Coal isobaric controllable quantitative water injection gas desorption system and method under adsorption state

Abstract

The present application relates to the technical field of gas prevention and control, and provides a gas desorption system and method for isobaric controllable quantitative water injection of coal under adsorption state. In the system, the gas supply unit, the degassing unit and the desorption unit are respectively connected to the adsorption unit pipeline, the gas supply unit is used to provide gas to the adsorption unit, the degassing unit is used to evacuate the adsorption unit, and provide a vacuum environment for the coal sample to adsorb gas, and the desorption unit is used to monitor the gas desorption amount of the coal sample in the adsorption unit in real time; the reference tank is connected to the gas supply unit pipeline, the coal sample tank is connected to the reference tank pipeline, and a pressure switch valve is provided on the connecting pipeline between the reference tank and the coal sample tank; the isobaric water injection device is detachably installed in the coal sample tank, and is used to uniformly inject water in equal amounts into the coal sample after the adsorption gas reaches equilibrium, and the coal sample placement device is located in the coal sample tank and below the isobaric water injection device, and is used to place the coal sample; a constant temperature environment is provided on the outside of the coal sample tank through a constant temperature unit.

Description

Technical Field

[0001] The present application relates to the technical field of gas prevention and control, and in particular to a coal isobaric controllable quantitative water injection gas desorption system and method under adsorption state. Background Art

[0002] Coal and gas outburst is one of the main types of disasters that currently restrict safe and efficient deep coal mining. In order to eliminate the danger of coal and gas outburst during deep coal mining, detailed rules for the prevention and control of coal and gas outburst have been formulated, and regional comprehensive outburst prevention measures and local comprehensive outburst prevention measures have been clarified. At the same time, methods and measures for early intervention in high gas pressure and high ground stress in coal seams have been proposed, including gas extraction, hydraulic measures, and mining of protective layers, all of which have achieved good results in preventing coal and gas outbursts.

[0003] Among these coal mine outburst prevention measures, hydraulic measures are most frequently used in coal mines due to their advantages of good outburst prevention effect, high efficiency, strong reliability and low cost. They mainly include: hydraulic cutting, hydraulic hole expansion, hydraulic fracturing, hydraulic extrusion, hydraulic punching, etc. As one of the effective measures to reduce coal and gas outburst, it is of great significance to accurately determine the inhibitory effect of coal seam water injection on coal seam gas desorption. Summary of the invention

[0004] The purpose of the present application is to provide a coal isobaric controllable quantitative water injection gas desorption system and method under adsorption state to solve or alleviate the problems existing in the above-mentioned prior art.

[0005] In order to achieve the above objectives, this application provides the following technical solutions:

[0006] The present application provides a coal isobaric controllable quantitative water injection gas desorption system under adsorption state, comprising: a gas supply unit, a degassing unit, a constant temperature unit, an adsorption unit and a desorption unit, wherein the gas supply unit, the degassing unit and the desorption unit are respectively connected to the adsorption unit pipeline; wherein the gas supply unit is used to provide gas to the adsorption unit; the degassing unit is used to evacuate the adsorption unit to provide a vacuum environment for the coal sample to adsorb the gas; the desorption unit is used to monitor the gas desorption amount of the coal sample in the adsorption unit in real time;

[0007] The adsorption unit includes: a reference tank, a coal sample tank, an isobaric water injection device and a coal sample placement device; the reference tank is connected to the gas supply unit pipeline, the coal sample tank is connected to the reference tank pipeline, and a pressure switch valve is provided on the connecting pipeline between the reference tank and the coal sample tank; the isobaric water injection device can be detachably installed in the coal sample tank, and is used to uniformly inject equal amounts of water into the coal sample after the gas is adsorbed to a balance; the coal sample placement device is located in the coal sample tank and below the isobaric water injection device, and is used to place the coal sample; the constant temperature unit is used to provide a constant temperature environment for the coal sample tank of the adsorption unit.

[0008] Preferably, the coal sample placement device includes: a coal sample fixing net and a first standard sampling sieve, the coal sample fixing net is arranged in the first standard sampling sieve, and is used to fix the coal sample; a second standard sampling sieve is stacked above the first standard sampling sieve, and a sampling sieve chassis is stacked below; wherein, the lower part of the isobaric water injection device is located in the second standard sampling sieve, and is opposite to the coal sample fixing net.

[0009] Preferably, the isobaric water injection device comprises: a water injection tank body, a transition water storage instrument and a uniform water injection instrument, the water injection tank body is a shell structure with a closed lower end, and the shell structure is detachably connected to the inner wall of the coal sample tank through a support column, and the outer wall of the shell structure is provided with a water outlet;

[0010] The upper end of the transition water storage device is connected to the bottom surface of the shell structure, and a water storage area and a transition water outlet are provided on the transition water storage device. A water inlet is provided on the side wall corresponding to the water storage area, and the water inlet is connected to the water outlet through a water inlet pipe; the transition water outlet is far away from the water inlet and is located on the bottom plate of the transition water storage device;

[0011] The upper end of the uniform water injection instrument is connected to the bottom surface of the transition water storage instrument and is communicated with the transition water outlet. The lower end of the uniform water injection instrument is evenly distributed with a plurality of uniform water injection dispersion holes.

[0012] Preferably, a first gas pressure equalizing hole is provided on the water injection tank body, and a second gas pressure equalizing hole is provided on the side wall of the uniform water injection instrument.

[0013] Preferably, the constant temperature unit comprises: a flame retardant electric heating tape, and the flame retardant electric heating tape is evenly wound around the outer surface of the coal sample tank.

[0014] Preferably, the desorption unit includes: a water drainage gas collecting desorption instrument, a pressure differential transmitter and a gas desorption data acquisition instrument; the water drainage gas collecting desorption instrument is connected to the coal sample tank pipeline, and is used to measure the gas desorption amount in the coal sample tank through the water column height; the pressure differential transmitter is connected to the water drainage gas collecting desorption instrument pipeline, and is used to record in real time the water column height in the water drainage gas collecting desorption instrument during the gas desorption process; the gas desorption data acquisition instrument is connected to the pressure differential transmitter via a USB data cable.

[0015] Preferably, the degassing unit comprises: a vacuum pump, the vacuum pump is connected to the coal sample tank pipeline, and a vacuum gauge is arranged on the connecting pipeline.

