DE3808633A1 - Method for producing dissolved salts and acids by ion exchanger resins - Google Patents

Abstract

A method for producing dissolved salts and acids from other available products using ion exchanger resins is described. The method is carried out in two stages, with provision of the exchanger resin in columns. In the first stage, the resin is loaded with the cation, corresponding to the salt to be produced, by passing a solution of an appropriate salt through the resin. The charged resin is taken off from the column cyclically, the resin taken off being simultaneously replaced by regenerated resin which originates from the second stage of the method. Before transfer of the resin from the first stage to the second stage, the salt solution with which the resin is loaded is removed by draining and washing with water or by displacement with another solution. In the second method stage, the resin is regenerated by the same solution of a salt or an acid, the anion of which corresponds to the desired salt.

Description

The invention relates to a method for producing dissolved Salts and acids using ion exchange resins of a cationic nature, with which salt and acid solutions Be subjected to ion exchange so that in this way Solutions of other products can be obtained.

According to the invention, sulfonated ion exchange resins are used Copolymers of styrene and divinylbenzene with a macroporous structure in question as solids in the form of beads with a Diameter of about 0.6 mm. Such products are available available worldwide in the form of numerous commercial products.

Such resins are resistant to osmotic changes by contact with solutions of different concentrations standing, stable and are not subject to any physical Changes that change their shape. With these resins is a transition from the acid form to the salt form and vice versa Preserve their structure as often as possible. You are opposite largely oxidizing or reducing influences of solutions resistant.

Such cationic ion exchange resins are concerned are sulfonic acids that behave like strong acids. At Contact with a salt solution results in an acid-salt equilibrium important according to the following reversible reaction equation:  

RH + KA = RK + HA

in which
RH means the resin in the acid form,
RK means the resin in the salt form
K means the cation of the salt in solution,
A means the anion of the salt in solution and
H is a hydrogen ion or a cation different from the cation K.

When an ion exchange resin changes to the salt form one speaks of a loading and when returning to the Acid form from regeneration.

If an ion exchange resin is in the acid form in the form of a sufficiently high column in an appropriate container is and if through the immobile resin from bottom to top a saline solution, e.g. B. a potassium chloride solution (KCl) slowly circulates, ions find between the resin and the solution exchanges take place that lead to each point the column establishes a physical-chemical equilibrium. As a result of this ion exchange process, the solution becomes all the more acidic, the further it moves in the resin until finally the salt is completely converted into the acid. Doing so load the resin with the appropriate cation. In this way arises within the column in a certain zone removable concentration gradient of the salt and an increasing concentration gradient of the acid, above this zone only resin in the acid form and the supplied salt corresponding acid and below this zone only loaded resin and saline are available.

The ion exchange zone formed moves when the Saline solution from the bottom up in the column, taking the back side of the zone loaded resin in the presence of saline remains and on the front a solution of the salt ent  speaking acid is formed by the upper part is pulled.

The concentration of the An corresponding to the salt added ions remains practically constant throughout the column, whereby minor changes due to different solvations grade of the resin in acid and salt media.

The height of the ion exchange zone in the column depends on the Affinity of the resin for the cation of the salt in comparison to hydrogen ions (protons). This affinity is greater if the cation has a larger volume and a higher valency owns.

If you look at the direction of circulation of the resin flowing around the resin reverses by passing acid solution through the top of the Feeds the column and removes salt from the floor, so moved the ion exchange zone down in the same direction tion like the solution. The resin is reversible regenerates. In this case there is a different one Extension of the ion exchange zone depending on the un different affinity of the resin for the cations H⁺ and K⁺.

Is a regenerated cation exchange resin, which in A pillar of sufficient height is provided, a saline solution in the ascending direction and with adequate Given speed, so result in agreement with the above explanations the following effects:

• - The resin increases in ascending direction in the column taking loaded;
• - The ion exchange zone comprises a defined volume of resin within the column, which depends on the type of cations that to be exchanged between resin and solution depends on;  
• - The ion exchange zone shifts within the column in the direction of movement of the solution;
• - Above the ion exchange zone, a solution of acid corresponding to the salt supplied.

The amount of acid formed is in a stoichiometric Ver ratio to that of the loaded resin. Currently for ver Available macroporous ion exchange resins have one Exchange capacity of about 2 equivalents per liter.

If you look at the direction of circulation of the solutions inside the column reverses by passing an acid solution through the top of the Feeds the column and removes a salt solution from the lower part, the following results:

• - the ion exchange zone is increasingly shifting downwards, the resin being regenerated at the same time; and
• - It forms a saline solution, the amount of which in the stoichiome relationship to the regenerated salt.

