Method for checking and accepting anthracite special for bituminous coal caking index measurement

Abstract

The invention discloses a method for checking and accepting anthracite special for bituminous coal caking index measurement. The method is characterized by comprising the following specific operation steps: 1) particle size measurement; 2) moisture Mad determination; 3) ash content Ad determination; (4) measuring volatile components (Vdaf); and (5) determining the reflectivity of vitrinite. The invention aims to provide the method for checking and accepting the anthracite special for bituminous coal caking index determination, so that the coal quality difference of the anthracite special for bituminous coal caking index determination can be rapidly and accurately identified, the checking and accepting index is increased for lithofacies detection, and the anthracite can be accurately detected under the condition that the granularity, moisture, ash content and volatile components are qualified. And the coal quality difference of the special anthracite can be quickly and effectively distinguished, a single high-coal-grade coal type which is uniform, narrow in vitrinite reflectivity measurement value range, small in standard deviation and free of notches is selected through lithofacies detection, and the influence on bituminous coal caking index measurement is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of coal coke detection, and particularly relates to a method for accepting special anthracite for determining the caking index of bituminous coal. Especially in terms of differentiating coal quality, it is characterized in that it can quickly and effectively distinguish the quality of coal even when other acceptance indicators: particle size, moisture, ash content, and volatile matter all meet the requirements, and can assist in judging whether it is applicable. Background Art

[0002] The relevant technical requirements in the national standard GB / T 14181-2010 "Technical Conditions for Special Anthracite for Determining the Caking Index of Bituminous Coal" stipulate: 3.1 Coal source The special anthracite for determining the caking index of bituminous coal (hereinafter referred to as special anthracite) is made from the lower stratified coal of the second coal seam on both sides of the Xigou Pingdong in Ruqigou Coal Mine, Ningxia. 3.2 Particle size The particle size of the special anthracite should be (0.1 - 0.2) mm. Among them, the mass fraction of the oversize material with a particle size greater than 0.2 mm should not be greater than 4.00%; the mass fraction of the undersize material with a particle size less than 0.1 mm should not be greater than 6.00%. 3.3 a) Moisture (M ad ) is less than 2.50%; b) Ash content (A d ) is less than 4.00%; c) Volatile matter (V daf ) is less than 8.00%. 3.4 The caking index values measured for 4 different levels of bituminous coal samples with the special anthracite sample and the caking index values measured with the special anthracite reference sample: There is no significant difference in the test, and the difference between the caking index values measured for each bituminous coal sample with two kinds of anthracite is not large.

[0003] The special anthracite purchased by the laboratory is accompanied by an ex-factory certificate. During acceptance, the particle size, moisture (M ad ), ash content (A d ), and volatile matter (V daf ) all meet the standard regulations. However, there are still large fluctuations in the test results when using special anthracite from different manufacturers or different batches of the same manufacturer to detect the caking index of bituminous coal. Sometimes it is difficult to find the reason in time, bringing many inconveniences to the detection process.

[0004] In view of this, it is particularly important to invent this method. The present invention provides a more rapid and accurate auxiliary acceptance method for the acceptance of special anthracite for determining the caking index of bituminous coal. The inventive method is to simultaneously accept the indicators of the particle size, moisture, ash content, and volatile matter of the special anthracite, and assist in using a coal petrographic analyzer to measure the maximum vitrinite reflectance and standard deviation in the special anthracite, so as to effectively distinguish the coal quality of the special anthracite, and thus judge whether the special anthracite has an impact on the test results of the caking index of bituminous coal and determine whether it is applicable to the determination of the caking index of bituminous coal. Summary of the Invention

[0005] The object of the present invention is to provide a method for accepting special anthracite for the determination of the caking index of bituminous coal, so as to quickly and accurately identify the quality differences of special anthracite for the determination of the caking index of bituminous coal. The acceptance index adds petrographic detection. Even when the particle size, moisture, ash content, and volatile matter are all qualified, it can also quickly and effectively distinguish the quality differences of special anthracite. Through petrographic detection, a single high-rank coal type with uniformity, a narrow range of vitrinite reflectance measurements, a small standard deviation, and no notches is selected to reduce the impact on the determination of the caking index of bituminous coal.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A method for accepting special anthracite for the determination of the caking index of bituminous coal according to the present invention specifically includes the following steps:

[0008] 1) Particle size determination: Stack the 0.2 mm and 0.1 mm square-hole sieves from top to bottom. Weigh a certain amount of the special anthracite to be accepted and place it on the 0.2 mm sieve. Place the coal-containing sieve on a vibrating sieve machine and screen for 4 - 8 minutes in total; after screening, weigh the mass of the materials on each sieve and under the sieve for each particle size grade and calculate the mass fraction.

