CA1240419A - Process and device for treating liquids with cation exchangers and anion exchangers - Google Patents
Process and device for treating liquids with cation exchangers and anion exchangersInfo
- Publication number
- CA1240419A CA1240419A CA000484275A CA484275A CA1240419A CA 1240419 A CA1240419 A CA 1240419A CA 000484275 A CA000484275 A CA 000484275A CA 484275 A CA484275 A CA 484275A CA 1240419 A CA1240419 A CA 1240419A
- Authority
- CA
- Canada
- Prior art keywords
- exchanger
- layer
- anion
- filter
- anion exchanger
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J47/00—Ion-exchange processes in general; Apparatus therefor
- B01J47/02—Column or bed processes
- B01J47/022—Column or bed processes characterised by the construction of the column or container
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J39/00—Cation exchange; Use of material as cation exchangers; Treatment of material for improving the cation exchange properties
- B01J39/04—Processes using organic exchangers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J49/00—Regeneration or reactivation of ion-exchangers; Apparatus therefor
- B01J49/05—Regeneration or reactivation of ion-exchangers; Apparatus therefor of fixed beds
- B01J49/08—Regeneration or reactivation of ion-exchangers; Apparatus therefor of fixed beds containing cationic and anionic exchangers in separate beds
Abstract
Process and device for treating liquids with cation exchangers and anion exchangers A b s t r a c t Upward-flow process for treating liquids in ion exchange filters containing cation exchangers and anion exchangers in separate layers arranged one on top of the other, in which the cation and anion exchangers are separated from one another by a resin layer which does not participate in the ion exchange, the anion exchanger is regenerated externally and the cation exchanger, which remains in the filter, is regenerated in the counter-current and the anion exchanger is removed from and recycled to the filter without whirling up the separating layer and cation exchanger layer. The inven-tion furthermore relates to a new counter-current ion exchange filter for carrying out the process.
Description
The invention re~ates to a new process for treat-ing liquids with cation exchangers and anion exchangers and a new device for carrying out the process.
S Processes ~or treating liquids, in part;cular for the desaLination of water or aqueous solu~ions, for example sugar or glycerol solutions, are known. Combina-tions of strongly acid cation exchangers ~ith strongly or weakly basic anion exchangers are used for desalina-tion. The various known processes differ in the manner in ~hich the various types of ion exchanger, ~hat is to say cation exchanger and anion exchanger~ are arranged.
In mixed bed filters, the cation exchanger and anion exchanger are present in the form of an intimate mixture during the operating phase. For regeneration~ the exhausted resin mass is separated into the two components hydraulically on the basis of the different specific gravities of the cation exchanger and anion exchanger.
Each of the two layers is regenerated and ~ashed out separately, by itself. Mixed bed filters ha~e the seri-ous disadvantage that the exhausted resin mass cannot be separated completely intb cation exchanger and anion exchanger, but that the one type of ion exchanyer still contains certain amounts oF the other type of ion exchanger. Regeneration of the cation exchanger and anion exchanger therefore al~ays leads to a certain amount of mis-loaded cation and anion exchanger.
The consequences of this mis-loading are unsatis-factory quality of the liquid treated and disproportion-ately low operating capacities of the mixed bed filterc.
In the case of mixed bed fiLters ~i~h internalregeneration, the mis-loading of the cation and an;on exchanger caused by incomplete separat;on is accompan;ed by the unavoidable mis-loading oF the Le A 23 113 .
~2~
ion exchanger situated close to the cation exchanger/anion exchanger interface as a result of penetration of the regenerating agen~ for one component in~o the layer of the other component. Althou0h the mis-loading by penetration of the regenerating agent of one component into the layer of ~he counter-component can be prevented by using separating layer resins, as is rerommended, for example, in German Patent Specification 971,771 and U.S.
Patent Specification 2,666,7~tl, the mis-loading as a result of incomplete separation into cation exchanger and anion exchanger cannot be avoided. The use of the separating layer resins therefore has only a limited value.
Cation and anion exchangers are also very fre-quently accommoda~ed in separate filters or in separate adjacent chambers of a filter (see, for example, German Offenlegungsschrift 2,137,796, U.S. Patent Specifications 3,136,719 and 3,719,591 or European Patent A 1-0,050,813).
The disadvantage of these arrangements is the high expen-diture on apparatus and - if the ion exchangers are in separate chambers of a filter - the high pressure loss caused by the nozzle trays which separate the chambers from one another and the devices required for distribu-tion of the liquid within ~he chamhers.
German Offenlegungsschrift 1,642,~48 and Japanese Published Application JA-B-80/015,Z59 describe counter-current processes for the desalinatinn of water, in which cation and anion exchangers are arranged in a filter in separate, immediately adjacent layers lying one on top of the other. Because it has a higher specific gravity than the anion exchanger, the cation exchanger forms the lower layer, and the anion exchanger forms the upper layer. During loading, the agent flows through both resin layers in succession. The direction of flow during regeneration is opposi~e to the direction of flo~ during loading. Mixing of the two resin layers during upward-Le A 23 113 flow loading is counteracted by customary measures, for example an auxiliary flow directed onto the surface of~
the anion exchanger layer or by completely filling the fitter with ion exchangers. The two processes differ in the regeneration procedure. According to JA-B-80/015,529, H2S0~ initially flows through the anion and cation exchangers from the top downwards. The anion exchanger converted into the sulphate form in this manner is con-verted into the OH form in a second regeneration step by treatment with NaOH, a layer of anion exchanger in the sulphate form remaining between the central drainage accom-modated in the anion exchanger and the cation exchanger.
In contrast, accord;ng to the German Offenlegungsschrift, the anion exchanger and cation exchanger are regenerated separately, the spent regenerating alkali being removed at the central drainage and, at a different point in time, the regenerating acid being introduced at the cen-tral drainage.
A serious disadvantage of both processes is that in the operation thereof ~i~loading of the ion exchangers cannot be avDided and, 3S a result, also the consequences of mis-loading - inadequate qua~ity of the water treated and low operating capacity of the filter~ As a result of the position of the central drainage, determined by the type of process, close to the cation exchanger/anion exchanger interface, mutual con-tamination of the one ion exchanger by the regenera~ing agent of the counter-component is unavoidable, especially in the process according to German Offenlegungsschrift 1,642,84~. In addition, the unavoidable upward and do~n-ward movement of the ion exchanger mass in the filter during starting up of the filter and as a result of the change in volume of the ion exchanger during loading and regeneration leads to mixing of the cation exchanger and anion exchanger at the interface region between the two exchangers~
Le A 23 113 .
The process described in German ~ffenlegungs-schrift 1,642,8~8 also has the disa~vantage that a com-plicated filter is required for carrying out the process, in particular a fiLter which consists of ~wo cylindricaL
sections o~ different diameter and ~hich is ~quipped with devices which prevent rearrangement when ~he exchanger mass is subjected to upward fLow. The process described in JA-B-80/û15,259 has the particuLar disadvantage of an e~ceptionaLly high consumption of regenerating agent.
During`acid treatment of the ion exchangers in the first regenerating step, the anion exchanger is compLeteLy loaded with S0~~ ions. These S04-- ions must be dispLaced again by subsequent treatment with alkali.
It has now been found that a substantially sim-1~ pler but nevertheless more effective process for treating liquids with cation exchangers and anion exchangers which does not have the disadvantages of the known processes is achieved if the cation and anion exchanger are arranged in separate layers one on top of the other, the cation exchanger being the lower Layer and the anion exchanger being the upper Layer, in an ion exchange fiLter custom-ary for counter-current processes with upward flow loading, the two ion exchangers are separated fron one another by an inert resin Layer of a certain height which does not participate in the ion exchange~ the anion exchanger is removed from the filter for regeneration, without whirling up the cation exchanger and separating layer, the cation exchanger, which remains in the filter, is regenerated in counter-current and the anion exchanger, 3D rem~ved fron the filter, is regenerated externaLly in the usual manner~ that is to say ;n a separate vessel, and the regenerated anion exchanger is recycled again to the wor~ing filter for the loading phase, again without whirling up the cation exchanger and separating layer.
