Sea water desalination

As per a study by the International Desalination Association, 14,451 desalination plants were in operation worldwide in 2009, producing 59.9 million m of water per 

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Fresh water is also in short supply in many areas. Plentiful inexpensive energy allows sea water desalination to provide almost unlimited supplies of fresh water. 

Data of WRPC. The Water Reuse Promotion Center(WRPC) in JAPAN has been engaged in development of sea water desalination by reverse osmosis since 197. At IDEA meeting at Mexico city 1976,the first redults were reported with two types of modules, du Dont hollow fine fiber module B-10 and UOP s cellulose triacetate ultrathin spiral wound module,tested at their laboratory at Chigasaki beach. Then the WRPC has adopted two types of modules made in Japan, Toray new type of spiral wound module made from cellulose acetate and Toyobo s cellulose triacetate hollow fine fiber module. 

The successful development of asymmetric cellulose acetate membranes by Loeb and Sourirajan in the early sixties, at the University of California, Los Angeles, has been primarily responsible for the rapid development of Reverse Osmosis (RO) technology for brack sh/sea water desalination. Reverse Osmosis approaches a reversible process when the pressure barely exceeds the osmotic pressure and hence the energy costs are quite low. Theenergy requirement to purify one litre of water by RO is only O.OO3 KW as against 0,7 KV required just to supply the vaporisation energy to change the phase of one litre of water from liquid to vapour by evaporation. Thus RO has an inherent capability to convert brackish water to potable water at economic cost and thus contribute effectively to the health and prosperity of all humanity. 

The chemical modification of poly(arylene ether sulfone)s has already been described in numerous papers. They relate to sulfonation, fluorination, and halomethylation. These derivatives are particularly suitable for the preparation of hydrolysis- and temperature-resistant separation membranes. They are used already for sea water desalination, and also for the separation of gas mixtures. 

M. Kurihara, N. Harumiya,N. Kannamaru, T. TonomuraandM. Nakasatomi, Development of the PEC-1000 Composite Membrane for Single Stage Sea Water Desalination and the Concentration of Dilute Aqueous Solutions Containing Valuable Materials, Desalination 38, 449 (1981). 

K. Marquardt, Sea Water Desalination by Reverse Osmosis, GVC/VDI Gesellschaft Verfahrenstechnik und Chemieingenieurwesen Seawater Desalination-Water Pretreatment and Conditioning, VDI Verlag, Diisseldorf (1981). 

Linnikov O. D. and Podberezny V. L. (1996) Prevention of sulfate scale formation in desalination of Aral Sea water. Desalination 105, 143—150. 

Reverse osmosis membranes. The exceptionally hi moisture regain observed with polybenzimidazole fibers prompted a team at Ctelanese Research Co to investigate the utility of polybenzimidazole films as semipermeable membranes for reverse osmosis processes, sudi as sea water desalination A continuous process was devised in which films were... 

More specifically, these systems, whether operated in the conventional mode or as rotary units have been successfully utilized in applications such as the recovery of protein and lactose from cheese whey, separation of fermentation products, concentration of fluids foods and juices, manually operable sea water desalinators, recovery of starch from potato processing fluids, and processlng/separatlon of pharmaceutical and chemical mixtures. 

During a study of the applicability of "spray" or "fog" evaporation to sea water desalination, it was found that this technique was particularly useful for scale deposition studies. Thus, test conditions are reproducible and heat transfer coefficients are very high, so that the effect of scale formation is readily apparent. Three novel methods for the control of scale deposits on the evaporating surfaces of a spray evaporator were explored. One involves the addition of small quantities of low molecular weight polyacrylic acid to the feed water, which prevents the formation of adherent scale. The methods are applicable under certain conditions to scales formed from sea water containing substantial amounts of calcium sulfate in addition to alkaline scale-forming substances. While spray evaporation appears to be of limited application in water desalination, the scale-control methods developed are probably applicable to other types of evaporator, particularly of the long-tube type. 

Cellulose acetate with a slightly higher degree of esterification (38.7-40.1% acetyl) is usually preferred for the preparation of fibers, films, and lacquers because of the greater water resistance. A significant application of cellulose acetate film has been found in sea-water desalination by reverse osmosis. 

Originally, the purpose of the heating reactor is to supply heat for Buildings in cities. Now we want to extended its application to propulsion, heat-electro-cogeneration, sea water desalination and refrigeration (for air condition) etc. 

Heat and power cogeneration (for sea water desalination and propulsion) will improve the economic features of the reactor. 

Using the heat, generated from the Heating Reactor to drive a back pressure turbine. Then the steam goes to tlie sea water desalination plant to produce fresh water. 

Steam produced from the steamgenerator can be used for propulsion or electrogeneration. It also can be used for sea water desalination. 

When the steam produced from OTSG is used for sea water desalination. It goes to a desalination plant steam generator. Where the secondary steam (pressure of the secondary steam is P=1.72MPa and temperature is 205 ) is produced and used for desalination. Its condensate goes back to the plant... 

In the design the pressure increases to 4.1 MPa, steam temperature is 252 C Power efficiency reached 32%. The water temperature at the core inlet is 204 "C. At the same time part of reactor water is parallelly leaded to a steam generator. Secondary steam (pressure 1 72MPa, temperature 205 C) can be used for sea water desalination. 

Small-scale reactors have more advantages than large-scale reactors in variety of energy utilization, construction, maintenance and adoption of innovative technologies, while the latter have scale merits in construction cost. The nuclear energy utilization of small-scale reactors are ship propulsion, electricity generation, heat supply, and sea water desalination, etc. Construction and maintenance for small-scale reactors can be made in factories exclusive use for them, but not at the site of the plant. In small-scale reactors, the safety can be enhanced sometimes by new technologies. 

The MRX can be also used for a multi-purpose utilization such as electric power generation for a distance district, sea water desalination, and heat supply. Features of MRX, i.e., being easy movable, light-weighted, compact, simple and safe can be also suitable for these multipurpose utilization. 

The concept of a nuclear seawater desalination plant is shown in Fig. 16. The sea water desalination plant is planned based on a two stage reverse osmosis system with a capacity of240000mVday x 7 lines by using a single 4S plant. The plant can be constmcted on a site of about 210m x 140m. 

Since the island system is employed, an auxiliary power facility of 5000kW is required to startup the 4S and a gas turbine plant is constructed for this purpose. The electric power consumption of the reverse osmosis system is about 5kWh/m . Assuming IkWh/m is required to pump tiie water produced, about 6 kWh/m in total is required to operate the sea water desalination plant. Since the house load of the nuclear plant is 4100kW, a total power of 46MWe is required for the plant. 

Kawada I, Development of high efficiency sea water desalination RO membrane. Membrane 1999, 24, 336-341. 

Kunisada Y and Murayama Y, Long term experiments on sea water desalination at the Chigasaki Laboratory, Desalination 1978, 27, 333-344. 

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