​Comparing the Electrostatic Effects of Different Abrasive Media on Sulfur Powder

Abstract:

In this study, high-frequency vibrational ball milling was used to grind sulfur, and the electrostatic characteristics of sulfur powder during the grinding process were tested and analyzed. The results indicate that at grinding speeds of 1200, 1500, and 1800 r/min, the time for thin-sheet sulfur to reach its saturation electrostatic charge was 40, 60, and 100 seconds, with charge-to-mass rate values of 0.269, 0.470, and 0.700 nC/(g·s). Powdered sulfur, on the other hand, reached its saturation electrostatic charge in 30, 40, and 70 seconds, with charge-to-mass rate values of 0.416, 0.701, and 0.979 nC/(g·s). When using tungsten carbide as the abrasive material, the electrostatic charge of ground sulfur was lower, with stainless steel being 1.39 times that of tungsten carbide, and zirconia being 3.82 times that of tungsten carbide. The moisture content of sulfur powder effectively reduced the electrostatic charge during the grinding process, with the saturation electrostatic charge nearly reducing to zero when the moisture content was 0.8%.

Introduction:In this study, we employed the MM440 model Retsch high-frequency vibrational ball mill to quantitatively analyze the electrostatic characteristics of sulfur during the grinding and crushing process. We explored the impact of grinding intensity, grinding time, grinding material, and moisture content of sulfur. These findings are significant for guiding the production of dry-milled sulfur, particularly in the selection of production equipment and process conditions.

Materials and Methods:Materials: Powdered sulfur (d90=72.17 μm, d50=24.50 μm) and thin-sheet sulfur (approximately 5 mm in diameter and 3 mm in thickness), produced by Jiangyou City Chuannorth Poly-Optimize Chemical Industry Co., Ltd., as shown in Figure 1. The main composition is listed in Table 1.

Equipment: MM440 model Retsch ball mill equipped with 50 mL stainless steel, tungsten carbide, and zirconia grinding jars, as well as Φ20mm stainless steel, tungsten carbide, and zirconia beads, produced by Retsch GmbH; LS13320 laser particle analyzer (dry method) produced by Beckman Coulter, Inc.; JCI-178 digital charge instrument with a range of 0-200 nC, equipped with the JCI-150 Faraday cup, produced by Chilworth Ltd.; GZX-9070MBE electric blast drying oven produced by Shanghai Boxun Industrial Equipment Factory; WQG-11 dry-wet bulb temperature and humidity measuring instrument produced by Changzhou Ruiming Instrument Co., Ltd.; electronic balance, stopwatch, and more.

Results and Discussion:

• Impact of Grinding Speed and Time on Sulfur Charge-to-Mass Ratio:

• Thin-sheet sulfur and powdered sulfur both reach saturation electrostatic charges as grinding time increases. Faster grinding speeds lead to shorter times for sulfur to reach its saturation electrostatic charge, with a quicker charge-to-mass rate. Finer sulfur particles exhibit larger saturation electrostatic charges and shorter times to reach saturation.

• Influence of Contact Material on Sulfur Powder Saturation Electrostatic Charge:

• Different grinding materials significantly affect sulfur charge-to-mass ratios. Tungsten carbide results in the lowest charge, followed by stainless steel and zirconia. The charge-to-mass ratio of sulfur ground with zirconia jars is 3.8 times that of tungsten carbide and 1.9 times that of stainless steel. It is suggested that using materials close to sulfur in the electrostatic sequence during grinding can effectively reduce the electrostatic charge.

• Effect of Moisture Content on Saturation Electrostatic Charge:

• Moisture content has a notable impact on sulfur's electrostatic charge. An increase in moisture content decreases the electrostatic charge, with a nearly complete reduction to zero when the moisture content is 0.8%. The relationship between moisture content and saturation electrostatic charge fits an exponential function.

Conclusion:

1. Grinding sulfur leads to saturation electrostatic charges, with finer particles achieving larger charges more quickly. Faster grinding speeds further expedite the process.

2. Different grinding materials have a significant impact on sulfur charge-to-mass ratios. Tungsten carbide results in the lowest charge, followed by stainless steel and zirconia.

3. Increased moisture content effectively reduces sulfur's electrostatic charge. The relationship between moisture content and saturation electrostatic charge fits an exponential function, with a nearly complete reduction to zero at 0.8% moisture content.