CN115267026A - A high-pressure and low-temperature phase equilibrium measuring device - Google Patents

Abstract

The invention discloses a high-pressure low-temperature phase balance measuring device, which comprises a phase balance system, a refrigerating system, a sampling analysis system and a human-computer interaction system, wherein the phase balance system comprises a phase balance system body, a sampling analysis system and a human-computer interaction system; the phase balance system mainly comprises a high-pressure balance kettle, wherein the main body of the phase balance kettle is made of corrosion-resistant stainless steel, and windows are arranged on two sides of the main body; the refrigeration system is composed of a thermostatic bath and bath liquid external circulation of a low-temperature refrigerator, and a high-pressure balance kettle is arranged in the thermostatic bath during experiments; in a sampling analysis system, gas and liquid phase samples are subjected to composition analysis by using a gas chromatograph in an online sampling mode; the man-machine interaction system comprises a man-machine interface and monitoring parameter integration, and parameter monitoring is completed by a thermocouple and a pressure sensor. The high-pressure low-temperature phase balance measuring device provided by the invention is suitable for measuring gas-liquid phase balance data at the temperature of-80-200 ℃ and the pressure of 0-10 MPa, and has the advantages of short phase balance time, convenience in operation, accurate data and the like.

Description

A high-pressure low-temperature phase equilibrium measurement device

technical field

The invention relates to the technical field of phase balance measurement, in particular to a high-pressure and low-temperature phase balance measurement device.

Background technique

At present, fossil energy such as coal, oil, and natural gas occupies an important position in the energy structure of all countries in the world. With the gradual consumption of fossil energy, people pay more and more attention to whether it can be clean and efficient in the process of energy use. In view of my country's national conditions of "rich in coal, short of oil, and low in gas", coal occupies a dominant position in my country's fossil energy structure. In the field of chemical industry, the use of coal is mainly in two aspects: 1. As a fuel for direct combustion to obtain heat; 2. As a raw material through coal gasification reaction to obtain synthesis gas with CO and _H2 as the main components, both of which involve the generation of acid gases purify. For example, the toxic sulfides in the coal-fired flue gas of coal-fired power plants and cement plants need to be removed before discharge, and part of CO ₂ should be recovered to reduce carbon emissions; in coal chemical industry, the crude synthesis produced after coal gasification Gas needs to be removed under certain temperature and pressure by absorbents such as H ₂ S and CO ₂ . The purpose of removing H ₂ S is to prevent it from poisoning the subsequent reaction catalyst, and the purpose of removing CO ₂ is to reduce the inert components in the raw gas. Ratio, improve the reaction conversion rate. For the development of the above processes, it is necessary to select the solvent. Therefore, it is very important to measure the gas-liquid phase equilibrium data of each component gas and solvent under different temperature and pressure conditions. These basic data are indispensable for the development and numerical simulation of new acid gas absorbents in the fields of natural gas, coal gas and industrial tail gas. At the same time, the gas-liquid phase equilibrium data can also provide a basis for further process optimization and energy recovery.

Because the solubility of gas in liquid varies greatly with temperature and pressure, especially under high pressure and low temperature, the measurement of gas-liquid phase equilibrium data is more difficult, and it is difficult to obtain accurate values from experimental results. Compared with normal pressure, the determination of gas solubility under high pressure also needs to ensure that the gas phase and liquid phase are fully mixed; compared with normal temperature, it is much more difficult to control the temperature, sample, and analyze the dissolved gas at low temperature. Moreover, high pressure and low temperature gas-liquid equilibrium data and corresponding test methods are very scarce.

In order to ensure that the gas-liquid phase equilibrium data can be accurately measured under low temperature and high pressure conditions, the device proposed by the present invention has been improved in terms of experimental conditions, balance tank structure, and sampling methods. First of all, this device uses a low-temperature refrigerator as a cold source, and the low-temperature bath liquid is used to cool the balance tank, and the experimental temperature range can be set between -80 and 200°C; secondly, compared with the patents described in CN205146108U and CN107727805B The complex mechanical stirring structure used in the high-pressure balance kettle in the device, the device of the present invention adopts the magnetic stirring method, which can not only improve the sealing performance at low temperature, but also make the balance kettle simple in structure, easy to disassemble, and easy to clean the inside of the balance kettle; finally, in the In the liquid phase sampling analysis, compared with the off-line sampling method that relies on the micro-sampling needle used in the patent CN107727805B, this device combines valve switching, carrier gas purging, heating and gasification, etc. Sampling and analysis of liquid phase samples minimizes the impact of liquid phase sampling on the phase balance of the system to be measured in the high-pressure equilibrium kettle; especially under low temperature conditions, the solubility of gases is more sensitive to temperature changes.

In order to improve the deficiencies of the above-mentioned prior art, the present invention is hereby proposed.

Contents of the invention

The invention aims to make up for the gap that the prior art cannot accurately measure gas-liquid phase balance data under high-pressure and low-temperature conditions, and provides a high-pressure and low-temperature phase balance measurement device.