[0016] Preferably, a first pressure gauge is provided on the reference tank, a second pressure gauge is provided on the coal sample tank, and the second pressure gauge is connected to the gas adsorption data acquisition instrument via a USB data cable.

[0017] The embodiment of the present application also provides a method for desorbing coal gas by isobaric controllable quantitative water injection under adsorption state, wherein any of the above-mentioned coal isobaric controllable quantitative water injection gas desorption systems under adsorption state is used to measure the coal sample, and the desorption method comprises: step S101, weighing a certain mass of water and storing it in the isobaric water injection device of the adsorption unit; at the same time, placing the coal sample to be tested in the coal sample placing device, and weighing the weight m1 of the coal sample and the coal sample placing device;

[0018] Step S102, placing the isobaric water injection device and the coal sample placement device in the coal sample tank of the adsorption unit, and stacking the isobaric water injection device on top of the coal sample placement device, and sealing the coal sample tank;

[0019] Step S103, performing constant temperature control on the coal sample tank through a constant temperature unit, opening a degassing unit to evacuate the adsorption unit to a preset vacuum degree, and closing the degassing unit;

[0020] Step S104, open the gas supply unit, and inflate the reference tank of the adsorption unit until the gas pressure in the reference tank reaches a first predetermined pressure value, and then close the gas supply unit; open the pressure switch valve provided on the connecting pipe between the reference tank and the coal sample tank, and fill the coal sample tank with gas from the reference tank until the pressure in the coal sample tank reaches a second predetermined pressure value, and then close the pressure switch valve; and leave the coal sample tank to stand for 12 hours under a constant temperature environment;

[0021] Step S105, after the gas adsorption in the coal sample tank is balanced, the coal sample tank is tilted for a preset time and then laid flat, so as to uniformly inject a set amount of water in the isobaric water injection device into the gas-containing coal sample; if the water injection amount needs to be increased, the coal sample tank is repeatedly tilted to repeatedly inject the set amount of water;

[0022] Step S106: After the water injection of the gas-containing coal sample is completed, the desorption unit is turned on to collect gas desorption data in real time;

[0023] Step S107, after the gas desorption is completed, open the coal sample tank, take out the isobaric water injection device, weigh the weight m2 of the coal sample after the water injection and the coal sample placement device; and determine the water content of the coal sample under different water injection amounts and different pressure conditions based on the weight m1 and the weight m2.

[0024] Beneficial effects:

[0025] In the coal isobaric controllable quantitative water injection gas desorption system under adsorption state provided in the embodiment of the present application, the gas supply unit, the degassing unit and the desorption unit are respectively connected to the adsorption unit pipeline, the gas supply unit is used to provide gas to the adsorption unit, the degassing unit is used to evacuate the adsorption unit to provide a vacuum environment for the coal sample to adsorb the gas, and the desorption unit is used to monitor the gas desorption amount of the coal sample in the adsorption unit in real time.

[0026] The adsorption unit includes a reference tank, a coal sample tank, an isobaric water injection device and a coal sample placement device, wherein the reference tank is connected to the gas supply unit pipeline, the coal sample tank is connected to the reference tank pipeline, and a pressure switch valve is provided on the connecting pipeline between the reference tank and the coal sample tank; the isobaric water injection device can be detachably installed in the coal sample tank, and is used to inject equal amounts of water evenly into the coal sample after the adsorbed gas reaches equilibrium; the coal sample placement device is located in the coal sample tank and below the isobaric water injection device, and is used to place the coal sample; a constant temperature environment is provided on the outside of the coal sample tank through a constant temperature unit.

[0027] Therefore, the isobaric water injection device can be detachably installed in the coal sample tank. During the isobaric water injection process after the coal sample gas adsorption reaches a equilibrium state, the water in the isobaric water injection device only changes its relative position in the coal sample tank. Before and after the coal sample water injection, the volume of the remaining space in the coal sample tank does not change. Compared with the traditional water injection process outside the coal sample tank, the water injection in the tank of the present application does not change the gas pressure in the coal sample tank during the water injection process, thereby ensuring the accuracy of the coal sample gas adsorption-water injection-gas desorption experimental data.

[0028] Moreover, the isobaric water injection device of the present application realizes completely isobaric water injection, which effectively solves the problem that when water is injected into the tank through a single water injection port outside the coal sample tank, the water jet formed by the high water injection pressure causes impact damage to the coal sample's own structure, causing cracks or splitting in the coal body, thereby increasing the porosity of the coal sample, resulting in the inability to clearly judge whether water injection promotes or inhibits gas desorption during gas desorption. Through isobaric water injection, the integrity of the coal sample's own structure is guaranteed to the greatest extent, and the accuracy and authenticity of the gas desorption data measurement after water injection of the coal sample are improved, providing support for clearly judging the mechanism of the effect of water injection on the gas desorption amount of the coal sample. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings constituting part of the present application are used to provide a further understanding of the present application. The exemplary embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. Among them:

[0030] Figure 1 A schematic diagram of the structure of a coal isobaric controllable quantitative water injection gas desorption system under adsorption state provided according to some embodiments of the present application;

[0031] Figure 2 It is a structural schematic diagram of an isobaric water injection device provided according to some embodiments of the present application;

[0032] Figure 3 A cross-sectional view of a coal sample tank provided according to some embodiments of the present application;

[0033] Figure 4 for Figure 3 A partial view at A in the view shown;

[0034] Figure 5 A schematic flow chart of a method for coal isobaric controllable quantitative water injection gas desorption under adsorption state provided according to some embodiments of the present application.

