A high-purity organic matter purity measurement device based on freezing point depression method

Abstract

The invention discloses a high-purity organic purity measuring device based on a freezing point depression method. The device comprises a dewar flask, a sample insulation environment providing unit, and a sample pool. The lower part of the upper cover of the dewar flask is provided with an insulation vacuum chamber in the shape of a spherical segment. The upper cover is provided with a line pipe, a liquid nitrogen level gauge, a liquid nitrogen delivery pipe, a vacuum pipe, and a nitrogen pressure relief pipe. A heater well with a built-in heater is provided in the sample pool. A platinum resistance temperature sensor is provided on the outer side of the sample pool. Two capillaries are provided on the sample pool. The sample insulation environment comprises multiple layers of insulation screens and a vacuum chamber. Each layer of insulation screen is wound with a manganese copper wire as a heater. The sample pool is suspended in the innermost insulation screen. The inner insulation screen of two adjacent layers of insulation screens is suspended in the outer insulation screen. The outermost insulation screen is suspended in the vacuum chamber. The vacuum chamber is arranged in the dewar flask. The vacuum chamber is connected with the insulation vacuum chamber. Multiple pairs of reversed thermocouples are provided between the sample pool and the inner insulation screen and between adjacent insulation screens.

Description

Technical Field

[0001] The invention relates to a high-purity organic matter purity measuring device, in particular to a high-purity organic matter purity measuring device based on a freezing point depression method. Background Art

[0002] At present, my country generally uses gas chromatography to measure the purity of organic matter. For organic samples with a purity greater than 95%, the purity measurement uncertainty is 0.3%, which cannot meet the measurement needs of ultra-clean and high-purity organic purity. The freezing point depression method is based on the colligative principle of the solvent. When a dilute solution is cooled to the freezing point, when only pure solvent is precipitated, the value of the freezing point decrease is proportional to the amount of solute contained in the dilute solution and has nothing to do with the type of solute. The freezing point depression method is suitable for the measurement of organic purity with a purity of more than 98%. Its expanded uncertainty can reach 0.004%, and the higher the purity of the organic sample, the better its accuracy. Therefore, the freezing point depression method for measuring the purity of organic matter is an accurate and reliable classic measurement method.

[0003] There is no reliable device for measuring the purity of high-purity organic matter based on the freezing point depression method in the prior art. Summary of the invention

[0004] In view of the above-mentioned defects existing in the prior art, the present invention provides a high-purity organic matter purity measuring device suitable for measuring the purity of organic matter by a freezing point depression method.

[0005] The present invention is realized by the following technical scheme: a high-purity organic matter purity measuring device based on the freezing point depression method, characterized in that: it comprises a Dewar flask, a sample insulation environment providing unit, and a sample pool, the Dewar flask comprises a bottle body and an upper cover detachably connected to the bottle body, the lower part of the upper cover has a spherical segment-shaped insulation vacuum chamber, the spherical crown surface of the insulation vacuum chamber is located inside the Dewar flask, the upper cover is provided with a line pipe, a liquid nitrogen level gauge, a liquid nitrogen delivery pipe, a vacuum pipe, and a nitrogen pressure relief pipe, a heater well is provided in the sample pool, a heater is provided in the heater well, a platinum resistance temperature sensor is provided on the outside of the sample pool, two capillaries communicating with the inside of the sample pool are provided on the sample pool, and the sample insulation environment comprises a capillary provided in the sample pool, and a pressure relief pipe provided in the sample pool. The sample pool is surrounded by multiple layers of thermal insulation screens and a vacuum chamber, each layer of thermal insulation screen is wrapped with manganese copper wire as a heater, the sample pool is suspended in the innermost thermal insulation screen, the inner thermal insulation screen of two adjacent layers of thermal insulation screens is suspended in the outer thermal insulation screen, and the outermost thermal insulation screen is suspended in the vacuum chamber, the vacuum chamber is arranged in the Dewar flask, a flange sealing connection is provided on the upper part of the vacuum chamber, the vacuum chamber is connected to the insulated vacuum chamber through a vacuum chamber connecting pipe, a plurality of pairs of reversed thermocouples are arranged between the sample pool and the inner thermal insulation screen and between adjacent thermal insulation screens, and the wires of the heater in the sample pool, each thermocouple, platinum resistance temperature sensor, and the heater of each thermal insulation screen are all led out to the outside of the Dewar flask through the vacuum chamber connecting pipe and the line pipe.

