Micromixing in the Submerged Circulative Impinging Stream Reactor

Micromixing in the submerged circulative impinging stream reactor (SCISR) developed by the authors is investigated with the Bourne's reaction scheme. The values measured for the impinging velocity, u0, under the conditions of SCISR normal operation, only is of the order of 0.1m·s^-1, are much slower than that inferred,suggesting low power requirement for operation. The values of the characteristic time constant for micromixing,tM, determined in the impinging velocity range of 0.184m·s^-1 < u0 < 0.326m·s^-1 are ranged from 192ms to 87 ms, showing that impinging streams promotes micromixing very efficiently. The data follow approximately the relationship of tM∝ u0^-1.5. A comparative study shows that the micromixing performance of SCISR is much better than that of the traditional stirred tank reactor. The tM values predicted with the existing theoretical model are systematically longer than those measured by about 2--3 times, implying that the regularity of impinging streams promoting micromixing is unclear yet.

Optimal Conditions for Preparing Ultra-Fine CeO_2 Powders in A Submerged Circulative Impinging Stream Reactor

Cerium carbonate powders were produced in a submerged circulation impinging stream reactor （SCISR） from Ce（NO3）3· 6H2O. NH4HCO3 was used as a precipitant in the reaction. Cerium carbonate powders were roasted to produce ultra-fine cerium dioxide （CeO2） powders. The optimal conditions of such production process were obtained by orthogonal and one-factor experiments. The results showed that ultra-fine and narrowly distributed cerium carbonate powders were produced under the optimal flowing conditions. The concentrations of Ce（NO3）3 and NH4HCO3 solutions were 02,5 and 0.3 mol · L^-1, respectively. The concentration of PEG4000 added in these two solutions was 4 g · L^-1. The stirring ratio, reaction temperature, feeding time, solution pH, reaction time and digestion time were 900 r · min^- 1,80 ℃, 20 min, 5 - 6, 5 min and 1 h, respectively. The final product, CeO2 powders, was obtained by roasting the produced cerium carbonate in air for 3 h at 500 ℃. The finally produced CeO2 powders were torispherical particles with a narrow size distribution of 0.8 -2.5 μm. The crystal structure of CeO2 powders belonged to cubic crystal system and its space point 5 group was OH^5-FM3M. Under optimal conditions, powders produced by SCISR were finer and more narrowly distributed than that by Stirred Tank Reactor （STR）.

Pressure Fluctuation in the Submerged Circulative Impinging Stream Reactor

Pressure fluctuation in the submerged circulative impinging stream reactor （SCISR） is studied by measuring the dynamic pressure with micro pressure sensors of high accuracy, with water as the process material. Experimental results show that the maximum amplitude of fluctuation can be up to about 1.6kPa. On the power spectra the fluctuation is relatively concentrated in the range of 〈1000Hz, with some weak peeks in acoustic wave range. The space profile of intensive fluctuation region in the reactor is determined. The region is found to take the form of a couple truncated cones of empty core, with coincided bottoms, and is symmetrical with respect to the impinging plane and approximately symmetrical about the axis, essentially independent of u0. The integral intensity of fluctuation increases as the impinging velocity, Uo increasing.

Pressure Fluctuation in the Submerged Circulative Impinging Stream Reactor

Pressure fluctuation in the submerged circulative impinging stream reactor (SCISR) is studied by meas- uring the dynamic pressure with micro pressure sensors of high accuracy, with water as the process material. Ex- perimental results show that the maximum amplitude of fluctuation can be up to about 1.6kPa. On the power spectra the fluctuation is relatively concentrated in the range of <1000Hz, with some weak peeks in acoustic wave range. The space profile of intensive fluctuation region in the reactor is determined. The region is found to take the form of a couple truncated cones of empty core, with coincided bottoms, and is symmetrical with respect to the impinging plane and approximately symmetrical about the axis, essentially independent of u0. The integral intensity of fluctua- tion increases as the impinging velocity, u0 increasing.

