Determination of kinetics in batch cooling crystallization processes—A sequential parameter estimation approach

A comprehensive methodology to carry out a sequential parameter estimation approach has been developed and validated for the determination of the kinetic parameters of the crystallization of a generic organic compound. The strength of the approach lies in the thorough design of isothermal experiments which facilitate the isolation and/or decoupling of the different crystallization phenomena. This methodology has been applied for the parameter estimation of primary and secondary nucleation, growth and agglomeration kinetics. The resulting crystallization model has been able to reproduce the quantiles , and of the volume‐based particle size distribution of an independent seeded validation experiment with an error below 10 μm. The deviation in the prediction has been increased in the case of an independent unseeded experiment, although errors below the uncertainty of the measurement have been always obtained. The methodology here proposed is intended to be an efficient strategy for rapid modeling of batch crystallization processes. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3992–4012, 2016     

Kinetics of RAFT emulsion polymerization of styrene mediated by oligo(acrylic acid‐b‐styrene) trithiocarbonate

The kinetics of ab initio reversible addition‐fragmentation chain transfer (RAFT) emulsion polymerization of styrene using oligo(acrylic acid‐b‐styrene) trithiocarbonate as both polymerization mediator and surfactant were systematically investigated. The initiator concentration was set much lower than that in the conventional emulsion polymerization to significantly suppress the irreversible termination reaction. It was found that decreased rapidly but the nucleation efficiency of micelles increased with the decrease of the initiator concentrations due to the significant radical exit. The particle number ( ) did not follow the classic Smith–Eward equation but was proportional to [I]^?0.4[S]^0.7. It was suggested that RAFT emulsion polymerization could be fast enough for commercial use even at extremely low initiator concentrations and low macro‐RAFT agent concentrations due to the higher particle nucleation efficiency at lower initiator concentration. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2126–2134, 2016     

A positron emission particle tracking investigation of the scaling law governing free surface flows in tumbling mills

Positron Emission Particle Tracking (PEPT) measurements are used to track the flow of glass beads within a rotating drum fitted with (and without) lifter bars and operated in the cascading and cataracting Froude regimes. After converting the Lagrangian trajectories of a representative radio‐labeled glass bead (the tracer) into Eulerian fields under the ergodic assumption, the bed shape and kinematics are extracted for steady, fully developed flow conditions. Notwithstanding the azimuthal wall effects introduced by the lifter bars, we show a linear scaling of the local flowing layer thickness (h) with local depth‐averaged velocity and a constant average shear for direct measurements spanning the entire flowing layer (not just the central region), and high Froude regimes (cascading and cataracting) not previously investigated by scaling analysis in the literature. © 2016 American Institute of Chemical Engineers AIChE J, 63: 903–913, 2017     

Predicting effective conductivities based on geometric microstructure characteristics

Empirical relationships between effective conductivities in porous and composite materials and their geometric characteristics such as volume fraction , tortuosity τ and constrictivity β are established. For this purpose, 43 virtually generated 3D microstructures with varying geometric characteristics are considered. Effective conductivities are determined by numerical transport simulations. Using error‐minimization the following relationships have been established: and (simplified formula) with intrinsic conductivity σ₀, geodesic tortuosity and relative prediction errors of 19% and 18%, respectively. We critically analyze the methodologies used to determine tortuosity and constrictivity. Comparing geometric tortuosity and geodesic tortuosity, our results indicate that geometric tortuosity has a tendency to overestimate the windedness of transport paths. Analyzing various definitions of constrictivity, we find that the established definition describes the effect of bottlenecks well. In summary, the established relationships are important for a purposeful optimization of materials with specific transport properties, such as porous electrodes in fuel cells and batteries. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1834–1843, 2016     

Heat transfer coefficient for condensation of steam on freely formed falling liquid jets

This article presents the research results of direct contact condensation of steam on freely formed falling liquid jets. After the comparison of experimental data and open literature correlations it was concluded that published correlations does not provide accurate coverage of experimental data. A new correlation was established in the following form © 2016 American Institute of Chemical Engineers AIChE J, 62: 2579–2584, 2016     

Large eddy simulation of inertial fiber deposition mechanisms in a vertical downward turbulent channel flow

