Temperature control method and apparatus for rock thermal desorption pyrolysis gas chromatography analysis

Abstract

The application discloses a temperature control method and device for rock thermal desorption pyrolysis gas chromatography analysis, and the method comprises the following steps: storing a predetermined volume of liquid nitrogen in a second Dewar flask, and connecting the first Dewar flask and the second Dewar flask through a communicating vessel; wherein a U-shaped tube is installed in the first Dewar flask; the opening and closing of the communicating vessel is controlled through a liquid nitrogen adjusting device, so that the filling and releasing of the liquid nitrogen in the first Dewar flask and the second Dewar flask are realized; the height of the second Dewar flask is controlled through the liquid nitrogen adjusting device, so that the liquid surface of the liquid nitrogen in the first Dewar flask is ensured to immerse the U-shaped tube, and the liquid surface height of the liquid nitrogen in the first Dewar flask is kept unchanged. The volume of the liquid nitrogen in the Dewar flask is automatically and on-demand adjusted, the experimental efficiency is improved, and the stability and service life of the equipment are improved.

Description

Technical Field

[0001] This invention relates to the field of shale oil and gas exploration and development technology, and in particular to a temperature control method and apparatus for gas chromatography analysis of rock thermal desorption pyrolysis. Background Technology

[0002] Rock thermal desorption-pyrolysis gas chromatography (RTGC) is an important analytical technique for shale oil organic geochemical research. In RGC experiments, a U-shaped trap is installed between the injection port and the column in the gas chromatography column oven. The U-shaped tubing is immersed in liquid nitrogen in a Dewar flask and kept at a low temperature to collect the thermal desorption / pyrolysis products. The Dewar flask containing liquid nitrogen is removed by pushing down a pull rod connected to the outside of the column oven. Subsequently, the heating module activates, releasing the products into the chromatographic column.

[0003] The current cold trap design has the following problems:

[0004] (1) The operation is complicated. Liquid nitrogen needs to be manually filled before each experiment begins; the Dewar flask needs to be manually and quickly lowered a few seconds before the U-tube is heated, otherwise the experimental results will be affected.

[0005] (2) Waste of liquid nitrogen. To ensure the quality of freezing, an excessive amount of liquid nitrogen needs to be added. After heating, a large amount of liquid nitrogen evaporates and cannot be recovered.

[0006] (3) Affects equipment stability. Each time liquid nitrogen is filled, the column oven door needs to be opened and closed. If you are not careful, you may touch the chromatographic column or its interface, causing it to loosen and affecting the experimental results.

[0007] (4) Affects equipment lifespan. Currently, liquid nitrogen removal is achieved by using a lifting rod at the top of the column box to move the Dewar bottle vertically downwards to detach it from the U-shaped pipeline. The lifting rod is constantly baked at high temperatures in the column box (up to 310℃), making it extremely prone to aging, bending, and breakage.

[0008] (5) Potential risk of frostbite / scald. The liquid nitrogen pouring step may cause frostbite to the experimenters; during the column oven heating stage (up to 310°C), heat will be transferred to the end of the lifting rod, and accidental contact by the experimenters may cause scald. Summary of the Invention

[0009] The purpose of this invention is to provide a temperature control method and apparatus for gas chromatography analysis of rock thermal desorption pyrolysis, which enables automatic and on-demand adjustment of the liquid nitrogen volume in the Dewar flask, thereby improving experimental efficiency, equipment stability and lifespan.

[0010] To achieve the above objectives, the present invention provides a temperature control method for gas chromatography analysis of rock thermal desorption pyrolysis, comprising the following steps:

[0011] A predetermined volume of liquid nitrogen is stored in the second Dewar flask, and the first and second Dewar flasks are connected by a communicating vessel; wherein, a U-shaped tube is installed inside the first Dewar flask;

[0012] The opening and closing of the communicating vessel is controlled by a liquid nitrogen regulating device to allow for the filling and release of liquid nitrogen in the first and second Dewar flasks;

[0013] The height of the second Dewar flask is controlled by a liquid nitrogen regulating device to ensure that the liquid nitrogen level in the first Dewar flask is submerged in the U-shaped tube and to keep the liquid nitrogen level in the first Dewar flask constant.

