GB1590103A - Ion exchange process - Google Patents

Description

(54) ION EXCHANGE PROCESS (71) We, ROHM AND HAAS COM PANY, a corporation organized under the laws of the State of Delaware, United States of America, of Independence Mall West, Philadelphia, Pennsylvania 19105, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in andby the following statement: This invention is concerned with a process and apparatus for ion exchange by use of thermally regenerable resin continuously or intermittently moving between loading and regeneration zones in a single column.

In ion exchange treatments using ion exchange resins of the type which are chemically regenerated, when the treatment is performed in a fixed bed ion exchange system, the ion exchange treatment and the regeneration treatment are not performed simultaneously within one and the same column. Rather, one of the two treatments is shut down while the other treatment is in progress. Even in the continuous moving bed ion exchange system which has been developed and is in practical use regeneration and loading must be carried out in separate columns so that the cost of equipment is high.

Thermally regenerable resins, such as those used in the present invention, are resins which, unlike conventional chemically regenerable ion exchange resins, can have their ion exchange capacity regenerated by hot water alone. Such resins are now commercially available, one example being the heterogeneous thermally regenerable resin "Amberlite" (registered trademark) XD-2, a product of Rohm and Haas Company, U.S.A.

The process and apparatus of this invention requires only a single column, packed with a thermally regenerable resin, but permits ion exchange treatment and regeneration treatment to be carried out continuously and efficiently in that single column.

In the regeneration of a thermally regenerable resin, it is naturally desirable from the standpoint of economics to decrease as much as possible the amount of hot water used for the regeneration. However in an up-flow loading column the liquid to be treated must be fed at a rate high enough to support and expand the resin bed to ensure efficient contact of the liquid with the resin.

Consequently, the lower limit of flow rate of raw liquid is fixed by the specific gravity of the resin and other factors. If the flow rate in any part of a column of resin is below this lower limit, other measures must be taken to support the resin which is not supported by the upwardly flowing liquid, for example forming a supporting zone beneath a regeneration zone by feeding resin in this supporting zone with water at such a rate that this resin will expand to support the resin in the regneration zone in a relatively fixed position. If such a supporting zone is adopted means must also be adopted to prevent loss of heat from the regeneration zone down into the supporting zone, that is to say a thermal buffer zone must be formed.

We have now surprisingly found that in such a system ion exchange may be effected between the resin and water in the supporting zone and consequently have developed a system wherein ion exchange and regeneration may be effected in a single column.

According to the invention there is provided an ion exchange process wherein loading and regeneration of the resin are carried out in a single column of resin the resin being continuously or intermittently transferred from an upper, regeneration, zone in the column, through an intermediate, thermal buffer, zone to a lower, loading, zone in the column, loaded resin being transferred from the loading to regeneration zones by means external to the column and wherein regenerant and loading liquids flow through their respective zones, in the case of the loading liquid this flow being upwards, the regenerant liquid being at a higher temperature than the loading liquid and wherein only such amounts of the loading and/or regenerant liquids are allowed to pass into the buffer zone that a temperature is maintained between the proximate ends of the regeneration and loading zones.

Go embodiment of the invention is a process for 'ontnuois or semi-continuous ion exchange treatment based on a column packed with a heterogeneous thermally regenerable ion exchange resin in a single bed wherein the bed has a loading zone, a heal displacement zone above the loading zone, and a regeneration zone above the heat displacement zone. In this process, the steps are: (a) flowing an aqueous feed liquid having an undesirably high concentration of ions upwardly through the loading zone to substantially reduce the concentration of ions, and withdrawing resultant treated liquid as product liquid from the vicinity of the top of the loading zone with some product liquid passing into the heat displacement zone; (b) flowing an aqueous liquid regenerant at a higher temperature than the temperature of the feed liquid, through the resin in the regeneration zone to regenerate the resin; (c) controlling the flow of aqueous liquid in the thermal buffer (alternatively known as heat displacement) zone to maintain a temperature differential between the loading zone and the regeneration zone; (d) transferring, outside the column, loaded resin from the loading zone to the regeneration zone; and (e) displacing regenerated resin downwardly in the column to replace the transferred resin.

Steps (a) and (b) may be effected simultaneously or independently. Preferably, a portion of the product liquid removed from the loading zone in step (a) is heated and utilized as the hot regenerant liquid in step (b).

