Partially miscible solution liquid phase equilibrium test system and test method thereof

Abstract

The application discloses a partially miscible solution liquid phase equilibrium test system and a test method thereof. The test system comprises a solution supply module, a temperature regulation module, a phase separation module and a test sampling module. The solution supply module comprises a heavy phase solution storage tank, a light phase solution storage tank and a metering pump. The phase separation module comprises a phase separator and a circulating pump. The outlet of the metering pump is connected with the inlet of the circulating pump. The temperature regulation module is used for regulating the temperature of the solution entering the phase separator. The outlet of the circulating pump is connected with the inlet of the temperature regulation module. The outlet of the temperature regulation module is connected with the solution inlet of the phase separator. The test sampling module comprises a light phase flow meter, a light phase densimeter, a light phase flow regulating valve, a light phase sampling pipe, a heavy phase flow meter, a heavy phase densimeter, a heavy phase flow regulating valve and a heavy phase sampling pipe. The light phase solution outlet of the phase separator and the heavy phase solution outlet of the phase separator are respectively connected with the inlet of the circulating pump. The test system can collect the phase separation process parameters in real time, and improves the test efficiency and precision.

Description

Technical Field

[0001] This invention relates to the field of liquid-liquid separation technology, and in particular to a liquid-phase equilibrium testing system and method for partially miscible solutions. Background Technology

[0002] In industries such as chemical, petroleum, and pharmaceutical, liquid-liquid separation is a crucial unit operation aimed at separating two immiscible or partially miscible liquid mixtures. In chemical production, liquid-liquid phase equilibrium data is used to determine safe operating temperature zones, preventing the localized accumulation of flammable, explosive, or toxic components due to solution stratification caused by partially miscible raw materials. In industrial water treatment, liquid-liquid phase equilibrium data helps select appropriate treatment methods, improve pollutant removal efficiency, and reduce treatment costs. In biotherapy, liquid-liquid phase diagrams determine the solubility of drugs in oil and aqueous phases, optimizing dosage forms to improve bioavailability. In the daily chemical industry, liquid-liquid phase diagrams determine product formulations and storage temperatures to ensure the stability of cosmetic quality. Accurate testing of liquid-liquid phase equilibrium data is of great significance for safe production and new product development in the fields of chemistry, materials science, pharmaceuticals, and chemical engineering.

[0003] In conventional liquid-liquid equilibrium or liquid-liquid phase diagram testing, the cloud point observation method is used to determine the phase transition process (from a completely miscible state to a separated phase state or vice versa). However, this method suffers from low accuracy, low efficiency, and strong subjectivity. Furthermore, the cloud point observation method is no longer applicable to solutions with deep colors or unclear turbidity critical points. Summary of the Invention

[0004] To address the problems of the existing technology described above, this invention provides a partially miscible liquid phase equilibrium testing system that collects phase separation process parameters in real time and determines the phase transition process by measuring the density changes at the outlets of the light phase solution and the heavy phase solution in the phase separator. This overcomes the drawbacks of manual judgment based on the cloud point and improves testing efficiency and accuracy. To this end, this invention also provides a testing method for the above-mentioned testing system.

[0005] A first aspect of the present invention provides a partially miscible liquid-phase equilibrium testing system, comprising: a solution supply module, a temperature control module, a phase separation module, and a test sampling module.

[0006] The solution supply module includes a heavy phase solution storage tank, a light phase solution storage tank, and a metering pump. The outlets of the heavy phase solution storage tank and the light phase solution storage tank are respectively connected to the inlet of the metering pump.

[0007] The phase-splitting module includes a phase splitter and a circulating pump, and the outlet of the metering pump is connected to the inlet of the circulating pump.

[0008] The temperature control module is used to regulate the temperature of the solution entering the phase separator. The outlet of the circulation pump is connected to the inlet of the temperature control module, and the outlet of the temperature control module is connected to the solution inlet of the phase separator.

[0009] The test sampling module includes a light phase flow meter, a light phase density meter, a light phase flow regulating valve, and a light phase sampling tube installed at the light phase solution outlet of the phase separator, and a heavy phase flow meter, a heavy phase density meter, a heavy phase flow regulating valve, and a heavy phase sampling tube installed at the heavy phase solution outlet of the phase separator. The light phase solution outlet and the heavy phase solution outlet of the phase separator are respectively connected to the inlet of the circulation pump.

[0010] In a preferred embodiment, the heavy phase solution storage tank and the light phase solution storage tank are respectively provided with vacuum ports, which are connected to a vacuum pump.

[0011] In a preferred embodiment, the temperature control module includes a heat exchanger, a temperature control pump, and a high-low temperature constant temperature unit connected in sequence. The heat exchanger, temperature control pump, and high-low temperature constant temperature unit form a circulation system. The outlet of the circulation pump is connected to the inlet of the heat exchanger, and the outlet of the heat exchanger is connected to the solution inlet of the phase separator.

[0012] In a preferred embodiment, the heavy phase solution storage tank is provided with a heavy phase solution reflux port, and the light phase solution storage tank is provided with a light phase solution reflux port; the heavy phase solution outlet of the phase separator is connected to the heavy phase solution reflux port, and a shut-off valve is provided on the connecting pipeline; the light phase solution outlet of the phase separator is connected to the light phase solution reflux port, and a shut-off valve is provided on the connecting pipeline.

[0013] In a preferred embodiment, the phase separator is a gravity-type phase separator or a vortex-type phase separator.

[0014] In a preferred embodiment, the heat exchanger is selected from plate type, shell and tube type, coaxial type, and spiral plate type heat exchangers.