[0014] Furthermore, the height of the second Dewar flask is controlled by a liquid nitrogen regulating device to ensure that the liquid nitrogen level in the first Dewar flask submerges the U-shaped tube and maintains a constant liquid nitrogen level in the first Dewar flask, including:

[0015] The electric lifting platform in the lifting device is controlled by the control system to adjust the height of the second Dewar flask so that the liquid nitrogen level in the first Dewar flask is submerged in the U-shaped tube and remains constant.

[0016] The liquid nitrogen regulating device includes a control system and a lifting device. The lifting device includes an electric lifting platform and a base. The electric lifting platform is installed above the base, and the second Dewar flask is located above the electric lifting platform. The control system is connected to the electric lifting platform.

[0017] Furthermore, adjust the height of the second Dewar flask so that the liquid nitrogen level in the first Dewar flask submerges the U-shaped tube and remains constant, including...

[0018] In the temperature control program of the control system, the initial height of the lifting device, the initial height of the first Dewar bottle when the liquid level is full from the base, and the initial height of the first Dewar bottle when the liquid level is empty from the base are input.

[0019] Through the calculations of the temperature control program, the control system controls the electric lifting platform to adjust the height of the second Dewar flask, so that the liquid nitrogen level in the first Dewar flask is always submerged in the U-shaped tube and remains unchanged.

[0020] Furthermore, while the control system controls the electric lifting platform to adjust the height of the second Dewar flask, it also detects the liquid nitrogen level in the second Dewar flask using a liquid level detector and feeds the data back to the control system. This allows for easy observation of the liquid nitrogen storage capacity in the second Dewar flask, facilitating the experiment.

[0021] The second Dewar flask is equipped with a liquid level gauge, which is connected to the control system.

[0022] Furthermore, before controlling the height of the second Dewar flask using the liquid nitrogen regulating device, the communicating vessel is also opened using the liquid nitrogen regulating device.

[0023] When it is necessary to remove the liquid nitrogen from the first Dewar flask, the height of the second Dewar flask is lowered using the liquid nitrogen regulating device, and the liquid nitrogen level in the first Dewar flask is lower than that in the U-tube. Then, the communicating vessel is closed using the liquid nitrogen regulating device.

[0024] Furthermore, the opening and closing of the communicating vessels are controlled via a liquid nitrogen regulating device, including:

[0025] The opening and closing of the solenoid valve is controlled by a liquid nitrogen regulating device to control the conduction of the vacuum insulation tube.

[0026] The communicating vessel includes a vacuum insulation tube and a solenoid valve. One end of the vacuum insulation tube is connected to the first Dewar flask, and the other end of the vacuum insulation tube is connected to the second Dewar flask.

[0027] Based on the unified inventive concept, the present invention also provides a temperature control device for gas chromatography analysis of rock thermal desorption pyrolysis, including a first Dewar flask, a second Dewar flask, a liquid nitrogen regulating device, a U-tube, and a communicating vessel;

[0028] The U-shaped tube is placed inside the first Dewar flask;

[0029] The first Dewar flask is used to fill with liquid nitrogen, so that the liquid level submerges the U-shaped tube;

[0030] The second Dewar flask is used to store a predetermined volume of liquid nitrogen, and the first and second Dewar flasks are connected by a communicating vessel.

[0031] The liquid nitrogen regulating device is used to control the opening and closing of the communicating vessel and to control the height of the second Dewar flask, so as to keep the liquid nitrogen level in the first Dewar flask constant.

[0032] Furthermore, the liquid nitrogen regulating device includes a control system and a lifting device;

[0033] The lifting device is located below the second Dewar flask and is used to adjust the height of the second Dewar flask.

[0034] A liquid level gauge is installed inside the second Dewar flask, which is used to detect the liquid nitrogen level inside the second Dewar flask;

[0035] The control system is connected to the lifting device, the communicating vessel, and the liquid level gauge, respectively.

[0036] Furthermore, the lifting device includes an electric lifting platform and a base, the electric lifting platform being disposed above the base, and the second Dewar flask being disposed on the electric lifting platform;

[0037] The control system is connected to the electric lifting platform.

[0038] Furthermore, the communicating vessel includes a vacuum insulation tube and a solenoid valve, the solenoid valve being mounted on the vacuum insulation tube, one end of the vacuum insulation tube being connected to the first Dewar flask, and the other end of the vacuum insulation tube being connected to the second Dewar flask.

[0039] The control system is connected to the solenoid valve.

