Method and apparatus for advanced vacuum membrane distillation

Abstract

Embodiments provide methods and structures for purification or volume reduction of a brine by an advanced vacuum distillation process (AVMD) to achieve higher flux by passage of vapors through an AVMD distillation unit. In one example, brine is circulated in a tank. The tank may include one or more membrane pouches that are submerged in the circulating brine or placed above the water level of the hot circulating brine. In other embodiments the membrane pouches are outside of the tank that includes the hot circulating brine but still in communication with it. The circulating brine is heated, allowing creation of water vapor. Using a vacuum, the water vapor is drawn through the membrane, where it may be condensed and subjected to further beneficial use. This process can concentrate to levels to generate crystals or solids, which can be separated and utilized.

Claims

1. A method for membrane distillation and brine concentration, comprising: in an enclosed brine tank, recirculating a hot brine, wherein said hot brine has a water level below a top of the brine tank; creating a negative pressure inside at least one membrane cartridge, said membrane cartridge comprising a plurality of membrane envelopes or membrane tubes, that is in communication with the enclosed brine tank and that is above the surface level of the hot brine; drawing water vapor from the enclosed brine tank through the plurality of membrane envelopes in the at least one membrane cartridge, thereby creating a first purified water stream and a concentrated brine stream; and treating the concentrated brine stream to near saturation or crystallization, wherein when the concentrated brine stream becomes further concentrated a second purified water stream is created, wherein the hot brine is maintained at a temperature between 60° C. and 90° C. throughout the entire method.

2. The method of claim 1, wherein the membrane cartridge is within the enclosed brine tank and above the surface level of the hot brine.

3. The method of claim 1, wherein the membrane cartridge is outside the enclosed brine tank.

4. The method of claim 1, wherein said hot brine is maintained at a temperature between 80 to 85° C. throughout the entire method.

5. The method of claim 1, further comprising producing salt crystals in the brine tank and removing the salt crystals from the brine tank.

6. The method of claim 1, further comprising condensing the water vapor into distilled water.

7. The method of claim 1, further comprising compressing the water vapor and exchanging heat from the water vapors with the recirculating hot brine for further membrane distillation and brine concentration to reduce energy consumption.

8. The method of claim 1, wherein the water vapor through the at least one membrane pouch has a flux between 15 to 18 Lm.sup.2h at a pressure between 400 to 600 mmHg.

9. The method of claim 1, further comprising evaporating water from the concentrated brine stream to result in a zero liquid discharge.

10. The method of claim 1, wherein the membrane tubes comprise ceramic membrane tubes.

11. The method of claim 1, wherein the membrane cartridge is inorganic.

12. The method of claim 1, wherein the concentrated brine stream is sent to a crystallizer.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1A shows a complete membrane pouch 12 (which may also be referred to as an “envelope”) after sealing from all sides.

(2) FIG. 1B shows a complete membrane pouch wherein membranes 1 and 2 are sealed on a polymeric plate.

(3) FIG. 2A shows a cut section of assembled multi-membrane pouches 12 explaining the assembly art by developing appropriate components to do that. Header 7 can accommodate number of membrane pouches 12 to be assembled. The vapor spacer 6 of membrane pouch 12 is mated with gasket 9 outside the membrane pouch 12. This is followed by another spacer 8 which is used to maintain a defined gap between two membrane pouches 12. Components 10 and 11 are used for tightening multi-membrane pouches 12 and to make pouches leak proof.

(4) FIG. 2B shows a cut section of assembled multi-membrane pouches with polymeric plate. Process wise membrane assembly can be used in a submerged membrane distillation (Method a) or in suspended membrane distillation (Method b or c)

(5) FIG. 3 shows a submerged vacuum membrane distillation unit 24 used in method (a) describing membrane pouches 12 assembly by immersing in a tank 14. The tank 14 essentially has inlet port 15 which allows the feed inflow at the bottom. At the top there is outlet port 16 for hot water to go back to hot water source. Vapor entering the pouch through the hydrophobic membrane pouches 12 and finds outlet through the header 7 and finally through pipe 13 are condensed in an external condenser 25 to produce distillate 32 as shown in FIG. 4.

