CN109692500B - Method for improving mass transfer rate of stable annular flow in microchannel - Google Patents
Method for improving mass transfer rate of stable annular flow in microchannel Download PDFInfo
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- CN109692500B CN109692500B CN201811653603.6A CN201811653603A CN109692500B CN 109692500 B CN109692500 B CN 109692500B CN 201811653603 A CN201811653603 A CN 201811653603A CN 109692500 B CN109692500 B CN 109692500B
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D11/00—Solvent extraction
- B01D11/04—Solvent extraction of solutions which are liquid
- B01D11/0496—Solvent extraction of solutions which are liquid by extraction in microfluidic devices
Abstract
The invention relates to a method for improving the mass transfer rate of a stable annular flow in a microchannel, which is characterized in that a linear central plug-in with a regularly-changed outline is arranged in the microchannel, when in operation, fluid forming an outer ring is firstly input into the microchannel at a certain flow rate, after the microchannel is filled with the fluid forming the outer ring, the fluid forming an inner ring is input into the microchannel at a certain flow rate, and two fluids are subjected to mass transfer in the microchannel by flowing in a regularly-deformed stable annular flow pattern; controlling the flow rate of the fluid forming the inner ring to be 0.8-20 mL/min, wherein the flow rate ratio of the fluid forming the inner ring to the fluid forming the outer ring is 1 (0.2-20); when the fluid forming the outer ring is a water phase and the fluid forming the inner ring is an organic phase, the linear center plug is made of oleophilic materials, and the outer pipe is made of hydrophilic materials; when the fluid forming the outer ring is an organic phase and the fluid forming the inner ring is an aqueous phase, the linear center insert is made of a hydrophilic material and the outer tube is made of a lipophilic material.
Description
Technical Field
The invention belongs to the technical field of chemical process reinforcement, and particularly relates to a method for improving the mass transfer rate of a stable annular flow in a microchannel.
Background
The micro chemical technology is widely applied to liquid-liquid extraction. When liquid-liquid extraction is carried out in the microchannel, due to the microscale effect of the microchannel, the mass transfer distance between two phases is greatly shortened, the specific interfacial area of the two phases is greatly increased, a certain extraction and separation task is completed, and the required extraction time is greatly shortened. Compared with the traditional extraction operation, the liquid-liquid extraction in the micro-channel has higher mass transfer rate.
The liquid-liquid two-phase flow pattern in the micro-channel can significantly influence the extraction rate and the phase separation condition of the fluid at the outlet of the device. Therefore, much attention has been paid to the study of the liquid-liquid two-phase flow pattern in the microchannel. Research on two-phase fluid in the micro-channel shows that the liquid-liquid two-phase fluid in the micro-channel can form a series of flow patterns such as elastic flow, drop flow, parallel flow, annular flow and the like. Compared with other flow patterns, the annular flow has wider flow ratio range of two-phase fluid when being formed, thereby having wider application range; compared with parallel flow, the annular flow has larger phase interface area of two-phase contact and higher mass transfer rate, thereby being more suitable for the liquid-liquid two-phase mass transfer process. However, the annular flow two-phase interface formed in the existing microchannel is unstable and has random fluctuation phenomenon, and the fluctuation amplitude is increased along with the increase of the flow velocity of the fluid, so that the two-phase fluid cannot be subjected to phase separation in time when flowing out of the microchannel. In order to eliminate the random fluctuation phenomenon of the annular flow and construct stable annular flow in the microchannel, the inventor of the application arranges a linear central plug-in with the same diameter and circular cross section in the microchannel, and selects the manufacturing materials of the linear central plug-in and the outer tube according to the properties of the inner ring fluid and the outer ring fluid, so that the water phase and organic phase two-phase fluid can maintain the annular flow pattern with clear and stable interface in the microchannel in a wider flow rate and flow ratio range, and the two-phase fluid can be subjected to phase splitting immediately when flowing out of the microchannel. However, experiments have shown that the mass transfer rate of the resulting stable annular flow needs to be further increased.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a method for improving the mass transfer rate of a stable annular flow in a microchannel so as to strengthen the mass transfer under the condition of maintaining the stable two-phase interface of the annular flow.
The microchannel comprises an outer tube and inner tubes respectively combined with inner holes at two ends of the outer tube, wherein the center line of the inner tube is superposed with the center line of the outer tube, the inner diameter of the outer tube is not more than 1.5mm, the inner diameter of the inner tube is not more than 0.8mm, and the gap between the outer wall of the inner tube and the inner wall of the outer tube is 0.1-0.4 mm.
