US3751362A - Continuous fluid-solid contact process - Google Patents

Abstract

THIS INVENTION RELATES GENERALLY TO FLUID-SOLID CONTACT PROCESSING SYSTEMS, AND, MORE PARTICULARLY, TO SUCH SYSTEMS AS MAY BE USEFUL IN ION EXCHANGE PROCESSES, WHICH PROCESSES OPERATE IN A TRULY CONTINUOUS MANNER AND EMPLOY CONTINUOUSLY MOVING POROUS BEDS FOR PROVIDING THE FLUID-SOLID REACTION, REGENERATION, AND WASHING OPERATIONS, AS DESIRED, AND WHICH UTILIZE UNIQUE MEANS FOR ISOLATING THE FLUID FLOW BETWEEN OPERATION ZONES THEREOF TO PROVIDE HIGH FLOW RATES FOR THE PROCESSED OUTPUT PRODUCTS INVOLVED.

Description

Aug. 7, 1973 so ET AL 3,751,362

CONTINUOUS FLUID-SOLID CONTACT PROCESS Filed July 8, 1971 4 Sheets-Sheet 1 102 lol m I07 I08 }ll6 '00 103 INVENTORS AIN A.SON|N RONALD F. PROBSTEIN @EF SHWARTZ Fle r BY 57 M" T T'Ys Aug. 7, 1973 A, SONIN ET AL 3,751,362

CONTINUOUS FLUID-SOLID CONTACT PROCESS Filed July 8, 1971 4 Sheets-Sheet 2 UNTREATED I9 I 3| 2 PRESSURE.

LIQUID PRIMARY REACTION zoNE II 38 2| 2o TREATED LIQUID e OUTPUT PRODUCT POROUS II BED I8 37 38 WASHING DILUT ED 5 39 AND REGENERANT REGENERANT SEPARATION LIQUID REGENERANT ZONE 4I Q INPUT PUMP \P4 27 28 35 REGENERATION WASTE 36 ZONE I2 3 OUTPUT A 26 40E SEPARATION 25 ZONE 42 RESIN DRIVER l4 zoNE I3 FIGS 33 I ATMOSPHERIC I FIGSA Aug. 7, 1973 A. A. SONIN ET AL 3,751,362

CONTINUOUS FLUID SOLID CONTACT PROCESS Filed July 8, 1971 4 Sheets-Sheet 4 UNTREATED .I l L I I I I INPUT /|7 -Q 32 i, FEED PUMP PRIMARY REACTION M J SS ZONE l| TREATED J L LIQUID OUTPUT 2O PRODUCT RESIN 25 26 DRIVER 38 ZONE l3 37 p 39 To FEED PUMP I7 40 36 D WASTE REGEN. OUTPU REGENERANT PUMP LIQUID as INPUT REGE NERATION ZONE I2 United States Patent 3,751,362 CONTINUOUS FLUID-SOLID CONTACT PROCESS Ain A. Sonin, Boston, and Ronald E. Probstein, Brookline, Mass, and Josef Shwartz, Haifa, Israel, assiguors to Avco Corporation, Cincinnati, Ohio Filed July 8, 1971, Ser. No. 160,601 Int. Cl. 301d 15/02 US. Cl. 210-33 17 Claims ABSTRACT OF THE DESCLOSURE This invention relates generally to fluid-solid contact processing systems, and, more particularly, to such systems as may be useful in ion exchange processes, which processes operate in a truly continuous manner and employ continuously moving porous beds for providing the fluid-solid reaction, regeneration, and washing operations, as desired, and which utilize unique means for isolating the fluid flow between operation zones thereof to provide high flow rates for the processed output products involved.

DESCRIPTION OF THE PRIOR ART Many fluid-solid contact systems have been used or suggested for use in the prior art and, from the viewpoint of operating continuity, such systems generally can be said to fall into three main categories: a first category sometimes identified as batch or discontinuous processing systems; a second category which can be most accurately identified as semi-continuous or nearly continuous processing systems (although, in some cases, such systems have been inaccurately referred to as continuous even though intermittent operation occurs therein); and a third category which accurately can be referred to as truly continuous processing systems.

A useful summary of the historical development of such fluid-solid contact processing systems, particularly of the latter two types as applied to processes involving ion exchange principles, is given in the publication Systematic Analyses of Continuous and Semi-Continuous Ion Exchange Techniques and the Development of a Continuous System, by R. C. Clayton, presented at the Society of the Chemical Industry Conference on Ion Exchange in the Process Industries, July 16-18, 1969, the proceedings of which were published by the Society in London, England in 1970. This paper traces primarily the development of nearly continuous and continuous ion exchange systems from the middle 1950s when recent interest in providing improved systems utilizing improved resins was begun.

Perhaps the most Widely known nearly continuous systems currently proposed and available for use are those developed by I. R. Higgins, examples of which are described in US. Pat. No. 2,815,322 issued to I. R. Higgins on Dec. 3, 1957, and in the publications, Chem- Seps Continuous Ion Exchange Contactor and Its Applications to De-mineralization Processes, by I. R. Higgins and R. C. Chopra, published as part of the above referenced conference, and Continuous Ion Exchange of Process Water, by I. R. Higgins, published in Chemical Engineering Progress, vol. 65, No. 6, in June 1969, as well as those developed by the Asahi Kasei Koygo Kabushiki Kaisha Corporation of Japan, various embodiments of which are described, for example, in US. Pat. No. 3,152,- 072 and British Pat. Nos. 1,022,921; 1,023,943; 1,036,065; 1,036,560; 1,036,559; 1,036,429; 1,033,649 and 1,031,299 as well as a recent publication Development of the Degremont-Asahi Continuous Ion Exchange Process, by I. Bouchard, also included as part of the above-referenced conference.

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Both the Higgins and the Asahi systems, as described in the patents and publications listed above, provide what are best referred to as nearly continuous systems, the operations thereof not being truly continuous, the latter term as used herein meaning all elements of the system remain in continuous operation without any interruption during the overall reaction, regeneration, and rinsing steps of the process. Both the Higgins and the Asahi systems are appropriately programmed so that processing is interrupted at some point during the overall operation for a finite time period. Such operation has been referred to as one using an intermittently moved, fixed bed process and is further discussed in the publication, Development of a Continuous Ion-Exchange Process, by D. G. Stephenson, also published in the proceedings of the abovementioned conference.

