Uncertainty-conscious methodology for process performance assessment in biopharmaceutical drug product manufacturing AlChE J. (IF 2.836) Pub Date : 2017-11-20 Gioele Casola, Hirokazu Sugiyama, Christian Siegmund, Markus Mattern
This work presents an uncertainty-conscious methodology for the assessment of process performance—for example, run time—in the manufacturing of biopharmaceutical drug products. The methodology is presented as an activity model using the type 0 integrated definition (IDEF0) functional modeling method, which systematically interconnects information, tools, and activities. In executing the methodology, a hybrid stochastic–deterministic model that can reflect operational uncertainty in the assessment result is developed using Monte Carlo simulation. This model is used in a stochastic global sensitivity analysis to identify tasks that had large impacts on process performance under the existing operational uncertainty. Other factors are considered, such as the feasibility of process modification based on Good Manufacturing Practice, and tasks to be improved is identified as the overall output. In a case study on cleaning and sterilization processes, suggestions were produced that could reduce the mean total run time of the processes by up to 40%. © 2017 American Institute of Chemical Engineers AIChE J, 2017
A branch and bound algorithm to solve large-scale multistage stochastic programs with endogenous uncertainty AlChE J. (IF 2.836) Pub Date : 2017-11-20 Brianna Christian, Selen Cremaschi
The growth in computation complexity of multistage stochastic programs (MSSPs) with problem size often prevents its application to real-world size problems. We present two variants of branch-and-bound algorithm, which reduce the resource requirements for the generation and solution of large-scale MSSPs with endogenous uncertainty. Both variants use Knapsack-problem based Decomposition Algorithm (Christian and Cremaschi, Comput Chem Eng. 2015;74:34–47) to generate feasible solutions and primal bounds. First variant (PH-KDA) uses a progressive hedging dual-bounding approach; the second (OSS-KDA) solves the MSSP removing all nonanticipativity constraints. Both variants were used to solve several instances of the pharmaceutical clinical trial planning problem. The first iteration of both algorithms provides a feasible solution, and a primal bound and a dual bound for the problem. Although the dual-bounds of OSS-KDA were generally weaker than PH-KDA, they are generated considerably faster. For the seven-product case the OSS-KDA generated a solution with a gap of 9.92% in 115 CPU seconds. © 2017 American Institute of Chemical Engineers AIChE J, 2017
DEM study on the discharge characteristics of lognormal particle size distributions from a conical hopper AlChE J. (IF 2.836) Pub Date : 2017-11-20 Ya Zhao, Shiliang Yang, Liangqi Zhang, Jia Wei Chew
This study employs the discrete element method (DEM) to investigate the impact of the widths of lognormal particle size distributions (PSDs) with the same mean particle diameter on hopper discharge behaviors, namely, discharge rate, particle velocities, and size-segregation. Results reveal that (i) the hopper discharge rate decreases as PSD width increases; (ii) the mean discharge rates are constant with time, but the fluctuations increase as the PSD width increases; (iii) the overall size-segregation increases with PSD width; (iv) the overall mean particle diameters of the narrower PSDs do not exceed the initial mean of 5 mm, whereas that of wider ones do; (v) the relationship between PSD width and particle velocities is non-monotonic with no consistent trends; and (vi) no direct correlation exists between particle velocity and size-segregation. The results here provide valuable insights on the behavior of the prevalent polydisperse mixtures in hoppers. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Two-step continuous production of monodisperse colloidal ellipsoids at rates of one gram per day AlChE J. (IF 2.836) Pub Date : 2017-11-14 Joseph A. Ferrar, Leonid Pavlovsky, Eric Viges, Yanliang Liu, Michael J. Solomon
We report a two-step process for the continuous production of monodisperse polystyrene colloidal ellipsoids of aspect ratios up to 6.8 at rates that exceed 1.0 g per day, an improvement on previously reported synthetic batch processing rates of nearly a factor of 20. This scale up is accomplished by continuous evaporative processing of a polymer solution into an elastomeric film embedded with colloidal spheres. Subsequently, the film is continuously elongated at a temperature that stretches the embedded spheres into ellipsoids. The method is used to deform initially 1.0 μm diameter spheres into ellipsoids of aspect ratio 1.27 ± 0.15, 3.31 ± 0.44, 3.91 ± 0.72, 4.14 ± 0.47, and 6.77 ± 1.01. The particle production rate reported here opens new possibilities for applications of monodisperse ellipsoids, such as self-assembly and optical characterization of complex crystalline unit cells, as well as rheological characterization of dilute gels and dense suspensions. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Joint capacity planning and distribution network optimization of coal supply chains under uncertainty AlChE J. (IF 2.836) Pub Date : 2017-11-09 Rui-Jie Zhou, Li-Juan Li
A two-stage stochastic integer programming model is developed to address the joint capacity planning and distribution network optimization of multiechelon coal supply chains (CSCs) under uncertainty. The proposed model not only introduces the uses of compound real options in sequential capacity planning, but also considers uncertainty induced by both risks and ambiguities. Both strategic decisions (i.e., facility locations and initial investment, service assignment across the entire CSC, and option holding status) and scenario-based operational decisions (i.e., facility operations and capacity expansions, outsourcing policy, and transportation and inventory strategies) can be simultaneously determined using the model. By exploiting the nested decomposable structure of the model, we develop a new distributed parallel optimization algorithm based on nonconvex generalized Bender decomposition and Lagrangean relaxation to mitigate the computation resource limitation. One of the main CSCs in China is studied to demonstrate the applicability of the proposed model and the performance of the algorithm. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Insight in kinetics from pre-edge features using time resolved in situ XAS AlChE J. (IF 2.836) Pub Date : 2017-11-07 N.V.R.A. Dharanipragada, Vladimir V. Galvita, Hilde Poelman, Lukas C. Buelens, Guy B. Marin, Alessandro Longo
The kinetics of reduction of a 10 wt %Fe2O3-MgAl2O4 spinel were investigated using XRD and time resolved Fe-K QXANES. The Rietveld refinement of the XRD pattern showed the replacement of Al with Fe in the spinel structure and the formation of MgFeAlOx. The XANES pre-edge feature was employed to study the reduction kinetics during H2-TPR (Temperature Programmed Reduction) up to 730°C. About 55% of the Fe3+ in MgFeAlOx was reduced to Fe2+. A shrinking core model, which takes into account both solid-state diffusion via an oxygen diffusion coefficient, and gas-solid reaction through a reaction rate coefficient, was applied. The activation energy for chemical reaction showed a linear dependence on the conversion, increasing from 104 to 126 kJ/mol over the course of material reduction. The good accordance between the shrinking core model description and the experimental data indicates that XANES pre-edge features can be used to correlate changes in material structure and reaction kinetics. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Effect of viscosity on liquid curtain stability AlChE J. (IF 2.836) Pub Date : 2017-11-06 Alireza Mohammad Karim, Wieslaw J. Suszynski, Lorraine F. Francis, Marcio S. Carvalho
The effect of viscosity on liquid curtain stability was explored by high-speed visualization. Measurements of the velocity within the curtain revealed the presence of a viscous boundary layer along the edge guides. The critical condition at the onset of curtain breakup was determined by identifying the flow rate below which the curtain broke for two different edge guide geometries: parallel and convergent. Curtain breakup was initiated by the expansion of a hole within the curtain. For low viscosity liquid, the measured hole retraction speed is independent of the viscosity and equal to the Taylor-Culick speed. For high viscosity liquids, the retraction speed is lower than the Taylor-Culick speed due to viscous forces that resist the flow. The results also show the effect of liquid viscosity on the curtain stability is a strong function of the edge guide design. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Enhancing CO2 absorption efficiency using a novel PTFE hollow fiber membrane contactor at elevated pressure AlChE J. (IF 2.836) Pub Date : 2017-11-06 Fushan Wang, Guodong Kang, Dandan Liu, Meng Li, Yiming Cao
