Abstract:
The invention relates to a system for separating a product contained as solvent in a solution to be processed, comprising at least one forward osmosis device ( 816 ) through which the solution to be processed and a draw solution flow, and a device connected downstream thereof for obtaining the product ( 56, 62 ) from the diluted draw solution exiting the forward osmosis device, wherein the forward osmosis device comprises at least one flow channel conducting the solution to be processed and at least one flow channel conducting the draw solution, the inner space of a respective flow channel conducting the solution to be processed is delimited at least partially by a semi-penneable membrane wall that is peimeable to the solvent of the solution to be processed but not to the substance dissolved therein, and at least one flow channel conducting the draw solution is delimited on opposite sides by membrane walls that are associated with two adjoining flow channels conducting the solution to be processed, such that solvent from the solution to be processed passes through the membrane walls into the adjoining flow channels conducting the draw solution.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a US National Stage of PCT/EP2011/004988 filed Oct. 6, 2011, which claims priority of German Patent Application No. DE 10 2010 050 892.6 filed Nov. 10, 2010, the entire contents of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a system for separating a product contained as a solvent in a solution to be processed. Such a system can, for example, be used for seawater desalination or for recovering drinking water from seawater, with in this case the seawater being the solution to be processed. 
       BACKGROUND OF THE INVENTION 
       [0003]    Systems for separating a product contained as a solvent in a solution to be processed are known from the documents WPO 2007/147013 A1, J. R. McCutcheon, R. L. McGinnis, M. Elimelech: “A novel ammonia-carbon dioxide forward (direct) osmosis desalination process” (published in Desalination, Vol. 174, No. 1, 2005, pages 1 to 11), US 2006/0144789 A1 and WO 2007/146094 A2. 
       SUMMARY OF THE INVENTION 
       [0004]    It is the aim of the invention to provide an improved system of the initially named kind which ensures a reliable, efficient separation with a compact design which is as simple as possible. 
         [0005]    This object is satisfied in accordance with the invention by a system for separating a product contained as a solvent in a solution to be processed having at least one forward osmosis device flowed through by the solution to be processed and by a draw solution and having a device connected downstream thereof for recovering the product from diluted draw solution exiting the forward osmosis device, wherein the forward osmosis device comprises at least one flow passage conducting the solution to be processed and at least one flow passage conducting the draw solution, wherein the inner space of a respective flow passage conducting the solution to be processed is at least partly bounded by a semipermeable membrane wall which is permeable for the solvent of the solution to be processed, but not for the substance dissolved therein, and wherein at least one flow passage conducting the draw solution is bounded on mutually oppositely disposed sides by membrane walls which are associated with two adjacent flow passages conducting the solution to be processed such that solvent from the solution to be processed arrives in the adjacent flow passages conducting the draw solution through the membrane walls. 
         [0006]    Due to this configuration, the system can be kept relatively simple and compact with a relatively large separation power. A larger number of flow passages conducting the solution to be processed and of flow passages conducting the draw solution can in particular also be provided without problem, whereby the efficiency of the system is correspondingly increased. 
         [0007]    In contrast to reverse osmosis, it is not the hydraulic pressure which serves as the driving force for the transport of the solvent of the solution to be processed through the membrane, but rather the osmotic pressure gradient. The solute contained in the draw solution has a higher so-called osmotic potential than the solute contained in the solution to be processed. From a specific concentration of the draw solution onward, the osmotic potential on the permeate side is always higher than the osmotic potential on the side of the solution to be processed, i.e. the retentate. 
         [0008]    Since the pressure gradient built up via the draw solution is larger than the hydraulic pressure gradient, a higher yield is achieved. 
         [0009]    In the case of a use of the system for seawater desalination, in particular a semipermeable membrane can be used which is permeable for water, but not for the salt. 
         [0010]    Saline solutions in particular with NaCL, CaCl 2 , KCl, organic compounds such as sugar or also, for example, ammonium hydrogen carbonate dissolved in water, etc. can be used, for example as draw solution providing the driving force for the forward osmosis. 
         [0011]    Reverse osmosis membranes can, for example, also be used as forward osmosis membranes. 
         [0012]    In addition to saline solutions, solutions with organic compounds such as sugar can inter alia also be used as the draw solution. In long-chain organic compounds without vapor pressure, it is desirable if they are so large that the product, water in seawater desalination, for example, can be separated via a microfiltration or ultrafiltration membrane. The water represents the permeate here. 
         [0013]    The use of solutions as the draw solution is in particular also conceivable when said solutions can be separated and regenerated via the vapor pressure such as ammonium hydrogen carbonate in water. Ammonium hydrogen carbonate can thus be dissolved in water, for example, whereby a draw solution is obtained. If this solution is heated, gaseous NH 3  and CO 2  is released. Pure water remains. 
         [0014]    The draw solution preferably flows through the forward osmosis device in counter-flow to the solution to be processed. Generally, however, such configurations are also conceivable in which the draw solution flows through the forward osmosis device in parallel flow to the solution to be processed. 
         [0015]    The forward osmosis device advantageously comprises a plurality of flow passages in parallel with one another and conducting the solution to be processed as well as a plurality of flow passages in parallel with one another and conducting the draw solution. 
         [0016]    In this respect, the flow passages conducting the draw solution are preferably each bounded on mutually oppositely disposed sides by membrane walls which are associated with two adjacent flow passages conducting the solution to be processed. 
         [0017]    A preferred practical embodiment of the system in accordance with the invention is characterized in that the product recovery device has a heating stage which is flowed through by the diluted draw solution exiting the forward osmosis device and which comprises at least one heating unit and at least one evaporator unit, wherein a respective heating unit comprises a heating fluid space at least partly bounded by a fluid-tight, heat-conducting wall and a respective evaporator unit comprises a vapor space at least partly bounded by a vapor-permeable, liquid-tight membrane wall, and wherein at least one flow passage, which is formed between a heating unit and an evaporator unit adjacent thereto and which conducts the draw solution, is provided in the heating stage such that the draw solution is heated via the fluid-tight, heat-conducting wall and the vapor arising from the draw solution arrives in the vapor space through the membrane wall. 
         [0018]    It is of advantage in this respect if the product recovery device has at least one condensation/evaporation stage which is flowed through by the draw solution exiting the heating stage, which is supplied with vapor arising in the heating stage and which comprises at least one condensation unit and at least one evaporator unit, wherein a respective condensation unit comprises a first vapor space at least partly bounded by a condensation wall and a respective evaporator unit comprises a second vapor space at least partly bounded by a vapor-permeable, liquid-tight membrane wall, and wherein at least one flow passage, which is formed between such a condensation unit and such an evaporator unit adjacent thereto and which conducts the draw solution, is provided in a respective condensation/evaporation stage such that the draw solution is heated via the condensation wall and the vapor arising from the draw solution arrives in the second vapor space through the membrane wall, with preferably the draw solution exiting the last condensation/evaporation stage again being supplied to the forward osmosis device. 
