Note: Descriptions are shown in the official language in which they were submitted.
1(1 7~ ~78
The invention relates to the process for increasing the
exchange yield in ion exchange processes.
The ion exchange procedure is today most frequently
employed for the preparation of raw or untreated water. It is
possible by ion exchange to produce a high separation effect
between the water and the dissolved ions. By way of-example,
with the extraction of salt from untreated water, the content of
cations and anions can be reduced to about 0,15 to 0,30 per cent,
as a result of which the treated water satisfies the normal
requirements. The effective volume capacity of the exchanger
bed (generally indicated by EVC) is 70 to 80% of the total
capacity of the exchanger bed, which hereinafter will be briefly `
designated as "bed". These reactions are generally indicated
as charging, exhaustion or utilisation. They are terminated
when the supply of ions contalned at the commencement in the bed
is exhausted. These are brought in the counter-reaction to the
bed, which is generally referred to as regeneration.
-~or being able to describe these operations simply,
and according to F. Helfferich, "Ion Exchange", McGraw-Hill,
New York, 1962 , the ions participating in the ion exchange are
referred to as counter-ions, the oppositely charged ions fixedly
anchored on the frame work of the exchanger as poly-ions and
those ions of the solution which have the same charge as the poly-
ions are referred to as co-ions (see Helfferich, pages 6 and 7).
The affinity relationships between the counter-ions and the
poly-ions or co-ions are characterised by the separation factor
(see Helfferich, page 153).
In order to distinguish the counter-ions from one
another, those which are contained in the solution used for the
reaction carried out according to the invention, for example,
the regeneration, are referred to as "exchanging" counter-ions
and those of the bed as counter~ions "to be exchanged". The
~ ~ 10~1778 r
exchanging counter-ions have with the regeneration of a strongly
dissociated ion exchanger a lower affinity to the poly-ions than
those which are to be exchanged. With the exhaustion which is
connected therewith, the counter-ions which are to be exchanged
reach the bed, which is charged at the commencement of this
~r reaction with the exchanging counter-ions.
With the exhaustion, the separation factor has a
.; .
considerably higher value than 1, i.e~ the counter-ions to be
exchanged have a much higher affinity for the poly-ions than
the exchanging counter-ions. With the regeneration, the last-
:;
; ~ mentioned counter-ions have to be once again applied to the bed. ~ -
In this case, the SeparatiQn factor with strongly dissociated ~
.: ~
; ~ ion exchangers is smaller than 1. If it is a question of the
,~ regeneration of weakly dissocated ion exchangers, the value of
the separation factor is greater than 1, because of the content
of hydrogen ions (cation exchangers) or hydroxyl ions (anion ``
exchangers) in the regeneration solution. The dissociation data
~ - are related with the cation exchangers to the poly-ions charged
; with hydrogen ions and with the anion exchangers to the poly-
..
ions charged with hydroxyl ions.
;~ The industrial ion exchange has until a few years ago
been determined by the simple co-cur-rent procedure, with which
,~
the liquids in both exchange reactions of an exchange cycle are
conveyed downwardly through the fixed bed. The term "simple"
; is intended to express that all liquids flowing from the bed are
immediately carried away, i.e. removed from the system. On
account of the aforementioned size ratios of the separation
factors, it is here necessary to use in the regeneration a
; considerable excess of the exchanging counter-ions in order to
remove the counter-ions which are to be exchanged from the bed
in such quantity that the initially mentioned high se~aration
effects can be produced with the charging.
' ` .
-- 2 --
`` ~0717~8
So that this process may be compared with the other
known processes, the regeneration which can be carried out under
defined conditions of a cation exchanger charged with sodium ions
by hydrochloric acid is hereinafter used as an example. In the
present case, approximately 180 to 200~i of hydrochloric acid,
^i related to the sodium ions removed from the bed - both measured
. . .
in chemical equivalents ~equ)~- are necessary for charging the
bed up to 90% of its total capacity with hydrogen ions. The
- concentration of all the waste waters which are formed with
this ion exchange and referred to hereafter as secondary waste
water amounts to about 1 to 3% by weight.
So as to reduce the excess of regenerating agents,
.
processes with stored fractions have already been used with the
commencement of the industrial use of the ion exchange procedure,
in-which processes the fixed bed had delivered thereto with the
regeneration one fraction or more than one fraction which were
j .
obtained in the preceding exchange cycle, and only after the
said fraction or fractions, the unused regenerant solution
supplied to the system from outside and finally water. At the
same time from the bed were obtained: water and the spent
regenerate, which were discharged, as well as one or more than
: ~ '
one fraction, which had to be stored again. Thereafter, also
.
spent washing water was obtained, and this likewise was dis-
charged. The number of the fractions usually amounted to 1,
seldom to 2 to 4 and in a few cases, when using fractions having
very small volume, to 7 to 15. With this process, the hydro-
chloric acid requirement in the above comparison çxample could
be reduced to 150 to 170% with an otherwise identical result.
The concentration of the secondary waste waters here also amounted
- 30 to-about 1 to 3% by weight. This so-called simple fractionation
procedure which is described by wa~ of example in German Patent
~; - Specifications 3 93 044 and 3 97 848 could not be introduced in
.~
. - ::: :: , :
1071778
the practice however, despite great effort, because the effect
achieved did not justify the technical expense. Today, it is
` scarcely used.
The simple counter-current process which has been used
for about ten years and in which the liquids in one of the
reactions of the exchange cycle are conveyed from top to bottom
; .
and in the other from bottom to top through the fixed bed,
represents an important development. The discharging liquids
are immediately carried away. In this process, it is not
necessary to conduct the regeneration of the bed to such an
extent as with the prior known processes, since it is possible
with the counter-current principle to produce simultaneously
high exchange yields in both reactions. The chemicals used in
the regeneration are therefore employed with a good yield and
the separation effect at the time of charging is even higher
than in the simple co-current process. Nevertheless, this can
only be achieved with a relatively low value of the EVC. In the
comparison example, the consumption of hydrochloric acid by
this process amounts to 120 to 130% with an EVC of 75% of the
total capacity. The concentration of the secondary waste waters
is here also at about 1 to 3% by weight. `~
- Almost simultaneously with the counter-current process,
several processes have been developed with which the exchange
reactions are carried out with unmoved fillings of the exchanger
in the simple co-current process, the solutions and the water
which are supplied from outside being simultaneously introduced
into the filling at positions which are spaced from one another.
If a predeter~ined limiting value of a characteristic property
; is reached in the effluent, the supply of the liquids is shut off
and the filling is displaced in its container by a certain
section opposite to the direction of flow of the liquids and the
front section transported to the counter reaction. The space
-- 4 --
1~71778
which thereby has become free is filled with freshl~ regenerated
or charged exchanger resin. The liquids are then once again
supplieduntil the limit value is reached again. The number of
the sections traversed in the regeneration is larger than those
` traversed in the exhaustion. Using these processes, the
- regenerating ions are used practically just as well as with the
simple counter-current process and the value for the EVC is also
of approximately the same siæe. It is also possible when using
these processes to work with solutions which are of higher con-
centration then that which was possible in the processes alrealy
referred to above. The regenerates which are obtained have a
concentration of 40 to 60% of the solution supplied from out-
side and the concentration of the secondary waste waters lies at
about 4 to 8% by weight. However, in spite of these advant-
ages, these known processes were unable to suppliant the simple
counter-current process, because the installations necessary for
carrying out the said process are too complicated.
At approximately the same time, there was also develop-
ed a fifth process, in which there were certainly used stored
fractions, as with the simple fraction procedure, but which
nevertheless differed fundamentally from the latter. According
to this process, stored fractions are not only used in the ex-
change reaction, but also after the completion thereof with the
displacement of the reaction solution by water and advantage-
ously also before commencement of the exchange reaction with the
displacement of the water contained in the bed by the reaction
solution. The mixing of the fractions obtained from the bed
until they are used again in the next cycle is intentionally
prevented or at least controlled. Specific measures serve to
guarantee a uniform flow of the liquids through the stationary
bed. This process, which is described for example in German
Patent Specification 14 42 500 and U.S. Patent Specification
~ -
1C~71778
~ . .
