Method for measuring amount of retention gas of combustible gas in coal sample

Abstract

The invention provides a method for measuring the retention gas amount of combustible gas in a coal sample. The method comprises the following steps: equally dividing the coal sample into a first sample and a second sample; crushing the second sample to obtain a crushed sample; carrying out degassing treatment on the crushed sample, and removing combustible gas retained in the crushed sample to obtain a degassed sample; respectively taking the first sample and the degassed sample as samples to be measured, measuring the dry basis high calorific value of the sample to be measured in unit mass after the sample to be measured is completely combusted, taking the dry basis high calorific value of the first sample in unit mass as a first unit calorific value, and taking the dry basis high calorific value of the degassed sample in unit mass as a second unit calorific value; calculating a difference value between the first unit heat value and the second unit heat value; and dividing the combustion heat value of the combustible gas in unit volume by the difference value to obtain the volume of the combustible gas in the coal sample in unit mass. According to the method, high-accuracy quantitative analysis on the coal sample retention gas quantity is realized.

Description

Technical Field

[0001] This application relates to the field of coalbed methane exploration and development technology, and in particular to a method for measuring the amount of combustible gas retained in a coal sample. Background Technology

[0002] Accurately determining the gas content of combustible gases in coal seams is the most critical geological parameter for evaluating coalbed methane resource potential, calculating reserves, predicting production capacity, and formulating development plans. Therefore, accurately determining the gas content of combustible gases in coal seams has always been an important goal of technological development in this field.

[0003] Currently, the industry generally follows the national standard "Method for Determination of Coalbed Methane Content GB / T 19559-2021" for determining gas content. This standard method decomposes the total gas content of combustible gases in the coal seam into three parts for measurement and calculation: First, the gas loss during the core sampling and filling process is estimated using models such as the USBM method; second, the amount of naturally desorbed gas released by the coal core under normal pressure is directly measured in a closed desorption tank; finally, the residual gas released is measured after the coal sample is crushed to a certain particle size (e.g., 60 mesh). The total gas content is the sum of the gas contents of the above three parts.

[0004] However, the aforementioned standard methods have the following problems: For medium-deep, low-permeability tight coal seams, the micropores (or "blind pores") in the coal body are extremely well-developed. Even after completing the residual gas measurement specified in the standard, a portion of the gas remains firmly trapped in these micropores and cannot be naturally desorbed; this portion of gas is called "retained gas." Existing standard methods cannot effectively measure retained gas, resulting in a systematically low final total gas content measurement result, which seriously affects the accuracy of subsequent resource assessments. Summary of the Invention

[0005] This application provides a method for measuring the amount of combustible gas retained in a coal sample, which solves the problem that existing methods cannot measure the amount of gas retained in the micropores (blind pores) of the coal sample when measuring the gas content.

[0006] In a first aspect, this application provides a method for measuring the amount of combustible gas retained in a coal sample, the method comprising:

[0007] The coal sample was divided into a first sample and a second sample.

[0008] The second sample is crushed to obtain a crushed sample;

[0009] The crushed sample is degassed to remove the combustible gas remaining in the crushed sample, resulting in a degassed sample.

[0010] The first sample and the degassed sample are respectively used as test samples. The dry basis higher heating value of the test sample per unit mass after complete combustion is measured. The dry basis higher heating value of the first sample per unit mass is used as the first unit heating value, and the dry basis higher heating value of the degassed sample per unit mass is used as the second unit heating value.

[0011] Calculate the difference between the first unit calorific value and the second unit calorific value;

[0012] Divide the difference by the calorific value of the combustible gas per unit volume to obtain the volume of the combustible gas per unit mass of the coal sample.

[0013] In one possible implementation, the step of crushing the second sample to obtain a crushed sample includes:

[0014] The second sample is crushed using a crushing device to obtain the crushed sample.

[0015] In one possible implementation, the step of crushing the second sample to obtain a crushed sample includes:

[0016] The second sample is placed in a low-temperature medium for a first duration.

[0017] The second sample is removed from the low-temperature medium and placed in the high-temperature medium for a second duration to obtain the broken sample.

[0018] In one possible implementation, the degassing treatment of the crushed sample includes:

[0019] The crushed sample is heated to remove the combustible gas remaining in the crushed sample.

[0020] In one possible implementation, the degassing treatment of the crushed sample includes:

[0021] The crushed sample is placed in a vacuum environment for degassing to remove the combustible gas remaining in the crushed sample.

[0022] In one possible implementation, the degassing treatment of the crushed sample includes:

[0023] The broken sample was purged with an inert gas to remove any flammable gas remaining in the broken sample.

[0024] In one possible implementation, the degassing treatment of the crushed sample includes:

[0025] The broken sample is placed in a liquid medium, and ultrasonic waves are applied to the liquid medium to remove the combustible gas remaining in the broken sample.

[0026] In one possible implementation, measuring the dry basis higher heating value of a unit mass of the test sample after complete combustion includes:

[0027] The sample to be tested is divided into multiple sub-samples;

[0028] Measure the dry basis higher calorific value of each of the subsamples;

[0029] Calculate the average dry basis higher heating value of multiple samples;

[0030] Based on the average value, the dry basis higher heating value of the sample per unit mass is determined.

[0031] In one possible implementation, measuring the dry-basis higher calorific value of each of the subsamples includes:

[0032] The subsample was placed in the oxygen bomb of the oxygen bomb calorimeter, and oxygen was introduced into the oxygen bomb.

[0033] Measure the first temperature value of the water surrounding the oxygen bomb;

[0034] Ignite the sub-sample to make it burn completely;

[0035] Measure the second temperature value of the surrounding water body;

[0036] Subtract the first temperature value from the second temperature value to obtain the temperature change value;

[0037] Based on the temperature change value, the mass of the surrounding water body, and the specific heat capacity of the oxygen bomb, the dry basis upper heating value of the subsample is determined.

[0038] In one possible implementation, determining the dry-basis higher heating value of the subsample based on the temperature change value, the mass of the surrounding water body, and the specific heat capacity of the oxygen bomb includes:

[0039] The water content and sulfur content of the sample to be tested were measured.

[0040] The calorific value of the subsample is calculated based on the temperature change value, the mass of the surrounding water body, and the specific heat capacity of the oxygen bomb.

[0041] The calorific value of the bomb is corrected based on the moisture content and the sulfur content to obtain the dry basis higher calorific value of the subsample.