In order to achieve the above object, the present invention adopts the following technical solutions:

A high-pressure and low-temperature phase balance measurement device, including a phase balance system, a sampling analysis system, a refrigeration system and a human-computer interaction system; the phase balance system mainly includes a high-pressure balance kettle, and the high-pressure balance kettle is composed of a balance kettle body, an inner flange, and an outer flange , gaskets, bolts and sapphire. Among them, the outer flange, sapphire, inner flange, bolts and gaskets together constitute the viewing window; a magnetic stirrer is placed at the inner bottom of the high-pressure balance kettle; The sampling pipeline, the first thermocouple and the first pressure transmitter; the sampling of the gas and liquid phase samples share a sampling pipeline, and the sampling pipeline is directly connected to the cylinder of the gas to be measured through the fourth shut-off valve; The fourth control valve is connected to the solvent sampling funnel; the refrigeration system is composed of a constant temperature tank and the bath liquid outer circulation of the low-temperature refrigerator; the high-pressure balance kettle is directly placed in the constant temperature tank during the experiment, and the liquid temperature of the low temperature bath liquid in the constant temperature tank is maintained. The surface is higher than the upper surface of the balance kettle body; the first stop valve, the second stop valve and the first control valve are arranged on the circulation pipeline of the low-temperature bath liquid, and the replacement speed and liquid The height of the surface ensures the dynamic stability of the low temperature environment; the sampling and analysis system includes two parts: gas phase sampling and liquid phase sampling; The phase sampling pipeline is connected to the lower part of the balance kettle body; both the gas phase sampling pipeline and the liquid phase sampling pipeline use stainless steel capillary tubes with an inner diameter of 0.4-1.4 mm; the sampling pipeline, gas phase sampling pipeline and liquid phase sampling pipeline pass through the valve It is connected to the vacuum tank; the gas and liquid phase samples after sampling are analyzed by gas chromatography; the human-computer interaction system includes the human-computer interface and the first thermocouple in the balance tank body communicating with it, the first pressure transmitter and the gasification chamber The second thermocouple and second pressure transmitter; the man-machine interface can display and record the measurement data of the above thermocouples and pressure transmitters in real time; at the same time, control the heating temperature of the vaporization chamber and its auxiliary pipelines The system is integrated into the human-machine interface.

The further improvement of the present invention is that: the high-pressure balance kettle, pipelines, valves and joints in the device are all made of stainless steel, and the good corrosion resistance of this material can adapt to the measurement of corrosive liquid and corrosive gas-liquid phase equilibrium data .

The further improvement of the present invention is that: the viewing window is composed of flanges, sapphires, gaskets and fixing bolts, with simple structure, convenient disassembly and assembly, and is beneficial to cleaning inside the balance kettle.

The further improvement of the present invention lies in: the balanced kettle body is set as a flat rectangular straight cylinder, the bottom surface is square, and the side length is 2 to 5 times the height of the balanced kettle body; when the volume of solvent added is constant, the structure setting can increase the gas-liquid contact area , improve mass transfer efficiency, and reduce the time for the system to be tested in the high-pressure equilibrium kettle to reach phase equilibrium.

The further improvement of the present invention lies in: a stirring rotor is placed in the high-pressure balance kettle, a magnetic stirrer is placed at the bottom of the constant temperature tank, and disturbance is added to the inside of the high-pressure balance kettle through magnetic stirring to increase the mass transfer rate. The magnetic stirring method is used instead of the traditional mechanical stirring, which enhances the sealing performance of the balance tank and expands the measurable pressure range of the phase balance experiment.

The further improvement of the present invention lies in that the sampling pipelines and analysis systems for the gas and liquid phase samples are respectively arranged to eliminate the error caused by the gas and liquid phases sharing one sampling pipeline and analysis system; the separation of the pipelines can also ensure that the gas and liquid phase Samples can be taken at the same time to make the measurement results more accurate.

The further improvement of the present invention lies in that the gas and liquid phase sampling pipelines use stainless steel capillary tubes with an inner diameter of 0.4-1.4 mm to reduce the influence of the dead volume of the pipelines on the measurement results. The incision of the connecting part of the pipeline and the fittings is smooth, and there are no rough burrs inside the pipeline and fittings, so as to ensure the sufficient flow of the sample during sampling.

The further improvement of the present invention lies in: the liquid phase sampling part of the device realizes the online sampling and analysis of the liquid phase sample through pipeline switching, carrier gas purging, heating and gasification, etc. , which can greatly reduce the damage to the phase balance that has been achieved during the sampling process, making the measurement results more accurate.

The further improvement of the present invention is that: the solvent feeding tank uses a variable-diameter stainless steel funnel, and a needle valve with relatively sensitive control is used at the bottom. When feeding, the rate of solvent input into the balance tank can be controlled to be 20-100mL/min. After feeding, a certain liquid level can be maintained in the funnel to prevent air inhalation.

The further improvement of the present invention lies in: the constant temperature tank is provided with an inlet and outlet for circulation of low-temperature bath liquid, and a valve is added at the entrance of the bath liquid, and the rate of renewal of the bath liquid in the constant temperature tank is controlled by controlling the opening of the valve, and then the solvent in the kettle is controlled. cooling rate.

The further improvement of the present invention lies in: the pressure transmitter and thermocouple signals are transmitted to the man-machine interface, and with the help of the display and recording functions of the device, the pressure and temperature changes in the balance tank can be reflected and recorded in real time, and the temperature, pressure The change curve is convenient for experimenters to directly judge the phase equilibrium stability of the system in the high-pressure equilibrium kettle.

The further improvement of the present invention lies in that the vacuum pump is connected with the high-pressure balance kettle, the gas and liquid phase sampling pipelines and the vaporization chamber through the vacuum tank and various valves. At the beginning of the experiment, the autoclave can be pumped to a vacuum state to reduce the time for gas replacement in the autoclave, and then the solvent can be sucked into the autoclave by means of the pressure difference between the autoclave and the outside atmosphere. Before sampling in the experiment, the sampling pipeline and vaporization chamber can be evacuated to remove the influence of residual samples in the pipeline after the previous sampling on this sampling.

