INTER-PLANT WATER CONSERVATION BY PROCESS OPTIMIZATION: CASE STUDY FOR A CHINESE ALUMINA INDUSTRY

摘要

A case study for inter-plant water system optimization between an alumina plant and a steam power plant located in Shandong Province, China, is carried out to promote water conservation. The combined freshwater consumption of the two plants is 1665.23 t/h and the wastewa-ter discharge is 411.83 t/h before modification. On the basis of analysis of each plant's current water network, the water sources and water sinks were identified, and suspended solids (SS) and total hardness (TH) were determined as key contaminants together with their limiting concentrations. A mixed integer nonlinear program (MINLP) model, which can deal with multiple contaminants along with water temperature as a control factor, was used to develop the integrated inter-plant water system. The model was optimized by using commercial software LINGO v11. The results showed that the freshwater consumption and waste-water discharge can be greatly reduced.