GB/T 4632-2008Determination of moisture-holding capacity of coal (English PDF)

5.3 Nitrogen oven. it is allowed to choose any one type from the following two

types.

5.3.1 Small space nitrogen oven. the oven is tight, having relatively smaller free

space; it has nitrogen inlet and outlet as well as automatic temperature control

device, which can maintain the temperature at 105°C ~ 110°C.

5.3.2 Normal nitrogen oven (Figure 2). it can control the temperature at 105°C

~ 110°C; in the thermostatic region is installed a metal cartridge in the size of

200mm × 100mm × 60mm. In the cartridge, there is one tray which can

accommodate 6 weighing bottles. At one end of the cartridge is provided with a

nitrogen inlet, which is connected through a silicone tube to the nitrogen cylinder,

and the entrance is covered by several layers of metal mesh, so as to disperse

the gas; the other end has a small door, so as to allow the free access of the

tray, being used as nitrogen outlet.

soaked with water, AND stored in a sealed container for use). USE double layer

filter paper to wrap it; USE hand to forcefully grip it; PLACE it at the upper sieve

in the humidity chamber (5.12). Inside the chamber is placed two sieves, the

upper sieve aperture is 0.60mm AND the lower sieve aperture is 0.45mm, AND

on each sieve is placed some permanent wet paper (5.11). Then MIX the coal

sample and permanent wet paper, and MAKE the coal mass scatter and fall

onto the below sieve. REPEAT this operation, until the coal sample falls onto

the bottom Dowling paper. TAKE 1g ~ 2g of coal sample from it; PLACE it into

a known mass weighting bottle; PAVE it level; PLACE it in the humidifier.

7.3 Humidity regulation

PLACE the weighing bottle on the weighing bottle holder in the humidifier; USE

the positioning pin to position the weighing bottle (just below the gas circulator

bell mouth); OPEN the weighing bottle lid. COVER the humidifier; MAKE it

airtight; START the propeller, so as to make the nitrogen circulate for 10min at

the flow rate of 1L/min; then CLOSE the nitrogen inlet. RECORD the

humidification start time; when the coal sample basically reaches to humidity

balance (bituminous coal and anthracite generally requires 24h, lignite requires

24h ~ 48h), OPEN the humidifier cover; immediately COVER tightly the

weighing bottle; TAKE it out; WIPE the weighing bottle clean; LET it settle at

room temperature for 5min; then WEIGH it, accurate to 0.0002g. Afterwards,

CONDUCT weighing once every 6 hours, until the difference of the consecutive

two mass weighed does not exceed 0.3% of the sample mass, which indicates

that it reaches to humidity balance. To facilitate test, it shall conduct tests of

same coal types simultaneously.

7.4 Moisture measurement

7.4.1 Use of small space nitrogen oven

FOLLOW the nitrogen drying method in GB/T 212 to conduct moisture

measurement for the coal sample after permanent wetting.

7.4.2 Use of normal nitrogen oven In accordance with Figure 2, INSTALL the

metal cartridge into the 105°C ~ 110°C thermostatic region in the oven;

CIRCULATE nitrogen into the cartridge at the flow rate of 350mL/min; HALF-

OPEN the weighing bottle lid and PLACE it on the tray in the cartridge; MAKE

the coal sample subject drying in the nitrogen stream for 1.5h ~ 2h. TAKE out

the weighing bottle and COVER it tight; COOL it under room temperature for

5min; then TRANSFER it into the oven for 15min; WEIGH it, accurate to

0.0002g. Then USE the same procedure to conduct inspection drying (30min

per time), until the mass reduction of the consecutively dried (two times) coal

sample does not exceed 0.0010g, OR otherwise until the mass starts increase.

Appendix B

(Informative)

Technical difference & causes between this standard and ISO

1018.1975

Table B.1 provides the comparison list of the technical differences & causes

between this standard...

......