34 48 043, which is also reerred to as an intensive fraction
process (abbreviated as IFP) has been developed for use for
preparative purposes, with which, in at least one ion exchange
reaction of the cycle, solutions are obtained of which the salt
content has such a value that the higher expense for one installa-
tion and the operation thereof is justified. With the IFP, the
exchanging counter-ions can always be used to a high degree and
it is possible to work with concentrated solutions, so that the !~
concentration of the solutions which are produced can reach 80 to
90% of that of the solutions being used. In the co~parison
example, the consumption of hydrochloric acid falls to 103 to
104% with the IFP procedure, the EVC being at 85 to 90% of the s `~
total capacity. The concentration of the secondary waste waters
amounts to about 10 to 15~ by weight. Corresponding results are
achieved with the regeneration of the ion exchangers which are
used in the cases initially referred to for the treatment of
raw water.
` In spite of these good results, the IFP has not found
,
general use in connection with the treatment of raw water. It ~ !
is true that this process has an advantage as compared with the
simple counter-current ~ cess as usually employed at the presen~
time as regards the use of the regenerating agent, but this in
~ itself is not sufficient to compensate for the greater expense
for the installation and the running thereof. The considerably
higher concentration of the secondary waste waters has not so
far had any such great significance that it could play a part
as regards the compensation.
- For a number of years, the protection of the environment
has become of increasing importance. Already at the present
time considerable standards are set as regards the purity of the
discharged waste waters or sewage. In many industries, waste
waters are formed which may no longer be discharged into rivers
- 6 -
1071778
or into the sea. Because of the high separation-effect initially
referred to, the ion exchange for removing the harmful or toxic
ions or the salts which are present in excessive quantities is
per se better suitable than all other known processes,as for
example electrodialysis or reverse osmosis. However, the first
disadvantage of the ion exchange consists in that, in the second-
ary waste water, with the cation exchange, there is additionally
obtained at least one e~uivalent of salt per equivalent of
removed ion and, with the demineralization, additionally at
least two equivalents of salt per equivalent of removed salt.
These minimum quantities would also be obtained if one were able
to manage with the equivalent quantity of the regenerating agent.
The second disadvantage is that the concentration of the second-
ary waste waters is too low, so that the disposal thereof
raises at least the same problems as the original waste water.
For the ion exchange to be able to be used in connec-
tion with the elimination of the waste waters in industry and
possibly also in the municipalities, it must conform to the
following conditions:
1. The consumption of the exchanging counter-ions necessary for
the regeneration is to be very close to the value which is ~ 3
equivalent to the counter-ions to be exchanged.
2. The secondar~ waste water of the iron exchange is to have a
highest possible concentration, so that the disposal thereof
does not raise any insoluble problems. These problems are
completely avoided if the salt or salts of the secondary
waste water can be exploited. The exploitation, with which
usually the water has to be separated from the dissolved
salt, is influenced by the concentration of the solution which
is obtained. It bears a part or in certain circumstances
also all the disposal costs. However, even when the secondary
waste water is to be chemically treated, deposited or trans-
1071778
ported into the sea, the costs for this depend on the con-
centration of the secondary waste water.
3. The overall eficiency is to be as favourable as possible,
i.e. the sum of all costs which are caused with the ion
exchange by the establishment and the operation of the in-
.` ~ stallation and the disposal of the secondary waste water is
to be as low as possible, so as more particularly to promote
environmental protection.
None of the known ion exchange processes is able to
satisfy all these conditions. The process which comes closestto this target is the ~FP, which meets the first two conditions,
but can only partly comply with the third condition because of
the expense for the installation. Th~ judgement concerning the
use of ion exchange for the elimination of waste waters is
- therefore generally critical. In Winnacker-K~chler, "Chemische
Technologie", C. Hanser Verlag, Munich, 1975, Volume 7, page 700,
it reads that the demineralization from waste waters by means of
ion exchange is not a practical solution capable of general use.
The invention has for its object to carry out ion
exchange processes in such a way that the previously mentioned
disadvantages are avoided,with a lowest possible expense for the~
establishment and operation of the installation, a highest possi-
ble exchange yield or rate is to he obtained, while the exchange
products to be discharged from the installation are to be able
to be disposed of at lowest possible expense, so as more
particularl~ to be able to satisfy the conditions prescribed
for environmental protection. The exchange yield is to be
- increased with the same or even smaller consum~tion of chemicals,
for example, or the regeneration.
The basis for the achievement of this object is the
simple fraction process with one or more reaction fractions,
wherein one or more than one reaction fraction stored with the
-- 8 --
} ` ~ -
~071778
.
previous carrying out of the same exchange reaction, a solution
of the exchanging ions supplied from outside and wate~ are
delivered to the washed bed which is filled with water and which
is charged wit~ the ions which are to be exchanged, and after
the discharge from the bed of the water and of a solution
~ . ~
obtained as product the same number of reaction fractions with
the same volume is collected and stored as the number as that
previously supplied, in order to be delivered as previously
with the next carrying out of the same exchange reaction in
the identical manner and in the same sequence.
According to the invention, the process is character-
ized in that: - ;
a) a displacement occurring in the direction of flow and
relatively to one another of those liquid particles which are
delivered simultaneously or in immediate succession to the
~;~ bed is substantially preventeduntil the discharge from the
container of the bed is reached, and
b) the co-ion content of the reaction fraction or fractions is
kept constant by keeping constant the volume of the reaction
~1
`~1 20 fraction or fractions of the solution supplied from outside
~ ~ 1
and of the liquids discharged from the system and of the
` co-ion content of the solution supplied from outside.
In accordance with the invention, for preventing, or
; at least reducing, the relative displacement of the liquid
.: ,
; particles delivered from the supply line simultaneously to the.~ ,
` bed n the direction of the flow, the-liquid to be deIivered to
the bed, after leaving the supply line, is distributed in the air
space above the bed uniformly on to the bed cross-section.
Rnown devices, as for example a spiral nozzle, are used for this
purpose. For the same purpose, the height of the liquid layer
which is disposed above the exchanger la~er of the bed is kept
as small as possible, advantageously between about 1 and 5 cm.
,': . _ g _
- 1~71778
The regulation o the height o~ the la~er is effected b~ means
of known devices, as or example, a pair of floats, one of which
responds to the level of the exchanger layer of the bed and the
other to the level of the liquid layer, and the difference in
height of the two 1Oats serves to deliver an impulse for
regulating the speed of the supply and/or discharge of the
- liquids. The harmful effect of the dead volume of this liquid
layer is eliminated by the jets of liquid from the supply line
striking the said layer at high velocity, as a result of which
the layer maintains a steady and strong motion.
Disadvantageous displacement of the liquid particles
relatively to one another can also occur inside the bed itself, `~
i.e. inside the exchanger layer. Of significance in this
respect are the displacements which occur in the direction of
flow of the bed,i.e. in its longitudinal direction. In order to
prevent or at least substantially to reduce these displacements,
the base on which the bed is resting inside the exchanger con-
tainer is provided in known manner with uniformly distributed
narrow throughflow gaps (filter nozzles), which do not allow the
resin granules to pass through and cause a damming action in
` the flow, whereby the said flow is distiributed uniformly on to
the said gaps. Together with the uniform delivery of the liquid
to the surface of the bed,it is hereb~ guaranteed that the flow
inside the bed is in practice always distributed uniformly over
the cross-section thereof and any accelerated displacement or a
lagging of individual liquid particles is at least substantially
- prevented.
Relative displacements can also occur in the space
.
between the base supporting the bed, the so-called nozzle base,
and the container base proper. This space is filled during the
exchange reaction with liquid. Entire component quantities of
liquid which si~ultaneously emerge from the bed are also able to
-- 10 --
.. . ... ,.~. ;
1(:1i71778
be displaced relatively to one another in this space. By liquid
component quantity is to be understood the total o~ all liquid
particles which leave the bed immediately following one another
within a prescribed finite time period, of for example several
- seconds. These liquid component quantities are displaced relati-
vely to one another in the space beneath the nozzle base, more
especially when the density of the quantities following one
another increases. By the relative displacement between the
said quantities, there is caused a large displacement between
liquid particles delivered in immediate succession to the bed.
