Mixing regime simulation and cellulose particle tracing in a stacked frame photocatalytic reactor

Abstract

To sustainably meet the global energy demand, unconventional methods to produce renewable energy must emerge. Biofuels from cellulose (via fermentable sugar production) mediated via photocatalysis provides an alternative to conventional fossil fuels. In order to effectively drive photocatalytic processes an effective reactor design is required, the design of which is influenced by a number of key factors such as the catalyst to reactant ratio and residence time, catalyst illumination time, light penetration and distribution for the system, mass transfer limitations (mixing) and product recovery. In this study we use COMSOL Multiphysics ® to simulate and assess one of the mentioned parameters -mixing regime of cellulose particles in a Stacked Frame Photocatalysis Reactor (SFPR). In the reactor design, we compare two mixers: a 'plus' shaped magnetic stirrer bar and an 8 blade Rushton impeller.The simulations reveal that the Rushton impeller offers a radial mixing pattern with a higher fluid velocity of 1.2 m/s when compared to the stirrer bar that offers a fluid velocity of 0.9 m/s. Cellulose particle tracing simulations confirm that the particle dispersion is superior in the case of the Rushton impeller as the vorticity generated during the mixing push the particles to the reactor's walls. Since the particles are forced towards the walls, there is a probability of more particles being illuminated than in the case of no or improper mixing.

Intensification of Acidogenic Fermentation for the Production of Biohydrogen and Volatile Fatty Acids—A Perspective

“…While AD and thermochemical routes are already commercially exploited, physico-chemical routes are on the lower end of the technology readiness level (TRL) spectrum (<TRL 3). This is primarily due to the heterogeneity of the biomass, with both the catalyst and biomass being solids suspended in a liquid phase, leading to mass transfer limitations [15], non-specificity of biomass breakdown [4,8] and lower biomass conversion rates [6]. While current literature has extensive information on the conversion of biomass derivatives to value-added compounds [16][17][18], information on direct conversion is limited.…”

Development and Optimization of an Immobilized Photocatalytic System within a Stacked Frame Photoreactor (SFPR) Using Light Distribution and Fluid Mixing Simulation Coupled with Experimental Validation

“…17 One such reactor is the stacked frame photocatalytic reactor (SFPR) proposed by Nagarajan et al, who carried out the modeling of mixing regimes and cellulose particle tracing. 18 As part of reactor design and subsequent manufacture, simulation and modeling have been demonstrated to provide valuable insights into reactor operation and optimization, 12,19 and hence aid the reactor development process. Nevertheless, modeling can only provide an indication on how efficient a new photocatalytic process may be, and information surrounding the chemistry of a reaction, especially regarding kinetics, can only be provided by experimental validation.…”

“…Despite recent interest in reactor design, photocatalysis still requires the development of novel photoreactors which are adaptable and scalable, with capability of being utilized for a multitude of applications . One such reactor is the stacked frame photocatalytic reactor (SFPR) proposed by Nagarajan et al, who carried out the modeling of mixing regimes and cellulose particle tracing . As part of reactor design and subsequent manufacture, simulation and modeling have been demonstrated to provide valuable insights into reactor operation and optimization, , and hence aid the reactor development process.…”