Abstract:
An apparatus and method for the desalinization of salt water utilizing a humidity chamber under partial vacuum and a water collection structure to collect fresh water product. Saltwater having a first temperature and cooling water contained in a condenser having a second temperature lower than the first temperature are introduced into the humidity chamber via a solar powered vacuum pump. A temperature gradient created by a difference in temperature between the saltwater and cooling water in combination with a partial vacuum (e.g., 10-20%) created by a solar powered vacuum pump is used to distill salt-free water from the saltwater with high efficiency. The temperature gradient is created in part by the use of a salinity gradient solar pond. The salt-free water is obtained by condensation of the water on a collection surface cooled by the cooling water followed by collection of the water in a storage apparatus.

Description:
CROSS REFERENCE TO PROVISIONAL APPLICATION 
       [0001]    This application is based upon and claims the benefit of priority from U.S. Provisional Patent Application No. 61/040,569 (Attorney Docket No. 081793-0011) filed on Mar. 28, 2008, the entire contents of which are incorporated by reference herein. 
     
    
     FIELD OF DISCLOSURE 
       [0002]    This disclosure relates to the field of salt-water purification via evaporative desalinization of salt water. 
       BACKGROUND 
       [0003]    Fresh water is a fundamental requirement for modern day societies. Without convenient access to fresh water, resources normally spent in day-to-day activities forwarding the progress of civilization are directed to acquiring water for basic survival. Regions without access to fresh water must either import water, a very costly endeavor, or develop methods to generate fresh water. One method of water generation is desalinization of salt water. 
         [0004]    However, in order to provide enough fresh water for a medium to large size city, desalinization on a large scale must be performed. Large-scale desalination typically requires large amounts of energy as well as specialized, expensive infrastructure, making it very costly compared to the use of fresh water from rivers or groundwater. A number of factors determine the capital and operating costs for desalination: capacity and type of facility, location, feed water, labor, energy, financing and concentrate disposal. As such, one way to lower the cost of a desalinization plant is to utilize cheap and renewable power. In addition, an added benefit of renewable power is in lowering of environmental impact due to the lack of pollutant by-products during the generation of the power. Another method to lower cost is to ensure that the desalinization method is energy efficient and results in a high rate of conversion of salt water to fresh water product. 
         [0005]    U.S. Pat. No. 6,607,639 described a system and method for desalinization featuring condensation of water. However, it does not disclose use of lowering pressure to allow for easier evaporation of saltwater, or the use of solar powered vacuum pumps to save fossil fuels. 
       BRIEF SUMMARY 
       [0006]    The present disclosure addresses the above mentioned problems with an apparatus for the desalinization of salt water utilizing a humidity chamber under partial vacuum and a water collection structure to collect fresh water product. Saltwater having a first temperature and cooling water contained in a condenser having a second temperature lower than the first temperature are introduced into the humidity chamber. A temperature gradient created by a difference in temperature between the saltwater and cooling water in combination with a partial vacuum (e.g., 10-20%) is used to distill salt-free water from the saltwater with high efficiency. The temperature gradient is created in part by the use of a salinity gradient solar pond which heats the salt water to be purified in an economic and pollution free manner. The salt-free water is obtained by condensation of the water on a collection surface cooled by the cooling water followed by collection of the water in a storage apparatus. The evaporation of the water is expedited by the use of a solar powered vacuum pump. 
         [0007]    It is to be understood that the invention is not limited in its application to the details of the construction and arrangement of parts illustrated in the accompanying drawings. The invention is capable of other embodiments and of being practiced or carried out in a variety of ways. It further is to be understood that the phraseology and terminology employed herein are for the purpose of description and not of limitation. 
         [0008]    One embodiment of the present disclosure implements a humidity chamber comprising a saltwater container providing saltwater at a first temperature; a cooling water condenser providing cooling water at a second temperature lower than the first temperature; and a fresh water collection structure. The temperature difference between the saltwater and the relatively cooler water creates a temperature gradient. 