[0035] Description of reference numerals:

[0036] 1. Methane gas cylinder; 2. Pressure reducing valve; 3. First gas valve; 4. First pressure gauge; 5. Reference tank; 6. Coal sample tank; 7. Second pressure gauge; 8. Pressure switch valve; 9. Intelligent digital display temperature controller; 10. Flame retardant electric heating belt; 11. Drainage gas collection and desorption instrument; 12. Gas desorption data acquisition instrument; 13. Pressure differential transmitter; 14. Third gas valve; 15. Fourth gas valve; 16. Fifth gas valve; 17. Sixth gas valve; 1 8. Vacuum pump; 19. Vacuum gauge; 20. Tee; 21. Gas adsorption data acquisition instrument; 22. Support column; 23. Water injection tank; 24. Transition water storage instrument; 25. Uniform water injection instrument; 26. Second standard sample sieve; 27. First standard sample sieve; 28. Coal sample fixing net; 29. ​​Sample sieve chassis; 30. Water diversion pipe; 31. Transition water outlet; 32. Second gas equalizing pressure hole; 33. Water injection uniform dispersion hole; 34. First gas equalizing pressure hole. DETAILED DESCRIPTION

[0037] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments. Each example is provided by way of explanation of the present application and does not limit the present application. In fact, it will be clear to those skilled in the art that modifications and variations may be made in the present application without departing from the scope or spirit of the present application. For example, a feature shown or described as a part of an embodiment may be used in another embodiment to produce yet another embodiment. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the embodiments of the present invention should belong to the scope of protection of the embodiments of the present invention.

[0038] Different hydraulic measures have changed the original structure of coal and the amount of water attached to the coal body to varying degrees. Therefore, after water injection into the coal body, its gas desorption performance has changed to a certain extent, which can effectively change the degree of coal seam outburst danger. The reasons why coal seam water injection measures reduce the danger of coal and gas outburst in coal seams are as follows: (1) High-pressure water injection destroys the original structure of coal, increases the number of cracks and voids in coal, improves the permeability coefficient of coal seams, and can effectively increase the efficiency of gas extraction; (2) According to the priority of coal adsorption of gas and adsorption of water, after water injection into gas-bearing coal seams, water can replace adsorbed gas, promote the desorption of adsorbed gas, and increase the emission of free gas; (3) After water injection into coal seams, water can form a water lock effect on the pores and cracks of gas desorption in the coal body, effectively reducing the desorption rate of free gas, thereby reducing the amount of coal seam gas desorption to a certain extent.

[0039] At present, according to the status of the original gas in coal seams, experimental tests are often carried out to measure the gas desorption amount of coal samples after gas adsorption by coal samples and water injection into gas-containing coal samples, so as to simulate the actual water injection process on the coal mine site to the maximum extent, determine the mechanism of action of coal seam water injection on coal sample gas desorption, and provide theoretical and experimental technical support for the prevention mechanism and effect of coal seam water injection measures. In the existing technology, there are limitations in the water injection process after coal samples adsorb gas:

[0040] (1) Before the coal sample undergoes the gas adsorption process, the volume of the remaining space in the coal sample tank excluding the coal sample has been accurately measured. During the water injection process using the external water injection device, water is injected into the tank from the outside of the coal sample tank. The volume of the remaining space in the coal sample tank is reduced, which increases the gas pressure in the coal sample tank and changes the gas adsorption environment of the coal sample before gas desorption.

[0041] (2) During the process of injecting water outside the coal sample tank, the existing water injection device injects water through the external water injection pipe of the coal sample tank. The water injection port is basically a single port, and in order to prevent the gas in the coal sample tank from leaking out through the water injection port, the water injection pressure is usually slightly higher than the gas pressure in the coal sample tank. Under the higher water injection pressure, water is injected into the coal sample tank in a jet state, which is easy to cause impact damage to the structure of the coal body itself, causing cracks or splits in the coal body, increasing the porosity of the coal sample, and causing gas desorption. It is impossible to clearly judge whether the water injection promotes or inhibits gas desorption.

[0042] (3) In order to increase the uniformity of the coal sample water injection process, the coal sample is stirred using a stirring device. Since the hardness of the stirring device is significantly higher than that of the coal sample, the mutual friction between the two will inevitably damage the coal sample during the stirring process, causing cracks or splits in the coal sample, changing the original state of the coal sample, and ultimately resulting in large errors in the gas desorption data after the coal sample is injected with water.

[0043] (4) After the coal sample absorbs gas to an equilibrium state, water is injected into the gas-containing coal sample through a water injection device, and the water completely immerses the gas-containing coal sample. This is inconsistent with the current situation in which only part of the water flows into the coal after drilling and water injection at the coal seam on-site in the coal mine.

[0044] (5) When the water flow is controlled by the ball control valve in the external liquid linkage device, after the valve is opened, water immediately flows into the coal sample through the uniform disperser. This process cannot clearly estimate the amount of water that invades the coal sample at a single time, and cannot achieve quantitative water injection.

[0045] Based on this, the present application proposes a coal isobaric controllable quantitative water injection gas desorption system under adsorption state, so as to accurately measure the effect of coal seam water injection measures on reducing and preventing the danger of coal and gas outburst under the original state of coal seam, clarify the effect law of isobaric water injection on the gas desorption amount of gas-containing coal, and avoid the measurement error of gas desorption amount after coal water injection caused by ignoring the influence of high-pressure water injection, water injection outside the tank, mechanical stirring, etc. on the coal sample’s own structure and the stored gas pressure, as well as the complete immersion of coal sample in water.

[0046] like Figures 1 to 4 As shown, the coal isobaric controllable quantitative water injection gas desorption system under the adsorption state includes: a gas supply unit, a degassing unit, a constant temperature unit, an adsorption unit and a desorption unit. Among them, the gas supply unit, the degassing unit and the desorption unit are respectively connected to the adsorption unit pipeline. The gas supply unit is used to provide gas to the adsorption unit, the degassing unit is used to evacuate the adsorption unit to provide a vacuum environment for the coal sample to adsorb gas, the desorption unit is used to monitor the gas desorption amount of the coal sample in the adsorption unit in real time, and the constant temperature unit is used to provide a constant temperature environment for the adsorption unit.

[0047] In the present application, the gas supply unit includes a methane gas cylinder 1 and a pressure reducing valve 2. The methane gas cylinder 1 is connected to the reference tank 5 of the adsorption unit through a pipeline, and methane gas is filled into the reference tank 5 through the methane gas cylinder 1. The pressure reducing valve 2 is arranged on the connecting pipeline between the methane gas cylinder 1 and the reference tank 5, and the first gas valve 3 is arranged between the pressure reducing valve 2 and the reference tank 5. At the same time, the first gas valve 3 controls the filling process of the methane gas cylinder 1 into the reference tank 5, and the first gas valve 3 is opened during filling.

