微撞击流反应器过程强化机理与应用研究

发布时间：2018-09-11 20:32

【摘要】：反应器是化工生产中实现反应过程的关键设备,反应器的过程强化机理一直是化工界研究的热点及重点。撞击流、CIJR)、微/毛细通道、旋转式等各类反应器相继得到发展。这些反应器的提出,都是基于提高单位时间的传递量这一思路,具体则是通过增大流体间接触面积或增大流体间相对速度实现过程强化。相比于传统的搅拌反应器,这些新型反应器的微观混合性能都有显著的提高,并被广泛地应用于纳米材料制备、萃取过程、吸收、聚合反应等方面。然而,上述反应器存在设计加工困难、管路易堵塞、成本高等问题,以至于限制了它们的工业应用。基于上述分析,本文提出了微撞击流反应器(MISR)的概念,并利用商用三通、不锈钢毛细管(～1 mm)成功构建了微撞击流反应器。MISR反应器基于微尺度的设计理念,同时引入撞击流技术优势。该反应器采用短粗的放大出口,两股流体在有限空间内发生强烈撞击而达到快速的微观混合。可见,MISR反应器具有强化流体混合、降低构建难度、减轻管路堵塞的优势。鉴于微撞击流反应器具备良好的微观混合性能,因此可用于实现液-液相传质以及粉体材料的制备等过程的强化。本文的主要研究内容如下：(1)利用商用三通以及不锈钢毛细管构建MISR反应器,通过Iodide-Iodate平行竞争反应体系考察MISR反应器的微观混合性能,并采用离集指数(Xs)进行定量分析。研究发现：增大入口雷诺数(Rej),Xs随之减小,当Rej3000时,Xs≈0.0003,表明MISR反应器具备较高的微观混合效率；体积流量不一致会导致微观混合效率变低；流速恒定,入口管径(di)扩大能促进微观混合；而出口管长(L)对微观混合基本没有影响,去掉出口管有利于撞击流的形成。(2)进一步借助计算流体力学(CFD)模拟,可视化研究MISR反应器的流体力学特性和微观混合-反应作用过程。模拟采用标准κ-ε模型,并通过DQMOM-IEM建模方法,探究MISR反应器的微观混合-反应作用机制。当Rej3000时,MISR反应器中心处形成高湍动能的撞击核心区,反应在极短的时间内就进行完全；模拟结果表明,窄长的出口结构不利于MISR反应器内撞击流的发展；模拟经实验数据对比验证为合理的。(3)基于实验数据,并结合团聚模型,得到tm与Rej的关系：当Rej1000时,tm=0.84Re-1.07；当Rej1000时,tm=27.67Re-1.58；对于MISR反应器,tm=0.1～5.0 ms,明显短于传统搅拌器的微观混合时间。利用多种反应器的微观混合/反应协同“操作曲线图”,并根据反应特征时间,能够初步筛选反应器类型,确定能够实现“微观混合/反应协同”的操作条件。(4)以液-液两相流动体系,研究MISR反应器两相流动中的传质特性。结果表明,水相入口雷诺数(Reaq)、体积流量比(R)、反应器结构以及水相粘度等对反应器的总体积传质系数(KLα)有显著影响。经拟合计算可知,KLα∝(Reαq)1.6,KLα∝(R)-1.2;当Reaq=3400,R=1时,MISR反应器的总传质系数约为20 s-1,比传统的设备高出2-3个数量级。应用MISR设备提纯芦丁：采用超声、微波组合浸取天然苦荞芦丁,经正交实验法,获得最优条件下芦丁的浸取率为1.7%；通过MISR设备对浸取液中芦丁进行萃取纯化,最优条件下芦丁的萃取率为78.8%。(5)MISR反应器应用于超细二氧化锰的制备。实验结果表明：增大入口流速,采用搅拌陈化处理,都能提高材料的性能；体积流量不一致会引起产物的比容量降低；最优条件下制得球形α-MnO2,粒径约为120 nm,比表面积～200 m2·g-1,最高放电比容量达211 F·g-1,循环1000次后衰减18%。利用MISR反应器对二氧化锰进行掺铁改性：以FeCl3为铁源,Mn:Fe=20:1的条件下,产物比容量为200 F·g-1,经1000次循环后衰减7%,稳定性较未掺铁的材料(33%)有显著提升。
[Abstract]:Reactor is the key equipment to realize the reaction process in chemical production. The mechanism of process intensification has always been the focus of chemical research. Impinging stream, CIJR, micro/capillary channel, rotating reactor and other types of reactors have been developed one after another. Compared with conventional stirred reactors, these new reactors have significantly improved micro-mixing performance and are widely used in the preparation of nanomaterials, extraction processes, absorption, polymerization and other aspects. Based on the above analysis, the concept of micro impinging stream reactor (MISR) is proposed, and a micro impinging stream reactor (MICR) is successfully constructed using commercial tee and stainless steel capillary (~1 mm). The MISR reactor is based on the design concept of micro-scale. This reactor adopts a short and thick enlarged outlet, and the two fluids collide strongly in a limited space to achieve rapid micro-mixing. It can be seen that the MISR reactor has the advantages of strengthening fluid mixing, reducing the difficulty of construction, and reducing pipeline blockage. The main research contents of this paper are as follows: (1) The MISR reactor was constructed by commercial tee and