Coal seam gas content measuring method and measuring device based on isovolumetric variable pressure principle

Abstract

The invention belongs to the field of coal mine gas parameter determination, and relates to a coal seam gas content determination method and determination device based on an isovolumetric variable pressure principle. The determination method comprises the following steps: placing a coal sample in a detection device with a known volume and a crushing function, and collecting the desorption pressure and temperature of the coal sample at t1 time after loading is completed; crushing the coal sample for t2 until the specified particle size requirement is met; standing the crushed coal sample for t3 time until the desorption pressure and temperature of the coal sample reach a stable state, and collecting the desorption pressure and temperature of the coal sample at t3 time; calculating the content Q residual of residual gas which is not desorbed from the coal sample; the exposure time is t0 before the coal sample starts to be drilled and loaded in the detection device, and the lost gas quantity Q'loss of the coal sample within the exposure time t0 is obtained through data fitting conversion; calculating the desorption gas amount # imgabs0 # of the coal sample in the time period t1-t3, and calculating the total gas content of the coal sample; by improving the determination method, the technical difficulty and the manufacturing cost are remarkably reduced.

Description

Technical Field

[0001] The invention belongs to the field of coal mine gas parameter measurement, and relates to a coal seam gas content measurement method and a measurement device based on the isochoric pressure transformation principle. Background Art

[0002] In the field of coal mining and safe production, the precise determination of coal seam gas content has always been a research focus in the industry. Gas content is not only related to the safe production of mines, but also directly affects the evaluation of gas extraction effects and the scientific prediction and prevention of disasters such as coal and gas outbursts. Traditionally, the determination of coal seam gas content mainly follows the relevant provisions of the "Direct Underground Determination Method of Coal Seam Gas Content" and adopts the normal pressure natural desorption method. This process requires the coal sample to be placed in an open environment at atmospheric pressure and temperature for desorption, and the determination process is divided into two stages: underground in the coal mine and ground laboratory. The reason is that during the period when the standard was formulated, there was no technical means to complete the crushing of coal samples underground in the coal mine.

[0003] In terms of the measurement of desorbed gas, the drainage gas collection volume measurement method was mainly used in the early days. The instruments used, such as the measuring tube, were not only bulky, but also required manual readings. The level of automation and informatization was extremely low, making it difficult to meet the efficient and safe production needs of modern coal mines. With the advancement of technology, an automated measurement device for the desorbable gas content of coal seams has appeared on the market. While maintaining the original measurement process, the device has innovated the measurement method of desorbed gas, adopted the drainage weighing method, and achieved partial automation and informatization through the application of industrial control software and electronic sensors, improving the efficiency and accuracy of the measurement.

[0004] In order to further simplify the measurement process and improve the measurement efficiency, the "One-stop Automated Measurement Method for Gas Content in Coal Seams" introduced an electronic flowmeter and a small pulverizer driven by compressed air in coal mines, realizing one-stop measurement of gas content in coal mines. This method is also based on the natural desorption method at normal pressure, but thanks to the application of pneumatic pulverizers, coal samples can be directly crushed in coal mines, thus eliminating the ground measurement link. At the same time, the use of integral electronic flowmeters not only greatly reduces the number and volume of instruments and equipment, but also realizes the automatic collection and processing of desorption data, so that the gas content measurement results can be obtained immediately in coal mines. However, although this method has brought significant progress, there are still some problems that need to be solved. On the one hand, high-precision micro-flow electronic flowmeters, as key components of this method, are still imported. On the other hand, the device designs the pneumatic pulverizer and flow meter as split types, connected by silicone tubes, which not only increases the difficulty of carrying, but also may affect the stability and accuracy of the measurement.

[0005] In summary, although the current coal seam gas content determination technology has made certain progress, there are still problems such as insufficient automation, reliance on imports for key components, and inconvenient equipment to carry. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a coal seam gas content determination method and device based on the isochoric pressure transformation principle, to detect temperature and pressure in a detection device with a known volume and a crushing function, and to further calculate the gas content, which significantly reduces the technical difficulty and manufacturing cost.