[0048] The adsorption unit includes: a reference tank 5, a coal sample tank 6, an isobaric water injection device and a coal sample placement device. The reference tank 5 is connected to the methane gas cylinder 1 of the gas supply unit by a pipeline, and the coal sample tank 6 is connected to the reference tank 5 by a pipeline. A pressure switch valve 8 (a second gas valve) is provided on the connecting pipeline between the reference tank 5 and the coal sample tank 6. The pressure switch valve 8 controls the gas filling process of the reference tank 5 into the coal sample tank 6. When the second gas valve is opened, the reference tank 5 fills the coal sample tank 6. Therefore, the reference tank 5 is provided between the methane gas cylinder 1 and the coal sample tank 6 to calibrate the free space volume in the coal sample tank 6 (calibrated by the ideal gas state equation), as well as the transition gas storage function during the gas filling process, so as to avoid the phenomenon that the gas pressure in the coal sample tank 6 is too high or too low when the coal sample tank 6 is directly filled with gas.

[0049] When the free space volume in the coal sample tank 6 is calibrated by the reference tank 5, first, the coal sample tank 6 is vacuum degassed until the vacuum indication is 5Pa, the valves between the vacuum pump 18 and the coal sample tank 6 and the coal sample tank 6 and the reference tank 5 are closed, the reference tank 5 is connected to the air compressor, and the air compressor is used to inject 1MPa of air into the reference tank 5, and the valve between the air compressor and the reference tank 5 is closed. The valve between the coal sample tank 6 and the reference tank 5 is slowly opened to control the air pressure in the coal sample tank 6 so that the air pressure of the coal sample tank 6 and the reference tank 5 form a pressure difference, the valve between the coal sample tank 6 and the reference tank 5 is closed, and after stabilization for 10 minutes, the gas pressure in the tank displayed on the corresponding pressure gauge of the coal sample tank 6 and the reference tank 5 is recorded. Then, the valve between the coal sample tank 6 and the reference tank 5 is fully opened to make the coal sample tank 6 and the reference tank 5 fully connected, and after stabilization for 10 minutes, the pressure of the reference tank 5 and the coal sample tank 6 in the gas equilibrium state is recorded. Then, a standard steel ball of known volume is placed in the coal sample tank 6, and the above process is repeated to correspond the gas pressures in the coal sample tank 6 and the reference tank 5, and then the volumes of the reference tank 5 and the coal sample tank 6 are calibrated according to the ideal gas state equation.

[0050] At the same time, the reference tank 5 and the coal sample tank 6 are respectively provided with a first pressure gauge 4 and a second pressure gauge 7, wherein the first pressure gauge 4 and the second pressure gauge 7 are respectively connected to the top of the reference tank 5 and the coal sample tank 6 by means of mating threads, and the connection is sealed with a polytetrafluoroethylene gasket. The gas pressure in the reference tank 5 is monitored in real time by the first pressure gauge 4, and the gas pressure in the coal sample tank 6 is monitored in real time by the second pressure gauge 7, and the second pressure gauge 7 is connected to the gas adsorption data acquisition instrument 21 via a USB data cable, and the gas pressure of the gas in the coal sample tank 6 is collected in real time by the gas adsorption data acquisition instrument 21 during the gas adsorption process of the coal sample.

[0051] In the present application, the coal sample tank 6 provides a closed cavity for the coal sample to undergo gas adsorption, and the coal sample in a gas adsorption equilibrium state completes the isobaric water injection process. Specifically, the isobaric water injection device can be detachably installed in the coal sample tank 6, and is used to uniformly inject equal amounts of water into the coal sample after the adsorption of gas gas reaches equilibrium; the coal sample placement device is located in the coal sample tank 6 and below the isobaric water injection device, and is used to place the coal sample.

[0052] The isobaric water injection device and the coal sample are pre-placed together in the coal sample tank 6 before the coal sample tank 6 is sealed and assembled. The coal sample placement device includes: a coal sample fixing net 28 and a first standard sample separation screen 27. The coal sample is placed in the coal sample fixing net 28. Specifically, the coal sample fixing net 28 is an annular mesh structure with openings at both ends. The coal sample is located in the annular mesh structure to ensure that water can completely flow through the coal sample accumulated in the coal sample fixing net 28 during water injection. The coal sample fixing net 28 is arranged in the first standard sample sieve 27, which is fixed by hot melt adhesive and is located directly below the uniform water injection instrument 25; the second standard sample sieve 26 is stacked above the first standard sample sieve 27, that is, the first standard sample sieve 27 and the second standard sample sieve 26 are both open cylindrical structures, and the bottom plate is a mesh plate with multiple sieve holes, the coal sample fixing net 28 is located in the cylindrical structure of the first standard sample sieve 27, the lower end orifice plate of the second standard sample sieve 26 is located at the upper end opening of the first standard sample sieve 27, the lower part of the isobaric water injection device is located in the second standard sample sieve 26, and is opposite to the coal sample fixing net 28; the sample sieve chassis 29 is stacked below the first standard sample sieve 27.

[0053] Here, the radial dimensions of the first standard sample sieve 27 and the second standard sample sieve 26 are adapted to the inner diameter of the coal sample tank 6 to ensure that the first standard sample sieve 27 and the second standard sample sieve 26 will not move relative to the coal sample tank 6 when water is poured at an angle.

[0054] In the present application, water is uniformly injected into the coal sample through an isobaric water injection device, which is used for isobaric water injection after the coal sample absorbs gas to a balanced state. Among them, the height of the isobaric water injection device is approximately equal to the inner height of the coal sample tank 6 (the height from the bottom of the coal sample tank 6 to the lower flange) to ensure that the isobaric water injection device does not move up and down during water injection. Specifically, the isobaric water injection device includes: a water injection tank body 23, a transition water storage device 24 and a uniform water injection device 25. Among them, the two ends of the transition water storage device 24 are respectively connected to the lower part of the water injection tank body 23, and are connected to the upper part of the uniform water injection device 25, and the connection is bonded and fixed with hot melt adhesive.

[0055] The water injection tank body 23 is a shell structure with a closed lower end, and the shell structure of the water injection tank body 23 is detachably connected to the inner wall of the coal sample tank 6 through the support column 22, and a water inlet is also provided on the outer wall of the water injection tank body 23. The support column 22 is fixed on both sides of the inner and outer surfaces of the water injection tank body 23 by nuts, and the support column 22 is located above the water inlet and is evenly spaced at 120 degrees in the circumferential direction, so that the support column 22 ensures that when water is injected into the coal sample, the position of the isobaric water injection device relative to the inner wall of the coal sample tank 6 remains unchanged.