(6) FIG. 4A shows flow diagram of one embodiment of invention by which a AVMD device 24 can be used for purification or concentration of saline hot water 36.

(7) FIG. 4B shows flow diagram of one embodiment of invention by which AVMD device can be used for concentration of saline hot water with the help of blower/vacuum ejector.

(8) FIG. 5 shows a flow diagram of integrated submerged vacuum membrane distillation and inorganic forced circulation membrane distillation to crystallization of salts as another embodiment of invention. FIG. 5 also shows a multistage membrane distillation unit where the heat of condensation in first unit heat exchanger used as condenser is used in heating feed brine water for stage 2 membrane distillation.

(9) FIG. 6A shows a side cutaway view of a ceramic membrane module. FIG. 6B shows a top view of an array of ceramic tubes.

(10) FIG. 7A shows flow diagram of one embodiment of invention by which membrane cartridge device can be used for concentration of saline hot brine up to 30% to 40% salt concentration and up to 50%. In this membrane brine concentration Method (b) process the membrane cartridge is placed inside the brine tank suspended in vapor space and it is an integral part of brine tank.

(11) FIG. 7B shows flow diagram of the membrane brine concentration process, Method (c), where membrane cartridge unit is assembled outside of brine tank. In this configuration also concentration of beyond saturation can be achieved beyond crystallization.

DETAILED DESCRIPTION OF THE INVENTION

(12) In an embodiment of the invention a device 24 has been made, as shown in FIG. 3 and FIG. 4A, which can be used for desalination and concentration of hot brine water by a process where membrane pouches 12 as shown in FIG. 2A or FIG. 2B are submerged into a tank 14 as shown in FIG. 3 and hot brine water 29 is circulated in the tank 14 with minimum velocity, which can keep the tank water agitated and membrane surface flushed. The vacuum 28 is applied to the submerged membrane distillation unit 24 inside the membrane pouch 12. The water vapors 31 are recovered by applying vacuum 28 through the device 24 and turning the water vapors to condensate and formed distillate 32 in an external condenser 25. The device 24 is prepared by assembly of multi membranes pouch 12 and is submerged in a tank 14 that contains hot brine water 29 and, with the help of a vacuum 28, a distillation process is carried out. For this reason process embodiments may be referred to herein as Advanced Vacuum membrane distillation process” (AVMD Process) and the unit may be called an AVMD unit. Embodiments of the AVMD unit and process may involve one or more of the following steps:

(13) 1. Preparation of Membrane Pouch or single membrane unit

(14) 2. Assembly of Multi Membrane Pouches to make a AVMD unit or a cartridge

(15) 3. Application of AVMD unit for brine concentration by a AVMD process.

(16) Preparation of Membrane Pouch:

(17) As shown in FIG. 1A, two hydrophobic membranes 1 and 2 are sealed at periphery 3 together first from three sides to form a sealed bag or pouch. The membrane surface is kept on the outer side to face the feed water. Internal membrane surface has the support fabric and between the two surfaces a polymer net is introduced to maintain a minimum gap of 4 to 10 mm, preferably 6 mm, between membranes 1 and 2. At one point of the flat surface a hole 4, is made as an opening in both the membranes. The distillate collection openings are strengthened by using a suitable vapor collector 6, of polymeric material. After this the fourth side of membranes 1 and 2, is also sealed, forming a membrane pouch 12 (FIG. 1A). The sides developed beyond sealing portion 3, holes 5, are drilled which are used to tie up for assembly as multiple pouches in the assembly. The membranes 1 and 2 can also be welded on both sides of a polymeric plate as shown in FIG. 1B, which creates a cavity at the center to apply vacuum. The central plate has a hole 4 for applying vacuum and pulling vapors passing through the membranes.

(18) The vapor collector may be a ring or may have another shape. Typically it encloses the edges of the hole in each membrane and places the opening of the membranes in communication with the environment inside the membrane pouch assembly through one or more holes, slots, or other openings.

