Method for evaluating coal quality level by using coal coke lithofacies detection indexes

Abstract

The invention discloses a method for evaluating the coal quality level by using coal coke lithofacies detection indexes, which comprises the following steps: S1, measuring the macerals of coal, including the mineral content and the active-inert ratio; s2, measuring coke optical structure indexes of the coal, wherein the coke optical structure indexes comprise an inlaid structure, an anisotropic silk structure and a fragment structure with the coke optical isochromatic zone size of 0-10 microns; s3, calculating an optical tissue coefficient (OTI); and S4, evaluating the coal quality according to the evaluation standard. According to the method, the accuracy and reliability of coal quality evaluation are improved, so that coal quality misjudgment of coal types with various metamorphic degrees is avoided, coal quality resources are reasonably utilized, and high-quality resources are saved and the coal blending cost is reduced on the premise of ensuring the metallurgical performance of coke.

Description

Technical Field

[0001] The present invention relates to the technical field of coal quality evaluation, and in particular to a method for evaluating coal quality levels by utilizing coal coke petrographic detection indicators. Background Art

[0002] Faced with the challenges of limited coal resources and high-cost raw materials in the steel industry, there is an urgent need to establish a system for evaluating coal quality using coal coke petrographic indicators and to establish coal petrographic evaluation systems within each enterprise. This system aims to protect my country's dwindling high-quality coal resources, reduce production costs, and enhance the competitiveness of enterprises.

[0003] Coal vitrinite reflectance is an important indicator of coal metamorphism and effectively characterizes its rank. Coal rock blending technology can promptly identify coal blending that is difficult to determine using traditional coal quality analysis methods, thereby ensuring accurate coal quality assessment.

[0004] Coke, as a porous and brittle material, plays a key role in the skeleton of blast furnace ironmaking. Its macroscopic mechanical strength is mainly measured by its crushing strength (M 40 ) and wear resistance (M 10 ) is used to measure coke strength. In the blast furnace, coke is not only subjected to compression, collision, and abrasion, but also burns at high temperatures and reacts with CO2, causing the coke's pore walls to thin, increasing its porosity and thus reducing its strength. Due to the complex structure of coke, measuring its microstructure and establishing a relationship with coal quality is of great significance for guiding coal quality evaluation and coal blending for coking.

[0005] With the expansion of coke ovens and the development of pulverized coal oxygen-enriched injection technology, blast furnace production has placed increasingly stringent demands on coke quality, particularly hot coke strength. The optical structure of coke is closely related to its hot strength. Therefore, using petrographic microscopic indicators of coal coke to guide ramming coking coal blending is crucial for improving coal quality assessment. Most coking companies have begun using coal petrographic analysis data to scientifically classify coking coal for accurate quality assessment and guidance in coal blending. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for evaluating coal quality level by using coal coke petrographic detection indicators, which can accurately evaluate coal quality.

[0007] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows.

[0008] A method for evaluating coal quality using coal coke petrographic detection indicators comprises the following steps: S1. Determine the microscopic composition of coal, including mineral content and active-inert ratio; S2. Determination of the optical structure of coal coke, including the mosaic structure, anisotropic silky structure, and flaky structure in the coke optical isochromatic zone of 0 to 10 μm; S3. Calculate the optical tissue index (OTI); S4. Evaluate coal quality according to the evaluation criteria.

[0009] Preferably, the mineral content and active-inert ratio in step S1 are determined according to GB / T 8899-2013 "Methods for determination of microscopic components and mineralogy of coal".

[0010] Preferably, the mosaic structure, anisotropic silky structure and flaky structure of the coke with an optical isochoric zone size of 0um to 10um in step S2, and the optical structure coefficient OTI in step S3 are measured in accordance with YB / T 077-2017 "Determination Method of Optical Structure of Coke", and the single-type coal coke is obtained by coking in a 40kg bottom-loaded test coke oven.

