A method for correcting sample particle size on bituminous coal caking index

Abstract

The present application relates to coal physicochemical detection technical field, especially to a kind of sample particle size correction method for bituminous coal caking index, including preparation n samples, in n samples, the proportion of each sample particle size 0.1mm~0.2mm coal sample is respectively marked as X1, X2, X3……X n , n samples are tested, the caking index of each sample is determined, the caking index of the sample is calculated, the linear equation=aX+b of n samples is established, the caking index of any proportion X between the high and low points X1~Xn of the linear relationship is calculated, and the caking index under the X proportion is taken as the final result; the present application can effectively eliminate the influence of the change of the proportion of coal sample with particle size of 0.1mm~0.2mm on the determination of caking index, effectively eliminate the measurement error of laboratory internal and interlaboratory, improve the precision and accuracy of bituminous coal caking index determination method.

Description

Technical Field

[0001] This invention relates to the field of physical and chemical testing technology for coal, and in particular to a method for correcting the caking index of bituminous coal based on sample particle size. Background Technology

[0002] Currently, the standard for determining the caking index of coal is GB / T5447-2014, which is applicable to bituminous coal. The international standard is ISO15585-2019, and the "Rujigou anthracite" specified in the standard is the benchmark coal for caking index determination in China.

[0003] The limitations of the existing test method GB / T5447-2014 are reflected in the following aspects: 1. Practice has proven that the particle size range in the test is one of the key factors in determining the bonding index. GB / T5447-2014 stipulates the following regarding sample preparation: "6.1 The test coal sample shall be prepared into a general analytical test coal sample with a particle size of less than 0.2 mm by stepwise crushing and reduction according to GB474, wherein the proportion of coal sample with a particle size of 0.1 mm to 0.2 mm should be between 20% and 35%." However, it does not provide a detailed method to achieve the requirement that "the proportion of coal sample with a particle size of 0.1 mm to 0.2 mm should be between 20% and 35%", leading to various laboratories using manual sieving, mechanical sieving, or even some laboratories relying on empirically prescribed grinding amounts and times without particle size sieving. Verification of sample sieving from five laboratories revealed that the proportion of coal sample with a particle size of 0.1 mm to 0.2 mm ranged from 10% to 40%, with a predominance of samples with a particle size less than 20%.

[0004] 2. In actual production, the proportion of coal samples with a particle size of 0.1mm to 0.2mm fluctuated between 20% and 35% after measurement. The maximum fluctuation range of the caking index within the laboratory reached 4, and the maximum fluctuation range between laboratories reached 7. The main reason is that the sample preparation process parameters, the use of manual or mechanical equipment, equipment functions, and personnel skills of each laboratory are different, which leads to a large difference in the proportion of coal samples with a particle size of 0.1mm to 0.2mm in the sample preparation process. Some laboratories even fail to meet the requirement that "the proportion of coal samples with a particle size of 0.1mm to 0.2mm should be between 20% and 35%".

[0005] 3. Clause 8 of GB / T5447, in the result calculation section, only the mass m of the coking sample in the testing process is used for calculation, see "Formula (1) G=10+(30m1+70m2) / m", "Formula (2) G=(30m1+70m2) / 5m". When the laboratory publishes the results, only the adhesion index G is included. R,I,The information lacks details regarding the proportion of coal samples with a particle size of 0.1mm to 0.2mm, and it also fails to consider corrections for different proportions of coal samples with a particle size of 0.1mm to 0.2mm. This results in significant differences in the bonding index obtained by users from different laboratories.

[0006] Considering the limitations of the above three points, the sample preparation method, and the proportion of coal samples with a particle size of 0.1 mm to 0.2 mm have a crucial impact on the determination of the caking index, seriously affecting the quality judgment of bituminous coal in the trade settlement process. Therefore, it is necessary to consider the impact of changes in the proportion of coal samples with a particle size of 0.1 mm to 0.2 mm on the test results.