[0040] Furthermore, the liquid level gauge is installed on the cap of the second Dewar flask;

[0041] The two ends of the vacuum insulation tube are respectively connected to the bottom of the first Dewar flask and the second Dewar flask.

[0042] The technical effects and advantages of this invention are as follows: The temperature control device of this invention automates experimental steps that require timely and mechanized operation, avoiding cumbersome operations; it enables precise filling and recovery of liquid nitrogen, avoiding liquid nitrogen waste; and it eliminates the need to open the column oven during the entire experiment, requiring only automated operation through the control system, thus improving equipment stability and lifespan. It also reduces the frequency of liquid nitrogen contact and replaces the heat transfer lifting rod structure, reducing the potential risk of burns / frostbite for operators.

[0043] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a flowchart of a temperature control method for gas chromatography analysis of rock thermal desorption pyrolysis according to an embodiment of the present invention;

[0046] Figure 2 This is a schematic diagram of the temperature control device for gas chromatography analysis of rock thermal desorption pyrolysis according to an embodiment of the present invention;

[0047] In the diagram, 1. First Dewar flask cap; 2. First Dewar flask; 3. Second Dewar flask cap; 4. Second Dewar flask; 5. Liquid level gauge; 6. Electric lifting platform; 7. Vacuum insulation tube; 8. Solenoid valve; 9. Control system; 10. Base. Detailed Implementation

[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] To address the shortcomings of existing technologies, embodiments of the present invention provide a temperature control method for gas chromatography analysis of rock thermal desorption pyrolysis, such as... Figure 1 As shown, it includes the following steps:

[0050] The second Dewar flask 4 stores a predetermined volume of liquid nitrogen, and the first Dewar flask 2 and the second Dewar flask 4 are connected by a communicating vessel; wherein, a U-shaped tube is installed inside the first Dewar flask 2;

[0051] The opening and closing of the communicating vessel is controlled by a liquid nitrogen regulating device so that liquid nitrogen can be filled and released in the first Dewar flask 2 and the second Dewar flask 4;

[0052] Keeping the height of the first Dewar flask 2 constant, the height of the second Dewar flask 4 is controlled by the liquid nitrogen regulating device to ensure that the liquid nitrogen level in the first Dewar flask 2 is submerged in the U-shaped tube and to keep the liquid nitrogen level in the first Dewar flask 2 constant.

[0053] In some specific embodiments, the height of the second Dewar flask 4 is controlled by a liquid nitrogen regulating device to ensure that the liquid nitrogen level in the first Dewar flask 2 is just completely submerged in the U-shaped tube and to keep the liquid nitrogen level in the first Dewar flask 2 constant. This includes the following steps:

[0054] The electric lifting platform 6 in the lifting device is controlled by the control system 9 to adjust the height of the second Dewar flask 4 so that the liquid nitrogen level in the first Dewar flask 2 is submerged in the U-shaped tube and remains constant.

[0055] The liquid nitrogen regulating device includes a control system 9 and a lifting device. The lifting device includes an electric lifting platform 6 and a base 10. The electric lifting platform 6 is installed above the base 10. The second Dewar flask 4 is located above the electric lifting platform 6. The control system 9 is connected to the electric lifting platform 6.

[0056] Because no matter how the height of the second Dewar flask 4 changes, the liquid nitrogen level in the first Dewar flask 2 and the liquid nitrogen level in the second Dewar flask 4 always remain the same.

[0057] Therefore, when the liquid nitrogen level in the first Dewar flask 2 is consumed and falls below the liquid nitrogen level that just completely submerges the U-tube, the height of the second Dewar flask 4 needs to be increased so that the liquid nitrogen in the second Dewar flask 4 flows to the first Dewar flask 2, so that the liquid nitrogen level in the first Dewar flask 2 again just completely submerges the liquid nitrogen level in the U-tube.

[0058] Before the experiment begins, the liquid nitrogen level in the first Dewar flask 2 is adjusted to completely submerge the U-shaped tube. If there is too much liquid nitrogen in the first Dewar flask 2, the height of the second Dewar flask 4 can be lowered through the electric lifting platform 6 of the liquid nitrogen adjustment device, so that the liquid nitrogen in the first Dewar flask 2 flows into the first Dewar flask 2, and the liquid nitrogen level in the first Dewar flask 2 just completely submerges the U-shaped tube.