[0015] In a preferred embodiment, the heavy phase flow meter or light phase flow meter is selected from float-type flow meters, electromagnetic flow meters, vortex flow meters, or ultrasonic flow meters.

[0016] In a preferred embodiment, the heavy phase density meter and the light phase density meter are selected from tuning fork density meters.

[0017] In a preferred embodiment, the high and low temperature constant temperature unit includes a plurality of constant temperature water baths connected in series, and the temperature control range of the high and low temperature constant temperature unit is -80℃ to 150℃.

[0018] A second aspect of the present invention provides a testing method for a partially miscible liquid-phase equilibrium testing system, comprising the following steps:

[0019] S1. The heavy phase component in the heavy phase solution storage tank and the light phase component in the light phase solution storage tank are respectively discharged into the phase separator by a metering pump. The mass concentration of the heavy phase component in the phase separator is 40%-60%.

[0020] S2. Start the circulation pump and temperature control module;

[0021] S3. Adjust the temperature of the test solution in the phase separator using the temperature control module to bring the test solution into a phase-separated state. Gradually reduce the opening of the heavy phase flow regulating valve and observe the reading of the heavy phase flow meter. Q 重 and the readings of the phase density meter r 重 ,when r 重 along with Q 重 When the flow rate remains unchanged, stop the adjustment of the heavy phase flow control valve, collect the heavy phase conjugate solution through the heavy phase sampling tube, and test the concentration of the heavy phase component in the heavy phase conjugate solution; restore the heavy phase flow control valve to its initial opening, gradually reduce the opening of the light phase flow control valve, and observe the reading of the light phase flow meter. Q 轻 and light phase density meter readings r 轻 ,when r 轻 along with Q 轻 When the flow rate remains unchanged, stop the adjustment action of the light phase flow regulating valve, collect the light phase conjugate solution by the light phase sampling tube, and test the concentration of the heavy phase component in the light phase conjugate solution;

[0022] S4. Increase or decrease the temperature of the test solution, repeat step S3, and test the concentration of the heavy phase component in the heavy phase conjugate solution and the light phase conjugate solution at different temperatures; at a specific temperature, ( r 重 - r 轻 ) / r 重 <0.5% and when r 重 along with Q 重、 r 轻 along with Q 轻 When all remain constant, the concentration of the heavy phase component at the highest or lowest melting point is obtained.

[0023] As a preferred embodiment, before step S1, step S0 is also included: a step of evacuating the test system.

[0024] In a preferred embodiment, after step S2, the steps of determining the solution phase region and determining the liquid-liquid phase diagram morphology are further included:

[0025] Solution phase region determination steps: Adjust the temperature of the test solution in the phase separator to temperature T, and compare the readings with those of the light phase density meter. r 轻 and the readings of the phase density meter r 重 The relationship, if ( r 重 - r 轻 ) / r 重 If <0.5%, then the mixed solution at temperature T is completely miscible; if ( r 重 - r 轻 ) / r 重 When the concentration is ≥0.5%, the mixed solution at temperature T is in a phase-separated state.

[0026] Liquid-liquid phase diagram morphology determination steps: When the mixed solution at temperature T is in a completely miscible state, raise or lower the temperature of the test solution in the phase separator and compare... r 重 , r 轻 The relationship between the difference and temperature change, if r 重 , r 轻 If the difference between the two values ​​increases with increasing temperature or decreases with decreasing temperature, the mixed solution is determined to be a partially miscible solution with the lowest melting point. When the mixed solution at temperature T is in a phase-separated state, the solution temperature in the phase separator is increased or decreased, and the values ​​are compared. r 重 , r 轻 The relationship between the difference and temperature change, if r 重 , r 轻 The difference between them decreases as the temperature increases or increases as the temperature decreases, and at a specific temperature... r 重 = r 轻 If the test solution is found to be partially miscible with the lowest melting point, then the test solution is determined to be such that it is a partially miscible solution.

[0027] As a preferred embodiment, after step S4, a step of drawing a liquid-liquid phase diagram with the highest melting point temperature or the lowest melting point is also included.

[0028] Beneficial effects:

[0029] (1) The partial interphase liquid equilibrium test system of the present invention can collect phase separation process parameters in real time and judge the phase change process by the density change of the light phase solution outlet and the heavy phase solution outlet of the phase separator. This overcomes the drawback of manual judgment by turbidity point and improves test efficiency and test accuracy.

[0030] (2) The liquid phase equilibrium test system of the present invention operates in a closed state, realizing high pressure test, avoiding the problem that low boiling point components (such as n-pentane) cannot be liquefied under high temperature conditions in conventional methods, which makes it difficult to test their liquid-liquid phase separation performance.

[0031] (3) The liquid phase equilibrium test system of the present invention uses a temperature control module to keep the phase separator in a constant temperature state. The conjugate solution is collected at the outlet of the light phase solution and the outlet of the heavy phase solution of the phase separator to obtain the left and right curves of the liquid phase diagram and the concentration points of the highest melting point / lowest melting point at different temperatures. The test process is simple and convenient.

[0032] (4) The liquid phase equilibrium test system of the present invention can simultaneously collect multiple parameters such as temperature, flow rate, density, and phase separation time. Multiple performance indicators such as phase separation rate and phase separation efficiency can be obtained through theoretical calculation, providing test data support for the optimization of liquid-liquid separation process and the design of phase separator. It can be applied to multiple fields such as chemical, petroleum, and pharmaceutical industries.

[0033] (5) The partial miscible liquid phase equilibrium test system of the present invention can realize pressure-bearing sealing test, avoid problems such as toxicity of the liquid, and has a wider range of applications.

