Abstract:
A cell for direct treatment of liquid using electrolysis uses a modular construction of electrode plates and spacer assemblies positioned between end plates. Changes in the liquid flow capacity of the cell may be made by changing the number of module housing sections and electrode plate assemblies. The design includes electrode plates that lock into a mating module housing section to resist the pressure of the fluid being treated. The design further provides for multiple fluid flow paths and for automatic cleaning of the cell using standard clean-in-place methods.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application 61/248,077 filed Oct. 2, 2009 hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a flow-through cell for the treatment of liquid streams using electrochemical liquid treatment (electrolysis) and, in particular, to a treatment cell having a modular plate design readily adapted to different flow rates. Liquid treatment may include disinfection or oxidation of biological or chemical species, or other use for which electrolysis is appropriate, such as electroflocculation or electrowinning. Electrolysis includes but is not limited to methods using direct current, alternating current, switched direct current, or pulsed power. 
     Electrochemical liquid treatment systems have been used in a variety of industries for different applications. Chlorine gas and caustic soda are produced commercially by the electrolysis of highly concentrated salt water solutions (brine). Other systems electrolyze brine to produce hypochlorite, and this stream is then injected into another liquid to provide disinfection. Related systems may be used to directly disinfect low salinity swimming pool water as a replacement liquid chlorine disinfecting solutions. 
     In most cases this electrolytic treatment takes place in a flow-through treatment cell that in its simplest form is a housing with a liquid inlet and outlet, and containing two electrodes, one of which is an anode and the other a cathode. In most cases low voltage DC power is applied, but sometimes the polarity may be switched every several hours to help prevent electrode fouling. A new process provides for AC or switched DC electrochemical treatment. This invention applies to all such methods of electric power. 
     Until now most of these designs consisted of two or more electrodes, usually flat plates arranged in a stack with insulated separators between them. The housing was a separate shell containing one or more plate stacks and the liquid treatment volume. Flow rates and treatment volumes were limited to selected standard models or required custom fabrication. Little attention was placed on the cleanability and sanitation of the internal flow chamber and the electrode components, preventing its use in applications such as food, beverage and pharmaceutical processing. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved modular design for an electrolysis system that allows additional electrode plates and treatment channels to be readily added or removed depending on the application requirements. The ability to precisely tailor the number of electrode plates to the application can be important in ensuring the residence time necessary for effective treatment of the liquid and may significantly affect the electrical efficiency of the treatment process. The modular construction also permits the use of standard components to provide flow rates that precisely meet customer needs and the customer&#39;s ability to expand capacity to accommodate growth. 
     In addition, the design includes an innovative method to support the outer housing with the electrode plates themselves to counteract the outward pressure from the liquid contained in the treatment cell. Design elements also make the treatment cell suitable for automated cleaning without disassembly, called “clean-in-place or “CIP”, a necessary requirement for use in applications with demanding sanitation requirements, such as those in the food, beverage and pharmaceutical industries. 
     Specifically then, the present invention provides a flow-through treatment cell for the electrolytic treating a liquid flow and having substantially planar first and second endplates together supporting at least one inlet port and one output port through an end plate. At least two electrode plates each having first and second opposed edge pairs are provided, and at least one module housing section having a central aperture provides an inner lip receiving the first opposed edge pair of at least one electrode plate against the lip and exposes the second electrode edge pair spanning a central aperture. A clamping means is attachable to the first and second end plates to assemble the system by drawing the end plates against a variable number of module housing sections positioned therebetween to provide a continuous channel for flow between the inlet port and the outlet port so that the flow divides to pass across the second electrode edge pairs of each electrode. 
     It is thus a feature of at least one embodiment of the invention to provide a liquid treatment system that may be readily tailored to a particular flow rate by changing the number of electrodes and module housing sections and adjusting the clamping means accordingly. It is also a feature of at least one embodiment of the invention to provide for the alignment and support of each section of the treatment cell via the clamping means. 
     The first and second end plates and module housing sections may be an electrically insulating material. In one embodiment the first and second end plates and the module housing sections are a polymer. 
     It is thus a feature of at least one embodiment of the invention to provide a design that ensures electrical insulation between the plates and that can also withstand substantial liquid pressure. 
     The use of a series of module housing sections allows efficient fabrication and stocking of components of the system while permitting an arbitrarily large treatment cell to be created using readily obtained and fabricated sheet materials. 
     The liquid treatment system may further include a set of gaskets providing apertures corresponding to the central aperture of the module housing sections and positionable between each of the module housing sections to seal between module housing sections and/or between module housing sections and end plates to prevent fluid leakage. These gaskets may also be designed to standards permitting automated CIP sanitation. 