[0007] In a first aspect, the present invention provides a method for determining coal seam gas content based on the isochoric pressure transformation principle, comprising the following steps:

[0008] The coal sample is placed in a detection device with a known volume and a crushing function, and the desorption pressure and temperature of the coal sample at time t1 are collected after the loading is completed;

[0009] The coal sample is crushed until more than 95% of the coal sample has a particle size less than 0.25 mm, and the crushing time is t2;

[0010] The crushed coal sample is left to stand for t3 time until its desorption pressure and temperature reach a stable state, and the desorption pressure and temperature of the coal sample at t3 time are collected;

[0011] Calculate the residual gas content Q in the coal sample that has not been desorbed 残留 ;

[0012] The exposure time t0 is from the start of drilling to the completion of loading in the detection device. The gas loss Q′ of the coal sample within the exposure time t0 is obtained by fitting and converting the desorption pressure and temperature data per unit time in the period t1. 损失 ;

[0013] Calculate the desorbed gas amount of the coal sample during the time period t1 to t3 The total gas content of the coal sample is calculated using the following formula:

[0014]

[0015] Optionally, the following formula is used to calculate the residual gas content Q in the coal sample that has not been desorbed: 残留 ,

[0016]

[0017] Where P0 is the atmospheric pressure at the location where the gas content is measured, P 终 is the pressure after the gas desorption of the coal sample reaches a stable state, T 终 is the temperature at which the gas desorption of the coal sample reaches a stable state, a and b are the adsorption constants of the coal, and A ad is the ash content of the coal sample, Mad is the moisture content of the coal sample, F is the porosity of the coal sample, ARD is the apparent density of the coal sample, and n is the pressure correlation coefficient.

[0018] Optionally, the following method is used to calculate the gas loss Q′ 损失 :

[0019] Using the ideal gas state equation PV = nRT, the desorption pressure and temperature per unit time in the period t1 are converted into the desorption gas volume per unit time;

[0020] Adopt Q t =a(t-t0) i +Q 损失 Fit the desorption data in all time periods t1, where a is the fitting coefficient and i is the particle size characteristic value of the coal sample with a fixed particle size;

[0021] The Q obtained by fitting 损失 Converted to the gas loss under standard working conditions Q' 损失 .

[0022] Optionally, the desorption gas amount can be calculated by the following method:

[0023] Using the ideal gas state equation PV = nRT, the change in desorption temperature and pressure during the time period t1 to t3 is converted into the desorption gas volume during the time period t1 to t3

[0024] The amount of desorbed gas Converted to desorption gas volume under standard working conditions

[0025] In the second aspect, the present invention provides a coal seam gas content measuring device based on the isochoric pressure transformation principle, comprising a tank body and a tank cover detachably mounted on the tank body; the tank body is provided with a detection cavity, and the tank cover is provided with a receiving cavity; a crushing blade is arranged in the detection cavity, and the coal sample is placed in the detection cavity, and the crushing blade rotates at high speed to crush the coal sample; an integrated circuit board is arranged in the receiving cavity, and a pressure sensor and a temperature sensor facing the tank body are arranged on the bottom surface of the tank cover to collect the pressure and temperature data of the coal sample in the tank before and after crushing; the pressure sensor and the temperature sensor are electrically connected to the integrated circuit board, and the desorbed gas amount and the total gas content of the coal sample are calculated through the measurement data of the two.

[0026] Optionally, a Bluetooth communication module is provided on the integrated circuit board for wireless communication with a mobile terminal; the mobile terminal calculates the amount of desorbed gas of the coal sample through measurement data from the pressure sensor and the temperature sensor.

[0027] Optionally, the pneumatic motor is arranged outside the device, and the output shaft of the pneumatic motor is connected to the crushing blade in a rotationally sealed manner with the tank body to drive the crushing blade to rotate at a high speed.

[0028] Optionally, the lower part of the tank body is connected to an assembly bracket, two first connecting shafts are relatively arranged on both sides of the lower part of the tank body, and two second connecting shafts are relatively arranged on both sides of the lower part of the tank body and are located below the first connecting shaft; the first connecting shaft is rotatably installed on the assembly bracket so that the tank body rotates around the first connecting shaft; a locking bolt is provided on the assembly bracket at a position corresponding to the position of the second connecting shaft, and the locking bolt passes through the assembly bracket and is inserted into the second connecting shaft to limit the rotation of the tank body.

[0029] Optionally, a first annular connecting ear is provided on the bottom surface of the tank cover, and a second connecting ear matching with the first connecting ear is provided on the top surface of the tank body, and the first connecting ear and the second connecting ear are fixed by a clamp; wherein a first O-ring is embedded in the contact surface between the first connecting ear and the second connecting ear.

