Abstract:
The invention discloses a method of removing dissolved elements from a liquid. The method comprises a first heating step for heating the liquid using a first heat source, a plurality of distillation steps for purifying the liquid heated by the first heating step, each of the plurality of distillation steps comprising at least one evaporation step and at least one condensation step, and a second heating step, using a second heat source to heat a plurality of flashing chambers, each generating a volume of vapor; wherein the vapor from at least one of the plurality of flashing chambers of the second heating step is introduced into at least one of the plurality of distillation steps.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a 371 U.S. National Stage of International Application No. PCT/AU2015/050156, filed Apr. 3, 2015, which claims the benefit of and priority to Australian Patent Applications No. 2014901335, filed Apr. 11, 2014 and 2015901007, filed Mar. 20, 2015. The disclosures of the above applications are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a thermal separation desalination process, more particularly, to an improved low grade heat driven process and system as applied for desalination. 
       BACKGROUND OF THE INVENTION 
       [0003]    Most of the water on the surface of earth is saline and cannot be used for domestic purposes. In areas where fresh water is scarce there is a need to desalinate salt water. Conventional desalination of water is an energy intensive process. Depletion of fossil fuels, high greenhouse gas emissions and rising costs of energy have necessitated the use of unconventional energy sources. Low grade heat sources, whose temperature is not substantially above 100° C., are one such source. Examples of such low grade heat sources may include hot industrial waste fluids like hot water, steam, exhaust gases, process liquor etc. or renewable energies such as geothermal heat, all of which can be used as heat source or a liquid source to be desalinated. 
         [0004]    Desalination can be generally categorized into two types: thermal (distillation) systems like MED (Multi Effect Distillation), MSF (Multi Stage Flashing), HD (Humidification-Dehumidification); and membrane systems like RO (Reverse Osmosis). 
         [0005]    Low grade heat sources are particularly suitable for the use in thermal desalination methods. Particularly MED including MED process and Vapor Compression (VC) MED process such as Thermal Vapor Compression (TVC) MED process and MSF systems have been developed to use heat from low grade heat sources. Such systems use a heat exchanger coupled to a low grade heat source to heat saline water which is then fed to either an “effect” of a MED system or a “stage” of an MSF system. In such a system, a substantial amount of heat of the low grade heat source remains unused, as it is not transferred to the saline water. Due to this, energy extraction from the low grade heat source is limited. This further results in a heating medium output that is still hot and the saline water obtained can be used for further desalination. 
         [0006]    An improvement over the conventional low grade heat source driven MED system is the so called “boosted MED” system. In boosted MED the unused heat from the low grade heat source is reused to heat saline water, which then introduces the generated vapor into an effect of the MED system. This system incrementally improves the efficiency of extraction of heat from the low grade heat source as well as the yield of fresh water. However, the method fails to extract the maximum possible heat energy from the low grade heat source. 
         [0007]    According to the foregoing discussion, there still remains a need to improve the efficiency of thermal desalination processes to make desalination environmentally and financially more viable. 
       SUMMARY OF THE INVENTION 
       [0008]    In one aspect, the present invention provides a method of purification of a liquid using a first heat source and a second heat source. The heat sources can be either connected in series or in parallel. The liquid to be purified is heated by the first heat source followed by a plurality of distillation steps, each step including an evaporation step and a condensation step. Fluid in the form of a vapor heated by the second heat source is introduced into the plurality of distillation steps via a plurality of inputs such that temperature of the fluid/vapor introduced is decreasing from the first input to the last input. 
         [0009]    In another aspect the present invention provides a system of purification of a liquid. The system includes a first heat source coupled to a first heat exchanger and a second heat source. The first heat exchanger being used to heat the preheated or unheated liquid. Further included is a plurality of distillation chambers in series, each having at least a condensing means and an evaporating means, the distillation chambers being configured to receive the heated liquid heated from upstream stage/process or the first heat exchanger, respectively for boosted MED and boosted MSF processes. Each of the plurality of chambers produces a distillate and a concentrate residue. The system further includes a plurality of inputs coupled to the plurality of distillation chambers introducing heated fluid/vapor into the plurality of distillation chambers such that the temperature of the heated fluid/vapor so introduced decreases from the first input to the last input of the plurality of inputs, the heated fluid/vapor being heated by heat of the second heat source. 
