Method of phase mixing of two liquid phases, and device therefor

Abstract

To provide a method of phase mixing of two liquid phases, capable of arbitrarily setting, a ratio of volume of each liquid phase which is subjected to phase mixing, completely independently from a ratio of a liquid feeding speed of each liquid phase in a practical functional relationship with respect to an extraction ratio and a reverse extraction ratio.SOLUTION: In operation for feeding two liquid phases into one reaction vessel for performing phase mixing, in the reaction vessel, a region of a phase mixing and a region of a phase separation are made coexist in a constant range.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for phase mixing, characterized in that the volume ratio of each liquid phase participating in phase mixing in a single reaction vessel can be set arbitrarily, completely independently of the ratio of the liquid phase flow rates, which are in an effective functional relationship with the extraction rate and stripping rate. [Background technology]

[0002] Two-liquid phase separation, consisting of two immiscible liquid phases, is widely used in chemical techniques such as solvent extraction. For example, it is one of the most important technologies for separating and refining metallic elements and organic compounds, supporting key industries such as the metallurgical and chemical industries, and for separating and refining rare metals, which are essential in high-tech industries.

[0003] On the other hand, solvent extraction is prone to oil entrainment in wastewater, making it a method with a large environmental impact. Furthermore, depending on the volume ratio of the aqueous and oil phases being mixed, the region involved in the phase mixing (called the mixed phase) may be unstable, the mixed phase may be difficult to flow, or phase separation after the extraction reaction may be difficult, making solvent extraction less efficient.

[0004] Phase mixing refers to the mixing of two immiscible liquid phases that form an interface by stirring, shaking, or the like. This results in the formation of finer liquid phases and an increased interface area, resulting in an emulsion. In an emulsion, the interphase transfer of substances is promoted, making it easier to reach chemical equilibrium in the extraction reaction. While stirring and shaking are common methods of phase mixing, a method of phase mixing until an emulsion is reached by droplet ejection has also become known (see, for example, Patent Documents 1 and 2). Phase separation refers to the re-separation of two mixed liquid phases into their respective liquid phases. Common methods include natural separation using gravity and buoyancy, and mechanical separation using centrifugal force.

[0005] In a batch test, an aqueous phase containing the component to be extracted and an oil phase mainly composed of a water-immiscible solvent are placed in a container such as a test tube at a fixed volume ratio and shaken thoroughly until the extraction reaction reaches chemical equilibrium. The extraction rate of the component to be extracted into the oil phase depends on the volume ratio of the two phases at that time (here, the volume ratio of the oil phase to the aqueous phase at this time is referred to as the effective oil / aqueous phase volume ratio). In other words, at the time of chemical equilibrium of the extraction reaction, the extraction rate (= E%) and the effective oil / aqueous phase volume ratio (= R V The relationship between the concentration of a solute in the oil phase and the concentration of a solute in the aqueous phase is expressed as E% = 100 × R via the partition ratio (the ratio of the concentration of the solute in the oil phase to the concentration of the solute in the aqueous phase = D). V ×D / (R V × D + 1). For example, if you want to increase the extraction rate of the target component, you can increase the effective oil / water volume ratio.

[0006] When industrially performing continuous solvent extraction while pumping the aqueous and oil phases, the ratio of the oil phase to the aqueous phase pumping rate (referred to as the oil / aqueous phase pumping rate ratio) usually corresponds to the oil / aqueous phase volume ratio involved in the phase mixing (referred to as the oil / aqueous phase volume ratio in the mixed phase), which coincides with the effective oil / aqueous phase volume ratio mentioned in the above-mentioned batch test. In other words, in conventional continuous solvent extraction methods and apparatuses, the relationship of oil / aqueous phase pumping rate ratio = oil / aqueous phase volume ratio in the mixed phase = effective oil / aqueous phase volume ratio holds.

[0007] In this case, the volume ratio of the aqueous phase to the oil phase during phase mixing, i.e., the volume ratio of the two phases in the mixed phase, is determined by the ratio of the liquid flow rates of the two phases. On the other hand, the physical properties of the mixed phase (stability, phase separation, fluidity, likelihood of entrainment, etc.) depend on the volume ratio of the aqueous phase to the oil phase that form the mixed phase. In other words, in conventional methods and apparatuses, the physical properties of the mixed phase are dependent on the ratio of the liquid flow rates of the two phases. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 5305382 [Patent Document 2] Patent No. 5565719 Summary of the Invention [Problem to be solved by the invention]

[0009] When two liquid phases with different volumes are mixed in a single reaction vessel, the liquid phase with the smaller volume is more likely to be mixed with the other liquid phase as fine droplets. In other words, the liquid phase with the smaller volume is more likely to experience so-called entrainment.

