The development and optimisation of an immobilised photocatalytic system within a Stacked Frame Photo Reactor (SFPR) using light distribution and fluid mixing simulation coupled with experimental validation

Recently, photocatalytic reactors have been designed with a view towards overcoming mass transfer limitations especially in systems with immobilised catalysts. This paper reports the design of a titanium “bladed” propeller with TiO2 immobilised on the blades. To evaluate the propeller efficiency, modelling using COMSOL Multiphysics® was validated experimentally using coumarin as a probe molecule allowing for OH radical quantification. Modelling of light distribution and catalyst irradiance at varying irradiation distance was performed using ray optics, which, alongside experimental work, showed that irradiation at 4 and 5 cm from the propeller yielded the highest irradiance (29.3 and 22.1 mW/cm2) and OH radical concentrations (5.38 and 5.56 µM respectively). Propeller rotation was modelled and compared against experimental data to assess mass transfer limitations at varying rotation speeds. This showed that 300 RPM provided the highest rate of coumarin degradation (0.32 µM/min) despite the model showing higher fluid velocities at 400 RPM.