     It is thus a feature of at least one embodiment of the invention to permit the construction of a modular system with practical manufacturing tolerances and to meet the requirements for CIP sanitation. 
     It is also important to shield the electrode plates to protect them from exterior contact with metal parts that could cause a short circuit, from plant washdown liquids that could corrode the plates and provide a path for current leakage to the exterior, and from contact with plant personnel to prevent possible electrical shock. 
     It is thus a feature of at least one embodiment of the invention to provide a secondary sealing means to insulate the electrode plates from exposure to external contact. 
     The liquid treatment system may include a means of attaching the first opposed edges of an electrode plate to a corresponding module housing section both to tension the second opposed edges of the electrode plate and to prevent the module housing section from deflecting outwards due to the pressure of the liquid inside. 
     It is thus a feature of at least one embodiment of the invention to provide an attachment means between the electrode plates and the modular housing sections whereby the electrode plates are stiffened by the pressure of the treatment liquid on the housing sections and these housing sections are prevented by the electrode plates from expanding outwards under the pressure of the treatment liquid. 
     One implementation of this attachment means is provided by bending the first opposed edges of an electrode plate so that the bent edges that fit into mating slots in the corresponding housing section. 
     It is thus a feature of at least one embodiment of the invention to have the attachment means for the electrode plate be a bent configuration of the first opposed edges of the plate. 
     Another implementation of this attachment means is two electrical busbars attached to the first opposed edges of an electrode plate that fits into mating slots in the corresponding module housing section. This implementation also provides improved current distribution through an electrode fabricated from thin plate material to maximize liquid flow volume. 
     It is thus a feature of at least one embodiment of the invention to have the attachment means for the electrode plate be two busbars attached to the first opposed edges of the plate. 
     The system may provide one or more electrical conductors extending outward from at least one busbar to extend beyond a wall of a module housing section surrounding the central aperture and to connect with one or more corresponding electrical terminals. 
     It is thus a feature of at least one embodiment of the invention to provide a simple and modular electrical interconnection system that accommodates the modularity of the electrical plates allowing each plate to be interconnected by an easily modifiable electrical harness. 
     The electrodes may include first and second electrode plates having electrical conductors attached at different locations to stagger the electrical terminals to two or more positions along an outer edge of the module housing sections for alternate electrode plates. 
     It is thus a feature of at least one embodiment of the invention to permit close spacing of the electrical plates without interference among the connectors and to provide a visual segregation between connector polarities. 
     The busbars may be held by bolts through corresponding apertures in walls of the module housing sections to attach the electrode plates to the module housing sections. 
     It is thus a feature of at least one embodiment of the invention to provide a robust physical attachment of the electrode plates to the module housing sections simplifying the assembly process. 
     The system may include a support frame providing a first set of horizontally extending rails supporting lower edges of the end plates and module housing sections and a second set of horizontally extending rails abutting vertical edges of the end plates and module housing sections. 
     It is thus a feature of at least one embodiment of the invention to provide an external skeletal structure providing additional resistance against pressure distending the assembly of the end plates and module housing sections. 
     The electrode plates are fabricated from an electrically conductive material including metals, metal oxides and doped diamond, some of which may act as process catalysts. 
     It is thus a feature of at least one embodiment of the invention to provide a system compatible with relatively thin metallic plates. It is further a feature of at least one embodiment of the invention to provide a system allowing ready access to the plates for cleaning. 
     The clamping means may be a multiple threaded bar passing through bores extending between the end plates and through walls of module housing sections positioned therebetween to clamp the end walls about the module housing sections through corresponding releasable nuts threadably received on the threaded bars. 
     It is thus a feature of at least one embodiment of the invention to provide a clamping system that is simple, adjustable, and that can provide distributed clamping forces compatible with construction of the housing of the system from insulating polymer materials or like. 
     The electrode plates are substantially parallel with a spacing of greater than 5 mm when the system is assembled. 
     It is thus a feature of at least one embodiment of the invention to provide a system suitable for direct use with liquid that may contain suspended solids and high viscosities. 
     The inlet and outlet ports may be positioned near opposite edges of a single end plate. 
     It is thus a feature of at least one embodiment of the invention to provide a system having proximate inlets and outlets permitting adjustment of the number of electrical plates without replumbing the ports to the system. 
     To accommodate more complex liquid distribution arrangements, both end plates may include inlet and/or and outlet ports. 
     It is thus a feature of at least one embodiment of the invention to provide a means to combine or distribute liquid streams flowing through the treatment cell. 
     Both end plates may include inlet and outlet ports combined with a solid separator plate within the modular assembly. 
