Abstract:
An apparatus for recovering energy from an osmotic system, said apparatus comprising: (i) a feed stream ( 143,251 ); (ii) pressure means ( 140,150, 250, 254 ) to pressurise said feed stream; (iii) a manipulated osmosis unit ( 110,220,230 ); (iv) an energy recovery unit ( 120, 240, 260 ) in fluid connection with second solution side of the manipulated osmosis unit; (v) a reverse osmosis unit ( 130 ) receiving a feed from the energy recovery unit.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to methods and apparatus for a solvent removal process by a pressure driven process at lower applied pressure utilizing Manipulated Osmosis (MO) and Reverse Osmosis (RO) combined with Energy Recovery Devices (ERD), to methods and apparatus for osmotic energy recovery utilizing Energy Recovery Turbines with forward osmosis units, and to methods and apparatus for transforming energy from a heat source into a usable form using a working fluid such as ammonia—water that is expanded and regenerated. Embodiments of this invention further relate to a method and apparatus for improving the heat utilization efficiency of a thermodynamic cycle. The present invention utilizes an Energy Recovery Turbine, which is an Energy Recovery Device (ERD), in the cycle to maintain the working fluid, for example ammonia-water solution at a similar level of concentration) between the evaporator (boiler) and the condenser (absorber) by linked them together through a heat exchanger in conjunction with an Energy Recovery Turbine 
       BACKGROUND TO THE INVENTION 
       [0002]    Forward Osmosis (FO) or Manipulated Direct Osmosis (MDO) processes, and their related applications, are well described in WO 2005/012185 and WO 2005/120688 in the name of University of Surrey and in my UK filed patent no. 0718334.6 dated on 20 Sep. 2007. In addition, a number of seawater and brackish water desalination applications are explained and described in WO 2005/012185, and cooling tower water treatment applications using FO are explained in WO 2005/120688. The text of WO2005/012185 and WO2005/120688 are hereby imported by reference and are intended to form an integral part of this description. This description should be read, and the terms of this description should be understood, in relation to the disclosure in those earlier documents. 
         [0003]    In my patent No. 0718334.6 dated on 20 Sep. 2007, many novel options for producing fresh water from solar ponds and cooling towers have been discussed, based upon utilizing FO &amp; Energy Recovery Devices ERDs. 
         [0004]    Energy Recovery Devices are used for energy recovery from a high pressure liquid stream to another liquid stream at lower pressure, such as a hydraulic energy exchanger located between a high-pressure rejected stream and a low-pressure feed stream in reverse osmosis RO plants. There are many types of commercial ERDs available in the market such as Pelton turbines, Hydraulic Turbochargers, Piston Isobaric and Rotary Isobaric devices. 
         [0005]    Energy Recovery Turbines or Turbo Chargers are examples of energy recovery devices which could be used with this invention. FEDCO and Pump Engineering Inc (PEI) are both producing these types of ERDs. Today, thousands of ERDs from different manufacturers are used in desalination plants around the world to save energy, especially with seawater RO plants. It should be understood that the system designer will select the most suitable ERD for the application involved. 
         [0006]    Generally, fresh water is produced from seawater or brackish water by a RO process which requires high pressure applied to the membrane in the reverse osmosis unit in order to separate the solvent (water). The amount or magnitude of the applied pressure is mainly dependent on the feed&#39;s osmotic pressure and the design recovery ratio of the plant. For example, seawater of TDS between 30,000-50,000 ppm could be treated by RO to produce fresh water by applying a pressure between 50-80 bar with a recovery ratio between 30-50%. Using such a high-pressure process will have an impact on the cost because of the highly costly pressure pumps required and operating costs to run them. Consequently, achieving an RO process with lower working pressures is considered to be imperative as it impacts on both fixed and operational costs. If a lower operating pressure can be achieved then less expensive lower pressure pipework and fittings could be used. 
       SUMMARY OF THE INVENTION 
       [0007]    According to a first aspect of the present invention there is provided an apparatus for recovering energy from an osmotic system, said apparatus comprising:—
       (i) a feed stream;   (ii) pressure means to pressurise said feed stream;   (iii) a manipulated osmosis unit working according to reverse osmosis principles;   (iv) an energy recovery unit in fluid connection with second solution side of the manipulated osmosis unit;   (v) a reverse osmosis unit receiving a feed from the energy recovery unit.       
 
         [0013]    This arrangement allows a pure solvent stream to be produced at lower operating pressures than would otherwise be possible, by recovering energy as the various liquid streams circulate. 
         [0014]    Preferably said manipulated osmosis unit houses a selective membrane for separating a first solution from a second solution, said membrane being configured to selectively allow solvent to pass from the first solution side of the membrane to the second solution side of the membrane. 
         [0015]    Preferably the reverse osmosis unit houses a second selective membrane for separating a third solution from a fourth solution, said second membrane being configured to selectively allow solvent to pass from the said third solution to said fourth solution. 
         [0016]    Preferably the pressure means comprises a pump. A pump is required to generate the pressure required to operate the manipulated osmosis unit. 
         [0017]    Preferably the pressure means further comprises an energy recovery unit, which may augment the pump. 
         [0018]    In a particularly preferred embodiment the pressure means comprises an energy recovery unit and a pump. 
         [0019]    Preferably the energy recovery unit comprises an energy recovery turbine. 
         [0020]    Preferably said apparatus further comprises a second manipulated osmosis unit and preferably the first and second manipulated osmosis units are connected in a loop. 
         [0021]    Preferably the second manipulated osmosis unit houses a third selective membrane for separating a fifth solution from a sixth solution, said membrane being configured to selectively allow solvent to pass from the fifth solution side of the membrane to the sixth solution side of the membrane. 
         [0022]    Preferably a feed stream is provided to the first solution in said first manipulated osmosis unit and said second solution provides a feed to the fifth solution in said second manipulated osmosis unit. 
         [0023]    Preferably said feed to the fifth solution proceeds via an energy transfer means. 
         [0024]    Preferably said sixth solution provides a feed to the third solution in the reverse osmosis unit. 
         [0025]    Preferably said feed proceeds to the reverse osmosis unit via a pump. 
         [0026]    Where two manipulated osmosis units are provided, it is preferred that the apparatus further comprises a second energy recovery unit. 
         [0027]    Preferably the second energy recovery unit is in fluid connection with the second manipulated osmosis unit and with the reverse osmosis unit. 
         [0028]    Preferably one or more of the energy recovery units comprise an energy recovery turbine. 
         [0029]    According to a second embodiment of the first aspect of the present invention there is provided a process for recovering energy from an osmotic system, said process comprising:—
       (i) positioning a selective membrane in a manipulated osmosis unit between a first solution and a second solution, such that the solvent from the first solution passes across the membrane to dilute the second solution;   (ii) providing a feed stream to the first solution in the manipulated osmosis unit operating according to reverse osmosis principles;   (iii) extracting solvent from the second solution using a reverse osmosis unit, a feed line connecting the second solution in the manipulated osmosis unit and the reverse osmosis unit;   (iv) providing an energy recovery unit in the feed line between the manipulated osmosis unit and the reverse osmosis unit.       
 