Moreover, in the operation of such systems, separate columns or regions separated by valves are utilized for the ion exchange portion of the overall process, the regeneration portion thereof and the rinsing or washing portion thereof. The exchange step effectively takes place with the use of a fixed bed of ion exchange resin which is intermittently moved so that the depleted resin can be conveyed from the ion exchange column to the regeneration column and regenerated resin can be inserted into the ion exchange column during the period of intermittent bed movement. During such periods the supply of untreated liquid is shut off so that no such liquid enters the ion exchange column until the depleted and regenerated resins are appropriately moved into position.

Moreover, in both the Higgins and the Asahi systems the depleted or regenerated resin materials which are moved from one station within the system to another are conveyed through a plurality of valves, or other mechanical devices, the use of which tends to cause a deterioration of the resin material and, hence, an attrition thereof.

Examples of truly continuous processing systems are briefly discussed in the above-mentioned paper of Clayton and are more completely described in the articles Countercurrent Ion Exchange, by T. A. Arehart et al. in Chemical Engineering Progress, vol. 52, No. 9, September 1956, p. 353; Semicontinuous Countercurrent Apparatus for Contacting Granular Solids and Solution, by C. W. Hancher and S. H. Jury, Chemical Engineering Progress Symposium Series, vol. 55, No. 24, 1959, pp. 96-97; and Exchange Rates Going Up, in Chemical & Engineering News, Oct. 22, 1956, p. 5200.

Such systems suffer from several defects which have prevented them from being accepted for use by those in the art. In the system described in the Chemical & Engineering News article, for example, the resin particles move downwardly with gravity through the upwardly flowing liquid and tend to become fluidized if the liquid flow upwardly through the resin becomes too high. Such tendency can be overcome as shown in the system described in the Arehart et al. article by the use of a hydraulic ram which tends to compress the resin and to maintain the bed in a packed porous state, the bed in turn being allowed to move downwardly by the use of a jet device at the end of the column. The major disadvantage of these systems, as pointed out in the above mentioned Clayton article, lies in the extreme difliculty of maintaining the delicate balance of pressures required at several points along the ion exchange column in order to isolate the fluid flow in adjacent zones thereof. Isolation is achieved in such systems by creating intermediate re gions containing virtually stagnant liquid, across which the pressure difference is maintained at zero. At higher flow rates, pressure imbalances tend to occur, producing unstable operation of the entire system, and producing an undesirable mixing of the fluids in adjacent zones so that the desired isolation is not achieved. The critically of such pressure balances can be alleviated to some extent, if the flow rates involved are reduced to a low enough value. However, the elimination of such instabilities can only be assured at flow rates which are lower than those required for a practically operating system competitive with discontinuous or nearly continuous systems.

Thus, in the above described types of truly continuous systems of the prior art, the maximum flow rates of output product that can be achieved with stable operation are only up to about 100 gallons per hour per square foot of column area, as set forth in the Chemical & Engineering News article. Such output product flow rates are far lower than those achievable with the system for carrying out the process of our invention, as discussed more fully below.

STATEMENT OF THE INVENTION The method of this invention overcomes the defects of prior art systems discussed above and provides a truly continuous system which operates at sufficiently high flow rates to provide a high product output which is at least one order, and in some cases two orders, of magnitude higher than those provided by continuous or semicontinuous systems presently available or suggested for use By the art at comparable installation and operating costs.

The high output product flow rates are obtainable in the system for carrying out the process of the invention by the use of an improved method for providing isolation between fluid flows of adjacent operating zones of the system. For clarity, the basic structural components and operation thereof as used to so isolate the fluid flow therein provide a separation region or zone in which, as described in more detail below, fluid flows can be continuously maintained during operation so that the stagnant or zero-flow region of prior art continuously operating systems is not needed. The use of such unique isolation zones permits the operation of the system at flow rates which,

provide output product flows of, for example, about 7000 gallons per hour per square foot of column area as opposed to the output product flow rates of less than 100 gallons per hour per square foot in the prior art. Unlike the prior art systems, the output product flow rates in the system for carrying out the process of the invention are limited only by the maximum allowable compressive stress on the solid material (e.g., the resin beads) and not by any fundamental limitations or problems inherent in the flow system.

Although not limited thereto, the invention can be specifically prwticed, for example, in a single column appartus for providing a truly continuous ion exchange operation, either of a cation or anion nature. A plurality of solid particles, such as an ion exchange resin material, are formed as a packed porous bed in a non-fluidized state, that is, a porous bed in which the solid particles do not move within the bed itself. The porous bed of solid resin material is initially formed from a slurry of such resin material in a non-regenerated form in a driver zone of a column, the method of formation thereof being substantially that described in US. patent application Ser. No. 748,811, filed on July 30, 1968, by R. F. Probstein and J. Shwartz, now Pat. No. 3,587,859. The porous bed is caused to move through the regeneration and primary reaction zones of the column and independent control of the rate of such movement is provided by a control of either the resin removal rate in the column or of the restraining forces, together with an appropriate choice of the pressure differences between the various inlet and outlet ports. The porous bed of resin material is removed from the column following its contact with the fluid in the primary reaction zone of the column and is combined with a portion of the untreated fluid and the slurry is thereupon conveyed to the initial driver zone for reformation of the porous bed therein. In the system for carrying out the process of the invention it is not necessary to convey the solid material through an excessive number of mechanical devices, such as valves, pumps, or other devices, and, in one preferred embodiment thereof, the system is arranged so that such material passes only through a single slurry pump, thereby minimizing the resin attrition, and a scraper which acts as a restraining force and control at the top of the column. The scraper may be designed to have relatively little physical effect on the solid particles.