stainless steel capillary. The micro-mixing performance of the MISR reactor was investigated by Iodide-Iodate parallel competitive reaction system, and the separation index (Xs) was used. Quantitative analysis was carried out. It was found that with the increase of Rej, Xs decreases. When Rej 3000, Xs_0.0003 indicates that MISR reactor has a high micro-mixing efficiency; inconsistent volume flow leads to low micro-mixing efficiency; constant flow rate, enlarged inlet diameter (di) can promote micro-mixing; and outlet pipe length (L) is relatively small. (2) With the help of computational fluid dynamics (CFD), the hydrodynamic characteristics and micro-mixing-reaction process of MISR reactor were visualized. The standard k-e model was used to simulate the micro-mixing-reaction process of MISR reactor, and the DQMOM-IEM modeling method was used to explore the micro-mixing-reaction process of MISR reactor. Reaction mechanism. When Rej3000, a high turbulent kinetic energy impinging core zone was formed in the center of MISR reactor, and the reaction was completed in a very short time. The simulation results show that the narrow and long exit structure is not conducive to the development of impinging stream in MISR reactor. The simulation results are verified to be reasonable by comparing the experimental data. (3) Based on the experimental data, the reaction is completed. The relationship between TM and Rej was obtained by agglomeration model: when Rej 1000, TM = 0.84 Re-1.07; when Rej 1000, TM = 27.67 Re-1.58; for MISR reactor, TM = 0.1-5.0 ms, obviously shorter than the micro-mixing time of traditional agitator. (4) Mass transfer characteristics in the two-phase flow of a MISR reactor were studied in a liquid-liquid two-phase flow system. The results showed that the total mass transfer of the reactor was affected by the Reynolds number at the inlet of the water phase (Reaq), the volume flow ratio (R), the structure of the reactor and the viscosity of the water phase. The results show that the total mass transfer coefficient of MISR reactor is about 20 S-1 when Reaq = 3400 and R = 1, which is 2-3 orders of magnitude higher than that of traditional equipment. The extraction rate of Rutin in the leaching solution was 78.8%. (5) MISR reactor was applied to the preparation of ultrafine manganese dioxide. The results showed that the performance of the material could be improved by increasing the inlet flow rate and agitating and aging treatment. Under the optimum conditions, spherical alpha-MnO2 with a particle size of 120 nm, a specific surface area of 200 m2.g-1, a maximum discharge specific capacity of 211 F.g-1 and a decay of 18% after 1000 cycles were prepared. 00 F? G-1, after 1000 cycles of attenuation 7%, and stability than non iron doped material (33%) has significantly improved.
【学位授予单位】：北京化工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ052

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