Abstract:
A single chamber adsorption concentrator unit is described that utilizes low grade heat to drive an adsorbent/adsorbent working pair to separate a solvent from a solute/solvent mixture. One preferred application of the device of the present invention is separating water from the salt brine produced by the aluminum smelting industry. The brine solution is introduced into a single chamber shell proximate the concentrator evaporator where the water in the brine can freely evaporate and the resulting water vapor freely flow without inhibition to be either absorbed into the adsorbent modules or condensed by the condenser. The free flow of water vapor is facilitated by continuous operation of the condenser and by maintaining the brine solution at a higher temperature than the cooling fluid driving the condenser. A mist eliminator with a wash down feature located intermediate to the evaporator and the silica gel is provided to collect contaminants that may be carried from the evaporator by the vigorous boiling.

Description:
INTRODUCTION 
       [0001]    This invention relates generally to the application and utilization of a heat driven engine to improve the efficiency of separation of a brine waste stream. Specifically this invention describes the use of low grade waste heat to drive a novel, single chamber adsorption type heat driven engine that removes the excess solvent, water, from the brine offal of the secondary aluminum smelting process, reducing the need to provide higher quality energy to this separation process. The device is also useful for extracting water from other solute/solvent mixtures. 
         [0002]    Heat driven engines, including adsorption chillers, are well known by those in the art. The work output of an adsorption chiller is typically chilled water used for air conditioning, process cooling or numerous other useful purposes. The chilled water circuit in a typical adsorption chiller is a closed loop, sometimes with the end load in communication with the chiller and often with a heat exchanger in the loop to isolate the chiller from the potential contaminates of the end load. A typical adsorption chiller comprises multiple chambers separated by valved walls or barriers. 
         [0003]    Co-pending application Ser. No. 12/550,290 entitled “Improved Adsorbent—Adsorbate Desalination Unit And Method,” describes an open loop adsorption concentrator system having an internally divided housing and utilizing silica gel and water as the preferred working pair (the “&#39;290 Application”). The &#39;290 Application introduces an economizing heat exchanger and a mist eliminator as new techniques to handle the needs of such an open loop system. As with prior art adsorption chillers, the pressure vessel of the &#39;290 Application is a multi-chambered shell interconnected by a plurality of valves which open and close to intermittently prohibit and allow the flow water vapor from chamber to chamber within the pressure vessel. 
         [0004]    The present invention describes an open loop in the evaporator of a single, open chamber adsorbent/adsorbate system optimized for use as a concentrator for the heavy salt brines found as an offal or waste product of the aluminum smelting industry. The challenges involved in handling and separating such heavy salt brines require further improvements to an open loop system as described in the &#39;290 Application. The construction of the concentrator is simplified to eliminate the internal vapor barriers and moving valves to avoid contamination and malfunction of these features. The elimination of the vapor valves opens the condenser to the uninhibited vapor flow from the evaporator. Another innovation in the present invention is the circulation of cooling water in the condenser at all times, without the cycling typically found in a standard adsorption chiller. After cooling water is run through the condenser, it is selectively used to cool the adsorbent and thus drive the adsorption cycle. In this manner, the isosteric heat of adsorption may then be reclaimed by the cooling water and put back into the concentrator system by feeding it into the brine heat exchanger. 
         [0005]    A wash down feature on the mist eliminator is also added to maintain proper function in light of the high levels of salt drift contamination. 
         [0006]    Another novel feature of the present invention is the use of a brine heat exchanger and an optional degasser, external to the vacuum shell, to heat and de-gas the brine before it is introduced into the evaporator. Recirculation of brine through the brine heat exchanger is essential to maintaining the brine at a temperature above that of the cooling water and the condenser so that a partial pressure differential is maintained between the upper area and lower areas within the shell, thereby creating a continuous vapor flow within the shell. 
         [0007]    Yet another feature of a preferred embodiment of the present invention is the utilization of an evaporator within the shell. Finally, evaporation may also be enhanced by flowing the brine over a high surface area, porous fill media. 
         [0008]    This disclosure will describe specifically a single chamber adsorption concentrator with an open loop in the evaporator for the extraction of water from a solute/solvent mixture having particular application to the brine slurry produced as a waste stream from the aluminum smelting process. For this application, silica gel and water or zeolite and water are the preferred choices for the adsorbent/adsorbate working pair of this invention. The novel modifications of a typical adsorption chiller necessary to support this heavy brine in an open loop system will be evident upon examining the detailed description and associated figures included in this specification. 