[0011] Preferably, the evaluation criteria in step S4 include: coal mineral content ≤ 6%, active-inert ratio between 1.0 and 2.0, mosaic structure with a coke optical isochromatic zone size of 0um to 10um ≥ 35%, anisotropic silky and flaky structure ≤ 50%, and optical structure coefficient OTI ≥ 65, indicating high-quality gas coal.

[0012] Preferably, the evaluation criteria in step S4 include: coal mineral content ≤6%, activity-inertness ratio between 1.0 and 3.0, mosaic structure with coke optical isochromatic zone size of 0um to 10um ≥70%, anisotropic silky and flaky structure ≤30%, optical structure coefficient OTI ≥85, and it is a high-quality gas fertilizer coal.

[0013] Preferably, the evaluation criteria in step S4 include: coal mineral content ≤6%, active-inert ratio between 1.0 and 3.0, mosaic structure with a coke optical isochromatic zone size of 0um to 10um ≥50%, anisotropic silky and flaky structure ≤50%, and optical structure coefficient OTI ≥60, which is high-quality 1 / 3 coal.

[0014] Preferably, the evaluation criteria in step S4 include: coal mineral content ≤ 6%, active-inert ratio between 1.0 and 3.0, mosaic structure with a coke optical isochromatic zone size of 0 μm to 10 μm ≥ 55%, anisotropic silky and flaky structure ≤ 45%, and optical structure coefficient OTI ≥ 100, indicating high-quality fat coal.

[0015] Preferably, the evaluation criteria in step S4 include: coal mineral content ≤ 6%, active-inert ratio between 1.0 and 3.0, mosaic structure with optical isochromatic zone size of 0um to 10um of coke ≥ 60%, anisotropic silky and flaky structure ≤ 40%, and optical structure coefficient OTI ≥ 115, which is high-quality coking coal.

[0016] Preferably, the evaluation criteria in step S4 include: coal mineral content ≤6%, active-inert ratio between 1.0 and 2.0, mosaic structure with coke optical isochromatic zone size of 0um to 10um ≥35%, anisotropic silky and flaky structure ≤55%, optical structure coefficient OTI ≥80, and it is high-quality lean coal.

[0017] Preferably, in the method, the proportion of mosaic tissue with a diameter of 0 μm to 10 μm is used as the first-level classification index of coke, and the anisotropic silky and flaky tissues are used as the second-level classification index of coke.

[0018] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is as follows.

[0019] The present invention can improve the accuracy of coal quality evaluation: by accurately measuring the microscopic components of coal and the optical structure of coke, the coal quality can be evaluated more accurately and reliably, avoiding the misjudgment that may be caused by traditional methods.

[0020] The present invention can optimize the coal blending strategy: it can guide enterprises to carry out scientific coal blending according to coal quality characteristics, rationally utilize various types of coal, improve coal blending efficiency, and ensure the stability of coke quality.

[0021] The present invention can reduce costs: by accurately evaluating coal quality, enterprises can not only avoid using low-quality coal, reduce resource waste, lower production costs, and improve economic benefits, but also produce high-quality coke to meet the market demand for high-quality raw materials.

[0022] The present invention can protect high-quality resources: it helps to identify and protect high-quality coal resources, avoid over-exploitation and waste, and ensure the sustainable use of resources.

[0023] The present invention can improve the performance of coke: through in-depth analysis of the coke microstructure, we can better understand the behavior of coke in the blast furnace, optimize the ironmaking process, and improve the hot strength and metallurgical properties of coke. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Flowchart of the present invention. DETAILED DESCRIPTION

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] A method for evaluating coal quality using coal coke petrographic detection indicators, combined with Figure 1 As shown, the following steps are included: S1. Determine the microscopic composition of coal, including mineral content and active-inert ratio.

