GB/T 1575-2018Determination of yield of benzene-soluble extract in brown coals (English PDF)

4.1 Benzene. rho = 0.876 g/mL, distillation range 80 ° C ~ 81 ° C, at least 95% is

distilled off.

4.2 Filter paper tube. phi25 mm x 80 mm, commercially available or made as

5.2.2.1 Extraction test

5.2.2.1.1 Weigh 2 g of general analytical test coal sample (accurate to 0.0002

g) which is mixed uniformly, put it into the filter paper tube, put a group of

absorbent cotton on the top of the paper tube and make the edge as close as

possible to the paper tube, place the filter paper tube with coal sample into the

extraction chamber. In a conical flask which is pre-dried to a constant mass and

weighed, add 60 mL ~ 70 mL of benzene. Connect all parts of the automatic

extractor.

5.2.2.1.2 When the power is turned on and the program switch is pressed, the

instrument automatically performs extraction-rinsing-evaporation in accordance

with the preset procedure. The extraction-rinsing-evaporation device is lowered

until the conical flask is immersed in the water bath to a predetermined position,

the condenser is tilted until the benzene liquid can be dripped back to the

extraction chamber, the cooling water circulation device starts to work, at the

same time the water bath starts to heat.

5.2.2.1.3 When the temperature rises to the pre-set extraction temperature, the

pump starts, the hot water in the water bath enters the extraction chamber

jacket, and circulates between the two, the benzene in the conical flask

evaporates to the condenser, condensates there, dripped back into the filter

paper tube of the extraction chamber, the extraction starts. After 180 min (or

other set time), the pump stops and the extraction ends.

5.2.2.1.4 The extraction chamber is cooled by the hot water flowing back into

the water bath in the jacket, where the benzene vapor condenses and wash the

extract adhering to the inner wall of the extraction chamber into the conical flask,

the rinsing starts. After about 10 minutes, the rinsing is stopped, the condenser

is further tilted until the benzene liquid can flow out of the measuring system

and enter the recovery container, the pump starts again, the hot water enters

the extraction chamber jacket, the benzene vapor condenses in the condenser

and flows into the receiver, the evaporation starts. After about 50 minutes, the

evaporation ends and the extraction-rinsing-evaporation system raise to its

original position.

5.2.2.1.5 Remove the conical flask with the extract and place it in an air drying

box at a temperature of 105 °C ~ 110 °C or a vacuum drying box at a

temperature of (80 +/- 2) °C and a pressure of 50 kPa to dry it to constant mass.

Note. Generally, the first drying is 1.5 h, then the inspection drying is performed

for 30 min each time. When the mass difference between two consecutive

dryings is less than 0.0010 g, the mass is constant.

5.2.2.2 Blank test

Except that no sample is added, the remaining steps are the same as 5.2.2.1.

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