         [0009]    While this invention will describe the application of a silica gel and water working pair to the application of separating water from the aluminum brine in an adsorption concentrator, it is understood by the inventors that this same process could be adapted to solvent extraction from many different types of brines, slurries, contaminated streams of solvents and similar mixtures provided that the solute is non-volatile in a vacuum. Silica gel and zeolite are suitable choices where water is the solvent; however other types of adsorption working pairs would also make it possible to extract other solvents from additional types of fluid slurries or mixtures. Such mixtures might be alcohol and water or water and oil. 
       BACKGROUND OF THE INVENTION 
       [0010]    In the aluminum industry there are two general types of processing plants: primary smelting operations and secondary smelting operations. The primary processing plants start with the mining operations and the conversion of raw alumina ore into the finished aluminum ingots or products. Secondary smelting plants use scrap aluminum as the raw materials to be processed. The two processes share many similarities once the basic aluminum is formed. Both produce a series of waste products that must be cleaned, separated, recycled and reclaimed. 
         [0011]    Aluminum secondary smelting (scrap recycling) accounts for approximately 33% of all aluminum produced in the U.S. There are approximately 68 major secondary processing plants in the U.S. These processing plants are typically located near large urban areas where large supplies of scrap aluminum are available. Such locations, however, also place these plants in areas where the environmental impact of the plant&#39;s operations is carefully measured and monitored. 
         [0012]    The re-melting process of the aluminum produces a solute/solvent mixture or brine which typically comprises one or more solvents, typically substantially water, and one or more solutes including but not limited to metallic aluminum (typically about 10% by weight), aluminum oxide (typically about 50% weight), and a mixture of potassium salts and chloride salts, notably potassium chloride and sodium chloride (typically about 40% weight), and other solutes resulting from aluminum smelting processes. In current processes, the salts are separated from the insoluble aluminum oxide in a hot leach step. The solution of saturated potassium chloride and sodium chloride contained in the brine are then crystallized by evaporating the water in an energy intensive process, typically electric motor-driven vapor recompression or fuel-fired thermal brine concentration. The present invention relates to an improved means and method to remove water from the brine, making the process more efficient and economical. The resulting products of the separation, the distilled water and the concentrated salts, can all be reclaimed and recycled. 
       BRIEF SUMMARY OF THE INVENTION 
       [0013]    This invention describes the application of low grade heat to drive a heat driven engine that will separate water from a brine solution. Specifically, this invention will describe a heat driven engine of the adsorption type using an adsorbent/adsorbate working pair. In this invention, the preferred working pair is silica gel and water and the evaporator section of the device will be an open loop system. The pressure vessel or shell of the present invention is a hollow, single, relatively open space, not divided into compartments or chambers. The solvent is water and the solute is a combination of potassium-chloride and sodium-chloride salts. The water for the working pair will be the water being evaporated from the brine that is continuously or intermittently introduced into the evaporator from other processes. 
         [0014]    Closed loop process fluid (water) will be used to connect the adsorption concentrator heat exchangers to the external sources of the cooling and heating. 
         [0015]    The heat required to drive the adsorption concentrator will be available as low quality waste heat from the smelting process that would otherwise typically be rejected to the atmosphere as a heat sink by means of a heat dump such as a body of water or an atmospheric cooling tower. 
         [0016]    This adsorption concentrator uses an adsorbent-adsorbate working pair of silica gel and water cycling between adsorption and desorption. During the adsorption period, water is evaporated from the brine and adsorbed in the silica gel. The heat of evaporation is removed from the brine. The isosteric heat of adsorption is deposited into the silica gel as it adsorbs the water vapor. This isosteric heat is removed from the adsorbent silica gel during this period by circulating cooling water through the silica gel modules. The heat of evaporation removed from the brine is replaced with isosteric heat by use of an external heat exchanger in the recirculating brine loop. 
         [0017]    When the silica gel is saturated, the adsorption process is halted and the desorption process is initiated. The desorption period dehydrates the silica gel by reintroducing the isosteric heat to the silica gel, warming the silica gel and driving the water vapor from the silica gel. The water vapor is condensed back into liquid water in the condenser. This desorption process creates a demand for low quality waste heat that was previously discarded and provides an opportunity for a gain in efficiency in the overall smelting process. 
         [0018]    In the preferred embodiment, a new supply of source brine is continuously introduced into the evaporator of the adsorption concentrator. Upon introduction, the temperature of the brine will be relatively hot as a result of the smelting process through which it was created. The introduction of relatively hot brine to the evaporator hastens the evaporation of the water from the brine. The water being evaporated from the brine is adsorbed and stored in the silica gel or, since all components are housed within the single chamber of the hollow shell, may be condensed directly by the condenser. 