[0034] (6) In the test method of the present invention, the opening of the flow regulating valve on the sampling side is gradually reduced during the test, and the concentration change of the solution on the sampling side is judged by the density change on the sampling side, so as to obtain the concentration value of the sampling side in a stable state, which effectively avoids the influence of the layer interface movement on the test results.

[0035] (7) Using the test method of the present invention, the concentration points of the left and right curves of the phase diagram of the partially miscible solution are only related to the solution temperature and are not related to the initial concentration of the solution. Using a mass concentration of 40%-60% of the heavy phase component can cover the phase diagram concentration requirements of most phase-separated solutions.

[0036] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a flowchart of the partial miscible liquid phase equilibrium testing system in Embodiment 1 of the present invention;

[0039] Figure 2 This is a liquid phase diagram of a partially miscible solution with the highest melting point in Example 1;

[0040] Figure 3 This is a flowchart of the partial miscible liquid phase equilibrium testing system in Embodiment 2 of the present invention;

[0041] Figure 4 This is a liquid phase diagram of a partially miscible solution with the lowest melting point in Example 2.

[0042] Explanation of reference numerals in the attached figures:

[0043] 1-Heavy phase solution storage tank, 2-Light phase solution storage tank, 3-Vacuum pump, 4-Metering pump, 5-Circulation pump, 6-Heat exchanger, 7-Temperature control pump, 8-High and low temperature constant temperature unit, 9-Phase separator, 10-Light phase flow meter, 11-Light phase density meter, 12-Light phase flow regulating valve, 13-Heavy phase flow meter, 14-Heavy phase density meter, 15-Heavy phase flow regulating valve, 16-Light phase sampling tube, 17-Heavy phase sampling tube. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, the term "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0046] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0047] If an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. If so, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application are for illustrative purposes only and do not represent the only possible implementation.

[0048] For partially miscible solutions, accurate testing of liquid-liquid phase diagrams or liquid-liquid equilibrium data is of great significance for safe production and new product development in fields such as chemistry, materials, medicine, and chemical engineering. Traditional methods rely on observing the cloud point to determine whether the test solution is in a phase-separated state or a completely miscible state, which is highly subjective and lacks high accuracy.

[0049] This invention provides a partially miscible solution liquid phase equilibrium testing system, including a solution supply module, a phase separation module, a temperature control module, and a test sampling module.

[0050] The solution supply module is used to supply two test solutions to the phase separation module. The solution supply module includes a heavy phase solution storage tank, a light phase solution storage tank, and a metering pump. The outlets of the heavy phase solution storage tank and the light phase solution storage tank are respectively connected to the inlet of the metering pump.

[0051] The phase separation module is used to thoroughly mix and separate the two test solutions. The module includes a phase separator and a circulation pump. The phase separator can be a gravity-type or cyclone-type phase separator. The outlet of the metering pump is connected to the inlet of the circulation pump. The heavy phase component and light phase component in the heavy phase solution tank and light phase solution tank are metered by the metering pump and then circulated into the phase separator for phase separation.

[0052] The temperature control module is used to regulate the temperature of the test solution in the phase separator. The module includes a heat exchanger, a temperature control pump, and a high-low temperature constant-temperature unit connected in sequence. These components form a circulation system: the outlet of the circulation pump is connected to the solution inlet of the heat exchanger; the solution outlet of the heat exchanger is connected to the inlet of the temperature control pump; the outlet of the temperature control pump is connected to the solution inlet of the high-low temperature constant-temperature unit; and the solution outlet of the high-low temperature constant-temperature unit is connected to the solution inlet of the heat exchanger. Thus, the test solution circulates repeatedly from the heat exchanger into the high-low temperature constant-temperature unit under the action of the temperature control pump until the predetermined temperature is reached. At this point, the test solution in the heat exchanger is discharged into the phase separator for phase separation.

[0053] The heat exchangers are selected from plate type, shell and tube type, coaxial type, and spiral plate type heat exchangers. The high and low temperature constant temperature unit includes multiple constant temperature water baths connected in series. The temperature control range of the high and low temperature constant temperature unit is -80℃ to 150℃.

[0054] The test sampling module is used to collect flow rate, density, and phase diagram data in real time during the phase separation test. The test sampling module includes a light phase flow meter, a light phase density meter, a light phase flow regulating valve, and a light phase sampling tube installed at the light phase solution outlet of the phase separator, and a heavy phase flow meter, a heavy phase density meter, a heavy phase flow regulating valve, and a heavy phase sampling tube installed at the heavy phase solution outlet of the phase separator. The light phase solution outlet and the heavy phase solution outlet of the phase separator are respectively connected to the inlet of the circulating pump. The heavy phase flow meter and the light phase flow meter are selected from float-type flow meters, electromagnetic flow meters, vortex flow meters, or ultrasonic flow meters, and the heavy phase density meter and the light phase density meter are selected from tuning fork density meters.

[0055] During the test, the circulation pump was turned on, and the test solution circulated in the phase separator and temperature control module.

[0056] The heavy phase solution storage tank and the light phase solution storage tank are each equipped with a vacuum port, which is connected to a vacuum pump.

[0057] By setting up a vacuum pump, the entire testing system is evacuated before the material is poured in.

[0058] The heavy phase solution storage tank is equipped with a heavy phase solution reflux port, and the light phase solution storage tank is equipped with a light phase solution reflux port; the heavy phase solution outlet of the phase separator is connected to the heavy phase solution reflux port, and a shut-off valve is installed on the connecting pipeline; the light phase solution outlet of the phase separator is connected to the light phase solution reflux port, and a shut-off valve is installed on the connecting pipeline.

