A quantitative research method for coal quality firmness coefficient based on micro-molecular structure characteristics

Abstract

The application discloses a kind of coal quality firmness coefficient quantitative research method based on micro molecular structure characteristics, it is related to coal mine safety engineering technical field.The method includes: collecting different coal rank lump coal sample, first, use drop hammer crushing method to measure firmness coefficient after pretreatment;Further ground coal sample is measured infrared structure characteristics by fourier transform infrared spectrometer, and spectrum is obtained, four wave bands are divided and the area ratio of functional group is calculated;Then, the pore size of coal sample is measured, then the correlation fitting of the above parameters and firmness coefficient is carried out, the influence weight is determined, and the correlation equation is constructed, and the coal quality firmness coefficient quantitative research is carried out accordingly.The present application is based on the test analysis means and method of the chemical structure characteristics and pore structure characteristics of coal body microcosmic and firmness coefficient, establishes the relationship equation of firmness coefficient and chemical structure characteristics and pore structure characteristics, provides microcosmic perspective for coal and gas outburst mechanism research, and has practical guiding significance to the safety production of mine.

Description

Technical Field

[0001] This invention relates to the field of coal mine safety engineering technology, and in particular to a quantitative research method for the coal quality robustness coefficient based on microscopic molecular structure characteristics. Background Technology

[0002] Existing coal quality soundness coefficient ( f The determination relies on physical crushing experiments (such as the falling hammer method) or is based on coal rank ( V daf Empirical formulas are used to estimate the percentage (%). This type of method has two major limitations: it cannot explain the same coal rank in coal bodies. f Differences in values ​​(such as coals with varying vitrinite content); neglecting the influence of microscopic chemical structure and pore structure on coal body strength characteristics leads to misjudgments of gas outburst risk. Currently, it is known that coal body strength is related to functional group and pore structure characteristics, but quantitative structural parameters are lacking. f The value mapping model hinders the microscopic explanation of the prominent mechanism. Summary of the Invention

[0003] The purpose of this invention is to provide a quantitative research method for the coal quality robustness coefficient based on microscopic molecular structure characteristics, aiming to solve or improve at least one of the above-mentioned technical problems.

[0004] To achieve the above objectives, the present invention provides the following solution: A quantitative research method for coal robustness coefficient based on microscopic molecular structure characteristics, comprising: Lump coal samples of different coal ranks were collected, and after pretreatment, the soundness coefficient of the coal samples was determined by the drop hammer crushing method; the pretreatment included crushing and grinding to 60-80 mesh; The collected blocky coal samples were crushed and ground to below 200 mesh, and the infrared structural characteristics of the coal samples were tested using a Fourier transform infrared spectrometer to obtain the infrared spectrum of the coal samples. Based on the amplitude characteristics of different types of functional groups, the infrared spectrum is divided into 4 bands; The area integral of the original spectral lines in each band is performed to calculate the area ratio of the functional groups. The pore size of coal samples with a mesh size of less than 200 was measured to obtain the micropore volume, mesopore volume, and macropore volume, respectively. The area ratio of each functional group, the volume of micropores, the volume of mesopores, the volume of macropores, and the robustness coefficient were correlated and fitted to determine the influence weight of each parameter on the robustness coefficient. Based on the weights, a correlation equation was constructed between the robustness coefficient of the medium and the microchemical and pore structure parameters, and a quantitative study of the robustness coefficient of coal was conducted based on the correlation equation.

[0005] Optionally, the pretreatment further includes: vacuum drying for 48 h at a drying temperature of 60 °C.

[0006] Optionally, the scanning range of the Fourier transform infrared spectrometer is 0-4000 cm⁻¹. -1 .

[0007] Optionally, the four bands are divided into: the absorption peak band of hydroxyl groups 3700-3000 cm⁻¹. -1 Absorption peaks of aliphatic hydrocarbons: 3000-2700 cm⁻¹ -1 The absorption peak band of oxygen-containing functional groups is 1800-1000 cm⁻¹. -1 And the absorption peak band of aromatic hydrocarbons at 900-700 cm⁻¹ -1 .

[0008] Optionally, the step of measuring the pore size of coal samples with a mesh size of less than 200 to obtain the micropore volume, mesopore volume, and macropore volume specifically includes: The pore size of coal samples with a mesh size of less than 200 mesh was measured by liquid nitrogen adsorption method, and the pore volume of micropores with a size of 0-2 nm and mesopores with a size of 2-50 nm were obtained. The lumpy coal sample was prepared into a cylinder of a set size, and the transverse relaxation time was measured using a nuclear magnetic resonance analyzer to obtain the pore volume of macropores with a size of 50~10000 nm.