         [0019]    Water evaporation from the brine results in an increase of the concentration of the solutes in the brine collected in the sump. In other words, the brine not evaporated has a greater solute concentration than the source brine. The un-evaporated brine is recirculated to be sprayed over the evaporator multiple, times with reheating through a brine heat exchanger on each pass. In practice, the temperature of the brine heat exchanger, the rate of introduction of relatively hot source brine, the rate of recycling of un-evaporated brine, and the rate at which concentrated un-evaporated brine is removed from the concentrator can be coordinated in order to achieve a desired equilibrium in the solute concentration of the un-evaporated brine in the sump. These process variables can be optimized to produce a concentrate brine that has a much greater concentration of solutes than the source brine. Constant recirculation and the agitation caused by re-introduction of the brine into the concentrator are essential to achieving the desirable higher concentration of solutes in the concentrated brine. This constant circulation keeps the brine in a uniform concentration and at a relatively high temperature. 
         [0020]    When the silica gel becomes saturated, the adsorption process will be halted and a desorption cycle is initiated. During the desorption cycle, hot water is introduced to the silica gel modules to warm them and drive off the water vapor through desorption. The water vapor will be drawn to the condenser along a vapor pressure differential created between the condenser and the areas surrounding the silica gel and the evaporator. In the condenser, the vapor is condensed to a liquid and withdrawn from the concentrator through a sump as distilled water. 
         [0021]    Cooling water is circulated through the condenser at all times. After passing through the condenser, the cooling water will be selectively passed through the silica gel modules during the adsorption cycle or passed directly to a cooling tower heat exchanger for cooling and recirculation back to the condenser. 
         [0022]    When the concentrator is in the adsorption period, because the shell is open throughout without any compartmentalization or intermittent barriers such as opening and closing valves, some water vapor will be condensed directly from the evaporator as allowed by the differences in the temperatures and partial pressures. During the desorption period, the area within the shell about the condenser will have the lowest relative partial pressure compared to other areas within the shell because the cooling is continued during the desorption period, resulting in water vapor condensing out of the vapor phase and into the liquid phase. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    The particular features and advantages of the invention as well as other objects will become apparent from the following description taken in connection with the accompanying drawings in which: 
           [0024]      FIG. 1  is a schematic view of the adsorption concentrator of the present invention. 
           [0025]      FIG. 2  is a schematic view of one embodiment of the adsorption concentrator of the present invention. 
           [0026]      FIG. 3A  is a schematic diagram of the four-way valve shown in  FIG. 2  as reference  65  as positioned during the desorption cycle. 
           [0027]      FIG. 3B  is a schematic diagram of the four-way valve shown in  FIG. 2  as reference  65  as positioned during the adsorption cycle. 
           [0028]      FIG. 4  is a schematic view of a second embodiment of the adsorption concentrator of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0029]      FIG. 1  shows the principal elements of an adsorption concentrator  5  according to the present invention. These elements are housed in a single chamber, substantially hollow, vacuum tight enclosure of a concentrator housing or shell  10 . A vacuum is maintained within the shell  10 . At or near the lower area or lower end  40  of the shell  10 , within the shell  10 , is an open loop evaporator  11 . A source solute/solvent mixture or brine solution to be distilled is fed into an open loop evaporator  11  through the hot brine input line  12  and is substantially continuously distributed about, across or upon the evaporator  11 , such as by spraying it through one or a plurality openings, such as brine spray nozzles  13  positioned about the portion of the hot brine input line  12  within the shell  10 . That portion of the brine that is not evaporated upon introduction into the near vacuum about the evaporator  11  falls and is collected as a concentrated brine in an evaporator sump  14  at the lower end  40  of the concentrator shell  10  where it is pulled, such as by a pump means (not shown), through a vacuum trap or other pressure-maintaining drain  43  designed to allow removal of the concentrated brine solution without significantly affecting or changing the pressure within the shell  10 . The drain  43  is connected to a brine output line  15  and recirculated across the evaporator  11 . The concentrated brine is directed through the brine output line  15  or other appropriate plumbing, either back into the hot brine input line  12 , or, alternately, to a brine output line (not shown in  FIG. 1 ). During the start-up of the concentrator  5 , it may be necessary to recirculate all of the concentrated brine until the desired concentration of solutes in the concentrated brine is achieved. Otherwise, once the desired solute concentration is achieved, a portion of the concentrated brine is substantially continuously recirculated while a second portion of the concentrated brine is substantially continuously removed through the brine output line (shown as  26  in  FIG. 2 ). 