[0059] By setting up reflux ports for heavy and light phase solutions, the content of heavy or light phase components in the test solution can be adjusted to obtain phase diagrams of the test solution with different compositions, which can be used to evaluate the stability of the test system and the accuracy of the test results.

[0060] The present invention also provides a testing method for the above-mentioned testing system, comprising the following steps:

[0061] The first step is to connect the vacuum pump to the vacuum ports in the heavy phase solution storage tank and the light phase solution storage tank to evacuate the system.

[0062] The second step involves using a metering pump to discharge the heavy phase component from the heavy phase solution storage tank and the light phase component from the light phase solution storage tank into the phase separator, respectively. The mass concentration of the heavy phase component in the phase separator is 40%-60%.

[0063] At this initial concentration, the liquid-liquid phase diagram tests of most partially miscible solutions met the requirements.

[0064] The light phase component refers to the component with a relatively low boiling point, while the heavy phase component refers to the component with a relatively high boiling point. Taking n-pentane-DMF as an example, the light phase component is n-pentane, and the heavy phase component is DMF. In the isopropylamine-water system, the light phase component is isopropylamine, and the heavy phase component is water.

[0065] Third step: Turn on the circulation pump and temperature control module.

[0066] Step 4: Determine the phase region of the test solution. The specific criterion is as follows: Adjust the temperature of the test solution in the phase separator to temperature T, and compare the reading of the light phase density meter. r 轻 and the readings of the phase density meter r 重 The relationship, if ( r 重 - r 轻 ) / r 重 If <0.5%, then the mixed solution at temperature T is completely miscible; if ( r 重 - r 轻 ) / r 重 When the concentration is ≥0.5%, the mixed solution at temperature T is in a phase-separated state.

[0067] Step 5: Liquid-Liquid Phase Diagram Morphology Determination: When the mixed solution at temperature T is in a completely miscible state, raise or lower the solution temperature in the phase separator and compare... r 重 , r 轻 The relationship between the difference and temperature change, if r 重 , r 轻If the difference between the two values ​​increases with increasing temperature or decreases with decreasing temperature, the mixed solution is determined to be a partially miscible solution with the lowest melting point. When the mixed solution at temperature T is in a phase-separated state, the solution temperature in the phase separator is increased or decreased, and the values ​​are compared. r 重 , r 轻 The relationship between the difference and temperature change, if r 重 , r 轻 The difference between them decreases as the temperature increases or increases as the temperature decreases, and at a specific temperature... r 重 = r 轻 If the time is right, then the mixed solution is determined to be a partially miscible solution with the highest melting point.

[0068] By following the steps above, it can be directly determined whether the test solution is a partially miscible solution with the lowest melting point or a partially miscible solution with the highest melting point. Of course, even without determining the solution phase region and liquid-liquid phase diagram morphology, subsequent testing steps alone can distinguish between partially miscible solutions with the lowest melting point and partially miscible solutions with the highest melting point.

[0069] Step 6: Adjust the temperature of the test solution inside the phase separator using the temperature control module to bring the test solution into a phase-separated state. Gradually reduce the opening of the heavy phase flow regulating valve and observe the reading of the heavy phase flow meter. Q 重 and the readings of the phase density meter r 重 ,when r 重 along with Q 重 When the flow rate remains unchanged, stop the adjustment of the heavy phase flow control valve, collect the heavy phase conjugate solution through the heavy phase sampling tube, and test the concentration of the heavy phase component in the heavy phase conjugate solution; restore the heavy phase flow control valve to its initial opening, gradually reduce the opening of the light phase flow control valve, and observe the reading of the light phase flow meter. Q 轻 and light phase density meter readings r 轻 ,when r 轻 along with Q 轻 When the flow rate remains unchanged, stop the adjustment action of the light phase flow regulating valve, collect the light phase conjugate solution by the light phase sampling tube, and test the concentration of the heavy phase component in the light phase conjugate solution.

[0070] The temperature of the test solution inside the phase separator is adjusted by the temperature control module, such as T', to bring the test solution into a phase-separated state. The opening of the heavy phase flow regulating valve is gradually reduced, while the opening of the light phase flow regulating valve is maintained at its initial state. Because the test solution inside the phase separator is constantly circulating, the phase separation interface will gradually shift towards the light phase component. The flow rates are read by the heavy phase flow meter and the heavy phase density meter, respectively. Q 重 and density value r 重 ,when r 重 along with Q 重 When the flow rate remains constant, the adjustment of the heavy phase flow control valve is stopped, and the heavy phase conjugate solution is collected by the heavy phase sampling tube to test the concentration of the heavy phase component in the heavy phase conjugate solution. When testing the content of each component in the heavy phase conjugate solution, the opening of the heavy phase flow control valve is reduced to effectively avoid the influence of liquid level fluctuations on sampling and ensure the accuracy of the test.

[0071] Conversely, when it is necessary to test the concentration of the heavy phase component in the light phase conjugate solution, the same method is used to gradually reduce the opening of the light phase flow regulating valve and maintain the opening of the heavy phase flow regulating valve at its initial state.

[0072] Step 7: Increase or decrease the temperature of the test solution, repeat step 6, and test the concentration of the heavy phase component in the heavy phase conjugate solution and the light phase conjugate solution at different temperatures; at a specific temperature, ( r 重 - r 轻 ) / r 重 <0.5% and when r 重 along with Q 重、 r 轻 along with Q 轻 When all remain constant, the concentration of the heavy phase component at the highest or lowest melting point is obtained.