         [0019]    It is in particular also of advantage if the product recovery device comprises a condensation stage having at least one cooling unit and at least one condensation unit, wherein a respective cooling unit comprises a cooling fluid space preferably at least partly bounded by a fluid-tight, heat-conducting wall and a respective condensation unit comprises a vapor space at least partly bounded by a condensation wall, and wherein at least one cooling unit is directly adjacent to at least one condensation unit in the condensation stage such that the condensation wall of the respective condensation unit is cooled via the cooling unit, and wherein vapor preferably arising in a preceding condensation/evaporation stage is supplied to the condensation stage and the product can preferably be led off from the condensation stage in the form of the distillate arising in the condensation stage. 
         [0020]    The heating stage can be heated by solar power, for example. A respective heating unit of the heating stage can therefore be flowed through by a heating fluid which is, for example, heated by solar power. The condensation stage can, for example, be cooled with cooling water. As already mentioned, the product can e.g. be recovered in the form of the distillate arising in the condensation stage. 
         [0021]    If the product recovery device comprises, as previously mentioned, a heating stage, at least one condensation/evaporation stage and preferably a condensation stage, this concentration device is preferably in a vacuum; the cooling fluid and the heating fluid are preferably at environmental pressure and the draw solution is preferably in a vacuum. In the condensation/evaporation stage(s) and in the heating stage, the draw solution can in particular be at the boiling temperature corresponding to the absolute pressure in the vapor space of a respective adjacent evaporator unit over all stages, as is described in WO 2007/054311 which is herewith included in the disclosure content of the present application. 
         [0022]    The draw solution to be processed and the draw solution can generally flow in counter-flow or also in parallel flow. 
         [0023]    The forward osmosis device can be immersed into the solution to be processed, e.g. seawater, or it can be flowed through externally by the solution to be processed. If the forward osmosis solution is immersed into the solution to be processed, provision must expediently be made that the solution to be processed flows along the membrane wall to avoid a concentration polarization. 
         [0024]    The solution diluted by the product, e.g. water, can therefore be supplied, for example, to a process for concentration such as is described in WO 2007/054311. This process for concentration can, however, generally also be replaced, in particular for seawater desalination, for example, with other processes such as in particular reverse osmosis, an MSF (multistage flash evaporation) process, an MED (multi-effect distillation) process, an MVC (mechanical vapor compression=desalination based on the MVC process) process. 
         [0025]    In accordance with the invention, the product recovery device has a heated desorber stage which is flowed through by the diluted draw solution exiting the forward osmosis device and which comprises at least one gas space as well as at least one flow passage conducting the diluted draw solution, wherein a respective gas space is at least partly bounded by a vapor-permeable, liquid-tight membrane wall and wherein at least one flow passage is provided which is formed between such a gas space and a heating unit adjacent thereto and which conducts the draw solution such that the gas mixture expelled from the draw solution arrives in the gas space through the membrane wall and the product can preferably be led off in the form of draw solution exiting the heated desorber stage and purified of the gas mixture. The sodium hydrogen carbonate can advantageously be used as the draw solution, for example. 
         [0026]    A respective heating unit in this respect expediently comprises a heating fluid space at least partly bounded by a fluid-tight heat-conducting wall. 
         [0027]    In accordance with the invention, the gas mixture arising in the heated desorber stage is supplied to a combined absorber/solution cooler stage for generating regenerated draw solution, with the regenerated draw solution obtained through this absorber/solution cooler stage preferably again being supplied to the forward osmosis device. 
         [0028]    It is of advantage in this respect if some of the purified draw solution exiting the heated desorber stage or some of the diluted draw solution exiting the forward osmosis device is moreover supplied to the combined absorber/solution cooler stage, wherein in the latter case preferably only such a partial amount of the diluted draw solution exiting the forward osmosis device is supplied to the heated desorber stage by which the mass of the concentrated draw solution increased on flowing through the forward osmosis device, while the remaining partial amount of diluted draw solution is supplied to the combined absorber/solution cooler stage. 
         [0029]    In accordance with the invention, the absorber/solution cooler stage comprises at least one gas space which is preferably acted on by vacuum and contains gas mixture from the heated desorber stage as well as at least one flow passage conducting the purified or diluted draw solution, wherein a respective gas space is at least partly bounded by a vapor-permeable, liquid-tight membrane wall and wherein at least one flow passage is provided which is formed between such a gas space and a cooling unit adjacent thereto and which conducts the draw solution such that the gas mixture flows from the gas space through the membrane wall into the flow passage conducting the purified or diluted draw solution and is dissolved in the purified or diluted draw solution cooled by the cooling unit. 
         [0030]    A device for drying and cooling gas, in particular air, by means of a hygroscopic solution is advantageously provided for supplying the absorber/solution cooler stage or its cooling units with cooling fluid. 
         [0031]    In this respect, it is in particular advantageous if the gas drying/cooling device has a gas cooler/absorber stage which comprises at least one gas flow passage as well as a flow passage conducting the hygroscopic solution, wherein the inner space or gas space of a respective gas flow passage is bounded at least partly by a vapor-permeable, liquid tight membrane wall and at least one flow passage is provided which conducts hygroscopic solution between such a gas flow passage and a further such gas flow passage adjacent thereto or an adjacent cooling unit such that moisture, in particular water vapor, is transferred from the gas via the membrane wall into the hygroscopic solution and is absorbed therein. 
         [0032]    In this respect, the gas cooler/absorber stage preferably comprises a plurality of gas flow passages in parallel with one another as well as a plurality of flow passages in parallel with one another and conducting the hygroscopic solution. It is in particular of advantage in this respect if the flow passages of the gas cooler/absorber stage conducting the hygroscopic solution are respectively formed between two mutually adjacent gas flow passages. 
         [0033]    Such embodiments are, however, generally also conceivable in which the flow passages of the gas cooler/absorber stage conducting the hygroscopic solution are respectively formed between a gas flow passage and an adjacent cooling unit. 
         [0034]    The gas cooler stage/absorber stage can be supplied as gas, for example as inflow air. The dried gas, e.g. air, exiting the gas cooler/absorber stage can in particular be supplied to the combined absorber/solution cooler stage via an interposed cooler. The gas space or spaces of the absorber/solution cooler stage is/are preferably acted on by vacuum to assist the transport of the gas mixture coming from the heated absorber stage. The gas spaces of the absorber/solution cooler stage are expediently connected to a vacuum system with a condenser. 