The object of the invention is to provide a method for producing provide dissolved salts and acids, in which an ion exchange process using ion exchange resins to be carried out in separate stages.

The inventive method allows the construction of Production facilities that can be largely automated. It also allows independent control of the two levels of the procedure. It is possible to contribute to the ion exchange processes Temperatures close to atmospheric or ambient temperature to carry out, whereby minimal amounts of energy are required. The method can also be at much higher temperatures are driven with the restriction that among those in each In case of prevailing conditions the resin will not be damaged.

The use of macroporous ion exchange resins on the basis  of sulfonated copolymers of styrene and divinylbenzene, the are very resistant to osmotic shocks it is possible to work with concentrated solutions without the Change structure of the resin, with the advantage that one is crystalline line products. These types of resins are simultaneous very resistant to rubbing or pulverizing, so that they endure a large number of work cycles and in the pro zeß can be used without significant deterioration suffering. The small amount of abrasion or dust, which are inevitable when handling the resin, are usually separated during the washing process.

The ion exchange resin that is preferably used is is a cationic resin made from a sulfonated copo lymeren of styrene and divinylbenzene and in the form of Beads with an average diameter of 0.6 mm is present. In addition, in the method according to the invention other types of resins, including anionic exchangers resins used if they are firm, possess a similar form and are compared to the physico-chemical Conditions of the procedure persistent.

The essence of the method according to the invention is that the processes of loading and regeneration of the resin in two separate stages and carried out in different columns will.

Further details and advantages as well as exemplary embodiments the invention are described below with reference to the drawing ben.

Fig. 1 is a schematic representation of a first example of an arrangement of devices and elements for performing the method.

Fig. 2 is a schematic representation of a second similar union embodiment.

In a first column 10 ( FIG. 1) the resin is loaded with a salt solution, a solution of the acid corresponding to the salt being formed.

As can be seen from the drawing, the column 10 consists of a vertically arranged, cylindrical container. At the upper and lower ends, valves for removing and filling the resin are arranged. A pipe 11 for feeding the saline solution is arranged laterally in the vicinity of the lower end, while a pipe 12 for removing the acid solution (or saline solution) formed in the process is seen in the vicinity of the upper end. Both tubes are connected inside with liquid distributors, which ensure a uniform flow of the solutions that circulate through the resin in the area of the entire column cross section. The manifolds are designed to allow liquids to pass through but retain the resin. They are arranged so that the resin can move through the column when the resin is transferred.

The dimensions of the column 10 , ie diameter and height, can vary within wide limits depending on the intended production capacity.

Serves to explain the method according to the invention in more detail the preferred embodiment described below, at which is the step of loading the resin with a potassium chloride solution (KCl) is carried out as a saline solution. It will be one Solution of potassium chloride (KCl) in a concentration of 3 n manufactured at ambient temperature (20 ° C). Fixed or loosened Impurities that interfere with the method according to the invention or may affect the resin.

In the first stage of the process according to the invention, the loading column 10 is filled with ion exchanger resin, which is in acid form and is washed with 3N hydrochloric acid solution (HCl). This ion exchange resin used for charging is located in the container 13 . After filling the column 10 with the resin and after closing the valves serving to transfer the resin, 3 N potassium chloride solution is started to be fed through the lower tube 11 of the column. At the same time, hydrochloric acid solution is removed through the upper tube 12 .

The supply amount of the saline solution becomes equivalent to one resin volume in the column per unit of time poses when working with 3N potassium chloride solution. The The amount of saline is determined so that there is a short and well differentiated ion exchange zone within the column gives, above this zone only resin in the acid form, d. H. RH, and the solution corresponding to the salt added Acid are present simultaneously, while below this zone only Loaded resin, i.e. H. RK, and the solution of the fed Salt are present at the same time. This state varies inter alia depending on the salt concentration, the physico-chemical affinity of the salt cation (K⁺) to the resin, the type of cation to be substituted (H⁺) and the grain size ver division curve of the resin.

During the feeding of the saline solution, the ion exchange zone moves upward from the bottom of the column, whereby an amount of hydrochloric acid solution is formed which corresponds to the amount of the loaded resin. When the ion exchange zone comes close to the upper tube 12 through which the hydrochloric acid solution is drawn off, the salt supply is switched off. In this way, all of the resin in the column below the ion exchange zone is converted into the loaded form, ie RK.

