SU138226A1 - Method for conducting ion-exchange two-temperature mixture separation processes - Google Patents

Description

Ion exchange as a method for separating cations of similar properties in recent years has become widespread.

The known methods of countercurrent ion exchange as applied to the separation of binary or multicomponent mixtures of cations that are similar in their properties, as well as isotopes, have not become widespread due to the difficulties of cationite movement, which leads to deterioration of hydrodynamic conditions under countercurrent separation, which in turn increases WATT, i.e. one of the quantities characterizing the efficiency of the process.

The two-temperature method of separation of mixtures is known (for example, the separation of hydrogen isotopes, isotopic exchange between water and hydrogen sulfide).

A method is proposed for separating a mixture of cations of similar properties as well as isotopes by a two-temperature ion-exchange method based on the dependence of ion-exchange separation coefficients on temperature.

The separation of the mixture is carried out as a result of a continuous countercurrent ion-exchange process with a fixed cationite and a moving temperature field.

The installation contains a series of sections connected in series between themselves, filled with an ion-exchange resin, through which the flow of working solution passes through a circulation pump. Each section is equipped with a heater and heat exchanger for the coolant. In one part of the total number of the installation section, the temperature is maintained, for example, 5-6 °, while in the other sections - 60-65 °. Thus, the chain of sections forms two zones with different temperatures.

After a certain period of time has passed, the head section of the cold zone, by switching over the heat and coolants, begins

№ 138226-2 to work as the tail section of the hot zone, and the tail section of the hot zone - as the head section of the cold zone.

The heat exchangers between the sections prevent the "erosion of the boundary between the cold and hot zones and serve to recover energy.

The proposed method is the original version of the countercurrent continuous two-temperature process. This kind of ion exchange processes are unknown.

The advantage of the method is the continuity of the process, its efficiency, as well as the elimination of the movement of the cation exchanger, which is replaced by the movement of the temperature field.

From the literature it is known that the magnitude of the separation factor of two ions when exchanging them between the solution and the cationite depends on the temperature. The presence of the temperature dependence of the separation factor makes it possible to carry out ion-exchange separation according to a two-temperature scheme, in which chemical regeneration of the ion-exchange resin will be absent.

FIG. Figure 1 shows a schematic diagram of a two-temperature separation unit, explaining the proposed method.

The unit for the separation of ions and isotopes consists of two A n B columns, each of which is maintained at a certain temperature. The columns carry out a countercurrent of the solid phase (cation resin-LI flow) and solution (solution flow-L2). The cation exchanger should have a pronounced temperature dependence of the separation factor (e.g. SBS) with respect to the ions (or isotopes) to be separated. The second, liquid phase is a solution containing separable ions (or isotopes).

In column L, the separation occurs at a temperature TI, with the separation factor ai corresponding to that temperature. In column B, the oimen occurs at temperature T, at which the partition coefficient & | {and az will be less. For increasing the separation efficiency, the temperature TZ should be maximum, which still will not occur destruction of the cation exchanger (for SBS 80 °). The phase flow of the cation exchanger can be closed. The feed F is in the form of a solution introduced into the lower part of the column, where the concentration of the ion to be separated in the solution is equal to its concentration in the feed stream. The selection of product P with concentration Xk is made from the solution flow between the columns. The solution flow at the exit from column A, where the concentration of the released ion is minimal, goes to the dump.

Since 02 is the concentration in the enriched stream B in the enriched stream LI will be higher than the equilibrium for the temperature T in column B. As a result, in column B there will be a process towards the establishment of a new equilibrium. This process will lead to desorption from the LI stream of the enriched cation and its transfer to the stream L.

The countercurrent exchange process is carried out without special treatment of the phases. The concentration Xn of the released ion in the stream W going to the dump will, with an infinitely large number of steps, go to (lim Y) there will be less concentration in the feed

solution - X (tU azX). Due to the concentration difference in the incoming and outgoing flows, enrichment and product selection takes place.