         [0035]    The respective portion of concentrated draw solution arising in the heated absorber stage can be supplied to the absorber/solution cooler stage via a cooler cooled by seawater, for example, in the case of seawater desalination. 
         [0036]    The hygroscopic solution exiting the gas cooler/absorber stage is advantageously supplied to a regeneration stage in which it is regenerated, with the regenerated hygroscopic solution preferably in particular again being supplied to the gas cooler/absorber stage via a cooler. 
         [0037]    It is in particular of advantage in this respect if the regeneration stage comprises at least one gas flow passage which is in particular flowed through by environmental air, as well as at least one flow passage which conducts the hygroscopic solution, wherein the inner space or gas space of a respective gas flow passage is at least partly bounded by a vapor-permeable, liquid-tight membrane wall and wherein at least one flow passage is provided which is formed between such a gas flow passage and a further such gas flow passage adjacent thereto and which conducts the hygroscopic solution such that moisture, in particular water vapor, is transferred from the hygroscopic solution via the membrane wall into the gas, in particular environmental air, conducted in the gas flow passage and the hygroscopic solution is concentrated. 
         [0038]    The regeneration stage preferably comprises a plurality of gas flow passages in parallel with one another as well as a plurality of flow passages in parallel with one another and conducting the hygroscopic solution, wherein the flow passages of the regeneration stage conducting the hygroscopic solution are preferably respectively formed between two mutually adjacent gas flow passages. 
         [0039]    The gas, e.g. environmental air, supplied to the regeneration stage can have previously been heated via a gas heater, optionally an air heater. The gas exiting the regeneration stage can be led off as exhaust air, for example. 
         [0040]    In accordance with another advantageous practical embodiment of the system in accordance with the invention, the regeneration stage provided for regenerating the hygroscopic solution can also have a heating stage which is flowed through by the hygroscopic solution exiting the gas cooler/absorber stage and which comprises at least one heating unit and at least one evaporator unit, wherein a respective heating unit comprises a heating fluid space at least partly bounded by a fluid-tight, heat-conducting wall and a respective evaporator unit comprises a vapor space at least partly bounded by a vapor-permeable, liquid-tight membrane wall, and wherein at least one flow passage, which is formed between a heating unit and an evaporator unit adjacent thereto and which conducts the hygroscopic solution, is provided in the heating stage such that the hygroscopic solution is heated via the fluid-tight, heat-conducting wall and the vapor arising from the hygroscopic solution arrives in the vapor space through the membrane wall. 
         [0041]    It is in particular also of advantage if the regeneration stage has at least one condensation/evaporation stage which is flowed through by the hygroscopic solution exiting the heating stage, which is supplied with vapor arising in the heating stage and which comprises at least one condensation unit and at least one evaporator unit, wherein a respective condensation unit comprises a first vapor space at least partly bounded by a condensation wall and a respective evaporator unit comprises a second vapor space at least partly bounded by a vapor-permeable, liquid-tight membrane wall, and wherein at least one flow passage, which is formed between such a condensation unit and such an evaporator unit adjacent thereto and which conducts the hygroscopic solution, is provided in a respective condensation/evaporation stage, such that the hygroscopic solution is heated via the condensation wall and the vapor arising from the hygroscopic solution arrives in the second vapor space through the membrane wall, with preferably the hygroscopic solution ( 70 ) exiting the last condensation/evaporation stage being again supplied to the gas cooler/absorber stage. 
         [0042]    The regeneration stage preferably also comprises a condensation stage having at least one cooling unit and at least one condensation unit, wherein a respective cooling unit comprises a cooling fluid space preferably at least partly bounded by a fluid-tight, heat-conducting wall and a respective condensation unit comprises a vapor space at least partly bounded by a condensation wall and wherein at least one cooling unit is directly adjacent to at least one condensation unit in the condensation stage such that the condensation wall of the respective condensation unit is cooled via the cooling unit, and wherein vapor preferably arising in a preceding condensation/evaporator stage is supplied to the condensation stage. 
         [0043]    If the regeneration stage serving for regenerating the hygroscopic solution comprises, as previously mentioned, a heating stage, at least one condensation/evaporation stage and a condensation stage, this regeneration stage is preferably again in a vacuum; the cooling fluid and the heating fluid are preferably at environmental pressure and the hygroscopic solution is preferably in a vacuum. In the condensation/evaporation stage(s) and in the heating stage, the hygroscopic solution can in particular be at the boiling temperature corresponding to the absolute pressure in the vapor space of a respective adjacent evaporator unit over all stages, as is described in WO 2007/054311 which is herewith included in the disclosure content of the present application. 
         [0044]    The heating stage can in particular again be heated by solar power. The condensation stage can be cooled by cooling water or also by another cooling fluid. The distillate arising in a respective condensation unit can be led off. The gas spaces of the absorber/solution cooler stage and the at least one condensation unit of the regeneration stage serving for regenerating the hygroscopic liquid can again be connected to a vacuum system with a condenser, for example via a vacuum line. 
         [0045]    In accordance with a preferred practical embodiment of the system in accordance with the invention, it is designed as a modular flow system having a plurality of frame elements. In this respect, the different functional units such as in particular a respective flow passage conducting the solution to be processed, a respective heating unit, a respective evaporator unit, a respective condensation unit, a respective cooling unit, a respective gas space and/or a respective gas passage can each be provided in the form of such a frame element. 
         [0046]    The frame elements are preferably provided with web structures via which they can in particular be connected to one another for forming the forward osmosis device, a respective heating stage, a respective condensation/evaporation stage, a respective condensation stage, the heated desorber stage, the combined absorber/solution cooler stage, the gas cooler/absorber stage and/or the regeneration stage provided for regenerating the hygroscopic solution. 
         [0047]    The frame elements can each comprise an inner region which is surrounded by an outer frame and which is preferably provided with an in particular grid-like spacer to whose two sides a respective corresponding functional surface, preferably in the form of a film or membrane, is in particular applied for forming a respective inner space, a respective heating fluid space, a respective vapor space, a respective cooling fluid space, a respective gas space or a respective inner space or gas space. 
         [0048]    The web structures via which the individual frame elements, and optionally end-side plate elements, can be connected to one another can, for example, be welded web structures or bonded structures via which the frame elements are welded or bonded to one another. In the case of welded web structures, a friction welding process, a laser welding process and/or a heating element welding process can be used, for example, for connecting the frame elements. 