The invention relates to a method for improving the mass transfer rate of a stable annular flow in a microchannel, which is characterized in that a linear central plug-in with a regularly changed outline is arranged in the microchannel, when in operation, a fluid forming an outer ring is firstly input into the microchannel at a certain flow rate, after the microchannel is filled with the fluid forming the outer ring, the fluid forming an inner ring is input into the microchannel at a certain flow rate, two fluids are subjected to mass transfer in the microchannel in a regularly deformed stable annular flow pattern flow, after the mass transfer is finished, the fluid forming the inner ring flows out of the microchannel from an inner tube to an inner ring fluid outlet, and the fluid forming the outer ring flows out of the microchannel from an outer tube to an outer ring fluid outlet; the fluid forming the outer ring is an aqueous phase, the fluid forming the inner ring is an organic phase, or the fluid forming the outer ring is an organic phase and the fluid forming the inner ring is an aqueous phase, the flow rate of the fluid forming the inner ring is controlled to be 0.8-20 mL/min, and the flow rate ratio of the fluid forming the inner ring to the fluid forming the outer ring is 1 (0.2-20); when the fluid forming the outer ring is a water phase and the fluid forming the inner ring is an organic phase, the linear center plug is made of oleophilic materials, and the outer pipe is made of hydrophilic materials; when the fluid forming the outer ring is an organic phase and the fluid forming the inner ring is an aqueous phase, the linear center insert is made of a hydrophilic material and the outer tube is made of a lipophilic material.
In the method for improving the mass transfer rate of the stable annular flow in the microchannel, the linear central plug-in with the regularly changed outline is a twisted, spiral, bead string, baffle or twisted string linear body.
In the method for improving the mass transfer rate of the stable annular flow in the microchannel, the maximum radial dimension of the linear central plug with the regularly changed outline is not more than 1/2 of the inner diameter of the inner tube.
In the above method for increasing the mass transfer rate of a stationary annular flow in a microchannel, the length of the outer tube is at least 50mm, so that the formation of the stationary annular flow is stabilized.
According to the method for improving the mass transfer rate of the stable annular flow in the microchannel, the lipophilic material for manufacturing the linear central plug-in component is preferably polyethylene, polypropylene or nylon, and the hydrophilic material is preferably low-carbon steel, medium-carbon steel, stainless steel or titanium; the oleophylic material for manufacturing the outer tube is preferably polyethylene, polypropylene, polymethyl methacrylate or nylon, and the hydrophilic material is preferably quartz glass, stainless steel or titanium.
The invention has the following beneficial effects:
1. the method of the invention not only forms stable annular flow for the water phase and organic phase two-phase fluid in the micro-channel, but also forms secondary circulation flow in the fluid by selecting the manufacturing materials of the linear central plug-in and the outer tube according to the properties of the inner ring fluid and the outer ring fluid, thereby strengthening the mass transfer between the two-phase fluid and improving the mass transfer rate (see the embodiment and the comparative example).
2. The method of the present invention can make the interface of the water phase and the organic phase in the micro channel change regularly, so the contact interface area of the two-phase fluid is increased, the mass transfer rate is increased, the time required by mass transfer is reduced, and the processing capacity is increased.
3. The method of the invention can make the water phase and the organic phase in the micro-channel form stable annular flow, so that the two-phase fluid can be subjected to phase splitting immediately when flowing out of the micro-channel, thereby saving the subsequent phase splitting process and simplifying the process flow.
4. The method of the invention mainly increases the mass transfer rate of the stable annular flow by adding the linear central plug-in with the regularly changed outline in the micro-channel, thereby being very simple, convenient to implement and beneficial to practical application and popularization.
Drawings
FIG. 1 is a schematic diagram of the method of increasing the mass transfer rate of a stable annular flow in a microchannel according to the present invention;
FIG. 2 is a schematic view of a twisted wire-like center insert in the method of the present invention;
FIG. 3 is a schematic view of a beaded wire center insert used in the method of the present invention;
FIG. 4 is a schematic view of a baffle-like wire-like center insert in the process of the present invention;
FIG. 5 is a schematic view of a helical wire-like center insert in the method of the present invention;
FIG. 6 is a schematic view of a twisted string-like center insert in the method of the present invention;
FIG. 7 is a schematic view of a linear center insert of equal diameter circular cross section as provided in a comparative example;
FIG. 8 is a flow pattern diagram of a two-phase fluid in the microchannel in example 1;
FIG. 9 is a flow pattern photograph of a two-phase fluid in the microchannel in comparative example 1;
FIG. 10 is a microchannel apparatus for forming a steady annular flow provided in accordance with the schematic diagram of FIG. 1;
FIG. 11 is a side view of FIG. 10;
FIG. 12 is a sectional view A-A of FIG. 10;
fig. 13 is a sectional view B-B of fig. 10.
