GB2203964A

GB2203964A - Ion exchange process

Info

Publication number: GB2203964A
Application number: GB08806340A
Authority: GB
Inventors: Manuel Olivo Gonzalez; Manuel Bravo
Original assignee: FERTILIZANTES EMPRESA NAC; Industrial Quimica del Nalon SA
Current assignee: FERTILIZANTES EMPRESA NAC; Industrial Quimica del Nalon SA
Priority date: 1987-03-18
Filing date: 1988-03-17
Publication date: 1988-11-02
Anticipated expiration: 2008-03-17
Also published as: AR245018A1; AU1320888A; IL85745A0; FR2612423A1; MA21219A1; PT84807A; IT8819825A0; DK150588D0; NO881163L; DE3808633A1; DK150588A; SE8800974L; MX168146B; BE1001098A5; AU611423B2; GB8806340D0; BR8801332A; IL85745A; IT1216130B; LU87168A1

Abstract

A process for obtaining dissolved salts and acids from other available ones, by means of ion exchanging resins, is done in two stages, placing the changing resin in columns 10, 20. In the first stage the resin 10 is charged with the cation corresponding to the salt which it is desired to obtain by passing a solution of a suitable salt through the resin. The resin thus charged is cyclically extracted from the column 10 at the same time that it is replaced by regenerated resin from the second stage of the process. Before making the resin used in the first stage 10 pass to the second 20, it is released from the salt solution with which it was charged (at 14), by means of draining and washing with water, or by shifting with another solution. In the second stage of the process, the resin 20 is regenerated by having it pass through a solution of a salt or an acid, the anion of which is the one corresponding to the salt which it is desired to obtain. <IMAGE>

Description

PROCEDURE DURE FOR OBTAINING DISSOLVED SALTS AND ACIDS FROM OTHERS AVAILABLE, BY MEANS OF ION EXCHANGING RESINS The procedure covered by this invention is based upon the utilization of ion exchanging resins of a cationic nature, in order to make ionic changes with saline and acid solutions and thus to obtain solutions of other products.

The ion exchanging resin is a copolymer of styrene and divinylbenzene sulphonate of macroporous structure, which appears as a solid in the form of spheres of a diameter close to 0.6 mm. Several companies manufacture these types of resins and they are available on the world market.

Such resins resist the osmotic changes originated by contact with dissolutions of different concentrations, without experiencing physical changes which alter their form. They can pass from the acid form to the saline form and the reverse, an indefinite number of times, maintaining their structure, and they resist the oxidizing or reducing action of some dissolutions well.

The cationic ion exchanging resins are sulphonic acids and behave like a strong acid. In contact with a dissolution of a salt, an acidlsalt equilibrium is is established which can be represented by the reversible equation: RK + KA = RK + HA in which (RH) is the resin in acid form; (RK) is the resin in saline form; (K) is the cation of the salt in dissolution; (A) is the anion of the salt in dissolution, and (H) is the hydrogen ion or a oation other than the (K) cation.

It is said that an ion exchanging resin is charged when it passes into the saline form and that it is regenerated when it passes into the acid form.

When an ion exchanging resin in acid form is available in column form sufficiently high in an adequate receptacle and a dissolution of a salt like potassium chloride (KC1) is made to circulate slowly through the immobile resin from bottom to top, exchange of ions takes place between the resin and the dissolution which tend to establish a physical-chemical equilibrium at each point of the column.

As a consequence of the ion exchange, the dissolution becomes more acid as it advances through the resin until it transforms all of the salt into acid, and the resin is charged with the corresponding cation. Thus, there is established within the column a gradient of concentration of salt which is lower toward the top, within a zone above which there is only present resin in acid form and solution of acid corresponding to the salt introduced, and below which there are present only charged resin and saline dissolution.

The zone of ion exchange which is established advances toward the top of the column as the solution of salt is introduced through the lower part, leaving behind the charged resin in the presence of saline solution, and generating the front of it dissolution of the acid corresponding to the salt, which is extracted through the upper part.

The concentration of the anion corresponding to the salt which is introduced maintains itself practically constant in the whole column, with small variations due to the different degrees of solvation of the resin in acid and saline media. The height of the ionic exchange zone of the column depends on the affinity of the resin to the cation of the salt with respect to the hydrogen ion. This affinity is greater in proportion to the greater volume and valency that the cation has.

If the direction of circulation of the solutions which f 1 nnd

the resins is inverted,

acid solution through the supper part of the column and extracting salt through the bottom, the zone of ion exchange is shifted upward, in the same direction as the solution, and the resin is regenerated in reversible form. In this case, the width of the zone of ion exchange is different, in function of the different affinity of the resin to the H+ and K+ cations.

