Controllable fabrication and catalytic performance of nanosheet HZSM‐5 films by vertical secondary growth AlChE J. (IF 2.836) Pub Date : 2018-03-22 Yajie Tian; Hong Liu; Li Wang; Xiangwen Zhang; Guozhu Liu
Nanosheet HZSM‐5 film vertically grown on the substrate with the tailorable macro‐ and meso‐pores between the layers of nanosheets is hydrothermally synthesized by seed‐assisted secondary growth method. The as‐prepared nanosheet HZSM‐5 film exhibits reaction rate enhancement up to 312% in catalytic cracking of n‐dodecane as well as twice light olefins selectivity, ascribed to the better mass transfer of reactants in the hierarchical porous structure and the ultra‐thin b‐axis pores of nanosheets. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Direct numerical simulation of surfactant solution flow in the wide‐rib rectangular grooved channel AlChE J. (IF 2.836) Pub Date : 2018-03-22 Chonghai Huang; Dongjie Liu; Jinjia Wei; Bo Yu; Hongna Zhang; Jianping Cheng
The turbulent flow of surfactant solution in the wide‐rib rectangular grooved channels was studied by direct numerical simulation. Moreover, the variations of near‐wall streamwise vortices with time were discussed and the distributions of streamwise vortex radius, swirling strength and density were quantitatively investigated. It was found that the influence of microgrooves on the fluid mainly occurred within the buffer layer and microgrooves could induce numerous streamwise vortices with small size and swirling strength within the grooved valleys. The drag‐reducing enhancement mechanism of microgroove in the surfactant solution could be mainly considered as the competing results between the “restriction effect” and “tip effect” of microgroove, and the essential factor should be the numerous secondary streamwise vortices with small size and swirling strength within the grooved valleys. Furthermore, a predicted method for the optimal drag‐reducing size of microgroove was proposed, and the prediction values agreed well with the numerical results. © 2018 American Institute of Chemical Engineers AIChE J, 2018
The trail of perfumes AlChE J. (IF 2.836) Pub Date : 2018-03-22 Joana Pereira; Patrícia Costa; Maria C. Coimbra; Alírio E. Rodrigues
A methodology is proposed for modeling the diffusion of fragrances released from a moving source. First, we started with a one‐dimensional model considering molecular diffusion of α‐pinene in air as the only mass transport mechanism. The validation was performed in a diffusion tube, and a system was developed to move the scented source along the axial direction. Results showed that experimental data fitted well with the numerical simulation, suggesting this model as a valid tool to describe the trail of a fragrance released from a moving source for low Re of the order of 10. In the case of a person walking at the speed of 1.34 m/s in a room or corridor inside a building, three‐dimensional models are required and mass transport of the perfume to the surrounding air will be dominated by turbulent diffusion or eddy diffusion Dt which is two orders of magnitude higher than molecular diffusion. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Product design: A pricing framework accounting for product quality and consumer awareness AlChE J. (IF 2.836) Pub Date : 2018-03-22 Yuk C. Chan; Ka Y. Fung; Ka M. Ng
A systematic framework has been developed to determine the optimal price of a completely new (or existing but improved) chemical product that is being launched (or relaunched) in the presence of a competing product. It has four elements. The first is a pricing model derived from a utility function with constant elasticity of substitution. It accounts for consumers' awareness of the product under consideration and consumer preferences. The second is a set of relationships relating the consumer preferences and the relevant sales data available to a relaunched product to the parameters of the pricing model. In the absence of sales data for a completely new product, the third element is a set of heuristics for choosing a pricing strategy and estimates of the pricing model parameters. The optimal price is finally determined in a profit maximization problem subject to the market size as well as any other constraints. This pricing framework allows simultaneous optimization of product quality and price using product specifications as design variables. It is illustrated with an example on energy drinks. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Highly efficient methane reforming over a low‐loading Ru/γ‐Al2O3 catalyst in a Pd‐Ag membrane reactor AlChE J. (IF 2.836) Pub Date : 2018-02-01 David S. A. Simakov; Yuriy Román‐Leshkov
