A method for evaluating the quality stability of coke

Abstract

The present invention belongs to the technical field of metallurgical production, and particularly relates to a method for evaluating the quality stability of coke. The method for evaluating the quality stability of coke includes the following steps: (1) calculating the variance of each index of each single type of coke respectively; (2) performing quantile calculation on the variance values of various indexes of the coke obtained in step (1), and establishing a variance grade scoring system according to the calculation results; (3) establishing a weight scoring system for the influence of each index of coke on the quality stability of coke according to the weight analysis of the influence of each index of coke on the quality stability of coke, and assigning weight scores to the single index of each single type of coke; (4) calculating the quality stability values of various cokes. The magnitude of this score can represent the quality stability of various cokes, which is convenient for operators to blend coke according to the stability of various cokes, and plays an important role in avoiding adverse phenomena such as poor blast furnace permeability, furnace condition fluctuations, and increased coke ratio caused by coke stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of metallurgical production, and particularly relates to a method for evaluating the quality stability of coke. Background Art

[0002] Coke is the main raw fuel for blast furnace smelting. As a reducing agent, energy source, and carbon supplier, the quality and its stability of coke are important factors affecting the operation and running of the blast furnace, and play an important role in reducing the fuel ratio and ensuring the stable and smooth operation of the blast furnace. The properties of coke are directly related to the efficiency and cost of blast furnace smelting.

[0003] The larger the volume of the blast furnace and the higher the coal injection ratio, the more crucial the role of coke as the skeleton support in the blast furnace. Therefore, as a loose skeleton to ensure the permeability of the blast furnace burden column, higher quality requirements are imposed on coke. In addition to requiring lower ash content, sulfur content, and higher cold and hot strength, the long-term continuous stability of various quality indicators is even more crucial. Because stability is the foundation, without coke with stable quality, the basis for intensified smelting of the blast furnace is lost.

[0004] The amount of coke produced by most steel plants cannot meet the production needs, and coke needs to be purchased externally. However, during the same period, there are sometimes more than a dozen types of externally purchased coke used in the same blast furnace. In addition, coke can be divided into top-charged coke and stamped coke according to the charging method, and can be divided into dry quenched coke and wet quenched coke according to the quenching method, and each has its own production process, resulting in different quality stabilities of each type of externally purchased coke. Although samples are taken and tested for each batch of externally purchased coke when it enters the factory, single sampling and testing have contingency, and the sample test results do not necessarily truly reflect the quality of this type of coke. If coke blending production is carried out without scientifically and reasonably mastering the quality stability of coke, it may lead to poor blast furnace permeability; furnace conditions fluctuate; coke ratio increases and other phenomena.

[0005] Gao Bing, Zhang Jianliang, Zuo Haibin, etc. Evaluation of Coke Quality in 2000m 3 Blast Furnace [J]. Iron & Steel, 2014(2): 9-14. gives a method for evaluating coke quality. This method is obtained by adding the score values of 6 indicators; the scoring of each indicator is based on its influence on the blast furnace production indicators, that is, the coke ratio is selected as the evaluation standard. And the influence of each indicator on the blast furnace coke ratio is based on the currently recognized empirical data, which belongs to the smelting law applicable to 2000m 3 Blast furnace. To comprehensively consider the role of each indicator in the blast furnace and its influence on the change of coke ratio, corresponding weights are assigned according to the influence of each indicator on the blast furnace coke ratio, so as to obtain the coke evaluation score. It is stipulated that the total score is 100 points, among which the ash content, M10, CRI, and CSR are each at most 20 points, M40 is at most 15 points, and the sulfur content is at most 5 points. The data used in the coke quality evaluation model in the said evaluation method is still the sampling test result of a single batch of externally purchased coke to be detected.

[0006] Even when modifying the scoring criteria for each index of coke according to the actual situation of the blast furnace, the sum of the scores of each index must be 100 points; after any one of the upper and lower limits, influence factors, and scores of each index is modified, it is necessary to ensure that the difference between the product of the influence factor and the index range and the total score value of a single item is within 1.

[0007] Thus, it can be seen that this coke quality evaluation method has great limitations and contingency. The evaluation result can only show the quality of this batch of coke, but cannot accurately grasp the quality stability of coke.