In the figure, 1-a first inlet, 2-a second inlet, 3-1-a first inner tube, 3-2-a second inner tube, 4-a linear central insert, 5-an outer tube, 6-a first outlet, 7-a second outlet, 8-an aqueous phase fluid, 9-an organic phase fluid, 10-a base, 11-a first support, 12-a second support, 13-a guide rail, 14-a first diversion guide clamp, 14-1-a first housing, 14-2-a first diversion fixture block, 14-3-a first front end cap, 14-4-a first rear end cap, 14-5-a first stopper, 14-6-a first rubber sealing plug, 15-a second diversion guide clamp, 15-1-a second housing, 15-2-a second diversion fixture block, 15-3-a second front end cap, 15-4-a second rear end cap, 15-5-a second stopper, 15-6-second rubber sealing plug.
Detailed Description
The method for establishing a stable annular flow in a microchannel according to the present invention will be further described by way of examples with reference to the accompanying drawings. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the following examples, comparative examples, flow pattern pictures of two-phase fluid in the microchannel were taken from below the outer tube using a digital camera coupled inverted optical microscope.
In the following examples and comparative examples, the extraction rate was calculated by the following formula:
in the following examples and comparative examples, when the organic phase was washed, the change in the mass of the organic phase before and after washing was ignored, and the washing rate was calculated as:
example 1
In this embodiment, a microchannel is arranged according to fig. 1 and a linear central plug-in is arranged in the microchannel, the microchannel includes an outer tube 5 and a first inner tube 3-1 and a second inner tube 3-2 respectively combined with two ends of the outer tube, the central lines of the first inner tube and the second inner tube are both overlapped with the central line of the outer tube, the outer tube 5 is a transparent quartz capillary tube with an outer diameter of 3mm, an inner diameter of 0.9mm and a length of 150mm, the outer diameters of the first inner tube 3-1 and the second inner tube 3-2 are both 0.7mm and the inner diameters are both 0.5mm and are both made of 316L stainless steel, and the joint of the first inner tube 3-1 and the left end of the outer tube and the joint of the second inner tube 3-2 and the right end of the outer; the linear central plug-in 4 with the regularly changed outline is a twisted linear body shown in figure 2, is made of polyethylene, has the maximum radial dimension of 0.2mm, is inserted into the microchannel, has two ends fixed outside the microchannel respectively, and is in a tensioned state when being fixed, and is sealed at the joint of the linear central plug-in and the end parts of the first inner tube 3-1 and the second inner tube 3-2 to avoid liquid leakage; the first inner pipe 3-1 is communicated with the first liquid inlet 1, the liquid inlet at the left end of the outer pipe 5 is communicated with the second liquid inlet 2, the second inner pipe 3-2 is communicated with the first liquid outlet 6, and the liquid outlet at the right end of the outer pipe 5 is communicated with the second liquid outlet 7.
A variety of different configurations of microchannel devices can be designed by arranging microchannels and providing linear center inserts in the microchannels in the above-described manner, and the present embodiment is preferably a microchannel device in which microchannels are arranged and linear center inserts are provided in microchannels in the above-described manner, and has a configuration as shown in fig. 10 to 13, including a base 10, a first split flow guide jig 14, a second split flow guide jig 15, a first inner tube 3-1, a second inner tube 3-2, an outer tube 5, a linear center insert 4, a first support 11, a guide rail 13, and a second support 12. The first diversion guide clamp 14 is mainly formed by combining a first shell 14-1, a first front end cover 14-3, a first rear end cover 14-4, a first limiting sheet 14-5, a first diversion retaining block 14-2 and a first rubber sealing plug 14-6; a first liquid inlet 1 and a second liquid inlet 2 are arranged on the side surface of the first shell 14-1, a linear central plug-in first through hole, a first inner ring fluid storage tank, a first inner pipe retaining hole, a first outer ring fluid storage tank and a first outer pipe retaining hole are sequentially arranged at the central part of the first shunting retaining block 14-2, the central lines of the linear central plug-in first through hole, the first inner ring fluid storage tank, the first inner pipe retaining hole, the first outer ring fluid storage tank and the first outer pipe retaining hole are all coincided with the central line of the first shunting retaining block, the first inner ring fluid storage tank corresponds to the first liquid inlet 1, a first liquid inlet hole for communicating the first liquid inlet 1 with the first inner ring fluid storage tank is arranged between the first inner ring fluid storage tank and the first shunting retaining block side surface, the first outer ring fluid storage tank corresponds to the second liquid inlet 2, and a second liquid inlet 2 for communicating the first outer ring fluid storage tank with the first shunting retaining block side surface are arranged