| Reactors are key equipments for reaction processes in chemical industry and the mechanisms of process intensification in reactors have drawn a lot of attentions. Mnay types of reactors have been developed recently, e.g., impinging steam/CIJR reactors, micro-/capillary-channel reactors, rotating reactors and so on. The principles of these reactors are besed on the improved amount of transfer per unit time. That means the process in these reactors would be intensificated by increasing contact area between fluids or by increasing relative velocity of fluids. Compared with traditional reactors, these novel reactors can remarkably improve micromixing performance, and they can be used in preparation of nano-materials, exctaction process, absorption, polymerization, etc. However, some problems still limit their industrial applications, such as difficults in design and fabrication, blocking problem and high cost.A micro-impinging stream reactor (MISR) at the size of～1 mm has been developed based on above analyses. The MISR reactor can be built from commercial T-junctions and steel micro-capillaries, which has both characteristics of micro-scale and impinging stream techology. By using a large-sized and very short outlet tube, the two injecting streams could impinge intensely within the limited chamber of the reactror to achieve a quick mixing at the micro-scale. It is clear that MISR reactor has advantages of intensified micromixing, easy construction and no-blocking, which can intensify process of mass transfer in liquid-liqiud system and preparation of powder materials. The major innovative work of this thesis is as follows:(1) The MISR reactors were built from commercial T-junctions and steel micro-capillaries. Micromixing efficiency in MISR reactors was investigated by Iodide-Iodate parallel competing reaction. The micromixing efficiency can be represented by segregation index (Xs). With increasing inlet Reynolds number (Rej), Xs decreased and then approached to 0.0003 at Rej> 3000, indicating the well micromixing efficiency in MISR reactors. Unequal volumetric flow ratio caused low micromixing efficiency. Big inlet diameter (di) was benefitial for micromixing at the same velocity. The effects of outlet channel length (L) were insignificant, and the impinging stream would fully develop without outlet channel.(2) With help of computational fluid dynamics (CFD) simulation, process of fluid flow and micromixing-reaction in MISR reactors can be investigated visually. The κ-ε model and DQMOM-IEM methods were used to study the micromxing-reaction in MISR reactors. The impinging region would be formed in the center of reactor when Rej> 3000. The reaction completed in short time in MISR reactors. Numerical results demonstrated that a narrower and longer tube would against the development of impinging stream. Both experimental and numerical results agreed well.(3) Based on experimental data and incorporation model, the relationship between tm and Rej of MISR was found:Rej< 1000, tm= 0.84Re-1.07; Rej> 1000, tm= 27.67Re-1.58. For MISR reactors, tm= 0.1～5.0 ms, which was much smaller as compared with traditional stirrred reactors. Finally, the micromixing-reaction operating curves have been built to provide the theoretical foundation for selection of reactors and operating conditions according to the characteristic reaction time.(4) The mass transfer performance in the MISR reactors was investigated by a liquid-liquid extraction system. It was demenstrated that the overall volumetric mass transfer coefficient (KLa) was affected by inlet Reynolds number of water phase (Reαq), volumetric flow ratio (R), and configurations of reactors. It was found that KLα ∝ (Reαq)1.6, KLα∝(R)-1.2. The value of KLα is～20 s-1 at Reαq= 3400, R=1, which is 2-3 orders of magnitude higher than that of conventional liquid-liquid contactors. MISR equipments were applied to extract natural rutin, which was leached by ultrasound combined with microwave. The leaching rate of 1.7% was obtained by using orthogonal method. Then the rude rutin in leaching liquid was extracted by MISR equipments, and the extraction rate reached a high value of 78.8%.(5) Ultrafine manganese dioxide was synthesized by MISR reactors. The performance of this material could be improved either by increasing inlet velocity or by introducing stirring in aging process. Unequal volumetric flow ratio resulted in low specific capacity. The prepared α-MnO2 under optimized conditions had spherical morphology with-120 nm in diameter,～200 m2·g-1 in specific surface area and a discharge specific capacity of～211 F·g-1, which showed a capacity decline of～18% after 1000 cycles. Fe-doped manganese dioxide was prepared by MISR reactors as well. In condition of FeCl3 source and Mn:Fe= 20:1, samples had discharge specific capacity of～200 F·g-1 with a decline of～7% after 1000 cycles, which showed better stability than undoped materials (33%). |
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