Abstract:
An internally plumbed housing for containing fluid purification media especially suitable for the production of ultrapure water. The device may be installed in a system for the production of laboratory grade water or may be used with pressurized feed for the delivery of purified water or other fluids in multiple applications.

Description:
BACKGROUND OF THE INVENTION 
     The production of laboratory grade ultrapure water or other fluid reagents often requires contacting the fluid feed with various solid filtration and/or adsorption media to free the water from minute quantities of pollutants such as organic compounds, flocculants and dissolved ionic material. See, for example, U.S. Pat. Nos. 5,868,924 and 5,925,240. There is a need in the art for appropriately designed devices for containing such solid media to maximize efficient contact between the fluid and the media. 
     BRIEF SUMMARY OF THE INVENTION 
     The media housing of the present invention consists of top and bottom end caps secured to a dual cartridge media container provided with internal flow conduits and flow distributors and with recesses at the inlet and outlet of each cartridge to accommodate porous discs or screens that act as prefilters and to contain purification media within the cartridges. The inside diameter of each cartridge is such as to accommodate linear cross sectional velocity requirements for ion exchange resin applications, while the overall volume of the dual cartridge is such as to provide sufficient empty bed contact time and depth to satisfy application and design requirements for the use of activated carbons, ion exchange resins, catalysts and other purification and filtration media. 
     The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is a perspective view of the dual cartridge media housing of the present invention. 
     FIG. 2 is a cross sectional view taken through  2 — 2  of FIG.  1 . 
     FIG. 3 is an exploded view of FIG.  1 . 
     FIG. 4 is an elevational view of the outside of the top end cap. 
     FIG. 5 is an elevational view of the inside of the top end cap. 
     FIG. 6 is an elevational view of the outside of the bottom end cap. 
     FIG. 7 is an elevational view of the inside of the bottom end cap. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An exemplary device of the present invention includes two cartridges molded together as a single piece with a common wall and having two smaller conduits or plenums located adjacent the common wall between the two cartridges. One of the smaller conduits is used for fluid communication between the bottom of the first cartridge and the top of the second cartridge when the end caps are attached. The second smaller conduit is used to allow fluid to flow from the bottom of the second cartridge to the outlet for delivery of permeate or purified fluid from the device. 
     In an especially preferred embodiment the cartridges are cylindrical and the smaller conduits have a triangular cross sectional shape. The triangular cross sectional shape of these smaller conduits or plenums adds strength to the device while saving space. Advantages of such a dual cartridge design include the minimization of parts and reduction in assembly time. As compared to standard external plumbing typically used to hydraulically connect multiple media containers in similar applications, the internal plumbing of the present invention leads to an efficient use of space. 
     Turning to the drawings, wherein like numerals refer to the same elements, there is shown a dual cartridge media housing  1  comprising a housing body  10  having a top end cap  12  and a bottom end cap  14 . End caps  12  and  14  are preferably provided with reinforcing ribs  30 . Top end cap  12  is provided with fluid inlet port  18  and permeate outlet port  28 . Top end cap  12  may also be provided with a latch boss  13  and mounting bosses  13 ′ for securing an inlet and outlet nozzle assembly (not shown), said assembly being the subject of copending application Ser. No. 09/733,588, filed concurrently. Housing body  10  and end caps  12  and  14  may be made of any suitable material such as 316 or 316L stainless steel or thermoplastic polymers, preferably the latter and the three components may be secured together by any suitable means; in the case of thermoplastic polymers the three components are preferably welded together. Preferred polymeric materials of construction include polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, fluorinated ethylene/perfluoroalkyl vinyl ether copolymer and polyetheretherketone. 
     Housing body  12  includes first cartridge  20  and second cartridge  24  bound together by common wall  20 - 24 . Both ends of both first cartridge  20  and second cartridge  24  are fitted with porous screens  16  to act as both a prefilter for large particles and to retain filtration and/or adsorption media/ the screens fitting into screen-receiving recesses  17  countersunk into housing body wall  11  and common wall  20 - 24 . The porous screens in the cartridge pack may be constructed of the same types of material as the cartridge pack. 