The invention thus relates to a process for treating l;quids in ion exchange filters which rontain Le ~ 23 113 the cation exchanger and anion exchanger in separate layers arranged one on top of the other, the cation exchanger being the lower layer and the anion exchanger being the upper layer~ and in which the ion exchangers are loaded in an upward flow of liquid and the exhausted ion exchangers are regenerated and washed out separately, which is characterised in that a) the cation exchanger and anion exchanger are separated from one another by a resin layer o~ a certain height which does not partici-pate in the ion exchange; b) when the up~ard-flow loadin~
has ended, the anion exchanger is removed from the filter, without whirling up the separating layer and cation exchanger, and is regenerated and washed out externally in a known manner in a separate container, and the cation exchanger, which remains in the filter and ;s covered by the separating layer~ is regenerated and ~ashed out in counter-current in a known manner; and c) after the re-generation of the cation and anion exchanger, the anion exchanger is recycled back to the ~ilter and the anion exchanger layer ;s ~u;lt up again, without whirling up the separating layer and cation exchanger layer.
Although the process according to the invention is a counter-current process only in respect of the cation exchanger, being an ion exchange process with external regenera~ion in respect of the anion exchanger, never-theless ;t has been found that with the resin layer sequence claimed: cation exchanger regenerated in ~ counter-current/separating layer of certain height/exter-; nally regeneratecl anion exchanger, a liquid ~uality is achieved such as is given per se only by pure counter-current processes, that is to say processes ;n which the cation exchanger and anion exchanger are regenerated in counter-current. In addition, the process according to the invention shows, for regeneration of the cation exchanger, the Low regenerating agent requirement charac-teristic of counter-current processes.
Le A 23 113 The process according to the invention combines the advantages of the counter current processes, in ~hich the cation and anion exchangers are accommodated in separate filters or chambers, ~hat is to say the high quality of the treated liquid and Low regenerating agent requirement~ with the advantages of the ion exchange pro-cesses, in ~hich the cation and anion exchangers are accomnodated in separate layers, arranged one on top of the other, in one filter and are regenera~ed in these layers with the various regenerating agents, tha~ is to say simplicity and economy, without disolaying the dis-advantages of these processes, that is to say higher expenditure on apparatus, unsatisfactory quality of the liquid treated, low operating capacity of the filters and high regenerating agent requirement.
Since the process according to ~he invention operates without central drainage, the quantitative ratio of cation exchanger to anion exchanger can be changed in the process as desired; consequently, the process has the further advantage over the processes described in German Offenlegungsschrift 1,642,848 and in Japanese Application B-80/015,259 that it can be very much more easily adapted to the composition of the liquid to be treated. Further-more, it also does not require additional vessels for backwashing the cation and anion exchanger. The vessel required for external regeneration of the anion exchanger can also be used directly for back~ashing the anion exchanger; the cation exchanger is backwashed in the working filter itself.
The separating layer resins which are used for separat;ng layers ;n mixed bed filters and also the loaded form of the anion exchanger used in the process are suit-able as the resin layer which does not participate in the ion exchange and which separates the cation exchanger and anion exchanger from one another. The use of the loaded anion exchanger as the separating layer is preferred; it Le A 23 113 provides the advantage that a) no thircl resin is required, b) as a result of the greater difference in the specific gravity of cation exchanger/anion exchanger than in the specific gravity o~ cation exchanger/separating layer resin and separating layer resin/anion exchanger, a sharper separating layer is formed between the cation exchanger and anion exchanger than between the cation exchanger/separating layer resin and separating Layer resinlanion exchanger, and c) the height of ~he separat-ing layer can be particularly easily adjusted between theindividual working cycles by removing a larger or smaller amount of the loaded anion exchanger from the filter For external regeneration.
The resins used as the separa~ing layer resin in the mixed beds are in general bead tco)poLymers of sty-rene, vinyl chloride9 methacrylates, divinylbenzene and acrylonitrile, and furthermore acrylonitrilelbutadiene~
styrene resins, epoxy resins, polyamide resins and poly-styrene resins (see European Patent A 2-0,010,265, column 1).
So that sharp separating layers are formed bet-ween the cat;on exchanger and separat;ng layer resin on the one hand and the separating layer res;n and anion exchanger on the other hand when separating layer resins are used, the separating layer resin should fulfil cer-tain cond;t;ons in respect of particle size and spec;fic gravity: the separating layer resin should have about the same particle size as the finest s;eve fraction of the cation exchanger. The specific gravity of the separating layer resin should be at least 0.02 g/ml, preferably at least 0.04 g/ml and particularly preferably at least D.05 g/mL, lower than that of the cat;on exchanger and at least 0~02 g/ml, preferabLy at least 0.04 g/ml and part;cularly preferably at least 0~05 g/ml, higher than that of the anion exchanger.
In the context of the process accord;ng to the Le A 23 113 .
invention, the finest sieve fraction of the cation exchanger is ~o be understood as meaning the fraction of the cation exchanger which is obtained as the finest particle size range when the cation exchanger is separa-ted into three different particle size ranges.
The height of the resin Layer which does not participate in the ion exchange and separates the cation and anion exchan~er from one another (abbreviated below to "separating layer") is of decisive importance for the efficiency of the process accord;ng to the invention; in order reliably to avoid mixing of the cation exchanger and anion exchanger, the separating layer must be a~
least 30 mm, preferably 30 to 90 mm, larger than the height of the free space in the filter at ~he start of the loading operation, and at least 100 mm high.
In the context of the present invention, the free space of an ion exchange filter is to be understood as the space~ in the filter chamber which is not filled with ion exchanger; as a result of the change in volume (swelling and shrinkage) of the ion exchangers during loading and regeneration, the free space can both decrease and increase in the course of a working cycle.
The usual, strongly acid cation exchangers based on polystyrene-sulphonic acids crosslinked with divinyl-benzene are used as the cation exchanger in the processaccording to the invention. ~he particle size of the cation exchanger should be greater than 0.3 mm, advan-tageously greater than 0.4 mm and preferably greater than 0.~ mm, and its specific gravity should be at least 0.05 g/ml~ preferably a~ least 0.07 g/ml, greater than the specific gravity of the anion exchanger.
The usual, strongly and weakly basic anion exchan-gers based on polyvinylbenzylamines crossl;nked with di-vinylbenzene or crosslinked N alkylated poly(meth~acryl-anides are used as the anion exchanger in the processaccording to the invent;on. The particle size of the Le A 23 113 _ 9~
anion exchanger should be below 1.~0 mm, advantageou~ly below 1.10 mm and preferably below 1u05 mmO
The removal, according to the invention, of the anion exchanger from the ~orking filter without uhirling up the separating layer and cation exchanger can be par~
ticularly easily effected by hydraulic conveying.
~ydraulic conveying of the anion exchanger from the work ing filter can be effected, for example, by siphoning off the anion exchanger layer by means of one (or more) siphon (or siphons) extending down to ~he anion exchanger/
separating layer interface or with one ~or more) ascend-ing tube (ascending tubes) inserted vertically into the anion exchanger down to the anion exchanger/separat-ing layer interface. Recycling of the ex~ernally re--generated and washed out anion exchanger into the ~orkingfiLter without whirling up the separating layer and cation exchanger layer which remain in the filter can be achieved, for example, by allowing the anion exchanger to trickle down Yia a feed line, which discharges into the free space o~ the ~ilter and is suitable for the ~rans-portation of ion exchangers.
The invention there~ore also relates to a counter-current filter for carrying out the process claimed. This counter-current filter according to the invention is characterised in tha~ it consists of a one-chamber ion exrhange filter which is customary for counter-current processes with upward-flow loading, but which is additionally equipped with the following devices:
a) a device with which the anion exchanger layer can be removed from the filter without ~hirling up the ad3acent separating layer and the cation exchanger layer below this; and b) a device with which the externally regenera-ted anion exchanger can be recycled back into the ~iLter without wh;rling up the separating layer and cation exchanger layer remaining in the ~ilter~
1-Chamber ion exchange filters ~h;rh are usually Le A 23 113 .
231g9-6012 employed for counter-current processes with loading in upward flow in general consist of a cylindrical vessel which is provided with closable liquid feed and discharge lines and can be closed at the top and bottom with dished ends, the cylindrical interior space of which is closed off at the bot-tom and top by a device which is per-meable to liquid (for example a noz~le tray).
~ evice (a) with which an upper ion exchanger layer can be conveyed from an underlying ion exchanger layer out of an ion ex-change filter without causing whirling are known. Hydraulic convey-ing by means of one or more ascending tube(s) has proved particular-ly suitable. The device (b) consists of a feed line which dischar-ges into the free space of the filter and is suitable for the trans-portation of ion exchangers.