[0030] Optionally, a pressure balancing hole is opened on the side wall of the tank body, and the pressure balancing hole is a threaded hole. A flange extending outward along the side wall of the tank body is arranged at the hole mouth; a sealing bolt is inserted into the flange to isolate the environment inside and outside the tank wall; wherein a second O-ring is arranged between the sealing bolt and the flange.

[0031] The beneficial effects of the present invention are:

[0032] The coal seam gas content determination method based on the isochoric pressure-changing principle of the present invention integrates the coal sample desorption, crushing, and determination functions and structures into an integrated design, realizing the underground one-stop determination of the coal seam gas content, eliminating the ground determination link. In actual applications, after the underground determination personnel input the coal sample information through the explosion-proof mobile phone, the fresh coal sample is loaded into the coal seam gas content determination device designed based on the isochoric pressure-changing principle and sealed, and then the determination program is started. The process includes two stages: determination before crushing and determination after crushing. The device will collect the pressure and temperature data of the coal sample gas desorption process in real time, and transmit these data to the explosion-proof mobile phone, and use the ideal gas state equation to convert the temperature and pressure changes in the confined space into the volume data of the desorbed gas, and then calculate the coal seam gas content through the algorithm model in the explosion-proof mobile phone software.

[0033] Unlike the normal pressure natural desorption method, in which the coal sample is desorbed in an open environment, the determination method provided by the present invention places the coal sample in a closed container with a known volume and a crushing function, and converts the desorption amount by detecting the pressure and temperature changes in the container caused by gas desorption before and after the coal sample is crushed, thereby avoiding the measurement error caused by the influence of external factors on gas desorption in an open environment. The determination method provided by the present invention simplifies the traditional gas content measurement process up and down the well into a one-stop completion in the well, avoids the use of the drainage gas collection method of a large-volume measuring cylinder, and does not have to rely on high-precision micro-flow electronic flowmeters of foreign technology. Only high-precision pressure and temperature sensors that are easier to obtain and integrate can be used to achieve accurate determination of coal seam gas content, effectively reducing technical difficulty and manufacturing costs.

[0034] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0036] Figure 1 A flow chart of a method for determining gas content in a coal seam based on the isochoric pressure transformation principle provided by the present invention;

[0037] Figure 2 A schematic diagram of the structure of a coal seam gas content measuring device based on the isochoric pressure transformation principle provided by the present invention;

[0038] Figure 3 A schematic diagram of the local structure of the pressure balance hole of the coal seam gas content measuring device based on the isochoric pressure transformation principle provided by the present invention.

[0039] Reference numerals:

[0040] 1-tank cover, 1.1-accommodating cavity, 1.2-first connecting ear, 1.3-first O-type sealing ring, 2-tank body, 2.1-second connecting ear, 2.2-first connecting shaft, 2.3-second connecting shaft, 2.4-detection cavity, 2.5-pressure balance hole, 2.6-flange, 3-clamp, 4-pressure sensor, 5-temperature sensor, 6-LCD display, 7-integrated circuit board, 8-lithium battery, 9-Type-c charging port, 10-charging port protection cover, 11-panel, 11.1-button, 12-assembly bracket, 12.1-foot pad, 12.2-locking bolt, 13-crushing blade, 14-rotating seal, 14.1-transmission shaft, 15-pneumatic motor, 15.1-output shaft, 16-sealing bolt, 16.1-second O-type sealing ring. DETAILED DESCRIPTION

[0041] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0042] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0043] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0044] In order to solve the defects of the existing coal seam gas content determination technology such as insufficient automation, reliance on imported key components, and inconvenient equipment to carry, the present invention provides a coal seam gas content determination device and method based on the isochoric pressure transformation principle. The coal sample is placed in a container with a known volume and a crushing function, and the changes in pressure and temperature in the container caused by the gas desorption process before and after the coal sample is crushed in a closed environment are detected, so as to calculate the desorbed gas amount and the total gas content of the coal sample.

[0045] Example 1

[0046] like Figure 2 As shown, the present invention provides a coal seam gas content measuring device based on the isochoric pressure transformation principle. The measuring device has a known volume and has a crushing function. It mainly includes a tank body 2, a tank cover 1 detachably mounted on the tank body, an assembly bracket 12 for supporting the tank body 2, and a crushing blade 13, a rotating seal 14, a pneumatic motor 15, etc. arranged in the assembly bracket 12.

