Ion exchange process with counter-current fractional regeneration

In an ion exchange process wherein an ion exchange bed is successively charged and discharged during an exchange cycle with an ion, here designated as "X" ion, with "Y" being used to designate the replacing ion and "Z" the oppositely charged ion associated with X and Y, by passing aqueous solutions of the ions through the bed, with the flow thereof during charging being in one direction and during discharging in the opposite direction; the improvement with respect to the discharge portion of the cycle starting with the bed charged with X ions and filled with water substantially free of X, Y and Z ions, comprising passing at least four groups of fractions through said bed, as follows: PA1 1) a first feed group of fractions, containing X, Y and Z ions, the concentration of Z ions remaining substantially constant, the concentration of X ions successively decreasing downwardly to or near to zero and the concentration of Y ions correspondingly increasing. PA1 2) a second feed group of fractions containing Y and Z ions at the concentration of Z ion substantially equal to the concentration of said ions in the previous group and free of X ions, being introduced as feed to the process. PA1 3) a third feed group of fractions containing Y and Z ions, the concentration of which successively decrease to or near to zero, and PA1 4) a fourth feed group of fractions consisting essentially of pure water free of X, Y and Z ions; And recovering from the bed at least 3 effluent groups of fractions, as follows: PA1 A) a first effluent group of fractions which may contain the displaced water content of the bed and contains a solution containing predominantly X ions and minor amounts of Y ions, both associated with Z ions, which group is at least in part removed from the process as product, PA1 B) a second effluent group of fractions, identical to the first feed group, and PA1 C) a third effluent group of fractions, identical to the third feed group, And collecting the second and third effluent groups and using the same in a subsequent discharge portion of a cycle. The charging portion of the cycle may be improved in the same way.

PREAMBLE 
An ion exchange cycle consists of at least two, and in some cases more, 
exchange reactions. If, for example, an ion exchange cycle consists of 
only two exchange reactions, the exchanger bed is charged at the beginning 
of a reaction with the type of ion that is to be replaced. The exchanger 
bed often unavoidably contains small amounts of the type of ion that is to 
serve as the replacing ion. In the first stage of the process, a solution 
of replacing ions is charged into this exchanger bed. The product 
recovered from the reaction is composed of a mixture of replacing ions and 
ions to be replaced. 
A second exchange reaction is then carried out in the exchanger bed in 
which the roles of the two types of ions are reversed, i.e., those which 
were formerly the ions to be replaced are now charged in solution form 
into the exchanger bed, so as to displace what were formerly the replacing 
ions. As a result, again, a mixture of ions to be replaced and replacing 
ions is obtained as the product of the reaction. This second reaction 
completes the ion exchange cycle. 
The two exchange reactions are separated by introducing water into the 
exchanger bed which displaces the solutions from the exchanger bed. The 
result is that, at the beginning of each exchange reaction of a cycle, the 
exchanger bed is usually filled with water which is displaced from the 
exchanger bed by the reaction solution. In one exchange cycle, therefore, 
the following steps must be carried out for each of the two reactions of 
the cycle: displacement of the water in the exchanger bed by the reaction 
solution, replacement of the ions to be replaced by the replacing ions of 
the reaction solution, and displacement of the reaction solution from the 
exchanger bed by water. 
In order to be able to carry out the ion exchange process with satisfactory 
results, it is necessary to ensure that the solution that forms as the 
product of the exchange reaction contains the ions to be replaced in the 
greatest possible amounts. The exchange reaction product is considered to 
be pure only if it contains nothing but the ions to be replaced. This, 
however, is achieved in the known so-called classic or parallel downflow 
ion exchange process only when just a small part of the capacity of the 
exchanger bed is charged with the replacing ions. The exchanger bed used 
for the second exchange reaction thus contains only a minor amount of ions 
which can be replaced, so that the product of this exchange reaction has a 
very unfavorable composition, since even the first effluent fractions of 
the solution to be taken as the product contain both types of ions. If it 
is desired to heavily charge the exchanger bed in one reaction with 
replacing ions, so as to obtain the product of the other reaction in as 
pure a state as possible, i.e., substantially only ions to be replaced are 
present, it is necessary in the first reaction to introduce a large excess 
of the replacing ions to the exchanger bed. The product of the first 
exchange reaction will then contain large amounts of the replacing ions. 