         [0010]    In some embodiments, the method and the system of purification can further include a second heating step for heating the liquid, using heat from the concentrate of the at least one condensation step, such that the said heated liquid can be introduced as either the liquid in the first heating step or heated fluid/vapor in one or more of the distillation steps. 
         [0011]    In some embodiments, the plurality of distillation steps is a Multi-Effect Distillation (MED) process, or a Multi-Stage Flash Distillation (MSF) process, or a Vapor Compression MED (VC-MED) process such as Thermal Vapor Compression MED process (TVC-MED). 
         [0012]    In some embodiments, the method and the system of purification can further include flashing a liquid in a plurality of flashing chambers and introducing the generated vapor from the plurality of flashing chambers to at least one corresponding distillation step. 
         [0013]    In some embodiments, the residual concentrate from the plurality of flashing chambers can be recirculated in the plurality of flashing chambers. 
         [0014]    In some embodiments, the residual concentrate from the plurality of flashing chambers can be introduced into the one or more of the desalination steps as feed liquid. 
         [0015]    In some embodiments, the method and the system of purification can further include using part of the heat from the residual concentrate of the plurality of flashing chambers to preheat feed liquid. 
         [0016]    In some embodiments, the heat carrying fluid of the second heat source can be introduced into either one of the plurality of distillation steps or the plurality of flashing chambers. 
         [0017]    In a further embodiment the vapor generated from one of the plurality of flashing chambers heated by the second heating step may be upgraded by means of a vapor compressor before being introduced into at least one of the plurality of distillation steps. 
         [0018]    In a further embodiment the vapor generated from the plurality of flashing chambers heated by the second heating step may be combined at least partially and then upgraded by means of a vapor compressor before being introduced into at least one of the plurality of distillation steps. 
         [0019]    In some embodiments, the primary purpose of the system may be to concentrate the liquid feed, with freshwater production being a secondary outcome. 
         [0020]    Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating various embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    A more complete appreciation of embodiments of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings which are presented solely for illustration and not limitation of the invention, and in which: 
           [0022]      FIG. 1  illustrates conventional MED (Multi-Effect Distillation) system [PRIOR-ART]; 
           [0023]      FIG. 2  illustrates a conventional boosted MED [PRIOR-ART]; 
           [0024]      FIGS. 3 a  and 3 b    illustrate flash boosted MED in accordance with some exemplary embodiments of the present invention; 
           [0025]      FIG. 4  illustrates an exemplary scenario where residual concentrate residue from a flashing unit is used to preheat saline water, in accordance with an embodiment of the present invention; 
           [0026]      FIGS. 5 a  and 5 b    illustrate exemplary scenarios effecting an embodiment of the present invention where fluid from the heat source is directly used for flashing, in accordance with an embodiment of the present invention; 
           [0027]      FIG. 6  illustrates exemplary scenarios effecting an embodiment of the present invention where no heat exchanger is used for heating and only flashing is utilized for heating fluid being introduced into the desalination chambers, in accordance with an embodiment of the present invention; 
           [0028]      FIG. 7  illustrates a boosted MSF in accordance with some exemplary embodiments of the present invention; and 
           [0029]      FIG. 8  is a graphical representation comparison of performance data of a conventional MED, a boosted MED and implementation of an exemplary embodiment of the present invention. 
           [0030]      FIG. 9 a    illustrates a prior art Thermal Vapor Compression Multi Effect Distillation (TVC-MED) system 
           [0031]      FIG. 9 b    illustrates a Flash Boosted Thermal Vapor Compression Multi Effect Distillation (FB-TVC-MED) system incorporating flash boosting of the primary MED module with steam from a flash vessel driven by a waste heat source. 
       