Theoretical analysis of fluid mixing time in liquid-continuous impinging streams reactor

The mixing time of impact zone in liquid-continuous impinging streams reactor(LISR) is theoretically calculated by empirical model and modern micromixing model of the fluid mixing process, and the variation laws of macromixing time and micromixing time are quantitatively discussed. The results show that under a continuous and stable operating condition, as the paddle speed increases, the macromixing time and micromixing time calculated by the two models both decrease, even in a linkage equilibrium state. Simultaneously, as the paddle speed increases, the results figured by the two models tend to be consistent. It indicates that two models both are more suitable for calculation of mixing time in high paddle speed. Compared with the existing experimental results of this type of reactor, the mixing time computed in the speed of 1500 r/min is closer to it. These conclusions can provide an important reference for systematically studying the strengthening mechanism of LISR under continuous mixing conditions.

水平对置撞击流反应器强化液-液萃取及传质特性

为了研究撞击流技术强化水相从煤油相中萃取乙酸,考察操作条件和溶液性质对萃取效果和传质特性的影响,测定液滴分散程度,利用响应面法优化萃取工况。结果表明:随煤油相进口体积流量和相比(水相与煤油相的体积流量比)的增加,分散相液滴粒径分布范围先缩小后扩大,Sauter平均直径d32先减小后增大。萃取率和总体积传质系数随煤油相进口体积流量的增加、水相黏度的增加和表面张力的减小而先增大后减小,随相比的增加呈先增后减再增加的趋势。各因素对萃取率的影响程度为:相比>煤油相进口体积流量>十六烷基三甲基溴化铵(CTAB)质量浓度,且交互作用显著。最佳工况下萃取率为93.11%,较传统萃取工艺提高了5.11%。

基于场协同原理的涡发生器强化撞击流反应器混合性能分析

为了提高撞击流反应器的混合性能,采用数值模拟的方法分析了置入矩形翼涡发生器后撞击流反应器内的流场特性与混合特性,并且优化了矩形翼涡发生器参数。研究了矩形翼涡发生器尺寸参数与位置参数对撞击流反应器混合强度的影响,以及涡发生器位置参数对反应器内速度分布和湍动能分布的影响,运用传质场协同原理分析了设置矩形翼涡发生器和未设置矩形翼涡发生器的撞击流反应器内速度场和浓度场的协同性。结果表明,随着径向间距r的增加混合强度呈现出先增后减的趋势,当翼宽h、转轴间距d和迎流攻角β逐渐增加时混合强度波动变化,在矩形翼涡发生器的翼宽h=10 mm,转轴间距d=8 mm,径向间距r=30 mm,迎流攻角β=30°时,反应器内混合强度最大,得到的混合效果最佳;在两股流体充分撞击的情况下,撞击流反应器内径向射流区域的速度分布呈现为“双峰”分布规律,涡发生器位置参数的改变可以提高径向速度,在转轴间距d=8 mm、迎流攻角β=30°时径向速度最高,反应器内径向射流区域的湍动能分布呈现出“单峰”分布规律,但涡发生器位置参数的变化对于湍动能分布的影响不大;从场协同的角度分析可知,矩形翼涡发生器的加入改变了撞击流反应器内径向射流的速度大小和方向,进而改善了撞击流反应器内速度场与浓度场的协同性,提高了撞击流反应器的混合性能。

Characterization of micro-mixing in a novel impinging streams reactor

This paper presents an experimental investiga-tion of a novel impinging stream reactor(ISR)with the aim of high mixing intensity.The integral mixing quality in the reactor was measured with the iodide-iodate reaction and showed excellent mixing performance.The impact of the operating parameters,such asfluxes,circulation and inter-nozzle distances,was investigated in terms of segregation index.The results showed that the increase offlux,the decrease of inter-nozzle distance and a suitable circulation can improve the micro-mixing efficiency.Based on turbulence theory,it was estimated that the characteristic micro-mixing time was 0.002–0.02 s,which was much shorter than that in the stirred tank reactor.The micro-mixing time was related to the segregation index,which was in good agreement with those in the literature.