[0056] The upper end of the transition water storage instrument 24 is connected to the bottom surface of the shell structure of the water injection tank body 23. The transition water storage instrument 24 is provided with a water storage area and a transition water outlet 31. The side wall corresponding to the water storage area is provided with a water inlet, which is connected to the water outlet provided on the side wall of the water injection tank body 23 through a water inlet pipe 30; the transition water outlet 31 is far away from the water inlet and is located on the bottom plate of the transition water storage instrument 24. Specifically, the transition water storage instrument 24 is a circular container with a semi-open bottom, and a water inlet is provided on the side wall corresponding to the closed side of the semi-closed bottom plate, and the water inlet is connected to the water outlet from the outside through a pipeline. Thus, when the coal sample tank 6 is tilted, the water in the water injection tank body 23 flows into the transition water storage instrument 24 through the water inlet pipe 30, and is blocked by the semi-closed bottom plate to perform quantitative water storage. Then, the coal sample tank 6 is leveled, and the water stored by the semi-closed bottom plate flows out from the semi-closed bottom opening. In this way, multiple quantitative water injections of coal samples are achieved.

[0057] The upper end of the uniform water injection instrument 25 is connected to the bottom surface of the transition water storage instrument 24 and is connected to the transition water outlet 31. The lower end of the uniform water injection instrument 25 is evenly distributed with multiple water injection uniform dispersion holes 33. Specifically, the uniform water injection instrument 25 is a cylindrical structure with an upper opening and multiple water injection uniform dispersion holes 33 at the lower end. The upper opening is connected to the bottom semi-opening of the transition water storage instrument 24. The water stored by the semi-enclosed bottom plate flows into the uniform water injection instrument 25 from the bottom semi-opening of the transition water storage instrument 24, and then is evenly dispersed through multiple water injection uniform dispersion holes 33, so that all parts of the coal sample can be infiltrated. Here, a first gas equalizing hole 34 is provided on the water injection tank body 23, and a second gas equalizing hole 32 is provided on the side wall of the uniform water injection instrument 25 to effectively ensure that when isobaric water injection is performed, water can flow out smoothly from the isobaric water injection device.

[0058] Thus, the transition water storage device 24 allows the water in the water injection tank body 23 to flow into the transition water storage device 24 through the water diversion pipe 30 during the process of tilting the coal sample tank 6, rather than directly flowing into the uniform water injection device 25 from the water diversion inlet side, effectively preventing water from entering the coal sample from the water injection uniform dispersion holes 33 near the water diversion pipe 30, while no water is infiltrating the coal sample on the side away from the water diversion inlet. In other words, by using the transition water storage device 24, each time the coal sample tank 6 is tilted, the water in the water injection tank body 23 can first flow to the water storage area of ​​the transition water storage device 24, which can quantitatively control the water infiltrating the coal sample on the one hand, and evenly disperse the water through multiple water injection uniform dispersion holes 33 on the other hand, so that all parts of the coal sample can be infiltrated.

[0059] Here, the multiple water injection uniform dispersion holes 33 are independent of each other, thereby ensuring that the water in the water storage area can be dispersed into multiple streams after flowing into the uniform water injection device 25 through the transition water outlet 31, and flow out from the multiple water injection uniform dispersion holes 33 respectively, thereby achieving uniform dispersion of water and allowing all parts of the coal sample to be infiltrated; effectively avoiding the phenomenon that the water flowing in from the transition water outlet 31 forms a stream under the action of surface tension, resulting in only partial infiltration of the coal sample.

[0060] In the present application, the constant temperature unit is used to provide a constant temperature environment for the coal sample tank 6 of the adsorption unit. Specifically, the flame retardant electric heating belt 10 is evenly wound around the outer surface of the coal sample tank 6, and the coal sample tank 6 is controlled at a constant temperature by the intelligent digital display temperature controller 9 during the entire experiment. According to the temperature data of the coal sample tank 6 fed back by the intelligent digital display temperature controller 9, the cooling or heating of the flame retardant electric heating belt 10 is controlled, thereby realizing the constant temperature setting of the coal sample tank 6.

[0061] In the present application, the desorption unit includes: a drainage gas collection desorption instrument 11, a differential pressure transmitter 13 and a gas desorption data acquisition instrument 12. Among them, the drainage gas collection desorption instrument 11 is connected to the coal sample tank 6 pipeline, and is used to measure the gas desorption amount in the coal sample tank 6 by the water column height; the differential pressure transmitter 13 is connected to the drainage gas collection desorption instrument 11 pipeline, and is used to record the water column height in the drainage gas collection desorption instrument 11 in real time during the gas desorption process, and a sixth gas valve 17 is also provided on the connecting pipeline between the differential pressure transmitter 13 and the drainage gas collection desorption instrument 11; the differential pressure transmitter 13 is connected to the gas desorption data acquisition instrument 12 via a USB data cable. Among them, the connection points of the drainage gas collection desorption instrument 11, the differential pressure transmitter 13 and the gas desorption data acquisition instrument 12 are all sealed with polytetrafluoroethylene gaskets. Thus, the change of water column height in the drainage gas collecting desorption instrument 11 can reflect the amount of gas desorption in real time, and the water column height data in the drainage gas collecting desorption instrument 11 discharged by the gas during the gas desorption process can be recorded in real time by the differential pressure transmitter 13. The collected physical data (water column height) can be converted into an electrical signal by the differential pressure transmitter 13 and sent to the gas desorption data acquisition instrument 12.

