HU203843B - Method and apparatus for multi-stage, quasi-continuous, countercurrent contacting a liquid phase and a solid and/or immiscible liquid-phase of different thickness - Google Patents

Abstract

A sloping cascade (e.g. at 30 DEG to the horizontal) is composed of a series of stages of the construction illustrated. Attached to the mixing/settling vessel 2 by tube 4 is a separate vessel 3, at the top of which are valves 12a, for supplying compressed air, and 12b, for connection to the atmosphere. The phases in vessels 2 are agitated by means of gas supplied by lines 18. After the phases have settled, valves 12a are opened, in sequence, from the lowermost stage up. This causes the lighter phase to spill over, through lower connection 5, to the stage under it. Closing valve 12a, and opening 12b, restores the liquid to its former position. The heavy phase is discharged from the top stage by air-lift 22 and then, in succession, the heavy phase is moved up from each stage to the next higher, where it may be introduced into either of vessels 2 or 3. Mechanical agitation may be used; pumps may replace air-lifts 22; the lighter phase may be expelled by introducing the heavier below it. Both phases may be liquid, or one may be solid. Exemplified is treatment of a cation-exchange resin with sulphuric acid. <IMAGE>

Description

The present invention relates to a process and apparatus for multi-stage, quasi-continuous, countercurrent contact of a liquid phase and a solid and / or immiscible liquid phase of a different density.

The countercurrent contact of a liquid phase and a solid and / or immiscible liquid phase of a different density is of great practical importance and many methods are known to solve it (Ahell, King, New Developments in Liquid-Liquid Extractors, AIChE Symp.Ser. 80/238/1984). ).

There are three basic groups of procedures used:

- operating units based on simultaneous mixing and separation,

- processes for mixing and separation in separate equipment,

- and cyclically operating mixer separation methods.

The first group of processes is characterized by the fact that mixing and separation take place simultaneously and simultaneously in space. This group includes e.g. rotary disk extractors, where the non-immiscible phases of the spontaneous countercurrent flow are mixed in superimposed space by mechanical stirring elements (e.g., Kosters, WCG: Rotating-Disk Contactor, Lo, TC, Baird, MJU. and Hanson, C. eds: Handbook of Solvent Extraction, Wiley-Interscience, New York, 1983). These methods are primarily suitable for contacting two liquids and are less reliable in the presence of solids.

The other group of operation units is characterized in that the mixture and the separation are carried out in two separate units, e.g. mixing in a mechanically stirred tank and separation in a settling centrifuge (filter / centrifuge in the case of a solid / liquid system). These processes can be operated in both batch and continuous mode. Instead of mechanical mixing, pneumatic mixing is possible.

The closest embodiment of the invention is a moving part mixer settler extraction process and apparatus, as described by M.Venkataraman, R.Natarajan and GRBalasubramanin (Air pulsed mixer settler - somé design experience, Ahell, RJB. And King. Liquid-Liquid Extractors, AIChE Symp. Ser. 80 (238), 1984, pp.6469). The equipment was developed for extraction used in reprocessing spent fuel reactors in nuclear reactors. In a horizontally arranged unit consisting of series-connected stages, a lighter (organic) and a heavier (aqueous) phase are contacted in countercurrent. Each stage comprises a mixing space and a settling space connected therewith by pipeline. Two mixing probes extend into the mixing chamber from above, which are alternated with a 180 * phase shift and a pressurized container. they are connected to a vacuum container. In this way, pulsating mixing is carried out without, however, changing the liquid level in the mixing chamber. The aqueous and organic phases enter the mixing chamber from below and the mixture is transferred to the settling chamber at the top. Here, the organic phase, which is separated by gravity, is discharged by overflow and then transported to the next mixer by a pneumatic pump (aerolift) operating on the principle of a pressurized water lift. The aqueous phase exits at the bottom of the settler and is also conveyed by a pneumatic pump to the next unit. Phase transfer is controlled by sensing the levels. In particular, the costly design of separation units increases the investment required for mixing and separation solutions in a separate operation unit.

The third group comprises cyclically operating mixer separation processes. In these operating units, mixing and phase separation take place in the same space but in succession. A disadvantage of mixer-separation processes is that in the presence of a solid phase, material transfer is difficult.