         [0049]    The system in accordance with the invention can be designed in a particularly simple manner and can be varied in the desired manner using the frame elements in accordance with the invention. The frame elements or the units or stages obtained via them are characterized by a relatively simple shape and provide different possibilities for conducting solution, gas or air, cooling fluid and heating fluid, etc. Depending on the function, frame elements are inter alia conceivable which are each provided on both sides with a membrane, are each provided on both sides with a film, or are provided with a membrane on one side and with a film on the other side. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0050]    The invention will be explained in more detail in the following with reference to embodiments and to the drawing; there are shown in this: 
           [0051]      FIG. 1  a schematic representation of an exemplary embodiment of a system for separating a product contained as a solvent, e.g. water, in a solution to be processed such as seawater; 
           [0052]      FIG. 2  a schematic representation of an exemplary embodiment of a system for separating a product contained as a solvent, e.g. water, in a solution to be processed such as seawater having a heated desorber stage, a combined absorber/solution cooler stage and a gas drying/cooling device having a gas cooler/absorber stage flowed through by a hygroscopic solution and having a regeneration stage serving for regenerating the hygroscopic solution; 
           [0053]      FIG. 3  an exemplary embodiment of the system comparable with the embodiment in accordance with  FIG. 2  in which, however, only the product flow is liberated from the gas mixture in the heated desorber stage; 
           [0054]      FIG. 4  an exemplary embodiment of the system comparable with the embodiment in accordance with  FIG. 2  with an alternative regeneration stage serving for the regeneration of the hygroscopic solution; 
           [0055]      FIG. 5  a schematic representation of an exemplary embodiment of a forward osmosis device in the form of a parallel flow/counter flow exchanger with e.g. two forward osmosis units connected after one another; 
           [0056]      FIG. 6  a schematic representation of an exemplary embodiment of a forward osmosis device in the form of a counter-flow exchanger with e.g. two forward osmosis units connected after one another; 
           [0057]      FIG. 7  a schematic representation of an exemplary embodiment of a frame element; and 
           [0058]      FIG. 8  a schematic, exploded representation of an exemplary realization of the forward osmosis device in accordance with  FIG. 6  provided in the form of a counter-flow exchanger e.g. using frame elements of the kind shown in  FIG. 7  and using e.g. end-side plate elements. 
       
    
    
     DETAILED DESCRIPTION 
       [0059]      FIG. 1  shows in a schematic representation an exemplary embodiment of a system  10  for separating a product  14  contained as a solvent in a solution  12  to be processed. In this respect, the solution  12  to be processed can, for example, be seawater and the product  14  can, for example, be water. 
         [0060]    The system  10  comprises at least one forward osmosis device  16  flowed through by the solution  12  to be processed and by a draw solution  20  as well as a device  28  connected downstream thereof for recovering the product  14  from diluted draw solution  20 ′ exiting the forward osmosis device  16 . 
         [0061]    The forward osmosis device  16  comprises at least one flow passage  18  conducting the solution  12  to be processed and at least one flow passage  22  conducting the draw solution  20 . 
         [0062]    In this respect, the inner space  24  of a respective flow passage  18  conducting the solution  12  to be processed is at least partly bounded by a semipermeable membrane wall  26  permeable for the solvent of the solution  12  to be processed, but not for the substance, e.g. seawater, dissolved therein. In addition, at least one flow passage  22  conducting the draw solution  20  is bounded on mutually oppositely disposed sides by membrane walls  26  which are associated with two adjacent flow passages  18  conducting the solution  12  to be processed such that solvent from the solution  12  to be processed arrives in the adjacent flow passages  22  conducting the draw solution  20  through the membrane walls  26 . The concentrated solution  12 ′ to be processed, e.g. concentrated seawater, exiting the forward osmosis device  16  can be led off. 
         [0063]    The draw solution  20  can flow through the forward osmosis device  16  in counter-flow or also in parallel flow to the solution  12  to be processed. 
         [0064]    As can be recognized with reference to  FIG. 1 , the forward osmosis device  16  can comprise a plurality of flow passages  18  in parallel with one another and conducting the solution to be processed as well as a plurality of flow passages  22  in parallel with one another and conducting the draw solution  20 . 
         [0065]    In this respect, the flow passages  22  conducting the draw solution  20  can each be bounded on mutually oppositely disposed sides by membrane walls  26  which are associated with two adjacent flow passages  18  conducting the solution  12  to be processed. 
         [0066]    As can again likewise be recognized with reference to  FIG. 1 , the product recovery device  28  can have a heating stage  30  flowed through by the diluted draw solution  20 ′ exiting the forward osmosis device  16 . Such a heating stage  30  comprises a heating unit  32  and at least one evaporator unit V. In this respect, a respective heating unit  32  comprises a heating fluid space  36  at least partly bounded by a fluid-tight, heat-conducting wall  34  and a respective evaporator unit V comprises a vapor space  40  at least partly bounded by a vapor-permeable, liquid-tight membrane wall  38 . At least one flow passage  22 , which is formed between a heating unit  32  and an evaporator unit V adjacent thereto and which conducts the draw solution  20 , is provided in the heating stage  30  such that the draw solution  20  is heated via the fluid-tight, heat-conducting wall  34  and the vapor arising from the draw solution  20  arrives in the vapor space  40  through the membrane wall  38 . 
         [0067]    The product recovery device  28  can additionally have at least one condensation/evaporation stage  42  flowed through by the draw solution  20  exiting the heating stage  30  and supplied with vapor  92  arising in the heating stage  30 . Such a condensation/evaporation stage  42  comprises at least one condensation unit K and at least one evaporator unit V. A respective condensation unit K comprises a first vapor space  46  at least partly bounded by a condensation wall  44 , while a respective evaporator unit V comprises a second vapor space  48  at least partly bounded by a vapor-permeable, liquid-tight membrane wall  38 . 
         [0068]    In this respect, at least one flow passage  22 , which is formed between such a condensation unit K and such an evaporator unit V adjacent thereto and which conducts the draw solution  20 , is provided in a respective condensation/evaporation stage  42  such that the draw solution  20  is heated via the condensation wall  44  and the vapor arising from the draw solution  20  arrives in the second vapor space  48  through the membrane wall  38 . The draw solution  20  exiting the last condensation/evaporation stage  42  can again be supplied to the forward osmosis device  16 . 
         [0069]    As can likewise be seen from  FIG. 1 , the product recovery device  28  can additionally comprise a condensation stage  50  having at least one cooling unit  52  and at least one condensation unit K. A respective cooling unit  52  comprises a cooling fluid space  54  preferably at least partly bounded by a fluid-tight, heat-conducting wall  34  while a respective condensation unit K comprises a vapor space  46  at least partly bounded by a condensation wall  44 . 
         [0070]    At least one cooling unit  52  is directly adjacent to at least one condensation unit K in the condensation stage  50  such that that the condensation wall  44  of the respective condensation unit K is cooled via the cooling unit  52 . 