The further improvement of the present invention lies in: selecting the type of valve according to the use position and purpose of use of each valve, selecting a more sensitive needle valve at the place where the fluid flow rate needs to be controlled, and using a ball valve at the place where it is only necessary to control the opening and closing of the pipeline; for example, solvent The injection port needs to control the inhalation speed of the solvent to prevent air from entering the equilibrium kettle. Here, a needle valve with a controllable opening is preferred.

The further improvement of the present invention lies in: the device can complete the gas-liquid phase equilibrium measurement experiment under the temperature condition of -80-200° C. and the pressure condition of 0-10 MPa.

Compared with the prior art, the present invention has the following technical advantages:

(1), the balance kettle body of the high-pressure balance kettle is set as a flat rectangular straight cylinder, the bottom surface is square, and the side length is 2 to 5 times the height of the balance kettle body. This structure increases the contact area of gas and liquid, and can reduce the two phases to reach The time required for phase equilibrium.

(2) Sight glasses are installed on both sides of the autoclave, which can be used to observe the solvent level in the autoclave, the disturbance of the stirrer to the solvent, and the phase balance and mass transfer; Cleaning of the inside of the balance kettle.

(3) A vacuum pump and a vacuum tank are added to the device, which can pump the high-pressure balance kettle and gasification chamber to a vacuum state, reducing the number of gas replacements before the experiment. Vacuum the sampling pipeline before sampling, which can eliminate the influence of the residual sample attached to the inner wall of the pipeline after the previous set of sampling on the sampling results of this time, and improve the accuracy of the measurement results.

(4) The man-machine interface records the temperature, pressure and other parameters of the high-pressure balance kettle and the gasification chamber in real time, and draws the temperature and pressure change curves, which is convenient for the experimenters to judge the stable state of the phase balance.

(5), the analysis sampling analysis system is simple, easy to operate, and has high accuracy at the same time. It is suitable for the determination of gas-liquid phase equilibrium data under various medium and high pressure and low temperature conditions.

Description of drawings

Fig. 1 is the structural representation of high-pressure low-temperature phase equilibrium measuring device of the present invention;

Fig. 2 is a structural diagram of a high-pressure balanced kettle of the present invention;

Among them: 1 is the carrier gas cylinder; 2 is the gas cylinder to be tested; 3 is the man-machine interface; 4 is the low-temperature refrigerator; 5 is the high-pressure balance kettle; 6 is the bolt; 7 is the outer flange; 8 is the inner flange; 9 is Sapphire; 10 is a magnetic stirrer; 11 is a magnetic stirrer; 12 is a constant temperature tank; 13 is a vaporization chamber; 14 is a pressure relief port; 15 is a solvent sampling funnel; 16 is a vacuum pump; 17 is a vacuum tank; 18 is a gas phase Chromatography; 19 is the sampling pipeline; 20 is the gas phase sampling pipeline; 21 is the liquid phase sampling pipeline; 22 is the quantitative sampling pipeline; 23 is the first thermocouple; 24 is the second thermocouple; 25 is the first pressure Transmitter; 26 is the second pressure transmitter; 27 is the vacuum gauge; 28 is the first three-way ball valve; 29 is the second three-way ball valve; 30 is the first stop valve; 31 is the second stop valve; 32 is The third shut-off valve; 33 is the fourth shut-off valve; 34 is the fifth shut-off valve; 35 is the sixth shut-off valve; 36 is the seventh shut-off valve; 37 is the eighth shut-off valve; 38 is the ninth shut-off valve; 39 is the first shut-off valve Ten stop valve; 40 is the first control valve; 41 is the second control valve; 42 is the third control valve; 43 is the fourth control valve; 44 is the fifth control valve; 45 is the sixth control valve; 46 is the gasket 47 is the balance still body.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

Referring to Fig. 1 and Fig. 2, this article provides a high-pressure low-temperature phase balance measurement device, including a high-pressure balance kettle, a sampling and analysis system, a refrigeration system and a human-computer interaction system.

The high-pressure balance kettle 5 uses corrosion-resistant stainless steel as the balance kettle body 47 and pipeline material, and uses sapphire 9 as the window material to ensure that the device can cope with the detection of corrosive sample phase balance, and at the same time expand the pressure range that can be measured in the experiment. The balance kettle body 47 of the high-pressure balance kettle is a flat rectangular straight tube with a square bottom surface, and the side length is 2 to 5 times the height of the balance kettle body 47, so as to increase the gas-liquid phase contact area. There are windows symmetrically arranged on both sides of the high-pressure balance kettle 5, and the windows include the inner flange 8, the outer flange 7, the sapphire 9, the gasket 46 and the bolt 6; the solvent liquid level inside the high-pressure balance kettle and the two-phase transmission can be observed through the windows. At the same time, it is necessary to adjust the rotation rate of the magnetic stirrer 10 in the autoclave 5 to a suitable state according to the level of the solvent. If the stirring rate is too high, the liquid will splash and affect the gas phase sample analysis; if the stirring rate is too low, the mass transfer will be slow. , to prolong the time for phase equilibrium stability.

