GB/T 211-2017Determination of total moisture in coal (English PDF)

3.1 Method A (two-stage method)

3.1.1 Method A1.drying under nitrogen

Weigh-take a certain amount of 13mm coal samples; dry them in the environment

where the temperatures do not exceed 40°C, until the constant mass is reached.

Crush the sample into particle size lower than 3mm; dry them under nitrogen at

(105~110) °C, until the constant mass is reached. Calculate the total moisture from

the loss in mass at each of the two stages in accordance with the samples.

3.1.2 Method A2.drying in air

Weigh-take a certain amount of 13mm coal samples; dry them in the environment

where the temperatures are lower than 40°C, until the constant mass is reached.

Crush the samples into maximum particle size of 3mm;

3.2 Method B (single-stage method)

3.2.1 Method B1.drying under nitrogen

Weigh-take a certain amount of 6mm coal samples (or 13mm); dry them under

nitrogen at (105~110) °C, until the constant mass is reached. Calculate the total

moisture from the loss in mass in accordance with the samples.

4.1 Anhydrous calcium chloride. chemically pure and granular.

4.2 Allochronic silica gel. industrial products.

4.3 Nitrogen. purity >= 99.9%, the oxygen content < 0.01%.

4.4 Tray. made from enamel, stainless steel, galvanized iron or aluminum plate, heat

resistant and corrosion resistant materials; the specification shall be able to

accommodate 500g sample, and the load per unit-area shall not exceed 1g/cm2.

4.6 Sampling instrument. applicable to 13mm or 6mm sample, and the opening size

shall be at least 3 times of the corresponding particle size.

5.1 Air-drying oven. with devices for automatic temperature control and air blow,

with inlet and outlet for air, capable of being controlled at (30~40)°C and (105~110)°C,

with a sufficiently rapid rate of atmosphere change, for instance, more than 5 times

per hour.

5.2 Nitrogen-flushed oven. with device for automatic temperature control, capable of

being controlled at (105~110)°C, able to accommodate appropriate weighing bottles

with a little more room to spare, with inlet and outlet for nitrogen, and allow more than

5.6 Flow meter. with a measuring range of (100~1000)mL/min.

5.7 Drying tower. with a volume of 250ml and contain allochronic silica gel or granular

anhydrous calcium chloride.

6.1 According to GB 474 or GB/T 19494.2, prepare the sample for total moisture. In

which, for 13mm coal sample for total moisture, it shall not be less than 3kg; for 6mm

sample for total moisture, it shall not be less than 1.25kg.

6.2 Before determining the total moisture in coal sample, it shall firstly check the

sealing condition of the container. Afterwards, clean the surface; weigh the sample

with an industrial balance to the nearest 0.1% of its total mass; check the result with

the total mass indicated on the label. If there's a loss of mass and it can be

ascertained that there is no sample loss during transportation or storage, then the

mass reduced shall be regarded as that of the lost moisture.

7.1 Method A (two-stage method)

7.1.1 Free moisture (Methods A1 and A2, drying in air)

Use a pre-dried and weighed tray to quickly take-weigh 490g~510g (accurate to 0.1g)

of 13mm coal sample; spread it evenly; dry it in an air drying oven at ambient

temperature not exceeding 40°C, until the constant mass is reached (with continuous

drying for 1h and mass variation not exceeding 0.5g); record the mass (accurate to

0.1g). If an air drying oven is to be used, the coal sample shall be placed in laboratory

environment until it reaches moisture equilibrium again.

7.1.2 Inherent moisture (Method A1, drying under nitrogen)

7.1.2.1 After the determination of free moisture, immediately crush the sample into

maximum particle size of 3mm. Use a pre-dried and weighed weighing bottle to

weigh-take 9g~11g (accurate to 0.001g) of the sample; spread it evenly.

7.1.3 Inherent moisture (Method A2, drying in air)

Except that the nitrogen-flushed oven is replaced by the air-drying oven, the other

procedures are the same as that in 7.1.2.

7.1.4 Result calculation

The total moisture in coal shall be calculated in accordance with Formula (3);

7.2 Method B (single-stage method)

7.2.1 Method B1 (drying under nitrogen)

7.2.1.1 Use a pre-dried and weighed weighing bottle to quickly weigh-take (10~12)g

of 6mm coal sample (accurate to 0.001g); spread it evenly.

7.2.1.2 Open the lid of bottle; put it into an oven which has been aerated with dry

nitrogen and preheated to (105~110)°C. For bitumite, dry for 2h; for lignite and blind

coal, dry for 3h.

7.2.2 Method B2 (drying in air)

7.2.2.1 Total moisture in 13 mm coal sample

7.2.2.1.1 Use a pre-dried and weighed tray to quickly weigh-take 490g~510g

(accurate to 0.1g) of 13 mm coal sample; spread it evenly.

7.2.2.1.2 Put the tray in an air-drying oven which has been preheated to

(105~110)°C. Under the condition of air-blowing, for bitumite, dry for 2h; for blind coal,

dry for 3h.

7.2.2.1.3 Remove the tray and weigh it (accurate to 0.1g) while it is still hot.

7.2.3 Result calculation

Total moisture in coal shall be calculated in accordance with Formula (4);

7.4 Moisture loss correction during the preparation

If the coal sample is air dried before the preparation of the total moisture sample,

which leads to a mass loss of the coal sample, then, the value of corrected total

moisture shall be calculated in accordance with Formula (6).