The invention will be further described with reference to the accompanying drawings in which:
figures 1 and 2 are schematic representations of apparatus for carrying out the process of the invention.
The cation exchanger (3), separating layer (5) and anion exchanger (4) rest in separate layers, arranged immediately one on top of the other, on the lower device (2), which is permeable to liquid~ of the chamber formed by the cylindrical part of the filter column (1) and the two devices (2) which are permeable to liquid.
~bove the anion exchanger (4) is the free space (6). The upper device (2), which is permeable to liquid, forms the upper boundary of the free space (6).
In the loading phase~ the liquid to be treated enters the filter (1) through the feed line (9). Lines (7) and (8) are closed '1~ - 1 0 - lOa - 23189-6012 by the shut-off devices (13) and (14). The treated liquid leaves the fil.t:er through line (11). After the loading, the anion e~chan-ger (4) is siphoned off into a second, separate container via line (7), with the shut-off devices (10) and (14) closed and the shut-off device (12) open.
During this hydraulic conveying of the-anion - lOa -~i, exchanger (~) out cf the filter ~1), no whirling up of the separating layer ~5) and cation exchanger (3) occurs.
The anion exchanger (4) is regenera~ed ~ith dilute aqueous sodiu~ hydroxide solution in the usual manner in a separate container for external regeneration, and is then ~ashed until the ~ashing water runnings from the anion exchanger exhibit only the desired residual conductivity.
During or after regeneration of the anion exchanger t4), the cation exchanger (3), which remains in the working filter (1), is regenerated with dilute aqueous mineral acids, preferably dilute aqueous hydro-chloric acid, in the cus~omary manner for counter-current regeneration. The regenerating acid is fed in ~hrough line (11)~ with the shut-off devices (13) and (14~ closed, and, after flowing through the separat;ng layer (5~ and the cation exchanger layer t3), is removed through line ~9). The regenerating acid is washed out of the separat-ing layer and cation exchanger in the same direction of flow as the regenerat;on.
As soon as the washing water runnings from the cation exchanger (3) display only the desired residual conductivity, the washing operation is ended and the shut-off device (1D) is closed.
The anion exchanger (4) is then recycled back into the filter (l) through line (8), with the shut-off devices (10) and (13) closed and the shut-off devices ~12) and (14) open. During this recycling, again no wh;rLing up of the separating l2yer (5) and cation 3~ exchanger layer (3) occurs. After the anion exchanger layer (4~ has been built up on the separating layer (5), the shut-off device (14) is closed again, shut-off devices (10) and (12) ~re opened and the loading operation re-starts.
A particularly practical embodiment of the pro-cess and filter according to the invention is sho~n in Le A 23 113 . .
Figure 2. In this embodi~ent, the upper device (2), which is permeabLe to liquid~ of the filter (1) is pro-tected from blockages by a floating layer (15~ of inert material.
Granules of organic, syn~hetic materiaLs, for example, of polyethylene or polypropylene, are su;table as the inert material for the floating layer. These inert materials should have a density which is lower than that of the liquids ~ith which they come into contact, that is to say they must float on the liquids which flow through them. The particle size of the granules should advantageously be about û.2 to 2~0 mm.
The regeneration container (16) required for external regeneration of the anion exchanger is also additionally sho~n in Figure 2. When the loading has ended, the anion exchanger (4) is forced into the re-generation container ~16) via the ascending tube (7), with shut-off devices t12), (13) and (21) open and shut-off devices (10), (14) and (19) closed. For trouble-free conveying, it is advantageous for the anion exchanger (4) to trirkle into the regeneration container from the top, as shown in Figure 2. As soon as the anion exchanger (4) to be regenera~ed is in the regeneration container ~16), the shut~off device (13) is closed and, ~ith shut-off devices (19) and (21) open, the regenerating alkali is filtered through line (18) over the anion exchanger (4) resting on the device (for examplenozzle tray) (17), which is permeable to liquid, and is removed through line (20).
After the regeneration~ the anion exchanger ;s washed out in the same direction of flow. When the ~ashing-out has ended, the shut off device (Z1) is closed. The re- -generated, washecd-out anion exchanger (~) is forced back into the filter (1) hydraulically via line (8), ~ith shut-off devices (12~, (14) and ~19) open and shut-off devices (10), (13) and (21) closed.
Le A 23 113 Exampl The fil~er arrangement described in Figure Z is used.
The filter (l) has an in~ernal diameter of 30û
mm; its cylindrical height ~= chamber height = distance bet~een the bottom and top nozzle tray (2~) is 2,200 mm.
The end of the ascending ~ube 67) immersed in the anion exchanger layer (4~ is in the anion exchanger/separating layer interface. The height of the free space (6~ (at the start of loading) is 70 mm, and the heigh~ of the floating layer t15) is 200 mm.
The filter (1) is fiLled ~ith:
70 litres of strongly acid, macroporous cation exchanger height of the cation exchanger layer ~3):
1,000 mm;
specific gravity: 1.21 g/ml;
particle size: 1.25 - O.S mm 56 litres of strongly basic anion exchanger in gel form height of the anion exchanger layer t4):
800 mm;
specific gravity: 1O07 g/ml;
particle size: 1.12 - 0.4 mm and 9 litres of separating layer resin (according to Europ-ean Patent A 2-0,010,265, Example 12~
height of the separating layer (5~: 130 mm;
specific gravity: 1.15 g/ml;
particle size: D.5-0.7 mm Tap ~ater ~ith the following content of anions and cations (data in meq/l) is used for loading:
Ca2t + M92~ 5.3 Na+ ~ K+ 3.6 Cl ~ So42 + N3 6.4 ~co3 2.5 35 C2 (free) D 07 SiOz 0.13 Le A 23 113 _ The regeneration con~ainer ~16) has an internal diameter of 300 mm and a cylindrical jacket height of 1,600 mm. The distance from the verticaL end of line (8) to the bottom nozzle tray (17) is SO mm.
After each loading, the ca~ion exchanger is regenerated in counter-current with 10 kg of 30% strength hydrochloric acid (in the form of a 6X strength aqueous solution~ and the anion exchanger is regenerated extern-ally with 9 kg of 50X strength sodium hydroxide solution (in the form of a 4% strength aqueous solution).
The water to be desalinated is passed through the filter (1) from ~he bottom upwards with a flow rate of 1~200 l/hour. The average conductivity of the desalina-ted water flowing out of ~he filter (1) is 2 to 3 ~S/cm and its silicic acid con~ent is less than 0.1 mg of SiO2/l. Loading is interrupted as soon as the conduc-tivity of the desaLinated water rises to above 5 ~SIcm.
The amount of desalinated water obtained before this breakthrough value is reached is 4,535 l ~average value from six working cycles).
If the ion exchangers are used in the counter-current process described in German Offenlegungsschrift 1~642,848 instead of in the process according to the invention~ desalinated water ~ith an average conductivity of only 10 ~S/cm is obtained; the amount of desalinated water obtained before an breakthrough value of 20 ~S/cm is reached is only 3,960 litres.
Exa 2 The procedure followed ;s as described in Example 1, but the separating layer (5) is built up from 9 l of the strongly basic anion exchanger used, in gel form, and not from 9 l of separat;ng layer resin. These 9 l of anion exchanger are not discharged into the regeneration container ~16~ after loading, but serve as the separating layer ~5) which no longer participa~es in the ion exchange.
The same results as in Exan~ple 1 are obtained Le A 23 113 .-- _ with ~he filter -filled in this manner. The only differ-ence is ~hat more washing ~ater is required for washing the regenerating acid out of the separating layer ~
cation exchanger ~700 L instead of the 280 L in Example 1).
Example 3 The procedure followed is as described in xample 1, except that, for filLing the filter (1), a strongly acid cation exchanger in the form of a gel (specific gravity: 1.23 g/ml; particle size: 1.25 - 0.5 mm) is used as the strongly acid cation exchanger and a strongly basic, macroporous anion exchanger (specific gravity:
1.09 g/mL; par~icle size: 1.0 - 0.45 mm) is used as the separa~ing layer t9 l) and as the anion exchanger (56 l).