[0027] Specifically, the mineral content and active-inert ratio are determined in accordance with GB / T 8899-2013 "Methods for determination of microscopic components and mineralogy of coal". The details are as follows: Drop oil immersion liquid on the polished surface of the leveled pulverized coal light sheet, and place it on the stage of the reflective polarizing microscope. Focus and correct the center of the objective lens, adjust the light source, aperture diaphragm and field of view aperture to make the field of view moderate brightness, uniform light and clear imaging.

[0028] When determining the step length of the stage push ruler, it should be ensured that there are no less than 500 effective measuring points evenly distributed over the entire film. The point pitch should generally be 0.4 mm to 0.6 mm, and the line spacing should not be less than the point spacing.

[0029] Starting from one end of the sample, move along a fixed direction according to a predetermined step length; identify the microscopic components or minerals located under the intersection of the crosshairs and record them in the corresponding counting keys. If cements, cell cavities, holes, cracks in microscopic components, and unidentifiable tiny particles are encountered, they will be regarded as invalid points and not counted.

[0030] When the statistics of one row are finished, the system moves one step in a fixed direction with a predetermined row spacing and continues to count another row until the measurement points cover the entire film.

[0031] When the crosshairs fall on the boundary of different components, starting from the upper right quadrant, the microscopic component or mineral that first fills the quadrant angle should be selected as the statistical object in a clockwise order.

[0032] S2. Determine the optical structure indicators of coal coke, including the mosaic structure, anisotropic silky structure and flaky structure of the coke optical isochromatic area with a size of 0um to 10um.

[0033] S3. Calculate the optical tissue index (OTI).

[0034] Specifically, the mosaic structure, anisotropic silky structure and flaky structure of the optical isochoric zone of coke with a size of 0 μm to 10 μm in step S2 and the optical structure coefficient OTI in step S3 are measured in accordance with YB / T 077-2017 "Determination Method of Optical Structure of Coke", and the single-type coal coke is obtained by coking in a 40 kg bottom-loaded test coke oven.

[0035] The method for obtaining single-type coal coke by coking in a 40kg bottom-loaded test coke oven is as follows: Divide the prepared coal sample into four equal portions and load them into the coal box in four batches. After each batch, use a dedicated bulk density leveling plate to smooth the surface of the coal. Then, use a dedicated bulk density briquetting device to compact the coal to the specified height, ensuring a total height of (90 ± 0.2) mm after each batch. After the second batch of coal, embed a thermocouple iron tube in the center of the coke cake. After batching, ensure a dry bulk density of (800 ± 10) kg / m³. Packing should be completed within 30 minutes.

[0036] A fiber cotton board with a size of 400mm×320mm×10mm is placed on the surface of the coal sample entering the furnace, and there is a circular hole with a diameter of 20mm in the center of the fiber cotton board.

[0037] The furnace temperature is raised to 800℃ and kept constant for more than 3 hours. Then the coal box is quickly raised into the furnace and the furnace door is closed. A thermocouple is inserted into the center of the coke cake.

[0038] If the center temperature of the coke cake reaches 950℃ within 6 hours of constant temperature maintenance of the furnace wall and remains above 950℃ for 30 minutes, it can be taken out of the oven based on the total constant temperature maintenance time of 6 hours.

[0039] Stop the temperature control program, remove the thermocouple from the center of the coke cake, open the furnace door, remove the coal bin, and place it in a dedicated quenching device. Use water spray to quench the coke until there is no red coke. The time from unloading to quenching is controlled within 10 minutes, the quenching water consumption is 20kg, and the quenching time is less than 3 minutes.

[0040] The method for determining the optical structure coefficient (OTI) is as follows: Prepare a representative coke sample (at least 2 kg) with particles less than 3 mm in diameter. Mix and reduce a 1 kg sample, crushing it to a size of less than 1 mm. Mix the sample crushed to 1 mm and reduce it to 40-50 g. The particle size must all be less than 1.0 mm (using a square mesh sieve). Discard any fines smaller than 0.071 mm. However, avoid excessive crushing; the fraction of fines smaller than 0.071 mm should not exceed 15% of the total weight. If the fraction of particles smaller than 0.071 mm exceeds 15% of the total weight, re-prepare the sample until it meets the requirements. Take 4-5 g of the 0.071-1.0 mm sample for tableting.

