CO2 coal seam CH4 gas competitive adsorption heat effect testing device

Abstract

The utility model discloses a CO2 coal seam CH4 gas competitive adsorption heat effect testing device, and belongs to the field of coal mines. The device comprises a CH4 gas tank, a rare gas tank, a first high-pressure buffer tank, a first reference tank, a non-contact temperature measurement coal sample tank, an infrared thermal imager, a data acquisition and storage mechanism, a second reference tank, a second high-pressure buffer tank, a CO2 gas tank, a constant-temperature water bath, a vacuumizing mechanism, first and second pressure gauges, first to twelfth valves, first and second tee joints, first to third four-way joints, first and third pressure sensors, a CO2 concentration sensor and a CH4 concentration sensor. And connecting the components. The method has no influence on the replacement effect during testing, enables the measurement result to be accurate, can obtain the gas competitive adsorption and gas reciprocal diffusion rules in the process of replacing the CH4 in the coal seam by the CO2, can deeply analyze the driving mechanism and the action efficiency of the CH4 in the coal seam by the CO2 from the perspective of energy migration, and can improve the detection accuracy. And a theoretical support is provided for realizing reasonable optimization and efficiency maximization of key control parameters.

Description

Technical Field

[0001] The present application relates to the field of coal mine technology, and in particular to a device for testing the thermal effect of competitive adsorption of CH4 gas in a CO2 coal seam. Background Art

[0002] Mine gas (coalbed methane) combines the characteristics of a "hazardous gas," a "greenhouse gas," and an "energy gas." It is not only the primary threat to coal mine safety and production, but also a major contributor to the greenhouse effect. Furthermore, it is a clean, high-quality, unconventional natural gas resource. Efficient development of coalbed methane is highly beneficial for increasing energy reserves, while also eliminating coal mine gas outbursts and reducing gas accidents.

[0003] Gas extraction is a fundamental measure for mine gas control and coalbed methane development. However, utilizing the naturally occurring pressure gradient between underground coal seam pressure and atmospheric pressure can only recover 20% to 60% of CH4. This is primarily due to the heterogeneity of the adsorption potential wells on the coal surface. The smaller the adsorption capacity, the deeper the potential well depth occupied by the adsorbed CH4 molecules, and the less sensitive the adsorption state is to the adsorption pressure. To increase the CH4 recovery rate from coal seams, gas-enhanced desorption technologies such as heat injection, CO2 injection (liquid / gas / supercritical), N2 injection, acoustic waves, and shock waves have rapidly developed. A common characteristic of these technologies is that gas desorption depends on the disturbance of the original coal seam equilibrium and requires energy supply.

[0004] Coal has a greater ability to absorb CO₂ than CH₄. Therefore, the use of CO₂ to displace CH₄ from coal seams has become widely used, as it improves coal seam gas recovery, achieves geological storage of CO₂, and contributes to the "dual carbon" goals. Maximizing the displacer efficiency (displacement ratio) is a key focus of engineering applications of this technology. However, actual research on displacer ratios under practical conditions is limited by site constraints. Therefore, experimental research on displacer ratios is conducted, and the results provide a theoretical basis for practical application.

[0005] During the process of CO2 replacing CH4 in coal seams, CO2 diffuses into the coal matrix and is adsorbed by the coal body, releasing heat, reducing the internal energy of CO2 and increasing the temperature of the coal body. The adsorbed CH4 absorbs the heat of the coal body and transforms into a free state, diffusing out of the coal matrix, increasing the internal energy of CH4 and reducing the temperature of the coal body. Therefore, the replacement process is accompanied by the migration of energy within the system, that is, the entropy and enthalpy of the system change. Macroscopically, it manifests as a change in the temperature of the coal body (thermal effect) and the reciprocal diffusion of gases, the magnitude of which determines the final effect of the replacement, that is, the replacement ratio. The existing test method is affected by the pressure gradient, and the replacement effect is disturbed. This affects the replacement effect when testing the competitive adsorption thermal effect of CO2 replacing CH4 in coal seams, making the measurement results inaccurate. In addition, most of the existing testing methods are explained from the aspects of CO2 multi-layer adsorption and CO2 preferential adsorption on vacant adsorption sites in the coal body. They do not conduct in-depth analysis of the driving mechanism and effectiveness of CO2 replacement of coal seam CH4 from the perspective of energy migration, quantify the corresponding relationship between the two, and provide theoretical support for the rational optimization of key control parameters and the maximization of replacement efficiency, which seriously restricts the engineering application and promotion of CO2 replacement of coal seam CH4 technology. Utility Model Content

[0006] The embodiment of the present application provides a CO2 coal seam CH4 gas competitive adsorption thermal effect testing device, which can solve the problems that the existing testing method is affected by the pressure gradient and the replacement effect is disturbed, which affects the replacement effect when testing the CO2 replacement coal seam CH4 gas competitive adsorption thermal effect, making the measurement results inaccurate and failing to conduct an in-depth analysis of the driving mechanism and action efficiency of CO2 replacement of coal seam CH4 from the perspective of energy migration.