SUMMARY OF THE INVENTION The object of the present invention is to improve the known solutions and to provide a process and apparatus which can be used for any phase system (two immiscible liquids, a settling solid, a floating solid and in these cases a gas phase) and multistage countercurrent contacting. the securing device can be formed from simple elements.

The invention is based on the realization that by using the tools of modern computing and control technology, operating units consisting of simple elements (pipes, pipe fittings, mixed spaces, pumps, etc.) can be organized into a functional unit.

According to the invention, the object is solved by a process wherein the lighter phase is introduced into the first stage of a cascade consisting of several series-connected stages and the heavier phase is introduced into the last stage, the stages being mixed in each stage, the phases separated spontaneously between the adjacent stages, at least partially in countercurrent, and the first and second steps of the cascade. from his last grade. The phases are mixed and separated in each stage in a mixer-separator space, the lighter phase is introduced externally into the first-stage mixer-separator space, the phases are mixed in the mixer-separator space at least once per cycle and then separated from the last stage to the first stage. step-by-step, step-by-step introduction of each stage into the lower part of the mixer separator space by a predetermined amount of heavier phase from an auxiliary space of stage, thereby displacing the corresponding amount of lighter phase from the mixer-separator space into or into the space. dispensing from the last stage, while the heavier phase is added to the mixing space and / or auxiliary space of the last stage, from the bottom of the mixing space and / or auxiliary stage of each stage to the mixing space and / or auxiliary space of the respective stage; from the bottom of the separation space.

HU 203 843 A

It is advantageous to introduce the lighter phase displacement heavier phase from the auxiliary space connected to the mixer-separator space by increasing the pressure of the gas space above the heavier phase to the mixer-separator space, and then to create and eliminate overpressure, e.g. This can be done by actuating valves or other shut-off valves by alternately connecting the gas space to a manostat of higher and then lower pressure. The operation of the assemblies is accomplished by an arbitrary clock transmitter, preferably by a programmable microprocessor control unit. In this variant of the process, it is expedient to successively displace and dispense the lighter phase in successive stages in all stages and then to sequentially dispense the heavier phase sequentially from the first stage.

In another preferred embodiment of the process, the heavier phase displacing the lighter phase is introduced from the auxiliary space into the mixer-separation space by gravity. In this case, it is preferable, in each step, to displace the lighter phase and to overdose the heavier phase, starting from the last stage.

According to the method, a portion of the heavier phase 25, which is further dispensed from the mixer-separator space of each stage, is sometimes returned to the auxiliary stage of the stage.

According to the method, it is expedient to perform a level sensing in the mixer-separator space and the auxiliary space and to adjust the dosages accordingly.

In the process, the heavier phase, even the lighter phase 30, may be a solid which settles out of the liquid or solid during separation. crawls into the upper part of the fluid space. Meanwhile, the liquid phase may also contain gas bubbles. During the process, the individual components of the phases may interact physically and / or chemically with each other.

The apparatus according to the invention has series-connected stages with mixing elements, the underside of which is connected to the previous stage via connectors and pumps for carrying the heavier phase. Each stage comprises a mixer-separating space and an auxiliary space connected to the underside thereof by a pipe, and is provided with fittings for controlling the flow of the heavier phase through the pipe, preferably with valves or pumps. The steps are arranged in a sloping row, and the upper portions of the mixer-separating spaces of the adjacent stages are provided for dispensing and dispensing the lighter phase. they are connected to each other and / or their surroundings via sloping material transfer channels suitable for gravity transfer between each stage.

In a preferred embodiment of the apparatus, the auxiliary compartment is closed at the top and is disposed adjacent to the mixer-separator space and is connected to it in a converging manner and has a gas passage or a gas passage. 55 are fitted with gas discharge valves and valves.

Preferably, the bottom of the mixing separation space is connected via the pump to the mixing separation space and / or auxiliary space of the adjacent higher stage.

In another preferred embodiment, the auxiliary space 60 is open and disposed above the mixer separation space and is connected to it by means of a shut-off valve, preferably a valve.

In another preferred embodiment, the bottom of the mixer-separator space is connected through the pump and shut-off valves, preferably through valves, to the auxiliary area of the same stage and the adjacent higher stage.

In the apparatus, the fittings, preferably the valves, are preferably connected to a microprocessor controlled pulse.

