An experimental device and application method for accurately obtaining gas desorption law in coal

Abstract

The application discloses an experimental device for accurately obtaining gas desorption rules in coal and an application method. The experimental device for accurately obtaining gas desorption rules in coal comprises a gas injection system, a vacuum degassing system, an isothermal adsorption system and a gas desorption amount testing system. Through high-efficiency cooperation of the gas injection system, the vacuum degassing system, the isothermal adsorption system and the gas desorption amount testing system, the problem of inaccurate desorption amount caused by human judgment error is effectively solved, and an accurate value of the gas desorption amount in coal can be obtained, which has important significance for studying the gas desorption rules in coal.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of coal mine gas exploitation and utilization, and particularly relates to an experimental device for accurately obtaining gas desorption law in coal and an application method. BACKGROUND

[0002] Coal is a porous medium, which contains abundant pore and fissure volume and huge specific surface area, and thus can store a large amount of gas. The gas in coal mainly has two occurrence forms: adsorbed state and free state. According to research, 80-90% of the gas in coal is in adsorbed state. In the original coal seam, the gas is in a dynamic adsorption equilibrium state. When the coal seam is affected by mining, the integrity of the coal seam is destroyed, the dynamic adsorption equilibrium state of the gas in the coal is broken, and the desorption of the gas in the coal is caused. This not only causes coal and gas outburst accidents, but also causes the gas concentration in the roadway to increase due to the slow accumulation of the desorbed gas in the roadway, which may cause gas explosion accidents. The desorption process of the gas in the coal needs a certain time, and thus the gas desorption amount is a function of time for the coal-gas system. A large number of studies have shown that the coal and gas outburst accident is accompanied by a rapid desorption process of the gas in the coal, and the desorption law of the gas directly relates to the gas production and the difficulty of exploitation in the process of coalbed methane development. Therefore, accurately obtaining the desorption law of the gas in the coal has important practical significance for mine gas disaster prevention and efficient utilization of gas resources.

[0003] At present, the volume method is mainly used to obtain the desorption law of the gas in the coal in the laboratory. Specifically, first, the coal sample tank is brought to an isothermal adsorption equilibrium state, then the exhaust valve is quickly opened to release the free state gas to the atmosphere to depressurize, when the pressure in the coal sample tank is reduced to 0 MPa, the exhaust valve is quickly connected with the measuring cylinder, and the desorption amount of the gas in the coal is tested by the drainage method. However, in this process, whether the coal sample tank is completely depressurized is mainly determined by human judgment, and the timing and speed of connecting the exhaust valve with the measuring cylinder directly determine whether the free state gas in the coal sample tank is completely discharged and whether the adsorbed state gas is also discharged. Therefore, the obtained desorption amount of the gas in the coal has a large gap with the true value, and the desorption law of the gas in the coal cannot be accurately reflected. SUMMARY

[0004] The purpose of the present application is to provide an experimental device for accurately obtaining the desorption law of the gas in the coal and an application method, so as to solve the problems existing in the prior art.

[0005] In order to achieve the above purpose, the present application provides an experimental device for accurately obtaining the desorption law of the gas in the coal, which comprises:

[0006] The gas injection system comprises a high-pressure gas cylinder (1), a buffer tank (2), a pressure gauge (3), a valve (4), a valve (5) and corresponding pipelines; the high-pressure gas cylinder (1) is used for injecting high-pressure gas into the coal sample tank (9); the buffer tank (2) is used for adjusting the pressure of the high-pressure gas when the gas is injected into the coal sample tank (9); and the pressure gauge (3) is used for monitoring the pressure of the gas in the buffer tank (2);

[0007] The vacuum degassing system comprises a vacuum pump (6), a vacuum gauge (7), a three-way valve (8) and corresponding pipelines; the vacuum pump (6) is used for removing impurity gas from the coal sample tank (9) and the coal sample; and the vacuum gauge (7) is used for monitoring the vacuum degree in the coal sample tank (9) and the corresponding pipelines during the vacuum degassing process;

[0008] The isothermal adsorption system comprises a coal sample tank (9), a pressure gauge (10), a constant-temperature water bath (11), a valve (12), a valve (13) and corresponding pipelines; the coal sample tank (9) is used for containing the coal sample and completing the isothermal adsorption and desorption of the gas in the coal sample; the pressure gauge (10) is used for monitoring the gas pressure in the coal sample tank (9); and the constant-temperature water bath (11) is used for keeping the temperature in the coal sample tank (9) constant;

[0009] The gas desorption amount testing system comprises a measuring cylinder (14), a gas sample bag (15), a three-way valve (16) and corresponding pipelines; the measuring cylinder (14) is used for testing the change rule of the gas desorption amount in the coal sample with time; and the gas sample bag (15) is used for collecting the gas emitted from the coal sample tank (9) when the pressure is released.

