Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
METHOD AND SYSTEM FOR DISPOSAL OF BRINE SOLUTION
Document Type and Number:
WIPO Patent Application WO/2012/000558
Kind Code:
A1
Abstract:
The invention relates to a method and a system of disposing a brine solution generated during a desalination process, wherein the method comprises feeding the brine solution under a hydraulic pressure into a first pathway (32) being defined at least partially by a first face of a semipermeable membrane (30), feeding a diluted solution having a lower salinity concentration than the brine solution into a second path¬ way (34) being defined at least partially by a second face of the semipermeable membrane (30), the second face being opposite to the first face, such that part of the solvent of the diluted solution passes through the semipermeable membrane (30) forming a diluted brine solution in the first pathway (32) having a higher volume than the brine solution fed, generating energy from a potential pressure energy of the diluted brine solution, and disposing the diluted brine solution into the environment.

Inventors:
BRANSTON DAVID WALTER (DE)
Application Number:
PCT/EP2010/059397
Publication Date:
January 05, 2012
Filing Date:
July 01, 2010
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
SIEMENS AG (DE)
BRANSTON DAVID WALTER (DE)
International Classes:
H01M8/22; B01D61/02; C02F1/44; F03G7/00; C02F103/08
Domestic Patent References:
WO2010008275A12010-01-21
Foreign References:
US3906250A1975-09-16
EP1746680A12007-01-24
US4283913A1981-08-18
Other References:
None
Attorney, Agent or Firm:
SIEMENS AKTIENGESELLSCHAFT (München, DE)
Download PDF:
Claims:
Patent Claims:

1. A method of disposing a brine solution generated during a desalination process, the method comprising:

- feeding the brine solution under a hydraulic pressure into a first pathway (32) being defined at least partially by a first face of a semipermeable membrane (30),

- feeding a diluted solution having a lower salinity than the brine solution into a second pathway (34) being defined at least partially by a second face of the semipermeable mem¬ brane (30), the second face being opposite to the first face, such that part of the solvent of the diluted solution passes through the semipermeable membrane (30) forming a diluted brine solution in the first pathway (32) having a higher volume than the brine solution fed,

- generating energy from a potential pressure energy of the diluted brine solution, and,

- disposing the diluted brine solution into the environment.

2. The method according to claim 1, wherein the diluted solu¬ tion is seawater.

3. The method according to claim 1 or 2, wherein the energy is generated by passing the diluted brine solution through a turbine .

4. The method according to any of the claims 1 to 2, wherein the turbine is further rotationally coupled to an electrical generator (43) for generating an electrical energy.

5. The method according to anyone of the claims 1 to 4, wherein the feeding of the brine solution into the first pathway (32) includes controlling a first flow rate of the brine solution into the first pathway (32) and the feeding of the diluted solution into the second pathway (34) includes controlling a second flow rate of the diluted solution into the second pathway (34) .

6. The method according to claim 5, wherein the first flow rate is controlled such that the salinity of the diluted brine solution in the first pathway (32) is reduced below a threshold value, the threshold value being chosen such that the salinity complies to environmental standards, and the second flow rate is controlled such that the salinity of the diluted solution in the second pathway (34) is maintained be¬ low the threshold value. 7. The method according to any of the claims 1 to 6, wherein the hydraulic pressure is lower than an osmotic pressure dif¬ ference between the brine solution and the diluted solution.

8. The method according to any of the claims 1 to 7, wherein the brine solution is passed through the first pathway (32) to flow in a first direction and the diluted solution is passed though the second pathway (34) to flow in a second di¬ rection, the first direction being opposite to the second di¬ rection .

