Mathematical model for optimal operation of an ex-situ hydrogenotrophic methanation bio-trickling filter reactor

To upgrade biogas to biomethane, a mathematical model approach for a hydrogenotrophic methanation process is formulated in a biotrickling filter (BTF) reactor. The model partitions the trickling bed (TB) space in arbitrary levels of possibly different volumes and uses the first Fickian diffusion law along the vertical axis and through the biofilm layer attached to the inert bed material. To calculate gas flows among TB levels, the model is subject to the ideal gas law and to the partial pressures Dalton’s law, assuming a fixed amount of gaseous moles in each TB level. In addition to the available control variables, such as the liquid recirculation rate and the gaseous inflow rate, the gaseous effluent recirculation rate is tested as a new control variable for the model. The simulations performed of the model accurately describe experimental results of an ex-situ hydrogenotrophic methanation in a BTF. Finally, an optimal steady-state operation study for BTFs with certain physicochemical parameters is provided for any TB reactor size, and other operational improvements for the model, such as additional gaseous influent injections along the TB, are outlined. • Fickian diffusion-based mathematical model proposal fits well the experimental data. • Analysis of effluent gaseous recirculation as control variable. • Steady-state operation directive for maximising biomethane productivity and purity.