Co-combustion of refuse plastic fuel from marine plastics with wood pellets in a fixed-bed: Identification of minimum cofiring ratio and ideal air flow rate

Energy recovery from marine plastic waste after the collection and pretreatment of refuse plastic fuel (RPF) offers a practical measure to prevent the formation of microplastics, which pose a threat to marine biota and human health. This study investigated the fixed-bed combustion of RPF by visual observation and detailed measurement of the key combustion parameters. Unlike the fluff form, densely compacted RPF particles were not suitable for dedicated combustion in a fixed bed reactor because they melted and subsequently blocked the air passages. However, cofiring with 20 wt% or a larger amount of wood pellets (WP) successfully stabilized the flame propagation because the WP particles secured the air passages. The RPF-WP blend (6:4) exhibited the characteristic behaviors of fixed bed combustion in which the downward flame propagation and burning rate accelerated with increase in air flow rate and reached a peak. The combustion gas was highly fuel-rich mainly due to the hydrocarbons released from RPF, indicating that a large amount of additional air is required to complete oxidation above the bed. The experimental approach of this study to derive combustion parameters for particular RPF-biomass mixtures can be useful for guiding the primary design variables of industrial-scale grate furnaces.