         [0009]    The humidity chamber of the inventive apparatus may comprise a rectangular box configuration having an interior and an exterior. A portion of the saltwater structure may be located along the interior bottom of the humidity chamber, while a portion of the cooling water structure may be located proximate to the interior top of the humidity chamber. A portion of the fresh water collection structure may be located between those portions of the saltwater structure and the cooling water structure found within the interior of the humidity chamber. It will be understood by those skilled in the art that the humidity chamber can assume various configurations including but not limited to a rectangular or a cylindrical configuration. 
         [0010]    A linear relationship exists between the temperature gradient and the rate of condensation induced. The greater the difference between the temperature of the salt water and the temperature of the condensation surfaces in the humidity chamber, the higher the rate at which desalinated water will be produced. Accordingly, it is desirable to create as large a temperature gradient within the humidity chamber as is feasible. 
         [0011]    An embodiment of the saltwater structure comprises a flat plat solar collector in a closed loop configuration with an insulated tank. Heating water which is within the closed loop is heated to a third temperature and stored within the insulated tank. The temperature of the heating water is relatively hotter than the saltwater&#39;s temperature. The heating water is applied to one or more heating coils located within the saltwater basin. Heat emitted from the heating coils will heat the saltwater to a desired temperature. This heated water can be utilized for heating the water to be purified either independently or in combination with other saltwater heating processes, such as thermal tubes. When used in combination, one heating apparatus maintains the temperature of the heated saltwater in the event the companion saltwater heating process is unable to provide adequate heat due to dark period, early morning hours or during periods of non-conducive periods. 
         [0012]    In another embodiment of the present disclosure, a warm water heat exchanger in which water is heated to temperatures as high as 180-190° F. is used to raise the temperature of the salt water. The warm water heat exchanger supplies warm water from a salinity gradient solar pond. A salinity gradient solar pond generally is a body of water that collects and stores solar energy. The salinity gradient pond utilizes the relatively high density of saline over salt-free water to prevent the natural convection of solar heated water. The density of water increases with increasing concentration of salt. Typically, when water is heated, it becomes less dense and rises to the surface of the body of water. However, if the heated water is more dense than the layer of water above, the water will not rise. Accordingly, convection may be significantly reduced or eliminated by having layers of varying salinity. 
         [0013]    A typical salinity gradient solar pond contains three layers: an upper surface layer is cold and is homogeneous with no or low salt content; the bottom layer is hot and homogeneous with a high salt content and therefore is dense and will not rise. The middle gradient layer has a salt content that increases with increasing depth of the pond. In the middle gradient layer, water cannot rise because water above it is lighter, and it cannot fall because the water beneath it is heavier. As a result, the stable gradient layer suppresses convection and acts as a transparent insulator, permitting sunlight to penetrate the upper two layers and heat the bottom layer as well as reducing heat loss from the bottom layer to the upper layer. The heat in the bottom layer can then be withdrawn by pumping the hot brine through an external heat exchanger or by pumping a heat transfer fluid, for example fresh water, through a heat exchanger placed on the bottom of the pond. Salinity gradient solar ponds have the potential to produce low cost thermal energy from a renewable source at large scale for industrial applications. This is due in part to the ability of salinity gradient solar pond to function as a heat storage device. Thus, the solar pond is capable of producing and retaining heat 24 hours per day throughout the summer and winter months. 
         [0014]    As a result from the use of the salinity gradient solar pond, a temperature gradient of from 10 to 70° C. can result between the heated saltwater to be purified and the cooling water which is maintained at a temperature range over a period of time varying from 15 to 70° C. at low cost and low impact to the environment. 
         [0015]    Adjusting the atmospheric pressure affects the boiling point of water. According to Boyle&#39;s law (V 1 P 1 /T 1 =V 2 P 2 /T 2 ), by decreasing pressure, the boiling point of a liquid will be decreased under constant volume. Normally, the boiling point of water is 100° C. at atmospheric pressure (1 barr or 760 torr). A pressure of 0.25 barr (180 torr) is sufficient to lower the boiling point of water to 65° C. A pressure of 0.1 barr (76 torr) will lower the boiling point of water to 45° C. 
