COMPARATIVE ANALYSIS OF MIXING REGIMES IN BIOGAS PLANTS FOR OPTIMIZATION OF THE STIRRING PROCESS
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https://doi.org/10.31489/2026N2/47-56Keywords:
anaerobic digestion, mixing efficiency, gas and heat transfer, substrate degradation, biogas yieldAbstract
Effective mixing in anaerobic bioreactors plays a crucial role in ensuring uniform temperature and substrate distribution, which directly affects the efficiency of organic matter degradation and biogas yield. This study investigates the influence of mixing intensity and regime on gas transfer, heat transfer, and substrate degradation during anaerobic digestion. Special attention was given to the experimental data obtained from the pilot solar-powered biogas plant. The results demonstrated that intermittent mixing (e.g., 5 minutes per hour) provided the same biogas yield as continuous mixing, but with substantially lower energy consumption. Continuous mixing did not result in a significant increase in methane yield compared to intermittent operation, while it was associated with markedly higher energy demand. In contrast, the absence of mixing impaired reactor performance—the volume of gas produced decreased, and temperature stratification was observed, indicating uneven heating of the medium and incomplete substrate degradation. In this work, international studies (2019–2024), including experimental investigations and CFD models, were analyzed to assess the effects of mixing regimes on decomposition kinetics, temperature uniformity, and methane yield, and to compare them with our results. For quantitative evaluation, energy balance equations (e.g., the Lindorfer model) and stoichiometric formulas were applied. The findings indicate that intermittent mixing is the optimal strategy, as it ensures a high degree of organic matter degradation and biogas yield while requiring significantly less energy than continuous mixing.References
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