9. A desalination system (10), comprising:

- a desalinator (15) for desalinating an aqueous salt solution, the desalinator (15) producing a desalinated solution and a brine solution,

- an osmosis unit (20) comprising a semipermeable membrane (30), a first face of the semipermeable membrane (30) de¬ fining at least partially a first pathway (32) and a second face opposite to the first face of the semipermebale mem¬ brane (30) defining at least partially a second pathway (34),

- a first feeder (36) for feeding the brine solution under a hydraulic pressure into the first pathway (32),

- a second feeder (38) for feeding a diluted solution having a lower salinity than the brine solution into the second pathway (34), wherein the semipermeable membrane (30) al¬ lowing part of the solvent of the diluted solution to pass through forming a diluted brine solution in the first path- way (32) having a higher volume than the brine solution fed,

- a turbine (42) in fluid communication with the first pathway (32) to receive the diluted brine solution to generate energy from a potential pressure energy of the diluted brine solution, and

- means for disposing the diluted brine solution into the en¬ vironment from the turbine (42) . 10. The system according to claim 9, wherein the diluted solution is seawater.

11. The system according to any of the claims 9 to 10, wherein the turbine (42) is further rotationally coupled to an electrical generator (43) .

12. The system according to any of the claims 9 to 12, wherein the first feeder (36) comprises a first flow control¬ ler (52) for controlling a first flow rate of the brine solu- tion into the first pathway (32) and the second feeder (38) comprises a second flow controller (54) for controlling a second flow rate of the diluted solution into the second pathway ( 34 ) . 13. The system according to claim 13, wherein first flow controller (52) is adapted to control the first flow rate such that salinity of the diluted brine solution in the first pathway (32) is reduced below a threshold value, the thresh¬ old value being chosen such that the salinity of the diluted brine solution complies with environmental standards, and the second flow controller (54) is adapted to control the second flow rate such that the salinity of the diluted solution in the second pathway (34) is maintained below the threshold value .

14. The system according to any of the claims 9 to 13, wherein the hydraulic pressure is less than an osmotic pres- 1 b

sure difference between the brine solution and the diluted solution .

Description:
Description

Method and system for disposal of brine solution The present invention relates to a method and a system for disposal of brine solution generated during a desalination process .

Desalination refers to one of several processes that remove excess salt and other minerals from an aqueous solution.

Typically, water is desalinated in order to be converted to potable water suitable for human or animal consumption, or for irrigation. The choice of the desalination process depends on many factors including salinity levels of the raw water, quantities of water needed, and the form of available energy. For example, the desalination process includes, but is not limited to, reverse osmosis and electrodialysis . Re ¬ gardless, of the desalination process used, there is always a highly concentrated waste product comprising of the salt re- moved from the potable water created. Typically, the concen ¬ trated waste product is referred to as a brine solution. For example, recovery of potable water from sea water (35,000 ppm of salinity) , produces a brine solution having salinity of about 70,000 ppm or above. The term salinity refers to a con- centration of salt dissolved in a solution. Disposal of such brine solutions presents significant costs and challenges for the desalination industry, which results in higher cost of water. For example, the salinity of the concentrated brine solution may be above environmental standards which when dis- posed into the ocean may affect the inhabiting marine organ ¬ isms. Environmental standards define salinity gradient which will not impact the marine organisms when a solution is dis ¬ posed into the ocean. Thus, typically, ocean outfalls are used for disposing the brine solution into oceans to minimize the size of zone of discharge in which the salinity is ele ¬ vated above the environmental standards. It is an object of the embodiments of the invention to reduce salt concentration of the brine solution generated during a desalination process for disposal. The above object is achieved by a method of disposing a brine solution generated during a desalination process according to claim 1 and a desalination system according to claim 10.

As the salt concentration of the brine solution and the di- luted solution is different, the solutions will have differ ¬ ent osmotic pressures. Due to the difference in osmotic pres ¬ sures of the brine solution and the diluted solution, part of the solvent of the diluted solution will pass through the semipermeable membrane into the first pathway forming a di- luted brine solution. As solvent from the diluted solution is added to the brine solution to form the diluted brine solu ¬ tion, the later will have a higher volume than the brine so ¬ lution originally fed into the first pathway. As the diluted brine solution is under the hydraulic pressure, the total po- tential pressure energy will increase with expansion of the diluted brine solution, which can be used to generate energy. Thereafter, the diluted brine solution can be disposed into the environment, for example, sea. According to another embodiment, seawater having a lower salinity than the brine solution is used as the diluted solu ¬ tion. As desalination plants are typically located at the vi ¬ cinity of ocean or sea, availability of seawater is in abun ¬ dance .