According to the behavior described, if on a regenerated cationic resin placed in the form of a column of sufficient height, a saline solution is passed in an ascending direction and at adequate speed: - the resin is progressively charged in an ascending direction within the column; - the ionic exchange zone represents a defined volume of resin within the column, which is a function of the type of cations to be exchanged between resin and solution; - the ionic exchange zone shifts within the column in the same direction as the solution, and - above the ion exchange zone there is produced an acid corresponding to the salt which is introduced.

The quantity of acid produced keeps stoichiometry with that of charged resin. The macroporous ion exchanging resins currently available have a capacity of change close to two equivalents per liter.

If the direction of circulation of the solutions within the

column is inverted,

an acid solution through the upper part of the column and extracting saline solution through the lower part: - the ion exchange zone shifts progressively downward, at the same time as the resin is regenerating and - saline dissolution is produced in a quantity which keeps stoichiometry with the regenerated resin.

As has been said, the object of the invention is a procedure for obtaining salts and acids in dissolution, based on ion exchange with ion exchanging resins in separate stages, which gives rise to the advantages which are mentioned in the following paragraphs.

The procedure of the invention permits the design of productive units susceptible of a high degree of automation. It also allows independent regulation of the two stages of the process. It makes it possible to carry out the ionic exchange processes at temperatures close to the atmospheric temperature, with minimal energy required; it can be operated at much higher temperatures with the sole limitation of not damaging the resin under the conditions inherent in each case.

The utilization in the procedure under the invention of

macroporous ion exchanging

on the bases of copolymers of styrene and divinylbenzene sulphonates, highly resistant to osmotic shocks, makes it possible to operate with concentrated solutions without altering the structure of the resin, with the advantages which that provides in obtaining crystalline products. This type of resins are at the same time very resistant to attrition, so that they can resist a large number of cycles and be handled in the process without experiencing any significant deterioration. The small proportion of fines which are inevitably produced in handling the resin are normally separated in its washing operations.

The preferable ion exchanging resin is a cationic resin formed by a copolymer of styrene and divinylbenzene sulphonate, in the form of spheres of 0.6 mm. average diameter, although other types of resins can also be utilized in this procedure, including the anionic ones, as long as they are solid, have a similar form and are resistant to the physical-chemical conditions of the process.

Basically the procedure consists in conducting the processes of charging and regeneration of the resin in two separate stages and in different columns and for their description reference will be made to the pages of drawings attached, in which: Figure 1 is a schematic representation of an example of organization of the devices and elements involved in the procedure covered by the invention in a first form of execution, and Figure 2 is'a schematic representation, similar to the above, of a second form of execution.

In a first column the process of charging the resin with a salt in solution is carried out, at the same time that an acid solution corresponding to the salt is generated. In the attached figures this column is designated by the reference number (10).

This column (10), as it is represented schematically, is a receptacle in cylindrical form, arranged vertically. In its upper and lower ends it ends in isolation valves and resin movinq valves. Near the lower end and laterallv it carries

a

(11) for introduction of saline solution, and near

the upper end it has another

(12) for extraction of the acid (or saline) solution which is generated in the

process. Both the

are connected internally to the distributors of liquids intended to guarantee a uniform flow of the solutions which are circulated through the resin, in the whole section of the column.The distribútors are designed to permit the passage of liquids and retention of resin, and arranged so that they permit the movement of the resin through the column in operations of moving it.

The dimensions in diameter and height of the column (10) may vary between wide limits, in function of the capacity of production which is projected.

For greater clarity of explanation, the description of the procedure for the charging stage of the resin will be made on the basis of utilizing a solution of potassium chloride (KCl) as a saline solution. Potassium chloride (KCl) is prepared in 3 N solution, at room temperature (20 C) and free of solid impurities or in solution which can disturb the operation or damage the resin.

In the first stage of the procedure covered by the invention, one begins by filling the charging column (10) with ion-changing resin in acid form and flooding in solution 3 N of hydrochloric acid (HCl) contained in a

(13). Once the column (10) is full of resin and the

resin moving valves are closed, one proceeds to

potassium chloride 3 N solution through the lower

(11) of the column and to extract solution of hydrochloric acid through the upper one (12).

