Method for measuring and distinguishing isotropic optical structure reactivity of coke

Abstract

The invention discloses a method for measuring and distinguishing isotropic optical structure reactivity of coke. The method comprises the following steps: S1, preparing a coke optical analysis sample before and after reaction with CO2; s2, measuring the content and reflectivity of isotropic optical tissues in the coke optical analysis sample; and S3, calculating the reactivity of the isotropic optical tissue. According to the method, the isotropic optical structures are distinguished by adopting the reflectivity parameters, the reactivity of the isotropic optical structures with different reflectivity is quantitatively calculated, the property difference between the isotropic optical structures is effectively identified, and a coke quality evaluation system is perfected.

Description

Technical Field

[0001] The present invention relates to blast furnace smelting and coal blending coking technology in iron and steel metallurgy, and more particularly to a method for measuring and distinguishing the isotropic optical structure reactivity of coke. Background Art

[0002] As blast furnace capacity increases, unit investment, energy consumption, and pollution emissions decrease, while labor productivity increases. Therefore, the large-scale blast furnace has become a trend in contemporary blast furnace smelting technology. With the increase in blast furnace size, the quality requirements for raw materials have also become increasingly stringent. In particular, the quality of coke is crucial to the smooth operation and technical and economic indicators of the blast furnace. There is even a saying that blast furnace production depends on "70% on raw materials and 30% on operation." When evaluating coke quality, blast furnace operators not only focus on indicators such as ash content, sulfur content, and mechanical strength, but also pay more attention to the thermal properties of coke, namely the reactivity with CO2 (CRI) and the post-reaction strength (CSR). These indicators are directly related to the coke's role as a skeletal support in the blast furnace, a role that no other material can replace.

[0003] The reactivity and post-reaction strength of coke are primarily influenced by multiple factors, including pore structure, pore wall structure, and ash composition. Existing research indicates that the pore walls of coke are composed of different microscopic optical structures. These structures can be categorized as isotropic, filamentous carbon, and fragmentary (the optical properties of all three are isotropic and can be considered generalized isotropy, with their sum represented by ∑ISO), fine-grained mosaic, coarse-grained mosaic, fluidic, lamellar, and fundamentally anisotropic. The optical properties of the latter five exhibit varying degrees of anisotropy. Numerous studies have examined the reactivity of various optical structures in coke with CO₂, such as those by Zhou Shiyong (see "Coking Coal Properties and Blast Furnace Coke Quality," Metallurgical Industry Press, 1st edition, June 2005) and by Chen Hongbo, Bai Xiangfei, et al. (see "Research on the Relationship between Coke Optical Structure and Coal and Coke Quality," Clean Coal Technology, No. 6, 2009). These studies share a common underlying principle: the reactivity of all isotropic materials (including filament-like carbon and fragments) with CO₂ is considered equal, while the reactivity of anisotropic optical structures differs significantly from that of isotropic materials, with the latter being higher than the former. Therefore, the reactivity of coke essentially depends on the content of isotropy and the five anisotropies in the microscopic optical structure. Under normal conditions, the higher the content of isotropic optical structure in the coke, the higher the reactivity, i.e., the worse the thermal properties of the coke. This is because isotropic optical structures primarily originate from weakly caking coals such as gas coal and 1 / 3 coking coal in the coking feedstock, while anisotropic optical structures primarily originate from strongly caking coals such as coking coal and fat coal in the coking feedstock. As is well known, the price of strongly caking coal is much higher than that of weakly caking coal. To control the isotropic content in the final coke, the proportion of weakly caking coal used must be strictly controlled, which is detrimental to reducing coke production costs.

[0004] In-depth research on the reactivity of isotropic optical structures has revealed that even isotropic microscopic optical structures may have different reflectivity indicators, which means that the "molecular weight" of the unit structures that make up these microscopic optical structures may be different. In theory, differences in "molecular weight" may lead to differences in chemical reactivity. Therefore, the chemical reactivity of all isotropic optical structures cannot be considered equal, but should be differentiated. The purpose of differentiation is, on the one hand, to more accurately and scientifically describe the chemical properties of microscopic optical structures, and on this basis, to comprehensively and correctly evaluate the quality of coke. On the other hand, differentiation can determine which isotropic optical structures have better thermal properties than other isotropic optical structures, and which type of raw coal these better isotropic optical structures come from. With this information, it is possible to further optimize the coal blending structure, improve coke quality, and reduce production costs. Summary of the Invention