According to yet another embodiment, the energy is generated by passing the diluted brine solution through a turbine. A readily available standard turbine may be used for generating energy. Thus, mechanical energy can be generated easily.

According to yet another embodiment, the turbine is further rotationally coupled to an electrical generator for generat- ing an electrical energy. Electrical energy can easily be transported and used. It can also be sold to create revenue.

According to yet another embodiment, the feeding of the brine solution into the first pathway includes controlling a first flow rate of the brine solution into the first pathway and the feeding of the diluted solution into the second pathway includes controlling a second flow rate of the diluted solu ¬ tion into the second pathway. This enables in controlling the rate of reduction of salinity of the diluted brine solution and the rate of increase of the salinity of the diluted solu ¬ tion .

According to yet another embodiment, the first flow rate is controlled such that the salinity of the diluted brine solu ¬ tion in the first pathway is reduced below a threshold value, the threshold value being chosen such that the salinity com ¬ plies with environmental standards, and the second flow rate is controlled such that the salinity of the diluted solution in the second pathway is maintained below the threshold value. The reduction in the salinity of the diluted brine so ¬ lution below the threshold value enables in maintaining the salinity of the area of the sea where the diluted brine solu ¬ tion is disposed to a range tolerable to the marine organisms inhabiting the area. Additionally, maintaining the salinity of the diluted solution below the threshold value enables in disposing the diluted solution without affecting the marine organisms inhabiting the area of the sea where the diluted solution is disposed.

According to yet another embodiment, the hydraulic pressure is lower than an osmotic pressure difference of the brine so ¬ lution and the diluted solution. This enables in passing of the solvent of the diluted solution through the semipermeable membrane.

According to yet another embodiment, the brine solution is passed though the first pathway to flow in a first direction and the diluted solution is passed though the second pathway to flow in a second direction, the first direction being opposite to the second direction. This enables in increasing the life of the semipermeable membrane.

Embodiments of the present invention are further described hereinafter with reference to illustrated embodiments shown in the accompanying drawings, in which:

FIG 1 illustrates a block diagram of a desalination system according to an embodiment herein,

FIG 2 illustrates an osmosis unit having a brine solution in a first pathway and a diluted solution in a second pathway separated by a semipermeable membrane,

FIG 3 illustrates a first feeder and a second feeder in

fluid communication with the osmosis unit according to another embodiment herein,

FIG 4 illustrates a desalination system 10 according to yet another embodiment herein, and

FIG 5 is a flow diagram illustrating a method of disposing a brine solution generated during a desalination process according to an embodiment herein.

Various embodiments are described with reference to the draw ¬ ings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purpose of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. It may be evident that such embodiments may be practiced without these specific details.

FIG 1 illustrates a block diagram of a desalination system according to an embodiment herein. The desalination system 10 comprises a desalinator 15, an osmosis unit 20 in fluid com- munication with the desalinator 15 via a first feeder 36, a second feeder 38, a turbine 42 for generating energy and an electrical generator 43. The aqueous solution, for example seawater to be desalinated, is fed to the desalinator 15, as shown by arrow 22. The desalinator 15 processes the aqueous solution to remove salts and other constituents so that the desalinated solution may be used, for instance, for human or animal consumption or for irrigation. For example, if the aqueous solution is seawater, the salinity of the seawater may be reduced by the desalination process. Desalination of the aqueous solution produces a brine solution comprising the salts removed from the aqueous solution. The desalinator 15 may include, but not limited to, an electrodialysis device, a reverse osmosis device, and the like.