[0009] 2) Moisture M ad Determination: Weigh the special anthracite to be accepted with a particle size less than 0.2 mm in a pre-dried and pre-weighed weighing bottle, spread it evenly in the weighing bottle, open the weighing bottle cap, place it in a drying oven that has been pre-blasted and heated to 105 - 110 °C, and dry it for 1.5 h under the condition of continuous blasting. Take out the weighing bottle from the drying oven, immediately cover the cap, place it in a desiccator and cool it to room temperature before weighing; conduct checking drying, 30 minutes each time, until the mass reduction of the coal sample in two consecutive dryings does not exceed 0.0010 g or until the mass increases; in the latter case, use the mass before the mass increase as the calculation basis.

[0010] 3) Ash content A d Determination: Weigh the special anthracite to be accepted with a particle size less than 0.2 mm in a crucible that has been pre-ignited to a constant mass, spread it evenly in the crucible so that the mass per square centimeter does not exceed 0.15 g; send the crucible into the constant-temperature zone of a muffle furnace with a furnace temperature not exceeding 100 °C, close the furnace door and leave a 15 mm gap in the furnace door, slowly raise the furnace temperature to 500 ± 10 °C in not less than 30 minutes and maintain this temperature for 30 minutes; continue to raise the temperature to 815 ± 10 °C and burn at this temperature for 1 h; take out the crucible from the furnace, place it on a heat-resistant porcelain plate or asbestos plate, cool it in the air, and then transfer it to a desiccator and cool it to room temperature before weighing;

[0011] 4) Volatile matter (V daf)Determination: Weigh the special anthracite for acceptance with a particle size less than 0.2 mm in a covered porcelain crucible that has been pre-ignited to a constant mass at a temperature of 900 ± 10 °C. Then gently vibrate the crucible to flatten the coal sample, cover it, and place it on the crucible rack; preheat the muffle furnace to 920 ± 10 °C; open the furnace door, quickly send the crucible rack with the crucible into the constant temperature zone, immediately close the furnace door and start timing, and accurately heat for 7 minutes; after the crucible and crucible rack are placed, it is required that the furnace temperature return to 900 ± 10 °C within 3 minutes, and then remain at 900 ± 10 °C, otherwise this operation is invalid, and the heating time includes the temperature recovery time; take out the crucible from the furnace, cool it in the air for about 5 minutes, transfer it to a desiccator and cool it to room temperature before weighing;

[0012] 5) Determination of vitrinite reflectance: Take the special anthracite for acceptance and the embedding powder in a volume ratio of 2:1, place them in a porcelain crucible, stir well, heat at 135 °C, and press and form with an embedding machine at 3.5 MPa; polish the formed special anthracite sample block for acceptance until there are no scratches, it has a shiny feeling, there is no distinction between light and dark, and the coal particle boundaries are clear. Under the conditions of a microscope oil immersion objective lens and reflected light with a vertical incident light of λ = 546 nm, use a microscope camera and an automatic stage to collect the microscopic images of the reference material and the sample in sequence. Perform gray-scale determination on all measurement points of the microscopic images of the reference material and the sample. Use the reference material to establish a gray-scale - random reflectance relationship model. According to this model, obtain the random reflectance values of all measurement points in the sample image. Automatically identify the effective vitrinite measurement points among them through the vitrinite recognition model, and statistically analyze the random reflectance values of each effective vitrinite measurement point to obtain the average value and standard deviation of the vitrinite random reflectance of the sample.

[0013] Further, in step 2), the temperature of the drying oven is 105 °C.

[0014] Further, in step 2), when the moisture content is less than 2.00%, there is no need to perform check drying.

[0015] Compared with the prior art, the beneficial technical effects of the present invention:

[0016] Currently, the special anthracite for acceptance is subject to compliance acceptance according to the indicators required in the national recommended standard. In addition to the acceptance of particle size, moisture (M ad ), ash content (A d ), volatile matter (V daf) In addition, the determination value of the caking index of bituminous coal must also be inspected. For the determination of the caking index of bituminous coal, the test sample and the reference sample are used as inert substances respectively, and the caking index is determined for 4 bituminous coals (the caking index G value ranges from 20% to 90%, with an interval of about 20%). The test sample and the reference sample are each repeatedly determined 6 times for each bituminous coal sample. Calculate the average value and standard deviation of the repeated determinations of the test sample and the reference sample for each bituminous coal sample respectively. Use the specified t-test method to compare whether there is a significant difference between the average values of the caking indices measured for the 4 bituminous coals by the test sample and the reference sample. This acceptance method is slow, consumes a large amount of reference samples and causes waste, the result evaluation operation is complex, and the entire acceptance process is long.

[0017] However, the present invention can greatly shorten the acceptance cycle, simplify the acceptance process, reduce the acceptance cost, and can quickly and accurately judge whether the special anthracite meets the conditions for determining the caking index of bituminous coal. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below in conjunction with the drawings.