The internal structure design of membrane module is very important for gas removal performance using membrane contactor via physical absorption. In this study, a novel membrane contactor developed by weaving polytetrafluoroethylene (PTFE) hollow fibers was applied to remove CO2 from 60% N2 + 40% CO2 mixture (with CO2 concentration similar to that of biogas) at elevated pressure (0.8 MPa) using water as absorbent. Compared with the conventional module with randomly packed straight fibers, the module with woven PTFE fibers exhibited much better CO2 absorption performance. The weaving configuration facilitated the meandering flow or Dean vortices and renewing speed of water around hollow fibers. Meanwhile, the undesired influences such as channeling and bypassing were also eliminated. Consequently, the mass transfer of liquid phase was greatly improved and the CO2 removal efficiency was significantly enhanced. The effects of operation pressure, module arrangement, feed gas, and water flow rate on CO2 removal were systematically investigated as well. The overall mass-transfer coefficient (KOV) varied from 1.96 × 10−5 to 4.39 × 10−5 m/s (the volumetric mass-transfer coefficient KLa = 0.034–0.075 s−1) under the experimental conditions. The CO2 removal performance of novel woven fiber membrane contactor matched well with the simulation results. © 2017 American Institute of Chemical Engineers AIChE J, 2017
3D-foam-structured nitrogen-doped graphene-Ni catalyst for highly efficient nitrobenzene reduction AlChE J. (IF 2.836) Pub Date : 2017-11-06 Zhiyong Wang, Yuan Pu, Dan Wang, Jie Shi, Jie-Xin Wang, Jian-Feng Chen
We report the preparation of a porous 3D-foam-structured nitrogen-doped graphene-Ni (NG/NF) catalyst and the evaluation of its performance in the reduction of nitrobenzene (NB) through detailed studies of the kinetics. The NG/NF catalyst showed a significantly higher reaction rate than pure Ni foam (NF). Moreover, the separation of the 3D-foam-structured catalyst from the products was more convenient than that of NG powdered catalysts. The obtained kinetics data fit well to the Langmuir-Hinshelwood model, with an error ratio below 10%. Density functional theory (DFT) calculations indicated that the adsorption of sodium borohydride (NaBH4) on the NG/NF surface was stronger than that of NB, which strongly agreed with the kinetic parameters determined from the Langmuir-Hinshelwood model. The excellent catalytic efficiency of the 3D-foam-structured catalyst combined with the knowledge of the kinetics data make this catalyst promising for application in larger scale nitrobenzene reduction. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Multivariable model predictive control of a novel rapid pressure swing adsorption system AlChE J. (IF 2.836) Pub Date : 2017-11-02 Matthew D. Urich, Rama Rao Vemula, Mayuresh V. Kothare
A multivariable model predictive control (MPC) algorithm is developed for the control and operation of a rapid pressure swing adsorption (RPSA)-based medical oxygen concentrator. The novelty of the approach is the use of all four step durations in the RPSA cycle as independent manipulated variables in a truly multivariable context. The RPSA has a complex, cyclic, nonlinear multivariable operation that requires feedback control, and MPC provides a suitable framework for controlling such a multivariable system. The multivariable MPC presented here uses a quadratic optimization program with integral action and a linear model identified using subspace system identification techniques. The controller was designed and tested in simulation using a complex, highly coupled, nonlinear RPSA process model. The model was developed with the least restrictive assumptions compared to those reported in the literature, thereby providing a more realistic representation of the underlying physical phenomena. The resulting MPC effectively tracks set points, rejects realistic process disturbances and is shown to outperform conventional PID control. © 2017 American Institute of Chemical Engineers AIChE J, 2017
A pseudo-transient optimization framework for periodic processes: Pressure swing adsorption and simulated moving bed chromatography AlChE J. (IF 2.836) Pub Date : 2017-11-02 Calvin Tsay, Richard C. Pattison, Michael Baldea
Periodic systems are widely used in separation processes and in reaction engineering. They are designed for and operated at a cyclic steady state (CSS). Identifying and optimizing the CSS has proven to be computationally challenging. A novel framework for equation-oriented simulation and optimization of cyclic processes is introduced. A two-step reformulation of the process model is proposed, comprising, (1) a full discretization of the time and spatial domains and (2) recasting the discretized model as a differential-algebraic equation system, for which theoretical stability guarantees are provided. Additionally, a mathematical, structural connection between the CSS constraints and material recycling is established, which allows us to deal with these conditions via a “tearing” procedure. These developments are integrated in a pseudo-transient design optimization framework and two extensive case studies are presented: a simulated moving bed chromatography system and a pressure swing adsorption process. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Low Reynolds number isotope transient kinetic modeling in isothermal differential tubular catalytic reactors AlChE J. (IF 2.836) Pub Date : 2017-11-02 Masood Otarod, Ronald M. Supkowski
A novel method is presented for modeling steady state isotope transient kinetics of heterogeneous catalytic reactions when the flow regime is laminar and conversion is differential. It is based on a factorization theorem which is deduced from the observation that transport functions fluctuate radially in porous beds. Factorization separates the radial from axial and temporal coordinates of the flow rate and concentration functions. It is shown that in transient tracing with a differential conversion, the radial components of the transport functions in the material conservation equations can be integrated into constant parameters to be determined from experimental data. The method is in particular useful as the knowledge of the radial profile of velocity and other transport functions and parameters are not prerequisites for data correlation. The methodology was successfully applied to the adsorption of carbon monoxide in Boudouard reaction on an alumina supported palladium catalyst. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Issue information AlChE J. (IF 2.836) Pub Date : 2017-11-02
Highly efficient separation of strongly hydrophilic structurally related compounds by hydrophobic ionic solutions AlChE J. (IF 2.836) Pub Date : 2017-11-01 Qiwei Yang, Shaocong Guo, Xianxian Liu, Zhiguo Zhang, Zongbi Bao, Huabin Xing, Qilong Ren
The selective separation of strongly hydrophilic structurally related compounds in aqueous solutions is a long-standing challenge due to a trade-off between separation selectivity and capacity. This work shows a new method to separate strongly hydrophilic structurally related compounds through hydrophobic ionic solution-based liquid-liquid extraction, with L-ascorbic acid 2-glucoside (AA-2G) and L-ascorbic acid as model compounds. Extraordinary distribution coefficient, superb molecular selectivity, large extraction capacity and good recyclability without using strong acids and salts were all achieved, with a small consumption of phosphonium bromide ionic liquid and aprotic molecular diluent. The essence of this method is the successful combination of both strong hydrogen-bond basicity and good hydrophobicity along with significant preferential solvation phenomena of the constructed ionic solutions. Even if at a high feed concentration of 100 mg/mL, the purity of AA-2G could be greatly elevated from 50% to 96.2% with an ultrahigh yield of almost 100% after five-stage countercurrent extraction. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Receding horizon optimal operation and control of a solar-thermal district heating system AlChE J. (IF 2.836) Pub Date : 2017-11-01 Xiaodong Xu, Yuan Yuan, Stevan Dubljevic
This work focuses on the receding horizon optimal control for a solar-thermal district heating (STDH) system containing lumped parameter and distributed parameter subsystems. A common STDH system includes solar collector system, a short-term energy storage tank and a district heating loop system with a secondary gas boiler system. The inclusion or exclusion of these components leads to different operational and working modes. Detailed system description and mathematical models are provided, and three working modes are introduced and in each mode several operations are demonstrated and addressed. Single-objective and multiobjective problems are formulated. Moreover, in the mode where gas boiler system is included to help addressing the district heating demand, the internal model based boundary servo-control approach is proposed and applied to obtain desired boiler water temperatures such that the expected district heating demand can be satisfied. Moreover, a boundary state observer is designed for the considered solar collector system. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Improving mixing characteristics with a pitched tip in kneading elements in twin-screw extrusion AlChE J. (IF 2.836) Pub Date : 2017-10-30 Yasuya Nakayama, Hiroki Takemitsu, Toshihisa Kajiwara, Koichi Kimura, Takahide Takeuchi, Hideki Tomiyama