Natural gas can be reformed to syngas (CH4 + H2O = CO + 3H2), at temperatures above 850°C. Membrane catalytic reformers can provide high CH4 conversions at temperatures below 650°C, by separating H2 from the reactive mixture. Traditional Ni‐based catalysts suffer from low activity at low temperatures and deactivate rapidly by coking, particularly at low steam/carbon ratios. In this study, an ultralow loading (0.15 wt %) Ru/γ‐Al2O3 catalyst was implemented in a lab‐scale membrane reformer, using a supported 5μm Pd‐Ag film membrane. Methane conversions above 90% were achieved at 650°C, 8 bar, and H2O/CH4 = 2, 3 with contact times of ca. 10 s. The system generated up to 3.5 mol of ultrapure H2 per mol of CH4 fed, with a maximum power density of 0.9 kW/L. No significant deactivation was observed after 200 h time on stream, even when using low H2O:CH4 ratios. © 2018 American Institute of Chemical Engineers AIChE J, 2018
On the mechanisms of secondary flows in a gas vortex unit AlChE J. (IF 2.836) Pub Date : 2018-02-01 Kaustav Niyogi; Maria M. Torregrosa; Guy B. Marin; Geraldine J. Heynderickx; Vladimir N. Shtern
The hydrodynamics of secondary flow phenomena in a disc‐shaped gas vortex unit (GVU) is investigated using experimentally validated numerical simulations. The simulation using ANSYS FLUENT® v.14a reveals the development of a backflow region along the core of the central gas exhaust, and of a counterflow multivortex region in the bulk of the disc part of the unit. Under the tested conditions, the GVU flow is found to be highly spiraling in nature. Secondary flow phenomena develop as swirl becomes stronger. The backflow region develops first via the swirl‐decay mechanism in the exhaust line. Near‐wall jet formation in the boundary layers near the GVU end‐walls eventually results in flow reversal in the bulk of the unit. When the jets grow stronger the counterflow becomes multivortex. The simulation results are validated with experimental data obtained from Stereoscopic Particle Image Velocimetry and surface oil visualization measurements. © 2018 The Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers AIChE J, 2018
A square‐force cohesion model and its extraction from bulk measurements AlChE J. (IF 2.836) Pub Date : 2018-02-03 Peiyuan Liu; Casey Q. LaMarche; Kevin M. Kellogg; Christine M. Hrenya
Accurate modeling of interparticle forces in DEM is critical to predicting the rheology of cohesive particles. Rigorous cohesion models usually include parameters associated with particle surface roughness. However, both roughness measurement and its distillation into appropriate model parameters remain challenging. We propose a square‐force cohesion model, where cohesive force remains constant until a cutoff separation, above which cohesion vanishes. We demonstrate the square‐force model is a valid surrogate of more rigorous models. Specifically, when two parameters of square‐force model are chosen to match the two key quantities governing dense and dilute flows, namely maximum cohesive force and critical cohesive energy, respectively, DEM results using square‐force and more rigorous models show good agreement. For practical application of the square‐force model to lightly cohesive systems, a method is established to extract its parameters via defluidization, enabling determination of particle–particle cohesion from simpler bulk measurements than complicated and expensive scans on individual grains. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Ecosystems as unit operations for local techno‐ecological synergy: Integrated process design with treatment wetlands AlChE J. (IF 2.836) Pub Date : 2018-02-03 Varsha Gopalakrishnan; Bhavik R. Bakshi
Despite the critical importance of ecological systems for sustaining all chemical and manufacturing processes, process design has kept nature outside its system boundary. Recent efforts for sustainable process design aim to reduce environmental impact, but no design method considers the capacity of ecosystems to supply the goods and services that are needed to sustain a process. Overcoming this deficiency of conventional process design is essential to transform the chemical industry into an activity that respects ecological constraints and results in a net positive societal impact. As an important step toward meeting this goal, this work expands the boundary of process design to include ecosystems as unit operations in traditional design. Similar to tasks performed by conventional unit operations, ecological processes perform ecosystem functions resulting in goods and services required by the technological system. The goal behind designing integrated techno‐ecological process flowsheets is to balance the ecosystem service demand of technological systems with the ecosystem service supply of ecological systems. Systems are optimized to balance the demand and supply subject to unit operation level constraints of technological and ecological systems, and interactions between detailed process level variables and ecological variables are explored. The Techno‐Ecological Synergy (TES) Design method is developed and applied to a biofuel production system, considering ecosystem services like water provisioning and water quality regulation provided by wetland ecosystems. Comparing the integrated TES design with conventional techno‐centric design shows that TES design can result in net positive impact manufacturing: a case where the ecosystem service supply is equal to or exceeds the demand, with little or no compromises in process profitability. These results should encourage close integration between technological and ecological systems while designing sustainable processes, and identify many challenges for developing TES of individual processes and across the life cycle. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Continuous‐time formulations for the optimal planning of multiple refracture treatments in a shale gas well AlChE J. (IF 2.836) Pub Date : 2018-02-03 Diego C. Cafaro; Markus G. Drouven; Ignacio E. Grossmann
