On the performance of a spouted bed type device for feeding spent coffee grounds to a circulating fluidized bed reactor

Abstract

Using solid biomass wastes as feedstocks for industrial generation of renewable energy is appealing to meet company's energy demands with environmental awareness; however, maintain continuous feeding of wastes to reactors remains a challenge in processing. In this study, the performance of a non-mechanical spouted bed (SB) feeder was evaluated for handling dry and moist spent coffee ground (SCG) powders to a circulating fluidized bed reactor. A comprehensive experimental study was carried out to investigate the effects of operating variables and air inlet nozzle configuration on the solids circulation rates and pressure profiles. Using a convergent nozzle at the air inlet improved feeding stability compared to a conventional orifice air inlet. The circulation rates could be varied from 3.0<WS<11.0g/s by adjusting the air flowrate and the entrainment length. Although SB performance was affected by the powder's flowability, the feeder operation was rather stable, with fluctuations less than 20% in WS. Moreover, WS could be accurately predicted from pressures measured at the feeder and riser. The SB showed enhanced flexibility in handling SCGs with different properties compared to a non-mechanical L-valve. It suggests that SBs might be an appealing alternative to feed waste biomass powders into reactors in a continuous mode.