[0047] Specifically, the tank cover 1 has a receiving cavity 1.1, and the integrated circuit board 7 is arranged in the receiving cavity 1.1. The top surface of the tank cover 1 is a liquid crystal display screen 6, which is electrically connected to the integrated circuit board 7. The bottom surface of the tank cover 1 is provided with a pressure sensor 4 and a temperature sensor 5 facing the tank body 2, and the two are electrically connected to the integrated circuit board 7; the integrated circuit board 7 is also equipped with a Bluetooth communication module to wirelessly communicate with the mobile terminal, and the mobile terminal calculates the desorbed gas amount of the coal sample through the measurement data of the pressure sensor 4 and the temperature sensor 5. The mobile terminal is preferably a matching explosion-proof mobile phone, and the explosion-proof mobile phone establishes wireless communication with the integrated circuit board 7 to realize remote control of the measurement process and read the measurement data of the pressure sensor 4 and the temperature sensor 5, and further calculates the desorption amount and the final gas content of the coal sample before and after crushing through an embedded algorithm.

[0048] In some optional embodiments, a lithium battery 8 and a button 11.1 are also provided in the accommodating cavity 1.1 to provide power support to the integrated circuit board 7 and control the opening and closing of the device. A hard panel 11 is provided on the top surface of the tank cover 1, and a transparent window is provided in the middle of the panel, facing the liquid crystal display 6 on the integrated circuit board 7 to display the working status of the device and the real-time data of coal sample desorption. The position corresponding to the panel 11 and the button 11.1 is a soft film area, and pressure is applied to the soft film area to press the button 11.1. The side of the tank cover 1 is equipped with a Type-c charging port 9 for convenient charging of the lithium battery 8. A charging port protective cover 10 is provided outside the Type-c charging port 9 to play a role in dust and water resistance, while also preventing physical damage and foreign matter from entering, providing safety protection, reducing the risk of electrostatic discharge and accidental touch, and keeping the appearance of the device neat and beautiful, improving the overall user experience.

[0049] The tank body 2 has a detection cavity 2.4, which is used to accommodate the coal sample to be tested. Furthermore, a high-speed rotating crushing blade 13 is provided at the bottom of the detection cavity 2.4 to crush the coal sample to be tested in the detection cavity 2.4. The driving force of the crushing blade 13 comes from the pneumatic motor 15 arranged outside the tank body 2, and the output shaft 15.1 of the pneumatic motor 15 is connected to the crushing blade 13 in the tank body 2 through the rotating seal 14. Specifically, a boss is provided on the bottom surface of the tank body 2, and an axial hole vertically connecting the inside and outside of the tank is provided in the boss. One end of the rotating seal 14 is a transmission shaft 14.1 with a smaller diameter, and the transmission shaft 14.1 penetrates into the tank through the axial hole and is fixedly connected to the crushing blade 13; the other end of the rotating seal 14 is connected to the output shaft 15.1 of the pneumatic motor 15, so as to drive the crushing blade 13 to rotate at a high speed through the pneumatic motor 15, thereby crushing the coal sample and accelerating the gas desorption of the coal sample.

[0050] In some optional embodiments, a flange is provided at one end of the rotary seal 14 that cooperates with the boss at the bottom of the tank body 2 to achieve a rotary seal effect and prevent the gas in the tank from overflowing and affecting the measurement accuracy. A D-shaped groove is provided at the other end of the rotary seal 14 connected to the pneumatic motor 15, and the output shaft 15.1 of the pneumatic motor 15 is a D-shaped shaft, and the output shaft 15.1 is inserted into the D-shaped groove of the rotary seal 14. Furthermore, a flange is also provided at one end of the rotary seal 14 that cooperates with the pneumatic motor 15.

