Corrosion of heat exchanger in thermal desalination plants and current trends in material selection

Abstract

Heat Exchanger constitutes an integral component of thermal desalination plants. Heat exchanger plays an immensely important role since the success of the whole process of low pressure evaporation and condensation depends upon the efficiency of heat transfer. The chemically aggressive environment surrounding the different sections of the thermal desalination plant including heat exchangers can cause failure due to corrosion and/or erosion. The cases of heat exchanger failure in seawater processing plants including desalination plants have been reported frequently. Besides investigating the cause(s) of failure in heat exchanger, the selection of appropriate heat exchanger material is the important issue in the realm of desalination technology. The work of a number of investigations related to erosion and corrosion of heat exchanger materials in thermal desalination plants reported in recent literature has been cited. The analysis of the published information provides in-depth knowledge of heat exchanger materials under plant operational conditions and assisted in formulating the selection of best and cost effective material for the plant. This paper presents some recent cases of failure of heat exchangers in thermal desalination plants. The studies include investigations on the mechanistic and causes of failure, and finally the recommendations concerning with the prevention or combating the failure. From the results of the case studies, an overall picture of the behavior of materials in respective operating environment emerges and consequently, initiates selection of better material. The paper also encompasses the recent trends in material selection of heat exchanger for thermal desalination plants. Besides the applications of conventional materials which include cupronickel and titanium, the potential of some recently developed plastic based composite is discussed.

Keywords:

• Condenser tubes
• Multi-effect and MSF desalination plant
• Localized corrosion
• Crevice corrosions
• Galvanic corrosions
• Non condensing gas
• Venting system
• Plastic hear exchangers

Notes

Presented at the Conference on Desalination for the Environment: Clean Water and Energy 11–15 May 2014, Limassol, Cyprus