         [0016]    In one embodiment of the present disclosure, the pressure of the humidity chamber is decreased by use of a solar powered vacuum pumping system. The solar powered vacuum pump is designed to move water through the closed loop hot and cold heat exchangers. The vacuum is created by the solar powered pumps by creating vacuum in a large cylinder during the day when the pumps receive energy to run, and then the vacuum is stored in the cylinder for night time operations of the water in the heat exchangers. Air is evacuated from the chamber such that the atmospheric pressure is reduced by 10-20%. This pressure lowering is sufficient to increase the rate at which water evaporates and condenses within the humidity chamber. 
         [0017]    Oil sealed pumps and dry rotary pumps may be used in the solar powered vacuum pumping system of the present disclosure. In general, both types of pump rely on confining a volume of gas in a pumping chamber that is reduced in volume before exhausting on the high pressure side of the pump. Various geometric configurations are used in rotary vacuum pumps, including rotary vane pumps and interdigitated shapes rotating on parallel shafts. 
         [0018]    Oil sealed rotary vane pumps comprise a single shaft driving a rotor with sliding vanes; the rotor and vanes rotate within an eccentric stator. The pump may have a single stage or may have two stages in series, with the larger first stage exhausting into a smaller secondary stage. The entire mechanism is immersed in oil for lubrication, sealing and cooling. 
         [0019]    Known configurations of dry pumps include hook and claw, tongue and groove and screw geometries, and Roots pumps, among others. There is no oil in the dry pump mechanism; sealing is instead effected by close running clearances. While the use of oil sealed and dry rotary vacuum pumps are illustrated in this example, those skilled in the art will understand that other known vacuum pumps and methods or reducing the pressure within the humidity chamber are within the scope of this invention. One preferred embodiment is described as follows: Saltwater is fed into the humidity chamber via a saltwater intake line and collected in a salt water container located along the interior bottom of the humidity chamber. The interior bottom of the humidity chamber may be insulated. The saltwater is heated by warm water pumped into the humidity chamber from a warm water exchanger via a warm water intake line. The temperature of the heating water is relatively higher than the temperature of the salt water. The heat emitted from the heated water from the warm water exchanger will heat the saltwater to be purified to a desired temperature. The warm water heats the salt water, and then returns to the warm water exchanger via a warm water return line. As a result of the heating and reduced pressure present in the humidity chamber, the water evaporates into water vapor, leaving behind the other components of the salt water, mainly salt. 
         [0020]    A cooling water condenser is located at the interior top of the humidity chamber. Cooling water is fed from a cool water exchanger into the condenser via a cool water intake line and returned to the cool water exchanger via a cool water return line. One aspect of the cooling water structure of the inventive apparatus comprises a cooling coil located within the humidity chamber and a cold water feed container located outside the humidity chamber which supplies cooling water to the cooling coil by a cold water feed tube. The cooling water is of a temperature sufficient to create a temperature gradient between the temperature of the heated water vapor and the atmosphere in the humidity chamber. As a result of the difference, the water vapor condenses to form desalinized water. A fresh water collection structure is located between those portions of the saltwater container and the cooling water condenser found within the interior of the humidity chamber. During operation of the apparatus, desalinated water is collected via condensation of the water and pumped to a fresh water collection chamber. After operation, the remaining concentrated brine left as a result of evaporation of the water from the salt water is pumped out of the salt water container via a brine concentrate return line. 
         [0021]    One aspect of the fresh water collection structure of the inventive apparatus comprises one or more condensation sheets each of which has a fresh water collection trough. The salt-free water vapor forms as condensation as salt-free water droplets along the condensation sheets. These salt-free water droplets transfer by gravity to the collection trough. The salt-free water is then collected in a salt-free water storage container located outside the humidity chamber by a salt-free water feed tube. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  provides a schematic outline of an embodiment of a process for desalinization provided by the present disclosure. 
