Modelling methane production in trickle bed reactors: A biokinetic approach.

Area of Science:

• Biotechnology and Bioengineering
• Chemical Engineering
• Environmental Science

Background:

• Ex-situ biomethanation is a key process for upgrading biogas from anaerobic digestion.
• Trickle-bed reactors (TBRs) are utilized for efficient gas-product generation.
• Optimizing TBR performance requires understanding complex biokinetic and mass transfer phenomena.

Purpose of the Study:

• To develop and validate a mechanistic biokinetic model for ex-situ biomethanation in a TBR.
• To investigate the influence of mass transfer, kinetics, and operational parameters on reactor performance.
• To provide a predictive tool for designing and optimizing biomethanation processes.

Main Methods:

• Development of a mechanistic biokinetic model incorporating spatial discretization, interphase mass transfer, axial dispersion, Monod kinetics with pH inhibition, and solid retention time (SRT) constraints.
• Experimental validation using gas-phase data at three different temperatures.
• Calibration of transport parameters, including mass transfer coefficient (kLa) and effective axial dispersion.

Main Results:

• The model accurately reproduced measured axial gas-phase concentration profiles and outlet flows.
• Reactor performance was found to be mass-transfer-limited across various operating conditions.
• Increased inlet flow enhanced methane production capacity but decreased conversion and purity, producing hydrogen/methane mixtures (hythane) when desired.

Conclusions:

• The developed model serves as a practical design tool for TBR biomethanation.
• Reactor performance is significantly influenced by mass transfer limitations and axial dispersion.
• The findings guide further experimental studies for advancing TBR biomethanation technology.