[0042] The method for measuring the amount of combustible gas retained in coal samples provided in this application has the following technical advantages:

[0043] 1. This method increases the specific surface area of ​​coal samples through crushing, disrupting the microporous structure. Combined with degassing, it provides ample escape channels and energy for trapped gases. The synergistic effect of these two methods can release and remove as thoroughly as possible the gas that remains trapped in the "blind holes" after traditional residual gas measurement, thus enabling subsequent comparative tests.

[0044] 2. By measuring and calculating the difference in the higher heating value per unit mass (dry basis) after combustion of two samples, the problem of trace gas volume, which is difficult to measure directly, is transformed into a problem of heat difference that can be accurately measured by modern calorimetry instruments. Using the known calorific value per unit volume of combustible gas for conversion, a highly accurate quantitative analysis of the amount of retained gas is ultimately achieved. Attached Figure Description

[0045] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0046] Figure 1 A schematic flowchart of a method for measuring the amount of combustible gas retained in a coal sample, provided in an embodiment of this application.

[0047] Figure 2 A schematic flowchart of a method for measuring the dry basis higher calorific value of a sample by unit mass provided in an embodiment of this application;

[0048] Figure 3 Table 1, a comparison table of experimental data for gas content testing by combustion method provided in the embodiments of this application;

[0049] Figure 4 Table 2 compares experimental data of gas content testing by combustion method provided for embodiments of this application;

[0050] Figure 5 A comparison table of gas content test results provided for embodiments of this application.

[0051] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0052] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments matching this application. Rather, they are merely examples of apparatuses and methods matching some aspects of this application as detailed in the appended claims.

[0053] To address the problem that existing methods for measuring the gas content of coal samples cannot detect the amount of residual gas in the micropores (blind pores) of the coal sample, the inventors considered dividing a coal sample into two equal parts. One part is crushed to disrupt its micropore structure, and then degassed to remove any residual combustible gases. The difference between the two samples lies in the fact that the untreated sample retains combustible gases, while the crushed and degassed sample has them removed. Since the coal sample is divided into two equal parts, the combustible gas content and other components of the two samples are theoretically identical. Therefore, it is only necessary to measure the difference in calorific value after complete combustion of the two samples. Clearly, since the two samples are identical in composition except for the combustible gas content, the difference in calorific value is due to the removal of combustible gases in the crushed and degassed sample. Therefore, the combustible gas content per unit mass of the untreated coal sample can be deduced from the calorific value difference and used as the overall combustible gas content per unit mass of the coal sample.

[0054] Based on the above ideas, the technical concept of this application is as follows: A coal sample is divided into two equal parts. One part is processed, including crushing the sample and then degassing it to remove any residual combustible gas. Next, the higher heating value per unit mass of the two samples is measured after complete combustion. The difference between the higher heating values ​​per unit mass of the two samples is calculated. This difference is then divided by the calorific value per unit volume of the combustible gas to obtain the volume of combustible gas per unit mass of the coal sample.

[0055] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0056] Figure 1 A schematic flowchart of a method for measuring the amount of combustible gas retained in a coal sample, provided in an embodiment of this application, is shown. The method includes:

[0057] S101. Divide the coal sample into a first sample and a second sample;

[0058] First, it should be noted that the coal sample has been tested for lost gas, natural desorption gas and residual gas in accordance with the national standard GB / T19559-2021 "Method for Determination of Coalbed Methane Content". The coal sample used in this embodiment is the residual coal sample after the above tests are completed, and its initial particle size can be, for example, 60 mesh (about 0.25 mm).

[0059] In this step, it can be done manually using a high-precision electronic analytical balance. Weigh about 40 grams of the residual coal sample mentioned above, and then divide it equally using the laboratory standard cone quartering method: pile the coal sample into a cone, flatten it, and divide it into four equal parts through the center point. Take the two diagonally opposite parts and combine them into the first sample (Group A), about 20 grams; combine the other two parts into the second sample (Group B), about 20 grams. The goal of the equal division is to make the A and B samples as consistent as possible in composition and properties.

[0060] This step can also be completed by an automated sample distribution robot. For example, the robotic arm grabs the total sample from the sample chamber, weighs it using a built-in high-precision balance, and then uses a mechanical device to perform standardized rotational reduction or cutting sample division to ensure the uniformity and accuracy of the sample division, and places the two samples into containers labeled "A" and "B" respectively.

[0061] S102. The second sample is crushed to obtain a crushed sample.

[0062] In this step, the second sample can be crushed using a crushing device to obtain a crushed sample. The crushing device can be, for example, a ball mill, a pulverizer, or an automatic crushing system; this application does not specifically limit its application to this. Specifically, all of the B group sample (the second sample) can be poured into the grinding jar of a small experimental planetary ball mill. An appropriate amount of carbide grinding balls is added to the jar, the machine is sealed, and the machine is started. The rotation speed is set, for example, to 300 rpm, and the grinding time to, for example, 10 minutes. After crushing by the ball mill, all samples are removed and sieved using a 200-mesh (75 micrometers) standard sieve to ensure that the particle size of the crushed sample is all less than 200 mesh.

[0063] Similarly, the above-mentioned crushing process can be implemented by machines. For example, a sample distribution robot transports the sample containers of group B to the feed inlet of an automatic crushing system. The automatic crushing system automatically sucks the samples into a ball mill and completes the crushing according to preset speed and time parameters. After crushing, the automatic crushing system uses an integrated automatic vibrating screen to sieve the samples. Powder that meets the particle size requirements is automatically collected into the next processing tank, while coarse particles are discarded or returned for further crushing.

[0064] Optionally, the second sample is crushed to obtain a crushed sample, including:

[0065] The second sample was placed in a low-temperature medium for a first duration.

[0066] The second sample was removed from the low-temperature medium and placed in the high-temperature medium for a second duration to obtain the broken sample.

[0067] It should be noted that, since coal is a brittle and porous medium, the coefficients of thermal expansion of its different mineral components vary. When a coal sample is rapidly cooled (e.g., immersed in liquid nitrogen), it contracts as a whole and generates tensile stress inside. Subsequently, when it is rapidly heated (e.g., placed in a high-temperature environment), the exterior of the coal sample expands rapidly while the interior heats up later, generating huge thermal stress. This drastic temperature change caused by alternating heating and cooling leads to the concentration of thermal stress at the micro-defects and grain boundaries of the coal sample, exceeding its tensile strength, thereby causing the sample to fracture and achieve the effect of breakage.