[0010] Furthermore, the physical properties of mixtures consisting of two liquid phases often vary significantly depending on the mixture ratio. For example, in a mixture consisting of two liquid phases, water and oil, the stability, flowability, likelihood of entrainment, and time required for phase separation can vary significantly depending on whether the mixture is water-rich or oil-rich.

[0011] In particular, in multi-stage equipment where unit operations are repeated across multiple stages, the likelihood of entrainment and differences in the physical properties of the mixed phases described above significantly affect the feasibility of the equipment or plant. This can lead to problems such as inability to proceed to the next stage due to inability to separate the phases or flow, or inability to remove impurities according to the number of stages set due to entrainment.

[0012] In a typical phase mixing method in which a phase mixing region (mixed phase) is created throughout a single reactor, the ratio of the volumes of the liquid phases that make up the mixed phase in the reactor coincides with the ratio of the liquid feed rates of the liquid phases. That is, a liquid phase with a slow liquid feed rate has a small volume in the mixed phase, and therefore is prone to entrainment. Furthermore, depending on the ratio of the liquid feed rates of the liquid phases, the mixed phase may be unstable or difficult to flow, which may cause operational problems. Furthermore, the likelihood of entrainment or the long duration of phase separation may cause problems with drainage, etc.

[0013] In actual solvent extraction processes, it is often necessary to increase the oil phase flow rate to increase the extraction rate into the oil phase, or to increase the aqueous phase flow rate to increase the stripping rate into the aqueous phase, and each time such adjustments are made, the above-mentioned problems arise. Furthermore, since these problems cannot always be solved, the solvent extraction process itself may not be viable.

[0014] Therefore, as a result of extensive research aimed at solving these problems, the researchers discovered that by utilizing a mechanism in which phase mixing and phase separation occur simultaneously in a single reaction vessel, the ratio of the volumes of the liquid phases involved in the phase mixing can be arbitrarily set completely independently of the ratio of the liquid flow rates of the liquid phases, and that the ratio of the liquid flow rates of the liquid phases has an effective functional relationship with the extraction rate or stripping rate.

[0015] That is, by adjusting the liquid sending rate ratio, it is possible to improve the extraction rate or back-extraction rate, and at the same time, it is possible to arbitrarily determine the volume ratio of the aqueous phase and the oil phase involved in the phase mixing so that the mixed phase has high stability, fluidity, and phase separation properties, and is less likely to cause entrainment.

[0016] Therefore, the object of the present invention is to provide a method and apparatus for mixing two liquid phases, which allows the volume ratio of each liquid phase participating in the phase mixing to be set arbitrarily and completely independent of the ratio of the liquid flow rates of each liquid phase, which has an effective functional relationship with the extraction rate and stripping rate. Regarding the apparatus, the present invention is particularly focused on multi-stage apparatus, where the susceptibility to entrainment and the influence of differences in the physical properties of the mixed phases become more pronounced. [Means for solving the problem]

[0017] By utilizing a mechanism in which phase mixing and phase separation occur simultaneously in a single reaction vessel, the volume ratio of each liquid phase involved in the phase mixing can be set arbitrarily, completely independent of the liquid flow rate ratio of each liquid phase, and the liquid flow rate ratio of each liquid phase can be made to have an effective functional relationship with the extraction rate or stripping rate.

[0018] A fundamental feature of the present invention is that, in an operation of mixing two liquid phases while feeding them into a single reaction vessel, a phase mixing region and a phase separation region coexist within a certain range within the reaction vessel, so that the oil / aqueous phase volume ratio in the mixed phase where the aqueous phase and the oil phase participate in the phase mixing in the phase mixing region (mixed phase) can be set arbitrarily, completely independent of the oil / aqueous phase feed rate ratio. Here, the gist of the present invention is that the oil / aqueous phase feed rate ratio can ideally be regarded as the effective oil / aqueous phase volume ratio, which is a parameter in the chemical equilibrium function for extraction yields and stripping yields. [Effects of the Invention]

[0019] In the past, in terms of the stability, fluidity, phase separation, or entrainment of the mixed phase, the volume ratio of the aqueous phase to the oil phase involved in the phase mixing had to be set under unfavorable conditions. However, the method and apparatus of the present invention make it possible to arbitrarily set the volume ratio under favorable conditions that do not cause these problems.