A pump may be installed in the pipe connecting the auxiliary space to the mixer-separator space. In the auxiliary compartments mixing elements as well as level sensors can be placed. The pumps and mixers are of mechanical and / or pneumatic design. Preferably, the shut-off valves, preferably valves, are connected to the pumps, mixers and level sensors by a microcomputer.

The invention will now be described in more detail by way of examples and drawings. In the drawings it is

Fig. 1 is a side view of a preferred embodiment of the stage of the invention, a

Figure 2 is a front view of the grade of Figure 1, a

Figure 3 is a top view of the grade of Figure 1, a

Figure 4 is a schematic of a six-stage device, the

Figure 5 is a detailed plan view of the apparatus of Figure 4, a

Fig. 6 shows the pneumatic mixer or a schematic of a possible connection of the pump, a

Figure 7 is a detail view of Figure 6, a

Fig. 8 shows the pneumatic mixer or another version of the pump circuit diagram, a

Figure 9 is a detailed top view of Figure 8;

Figure 10 is a diagram illustrating the periodic operation of the apparatus; and a

Figure 11 is a schematic diagram of another embodiment of the apparatus of the invention.

1-3. FIGS. 6A to 5A are side, front, and top views of a preferred embodiment of the apparatus of the present invention. The stage consists of a cylindrical mixer-separating space 2 and a closed auxiliary space 3 connected to the lower part thereof via a pipe 4 in a transportable manner. Approx. The material passageways 5 are provided at an angle of 70' to pass the lighter phase. In order to mix the phases in the mixer-separator space 2, a pneumatic mixing element 18 (aerolift) is connected to the device body from the outside, into which air flow can be introduced through the valve 25. Figure 1 shows the nominal charge level 26 of the apparatus. Above the nominal charge level 26 of the auxiliary compartment 3, there is a closed gas space, to which tops are connected by monostats of different pressures via valves 12a and 12b. The pipe 4, which is connected to the bottom of the mixer-separator space 2, is provided with a connector 7 for discharging the heavier phase. Connected to the connector 7 is a pneumatic spout 22 (aerolift) operating on the principle of air pressure lifting, into which air flow can be introduced through valve 19.

HU 203 843 A

During operation of the apparatus, the phases in the mixer-separator space 2 of the stage filled up to the nominal filling level 26 are mixed by means of an air-operated pneumatic mixing element 18 introduced through the valve 25. After mixing is switched off, the phases are spontaneously separated and the lighter phase is layered on top. Air is then introduced into the auxiliary space 3 via valve 12a and the pressure in the enclosure is increased. As a result, the equilibrium of the transport vessel is disrupted, the level in the mixer-separator space 2 rises, and the lighter phase deposited on the top exits the lower material passage 5 by spontaneous gravity flow. The lighter phase is fed through the upper material passage 5 from the adjacent step of the same configuration located higher. The heavier layer layered down is discharged through the connector 7 into the pneumatic pump 22 via an air flow through the valve 19. The heavier phase may be added either to the mixer separation space 2 or to the auxiliary space 3.

Figure 4 is a schematic front view of a six-stage apparatus. The unit is made up of I-VI stages connected in a slope row. The lighter phase passes from the dispenser 17 to the stage I, flows through the material transfer channels 5 by gravity between the stages, and is finally passed to the vibrating screen 28. The heavier phase is conveyed by the mechanical pump 29 through the connector 27 to the VI stage, passed between the individual stages by the pneumatic pump 22 (Fig. 2) and discharged from the I stage through the 7 connector.

Figure 5 is a plan view of the apparatus of Figure 4. Each of the stages I to VI comprises a pneumatic mixing element 18 which performs an external circulation mixing of the phases at the mixing rate and a pneumatic pump 22 which feeds the heavier phase into the adjacent higher stage.

6-9.

Figures 1 to 5 show two variants of the connection of the pneumatic mixing elements 18 and the pumps 22. In the embodiment of Figures 6 and 7, the heavier phase is fed from the bottom of the stage to the adjoining higher stage mixer separation space 2 by means of the pneumatic pump 22. 8 and 9, the heavier phase is returned from the bottom of the stage to the auxiliary space 3 of the adjacent higher stage. Of course, the pneumatic mixing elements 18 recycle the material into the mixing-separating space 2 of their respective stages.