The resin displacement step (e) may, in another aspect of the invention, be practiced by pulsing, utilizing in each pulse the steps of: (1) discontinuing the flow of aqueous feed liquid in step (a) while draining feed liquid from the loading zone, for a period of time effective for dis placement of resin downwardly in the column, and (2) thereafter reactivating the flow of aqueous feed liquid while discon tinuing the draining of feed liquid from the loading zone, entraining loaded resin with a portion of feed liquid to form a resin slurry, and transferring the resin slurry to the regeneration zone.

The invention further provides apparatus comprising the aforemen tioned column. associated liquid and resin transfer lines, and resin feed means.

The thermally regenerable resins useflil in the present invention are primarily "heterogeneous thermally regenerabie resins". Thcse are thermally regenerable ion exchange resins having mixed ion exchange functional units within a single particle as distinguished from the so-called "mixed beds" known in the art which consist of a physical admixture of cationic resins and anionic resins. Heterogeneous resins useful in the present process include "hybrid" ion exchange resin materials (see, for example, U.S. Patent 3,991,017), various "composite" ion exchange materials formed by binding acidic and basic functional resins within a single particle (see, for example, U.S. Patent ,645, 922) and "flocs" or dispersions of finely divided particles (micron sized) having mixed functionality held together by electrostatic charge or the like.

Further heterogeneous resins include amphoteric resins of various types wherein mixed functional groups are contained within particles on a molecular level (e.g.

along a polymer chain). Such amphoteric resins may be useful in the process if they are capable of thermal regeneration. The foregoing class of materials include the socalled "ion retention agents". (See, for example, U.S. Patent 3,351,549).

Figure 1 of the accompanying drawings is a schematic representation of one embodi mentofaparatus of the invention for carrying out a desalination process of this invention.

Figure 2 depicts typical steady state conditions for a process carried out in the apparatus of Figure 1 With reference to Figure 1, which is representative of a treatment for desalination, a vertical treating column 2 having a main resin feed hopper 1 disposed thereon is packed with a thermally regenerable resin in the form of a bed divided into a regeneration zone 3, a heat displacement zone 4 and a loading zone 5 in descending order in the column. Liquid distributing means such as a distributor plate 6 or similar device is positioned at the lower end of the loading zone 5. Raw feed liquid (such as sea water) is admitted to loading zone 5 through a raw liquid feed line 7 incorporating a valve 11.

At the upper level of loading zone 5, a treated liquid effluent line 8 is connected to column 2 via distributor 6a. j'Prie distributors herein designated as 6, a, 6b, 6c and 6d are known liquid distributing devices, such as perforated vessels generally concentric with the column but having a diameter less than the column to permit resin flow around the vessel).

At the lower level of the regeneration zone 3, a hot liquid regenerant entry line 9 from a heating deaerator 16 (a known device) having a steam line 18 is connected to column 2 via distributor 6b. At the upper level of the regeneration zone 3 a spent liquid regenerant exit line 10 leads to a heat exchanger 20 from a distributor 6c in col urnn 2. Heat exchanger 20 and heat deaerator 16 communicate by a heat recovery line 21 and serve to recover heat from the spent water, and in the case of the deaerator, to remove bubbles of oxygen from hot water destined to enter column 2 via line 9.

The bottom of treating column 2 and the upper portion of a resin metering hopper 14 communicate through a resin transfer line 17 which serves to convey the portion of thermally regenerable resin which has adsorbed ions thereon and which has fallen to the vicinity of the inner bottom of column 2. The bottom of metering hopper 14 and the upper portion of amin hopper 1 communicate via a transfer line 19 having a valve 15.

In operation, valve 11 is opened to deliver raw liquid to be subjected to ion exchange upward through the distributor 6 into adsorption zone 5 to undergo desalination by the action of the thermally regenerable resin which is in a regenerated state. The raw liquid has a temperature lower than that of the hot regeneration liquid (which, as indicated, may also be liquid which has been subjected to ion exchange in accordance with the invention). The resulting treated (demineralized) liquid is discharged through the treated liquid line 8 in the upper level of adsorption zone 5. At the same time, hot liquid for regeneration, commonly hot water, is introduced via the hot water line 9 for up-flow into the regeneration zone 3 so as to regenerate the thermally regenerable resin. After the regeneration, the spent water is discharged through the spent water line 10 in the upper level of the regeneration zone 3. The spent water may be passed through the heat exchanger 20 and the heat recovery line 21, with the result that the heat of the spent water is recovere'd by the heat deaerator 16. The ion exchange (desalination) treatment and the regeneration treatment may be carried out independently of each other by utilizing as the liquid regenerant, a stream other than the treated liquid stream from line 8. However, a portion of the treated liquid stream of line 8 is an ideal liquid for regeneration since the liquid is low in interfering ion content.