In order to eliminate or at least to reduce this effect of the
bottom space, its volume is reduced in size to the extent which
is technically possible in accordance with the invention. The
remaining space can then also be filled, for example, in known
manner, with filler bodies.
With the process according to the invention, it is
further proposed that the co-ion content of the one or more
reaction fractions in the series of the identical exchange
reactions which follow one another should be kept constant,-for
which purpose the volume of the reaction fraction or fractions,
the volume and also the co-ion content of the solution supplied
from outside and the volume of the liquids dlscharged from the
system are kept constant.
The state or condition as described here is not
immediately reached with the commencement of a new series of
exchange cycles, but can only be reached after carrying out
several cycles with the said volume and co-ion content kept
constant. In this stationary state, the composition of all
I liquids participating in the exchange remains constant, except
for the random deviations. This reproducibility of the composi-
tion is necessary for achieving the advantageous industrial
results of the process according to the invention.
-- 11 --
.. .. .
. ~ ~
1071778
. .
Using the measures which have been previously referred '
to there is already produced a decided improvement in the exchange
yield which can be achieved with the simple fraction process by
a comparatively small expense for the establishment and operation
of the installation. An additional improvement as regards the
results obtained b~ the process is achieved if each re?ction
fraction is in itself mixed in its conta ner. The uncontrolled
relative displacement of the liquid particles or liquid component
quantities is avoided in this way. The fractions are mixed as
thoroughly as possible during or shortly after their deposition.
This can be achieved in known manner, for example, by means
of stirrer mechanisms'or by a suitably strong whirling action
with the introduction into the containers.
The fraction or the fractions and the solution
supplied from outside, in the case where it is ~'ed to the bed by
'the same pump, are generally not supplied directly to the pump
which feeds them to the bed, but through a common storage con-
tainer. So that the mixing of solutions to be supplied in succes- -
sion is kept as low as possible, it is proposed that the volume
.
-~ '20 of the storage container should be kept as small as posslble and
that this should possibly also be filled with filler bodies.
; -
For establishing whether or not the co-ion content of
at least one reaction fraction ~s constant, it is in principle
possible for the reaction fractions themselves to be investigated.
However, it is more advantageous to check the composition o a
solution obtained from the bed after the reaction fraction or,
with several fractions, after the last reaction fraction. As
long as the co-ion content of the control solution is changing,
the stationary state is still not reached or is no longer
existing.
For correctly complying with this indicator function,
the co-ion content of the control solution should be changed in a
- 12 -
107177~
manner which can be easily measured, also with small alterations
in the system. Conseauently, it has been proved to be advant-
ageous to collect the control solution immediately after the
reaction fraction or the last reaction fraction. In this case,
the co-ion content of the solution is sufficiently large for
being able to determine it accurately, and it quickly reacts
to the changes in the system.
The arrival to the stationary state in the manner is
described still does not mean that the system is in the optimal
state. This is only achieved when the co-ion content of the
reaction fractions with a fixed volume is at its maximum. It is
hereby ensured that the ion exchange taking place in each
fraction leads to a maximum conversion under the given condi-
tions. The size of the maximum value also depends on the process
which is used for the displacement of the reaction solution from
the bed. The method of displacement determines the loss of co-
ions and the counter-ions connected therewith in the spent
washing water which is discharged from the system. The greater
the loss, the smaller is the co-ion content of the reaction
2a fraction or fractions. On the other side the displacement method
prohibits the dilution of the reaction fraction or fractions by
the water used for displacementO The greater the dilution, the
smaller is the co-ion content of the said fraction with constant
volume.
A considerable improvement in the results of the
simple fraction process is already obtained by maintaining the
technical processing conditions whi~h have been discussed, even
although they still do not reach the results which are produced
by the IFP method and which of course are obtained with a greater
expense for equipment, but under otherwise identical conditions.
It has now been found that the results of the process according
to the invention, operating with a considerably smaller number
- 13 -
1071778
of fractions, can be further improved if the size of the frac-
tions is established in a suitable manner.
In accordance with this discovery, it was attempted
to provide a rule which is capable of general application and ` ;
which can be used independently of the exchange reaction and the
conditions under which it is carried out. It can also be used
with advantage outside the scope of the invention, since it
; leads to a reduction in the number of the reaction fractions in
every case, i.e. also independently of the aforesaid technical
measures used in the process.
- According to the invention, the exchange yield pro-
!, ~i
` duced in the reaction fraction when it comes into contact with
the bed is used as a characteristic feature of the said fraction.
( . .
- So as to be able to indicate the yield with a number having no
; dimensions, the yield achieved in the reaction fraction has been
related to the exchange yield which is the maximum possible under
the given conditions and expressed as a percentage of the latter.
The maximum possible exchange yield - hereinafter referred to as
MY - is influenced by the composition of the reaction fraction
and of the bed at the time of supply, the separation factor of
the reaction under these conditions, the temperature, the ~t~
through-flow velocity of the fraction, etc., that is to say, by
all the working conditions which determine the manner in which
the ion exchange reaction proceeds. The value of MY therefore
differs from case to case; by indicating as a percentage the
yield which is produced with the passage of the reaction fraction
being used, a value is however providea which is equally valid
for each exchange reaction.
, With the determination of the MY, it is advantageous
to start from a state of charging of the bed which does not exist
at all with the actual conduction of the process. For this
purpose, a solution, of which the composition corresponds to
- 14 -
"
. . .
1~71778
that of the solution which is supplied before the reaction
fraction and which possibly is also a fraction is supplied to
the bed until an equilibrium between the two is established,
the conditions as regards the actual conduction of the process
being maintained. The bed is thereafter washed out. This state
is completely-defined and can be reproduced. Another solution,
; the composition of which is the same as that of the reaction
fraction to be investigated, is now supplied to the bed as thus
prepared. Under the conditions which prevail when actually
10 carrying out the process, the said solution is conducted through
the bed until the equilibrium is reached, i.e. the effluent has
the same composition as the inflow. The collected effluent is
then analysed and the quantity of the exchanged counter-ions is
determined. This quantity represents the MY.
The co-ion content of the reaction fraction or frac-
tions is now chosen to be sufficiently large that the exchange
yield which occurs with the passage of the reaction fraction or
fractions amounts, in accordance with the invention to more than
50%, advantageously more than 70% and with particular advantages
more than 95%.
The displacement of the one reaction fraction, or ~
when there are several, the last reaction fraction, from the bed
can take place in accordance with the principles of the IFP by
a stored displacement fraction which, after the reaction fraction,
or the last reaction fraction, is recovered, stored and is used
again in the same manner in the next exchange cycle. The dis-
placement fraction is advantageously mixed in the container.
This displacement has the advantage that the concentration of the
co-ions in the reaction fraction or fractions has the maximum
value which can be achieved, since with this displacement method
the loss of ions in the spent washing water of the bed is at the
lowest possible value. The concentration of the co-ions reaches,
- 15 - -
, ~
., ~ ..
"
1(~71778
in the reaction fraction, or the last reaction fraction a value
which is practically the same as that in the solution which is
supplied from outside, except for the quantity of water which
the bed gives off or takes up as a consequence of the change in ~
its hydration during the ion exchange. This water quantity '
differs from case to case and therefore always has to be
determined experimentally.
- The co-ion concentration of the displacement fraction
is preferably adjusted between 30% and 70%, advantageously
between 40% and 60~. In this case, the co-ion concentration of
the reaction fraction or the last reaction fraction is preferably - ~'
kept practically equal to that of the solution supplied from
outside. It is necessary in this connection to take into account
the swelling pressure which occurs with the decrease in the
concentration of the delivered solution, especially with highly
dissociated ion exchangers, in the exchanger grain, the grain
extracting water from the increasingly dilute solution. Whe'n the
difference -between the concentration of the reaction fraction
or the last reaction fraction and'that of the liquid used for
'the displacement is too large, the swelling pressure is able to
cause the exchanger grain to burst. The concentration of the ~'
displacement fraction, when adjusted as above-mentioned! avoids '~
any such damage to the exchanger grain. The concentration is to
be so established within'the indicated limits that the difference
of the co-ion concentration from the solution supplied from
outside and the displacement fraction does not exceed 2.0 to 2.5
equ/l. This value can only be established by experimentation,
by testing displacement fractions of different concentration in
a longtime test or during the operation of the installation. -`
:
' 30 The same disadvantages effect also occurs when the
co-ion concentration of the displacement fraction is higher than
'~ 2.0 to 2.5 equ/l. In such cases, this displacement fraction,
- 16 -
, . .