[0005] In response to the defects in the prior art, the purpose of the present invention is to provide a method for measuring and distinguishing the reactivity of isotropic optical tissue in coke. The reflectivity parameter is used to achieve the distinction of isotropic optical tissue, and the reactivity of isotropic optical tissue with different reflectivities is quantitatively calculated, which effectively identifies the property differences between isotropic optical tissues and improves the coke quality evaluation system.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for determining and distinguishing the isotropic optical tissue reactivity of coke comprises the following steps:

[0008] S1, preparing coke optical analysis samples before and after reaction with CO2;

[0009] S2, determining the content and reflectivity of the isotropic optical structure in the coke optical analysis sample;

[0010] S3, Calculation of isotropic optical tissue reactivity.

[0011] Preferably, the step S1 specifically includes:

[0012] The coke before and after reaction with CO2 is crushed respectively, and then the coke powder is mixed with a binder to form a block. The block is ground and polished to obtain a coke optical analysis sample that meets the requirements of microscope analysis.

[0013] Preferably, the particle size of the crushed coke is 0.1 to 1 mm.

[0014] Preferably, the step S2 specifically includes:

[0015] A single polarizing optical microscope with a 20x oil immersion objective was used;

[0016] The coke optical analysis sample is observed under a microscope to identify the isotropic optical structure in the coke pore wall. The ratio of the area of ​​the isotropic optical structure to the total area of ​​the pore wall is calculated, and the ratio is the isotropic optical structure content.

[0017] Preferably, when measuring the reflectivity of an isotropic optical tissue, the number of fields observed under the microscope is no less than 200.

[0018] Preferably, the calculation formula of step S3 is as follows:

[0019]

[0020] Where, CRI ISO is the calculated isotropic optical structure reactivity of coke; ∑ISO BRis the isotropic optical structure content of coke before reaction; ∑ISO AR is the isotropic optical structure content of coke after the reaction; CRI is the reactivity index of coke, that is, the percentage of weight loss of coke before and after the reaction with CO2.

[0021] The present invention provides a method for measuring and differentiating the reactivity of isotropic optical structures in coke. This method uses reflectivity parameters to differentiate isotropic optical structures and quantitatively calculates the reactivity of isotropic optical structures with different reflectivities, effectively identifying the differences in properties between isotropic optical structures and improving the coke quality evaluation system. Furthermore, this differentiation can determine which isotropic optical structures exhibit superior thermal properties compared to others. This allows for further optimization of coal blending, improved coke quality, and reduced production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 1 is a schematic flow chart of a method for determining and distinguishing isotropic optical tissue reactivity of coke according to the present invention;

[0023] Figure 2 2 is a schematic diagram of a coke isotropic optical tissue reflectivity measuring device in an embodiment of a method for measuring and distinguishing coke isotropic optical tissue reactivity of the present invention;

[0024] Figure 3 1 is a schematic diagram of a curve showing a corresponding relationship between pixel values ​​and reflectance obtained by calibration with a standard substance in an embodiment of a method for measuring and distinguishing isotropic optical tissue reactivity of coke according to the present invention;

[0025] In the accompanying drawings: 1—microscope light source, 2—polarizer, 3—stage, 4—sample to be measured, 5—objective lens, 6—eyepiece, 7—digital camera, 8—computer. DETAILED DESCRIPTION

[0026] In order to better understand the above technical solutions of the present invention, the technical solutions of the present invention are further described below with reference to the accompanying drawings and embodiments.

[0027] Combine Figure 1 As shown, the present invention provides a method for measuring and distinguishing the isotropic optical tissue reactivity of coke, comprising the following steps:

[0028] S1, preparing coke optical analysis samples before and after reaction with CO2. Specifically including:

[0029] The coke before and after the reaction with CO2 is crushed into 0.1-1 mm respectively, and then the coke powder is mixed with a binder to form a block. The block is ground and polished to obtain a coke optical analysis sample that meets the requirements of microscope analysis.

[0030] S2, determining the content and reflectivity of isotropic optical structure in the coke optical analysis sample. Specifically including:

[0031] A single-lens optical microscope with a 20x oil-immersion objective was used to observe the coke optical analysis sample. The isotropic optical structure in the coke pore walls was identified, and the ratio of the isotropic optical structure area to the total pore wall area was calculated. This ratio was the isotropic optical structure content (∑ISO). After the isotropic optical structure was identified, the reflectivity of the isotropic optical structure was measured. When measuring the reflectivity of the isotropic optical structure, the number of fields observed under the microscope should be no less than 200.