On the balanced kettle body, respectively connect the sampling pipeline 19, the gas phase sampling pipeline 20, the liquid phase sampling tube 21, the first thermocouple 23 and the first pressure transmitter 25; The sample pipeline 19; the sample injection pipeline 19 is directly connected with the gas cylinder 2 to be measured through the fourth shut-off valve 33; the fourth control valve 43 is connected with the solvent sampling funnel 15; the sample injection pipeline 19 passes through the fifth shut-off valve 34 It is connected with the ninth shut-off valve 38 and the vacuum tank 17 . The autoclave 5 needs to be evacuated before solvent sampling, and the steps are: close the fifth stop valve 34 and the ninth stop valve 38, start the vacuum pump 16 to pump the vacuum tank 17 to a vacuum state, open the fifth stop valve 34 and the ninth stop valve Nine shut-off valves 38 , pump the inside of the high-pressure balance kettle 5 to a vacuum state, and close the fifth shut-off valve 34 and the ninth shut-off valve 38 . The solvent sampling step is as follows: ensure that the inside of the high-pressure balance kettle 5 is in a vacuum state, add an appropriate amount of solvent in the solvent sampling funnel 15, slowly adjust the fourth control valve 43 at the bottom of the solvent feeding funnel 15, and adjust the solvent to be under the action of the pressure difference. The rate of 20-100mL/min is sucked into the high-pressure balance kettle 5 until the liquid level of the solvent in the kettle reaches the middle of the sapphire 9, and the fourth control valve 43 is closed; position to prevent air inhalation. The gas sampling steps are as follows: keep the fourth cut-off valve 33 closed, adjust the pressure reducing valve at the outlet of the gas cylinder 2 to the required measurement pressure, then open the fourth cut-off valve 33, and gradually input the gas to be tested into the kettle; start the magnetic force The stirrer 11 adjusts the rotating speed of the magnetic stirrer 10 to a suitable state to add disturbance to the solvent in the kettle. During the temperature drop of the experiment, the pressure reducing valve at the outlet of the gas cylinder 2 and the fourth cut-off valve 33 can be kept open, so that the gas to be tested is always in the input state during the temperature drop; Stablize. When the pressure and temperature in the high-pressure equilibrium kettle 5 remain unchanged for 2 to 4 hours, it can be considered that the two phases in the kettle have reached equilibrium, and the gas and liquid phase samples are respectively sampled for analysis.

The sampling analysis system includes two parts: gas phase sampling and liquid phase sampling; in the gas phase sampling part, the gas phase sampling pipeline 20 is connected to the top of the high-pressure balance kettle 5, and the pipeline port needs to be inserted a little above the balance kettle body 47; the liquid phase sampling pipeline 21 It is connected with the bottom of the high pressure balance kettle 5. The gas phase sampling part includes a gas phase sampling pipeline 20 , a seventh cut-off valve 36 , a sixth control valve 45 and a sixth cut-off valve 35 . Before gas phase sampling, it is necessary to evacuate the pipeline first. The steps are: keep the seventh stop valve 36, the sixth control valve 45 and the sixth stop valve 35 closed, start the vacuum pump 16, and wait for the vacuum tank 17 to be evacuated to a vacuum state Afterwards, the sixth cut-off valve 35 and the ninth cut-off valve 38 are opened, the inside of the pipeline to be connected thereto is evacuated to a vacuum state, and the sixth cut-off valve 35 and the ninth cut-off valve 38 are closed. During gas phase sampling, keep the sixth cut-off valve 35 closed, open the seventh cut-off valve 36, the sample enters the pipeline under pressure, and control the gas phase sampling rate by adjusting the opening of the sixth control valve 45 to transport the gas phase sample into gas chromatography for compositional analysis.

The liquid phase sampling part includes the liquid phase sampling pipeline 21, the eighth stop valve 37, the third stop valve 32, the carrier gas cylinder 1, the first three-way ball valve 28, the quantitative sampling tube 22, the second three-way ball valve 29, the second The control valve 41 , the tenth stop valve 39 , the vaporization chamber 13 , and the fifth control valve 44 . Before liquid phase sampling, it is necessary to complete the purging of the quantitative sampling pipeline 22 and the gas replacement in the gasification chamber 13. The steps are: adjust the pressure reducing valve of the carrier gas cylinder 1 to 0.2MPa, and keep the third shut-off valve 32 at Open, switch the first three-way ball valve 28 to the side of the carrier gas cylinder 1, switch the second three-way ball valve 29 to the side of the sampling port, adjust the valve of the second control valve 41 to the maximum opening, use the carrier gas to carry out quantitative sampling pipeline 22 Purging, after purging, close the second control valve 41 to complete the purging work of the quantitative sampling pipeline 22 . Next, switch the second three-way ball valve 29 to the gasification chamber 13 side, inflate the inside of the gasification chamber 13 to 0.2 MPa, and close the second three-way ball valve 29 . Start the vacuum pump 16, and after the vacuum tank 17 is evacuated, open the tenth shut-off valve 39, so that the inside of the gasification chamber 13 is pumped to a vacuum state, and close the tenth shut-off valve 39; then switch the second three-way ball valve 29 to On the gasification chamber 13 side, the gasification chamber 13 is refilled with air. Repeat the gasification and pumping of the gasification chamber 13 for 2 to 5 times according to the above steps, so as to fully replace the inside of the gasification chamber 13 . After the replacement, keep the gasification chamber 13 in a vacuum state, and switch all the above-mentioned valves to close. When sampling the liquid phase sample, switch the first three-way ball valve 28 to the direction of the high-pressure balance kettle 5, and the second three-way ball valve 29 to the direction of the sampling port, open the eighth stop valve 37, and the liquid phase sample is passed from the high-pressure balance kettle 5 under pressure. It flows into the liquid phase sampling pipeline 21, and the rate of liquid phase sample sampling is adjusted by adjusting the valve opening of the second control valve 41 at the sampling port. After part of the liquid phase sample with insufficient mass transfer is drained, all valves are closed, and at this time, the inside of the quantitative sampling tube 22 is filled with the liquid phase sample to be analyzed. To adjust the pressure reducing valve pressure of the carrier gas cylinder 1, first open the third stop valve 32, switch the second three-way ball valve 29 to the direction of the vaporization chamber 13, then switch the first three-way ball valve 28 to the direction of the carrier gas cylinder 1, and pass the carrier gas The liquid phase sample is brought into the gasification chamber 13 by the flow, and the first three-way ball valve 28 and the second three-way ball valve 29 are closed. Through the man-machine interface 3, the heating temperature of the vaporization chamber 13 is adjusted, and the liquid phase sample inside the vaporization chamber is heated into a gas. After the temperature and pressure in the gasification chamber 13 are stabilized, slowly adjust the valve opening of the fifth control valve 44, and the vaporized liquid phase sample enters the gas chromatograph 18 under pressure for composition analysis.

