Abstract:
Systems and methods are described for flushing one or more filters using a pressurized permeate stream. The permeate stream can be pressurized within a front flush unit, which can also receive a feed water stream. Energy needed to increase the pressure of the permeate stream to a pressure sufficient to cause flushing of the filters can be generated through work exchange with the pressurized feed water stream.

Description:
[0001]    This application claims priority to U.S. provisional patent application having Ser. No. 61/680632 filed Aug. 7, 2012. This and all other extrinsic materials discussed herein are incorporated by reference in their entirety. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The field of the invention is filtration systems and methods. 
       BACKGROUND 
       [0003]    To reduce the energy requirements of a reverse osmosis (RO) pump system, it is known to include a pumping system that can conserve a portion of the pressure of an incoming stream to thereby increase the pressure of a second stream. See, e.g., U.S. pat. publ. no. 2008/0296224 to Cook, et al. (publ. December 2008). However, such pumping system requires electricity to operate, which increases the overall energy use of the RO system. 
         [0004]    To further reduce the energy requirements of filtrations systems, it is known to utilize a work exchange pump, such as that discussed in U.S. pat. publ. no. 2005/0035048 to Chancellor et al. (publ. February 2005) and U.S. Pat. No. 6,017,200 to Childs, et al. Such systems are generally complex, however, increasing their energy and maintenance costs. 
         [0005]    Thus, there is still a need for filtration systems that further reduce energy requirements. 
       SUMMARY OF THE INVENTION 
       [0006]    The inventive subject matter provides apparatus, systems and methods in which one can reduce the energy requirements of a filtration system by utilizing an energy recovery unit fluidly coupled to the filtration system. 
         [0007]    Preferred filtration systems include one or more filters, and preferably at least two filters, which can receive a pressurized feed water stream. As the feed water is fed into the filter, a filtered permeate stream and a reject stream are produced, which exit the filter via a permeate conduit and a reject conduit, respectively. 
         [0008]    Such systems can also include a front flush unit configured to allow for automatic flushing of the one or more filters during operation of the system. This advantageously leads to less downtime due to maintenance. The front flush unit can be fluidly coupled to the one or more filters and configured to (a) receive at least a portion of a feed water stream and (b) produce a pressurized flushing stream that includes at least some of the permeate stream produced by the one or more filters. The pressurized flushing stream is preferably produced primarily via work exchange with the portion of the feed water stream received by the unit, which eliminates the need for additional pumps and other components and thereby reduces the overall energy cost of the system. It is especially preferred that the pressurized flushing stream is solely produced via work exchange with the portion of the feed water stream received by the unit. 
         [0009]    Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a schematic of one embodiment of filtration system shown configured for normal filtration. 
           [0011]      FIG. 2  is a schematic of the filtration system of  FIG. 1  shown configured for flushing of the filters. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed. 
         [0013]      FIGS. 1-2  illustrate an embodiment of a filtration system  100  having a positive displacement pump  134  that preferably includes a cylindrical unit  130  and piston  132 . The positive displacement pump  134  can be used to enable a permeate water front flush of filters  110  and  112  using at least a portion of permeate stream  104 , which is designated as permeate stream  105 . 
         [0014]    Preferably, system  100  can include one or more flow sensors that are configured and disposed to monitor a flow rate of the permeate stream  104 . If the one or more sensors detect that the flow rate decreases below a predetermined threshold, the one or more sensors can send one or more signals to a flow switch, for example, which can be used to alert the need to flush filters  110  and  112 . 
         [0015]    In such embodiments, it is contemplated that the system  100  can automatically close valve  141  allowing pressure to build on permeate streams  104  and  105  thereby translating piston  132  to the bottom of unit  130 . When a pressure of the permeate stream  104  reaches a predetermined threshold at or near the pressure of reject stream  108 , sensors can send one or more signals to a controller or valve actuator(s) to cause valve  133  to rotate, thereby inducing a portion of stream  111  feed water into pump  134 . Piston  132  will translate upward and force permeate streams  104  and  105  to reverse direction. Permeate stream  105  can be separated into streams  105 A and  105 B, which respectively flow into the filters  110  and  112  via the permeate outlets. The back flow of permeate streams  105 A and  105 B advantageously can reduce build-up on the filters  110  and  112 . The permeate streams  105 A and  105 B, build-up pressure, and reject fluid can exit the filters  110  and  112  as reject stream  108 , which can then (i) exit system  200 , (ii) be fed to pump P 3 , and/or (iii) be merged with feed water stream  103 A and flowby stream  106 . Contrary to prior art systems, system  200  can front flush the filters during operation of the system  200 , which significantly reduces system downtime. This new front flush system may also be called an Automatic Membrane ‘Clean In Place’ Powered Up System. 
         [0016]    In this manner, the permeate streams  104  and  105  will reverse flow through filters  110  and  112  relative to a flow direction during normal (filtration) operation of system  100 . The reverse flow of permeate through the permeate collection pipes within filters  110  and  112  will facilitate the dislodging of particulate and other buildup from the membranes within filters  110  and  112  that may have reduced the flow rate of permeate stream  104 . 
