Method for analyzing coking coal type through residual carbon structure

Abstract

The invention relates to a method for analyzing coking coal types through residual carbon structures, and the method specifically comprises the following steps: heating a sample at 700 + / -10 DEG C, carrying out solid-state nuclear magnetic analysis after combustion, and carrying out peak-dividing fitting on a 13C NMR spectrogram of the sample by using Origin software; the types of carbon are divided into saturated carbon and unsaturated carbon, and the ratio R of the saturated carbon to the unsaturated carbon is equal to Y / X; when the value of R is 1 + / -0.2 and R is greater than 1, determining that the coal type is coking coal, and when R is less than 1, determining that the coal type is fat coal; when the value of R is 0.5 + / -0.2 and R is greater than 0.5, determining that the coal type is lean coking coal; and when R is less than 0.5, determining that the coal type is 1 / 3 coking coal. Aiming at the difficulty of coal type classification, the rapid classification of coal types is carried out according to the quantity ratio of saturated carbon to unsaturated carbon by utilizing the solid nuclear magnetic representation of substances after coal pyrolysis, particularly residual carbon structures.

Description

Technical Field

[0001] This application relates to the technical field of coal classification in the coking industry, and particularly relates to a method for analyzing coking coal types through the residual carbon structure. Background Art

[0002] In recent years, the steel production in China has been continuously increasing, the demand for coke has been expanding, and the contradiction between coking coal resources and coke demand has become increasingly prominent. At the same time, the continuous enlargement of blast furnaces and smelting technologies such as oxygen enrichment and pulverized coal injection have put higher and higher requirements on the quality of coke. Considering economic benefits and actual situations, coking plants at home and abroad are all committed to the research of coal blending schemes. There are many types of coking coal. Applying coal blending technology can not only ensure the quality of coke, but also rationally utilize coal resources, save high-quality coking coal, and expand coking coal resources. Coal blending technology involves multiple technological properties of coal, coking characteristics, and the combined properties of ash, sulfur, and volatile matter, as well as the coking mechanism of coal. For a long time, coal blending tests have always been an indispensable coal blending technology procedure for selecting coal blending schemes and verifying coke quality. Although the schemes vary widely, they are nothing more than the three principles of the overlap of the plastic layer, the principle of interchangeability, and the principle of co-carbonization. These methods are all macroscopic manifestations of the microscopic structure of coal. Therefore, in-depth research on the coal structure is more helpful for accurately classifying coal types and achieving the goal of optimizing coal blending technology.

[0003] Coal is a complex organic macromolecule composed of multiple functional groups and multiple chemical bonds. At present, the structural models of coal at home and abroad are generally traditional chemical structure models, physical structure models, comprehensive models, etc. Many research scholars have also deduced the composition structure of coal. However, for coking chemistry, the carbon structure of condensed rings generally affects the quality of coke, while the side chains on the condensed rings generally only affect the quality of coke oven gas. Therefore, when analyzing coal types using the coal structure, the types of carbon that need to be distinguished are relatively few, and the analysis difficulty is also greatly reduced. According to the decomposition and condensation behavior of coal during the coking process, understanding the structure of the residual carbon after pyrolysis can more accurately classify coal types, which is of great help to the procurement classification of coal types in the early stage and coal blending coking in the later stage.