The salts present in the aqueous solution are separated by the desalinator 15. The process of separating the slats from the aqueous solution increases the salinity of the brine so ¬ lution. In accordance to an embodiment, the salinity of the brine solution increased during the desalination process is reduced using a pressure-retarded-osmosis process. The brine solution with increased salinity is fed to the osmosis unit 20 from the desalinator 15, as shown by arrow 24. A diluted solution having a lower salinity than the brine solution is also fed to the osmosis unit 20, as shown by arrow 26. Advan ¬ tageously, when the aqueous solution to be desalinated using the desalinator 15 is seawater, the diluted solution to be fed to the osmosis unit 20 may also be seawater as seawater may be readily available. The salinity of seawater is typi- cally lower than the brine solution.

Referring still to FIG 1, the osmosis unit 20 comprises a vessel 28 and a semipermeable membrane, generally designated as 30. The semipermeable membrane 30 divides the vessel 28 into two pathways 32, 34 for the brine solution and the di ¬ luted solution respectively. Thus, the pathways 32, 34 are separated by the semipermeable membrane 30. The semipermeable membrane 30 used is permeable to solvent and relatively im- permeable to solute present in a solution. A solvent dis ¬ solves a solute to form a solution. For example, if seawater is considered, water is the solvent and the salts present in water are the solutes.

Referring still to FIG 1, in an aspect, the brine solution having a first osmotic pressure is fed into the first pathway 32 of the osmosis unit 20 using a first feeder 36. The first osmotic pressure of the brine solution is due to the salinity of the brine solution. The feeder 36 is configured to feed the brine solution into the first pathway 32 under a hydrau ¬ lic pressure P. In the shown example of FIG 1, the feeder 36 comprises a hydraulic pump 37 to feed the brine solution un ¬ der the hydraulic pressure P. The brine solution fed into the first pathway 32 is in contact with a first face of the semipermeable membrane 30. The diluted solution having a sec ¬ ond osmotic pressure is fed into second pathway 34 using a second feeder 38. The diluted fed into the second pathway 34 is in contact with a second face of the semipermeable mem- brane 30. The second face of the semipermeable membrane 30 is opposite to the first face. The second osmotic pressure of the diluted solution is due to the salinity of the diluted solution, which is different from the first osmotic pressure. In the shown example of FIG 1, the second feeder comprises a pump 39 for feeding the diluted solution into the second pathway 34.

FIG 2 illustrates the osmosis unit 20 having the brine solu ¬ tion in the first pathway 32 and the diluted solution in the second pathway 34 separated by the semipermeable membrane 30 in more detail. The brine solution in the first pathway 32 illustrated is under the hydraulic pressure P. The hydraulic pressure P is selected such that the same is less than an os ¬ motic pressure difference of the brine solution and the di- luted solution. As the hydraulic pressure P is less than the osmotic pressure difference, part of the solvent from the di ¬ luted solution in the second pathway 34 will pass through the membrane 30 into the first pathway against the hydraulic pressure P as illustrated by the arrow 40.

Referring now to FIG 1, the second osmotic pressure of the diluted solution is lower than the first osmotic pressure of the brine solution as the diluted solution is less concen ¬ trated than the brine solution. In the shown example of FIG 1, the brine solution is passed though the first pathway 32 to flow in a first direction and the diluted solution is passed though the second pathway 34 to flow in a second di ¬ rection. The first direction is opposite to the second direc ¬ tion. Thus, the brine solution flows though the first pathway 32 in counter-flow to the flow of the diluted solution in the second pathway 34. Alternatively, the first direction and the second direction may be same, and thus, the diluted solution may flow through the second pathway 34 in the same direction of flow of the brine solution in the first pathway 32.