The deposition pattern of elongated inertial fibers in a vertical downward turbulent channel flow is predicted using large eddy simulation and Lagrangian particle tracking. Three dominant fibers deposition mechanisms are observed, namely, diffusional deposition for small inertial fibers, free‐flight deposition for large inertial fibers, and the interception mechanism for very elongated fibers. The fibers are found to exhibit orientation anisotropy at impact, which is strongly dependent on the fiber elongation. An increase in the fiber elongation increases the wall capture efficiency by the interception mechanism. The diffusional deposition mechanism is shown to dominate for fibers with large residence time, , in the accumulation zone and small deposition velocities, , while the free‐flight mechanism governs deposition for fibers with small and large . This study describes how particles deposit on a surface and, ultimately for many practical applications, how such deposition may promote fouling. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1451–1465, 2017     

NMR spectroscopic study of chemical equilibria in solutions of formaldehyde,water, and butynediol

Liquid mixtures of formaldehyde, water, and butynediol are complex reacting multicomponent systems in which formaldehyde forms oligomers both with water and butynediol. ‐ and ‐NMR spectra of these mixtures are elucidated. The species distribution of the oligomers is quantitatively determined by ‐NMR spectroscopy. The measurements cover temperatures from 293 to 366 K, overall formaldehyde mass fractions from to , and overall butynediol mass fractions from to . A mole fraction‐based and an activity‐based model of the chemical equilibrium in the studied system are developed and chemical equilibrium constants are reported. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4442–4450, 2017     

Effect of dead volumes on the performance of an industrial‐scale simulated moving‐bed Parex unit for p‐xylene purification

The cyclic steady state (CSS) of the industrial‐scale, seven‐zone, simulated moving‐bed (SMB) unit for p‐xylene (p‐x) purification (Parex unit) with three types of dead volumes—bed lines, push‐around and pump‐around circulation lines, and bed heads—is analyzed. In particular, the effects of the size and level of hydrodynamic dispersion of each dead volume on process performance and on its CSS are studied in detail. The circulation lines change the CSS behavior from ‐periodic to ‐periodic, where is the switching interval and is the number of columns in each adsorbent chamber. A high level of axial dispersion in the bed lines, characterized by Péclet numbers smaller than 100, affects the p‐x purity. Moreover, the bed lines lower the average p‐x concentration in the extract, which reduces the p‐x recovery. If the small time lags introduced by the circulation lines are neglected, it is possible to develop a detailed process model that considers the operation of the Parex unit over a single switching interval as opposed to a full cycle, and whose CSS solution can be efficiently computed using a full‐discretization approach. Finally, it is shown that the volume of the bed heads influences significantly the performance of the Parex unit, and that its impact on the location of the operating point with respect to the boundaries of the separation region can be approximately taken into account using the standard true moving‐bed‐SMB equivalence rules if they are corrected for the presence of extra interparticle fluid. © 2015 American Institute of Chemical Engineers AIChE J, 62: 241–255, 2016     

Convective condensation in a stator–rotor–stator spinning disc reactor

Centrifugal intensification of condensation heat transfer in the rotor–stator cavities of a stator–rotor–stator spinning disc reactor (srs‐SDR) is studied, as a function of rotational velocity ω, volumetric throughflow rate , and average temperature driving force . For the current range of ω, heat transfer from the vapor bubbles to the condensate liquid is limiting, due to a relatively low gas–liquid interfacial area a_GL. For rad s^?1, a strong increase of a_GL, results in increasing the reactor‐average condensation heat transfer coefficient h_c from 1600 to 5600 W m^?2 K^?1, for condensation of pure dichloromethane vapor. Condensation heat transfer in the srs‐SDR is enhanced by rotation, independent of the vapor velocity. The intensified condensation comes at the cost of relatively high energy dissipation rates, indicating condensation in the srs‐SDR is more suited as a means to supply heat (e.g. in an intensified reactor‐heat exchanger), rather than for bulk cooling purposes. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3784–3796, 2016     

Ionic liquids in supercritical methanol greatly enhance transesterification reaction for high‐yield biodiesel production

Biodiesel production is one of the most promising future alternatives to replacing fossil fuels. This work studies the use of ionic liquids (ILs) as potential catalysts in supercritical methanol for biodiesel production from non‐edible oil. The transesterification reaction of karanja oil was investigated in supercritical methanol in the presence of two respective ILs, [BMIM⁺][ ] and [Chol⁺][H₂ ]. The reaction was performed in a one‐step batch process at several temperatures and percentages by weight of catalyst (w/w_oil). The results obtained show that the IL [Chol⁺][H₂ ] allows a high yield of fatty acid methyl esters to be achieved in a short reaction time (above 95% in 45 min). A catalytic mechanism is also proposed for the IL that offered significant catalytic activity. This work investigates the effects of the use of ionic liquids as potential catalysts in supercritical methanol for the transesterification reaction of non‐edible oil. The reported reaction times to obtain biodiesel yields above 90% through the transesterification reaction of karanja oil range between 90 min and 8 h. ILs as catalysts in supercritical methanol drastically reduce reaction time (45 min) to obtain high fatty acid methyl ester yield (95.6%). © 2016 American Institute of Chemical Engineers AIChE J, 62: 3842–3846, 2016     

