Integrated system and process for recovery of potable water and salts from seawater leading to zlds

Abstract

The present invention relates to an integrated system and an integrated process for recovery of potable water in excess of 90% and salts from sea water. The present invention therefore leads to a zero liquid discharge for desalination plant.

Description

[0001] INTEGRATED SYSTEM AND PROCESS FOR RECOVERY OF POTABLE WATER AND SALTS FROM SEAWATER LEADING TO ZLDS

[0002] Field of the Invention:

[0003] The present invention relates to an integrated system and an integrated process for recovery of potable water in excess of 90% and salts from sea water. The present invention therefore leads to a zero liquid discharge for desalination plant.

[0004] Background of the Invention:

[0005] The scarcity of freshwater due to the rapid growth of population and industrial activities has increased attention on desalination process as an alternative freshwater supply. Desalination process refers to the removal of salts from saline water, such as brackish water and seawater, in order to obtain fresh water for domestic or industrial purposes. Generally, there are two classes of desalination processes, namely thermal-based and membrane-based processes.

[0006] The main thermal desalination processes for seawater desalination are multi-stage flash process, multi-effect distillation process, and vapour compression process.

[0007] In the membrane-based desalination processes, the saline water is treated into two streams. The first stream is fresh water containing a low concentration of salt while the second one is the brine with concentrated salt. In the membrane-based desalination processes, desalination occurs as a result of permeation of components through a selective permeable membrane. Reverse osmosis (RO), nano -filtration (NF), forward osmosis (FO), and membrane distillation (MD), electro-dialysis (ED), electro -de-ionization (EDI), and microbial desalination cell (MDC), are some of the membrane-based desalination processes.

[0008] Among the membrane-based desalination processes, reverse osmosis (RO) process is the most widely due to remarkable advances of this technology. The advances lead to significant cost reduction of RO process. Sorek desalination plant is an example of the largest sea water reverse osmosis (SWRO) plant which is located in Sorek, Israel, with a production capacity of 624,000 m3 / day. In reverse osmosis technology, dissolved solutes including charged ion from water are separated via a semi-permeable membrane that allows passing water in preference to the solute. The driving force is a pressure difference between the two membrane sides, i.e. feed side and permeate side. If a saline solution is pumped into RO unit and a pressure gradient is applied (pressure required to exceed the osmotic pressure of solution) the water migrates across the membrane toward the permeate side while the salts and other components are retained by the membrane on the feed side. The overall result is two streams with different concentration of salt. The first stream is brine with increased concentration in concentrate side while the other is depleted of salts in the permeate side.

[0009] Typically, membrane-based desalination processes discharges brine (hereinafter referred to as desalination plant brine reject) back into the environment. The desalination plant brine reject contains a high concentration of salt and other pollutants. The pollutant components in the desalination plant brine reject can be classified as corrosion products, anti-scaling additives, anti-fouling additives, halogenated organic compounds, anti-foaming additives, oxygen scavengers, acid, and concentrate.

[0010] The desalination plant brine reject brings negative impact on the environment due to its salt concentration and chemical content. For example, the environment where the desalination plant brine reject is being discharged experiences physicochemical impact due to salinity, temperature, etc. which tend to alter the physicochemical properties of receiving water and adversely effects on the marine life. Other impacts of discharge of desalination plant brine reject are reported in literature.

[0011] Technologies oriented to commercial salt recovery from desalination plant brine reject are an attractive option. Valuable recovered salt can be used to reduce the overall desalination cost. This option provides the possibility to obtain valuable components, both water and salts, that result in increased water recovery and reduced the overall water production cost. By doing so, a dual-purpose plant for desalination and salt production is achieved.

[0012] Geo-Processors USA, Inc. have reported an integrated process for desalination followed by extraction of dissolved solid from managing the desalination plant brine reject. Typically, the process involves one or more steps of reaction and evapo-cooling supplemented by conventional mineral and chemical processing steps.