This work presents a continuous‐time optimization model for planning multiple refracture treatments over the lifespan of a shale gas well. We demonstrate that continuous‐time models can handle multiple restimulations very efficiently, increasing the net present value of the well development and refracturing plan. Well productivity is represented by a piecewise hyperbolic function, which accounts for when and how often the well has been refractured. We illustrate the application and effectiveness of the proposed approach for both the maximization of the total gas recovered and the maximization of the net present value. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Method to estimate uncertainty associated with parcel size in coarse discrete particle simulation AlChE J. (IF 2.836) Pub Date : 2018-02-03 Liqiang Lu; Sofiane Benyahia
Coarse grained particle methods significantly reduce the computation cost of large‐scale fluidized bed simulation by lumping many real particles into a computation parcel. This research provides a method to estimate the errors associated with parcel size in large‐scale fluidized bed simulations. This uncertainty is first quantified in small scale domains by comparing results of discrete particle method with that employing coarse parcels of different sizes. Then, this uncertainty is correlated with parcel size and simulation domains consisting of a simple homogeneous cooling system and more complex bubbling and circulating fluidized beds. These correlations allow us to accurately estimate the uncertainty in large‐scale fluidized beds based solely on data obtained in smaller systems. The ability to estimate model‐related uncertainty in larger systems makes this method relevant for industrial applications. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Metal nanoparticles in ionic liquid‐cosolvent biphasic systems as active catalysts for acetylene hydrochlorination AlChE J. (IF 2.836) Pub Date : 2018-02-03 Lifeng Yang; Qiwei Yang; Jingyi Hu; Zongbi Bao; Baogen Su; Zhiguo Zhang; Qilong Ren; Huabin Xing
Ionic liquid (IL)‐stabilized metal nanoparticles (NPs) have attracted increased attention as novel catalysts for various reactions due to their excellent stability and high activity. However, the high viscosity of ILs limits their applications. Here, for the first time, we reported an NPs@IL‐cosolvent liquid–liquid biphasic system for metal NPs catalysis. The NPs were successfully confined to IL phase, and abundant IL droplets containing NPs were generated under the reactant flow. The NPs@IL droplets served as microreactors for the catalysis; while the low viscosity organic phase enabled the rapid mass transfer of substances. The biphasic system exhibited improved performance for acetylene hydrochlorination than that of the pure IL system. An acetylene conversion of 98% and a selectivity of 99.5% were achieved along with a 90% decrease on IL usage. The tolerable gas hourly space velocity in the biphasic system for a satisfactory conversion was almost double that of the pure IL system. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Preparation of high‐performance zeolite NaA membranes in clear solution by adding SiO2 into Al2O3 hollow‐fiber precursor AlChE J. (IF 2.836) Pub Date : 2018-02-03 Nanke Ma; Rui Wang; Gaohong He; Zhengbao Wang
Zeolite NaA membranes were prepared in a clear synthesis solution without the aid of nanoseeds. To improve the properties of the membranes formed in a clear solution, alumina hollow fibers were fabricated by adding silica powder to the conventional spinning slurry, resulting in hollow fibers with a mullite phase. Prior to the membrane synthesis, the hollow fibers were pretreated by dipping in an aged synthesis solution diluted with isopropanol. Dense zeolite NaA membranes on mullite‐containing alumina hollow fibers were successfully obtained at 100°C for 2 h without the aid of nanoseeds. The membranes have a good pervaporation performance with a high flux of 10.8 kg m−2 h−1 and a separation factor of over 10,000. The abundant mullite‐phase hydroxyl groups on the support surface promote the nucleation and growth of zeolite crystals on the support, resulting in dense membranes. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Real‐time multivariable model predictive control for steam‐assisted gravity drainage AlChE J. (IF 2.836) Pub Date : 2018-02-06 Sagar N. Purkayastha; Ian D. Gates; Milana Trifkovic