[0020] In conventional methods, the aqueous phase and the oil phase are mixed throughout the reaction vessel, and the mixed phase flows into a stationary vessel located next to the reaction vessel, where the two phases are separated by gravity. In contrast, in the method of the present invention, the mixed phase and the separated aqueous and oil phases coexist within a certain range in the reaction vessel, so no stationary vessel is required, and there is no need to wait for the mixed phase to separate by gravity.

[0021] Furthermore, as will be described below as the gist of the present invention, in conventional methods, when the liquid feed rate of the aqueous phase, the oil phase, or both is changed, the volume ratio of the aqueous phase to the oil phase in the mixed phase also changes, and accordingly, the physical properties of the mixed phase and the state of entrainment also change. Therefore, in order to accommodate this change, it is essential to perform an operation such as adjusting the interface position in the stationary vessel. In contrast, in the method of the present invention, in which the volume ratio of the aqueous phase to the oil phase in the mixed phase is not affected by the liquid feed rates of the two phases, the physical properties of the mixed phase and the state of entrainment are always constant, and therefore the various adjustment operations (e.g., adjusting the interface position in the stationary vessel) that are essential in conventional methods due to changes in the liquid feed rate are not necessary.

[0022] Furthermore, in conventional methods, the aqueous phase and the oil phase are mixed throughout the entire reaction vessel, which inevitably exposes the mixed phase (the region disturbed by the phase mixing) to air. In contrast, in the method of the present invention, the mixed phase is always located below the phase-separated oil phase (the undisturbed region), so the disturbed mixed phase does not come into contact with air. Therefore, for example, when a target component that is easily oxidized (easily affected by oxygen in the air) is the target of solvent extraction, the extraction operation can be performed while suppressing the influence of oxygen in the air. [Brief explanation of the drawings]

[0023] [Figure 1(A)] Relationship between the extraction rates of Tb, Dy, and Ho and the effective oil / aqueous volume ratio in batch tests or the oil / aqueous flow rate ratio in continuous flow tests. [Figure 1(B)] Relationship between the extraction rates of Er, Tm, Yb, and Lu and the effective oil / water volume ratio in batch tests or the oil / water flow rate ratio in continuous flow tests. [Figure 2] A mechanically agitated phase mixing unit with upper and lower agitation liquid flow interruption plates, in which the light liquid phase is introduced from above while being discharged from above, and the heavy liquid phase is introduced from below while being discharged from below. [Figure 3]A mechanically agitated phase mixing unit with a mixing liquid flow interrupter only at the bottom, in which the light liquid phase is introduced from below while being discharged from above, and the heavy liquid phase is introduced from below while being discharged from below. [Figure 4] A mechanically agitated phase mixing unit with agitation liquid flow interruption plates above and below, in which the light liquid phase is introduced from below while being discharged from above, and the heavy liquid phase is introduced from below while being discharged from below. [Figure 5] Figure 2 shows the distribution of phase mixing and phase separation regions in the mechanically stirred phase mixing unit. [Figure 6] A three-stage mechanically agitated phase mixing device with upper and lower agitation liquid flow interruption plates, in which the light liquid phase is introduced from above while being discharged from above, and the heavy liquid phase is introduced from below while being discharged from below. [Figure 7] A three-stage mechanically agitated phase mixer with a mechanism in which the light liquid phase is introduced from below while being discharged from above, and the heavy liquid phase is introduced from below while being discharged from below, with an agitation liquid flow interrupter only at the bottom. [Figure 8] The distribution of the phase mixing and phase separation regions in the three-stage mechanically stirred phase mixing device shown in Figure 7. [Figure 9] A droplet ejection type phase mixing unit with flow path cross-sectional area changing plates on the top and bottom, in which the light liquid phase is introduced from below while being discharged from above, and the heavy liquid phase is introduced from below while being discharged from below. [Figure 10] Figure 9 shows the distribution of phase mixing and phase separation regions in the droplet ejection phase mixing unit. [Figure 11] A three-stage droplet ejection type phase mixing device with flow path cross-sectional area changing plates at the top and bottom, in which the light liquid phase is introduced from below while being discharged from above, and the heavy liquid phase is introduced from below while being discharged from below. [Figure 12] Figure 11 shows the distribution of phase mixing and phase separation regions in a three-stage droplet ejection type phase mixing device. DETAILED DESCRIPTION OF THE INVENTION

[0024] Typically, the volume ratio of the aqueous phase to the oil phase in the phase mixing region in solvent extraction is equal to the ratio of the liquid transport rates of the aqueous phase and the oil phase fed into the phase mixing region. For example, in the mixer section of a mixer settler, which is a typical industrial solvent extraction device, the entire mixer section forms the phase mixing region (mixed phase), and the volume ratio (volume ratio of the two phases in the mixed phase) and the liquid transport rate ratio (ratio of the liquid transport rates of the two phases) are equal.