[0041] Place the specimen on a slide with mortar, flatten it, and then place it on the stage to focus. Correct the center of the objective lens. Adjust the light source, aperture, and field of view diaphragm to ensure moderate brightness, uniform lighting, and a clear image. Adjust the polarizer and analyzer to orthogonal alignment. Insert a gypsum test board (1λ) so that the field of view exhibits the interference color of primary red.

[0042] Determine the step length of the stage moving ruler to ensure that more than 500 effective measuring points are evenly distributed over the entire film. The point pitch should be 0.3mm to 0.5mm, and the line pitch should be 0.4mm to 0.8mm, which should not be less than the point pitch.

[0043] Starting from one end of the specimen, identify the optical structure of the material under the intersection of the crosshairs and count it in the corresponding counting key. Then move one step in a fixed direction according to the predetermined step length. If any cement, pores, cracks, or cavities in the optical structure are encountered, they are considered invalid points and not counted. When the crosshairs fall on the boundary between different optical structures, proceed according to GB / T8899, starting from the upper right quadrant, and in a clockwise direction, select the microscopic component or mineral that first fills the quadrant angle as the statistical object. When the measurement of a row is completed, move one row at the predetermined row spacing and continue measuring until the entire sample is covered with measurement points.

[0044] S4. Evaluate coal quality according to the evaluation criteria.

[0045] Evaluation criteria include: The coal mineral content is ≤6%, the activity-inertness ratio is between 1.0 and 2.0, the mosaic structure of the coke optical isochromatic zone size of 0um to 10um is ≥35%, the anisotropic silky and flaky structure is ≤50%, and the optical structure coefficient OTI is ≥65, which is a high-quality gas coal.

[0046] The coal mineral content is ≤6%, the activity-inertness ratio is between 1.0 and 3.0, the mosaic structure with the optical isochromatic zone size of 0um to 10um of the coke is ≥70%, the anisotropic silky and flaky structure is ≤30%, and the optical structure coefficient OTI is ≥85, which is a high-quality gas fertilizer coal.

[0047] The coal mineral content is ≤6%, the active-inert ratio is between 1.0 and 3.0, the mosaic structure with the optical isochromatic zone size of 0um to 10um of the coke is ≥50%, the anisotropic silky and flaky structure is ≤50%, and the optical structure coefficient OTI is ≥60, which is a high-quality 1 / 3 coal.

[0048] The coal mineral content is ≤6%, the activity-inertness ratio is between 1.0 and 3.0, the mosaic structure of the coke optical isochromatic zone size of 0um to 10um is ≥55%, the anisotropic silky and flaky structure is ≤45%, and the optical structure coefficient OTI is ≥100, which is a high-quality fat coal.

[0049] The coal mineral content is ≤6%, the active-inert ratio is between 1.0 and 3.0, the mosaic structure of the coke optical isochromatic zone size of 0um to 10um is ≥60%, the anisotropic silky and flaky structure is ≤40%, and the optical structure coefficient OTI is ≥115, which is a high-quality coking coal.

[0050] The coal mineral content is ≤6%, the activity-inertness ratio is between 1.0 and 2.0, the mosaic structure of the coke optical isochromatic zone size of 0um to 10um is ≥35%, the anisotropic silky and flaky structure is ≤55%, and the optical structure coefficient OTI is ≥80, which is a high-quality lean coal.

[0051] The reasons for selecting the mosaic structure, anisotropic silky structure and flaky structure of the coke optical isochromatic zone size of 0um to 10um to evaluate the coal quality of each metamorphic degree are as follows: Research has found that the reactivity of coke components is roughly in the following order: isotropic, silky, and fragmented > fine-grained mosaic > medium-grained mosaic > coarse-grained mosaic > fibrous > lamellar. A higher content of isotropic, lamellar, silky, and fragmented coke structures indicates a higher CRI. A higher content of mosaic structures in the coke optical structure indicates a higher CSR.