The refrigeration system includes a cryogenic refrigerator 4 and a constant temperature tank 12 . In terms of the choice of low-temperature bath, when the use temperature is above 10°C, you can choose to use distilled water or deionized water as the bath liquid; when the use temperature is -30°C, you need to use 99% (mass fraction) ethanol. The refrigeration temperature is set by the cryogenic refrigerator 4 . Through the first cut-off valve 30 and the second cut-off valve 31, the opening and closing of the low-temperature bath liquid external circulation pipeline is controlled, and by adjusting the opening of the first control valve 40, the circulation speed of the bath liquid in the constant temperature tank is controlled, thereby controlling The internal cooling and heating rate of the high-pressure equilibrium kettle 5 and the liquid level height of the bath liquid.

In the human-computer interaction system, the human-machine interface 3 is used to communicate with the thermocouple and pressure sensor in the device, mainly including the first thermocouple 23 in the balance kettle body, the first pressure transmitter 25 and the second thermocouple 24 in the gasification chamber, The second pressure transmitter 26 . Among them, the temperature and pressure in the high-pressure balance kettle 5 are monitored and recorded in real time, and the temperature and pressure change curves in the period of time are drawn to help the experimenter more intuitively judge whether the phase equilibrium system in the kettle is stable; the pressure in the gasification chamber 13 , temperature to help experimenters judge whether the liquid phase sample in the vaporization chamber is completely vaporized. At the same time, the heating temperature of the vaporization chamber 13 and its auxiliary pipelines can be set on the man-machine interface 3, and the temperature can be freely selected according to the properties of the liquid phase sample.

In order to describe the present invention more specifically, the following describes the present invention in detail through Example 1 to Example 3, but is not limited to the protection scope of the present invention.

Embodiment one

(1) Before the experiment is carried out, disassemble the high-pressure balance kettle 5, use deionized water to clean all parts and accessories, and use methanol to fully rinse; after drying and fully cooling in the drying oven, reinstall the parts of the high-pressure balance kettle 5, and Connect to the device. Use the carrier gas to inflate the high-pressure balance kettle 5 and the device pipeline to 3-5 MPa, and check the air tightness of the device. If there is no obvious pressure drop within 3 hours, the air tightness test is qualified.

(2) Start the vacuum pump 16 to pump the inside of the high-pressure balance kettle 5 to a vacuum state. Adjust the pressure reducing valve of _CO2 gas cylinder 1 to 0.2MPa, inject _CO2 gas into the high-pressure balance kettle 5, remove the internal pressure of the high-pressure balance kettle 5 to atmospheric pressure through the pressure relief port 14 on the top of the device, and then use the vacuum pump 16 to pump out the inside of the kettle. to a vacuum state. Repeat several times until there is no impurity gas in the autoclave 5, and the gas replacement inside the autoclave 5 is completed. Evacuate the high-pressure balance kettle 5 to a vacuum, inject methanol into the high-pressure balance kettle 5 through the solvent feed funnel 15, and adjust the opening of the fourth control valve 43 to control the methanol inhalation rate. When the feeding is completed, a certain amount of methanol liquid level should remain in the solvent feeding funnel 15 to prevent air from being sucked. During the feeding period, it is necessary to observe the methanol liquid level in the high-pressure balance kettle 5 at all times, and it is best if the liquid level reaches half of the height of the sight glass. Start the magnetic stirrer 11 at the bottom of the constant temperature tank 12, and adjust the magnetic stirrer 10 in the kettle to a suitable speed.

(3) Open the CO ₂ gas cylinder 2, inject CO ₂ into the high-pressure balance kettle 5, and adjust the pressure reducing valve of the CO ₂ cylinder to the pressure to be measured at 0.689 MPa. Use absolute ethanol as the bath liquid, start the low-temperature refrigerator 4 external circulation pump, open the external circulation of the bath liquid between the low-temperature refrigerator 4 and the constant temperature tank 12, adjust the opening of the first control valve 1 so that the bath liquid is in the constant temperature tank 12 The liquid level is kept constant. Start the refrigeration function of the low-temperature refrigerator 4, and set the temperature at -25.2°C. Wait for a period of time until the temperature in the autoclave 5 reaches -23.2° C. and does not continue to drop, then close the fourth cut-off valve 33 between the CO gas cylinder ₂ and the autoclave 5 . When the temperature and pressure in the kettle are stabilized, read from the man-machine interface 3 that the temperature inside the high-pressure equilibrium kettle 5 is -23.2°C and the pressure is 0.689MPa, and record it. The gas and liquid phase samples are respectively sampled to the gas chromatograph 18 for analysis.