         [0017]    This sequence will be reversed by rotating valve  133  to a drain position allowing pressure in permeate streams  104  and  105  to expel water from pump  134  and push piston  132  downward towards the feedwater tank, to await the next flow rate reduction of permeate stream  104 . Thus, the system  200  can automatically front flush the filters  110  and  112  anytime the flow rate of permeate stream  104  is reduced below a predefined threshold. 
         [0018]    During normal operation, system  100  can receive a feed water stream  102  that can flow past one or both of pumps P 1  and P 2 , which thereby increase a pressure of the feed water stream  102  to approximately 150 psi, although the specific pressure can vary depending upon the application. For example, the pressure of a feed water stream comprising blackish water will likely be less than that of a feed water stream comprising salt water. 
         [0019]    Filter  110  can receive at least a portion of feed water stream  102  and produce a permeate stream, which can then be fed into the second filter  112  to produce a second permeate stream and reject stream  108 . In this manner, the feed water stream  102  can be passed through multiple filters to remove a larger percentage of impurities from the stream  102  and it is contemplated that the stream  102  could be passed serially through three or more filters although the specific number of filters will depend upon the application. 
         [0020]    The permeate streams can optionally be merged downstream of the filters  110  and  112  as a combined stream. Optionally, a portion of the combined stream can be removed and fed into pump  134 , which causes piston  132  to move downwardly, and thereby increase the pressure of, and expel, the liquid below the piston  132 . 
         [0021]    A first portion of the reject stream  108  can bypass pump P 3  to increase its pressure before it is merged with the feed water stream  102  downstream of pump P 2 . By using a smaller pump P 3  rather than pump P 2  to pressurize the reject stream  108 , less energy is advantageously consumed. P 2  is used primarily to boost pressure of reject stream  108  and thereby recirculate reject water back into feed water  103   a  (i.e., P 2  discharge). 
         [0022]    As shown in the Figures, a second portion  109  of the reject stream  108  can optionally be diverted upstream of pump P 3  and fed into a lower portion of a positive displacement pump  118  having a cylindrical unit  120  and piston  122 . Preferably, piston  122  is a zero-buoyancy piston to reduce blowby around the piston  122  plus the pressure loss and friction between the piston  122  and unit  120 . 
         [0023]    The higher pressure reject stream  109  causes a piston  122  to translate upwardly within pump  118 , which thereby expels a liquid above the piston  122  through check valve  128 . The liquid can be fed into a venturi valve  140  as a result of the negative pressure created as reject stream  108  flows through the venturi valve  140 . This advantageously reduces the energy costs of system  100 , as the reject stream  108  does not require a pump between valve  140  and pump  118 . 
         [0024]    To reduce the amount of fluids exchanged between opposite sides of the pistons, it is preferred that the difference in pressure between the fluids on each side is less than  10  psi. 
         [0025]    After piston  122  reaches an upper portion of pump  118 , a sensor can send a signal to cause L-diverter valve  125  to be rotated to stop flow of the portion  109  of the reject stream  108  to the pump  118 , as shown in  FIG. 50 . Although valves  128  and  129  are shown as separate valves, it is contemplated that a three-way valve could be substituted for the valves  128  and  129  to thereby further reduce the complexity of system  100 . In addition, rather than use L-diverter valve  125 , any commercially suitable valve(s) could be used including, for example, actuated gate valves, and ball valves. Separate valves could also be used in place of valve  125  to regulate flow into and out from the pump  118 , respectively. 
         [0026]    With valve  129  opened and valve  128  closed, the  103  portion of the feed water stream  102  can be removed upstream of pump P 2  and fed into pump  118 , which causes piston  122  to translate downwardly and expels a lower pressure reject stream from pump  118  through valve  125 . 
         [0027]    Preferred filters include reverse osmosis (RO) filters, and especially preferred RO filters include a filter element and a casing formed about the filter element, such as those described in U.S. utility application titled “Water Purification System With Entrained Filtration Elements” having Ser. No. 13/263819 filed on Oct. 10, 2011. As used herein, the term “filter element” is defined to include all commercially suitable filters including, for example, sand, charcoal, paper, and other media, and any membrane capable of filtering a fluid. The filter element could be of any type, size or manufacturer, and preferably the filter element is selected based upon the commercial application. Of course, any commercially suitable filter could be used without departing from the scope of the invention. 
         [0028]    In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements. 
         [0029]    As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise. 
         [0030]    The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention. 
         [0031]    Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims. 
         [0032]    Unless the context dictates the contrary, all ranges set forth herein should be interpreted as being inclusive of their endpoints, and open-ended ranges should be interpreted to include commercially practical values. Similarly, all lists of values should be considered as inclusive of intermediate values unless the context indicates the contrary. 
         [0033]    As used herein, and unless the context dictates otherwise, the term “coupled to” is intended to include both direct coupling (in which two elements that are coupled to each other contact each other) and indirect coupling (in which at least one additional element is located between the two elements). Therefore, the terms “coupled to” and “coupled with” are used synonymously. 
         [0034]    It should be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the scope of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refers to at least one of something selected from the group consisting of A, B, C . . . and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.