Further, the fluid flows in the primary reaction zone and in the regeneration zone are isolated from each other and the fluid flows in the regeneration zone and in the driver zone are also isolated from each other. The isolation is achieved by the formation of isolation zones which are maintained in a stable condition through the use of fluid displacement techniques so that instability of operation cannot occur even under conditions of high flow rates as discussed more fully below.

Once the system for carrying out the process of the invention has been set into motion no programmed operation thereof, particularly one which provides for some intermittent or non-continuous operation, is necessary and the system continues its operation without interruption and merely requires appropriate monitoring means to determine that no unwarranted or accidential operating problems have arisen. Alternatively, it is within the scope of the invention that the system for carrying out the process of the invention may be programmed for a specific purpose desired in a particular use of the invention. For example, it may be desired that the rates of product removal required may be different over difierent time periods and the operation of the system may be purposely programmed to provide such varied rates.

Because of the presence of stable isolation zones, the ion exchange operations which occur in the process, whether in the primary reaction zone or in the resin regeneration zone, can be substantially localized so as to remain in elfectively stationary positions within the column, and, because all of the zones that are used can be of substantially limited lengths, the overall inventory of solid material for the process is reduced considerably from that which has been necessary in previously used processes of the prior art.

The system for carrying out the process of the invention provides an improved efiiciency of operation over that obtainable by systems of the prior art both with regard to the primary ion exchange reaction process and the resin regeneration ion exchange process because of the systems truly continuous operation. Further, such efiiciency is obtained at lower costs than those required with presently known systems since in a preferred embodiment only a single column providing greater output flow rates per unit of column volume need be used, less solid resin material required to produce the same output production rate using the same materials need be used, less regenerant material need be used, and a much less complex control system need be used, all as compared to known prior art systems.

DESCRIPTION OF THE DRAWINGS A more detailed description of the invention as used, for example, for ion exchange processes, is described below with reference to the following drawings wherein:

FIGS. l, 1A, 2, 3 and 4 show various embodiments of the basic isolation zone configurations used in connection with the invention;

FIG. 5 shows in diagrammatic form one preferred embodiment of an overall operating column representing the system of the invention;

FIG. 5A shows a graph of the pressure distribution along the column shown in FIG. 5;

FIG. 6 shows an alternate columnar embodiment of the system of the invention;

FIG. 6A shows a graph of the pressure distribution along the column shown in FIG. 6; and

FIG. 7 shows a portion of another alternate embodiment of the invention.

FIGS. 1, 1A, 2, 3 and 4 show various forms of a basic operating component used in particular embodiments of the invention for providing eflective isolation of the fluid flows present in adjacent operating zones of the system.

As shown in FIGS. 1, and 2, isolation can be provided between the flows of fluids outwardly from adjacent zones of a column filled with a continuously moving porous bed of solid material in which bed the fluids in such zones flow in opposite directions. In the first case (FIG. 1) both fluids are to be extracted from the column in pure, or unmixed, form. Thus, in a column 100 a first fluid 102 flows in one direction from a zone 101 as shown by the arrows associated therewith in the figure, While a second fluid 104 flows in the opposite direction from a zone 103 toward the first fluid, also as shown by the arrows associated therewith. A separation, or isolation, zone 105 is present intermediate zones 101 and 103 and small portions of fluid 102 and 104 flow in the isolation zone and together flow outwardly from a port 106 therein. The major portions of fluids 102 and 104 flow outwardly from the column at ports 107 and 108 in their pure form respectively. It is assumed, for example, that the porous bed is moving Within the column from zone 103 to zone 101. A portion of the fluid 104 from zone 103 is carried into zone 105 with the solid particles of the bed and is displaced by a portion of the fluid 102 flowing into zone 105 from zone 101 in a countercurrent washing action and the displaced portion of fluid 104 together with the displacing portion of fluid 102 flows out through port 106. An isolation crown 109 is formed near port 106 and none of fluid 104 is permitted to flow beyond crown 109 into zone 101, while at the same time none of fluid 102 is permitted to flow in the other direction beyond crown 109 into zone 103.

The portions of fluids 102 and 104 which exit at port 106 can be kept very small by an appropriate choice of pressures at ports 106, 107 and 108 providing the desired pressure differentials along the column between such ports as discussed more fully below in connection with FIGS. 5, 5A, 6 and 6A. Thus, while small portions of the fluids are in eflect lost due to their flow outwardly at port 106, any loss thereof can be kept very small and the advantage gained in maintaining a stable isolation zone far o'tfsets any disadvantage in such losses, because the fluid flow rates in the system can be increased markedly so that the product output rate is at a relatively high value in comparison to prior art values. Thus, in an operating column using the techniques of the invention, the output product flow rate can be improved by one or more orders of magnitude in comparison with the product output rate in continuous columns of the prior art using stagnant zone separation with its inherent instabilities at other than minimal flow rates.

FIG. 1A shows a similar situation in which fluid flows in adjacent zones are in opposite directions. In this case both fluids are to be inserted into the column and must flow therein in pure, or unmixed, form. Accordingly, fluid 112 in zone 111 is fed into a column 110 through port 113 to move in the direction of movement of a porous bed assumed to be moving from zone 116 to zone 111. A fluid 115 in zone 115 is fed into the column through port 117 to move in a counterdirection to the movement of the bed. Small portions of each fluid move toward each other in isolation zone 118 located intermediate zones 111 and 115 and such portions exit together at port 119. In the same manner discussed above, the pressures at ports 113, 117 and 119 are arranged to provide pressure diflerentials appropriate for forming an isolation crown 120 near port 119 and for controlling the portions of each fluid which flows outwardly from zone 118 so that none of fluid 112 can enter zone 116 and none of fluid 115 can enter zone 111.

In FIG. 2, isolation is achieved between two zones in which fluids also are flowing in opposite directions. However, in this case, only one of the fluids need be extracted from the column in pure or undiluted form. Accordingly, a fluid 121 flows in zone 122 in a direction opposite to an assumed direction of movement of a porous bed within a column 123, while a fluid 124 flows in zone 125 in the same direction as such bed movement. Fluid 124 is to be extracted at port 126 in pure form and fluid 121 which is extracted from port 127 may be permitted to be mixed with a small amount of fluid 124. The pressures at ports 126 and 127 are arranged to form isolation zone 129 so that the major portion of fluid 124 exits at port 126 and a small portion of fluid 124 moves with the bed toward port 127. Such portion is displaced by a portion of fluid 121 and an isolation crown 128 is formed near port 127 at Which port all of the fluid 121 exits together with such small portion of fluid 124 which has been displaced so that none of fluid 121 moves into zone 125 and none of fluid 124 moves into zone 122.