[0009] Optionally, the range of the lateral relaxation time test is 0-10000 ms.

[0010] Optionally, the set dimensions are 50 mm in diameter and 100 mm in height.

[0011] Optionally, the correlation equation is specifically expressed as: f = β 0+ β 1 C H + β 2 C A + β 3 C O + β 4 C Ar + β 5 V micro + β 6 V meso + β 7 V macro in, β 0、 β 1. β 2. β 3. β 4. β 5. β 6. β 7 represents the fitting weights. f The coal quality soundness coefficient. C H This represents the area percentage of the hydroxyl band. C A This represents the area ratio of the aliphatic hydrocarbon band. C O This represents the area percentage of the oxygen-containing functional group band. C Ar This represents the area ratio of the aromatic hydrocarbon band. V micro For micropore volume, V meso For mesopore volume, V macro This refers to the volume of the macropore.

[0012] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects: This invention discloses a quantitative research method for the coal robustness coefficient based on microscopic molecular structure characteristics. The method includes collecting blocky coal samples of different ranks, pre-treating them, and then measuring the robustness coefficient using a drop hammer crushing method. Next, the coal samples are crushed and ground to below 200 mesh, and the infrared structural characteristics are measured using a Fourier transform infrared spectrometer to obtain a spectrum, which is divided into four bands and the functional group area ratio is calculated by integration. Then, the pore size of the coal samples is measured to obtain the volumes of micropores, mesopores, and macropores. Next, the correlation between each parameter and the robustness coefficient is fitted to determine the influencing weights. Finally, a correlation equation is constructed based on the weights, and the quantitative research on the coal robustness coefficient is carried out accordingly. This invention is based on the microscopic chemical structure characteristics and pore structure characteristics of coal and the robustness coefficient. f Value testing and analysis methods to establish robustness coefficient f The equation relating the values ​​to chemical and pore structure characteristics provides a microscopic perspective for the study of coal and gas outburst mechanisms and has practical guiding significance for safe production in mines. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a flowchart of the quantitative research method for the coal quality robustness coefficient in this embodiment; Figure 2 This is the infrared spectrum of anthracite in this embodiment; Figure 3 This is the infrared spectrum of bituminous coal in this embodiment; Figure 4 This is the infrared spectrum of lignite in this embodiment; Figure 5 This is a pore size distribution curve of anthracite in this embodiment; Figure 6 This is a graph showing the pore size distribution of bituminous coal in this embodiment; Figure 7 This is a graph showing the pore size distribution of lignite in this embodiment; Figure 8 This is the nuclear magnetic resonance transverse relaxation time spectrum of anthracite in this embodiment; Figure 9 This is the nuclear magnetic resonance transverse relaxation time spectrum of bituminous coal in this embodiment; Figure 10 This is the nuclear magnetic resonance transverse relaxation time spectrum of lignite in this embodiment. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] The purpose of this invention is to provide a quantitative research method for the coal quality robustness coefficient based on microscopic molecular structure characteristics, aiming to solve or improve at least one of the above-mentioned technical problems.

[0017] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] like Figure 1 As shown, this invention provides a quantitative research method for the coal robustness coefficient based on microscopic molecular structure characteristics, including functional group and pore structure characteristics. Taking Shanxi anthracite, Shaanxi bituminous coal, and Inner Mongolia lignite as examples, the method includes the following steps: a. Collect lump coal samples of different coal ranks (lignite, bituminous coal, anthracite), crush and grind them to 60-80 mesh, and vacuum dry them for 48 h at a drying temperature of 60 ℃; take samples for analysis using the falling hammer crushing method. f The values ​​are recorded as 1.2, 0.9, and 0.6.

[0019] b. Crush and grind the coal sample collected in step a to below 200 mesh. Use a Fourier transform infrared spectrometer to test the infrared structural characteristics of the ground coal sample. The spectrometer scanning range is 0-4000 cm⁻¹. -1 The instrument resolution is 0.06 cm. -1 With wavenumber accuracy > 0.01 cm and transmittance accuracy > 0.1% T, the infrared spectrum of the coal sample was obtained. Figures 2-4 ).