[0007] In order to achieve the above purpose, the technical solution of the embodiment of the utility model is:

[0008] The embodiment of the utility model provides a CO2 coal seam CH4 gas competitive adsorption thermal effect testing device, comprising: a CH4 gas tank, a rare gas tank, a high-pressure buffer tank 1, a reference tank 1, a non-contact temperature measurement coal sample tank, an infrared thermal imager, a data acquisition and storage mechanism, a reference tank 2, a high-pressure buffer tank 2, a CO2 gas tank, a constant temperature water bath, a vacuum pumping mechanism, a pressure gauge 1, a pressure gauge 2, a valve 1, a valve 2, a valve 3, a three-way valve 1, a valve 4, a valve 5, a four-way valve 1, a valve 6, a four-way valve 2, a valve 7, a four-way valve 3, a valve 8, a three-way valve 2, a valve 9, a valve 10, a valve 11, a valve 12, a pressure sensor 1, a pressure sensor 2, a pressure sensor 3, a CO2 concentration sensor, and a CH4 concentration sensor;

[0009] Connecting the CH4 gas tank to the high-pressure buffer tank 1 through a first pipeline, and installing the valve 1 on the first pipeline;

[0010] Connecting the rare gas tank to the first high-pressure buffer tank via a second pipeline, and providing the second valve on the second pipeline;

[0011] The high-pressure buffer tank 1 is connected to the four-way valve 1 through a third pipeline, and the valve 3, the three-way valve 1, and the valve 5 are sequentially arranged on the third pipeline in the direction from the high-pressure buffer tank 1 to the four-way valve 1;

[0012] The pressure gauge 1 is provided on the high-pressure buffer tank 1;

[0013] Connecting the three-way valve 1 and the vacuum pumping mechanism through a fourth pipeline, and installing the valve 4 on the fourth pipeline;

[0014] Connect the four-way valve 1 and the four-way valve 2 through a fifth pipeline, and install the valve 6 on the fifth pipeline;

[0015] The reference tank 1 and the pressure sensor 1 are respectively connected to the four-way 1;

[0016] The non-contact temperature measuring coal sample tank and the second pressure sensor are respectively connected to the second four-way port;

[0017] The four-way valve 3 and the high-pressure buffer tank 2 are connected through a sixth pipeline, and the valve 8, the three-way valve 2 and the valve 10 are sequentially arranged on the sixth pipeline in the direction from the four-way valve 3 to the high-pressure buffer tank 2;

[0018] The second pressure gauge is provided on the second high-pressure buffer tank;

[0019] Connecting the CO2 gas tank and the second high-pressure buffer tank via a seventh pipeline, and installing the eleventh valve on the seventh pipeline;

[0020] Connect the four-way valve 2 and the four-way valve 3 through an eighth pipeline, and install the valve 7 on the eighth pipeline;

[0021] The valve 12 is provided on the output pipe at the bottom of the high-pressure buffer tank 1;

[0022] The non-contact temperature measurement coal sample tank comprises a tank body, a tank cover and an infrared light high permeability single crystal;

[0023] The tank cover is arranged at the opening of the tank body to close the tank body, a mounting hole is arranged in the middle of the tank cover, and the infrared light high permeability single crystal is arranged in the mounting hole;

[0024] The infrared thermal imager is arranged above the infrared light high permeability single crystal;

[0025] The reference tank 2 and the pressure sensor 3 are both connected to the four-way 3;

[0026] The CO2 concentration sensor is set on the non-contact temperature measurement coal sample tank, and the CH4 concentration sensor is set on the reference tank 2;

[0027] The pressure sensor 1, the pressure sensor 2, the pressure sensor 3, the CO2 concentration sensor, the CH4 concentration sensor, and the infrared thermal imager are all electrically connected to the data acquisition and storage mechanism;

[0028] The first reference tank, the non-contact temperature measurement coal sample tank and the second reference tank are arranged in the constant temperature water bath.

[0029] In a possible implementation, the CO2 coal seam CH4 gas competitive adsorption thermal effect test device further includes valve nine and an exhaust gas collection bag;

[0030] The tail gas collection bag and the two tee joints are connected via a ninth pipeline, and the ninth valve is provided on the ninth pipeline.

[0031] In a possible implementation, the reference tank 1 and the reference tank 2, the valve 5 and the valve 8, the four-way 1 and the four-way 3 are symmetrically distributed with the central axis of the non-contact temperature measurement coal sample tank as the axis of symmetry.

[0032] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0033] The CO2 coal seam CH4 gas competitive adsorption thermal effect test device provided by the embodiment of the present invention can avoid the influence of pressure gradient on the replacement effect by setting reference tank one and reference tank two, so that the replacement effect is not disturbed, and thus the replacement effect is not affected during the CO2 replacement coal seam CH4 gas competitive adsorption thermal effect test, so that the measurement results are accurate, and the gas competitive adsorption and gas mutual counter-diffusion laws of the CO2 replacement coal seam CH4 process can be obtained. By real-time monitoring the temperature change law of the dry coal sample during the adsorption process of CH4 gas adsorption dry coal sample, real-time monitoring the mutual counter-diffusion and competitive adsorption temperature of CO2 and CH4 dry coal sample, the pressure of the non-contact temperature measurement coal sample tank and the pressure change law of reference tank two, it is possible to conduct an in-depth analysis of the driving mechanism and action efficiency of CO2 replacement coal seam CH4 from the perspective of energy migration, and provide theoretical support for the reasonable optimization of key control parameters and the realization of efficiency maximization. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments of the present invention or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 A schematic diagram of the structure of a device for testing the thermal effect of competitive adsorption of CH4 gas on CO2 coal seams provided in an embodiment of the present application;

[0036] Figure 2 A cross-sectional view of a non-contact temperature measurement coal sampling tank provided in an embodiment of the present application;

[0037] Figure 3 A top view of the non-contact temperature measurement coal sample tank provided in an embodiment of the present application.