[0007] Through long-term research on the accuracy and precision of the caking index test, it was found that the higher the proportion of coal samples with a particle size of 0.1mm to 0.2mm, the lower the caking index result, indicating a strong negative correlation. A method was proposed to correct for fluctuations in the caking index result caused by different proportions of coal samples with a particle size of 0.1mm to 0.2mm. This correction is then included in the final result presentation, specifying the proportion of the 0.1mm to 0.2mm portion of the coal sample corresponding to the caking index published by the laboratory test. This makes the test results more accurate and provides users with a more reliable basis for judging the quality of coal samples.

[0008] Currently, there are many research papers on the methodology of bituminous coal caking index in China, such as reference document 1: Wang Wenguang et al., 2007, Chinese Society for Metals Conference, "Research on Sample Preparation Method of Coking Coal Caking Index (G Value)," etc. Reference document 2, application number 202411029866.5, "A Calibration Method for Bituminous Coal Caking Index," mentions using standard substances to correct the results, which is a common correction method in analytical chemistry. Reference document 2 calibrates the difference between the standard substance measurement results and the standard value during the coking and drum measurement processes using standard substances. It corrects for the deviation of the measurement system. The standard substance is a pre-prepared sample with a fixed particle size distribution; it does not involve the sample preparation process and cannot correct for changes during sample preparation. Summary of the Invention

[0009] This invention provides a method for correcting the caking index of bituminous coal by sample particle size. It establishes a quantitative relationship between the influence of varying coal sample proportions with particle sizes of 0.1 mm to 0.2 mm on the caking index. This method effectively eliminates the influence of these proportions on the determination of the caking index, effectively eliminating measurement errors within and between laboratories, and improving the precision and accuracy of the bituminous coal caking index determination method. Furthermore, the corrected result, incorporating particle size composition information, makes the caking indices published by different laboratories comparable, eliminating trade friction caused by measurement errors for both parties in commodity trading, and ensuring a fair assessment of bituminous coal quality.

[0010] To achieve the above objectives, the present invention employs the following technical solution: A method for correcting the caking index of bituminous coal by sample particle size includes the following steps: S1. Sample preparation: Prepare n bituminous coal samples, where n≥3; The preparation process for each sample is as follows: After grinding, the sample is screened through a vibrating sieve with a mesh size of 0.2 mm to obtain the required total sample. The sample is then divided into two portions using a divider. One portion is used to measure the caking index, and the other portion is used to measure the proportion of coal samples with a particle size of 0.1 mm to 0.2 mm. The mass of the other portion of the sample is denoted as M. This other portion is then sieved through a vibrating sieve with a mesh size of 0.1 mm until the amount passing through twice is less than 0.5% of the mass of the other portion of the sample. Finally, coal samples with a particle size of 0.1 mm to 0.2 mm are selected, and their weight is denoted as M1. X = M1 * 100 / M; Where X represents the proportion of coal samples with a particle size of 0.1 mm to 0.2 mm in another sample; the proportion of coal samples with a particle size of 0.1 mm to 0.2 mm in each of the n samples is denoted as X1, X2, X3...X n ; S2. Test n samples: For the samples used to measure the caking index, if the caking index of the bituminous coal measured for the first time for each sample is <18, use special anthracite and test coal samples in a ratio of 3:3, mix them evenly, and then re-test the caking index. The results of the re-test are calculated using the following formula: ; When the initial caking index of each sample is ≥18, the following procedures are completed: sample weighing, mixing, stirring, briquetting, heating, cooling, secondary drum test, and sieving analysis. The caking index is then calculated using the following formula: ; in, The bonding index of the nth sample; m nFor the nth sample, the total mass of coke residue after coking treatment, in g; m n1 For the nth sample, the mass of the material remaining on the sieve after the first drum test, all in g; m n2 For the nth sample, the mass of the material remaining on the sieve after the second drum test, all in g; S3, Result Correction: X1, X2, X3...X n Corresponding adhesion index calculation results , , ... Establish X and n samples Linear equations =aX+b, the square of the correlation coefficient is at least greater than 0.97, otherwise the number of samples to be measured is increased, where a is the slope of the linear equation and b is the intercept of the linear equation. S4. Result Reporting: Calculate the high and low points X1 to X2 of the linear relationship based on the linear equation. n The adhesion index at any ratio X between X and X is the adhesion index at that ratio X. For the final result, and after rounding the result to the nearest integer, X and Report them together.