`` - `` 1~71778
instead of being displaced from the bed by means of water, is
displaced therefrom by at least one additional displacement
fraction, which is likewise stored and is stored again after it
has been used. The co-ion concentration between the respective
displacement fractions advantageously decreases in each case by
about 60 to 80~, while the water for the displacement after at
least one additional displacement fraction is supplied to the bed.
Another object of the invention is to provide a
process in which a previously stored displacement fraction of
constant volume is used for the displacement of the reaction
fraction from the bed, said displacement fraction having a co-ion
concentration which is lower than that of the solution supplied
from outside and which, after recovery of the reaction fraction
or the last reaction fraction from the bed, is collected, stored
and, when next carrying out the same exchange reaction, is used
again in the same manner as that in which it had been formed, the
displacement fraction being displaced from the bed by water. The
co-ion concentration of the displacement fraction is kept at 30
to 70%, advantageously 40 to 60%, of the co-ion concentration of
the solution supplied from outside. In this case, it is the
first displacement fraction which is used as the control solution.
- To decrease the expenses further in the process
according to the invention it is advantageously foreseen, to
discard the solution, obtained after the reaction fraction or
after the last reaction fraction to be stored, instead of storing
it too as one or more displacement fraction (fractions).
If the concentration of the solution supplied from
outside does not exceed 2.0 to 2.5 equ/1, this can be directly
displaced from the bed by water. As a result, the installation
is more simple than in the preceding case. In this case, some
water is mixed with the reaction fraction or the last reaction
fraction and a part of the solution supplied from outside is
- 17 -
10~1778
mixed with the discharged washing water. It has been proved
to be advantageous to terminate the withdrawal of the reaction
fraction or the last reaction fraction when its average co-ion
concentration has reached a value higher than 65~i, advantageous-
ly higher than 75%.
.
If water is used for displacing the reaction fraction,
the solution discharging from the bed after recovery of the
reaction fraction is used as control solution. The volume of
the control solution is advantageously Less than 50% of the bed
volume, in order to adjust its concentration to a value which
can be easily determined. The control solution is discharged
after its composition has been established.
In those cases in which the co-ion concentration of
; the solution supplled from outside is higher than 2.0 to 2.5
equ/l!the use of water for displacement purposes would be harmful.
In those cases one or more than one solution is used for the
displacement of the reaction fraction or the last reaction
fraction, which solution or solutions~are freshly prepared in each
exchange cycle from the solution supplied from outside and water.
The major part of the ion content of this solution or solutions
- ~ reached the (last) reaction fraction, while a far smaller part
passes as a loss into the spent washing water of the bed.
The co-ion concentration of the first, newly prepared
solution is adjusted to approximately 30 to 70% and advantageous-
ly to 40 to 60% of the co-ion concentration of the solution
supplied from outside and the co-ion concentration of the possibly
additional newly prepared solution or solutions is respectively
adjusted to about 20 to 30% of the co-ion concentration of the
. .
preceding, newly prepared solution. Here also the difference
between the concentration of the solution supplied from outside
.i
~~ and the newly prepared solution, or between the newly prepared
. . .
;~ solution and water, is not to exceed 2.0 to 2.5 equ/l. If this
- 18 -
.. ~ . ' .
1(~7~7~8
were the case, a second solution and possibly also additional
solutions with correspondingly reduced concentration will be
newly prepared.
The volume of the newly ~repared solution or solu-
tions is given bv the limitation of the quantity of water usea for
dilution purposes. This quantity of the water used for the
newly prepared solution or solutions is equal to, or sub-
stantiall~ equal to, the quantity of water which the bed extracts
from the newly prepared solution or solutions during the passage
therethrough. The result hereby obtained is that the co-ion con-
centration of the (last) reaction fraction is only slightly re-
duced and the ion loss which occurs is kept low. This co-ion
concentration is thereby adjusted to about i5 to 85% of the con-
centration of the solution supplied from outside.
The control solution to be used is in this case, taken
up by water after recovery of the (last) reaction fraction with
the displacement of the newly prepared solution from the bed.
- Th~ volume of said solution advantageously amounts to less then
50~ of the bed volume.
In each case which has been discussed, it is suffi-
cient if, in accordance with the foregoing, for only the co-ion
concentration of the last reaction fraction to be observed when
there are several reaction fractions. The penultimate fraction
is in fact formed in the next exchange cycle from the last
-~ fraction and that supplied beforehand from the penultimate frac-
tion, etc.. All concentration values compared with one another
must always be corrected in accordance with the said change in
-j hydration of the bed.
. . ~ .
The examination of the control solution can be carried
out by analysing the mixed solution, and this is advantageously
done with an automatic analysis instrument. There is simultan-
e~ously obtained the co-ion content of this solution, which
- 19 -
-`~ 10~1778
content is p~actically equal to the ion loss when the disp]ace-
ment is with water or respectively newly prepared solutions.
However, it is more expedient, to-investigate a predetermined
; part of the control solution. Known physical methods are
advantageously used for this purpose, for example, pH, conduc-
tivity, densit~ or colour measurement, with which the value
to be established is immediately obtained.
- After the stationary state has been adjusted, the ion
content is used for establishing the other measures which are to
be taken. The necessary change in the state of the system is
carried out in accordance with the following: the total volume
of the liquids discharged at the commencement of the exchange
reaction is utilised for adapting the composition of the solution
obtained after the reaction fraction or the last reaction frac- -~
tion from the bed. Further it is possible for the concentration
of the solution to be reduced by increasing the total volume
't . : -
or to be increased by reducing the total volume. The maximum
value of the co-ion content of the reaction fraction or fractions
is then obtaïned when the co-ion content of the solution collec-
ed after the displacement fraction or the last displacement frac-
tion is adjusted to below 0.5% and advantageously to below 0.5% .
of the co-ion content of the solution supplied from outside and
the co-ion content-of the control solution is adjusted to below '
4% and advantageously to below 3% of the co-ion content of this
solution supplied from outside, the co-ion content of the control
solution is adjusted to below 2% and advantageously to below 1.2%
of the co-ion content of this solution supplied from outside.
The extent of the loss is also important, because the correspond-
, . .~ ing ion quantity is carried away with the secondary waste water.
-~ 30 The process according to the invention makes possible
an operation with concentrated solutions. It has been found that
` the value of the MY in a reaction between hydrochloric acid and
' .
- 20 - ~
,. '
. .
71778
the sodium ions of a strong acid cation exchanger in concentrated
solutions is greater than in more dilute solutions under the
same conditions. For example, the value of the MY when using
a 4 N-chloride solution was 556 m.equ, while it was only 475 m.
equ with a 1.8 N-chloride solution. In both cases, the con-
centration of the solution as regards hydrogen ions was 55~
and as regards sodium ions 45~ of the total concentration. The
total capacity of the bed, a strongly acid cation exchanger
consisting of polystyrene-sulphonic acid, was 1200 m.equ. It
is accordingly desirable for the co-ion concentration of the
solution supplied from outside to be chosen so that the co-ion
concentration of the reaction fraction or fractions is adjusted
to higher than 2N, or 3N. The ratio between the co-ion con-
centration of the solution supplied from outside and the reaction
fraction is obtained from the displacement method which is
employed.
With even higher concentrations, in the range of about
5 N, there is a constriction of the internal capillaries of the
exchanger grain, as a result of which the speed of diffusion is
reduced. Accordingly, it takes longer for a certain state to be
- reached than is the case with a lower concentration. Here also
there is once again to be found the advantage of the invention,
with which the measurement of the fractions is effected in .