         [0034]    Preferably a pressure means is provided to pressurise the feed stream into the manipulated osmosis unit. 
         [0035]    Preferably the pressure means comprises either a pump, or an energy transfer means, or both. 
         [0036]    Preferably the second solution from the manipulated osmosis unit is directed to a second manipulated osmosis unit. 
         [0037]    Preferably the first manipulated osmosis unit and the second manipulated osmosis unit are connected in a loop. 
         [0038]    Preferably energy recovery units are positioned/located between the respective osmosis units. 
         [0039]    In summary this embodiment of the invention, in one sense, involves providing and operating an apparatus according to the first aspect of the invention as set out above and as described in more detail below. 
         [0040]    Therefore, in an embodiment of the first aspect of the present invention, fresh water may be produced via a membrane method (pressure driven process), such as RO desalination for both seawater and brackish water using a lower applied pressure in comparison with higher pressures required in conventional RO plants in which the same or similar osmotic—potential solution is used. The lower operation pressure may be achieved by using Manipulated Osmosis MO and RO in conjunction with ERD. The MO unit&#39;s features are similar to those of FO units with the exception of applying higher pressure on the feed side to reverse the effect of the osmotic potentials resultant of the two solutions, allowing the solvent (typically water) to move from the feed solution to the manipulated solution side. The direction of water flow inside the MO unit in this invention will be from the feed side (high salt concentration) to the manipulated side (low salt concentration) and could be observed as a reverse osmosis process. As a result, the required applied pressure for a certain water flux through the membrane of the MO unit from the feed side to the manipulated solution side will be lower in comparison with the required applied pressure if RO is used alone, without use of a manipulated solution according to this invention. The following equation could represent the resultant effecting pressure on both sides of the membrane inside the MO unit: 
         [0000]      =ΣΔP osmotic +ΣΔP applied    
         [0041]    The manipulated osmosis unit has a semi-permeable membrane (selective membrane) separating a first solution (the feed) and a second solution (the manipulated solution). The osmotic potential (solutes concentration) of the feed solution (first solution) is higher than the osmotic potential (solutes concentration) of the manipulated solution (second solution). That means the solvent (water) moves across the selective membrane from a first to a second solution only when an external pressure exceeding the potential difference the two solutions are applied. 
         [0042]    Water may also be separated from seawater by reverse osmosis. In reverse osmosis, seawater is placed on one side of a semi-permeable membrane and subjected to pressures of 5 to 8 MPa. The other side of the membrane is maintained at atmospheric pressure. The resulting pressure differential causes water to flow across the membrane, leaving a salty concentrate on the pressurized side of the membrane. 
         [0043]    Typically, these semi-permeable membranes have an average pore size of, for example, 1 to 5 Angstroms. After a period of operation, the pores of the semi-permeable membrane may become obstructed by deposited salts, biological contaminants and suspended particles in the seawater. Thus, higher pressures may be required to maintain the desired level of flow across the membrane. The increased pressure differential may encourage further clogging to occur. Thus, the membranes must be cleaned and replaced at regular intervals, interrupting the continuity of the process and increasing operational costs. 
         [0044]    Any suitable selective membrane may be used in the process of the present invention. The membrane may have an average pore size of 1 to 80 Angstroms, preferably, 1 to 20 Angstroms, more preferably, 5 to 10 Angstroms. 
         [0045]    Suitable selective membranes include integral membranes and composite membranes. Specific examples of suitable membranes include membranes formed of cellulose acetate (CA) and membranes formed of polyamide (PA). Preferably, the membrane is an ion-selective membrane. Conventional semi-permeable membranes may also be employed. 
         [0046]    The membrane may be planar or take the form of a tube or hollow fibre. If desired, the membrane may be supported on a supporting structure, such as a mesh support. The membrane may be corrugated or of a tortuous configuration. 
         [0047]    In one embodiment, one or more tubular membranes may be disposed within a housing or shell. The first solution may be introduced into the housing, whilst the second solution may be introduced into the tubes. As the solvent concentration of the first solution is lower than that of the second, solvent will diffuse across the membrane from the first solution into the second solution when external pressure is applied to achieve the reverse osmosis process. Thus, the second solution will become increasingly diluted and the first solution, increasingly concentrated. The diluted second solution may be recovered from the interior of the tubes, whilst the concentrated first solution may be removed from the housing. 
         [0048]    When a planar membrane is employed, the sheet may be rolled such that it defines a spiral in cross-section. 
         [0049]    In a preferred embodiment, the first solution comprises a plurality of solutes such as seawater or fruit juice, whilst the second solution is formed by dissolving one or more known solutes in a solvent. 
         [0050]    Preferably, the second solution has a known composition. 
         [0051]    For example, the second solution is formed by introducing a known quantity of a solute into a known quantity of solvent. Preferably, the second solution consists essentially of a selected solute dissolved in a selected solvent. By forming the second solution in this manner, a substantially clean solution may be produced. 
         [0052]    Preferably, the second solution has a reduced concentration of suspended particles, biological matter and/or other components that may cause fouling of the apparatus used to extract solvent from the second solution. More preferably, the second solution is substantially free of such components. Thus, membrane techniques may be used to extract solvent from the second solution without fear of the pores of the membrane being subjected to unacceptably nigh levels of fouling, for example, by biological matter or suspended particles. 
         [0053]    The solvent in the second solution is preferably water. 
         [0054]    The solute (osmotic agent) in the second solution is preferably a water-soluble solute, such as a water-soluble salt. Suitable salts include ammonium salts and metal salts, such as alkali metals (e.g. Na, K) and alkaline earth metals (e.g. Mg and Ca). The salts may be fluorides, chlorides, bromides, iodides, sulphates, sulphites, sulphides, carbonates, hydrogencarbonates, nitrates, nitrites, nitrides, phosphates, aluminates, borates, bromates, carbides, perchlorates, hypochlorates, chromates, fluorosilicates, fluorosilicates, fluorosuiphates, silicates, cyanides and cyanates. One or more salts may be employed. 
         [0055]    As the second solution circulates in a substantially closed loop, additional additives selected from, for example, scale inhibitors, corrosion inhibitors, biocides and/or dispersants may be added to the closed loop to enhance the separation process in the manipulated osmosis MO and in the Reverse osmosis RO units. 
         [0056]    For example, in one embodiment of the first aspect of the present invention untreated seawater (first solution) is pumped to enter one side of the membrane in a MO unit to achieve a reverse osmosis process, whereas a less concentrated manipulated solution (second solution) at a lower applied pressure enters the other side of the membrane. Due to the resultant differences of osmotic and applied pressures between the two sides of the membrane, the solvent (water) passes across the membrane from the feed side to the process (manipulated) side and accordingly makes the manipulated solution (second solution) more diluted. The high concentration stream (rejected seawater) leaves the MO unit at a high pressure to enter the ERD and transfers its hydraulic (pressure) energy to the outlet manipulated stream (diluted). The diluted manipulated stream gains a pressure or hydraulic energy through the ERD, before entering the RO unit for treatment. Fresh water can be collected from the RO as a permeate whereas the rejected stream (concentrated second solution) leaves the RO at a high pressure and enters another ERD to transfer its hydraulic energy to the seawater (first solution)(which should be pumped to a sufficient pressure by the main pump to achieve the reverse osmosis in the two membrane units (MO &amp; RO units).  FIG. 1  illustrates this process. 
         [0057]    In a second preferred embodiment of this aspect of the present invention, certain additives can be added to the manipulated solution and immobilised in a substantially closed loop. These immobilised additives for example could be antiscalants, biocides and cleaning chemicals. 
         [0058]    In a third preferred embodiment of this aspect of the present invention, a controlled pore size membrane with larger pore size similar to the nano filtration NF membrane can be used in the MO unit and or in the RO unit to enhance the water flux through the membranes of the MO and RO units. 
         [0059]    Accordingly, nanofiltration membranes may be employed to extract solvent from the second solution. 
         [0060]    Nanofiltration is particularly suitable for separating the large solute species of the second solution from the remainder of the solution. 
         [0061]    Suitable nanofiltration membranes include cross-linked polyamide membranes, such as crosslinked aromatic polyamide membranes. The membranes may be cast as a “skin layer” on top of a support formed, for example, of a microporous polymer sheet. The resulting membrane has a composite structure (e.g. a thin-film composite structure). 
         [0062]    Typically, the separation properties of the membrane are controlled by the pore size and electrical charge of the “skin layer”. The membranes may be suitable for the separation of components that are, for example, 0.01 to 0.001 microns in size with molecular weights of 100 gmol-1 or above, for example, 200 gmol-1 and above. 
         [0063]    As well as filtering particles according to size, nanofiltration membranes can also filter particles according to their electrostatic properties. For example, in certain embodiments, the surface charge of the nanofiltration membrane may be controlled to provide desired filtration properties. For example, the inside of at least some of the pores of the nanofiltration membrane may be negatively charged, restricting or preventing the passage of anionic species, particularly multivalent anions. 
         [0064]    Examples of suitable nanofiltration membranes include Desal-5 (Desalination Systems, Escondido, Calif.), NF 70, NF 50, NF 40 and NF 40 HF membranes (FilmTech Corp., Minneapolis, Minn.), SU 600 membrane (Toray, Japan) and NRT 7450 and NTR 7250 membranes (Nitto Electric, Japan). 
         [0065]    The nanofiltration membranes may be packed as membrane modules. By way of example, spiral wound membranes, and tubular membranes for example enclosed in a shell may be employed. 
         [0066]    In a fourth preferred embodiment of this aspect of the present invention, multi MO units can be used in sequence to decrease the applied working pressure.  FIG. 2  illustrates this process. 
         [0067]    In a fifth preferred embodiment of this aspect of the present invention, food solutions such as fruit juices or dairy products can be concentrated. 
         [0068]    RO is a more cost-effective process for concentrating food liquids (such as fruit juices) than conventional heat-treatment processes. Besides the lower operating costs advantages of the present invention, these methods avoid heat treatment processes, which makes them suitable for treating heat-sensitive substances such as the proteins and enzymes found in most food products. 
         [0069]    RO is extensively used in dairy industry for the production of whey protein powder and for the concentration of milk to reduce shipping costs. Accordingly, the feed enters the manipulated unit at low concentration and leaves at higher concentration whereas the extracted solvent (water) can be collected as a permeate from the RO unit. 
         [0070]    Pharmaceutical solutions can be concentrated by the same means and in the same manner. 
         [0071]    According to a second aspect of the invention there is provided an osmotic energy recovery apparatus, said apparatus comprising:—
       (i) a first feed stream;   (ii) a first, forward osmosis unit;   (iii) a first energy transfer means located on an exit stream from the forward osmosis unit;   (iv) a second, reverse osmosis unit;   (v) a second energy transfer means located adapted to derive energy from the high pressure side of the reverse osmosis unit.       
 
