Melting/gasification Characteristics of Pellet Fuel for a Waste Plastic Firing System

摘要

We have devised a novel combustor firing waste plastics, which are mainly composed of LDPE (Low Density Polyethylene) or PP (Poly propylene). The system includes a pre-combustor, which gasifies the plastics. To design the pre-combustor, we have studied the melting/gasification characteristics of the plastic pellets produced as the fuel for the system. The pellets are placed in a test section made of quartz and exposed to the hot gas, whose temperature ranges from 500℃ to 900℃. Their sizes are between 5 to 40 mm. We have also conducted the numerical simulation based on the VOF method, to investigate the detailed physics of the melting phenomena. The pellets are melted down via an oval shape from the initial cylindrical shape at each temperature, although the firing has been observed at the high temperature of 900℃. The PP yields higher melting rate than the LDPE in spite of its higher melting temperature. The melting process can be predicted by a simple heat balance when the sample diameter is small. The detailed melting process for the larger sample is predicted by the numerical simulation.