[0038] Icons: 1-CH4 gas tank, 2-rare gas tank, 3-high pressure buffer tank 1, 4-reference tank 1, 5-non-contact temperature measurement coal sample tank, 51-tank body, 52-tank cover, 53-infrared light high permeability single crystal, 54-inlet and outlet pipes, 55-fixing parts, 56-first set of buckles, 57-second set of buckles, 58-O-ring 1, 59-O-ring 2, 6-infrared thermal imager, 7-data acquisition and storage mechanism, 71-data acquisition instrument, 72-computer, 8-reference tank 2, 9-high pressure buffer tank 2, 10-CO2 gas tank, 11-constant temperature water bath, 12-vacuum mechanism, 13-pressure Force gauge 1, 14-Pressure gauge 2, 15-Valve 1, 16-Valve 2, 17-Valve 3, 18-Tee 1, 19-Valve 4, 20-Valve 5, 21-Four-way 1, 22-Valve 6, 23-Four-way 2, 24-Valve 7, 25-Four-way 3, 26-Valve 8, 27-Tee 2, 28-Valve 9, 29-Valve 10, 30-Valve 11, 31-Valve 12, 32-Valve 13, 33-Pressure sensor 1, 34-Pressure sensor 2, 35-Pressure sensor 3, 36-CO2 concentration sensor, 37-CH4 concentration sensor, 38-Dry coal sample. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0040] In the description of the embodiments of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limitations on the present invention. The terms "first", "second" and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance. In addition, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be a communication between the internal parts of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present invention can be understood according to the specific circumstances.

[0041] The embodiment of the present utility model provides a CO2 coal seam CH4 gas competitive adsorption thermal effect testing device, including: a CH4 gas tank 1, a rare gas gas tank 2, a high-pressure buffer tank 3, a reference tank 4, a non-contact temperature measurement coal sample tank 5, an infrared thermal imager 6, a data acquisition and storage mechanism 7, a reference tank 2 8, a high-pressure buffer tank 2 9, a CO2 gas tank 10, a constant temperature water bath 11, a vacuum pumping mechanism 12, a pressure gauge 13, a pressure gauge 2 14, a valve 15, a valve 2 16, a valve 3 17, a three-way 1 18, a valve 4 19, a valve 5 20, a four-way 1 21, a valve 6 22, a four-way 2 23, a valve 7 24, a four-way 3 25, a valve 8 26, a three-way 2 27, a three-way 2 27, a valve 10 29, a valve 11 30, a valve 12 31, a pressure sensor 1 33, a pressure sensor 2 34, a pressure sensor 3 35, a CO2 concentration sensor 36 and a CH4 concentration sensor 37.

[0042] A first pipeline connects CH4 gas tank 1 to high-pressure buffer tank 3, and a valve 15 is installed on the first pipeline. A second pipeline connects rare gas tank 2 to high-pressure buffer tank 3, and a valve 2 is installed on the second pipeline. A third pipeline connects high-pressure buffer tank 3 to four-way valve 21, and valves 3, 17, 18, and 20 are installed on the third pipeline in the order from high-pressure buffer tank 3 to four-way valve 21. A pressure gauge 13 is installed on high-pressure buffer tank 3. A fourth pipeline connects three-way valve 18 to vacuum pump 12, and a valve 4 is installed on the fourth pipeline.

[0043] A fifth pipeline connects 4-way 1 (21) and 4-way 2 (23), and a valve (6) (22) is installed on the fifth pipeline. Reference tank 1 (4) and pressure sensor 1 (33) are connected to 4-way 1 (21). Non-contact temperature measurement coal sample tank 5 and pressure sensor 2 (34) are connected to 4-way 2 (23).

[0044] A sixth pipeline connects four-way valve 3 (25) and high-pressure buffer tank 2 (9). Valve 8 (26), three-way valve 2 (27), and valve 10 (29) are installed in this order from four-way valve 3 (25) to high-pressure buffer tank 2 (9). A pressure gauge 2 (14) is installed on high-pressure buffer tank 2 (9). A seventh pipeline connects the CO2 tank 10 and high-pressure buffer tank 2 (9), and valve 11 (30) is installed on the seventh pipeline. Four-way valve 2 (23) and four-way valve 3 (25) are connected via an eighth pipeline, and valve 7 (24) is installed on the eighth pipeline. A valve 12 (31) is installed on the output pipeline at the bottom of high-pressure buffer tank 1 (3).

[0045] The non-contact temperature measurement coal sample tank 5 consists of a tank body 51, a tank lid 52, and a high-permeability infrared single crystal 53. The lid 52 is attached to the opening of the tank body 51 to seal it. The tank body 51 is made of stainless steel and is cylindrical in shape. Its interior measures 140 mm x 140 mm, with a wall thickness of 10 mm. It can hold 250 g to 300 g of 60-80 mesh coal sample. An air inlet and outlet pipe 54 is located 20 mm from the top of the tank body 51, ensuring that the pipe is positioned above the dry coal sample 38 to prevent disturbance of the dry coal sample by air in and out.