(4) Keep the temperature in the kettle constant at -23.2°C, change the opening of the pressure reducing valve of the _CO2 cylinder to adjust the internal pressure of the high-pressure balance kettle 5 to 1.034, 1.379, 1.586, and 1.655 MPa respectively, and wait for the pressure and temperature in the kettle to stabilize again , record the data of man-machine interface 3 and sample analysis, and record the gas-liquid phase equilibrium data of _CO and methanol as shown in Table 1, y ₁ is the molar fraction of methanol (component 1) in the gas phase sample, and x ₂ is Mole fraction of CO ₂ (component 2) in liquid phase samples.

Table 1 Phase equilibrium data of methanol (marked as component 1) and CO ₂ (marked as component 2)

Embodiment two

(1) Before the experiment is carried out, disassemble the high-pressure balance kettle 5, use deionized water to clean all parts and accessories, and use methanol to fully rinse; after drying and fully cooling in the drying oven, reinstall the parts of the high-pressure balance kettle 5, and Connect to the device. Use the carrier gas to inflate the high-pressure balance kettle 5 and the device pipeline to 3-5 MPa, and check the air tightness of the device. If there is no obvious pressure drop within 3 hours, the air tightness test is qualified.

(2) Start the vacuum pump 16 to pump the inside of the high-pressure balance kettle 5 to a vacuum state. Adjust the pressure reducing valve of _CO2 gas cylinder 1 to 0.2MPa, inject _CO2 gas into the high-pressure balance kettle 5, remove the internal pressure of the high-pressure balance kettle 5 to atmospheric pressure through the pressure relief port 14 on the top of the device, and then use the vacuum pump 16 to pump out the inside of the kettle. to a vacuum state. Repeat several times until there is no impurity gas in the autoclave 5, and the gas replacement inside the autoclave 5 is completed. Evacuate the high-pressure balance kettle 5 to a vacuum, inject methanol into the high-pressure balance kettle 5 through the solvent feed funnel 15, and adjust the opening of the fourth control valve 43 to control the methanol inhalation rate. When the feeding is completed, a certain amount of methanol liquid level should remain in the solvent feeding funnel 15 to prevent air from being sucked. During the feeding period, it is necessary to observe the methanol liquid level in the high-pressure balance kettle 5 at all times, and it is best if the liquid level reaches half of the height of the sight glass. Start the magnetic stirrer 11 at the bottom of the constant temperature tank 12, and adjust the magnetic stirrer 10 in the kettle to a suitable speed.

(3) Open the CO ₂ gas cylinder 2, inject CO ₂ into the high-pressure balance kettle 5, and adjust the pressure reducing valve of the CO ₂ cylinder to the pressure to be measured at 0.689 MPa. Use absolute ethanol as the bath liquid, start the external circulation pump of the low temperature refrigerator 4, open the external circulation of the bath liquid between the low temperature refrigerator 4 and the constant temperature tank 12, adjust the opening degree of the first control valve 1 so that the bath liquid is in the constant temperature tank 12 The liquid level is kept constant. Start the refrigeration function of the low-temperature refrigerator 4, and set the temperature at -46°C. Wait for a period of time until the temperature in the autoclave 5 reaches -40.2° C. and does not continue to drop, then close the fourth cut-off valve 33 between the CO gas cylinder ₂ and the autoclave 5 . When the temperature and pressure in the kettle are stabilized, the temperature inside the high-pressure equilibrium kettle 5 is read from the man-machine interface 3 as -40.2°C and the pressure is 0.689MPa and recorded. The gas and liquid phase samples are respectively sampled to the gas chromatograph 18 for analysis.

(4) Keep the temperature in the kettle constant at -40.2°C, change the opening of the pressure reducing valve of the CO ₂ cylinder to adjust the internal pressure of the high-pressure balance kettle 5 to 0.758, 0.821, 0.862, and 0.876 MPa respectively, and wait for the pressure and temperature in the kettle to stabilize again , read the man-machine interface 3 data and sample analysis, record _CO2 and the gas-liquid phase equilibrium number of methanol as shown in Table 2, _y1 is the molar fraction of methanol (component 1) in the gas phase sample, _x2 is the mole fraction of CO ₂ (component 2) in the liquid phase sample.

Table 2 Phase equilibrium data of methanol (marked as component 1) and CO ₂ (marked as component 2)

Embodiment three

(1) Before the experiment is carried out, disassemble the high-pressure balance kettle 5, use deionized water to clean all parts and accessories, and use methanol to fully rinse; after drying and fully cooling in the drying oven, reinstall the parts of the high-pressure balance kettle 5, and Connect to the device. Use the carrier gas to inflate the high-pressure balance kettle 5 and the device pipeline to 3-5 MPa, and check the air tightness of the device. If there is no obvious pressure drop within 3 hours, the air tightness test is qualified.