FIGS. 3 and 4 show situations in which both fluids are moving in the same direction in a column which also has a porous bed moving therein. In FIG. 3 it is desired that a first fluid which exits from one zone of the column be prevented from contaminating a second fluid which enters the column into an adjacent zone. Thus, a fluid 130 exits from a zone 131 of column 132 at port 133, while a fluid 134 enters the column into a zone 135 at port 136, both fluids flowing in the same direction within the column as shown by the associated arrows. A small portion of fluid 130 flows toward zone 135 and a small portion of fluid 134 flows toward zone 131 and both portions exit the column at port 137 from an isolation zone 138. The pressures at ports 133, 136 and 137 are arranged so that an isolation crown 139 is formed near port 137 and none of fluid 130 enters zone 135 and none of fluid 134 enters zone 131.

FIG. 4 shows a situation in which fluids in two adjacent zones flow in the same direction, one exiting from the column and one entering the column, and only the entering fluid is to be prevented from contamination by the exiting fluid. Thus, fluid 140 exits column 141 from zone 142 at port 143 and fluid 144 enters the column into zone 145 at port 146. The pressures at ports 143 and 146 are arranged to form isolation zone 143 adjacent zone 142, an isolation crown 147 being formed near port 143 so that all of the fluid 140 exits at such port together with a small controlled portion of fluid 144. The major portion of fluid 144 flows in zone 145 and none of fluid 140 enters zone 145 and none of fluid 144 enters zone 142.

The terms isolation zone, or separation zone, are used interchangeably in the description of the invention and are intended to refer to a region within a column, lying between two zones which are to be isolated, in which region controlled portions of both fluids flow and which region includes an isolation crown and a port through which such controlled portions are permitted to exit together from the column.

Thus, as can be seen in FIGS. 1, 1A and 3, the isolation zones 105, 118 and 138 are shown as including the parts of the column depicted. therein which lie between ports 107 and 108 in FIG. 1, between ports 113 and 117 in FIG. 1A and between ports 133 and 136 in FIG. 3. Accordingly, controlled portions of both fluids flow in isolatron zones 105, 118 and 138 and are permitted to exit from the isolation zones together at ports 106, 119 and 137, respectively.

In the configuration depicted in FIGS. 2 and 4, wherein the controlled portions of fluids 121 and 140 included all of such fluids which flow in zones 122 and 142, respectively, the isolation zones 129 and 148 are shown as effectively extending from ports 126 and 146, respectively, to locations above ports 127 and 143, respectively, so as to include isolation crowns 128 and 147, respectively. Accordingly, controlled portions of both fluids flow in the isolation zones 129 and 149 shown therein and such controlled portions are permitted to exit from the isolatron zones together at the ports 127 and 143, respectively. One or more of the above configurations can be used 1n various embodiments of overall systems for carrying out the process of the invention as discussed further below. FIG. shows one preferred embodiment of such an overall operating structure in accordance with the process of the invention, which structure, for example, utilizes a single column processing system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 5 there is shown a processing column 10 which can be used, for example, to remove calcium from a calcium carbonate solution, such as might be found with hard water, through a cation exchange operation wherein a suitable ion exchange resin including free sodium ions (Na is utilized for exchange with calcium ions (Ca+ in the solution to be treated. Such an ion exchange process is exemplary only and other ion exchange processes, or processes other than those utilizing ion exchange principles, can also make use of the column as described herein.

Three major operating zones are utilized in column 10 and are identified in FIG. 5 as including two principal ion exchange zones. The first, a primary reaction zone 11 for producing the output product, and the second, a regeneration zone 12 for regenerating the resin material; and a third, a resin driver zone 13. A washing and separation zone 41 intermediate zones 11 and 12 is also shown, although, as discussed in more detail below, the washing operation is not always needed in all applications of the invention. Further, a separation, or isolation, zone 42 is utilized intermediate regeneration zone 12 and driver zone 13.

The column has within it a moving packed porous bed 13 of an ion exchange resin, which bed extends from a position in driver zone 13 shown by dashed line 14 at the lower end of column 10 to a position above the primary reaction zone 11 near the top end of the column as shown by dashed line 15. The untreated fluid, in this case a calcium carbonate solution, is fed from a supply 16 thereof through feed pump 17 to an input port 19 shown at the top end of the column. Although not necessarily limited thereto, in the particular embodiment discussed in FIG. 5, the column is cylindrical and the fluid input and output ports used therein intermediate the ends of the column may extend about the entire periphery of the column, as shown.

The untreated liquid entering port 19 is thereby partly directed downwardly as shown by arrows 38 through the upper portion of porous resin bed 18 so that as the untreated liquid is contacted by the resin particles in the bed, the (Caions of the former are exchanged with, or replaced by, the free (Na+) ions of the latter, as is well known. At the lower end of primary reaction zone 11 the liquid has been fully processed, i.e., the calcium ions have been substantially completely removed and replaced by the free sodium ions, and treated liquid product is thereupon removed from the column through port 20 via a throttle valve 21.

During the ion exchange operation the porous bed 18 is continuously moving upwardly through the primary reaction zone 11 and the untreated liquid is moving in a counter direction downwardly through the zone. The resin particles which have moved in the porous bed 18 through the primary reaction zone and which are thereby present in the upper section of the column above zone 11 have at that point been depleted of their free sodium (Na ions to a predetermined level, and, accordingly, must be regenerated before they can be used again for that purpose. The particles in their depleted or non-regenerated form are mixed with a portion of the untreated liquid which enters through port 19 and the slurry removed from the column through port 32 as a result of the pres sure difference between inlet port 19 and port 32. The resin of the slurry is carried with the liquid through line 29 to a location below the column 10 where it is fed to a slurry pump 33 which moves the slurry into the lower end of column 10 via a slurry input port 34 at the bottom thereof.

