GB/T 6949-2010Determination of apparent relative density of coal (English PDF)

Foreword

This Standard replaces GB/T 6949-1998 Determination of apparent relative density of coal.

Compared with GB/T 6949-1998, main changes of this Standard are as follows.

- Modify Annex B. Use "10 Determination methods for lignite wax" of GB/T 2559-2005 Analysis of lignite wax to replace the Annex B of previous standard. Annex A and Annex B of this Standard are normative.

1 Scope

This Standard specifies the instruments and equipment, reagents, coal sample preparation, determination procedures, results calculation, and degree of precision for determination of apparent relative density of coal. This Standard applies to lignite, bituminous coal and anthracite.

2 Normative references

The articles contained in the following documents have become part of this Standard when they are quoted herein. For the dated documents so quoted, all the modifications (excluding corrections) or revisions made thereafter shall not be applicable to this Standard.

For the undated documents so quoted, the latest editions shall be applicable to this Standard.

GB 474 Method for preparation of coal sample (GB 474-2008, ISO 18283:2006, Hard coal and coke - Manual sampling, MOD)

GB 475 Method for manual sampling of commercial coal (GB 475-2008, ISO 18283. 2006, Hard coal and coke - Manual sampling, MOD)

GB/T 482 Sampling of coal seams

GB/T 19494.1 Mechanical sampling of coal - Part 1: Method for sampling (GB/T 19491.1-2004, ISO 13909-1:2001 Hard coal and coke - Mechanical sampling - Part 1.

General introduction, ISO 13909-2:2001, Hard coal and coke - Mechanical sampling - Part 2: Coal - Sampling from moving streams, ISO 13909-3:2001, Hard coal and coke - Mechanical sampling - Part 3: Coal - Sampling from stationary lots, NEQ) Specification of coal resources exploration and coal sampling 1989

3 Terms and definitions

For the purpose of this Standard, the following terms and definitions apply.

8 Determination procedures

8.1 Pave the coal particles from coal sample bottle onto plastic cloth (6.9); use checkerboard method to take out (20~30)g of coal samples; for the coal of which the ash content is greater than 30% or total sulfur is greater than 2%, weigh (40~60)g; place onto 1 mm square-hole sieve (6.8); use hair brush to repeatedly brush away pulverized coal on coal particle surface; weigh the mass (m1) of above-sieve substances, accurate to 0.000 2 g.

8.2 Place the weighed coal particles on mesh spoon (6.6); immerse into molten paraffin wax (5.1) that has been pre-heated to (70~80)°C by small aluminum pan; maintain paraffin wax temperature at (60~80)°C; use glass rod to quickly scatter the coal particles, until there is no air bubbles. Take out the mesh spoon immediately; after cooling slightly, spread the coal particles onto glass plate (6.7); and use glass rod to scatter the coal particles quickly so that they do not stick to each other. Cool to room temperature. Weigh the mass of waxed coal particles (m2), accurate to 0.000 2 g.

8.3 Put the waxed coal particles into density bottle (6.3); add sodium dodecyl sulfate solution (5.2) to fill up to two thirds of density bottle. Plug the stopper; shake with hands or tap density bottles with fingers gently, until there is no air bubbles on surface of waxed coal particle; then add solution until it is about 1 cm away from bottle neck [Translator note. 1cm below the bottle neck]. Place density bottle in a thermostat (6.10); maintain a constant temperature at (20±0.5)°C for 1 h, or leave it at room temperature for over 3 h; and write down the solution temperature.

8.4 Use pipette to add solution to the bottle drop-by-drop; plug the bottle stopper carefully so that the excess solution can overflow from the upper end of capillary tube of bottle stopper. Ensue that there is no air bubble in bottle and in capillary tube.

8.5 Quickly wipe the density bottle to dry. Weigh immediately (m3), accurate to 0.0002 g.

8.6 Determination of blank value. Determine the blank value while measuring coal sample.

Operate according to 8.3 and 8.4 (without adding coal sample). Weigh the mass (m4) of density bottle and aqueous solution, accurate to 0.0002 g. The difference of measured values of the same density bottle for two successive times must not exceed 0.0100g.

8.7 For coal sample of which the particle size is less than 10 mm, its apparent relative density may be calculated according to Annex A, but it shall be indicated in the report.

13 0.999 64 29 0.996 21 14 0.999 51 30 0.995 91 15 0.999 37 31 0.995 61 16 0.999 21 32 0.995 30 17 0.999 04 33 0.994 97 18 0.998 86 34 0.994 64 19 0.998 67 35 0.994 30 20 0.998 47 40 0.992 48

10 Precision of method

Repeatability and reproducibility critical difference of apparent relative density are shown in Table 2.

Annex A (Normative)

Empirical Formula of Calculating Apparent Relative Density Based on True Relative Density When apparent relative density cannot be determined, apparent relative density of coal may be calculated based on true relative density of coal. Standard uncertainty of its calculated values are generally not greater than 0.03%; for the coal of which the ash content is greater than 30% or sulfur content is greater than 2%, standard uncertainty of its calculated value is generally not greater than 0.06. Calculation formula is as follows.

For lignite and low-rank bituminous coal (long-flame coal, non-baking coal, etc.).

For medium and high-rank bituminous coal (gas coal, fat coal, 1/3 coking coal, lean coal, lean coal, weakly caking coal, etc.).

For anthracite and various types of coals of which the ash content is greater than 30% or sulfur content is greater than 2%. Where, - Apparent relative density of coal at 20°C;

- True relative density of coal at 20°C. dWax - Density of paraffin wax at 20°C, in grams per cubic centimeter (g/cm3); ma - Mass of empty density bottle, in grams (g); mb - Density of density bottle full of water, in grams (g); mc - Mass of density bottle filled with some paraffin wax, in grams (g); md - Mass of density bottle full of paraffin wax and water, in grams (g);

0.998 2 - Density of water at 20°C, in grams per cubic centimeter (g/c m3).

B.4.2 Take the arithmetic average value of repeated determination results as the determination results; round it to the fourth decimal.