[0073] Thus, taking the temperature T' of the test solution as an example, the concentration values ​​of the light phase conjugate solution and the heavy phase conjugate solution at different temperatures T', T'+ΔT', and T'-ΔT' can be obtained, thereby plotting the phase diagram curve of temperature change with the concentration of the heavy phase component.

[0074] Example 1

[0075] This embodiment uses the liquid-liquid phase equilibrium test of n-heptane-DMF as an example to introduce the liquid-liquid phase equilibrium test system and the liquid-liquid phase diagram test method with the highest melting point.

[0076] like Figure 1 The partial miscible liquid phase equilibrium testing system includes a solution supply module, a temperature control module, a phase separation module, and a test sampling module.

[0077] The solution supply module is used to supply two test solutions to the phase separation module. It includes a heavy phase solution storage tank 1, a light phase solution storage tank 2, a vacuum pump 3, and a metering pump 4. Both the heavy phase solution storage tank 1 and the light phase solution storage tank 2 are equipped with a discharge port, a reflux port, a vacuum port, and a feed port. The discharge port of the heavy phase solution storage tank 1 is connected to the inlet of the metering pump 4, and a shut-off valve is installed on the connecting pipeline. The discharge port of the light phase solution storage tank 2 is connected to the inlet of the metering pump 4, and a shut-off valve is installed on the connecting pipeline. The vacuum ports of both the heavy phase solution storage tank 1 and the light phase solution storage tank 2 are connected to the vacuum pump 3. The outlet of the metering pump 4 is connected to the inlet of the circulation pump 5, and a shut-off valve is installed on the connecting pipeline.

[0078] The temperature control module is used to control the solution temperature for liquid-liquid phase separation testing. The module includes a high-low temperature constant temperature unit 8, a temperature control pump 7, and a heat exchanger 6. The high-low temperature constant temperature unit 8, heat exchanger 6, and temperature control pump 7 are connected sequentially to form a closed loop. The high-low temperature constant temperature unit 8 consists of multiple constant temperature water baths connected in series. The series loop is filled with a heat transfer medium, which is water. The test solution enters each constant temperature water bath sequentially under the action of the temperature control pump 7 to heat or cool the solution. The outlet of the circulation pump 5 is connected to the liquid side inlet of the heat exchanger 6. Of course, if the expected power is achieved, the high-low temperature constant temperature unit 8 can also consist of only one constant temperature water bath.

[0079] The phase separation module is used to thoroughly mix and separate the two test solutions, including phase separator 9 and circulation pump 5.

[0080] The test sampling module is used to collect and control the flow and density parameters of the phase separation test process in real time. The phase diagram data of the layered conjugate phase solution is determined by sampling test. It includes light phase flow meter 10, light phase density meter 11, light phase flow regulating valve 12, heavy phase flow meter 13, heavy phase density meter 14, heavy phase flow regulating valve 15, light phase sampling tube 16, and heavy phase sampling tube 17.

[0081] Phase separator 9 is a gravity-type phase separator with a solution inlet on its side wall, a light phase solution outlet at the top, and a heavy phase solution outlet at the bottom. The feed liquid outlet of heat exchanger 6 is connected to the solution inlet of phase separator 9. A light phase outlet pipe is installed at the light phase solution outlet of phase separator 9. A light phase flow meter 10, a light phase density meter 11, and a light phase flow regulating valve 12 are installed on the light phase outlet pipe, and a light phase sampling pipe 16 is opened. A heavy phase outlet pipe is installed at the heavy phase solution outlet of phase separator 9. A heavy phase flow meter 13, a heavy phase density meter 14, and a heavy phase flow regulating valve 15 are installed on the heavy phase outlet pipe, and a heavy phase sampling pipe 17 is opened.

[0082] The light phase outlet pipe and the heavy phase outlet pipe of the phase separator 9 are connected to the inlet of the circulating pump 5 after they merge; the light phase outlet pipe of the phase separator 9 is connected to the reflux port of the light phase solution storage tank 2, and a shut-off valve is installed on the connecting pipe; the heavy phase outlet pipe of the phase separator 9 is connected to the reflux port of the heavy phase solution storage tank 1, and a shut-off valve is installed on the connecting pipe.

[0083] In this embodiment, heat exchanger 6 is a plate heat exchanger; phase separator 9 can be a gravity phase separator; light phase flow meter 10 and heavy phase flow meter 13 are float-type flow meters with a testing accuracy of ±0.5%; light phase density meter 11 and heavy phase density meter 14 can be tuning fork density meters with a testing accuracy of ±0.00001 g / cm³. 3 The high and low temperature constant temperature unit 8 adopts a constant temperature water bath unit with a temperature control range of -30℃ to 100℃ and a temperature control accuracy of ±0.1℃; the vacuum pump 3 adopts a dry screw vacuum pump.

[0084] The testing method and specific steps of this embodiment are as follows:

[0085] The volume of phase separator 9 was calibrated using pure water, and then the water was drained. Vacuum pump 3 was turned on to evacuate the light phase solution storage tank 2, the heavy phase solution storage tank 1, the phase separation module, and the connecting pipelines. The vacuum pump was turned off after the absolute pressure was reached 0.5 kPa. N-pentane was injected into the light phase solution storage tank 2, and DMF was injected into the heavy phase solution storage tank 1.

[0086] Open the valve of the heavy phase solution storage tank 1, start the metering pump 4, and inject DMF into the phase separation module. Then close the valve of the heavy phase solution storage tank 1 and open the valve of the light phase solution storage tank 2. Add n-pentane into the phase separation module through the metering pump 4 to adjust the mass concentration of DMF in the phase separation module. n 0 ≈50%.