         [0030]    The evaporator  11  of the present invention may comprise any suitable evaporator common in the art, including both passive or active evaporators  11 . In one preferred embodiment, the evaporator  11  comprises a passive evaporator functioning as a means for maximizing the surface area over which a fluid is distributed. A passive evaporator may comprise any physical structure providing suitable surface area over which fluid can traverse substantially unimpeded under the influence of gravity. Maximizing the surface area over which the brine is sprayed increases the rate of evaporation. Alternatively, the evaporator  11  may comprise an active evaporator such as a heat exchanger connected to an external heating source, such as a flow of hot fluid through the evaporator  11 . 
         [0031]    Returning to  FIG. 1 , in one preferred embodiment, the evaporator  11  may comprise a first portion of its surface  17  positioned above the normal operating level  19  of the solute/solvent mixture in the evaporator sump  14  and a second portion of its surface  18  positioned below the normal operating level  19  of the solute/solvent mixture in the sump  14 . In another embodiment, shown in  FIG. 2 , the portion  18  of the evaporator  11  below or within the level  19  of the solute/solvent mixture of the sump  14  may further comprise a porous, high surface area fill media  16  intended to add surface area and thereby enhance evaporation of the brine solution from the sump  14 . For purposes of this disclosure, the term “evaporator”  11  may comprise either submerged portion  18 , unsubmerged portion  17 , or both portions  18 ,  17  of the evaporator  11 . 
         [0032]    Interposed within the concentrator shell  10  between the evaporator  11  and the adsorbent modules, such as silica gel modules  50 , is a mist eliminator  35 . The mist eliminator  35  functions to substantially prevent brine contaminants from entering the adsorbent modules  50 . Adsorbent modules  50  are positioned within the shell  10  above the mist eliminator  35 , between the mist eliminator  35  and the condenser  75 , proximate to the upper area  41  of the concentrator shell  10  in which the condenser  75  is positioned. 
         [0033]    The mist eliminator  35  functions to prevent passage of water droplets and other brine contaminants and particulates upward from the evaporator  11  to the adsorbent modules  50  or condenser  75  and to collect water droplets and contaminants from the air and vapor stream and divert the liquid and contaminants back to the evaporator  11  and sump  14 . However, the mist eliminator  35  does not materially impede or inhibit the free flow of water vapor within the shell  10 . The mist eliminator  35  provides a large surface area in a small volume of space to collect liquid without substantially impeding air or vapor flow. Mist eliminator  35  may comprise any number of physical structures known in the art for creating a tortured path for an air stream to follow, thereby providing ample surface areas upon which water droplets in the air stream can collect. The results achieved by a mist eliminator  35  will depend on proper specification of mist eliminator type, such as mesh, vane or fiber bed (or a combination of types), orientation, thickness, internal details, support and spacing in the vessel, vapor velocity and flow pattern, and many other considerations. The mist eliminator  35  of the present invention may be designed in one or more elements or screens for easy removal from the shell  10  through a pressure-sealed opening (not shown) for cleaning or replacement. 
         [0034]    A mist eliminator input line  36  is provided to carry and dispense fluid with which to wash the captured contaminants and particulates from the mist eliminator  35 , either periodically or continuously, by injecting a hot fluid, such as the preferred water, or another suitable fluid, through a plurality of openings positioned about the portion of the mist eliminator input line  36 , within the shell  10  such as mist eliminator spray nozzles  37 . The fluid is dispensed upon the width and breadth of the mist eliminator  35  to wash captured contaminants and particulates back into the brine in the brine sump  14 . 
         [0035]    An array of one or more modules carrying an adsorbent which can be regenerated or, for short, adsorbent modules, such as silica gel modules  50 , is located near the upper area  41  of the concentrator shell  10 . The array of adsorbent modules  50  is alternately used for adsorption and desorption of water vapor by altering the temperature of the fluid, such as water, flowing through a module fluid circuit (comprising lines  51 ,  52  and modules  50 ) running through the modules  50 . When cooling fluid, such as cooling water, is pumped into the module input line  51 , the cooling fluid passes through the adsorbent modules  50  and the adsorbent will cool and adsorb water vapor rising from the evaporator  11 . Such adsorption creates a relatively lower partial pressure in the area  44  of the shell  10  about the adsorbent modules  50 . When hot temperature fluid, such as the preferred hot water, is pumped into the module fluid circuit, the adsorbent modules  50  will be heated to a higher temperature and will desorb the collected water back into water vapor. Desorption creates a relatively higher partial pressure in the area  44  within the shell  10  about the adsorbent modules  50  and the water vapor will tend to flow away from this zone of higher partial pressure towards the relatively constant area  41  of relatively lower partial pressure about the condenser  75  which is created as water vapor is condensed into water at the condenser  75 . 