[0020] c. Based on the different amplitudes of different functional groups, the infrared spectrum of coal samples can be divided into four bands: the hydroxyl (-OH) absorption peak band (3700-3000 cm⁻¹). -1 Absorption peaks of aliphatic hydrocarbons (-CH3, -CH2, -CH) (3000-2700 cm⁻¹) -1 Absorption peaks of oxygen-containing functional groups (C=O, COOH, CO) (1800-1000 cm⁻¹) -1 Aromatic hydrocarbon (C=C, CH) absorption peak band (900-700 cm⁻¹) -1 ).

[0021] d. Perform area integration on the original spectral lines of each band to calculate the hydroxyl band (3700-3000 cm⁻¹). -1 ), aliphatic hydrocarbon band (3000-2700 cm) -1 ), oxygen-containing functional group band (1800-1000 cm) -1 Aromatic hydrocarbon band (900-700 cm) -1 The area ratio of ) is shown in Table 1.

[0022] Table 1

[0023] e. According to the official IUPAC pore classification standard, pore size is divided into three categories: micropores (0~2 nm), mesopores (2~50 nm), and macropores (50~10000 nm). Liquid nitrogen adsorption is relatively accurate for testing the micropores and mesopores of coal samples, while nuclear magnetic resonance (NMR) is more accurate for testing the macropores. The coal samples collected in step a were crushed and ground to below 200 mesh. The micropore and mesopore structural characteristics of the prepared coal samples were tested using a specific surface area and pore size analyzer (liquid nitrogen adsorption method). The instrument scanning range was 0-100 nm, and the specific surface area was 0.0005 m². 2 / g, reading accuracy error ≤ 0.15%, to obtain the pore size characteristic distribution curve of the coal sample ( Figures 5-7 The micropore volume and mesopore volume of the coal sample were obtained, and the results are shown in Table 2.

[0024] Table 2

[0025] f. Prepare the coal sample collected in step a into a cylinder with a diameter of 50 mm and a height of 100 mm. Analyze the transverse relaxation time of the cylindrical coal sample using a nuclear magnetic resonance (NMR) analyzer. The relaxation time range is 0-10000 ms. The instrument uses a permanent magnet with a magnetic field strength of 0.5 ± 0.08 T and a main frequency of 21.3 MHz. Obtain the transverse relaxation time spectrum of the macropores (50~10000 nm) of the coal sample. Figures 8-10 The macropore volume of the coal sample was obtained, and the results are shown in Table 3.

[0026] Table 3

[0027] g. The relationship between the area percentage of hydroxyl groups, the area percentage of aliphatic hydrocarbons, the area percentage of oxygen-containing functional groups, the area percentage of aromatic hydrocarbons, the micropore volume, the mesopore volume, the macropore volume, and the coal body firmness coefficient ( ). f The correlation between the above-mentioned microchemical structure and pore structure parameters and the coal body firmness coefficient ( ) was fitted. f The influence weights of the results are shown in Table 4.

[0028] Table 4

[0029] h. Combining the weights, construct the coal body firmness coefficient ( f Correlation equations between ) and microchemical and pore structure parameters: f = β 0+ β 1 C H +β 2 C A + β 3 C O + β 4 C Ar + β 5 V micro + β 6 V meso + β 7 V macro in, β 0、 β 1. β 2. β 3. β 4. β 5. β 6. β 7 represents the fitting weights. f The coal quality soundness coefficient. C H This represents the area percentage of the hydroxyl band. C A This represents the area ratio of the aliphatic hydrocarbon band. C O This represents the area percentage of the oxygen-containing functional group band. C Ar This represents the area ratio of the aromatic hydrocarbon band. V micro For micropore volume, V meso For mesopore volume, V macro This refers to the volume of the macropore.

[0030] Based on the results of this embodiment, the parameters in the correlation equation are specifically represented as follows: f =0.82+0.05 C H -0.12 C A -0.09 C O +0.17 C Ar -2.1 V micro -0.7 V meso - 0.2 V macro in, CH and C O The larger the value, the higher the content of hydroxyl groups and oxygen-containing functional groups in the coal body, and the higher the coal body firmness coefficient ( ). f The value is relatively small; C A and C Ar The larger the value, the higher the content of aliphatic and aromatic hydrocarbons in the coal, and the higher the robustness coefficient. f The higher the value, the better the robustness coefficient. f The smaller the value; V micro and V meso The larger the pore size, the larger the volume of micropores and mesopores in the coal body, and the higher the strength coefficient. f The larger the value, the better; V macro The larger the pore size, the larger the pore volume of the coal body, and the higher the stability coefficient. f The smaller the value.

