Multistage flash desalination process

Some desalination plants combine distillation with reverse osmosis to produce both power and water. Multistage flash (MSF) processes are used to produce both power and distilled water. The combination of RO and MSF and the advantages of such a combination have been reported (111). 

A. S. Khan, Desalination Processes and Multistage Flash Distillation Practice, Elsevier, Amsterdam, the Netherlands, 1986. 

Potable Water RO and NF both play a major role in providing potable water, defined either by the WHO criterion of <1000 ppm total dissolved solids (TDS) or the U.S. EPA limit of 500 ppm TDS. RO is most prominent in the Middle East and on islands where potable-water demand has outstripped natural supply. A plant awaiting startup at Al Jubail, Saudi Arabia produces over 1 mVs of fresh water (see Table 22-17). Small units are found on ships and boats. Seawater RO competes with multistage flash distillation (MSF) and multieffect distillation (MED) (see Sec. 13 Distillation ). It is too expensive to compete with conventional civil supply (canals, pipelines, w ls) in most locations. Low-pressure RO and NF compete with electrodialysis for the desalination of brackish water. The processes overlap economically, but they are sufficiently different so that the requirements of the application often favor one over the others. 

Distillation processes, 26 61-73. See also Distillation(s) freeze-desalination, 26 71 materials and scaling issues in, 26 71-73 multi-effect distillation, 26 65-67 multistage flash evaporation, 26 61-65 vapor compression distillation, 26 67 Distillation reactors, 21 332 Distillation region diagrams (DRD), 22 302, 303, 331... 

Multistage flash (MSF) processes, 21 650 Multistage flash desalination, 26 59 Multistage flash evaporation, 26 61-65, 97 energy required by, 26 86 in hybrid desalination systems, 26 95-96 schematic flow and temperature diagram of, 26 62... 

Fig. 2. Multistage flash evaporation process used in desalination...

H. Ettouney, H. El-Dessouky, and F. Al-Juwayhel, Performance of the Once-through Multistage Flash Desalination Process, Proc. of the Inst, of Mech. Eng. Part A, ]. Power Energy, 216(A3), 229-241 (2002). 

Nanofiltration is used for water pretreatment in both thermal and membrane desalination processes. Desalination processes may rely solely on membrane processes (e.g., reverse osmosis in combination with nanofiltration, microfiltration or ultrafiltration [126]) or a combination of membrane and thermal (e.g., multistage flash [127]). 

Seawater or brackish water is used for process applications or as potable water when fresh water is scarce. Six techniques are used for desalination. Five are evaporation processes multiple-effect thermocompression mechanical vapor compression once-through multistage flash and multistage flash with brine recirculation. The sixth process, reverse osmosis, uses membrane technology for desalination. 

Arndt, R.k (1977). Corrosion, Paper No. 91. Khan, A.H. (1956). Desalination Processes and Multistage Flash Distillation Plants, Elsevier, Oxford, UK. 

A very significant fraction of desalination is achieved via thermal desalination processes such as multistage flash, multieffect distillation, etc. (Section 10.2.1) (primarily in older plants). Pretreatment processes include filtration, chlorination, deaeration and scale control via acid addition, antisealant treatment, etc. Post-treatment processes include building up the dissolved salt concentration to the level of 50 ppm via blending with brackish ground water or addition of lime, etc. (Howe, 1974), since distilled water is highly corrosive. 

Fig. 3.16 shows a desalination cogeneration process designed for efficient recovery of the waste heat from a VH f R. Table 3.6 summarizes the design parameters of the process. A multistage flash (MSF) system is connected to the reactor plant cycle via... 

There are many different techniques for desalination. Among the main ones are the multistage flash (MSF) process and reverse osmosis. Countries that do not have an abiuidance of fresh water are prime candidates for the use of this technology. Quatar s installations include the Ras Abu Fontas B power and desalination plant, which cost 1 billion to build. Dubai in the United Arab Emirates (UAE) has a 60-million-gal/day desalination plant at Jebel AU. The plant s eight MSF units are part of a cogeneration power facility. The fresh water would have been at least as much incentive in the Middle East as the increased total thermal efficiency. The desalination equipment in both cases was supplied by Weir Westgarth (WW). 

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