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Coal sample preparation process

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1) after receiving the coal sample, it shall be checked item by item according to the sample label, and the coal type, variety, particle size, sampling location, packaging, coal sample quality, sample receiving and preparation time shall be recorded in the coal sample record book and numbered. If it is a commercial coal sample, the vehicle number and the shipped quality (ton) shall also be registered

2) coal samples shall be prepared into air dried coal samples in time according to the coal sample preparation procedure (Fig. 73.3), or laboratory coal samples with appropriate particle size shall be prepared first. If the moisture is too large to affect further crushing and shrinkage, it shall be properly dried at a temperature lower than 50 ℃ in advance

3) in addition to the use of combined crushing and dividing machine, the coal sample shall be crushed until it passes through the corresponding sieve before shrinkage and separation. Coal samples with particle size greater than 25mm are not allowed to be reduced without crushing

4) the preparation of coal samples can be completed at one time or processed in several parts. If it is divided into several parts, each part shall be divided into coal samples according to the same proportion, and then the coal samples of each part shall be combined as one coal sample

5) machines and tools shall be cleaned before and after each crushing and shrinkage. During the preparation of coal samples, the sample preparation personnel shall wear special shoes to avoid polluting the coal samples. For sealed crushers (such as Hammer Crushers) and combined crushing separators that are not easy to clean, when they are only used to process a large number of coal samples of a single variety, the coal taking the coal sample can be “washed” by the machine before each coal sample is processed, and the coal sample can be processed after the “washed” coal is discarded. After treatment, the machine shall be started and stopped repeatedly for several times to discharge the retained coal samples

6) for the shrinkage and division of coal samples, except for those with high moisture and unable to use mechanical shrinkage and division, dichotomy and shrinkage and division machinery should be used as far as possible to reduce the shrinkage and division error

7) see Fig. 73.3 for the corresponding relationship between sample quality and particle size after reduction. After the coal sample with particle size less than 3mm is reduced to 3.75kg, if all of them pass the 3mm Round hole sieve, it can be directly reduced by the divider to not less than 100g and not less than 500g, which are respectively used to prepare the coal sample for analysis and as the coal sample for storage. The preparation of coal samples for the test items with special particle size requirements shall be prepared by using corresponding equipment at the corresponding stage in accordance with the provisions of this method. At the same time, the step-by-step crushing method shall be adopted during crushing, that is, the crushing mouth of the crusher shall be adjusted so that only the particles larger than the required particle size are crushed, and the particles smaller than the required particle size are no longer repeatedly crushed

figure 73.3 preparation procedure of coal sample

8) the reducer must be inspected before use. To inspect the coal samples of the divider, including the further division of reserved samples and discarded samples, a dichotor must be used

9) the coal sample is reduced and divided by a dichotor, and there is no need to mix before reduction and separation. When feeding, the dustpan shall tilt to one side and swing back and forth along the whole length of the divider to make the coal sample pass through the divider more evenly. Take any coal sample on one side after shrinkage

10) coal sample reduction and separation by cone stacking quartering method is to shovel and stack the crushed and screened coal samples into a cone with a flat shovel, and then interactively shovel and stack them diagonally from both sides of the coal sample stack to the bottom one by one to form another cone. The coal samples from each shovel shall not be too much, and shall be scattered on the top of the new cone in two or three times to make it fall evenly around the new cone. This is repeated for 3 times, and then the coal samples are evenly spread (when there are more coal samples) or flattened (when there are fewer coal samples) from the center to the surrounding from the top of the coal sample pile to form a flat body with appropriate thickness. Place the cross dividing plate in the middle of the flat body and press it down to the bottom. The coal sample is divided into four equal sectors. Discard the two opposite fans, and prepare the two left fans into general analysis coal samples or other coal samples with appropriate particle size according to the particle size and quality limit specified in the procedure in Figure 73.3. The particle size and quality of coal samples gradually become smaller after gradual crushing and shrinkage. The shovel used for mixing coal samples shall be appropriately reduced or the number of coal samples shoveled each time shall be correspondingly reduced

11) before crushing into 0.2mm coal sample, use magnet to absorb the iron filings in the coal sample, then crush them all through the 0.2mm sieve and make them reach the air dry state, and then put them into the coal sample bottle (the amount of coal sample should not exceed 3 /4 of the volume of the coal sample bottle for mixing during use) and send them to the laboratory for analysis

the air drying method is as follows: put the coal sample into a plate, spread it into a uniform thin layer, and dry it at a temperature not exceeding 50 ℃. If the mass change of coal sample does not exceed 0.1% after continuous drying for 1h, it will reach the air drying state. Air drying can also be carried out before the coal sample is broken to 0.2 mm

12) the coal core coal sample can be reduced to 100g from the coal sample less than 3mm, and then prepared into the coal sample for analysis according to the provisions of 73.2.3 “preparation of coal sample” 11) in this section

figure 73.4 schematic diagram of point distribution of full moisture coal samples taken by nine point method

13) preparation of full moisture coal samples. The coal sample for measuring total moisture can be prepared from either the special coal sample for moisture or the general analytical coal sample. In addition to using a concentrator that can condense and separate a sufficient number of full moisture coal samples at one time, after the coal samples are crushed to the specified particle size, they are slightly mixed. After flattening, they are immediately shrunk by the nine point method (see Figure 73.4 for the distribution of points), put them into the coal sample bottle and sealed tightly (the sample loading volume shall not exceed 3 /4 of the volume of the coal sample bottle), weigh the quality, affix a label, and send them to the laboratory for determination of full moisture. The particle size and quality of full moisture coal samples are shown in Figure 73.3. The preparation of full moisture coal sample should be rapid

14) preparation of coal composition samples. Weigh a certain amount of air dried coal sample and place it in the ash dish, pave it so that it does not exceed 0.15g per square centimeter, send the ash dish to a high-temperature furnace with a temperature of no more than 100 ℃ (about 15mm gap is left in the natural ventilation and furnace door), raise the temperature to 500 ℃ within 30min and keep it for 60min, and continue to raise the temperature to (815 ± 10) ℃ and keep it for 90min. After cooling, grind it with agate mortar until the particle size is less than 120 mesh. Then put it into the ash dish and burn it at (815 ± 10) ℃ for another 30min until its mass change does not exceed 0.1% of the mass of the a
sh sample. After cooling, grind it with agate mortar until the particle size is less than 0.095mm (160 mesh), and put it into the dryer for standby

15) for storing coal samples, in addition to labeling on the container, the coal sample label shall also be put in the container and sealed. The label contents include: analysis number, sample number, coal mine name, coal sample type, sample sending unit, sample sending date, sample preparation date, analysis item and remarks

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