[0059] In some specific embodiments, the electric lifting platform 6 in the lifting device is controlled by the control system 9 to adjust the height of the second Dewar flask 4 so that the liquid nitrogen level in the first Dewar flask 2 submerges the U-shaped tube and remains constant. This includes the following steps:

[0060] The initial height of the lifting device, the initial height of the first Dewar flask 2 when the full page is at a distance from the base 10, and the initial height of the first Dewar flask 2 when the liquid level is empty from the base 10 are obtained.

[0061] Then, in the thermal desorption / pyrolysis trap temperature control program of the control system 9, input the initial height of the lifting device, the initial height of the first Dewar flask 2 full page from the base 10, and the initial height of the first Dewar flask 2 empty liquid surface from the base 10.

[0062] Through the calculations of the temperature control program, the control system 9 controls the electric lifting platform 6 to adjust the height of the second Dewar flask 4, so that the liquid nitrogen level in the first Dewar flask 2 always submerges the U-shaped tube and remains unchanged.

[0063] While the control system 9 controls the electric lifting platform 6 to adjust the height of the second Dewar flask 4, the liquid level detector 5 detects the liquid nitrogen level in the second Dewar flask 4 and feeds it back to the control system 9, so as to facilitate the observation of the liquid nitrogen storage capacity in the second Dewar flask 4 for the purpose of conducting the experiment.

[0064] The second Dewar flask 4 is equipped with a liquid level gauge 5, which is connected to the control system 9.

[0065] In some specific embodiments, the height of the second Dewar flask 4 is adjusted by controlling the electric lifting platform 6 in the lifting device through the control system 9, including the following steps:

[0066] Before controlling the height of the second Dewar flask 4 using the liquid nitrogen regulating device, the communicating vessel is opened using the liquid nitrogen regulating device.

[0067] When it is necessary to remove the liquid nitrogen from the first Dewar flask 2, the height of the second Dewar flask 4 is lowered using the liquid nitrogen regulating device, and the liquid nitrogen level in the first Dewar flask 2 is lower than that in the U-tube. Then, the communicating vessel is closed using the liquid nitrogen regulating device.

[0068] In some specific embodiments, the liquid nitrogen regulating device controls the opening of the communicating vessel, including:

[0069] The solenoid valve 8 is opened and closed by the control system 9 to conduct the vacuum insulation tube 7 in the communicating vessel.

[0070] The communicating vessel includes a vacuum insulation tube 7 and a solenoid valve 8. The solenoid valve 8 is installed on the vacuum insulation tube 7. One end of the vacuum insulation tube 7 is connected to the bottom of the first Dewar flask 2, and the other end of the vacuum insulation tube 7 is connected to the bottom of the second Dewar flask 4. The control system 9 in the liquid nitrogen regulating device is connected to the solenoid valve 8.

[0071] Based on the same inventive concept, embodiments of the present invention provide a temperature control device for gas chromatography analysis of rock thermal desorption pyrolysis, such as... Figure 2 As shown, it includes a first Dewar flask 2, a second Dewar flask 4, a liquid nitrogen regulating device, a U-tube, and a communicating vessel;

[0072] The U-shaped tube passes through the cap 1 of the first Dewar flask 2 and is placed inside the first Dewar flask 2. The first Dewar flask 2 is used to fill liquid nitrogen so that the liquid level just completely submerges the U-shaped tube.

[0073] The second Dewar flask 4 is used to store a predetermined volume of liquid nitrogen, and the first Dewar flask 2 and the second Dewar flask 4 are connected by a communicating vessel;

[0074] The communicating vessel is used to facilitate the flow of liquid nitrogen in the first Dewar flask 2 and the second Dewar flask 4;

[0075] The liquid nitrogen regulating device is used to control the opening and closing of the communicating vessel and to control the height of the second Dewar flask 4, so as to keep the liquid nitrogen level in the first Dewar flask 2 constant.

[0076] In some specific embodiments, the liquid nitrogen regulating device includes a control system 9 and a lifting device; the lifting device is located below the second Dewar flask 4 and is used to adjust the height of the second Dewar flask 4.

[0077] A liquid level gauge 5 is installed inside the second Dewar flask 4. The liquid level gauge 5 is installed on the cap 3 of the second Dewar flask 4. The liquid level gauge 5 is used to detect the liquid level of liquid nitrogen inside the second Dewar flask 4. The liquid level gauge 5 is a radar level gauge.