As an example of periodic operation of the unit! 10 is illustrated in Figure 10. The individual steps are as follows:

(a) Mixing

By opening the valves 25, the external pneumatic mixing elements 18 of each stage are switched on and the phases are mixed for a predetermined period. During mixing, the heavy phase introduced into the mixer-separator space 2 loosens the light phase floating on top of the solution from top to bottom. Increasing the flow rate, the pneumatic mixer 18 recirculates the suspension.

(b) Separation

When the valves 25 are closed, the stirring is stopped and then waiting for the prescribed time. During this time, the spontaneous separation of phases occurs.

c) light phase transfer

Moving backward from the lowest stage, the valve 12a of each stage is opened successively and the fluid level of the auxiliary space 3 is pressed from the base level L to the set lower transmission level G. As a result, the level of the mixer-separator space 2 is increased and the corresponding volume of light phase flows into the adjacent lower stage. Upon reaching the lower transfer level G, valve 12a is closed and valve 12b is opened. This removes the overpressure in the gas space 11 and restores the balance of the approaching vessel. The printing can be repeated several times in order to completely transfer a given volume of light phase. The step is performed in all stages starting from the lowest stage VI upwards and finally a light phase is introduced from the outside in stage I (Fig. 4). In the stages where the light phase has been added, the pneumatic mixing element 18 for circulating mixing is immediately switched back on.

d) Mixing

For the prescribed time, as in step a).

e) Separation

For the prescribed time as in step b).

f) Transmission of difficult phase

First, a heavy phase is dispensed from the lowest stage I (Fig. 4) with the pneumatic pump 22 to a pre-set level. Then, from stage Π, with the associated pneumatic pump 22, the heavy phase is added to stage I so that the baseline L is restored, and then the heavy phase is withdrawn in series. Finally, the mechanical pump 29 also charges the lowest stage VI. Thereafter, the apparatus proceeds with step a)

The equipment is operated by a microcomputer using a control algorithm. In addition to the above, the control system gives an alarm or alarm. stops when the lower boundary A or the upper boundary F is reached.

Another embodiment of the apparatus of the invention. 4a. In this solution, the device is made up entirely of conventional, mechanically mixed units and the material is transported by mechanical pumps.

The apparatus comprises four mixer-separating spaces 2, each with a 30-degree inclination, with mechanical mixing elements 20, and four

GB 203 843 The chanical consists of three I-IV stages consisting of 3 auxiliary spaces with mixing elements. The auxiliary spaces 3 are connected to the lower part of the mixer-separating spaces 2 by pipes 4 with a valve 13. The light phase passes step by step through the material passage 5. The heavy phase is fed by the mechanical pump 29 via the connector 27 to the auxiliary space 3 of the stage IV. The heavy phase discharged from the bottom of the mixer-separator spaces 2 through the connectors 7 is also transmitted by the mechanical pumps 21 via the valves 30 to the auxiliary space 3 of the adjacent higher stage. from stage I to the environment and through the valves 31 into the auxiliary space 3 of its own stage.

The operation of the tub is controlled by the liquid level in the auxiliary space 3. The steps of operation are as follows;

(a) Mixing

Mechanical nozzles 20 of the mixer-separation spaces 2 are performed on a nerve.

(b) Separation

By switching off the mixing elements 20 of the mixer-separation spaces 2, the system is allowed to rest for a certain period of time.

c) Forwarding

From the auxiliary space 3 of the stage AIV, a volume level (controlled by volume) corresponding to the amount of light phase to be dispensed is passed through the valve 13 and the pipe 4 into the mixing space 2.

The pump 29 delivers a given (level controlled) amount of heavy phase into the auxiliary space (3).

With the AIV stage pump 21 through the open valve 31 while the valve 30 is closed toward stage ΙΠ, a heavy phase is returned to the auxiliary space 3 of stage IV to restore its level. The valve 30 is then opened and the valve 31 is closed and the auxiliary space 3 of stage IH is leveled.

From the auxiliary space 3 of stage H1, a heavy phase (volume controlled) corresponding to the amount of light phase to be dispensed is discharged into the mixer-separator space 2.

- With the stage 21 pump (valve 30 closed, valve 31 open), a certain (level-controlled) amount of heavy phase is added to the auxiliary space 3 of the ΠΙ stage, then the valve 30 is opened and the valve 31 is closed to level 3 auxiliary space .