[0051] In some optional embodiments, in order to facilitate the dumping of the coal sample after the measurement, the tank body 2 is constructed to be able to flip 360° around a certain axis. Specifically, the lower part of the tank body 2 is connected to an assembly bracket 12, and two first connecting shafts 2.2 are relatively arranged on both sides of the lower part of the tank body 2. The two first connecting shafts 2.2 are rotatably mounted on the assembly bracket 12, so that the tank body 2 can flip around the first rotating shaft 2.2, thereby pouring out the coal sample in the tank. Further, the lower part of the tank body 2 is also provided with a second connecting shaft 2.3, and the two second connecting shafts 2.3 are arranged on opposite sides of the tank body 2 and are preferably located below the first connecting shaft 2.2. The assembly bracket 12 is provided with a locking bolt 12.2 at a position corresponding to the position of the second connecting shaft 2.3. When the device is in a working state of measuring the gas content, the locking bolt 12.2 passes through the assembly bracket 12 and is inserted into the second connecting shaft 2.3 to limit the flipping of the tank body 2, thereby fixing the position of the tank body 2.

[0052] In some optional embodiments, the assembly bracket 12 is a thin-walled steel plate assembly, consisting of a bottom plate and two side plates perpendicular to the bottom plate, and the upper parts of the two side plates are provided with a rotating shaft hole matched with the first connecting shaft 2.2 and a locking shaft hole matched with the locking bolt 12.2. The four feet of the bottom plate of the assembly bracket 12 are provided with height-adjustable foot pads 12.1.

[0053] Furthermore, the tank cover 1 and the tank body 2 are detachably connected. Specifically, the bottom surface of the tank cover 1 is provided with an annular first connecting ear 1.2, and the top surface of the tank body 2 is provided with a second connecting ear 2.1 that matches the first connecting ear 1.2. The first connecting ear 1.2 and the second connecting ear 2.1 are fixed by a clamp 3, so that the tank cover 1 and the tank body 2 are tightly connected. At the same time, a first O-ring 1.3 is embedded in the contact surface of the first connecting ear 1.2 and the second connecting ear 2.1 to isolate the gas from entering and exiting when the tank cover 1 and the tank body 2 are assembled, so as to ensure the sealing inside the tank body 2.

[0054] Furthermore, if Figure 3 As shown, a pressure balance hole 2.5 is provided on the side wall of the tank body 2. The pressure balance hole 2.5 is a threaded hole, and a flange 2.6 extending outward along the side wall of the tank body 2 is provided at the hole mouth. The sealing bolt 16 is inserted into the flange 2.6 to isolate the environment inside and outside the tank wall. In some optional embodiments, a second O-ring 16.1 is provided between the sealing bolt 16 and the flange 2.6. When the sealing bolt 16 is tightened, the sealing ring 16.1 is compressed to complete the sealing of the pressure balance hole 2.5.

[0055] Example 2

[0056] The present invention also provides a method for determining the gas content in coal seams based on the isochoric pressure-changing principle, such as Figure 1 As shown, the following steps are included:

[0057] Step S1, determination of desorption amount of coal sample before crushing: placing the coal sample in a detection device with a known volume and crushing function, and collecting the desorption pressure and temperature of the coal sample at time t1 after loading;

[0058] Step S2, coal sample crushing: crushing the coal sample until more than 95% of the coal sample particle size is less than 0.25 mm, and the crushing time is t2;

[0059] Step S3, measuring the desorption amount of the coal sample after crushing: the crushed coal sample is left to stand for t3 time until its desorption pressure and temperature reach a stable state, and the desorption pressure and temperature of the coal sample at t3 time are collected;

[0060] Step S4, calculation of residual gas content in coal sample: Calculate the residual gas content Q in the coal sample that has not been desorbed 残留 ;

[0061] Step S5, calculation of coal sample gas loss content: The exposure time t0 is from the start of coal sample drilling to the completion of loading in the detection device. The gas loss Q′ of the coal sample within the exposure time t0 is obtained by fitting and converting the desorption pressure and temperature data per unit time within the period t1. 损失 ;

[0062] Step S6: Calculate the total gas content of the coal sample: Calculate the desorbed gas content of the coal sample during the time period t1 to t3 The total gas content of the coal sample is calculated using the following formula:

[0063] Further, in step S4, the residual gas content Q in the coal sample that has not been desorbed is calculated using the following formula: 残留 ,

[0064]

[0065] Where P0 is the atmospheric pressure at the location where the gas content is measured, P 终 is the pressure after the gas desorption of the coal sample reaches a stable state, T 终 is the temperature at which the gas desorption of the coal sample reaches a stable state, a and b are the adsorption constants of the coal, and A ad is the ash content of the coal sample, M ad is the moisture content of the coal sample, F is the porosity of the coal sample, ARD is the apparent density of the coal sample, and n is the pressure correlation coefficient.