Therefore, in the simple prior art ion exchange process a product which is 
composed substantially only of ions to be replaced, and hence is pure, can 
be obtained only if a very impure product is permitted in the other 
reaction. 
Elimination of the aforesaid disadvantages associated with the simple ion 
exchange process was in part effected by counterflow operation. Whereas in 
the classic ion exchange process, each solution in each exchange reaction 
is fed in at the same end (e.g. top) of the exchanger bed, and is 
discharged at the opposite end (e.g. bottom) of the exchanger bed, but 
always at the same position, in the liquid counterflow process the 
reaction solutions in the different exchange reactions are introduced at 
different ends of the exchanger bed. The solution containing the replacing 
ions is fed in at that end of the exchanger bed which is rich in these 
replacing ions, and at the same time, at the other end, the ions to be 
replaced are removed from the exchanger bed at those points at which the 
said ions to be replaced are present in large quantities at the beginning 
of the reaction. 
The simplest type of liquid counterflow process consists in the reversal of 
the direction of flow of the liquids in the exchanger bed as the two 
reactions take place. That is, the liquid flow in the one reaction takes 
place from top to bottom, and in the other reaction it is carried out with 
the liquid flowing from the bottom to the top. The replacing ions in the 
solution that is charged into the bed are supposed to completely replace 
the ions to be replaced in the entering layers of the exchanger bed, while 
the replacing ions of the solution are to be completely replaced by the 
ions to be replaced in the layers found at the exit of the exchanger bed. 
The realization of this fundamentally simple principle has given rise to 
considerable difficulty in practice. On the one hand, the upward flow 
loosens the exchanger bed, thereby diminishing the rate of exchange, and 
on the other hand, the maintenance of the stratification of the exchanger 
packing is possible only if the packing loosened by the upward flow does 
not divide into pieces and become mixed. To prevent this disturbance of 
the exchanger packing it has been proposed to maintain a weak downward 
flow of water in the bed from the top to the exit point of the reaction 
solution, while the reaction solution is being pumped from the bottom 
upwardly to the exit point. Alternatively, it has been proposed to inflate 
an elastic balloon over the exchanger bed and to employ the same to hold 
the packing down. Still further, various apparatus have been proposed for 
installation in the exchanger bed in certain manners designed to preserve 
the stratification of the exchanger packing during the exchange reaction. 
An ion exchange process has been proposed in which an incomplete 
counterflow of liquids is used. In this process, two equal exchanger beds 
are used, the sequence of their use in the one reaction being the reverse 
of what it is in the other, so as to assure an incomplte liquid 
counterflow. The two exchanger beds are used simultaneously for each 
reaction until this reaction is terminated simultaneously in both beds. 
The ions to be replaced in the first bed are largely replaced by the 
replacing ions of the solution, while the replacing ions remaining in the 
solution can be largely replaced by the ions to be replaced in the second 
bed. This process is repeated in reverse sequence in the other reaction, 
so that products can be obtained in both reactions which consist mainly of 
only one type of ions. Carrying out this process offers no technical 
difficulties, and can be performed with comparatively simple apparatus. 
Both forms of the liquid counterflow process, however, have an important 
disadvantage. This can be appreciated from the fact that these processes 
are appropriate only when the capacity of the exchanger bed is used only 
to a limited extent, because only in this case will the resin at the exit 
end contain substantial amounts of the ions to be replaced. As a result 
the usable capacity is very low in both types of the liquid counterflow 
process. It is usually necessary to increase the volume of the exchanger 
bed as compared to the volume used in the classic process. Furthermore, 
the relative amount of wash water required for a particular exchange 
output is considerably greater. As a consequence, the amount of water 
diluting the product of the ion exchange increases quite considerably 
which is disadvantageous if it is desired to further process the ion 
exchange product for further uses. Consequently, it has been necessary in 
practice to abandon substantially pure reaction products, even though they 
are theoretically possible, and instead to be satisfied with products 
which contain only 70 to 80 percent of the ions to be replaced. In other 
words, with reference to the amount of the ions to be replaced, it has 
been necessary to use 130 to 140 percent of replacing ions measured in 
chemical equivalents. In terms of water processing technology, this 
consumption is referred to as 130 to 140 percent of theory. 
