Liquid purification or separation – Plural chambers with movement of granules therebetween
Reexamination Certificate
1991-08-23
2001-05-08
Cintins, Ivars (Department: 1724)
Liquid purification or separation
Plural chambers with movement of granules therebetween
C210S269000, C210S284000
Reexamination Certificate
active
06228257
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to methods and apparatus for treating particulate solids and fluids through facilitation of contact between a fluid and a particulate solid contact media, or between a particulate solid and a treatment fluid. The methods and apparatus in accordance with the present invention are particularly well suited for use in ion exchange operations wherein a fluid is contacted with a fluidizable solid ion exchange media such as a resin; or with filtration or adsorption operations where the fluids are contacted with a media such as activated carbon; or where exhausted contact media is regenerated by bringing the contact media in contact with a regeneration fluid.
Ion exchange processes for treating fluids are well known. Such ion exchange operations may include, for example; “water softening”, deionization, de-alkylizing, disilicizing, and organic scavenging. With respect to the present invention, these ion exchange processes will, for convenience, be discussed in terms of water treatment through use of resins. It should be clearly understood, however, that the methods and apparatus of the present invention may be utilized in the treatments of many other fluids, or may be utilized to treat any of a number of particulate solids, including, for example, the regeneration of contact media other than resins.
Typically, an ion exchange process is effected by flowing the water through a vertical column of an ion exchange contact media, typically a resin. As the water contacts the resin, ions in the water will be attracted to the resin from the water. One type of resin may be utilized to remove cations from the water (i.e., a cation exchange resin); and a second type of resin may be utilized to remove anions from the water (i.e., an anion exchange resin). Preferably, the separate resins will be contained in separate beds. However, conventional techniques of water deionization include the use of two resins mixed in a single bed.
The softening of water by ion exchange is accomplished by replacing the calcium and magnesium ions in the water by an equivalent number of sodium ions from the resin. Resin in the bed will contain only a finite number of exchangeable sodium ions. This number defines the “capacity of the resin”. When the capacity of the resin has been exhausted, i.e., when all of the exchangeable sodium ions on the resin have been replaced by calcium and magnesium ions from the water, the resin must be regenerated back to the sodium form. This regeneration is typically accomplished by passing a sodium chloride solution (a brine) or a sodium hydroxide solution through the resin. Additionally, the resin will be rinsed to remove excess brine, and will be backwashed to remove particulate matter which may have accumulated in the resin during the ion exchange step (“the service cycle”).
As water flows through a bed of resin, the majority of the ion exchange will take place in the portion of the resin which is first contacted by the fluid. In an ion exchange system where the fluid flows downwardly through the bed, this exchange creates an “exhausted band” of exhausted resin which expands downwardly through the bed as the operation continues. When the band approaches the bottom of the resin bed, the bed must be regenerated as discussed above.
Additionally, a vertical column of resin operating in a service cycle has an exchange zone, or active band, starting at the top and moving down through the bed of resin. The width of the active band varies with certain operating parameters of the system. For example, as the service flow is increased the active band will spread out. The resin bed must be removed from service and regenerated before the active band reaches the bottom of the column to prevent leakage of the ions being removed from the fluid. This prevents full utilization of the resin since there is resin not fully exhausted in and below the active band. When a column of resin in normal operation is regenerated, sufficient regenerate (such as salt, in the case of water softening), is used to regenerate the entire volume regardless of what percent of the bed was actually exhausted.
Similarly, when a contact media, such as the previously described resin, is regenerated (to replace the exhausted supply of exchangeable ions), by flowing the regeneration fluid through a bed or column of resin, the majority of the ion exchange (i.e., regeneration) will take place in the portion of the resin which is first contacted by the regeneration fluid. Accordingly, in an ion exchange system where the regeneration fluid flows downwardly through the bed, the complete regeneration of the resin requires that relatively large volumes of regeneration fluid be directed through the bed if the resin at the bottom of the bed is to be completely regenerated.
Many conventional vertical ion exchange columns are designed to function both as a column for the service cycle, i.e., for the initial ion exchange process, and for the regeneration cycle, and therefore also include provisions for backwashing, regeneration, and rinsing of the resin. This structure requires the fluid influent to be shut off from the column while the regeneration operation takes place, thereby interrupting the supply to service of treated fluid. When an uninterrupted supply of treated fluid is required, a second vertical column is typically provided. This second column will be regenerating during the service cycle of the first column and vice versa Conventional columns typically include a shell to contain the resin, a support for the resin, and means for distributing flow both upwardly and downwardly through the resin, (for both the service cycle and the regeneration and backwashing cycles). The shell must have sufficient space above the resin to allow the resin to expand during the backwashing operation. Valves and controls are typically necessary to bypass “raw” (untreated) fluid around the column during the regeneration cycle, to inject the regeneration fluid into the column, and to reverse the direction of fluid flow for backwashing.
Conventional vertical columns may include several disadvantages. Where a single large resin bed is utilized, fluid has a tendency to channel through the bed during periods of low flow rate, thereby reducing the effective contact of the fluid with the resin. Additionally, the requirement of additional space above the resin bed to facilitate the backwashing operation adds cost to the vessel. Where uninterrupted service is required and a second unit is provided, the additional unit adds significant cost and size to the unit. A significant factor in this cost is that a control valve must be provided to switch fluid flow from one vessel to the other. This control valve must be large enough to provide a significant flow of the influent into the column without placing an excessive pressure drop in the system. Large control valves of this type typically contribute a significant portion of the cost of conventional ion exchange units. These valves still often place an undesirable pressure drop in the system.
If only one column is provided, in typical conventional systems, not only must the flow of treated water be interrupted, but untreated water must be used with the unit itself for the backwashing, regeneration, and rinsing operations. This use of untreated water will, in itself, decrease the operating efficiency of the contact media regeneration, and will therefore similarly decrease the efficiency of the ion exchange process.
Because of the deficiencies discussed above, several attempts have been made to devise methods and apparatus for an uninterrupted, or continuous, ion exchange process in a single column. Typically, these processes involve the movement of the contact media downwardly through the column or ion exchange vessel while the fluid flows upwardly through the column. In some cases, the resins are actually fluidized, or suspended, in the fluid flow. This upward flow, and especially fluidization, typically provide less than optimal ion exchange. A maj
Cintins Ivars
Howrey Simon Arnold & White , LLP
Hydrotreat, Inc.
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