| Microfluidic systems, which can strengthen the process of mass, heat and momentum transfer and chemical reaction significantly, have been widely applied to various fields such as chemical industry and bio-pharmaceutical industry in recent years. As the core components of microfluidic systems, micromixers have drawn considerable attention both at home and abroad, and become a research focus in chemical engineering. The micro-mixing performance in micromixers directly influences the selectivity and yield of product in subsequent reactions.In this paper, firstly the iodide-iodate competing parallel reaction system was brought into studying the micro-mixing performance in a split-and-recombine micromixer and an interdigital micromixer. The effects of Re and volume flow ratio on segregation index were investigated under the suitable [H+] by experiments. Then theoretical analysis of experimental results was carried out. The results elucidate that for both micromixers, the increase of Re is beneficial to the improvement of micro-mixing performance. The segregation index of split-and-recombine micromixer and interdigital micromixer decreased from 0.2132 and 0.2284 at Re=78 to 0.0035 and 0.00605 at Re=3100, respectively. And segregation index increases with the increase of volume flow ratio. When the volume flow ratio is 1, the mixing performance of micromixers are the best. It is showed that the micro-mixing quality of the split-and-recombine micromixer is slightly better than that of the interdigital micromixer at the same Re.Secondly, based on the study of the micro mixing, the split-and-recombine micromixer was used to synthesize ZSM-5 zeolite. And the structures of synthesized samples were characterized by XRD, SEM and BET. This paper mainly investigated how the mixing of synthetic fluid influenced the synthesis of ZSM-5 zeolite. The results show that uniform mixing of synthetic fluid can be achieved in a very short period of time in the split-and-recombine micromixer, and its mixing effect is better than that of conventional stirred tank reactor. As a result, the relative crystallinity, specific surface area a of synthesized ZSM-5 zeolite are 100% and 235.6681 m2/g at 28mL/min respectively.Finally, based on the study of mixing mechanism, the mixing performance of a new planar passive micromixer which was designed based on the parametric curve was evaluated by numerical simulation at Re ranging from 0.1 to 80. In order to increase the disturbance of the fluid and make the microchannel generate the effect of split and recombination, the diamond blocks are puted in the microchannel. The arrangement manner of blocks and the number of mixing units all have influence on mixing performance. The relations between Re and the mixing index both in the balanced split micromixer with inner uniform diamond blocks and in the unbalanced split micromixer with staggered diamond blocks inside were investigated. It is demonstrated that the unbalanced splitmicromixer behaves better in micro-mixing..Results show that as the number of mixing units increases, the mixing index increases. However, after the number of the mixing units reaches to 5, the mixing index remains unchanged. In the range of studied Re, the mixing index of unbalanced splitmicromixer is over 0.9 with 5 mixing units(the length of micromixer is 3273μm). Particularly, when Re equals to 50 and the mixing index is more than 0.95, it is proved that this new type of micromixers all have a very good mixing performance with a range of Re from 0.1 to 80. |
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