[0066] In step S5, the gas loss amount Q' is calculated by the following method: 损失 :

[0067] Using the ideal gas state equation PV = nRT, the desorption pressure and temperature per unit time in the period t1 are converted into the desorption gas volume per unit time;

[0068] Adopt Q t =a(t-t0) i +Q 损失 Fit the desorption data in all time periods t1, where a is the fitting coefficient and i is the particle size characteristic value of the coal sample with a fixed particle size;

[0069] The Q obtained by fitting 损失 Converted to the gas loss under standard working conditions Q' 损失 .

[0070] In step S6, the desorbed gas amount is calculated using the following method:

[0071] Using the ideal gas state equation PV = nRT, the change in desorption temperature and pressure during the time period t1 to t3 is converted into the desorption gas volume during the time period t1 to t3

[0072] The amount of desorbed gas Converted to desorption gas volume under standard working conditions

[0073] It should be noted that since the underground temperature of each mine is different, the gas volume is converted to standard operating conditions to facilitate subsequent data comparison and data analysis.

[0074] Example 3

[0075] The coal seam gas content measuring device in Example 1 is used to implement the measuring method provided in Example 2 of the present invention, which specifically includes the following steps:

[0076] (1) Coal sample loading

[0077] The underground measurement personnel need to turn on the device at the sampling site and use the matching explosion-proof mobile phone for Bluetooth pairing. After entering the corresponding sampling information, the device can enter the standby state. Subsequently, the sealing bolt 16 on the pressure balance hole 2.5 is loosened to connect the inside of the tank body 2 with the external environment. Open the clamp 3, separate the tank cover 1 and the tank body 2, and then quickly load the fresh coal dust drilled from the coal mine into a fixed particle size (for example, 1 to 3 mm) of a certain mass into the tank body 2, and immediately cover the tank cover 1 and seal it with the clamp 3. At the same time, tighten the sealing bolt 16 to completely isolate the inside and outside of the tank body 2. Record the time t0 taken from drilling to loading of the coal sample. This is the exposure time of the coal sample. During this period of time, the gas desorbed from the coal sample is not detected by the temperature sensor and pressure sensor. After collecting the exposure time t0 of each coal sample on the explosion-proof mobile phone, click the start desorption button on the matching APP. At this time, the device will automatically collect the desorption pressure and temperature of the coal sample every minute until the measurement process ends.

[0078] (2) Determination of desorption amount of coal sample before crushing

[0079] Quickly load the weighed fresh coal sample with fixed particle size into the device. After clicking the start desorption button, the device will automatically collect the desorption pressure and temperature of the coal sample every minute, and transmit it to the explosion-proof mobile phone in real time. When the collection time reaches t1, the desorption amount measurement process before crushing will automatically end, prompting that the coal sample can be crushed.

[0080] (2) Determination of desorption amount after coal sample crushing

[0081] Start the pneumatic motor and crush the coal sample at a speed of not less than 10000r / min. When more than 95% of the coal samples in the tank have a particle size less than 0.25mm after crushing for t2 time, turn off the pneumatic motor and the crushing is finished. During this process, the device continuously collects the desorption pressure and temperature of the coal sample every minute. When the time t3 has passed and the temperature and pressure have reached stability, the desorption amount measurement process after crushing is automatically terminated. After the device is stable, the pressure P is collected. 终 , Temperature T 终 , prompting that the gas content of the coal sample can be calculated.

[0082] (3) Data processing and calculation

[0083] Data processing and calculation are automatically completed by the built-in APP of the explosion-proof mobile phone. The specific calculation steps are as follows:

[0084] ① After the pressure and temperature in the tank are stable, there is still a part of gas in the coal sample that has not been desorbed, that is, Q 残留 Assuming the atmospheric pressure of the gas content measurement site is P0, the Langmuir formula is used to combine the coal adsorption constants a, b values, and industrial analysis of Q 残留 Perform calculations.

[0085]

[0086] In the formula, a and b are the adsorption constants of coal, A ad is the ash content of the coal sample, M ad is the moisture content of the coal sample, F is the porosity of the coal sample, ARD is the apparent density of the coal sample, and n is the pressure correlation coefficient.