[0013] Dow Chemical Company has reported a chemical process which can be used to produce magnesium metal from desalination plant brine reject. Investigation on the use of this process for magnesium production from Arabian Gulf desalination brine has been reported. In this process calcination, slaking, precipitation, and hydrochlorination reactions are involved. Turek et al., have investigated some integrated processes that involve membrane (electrodialysis, nano filtration, and reverse osmosis) based desalination process for producing potable water and subjecting the desalination plant brine reject to multi-stage flash process.

[0014] Another integrated process that has been investigated includes ultra filtration process (UF), which is followed by nano-filtration based process (NF), which is followed by multi-stage flash process (MSF) which is followed by crystallization process.

[0015] Yet another integrated process that has been investigated includes ultra filtration process (UF), which is followed by nano-filtration based process (NF), which is followed by reverse osmosis filtration (RO), which is followed by multi-stage flash process (MSF) which is followed by crystallization process.

[0016] Another integrated process which has been reported for desalination of water and recovery of salt from the desalination plant brine reject combines UF, NF, RO, membrane distillation (MD), and membrane crystallization (MCr). NF is used to remove bivalent ions from the feed stream. The NF permeate with reduced salt is delivered to RO unit. Due to lower osmotic pressure as the result of NF softening step, RO can reach higher water recovery. To recover more water from NF and RO, MD and MCr are introduced. MCr increases solute concentration of solution above its saturation limit in which crystal nucleate and growth.

[0017] Another integrated process which has been reported for desalination of water and recovery of salt from the desalination plant brine reject combines RO, ED, evaporation, and electrolysis processes. ED is used after RO unit to improve water recovery and to increase concentration factor of RO brine prior to evaporation. In evaporation unit, edible salt and bittern are produced. After purification, the solution from evaporation unit is processed in electrolysis in which hydrogen, chloride, and alkali are additionally produced.

[0018] While many integrated processes have been reported, most of the integrated processes are in conceptual stage and have therefore not been subjected to extensive field trials and none of them have been implemented on a commercial scale. As the efficiency of any integrated processes including the percentage recovery of potable water from the sea water and the percentage recovery of salts and the purity of the recovered salts play a vital role, there exists a need to provide an integrated process and an integrated for producing potable water in excess of 90% and different salts from sea water thereby making the desalination plant a zero liquid discharge system.

[0019] Summary of the Invention:

[0020] This summary is provided to introduce a selection of concepts in a simplified format that is further described in the detailed description of the invention. This summary is neither intended to identify key or essential inventive concepts of the invention nor is it intended for determining the scope of the invention.

[0021] Accordingly, the present invention provides an integrated system (100) for recovery of potable water in excess of 90% and salts from sea water, said system (100) comprises: an intake sub-system (102) adapted to draw sea water; a pre-treatment sub-system (104) adapted to receive the sea water drawn by the intake subsystem (102) and remove one or more of suspended solids, organic matter, and other impurities to produce pre-treated sea water; a set of high-pressure pumps (106) adapted to receive pre-treated sea water from the pretreatment sub-system (104) and pressurize the same to a first pressure level to produce pressurized pre-treated sea water; a set of reverse osmosis membranes (108) adapted to receive the pressurized pre-treated sea water from the first set of high-pressure pumps (106) and to produce a first stage permeate solution and a first stage reject solution; a falling film evaporator (110) adapted to receive the first stage reject solution from the first set of reverse osmosis membranes (108) and producing therefrom a first stage water vapour and a first stage concentrate; an evaporative crystallizer (112) adapted to receive the first stage concentrate from the falling film evaporator (110) and produce a second stage water vapour and a second stage concentrate; a mechanical thickening device (114) adapted to receive the second stage concentrate from the evaporative crystallizer (112) and produce a third stage concentrate and a purge; at least one condensing unit (116) adapted to receive the first stage water vapour from the falling film evaporator (110) and the second stage water vapour from the evaporative crystallizer (112) and produce a second stage permeate solution; a post treatment sub-system (118) adapted to receive the first stage permeate solution from the first set of reverse osmosis membranes (108), and the second stage permeate solution from the at least one condensing unit (116), the post treatment sub-system (118) being adapted to carry out at least one of pH adjustment, remineralization, disinfection, filtration and a combination thereof on the first stage permeate solution and the second stage permeate solution to produce potable water; a first recovery device (120) adapted to receive the third stage concentrate from the mechanical thickening device (114) and recover a salt substantially rich in sodium chloride from the third stage concentrate; and at least one further recovery device (122) adapted to receive the purge from the mechanical thickening device (114) and recover a mixture of salts from the purge.