THIS INVENTION 
This invention is a process for carrying out ion exchange reactions whereby 
it is possible in the discharging reaction to extensively replace the 
replacing ions by the ions to be replaced and vice versa in the charging 
reaction so that the working capacity of the exchanger beds is not less 
than their capacities as conventionally realized in the classic process. 
In the present ion exchange process, an ion exchange bed is successively 
charged and discharged during an exchange cycle with an ion, here 
designated as "X" ion, with "Y" being used to designate the replacing ion 
and "Z" the oppositely charged ion associated with X and Y, by passing 
aqueous solutions of the ions therethrough, with the flow thereof during 
charging being in one direction and during discharging in the opposite 
direction. 
The improvement of this invention with respect to the discharging portion 
of the cycle starting with the bed charged with X ions and filled with 
water substantially free of X, Y, and Z ions, comprises passing at least 
four groups of fractions through said bed, as follows: 
(1) a first feed group of fractions, containing X, Y and Z ions, the 
concentration of Z ions remaining substantially constant, the 
concentration of X ions, successively decreasing downwardly to or near to 
zero and the concentration of Y ions correspondingly increasing, 
(2) a second feed group of fractions containing Y and Z ions at the 
concentration of each Z ions and Y ions substantially equal to the 
concentration of Z ions in the previous group and free of X ions, being 
introduced as feed to the process, 
(3) a third feed group of fractions containing Y and Z ions, the 
concentrations of which successively decrease to or to near zero, and 
(4) a fourth feed group of fractions consisting essentially of pure water 
free of X, Y and Z ions; 
and recovering from said bed at least 3 effluent groups of fractions, as 
follows: 
(a) a first effluent group of fractions which may contain the displaced 
water of the bed and contains a solution containing predominantly X ions 
and minor amounts of Y ions, both associated with Z ions, which group is 
removed from the process, 
(b) a second effluent group of fractions, identical to the first feed 
group, and 
(c) a third effluent group of fractions, identical to the third feed group. 
The second and third effluent groups are collected and used in a subsequent 
discharging portion of a cycle of the process. 
The present process can be applied to the multi-bed liquid counterflow 
process in which the liquid counterflow process is carried out with two or 
more exchanger beds whose sequence is reversed in the different exchange 
reactions, and through all of which the fractions flow downwardly. 
In the production of certain products, it may be important to maintain the 
concentration of the reaction products as high as possible. This would 
make it undesirable for the water content of the exchanger beds to be 
added to the solution recovered as the product. In these cases it is 
advantageous to carry out the process of the invention in such a manner 
that, prior to charging the first group, to first charge an additional 
group of fractions (1a), which additional fractions contain predeminately 
the ions X and minor amounts of Y, both associated with Z ions, the ion Z 
being in a concentration which increases but does not equal the Z ion 
concentration of the first group. In this embodiment, the following 
fractions are first discharged from the beds: 
(ai) a predetermined amount of solution which by and large contains the 
original water content of the bed with minor amounts of X, Y and Z ions, 
which is discarded as waste, 
(aii) an additional effluent group of fractions identical to the additional 
feed group of fractions, and which is used as such in a succeeding cycle, 
and 
(aiii) a predetermined amount of solution which contains predominately X 
and minor amounts of Y-ions, both associated with Z ions, the Z ions in a 
concentration about equal to the overall concentration thereof in the 
originally described first effluent group, which is removed from the 
process as product. 