(19) Assembling Multi-Membrane pouch:

(20) As shown in FIG. 2A or FIG. 2B, multiple membrane pouch 12, assembled together with the help of header 7. A defined gap is maintained between two membrane pouches by spacer 8, such that even after the expansion of pouch there is minimum free space remaining. After a number of membrane pouches 12 have been assembled, the device is tightened from two ends 10 and 11. One end 10 of the header is closed and the other end 11 is open. The open end is connected with a pipe 13.

(21) The multi membrane pouch assembly with the header can now be immersed in a suitable tank 14 with outlet pipe 13 coming out of the tank as shown in FIG. 3. The tank 14 may be, for example, polypropylene (PP) or fiber-reinforced plastic (FRP). The tank 14 typically has one inlet port 15 and one outlet port 16 for hot brine water circulation. The tank may also include a lid 17 for covering the tank to make it leak proof. The device 24 (AVMD Unit) can now be used for a vacuum membrane distillation process, and is referred to as a AVMD unit 24.

(22) Application of a AVMD Unit for Brine Concentration by a AVMD process:

(23) As explained in FIG. 4A, AVMD Unit 24 can now be used for submerged membrane distillation process for desalination and concentration of brine water 36 by connecting the outer pipe 13 to a condenser 25, which is being cooled by water 26 and 27 on one side. A vacuum pump 28 is connected to the other side of the condenser 25 where the condenser 25 inlet is connected with the header pipe line 13 out of the AVMD unit 24. It can be operated as flow diagram shown in FIG. 4A. Hot brine water 29 of temperature 60 to 90° C., preferably 80° C., which needs to be purified or concentrated, is circulated through AVMD unit 24 through inlet port 15 and passes through the membrane pouches 12 touching their outer surface and finding the outlet port 16 to return into the hot water tank 30. In a condenser 25 cool water 26 and 27 is started and vacuum 28 is applied.

(24) Due to negative pressure inside the membrane pouches 12 and hot water 29 circulating outside the membrane pouch 12, the vapors enter the membrane pouch 12 and are sucked into the condenser 25 through the header 7 and pipe 13 of AVMD unit 24. The vapors 31 are condensed and collected as distillate 32. The reject water 33 of the AVMD unit 24 circulates back into hot water tank 30 where it gains heat and again circulates through the AVMD tank 24.

(25) In this manner the brine water 36 gets concentrated to a desired level, and distillate water 32 is continuously generated. The flux achieved through the AVMD unit 24 is typically very high, usually 20 to 50 Lm2h. This is significantly better in comparison to a plate and frame configuration and makes a AVMD system economical for industrial application. Heat recovery further can be achieved by recovering heat by operation of AVMD unit in stages as explained in FIG. 5. In this concept of AVMD the frame part of the assembly can be avoided which is a standard feature in the plate and frame configuration. To increase the capacity multiple membrane modules can be installed and operated in parallel.

(26) AVMD unit 24 can also be operated as flow diagram shown in FIG. 4B where distillate liquid is not required. Hot brine 29 can be concentrated by releasing distillate vapors 35 into the atmosphere with the help of blower/vacuum ejector or other vapor compression or vapor pumping devices 34, if permitted by the local environmental regulations.

(27) FIG. 5 shows an embodiment of multistage AVMD and an integrated system where the initial concentration or volume reduction happens through a submerged polymeric membrane distillation to near saturation levels followed by a forced circulation ceramic tubular membrane distillation unit where the further concentration happens and crystals are precipitated and separated. Before the brine is sent to membrane distillation unit it is pretreated through an ultrafiltration system to avoid any particulate matter build up in the polymeric membrane distillation units. This step is required only if the feed water to be treated or concentrated contains particulate matter which can cause erosion of membrane surface.

(28) The feed brine is passed through an ultra-filtration unit 19 through pump 18A and taken into a feed tank 20. The water is then processed through MD units 24A and 24B through their pumps 29A and 29B respectively to achieve a temperature of 60-85° C. and preferably around 80-85° C. thorough tank 30A and 30B heaters respectively. The submerged membrane distillation units operate under vacuum and generate distillate after condensation through heat exchangers 25A and 25B. The heat of condensation or latent heat of vapors in 25A is recovered to heat feed water for feeding membrane distillation in the subsequent stage unit 24B. The vapors generated by the membrane distillation units can also be compressed by a mechanical compressor or thermo compressor and used to drive evaporation in a forced circulation heat exchanger for subsequent membrane distillation units.