The resin particles which enter the column in the slurry subsequently are formed into a compact porous bed in driver zone 13, which bed is forced upward by the fluid flow in the driver zone. The untreated liquid portion of the slurry is permitted to exit from the column at port 25 and is then fed via throttle valve 26 to the input line at feed pump 17 where it is returned to the supply of untreated liquid from supply 16.

An isolation, or separation, zone 42 is present between regeneration zone 12 and resin driver zone 13 so that the depleted regenerant liquid from zone 12 is prevented from reaching and mixing with the untreated fluid which exits via port 25 and is returned to the feed. In this separation operation the depleted regenerant liquid which has passed downwardly through the moving porous bed in regeneration zone 12 is used to displace any portions of the untreated liquid which are present in the bed as it moves upwardly from zone 13 and the depleted regenerant liquid together with such untreated liquid portion both exit at port 36 to be pumped as output waste products. Such operation is the type discussed above with reference to FIG. 2, for example. Accordingly isolation, or separation, zone 42 extends to a location above port 36 and an isolation crown 40 is formed near port 36 so that the regeneration zone 12 is effectively separated from the driver zone 13 and depleted regenerant liquid is prevented from moving downwardly into zone 13 from zone 12, while untreated liquid is prevented from moving upwardly from zone 13 into zone 12. The pressures along the column, as discussed below, are arranged so that only a small, and controlled, amount of untreated liquid need be lost through port 36 to achieve the separation. Although some regeneration takes place in the upper region of isolation zone 42, it is clear that most of the regeneration action occurs in the regeneration zone 12.

Since the resin particles in the slurry entering the bottom of the column are partially or wholly depleted of their exchangeable ions, such ions must be replaced through a regeneration process, which operation occurs in regeneration zone 12. The regeneration liquid which in the example under discussion may be a concentrated sodium chloride (NaCl) solution is fed to the column from a supply 27 via regenerant pump 28 through input port 35. The major portion of the regenerant solution forced under a pressure difilerence downwardly through the upwardly moving porous bed in a countercurrent operation and in the process of moving therethrough the free sodium (Na+) ions therewith replace the calcium (Ca++) ions present in the depleted resin particles in regeneration zone 12. The depleted regenerant solution then exits from the column via port 36 where it can be dumped as waste output material. Although, as mentioned above, most of the regeneration action occurs in regeneration zone 12, a small amount of regeneration takes place in the upper region of separation zone 42 prior to the removal of depleted regenerant solution from the column.

The porous bed of regenerated resin particles which moves upwardly from regeneration zone 12 also contains a small portion of regenerant liquid. If the regenerant liquid is not removed from the porous bed it will be carried upwardly with the bed and will mix with the treated liquid product and will exit together with the treated liquid at port 20. While in some cases it may not be detrimental to have the treated liquid mixed with regenerant liquid, in many other cases it is undesirable to permit such mixing to occur. In the lattter instances any upwardly moving regenerant liquid must be removed before it reaches port 29. Such removal is accomplished in Washing and separation zone 41 in a manner as discussed above with reference to FIG. 3. Thus, a wash liquid, in the form of a small portion of the treated liquid product moving downwardly from primary reaction zone 11, is caused to move in a counter-current direction through the upwardly moving porous bed in a washing portion of zone 41, and accordingly, displaces the regenerant liquid which is present in the moving bed. An isolation crown 39, as discussed above, is formed as shown. The displaced regenerant liquid exits from the column at port 37 and is fed back to the input of regenerant pump 28 via throttle valve 38 where it is added to the regenerant fluid from supply 27. If the treated liquid which acts as a washing solution and which exits from port 37 is held to a minimum, the regenerant liquid which also exits therefrom is only slightly diluted therewith. The presence of such a relatively small amount of treated liquid in the regenerant liquid, which is combined ultimately with the regenerant liquid from supply 27, will cause a controlled change in the characteristics of the regenerant liquid so that the liquid supplied to zone 12 for the regeneration process has the desired concentration.

As discussed previously, the presence of isolation crown 39 formed near port 37 effectively separates the liquids in the regeneration zone 12 and in the primary reaction zone 11 and no regenerant liquid is carried upwardly beyond crown 39 to zone 11 and similarly no treated liquid is carried downwardly below crown 39, the small amount of the treated liquid which moves downwardly from zone 11 being forced to exit at port 37. Thus, a porous bed comprising regenerated resin particles enters the primary reaction zone Ill so that the ion exchange process is effectively carried out therein.

FIG. A shows the distribution of pressure along the column. The base pressure is, for example, arbitrarily taken to be atmospheric pressure P and in this case, exits at port 36 where the waste material is assumed to be dumped into the atmosphere. The pressure P at port 25 is held slightly greater than the pressure P its value being set by throttle valve 26. The maximum pressure in the column is at the lower end thereof, that is, at the input to the resin driver zone 13, and is identified as pres sure P The pressure P at port 19 at the upper end of the column is lower than P, so that the overall pressure drop (P P substantially provides the driving force for moving the porous bed upwardly through the column against the restraining forces therein. These restraining forces would include the frictional forces which may exist between the bed and the inner surface of the column and any additional restraining force which may be present, such as the force which exists in the column shown due to the stress exerted by the scraper 31 at the top of the column. In addition, if the column is oriented in a vertical direction, the weight of the porous bed will also contribute to such forces.

This rate of upward advance of the porous bed is governed either by the rate of removal of the resin by the scraper or by the balance of forces which exist on the porous bed as a whole.

The pressure P, is determined by the pressure generated by the regenerant pump 23 and is greater than the pressure P at port 37, the latter being set by adjusting throttle valve 38. Throttle valve 21 sets the pressure P at port 20 and the pressure P, at port 19 is determined by the feed pump 17. The pressure at the input of slurry pump 33 is somewhat lower than the pressure at the top of the column due to the pressure drop from the losses between the entrance port 19, and the entrance to the slurry pump 32.

