Water conservation through energy conservation

Abstract

South Africa is one of the driest countries in the world and rivers and dams are the main source of water. The continuous pollution of the rivers and streams as well as the growing demand for water has led to stringent environmental regulations to limit the consumption of water as well as to set the acceptable contamination levels of water before it is discharged to the main water cycle. Various techniques have been used to address the issue of the usage and contamination of water in industry. In recent years, Pinch Analysis has been extended to cooling water systems design following its success in heat exchanger networks (HENs) and mass exchanger networks (MENs). The most significant work on cooling water network design was developed by Kim and Smith (2001) where a graphical methodology for designing cooling water systems was developed. Research on cooling water networks was necessitated by the need to optimize the amount of cooling water used in process industries. It is always important to conserve water as well as reduce the amount of contaminated water that is discharged to the main sources of water. In this study, the consumption of water and effluent reduction opportunities in a nitric acid production plant at African Explosives Limited (AEL), Modderfontein, South Africa, was investigated. This investigation led to the development of a cooling water network design technique for systems with multiple cooling water sources. The results from this analysis have shown that there is potential to reduce the blowdown by 47%. Moreover, the cooling water used in the cooling water network could be reduced by 23% and freshwater makeup by 10%.