between the first outer ring fluid storage tank and the first shunting retaining block side surface A second inlet opening of the first outer ring fluid reservoir; the first shunting and retaining block 14-2 is arranged in an inner hole of the first shell 14-1, and when in installation, the first liquid inlet hole is connected with the first liquid inlet 1 on the side surface of the first shell, and the second liquid inlet hole is connected with the second liquid inlet 2 on the side surface of the first shell; the first limiting piece 14-5 is arranged in an inner hole of the first shell 14-1 and is attached to the end face of the first shunting and retaining block at the first through hole end of the linear central plug-in unit, the first rubber sealing plug 14-6 is arranged in the central hole of the first limiting piece 14-5, the first front end cover 14-3 is fixedly connected with one end of the inner hole of the first shell 14-1, which is provided with the first limiting piece, through a screw, and the first rear end cover 14-4 is fixedly connected with the other end of the first shell 14-1 through a screw. The second shunt guide clamp 15 is mainly formed by combining a second shell 15-1, a second front end cover 15-3, a second rear end cover 15-4, a second limiting piece 15-5, a second shunt retaining block 15-2 and a second rubber sealing plug 15-6, wherein a first liquid outlet 6 and a second liquid outlet 7 are arranged on the side surface of the second shell 15-1, a linear central plug-in second through hole, a second inner ring fluid storage tank, an inner tube second retaining hole, a second outer circulation fluid storage tank and an outer tube second retaining hole are sequentially arranged at the central part of the second shunt retaining block, the central lines of the linear central plug-in second through hole, the second inner ring fluid storage tank, the inner tube second retaining hole, the second outer circulation fluid storage tank and the outer tube second retaining hole are all coincided with the central line of the second shunt retaining block, and the second inner ring fluid storage tank corresponds to the first liquid outlet 6, a first liquid outlet hole for communicating the first liquid outlet 6 with the second inner ring fluid storage tank is arranged between the second inner ring fluid storage tank and the side surface of the second split retaining block, the second outer ring fluid storage tank corresponds to the second liquid outlet 7, and a second liquid outlet hole for communicating the second liquid outlet 7 with the second outer ring fluid storage tank is arranged between the second outer ring fluid storage tank and the side surface of the second split retaining block; the second shunting fixing block 15-2 is arranged in an inner hole of the second shell 15-1, and when the second shunting fixing block is arranged, the first liquid outlet hole is connected with a first liquid outlet 6 on the side surface of the second shell, and the second liquid outlet hole is connected with a second liquid outlet 7 on the side surface of the second shell; the second limiting piece 15-5 is arranged in an inner hole of the second shell 15-1 and is attached to the end face of the second cross hole end of the second shunting fixing block provided with the linear central plug-in, the second rubber sealing plug 15-6 is arranged in the central hole of the second limiting piece 15-5, the second front end cover 15-3 is fixedly connected with one end of the inner hole of the second shell 15-1 provided with the second limiting piece through a screw, and the second rear end cover 15-4 is fixedly connected with the other end of the second shell 15-1 through a screw. The two second supports 12 are respectively installed on the base 10 and located at two ends of the base, the two guide rails 13 are installed on the second supports 12 in parallel at an interval, and the two first supports 11 are respectively installed at two ends of the base 10 and located at the outer sides of the second supports 12; the first shunt guide clamp 14 and the second shunt guide clamp 15 are placed on the guide rail 13, when placed, a first front end cover 14-3 of the first shunt guide clamp and a second front end cover 15-3 of the second shunt guide clamp respectively face two ends of the base 10, and a central line of the first shunt guide clamp 14 is coincident with a central line of the second shunt guide clamp 15; one end of a first inner pipe 3-1 is inserted into a first inner pipe retaining hole arranged in a first shunt retaining block 14-2 in a first shunt guiding clamp, is fixed by the inner pipe retaining hole and is connected with the first inner ring fluid storage tank, the other end of the first inner pipe extends out of the first shunt guiding clamp, one end of a second inner pipe 3-2 is inserted into a second inner pipe retaining hole arranged in a second shunt retaining block 15-2 in a second shunt guiding clamp, is fixed by the inner pipe retaining hole and is connected with the second inner ring fluid storage tank, and the other end of the second inner pipe extends out of the second shunt guiding clamp; one end of the outer pipe 5 is sleeved with the first inner pipe 3-1 and is inserted into an outer pipe first retention hole arranged on a first shunt retention block in the first