`~ - accordance with the effectively achieved exchange yield. With
these high concentrations, it is necessary to raise the ion
~ content of the fraction, so as to achieve the same yield, express-
-~ ed as a certain percentage of the MY, as that obtained at a lower
- concentration.
, ~ .
~ Using the process according to the invention, it is
30 advantageously possible substantially to obtain the results of
the IFP method with one reaction fraction or slightly more than
one reaction fraction, the cost for the establishment and
- 21 -
:'
1071778
operation of the relevant installation being however very much
lowec, so-that the ion exchange, contrary to the general opinion,
can also be used with advantage in connection with the
elimination of the waste waters.
It is a requirement in many cases that the product
to be discharged from the system has a highest possible con-
centration. To be understood by the term "product" is also
the spent regenerate which is to be carried away, i.e. the
`~ product can be exploited or it can also be useless. In order to
achieve a highest possible concentration, the water flowing
: . .
~; at the start of the exchange reaction from the bed and the
product solution subsequently obtained are separated from one
another. In accordance with the invention, it is proposed for
,,' : .
-~ this purpose, that the volume of the first part of the llquid
obtained from the bed at the commencement of the exchange
reaction is to be of such a quantity that the concentration of ~
the remaining product solution amounts to about 70 to 80% of the *
concentration of the solution supplied from outside. The value
. .1 , .
of the latter solution is corrected by taking into account the r
.- 20 said quantity of water which the bed discharges or takes up
during the exchange reaction. The ion loss which occurs under
r~
the given circumstances by the discharge of the first part
makes up about 2 to 10% of the ion content o the product.
In order to mlnimise the mixing of the first part of
- the discharging liquid and the product solution, displacement
fraction or fractions are advantageously used for separating the
first liquid part to be discharged from the solution obtained as
;;~- product, which fraction or fractions is or are initially applied
~ to the bed filled with water and is or are obtained from the bed
~, .
` 30 after the first liquid part which is to be carried away, is or
,
are stored and used again in the next exchange reaction in the
same way.
- 22 - -
, ~ ,. . .. .
071778
With the process according to the present invention,
salt-containing waste waters are formed at two location: With
the commencement of the exchange reaction, the ion loss makes
up about 2 to 10~ of the ion content of the solution supplied
from outside, ar;d finally about 0.2 to 4%. These ions are once
again found in the secondary waste water leaving the system.
For the purpose of eliminating these ions, it is proposed
according to the invention to admix the di]ute solutions obtained
in addition to the product with the water which is to be treated,
as a result of which its salt content increases by about 3 to
15%. It is true that this causes a correspondingly higher
consumption of regenerating agent, but the result is thereby
; obtained that only the concentrated regenerate, of which the
concentration is only slightly lower than that of the solution
supplied from outside, and the treated water, which can be
discarded or used again without any difflculties, emerge from
the system.
The process according to the invention can with
advantage be used not only in connection with the treatment of r
waste water, but also in connection with the remo~al of salt from
brackish water and in connection with the softening or deminera-
lization of raw or untreated water. In many cases, it is also
; possible to use the process for the production of chemical
products from their raw materials, i.e. for preparative
purposes.
The invention provides the greatest advantage when it
is used in those exchange reactions of which the separation
factor is smaller than 1 and is carried out with concentrated
solutions. Included in such reactions is the regeneration of
higher dissociated ion exchangers. However, it can also be
advantageously employed in other cases. When working with con-
centrated solutions, the exchange isoplane or break-through
- 23 -
. ~071778
..
curve (see Helfferich, page 424) also has a considerable
dimension when the value of the separating factor is greater
than 1, i.e. the quantity of the solution flowing from the bed
between the break-through of the exchanging ions until their
entry concentration is reached is considerable. This is
especially applicable when the aim is to operate with a high
EVC. The quantity of the water which enters the product as a
consequence of mixing is proportional to the volume of the bed
and independent on the value of the EVC. Therefore, when
operating the same bed at a higher EVC, i.e. when a larger
quantity of the counter-ions is exchanged, the quantity of the
water mixed into the solution is by percentage a smaller amount.
Consequently, under otherwise unchanged conditions, the concen- .*
tration of the product is higher in proportion as the EVC is
. . -
greater.
The process according to the inventlon is hereinafter
more fully explained by reference to the four following ~-
examples.
/
~,. ~ , . / :
`.......... ' /
I /
.. , /
/
- /
~ - 24 -
i. . , .~ , . .
.: ,
.
107177'8
~xample l
~ elow, the re~ult~ obtai.ned in the proce3~ according
to the in~e~tion are compaxed with tho~0 of the simple fraction
process, on one hand, and with tho~e of the intensive fraction
process (I~P), on the othex.
a) Simple ~raction ~roce~
Under laborat~ry conditions, it i8 difficult to ~imu-
late the ~imple fraction proce~s carried out to commercial ~cale
~ince the dime~ion~ of the bed and, a~ a consequence, those o~
it~ contain~r are highly different. Under laborator~ condi-
` tion~, the diameter of the bed i~ at laa~t 50-lO0 mm, it~ height
40~ to lO00 mm, but under commercial condition~ even value~
.- occur which are a~ high a~ 1000-4000 mm in diameter and lO00-
2000 mm in length. Under laboratory condition~, not o~ly i9 it
easier to distribute uniformly the liquid~ flowing through the
cro~s-section of the bed, but more co~ve~i~nt are al~o the
mlxing conditions, which cau~e the relati~e ~hift of the liquid
particles with respect to each other, than they are under
commercial conditio~. In order to approximate these condi-
tions, alteration~ had to be made in the laboratory apparatu~
u~ed eommonly.
~ he ~pace abo~e the bed was filled up with water and
the inflow of the liquids took place at an about 20 mm height
- above the bed, thereby taking a bed in the regenerated and
flaahed back state as a basi~. Further more, above the bed
a ~pace wa~ provided whose relative volume was ~maller than
the common bottom apace under co~mercial co.nditions. Here,
the spaoe wa~ o~ly a 20 % of the volume of the bed instead of
~0 %. After filling it ~p with water, the apace over the bed
wa~ somewhat le8~ than 20 % o~ the bed volume at thia deepest
~tats in the cycle.
~he volume of the bed u~ed was 540 ml; its total
-25-
. .
1071778
~ .
capacity ~080 m.equ~ It contained a ~troDgly acidi~,polyst~rol
sulfonic acid cation exchanger (~ewatit (R) S lO0, Bayer AG,
~everku8en). The exchange of calclum ion~ o~ the bed by the
; hydrogen ion~ of 4 N hydrochloric acid was chosen a3 the re~
action for e~ery variation described below. It i5 this reactlon
that repreaent~ the central point in the raw water demineraliza-
tion. ID order to make it po~sible a compariso~ with the proc-
e~ses de~cribed below, the con¢entration wa~ aeliberatel~ -
chosen higher than commonly the case is in the ~imple fraction
process. The throughput ~elocity of the liquid was 50 ml/min.
~he fraction volume was cho~en as 60 ~ o~ the bed
~olume, or 120 % Or the ~olume of solution supplied from out-
i ~ide. In order to di~place this ~olution from the bed, the
~` amount of water wa~ ad~u~ted in ~uch a manner that the loss in
" .
control ~olution and iD the u~ed wa~hing water, collected
separately, ~arY withi~ the 2.0 and 2.5 % range. In thi~ way,
on an a~erage, a l.9 co-ion concentratlon of the fra¢tion3 was
obtained. ~hree reaction fractionæ were used. ~he 5 eo-ion
content of the reaction fraction wa3 kept co~taDt l~ order to
reach the correct ~tationary state also in the ~imple fractioD
proces~.
The e~change yield wa~ found from the determination
of the calcium ion content in the solutioD di~charged as the
product. Charging the bed with calcium ion~ was carried out
with 1_N calcium chloride solution until reaching the equality
Or the inflow and outflow. The entire outflow wa~ accumulated,
and its hydroge~ ion conte~t, ~er~ing as a control for the
exchange yield, determined. In the stationary state, the
hydrogeD ion ¢o~tent in the product was e~ual to that in the
chargi~g solutio~ ~lown QUt~
-26-
, ~, . .. .