     In operation, fluid to be filtered or otherwise treated with media such as activated carbon or ion exchange media enters fluid inlet port  18  in top end cap  12 , flows downwardly through porous screen  16  and first cartridge  20 , then downwardly through media contained in first cartridge  20  through lower screen  16 , then encounters first cartridge flow collector  21  which directs the first cartridge permeate upwardly through first cartridge permeate plenum  21  to the top of second cartridge  24 . At the top of second cartridge  24  the fluid permeate from the first cartridge encounters second cartridge flow distributor  23 , which causes the flow to be distributed uniformly downwardly through porous screen  16  and the media of second cartridge  24 . At the bottom of second cartridge  24  the permeate flows through screen  16  and encounters second cartridge flow collector  25  which directs the fluid permeate upwardly through second cartridge permeate plenum  26  and out through permeate outlet port  28 . 
     Fabrication of the housing of the invention is straightforward, comprising placing the two porous screens  16  into the recesses  17  provided inside the end of each cartridge  20  and  24 . The top or bottom end cap  12  or  14  is then secured to the dual cartridges  20  and  24 , preferably by welding. The welding operation captures the porous screens  16  in the welding flash while the end cap  12  or  14  is welded to the dual cartridges. The cartridges are then loaded with fluid filtration/treatment media and the other end cap is secured to the housing body. In general when more than one medium is utilized, the media are placed in the device in discrete layers. One layer of media is normally used to remove a particular contaminant before it reaches a subsequent media layer. For example, activated carbon may be used to remove chlorine and organic contaminants from the fluid feed before it reaches ion exchange resin media to prevent oxidation or fouling. Some media, such as mixed bed ion exchange resins and multimedia material, are supplied as mixed materials and used in that form. 
     The size of the device can be adjusted to meet linear cross sectional velocity (flow rate) and empty bed contact time requirements for a given application. In an exemplary embodiment the device has a nominal tube diameter of 3 inches with a nominal 12-inch internal length from screen to screen with a single tube volume of about 1.4 L or 2.8 L for the dual cartridge. For ion exchange applications the cross sectional area of the tube will allow for a linear cross sectional velocity of from approximately 1 to about 4 L/min. Higher or lower flow rates may be utilized depending on feed solution characteristics and desired effluent quality. Flow rates can be adjusted externally to accommodate desired empty bed contact time relative to feed solution characteristics and effluent quality requirements. For example, a flow rate of 1.0 L/min. would have an empty bed contact time of 2.8 minutes when activated carbon is used as the media. 
     The flow distributors and collectors of the housing of the present invention contribute greatly to the efficiency of operation. Fluid passing through the bottom screen  16  travels to the permeate plenum  22  via flow collector  21 , which splits the stream into two opposing directions which cancel each other to provide an even flow pattern. Thus, flow collector  21  collects fluid from both clockwise and counterclockwise directions to eliminate or reduce the potential for channeling in the upstream media. Once the fluid reaches permeate plenum  22  it travels upwardly to top end cap  12 , then passes through a flow distributor  23  for clockwise and counterclockwise fluid distribution over top porous screen  16 . Once enough fluid is collected and pressure is generated, the fluid passes downwardly through porous screen  16  and the media located in the second cylinder. Fluid passing through the bottom porous screen  16  of the second cylinder passes through yet another flow collector  25 , which functions in the same fashion as flow collector  21  to create even flow of the fluid from the media. The fluid than travels upwardly again in a second permeate plenum  26  to the top end cap  12  through outlet port  28  for delivery of the purified fluid. In addition to the advantages noted above, such flow collector/distributors further provide flow path for the solution should one of the openings be plugged or restricted with welding flash. 
     Two or more of the dual cartridge housings of the present invention may be placed in fluid communication with each in series whereby, for example, the outlet of a first housing is placed in fluid communication with the inlet of a second housing, the outlet of the second housing is placed in fluid communication with a third housing, and so on, so as to achieve further treatment stages. 
     The terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.