shunt guide clamp, and is fixed through the hole and is connected with the first outer ring fluid storage tank, and the other end of the outer pipe 5 is sleeved with the second inner pipe 3-2 and is inserted into an outer pipe second retention hole arranged on a second shunt retention block in the second shunt guide clamp, and is fixed through the hole and is connected with the second outer ring fluid storage tank; the linear central plug-in 4 is inserted into the first inner tube 3-1, the second inner tube 3-2 and the outer tube 5, two ends of the linear central plug-in extend out of a first front end cover 14-3 of the first shunt guide clamp and a second front end cover 15-3 of the second shunt guide clamp respectively and are fixed on first brackets 11 at two ends of the base respectively, and the linear central plug-in is in a tensioned state when being fixed; after the linear central plug-in 4, the first inner tube 3-1, the second inner tube 3-2 and the outer tube 5 are installed in place, the first shunt guide clamp 14 and the second shunt guide clamp 15 are fixedly connected with the base through bolts. The first shunt retaining block 14-2 and the second shunt retaining block 15-2 are made of corrosion-resistant elastic high polymer material polytetrafluoroethylene or polyformaldehyde, and the first shell 14-1, the first front end cover 14-3, the first rear end cover 14-4, the first limiting sheet 14-5, the second shell 15-1, the second front end cover 15-3, the second rear end cover 15-4 and the second limiting sheet 15-5 are made of medium carbon steel or stainless steel.
This example was carried out at room temperature of 25 ℃ using an aqueous solution of phosphoric acid-calcium chloride (phosphoric acid mass fraction: 10.77%; calcium chloride mass fraction: 24.81%, density: 1.35 g/cm)3) The aqueous phase is extracted by tributyl phosphate as an extractant. Inputting the water phase forming the outer ring into the microchannel through the second liquid inlet 2 and the liquid inlet at the left end of the outer pipe 5 at the flow rate of 3mL/min by using an injection pump and an injector arranged on the injection pump, inputting the organic phase forming the inner ring into the microchannel through the first liquid inlet 1 and the first inner pipe 3-1 at the flow rate of 3mL/min after the microchannel is filled with the fluid forming the outer ring, wherein the organic phase fluid 9 flows in the horizontal direction attached to the twisted linear central plug-in piece in the microchannel, the water phase fluid 8 surrounds the organic phase fluid 9 and flows in the horizontal direction attached to the organic phase fluid 9The fluid 9 flows in contact with the inner wall of the outer tube 5, forming a steady annular flow of regular deformation (see fig. 8). After extraction is finished, the organic phase fluid 9 forming the inner ring flows out of the microchannel from the second inner tube 3-2 to the first liquid outlet 6, and the aqueous phase fluid 8 forming the outer ring flows out of the microchannel from the liquid outlet at the right end of the outer tube 5 to the second liquid outlet 7.
Collecting the extracted organic phase at regular time, measuring the mass of the extracted organic phase collected in the collection time period, and calculating the mass flow of the extracted organic phase to be 3.36 g/min; the mass fraction of phosphoric acid in the collected organic phase of the extraction was measured to be 7.08%. The phosphoric acid extraction rate of this example was 54.54% as calculated from the calculation formula of the extraction rate.
Comparative example 1
In this comparative example, the arrangement of the microchannels was the same as in example 1, the material and dimensions of the outer tube 5 and the first and second inner tubes 3-1 and 3-2 were the same as in example 1, and the microchannel apparatus used was the same as in example 1. The difference from the embodiment 1 is that: the linear central insert 4 provided in the microchannel was a linear body of uniform diameter circular cross section as shown in FIG. 7, and was made of nylon and had a wire diameter of 0.2 mm.
In the comparative example, the implementation temperature is the same as that of example 1, the aqueous phase and the organic phase are the same as that of example 1, the aqueous phase forming the outer ring is input into the microchannel through the second liquid inlet 2 and the liquid inlet at the left end of the outer tube 5 at the flow rate of 3mL/min by the injection pump and the injector arranged on the injection pump, and after the microchannel is filled with the fluid forming the outer ring, the organic phase forming the inner ring is input into the microchannel through the first liquid inlet 1 and the first inner tube 3-1 at the flow rate of 3 mL/min. The flow pattern of the two-phase fluid in the microchannel is shown in fig. 9, and it can be seen from fig. 9 that the two-phase fluid forms a stable annular flow with a clear interface in the microchannel. After extraction is finished, the organic phase forming the inner ring flows out of the micro-channel from the second inner tube 3-2 to the first liquid outlet 6, and the aqueous phase forming the outer ring flows out of the micro-channel from the liquid outlet at the right end of the outer tube 5 to the second liquid outlet 7.