Referring still to FIG 1, pressure-retarded-osmosis is ef- fected through the semipermeable membrane 30 in the direction of the arrow 40. Part of the solvent of the diluted solution will pass through the semipermeable membrane 30 into the first pathway 32 at a rate governed by the difference of the osmotic pressure difference and the hydraulic pressure. The solvent passing through the membrane 30 into the first path ¬ way 32 will dilute the salinity of the brine solution to form a diluted brine solution. This reduces the salinity of the diluted brine solution such that the salinity of the same shall not pose threat to the environment when disposed. The passing of the solvent of the diluted solution into the first pathway 32 causes increase in the volume of the diluted brine solution under the hydraulic pressure P, and thus, is higher than the volume of the brine solution fed into the first pathway 32. The diluted brine solution thus compressed has a potential for furnishing energy when passed though the turbine 42. The energy is generated from the potential pressure energy of the diluted brine solution. The energy generated shall exceed the energy originally consumed for pressurizing the brine solution by a fraction AV/V where AV is the volume of solvent which has passed through the semipermeable mem ¬ brane 30 and V is the original volume of the brine solution. Thus, the brine solution gains energy which is in excess of that expended in pressurizing the brine solution by the hy ¬ draulic pump 37. For example, the excess mechanical energy which may be furnished is given by PAV.

Referring still to FIG 1, the turbine 42 illustrated is in fluid communication with the first pathway 32 of the osmosis unit 20. The diluted brine solution in the fist pathway 32 is passed through the turbine 42 to furnish energy from the potential energy of the diluted brine solution. The turbine 42 generates mechanical energy when the diluted brine solution is passed through the same. After passing though the turbine 42, the diluted brine solution having reduced salinity can be disposed into the environment, as indicated by the arrow 44. In the shown example of FIG 1, the system 10 further comprises an electrical generator 43 rotationally coupled to the turbine 42. The electrical generator 43 enables in converting the mechanical energy generated by the turbine 42 to electri ¬ cal energy.

Reduction in salinity of the diluted brine solution ensures that the affect to the inhabiting marine organisms is reduced in the area of the ocean the solution is disposed. This re ¬ duces the cost of disposing concentrated brine solution gen ¬ erated during desalination process as the diluted brine solu ¬ tion obtained as per the embodiments herein can be disposed into the ocean directly without the requirement of complex ocean outfalls. Moreover, as the desalination plants are lo ¬ cated in the vicinity of sea or ocean, the reduction of the salinity of the brine solution such that the same may be dis ¬ posed into the sea or ocean provides additional advantage. Additionally, sea water may be used as the diluted solution which is available in abundance as desalination plants are typically in the vicinity of sea or ocean. The diluted solu- tion is discharged from the second pathway 32, as indicated by the arrow 46.

Referring still to FIG 1, in an aspect, the hydraulic pump 37 and the pump 39 may be mechanically connected to the turbine 42. Thus, the hydraulic pump 37 and the pump 39 may be oper ¬ ated using external energy during the initial start-up phase. When energy is being generated by the turbine 42, the energy to drive the hydraulic pump 37 and the pump 39 may be pro- vided by the turbine 42. Alternatively, in embodiments wherein the system 10 comprises the electrical generator 43, the hydraulic pump 37 and the pump 39 may be electrically connected to the electrical generator 43 and thus, may be op ¬ erated using the electrical energy generated by the electri- cal generator 43. This will reduce the consumption of external energy and thus reduce the operation cost. Additionally, in an aspect, the energy generated from the diluted brine so ¬ lution may be provided to the desalinator 15. FIG 3 illustrates a first feeder 36 and a second feeder 38 in fluid communication with the osmosis unit 20 according to another embodiment herein. In the shown example of FIG 3, the first feeder 36 further comprises a first flow controller 52 to control a first flow rate of feeding the brine solution into the first pathway 32 and the second feeder 38 further comprises a second flow controller 54 to control a second flow rate of feeding the diluted solution into the second pathway 34. By controlling the flow rate of the brine solu ¬ tion and the diluted solution into first pathway 32 and into the second pathway 34 respectively, the rate at which the sa ¬ linity of the brine solution is reduced can be controlled. Flow rate of the brine solution and the diluted solution is one of the parameters on which the rate of reduction of sa ¬ linity of the brine solution may depend in a pressure- retarded-osmosis process.