[0087] ② Using the ideal gas state equation PV = nRT, the desorption pressure and temperature per unit time in the t1 period are converted into the desorption gas volume per unit time, using Q t =a(t-t0) i +Q 损失 The desorption data in all t1 periods are fitted, where a is the fitting coefficient and i is the particle size characteristic value of the fixed particle size coal sample. Through experimental investigation, the Q obtained by fitting is 损失 Then, the gas loss Q′ can be obtained by converting under standard working conditions. 损失 .

[0088] ③ Using the ideal gas state equation PV = nRT, the pressure and temperature changes during the period t1 to t3 are used to convert the desorbed gas volume during the entire period. Then, the conversion under standard working conditions can be performed to obtain the desorbed gas volume under constant volume and variable pressure environment.

[0089] ④The gas content of the coal sample is:

[0090] (4) Coal sample unloading

[0091] After the gas content determination is completed, loosen the sealing bolt 16 to release the gas. After the pressure inside and outside the tank body is balanced, open the clamp 3, separate the tank cover 1 and the tank body 2, and rotate the tank body 2 180° so that the tank mouth faces downward. Pour out the coal sample after the determination, clean the detection cavity 2.4, and prepare for the next determination.

[0092] The present invention changes the traditional up-and-down measurement of gas content in the well into a one-stop underground measurement, eliminating the method of measuring the desorbed gas volume by the water drainage gas collection method using a large-volume measuring cylinder, while avoiding the use of high-precision micro-flow electronic flowmeters that are restricted by foreign technology. It only uses easily available high-precision pressure and temperature sensors combined with the isochoric variable pressure environment desorption volume measurement principle to achieve accurate measurement of coal seam gas content, greatly reducing technical difficulty and manufacturing costs.

[0093] The present invention uses the isochoric pressure-variation method to convert the pressure and temperature generated by the gas desorption of the coal sample in a fixed volume space into the desorption amount, replacing the traditional isobaric volume-variation method, such as the water drainage and gas collection method, or the recently emerged electronic flowmeter method. Compared with the water drainage and gas collection method, the structure of the device of the present invention is more compact and does not require the provision of an additional measuring cylinder with a larger volume; compared with the electronic flowmeter method, the present invention does not require the additional attachment of a high-precision micro-flow electronic flowmeter. At the same time, the present invention realizes the integrated design of coal sample desorption, crushing, and measurement functions and structures, and can complete the gas content determination of coal samples in one stop underground, which brings great convenience and efficiency improvement to this work.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A method for determining coal seam gas content based on the isochoric pressure transformation principle, characterized in that: The following steps are involved: The coal sample is placed in a detection device with a known volume and a crushing function, and the desorption pressure and temperature of the coal sample at time t1 are collected after the loading is completed; The coal sample is crushed until more than 95% of the coal sample has a particle size less than 0.25 mm, and the crushing time is t2; The crushed coal sample is left to stand for t3 time until its desorption pressure and temperature reach a stable state, and the desorption pressure and temperature of the coal sample at t3 time are collected; Calculate the residual gas content Q in the coal sample that has not been desorbed 残留 ; The exposure time t0 is from the start of drilling to the completion of loading in the detection device. The gas loss Q′ of the coal sample within the exposure time t0 is obtained by fitting and converting the desorption pressure and temperature data per unit time in the period t1. 损失 ; Calculate the desorbed gas amount of the coal sample during the time period t1 to t3 The total gas content of the coal sample is calculated using the following formula:

2. The method for determining coal seam gas content based on the isochoric pressure transformation principle according to claim 1 is characterized in that: The following formula is used to calculate the residual gas content Q in the coal sample that has not been desorbed 残留 , Where P0 is the atmospheric pressure at the location where the gas content is measured, P 终 is the pressure after the gas desorption of the coal sample reaches a stable state, T 终 is the temperature at which the gas desorption of the coal sample reaches a stable state, a and b are the adsorption constants of the coal, and A ad is the ash content of the coal sample, M ad is the moisture content of the coal sample, F is the porosity of the coal sample, ARD is the apparent density of the coal sample, and n is the pressure correlation coefficient.

