Acceleration of mass transfer in loop reactors

Gas bubbles entrapped in biocatalyst particles subjected to hydrostatic pressure oscillations, e.g. during recirculation in loop reactors, will induce intraparticle liquid flows, and thereby enhance mass transfer in excess of diffusion. This ‘breathing particle’ mechanism was demonstrated in methanogenic granules, and led to a typical activity increase of 13% compared with static pressure conditions. From these experimental results and model predictions, it is concluded that convective acceleration of mass transfer in gas-producing systems offers interesting perspectives for the optimisation of biofilm processes in loop reactors. Development of special carrier materials with a central gas-filled cavity could lead to a novel type of bioreactor in which liquid flow through the biocatalyst is decisive.