         [0071]    Vapor arising in a preceding condensation/evaporation stage  42  can be supplied to the condensation stage  50 . The product  14  is then in particular led off from the condensation stage  50  in the form of the distillate arising in the condensation stage  50 . 
         [0072]    The product recovery device  28  comprising the heat stage  30 , the at least one condensation/evaporation stage  42  and preferably also the condensation stage  50  and marked by a dashed line is preferably in a vacuum; the cooling fluid and the heating fluid are preferably at environmental pressure and the draw solution  20  is preferably in a vacuum. The draw solution  20  can in particular be at the boiling temperature corresponding to the absolute pressure in the vapor space of a respective adjacent evaporator unit over all stages in the condensation/evaporation stages  42  and in the heating stage  50 , as is described in WO 2007/054311. 
         [0073]    A respective heating unit  32  can be flowed through by a heating fluid which is, for example, heated by solar power. 
         [0074]    The condensation stage  50  can be cooled by a cooling fluid  94 , for example cooling water. 
         [0075]    A forward osmosis device can therefore, for example, be combined with a product recovery device comprising e.g. a heating stage, at least one condensation/evaporation stage and a condensation stage. The forward osmosis device can be built up of frame elements and, optionally, end-side plate elements, which are provided with membranes suitable for forward osmosis. Passages for the solution to be processed and for the draw solution are formed on the setting up of the frame stacks or plate stacks. The solution to be processed and the draw solution can flow in counter-flow or also in parallel flow. 
         [0076]    The forward osmosis device can be immersed into the solution to be processed, e.g. seawater, or it can be flowed through externally by the solution to be processed. If the forward osmosis device is immersed into the solution to be processed, provision must expediently be made that it flows along the membranes to avoid a concentration polarization. 
         [0077]    The draw solution diluted by the product, here water, for example, can be supplied to a concentration device comprising a heating stage, at least one condensation/evaporation stage and a condensation stage. 
         [0078]    The previously described concentration process can in particular also be replaced with other processes such as in particular reverse osmosis, an MSF process, an MED process or an MFC process on the desalination of seawater. 
         [0079]    In addition to saline solutions, solutions with organic compounds such as sugar can also be used. If these organic compounds are long-chain compounds and if they do not have any vapor pressure, it is desirable that they are so large that the product, e.g. water on a seawater desalination, can be separated via a microfiltration or ultrafiltration membrane. In this case, the water is the permeate. The unit for recovering the product and for concentrating the draw solution can in particular be made up of frame elements provided with web structures. 
         [0080]    Solutions can in particular also be used as draw solutions which can be both separated and regenerated via the vapor pressure, with e.g. ammonium hydrogen carbonate dissolved in water e.g. being named. Ammonium hydrogen carbonate can be dissolved in water such that a corresponding draw solution is obtained. If this solution is heated, gaseous NH 3  and CO 2  is released. Pure water remains. 
         [0081]      FIG. 2  shows in an exemplary embodiment a system  10  for separating a product  14  contained as a solvent, e.g. water, in a solution  12  to be processed such as seawater having a heated desorber stage  56 , a combined absorber/solution cooler stage  62  and a gas drying/cooling device  66  having a regeneration stage  80  flowed through by a hygroscopic solution  70  and serving for regenerating the hygroscopic solution  70 . 
         [0082]    As can be seen from  FIG. 2 , the product recovery device  28  can e.g. have a heated desorber stage  56  which is flowed through by the diluted draw solution  20 ′ exiting the forward osmosis device  16  and which comprises at least one gas space  58  as well as at least one flow passage  22  conducting the diluted draw solution  20 ′. 
         [0083]    In this respect, a respective gas space  58  is at least partly bounded by a vapor-permeable, liquid-tight membrane wall  38 . At least one flow passage  22  is provided which is formed between such a gas space  58  and a heating unit  32  adjacent thereto and which conducts the diluted draw solution  20 ′ such that the gas mixture  60  expelled from the diluted draw solution  20 ′ arrives in the gas space  58  through the membrane wall  38  and the product  14  can preferably be led off in the form of draw solution  120  which exits the heated desorber stage  56 , which is purified from the gas mixture  60  and which can be pure water in the case of seawater desalination, for example. 
         [0084]    In this respect, a respective heating unit  32  can comprise a heating fluid space  36  at least partly bounded by a fluid-tight, heat-conducting wall  34 . 
         [0085]    Some of the draw solution  120  exiting the heated desorber stage  56 , purified of the gas mixture  60  and in particular present in the form of pure water and the gas mixture  60  separated in the heated desorber stage  56  can be supplied to a combined absorber/solution cooler stage  62  for generating regenerated draw solution  20 . The regenerated draw solution  20  obtained through this absorber/solution cooler stage  62  can again be supplied to the forward osmosis device  16 . 
         [0086]    The absorber/solution cooler stage  62  can comprise at least one gas space  58  preferably acted on by vacuum and containing gas mixture  60  from the heated desorber stage  56  and can also comprise at least one flow passage  22  conducting the draw solution  120  purified of the gas mixture  60 . In this respect, a respective gas space  58  is at least partly bounded by a vapor-permeable, liquid-tight membrane wall  38 . 
         [0087]    In addition, at least one flow passage  22  is provided which is formed between such a gas space  58  and a cooling unit  52  adjacent thereto and which conducts the purified draw solution  20  such that the gas mixture flows from the gas space  58  through the membrane wall  38  into the flow passage  22  conducting the purified draw solution  120  and is dissolved in the purified draw solution  120  cooled by the cooling unit  52 . 
         [0088]    As can additionally be seen from  FIG. 2 , a device  66  for drying and cooling gas  68 , for example air, in particular inflow air, by means of a hygroscopic solution  70  can be provided for supplying the absorber/solution cooler stage  62  or its cooling units  52  with cooling fluid  64 , e.g. cold air. 
         [0089]    The gas drying/cooling device  66  can in particular have a gas cooler/absorption stage  72  having at least one gas flow passage  74  as well as at least one flow passage  76  conducting the hygroscopic solution  70 . In this respect, the inner space or gas space  78  of a respective gas flow passage  74  is at least partly bounded by a vapor-permeable, liquid-tight membrane wall  38 . 
         [0090]    At least one flow passage  76  is provided which is formed between such a gas flow passage  74  and a further such gas flow passage  74  adjacent thereto and which conducts the hygroscopic solution  70  such that moisture, in particular water vapor, is transferred from the gas  68  via the membrane wall  38  into the hygroscopic solution  70  and is absorbed therein. 
