WO2022034353A1

WO2022034353A1 - Solvent extraction water treatment process for wide range of salinity with no liquid waste discharge

Info

Publication number: WO2022034353A1
Application number: PCT/IB2020/057506
Authority: WO
Inventors: Hossein PAJOOHI; Ali TAZARI
Original assignee: Pajoohi Hossein; Tazari Ali
Priority date: 2020-08-10
Filing date: 2020-08-10
Publication date: 2022-02-17

Abstract

The invention of solvent extraction water treatment process for wide range of salinity with no liquid waste discharge is a method for treating saline waters based on directional solvent extraction technique. The novelty of this invention is the utilization of this method in treating saline water, ranging from low concentration salt water (lower than seawater concentration) to ultrahigh-salinity industrial waste water. This eco-friendly method is membrane-less and not based on evaporation phase change so its energy consumption is lower. Moreover,simplicity, flexibility and scalability in different industrial processes and applications are its other important advantages.This process is based on absorbing water from saline water using solvents and extracting absorbed water from solvent by changing the temperature. For better purification of extracted water, pre-filtration and post-treatment units (such as RO)are proposed.This method provides high water recovery ratio, zero liquid waste discharge and valuable solid salts as a by-product.

Description

TITLE OF THE INVENTION

SOLVENT EXTRACTION WATER TREATMENT PROCESS FOR WIDE RANGE OF SALINITY WITH NO LIQUID WASTE DISCHARGE

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the water treatment methods of saline water ranging from low-concentration salt water (lower than seawater concentration) to ultra-high salinity industrial wastewater, and also relates to systems and methods for treating industrial saline wastewater and also relates to the water treatment methods using one or more solvents as well as water treatment systems using small changes in temperature and also relates to systems for exchanging heat for transferring heat from one part of the system to another part and also relates to controlling the process using heat pumps and also relates to water absorption from saline water by the solvent and separating concentrated brine and very low concentration treated water and also relates to treating large volume of saline water with different salinity levels, with no liquid waste discharge and making no saline waste waters, while producing valuable solid salts as byproduct of the process.

BACKGROUND OF INVENTION

The limited fresh water resources on Earth have been put under a considerable pressure by world population growth resulting in water scarcity in many regions. Climate change and global warming have exacerbated this crisis. Consequently, there has been a great interest in protecting existing water resources in recent years. This has led to the extensive use of desalination technology for treating salt water, especially seawater, and efforts have been made by research teams across the world to improve these methods over the last decades. Oldest technologies such as heating boilers for evaporation and then condensation of water, have been replaced by more economical methods, so water desalination and treatment is gradually improving.

The desalination technologies used so far include, Evaporation processes, Membrane processes, Electro Dialysis (ED), Capacitive Deionization (CDI) etc. However, the three globally popular technologies in recent years are reverse osmosis (RO), multi-stage flash (MSF) and multiple effect distillation (MED). MSF and MED are thermal distillation methods long favored for their large production capacity, but the evaporation process requires large amounts of energy to overcome water latent heat (about 539 kcal/kg) which in economical computation of treatment project, accounting as 40-50% of the operating costs. Furthermore, calcium crystallization causes unavoidable substantial depreciation of value of the said technologies and reduced lifetime of expensive MSF and MED facilities. RO technology has attracted great interest and grown faster than the competing technologies because of high efficiency, ease of use, lower energy consumption than MSF and MED, and flexibility in applicable scale from small to large-size plants.

Despite all RO advantages, the major problem facing this technology is the need for high pressure to induce osmotic pressure. The electrical energy used in treating seawater using RO (SWRO) accounts for about 44% of the total costs. In addition to high electrical energy consumption, RO membranes are susceptible to fouling, rupture or leakage problems and high operating pressures necessitating frequent membrane replacement and cleaning. Although RO systems have been extensively employed for desalinating seawater, the need for high osmotic pressure (about 60-70 bars) and expensive membranes pose problems in utilizing this technology. The RO membranes degrade rapidly and should be replaced frequently because they are exposed to high-salinity seawater and high operating pressures. More salt concentration (more TDS) needs more osmotic pressure and more expensive and High-Tech membrane. So this method is not suitable for medium/high concentration saline waters.

Electro Dialysis (ED) is a membrane-based technology that utilizes electric potential difference. However, due to its high energy consumption, this method is only used for treating low-TDS water (i.e. brackish water).

Recently, Forward Osmosis (FO) has attracted considerable interest recently of less energy consumption than SWRO. The FO process uses the osmotic pressure difference between the feed solution and draw solutions as the driving force for transporting water across semi permeable membranes. This method requires lower energy, but there are still ambiguities regarding the FO mechanism. The behavior of water molecules and ions in this process is not well understood. Also, effective recovery of the draw solution in FO process should be solved in order to propose this method to full-scale plants. Most of said methods are suitable only for treatment of low salinity water. Only thermal methods could be used for medium\high concentration brine with high energy consumption and High costs and depreciation of facilities.

Solvent extraction, also called Directional Solvent Extraction (DSE) is a method for purifying water soluble salts. The idea of this directional solvent extraction for salt production and purification was firstly proposed in the 1960s. This method separates the water from saline water by using the difference in the solubility between water and non-polar solvent according to the temperature change. In addition to non-polar solvents, some edible oils and long-chain carboxylic acids are able to absorb water molecules and repel salt ions (G afe ). This ability can be utilized to desalinate salt waters. Eow energy consumption compared to the other desalination processes, simplicity of process stages and flexibility in applicable scale from small to large-size plants, are the most important benefits of this method. Followings are some of the important inventions and researches presented in this field:

US Patent No. US3088909A (Davison et al.) describes an invention relates to the extraction of water from saline solutions. Saline waters include brackish waters, sea water, and in general salt solutions of any kind in which the solvent system is compatible. A method for the recovery of fresh water from saline waters employing various solvents, especially amines, has been proposed. See, for example, the article by Davison and Hood in Saline Water Conversion, publication 1958, pp. 408-416, 568, National Academy of Science-National Research Council; and the article in Chemical and Engineering News, Feb. 2, 1959, pp. 40, 42. Essentially, the method consists in employing solvents which have a large change in solubility for water at different temperatures, and which contain strong electro-negative atoms within the molecule that have the property of forming hydrogen bonds with water molecules. However, the presences of hydrophobic side chains in the solvent molecule draw the water- solvent couple into the solvent phase.