The system of throttle valves and pumps shown in FIG. 5 is used for illustration only. Various other types of controls may be used to achieve the pressure distribution (shown in FIG. 5A) which is necessary for correct operation of the column.

The embodiment discussed above with reference to FIG. 5 shows a system which utilizes a single resin driver zone shown as zone 13 at the lower end of the column. In some cases, however, depending upon the geometry of the column, the fractional forces present between the porous bed and the inner surface of the column may be high enough that the use of such a single driver zone may not be adequate to overcome such forces so as to maintain the upward motion of the bed without an excessive stress on the resin beads. This effect is particularly noticeable for relatively long columns inasmuch as such forces build up rapidly as a function of the length of the column, as discussed generally by H. L. Brandt and B. M. Johnson in the article Forces in a Moving Bed of Particulate Solids With Interstitial Fluid Flow, in Al. Ch. B. Journal, vol. 9, No. 6 November 1963, p. 771. In such instances it may be desirable to utilize one or more additional driver zones inserted at appropriate locations along the column.

Such a structure is shown in FIG. 6, for example, in which corresponding reference numerals identify elements corresponding to those of FIG. 5 and in which an additional auxiliary driver zone 45 is positioned between the primary reaction zone 11 and the wash and separation zone 41. As shown, a drive pump 46 is used to pump a portion of the treated liquid which exits from port 20 back into the column at port 47. Thus, a first portion of the treated liquid entering port 47 is used to force the porous bed upwardly through driven zone 45.

In this structure all of the liquid flowing upwardly in auxiliary driver zone 45 and all of the liquid flowing downwardly in primary reaction zone 11 exit together from the column at port 20. Unlike the isolation operation discussed previously with reference to separation zones 41 and 42, no isolation, or separation, zone is formed between primary reaction zone 11 and auxiliary driven zone 45. Instead, the operation at port 20 is similar to that described in the above reference Probstein and Shwartz patent application wherein both liquids are permitted to interact, or mix, completely in their simultaneous exit from port 28. Although an effective liquid displacement action occurs so as to form a crown 48 near port 20 where both liquids exit, there is no need to control the amount of mixing thereof since, at such point, both liquids are the same (i.e., treated liquids). Hence, a complete mixing of them can be permitted and the need for the formation of an isolation zone in accordance with the invention is avoided. The operation at port 20, therefore, can be contrasted with the operation of separation zones 41 and 42 where, as discussed previously, only a small, and controlled, amount of one liquid is permitted to mix with another different liquid and a complete mixing, or interaction, between the two different liquids is prevented.

A second smaller portion of the liquid entering port 47 is forced downward into the wash and separation zone 41, the latter zone isolating the auxiliary driver zone 45 from regeneration zone 12 essentially in the same manner as discussed previously with reference to FIG. 5. Further, a throttle valve 49 has been added at the output of port 36 to allow the pressure P at port 36 to be greater than the base atmospheric pressure.

FIG. 6A shows the pressure distribution along the column for the configuration of FIG. 6. In this particular embodiment the base atmospheric pressure P is at port 20 at which port the output treated fluid product exits. The pressure at port 47 is identified as P and is well above the pressure P at port 20 and also above the pressure P at port 37. The relationship among the pressures P P P P and P is substantially the same as that shown in FIG. 5A, all of such pressures in efiect having been pressure biased upwardly as a result of the insertion of driver zone 45.

Other insertions of additional driver zones at other alternative locations along the column may be required in any particular application of the invention and can be readily worked out for specifically desired operating conditions in accordance with the principles of the invention.

As one particular example of the possible dimensions and pressures involved in a column of the invention, the following exemplary values are given, such values being related, for example, to the embodiment shown in and discussed with reference to FIGS. 6 and 6A above.

DIMENSIONS Total column length feet 10.5 Column diameter (at primary reaction zone 11) inch 8 Column diameter (at regeneration zone 12) do 4 Length of primary reaction zone 11 feet 2 Length of driver zone 45 do 2 Length of Washing zone 14 do 1 Length of separation zone 41 do 1 Length of regeneration zone 12 do 2 Length of separation zone 42 do 1 Length of resin driver zone 13 do 1.5

PRESSURES P =Between 9 to 9.5 atmospheres P =ApproX. 9 atmospheres (below P but above P P '=Approx. 9 atmospheres (below P P =Approx. 9 atmosphers (above P and P P '=Approx. 9 atmospheres (below P and P P '=Approx. 9 atmospheres (above P but below P P =1 atmosphere 1 :3 atmospheres For a column of such size and pressure relationships, the rate of removal of treated liquid product will be approximately 60,000 gallons per day. Such a figure can be compared with the maximum output of about 800 gallons per day for comparably sized continuously operating columns of the prior art described above. In general, for product output rates lower than above mentioned design values for the system for carrying out the process of the invention, all pressure differences used in the columns will be scaled down approximately proportionately to the reduction in product rate.

In a single vertical column of the types described with reference to FIGS. 5 and 6, for example, the regeneration zone 12 and the resin driver zone 13 at the bottom of the column are eiiectively isolated as discussed above in the vicinity of port 36 by the crown 40 formed as shown and the regeneration zone 12 is effectively isolated from either the primary reaction zone 11 or the auxiliary drive zone 45 in the vicinity of port 37 by crown 39. The formation of such isolation crowns will occur without instabilities if the density of the uppermost liquid is substantially the same as, or less than, that of the lowermost liquid at the crown in question. Such isolation can still prevail even if the uppermost liquid has a slightly higher density than that of the lowermost liquid provided the fluid allow rates through the resin bed are high enough to prevent instabilities which lead to the passage of the heavier fluid into the lighter one via finger-shaped regions (fingering instability), a phenomenon generally discussed, for example, in the article, Mechanisms Affecting Dispersion and Miscible Displacement, by Richard I. Nunge and William N. Gill, published in Flow Through Porous Media, pp. 179-196, American Chemical Society, Washington, DC, 1970.

