Modeling and control strategies for anoxic biotrickling filtration in biogas purification

BACKGROUND: Anoxic biotrickling filters have been used to 'sweeten' biogas. Nevertheless, the cost and availability of large amounts of nitrate could limit the use of this technology in comparison with aerobic biotrickling filters. The development of a dynamic mathematical model would be useful for the design of control strategies with regard to nitrate dosage. RESULTS: A dynamic model has been developed to describe the performance of an anoxic biotrickling filter for biogas desulfurization. The model considers the most relevant phenomena involved in biotrickling filter operation: advection, absorption, diffusion and biodegradation. Moreover, a fraction of the liquid phase is stagnant - an assumption that increases the importance of diffusion phenomena for low liquid flow rates. Once the model had been validated, six control strategies were analyzed for different scenarios and purposes: i.e. to minimize nitrate consumption and/or to maximize H2S removal efficiency. CONCLUSION: The mathematical model developed from the description of the phenomena involved in the process is a powerful tool to evaluate all possible strategies when considering and quantifying the savings and improvements in different operating modes. (C) 2015 Society of Chemical Industry