           [0023]      FIG. 2  provides a schematic outline of an embodiment of a process for the heating of the saltwater as utilized in the inventive process of the present disclosure. 
           [0024]      FIG. 3  provides a schematic of an additional embodiment of the process for the heating of the saltwater as utilized in the inventive process of the present disclosure. 
           [0025]      FIG. 4  provides a schematic of an embodiment  150  to heat saltwater located within the saltwater basin. 
           [0026]      FIG. 5  provides a perspective view of an embodiment of an apparatus for desalinization provided by the present disclosure. 
           [0027]      FIG. 6  provides a perspective view of an embodiment of a saltwater structure provided by the present disclosure. 
           [0028]      FIG. 7  provides a perspective view of an additional embodiment of a saltwater structure provided by the present disclosure. 
           [0029]      FIG. 8  provides a perspective view of an embodiment of a cooling structure provided by the present disclosure. 
           [0030]      FIG. 9  provides a cross-sectional view of an embodiment of salt-free water condensation and collection structure provided by the present disclosure. 
           [0031]      FIG. 10  provides a side cross-sectional view of an embodiment of salt-free water condensation and collection structure provided by the present disclosure. 
           [0032]      FIG. 11  provides a perspective view of an embodiment of a desalinization plant according to the present disclosure. 
           [0033]      FIG. 12  provides a side view of an embodiment of the solar powered vacuum pump system controlling the water level in the water tank. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]      FIG. 11  illustrates the general desalinization operation of one embodiment of the present disclosure. Saltwater is fed into the humidity chamber  12  via a saltwater intake line  24 . The saltwater is heated by warm water pumped into the humidity chamber  12  from a warm water exchanger  90  via a warm water intake line  96   a . The temperature of the heating water is relatively higher than the temperature of the salt water. The heat emitted from the heated water from the warm water exchanger will heat the saltwater to be purified to a desired temperature. The warm water heats the salt water, and then returns to the warm water exchanger  90  via a warm water return line  96   b . Vacuum pump  8  evacuates air from the humidity chamber  12  such that the pressure in the humidity chamber  12  is reduced allowing for more efficient evaporation of water. As a result of the heating and reduced pressure present in the humidity chamber  12 , the water evaporates into water vapor, leaving behind the other components of the salt water, mainly by salt. 
         [0035]    Cooling water is fed from a cool water exchanger  44  into the humidity chamber  12  via a cool water intake line  46   a  and returned to the cool water exchanger  12  via a cool water return line  6 . The cooling water is of a temperature sufficient to create a temperature gradient between the temperature of the heated water vapor and the atmosphere in the humidity chamber  12 . As a result of the difference, the water vapor condenses to form desalinized water. During operation of the apparatus, desalinated water is collected via condensation of the water and pumped to a fresh water product collector  60 . After operation, the remaining concentrated brine left as a result of evaporation of the water from the salt water is pumped out of the humidity chamber  12  to be stored in a brine concentrate collector  9  before removed via the brine concentrate return line  11 . 
         [0036]      FIG. 1  illustrates a schematic of an embodiment  100  of the process of the present disclosure. Embodiment  100  comprises introducing saltwater having a first temperature and cooling water having a second temperature, which is cooler than the first temperature of the saltwater, into a humidity chamber as illustrated in steps  110  and  112 . The temperature difference creates a temperature gradient which establishes an atmosphere suitable for the evaporation of saltwater as illustrated in steps  114  and  116 . When the saltwater is evaporated, the salt-free water molecules separate as salt-free water vapor from the salt-related constituent compounds; The salt-free water vapor then condenses as droplets on a salt-free water collection structure as illustrated in step  118 . The salt-free water droplets are then collected as illustrated in  120 . 
         [0037]      FIG. 2  illustrates a schematic of an embodiment  130  of the process for the heating of the saltwater as utilized in a process of the present disclosure. Embodiment  130  comprises storing saltwater in a saltwater storage container, as illustrated in step  132 , then introducing the saltwater into a series of thermal tubes, as illustrated in step  134 . The saltwater is then heated to a first temperature and then introduced into a saltwater basin located within the humidity chamber, as illustrated in steps  136  and  138 , where it will then evaporate. 