[0062] In the present application, the third gas valve 14 and the fourth gas valve 15 are sequentially arranged on the connecting pipe between the coal sample tank 6 and the drainage gas collecting desorber 11. After the water injection of the gas-containing coal sample is completed, the differential pressure transmitter 13 and the gas desorption data acquisition instrument 12 are opened; at the same time, the second gas valve is closed, and the connecting pipe between the second gas valve and the reference tank 5 is disconnected (so that the gas in the reference tank 5 is slowly released); the second gas valve is opened, and the gas in the free space of the coal sample tank 6 is quickly released (about 2 seconds). When the second pressure gauge 7 installed on the coal sample tank 6 shows 0, the second gas valve is immediately closed, and the third gas valve 14 and the fourth gas valve 15 are quickly opened. The adsorbed gas in the coal sample flows into the drainage gas collecting desorber 11 through the double valves (the third gas valve 14 and the fourth gas valve 15), and the gas desorption amount is judged by the change of the water column height in the drainage gas collecting desorber 11. When the water column height remains unchanged within 30 minutes, the third gas valve 14 and the fourth gas valve 15 are closed, and the gas desorption process ends. Based on the desorption data recorded by the gas desorption data acquisition instrument 12 and the pressure difference transmitter 13, the gas desorption amount after water injection into the coal sample is calculated.

[0063] In the present application, the degassing unit includes a vacuum pump 18, which is connected to the coal sample tank 6 pipeline, and a vacuum gauge 19 is provided on the connecting pipeline. Specifically, the vacuum pump 18 is connected to the gas outlet of the coal sample tank 6, and the vacuum gauge 19 is connected to the connecting pipeline through a tee 20, and a fifth gas valve 16 is provided between the vacuum gauge 19 and the gas outlet of the coal sample tank 6, that is, the fifth gas valve 16 is provided between the vacuum gauge 19 and the third gas valve 14. The vacuum degassing of the coal sample tank 6 is achieved through the fourth gas valve 15 and the fifth gas valve 16.

[0064] During the experiment, before inflating the coal sample tank 6, close the first gas valve 3, open the second gas valve 8, the third gas valve 14, and the fifth gas valve 16, and turn on the vacuum gauge 19 and the vacuum pump 18 at the same time, and record the degassing vacuum degree during the vacuum degassing process in real time. When the preset degassing vacuum degree is reached, close the vacuum pump 18 and the fifth gas valve 16, the third gas valve 14, the second gas valve and the first gas valve 3, and prepare to inflate the coal sample tank 6.

[0065] When the coal sample is measured by the isobaric controllable quantitative water injection gas desorption system under adsorption state of the embodiment of the present application, Figure 5 As shown, including:

[0066] Step S101, weigh a certain mass of water and store it in the isobaric water injection device of the adsorption unit; at the same time, place the coal sample to be tested in the coal sample placing device, and weigh the weight m1 of the coal sample and the coal sample placing device.

[0067] Among them, when a certain mass of water is weighed and stored inside the isobaric water injection device, the liquid level of the water should be lower than the connection between the water injection tank body 23 of the isobaric water injection device and the water outlet, and the tank cover of the isobaric water injection device is tightened. Coal particles with a particle size of 2-3 mm are weighed as experimental coal samples to be tested, placed in the coal sample fixing net 28, and the coal sample, coal sample fixing net 28, and sieve (including the first standard sample sieve 27 and the second standard sample sieve 26) are loaded, that is, m1.

[0068] The step is 102 , placing the isobaric water injection device and the coal sample placement device in the coal sample tank 6 of the adsorption unit, and stacking the isobaric water injection device on top of the coal sample placement device, and sealing the coal sample tank 6 .

[0069] Place the isobaric water injection device as a whole in the screen, stack the screen and the chassis, and pre-place the isobaric water injection device and the coal sample in the coal sample tank together. Use screws and nuts to tighten the upper flange and the lower flange on the top of the coal sample tank 6, and seal the upper flange and the lower flange with an O-ring to ensure the sealing of the coal sample tank 6.

[0070] Step S103, the constant temperature unit is used to control the temperature of the coal sample tank 6, and the degassing unit is turned on to evacuate the adsorption unit to a preset vacuum degree, and the degassing unit is turned off.

[0071] Specifically, the flame-retardant electric heating tape 10 is evenly wound around the outer surface of the coal sample tank 6 and the surface of the upper flange, and the intelligent digital temperature control meter is turned on to perform constant temperature control on the coal sample tank 6 .

[0072] Close the first gas valve 3, open the second gas valve (pressure switch valve 8), the third gas valve 14, and the fifth gas valve 16, and simultaneously open the vacuum gauge 19 and the vacuum pump 18 to record the degassing vacuum degree during the vacuum degassing process. When the vacuum gauge 19 shows the preset vacuum degassing degree, close the vacuum pump 18 and the second gas valve, the third gas valve 14, and the fifth gas valve 16.

[0073] Step S104, open the gas supply unit, and inflate the reference tank 5 of the adsorption unit until the gas pressure in the reference tank 5 reaches a first predetermined pressure value, and then close the gas supply unit; open the pressure switch valve 8 provided on the connecting pipe between the reference tank 5 and the coal sample tank 6, and fill the coal sample tank 6 with gas from the reference tank 5 until the pressure in the coal sample tank 6 reaches a second predetermined pressure value, and then close the pressure switch valve 8, and leave the coal sample tank 6 in a constant temperature environment for 12 hours.

[0074] Specifically, the methane cylinder 1, the pressure reducing valve 2 and the first gas valve 3 are opened to inflate the reference tank 5 until the indication of the first pressure gauge 4 on the top of the reference tank 5 reaches the first predetermined pressure value, and then the methane cylinder 1, the pressure reducing valve 2 and the first gas valve 3 are closed. The gas adsorption data acquisition instrument 21 is opened to monitor the pressure of the gas filled in the coal sample tank 6 in real time.

[0075] Open the second gas valve and fill the coal sample tank 6 with gas. When the second pressure gauge 7 reaches the second predetermined pressure value, close the second gas valve and leave the coal sample tank in a constant temperature environment for 12 hours.

[0076] Step S105, after the coal sample reaches the gas adsorption equilibrium state, tilt the coal sample tank 6 for a preset time and then level the coal sample tank 6 to evenly inject the set amount of water in the isobaric water injection device into the gas-containing coal sample; if the injection amount needs to be increased, repeatedly tilt the coal sample tank 6 to repeatedly inject the set amount of water.

