Liquid purification or separation – Processes – Ion exchange or selective sorption
Reexamination Certificate
2000-11-10
2004-05-04
Cintins, Ivars C. (Department: 1724)
Liquid purification or separation
Processes
Ion exchange or selective sorption
C210S678000, C210S136000, C210S289000
Reexamination Certificate
active
06730229
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to fluid purification and particularly relates to a nozzle for use in a fluid treatment vessel.
BACKGROUND OF THE INVENTION
Fluids are commonly processed for purification or chemical treatment. More particularly, water and various chemicals, in liquid or gaseous form, are purified or otherwise treated for consumption, manufacturing or industrial processes. For example, water from an available source, such as a river, lake, ocean or deep well, usually contains undesired impurities, including suspended solids, and organic and inorganic impurities. The impurities must be removed to meet certain purity requirements, depending upon the intended use for the water. Public water systems are governmentally regulated so that impurities do not exceed levels considered safe for consumption. Certain industrial applications require even fewer impurities than the typical levels for drinking water. Semiconductor processing, pharmaceutical manufacturing, and steam boilers are sonic examples of applications requiring water with extremely low levels of impurities.
Fluid treatment systems are known for purifying water and otherwise processing fluids, including various liquid-from-liquid, liquid-from-solid, and liquid-from-gas separation processes. Fluid treatment systems often include more than one reactor vessel. For example, at least two reactor vessels are used in a typical water demineralizer purification system for a community, populated facility, or industrial facility that uses large amounts of purified water for industrial processes such as boiler feed or washing off electronics parts. Other reactor vessel treatment systems are known for processing steam, acid, caustic, and a variety of other gases or liquids.
Conventionally, a reactor vessel includes a large tank which contains a granular processing medium. Such as sand, anthracite, carbon, cation exchange resins, anion exchange resins, and mixed-bed resins. The processing medium occupies a lower portion of the vessel's interior chamber. A typical later demineralizer purification system includes at least two reactor vessels—a first containing a cation exchange resin medium and a second containing an anion exchange resin medium.
To treat the fluid, the fluid is brought into contact with the processing medium, such as ion exchange resin. The vessel includes an upper manifold for introducing a flow of the fluid into an upper portion of the vessel, from where it falls onto the processing medium. As the fluid flows downwardly through the processing medium, the fluid reacts with the processing medium during the physical contact. The treated fluid is then removed through a lower manifold that is immersed in the processing medium at a bottom portion of the vessel.
The lower manifold, which feeds to a common duct, includes an array of conventional nozzles which are generally spaced across the bottom portion of the vessel. To separate the fluid from the medium, each of the conventional nozzles has an exterior screen with narrow openings sized to prevent the passage of the processing medium. For example, in a system having an ion exchange resin as a process medium, which is typically comprised of resin beads, each having a diameter of generally about 2 mm (15-40 mesh), the nozzle screen openings are designed to be very narrow—only a few thousands of an inch wide.
In most prior art nozzles, the flow rate is governed by the collective open area of the screen. For reasons explained in greater detail below, it is desirable that each nozzle has a predetermined flow rate. Specifically, the flow rates are desirably consistent among the nozzles withdrawing fluid in order to promote an optimal flow profile. Therefore, in conventional nozzles, the screen must be manufactured with a high degree of precision to provide a predetermined total open area, in turn providing, a desired flow rate.
Unfortunately, prior art fluid treatment systems have been known to lose treatment effectiveness, worsening over time. Some inefficiencies have been attributed to differences in flow rates that develop among a nozzles on a particular manifold. For example, a common problem is known as “channeling,” wherein the fluid favors a particular flow path or “channel” through the medium. Particularly, a majority of the fluid flows along a path of least resistance toward a nozzle having the greatest available open area. Of course, the processing medium in the “channel” soon becomes exhausted, because it is subjected to a disproportionate rate of fluid contact. At the same time, the medium in other areas of the vessel is not effectively utilized. Thus, channeling causes a reactor vessel to rapidly deplete its overall effectiveness, including loss of productivity, increased chemical usage, and increased waste.
In most conventional nozzles, the flow rate and fluid flow restriction is a function of the open area of the collective holes in the nozzle screen. Accordingly, a manifold is assembled using a plurality of like nozzles having equivalent screen open areas. Such nozzles have relatively equal flow rates, at least initially upon installation. Unfortunately, over time, some screen openings are known to become plugged with foreign matter or broken medium beads, reducing the open area and reducing the flow rate in the plugged nozzles. At the same time, the flow increase through unplugged screen openings has a wearing effect. The flow wear enlarges the unplugged openings, thereby increasing the flow through those unplugged openings.
Notably an increasing flow rate through an opening results in wear rate on the adjacent screen material. Further increasing the screen openings of the favored nozzles. Moreover, the wire used to form such screens typically has a triangular cross section, for reasons explained below. When new, this triangular wire has edges formed by acute surfaces, but as these edges wear, the opening adjacent the screen rapidly expands at a non-linear rate due to the wire geometry.
Over time, the combination of screen plugging and screen wear result in a significant disparity in the open areas, and flow rates, among the conventional nozzles of a particular system. The drainage flow through the lower manifold therefore favors nozzles having the greatest screen opening areas, thus leading to the undesired channeling effect and associated operating inefficiencies. These inefficiencies result in lost productivity, an increase in required manpower due to increased regeneration requirements, and poor product quality.
In one known system, a restrictor plate was positioned across the duct mounted to the screen to provide communication between the manifold and the cavity defined by the screen. In this nozzle, however, the orifice was not positioned to optimally control a direction of flow through the screen for maximal efficiency.
Most treatment systems require a periodic regeneration or reconditioning of the processing medium. For example, in a vessel wherein the processing medium is ion exchange resin heads, charged sites on each bead become bonded with molecules of the impurities of the treated fluid, until the sites are used. In order for the medium to be effective, the beads must be periodically reconditioned with a chemical bath that takes away the molecules from the charge sites on the ion exchange medium. For introducing such reconditioning chemicals, a reactor vessel is typically equipped with an internal distributor in an upper or middle portion of the vessel to introduce a flow of the chemicals above the processing medium. The chemicals flow down through the medium and are extracted through the nozzles of the lower manifold near the bottom of the tank.
Another conventional nozzle is known as a pipe-based filter screen nozzle. Such a pipe-based nozzle is basically an elongated filter screen nozzle of the type described above. In a treatment vessel employing pipe-based nozzles, a plurality of the pipe-based nozzles are mounted to a central hub near the bottom of the medium, the nozzles projecting radially ou
AWTS, Inc.
Cintins Ivars C.
Leydig , Voit & Mayer, Ltd.
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