JPH04256853A - Strength testing method after reaction of coke - Google Patents

Abstract

PURPOSE:To obtain the strength testing method after the reaction of coke characterized by high testing accuracy and high representativeness of a sample under test. CONSTITUTION:The testing accuracy can be improved by setting the particle size of a sample under test at 15mm or less and/or shortening the reaction time to less than 2 hours and more than 0.5 hour. When the amount of the sample of lump coke is set at 20kg or less, the testing accuracy can be further improved. When the range of the particle size of the sample under test us set at 3mm or more, the yield of the samples is improved, and the representativeness of the sample under test can be enhanced.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for testing post-reaction strength, which is one of the quality control indices for metallurgical coke.

0002

[Prior Art] Methods for testing the post-reaction strength of metallurgical coke include Japanese Patent Publication No. 16165/1972 and Coke Circular, Vol. 23, No. 2, pp. 82-87 (published in 1972) published by Japan Fuel Association. There is a method described in This test method consists of: (1) reducing the sampled lump coke to obtain a 10 kg sample; (2) crushing and sieving this 10 kg sample to obtain a 19-21 mm sample;
The process consists of four steps: a sample of 9 to 21 mm is reduced to 200 g to prepare a test sample, and (1) this test sample is reacted with carbon dioxide gas for 2 hours, and then the strength is measured.

The post-reaction strength of coke measured by this method is widely used as one of the important coke quality control indices not only in Japan but also in other countries.

0004

[Problems to be Solved by the Invention] However, compared to other quality control indices such as the cold strength of coke, this method has somewhat larger test variations, and further improvement in test accuracy is desired.

In addition, in this method, the sampled lump coke is crushed and sieved to obtain coke with a particle size range of 19 to 21 mm, which is used in the test.
Since the yield of coke in the 1 mm particle size range is low at 15-20%, there is a problem that the representativeness of this sample is rather low as to whether it is representative of the quality of the original lump coke as a whole.

[0006]

[Means and effects for solving the problem] In order to improve the accuracy of testing the strength of coke after reaction, the present invention sets the average value of the sample particle size to 15 mm or less, and/or the reaction time is less than 2 hours. .Adopt a method that requires at least 5 hours. In addition, in order to further improve the test accuracy, a method is adopted in which a test sample is obtained by crushing, sieving, and reducing 20 kg or more of lump coke.

[0007] Furthermore, the present invention employs a method in which the particle size range of the test sample is set to 3 mm or more in order to improve the representativeness of the test sample with respect to the overall quality of the original lump coke.

[0008] As a result of examining the test errors in each step of the conventional post-reaction strength testing method, the inventor found that 19 to 21
It was found that the test error in the process of reducing a mm sample to 200 g was extremely large. Also, this cause is from 19 to
Since the range of strength after reaction of each 21 mm coke particle is distributed over a very wide range, it is reduced to 200 g.
It was found that if the number of particles is set to about 1, the reduction accuracy deteriorates.

[0009] To solve this problem, it is possible to increase the number of particles in the test sample, but if the weight of the test sample is increased by 200 g, the test equipment must be increased in size, and the amount of carbon dioxide required for the test must be increased. The amount of carbon gas increases and the test cost also increases. Therefore, we invented a method to increase the number of particles while keeping the weight of the sample constant at 200 g by reducing the particle size of the sample to improve the reduction accuracy. The number of test samples is approximately 3 of the sample particle size.
Since it is inversely proportional to the second power, it is sufficient that the sample particle size is 15 mm or less. However, from the standpoint of measuring the strength of coke lumps, the sample particle size must be at least 5 mm or more.

Furthermore, by shortening the reaction time with carbon dioxide, which is 2 hours in the conventional method, test errors can be reduced.
We also found that the ability to detect differences between samples is improved because the differences between samples do not change. However, in consideration of compensation for the drop in sample temperature at the initial stage of the reaction, a minimum reaction time of 0.5 hours is required.