[0004] Patent ZL201710439472.0 discloses a quantitative analysis method for detecting coal structure parameters using solid-state nuclear magnetic carbon spectroscopy. By measuring the solid-state nuclear magnetic carbon spectra of model compounds, the errors of carbon structure parameters of different model compounds are determined. The fitting values of aliphatic carbon and aromatic carbon obtained by peak fitting of the model compound carbon spectra are respectively regressed with the theoretical values to obtain a regression curve equation for correcting the test errors of the solid-state nuclear magnetic carbon spectra. Patent CN104091504A discloses a method for constructing a coal structure model, which can construct a coal structure model, thereby enabling an understanding of the structure and properties of coal from a chemical perspective and guiding the efficient conversion and utilization of coal. Patent CN116386763A discloses a method for constructing a coal organic macromolecular structure model, which constructs macromolecules of coal based on the modern concept of coal structure, physical characterization structure parameters, pyrolysis information fragments, and comparison of 13C NMR spectra, realizing a macromolecular structure with comprehensive, complete, quantitative data support and accurate nuclear magnetic results as reference indicators. Patent CN106169016A discloses a method for constructing a sulfur-containing macromolecular structure model of coking coal. By performing elemental analysis, FTIR, XPS, and 13C NMR physical characterization on coking coal, a sulfur-containing macromolecular structure model of coking coal is established. Patent CN106898220A discloses a method for constructing a macromolecular structure model of lignite organic matter. Based on the yield and distribution of benzene carboxylic acid, the selective oxidation product of lignite, and using physical characterization to obtain coal structure information, a lignite structure model is constructed. The above patents all take raw coal as the research object, and after removing impurities, solid-state nuclear magnetic characterization is performed to study the model of the macromolecular organic structure of coal, usually supplemented with other physical characterization methods. For the coking process, the carbon structure of the polycyclic side chain has little effect on coal coking. It is mainly the carbon of the polycyclic molecule and the protonated aromatic carbon conducive to condensation that contribute the most to the coking structure. Therefore, it is of little significance to analyze the carbon in the volatile matter at the cost of a large amount of time and detection cost, which cannot improve the accuracy of coal blending for coking and cannot accurately distinguish different coal types. Summary of the Invention

[0005] The object of the present invention is to provide a method for analyzing coking coal types through residual carbon structure. Aiming at the difficulties in coal type classification, the present invention uses the substances after coal pyrolysis, especially the solid-state nuclear magnetic characterization of the residual carbon structure, and performs rapid classification of coal types according to the ratio of the number of saturated carbon and unsaturated carbon.

[0006] To achieve the above object, the present invention is realized by adopting the following technical solutions:

[0007] A method for analyzing coking coal types through residual carbon structure, specifically including the following steps:

[0008] 1) Sample sampling: Take 500 - 1000 g of single - type coal, and use the quartering method to take a sample. Dry it in an oven at 105 ± 5 °C for 1 h, and grind the sample into fine powder with a particle size of 0.050 - 0.075 mm for standby.

[0009] 2) Sample preparation: Take 100 mg of the sample and place it in a muffle furnace. Heat it at 700 ± 10 °C for 20 ± 2 min under the condition of air isolation, and take out the solid residue after cooling to room temperature.

[0010] 3) NMR experiment: Take 5 - 8 mg of the solid residue from step 2) for solid - state NMR analysis; The test uses a Varian INOVA300 superconducting nuclear magnetic resonance spectrometer, and the parameter settings are as follows: The magic - angle spinning speed is 8000 kHz, the sampling time is 0.05 s, the recycle time is 5 s, the pulse width is 4.2 μs, scan 3000 - 5000 times, and the resonance frequency for carbon signal detection is 75.43 MHz. Use the cross - polarization technique, the contact time is 5 ms, and the spectral width is 30000 Hz.

[0011] 4) Data analysis: Use Origin software to perform peak - fitting on the 13C NMR spectrum of the sample; When fitting the spectrum, the baseline for background subtraction uses the minimum constant, the peak shape is selected as Gaussian, and the extra peaks are removed after peak searching and then fitting. Since there is a multi - peak superposition phenomenon in the NMR spectrum of coal, the peak parameters need to be fine - tuned during the spectrum - fitting process to obtain the best fitting effect.

[0012] The principle of the present invention is:

[0013] When coal is heated in an air - isolated environment at high temperature, the organic matter undergoes pyrolysis reactions. The percentage of organic matter remaining in solid form in the coal sample is called fixed carbon. For coking coal, the structure of fixed carbon is the most influential factor on coke quality. The structure and proportion of fixed carbon determine the cold strength and hot strength of coke. For coking coals with different degrees of metamorphism, the side - chain and polycyclic ring structures often vary greatly. By carrying out pyrolysis reactions under air - isolated conditions, side - chain groups can be removed, and the structure analysis of fixed carbon can be made more accurate. Through solid - state NMR analysis, the structure of fixed carbon can be roughly classified, which helps to more intuitively understand the process of coal coking.