[0046] The middle of the tank cover 52 is provided with a mounting hole, and a single crystal 53 with high infrared permeability is provided at the mounting hole to form a projection hole. The tank cover 52 is made of stainless steel and is designed to be cylindrical with a diameter of 200mm×10mm. Figure 2 and Figure 3 As shown, an annular fixing member 55 secures the high-infrared-permeability single crystal 53. Multiple first buckles 56 then secure the fixing member 55 to the mounting holes of the can lid 52, achieving a seal. The can lid 52 is then secured to the can body 51 using second buckles 57. An O-ring 1 58 is positioned on the top surface of the can body 51 and the bottom surface of the can lid 52. An O-ring 2 59 is positioned at the contact point between the high-infrared-permeability single crystal 53 and the can lid 52, achieving a seal.

[0047] Infrared thermal imager 6 is positioned above high-infrared-light-transmittance single crystal 53. This monitors the temperature changes of dried coal sample 38 in real time through the high-infrared-light-transmittance single crystal. The high-infrared-light-transmittance single crystal is made of germanium, with a transmittance of up to 95%, and is designed in a circular shape of φ120mm x 10mm.

[0048] The reference tank 2 8 and the pressure sensor 3 35 are both connected to the cross-connect 3 25 .

[0049] A CO2 concentration sensor 36 is installed on the non-contact temperature-measuring coal sample tank 5, and a CH4 concentration sensor 37 is installed on the reference tank 2 8. Pressure sensor 1 33, pressure sensor 2 34, pressure sensor 35, CO2 concentration sensor 36, CH4 concentration sensor 37, and infrared thermal imager 6 are all electrically connected to a data acquisition and storage mechanism 7 (which includes a data acquisition device 71 and a computer 72, which are electrically connected). Reference tank 1 4, the non-contact temperature-measuring coal sample tank 5, and reference tank 2 8 are placed in a constant-temperature water bath 11. By controlling the water temperature in the constant-temperature water bath 11, a constant temperature environment is provided for the CO2-coalbed CH4 gas competitive adsorption thermal effect test device.

[0050] Pressure sensor 1 33 monitors the pressure of reference tank 1 4 in real time. Pressure sensor 2 34 monitors the pressure of non-contact temperature measurement coal sample tank 5 in real time. Infrared thermal imager 6 monitors the temperature of dry coal sample 38 in non-contact temperature measurement coal sample tank 5 in real time. CO2 concentration sensor 36 monitors the CO2 concentration in the gas within non-contact temperature measurement coal sample tank 5 in real time. CH4 concentration sensor 37 monitors the CH4 concentration in the gas within reference tank 2 8 in real time. Pressure sensor 35 monitors the pressure of reference tank 2 8 in real time. Data acquisition device 71 collects data from pressure sensor 1 33, pressure sensor 2 34, infrared thermal imager 6, CO2 concentration sensor 36, CH4 concentration sensor 37, and pressure sensor 35. Computer 72 analyzes and plots the data collected by data acquisition device 71.

[0051] The specific operating steps of the CO2 coal seam CH4 gas competitive adsorption thermal effect testing device provided by the embodiment of the utility model are as follows:

[0052] Step 1: Load the dry coal sample 38 into the non-contact temperature measurement coal sample tank 5 (weigh 300g of dry coal sample 38 and load it into the non-contact temperature measurement coal sample tank 5), according to Figure 1 Connect the CO2 coal seam CH4 gas competitive adsorption thermal effect test device, check the airtightness and integrity of the device, and measure the free space volume V0 in the non-contact temperature measurement coal sample tank 5.

[0053] Among them, the preparation method of dry coal sample 38 is: collect large pieces of coal samples underground, seal them tightly and transport them to the laboratory, break the surface oxide layer, manually crush them into 60-80 mesh, put them into a vacuum drying oven and dry them at a constant temperature of 40°C for 24 hours to obtain dry coal sample 38, and put the dry coal sample 38 into a sealing tape for standby use.

[0054] The process of measuring the free space volume V0 in the non-contact temperature measuring coal sample tank 5 includes:

[0055] Step 11: Repeat the second step multiple times to obtain multiple second data groups, that is, obtain multiple sets of gas state equations about the pressure of the non-contact temperature measurement coal sample tank 5, each set of second data groups includes the first initial temperature T1 of the reference tank 4, in K; the first initial pressure value P1 in the reference tank 4, in MPa; the second initial temperature T2 of the non-contact temperature measurement coal sample tank 5, in K; the second initial pressure P2 in the non-contact temperature measurement coal sample tank 5, in MPa; the temperature T after the adsorption equilibrium between the rare gas and the dry coal sample 38 pin , unit is K; pressure P after adsorption equilibrium between rare gas and dry coal sample 38 pin , unit is MPa. The noble gas may be He gas.