[0068] Therefore, based on the above principles, the crushing process can be carried out through the following steps:

[0069] Step 1 (Low-temperature embrittlement treatment):

[0070] In an open Dewar flask or a dedicated cryogenic treatment container, inject sufficient liquid nitrogen (the cryogenic medium) at a constant temperature of -196°C. Next, place the second sample (approximately 20 grams, 60-mesh particle size) separated from S101 into a porous material (such as a fine metal mesh bag) or a thin-walled metal container with good thermal conductivity (such as a small aluminum box) to ensure sufficient and rapid contact between the second sample and the cryogenic medium. Then, using pre-cooled tweezers or clamps, hold the container and quickly and completely immerse it in the liquid nitrogen. Start timing at this point; for example, the initial time can be set to 30 minutes. During this process, the second sample must remain completely submerged in the cryogenic medium to allow the entire sample to fully freeze and embrittle.

[0071] Step Two (High-Temperature Thermal Shock Treatment):

[0072] After the first duration is reached, the container containing the deep-frozen second sample is quickly removed from the liquid nitrogen using clamps. Immediately afterward, the container is transferred and completely immersed in a preheated high-temperature medium at a constant temperature of 105°C. This high-temperature medium can be a constant-temperature oil bath (such as silicone oil) or a fluidized sand bath. Timing begins at this point; for example, the second duration can be set to 10 minutes. During this process, the heat from the high-temperature medium is rapidly transferred to the ultra-low-temperature sample, triggering a severe thermal shock.

[0073] Step 3: After reaching the second time interval, remove the second sample container from the high-temperature medium. If an oil bath was used in Step 2, the second sample, along with its container, needs to be placed in a beaker containing an organic solvent (such as petroleum ether) for ultrasonic cleaning to remove oil stains adhering to the surface of the coal sample. After cleaning, separate the coal sample and solvent by filtration. If a sand bath or a non-polluting medium is used, the cleaning step can be omitted, and proceed directly to the next step.

[0074] Drying: Spread the treated second sample evenly in a petri dish and place it in a 60°C forced-air drying oven for 2 hours to completely remove any possible residual solvent or moisture.

[0075] Finally, since the dried coal sample will become very brittle, it can be gently poured onto the top layer of a standard sieve and vibrated for 5 minutes using a vibrating sieve machine, or gently shaken manually. The powder that passes through a 200-mesh (75-micron) sieve is collected; this portion is the required crushed sample. Larger particles that do not pass through the sieve can be discarded or returned to step one for reprocessing.

[0076] The above-mentioned crushing and processing method has the following technical effects:

[0077] 1. This method does not rely on preventing the impact and friction between the metal grinding media and the second sample. Therefore, it can avoid the mixing of metal abrasive particles (such as iron, tungsten, cobalt, etc.) into the coal sample, prevent the combustion of foreign metal particles from introducing additional heat, and avoid errors in the calorific value calculation. This improves the accuracy and reliability of the residual gas volume calculation.

[0078] 2. Compared with mechanical grinding and crushing, this method can more effectively open closed or poorly connected nanoscale micropores, creating favorable conditions for the next degassing process, and allowing the combustible gases trapped inside to be released more fully and quickly.

[0079] S103. Degas the crushed sample to remove the combustible gas remaining in the crushed sample and obtain the degassed sample.

[0080] In this step, the crushed sample can be heated to remove any residual combustible gases. Specifically, the crushed sample (Group B) can be evenly spread in a ceramic boat, then placed in a forced-air drying oven. The oven door is then closed, the heating temperature is set to 105°C, and the forced-air function is activated to accelerate gas dissipation. Heating continues for 60 minutes. After heating, the sample is allowed to cool slightly inside the oven before being quickly transferred to a desiccator for storage to prevent moisture absorption. This yields the degassed sample.

[0081] The heating steps described above can be implemented by machine, for example, by transporting a container containing the crushed sample to a programmable temperature-controlled heating device (such as an automated oven) via a conveyor belt. A robotic arm automatically opens the container lid and places the container into the heating chamber. The heating device then heats and blows air according to a preset program (105°C, 60 minutes). After processing, the sample is automatically transferred to a sealed cooling chamber.

[0082] S104. The first sample and the degassed sample are respectively used as test samples. After the test samples are completely burned, the dry basis higher heating value of a unit mass of the test sample is measured. The dry basis higher heating value of a unit mass of the first sample is used as the first unit heating value, and the dry basis higher heating value of a unit mass of the degassed sample is used as the second unit heating value.

[0083] In this step, this application provides a fully automated calorimetric system for measuring the dry-basis higher heating value of a unit mass of a sample. The system may include a precision balance, a robotic arm for grasping the sample and placing the oxygen bomb, a high-pressure oxygen filling system, an ignition circuit, a high-precision temperature sensor, and an embedded computer. The embedded computer controls all hardware to work collaboratively and has a built-in algorithm to automatically perform a correction calculation from the bomb calorimeter value to the dry-basis higher heating value based on the measured temperature rise, the known water equivalent (including the heat capacity of water and the oxygen bomb), and the pre-input or measured sample moisture and sulfur content. Finally, the dry-basis higher heating value of a unit mass of the sample is displayed on the screen.

[0084] S105. Calculate the difference between the first unit calorific value and the second unit calorific value;

[0085] In this step, the embedded computer of the fully automatic heating system can communicate with the host computer. The host computer automatically reads the first unit calorific value and the second unit calorific value, and performs a subtraction operation. The difference is equal to the first unit calorific value minus the second unit calorific value. In this embodiment, the unit of the difference can be J / g.

[0086] S106. Divide the difference by the calorific value of the combustible gas per unit volume to obtain the volume of combustible gas per unit mass of coal sample.

[0087] In this step, the host computer can access a pre-stored constant in the database, namely the calorific value of a unit volume of combustible gas. In this embodiment, the combustible gas is methane, and its calorific value per unit volume is:

[0088]

[0089] Subsequently, the host computer can perform the division operation:

[0090]

[0091] in, The difference calculated for S105, This refers to the volume (in milliliters) of retained gas contained in a unit mass of coal sample (grams).