[0006] In the present invention, the heater arranged in the heater well of the sample pool is used to heat the sample in the sample pool, the platinum resistance sensor arranged on the outer side of the sample pool is used to detect the temperature of the sample pool, the multi-layer insulation screen and the vacuum chamber arranged on the periphery of the sample pool are used to provide an insulation environment for the sample, and the thermocouples arranged between the sample pool and the insulation screen and between the insulation screens are used to measure the temperature difference, so as to control the temperature difference between the sample pool and the insulation screen to be 0.001°C. When the present invention is used, the liquid nitrogen delivery pipe is connected to the liquid nitrogen supply device, the vacuum pipe is connected to the vacuum pumping equipment, the heater in the sample pool, each thermocouple, the platinum resistance temperature sensor, and the heater of each insulation screen are respectively connected to the sample melting electric power supply and measurement unit and the sample melting temperature measurement unit, liquid nitrogen is introduced into the Dewar flask through the liquid nitrogen supply device, the temperature in the Dewar flask is reduced by liquid nitrogen, and a low-temperature measurement environment is provided for the sample, the vacuum chamber and the heat-insulating vacuum chamber are evacuated through the vacuum pumping equipment, and the heating of the sample pool and data collection are controlled through the sample melting electric power supply and measurement unit and the sample melting temperature measurement unit. After the heat-insulating vacuum chamber of the present invention is evacuated, a vacuum is formed in the spherical part thereof, which can effectively reduce the heat exchange between the interior of the Dewar flask and the laboratory environment. The two capillaries arranged on the sample pool of the present invention are used to clean the sample pool. When in use, one of the capillaries is connected to a high-purity gas, and the liquid in the sample pool is discharged from the other capillary through a high-speed airflow, and the sample pool is cleaned after multiple operations.

[0007] Furthermore, in order to facilitate connection and ensure the safety of the measurement process, the body of the Dewar flask and the upper cover are connected by a flange.

[0008] Furthermore, in order to ensure the sealing of the vacuum chamber, a polytetrafluoroethylene gasket is arranged between the upper flanges of the vacuum chamber, and two sealing rings with triangular cross-sections are respectively arranged on the sealing surfaces of the two flanges, and the two flanges are connected by spring bolts. The two sealing rings with triangular cross-sections arranged on the flange sealing surfaces cooperate with the polytetrafluoroethylene gasket to greatly improve the flange sealing effect, improve the sealing effect of the vacuum chamber, and isolate the vacuum chamber from the Dewar flask. The two flanges are connected by spring bolts, and the flanges are pressed by the spring bolts. The spring is always in a pressed state. During the entire test process, the spring bolts automatically apply pressure to keep the sealing rings of the two flanges pressed against the polytetrafluoroethylene gasket, and will not fail due to factors such as temperature drop and vacuuming in the vacuum chamber, thereby ensuring the sealing of the vacuum chamber.

[0009] Furthermore, one end of the vacuum chamber connecting pipe is fixedly connected to the bottom of the thermal insulation vacuum chamber, and the other end thereof is fixedly connected to the flange at the top of the vacuum chamber.

[0010] Furthermore, the vacuum chamber and the thermal insulation shield are both cylindrical structures.

[0011] Furthermore, the liquid nitrogen delivery pipe is connected to the bottom of the Dewar flask.

[0012] Furthermore, the platinum resistance temperature sensor is fixed to the center of the outer wall of the sample cell by gluing.