After the raw liquid and the regeneration liquid have been delivered as described above for respectively fixed periods, the system is pulsed at intermittent intervals, either manually or by using known automatic valve control means. The pulsing steps are as follows.

Valve 11 in the raw liquid line 7 is closed to discontinue the supply of raw liquid and the valve 12 in the raw liquid withdrawal line 22 branching off the raw liquid line 7 is opened to withdraw a predetermined volume of raw liquid from within column 2. By so doing the thermally regenerable resin which has adsorbed ions and is now retained in the lower portion of the adsorption zone 5, is caused to fall below the distributor 6 and, at the same time, the entire bed of thermally regenerable resin falls downwardly. This lowering of the entire bed of thermally legenerable resin may also be achieved by removing the portion of loaded resin which is in the bottom of column 2.

Simultaneously, the ball check valve 13 for checking backflow, which is interposed between the hopper 1 and the treating column 2, falls and synchronously permits the resin stored in hopper 1 and which requires regeneration, to fall into column 2. The resin is normally in slurry form. Excess water may be removed from the slurry via distributor 6d and a slurry water effluent line 6e. Then, as valve 12 in the raw liquid withdrawal line 22 is closed, the valve 11 and the raw liquid line 7 is opened and the introduction of raw liquid restarted. Consequently, ball check 13 rises to discontinue the fall of the resin. The portion of the ion adsorbed resin which has fallen below the raw liquid distributor 6 is caused by the pressure of the raw liquid to flow through transfer line 17 and thus to reach the metering hopper 14 for storage therein. By opening valve 15 and transfer line 19, the resin in metering hopper 14 is transferred to and stored in the hopper 1, awaiting the subsequent repacking of column 2. Generally, hopper 1 has a larger inner volume than the metering hopper 14 and is utilized for receiving freshly supplied thermally regenerable resin and for removal of exhausted (crushed) resin via line la. Means for separation of crushed resin from fresh resin or resin to be regenerated are well-known, such as particle classifying baffles, sleeves and the like. Such devices commonly utilize a back-washing procedure, also well-known in the art.

The heat displacement zone 4 serves to cool the regenerated and consequently hot resin and, at the same time, functions as a buffer between regeneration zone 3 and loading zone 5. Stated otherwise, the heat displacement zone separates the loading and regeneration zones in order to minimize thermal dispersion. Without the heat displacement zone, the loading zone would tend to be unduly warm and the regeneration zone would tend to be unduly cool, thus lowering the working resin capacity of the system. Suitable valving and control devices (not shown) may be included to close or open the valves controlling the flow in lines 9 and 10, thus controlling the dimensions of the heat displacement zone.

Such conditions as flow rate and temperature of the raw liquid and the regeneration liquid, and intervals of time for introduction and withdrawal of the liquids, are suitably fixed in accordance with the character and capacity of the thermally regenerable resin, quality of the raw liquid, and other similar conditions of treatment. Also, such factors as diameter and length of the treating column 2 and lengths of the zones within the column may be fixed to suit the capacity of the thermally regenerable resin and other operating conditions. Preferred operating temperatures are 10-20"C (loading zone) and 90-95"C (regeneration zone) but wide variation is possible.

In the manner described above, regenerated and cooled thermally regenerable resin is constantly supplied to the loading zone 5 in treating column 2. Since the thermally regenerable resin at its optimum adsorbing capacity is constantly supplied to the upper portion of the loading zone 5, the ion exchange and regeneration treatments can be efficiently effected within one treating column. It is further possible to obtain treated water continuously with intermissions for withdrawal of the raw liquid.