[0092] For example, if:

[0093]

[0094] but:

[0095]

[0096] The calculation results can be converted into commonly used methods in the oil and gas field. unit.

[0097] By using the above method, the amount of gas retained in a unit mass of coal sample can be measured. Then, by adding this value to the total gas content measured by the national standard, a more complete and accurate total gas content data of coalbed methane can be obtained.

[0098] The above method for measuring the amount of combustible gas retained in coal samples has the following technical advantages:

[0099] 1. This method increases the specific surface area of ​​coal samples through crushing, disrupting the microporous structure. Combined with degassing, it provides ample escape channels and energy for trapped gases. The synergistic effect of these two methods can release and remove as thoroughly as possible the gas that remains trapped in the "blind holes" after traditional residual gas measurement, thus enabling subsequent comparative tests.

[0100] 2. By measuring and calculating the difference in the higher heating value per unit mass (dry basis) after combustion of two samples, the problem of trace gas volume, which is difficult to measure directly, is transformed into a problem of heat difference that can be accurately measured by modern calorimetry instruments. Using the known calorific value per unit volume of combustible gas for conversion, a highly accurate quantitative analysis of the amount of retained gas is ultimately achieved.

[0101] This embodiment presents several other optional degassing methods, which can be used alone or in combination with the above-described heating degassing method:

[0102] 1. Place the crushed sample in a vacuum environment to degas it in order to remove the combustible gas remaining in the crushed sample.

[0103] This degassing method requires a vacuum degassing device, which may consist of the following components: one or more sample chambers (e.g., made of stainless steel, pressure-resistant, and with smooth inner walls), a vacuum pump (capable of generating a high vacuum), a vacuum gauge (for accurate pressure monitoring), valves (for controlling the gas passage), and a gas collection unit (such as a gas collection bag or gas meter) for collecting the degassed gas. All components are connected via vacuum tubing to ensure the airtightness of the device.

[0104] The specific degassing process may include the following steps:

[0105] 1. Carefully transfer all or a representative portion of the second sample (Group B) that has undergone crushing treatment (e.g., 200 mesh) to a clean, dry sample chamber. To increase degassing efficiency, the sample can be spread into a thin layer in the sample chamber, avoiding excessive accumulation. Then, tightly close the sample chamber, ensuring all valves are closed.

[0106] 2. Slowly open the valve connecting the sample chamber and the vacuum pump, start the vacuum pump. As the pressure in the sample chamber decreases, the gas in the pores of the coal sample begins to desorb and be discharged.

[0107] 3. Once the sample chamber pressure has dropped to a lower level, maintain the vacuum pump running for a period of time (e.g., continuously evacuate for 2 to 4 hours). For more thorough degassing, the sample chamber can be gently heated, for example, by placing it in a thermostat controlled at 60°C ± 5°C. The heat provides additional kinetic energy to the gas molecules, helping them overcome their adsorption barriers in the micropores. This, combined with the vacuum negative pressure, accelerates the degassing process.

[0108] The above steps can be continuously monitored by a vacuum gauge to check the pressure inside the sample chamber. When the pressure drops to a stable low value and does not decrease significantly for a long time, the degassing can be considered to be basically completed.

[0109] After degassing is complete, first close the valve connecting the sample chamber and the vacuum pump, then slowly fill the system with high-purity inert gas (such as nitrogen or argon) until atmospheric pressure is reached. The purpose of filling with inert gas is to prevent the degassed coal sample from coming into contact with air when it is removed, thus avoiding oxidation or adsorption of moisture from the air.

[0110] Next, open the sample chamber and quickly transfer the degassed coal sample to a sealed container or desiccator filled with inert gas for storage, in preparation for subsequent calorific value measurement. This sample is the degassed sample.

[0111] The above-mentioned vacuum degassing solution has the following technical effects:

[0112] 1. Because a vacuum environment can significantly reduce gas partial pressure and create a strong concentration gradient, it can effectively remove gases that are difficult to escape by heating alone and are strongly adsorbed in the micropores ("blind pores"). Compared with atmospheric pressure heating, the combination of "vacuum + micro-heating" can achieve the same or even better degassing effect at a lower temperature, thus ensuring that the combustible gas content of Group B samples is close to zero. This makes the difference in calorific value between Group B and Group A samples more accurately reflect the amount of retained gas, ultimately improving the accuracy of retained gas measurement.

[0113] 2. By controlling the vacuum level and auxiliary heating temperature (e.g., 60°C), the risk of pyrolysis or oxidative deterioration of the coal sample itself due to high temperature (e.g., 105°C or higher) can be avoided, ensuring that the degassing of Group B sample is only the externally adsorbed hydrocarbon gas, while the chemical properties of its solid matrix are consistent with those of Group A sample, thus meeting the most critical prerequisite of "same properties except for gas" in the calorific value comparison experiment.

[0114] To automate the aforementioned vacuum degassing process, this embodiment provides a fully automated vacuum degassing system, which may include, for example, the following modules:

[0115] Robotic transfer module: It can use a multi-axis robotic arm to receive containers containing crushed samples from upstream and place them precisely at the workstation in the sample chamber.

[0116] Multi-station sample chamber: The system can be equipped with multiple sample chambers to process multiple samples in parallel, and each sample chamber can be equipped with an automatic opening and closing cover mechanism and a pneumatic sealing device.

[0117] Vacuum and temperature control module: integrates a high vacuum pump set, precision solenoid valve, vacuum sensor and a programmable temperature heating jacket surrounding the sample chamber. All components in this module can be managed by a central controller.

[0118] Gas management module: includes inert gas source, mass flow controller and corresponding valves, used to automatically complete the inert gas filling when the air is broken.

[0119] Control module: including programmable logic controller (PLC) and human-machine interface (HMI): serving as the system brain. Operators set degassing process parameters, such as target vacuum level, degassing time, and heating temperature, through the HMI screen.

[0120] The automated execution process for the above vacuum degassing treatment is as follows:

[0121] 1. The robotic arm transports the sample container to the designated workstation, the sample chamber automatically opens, the robotic arm pours the sample into the chamber, and then the chamber lid automatically closes.

[0122] 2. The PLC opens the corresponding valves in sequence according to the preset program and starts the vacuum pump. During this process, the system automatically adjusts the pumping process based on the feedback from the vacuum sensor.

[0123] 3. Once the set vacuum level is reached, start the heating mantle to heat the sample chamber and maintain it at the set temperature.