[0056] Step 12: Based on the third formula and the plurality of second data groups, a plurality of first equations are obtained, and the plurality of first equations are solved simultaneously to obtain the free space volume V0 in the non-contact temperature measurement coal sample tank 5, wherein the third formula is:

[0057]

[0058] Where V0 is the free space volume in the non-contact temperature measurement coal sample tank 5, in cm 3 ; V r is the volume of reference tank 4, in cm 3 ; Y is the volume ratio, dimensionless; Z1 is the compressibility factor of the noble gas at the first initial pressure value P1 in the reference tank 4, dimensionless; Z pin is the pressure P after the adsorption equilibrium between the rare gas and the dry coal sample 38 pin Z2 is the rare gas compression factor at the second initial pressure P2 in the contact temperature measurement coal sample tank, which is dimensionless.

[0059] The second step includes:

[0060] Step 111: Open valve three 17, valve four 19, valve five 20, valve six 22, and activate the vacuum pumping mechanism 12 to vacuum the high-pressure buffer tank 3, reference tank 4, and non-contact temperature measurement coal sample tank 5 (due to the entire installation and connection of the device, when vacuuming the high-pressure buffer tank 3, reference tank 4, and non-contact temperature measurement coal sample tank 5, open valve three 17, valve four 19, valve five 20, valve six 22, valve seven 24, valve eight 26, and valve ten 29, activate the vacuum pumping mechanism 12, and simultaneously vacuum the high-pressure buffer tank 3, reference tank 4, non-contact temperature measurement coal sample tank 5, reference tank two 8, high-pressure buffer tank two 9, and pipelines). Maintain a negative pressure of 0.9 MPa for 30 minutes, then close valve three 17, valve four 19, valve five 20, and valve six 22 (and simultaneously close valve eight 26 and valve ten 29). At this time, the pressure sensor 1 33 measures the pressure in the reference tank 1 4 , and the pressure sensor 2 34 measures the pressure in the non-contact measurement coal sample tank, both of which are P0.

[0061] Step 112: Adjust the constant temperature water bath 11 to the first experimental temperature T0, and place the reference tank 4 and the non-contact temperature measurement coal sample tank 5 in the constant temperature water bath 11. After stabilization, the reference tank 4 is brought to the first initial temperature T1 and the non-contact temperature measurement coal sample tank 5 is brought to the second initial temperature T2 through the constant temperature water bath, and T1=T2.

[0062] Step 113: Open valve 2 16 and fill high-pressure buffer tank 1 3 with rare gas through rare gas tank 2 until the pressure inside high-pressure buffer tank 3 reaches a first preset pressure. That is, when pressure gauge 13 indicates that the pressure inside high-pressure buffer tank 3 reaches the first preset pressure (> the test pressure), close valve 2 16 to stop supplying rare gas to high-pressure buffer tank 3. This provides a constant-pressure rare gas source.

[0063] Step 114: When the pressure in the inner cavity of the high-pressure buffer tank 3 is stable, first open valve five 20, then slowly open valve three 17, and slowly fill the reference tank 4 with rare gas through the high-pressure buffer tank 3. When the pressure sensor 33 measures the pressure in the reference tank 4 to the first initial pressure P1, close valve five 20 and valve three 17, stop inputting rare gas, and the pressure sensor two 34 measures the pressure in the non-contact temperature measurement coal sample tank 5 to be the second initial pressure P2.

[0064] Step 115: Slowly open valve 6 22 to connect the reference tank 1 4 and the non-contact temperature measurement coal sample tank 5. When the pressure in the reference tank 1 4 measured by pressure sensor 1 33 and the pressure in the non-contact temperature measurement coal sample tank 5 measured by pressure sensor 2 34 are stable and equal, balance for 6 to 8 hours. At this time, the noble gas and the dry coal sample 38 placed in the non-contact temperature measurement coal sample tank 5 are in adsorption equilibrium. When the pressure in the reference tank 1 4 and the non-contact temperature measurement coal sample tank 5 is equal, the pressure P after the noble gas and the dry coal sample 38 are in adsorption equilibrium is obtained. pin , the temperature T after the adsorption equilibrium between the rare gas and the dry coal sample 38 pin , there exists T pin =T1=T2.

[0065] Step 2: Set different ambient temperatures (i.e., the second experimental temperature to which the constant temperature water bath 11 is adjusted during the CH4 gas adsorption drying process). ), the pressure at which CO2 and CH4 reach the second equilibrium state through mutual diffusion and competitive adsorption Repeat the first step multiple times to obtain multiple sets of first data groups to obtain η and ΔT relationship curves, each set of first data group includes the CO2 and CH4 gas competitive adsorption replacement ratio η and the competitive adsorption equilibrium coal sample thermal effect ΔT.

[0066] The first step includes:

[0067] Step 21: Obtain the initial amount of CH4 gas in the reference tank 4 The reference tank 1 is used to fill the non-contact temperature measurement coal sample tank 5 with CH4 gas so that the CH4 gas adsorbs the dry coal sample 38 until the adsorption reaches the first equilibrium state and the first equilibrium temperature is obtained. First balance pressure The amount of CH4 gas adsorbed by dry coal sample 38

[0068] Wherein, step 21 (i.e., CH4 isothermal adsorption process) includes:

[0069] Step 211: Slowly open valve 3 17, valve 5 20, and valve 12 31 (valve 6 22 is open in the previous step) to discharge the rare gas from high-pressure buffer tank 1 3, reference tank 1 4, and non-contact temperature measurement coal sample tank 5. Close valve 12 31.

