Iodide Iodate Reaction System Research Articles

Feasibility study on micromixing intensification in a spinning disk reactor utilizing heterogeneous surface wettability

The micromixing intensification of reactor is the research hotspot in process intensification filed. In this work, the micromixing intensification of spinning disk reactor (SDR) was studied by utilizing heterogeneous surface wettability for the first time. Several partial hydrophobic modified disks were designed and employed to realize the heterogeneous surface wettability. The micromixing performance of SDR was evaluated by iodide-iodate reaction system. Results showed that micromixing efficiency of SDR with partial hydrophobic modified disk was higher than that of non-modified disk. The wettability of liquid inlet zone on the disk surface had a significant influence on results. Hydrophobic modified zone was more crucial in comparison with the modified area. The values of XS maximally decreased by 49.9% in SDR with partial hydrophobic modified disk compared to the non-modified disk. This preliminary study provided a feasible path for micromixing intensification in SDR by utilizing heterogeneous surface wettability, displaying considerable application prospects.

Green synthesis of sub 10 nm silver nanoparticles in gram scale using free impinging jet reactor

In this paper we report controlled synthesis of sub 10 nm silver nanoparticles at 30 g/day at room temperature condition using a green protocol using a free impinging jet reactor. The focus is on impingement of low velocity liquid jets to ensure process completion in the film. Identical liquid jets of 400-micron diameter with low Weber number (We = 10–40) were impinged at different approach angles (90°–150°) to explore mixing characteristics using iodide-iodate reaction system. The regime showed monotonic improvement in silver nanoparticle mean size and polydispersity with increase in We. The smallest and most uniform (5.2 ± 0.9 nm) particles could be synthesized at We = 40. The study also establishes the horizontal component of jet velocity as a parameter to control mixing and particle size. Under identical reaction condition a free impinging jet reactor outperformed two other continuous reactors viz. a spinning disc reactor and a spinning disc spinning bowl reactor in terms of mean particle size.

Micromixing efficiency in a rotating foam stirrer reactor with various reactor configurations and liquid viscosities

AbstractBACKGROUNDThe rotating foam stirrer reactor (RFSR) has shown its high mass transfer efficiency. Nevertheless, its micromixing efficiency, which is one of the significant parameters, still needs more comprehensive study for its better application and optimization. This work therefore employed the iodide–iodate reaction system to analyze the micromixing efficiency in an RFSR, and the effects of reactor configuration and liquid viscosity on micromixing efficiency were investigated.RESULTSThe results show that high micromixing efficiency can be achieved when the feed location is at the outer edge of the rotor. Solid foam with low pores per linear inch (ppi) and equipping baffles on the reactor wall can also considerably improve the micromixing efficiency. The results further reveal that the micromixing efficiency decreased with increasing liquid viscosity. Micromixing times in an RFSR with various configurations, estimated based on the incorporation model, ranged from 2.1 × 10−4 to 2.0 × 10−2 s. The minimum value is smaller than that of many conventional reactors and is competitive with that of some novel reactors. In addition, a correlation to predict the micromixing time based on the average energy dissipation rate was developed, which agreed well with experimental values.CONCLUSIONThis study indicates that the RFSR has excellent micromixing efficiency and also provides fundamental information for optimization of the RFSR and its application in process industries. © 2019 Society of Chemical Industry

Micromixing efficiency in a rotating packed bed with non-Newtonian fluid

Micromixing performance of reactors has great influence on fast reactions such as polymerization, pharmaceutical and crystallization applications. In this work, based on Villermaux–Dushman iodide–iodate reaction system, an experimental investigation of micromixing with non-Newtonian fluid (CMC solution) in a rotation packed bed (RPB) was carried out. And a two-dimensional RPB Computational Fluid Dynamics (CFD) model coupled with shear-thinning rheological property was developed. Both experimental and numerical results indicated that increasing rotational speed could dramatically improve the micromixing performance due to the shear-thinning behavior in the RPB. Especially, the CMC concentration was an important factor that should be carefully considered, which showed quite different impacts on micromixing efficiency with liquid flow rate. In addition, based on incorporation model and experimental results, the micromixing time of the RPB with non-Newtonian fluid was determined as 4.1 × 10−4 s–1.9 × 10−3 s. This fundamental research had guiding significance for practical operations of RPBs when processing non-Newtonian fluids.