[0019] Figure 1 、 Figure 2 、 Figure 3 They are the average vitrinite random reflectance and standard deviation reports of the 1#, 2#, and 3# samples respectively. DETAILED DESCRIPTION OF THE INVENTION

[0020] The technical solution of the present invention will be further described below in conjunction with examples, so that those skilled in the art can further understand the present invention, but it does not constitute a limitation on the rights of the present invention.

[0021] Example 1:

[0022] A method for accepting special anthracite for the determination of the caking index of bituminous coal, the specific operation is as follows:

[0023] Particle size determination: Stack the 0.2mm and 0.1mm square-hole sieves from top to bottom, weigh (50 ± 0.5) g of the special anthracite to be accepted and place it on the 0.2mm sieve, and place the coal-containing sieve on the vibrating sieve machine for cumulative screening for 6 minutes. After the screening is completed, weigh the masses of the materials on the sieves and under the sieves of each particle size respectively and calculate the mass fractions.

[0024] Moisture determination: Weigh (1 ± 0.1) g of the special anthracite to be accepted in a pre-dried and weighed weighing bottle, accurate to 0.0002 g, and spread it evenly in the weighing bottle. Open the weighing bottle cap and place it in a drying oven that has been pre-blasted and heated to (105 - 110) °C. Dry it for 1.5 h under the condition of continuous blasting, take out the weighing bottle from the drying oven, immediately cover the cap, and place it in a desiccator to cool to room temperature (about 20 min) and then weigh and calculate.

[0025] Ash determination: Weigh (1 ± 0.1) g of the special anthracite for acceptance in a crucible that has been pre-ignited to a constant mass, accurate to 0.0002 g. Spread it evenly in the crucible so that the mass per square centimeter does not exceed 0.15 g. Place the crucible in the isothermal zone of a muffle furnace with a furnace temperature not exceeding 100 °C. Close the furnace door and leave a gap of about 15 mm. Slowly raise the furnace temperature to 500 °C in not less than 30 min and maintain this temperature for 30 min. Continue to raise the temperature to (815 ± 10) °C and calcine at this temperature for 1 h. Take out the crucible from the furnace, place it on a heat-resistant porcelain plate or asbestos board, cool it in the air for about 5 min, transfer it to a desiccator, and weigh and calculate after cooling to room temperature (about 20 min).

[0026] Volatile matter determination: Weigh (1 ± 0.01) g of the special anthracite for acceptance in a covered porcelain crucible that has been pre-ignited to a constant mass at 900 °C, accurate to 0.0002 g. Then gently vibrate the crucible to level the coal sample, cover the lid, and place it on a crucible rack. Preheat the muffle furnace to 920 °C. Open the furnace door, quickly send the crucible rack with the crucible into the isothermal zone, immediately close the furnace door and start timing, and heat accurately for 7 min. After the crucible and crucible rack are placed, the furnace temperature should return to (900 ± 10) °C within 3 min, and then remain at (900 ± 10) °C. The heating time includes the temperature recovery time. Take out the crucible from the furnace, cool it in the air for 5 min, transfer it to a desiccator, and weigh and calculate after cooling to room temperature (about 20 min).

[0027] Vitrinite reflectance determination: Take the special anthracite for acceptance and the embedding powder in a volume ratio of 2:1, place them in a porcelain crucible, stir well, heat at 135 °C, and press and form under 3.5 MPa with an embedding machine. Polish the formed special anthracite sample block for acceptance until there are no scratches, it has a shiny appearance, no light and dark differences, and the coal particle boundaries are clear. Under a fully automatic coal petrographic microscope, perform gray scale determination on all measurement points of the microscopic images of the standard substance and the sample to obtain the average value and standard deviation of the random reflectance of vitrinite of the sample.

[0028] The specific measurement results are as follows:

[0029]

[0030] The average value and standard deviation of the random reflectance of vitrinite of the sample are reported as follows Figures 1-3 , because the manufacturer's name is involved in the report, the sample name and number are marked separately.

[0031] It can be seen from the data that the mass fractions of oversize materials with particle sizes greater than 0.2 mm, the mass fractions of undersize materials with particle sizes less than 0.1 mm, the inherent moisture, ash content, and volatile matter results of the special anthracite samples numbered 1#, 2#, and 3# all meet the index requirements. Through these indexes, it is impossible to quickly and effectively distinguish the quality differences of the special anthracite. However, through the determination of the vitrinite reflectance of the coal, it can be known that the 1# special anthracite is a single coal seam coal without notches, and the 2# and 3# special anthracites are both mixed coals with more than 2 notches. The average value of the random reflectance of vitrinite is sorted as 3# < 2# < 1#. At the same time, the caking index of the same bituminous coal standard sample is measured with these three special anthracites. The deviation of the 1# special anthracite is the smallest. Therefore, it is determined that the 1# special anthracite is the best, and the 2# and 3# special anthracites are judged as mixed coal types and regarded as unqualified. This method can quickly and effectively evaluate the quality differences of coal and prevent the fluctuation of the measured caking index of bituminous coal caused by uneven quality of special anthracite.