[0070] Step 212: Open valve four 19 (valve three 17, valve five 20 and valve six 22 are in the open state in the previous step, valve seven 24, valve eight 26, three-way valve two 27 and valve ten 29 are in the closed state in the previous step), open the vacuum mechanism 12, vacuum the high-pressure buffer tank 3, reference tank 4 and non-contact temperature measurement coal sample tank 5, maintain the negative pressure of 0.9 MPa, continue vacuuming for 30 minutes, and close valve three 17, valve four 19, valve five 20 and valve six 22.

[0071] Step 213: Adjust the constant temperature water bath 11 to the second experimental temperature The reference tank 14 and the non-contact temperature measurement coal sample tank 5 are placed in a constant temperature water bath 11. After stabilization, the reference tank 14 is brought to a third initial temperature by a constant temperature water bath. Make the non-contact temperature measurement coal sample tank 5 to the fourth initial temperature exist

[0072] Step 214: Open valve 15 to charge CH4 gas into high-pressure buffer tank 3 through CH4 gas tank 1 until the pressure gauge 13 shows that the pressure in high-pressure buffer tank 3 reaches the second preset pressure. Then, close valve 15 and stop feeding CH4 gas into high-pressure buffer tank 3, thereby obtaining a CH4 gas source with a constant pressure.

[0073] Step 215: When the pressure in the high-pressure buffer tank 3 is stable, first open valve 5 20, then slowly open valve 3 17, and slowly fill CH4 gas into the reference tank 4 through the high-pressure buffer tank 3. When the pressure sensor 33 measures that the reference tank 4 is at the third initial pressure, When the valve 5 20 and the valve 3 17 are closed, the input of CH4 gas is stopped, and the pressure sensor 2 34 measures the pressure in the non-contact temperature measurement coal sample tank 5 to be the fourth initial pressure value.

[0074] Step 216: Calculate the initial amount of CH4 gas in the reference tank 4 using the fourth formula The unit is mol, and the fourth formula is:

[0075]

[0076] in, V is the third initial pressure of the reference tank 4, in MPa; r is the volume of reference tank 4, in cm 3 ; The third initial pressure The CH4 gas compressibility factor is dimensionless; R is the gas constant, which is 8.314 J / (mol·K); The third initial temperature of the reference tank 4 is K.

[0077] Step 217: Slowly open the valve 22 to connect the reference tank 4 and the non-contact temperature measuring coal sample tank 5, and fill the CH4 gas into the non-contact temperature measuring coal sample tank 5 through the reference tank 4 to make the CH4 gas adsorb the dry coal sample 38, and monitor the temperature change rule of the dry coal sample 38 in the adsorption process in real time through the infrared thermal imager 6 until the first equilibrium temperature is obtained when the adsorption reaches the first equilibrium state. The first equilibrium pressure The amount of substance of the CH4 gas adsorbed by the dry coal sample 38 That is, when the pressure in the reference tank 4 measured by the pressure sensor 33 and the pressure in the non-contact temperature measuring coal sample tank 5 measured by the pressure sensor 34 are stable and equal, the equilibrium is 6h-8h, at this time, the reference tank 4 and the non-contact temperature measuring coal sample tank 5 reach equilibrium, and the first equilibrium pressure is The first equilibrium temperature is There is

[0078] Step 218: Calculate the amount of substance of CH4 gas in the reference tank 4 and the non-contact temperature measuring coal sample tank 5 by the fifth formula The unit is mol, and the fifth formula is:

[0079]

[0080] In the formula, V r is the volume of the reference tank 4, the unit is cm 3 ; V0 is the free space volume in the non-contact temperature measuring coal sample tank 5, the unit is cm 3 ; is the first equilibrium pressure The CH4 gas compression factor, dimensionless; R is the gas constant, whose value is 8.314 J / (mol·K).

[0081] Step 219: The amount of substance of the CH4 gas adsorbed by the dry coal sample 38

[0082] Prior to step 22, the reference tank 2 8 and the high-pressure buffer tank 2 9 are evacuated. Specifically, when evacuating the high-pressure buffer tank 1 3, the reference tank 1 4, and the non-contact temperature measurement coal sample tank 5, valves 3 17, 4 19, 5 20, 6 22, 7 24, 8 26, and 10 29 are opened, and the vacuuming mechanism 12 is activated. Simultaneously, the high-pressure buffer tank 1 3, the reference tank 1 4, the non-contact temperature measurement coal sample tank 5, the reference tank 2 8, and the high-pressure buffer tank 2 9 are evacuated, maintaining a negative pressure of 0.9 MPa for 30 minutes. Thereafter, valves 3 17, 4 19, 5 20, 6 22, 7 24, 8 26, and 10 29 are closed.

[0083] Step 22: After step 21, close valve 6 22 and slowly open valve 11 30 to fill high-pressure buffer tank 2 9 with CO2 via the CO2 cylinder 10. When the pressure gauge 2 14 indicates that the pressure in high-pressure buffer tank 2 9 reaches a third preset pressure (> the test pressure), close valve 11 30, effectively stopping the flow of CO2 into high-pressure buffer tank 2 9. This provides a constant-pressure CO2 gas source.