In twin-screw extrusion, the geometry of a mixing element mainly determines the basic flow pattern, which eventually affects the mixing ability as well as the dispersive ability of the mixing element. The effects of geometrical modification, with both forward and backward pitched tips, of a conventional forward kneading disks element (FKD) in the pitched-tip kneading disks element on the flow pattern and mixing characteristics are discussed. Numerical simulations of fully filled, nonisothermal polymer melt flow in the melt-mixing zone were performed, and the flow pattern structure and the tracer trajectories were investigated. The pitched tips largely affect the inter-disk fluid transport, which is mainly responsible for mixing. These changes in the local flow pattern are analyzed by the distribution of the strain-rate state. The distribution of the finite-time Lyapunov exponent reveals a large inhomogeneity of the mixing in FKD is suppressed both by the forward and backward tips. By the forward tips on FKD, the mixing ability is relatively suppressed compared to FKD, whereas for the backward tips on FKD, the mixing ability is enhanced while maintaining the same level of dispersion efficiency as FKD. From these results, the pitched tips on the conventional KD turn out to be effective at reducing the inhomogeneity of the mixing and tuning the overall mixing performance. © 2017 American Institute of Chemical Engineers AIChE J, 2017
A pore network study of evaporation from the surface of a drying non-hygroscopic porous medium AlChE J. (IF 2.836) Pub Date : 2017-10-30 Alireza Attari Moghaddam, Abdolreza Kharaghani, Evangelos Tsotsas, Marc Prat
The phenomena occurring at the surface of a porous medium during drying in the capillary regime are investigated by pore network simulations. The impact of the formation of wet and dry patches at the surface on the drying rate is studied. The simulations indicate an edge effect characterized by a noticeable variation of saturation in a thin layer adjacent to the porous surface. Also, the results indicate a significant nonlocal equilibrium effect at the surface. The simulation results are exploited to test Schlünder's classical model which offers a simple closure relationship between the evaporation rate and the degree of occupancy of the surface by the liquid. In addition to new insights into the surface phenomena, the results open up new prospects for improving the continuum models of the drying process. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Liquid–liquid two-phase flow in ultrasonic microreactors: Cavitation, emulsification, and mass transfer enhancement AlChE J. (IF 2.836) Pub Date : 2017-10-27 Shuainan Zhao, Zhengya Dong, Chaoqun Yao, Zhenghui Wen, Guangwen Chen, Quan Yuan
The effects of ultrasound on the hydrodynamic and mass transfer behaviors of immiscible liquid–liquid two-phase flow was investigated in a domestic ultrasonic microreactor. Under ultrasonic irradiation, cavitation bubble was generated and underwent violent oscillation. Emulsification of immiscible phases was initiated by virtue of oscillating bubbles shuttling through the water/oil interface. The pressure drop was found to decrease with increasing ultrasound power, with a maximum decrement ratio of 12% obtained at power 30 W. The mass transfer behavior was characterized by extraction of Rhodamine B from water to 1-octanol. An enhancement factor of 1.3–2.2 on the overall mass-transfer coefficient was achieved under sonication. The mass transfer performance was comparable to passive microreactor at similar energy dissipation rate (61–184 W/kg). The extraction equilibrium was reached under a total flow velocity 0.01 m/s and input power 20 and 30 W, exhibiting its potential use in liquid-liquid extraction process. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Simulation on hydrogen storage properties of metal-organic frameworks Cu-BTC at 77–298 K AlChE J. (IF 2.836) Pub Date : 2017-10-27 Shumin Chen, Yumei Shi, Bo Gu
In recent years, many researchers have studied on the hydrogen storage properties of metal-organic frameworks (MOFs) by grand canonical Monte Carlo (GCMC) simulation. At present, the GCMC studies of Cu-BTC (BTC: benzene-1,3,5-tricarboxylate) which is a prototypical metal-organic framework mainly adopt the classical force fields, the simulation temperatures are mainly focus on 298 and 77 K, and most researchers did not consider the effects of quantum effects at low temperature. Therefore, we used the quantum effects to correct the classical force fields and the force fields with more accurate simulation results were used to simulate the hydrogen adsorption performances of Cu-BTC in the temperature range of 77–298 K and the pressure range of 1–8 MPa at each temperature. The results show that the effects of quantum effects on the hydrogen storage of Cu-BTC cannot be neglected and the corrected Dreiding force field can simulate hydrogen adsorption performances of Cu-BTC more accurately at low temperature. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Modeling the deposition of fluorescent whitening agents on cotton fabrics AlChE J. (IF 2.836) Pub Date : 2017-10-27 Laura Bueno, Carlos Amador, Serafim Bakalis
The adsorption of two widely used fluorescent whitening agents (FWAs) on unbrightened cotton fabrics has been investigated as a function of temperature, hardness of the wash liquor, initial concentration of FWA in solution, and fabric to wash liquor ratio. Sorption efficiencies of FWAs have been studied using a UV spectrophotometry technique. A mechanistic model has been developed to describe the dissolution process of FWAs, convective mass transport into the fabrics, diffusion in the stagnant layer to the fabrics' surface, and adsorption of FWAs on cotton fabrics. Dual porosity of the fabrics (inter-yarn and intra-yarn porosity) has been considered by allowing two different regions (outer and inner areas of the cotton fabrics) where FWAs molecules can diffuse and adsorb. Good agreement between experimental and predicted whiteness benefit by the proposed mathematical model has been observed for the range of variables considered. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Chemical hydrodynamics of a downward microbubble flow for intensification of gas-fed bioreactors AlChE J. (IF 2.836) Pub Date : 2017-10-27 Manizheh Ansari, Damon E. Turney, Roman Yakobov, Dinesh V. Kalaga, Simon Kleinbart, Sanjoy Banerjee, Jyeshtharaj B. Joshi
Bioreactors are of interest for value-upgrading of stranded or waste industrial gases. Reactor intensification requires development of low cost bioreactors with fast gas–liquid mass transfer rate. Here we assess published reactor technology in comparison with a novel downward bubble flow created by a micro-jet array. Compared to known technology, the advanced design achieves higher volumetric gas transfer efficiency (kLa per power density) and can operate at higher kLa. We measure the effect of four reactor heights (height-to-diameter ratios of 12, 9, 6, and 3) on the gas transfer coefficient kL, total interfacial area a, liquid residence time distribution, energy consumption, and turbulent hydrodynamics. Leading models for predicting kL and a are appraised with experimental data. The results show kL is governed by “entrance effects” due to Higbie penetration dominate at short distances below the micro-jet array, while turbulence dominates at intermediate distances, and finally terminal rise velocity dominates at large distances. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Integrated solvent and process design for continuous crystallization and solvent recycling using PC-SAFT AlChE J. (IF 2.836) Pub Date : 2017-10-27 Jiayuan Wang, Richard Lakerveld
Solvent usage is a major source of environmental waste in pharmaceutical industry. The current paradigm shift toward continuous manufacturing in pharmaceutical industry has renewed the interest in continuous crystallization, which offers the prospect of easy solvent recycling. However, the selection of solvents for an integrated crystallization processes is nontrivial due to the likely trade-off between optimal solvent properties for crystallization and solvent separation and recycling. A systematic approach for the simultaneous optimization of process conditions and solvent selection for continuous crystallization including solvent recycling is presented. A unified perturbed-chain statistical associating fluid theory model framework is applied to predict thermodynamic properties related to solubility and vapor-liquid equilibrium, which is integrated with a process model. A continuous mapping procedure is adopted to solve the optimization problem effectively. A case study based on continuous antisolvent crystallization of paracetamol with solvent separation via flash demonstrates the approach. © 2017 American Institute of Chemical Engineers AIChE J, 2017
A dynamic game theoretic framework for process plant competitive upgrade and production planning AlChE J. (IF 2.836) Pub Date : 2017-10-26 Philip Tominac, Vladimir Mahalec