(29) The concentrated brine from 24A and 24B through tanks 30A and 30B are sent to crystallization tank 37. The concentrated brine is further heated as required to maintain temperature of 60-90° C., preferably around 80-90° C. and circulated through the tubes of ceramic membrane unit 39, A typical example of configuration of ceramic membrane is shown in FIG. 6A and FIG. 6B. The ceramic membranes will allow only pure vapors to pass through the tubes and will retain brine inside the tubes and return to the tank. The membranes reject more than 99.9% salt and will not lose and salt rejection properties even if some crystals are sitting on the surface of the membrane unlike polymeric membranes, which can not handle crystallization. The shell material of this module can be stainless steel 316 or high alloy stainless steel based on the analysis of brine and its corrosion behavior.

(30) The ceramic membrane operates under the influence of vacuum and distillate is generated by condenser 40 by passing cooling water through this. As the distillate 41 is extracted and collected in tank 32 and brine gets further concentrated beyond saturation levels, crystals start precipitating in tank 37 and inside the tubes of ceramic membrane 39. The crystals are not accumulated in the membrane 39 due to recirculating brine are transferred to tank 37. The crystals are removed from tank 37 through pump 42 through a solid removal device 43 which can be a centrifuge, belt press or any other solids separation and removal device. The crystals can be used as such, further processed by drying or disposed off. The distillate is collected and may be used for beneficial purpose of disposed of. To increase the capacity multiple membrane modules can be installed and operated in parallel.

(31) In one embodiment of the invention a membrane brine concentration process has been invented as shown in FIG. 7A and FIG. 7B by which high salinity liquid (brine or RO reject water) can be concentrated above saturation level i.e. up to crystallization stage, 30% to 40% of salt concentration. In this invention the membrane cartridge as shown in FIG. 2B and FIG. 3, is assembled within the brine tank as shown in FIG. 7A or assembled outside the brine tank as shown in FIG. 7B, only pure water vapors are comes in contact with membranes. The hot brine liquid circulated in the brine tank through a brine circulation pump and water vapors that generated in the brine tank will be drawn through membrane unit with the help of negative suction pressure of vacuum pump. The hot brine may have a temperature, for example, between 45 and 90° C., preferably between 80 and 85° C., and also preferably below 85° C. By this process consistent distillate flux in the range of 10 Lm.sup.2h to 25 Lm.sup.2h, preferably around 15 Lm.sup.2h to 20 Lm.sup.2h is easily achieved with distillate TDS as low as 10 ppm. The main advantages of this process is that the brine or RO reject can be easily concentrated up to 40% (super saturation level) and high purity distillate can be extracted through membrane unit without affecting distillate flux and quality. The salt removal efficiency in distillate is always more than 99.9%. Table-4 data shows the performance of this membrane brine concentration process performs consistently with respect to consistent and steady distillate flux and quality from a brine liquid concentrated from 5% to 40% salt concentration.

(32) In an embodiment of this membrane brine concentration process as shown in FIG. 7A and FIG. 7B, the brine liquid is circulated in brine tank 101 through brine feed pump 102. The brine liquid is heated up to 70° C. to 90° C., preferably 80° C. to 85° C. through heat exchanger 103 during circulation. The hot liquid of heating source 104 is circulated through heat exchanger 103 for transfer of heat to brine liquid. This heat source can be solar, hot water or oil or steam depending on the availability of heat source. The heated brine liquid entered in to brine tank 101 through spray nozzles 105 and water vapors collected towards top of brine tank and passed through membrane unit 106 and then condenser 107 due to negative suction pressure in brine tank and condenser applied through vacuum pump 108. The brine tank further includes baffles between the recirculating brine and the membrane unit. In condenser 107 the water vapors (distillate) condensed into liquid form through condenser 107 secondary cooled water flow and collected in the distillate trap 109. Raw brine or RO reject water 110 is collected in feed tank 111 and through feed pump 112 it is fed in to brine tank 101 to maintain the liquid level in brine tank 101. By this way the brine can be concentrated up to desired salt level and process can be operated in batch wise or continuous mode. The excess salt from brine tank 101 can be separated through a solid removal device 113 which can be a centrifuge, belt press or any other solids separation and removal device and liquid of salt removal device 113 is again fed into the brine tank 101 for further concentration.

