A cryostat system for integrated mixture phase equilibrium data determination

Abstract

The application provides a low-temperature thermostat system for integrated mixture phase equilibrium data determination, comprising: a phase equilibrium system, including an adiabatic container, a cold shield, a heating kettle and a balance kettle; a vacuum system, vacuumizing the space inside the adiabatic container, the cold shield and the heating kettle; a vacuumizing and sample feeding system, vacuumizing the balance kettle and feeding the gas to be determined into the balance kettle; a temperature control system, including a cold shield heat exchange coil, a heating film and a liquid nitrogen supply device; a sampling and analysis system, including a sampling buffer and a gas chromatography analysis device; and a data acquisition system, recording the data of the phase equilibrium system, controlling parameters and obtaining the results of the sampling and analysis system. The low-temperature thermostat system for integrated mixture phase equilibrium data determination provided by the application can fully eliminate the influence of the gas medium on the temperature uniformity when data determination is performed, the temperature uniformity of the whole balance kettle internal space is kept accurate and good, the applicable temperature is in the range of-180-0 DEG C, and the pressure is in the range of 0-10 MPa, so the system is suitable for vapor-liquid phase equilibrium determination.

Description

Technical Field

[0001] This invention belongs to the field of phase equilibrium measurement technology, specifically relating to a low-temperature isothermal system for integrating phase equilibrium data measurement of mixtures. Background Technology

[0002] In aerospace, energy and chemical engineering, and cryogenic refrigeration applications, accurate and complete phase equilibrium data of mixed working fluids are crucial for process design and simulation optimization. For example, at temperatures below -150°C, the phase equilibrium characteristics between the solid, liquid, and vapor phases of hydrocarbon mixed refrigerants determine the lowest achievable temperature in a Joule-Thomson throttling refrigeration cycle using such working fluids. Therefore, appropriately selecting the mixed working fluid composition results in a wider refrigeration temperature range and higher efficiency, enabling the provision of a stable cold source for high-temperature superconducting equipment. Furthermore, cryogenic thermophysical property data for mixed working fluids such as methane, ethane, and nitrogen are helpful for optimizing the cryogenic liquefaction or purification processes of gaseous working fluids like natural gas and air in the chemical industry, as well as the utilization of hydrocarbon propellants in the aerospace field. However, at present, the cryogenic phase equilibrium behavior of most mixed systems remains unknown, lacking substantial experimental data, which severely restricts the establishment of predictive models and equations of state. Therefore, there is an urgent need to build a phase equilibrium experimental testing platform covering a cryogenic range to obtain accurate phase equilibrium data for mixed working fluids.

[0003] Chinese invention patent CN115267026A discloses a high-pressure, low-temperature phase equilibrium measurement device. This device controls the temperature in a high-pressure equilibrium vessel through a constant-temperature bath and a refrigerant circulation system. During sampling, the liquid phase vaporizes in a separate vaporization chamber, and online sampling is used to separately detect the gaseous and liquid phase components. However, due to the limitations of the temperature control system structure, the applicable temperature range is only -80 to 200°C. Furthermore, the bath temperature control results in a large temperature gradient in the vertical direction within the equilibrium vessel, which cannot meet the requirements for high-precision measurement. Chinese utility model patent CN218824106U discloses a device for measuring the vapor-liquid phase equilibrium of chlorosilanes. It uses a constant-temperature bath to control the temperature of the constant-temperature medium, thereby controlling the temperature of the equilibrium vessel immersed in the medium. Simultaneously, a stirring paddle extends from the top of the equilibrium vessel into the vessel, and an external magnetic coupler drives the paddle to rotate, thus promoting vapor-liquid phase equilibrium. However, due to the limitations of the constant-temperature medium bath, the device is not suitable for low-temperature ranges, and the stirring paddle located in the liquid phase of the equilibrium vessel cannot eliminate the vertical temperature gradient throughout the vessel. Furthermore, the intermittent sampling method of this device is not conducive to the determination of large-scale, accurate data. Chinese invention patent CN113624570B discloses a device for measuring the vapor-liquid phase equilibrium of fluorinated hydrocarbons containing hydrogen fluoride. Considering negative pressure sampling, it sets up a negative pressure sampling bottle structure and adds a vapor phase equilibrium tube to maintain the vapor-liquid phase equilibrium state of the entire system during sampling. This system is suitable for ambient low-temperature ranges above -40℃, but the problem of the vertical temperature gradient in the equilibrium vessel remains unresolved.

[0004] The aforementioned patents all have shortcomings in terms of temperature uniformity throughout the equilibrium vessel. Furthermore, existing devices and methods for measuring phase equilibrium data in low-temperature ranges also have similar limitations. Chinese utility model patent CN205146108U provides a rapid gas-liquid phase equilibrium device under high pressure. The equilibrium vessel is placed in a cold trap constant-temperature container, utilizing a combination of an active refrigeration system and efficient insulation technology to achieve extremely high temperature control accuracy, with an applicable minimum temperature as low as -160°C. While the mechanical stirring structure at the bottom of the equilibrium vessel can slightly reduce the vertical temperature gradient in the liquid phase, it is detrimental to low-temperature sealing performance and vessel cleaning. Chinese invention patent CN108955098B provides a low-temperature system integrating constant temperature, cooling, and vacuum freeze-drying. It controls the temperature of the constant-temperature medium inside the insulation chamber through a refrigerator and heater. The medium inside the chamber is divided into an internal test bath and an external control bath. A bottom stirring unit circulates the medium between the control bath and the test bath. Simultaneously, the equilibrium test tube can rotate around a fixed axis, resulting in a uniform temperature distribution in the horizontal direction, while a certain temperature gradient still exists in the vertical direction.

[0005] It is evident that most current phase equilibrium data measurement systems suffer from limitations such as inapplicability to low-temperature conditions and poor vertical temperature uniformity. This invention addresses these shortcomings by providing a low-temperature isothermal system for measuring mixture phase equilibrium data with uniform spatial temperature distribution within a temperature range of -180 to 0°C. Summary of the Invention

[0006] This invention was made to solve the above-mentioned problems, and its purpose is to provide a low-temperature isothermal system for measuring integrated mixture phase equilibrium data with uniform temperature distribution.

[0007] This invention provides a low-temperature isothermal system for integrating mixture phase equilibrium data determination, characterized by comprising: a phase equilibrium system including an adiabatic container, a cold shield, a heating vessel, and an equilibrium vessel, wherein the cold shield, heating vessel, and equilibrium vessel are coaxially mounted from the outside in inside the adiabatic container; the adiabatic container, cold shield, and heating vessel are interconnected; a vacuum system connected to and communicating with the phase equilibrium system, which evacuates the space inside the adiabatic container, cold shield, and heating vessel; a vacuum-assisted sample loading system connected to and communicating with the equilibrium vessel, which evacuates the equilibrium vessel and introduces the gas to be tested into the equilibrium vessel; and a temperature control system connected to the phase equilibrium system, which controls the temperature of the phase equilibrium system. The system includes a cold shield heat exchange coil, a heating film, and a liquid nitrogen supply device. The cold shield heat exchange coil is installed on the outer surface of the cold shield, and the heating film is tightly attached to the outer surface of the heating vessel. The liquid nitrogen supply device is connected to the cold shield heat exchange coil and supplies liquid nitrogen to it. A sampling and analysis system is connected to and communicates with the phase equilibrium system, including a sampling buffer and a gas chromatograph. The gas to be tested in the equilibrium vessel is transferred to the gas chromatograph via the sampling buffer. A data acquisition system is also connected to the phase equilibrium system and records data and controls parameters of the phase equilibrium system. The data acquisition system is also connected to the sampling and analysis system to obtain the compositional analysis results of the sampling and analysis system.