[0025] In this case, the oil / aqueous phase flow rate ratio is equal to the oil / aqueous phase volume ratio in the phase mixing region (mixed phase), and can be considered to be the same as the effective oil / aqueous phase volume ratio (oil / aqueous phase volume ratio in the batch test mentioned above), which is functionally related to the extraction rate and back-extraction rate. In fact, when the liquid in the phase mixing region (mixed phase) is sampled with a dispenser such as a pipette and then allowed to separate, the oil / aqueous phase volume ratio at that time coincides with the oil / aqueous phase flow rate ratio.

[0026] On the other hand, if the phase mixing region in the reaction vessel where the aqueous phase and the oil phase participate in phase mixing is partial and remains within a certain range, the relationship that the mixing volume ratio and the liquid feed rate ratio are equal does not hold. In other words, in a system in which phase mixing and phase separation proceed simultaneously in a single reaction vessel and each region coexists within a certain range, the ratio of the liquid feed rates of the aqueous phase and the oil phase can be freely changed while maintaining a constant volume ratio of the aqueous phase to the oil phase in the phase mixing region.

[0027] In this case, when the liquid in the phase mixing region (mixed phase) was actually sampled using a pipette or other dispenser and then phase separated, the oil / aqueous volume ratio remained constant, independent of the oil / aqueous flow rate ratio. For this reason, the oil / aqueous flow rate ratio has not been discussed in relation to the effective oil / aqueous volume ratio (the oil / aqueous volume ratio in the batch test described above). In other words, the oil / aqueous volume ratio in the mixed phase is maintained at the set state, such as the volume ratio of the two phases installed in the device container, regardless of the oil / aqueous flow rate ratio. Therefore, it was difficult to imagine that a difference in the "mixing method," i.e., a different flow rate while the oil / aqueous volume ratio in the mixed phase remains unchanged, would result in a difference in the effective oil / aqueous volume ratio, which should be identical to the oil / aqueous volume ratio in the mixed phase.

[0028] For example, if the oil / aqueous volume ratio in the phase mixing region (oil / aqueous volume ratio in the mixed phase) is set to 1 / 1 and the oil / aqueous flow rate is increased while the aqueous phase flow rate remains unchanged, the extraction rate actually increases. However, this phenomenon was interpreted as occurring because phase mixing is promoted and the mixture approaches chemical equilibrium. In other words, the above assumption was that the effective oil / aqueous volume ratio is 1 / 1. Therefore, in a system in which phase mixing and phase separation coexist within a certain range within the same reaction vessel, the relationship between the effective oil / aqueous volume ratio and the oil / aqueous flow rate ratio has not been considered until now.

[0029] On the other hand, even if the oil phase / aqueous phase volume ratio in the mixed phase is always constant, if the ratio of the oil phase to the aqueous phase flow rate increases, the oil phase will have more opportunities to come into contact with the aqueous phase at a frequency corresponding to the flow rate ratio. Therefore, while the oil phase / aqueous phase volume ratio in the mixed phase is maintained constant, the oil phase / aqueous phase flow rate ratio can also be considered to correspond to the above-mentioned effective oil phase / aqueous phase volume ratio.