Residence time distribution and modeling of the liquid phase in an impinging stream reactor

Based on some experimental investigations of liquid phase residence time distribution(RTD)in an impinging stream reactor,a two-dimensional plug-flow dispersion model for predicting the liquid phase RTD in the reactor was proposed.The calculation results of the model can be in good agreement with the experimental RTD under different operating conditions.The axial liquid dispersion coefficient increases monotonously with the increasing liquid flux,but is almost independent of gas flux.As the liquid flux and the gas flux increase,the liquid dispersion coefficient of center-to-wall decreases.The axial liquid dispersion coefficient is much larger than that of center-to-wall,which indicates that the liquid RTD is dominated mainly by axial liquid dispersion in the impinging stream reactor.

液体连续相撞击流强化过程特性及相关技术装备的研发和应用

液体连续相撞击流(LIS)具有高效微观混合、强烈压力波动和促进过程动力学等对分子尺度过程极有价值的性质。本文在浸没循环撞击流反应器(SCISR)中深入研究了这些性质及其规律,进行了反应-沉淀法制取多种"超细"和纳米材料的实验,制得粒径更细小、分布更窄、形貌可控的超细粉体;研发了"无旋立式循环撞击流反应器"等多种基于应用LIS的反应、结晶技术装备并已付诸应用;描述了这些装备的流动结构、工作原理和工业应用情况。

液体连续相撞击流反应器中流体混合时间的数值模拟

在混合时间理论计算基础上利用CFD技术模拟连续操作的LISR混合过程,数值计算与验证混合时间的变化规律。结果表明,随着输入比有效功率增大,混合时间先急剧减小后逐渐趋于平稳;LISR撞击区一次撞击局部混合时间在0.25 s以内,与经验公式或理论公式计算所得结果在数量级上完全一致,证明数值方法分析一次撞击局部混合时间是可行的,而且可以弥补实验无法测定中间过程参量的不足;进一步数值分析宏观混合时间与微观混合时间发现,二者大小相差1个数量级,但二者变化规律处于一种联动平衡状态,该结果与前期理论分析结果一致;本研究所得结论可为后续LISR混合强化机理与性能研究提供定量参考。

立式循环撞击流反应器不同撞击间距下混合性能分析

为优化和改进立式循环撞击流反应器的结构布局,提高其混合性能,本文采用Fluent软件对立式循环撞击流反应器在导流筒不同间距结构下的流场进行数值模拟,反应器上下两导流筒的间距D设置为60 mm、80 mm、100 mm、120 mm,反应在3组转速下分别进行w=5 r/s、15 r/s、25 r/s。计算结果表明:在相同转速下,导流筒间距D=80 mm时的特征撞击面上的平均速度最大,说明该结构下对应的传质效果更好;在相同转速下,导流筒间距D=60 mm时撞击面径向速度分布的均方根差σ最大,表明该结构下速度分布的梯度最大,流场剪切混合效果更好。

混合过程强化及其设备的研究进展

流体流动和混合是影响化学反应的重要因素,离集指数是表征流体混合程度的常用参数,平均停留时间及停留时间分布是衡量反应器内流体返混的一个量度。文中分析了反应器内流体的混合机理,介绍了两种实验测定离集指数的方法以及数学模拟法;在微观混合的基础上提出了过程与设备的强化方法,借助外界能量或改变流体流动型态和流速等方法强化流体的混合程度,总结了搅拌釜反应器、撞击流反应器、静态混合反应器、超重力旋转床反应器等设备的混合机理及其优缺点。

撞击流—旋转填料床反应器的微观混合性能研究

采用化学偶合法 ,对撞击流—旋转填料床反应器内微观混合进行了实验研究 ,得到了转速、喷嘴间距、射流速度及浓度等因素对离集指数Xs的影响规律 ,并对其进行了定性的分析。结果表明撞击流—旋转填料床反应器中微观混合能被极大地强化 。

撞击流反应器用于甲醇合成反应

撞击流反应器用于气液固三相甲醇合成反应可以充分发挥其优良的传热、传质性能。在撞击流反应器内,催化剂浆料经喷嘴雾化后成微米尺度的液滴,气液相间接触面积远大于其他三相合成反应器。考察了温度、压力、气体流量、浆料循环量以及喷嘴个数对甲醇合成反应的影响,结果表明,当压力从3.8MPa上升到5MPa时,反应器的时空产率增长了近1倍,气体流量达22.4L.min-1后时空产率几乎不再变化,增加浆料循环量以及在同一循环量下采用多喷嘴对置都可以增加催化剂时空产率。同时,与固定床、搅拌釜和浆态鼓泡床甲醇合成进行了对比,结果表明,在低空速下撞击流反应器与其他反应器时空产率相当,而在高空速下要优于其他反应器。