[0031] Therefore, this invention breaks through the limitations of traditional methods that rely solely on macroscopic coal rank by establishing quantitative equations relating chemical and pore structure characteristics to the robustness coefficient f-value. The combined use of three technologies (infrared spectroscopy + cryogenic liquid nitrogen adsorption + nuclear magnetic resonance) enables full-scale analysis from both chemical and pore structure perspectives. By identifying key structural factors affecting the f-value, it allows for the preliminary prediction of the mechanical properties of unknown coal samples based solely on microscopic chemical and pore structure analysis. This provides a theoretical basis and predictive evidence for permeability enhancement techniques targeting specific coal seams (such as acid treatment to remove minerals and microwave treatment to cleave fatty side chains).

[0032] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0033] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A quantitative research method for coal robustness coefficient based on microscopic molecular structure characteristics, characterized in that, include: Lump coal samples of different coal ranks were collected, and after pretreatment, the soundness coefficient of the coal samples was determined by the drop hammer crushing method; the pretreatment included crushing and grinding to 60-80 mesh; The collected blocky coal samples were crushed and ground to below 200 mesh, and the infrared structural characteristics of the coal samples were tested using a Fourier transform infrared spectrometer to obtain the infrared spectrum of the coal samples. Based on the amplitude characteristics of different types of functional groups, the infrared spectrum is divided into four bands; the four bands include: the absorption peak band of hydroxyl groups 3700-3000 cm⁻¹. -1 Absorption peaks of aliphatic hydrocarbons: 3000-2700 cm⁻¹ -1 The absorption peak band of oxygen-containing functional groups is 1800-1000 cm⁻¹. -1 And the absorption peak band of aromatic hydrocarbons at 900-700 cm⁻¹ -1 ; The area integral of the original spectral lines in each band is performed to calculate the area ratio of the functional groups. The pore size of coal samples with a mesh size of less than 200 was measured to obtain the micropore volume, mesopore volume, and macropore volume, respectively. The area ratio of each functional group, the volume of micropores, the volume of mesopores, the volume of macropores, and the robustness coefficient were correlated and fitted to determine the influence weight of each parameter on the robustness coefficient. Based on the weights, a correlation equation was constructed between the robustness coefficient of the medium and the microchemical and pore structure parameters, and a quantitative study of the robustness coefficient of coal was conducted based on the correlation equation.

2. The method for quantitatively studying the coal robustness coefficient based on microscopic molecular structure characteristics according to claim 1, characterized in that, The pretreatment also includes: vacuum drying for 48 h at a drying temperature of 60 °C.

3. The method for quantitatively studying the coal robustness coefficient based on microscopic molecular structure characteristics according to claim 1, characterized in that, The scanning range of the Fourier transform infrared spectrometer is 0-4000 cm⁻¹. -1 .

4. The method for quantitatively studying the coal robustness coefficient based on microscopic molecular structure characteristics according to claim 1, characterized in that, The process of measuring the pore size of coal samples with a mesh size of less than 200 to obtain the micropore volume, mesopore volume, and macropore volume specifically includes: The pore size of coal samples with a mesh size of less than 200 mesh was measured by liquid nitrogen adsorption method, and the pore volume of micropores with a size of 0-2 nm and mesopores with a size of 2-50 nm were obtained. The lumpy coal sample was prepared into a cylinder of a set size, and the transverse relaxation time was measured using a nuclear magnetic resonance analyzer to obtain the pore volume of macropores with a size of 50~10000 nm.

5. The method for quantitatively studying the coal robustness coefficient based on microscopic molecular structure characteristics according to claim 4, characterized in that, The range of the lateral relaxation time test is 0-10000 ms.

6. The method for quantitatively studying the coal robustness coefficient based on microscopic molecular structure characteristics according to claim 4, characterized in that, The specified dimensions are 50 mm in diameter and 100 mm in height.

7. The method for quantitatively studying the coal robustness coefficient based on microscopic molecular structure characteristics according to claim 1, characterized in that, The correlation equation is specifically expressed as follows: f = β 0+ β 1 C H + β 2 C A + β 3 C O + β 4 C Ar + β 5 V micro + β 6 V meso + β 7 V macro in, β 0、 β 1. β 2. β 3. β 4. β 5. β 6. β 7 represents the fitting weights. f The coal quality soundness coefficient. C H This represents the area percentage of the hydroxyl band. C A This represents the area ratio of the aliphatic hydrocarbon band. C O This represents the area percentage of the oxygen-containing functional group band. C Ar This represents the area ratio of the aromatic hydrocarbon band. V micro For micropore volume, V meso For mesopore volume, V macro This refers to the volume of the macropore.

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