After loading the resin contained in column 10 , ie after the formation of RK, the inlet and outlet valves for the solutions are closed and the volume of the regenerated resin corresponding to one cycle is circulated through the column. This volume of the regenerated resin is in the container 13 , which is arranged above the column 10 and is connected to this via a valve. The resin is flushed from the acid solution from the process, which enters through the tube 17 . Loaded resin in the form of RK emerges through the valve on the bottom of the column.

In this process, the ion exchange zone, which was originally in the vicinity of the upper tube 12 of the column, sinks during the resin circulation until it reaches a position above and near the lower tube 11 . At this time the resin circulation through the column is stopped by closing the corresponding valves. The circulating resin volume is kept constant in each cycle to facilitate the process.

Then the inlet and outlet valves for the solutions are opened again and saline solution is fed in until the ion exchange zone comes close to the upper tube 12 of the column.

This way, at the first stage of the process and when repeating the cycles that into the acidic form, d. H. RH regenerated resin in loaded resin in the salt form, d. H. RK, transferred, the fed saline solution into the ent speaking acid solution is transferred.

The total amount of the solution in the form of each cycle salt fed corresponds to the amount required to load the circulating amount of resin plus the amount of salt that leaves the column with the resin at each cycle. The formed or moved in the form of a solution in each cycle Acid corresponds stoichiometrically to the amount of resin loaded plus the amount of acid used in each cycle to wash the resin is fed.

To ensure that the ion exchange zone at each Cycle in the column moves within the defined limits,  so that it is ensured that only acid solution without Contamination with salt and loaded resin RK, without contamination cleaning with regenerated resin RH, leak, ion end tectors placed near these limits. The signals These detectors are used to measure the amount of each Adjust the cycle of saline solution.

The first phase of the process can serve not only to convert a salt to the corresponding acid, but also to convert a salt to another salt with the same anion. In the latter case, the resin fed into the column 10 at each cycle must be loaded with the cation corresponding to the salt that is desired to be obtained. If the resin is loaded with sodium, ie RNa, and if potassium chloride (KCl) is fed into the column, a solution of sodium chloride NaCl and potassium-loaded resin RK are obtained. In this case, the concentration limits of the solutions involved are determined by the solubility of the less soluble salt.

In the process according to the invention, the resin and the solution always circulate in countercurrent. In the present example, the resin circulates within the column 10 downward and the solutions upward, but this direction of circulation can be reversed. The criterion for determining the direction of circulation is preferably that the less dense solution is located in the upper part of the column in order to avoid disturbances in the ion exchange zone due to differences in density.

The loaded resin in the form RK, which emerges from the column 10 in each cycle, is washed with the salt solution used for loading. Before transferring this resin to a second column 20 to carry out the second stage of the process, it is necessary to remove the anion of this salt from the resin in order to avoid salt contamination in the products obtained. For this purpose, as shown in FIG 1. The cover of the salt solution, the resin is withdrawn from the column 10, transferred to a container 14 having the form of a vertical column. This container 14 is equipped with a double bottom in the form of a grid which retains the resin and allows liquid materials to pass through. First, the brine that is returned through a pipe 15 is drained, and then the resin is washed with water that enters through a pipe 16 to remove the salt. The diluted salt solution obtained, which goes out through the pipe 15 , is used to dissolve additional salt and is reused in the process after appropriate adjustment of the concentration.

The washed and drained resin in container 14 is available for use in the second stage of the process. For this purpose, it is placed in a container 23 in the solution of the salt obtained in the column 20 , which salt solution enters through a tube 27 .

The second stage of the process is an ion exchange between the resin loaded in the first process stage and an acid or a salt in solution, the anion and the cation being different from the ions used in the first process stage. The ion exchange is carried out in column 20 , which is constructed similarly to column 10 .

The mechanism of this stage of the process is similar to that of the first stage, but vice versa. The resin volume corresponding to each cycle, which comes from the first stage, is fed into the column 20 together with the rinsing saline solution obtained in this column. Simultaneously with the loading of the loaded resin in the form RK through the lower part of the column, the same volume of regenerated resin is drawn off through the upper part of the column. In each cycle, the resulting ion exchange zone shifts from the bottom of the column to the top.

While the ion exchange zone is in the upper part of the column 20 and the valves for decanting the resin are closed, acid solution is fed through the upper tube 21 of the column. At the same time, the corresponding salt solution is drawn off through the lower tube 22 . In this way, the ion exchange zone is shifted downward from the position before the introduction of the resin, and an amount of salt is formed which is equivalent to the volume of the regenerated resin.