After each loading, the cation exchanger is re-generated in counter-current with 12 kg of 30% s~rength hydrochloric acid (in the form of a 6% strength aqueous solution) and the 56 l of anion exchanger are regenerated externally with 9 kg of 50~ stren3th sodium hydroxide solution (in the form of a 4% strength aqueous solution).
Z0 The water to be desalinated is passed through the filter ~1) from the bottom upwards with a flow rate of 1,400 l/hour. The average conductivi~y of the desalina-ted water leaving the filter is 0.6,uS/cm and its silicic acid content is 0.05 mg of SiO2/l. Loading is interrupted Z5 as soon as the conductivity of the desal;nated water rises above 0.6~uS/cm. The amount of desalinated water ~hich can be obtained before this breakthrough value is reached is 5~800 l (average value from 5iX ~c~rking cycles~.
Example 4 The procedure followed is as in Example 3, except that the separating layer (5) is built up from 9 l of the separating layer resin described in Example 1.
The same results as in Example 3 are obtained with the filter filled in this way. The only difference is that the wash;ng water required for washing the re-generating acid out of the cat;on exchanger falls from Le A 23 113 - 16 - ~ 40 the 650 l required in Example 3 to 210 l~
Example 5 An effluent containing an excess o-f free acid is used for loading the ion exchangers~ in total, the water ~o be desalinated contains the follo~ing a~ounts ~in meq/
l) of cations, anions, carbonic acid and silicic acid:
Cations 3D6 Cl + s~2 + N03 5-3 CO2 ~ ~i2 The filter (1~ of the filter arrangement des-cribed in Figure 2 is filled with:
49 litres of the strongly acid, macroporous cat;on exchan-ger described in Example 1 height of the cation exchanger layer ~3a 70D mm 86 litres of the strongly basic anion exchanger in the form of a gel described in Example 1; of ~hese 86 l, 77 l serve as the anion exchanger;
height of the anion exchanger layer (4):
1,100 mm and 9 l serve as the separating layer;
height of the separating layer (5): 130 mm The end of the ascending tube (7) immersed in the anion exchanger is in the anion exchanger layer (4) /
separating layer (5) interface.
After each loading, the cation e~changer is re-generated in counter-current with 7 kg of 30% strength hydrochloric acid (in the form of a 6% strength aqueous solution) and the 77 l of anion exchanger are regenerated externally with 12.5 kg of 50X strength sodium hydroxide solution (in the form of a 4~ strength aqueous solution).
The ~ater to be desalinated is passed ~hrough the filter (1) ~ith a flow rate of 1,000 l/hour. The average conductivity of the desalinated water leaving the filter is 5 ~S/cm and its silicic acid content is 0.1 mg of SiO2/l~ The amount of desalina~ed water which can be obtained before the interruption value of 10~uS/cm is reached is 90600 l of effluent (average value from six ~orking cycles).
Exa 6 The ion exchangers are load~d with the water des-cribed in Example 1 but ~ithout bonding the carbonic acid and silicic acid.
The filter ~1) of the filter arrangement des cribed in Figure 2 is filled in this case with: û 80 litres of the strongly acid cation exchanger in the form of a geL described in Example 3 heigh~ of the cation exchanger layer t3):
1,1S0 mm 46 litres of a weakly basic, macroporous anion exchanger based on acrylamide height of the anion exchanger layer (4):
660 mm specific gravity: 1YOS ~/ml;
particle size: 1.12 - 0.3 mm 0 and 9 litres of the separating layer resin described in Example 1.
The end of the ascending tube (7) immersed in the anion exchanger is in the anion exchanger/separat;ng layer interface.
The cation exchanger is regenerated in counter-current with 16 kg of 30X strength hydrochloric acid Sin the ~orm of a 6% strength aqueous solution) and the anion exchanger is regenerated externally with 5.6 kg of SOX
strength sodium hydroxicle solution (in the form of a 4X
strength aqueous solution).
The water to be desalinated is passed through the filter (1) with a flow rate of 950 l/hour. The average conductivity~of the desalinated water leaving the filter ;s 20~uS/cm, and its content of chloride ions is 2 mg/L.
Loading is interrupted as soon as the conductivity of the Le A 23 113 desalinated water rises above 25 ~SIcm. The amount of desalinated ~ater which can be obtained before this breakthrough value is reached is 7,550 l (average value from six ~orking cycles).
S;nce the anion exchanger swells by about 10~. by volume during loading, whilst the cation e~changer shrinks by about 5% by volume, a free space (6) of 70 mm is adequate.
Le A 23 113
S Processes ~or treating liquids, in part;cular for the desaLination of water or aqueous solu~ions, for example sugar or glycerol solutions, are known. Combina-tions of strongly acid cation exchangers ~ith strongly or weakly basic anion exchangers are used for desalina-tion. The various known processes differ in the manner in ~hich the various types of ion exchanger, ~hat is to say cation exchanger and anion exchanger~ are arranged.
In mixed bed filters, the cation exchanger and anion exchanger are present in the form of an intimate mixture during the operating phase. For regeneration~ the exhausted resin mass is separated into the two components hydraulically on the basis of the different specific gravities of the cation exchanger and anion exchanger.
Each of the two layers is regenerated and ~ashed out separately, by itself. Mixed bed filters ha~e the seri-ous disadvantage that the exhausted resin mass cannot be separated completely intb cation exchanger and anion exchanger, but that the one type of ion exchanyer still contains certain amounts oF the other type of ion exchanger. Regeneration of the cation exchanger and anion exchanger therefore al~ays leads to a certain amount of mis-loaded cation and anion exchanger.
The consequences of this mis-loading are unsatis-factory quality of the liquid treated and disproportion-ately low operating capacities of the mixed bed filterc.
In the case of mixed bed fiLters ~i~h internalregeneration, the mis-loading of the cation and an;on exchanger caused by incomplete separat;on is accompan;ed by the unavoidable mis-loading oF the Le A 23 113 .
~2~
ion exchanger situated close to the cation exchanger/anion exchanger interface as a result of penetration of the regenerating agen~ for one component in~o the layer of the other component. Althou0h the mis-loading by penetration of the regenerating agent of one component into the layer of ~he counter-component can be prevented by using separating layer resins, as is rerommended, for example, in German Patent Specification 971,771 and U.S.
Patent Specification 2,666,7~tl, the mis-loading as a result of incomplete separation into cation exchanger and anion exchanger cannot be avoided. The use of the separating layer resins therefore has only a limited value.
Cation and anion exchangers are also very fre-quently accommoda~ed in separate filters or in separate adjacent chambers of a filter (see, for example, German Offenlegungsschrift 2,137,796, U.S. Patent Specifications 3,136,719 and 3,719,591 or European Patent A 1-0,050,813).
The disadvantage of these arrangements is the high expen-diture on apparatus and - if the ion exchangers are in separate chambers of a filter - the high pressure loss caused by the nozzle trays which separate the chambers from one another and the devices required for distribu-tion of the liquid within ~he chamhers.
German Offenlegungsschrift 1,642,~48 and Japanese Published Application JA-B-80/015,Z59 describe counter-current processes for the desalinatinn of water, in which cation and anion exchangers are arranged in a filter in separate, immediately adjacent layers lying one on top of the other. Because it has a higher specific gravity than the anion exchanger, the cation exchanger forms the lower layer, and the anion exchanger forms the upper layer. During loading, the agent flows through both resin layers in succession. The direction of flow during regeneration is opposi~e to the direction of flo~ during loading. Mixing of the two resin layers during upward-Le A 23 113 flow loading is counteracted by customary measures, for example an auxiliary flow directed onto the surface of~
the anion exchanger layer or by completely filling the fitter with ion exchangers. The two processes differ in the regeneration procedure. According to JA-B-80/015,529, H2S0~ initially flows through the anion and cation exchangers from the top downwards. The anion exchanger converted into the sulphate form in this manner is con-verted into the OH form in a second regeneration step by treatment with NaOH, a layer of anion exchanger in the sulphate form remaining between the central drainage accom-modated in the anion exchanger and the cation exchanger.
In contrast, accord;ng to the German Offenlegungsschrift, the anion exchanger and cation exchanger are regenerated separately, the spent regenerating alkali being removed at the central drainage and, at a different point in time, the regenerating acid being introduced at the cen-tral drainage.