Most of the solvents proposed in this invention have a boiling point and specific gravity higher than pure water. This leads to the impossibility of complete separation and recycling of solvent from water. Moreover, treatment process with these solvents with higher boiling point consume too much energy.

Also in a US Patent No. US3177139, April 6, 1965 (Kimberlin et al.) presented a technique for the solvent extraction of water from an aqueous solution. Particularly, this invention relates to a process of solvent extraction of water from saline solutions. The invention relates to a process of selectively- extracting water from an aqueous saline solution by countercurrent contact of the saline solution with an amine solvent selective for water at a temperature at which the solvent is partially miscible with the water in the saline solution and selectively extracts water over salt. The critical feature of the extraction step is that a temperature gradient is imposed on the countercurrent extraction step and the extraction is carried out over a specified temperature range.

This process is limited in application to brackish waters containing only about 3000 to 5000 parts per million of salt. Another characteristic of the solvent is that even though the solvent is miscible with water at lower temperatures, at relatively slight increases in temperature the solvent is almost totally immiscible with water. Therefore, the water can be extracted from the saline solution by solvent extraction and then the water can be separated from the solvent by only a slight increase in temperature. These characteristics greatly decrease the energy requirements of the system for recovering, for example, potable Water from a saline solution.

US Patent No. US3239459 (Patterson) describes a method of recovering water which is substantially salt-free water from a saline solution, which comprises contacting the salt water, with a hydrophilic solvent comprising an organic compound having a hydrocarbon radical attached to a terminal oxygen containing group to effect: an initial separation of water from the saline solution and produce an extract of water in solvent. The invention, while applicable to any aqueous solution of an inorganic or mineral salt, has primary application to naturally occurring solutions wherein sodium chloride is the predominant salt. It has been recognized that certain organic liquid solvents will enter into solution with water, but will have little or no affinity for salt carried in solution by the water, so that when such a solvent is grough into intimate contact with sea water, there may be produced two solutions, one in which water is dissolved in the solvent with little or no salt, and one comprising water with some solvent and practically all of the salt. Subsequently it uses a hydrophobic organic solvent, that is one which has little or no affinity for water, but which will readily dissolve the hydrophilic solvent first used. The second solvent rejects the water and enters into solution with the first solvent, the mixed solvents being then easily separated at least to a substantial extent by gravity from the water.

Through this use of a hydrophilic solvent succeeded by the use of a hydrophobic solvent, it can produce potable water having only a trace of the solvents, a brine having only a trace of the second solvent and a solution of the two solvents.

US Patent No. US3314882A (Schoroeder) describes a method for desalination of salt water and is particularly concerned with a process and apparatus for the desalination of salt water using solvent extraction techniques. The principal object of the invention is to provide an economical solvent extraction process for the desalination of salt water. Another object is to develop a group of solvent extraction compounds which are readily recoverable from the extract for reuse, if desired, on a continuous basis. Still another is to develop techniques for recovering and reusing the solvents in the most expeditious manner. Other objects include developing techniques and apparatus which employ means such as a heat pump for preserving and carrying over the process heat from one stage to another so that the heat can be reused on a continuous basis. In the solvent extraction of water from salt water, the solution is the salt water, and the additional solute, the solvent extraction compound. In the extraction process, the two are contacted in liquid form and by countercurrent flow, and two products are drawn from the extractor, one of which is a more concentrated raffinate and the other is an extract containing water of low salinity. The solvent is there after recovered from the extract, thus leaving the water as a product. Moreover, if desired, it may be recycled indefinitely through the displacement step. According to the invention the organic compounds which is employed are solid at room temperature, are sparingly soluble in water and when added in greater than saturating amounts to the same at temperatures above their crystallization melting points in the water-organic system, they form a pair of liquid phases with the water of which one has a high concentration of the compound and the other has a low concentration of the same. If the two solutions are directed countercurrent to one another by any one of the several conventional liquid extraction techniques, a pair of products can be produced in one of which there is an increased salt concentration and in the other of which there is a depleted salt concentration.

US Patent No. US3536454 (Vuillemey) presented the technology of an apparatus for extraction of water from saline solutions. The invention is primarily applicable to the separation of fresh water from sea water, and to processes in which the water is extracted by means of a solvent, then separated from the solvent at a higher temperature than that of the extraction process. There are usually employed for this purpose organic solvent having an amine base in which the salts contained in sea water are insoluble at ordinary temperature. The fresh water is then separated from the solvent by heating to approximately 50°C. The main objective of this invention is to reduce the power and so the cost of application of solvent extraction processes to the treatment of sea water under profitable economic conditions from an industrial viewpoint. To this end, the invention consists in recovering the dissolution energy which is released at the extraction stage in order to take part in the heating which is necessary for the separation stage. The invention is further concerned with a process for the purification of water from a saline solution, said process being primarily intended for the production of fresh water from sea water and essentially characterized in that it comprises a first stage of extraction performed at progressively decreasing temperatures by circulating said solution countercurrent to a solvent for the water, and a second stage of separation performed at progressively increasing temperatures by circulating the loaded solvent countercurrent to pure water, said stages being carried out on each side of a heat-transfer wall and the solvent being circulated in a closed cycle and respectively in two opposite directions on each side of said wall. The present invention is also concerned with an apparatus for the practical application of the process referred to above. In this apparatus, the two aforesaid stages are carried out in two coaxial columns in which the solvent is circulated in two opposite directions countercurrent respectively to the saline solution and to the fresh water.