[0077] If the pressure shown on the second pressure gauge 7 remains stable within 2 hours and reaches the coal sample gas adsorption equilibrium state, the gas adsorption process ends. When water is needed to immerse the gas-containing coal sample, tilt the coal sample tank 10° to 55°, and the single tilting time is 3 seconds. The specific tilting time is determined according to the experimental requirements, so that the water in the water injection tank body 23 of the isobaric water injection device flows into the transition water storage device 24 through the water diversion pipe 30, and the water storage area of ​​the transition water storage device 24 is full of water. After the tank body is tilted once to fill the transition water storage area with water, the coal sample tank 6 is leveled, and the water in the water storage area of ​​the transition water storage device 24 flows into the uniform water injection device 25 through the transition water outlet 31 of the transition water storage device 24, and is injected into the gas-containing coal sample through the water injection uniform dispersion hole 33.

[0078] Water flows through the coal sample under its own gravity and flows into the bottom plate 29 of the sample sieve, so that the moisture content of the coal sample can be calculated after the gas desorption experiment. After a single water injection process, if the amount of water injected into the gas coal sample needs to be increased, the coal sample tank 6 is repeatedly tilted to inject water into the coal sample. However, when repeatedly injecting water, the tilt angle of the coal sample tank 6 must be gradually increased to ensure that the water storage area of ​​the transition water storage device 24 is fully stored.

[0079] Therefore, before the vacuum degassing of the coal sample begins, the isobaric water injection device and the experimental coal sample are pre-placed in the coal sample tank 6, and the upper flange and the lower flange on the top of the coal sample tank 6 are fastened by screws and nuts, and the upper and lower flanges are sealed by O-rings to ensure the sealing of the coal sample tank 6. During the isobaric water injection process after the coal sample gas adsorption reaches the equilibrium state, the water in the isobaric water injection device only changes in the relative position in the coal sample tank 6. Before and after the coal sample water injection, the volume of the remaining space in the coal sample tank 6 does not change. Therefore, unlike the water injection process outside the coal sample tank 6, the water injection process of the present application does not change the gas pressure in the coal sample tank 6, ensuring the accuracy of the coal sample gas adsorption-water injection-gas desorption experimental data.

[0080] The isobaric water injection device and the coal sample are simultaneously pre-placed in the coal sample tank 6, which avoids the impact damage to the structure of the coal sample caused by the water jet formed by the high water injection pressure when the existing water injection device injects water into the tank from the outside of the coal sample tank 6 through a single water injection port, thereby causing cracks or splits in the coal body, increasing the porosity of the coal sample, and causing gas desorption and adsorption, and it is impossible to clearly judge whether the water injection promotes or inhibits gas desorption. The fully isobaric water injection of this application provides support for clearly judging the mechanism of water injection on the gas desorption amount of coal samples.

[0081] In addition, during water injection, after the coal sample tank 6 is tilted, the water is injected into the water storage area of ​​the transition water storage device 24, thereby realizing multiple quantitative water storage and multiple quantitative water injection. After the coal sample tank 6 is leveled, the water flows into the uniform water injection device 25 from the transition water outlet 31 of the transition water storage device 24. The water flows evenly through the coal sample placed in the coal sample fixing net 28 under the action of its own weight and the dispersion of the uniform water injection dispersion holes. The excess water after flowing through the coal sample is stored in the sampling screen chassis 29 of the isobaric water injection device. Therefore, during the water injection process, only part of the flowing water penetrates into the gas-containing coal sample, thus avoiding the phenomenon that the gas-containing coal sample is completely immersed in water after water injection, which is more in line with the current situation that only part of the water flows through the coal after drilling and water injection in the coal seam at the coal mine site.

[0082] At the same time, under the dispersion of uniform water injection dispersion holes, the water flows evenly through the coal sample placed in the coal sample fixing net 28, so that the coal sample is fully infiltrated, and the stirring device stirs the coal sample. During the mutual friction between the gas-containing coal sample and the stirring device, the coal sample is avoided from splitting and increasing cracks. The integrity of the coal sample's own structure is guaranteed to the greatest extent, and the accuracy and authenticity of the gas desorption data measurement after the coal sample is injected with water is improved.

[0083] Step S106: After the water injection of the gas-containing coal sample is completed, the desorption unit is turned on to collect gas desorption data in real time.

[0084] In this application, after the gas-containing coal sample is injected with water, the differential pressure transmitter 13 and the gas desorption data acquisition instrument 12 are turned on to collect gas desorption data in real time. The connection between the second gas valve and the reference tank 5 is disconnected, and at the same time, the second gas valve is opened to release the gas in the free space of the coal sample tank. When the second pressure gauge 7 shows 0MPa, the second gas valve is closed. The third gas valve 14 and the fourth gas valve 15 are opened, and the adsorbed gas in the coal sample flows into the drainage gas collection desorption instrument 11 through the double valves. The gas desorption amount is judged by the height change of the water column in the drainage gas collection desorption instrument 11. When the height of the water column remains unchanged within 30 minutes, the coal sample gas desorption reaches a balanced state, and the third gas valve 14 and the fourth gas valve 15 are closed, and the gas desorption process ends. According to the desorption data recorded by the gas desorption data acquisition instrument 12 and the differential pressure transmitter 13, the gas desorption amount after the coal sample is injected with water is calculated.

[0085] Step S107, after the gas desorption is completed, open the coal sample tank 6, take out the isobaric water injection device, weigh the weight m2 of the coal sample and the coal sample placement device after the water injection is completed; and determine the water content of the coal sample under different water injection amounts and different pressure conditions based on the weight m1 and the weight m2.

[0086] That is to say, after the gas desorption is completed, the coal sample tank is opened, the isobaric water injection device is taken out, and the coal sample, the coal sample fixing net 28 and the screen after the water injection are carried out as a whole, which is recorded as m2. Then m2-m1 is the total weight of the water injected into the coal sample, and the water content of the coal sample under different water injection amounts and different pressure conditions can be obtained.

[0087] The coal isobaric controllable quantitative water injection and gas desorption system under the adsorption state of the present application is highly practical, simple to manufacture, low in cost, has a high water injection success rate, can meet the requirements for uniformity of water injection of coal samples, has high accuracy in gas desorption data measurement, and can achieve the requirements for coal sample gas adsorption-water injection-gas desorption experimental data measurement.

