex. The material balance equations that relate all types of water are integrated in the model. The commercial software, GAMS, is used for modelling and solving a water system for a certain large coal-based chemical plant. A case study shows that the freshwater flowrate for the whole coal chemical plant can be calculated effectively via the proposed optimization model and it demonstrates the applicability of the model.