The molar concentration of the acid fed in corresponds to about the concentration of the saline solution obtained. This con concentration is stronger due to the saturation concentration limited insoluble connection at the operating temperature.

If a solution of a is used to regenerate the resin Salt, the exchange mechanism is similar Way, instead of resin in the acid form, i.e. H. RH, Resin in the form of the corresponding salt.

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

The regenerated resin leaving column 20 in each cycle is washed by the acid or salt solution used to regenerate the resin. Before the resin is transported into the first column 10 to carry out the first stage of the process and to close the resin cycle, it is necessary to appropriately separate the solution washing around the resin. For this purpose, the resin carried in the solution is transported into the column-shaped container 24 , which is constructed similarly to the container 14 described above. The solution is then removed and returned through tube 25 and the resin is washed with water entering through tube 16 to conveniently remove the ion from the solution.

The washed and drained resin is transported into the container 13 with the solution of the acid (or salt) obtained in the column 10 , which enters through the line 17 , after which it is available again for the first process stage.

Another possibility is to separate the salt solution from the resin by displacement with the solution of the other salt obtained in the second stage of the process. The latter alternative is explained by Fig. 2.

The loaded resin RK, which is withdrawn from the first column 100 in each cycle, is transferred into a column-shaped container 130 , which has similar design features as the column 100 . Then, through the lower pipe 140, a volume of the saline solution obtained in a second column 200 in the second stage of the process is fed into the container 130 , which corresponds to the fed-in volume of the saline solution originating from the column 100 together with the resin. At the same time, the corresponding volume of the saline solution that has entered the column with the resin is drawn off through the upper tube 150 of the column 130 .

A zone of a salt mixture is formed between the solutions of the salts in the container 130 , in which the two anions form around inverted concentration gradients. Above this zone is only the resin and the solution entering the column together with the resin. The resin does not change during this phase.

This zone of the salt mixture moves from one end of the column 130 to the other at each cycle within semi-defined limits so that there is never a case in which the salt mixture is withdrawn with the extracted materials. At the beginning of the resin transfer, the zone of the salt mixture must be in the upper part of the column 130 , which is always kept full of resin, which is washed with salt solutions. In the phase of the circulation cycle, the resin exiting column 130 enters column 200 after passing a valve.

In the second stage of the process, the solution can be separated from the resin by displacement with another solution. This process is carried out in the container 230 , the construction and operation of which is similar to the container 130 described above. In each cycle, the resin withdrawn from the column 200 is fed into the container 230 through the lower part, with an equal volume being withdrawn through the upper part at the same time. The displacement of the solution introduced into the container together with the resin is carried out by injecting an amount equal to the amount of the solution formed in the column 100 of the first process step through the upper tube 250 and countercurrent to the resin in each cycle Acid or salt is equivalent. The displacement mechanism of the solution is similar to the mechanism taking place in container 130 .

The resin leaving container 230 is collected in a container 300 in each cycle, from where it is transported to a container 310 for feeding into column 100 . In this procedure, the movement of the resin corresponding to each cycle is synchronized in all pieces of equipment, the resin being measured from the container 310 and set in motion.

In Fig. 2, the reference numerals for those elements (pipes, valves, etc.) are omitted, the function of which can be seen from the description, from the similarity between the exemplary embodiments and the individual stages and from the arrows indicated.

example 1

The following basic features are realized in a production unit for the production of potassium nitrate (KNO ₃ ) and hydrochloric acid (HCl) from potassium chloride (KCl) and nitric acid (HNO ₃ ) with an approximate potassium nitrate capacity of 5000 tons per year:

• - dimensions of the columns: diameter 1.2 m, height 5 m;
• - volume of resin moved in each cycle: 1 m ³ ,
• - Number of cycles per hour: 3;
• - approximate amount of ion exchange resin in the circuit: 15 m ³ .

In the first stage of the process, the resin is loaded with potassium ions using a 3N potassium chloride solution (KCl) to form RK. A hydrochloric acid solution is simultaneously obtained with a concentration of 2.8 n. In the second stage of the process, the resin is regenerated into the acid forms RH using a 3 n nitric acid solution. At the same time, potassium nitrate (KNO ₃ ) is obtained in the form of a solution with a concentration of about 3 n.

Example 2

In the same production unit, potassium nitrate (KNO ₃ ) can be produced in solution using sodium nitrate (NaNO ₃ ) as the starting material. For this purpose, the resin is regenerated in the second stage with 3N sodium nitrate solution (NaNO ₃ ). In the first stage, when the resin is loaded with a 3N potassium chloride solution (KCl), a 3N sodium chloride solution (NaCl) is obtained at the same time.