A serious disadvantage of both processes is that in the operation thereof ~i~loading of the ion exchangers cannot be avDided and, 3S a result, also the consequences of mis-loading - inadequate qua~ity of the water treated and low operating capacity of the filter~ As a result of the position of the central drainage, determined by the type of process, close to the cation exchanger/anion exchanger interface, mutual con-tamination of the one ion exchanger by the regenera~ing agent of the counter-component is unavoidable, especially in the process according to German Offenlegungsschrift 1,642,84~. In addition, the unavoidable upward and do~n-ward movement of the ion exchanger mass in the filter during starting up of the filter and as a result of the change in volume of the ion exchanger during loading and regeneration leads to mixing of the cation exchanger and anion exchanger at the interface region between the two exchangers~
Le A 23 113 .
The process described in German ~ffenlegungs-schrift 1,642,8~8 also has the disa~vantage that a com-plicated filter is required for carrying out the process, in particular a fiLter which consists of ~wo cylindricaL
sections o~ different diameter and ~hich is ~quipped with devices which prevent rearrangement when ~he exchanger mass is subjected to upward fLow. The process described in JA-B-80/û15,259 has the particuLar disadvantage of an e~ceptionaLly high consumption of regenerating agent.
During`acid treatment of the ion exchangers in the first regenerating step, the anion exchanger is compLeteLy loaded with S0~~ ions. These S04-- ions must be dispLaced again by subsequent treatment with alkali.
It has now been found that a substantially sim-1~ pler but nevertheless more effective process for treating liquids with cation exchangers and anion exchangers which does not have the disadvantages of the known processes is achieved if the cation and anion exchanger are arranged in separate layers one on top of the other, the cation exchanger being the lower Layer and the anion exchanger being the upper Layer, in an ion exchange fiLter custom-ary for counter-current processes with upward flow loading, the two ion exchangers are separated fron one another by an inert resin Layer of a certain height which does not participate in the ion exchange~ the anion exchanger is removed from the filter for regeneration, without whirling up the cation exchanger and separating layer, the cation exchanger, which remains in the filter, is regenerated in counter-current and the anion exchanger, 3D rem~ved fron the filter, is regenerated externaLly in the usual manner~ that is to say ;n a separate vessel, and the regenerated anion exchanger is recycled again to the wor~ing filter for the loading phase, again without whirling up the cation exchanger and separating layer.
The invention thus relates to a process for treating l;quids in ion exchange filters which rontain Le ~ 23 113 the cation exchanger and anion exchanger in separate layers arranged one on top of the other, the cation exchanger being the lower layer and the anion exchanger being the upper layer~ and in which the ion exchangers are loaded in an upward flow of liquid and the exhausted ion exchangers are regenerated and washed out separately, which is characterised in that a) the cation exchanger and anion exchanger are separated from one another by a resin layer o~ a certain height which does not partici-pate in the ion exchange; b) when the up~ard-flow loadin~
has ended, the anion exchanger is removed from the filter, without whirling up the separating layer and cation exchanger, and is regenerated and washed out externally in a known manner in a separate container, and the cation exchanger, which remains in the filter and ;s covered by the separating layer~ is regenerated and ~ashed out in counter-current in a known manner; and c) after the re-generation of the cation and anion exchanger, the anion exchanger is recycled back to the ~ilter and the anion exchanger layer ;s ~u;lt up again, without whirling up the separating layer and cation exchanger layer.
Although the process according to the invention is a counter-current process only in respect of the cation exchanger, being an ion exchange process with external regenera~ion in respect of the anion exchanger, never-theless ;t has been found that with the resin layer sequence claimed: cation exchanger regenerated in ~ counter-current/separating layer of certain height/exter-; nally regeneratecl anion exchanger, a liquid ~uality is achieved such as is given per se only by pure counter-current processes, that is to say processes ;n which the cation exchanger and anion exchanger are regenerated in counter-current. In addition, the process according to the invention shows, for regeneration of the cation exchanger, the Low regenerating agent requirement charac-teristic of counter-current processes.
Le A 23 113 The process according to the invention combines the advantages of the counter current processes, in ~hich the cation and anion exchangers are accommodated in separate filters or chambers, ~hat is to say the high quality of the treated liquid and Low regenerating agent requirement~ with the advantages of the ion exchange pro-cesses, in ~hich the cation and anion exchangers are accomnodated in separate layers, arranged one on top of the other, in one filter and are regenera~ed in these layers with the various regenerating agents, tha~ is to say simplicity and economy, without disolaying the dis-advantages of these processes, that is to say higher expenditure on apparatus, unsatisfactory quality of the liquid treated, low operating capacity of the filters and high regenerating agent requirement.
Since the process according to ~he invention operates without central drainage, the quantitative ratio of cation exchanger to anion exchanger can be changed in the process as desired; consequently, the process has the further advantage over the processes described in German Offenlegungsschrift 1,642,848 and in Japanese Application B-80/015,259 that it can be very much more easily adapted to the composition of the liquid to be treated. Further-more, it also does not require additional vessels for backwashing the cation and anion exchanger. The vessel required for external regeneration of the anion exchanger can also be used directly for back~ashing the anion exchanger; the cation exchanger is backwashed in the working filter itself.
The separating layer resins which are used for separat;ng layers ;n mixed bed filters and also the loaded form of the anion exchanger used in the process are suit-able as the resin layer which does not participate in the ion exchange and which separates the cation exchanger and anion exchanger from one another. The use of the loaded anion exchanger as the separating layer is preferred; it Le A 23 113 provides the advantage that a) no thircl resin is required, b) as a result of the greater difference in the specific gravity of cation exchanger/anion exchanger than in the specific gravity o~ cation exchanger/separating layer resin and separating layer resin/anion exchanger, a sharper separating layer is formed between the cation exchanger and anion exchanger than between the cation exchanger/separating layer resin and separating Layer resinlanion exchanger, and c) the height of ~he separat-ing layer can be particularly easily adjusted between theindividual working cycles by removing a larger or smaller amount of the loaded anion exchanger from the filter For external regeneration.
The resins used as the separa~ing layer resin in the mixed beds are in general bead tco)poLymers of sty-rene, vinyl chloride9 methacrylates, divinylbenzene and acrylonitrile, and furthermore acrylonitrilelbutadiene~
styrene resins, epoxy resins, polyamide resins and poly-styrene resins (see European Patent A 2-0,010,265, column 1).
So that sharp separating layers are formed bet-ween the cat;on exchanger and separat;ng layer resin on the one hand and the separating layer res;n and anion exchanger on the other hand when separating layer resins are used, the separating layer resin should fulfil cer-tain cond;t;ons in respect of particle size and spec;fic gravity: the separating layer resin should have about the same particle size as the finest s;eve fraction of the cation exchanger. The specific gravity of the separating layer resin should be at least 0.02 g/ml, preferably at least 0.04 g/ml and particularly preferably at least D.05 g/mL, lower than that of the cat;on exchanger and at least 0~02 g/ml, preferabLy at least 0.04 g/ml and part;cularly preferably at least 0~05 g/ml, higher than that of the anion exchanger.
In the context of the process accord;ng to the Le A 23 113 .
invention, the finest sieve fraction of the cation exchanger is ~o be understood as meaning the fraction of the cation exchanger which is obtained as the finest particle size range when the cation exchanger is separa-ted into three different particle size ranges.
The height of the resin Layer which does not participate in the ion exchange and separates the cation and anion exchan~er from one another (abbreviated below to "separating layer") is of decisive importance for the efficiency of the process accord;ng to the invention; in order reliably to avoid mixing of the cation exchanger and anion exchanger, the separating layer must be a~
least 30 mm, preferably 30 to 90 mm, larger than the height of the free space in the filter at ~he start of the loading operation, and at least 100 mm high.
In the context of the present invention, the free space of an ion exchange filter is to be understood as the space~ in the filter chamber which is not filled with ion exchanger; as a result of the change in volume (swelling and shrinkage) of the ion exchangers during loading and regeneration, the free space can both decrease and increase in the course of a working cycle.
The usual, strongly acid cation exchangers based on polystyrene-sulphonic acids crosslinked with divinyl-benzene are used as the cation exchanger in the processaccording to the invention. ~he particle size of the cation exchanger should be greater than 0.3 mm, advan-tageously greater than 0.4 mm and preferably greater than 0.~ mm, and its specific gravity should be at least 0.05 g/ml~ preferably a~ least 0.07 g/ml, greater than the specific gravity of the anion exchanger.