Micromixing performance and the modeling of a confined impinging jet reactor/high speed disperser

In order to get a better micromixing performance, an intensification reactor that couples a confined impinging jet reactor and high speed disperser (CIJR-HSD) was designed. The influences of operating and structural parameters on the micromixing performance were investigated by using the iodide-iodate reaction system. The results showed that the segregation index decreased with the increase of both the rotational speed and the number of rotors; whilst there was little influence due to both inlet flow rate and the presence of packing. The coupling distance between the centre of the CIJR and the first rotor of the HSD also had a non-negligible effect on segregation index. The micromixing time was determined by the Engulfment model, and could also be evaluated by the energy dissipation model based on fluid energy transformation. It was found that the micromixing time for the CIJR-HSD device was in the range of 0.1–0.3 ms, while that for a single CIJR was in the range of 0.35–0.5 ms.

Investigation of micromixing and precipitation process in a rotating packed bed reactor with PTFE packing

A rotating packed bed (RPB) reactor plays an important role in process intensification of micromixing and mass transfer. However, the commonly used stainless steel wire mesh packing suffers from serious corrosion in various chemical processes. Polytetrafluoroethylene (PTFE) material, which is well-known for its excellent anticorrosion property, was employed as packing in the RPB reactor. Micromixing efficiency of the RPB reactor with PTFE packing was studied experimentally by adopting the iodide-iodate reaction system. Results showed that the micromixing efficiency of the RPB reactor with PTFE packing was better than that with the conventional stainless steel wire mesh packing. The micromixing time (tm) was calculated using an incorporation model based on the experimental data. Furthermore, the RPB reactor with PTFE packing was applied to a precipitation process for the preparation of magnesium hydroxide (Mg(OH)2) nanoparticles. The obtained Mg(OH)2 nanoparticles have small size and narrow particle size distribution, which indicates that the RPB reactor with PTFE packing is a promising reactor for preparing small size nanoparticles with its excellent micromixing efficiency.

Flow characteristics and micromixing modeling in a microporous tube-in-tube microchannel reactor by CFD

Micromixing performance in reactor is one of the key factors for fast reaction systems, such as fine chemicals, pharmaceutical and crystallization. In this work, a three-dimensional CFD model was developed for analyzing flow characteristics and micromixing efficiency in microporous tube-in-tube microchannel reactor (MTMCR). PDF transport model based on Lagrangian Monte Carlo method and a modified Finite-rate/Eddy dissipation model were used to build micromixing model, respectively. The effects of Reynolds number and flow ratio on micromixing efficiency were studied using Villermaux–Dushman iodide–iodate reaction system. The segregation index XS is used to quantify the micromixing performance. The results showed that XS decreased with the increasing of Re and the decreasing of flow ratio R, and simulated values agreed well with published experimental data. Based on the modified Finite-rate/Eddy dissipation model, the parallel competing reaction system was analyzed by taking into account mixing-controlled and kinetic-controlled factors, which explained how this model worked. Moreover, porous diameter and width of annular channel were optimized to improve the micromixing efficiency of MTMCR, and the optimal values were 20μm and 250μm, respectively.

Geometrical improvement of inline high shear mixers to intensify micromixing performance

The micromixing performance of two inline high shear mixers (HSMs) was studied using the iodide-iodate reaction system, considering the effects of rotor speeds, flux ratios, viscosities and fluid concentrations. The segregation index (Xs) was adopted to assess the micromixing performance. It is indicated that the value of Xs decreases with the increase of rotor speed and the flux ratio of two feed solutions. The dual rows ultrafine-teethed HSM exhibits the poorer micromixing performance at low rotor speeds, comparing with the single-row blade-screen HSM. Then we modified the geometric configurations of the teethed HSM with the aid of computational fluid dynamics (CFD) analysis, including the modification of the clamp nut with blades and the addition of a liquid distributor, and reevaluated the micromixing performance in the modified HSM in order to improve mixing in the reactor. The results indicate that the fluid dispersion and turbulence intensity in the inlet region of the HSM play an important role in enhancing the micromixing level, the liquid distributor can greatly improve the micromixing performance of the dual rows ultrafine-teethed HSM and the estimated micromixing time can reach 10−5s. The results obtained here will provide much insight for the applications of the inline HSMs and other reactors in the field of intensifying fast chemical reaction.