(33) Embodiments of the invention will now be further explained by reference to certain examples, which are presented as exemplary embodiments.

(34) Experimental Details:

(35) Experiment-1:

(36) A single membrane pouch 12 was made as shown in FIG. 1A. The membrane active area in the membrane pouch was 0.16 m.sup.2. The single membrane pouch 12 was assembled in a tank 14 in a similar way as shown in FIG. 3 and tested in a AVMD process as shown in FIG. 4A with brine water of 120000 ppm TDS. Brine water was heated up to 84° C. and circulated through the AVMD unit 24 with a flow rate of 1000 Lph. Vacuum 28 was applied at distillate port 13 and water vapors 31 condensed in a condenser 25 to achieve 17.5 Lm.sup.2h to 36.8 Lm.sup.2h flux at 490 mmHg to 600 mmHg vacuum respectively. Distillate TDS was found less than 5 ppm in all cases with salt reduction more than 99.99%. Experiment-1 test results are shown in Table-1, below.

(37) TABLE-US-00001 TABLE 1 Feed Distillate Salt Feed Feed Flux TDS TDS Redn. Flow Temp. Vacuum Lm2h ppm ppm % Lph ° C. mmHg 17.5 118329 4 99.996 1093 84.1 490 18.8 118329 4 99.997 1039 83.5 500 19.5 120000 5 99.996 1031 84.9 510 21.0 120000 4 99.997 1042 83.8 510 21.9 120000 4 99.997 995 83.8 520 26.3 118329 5 99.996 1060 83.5 520 28.8 118329 3 99.997 1032 83.5 540 32.5 118329 4 99.997 1023 83.5 560 35.3 121080 3 99.998 1072 83.4 580 34.0 121080 2 99.998 1060 84.1 580 36.3 121080 2 99.999 1078 83.5 600 35.0 121080 1 99.999 1063 83.6 600 36.8 121080 1 99.999 1050 83.8 600

(38) Experiment-2:

(39) In another experiment, five membrane pouches 12 were made as shown in FIG. 1A and assembled as described in FIG. 2A. The assembled membrane pouches 12 were then immersed in a tank as shown in FIG. 3 to operate in AVMD mode. The active membrane area of this AVMD unit was 0.8 m.sup.2. The prepared AVMD unit was then tested in the AVMD process as described in FIG. 4A for hot brine water containing TDS level from 12000 ppm (1.2% salinity) to 183600 ppm (18.36% salinity). Brine water was heated to 80° C. to 85° C. and circulated through AVMD unit 24 with a flow rate of 100 Lph to 1500 Lph. Vacuum of 500 to 550 mmHg was applied through distillate pipe 13, and water vapor was made to condensate at an external condenser 25 to get pure distillate 32. The AVMD unit 24 was tested for 200 hrs and consistent 15 to 18 Lm.sup.2h flux was achieved with salt reduction of 99.99%. Experiment-2 test results are summarized in Table-2, below.