The apparatus in accordance with the invention for the purification of water from a saline solution by solvent extraction followed by separation of the solvent at a different temperature is essentially characterized in that it comprises: two coaxial vertical columns, namely an extraction column and a separating column; means for circulating said solvent in a closed cycle respectively in two opposite directions within said columns; means for circulating the saline solution within the extraction column countercurrent to the solvent; means for circulating pure water through the separating column countercurrent to the solvent, said means comprising in a first of said columns means for circular agitation and a helical fin for producing an upward progression of the phase which has the higher density and which is projected onto the fin under the action of centrifugal force. In the second of said columns, the progression of the two phases takes place in the natural direction, and the lighter phase flows upwards within the downflowing heavier phase. In the usual case in which the solvent employed is of lower density than pure water and the saline solution, said first column is the extraction column, said extraction column being preferably placed inside the separating column.

US Patent No. US3424675A (Davison et al.) explains that efficiency of a water extraction process using an amine solvent is increased by vaporizing part of the fluids in the extraction zone, compressing those vapors and utilizing the latent heat of vaporization and the heat of compression to effect a separation of the extract into water-rich and solvent-rich phases.

US Patent No. US3386913A (Leon) provides an improved process for treating salt containing water wherein saline free water is continuously extracted from a continuous stream of salt containing water by contacting the same with a selected solvent having a large capacity for water enrichment at a critical temperature related to the solvent; the water enriched solvent being separable at another temperature into substantially solvent free water and solvent phases, thereby providing a potable water product; while permitting the solvent phase to be continuously recycled to continuously extract further amounts of water of reduced saline content from the salt containing water.

PCT International Application No. WO2013066662 (Sun et al.) provides a treatment process and a treatment system for treating an aqueous saline solution. The treatment process comprises contacting an aqueous saline solution with an effective amount of a miscible organic solvent to precipitate dissolved salts and produce a mixture of precipitated solid salts and a liquid and then removing the precipitated solid salts from the liquid. The treatment process further comprises cooling the liquid to produce an organic phase comprising the miscible organic solvent and an aqueous phase comprising the miscible organic solvent and the dissolved salts and then removing the organic phase from the aqueous phase. The treatment process further comprises introducing the aqueous phase into a membrane device to remove the miscible organic solvent and the dissolved salts from the aqueous phase.

US Patent Application Publication No. US20140158616A1 (Govind et al.) describes a system, method, and apparatus for precipitating a water soluble salt or water soluble salts from water, including adding a water-miscible solvent to a water solution including an inorganic salt. The system, method and apparatus also allow for the separation of the precipitated salt, and for separation of the solvent from the water. In doing so, reclamation of water is provided. The recovery of water will be possible in this method. In this invention the infinite solubility of water is at 25° C, the boiling point is greater than 25° C. at 0.101 MPa and heat of vaporization is about 0.5 cal/g or less. US Patent No. US9428404B2 (Bajpayee et al.) claims purified water can be obtained via a continuous or semi-continuous process by mixing a liquid composition (e.g., sea water or produced fresh water) including water with a directional solvent to selectively dissolve water from the liquid composition into the directional solvent. The concentrated remainder of the liquid composition (e.g., brine) is removed, and the water is precipitated from the directional solvent and removed in a purified form. The solvent is then reused as the process is repeated in a continuous or semi-continuous operation.

US Patent No. US8501007B2 (Bajpayee et al.) describes substantially pure water is produced via desalination using a directional solvent that directionally dissolves water but does not dissolve salt. The directional solvent is heated to dissolve water from the salt solution into the directional solvent. The remaining highly concentrated salt water is removed, and the solution of directional solvent and water is cooled to precipitate substantially pure water out of the solution. In an example of the method, a saline solution (e.g., sea water) is brought into contact with a directional solvent. The directional solvent can include a carboxylic acid (i.e., a compound that includes a carboxyl group, R — COOH), such as decanoic acid. The saline solution and solvent are heated before or after contact to enhance the directional dissolution of water into the solvent and to thereby produce distinct phases, a first phase that includes the solvent and water from the saline solution and a second phase that includes a highly concentrated remainder of the saline solution. The first phase separates from the second phase and is extracted. Alternatively, the second phase can be extracted from the first phase.

Research Paper titled “Zero Liquid Discharge of Ultrahigh-Salinity Brines with Temperature Swing Solvent Extraction” (Boo et al.), demonstrates Zero Liquid Discharge (ZLD) of ultrahigh- salinity brines using Temperature Swing Solvent Extraction (TSSE), a membrane-less and nonevaporative desalination technology. TSSE utilizes a low-polarity solvent to extract water from brine and then releases the water as a product with the application of low-temperature heat. Complete extraction of water from a hyper saline feed, simulated by 5.0 M NaCl solution ( =292 g/L TDS), was achieved using di-isopropylamine solvent. Practically all of the salt is precipitated as mineral solid waste and the product water contains <5% of NaCl relative to the hypersaline feed brine. Consistent ZLD performance of high salt removals and product water quality was maintained in three repeated semi-batch TSSE cycles, highlighting recyclability of the solvent. The practical applicability of the technique for actual field samples was demonstrated by ZLD of an irrigation drainage water concentrate. This study establishes the potential of TSSE as a more sustainable alternative to current thermal evaporation methods for zero liquid discharge of ultrahigh- salinity brines. But in this research, very large volume of solvent (more than 50 times the volume of salt water) must be used, which is impractical and cost inefficient because of the need for large amounts of solvent, energy, and large storage and separation systems.