Micromixing efficiency of a novel helical tube reactor: CFD prediction and experimental characterization

A novel helical tube reactor (HTR) consisting of a pre-mixer and a helical tube was designed for mixing and reaction process intensification. The pre-mixer was used to adjust and change the premixing behavior between the involved reactants, which eventually determines the environment for micromixing. Two types of pre-mixers, co-current flow pre-mixer (CCM) and cross-flow pre-mixer (CRM), were employed and their mixing performance was studied by computational fluid dynamics (CFD) simulations. Results revealed that the CRM has better mixing performance than the CCM, suggesting that the predicted micromixing efficiency of the HTR consisting of the CRM (CRM-HTR) may be better than that comprising the CCM (CCM-HTR). Furthermore, the iodide–iodate reaction system was used separately to characterize the micromixing efficiency of the HTR comprising the different types of pre-mixers, and the results are in agreement with those of CFD which predicted better micromixing performance in the CRM-HTR than the CCM-HTR. Additionally, the effects of feed position and initial dispersion size of acid solution, volumetric flow ratio, and viscosity on micromixing efficiency of the CRM-HTR were investigated. A comparison between the CRM-HTR and a straight tube reactor (CRM-TR) with a length equivalent to that of the CRM-HTR revealed that CRM-HTR has better micromixing efficiency. Moreover, the effects of curvature ratio and number of turns on micromixing efficiency of the CRM-HTR were also conducted. The results demonstrated that the curvature ratio had an important influence on the micromixing. This work shows that the novel CRM-HTR has great potential for chemical reaction process intensification.

Computational Fluid Dynamics Analysis of the Micromixing Efficiency in a Rotating-Packed-Bed Reactor

Micromixing in rotating-packed-bed (RPB) reactors is of great significance for their process-intensifying performance. On the basis of the iodide–iodate reaction system, a two-dimensional computational framework of RPB was developed to investigate the micromixing efficiency in a RPB. The volume-of-fluid multiphase model, laminar finite-rate model, and the Reynolds stress model were adopted to simulate the volumetric fraction of the liquid phase, the concentration distributions, and the effects of rotating speed and liquid flow velocity on the micromixing performance of a RPB. The computational fluid dynamics results showed that the micromixing and reaction processes occurred mainly in the inlet region of RPB packing, which further confirmed the end effect of the packing. An increase of the rotating speed and liquid flow velocity could remarkably enhance the micromixing efficiency in a RPB. On the basis of the incorporation model, the micromixing time in a RPB was estimated as 0.05−0.30 ms, indicating a re...

The influence of feeding location on the micromixing performance of novel large-double-blade impeller

The large-double-blade impeller has a broad application prospects in rapid reactions of viscous systems. In syrup aqueous solution with viscosity of 0.8 Pa s, the influence of feeding location on the micromixing performance of the novel large-double-blade impeller was studied experimentally by adopting the iodide–iodate reaction system, and the distribution of energy dissipation rate in the stirring vessel was obtained by numerical simulation method for the micromixing based on standard E model and eddy-dissipation-concept (EDC) model. The results of simulation agreed well with the experimental data, both of which showed that the feeding location has an important effect on the micromixing performance. Feeding in the blade area is more favorable to reducing by-products and improving micromixing quality than in other areas under the same conditions for its comparatively large local energy dissipation rate. These results provide useful guidelines for the optimal design and operation of the novel large-double-blade impeller in rapid reactions of viscous system.

New protocol of the Villermaux–Dushman reaction system to characterize micromixing effect in viscous media

This paper presents the results of the characterization of a new method for quantification of the micromixing efficiency in a viscous medium in stirred tank reactors. The used method is inspired by a chemical system based on two competitive reactions, the iodide–iodate reaction system (Villermaux–Dushman method), whose products selectivity is a measure of the mixing efficiency. The approach proposes a new protocol based on a phosphate buffer and the use of HydroxyEthylCellulose (HEC, 720, 000g/mol) as an inert viscosifying agent, exhibiting various interesting properties (no disturbance of the spectrophotometric measure, low cost, low required amount, eco-friendly product). This agent is almost Newtonian up to 0.25wt% in water and becomes non-Newtonian above 0.5wt%. By means of its use, the viscosity of the reactive medium can be raised by around two orders of magnitude while adding less than 1wt% HEC to the water solution. Preliminary micromixing results of moderate viscous solutions (50mP as with HEC 0.5wt%) in a stirred tank reactor are presented.