The usual, strongly and weakly basic anion exchan-gers based on polyvinylbenzylamines crossl;nked with di-vinylbenzene or crosslinked N alkylated poly(meth~acryl-anides are used as the anion exchanger in the processaccording to the invent;on. The particle size of the Le A 23 113 _ 9~
anion exchanger should be below 1.~0 mm, advantageou~ly below 1.10 mm and preferably below 1u05 mmO
The removal, according to the invention, of the anion exchanger from the ~orking filter without uhirling up the separating layer and cation exchanger can be par~
ticularly easily effected by hydraulic conveying.
~ydraulic conveying of the anion exchanger from the work ing filter can be effected, for example, by siphoning off the anion exchanger layer by means of one (or more) siphon (or siphons) extending down to ~he anion exchanger/
separating layer interface or with one ~or more) ascend-ing tube (ascending tubes) inserted vertically into the anion exchanger down to the anion exchanger/separat-ing layer interface. Recycling of the ex~ernally re--generated and washed out anion exchanger into the ~orkingfiLter without whirling up the separating layer and cation exchanger layer which remain in the filter can be achieved, for example, by allowing the anion exchanger to trickle down Yia a feed line, which discharges into the free space o~ the ~ilter and is suitable for the ~rans-portation of ion exchangers.
The invention there~ore also relates to a counter-current filter for carrying out the process claimed. This counter-current filter according to the invention is characterised in tha~ it consists of a one-chamber ion exrhange filter which is customary for counter-current processes with upward-flow loading, but which is additionally equipped with the following devices:
a) a device with which the anion exchanger layer can be removed from the filter without ~hirling up the ad3acent separating layer and the cation exchanger layer below this; and b) a device with which the externally regenera-ted anion exchanger can be recycled back into the ~iLter without wh;rling up the separating layer and cation exchanger layer remaining in the ~ilter~
1-Chamber ion exchange filters ~h;rh are usually Le A 23 113 .
231g9-6012 employed for counter-current processes with loading in upward flow in general consist of a cylindrical vessel which is provided with closable liquid feed and discharge lines and can be closed at the top and bottom with dished ends, the cylindrical interior space of which is closed off at the bot-tom and top by a device which is per-meable to liquid (for example a noz~le tray).
~ evice (a) with which an upper ion exchanger layer can be conveyed from an underlying ion exchanger layer out of an ion ex-change filter without causing whirling are known. Hydraulic convey-ing by means of one or more ascending tube(s) has proved particular-ly suitable. The device (b) consists of a feed line which dischar-ges into the free space of the filter and is suitable for the trans-portation of ion exchangers.
The invention will be further described with reference to the accompanying drawings in which:
figures 1 and 2 are schematic representations of apparatus for carrying out the process of the invention.
The cation exchanger (3), separating layer (5) and anion exchanger (4) rest in separate layers, arranged immediately one on top of the other, on the lower device (2), which is permeable to liquid~ of the chamber formed by the cylindrical part of the filter column (1) and the two devices (2) which are permeable to liquid.
~bove the anion exchanger (4) is the free space (6). The upper device (2), which is permeable to liquid, forms the upper boundary of the free space (6).
In the loading phase~ the liquid to be treated enters the filter (1) through the feed line (9). Lines (7) and (8) are closed '1~ - 1 0 - lOa - 23189-6012 by the shut-off devices (13) and (14). The treated liquid leaves the fil.t:er through line (11). After the loading, the anion e~chan-ger (4) is siphoned off into a second, separate container via line (7), with the shut-off devices (10) and (14) closed and the shut-off device (12) open.
During this hydraulic conveying of the-anion - lOa -~i, exchanger (~) out cf the filter ~1), no whirling up of the separating layer ~5) and cation exchanger (3) occurs.
The anion exchanger (4) is regenera~ed ~ith dilute aqueous sodiu~ hydroxide solution in the usual manner in a separate container for external regeneration, and is then ~ashed until the ~ashing water runnings from the anion exchanger exhibit only the desired residual conductivity.
During or after regeneration of the anion exchanger t4), the cation exchanger (3), which remains in the working filter (1), is regenerated with dilute aqueous mineral acids, preferably dilute aqueous hydro-chloric acid, in the cus~omary manner for counter-current regeneration. The regenerating acid is fed in ~hrough line (11)~ with the shut-off devices (13) and (14~ closed, and, after flowing through the separat;ng layer (5~ and the cation exchanger layer t3), is removed through line ~9). The regenerating acid is washed out of the separat-ing layer and cation exchanger in the same direction of flow as the regenerat;on.
As soon as the washing water runnings from the cation exchanger (3) display only the desired residual conductivity, the washing operation is ended and the shut-off device (1D) is closed.
The anion exchanger (4) is then recycled back into the filter (l) through line (8), with the shut-off devices (10) and (13) closed and the shut-off devices ~12) and (14) open. During this recycling, again no wh;rLing up of the separating l2yer (5) and cation 3~ exchanger layer (3) occurs. After the anion exchanger layer (4~ has been built up on the separating layer (5), the shut-off device (14) is closed again, shut-off devices (10) and (12) ~re opened and the loading operation re-starts.
A particularly practical embodiment of the pro-cess and filter according to the invention is sho~n in Le A 23 113 . .
Figure 2. In this embodi~ent, the upper device (2), which is permeabLe to liquid~ of the filter (1) is pro-tected from blockages by a floating layer (15~ of inert material.
Granules of organic, syn~hetic materiaLs, for example, of polyethylene or polypropylene, are su;table as the inert material for the floating layer. These inert materials should have a density which is lower than that of the liquids ~ith which they come into contact, that is to say they must float on the liquids which flow through them. The particle size of the granules should advantageously be about û.2 to 2~0 mm.
The regeneration container (16) required for external regeneration of the anion exchanger is also additionally sho~n in Figure 2. When the loading has ended, the anion exchanger (4) is forced into the re-generation container ~16) via the ascending tube (7), with shut-off devices t12), (13) and (21) open and shut-off devices (10), (14) and (19) closed. For trouble-free conveying, it is advantageous for the anion exchanger (4) to trirkle into the regeneration container from the top, as shown in Figure 2. As soon as the anion exchanger (4) to be regenera~ed is in the regeneration container ~16), the shut~off device (13) is closed and, ~ith shut-off devices (19) and (21) open, the regenerating alkali is filtered through line (18) over the anion exchanger (4) resting on the device (for examplenozzle tray) (17), which is permeable to liquid, and is removed through line (20).
After the regeneration~ the anion exchanger ;s washed out in the same direction of flow. When the ~ashing-out has ended, the shut off device (Z1) is closed. The re- -generated, washecd-out anion exchanger (~) is forced back into the filter (1) hydraulically via line (8), ~ith shut-off devices (12~, (14) and ~19) open and shut-off devices (10), (13) and (21) closed.
Le A 23 113 Exampl The fil~er arrangement described in Figure Z is used.
The filter (l) has an in~ernal diameter of 30û
mm; its cylindrical height ~= chamber height = distance bet~een the bottom and top nozzle tray (2~) is 2,200 mm.
The end of the ascending ~ube 67) immersed in the anion exchanger layer (4~ is in the anion exchanger/separating layer interface. The height of the free space (6~ (at the start of loading) is 70 mm, and the heigh~ of the floating layer t15) is 200 mm.
The filter (1) is fiLled ~ith:
70 litres of strongly acid, macroporous cation exchanger height of the cation exchanger layer ~3):
1,000 mm;
specific gravity: 1.21 g/ml;
particle size: 1.25 - O.S mm 56 litres of strongly basic anion exchanger in gel form height of the anion exchanger layer t4):
800 mm;
specific gravity: 1O07 g/ml;
particle size: 1.12 - 0.4 mm and 9 litres of separating layer resin (according to Europ-ean Patent A 2-0,010,265, Example 12~
height of the separating layer (5~: 130 mm;
specific gravity: 1.15 g/ml;
particle size: D.5-0.7 mm Tap ~ater ~ith the following content of anions and cations (data in meq/l) is used for loading:
Ca2t + M92~ 5.3 Na+ ~ K+ 3.6 Cl ~ So42 + N3 6.4 ~co3 2.5 35 C2 (free) D 07 SiOz 0.13 Le A 23 113 _ The regeneration con~ainer ~16) has an internal diameter of 300 mm and a cylindrical jacket height of 1,600 mm. The distance from the verticaL end of line (8) to the bottom nozzle tray (17) is SO mm.