[0011] Furthermore, the sample preparation employs a sealed vibratory mill and a reciprocating vibrating screen.

[0012] Furthermore, in step S1, after the sample is reduced in size, it is dried at a temperature below 40°C for 3 to 4 hours.

[0013] Furthermore, the amount of material to be ground before grinding is 50-60 grams, each grinding lasts 1-5 seconds, and all samples are passed through a 0.2mm reciprocating vibrating screen. The samples on the screen are ground repeatedly until all samples pass through the 0.2mm reciprocating vibrating screen.

[0014] Furthermore, the adhesion index Results are calculated to one decimal place, with the result for each sample being the arithmetic mean of two repeated measurements.

[0015] Furthermore, X is 10% to 60%, and at least one of the n samples is required to have X of 20% to 35%.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1) The sample preparation process is specified, and a quantitative relationship is established for the influence of the proportion of coal samples with a particle size of 0.1 mm to 0.2 mm on the caking index. This effectively eliminates the influence of the proportion of coal samples with a particle size of 0.1 mm to 0.2 mm on the determination of the caking index, and effectively eliminates measurement errors within and between laboratories. At the same time, the result format with particle size composition information after correction by this method is specified, making the caking index published by different laboratories comparable, eliminating trade friction caused by measurement errors for both parties in commodity trading, and ensuring fair judgment on the quality of bituminous coal. 2) It can effectively eliminate the large error caused by the difference in X value during each sample preparation in the laboratory, and effectively improve the precision and accuracy of the bituminous coal caking index determination method; 3) At the same time, it more effectively eliminates the differences in the proportion of coal samples with a particle size of 0.1mm to 0.2mm between laboratories due to different sample preparation processes, and greatly reduces the error of the caking index. Attached Figure Description

[0017] Figure 1 This describes the relationship between particle size ratio and bonding index in embodiments of the present invention. Detailed Implementation

[0018] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings: Different laboratories used varying sample preparation processes, resulting in different proportions of coal samples with particle sizes ranging from 0.1 mm to 0.2 mm. This led to significant errors in the caking index measurement of the same sample. Experiments revealed a strong correlation between the caking index of bituminous coal and the proportion of coal samples with particle sizes of 0.1 mm to 0.2 mm; a higher proportion of these particles resulted in a lower caking index. Based on this correlation, a binary relationship was established between the proportion of coal samples with particle sizes of 0.1 mm to 0.2 mm and the caking index: Y = aX1 + bX2. 2 +C, where X2 represents the proportion of samples with particle sizes smaller than 0.1 mm, and X1 represents the proportion of samples with particle sizes between 0.1 mm and 0.2 mm. If all samples are required to pass through a particle size of 0.2 mm, then X1 + X2 = 1, and the influence of the bonding index on the sample particle size proportion becomes a univariate relationship, i.e., Y = aX + b. Figure 1The relationship between particle size distribution and caking index shows a highly negative correlation between the sample particle size distribution and the caking index. Using this correction relationship, by measuring the caking index at least three different proportions (coal sample proportions with particle sizes ranging from 0.1 mm to 0.2 mm), a correction relationship can be established for the caking index of coal sample proportions with particle sizes from 0.1 mm to 0.2 mm. This correction relationship allows the calculation of the caking index for any proportion between the high and low points of this linear relationship. The results are expressed as G. R,I（X） In formal expression, X represents the proportion of coal samples with a particle size of 0.1 mm to 0.2 mm, and G... R,I（X） This represents the caking index of bituminous coal at a proportion of coal samples with a particle size of 0.1 mm to 0.2 mm; when publishing the results, it is expressed as G. R,I（X） The formal representation of the caking index indicates that the sample size (X) corresponding to the caking index is measured at a coal sample ratio (X) of 0.1mm to 0.2mm. Caking indices published by different laboratories are only comparable when measured at the same coal sample ratio (X) with the same particle size (0.1mm to 0.2mm). Alternatively, the trading parties may agree in advance in the contract to determine the quality of bituminous coal based on the caking index at a fixed coal sample ratio (X) of 0.1mm to 0.2mm. For example, it may be agreed in advance that when X=25%, the caking index is measured using G... R,I（25） As a basis for judging the quality of bituminous coal, it eliminates the error in the caking index caused by the different proportions of coal samples with particle sizes of 0.1mm to 0.2mm, and achieves the purpose of correcting the caking index by sample particle size.