Evaluation of the performance of a constructal mixer with the iodide–iodate reaction system

A novel fluidic mixer, which takes advantage of impingement mixing and is designed according to the constructal approach, is evaluated by the Villermaux/Dushman method. The effects of different configurations (including the structure of the fluid collector and the diameter of the nozzles on the fluid injector) on the mixing performance (i.e. the segregation index and the energy dissipation rate) are determined. The segregation index is smaller, or in other words the degree of mixing is better, when a branch type fluid collector or smaller nozzles are used, however, at the cost of higher energy dissipation rate. When the flow rate is sufficiently high, mixing caused by the impingement of streams is almost complete, rendering the mixing in the branched channels unnecessary. As a result, if very high degree of mixing is pursued, the collector with a simple empty space should be used in the mixer to reduce energy consumption.

A new impinging stream–rotating packed bed reactor for improvement of micromixing iodide and iodate

A novel concept of a liquid–liquid contact reactor, the so-called impinging stream–rotating packed bed (IS–RPB), was presented for improvement of micromixing iodide and iodate. The micromixing efficiency of IS–RPB was studied by adopting iodide–iodate reaction system. The effects of operational conditions (e.g. high gravity factor, liquid flow rate, liquid flow ratio and acid concentration) on micromixing efficiency (characterized by segregation index X s ) were investigated. In addition, the effects of different impinging distance and impinging angle on micromixing efficiency were also considered. Besides, IS, RPB and IS–RPB reactors were contrasted with micromixing characteristics in the same experimental conditions. Comparison with other mixing devices, IS–RPB reactor has better micromixing characteristics than other reactors, which has a good application prospect.

Determination of the Segregation Index to Sense the Mixing Quality of Pilot- and Production-Scale Microstructured Mixers

The performance of the microstructured mixer Star-Laminator300 ( StarLam300) with stacked star-shaped foils has been examined experimentally by the use of the adapted Villermaux/Dushman parallel-competitive iodide-iodate reaction system in continuous processes. The mixing efficiency was quantitatively determined by the segregation index derived from the UV absorption. The mixing performance of the microstructured mixer is analysed in terms of the total volume flow and turbulent energy dissipation rate. The influence of the geometry of the injection nozzles and the mixing chamber and the variation of foil number is also presented and discussed. The latter touches upon the numbering-up concept of microstructured devices. Since mixing efficiencies much better as for conventional equipment at throughputs up to 320 l h −1 were found (with pressure-loss curves showing further potential to 1000 l h −1), this microstructured mixer proved potential to act as process-intensification (PI) equipment.

Characterisation of micromixing efficiency by the iodide–iodate reaction system. Part II: kinetic study

In a previous paper (Part I), the operating conditions of the iodide–iodate reaction system used to quantify micromixing phenomena in chemical reactors and mixers has been presented. In order to determine the micromixing time through models, the complete kinetics of the reactions must be known. This paper presents the kinetics of the Dushman reaction obtained in operating conditions close to the micromixing test conditions. The results confirm the single fifth-order process widely reported in published work and establish the rate constant as a function of ionic strength ranging between 0 and 2 M.

Characterisation of micromixing efficiency by the iodide–iodate reaction system. Part I: experimental procedure

This paper describes in a very practicable way the operating conditions of the iodide–iodate reaction system used to quantify micromixing phenomena in chemical reactors and mixers. Several operating procedures are given for batch and continuous mixers. Recommendations to adapt these procedures to any specific mixers and complete analysis procedures are also provided. Finally, a simple micromixing model is used to calculate micromixing time t m . It is checked that t m is non-dependent on the reactant concentrations at constant hydrodynamic conditions. In a second following paper (Part II), the reactions kinetics, essential for a knowledge of micromixing time t m , are presented.