Feeding Spent Coffee Grounds into Reactors: TFM Simulation of a Non-Mechanical Spouted Bed Type Feeder

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Feeding Spent Coffee Grounds into Reactors:

TFM Simulation of a Non-Mechanical Spouted Bed Type Feeder

Lucas Massaro Sousa^{1, 2}, Maria C. Ferreira², Qinfu Hou^[1]*and Aibing Yu^{1, 3}

¹ARC Research Hub for Computational Particle Technology, Chemical Engineering Department, Monash University, Clayton, VIC 3800, Australia

²Drying Center for Pastes, Suspensions, and Seeds, Chemical Engineering Department, Federal University of São Carlos, P.O. Box 676, 13565-905 São Carlos, Brazil

³Centre for Simulation and Modelling of Particulate Systems, Southeast University−Monash University Joint Research Institute, Suzhou 215123, PR China

* Corresponding author. E-mail address: qinfu.hou@monash.edu

ABSTRACT

Due to the increasing coffee production, Spent Coffee Grounds’ (SCGs) generation has grown dramatically, hence appropriate management of this solid biomass waste is imperative. SCGs can be used as feedstocks for renewable energy and fuel generation provided that a stable feeding of powders to reactors is maintained. Recently, a non-mechanical spouted bed feeder proved itself an excellent alternative in feeding SCGs to a pilot-scale circulating fluidized bed reactor. Nonetheless, further studies are necessary for the feeder’s implementation in commercial applications. Here the feeding of SCGs with the spouted bed feeder is addressed by using Computational Fluid Dynamics. Firstly, a Two-Fluid Model (TFM) is validated against experimental data, and then the effects of five operating and design parameters were analyzed aiming at improving the handling of SCGs. The solids flowrate (W_S) in the reactor could be stably controlled from 4 to 30 g/s depending on the settings. The feeder performance is enhanced by operating it under high gas flowrate (Q), high entrainment length (z), and high mass of solids in the feeder (H_S). Using feeders with low cone angle (γ) or reactors with large diameter (D_R) increases W_S, which is appealing for the operation of medium-to large-scale units. The proposed TFM is a cost-effective tool for implementing spouted bed feeders in commercial applications. With the feeder coupled to the process, SCGs are treated continuously in the reactor for energy generation, thus reducing the disposal problems associated with this waste and improving the management of SCGs globally.

Keywords: feeding device; spent coffee grounds; two-fluid model; spouted bed; CFD.