GB/T 214-2026Determination of total sulfur in coal (English PDF)

0.1 g) of Aldrin. Take

0.5 g of coal sample when the total sulfur content is 5%~10%; and take

0.25 g of coal sample when the total sulfur content is greater than 10%.

5.4.2 Transfer the crucible containing the coal sample into a well-ventilated muffle furnace. Gradually heat the sample from room temperature to 800°C~850°C over 1h ~ 2h; and maintain this temperature for 1h ~ 2h.

5.4.3 Remove the crucible from the muffle furnace and allow it to cool to room temperature. Carefully loosen and break up (if any unburned particles are found, continue igniting for 30 min) the ignited material in the crucible with a glass rod. Then transfer the ignited material to a 400 mL beaker. Rinse the inside of the crucible with hot water; collect the washings in the beaker; and add 100 mL~150 mL of freshly boiled water; stir thoroughly. If black particles are still floating on the surface of the liquid, then the determination is invalid.

5.4.4 Filter the solution using medium-speed qualitative filter paper via decantation. Rinse 3 times with hot water. Transfer the residue to the filter paper and wash thoroughly with hot water at least 10 times, producing a total washing solution volume of 250mL ~ 300mL.

5.4.5 Add 2 ~ 3 drops of methyl orange indicator to the filtrate. Neutralize with hydrochloric acid solution, adding an excess of 2 mL, to make the solution slightly acidic. Heat the solution to boiling and slowly titrate 10 mL of barium chloride solution while stirring constantly. Maintain this gentle boiling state for approximately 2 h, until the final solution volume is approximately 200mL.

5.4.6 After cooling or allowing the solution to stand overnight, filter it using dense, ashless quantitative filter paper; and wash with hot water until no chloride ions are present (the solution shall not be turbid when tested with silver nitrate solution).

5.4.7 Transfer the filter paper with precipitate to a known-mass porcelain crucible. After low- temperature ashing of the filter paper, ignite it in a muffle furnace at 800°C~850°C for 20 min ~ 40 min. Remove the crucible; cool it slightly in air; and then place it in a desiccator to cool to room temperature before weighing.

5.5 Blank test When preparing each batch of Aldrin or changing any other reagent, 2 or more blank tests shall be performed (without adding coal samples, follow 5.4). The mass range of barium sulfate precipitate in the blank tests shall be less than 0.0010 g. Take the arithmetic mean of the blank test results as the blank value.

5.2 Reagents and materials...

5.2.5 Methyl orange solution. 2 g/L; dissolve

0.2 g of methyl orange in 100 mL of water.

5.2.6 Porcelain crucibles. Capacities of 30 mL and 10~20 mL, respectively.

5.2.7 Filter paper. Medium-speed qualitative filter paper and dense ashless quantitative filter paper.

5.3.1 Analytical balance. Graduation value

0.1 mg.

5.3.2 Muffle furnace. Equipped with a temperature control device, capable of heating to 900 °C, temperature adjustable and ventilated.

5.4 Determination...

5.4.1 Weigh (1.00±0.01) g (accurate to 0.0002

g) of general analytical test coal sample and

2.0 g (accurate to

5.6 Calculation and expression of results

5.6.1 Calculation of results The determination results are calculated according to Formula (1). Where. St,ad - total sulfur mass fraction in coal samples for general analysis, expressed by %; m1 - mass of barium sulfate, in g; m2 - mass of barium sulfate in blank tests, in g; 0.1374 - coefficient for converting barium sulfate to sulfur; m - mass of coal sample, in g.

5.6.2 Expression of results The total sulfur content (mass fraction, %) of the tested coal sample is the average of repeated determinations, rounded off to 0.01% according to GB/T 483.

5.7 Precision of method The precision of the Eschka method for determining total sulfur in coal is specified in Table 1.

6.2 Reagents and materials...

6.2.1 Electrolyte. Take

5.0 g each of potassium iodide and potassium bromide; dissolve in 250 mL ~ 300 mL of water; and add 10 mL of glacial acetic acid.

6.2.2 Tungsten trioxide.

6.2.3 Sodium hydroxide. Chemically pure.

6.2.4 Color-changing silica gel.

6.2.5 Certified coal reference material.

6.2.6 Combustion boat. Made of ceramsite or corundum, with a sample loading section approximately 60 mm long, and heat resistant to temperatures above 1200°C.

6.2.7 Quartz tray. Capable of holding the combustion boat, allowing it to move in and out of the combustion tube according to a programmed sequence and to a designated position.

6.2.8 Glass wool.

6.2.9 Aluminosilicate wool.

6.3 Instruments and equipment

6.3.1 Coulometric sulfur analyzer It mainly includes a controller, tubular high-temperature furnace, coulometric integrator, electrolytic cell, electromagnetic stirrer, and air supply and purification device. The reducing combustion tubes of the tubular high-temperature furnace shall be tightly connected end-to-end to the piston and electrolytic cell; and sealed with silicone rubber tube.

a) Tubular high-temperature furnace. Capable of heating to above 1200 °C, with a high- temperature isothermal zone of at least 70 mm long at (1150±10) °C; equipped with a platinum-rhodium-platinum thermocouple temperature measurement and control device; and containing a reducing combustion tube with a temperature resistance of above 1300 °C. The outlet of the combustion tube is filled with clean, dry glass wool; at a distance of 80 mm ~ 100 mm from the outlet end, it is filled with a layer of aluminosilicate wool with a thickness of approximately 3 mm.

b) Electrolytic cell and electromagnetic stirrer. The electrolytic cell is 120 mm ~ 180 mm high, with a capacity of no less than 400 mL, and contains a platinum electrolytic electrode pair with an area of approximately 150 mm^2 and a platinum indicator electrode pair with an area of approximately 15 mm^2. The response time of the indicator electrode shall be less than 1 s; and the speed of the electromagnetic stirrer shall be approximately 500 r/min and continuously adjustable.

c) Coulometric integrator. The linearity error of the integral shall be less than 0.1% within the electrolysis current range of 0 mA ~ 350 mA.

d) Sample injection program controller. Capable of advancing, stopping, and reversing according to a prescribed program, placing the coal sample at the 500 °C pre- decomposition and 1150 °C high-temperature decomposition positions in the combustion tube.