[0022] The present invention furthermore provides an integrated process (200) for recovery of potable water in excess of 90% and salts from sea water, said process (200) comprises: drawing (202) sea water via an intake sub-system (102); pre-treating (204) the sea water to remove one or more of suspended solids, organic matter, and other impurities to produce pre-treated sea water; pressurizing (206) the pre-treated sea water to a first pressure level to produce pressurized pretreated sea water; passing (208) the pressurized pre-treated sea water through a first set of reverse osmosis membranes to produce a first stage permeate solution and a first stage reject solution; passing (210) the first stage reject solution through a falling film evaporator to produce a first stage water vapour and a first stage concentrate; passing (212) the first stage concentrate through an evaporative crystallizer to produce a second stage water vapour and a second stage concentrate; mechanically thickening (214) the second stage concentrate to produce a third stage concentrate and a purge; condensing (216) the first stage water vapour and the second stage water vapour to produce a second stage permeate solution; post-treating (218) the second stage permeate solution and the third stage permeate solution to produce potable water, the post-treating being selected from a group comprising pH adjustment, remineralization, disinfection, filtration and a combination thereof; recovering (220) a salt rich in sodium chloride from the third stage concentrate; recovering (222) a mixture of salts from the purge. To further clarify advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings.

[0023] BRIEF DESCRIPTION OF THE DRAWINGS:

[0024] These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: Figure 1 demonstrates a block diagram of the integrated system for producing potable water and salts from sea water;

[0025] Figure 2 demonstrates a block diagram of the pre-treatment sub- system in accordance with an embodiment of the invention;

[0026] Figure 3 demonstrates a block diagram of the post treatment sub-system in accordance with an embodiment of the invention; and

[0027] Figure 4 demonstrates a flow chart of the integrated process for producing potable water and salts from sea water.

[0028] Further, skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and may not have been necessarily been drawn to scale. For example, the flow charts illustrate the method in terms of the most prominent steps involved to help to improve understanding of aspects of the present invention. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.

[0029] DETAILED DESCRIPTION OF THE INVENTION:

[0030] For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

[0031] It will be understood by those skilled in the art that the foregoing general description and the following detailed description are explanatory of the invention and are not intended to be restrictive thereof.

[0032] Reference throughout this specification to “an aspect”, “another aspect” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase “in an embodiment”, “in another embodiment” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

[0033] The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices or sub-systems or elements or structures or components proceeded by "comprises... a" does not, without more constraints, preclude the existence of other devices or other sub- systems or other elements or other structures or other components or additional devices or additional sub- systems or additional elements or additional structures or additional components.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skilled in the art to which this invention belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.

[0035] Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

[0036] Referring to Figure 1, there is illustrated a block diagram of an integrated system (100) for recovery of potable water in excess of 90% and salts from sea water. In an embodiment of the invention, the integrated system (100) comprises: an intake sub-system (102) adapted to draw sea water; and a pre-treatment sub-system (104) adapted to receive the sea water drawn by the intake sub-system (102) and remove one or more of suspended solids, organic matter, and other impurities to produce pre-treated sea water.

[0037] In an embodiment of the invention, the integrated system (100) further comprises a set of high- pressure pumps (106) adapted to receive pre-treated sea water from the pre-treatment subsystem (104) and pressurize the same to a first pressure level to produce pressurized pre-treated sea water; and a set of reverse osmosis membranes (108) adapted to receive the pressurized pre-treated sea water from the first set of high-pressure pumps (106) and to produce a first stage permeate solution and a first stage reject solution.

[0038] In another embodiment of the invention, the integrated system (100) further comprises a falling film evaporator (110) adapted to receive the first stage reject solution from the set of reverse osmosis membranes (108) and producing therefrom a first stage water vapour and a first stage concentrate; and an evaporative crystallizer (112) adapted to receive the first stage concentrate from the falling film evaporator (110) and produce a second stage water vapour and a second stage concentrate.

