Modeling of the Process of Functioning of the Digester of a Biogas Plant during Methane Fermentation of Сow Manure

Abstract

Ensuring high and stable biogas output during digester operation is ensured by regulating and monitoring values of control parameters. The purpose of article is to develop model of process of functioning of digester during methane mono-fermentation of cow manure with establishment of values of control parameters. A solution to model was found to obtain dynamics of biogas yield, while experimental and simulated dynamics of biogas yield were as close as possible. The developed model is system of differential equations that describe changes in concentrations of substrate nutrients , methanogen biomass and dynamics of biogas output in digester. The system of differential equations was solved in Simulink package , obtaining dependencies and . The dependence was compared with results of studies conducted on laboratory biogas plant with digester with useful volume of 30 liters at temperature of 37°C with periodic substrate loading system. By selecting parameters of model, resulting function was compared with similar one obtained experimentally. It has been established that in model of digester functioning process during methane mono-fermentation of cow manure, following coefficients have following meaning: bacterial growth rate m3/(kg day); substrate assimilation ; bacterial growth rate m3/(kg day); rate of conversion of nutrients into biogas m6/kg. The obtained values of coefficients make it possible to carry out modeling of process of methane mono-digestion of cow manure and predict biogas yield at different initial values of concentration of methanogen biomass, concentration of substrate nutrients, digester volume, which is used in industrial biogas plants.