[0032] S3, calculate the reactivity of isotropic optical tissue. The calculation formula is as follows:

[0033]

[0034] Where, CRI ISO is the calculated isotropic optical structure reactivity of coke; ∑ISO BR is the isotropic optical structure content of coke before reaction; ∑ISO AR is the isotropic optical structure content of coke after the reaction; CRI is the reactivity index of coke, that is, the percentage of weight loss of coke before and after the reaction with CO2.

[0035] Example 1

[0036] This embodiment provides a method for measuring and distinguishing the isotropic optical tissue reactivity of coke, comprising the following steps:

[0037] S1, preparation of coke optical analysis samples before and after reaction with CO2:

[0038] Take approximately 200g of a reactive coke sample prepared according to the GB / T4000-2008 standard, crush it completely, and sieve it to obtain 0.1-1mm coke powder. Take approximately 5g of the 0.1-1mm coke powder and mix it with a binder (epoxy resin) at a weight ratio of 1:2. The mixed powder is pressed under a certain temperature and pressure to form a block with a diameter of no less than 25mm. The pressing temperature and pressure depend on the selected binder. After grinding and polishing, the block becomes a sample suitable for optical analysis, suitable for observation under an optical microscope.

[0039] S2, analyze the isotropic optical structure content and reflectivity of the coke before reaction:

[0040] Combine Figure 2As shown, the coke optical analysis sample 4 prepared in step S1 is placed on the stage 3 in preparation for analysis. Computer 8 controls the polarizer 2 via a transmission system to rotate a certain angle, thereby converting natural light incident from light source 1 into polarized light with different polarization angles. Computer 8 also controls the stage 3 via the transmission system to move in three dimensions: front-to-back, left-to-right, and up-and-down, thereby enabling image capture of multiple observation zones on the surface of the coke optical analysis sample 4. The image of the coke optical analysis sample 4, after being magnified 20x by the microscope objective lens 5, can be captured and photographed by a digital camera 7 or viewed directly through the eyepiece 6.

[0041] During image acquisition, the number of viewing zones to be analyzed is first set; in this embodiment, 200 is used. Based on the size and number of viewing zones of the coke optical analysis sample 4 to be analyzed, the spacing between adjacent viewing zones can be calculated to achieve a uniform distribution of the 200 viewing zones across the surface of the coke optical analysis sample 4. The calculated spacing between the viewing zones is used as the step length for each movement of the stage 3.

[0042] When collecting images of each field of view, the computer 8 controls the polarizer 2 to rotate to 10 different angles, namely 0°, 18°, 36°, 54°, 72°, 90°, 108°, 126°, 144° and 162°, and collects an image of the field of view at each angle, that is, each field of view obtains a group of 10 digital photos at different rotation angles. After collecting 10 photos, the computer controls the stage to move to the next field of view and perform the same image collection again until all the images of the 200 fields of view are collected. Finally, 200 groups of 10 photos each, totaling 2,000 digital images, are obtained. Each digital image contains 1388*1040 pixels, totaling 1.44 million pixels, and each pixel has a pixel value. According to the standard curve of the corresponding relationship between pixel value and reflectivity obtained by calibration of standard substances, as shown in FIG. Figure 3 As shown, the pixel value of each pixel can be converted into reflectivity.

[0043] Since a set of 10 digital images is collected at 10 angles in the same field of view, it is equivalent to each pixel in the field of view being collected 10 times, obtaining 10 pixel values, corresponding to 10 reflectance values. The maximum value of the 10 reflectances is the maximum reflectance R of the pixel in the field of view. max The minimum value among the 10 reflectances is the minimum reflectance R of the pixel in the field of view. min , maximum reflectivity R max and minimum reflectivity R min The difference is the double reflectivity R of the pixel point in the field of view bi . R max Pixels with a value less than 2.0 are basically holes in the binder and coke, and are invalid pixels. maxPixels with a value greater than or equal to 2.0 correspond to the pore walls of coke and are valid pixels. In order to ensure that the repeatability of the analysis results is within a relatively good acceptable range, the total number of valid pixels in the 200 viewing areas must reach more than 50 million. If it is less than 50 million, the number of viewing areas to be observed should be appropriately increased. Among the valid pixels, R bi Pixels with an optical density less than 0.25 are considered isotropic. The total number of isotropic pixels divided by the total number of effective pixels is the isotropic optical tissue content ∑ISO BR , R of all isotropic pixels max The average value is the reflectivity R of the isotropic optical tissue ISO .