[0087] The circulating pump 5 was turned on to circulate the test solution within the phase separation module. The high and low temperature constant temperature unit 8 and the temperature control pump 7 were also turned on, and the inlet solution temperature of the phase separator 9 was set to 30℃. The openings of the light phase flow regulating valve 12 and the heavy phase flow regulating valve 15 were adjusted together to change the flow rates of the light and heavy phase solutions. Testing revealed that the lower limit of the light phase solution density during flow adjustment was 634 kg / m³. 3 The upper limit of the density of the heavy phase solution is 887 kg / m³. 3 The difference in extreme densities between the light and heavy phases is 253 kg / m³. 3 When the test solution is heated to 50°C, the lower limit of the light phase solution density under the flow rate control of phase separator 9 is 626 kg / m³. 3 The upper limit of the density of the heavy phase solution is 833 kg / m³. 3 The difference in extreme densities between the light and heavy phases is 207 kg / m³. 3In other words, as the test solution temperature increased, the density difference between the light and heavy phases gradually decreased, initially indicating that n-pentane-DMF was a partially miscible solution with a "maximum melting point temperature". When the test solution was further heated to 77.5℃, it was found that the densities of the light and heavy phase solutions in the phase separator were identical, both being 698 kg / m³. 3 Furthermore, the density value is independent of the flow rate, indicating that the test solution has entered a completely miscible state. Therefore, it can be concluded that the n-pentane-DMF solution is a partially miscible solution with the highest melting point temperature, and its liquid-liquid phase diagram opens downwards.

[0088] The temperature of the test solution was restored to 30℃ using the temperature control module. The opening of the heavy phase flow regulating valve 15 was then slowly reduced, and the density of the heavy phase solution gradually increased before stabilizing at 887 kg / m³. 3 When the opening of the heavy phase flow regulating valve 15 is further reduced, the density of the heavy phase solution no longer changes. At this time, the phase separation interface of the phase separator 9 has shifted to the light phase outlet side of the phase separator (because the system is constantly circulating, when taking the heavy phase solution, the opening of the heavy phase flow regulating valve 15 is reduced so that the phase separation interface is close to the light phase solution, and the heavy phase solution is taken at the bottom to ensure the accuracy of the test results). That is, the heavy phase solution outlet is the heavy phase solution with conjugate composition at 30℃. After stable operation for 15 minutes, a sample is taken through the heavy phase sampling tube, and the concentration of the sampled solution is tested by gas chromatography. The mass content of DMF in the heavy phase solution is 87.8%, thus determining the melting point on the right side of the liquid-liquid phase diagram at 30℃. T =30℃, n 2 = 87.8%).

[0089] Return the heavy phase flow regulating valve 15 to its initial opening, and slowly reduce the opening of the light phase flow regulating valve 12. The density of the light phase solution gradually decreases and then stabilizes at 634 kg / m³. 3 When the opening of the light phase flow regulating valve 12 is further reduced, the density of the light phase solution no longer changes. At this time, the phase separation interface of the phase separator 9 has shifted to the heavy phase outlet side of the phase separator 9, that is, the light phase solution outlet is the light phase solution under the conjugate composition at 30℃. After stable operation for 15 minutes, a sample is taken through the light phase sampling tube 16, and the concentration of the sampled solution is tested by gas chromatography. The mass content of DMF in the light phase solution is tested to be 7.2%. Thus, the melting point on the left side of the liquid-liquid phase diagram at 30℃ is determined. T =30℃, n 1 = 7.2%.

[0090] The test solution was heated and cooled at 5°C intervals, and the temperature at each temperature was measured using the method described above. n 1 , n2 Concentration; in the high-temperature region, when the density difference between the light and heavy phase solutions is less than 10 kg / m³ 3 At that time, the increment interval was reduced to 0.5℃ to search for the accurate maximum melting point temperature of the test solution. When the test solution was heated to 77.5℃, the light phase solution and the heavy phase solution of the phase separator had the same density, and the density was independent of the flow rate. The mass content of DMF in the sampled test solution was 48.6%, which is the maximum melting point of n-pentane-DMF. T s =77.5℃, n s = 48.6%

[0091] like Figure 2 As shown, by connecting the melting points obtained from each test in sequence, the liquid-liquid phase diagram of n-pentane-DMF can be obtained.

[0092] This embodiment provides a test method and procedures for liquid-liquid phase equilibrium of a liquid with the highest melting point. The stability of the solution concentration is determined by the density change trend of the sampled solution, and small flow rate control at the sampling side ensures minimal fluctuations in the sampled solution, effectively avoiding the influence of layering interface movement on the test results. Furthermore, this embodiment operates in a closed state, achieving high-pressure testing and avoiding the problem of n-pentane's inability to liquefy at high temperatures during atmospheric pressure testing, which leads to difficulties in testing its liquid-liquid phase separation performance.

[0093] Example 2:

[0094] This embodiment uses the liquid-liquid phase equilibrium test process of isopropylamine-water as an example to introduce the liquid-liquid phase equilibrium test system and the test method of the liquid-liquid phase diagram with the lowest melting point temperature.

[0095] like Figure 3 As shown, the system composition and device connection method of this embodiment are the same as those of Embodiment 1, and will not be repeated here. Unlike Embodiment 1, the phase separator 9 in this embodiment adopts a cyclone phase separator, which achieves the separation of light and heavy phase solutions through the difference in centrifugal force of the solution.

