CFD-PBE simulation of a bubble column in OpenFOAM

A general CFD-PBE(computational fluid dynamics-population balance equation) solver for gas–liquid poly-dispersed flows of both low and high gas volume fractions is developed in OpenFOAM(open-source field operation and manipulation) in this work. Implementation of this solver in OpenFOAM is illustrated in detail. The PBE is solved with the cell average technique. The coupling between pressure and velocity is dealt with the transient PIMPLE algorithm, which is a merged PISO-SIMPLE(pressure implicit split operator-semi-implicit method for pressure-linked equations) algorithm. Results show generally good agreement with the published experimental data, whereas the modeling precision could be improved further with more sophisticated closure models for interfacial forces, the models for the bubble-induced turbulence and those for bubble coalescence and breakage.The results also indicate that the PBE could be solved out the PIMPLE loop to save much computation time while still preserving the time information on variables. This is important for CFD-PBE modeling of many actual gas–liquid problems, which are commonly high-turbulent flows with intrinsic transient and 3 D characteristics.

CFD-based optimization and design of multi-channel inorganic membrane tubes

As a major configuration of membrane elements,multi-channel porous inorganic membrane tubes were studied by means of theoretical analysis and simulation.Configuration optimization of a cylindrical 37-channel porous inorganic membrane tube was studied by increasing membrane filtration area and increasing permeation efficiency of inner channels.An optimal ratio of the channel diameter to the inter-channel distance was proposed so as to increase the total membrane filtration area of the membrane tube.The three-dimensional computational fluid dynamics(CFD) simulation was conducted to study the cross-flow permeation flow of pure water in the 37-channel ceramic membrane tube.A model combining Navier–Stokes equation with Darcy's law and the porous jump boundary conditions was applied.The relationship between permeation efficiency and channel locations,and the method for increasing the permeation efficiency of inner channels were proposed.Some novel multichannel membrane configurations with more permeate side channels were put forward and evaluated.

Comparative experimental study on reactive crystallization of Ni(OH)2 in an airlift-loop reactor and a stirred reactor

The objective of this work is to study the reactive crystallization in an airlift-loop reactor(ALR)using the precipitation of Ni(OH)_2 as a model reaction.The growth of Ni(OH)_2 particles in an ALR and a stirred tank was quantified by scanning electronic microscope(SEM),X-ray diffraction(XRD),laser particle analyzer,tap densitometer and optical microscope,and the growth process of Ni(OH)_2 particles is analyzed.It is found that the Ni(OH)_2 particles prepared in an ALR have a better sphericity than those in a stirred tank and the growth of Ni(OH)_2 particle tap density mainly depends on the size of crystallites:the bigger the size of crystallites,the bigger the tap density is.Based on these,the growth process of Ni(OH)_2 particles in ALR is elaborated.Crystallites precipitated from solution aggregate to form large particles with much void.These constituting crystallites continue to grow up,that takes up the void inside particles and makes the tap density increase.

Experimental study by online measurement of the precipitation of nickel hydroxide: Effects of operating conditions

The objective of this work is using the online measurement method to study the process of precipitation of nickel hydroxide in a single-feed semi-batch stirred reactor with an internal diameter of D = 240 mm. The effects of impeller speed, impeller type, impeller diameter and feed location on the mean particle size d43 and particle size distribution(PSD) were investigated. d43 and PSD were measured online using a Malvern Insitec Liquid Process Sizer every 20 s. It was found that d43 varied between 13 μm and 26 μm under different operating conditions,and it decreased with increasing impeller diameter. When feeding at the off-bottom distance of D/2 under lower impeller speeds, d43 was significantly smaller than that at D/3. PSDs were slightly influenced by operating conditions.

Influences of fluid physical properties,solid particles,and operating conditions on the hydrodynamics in slurry reactors

Slurry reactors are popular in many industrial processes,involved with numerous chemical and biological mixtures,solid particles with different concentrations and properties,and a wide range of operating conditions.These factors can significantly affect the hydrodynamic in the slurry reactors,having remarkable effects on the design,scale-up,and operation of the slurry reactors.This article reviews the influences of fluid physical properties,solid particles,and operating conditions on the hydrodynamics in slurry reactors.Firstly,the influence of fluid properties,including the density and viscosity of the individual liquid and gas phases and the interfacial tension,has been reviewed.Secondly,the solid particle properties(i.e.,concentration,density,size,wettability,and shape)on the hydrodynamics have been discussed in detail,and some vital but often ignored features,especially the influences of particle wettability and shape,as well as the variation of surface tension because of solid concentration alteration,are highlighted in this work.Thirdly,the variations of physical properties of fluids,hydrodynamics,and bubble behavior resulted from the temperature and pressure variations are also summarized,and the indirect influences of pressure on viscosity and surface tension are addressed systematically.Finally,conclusions and perspectives of these notable influences on the design and scale-up of industrial slurry reactors are presented.

