GB/T 211—2007 Method for determination of total moisture in coal - Master's thesis - Dissertation

GB/T 211—2007 Method for determination of total moisture in coal

GB/T 211-2007 Replace GB/T 211-1996 1 Scope This standard specifies the reagents, equipment, operation steps, calculation of results and precision of determining the total moisture in coal. The method of drying in a nitrogen stream (Method A1 and Method B1) is applicable to all coal types; the method of drying in air stream (Methods A2 and B2) is applicable to bituminous coal and anthracite; the microwave drying method (Method C) is applicable to bituminous coal And lignite.

Method A1 is used as the arbitration method.

2 Normative references

The terms in the following documents become the terms of this standard by reference to this standard. For dated references, subsequent Amendments (not including errata content) or revisions do not apply to this standard. However, parties to agreements based on this standard are encouraged to study whether the latest versions of these documents are available. . For undated references, the latest edition applies to this standard.

Preparation method of GB 474 coal sample

GB/T 19494.2 Mechanized sampling of coal - Part 2: Preparation of coal samples (GB/T 19494.2-2004, ISO 13909-4:2001, NEQ)

Industrial analysis method for GB/T 212 coal (GB/T 212-2001, eqv ISO 11722:1999, eqv ISO 1171:1997, eqv ISO 562:1998)

3 Method summary

3.1 Method A (two-step method)

3.1.1 Method A1: Drying in a stream of nitrogen

A certain amount of coal sample with a particle size of <13mm is dried to a constant mass in an environment where the temperature is not higher than 40 °C, and then the coal sample is crushed to a particle size of <3 mm, and dried at a flow rate of (105-110) ° C in a nitrogen stream. The quality is constant. The total moisture is calculated based on the mass loss after the two-step drying of the coal sample.

3.1.2 Method A2: Drying in air stream

A certain amount of coal sample with a particle size of <13mm is dried to a constant mass in an environment where the temperature is not higher than 40 °C, and then the coal sample is crushed to a particle size of <3 mm, and dried in an air stream at (105-110) °C. The quality is constant. The total moisture is calculated based on the mass loss after the two-step drying of the coal sample.

3.2 Method B (one-step method)

3.2.1 Method B1: Drying in a stream of nitrogen

GB/T 211—2007

A certain amount of coal sample with a particle size of <6 mm was weighed and dried at a flow rate of (105-110) ° C in a nitrogen stream until the mass was constant. The total moisture is calculated based on the mass loss after drying of the coal sample.

3.2.2 Method B2: Drying in air stream

A certain amount of coal sample with a particle size of <13 mm (or <6 mm) was weighed and dried in a stream of air at (105-110) °C until the mass was constant. The total moisture is calculated based on the mass loss after drying of the coal sample.

3.3 Method C (microwave drying method)

A certain amount of coal sample with a particle size of <6 mm was weighed and placed in a microwave oven. Under the action of the alternating electric field of the microwave generator, the water molecules in the coal generate frictional heat at high speed, so that the water evaporates quickly. Calculate the total moisture based on the mass loss of the coal sample after drying (see Appendix A).

4 reagents

4.1 Nitrogen (GB/T8979): purity 99.9%, oxygen content less than 0.01%.

4.2 anhydrous calcium chloride (HGB3208): chemically pure, granular.

4.3 Color changing silica gel (GB/T7822): industrial supplies.

5 instruments (method A and method B)

5.1 Air drying box: with automatic temperature control and air blowing device, can control the temperature in the range of (30 ~ 40) °C and (105 ~ 110) °C, there are gas inlet and outlet, there is enough ventilation, such as each It can be ventilated more than 5 times in hours.

5.2 Nitrogen drying oven: with automatic temperature control device, can keep the temperature in the range of (105 ~ 110) °C, can accommodate the right amount of weighing bottle, and has a small free space, with nitrogen inlet and outlet, hourly Can be ventilated more than 15 times.

5.3 Shallow plate: It is made of heat-resistant and corrosion-resistant materials such as galvanized iron plate or aluminum plate. Its specifications should be able to accommodate 500g coal sample, and the load per unit area should not exceed 1g/cm2.

5.4 Glass weighing bottle: diameter 70mm, height (35 ~ 40) mm, with a tight grinding cap.

5.5 Analytical balance: 0.001g.

5.6 Industrial balance: The sensitivity is 0.1g.

5.7 Dryer: Contains discolored silica gel or granular anhydrous calcium chloride.

5.8 Flowmeter: Range (100~1000) mL/min.

5.9 Drying tower: The capacity is 250mL, containing color-changing silica gel or granular anhydrous calcium chloride.

6 samples

6.1 Coal sample

The whole moisture coal sample with particle size <13mm, the coal sample is not less than 3kg; the coal sample with the particle size <6mm, the coal sample is not less than 1.25kg.

6.2 Preparation of coal samples

6.2.1 Full-water coal samples with a particle size of <13 mm are prepared in accordance with the provisions of GB474 or GB/T19494.2.

6.2.2 For the whole moisture coal sample with particle size <6mm, the whole moisture coal sample will be crushed once to a particle size of <6mm by the crusher with no obvious loss of water during the crushing process, and the coal sample will be quickly reduced by the divider by not less than 1.25kg. Load into a sealed container.

1) 1) “No obvious loss of moisture” means that the measured results of the total moisture of the broken coal sample are compared with the measured results before the crushing. There is no significant difference by t test, or there is a difference, but the confidence range is small.

GB/T 211—2007

6.3 Before measuring the total moisture, first check the sealing of the coal sample container. The surface is then wiped clean and weighed to 0.1% of the total mass with an industrial balance and checked against the total mass indicated on the container label. If the total mass weighed is less than the total mass indicated on the label (not more than 1%) and it can be determined that there is no loss during the transportation of the coal sample, the reduced mass should be used as the moisture loss of the coal sample during transportation. The amount, the percentage of moisture loss is calculated, and the water loss correction is performed as described in 7.3.

6.4 The coal sample in the sealed container should be thoroughly mixed for at least 1 min before weighing the coal sample.

7 Determination steps

7.1 Method A (two-step method)

7.1.1 External moisture (Methods A1 and A2, air dried)

Quickly weigh <500mm coal sample (500±10)g (weighed to 0.1g) in pre-dried and weighed shallow pan, spread evenly in shallow pan at ambient temperature or not higher than 40 °C Dry in air drying oven to a constant mass (continuous drying for 1 h, mass change not exceeding 0.5 g), and record the constant mass (weighed to 0.1 g). For the case of drying with an air drying oven, the coal sample should be re-equilibrated in the laboratory environment before weighing.

Calculate the external moisture according to formula (1):

In the formula:

Mf - the external moisture of the coal sample, expressed in mass fraction, %;

M——the mass of the <13mm coal sample weighed, in grams (g);

M1——the mass loss after drying of the coal sample, in grams (g).

7.1.2 Intrinsic moisture (method A1, drying with nitrogen)

7.1.2.1 Immediately break the coal sample after the determination of external moisture to a particle size of <3 mm, and quickly weigh (10 ± 1) g of coal sample (weighed to 0.001 g) in a pre-dried and weighed weighing bottle. , spread evenly in the weighing bottle.

7.1.2.2 Open the weighing cap and place it in a nitrogen-passing drying oven (5.2) that has been preheated with dry nitrogen and heated to (105-110) °C. The nitrogen is ventilated more than 15 times per hour. Bituminous coal drying for 1.5h, lignite and anthracite