Desalination 222 (2008) 431–440 Presented at the conference on Desalination and the Environment. Sponsored by the European Desalination Society and Center for Research and Technology Hellas (CERTH), Sani Resort, Halkidiki, Greece, April 22–25, 2007. Process modelling in desalination plant operations Walid ElMoudir*, Mohamed ElBousiffi, Salah Al-Hengari Libyan Petroleum Institute, P.O. Box 6431, Tripoli, Libya Tel. +21892 5227107; Fax +21821 4830031; email: walid_elmudir@yahoo.com Received 5 January 2007; accepted 10 January 2007 Abstract Operation of desalination process is sometimes a difficult task, especially when the plant is getting older. Process engineers and operators are required to follow-up any changes or variations in process parameters either in control room or on-site measurements. Undetectable deviation and/or malfunctioning in any of measurement devices could occur specially during long-time successful operation without major shutdown for the entire plant or when the process is part of very complex integrated processes in an industrial site. This deviation, inaccurate-reading or malfunctioning values can be due to un-calibrated devices (i.e. flow-meters) or fouling of measurement devices (i.e. thermo-couples). Practically, process modelling is a useful tool that can assure and confirm that the process measurements parameters are accurate. Incorrect balancing of mass and/or energy can be detected easily as well as the productivity of the plant. In this paper, multi stage flash (MSF) desalination plant was illustrated and evaluated. Malfunction of measurement device showed the plant was producing distillate more than what was really measured or received by down stream processes. Excel spreadsheets was developed and utilized for process modelling and confirming the results. Keywords: MSF desalination process; Process modelling; Plant data; Maloperation 1. Introduction Desalination is used whenever there is a shortage of water from natural resources. In industrial sites, high quality water is essentially needed for production of steam or for possessing purposes. Many desalination technologies find their way for industrial application and this includes multi stage flashing process (MSF). This process has gained good reputation for years due to its high productivity capability, operability and flexibility (110–70% design capacity [1,4]). MSF consumes energy from low grade sources (i.e. LP steam generated by waste steam genera- tor). In many regions in the world, good operat- ing experiences are gained from running this technology, for years. *Corresponding author. 0011-9164/06/$– See front matter © 2006 Published by Elsevier B.V. doi:10.1016/j.desal.2007.01.170