[0014] According to the characteristics of different coals with different fixed carbon structures, the invention uses the residual carbon after heating at 700 °C for structural analysis to distinguish different coking coal types. Through a large number of solid-state nuclear magnetic experiments on residual carbon, statistical analysis has confirmed this rule, that is, due to the different structures of different coking coals, there are significant differences in the chemical shifts of C in the nuclear magnetic carbon spectrum, and there are obvious differences in the types of carbon. In order to perform data analysis more simply and intuitively, considering phenomena such as peak fitting error and chemical shift drift, the types of carbon are only divided into two types: saturated carbon and unsaturated carbon. The chemical shift of unsaturated carbon is greater than 115 ppm, and its content is marked as X. The chemical shift of saturated carbon is less than 115 ppm, and its content is marked as Y.

[0015] 5) Identification of coking coal types: According to the fitting results in step 4), the types of carbon are divided into two types: saturated carbon and unsaturated carbon. The chemical shift of unsaturated carbon is greater than or equal to 115 ppm, and its content is marked as X. The chemical shift of saturated carbon is less than 115 ppm, and its content is marked as Y;

[0016] The ratio R of saturated carbon to unsaturated carbon = Y / X; when the R value is 1 ± 0.2, when R > 1, it is determined that the coal type is coking coal. When R < 1, it is determined that the coal type is fat coal; when the R value is 0.5 ± 0.2, when R > 0.5, it is determined that the coal type is lean coking coal; when R < 0.5, it is determined that the coal type is 1 / 3 coking coal.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] The present invention first proposes to use the nuclear magnetic carbon spectrum of residual carbon to identify coking coal types. Different types of coking coals have different degrees of metamorphism, and there are significant differences in the types and quantities of fixed carbon, resulting in significant differences and easy to distinguish between unsaturated carbon and saturated carbon in the residual carbon substances after pyrolysis. Therefore, the mechanism of this detection method is clear and reliable, and there are fewer and controllable interference factors in the analysis process. The detection results have strong repeatability, short detection time, and simple detection method, providing a convenient and fast method for identifying different coal types for the next step of coal blending coking. Description of the Drawings

[0019] Figure 1 It is the peak splitting spectrum of the solid-state nuclear magnetic carbon spectrum of the residual carbon of coking coal. Detailed Embodiments

[0020] The following further describes the specific embodiments of the present invention in conjunction with embodiments. The following embodiments are used to specifically illustrate the content of the present invention. These embodiments are only general descriptions of the content of the present invention and do not limit the content of the present invention.

[0021] The present invention analyzes the structure of coal, especially the residual carbon structure after coal pyrolysis, to obtain the chemical structure information of different single types of coal and classify different types of coal. The method is simple to operate and uses a conventional nuclear magnetic resonance instrument; at the same time, the experimental response time is short and it is more accurate than the traditional coal quality analysis method. It is helpful for the entire industry to quickly detect single types of coal and has great room for promotion.

[0022] The present invention provides a method for analyzing coking coal types by residual carbon structure, which is achieved through the following steps:

[0023] 1) Sample collection: Take 500g of a single type of coal, use the quartering method to take a sample, and dry it in an oven at 105℃ for 1h. Grind the sample into fine powder with a particle size of 0.050-0.075mm for later use;

[0024] 2) Sample preparation: Take 100 mg of sample and place it in a muffle furnace. Heat it at 700°C for 20 min in an airtight condition. After cooling to room temperature, take out the solid residue.

[0025] 3) Nuclear magnetic resonance experiment: 8 mg of solid was taken for solid-state nuclear magnetic resonance analysis. The test used a Varian INOVA300 superconducting nuclear magnetic resonance instrument with the following parameters: magic angle speed of 8000kHz, sampling time of 0.05s, cycle time of 5s, pulse width of 4.2μs, scanning of 3000 to 5000 times, and the resonance frequency of carbon signal detection of 75.43MHz. The cross-polarization technique was used, the contact time was 5ms, and the spectrum width was 30000Hz.

[0026] 4) Data analysis: Origin software was used to perform peak fitting on the 13C NMR spectrum of the sample. When fitting the spectrum, the minimum constant was used for the baseline after deducting the background, and Gaussian was selected for the peak type. After peak finding, the redundant peaks were removed and then fitted. Since there is a multi-peak superposition phenomenon in the NMR spectrum of coal, the peak parameters need to be fine-tuned during the spectrum fitting process to obtain the best fitting effect.