- 1071778
This known proce~s was carried out according to the
rollowing schedule:
Inflow . Outflow
!~ ~olume, Volume,
i~ ml ~ ml , ,,
Fraction 1 ~00 First running~ 920
+ product
n 2 ~00 Fraction 1 300
n ~ 300 n 2 300
Solution ~upplied ~ 3 300
4 ~ HCl 250
Water a~
required Control solutlon 390
Designation "as required~ means that the volume of
water wa~ calculated iD ~uch a manner that the 301ution named
`'. last, in thi~ca~e the control 301ution, be obtainad in the
outflow ~rom the bed.
Allfractions are reactio~ fractions.
The volume of the discharged ~olution, first running~ +
product, wa~ 80 ad~usted that the 1083 be about 2 % of the co-
ion content of the introduced solution.
Aftex 8 operation ~ycles, the stationar~ ætate was
set and the folla~ing re~ult~ were obtainb.d in it:
Calciu~ ion ¢orte~t in the first running3 ~ product 732 m.equ
Chlorid~ lon content N n ~ 99o N
Hydroge~ i~n co~te~t in the exhaustion solutio~ 730 n
Acid consum~tion, as a % of the co-ion~ removed 1~7%
~o~ the control ~olution and used washing
water related to the ¢o-io~ co~tent in the
solutio~ fed ln from outside 2.0%
Co-ion coDcentration in the fractions on an average 1.9 N
b) Proce~ according to the in~ention. Displacement with
water
-27-
~~` 10 7 ~ 7 7 8
~he proce~s accordiD~ to the i~ventio~ was carried ou~
as the second varlation. For thiB aim, th~ ~olume was reduced r
at the places in the apparatu~ where the relative shifting of
the ~olution particles takes place to ~uch an extent that the
operatioD could just be maintai~ed. ~or obtaini~g thi~, the
amount of li~uid over the bed wa~ reduced to 5-25 ml, corre~
~ponding to a height of liquid of 0.4-2 cm, and the space abore
the bed decreased to 2.5 % o~ the ~olume of the bed.
The operatio~ schedule was as follows:
Inflow Outflow
Volume, Volume,
in ml in ml
~raction 1 ~0~ First running~ 593
+ product
Fraction 2 300 Fraction 1 300
" 3 300 " 2 300
Solution supplied i' ~ 300
4 N HCl 250
Water a8
required Control solution 300
~y the u~e of correctly calculated "f~rst run:nin~8 +
product" ~olume, the 10~8, here, wa~ reduced to 1.5 %. ~he
exchange yield in the three reactio~ fraction~ ~a8 within the
85 and 95 % of the MY (maxlmum possible excha~ge yield).
After 10 operatio~ cycle~, the stati~nary state wa3
set and the following re~ult~ ~ere obtained in it:
Calcium ion content in the ~irQt ru~ning~ ~ product 771 m.equ.
Chloride io:n ¢onte:nt " n n t1 n 993
~drogen Co~2teDt i:n the ~ e~austioD 901utio~ 772
Hydrochloric acid conoumption, a~ a % of the calcium
ions removed . 130 %
~oæs i~ the control solution ana us~d washing water
related to the co-io~ content in the solution
fed from outæide 1.5 %
Co-ion concentrations in the fractions 3.4 - 3.5 N
-28-
1071778
Reducing the relative shift of the liquid particle~
led to the followin~ results:
The hydrochloric acid co~sumptio~ decreased ~rom
137 % to 130 %; the regenerated capacity increased from 732
m.equ. to 771 m~equ; and the volume of first running~ ~ product
was reduced ~rom 920 ml to 593 ml. ~hat mean~ that the proce~
according to the invention, even iD its simple~t ~ariation, led
to conæid~rably improved re~ults.
c) Proces~ accordiDg to the invention; displa¢ement with
layer~d fraction
,,
Such reali~ation of the process was chose~ as the
third variation i~ which the di~placeme~t of the fed solution
from the bed was carried out by layered fractio~s. A~ known,
it i~ obtained in this way that the reaction fractions have
the highest po~sible conce~tration, namely practically the same
a~ that of the solution æupplied, andthat the los~ be the lowest.
~he volume of the reaction fractions was reduced ~rom 300 to
200 ml under co~æideration that the ion content in a fraction
in the prevlous case was within the 1020-1050 m,equ. range while
here, under retaining the 300 volume, it should ha~e been within
the 1260-1275 m.equ. rang~ the ca~e of a 200 ml fraction
~olume, it~ ion co~tent decrea3ed to 840-850 m.equ. ~he ex-
change yield decreased only slightly as compaxed with the
~raction~ containi~g 1020-1050 m.equ. Here, it~ value wa~
between the 80-90 % range of MY.
~he operation ~chedule wa~ a~ follows:
-29-
- 10~1778
Inflow Outflow
Volume, Volume,
in ml, in ml,
Eraction 1 200 First ruDning~
+ product 547
" 2 200 ~ractioD 1 200
3 200 " 2 200
Solution supplied
; 4 N ~CI 250 ~ 3 200
~raction 4 100 " 4 100
10 " 5 100 ~ 5 100
Water a~ -
required
~ raction~ 1 to 3 are reaction fractlon~ and 4 and 5
are displacem~nt fractio~.
After 12 cycles, the stationary state was ~et, and
the followi~g re~ults wer~ obtained in it:
Calcium io~ content in the ~irst running~product 769 m.equ.
Chloride io2 conte:nt H n n n u 1016 n
Hydrogen ion conte~t in the exhaustion solution 773
Hydrochloric acid con3umption as a % of the
calcium io~ removed 130 %
~09~ in the u~ed washi~g water related to the ~o-ion
content in the solution supplied 0.3 %
Co-ion co.ncentration in the fraction~ 4.2 - 4.25 N
The differences betwee~ th~e result~ and those
obtai~ed in variation b) are ~o ~mall that one may establish
the practical equivalency of the displacement of ~olutio~
supplied ~rom out~ide by water with the displacement by layered
fra¢tions when one proceed~ in the fir~t case accordi~g to the
rule to the proce~ according to the i~vention. In many case3
occurxing i~ the practice, lt will al~o be fully sufIicient
to carry out the di~placement with water only.
-30-
` `` 1 07 1 7 ~ 8
d) Process according to the invention; double fraction size
~ he aim of thi~ variatio~ was to establi~h the effect
caused by the increa~e in the reaction fraction~. It should
be considered in this case that the operation even in both last
~ariations was carried out with fractions in which the ex-
change yield was within, or close to, the optimum region.
~ he ~olume of the reaction fraction~ wag doubled,
thereb~ obtaining a total volume of 1200 ml with its total ion
content of about 5000 m,equ. The exchange yield in the ~rac-
tion~ was between the 96-99 % range of the MY.
T~e operation ~chedule ~ as follow~:
Inflow Outflow
Volume, Volume,
in ml in ml
~raction 1 400 Fir~t run~ing~ 547
2 400 Fraction 1 400
n 3 400 ~raction 2 400
Solutio~ supplied
4 ~ HCl 250 " 3 400
~raction 4 100 n 4 100
~l 5 100 " 5 lOû
Water a3
required
Here again, fraction~ 1 ta 3 are reaction fraction~
and 4 and 5 are di~pla¢ement fr~ction~
~ he following result~ were found in the statio~ary
state obtained aftex 20 operatio~ cycles~
//
-31-
- .; . .. ..
```-- 1071~7~
Calcium content i~ the ~ir~t runnin~s + product 798 m.equ
Chloride ion co~tent n l' n n . 1003
Hydrogen ion co~tent in the exhaustion ~olution 792
Acid con~umption as a % of the calcium ion remo~ed 126 %
Loss in the used wa~hing water relatsd to the co-ion
conte~t in the solution fed in 0.25 %
Co-ion concentration in the fraction~ 4.2 - 4.5 N
It was found in a comparison with variation c) that
the increase in the fraction ~iZ5 had resulted in a 4 %
decrease in the acid consumption.