On

the saline solution, the flow is regulated at the equivalent of a volume of resin contained in the column by the hour, when operating with a potassium chloride 3 N solution. The condition which defines the flow of the saline solution is that of achieving a short and well differentiated zone of ionic exchange inside the column, above which only resin in acid form (RH) and solution of the acid corresponding to the salt which is introduced coexist;

and under which only resin

charged form (RK) and solution of the salt which introduced coexist. This condition varies, among other parameters, in function of the concentration of the salt, the physical-chemical affinity of the cation of the salt (K+) to the resin, in'relation to that of the one it replaces (H+), and of the granulometric curve of the resin.

As the salt solution is

the ionic exchange zone shifts from the bottom of the column upward, generating a quantity of hydrochloric acid in solution equivalent to that of the resin which is being charged. When the zone o' ionic

exchange arrives at the proximity of the upper

from whence the dissolution of hydrochloric acid is

extracted, the

of salt is stopped. In this way all the resin located in the column below the zone of ion exchange is charged in form of (RK).

Once the resin contained in the column (10) is charged in form of (RK), the admission and outlet valves for dissolutions are closed and one proceeds to circulate through the column the volume of regenerated resin corresponding to one cycle. This volume of regenerated

resin is contained in the

arranged above the column (10) and connected to it by a valve. The resin is flooded by acid solution coming from the process itself

which

through the pipes (17) as will be explained later. Through the valve at the bottom of the column resin charged in form of (RK) goes out.

In this operation the ion exchange zone which was initially

near the upper

descends as the resin circulates, until it is located above and near the lower

At that time the circulation of resin through the column is stopped, closing the corresponding valves.

The volume of resin circulating is maintained constant in each cycle to facilitate the operation.

Afterward the intake and outlet valves of the dissolutions

are opened and saline solution is

until the ion exchange zone locates itself in the zone next to the upper

of the column.

In this way, in the first stage of the procedure and repeating cycles, the regenerated resin in acid form (RH) is transformed into charged resin in saline form (RK) and the

salt solution which is

is transformed into corresponding acid solution.

The total quantity of salt in solution form

in each cycle is'that which is necessary to charge the quantity of resin which is circulated, plus the amount of salt that goes out of the column accompanying the resin in each cycle.

The quantity of the acid in solution form which is moved in each cycle is what corresponds stoichiometrically to the quantity of resin which is charged, plus the quantity of acid which enters the column flooding the resin in each cycle.

In order to assure that the ion exchange zone is moved in the column in each cycle within the established limits, to guarantee that the only dissolution of acid goes out of the column without contaminating it with salt, and charged resin (RK) without contaminating it with regenerated resin (RH), ion detectors are installed in the proximity of said limits.

The signals of these detectors are utilized to adjust the

quantity of salt solution

in each cycle.

The first stage of the procedure covered by the invention is not only valid for transforming a salt into the corresponding acid, but serves also to transform one salt into another of the same anion. In this case, the resin

which is

into the column (10) in each cycle must be charged with the cation corresponding to the salt which it is desired to obtain. Thus, if the resin is charged with sodium, in the form of(RNa), and potassium chloride (KCl)

solution is

into the column a sodium chloride solution (NaCl) and potassium charged rein (RK) will be obtained. In this case, the limit of concentrations of the solutions involved is set by the solubility of the less soluble salt.

In the procedure covered by the invention, the resin and the

dissolutions always circulate

couArTI nrace -current.

In the example given it is established that the resin circulates downward and the dissolutions upward within the column (10), but this direction can be reversed. As a criterion to establish the direction of circulation, it is preferred that the less dense solution of the ion exchange zone be in the high part of the column in order to avoid disturbances of the ion exchange zone originating from differences of densities.

The charged resin in the form of (RK) which comes out of the column (10) in each cycle is flooded by the solution of the

salt

employed to charge it. Before transferring this resin into a second column (20), to carry out the second

stage of the process, it is necessary to suitably

the anion of that salt from the resin to avoid saline contaminations in the products to be obtained. For this, in accordance with the diagram of Figure 1, the resin accompanied by the saline solution which is extracted from

the column (10) is transferred to a

in the form of

a vertical column. This

is equipped with a double bottom in the form of a grating which retains the resin and allows the liquid materials to pass through.First, the

solution is drained, and is then extracted through the

(15) and the resin is washed with water which

through (16) until the salt is eliminated. The

diluted solution which is extracted through the

is used to dissolve more salt and it is reutilized in the process once the concentration is adjusted.

The washed and drained resin in the

is available for utilization in the second stage of the procedure. For

this purpose it is transferred into a

conveying it in salt solution obtained in the column (20) which

through the

The second stage of the procedure covered by the invention consists in an ion exchange between the resin charged in the first stage of the procedure and an acid or salt in solution, with different anion and cation from those used in the first stage. The ion exchange process is performed in the column (20) of similar design and construction to those of the first column (10).