However, if the density of the uppermost liquid is higher than that of the lowermost liquid and the fluid flow rates are insufiicient, an unstable condition will occur and the heavier liquid will tend to move downwardly through the crown in question and efiFective stabilization cannot be maintained for purposes of isolation as desired.

For example, if the regenerant liquid is heavier than the liquid under treatment, an instability can occur at crown 40 where the regenerant liquid will tend to move down- 'wardly through crown 40 toward the bottom of the column. In such case no instability occurs at crown 39 since the heavier regenerant liquid is below the crown and the lighter treated liquid is above the crown. In such a case, an alternative embodiment of the invention, as shown in FIG. 7, may be used-to overcome the possibility that such instability may occur.

As can be seen in FIG. 7, the portion 50 of the column, effectively representing the regeneration zone 12 is formed in a U-shaped configuration, the structure and reference numerais relating to the remainder of the column corresponding to those shown in FIG. 5. In such configuration, the heavier regenerant liquid is then effectively placed below the lighter untreated liquid in the driver zone at a position near port 36, which, as shown, therein, is at the righthand end of U-shaped portion 50. Accordingly, while the overall operation of the coumn remains essentially the same as before, the potential instability is removed and, as before, the crown 40 is formed at port 36 so that isolation occurs between the resin driver zone 13 and the regeneration zone 12. The untreated liquid in driver zone 13 is moving downwardly in the column at the right and is thereby prevented from entering the regeneration zone while the regenerant liquid which is moving upwardly in the column at the right is prevented from passing into the resin driver zone. In all other respects the overall operation of the column is substantially the same as that shown and described with reference to FIG. 5.

Alternatively, if the liquid under treatment in the embodiment of FIG. 5, for example, is heavier than the regenerant liquid, an instability can occur at crown 39, and the entire system shown in FIG. 7 may be inverted so that the curved section 50 has the highest elevation. The heavier treated liquid is then below crowns 39 and 40 formed at port 37 and 36 respectively, and the lighter regenerant liquid is above, as required for stability.

In the embodiments shown and discussed above, which represent exemplary embodiments of the invention, the advantages of the system for carrying out the process of the invention are readily apparent when the operation and structure thereof are compared to presently available fiuid solid contact processing systems. Insofar as the inventors presently know, this invention represents the only etfective, truly continuous fluid-solid contact process that can achieve high output product rates with stable operation. In contrast with semi-continuous systems, no intermittent operation of any portion of the system is required. Moreover, the steps of the process of the inven tion are adapted to permit the effective embodiment of the systems in a single column, wherein a packed porous bed of solid material is continuously moved through the various operating zones of the column and eiiective isolation of such zones is achieved, where necessary, by using stably operated fluid displacement techniques. The rate of rise of the porous bed can be controlled in a substantially independent fashion (i.e., such rate of rise is not dependent to any great degree upon any other characteristics of the system, once the pressures P P P P P (if present), and P are selected for a desired operating condition) by maintaining an appropriate overall pressure difference (P -P across the column and controlling the scraping rate at the top of the column. The capability of using a single column in a preferred embodiment of the invention to perform all of the operating steps involved avoids the need for a plurality of valves, or other mechanical devices for controlling the passage of solid material or other material from one column to another as is required in a multi-column structure. Thus, the physical characteristics of the solid material are not subject to any substantial alteration because of the use of such mechanical devices. The only regions of the system for carrying out the process of the invention in which the solid material is subjected to mechanical perturbations in the embodiments discussed above are at the slurry pump and at the scraper means.

However, the invention is also adaptable to multiple column operation which may be desirable in some applications, particularly where mixed bed operation is to be achieved.

Since the operation of the system of the invention is truly continuous, there is no need to program the operation of any of the steps in the overall process in an intermittent fashion, as in the Asahi or Higgins systems, or other nearly continuous systems, presently known in the prior art. Thus, once the system has been set into operation, no further control or programming is required other than for the provision of a convenient method for monitoring various operating characteristics of the system to determine whether the desired operation is being achieved. In some applications, as mentioned previously it may be desirable to program the operation of the invention even though a programmed operation is not necessary to the basic principles of the operation thereof. In such instances, for example, the amount of treated liquid removed from the system (i.e., the production rate) may be varied, if desired, by programming the pressure relationships set up for operation to produce the variations required.

In operation of the system for carrying out the process of the invention, the primary reaction zone 11 and the regeneration zone 12 remain in substantially the same locations within the column and need only be of suflicient length to provide for an eflicient ion exchange operation. Thus, in the primary reaction zone 11 ion exchange resin is depleted to a predetermined value when it reaches the top of the zone and the untreated liquid is processed by the time it reaches port 20.

Further, in the regeneration zone 12 the depleted resin is regenerated by the time it reaches the separation zone 41 and the regenerant liquid is depleted when it reaches port 36. Thus, the overall resin inventory is reduced considerably from that required in prior art systems. In the preferred embodiments of the invention described above only a single transfer line, i.e., the slurry line 29, for example, is required for conveying solid particles, as contrasted with the multitude of transfer lines for the resin material that are used in the multi-column systems of the prior art.

The overall operation, therefore, provides great improvement in ion exchange efliciency both in the primary reaction zone and in the regeneration zone and considerably reduced costs of initial installation and subsequent operation.

Although the above embodiments have been described, for clarity, as utilizing a single column construction, the principles of the invention utilizing the continuous operation of the ion exchange and driver zones therein as well as the washing and separation zones therein can in some applications be embodied in more than one columnar entity, if desired, with appropriate means for feeding materials from one zone to another between columns. Further, though the above discussion, again for clarity, is shown with reference to vertically oriented structures, it is clear that the apparatus may be horizontally oriented, or oriented somewhere in-between, for some applications. The system is not dependent on gravity force components for its operation and, accordingly, its orientation can be set entirely independent thereof.