[0019] The present invention provides a method for correcting the caking index of bituminous coal based on sample particle size, comprising the following steps: S1. Sample Preparation: Prepare n bituminous coal samples, n≥3; the preparation process for each sample includes the following steps: S1.1. Samples are prepared using a sealed vibrating mill and a reciprocating vibrating screen; S1.2 After the sample is reduced, dry it at below 40°C for about 3 to 4 hours; S1.3, The amount of material to be ground in the test is 50-60 grams; S1.4 Grinding: Each grinding session lasts 1 to 5 seconds. All samples pass through a reciprocating vibrating screen with a screen size of 0.2 mm. The samples remaining on the screen are ground repeatedly. The grinding time is adjusted according to the amount remaining on the screen until all samples pass through the 0.2 mm reciprocating vibrating screen. S1.5. Use a divider to divide the sample into two parts, and use one part of the sample to measure the adhesion index. Another sample is used to measure the proportion of coal samples with a particle size of 0.1 mm to 0.2 mm; the total mass of the other sample is weighed as M, and it is passed through a 0.1 mm vibrating sieve. The sieve endpoint is when the amount passing through twice is less than 0.5% of the total mass of the other sample; the amount on the 0.1 mm sieve is weighed as M1, and the proportion of the total mass of the sample is calculated and recorded as X. X = M1 * 100 / M; X is 10%–60%, and at least one of the n samples must have X of 20%–35%. Record X accurately, retaining two decimal places. The proportion of coal samples with a particle size of 0.1 mm–0.2 mm in each of the n samples is denoted as X1, X2, X3…X… n .

[0020] S2. Test n samples; S2.1. For the samples used to measure the caking index, if the caking index of the bituminous coal measured for the first time for each sample is <18, the ratio of special anthracite to test coal sample shall be 3:3, that is, 3.00g of special anthracite and 3.00g of test coal sample shall be weighed and the test shall be repeated. The results shall be calculated according to the following formula: ; Sample preparation, particle size result correction, and result representation should refer to the case where the adhesion index is ≥18. When the initial caking index of each sample is ≥18, the following procedures are completed: sample weighing, mixing, stirring, briquetting, heating, cooling, secondary drum test, and sieving analysis. The caking index is then calculated using the following formula: ; in, The bonding index of the nth sample; m n For the nth sample, the total mass of coke residue after coking treatment, in g; m n1 For the nth sample, the mass of the material remaining on the sieve after the first drum test, all in g; m n2 For the nth sample, the mass of the material remaining on the sieve after the second drum test, all in g; Cohesion Index Results are calculated to one decimal place, with the result for each sample being the arithmetic mean of two repeated measurements.

[0021] S3, Result Correction; S3.1, the proportions of n (n≥3) coal samples with a particle size of 0.1mm to 0.2mm are X1, X2, X3...X n The corresponding adhesion index calculation results , , ... As shown in Table 1: Table 1. Proportion and caking index of coal samples with particle size of 0.1 mm to 0.2 mm. S3.2. Based on Table 1, establish the X and G relationships for n samples. R,I Linear equations =aX+b, the square of the correlation coefficient is at least greater than 0.97, otherwise the number of samples to be measured is increased, where a is the slope of the linear equation and b is the intercept of the linear equation.

