Optimizing Asset Value and Operational Costs for Sustainability in Industrial Water Systems: A Case Study of a Steel Plant

Sustainable industrialization and efficient water management are among the crucial objectives of the United Nations’ sustainable development agenda. These objectives can be achieved by adopting water-saving technologies, optimizing resource usage, and refining plant operations for improved sustainability. Cooling systems are an essential part of several process industries in which cooling operations are frequently impaired by the deposition of impurities in water. In this paper, a superstructure-based optimization framework along with various objective functions is used to analyze the interaction among freshwater requirement, scaling potential, and water flow within the water network. The goal is to evolve and understand the characteristics of an operation strategy that ensures a sustainable water network. Deposition of calcium carbonate is a major challenge in cooling system networks. The Langelier Saturation Index (LSI) (Roberge, P. R. Corrosion Inspection and Monitoring; Wiley Online Library, 2007) is used to estimate the scaling potential of calcium carbonate in the cooling network. An objective function termed avg. LSI (average LSI) which is a weighted sum of LSIs of the water streams emerging out of cooling systems (blowdown water) is introduced to measure the scaling potential of the water network. It was observed that achieving these objectives simultaneously presents an opportunity for innovation and strategic planning of operations in the cooling water network. The results of this study highlight the interdependency between the freshwater requirement, avg. LSI, and total water flow (that determines the pumping costs) within the network. The characteristics of such networks are also presented in this work. The application of this approach to a representative cooling water network from the steel industry is presented to demonstrate the efficacy and utility of the proposed approach.