By controlling the flow rate of feeding the brine solution and the diluted solution into the osmosis unit 20, the in- crease in the salinity of the diluted solution due to the pressure-retarded-osmosis process may also be controlled. In an aspect, the salinity of the diluted brine solution in the first pathway 32 and the salinity of the diluted solution in the second pathway 34 may be monitored such that the flow rate of the brine solution and the diluted solution may be controlled appropriately. Advantageously, the salinity of the diluted brine solution may be reduced below a threshold value. The threshold value being chosen such that the salin- ity of the diluted brine solution complies with environmental standards, such that, marine organisms are not affected.

Also, the increase in the salinity of the diluted solution may be controlled such that the salinity of the diluted solu ¬ tion is maintained below the threshold value. Thus, the di- luted brine solution with reduced salinity and the diluted solution may be disposed without causing any harm to the en ¬ vironment as indicated by the arrows 44, 46 of FIG 1 respec ¬ tively. As the salinity of the diluted solution is also main ¬ tained below the threshold valve, disposing the same into the sea provides the advantage as desalination plants are in the vicinity of sea or ocean.

Referring still to FIG 3, in an aspect, the rate of flow of the brine solution into the first pathway 32 and the rate of flow of the diluted solution into the second pathway 34 may be controlled such that the osmotic pressure difference be ¬ tween the brine solution and the diluted solution is maintained substantially higher than the hydraulic pressure. This shall provide the advantage of reducing the salinity of brine solution efficiently and also enable generation of increased energy as the volume of solvent passing though the membrane 30 into the first pathway 32 may be relatively higher.

FIG 4 illustrates the desalination system 10 according to yet another embodiment. In the shown example FIG 4, the system 10 further comprises a pressure exchanger 60 arranged in fluid communication between the first feeder 36 and the osmosis unit 20. Part of the diluted brine solution is provided to the pressure exchanger 60, as indicated by the arrow 62. The pressure exchanger 60 is adapted to pressurize the brine so ¬ lution being fed into the first pathway 32 of the osmosis unit 20 using the pressure of the diluted brine solution. However, the pressure of the diluted brine solution can only be used once the pressurized diluted brine solution is avail ¬ able. Thus, during the initial start-up of the osmosis unit 20, the hydraulic pump 37 may be used to pressurize the brine solution. Once the diluted brine solution is available, the same may be utilized in pressurizing the brine solution being fed into the first pathway 32. Thereafter, the diluted brine solution may be discharged from the pressure exchanger 60 and be disposed into the environment, as indicated by the arrow 66. This may reduces the consumption of external energy and thus reduce the operation cost.

FIG 5, with reference to FIG 1 through FIG 4, is a flow dia ¬ gram illustrating a method of disposing a brine solution generated during a desalination process according to an embodi- ment herein. At block 72, the brine solution is fed under a hydraulic pressure into a first pathway 32 being defined at least partially by a first face of a semipermeable membrane 30. Next at block 74, a diluted solution having a lower salinity than the brine solution is fed into a second pathway 34 being defined at least partially by a second face of the semipermeable membrane 30, the second face being opposite to the first face, such that part of the solvent of the diluted solution passes through the membrane 30 forming a diluted brine solution in the first pathway 32 having a higher volume than the brine solution fed. Moving next to block 76, energy is generated from potential pressure energy of the diluted brine solution. At block 78, the diluted brine solution is disposed into the environment. The embodiments described herein enable in reducing the sa ¬ linity of the brine solution generated during a desalination process. The reduction of the salinity of the brine solution enables is disposing the brine solution without impacting the environment. Additionally, energy may be generated using the brine solution with reduced salinity prior to disposing the same into the ocean. The energy generated may be converted to mechanical energy, electrical energy, and the like.

While this invention has been described in detail with refer ¬ ence to certain preferred embodiments, it should be appreci ¬ ated that the present invention is not limited to those pre ¬ cise embodiments. Rather, in view of the present disclosure which describes the current best mode for practicing the in ¬ vention, many modifications and variations would present themselves, to those of skill in the art without departing from the scope and spirit of this invention. The scope of the invention is, therefore, indicated by the following claims rather than by the foregoing description. All changes, modifications, and variations coming within the meaning and range of equivalency of the claims are to be considered within their scope.