Research progress on preparation and purification of fluorine-containing chemicals in lithium-ion batteries

With the development of digital products,electric vehicles and energy storage technology,electronic chemicals play an increasingly prominent role in the field of new energy such as lithium-ion batteries.Electronic chemicals have attracted extensive attention in various fields.Characteristics of high-end electronic chemicals are high purity and low impurity content,which requires a very strict separation and purification process.At present,crystallization is a key technology for their separation and purification of electronic chemicals.In this work,the representative fluorine-containing compounds in cathode and anode materials,separator and electrolyte of lithium-ion batteries are introduced.The latest technologies for the preparation and purification of four kinds of fluorine-containing battery chemicals by crystallization technology are reviewed.In addition,the research prospects and suggestions are put forward for the separation of fluorine-containing battery chemicals.

Micromixing of a Two Phase System in a Stirred Tank with Multiple Impellers

The competitive iodide/iodate reaction scheme was used to ascertain the micromixing in the stirred solid-liquid systems. Two different glass beads from 450 to 1250 μm were tested. The effect of solid particles on reaction selectivity with multiple impellers at different feed points has been investigated. It was confirmed that glass beads as a second phase were suitable for the study. The segregation index has changed significantly only for the medium-sized particles at relatively high solid holdups. The cloud formation was clearly observed for the medium-sized particles at a concentration of 12.12 wt. %. When feeding into the clear liquid above the cloud, the value of the segregation index increased significantly. However, in the presence of particles of 1-1.25 mm, the influence on the selectivity was negligible when the agitation speed was increased.

Advances in reactive co-precipitation technology for preparing high-performance cathodes

Reactive crystallization plays an essential role in the synthesis of high-quality precursors with a narrow particle size distribution,dense packing,and high sphericity.These features are beneficial in the fabrication of high-specific-capacity and long-cycle-life cathodes for lithium-ion and sodium-ion batteries.However,in industrial production,designing and scaling-up crystallizers involves the use of semi-empirical approaches,making it challenging to satisfactorily meet techno-economic requirements.Furthermore,there is still a lack of in-depth knowledge on the theoretical models and technical calculations of the current co-precipitation process.This review elaborates on critical advances in the theoretical guidelines and process regulation strategies using a reactive crystallizer for the preparation of precursors by co-precipitation.The research progress on the kinetic models of co-precipitation reactive crystallization is presented.In addition,the regulation strategies for the reactive crystallization process of lithium-ion ternary cathodes are described in detail.These include the influence of different reactive crystallizer structures on the precursor's morphology and performance,the intelligent online measurement of efficient reactive crystallizers to ensure favorable conditions of co-precipitation,and preparing the precursor with a high tap density by increasing its solid holdup.A controllable reactive crystallization process is described in terms of the structural design with concentration gradient materials and bulk gradient doping of advantageous elements(such as magnesium ion)in lithium-ion cathodes and the fabrication of sodium-ion cathodes with three typical materials-Prussian blue analogues,transition metal oxides,and polyanionic phosphate compounds being involved.

Machine learning-based solubility prediction and methodology evaluation of active pharmaceutical ingredients in industrial crystallization

Solubility has been widely regarded as a fundamental property of small molecule drugs and drug candidates,as it has a profound impact on the crystallization process.Solubility prediction,as an alternative to experiments which can reduce waste and improve crystallization process efficiency,has attracted increasing attention.However,there are still many urgent challenges thus far.Herein we used seven descriptors based on understanding dissolution behavior to establish two solubility prediction models by machine learning algorithms.The solubility data of 120 active pharmaceutical ingredients(APIs)in ethanol were considered in the prediction models,which were constructed by random decision forests and artificial neural network with optimized data structure and model accuracy.Furthermore,a comparison with traditional prediction methods including the modified solubility equation and the quantitative structure-property relationships model was carried out.The highest accuracy shown by the testing set proves that the ML models have the best solubility prediction ability.Multiple linear regression and stepwise regression were used to further investigate the critical factor in determining solubility value.The results revealed that the API properties and the solute-solvent interaction both provide a nonnegligible contribution to the solubility value.

Numerical investigation of the influence of kinetics and shape factor on barium sulfate precipitation in a continuous stirred tank

The effect of kinetics and shape factor on barium sulfate precipitation in a continuous stirred tank has been investigated numerically through solving the standard momentum and mass transport equations in combination with the moment equations for crystal population balance.The numerical method was validated with the literature data.The simulated results include the distribution of the local supersaturation ratio in the reactor,the mean crystal size,and the coefficient of variation.The simulation results show that the value of shape factor used in the model affected greatly the mean crystal size and the moments of the crystal size distribution.The influence of the kinetic expressions on the simulation is also analyzed.It is important to investigate the relationship of the shape factor with the precipitator type and other operation conditions to obtain reliable simulation results and suitable kinetic equations of crystal nucleation and growth rates.