Further in the present invention, the heat displacement zone 4 prevents the hot water for regeneration from losing heat through diffusion and, where necessary, the heat exchanger may be used to recover the heat from the spent regeneration water. Thus, the heat efficiency is so high that, even if the ratio of the volume of the hot water for regeneration to that of the thermally regenerable resin in circulation is lowered to 0.5, thorough and effective regeneration can be obtained. Thus, the amount of hot water used for regeneration is notably small. The heat deaerator 16, which is optionally used to treat the hot regenerant water, provides ample and effective oxygen removal (via line 16a) and consequently contributes to lengthening the service life of the thermally regenerable resin.

Moreover, since in this invention one treating column will suffice for the ionexchange treatment, the ion-exchange system is less expensive to manufacture than the continuous moving-bed type ion exchange system which has an adsorption column and a regeneration column disposed separately of each other, therefore requiring lines, valves and control mechanisms for each of the two columns. The one-column system of the invention is operated very simply, dispenses with complicated plant management, and brings about a notable reduction in the unit cost of treatment.

Compared with the two-column type treating system, the system of the present invention offers minimal liquid loss during the withdrawal and transfer of liquid because the resin beads subsequent to the fall of resin bed within the treating column are recompacted and the number of transfers of resin outside the treating column are respectively halved. At the same time, the possibility of size reduction of the resin beads due to friction is small. Thus, the system enjoys the advantage that the volume of water required per unit volume of water treated is improved and the service life of the resin is lengthened.

While in its preferred aspects the process of the invention is operated continuously or semi-continuously, in the sense of steady state (equilibrium) conditions providing essentially uninterrupted production of treated liquid, the process may also be operated batch-wise, wherein the liquid flows, and resin displacements and transfers are lengthened, interrupted irregularly, or activated independently.

The invention has particular benefit for desalination of industrial, municipal and household waters but is also beneficial for removal of salts and other compounds from sea water and other sources.

While it is preferred to use a portion of the treated liquid product effluent from line 8 as regenerant liquid, any other aqueous fluid low in dissolved salts may also be utilized, alone or in combination with the liquid product. Such other fluids include various forms of purified water such as previously softened or deionized water.

The process and apparatus described herein may be combined with other new or known methods of deionizing aqueous streams or regenerating resins, the ormer embracing such techniques as filtration, ultrafiltration (see Dutch Specification 7 804 399), and ion exchange with the latter including techniques for regenerating a second ion exchange bed with the spent regenerant effluent from a first zone or bed (see German Offenlegungschrift 2,822,280). In particular, it is common to remove ions which interfere with sorbtion of a thermally regenerable bed by means of pretreatment of an influent in a separate ion exchange column located upstream of the thermally regenerable bed (supra USSN 802,142).

The invention is further described below with reference to a typical working example and Fig. 2.

EXAMPLE 1 Apparatus essentially as depicted in Fig. 1 was set up. The treating column was 7 m. in height and 0.25 m. in diameter and had a regeneration zone 2 m. in height in the upper section, a heat displacement zone 1 m. in height below the regeneration zone and a loading zone 2.5 m. in height below the heat displacement zone. As a heterogeneous thermally regenerable resin, Amberlite (registered trademark) XD-2 resin (product of Rohm and Haas Company, U.S.A.) was used. In the system thus formed, a continuous desalination treatment was carried out using the following conditions. The volume of thermally regenerable resin circulated for the unit time (hours), namely, the inner volume of the metering hopper, was 120 liters, the volume of hot water for regeneration fed per hour was 60 liters, the temperature of the hot water was fixed at 900C and raw water containing 1,100 ppm (as CaCO3) of dissolved salts (NaCl, Na2S4) and kept at 16.50C was treated at a rate of 920 liters per hour. Consequently, there was obtained demineralized water containing 350 ppm (as CaCO3) of dissolved salts. Both the water for regeneration and the raw water were fed upflow and the resin was caused to fall inside the treating column at fixed intervals of 3 minutes.

The treated water was used as the hot water for regeneration. Heat was recovered from the spent regeneration water by passage through a plate type heat exchanger. The raw water was preheated with this recovered heat up to 570C and further heated by introduced steam up to 900C. The hot water thus obtained was then deaerated and thereafter put to use.

As a result, for 1 liter (0.115 equivalent) of the thermally regenerable resin, desalination was obtained at a rate of about 6.5 meq.

per Kcal of heat. After 4,000 hours of operation, the rate of comminution of the thermally regenerable resin as determined in the proportion of comminuted resin beads passing a 50-mesh sieve was less than 1% compared with about 2% obtained in the conventional two-column type treating system.