Forced convection boiling in a stator–rotor–stator spinning disc reactor

Boiling of a pure fluid inside the rotor–stator cavities of a stator–rotor–stator spinning disc reactor (srs‐SDR) is studied, as a function of rotational velocity ω, average temperature driving force and mass flow rate . The average boiling heat transfer coefficient h_b increases a factor 3 by increasing ω up to 105 rad s^?1, independently of and . The performance of the srs‐SDR, in terms of h_b vs. specific energy input ?, is similar to tubular boiling, where pressure drop provides the energy input. The srs‐SDR enables operation at Wm , yielding values of h_b not practically obtainable in passive evaporators, due to prohibitively high pressure drops required. Since h_b is increased independently of the superficial vapor velocity, h_b is not a function of and the local vapor fraction. Therefore, the srs‐SDR enables a higher degree of control and flexibility of the boiling process, compared to passive flow boiling. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3763–3773, 2016     

Maldistribution susceptibility of monolith reactors: Case study of glucose hydrogenation performance

In this work an ultrafast electron beam X‐ray modality was applied for the first time to characterize the gas–liquid Taylor flow inside each channel of an opaque honeycomb monolith structure ( ) for and . Significant spatial and temporal deviations in the phase holdup as well as in the gas bubble and liquid slug lengths were found. To evaluate the impact of Taylor flow maldistribution on the reactor performance, the data of more than unit cells were used to simulate the reactor productivity in the hydrogenation of glucose. The results verify that a monolith reactor solely designed by using superficial velocities and empirical correlations for gas bubble and liquid slug lengths fails significantly in achieving high product selectivity and the desired conversion. The developed methods are a solid base to design and select proper distributors ensuring the favorable flow configurations for specific chemical processes. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4346–4364, 2016     

Property prediction and consistency analysis by a reference series method

Data analysis and prediction of pure component properties of long‐chain substances is considered. The emphasis is on homologous series and properties for which insufficient data are available. A two‐stage procedure is recommended, whereby a linear (or nonlinear) quantitative structure–property relationship (QSPR) is fitted to a “reference” series, for which an adequate amount of precise data is available. This QSPR should represent correctly both the available data and the asymptotic behavior of the property. In the second stage a quantitative property‐property relationship (QPPR) is derived to represent the predicted property values of a “target” series in terms of the property values of the reference series. The procedure is applied for properties which are highly correlated with the number methylene groups in homologous series: and . It is shown that the method is very useful for consistency analysis of property data and enables a reliable prediction of and , and, thus, also of for long‐chain substances. © 2012 American Institute of Chemical Engineers AIChE J, 59: 420–428, 2013     

Framework for correlating the effect of temperature on nonelectrolyte and ionic liquid activity coefficients

A power‐law expression is proposed for correlating the temperature dependence of infinite‐dilution activity coefficients ( ) for nonelectrolyte solute–solvent binary pairs and for pairs including an ionic liquid: , where θ_ij = 0 for Lewis–Randall ideal solutions, θ_ij = 1 for classic enthalpy‐based Scatchard–Hildebrand regular solution and van Laar models, and ?5 < θ_ij < 5 for most real binaries. The exponent θ_ij is a function of partial molar excess enthalpy ( ) and entropy ( ) such that . Real binaries are classified into seven types corresponding to distinct domains of and θ_ij. The new method provides a framework for correlating phase‐equilibrium driven temperature effects for a wide variety of chemical and environmental applications. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3675–3690, 2014     

Integrated crude selection and refinery optimization under uncertainty

Crude oil selection and procurement is the most important step in the refining process and impacts the profit margin of the refinery significantly. Due to uncertain quality of the crudes, conventional deterministic modeling and optimization methods are not suitable for refinery profitability enhancement. Therefore, a novel optimization scheme for crude oil procurement integrated with refinery operations in the face of uncertainties is presented. The decision process comprises two stages and is solved using a scenario‐based stochastic programming formulation. In Stage I, the optimal crude selections and purchase amounts are determined by maximizing the expected profit across all scenarios. In Stage II, the uncertainties are realized and optimal operations for the refinery are determined according to this realization. The resulting large‐scale mixed‐integer nonlinear programming formulation incorporates integer variables for crude selection and continuous variables for refinery operations, as well as bilinear terms for pooling processes. Nonconvex generalized Benders decomposition is used to solve this problem to obtain an global optimum efficiently. © 2015 American Institute of Chemical Engineers AIChE J, 62: 1038–1053, 2016     

