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The handling of multiphase systems applied in mixer-settler processes, in which phase separation characteristics are exploited, is to date still a challenge for the chemical industry. Approaches for analyzing the influencing parameters on these systems can be of use, especially regarding equipment design and technical applicability. In this contribution, a guideline is presented and applied in a case study for a surfactant-containing multiphase system implemented in a hydroformylation mini-plant. Herein, the most relevant investigated parameters such as temperature, concentrations of reactants, system pressure, and stirrer characteristics are analyzed. This is followed by an analysis of various internal fittings including their influence on the temperature profile within the settler. The results of the systematic analysis are used to design a highly flexible, modular, and efficient settler for the separation of up to three liquid phases. [ABSTRACT FROM AUTHOR]

Emulsificationof crude oil and water may significantly affectthe flow characteristics of the multiphase flow in gathering lines.Obviously, emulsification of a crude oil–water system is greatlyaffected by conditions such as shear intensity, water fraction, andtemperature. However, there has been a lack of quantitative studyof the emulsified water fraction of crude oil–water systemsunder various conditions of water fraction, temperature, and shearintensity. In this work, experiments were conducted by using a stirredvessel calibrated for the determination of mean shear rate, and theemulsified water fractions under flowing conditions were determinedby extrapolation of the separated water volume to the moment whenstirring was just terminated. Full emulsification of water was observedin a specific range of shear rates and below a critical water fraction,and only partial emulsification might occur above this critical waterfraction. The range of shear rates in which full emulsification mightoccur became larger with a decrease in the water fraction, but itdid not change with temperature in the studied range from 40 to 90°C. For partial emulsification, the emulsified water fractionunder flowing conditions was found to correlate well with the entropyproduction rate of viscous flow or energy dissipation rate regardlessof the differences in water fraction, temperature, and shear rate,and a power law equation might well fit the data. [ABSTRACT FROM AUTHOR]

A multiphase reactive fluid dynamicmodel has been applied to simulatea complete chemical looping reforming (CLR) system, including an airreactor (AR), a fuel reactor (FR), a cyclone, and a loop seal. A two-fluidmodel with consideration of frictional stress between particles athigh solid concentrations is used. A bubble-structure-dependent dragcoefficient model is proposed and incorporated into the computationalfluid dynamics (CFD) code to account for the effect of multiscalestructures in the bubbling fluidized reactor. The predictions by themodel are in good agreement with the experimental results. Flow pattern,profiles of bubbles, and distributions of gas compositions and temperaturesare obtained. In addition, the influence of reaction temperature,operating velocity, and H2O/CH4molar ratioon the gas concentration is also investigated. [ABSTRACT FROM AUTHOR]

A comprehensive, real-time PAT processmonitoring scheme of usingnear-infrared (NIR) spectroscopy, focused beam reflectance measurement(FBRM), and particle vision microscopy (PVM) was established for processcharacterization and process understanding of a model dynamic multicomponentpharmaceutical antisolvent crystallization system. The NIR spectrawere subjected to principal component analysis (PCA) to constructthe process trajectory; and the final products were characterizedby X-ray powder diffraction (XRPD), raman spectrometry, and microscopy.Regardless of the PAT technique (i.e., the NIR–PCA method,the FBRM method, and the PVM method) used, this study shows that thenucleation induction time (tind) increaseswith temperature. In addition, correlations were observed with R2of 0.70–0.98 between PVM method andFBRM method and of 0.58–0.84 between NIR–PCA methodand FBRM method. Accounting for the dynamic nature of the experimentsand changes in the liquid volume (V) as a functionof time, a simplified classical nucleation theory model was derivedto reveal the relationship between ln(tindV) and (ln S)−2(Sis the supersaturation ratio). Regions of verystrong and very weak dependence on (ln S)−2were identified. Final product characterization and in-process observationsof particle morphology at t= tindcollectively support that heterogeneous- and homogeneous-nucleationmechanisms are responsible for low Sand high Sregions, respectively. Therefore, the utility of an integrated-PATapproach for understanding a dynamic multicomponent antisolvent crystallizationprocess and elucidating the nucleation mechanism was demonstrated. [ABSTRACT FROM AUTHOR]