         [0036]    To drive condensation, a cooling fluid, preferably water, preferably having a temperature lower than the temperature of the brine, will be circulated through the condenser  75  positioned within the upper area  41  of the concentrator shell  10  substantially continuously during operation of the concentrator  5 . When the adsorbent modules  50  are in the desorption mode, desorbed water vapor will collect in the area  41  about the condenser  75  quickly as it is driven from the higher temperature and higher partial pressure area  44  about the adsorbent modules  50  and will condense back to a liquid form. When the adsorbent modules  50  are in an adsorption mode, the area  41  about condenser  75  may still be at a sufficiently low temperature and partial pressure relative to the area  44  about the modules  50  to continuously attract and condense some water vapor formed at the evaporator  11 , albeit at a slower rate. Additionally, because the shell  10  is not compartmentalized, that is, it is without non-permeable barriers dividing the interior of the shell  10  to restrict or otherwise permanently or temporarily or intermittently inhibit the substantially free flow of gas or water vapor to all areas within the shell  10  (such as with valves that are opened and closed periodically), it is contemplated that at least a portion of the water vapor from the evaporator  11  may bypass adsorption into the silica gel of the adsorbent modules  50  and be directly condensed into water at the condenser  75 . 
         [0037]    The condensate or distilled water from the condenser  75  is collected in a condenser sump  100  where it is directed out of the concentrator shell  10  through a vacuum trap or other pressure-maintaining drain  43  to a condenser drain line  101 . The distilled condensate water leaving the adsorption concentrator  5  represents one of the useful products of the invention. This condensate water is a clean, pure, distilled water that can be used for any desired purpose. 
         [0038]    A vacuum pump  110  is provided to create and maintain the initial vacuum within the shell  10 , and, as needed, to reduce the gas pressure inside the concentrator shell  10  by removing any non-condensable gases that may be introduced into the concentrator shell  10  by the brine. The reduced pressure created by the vacuum pump  110  inside the concentrator shell  10  improves the efficiency of the invention by reducing the temperature at which the water will boil from the brine and enhancing the desorption process. The vacuum pump  110  is connected to the concentrator shell  10  by a vacuum pump line  111 . 
         [0039]    The temperature of the condenser  75  is limited by the temperature of the cooling fluid entering the condenser input line  71 , circulating through the condenser  75  and exiting through the condenser output line  72 . In contrast, the temperature of the adsorption modules  50  varies depending upon whether cooling fluid or heating fluid is circulated through the module fluid circuit. Similarly, because of the heat of the relatively hot source brine and the re-heating by the brine heat exchanger through which it is passed, the recirculated condensed brine is maintained at a temperature higher than the condenser  75  and the cooling fluid by which the condenser  75  is driven. Maintaining the brine and the area  40  within the shell  10  about the evaporator  35  at a higher temperature than the temperature of the condenser  75  and the area  41  within the shell  10  about the condenser  75  creates a temperature gradient and partial pressure differential along which the water vapor will flow continuously during operation of the condenser  5 . 
         [0040]      FIG. 2  illustrates the complete brine concentrator system  30 , including ancillary equipment and components that are used to control the function of the adsorption concentrator  5 . Certain of these components may comprise an integral part (i.e., within the shell  10 ) of the adsorption concentrator  5  unit itself, while other components, such as heat exchangers  20 ,  80  and pumps  25 ,  70 ,  83  and external plumbing would typically be external to the concentrator  5  and are specifically adapted to suit the physical environment in which the concentrator  5  is to operate. 
         [0041]    Brine from a source (not shown) is introduced to the concentrator system  30  through a brine feed line  21  which passes the brine through a conventional degasser  27 . The degasser removes the volatile gases from the brine before it enters the adsorption concentrator  5 , reducing the load on the vacuum pump  110 . The degasser also increases the efficiency of the adsorption concentrator  5  by improving the vacuum level in the evaporator  11 . As illustrated in  FIG. 2 , the degasser  27  may be positioned along the brine feed line  21  before the brine heat exchanger  20 . 
         [0042]    The brine is introduced into the shell  10  at a relatively hot temperature from between about 100° F. to about 120° F., typically about 110° F., or such other temperature at which it may be substantially upon being generated through the smelting process. In practice, it is preferable to maintain the brine at a temperature above the temperature of the cooling fluid used to drive the condenser  75  and adsorption in the adsorbate modules  50 . 