    
    
     BRIEF DESCRIPTION OF TABLES 
       [0032]    Table 1. Lists the assumptions made in a simulation comparing MED systems; and 
         [0033]    Table 2. Lists the results of a simulation comparing various MED systems. 
       DETAILED DESCRIPTION 
       [0034]    The various embodiments of the invention are described hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. However, the various embodiments may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to illustrate various aspects of the invention. 
         [0035]    Aspects of embodiments of the invention are disclosed in the following description and related drawings directed to specific embodiments of the invention. Alternate embodiments may be devised without departing from the scope of the invention. Alternate embodiments arising out of combination of the below exemplary embodiments are well within the scope of the present invention as will be evident to a person skilled in the art. Additionally, well known elements of the invention will not be described in detail or will be omitted so as not to obscure the relevant details of embodiments of the invention. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting the invention. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and relevant art and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein. Well-known functions or constructions may not be described in detail for brevity and/or clarity. 
         [0036]    Throughout the specification reference will be made to a first and second heat source it would be understood to a person skilled in the art that the use of these terms is for clarity in this specification and that in practice the heat could come from a plurality of heat sources. 
         [0037]    The words “exemplary” and/or “example” are used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” and/or “example” is not necessarily to be construed as preferred or advantageous over other embodiments. Likewise, the term “embodiments of the invention” does not require that all embodiments of the invention include the discussed feature, advantage or mode of operation. 
         [0038]    Moving on there is shown in  FIG. 1  a Multi-Effect Distillation system  100  as existing in PRIOR ART. The system  100  is shown to include a first heat source  101  coupled to a first heat exchanger  102 . Feed Liquid  108  is preheated in a second heat exchanger  109  and is introduced into a plurality of desalination chambers  103 , called effects, via a plurality of inputs  104 . 
         [0039]    In  FIG. 1  the preheated feed liquid form the second heat exchanger  109  is depicted to be fed in parallel into a plurality of desalination chambers  103 , but in practice the same preheated feed liquid can also be fed in series, where forward feeding in series is being more common, or in a combination thereof or even in a counterflow manner. 
         [0040]    A person skilled in the art will understand that there is a relationship between saturated temperature and pressure when applied to thermal desalination systems. For clarity in this specification we will refer to temperature only. 
         [0041]    Each distillation chamber  103  has a working temperature/pressure at which water vapor from one chamber  103  escapes into an adjacent chamber  103  that is at a lower temperature where it condenses in an condenser/evaporator  125  forming a condensate releasing heat to the corresponding desalination chamber  103 . 
         [0042]    The general configuration includes a number of chambers, the first distillation chamber  103   a  is at a higher working temperature then the last distillation chamber  103   b    
         [0043]    The distillation chambers  103  contain at least one evaporator and at least one condenser in close thermal coupling. The condenser/evaporator  125  are complementary parts where on one side vapor is condensed and on the other side the heat released from the condensing vapor is transferred in to the distillation chamber  103  to evaporate further liquid. 
         [0044]    The condensate from the plurality of desalination chambers  103  is collected by a condensate line  110  into a fresh water output  107 . In each chamber  103 , residual concentrate  130  is left as residue and collected by residual concentrate line  111 , into a residual concentrate reservoir  106 . 