         [0091]    The gas cooler/absorber device  72  can in particular comprise a plurality of gas flow passages  74  in parallel with one another as well as a plurality of flow passages  76  in parallel with one another and conducting the hygroscopic solution  70 . 
         [0092]    In this respect, the flow passages  76  of the gas cooler/absorber stage  72  conducting the hygroscopic solution  70  can in particular respectively be formed between two mutually adjacent gas flow passages  74 . 
         [0093]    As can additionally be seen from  FIG. 2 , the hygroscopic solution  70  exiting the gas cooler/absorber stage  72  can be supplied to a regeneration stage  80  in which it is regenerated. The regenerated hygroscopic solution  70  can in particular again be supplied to the gas cooler/absorber stage  72  via a cooler  82 . 
         [0094]    The regeneration stage  80  can comprise at least one gas flow passage  74  in particular flowed through by environmental air and can also comprise at least one flow passage  76  conducting the hygroscopic solution  70 . 
         [0095]    In this respect, the inner space or gas space  78  of a respective gas flow passage  74  is at least partly bounded by a vapor-permeable, liquid-tight membrane wall  38 . 
         [0096]    At least one flow passage  76  is provided which is formed between such a gas flow passage  74  and a further such gas flow passage  75  adjacent thereto sand which conducts the hygroscopic solution  70  such that moisture, in particular water vapor, is transferred from the hygroscopic solution  70  via the membrane wall  38  into the gas, in particular environmental air, conducted into the gas flow passage  74  and the hygroscopic solution  70  is concentrated. 
         [0097]    The regeneration stage  80  can in particular comprise a plurality of gas flow passages  78  in parallel with one another as well as a plurality of flow passages in parallel with one another and conducting the hygroscopic solution  70 . In this respect, the flow passages  76  of the regeneration stage  80  conducting the hygroscopic solution  70  can in particular respectively be formed between two mutually adjacent gas flow passages  74 . 
         [0098]    The hygroscopic solution  70  exiting the regeneration stage  80  can be conducted back to the gas cooler/absorption stage  72  via a cooler  82 . The gas, e.g. environmental air, can be supplied to the regeneration stage  80  via a gas heater  96 , optionally an air heater. The gas exiting the regeneration stage  80  can therefore in particular be led off as exhaust air. 
         [0099]    The gas  68  supplied to the gas cooling/absorber stage  72  can in particular be inflow air. The gas, e.g. dried air, exiting the gas cooler/absorber stage  72  can be supplied to the absorber/solution cooler stage  62  via a cooler  98 . The absorber/solution cooler stage  62  is therefore supplied with cool gas or cool air. The gas again exiting the absorber/solution cooler stage  62  can be led off as exhaust gas or exhaust air  122 . 
         [0100]    The respective portion of the purified draw solution  120  or pure water exiting the heated desorber stage  56  can be supplied to the absorber/solution cooler stage  62  via a cooler  100 , with seawater optionally being able to be used for cooling. 
         [0101]    The forward osmosis device  16  can in particular again at least essentially be designed like the forward osmosis device  16  described with reference to  FIG. 1 . 
         [0102]    The forward osmosis process can in particular be carried out using sodium hydrogen carbonate with this system described with reference to  FIG. 2 . Seawater and the draw solution can thus e.g. be conducted in counter-flow in the forward osmosis device  16 , for example. Water e.g. flows through the semipermeable membrane walls at the osmotic pressure of the draw solution into the draw solution such that the latter is diluted. The diluted draw solution  20 ′ flows in the desorber stage  52  heated e.g. by solar energy. Said desorber stage contains passages for the diluted draw solution  20 ′ and for the heating fluid as well as for the expelled gases, here NH 3  and CO 2 , for example, with water vapor being contained in this gas mixture in accordance with its vapor pressure. 
         [0103]    The distillate purified, for example, of the gases NH 3  and CO 2  and recovered in the desorber  56  is expelled from the circuit. 
         [0104]    Due to its pressure gradient, the gas mixture  60  flows to the combined absorber/solution cooler stage  62 . It comprises passages for air, for example, which may in particular be bounded by films; passages for the gas mixture which may be bounded by a water-tight, vapor-permeable membrane; as well as passages for the purified draw solution  120  which may be delineated from the adjacent passage on one side respectively by a membrane and on the other side respectively by a film. Gas mixture  60  and draw solution  120  purified of the gas mixture  60 , for example pure water, flow from the heated desorber stage  56  toward the absorber/solution cooler stage  62  in parallel flow, for example. 
         [0105]    The purified draw solution  120  or the water can be precooled on the way to the absorber/solution cooler stage  62  via a cooler or heat exchanger  100 . 
         [0106]    Cooling fluid  64 , here cold air, for example, in particular flows toward the absorber/solution cooler stage in counter-flow to the gas mixture and water. In the system shown in  FIG. 2 , inflowing air comes, for example, as dried air from the gas cooler/absorber stage  72  and can then be further cooled via an interposed cooler  98 , here an air cooler, for example. 
         [0107]    NH 3  and CO 2 , for example, flow from the passage for the gas mixture  60  through the microporous, water-tight membranes of the absorber/solution cooler stage  62  and are dissolved in the water which is cooled here, for example, by the airflow. The volume reduction of the gas mixture by absorption of NH 3  and CO 2  ensures that gas mixture always flows on from the heated desorber stage  56 . The water vapor remaining in the passage can be supplied via a vacuum system  124  to a condenser and can be condensed there. This vacuum system also results in a flowing of the gas mixture from the heated desorber stage  56  to the combined absorber/solution cooler stage  62 . A new draw solution  20  exits the latter and can again be supplied to the forward osmosis device  16 . 
         [0108]    The air supplied to the combined absorber/solution cooler stage comes from the gas cooler/absorber stage  72  to which the regeneration stage  80  serving for regenerating the hygroscopic solution  70  can be connected in parallel. Gas  68 , here air for example, can be dried in this circuit by the hygroscopic liquid  70  in the gas cooler/absorber stage  72 . The hygroscopic solution  70  diluted by the taking up of the water vapor can be supplied to the regeneration stage  80  in particular acting as a desorber for concentration. After the desorption of the previously taken up water vapor, the hygroscopic liquid  70  can, for example, be cooled in the cooler  82  before it is again supplied to the gas cooler/absorber stage  72  for drying the gas  68  or air. 
         [0109]    As can be seen from  FIG. 2 , the total diluted draw solution  20 ′ exiting the forward osmosis device  16  can, for example, be supplied to the heated desorber stage  56 . In this case, some of the draw solution  120  exiting the desorber stage  56  purified of the gas mixture  60 , in particular pure water, can be supplied to the combined absorber/solution cooler stage  62  for regenerating regenerated draw solution  20 . The diluted draw solution  20 ′ exiting the forward osmosis device  16  and supplied to the heated desorber stage  56  therefore exits the heated desorber stage  56  as draw solution  120  purified of the gas mixture  60 , in particular as pure water. Some of this draw solution  120  purified of the gas mixture  60  or some of this pure water serves as a basis for the draw solution  20  to be formed again in the absorber/solution cooler stage  62 . 