US Patent No. US3408290 (Scheibel) describes a process that involves extraction of an aqueous saline solution like sea water with such a Solvent at a temperature for optimum extraction of water from the aqueous saline solution, followed by heating the Solvent extract to effect phase separation. The heating Step is effected by direct countercurrent contact between the extract and recycled desalinated water. Similarly (as part of the extraction step), the saline raffinate is heated by direct countercurrent contact with heated recycled Solvent. Direct countercurrent contact heating so associated with extraction results in a saline raffinate having relatively little solvent therein, and a separated desalinated water phase having relatively little solvent therein.

US Patent No. US3415744 (Buetow), describes a solvent extraction method for reducing salt content in saline solution, and more particularly relates to a method for extracting potable water from sea water by liquid-liquid extraction. In the method of this invention water containing dissolved mineral salt is contacted by a solvent in which water dissolves preferentially to salt causing two liquid phases to form, one as a brine and solvent raffinate layer and the other as a potable water (with respect to salt content) and solvent extract layer; the two phases are separated and each may again be contacted with a solvent to cause aqueous and organic phases to separate from each separated fraction. It is another object of this invention to provide an economical method for rendering saline water potable and suitable for large scale agricultural and industrial use.

US Patent No. US3318805 (Hess et al.) describes a process for separating water from a salt solution or brine by extraction of the water with an organic liquid characterized by the property of extracting a greater amount of water at an elevated temperature and pressure than at a lower temperature and having the property of releasing water from the extract as the pressure is increased above the extraction pressure. In carrying out the process of this invention, the organic liquid is brought into contact with the brine at an elevated temperature and pressure. Water is recovered from the complex by subjecting the complex to increased pressure at the temperature of the extraction step or at a lower temperature. The complex which may be in liquid phase or dense vapor phase at the elevated pressure is immiscible with the residual brine and is separated from the brine by gravity.

US Patent No. US3171808 (Todd) describes a method and apparatus for extracting fresh water from ocean salt water by separation of solute such as salts from solvent such as water as a result of their unequal diffusion rates through semi permeable osmotic membranes, wherein a pressure drop is maintained across the membranes by the natural hydrostatic pressure of sea water to maintain water flow from the salt water side to the fresh water side. EXISTED PROBLEMS IN THE FIELD OF TECHNOLOGY

Despite the great interest in the use of DSE technology for desalinating water in recent years, there have been no considerable advances on industrial scale.

Nevertheless, this method has not reached complete maturity and growth and development, and this technology is only used for treating low- salinity water with a salt concentration of less than 5000 ppm. There are limited studies on DSE mainly due to technical problems and the lack of knowledge on the interaction of water molecules, salt ions, and solvents used in this method.

There are more technical and practical problems in most of aforementioned innovations and studies, which are mentioned below:

According to recent studies, water extracted using DSE method is not acceptable for reuse despite low salt content. Also in this method, the watersolvent mixture should be exposed to alternating heating/cooling cycles from the temperature T1 to T2 and vice versa. Each solvent has its own specific T1 and T2. If the difference between T1 and T2 is large, or if T2 is close to the boiling temperature of water or the solvent, there will be technical problems when the technology is used on an industrial scale. These problems arise from evaporation of water or the solvent followed by increased pressure and cavitation. Moreover, energy consumption increases with increasing the difference between T1 and T2.

In this method, the water and solvent mixture forms two phases (the solventrich phase and the water-rich phase). These two phases must be rapidly and completely separated from each other through a complicated and difficult process.

Following the treatment process, the complicated process of separating the solvent from the wastewater and the treated water must be carried out. Desalination technologies are usually accompanied by the division of the salt water inflow into two liquid outflows. One of these outflows is the treated water and the other, the concentrated salt water with other contaminants. Management and discharge of this high concentrated saline water are other important problems faced by the commonly used water treatment methods because its discharge to the environment will have destructive effects on ecosystems.

The purpose of this invention is to introduce a new method for treating waters containing various types of salts, inorganic solutes and metal ions at different concentrations to resolve the above-mentioned problems. The proposed method is capable of recovering large volumes of water and valuable salts without producing waste liquid discharge through the direct solvent extraction (DSE) technique and other useful technologies.

INVENTIVE STEP OF THE INVENTION

The inventive step of this invention is based on an eco-friendly water treatment method characterized by optimal energy consumption and low CO2 emissions and can be used for treating saline water ranging from low-concentration salt water (lower than seawater concentration) to ultra-high salinity industrial wastewater. This method is able to convert saline brine into high purity water such as potable water or treated water with acceptable quality for certain industrial uses, irrigation or etc.

DESCRIPTION OF THE INVENTION

The invention will now be described with reference to the drawing, wherein preferred embodiments are described in detail to enable practice of the invention. Although the invention is described with reference to these specific preferred embodiments, it will be understood that the invention is not limited to these preferred embodiments. To the contrary, the invention includes numerous alternatives, modifications, and equivalents as will become apparent from consideration of the following detailed description.

Water with solute, salts or in-organic ions with various concentration from low/medium salinity (for example: sea water with salt concentration of about 35 gr/lit.) to high and ultra-high salinity industrial waste water (100 to more than 300 gr/lit.) could be treated with this method with zero liquid waste discharge described below:

This invention disclosed a method for treatment of saline water and super saline water. According to FIG 1, a flow diagram shows this treatment method. Low/medium concentration Saline water la passes through prefiltration and sedimentation unit 2a and then is stored in saline water tank 3. This saline water is pumped into first desalination unit 10. Solvent “A” is stored in tank 4. Solvent” A” 4 and saline water 3 are mixed with predetermined ratio. Mixture temperature 5 is reduced to temperature Tl. The resulting mixture is entered to cold separator 6. Due to the specific volume of cold separator 6, stream velocity is reduced and the mixture is divided into two phases. In top phase, low density solvent-rich phase includes solvent and water with low salt concentration is separated and is placed on top of concentrated brine. The solvent-rich phase has been discharged from cold separator 6, after heating 7 and temperature increase to T2, it will be transported to warm separator 8. And concentrated brine is collected at the bottom of cold separator 6. This brine water with little dissolved solvent is moved to solvent recycler unit 9 in order to completely separate dissolved solvent. Recycled solvent is returned to the solvent “A” tank 4 for reuse. Remaining concentrated brine will be transferred to the zero liquid discharge crystallizer unit 16. The Solvent-rich phase that leaves cold separator 6_will be heated 7 and entered to warm separator 8. This stream forms two separated phases; separated low density solvent phases at the top which is returned to the solvent “A” tank 4 and, extracted water phase 10a at the bottom.

