Sizing-Up Effects On Micromixing Performance Of Microchannel Reactors And Their Application In The Preparation Of Ni-Co-S Composites

As a key step of chemical reaction process,the degree of mixing directly affects the conversion and yield of chemical reactions,which in turn determines the quality of products and the cost of subsequent separation processes.Microchannel reactors have been widely studied as one of the effective means to enhance mixing,but there are two significant drawbacks of easy clogging of microchannels and small processing capacity in the practical applications,which have limited the engineering application of microchannel reactors.Based on the above analysis,this work investigated the sizing-up of 0.6mm i.d.microchannel reactor to 2.0 mm,3.0 mm i.d.and 4.0 mm i.d.tube reactor step by step and their micromixing performance as well as material preparation.The main contents and results are as follows:（1）Experimental studies on the micromixing performance of the above tube reactors were carried out using the I^-/IO₃^–parallel competitive reaction system.Results showed that the X_Sof all different tube reactors became almost～3.4×10^-4when Re was bigger than 5584 and remained constant with further increase of Re,which indicated that the microchannel reactor has no amplification effect when scaled up in a proper range at sufficiently high Re.By varying the outlet tube length L of the reactor,it was found that an outlet tube length of 25 mm is sufficient to complete the micromixing process and no additional pressure drop was required,and the micromixing effect was best with the volumetric flow ratio R=1.（2）Ni-Co-S composites were prepared using the sized-up tube reactors and characterized as follows:the electrochemical properties of the materials prepared by both the microchannel reactor and the sized-up tube reactors were best at Re=6700,with the specific capacity reaching about 580 C·g^-1and the initial capacity retention rate above 70%after 1000 charging-discharing cycles;and the physical and electrochemical properties of the prepared Ni-Co-S composites were almost the same,further demonstrating the negligible sizing-up effects of the microchannel reactor at high Re.（3）Ni-Co-S/CNTs composites were prepared using the 4 mm i.d.tube reactor,and the prepared materials were characterized with the following main conclusions:The optimal CNTs doping amount is 1 mg per ml of Ni-Co mixed solution,and the initial capacity retention of the prepared materials remained86.51%after 2000 cycles of charge and discharge;in the mixing process of liquid phase and solid liquid suspension,the sizing-up reactor still has good performance.This work provided new findings for the sizing-up of microchannel reactor,and the sizing-up reactors not only increase the processing capacity,but also avoid the clogging problem of precipitation reaction,which has great potential for industrial applications.