After each loading, the ca~ion exchanger is regenerated in counter-current with 10 kg of 30% strength hydrochloric acid (in the form of a 6X strength aqueous solution~ and the anion exchanger is regenerated extern-ally with 9 kg of 50X strength sodium hydroxide solution (in the form of a 4% strength aqueous solution).
The water to be desalinated is passed through the filter (1) from ~he bottom upwards with a flow rate of 1~200 l/hour. The average conductivity of the desalina-ted water flowing out of ~he filter (1) is 2 to 3 ~S/cm and its silicic acid con~ent is less than 0.1 mg of SiO2/l. Loading is interrupted as soon as the conduc-tivity of the desaLinated water rises to above 5 ~SIcm.
The amount of desalinated water obtained before this breakthrough value is reached is 4,535 l ~average value from six working cycles).
If the ion exchangers are used in the counter-current process described in German Offenlegungsschrift 1~642,848 instead of in the process according to the invention~ desalinated water ~ith an average conductivity of only 10 ~S/cm is obtained; the amount of desalinated water obtained before an breakthrough value of 20 ~S/cm is reached is only 3,960 litres.
Exa 2 The procedure followed ;s as described in Example 1, but the separating layer (5) is built up from 9 l of the strongly basic anion exchanger used, in gel form, and not from 9 l of separat;ng layer resin. These 9 l of anion exchanger are not discharged into the regeneration container ~16~ after loading, but serve as the separating layer ~5) which no longer participa~es in the ion exchange.
The same results as in Exan~ple 1 are obtained Le A 23 113 .-- _ with ~he filter -filled in this manner. The only differ-ence is ~hat more washing ~ater is required for washing the regenerating acid out of the separating layer ~
cation exchanger ~700 L instead of the 280 L in Example 1).
Example 3 The procedure followed is as described in xample 1, except that, for filLing the filter (1), a strongly acid cation exchanger in the form of a gel (specific gravity: 1.23 g/ml; particle size: 1.25 - 0.5 mm) is used as the strongly acid cation exchanger and a strongly basic, macroporous anion exchanger (specific gravity:
1.09 g/mL; par~icle size: 1.0 - 0.45 mm) is used as the separa~ing layer t9 l) and as the anion exchanger (56 l).
After each loading, the cation exchanger is re-generated in counter-current with 12 kg of 30% s~rength hydrochloric acid (in the form of a 6% strength aqueous solution) and the 56 l of anion exchanger are regenerated externally with 9 kg of 50~ stren3th sodium hydroxide solution (in the form of a 4% strength aqueous solution).
Z0 The water to be desalinated is passed through the filter ~1) from the bottom upwards with a flow rate of 1,400 l/hour. The average conductivi~y of the desalina-ted water leaving the filter is 0.6,uS/cm and its silicic acid content is 0.05 mg of SiO2/l. Loading is interrupted Z5 as soon as the conductivity of the desal;nated water rises above 0.6~uS/cm. The amount of desalinated water ~hich can be obtained before this breakthrough value is reached is 5~800 l (average value from 5iX ~c~rking cycles~.
Example 4 The procedure followed is as in Example 3, except that the separating layer (5) is built up from 9 l of the separating layer resin described in Example 1.
The same results as in Example 3 are obtained with the filter filled in this way. The only difference is that the wash;ng water required for washing the re-generating acid out of the cat;on exchanger falls from Le A 23 113 - 16 - ~ 40 the 650 l required in Example 3 to 210 l~
Example 5 An effluent containing an excess o-f free acid is used for loading the ion exchangers~ in total, the water ~o be desalinated contains the follo~ing a~ounts ~in meq/
l) of cations, anions, carbonic acid and silicic acid:
Cations 3D6 Cl + s~2 + N03 5-3 CO2 ~ ~i2 The filter (1~ of the filter arrangement des-cribed in Figure 2 is filled with:
49 litres of the strongly acid, macroporous cat;on exchan-ger described in Example 1 height of the cation exchanger layer ~3a 70D mm 86 litres of the strongly basic anion exchanger in the form of a gel described in Example 1; of ~hese 86 l, 77 l serve as the anion exchanger;
height of the anion exchanger layer (4):
1,100 mm and 9 l serve as the separating layer;
height of the separating layer (5): 130 mm The end of the ascending tube (7) immersed in the anion exchanger is in the anion exchanger layer (4) /
separating layer (5) interface.
After each loading, the cation e~changer is re-generated in counter-current with 7 kg of 30% strength hydrochloric acid (in the form of a 6% strength aqueous solution) and the 77 l of anion exchanger are regenerated externally with 12.5 kg of 50X strength sodium hydroxide solution (in the form of a 4~ strength aqueous solution).
The ~ater to be desalinated is passed ~hrough the filter (1) ~ith a flow rate of 1,000 l/hour. The average conductivity of the desalinated water leaving the filter is 5 ~S/cm and its silicic acid content is 0.1 mg of SiO2/l~ The amount of desalina~ed water which can be obtained before the interruption value of 10~uS/cm is reached is 90600 l of effluent (average value from six ~orking cycles).
Exa 6 The ion exchangers are load~d with the water des-cribed in Example 1 but ~ithout bonding the carbonic acid and silicic acid.
The filter ~1) of the filter arrangement des cribed in Figure 2 is filled in this case with: û 80 litres of the strongly acid cation exchanger in the form of a geL described in Example 3 heigh~ of the cation exchanger layer t3):
1,1S0 mm 46 litres of a weakly basic, macroporous anion exchanger based on acrylamide height of the anion exchanger layer (4):
660 mm specific gravity: 1YOS ~/ml;
particle size: 1.12 - 0.3 mm 0 and 9 litres of the separating layer resin described in Example 1.
The end of the ascending tube (7) immersed in the anion exchanger is in the anion exchanger/separat;ng layer interface.
The cation exchanger is regenerated in counter-current with 16 kg of 30X strength hydrochloric acid Sin the ~orm of a 6% strength aqueous solution) and the anion exchanger is regenerated externally with 5.6 kg of SOX
strength sodium hydroxicle solution (in the form of a 4X
strength aqueous solution).
The water to be desalinated is passed through the filter (1) with a flow rate of 950 l/hour. The average conductivity~of the desalinated water leaving the filter ;s 20~uS/cm, and its content of chloride ions is 2 mg/L.
Loading is interrupted as soon as the conductivity of the Le A 23 113 desalinated water rises above 25 ~SIcm. The amount of desalinated ~ater which can be obtained before this breakthrough value is reached is 7,550 l (average value from six ~orking cycles).
S;nce the anion exchanger swells by about 10~. by volume during loading, whilst the cation e~changer shrinks by about 5% by volume, a free space (6) of 70 mm is adequate.
Le A 23 113
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Process for treating liquids in ion exchange filters which contain the cation exchanger and anion exchanger in separate layers arranged one on top of the other, the cation exchanger being the lower layer and the anion exchanger being the upper layer, and in which the ion exchangers are loaded in an upward flow of liquid and the exhausted ion exchangers are regenerated and washed out separa-tely, which is characterized in that a) the cation exchanger and anion exchanger are separa-ted from one another by a resin layer of a certain height which does not participate in the ion exchange;
b) when the upward-flow loading has ended, the anion ex-changer is removed from the filter, without whirling up the separa-ting layer and cation exchanger, and is regenerated and washed out externally in a known manner in a separate container, and the cation exchanger, which remains in the filter and is covered by the separa-ting layer, is regenerated and washed out in counter-current in a known manner; and c) after the regeneration of the cation exchanger and anion exchanger, the anion exchanger is recycled back to the filter and the anion exchanger layer is built up again, without whirling up the separating layer and cation exchanger layer.
b) when the upward-flow loading has ended, the anion ex-changer is removed from the filter, without whirling up the separa-ting layer and cation exchanger, and is regenerated and washed out externally in a known manner in a separate container, and the cation exchanger, which remains in the filter and is covered by the separa-ting layer, is regenerated and washed out in counter-current in a known manner; and c) after the regeneration of the cation exchanger and anion exchanger, the anion exchanger is recycled back to the filter and the anion exchanger layer is built up again, without whirling up the separating layer and cation exchanger layer.