(2) Start the vacuum pump 16 to pump the inside of the high-pressure balance kettle 5 to a vacuum state. Adjust the pressure reducing valve of _CO2 gas cylinder 1 to 0.2MPa, inject _CO2 gas into the high-pressure balance kettle 5, remove the internal pressure of the high-pressure balance kettle 5 to atmospheric pressure through the pressure relief port 14 on the top of the device, and then use the vacuum pump 16 to pump out the inside of the kettle. to a vacuum state. Repeat several times until there is no impurity gas in the autoclave 5, and the gas replacement inside the autoclave 5 is completed. Evacuate the high-pressure balance kettle 5 to a vacuum, inject methanol into the high-pressure balance kettle 5 through the solvent feed funnel 15, and adjust the opening of the fourth control valve 43 to control the methanol inhalation rate. When the feeding is completed, a certain amount of methanol liquid level should remain in the solvent feeding funnel 15 to prevent air from being sucked. During the feeding period, it is necessary to observe the methanol liquid level in the high-pressure balance kettle 5 at all times, and it is best if the liquid level reaches half of the height of the sight glass. Start the magnetic stirrer 11 at the bottom of the constant temperature tank 12, and adjust the magnetic stirrer 10 in the kettle to a suitable speed.

(3) Open the CO ₂ gas cylinder 2, inject CO ₂ into the high-pressure balance kettle 5, and adjust the pressure reducing valve of the CO ₂ cylinder to the pressure to be measured at 0.689 MPa. Use absolute ethanol as the bath liquid, start the low-temperature refrigerator 4 external circulation pump, open the external circulation of the bath liquid between the low-temperature refrigerator 4 and the constant temperature tank 12, adjust the opening of the first control valve 1 so that the bath liquid is in the constant temperature tank 12 The liquid level is kept constant. Start the refrigeration function of the low-temperature refrigerator 4, and set the temperature at -3°C. Wait for a period of time until the temperature in the autoclave 5 reaches 0° C. and does not continue to decrease, then close the fourth cut-off valve 33 between the CO gas cylinder ₂ and the autoclave 5 . When the temperature and pressure in the kettle are stable, read from the man-machine interface 3 that the temperature inside the high-pressure equilibrium kettle 5 is 0°C and the pressure is 0.689MPa, and record it. The gas and liquid phase samples are respectively sampled to the gas chromatograph 18 for analysis.

(4) Keep the temperature in the kettle constant at 0°C, and adjust the internal pressure of the high-pressure balance kettle 5 to 1.379, 1.724, 2.069, 2.758, and 3.082 MPa by changing the opening of the pressure reducing valve of the _CO2 steel cylinder, and wait until the pressure and temperature in the kettle are restored. After stabilization, read the man-machine interface 3 data and sample analysis, record CO _The gas-liquid phase equilibrium number of methanol and as shown in table 3, y ₁ is the molar fraction of methanol (component 1) in the gas phase sample, x ₂ is the mole fraction of CO ₂ (component 2) in the liquid phase sample.

Table 3 Phase equilibrium data of methanol (marked as component 1) and CO ₂ (marked as component 2)

Claims (10)