A dynamic potential game theoretic production planning framework is presented in which production plants are treated as individual competing entities and competition occurs dynamically over a discrete finite time horizon. A modified Cournot oligopoly with sticky prices provides the basis for dynamic game theoretic competition in a multimarket nonlinear and nonconvex production planning model wherein market price adapts to a value that clears cumulative market supply. The framework is used to investigate a petrochemical refining scenario in which a single inefficient refiner faces elimination by its competitors; we demonstrate that there exist conditions under which the threatened refiner may upgrade itself to become competitive and escape the threat, or alternatively in which the threat of elimination is illegitimate and the refiner is effectively safe in the given market configuration. Globally optimal dynamic Nash equilibrium production trajectories are presented for each case. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Pressure drop through platinized titanium porous electrodes for cerium-based redox flow batteries AlChE J. (IF 2.836) Pub Date : 2017-10-25 Luis F. Arenas, Carlos Ponce de León, Frank C. Walsh
The pressure drop, , across a redox flow battery is linked to pumping costs and energy efficiency, making fluid properties of the electrolyte important in scale-up operations. The at diverse platinized titanium electrodes in Ce-based redox flow batteries is reported as a function of mean linear electrolyte velocity measured in a rectangular channel flow cell. Darcy's friction factor and permeability vs. Reynolds number are calculated. Average permeability values are: 7.10 × 10−4 cm2 for Pt/Ti mesh, 4.45 × 10−4 cm2 for Pt/Ti plate + turbulence promoters, 1.67 × 10−5 cm2 for Pt/Ti micromesh, and 1.31 × 10−6 cm2 for Pt/Ti felt. The electrochemical volumetric mass transport coefficient, , is provided as a function of . In the flow-by configuration, Pt/Ti felt combines high values with a relatively high , followed by Pt/Ti micromesh. Pt/Ti mesh and Pt/Ti plate gave a lower but poorer electrochemical performance. Implications for cell design are discussed. © 2017 American Institute of Chemical Engineers AIChE J, 00: 000–000, 2017
The promotion of Argon and water molecule on direct synthesis of H2O2 from H2 and O2 AlChE J. (IF 2.836) Pub Date : 2017-10-23 Yanhui Yi, Li Wang, Juan Yu, Hongchen Guo, Jialiang Zhang, Changgong Meng
Direct synthesis of hydrogen peroxide (H2O2) from H2 and O2 is an ideal route. H2/O2 plasma has a great potential for direct synthesis of high purity H2O2 without purification operations. However, low yield and high energy consumption limits the application of H2/O2 plasma in industry. This article reports that gas state Ar and H2O molecule serving as molecular catalysts promoted the synthesis of H2O2 from H2/O2/Ar/H2O plasma dramatically: the H2O2 yield was enhanced by 244% and the energy consumption was reduced by 70.9%. Ar not only increased the electron density, but also selectively accelerated the dissociation of H2 toward the formation of •HO2, a key intermediate species in H2O2 synthesis. While H2O facilitated the formation of •HO2 radical and stabilized it by forming a HO2•H2O complex, resulting in enhancing the H2O2 production. This single molecular catalysis reduced the cost of H2O2 synthesis more than 50%. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Synergistic effects of sulfur poisoning and gas diffusion on polarization loss in anodes of solid oxide fuel cells AlChE J. (IF 2.836) Pub Date : 2017-10-23 Yinghua Niu, Weiqiang Lv, Zhaohuan Wei, Weirong Huo, Weidong He
Poisoning effects of sulfur compounds on the performances of solid oxide fuel cells are non-trivial. However, the synergistic effects of gas diffusion, adsorption, desorption and reaction in anodes are typically neglected. In this work, an analytical model is derived to quantitatively evaluate the poisoning effects of H2S. The results show that sulfur poisoning correlates closely with inefficient gas diffusion for small anode pore size, small porosity/tortuosity, and low working temperatures. As compared with concentration polarization, H2S-diffusion-induced activation polarization in thin anodes with a large is detrimental, especially for low-temperature operations with a high H2S concentration and a low current density. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Detailed thermodynamics for analysis and design of Ranque-Hilsch vortex tubes AlChE J. (IF 2.836) Pub Date : 2017-10-20 John P. O'Connell
The Ranque-Hilsch vortex tube is a device for continuously separating an inlet pressurized fluid stream into two outlet streams of warmer and cooler temperatures at lower pressures, with no moving parts and without any heat or work effects. It has been applied to cool or heat small systems where refrigeration is impractical. Studies of the fluid mechanics inside the tube have not fully established the flow structure that provides the separation. Thermodynamic energy and entropy balances giving relations among properties and the relative amounts of the three fluid streams have been examined to determine consistency among measured data along with sensitivity of the phenomena to tube configuration, measurement error, and properties. The strong response of the temperature separation to small variations in entropy generation is shown to limit the possibilities for generalized prediction of vortex tube behavior. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Model based analysis of lithium batteries considering particle-size distribution AlChE J. (IF 2.836) Pub Date : 2017-10-20 E. R. Henquín, P. A. Aguirre
Performance of lithium ion batteries whose electrodes are composed of particles of different sizes is studied. Simplified model developed in (Henquín and Aguirre, AIChE J. 2015; 61:90–102) is extended and the simulations are compared with experiments from the literature so as to validate this new model. The differences in current density observed in particles of different sizes, which are in contact, depend on particle size and state of charge. Internal particle to particle discharge currents are observed during relaxation times. A parametric study of the applied current and particle sizes of electrodes is performed to evaluate cell performance, with emphasis on cell voltage and final capacity measurement. The evolution of reaction rates on the surface of electrode particles and their corresponding states of charge are depicted. An analysis of relaxation times in terms of cell voltage, current density, equilibrium potentials, and overpotentials is included. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Globally optimal linear approach for the design of process equipment: The case of air coolers AlChE J. (IF 2.836) Pub Date : 2017-10-20 Priscila A. Souza, André L. H. Costa, Miguel J. Bagajewicz
In a recent article, Gonçalves et al., introduced a linear and rigorous methodology for equipment design, in particular shell-and-tube heat exchanger. Here, we explore its application to air coolers, a problem that we solve globally for the first time. Because the approach is linear, results are globally optimal. The objective function is the total annualized cost. The constraints include the thermal and hydraulic modeling of the process stream flow in the tube bundle and the air flow through the finned surface. In addition, we worked on reducing computing time, through an analysis of different alternatives for the description of the original discrete variables organized in sets of binary variables. The performance of the proposed approach is illustrated through its comparison with an air cooler described in the literature. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Computer-aided design of ionic liquids as solvents for extractive desulfurization AlChE J. (IF 2.836) Pub Date : 2017-10-19 Zhen Song, Chenyue Zhang, Zhiwen Qi, Teng Zhou, Kai Sundmacher
Although ionic liquids (ILs) have been widely explored as solvents for extractive desulfurization (EDS) of fuel oils, systematic studying of the optimal design of ILs for this process is still scarce. The UNIFAC-IL model is extended first to describe the EDS system based on exhaustive experimental data. Then, based on the obtained UNIFAC-IL model and group contribution models for predicting the melting point and viscosity of ILs, a mixed-integer nonlinear programming (MINLP) problem is formulated for the purpose of computer-aided ionic liquid design (CAILD). The MINLP problem is solved to optimize the liquid-liquid extraction performance of ILs in a given multicomponent model EDS system, under consideration of constraints regarding the IL structure, thermodynamic and physical properties. The top five IL candidates preidentified from CAILD are further evaluated by means of process simulation using ASPEN Plus. Thereby, [C5MPy][C(CN)3] is identified as the most suitable solvent for EDS. © 2017 American Institute of Chemical Engineers AIChE J, 2017
The lift on a disc immersed in a rotating granular bed AlChE J. (IF 2.836) Pub Date : 2017-10-19 Bhanjan Debnath, K. Kesava Rao, Prabhu R. Nott
The discrete element method has been used to study the lift FL on a stationary disc immersed coaxially in a slowly rotating cylinder containing a granular material. In a tall granular column, FL rises with the immersion depth h, but reaches a roughly constant asymptote at large h, in agreement with previous studies. Our results indicate that the argument in some earlier studies that FL is proportional to the static stress gradient is incorrect. Instead, our results show that the lift is caused by an asymmetry in the dilation and shear rate between the regions above and below the disc. We argue that the cause of the lift is similar to that in fluids, namely that it arises as a result of the disturbance in the velocity and density fields around the body due to its motion relative to the granular bed. © 2017 American Institute of Chemical Engineers AIChE J, 2017