[0027] 5) Calculation of results.

[0028] Example 1:

[0029] A coking coal blending plant uses main coking coal. The results after peak separation are shown in Table 1:

[0030] Table 1

[0031] Peak Percentage 68.5 37.98 89.33 16.62 119.78 20.13 132.77 1.27 140.30 3.96 153.98 9.51 180.66 10.52

[0032] R=Y / X=1.2, it is determined to be main coking coal, which is consistent with the actual situation.

[0033] Example 2:

[0034] A coking coal blend uses fat coal, and the results after peak separation are:

[0035] Peak Percentage 8.85 0.19 23.06 10.77 33.39 1.24 54.61 5.96 73.38 11.12 83.41 4.89 101.60 15.12 115.25 7.76 126.07 10.35 138.21 8.13 153.84 10.72 180.30 13.74

[0036] R = Y / X = 0.97, determined to be fat coal, in line with the actual situation.

[0037] Example 3:

[0038] A semi-soft coking coal for coking coal blending, the result after peak separation is:

[0039] Peak Percentage 26.47 1.65 34.99 0.8 54.93 6.35 76.95 12.17 85.19 1.9 102.01 15.54 119.29 13.07 128.89 2.85 137.71 11.42 152.19 12.22 170.07 15.55 199.14 6.46

[0040] R = Y / X = 0.62, determined to be semi-soft coking coal, in line with the actual situation. Example 4:

[0041] A 1 / 3 coking coal for coking coal blending, the result after peak separation is:

[0042]

[0043]

[0044] R = Y / X = 0.44, determined to be 1 / 3 coking coal, in line with the actual situation.

Claims

1. A method for analyzing coking coal by residual carbon structure, characterized in that: The specific steps include: 1) Sample sampling: Take a single type of coal using the quartering method, dry it in an oven, and grind it into fine powder with a particle size of 0.050-0.075 mm for later use; 2) Sample preparation: Place the sample in a muffle furnace, heat at 700±10℃ for 20±2min in an airtight condition, and take out the solid residue after cooling to room temperature; 3) NMR experiment: taking the solid residue from step 2) for solid-state NMR analysis; 4) Data analysis: Origin software was used to perform peak fitting on the 13C NMR spectrum of the sample; 5) Identification of coking coal types: According to the fitting results of step 4), the types of carbon are divided into saturated carbon and unsaturated carbon. The chemical shift of unsaturated carbon is greater than or equal to 115 ppm, and the content is marked as X. The chemical shift of saturated carbon is less than 115 ppm, and the content is marked as Y. The ratio of saturated carbon to unsaturated carbon is R=Y / X; when the R value is 1±0.2, R>1, the coal is identified as coking coal, and when R<1, the coal is identified as fat coal; when the R value is 0.5±0.2, R>0.5, the coal is identified as lean coking coal; when R<0.5, the coal is identified as 1 / 3 coking coal.

2. A method for analyzing coking coal by residual carbon structure according to claim 1, characterized in that: In the step 1), 500-1000 g of a single type of coal is taken, a sample is taken using the quartering method, and dried in an oven at 105±5° C. for 1 hour.

3. The method for analyzing coking coal by residual carbon structure according to claim 1, characterized in that: In the step 2), 100 mg of sample was placed in a muffle furnace.

4. The method for analyzing coking coal by residual carbon structure according to claim 1, characterized in that: The solid residue taken in the step 3) is 5 to 8 mg, and the nuclear magnetic resonance analysis parameters are: magic angle speed is 8000 kHz, sampling time is 0.05 s, cycle time is 5 s, pulse width is 4.2 μs, scanning is 3000 to 5000 times, and the resonance frequency of carbon signal detection is 75.43 MHz; cross-polarization technology is used, the contact time is 5 ms, and the spectrum width is 30000 Hz.

5. The method for analyzing coking coal by residual carbon structure according to claim 1, characterized in that: In the step 4), when fitting the spectrum, the minimum constant is used for the baseline after deducting the background, Gaussian is selected for the peak type, and after peak finding, the redundant peaks are removed, followed by fitting.

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