GB/T 2566-2010Determination of transmittance for low rank coal (English PDF)

Foreword

This Standard replaces GB/T 2566-1995 "Determination of transmittance for low rank coal".

Compared with GB/T 2566-1995, this Standard has mainly made the following modifications.

- According to the requirements of GB/T 1.1, MODIFY the format of the standard accordingly;

- REORGANIZE relevant clauses of the standard;

- ADD Table A.2 in Annex A;

- ADJUST repeatability and reproducibility values for different transmittance ranges (see Clause 7).

Annex A and Annex B of this Standard are informative annexes.

1 Scope

This Standard specifies the reagents and materials, instruments and equipment used to determine the transmittance of low rank coal, as well as determination procedure, expression and precision of determination results. This Standard applies to lignite and low rank bituminous coal.

2 Method principle

Low rank coal reacts with mixed acid of nitric acid and phosphoric acid under the specified test conditions and produces a colored solution. According to the color depth of the solution, use potassium dichromate solution with different concentrations as the standard, determine the transmittance of the coal sample by visual colorimetry.

3 Reagents and materials

3.1 10 % sulfuric acid (GB/T 625, chemically pure) solution (volume fraction).

3.2 Potassium dichromate (GB/T 642, analytically pure). Before use, it shall be dried at 110 °C ~ 120 °C for 2 h.

3.3 (1 + 9) phosphoric acid (GB/T 1282, chemically pure) solution (volume fraction).

3.4 Nitric acid (GB/T 626, chemically pure). Yellow nitric acid cannot be used.

3.5 Mixed acid. Prepared by mixing 1 volume of nitric acid, 1 volume of phosphoric acid and 9 volumes of distilled water.

3.6 Potassium dichromate preparation solution.

4 Instruments and apparatuses

4.1 Analytical balance. with a sensitivity of 0.000 2 g.

4.2 Colorimetric tube. 25 mL, internal diameter 17 mm ± 0.5 mm, scaled at 10 mL, with tight stopper.

4.4 Mercury thermometer. The measuring range is 0 °C ~ 100 °C, and the graduation is less than 0.2 °C. It is used after calibration.

4.6 Small glass funnel. The funnel mouth inner diameter is 30 mm, the funnel handle length is about 40 mm, and the inner diameter is 4 mm ~ 5 mm.

5 Determination procedure

5.1 WEIGH test coal sample for general analysis (require raw coal sample or floating coal sample with ash Ad <= 10 %, but it may use raw coal sample for lignite that is easily argillized in water) equivalent to 1.000 0 g (accurate to 0.000 2 g) of dry ash-free coal, TRANSFER into a dry 100 mL volumetric flask.

5.3 After heating for 90 min, REMOVE the volumetric flask from the water bath and allow it to quickly cool to room temperature. USE (1 + 9) phosphate (3.3) to rinse the small funnel and volumetric flask neck, then ADD (1 + 9) phosphoric acid (3.3) to the volumetric flask to the mark. SHAKE after stoppering.

5.4 After standing for 15 min to 30 min, filter with dry funnel and dense qualitative filter paper. FILTER the filtrate into a dry 100 mL Erlenmeyer flask (it shall take care to prevent extremely fine pulverized coal from diafiltration, otherwise it shall be filtered again), DISCARD a small amount of filtrate that is originally filtered out. After filtration, discard the residue. The filtrate shall be determined for transmittance by visual colorimetry on the same day.

5.5 When performing colorimetric analysis, proceed as follows

6 Expression of determination results

The transmittance (PM) determination result may be read to 1 %. For coal samples with PM less than 16 %, it is filled in as less than 16 % when reporting results.

7 Precision

The precision of transmittance (PM) determination shall comply with the specifications of Table 1.

Annex A (Informative) Potassium dichromate standard series solution

Annex A provides the correspondence between the concentration of the standard solution and the volume of the potassium chromate solution (3.6.1 and 3.6.2) required when preparing 50 mL of potassium dichromate standard series solution.

According to actual work requirements, potassium dichromate standard solution can be prepared according to Table A.1 and Table A.2, respectively. […]