[0030] The first significance of the present invention is the discovery that even in cases where the oil / aqueous phase volume ratio in the phase mixing region (oil / aqueous phase volume ratio in the mixed phase) is always maintained constant regardless of the liquid feed rates of both phases, the oil / aqueous phase liquid feed rate ratio corresponds to the effective oil / aqueous phase volume ratio (oil / aqueous phase volume ratio in the batch test described above). In fact, in a system in which phase mixing and phase separation proceed simultaneously in a single reaction vessel, it was found that even though the oil / aqueous phase volume ratio in the mixed phase is constant, the oil / aqueous phase liquid feed rate ratio corresponds to the effective oil / aqueous phase volume ratio, and the rare earth extraction rate changes according to this liquid feed rate ratio. The results are shown in Example 1. [Example]

[0031] Rare earth extraction test using droplet ejection unit

[0032] The aqueous phase consisted of a pH 2 nitric acid solution containing 100 ppb each of Tb, Dy, Ho, Er, Tm, Yb, and Lu, and the oil phase consisted of an organic solution containing 35 mM 2-ethylhexyl (2-ethylhexyl)phosphonate (PC88-A) dissolved in a mixed solvent of 90 vol% D70 (alkane solvent) and 10 vol% 2-ethylhexanol. The rare earths extracted into the oil phase were back-extracted with 0.5 M nitric acid, and their concentrations were measured using an inductively coupled plasma optical emission spectroscopy (ICP-OES).

[0033] The extraction rate (%) of the rare earth elements relative to the oil / aqueous phase flow rate ratio was determined by a continuous flow test using a droplet-jet unit, and this was compared with the extraction rate (%) of the rare earth elements relative to the effective oil / aqueous phase volume ratio obtained by a batch test. That is, it was verified whether changes in the oil / aqueous phase flow rate ratio in the continuous flow test correspond to changes in the effective oil / aqueous phase volume ratio in the batch test, and whether changing the oil / aqueous phase flow rate ratio would result in an extraction rate (%) of the rare earth elements similar to that obtained when the effective oil / aqueous phase volume ratio was changed.

[0034] First, in the continuous flow test, the oil phase flow rate was fixed at 30 mL / min, and the aqueous phase flow rate was varied to 7.5, 15, 30, 60, and 90 mL / min, resulting in an oil / aqueous phase flow rate ratio (oil phase flow rate / aqueous phase flow rate) of 4, 2, 1, 1 / 2, and 1 / 3, respectively.

[0035] In the continuous flow test, the oil / aqueous phase volume ratio in the phase mixing region (mixed phase) was set to 1 / 1. That is, equal volumes of aqueous and oil phases were placed in each droplet-ejecting unit. The oil / aqueous phase volume ratio in the mixed phase can be set arbitrarily depending on the volume ratio of the aqueous and oil phases placed.

[0036] On the other hand, in the batch test, the effective oil / aqueous phase volume ratio (the volume ratio of the oil / aqueous phase actually placed in the test tube) was set to 4, 2, 1, 1 / 2, and 1 / 3, as in the continuous flow test, and the mixture was shaken sufficiently until the extraction reaction reached chemical equilibrium.

[0037] Furthermore, in the continuous flow test, whenever the oil phase / aqueous phase flow rate ratio was changed, the mixed phase was sampled with a pipette to confirm that the oil phase / aqueous phase volume ratio had not changed from the set value of 1 / 1.

[0038] Figure 1(A) and Figure 1(B) show a comparison of the results of the continuous flow test and the batch test. Figure 1(A) shows the results for Tb, Dy, and Ho, and Figure 1(B) shows the results for Er, Tm, Yb, and Lu.

[0039] The extraction rates (%) of each rare earth element in the continuous flow test were slightly lower than those in the batch test because the extraction reaction did not reach chemical equilibrium, but the relationship between the oil / aqueous phase pumping rate ratio in the continuous flow test and the effective oil / aqueous phase volume ratio in the batch test and the rare earth extraction rate (%) was in good agreement. In other words, it was shown that, ideally, the oil / aqueous phase pumping rate ratio can be considered to be the same as the effective oil / aqueous phase volume ratio.

[0040] In ordinary continuous phase mixing (e.g., phase mixing in a mixer settler), the oil / aqueous phase liquid flow rate ratio, which can be regarded as the effective oil / aqueous phase volume ratio, is uniquely equal to the oil / aqueous phase volume ratio in the mixed phase. However, the results shown in Example 1 demonstrate that the method of the present invention allows the oil / aqueous phase volume ratio in the mixed phase to be set to any value (e.g., 1 / 1), while at the same time allowing the effective oil / aqueous phase volume ratio to be freely changed by the oil / aqueous phase liquid flow rate ratio.

[0041] As described above, the present invention is based on a phenomenon that occurs in a system in which phase mixing and phase separation occur simultaneously in a single reaction vessel. Therefore, in the following, specific diagrams are used to illustrate examples of an apparatus in which phase mixing and phase separation occur simultaneously in a single reaction vessel, but the present invention is not limited to these.