- We went from step Π to step I as above.

Finally, a heavy phase from stage I is dispensed through valve 30.

The following examples illustrate the use of the invention.

Example 7

1-3. 3 to 4, the auxiliary spaces 3 have a diameter of 300 mm and a total height of 2000 mm. Sulfonated cation exchange resin (1001 / h) in 90% sulfuric acid solution (65 kg / h) was added to stage I of the apparatus. Sulfuric acid solution (167 kg / h) at a concentration of 48-50% by weight is introduced into stage IV. The resin floats on top of the solution in all stages. 80 g% sulfuric acid is added from Stage I at a flow rate of 82 kg / h, and 50 g% sulfuric acid is added from Stage IV at 1001 g / h ion exchange resin at 150 kg / h.

The operating cycles of the equipment are as follows:

a) Mixing: 4 minutes.

b) Phase separation: 4 minutes.

c) Resin dosage

From Grade IV to vibrito screen

ΙΠ from gear to gear IV

From gear I to gear feeder to gear I

d) Stirring: 4 minutes

e) Phase separation: 4 minutes.

(f) Dosage of solution

Out of grade I

From Q to I

From Π gear to Π gear

From stage IV to stage val with pump to stage IV

The resin is dosed with air introduced into the auxiliary space, based on the level measured in the auxiliary compartment. Pneumatic pumps and mixtures are used to add the solution and mix the mixer-separation spaces.

Example 2

1-7. 6 and 10 show a mixer-separation chamber 90 mm in diameter, auxiliary spaces 40 mm in diameter and a total height of 400 mm. Carbon tetrachloride containing 5% (w / w) ethyl alcohol (1 kg / h) was added to stage I of the apparatus. The purpose of six-step countercurrent liquid-liquid extraction is to remove ethanol from the carbon tetrachloride phase.

The operating cycles of the equipment are as follows:

- Mixing (6 minutes),

- Phase separation (6 minutes),

- addition of water from stage VI, stage V to stage VI, stage IV to stage V, stage ΙΠ to stage IV, stage Π to stage,, stage I to stage,, stage I,

- Mixing (6 minutes),

- Phase separation (6 minutes)

- Addition of carbon tetrachloride from stage I, stage Π to stage I, stage ΠΙ to stage Π, stage VI to stage IH, stage V to stage IV, stage VI to stage V, stage VI.

The dosing of water is based on the level of air introduced into the auxiliary space, based on the levels measured in the auxiliary compartment. For the addition of the carbon tetrachloride phase or for mixing the mixer-separation spaces

GB 203 843 Pneumatic pumps and mixers are used.

From grade I, approx. 1.9 kg / h of carbon tetrachloride containing 05% ethyl alcohol, from about grade VI to ca. Water (1.1 kg / h) containing 9.08% ethyl alcohol was removed.

An advantage of the method and apparatus according to the invention is that it is possible to achieve, by means of simple construction elements, a multi-stage, quasi-continuous, countercurrent contact between a liquid phase and a solid and / or immiscible liquid of varying density. The present invention is applicable to countercurrent contacting of solids that settle in and liquid out of the liquid and that the liquid phase (s) may also contain gas bubbles. The transfer of the lighter phase between stages involves the introduction of a heavier phase which requires only the opening and closing of the shut-off valves. In the first embodiment, the fittings meet only the gas auxiliary phase. In addition to mechanical pumps, pneumatic pumps may be used to transfer the heavier phase. It is also possible to have an embodiment which does not contain any mechanically moving elements in contact with the phases.

The invention is, of course, not limited to the exemplary embodiments of the process or to the embodiments of the apparatus shown in the drawings, but may be practiced in many other ways.