         [0110]      FIG. 3  shows an exemplary embodiment of the system  10  comparable with the embodiment in accordance with  FIG. 2  in which, however, only the product flow is liberated from the gas mixture  60  in the heated desorber stage  56 . In this case, some of the diluted draw solution  20 ′ exiting the forward osmosis device  16  is supplied to the combined absorber/solution cooler stage  62  for new formation of the draw solution  20 . In this respect, in particular only such a part quantity of the diluted draw solution  20 ″ exiting the forward osmosis device  16  is supplied to the heated desorber stage  56  by which the mass of the concentrated draw solution  20  increased on flowing through the forward osmosis device  16 . The gas mixture  60 , here NH 3  and CO 2 , is now separated from this additional volume flow in the heated desorber stage  56  to form the product  14 . The remaining part quantity of diluted draw solution  20 ′ from the forward osmosis device  16  is supplied to the combined absorber/solution cooler stage  62 . The separated gas mixture  60  or NH 3 , CO 2 , is then supplied to this remaining part quantity of diluted draw solution  20 ′ in the absorber/solution cooler stage  62 . 
         [0111]    In another respect, this embodiment of the system  10  described with reference to  FIG. 3  can in particular again at least substantially have the same design as the system described with reference to  FIG. 2 . Mutually corresponding parts have the same reference numerals associated with them. 
         [0112]      FIG. 4  shows an exemplary embodiment of the system  10  comparable with the embodiment in accordance with  FIG. 2  having an alternative regeneration stage  80  serving for regenerating the hygroscopic solution. 
         [0113]    As can be seen from this  FIG. 4 , the regeneration stage  80  provided for regenerating the hygroscopic solution  70  can alternatively have a heating stage  30  which is flowed through by the hygroscopic solution  70  exiting the gas cooler/absorber stage  72  and which comprises at least one heating unit  32  and at least one evaporator unit V, wherein a respective heating unit  32  comprises a heating fluid space  36  at least partly bounded by a fluid-tight, heat-conducting wall  34  and a respective evaporator unit V comprises a vapor space  40  at least partly bounded by a vapor-permeable, liquid-tight membrane wall  38 . 
         [0114]    At least one flow passage  76 , which is formed between a heating unit  32  and an evaporator unit V adjacent thereto and which conducts the hygroscopic solution  70 , is provided in the heating stage  30  such that the hygroscopic solution  70  is heated via the fluid-tight, heat-conducting wall  34  and the vapor arising from the hygroscopic solution  70  arrives in the vapor space  40  through the membrane wall  38 . 
         [0115]    The regeneration stage  80  can also have at least one condensation/evaporation stage  42  which is flowed through by the hygroscopic solution  70  exiting the heating stage  30  and supplied with vapor  92  arising in the heating stage  30  and which comprises at least one condensation unit K and at least one evaporator unit V. 
         [0116]    A respective condensation unit K comprises a first vapor space  46  at least partly bounded by a condensation wall  44 , while a respective evaporator unit V comprises a second vapor space  48  at least partly bounded by a vapor-permeable, liquid-tight membrane wall  38 . 
         [0117]    At least one flow passage  76 , which is formed between such a condensation unit K and such an evaporator unit V adjacent thereto and which conducts the hygroscopic solution  70 , is provided in a respective condensation/evaporation stage  42  such that the hygroscopic solution  70  is heated via the condensation wall  44  and the vapor arising from the hygroscopic solution  70  arrives in the second vapor space  48  through the membrane wall  38 . 
         [0118]    The hygroscopic solution  70  exiting the last condensation/evaporation stage  42  can in particular again be supplied to the gas cooler/absorber stage  72  via a cooler. 
         [0119]    As can additionally be seen from  FIG. 4 , the regeneration stage  80  can moreover comprise a condensation stage  50  having at least one cooling unit  52  and at least one condensation unit, wherein a respective cooling unit  52  comprises a cooling fluid space  54  preferably at least partly bounded by a fluid-tight, heat-conducting wall and a respective condensation unit K comprises a vapor space  46  at least partly bounded by a condensation wall  44 . 
         [0120]    At least one cooling unit  52  is directly adjacent to at least one condensation unit K in the condensation stage  50  such that that the condensation wall  44  of the respective condensation unit K is cooled via the cooling unit  52 . 
         [0121]    Vapor  92  arising in a preceding condensation/evaporation stage  42  can be supplied to the condensation stage  50 . 
         [0122]    The regeneration stage  80  marked by a dashed line in  FIG. 4  and comprising a heating stage  30 , at least one condensation/evaporation stage  42  and preferably a condensation stage  50  is preferably in a vacuum; the cooling fluid and the heating fluid are preferably at environmental pressure and the hygroscopic solution  70  is preferably in a vacuum. In the condensation/evaporation stage(s)  42  and in the heating stage  30 , the hygroscopic solution  70  can in particular be at the boiling temperature corresponding to the absolute pressure in the vapor space of a respective adjacent evaporator unit V over all stages, as is described in WO 2007/054311. 
         [0123]    The heating stage  30  can in particular be flowed through by a heating fluid heated by solar power, for example. 
         [0124]    The gas spaces  58  of the absorber/solution cooler stage  62  and the vapor space  46  of the condensation stage  50  can be connected, for example, via a vacuum line  102  to a vacuum system and to a condenser. The condensation stage  50  is cooled via a cooling fluid  94 , here water for example. Distillate arising in the vapor space  46  of the condensation stage  50  can be led off via a line  104 , for example. 
         [0125]    In another respect, this system described with reference to  FIG. 4  can in particular again at least substantially be designed as was described with reference to  FIG. 2  or  3 . Mutually corresponding parts have the same reference numerals associated with them. 
         [0126]    In particular a solution can again be used as a draw solution for this system described with reference to  FIG. 4  which can be separated and regenerated via vapor pressure differences. 
         [0127]      FIG. 5  shows in a schematic representation an exemplary embodiment of a forward osmosis device  16  in the form of a parallel flow/counter-flow exchanger having e.g. two forward osmosis units  16 ′,  16 ″ connected after one another. 
         [0128]    As can be recognized with reference to  FIG. 5 , the solution  12  to be processed, e.g. seawater, and the draw solution or forward osmosis solution  20  are supplied at one side of the two-stage forward osmosis device  16 . The solutions flow toward one another in every stage or unit  16 ′,  16 ″. 