         [0045]    The feed liquid  108  is preheated at a second heat exchanger  109 . The second heat exchanger  109  derives the heat required for heating the feed liquid  108  from the condensation in the last distillation chamber  103   b  and the heat transfer from the condensation being exchanged with the feed liquid  108 . The preheated feed liquid when introduced into the distillation chambers  103  is further heated by the first heat exchanger  102  in the first distillation chamber  103   a  or subsequently by the evaporator/condenser  125  of the plurality of desalination chambers  103 . 
         [0046]    Moving on there is shown in  FIG. 2 , a known improvement over the conventional MED system of  FIG. 1 . The system of  FIG. 2  additionally includes a third heat exchanger  112 , coupled to the first heat exchanger  102 . It uses the heat left unused by the first heat exchanger  102  to heat further preheated feed liquid  108 . The vapor produced in chamber  112  is introduced to one of the distillation chambers  103 , according to its saturated temperature/pressure. 
         [0047]    The present invention seeks to substantially improve upon the 1 prior art as shown in  FIG. 1  and  FIG. 2 . 
         [0048]    There is shown in  FIG. 3 a    an exemplary embodiment of the present invention. The  FIG. 3 a    shows a system  300 , as per an embodiment of the present invention. The system  300  includes a first heat source  101 , a first heat exchanger  102 , a plurality of distillation chambers  103 , a condensate line  110 , a fresh water store  107  a second heat exchanger  109 , a plurality of inputs  104 , a third heat exchanger  112 , and a plurality of flashing chambers  318 . 
         [0049]    In an embodiment, the first heat source  101  can be coupled to a first heat exchanger  102 . The first heat exchanger  102  can heat liquid containing dissolved elements that is desired to separate from the water contained in the liquid for example salt water or industrial process liquid. The preheated feed liquid may then be introduced into a first distillation chamber  103   a  (highest temperature) of the plurality of distillation chambers  103  for purification of the liquid. 
         [0050]    In an embodiment, the distillation system may be effected as a Multi-Effect Distillation process (MED), Multi-Stage Flash process (MSF) (illustrated in  FIG. 7 ), or a Vapor Compression MED process such as Thermal Vapor Compression MED (TVC-MED) process (illustrated in  FIG. 9 ). 
         [0051]    In  FIG. 3 , a MED process has been illustrated where each chamber of the plurality of distillation chambers  103  includes at least one evaporator/condenser  125  and are in intimate thermal contact. 
         [0052]    Each distillation chamber  103  operates a particular working temperature by convention the highest temperature chamber is called the first effect or first distillation chamber  103   a.  Evaporated liquid from a distillation chamber at a higher temperature is able to pass to a subsequent chamber  103  that is at a lower temperature where it condenses in a condenser/evaporator  125  releasing the heat it carries into the distillation chamber  103 . The condensate can be collected in the condensate line  110  and stored into a fresh water store  107 . 
         [0053]    There is also provided the second heat exchanger  109  that is configured to use the heat from the condenser of the last distillation chamber  103   b  to preheat feed liquid  108  that is to be introduced into the plurality of distillation chambers  103  via the plurality of inputs  104 . The third heat exchanger  312  is also provided and in an embodiment may be coupled to the first heat exchanger  102  to use unused heat from the first heat exchanger  102 . 
         [0054]    The third heat exchanger  312  is configured to further heat preheated feed liquid received from the second heat exchanger  109  by utilizing the remaining heat in the feed liquid  108  exiting the first heat exchanger  102  to form a hot feed liquid which is subsequently introduced into the plurality of desalination chambers  103  via a plurality of inputs. The introduction being such that the introduced hot feed liquid, which may now be in vapor form, has a temperature substantially approaching the working temperature of the corresponding distillation chamber  103  it is being introduced into. 
         [0055]    In another embodiment, the second heat exchanger  109  may not be provided and the heat from the condensate received from the condenser/evaporator  125  of the distillation chambers  103  may be directly introduced into the third heat exchanger  112 . 