[0008] The low-temperature isothermal system for measuring integrated mixture phase equilibrium data provided by this invention may also have the following features: the insulated container includes: a container body; a container flange disposed on the upper part of the container body; a flange cover, which is sealed to the container flange by rubber sealing, magnetic fluid sealing, adhesive sealing or metal sealing, and has holes or U-grooves on its edges, and is fixed to the container flange by bolts and nuts or hook pins; a first vacuum cylindrical sleeve inlet and a first vacuum cylindrical sleeve outlet, which are respectively disposed on the flange cover and communicate with the container body; a second vacuum cylindrical sleeve inlet and a second vacuum cylindrical sleeve outlet, which are respectively disposed on the lower part and the middle part of the container body and communicate with the container body; and an aviation plug disposed on the flange cover and communicate with the container body, the aviation plug being connected to the balance vessel, the heating vessel, the cold shield and the heating film to obtain pressure and temperature data inside the balance vessel, temperature data of the heating vessel, temperature data of the cold shield and control of the heating film.

[0009] The low-temperature isothermal system for integrated mixture phase equilibrium data determination provided by this invention may also have the following features: The cold screen includes: a fixing unit comprising a hanging rod, a circumferential support, and a bottom support, made of materials with good vacuum low-temperature performance and mechanical properties, including special plastic materials, ceramic materials, or glass fiber composite materials; an upper cold screen, which is a downward-facing hemispherical structure, connected and fixed to a flange cover via a top hanging rod, the inner surface of which is coated with black paint or blackened with a metal blackening agent; and a lower cold screen, which is not fixedly connected to the upper cold screen, and is an integrally formed structure composed of a cylindrical structure without upper and lower bottom surfaces and a hemispherical structure with an upward-facing opening and the same diameter as the cylindrical structure of the lower cold screen, fixed inside the container body via the circumferential support and the bottom support, the diameter of the cylindrical structure of the lower cold screen being the same as the diameter of the hemispherical structure of the upper cold screen, the inner surface of which is coated with black paint or blackened with a metal blackening agent.

[0010] The low-temperature isothermal system for measuring integrated mixture phase equilibrium data provided by the present invention may also have the following features: wherein the vacuum system includes: a first vacuum pump group for providing suction for the process of evacuating the space inside the insulated container, cold shield and heating vessel; a first vacuum pipeline, one end of which is connected to the container body and the other end of which is connected to the first vacuum pump group; and a first high vacuum baffle valve, which is installed on the first vacuum pipeline for controlling the evacuation of the vacuum system. The vacuum sampling system includes: a second vacuum pump unit, used to provide suction for the vacuuming process inside the equilibrium vessel; a vacuum pipeline, one end of which passes through the container body and connects to the inside of the equilibrium vessel, and the other end of which connects to the second vacuum pump unit; a second high-vacuum baffle valve, installed on the vacuum pipeline, used to control the vacuum system to evacuate; several gas cylinders containing the gas to be tested; several sampling branches, one end of which connects to the gas cylinders and the other end of which connects to the vacuum pipeline, with the connection point between the sampling branches and the vacuum pipeline located between the second high-vacuum baffle valve and the equilibrium vessel; and several sampling rotary valves, respectively installed on several sampling branches, used to control the sampling of the gas cylinders.

[0011] The low-temperature isothermal system for integrated mixture phase equilibrium data determination provided by this invention may also have the following features: the upper part of the equilibrium vessel is connected to and communicates with the evacuation pipeline; the equilibrium vessel's suspension position inside the container is determined by its connection to the evacuation pipeline; high-precision temperature probes are symmetrically arranged in the vertical direction on the equilibrium vessel; a spacer is provided at the upper part of the equilibrium vessel; a support is provided at the lower part of the equilibrium vessel; the equilibrium vessel is fixed inside the heating vessel by the spacer and the support; the materials used for the spacer and the support have good vacuum low-temperature performance and mechanical properties, including special plastic materials and ceramics. The balancing vessel, made of ceramic or glass fiber composite material, is an integrally molded closed structure consisting of a cylindrical surface without upper or lower bottom surfaces and two hemispherical surfaces with the same diameter at both ends of the cylindrical surface of the balancing vessel. The heating vessel is located inside the cold shield and its position is fixed by the balancing vessel, which is fixed in a predetermined position by an internal spacer and a support component. The heating vessel is also a structure consisting of a cylindrical surface without upper or lower bottom surfaces and two hemispherical surfaces with the same diameter at both ends of the cylindrical surface of the heating vessel. Process holes are opened on the side wall of the cylindrical surface of the heating vessel.

[0012] The cryogenic isothermal system for integrated mixture phase equilibrium data determination provided by this invention may also have the following features: the liquid nitrogen supply device includes: a Dewar flare; a liquid nitrogen box, which is a vacuum-insulated container, installed at an elevation 0.5m higher than the elevation of the insulated container; a filling pipeline, one end connected to the Dewar flare and the other end connected to the top of the liquid nitrogen box, for supplying liquid nitrogen to the liquid nitrogen box from the Dewar flare; a liquid nitrogen rotary valve, installed on the filling pipeline, for controlling the flow rate of liquid nitrogen in the filling pipeline; a first liquid nitrogen flow path and a second liquid nitrogen flow path, each with one end connected to the bottom of the liquid nitrogen box and the other end connected to a cold shield heat exchange coil, connecting and communicating between the liquid nitrogen box and the cold shield heat exchange coil; and a liquid nitrogen venting pipeline, one end connected to the top of the liquid nitrogen box and communicating with the outside environment, the other end of which is the outlet to the external environment, to avoid excessive internal pressure caused by the vaporization of liquid nitrogen in the liquid nitrogen box. The filling pipeline, the liquid nitrogen venting pipeline, the first liquid nitrogen flow path, and the second liquid nitrogen flow path are all vacuum-insulated pipelines.

[0013] The cryogenic isothermal system for integrated mixture phase equilibrium data determination provided by this invention may also have the following features: The cold screen heat exchange coil includes: an upper cold screen heat exchange coil, coiled on the outer surface of the upper cold screen, comprising a lower first inlet and an upper first outlet, the first outlet being connected to a first vent pipe; and a lower cold screen heat exchange coil, coiled on the outer surface of the lower cold screen, comprising a lower second inlet and an upper second outlet, the second outlet being connected to a second vent pipe. The first liquid nitrogen flow path passes through the inlet of the first vacuum cylindrical sleeve and is connected to and communicates with the first inlet; one end of the first vent pipe is connected to the first outlet, and the other end of the vent pipe, after passing through the outlet of the first vacuum cylindrical sleeve, is open to the external environment. The second liquid nitrogen flow path passes through the inlet of the second vacuum cylindrical sleeve and is connected to and communicates with the second inlet; one end of the second vent pipe is connected to the second outlet, and the other end of the vent pipe, after passing through the outlet of the second vacuum cylindrical sleeve, is open to the external environment. The liquid nitrogen in the upper and lower cold screen heat exchange coils flows clockwise or counterclockwise from lower to higher elevations. Both the first and second venting lines are vacuum-insulated pipes. Venting both to the external environment can prevent excessive pressure caused by the vaporization of liquid nitrogen inside the cold shield heat exchange coil, which could lead to adverse consequences.