         [0038]      FIG. 3  illustrates a schematic of an additional embodiment  140  of the process for the heating of the saltwater as utilized in a process of the present disclosure. Embodiment  140  comprises introducing saltwater from a saltwater storage container into a saltwater basin located within the humidity as illustrated in steps  142  and  144 . The saltwater is then heated to a first temperature by way of a closed loop heated water assembly as illustrated by step  146 . 
         [0039]      FIG. 4  illustrates a schematic of an embodiment  150  to heat saltwater located within the saltwater basin. As illustrated in steps  152  and  154 , water is heated by a flat plate solar collector and stored in an insulated tank or obtained from a salinity gradient solar pond. The heated water is then released in to heating coils located within the saltwater basin residing in the humidity chamber, as illustrated in steps  156 . The saltwater located within the saltwater basin is then heated via the heated water to an acceptable temperature for evaporation as illustrated in steps  158 . While the close loop heating process is illustrated as being used independently, those skilled in the art will recognize that this process can be used in combination with other heating processes, such as the thermal tube heating process. 
         [0040]    As shown in  FIG. 5 , an embodiment  10  of the apparatus comprises a humidity chamber  12 , a saltwater container  20 , a cooling water container  40  and a salt-free water collecting container  50 . Saltwater container  20  provides saltwater  30  having a first temperature into humidity chamber  12 . Cooling water container  40  provides cooling water  48  having a second temperature, which is relatively cooler than the temperature of the saltwater, into humidity chamber  12 . The temperature difference between saltwater  30  and cold water  48  creates a temperature gradient which establishes suitable atmospheric conditions for the evaporation of the saltwater. During this evaporation process, salt-free water evaporates into water vapor while the salt and salt-related constituent compounds do not. The salt-free water vapor then condenses on salt-free water condensing and collection container  50 . The salt-free water condensation is then collected for later use. 
         [0041]    Humidity chamber  12  is shown in a general rectangular box configuration having a top  16  a bottom  18  and four side walls  14 . While humidity chamber  12  is shown in a generally rectangular configuration, those skilled in the art will understand that such configuration is for illustrative purposes and other various configurations, including, but not limited to a cylindrical configuration, can be utilized and is within the scope of this invention. 
         [0042]    As shown in  FIG. 6 , one embodiment of saltwater container as comprising a thermal tube apparatus  27  having a saltwater feed container  28  located outside of the humidity chamber  12 , a saltwater basin  26  located within the humidity chamber  12  and one or more thermal tubes  22  which can be located atop humidity chamber  12 , each of which are connected by various portions of saltwater feed tube  24 . Thermal tubes  22  can be made of any material which can heat saltwater to a sufficient first temperature, such as but not limited to plastic or aluminum. While thermal tubes  22  are illustrated atop humidity chamber  12 , those skilled in the art will understand that thermal tubes  22  could be located at some other location still stay within the scope of this invention. 
         [0043]    Saltwater  30  is stored within saltwater feed container  28 . It is then provided to thermal tubes  22  through a portion of saltwater feed tube  24  where it is heated to a first temperature. After it has been heated, saltwater  30  is then provided into saltwater basin  26  to await evaporation once sufficient atmospheric conditions are created. 
         [0044]    As shown in  FIG. 7 , another embodiment of saltwater container  20  comprises a saltwater feed container  28  located outside of the humidity chamber  12 , a saltwater basin  26  located within the humidity chamber  12 , each of which are connected by various portions of saltwater feed tube  24 , and water heating structure  90 . Water heating structure  90  comprises a flat plate solar collector  92  in communication with an insulated tank  94  via a series of heat tubes  96  in a closed loop. One or more heat coils  98  resides within saltwater basin  26 . Heating water  93  is stored in insulated tank  94  and is heated by solar collector  92 . As heating water  93  flows through heat coils  98 , the saltwater  30  which is located within saltwater basin  26  is heated. 