[0039] In a further embodiment of the invention, the integrated system (100) further comprises a mechanical thickening device (114) adapted to receive the second stage concentrate from the evaporative crystallizer (112) and produce a third stage concentrate and a purge; and at least one condensing unit (116) adapted to receive the first stage water vapour from the falling film evaporator (110) and the second stage water vapour from the evaporative crystallizer (112) and produce a third stage permeate solution.

[0040] In a furthermore embodiment of the invention, the integrated system (100) further comprises a post treatment sub-system (118) adapted to receive the first stage permeate solution from set of reverse osmosis membranes (108), and the second stage permeate solution from the at least one condensing unit (116) and produce potable water; a first recovery device (120) adapted to receive the third stage concentrate from the evaporative crystallizer (112) and recover salt rich in sodium chloride from the third stage concentrate; and at least one further recovery device (122) adapted to receive the purge from the evaporative crystallizer (116) and recover other salts from the purge. In another embodiment of the invention, the set of high-pressure pumps (106) applies first pressure level in the range of 600 to 1,200 pounds per square inch (psi) or 4.1 to 8.3 megapascals (MPa) and the set of reverse osmosis membranes (108) operate at a pressure in the range of 600 to 1,200 psi or 4.1 to 8.3 MPa. It can be seen that both the high-pressure pumps (106) and the reverse osmosis membranes (108) are being made to operate at substantially the same pressure.

[0041] In an embodiment of the invention, the set of reverse osmosis membranes comprises 4 stages of RO membranes. In another embodiment of the invention, the set of reverse osmosis membranes comprises 4 stages of RO membranes connected in series.

[0042] In an embodiment of the invention, the 4 stages of RO membranes connected in series comprises a first stage RO membrane, a second stage RO membrane, a third stage RO membrane, and a fourth stage RO membrane.

[0043] In an embodiment of the invention, the first stage RO Membrane comprises a semi-permeable membrane having tiny pores that allow water molecules to pass through while blocking dissolved solids, contaminants, and impurities. The first stage RO Membrane effectively removes dissolved salts and other impurities from the sea water. In an embodiment of the invention, the first stage RO Membrane has a first set of pore sizes, a first type of structure, a first set of density values, a first type of distribution of small pathways, and a first type of charge values. Based one or more of the aforesaid characteristics, the first stage RO Membrane has a first set of rejection capability.

[0044] In an embodiment of the invention, after passing through the first RO membrane, the water moves on to the second stage, where it encounters the second stage RO membrane. The second stage RO membrane acts as an additional barrier to further enhance the purification process. The second stage RO membrane removes any remaining impurities that may have bypassed the first stage RO membrane, ensuring a higher level of purification. In an embodiment of the invention, the second stage RO Membrane comprises a semi-permeable membrane having tiny pores that allow water molecules to pass through while blocking dissolved solids, contaminants, and impurities. The second stage RO Membrane effectively removes dissolved salts and other impurities from the sea water. In an embodiment of the invention, the second stage RO Membrane has a second set of pore sizes, a second type of structure, a second set of density values, a second type of distribution of small pathways, and a second type of charge values. Based one or more of the aforesaid characteristics, the second stage RO Membrane has a second set of rejection capability.

[0045] In an embodiment of the invention, the partially purified water from the second stage RO Membrane enters the third stage RO Membrane. The third stage RO Membrane continues the purification process by removing any remaining contaminants or impurities that might have passed through the previous membranes. The third stage RO Membrane provides an extra layer of purification and helps ensure the water is thoroughly purified. In an embodiment of the invention, the third stage RO Membrane comprises a semi-permeable membrane having tiny pores that allow water molecules to pass through while blocking dissolved solids, contaminants, and impurities. The third stage RO Membrane effectively removes dissolved salts and other impurities from the sea water. In an embodiment of the invention, the third stage RO Membrane has a third set of pore sizes, a third type of structure, a third set of density values, a third type of distribution of small pathways, and a third type of charge values. Based one or more of the aforesaid characteristics, the third stage RO Membrane has a third set of rejection capability.