The operating mechanism of the second stage is similar to that of the first but reversed. The volume of resin corresponding to each cycle and resulting from the first stage is introduced into the column (20) flooding with salt solution which is obtained from it. At the same time as the charged resin in the form of (RK) is introduced through the lower part of the column, the same volume of regenerated resin is extracted through the upper part. In each cycle, the zone of. ion exchange which is established is shifted from the lower part of the column to the upper part.

With the ion exchange zone in the upper part of the column (20) and the resin moving valves closed, an acid solution is

through the upper

at the time that the corresponding salt solution is extracted through the

lower

this way the ion exchange zone is shifted to the lower part of the column, where it was before the resin was introduced and a quantity of salt equivalent to the volume of regenerated resin is generated.

The molar concentration of the acid which is

corresponds approximately to thatof the salt which is obtained, and it is limited by the concentration of saturation of the most insoluble compound at the temperature of operation.

If a dissolution of a salt is used to regenerate the resin1 the exchange mechanism is produced similarly, obtaining instead of resin in acid form (RH) resin in form of the corresponding salt.

The circulation of resin and that of dissolutions in each cycle can be synchronized in the two stages of the process.

The regenerated resin which comes out of the column (20) in each cycle is flooded by the solution of acid or of salt employed for its regeneration. Before transferring this resin to the first column (10) to conduct the first stage of the process and close the run of the resin, it is necessary to separate the dissolution suitably which floods it. For this the resin and the solution which floods it are

transferred to a

in column shape, of design

similar to the

previously described. Afterward the dissolution which is recycled through the pipes (25) is

drained and the resin is washed with water which

through (16) until the anion of the dissolution is suitably eliminated.

The washed and drained resin is conveyed to the

in acid (or salt) dissolution obtained in the column (10) which

through the

(17), thus remaining available to pass to the first stage of the process.

In a second way of conducting the procedure covered by the invention, the salt solution can be separated from the resin by replacing the solution with another salt solution obtained in the second stage of the process. The diagram of the functioning of this second way of doing it is illustrated in Figure 2.

The charged resin in form of (RK) that comes out from each

cycle from a first column (100) is transferred to a

(130)' in column shape and with design characteristics similar to those of the column (100). Afterward there is

into that

through the lower

(140) a volume of dissolution of salt obtained in a second column (200) in the second stage of the process, equal to

the volume of salt solution

with the resin coming from the column (100). Simultaneously the corresponding volume of salt solution that entered with the resin is

extracted through the upper

(150) from the yLrSSEL L (130).

Between the dissolutions of salts in the

a zone of saline mix is established in which the two anions have inverted gradients of concentration and above which there only coexists with the resin the solution of salt which is

The resin does not suffer transformations in this phase.

This zone of saline mixture is shifted in each cycle from

one end to the other of the

within 'limits established so that it never goes out of it with the

gw7g / xS surodeses which are extracted. When the movement of the resin is started the saline mixture zone in the upper part

of the

is made to coincide, which is always kept full of resin flooded by the saline dissolutions. In the phase of the circulation cycle, the resin that comes out of (130) enters through a valve in the column (200).

In the second stage of the procedure, the solution can also be separated form the resin by shifting with another solution. In this case, the operation is performed in the

the design and function of which are similar to those of the (130) previously described. In each cycle, the corresponding resin that comes out of the column (200) is

through the lower part, at the same time that an equal volume comes out through the upper part. The shifting of the dissolution which enters

the resin is done by

through the

upper

(250) in each cycle and

Co & Ae?? r-Q-current with the resin an equivalent quantity of the acid (or salt) dissolution produced in the column (100) in the first stage of the procedure.The shifting mechanism for the dissolution is similar to the one that takes place in the

The resin that comes out from the

in each cycle

is received in a

for its movement to another

feeder

for the column (100). In this way of accomplishing the procedure covered by the invention, the movement of the resin corresponding to each cycle is synchronized among all of the elements or equipment, and the

resin is measured and driven from the

In Figure 2 the assignment of numerical references to

elements of the diagram

etc.) whose function can be understood from the explanation, from the similarity among stages and illustrated arrows, have been omitted.

EXAMPLE 1 A productive unit designed to obtain potassium nitrate (KNO3) and hydrochloric acid (HCl) from potassium chloride (KCl) and nitric acid (HNO3) with an approximate capacity of 5,000 MT per year of potassium nitrate, would have the following basic characteristics: - Dimensions of th columns: Diameter 1.2 m; height 5 m.