         [0045]    Another embodiment of saltwater container involves the incorporation of both the thermal tubes apparatus  27  and the water heating structure  90 . The thermal tube apparatus  27  is configured and used as set out above. The water heating structure  90  heats and stores heating water  93  in the insulated tank  94  as set out above. During dark periods or extended periods without sunlight, the temperature of saltwater  30  drops. To keep this temperature at an acceptable level, water heating structure  90 , through the use of a thermostat controlled valve, circulates heating water  93  through heat coils  98 . 
         [0046]    As shown in  FIG. 8 , one embodiment of cooling container  40  comprises a cooling coil  42  located proximate to the top  16  of humidity chamber  12 . A cold water feed container  44  provides cold water  48  through the cooling coil  42  through cold water feed tube  46 . Cold water  48  has a second temperature which is less than the temperature of saltwater  30 , the difference between which creates a temperature gradient. 
         [0047]    Cooling coil  42  is generally shown in a general switchback configuration. However, to those skilled in the art, various other configurations are within the scope and spirit of this invention. Additionally, cold water feed tube  46  and saltwater feed tube  24  can be made from any suitable material such as but not limited to copper piping. 
         [0048]    As shown in  FIGS. 9 and 10 , one embodiment of salt-free water condensation and collection container  50  is illustrated and- comprises a condensation sheet  52  located within humidity chamber  12  between saltwater basin  26  and cooling coil  42 . The portion of condensation sheet  52  proximate to cooling coil  42  is referred herein as upper portion  54 . The portion of condensation sheet  52  proximate to saltwater basin  26  is referred herein as lower portion  56 . 
         [0049]    Upper portion  54  is secured to cooling coil  42  by way of a transfer sheet  55 . Transfer sheet  55  can be made from any suitable material. One preferred material is, but not limited to, copper. While the use of transfer sheet  55  is illustrated to connect upper portion  54  to cooling coil  42 , those skilled in the art will understand that other known connection devices and methods are within the scope of this invention. 
         [0050]    Due to the varying temperatures within the chamber  12 , the salt-free water vapor will condense on condensation sheet  52  as salt-free water droplets  64  which cascade down into salt-free water collection trough  58  which is secured to lower portion  56  of condensation sheet  52 . The collected salt-free water  64  is then provided into salt-free water collection basin  60  by way of salt-free water collection tube  62 . 
         [0051]    As is shown in  FIG. 9 , the present disclosure may utilize a single collection sheet  52 , or multiple collection sheets and collection troughs  58  may be utilized. 
         [0052]    The operation of one embodiment of the solar powered pump  200  is described in  FIG. 12 . Instead of stored vacuum in a cylinder, a solar powered vacuum pump is used. The brown tubing represents one closed loop heat exchanger  210  and the water throughout the system is maintained at a constant water level in the water tank  240 . To operate the system, Valve A and Valve B are opened and Valve C and Valve D are closed. Valve A admits water into the water elevation column  220  which then rises because Valve B is opened to the vacuum chamber and the vacuum pump  200 , and the reduced air pressure in the column relative to ambient pressure causes the water  230  to rise. Once the rise reaches a maximum level, Valve A and Valve B are closed and Valve C and Valve D are opened. Valve C admits outside air returning the air pressure in the water elevation column  220  to ambient and the water in the water elevation column  220  flows through Valve D and into the water tank  240  and ultimately the feed end of the closed loop heat exchanger  210 . Only a small fraction of the stored vacuum energy is used during each cycle, so pumping large amounts of water through the heat exchanger system can be accomplished 24 hours per day. Moreover, as the pump only uses solar energy, no power will be required from grid electricity or fossil fuels for pumping purposes. 
         [0053]    While the invention has been described with a certain degree of particularity, it is manifest that many changes may be made in the details of construction and the arrangement of components without departing from the spirit and scope of this disclosure. It is understood that the invention is not limited to the embodiments set forth herein for purposes of exemplification, but is to be limited only by the scope of the attached claims, including the full range of equivalency to which each element thereof is entitled.