A thermodynamic investigation of adsorbate-adsorbate interactions of carbon dioxide on nanostructured carbons AlChE J. (IF 2.836) Pub Date : 2017-10-19 Maxwell Murialdo, Channing C. Ahn, Brent Fultz
A thermodynamic study of carbon dioxide adsorption on a zeolite-templated carbon (ZTC), a superactivated carbon (MSC-30), and an activated carbon (CNS-201) was carried out at temperatures from 241 to 478 K and pressures up to 5.5•106 Pa. Excess adsorption isotherms were fitted with generalized Langmuir-type equations, allowing the isosteric heats of adsorption and adsorbed-phase heat capacities to be obtained as a function of absolute adsorption. On MSC-30, a superactivated carbon, the isosteric heat of carbon dioxide adsorption increases with occupancy from 19 to 21 kJ•mol−1, before decreasing at high loading. This increase is attributed to attractive adsorbate–adsorbate intermolecular interactions as evidenced by the slope and magnitude of the increase in isosteric heat and the adsorbed-phase heat capacities. An analysis of carbon dioxide adsorption on ZTC indicates a high degree of binding-site homogeneity. A generalized Law of Corresponding States analysis indicates lower carbon dioxide adsorption than expected. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Enhanced solubility of hydrogen and carbon monoxide in propane- and propylene-expanded liquids AlChE J. (IF 2.836) Pub Date : 2017-10-16 Dupeng Liu, Raghunath V. Chaudhari, Bala Subramaniam
Conventional propylene hydroformylation occurs in a gas-expanded liquid phase. Reliable knowledge of the phase equilibria of such systems, including the solubilities of CO and H2 in propylene-expanded solvents, is essential for rational process design and development. Herein, we report the vapor–liquid equilibrium (VLE) data of the following ternary systems involving CO, H2, propane, propylene, toluene and NX-795 at temperatures from 70 to 90°C and pressures up to 1.5 MPa: propane/H2/toluene, propane/CO/toluene, propylene/H2/toluene, propylene/CO/toluene, propane/H2/NX-795, propane/CO/NX-795, propylene/H2/NX-795 and propylene/CO/NX-795. The solubilities of H2 and CO in either propane-expanded or propylene-expanded phases are observed to be greater than those in the neat organic solvents, by as high as 78% at 70°C and 1.5 MPa. By modeling the vapor and the liquid phases as pseudo-binary systems, the Peng-Robinson equation of state (PR-EoS) with van der Waals’ mixing rules and binary interaction parameters is shown to satisfactorily predict the experimental VLE data. © 2017 American Institute of Chemical Engineers AIChE J, 2017
A tribute to professor Roy Jackson: Intellectual leader, scholar, mentor AlChE J. (IF 2.836) Pub Date : 2017-10-16 Sankaran Sundaresan, Martin Feinberg, K. Kesava Rao, Prabhu R. Nott
This article, and this entire issue of the AIChE Journal, are meant to honor Professor Roy Jackson, whose contributions to chemical engineering have been profound and exceptionally broad. It is often said of Roy Jackson that few, if any, scholars have so deep a command of the full range of highly varied subjects that comprise the chemical engineering discipline. A hardly complete description of Professor Jackson's wide-ranging academic journey was attempted, both geographic (Cambridge, London, Edinburgh, Houston, Pasadena, Princeton) and intellectual (fluidization, mechanics of granular flows, process optimization, chemical reaction network theory, diffusion and reaction in porous catalyst pellets). The contributions of friends and colleagues appearing elsewhere in this issue are a testament to the broad range of subjects in which Professor Jackson had interest. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Packaging of yield stress fluids: Flow patterns AlChE J. (IF 2.836) Pub Date : 2017-10-16 Fanny Rasschaert, Emeline Talansier, Didier Blésès, Albert Magnin, Maud Lambert
The packaging or filling of a container with a non-Newtonian fluid without quality failures is a current issue encountered at the final step of industrial product processes. In this work, the container filling of viscoplastic fluids is studied using an experimental laboratory plant able to reproduce the industrial transitory packaging conditions. First, a Newtonian validation was conducted to compare and to confirm our setup results with available literature data. Second five flow patterns including dripping, jet buckling, mounding, planar filling, and air entrainment were observed and characterized for the viscoplastic container filling. Most of them present different types of instabilities during the filling, except the planar filling, which seems to be ideal according to industrial specifications. A flow pattern distribution depending on relevant dimensionless numbers was developed. Finally, flow pattern transition criteria are determined highlighting the influence of rheological and process parameters on container filling. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Iron-based electrochemically mediated atom transfer radical polymerization with tunable catalytic activity AlChE J. (IF 2.836) Pub Date : 2017-10-12 Jun-Kang Guo, Yin-Ning Zhou, Zheng-Hong Luo
An iron-based electrochemically mediated atom transfer radical polymerization (eATRP) system with tunable catalytic activity was developed by adjusting the supporting electrolyte formula. Kinetic behaviors of the systems using four typical supporting electrolytes (namely, TBABr, TBAPF6, TBACl, and TBABF4) were investigated. The type of anions was found to significantly affect the polymerization kinetics. TBAPF6 system proceeded with a considerable polymerization rate, whereas TBABr system showed better controllability. Importantly, the effect of supporting electrolyte on eATRP kinetics (mainly on ATRP equilibrium) was confirmed through kinetic modeling. Furthermore, the effect of catalyst loading using TBAPF6 as supporting electrolyte was also studied, and the results showed an uncontrolled polymerization for catalyst loading lower than 500 ppm. When hybrid supporting electrolyte (TBAPF6/TBABr) was used to tune catalytic activity, the polymerization slows down and the dispersity decreases with the increase in TBABr ratio. Polymers with a narrow molecular weight distribution (dispersity index <1.5) were obtained using 100% TBABr under 100 ppm catalyst. Besides, experimental attempt to improve the controllability by adding halogen donors was made, whereas the halogen donors just prolonged the induction period and no improvement was achieved. As a whole, a deeper understanding of kinetic studies is obtained by these controlled trials. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Mixing processes in the cavity transfer mixer: A thorough study AlChE J. (IF 2.836) Pub Date : 2017-10-11 Giovanna Grosso, Martien A. Hulsen, Arash Sarhangi Fard, Patrick D. Anderson, Andrew Overend
In many industrial applications, the quality of mixing between different materials is fundamental to guarantee the desired properties of products. However, properly modeling and understanding polymer mixing presents noticeable difficulties, because of the variety and complexity of the phenomena involved. This is also the case with the Cavity Transfer Mixer (CTM), an add-on to be mounted downstream of existing extruders, to improve distributive mixing. The present work proposes a fully three-dimensional model of the CTM: a finite element solver provides the transient velocity field, which is used in the mapping method implementation to compute the concentration field evolution and quantify mixing. Several simulations are run assessing the impact on mixing of geometrical and functioning parameters. In general, the number of cavities per row should be limited and the cavity size rather big to guarantee good mixing quality. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Issue information AlChE J. (IF 2.836) Pub Date : 2017-10-10
Understanding interfacial behaviors of isobutane alkylation with C4 olefin catalyzed by sulfuric acid or ionic liquids AlChE J. (IF 2.836) Pub Date : 2017-10-10 Weizhong Zheng, Huanying Wang, Wenxiu Xie, Ling Zhao, Weizhen Sun
The interfacial properties between the hydrocarbon phase including isobutane and 2-butene and the catalyst phase including H2SO4 or ionic liquids (ILs) with various alkyl chain length on their imidazolium cations have been investigated using molecular dynamics (MD) simulations. Compared to H2SO4, ILs can obviously improve the interfacial width, solubility and diffusion of reactants at the interface. The ILs with longer chains on cations exhibit a significant density enrichment of alkyl chains at the interface and tend to orient themselves with alkyl chains perpendicular to the interface and protruding into the reactant phase, which is in good agreement with the van der Waals energy between the reactants and cations of the ILs. The ILs with longer chains can improve the interfacial width and facilitate the dissolution of isobutane in catalyst phase, and thus exhibit a better catalytic performance, which agrees well with alkylation experiments in this work. © 2017 American Institute of Chemical Engineers AIChE J, 2017