3. The method for determining coal seam gas content based on the isochoric pressure transformation principle according to claim 1 is characterized in that: The gas loss Q' is calculated by the following method: 损失 : Using the ideal gas state equation PV = nRT, the desorption pressure and temperature per unit time in the period t1 are converted into the desorption gas volume per unit time; Adopt Q t =a(t-t0) i +Q 损失 Fit the desorption data in all time periods t1, where a is the fitting coefficient and i is the particle size characteristic value of the coal sample with a fixed particle size; The Q obtained by fitting 损失 Converted to the gas loss under standard working conditions Q' 损失 .

4. The method for determining coal seam gas content based on the isochoric pressure transformation principle according to claim 1 is characterized in that: The desorption gas volume is calculated by the following method: Using the ideal gas state equation PV = nRT, the change in desorption temperature and pressure during the time period t1 to t3 is converted into the desorption gas volume during the time period t1 to t3 The amount of desorbed gas Converted to desorption gas volume under standard working conditions 5. A coal seam gas content measuring device based on the isochoric pressure transformation principle, characterized in that: The invention comprises a tank body (2) and a tank cover (1) detachably mounted on the tank body (2); the tank body (2) has a detection cavity (2.4) in it, and the tank cover (1) has a receiving cavity (1.1) in it; wherein: A crushing blade (13) is arranged in the detection cavity (2.4), the coal sample is placed in the detection cavity (2.4), and the crushing blade (13) rotates at a high speed to crush the coal sample; An integrated circuit board (7) is arranged in the accommodating cavity (1.1), and a pressure sensor (4) and a temperature sensor (5) facing the tank body (2) are arranged on the bottom surface of the tank cover (1) to collect pressure and temperature data of the coal sample in the tank before and after crushing; the pressure sensor (4) and the temperature sensor (5) are electrically connected to the integrated circuit board (7), and the desorbed gas amount and the total gas content of the coal sample are calculated through the measurement data of the two.

6. The coal seam gas content measuring device based on the isochoric pressure transformation principle according to claim 5 is characterized in that: The integrated circuit board (7) is provided with a Bluetooth communication module for wireless communication with a mobile terminal; the mobile terminal calculates the desorbed gas amount and the total gas content of the coal sample through the measurement data of the pressure sensor (4) and the temperature sensor (5).

7. The coal seam gas content measuring device based on the isochoric pressure transformation principle according to claim 5 is characterized in that: The pneumatic motor (15) is arranged outside the device, and its output shaft (15.1) is connected to the crushing blade (13) in a rotationally sealed manner with the tank body (2) to drive the crushing blade (13) to rotate at a high speed.

8. The coal seam gas content measuring device based on the isochoric pressure transformation principle according to any one of claims 5 to 7, characterized in that: The lower part of the tank body (2) is connected to an assembly bracket (12), two first connecting shafts (2.2) are relatively arranged on both sides of the lower part of the tank body (2), and two second connecting shafts (2.3) are relatively arranged on both sides of the lower part of the tank body (2) and are located below the first connecting shafts (2.2); The first connecting shaft (2.2) is rotatably mounted on the assembly bracket (12) so that the tank body (2) rotates around the first connecting shaft (2.2); A locking bolt (12.2) is provided on the assembly bracket (12) at a position corresponding to the second connecting shaft (2.3); the locking bolt (12.2) passes through the assembly bracket (12) and is inserted into the second connecting shaft (2.3) to limit the rotation of the tank body (2).

9. The coal seam gas content measuring device based on the isochoric pressure transformation principle according to any one of claims 5 to 7, characterized in that: The bottom surface of the tank cover (1) is provided with a first annular connecting ear (1.2), and the top surface of the tank body (2) is provided with a second connecting ear (2.1) matching with the first connecting ear (1.2), and the first connecting ear (1.2) and the second connecting ear (2.1) are fixed by a clamp (3); wherein a first O-ring (1.3) is embedded in the contact surface between the first connecting ear (1.2) and the second connecting ear (2.1).

10. The coal seam gas content measuring device based on the isochoric pressure transformation principle according to any one of claims 5 to 7, characterized in that: A pressure balancing hole (2.5) is provided on the side wall of the tank body (2); the pressure balancing hole (2.5) is a threaded hole, and a flange (2.6) extending outward along the side wall of the tank body (2) is provided at the hole mouth; a sealing bolt (16) is inserted into the flange (2.5) to isolate the environment inside and outside the tank wall; wherein a second O-ring (16.1) is provided between the sealing bolt (16) and the flange (2.6).

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