[0013] The beneficial effects of the present invention are as follows: the present invention adopts a Dewar flask, and provides a low-temperature insulation environment for the sample through liquid nitrogen and a vacuum device in the Dewar flask, which can reduce the heat exchange of the sample caused by thermal radiation and air convection near the solidification point to ensure the accuracy and reliability of the experimental process; the design of a multi-layer radiation-proof insulation screen under a vacuum environment can further improve the insulation performance of the sample pool sample environment. The present invention can provide a strict insulation environment for the sample to be tested, has extremely high measurement accuracy and reliability, and can be used as a standard device for measuring the purity of certain substances and a research and development device for standard substances to achieve the value traceability of purity measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural schematic diagram of a specific implementation mode of the present invention;

[0015] Figure 2 yes Figure 1 Schematic diagram of the structure of the sample pool part;

[0016] Figure 3 It is a schematic structural diagram of the vacuum chamber in the present invention;

[0017] Figure 4 It is a schematic diagram of the flange sealing structure of the vacuum chamber in the present invention;

[0018] Figure 5 yes Figure 4 Schematic diagram of the upper flange in FIG.

[0019] Figure 6 yes Figure 4 Schematic diagram of the lower flange in;

[0020] Figure 7 is a schematic diagram of instrument connection in a specific embodiment of the present invention;

[0021] Figure 8 is a time-temperature curve of a blank sample cell to which no sample is added in a specific embodiment;

[0022] Fig. 9 is a time-temperature curve of a sample cell to which benzene is added in a specific embodiment;

[0023] Fig.10 is the power-temperature curve of a blank sample cell without adding a sample in a specific embodiment;

[0024] Fig.11is the electrical work-temperature curve of the sample cell to which benzene is added in a specific embodiment;

[0025] Fig.12 is the electric power-temperature curve of the sample under test after deducting the heat absorbed by the blank sample cell by interpolation in a specific embodiment;

[0026] In the figure, 1. line pipe, 2. liquid nitrogen level gauge, 3. liquid nitrogen delivery pipe; 4. vacuum pipe; 5. nitrogen pressure relief pipe; 6. upper cover of Dewar flask; 7. bolt; 8. thermal insulation vacuum chamber; 9. spherical crown surface of vacuum chamber; 10. vacuum chamber connecting pipe; 11. flange of vacuum chamber; 111. lower flange of vacuum chamber; 112. upper flange of vacuum chamber; 12. spring bolt; 13. sealing ring; 14. polytetrafluoroethylene sealing pad; 15. vacuum chamber; 16. insulation screen; 17. insulation screen hanging wire; 18. support rod; 19. insulation screen; 20. capillary; 21. sample pool; 22. heater trap; 23. Dewar flask; 24. platinum resistance temperature sensor; 25. hook; 26. heater; 27. thermocouple. DETAILED DESCRIPTION

[0027] The present invention will be further described below by way of non-limiting embodiments and in conjunction with the accompanying drawings:

[0028] As attached Figure 1-Figure 6As shown, a high-purity organic purity measuring device based on the freezing point depression method includes a Dewar flask 23, a sample insulation environment providing unit, and a sample pool 21. The Dewar flask 23 is made of stainless steel plate, and includes a bottle body and an upper cover 6. The bottle body and the upper cover 6 are connected by a flange structure. The lower part of the upper cover 6 has an insulated vacuum chamber 8 in the shape of a spherical segment, and the spherical crown surface 9 of the insulated vacuum chamber 8 is located inside the Dewar flask 23. The upper cover 6 is provided with a line pipe 1, a liquid nitrogen level gauge 2, a liquid nitrogen delivery pipe 3, a vacuum pipe 4, and a nitrogen pressure relief pipe 5. Preferably, the liquid nitrogen delivery pipe 3 is connected to the bottom of the Dewar flask 23. The sample pool 21 is made of copper tube, and a heater well 22 is provided in the sample pool 21, and a heater is provided in the heater well 22 for heating the sample. A platinum resistance temperature sensor 24 is arranged on the outside of the sample pool 21. Preferably, the length of the platinum resistance temperature sensor 24 is one quarter of the sample pool, and it is fixed to the center of the outer wall of the sample pool 21 by gluing. Two capillaries 20 are arranged on the sample pool 21 and communicate with the inside thereof. The functions of the two capillaries 20 are: injecting the sample to be tested into the sample pool with a syringe, connecting one of the capillaries with high-purity gas, and discharging the liquid in the sample pool from the other capillary through high-speed airflow, and washing the sample pool after multiple operations. The sample insulation environment includes a multi-layer insulation screen and a vacuum chamber 15 arranged on the periphery of the sample pool 21. The insulation screen is made of copper plate and nickel-plated to increase the smoothness. The insulation screen is preferably a cylindrical structure. The vacuum chamber 15 is a cylindrical structure, and a flange 11 is provided on the upper part of the vacuum chamber 15, including an upper flange 112 and a lower flange 111, a polytetrafluoroethylene sealing gasket 14 is provided between the upper flange 112 and the lower flange 111, and two sealing rings 13 with triangular cross-sections are provided on the sealing surfaces of the upper flange 112 and the lower flange 111, respectively. The upper flange 112 and the lower flange 111 are connected by spring bolts 12, and the spring is always in a compressed state. The vacuum chamber 15 is arranged in the Dewar flask 23. A layer of low-temperature resistant heat-conductive insulating paint is applied on the side and upper and lower bottom surfaces of each insulation screen, and a manganese copper wire is wound around the outside of each insulation screen as a heater. The sample pool 21 is suspended in the innermost insulation screen through the hook 25 on the upper part thereof. The inner insulation screen of the two adjacent insulation screens is suspended on the support rod 18 provided on the upper part of the outer insulation screen through the insulation screen suspension line 17. The outermost insulation screen is suspended in the vacuum chamber 15 and is suspended on the lower flange of the vacuum chamber 15. A vacuum chamber connecting pipe 10 is provided between the vacuum chamber 15 and the insulation vacuum chamber 8. One end of the vacuum chamber connecting pipe 10 is fixedly connected to the bottom of the insulation vacuum chamber 8, and the other end is fixedly connected to the upper flange 112 of the vacuum chamber 15. The vacuum chamber 15 and the insulation vacuum chamber 8 are connected through the vacuum chamber connecting pipe 10. A plurality of pairs of reversed thermocouples are provided between the sample pool 21 and the inner insulation screen and between adjacent insulation screens.The wires of the heater 26 in the sample pool 21 , each thermocouple, platinum resistance temperature sensor, and heaters of each insulation screen are all led out to the outside of the Dewar flask 23 through the vacuum chamber connecting pipe 10 and the line pipe 1 .

[0029] As attached Figure 7 As shown, when the present invention is used, a temperature controller, a programmable constant current source, a standard resistor, and a data acquisition instrument are provided to connect with each heater, thermocouple, and sensor. Among them, the heater of the insulation screen, the sample pool, and the thermocouple of the insulation screen are all connected to the temperature controller, and the temperature difference between the sample pool and the insulation screen is controlled by the temperature controller; the standard resistor is connected in series with the heater in the sample pool and the current channel of the data acquisition instrument, and in parallel with its voltage channel, and then connected to the voltage output terminal of the programmable constant current source, and the programmable constant current source is connected to the industrial computer. The heating electric work of the sample is calculated by measuring the voltage at both ends of the standard resistor, the heating time, and the standard value of the resistor. The platinum resistance temperature sensor of the sample pool is connected to the temperature measuring instrument, and the temperature measuring instrument is connected to the industrial computer.