[0046] In an embodiment of the invention, the water finally passes through the fourth stage RO Membrane. The fourth stage RO Membrane serves as the final purification step in the series connection. The fourth stage RO Membrane further removes any remaining traces of impurities and ensures the water is purified to the desired level. In an embodiment of the invention, the fourth stage RO Membrane comprises a semi-permeable membrane having tiny pores that allow water molecules to pass through while blocking dissolved solids, contaminants, and impurities. The fourth stage RO Membrane effectively removes dissolved salts and other impurities from the sea water. In an embodiment of the invention, the fourth stage RO Membrane has a fourth set of pore sizes, a fourth type of structure, a fourth set of density values, a fourth type of distribution of small pathways, and a fourth type of charge values. Based one or more of the aforesaid characteristics, the fourth stage RO Membrane has a fourth set of rejection capability.

[0047] In an embodiment of the invention, the first set of pore sizes, the second set of pore values, the third set of pore values and the fourth set of pore values may fall in different ranges, with some overlap between the ranges.

[0048] In an embodiment of the invention, the first type of structure, the second type of structure, the third type of structure and the fourth type of structure may be same or different. In an embodiment of the invention, the first set of density values, the second set of density values, the third set of density values and the fourth set of density values may fall in different range with some overlap between the ranges.

[0049] In an embodiment of the invention, the first type of distribution of small pathways, the second type of distribution of small pathways, the third type of distribution of small pathways and the fourth type of distribution of small pathways may be same or different.

[0050] In an embodiment of the invention, the first set of charge values, the second set of charge values, the third set of charge values and the fourth set of charge values may fall in different range with some overlap between the ranges.

[0051] Thus, the rejection capability of the first stage RO Membrane, the rejection capability of the second stage RO Membrane, the rejection capability of the third stage RO Membrane, and the rejection capability of the fourth stage RO Membrane may be same or different.

[0052] By connecting these four stages of RO Membranes in series, the water undergoes multiple rounds of filtration through RO membranes, with each membrane contributing to the removal of impurities. This configuration enhances the purification efficiency and ensures the water is thoroughly treated, resulting in clean and purified water suitable for various applications.

[0053] In still another embodiment of the invention, the integrated system (100) may further comprise a first set of nano -filtration membrane located downstream of the fourth stage RO Membrane (112) and upstream of the post treatment sub-system (122) such that the first set of nanofiltration membranes further purifies the water coming out of the fourth stage RO Membrane prior to feeding the same to the post treatment sub- system (122).

[0054] In a further embodiment of the invention, the integrated system (100) may further comprise a second set of nano -filtration membranes located downstream of the pre-treatment sub-system (106) and upstream of the first stage RO Membrane such that the second set of nano -filtration membranes further purifies the pre-treated sea water prior to feeding the same to the first stage RO Membranes.

[0055] In a furthermore embodiment of the invention, the falling film evaporator (114) is a multieffect falling film evaporator. Referring to Figure 2, in a further embodiment of the invention, the pre-treatment sub-system (104) comprises at least one of a screening device (140) adapted to remove larger particles such as twigs, leaves, or plastics; a coagulation and flocculation device (142) adapted to mix coagulants and flocculants to the sea water to induce the aggregation of smaller particles into larger clumps; a sedimentation device (144) adapted to allow heavier particles and flocculants to settle due to gravity; a filtration device (146) adapted to trap impurities as water passes therethrough; and a combination thereof.

[0056] Referring to Figure 3, in a further more embodiment of the invention, the post treatment subsystem (122) comprises at least one of a pH adjustment device (148); a remineralization device (150); a disinfection device (152); a filtration device (154), and a combination thereof. In another embodiment of the invention, the first set of reverse osmosis membranes (108) and the first set of reverse osmosis membranes (112) comprises polyamide layer supported by a porous substructure.

[0057] Now referring to Figure 4, there is illustrated a process flow chart of am integrated process (200) for recovery of potable water in excess of 90% and salts from sea water. In an embodiment of the process (200) comprises drawing (202) sea water via an intake sub- system (102); and pre-treating (204) the sea water to remove one or more of suspended solids, organic matter, and other impurities to produce pre-treated sea water.

