Forty-year design life: the next target Material selection and operating conditions in thermal desalination plants

Abstract

The operational experience on the first generation of large MSF desalination plant has demonstrated that the original expected life of these units has been largely exceeded. Several contracts for the rehabilitation and upgrading of desalination units installed 20 years ago have been recently awarded, aiming at extending the life of these units by a further 15 years. Developments in materials technology have resulted in the adoption of nobler materials, and it is expected that the second generation of large MSF desalination plants installed in the last 10 years will last for more than 30 years with minimum maintenance and minor overhauling. On this basis, it is assumed that a 40- to 50-year design life is a reasonable target which can be obtained if the material selection is optimized in respect of the operating conditions. The gradual emergence of the MED process in the market portion previously belonging to MSF technology suggests that an evaluation of the operating conditions and material selection for MED plants can also grant an expected life of 50 years. The sharp influence of material selection on plant cost has previously been demonstrated; therefore, the choice of “where” and “how” to invest in upgrading materials and the evaluation of the financial revenue, in term of extension of plant life and reduction of maintenance, are key technical aspects for the future of desalination. By comparing the various operating conditions occurring in the desalination units and the impact on corrosion/erosion of the materials used, this paper aims at giving guidelines that will allow material selection to be optimized with respect to the plant costs.