[0014] The low-temperature isothermal system for measuring integrated mixed-phase equilibrium data provided by this invention may also have the following features: the sampling buffer section includes: a gas phase sampling buffer pipeline, the inlet of which is located at the upper part of the equilibrium vessel, and a first diaphragm valve, a first buffer tank, and a second diaphragm valve are sequentially arranged on the gas phase sampling buffer pipeline; a normal liquid phase sampling buffer pipeline, the inlet of which is located at the lower part of the equilibrium vessel, and a third diaphragm valve, a second buffer tank, and a fourth diaphragm valve are sequentially connected on the normal liquid phase sampling buffer pipeline; and a stainless steel microporous aeration head liquid phase sampling buffer pipeline, the inlet of which is located at the lower part of the equilibrium vessel, and a fifth diaphragm valve, a third buffer tank, and a sixth diaphragm valve are sequentially connected on the stainless steel microporous aeration head liquid phase sampling buffer pipeline, the inlet of which is a stainless steel microporous aeration head, and the surface of the stainless steel microporous aeration head is uniformly distributed with microporous aeration holes. The first, second, and third buffer tanks are equipped with a first safety valve, a second safety valve, and a third safety valve, respectively, with a starting pressure of less than 1.0 MPa. The outlets of the gas phase sampling buffer pipeline, the ordinary liquid phase sampling buffer pipeline, and the stainless steel microporous aeration head liquid phase sampling buffer pipeline are all connected to the gas chromatography analysis device. The second diaphragm valve, the fourth diaphragm valve, and the sixth diaphragm valve control the entry of samples from the first, second, and third buffer tanks into the gas chromatography analysis device.

[0015] The low-temperature isothermal system for integrated mixture phase equilibrium data determination provided by this invention may also have the following features: the gas chromatography analysis device includes: a gas chromatograph connected to the outlets of a gas phase sampling buffer line, a conventional liquid phase sampling buffer line, and a stainless steel microporous aeration head liquid phase sampling buffer line; a carrier gas cylinder, the working fluid of which is any one of hydrogen, nitrogen, helium, and argon; a carrier gas line for connecting the gas chromatograph and the carrier gas cylinder; and a carrier gas rotary valve, located on the carrier gas line, for controlling the gas in the carrier gas cylinder to enter the gas chromatograph.

[0016] The low-temperature isothermal system for integrated mixture phase equilibrium data determination provided by this invention may also have the following features: the data acquisition system includes: a first control cabinet, connected to an aviation connector and displaying and recording in real time the pressure and temperature of the equilibrium vessel, the temperature of the heating vessel, and the temperature of the cooling screen, and controlling the heating film to match the cooling and heating capacities in the temperature control system to achieve the set temperature; and a second control cabinet, connected to a gas chromatograph, recording and storing the compositional analysis results of the gas chromatograph. The line connecting the first control cabinet to the aviation connector is equipped with a pressure transmitter, a temperature sensor, and a heating film heating control module to assist the first control cabinet in better controlling the temperature changes within the phase equilibrium system.

[0017] The role and effect of invention

[0018] The low-temperature isothermal system for measuring integrated mixture phase equilibrium data according to the present invention includes a phase equilibrium system, a vacuum system, a vacuum sampling system, a temperature control system, a sampling and analysis system, and a data acquisition system. The phase equilibrium system includes an adiabatic container, a cold shield, a heating vessel, and an equilibrium vessel. The cold shield, heating vessel, and equilibrium vessel are installed coaxially from the outside in inside the adiabatic container, and are interconnected. The vacuum system is connected to and communicates with the phase equilibrium system, and evacuates the space inside the adiabatic container, cold shield, and heating vessel. The vacuum sampling system is connected to and communicates with the equilibrium vessel, evacuates the equilibrium vessel, and introduces the gas to be measured into the equilibrium vessel. The temperature control system is connected to and communicates with the phase equilibrium system. The equilibrium system is connected to and controls the temperature of the phase equilibrium system. It includes a cold shield heat exchange coil, a heating film, and a liquid nitrogen supply device. The cold shield heat exchange coil is installed on the outer surface of the cold shield, and the heating film is installed in close contact with the outer surface of the heating vessel. The liquid nitrogen supply device is connected to the cold shield heat exchange coil and supplies liquid nitrogen to it. The sampling and analysis system is connected to and communicates with the phase equilibrium system. It includes a sampling buffer section and a gas chromatography analyzer. The gas to be tested in the equilibrium vessel is transferred to the gas chromatography analyzer through the sampling buffer section. The data acquisition system is connected to the phase equilibrium system and records data and controls parameters of the phase equilibrium system. The data acquisition system is also connected to the sampling and analysis system and obtains the compositional analysis results of the sampling and analysis system.

[0019] Therefore, in the low-temperature isothermal system for measuring integrated mixture phase equilibrium data provided by this invention, when phase equilibrium data is measured in the equilibrium vessel, the space from the adiabatic container through the cold screen and the heating vessel to the outside of the equilibrium vessel is in a high vacuum state, which fully eliminates the influence of the gas medium on temperature uniformity. At this time, the heat exchange coil of the cold screen outside the cold screen is filled with liquid nitrogen. Through metal conduction, the temperature of the entire inner surface of the cold screen is maintained at the liquid nitrogen temperature, continuously absorbing the heat radiated by the internal heating vessel and the equilibrium vessel. At the same time, the heating film closely attached to the heating vessel can provide a uniformly distributed heat flux density. Through the control of the cold screen heat exchange coil and the heating film, the entire internal space of the equilibrium vessel can maintain good temperature uniformity and accurately control the temperature. It is suitable for vapor-liquid phase equilibrium measurement in the temperature range of -180 to 0℃ and pressure range of 0 to 10 MPa. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the low-temperature isothermal system for integrating mixture phase equilibrium data measurement in an embodiment of the present invention;

[0021] Figure 2 yes Figure 1 Enlarged view of the middle phase equilibrium system section;

[0022] Figure 3 This is a schematic diagram of the structure of the heating film unfolded and laid flat in an embodiment of the present invention. Detailed Implementation

[0023] <Example>

[0024] To make the technical means, creative features, objectives and effects of the present invention easy to understand, the following embodiments, in conjunction with the accompanying drawings, specifically illustrate a low-temperature isothermal system for measuring phase equilibrium data of a mixture according to the present invention.

[0025] Figure 1 This is a schematic diagram of the low-temperature isothermal system for measuring integrated mixture phase equilibrium data according to an embodiment of the present invention; Figure 2 yes Figure 1 Enlarged view of the middle phase equilibrium system section; Figure 3 This is a schematic diagram of the structure of the heating film unfolded and laid flat in an embodiment of the present invention.

[0026] like Figure 1 , 2 As shown in Figure 3, this embodiment provides a low-temperature isothermal system 100 for integrating mixture phase equilibrium data measurement, including a phase equilibrium system A, a vacuum system B, a vacuum sampling system C, a temperature control system D, a sampling and analysis system E, and a data acquisition system F.

[0027] The phase balance system A includes an adiabatic container 10, a cold shield 20, a heating vessel 30, and a balance vessel 40 arranged coaxially from the outside to the inside, and the adiabatic container 10, the cold shield 20, and the heating vessel 30 are spatially connected.

[0028] The heat-insulating container 10 includes a container body 11, a body flange 13, a flange cover 14, a first vacuum cylindrical sleeve inlet 15 and a first vacuum cylindrical sleeve outlet 16, a second vacuum cylindrical sleeve inlet 17 and a second vacuum cylindrical sleeve outlet 18, and an aviation plug 19. A cylindrical flange 13 is located on the upper part of the container cylinder 11; a rubber seal is used between the flange cover 14 and the cylindrical flange 13, and a U-shaped groove is opened on the edge and fixed with a hook pin 12; the first vacuum cylindrical sleeve inlet 15 and the first vacuum cylindrical sleeve outlet 16 are respectively located on the far left and slightly left side of the flange cover 14 and communicate with the container cylinder 11; the second vacuum cylindrical sleeve inlet 17 and the second vacuum cylindrical sleeve outlet 18 are respectively located on the lower side and middle of the container cylinder 11 and communicate with the container cylinder 11; an aviation plug 19 is located on the right side of the flange cover 14 and communicates with the container cylinder 11. The aviation plug 19 is connected to the balance vessel 40, the heating vessel 30, the cold screen 20 and the heating film 80 to obtain the pressure and temperature data inside the balance vessel 40, the temperature data of the heating vessel 30, the temperature data of the cold screen 20 and control the heating film 80.