         [0043]    A brine feed control valve  22  controls the source of the brine input to the brine heat exchanger  20  by selectively allowing a feed of brine from one or more sources. A portion of the hot brine input line  12  passes into the shell  10  for spraying or disbursing the brine proximate to the evaporator  11 . 
         [0044]    To enhance evaporation of water and separation of water from the solutes in the brine, the brine is substantially continuously recirculated through a brine recirculating circuit between the evaporator sump  14  and the brine heat exchanger  20  and back to the sump  14  after having been disbursed again across the evaporator  11 . The brine is recirculated by a pump means, such as brine recirculation pump  25  in the brine recirculating circuit. The brine recirculating circuit comprises brine output line  15 , pump means  25 , brine recirculation line  23  running to a brine heat exchanger  20 , and evaporator input line  12  for circulating heated brine from the brine heat exchanger  20  back into the area  40  about the evaporator  11 . In this circuit, brine from the sump  14  is reheated then carried back through the evaporator input line  12  for re-distribution across the evaporator  11 . The recirculated brine passes through the brine heat exchanger  20  on each recirculation pass. After initial start-up of the concentrator  5 , once the concentration of solutes in the brine in the sump  14  reaches the desired level, the brine recirculation valve  24  is partially opened to allow a portion of the concentrated brine to be removed from the concentrator system  30  through the brine output line  26  at the desired rate while another portion of the concentrated brine is recirculated. Though not essential to the proper functioning of the concentrator  5 , it is preferable that the operation of the brine recirculation valve  24  and the brine feed control valve  22  be coordinated so that fresh brine is substantially continuously added along with the recirculated concentrated brine. Similarly, through not essential, it is preferable that concentrated brine is continuously removed from the concentrator  5  once the desired concentration has been achieved. 
         [0045]    The area  40  of the adsorption concentrator  5  about the evaporator  11  is maintained at a relatively high temperature by the introduction of relatively hot source brine and the recirculation of concentrated brine through the brine heat exchanger  20  to promote the evaporation of water in the brine. The relatively high temperature of the brine in the evaporator  11  and the evaporation of water from the brine into water vapor produces a relatively high partial pressure in the area  40  about the evaporator  11  within the adsorption concentrator  5 . 
         [0046]    The heat that is added to the brine as it passes through the brine heat exchanger  20  is provided from a hot water supply line  56  that supplies hot water from a hot water source (not shown) to the brine heat exchanger  20 . In one preferred embodiment, heat may also be provided in part by directing all or a portion of the cooling fluid which has gained isosteric heat of adsorption in the adsorption modules  50  as it was used to drive adsorption during the adsorption cycle. 
         [0047]    During the adsorption period of the cycle, the silica gel in the modules  50  is cooled by the introduction of cooling water at a temperature range expected to be between about 50° F. to about 100° F., preferably at a temperature below the temperature of the brine as it is introduced into the adsorption concentrator  5 , such as at about 85° F. to about 90° F. This cooling water removes the isosteric heat of adsorption from the adsorbent modules  50  that has been deposited during the adsorption process. This allows the silica gel itself to create a partial pressure near zero in the area  44  about the modules  50 . The differential pressure between the area  44  within the shell  10  about the adsorbent modules  50  and the area  40  within the shell  10  about evaporator  11  quickly moves the water vapor from the evaporator  11  to the adsorbent modules  50 . 
         [0048]    This rapid flow of the water vapor creates the need to provide a mist eliminator  35  within the shell  10  between the evaporator  11  and the adsorbent modules  50 . The mist eliminator  35  collects mist (water droplets) and airborne contaminants such as the salts from the brine. These airborne contaminants are collected on the mist eliminator  35  and are washed from the surfaces of the mist eliminator  35  from time to time using a wash down feature. In a preferred embodiment, the wash down is accomplished by introducing fluid, such as all or portion of the hot water or cooling water leaving the modules  50  through module output line  50 , through a mist eliminator input line  36  having a plurality of openings, such as mist eliminator spray nozzles  37  that are positioned about that portion of the mist eliminator input line  36  within the shell  10 , to adequately wash the surfaces of the mist eliminator  35 . The wash down fluid is gravitationally pulled to the evaporator  11  where it mixes with the brine and eventually distilled by the concentrator  5  like any other water in the brine. 
