This standard specifies the reagents, materials, instruments, equipment, measurement steps, expression and precision of the measurement results for the determination of light transmittance of low-rank coal. This standard is applicable to lignite and low-rank bituminous coal. GB/T 2566-1995 Method for determination of light transmittance of low-rank coal GB/T2566-1995 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Determination of transmittance for low rank coal
Determination of transmittance for low rank coal1 Subject content and scope of application
GB/T2566--1995
Replaces GB2566--81
This standard specifies the reagents, materials, instruments, equipment, measurement steps, expression and precision of the measurement results for the determination of the transmittance of low rank coal.
This standard is applicable to lignite and low rank bituminous coal. 2 Method summary
Low rank coal reacts with a mixed acid of nitric acid and phosphoric acid under specified test conditions to produce a colored solution. According to the color depth of the solution, the transmittance of the coal sample is determined by visual colorimetry using potassium dichromate sulfuric acid solution of different concentrations as the standard. 3 Reagents and materials
3.1 Sulfuric acid (GB625): concentration 95%~98% and 10% sulfuric acid solution (i.e. 10mL sulfuric acid is prepared into 100mL aqueous solution). 3.2 Potassium dichromate (GB642): powder, content not less than 99.8%, dry at 110~120℃ for 2h before use. 3.3 Phosphoric acid (GB1282): concentration not less than 85% and (1+9). 3.4 Mixed acid: 1 volume of nitric acid (GB626) with a concentration of 65%~68%, 1 volume of phosphoric acid with a concentration not less than 85% and 9 volumes of water. Yellow nitric acid cannot be used. 3.5 Potassium dichromate stock solution
3.5.1 Weigh 2.5000g (accurate to 0.0002g) of potassium dichromate powder and prepare 250mL solution in a volumetric flask with 10% sulfuric acid (3.1).
This solution is used to prepare a series of standard solutions with transmittance between 30% and 100%. 3.5.2 Weigh 5.0000g (accurate to 0.0002g) of potassium dichromate powder and prepare 250mL of solution in a volumetric flask with 10% sulfuric acid (3.1).
3.6 Potassium dichromate standard series solution
According to the provisions in Appendix A, use a straight pipette (or microburette) with a fine scale of 1, 2, 5 or 10mL to draw the required volume of standard solution from the potassium dichromate standard solution (3.5.1 and 3.5.2) in turn, put it into a 50mL volumetric flask, and then dilute it to the scale with 10% sulfuric acid.
Rinse the dried colorimetric tube once with the prepared standard series solution. Then pour the standard series solution into the 10mL scale of the colorimetric tube (the height of the liquid column in each colorimetric tube is consistent). The standard series solution can generally be used for 2 months. If the room temperature during colorimetry and the preparation of the standard series solution changes by more than 10°C, the standard series solution should be re-prepared.
3.7 Qualitative filter paper: requires denseness.
Approved by the State Administration of Technical Supervision on August 7, 1995 274
Implementation on April 1, 1996
4 Instruments and equipment
4.1 Analytical balance: sensitivity 0.0002g.
GB/T2566--1995
4.2 Colorimetric tube: 25mL, inner diameter 17±0.5mm, with scale at 10mL, with tight stopper. 4.3 Water bath: closed, can be heated to 100°C. 4.4 Mercury thermometer: measuring range 0~100°C, graduation value less than 0.2°C. Need to be calibrated before use. 4.5 Volumetric flask: 100mL.