         [0056]    In one configuration the feed liquid may be heated in a second heating step such as the third heat exchanger  112 . This heated feed liquid may be introduced into a plurality of flashing chambers  318 , from where vapor is produced, said vapor may be introduced or injected into the plurality of distillation chambers  103  according to their working temperature such that the temperature of the vapor introduced into a distillation chamber  103  is above or approaching the working temperature of that distillation chamber  103 . 
         [0057]    For optimum performance the temperature of the liquid/vapor introduced into the distillation chamber  103  decreases from the first input to the last input so as to keep the temperature of the introduced vapor/liquid about that of the working temperature of the distillation chamber  103 . 
         [0058]    The system is designed such that the flashing chamber outputs  314  correspond to the plurality of inputs  104  at the distillation chambers  103  and that the temperature of the injected vapor decreases from the injection into a distillation chamber  103  to the injection into subsequent distillation chambers  103 . 
         [0059]    In yet another exemplary embodiment a residual concentrate recirculation line  320  may be provided to recycle residual concentrate  130  within the flashing chambers  318 . In some embodiments, the residual concentrate recirculation line  320  may be further connected to a deaerator (not shown) for removal of oxygen and other dissolved gases from the recirculated residual concentrate. 
         [0060]    In other embodiments, as illustrated in  FIG. 3 b   , arrangements may be provided in the form of a plurality of fluid couplings  322  that can allow the heated vapor from the plurality of flashing chambers  318  to be introduced into at least one of the plurality of distillation chambers  103 . Similarly, there may be arrangements provided for introducing preheated feed from the second heat exchanger  109  via path  324  directly into at least one of the distillation chambers  103 , according to some embodiments. Further the residual concentrate  130  may be introduced directly in to one of the distillation chambers  103  or alternatively used to preheat the feed liquid  108 . 
         [0061]    In other embodiments a shown in  FIG. 4 , residual concentrate  130  from the plurality of flashing chambers  318  may be passed through one or more preheaters  326 , which in some embodiments may be in the form of a heat exchanger. This preheater  326  may be configured to preheat feed liquid either from the second heat exchanger  109  or feed liquid  108 . In some embodiments the liquid so preheated may be introduced into at least one of the distillation chambers  103  while in some embodiments the liquid so preheated may be introduced into at least one of the flashing chambers  318 . 
         [0062]    In other exemplary embodiments as shown in  FIG. 5 a    and  FIG. 5 b   , heat containing fluid from the first heat exchanger  102  may be introduced directly into the flashing chambers  318  wherefrom it may be introduced into distillation chambers  103  as described above in previous embodiments. In some embodiments a preheater  326  may be included to use the heat from the residual concentrate  130  from the flashing chambers  318  to preheat feed liquid  108 . 
         [0063]    In another embodiment as shown in  FIG. 6 , the first heat exchanger  102  may not be provided and the feed liquid  108  may be introduced directly into the flashing chambers  318  wherefrom it may be introduced into distillation chambers  103  as described above in previous embodiments. 
         [0064]    Referring to  FIG. 7  there is shown a boosted MSF system  700  as per the embodiments of the present invention. This MSF system  700  can be used in low-grade heat source applications. 
         [0065]    There is shown in  700  a feed liquid  108  to come through a series of condensers  730  and is heated up in a residual concentrate heater  734  and then goes into the plurality of flashing chambers  318  for evaporation. 
         [0066]    The residual concentrate heater is fed with a liquid heat source  710 . This liquid heat source is used in the first residual concentrate heater  734  where a significant portion of the heat from the liquid heat source is removed. The liquid heat source  710  is then used in a second residual concentrate heater  745  after passing through the first residual concentrate heater  734  where more of the heat is extracted from the liquid heat source. It will be clear to a person skilled in the art that not all the heat can be extracted from the liquid heat source  710 . However the advantage of the inventive system disclosed by this patent is that more of the heat is extracted from the liquid heat source using the arrangements described than would otherwise occur with the prior art systems. 