[0052] The microstructure of coke largely determines its thermal properties. This is primarily because carbon atoms react with CO2 primarily through adsorption of CO2 by surface-active carbon atoms, which are primarily located at the edges and corners of the layers. Lamellar structures have a high degree of graphitization, and their structural units are arranged in planar microcrystals. This makes them susceptible to fracture along the graphite regions when subjected to external forces. Lamellar structures, on the other hand, are primarily held together by molecular forces, making them prone to sliding between layers under external forces, making them susceptible to contact and reaction with CO2. Fibrous structures have larger optical units, densely packed and orderly, and contain fewer active carbon atoms. Mosaic structures have smaller structural units than fibrous structures and contain more active carbon atoms, resulting in slightly greater reactivity. Isotropic carbon layers are randomly packed and arranged, resulting in numerous micropores and active carbon atoms. These carbon layers can adsorb CO2 in all directions, leading to the fastest reaction rate with CO2.

[0053] According to the above data analysis, the distribution of optical structure components in coke is closely related to the degree of metamorphism of the coal type, coal quality, and origin. This is mainly because the vitrinite and stabilizing groups in the coal generate isotropic and anisotropic structures in the coke after heating and solidification; while the inertinite and other components in the coal do not undergo the above process during heating, but directly produce silky and flaky structures. For low-coalification coal, most of the coke is isotropic. As the coalification degree of the coal continues to increase, the isotropy in the coke decreases rapidly, and the mosaic structure in the coke gradually increases. When the quality of the vitrinite group of the coal is improved to a certain level, the content of fibrous tissue in the coke will increase significantly and reach a maximum value. At this time, the lamellar structure also increases rapidly. The present invention uses the proportion of mosaic structure of 0um to 10um as the first-level classification indicator of coke, and anisotropic silky and flaky structures as the second-level classification indicators of coke.

[0054] In the present invention, gas coal, gas fat coal, 1 / 3 coking coal, fat coal, coking coal and lean coal are classified according to the national standard of China's coal classification "GB / T 5751-2009 China Coal Classification".

[0055] The present invention is further described in detail below with reference to specific embodiments.

[0056] A certain factory has 6 types of coking coal resources. The microscopic components of each type of coking coal and the optical structure of the coke produced by each type of coal were measured. The coal quality was evaluated according to the evaluation method of the present invention. The evaluation results are shown in Table 1. Table 1 Microscopic components, coke optical structure and coal quality evaluation of each single coal

[0057] The following describes in detail embodiments of the present invention. The embodiments are illustrative and intended to explain the present invention, but are not to be construed as limiting the present invention.

[0058] The microscopic components and optical structure of coke formed by the same type of coal in a certain factory were measured, and the coal quality level was evaluated by comparing the above-mentioned A coal indicators according to the evaluation method of the present invention. Example 1

[0059] Table 2 Microscopic components of gas coal, optical structure of coke and coal quality evaluation

[0060] Example 2

[0061] Table 3 Microscopic components, coke optical structure and coal quality evaluation of gas fertilizer coal

[0062] Example 3 Table 4 Microscopic components, coke optical structure and coal quality evaluation of 1 / 3 coking coal

[0063] Example 4 Table 5 Microscopic components, coke optical structure and coal quality evaluation of fat coal

[0064] Example 5 Table 6 Coking coal microstructure, coke optical structure and coal quality evaluation Example 6

[0065] Table 7 Lean coal microstructure, coke optical structure and coal quality evaluation 。

Claims

1. A method for evaluating coal quality using coal coke petrographic detection indicators, characterized by: The following steps are involved: S1. Determine the microscopic composition of coal, including mineral content and active-inert ratio; S2. Determination of the optical structure of coal coke, including the mosaic structure, anisotropic silky structure, and flaky structure in the coke optical isochromatic zone of 0 to 10 μm; S3. Calculate the optical tissue index (OTI); S4. Evaluate coal quality according to the evaluation criteria.