         [0077]    Preferably said forward osmosis unit houses a first selective membrane for separating a first solution from a second solution, said first membrane being configured to selectively allow solvent to pass from said first solution to said second solution and thus to build up pressure in the second solution. 
         [0078]    Preferably said second osmosis unit houses a second selective membrane for separating a third solution from a fourth solution, said second membrane being configured to selectively allow solvent to pass from said fourth solution to said third solution; said second osmosis unit receiving a feed stream pressurised by the energy transfer means. 
         [0079]    Preferably the apparatus further comprises a solar pond, said solar pond receiving the second solution from the first osmosis unit by way of the first energy transfer means. 
         [0080]    Preferably the apparatus further comprises a pump to raise water from the solar pond. 
         [0081]    Preferably the apparatus further comprises a desalination plant, said desalination plant receiving the second solution from the first osmosis unit by way of the first energy transfer means. 
         [0082]    Preferably the apparatus further comprises a pump to deliver a fluid stream from the desalination plant towards the first osmosis unit via the second energy transfer means. 
         [0083]    Preferably the second solution in the first osmosis unit, the first energy transfer means, and the second energy transfer means form a loop. 
         [0084]    In an alternative preferred embodiment the apparatus further comprises a cooling tower and preferably the second solution in the first osmosis unit, the first and second energy transfer means and the cooling tower form a loop. 
         [0085]    According to a second embodiment of the second aspect of the present invention there is provided a process for recovering energy from an osmotic system said process comprising:—
       (i) providing a first, forward osmosis unit;   (ii) providing a second, reverse osmosis unit;   (iii) providing a first energy transfer means to transfer energy from an output stream from the forward osmosis unit to an input stream to the reverse osmosis unit;   (iv) providing a second energy transfer means to transfer energy from an output stream from the reverse osmosis unit to an input stream to the forward osmosis unit.       
 
         [0090]    Preferably said first osmosis unit houses a first selective membrane for separating a first solution from a second solution, said first membrane being configured to selectively allow solvent to pass from said first solution to said second solution, and thus build up pressure in the second solution. 
         [0091]    Preferably said reverse osmosis unit houses a second selective membrane for separating a third solution from a fourth solution, said second membrane being configured to selectively allow solvent to pass from said fourth solution to said third solution. 
         [0092]    Preferably the process involves providing a solar pond, said solar pond receiving an output from the forward osmosis unit by way of the first energy transfer means. 
         [0093]    Preferably a pump is located between the solar pond and an input to the forward osmosis unit to raise water from the pond. 
         [0094]    In an alternative preferred embodiment the process involves providing a desalination plant, said desalination plant receiving an output from the forward osmosis unit by way of the first energy transfer means. 
         [0095]    Preferably a fluid loop is created between a more concentrated solution side of the forward osmosis unit, a first energy transfer means, a source of concentration such as solar pond, desalination plant or a cooling tower, a second energy transfer means, returning to the more concentrated solution side of the forward osmosis unit, said loop providing energy to an input stream for the reverse osmosis unit and deriving energy from an output stream from the reverse osmosis unit. 
         [0096]    Preferably an output stream from a more dilute solution side of the reverse osmosis unit is directed as a feed into a more dilute side of the forward osmosis unit. 
         [0097]    In summary, this embodiment of the invention, in one sense, involves providing and operating an apparatus according to the second aspect of the invention as set out above and as detailed below. 
         [0098]    Therefore, according to a second aspect of the present invention, fresh water may be produced via membrane methods, such as RO, from solar ponds. Generally solar ponds have a very high concentration of salt solution due to the continuous natural water evaporation caused by solar heating. This high concentration is considered to be a good source of a driving force that can create high osmotic pressure due to the water flow through a selective semi-permeable membrane, which is placed in the Forward Osmosis FO unit, as described in patents WO 2005/012185 and WO 2005/120688. 
         [0099]    The influx of liquid across the selective membrane generates pressure (e.g. hydrostatic pressure) in the solution. The pressurised solution leaving the FO is used directly to extract its hydraulic energy via Energy Recovery turbine that can transfer the hydraulic energy from the FO outlet to another stream (such as the untreated solution input stream to a reverse osmosis unit). 
         [0100]    Any suitable selective membrane may be used in the FO unit the membrane may have an average pore size of 1 to 60 Angstroms, preferably 2 to 50 Angstroms. 
         [0101]    The average pore size of the membrane is preferably smaller than the size of the solutes in the solution. 
         [0102]    Advantageously, this prevents or reduces the flow of solute across membrane by diffusion, allowing liquid to flow across the membrane along the osmotic (entropy) gradient. The flux of liquid across the membrane is influenced by the pore size of the membrane. Generally, the larger the pore size, the greater the flux. 
         [0103]    Suitable selective membranes include integral membranes and composite membranes. Specific examples of suitable membranes include membranes formed of cellulose acetate (CA) and membranes formed of polyamide (PA). Preferably, the membrane is an ion-selective membrane. Conventional semi-permeable membranes may also be employed. 
         [0104]    The membrane may be planar or take the form of a tube or hollow fibre. If desired, the membrane may be supported on a supporting structure, such as a mesh support. The membrane may be corrugated or of a tortuous configuration. 
         [0105]    An Energy Recovery Turbine can extract most of the hydraulic energy from the high pressure outlet which leaves the Forward Osmosis unit after being diluted there. Ideally, the Energy Recovery Turbine operates to transfer the hydraulic energy from the high pressure stream to another stream, which could be any untreated water stream. This untreated water is pressurised to enter the RO unit, thus producing fresh water with less dissolved salts and contaminants. Another Energy Recovery Turbine can be implemented to transfer the hydraulic energy from the rejected stream of this RO unit to the highly concentrated stream coming from the solar pond or from any other re-concentrating means, such as thermal concentrators, which is in turn pressurised to enter the Forward Osmosis unit.  FIG. 4  and its associated key illustrate this process. 
         [0106]    In a second preferred embodiment of this aspect of the present invention, fresh water can be produced from thermal desalination plants, such as Multi-Stage Flash (MSF), Multi Effect Distillation (MED) and Mechanical Vapour Compression (MVC) plants or any concentrator means such RO rejected streams. In this embodiment the high concentration stream from the MSF, MED, MVC and RO reject replaces the high concentration stream from the solar pond to derive the process of producing fresh water. The description of this method is similar to that described in the first embodiment above and is shown in  FIG. 5 . 
         [0107]    In a third embodiment of this aspect of the present invention that is summarised in  FIG. 6 , along with applying cooling towers to different water sources such as waste water, industrial water, agriculture water, brackish water, or seawater, can be used to produce fresh water. In general, all evaporative cooling tower&#39;s water have a high concentration of salts, and these solutions can be fed to the Forward Osmosis unit. This concentrated solution is diluted by passing into the Forward Osmosis unit, due to water passage through the semi-permeable membrane, into order to balance the osmotic potential between the two sides of membrane. Application of an Energy Recovery Turbine allows the transfer of hydraulic energy from the higher concentration stream coming out from the Forward Osmosis unit, to the lower concentration stream leaving the Forward Osmosis unit. The pressurised stream coming out of the Energy Recovery Turbine enters the RO Unit, resulting in fresh water permeation. The rejected stream from the RO unit however, enters another Energy Recovery Turbine to pump the high concentrated cooling tower&#39;s solution into the forward osmosis unit. 
         [0108]    A fourth embodiment of this aspect of the present invention is shown in  FIG. 7  This describes using cooling tower water to augment the process described in the invention WO 2005/120688, by minimising or indeed, preventing any possibly serious contaminations in the forward osmosis unit and in the whole cooling tower unit. Another advantage of using the aforementioned arrangement is that fresh water can be produced. 
         [0109]    In this method, fresh water is produced by the RO unit and is fed into the Forward Osmosis unit, hence minimising contamination in the Forward Osmosis unit and cooling tower, in addition to increasing the flux through the Forward Osmosis membrane. In a similar manner to that described above and detailed below, the rejected stream from the RO unit is used to pump a concentrated solution from a cooling tower into the forward osmosis unit by using an Energy Recovery Turbine. A second Energy Recovery Turbine is used to pump the cooling tower feed water into the RO unit, the Energy Recovery Turbine utilising the high pressure stream leaving the forward osmosis unit. An excess of fresh water can also be produced by this method, depending on the quality and concentration of the feed water. 
         [0110]    According to a third aspect of the invention there is provided an ammonia-water engine apparatus, said apparatus comprising:—
       (i) an evaporator containing a liquid solution of ammonia in water in the presence of a vapour over the liquid solution;   (ii) a heating source to heat the evaporator;   (iii) a turbine adapted to receive vapour from the evaporator;   (iv) a condenser adapted to condense vapour from the turbine to provide a condensate;   (v) an energy transfer means adapted to derive energy from a condensate stream on route from the evaporator to the condenser;   (vi) a heat exchanger adapted to heat the condensate stream.       
 