[0032] The embodiments described above are only used to describe the preferred mode of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solution of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for accepting special anthracite for determining the caking index of bituminous coal, characterized in that: The specific operations include the following steps: 1) Particle size determination: Stack the 0.2 mm and 0.1 mm square-hole sieves from top to bottom. Weigh a certain amount of the special anthracite for acceptance and place it on the 0.2 mm sieve. Place the coal-filled sieve on a sieve shaker and sieve for a cumulative 6 minutes. After sieving, weigh the masses of the materials on each sieve and under the sieve for each particle size and calculate the mass fractions; 2) Moisture M ad Determination: Weigh the special anthracite for acceptance inspection with a particle size less than 0.2 mm in a pre-dried and weighed weighing bottle, spread it evenly in the weighing bottle, open the lid of the weighing bottle, and place it in a drying oven that has been pre-ventilated and heated to 105 - 110 °C. Dry it for 1.5 h under the condition of continuous ventilation. Take out the weighing bottle from the drying oven, immediately cover the lid, place it in a desiccator and cool it to room temperature before weighing; conduct check drying, 30 min each time, until the mass reduction of the coal sample in two consecutive dryings does not exceed 0.0010 g or the mass increases; in the latter case, use the mass of the previous time when the mass increased as the calculation basis; 3) Ash content A d Determination: Weigh the special anthracite for acceptance with a particle size less than 0.2 mm in a crucible that has been pre-ignited to a constant mass, evenly spread it out in the crucible so that the mass per square centimeter does not exceed 0.15 g; send the crucible into the constant temperature zone of a muffle furnace with a furnace temperature not exceeding 100 °C, close the furnace door and leave a 13 - 17 mm gap in the furnace door, slowly raise the furnace temperature to 500 ± 10 °C within no less than 30 min and maintain this temperature for 30 min; continue to raise the temperature to 815 ± 10 °C and ignite at this temperature for 1 h; take out the crucible from the furnace, place it on a heat-resistant porcelain plate or asbestos plate, cool it in the air, transfer it to a desiccator, cool it to room temperature and then weigh it; 4) Volatile matter V daf Determination: Weigh the special anthracite for acceptance with a particle size less than 0.2 mm in a covered porcelain crucible that has been pre-ignited to a constant mass at a temperature of 900 ± 10 °C. Then gently vibrate the crucible to level the coal sample, cover it, and place it on the crucible rack; pre-heat the muffle furnace to 920 ± 10 °C; open the furnace door, quickly send the crucible rack with the crucible into the constant temperature zone, immediately close the furnace door and start timing, and accurately heat for 7 minutes; after the crucible and crucible rack are placed, it is required that the furnace temperature recover to 900 ± 10 °C within 3 minutes, and then remain at 900 ± 10 °C. Otherwise, this operation is invalid, and the heating time includes the temperature recovery time; take out the crucible from the furnace, cool it in the air for 5 minutes, transfer it to a desiccator and cool it to room temperature before weighing and calculating; 5) Vitrinite reflectance determination: Take the special anthracite for acceptance and the embedding powder in a volume ratio of 2:

1. Put them in a porcelain crucible, stir well, heat at 135 °C, and press and form under a pressure of 3.5 MPa by an embedding machine. Polish the formed special anthracite sample block for acceptance until there are no scratches, it has a shiny appearance, no distinction between light and dark, and the boundaries of coal particles are clear. Under the conditions of a microscope oil immersion objective lens and reflected light with a vertical incident light of λ = 546 nm, use a microscope camera and an automatic stage to sequentially collect the microscopic images of the reference material and the sample. Perform gray-scale determination on all measurement points of the microscopic images of the reference material and the sample. Establish a gray-scale - random reflectance relationship model using the reference material. According to this model, obtain the random reflectance values of all measurement points in the sample image. Automatically identify the effective measurement points of vitrinite in it through a vitrinite recognition model, and statistically analyze the random reflectance values of each effective measurement point of vitrinite to obtain the average value and standard deviation of the vitrinite random reflectance of the sample.

2. The method for accepting the special anthracite for determining the caking index of bituminous coal according to claim 1, wherein: In step 2), the temperature of the drying oven is 105 °C.

3. The method for accepting anthracite dedicated to the determination of the caking index of bituminous coal according to claim 1, wherein: In step 2), when the moisture content is less than 2.00%, inspection drying does not need to be carried out.

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