Experimental study of methanol atomization and spray explosion characteristic under negative pressure

Abstract

Leakage of methanol under negative pressure may cause high dangerous spray explosion in the process industry. The explosion characteristics of methanol spray under the combined effects of multi-factor have not yet been studied. Hence, combined effects of spray concentration (198.0–514.8 g/m3), ambient temperature (298.15–323.15 K) and injection pressure (13–21 bar) on atomization and spray explosion of methanol (308.15 K) in 20 L spherical vessel under negative pressure (0.80–1.00 bar) were studied in this paper. The results showed that the decrease of methanol concentration, the increase of ambient temperature and injection pressure all promoted the breakage of methanol spray with linear trend. Based on the negative pressure, the effect weights of concentration, ambient temperature, and injection pressure were 113.7 µm/bara, 243.3 µm/bara, 64.24 µm/bara, respectively. The “peak plateau” of explosion temperature lasted for 237.6 ms due to the multi-point source ignition. In contrast to the explosion pressure change, the temperature of methanol spray slightly decreased in delayed ignition region. The increase of spray concentration provided more combustibles and contributed to the spray explosion when the methanol concentration was below 356.4 g/m3. As the concentration continued to rise, the maximum explosion pressure under room pressure (0.1 bar) decreased inhibited by the poor oxygen, while the maximum explosion pressure under negative pressure (0.80–0.95 bar) slowly increased. The increase of ambient temperature promoted the maximum explosion pressure, temperature and the rate of pressure rise, especially the promotion under negative pressure, was more significant. The variation of the maximum explosion pressure and maximum rate of pressure rise was consistent with that of the spray particle size when influenced by injection pressure. The experimental results showed that the methanol spray was more explosive and dangerous under negative pressure.