(40) TABLE-US-00002 TABLE 2 Feed Water Distillate Salt Op. Cross flow TDS Temp. Temp. Drop Vacuum Flux Flow TDS Redn. Hrs Lph mg/L ° C. ° C. mmHg Lmh Lph mg/L % 1 1011 12180 80.6 7.9 500 17.5 14 17 99.862 5 1566 12180 81 5.2 480 17.5 14 6 99.951 10 1540 12000 81.6 5.1 480 17.2 13.7 2 99.987 15 1542 12300 80.4 4.8 480 16.8 13.4 2 99.987 20 1537 12300 81.5 5.3 480 17.1 13.7 2 99.987 25 1542 16800 81.2 4.9 480 16.9 13.5 1 99.993 30 1579 30300 80.1 4.6 480 16.6 13.2 2 99.995 35 1509 30600 80 4.7 480 15.5 12.4 2 99.995 40 1550 30600 80.9 4.7 480 15.7 12.6 2 99.995 45 1547 31020 81.1 4.8 470 14.8 11.8 2 99.994 50 1551 31020 80.8 4.6 470 15.4 12.3 2 99.995 55 1539 31920 81.7 4.6 470 15.9 12.7 2 99.995 60 1517 32640 82.3 3.7 430 12.1 9.7 2 99.994 65 1519 33480 79.4 5.7 530 19.6 15.7 12 99.964 70 1523 33480 79.6 5.7 520 19.8 15.8 1 99.996 75 1065 34380 79.4 8.1 530 17.5 14 1 99.997 80 1054 39300 80.2 8.3 520 17.2 13.7 1 99.997 85 1058 63333 79.6 7.1 520 17.1 13.7 2 99.996 90 1023 61200 79.4 7 530 18 14.4 2 99.996 95 1023 61200 80.3 5.8 460 12.5 10 2 99.996 100 1035 84000 79 7.6 530 17.1 13.7 1 99.998 105 1023 84000 79.7 6.4 530 14.6 11.7 3 99.995 110 1041 84000 79 8 530 17.5 14 1 99.998 115 1021 84000 79.3 7.8 530 17.4 13.9 1 99.998 120 1024 100000 78.8 7.8 530 16.8 13.4 2 99.998 125 1057 100000 79.6 8.1 530 17.3 13.8 2 99.998 130 1023 100000 79.1 7.7 530 16.8 13.4 2 99.998 135 1036 100000 80.3 8.7 530 16.5 13.2 2 99.998 140 1046 121740 83.8 5.6 500 13.5 10.80 76 99.937 145 1029 121740 83.1 6.4 500 13.1 10.50 32 99.973 150 1055 126000 81.5 7.6 550 16.9 13.50 6 99.995 155 1014 126000 85.4 8.3 550 16.0 12.80 4 99.997 160 1063 136680 84.3 7.3 540 15.1 12.04 6 99.996 165 1068 136680 84.8 7.3 540 15.3 12.20 5 99.997 170 1023 144120 82.8 7.2 550 12.8 10.20 4 99.997 175 1063 144120 84.3 5.3 500 12.0 9.60 6 99.996 180 1033 168000 85.3 6.0 500 12.5 10.00 5 99.997 185 1053 168000 83.2 5.6 550 14.5 11.60 26 99.984 190 1074 178200 83.3 5.7 530 12.5 10.00 7 99.996 195 1032 183600 83.4 5.7 530 12.5 9.98 5 99.997 200 1061 183600 84.2 5.8 550 12.8 10.20 4 99.998

(41) Results of Experiment-2:

(42) The hot water feed used was of temperature 82+/−3° C. and vacuum applied was between 400 and 600 mmHg. The operation was with single effect that is with no heat recovery. Flux achieved was between 15 and 18 Lm.sup.2h. Purity of distillate was always more than 99.99%. Gain Output ratio (GOR) achieved was between 0.8 and 1.0 confirms the process working efficiently. Ratio of feed cross flow v/s distillate water generated was 30-80:1 time. The concept of multi stage AVMD improves the GOR as we increase the number of stages. The feed water was concentrated up to 180000 mg/L (18% salt) and no impact of salt concentration on distillate purity and flux were observed. Experiment results conclude that AVMD device and process can easily, economically and efficiently concentrate the brine up to 18% of salt concentration.

(43) Experiment-3:

(44) In this experiment a ceramic hydrophobic membrane was used for forced circulation membrane distillation to crystallize the salt. The ceramic membrane module used for the experiment had the following specifications:

(45) Membrane area=0.04 m.sup.2

(46) Membrane Type=Tubular

(47) Membrane tube Inner diameter=3.6 mm

(48) Membrane Tube length=760 mm and tube quantity=04 nos.

(49) The ceramic module was tested with cross flow of 309 Lph to 410 Lph (velocity 2.1 m/s to 2.8 m/s) with feed TDS of 12025 ppm. Feed water temperature was maintained between 80° C. and 90° C. The feed water was concentrated up to saturation level, which was 340000 ppm TDS under circulation, and achieved around 5-8 Lm.sup.2h flux at 500 to 700 mmHg vacuum. During the experiment salt reduction was always above 99.8%. The results of experiment are summarized in Table 3, below.