[0124] 4. The system monitors pressure and temperature in real time. When the set degassing time is reached and the pressure stabilizes, the degassing is considered complete.

[0125] Subsequently, the PLC closes the vacuum line valve and opens the inert gas line valve according to the program, filling the system with inert gas to atmospheric pressure at the set flow rate and time.

[0126] Finally, the sample chamber cover opens automatically, and the robotic arm removes the degassed sample.

[0127] 2. Use inert gas to purge the broken sample to remove any flammable gases remaining in the broken sample.

[0128] The specific implementation process of this method is as follows:

[0129] 1. Prepare the purging apparatus. Specifically, take a pressure-resistant glass or metal sample tube (such as a quartz tube or stainless steel tube), with an inlet at one end and an outlet at the other. The outlet can be connected to a gas flow meter or directly into a fume hood. Place a porous filter plate or fill it with a small amount of quartz wool in the middle of the sample tube as a support for the sample bed. Next, transfer all and evenly the crushed sample (Group B, 200-mesh powder) obtained in step S102 onto the filter plate in the sample tube, and gently compact it to form a loose powder bed, ensuring that the gas can pass through evenly.

[0130] 2. Connection and sealing steps: Specifically, connect the sample tube's inlet to a high-purity inert gas source (such as a high-purity nitrogen or argon cylinder) via a pressure-resistant pipeline. Then, sequentially connect a pressure reducing valve, a gas purifier (to remove any residual oxygen and moisture from the gas), and a precision flow control valve to the gas path. Finally, seal all interfaces of the sample tube to ensure good system airtightness.

[0131] 3. Purging and degassing: Specifically, slowly open the main valve of the inert gas cylinder. Adjust and stabilize the gas flow rate within a low range, such as 50 ± 10 ml / min, using the pressure reducing valve and precision flow control valve. Too low a flow rate will result in low degassing efficiency, while too high a flow rate may scatter the sample.

[0132] Next, purging begins. During purging, inert gas flows through the pores of the sample powder, removing trapped combustible gases (mainly methane) through the following two main mechanisms:

[0133] Dilution and carrying effect: The flowing inert gas continuously dilutes the concentration of combustible gas in the pores of the sample, forming a concentration gradient, which promotes the desorption and diffusion of gas from the coal matrix and is carried away by the gas flow.

[0134] Pressure reduction effect: The continuous introduction of inert gas creates a weak dynamic flow pressure environment in the local sample bed, which helps to overcome the adsorption force of gas in the micropores.

[0135] It should be noted that the purging process needs to last for a sufficiently long time to ensure complete degassing. For example, the purging time can be set to 4 to 6 hours. For denser coal samples, the purging time can be appropriately extended.

[0136] 4. After purging, transfer the sample. Specifically, after the predetermined purging time has elapsed, turn off the inert gas supply. Then, under an inert gas atmosphere, transfer the degassed sample from the sample tube to a pre-weighed, sealable sample bottle (such as a glass bottle with a sealing gasket). Immediately tighten the cap to prevent air from entering and the sample from absorbing moisture. The degassed sample is now ready for subsequent calorific value determination.

[0137] The above-mentioned purging and degassing treatment method has the following technical effects:

[0138] 1. The entire degassing process is carried out at or near room temperature, which avoids the risk of low-temperature oxidation or thermal deterioration of coal samples that may be caused by heating methods (such as 105°C), and improves the reliability of the measurement of retained gas volume.

[0139] 2. The flowing inert gas can provide a continuous and gentle desorption force, which can effectively displace the gas trapped in the micropores. It is especially effective for fine powder samples with a large specific surface area. Compared with the "boiling" effect that vacuum degassing may produce on some fragile coal structures, the purging degassing method is gentler.

[0140] 3. The flammable gas purged out is diluted with a large amount of inert gas before being released, which greatly reduces the risk of combustion or explosion and is safer than directly heating the sample.

[0141] To automate the above-mentioned purging and degassing process, this embodiment provides a fully automatic purging and degassing system, which may include, for example, the following modules:

[0142] Sample tube loading position: The robotic arm picks up the broken sample canister (designed with a standard interface that can automatically dock with the purge line) and places it into the purge station.

[0143] Automatic connector: Under program control, it can automatically seal and connect to the inlet and outlet of the sample container via pneumatic means.

[0144] Integrated gas supply and control system: The system can be equipped with a built-in high-purity inert gas source and a mass flow controller to accurately set and control the flow rate and total purging volume of the purging gas.

[0145] Timing controller: The programmable logic controller sets the timing of the entire purging process, including pre-purging (cleaning the pipeline), formal purging, purging duration, etc.

[0146] The fully automatic purging and degassing system operates as follows:

[0147] 1. Loading: The robotic arm transports the standard container containing the crushed samples of Group B to the purging station.

[0148] 2. Sealing and purging: The automatic connector automatically descends and seals with the container interface. Then, the system automatically purges according to preset parameters (e.g., nitrogen, flow rate 50 mL / min, time 300 minutes).

[0149] 3. Sample transfer: After purging, the system can briefly fill the container with inert gas to create positive pressure, and then the robotic arm will remove the container and transport it to an inert atmosphere glove box.

[0150] 4. Sealed packaging: In the anhydrous and oxygen-free environment of the glove box, another robotic arm opens the container, dispenses the degassed sample into the final analytical sample bottle and seals it to obtain the degassed sample.

[0151] 3. Place the crushed sample in a liquid medium and apply ultrasonic waves to the liquid medium to remove the flammable gas remaining in the crushed sample.

[0152] First, it should be noted that, considering the special characteristics of coal sample degassing, the selection and preparation of the liquid medium in this method must meet the following conditions:

[0153] 1. Chemically inert: It does not react chemically with coal samples or residual combustible gases (mainly methane).

[0154] 2. Low boiling point and easy to volatilize: This makes it easy to completely remove from the coal sample in subsequent steps, avoiding residues that may affect the calorific value measurement.

[0155] 3. Low viscosity: This is beneficial for the transmission of ultrasonic energy and the generation of cavitation effect.

[0156] 4. It has good ultrasonic wave conduction properties.

[0157] Taking the above conditions into consideration, the liquid medium used in this embodiment is high-purity n-hexane or methanol. These two liquid media can meet the above requirements and are easily removed by evaporation. Since other possible liquid media may exist, this application does not specifically limit the liquid medium.

