Combining thermal model and kinetics: Implications in dynamic simulation of anaerobic digesters

Area of Science:

• Biochemical Engineering
• Anaerobic Digestion Modeling
• Thermal Process Simulation

Background:

• Accurate modeling of biogas digesters requires integrating biochemical and thermal processes.
• Existing models may overestimate heat demand, impacting operational efficiency.
• Environmental factors like climate significantly influence digester performance.

Purpose of the Study:

• To couple ADM1-based kinetics with a comprehensive thermal model for biogas digesters.
• To improve the accuracy of heat demand calculations and thermal inertia representation.
• To assess the impact of climate and insulation on digester performance and optimize design.

Main Methods:

• Integrated ADM1 (Anaerobic Digestion Model No. 1) kinetics with a detailed thermal model.
• Calculated bioreaction energy based on kinetic rates, avoiding feedstock degradation heat estimations.
• Simulated digester performance under different climatic conditions and insulation levels.

Main Results:

• Bioreaction energy calculation reduced heat exchanger demand overestimation by approximately 20%.
• Improved representation of digester thermal and reactional inertia.
• Simulations showed significant climate-dependent performance variations; UK reactor had 23% higher biogas auto-consumption than in France.
• Enhanced insulation reduced heat losses by 37% in the UK.

Conclusions:

• Coupling kinetic and thermal models provides deeper insights for biogas digester optimization.
• Digester design and construction must be tailored to specific climatic conditions.
• Improved thermal management through insulation and climate-specific design enhances biogas production efficiency.