[0078] The control system 9 is connected to the lifting device, the communicating vessel and the liquid level gauge 5 respectively, so as to control the height of the second Dewar flask 4 and ensure that the liquid nitrogen level in the first Dewar flask 2 is always completely submerged in the U-shaped tube.

[0079] In some specific embodiments, the lifting device includes an electric lifting platform 6 and a base 10. The electric lifting platform 6 is located above the base 10, and the second Dewar flask 4 is located on the electric lifting platform 6. The control system 9 is connected to the electric lifting platform 6, and the control system 9 sends lifting commands to control the electric lifting platform 6 to lift the second Dewar flask 4.

[0080] In some specific embodiments, the communicating vessel includes a vacuum insulation tube 7 and a solenoid valve 8. The solenoid valve 8 is installed on the vacuum insulation tube 7. One end of the vacuum insulation tube 7 is connected to the bottom of the first Dewar flask 2, and the other end of the vacuum insulation tube 7 is connected to the bottom of the second Dewar flask 4.

[0081] The control system 9 is connected to the solenoid valve 8, and the control system 9 sends opening and closing commands to control the opening and closing of the solenoid valve 8.

[0082] In some specific embodiments, one end of the U-tube is used to inject the sample solution, and the other end of the U-tube is connected to one end of the capillary column, and the other end of the capillary column is connected to the FID detector of the chromatographic analyzer.

[0083] Working principle of the temperature control device: Before use, the temperature control program of the thermal desorption / pyrolysis trap, the initial height of the electric lifting platform 6, the initial height of the first Dewar flask 2 (full liquid level) from the base 10, and the initial height of the first Dewar flask 2 (empty liquid level) from the base 10 are input into the circuit control system 9. An appropriate amount of liquid nitrogen is filled into the second Dewar flask 4. After the trap temperature control program starts, the circuit control system 9 accurately controls the filling and releasing of liquid nitrogen in the first Dewar flask 2 according to the program. When the first Dewar flask 2 is being filled with liquid nitrogen, the solenoid valve 8 is opened. The circuit control system 9 calculates and adjusts the height of the electric lifting platform 6 until the liquid nitrogen level in the first Dewar flask 2 is just completely submerged in the U-shaped tube. The U-shaped tube traps the thermal desorption / pyrolysis products at low temperature. After the predetermined trapping time ends, the liquid nitrogen is removed. The height of the second Dewar flask 4 is lowered by controlling the electric lifting platform 6 so that the liquid nitrogen level in the first Dewar flask 2 is lower than the U-shaped tube. Then, the solenoid valve 8 is closed, and the U-shaped tube heating program is used to release the trapped products into the gas chromatograph.

[0084] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A temperature control method for gas chromatography analysis of rock thermal desorption pyrolysis, characterized in that, Includes the following steps: A predetermined volume of liquid nitrogen is stored in the second Dewar flask (4), and the first Dewar flask (2) and the second Dewar flask (4) are connected by a connector; wherein, a U-shaped tube is installed inside the first Dewar flask (2); The opening and closing of the communicating vessel is controlled by a liquid nitrogen regulating device so that liquid nitrogen can be filled and released in the first Dewar flask (2) and the second Dewar flask (4); The height of the second Dewar flask (4) is controlled by the liquid nitrogen regulating device to ensure that the liquid nitrogen level in the first Dewar flask (2) is submerged in the U-shaped tube and to keep the liquid nitrogen level in the first Dewar flask (2) constant. The height of the second Dewar flask (4) is controlled by a liquid nitrogen regulating device to ensure that the liquid nitrogen level in the first Dewar flask (2) is submerged in the U-shaped tube and to maintain a constant liquid nitrogen level in the first Dewar flask (2), including... The electric lifting platform (6) in the lifting device is controlled by the control system (9) to adjust the height of the second Dewar bottle (4) so ​​that the liquid nitrogen level in the first Dewar bottle (2) is submerged in the U-shaped tube and remains unchanged. The liquid nitrogen regulating device includes a control system (9) and a lifting device. The lifting device includes an electric lifting platform (6) and a base (10). The electric lifting platform (6) is installed above the base (10). The second Dewar bottle (4) is located above the electric lifting platform (6). The control system (9) is connected to the electric lifting platform (6). Adjust the height of the second Dewar flask (4) so ​​that the liquid nitrogen level in the first Dewar flask (2) submerges the U-tube and remains constant, including, In the temperature control program of the control system (9), the initial height of the lifting device, the initial height of the first Dewar bottle (2) from the base (10) when the liquid level is full, and the initial height of the first Dewar bottle (2) from the base (10) when the liquid level is empty are input. Through the calculation of the temperature control program, the control system (9) controls the electric lifting platform (6) to adjust the height of the second Dewar flask (4) so ​​that the liquid nitrogen level in the first Dewar flask (2) is always submerged in the U-shaped tube and remains unchanged.