[0096] The testing method and specific steps of this embodiment are as follows:

[0097] The volume of phase separator 9 was calibrated using pure water, and then the water was drained. Vacuum pump 3 was turned on to evacuate the light phase solution storage tank 2, the heavy phase solution storage tank 1, the phase separation module, and the connecting pipelines. The vacuum pump was turned off after the absolute pressure reached 0.5 kPa. Isopropylamine was added to the light phase solution storage tank 2, and pure water was added to the heavy phase solution storage tank 1.

[0098] Open the valve of the heavy phase solution storage tank 1, start the metering pump 4, and inject water into the phase separation module. Then close the bottom valve of the heavy phase solution storage tank 1 and open the valve of the light phase solution storage tank 2. Use the metering pump 4 to add isopropylamine into the phase separation module to adjust the mass concentration of water in the phase separation module. n 0 ≈50%.

[0099] The circulation pump 5 was turned on to circulate the test solution within the phase separation module. The high and low temperature constant temperature unit 8 and the temperature control pump 7 were also turned on, and the inlet solution temperature of the phase separator 9 was set to 40℃. The openings of the light phase flow regulating valve 12 and the heavy phase flow regulating valve 15 were adjusted to change the flow rates of the light and heavy phase solutions. Testing revealed that the lower limit of the light phase solution density during flow adjustment was 737 kg / m³. 3 The upper limit of the heavy phase density is 949 kg / m³. 3 The difference in extreme values ​​of light and heavy phase densities is 212 kg / m³. 3 When the test solution is heated to 60℃, the lower limit of the light phase solution density under flow rate control is 678 kg / m³. 3 The upper limit of the heavy phase density is 938 kg / m³. 3 The difference in extreme densities between the light and heavy phases is 260 kg / m³. 3 In other words, as the test solution temperature increased, the density difference between the light and heavy phases gradually increased, initially determining that isopropylamine-water was a partially miscible solution with a "lowest melting point temperature". Cooling the test solution to 21.5 ℃ revealed that the density of the light phase solution at the outlet of phase separator 9 was the same as the density of the heavy phase solution at the outlet of the heavy phase solution, both being 870 kg / m³. 3 Furthermore, the density value is independent of the flow rate, indicating that the solution has entered a completely miscible state. Therefore, it can be concluded that isopropylamine-water is a partially miscible solution with a "minimum melting point temperature", and its liquid-liquid phase diagram opens upward.

[0100] The solution temperature was raised to 70℃ using the temperature control module. The heavy phase flow rate regulating valve 15 was then slowly reduced, causing the density of the heavy phase solution to gradually increase and eventually stabilize at 937 kg / m³. 3 When the opening of the heavy phase flow regulating valve is further reduced, the density of the heavy phase solution no longer changes. At this time, the phase separation interface of the phase separator 9 has shifted to the light phase outlet side of the phase separator 9, that is, the heavy phase solution outlet is the heavy phase solution with the conjugate composition at 70℃. After stable operation for 15 minutes, a sample is taken through the heavy phase sampling tube, and the concentration of the sampled solution is tested by gas chromatography. The mass content of water in the heavy phase solution is 96.4%. Therefore, the melting point on the right side of the liquid-liquid phase diagram at 70℃ is determined. T =70℃, n 2 =96.4%.

[0101] Restore the heavy phase flow control valve 15 to its initial opening, and slowly reduce the light phase flow control valve 12. The density of the light phase solution gradually decreases and then stabilizes at 648 kg / m³. 3 When the opening of the light phase flow regulating valve 12 is further reduced, the density of the light phase solution no longer changes. At this time, the phase separation interface of the phase separator 9 has shifted to the heavy phase outlet side of the phase separator 9, that is, the light phase solution outlet is the light phase solution under the conjugate composition at 70℃. After stable operation for 15 minutes, a sample is taken through the light phase sampling tube, and the concentration of the sampled solution is tested by gas chromatography. The mass content of water in the light phase solution is tested to be 4.1%. Thus, the melting point on the left side of the liquid-liquid phase diagram at 70℃ is determined. T =70℃, n 1 = 4.1%).

[0102] The solution was cooled at 5°C intervals, and the temperature at each temperature was measured using the method described above. n 1 , n 2 Point concentration; when the solution is cooled to 25℃, the density difference between the light and heavy phases is less than 10 kg / m³. 3 At this point, the increment interval was reduced to 0.5℃ to search for the accurate minimum melting point temperature. When the solution cooled to 21.5℃, the light phase solution and the heavy phase solution in phase separator 9 had the same density, and the density was independent of the flow rate. When sampling and testing at this temperature, the mass concentration of water in the solution was 44.3%, which is the minimum melting point of isopropylamine-water. T s =21.5℃, n s = 44.3%.

[0103] like Figure 4 As shown, by connecting the melting points obtained from each test in sequence, the liquid-liquid phase diagram of isopropylamine-water can be obtained.

[0104] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0105] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A partially miscible solution liquid-phase equilibrium testing system, characterized in that, include: Solution supply module, temperature control module, phase separation module, and test sampling module. The solution supply module includes a heavy phase solution storage tank, a light phase solution storage tank, and a metering pump. The outlets of the heavy phase solution storage tank and the light phase solution storage tank are respectively connected to the inlet of the metering pump. The phase-splitting module includes a phase splitter and a circulating pump, and the outlet of the metering pump is connected to the inlet of the circulating pump. The temperature control module is used to regulate the temperature of the solution entering the phase separator. The outlet of the circulation pump is connected to the inlet of the temperature control module, and the outlet of the temperature control module is connected to the solution inlet of the phase separator. The test sampling module includes a light phase flow meter, a light phase density meter, a light phase flow regulating valve, and a light phase sampling tube installed at the light phase solution outlet of the phase separator, and a heavy phase flow meter, a heavy phase density meter, a heavy phase flow regulating valve, and a heavy phase sampling tube installed at the heavy phase solution outlet of the phase separator. The light phase solution outlet and the heavy phase solution outlet of the phase separator are respectively connected to the inlet of the circulation pump.