[0058] In another embodiment of the invention, the integrated process (200) comprises pressurizing (206) the pre-treated sea water to a first pressure level to produce pressurized pre-treated sea water; and passing (208) the pressurized pre-treated sea water through a set of reverse osmosis membranes to produce a first stage permeate solution and a first stage reject solution.

[0059] In still another embodiment of the invention, the integrated process (200) comprises passing (210) the first stage reject solution through a falling film evaporator to produce a first stage water vapour and a first stage concentrate; and passing (212) the first stage concentrate through an evaporative crystallizer to produce a second stage water vapour and a second stage concentrate.

[0060] In still another embodiment of the invention, the integrated process (200) comprises mechanically thickening (214) the second stage concentrate to produce a third stage concentrate and a purge; and condensing (216) the first stage water vapour and the second stage water vapour to produce a second stage permeate solution.

[0061] In a further embodiment of the invention, the integrated process (200) comprises post-treating (218) the first stage permeate solution and the second stage permeate solution to produce potable water, the post-treating being selected from a group comprising pH adjustment, remineralization, disinfection, filtration and a combination thereof; recovering (220) a salt rich in sodium chloride from the third stage concentrate; and recovering (222) at least one further salt from the purge.

[0062] While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the present disclosure. Indeed, the novel methods, devices, and systems described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions, and changes in the form of the methods, devices, and systems described herein may be made without departing from the spirit of the present disclosure.

[0063] Example 1:

[0064] About 105 tons of sea water was taken as input and subjected to pre-treatment to remove impurities therefrom and produce 104.71 tons of pre-treated sea water. The pre-treated sea water has a specific density of 1.020. The pre-treated sea water has a total dissolved solid content of about 3.60% w / w. The pre-treated sea water had approximately about 2.7% w / w of sodium chloride. The remaining part of the dissolved solid content is a mixture of various salts including but not limited to magnesium sulphate, magnesium chloride, magnesium bromide, potassium sulphate, potassium chloride, etc.

[0065] The pre-treated sea water was fed to a 4-stage RO membrane using a high-pressure pump. For feeding the pre-treated sea water to the 4-stage RO membrane, the high-pressure pump consumed roughly 3KW of power per litre of pre-treated sea water.

[0066] After passing through all the four stages of the reverse osmosis membranes, roughly 46.20 tons of first stage permeate solution and about 58.50 tons of a first stage reject solution was produced. The first stage permeate solution was substantially devoid of dissolved solids including dissolved salts. The first stage reject solution had a specific gravity of about 1.036 and a pH value of about 8.27. The pre-treated sea water has a total dissolved solid content of about 6.44% w / w. The pre-treated sea water had approximately about 4.83% w / w of sodium chloride. The remaining part of the dissolved solid content is a mixture of various salts including but not limited to magnesium sulphate, magnesium chloride, magnesium bromide, potassium sulphate, potassium chloride, etc.

[0067] The first stage reject solution was fed to a seven-effect falling film evaporator and dry steam was used to heat the first stage reject solution. The seven effect falling film evaporator produced a first stage water vapour and a first stage concentrate. The first stage water vapour upon condensation produced about 43.42 tons of water. The amount of first stage concentrate was about 15.08 tons. The first stage concentrate had a total dissolved solid content of about 25.00% w / w. The exact weight percentage of sodium chloride and other salts was not determined.

[0068] The first stage concentrate was fed to a four-effect forced circulation evaporator, which is a type of evaporative crystallizer and dry steam was used to heat the first stage concentrate. Due to condensation of some amount of dry steam and mixing of the same with the first stage concentrate, the amount of liquid getting processed marginally increases. The four-effect forced circulation evaporator produced a second stage water vapour and a second stage concentrate. The second stage water vapour upon condensation produced about 8.92 tons of water. The amount of second stage concentrate was about 8.07 tons. The first stage concentrate had a total dissolved solid content of about 55.00% w / w. The exact weight percentage of sodium chloride and other salts was not determined.