FIG. 2 graphically depicts the process occurring in a column of the considered scheme in the coordinate system X - Y,

where: X is the concentration of the component in the lean phase; Y is the concentration of the component in the enriched phase. Denote:

at 1 - l: -, equilibrium is the curve of the low-temperature zone in

column (L in Fig. 1);

411V «2 - Г equilibrium with the curve of the high-temperature zone in

column (B in Fig. 1).

The working line of column A is the straight line described by the following equation:

Y, (X-X,) + Y ,,

The working line of column B is expressed as: (XX) +},

By feeding at a point below the upper end of column A, it is possible to create an ion-exchange separation process with exhaustion, the scheme of which is shown in FIG. 3. In this case, from the column A will go to the dump notes of the solution with the concentration of the emitted ion, less than the original. The process occurring in the column with exhaustion is graphically depicted in the coordinates X - Y in FIG. 4. Values, 2 and 1h for the process depicted in FIG. 3 are calculated in the same way as for the process shown in FIG. 1, using the equations of material balance.

Based on the foregoing, the following version of the two-temperature installation of ion-exchange ion separation is proposed (in particular, the method can be applied for the separation of isotopes).

The separation of ions can be carried out according to the following scheme (Fig. 5). In the ion exchange column, a cation exchanger with a pronounced temperature dependence of the ion separation factor (e.g., SBS) is fixedly positioned. The cation exchanger is saturated with separated ions. A solution of the salts of the separated ions is passed through the ion exchanger. An elevated temperature is created in a certain part of the separation column. The high temperature zone is moving at a speed less than the velocity of the solution in the column. The direction of movement of the temperature zone should coincide with the direction of movement of the solution. At certain installation parameters, the ratio of the flow rates of the solution and the temperature zone determine the ratio of the flows in the separation column. If at T the separation factor is greater than at ha, then when the solution and temperature zones move upwards, the more adsorbed ion will concentrate more easily at the upper end of the low-temperature zone, and another ion will be concentrated at the lower end.

The circuit in FIG. 5 is given for the case of the concentration of a less easily sorbed ion from the initial mixture. When the process is carried out with the aim of concentrating the other ion, the points of selection, feeding, and heap change accordingly.

By feeding through the point of the column located inside the temperature zone, it is possible to carry out the process of concentration of both ions (exhaustion process).

- 3 No. 138226

L., where

where i-, - :. LI

No. 138226-4. In FIG. 6 is a diagram of such a process. At the point from the diagram in FIG. 6, the selection is carried out, the ion that is more difficult to sorb by the ion exchanger is concentrated. A different ion will be taken from the dump point.

The movement of the temperature zone through the column can be accomplished either by moving the heater through the column, or by breaking the column into a number of sections, supplying coolant to one section and coolant to the rest and making appropriate switchings of the cold and hot agent.

Example. The results of the separation of lithium and ammonium, obtained in a laboratory setup.

The A t B columns (see Fig. 5) are made in the form of 12 glass cells filled with SBS cationite. The movement of temperature zones is carried out by alternately switching cell heaters that are at a given time at the ends of the zone from operation at temperature T to operation at temperature TZ and vice versa. The results of one of the experiments are presented in the form of a graph (see Fig. 7), which shows the distribution of lithium concentrations among the separation cells.

Subject invention

The method of conducting ion-exchange two-temperature separation processes of mixtures in solution by passing them through cation resin with a pronounced temperature dependence of the separation coefficient, characterized in that, in order to ensure efficiency and continuity of the process, the separation is carried out in a partitioned column filled with a fixed cation resin, while gradually moving along the length of the column of hot and cold zones by appropriately switching the heat and coolant washing the sections through the wall.

FIG. I

i / s. J

OmSa / i

D Selection

L /.

Nutrition

Fig 5

FIG. 2

Of /

n . kx

Fy

From & an

Power D

OmSop B

FIG P

T in to to ff t TG

 7