2. The method for evaluating coal quality using coal coke petrographic detection indicators according to claim 1, characterized in that: The mineral content and active-inert ratio in step S1 are determined in accordance with GB / T 8899-2013 "Methods for determination of microscopic components and mineralogy of coal".

3. The method for evaluating coal quality using coal coke petrographic detection indicators according to claim 1, characterized in that: The mosaic structure, anisotropic silky structure and flaky structure of the optical isochoric zone of the coke in step S2 with a size of 0 μm to 10 μm, and the optical structure coefficient OTI in step S3 are measured in accordance with YB / T 077-2017 "Determination Method of Optical Structure of Coke", and the single-type coal coke is obtained by coking in a 40 kg bottom-loaded test coke oven.

4. The method for evaluating coal quality using coal coke petrographic detection indicators according to claim 1, characterized in that: The evaluation criteria in step S4 include: coal mineral content ≤ 6%, active-inert ratio between 1.0 and 2.0, mosaic structure with a coke optical isochromatic area size of 0 μm to 10 μm ≥ 35%, anisotropic silky and flaky structure ≤ 50%, and optical structure coefficient OTI ≥ 65, indicating high-quality gas coal.

5. The method for evaluating coal quality using coal coke petrographic detection indicators according to claim 1, characterized in that: The evaluation criteria in step S4 include: coal mineral content ≤ 6%, active-inert ratio between 1.0 and 3.0, mosaic structure with a coke optical isochromatic zone size of 0 μm to 10 μm ≥ 70%, anisotropic silky and flaky structure ≤ 30%, and optical structure coefficient OTI ≥ 85, indicating that the coal is a high-quality gas fertilizer coal.

6. The method for evaluating coal quality using coal coke petrographic detection indicators according to claim 1, characterized in that: The evaluation criteria in step S4 include: coal mineral content ≤ 6%, active-inert ratio between 1.0 and 3.0, mosaic structure with a coke optical isochromatic zone size of 0 μm to 10 μm ≥ 50%, anisotropic silky and flaky structure ≤ 50%, and optical structure coefficient OTI ≥ 60, which is considered high-quality 1 / 3 coal.

7. The method for evaluating coal quality using coal coke petrographic detection indicators according to claim 1, characterized in that: The evaluation criteria in step S4 include: coal mineral content ≤ 6%, active-inert ratio between 1.0 and 3.0, mosaic structure with a coke optical isochromatic zone size of 0 μm to 10 μm ≥ 55%, anisotropic silky and flaky structure ≤ 45%, and optical structure index (OTI) ≥ 100, indicating high-quality fat coal.

8. The method for evaluating coal quality using coal coke petrographic detection indicators according to claim 1, characterized in that: The evaluation criteria in step S4 include: coal mineral content ≤ 6%, active-inert ratio between 1.0 and 3.0, mosaic structure with optical isochromatic area of ​​coke of 0 μm to 10 μm ≥ 60%, anisotropic silky and flaky structure ≤ 40%, and optical structure coefficient (OTI) ≥ 115, indicating high-quality coking coal.

9. The method for evaluating coal quality using coal coke petrographic detection indicators according to claim 1, characterized in that: The evaluation criteria in step S4 include: coal mineral content ≤ 6%, active-inert ratio between 1.0 and 2.0, mosaic structure with optical isochromatic area of ​​coke of 0um to 10um size ≥ 35%, anisotropic silky and flaky structure ≤ 55%, optical structure coefficient OTI ≥ 80, and it is high-quality lean coal.

10. The method for evaluating coal quality using coal coke petrographic detection indicators according to claim 1, characterized in that: In the method, the proportion of mosaic-like structures with a size of 0 μm to 10 μm is used as a first-level classification index for coke, and the anisotropic silky and flaky structures are used as second-level classification indexes for coke.

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