         [0129]      FIG. 6  shows in a schematic representation an exemplary embodiment of a forward osmosis device  16  in the form of a counter-flow exchanger having e.g. two forward osmosis units  16 ′,  16 ″ connected after one another. The solution  12  to be processed, e.g. seawater, and the draw solution or forward osmosis solution  20  are supplied at different sides of the two-stage forward osmosis device  16 . The solutions flow toward one another in every stage or unit  16 ′,  16 ″. 
         [0130]    The system  10  in accordance with the invention for separating a product  14  contained as a solvent in a solution  12  to be processed can in particular be configured as a modular flow system having a plurality of frame elements  112  and, optionally, in particular end-side plate elements  114  (see also  FIGS. 6 and 7 ). In this respect, the different functional units such as in particular a respective flow passage  18  conducting the solution  12  to be processed, a respective heating unit  32 , a respective evaporator unit V, a respective condensation unit K, a respective cooling unit  52 , a respective gas space  58  and/or a respective gas passage  74  can each be provided in the form of such a frame element. 
         [0131]    In this respect, the frame elements  112  can, such as can in particular also be recognized with reference to  FIGS. 7 and 8 , be provided with web structures  84  via which they can in particular be connected to one another for forming the forward osmosis device  16 , a respective heating stage  30 , a respective condensation/evaporation stage  42 , a respective condensation stage  50 , the heated desorber stage  56 , the combined absorber/solution cooler stage  62 , the gas cooler/absorber stage  72  and/or the regeneration stage  80  provided for regenerating the hygroscopic solution  70 . 
         [0132]    The frame elements  112  can, as likewise again visible from  FIGS. 7 and 8 , each comprise an inner region  88  which is surrounded by an outer frame  86  and which can be provided with an in particular grid-like spacer  90  to whose two sides in particular a respective corresponding functional surface, preferably in the form of a film or membrane, is applied for forming a respective inner space  24 , a respective heating fluid space  36 , a respective vapor space  40 ,  46 ,  48 , a respective cooling fluid space  54 , a respective gas space  58  or a respective inner space or gas space  78 . 
         [0133]    In this respect, depending on the function to be satisfied, a respective frame element can be provided on both sides with a respective membrane, on both sides with a respective film or on the one side with a membrane and on the other side with a film. 
         [0134]    The web structures  84  via which the individual frame elements  112  can be connected to one another can, for example, be welded web structures or bonded structures via which the frame elements are welded or bonded to one another. In the case of welded web structures, a friction welding process, a laser welding process and/or a heating element welding process can be used, for example, for connecting the frame elements. The system in accordance with the invention can be designed in a particularly simple manner and can be varied in the desired manner using the frame elements in accordance with the invention. The frame elements or the devices, units or stages obtained via them are characterized by a relatively simple form and provide different possibilities of the solution supply, gas supply or air supply, cooling fluid supply and heating fluid supply. 
         [0135]      FIG. 7  shows in a schematic representation an exemplary embodiment of a frame element  112  having an inner region  88  which is surrounded by an outer frame  86  and which is provided with a spacer  90  which is grid-like in the present case, for example. As already stated, a respective corresponding functional surface, in particular in the form of a film or membrane, can be applied to the two sides of such a frame element  112 . 
         [0136]    The frame element  112  is here provided e.g. in the corner regions with leadthroughs  106  which are each delineated by a web section  108  from the inner region  88 . A respective further leadthrough  110  is provided in the region of these leadthroughs. As can be recognized with reference to  FIG. 6 , these leadthroughs  110  are, unlike the leadthroughs  106 , not delineated by an additional web section  108 . 
         [0137]      FIG. 8  shows in a schematic, exploded representation an exemplary realization of the forward osmosis device  16  provided in the form of a counter-flow exchanger in accordance with  FIG. 6  using frame elements of the kind shown in  FIG. 7 . In this respect, mutually corresponding parts have the same reference numerals associated with them. 
         [0138]    As can be recognized with reference to  FIG. 8 , two such frame element  112  are provided between two end-side plate elements  114 . 
         [0139]    In the present case, the two frame elements  112  are, for example, each provided with membranes (not shown) at both sides. The frame elements  112 , and preferably also the plate elements  114 , are connected to one another via web structures  84 . 
         [0140]    As can be recognized with respect to  FIG. 8 , the plate elements  114  are also provided with leadthroughs  116 ,  118 . In this respect, the leadthroughs  116  of the plate elements  114  can be aligned in the assembled state with the leadthroughs  106  of the frame elements  112  and the leadthroughs  118  of the plate elements  114  can be aligned with the leadthroughs  110  of the frame elements  112 . The course of the solution  12  to be processed as well as of the draw solution  20  through the assembled forward osmosis device is shown schematically by corresponding lines. 
       REFERENCE NUMERAL LIST 
       [0000]    
       
           10  system 
           12  solution to be processed 
           12 ′ concentrated solution to be processed 
           14  product 
           16  forward osmosis device 
           16 ′ forward osmosis unit 
           16 ′ forward osmosis unit 
           18  flow passage conducting solution to be processed 
           20  draw solution 
           20 ′ diluted draw solution 
           22  flow passage conducting draw solution 
           24  inner space 
           26  semipermeable forward osmosis membrane wall 
           28  product recovery device 
           30  heating stage 
           32  heating unit 
           34  fluid-tight, heat-conducting wall 
           36  heating fluid space 
           38  vapor permeable or gas-permeable, liquid-tight membrane wall 
           40  vapor space 
           42  condensation/evaporation stage 
           44  condensation wall 
           46  first vapor space 
           48  second vapor space 
           50  condensation stage 
           52  cooling unit 
           54  cooling fluid space 
           56  heated desorber stage 
           58  gas space 
           60  gas mixture 
           62  combined absorber/solution cooler stage 
           64  cooling fluid 
           66  gas drying device/cooling device 
           68  gas 
           70  hygroscopic solution 
           72  gas cooler/absorber stage 
           74  gas flow passage 
           76  flow passage conducting hygroscopic solution 
           78  inner space or gas space 
           80  regeneration stage 
           82  cooler 
           84  web structure 
           86  outer frame 
           88  inner region 
           90  spacer 
           92  vapor 
           94  cooling fluid 
           96  gas heater 
           98  cooler 
           100  cooler 
           102  vacuum line 
           104  line 
           106  leadthrough 
           108  web section 
           110  leadthrough 
           112  frame element 
           114  plate element 
           116  leadthrough 
           118  leadthrough 
           120  purified draw solution 
           122  exhaust gas, exhaust air 
           124  vacuum system 
         K condensation unit 
         V evaporator unit