[0042] In the diagrams shown below, the distinction between heavy and light liquid phases is used, rather than the distinction between water and oil phases. This is because, in the mechanism of the device of the present invention, it is important to determine which liquid phase has a higher specific gravity and is located lower across the interface. In many cases, the oil phase is lighter than the water phase, but conversely, there are also oil phases that are heavier than the water phase. In other words, the oil phase is not necessarily a light liquid phase, and the water phase is not necessarily a heavy liquid phase.

[0043] There is also a difference in the mechanism of phase separation between a mechanism that mixes phases by mechanical stirring (called the mechanical stirring type) and a mechanism that mixes phases by droplet ejection (called the droplet ejection type).

[0044] When phase mixing is achieved by mechanical agitation, phase separation can be promoted by altering the flow caused by the rotation of the impeller, examples of which are shown, but not limited to, in Figures 2, 3, and 4.

[0045] Figure 2 shows a mechanically agitated phase mixing device with two agitation liquid flow interruption plates on the top and bottom. The agitation blades of the mechanical agitator are positioned slightly below the vessel, and the light liquid phase is pumped in from above while being discharged from above, while the heavy liquid phase is pumped in from below while being discharged from below. This device is a unit that can be connected in series, and can be assembled into a multi-stage device with any number of stages (see Figure 6).

[0046] Figure 3 shows a mechanical agitator with the same impeller arrangement as in Figure 2, in which the light liquid phase is pumped in from below while being discharged from above, and the heavy liquid phase is pumped in from below while being discharged from below at the same time, and is a mechanical agitation-type phase mixing device with two agitation liquid flow interruption plates only at the bottom. Note that, like Figure 2, this device is a unit that can be connected in series, and can be assembled into a multi-stage device with any number of stages (see Figure 7).

[0047] Figure 4 shows a mechanical agitator with the same impeller arrangement as in Figures 2 and 3, in which the light liquid phase is pumped in from below while being discharged from above, and the heavy liquid phase is simultaneously pumped in from below while being discharged from below, and is a mechanical agitation-type phase mixing device with two agitation liquid flow interruption plates on the top and bottom. Note that, like Figures 2 and 3, this device is also a unit that can be connected in series, and can be assembled into a multi-stage device with any number of stages (not shown).

[0048] Hereinafter, as Example 2, an example of the distribution of phase-mixed regions and phase-separated regions coexisting in a mechanically stirred unit device will be shown. [Example]

[0049] Distribution of phase mixing and phase separation regions in a mechanically stirred unit device

[0050] The apparatus shown in Figure 2 was selected as a representative example. The heavy and light liquid phases were placed in the apparatus with equal volumes. The apparatus was operated as described above. The distribution of the phase mixing and phase separation regions was investigated. The results are shown in Figure 5. Water containing inorganic salts was used as the heavy liquid phase, and D70 (an alkane-based solvent) was used as the light liquid phase. The mechanical agitator's impeller was positioned slightly below the liquid-liquid interface. The volume ratio of the light liquid phase to the heavy liquid phase in the mixed phase generated by mechanical agitation was always 1 / 1, regardless of the light liquid phase / heavy liquid phase flow rate ratio. By actually sampling the mixed phase with a pipette, we found that the volume ratio of the light liquid phase to the heavy liquid phase in the mixed phase was always 1 / 1. Note that if the mechanical agitator's impeller is positioned too high or too low, the volume ratio of the light liquid phase to the heavy liquid phase in the mixed phase will not be 1 / 1; therefore, the impeller must be positioned appropriately.

[0051] As shown in Figure 5, in the apparatus shown in Figure 2, a cross-shaped region of phase mixing occurred in the center of the vessel. The action of two agitation liquid flow interruption plates, installed above and below, blocked the agitation liquid flow caused by the rotation of the agitation impeller, resulting in the appearance of two phase separation regions in the lower part of the vessel (on the right and left sides) and three in the upper part of the vessel (on the right, left, and upper center). Furthermore, although the ratio of the phase mixing region to the phase separation region varied slightly by changing the rotation of the agitation impeller, the ratio of the two regions was not affected by the ratio of the light liquid phase / heavy liquid phase flow rates.

[0052] Figures 2, 3, and 4 show mechanically agitated phase mixing equipment, which are designed as unit units with a structure that can be easily multi-staged. As examples of multi-staged equipment, a multi-stage (3-stage) equipment using the unit unit of Figure 2 is shown in Figure 6, and a multi-stage (3-stage) equipment using the unit unit of Figure 3 is shown in Figure 7, but this is not limited to these.