EXAMPLE 2 A feed water containing about 1000 ppm (as CaCO3) of dissolved salts (NaCl, Na2 SO4) is treated in a system essentially as illustrated in Fig. 1 and as described in Example 1, except that the column height is 5.1 m., column diameter is 25 cm., and the lengths of the loading, heat displacement and regeneration zones are 2m., 80 cm. and 1.5 m., respectively. The loading zone is at a temperature of about 20"C and the regeneration zone is at a temperature of about 90"C. The feed water enters the bottom of the column at a flow rate of 1.35 m.3/hr., of which 1.00 m.3 is recovered as treated product water containing about 100 ppm (as CaCO3) of the dissolved salts, and the remainder is used to entrain loaded resin to form a resin slurry for transfer to the metering hopper and to drop the resin bed during each pulse. The system is operated by pulsing, typically as follows: (a) Valve 12 (Fig. 1) is opened for 15 seconds while valve 11 in feed line 7 is closed. This provides a net water flow down the column of 16 2/3 liters through the drain line 22, causing the resin bed to drop and to pack at the bottom of the column.

(b) Valve 12 is then closed and valve 11 opened for 3 min. and 45 sec. The liquid flow is thereby split into two directions: 66 2/3 liters moves upwards above feed line 7 and 6 2/3 liters moves out through line 17 entraining 8 liters of resin.

The foregoing procedures of Examples 1 and 2 provide, subject to the pulsation in (a), substantially continuous water flow and treatment although it will be noted that resin flow is not continuous. Resin flow is controlled by the metering hopper 14. For example, under the conditions set forth in this example, once the 8 liters of resin are transferred via the resin slurry, the metering hopper is filled and no more resin can be transferred until the hopper empties in the next pulse. However, the main resin hopper 1 may initially contain enough resin for several pulses.

Fig. 2 illustrates steady state conditions along the length of a column operated as described in Example 2. Fig. 2 shows the relationships between temperature, concentration of salts in feed and product streams, and resin condition at discrete points in the column. It will be noted that the temperature gradient is such as to maximize both the loading and the regeneration treatments.

It will be evident from the foregoing description and Examples 1 and 2 that the steady state conditions are achieved by pulsing wherein each pulse comprises the steps of: (1) discontinuing the flow of feed liquid while draining feed liquid from the loading zone, over a period of time effective for displacement of resin downwardly in the column, followed by (2) reactivating the flow of feed liquid upwardly through the loading zone while discontinuing the draining of feed liquid, entraining loaded resin to form a resin slurry, and transfer ring the resin slurry to the regenera tion zone.

The frequency and length of the pulses as well as the periods of activation or inactivation of the conditions comprising the steps of each pulse, may be varied in accordance with resin capacity, salt content of feed liquid, desired quality of products, dimensions of the column and zones thereof, and similar parameters.

WHAT WE CLAIM IS: 1. An ion exchange process wherein loading and regeneration of the resin are carried out in a single column of resin, the resin being continuously or intermittently

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (18)