In this paper, a coupled system model of partial differentialequations(PDEs) concerning pressure, temperature, velocity, and holdup fora gas–oil–water three-phase steady flow in high-temperature–high-pressure(HTHP) wells is presented. A solution framework shared by the basicmodels is built, making it convenient to perform to solve. An algorithmsolution model using the fourth-order Runge–Kutta method isgiven. Basic data from “X Well” (HTHP well, 7110 m deep,in Sichuan, PRC) is used as a case study for calculations and a sensitivityanalysis is performed on the model. Pressure, temperature, velocity,and hold-up curve graphs, along with the depth of the well, are plottedat different depths. A trend and sensitivity analysis are conductedto test the parameter characteristics. In addition, a comparison betweenthe present model and other models is conducted to illustrate theeffectiveness of the model and the algorithm. The results provideboth technical reliability for well test design in HTHP gas wellsand provides a dynamic analysis of production. [ABSTRACT FROM AUTHOR]

To supply biodiesel with the quality levels required by the standards for alternative fuels, the separation and purification units are extremely important in the biodiesel production plants. The correct knowledge and description of the phase equilibria in systems composed by transesterification products is essential for a correct operation and optimization of the purification process. For that purpose, the cubic-plus-association equation of state (CPA EoS) was here applied to model the phase equilibria of multicomponent systems common to biodiesel production and purification processes. It is shown that the CPA EoS can provide a good description of the liquid−liquid equilibria of multicomponent mixtures containing alcohols, glycerol, and fatty acid esters in the temperature range of operation of the separation units in biodiesel plants. As the liquid−liquid phase equilibrium description depends on the EoS parameters, a discussion is also presented about the best set of parameters and the method to estimate them. [ABSTRACT FROM AUTHOR]

A comprehensive model has been developed to analyze the multiphase flow and heat transfer in the radiant syngas cooler (RSC) of an industrial-scale entrained-flow coal gasification. The three-dimensional multiphase flow field and temperature field were reconstructed. The realizable k−ϵ turbulence model is applied to calculate the gas flow field, while the discrete random walk model is applied to trace the particles, and the interaction between the gas and the particle is considered using a two-way coupling model. The radiative properties of syngas mixture are calculated by weighted-sum-of-gray-gases model (WSGGM). The Ranz−Marshall correlation for the Nusselt number is used to account for convection heat transfer between the gas phase and the particles. The discrete ordinate model is applied to model the radiative heat transfer, and the effect of ash/slag particles on radiative heat transfer is considered. The model was successfully validated by comparison with the industrial plant measurement data, which demonstrated the ability of the model to optimize the design. The results show that a torch shape inlet jet was formed in the RSC, and its length increased with the diameter of the central channel. The recirculation zones appeared around the inlet jet, top, and bottom of the RSC. The overall temperature decreased with the heat-transfer surface area of the fins. The concentration distribution, velocity distribution, residence time distribution, and temperature distribution of particles with different diameters have been discussed. Finally, the slag/ash particles size distribution and temperature profile at the bottom of the RSC have been presented. [ABSTRACT FROM AUTHOR]

We have experimentally investigated multicomponent diffusion in a protein−polymer−salt−water quaternary system. Specifically, we have measured the nine multicomponent diffusion coefficients, Dij, for the lysozyme−poly(ethylene glycol)−NaCl−water system at pH 4.5 and 25 °C using precision Rayleigh interferometry. Lysozyme is a model protein for protein-crystallization and enzymology studies. We find that the protein diffusion coefficient, D11, decreases as polymer concentration increases at a given salt concentration. This behavior can be quantitatively related to the corresponding increase in fluid viscosity only at low polymer concentration. However, at high polymer concentration (250 g/L), protein diffusion is enhanced compared to the corresponding viscosity prediction. We also find that a protein concentration gradient induces salt diffusion from high to low protein concentration. This effect increases in the presence of poly(ethylene glycol). Finally, we have evaluated systematic errors associated with measurements of protein diffusion coefficients by dynamic light scattering. This work overall helps characterize protein diffusion in crowded environments and may provide guidance for further theoretical developments in the field of protein crystallization and protein diffusion in such crowded systems, such as the cytoplasm of living cells. [ABSTRACT FROM AUTHOR]