Collecting the extracted organic phase at regular time, measuring the mass of the extracted organic phase collected in the collection time period, and calculating the mass flow of the extracted organic phase to be 3.34 g/min; the mass fraction of phosphoric acid in the collected organic phase of the extraction was measured to be 6.65%. According to the calculation formula of the extraction rate, the extraction rate of phosphoric acid of the comparative example is 50.92%.
Example 2
In this embodiment, a microchannel is arranged according to fig. 1 and a linear central plug-in is arranged in the microchannel, the microchannel includes an outer tube 5 and a first inner tube 3-1 and a second inner tube 3-2 respectively combined with two ends of the outer tube, the central lines of the first inner tube and the second inner tube are both overlapped with the central line of the outer tube, the outer tube 5 is a transparent quartz capillary tube with an outer diameter of 3mm, an inner diameter of 0.9mm and a length of 200mm, the outer diameters of the first inner tube 3-1 and the second inner tube 3-2 are both 0.7mm and the inner diameters are both 0.5mm and are both made of 316L stainless steel, and the joint of the first inner tube 3-1 and the left end of the outer tube and the joint of the second inner tube 3-2 and the right end of the outer; the linear central plug-in 4 with the regularly changed outline is a twisted linear central plug-in shown in figure 2, is made of polyethylene, has the maximum radial dimension of 0.2mm, is positioned at the section in the microchannel, has two ends fixed outside the microchannel respectively, and is in a tensioned state when being fixed, and avoids liquid leakage by sealing at the joint of the linear central plug-in and the end parts of the first inner tube 3-1 and the second inner tube 3-2; the first inner pipe 3-1 is communicated with the first liquid inlet 1, the liquid inlet at the left end of the outer pipe 5 is communicated with the second liquid inlet 2, the second inner pipe 3-2 is communicated with the first liquid outlet 6, and the liquid outlet at the right end of the outer pipe 5 is communicated with the second liquid outlet 7.
A number of different configurations of microchannel devices can be designed by arranging the microchannels and providing the linear central inserts in the microchannels in the manner described above, and the preferred microchannel device of this embodiment, which is arranged in the manner described above and provided with the linear central inserts in the microchannels, is the same as that of example 1.
This example was carried out at room temperature of 25 ℃ using an aqueous solution of phosphoric acid-calcium chloride (phosphoric acid mass fraction: 10.77%; calcium chloride mass fraction: 24.81%, density: 1.35 g/cm)3) Is an aqueous phase and is an organic phase by taking tributyl phosphate as an extracting agent. The water phase forming the outer ring is input into the micro-channel through the second liquid inlet 2 and the liquid inlet at the left end of the outer tube 5 at the flow rate of 2mL/min by an injection pump and an injector arranged on the injection pump,after the microchannel is filled with the fluid forming the outer ring, the organic phase forming the inner ring is input into the microchannel through the first liquid inlet 1 and the first inner tube 3-1 at a flow rate of 8mL/min, the organic phase fluid 9 flows along the horizontal direction attached to the twisted linear central plug-in piece in the microchannel, and the aqueous phase fluid 8 surrounds the organic phase fluid and flows in a state of contacting with the organic phase fluid and the inner wall of the outer tube 5 to form a regularly deformed stable annular flow. After extraction is finished, the organic phase fluid 9 forming the inner ring flows out of the microchannel from the second inner tube 3-2 to the first liquid outlet 6, and the aqueous phase fluid 8 forming the outer ring flows out of the microchannel from the liquid outlet at the right end of the outer tube 5 to the second liquid outlet 7.
Collecting the extracted organic phase at regular time, measuring the mass of the extracted organic phase collected in the collection time period, and calculating the mass flow of the extracted organic phase to be 8.36 g/min; the mass fraction of phosphoric acid in the collected organic phase of the extraction was measured to be 2.95%. The extraction rate of phosphoric acid according to this example was 84.81% as calculated from the calculation formula of the extraction rate.
Comparative example 2
In this comparative example, the arrangement of the microchannels was the same as in example 2, the material and dimensions of the outer tube 5 and the first and second inner tubes 3-1 and 3-2 were the same as in example 2, and the microchannel apparatus used was the same as in example 2. The difference from the embodiment 2 is that: the linear central insert 4 provided in the microchannel was a linear body of uniform diameter circular cross section as shown in FIG. 7, and was made of nylon and had a wire diameter of 0.2 mm.
