Completion of thermal runaway criteria: Two new criteria to define runaway limits

Design, Heat Transfer, and Visualization of the Milli-Reactor by CFD and ANN

This paper proposes a milli-reactor design method incorporating reactor runaway criteria. Based on Computational Fluid Dynamic (CFD) simulation, neural networks are applied to obtain the optimal reactor structure according to the target reaction requirements. Varma’s theory, the critical Nusselt number for stable operation of the flow reactor, is derived. Inserts of the multi-blade structure are designed and investigated to enhance mixing and heat transfer performance. The flow field and heat transfer capacities are obtained by CFD calculations in the range of Re 50–1800. The internal components increase the heat transfer performance up to 21 times, and the pressure drop up to 16 times. The inclined angle of the blade is recommended to be 45°, which can effectively improve heat transfer without generating excessive pressure drop. By partial least squares regression (PLS) analysis, Re and the number of blades are the most critical factors affecting heat transfer, and the five blades and smaller tilt angles are recommended. The CFD calculation results are in good agreement with the Particle Image Velocimetry (PIV) experimental results.

Simultaneous determination of enthalpy of mixing and reaction using milli-scale continuous flow calorimetry

A simultaneous determination of the enthalpy of mixing and reaction in a scalable continuous milli-scale flow calorimeter is investigated. As obtained calorimetric data is pivotal for the safety assessment of chemical reactions and processes. The acid-catalysed selective, homogeneous hydrolysis of acetic anhydride with half-lives from a few seconds to a few minutes is investigated as a model reaction. For the enthalpy of mixing 7.2 ± 2.8 kJ/mol and for the enthalpy of reaction −60.8 ± 2.5 kJ/mol were determined. For reactions that show complete conversion in the continuous reactor, a technique is introduced to further improve the accuracy of the reaction enthalpy determination. Thereby, the resolution of the observed temperature profile is increased by measuring the profile at different flow rates. Applying this procedure, the reaction enthalpy of −62.5 kJ/mol was determined which is in good agreement with literature values for this model reaction.

Graphical abstract