2) U3e of the i~tensive fraction process (I~P)
A~ earlier experimental series, in which the I~P had
been used, was applied as the last ~ariation in the comparison.
In this serie~ of experiment~, the volume of the reaction
fractions at the same concentration had been half a3 much but
the number of the fra¢tions had bee~ twice as much as in
variation ~, 80 that the volume of the layered reaction frac-
tions had been the ~ame. Al~o the total co-io~ content wa~ thc
same. In thi~ ~erie~ of experime~t, a 790 m.equ had bee~ ob-
tained for the exchange yield, being practic~lly the ~ame asthe value obtai~ed in variation d).
~ hi~ comparison ~hows that the reductio~ of the
number o~ reactio~ fractio~s in the ~en~e of the proce~ accord-
ing to the iD~ention did not i~luence the exchange yield of
the reaction.
In conclusio~, it 2ay be e~tablished that the process
accoxding to the invention even in it~ simplest form results
in co~ iderable advantage~. It ha8 al80 been e~tablished that
~educin~ the :~umber of fxactions aæ compaxed with the IFP ha~
30 ~o det~riorating effect on the result~.
-32-
7177~
.
Example 2
The proce~s according to the in~entio~ wa~ now check-
ed in the exchange reaction betwee~ monovalent ions and in
comparison with the I~P.
~ artaric acid was to be produced from it~ sodium ~altwith the aid of a stro.ng acid cation exchanger charged with
hydrogen ion~. With the rege~eratio~, a 4N-hydrochloric acid
was t~ be used in the I~P.
~ he bed contained 500 ml of ~ewatit~S100, it~ total
capacity a~ounting to 1000 m.equ. ~he throughput velocity of
the liquids was 400 ml/h with the char~ing and 3000 ml/h with
the regeneration.
Fir~t of all9 for ~etting the working co~ditions of
the regeneration, a charging wa~ carried out with a ~odium
chloride solution. For the following regeneration, the IFP
was used with the followi~g operating schedule:
Inflow Outflow
Vol. in ml Vol. in ml
Fraction 1 150 ~irst runnings 540
+ product
~0 ~ 2 150 Fraction 1 150
n 3 150 n 2 150
" 4 150 " 3 150
n 5 150 " 4 150
" 6 150 " 5 150
" 7 150 " 6 150
n 8 150 " 7 150
Solution ~upplied
4N HOl 245 n 8 150
Fraction 9 100 " 9 100
n 10 100 " 10 100
n 11 100 " 11 100
Water as required
.~ .
``-` 1~71778
The fraction~ 1 to 8 are reaction fraction~ aDd 9 to
11 are di~placement fractions.
After reaching the statio.nary ~tate, the solution
(first running~ + product) discharged at the ~tart of the
regeneration contain~d 970 m.equ. of chloride ion3, 903 m.equ.
of sodium ion~ and 67 m.equ. of hydrogen ion~.
~he co-ion concentratio~ of the la3t reaction fraction,
fraction 8, wa~ 4.04N and that of the first displac~m~nt frac-
tion, the fraction 9, used a~ co~trol 901utio~, wa~ 2.5 ~ The
acid co~umption was therefore 108.5, and the ~VC was 90.8 %
of the total capacity.
For carrying out the proce~s according to the in-
ventio~, ~irst o~ all the value of the MY was e~tablished with
~ 901utio~ of different compo~ition, so a~ to e~tabli~h the
in~lueDce o~ a separation factor which i3 po3sibly ~aried with
the bed composition :
1. Supplied to the bed completely charged with ~odiu~
io~ was a solutior which contain~d 4 equ/l of chlor-
ide ions.and 2 equ/l each of sodium ions and hydroge~
ions. After the effluent solution had reached the
~ame compo~ition a~ the inflow, the entire outflow
wa~ analy~ed. It wa~ 3hown from thi~ that the bed
had ab~orbed 465 m.equ. of hyd~oge~ ion~. ~hi3 iS
th~ ue for th~ MY.
2. Sup~lied to the bed which once again was completely
charged with sodium ions was a ~olution of which the
chloride ion co~centrat~on al80 here amounted to 4 equ/l,
but which contained 3~1 equ/l of sodium lon~ d 0.~
egu/l of hydroge:n io~s. In th~s case, the MY amounted
to 256 m.equ.
3. ~he bed was charged.with 745 m.equ.of sodium ions and
256 m.equ. of hydrogen ions. ~he solution added to
it again co:ntai:ned 4 eq~/l of chloride io:ns with
--34--
1071 778
.
1.98 squ/l of sodium ions and 2.02 equ/l of hydrogen
ion~. The MY amounted here to 238 m.equ. With the
determination of the MY, there wa~ also produced the
charging curve of the bed, this curve repre3enting
the quantity of exchanging ions (H-ions) taken up by
the bed i~ depen~ence o.n the quantity of the co-ions
(Cl-ion~) which had pa~sed th~rethrough.
It wa~ apparent from the~e measureme~ts that a .
chloride ion quantity of about 1200 m.equ ha~ to be contained
in the separate reaction fractions for an intended exchange
~ield of 91 to 93 % of the M~. With a 4N-concentration, it
was apparent there~rom that the volume of the ~eparate re-
actio.n fractions was 30Q mlO Three reaction fractioDs were
prepared; thereafter the process of the invention wa~ carried
out in accordance with ~he following schedule.
Inflow Outflow
Vol. iD ml. Vol. in ml.
: Fraction 1 300 ~irst r~nnings 520
- ~ product
n 2 300 ~raction 1 300 ;
300 ~ 2 300
Solution ~upplied 245 " 3 300
4~ HCl
Era¢tion 4 100 N 4 100
n 5 100 n 5 100
n 6 100 6 100
Water a~ required
- After r~achiDg the ~tationary state~ the effluent
with th2 comme~cement of the regeneration co~tained 975 ~.equ
of chloride ions, 91~ m.equ of sodium ions and 65 m.e~u of
hydrogen ions.
The co-ion conce~tratio~ of t~e last reaction
fra¢tion, fraction 3, was 4.1N, that of th~ first displacement
-~5-
. - .. . .
. .
. . ..
. .
~ 71778
fractioD~ fraction 4, used a~ co~trol solutio~ wa~ 2.5N a~d
that of the last di6placeme~t fra¢tlon, fraction 6, wa~ 0.26N.
~he lo~ wa3 0.5 m.equ.
The acid consumption wa~ here 107.7 ~ and the EVC wa~
91.0 % of the total capacity.
The result~ in the two processes æ e there~ore practi-
cally the ~ame. The reduction i~ the Dumber o~ the reaction
fractions from 8 to ~ did not infl~ence the re~ult~. ~he total
rolume o~ the reaction ~ractions was lower by 25 % with the
proce~6 of the in~ention than with the IFP, without thereby
ha~ing cau~ed any red~ction iD the exchang~ yield.
The problem as iDitially stated of recovering tar-
tario acid from sodium tart~ate had now be~n fulfilled, by
havin~ u6ed the ~odium tartrate ~olution in~tead of the ~odium
chloride solutio~ with the charging. ~he solution a~ produced
contained 150 g/l of tartarlc acid. After reaching the ~tation-
ary state, 900 m.equ. of sodium ion~ were take~ up by the bed
~rom the tartrate solutio~. In the tartaric acid solutio~ a~
obtalDed, the sodium ion co~tent wa~ 80 ppm, related to lO0 %
tartaric acld.
E~ample 3
A waste water or efflue~t co~tain~, calculated as
citri¢ acid~ about 5 g/l of ~odium citrate. ~he solution is o~
the on~ hand too dilute for bei~g directl~ processed again in
this state, but on the other hand the citrio acid which can be
reco~ered therefrom i~ o~ value. ~he solu$ion of the ~odium
citrate was co~veyed over a strongly acid cation exchanger
of ~ewatit S lO0, for replacing the 90dium ions by hydrogen
ions. ~he solution of citric acid a~ thu3 obtained was sup-
~o plied to a weaXly basic anio~ exchanger of a partially substi-
tuted amine o~ a pol~styrene framework, ~ewatit ~P 62. ~he
catio~ ~xcha~ger wa~ regen~rated according to the i~ve~tion
-36-
1~71778
with h~drochloric acid, whereas the anion exchanger was regener-
ated with a 2,5N sodium hydroxide ~olution in a simple co-
current proce~ h~ sodium citrate which wa~ obtained and of
which the concentration ~xceeded 100 g/l, was returned to the
manufacturing proce~.