         [0049]    The temperature of the adsorbent modules  50  is determined by the temperature of the cooling water that is circulated into the modules  50  through a module fluid circuit comprising module input line  51 , the modules  50 , and module output line  52 . In the preferred embodiment shown in  FIG. 2 , whether the fluid passing through the module fluid circuit is hot (for desorption) or cooler (for adsorption) is controlled by four-way valve  65 . During the adsorption cycle, cooling fluid from the condenser  75  is routed through the four-way valve  65  to the module fluid circuit. The module output line  52  of the module fluid circuit connects to the brine heat exchanger  20  and may also include mist eliminator valve  38  to selectively direct all or a portion of the fluid through mist eliminator input line  36 . 
         [0050]    In the adsorption cycle, the cooling fluid will pass through the brine heat exchanger  20 , exiting through brine heat exchanger outlet line  91  to the brine heat exchanger valve  90  which, in the adsorption cycle, directs the cooling fluid to alternate cooling water return line  92  which returns the cooling fluid to the cooling tower heat exchanger  80  where it is cooled for reuse through the condenser input line  71 . 
         [0051]    A cooling tower heat exchanger  80  is included in this path to isolate the cooling water that is run through the adsorption concentrator  5  from the heat sink, such as a body of water (not represented) or, as illustrated here, a cooling tower  82 . Both types of heat sinks are well known sources of contaminants that can be isolated from the cooling water used to drive the heat driven engine  5  with a simple heat exchanger such as the cooling tower heat exchanger  80 . 
         [0052]    The cooling tower water is circulated with a cooling tower pump  83  that draws cooling water from the cooling tower  82 . The water is pumped through a cooling tower output line  84 , to the cooling tower heat exchanger  80  and back to the cooling tower  82  by way of a cooling tower input line  81 . Any waste heat from the condenser  75  and the adsorbent modules  50  that is not taken back into the system as heat added to the recirculating brine in the brine heat exchanger  20  is expelled to the environment, in this case by the air flow  85  through the cooling tower  82 . 
         [0053]    During the desorption cycle, the four-way valve  65  is selected to direct cooling fluid exiting the condenser  75  through cooling water return line  66  connected to the cooling tower heat exchanger  80 . At the same time, the four-way valve  65  directs hot water from hot water supply line  56  to the adsorbent modules  50  through the lines of the module fluid circuit. Hot water exiting the modules  50  is fed to the brine heat exchanger  20  where its heat is utilized to heat the recirculated brine. Again, the mist eliminator valve  38  may direct all or a portion of the hot water into the mist eliminator  35  but otherwise simply directs the hot water to the brine heat exchanger  20  and then on to the brine heat exchanger outlet  91 . In the desorption cycle, brine heat exchanger valve  90  is selected to direct hot water to hot water return line  57 . 
         [0054]    Alternately, circulating both the cooling fluid used to drive the adsorption cycle and the hot water used to drive the desorption cycle through the brine heat exchanger  20  will result in a slight fluctuation of the temperature of the recirculated brine being introduced into the area  40  of the shell  10  about the evaporator  11 , but the temperature fluctuation will not result in the net temperature of the source brine and the recirculated brine in the shell  10  dropping below the temperature of the condenser  75  or the cooling fluid as it passes into and out of the condenser  75 . 
         [0055]    A vacuum pump  110  is operated at all times to remove non-condensable gases from the adsorption concentrator  5  that may be introduced by the brine. The vacuum pump  110  is connected to the concentrator shell  10  by a vacuum pump line  111 . The vacuum pump  110  has a water vapor filter (not shown) to prevent it from pulling water vapor from the concentrator  5 . 
         [0056]      FIGS. 3A and 3B  schematically illustrate the flow of fluids through the four-way valve  65  of the brine concentrator system  30  of  FIG. 2 .  FIG. 3A  illustrates the positioning of the four-way valve  65  during the desorption cycle. Cooling fluid leaving the condenser  75  through condenser output line  72  is routed through connector  47  to cooling water return line  66  connected to the cooling tower heat exchanger  80 . Simultaneously, hot fluid from a hot water source (not shown) flowing through hot water supply line  56  is routed through connector  45  to the modules  50  through module input line  51 . During the desorption cycle, connector  46  is not used and is substantially empty. 
         [0057]    When the brine concentrator  30  enters the adsorption cycle, four-way valve  65  switches from the position shown in  FIG. 3A  to the position shown in  FIG. 3B . During the adsorption cycle, connector  46  connects the condenser output line  72  to the module input line  51  allowing cooling fluid leaving the condenser  75  to pass to the modules  50  to drive desorption. The flow of hot fluid through hot water supply line  56  is halted as is the flow of water into cooling water return line  66 . Connectors  46  and  47  are disengaged and remain empty during the desorption cycle. 