Claims (16)

A process for contacting a liquid phase with a different density solid and / or immiscible liquid phase by stepwise, quasi-continuous, countercurrent contact, wherein the lighter phase is introduced into the first stage of the cascade of several series-connected stages and the heavier phase is introduced into the last stage. in stages, the phases are mixed, spontaneously separated by gravity, the separated phases are at least partially subdivided countercurrently between adjacent stages, and the first and second stages of the cascade. characterized in that mixing and separation of the phases is carried out in each stage in a mixer-separator space (2), the lighter phase is introduced from the outside into the mixer-separator space (1) of first stage (I), in space (2) at least once per cycle and then separating, from the last stage to the first stage, step by step in each stage (I-VI), after phase separation, into the lower part of the mixer-separating space (2) from an auxiliary stage ), a predetermined amount of heavier phase is introduced, thereby displacing a corresponding amount of lighter phase from the mixer-separator space (2), gravitationally introducing it into the adjacent further stage's mixer-separator space (2). dispensing from the last stage, while the heavier phase is introduced into the mixing separation space (2) and / or auxiliary space of the final stage, from the bottom of the mixing separation space (2) of each stage into the mixing separation space (2) of the preceding stage; conveyed to its auxiliary space (3) and dispensed from the bottom of the mixer separation space (2) of the first stage (I). Method according to claim 1, characterized in that the heavier phase displacement of the lighter phase is introduced from the auxiliary space (3) connected to the mixer separator space (2) by increasing the pressure of the gas space above the heavier phase into the mixer separator space (2). , then relieve the overpressure to restore the balance of the vessel. Method according to claim 2, characterized in that the successive stages are successively displaced and dispensed in successive stages in all stages, followed by successive dispenses of the heavier phase sequentially from the first stage (0). Method according to claim 1, characterized in that the heavier phase displacing the lighter phase is introduced from the auxiliary space (3) into the mixer separation space (3) by gravity. 5. The method of claim 4, wherein starting from the last stage, the lighter phase is displaced and the heavier phase is delivered in each stage. Method according to claim 4, characterized in that a portion of the heavier phase which has been further delivered from the mixing-separating space (2) of each stage is returned to the auxiliary space (3) of the stage. 7. A method according to any one of claims 1 to 3, characterized in that level sensing is carried out in the mixer-separator space (2) and / or the auxiliary space (3), and the dosages are controlled accordingly. 8. Apparatus for contacting a liquid phase and a solid and / or immiscible liquid phase having a different density, in a quasi-continuous, countercurrent contact, in particular as shown in FIGS. A method according to any one of claims 1 to 5, wherein the apparatus comprises series-connected stages with mixing elements, the bottom of which is connected to the previous stage via connectors and pumps for transferring the heavier phase, characterized in that each stage (I-VI) is a mixing ) and a lower auxiliary space (3) connected therewith to the lower part thereof, and auxiliary space (3) connected to the heavier phase via a pipe and fittings controlling the flow of the heavier phase through the pipe (4), preferably with valves (12a, 12b, 13) provided with buttermilk stitches, furthermore the stages (I-VI) are arranged in a sloping row, and the upper parts of the mixing-separating spaces (2) of the adjacent stages (I-VI) are used for feeding and dispensing the lighter phase. they are connected to each other and / or their surroundings by means of sloping material transfer channels (6) suitable for gravitational transmission between the respective stages (I-VI). Apparatus according to Claim 8, characterized in that the auxiliary compartment (3) is closed at the top and is disposed adjacent to the mixer-separating space (2) in a manner communicating therewith and sits in a gas inlet. gas discharge fittings, preferably valves (12a, 12b). Apparatus according to claim 9, characterized by 843 As the auxiliary space (3) is open and is located above the mixer separation space (2) and is connected to it via a pipe (4) provided with a shut-off valve, preferably with a valve (13). Apparatus according to claim 8 or 9, characterized in that the bottom of the mixing separation space (2) is provided with a mixing separation space (2) and / or auxiliary space (3) adjacent to the higher stage through the pump (22). connected. Apparatus according to Claim 8 or 10, characterized in that the bottom of the mixing-separating space (2) through the pump (21) and shut-off valves, preferably through valves (30,31), with auxiliary space of the same stage and adjacent higher stage (3) is connected. 13. A 8-13. Apparatus according to any one of claims 1 to 3, characterized in that a pump (4) is provided in the pipe (4) connecting the auxiliary space (3) with the mixing space (2). 14. A10. Device according to claim 1, characterized in that a mixing element (14) is arranged in the auxiliary space (3). 15. A 8-14. Apparatus according to any one of claims 1 to 4, characterized in that the pumps (21,22) and the mixing elements (14, 18, 20) are of mechanical and / or pneumatic design. 16. Device according to any one of claims 1 to 3, characterized in that level sensors are arranged in the auxiliary spaces (3).