[0053] Figure 6 shows a three-stage device using the unit shown in Figure 2, with each stage separated by a stage divider. The top and bottom of the stage dividers are connected, with the light liquid phase moving to the next stage through the upper connecting port and the heavy liquid phase moving to the next stage through the lower connecting port.

[0054] Figure 7 shows a three-stage device using Figure 3 as a unit, and like Figure 6, each stage is separated by a stage divider. In Figure 6, the top and bottom of the stage divider are connected, but in Figure 7, the top is not connected, and the light liquid phase moves to the next stage by pumping rather than through a connecting port. On the other hand, the heavy liquid phase moves to the next stage through the connecting port at the bottom, just like in Figure 6.

[0055] In addition, an example of the distribution of phase-mixed regions and phase-separated regions coexisting in a mechanically stirred multi-stage device will be shown below as Example 3. [Example]

[0056] Distribution of phase mixing and phase separation regions in a mechanically stirred multi-stage reactor

[0057] As an example of a mechanically stirred multistage apparatus, the three-stage apparatus shown in Figure 7 was used. Figure 8 shows the distribution of the phase mixing and phase separation regions when the heavy liquid phase (water containing inorganic salts) and the light liquid phase (D70) were placed in the apparatus at equal volumes. The impellers of the mechanical stirrer were placed slightly below the liquid-liquid interface in each stage. Furthermore, in the multistage (three-stage) apparatus, as in the individual unit apparatus, the volume ratio of the light liquid phase to the heavy liquid phase in the mixed phase was always 1 / 1 in all stages, regardless of the ratio of the light liquid phase to the heavy liquid phase flow rate (the mixed phase was actually collected with a pipette).

[0058] As shown in Figure 8, in the apparatus shown in Figure 7, phase mixing regions were generated in the form of T-shaped structures connected in series. The action of two agitation liquid flow interruption plates installed below each stage blocked the agitation liquid flow generated by the rotation of the agitation impeller, resulting in the appearance of two phase separation regions (on the right and left) at the bottom of each stage. At the connecting section of each stage, the left and right phase separation regions (both of which are heavy liquid phase separation regions) are connected via a communication port installed below the stage divider plate. On the other hand, although no agitation liquid flow interruption plates were installed above the apparatus, the light liquid phase easily separated when pumped from below.

[0059] Next, we will show an example of an apparatus when phase mixing is achieved by droplet ejection. In the droplet ejection type, phase separation can be promoted by increasing the cross-sectional area of ​​the part through which the flow generated by droplet ejection passes. An example of such an apparatus is shown in Figure 9, but it is not limited to this.

[0060] Figure 9 shows a droplet ejection type phase mixing device in which a light liquid phase is pumped in from below through a droplet ejector while being discharged from above, and at the same time a heavy liquid phase is pumped in from below while being discharged from below, with one flow path cross-sectional area changing plate arranged above and one above. This device is a unit that can be connected in series, and can be assembled into a multi-stage device with any number of stages (see Figure 11).

[0061] Hereinafter, as Example 4, an example of the distribution of phase-mixed regions and phase-separated regions coexisting in a droplet-jetting type unit device will be shown. [Example]

[0062] Distribution of phase-mixed and phase-separated regions in a droplet-ejecting unit device

[0063] Figure 10 shows the results of investigating the distribution of phase mixing and phase separation regions when a heavy liquid phase (water containing inorganic salts) and a light liquid phase (D70) were placed in equal volumes in the droplet ejection-type unit device shown in Figure 9 and operated as described above. In this case, it was found by actually sampling the mixed phase with a pipette that the light liquid phase / heavy liquid phase volume ratio in the mixed phase generated by droplet ejection was always 1 / 1, regardless of the light liquid phase / heavy liquid phase liquid feed rate ratio.

[0064] As shown in Figure 10, the device shown in Figure 9 can produce a phase-mixed region over a wide area. The mixed phase generated by droplet ejection can be phase-separated by increasing the cross-sectional area through which the flow passes. Furthermore, the phase-separated region appears on either the left or right side of the upper or lower part of the device container. Furthermore, even if the liquid delivery speed of the heavy liquid phase, the light liquid phase, or both is changed, the ratio of the phase-mixed region to the phase-separated region hardly changes as long as it is within an appropriate liquid delivery speed range (as long as it is not too fast for the device size). Similarly, the ratio of the two regions is hardly affected by the ratio of the light liquid phase / heavy liquid phase delivery speeds as long as it is within an appropriate liquid delivery speed range.