[0088] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0089] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0090] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0091] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0092] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0093] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A coal isobaric controllable quantitative water injection gas desorption system under adsorption state, characterized in that: include: Gas supply unit, degassing unit, constant temperature unit, adsorption unit and desorption unit, The gas supply unit, the degassing unit, and the desorption unit are respectively connected to the adsorption unit pipeline; wherein the gas supply unit is used to provide gas to the adsorption unit; the degassing unit is used to evacuate the adsorption unit to provide a vacuum environment for the coal sample to adsorb the gas; the desorption unit is used to monitor the gas desorption amount of the coal sample in the adsorption unit in real time; The adsorption unit comprises: a reference tank, a coal sample tank, an isobaric water injection device and a coal sample placement device; the reference tank is connected to the gas supply unit pipeline, the coal sample tank is connected to the reference tank pipeline, and a pressure switch valve is provided on the connecting pipeline between the reference tank and the coal sample tank; the isobaric water injection device is detachably installed in the coal sample tank, and is used to uniformly inject equal amounts of water into the coal sample after the gas is adsorbed to a balance; the coal sample placement device is located in the coal sample tank and below the isobaric water injection device, and is used to place the coal sample; wherein the isobaric water injection device comprises: a water injection tank body, a transition water storage instrument and a uniform water injection instrument; the water injection tank body is a shell structure with a closed lower end, and the shell structure is detachably connected to the inner wall of the coal sample tank through a support column, and the outer wall of the shell structure is provided with a water outlet; The upper end of the transition water storage device is connected to the bottom surface of the shell structure, and a water storage area and a transition water outlet are provided on the transition water storage device. A water inlet is provided on the side wall corresponding to the water storage area, and the water inlet is connected to the water outlet through a water inlet pipe; the transition water outlet is far away from the water inlet and is located on the bottom plate of the transition water storage device; The upper end of the uniform water injection instrument is connected to the bottom surface of the transition water storage instrument and communicated with the transition water outlet, and the lower end of the uniform water injection instrument is evenly distributed with a plurality of uniform water injection dispersion holes; The constant temperature unit is used to provide a constant temperature environment for the coal sample tank of the adsorption unit.

2. The coal isobaric controllable quantitative water injection gas desorption system under adsorption state according to claim 1 is characterized in that: The coal sample placement device comprises: a coal sample fixing net and a first standard sample separation screen, wherein the coal sample fixing net is arranged in the first standard sample separation screen and is used to fix the coal sample; A second standard sample grading sieve is stacked above the first standard sample grading sieve, and a sample grading sieve chassis is stacked below the first standard sample grading sieve; wherein the lower part of the isobaric water injection device is located inside the second standard sample grading sieve and directly faces the coal sample fixing net.

3. The coal isobaric controllable quantitative water injection gas desorption system under adsorption state according to claim 1 is characterized in that: The water injection tank body is provided with a first gas pressure equalizing hole, and the side wall of the uniform water injection instrument is provided with a second gas pressure equalizing hole.

4. The coal isobaric controllable quantitative water injection gas desorption system under adsorption state according to claim 1 is characterized in that: The constant temperature unit comprises: a flame retardant electric heating belt, and the flame retardant electric heating belt is evenly wound around the outer surface of the coal sample tank.

5. The coal isobaric controllable quantitative water injection gas desorption system under adsorption state according to claim 1 is characterized in that: The desorption unit comprises: a drainage gas collection desorption instrument, a differential pressure transmitter and a gas desorption data acquisition instrument; The drainage gas collection desorption instrument is connected to the coal sample tank pipeline and is used to measure the gas desorption amount in the coal sample tank through the water column height; The differential pressure transmitter is connected to the drainage gas collecting desorption instrument pipeline and is used to record the height of the water column in the drainage gas collecting desorption instrument in real time during the gas desorption process; The gas desorption data acquisition instrument is connected to the pressure difference transmitter via a USB data cable.

6. The coal isobaric controllable quantitative water injection gas desorption system under adsorption state according to claim 1, characterized in that: The degassing unit comprises: a vacuum pump, the vacuum pump is connected to the coal sample tank pipeline, and a vacuum gauge is arranged on the connecting pipeline.

7. The coal isobaric controllable quantitative water injection gas desorption system under adsorption state according to claim 1 is characterized in that: The reference tank is provided with a first pressure gauge, the coal sample tank is provided with a second pressure gauge, and the second pressure gauge is connected to the gas adsorption data acquisition instrument via a USB data cable.

8. A method for desorption of coal gas by isobaric controllable quantitative water injection under adsorption state, characterized in that: The coal sample is measured by using the coal isobaric controllable quantitative water injection gas desorption system under adsorption state according to any one of claims 1 to 7, and the desorption method comprises: Step S101, weigh a certain mass of water and store it in the isobaric water injection device of the adsorption unit; at the same time, place the coal sample to be tested in the coal sample placing device, and weigh the weight m1 of the coal sample and the coal sample placing device; Step S102, placing the isobaric water injection device and the coal sample placement device in the coal sample tank of the adsorption unit, and stacking the isobaric water injection device on top of the coal sample placement device, and sealing the coal sample tank; Step S103, performing constant temperature control on the coal sample tank through a constant temperature unit, opening a degassing unit to evacuate the adsorption unit to a preset vacuum degree, and closing the degassing unit; Step S104, open the gas supply unit, and inflate the reference tank of the adsorption unit until the gas pressure in the reference tank reaches a first predetermined pressure value, and then close the gas supply unit; open the pressure switch valve provided on the connecting pipe between the reference tank and the coal sample tank, and fill the coal sample tank with gas from the reference tank until the pressure in the coal sample tank reaches a second predetermined pressure value, and then close the pressure switch valve; and leave the coal sample tank to stand for 12 hours under a constant temperature environment; Step S105, after the gas adsorption in the coal sample tank is balanced, the coal sample tank is tilted for a preset time and then laid flat, so as to uniformly inject a set amount of water in the isobaric water injection device into the gas-containing coal sample; if the water injection amount needs to be increased, the coal sample tank is repeatedly tilted to repeatedly inject the set amount of water; Step S106: After the water injection of the gas-containing coal sample is completed, the desorption unit is turned on to collect gas desorption data in real time; Step S107, after the gas desorption is completed, open the coal sample tank, take out the isobaric water injection device, weigh the weight m2 of the coal sample after the water injection and the coal sample placement device; and determine the water content of the coal sample under different water injection amounts and different pressure conditions based on the weight m1 and the weight m2.

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