         [0117]    Preferably the apparatus further comprises an auxiliary pump. 
         [0118]    Preferably the apparatus further comprises a high pressure feed from the liquid in the evaporator to the heat exchanger, said feed passing through the energy transfer means where it leaves at a lower pressure on route to the condenser. 
         [0119]    Preferably the turbine is connected to a pump, the energy from the turbine being used to drive the pump. 
         [0120]    Preferably the turbine is connected to a vapour compressor, the energy from the turbine being used to drive the compressor. 
         [0121]    In relation to the third aspect of the present invention, the Rankine cycle is the heating engine operating cycle used by all steam engines since the start of the industrial age. As with most engine cycles, the Rankine cycle is a four-stage process. Simply put, the working fluid (usually water) is pumped into a boiler. While the fluid is in the boiler, an external heat source superheats the fluid. The hot water vapour then expands to drive a turbine. Once past the turbine, the steam is condensed back into liquid and recycled back to the pump to start the cycle all over again. Pump, boiler, turbine and condenser are the four parts of a standard steam engine and represent each phase of the Rankine cycle. The organic Rankine cycle (ORC) is a non-superheating thermodynamic cycle that uses an organic working fluid to generate electricity. The working fluid is heated to boiling, and the expanding vapour is used to drive a turbine. This turbine can be used to drive a generator to convert the work into electricity. The working-fluid vapour is condensed back into liquid and fed back through the system to do the work again. The organic chemicals used by an ORC include Freon and most of the other traditional refrigerants such as isopentane, CFCs, HFCs, butane, propane and ammonia. Today, ORC systems are being evaluated to improve the working efficiency of distributed generation systems, to generate electricity from geothermal or solar natural heat sources, or to recover waste heat from industrial processes. The Kalina cycle uses ammonia/water as an organic working fluid which operates in a similar way to the Rankine cycle but with a higher efficiency. 
         [0122]    Methods for converting the thermal energy of low grade energy sources (low temperature heat sources) into electric power present a significant area of potential power generation. There is a necessity for a method and apparatus for increasing the efficiency of the conversion of such low temperature heat to electric power that improves the efficiency of the standard Rankine cycles or the Kalina cycle. This invention presents such a method and apparatus. 
         [0123]    The Kalina cycle is a modified Rankine cycle, or rather a reversed absorption cycle utilizing ammonia-water working fluid and patented by Exergy Inc and A. Kalina. The Kalina cycle is a thermodynamic cycle for converting thermal energy to mechanical power which utilizes a working fluid that is comprised of at least two components. The ratio between those components is varied in different parts of the system to increase thermodynamical reversibility and therefore increase thermodynamic efficiency. There are multiple variants of Kalina cycle systems specifically applicable for different types of heat sources. 
         [0124]    The Kalina cycle has proved theoretically and practically to have higher efficiency than other Rankine cycles such as organic Rankine cycle (ORC) but at the same time there are inherent limitations and higher initial costs. The present invention could provide higher efficiency than a convention Kalina cycle using less equipment, leading to low fixed costs and higher output. 
         [0125]    The Kalina cycle uses the four typical Rankine cycle phases: evaporation through the evaporator, expansion through the turbine, condensation by the absorber and liquid feed pumping back into the evaporator. The present invention presents a new cycle (Mayahi cycle) and uses three typical significant phases: evaporation, expansion and condensation whereas pumping the condensate by conventional pump is avoided by using a hydraulic Energy Recovery Turbine (Energy Recovery Turbine) and a heat exchanger (HE). 
         [0126]    A hydraulic Turbo Charger (Energy Recovery Turbine) is an energy exchanger for transferring hydraulic energy between two liquid streams, wherein one stream is at a comparatively higher pressure than the other, comprising a suitable related centrifugal mechanism. An example where an Energy Recovery Turbine finds application is in the production of potable water using a reverse osmosis RO membrane process. In the RO process, a feed saline solution is pumped into a membrane unit at high pressure. The input saline solution is then divided by the membrane array into high concentration saline solution (brine) at high pressure and permeate water at low pressure. Whereas the high-pressure brine is no longer useful in this process as a fluid, the hydraulic or pressure energy that it contains is important. A hydraulic Energy Recovery Turbine is employed to recover the hydraulic energy (pressure energy) in the brine and transfer it to the feed saline solution. After transfer of the pressure energy in the brine flow, the brine is directed at low pressure to drain. For example, FEDCO and Pump Engineering Inc (PEI) are both producing those Energy Recovery Turbines and Turbo Chargers. Today, thousands of energy recovery devices are used in desalination plants around the world to save energy, especially with seawater RO plants. 
         [0127]    For the time being, Turbo Chargers from PEI or Energy Recovery Turbines from FEDCO, among other available energy recovery devices, are the most practical choice to be implemented according to this patent. But they are not the only devices that could be used. 
         [0128]    Thus, in accordance with an embodiment of this aspect of the present invention, a hydraulic Energy Recovery Turbine together with a heat exchanger are used in conjunction for an ammonia-water heat engine (power plant) instead of the conventional pump that is commonly used to pump the working fluid from the condenser (absorber) to the boiler (evaporator). The advantage of using a heat exchanger in conjunction with a hydraulic Turbo Charger (Energy Recovery Turbine) is that it minimises the heat losses through the mixing process between the contents of the boiler (evaporator) and the condenser (absorber). This Mayahi cycle can utilize any available energy sources for heating the evaporator (boiler) with a temperature range from 50° to 150° C. and most preferably with a temperature range from 80° to 120° C. Cooling the absorber can be achieved by any available cooling source with a temperature range from minus 20° to 50° C. Preferably, any available cooling source such as seawater, river water, cooling towers and air cooling can be employed. 
         [0129]    Ammonia concentration in the Mayahi Engine can be varied from 10 to 90% in the liquid phase and the preferred concentration depends on the temperatures of heating and cooling. Generally, higher concentrations of ammonia means higher working pressure on both the boiler and the absorber according to the thermodynamic equilibrium between concentration, pressure and temperature. 
         [0130]    Mayahi Cycle (Engine) efficiency, like any heat engine, is limited to the Carnot efficiency. The theoretical Carnot efficiency value of a cycle is equal to the temperature difference in degrees Kelvin between the high temperature in the boiler and low temperature in the condenser divided by the high temperature value of the boiler in Degree Kelvin. Practically, a Mayahi Engine could have a higher efficiency than previous engines due to the saving of the pumping energy for the condensate back to the boiler. Wasting this energy cannot be avoided in other cycles such as the Kalina cycle. 
         [0131]    In a further preferred embodiment of this aspect of the present invention, the ammonia turbine is used to pump liquids instead of generating electricity. For example, untreated water for certain applications can be pumped, such as in membrane separation applications. This application has uses in pressure driven processes that are widely used in industry for water treatment, wastewater treatment, brackish water desalination and seawater desalination. Accordingly, a seawater desalination processes or other pressure driven processes could be achieved with minimal power consumption. Indeed, those processes can now utilize any available low grade energy source to run a Mayahi cycle (engine). The engine substitutes the requirement for an electrical power source to run the pump. In this case the Ammonia Turbine will produce mechanical energy in the form of a rotating shaft that can replace the electrical motor of a pump, which is preferably to be a centrifugal type, 
         [0132]    In a still further preferred embodiment of this aspect of the present invention, the ammonia turbine could be used to compress gases instead of generating electricity. For example, water vapour (steam) for certain applications can be compressed using this engine, such as in a Mechanical Vapour Compression (MVC) desalination method. MVC is widely used for seawater desalination utilizing an electrically driven vapour compressor. Accordingly, a seawater desalination process based on vapour compression (VC) method could be achieved with minimal power consumption utilizing any available low grade energy sources to run a Mayahi cycle (engine) that replaces the otherwise required electrical power source to run the vapour compressor. In this case the Ammonia Turbine will be designed to produce mechanical energy in the form of rotating shaft that can replace the electrical motor of a compressor which is preferably of a centrifugal type. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0133]    The above aspects of this invention are more particularly described hereinafter, by way of example only, with reference to the accompanying figures and in which include:— 
           [0134]      FIG. 1  is a schematic diagram for an RO plant to produce fresh water from seawater or brackish water by using a Manipulated Osmosis (MO) and energy recovery devices (ERD&#39;s); 
           [0135]      FIG. 2  is a schematic diagram for an RO plant to produce fresh water from seawater or brackish water by using multi-stage Manipulated Osmosis (MO) units and energy recovery devices ERD&#39;s; 
           [0136]      FIG. 3  shows the arrangement in  FIG. 2  on to which have been superimposed typical operating pressures; 
           [0137]      FIG. 4  is a schematic diagram illustrating fresh water production from solar ponds by using a Forward Osmosis unit and Energy Recovery Turbine; 
           [0138]      FIG. 4   a  shows the arrangement in  FIG. 4  on to which have been superimposed typical operating conditions; 
           [0139]      FIG. 5  shows a system similar to that in  FIG. 4  for fresh water production from a thermal desalination plant, by implementing a Forward Osmosis unit and Energy Recovery Turbine; 
           [0140]      FIG. 6  shows a schematic diagram illustrating fresh water production from cooling towers using a Forward Osmosis unit and Energy Recovery Turbines; 
           [0141]      FIG. 7  shows a schematic diagram for the treatment of cooling tower water using a Forward Osmosis unit and Energy Recovery Turbine; 
           [0142]      FIG. 8  shows a schematic diagram for a Mayahi Cycle used to pump liquids for different applications utilizing low grade energy sources; 
           [0143]      FIG. 9  shows a schematic diagram for a Mayahi Cycle used to compress gases for different applications utilizing low grade energy sources. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0144]    Various aspects of the present invention will now be described by way of example only. These are not the only ways that the invention can be put into practice, but they are the best ways currently known to the applicant. 
         [0145]    Referring to  FIG. 1 , this illustrates a solvent removal apparatus  100 . A manipulated Osmosis MO unit  110  has two different concentration solutions separated by a semi-permeable membrane (selective membrane). Pumped seawater or brackish water at a high pressure enters unit  110  via line  151  and leaves via line  112  after losing some of its water, which passes through the membrane to the manipulated solution which has less osmotic pressure (less salt concentration). The concentrated high pressure stream  112  enters an energy recovery turbine  120 , and in the process transferring its hydraulic energy, and leaves via line  121  as a rejected effluent. The diluted manipulated solution leaves  110  via line  111  to enter unit  120  gaining hydraulic energy and leaves at higher pressure via line  122  and enters an RO unit  130 . In the RO unit  130  the diluted manipulated solution will be separated to two streams. A fresh water stream could be produced and collected via line  131  whereas the rejected stream leaves via line  132  at high pressure. The rejected stream enters another energy recovery turbine  140  transferring its hydraulic energy to the feed stream  143  and leaves via line  142  back to unit  110 . Seawater or brackish water (the feed), enters the process via line  143  to the energy recovery turbine  140  gaining hydraulic energy and leaves at higher pressure via line  141  to enter the main pump  15 . The pressurised feed leaves the pump  150  via line  151  to enter MO unit  110  where some of its water will pass through the membrane to the manipulated solution due to RO concept. 