[0069] The second stage concentrate was fed to a thickener and a centrifuge to produce a third stage concentrate and a purge. The third stage concentrate was in the form of wet powders which was dried in a fluidized bed dryer to produce 2.55 tons of dry powders having about 0.2% w / w of moisture. The dry powders were analyzed and were found to contain more than 99.5% w / w of sodium chloride.

[0070] The purge whose quantity was about 3.51 tons was fed to a triple effect forced circulation evaporator to produce about 2.5 tons of a fourth stage concentrate. The fourth stage concentrate had a total dissolved solid content of about 60.00% w / w. The fourth stage concentrate was then fed to a Vertical / Agitated Thin Film Dryer to produce 1.23 tons of dry powders having about 6.0 w / w of moisture. The dry powders were analyzed and were found to contain a mixture of magnesium sulphate, magnesium chloride, magnesium bromide, potassium sulphate, potassium chloride, and sodium chloride.

[0071] In an embodiment of the invention, the amount of water which is produced by the present invention from 105 tons of sea water is 98.54 tons (46.20 + 43.42 + 8.92). Thus, the invention produces potable water in excess of 90% from sea water. In an embodiment of the invention, processing of purge in the triple effect forced circulation evaporator also produces water vapours, which upon condensation could produce about 1.46 tons of water. Thus, in an embodiment of the invention the amount of water which is produced by the present invention from 105 tons of sea water is 100 tons (46.20 + 43.42 + 8.92 + 1.46).

[0072] Additionally, the invention produces about 2.55 tons of salts which is rich in sodium chloride and about 1.23 tons of dry mix salts having about 6.0 w / w of moisture. The dry powders were analyzed and were found to contain a mixture of magnesium sulphate, magnesium chloride, magnesium bromide, potassium sulphate, potassium chloride, and sodium chloride. It may be noted that the quantity of salt rich in sodium chloride and a quantity of the mixture of salts obtained will depend upon the total dissolved solid content in the sea water and can therefore increase or decrease.

[0073] An advantage of the invention is that it provides a very cost effective for the reasons that from 105 tons of sea water is 100 tons of potable water is produced. Also, the salt which is rich in sodium chloride as produced in the process (whose quantity is roughly 2.55 tons) can be sold for commercial gains. Likewise, the dry mix salts (whose quantity is roughly 1.23 tons) which contains a mixture of magnesium sulphate, magnesium chloride, magnesium bromide, potassium sulphate, potassium chloride, and sodium chloride can be easily subjected to fractional crystallization to get individual salts and the same can be sold for commercial gains.

[0074] The present invention has been described using detailed descriptions of embodiments thereof that are provided by way of example and are not intended to limit the scope of the invention.

[0075] While certain present preferred embodiments of the invention have been illustrated and described herein, it is to be understood that the invention is not limited thereto. Clearly, the invention may be otherwise variously embodied, and practiced within the scope of the following claims.

Claims

CLAIM:

1. An integrated system (100) for recovery of potable water in excess of 90% and salts from sea water, said integrated system (100) comprises: an intake sub-system (102) adapted to draw sea water; a pre-treatment sub-system (104) adapted to receive the sea water drawn by the intake subsystem (102) and remove one or more of suspended solids, organic matter, and other impurities to produce pre-treated sea water; a set of high-pressure pumps (106) adapted to receive pre-treated sea water from the pretreatment sub-system (104) and pressurize the same to a first pressure level to produce pressurized pre-treated sea water; a set of reverse osmosis membranes (108) adapted to receive the pressurized pre-treated sea water from the set of high-pressure pumps (106) and to produce a first stage permeate solution and a first stage reject solution; a falling film evaporator (110) adapted to receive the first stage reject solution from the set of reverse osmosis membranes (108) and producing therefrom a first stage water vapour and a first stage concentrate; an evaporative crystallizer (112) adapted to receive the first stage concentrate from the falling film evaporator (110) and produce a second stage water vapour and a second stage concentrate; a mechanical thickening device (114) adapted to receive the second stage concentrate from the evaporative crystallizer (112) and produce a third stage concentrate and a purge; at least one condensing unit (116) adapted to receive the first stage water vapour from the falling film evaporator (110) and the second stage water vapour from the evaporative crystallizer (112) and produce a third stage permeate solution; a post treatment sub-system (118) adapted to receive the first stage permeate solution from set of reverse osmosis membranes (112), and the second stage permeate solution from the at least one condensing unit (116) and produce potable water; a first recovery device (120) adapted to receive the third stage concentrate from the evaporative crystallizer (112) and recover salt rich in sodium chloride from the third stage concentrate; andat least one further recovery device (122) adapted to receive the purge from the evaporative crystallizer (112) and recover a mixture of salts from the purge.