[0008] At present, there is an urgent need for a more reasonable and objective coke quality stability evaluation method that can effectively evaluate the stability of the coke quality used in blast furnace production, obtain more reasonable coke performance data, and use this data to guide coke blending, which is more conducive to the stable production of blast furnace. Summary of the Invention

[0009] The present invention provides a method for evaluating the quality stability of coke. This method conducts statistical analysis on the long-term existing detection data of various cokes; calculates the quality stability score of coke, and the magnitude of this score can characterize the quality stability of coke, which is convenient for operators to blend coke according to the stability of various cokes, and plays an important role in avoiding adverse phenomena such as poor blast furnace permeability, furnace condition fluctuations, and increased coke ratio caused by coke stability.

[0010] The specific technical solution is as follows:

[0011] A method for evaluating the quality stability of coke includes the following steps:

[0012] (1) Calculate the variance of each index of each single coke respectively, and the calculation formula is as follows:

[0013]

[0014] In the formula, S 2 - The variance of a certain index of a single coke;

[0015] x1~x n - The existing detection data of this index of this single coke within the selected time period;

[0016] - The average value of the existing detection data sample x1~x n ;

[0017] n - The number of samples of existing detection data;

[0018] Taking the average particle size index of a certain single type of coke as an example for illustration: Using a total of 280 sets of existing average particle size test results of this single type of coke within one year as samples, calculate the variance of the average particle size of this single type of coke. Then n is 280, and x1 to x n are the 1st data to the 280th data respectively, is the average value of the 280 data, and the calculated S 2 is the variance of the average particle size of this single type of coke. Calculate the variance values of the various indicators of all types of coke within this year in this way successively.

[0019] (2) Conduct quantile calculations on the variance values of the various indicators of each single type of coke obtained in step (1), and establish a variance level scoring system according to the calculation results;

[0020] List the variance values of the various indicators of all types of coke calculated in a table, and conduct quantile calculations on the variances of the same indicator in this table. Quantiles refer to the numerical points that divide the probability distribution range of a random variable into several equal parts. Commonly used ones include the median (i.e., the quantile), quartiles, percentiles, etc.

[0021] (3) Based on the weight analysis of the influence of the various indicators of coke on the quality stability of coke, establish a weight scoring system for the various indicators of coke on the quality stability of coke, and assign weight scores to the single indicators of single types of coke;

[0022] (4) Calculate the quality stability values of each single type of coke. The calculation formula is as follows:

[0023] Coke quality stability value = ∑(variance level scoring value of a single indicator of a single type of coke × weight score of a single indicator of a single type of coke) / 100.

[0024] In the present invention, the various indicators in step (1) of the method for evaluating the quality stability of coke include average particle size, coke fines < 25mm, Mt, Vd, Ad, St,d, M40, M10, CRI, and CSR.

[0025] Among them, coke fines < 25mm means the coke with a particle size < 25mm in the sample coke; Mt means the total moisture of coke; Vd means the volatile matter of dry - basis coke; Ad means the ash content of dry - basis coke; St,d means the S content of dry - basis coke; M40 means the cold - state mechanical strength index of coke; M10 means the abrasion resistance strength index of coke; CRI means the reactivity index of coke. CSR means the strength after reaction index.

[0026] In the present invention, in step (2) of the method for evaluating the quality stability of coke, the quantile calculation is respectively performed on the variance values of the same index of all types of coke to obtain the minimum value, 25th percentile value (lower quartile value), 50th percentile value, 75th percentile value (upper quartile value), and maximum value of the variance of the same index.

[0027] Furthermore, in the method for evaluating the quality stability of coke, according to the quantile calculation results, the variance values of the same index of all types of coke are divided into four range intervals: the minimum value - 25th percentile value interval, 25th percentile value - 50th percentile value interval, 50th percentile value - 75th percentile value interval, and 75th percentile value - maximum value interval; and the variance is divided into four grades according to the four range intervals: the variance value in the minimum value - 25th percentile value interval is grade 1; the variance value in the 25th percentile value - 50th percentile value interval is grade 2; the variance value in the 50th percentile value - 75th percentile value interval is grade 3; the variance value in the 75th percentile value - maximum value interval is grade 4.

[0028] Even further, in the method for evaluating the quality stability of coke, the score for grade 1 is 100 points; the score for grade 2 is 90 points; the score for grade 3 is 80 points; the score for grade 4 is 70 points. The smaller the variance, the smaller the data fluctuation, and the better the coke quality.