An exchanger bed into which the solution of the replacing ions (Y) has been 
introduced only to the break-through point or slightly beyond still has a 
portion of its capacity, in the vicinity of the exit point of the 
solution, charged with the ions X to be replaced. This portion is referred 
to as the residual capacity. After the completion of one exchange 
reaction, the order of the exchanger beds is reversed, so that the 
residual capacity is now located in the middle -- at the exit end of the 
bed which now constitutes the first bed. The reaction solution consisting 
of XZ is now charged first to this bed, and first takes up the ions Y to 
be replaced from the layers at the point of entry, but then exchanges them 
for the replacing ions X of the residual capacity. As a result a solution 
is charged to the second exchanger bed, which contains considerable 
amounts of the replacing X ions. These replacing ions in turn react with 
the Y ions to be replaced which are present in that bed. The replacing X 
ions held by the residual capacity at the beginning of the charging 
reaction are thus displaced by the inflowing solution toward the outlet 
point. They leave the second exchanger bed sooner than do the same ions of 
the input solution and thus they signify a loss of replacing ions. 
It has now been found that the capacity-reducing effect of the replacing 
ions from the residual capacity can be diminished advantageously by 
fractions whose main purpose is to displace water from the exchanger beds. 
Although these displacement fractions are more dilute than the fractions 
of the reaction solution, they still contain enough exchangeable ions to 
absorb the replacing ions of the residual capacity. 
At the beginning of the charging reaction, the residual capacity is in the 
middle of the system, i.e. at the outlet point of the exchanger bed that 
is now connected as the first bed. The Y ions to be replaced of the 
displacement fractions (1a) that have reached this point take the place of 
the replacing ions X of the residual capacity. It is advantageous not to 
introduce these fractions to the second exchanger bed, but to store them 
after they leave the first bed (charging reaction). In the next cycle 
these displacement fractions (1a) are returned to the first bed. They 
contain both types of ions. The top layer of the exchanger bed contains, 
during the displacement, the ions Y to be replaced solely, or largely, and 
these ions are then replaced by the replacing ions X from the fractions. 
So the fractions that reach the lower strata contain nothing but the Y 
ions to be replaced, i.e. they absorb the X-ions from the exit layers and 
at their emergence they are of the same composition as in the preceding 
cycle. 
The process described is then repeated in each cycle. The replacing ions of 
the residual capacity in the exit layers of the first bed are replaced by 
the ions to be replaced and thus arrive at the next cycle during the 
displacement in the entry layers. Consequently they are the greatest 
possible distance from the exit layer. This makes it possible to make use 
of a larger part of the capacity prior to the break-through of the 
replacing ions. Therefore the displacement fractions in this part of the 
process have to be divided into two parts, the first being fed through the 
one exchanger bed only, and the second being fed through the second 
exchanger bed only. 
Accordingly, the present process can be conducted in such a manner that 
fraction 1a of the first feed group is subdivided into as many 
sub-fractions, 1aa, 1ab, etc., as there are exchanger beds in the series, 
sub-group 1aa being fed only to the first exchanger bed, sub-group lab 
only to the second bed, etc. The water content of the individual exchanger 
beds, ai-a, ai-b, etc., (the first of the effluent fractions) and the 
succeeding groups aii-a, aii-b, etc., and aiii-a, aiii-b, etc. from each 
exchanger bed are collected separately. First the fractions of group 1 are 
fed through the entire series and groups aii-a, aii-b, etc., are used in 
the next cycle as fraction groups 1aa, 1ab, etc. The fractions by which 
the reaction solution is displaced from the exchanger beds would also 
transfer from the exit bed to the entry bed the replacing ions occupying 
the residual capacity. Since the order of the beds is reversed during 
regeneration reaction (second reaction), these ions would be located 
closer to the point of emergence from the bed and would break through 
prematurely and contaminate the product. For this reason it is 
advantageous for feed group 3 to be divided into as many subgroups 3a, 3b, 
etc., as there are exchanger beds in the series, 3a being delivered only 
to the first exchanger bed, 3b only to the second, etc., and for effluent 
group c to be divided into as many sub-groups c-a, c-b etc., as there are 
exchanger beds, c-a being taken separately from the first exchanger bed, 
c-b from the second, etc., and for c-a, c-b, etc., to be used in the next 
cycle as sub-groups 3a, 3b, etc. 
