Effect of high solids loading on gas–liquid mass transfer in an oscillatory flow reactor for process intensification

Abstract

A wide range of chemical processes involves three phases, where common systems have inefficient mixing and mass transfer is limited. This study uses the oscillatory flow reactor with smooth periodic constrictions (OFR-SPC) according to the patent EP3057694 (B1) to evaluate its potential on O2 mass transfer at high solids loading (10–50 % (v/v)). For that, the effect of solids (EPS, PVC) properties (concentration, density, and size) on the performance of the volumetric liquid-side mass transfer coefficient (kLa), gas holdup (εG) and Sauter mean bubble diameter (d32) using several operational conditions (oscillation amplitude and frequency, superficial gas velocity) was assessed. Results show that oscillatory conditions can influence the solids effect on kLa. At solid load (≥ 30 % (v/v)) under low oscillations, kLa decreased, εG and d32 increased, slug flow regime emerged and the OFR-SPC behaved as fixed bed reactor. Contrary, no significant influence of solid properties on kLa, and εG was observed at higher oscillations, where the reactor behaved as fluidized bed in a homogeneous flow regime. Notably, solids’ concentration (<30 % (v/v)), size and density revealed a negligible influence on mass transfer for all range of oscillations, contrary to the widespread consensus where kLa tends to decrease in conventional reactors at lower solid’s load (<15 % (v/v)), making the OFR-SPC a valuable resource for catalytic processes. The OFR-SPC demonstrated higher mass transfer rates (∼3 − fold) than conventional multiphase devices with reasonable power consumption (∼100 W/m−3(−|-)). These are remarkable results, which indicate the OFR-SPC for three-phase industrial processes intensification.