A mesoscale model for diffusion and permeation of shale gas at geological depth AlChE J. (IF 2.836) Pub Date : 2017-10-10 Tiexin Tong, Dapeng Cao
The demand on energy is rising and shale gas as an important unconventional energy resource has received worldwide attention. It has shown a significant effect on the world's energy structure after the commercial exploitation of shale gas in the United States. Understanding diffusion and permeation of shale gas at geological depths is quite essential, but it cannot be described by traditional Fick or Knudsen diffusion models. In this work, we use dual control volume–grand canonical molecular dynamics method to systematically investigate the permeation process of shale gas in montmorillonite (i.e., a clay mineral of shale) at different geological depths. Results indicate that temperature, pressure, and pore size have an important effect on the permeability, and Knudsen equation cannot describe the permeability of shale gas. Accordingly, on the basis of these simulated data, we propose a new mesoscale model to describe the permeability of shale gas at geological depths. The new mesoscale model shows extensive applicability and can excellently reproduce the extrapolation testing data, and it satisfactorily bridges the gap between Knudsen diffusion and Fick diffusion, which provides important fundamentals for exploitation of shale gas. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Characterization of liquid–liquid mass transfer performance in a capillary microreactor system AlChE J. (IF 2.836) Pub Date : 2017-10-10 Guangxiao Li, Minjing Shang, Yang Song, Yuanhai Su
Liquid–liquid mass transfer performance in a capillary microreactor system was studied with an improved experimental method. Proper sampling modes were chosen to eliminate the effect of the sampling zone on the mass transfer characterization in capillary microreactor systems. The overall volumetric mass transfer coefficients in the T-micromixer and the capillary microreactor system were found to smoothly increase and then significantly increase with increasing the Reynolds number of two immiscible liquid phases. Other factors such as the inlet mode and inner diameter of T-micromixer, the capillary length, and the volumetric flux ratio of the aqueous phase to the organic phase affected the mass transfer performance in the T-micromixer and the capillary microreactor system. Furthermore, the contribution of the mass transfer in the T-micromixer zone to the capillary microreactor system was found to be in a range of 34–78% under the involved experimental conditions, which was emphasized in the proposed empirical correlations. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Multiple order model migration and optimal model selection for online glucose prediction in Type 1 diabetes AlChE J. (IF 2.836) Pub Date : 2017-10-06 Hong Zhao, Chunhui Zhao, Chengxia Yu, Eyal Dassau
To address the problem of insufficient available modeling data for glucose prediction, as well as modeling burden, a model migration method was developed in a previous work to quickly transfer an old model to a new subject using a simple parameter adjustment. However, this method, which is referred to as first-order model migration (FOMM), only considers a single order for each exogenous input, and may not produce an optimal model structure for accurate prediction. To overcome this problem, a multiple order model migration (MOMM) algorithm is proposed in this study. For different numbers of modeling samples, including glucose and two exogenous inputs (meal and insulin), the optimal modeling method may be different, and therefore, must be properly determined for each modeling scenario. First, the optimal model order is determined for each input and a multiple order prediction model is used. Then, a MOMM algorithm is developed based on particle swarm optimization (PSO) to simultaneously revise multiple parameters. The multiple order parameters of each input in the old model are quickly customized so that the revised model can be used for new subjects with desirable prediction accuracy. In particular, the influence of the number of modeling samples is analysed to check the applicability of different methods; this analysis determines the appropriate selection guidelines for the optimal model in response to different data sizes. The proposed method was evaluated using thirty in silico subjects and clinical data from seven individuals with Type 1 diabetes mellitus (DM). Overall, the MOMM algorithm presented superior results when the time period for collecting the samples was larger than 10 h (50 samples). In particular, the size of the modeling samples was separated into three different regions by evaluating the glucose prediction performance and the comparison between different algorithms for both in silico and clinical subjects. In Region I, the FOMM method achieves the best performance. In Region II, the MOMM method should be used and the prediction accuracy is superior in Region II in general. With enough samples (Region III), the subject-dependent model (SM) algorithm can be chosen. The MOMM algorithm is demonstrated to be able to transfer models for new subjects with improved model structure. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Catalytic combustion of SOFC stack flue gas over CuO and Mn2O3 supported by La0.8Sr0.2Mn0.67Cu0.33O3 perovskite AlChE J. (IF 2.836) Pub Date : 2017-10-06 Jae Gi Sung, Taewook Kim, Han Kyu Jung, Hwan Kim, Jong Shik Chung
An efficient oxidation catalyst was developed to increase the combustion efficiency of unreacted CO, H2, and CH4 in flue gas of solid oxide fuel cell (SOFC) stack. Amorphous Cu-Mn oxide catalyst (CuMnLa/Alumina) showed high catalytic activity, but significant degradation occurred due to phase transition to spinel structure at high temperatures (T > 650°C). La0.8Sr0.2Mn0.67Cu0.33O3 perovskite (LSMC(p)) supported CuO or Mn2O3 exhibited improved thermal stability than CuMnLa/Alumina catalyst. Especially in case of 50Mn/LSMC(p), after the catalyst was exposed to 800°C for 24 h, T50 of CO, H2 and CH4 was achieved at 170, 230, and 600°C, respectively. This result is much lower than that of CuMnLa/Alumina, which was exposed to the same condition. The high combustion efficiency is due to retention of the Cu2+-Mn3+ redox couple, and supply of lattice oxygen from LSMC(p), especially at high temperature. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Numerical prediction of dust capture efficiency of a centrifugal wet scrubber AlChE J. (IF 2.836) Pub Date : 2017-10-05 Hassan Ali, Floren Plaza, Anthony Mann
The gas, liquid, and dust particle behavior inside a centrifugal wet scrubber was simulated and a submodel for predicting its collection efficiency was developed that also takes in account the reduction in collection efficiency due to droplet carryover. Centrifugal wet scrubbers are used in many industries and deliver a high scrubbing efficiency at relatively low capital and operational costs. However, they often experience problems such as droplet carryover at high gas flows and reduced collection efficiency at low gas flows. An improved understanding of flow processes inside the scrubbers is needed to develop a better scrubber design. An experimental test facility was setup for this purpose which also served to validate the CFD modeling results. Ideal operating parameters for maximum scrubbing efficiency and minimum droplet carryover were identified. © 2017 American Institute of Chemical Engineers AIChE J, 2017
A multicontinuum approach for the problem of filtration of oily-water systems across thin flat membranes: II. Validation and examples AlChE J. (IF 2.836) Pub Date : 2017-10-05 Amgad Salama, Mohamed Zoubeik, Amr Henni
In this second part, a validation exercise is conducted to investigate the accuracy of the multicontinuum approach in estimating the permeation capacity of membranes used for the filtration of oily-water systems. Comparisons with the experimental works found in the literature reveals that the multicontinuum approach is quite accurate and show excellent match. Although the comparisons with the experimental data have been with respect to macroscopic integral variables, like the rejection capacity of membranes, the multicontinuum approach provides myriad information about the permeation process that have neither been presented nor even measured. Such detailed information has been highlighted in two examples. Details about which of the oil continua is going to be rejected or permeated through which porous membrane continuum are obtained. Furthermore, the flux of each oil continuum through every porous membrane continua is likewise obtained. These informations are then lumped to calculate the rejection capacity of membranes. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Anticancer drug delivery systems based on inorganic nanocarriers with fluorescent tracers AlChE J. (IF 2.836) Pub Date : 2017-10-04 Jiangli Fan, Suzhen Wang, Wen Sun, Shigang Guo, Yao Kang, Jianjun Du, Xiaojun Peng