(50) TABLE-US-00003 TABLE 3 Forced Circulation Ceramic Membrane Distillation test conditions & Results. Membrane: Inorganic ceramic membrane Membrane Area: 0.04 m.sup.2 Feed Water Distillate Salt Cross flow TDS Temp. Temp. Drop Vacuum Flux Flow TDS Reduction Lph mg/L ° C. ° C. mmHg Lmh mL/hr mg/L % 398 12025 83.4 0.9 650 4.53 180 19 99.84% 371 12025 84.3 0.9 650 5.04 200 14 99.88% 376 52025 85.5 1.1 650 5.54 220 10 99.98% 365 52025 86.4 1.0 650 5.54 220 12 99.98% 397 102025 87.1 1.0 650 5.54 220 15 99.99% 390 102025 88.0 1.0 650 5.29 210 27 99.97% 410 150080 83.7 1.0 500 2.52 100 97 99.94% 390 150080 84.6 1.0 650 5.04 200 75 99.95% 370 205080 85.7 0.7 650 5.54 220 228 99.89% 375 205080 85.0 0.7 650 5.04 200 143 99.93% 360 255080 84.7 0.7 650 5.04 200 255 99.90% 333 250223 88.7 0.9 700 4.03 160 195 99.92% 325 310223 89.8 0.9 700 5.29 210 172 99.94% 309 310223 90.5 0.9 700 4.28 170 142 99.95% 318 340223 89.3 0.8 700 4.53 180 124 99.96% 318 340223 88.1 0.6 700 4.53 180 118 99.97%

(51) It is evident from the experiment-3 that saline water can be concentrated up to saturation level easily through forced circulation ceramic membrane distillation process.

(52) It is evident from experiment-2 and 3 that the Advanced vacuum membrane distillation process is ideal for generating higher flux and can concentrate water up to 16% to 24% salt level or closer to salt saturation levels depending on constituents of salt and their solubility and forced circulation ceramic membrane is ideal for further concentration of this water up to saturation level to crystallize the salts economically and effectively.

(53) Experiment-4:

(54) In this experiment, membrane brine concentration process was tested as per system shown in FIG. 7A. A brine tank 101 and membrane unit 106 used for the experiment had the following specifications:

(55) Brine tank volume=300 Ltr

(56) Brine liquid volume in tank=150 Ltr

(57) Membrane area=1.12 m2

(58) Heat exchanger area (at heating source and condenser)=2-3 m2 The membrane brine concentration process was tested with brine circulation flow between 1500 Lph and 3500 Lph in brine tank 101 with initial feed brine TDS of 5% (w/w). Inlet Brine liquid temperature was maintained between 75° C. and 85° C. through heating source 104 and heat exchanger 103. The brine liquid was concentrated up to 40% salt level (w/w) under circulation and achieved consistent 15-20 Lm2h membrane flux at 450 to 500 mmHg negative suction pressure through vacuum pump 108. The distillate was condensed through condenser 107 and collected in distillate trap 109. During the experiment the membrane flux remains steady and distillate TDS was below 300 ppm and in many reading it was less than 10 ppm. The salt rejection efficiency is more than 99.9%. The experiments results are summarized in table-4, below