**WARNING** start of CLMS field may overlap end of DESC **. resin (product of Rohm and Haas Company, U.S.A.) was used. In the system thus formed, a continuous desalination treatment was carried out using the following conditions. The volume of thermally regenerable resin circulated for the unit time (hours), namely, the inner volume of the metering hopper, was 120 liters, the volume of hot water for regeneration fed per hour was 60 liters, the temperature of the hot water was fixed at 900C and raw water containing 1,100 ppm (as CaCO3) of dissolved salts (NaCl, Na2SÒ4) and kept at 16.50C was treated at a rate of 920 liters per hour. Consequently, there was obtained demineralized water containing 350 ppm (as CaCO3) of dissolved salts. Both the water for regeneration and the raw water were fed upflow and the resin was caused to fall inside the treating column at fixed intervals of 3 minutes. The treated water was used as the hot water for regeneration. Heat was recovered from the spent regeneration water by passage through a plate type heat exchanger. The raw water was preheated with this recovered heat up to 570C and further heated by introduced steam up to 900C. The hot water thus obtained was then deaerated and thereafter put to use. As a result, for 1 liter (0.115 equivalent) of the thermally regenerable resin, desalination was obtained at a rate of about 6.5 meq. per Kcal of heat. After 4,000 hours of operation, the rate of comminution of the thermally regenerable resin as determined in the proportion of comminuted resin beads passing a 50-mesh sieve was less than 1% compared with about 2% obtained in the conventional two-column type treating system. EXAMPLE 2 A feed water containing about 1000 ppm (as CaCO3) of dissolved salts (NaCl, Na2 SO4) is treated in a system essentially as illustrated in Fig. 1 and as described in Example 1, except that the column height is 5.1 m., column diameter is 25 cm., and the lengths of the loading, heat displacement and regeneration zones are 2m., 80 cm. and 1.5 m., respectively. The loading zone is at a temperature of about 20"C and the regeneration zone is at a temperature of about 90"C. The feed water enters the bottom of the column at a flow rate of 1.35 m.3/hr., of which 1.00 m.3 is recovered as treated product water containing about 100 ppm (as CaCO3) of the dissolved salts, and the remainder is used to entrain loaded resin to form a resin slurry for transfer to the metering hopper and to drop the resin bed during each pulse. The system is operated by pulsing, typically as follows: (a) Valve 12 (Fig. 1) is opened for 15 seconds while valve 11 in feed line 7 is closed. This provides a net water flow down the column of 16 2/3 liters through the drain line 22, causing the resin bed to drop and to pack at the bottom of the column. (b) Valve 12 is then closed and valve 11 opened for 3 min. and 45 sec. The liquid flow is thereby split into two directions: 66 2/3 liters moves upwards above feed line 7 and 6 2/3 liters moves out through line 17 entraining 8 liters of resin. The foregoing procedures of Examples 1 and 2 provide, subject to the pulsation in (a), substantially continuous water flow and treatment although it will be noted that resin flow is not continuous. Resin flow is controlled by the metering hopper 14. For example, under the conditions set forth in this example, once the 8 liters of resin are transferred via the resin slurry, the metering hopper is filled and no more resin can be transferred until the hopper empties in the next pulse. However, the main resin hopper 1 may initially contain enough resin for several pulses. Fig. 2 illustrates steady state conditions along the length of a column operated as described in Example 2. Fig. 2 shows the relationships between temperature, concentration of salts in feed and product streams, and resin condition at discrete points in the column. It will be noted that the temperature gradient is such as to maximize both the loading and the regeneration treatments. It will be evident from the foregoing description and Examples 1 and 2 that the steady state conditions are achieved by pulsing wherein each pulse comprises the steps of: (1) discontinuing the flow of feed liquid while draining feed liquid from the loading zone, over a period of time effective for displacement of resin downwardly in the column, followed by (2) reactivating the flow of feed liquid upwardly through the loading zone while discontinuing the draining of feed liquid, entraining loaded resin to form a resin slurry, and transfer ring the resin slurry to the regenera tion zone. The frequency and length of the pulses as well as the periods of activation or inactivation of the conditions comprising the steps of each pulse, may be varied in accordance with resin capacity, salt content of feed liquid, desired quality of products, dimensions of the column and zones thereof, and similar parameters. WHAT WE CLAIM IS:

1. An ion exchange process wherein loading and regeneration of the resin are carried out in a single column of resin, the resin being continuously or intermittently

transferred from an upper, regeneration, zone in the column, through an intermedi ate, thermal buffer, zone to a lower, loading, zone in the column, loaded resin being transferred from the loading to regeneration zones by means external to the column, and wherein regenerant and loading liquids flow through their respective zones, in the case of the loading liquid this flow being upwards, the regenerant liquid being at a higher temperature than the loading liquid and wherein only such amounts of the loading and/or regenerant liquids are allowed to pass into the buffer zone that a temperature difference is maintained between the proximate ends of the regeneration and loading zones.

2. A process as claimed in claim 1 of continuous or semi-continuous ion exchange treatment based on a column packed with a heterogeneous thermally regenerable ion exchange resin in a single bed wherein the bed has a loading zone, a heat displacement zone above the loading zone, and a regeneration zone above the heat displacement zone, including the steps of: (a) flowing an aqueous feed liquid hav ing an undesirably high concentra tion of ions upwardly through the loading zone to substantially reduce the concentration of ions, and with drawing resultant treated liquid as product liquid from the vicinity of the top of the loading zone with some product liquid passing into the heat displacement zone; (b) flowing an aqueous liquid regener ant at a higher temperature than the temperature of the feed liquid, through the resin in the regeneration zone to regenerate the resin; (c) controlling the flow of aqueous liquid in the thermal buffer (alterna tively known as heat displacement) zone to maintain a temperature dif ferential between the loading zone and the regeneration zone; (d) transferring, outside the column, loaded resin from the loading zone to the regeneration zone; and (e) displacing regenerated resin down wardly in the column to replace the transferred resin.