2. The temperature control method for gas chromatography analysis of rock thermal desorption pyrolysis according to claim 1, characterized in that, The control system (9) controls the electric lifting platform (6) to adjust the height of the second Dewar flask (4), and at the same time, uses the liquid level detector (5) to detect the liquid nitrogen level in the second Dewar flask (4) and feeds it back to the control system (9) so as to facilitate the observation of the liquid nitrogen storage capacity in the second Dewar flask (4) for the purpose of conducting the experiment. The second Dewar flask (4) is equipped with a liquid level gauge (5), which is connected to the control system (9).

3. The temperature control method for gas chromatography analysis of rock thermal desorption pyrolysis according to claim 1 or 2, characterized in that, Before controlling the height of the second Dewar flask (4) with the liquid nitrogen regulating device, the communicating vessel is also opened using the liquid nitrogen regulating device. When it is necessary to remove the liquid nitrogen from the first Dewar flask (2), the height of the second Dewar flask (4) is lowered using the liquid nitrogen regulating device, and the liquid nitrogen level in the first Dewar flask (2) is lower than that in the U-tube. Then, the communicating vessel is closed using the liquid nitrogen regulating device.

4. The temperature control method for gas chromatography analysis of rock thermal desorption pyrolysis according to claim 3, characterized in that, The opening and closing of the communicating vessels are controlled by a liquid nitrogen regulating device, including... The opening and closing of the solenoid valve (8) is controlled by the liquid nitrogen regulating device to control the conduction of the vacuum insulation tube (7); The communicating vessel includes a vacuum insulation tube (7) and a solenoid valve (8). One end of the vacuum insulation tube (7) is connected to the first Dewar flask (2), and the other end of the vacuum insulation tube (7) is connected to the second Dewar flask (4).

5. A temperature control device for gas chromatography analysis of rock thermal desorption pyrolysis, characterized in that, Includes a first Dewar flask (2), a second Dewar flask (4), a liquid nitrogen regulating device, a U-tube, and a communicating vessel; The U-shaped tube is placed inside the first Dewar flask (2); The first Dewar flask (2) is used to fill with liquid nitrogen, so that the liquid surface is submerged in the U-shaped tube; The second Dewar flask (4) is used to store a predetermined capacity of liquid nitrogen, and the first Dewar flask (2) and the second Dewar flask (4) are connected by a communicating vessel; The liquid nitrogen regulating device is used to control the opening and closing of the communicating vessel and to control the height of the second Dewar flask (4) to keep the liquid nitrogen level in the first Dewar flask (2) constant. The liquid nitrogen regulating device includes a control system (9) and a lifting device; The lifting device is located below the second Dewar flask (4) and is used to adjust the height of the second Dewar flask (4); The second Dewar flask (4) is equipped with a liquid level gauge (5), which is used to detect the liquid nitrogen level in the second Dewar flask (4); The control system (9) is connected to the lifting device, the communicating vessel and the liquid level detector (5) respectively; The lifting device includes an electric lifting platform (6) and a base (10). The electric lifting platform (6) is located above the base (10), and the second Dewar flask (4) is located on the electric lifting platform (6). The control system (9) is connected to the electric lifting platform (6).

6. The temperature control device for gas chromatography analysis of rock thermal desorption pyrolysis according to claim 5, characterized in that, The communicating vessel includes a vacuum insulation tube (7) and a solenoid valve (8). The solenoid valve (8) is installed on the vacuum insulation tube (7). One end of the vacuum insulation tube (7) is connected to the first Dewar flask (2), and the other end of the vacuum insulation tube (7) is connected to the second Dewar flask (4). The control system (9) is connected to the solenoid valve (8).

7. The temperature control device for gas chromatography analysis of rock thermal desorption pyrolysis according to claim 6, characterized in that, The liquid level gauge (5) is installed on the cap of the second Dewar flask (4); The two ends of the vacuum insulation tube (7) are respectively connected to the bottom of the first Dewar flask (2) and the second Dewar flask (4).

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