[0084] When the pressure in the high-pressure buffer tank 29 is stable, first open valve 8 26, then slowly open valve 10 29, and slowly fill CO2 gas into the reference tank 28 through the high-pressure buffer tank 29. When the pressure sensor 3 35 measures the pressure in the reference tank 28 to the first equilibrium state, the pressure of the non-contact temperature measurement coal sample tank 5 is consistent. At this time, close valve eight 26 and valve ten 29, stop inputting CO2 gas, and the pressure in the non-contact temperature measuring coal sample tank 5 measured by pressure sensor two 34 is equal to the pressure in the reference tank three measured by pressure sensor three 35, and obtain the amount of CO2 gas in the reference tank two 8 at this time. (Where, The first equilibrium pressure The CO2 gas compression factor is dimensionless), and the amount of CH4 gas in the non-contact temperature measurement coal sample tank 5 is calculated.

[0085] Step 23: Open valve seven 24, connect the non-contact temperature measurement coal sample tank 5 and the reference tank two 8, and allow the counter-diffusion and competitive adsorption of CO2 and CH4 to continue for 6h to 8h, and use the infrared thermal imager 6 to monitor the real-time temperature T of the dry coal sample 38, the pressure sensor two 34 to monitor the pressure of the non-contact temperature measurement coal sample tank 5 in real time, and the pressure sensor three 35 to monitor the pressure change of the reference tank two 8 in real time until the second equilibrium state is reached, and the second equilibrium temperature under the second equilibrium state is obtained. Second balance pressure The CO2 concentration sensor 36 obtains the CO2 concentration change law in the non-contact temperature measurement coal sample tank 5 and the CO2 concentration in the second equilibrium state. The CH4 concentration variation law in the reference tank 2 8 and the CH4 concentration in the second equilibrium state are obtained by the CH4 concentration sensor 37. Competitive adsorption equilibrium thermal effect of coal samples The second equilibrium state is a state in which the pressure of the non-contact temperature measuring coal sample tank 5 measured by the second pressure sensor 34 and the pressure of the reference tank 2 8 measured by the third pressure sensor 35 display the same value, and the gas components of the non-contact temperature measuring coal sample tank 5 and the reference tank 2 8 are stable.

[0086] Step 24: Obtain the CH4 gas partial pressure using the first formula and CO2 gas partial pressure Among them, the first formula is:

[0087]

[0088] Step 25: Obtain the amount of CH4 gas in the reference tank 2 8 and the non-contact temperature measurement coal sample tank 5 using the second formula. and the amount of CO2 gas Among them, the second formula is:

[0089]

[0090] Among them, V r is the volume of reference tank 4, in cm 3 ; V0 is the free space volume in the non-contact temperature measurement coal sample tank, unit is cm 3 ; The second equilibrium pressure The CH4 gas compressibility factor is dimensionless; R is the gas constant, which is 8.314 J / (mol·K); The second equilibrium pressure The CO2 gas compressibility factor is dimensionless.

[0091] Step 26: Calculate CH4 desorption CO2 adsorption capacity

[0092] Step 27: Calculate the competitive adsorption replacement ratio of CO2 and CH4 gases

[0093] Step 3: Collect the exhaust gas.

[0094] Slowly open valve 8 26, valve 10 29, and valve 13 32 to discharge the CO2 in high-pressure buffer tank 2 9 and reference tank 2 8. Then close valve 13 32.

[0095] The CO2-coalbed CH4 gas competitive adsorption thermal effect test device provided by the embodiment of the present invention can avoid the influence of pressure gradient on the replacement effect by setting reference tank 1 4 and reference tank 2 8. The replacement effect is not disturbed, so that the replacement effect is not affected during the CO2-coalbed CH4 gas competitive adsorption thermal effect test, which makes the measurement result accurate and can obtain the gas competitive adsorption and gas mutual counter-diffusion laws during the CO2-coalbed CH4 replacement process. By real-time monitoring the temperature change law of the dry coal sample 38 during the adsorption process of the CH4 gas adsorption dry coal sample 38, real-time monitoring of the CO2 and CH4 mutual counter-diffusion and competitive adsorption temperature of the dry coal sample 38, the pressure of the non-contact temperature measurement coal sample tank 5 and the pressure change law of the reference tank 2 8, it is possible to conduct an in-depth analysis of the driving mechanism and action efficiency of the CO2-coalbed CH4 replacement from the perspective of energy migration, and provide theoretical support for the reasonable optimization of key control parameters and the realization of efficiency maximization.

[0096] Furthermore, the CO2-coalbed CH4 competitive adsorption heat effect test apparatus also includes valve 9 28 and an exhaust gas collection bag. The exhaust gas collection bag is connected to tee 2 27 via a ninth pipe, and valve 9 28 is installed on the ninth pipe. After the experiment, valve 9 28 is opened to collect exhaust gas from high-pressure buffer tank 1 3, valve 3 17, tee 1 18, valve 5 20, four-way 1 21, reference tank 1 4, valve 6 22, four-way 2 23, non-contact temperature measurement coal sample tank 5, valve 7 24, reference tank 2 8, four-way 2 23, tee 2 27, valve 10 29, and high-pressure buffer tank 2 9 through the exhaust gas collection bag.

[0097] The first to ninth pipelines are φ3mm steel pipes with a maximum pressure bearing capacity of 20MPa.

[0098] Reference tank 1 4 and reference tank 2 8, valve 5 20 and valve 8 26, four-way 1 21 and four-way 3 25 are symmetrically distributed with the central axis of the non-contact temperature measurement coal sample tank 5 as the symmetry axis to ensure that the free volume of the pipelines on both sides is consistent.