3. A process of claim 1 or 2 wherein the flow of regenerant liquid in the regeneration zone in step (b) is upwards.

4. A process of claim 2 or 3 wherein loading step (a) and regeneration (b) are effected simultaneously.

5. A process of any of claims 2 to 4 wherein regenerated resin is displaced downwardly in said column in step (e) by reversing the normally upward flow of feed liquid in said loading zone.

6. A process of any of claims 2 to 4 wherein regenerated resin is displaced downwardly in said column in step (e) by discontinuing the flow of feed liquid into the loading zone and withdrawing loaded resin therefrom.

7. A process of any of claims 2 to 6 wherein a portion of the feed liquid entrains loaded resin in the loading zone, whereby said resin is transferred in step (d) as a resin slurry.

8. A process of any of claims 2 to 7 wherein a portion of said product liquid is heated and utilized as the aqueous liquid regenerant in step (b).

9. A process of any of claims 2 to 8 wherein the temperature of the loading zone during step (a) is 10 to 200C and the temperature of the regeneration zone during step (b) is 90 to 950C.

10. A process of any of claims 3 to 9 wherein the lower boundary of the regeneration zone and the upper boundary of the loading zone define said heat displacement zone, and wherein the flow of aqueous liquid is controlled in step (c) by temperature responsive valve means controlling said feeding of regenerant liquid and said removal of product liquid.

11. A process of any of claims 2 to 10 wherein resin transfer is effected by intermittently pulsing as follows: (1) discontinuing said flow of aqueous feed liquid in step (a) while draining feed liquid from the loading zone, for a period of time effective for dis placement of resin downwardly in said column, and (2) thereafter reactivating said flow of aqueous feed liquid while discon tinuing said draining of feed liquid from the loading zone, entraining loaded resin with a portion of feed liquid to form a resin slurry, and transferring said resin slurry to the regeneration zone.

12. A process as claimed in claim 1 substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings or in the foregoing Examples.

13. Ion exchange apparatus comprising a column packed with a single bed of thermally regenerable resin, the column having a first set of inlet and outlet lines defining a zone in the upper part of the bed for contacting resin with liquid flowing between them, a second set of inlet and outlet lines defining a zone in the lower part of the bed for contacting resin with liquid flowing between them, the proximate lines from each set defining a third zone of resin between the upper and lower zones, the apparatus also including a line for transferring, outside the column, resin from the bottom of the lower zone to the top of the upper zone.

14. Apparatus as claimed in claim 13 for continuous ion exchange treatment wherein said bed has a regeneration zone in its upper portion, a loading zone in its lower portion, and a heat displacement zone between the loading and regeneration zones, said apparatus further including a feed line to said loading zone for feeding an aqueous feed liquid having an undesirably high concentration of ions to said loading zone, a drain line to said loading zone for draining said feed liquid therefrom, resin feed means, to which the resin transfer line connects, for feeding loaded resin to said regeneration zone, an effluent line for removing product liquid from said loading zone, and hot liquid regenerant entry and exit lines to said regeneration zone.

15. Apparatus as claimed in claim 14 further including liquid distributors in said column, a first said distributor being positioned at the lower boundary of said loading zone and connected to said feed line, and second and third distributors substantially defining the lower and upper boundaries of said heat displacement zone, the third distributor being connected to said hot liquid entry line.

16. Apparatus as claimed in claim 14 or 15 wherein said resin feed means comprises a first resin hopper connected to said regeneration zone and a second hopper for feeding measured amounts of loaded resin to said first hopper, said first hopper being adapted for supplying fresh heterogeneous thermally regenerable resin to said column and for separating crushed, waste resin from said fresh resin and said loaded resin.

17. Apparatus as claimed in any of claims 14 to 16 further including heat exchange means for transferring heat from said liquid regenerant, after said liquid regenerant leaves said regeneration zone, to incoming regenerant liquid.

18. Apparatus as claimed in claim 13 substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.