Ryuji Yamakita

Microscopic Approaches to Decomposition and Burning Processes of a Micro Plastic Resin Particle

From a fundamental and microscopic viewpoint to elucidate the possibility and availability of thermal recycling of wasted plastic resin, a series of heating processes of melting, thermal decomposition and burning of a spherical micro plastic resin particle having a diameter of about 200 μm are observed, when it is suddenly exposed to hot oxidizing combustion gas. Three ingenious devices are introduced; the first is a high-speed microscopic direct and schlieren system, the second is a pre-mixed mini-burner for abrupt heating, which is equipped with a pair of spark gaps at its exit and is discharged synchronously with the starting signal of high-speed camera, and the third is a single mini-puff generator, which enables to extinguish instantly all flames around the micro particle at an arbitrary assigned time after the spark ignition. Polyethylene terephthalate and polyethylene are used as two typical plastic resins. In this paper the dependency of internal and external appearances of residual plastic embers on the heating time and the initial plastic composition is optically analyzed, along with appearances of internal micro bubbling, micro jets and micro diffusion flames during abrupt heating. Based on temporal variations of the surface area of a micro plastic particle, the burning rate constant is also evaluated and compared with well-known volatile liquid fuels.Copyright

An Investigation on Thermal Recycling of Recycled Plastic Resin (Numerical Prediction of Unburnt Rate in PET-Resin Powder Combustion)

To burn PET-resin powder as an alternative fuel and to realize the effective thermal recycling of a great deal of recycled PET-resin, a series of experimental investigations has been made on the physical aspect of PET-powder combustion in the industrial burner. The results showed that a large amount of PET-powder of up to about 80% is exhausted without burn-up in the open atmospheric operation, whereas it is perfectly consumed in the high temperature in-furnace operation. Understanding of the relationship between the heating time and the unburnt rate of PET-powder is therefore necessary for getting an important knowledge to reduce the amount of unburnt PET-powder. In this paper, the behavior of particle diameter is first modeled according to those experimentally measured, a particle-size histogram of PET-powder is transformed to a particle-number distribution by stepping the particle diameter at 0.01 μm intervals, and finally a numerical prediction of the unburnt rate in the PET-powder combustion is attempted by introducing the parcel approximation. The results give good quantitative agreement between the unburnt rates of PET-powder measured experimentally and those predicted numerically.

An Investigation on Thermal Recycling of Recycled Plastic Resin (Burning Characteristics of PET-Resin Powder in High Temperature Oxidizing Atmosphere Formed by Annular Burner)

Energy recycling of recycled plastic-resin is focused in this investigation. Polyethylene terephthalate resin powder is employed as an auxiliary fuel, whereas high temperature oxidizing atmosphere is generated downstream of the annular burner. Temperature and O2 concentration fields downstream of the annular burner without PET-powder supply are first examined by varying the slit-jet and nozzle-jet velocities with both equivalence ratios kept constant at 1.0. PET-powder is then introduced into the high temperature oxidizing region by varying the slit-jet velocity, the nozzle-jet velocity and the median diameter of PET-powder. Variations of temperature and O2 concentration fields with PET-powder combustion are discussed qualitatively. According to the results, the dependency of the PET-powder unburnt rate on the properties of high temperature oxidizing atmosphere is examined.