[0158] The ultrasonic degassing process is described below:

[0159] Step 1: Pour the selected liquid medium into an ultrasonic treatment tank made of a chemically inert material (such as glass or 316L stainless steel). The volume of the liquid medium should be sufficient to completely submerge the coal sample to be added later.

[0160] Step 2: Transfer all of the second sample (Group B) that has been crushed (e.g., 200 mesh) into a porous sample basket made of corrosion-resistant metal mesh (e.g., stainless steel sieve), which allows the liquid to flow freely while effectively containing fine coal dust.

[0161] Subsequently, the sample basket containing the coal sample was completely immersed in the liquid medium to ensure that the coal sample was fully wetted.

[0162] Next, ultrasonic treatment is performed. Specifically, a laboratory ultrasonic cleaner or ultrasonic cell disruptor can be used. The parameters of the ultrasonic cleaner or ultrasonic cell disruptor can be set as follows: In terms of frequency, choose a medium to low frequency (such as 20-40kHz). The ultrasonic cavitation effect is stronger in this frequency range, which is conducive to breaking the liquid-solid interface and promoting gas desorption; in terms of power, a moderate power density (such as 50-100W / L) can be set according to the volume of the treatment tank and the amount of sample to avoid excessive sample crushing or a sharp increase in temperature; in terms of treatment time, the treatment time can be set to 20-30 minutes, and an intermittent mode (such as working for 5 seconds and pausing for 2 seconds) can be used during the process to prevent the liquid from overheating.

[0163] Meanwhile, during the ultrasonic degassing process, the ultrasonic treatment tank can be placed in an ice-water bath or an ultrasonic tank with a cooling jacket can be used to maintain the temperature at 25-30°C to prevent solvent evaporation and changes in gas solubility.

[0164] Step 3: After ultrasonic treatment, remove the entire sample basket from the liquid medium and allow it to stand for a period of time, allowing most of the attached liquid to flow back into the treatment tank. Optionally, a small amount of fresh, identical solvent can be used to quickly rinse the sample basket to replace any old solvent that may contain dissolved gases.

[0165] Step 4: Finally, dry the sample. Specifically, transfer the sample basket containing the wet coal sample to a vacuum drying oven and dry it for 2-4 hours, or until the sample reaches a constant weight.

[0166] The coal sample that has undergone the above treatment is the degassed sample.

[0167] The above-mentioned ultrasonic degassing treatment method has the following technical effects:

[0168] 1. The cavitation effect generated by ultrasound in liquids creates countless tiny bubbles that violently collapse, producing strong localized shock waves and microjets. This effectively scours and tears the microporous structure of coal, forcing gas trapped in deep blind pores to desorb and diffuse into the liquid, eventually escaping. Its degassing depth and uniformity are superior to static heating methods.

[0169] 2. For some coal samples containing easily pyrolytic organic matter, prolonged heating at 105°C may pose a risk of slightly altering the coal's quality. This method, performed at room temperature or low temperature, can preserve the original physicochemical properties of the coal sample.

[0170] To automate the above-mentioned ultrasonic degassing process, this application provides an integrated ultrasonic degassing system, which can be implemented in the following way:

[0171] 1. The robotic arm receives the container containing the broken sample and pours it into a special porous sample basket. Another robotic arm grabs the sample basket and accurately immerses it into an ultrasonic treatment tank with a pre-set liquid medium.

[0172] 2. The workstation's control system (PLC or industrial PC) automatically starts the ultrasonic generator according to the preset formula (such as media type, ultrasonic power, frequency, time, and temperature). A temperature sensor integrated into the treatment tank monitors the temperature in real time and automatically adjusts the temperature through the cooling system.

[0173] 3. After processing, the robotic arm lifts the sample basket above the liquid surface and drips it briefly. Then, the entire sample basket is transferred to the connected vacuum drying chamber. The robotic arm seals the chamber door, and the system automatically starts the vacuum pump and heating device to execute the drying procedure.

[0174] 4. After drying, the system releases the vacuum, the robotic arm removes the sample basket, and the processed degassed sample is vibrated and poured into the designated container.

[0175] Figure 2 This is a schematic flowchart of a method for measuring the dry basis higher calorific value of a unit mass of a sample to be tested, as provided in an embodiment of this application. Figure 2 As shown, the higher heating value per unit mass of the test sample on a dry basis is measured after complete combustion, including:

[0176] S201. Divide the sample to be tested into multiple subsamples;

[0177] Taking sample A (sample 1) as an example, firstly, the total mass of sample A can be weighed using an electronic balance, for example, 20.000 grams. Then, using a small spatula and the balance, through repeated weighing and minor adjustments, it is precisely divided into 10 subsamples, each with a target mass of 2.000 grams. In practice, the mass of each subsample may fluctuate between 1.950 grams and 2.050 grams, but the precise mass of each subsample must be recorded. (in =1 to 10).

[0178] In this step, each subsample can be wrapped separately with aluminum foil or ashless filter paper and numbered for later use. The same procedure should be performed on group B samples (samples after degassing).

[0179] S202. Measure the dry basis higher calorific value of each sample.

[0180] Optionally, an oxygen bomb calorimeter can be used to measure the dry-basis higher heating value of each sample. A brief introduction to the oxygen bomb calorimeter follows:

[0181] The oxygen bomb calorimeter mainly includes the following components:

[0182] 1. Oxygen Bomb: The core component of an oxygen bomb calorimeter, it is a thick-walled cylindrical container made of corrosion-resistant, high-pressure-resistant stainless steel. It includes a crucible for placing the sample, an ignition electrode (usually connected to a metal ignition wire of known calorific value) as the ignition source, an inlet valve for filling the inner cavity with high-pressure oxygen, and a vent valve for discharging combustion exhaust gases. The oxygen bomb cover is sealed with a robust nut to ensure safe combustion under high pressure.

[0183] 2. Inner cylinder (water tank): Made of metal, used to hold a certain amount of distilled water and to hold the oxygen bomb. A precision temperature sensor (such as a platinum resistance thermometer) is installed on the inner cylinder wall.

[0184] 3. Outer cylinder (jacket): Encloses the inner cylinder and is filled with water. Depending on the type (e.g., insulated or constant temperature), the outer cylinder provides a stable temperature environment and reduces heat exchange between the inner cylinder and the outside environment. In this embodiment, we assume the use of a constant temperature calorimeter that requires manual adjustment of the water temperature in the outer cylinder.