[0029] The cold shield 20 is disposed inside the heat insulation container 10. The cold shield 20 includes a fixing unit 21, an upper cold shield 22 and a lower cold shield 23. The fixing unit 21 includes a lifting rod 211, a circumferential support 212, and a bottom support 213, all made of materials with good vacuum low-temperature performance and mechanical properties, including special plastic materials, ceramic materials, or glass fiber composite materials (glass fiber composite materials are used in this embodiment); the upper cooling screen 22 is a hemispherical structure with the opening facing downwards and is connected and fixed to the flange cover 14 by the upper lifting rod 211, and the inner surface of the upper cooling screen 22 is coated with black paint; the lower cooling screen 23 is an integrally formed structure composed of a cylindrical structure without upper and lower bottom surfaces and a hemispherical structure with the opening facing upwards and the same diameter as the cylindrical structure of the lower cooling screen, and is fixed inside the container body 11 by the circumferential support 212 and the bottom support 213. The lower cooling screen 23 and the upper cooling screen 22 are not fixedly connected, and the inner surface of the lower cooling screen 23 is coated with black paint. The diameter of the cylindrical structure of the lower cooling screen 23 is the same as the diameter of the hemispherical structure of the upper cooling screen 22.

[0030] Vacuum system B is connected to and communicates with phase equilibrium system A, and evacuates the space inside the insulated container 10, cold shield 20, and heating vessel 30. Vacuum system B includes a first vacuum pump group 51, a first vacuum pipeline 52, and a first high vacuum baffle valve 53. The first vacuum pump group 51 is used to provide suction for the evacuation process of the space inside the insulated container 10, cold shield 20, and heating vessel 30; one end of the first vacuum pipeline 52 is connected to and communicates with the container body 11, and the other end is connected to the first vacuum pump group 51; the first high vacuum baffle valve 53 is installed on the first vacuum pipeline 52 and is used to control the evacuation of vacuum system B.

[0031] The vacuum sampling system C is connected to and communicates with the equilibrium vessel 40. It evacuates the equilibrium vessel 40 and introduces the gas to be tested into the equilibrium vessel 40. It includes a second vacuum pump group 56, a vacuum pipeline 54, a second high vacuum baffle valve 55, several gas cylinders to be tested 57, several sampling branch pipes 58, and several sampling rotary valves 59. The second vacuum pump group 56 is used to provide suction for the vacuuming process inside the balance vessel 40; one end of the evacuation pipeline 54 passes through the container body 11 and connects to the inside of the balance vessel 40, and the other end is connected to the second vacuum pump group 56; the second high vacuum baffle valve 55 is installed on the evacuation pipeline 54 and is used to control the vacuum system B to evacuate; several gas cylinders 57 contain the gas to be tested; one end of several sample dispensing branches 58 is connected to the gas cylinders 57 and is connected, and the other end is connected to the evacuation pipeline 54 and is connected, and the connection point between the sample dispensing branch 58 and the evacuation pipeline 54 is located between the second high vacuum baffle valve 55 and the balance vessel 40; several sample dispensing rotary valves 59 are respectively installed on several sample dispensing branches 58 and are used to control the dispensing of the gas cylinders 57.

[0032] The upper part of the balancing vessel 40 is connected to and communicates with the evacuation pipeline 54. The balancing vessel 40 is connected to the evacuation pipeline 54 to determine its suspension position inside the container body 11. Several high-precision temperature probes 41 are symmetrically arranged in the vertical direction on the balancing vessel 40. A spacer 42 made of glass fiber composite material is provided on the upper part of the balancing vessel 40, and a support member 43 made of glass fiber composite material is provided on the lower part of the balancing vessel 40. The balancing vessel 40 is fixed inside the heating vessel 30 by the spacer 42 and the support member 43. The balancing vessel 40 is an integrally formed closed structure composed of a cylindrical surface without upper and lower bottom surfaces and two hemispherical surfaces with the same diameter as the cylindrical surface of the balancing vessel 40 at both ends.

[0033] The heating vessel 30 is located inside the cold shield 20. The heating vessel 30 is fixed in position by the balanced vessel 40, which is fixed in a predetermined position by the internal spacer 42 and the support member 43. The heating vessel 30 is a structure composed of a cylindrical surface without upper and lower bottom surfaces and two hemispherical surfaces with the same diameter as the cylindrical surface of the heating vessel 30 at both ends. Process holes are opened on the side wall of the cylindrical surface of the heating vessel 30.

[0034] The temperature control system D is connected to the phase balance system A and controls the temperature of the phase balance system A. It includes a liquid nitrogen supply device 60, a cold shield heat exchange coil 70, and a heating film 80.

[0035] The liquid nitrogen supply device 60 includes a Dewar 61, a liquid nitrogen box 62, a filling line 63, a liquid nitrogen rotary valve 64, a first liquid nitrogen flow path 65 and a second liquid nitrogen flow path 66, and a liquid nitrogen venting line 67. The liquid nitrogen box 62 is a vacuum-insulated container, and its installation elevation exceeds the elevation of the insulation container 10 by 0.5m or more (0.5m in this embodiment); the filling pipeline 63 is a vacuum-insulated pipeline, with one end connected to the Dewar 61 and the other end connected to the top of the liquid nitrogen box 62, for supplying liquid nitrogen to the liquid nitrogen box 62 through the Dewar 61; the liquid nitrogen rotary valve 64 is installed on the filling pipeline 63 to control the flow rate of liquid nitrogen in the filling pipeline 63; the first liquid nitrogen flow path 65 and the second liquid nitrogen flow path 66 are both vacuum-insulated pipelines, with the first liquid nitrogen flow path 65 connected to the bottom right side of the liquid nitrogen box 62 and connected, and the second liquid nitrogen flow path 66 connected to the bottom left side of the liquid nitrogen box 62 and connected; the liquid nitrogen venting pipeline 67 is a vacuum-insulated pipeline, connected to the top of the liquid nitrogen box 62 and connected.

[0036] The cold screen heat exchange coil 70 includes an upper cold screen heat exchange coil 71 and a lower cold screen heat exchange coil 72.

[0037] The upper cooling screen heat exchange coil 71 is coiled on the outer surface of the upper cooling screen 22, including a lower first inlet 711 and an upper first outlet 712. The liquid nitrogen in the upper cooling screen heat exchange coil 71 moves clockwise from low to high. One end of the first liquid nitrogen flow path 65 is connected to the bottom of the liquid nitrogen box 62 and then passes through the first vacuum cylindrical sleeve inlet 15 and connects to the first inlet 711. The first outlet 712 is connected to the first vent pipe 713, which is a vacuum insulated pipe. The other end of the first vent pipe 713 after passing through the first vacuum cylindrical sleeve outlet 16 is the external environment.

[0038] The lower cooling screen heat exchange coil 72 is coiled on the outer surface of the lower cooling screen 23, including a lower second inlet 721 and an upper second outlet 722, so that the liquid nitrogen in the lower cooling screen heat exchange coil 72 moves counterclockwise from low to high. One end of the second liquid nitrogen flow path 66 is connected to the bottom of the liquid nitrogen box 62 and is in communication. Then the second liquid nitrogen flow path 66 passes through the second vacuum cylindrical sleeve inlet 17 and is connected to the second inlet 721. The second outlet 722 is connected to the second vent pipe 723, which is a vacuum insulated pipe. The other end of the second vent pipe 723 after passing through the second vacuum cylindrical sleeve outlet 18 is the external environment.

[0039] The heating film 80 is tightly attached to the entire outer surface of the heating vessel 30, and heating wires 81 are evenly distributed inside.

[0040] The sampling and analysis system E is connected to the phase equilibrium system A and includes a sampling buffer 90 and a gas chromatography analyzer 110. The gas to be tested in the equilibrium vessel 40 is transferred to the gas chromatography analyzer 110 via the sampling buffer 90.