         [0058]      FIG. 4  illustrates an alternate embodiment of the brine concentrator system  115  of the present invention. 
         [0059]    Brine is introduced to the concentrator system  115  through a brine feed line  21  which passes the brine through a conventional degasser  27  and a brine heat exchanger  20 . As illustrated in  FIG. 4 , the degasser  27  may be positioned along the brine feed line  21  before the brine heat exchanger  20 . However, the degasser  27  may alternately be located after the brine heat exchanger  20  on the hot brine input line  12  if that proves to be more effective and efficient to the operation of the concentrator system  115 . 
         [0060]    The brine heat exchanger  20  is provided on the brine feed line  21  to heat or raise the temperature of the brine before it is introduced into the shell  10  to a temperature from between about 100° F. to about 175° F., preferably to a temperature in the range of about 100° F. to about 120° F. 
         [0061]    A brine feed control valve  22  controls the source of the brine input to the brine heat exchanger  20  by selecting a feed from the brine recirculation line  23 , the brine feed line  21  or allowing a combination of both lines  21 ,  23 . Brine heated by the brine heat exchanger  20  is carried from the brine heat exchanger  20  through the hot brine input line  12 . A portion of the hot brine input line  12  passes into the shell  10  for spraying the brine proximate to the evaporator  11 . 
         [0062]    To enhance evaporation of water and separation of water from the solutes in the brine, the brine is substantially continuously recirculated from the evaporator sump  14  by a pump means, such as brine recirculation pump  25 . Brine output line  15  further comprises a brine recirculation line  23  for circulating brine from the sump  14  to the brine heat exchanger  20  for reheating. Recirculated and reheated brine is then carried back through the evaporator input line  12  for re-distribution across the evaporator  11 . 
         [0063]    The heat that is added to the brine as it passes through the brine heat exchanger  20  is provided from a hot water supply line  56  that supplies hot water from a hot water source (not shown) to the brine heat exchanger  20 . 
         [0064]    During the adsorption period of the cycle, the silica gel in the modules  50  is cooled by the introduction of cooling water at a temperature range expected to be between about 50° F. to about 100° F., preferably at a temperature below the temperature of the brine as it is introduced into the adsorption concentrator  5 , such as at about 85° F. 
         [0065]    A mist eliminator  35  is provided within the shell  10  between the evaporator  11  and the adsorbent modules  50 . Airborne contaminants are collected on the mist eliminator  35  and are washed from the surfaces of the mist eliminator  35  from time to time using a wash down feature comprising a mist eliminator input line  36  having a plurality of openings, such as mist eliminator spray nozzles  37  that are positioned about that portion of the mist eliminator input line  36  within the shell  10 . 
         [0066]    The temperature of the adsorbent modules  50  is limited by the temperature of the cooling water that is circulated into the modules  50  through module fluid circuit comprising module input line  51 , the modules  50 , module output line  52 , and a cooling water pump  70 . Cooling water enters through module input line  51  and, once circulated through the adsorbent modules  50 , the cooling water is removed through the module output line  52 . A cooling tower heat exchanger  80  is included in this path to isolate the cooling water that is run through the adsorption concentrator  5  from the heat sink, such as a cooling tower  82 . 
         [0067]    In a preferred embodiment of the present invention, a common control valve body  58  contains two coordinated valves, a module output valve  53  and a module input valve  54 . During adsorption, the module input valve  54  is open to the condenser input line  71  allowing cooling water from the cooling tower heat exchanger  80  to enter the adsorbent modules  50  and remove the isosteric heat of adsorption. That cooling water exits the adsorbent modules  50  and flows through the module output valve  53  where it is directed to the condenser output line  72  and returned to the cooling tower heat exchanger  80 . 
         [0068]    During the desorption process, hot water is directed to the adsorbent modules  50  using the valves  54 ,  53  of the common control valve body  58 . The module input valve  54  is open to the hot water line  55  and the hot water supply  56 . Simultaneously, the module output valve  53  is open to the hot water control line  59  that connects the module output valve  53  to the mist eliminator valve  38 . The mist eliminator valve  38  may direct all or a portion of the hot water into the mist eliminator  35  but otherwise simply directs the hot water to the hot water return line  57 . 
         [0069]    Although this invention has been disclosed and described in its preferred forms with a certain degree of particularity, it is understood that the present disclosure of the preferred forms is only by way of example and that numerous changes in the details of operation and in the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as hereinafter claimed.