(59) TABLE-US-00004 TABLE 4 Membrane Brine concentration process test conditions and results. Inlet Liquid (Brine) Circulation Distillate Salt Op. flow TDS Temp. Vacuum Flux Flow TDS Rejection Hrs Lph % mg/kg ° C. mmHg Lm.sup.2h Lph mg/kg % Experiment for Brine concentration from 5.2% to 40% salt level. 1 3784 5.2 52000 74.8 500 23.0 25.8 265 99.490 2 3561 6.7 67141 74.8 500 21.9 24.5 261 99.611 3 3052 7.5 75000 75.3 480 19.7 22.1 236 99.685 4 2907 8.2 82092 76.1 480 19.4 21.8 198 99.759 5 3298 8.9 89077 74.4 480 17.9 20.1 189 99.788 10 2163 11.3 113463 75.5 490 14.7 16.5 176 99.845 15 1851 13.6 135517 79.5 490 21.3 23.9 112 99.917 20 2766 16.3 162858 78.4 500 21.2 23.7 204 99.875 25 2090 19.8 198118 79.5 480 19.8 22.2 191 99.904 30 1728 22.3 222668 78.9 500 17.5 19.6 132 99.941 35 1885 24.4 244432 81.0 520 19.2 21.5 101 99.959 40 2144 26.6 266339 80.1 500 16.5 18.5 180 99.932 45 1901 29.6 295505 81.3 500 17.4 19.5 180 99.939 50 2436 34.2 341991 82.8 500 17.4 19.5 151 99.956 55 2097 34.6 346496 80.1 510 18.3 20.5 151 99.956 60 2237 33.1 330982 81.1 490 18.4 20.7 55 99.983 65 2046 36.5 365000 84.1 500 17.1 19.1 45 99.988 70 2445 38.5 385000 83.3 500 17.1 19.1 11 99.997 75 2271 40.5 405000 79.6 500 11.0 12.4 43 99.989 Experiment continued with maintaining 28% to 36% salt level in inlet brine 80 2808 30.0 300000 81.3 480 16.3 18.3 84 99.972 85 1701 32.5 324540 81.9 500 17.1 19.2 12 99.996 90 2652 30.4 304300 80.7 480 15.9 17.9 68 99.978 95 1854 33.0 329655 82.1 480 16.4 18.4 7.8 99.998 100 2223 33.7 337158 81.2 490 15.1 16.9 13 99.996 105 2213 31.7 316988 81.6 490 17.8 19.9 7.8 99.998 110 2155 32.9 329248 81.7 490 18.6 20.8 14 99.996 115 2434 32.0 320000 81.8 490 18.8 21.0 48 99.985 120 2298 28.8 288303 81.5 490 18.1 20.3 7.8 99.997 125 2374 33.2 331976 80.2 490 17.1 19.2 9.0 99.997 130 2635 29.0 290065 80.3 490 18.2 20.4 4.8 99.998 135 2489 33.3 333234 79.5 490 17.9 20.0 6.7 99.998 140 2430 33.3 333234 77.8 490 17.9 20.1 6.6 99.998 145 2402 28.0 280000 77.6 490 17.9 20.0 4.2 99.999 150 2215 29.5 295000 83.0 490 11.8 13.2 5.2 99.998 155 2250 28.8 287966 80.4 500 18.3 20.5 8.4 99.997 160 2798 29.0 290000 78.6 490 17.3 19.4 10 99.997 165 3383 29.9 299332 79.9 490 17.5 19.6 4.8 99.998 170 2875 30.4 303984 80.6 500 18.1 20.3 4.8 99.998 175 2062 32.3 323313 79.4 480 19.1 21.4 9.0 99.997

(60) It is evident from experiment-4 that saline water is concentrated above saturation level i.e. 30% to 40% salt level by utilizing AVMD membrane cartridge when operated as shown in FIG. 7A and only water vapors from brine tank passed through membrane and condensed through condenser to formed pure liquid under negative suction pressure. It is also evident that by this process even at above saturation level around 30% to 40% salt level in brine, distillate quality and membrane flux are unchanged. As shown in FIG. 7B, AVMD membrane cartridge may also be placed outside of the brine tank depending upon the size of the plant and can be utilized in similar manner as described in experiment-4.

(61) Based on experiment-2 and 3 results, an integrated process has been devised as shown in FIG. 5, in which feed water is first treated through AVMD unit in a submerged vacuum membrane distillation process and concentrated to a level just below the saturation point based on the salt solubility. The distillate is continuously collected by vacuum system in distillate tank. The feed water temperature maintained around 80° C. with the help of heater fitted in AVMD circulation tank. The concentrated brine of approximately 16-24% salt level is further concentrated up to above saturation levels through forced circulation ceramic membrane distillation system and finally crystallized salt will be formed in the crystallizer tank where it can be used for salt recovery or disposal as per the regulatory requirements.

(62) Embodiments of the invention have been described herein by reference to preferred embodiments. Those of skill in the art will recognize that other embodiments are possible, as they are within the scope and spirit of the appended claims.