Further advantages are obtained if the fractions which are introduced into 
the individual exchanger bed, are completely separated from each other. 
Each group is separately introduced into the bed A as well as into the bed 
B and is also removed separately. The pure solution of the exchange ions, 
feed fraction 2, is only introduced into bed A. There is then obtained 
from bed A as product of the partial exchange, a solution aiii/A. This 
solution is then introduced into bed B in place of the pure solution of 
the exchange ions as feed solution 2/B. Solution aiii/B is then the 
product of the exchange reaction. The groups ai/A and ai/B are removed as 
waste, the groups aii/A resp. aii/B are in the next cycle used as groups 
1a/A resp. 1a/B, the groups b/A resp. b/B as 1/A resp. 1/B and the groups 
c/A resp. c/B as 3/A resp. 3/B. 
The complete separation of all of the fractions has the advantage that 
contamination, i.e., transfer of any impurity from one bed through 
solutions obtained from the other exchanger bed, is avoided. In this way 
there are obtained products which have even a higher degree of purity than 
those so far obtained. 
Usually it is sufficient to operate with two exchanger beds. In some cases, 
however, it may be desired to conduct the reaction with such a small 
quantity of the replacing ions that the ions to be replaced of the first 
bed are not fully replaced. In other words, in this case an unused 
residual capacity is left. Often it is sufficient to divide up the 
displacement fractions in the manner that has been described. In other 
cases, it is advantageous instead of two equally large exchanger beds to 
use three or more equally large beds. The exahnger bed which is connected 
as the first bed, is treated with a larger quantity of the replacing ions 
in relation to its capacity than in the case of two exchanger beds. This 
increase can amount, for example, to 33 percent if three beds are used. 
In the desalting of aqueous solutions, several pairs of cation and anion 
exchanger beds are often connected in series to still further reduce the 
salt content. It has been found that the process of this invention can be 
used for the regeneration of these exchangers to special advantage, if the 
exchanger beds of the same kind are combined into groups after their 
exhaustion, and are regenerated within these groups in the reverse of the 
sequence in which they are used during the desalting. The process can be 
used independently of the nature of the exchanger used as the first bed. 
It is to be understood that what is said herein with respect to the 
discharging or charging portion of the cycle applies, respectively, to the 
charging and discharging portion. 
The process of this invention can be carried out in a single bed with 
liquid counterflow, the fractions being conducted downwardly in the one 
exchange reaction and upwardly in the other exchange reaction. If, 
however, a large, long, vertical exchanger bed is used to increase the 
capacity, the resistance at a high throughput may be too great, so that 
the liquid can no longer be satisfactorily forced through the bed. In 
these circumstances, it is desirable to divide the bed into smaller units. 
In this case, too, the process of the invention is carried out in such a 
manner that, in the one exchange reaction, the fractions are pumped 
upwardly through each bed, and in the other exchange reaction they are 
pumped downwardly through each bed. 
If it is desired to obtain the products of both exchange reactions as free 
as possible of the replacing ions, this can be achieved advantageously by 
reducing the quantity of the input ions. This reduction of the ions 
differs from case to case, and depends on the nature of the ion exchanger, 
on the exchange reaction performed, and on the throughput of the 
solutions. It is governed always by the reaction whose selectivity 
coefficient is smaller than 1, because in this reaction the replacing ions 
break through faster than in the counter-reaction. For example, it has 
been possible for the first time to regenerate a strong acid cation 
exchanger charged with calcium and sodium ions in a water desalting 
process, using 103 to 105 percent of the absorbed cations in hydrochloric 
acid, measured in chemical equivalents, and at the same time making a 
capacity usable which corresponded to more than 60 percent of the total 
capacity of the exchanger beds, and which, in other words, represented a 
usable capacity of ordinary magnitude of the classic process. 