[0022] S4. Result Reporting: Based on the equation =aX+b, calculate the high and low points X1~X of this linear relationship. n The adhesion index at any ratio X between X and X is the adhesion index at that ratio. The final result means that the bonding index is measured at a ratio of coal sample with a particle size of 0.1 mm to 0.2 mm; for example, using... The result report, in the form of (25%) = 56, indicates the caking index of the sample when the proportion of coal samples with a particle size of 0.1 mm to 0.2 mm is 25%. The measured value was 56.

[0023] For example, taking the data in Table 2 as an example, the laboratory measured the adhesion index G at X=14.5, 27.5, and 43.0 respectively. R,I =72.0, 69.7, 65.4, establish the particle size correction relationship Y=75.64-0.2330X; when X=25, the detection result is expressed as (25%) = 70, thus achieving unified use of results and eliminating large errors in test results between different proportions.

[0024] Table 2 Example of Measurement Data The following embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments. Unless otherwise specified, the methods used in the following embodiments are conventional methods.

[0025] Example: The present invention provides a method for correcting the caking index of bituminous coal based on sample particle size, comprising the following steps: S1. Sample Preparation: The sample is progressively crushed and reduced to coal samples with a particle size less than 10 mm, and three samples are prepared. The samples are dried at below 40℃ for approximately 4 hours. After drying, 50 grams of coal sample are extracted and placed in a sealed vibrating mill mortar for grinding. The first grinding lasts 5 seconds, followed by passing through a 0.2 mm sieve and vibrating for 30 seconds. The portion of the coal sample larger than 0.2 mm is re-ground for 3 seconds and passed through a vibrating sieve for 30 seconds. This process is repeated until all the sample passes through a 0.2 mm sieve. Using a divider, the sample is divided into two parts. One part is used to determine the caking index, and the other part is weighed (total mass M) and passed through a 0.1 mm vibrating sieve for 30 seconds. The amount passing through the 0.1 mm sieve is weighed (M1 < 0.5%M; otherwise, continue sieving until M1 < 0.5%M). The proportion of coal samples with a particle size of 0.1 mm to 0.2 mm is calculated as X = M1 * 100 / M. This proportion is recorded accurately. The X values ​​for the three samples are recorded as X1, X2, and X3, respectively, retaining one decimal place.

[0026] S2. Test 3 samples: For the samples used to measure the caking index, if the caking index of the bituminous coal measured for the first time for each sample is <18, use a ratio of 3:3 for the special anthracite and the test coal sample, that is, weigh 3.00g of special anthracite and 3.00g of test coal sample, and repeat the test. The results of the retest are calculated using the following formula: ; When the initial caking index of each sample is ≥18, the following procedures are completed: sample weighing, mixing, stirring, briquetting, heating, cooling, secondary drum test, and sieving analysis. The caking index is then calculated using the following formula: ; in, The bonding index of the nth sample; m n For the nth sample, the total mass of coke residue after coking treatment, in g; m n1 For the nth sample, the mass of the material remaining on the sieve after the first drum test, all in g; m n2 For the nth sample, the mass of the material remaining on the sieve after the second drum test, all in g; Cohesion Index Results are calculated to one decimal place, with the result for each sample being the arithmetic mean of two repeated measurements.

[0027] S3. Linear correlation correction of results: Calculation results of the bonding index corresponding to the proportions X1, X2, and X3 of n (n=3) coal samples with particle sizes of 0.1mm to 0.2mm. , , Establish X and X-axis of three samples Linear equations =aX+b, the square of the correlation coefficient is at least greater than 0.97, otherwise the number of samples to be measured is increased, where a is the slope of the linear equation and b is the intercept of the linear equation.

