Parametric analysis of torrefaction reactor operating under oxygen-lean conditions

Abstract

A small-to medium-scale, mobile torrefaction system has the potential to improve the economics of biomass torrefaction and expand its deployment in decentralized, rural areas. In order to simplify the reactor design for deployment in these contexts, a torrefaction reactor prototype operating under oxygen-lean conditions was proposed and developed in our earlier study. The goal of this study is to carefully quantify some key performance metrics of the aforementioned oxygen-lean reactor design under more realistic conditions and compare these metrics with torrefaction under inert conditions. For each condition, we characterized the product yield, energy yield, and energy densification for different feedstock. By using mass closure and elemental analysis, we further calculated the composition in the solid and volatile components. We show some differences in the reactor's performance in comparison with existing literature data obtained under inert torrefaction conditions. In general, under an oxygen-lean environment and at similar temperature and residence time, slightly over-torrefied products with reduced solid mass and energy yield were obtained, which is consistent with results reported in prior studies. These sacrifices in the reactor performance should be weighed against the benefits of a simplified design that has greater potential in remote areas. © 2019 Elsevier Ltd