Experimental And Theoretical Study On Micromixing Of Microreactors

As one of the most important means to intensify micromixing, micro-scale devices like micromixers and microreactors have attracted more and more attentions in both laboratories and commercial areas in recent years. The rapid development of microreaction and micromixing technology has led to a considerable variety of microreactors. However, the study on micromixing, which is the most significant procedure in chemical reaction process, in microreactors has been seldom reported. Microreactors have been, until now, insufficiently implemented from industrial point of view because of distribution and fouling problems. In this work, with the help of the new iodide-iodate parallel-competing test system, micromixing efficiency (indicated by segregation index Xs) of two typical microreactors—Y-type microreactor and line-type microreactor was characterized. To meet the requirements of industrial yield, a new microporous tube-in-tube reactor (MTTR) was designed and developed. Micromixing efficiency of this new microreactor was characterized, and the micromixing time was evaluated by the incorporation model. Based on previous visual study on mixing microelements, a slab-shrinking micromixing model was proposed to investigate the micromixing efficiency in MTTR. The major results obtained in this work are as follows:(1) The segregation index calculated from the experimental results reduces with the reduction of reactant concentration, especially the concentration of acid. For microreactors with different sizes and structures, the most sensitive hydrogen ion concentration range for measurement is different:0.02-0.06M for Y-type microreactor,0.06-0.08M for line-type microreactor and0.02-0.06for MTTR.(2) A new microporous tube-in-tube reactor (MTTR) was designed and developed. The maximum throughput reached9L/min under the experimental conditions, which means great potential in industrial applications. The effects of reactant concentration, flow rate, volume flow ratio, micropore size and channel width on micromixing were investigated. In particular, the increase of flow rate and the reduction of micropore size and the width of microchannel could dramatically intensify micromixing. Segregation index had a range of0.005-0.01at the general experimental conditions. The evaluated micromixing time was the magnitude of millisecond.(3) Expressions of energy dissipation rate of MTTR under laminar flow and turbulent flow were derived on the basis of the definition of energy dissipation rate and the assumption of plug-flow. Based on previous visual study on mixing fluid microelements, a slab-shrinking micromixing model was proposed to investigate the micromixing efficiency in MTTR. The agreement between model predictions and experimental data proved that the slab-shrinking model could predict the effects of experimental conditions on micromixing efficiency correctly.