         [0067]    In a preferred embodiment the feed liquid  108  is tapped into after is has passed through a number of the condensers  730  through a condenser line  760 . This stream is split three ways—the majority of the stream continues to go through the condensers  730  to the residual concentrate heater  734 . A small stream is discharged to waste via blowdown line  740  (this is done for mass balance of the plant). A third stream of medium proportion of the feed liquid  108  now called a boost stream  750  is directed to the second residual concentrate heater  745 . The boost stream  750  is injected into the MSF unit via an injection line  755 . 
         [0068]    The point of injection of the liquid from the second residual concentrate heater  745  is determined by the relationship of temperature and pressure in the flashing chambers  318  and the temperature of the boost fluid  755  coming from the second residual concentrate heater  745 . 
         [0069]    Thereafter, the principle of this embodiment is similar as previous embodiments involving the MED stage, in that the condensers  730  produce condensate that is collected via a condensate line  110  to a freshwater store  107 . The stream from the first residual concentrate heater  734  can go into the second residual concentrate heater  745  and release its energy to the boost stream  750 . 
         [0070]    In the example shown the boost stream  750  comes out from the condenser line  760  at the third stage of the MSF and is introduced back into the MSF at the same stage after the boost stream has picked up further heat from the second residual concentrate heater  745 . The same as above can be implemented with more residual concentrate heaters if the outlet temperature of the secondary residual concentrate heater is hot enough. 
         [0071]    In other embodiments, a plurality of heaters can be used for separate feeds and not necessarily for residual concentrate coming out of the condenser lines. 
         [0072]      FIG. 9 a    shows a Thermal Vapor Compression Multi Effect Distillation system  800 . The live steam  831  is mixed in a thermo-compressor  832  with a portion of wasted flashed vapor  835  generated in a flash vessel  834  using a liquid waste heat source  833 , to increase the pressure/temperature of the waste flashed vapor  835  to run an MED process. Part of the condensate generated in the first distillation chamber  836  is returned to the steam plant as live steam condensate ( 838 ), the remainder is fed to the freshwater output  839 . 
         [0073]      FIG. 9 b    shows a Flash Boosted TVC-MED system (FB-TVC-MED)  900 . In this system waste flashed vapor  835  generated from the first heat source  833  in a flash vessel  834  is fed in part to the thermo-compressor  832  to mix with live steam  831 . A portion of the waste flash vapor  835  is introduced (or “boosted”) into the 2 nd  distillation chamber  837 . 
         [0074]    In the example system shown, full use is made of the available waste flashed vapor ( 835 ) generated from the first heat source  833  in a flash vessel  834 . 
         [0075]    Compared to the TVC-MED system, a reduced quantity of live steam  831  is introduced into the first distillation chamber  836 , while the 2 nd  distillation chamber  837  receives an increased quantity of steam. 
         [0076]    The size of the distillation chambers must be designed to suit the revised operating conditions. Due to the high recovery of the available heat source the volume of live steam consumed  831  is reduced while at the same time increasing freshwater production. 
         [0077]    Simulation Results: 
         [0078]    To better illustrate and elucidate the advantages of this invention, the results of a simulation implementing the invention are presented below. 
         [0079]    However, the experiment provided should not be construed as limiting the scope of the invention in any way and is presented in an exemplary way only showing the advantages provided by the present invention. 
         [0080]    In this experiment, a conventional MED system as illustrated in  FIG. 1 , a boosted MED system as illustrated in  FIG. 2  and an MED system according to some exemplary embodiments of the present invention as illustrated in  FIG. 3 a    were compared under assumptions as per Table 1 below: 
         [0000]    
       
