Research on integrated optimization of the water system in iron and steel industry based on effective water efficiency

Abstract

Large-scale iron and steel industries have large water consumption and complex water system structures. Hence, determining the objective function is very important for the integrated optimization problem of the water system. However, most research considers water consumption, wastewater discharge, and cost as objective functions. This paper proposes a new objective function called effective water efficiency, which combines water quantity and quality into one evaluation index. An approach to maximizing effective water efficiency is undertaken, whereby a mixed integer nonlinear programming (MINLP) model is constructed to optimize the water system of a long-process iron and steel enterprise statically and dynamically. The results have shown improvement in the system's effective water efficiency, and the obvious effect of water saving and emission reduction is achieved. Under optimal conditions, the effective water efficiency is increased from 73.32% to 96.30%, and the freshwater quantity is reduced by 18.61%. Moreover, the quantity of wastewater out-drainage is reduced by 98.54%, demonstrating the evaluation index's scientificity. A new evaluation index and objective function are provided to optimize the process of industrial water systems.