         [0146]    Referring to  FIG. 2  this illustrates a further solvent removal apparatus and method  200 . This embodiment includes two Manipulated Osmosis MO units and each Manipulated Osmosis MO unit,  230  or  220  has two different concentration solutions separated by semi-permeable membrane (selective membrane). First, the seawater or brackish water at high pressure enters unit  230  via line  255  and leaves via line  232  after losing some of its water to the manipulated solution which has less osmotic pressure (ie less salt concentration). The concentrated, high pressure stream  232  enters an energy recovery turbine  240  transferring its hydraulic energy and leaves via line  241  as a rejected effluent from the process. The diluted manipulated solution leaves unit  230  via line  231  to enter unit  240  gaining hydraulic energy and leaves at a higher pressure via line  242  to enter another MO unit  220 . 
         [0147]    The manipulated solution at high pressure in the first loop, after losing some of its water through the membrane, leaves unit  220  via line  222  to enter an energy recovery turbine  260  which connects the two loops and allows line  222  to gain more hydraulic energy derived from line  212  in the second loop. The line  222  after gaining more energy via  260  enters another energy recovery device  250  where it transfers its hydraulic energy to the feed stream. Seawater or brackish water (the feed stream) enters the process via line  251  and leaves the energy recovery turbine  250  at higher pressure via line  253  to the main pump  254  and leaves via line  255  to enter unit  230 . A recycle stream  233  takes some of the reject (high concentration) material from unit  230  back to the feed stream at a point between the energy recovery turbine  250  and pump  254 . Referring to unit  220 , this contains another manipulated solution at a lower concentration, the diluted solution leaves via line  221  to enter pump  213  and from the pump enters the RO unit  210 . In unit  210 , the second diluted manipulated solution will be separated into two streams. Fresh water could be produced and collected via line  211  whereas the rejected streams at high pressure leaves via line  212  and enters the energy recovery turbine  260  leaving at lower pressure via line  214  back to unit  220 . 
         [0148]    To assist in understanding this process further,  FIG. 3  illustrates the arrangement shown in  FIG. 2 , in which typical operating pressures and typical operating concentrations are shown superimposed at strategic points around the system. A corresponding numbering system has been used to that in  FIG. 2 . 
         [0149]    A second aspect of the present invention is illustrated in  FIGS. 4 to 7  inclusive. 
         [0150]    Referring to  FIG. 4 , this illustrates an osmotic energy recovery system  300 . A Forward Osmosis unit  310  has two different concentration solutions separated by a semi-permeable membrane and such a unit is described in my patent WO 2005/012185 and WO 2005/120688. 
         [0151]    As for the low concentration side, a first solution consisting of an untreated water source  311  enters the Unit. This could consist of brackish water, seawater, waste water or any untreated water. Some of the solvent (water) passes through the membrane into the second solution and the rest leaves the Unit through line  313 . 
         [0152]    Line  314  from the Forward Osmosis Unit which is at high pressure enters an Energy Recovery Turbine unit  320  and leaves along line  323  after transferring its pressure to the feed stream which enters the unit through  321 . Line  321  could be any form of untreated water such as brackish water, seawater, waste water or any untreated water. Line  323  takes the depressurised second solution from unit  320  to a solar pond  330 . 
         [0153]    The untreated water leaves the Energy Recovery Turbine  320  at high pressure through line  322  and then enters an RO unit  340  as a fourth solution which produces fresh water as a third solution through line  341 , whereas the rejected pressurised stream leaves the RO unit via  352  and enters a second Energy Recovery Turbine unit  350 . The high concentration solution from solar pond  330  enters an auxiliary pump  332  via line  331 . This solution is pressurised through unit  350  by gaining its pressure from the RO unit&#39;s rejected stream which leaves via line  353  and may be forwarded to unit  330 . The high pressure stream coming out from unit  350  enters the unit  310  which is at a high pressure via line  312 . 
         [0154]    To assist in understanding this process further, the key to  FIG. 4 , at the end of this description, illustrates the arrangement shown in  FIG. 4 , in which typical operating pressures and typical operating concentrations are shown superimposed at strategic points around the system. This is also illustrated in  FIG. 4   a  in which a corresponding numbering system has been used to that in  FIG. 4 . 
         [0155]    Referring to  FIG. 5 , this illustrates a further preferred embodiment of an osmotic energy recovery system. All the units  410 ,  420 ,  440  and  450  are similar to those units in  FIG. 4 , namely  310 , 320 , 340  and  350 . The only difference is that Unit  430  could be used with any thermal desalination plant  430  such as MSF, MED or VC. Line  433  transfers the distilled water out of the unit and line  431  takes the concentrated solution out from the unit to an auxiliary pump  431  and finally to the Energy Recovery Turbine  450 . Other lines are the same as those described in  FIG. 4  layout and with similar numbering and explanations. 
         [0156]    Referring to  FIG. 6 , this illustrates a further preferred osmotic energy recovery system  500 . The concept of the process is the same as that described above in  FIG. 4  and  FIG. 5 . However, in this embodiment, the source of concentration is a cooling tower unit  540 . Unit  540  could be any type of evaporative cooling tower. The high concentrated solution leaves the cooling tower basin  545  via line  541  to an auxiliary pump  531  and then to the Energy Recovery Turbine Unit  530  via line  532 . The high concentration solution is pressurised, leaving unit  530 , to enter the Forward Osmosis unit  510  via line  533  as a second solution. Cooling Tower feed water enters unit  510  through line  511 . The source of the water could be any available water source such as river water, waste water, brackish water, seawater or any untreated water. A pure solvent (water) passes through the semi-permeable membrane from the lower concentration side, solution one, to the higher concentration side, solution  2 . The low concentration stream  513  enters a Energy Recovery Turbine unit  520  to be pressurised and then enters the RO unit  550  via line  523  as solution four. Fresh water leaves the unit  550  via line  553  as solution three whereas the rejected stream  551  transfers its pressure to the concentrated stream in unit  530  and is then dismissed. The pumped concentrated solution leaves from unit  520  back to the cooling tower via line  521  and is then mixed with recirculation water line  542  after pumping by the recirculating pump  543 . Both lines  521  and  542  come together in line  544  which sprays the recirculation water inside the cooling tower unit  540 . 
         [0157]    Referring to  FIG. 7 , this illustrates a further embodiment, somewhat different to the arrangement in  FIG. 6  in that it is used to minimize the contamination through the forward osmosis unit  610  by means of feeding it with the fresh permeated water produced by RO unit  650 . An excess of fresh water is also produced in this process. The concentrated stream from cooling tower unit  640  is pumped by an auxiliary pump  646  and is then directed to the Energy Recovery Turbine unit  630  via line  612 . The concentrated stream leaves  630  at high pressure and enters the forward osmosis unit  610  via line  612 . Unit  630  transfers hydraulic energy from the rejected stream that comes out form the RO unit  650  via line  651  to the concentrated stream line  612 . The depressurised rejected steam leaves the process via line  631  and is dismissed. 
         [0158]    The high pressure concentrated stream leaves unit  610  via line  614  after increasing its flow rate by dilution with pure water which passes across the semi-permeable membrane of the Forward Osmosis unit  610 , due to the osmotic pressure differences between the two solutions. Line  614  enters the second Energy Recovery Turbine unit  620  and leaves at lower pressure to return back to the cooling tower via line  621 . The feed water enters Unit  620  via line  623  and leaves at higher pressure to the RO Unit  650  where it is separated into two streams. 
         [0159]    The pure water (permeate)  653  from the RO unit  650  enters the unit  610  leaving at a lower flow rate as some of its water (solvent) passes to the other side of the membrane. The outlet stream is directed back to the cooling tower  640 . Any excess of pure water can be taken via line  654  as a product. The feed water to the cooling tower line  621  is mixed with the recirculation water which comes out from pump  641 . 
         [0160]    A third aspect of the present invention is illustrated in  FIGS. 8 and 9 . Referring to  FIG. 8 , this shows in schematic form an ammonia—water engine (Mayahi Cycle)  700 . An evaporator  710  is heated by a heating source which enters the evaporator via line  712  and leaves via line  713 . The evaporator  110  contains a liquid solution of ammonia dissolved in water in the presence of its vapour over the surface of the liquid. The vapour leaves unit  710  through line  711  and enters a turbine  750  at high pressure. It will leave the turbine  750  through line  721  at low pressure after converting its mechanical energy to run a pump  752 . The body of the turbine  751  is connected to the pump  752  through a solid shaft  755 . Any liquid stream can be pumped by pump  752 , entering the pump through  753  and leaving at higher pressure through line  754 . The vapour then condenses in condenser  720  (ammonia absorber). Condenser  720  is cooled by a cooling source which enters the condenser via  724  and leaves via  723 . 
         [0161]    To keep the process running, the concentration and amount of ammonia solution of both evaporator  710  and condenser  720  should remain substantially the same. To resolve this, a portion of the liquid from the condenser  720  is transferred to the evaporator  710  and visa versa an equal portion of the liquid from the evaporator  710  is transferred to the condenser  720 . The transfer of these liquids is done with the aid of an Energy Recovery Turbine  740  exchanging the high pressure of one liquid with the low pressure of the other. The high pressure stream from evaporator  710  leaves through line  731  and enters a heat exchanger  730  and leaves it via line  732  to enter the Energy Recovery Turbine  740  and leaves it at low pressure via line  741  to the condenser  720 . The low pressure stream from condenser  720  leaves through line  722  to enter an auxiliary pump  725  and leaves it via line  743  to enter the Energy Recovery Turbine  740  and leaves it at high pressure via line  742  and enters a heat exchanger  730  and leaves via line  733  to enter evaporator  710 . 
         [0162]    Referring to  FIG. 9 , this shows in schematic form a further ammonia—water engine (Mayahi Cycle)  800 . An evaporator  810  is heated by a heating source enters via line  812  and leaves via line  813 . The evaporator  810  contains a liquid solution of ammonia dissolved in water in the presence of its vapour over the surface of the liquid. The vapour leaves unit  810  through line  811  and enters a turbine  850  at high pressure. It leaves the turbine  850  through line  821  at low pressure after converting its mechanical energy to run a vapour compressor  852 . The turbine  851  is connected to a compressor  852  through a solid shaft  855 . Any gas or vapour to be compressed enters through line  853  and leaves at higher pressure through line  854 . 
         [0163]    The vapour then condenses in condenser  820  (ammonia absorber). Condenser  820  is cooled by a cooling source which enters via  824  and leaves via  823 . 
         [0164]    To keep the process running, the concentration and amount of ammonia solution of evaporator  810  and condenser  820  should remain substantially the same. To resolve this a portion of the liquid from the condenser  820  is transferred to the evaporator  810  and visa versa an equal portion of the liquid from the evaporator  810  is transferred to the condenser  820 . The transfer of these liquids is done via the aid of an Energy Recovery Turbine  840 , exchanging the high pressure of one liquid with the low pressure of the other. The high pressure stream from evaporator  810  leaves through line  831  and enters a heat exchanger  830  and leaves it via line  832  to enter the Energy Recovery Turbine  840  and leaves it at low pressure via line  841  to the condenser  820 . The low pressure stream from condenser  820  leaves through line  822  to enter an auxiliary pump  825  and leaves it via line  843  to enter the Energy Recovery Turbine  840  and leaves it at high pressure via line  842  and enters a heat exchanger  830  and leaves via line  833  to enter evaporator  810 . 
         [0165]    By way of information, Tables 1 and 2 show in tabulated form the concentration—temperature—pressure measurements for ammonia/water equilibrium in both pounds per square inch (psi) in Table 1 and atmospheres (bar) in Table 2. 
       Key to FIG.  3   
       [0000]    
       