[0099] The method and device for testing the thermal effect of competitive adsorption of CH4 gas in coal seams replaced by CO2, provided in the embodiments of the present invention, avoid the influence of pressure gradient on the replacement effect and only consider the mutually inverse diffusion processes of CO2 "diffusion-adsorption" and CH4 "desorption-diffusion". This helps to further explore the replacement effect of CO2 on CH4 in coal seams and clarify the storage capacity of CO2 and the desorption capacity of CH4. This is of great significance to the storage of CO2 and coalbed methane development in deep coal seams. In addition, the device adds a dry coal sample 38 temperature measurement system (infrared light high permeability single crystal 53 and infrared thermal imager 6), which can monitor the temperature change pattern of coal samples during the single-component gas adsorption / desorption and competitive adsorption of CO2 and CH4 in real time, facilitating the analysis of the thermal effect characteristics of coal bodies during the replacement of CH4 in coal seams by CO2, and helping to further explore the energy migration pattern and driving mechanism during the replacement of CH4 in coal seams by CO2.

[0100] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other. Each embodiment focuses on the differences from other embodiments.

[0101] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some or all of the technical features therein can be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. A device for testing the thermal effect of competitive adsorption of CH4 gas on CO2 coalbed, characterized in that: include: CH4 gas tank, rare gas tank, high-pressure buffer tank 1, reference tank 1, non-contact temperature measurement coal sample tank, infrared thermal imager, data acquisition and storage mechanism, reference tank 2, high-pressure buffer tank 2, CO2 gas tank, constant temperature water bath, vacuum pumping mechanism, pressure gauge 1, pressure gauge 2, valve 1, valve 2, valve 3, tee 1, valve 4, valve 5, four-way 1, valve 6, four-way 2, valve 7, four-way 3, valve 8, three-way 2, valve 9, valve 10, valve 11, valve 12, pressure sensor 1, pressure sensor 2, pressure sensor 3, CO2 concentration sensor and CH4 concentration sensor; Connecting the CH4 gas tank to the high-pressure buffer tank 1 through a first pipeline, and installing the valve 1 on the first pipeline; Connecting the rare gas tank to the first high-pressure buffer tank via a second pipeline, and providing the second valve on the second pipeline; The high-pressure buffer tank 1 is connected to the four-way valve 1 through a third pipeline, and the valve 3, the three-way valve 1, and the valve 5 are sequentially arranged on the third pipeline in the direction from the high-pressure buffer tank 1 to the four-way valve 1; The pressure gauge 1 is provided on the high-pressure buffer tank 1; Connecting the three-way valve 1 and the vacuum pumping mechanism through a fourth pipeline, and installing the valve 4 on the fourth pipeline; Connect the four-way valve 1 and the four-way valve 2 through a fifth pipeline, and install the valve 6 on the fifth pipeline; The reference tank 1 and the pressure sensor 1 are respectively connected to the four-way 1; The non-contact temperature measuring coal sample tank and the second pressure sensor are respectively connected to the second four-way port; The four-way valve 3 and the high-pressure buffer tank 2 are connected through a sixth pipeline, and the valve 8, the three-way valve 2 and the valve 10 are sequentially arranged on the sixth pipeline in the direction from the four-way valve 3 to the high-pressure buffer tank 2; The second pressure gauge is provided on the second high-pressure buffer tank; Connecting the CO2 gas tank and the second high-pressure buffer tank via a seventh pipeline, and installing the eleventh valve on the seventh pipeline; Connect the four-way valve 2 and the four-way valve 3 through an eighth pipeline, and install the valve 7 on the eighth pipeline; The valve 12 is provided on the output pipe at the bottom of the high-pressure buffer tank 1; The non-contact temperature measurement coal sample tank comprises a tank body, a tank cover and an infrared light high permeability single crystal; The tank cover is arranged at the opening of the tank body to close the tank body, a mounting hole is arranged in the middle of the tank cover, and the infrared light high permeability single crystal is arranged in the mounting hole; The infrared thermal imager is arranged above the infrared light high permeability single crystal; The reference tank 2 and the pressure sensor 3 are both connected to the four-way 3; The CO2 concentration sensor is set on the non-contact temperature measurement coal sample tank, and the CH4 concentration sensor is set on the reference tank 2; The pressure sensor 1, the pressure sensor 2, the pressure sensor 3, the CO2 concentration sensor, the CH4 concentration sensor, and the infrared thermal imager are all electrically connected to the data acquisition and storage mechanism; The first reference tank, the non-contact temperature measurement coal sample tank and the second reference tank are arranged in the constant temperature water bath.

2. The CO2 coalbed CH4 gas competitive adsorption thermal effect testing device according to claim 1 is characterized in that: Also included are valve nine and exhaust collection bags; The tail gas collection bag and the two tee joints are connected via a ninth pipeline, and the ninth valve is provided on the ninth pipeline.

3. The CO2 coalbed CH4 gas competitive adsorption thermal effect testing device according to claim 1 is characterized in that: The reference tank 1 and the reference tank 2, the valve 5 and the valve 8, the four-way 1 and the four-way 3 are symmetrically distributed with the central axis of the non-contact temperature measurement coal sample tank as the symmetry axis.

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