Hydrodynamics of a gas-liquid microreactor designed for the oxidation kinetics of organic compounds
Résumé
Liquid phase oxidation reactions are widely studied and optimized for industrial processes of interest such as the oxidation of cyclohexane. The slow oxidation of hydrocarbons, which takes place throughout their chain of use, is the cause of fuel deterioration known as fuel ageing. In recent years, the use of microfluidic tools for the investigation of such processes is expanding with the development of the technologies. Microfluidics enables the use of explosive conditions in a safer way than traditional processes and these tools can be adapted for the kinetic study of the oxidation of ground fuels and jet fuels. Their kinetics of oxidation are slow, and their study requires long residence times, which are not usually reached in the microfluidic field. The PEEK-ACHU rig, a microfluidic device with a heated silicon/glass microfluidic reactor designed for long residence times (from 16 min up to 230 min) and high pressure (up to 40 bar), was developed for the study of slow oxidation reactions of organic compounds. This work presents the design of the reactor and proposes a hydrodynamic study of the gas-liquid Taylor flow implemented in this tool to enable the study of oxidation reactions of fuels. A good understanding of the different diphasic flow regimes as a function of gas bubble generation was obtained for conditions in the explosive range. A correlation was found between the density and viscosity of a fuel and the length of gas bubbles and liquid slugs. The thickness of the residual liquid film at the wall and the reaction regime were characterized and demonstrate that the design of our microreactor enables the kinetic study of organic compounds oxidation, without oxygen mass transfer limitations, at high temperature and high pressure, for very long residence times.
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