This invention refers to the domain of natural salt water conversion (i.e. seawater. natural lake brine as well as industrial saline solutions).

There exist several methods of obtaining fresh water from seawater and other saline liquids, namely: vaporization boiling down (distillation), electrodyalisis, reverse osmosis, ion exchange (ionic replacement). The most widely used technique at present is reverse osmosis, energy expenditure per lm ³ being as high as 15 kW. The other disadvantages of this method, apart from that of the above mentioned energy consumption, consist in the need for high pressure application (50— 100 atm.), as well as the requirement for a eriodic replacement of high-cost membranes. Mention has to be made of the fact that all of the above quoted techniques, to the exception of the distillation method, are not capable of crystalline salt production, the latter being just dumped back into the sea in the form of high concentration brines.

To obtain crystalline salt, all of the relevant processes under consideration rely on brine vaporization by boiling it down, which involves high energy consumption (see US patent # 3, 676, 067 of 11/07/1972, PCT RU # 2005133756/15 of 11/01/2005, US patent # 8,021,557 of 05/08/2010 and RU Patent # 209,512).

The aim of this invention is to develop an economical and energy-saving method and setup for obtaining crystalline salt and fresh water from seawater and other saline liquids excluding the additional brine vaporization process.

The objective stated herein above is to be achieved by virtue of developing a set-up that would make it possible to implement all the processes involved as closed cycle (recirculation loop) ones to prevent heat efflux from the system and to perform direct heating of saline liquids and direct cooling of the resulting fresh water without resorting to the use of heat-conducting metal structures (heat exchangers), thus not only increasing the set-up efficiency but also reducing its steel intensity. The design of the set-up proposed herein also makes it possible to continuously obtain crystalline salt pulp and its saturated solution, which, upon the filtration thereof, will be recirculated to the set-up reactor, the resulting salt being the end-product suitable for use as is or for further processing.

The method thus proposed has been tested on a pilot set-up having a processing capacity of ~201 of salt water per hour.

Using the experimental set-up, raw salt liquids as follows were put to test: the Mediterranean Sea water; the Dead Sea water; the Palmachim desalting plant brine to be dumped back to sea the dead Sea plant brines being currently discharged back into the Dead Sea; salt water from one of Negev's artesian wells and the sewage water of the Beer-Shev poultry factory containing -10% of NaCl.

As a result of processing the raw saline liquids referred to above using the method and set-p described herein, high quality fresh water and salt were obtained, the latter being suitable for further use and processing. The reactor lcontaining salt water (to be desalinated) will be purged with air using a fan 2. The reactor 1 design features a conical shape bottom accommodating an agitator equipped with a raker. The raker/agitator assembly rotation speed is 2-3 revolutions per minute. The reactor 1 and all of the equipment, including the pipelines, shall be made of a corrosion-resistant material withstanding a temperature of up to 100°C and are to be thermally insulated with foamed polyurethane.

The specially designed fan 2, assuring the heating of the vapor-air mixture to 100°C (Rezirculazionie Ustanovki Aerodinamicheskogo Nagreva - Recirculation Set-ups for Aerodynamic Heating, Moscow, 1986, VI i, Tevis) will purge air into the reactor via a bubbler, the air thus saturated with water vapor being further on fed into the pipe 15, where it is to be additionally saturated with water vapor using the recirculation pump 3, which draws in the hot solution from the reactor to inject it into the pipe 21 via the pipe conduit 15 and the dedicated nozzles to mix up it with the head-on air flow. Excess water is to be recirculated into the reactor 1, whereas the water vapor-saturated air keeps on moving via the recirculation pipe 15, where, in the upper portion thereof, there occurs condensation and fresh water exudation. The above mentioned condensation phenomenon results from the water-saturated hot air contact with duly sprayed cooled fresh water as obtained using the set-up. The fresh water contained in the tank 1 1 is to be fed, using the pump 12 and via the tube 22, into the upper portion of the tube 15, where it is to be injected, via five rows of nozzles, into the pipe 15. The rows of injection nozzles shall have 3 nozzles each to be arranged at an angle of 120°, which makes it possible to arrange 5 water curtains all across the tube 15 cross-section, wherethrough hot air saturated with water vapor is to pass for cooling it down, water condensation being the result. AH of the water thus obtained will then be fed into segment A of the pipe 15 equipped with a catchment basin, wherefrom all of the water thus collected is to be discharged, via a tubular cooler 16, into the fresh water tank 11. The volume of water in the tank 11 shall be held constant, excess condensed water being herewith dumped into the intake tank 13, wherefrom it is to be delivered, via the pipeline 27, to the end user (consumer).

The tubular cooler 16 is to be cooled by the initially drawn seawater or any raw saline liquid to be processed as incoming from the storage tank 4 via the pipe 18 using the pum 5. The initial raw saline solution will be fed into the dedicated storage tank via the pipe 17.

The process schematic diagram alongside with the photo of an operating desalinating plant are presented in Fig. 1 and Fig. 2 respectively.

The cooling water, by virtue of passing it through the tubular cooler 16 will cool the fresh water down to 25-30°C, the cooling water itself being herewith heated up to 80°C. The hot water from the cooling jacket of the tubular cooler 16 will be discharged via the pipe 23 into the transfer tank 9, wherefrom it is to be fed using the pump 10 via the pipe 24 into the heater 14, using any available power source (solar energy, electrical heating, natural gas heating, diesel oil heating, etc.), whereupon the solution heated up to ~95°C is to be fed into the reactor 1 as a raw material, the initial stage of the process of obtaining fresh water and salts to be then performed.

As fresh water exudates, the salts concentration in the reactor 1 increases and reaches its saturation value at a concentration figure of>25%, whereupon the solution thus saturated will be dumped on a continuous basis through the lower drain tap into the scraped-surface exchanger (fluid-cooled crucible) 6, where it is to be cooled by the initially drawn in saline solution. The resulting crystals thus precipitated and the duly cooled saturated stock (mother) solution are to be fed into the band vacuum filter 7, wherefrom the salt will be dumped into the storage tank 8 to be either dispensed to the end user (consumer) or directed to a follow-up processing line, the stock solution being herewith transferred via the pipes 19, 20 into the storage tank 9. It is to the same storage tank 9 that the cooling solution from the scraped-surface exchanger 6 is to be dumped to be further heated and used in the process of obtaining fresh water and salts.

The tests and calculations performed have shown that all the systems' closed-circuit operation and the high degree of heat exchange and thermal insulation make it possible to recuperate no less than 90% of energy expenditure and to reduce it to a figure of -2.5 kW per m ³ of fresh water.