[0041] The sampling buffer section 90 includes a gas phase sampling buffer line 91, a general liquid phase sampling buffer line 92, and a stainless steel microporous aeration head liquid phase sampling buffer line 93.

[0042] The inlet of the gas sampling buffer line 91 is connected to the upper part of the equilibrium vessel 40, and the outlet is connected to the gas chromatography analysis device 110. The gas sampling buffer line 91 is sequentially equipped with a first diaphragm valve 911, a first buffer tank 912, and a second diaphragm valve 913. The second diaphragm valve 913 controls the sample from the first buffer tank 912 to enter the gas chromatography analysis device 110. The top of the first buffer tank 912 is equipped with a first safety valve 9121 with a starting pressure of less than 1 MPa (0.6 MPa in this embodiment).

[0043] The inlet of the ordinary liquid phase sampling buffer line 92 is connected to the lower part of the equilibrium vessel 40, and the outlet is connected to the gas chromatography analysis device 110. The ordinary liquid phase sampling buffer line 92 is sequentially connected to the third diaphragm valve 921, the second buffer tank 922 and the fourth diaphragm valve 923. The fourth diaphragm valve 923 controls the sample from the second buffer tank 922 to enter the gas chromatography analysis device 110. The top of the second buffer tank 922 is equipped with a second safety valve 9221 with a starting pressure of less than 1 MPa (0.6 MPa in this embodiment).

[0044] The inlet of the stainless steel microporous aerator liquid phase sampling buffer pipeline 93 is connected to the lower part of the equilibrium vessel 40, and the outlet is connected to the gas chromatography analysis device 110. The stainless steel microporous aerator liquid phase sampling buffer pipeline 93 is sequentially connected to the fifth diaphragm valve 931, the third buffer tank 932 and the sixth diaphragm valve 933. The sixth diaphragm valve 933 controls the sample from the third buffer tank 932 to enter the gas chromatography analysis device 110. The top of the third buffer tank 932 is equipped with a third safety valve 9321 with a starting pressure of less than 1 MPa (0.6 MPa in this embodiment). The inlet of the stainless steel microporous aerator liquid phase sampling buffer pipeline 93 is a stainless steel microporous aerator 934, and the surface of the stainless steel microporous aerator 934 is uniformly distributed with microporous aeration holes.

[0045] The gas chromatograph analysis apparatus 110 includes a gas chromatograph 111, a carrier gas cylinder 112, a carrier gas pipeline 113, and a carrier gas rotary valve 114. The gas chromatograph 111 is connected to the outlets of a gas phase sampling buffer pipeline 91, a conventional liquid phase sampling buffer pipeline 92, and a stainless steel microporous aerator liquid phase sampling buffer pipeline 93. The working medium in the carrier gas cylinder 112 can be any one of hydrogen, nitrogen, helium, and argon (hydrogen in this embodiment). The carrier gas pipeline 113 is used to connect the gas chromatograph 111 and the carrier gas cylinder 112. The carrier gas rotary valve 114 is installed on the carrier gas pipeline 113 to control the gas in the carrier gas cylinder 112 to enter the gas chromatograph 111.

[0046] The data acquisition system F is connected to the phase equilibrium system A and records data and controls parameters of the phase equilibrium system A. The data acquisition system F is also connected to the sampling analysis system E and obtains the composition analysis results of the sampling analysis system E. The data acquisition system F includes a first control cabinet 120 and a second control cabinet 130.

[0047] The first control cabinet 120 is connected to the aviation plug 19 and displays and records the pressure and temperature of the balance vessel 40, the temperature of the heating vessel 30 and the temperature of the cold screen 20 in real time. It also controls the heating film 80 to match the cooling and heating capacity in the temperature control system D to achieve the set temperature. The line connecting the first control cabinet 120 and the aviation plug 19 is equipped with a pressure transmitter 121, a temperature sensor 122 and a heating control module for the heating film 80 to assist the first control cabinet 120 in better controlling the temperature changes inside the phase balance system A.

[0048] The second control cabinet 130 is connected to the gas chromatograph 111, and records and saves the composition analysis results of the gas chromatograph 111.

[0049] <Operation Process of the Example>

[0050] Liquid nitrogen stored in Dewar 61 enters liquid nitrogen box 62 through filling pipe 63. Part of the liquid nitrogen in liquid nitrogen box 62 flows into the upper cooling screen heat exchange coil 71 through the first liquid nitrogen flow path 65 and the first inlet 711. It rises to the top, passes through the first outlet 712, and then through the first vent pipe 713 before vaporizing and overflowing into the external environment. The other part of the liquid nitrogen in liquid nitrogen box 62 flows into the lower cooling screen heat exchange coil 72 through the second vent pipe 66 and the second inlet 721. It rises to the top, passes through the second outlet 722, and then through the second vent pipe 723 before vaporizing and overflowing into the external environment. This process is continuously repeated during the phase equilibrium data measurement. During this process, vacuum system B maintains a vacuum in the space between the outside of the batch balance vessel 40 and the insulated container 10. Before each sample addition, vacuum-assisted sampling system C opens the second high-vacuum baffle valve 55 and uses the second vacuum pump group 56 to evacuate the balance vessel 40 through the vacuum pipeline 54. Then, it closes the second high-vacuum baffle valve 55, opens the sampling rotary valve 59, and introduces the sample from the gas cylinder 57 to be tested into the balance vessel 40 through the sampling branch pipe 58. In the subsequent sampling process, the sample is introduced into the gas chromatograph 111 for analysis via the gas phase sampling buffer pipeline 91, the ordinary liquid phase sampling buffer pipeline 92, and the stainless steel microporous aerator liquid phase sampling buffer pipeline 93. Throughout the temperature control, vacuuming, sampling, and sampling processes, the first control cabinet 120 monitors and adjusts the temperature and pressure data inside the phase balance system via the aviation connector 19, while the second control cabinet 130 records the analytical data of the gas chromatograph 111.

[0051] The role and effect of the embodiments

[0052] The low-temperature isothermal system for measuring integrated mixture phase equilibrium data according to this embodiment includes a phase equilibrium system, a vacuum system, a vacuum sampling system, a temperature control system, a sampling and analysis system, and a data acquisition system. The phase equilibrium system includes an adiabatic container, a cold shield, a heating vessel, and an equilibrium vessel. The cold shield, heating vessel, and equilibrium vessel are installed coaxially from the outside in inside the adiabatic container, and are interconnected. The vacuum system is connected to and communicates with the phase equilibrium system, and evacuates the space inside the adiabatic container, cold shield, and heating vessel. The vacuum sampling system is connected to and communicates with the equilibrium vessel, evacuates the equilibrium vessel, and introduces the gas to be measured into the equilibrium vessel. The temperature control system is connected to and communicates with the phase equilibrium system. The equilibrium system is connected and controls the temperature of the phase equilibrium system. It includes a cold shield heat exchange coil, a heating film, and a liquid nitrogen supply device. The cold shield heat exchange coil is installed on the outer surface of the cold shield, and the heating film is installed in close contact with the outer surface of the heating vessel. The liquid nitrogen supply device is connected to the cold shield heat exchange coil and supplies liquid nitrogen to it. The sampling and analysis system is connected to the phase equilibrium system and includes a sampling buffer and a gas chromatography analyzer. The gas to be tested in the equilibrium vessel is transferred to the gas chromatography analyzer via the sampling buffer. The data acquisition system is connected to the phase equilibrium system and records data and controls parameters of the phase equilibrium system. The data acquisition system is also connected to the sampling and analysis system and obtains the compositional analysis results of the sampling and analysis system.