In the comparative example, the implementation temperature is the same as that of example 2, the aqueous phase and the organic phase are the same as that of example 2, the aqueous phase forming the outer ring is input into the microchannel through the second liquid inlet 2 and the liquid inlet at the left end of the outer tube 5 at the flow rate of 2mL/min by the injection pump and the injector arranged on the injection pump, and after the microchannel is filled with the fluid forming the outer ring, the organic phase forming the inner ring is input into the microchannel through the first liquid inlet 1 and the first inner tube 3-1 at the flow rate of 8 mL/min. In the micro-channel, the two-phase fluid forms stable annular flow with clear interface in the micro-channel. After extraction is finished, the organic phase forming the inner ring flows out of the micro-channel from the second inner tube 3-2 to the first liquid outlet 6, and the aqueous phase forming the outer ring flows out of the micro-channel from the liquid outlet at the right end of the outer tube 5 to the second liquid outlet 7.
Collecting the extracted organic phase at regular time, measuring the mass of the extracted organic phase collected in the collection time period, and calculating the mass flow of the extracted organic phase to be 8.34 g/min; the mass fraction of phosphoric acid in the collected organic phase of the extraction was measured to be 2.73%. The extraction rate of phosphoric acid in this example was found to be 78.30% by calculation according to the calculation formula of the extraction rate.
Example 3
In this embodiment, a microchannel is arranged according to fig. 1 and a linear central plug-in is disposed in the microchannel, the microchannel includes an outer tube 5 and a first inner tube 3-1 and a second inner tube 3-2 respectively combined with two ends of the outer tube, the center lines of the first inner tube and the second inner tube are both overlapped with the center line of the outer tube, the outer tube 5 is a transparent polymethyl methacrylate tube with an outer diameter of 3mm, an inner diameter of 0.9mm and a length of 300mm, the outer diameters of the first inner tube 3-1 and the second inner tube 3-2 are both 0.7mm and the inner diameters are both 0.5mm and are both made of 316L stainless steel, and the joint of the first inner tube 3-1 and the left end of the outer tube and the joint of the second inner tube 3-2 and the right end of the outer tube are; the linear central plug-in 4 with the regularly changed outline is a spiral linear central plug-in shown in figure 5, is made of titanium wires, has the maximum radial dimension of 0.2mm, is positioned at the section in the microchannel, has two ends respectively fixed outside the microchannel, and avoids liquid leakage by sealing at the joint of the linear central plug-in and the end parts of the first inner tube 3-1 and the second inner tube 3-2; the first inner pipe 3-1 is communicated with the first liquid inlet 1, the liquid inlet at the left end of the outer pipe 5 is communicated with the second liquid inlet 2, the second inner pipe 3-2 is communicated with the first liquid outlet 6, and the liquid outlet at the right end of the outer pipe 5 is communicated with the second liquid outlet 7.
A number of different configurations of microchannel devices can be designed by arranging the microchannels and providing the linear central inserts in the microchannels in the manner described above, and the preferred microchannel device of this embodiment, which is arranged in the manner described above and provided with the linear central inserts in the microchannels, is the same as that of example 1.
This example was carried out at room temperature of 35 ℃ by washing tributyl phosphate loaded with phosphoric acid and calcium chloride with deionized water as the aqueous phase and tributyl phosphate loaded with phosphoric acid and calcium chloride (mass fraction of phosphoric acid 7.08%; mass fraction of calcium chloride 1.80%) as the organic phase. An organic phase forming an outer ring is input into the microchannel through a second liquid inlet 2 and a liquid inlet at the left end of an outer pipe 5 at a flow rate of 20mL/min through an injection pump and an injector arranged on the injection pump, after the microchannel is filled with fluid forming the outer ring, an aqueous phase forming an inner ring is input into the microchannel through a first liquid inlet 1 and a first inner pipe 3-1 at a flow rate of 1mL/min, the aqueous phase fluid 8 flows along the horizontal direction attached to the spiral linear central plug-in piece in the microchannel, and the organic phase fluid 9 surrounds the aqueous phase fluid and flows in a state of being in contact with the aqueous phase fluid and the inner wall of the outer pipe 5 to form a stable annular flow which deforms regularly. After the organic phase is washed, the water phase fluid forming the inner ring flows out of the micro-channel from the second inner tube 3-2 to the first liquid outlet 6, and the organic phase fluid forming the outer ring flows out of the micro-channel from the liquid outlet at the right end of the outer tube 5 to the second liquid outlet 7.
The washed organic phase was collected and the mass fractions of phosphoric acid and calcium chloride of the collected washed organic phase were measured to be 6.45% and 0.50%, respectively. The phosphoric acid and calcium chloride washing rates of this example were found to be 8.90% and 72.22% as calculated from the calculation formula of the washing rate.