         
               
             
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Assumptions made in a simulation comparing MED systems 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Top residual concentrate temperature (° C.) 
                 70 
               
               
                   
                 Heat source flow rate, {dot over (m)} hs  (kg/s) 
                 100 
               
               
                   
                 C P,hs  (kJ/kg · K) 
                 4.187 
               
               
                   
                 T cond,in  (° C.) 
                 28 
               
               
                   
                 T cond,out  (° C.) 
                 38 
               
               
                   
                 ΔT inj   #  (° C.) 
                 3 
               
               
                   
                 Liquid-to-Liquid heat exchanger approach 
                 3 
               
               
                   
                 temperature (° C.) 
               
               
                   
                 X f  (ppm), MED effects inlet 
                 35,000 
               
               
                   
                 X b (ppm), MED effects outlet 
                 78,750 
               
               
                   
                   
               
             
          
         
       
     
         [0081]    Water was taken as the heat source medium and its flow rate was fixed at 100 kg/s in all simulations. The inlet seawater temperature at the condenser was set as 28° C. and the salinity of the seawater was set as 35000 ppm. The top residual concentrate temperature was capped at 70° C. For the liquid-to-liquid heat exchanger the minimum temperature of approach was taken to be 3° C. For vapor injection to happen from the flashing chamber to the judicious effect in the primary MED plant, a pressure difference equivalent to 3° C. saturated temperature difference was considered to be sufficient. The results of the simulations at different heat source inlet temperatures are depicted in Table 2. 
         [0000]    
       
         
               
             
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Results of a simulation comparing various MED systems 
               
             
          
           
               
                   
                 Heat source inlet temp. (° C.) 
               
             
          
           
               
                   
                 65 
                 70 
                 75 
                 80 
                 85 
                 90 
               
               
                   
                   
               
             
          
           
               
                 Conventional MED #   
                 511 
                 723 
                 714 
                 942 
                 1489 
                 2046 
               
               
                 Freshwater yield (m 3 /day) 
               
               
                 Number of effects (Max.) 
                 5 
                 6 
                 8 
                 9 
                 9 
                 9 
               
               
                 Optimized Conventional MED 
                 619 
                 906 
                 1224 
                 1580 
                 1981 
                 2397 
               
               
                 Freshwater yield (m 3 /day) 
               
               
                 Number of effects 
                 3 
                 4 
                 5 
                 5 
                 6 
                 6 
               
               
                 Boosted MED 
                 820 
                 1171 
                 1553 
                 1998 
                 2470 
                 2952 
               
               
                 Freshwater yield (m 3 /day) 
               
               
                 Number of effects/Injected 
                 5/5 
                 6/6 
                 6/6 
                 7/6 
                 8/7 
                 8/7 
               
               
                 effect&#39;s number 
               
               
                 Flash Boosted MED [Present 
                 888 
                 1314 
                 1874 
                 2411 
                 2905 
                 3403 
               
               
                 invention] Freshwater yield 
               
               
                 (m 3 /day) 
               
               
                 Number of 
                 5/3 
                 6/4 
                 8/6 
                 9/7 
                 9/7 
                 9/7 
               
               
                 MED effects/Flashing stages 
               
               
                   
               
             
          
         
       
     
         [0082]    A comparative graphical representation of the simulation results is presented in  FIG. 8 . The graph compares the production rate of water with respect to the heat source inlet temperature for a conventional MED, a boosted MED and a flash boosted MED as per an exemplary embodiment of the present invention. It is evident from the graph in  FIG. 8  based on results from Table 2 that production rate of fresh water is substantially improved in the system implementing an exemplary embodiment of the current invention, over a conventional MED system or a boosted MED system. 
         [0083]    In summary improvements in production rate over conventional MED systems as high as 53% are realized in a simulatory implementation of an exemplary embodiment. 
         [0084]    Simulation results comparing the FB-TVC-MED (900) vs. TVC-MED (800) system for a particular application generated the following outputs: Reduction of live steam consumption from 0.4 kg/s to 0.2 kg/s, increase in freshwater production from 3.1 kg/s to 3.7 kg/s, while making full use of the flashed vapor generated from the waste heat source (1.5 kg/s instead of 0.5 kg/s) 
         [0085]    It should be further appreciated by those skilled in the art that the figures provided are for illustrative purposes only and the number of chambers shown are exemplary scenarios and the system according to the invention can include more or lesser number of chambers, within the scope of the present invention. 
         [0086]    Further, in the embodiment described above there may be advantages in utilizing all of the heat generated by the system, there may also be advantage in using externally applied heat sources to the system at different points. It will be appreciated that the specific arrangements of which will be determined by the skilled person and designed according to specific applications, all of which fall within the present invention. 
         [0087]    It will be further appreciated that the present invention is applicable to a range of different thermal separation systems and represents an increased efficiency which will provide a beneficial result when applied to said systems.