2. The partially miscible liquid-phase equilibrium testing system according to claim 1, characterized in that, The heavy phase solution storage tank and the light phase solution storage tank are each equipped with a vacuum port, which is connected to a vacuum pump.

3. The partially miscible liquid-phase equilibrium testing system according to claim 1, characterized in that, The temperature control module includes a heat exchanger, a temperature control pump, and a high-low temperature constant temperature unit connected in sequence. The heat exchanger, temperature control pump, and high-low temperature constant temperature unit form a circulation system. The outlet of the circulation pump is connected to the inlet of the heat exchanger, and the outlet of the heat exchanger is connected to the solution inlet of the phase separator.

4. The partially miscible liquid-phase equilibrium testing system according to claim 1, characterized in that, The heavy phase solution storage tank is equipped with a heavy phase solution reflux port, and the light phase solution storage tank is equipped with a light phase solution reflux port; the heavy phase solution outlet of the phase separator is connected to the heavy phase solution reflux port, and a shut-off valve is installed on the connecting pipeline; the light phase solution outlet of the phase separator is connected to the light phase solution reflux port, and a shut-off valve is installed on the connecting pipeline.

5. The partially miscible liquid-phase equilibrium testing system according to claim 1, characterized in that, The phase separator is a gravity phase separator or a vortex phase separator; the heavy phase flow meter and the light phase flow meter are selected from float flow meters, electromagnetic flow meters, vortex flow meters or ultrasonic flow meters.

6. The partially miscible liquid-phase equilibrium testing system according to claim 3, characterized in that, The high and low temperature constant temperature unit includes a plurality of constant temperature water baths connected in series, and the temperature control range of the high and low temperature constant temperature unit is -80℃ to 150℃.

7. A testing method, characterized in that, A test method for the partially miscible liquid phase equilibrium test system according to any one of claims 1-6 includes the following steps: S1. The heavy phase component in the heavy phase solution storage tank and the light phase component in the light phase solution storage tank are respectively discharged into the phase separator by a metering pump. The mass concentration of the heavy phase component in the phase separator is 40%-60%. S2. Start the circulation pump and temperature control module; S3. Adjust the temperature of the test solution in the phase separator using the temperature control module to bring the test solution into a phase-separated state. Gradually reduce the opening of the heavy phase flow regulating valve and observe the reading of the heavy phase flow meter. Q 重 and the readings of the phase density meter ρ 重 ,when ρ 重 along with Q 重 When the flow rate remains unchanged, stop the adjustment of the heavy phase flow control valve, collect the heavy phase conjugate solution through the heavy phase sampling tube, and test the concentration of the heavy phase component in the heavy phase conjugate solution; restore the heavy phase flow control valve to its initial opening, gradually reduce the opening of the light phase flow control valve, and observe the reading of the light phase flow meter. Q 轻 and light phase density meter readings ρ 轻 ,when ρ 轻 along with Q 轻 When the flow rate remains unchanged, stop the adjustment action of the light phase flow regulating valve, collect the light phase conjugate solution by the light phase sampling tube, and test the concentration of the heavy phase component in the light phase conjugate solution; S4. Raise or lower the temperature of the test solution, repeat step S3, and test the concentration of the heavy phase component in the heavy phase conjugate solution and the light phase conjugate solution at different temperatures; at a specific temperature, ( ρ 重 - ρ 轻 ) / ρ 重 <0.5% and when ρ 重 along with Q 重、 ρ 轻 along with Q 轻 When all remain constant, the concentration of the heavy phase component at the highest or lowest melting point is obtained.

8. The test method according to claim 7, characterized in that, Before step S1, there is also step S0: the step of evacuating the test system.

9. The test method according to claim 7, characterized in that, Following step S2, the steps also include determining the solution phase region and the liquid-liquid phase diagram morphology. Solution phase region determination procedure: Adjust the temperature of the test solution in the phase separator to temperature T, and compare the reading of the light phase density meter. ρ 轻 and the readings of the phase density meter ρ 重 The relationship, if ( ρ 重 - ρ 轻 ) / ρ 重 If <0.5%, then the test solution at temperature T is in a completely miscible state; if ( ρ 重 - ρ 轻 ) / ρ 重 When the concentration is ≥0.5%, the test solution at temperature T is in a phase-separated state. Liquid-liquid phase diagram morphology determination steps: When the test solution at temperature T is in a completely miscible state, raise or lower the temperature of the test solution in the phase separator and compare... ρ 重 , ρ 轻 The relationship between the difference and temperature change, if ρ 重 , ρ 轻 If the difference between the two values ​​increases with increasing temperature or decreases with decreasing temperature, the test solution is determined to be a partially miscible solution with a minimum melting point. When the test solution is in a phase-separated state at temperature T, the solution temperature in the phase separator is increased or decreased, and the values ​​are compared. ρ 重 , ρ 轻 The relationship between the difference and temperature change, if ρ 重 , ρ 轻 The difference between them decreases as the temperature increases or increases as the temperature decreases, and at a specific temperature... ρ 重 = ρ 轻 If the test solution is found to be partially miscible with the lowest melting point, then the test solution is determined to be such that it is a partially miscible solution.

10. The test method according to claim 7, characterized in that, Following step S4, a step of drawing a liquid-liquid phase diagram with the highest melting point or the lowest melting point is also included.

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