[0029] In the present invention, in the method for evaluating the quality stability of coke, the same weight scores are assigned to the ten indexes of average particle size, fines <25mm, Mt, Vd, Ad, St,d, M40, M10, CRI, and CSR. This application believes that the weights of these ten indexes for the quality stability of coke are quite the same, so the same weight scores are assigned, for example, the weight scores are all 1 point, and the total score is 10 points.

[0030] The beneficial effects of the present invention are as follows: The method for evaluating the quality stability of coke according to the present invention judges the quality stability based on the volatility of the long-term detection results of various indexes of single coke, and gives the calculation method and scoring standard. According to this method, the quality stability scores of various cokes can be obtained. The size of this score can represent the quality stability of various cokes. The larger the score, the better the quality stability of coke, which is convenient for operators to blend coke according to the stability of various cokes, and plays an important role in avoiding the adverse phenomena such as poor blast furnace permeability, furnace condition fluctuation, and increased coke ratio caused by coke stability. The detection results of each index of the current coke can also be corrected by the obtained stability score, so as to obtain more reasonable data of each index, and guiding coke blending with this data is more conducive to the stable production of the blast furnace. Specific embodiments

[0031] The following further illustrates the present invention with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0032] Example 1

[0033] The quality stability of 15 kinds of cokes from a certain steel plant in the past year was evaluated by the described method. The specific steps are as follows:

[0034] (1) The following ten indexes of coke are used: average particle size, fines < 25mm, Mt, Vd, Ad, St,d, M40, M10, CRI, and CSR. The variance of each of the ten indexes of 15 kinds of cokes is calculated respectively according to the following formula.

[0035]

[0036] In the formula, S 2 - The variance of a certain index among the ten indexes of a certain coke among 15 kinds of cokes A - O;

[0037] x1~x 280 - The existing test data of this index of this kind of coke within one year;

[0038] - The average value of the existing 280 test data x1~x 280 ; n is 280. The obtained results are shown in Table 1.

[0039] Table 1 Calculation results of variances of test data of 15 kinds of cokes from a certain steel plant in the past year

[0040]

[0041]

[0042] (2) According to the variance values of the ten indexes of 15 kinds of cokes A - O obtained in Table 1, the quantile calculation is carried out. First, the minimum value, 25th percentile value (lower quartile value), 50th percentile value, 75th percentile value (upper quartile value), and maximum value of the variance of the same index of 15 kinds of cokes are obtained.

[0043] Taking the average particle size index of 15 kinds of cokes A - O as an example, the calculation process is described in detail:

[0044] ① Sort the 15 values of the average particle size of cokes A - O from small to large: 0.012, 0.045, 0.056, 0.078, 0.545, 0.687, 0.982, 0.982, 1.012, 1.325, 1.451, 1.785, 3.347, 3.642, 6.541;

[0045] ② There are 14 intervals for 15 numbers. Therefore, each quartile has 14 / 4 = 3.5 numbers;

[0046] ③ Calculate the 25th percentile value: This value is the 1 + 3.5 = 4.5th number among the 15 numbers sorted in ①, that is, 0.078+(0.545 - 0.078)×0.5 = 0.3115;

[0047] ④ Calculate the 50th percentile value: This value is the 8th number among the 15 numbers sorted in ①, that is, 0.982;

[0048] ⑤ Calculate the 75th percentile value: This value is the 11.5th number among the 15 numbers sorted in ①, that is, 1.451+(1.785 - 1.451)×0.5 = 1.618.

[0049] Other indicators are calculated successively according to the above algorithm, and the percentile calculation results of the variance values of the 15 kinds of coke are shown in Table 2.

[0050] Table 2 Percentile calculation results of variance values of 15 kinds of coke in a steel plant

[0051]

[0052] Then, divide the variance values of the same indicator of the 15 kinds of coke into four range intervals: minimum value ~ 25th percentile value interval, 25th percentile value ~ 50th percentile value interval, 50th percentile value ~ 75th percentile value interval, and 75th percentile value ~ maximum value interval.

[0053] Divide the variance into four grades according to the four range intervals described above: The variance value in the minimum value ~ 25th percentile value interval is grade 1, with a score of 100 points;

[0054] The variance value in the 25th percentile value ~ 50th percentile value interval is grade 2, with a score of 90 points;

[0055] The variance value in the 50th percentile value ~ 75th percentile value interval is grade 3, with a score of 80 points;

[0056] The variance value in the 75th percentile value ~ maximum value interval is grade 4, with a score of 70 points.