Desalinated water 10a has a very small amount of salt compared to feed water 3. So it could be proposed for some uses such as industrial applications. But for better desalination, extracted water 10a could be treated in a secondary desalination unit 11. Based on salt concentration of feed water and in-demand treated water quality, secondary desalination unit 11 could be RO (Reverse Osmosis) treatment unit as shown in FIG. 1 or similar to the first desalination unit 10 (FIG. 2). Both methods are used linearly after the first desalination unit.

In the case of using a secondary desalination unit similar to the primary unit (FIG. 2), treated water 10a from the first desalination unit 10 will be entered to the second desalination unit 11. Solvent from tank 4a and saline water stream 10a are mixed with predetermined ratio. Mixture temperature 5a is reduced to temperature T3. The resulting mixture is entered the cold separator 6a. Due to the specific volume of cold separator 6a, stream velocity is reduced and the mixture is divided into two phases. In top phase, low density solvent-rich phase, which includes solvent and water with very low salt concentration, is separated and is placed on top of concentrated brine. The solvent-rich phase has been discharged from cold separator 6a, after heating 7a and increasing temperature to T4, it will be transported to warm separator 8a. The concentrated brine water with little dissolved solvent, from stream 12, is returned to the saline water tank 3 for re-treatment. This concentrated water is returned to the treatment process so mixed solvent recycling process is not necessary. The Solvent-rich phase that leaves cold separator 6a will be heated 7a and entered to warm separator 8a .This stream forms two separated phases; separated low density solvent phases at the top which is returned to the solvent “A” tank 4a for reuse and, extracted water phase Ila with a little mixed solvent at the bottom. Dissolved solvent in extracted water phase Ila will be completely removed in solvent recycler 13. Solvent recycler unit 13, process is similar to recycler unit 9. Recycled solvent is returned to the solvent “A” tank 4a and purified water from the second desalination unit 11, in stream 14, after passing post-filtration unit 15 will be stored in treated water tank 29.

In zero liquid discharge crystallizer unit 16, concentrated brine has been transferred from cold separator 6 will be mixed 18 with solvent “B” coming from solvent “B” tank 17. In filtration unit 19 wet salt crystals or slurry 20 are separated from water- solvent mixture 18 and discharged to dryer unit 21. In the dryer unit 21 solid salt crystals 22 will be produced. Extracted water-solvent mixture from the dryer unit 21 and diluted saline water discharged from filtration unit 19 join together to enter thermal separator 23.

After heating/cooling of solvent-water mixture in thermal separator 23, two separated phases are formed. Low density solvent part lies at the top and is returned to the solvent “B” tank 17 and low concentrated saline water is placed at the bottom which after solvent extraction process in solvent recycler unit 25, will be returned from stream 27, to the saline water tank 3 for re-treatment. Recycled solvent is returned to the solvent “B” tank 17 for reuse.

In order to desalinate high and ultra-high concentration brine with this method, the treatment process begins with the entry of this super-saline water from point lb (instead of entry from point la in the previous case). This stream is transferred to crystallizer unit 16 after passing through filtration unit 2b. The rest of the purification process will continue similar to the process described above.

In the described method, Tl, T2, T3 and T4 have low values and there is a small difference between Tl and T2 or T3 and T4. Based on the type of solvent used in this process, the initial temperature (mixing temperature) Tl or T3 varies from 5 to 20°C, and the secondary temperature (separation temperature) T2 or T4 varies from 45 to 65°C. Consequently, the best and least energy-intensive option for decreasing/increasing flow temperatures in various stages of this technique is to use heat exchanger between inlet and outlet flow of each unit. In addition, temperature range of this process (5 °C to 65 °C) is covered with operating temperature range of heat pumps. So heat pump 28 is proposed for transferring heat energy from cooling zones to heating zones. The thermal energy is absorbed in the cooling unit (evaporator) of the heat pumps directly or indirectly from the flow that needs to be cooled to Tl. This absorbed thermal energy is released directly or indirectly in the heating section (condenser) into the flow that must be heated to T2.

In the direct heat transfer, the flow is directly heated/cooled by the heat exchangers of the heat pump. However, in the indirect heat transfer, the heat pump heats/cools the working fluid after heating/cooling of an intermediate fluid such as water or oil and circulating it in the heat exchangers installed in the various parts of the project. Given the high efficiency, heat pumps could transfer heat energy about 4 to 6 times of its power consumption. This leads to a significant increase in the efficiency of the invented water treatment system.

If additional heat is required, it is possible to use electric, fuel, solar or other types of heaters in various stages. In case where extra cooling is needed, additional heat exchangers such as air-cooled or water-cooled exchangers can be employed. In this invention, two types of solvents (A and B) are used for the following reasons:

Based on the salt concentration of the inflow feed in this water treatment method, different solvents are used in the desalination and crystallization units. As mentioned, the inflows into the desalination units have low to medium salt contents. Consequently, low-polarity organic solvents such as amine solvents (Triethylamine, Diisopropylamine and etc.), Tetrahydrofuran and 1, 2 Dimethoxyethane and 2- Butanol must be used in the desalination unit. However, the use of ketones, alcohols and some amine solvents as the solvent is more suitable and efficient in the crystallization unit given the high-salinity inflow to this unit. In this invention, Triethylamine, Diisopropylamine, Tetrahydrofuran, 2- Butanol N,N-Diethylmethylamine, N,N- Dimethylisopropylamine, N-Ethylisopropylamine, N-Methylbutylamine and 1 ,2-Dimethylpropylamine are proposed to use as solvent” A” and Acetone, Butanone (MEK), Ethanol, 2- propanol, Acetonitril, Tert-Butanol, 1, 4-Dioxane, ethylene glycol dimethyl ether and Diethylamine are suggested for solvent “B”.