[0185] 4. Stirrer: Used to agitate the water in the inner cylinder, so that the water temperature is quickly and evenly distributed, ensuring the accuracy of temperature measurement.

[0186] 5. Control system: including temperature measurement circuit, ignition device, timer, and computer or processor for data recording and calculation.

[0187] The measurement principle of the oxygen bomb calorimeter is as follows:

[0188] The basic principle of an oxygen bomb calorimeter is the law of conservation of energy. A sample of known mass is completely burned within an oxygen bomb filled with high-pressure oxygen. The released heat is absorbed by the entire calorimetric system (including the inner water chamber, the oxygen bomb, the stirrer, and the inner cylinder), manifesting as an increase in the system's temperature. By accurately measuring this temperature change and multiplying it by the total heat capacity of the entire calorimetric system (i.e., the water equivalent, representing the heat required to raise the temperature by 1 degree Celsius), the total heat released by the sample combustion can be calculated. After correction, this heat value yields the bomb calorific value and the higher heating value (dry basis) of the sample.

[0189] Therefore, measuring the dry basis higher heating value of each sample includes:

[0190] Step 1: Place the subsample in the oxygen bomb of the oxygen bomb calorimeter and fill the oxygen bomb with oxygen.

[0191] Specifically, take a sample from group A, numbered 1, and place it in the crucible of the oxygen bomb. Then, connect the two ends of a known-mass ignition wire to the two electrodes of the oxygen bomb, ensuring good contact between the ignition wire and the sample. Tighten the oxygen bomb cap and fill the oxygen bomb with oxygen of 99.5% purity or higher through the conduit, maintaining a pressure of 2.8~3.0 MPa for 30 seconds to ensure complete oxygen replacement.

[0192] Step 2: Measure the first temperature value of the water surrounding the oxygen bomb;

[0193] Specifically, accurately measure a certain volume (e.g., 2000 mL) of distilled water into the clean inner cylinder. The water temperature should be pre-adjusted to be 0.5°C to 1.0°C lower than the water temperature in the outer cylinder. Then, carefully place the oxygen bomb, already filled with oxygen, into the inner cylinder and close the calorimeter lid. Start the stirrer and stir for 5 to 10 minutes to allow the system to reach thermal equilibrium. When the temperature change stabilizes, record the initial temperature. .

[0194] Step 3: Ignite the subsample and allow it to burn completely;

[0195] Specifically, pressing the ignition button connects the circuit, causing the ignition wire to melt rapidly and generate high temperature to ignite the sample. The sample then burns violently in high-pressure oxygen, releasing heat.

[0196] Step 4: Measure the second temperature value of the surrounding water body;

[0197] After combustion, heat is transferred through the oxygen bomb wall to the water in the inner cylinder, and the water temperature begins to rise. Continue stirring and monitoring the temperature until it reaches its highest point and begins to steadily decrease; record the final temperature at this point. .

[0198] Step 5: Subtract the first temperature value from the second temperature value to obtain the temperature change value;

[0199] Specifically, the temperature change is calculated using the following formula:

[0200]

[0201] Step 6: Determine the dry basis upper heating value of the subsample based on the temperature change value, the mass of the surrounding water body, and the specific heat capacity of the oxygen bomb.

[0202] In this step, based on the temperature change, the mass of the surrounding water body, and the specific heat capacity of the oxygen bomb, the dry-basis higher heating value of the subsample is determined, including:

[0203] Measure the moisture content and sulfur content of the sample to be tested;

[0204] The calorific value of the subsample is calculated based on the temperature change, the mass of the surrounding water, and the specific heat capacity of the oxygen bomb.

[0205] The calorific value of the bomb was corrected based on the moisture content and sulfur content to obtain the dry basis upper heating value of the subsample.

[0206] Specifically, first calculate the heat value of the cartridge:

[0207] calorific value It is the calorific value measured inside the oxygen bomb, calculated directly from the temperature rise. The calculation formula is:

[0208]

[0209] in:

[0210] The mass of the water in the inner cylinder;

[0211] The specific heat capacity of the water in the inner cylinder;

[0212] It is the total heat capacity (i.e., water equivalent) of components such as the oxygen bomb, inner cylinder, stirrer, and thermometer, which needs to be calibrated by burning a reference substance with a known calorific value (such as benzoic acid);

[0213] The heat generated by the burning ignition wire is a known value.

[0214] For the first The quality of the molecular sample.

[0215] Since the calorific value of the bomb includes the heat effect of sulfur and nitrogen generating acid and releasing heat in the oxygen bomb, as well as the effect of water evaporation absorbing heat, it needs to be corrected.

[0216] First, before step S201, the water content of samples A and B is measured to obtain the water content of the sample to be tested. ) and sulfur content ( Then the following standard formula can be used for correction:

[0217]

[0218] in:

[0219] For the first Higher heating value on a dry basis for molecular samples;

[0220] The calorific value coefficient (J / g) is corrected for acid by 1% sulfur.

[0221] The correction factor for the heat of nitric acid formation is typically 0.0010 or 0.0015, depending on the fuel type.

[0222] Repeat the above steps to measure all 10 subsamples of Group A and Group B in sequence, and obtain the dry basis upper heating value of the 10 subsamples of Group A and the dry basis upper heating value of the 10 subsamples of Group B, respectively.

[0223] S203. Calculate the average dry basis higher heating value of the multi-component sample;

[0224] In this step, the arithmetic mean of the 10 dry basis higher calorific values ​​of Group A and Group B is calculated. By calculating the average value, the random error that may exist in a single measurement is offset, and a value that is more representative of the true calorific value of the sample is obtained.

[0225] S204. Determine the dry basis higher heating value of a unit mass of the sample to be tested based on the average value.

[0226] The above average value is the dry basis higher heating value per unit mass (per gram) of sample.

[0227] The following is a case study of a possible implementation method of this application:

[0228] A certain well is a pressure-maintaining coring well on the eastern edge of the Ordos Basin. Gas content testing was conducted according to production needs, and the pressure-maintaining gas content of the sampled well section was measured to be 1.42 kJ / kg according to the relevant standards. Gas loss: 8.64 Natural desorption volume: 14.88 Residual gas volume: 0.36 The original calculation for the gas content of this layer was 29.24 m3 / t.