     It is thus a feature of at least one embodiment of the invention to provide a means to treat two separate liquid streams in one treatment cell assembly. 
     These particular objects and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a liquid treatment system in one embodiment of the present invention showing a main housing holding opposed planar electrodes between liquid inlets and outlets, a power distribution module, and a control unit; 
         FIG. 2  is a detailed block diagram of the components of  FIG. 1 ; 
         FIG. 3  is an exploded orthogonal view of the present invention showing modular components; 
         FIG. 4  is a simplified cross-section of three modular housing sections viewed along line  4 - 4  of  FIG. 3  showing support of the internal electrical plates to divide liquid flow among them and a staggering of associated electrical connectors; 
         FIG. 5  is an enlarged cross-sectional view of two module housing sections and an electrode plate taken along lines  5 - 5  of  FIG. 3 ; and 
         FIG. 6  is a partial cutaway of an assembled liquid treatment system of  FIG. 3  having four electrical plates. 
         FIG. 7  is a diagram illustrating liquid flow with one inlet port and two outlet ports. 
         FIG. 8  is a diagram illustrating liquid flow with two inlet ports and one outlet port. 
         FIG. 9  is a diagram illustrating liquid flow with two inlet ports and two outlet ports along with a divider to treat two separate liquid streams in one treatment cell assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIGS. 1 and 2 , a liquid treatment system  10  per the present invention may include a treatment unit  12  providing a liquid inlet  14  and outlet  16  to conduct liquid across internal plates  28 . The plates  28  are contained in an insulating housing  18  supported on frame  20 . A power distribution module  22  provides electrical connections  24  to the internally contained plates  28  for power received from a control unit  26 . The control unit  26  has a touchscreen user interface  27  for the display and entry of data including critical operation parameters. 
     Referring now to  FIG. 2 , the treatment unit  12  includes two or more generally planar and parallel electrical plates  28  held in a channel  36  between the inlet  14  and the outlet  16 . The plates  28  are separated along an axis  30  generally perpendicular to the flow of liquid by gaps  32  to receive liquid  34  therethrough. The separation of the plates  28  will be greater than 5 mm to permit the passage of untreated liquid  34  without undue risk of clogging. 
     One or more chemical sensors  40  may be positioned in sensor fitting  38  downstream from the plates  28  and channel  36  to measure chemical properties of the liquid and/or a flow sensor  42  may be positioned in the stream of liquid  34  to measure the flow across the plates  28 . The chemical sensors  40  may include those measuring pH, oxidation-reduction potential, chlorine level, free chlorine level, or total chlorine level. 
     The amount of flow through the channel  36  may be controlled by electrically driven pump  44  and/or valve  46  alone or in combination. 
     The plates  28  are electrically isolated from each other as held by the housing  18  but may be joined by the connections  24  from power distribution module  22  so that some or all of the plates  28  are electrically connected to electrical conductors  48   a  and  48   b . In some configurations alternating electrode plates may be connected to opposite power polarities, in others some plates may not be directly connected to the power supply but instead become electrically activated by the ionic currents in the liquids being treated, resulting in each side of such intermediate plates having opposite polarities. The electrical conductors  48   a  and  48   b  are connected to a switching unit  50  that is part of the electrochemical process. 
     The controller  60  includes a processor  70  and a control program  72 , the latter contained in the memory  81  communicating with the processor  70  as is generally understood in the art. In operation, the program  72  will read various parameters of the process including the plate current from current sensors  54 , the plate voltage from voltage sensing points  56 , user entered parameters through touchscreen  27 , chemical environment sensing from the chemical sensor  40 , and/or the flow rate from the flow sensor  42 , and will provide output signals on control line  51  controlling the switching unit  50  and the power supply  58 . In addition, output signals controlling the pump  44  and valve  46  and providing information on touchscreen  27  may be provided. 
     Referring now to  FIG. 3 , the housing  18  of the liquid treatment system  10  may be composed of first and second end plates  100  and  102  each being substantially planar and having parallel side walls  104  and top and bottom walls  106  describing long and short sides of a rectangular periphery of the plates  100  and  102 . The plates  100  and  102  may be arranged to be substantially parallel to each other and separated along an axis  107  normal to their broad faces. Each of the endplates will have vertical lips  116  to receive vertical opposed edges  114  of electrode plates  112  aligned with the apertures  110  of the modular housing sections  108 , both described below. 
     One or more module housing sections  108 , having top and bottom walls  106  and vertical walls  104  and thus conforming to the periphery of the end plates  100  and  102 , may be aligned with and positioned between the end plates  100  and  102 . These module housing sections  108  provide a central aperture  110  large enough to allow passage of the treatment liquid from the inlet  14  and to the outlet  16  either directly or through a corresponding aperture  110  of another module housing section  108 . 