The process of the invention can be used both for cation and for anion 
exchange. The number and volume of the fractions required are best 
determined beforehand in the laboratory by experiment. The results of the 
laboratory experiments are then applied on an industrial scale on the 
basis of the volume of the exchanger beds, i.e., the fractions must have 
the same relative volume as the bed volume. 
Often an exchange cycle consists of a plurality of exchange reactions. For 
example, with a juice obtained from sugar beets and clarified with lime 
and carbon dioxide, the so-called thin juice, the cations and the amino 
acids are both taken up by a cation exchanger. In order to obtain the 
amino acids separately, the cation exchanger is treated with an ammonia 
solution, whereupon the ammonium ions replace the amino acids. Then the 
exchanger bed is regenerated with acid. In this case, the process of the 
invention assures better utilization of the ammonia solution and 
production of a solution of amino acids with near the concentration of the 
ammonia solution. 
The process of the invention is further illustrated by the following 
Examples. It should be understood that, although these Examples may 
describe in particular detail some of the more specific features of this 
invention, they are given primarily for the purpose of illustration and 
the invention in its broader aspects is not be be construed as limited 
thereto.

EXAMPLES 
EXAMPLE 1 
The first reaction (discharging reaction) was: 
EQU (CaCl.sub.2 + NaCl) + R.sub.1 H = HCl + R.sub.1 (Ca+Na) 
R.sub.1 designates the exchange resin. The second reaction (charging 
reaction) was: 
EQU HCl + R.sub.1 (Ca + Na) = CaCl.sub.2 + NaCl + HCl + R.sub.1 H 
the replacing or "Y" ions are the H.sup.- the ions to be replaced, or the 
"X" ions, are the Ca.sup.+ and the Na.sup.+ ions, and Cl.sup.- is the "Z" 
ion. 
Two exchanger beds were used, each of which contained 150 ml of a strongly 
acid cation exchanger (Dow Chemical Company's Dowex 50W .times. 8, 20-50 
mesh). A solution was introduced into these beds which contained 50 meq of 
CaCl.sub.2 and 10 meq of NaCl per liter. When a cation concentration of 6 
meq had been reached in the outflowing solution, the introduction of the 
solution was discontinued. At that time 7.3 liters of solution had passed 
through the exchanger beds, and the pair of beds had in this time period 
absorbed 438 meq of cations. The average cation content of the total 
discharged solution amounted to 0.25 meq/1. 
The order of the exchanger beds was then reversed and the beds regenerated. 
For this purpose the following feed fractions were used: 
______________________________________ 
Composition of feed fractions, 
eq/l 
Group Fraction HCl CaCl.sub.2 
NaCl ml 
______________________________________ 
1 1.70 2.10 0.10 100 
2 2.32 1.73 0.10 100 
3 2.72 1.50 0.09 100 
4 2.80 1.28 0.07 100 
No. 1 5 2.92 1.18 0.05 100 
6 3.10 1.05 0.01 100 
7 3.17 0.90 0.01 100 
8 3.42 0.67 0.01 100 
9 3.55 0.45 0.00 100 
No. 2 [ 10 (input) 4.00 -- -- 150 
11 0.92 0.0 -- 60 
No. 3 
12 0.04 0.0 -- 60 
No. 4 [ 13 (water) -- -- -- 180 
______________________________________ 
The first effluent group withdrawn (a) consisted of 320 ml and was 
withdrawn from the process. The second effluent group (b) was then 
withdrawn, and was identical to the first feed group. Then the third 
effluent group (c) was collected, and was identical to the third feed 
group. 
In the classic prior art process with an ion exchanger bed with a volume of 
300 ml, it would have been necessary to charge into the bed 890 meq of 4N 
hydrochloric acid to assure the above-stated exchange capacity of 438 meg, 
which was accomplished by the method of the invention with 600 meq of 4N 
hydrochloric acid. However, an average cation content in the treated 
solution of 0.6 meq/1 would have been obtained instead of the 0.25 meq/1 
realized in accordance with this invention. To arrive at the low cation 
content that was obtained according to this invention, it would have been 
necessary to charge into the bed in the prior art process 1200 meq of 4N 
hydrochloric acid. The working capacity would have been increased 
somewhat, but the acid would have been used with much less efficiency. 