Comparative example 3
In this comparative example, the arrangement of the microchannels was the same as in example 3, the material and dimensions of the outer tube 5 and the first and second inner tubes 3-1 and 3-2 were the same as in example 3, and the microchannel apparatus used was the same as in example 3. The difference from the embodiment 3 is that: the linear central insert 4 provided in the microchannel is a linear central insert of equal diameter circular cross section as shown in fig. 7, made of titanium wire, with a wire diameter of 0.2 mm.
In the comparative example, the aqueous phase and the organic phase are the same as in example 3, the operation temperature is the same as in example 3, the organic phase forming the outer ring is input into the microchannel through the second liquid inlet 2 and the liquid inlet at the left end of the outer tube 5 at a flow rate of 20mL/min by the injection pump and the injector arranged on the injection pump, and after the microchannel is filled with the fluid forming the outer ring, the aqueous phase forming the inner ring is input into the microchannel through the first liquid inlet 1 and the first inner tube 3-1 at a flow rate of 1 mL/min. In the micro-channel, the two-phase fluid forms stable annular flow with clear interface in the micro-channel. After the organic phase is washed, the water phase fluid forming the inner ring flows out of the micro-channel from the second inner tube 3-2 to the first liquid outlet 6, and the organic phase fluid forming the outer ring flows out of the micro-channel from the liquid outlet at the right end of the outer tube 5 to the second liquid outlet 7.
The washed organic phase was collected and the mass fractions of phosphoric acid and calcium chloride of the collected washed organic phase were measured to be 6.49% and 0.56%, respectively. The phosphoric acid and calcium chloride washing rates of this comparative example were found to be 8.33% and 68.89% as calculated from the calculation formula of the washing rate.
Claims (5)
1. A method for improving the mass transfer rate of a stable annular flow in a microchannel, wherein the microchannel comprises an outer tube and an inner tube which is respectively combined with inner holes at two ends of the outer tube, the center line of the inner tube is superposed with the center line of the outer tube, the inner diameter of the outer tube is not more than 1.5mm, the inner diameter of the inner tube is not more than 0.8mm, and the gap between the outer wall of the inner tube and the inner wall of the outer tube is 0.1-0.4 mm, is characterized in that a linear central plug-in with a regularly-changed outline is arranged in the microchannel, when in operation, a fluid forming an outer ring is firstly input into the microchannel with a certain flow rate, after the microchannel is filled with the fluid forming the outer ring, the fluid forming the inner ring is input into the microchannel with a certain flow rate, the two fluids are subjected to mass transfer in the microchannel in a regularly-deformed stable annular flow pattern, and after the mass transfer is, the fluid forming the outer ring flows out of the microchannel from the outer pipe to the fluid outlet of the outer ring;
the fluid forming the outer ring is an aqueous phase, the fluid forming the inner ring is an organic phase, or the fluid forming the outer ring is an organic phase and the fluid forming the inner ring is an aqueous phase, the flow rate of the fluid forming the inner ring is controlled to be 0.8-20 mL/min, and the flow rate ratio of the fluid forming the inner ring to the fluid forming the outer ring is 1 (0.2-20);
when the fluid forming the outer ring is a water phase and the fluid forming the inner ring is an organic phase, the linear center plug is made of oleophilic materials, and the outer pipe is made of hydrophilic materials; when the fluid forming the outer ring is an organic phase and the fluid forming the inner ring is an aqueous phase, the linear center insert is made of a hydrophilic material and the outer tube is made of a lipophilic material.
2. The method of claim 1 wherein the linear central insert is a twisted, helical, beaded or baffled wire.
3. The process for increasing the mass transfer rate of a stable annular flow in a microchannel of claim 1 or 2, wherein the linear central insert has a radial maximum dimension no greater than 1/2 of the inner diameter of the inner tube.
4. The method of claim 1 or 2, wherein the lipophilic material of the linear central insert is polyethylene, polypropylene or nylon, and the hydrophilic material is low carbon steel, medium carbon steel, stainless steel or titanium; the oleophylic material for manufacturing the outer tube is polyethylene, polypropylene, polymethyl methacrylate or nylon, and the hydrophilic material is quartz glass, stainless steel or titanium.
5. The method of claim 3, wherein the lipophilic material used to fabricate the linear center insert is polyethylene, polypropylene, or nylon, and the hydrophilic material is mild steel, stainless steel, or titanium; the oleophylic material for manufacturing the outer tube is polyethylene, polypropylene, polymethyl methacrylate or nylon, and the hydrophilic material is quartz glass, stainless steel or titanium.
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