[0065] Figure 9 shows a droplet jet type phase mixing device, but it is designed as a unit structure that can be easily made into a multi-stage device. As an example of multi-stage construction, Figure 11 shows a multi-stage (3-stage) device using Figure 9 as a unit, but this is not limited to this.

[0066] Figure 11 shows a three-stage apparatus using the unit shown in Figure 9. Each stage is separated by a stage divider, but the stages above the dividers are not connected, only the stages below. In other words, the light liquid phase moves to the next stage by pumping, not through a connecting port, while the heavy liquid phase moves to the next stage through a connecting port below.

[0067] In addition, an example of the distribution of phase-mixed regions and phase-separated regions coexisting in a droplet-jetting type multistage device will be shown below as Example 5. [Example]

[0068] Distribution of phase mixing and phase separation regions in a droplet-ejection multistage device

[0069] As an example of a droplet-jetting type multistage apparatus, the distribution of the phase mixing region and phase separation region when a heavy liquid phase (water containing inorganic salts) and a light liquid phase (D70) are placed in the multistage (three-stage) apparatus shown in Figure 11 at equal volumes is shown in Figure 12. In the multistage (three-stage) apparatus, as in the individual unit apparatus, it was found that the volume ratio of the light liquid phase to the heavy liquid phase in the mixed phase was always 1 / 1 in all stages, regardless of the ratio of the light liquid phase to the heavy liquid phase delivery rate (the mixed phase was actually collected with a pipette).

[0070] As shown in Figure 12, it was found that even in a multi-stage device, a wide range of phase mixing regions can be generated, just like in a single unit. The mixed phase generated by droplet ejection in each stage can be phase-separated by increasing the cross-sectional area through which the flow passes, and phase-separated regions appear on either the left or right side of the upper or lower part of each stage. The separated heavy liquid phase moves to the next stage through a communication port provided at the bottom of the stage divider that separates each stage, while the light liquid phase moves to the next stage by pumping rather than through a communication port. [Industrial Applicability]

[0071] This invention relates to a new method for mixing two liquid phases and an apparatus (particularly a multi-stage apparatus) that utilizes this method, which is expected to be used in a wide range of industrial fields, such as solvent extraction and oil-water separation. For example, it is expected to be used as a separation and purification technology in key industries such as the metals and chemical industries, in the manufacture of high-tech parts that require rare metals, such as lithium-ion batteries and neodymium magnets, and in rare metal recycling. [Explanation of symbols]

[0072] 1: Agitation liquid flow blocking plate 2: Flow path cross-sectional area change plate 3: Mechanical stirrer 4: Tier divider 5:Droplet ejector

Claims

1. A phase mixing method in which immiscible light and heavy liquid phases are mixed while being fed into a vessel, and at the same time, the phases are separated and solvent extraction is performed, in which phase-mixed regions are generated between regions where the light liquid phase is phase-separated, or between regions where the heavy liquid phase is phase-separated, or both, A phase mixing method characterized in that, in a state of chemical equilibrium, the liquid delivery rate ratio can be equated with the effective light liquid phase / heavy liquid phase volume ratio in a function of the extraction rate or stripping rate at the time of chemical equilibrium.

2. A method of phase mixing as described in claim 1, characterized in that the mixed phase is formed below or to the side or both of the phase-separated light liquid phase and above or to the side or both of the phase-separated heavy liquid phase.

3. A method of phase mixing as described in claim 1 or 2, characterized in that the phase mixing is carried out by mechanical stirring or droplet ejection.

4. A method of phase mixing, which comprises: feeding an immiscible light liquid phase and a heavy liquid phase into a container, causing the two phases to mix, and simultaneously separating the two phases to perform solvent extraction, and generating a region of the phase mixture between a region of the phase-separated light liquid phase and a region of the phase-separated heavy liquid phase, A method of phase mixing, characterized in that the phase-separated heavy liquid phase region or the phase-separated light liquid phase region, or both regions, are generated so that they are surrounded by the phase mixing region and at least one plate selected from the group consisting of an agitation liquid flow interruption plate, a flow path cross-sectional area changing plate, and a stage partition plate.

5. A method of phase mixing as described in claim 4, characterized in that the phase mixing is carried out by mechanical stirring or droplet ejection.

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