Both solvents types (A and B) in this invention must have a lower boiling point and density than pure water, So that the solvent can be easily and completely separated and recycled from the water. The lower the density of the solvent, the faster and more complete the separation of the two phases (the solvent-rich phase and the water-rich phase). And the lower the boiling point, the easier and faster separation and recycling of the solvent. Moreover, using solvents with lower boiling points and densities leads to a significant reduction in energy consumption throughout the desalination process.

It is noteworthy that most solvents used in the crystallization unit cannot be utilized in the desalination unit because they do not form two phases. Moreover, given the high-salinity inflows to the crystallization unit, most of low-polarity solvents are not able to absorb considerable volumes of water because of their low polarity. Therefore, a larger volume ratio (about 40-60 times the volume of salt water) compared to the suggested solvents must be used, which is impractical and cost inefficient because of the need for large amounts of solvent and energy, and large storage and separation systems.

The invention of solvent extraction water treatment process for wide range of salinity with no liquid waste discharge includes at least a tank for maintaining and feeding the salt water and at least having a pre-filtration step for separation of suspended particles and at least a preliminary desalination cycle using solvent extraction method and at least a secondary cycle and at least a water purification system to produce potable water and at least a system for separation of salt from slurry and at least a crystallizer unit and at least a dryer system to dry separated salts and at least a complete cycle for returning the solvent to the fresh water production cycle.

Also this is a method for desalinating and treating various types of water containing various types of salts, inorganic solute and/or metallic ions with low to ultra-high concentrations. It has several stages consist of providing low/medium or high/ultra-high concentration salt water and supplying low- polarity organic solvent for desalination and providing a hydrophilic organic solvent for salt crystallization and mixing the low/medium concentration salt water (from Step A and/or diluted salt water coming from step M) with the solvent (Step B) and reducing the temperature of the resulting mixture to T1 to form two distinct phases (solvent-rich phase (SRP) and the water-rich phase (WRP)). The optimal relative quantity of solvents and T1 are selected in a way that the largest volume of water having the lowest salt concentration is absorbed by the solvent and separating SRP (Step D) and increasing the temperature to T2 to optimally form two separated phases (diluted low- salinity water and solvent at T2) to maximize dehydration of the selected solvent and recovering and transferring the dehydrated solvent (Step E) to Step D for reuse and transferring the low-salinity treated water (Step E) to the secondary RO treatment unit, or repeating the presented method from Step D to Step F, or a combination of both methods for final purification and returning waste water of this secondary treatment unit to step D for re-treatment and recovering the solvent mixed in concentrated WRP (Step D) and transferring the recovered solvent to Step D for reuse and mixing the solvent (Step C) with high or ultra- high concentration salt water (from step A and/or concentrated salt-water remained in Step H) to precipitate and separate salt crystals and slurry from the diluted salt water-solvent mixture and separating water in the salt crystals and slurry and producing solid dry salt and mixing water separated in Step J with the diluted salt water-solvent mixture coming from Step I and separating and recovering the solvent mixed with the diluted salt water (Step K) and recycling it to Step I for reuse and transferring the diluted salt water in Step L to Step D for re-treatment, by repeating the presented method from Step D to Step M.

This method can be used for treatment of low, medium, high and ultra-high concentration salt water wherein the solvent for desalination process in step B comprises low-polarity organic solvents and solvent for salt crystallization in step C comprises hydrophilic organic solvents. Both types of solvents have a boiling point and a density lower than pure water

This process begins with mixing the salt water and solvent and decreasing the temperature of resulted mixture to optimally form two separated phases (solvent-rich phase (SRP) and water-rich phase (WRP)). Separation of SRP and increasing the temperature employed as a part of treatment method to optimally form two phases and increase the process of dehydration of selected solvents to the last possible degree i.e. diluted water with small amount of salt and solvent. The recovery and transfer of dehydrated solvent to reuse can be employed as a part of treatment method. Also transferring the treated water with low salinity to the second desalination unit of RO, or repeating the provided method or a combination of both methods for the final treatment and returning the waste liquids of second treatment unit for retreating and recovery of mixed solvent in the warm separator and transferring the recovered solvent to reuse can be employed as a part of treatment method. The desalination solvent includes low- polarity organic solvents, specifically amine solvents, Triethylamine, Diisopropylamine, ethylene glycol dimethyl ether (DME), Tetrahydrofuran, 2- Butanol, N,N-Diethylmethylamine, N,N-Dimethylisopropylamine, N- Ethylisopropylamine, N-Methylbutylamine, 1,2-Dimethylpropylamine or any combination thereof. The desalination solvent in Step C includes semi-polarity organic solvents, specifically Acetone, Butanone (MEK), Ethanol, 2-propanol, Acetonitril, Tert-Butanol, 1, 4-Dioxane, ethylene glycol dimethyl ether and Diethylamine or any combination thereof.

