WO2015004650A1

WO2015004650A1 - A method and installation for production of crystal salt and fresh water from sea water and other saliferous solution

Info

Publication number: WO2015004650A1
Application number: PCT/IL2014/000033
Authority: WO
Inventors: Solomon Flaks; Eli ROZANSKI; Jehuda MAZUZ
Original assignee: Green Hydrometallurgy Proceccing Ltd.
Priority date: 2013-07-10
Filing date: 2014-07-07
Publication date: 2015-01-15
Also published as: IL227430A0

Abstract

A novel process and its hardware implementation are proposed herein, whereby the set-up will operate at a temperature of < 100°C, no process features like membranes, high pressure or vacuum being herewith required in desalinating water or other saline solutions in an ecologically friendly manner, eliminating any environmental discharges. The design of the set-up is such as to facilitate the implementation of a closed-loop process preventing heat efflux from the system as well as assuring direct heating of saline solutions and direct cooling of fresh water. The set-up is also capable of obtaining, on a continuous basis, crystalline salts contained in the input raw solution.

Description

A METHOD AND INSTALLATION FOR PRODUCTION OF CRYSTAL SALT AND FRESH WATER FROM SEA WATER AND OTHER SALIFEROUS SOLUTION

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 lm³ 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 m³ of fresh water.

Claims

1. A method and the related set-up for obtaining crystalline salt and fresh water from seawater and other saline solutions comprising structural elements as follows:

(i) a reactor equipped with an agitator designed to obtain salts and a hot vapor-water mixture; and

(ii) a high-pressure fan equipped with a mini-turbine for aerodynamic heating, the former being designed to feed hot air via a bubble condenser into the reactor filled with saline water, this process being the first phase of air saturation with water.

2. The process as per Claim 1, whereby the hot air, upon its initial water saturation phase, is to be fed into a sloping pipe to perform the second phase of water saturation, for which purpose the hot solution from the reactor will be fed via dedicated nozzles using a recirculation pump to be mixed with the air of the first phase saturation.

3. The process as per Claim 1 or 2, whereby air saturation with water can also be accomplished using an air washer as well as with the help of ultrasonic, rotor-, disk-, honeycomb- and turbo- type humidifiers.

4. The process as per claims 1 through 3, whereby the brine remaining after the 2^nd phase of air saturation with water will be gravitation-discharged via a sloping pipe back into the reactor, wherefrom it will continuously be incoming for the second phase of air saturation with water.

5. The process as per claims 1 through 3, whereby the vapor-air mixture will be fed into a reverse slope pipe to accomplish fresh water condensation and the cooling of the hot water-air mixture by virtue of a direct contact with pulverized cold fresh water.

6. The process as per claim 5, whereby the cold fresh water pulverization is to be accomplished using nozzles, injectors or any other type of an atomized spray-injector, whereas the cooling of the hot water thus obtained will be performed in a tubular heat exchanger equipped with a cooling jacket, whereto the initial cooling saline solution having a temperature of ~ 25°C is to be fed.

7. The process as per Claims 1 through 6, whereby all of the duly cooled fresh water, both injected and condensed, will be discharged into a recirculation tank wherefrom the smaller portion of it is to be fed back into the recirculation system for direct cooling, the larger portion thereof being dispensed to the end user (consumer).

8. The process as per Claim 6, whereby the initial saline solution used as a cooling liquid will itself be heated in the cooling process to a temperature of ~ 90°C, whereupon it will be additionally heated by virtue of direct heating using electrical, natural gas, solar energy or other types of power sources to a temperature of ~ 95°C, to be then fed into the reactor for use in the first stage of the production process, which makes it possible to save at least 90% of energy expenditure.

9. The process as per Claims 1 through 8, whereby all of the equipment and the tubing (pipelines) shall have a foamed polyurethane thermal insulation coating, which will make it possible to reduce the radiation heat loss to an ultimate figure of 3-5%.

10. The process as per Claim 1, whereby design arrangements shall be made for the reactor to have a conical shape bottom with a centrally located adapter sleeve intended for discharging the precipitated salt and saturated brine, the dumping process being herewith accomplished using an agitator equipped with a raker, the raker/agitator assembly rotating at a speed of 2-3 revolutions per minute.

11. The process as per Claim 4, whereby the length of the pipeline accommodating the 2^nd process phase of air saturation with water shall be set at such a value as to effect a simultaneous process of resaturation / brine droplet separation from the air-vapor phase, which makes it possible to avoid the use of dedicated purpose-oriented droplet separators.