If, however, a multi-fraction process according to the process of this 
invention is followed, but using a single exchanger bed containing 300 ml 
of exchanger only, 900 meq of 4N hydrochloric acid would have been 
required in order to assure the low overall cation content of the solution 
treated. 
EXAMPLE 2. 
The first reaction (discharging reaction) was: 
EQU NaCl + R.sub.2 OH = NaOH + R.sub.2 Cl 
The second reaction (charging reaction) was: 
EQU NaOH + R.sub.2 Cl = (NaCl + NaOH) + R.sub.2 OH 
the replacing or "Y" ions are the OH.sup.- ions, the ions to be replaced, 
or the "X" ions are the Cl.sup.- ions, and Na.sup.+ is the "Z" ion. The 
exchange resin was Dowex 2 .times. 8, 20-50 mesh, a strongly basic Type II 
exchange resin. 
There was pumped into a freshly regenerated pair of exchanger beds 
containing 85 ml of resin in bed A and 137 ml in bed B, 2 liters of a 
solution originally containing 50 meq/1 of NaCl, which had previously been 
passed through a similar pair of beds. Thereafter 3.25 liters of fresh 
solution was pumped into the beds. 3.25 liters were withdrawn from the 
process from the discharge of the pair of beds, and the following 2 liters 
fed into another freshly regenerated pair of beds. The said withdrawn 
solution contained 4.5 mval of NaCl and 45.5 meq of NaOH. The pair of beds 
had thus absorbed 148 meq of chloride ions. 
Regeneration was carried out by reversing the order of the beds and 
treating them with fractions identified in the table, at a flow rate of 16 
ml/m. 
______________________________________ 
Bed B 
Influent Effluent 
Sub- Fract. Sub- Fract. 
Group group No. ml Group group No. ml 
______________________________________ 
1a/B 1/B 50 ai/B 45 
(waste) 
1/B 2/B 3/B 4/B 5/B 
100 100 200 200 
a/B aii/B aiii/B + 
##STR1## 
50 
2/B 6/B 110 b/B b/B T/B 714 
3/B 7/B (in- put) 50 
4/B 8/B .about. 
c/B 9/B 50 
(wa- 
ter) 
______________________________________ 
______________________________________ 
Bed A 
Influent Effluent 
Sub- Fract. Sub- Fract. 
Group group No. ml Group group No ml 
______________________________________ 
1/A 50 ai/A 75 
(waste) 
1a/A aii/A 1/A 50 
2/A 50 a/A aii/A 2/A 50 
1/A aiii/A 
3/A 120 
(pro- 
duct) 
T/B 714 4/A 100 
2/A 5/A 100 
3/A 50 b/A 6/A 200 
3/A 4/A 50 7/A 200 
4/A 5/A .about. 8/A 50 
(wa- 
ter) c 9/A 50 
______________________________________ 
From the effluent of B 1/B and 8/B are in the next cycle used as 1/B and 
8/B. T/B is transferred to the bed A continuously, without dividing it in 
fractions. From the effluent of A 1/A and 2/A are used in the next cycle 
as 1/A and 2/A. 3/A is withdrawn as product of the reaction, 4/A, 5/A, 6/A 
and 7/A are used in the next cycle as 2/B, 3/B, 4/B and 5/B. 8/A and 9/A 
are used in the next cycle as 3/A and 4/A. 
The cycles were repeated 15 times, till the composition of the product 
(3/A) showed no more change. From this moment it contained 148 meq 
Cl-ions. Introducing with the input 110 ml 1,47 N NaOH, i.e. 163 meq, the 
caustic consumption corresponds to 109%. The utilizable capacity was 0.67 
eq/1. The composition of the recycled fractions was not determined. 