[0057] For the specific variance grade division situation, see Table 3 for details.

[0058] Table 3 Variance grade division

[0059]

[0060]

[0061] Assign scores to the variance values of each indicator of the 15 kinds of coke A - O according to Table 3, and the detailed results are shown in Table 4.

[0062] Table 4 Score assignment situation of variance values of each indicator of 15 kinds of coke

[0063]

[0064] (3) Based on the weight analysis of the influence of various coke indicators on the quality stability of coke, a weight scoring system for the influence of each coke indicator on the quality stability of coke is established, and weight scores are assigned to individual indicators of single cokes; the weight scores for the above ten indicators are all 1 point, and the total score is 10 points. See Table 5 for details.

[0065] Table 5 Weight scores of each coke indicator for the influence on the quality stability of coke

[0066]

[0067]

[0068] (4) Calculate the quality stability values of various cokes. The calculation formula is as follows:

[0069] Coke quality stability value = ∑(variance grade score value of single coke single indicator × weight score of single coke single indicator) / 100.

[0070] Take Coke A as an example to calculate its coke quality stability.

[0071] Coke A quality stability = (80×1 + 70×1 + 90×1 + 70×1 + 90×1 + 70×1 + 80×1 + 80×1 + 70×1 + 80×1) / 100 = 7.8. The quality stability values of the remaining types of cokes are calculated respectively according to this calculation method. See Table 6 for details.

[0072] Table 6 Quality stability values of 15 kinds of cokes

[0073] Coke type Mass stability value A 7.8 B 8.6 C 8.2 D 9.3 E 8.4 F 7.6 G 8.6 H 8.7 I 7.3 J 8.5 K 8.1 L 9.1 M 8.5 N 9.3 O 8.9

[0074] As can be seen from Table 6, the ranking of the quality stability of 15 kinds of cokes is D = N > L > O > H > G = B > J = M > E > C > K > A > F > I.

Claims

1. A method for evaluating the quality stability of coke, characterized in that, It includes the following steps: (1) Calculate the variance of each index of each single kind of coke respectively. The calculation formula is as follows: where S 2 - Variance of a certain index of a certain single kind of coke; x1 to x n - Existing test data of this single coke for this index during the selected time period; - The average value of the existing detection data samples x1 to x n ; n - the number of sample cases of existing detection data; (2) Calculate the quantiles of the variance values of each index of each single kind of coke obtained in step (1), and establish a variance level scoring system according to the calculation results; (3) Establish a weight scoring system for the influence of each index of coke on the quality stability of coke according to the weight analysis of the influence of each index of coke on the quality stability of coke, and assign weight scores to the single indexes of single kinds of coke; (4) Calculate the quality stability value of each single kind of coke. The calculation formula is as follows: Coke quality stability value = ∑(variance level score value of single index of single kind of coke × weight score value of single index of single kind of coke) / 100.

2. The method for evaluating the quality stability of coke according to claim 1, wherein In step (1), the indexes include average particle size, coke fines < 25mm, Mt, Vd, Ad, St,d, M40, M10, CRI and CSR.

3. The method for evaluating the quality stability of coke according to claim 1, characterized in that, In step (2), calculate the quantiles of the variance values of the same index of all kinds of coke respectively, and obtain the minimum value, 25th percentile value, 50th percentile value, 75th percentile value and maximum value of the variance of the same index.

4. The method for evaluating the quality stability of coke according to claim 3, characterized in that, According to the quantile calculation results, divide the variance values of the same index of all kinds of coke into four range intervals: minimum value - 25th percentile value interval, 25th percentile value - 50th percentile value interval, 50th percentile value - 75th percentile value interval and 75th percentile value - maximum value interval; and divide the variance into four levels according to the four range intervals: the variance value in the minimum value - 25th percentile value interval is level 1; the variance value in the 25th percentile value - 50th percentile value interval is level 2; the variance value in the 50th percentile value - 75th percentile value interval is level 3; the variance value in the 75th percentile value - maximum value interval is level 4.

5. The method for evaluating the quality stability of coke according to claim 4, characterized in that, The score of level 1 is 100 points; the score of level 2 is 90 points; the score of level 3 is 80 points; the score of level 4 is 70 points.

6. The method for evaluating the quality stability of coke according to claim 2, characterized in that, Assign the same weight scores to the indexes of average particle size, coke fines < 25mm, Mt, Vd, Ad, St,d, M40, M10, CRI and CSR.

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