Residence time distribution in two-phase flow mini-channel reactor

Mini-channel reactors have a high level of heat and mass transfer performance, and thus present great potential in highly exothermic reactions or those with explosion risks. Residence time distribution (RTD) and mean residence time (MRT) are important in reactor design and modelling. However, normally reported measurements of RTD and MRT were often conducted at room temperature and low pressure, significantly from actual reaction conditions. In the current work, the RTD and MRT of the two phases that flow in mini-channel reactors for both the toluene–nitrogen and cyclohexane–nitrogen systems were measured at 165 °C and 1 MPa, respectively. The RTD of the liquid phase was determined using the pulsing tracer method. The experimental data were fitted using a dispersion model. Results showed that the MRT of the liquid phase is much longer than that of the gas phase. It is preferred by the slow reactions such as the oxidation of hydrocarbons. The reaction experiments demonstrated that a longer liquid MRT is favorable for the reactions like the oxidation of hydrocarbons, which have a relatively lower reaction rate. In the plug flow zone, the MRT of the liquid phase decreased rapidly with both increasing gas and liquid flow. However, when the flow pattern shifted to the annular flow, the MRT of the liquid phase remained constant. An empirical model was developed to predict the MRTs in different flow patterns using dimensional analysis.