[0010] Optionally, the application further provides an application method of the experimental device for accurately obtaining the gas desorption rule in the coal sample.

[0011] a. drying the coal sample, testing the true density thereof, and weighing a preset mass of the dried coal sample and loading the coal sample into the coal sample tank (9);

[0012] b. adjusting the temperature of the constant-temperature water bath (11) to 60℃, closing the valve (13), opening the valve (12), adjusting the three-way valve (8) so that the vacuum pump (6) is communicated with the coal sample tank (9), starting the vacuum pump (6), and vacuum-degassing the coal sample tank (9) and the coal sample therein for 24 hours so as to remove the impurity gas in the coal sample tank and the coal sample; after the vacuum degassing is completed, first, the valve (12) is closed, and then the vacuum pump (6) is closed;

[0013] c. adjusting the temperature of the constant-temperature water bath (11) to 30℃, closing the valve (5), opening the cock of the high-pressure gas cylinder (1) and the valve (4), injecting high-pressure gas into the buffer tank (2), making the reading of the pressure gauge (3) reach a preset pressure value, and then successively closing the valve (4) and the cock of the high-pressure gas cylinder (1).

[0014] d. Adjust the three-way valve (8) to make the buffer tank (2) communicate with the coal sample tank (9), open the valve (5) and the valve (12), inject high-pressure gas into the coal sample tank (9), and make the reading of the pressure gauge (10) reach the pre-set isothermal adsorption equilibrium pressure value, and then close the valve (12) and the valve (5) in turn;

[0015] e. Repeat step d until the reading of the pressure gauge (10) remains at the pre-set isothermal adsorption equilibrium pressure value for 8h;

[0016] f. Fill the graduated cylinder (14) with saturated brine, adjust the three-way valve (16) to make the coal sample tank (9) communicate with the gas sample bag (15), open the valve (13), collect all the gas discharged from the coal sample tank (9) in the gas sample bag (15), quickly adjust the three-way valve (16) to make the coal sample tank (9) communicate with the graduated cylinder (14) when the reading of the pressure gauge (10) drops to 0MPa, and record the change rule of the saturated brine discharge amount in the graduated cylinder (14) with time, and the saturated brine discharge amount in the graduated cylinder (14) is the gas desorption amount of the coal sample in the coal sample tank (9).

[0017] Optionally, the coal gas desorption amount calculation and checking steps of the present application comprise:

[0018] a. Calculate the volume of the coal sample in the coal sample tank (9) by using the mass and the true density of the coal sample, and the relationship formula is as follows:

[0019]

[0020] Wherein, V1 represents the volume of the coal sample in the coal sample tank (9), mL; m represents the mass of the coal sample in the coal sample tank (9), g; and p represents the true density of the coal sample, g / mL;

[0021] b. After the coal sample in the coal sample tank (9) reaches the isothermal adsorption equilibrium state, calculate the volume of the free gas in the coal sample tank (9) under standard conditions, and the relationship formula is as follows:

[0022]

[0023] Wherein, V2 represents the volume of the free gas in the coal sample tank (9) after the coal sample reaches the isothermal adsorption equilibrium state; P1 represents the indoor atmospheric pressure when the coal sample reaches the isothermal adsorption equilibrium state; P0 represents the atmospheric pressure under standard conditions; T0 represents the gas temperature under standard conditions; T1 represents the indoor temperature when the coal sample reaches the isothermal adsorption equilibrium state; and V3 represents the internal space volume of the coal sample tank (9);

[0024] c.After the end of the desorption experiment, the volume of the collected gas in the gas sample bag (15) is calculated and checked to obtain the accurate value of the desorption amount of the gas in the coal at different times t, and the relationship is shown in the following formula:

[0025]

[0026] Q = V4 * (P2 / P3) * (T3 / T2) - V5 t Q represents the desorption amount of the gas in the coal at different times t under standard conditions, mL / g; T2 represents the indoor temperature during the desorption experiment, K; P2 represents the indoor atmospheric pressure during the desorption experiment, MPa; V4 represents the saturated brine discharge amount at different times t read by the measuring cylinder (14), mL; T3 represents the indoor temperature when the volume of the gas in the gas sample bag (15) is tested, K; P3 represents the indoor atmospheric pressure when the volume of the gas in the gas sample bag (15) is tested, MPa; V5 represents the volume of the collected gas in the gas sample bag (15), mL.