     Module housing section  109  is similar to the module housing sections  108  except that it does not receive an electrode plate  112  but serves simply as a spacer between the electrode plate  112  on the end plate  102  adjacent to the module housing section  109  and the electrode  112  on the module housing section  108  closest to the end plate  102  on the other side of module housing section  109 . 
     Electrode plates  112  may be positioned within the apertures  110  so that vertical opposed edges  114  (as shown) are supported by corresponding vertical lips  116  of the aperture  110  while the opposed horizontal edges  118  of the electrode plates  112  span the aperture  110 . The electrode plates  112  may have surfaces of metal or metal oxides and may include catalytic surfaces. 
     Referring now to  FIG. 4 , liquid flow  119  from the inlet  14  may pass through the apertures  110  to cross the horizontal edges  118  of the electrode plates  112  as it flows between the electrode plates  112  to the outlet  16  (not shown in  FIG. 4 ). 
     Referring now to  FIG. 5 , each electrode plate  112  may have a busbar  120  of substantially square cross-section and of greater thickness along axis  107  than the electrode plate  112  attached to the vertical edges  114  of the electrode plates  112 , for example, by brazing or welding to make electrical communication therewith. 
     The busbar  120  on one vertical edge  114  may also attach to one or more conductors  122  passing outwardly along the plane of the electrode plate  112  through one or more holes  126  in a vertical wall  104  of a corresponding module housing section  108 . The conductor  122  may lead to an electrical connector  124  providing one of the connections  24  shown in  FIG. 1 . 
     The busbars  120  provide for improved distribution of current through the electrode plate  112  as fed by a single centrally located conductor  122  and stiffen and retain the electrode plates  112  within the module housing sections  108 . In this latter capacity, the busbar  120  may be received in a corresponding groove  127  on an inner face of the module housing section  108  as sealed by a strip gasket  128 . Standoffs  134  may be attached to the vertical wall  104  of the module housing section  108  to bear against the support frame  20  to minimize contact area and crevices where dirt or pathogens could accumulate. 
     An opposed surface of the electrode plate  112 , displaced from the side attached to the busbar  120 , may be sealed by a ring gasket  130  received by corresponding retaining groove  132  in an opposed face of the module housing section  108 . Together the gaskets  130  and  128  prevent liquid leakage out of the housing  18  from a cavity formed by the combination of the apertures  110  of the module housing sections  108 . Gasket  130  also provides a secondary seal for gasket  128  and at the same time prevents exterior wash down water and other contaminants from contacting electrode plate  112 . 
     Referring now to  FIG. 6 , the housing  18  may be assembled by clamping the end plate  100  to the end plate  102  to sandwich multiple module housing sections  108 , gaskets  128  and  130 , and electrode plates  112  therebetween. A clamping means may be effected through the use of multiple threaded rods  140  passing through axially aligned bores  142  in the end plates  100 ,  102 , and intervening module housing sections  108 . Nuts  144  on exposed ends of the threaded rod  140  may be used to provide controlled compression of the end plates  100 ,  102  at multiple points to provide for a distributed and even compressive force without distortion or warping of the end plates  100 ,  102  and module housing sections  108 . 
     Referring again to  FIG. 1 , the support frame  20  may provide for lower rails  150  supporting the bottom wall  106  of the end plates  100 ,  102  and module housing sections  108  and side rails  152  pressing inward on the vertical walls  104  of the module housing sections  108  to resist outward distention of the polymer materials caused by internal pressure. 
     Referring again to  FIG. 4 , the conductors  122  and connectors  124  may be staggered vertically along the edges of the electrode plates  112  so as to provide for closer plate spacing without interference between the connectors  124  and to segregate the connectors  124  according to their relative polarity during each excitation period when an AC power source  154  (formed by power supply  58  and switching unit  50  of  FIG. 2 ) is applied across the connectors on  24  as depicted. 
     Referring now to  FIG. 7 , the flow from one inlet  14  may be distributed across two outlets  16 . 
     Referring now to  FIG. 8 , the flow from two inlets  14  may be combined into one outlet  16 . 
     Referring now to  FIG. 9 , two different liquid streams may be treated in one treatment cell assembly, with divider  200  separating the two liquid streams, each with one or more inlets  14  and outlets  16 . 
     The present invention has been described in terms of the preferred embodiment, and it is recognized that equivalents, alternatives, and modifications, aside from those expressly stated, are possible and within the scope of the appending claims.