[0028] S4. Result Reporting: Based on the linear equation =aX+b, calculate X for any value of X1, X2, or X3. Value, in Represented in the form of (X); based on a linear equation =aX+b, calculate when X=25%. A value of 58 indicates that when the proportion of coal samples with a particle size of 0.1 mm to 0.2 mm is 25%, the caking index of the sample is 58.

Claims

1. A method for correcting the caking index of bituminous coal based on sample particle size, characterized in that, Includes the following steps: S1. Sample preparation: Prepare n bituminous coal samples, where n≥3; The preparation process for each sample is as follows: After grinding, the sample is screened through a vibrating sieve with a mesh size of 0.2 mm to obtain the required total sample. The sample is then divided into two portions using a divider. One portion is used to measure the caking index, and the other portion is used to measure the proportion of coal samples with a particle size of 0.1 mm to 0.2 mm. The mass of the other portion of the sample is denoted as M. This other portion is then sieved through a vibrating sieve with a mesh size of 0.1 mm until the amount passing through twice is less than 0.5% of the mass of the other portion of the sample. Finally, coal samples with a particle size of 0.1 mm to 0.2 mm are selected, and their weight is denoted as M1. X = M1 * 100 / M; Where X represents the proportion of coal samples with a particle size of 0.1 mm to 0.2 mm in another sample; the proportion of coal samples with a particle size of 0.1 mm to 0.2 mm in each of the n samples is denoted as X1, X2, X3...X n ; S2. Test n samples: For the samples used to measure the caking index, if the caking index of the bituminous coal measured for the first time for each sample is <18, use special anthracite and test coal samples in a ratio of 3:3, mix them evenly, and then re-test the caking index. The results of the re-test are calculated using the following formula: ； When the initial caking index of each sample is ≥18, the following procedures are completed: sample weighing, mixing, stirring, briquetting, heating, cooling, secondary drum test, and sieving analysis. The caking index is then calculated using the following formula: ； in, The bonding index of the nth sample; m n For the nth sample, the total mass of coke residue after coking treatment, in g; m n1 For the nth sample, the mass of the material remaining on the sieve after the first drum test, all in g; m n2 For the nth sample, the mass of the material remaining on the sieve after the second drum test, all in g; S3, Result Correction: X1, X2, X3...X n Corresponding adhesion index calculation results , , ... Establish X and n samples Linear equations =aX+b, the square of the correlation coefficient is at least greater than 0.97, otherwise the number of samples to be measured is increased, where a is the slope of the linear equation and b is the intercept of the linear equation; S4. Result Reporting: Calculate the high and low points X1 to X2 of the linear relationship based on the linear equation. n The adhesion index at any ratio X between X and X is the adhesion index at that ratio X. For the final result, and after rounding the result to the nearest integer, X and Report them together.

2. The method for correcting the caking index of bituminous coal by sample particle size according to claim 1, characterized in that, The sample preparation was carried out using a sealed vibratory mill and a reciprocating vibratory screen.

3. The method for correcting the caking index of bituminous coal by sample particle size according to claim 1, characterized in that, In step S1, after the sample is reduced in size, it is dried at a temperature below 40°C for 3 to 4 hours.

4. The method for correcting the caking index of bituminous coal by sample particle size according to claim 1, characterized in that, The amount of material to be ground before grinding is 50-60 grams. Each grinding session lasts 1-5 seconds. All samples are passed through a 0.2mm reciprocating vibrating screen. The samples on the screen are ground repeatedly until all samples pass through the 0.2mm reciprocating vibrating screen.

5. The method for correcting the caking index of bituminous coal by sample particle size according to claim 1, characterized in that, The adhesion index Results are calculated to one decimal place, with the result for each sample being the arithmetic mean of two repeated measurements.

6. The method for correcting the caking index of bituminous coal by sample particle size according to claim 1, characterized in that, The value of X is 10% to 60%, and at least one of the n samples is required to have an X value of 20% to 35%.

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