2. The integrated system (100) as claimed in claim 1, wherein the first set of high pressure pumps (106) applies first pressure level in the range of 600 to 1,200 pounds per square inch (psi) or 4.1 to 8.3 megapascals (MPa) and the first set of reverse osmosis membranes (108) operate at a pressure in the range of 600 to 1,200 psi or 4.1 to 8.3 MPa.

3. The integrated system (100) as claimed in claim 1, the set of reverse osmosis membranes comprises 4 stages of RO membranes, namely first stage RO membranes, second stage RO membranes, third stage RO membranes and fourth stage RO membranes connected in series.

4. The integrated system (100) as claimed in claim 3, comprising a first set of nano-filtration membrane located downstream of the fourth stage reverse osmosis membranes and upstream of the post treatment sub-system (118) such that the first set of nano-filtration membranes further purifies the water prior to feeding the same to the post treatment subsystem (118).

5. The integrated system (100) as claimed in claim 3, comprising a second set of nanofiltration membranes located downstream of the pre-treatment sub-system (106) and upstream of the first stage reverse osmosis membranes such that the second set of nanofiltration membranes further purifies the pre-treated sea water prior to feeding the same to the first stage reverse osmosis membranes.

6. The integrated system (100) as claimed in claim 1, wherein the falling film evaporator (114) is a multi-effect falling film evaporator.

7. The integrated system (100) as claimed in any of claim 1, wherein the pre-treatment subsystem (104) comprises at least one of: a screening device (140) adapted to remove larger particles such as twigs, leaves, or plastics; a coagulation and flocculation device (142) adapted to mix coagulants and flocculants to the sea water to induce the aggregation of smaller particles into larger clumps;a sedimentation device (144) adapted to allow heavier particles and flocculants to settle due to gravity; a filtration device (146) adapted to trap impurities as water passes there-through; and a combination thereof.

8. The integrated system (100) as claimed in any of claim 1, wherein the post treatment subsystem (122) comprises at least one of: a pH adjustment device (148); a remineralization device (150); a disinfection device (152), a filtration device (154), and a combination thereof.

9. The integrated system (100) as claimed in claim 1, comprising a control and monitoring system that regulates at least one of pressure, flow rate, temperature, and water quality.

10. An integrated process (200) for recovery of potable water in excess of 90% and salts from sea water, said process (200) comprises: drawing (202) sea water via an intake sub-system (102); pre-treating (204) the sea water to remove one or more of suspended solids, organic matter, and other impurities to produce pre-treated sea water; pressurizing (206) the pre-treated sea water to a first pressure level to produce pressurized pre-treated sea water; passing (208) the pressurized pre-treated sea water through a set of reverse osmosis membranes to produce a first stage permeate solution and a first stage reject solution; passing (210) the first stage reject solution through a falling film evaporator to produce a first stage water vapour and a first stage concentrate; passing (212) the first stage concentrate through an evaporative crystallizer to produce a second stage water vapour and a second stage concentrate; mechanically thickening (214) the second stage concentrate to produce a third stage concentrate and a purge; condensing (216) the first stage water vapour and the second stage water vapour to produce a second stage permeate solution;post-treating (218) the first stage permeate solution and the second stage permeate solution to produce potable water, the post-treating being selected from a group comprising pH adjustment, remineralization, disinfection, filtration and a combination thereof; recovering (220) salt rich in sodium chloride salt from the third stage concentrate; and recovering (226) mixed salts from the purge.

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