EXAMPLE 3 
The exchanger, the exchange reaction, the replacing ions and the ions to be 
replaced are the same as in Example 1. 
Two exchanger beds each containing 300 ml of strongly acid cation exchanger 
were used. The solution charged into the beds contained 10 meq/1 of 
CaCl.sub.2 and 2 meq/1 of NaCl. Expressed as CaO, the cation content 
amounted to 34.degree., (1.degree. = 10 mg/1 CaO). It was possible to 
charge 67 liters of solution before realizing the break-through value of 
10 relative percent, 783 meq of cations being absorbed thereby. The cation 
slippage averaged 0.05 meq/1, equal to 1.4 ppm CaO. 
The following fractions were used at a flow rate of 15 ml/min. for the 
regeneration, the order of the exchanger beds having been reversed: 
______________________________________ 
Composition of Feed Fractions 
Fraction No. Concentration in eq/l 
Group (Vol. /ml) HCl CaCl.sub.2 
NaCl 
______________________________________ 
1 (200) 0.50 3.00 0.40 
2 (200) 0.92 2.80 0.33 
3 (200) 1.28 2.50 0.30 
4 (200) 1.75 2.22 0.13 
No.1 
5 (200) 2.00 1.88 0.07 
6 (200) 2.15 1.65 0.05 
7 (200) 2.38 1.48 0.03 
8 (200) 2.70 1.08 0.02 
No.2 [ 9 (HCl-200) 
4.00 -- -- 
10 (100) 0.85 -- -- 
No.3 
11 (100) 0.03 -- -- 
No.4 [ 12 (water-370) 
-- -- -- 
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No more than 102.5% HCl had to be used. 585 ml was first separated from the 
effluent solution as the regeneration product. The fractions for use as 
feed in the next cycle were then collected. 
EXAMPLE 4 
The exchanger, the exchange reaction, the replacing ions and the ions to be 
replaced are the same as in Example 1; only the composition of the anions 
(Z) was different; 70% of them were strong acid anions, Cl.sup.- and 
SO.sub.4.sup.- ions, 30% were HCO.sub.3.sup.- ions. The bed volume was 
1000 ml. The fractions were used in the same groups as described in 
Example 3. The volume of the product of the regeneration was 1050 ml, and 
the flow rate during the regeneration 25 ml/min. 
The water to be desalted was pumped upwardly from the bottom, and the 
regenerating fractions were pumped downwardly from the top. During the 
delivery of water to the bed, water which had already passed through the 
exchanger bed and whose composition was the same as that of the main 
stream of the desalted water, was caused to flow downwardly from the top 
through the bed. Underneath the topmost bed layer a pipe system was 
established having channels therein, through which both streams were 
conducted off. The water was conducted through the bed until the cation 
content had risen to 5 percent of the initial value. Then the bed was 
backwashed and regenerated. 
The water treated contained 20 German hardness degrees (1.degree. = 10 mg/1 
CaO) as cations at an alkalinity of 30 percent and a sodium content of 20 
percent. It was possible to pass 190 liters of water through until the 
desired point was reached. 1350 meq of cations were absorbed, i.e. the 
1380 meq of HCl were 98 percent utilized. 
The following fractions were introduced into the one-liter exchanger bed: 
______________________________________ 
Composition of Feed Fractions 
Fraction No. Concentraton in eq/l 
Group (Vol./ml) HCl CaCl.sub.2 
NaCl 
______________________________________ 
1 (350) 0.40 3.05 0.45 
2 (350) 0.88 2.82 0.35 
3 (350) 1.28 2.50 0.30 
4 (350) 1.75 2.22 0.13 
No. 1 
5 (350) 2.02 1.88 0.05 
6 (350) 2.17 1.66 0.04 
7 (350) 2.35 1.50 0.03 
8 (350) 2.70 1.09 0.01 
No. 2 [ 9 (HCl-345) 
4.00 -- -- 
10 (150) 0.95 -- -- 
No. 3 
11 (150) 0.05 -- -- 
No. 4 [ 12 (water) -- -- -- 
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