[0030] In this embodiment, the heater 26 of the sample pool 21 is connected in series with a 0.01 ohm standard resistor, and the voltage of the standard resistor is collected by a 34970A data acquisition instrument of Yes Technology, and the current passing through the heater 26 of the sample pool is calculated according to the standard value of the standard resistor. The temperature of the sample pool 21 is collected by a 34420A seven-and-a-half-digit nanovolt / microohm meter of Yes Technology. The E3641A programmable constant current source of Yes Technology is used to provide electrical energy to the heater 26 of the sample pool. The 350-type temperature controller (with a 3060 thermocouple card) of Lake Shore Company is used to collect the temperature difference between the sample pool and the insulation screen, the temperature difference between the insulation screens, and output electrical energy to the insulation screen. When the temperature of the inner layer is higher than the temperature of the outer layer, the temperature difference is a negative value. The 34420A 7.5-digit nanovolt / micro-ohm meter and the E3641A programmable constant current source are connected to the 610H industrial computer of Advantech through the R232 interface. The 34970A data acquisition instrument and the 350 temperature controller are connected to the 610H industrial computer of Advantech through the GPIB interface. The nEXT400 molecular pump unit of Edwards is connected to the vacuum chamber connecting pipe. The YDZ-200 liquid nitrogen tank of West Asia is connected to the liquid nitrogen delivery pipe 3. The control and analysis software is written in VBnet language. The working process is as follows: start the software, and test the software registration information, NI-VISA installation information, 34420A instrument, 34970A instrument, E3641A instrument and 350 instrument communication connection, etc. After the test is passed, enter the test interface, and give information after the test fails. On the test interface, first set each basic parameter and control parameter, and update the database information. The basic parameters mainly include sample mass, sample molar mass, temperature difference acquisition channel, electric power output channel, temperature point, PID parameters, etc.; the control parameters mainly include temperature, temperature difference temperature range and stabilization time, heater resistance value, output voltage, output current, heating time, number of data acquisition and data filtering range, etc. Liquid nitrogen is introduced into the Dewar flask, the temperature is lowered to the set temperature, the vacuum valve is opened, the vacuum pump is turned on, and the vacuum chamber 15 is evacuated to a vacuum degree below 10 -5Bar. Run the program, the software starts to judge the temperature of the sample pool, the temperature difference between the sample pool and the insulation screen, and the temperature difference between the insulation screens. When the temperature difference between the sample pool and the insulation screen, and the temperature difference between the insulation screens are greater than the set temperature difference, the 350-type temperature controller starts the electric power output, and adjusts the output electric power according to the set PID parameters until the sample pool temperature stabilizes within the set time and set temperature range, and the sample pool and the insulation screen temperature difference, and the insulation screen temperature difference stabilize within the set time and set temperature range. Stop the temperature and temperature difference judgment clock, turn on the E3641A programmable constant current source electric power output clock, the 350-type temperature controller controls the insulation screen temperature difference to track the sample pool temperature, and keeps the temperature difference between the sample pool and the inner insulation screen at 0.001℃. When heating to the set heating time, turn off the electric power output clock and turn on the temperature and temperature difference judgment clock. The electric power output process collects the initial electric power, the intermediate electric power and the electric power at the end, and takes the average electric power for calculation. The heating time takes the system running time of the heating process to participate in the calculation. The temperature data filtering of the sample pool is a combination of periodic integration time and limiting filtering to adjust the instrument. The resistance of the sample pool heater resistor at different temperature points is calibrated to obtain the resistance-temperature curve, and the heat released by the heater is calculated using the calibrated resistance value. The heating power of the sample is the heating power of the sample added at the corresponding temperature minus the heating power of the blank sample pool. The measurement software first measures the blank sample pool without sample added to obtain the power required for the blank sample pool at different temperatures, and then adds the sample to the sample pool to obtain the power of the sample added. The software deducts the heating power of the blank sample pool by interpolation. Figure 8 is the time-temperature curve of the blank sample cell without adding sample, Fig. 9 is the time-temperature curve of the sample cell with benzene added. Figure 8 and Fig. 9 In the process curve, each line segment collected is the temperature of the sample heat balance process after the heating process is completed. Set the sample temperature stabilization time and temperature range, such as 300 seconds and 0.01°C. After the conditions are met, collect the current temperature as the equilibrium temperature and then enter the next heating process. Fig.10 is the power-temperature curve of the blank sample cell without adding sample, Fig.11 is the power-temperature curve of the sample cell with benzene added. Fig.10 and Fig.11In the process curve, the heating power of the blank sample pool is linearly related to the sample temperature, and the heating power of the sample pool with benzene is linearly related to the solid phase and liquid phase of the sample temperature, and the solid-liquid phase temperature changes very little. The intersection of the solid phase data and the solid-liquid phase data is taken as the starting temperature, and the intersection of the solid-liquid phase data and the liquid phase data is taken as the ending temperature. According to the initial temperature and the ending temperature, the total heat absorbed by the sample during the melting process is calculated, and then the heat corresponding to each temperature is divided by the total heat to obtain the melting fraction at different temperatures. The reciprocal of the melting fraction is plotted against the temperature, and the melting point of the pure sample is extrapolated, and then the impurity content in the sample is calculated according to the freezing point depression formula.