In recent years, anticancer nanomedicines have mainly been developed for chemotherapy and combination therapy in which the main contributing anticancer drugs are delivered by deliberately designed nano drug delivery systems (nano-DDSs). Inorganic nanocarriers equipped with fluorescent tracers have become attractive tools to monitor the whole drug delivery and release processes. The fluorescence signal of tracers could be observed concomitantly with drug release, and thus, this strategy is of great benefit to evaluate the therapeutic effects of the nano-DDSs. This review provides a brief overview about three inorganic nanocarriers for drug delivery, including mesoporous silica, Fe3O4, and hydroxyapatite. We mainly discussed about their preparation processes, drug loading capacities, and the development of different fluorescent materials (fluorescent dyes, quantum dots, fluorescent macromolecules, and rare earth metals) hybridized to nanocarriers for real-time monitoring of drug release both in vitro and in vivo. This review also provides some recommendations for more in-depth research in future. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Reversible Cluster Aggregation and Growth Model for Graphene Suspensions AlChE J. (IF 2.836) Pub Date : 2017-09-30 Michail Alifierakis, Kevin S. Sallah, Ilhan A. Aksay, Jean H. Prévost
We present a reversible cluster aggregation model for 2-D macromolecules represented by line segments in 2-D; and, we use it to describe the aggregation process of functionalized graphene particles in an aqueous SDS surfactant solution. The model produces clusters with similar sizes and structures as a function of SDS concentration in agreement with experiments and predicts the existence of a critical surfactant concentration (Ccrit) beyond which thermodynamically stable graphene suspensions form. Around Ccrit, particles form dense clusters rapidly and sediment. At C ≪ Ccrit, a contiguous ramified network of graphene gel forms which also densifies, but at a slower rate, and sediments with time. The deaggregation–reaggregation mechanism of our model captures the restructuring of the large aggregates towards a graphite-like structure for the low SDS concentrations. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Spontaneous imbibition of liquids in glass-fiber wicks. Part I: Usefulness of a sharp-front approach AlChE J. (IF 2.836) Pub Date : 2017-09-28 M. Amin F. Zarandi, Krishna M. Pillai, Adam S. Kimmel
Spontaneous imbibition of a liquid into glass-fiber wicks is modeled using the single-phase Darcy's law after assuming a sharp flow-front marked by full saturation behind the front occurring in a transversely isotropic porous medium. An analytical expression for the height of the wicking flow-front as a function of time is tested through comprehensive experiments involving using eight different wicks and one oil as the wicking liquid. A good fit with experimental data is obtained without using any fitting parameter. The contact-angle is observed to be important for the success of the model—lower contact angle cases marked by higher capillary pressures were predicted the best. The proposed model provides a nice upper bound for all the wicks, thereby establishing its potential as a good tool to predict liquid absorption in glass-fiber wicks. However, the sharp-front model is unable to explain region of partial saturation, thereby necessitating the development of part II of this article series (Zarandi and Pillai, Spontaneous Imbibition of Liquid in Glass fiber wicks. Part II: Validation of a Diffuse-front Model. Submitted to AIChE journal 2017) using Richard's equation. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Flow dynamics in Taylor–Couette flow reactor with axial distribution of temperature AlChE J. (IF 2.836) Pub Date : 2017-09-28 Hayato Masuda, Saho Yoshida, Takafumi Horie, Naoto Ohmura, Makoto Shimoyamada
In this study, the flow dynamics of a Taylor–Couette flow with an axial distribution of temperature was experimentally investigated. The flow can be classified into three patterns based on the balance between the centrifugal force and the buoyancy. If the buoyancy is dominant, global heat convection is observed instead of Taylor vortices (Case I). When the buoyancy is comparable to the centrifugal force, the Taylor vortices and global heat convection appear alternately (Case II). If the centrifugal force is sufficiently high to suppress the buoyancy, stable Taylor vortices are observed (Case III). The characteristics of the mixing/diffusion are investigated by conducting a decolorization experiment on a passive tracer. In Case II, the tracer is rapidly decolorized in the presence of the global heat convection instead of the Taylor vortices. This result implies that the interaction between the centrifugal force and the buoyancy would induce an anomalous transport. © 2017 American Institute of Chemical Engineers AIChE J, 2017
A new insight into the stability of variable viscosity diffusive boundary layers in porous media under gravity field AlChE J. (IF 2.836) Pub Date : 2017-09-28 Nasser Sabet, Hassan Hassanzadeh, Jalal Abedi
We study the stability of gravitationally unstable transient diffusive boundary layers with variable viscosity in porous media. The previous studies characterize the effect of viscosity variation only in terms of viscosity contrast and generalize their findings. However, conclusions of different studies seem contradictory. Our results demonstrate that stability of diffusive fronts is governed by the boundary layer viscosity and not solely by the viscosity contrast. In other words, the use of viscosity contrast to ascertain the stability of the system cannot be generalized. Nonlinear simulations are conducted based on a finite difference scheme to validate the results of linear stability analysis for which the amplification theory is adopted. We also revisit other available scaling approaches used to characterize the effect of viscosity variation on the onset of convective dissolution and explain why previously made conclusions are not inclusive and sometimes appeared to be contradictory. A critical Rayleigh number is found to predict stability of Rayleigh-Darcy convection in a porous layer with variable viscosity. The results reveal that this critical value can differ highly from the conventional value of 4π2. © 2017 American Institute of Chemical Engineers AIChE J, 2017
A pinch-like targeting framework for systematic thermal process intensification AlChE J. (IF 2.836) Pub Date : 2017-09-28 Michael Baldea
The design of intensified systems remains an “Edisonian” effort, whereby new intensification schemes are the product of creativity rather than the result of applying systematic procedures. Under this motivation, this article presents a novel and systematic approach for identifying targets for thermal process intensification, defined as combining two or more heat sources and sinks present in a process flowsheet, possibly along with a thermal utility stream, in a single intensified device where heat exchange takes place. The targeting problem is formulated as a mixed-integer linear program. An extensive case study illustrating its application is presented. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Target bounds on reaction selectivity via Feinberg's CFSTR equivalence principle AlChE J. (IF 2.836) Pub Date : 2017-09-28 Jeffrey A. Frumkin, Michael F. Doherty
In this work, we show that the continuous flow stirred tank reactor (CFSTR) equivalence principle, developed by Feinberg and Ellison, can be used to obtain practical upper bounds on reaction selectivity for any chemistry of interest. The CFSTR equivalence principle allows one to explore the attainable reaction region by decomposing any arbitrary, steady-state reactor-mixer-separator system with total reaction volume V > 0 into a new system comprising CFSTRs (where is the number of linearly independent chemical reactions) with the same total reaction volume and a perfect separator system. This work further refines the allowable selectivities by incorporating capacity constraints into the CFSTR equivalence principle to prevent arbitrarily large recycle streams between the CFSTRs and the separators and infinitesimally small CFSTR conversions. These constraints provide practical upper bounds on reaction selectivities of chemistries completely independent of reactor design. We present the methodology and the results for a selection of realistic chemistries. © 2017 American Institute of Chemical Engineers AIChE J, 2017
On facilitated computation of mesoscopic behavior of reaction-diffusion systems AlChE J. (IF 2.836) Pub Date : 2017-09-28 Vu Tran, Doraiswami Ramkrishna
