Flame propagation characteristics of industrial flue gas on explosion of powder coating/air mixtures

Abstract

In order to prevent explosion accidents during the electrostatic spraying process of powder coatings, a typical coating production line was taken as an example. Two types of powder coatings, namely black sand profiling powder coating and glossy black powder coating were selected for research purposes. The study aimed to investigate the explosion propagation characteristics of organic and inorganic pigment powder coatings and evaluate the inerting effects of industrial flue gas using a self-built explosion test device with dimensions of 80mm × 80 mm (cross-section) and 800 mm (height). This research provides a theoretical foundation for developing precise strategies to prevent and control explosions in the electrostatic spraying process of powder coatings. The results show that the addition of organic pigments in powder coatings enhances the propagation of explosions, resulting in an increase in peak flame propagation velocity from 5.94 m/s to 7.49 m/s and improved continuity of flame combustion. The high temperature generated by the explosion flame triggers cross-linking and curing reactions between epoxy resin and polyester resin, leading to varying degrees of attenuation in flame propagation speed. Different types of powder coatings exhibit distinct inerting effects when utilizing combustion exhaust gas from a heating furnace. The former shows a gradual decrease in explosion intensity with increasing amounts of combustion exhaust gas, while for organic pigment powder coating, reducing oxygen content to 18% only delays ignition time without significantly weakening the process or peak velocity of explosion flame propagation. However, when oxygen content is reduced to 15%, ignition becomes more challenging, and self-sustaining flame propagation cannot be achieved.