两侧及轴向进料同向流水平撞击流反应器研究

以空气-水,空气-CMC(羧甲基纤维素)水溶液为体系,采用脉冲示踪和稳态微压差法测量了相关数据,研究了两侧及轴向进料同向流水平撞击流管式反应器中表观液速UL、气体喷出速度Ug、及液体粘度m在撞击流和非撞击流下对器内平均气含率eg的影响。得到了当气体喷速为170m·s-1,管内表观液速为0.6m·s-1时,气含率eg较大, 液相分散显著,使气液接触面增大的结果。实验测得了UL、Ug、液体的粘度 m 及撞击混合前后的压差Δh和混合时间t;将其关联后提出了在上述条件下该水平撞击流管式反应器平均气含率eg的关联式: 74.1573.0g56.1Lg1058.0-=meUU 以湿法磷酸(含P2O5 22%)-氨体系进行热态试验,结果表明:气氨喷速为170m·s-1、且磷酸进料流速为3.3m·s-1,管内物料表观流速为0.6m·s-1时,反应器内氨负荷较大、混合情况好、反应较彻底,而且氨逸出率最低。

立式循环撞击流反应器中桨叶垂直交错排布条件下的混合性能

立式循环撞击流反应器(VCISR)桨叶的倾角及其布置形式,是影响混合性能的重要因素。本文采用数值方法对VCISR桨叶不同角度垂直交错排布条件下的混合性能进行了研究。上下两对桨叶倾角θ均设置为45°,上下两对桨叶错位角分别设置为15°、30°、45°、60°,结果表明:上下两对桨叶错位角在45°时,VCISR特征撞击面上的速度均方根σ最大,达到3.81,混合性能最优;同工况条件下,当错位角为60°时,桨叶旋转能量消耗最小。

新型磁性纳米锂离子筛的合成

采用狭道式撞击流反应器,将Fe3O4爆发式成核过程与快速包覆MnCO3+Li2CO3薄膜的过程同步进行,制备出具有核壳结构的纳米Fe3O4/MnCO3+Li2CO3前驱体;然后,通过在450℃下高温焙烧和稀酸酸浸脱锂工艺得到一种组成为Fe3O4/HxMnyO4的磁性纳米锂离子筛。实验优化了爆发式成核过程与液相快速包膜过程的主要操作参数。采用BET、TEM、EDX、XRD等手段对产物进行了分析表征。结果表明,磁性纳米锂离子筛的平均粒径约为40 nm,比饱和磁化强度为27.581 emu.g-1,磁矫顽力为138.64 G。与普通锂离子筛相比,纳米锂离子筛薄膜在固相扩散方面优势明显,有望在海水提锂过程中发挥独特的作用。

浸没循环撞击流反应器中微观混合的影响因素

介绍了撞击流的基本原理和浸没循环撞击流反应器的结构,利用α-萘酚与对氨基苯磺酸重氮盐之间的串联竞争偶合反应对浸没循环撞击流反应器中微观混合的影响因素进行了研究.结果表明,提高螺旋桨转速、减小流量体积比可以提高微观混合效果;反应物初始浓度与分隔指数的关系验证了一定转数下微观混合时间只能达到一定的数值.

撞击流-沉淀法制取超细白炭黑中试研究

介绍了以工业级硫酸和工业级水玻璃为原料,利用撞击流反应-沉淀法制取超细白炭黑的中试试验。其反应过程在无旋立式循环撞击流反应器中进行。反应后物料经过陈化、过滤、洗涤,最后通过再浆进行喷雾干燥制得了超细白炭黑。用激光颗粒分析仪和比表面积-孔隙分析仪测定粒径及比表面积,结果表明:产品的平均粒径为2—3μm、比表面积高达822 m2/g,进一步证明了无旋立式循环撞击流反应器性能优越,操作稳定可靠,有利于制备超细粉体材料。