[0053] Therefore, in the low-temperature isothermal system for measuring integrated mixture phase equilibrium data provided in this embodiment, when phase equilibrium data is measured in the equilibrium vessel, the space from the adiabatic container through the cold screen and the heating vessel to the outside of the equilibrium vessel is in a high vacuum state, which fully eliminates the influence of the gas medium on temperature uniformity. At this time, the heat exchange coil of the cold screen outside the cold screen is filled with liquid nitrogen. Through metal conduction, the temperature of the entire inner surface of the cold screen is maintained at the liquid nitrogen temperature, continuously absorbing the heat radiated by the internal heating vessel and the equilibrium vessel. At the same time, the heating film closely attached to the heating vessel can provide a uniformly distributed heat flux density. Through the control of the cold screen heat exchange coil and the heating film, the entire internal space of the equilibrium vessel can maintain good temperature uniformity and accurately control the temperature. It is suitable for vapor-liquid phase equilibrium measurement in the temperature range of -180 to 0℃ and the pressure range of 0 to 10 MPa.

[0054] Furthermore, the insulated container includes: a container body; a body flange, located on the upper part of the container body; a flange cover, which is sealed with rubber and has a U-shaped groove on its edge, and is fixed to the body flange using a hook pin; a first vacuum cylindrical sleeve inlet and a first vacuum cylindrical sleeve outlet, respectively located on the far left and slightly to the left of the flange cover, and communicating with the container body; a second vacuum cylindrical sleeve inlet and a second vacuum cylindrical sleeve outlet, respectively located on the lower part and middle part of the container body, and communicating with the container body; and an aviation plug, located on the flange cover and communicating with the container body, the aviation plug being connected to the balance vessel, the heating vessel, the cold shield, and the heating film to obtain pressure and temperature data inside the balance vessel, temperature data of the heating vessel, temperature data of the cold shield, and control of the heating film. The use of rubber seals and hook-pin fixing methods ensures excellent cryogenic sealing performance while facilitating disassembly and maintenance. The four vacuum cylindrical sleeves—the first vacuum cylindrical sleeve inlet, the first vacuum cylindrical sleeve outlet, the second vacuum cylindrical sleeve inlet, and the second vacuum cylindrical sleeve outlet—protect the container body from the cooling effect of cryogenic liquid nitrogen at the inlet and outlet, preventing cold spots. They also provide good thermal insulation, reducing cold loss from the liquid nitrogen at these points. Using aviation connectors in cryogenic environments ensures the container's cryogenic sealing performance and the stability of signal transmission.

[0055] Furthermore, the cold shield includes: a fixing unit, including a hanger, a circumferential support, and a bottom support; an upper cold shield, which is a downward-facing hemispherical structure, connected and fixed to the flange cover by the top hanger; and a lower cold shield, which is an integrally formed structure composed of a cylindrical structure without upper and lower bottom surfaces and a hemispherical structure with an upward-facing opening and the same diameter as the cylindrical structure of the lower cold shield, fixed inside the container body by the circumferential support and the bottom support, wherein the diameter of the cylindrical structure of the lower cold shield is the same as the diameter of the hemispherical structure of the upper cold shield.

[0056] Preferably, the suspension rod, circumferential support, and bottom support are made of glass fiber composite material, which has good vacuum low temperature performance and mechanical properties. The inner surfaces of the upper and lower cooling screens are coated with black paint or blackened with a metal blackening agent. The upper and lower cooling screens are not fixedly connected, and hoisting equipment can be used to inspect and maintain the internal structure of the cooling screens.

[0057] Furthermore, the balancing vessel is an integrally formed closed structure consisting of a cylindrical surface without upper and lower bottom surfaces and two hemispherical surfaces with the same diameter at both ends of the cylindrical surface of the balancing vessel. The upper part of the balancing vessel is connected to and communicates with the evacuation pipeline. The balancing vessel's suspension position inside the container body is determined by its connection to the evacuation pipeline. High-precision temperature probes are symmetrically arranged in the vertical direction on the balancing vessel. A spacer is provided on the upper part of the balancing vessel, and a support is provided on the lower part of the balancing vessel. The balancing vessel is fixed inside the heating vessel by the spacer and the support.

[0058] Preferably, the materials used for the spacer and support have good vacuum cryogenic performance and mechanical properties, including special plastic materials, ceramic materials or glass fiber composite materials (glass fiber composite materials are used in this embodiment).

[0059] Furthermore, the heating vessel is located inside the cold shield. The heating vessel is fixed in position by a balanced vessel that is fixed in a predetermined position by an internal spacer and a support. The heating vessel is a structure composed of a cylindrical surface without upper and lower bottom surfaces and two hemispherical surfaces with the same diameter as the cylindrical surface of the heating vessel at both ends. Process holes are opened on the side wall of the cylindrical surface of the heating vessel.

[0060] Furthermore, the vacuum system includes: a first vacuum pump set, used to provide suction for the vacuuming process inside the insulated container, cold shield, and heating vessel; a first vacuum pipeline, one end of which is connected to the container body and the other end of which is connected to the first vacuum pump set; and a first high vacuum baffle valve, installed on the first vacuum pipeline, used to control the vacuuming process of the vacuum system. Vacuuming the space inside the insulated container, cold shield, and heating vessel can significantly reduce the influence of the external environment on the equilibrium vessel and the loss of liquid nitrogen cooling capacity.

[0061] Furthermore, the vacuum sampling system includes: a second vacuum pump unit, used to provide suction for the vacuuming process inside the equilibrium vessel; a vacuum pipeline, one end of which passes through the container body and connects to the inside of the equilibrium vessel, and the other end of which connects to the second vacuum pump unit; a second high-vacuum baffle valve, installed on the vacuum pipeline, used to control the vacuum system to evacuate; several gas cylinders containing the gas to be tested; several sampling branches, one end of which connects to the gas cylinders and the other end of which connects to the vacuum pipeline, and the connection point between the sampling branches and the vacuum pipeline is located between the second high-vacuum baffle valve and the equilibrium vessel; and several sampling rotary valves, respectively installed on several sampling branches, used to control the sampling of the gas cylinders to be tested.

[0062] Furthermore, the liquid nitrogen supply device includes: a Dewar; a liquid nitrogen box, which is a vacuum insulated container, installed at an elevation 0.5m higher than the elevation of the insulated container; a filling pipeline, one end connected to the Dewar and the other end connected to the top of the liquid nitrogen box, for supplying liquid nitrogen from the Dewar to the liquid nitrogen box; a liquid nitrogen rotary valve, installed on the filling pipeline, for controlling the flow rate of liquid nitrogen in the filling pipeline; a first liquid nitrogen flow path and a second liquid nitrogen flow path, each with one end connected to the bottom of the liquid nitrogen box and the other end connected to the cold shield heat exchange coil, connecting and communicating between the liquid nitrogen box and the cold shield heat exchange coil; and a liquid nitrogen venting pipeline, one end connected to the top of the liquid nitrogen box and communicating with the outside environment, the other end of which is the outlet to the external environment, to avoid excessive internal pressure caused by the vaporization of liquid nitrogen in the liquid nitrogen box.

[0063] Preferably, the filling pipeline, the liquid nitrogen venting pipeline, the first liquid nitrogen flow path, and the second liquid nitrogen flow path are all vacuum insulated pipelines, which can reduce the heat loss caused by the heat exchange between liquid nitrogen and the external environment.

[0064] Furthermore, the cold screen heat exchange coil includes: an upper cold screen heat exchange coil, coiled on the outer surface of the upper cold screen, comprising a lower first inlet and an upper first outlet, the first outlet being connected to a first vent pipe; and a lower cold screen heat exchange coil, coiled on the outer surface of the lower cold screen, comprising a lower second inlet and an upper second outlet, the second outlet being connected to a second vent pipe. A first liquid nitrogen flow path passes through the inlet of a first vacuum cylindrical sleeve and is connected to and communicates with the first inlet; one end of the first vent pipe is connected to the first outlet, and the other end of the first vent pipe, after passing through the outlet of the first vacuum cylindrical sleeve, is open to the external environment. A second liquid nitrogen flow path passes through the inlet of a second vacuum cylindrical sleeve and is connected to and communicates with the second inlet; one end of the second vent pipe is connected to the second outlet, and the other end of the second vent pipe, after passing through the outlet of the second vacuum cylindrical sleeve, is open to the external environment.