[0044] S3, determination of the reactivity of coke with CO2:

[0045] The gasification reaction of coke and CO2 is carried out according to the reaction conditions of GB / T4000-2008 standard to obtain the reactivity index CRI and the post-reaction strength CSR of the coke.

[0046] S4, preparing optical analysis samples of coke after reaction with CO2:

[0047] The coke reacting with CO2 is crushed and sieved to obtain fine coke of 0.1-1 mm in diameter. Approximately 5 g of this fine coke is mixed with a binder (epoxy resin) at a weight ratio of 1:2. The mixed powder is pressed under a specific temperature and pressure to form a block with a diameter of at least 25 mm. The pressing temperature and pressure depend on the selected binder. After grinding and polishing, the block is subjected to optical microscopy.

[0048] S5, analyze the isotropic optical structure content of the coke after reaction:

[0049] Combine Figure 2 As shown, the coke optical analysis sample 4 prepared in step S4 is placed on the stage 3 in preparation for analysis. Computer 8 controls the rotation of polarizer 2 via a transmission system to a certain angle, thereby converting natural light incident from light source 1 into polarized light with different polarization angles. Computer 8 also controls the movement of stage 3 in three dimensions (front-back, left-right, and up-down) via the transmission system, thereby enabling image capture of multiple observation fields on the surface of the coke optical analysis sample 4 to be tested. The image of the coke optical analysis sample 4, after being magnified 20 times by the microscope objective lens 5, can be captured and photographed by a digital camera 7 or viewed directly through the eyepiece 6.

[0050] During image acquisition, the number of viewing zones to be analyzed is first set; in this embodiment, 200 is used. Based on the size and number of viewing zones of the coke optical analysis sample 4 to be analyzed, the spacing between adjacent viewing zones can be calculated to achieve a uniform distribution of the 200 viewing zones across the surface of the coke optical analysis sample 4. The calculated spacing between the viewing zones is used as the step length for each movement of the stage 3.

[0051] When collecting images of each field of view, the computer 8 controls the polarizer 2 to rotate to 10 different angles, namely 0°, 18°, 36°, 54°, 72°, 90°, 108°, 126°, 144° and 162°, and collects an image of the field of view at each angle, that is, each field of view obtains a group of 10 digital photos at different rotation angles. After collecting 10 photos, the computer controls the stage to move to the next field of view and perform the same image collection again until all the images of the 200 fields of view are collected. Finally, 200 groups of 10 photos each, totaling 2,000 digital images, are obtained. Each digital image contains 1388*1040 pixels, totaling 1.44 million pixels, and each pixel has a pixel value. According to the standard curve of the corresponding relationship between pixel value and reflectivity obtained by calibration of standard substances, as shown in FIG. Figure 3 As shown, the pixel value of each pixel can be converted into reflectivity.

[0052] Since a set of 10 digital images is collected at 10 angles in the same field of view, it is equivalent to each pixel in the field of view being collected 10 times, obtaining 10 pixel values, corresponding to 10 reflectance values. The maximum value of the 10 reflectances is the maximum reflectance R of the pixel in the field of view. max The minimum value among the 10 reflectances is the minimum reflectance R of the pixel in the field of view. min , maximum reflectivity R max and minimum reflectivity R min The difference is the double reflectivity R of the pixel point in the field of view bi . R max Pixels with a value less than 2.0 are basically holes in the binder and coke, and are invalid pixels. max Pixels with a value greater than or equal to 2.0 correspond to the pore walls of coke and are valid pixels. In order to ensure that the repeatability of the analysis results is within a relatively good acceptable range, the total number of valid pixels in the 200 viewing areas must reach more than 50 million. If it is less than 50 million, the number of viewing areas to be observed should be appropriately increased. Among the valid pixels, R bi Pixels with an optical density less than 0.25 are considered isotropic. The total number of isotropic pixels divided by the total number of effective pixels is the isotropic optical tissue content ∑ISO AR .