           210  RO or MO Unit 
           211  Fresh water (permeate), 0% 
           212  3%, 12-22 bar 
           213  pump, 1.5%, 15-25 bar 
           214  3% 
           220 , 230  MO Units working as RO 
           221  1.5% 
           222  4%, 22-35 bar 
           231  2.5%, 1-2 bar 
           232  28-38 bar 
           233  recycled stream 
           232 + 233  6% 
           240  ERD 
           241  rejected, 6% 
           242  2.5%, 28-38 bar 
           250  ERD 
           251  Feed (sea water of brackish water), c=4% 
           252  2-3 bar, 4% 
           254  pump, p=15-25 bar 
           255  4%, p=30-40 bar 
           260  ERD 
           261  35-45 bar 
       
     
       Key to FIG.  4   
       [0000]    
       
           310  Forward Osmosis FO Unit, the low concentration side at low pressure and high concentration side at higher pressure 
           320 ,  350  Energy Recovery Turbines 
           330  Solar Pond (concentrator) 
           340  RO Unit (conventional) 
           311  any available water stream to dilute and drive the FO unit. C=0-3%, p=normal 
           321  any untreated stream (feed) such as brackish or sea water, c=1-4%, p=normal 
           312  concentrated stream, P=10−70 bar, c=5-25%, flow rate=V m3/hr 
           314  diluted stream out from the FO unit, P=8-68 bar, c=2-12%, flow rate=1.5-3 V m3/hr 
           323  non-pressurized stream 
           322  pressurized RO feed stream, P=6-66 bar, c=0-3%, flow rate==1.5-3 V m3/hr 
           431  Permeate, non pressurized, flow rate=1-2 V m3/hr 
           352  rejected stream, p=5-64 bar, flow rate=0.5-1.5 V m3/hr 
           332  auxiliary pump, P=1-5 bar, flow rate=V m3/hr 
           353  non-pressurized rejected stream 
       
     
       Key to FIG.  4   a    
       [0000]    
       
           901  RO Unit 
           902  Fresh water (permeate), P=normal, flow rate=1-2 Vm 3 /hr 
           903  Rejected stream, P=5-64 bar, flow rate=0.5-1.5 V 
           904  Energy Recovery Turbine 
           905  Reject, P=normal 
           906  auxiliary pump, P=1-10 bar, flow rate=Vm 3 /hr 
           907  Solar Pond, 
           908  RO Feed, P=6-66 bar, C=0-4%, flow rate=1.5-3 
           909  P=normal, C=2-12% 
           910  Untreated water, C=0-4%, P=normal 
           911  Diluted stream out of FO, P=8-68 bar, C=2-12%, flow rate=1.5-3Vm 3 /hr 
           912  Concentrated stream, P=10-70 bar, C=5-25%, flow rate= 
           913  FO Unit 
           914  Dilution water, C=0-3%, P=Normal 
       
     
         [0000]    
       
         
               
             
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                 Pressures are in pounds per square inch absolute 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Molal concentration of ammonia in the solutions in percentages 
               
               
                   
                 (Weight concentration of ammonia in the solutions in percentages) 
               
             
          
           
               
                   
                 0 
                 5 
                 10 
                 15 
                 20 
                 25 
                 30 
                 35 
                 40 
                 45 
                 50 
                 55 
               
               
                 t, ° F. 
                 (0) 
                 (4.74) 
                 (9.50) 
                 (14.29) 
                 (19.10) 
                 (23.94) 
                 (28.81) 
                 (33.71) 
                 (38.64) 
                 (43.59) 
                 (48.57) 
                 (53.58) 
               
               
                   
               
               
                 32 
                 0.09 
                 0.34 
                 0.60 
                 0.97 
                 1.58 
                 2.60 
                 4.20 
                 6.54 
                 9.93 
                 14.18 
                 19.40 
                 25.16 
               
               
                 40 
                 0.12 
                 0.45 
                 0.77 
                 1.24 
                 2.01 
                 3.25 
                 5.21 
                 8.06 
                 12.05 
                 17.20 
                 23.39 
                 30.20 
               
               
                 50 
                 0.18 
                 0.64 
                 1.05 
                 1.65 
                 2.67 
                 4.29 
                 6.75 
                 10.35 
                 15.34 
                 21.65 
                 29.26 
                 37.54 
               
               
                 60 
                 0.26 
                 0.86 
                 1.42 
                 2.21 
                 3.51 
                 5.55 
                 8.65 
                 13.22 
                 19.30 
                 27.05 
                 36.26 
                 46.23 
               
