Numerical modelling and experimental validation of an orifice plate-based hydrodynamic cavitation process for improving the biomass pretreatment.

Hydrodynamic cavitation can be used to pretreat biomass by utilizing the energy released during the collapse of cavitation bubbles. Delignification as pretreatment enhances the biodegradation of lignocellulosic composition. The present study employed a CFD model and experimental validation of the numerical analysis of hydrodynamic cavitation (HC) in multi-hole orifice (MHO) designs under various operating conditions. The total 14 geometry of the orifice plate depends on the plate thickness, the number of holes, and the hole orientation used to analyze and optimize geometry for the biomass pretreatment process. Three phases are used in numerical analysis and experimentation to investigate the effect of particles on cavitation. The simulated results regarding velocity and pressure gradients, turbulence quantities, and vapor volume fractions are critically analyzed and discussed. The cavitation number changes to 0.22 in the experiment and 0.16 in the simulation due to the presence of biomass particles. Orifice plate thickness was found to significantly influence cavitation inception and evolution. 4 mm thickness and nine holes with specific orientations were found to be an optimized geometry with the lowest cavitation number, maximum pressure drop, and highest throat velocity. In the experimentation, 0.8 mm biomass particles were used in the mixture (2 % w/w) to determine the effect of biomass particles on the flow. This result helps identify the critical operating and design parameters and the impact on the cavitation of particles to achieve the desired cavitation phenomena.