- Volume of resin moved in each cycle: 1 m3 - Number of cycles per hour to be done: 3 - Approximate quantity of ion changing resin in circuit: 15 m3 In the first stage of the process, the resin is charged with potassium ion (RK) by means of a solution of potassium chloride (KCl) 3 N, and hydrochloric acid is simultaneously

obtained in solution at a concentration of 2.8

In the second stage of the process the resin is generated to its acid form (RH) with nitric acid solution in concentration of 3 N and potassium nitrate (KNO3) is obtained simultaneously in solution of approximately 3 N concentration.

EXAMPLE 2 In the same production unit potassium nitrate (HNO3) can be obtained in solution, from sodium nitrate (NaNO3). Resin is regenerated in the second stage for this, with a solution of sodium nitrate (NaN03) of 3 N concentration. In the first stage, if the resin is charged with potassium chloride (KCl) solution of 3 N concentration, a solution of sodium chloride is simultaneously obtained, of 3 N concentration.

EXAMPLE 3 In the same production unit, monopotassium phosphate can also be obtained in solution from a solution of monocalcium phosphate. For this, the resin is charged in the first stage with potassium chloride (KCI) solution of 3 N concentration, and at the same time the solution of calcium chloride (CaC12) is obtained. In the second stage of the process, the resin is regenerated with a solution of moncalcium phosphate and a solution of monopotassium phosphate (KH2PO4) is obtained.

EXAMPLE 4 In the same production unit, phosphoric acid can also be obtained in solution from a solution of monocaicium ahnnahate. The resin is rharci for this Purpose, with

potassium chloride

solution in the first stage, simultaneously obtaining phosphoric acid (H3P04) in solution. In the second stage, the resin is regenerated with hydrochloric acid (HC1) in solution.

These examples are illustrative of the fact that the procedure covered by the invention applies to an infinity of combinations for obtaining salts and soluble acids of industrial and commercial value, from other available salts and acids.

Claims

1. A procedure for obtaining salts and acids in dissolution from other available ones, by ion exchange facilitated by ion exchanging resins, characterized by the stages of charging and regeneration of the resin being done in separate receptacles in column shape.

2. A procedure, according to claim 1, characterized by the first stage of the. process consisting of charging the ion exchanging resin with the cation corresponding to the salt which it is desired to obtain in the second column, circulating through it a dissolution of a salt the anion of which corresponds with that of the salt which it is desired to obtain; and in that the second stage of the process consisting of regenerating in the second column the resin charged in the first stage, circulating through it a dissolution of a salt or an acid, the anion of which corresponds with that of the salt or acid which it is desired to obtain, and the cation of which corresponds with that of the salt which it is desired to obtain in the first column.

3. A procedure, according to claim 1, characterized by the dissolutions which are circulated through the two columns to charge or regenerate the resin being fed through and end of the column and in sufficient quantity to carry the ion exchange zone as far as the region at the other end of the -column, without its going outside of it.

4. A procedure, according to claim 1, characterized by the fact that once the resin is charged with the corresponding cation in the first column, it is transferred to the second column for its regeneration, and in that once the resin is regenerated in the second column, it is transferred to he first column for charging, keeping the resin in closed cycle and operating c:.lioally.

5. A procedure, according to claim 1, characterized by the fact that before transferring the resin from one column to the other, it is separated from the dissolution which floods

it in a

for

purpose,

washing with water

with the dissolution which is

in the cclumn to which it is transferred.

6. A procedure, according to claim 1, characterized by the quantity of resin extracted from each column in each cycle being equivalent, and its being the amount necessary to carry the ion exchange zone from one end to the other of the column without going outside of it.

7. A procedure, according to claim 1, characterized by the fact that within the two columns corresponding to the two stages of the process, the ion exchanging resin and the solutions of products (salts and acids) involved in the

process circulate alternatively

CdLr s current and cyclically, shifting in each semi-cycle the ion exchange zone from one end to the other of the columns; and by the fact that the resin is transferred from one column to the other in closed circuit transporting the cation of the salt which it is desired to obtain in each stage of the process; and that the dissolutions of salts and acids involved are kept separate in the two stages of the productive process.

8. A procedure, according to claim 1, characterized by the

fact that the flow of the dissolutions which are

into the columns of the two stages is regulated to keep the three zones.of physical-chemical equilibrium which is established in each column well differentiated, that is, the zone of charged resin and dissolution of charge, ion exchange zone with the resin and zone of regenerated resin and corresponding dissolution.

9. A procedure, according to claim 1, characterized by the dimensions of the columns utilized in the process being of

cylindrical shape

relation of the diameter to the

height

one to five preferably, although not necessarily.