Feeding spent coffee ground powders with a non-mechanical L-valve: experimental analysis and TFM simulation

A better understanding of feeding operations is pressing for value-added processing of waste biomass powders. This paper examines the feeding of Spent Coffee Grounds (SCGs) using a non-mechanical L-valve both experimentally and numerically. L-valve provides stable solids feeding, showing different flow regimes. Powders' height in the standpipe must be monitored to guarantee smooth operations with the valve, and the data for SCGs differ significantly from those reported for glass and sand powders. A new correlation to predict the solids flowrate from simple pressure measurements was proposed for valve operating under high air flowrates. For low to medium air flowrates, a two-fluid model (TFM) was proposed and validated. The SCGs' flowrate in the feeder was accurately predicted by the TFM and the correlation. Furthermore, key information for the design of L-valves was obtained from the TFM simulation. The findings are useful for producing renewable thermal energy and fuels with biomass SCGs.