[0065] Preferably, the liquid nitrogen in the upper and lower cooling screen heat exchange coils flows from low to high in a clockwise or counterclockwise direction; both the first and second venting pipes are vacuum-insulated pipes, which can significantly reduce the heat loss caused by the liquid nitrogen exchanging with the external environment. Venting both to the external environment can prevent the adverse consequences caused by excessive pressure generated by the vaporization of liquid nitrogen inside the cooling screen heat exchange coils.

[0066] Furthermore, the sampling buffer unit includes: a gas phase sampling buffer pipeline, the inlet of which is located at the top of the equilibrium vessel and the outlet of which is connected to the gas chromatography analyzer; a first diaphragm valve, a first buffer tank, and a second diaphragm valve are sequentially installed on the gas phase sampling buffer pipeline, the second diaphragm valve controlling the sample from the first buffer tank to enter the gas chromatography analyzer; and a conventional liquid phase sampling buffer pipeline, the inlet of which is located at the bottom of the equilibrium vessel and the outlet of which is connected to the gas chromatography analyzer; a third diaphragm valve, a second buffer tank, and a fourth diaphragm valve are sequentially connected on the conventional liquid phase sampling buffer pipeline, the fourth diaphragm valve... The system controls the entry of samples from the second buffer tank into the gas chromatography analyzer; and a stainless steel microporous aerator liquid phase sampling buffer line, with its inlet located at the bottom of the equilibrium vessel and its outlet connected to the gas chromatography analyzer. The stainless steel microporous aerator liquid phase sampling buffer line is sequentially connected to a fifth diaphragm valve, a third buffer tank, and a sixth diaphragm valve. The sixth diaphragm valve controls the entry of samples from the third buffer tank into the gas chromatography analyzer. The inlet of the stainless steel microporous aerator liquid phase sampling buffer line is a stainless steel microporous aerator, with microporous aeration holes evenly distributed on its surface. When conducting phase equilibrium data determination under low-temperature conditions, there is a possibility of solid precipitation. Therefore, the liquid phase sampling line in the equilibrium vessel is divided into a conventional liquid phase sampling buffer line and a stainless steel microporous aerator liquid phase sampling buffer line. The microporous design prevents the liquid phase from mixing with solid phase and entering the sampling line, thus avoiding any impact on the accuracy of the gas chromatography analyzer.

[0067] Preferably, the top of the first buffer tank, the second buffer tank, and the third buffer tank are respectively equipped with a first safety valve, a second safety valve, and a third safety valve, and the starting pressure is less than 0.6 MPa.

[0068] Furthermore, the gas chromatography analysis device includes: a gas chromatograph connected to the outlets of a gas sampling buffer line, a conventional liquid sampling buffer line, and a stainless steel microporous aerator liquid sampling buffer line; a carrier gas cylinder containing hydrogen as the working medium; a carrier gas line for connecting the gas chromatograph and the carrier gas cylinder; and a carrier gas rotary valve located on the carrier gas line to control the entry of gas from the carrier gas cylinder into the gas chromatograph.

[0069] Furthermore, the data acquisition system includes: a first control cabinet, which connects to an aviation plug and displays and records in real time the pressure and temperature of the equilibrium vessel, the temperature of the heating vessel, and the temperature of the cold screen, and controls the heating film to match the cooling and heating capacity in the temperature control system to achieve the set temperature; and a second control cabinet, which connects to a gas chromatograph, records and saves the composition analysis results of the gas chromatograph.

[0070] Preferably, a pressure transmitter, a temperature sensor, and a heating film heating control module are installed on the line connecting the first control cabinet and the aviation plug to assist the first control cabinet in better controlling the temperature changes inside the phase balance system.

[0071] The present invention provides a low-temperature isothermal system for measuring integrated mixture phase equilibrium data, which is suitable for measuring vapor-liquid phase equilibrium in the temperature range of -180 to 0℃ and the pressure range of 0 to 10MPa. It adopts a vacuum radiation heat transfer method, which can achieve precise temperature control and ensure the uniformity of spatial temperature distribution, especially in the vertical direction.

[0072] In the description of this invention, it should be understood that the terms "bottom", "top", "middle", "upper", "leftmost", "slightly left", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the invention.

[0073] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "fixation," 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 connection of two components or the interaction between two components. Unless otherwise explicitly limited, those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0074] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to the embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A low-temperature isothermal system for integrating mixture phase equilibrium data determination, characterized in that, include: A phase balancing system includes an adiabatic container, a cold shield, a heating vessel, and a balancing vessel. The cold shield, the heating vessel, and the balancing vessel are installed coaxially from the outside to the inside inside the adiabatic container, and the adiabatic container, the cold shield, and the heating vessel are connected to each other. A vacuum system is connected and communicated with the phase balance system, and evacuates the space inside the insulating container, the cold shield, and the heating vessel. A vacuum sampling system is connected to and communicates with the equilibrium vessel to evacuate the equilibrium vessel and introduce the gas to be tested into the equilibrium vessel. A temperature control system, connected to the phase balance system, controls the temperature of the phase balance system. The system includes a cold screen heat exchange coil, a heating film, and a liquid nitrogen supply device. The cold screen heat exchange coil is installed on the outer surface of the cold screen, the heating film is tightly installed on the outer surface of the heating vessel, and the liquid nitrogen supply device is connected to the cold screen heat exchange coil and supplies liquid nitrogen to it. A sampling and analysis system, connected and in communication with the phase equilibrium system, includes a sampling buffer and a gas chromatograph, wherein the gas to be tested in the equilibrium vessel is transferred to the gas chromatograph via the sampling buffer; and A data acquisition system is connected to the phase equilibrium system to record data and control parameters of the phase equilibrium system. The data acquisition system is also connected to the sampling and analysis system to obtain the composition analysis results of the sampling and analysis system. The heat insulation container includes: Container body; A cylindrical flange is provided on the upper part of the container cylinder; The flange cover and the cylindrical flange are sealed with rubber, magnetohydrodynamic, adhesive or metal, and the edges are provided with holes or U-shaped grooves. The flange cover is fixed to the cylindrical flange with bolts and nuts or hook pins. The inlet and outlet of the first vacuum cylindrical sleeve are respectively located on the flange cover and are connected to the container body; The second vacuum cylindrical sleeve inlet and the second vacuum cylindrical sleeve outlet are respectively located at the lower part and middle part of the container body, and are connected to the container body; and An aviation connector, disposed on the flange cover and communicating with the container body, is connected to the balance vessel, the heating vessel, the cold shield, and the heating film to obtain pressure and temperature data inside the balance vessel, temperature data of the heating vessel, temperature data of the cold shield, and to control the heating film. The cold screen includes: The fixing unit, including the lifting rod, the circumferential support and the bottom support, is made of materials with good vacuum cryogenic performance and mechanical properties, including special plastic materials, ceramic materials or glass fiber composite materials; The upper cooling screen is a downward-facing hemispherical structure, connected and fixed to the flange cover by the top hanger. The inner surface of the upper cooling screen is coated with black paint or blackened with a metal blackening agent; and The lower cooling screen is not fixedly connected to the upper cooling screen. The lower cooling screen is an integrally formed structure composed of a cylindrical structure without top and bottom surfaces and a hemispherical structure with an upward-facing opening and the same diameter as the cylindrical structure of the lower cooling screen. It is fixed inside the container body by the circumferential support and the bottom support. The diameter of the cylindrical structure of the lower cooling screen is the same as the diameter of the hemispherical structure of the upper cooling screen. The inner surface of the lower cooling screen is coated with black paint or blackened with a metallic blackening agent. The vacuum system includes: The first vacuum pump unit is used to provide suction for the evacuation process of the space inside the insulating container, the cold shield, and the heating vessel. The first vacuum line has one end connected to the container body and in communication with it, and the other end connected to the first vacuum pump assembly. A first high-vacuum baffle valve is installed on the first vacuum pipeline and is used to control the vacuum system to evacuate. The vacuum sampling system includes: The second vacuum pump unit is used to provide suction for the evacuation process inside the balance vessel. The evacuation pipeline has one end passing through the container body and connecting to the inside of the equilibrium vessel, and the other end connecting to the second vacuum pump unit. A second high-vacuum baffle valve is installed on the evacuation pipeline and is used to control the vacuum system to evacuate. Several gas cylinders containing the gas to be tested. Several sample dispensing branches are provided, one end of which is connected to the gas cylinder to be tested and in communication, and the other end of which is connected to the evacuation pipeline and in communication. The connection point between the sample dispensing branch and the evacuation pipeline is located between the second high-vacuum baffle valve and the equilibrium vessel. Several sampling rotary valves are respectively installed on the several sampling branch pipes to control the sampling of the gas cylinder to be tested. The upper part of the balance vessel is connected to and communicates with the evacuation pipeline. The balance vessel's position suspended inside the container body is determined by its connection to the evacuation pipeline. The balance vessel is symmetrically equipped with high-precision temperature probes in the vertical direction. A spacer is provided at the top of the balance vessel, and a support member is provided at the bottom. The balance vessel is fixed inside the heating vessel by the spacer and the support. The materials used for the spacer and the support have good vacuum cryogenic performance and mechanical properties, including special plastic materials, ceramic materials, or glass fiber composite materials. The balancing vessel is an integrally formed closed structure consisting of a cylindrical surface without top and bottom surfaces and two hemispherical surfaces with the same diameter as the cylindrical surface at both ends of the balancing vessel. The heating vessel is located inside the cold shield. The heating vessel is fixed in position by the balanced vessel, which is fixed in a predetermined position by the internal spacer and the support member. The heating vessel is a structure composed of a cylindrical surface without upper and lower bottom surfaces and two hemispherical surfaces with the same diameter as the cylindrical surface of the heating vessel at both ends. Process holes are opened on the side wall of the cylindrical surface of the heating vessel.