2. Process according to Claim 1, characterized in that the resin layer which does not participate in the ion exchange and se-parates the cation exchanger and anion exchanger from one another is at least 30 mm greater than the height of the free space in the filter at the start of the loading operation, and is at least 100 mm high.
3. Process according to Claim 1 or 2, characterized in that the resin layer which does not participate in the ion exchange and separates the cation exchanger and anion exchanger from one another is formed from the usual separating layer resins or from the loaded anion exchanger.
4. Process according to Claim 1 or 2, characterized in that the resin layer which does not participate in the ion exchange and separates the cation exchanger and anion exchanger from one another is formed from the usual separating layer resins or from the loaded anion exchanger and that the usual separating layer resins are se-lected from bead (co)polymers of styrene, vinyl chloride, methacry-lates, divinylbenzene and acrylonitrile and acrylonitrile/buta-diene/styrene resins, epoxy resins, polyamide resins and polysty-rene resins.
5. Process according to Claim 1, characterized in that the separating layer resins have about the same particle sizes as the finest sieve fraction of the cation exchanger, and in that their specific gravity is at least 0.02 g/ml lower than the specific gra-vity of the cation exchanger and at least 0.02 g/ml higher than the specific gravity of the anion exchanger.
6. Process according to Claim 1, characterized in that the particle size of the cation exchanger is greater than 0.3 mm and its specific gravity is at least 0.05 g/ml greater than the specific gravity of the anion exchanger, and the particle size of the anion exchanger is less than 1.20 mm.
7. Counter-current ion exchange filter with upward flow changing for carrying out the process according to Claim 1, compri-sing a) means to remove an anion exchanger layer from the filter without whirling up the adjacent separating layer and the cation exchanger layer therebelow; and b) means to recycle externally regenerated anion exchan-ger back into the filter without whirling up the separating layer and the cation exchanger layer remaining in the filter.
8. Counter-current filter according to Claim 7, comprising an ion exchange filter provided with closable liquid feed and dis-charge lines, a cylindrical interior space closed off at the bottom and top by means permeable to liquid.
9. Counter-current filter according to Claim 7 or 8, charac-terized in that means a) includes at least one siphon, one leg of each said siphon arranged to extend down to an anion exchanger/separating layer interface, or means a) includes at least one ascending tube arranged to be capable of insertion vertically into an anion exchan-ger down to an anion exchanger/separating layer interface and means b) includes a feed line capable of discharging into free space in the filter and is suitable to transport an ion exchanger.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3422860.8 | 1984-06-20 | ||
| DE19843422860 DE3422860A1 (en) | 1984-06-20 | 1984-06-20 | METHOD AND DEVICE FOR TREATING LIQUIDS WITH CATIONAL EXCHANGERS AND ANION EXCHANGERS |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1240419A true CA1240419A (en) | 1988-08-09 |
Family
ID=6238799
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000484275A Expired CA1240419A (en) | 1984-06-20 | 1985-06-18 | Process and device for treating liquids with cation exchangers and anion exchangers |
Country Status (8)
| Country | Link |
|---|---|
| US (1) | US4645604A (en) |
| EP (1) | EP0166282B1 (en) |
| JP (1) | JPS6111155A (en) |
| AT (1) | ATE38945T1 (en) |
| AU (1) | AU4378685A (en) |
| CA (1) | CA1240419A (en) |
| DE (2) | DE3422860A1 (en) |
| ZA (1) | ZA854619B (en) |
Families Citing this family (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01143791A (en) * | 1987-11-26 | 1989-06-06 | Showa Alum Corp | Aluminum alloy filler metal |
| ES2075003T3 (en) * | 1988-03-24 | 1995-10-01 | Nippon Conlux Co Ltd | PRINTED PAPER DISPENSER DEVICE AND METHOD FOR CONTROLLING SUCH DEVICE. |
| US5626750A (en) * | 1995-07-26 | 1997-05-06 | Drake Recovery Systems, Inc. | Apparatus for treating a fluid in an ion exchange process |
| US5833867A (en) * | 1995-12-01 | 1998-11-10 | United States Filter Corporation | System and method for backwashing multiple filtration vessels |
| NL1006701C2 (en) * | 1997-07-31 | 1999-02-02 | Tno | A method for adsorbing solid dissolved constituents to solid adsorbent particles or for desorbing (extracting) soluble constituents in liquid from solid desorbent particles. |
| US6132612A (en) * | 1997-09-23 | 2000-10-17 | Ebbco, Inc. | Liquid deionizing twin bed apparatus |
| US6187192B1 (en) | 1999-08-25 | 2001-02-13 | Watervisions International, Inc. | Microbiological water filter |
| US20040232068A1 (en) * | 2000-04-21 | 2004-11-25 | Johnston Arthur W. | Formation of composite materials with expandable matter |
| WO2002070104A1 (en) * | 2001-03-02 | 2002-09-12 | Watervisions International, Inc. | Purification materials and method of filtering using the same |
| US20040159605A1 (en) * | 2002-02-01 | 2004-08-19 | Hughes Kenneth D. | Compositions of insoluble magnesium containing minerals for use in fluid filtration |
| US7201841B2 (en) * | 2003-02-05 | 2007-04-10 | Water Visions International, Inc. | Composite materials for fluid treatment |
| US8636919B1 (en) | 2004-03-26 | 2014-01-28 | Kenneth D. Hughes | Reactive solutions |
| US7383946B2 (en) | 2004-03-26 | 2008-06-10 | Hughes Kenneth D | Materials for storing and releasing reactive gases |
| CA2738015C (en) * | 2008-09-24 | 2016-12-13 | Siemens Water Technologies Corp. | Water filter apparatus incorporating walnut shell filter media and a draft tube system |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3497069A (en) * | 1968-11-01 | 1970-02-24 | Corning Glass Works | Apparatus for water purification by ion exchange |
| US3915861A (en) * | 1970-04-17 | 1975-10-28 | Hager & Elsaesser | Apparatus for the treatment of water solutions by ion exchange |
| NL185708C (en) * | 1977-05-27 | 1990-07-02 | Northern Eng Ind | METHOD FOR THE REGENERATION OF ION EXCHANGERS. |
| DE2936999A1 (en) * | 1979-09-13 | 1981-04-02 | Vereinigte Kesselwerke AG, 4000 Düsseldorf | Regenerating mixed bed ion exchangers - with sepn. into exchanger types by reverse flow washing through inert interlayer and removing exchanger(s) to an external regenerator |
| US4264439A (en) * | 1979-10-09 | 1981-04-28 | The Dow Chemical Company | Separation of anion and cation exchange resins in a mixed resin bed |
| GB2063094B (en) * | 1979-11-10 | 1983-07-20 | Permutit Boby Ltd | Water purification by ion exchange |
| DE3040616A1 (en) * | 1980-10-29 | 1982-06-03 | Bayer Ag, 5090 Leverkusen | COUNTERFLOW ADSORPTION FILTER FOR TREATING LIQUIDS AND METHOD FOR OPERATING THE FILTER |
-
1984
- 1984-06-20 DE DE19843422860 patent/DE3422860A1/en not_active Withdrawn
-
1985
- 1985-06-07 EP EP85107052A patent/EP0166282B1/en not_active Expired
- 1985-06-07 DE DE8585107052T patent/DE3566503D1/en not_active Expired
- 1985-06-07 AT AT85107052T patent/ATE38945T1/en not_active IP Right Cessation
- 1985-06-11 US US06/743,460 patent/US4645604A/en not_active Expired - Fee Related
- 1985-06-18 AU AU43786/85A patent/AU4378685A/en not_active Abandoned
- 1985-06-18 CA CA000484275A patent/CA1240419A/en not_active Expired
- 1985-06-19 ZA ZA854619A patent/ZA854619B/en unknown
- 1985-06-20 JP JP60133148A patent/JPS6111155A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| AU4378685A (en) | 1986-01-02 |
| DE3422860A1 (en) | 1986-01-02 |
| EP0166282A2 (en) | 1986-01-02 |
| ATE38945T1 (en) | 1988-12-15 |
| JPS6111155A (en) | 1986-01-18 |
| EP0166282A3 (en) | 1986-12-03 |
| US4645604A (en) | 1987-02-24 |
| EP0166282B1 (en) | 1988-11-30 |
| DE3566503D1 (en) | 1989-01-05 |
| ZA854619B (en) | 1986-02-26 |
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