Analysis and optimization of pressure retarded osmosis for power generation

Model‐based analysis and optimization of pressure retarded osmosis (PRO) for power generation is focused. The effects of membrane properties (hydraulic permeability and mass‐transfer characteristics), design conditions (inlet osmotic pressures, inlet flows, and membrane area) and operating condition (applied pressure) on power density and efficiency are systematically investigated. A dimensionless design parameter , originally developed in analysis and optimization of reverse osmosis, is used to quantify the effect of dilution in draw solution (DS) as water permeates through membrane. An optimization method is developed to maximize PRO performance. It is shown that dilution and concentration polarization significantly reduce the maximum power density, and the optimal shifts away from . Moreover, power density and efficiency follow opposite trends when varying process conditions including DS flow rate and membrane area. Enhancing membrane properties is crucial to improve the economic feasibility of PRO. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1233–1241, 2015     

Consensus algorithm‐based approach to fundamental modeling of water pipe networks

Modeling the flow dynamics of leaks in water pipe networks is an extremely difficult problem due to the complex entangled network structure and hydraulic phenomenon. A mathematical model for leak dynamics in water pipe networks based on consensus algorithm and water hammer theory is proposed. The resulting model is a simple and linearly interconnected system even though the dynamics of water pipe networks has considerable complexity. The model is then validated using experimental data obtained from real pipe network. A comparative study demonstrates the proposed model can describe the real system with high qualitative and quantitative accuracy and it can be used to develop model‐based leak detection and location algorithm based on state estimation. To show applicability of the proposed model, we apply cooperative estimation to the developed model. The results demonstrate the consensus‐based pipe model can be potentially used for leak detection and location with state estimation. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3860–3870, 2017     

Kinetics of the absorption of carbon dioxide into aqueous ammonia solutions

Experiments were performed in a customized double stirred tank reactor to study the kinetics of CO₂ absorption into NH₃ solutions at concentrations ranging from 0.42 to 7.67 kmol·m^?3 and temperatures between 273.15 and 293.15 K. The results show that the reactive absorption was first order with respect to CO₂ but fractional order (1.6–1.8) with respect to ammonia. Experimental data can be satisfactorily interpreted by a termolecular mechanism using and . © 2016 American Institute of Chemical Engineers AIChE J, 62: 3673–3684, 2016     

An elastic analog model for controlling the impingement point position in confined impinging jets

Confined impinging jets (CIJs) are highly efficient mixers. The scales of mixing in CIJs are controlled by the opposed jets interaction. A mechanistic model is described here, which accurately predicts the impinging position of the opposed jets for a large range of flow rate ratios. The impinging point position is shown to impact the dynamic properties of the flow and the achieved mixing quality. The opposed jets kinetic energy ratio is shown to have a critical impact on mixing, similar to the Reynolds number. A mixing chamber design relation is proposed and verified for the opposed injectors diameters ratio, , which enables to operate CIJs under optimum mixing conditions for large ranges of flow rate ratios, viscosity and density ratios between the opposed streams. Optimum values have asymptotes for large and small Reynolds number depending on the process stoichiometry, viscosity, and density ratios of the opposed jet streams. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2200–2212, 2016     

Quantitative relationships between microstructure and effective transport properties based on virtual materials testing

The microstructure influence on conductive transport processes is described in terms of volume fraction ε, tortuosity τ, and constrictivity β. Virtual microstructures with different parameter constellations are produced using methods from stochastic geometry. Effective conductivities are obtained from solving the diffusion equation in a finite element model. In this way, a large database is generated which is used to test expressions describing different micro–macro relationships such as Archie's law, tortuosity, and constrictivity equations. It turns out that the constrictivity equation has the highest accuracy indicating that all three parameters are necessary to capture the microstructure influence correctly. The predictive capability of the constrictivity equation is improved by introducing modifications of it and using error‐minimization, which leads to the following expression: with intrinsic conductivity . The equation is important for future studies in, for example, batteries, fuel cells, and for transport processes in porous materials. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1983–1999, 2014