[0027] The beneficial effects of the present application are:

[0028] The present application effectively solves the problem that whether the pressure relief is complete and whether the free state gas in the coal sample tank is discharged and the adsorbed state gas is also discharged in the coal gas desorption experiment process through the efficient cooperation of the gas injection system, the vacuum degassing system, the isothermal adsorption system and the gas desorption amount testing system, avoids the problem of inaccurate desorption amount caused by human error, and can obtain the accurate value of the coal gas desorption amount, which has important significance for studying the coal gas desorption rule. BRIEF DESCRIPTION OF DRAWINGS

[0029] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. The embodiments illustrated in the drawings, and their description, are presented to explain the present application and are not intended to limit the present application. In the drawings:

[0030] Figure 1 is a schematic diagram of the experimental device for accurately obtaining the coal gas desorption rule according to the present application;

[0031] Figure 2 is a whole flow chart of the experimental device and application method for accurately obtaining the coal gas desorption rule according to the present application.

[0032] In the figure: 1-high pressure gas cylinder; 2-buffer tank; 3, 10-pressure gauge; 4, 5, 12, 13-valve; 6-vacuum pump; 7-vacuum gauge; 8, 16-three-way valve; 9-coal sample tank; 11-constant temperature water bath; 14-measuring cylinder; 15-gas sample bag. DETAILED DESCRIPTION

[0033] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other in the case of no conflict. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0034] As shown in Figure 1 The present application provides an experimental device for accurately obtaining the desorption rule of gas in coal, comprising:

[0035] The gas injection system comprises a high-pressure gas cylinder (1), a buffer tank (2), a pressure gauge (3), a valve (4), a valve (5) and corresponding pipelines; the high-pressure gas cylinder (1) is used for injecting high-pressure gas into the coal sample tank (9); the buffer tank (2) is used for adjusting the pressure of the high-pressure gas when injecting gas into the coal sample tank (9); the pressure gauge (3) is used for monitoring the pressure of the gas in the buffer tank (2);

[0036] The vacuum degassing system comprises a vacuum pump (6), a vacuum gauge (7), a three-way valve (8) and corresponding pipelines; the vacuum pump (6) is used for removing impurity gas in the coal sample tank (9) and the coal sample; the vacuum gauge (7) is used for monitoring the vacuum degree in the coal sample tank (9) and the corresponding pipeline during the vacuum degassing process;

[0037] The isothermal adsorption system comprises a coal sample tank (9), a pressure gauge (10), a constant temperature water bath (11), a valve (12), a valve (13) and corresponding pipelines; the coal sample tank (9) is used for containing coal samples and completing the isothermal adsorption and desorption of gas in coal; the pressure gauge (10) is used for monitoring the gas pressure in the coal sample tank (9); the constant temperature water bath (11) is used for keeping the temperature in the coal sample tank (9) constant;

[0038] The gas desorption amount testing system comprises a measuring cylinder (14), a gas sample bag (15), a three-way valve (16) and corresponding pipelines; the measuring cylinder (14) is used for testing the change rule of the desorption amount of gas in coal with time; the gas sample bag (15) is used for collecting the gas ejected when the pressure of the coal sample tank (9) is released.

[0039] As shown in Figure 2 The present application provides an application method of the experimental device for accurately obtaining the desorption rule of gas in coal, comprising the following steps:

[0040] a. Dry the coal sample, test its true density, and weigh the dry coal sample of a predetermined mass and put it into the coal sample tank (9);

[0041] b. Adjust the temperature of the constant temperature water bath (11) to 60 DEG C, close the valve (13), open the valve (12), adjust the three-way valve (8), make the vacuum pump (6) and the coal sample tank (9) communicate; start the vacuum pump (6), and the coal sample tank (9) and the coal sample in it are vacuum degassed for 24h, to remove the impurity gas in the coal sample tank and the coal sample; after the vacuum degassing is finished, first close the valve (12), and then close the vacuum pump (6);

[0042] c. Adjust the temperature of the constant temperature water bath (11) to 30 DEG C, close the valve (5), open the plug and valve (4) of the high-pressure gas cylinder (1), inject high-pressure gas into the buffer tank (2), make the reading of the pressure gauge (3) reach the pre-set pressure value, and then close the valve (4) and the plug of the high-pressure gas cylinder (1) in turn;