1. A high-pressure low-temperature phase balance measuring device is characterized in that, comprising a phase balance system, a sampling analysis system, a refrigeration system and a human-computer interaction system; The phase balance system mainly includes a high-pressure balance kettle (5), which consists of a balance kettle body (47), an inner flange (8), an outer flange (7), a gasket (46), bolts (6) and sapphire (9); among them, the outer flange (7), sapphire (9), inner flange (8), bolts (6) and gaskets (46) together form the window; A magnetic stirring bar (10) is placed at the bottom; On the balanced kettle body (47), connect respectively the sampling line (19), the gas phase sampling line (20), the liquid phase sampling line (21), the first thermocouple (23) and the first pressure transmitter ( 25); wherein the sampling of the gas and liquid phase samples shares a sampling pipeline (19), and the sampling pipeline (19) is directly connected with the gas cylinder (2) to be measured by the fourth cut-off valve (33); Four control valves (43) link to each other with solvent sampling funnel (15); The refrigerating system is composed of a constant temperature tank (12) and a bath liquid external circulation of a low temperature refrigerator (4); during the experiment, the high-pressure balance kettle (5) is directly placed in the constant temperature tank (12), and the temperature inside the constant temperature tank (12) is kept low. The liquid level of the warm bath liquid is higher than the upper surface of the balance kettle body (47); a first shut-off valve (30), a second shut-off valve (31) and a first control valve (40) are arranged on the circulation pipeline of the low-temperature bath liquid, The replacement speed and liquid level height of the low-temperature bath liquid in the constant temperature tank (12) are controlled through the linkage of the above-mentioned valves, so as to ensure the dynamic stability of the low-temperature environment; The sampling and analysis system includes two parts: gas phase sampling and liquid phase sampling; the gas phase sampling pipeline (20) is connected to the top of the balance kettle body (47), and the pipeline port needs to be inserted into the upper plane of the balance kettle body (47) by 3-10mm; The sampling pipeline (21) is connected to the lower part of the balance kettle body (47); the gas phase sampling pipeline (20) and the liquid phase sampling pipeline (21) all use stainless steel capillary tubes with an internal diameter of 0.4 to 1.4 mm; the sampling pipeline (20 ), gas phase sampling pipeline (20) and liquid phase sampling pipeline (21) link to each other with vacuum tank (17) through valve; Gas and liquid phase samples after sampling use gas chromatography (18) to carry out compositional analysis; The man-machine interaction system includes the man-machine interface (3) and the first thermocouple (23) in the balance kettle body (47) communicating with it, the first pressure transmitter (25) and the second thermocouple in the gasification chamber (13). Thermocouple (24), second pressure transmitter (26); Man-machine interface (3) can display and record in real time the measurement data of above-mentioned each thermocouple, pressure transmitter; Simultaneously, the gasification chamber (13) The heating temperature control system of its auxiliary pipelines is integrated into the man-machine interface (3). 2. A kind of high-pressure and low-temperature phase balance measuring device according to claim 1, characterized in that, the volume of the high-pressure balance kettle (5) is 100～900mL, and the main part is made of corrosion-resistant stainless steel; the balance kettle body (47) is Flat rectangular straight tube, the bottom surface is a square, and the side length is 2 to 5 times the height of the balanced kettle body (47); when adding a certain volume of solvent, this structure can increase the gas-liquid contact area and improve the mass transfer efficiency; the balanced kettle body ( 47) It is surrounded by welding of 4 stainless steel plates with a thickness of 5-12 mm, and the left and right sides are connected with flanges. 3. a kind of high-pressure low-temperature phase equilibrium measuring device according to claim 1, is characterized in that, high-pressure balance kettle (5) both sides are symmetrically provided with window, and window is made of sapphire (9), inner flange (8), outer side flange (9), bolts (6) and gaskets (46); wherein the inner flange (8) and the outer flange (7) are provided with a viewing window at the center, and the viewing window is smaller in diameter than the balance kettle body (47 ) height circle; the inner flange (8) is provided with a circular groove on the outside, the depth is 1/5-1/3 of the thickness of the sapphire (9), which is as large as the sapphire (9), and the other side is a plane, and The balance kettle body (47) is connected; the outer flange (7) is provided with a circular groove inside, and the depth is 1/4 to 1/3 of the thickness of the sapphire (9), which is as large as the sapphire (9); the inner flange ( 8) Gaskets (49) are used as buffers and seals between the sapphire (9) and the sapphire (9) and the outer flange (7). The two flanges are connected by bolts (6) and clamped to fix the sapphire (9) As a viewing window; the bolt holes are evenly distributed around the viewing window according to a fixed center distance. 4. A kind of high-pressure low-temperature phase equilibrium measuring device according to claim 1, characterized in that, a magnetic stirrer (10) is placed at the bottom of the high-pressure balance kettle (5), and the length of the magnetic stirrer (10) is 2 to 5 cm The magnetic stirrer (11) is located under the constant temperature tank (12); compared with the traditional mechanical stirring method, the magnetic stirring selected by this device can greatly improve the sealing performance of the high-pressure balance kettle (5) under high pressure. 5. high-pressure low-temperature phase equilibrium measuring device according to claim 1, is characterized in that, is connected with vacuum tank (17) and vacuum pump (16) at pipeline tail end, and vacuum tank (17) passes through the ninth shut-off valve (38) ) is connected with the fifth stop valve (34) and the sampling line (9), connected with the gas phase sampling line (20) through the ninth stop valve (38) and the sixth stop valve (35), and connected with the gas phase sampling line (20) through the tenth stop valve (39) is connected with gasification chamber (13). 6. A kind of high-pressure low-temperature phase equilibrium measuring device according to claim 1, characterized in that, the liquid phase sampling part comprises a liquid phase sampling pipeline (21), an eighth shut-off valve (37), a third shut-off valve (32 ), carrier gas cylinder (1), first three-way ball valve (28), quantitative sampling tube (22), second three-way ball valve (29), second control valve (41), tenth stop valve (39), The vaporization chamber (13) and the fifth control valve (44); one side of the first three-way ball valve (28) is connected to the high-pressure balance kettle (5) through the eighth stop valve (37), and the other side is passed through the third stop valve (32) is connected to the carrier gas cylinder (1); one side of the second three-way ball valve (29) is connected to the atmosphere through the second control valve (41) as a liquid phase sampling port, and one side is directly connected to the vaporization chamber (13) ; The gasification chamber (13) is connected with the gas chromatograph (18) through the fifth control valve (44), and is connected with the vacuum tank (17) through the tenth shut-off valve (39). 7. a kind of high-pressure low-temperature phase equilibrium measuring device according to claim 1, is characterized in that, the first thermocouple (23) that joins with high-pressure balance kettle (5) and the first pressure transmitter ( 25), the real-time data of the second thermocouple (24) connected with the gasification chamber (13) and the second pressure transmitter (26) are transmitted to the man-machine interface (3) through the line. 8. A kind of high-pressure low-temperature phase equilibrium measuring device according to claim 1, characterized in that, it is the second three-way ball valve (29) of the liquid phase sampling part to the vaporization chamber (13), the vaporization chamber (13) All pipelines and pipe fittings to the gas chromatograph (18) are provided with heating bands; the heating temperature control system of the vaporization chamber (13) and its subsidiary parts is integrated into the man-machine interface (3). 9. A high-pressure low-temperature phase equilibrium measurement device according to claim 1, characterized in that the solvent sampling funnel (15) is connected to the sampling pipeline (9) through a fourth control valve (43). 10. A kind of high-pressure low-temperature phase equilibrium measuring device according to claim 1, characterized in that, the bath liquid external circulation pipeline of the low-temperature refrigerator (4) is provided with a first shut-off valve (30) and a second shut-off valve ( 31); the first control valve (40) is set at the inlet of the low-temperature bath liquid of the thermostatic tank (12).

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