Several
parameters influence anaerobic digestion, e.g., hydraulic
retention time, temperature, pH, pressure, C/N ratio, etc. This work
presents the influence of the C/N ratio of the substrate on biogas
production modeling. To do this, a mathematical model is developed
for predicting the molar composition of biogas as a function of the
C/N ratio. Inspired by the AM2HN model, this model is a system of
nine partial differential equations that have been solved numerically
in SCILAB software by the 4th-order Runge–Kutta method. Obtained
results show an increase in production of methane with the C/N ratio.
Thus, optimal production of methane is observed for a C/N value between
20 and 30. The proposed model is then tested with two other models;
these tests show that the results of the proposed model match well
with numerical results of those two models.
A model of the higher heating value on a dry basis from the proximity analysis of agricultural wastes in Benin has been proposed in this article. This model was developed using agricultural residues such as shea shells and cakes, cotton and soybean stalks, corn cobs and peanut shells identified as part of the implementation of an experimental system. The validity of this model has been established for the Higher Heating Value (HHV) between 18.07 MJ/kg to 25.91 MJ/kg, Volatile Matter rate (%VM) 66.8% to 79.87%, Fixed Carbon rate 13.83% to 29.59%, and Ash content (%Ash) 3.47% to 6.3%. The model has an average absolute error of 2.79% and a bias error of 0.034%, significantly better than the most accurate literature prediction model, which offers a mean absolute error of 5.97% and –4.66% for the bias error. This work presents as well the first data from the proximity analysis of agricultural residues in Benin. These analyzes are carried out using a well-structured methodology that respects the standards and measures of simple random sampling forsample collection. Samples prepared under appropriate conditions are analyzed using standardized protocols for the agricultural wastes studied.
Although the methanization process is already a relatively advanced and widely used technology, its control on an industrial scale is still the subject of extensive research. The search for appropriate models to be used in control theory is now a high priority to optimize fermentation processes and solve important problems related to process instability. The aim of this study is to prove how it is possible to find the digestion temperature for which biogas production is optimal, without going through an experiment. For this purpose, we have developed a numerical model based on mass balances, performed on microorganisms and on organic substrates. This model predicts the cumulative volume, volume flow rate and molar composition of biogas (methane and carbon dioxide) as a function of temperature. The influence of temperature on digestion was studied in the range of 20 to 40 °C in mesophilic regime. The results show that the daily production, the cumulative volume and the molar composition of the biogas are more influenced by the temperature inside the reactor. The cumulative volume of biogas increases as the temperature increases in the range of 20 °C-35 °C and peaks at 35 °C.
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