[0043] d. Adjust the three-way valve (8), make the buffer tank (2) and the coal sample tank (9) communicate, open the valve (5) and the valve (12), inject high-pressure gas into the coal sample tank (9), make the reading of the pressure gauge (10) reach the pre-set isothermal adsorption equilibrium pressure value, and then close the valve (12) and the valve (5) in turn;

[0044] e. Repeat step d until the reading of the pressure gauge (10) remains at the pre-set isothermal adsorption equilibrium pressure value for 8h;

[0045] f. Fill the graduated cylinder (14) with saturated brine, adjust the three-way valve (16), make the coal sample tank (9) and the gas sample bag (15) communicate, open the valve (13), collect all the gas when the coal sample tank (9) is depressurized in the gas sample bag (15), quickly adjust the three-way valve (16) when the reading of the pressure gauge (10) drops to 0MPa, make the coal sample tank (9) and the graduated cylinder (14) communicate, and record the change rule of the saturated brine discharge amount in the graduated cylinder (14) with time, and the saturated brine discharge amount in the graduated cylinder (14) is the gas desorption amount of the coal sample in the coal sample tank (9).

[0046] The coal gas desorption amount calculation and checking steps of the application comprise:

[0047] a. The volume of the coal sample in the coal sample tank (9) is calculated by using the mass and true density of the coal sample, and the relationship formula is as follows:

[0048]

[0049] Wherein, V1 represents the volume of the coal sample in the coal sample tank (9), mL; m represents the mass of the coal sample in the coal sample tank (9), g; and ρ represents the true density of the coal sample, g / mL;

[0050] b.After the coal sample in the coal sample tank (9) reaches the isothermal adsorption equilibrium state, the volume of the free state gas in the coal sample tank (9) under the standard condition is calculated, and the relationship is shown as follows:

[0051]

[0052] wherein V2 represents the volume of the free state gas in the coal sample tank (9) after the coal sample reaches the isothermal adsorption equilibrium state; P1 represents the indoor atmospheric pressure when the coal sample reaches the isothermal adsorption equilibrium state; P0 represents the atmospheric pressure under the standard condition; T0 represents the gas temperature under the standard condition; T1 represents the indoor temperature when the coal sample reaches the isothermal adsorption equilibrium state; and V3 represents the internal space volume of the coal sample tank (9);

[0053] c.After the desorption experiment is completed, the accurate value of the gas desorption amount in the coal under the condition of different time t is calculated and verified in combination with the volume of the collected gas in the gas sample bag (15), and the relationship is shown as follows:

[0054]

[0055] wherein Q t represents the gas desorption amount in the coal under the standard condition of different time t, mL / g; T2 represents the indoor temperature during the desorption experiment, K; P2 represents the indoor atmospheric pressure during the desorption experiment, MPa; V4 represents the saturated brine discharge amount at different time t read by the measuring cylinder (14), mL; T3 represents the indoor temperature when the volume of the gas in the gas sample bag (15) is tested, K; P3 represents the indoor atmospheric pressure when the volume of the gas in the gas sample bag (15) is tested, MPa; and V5 represents the volume of the collected gas in the gas sample bag (15), mL.