Various cellular and subcellular biological systems occur in the conditions where both reactions and diffusion take place. Since the concentration of species varies spatially, application of reaction-diffusion master equation has served as an effective method to handle these complicated systems; yet solving these equation incurs a large CPU time penalty. Counter to the traditional technique of generating many sample paths, this article introduces a method which combines Grima's effective rate equation approach (Grima, J Chem Phys. 2010;133:3) with a linear operator formalism for diffusion to capture averaged species behaviors. The formulation also shows correct results at various choices of compartment sizes, which have been found to be an important factor that can affect accuracy of the final predictions (Erban, Chapman, Phys Biol. 2009;6:4). It is shown that the method presented allows the computation of the mesoscopic average of reaction-diffusion systems at considerably accelerated rates (exceeding a thousand fold) over those based on sample path averages. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Surface layer modification of AEMs by infiltration and photo-cross-linking to induce monovalent selectivity AlChE J. (IF 2.836) Pub Date : 2017-09-28 Huimin Liu, Yuliang Jiang, Jincheng Ding, Wenhui Shi, Jiefeng Pan, Congjie Gao, Jiangnan Shen, Bart van der Bruggen
Surface modification of anion exchange membranes (AEMs) by attaching a negatively charged layer is the main method for preparing monovalent anion selective membranes. However, tremendous increase of membrane resistance and poor long-term stability of the modified membranes face great challenges. In this work, a photosensitive molecule (4,4-diazostilbene-2,2-disulfonic acid disodium salt [DAS]) was infiltrated into the membrane surface and immobilized in the structure by cross-linking under UV irradiation. This method introduced negative charge to the surface layer of the AEMs without increasing membrane thickness, leading to high performance membrane with high monovalent anion selectivity. The optimized membrane (D-5) shows the highest perm-selectivity of 11.21, which is superior to the commercial selective membrane Selemion® ASV and previously reported monovalent anion selective AEMs. Furthermore, the newly developed membrane exhibits excellent long-term stability, which can maintain constant selectivity during the 80 h ED experiment. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Dissipative particle dynamic simulation on the assembly and release of siRNA/polymer/gold nanoparticles based polyplex AlChE J. (IF 2.836) Pub Date : 2017-09-27 Xiaona Xie, Shouping Xu, Pihui Pi, Jiang Cheng, Xiufang Wen, Xuan Liu, Shengnian Wang
Dissipative particle dynamics simulation is used to reveal the loading/release of small interfering RNA (siRNA) in pH-sensitive polymers/gold nanoparticles (AuNPs) polyplex. The conformation dynamics of these polyplex at various Au/siRNA mass ratios, the original AuNPs sizes, polymer types, and pH values are simulated and compared to experimental results. At neutral conditions (pH = 7.4), spherical micelles with a multilayer structure are formed in siRNA/polyethyleneimine/cis-aconitic anhydride functionalized poly(allylamine)/polyethyleneimine/11-mercaptoundecanoic acid-gold nanoparticle (siRNA/PEI/PAH-Cit/PEI/MUA-AuNP) polyplex. Large polyplex are obtained with high Au/siRNA mass ratio and/or small original AuNPs size. The release dynamics of siRNA from AuNPs-polyplex systems were also simulated in the intracellular environment (pH = 5.0). A swelling-demicellization-releasing mechanism is followed while the release of siRNA is found much faster for polyplex involving charge-reversal PAH-Cit. These findings are qualitatively consistent with the experimental results and may provide valuable guidance in later design and optimization of delivery carriers for siRNA or other molecule probes. © 2017 American Institute of Chemical Engineers AIChE J, 2017
Coproduction of acetic acid and hydrogen/power from natural gas with zero carbon dioxide emissions AlChE J. (IF 2.836) Pub Date : 2017-09-26 Ibubeleye Somiari, Vasilios Manousiouthakis
A process plant flow sheet that coproduces acetic acid and hydrogen/power from natural gas with zero carbon dioxide emissions is developed. Two cases are explored: the production of acetic acid and hydrogen (Case 1) and the production of acetic acid and power (Case 2). This is realized by the selection of an appropriate reaction cluster whose sum results in the overall reaction that coproduces acetic acid and hydrogen/power. The concept of energetic self-sufficiency is introduced and it imposes constraints on the system defined in terms of the ratio of oxygen feed to acetic acid produced. Heat and power integration of the converged flow sheet reveals an operating range for each case that guarantees energetic self-sufficiency. Operating points are chosen to conduct a preliminary economic analysis and a carbon dioxide cost and performance metric calculation to quantify profitability and carbon capture potential of the overall process. © 2017 American Institute of Chemical Engineers AIChE J, 2017
A systematic method to synthesize all dividing wall columns for n-component separation—Part I AlChE J. (IF 2.836) Pub Date : 2017-09-26 Gautham Madenoor Ramapriya, Mohit Tawarmalani, Rakesh Agrawal
We present an easy-to-use step-wise procedure to synthesize an initial-dividing wall column (i-DWC) from any given n-component basic distillation column sequence or its thermally coupled derivative. The procedure to be used is dependent on the nature of the distillation column sequence that is to be converted into a DWC, and comprises of an intuitive set of steps that we demonstrate through examples. It is noteworthy that, even for a ternary distillation, 15 potentially useful DWCs, some of which had been missing from the literature, have now been identified. This work significantly expands the search space of useful DWCs to separate any given multicomponent mixture. © 2017 American Institute of Chemical Engineers AIChE J, 2017
A systematic method to synthesize all dividing wall columns for n-component separation: Part II AlChE J. (IF 2.836) Pub Date : 2017-09-26 Gautham Madenoor Ramapriya, Mohit Tawarmalani, Rakesh Agrawal
We present a simple rule that, for the first time, enables exhaustive enumeration of dividing wall columns (DWCs) corresponding to any given thermally coupled distillation column-configuration. With the successive application of our rule, every partition in a DWC can be extended all the way to the top and/or to the bottom of a column without losing thermodynamic equivalence to the original thermally coupled configuration. This leads to easy-to-operate DWCs with possible control/regulation of each and every vapor split by external means. As a result, we conclude that any given DWC can be transformed into a thermodynamically equivalent form that is easy-to-operate, and hence, there always exists at least one easy-to-operate DWC for any given thermally coupled distillation. Our method of enumerating and identifying easy-to-operate DWCs for an attractive thermally coupled configuration will contribute toward process intensification by providing ways to implement efficient and low-cost multicomponent distillations. © 2017 American Institute of Chemical Engineers AIChE J, 2017
A flowsheet model for the development of a continuous process for pharmaceutical tablets: An industrial perspective AlChE J. (IF 2.836) Pub Date : 2017-09-25 Salvador García-Muñoz, Adam Butterbaugh, Ian Leavesley, Leo Francis Manley, David Slade, Sean Bermingham
A dynamic model of a continuous direct compression process for pharmaceutical tablets is presented. The objective is to assess the impact of the variability from the feeder system on the concentration of drug in the powder in the feed frame of a tablet press. The model is based on principles of dispersed flow from the reaction engineering field. An estimability analysis was performed to understand the impact of the available measurements on the estimated parameters and suggest better ways to approach the parametrization. Predictions are successfully contrasted with experimental data. The model is used to produce residence time distributions at different process conditions and a graphical representation of the allowable range of disturbances in the feeders that can be mitigated by the process. The model was used in support of the method development for an online near infrared sensor. © 2017 American Institute of Chemical Engineers AIChE J, 2017
A theory of ultradeep hydrodesulfurization of diesel in stacked-bed reactors AlChE J. (IF 2.836) Pub Date : 2017-09-23 Teh C. Ho
Hydrodesulfurization catalysts have two types of active sites for hydrogenation and hydrogenolysis reactions. While hydrogenation sites are more active for desulfurizing refractory sulfur species, they are more susceptible to organonitrogen inhibition than hydrogenolysis sites. In contrast, hydrogenolysis sites are more resistant to organonitrogen inhibition but are less active for desulfurizing refractory sulfur species. This dichotomy is exploited to develop an ultradeep hydrodesulfurization stacked-bed reactor comprising two catalysts of different characteristics. The performance of such a catalyst system can be superior or inferior to that of either catalyst alone. A mathematical model is constructed to predict the optimum stacking configuration for maximum synergies between the two catalysts. The best configuration provides the precise environment for the catalysts to reach their full potentials, resulting in the smallest reactor and minimum hydrogen consumption. Model predictions are consistent with experimental results. A selectivity-activity diagram is developed for guiding the development of stacked-bed catalyst systems. © 2017 American Institute of Chemical Engineers AIChE J, 2017
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