Example 3

In the same production unit, monopotassium phosphate in solution can also be produced using a solution of monocalcium phosphate. For this purpose, the resin is loaded with a 3N potassium chloride solution (KCl) in the first stage, a calcium chloride solution (CaCl ₂ ) being obtained at the same time. In the second stage of the process, the resin is regenerated with monocalcium phosphate solution. A monopotassium phosphate solution (KH ₂ PO ₄ ) is obtained.

Example 4

In the same production unit, a phosphoric acid solution can also be produced using a monocalcium phosphate solution as the starting product. For this purpose, the resin is loaded with a monocalcium phosphate solution (Ca (H ₂ PO ₄ ) 2) in the first stage. At the same time, a phosphoric acid solution (H ₃ PO ₄ ) is obtained. In the second stage, the resin is re-generated with a hydrochloric acid solution (HCl).

These examples serve only to illustrate the invention and show that countless combinations for the production of indu strategically and economically valuable, soluble salts and Acids are possible, being available from others runs out of salts and acids.

The process allows the construction of production units, that can be automated to a high degree. Furthermore independent control of the two process stages is possible Lich.

The method enables ion exchange to be carried out occur at temperatures near ambient temperature minimal energy consumption. One can also at much higher ones Temperatures work, it is only important to ensure that the resin is not damaged by the respective conditions.

The use of macroporous ion exchange resins on the Based on sulfonated copolymers of styrene and divinylbenzene, which are largely resistant to osmotic shock, enables working with concentrated solutions without the resin structure is changed. This has the advantage that crystalline products can be obtained. Such resins are also very resistant to abrasion, making them one can survive a high number of cycles and ge can be handled without affecting them to any significant extent to be pregnant. The low fines content, the inevitable is formed when handling the resin, nor sometimes separated during the washing processes.

Claims (9)

1. A process for the preparation of dissolved salts and acids from other available salts and acids, by ion exchange using ion exchange resins, characterized in that the loading and the regeneration of the resin is carried out in separate containers in the form of columns. 2. The method according to claim 1, characterized in that

• - That the first stage consists in loading the ion exchange resin with the cation corresponding to the salt desired in the second column, in that a solution of a salt is circulated through the resin, the anion of which corresponds to that of the salt which is added wishes to get and
• - That the second stage consists in that the resin loaded in the first stage is regenerated in the second column, that a resin or an acid solution is circulated through the resin, the anion of which or that of the desired salt or the desired Acid speaks, and its or its cation corresponds to that of the salt that is desired in the first column.

3. The method according to claim 1, characterized in that the Solutions that are circulated through the two pillars to load or regenerate the resin, each by one end of a column and fed in sufficient quantity be to the ion exchange zone to an area at to move the other end of the column, but without the Leave pillar. 4. The method according to any one of the preceding claims, characterized characterized in that one in the first column with the ent speaking cation-extracted resin and extracted to rain ration to the second pillar, and that the the second column regenerated resin for reloading transferred to the first column so that the resin in a ge closed cycle and is cyclically moved. 5. The method according to any one of the preceding claims, characterized characterized in that prior to the transfer of the resin from one column into the other the solution washing around the resin in a container by washing with water or by Ver push with the solution of the corresponding column to which the transfer is made away. 6. The method according to any one of the preceding claims, characterized characterized in that the amounts of each column in each Cycle withdrawn resin are equivalent, and that the Be is chosen as it is necessary to discharge the ions exchange zone from one end to the other end of the column move, but without leaving the column. 7. The method according to any one of the preceding claims, characterized characterized in that within the two pillars, accordingly the two stages of the process, the ion exchange resin and the solutions of the products (salts and acids) on the Participate in procedures, alternatively in countercurrent and cyclically circulate, with ion exchange in each half cycle  area shifted from one end of the pillars to the other is that the resin from one column to the other in one closed circuit is transferred, the cation of the salt to be obtained at each stage of the Procedure is transported, and that the solutions of the be divided salts and acids in the two stages of the product tion process are kept separate. 8. The method according to any one of the preceding claims, characterized characterized that the flow of the solutions that the Sau len in the two stages are set so is that three zones with physico-chemical equilibrium Maintain weight clearly in each column become, namely a zone with loaded resin and loading solution, an ion exchange zone with the resin and a zone with regenerated resin and appropriate solution. 9. The method according to any one of the preceding claims, characterized characterized in that the columns used in the process cylindrical shape and preferably a ratio of Have diameters as high as 1: 5.