               
                 70 
                 0.36 
                 1.17 
                 1.84 
                 2.90 
                 4.56 
                 7.13 
                 11.01 
                 16.56 
                 24.05 
                 33.39 
                 44.42 
                 56.44 
               
               
                 80 
                 0.51 
                 1.52 
                 2.43 
                 3.76 
                 5.85 
                 9.06 
                 13.86 
                 20.61 
                 29.69 
                 40.96 
                 54.08 
                 68.19 
               
               
                 90 
                 0.70 
                 2.02 
                 3.15 
                 4.83 
                 7.43 
                 11.40 
                 17.23 
                 25.48 
                 36.34 
                 49.82 
                 65.32 
                 81.91 
               
               
                 100 
                 0.95 
                 2.62 
                 4.05 
                 6.13 
                 9.34 
                 14.22 
                 21.32 
                 31.16 
                 44.12 
                 59.99 
                 78.30 
                 97.68 
               
               
                 110 
                 1.27 
                 3.34 
                 5.14 
                 7.72 
                 11.64 
                 17.58 
                 26.07 
                 37.81 
                 53.16 
                 71.87 
                 93.19 
                 115.70 
               
               
                 120 
                 1.69 
                 4.27 
                 6.46 
                 9.63 
                 14.42 
                 21.54 
                 31.69 
                 45.62 
                 63.59 
                 85.33 
                 110.20 
                 136.20 
               
               
                 130 
                 2.22 
                 5.38 
                 8.07 
                 11.91 
                 17.67 
                 26.20 
                 38.25 
                 54.55 
                 75.55 
                 100.86 
                 129.50 
                 159.00 
               
               
                 140 
                 2.89 
                 6.70 
                 9.98 
                 14.63 
                 21.49 
                 31.54 
                 45.73 
                 64.78 
                 89.19 
                 118.24 
                 151.30 
                 185.40 
               
               
                 150 
                 3.72 
                 8.29 
                 12.23 
                 17.81 
                 26.00 
                 37.81 
                 54.43 
                 76.61 
                 104.65 
                 138.10 
                 175.40 
                 214.50 
               
               
                 160 
                 4.74 
                 10.16 
                 14.92 
                 21.54 
                 31.16 
                 45.02 
                 64.25 
                 89.88 
                 122.10 
                 160.20 
                 202.70 
                 247.00 
               
               
                 170 
                 5.99 
                 12.41 
                 18.01 
                 25.87 
                 37.11 
                 53.27 
                 75.55 
                 104.84 
                 141.75 
                 185.10 
                 233.20 
                 283.10 
               
               
                 180 
                 7.51 
                 15.00 
                 21.65 
                 30.86 
                 44.02 
                 62.68 
                 88.17 
                 121.68 
                 163.70 
                 212.60 
                 267.00 
                 323.10 
               
               
                 190 
                 9.34 
                 18.06 
                 25.87 
                 36.60 
                 51.81 
                 73.32 
                 102.56 
                 140.75 
                 188.10 
                 243.30 
                 304.30 
                 367.10 
               
               
                 200 
                 11.53 
                 21.60 
                 30.72 
                 43.14 
                 60.62 
                 85.33 
                 118.68 
                 161.81 
                 215.20 
                 277.00 
                 345.50 
                 415.10 
               
               
                 210 
                 14.12 
                 25.61 
                 36.26 
                 50.58 
                 70.72 
                 98.80 
                 136.42 
                 185.10 
                 245.10 
                 314.50 
                 390.70 
                 468.40 
               
               
                 220 
                 17.19 
                 30.27 
                 42.47 
                 59.00 
                 81.91 
                 113.81 
                 156.41 
                 211.24 
                 278.20 
                 355.10 
                 439.60 
                 525.50 
               
               
                 230 
                 20.78 
                 35.59 
                 49.60 
                 68.46 
                 94.43 
                 130.64 
                 178.28 
                 239.70 
                 314.50 
                 400.20 
                 493.40 
               
               
                 240 
                 24.97 
                 41.52 
                 57.65 
                 78.91 
                 108.60 
                 149.20 
                 202.74 
                 270.92 
                 354.10 
                 448.90 
                 552.30 
               
               
                 250 
                 29.83 
                 48.32 
                 66.67 
                 90.74 
                 124.08 
                 169.48 
                 229.62 
                 305.60 
                 397.60 
                 502.40 
               
               
                   
               
             
          
           
               
                   
                   
                 Molal concentration of ammonia in the solutions in percentages 
               
               
                   
                   
                 (Weight concentration of ammonia in the solutions in percentages) 
               
             
          
           
               
                   
                   
                 60 
                 65 
                 70 
                 75 
                 80 
                 85 
                 90 
                 95 
                 100 
               
               
                   
                 t, ° F. 
                 (58.62) 
                 (63.69) 
                 (68.79) 
                 (73.91) 
                 (79.07) 
                 (84.26) 
                 (89.47) 
                 (94.72) 
                 (100.00) 
               
               
                   
                   
               
               
                   
                 32 
                 31.16 
                 36.77 
                 42.72 
                 45.94 
                 49.28 
                 52.14 
                 54.90 
                 58.01 
                 62.29 
               
               
                   
                 40 
                 37.20 
                 43.73 
                 49.60 
                 54.43 
                 58.33 
                 61.64 
                 64.78 
                 68.32 
                 73.32 
               
               
                   
                 50 
                 45.93 
                 53.85 
                 60.87 
                 66.67 
                 71.29 
                 75.25 
                 79.07 
                 83.41 
                 89.19 
               
               
                   
                 60 
                 56.32 
                 65.90 
                 74.06 
                 80.96 
                 86.49 
                 91.08 
                 95.69 
                 100.66 
                 107.60 
               
               
                   
                 70 
                 68.46 
                 79.54 
                 89.36 
                 97.51 
                 104.08 
                 109.60 
                 114.86 
                 120.63 
                 128.80 
               
               
                   
                 80 
                 82.55 
                 95.69 
                 107.20 
                 116.54 
                 124.30 
                 130.64 
                 136.40 
                 143.72 
                 153.00 
               
               
                   
                 90 
                 98.61 
                 114.02 
                 127.42 
                 138.34 
                 147.15 
                 154.56 
                 161.81 
                 169.76 
                 180.60 
               
               
                   
                 100 
                 117.17 
                 135.01 
                 150.50 
                 163.16 
                 173.40 
                 182.10 
                 190.22 
                 199.22 
                 211.90 
               
               
                   
                 110 
                 138.10 
                 158.84 
                 176.54 
                 191.15 
                 203.26 
                 212.89 
                 222.34 
                 232.85 
                 247.00 
               
               
                   
                 120 
                 162.08 
                 185.70 
                 206.29 
                 222.68 
                 236.37 
                 247.38 
                 258.40 
                 270.10 
                 286.40 
               
               
                   
                 130 
                 189.00 
                 215.88 
                 239.33 
                 258.40 
                 273.30 
                 286.40 
                 298.67 
                 311.90 
                 330.30 
               
               
                   
                 140 
                 219.28 
                 249.66 
                 276.15 
                 297.81 
                 315.00 
                 329.40 
                 343.20 
                 358.60 
                 379.10 
               
               
                   
                 150 
                 252.65 
                 287.24 
                 317.30 
                 341.70 
                 361.10 
                 377.10 
                 392.80 
                 409.80 
                 432.20 
               
               
                   
                 160 
                 290.18 
                 329.40 
                 363.10 
                 390.20 
                 412.20 
                 430.40 
                 447.80 
                 466.60 
                 492.80 
               
               
                   
                 170 
                 331.70 
                 375.60 
                 413.30 
                 443.70 
                 467.80 
                 488.70 
                 508.20 
                 528.80 
                 558.40 
               
               
                   
                 180 
                 377.10 
                 426.60 
                 468.40 
                 502.40 
                 529.50 
                 552.30 
               
               
                   
                 190 
                 427.70 
                 452.50 
                 528.80 
               
               
                   
                 200 
                 483.00 
                 543.60 
               
               
                   
                 210 
                 542.90 
               
               
                   
                 220 
               
               
                   
                 230 
               
               
                   
                 240 
               
               
                   
                 250 
               
               
                   
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                 Pressures are in bars 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Molal concentration of ammonia in the solutions in percentages 
               
               
                   
                 (Weight concentration of ammonia in the solutions in percentages) 
               
             
          
           
               
                   
                 0 
                 5 
                 10 
                 15 
                 20 
                 25 
                 30 
                 35 
                 40 
                 45 
                 50 
                 55 
               
               
                 t, ° F. 
                 (0) 
                 (4.74) 
                 (9.50) 
                 (14.29) 
                 (19.10) 
                 (23.94) 
                 (28.81) 
                 (33.71) 
                 (38.64) 
                 (43.59) 
                 (48.57) 
                 (53.58) 
               
               
                   
               
               
                 0 
                 0.006 
                 0.023 
                 0.041 
                 0.066 
                 0.107 
                 0.177 
                 0.286 
                 0.445 
                 0.676 
                 0.965 
                 1.32 
                 1.712 
               
