Thermovapor compression desalters: energy and availability — Analysis of single- and multi-effect systems

• Published in: Desalination Vol. 110; no. 3; pp. 223 - 238
• Main Authors: Al-Najem, Najem M., Darwish, M.A., Youssef, F.A.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.09.1997; Elsevier
• Subjects: Applied sciences; Availability destruction; Desalting; Drinking water and swimming-pool water. Desalination; Exact sciences and technology; Gain ratio; Marine; Multi-effect desalters; Performance ratio; Pollution; Second law analysis; Steam ejector; Thermal compressor; Thermovapor compression desalters; Water treatment and pollution; France; Multi-effect desalters; Steam ejector; Desalting; Second law analysis; Availability destruction; Thermal compressor; Thermovapor compression desalters; Performance ratio; Gain ratio; Vapor compression; Desalination plant; Desalination; Multiple effect distillation; Seawater
• ISSN: 0011-9164; 1873-4464
• DOI: 10.1016/S0011-9164(97)00101-X

Sidem (France) has made some recent advancements in thermal vapor compression (TVC) systems [1,2] by installing four units, each having four effects, 1 migd in capacity with a gain ratio of 8, and another four units of 12 effects each, with 2 migd capacity per unit and a gain ratio close to 17. This increased the interest in the system particularly for plants of low and medium capacity. The new system is characterized by the following: (1) the compression of most of the generated vapor and its usage as a heating medium drastically reduce the primary heat source (boiler) and heat sink (i.e., cooling water and condenser), as compared to conventional single-effect desalting systems; (2) low energy consumption; (3) simple water pretreatment as compared with reverse osmosis (RO) systems, which are the main competitors of mechanical and thermal vapor compression systems in small and medium capacities; (4) low capital and operating costs; and (5) recently developed reliable thermocompressors. Since very little is known about the principles and design of the system, a parametric analysis, using the first and second laws of thermodynamics, was conducted for the TVC system components, e.g., steam ejector, evaporator, condenser, as well as the system as a whole. The analysis pinpoints the deficiencies in the system and the methods of overcoming these deficiencies.