[0031] The other parts of this embodiment are all prior art and will not be described in detail here.

Claims

1. A high-purity organic purity measuring device based on the freezing point depression method, characterized in that: The invention comprises a Dewar flask (23), a sample insulation environment providing unit, and a sample pool (21). The Dewar flask (23) comprises a flask body and an upper cover (6) detachably connected to the flask body. The lower part of the upper cover (6) comprises a spherical segment-shaped insulation vacuum chamber (8). The spherical crown surface (9) of the insulation vacuum chamber (8) is located inside the Dewar flask (23). The upper cover (6) is provided with a line pipe (1), a liquid nitrogen level gauge (2), a liquid nitrogen delivery pipe (3), a vacuum pumping pipe (4), and a nitrogen pressure relief pipe (5). The sample pool (21) is provided with a heater well (22). The heater well (22) is provided with a heater. The outer side of the sample pool (21) is provided with a platinum resistance temperature sensor. The sample pool (21) is provided with two capillaries (20) communicating with the interior thereof. The sample insulation environment comprises a multi-layer insulation screen arranged outside the sample pool (21). and a vacuum chamber (15), each layer of insulation screen is wound with manganese copper wire as a heater, the sample pool (21) is suspended in the innermost insulation screen, the inner insulation screen of two adjacent insulation screens is suspended in the outer insulation screen, and the outermost insulation screen is suspended in the vacuum chamber (15), the vacuum chamber (15) is arranged in the Dewar flask (23), a flange sealing connection is provided at the upper part of the vacuum chamber (15), the vacuum chamber (15) and the heat-insulating vacuum chamber (8) are connected through a vacuum chamber connecting pipe (10), a plurality of pairs of reverse-connected thermocouples are respectively arranged between the sample pool (21) and the inner insulation screen and between adjacent insulation screens, and the wires of the heater in the sample pool (21), each thermocouple, the platinum resistance temperature sensor, and the heater of each insulation screen are all led out to the outside of the Dewar flask (23) through the vacuum chamber connecting pipe (10) and the line pipe (1).

2. The high-purity organic matter purity measuring device based on the freezing point depression method according to claim 1 is characterized in that: The body of the Dewar flask (23) and the upper cover are connected by a flange.

3. The high-purity organic matter purity measuring device based on the freezing point depression method according to claim 1 is characterized in that: A polytetrafluoroethylene sealing gasket (14) is arranged between the upper flanges of the vacuum chamber (15), two sealing rings (13) with triangular cross sections are respectively arranged on the sealing surfaces of the two flanges, and the two flanges are connected by spring bolts (12).

4. The high-purity organic matter purity measuring device based on the freezing point depression method according to claim 3 is characterized in that: One end of the vacuum chamber connecting pipe (10) is fixedly connected to the bottom of the heat-insulating vacuum chamber (8), and the other end is fixedly connected to the flange at the top of the vacuum chamber (15).

5. The high-purity organic matter purity measuring device based on the freezing point depression method according to claim 1, 2, 3 or 4, characterized in that: The vacuum chamber (15) and the heat insulation screen are both cylindrical structures.

6. The high-purity organic matter purity measuring device based on the freezing point depression method according to claim 1, 2, 3 or 4, characterized in that: The liquid nitrogen delivery pipe (3) is connected to the bottom of the Dewar flask (23).

7. The high-purity organic matter purity measuring device based on the freezing point depression method according to claim 1 is characterized in that: The platinum resistance temperature sensor is fixed to the center of the outer wall of the sample pool (21) by adhesive bonding.

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