Cost reduction and design lifetime increase in thermal desalination plants: thermodynamic and corrosion resistance combined analysis for heat exchange tubes material selection

Abstract

Heat exchange tubes are by far the major cost item in thermal desalination plants. The budget for heat exchange tubes amount to 25–35% of the overall cost of the evaporator. Since the material for the heat exchange tubes has a substantial impact on the evaporator costs it is important to identify technical aspects in these components, which could lead to optimisation of material quantities and increased quality and reliability. The sharp reduction in the EPC price of thermal desalination plants which has been observed in the last decade is mainly attributable to the optimisation of the heat transfer coefficient which has allowed lower heat exchange surface with increased water capacities. Despite recent advances, which allow fabrication of low thickness tubes a combined analysis of the heat exchange tube material and specification from both a thermodynamic and erosion/corrosion perspective has not been done so far. This paper is probably the first paper combining corrosion/material selection and thermodynamic aspects for the analysis and the specification of thermal desalination plant tubing. The paper will aim at comparing the adoption of different alloys in terms of thermal resistance to heat transfer, and erosion/corrosion resistance. The economic impacts related to the choice of the various materials considered are evaluated against the plant lifetime design and guidelines for future optimisation in the technical specifications are given.