[0056] The above merely describes the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An application method of an experimental device for accurately obtaining gas desorption law in coal, characterized in that: The experiment device for accurately obtaining the coal gas desorption rule comprises: An injection system, comprising a high-pressure gas cylinder (1), a buffer tank (2), a pressure gauge (3), a valve (4), a valve (5) and corresponding pipelines; the high-pressure gas cylinder (1) is used for injecting high-pressure gas into the coal sample tank (9); the buffer tank (2) is used for adjusting the high-pressure gas pressure when injecting gas into the coal sample tank (9); the pressure gauge (3) is used for monitoring the gas pressure in the buffer tank (2); A vacuum degassing system, comprising a vacuum pump (6), a vacuum gauge (7), a three-way valve (8) and corresponding pipelines; the vacuum pump (6) is used for removing impurity gas in the coal sample tank (9) and the coal sample; the vacuum gauge (7) is used for monitoring the vacuum degree in the coal sample tank (9) and the corresponding pipeline during the vacuum degassing process; An isothermal adsorption system, comprising a coal sample tank (9), a pressure gauge (10), a constant-temperature water bath (11), a valve (12), a valve (13) and corresponding pipelines; the coal sample tank (9) is used for containing the coal sample and completing the isothermal adsorption and desorption of coal gas; the pressure gauge (10) is used for monitoring the gas pressure in the coal sample tank (9); the constant-temperature water bath (11) is used for keeping the temperature in the coal sample tank (9) constant; a gas desorption amount testing system, comprising a measuring cylinder (14), a gas sample bag (15), a three-way valve (16) and corresponding pipelines; the measuring cylinder (14) is used for testing the variation rule of the coal gas desorption amount with time; the gas sample bag (15) is used for collecting the gas ejected when the pressure of the coal sample tank (9) is released; The method comprises the following steps: a. drying the coal sample, testing its true density, and weighing a predetermined mass of dry coal sample and loading it into the coal sample tank (9); b. adjusting the temperature of the constant-temperature water bath (11) to 60 DEG C, closing the valve (13), opening the valve (12), adjusting the three-way valve (8) to make the vacuum pump (6) communicate with the coal sample tank (9), starting the vacuum pump (6), and vacuum degassing the coal sample tank (9) and the coal sample therein for 24 hours to remove impurity gas in the coal sample tank and the coal sample; after the vacuum degassing is completed, first, the valve (12) is closed, and then the vacuum pump (6) is closed; c. adjusting the temperature of the constant-temperature water bath (11) to 30 DEG C, closing the valve (5), opening the tap of the high-pressure gas cylinder (1) and the valve (4), injecting high-pressure gas into the buffer tank (2), making the reading of the pressure gauge (3) reach a pre-set pressure value, and then successively closing the valve (4) and the tap of the high-pressure gas cylinder (1); d. adjusting the three-way valve (8) to make the buffer tank (2) communicate with the coal sample tank (9), opening the valve (5) and the valve (12), injecting high-pressure gas into the coal sample tank (9), making the reading of the pressure gauge (10) reach a pre-set isothermal adsorption equilibrium pressure value, and then successively closing the valve (12) and the valve (5); e. repeating step d until the reading of the pressure gauge (10) always remains at the pre-set isothermal adsorption equilibrium pressure value in 8 hours. f. Fill the graduated cylinder (14) with saturated brine, adjust the three-way valve (16) to make the coal sample tank (9) communicate with the gas sample bag (15), open the valve (13), and collect all the gas in the coal sample tank (9) when it is depressurized in the gas sample bag (15), and quickly adjust the three-way valve (16) to make the coal sample tank (9) communicate with the graduated cylinder (14) when the pressure gauge (10) reading drops to 0 MPa, and record the change rule of the saturated brine discharge in the graduated cylinder (14) with time; after the desorption experiment is completed, use the graduated cylinder (14) filled with saturated brine again to test the volume of the gas collected in the gas sample bag (15).

2. The application method of the experimental device for accurately obtaining the gas desorption law of coal according to claim 1, characterized in that: The calculation and checking steps of the gas desorption amount in coal include: a. Calculate the volume of the coal sample in the coal sample tank (9) using the mass and true density of the coal sample, and the relationship is as follows: Wherein, V1 represents the volume of the coal sample in the coal sample tank (9); m represents the mass of the coal sample in the coal sample tank (9); and p represents the true density of the coal sample; b. After the coal sample in the coal sample tank (9) reaches the isothermal adsorption equilibrium state, calculate the volume of the free gas in the coal sample tank (9) under standard conditions, and the relationship is as follows: Wherein, V2 represents the volume of the free gas in the coal sample tank (9) after the coal sample reaches the isothermal adsorption equilibrium state; P1 represents the indoor atmospheric pressure when the coal sample reaches the isothermal adsorption equilibrium state; P0 represents the atmospheric pressure under standard conditions; T0 represents the gas temperature under standard conditions; T1 represents the indoor temperature when the coal sample reaches the isothermal adsorption equilibrium state; and V3 represents the internal space volume of the coal sample tank (9); c. After the desorption experiment is completed, combine the volume of the gas collected in the gas sample bag (15) to calculate and check the accurate value of the gas desorption amount in coal at different times t, and the relationship is as follows: wherein Q t represents the amount of gas desorbed from the coal at different times t under standard conditions; T2 represents the indoor temperature at the time of the desorption experiment; P2 represents the indoor atmospheric pressure at the time of the desorption experiment; V4 represents the saturated brine discharge amount at different times t as read by the graduated cylinder (14); T3 represents the indoor temperature at the time of the gas sample bag (15) volume measurement; P3 represents the indoor atmospheric pressure at the time of the gas sample bag (15) volume measurement; and V5 represents the volume of the gas collected in the gas sample bag (15).

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