Important roles of multiphase process in enhancement mechanism of micro plastic particle combustion

Thermal recycling of recovered plastic resin has been investigated by supplying plastic resin powder as an additional fuel to the proposed twin-fuel industrial burner. The results emphasize the necessity of fundamental investigations, such as high-speed microscopic observations of micro plastic particles under abrupt heating. To observe the multiphase process of macro plastic particles under abrupt heating and to elucidate their combustion enhancement mechanism, some original devises are introduced; one for optical imaging and three for abrupt heating and ceasing. The former is a mini optical composite which enables simultaneous photographing of the direct silhouetted and schlieren images. The latter three are reforming of a rugged resin particle into a spherical one, a vertical type circular mini-burner for abrupt heating, and a mini-puff generator for abrupt extinguishment. Three types of fine supports made of tungsten, silicon-carbide, and quartz glass are used. Detailed optical observations clarify many characteristics concerning the multiphase process of plastic resin particles under abrupt heating, such as the occurrence of multiple internal micro bubbling, multiple micro explosions and jets. The burning rate constant is also estimated based on the temporal reduction rate of the particle surface area. It is found that the values obtained for three supporting wires are greater than those of typical liquid fuels, and that the key factor to the prominent enhancement rate of micro PET particle combustion can be attributed to the occurrence of the multiphase process particular to micro plastic particles.