~ he regeneration of the cation exchanger, which wa~
contained in a bed of 530 ml with a total capacity of 1060
m.equ., wa~ carried out in accordance with the followi~g
proce~sing schedule
~ flow Out~low
; Vol. ~n ml Vol. iD ml
Reaction 600 ~irst runnings 598
Fraction + product
901ution ~upplied 175 Reaction 600
4N HCl fraction
Solution supplied 100 control solutio~ 200
2N HCl
Water as required
~ he throughput ~elocity wa~ 3000 ml/h.
After adjusting the statioDary state, the chloride
content of the di~charged ~olution was 8~0 m.equ. of which
870 m.equ. were sodiu~ chloride and 20 m.equ. hydrochloric
acid. 8 m.equ. o~ chloride ion~ were contained in the control
solution~ When the bed wa~ charged wlth ~odium ion~ of the
sodium citrate, 65 m.equ. of citric acid were produced.
With 900 m.equ. of hydrochloric acid, it was there-
fore possible ~or 870 m.equ. of ~odiu~ ions of the bed to be
replaced by h~drogen ion~, so that the acid con~umptio~ wa~
103.4 %. 82 % o~ the total capacity of the bed could be
utilized.
The exchange yield iD the Iractio~ of which the co-
ion concentration in the stationary ~tate wa~ 3.05N, was 96 ~
of the MY after repeated determlnationO ~he co-ion concentra~ion
-37-
1071778
of the control ~olution was 0.04N, ~o that the 109~ amounted to
0.8 %. It has thereore been shown that, in this ca~e, with
the u~e of a ~ingle reaction fraction, it i~ pos~ible to pro-
du¢e an effect which i~ equivalent to that with 3 reaction
fractlons in Ex~mple 2.
Example ~
~ wa~te water or effluent which i9 formed with the
production of ammonium nitrate and contains ~mall qu~tities of
this salt is to be demineralized. ~he effluent with 8 g/l of
10 ammonium nitrate is first of all con~e~ed through a strongly
acid cation exchanger and thereafter through a weakly basic
anion exchanger and thus completely demineralized. The charging
takes place in upward flow and the regeneration in downward
flow. The effluent is conveyed through two pairs of the a-
foresaid ioD exchangers, of which the second pair i~ freshly
rege~erated, while the first pair has already been used once in
the charging as second pair. A thixd pair i~ meanwhile re-
generated. When the first pair is exhausted, the second pair
takes its place and the freshl~ regenerated pair assume~ the
second posit~on~ The exhau~ted pair i~ regenerated. ~rom the
first cation exchanger, a dilute solution of nitric acid dls-
charged, the acid being for the major part taken up by the first
anion exchanger. The water emerging from the first bed pair
contained about 20 ppm sf ammonium ~itrate, but after the
second pair this content was only still 2 ppm.
A bed with 500 ml of ~EWATIT S 100 was u3ed as cation
exchanger and a bed with 750 ml of ~ewatit MP 62 wa3 u~ed as
anion excha~ger.
~ he working schedules with the regeneration of the
c~tio~ exchanger were according to the proce3s of the in~ention:
0 7 1 ~ 7 8
I~flow 0_lo
Vol. il~ ml Vol. i~ ml
~ractioD 1 400 ~ir~t ru~ings 354
n 2 3 00 ~raction 1 400
n 3 300 n 2 300
n 4 300 Pro~uct 210
Solution supplied
4.7N ~03 168 ~raction 3 ~00
Solution 3upplied
2.3N HN03 88 " 4 3
Water as reguired Control ~olution 300
After obtaining the control solution, the bed was once
again washed out with 1,5 litre~ of water, in order to reduce
the re~idual ¢ontent of ammonlum n~trate in the salt-fre~ water
which ~a3 produced.
~ he throughput velocity of the liquid wa~ 3600 ml/h.
The fractioDs 1 and 2 ~re di~placement fraction~ and 3 and 4
are reaction fractions. The exchange yield in the latter
amounted to 88 ~ a~d 93 %, re~peet~vely, o~ the MY.
~ he control ~olution ha~ in thi~ case and by way of
exception a high co~centratio~ of 0.18~, in order to eDs~re that
- the co-ion concentration of the rea¢tioD fraction~ i~ adju~ted
to a high val~e, which here is 405N. ~his corre~po~d3 to more
than 90 ~ of the concentratio~ o~ the supplied solutio~ of 5.0N
a~ corre¢ted iD accorda~ce with the water ab30rption.
The fir~t-runni~g water, the csntrol ~olution and the
u~ed washing water were delivered to the effluent to be deminer-
ali,zed and their salt conteDt wa~ the second time extracted in
the next exchange cycle. The ammonium ion content of the said
mixture was 55 m.equ. In the waste water to be demineralized,
30 the ammo~ium ~itrate conte~t wa~ 925 m~equ. The concentration
of the ammonium nitrate ~olution a~ obtained wa~ ~.9N, corre~
spo~ding to 27.5 % by weight, ~o that a concentratio~ almost
-3g-
. .
1C~71778
40 times greater was obtained of the solution demineralized.
The anio~ exoha~ger wa~ reg~nerated as follows in
accordance with the process of the i~vention:
I~flow Outflow
Vol. i~ ml Vol. in ml
Co~trol solution *) 200 Fir3t runni~gs 813
Fra~tion 1 300 Fractio~ 1 300
" 2 300 " 2 300
n 3 300 Product 252
" 4 300 Fraction 3 300
Solution supplied n 4 300
7.3N-~H40X 137 ~ 5 200
Fraction 5 200
" 6 200
" 6 200
Control solution 200
Water a~ required
) Obtained in the previou~ cyele
After obtaining the control ~olut~on, the bed was
once again washed out with 2.5 litre~ of water.
~he fractions 1 and 2, and 5 and 6, respe¢ti~ely are
displacement fractions and the fractions 3 and 4 are reaction
fractions. The exchange yield in the latter amounted to about
95% of the MY.
~he co-ion concentratioD of the la~t reaction fraction
amounted to 5.15N and that o~ the control solution to 0.046N.
~he use of the control ~olution a~ the solution to be first
~upplied makes possible, in known manner, the utilisation of
the hydro~yl ions which are contained therein.
Contained in the varlous, dilute ~olutions which
formed at the positio~s as mentioned abo~e were 70 m.equ. of
ammonium ion~. These dilute ~olution~ were also i~ this case
once again supplied to the waste water to be demineralized
and the salt was again removed. ~he concentrat~on of the
-4~-
1071~8
ammonium nitrate ~olution as obtai~ed was 28 % by weight.
The conce.ntration of the combined product solution~
of the cation and anion exchanger~ amounted to 27.7 % by weight.
~hl8 ~olution can be returned directly to the manufacturing
proces~ .
~ he con~umption of regenerating agent~ amounted to
118 %, related to that quantity of the introduced ammonium
nitrate expressed in equiYalent~. Since the ~uantity of ions
returned with the diluted solutions amounted together, related
to the iDtroduced quantity, to 13.5 %, the effecti~e con~umption
of regenerating agent was i~ the region of 104 b.
Usi~g the process accordi~g to the invention, it is
also possible to achieve th~ condition that it i~ pos~ible,
from a waste water ox effluent, to obtain a concentrate capable
of further processi.ng and a ~ery pure water which llkewi~e can
be directly used. ~he co.nsumptio~ of the regenerating agent~
is kept withi~ llmits which economically are tenable. ~he
process a~ described can be used in co~ectio.n with the working
up of effluents which, on the one hand, contain ammonia or
ammonium salt~ a~d, on the other hand, contain nitrate or
.nitric acid.
-41-
