Investigation on the effect of carbon powder structural characteristics derived from ethylene decomposition on powder explosion

In LDPE production, ethylene underwent polymerization under high temperature and pressure. However, the heat generated during polymerization could cause ethylene pyrolysis, leading to safety risks. More critically, the carbon powder produced could further decompose, posing additional hazards. This study examined the pyrolysis characteristics of high-pressure, high-temperature ethylene and the explosive behavior of the resulting carbon powder. The decomposition of ethylene was carried out under 80–200 °C and 80–200 MPa with the oxygen concentration of 1000–5000 ppm using ethylene explosive device, and the explosive testing of derived carbon powder was carried out in a 20 L sphere chamber under the powder concentration of 200 g/m³. It was found that higher initial ignition pressure, temperature, and oxygen concentration intensified ethylene pyrolysis. The size of resulting carbon powder ranged from 0.5 to 500 μm and fewer structural defects, leading to stronger explosive intensity due to a larger specific surface area and longer suspension time in the air. Conversely, carbon powder with larger particle sizes and more defects tended to agglomerate, reducing suspension time and explosion intensity. This research provided a theoretical foundation for understanding powder explosions caused by ethylene decomposition.