Towards Anaerobic Digestion (ADM No. 1) Model's Extensions and Reductions with In-situ Gas Injection for Biomethane Production

Abstract

The necessity to focus and work with renewable energy for value-added product generation has gained interest in recent years, which has led to the development of mathematical models that allow a better understanding and optimization of these processes. In this work an extension of the anaerobic digestion model (ADM No. 1) with H2 and CO external gas injection was proposed. Therefore, the modification of the volumetric mass transfer coefficient in terms of gas injection and the use of CO as a substrate of the process were proposed. Then, a model reduction was performed applying the principal process analysis (PPA) methodology with two threshold values δ=0.05 and δ=0.1. The R2, AICC criterium, and Global Relative Error (%Error) were used to compare the model and reductions performance. The threshold value δ=0.05 presented the best results with an R2 > 0.99 and AICC criterium of -114 compared to the experimental process. For the %Error, values of 2.32%, 1.38%, and 2.18% were achieved for H2, CH4, and CO outlet gas flowrates when the reduction δ=0.05 is compared with the complete model. This reduction also allowed to decrease the simulation time from 1.94s to 0.82s. Thus, concluding that a first reduced model approximation is possible for the biomethanation process.