For some samples that are prone to produce bubbles and bring out coal powder during heating treatment, it is advisable to use a special long-necked volumetric flask with the following dimensions: inner diameter of the mouth 15±1mm; height from the scale line to the bottle mouth 13.5±0.5mm. 4.6 Small glass funnel: inner diameter of the funnel mouth 30mm, funnel handle about 40mm long, inner diameter 4~～5mm. 5 Coal sample treatmentwwW.bzxz.Net
Weigh an air-dried coal sample equivalent to 1.0000g (accurate to 0.0002g) of dry ash-free coal (a floating coal sample or a raw coal sample with ash content A less than or equal to 10% is required, but a raw coal sample can be used for lignite that is easily muddied when exposed to water), and transfer it into a dry 100mL volumetric flask. When the water bath temperature rises to 99.5 ± 0.5°C (in plateau areas, a certain amount of glycerol can be added to the water to keep the water bath temperature at 99.5 ± 0.5°C), use a pipette to draw 25 mL of mixed acid into the volumetric flask, and shake the volumetric flask while adding acid to soak the coal sample. Put the volumetric flask into the water bath immediately after adding acid, and insert a small funnel (4.6) into the bottle mouth. The water bath temperature should rise to 99.5 ± 0.5°C within 5 minutes. After heating for 90 minutes, remove the volumetric flask from the water bath and quickly cool it to room temperature. Add (1+9) phosphoric acid (3.3) to the scale of the volumetric flask, add a stopper and shake well. After standing for 15 to 30 minutes, filter with a dry funnel and filter paper. Filter the filtrate into a dry 100 mL conical flask (be careful to prevent extremely fine coal powder from filtering through, otherwise it should be filtered again), and discard the small amount of filtrate filtered out initially. After filtering, discard the residue. The transmittance of the filtrate should be determined by gastroscopic colorimetry on the same day. 6 Determination
Pour the filtrate into a 25ml colorimetric tube (4.2) to the 10ml mark (the height of the liquid column should be adjusted to be the same as that of the potassium dichromate standard series solution), and visually compare the color with the standard series solution. The color comparison should be carried out in a bright place, but not under direct sunlight. When comparing the color, 2 to 3 pure white filter papers should be lined on the lower part of the colorimetric tube, but the filter paper and the colorimetric tube should be kept at a distance of about 30mm. When comparing the color, look vertically downward from the top of the colorimetric tube, and the positions of the standard series solution and the coal sample filtrate should be exchanged before comparing the color to facilitate the correct judgment of the result. When the color depth of the coal sample filtrate is between two adjacent standard series solutions or is equivalent to a certain standard series solution, the transmittance of the coal sample can be calculated. For coal samples with extremely low transmittance, the color tones of the standard series solution and the coal sample solution are not consistent. At this time, the lightness and darkness of the solution can be used as the basis for comparison to determine the transmittance of the coal sample.
7 Expression of measurement results
The transmittance (Pm) measurement result can be read to 1%. For coal samples with Pm less than 16%, fill in less than 16% when reporting the results. 8 Precision
The repeatability and reproducibility of transmittance shall comply with the provisions of the following table: Weight
Standard series
Transmittance
(Pm),%
GB/T2566
—-1995
Appendix A
Preparation method of transmittance (P) standard series solution (supplement)
When preparing 50ml of the standard series solution, it is necessary to use
Weight Volume of potassium chromate standard solution, ml
Standard series
Transmittance
(Pm), %
Volume of potassium dichromate standard solution required to prepare 50mL of standard series solution, ml
Note: The "*" in the table indicates that the standard series solution is the standard point determined directly after repeated comparison with coal samples, and the remaining points are obtained based on the working curve drawn according to the standard point or its extension line.
Weighed mass g
Volume flask number
Conical flask number
Colorimetric tube number
Pm, %
P average value, %
Review:
GB/T2566-1995
Appendix B
Original record of light transmittance determination of low-rank coal
(reference)
Determination:
Additional remarks:
This standard is proposed by the Ministry of Coal Industry.
GB/T2566
This standard is under the jurisdiction of the National Coal Standardization Technical Committee. 1995
This standard was jointly drafted by the Beijing Coal Chemistry Research Institute of the China Coal Research Institute and the Environmental Protection Research Institute of the East China Coal Group Corporation. The main drafters of this standard are Chen Wenmin, Yang Xingfu and Ma Yingjie. This standard was first issued in 1981.
This standard is entrusted to the Beijing Coal Chemistry Research Institute of the China Coal Research Institute for interpretation.
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