[0053] S6, Calculate the reactivity of isotropic optical tissue:

[0054] The reactivity of isotropic optical tissue was calculated according to the following formula:

[0055]

[0056] Where: CRI ISO is the calculated isotropic optical structure reactivity of coke; ∑ISO BR is the isotropic optical structure content of the coke before the reaction in step S2; ∑ISO AR is the isotropic optical structure content of the coke after the reaction in step S5; CRI is the coke reactivity index in step S3.

[0057] Example 2

[0058] In this Example 2, two types of gas coal are coked separately to obtain coke A and coke B. The analysis results of thermal properties, isotropic optical structure content, reflectivity, reactivity and other indicators of coke A and coke B are shown in Table 1 below.

[0059] Table 1

[0060] CRI CSR <![CDATA[∑ISO BR ]]> <![CDATA[R ISO ]]> <![CDATA[CRI ISO ]]> Coke A 50.4％ 23.8％ 92.6％ 7.38％ 52.2％ Coke B 66.2％ 14.7％ 84.0％ 7.26％ 69.5％

[0061] From the data in Table 1, the isotropic optical structure content ∑ISO of coke A BR Higher than coke B, according to the traditional view, the reactivity of isotropic optical structure in coke is higher than that of anisotropic optical structure, so the isotropic content (∑ISO BR ) The higher the coke reactivity index (CRI), the higher the coke reactivity index (CRI) should be, and the lower the strength after reaction (CSR) should be, that is, the CRI of A should be higher than B, and at the same time, the CSR of A should be lower than B, so the quality evaluation of A should be worse than B. However, the actual result is that the CRI of A is lower than B, while the CSR of A is higher than B, so the quality of coke A is better than B. This contradiction in the analysis results cannot be explained by the traditional coke quality evaluation method. If we further analyze the reflectivity index of the isotropic optical structure in the two cokes and calculate the reactivity of the isotropic optical structure, we can find that the isotropic reflectivity (R ISO ) is higher than B, corresponding to the isotropic reactivity of A (CRI ISO ) is lower than that of B. Therefore, although A contains more isotropic optical structure than B, the isotropic optical structure of A has a higher reflectivity, indicating that the "molecular weight" of the structural units constituting the isotropic optical structure in A is larger. Therefore, the isotropic reactivity of A is lower than that of B. As a result, the reactivity of coke A is actually lower than that of coke B, indicating that coke A has better quality, which is consistent with the analysis results of actual thermal properties.

[0062] Those skilled in the art should recognize that the above embodiments are merely intended to illustrate the present invention and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A method for determining and distinguishing the isotropic optical tissue reactivity of coke, characterized in that: The following steps are involved: S1, preparing coke optical analysis samples before and after reaction with CO2; S2, determining the content and reflectivity of the isotropic optical structure in the coke optical analysis sample; S3, Calculation of isotropic optical tissue reactivity.

2. The method for measuring and distinguishing the isotropic optical tissue reactivity of coke according to claim 1, characterized in that: The step S1 specifically includes: The coke before and after reaction with CO2 is crushed respectively, and then the coke powder is mixed with a binder to form a block. The block is ground and polished to obtain a coke optical analysis sample that meets the requirements of microscope analysis.

3. The method for measuring and distinguishing the isotropic optical tissue reactivity of coke according to claim 2, characterized in that: The particle size of the crushed coke is 0.1 to 1 mm.

4. The method for measuring and distinguishing the isotropic optical tissue reactivity of coke according to claim 2, characterized in that: The step S2 specifically includes: A single polarized optical microscope was used; The coke optical analysis sample is observed under a microscope to identify the isotropic optical structure in the coke pore wall. The ratio of the area of ​​the isotropic optical structure to the total area of ​​the pore wall is calculated, and the ratio is the isotropic optical structure content.

5. The method for measuring and distinguishing the isotropic optical tissue reactivity of coke according to claim 4, characterized in that: When measuring the reflectivity of isotropic optical tissue, the number of fields observed under the microscope shall be no less than 200.

6. The method for measuring and distinguishing the isotropic optical tissue reactivity of coke according to claim 4, characterized in that: The calculation formula of step S3 is as follows: Where, CRI ISO is the calculated isotropic optical structure reactivity of coke; ∑ISO BR is the isotropic optical structure content of coke before reaction; ∑ISO AR is the isotropic optical structure content of coke after the reaction; CRI is the reactivity index of coke, that is, the percentage of weight loss of coke before and after the reaction with CO2.

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