[0011] In this way, the average value of the sample particle size was set to 15 mm.
The test error is reduced by the following method and/or the reaction time is less than 2 hours and 0.5 hours or more. However, since the error variance of the entire test is the sum of the error variances of all processes, if the errors of other processes are large, the effect of reducing the overall test error becomes small. The inventor found that the process of reducing sampled lump coke to obtain a 10 kg sample had a large test error. The reduction of lump coke to 10 kg is also adopted in the dry method of the coke rolling strength test method of JIS K 2151. However, in the case of post-reaction strength tests, the range of post-reaction strength of each lump coke particle is distributed over a very wide range, so for a sample weight of 10 kg, the number of particles is small, around 100, and the reduction accuracy is low. There was found. To solve this problem,
It has been found that it is sufficient to take a lump coke sample of 20 kg or more, preferably 30 kg or more in order to cope with the case where the particle size of the lump coke is large.

[0012] The reason why the particle size range of the test sample is set to 2 mm in the conventional test method for post-reaction strength is to prevent large variations in the reaction rate, since the specific surface area and reaction rate vary depending on the sample particle size. This is to prevent this. However, the inventors have found that although the reaction rate does change when the sample particle size is changed, the post-reaction strength does not substantially change. From this, the range of sample particle size was set at 3 m.
We have devised a method for testing the post-reaction strength to ensure that the strength is at least m. According to this method, the representativeness of the test sample is improved because the yield of the test sample is increased. Furthermore, the accuracy of testing strength after reaction does not decrease.

[0013]

[Example] Example 1 Five samples of 10 kg were taken by reduction from a large sample of 250 kg sampled from one day's worth of coke from a coke oven, and each sample was reacted using the method shown in Table 1. The strength was measured. Both measurements of post-reaction strength are carried out at 2
I went there once. Such a test was repeated for 30 days. One-way analysis of variance was performed on the results to calculate the test error of the post-reaction strength. As shown in Table 1, in all cases of the methods of the present invention (Test Methods 2 to 5), the test errors were significantly improved compared to the conventional method (Test Method 1).

[0014] Furthermore, from this result, an SN ratio, which is defined by the following formula and represents the ability to detect differences between different coke samples, was calculated. As shown in Table 1, in all cases of the method of the present invention, the SN ratio was significantly improved compared to the conventional method.

[0015] SN ratio [dB] = 10 × log10 (variance between samples / error variance) In test method 5 of Table 1, the particle size range of the test sample is expanded to 4 mm by the method of the present invention, so that pulverization and The yield after sieving is high and the representativeness of the sample is improved.

[0016]

[Table 1]

Example 2 A large sample of 250 kg sampled from one day's worth of coke from a coke oven was reduced to 10 kg and 5 kg, respectively.
A sample of 0 kg was taken. Both are crushed and sieved to 8
The thickness was adjusted to ~12 mm, and 200 g of each sample was reduced and reacted with carbon dioxide for 1 hour, and the strength after the reaction was measured. The strength after the reaction was measured twice.

[0018] Such a test was repeated for 30 days. A one-way analysis of variance was performed on the results, and the test error of the post-reaction strength was calculated, as shown in Table 2.
The error variance when using a 10 kg sample using the conventional method is 1.
71, whereas the error variance when using the method of the present invention using a 50 kg sample was 0.91, which was significantly improved.

[0019]

[Table 2]

[0020]

[Effects of the Invention] According to the present invention, the accuracy and detection power of the post-reaction strength test of coke are greatly improved. This makes it possible to more appropriately change the blend of coking coal for quality control of coke and change the operation of coke ovens, thereby reducing the use of expensive coal and gas for heating coke ovens. The effect is large.

[0021] Furthermore, as a result of improving the accuracy of coke quality control, blast furnace operation becomes stable, and costs can be reduced by lowering the coke ratio and stabilizing the quality of hot metal.

Claims (4)

[Claims] Claim 1: The average particle size of the test sample is 15 mm or less, and/or the reaction time is less than 2 hours.
A method for testing the post-reaction strength of coke, characterized in that the test method is performed for a period of time or more. 2. The method for testing the post-reaction strength of coke according to claim 1, wherein the sample particle size range is 3 mm or more. 3. The method for testing the post-reaction strength of coke according to claim 1, wherein a test sample is obtained by crushing, sieving, and reducing lump coke weighing 20 kg or more. 4. The method for testing the post-reaction strength of coke according to claim 2, wherein the test sample is obtained by crushing, sieving, and reducing lump coke weighing 20 kg or more.