The heat-exchanger is used between inlet and outlet flows of cold separators to absorb thermal energy from inlet flow and decrease its temperature and transfer heat into the cooled outlet flows to increase their temperature and heatexchanger is used between inlet and outlet flows of warm and thermal separators and solvent recycler to absorb thermal energy from heated outlet flow and decrease its temperature and transfer heat into the inlet flows to increase its temperature. Also the heat-pump is used to absorb thermal energy from streams that need to be cooled and transferring the absorbed heat to streams that need to be heated. The separation of salt crystals and slurry and production of dried solid salts and separation and recovery of solvent mixed with diluted salt water and recycling the solvent for reuse can be employed as a part of the treatment method. Transferring of diluted salt water to RO unit for retreatment can make potable water. BRIEF DESCRIPTION OF FIGURES

Figure 1 shows the process of treating low/medium or high/ultra-high concentration salt water equipped with a Reversed Osmosis system for maximum reduction of salt concentration.

Figure 2 shows the process of treating low/medium or high/ultra-high concentration salt water equipped with a duplicated treating system to produce water that contains very low salts.

DESCRIPTION OF PRACTICAL SAMPLES

Materials and Chemical Solvents.

- Diisopropylamine from Merck KGaA was used as Solvent “A”.

- Diethylamine from Merck KGaA was used as Solvent “B”.

- Low concentration saline water was prepared by dissolving 35g/L salt powder (extracted from seawater) in ultra-pure water. The salt concentration of this water is similar to salinity of Indian, Atlantic and Pacific Oceans waters.

- High concentration saline water was prepared by dissolving 2.0 Mole/L (117 g/L) salt powder (extracted from seawater) in ultra-pure water.

- Super saline brine was prepared by dissolving 4.0 Mole/L (234 g/L) purified sodium chloride powder in ultrapure water.

- Ponceau 4R (El 24) as red color agent. This powder is a red azo dye which is stable to light, heat, and acids. This dye is soluble in water but insoluble in most solvents. To make a more visual distinction between two liquid phases (water-rich phase and solvent-rich phase), this red dye was dissolved in saline waters to yield less than 0.5 w/w% solutions.

- Johnson quantitative filter Papers’ Grade 354 with Intermediate pore size of 12-15 pm was used to filter salt precipitates.

Part 1: Low Concentration Salt Water Desalination and Treatment

In this experiment, low concentration salt water with salinity of 35 g/L (similar to that of seawater) was treated and desalinated. Diisopropylamine was selected as Solvent “A” for this purpose. First, 60 mL saline water (at 15 °C) was poured into an Erlenmeyer flask and 420 mL solvent A (at 15 °C) was added and the flask was closed.

The mixture was then stirred with a magnetic stirrer at 1400 rpm for 15 seconds. It is worth noting that the temperature of the mixture was kept at about 15 degrees in all stages with the help of a temperature stabilization bath. The resulting mixture was allowed 1 min to reach equilibrium and separate into a water-rich phase (WRP) with a higher density at the bottom and a solvent-rich phase (SRP) with a lower density at the top. Then, the SRP and WRP were transferred to two different containers using a separator funnel.

The WRP contained the concentrated brine and a small amount of solvent. Boiling point of solvent (83°C) is lower than water so, increasing the temperature of the mixture causes the dissolved solvent to boil and evaporate. After a while, the liquid was stopped boiling and more heating increased the temperature to over 85 °C, which means complete evaporation of the dissolved solvent. The remaining 11 mL liquid is the concentrated brine. To determine its content of soluble salts, it was transferred to a pre-weighed glass beaker and heated until the water completely evaporated. The resulting sediment weighed 1.71 grams. Therefore, the salinity of the concentrated brine was 155 g/L. The temperature of the SRP was raised to 60 °C, the water absorbed by the solvent was separated, and a higher-density phase was created under the solvent. This phase was separated from the solvent using a separator funnel. The treated water (50 mL) contained a very small amount of salt.

The concentration of salt in the treated water could be calculated by sampling, completely evaporating the sample water and weighing the remaining precipitate. However, for more accurate measurement, the entire treated water was first heated to 85 °C in order to evaporate the dissolved solvent. The remaining 46 ml water was then evaporated completely. The resulting precipitate weighed 0.3 g. Therefore the salinity of the treated water was 6.5 g/lit. The total volume of the treated water and concentrated brine was 56 mL, which was 4 mL less than the volume of the input saline water. This was due to the evaporation of this amount of water during the solvent separation processes. In practice, given the closed-cycle industrial water treatment process in the introduced method employed in this innovation, the mentioned evaporated water will be distilled and recovered as treated water. Also, vacuum pumps could be used to reduce boiling point of solvents which leads to reduction in operational temperature range of industrial process

Part 2: High and Ultra-high Concentration Salt Water Desalination and Treatment

20 ml high concentration saline water with salinity of 117 g/L (2 Moles/L) and 80 mL Diethylamine solvent (Solvent “B”) were mixed together. The precipitated slurry of salt crystals was then removed from the mixture using a filter paper. The filter paper and the remaining mixture on it were dried completely by gentle heating and then weighed. After subtracting the weight of the filter paper, the weight of the solid salt was determined (2.2 g). The mixture passing through the filter paper consisted of diluted saline water and solvent. By heating the mixture to 60 °C, the solvent (with the boiling point 55 °C ) was completely evaporated and 18 mL diluted saline water remained in the glass. The remaining water was 2 mL less than the input saline water due to the evaporation of this amount of water during salt drying and solvent separation processes. In practice, given the closed-cycle industrial water treatment process in the introduced method employed in this innovation, the mentioned evaporated water will be distilled and recovered as treated water.

The diluted saline water was completely dried by the heating and evaporating process and 0.12 g salt precipitated at the bottom of the container. Therefore the salinity of the diluted saline water was 6.7 g/L.

Regarding the treatment and desalination experiment of high saline water, the above process was repeated with 20 mL of this water (with salinity of 234 g/L) using 60 mL Diethylamine solvent. 18 mL treated water (diluted saline water) was obtained with 0.28 g dissolved salt with salinity of 15.5 g/L plus 4.35 g dried solid salts.