What is claimed is:

1. A process for isolating the flow of a first fluid flowing at a first rate in a first zone of a column from the flow of a second fluid flowing at a second rate in a second zone of said column in which column a packed porous bed of solid material is moving through said zones at a third rate, said process comprising the steps of:

permitting a controlled portion comprising at least a part of said first fluid to flow from said first zone toward said second zone at a fourth rate;

permitting a controlled portion comprising at least a part of said second fluid to flow toward said first zone at a fifth rate;

independently controlling said fourth and said fifth flow rates so as to permit the removal of said controlled portions of said first and second fluids simultaneously at a position intermediate said first and second zones, thereby forming an isolation Zone between said first and said second zones to prevent any of said first fluid from 14 entering said second zone and any of said second fluid from entering said first zone, and removing said controlled portions of said first and second fluids from said column at a position in said isolation zone.

2. A process in accordance with claim 1 wherein said controlled portion of said first fluid comprises all of said first fluid.

3. A process in accordance with claim 1 wherein said first fluid flows in said first zone in a direction opposite to the flow of said second fluid in said second zone.

4. A process in accordance with claim 1 wherein said first fluid flows in said first zone in the same direction as the flow of said second fluid in said second zone.

5. A continuous fluid-solid contact process comprising the steps of continuously supplying a first fluid material to a fluidsolid reaction zone;

continuously removing reacted portions of said first fluid material from said reaction zone;

continuously supplying a second fluid material to a second zone;

continuously forming a porous bed of solid material and moving said porous bed through said reaction zone and through said second zone in contact with said first and second fluid materials;

continuously permitting controlled portions of said first and said second fluid materials to flow in a first isolation zone intermediate said reaction zone and said second zone;

continuously removing said controlled portions of said reacted portions of said first fluid material and of said second fluid material from said first isolation zone; thereby forming an isolation crown in said first isolation zone to prevent said first fluid material from entering said second zone and said second fluid material from entering said reaction zone, and continuously removing the remainder of said second fluid at a point remote from said first isolation zone.

6. A continuous fluid-solid contact process in accordance with claim 5 wherein said first fluid material is an untreated fluid material,

said reacted portions are treated fluid material, and said fluid-solid reaction zone is a primary reaction zone;

wherein said second fluid material is a regenerant fluid material and said second zone is a regeneration zone; and further wherein said porous bed of solid material continuously moves through said regeneration zone, said first isolation zone, and said primary reaction zone in contact with said regenerant fluid material and in contact with said untreated fluid material.

7. A process in accordance with claim 6 wherein said porous bed is formed in a driver zone and further including the steps of continuously forming a slurry comprising said solid material of said porous bed leaving said primary reaction zone and said untreated fluid material; continuously moving said slurry to said driver zone; continuously removing a part of said untreated fluid material from said driver zone; permitting a controlled portion of said regenerant fluid and a controlled portion of said untreated fluid to flow in a second isolation zone intermediate said regeneration zone and said driver zone; and

continuously removing said controlled portions of said regeneration fluid and said untreated fluid from said second isolation zone;

thereby forming an isolation crown in said second isolation zone to prevent said regenerant fluid from entering said driver zone and said untreated fluid from entering said regeneration zone.

8. A process in accordance with claim 7 and further including the step of adding said part of said untreated 15 fluid material being removed from said driver zone to a supply of untreated fluid material, at least a part of which is beingsupplied to said primary reaction zone.

9. A process in accordance with claim 7 and further including the step of controlling the rate of movement of said porous bed by controlling the pressure difierence (P -P wherein P represents the pressure at which said slurry enters said driver zone and P represents the pressure, less than the pressure P at which said untreated fluid material is supplied to said primary reaction zone, whereby the rate of movement of said porous bed through said driver zone, said regeneration zone, said primary reaction zone and said first and second isolation zones is controlled.

10. A process in accordance with claim 9 and further including the step of independently controlling the pressure at which said part of said untreated fluid is being removed from said driver zone at a pressure P which is below said pressure P 11. A process in accordance with claim 10 and further including the step of independently controlling the pressure at which said controlled portions of said regenerant fluid and said untreated fluid are being removed from said second isolation zone at a pressure P which is below said pressure P 12. A process in accordance with claim 11 wherein said pressure P is maintained at atmospheric pressure.

13 A process in accordance with claim 11 and further including the step of independently controlling the pressure at which said regenerant fluid material is being supplied to said regeneration zone at a pressure R; which is above said pressure P 14. A process in accordance with claim 13 and further including the step of independently controlling the presl 6 sure at which said reacted portion of said untreated fluid material is being removed from said primary reaction zone at a pressure P which is below said pressure P7.

15. A process in accordance with claim 14 and further including the step of independently controlling the pressure at which said controlled portions are being removed from said first isolation zone at a pressure P which is below said pressure P 16. A process in accordance with claim 15 and further including the step of continuously moving said porous bed through an auxiliary driver zone positioned intermediate said regeneration zone and said primary reaction zone.

17. A process in accordance with claim 16 wherein a portion of said treated fluid material being removed from said primary reaction zone is supplied to said auxiliary driver zone at a pressure P which is above said pressure P References Cited UNITED STATES PATENTS 6/1972 Minart 210-33 OTHER REFERENCES SAMIH N ZAHARNA, Primary Examiner R. A. S-PITZER, Assistant Examiner U.S. Cl. X.R.

3 UNITED STATES PATENT OFFICE CEETH ICATE ()F CORRECTION Patent No. 751,362 Dated August 7, 1973 I Ain A. Sonin, Ronald F. Probstein, and Josef Shwartz It is certified that error appears in'the above-identified patent and that said Letters Patent are hereby corrected as shown below:

' Column 2, line 72, for "critically" read--criticality--; Column 5, line 61, for "115" (second occurrence) read--ll6--; Column 5, line 64,

for "115" read--ll6-; Column 8, line 22, for "pumped" read--dumped--; Column 9, line 64, for "32" read--33--; Column 9, line 75, for fraction'eml read--rictional-; Column 10, line 24, for "driven" read--driver-; Column 10, line 31, for "driven" read--driver--;

Column 10, line 36, for "28" read--20--; and Column 12, line 10,

for "coumn" read--column--.

Signed and sealed this 18th day er December 1973.

(SEAL) Attest:

EDWARD M. FLETCHER, JR. RENE D. TEGTMEYER Attesting Officer- Acting Commissioner of Patents

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