2. The low-temperature isothermal system for integrating mixture phase equilibrium data determination according to claim 1, Its features are: The liquid nitrogen supply device includes: Dewar; The liquid nitrogen box is a vacuum insulated container, and its installation elevation exceeds the elevation of the insulated container by more than 0.5 m. The filling pipeline is connected at one end to the Dewar and at the other end to the top of the liquid nitrogen box, for supplying liquid nitrogen to the liquid nitrogen box via the Dewar; A liquid nitrogen rotary valve is installed on the filling pipeline to control the flow rate of liquid nitrogen in the filling pipeline; Both the first liquid nitrogen flow path and the second liquid nitrogen flow path have one end connected to the bottom of the liquid nitrogen box and the other end connected to the cold screen heat exchange coil, thus connecting and communicating the liquid nitrogen box and the cold screen heat exchange coil; and The liquid nitrogen venting pipeline is connected to the top of the liquid nitrogen container at one end and has an outlet to the external environment at the other end, to prevent excessive internal pressure caused by the vaporization of liquid nitrogen in the container. The filling pipeline, the liquid nitrogen venting pipeline, the first liquid nitrogen flow path, and the second liquid nitrogen flow path are all vacuum-insulated pipelines.

3. The low-temperature isothermal system for integrating mixture phase equilibrium data determination according to claim 2, Its features are: The cold shield heat exchange coil includes: The heat exchange coil of the upper cooling screen is coiled on the outer surface of the upper cooling screen and includes a lower first inlet and an upper first outlet, the first outlet being connected to a first vent pipe; and The lower cooling screen heat exchange coil is coiled on the outer surface of the lower cooling screen and includes a lower second inlet and an upper second outlet. The second outlet is connected to a second vent pipe. The first liquid nitrogen flow path passes through the inlet of the first vacuum cylindrical sleeve and is connected to and communicates with the first inlet; one end of the first venting pipe is connected to the first outlet, and the other end of the pipe, after passing through the outlet of the first vacuum cylindrical sleeve, is open to the external environment. The second liquid nitrogen flow path passes through the inlet of the second vacuum cylindrical sleeve and connects to and communicates with the second inlet; one end of the second venting pipe is connected to the second outlet, and the other end of the pipe, after passing through the outlet of the second vacuum cylindrical sleeve, is open to the external environment. The liquid nitrogen in the upper and lower cooling screen heat exchange coils flows from lower to higher positions in a clockwise or counterclockwise direction. Both the first venting pipeline and the second venting pipeline are vacuum-insulated pipelines.

4. The low-temperature isothermal system for integrating mixture phase equilibrium data determination according to claim 1, characterized in that: in, The sampling buffer includes: A gas phase sampling buffer pipeline has its inlet located at the upper part of the equilibrium vessel, and a first diaphragm valve, a first buffer tank, and a second diaphragm valve are sequentially installed on the gas phase sampling buffer pipeline. A standard liquid phase sampling buffer line, with its inlet located at the bottom of the equilibrium vessel, is sequentially connected to a third diaphragm valve, a second buffer tank, and a fourth diaphragm valve; and The stainless steel microporous aerator liquid phase sampling buffer pipeline has its inlet located at the bottom of the equilibrium vessel. A fifth diaphragm valve, a third buffer tank, and a sixth diaphragm valve are sequentially connected to the pipeline. The inlet of the stainless steel microporous aerator liquid phase sampling buffer pipeline is the stainless steel microporous aerator head, and the surface of the stainless steel microporous aerator head has uniformly distributed microporous aeration holes. The first, second, and third buffer tanks are respectively equipped with a first safety valve, a second safety valve, and a third safety valve at their tops, with a release pressure of less than 1.0 MPa. The outlets of the gas phase sampling buffer line, the ordinary liquid phase sampling buffer line, and the stainless steel microporous aerator liquid phase sampling buffer line are all connected to the gas chromatography analysis device. The second diaphragm valve, the fourth diaphragm valve, and the sixth diaphragm valve respectively control the entry of samples from the first buffer tank, the second buffer tank, and the third buffer tank into the gas chromatograph analysis device.

5. A low-temperature isothermal system for integrating mixture phase equilibrium data determination according to claim 4, Its features are: The gas chromatography analysis apparatus includes: A gas chromatograph is connected to the outlets of the gas phase sampling buffer line, the ordinary liquid phase sampling buffer line, and the stainless steel microporous aeration head liquid phase sampling buffer line. The working fluid in the carrier gas cylinder can be any one of hydrogen, nitrogen, helium, and argon. Carrier gas tubing, used to connect the gas chromatograph and the carrier gas cylinder; and A carrier gas rotary valve is installed on the carrier gas pipeline to control the gas in the carrier gas cylinder to enter the gas chromatograph.

6. The low-temperature isothermal system for integrating mixture phase equilibrium data determination according to claim 5, Its features are: The data acquisition system includes: The first control cabinet connects to the aviation plug and displays and records in real time the pressure and temperature of the balance vessel, the temperature of the heating vessel, and the temperature of the cooling screen. It also controls the heating film to match the cooling and heating capacities in the temperature control system to achieve the set temperature. The second control cabinet is connected to the gas chromatograph and records and saves the composition analysis results of the gas chromatograph. The circuit connecting the first control cabinet to the aviation plug is equipped with a pressure transmitter, a temperature sensor, and a heating film heating control module to assist the first control cabinet in better controlling the temperature changes inside the phase balance system.

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