The obtained diluted saline water can be desalinated and treated almost completely using the method presented in the first experiment (part 1).

Conclusion

The results of the above experiments proved the suitable performance of the present innovation in desalinating and treating saline water with various concentrations of soluble salt (from low concentration salt water with the salinity of seawater to ultra-high concentration industrial waste water). The noteworthy achievement was the almost complete recycling of water without producing any salty effluents. Another important result was recovering valuable solid salts as a by-product of the treatment and desalination process.

Claims

What is claimed is:

1. The invention of Solvent extraction water treatment process for wide range of salinity with no liquid waste discharge includes at least a tank for maintaining and feeding the salt water and at least having a pre filtration step for separation of suspended particles and at least a preliminary desalination cycle with the help of solvent and at least a secondary cycle and at least a water purification system to produce potable water and at least a system for separation of salt from slurry and at least a crystallizer unit and at least a dryer system to dry separated salts and at least a complete cycle for returning the solvent to the fresh water production cycle.

2. The invention of claim one includes a method for desalinating and treating various types of water contains various type of salts, inorganic solute and/or metallic ions with low/medium and high/ultra-high concentrations having the following steps: a. Providing low/medium and/or high/ultra-high concentration salt water. b. Supplying low-polarity organic solvent for desalination. c. Providing a hydrophilic organic solvent for salt crystallization. d. Mixing the low/medium concentration salt water (from Step A and/or diluted salt water coming from step M) with the solvent (Step B) and reducing the temperature of the resulting mixture to T1 to form two distinct phases (solvent-rich phase (SRP) and the water-rich phase (WRP)). The optimal relative quantity of solvents and T1 are selected in a way that the largest volume of water having the lowest salt concentration is absorbed by the solvent. e. Separating SRP (Step D) and increasing the temperature to optimum temperature T2 to form two separated phases (diluted low-salinity treated water and solvent at T2) and maximize extracting treated water from selected solvent. f. Recovering and transferring the dehydrated solvent (Step E) to Step D for reuse. g. Transferring the low-salinity treated water (Step E) to the secondary RO treatment unit, or repeating the presented method from Step D to Step F, or a combination of both methods for final purification and returning waste water of this secondary treatment unit to step D for re-treatment. h. Recovering the solvent mixed in concentrated WRP (Step D) and transferring the recovered solvent to Step D for reuse. i. Mixing the solvent (Step C) with high or ultra-high concentration salt water (from step A and/or concentrated salt-water remained in Step H) to precipitate and separate salt crystals and slurry from the diluted salt water- solvent mixture. j. Separating water in the salt crystals and slurry and producing solid dried salt. k. Mixing water separated in Step J with the diluted salt water-solvent mixture coming from Step I. l. Separating and recovering the solvent mixed with the diluted salt water (Step K) and recycling it to Step I for reuse. m. Transferring the diluted salt water in Step L to Step D for retreatment, by repeating the presented method from Step D to Step M.

3. The invention of claim one which can be used for the treatment of low, medium, high and ultra-high concentrated salt water.

4. The invention of claim 2 wherein the solvent for desalination process in step B comprises low-polarity organic solvents with a boiling point and a density lower than pure water. The invention of claim 2 wherein the solvent for salt crystallization in step C comprises hydrophilic organic solvents with a boiling point and a density lower than pure water. The invention of claim one in which the process begins with mixing the salt water and solvent and decreasing the temperature of resulted mixture to optimally form two separated phases (solvent-rich phase (SRP) and water-rich phase (WRP)). The invention of claim one in which separation of SRP and increasing the temperature employed as a part of treatment method to optimally form two phases and increase the process of dehydration of selected solvents to the last possible degree i.e. diluted water with small amount of salt and solvent. The invention of claim one in which the recovery and transfer of dehydrated solvent for reuse can be employed as a part of treatment method. The invention of claim one in which transferring the treated water with low salinity to the second desalination unit of RO, or repeating the provided method or a combination of both methods for the final treatment and returning the waste liquids of second treatment unit for retreating can be employed as a part of treatment method. The invention of claim one in which recovery of separated solvent in the warm and thermal separators and transferring the recovered solvent for reuse can be employed as a part of treatment method. The invention of claim 2 wherein the desalination solvent in Step B includes low-polarity organic solvents, specifically amine solvents, Triethylamine, Diisopropylamine, ethylene glycol dimethyl ether (DME), Tetrahydrofuran, 2- Butanol, N,N-Diethylmethylamine, N,N- Dimethylisopropylamine, N-Ethylisopropylamine, N-Methylbutylamine, 1,2-Dimethylpropylamine or any combination thereof.

12. The invention of claim 2 wherein the crystallization solvent in Step C includes hydrophilic organic solvents, specifically Acetone, Butanone (MEK), Ethanol, 2-propanol, Acetonitrile, Tert-Butanol, 1,4-Dioxane, ethylene glycol dimethyl ether and Diethylamine or any combination thereof.

13. The method of claim one wherein heat-exchanger is used between inlet and outlet flows of cold separators to absorb thermal energy from inlet flow and decrease its temperature and transfer heat into the cooled outlet flows to increase its temperature.

14. The invention of claim one wherein heat-exchanger is used between inlet and outlet flows of warm and thermal separators and solvent recyclers to absorb thermal energy from heated outlet flow and decrease its temperature and transfer heat into the inlet flows to increase its temperature.

15. The invention of claim one wherein heat-pump is used to absorb thermal energy from streams that need to be cooled and transferring the absorbed heat to streams that needs to be heated.

16. The invention of claim one wherein the separation of salt crystals and slurry and production of dried solid salts can be employed as a part of treatment method.

17. The invention of claim one in which the separation and recovery of solvent mixed with diluted salt water and recycling the solvent for reuse can be employed as a part of treatment method.

18. The invention of claim one in which transferring of diluted salt water to RO unit for retreatment can make potable water.