This standard applies to the determination of total moisture of commercial coal samples, production coal samples and coal seam coal samples of lignite, bituminous coal and anthracite.

    Total moisture refers to the total amount of moisture contained in the coal sample when taken.

    This standard specifies three methods for the determination of total moisture in coal, of which Method A is only applicable to bituminous coal and anthracite, and is used as an arbitration method for the determination of total moisture in bituminous coal and anthracite. Methods B and C are suitable for lignite, bituminous coal and anthracite, and Method B is used as an arbitration method for the determination of total moisture in lignite.

Main points of the method: Coal samples were dried to constant weight in a drying oven at 105~ 110 ℃ or 145 ± 5 ℃, and the percentage of moisture content was calculated based on the weight loss of coal samples.

1 Equipment

1.1 Drying oven: with a blower and an automatic temperature control device, the temperature can be maintained within the range of 105 to 110 degrees Celsius or 145 ± 5 degrees Celsius.

1.2 Shallow plate: Made of corrosion-resistant and heat-resistant materials such as galvanized thin iron plate or aluminum plate, its area can accommodate 500g coal samples at a ratio of approximately 0.8g coal samples per square centimeter. And the weight of the plate should be less than 500g.

1.3 Tray balance: the sensitivity is 1g and 5g each.

1.4 Desiccant: built-in desiccant (color-changing silica gel or non-deliquescent bulk anhydrous calcium chloride).

1.5 glass weighing bottle: with a diameter of 70mm and a height of 35 to 40mm, and with a tight grinding cap.

1.6 Analytical balance: the sensitivity is 1mg.

2 Preparation of coal samples

2.1 Shrink coal samples in accordance with Article 3.9 of GB 474-83 "Preparation Method of Coal Samples".

2.2 Methods A and B use the maximum particle size not exceeding 13mm, and the coal sample volume is about 2kg. Method C uses the maximum particle size not exceeding 6mm, and the coal sample volume should not be less than 300g ①.

2.3 Before measuring the total moisture, first check the sealing condition of the container containing the coal sample, then wipe its surface clean, weigh it with a tray balance (1.3) ②, and check with the weight indicated on the label on the container. If the gross weight of the coal sample (i.e. the total weight of the coal sample and the container) is less than the gross weight indicated on the label (not more than 1%), and it can be determined that the coal sample has not been lost during transportation, the reduced weight should be used as the moisture loss of the coal sample during transportation. And calculate the percentage (W1) of this amount to the net weight of the coal sample (the gross weight of the coal sample on the label minus the weight of the container). When calculating the total moisture of the coal sample, this loss should be added, and the coal samples in the container should be fully mixed.

Note: ① In GB474-83 "Preparation Method of Coal Samples", the provisions 3.9.3 total moisture coal sample particle size is less than 3mm, and the amount of coal sample is 100g are changed to the provisions of this article.

When the total weight of the coal sample and the container does not exceed 1kg, a tray balance with a sensitivity of 1g should be used for weighing.

3 measurement steps

3.1 Method A

Weigh the coal sample 500g (calibrated to 1g) with a dry, clean shallow plate (1.2) of known weight, and spread the coal sample evenly in the plate. Place the shallow plate containing the coal sample in a drying box (1.1) with a pre-blast injection and heated to 105-110 ° C. Dry the bituminous coal for 2-2.5h and anthracite for 3-3.5h under constant blast conditions. Remove the shallow plate from the drying box and weigh it while it is hot. Then carry out the inspection test for 30min each time until the decrease of the coal sample does not exceed 1g or the weight increases. In the latter case, the one-time weight before the weight increase should be used as the basis for calculation. Note: Blowing starts 3-5min before placing the weighed coal sample in the drying box.

3.2 Method B

Weigh the coal sample 500g (to 1g) in a dry, clean shallow plate (1.2) of known weight, and spread the coal sample evenly in the plate. The shallow plate containing the coal sample is placed in a drying box (1.1) pre-blasted and heated to 150-160 ° C. Under the condition of 145 ± 5 ° C and continuous blasting, the bituminous coal is dried for 30min, the anthracite is dried for 1h, and the lignite is dried for 1.5h. Remove the shallow plate from the drying box and weigh it while it is hot. Then check tests are carried out for 15min each time until the decrease of the coal sample does not exceed 1g or the weight has increased. In the latter case, the one-time weight before the weight gain should be used as the basis for calculation.

3.3 Method C

Weigh a coal sample of 10-12g (to 0.01g) in a dry, clean weighing bottle (1.5) of known weight and shake the coal sample gently to lay it flat. Open the weighing bottle cap, put the weighing bottle containing the coal sample into a dry oven pre-blown and heated to 145 ± 5 ° C. Dry bituminous coal for 30min, lignite for 45min, anthracite for 60min under constant blowing conditions, then remove the weighing bottle from the drying oven, immediately cover it, cool it in air for about 5min, and then move it into a dryer (1.4) to continue cooling to room temperature (about 30min) before weighing. Then carry out inspection tests for 15min each time, until the reduction of the coal sample does not exceed 0.01g or the weight increases. In the latter case, the previous weight should be used as the basis for calculation.