GB/T 39769-2021Determination of forms of sulfur in coke (English PDF)

3.1 Principle

Boil the coke sample with dilute hydrochloric acid, extract the sulfate from it and make it precipitate barium sulfate, and calculate the coke sample based on the mass of barium sulfate Sulfate sulfur content.

3.2 Reagents and materials

Unless otherwise stated, only reagents confirmed to be analytically pure are used in the analysis.

3.2.1 Water. GB/T 6682, tertiary water.

3.2.2 Aluminum powder. CAS number 7429-90-5, purity >99%, 75µm~150µm.

3.2.4 Ethanol. the concentration is 95%.

3.2.5 Hydrochloric acid solution. 5mol/L. Take 417mL hydrochloric acid, add water to dilute to 1000mL, shake well and set aside.

3.2.6 Barium chloride solution. 100g/L. Weigh 11.73g of barium chloride (BaCl2·2H2O) dissolved in water and dilute to 100mL.

3.2.7 Potassium thiocyanate solution. 20g/L. Weigh 2 g of potassium thiocyanate and dissolve in 100 mL of water.

3.2.8 Silver nitrate solution. 10g/L. Weigh 1g of silver nitrate dissolved in 100mL of water, add a few drops of nitric acid, mix well, and store in a brown bottle.

3.2.9 Methyl orange indicator solution. 2g/L. Weigh 0.2g of methyl orange and dissolve it in 70°C water, cool and dilute to 100mL.

3.2.10 Filter paper. slow qualitative filter paper and slow quantitative filter paper.

3.3 Equipment

3.3.1 Muffle furnace. with programmed temperature controller, can be heated to 900 °C, furnace door with vent and chimney.

3.3.2 Drying box. It can be controlled in the temperature range of 105°C~150°C, and it is equipped with a blast device.

3.3.3 Electric heating plate. The temperature is adjustable, and the temperature can be increased to 500°C.

3.3.4 Analytical balance. Sensitivity is 0.0001g.

3.3.5 Desiccator. It contains color-changing silica gel.

3.3.6 Beaker. 250mL~300mL in capacity.

3.3.7 Watch glass. 100mm in diameter.

3.4 Sample

According to the provisions of GB/T 1997, the coke sample is made into a sample with a particle size of less than 0.2mm.

3.5 Measurement procedure

3.5.1 Accurately weigh (1±0.1)g of the sample, record it as m, weigh to 0.0002g, put it into a beaker (3.3.6), add 0.5mL~1.0mL Wet it with ethanol (3.2.4), then add 50 mL of hydrochloric acid solution (3.2.5), cover with a watch glass (3.3.7), shake well, add on the hot plate (3.3.3) Heat and boil for 30 minutes.

3.5.2 After it is slightly cold, accurately weigh the slow qualitative filter paper (3.2.10) (m1), filter it with the decanting method, and then wash the coke sample with hot water 3 times~ 4 times, transfer all the coke samples to filter paper, wash with hot water until no iron ions are detected (check with potassium thiocyanate solution (3.2.7), such as The solution is colorless, indicating that there is no iron ion], retain the filtrate for (3.5.4) determination of sulfate sulfur content.

3.5.3 If coke powder passes through the filter paper during filtration, re-filter; if the filtrate is yellow, add 0.1g aluminum powder (3.2.2), slightly heat to make the yellow disappear Then filter again. Rinse repeatedly with hot water until there is no chloride ion in the filtrate. Check with silver nitrate solution (3.2.8), if the solution is not turbid, it means that there is no chlorine ion. After filtering, fold the filtered material and filter paper together, put it in a drying oven (3.3.2) at 50°C for drying for 5h~6h, take it out, and place it Weigh in the desiccator (3.3.5) for about 25 minutes, and then perform check drying for about 1 hour each time until the difference between two consecutive weighings is less than 0.005g. Place the dried coke sample and filter paper in the atmosphere for 1 hour to balance the humidity with the atmosphere, and then weigh (m2) for measurement. Organic sulfur and calculation.

3.5.4 Add 2 to 3 drops of methyl orange indicator solution (3.2.9) to the filtrate in 3.5.2, neutralize with ammonia solution (3.2.3) until the solution turns yellow, and then After adding hydrochloric acid dropwise to adjust the solution to red, the excess is 2mL, heated to boiling, and 10% barium chloride solution (3.2.6)

10mL, a white precipitate is formed, placed on the electric hot plate and boiled for 2h or left overnight, and finally keep the volume of the solution at about 200mL.

3.5.5 Filter with slow quantitative filter paper (3.2.10) and wash with hot water until there is no chlorine ion. Check with silver nitrate solution (3.2.8), such as filtrate Not turbid, indicating that there is no chloride ion.

3.5.6 Move the filtered precipitate and filter paper into a porcelain crucible of constant weight, put it into the constant temperature zone of the muffle furnace, and raise it from room temperature to 300°C, slowly carbonize for 40min, then 20min, then heat up to 500°C, ash for 60min, continue to heat up to (850±10)°C and burn 40min. Take out the crucible and put it in a desiccator to cool to room temperature naturally, weigh and deduct the mass (m3) of the porcelain crucible.

3.5.7 Accurately weigh the quality of the slow qualitative filter paper (m4), and perform a blank test according to the steps specified in 3.5.1~3.5.6 (without adding coke samples) Set it as the blank value (m5).

3.5.8 Put the qualitative filter paper after the blank test (3.5.7) into the beaker, accurately weigh it, and record it as m6.

3.6 Result calculation

The sulfate sulfur content (Ss, ad) in the coke sample is calculated according to formula (1). (m3-m5)×0.1374 m ×100 (1) Where.

Ss,ad --- Sulfate sulfur content in coke sample, %; m3 --- the mass of barium sulfate determined by the sample, in grams (g); m5 --- the mass of barium sulfate measured in blank, in grams (g);

0.1374---The coefficient of conversion from barium sulfate to sulfur; m --- The mass of the coke sample, in grams (g). The calculation result is rounded to two decimal places.

3.7 Precision

The precision of the determination of sulfate sulfur content should meet the requirements of Table 1.

4.1 Principle

After the sulfate in the coke sample is leached by hydrochloric acid, the sulfide is converted into hydrogen sulfide gas and escapes. At this time, the remaining sulfur in the coke sample is all Organic sulfur, the total sulfur content in the residue is determined, and the organic sulfur content in the coke sample is converted by the yield.

4.2 Measurement procedure

4.2.1 Determine the sulfur content in the filtered residue (3.5.3) according to the method specified in GB/T 2286, which is the organic sulfur content S'o, ad.

4.2.2 Use formula (2) to calculate the organic sulfur content So,ad in the coke sample.

4.3 Result calculation

The organic sulfur content (So, ad) in the coke sample is calculated according to formula (2).

4.4 Precision

The precision of the determination of organic sulfur content should meet the requirements of Table 2.