               
                 4.444 
                 0.008 
                 0.031 
                 0.052 
                 0.084 
                 0.137 
                 0.221 
                 0.354 
                 0.548 
                 0.82 
                 1.17 
                 1.591 
                 2.054 
               
               
                 10 
                 0.012 
                 0.044 
                 0.071 
                 0.112 
                 0.182 
                 0.292 
                 0.459 
                 0.704 
                 1.044 
                 1.473 
                 1.99 
                 2.554 
               
               
                 15.56 
                 0.018 
                 0.059 
                 0.097 
                 0.15 
                 0.239 
                 0.378 
                 0.588 
                 0.899 
                 1.313 
                 1.84 
                 2.467 
                 3.145 
               
               
                 21.11 
                 0.024 
                 0.08 
                 0.125 
                 0.197 
                 0.31 
                 0.485 
                 0.749 
                 1.127 
                 1.636 
                 2.271 
                 3.022 
                 3.839 
               
               
                 26.67 
                 0.035 
                 0.103 
                 0.165 
                 0.256 
                 0.398 
                 0.616 
                 0.943 
                 1.402 
                 2.02 
                 2.786 
                 3.679 
                 4.639 
               
               
                 32.22 
                 0.048 
                 0.137 
                 0.214 
                 0.329 
                 0.505 
                 0.776 
                 1.172 
                 1.733 
                 2.472 
                 3.389 
                 4.444 
                 5.572 
               
               
                 37.78 
                 0.065 
                 0.178 
                 0.276 
                 0.417 
                 0.635 
                 0.967 
                 1.45 
                 2.12 
                 3.001 
                 4.081 
                 5.327 
                 6.645 
               
               
                 43.33 
                 0.086 
                 0.227 
                 0.35 
                 0.525 
                 0.792 
                 1.196 
                 1.773 
                 2.572 
                 3.616 
                 4.889 
                 6.339 
                 7.871 
               
               
                 48.89 
                 0.115 
                 0.29 
                 0.439 
                 0.655 
                 0.981 
                 1.465 
                 2.156 
                 3.103 
                 4.326 
                 5.805 
                 7.497 
                 9.265 
               
               
                 54.44 
                 0.151 
                 0.366 
                 0.549 
                 0.81 
                 1.202 
                 1.782 
                 2.602 
                 3.711 
                 5.139 
                 6.861 
                 8.81 
                 10.82 
               
               
                 60 
                 0.197 
                 0.456 
                 0.679 
                 0.995 
                 1.462 
                 2.146 
                 3.111 
                 4.407 
                 6.067 
                 8.044 
                 10.29 
                 12.61 
               
               
                 65.56 
                 0.253 
                 0.564 
                 0.832 
                 1.212 
                 1.769 
                 2.572 
                 3.703 
                 5.212 
                 7.119 
                 9.395 
                 11.93 
                 14.59 
               
               
                 71.11 
                 0.322 
                 0.691 
                 1.015 
                 1.465 
                 2.12 
                 3.063 
                 4.371 
                 6.114 
                 8.306 
                 10.9 
                 13.79 
                 16.8 
               
               
                 76.67 
                 0.407 
                 0.844 
                 1.225 
                 1.76 
                 2.524 
                 3.624 
                 5.139 
                 7.132 
                 9.643 
                 12.59 
                 15.86 
                 19.26 
               
               
                 82.22 
                 0.511 
                 1.02 
                 1.473 
                 2.099 
                 2.995 
                 4.264 
                 5.998 
                 8.278 
                 11.14 
                 14.46 
                 18.16 
                 21.98 
               
               
                 87.78 
                 0.635 
                 1.229 
                 1.76 
                 2.49 
                 3.524 
                 4.988 
                 6.977 
                 9.575 
                 12.8 
                 16.55 
                 20.7 
                 24.97 
               
               
                 93.33 
                 0.784 
                 1.469 
                 2.09 
                 2.935 
                 4.124 
                 5.805 
                 8.073 
                 11.01 
                 14.64 
                 18.84 
                 23.5 
                 28.24 
               
               
                 98.89 
                 0.961 
                 1.742 
                 2.467 
                 3.441 
                 4.811 
                 6.721 
                 9.28 
                 12.59 
                 16.67 
                 21.39 
                 26.58 
                 31.86 
               
               
                 104.4 
                 1.169 
                 2.059 
                 2.889 
                 4.014 
                 5.572 
                 7.742 
                 10.64 
                 14.37 
                 18.93 
                 24.16 
                 29.9 
                 35.75 
               
               
                 110 
                 1.414 
                 2.421 
                 3.374 
                 4.657 
                 6.424 
                 8.887 
                 12.13 
                 16.31 
                 21.39 
                 27.22 
                 33.56 
               
               
                 115.6 
                 1.699 
                 2.824 
                 3.922 
                 5.368 
                 7.388 
                 10.15 
                 13.79 
                 18.43 
                 24.09 
                 30.54 
                 37.57 
               
               
                 121.1 
                 2.029 
                 3.287 
                 4.535 
                 6.173 
                 8.441 
                 11.53 
                 15.62 
                 20.79 
                 27.05 
                 34.18 
               
               
                   
               
             
          
           
               
                   
                   
                 Molal concentration of ammonia in the solutions in percentages 
               
               
                   
                   
                 (Weight concentration of ammonia in the solutions in percentages) 
               
             
          
           
               
                   
                   
                 60 
                 65 
                 70 
                 75 
                 80 
                 85 
                 90 
                 95 
                 100 
               
               
                   
                 t, ° F. 
                 (58.62) 
                 (63.69) 
                 (68.79) 
                 (73.91) 
                 (79.07) 
                 (84.26) 
                 (89.47) 
                 (94.72) 
                 (100.00) 
               
               
                   
                   
               
               
                   
                 0 
                 2.12 
                 2.501 
                 2.906 
                 3.125 
                 3.352 
                 3.547 
                 3.735 
                 3.946 
                 4.237 
               
               
                   
                 4.444 
                 2.531 
                 2.975 
                 3.374 
                 3.703 
                 3.968 
                 4.193 
                 4.407 
                 4.648 
                 4.988 
               
               
                   
                 10 
                 3.124 
                 3.663 
                 4.141 
                 4.535 
                 4.85 
                 5.119 
                 5.379 
                 5.674 
                 6.067 
               
               
                   
                 15.56 
                 3.831 
                 4.483 
                 5.038 
                 5.507 
                 5.884 
                 6.196 
                 6.51 
                 6.848 
                 7.32 
               
               
                   
                 21.11 
                 4.657 
                 5.411 
                 6.079 
                 6.633 
                 7.08 
                 7.456 
                 7.814 
                 8.206 
                 8.762 
               
               
                   
                 26.67 
                 5.616 
                 6.51 
                 7.293 
                 7.928 
                 8.456 
                 8.887 
                 9.279 
                 9.777 
                 10.41 
               
               
                   
                 32.22 
                 6.708 
                 7.756 
                 8.668 
                 9.411 
                 10.01 
                 10.51 
                 11.01 
                 11.55 
                 12.29 
               
               
                   
                 37.78 
                 7.971 
                 9.184 
                 10.24 
                 11.1 
                 11.8 
                 12.39 
                 12.94 
                 13.55 
                 14.41 
               
               
                   
                 43.33 
                 9.395 
                 10.81 
                 12.01 
                 13 
                 13.83 
                 14.48 
                 15.13 
                 15.84 
                 16.8 
               
               
                   
                 48.89 
                 11.03 
                 12.63 
                 14.03 
                 15.15 
                 16.08 
                 16.83 
                 17.58 
                 18.37 
                 19.48 
               
               
                   
                 54.44 
                 12.86 
                 14.69 
                 16.28 
                 17.58 
                 18.59 
                 19.48 
                 20.32 
                 21.22 
                 22.47 
               
               
                   
                 60 
                 14.92 
                 16.98 
                 18.79 
                 20.26 
                 21.43 
                 22.41 
                 23.35 
                 24.39 
                 25.79 
               
               
                   
                 65.56 
                 17.19 
                 19.54 
                 21.59 
                 23.24 
                 24.56 
                 25.65 
                 26.72 
                 27.88 
                 29.4 
               
               
                   
                 71.11 
                 19.74 
                 22.41 
                 24.7 
                 26.54 
                 28.04 
                 29.28 
                 30.46 
                 31.74 
                 33.52 
               
               
                   
                 76.67 
                 22.56 
                 25.55 
                 28.12 
                 30.18 
                 31.82 
                 33.24 
                 34.57 
                 35.97 
                 37.99 
               
               
                   
                 82.22 
                 25.65 
                 29.02 
                 31.86 
                 34.18 
                 36.02 
                 37.57 
               
               
                   
                 87.78 
                 29.1 
                 30.78 
                 35.97 
               
               
                   
                 93.33 
                 32.86 
                 36.98 
               
               
                   
                 98.89 
                 36.93 
               
               
                   
                 104.4 
               
               
                   
                 110 
               
               
                   
                 115.6 
               
               
                   
                 121.1