Anaerobic digestion is a promising method of organic waste valorisation, particularly for fish farm waste, which has experienced a high growth rate in recent years. The literature contains predictive mathematical models that have been developed by various authors, allowing the prediction of the composition of bio-gas production from organic waste. In general, Monod’s kinetic expression is the basis for describing the enzymatic reaction rates for anaerobic digestion. In this work, several parameters are taken into account, such as temperature, cell growth inhibition, and other operating parameters, and systems of differential equations coupling the kinetics and stoichiometry for bio-reactions are applied to better describe the dynamics. Because of the high number of initial parameters that need to be defined for the anaerobic digester, the use of this model requires significant resources and a long calculation time. For this reason, a global sensitivity analysis (GSA) is applied to this predictive model based on the Sobol index method, in order to identify the most influential key parameters and the interactions between them. For the digestion of fish waste, it is observed that the key parameters influencing methane production are the lipid concentration of the waste, temperature, and hydraulic retention time (HRT).

This paper deals with an analytical method to assess the maximum temperature value along a tubular chemical reactor at steady state. This reactor is provided with a jacket in which a counter current cooling liquid flows. The thermal behavior of the chemical reactor is calculated with the McCormack numerical method. Comparison of the exothermic reaction generated flux with the removed flux from the separating wall leads to a two-part reactor subdivision. In the first part, the reactor behaves as an adiabatic reactor followed by a zone in which the flux removed from the wall is not negligible and remains constant. In the second part, the reactor behaves like a simple heat exchanger without internal energy source. Analytical integration of mass and energy balance equations in each subsystem was used to determine the analytical expression of maximum temperature.

The unsteady state temperature of the reactive mixture along a tubular reactor presents a maximum value resulting from the exothermicity of the chemical reaction.The knowledge of the maximum temperature, (position and value) is an important indicator for safety and quality of reactors in which a highly exothermic reaction takes place. This paper deals with experimental and theoretical estimation and localization of this maximum temperature along a chemical tubular reactor at unsteady state. This reactor is equipped with a jacket in which the refrigerating fluid flows in counter current configuration.The reaction undertaken in the inner tube of the reactor is oxidation of sodium thiosulfate by hydrogen peroxide.The unsteady state is described from the resolution of the model equations, obtained from mass and energy balances, with the numerical method of McCormack.The influences of hydrodynamic, thermal and chemical parameters on the value and position of the maximum temperature are studied.