[0229] By applying the method of this invention, the calorific value is determined using an oxygen bomb calorimeter, and the accurate gas content of the coal sample is further obtained.

[0230] (1) Rock sample pretreatment

[0231] Take 30-50g of coal sample for laboratory residual gas testing, divide it into two roughly equal parts, each weighing 15-25g, and label them A and B. Part A remains in its original state, while part B is shredded, that is, the original 60-mesh particle size of about 0.25mm is shredded into 200-mesh particle size of about 0.075mm. The moisture content, sulfur content and other relevant data of the two coal samples A and B are measured respectively.

[0232] (2) Determination of calorific value

[0233] Take 10g of rock samples from groups A and B, and divide each group into 10 equal subsamples, each with a mass of 1g. Use an oxygen bomb calorimeter (oxygen bomb tester) to measure the temperature change Δt of each of the 20 rock samples before and after combustion (from t1 to t2, Δt = t2 - t1), and determine and record the calorific value of each subsample. Figure 3 Table 1, a comparison table of experimental data for gas content testing using the combustion method provided in the embodiments of this application, Figure 3 The results of calorific value determination for groups A and B are shown.

[0234] (3) Determination of gas content

[0235] Since both groups of rock samples A and B were coal samples whose gas content was tested according to the standard, the fundamental difference lies in the fact that group A coal samples were tested without any treatment after the original experiment, while group B coal samples underwent further crushing and degassing at 105℃. It can be assumed that, apart from the difference in particle size, the only difference between the two groups is that group A rock samples contained a certain amount of methane gas, while group B, after crushing and heating, contained almost no combustible gas. Comparing the difference in the dry basis upper heating value of 10 rock samples from each group, it is believed that this difference in heating value originates solely from the methane gas contained in group A coal samples.

[0236] Figure 4 Table 2 provides a comparison of experimental data on gas content testing using the combustion method in the embodiments of this application. Figure 4 The figure shows the difference in calorific value between the untreated group A sample and the group B sample that underwent crushing, heating and degassing treatment.

[0237] Comparing the two sets of test results, it can be seen that after being crushed to 200 mesh, the calorific value of the crushed and degassed sample is lower than that of the directly measured sample. The average difference in dry basis calorific value between the two groups of coal samples is 279.9 J / g. Obviously, these calorific values ​​of the coal sample in group A come from the methane gas it contains.

[0238] The calorific value of methane gas is 40.02 J / mL (with liquid water as a product), indicating that there is approximately 6.99 mL / g of gas per gram of coal sample. Therefore, the gas content of the sampling section of a certain well was changed from the originally measured 29.24. Corrected to 36.23 The increase was 23.9%.

[0239] Figure 5 This is a comparison table of gas content test results provided in the embodiments of this application. Figure 5 The figure shows the amount of gas retained and the total gas content of the well sample after testing according to one possible implementation of this application.

[0240] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method for measuring the amount of combustible gas retained in a coal sample, characterized in that, The method includes: The coal sample was divided into a first sample and a second sample. The second sample is crushed to obtain a crushed sample; The crushed sample is degassed to remove the combustible gas remaining in the crushed sample, resulting in a degassed sample. The first sample and the degassed sample are respectively used as test samples. The dry basis higher heating value of the test sample per unit mass after complete combustion is measured. The dry basis higher heating value of the first sample per unit mass is used as the first unit heating value, and the dry basis higher heating value of the degassed sample per unit mass is used as the second unit heating value. Calculate the difference between the first unit calorific value and the second unit calorific value; Divide the difference by the calorific value of the combustible gas per unit volume to obtain the volume of the combustible gas per unit mass of the coal sample.

2. The method according to claim 1, characterized in that, The step of crushing the second sample to obtain a crushed sample includes: The second sample is crushed using a crushing device to obtain the crushed sample.

3. The method according to claim 1, characterized in that, The step of crushing the second sample to obtain a crushed sample includes: The second sample is placed in a low-temperature medium for a first duration. The second sample is removed from the low-temperature medium and placed in the high-temperature medium for a second duration to obtain the broken sample.

4. The method according to claim 1, characterized in that, The degassing treatment of the crushed sample includes: The crushed sample is heated to remove the combustible gas remaining in the crushed sample.

5. The method according to any one of claims 1-4, characterized in that, The degassing treatment of the crushed sample includes: The crushed sample is placed in a vacuum environment for degassing to remove the combustible gas remaining in the crushed sample.

6. The method according to any one of claims 1-4, characterized in that, The degassing treatment of the crushed sample includes: The broken sample was purged with an inert gas to remove any flammable gas remaining in the broken sample.

7. The method according to any one of claims 1-4, characterized in that, The degassing treatment of the crushed sample includes: The broken sample is placed in a liquid medium, and ultrasonic waves are applied to the liquid medium to remove the combustible gas remaining in the broken sample.

8. The method according to claim 1, characterized in that, The measurement of the higher heating value per unit mass of the test sample on a dry basis after complete combustion includes: The sample to be tested is divided into multiple sub-samples; Measure the dry basis higher calorific value of each of the subsamples; Calculate the average dry basis higher heating value of multiple samples; Based on the average value, the dry basis higher heating value of the sample per unit mass is determined.

9. The method according to claim 8, characterized in that, The measurement of the dry basis higher calorific value of each of the sub-samples includes: The subsample is placed in the oxygen bomb of the oxygen bomb calorimeter, and oxygen is introduced into the oxygen bomb. Measure the first temperature value of the water surrounding the oxygen bomb; Ignite the sub-sample to make it burn completely; Measure the second temperature value of the surrounding water body; Subtract the first temperature value from the second temperature value to obtain the temperature change value; Based on the temperature change value, the mass of the surrounding water body, and the specific heat capacity of the oxygen bomb, the dry basis upper heating value of the subsample is determined.

10. The method according to claim 9, characterized in that, The determination of the dry-basis higher heating value of the sub-sample based on the temperature change value, the mass of the surrounding water body, and the specific heat capacity of the oxygen bomb includes: The water content and sulfur content of the sample to be tested were measured. The calorific value of the subsample is calculated based on the temperature change value, the mass of the surrounding water body, and the specific heat capacity of the oxygen bomb. The calorific value of the bomb is corrected based on the moisture content and the sulfur content to obtain the dry basis higher calorific value of the subsample.

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