Thermal recovery techniques, such as steam‐assisted gravity drainage (SAGD), are used to recover the majority of the crude bitumen, in Western Canada. However, suboptimal production techniques have led to a large carbon footprint and a subsequent search for more efficient extraction techniques, than open loop manual control. This article summarizes research on the comparison of performance of a novel multi‐input multioutput (MIMO) model predictive controller (MPC) with steam trap and oil rate controls with a multi‐input single output (MISO) MPC with only steam trap control. An appropriate system identification technique was also used for periodic model update in compliance with changing system behavior. The real‐time control study was made possible by establishing a bidirectional communication between computer modeling group STARSTM (virtual reservoir) and MATLAB (onsite controller) software. The results show a 171% improvement in oil recovery for the novel MIMO MPC over the MISO MPC. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Nonspherical particles in a pseudo‐2D fluidized bed: Experimental study AlChE J. (IF 2.836) Pub Date : 2018-02-06 Vinay V. Mahajan; Johan T. Padding; Tim M. J. Nijssen; Kay A. Buist; J. A. M. Kuipers
Fluidization is widely used in industries and has been extensively studied, both experimentally and theoretically, in the past. However, most of these studies focus on spherical particles while in practice granules are rarely spherical. Particle shape can have a significant effect on fluidization characteristics. It is therefore important to study the effect of particle shape on fluidization behavior in detail. In this study, experiments in pseudo‐2D fluidized beds are used to characterize the fluidization of spherocylindrical (rod‐like) Geldart D particles of aspect ratio 4. Pressure drop and optical measurement methods (Digital Image Analysis, Particle Image Velocimetry, Particle Tracking Velocimetry) are employed to measure bed height, particle orientation, particle circulation, stacking, and coordination number. The commonly used correlations to determine the pressure drop across a bed of nonspherical particles are compared to experiments. Experimental observations and measurements have shown that rod‐like particles are prone to interlocking and channeling behavior. Well above the minimum fluidization velocity, vigorous bubbling fluidization is observed, with groups of interlocked particles moving upwards, breaking up, being thrown high in the freeboard region and slowly raining down as dispersed phase. At high flowrates, a circulation pattern develops with particles moving up through the center and down at the walls. Particles tend to orient themselves along the flow direction. © 2018 The Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers AIChE J, 2018
Impact of diversity of morphological characteristics and Reynolds number on local hemodynamics in basilar aneurysms AlChE J. (IF 2.836) Pub Date : 2018-02-06 Marjan Rafat; Howard A. Stone; Debra T. Auguste; Mahsa Dabagh; Amanda Randles; Martin Heller; James D. Rabinov
Morphological and hemodynamic parameters have been suggested to affect the rupture of cerebral aneurysms, but detailed mechanisms of rupture are poorly understood. The purpose of our study is to determine criteria for predicting the risk of aneurysm rupture, which is critical for improved patient management. Existing aneurysm hemodynamics studies generally evaluate limited geometries or Reynolds numbers (Re), which are difficult to apply to a wide range of patient‐specific cases. Association between hemodynamic characteristics and morphology is focused. Several two‐dimensional (2D) and three‐dimensional (3D) idealized and physiological geometries is assessed to characterize the hemodynamic landscape between flow patterns. The impact of morphology on velocity and wall shear stress (WSS) profiles were evaluated. Slight changes in aneurysm geometry is found or Re result in significant changes in the hemodynamic and WSS profiles. Our systematic mapping and nondimensional analysis qualitatively identify hemodynamic conditions that may predispose aneurysms to rupture. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Hydrothermal pretreatment for deconstruction of plant cell wall: Part II. Effect on cellulose structure and bioconversion AlChE J. (IF 2.836) Pub Date : 2018-02-06 Kun Yao; Qinfeng Wu; Ran An; Wei Meng; Mingzhu Ding; Bingzhi Li; Yingjin Yuan
Influences of both ultrastructural modification of cellulose after hydrothermal pretreatment and products derived from lignin‐carbohydrate complex (LCC) on the subsequent enzymatic digestibility and fermentation were studied in this study. Under hydrothermal conditions, it was found that the rearrangement of hydrogen bonding pattern in cellulose via allomorph and conformational changes which was mainly severity‐dependent increased the numbers of water‐exposed glycosidic bond and the formation of “amorphous‐like” cellulose fibril facilitated enzymatic hydrolysis. Pseudo lignin, soluble xylo‐oligomers, phenols and degradation products from high severity impeded enzymatic digestion. LCC and phenols which were rich in pH‐controlled prehydrolyzate did not sufficiently inhibit yeast while furans and some aromatics which were rich in high‐severity prehydrolyzate might be potential inhibitors. Trade‐off phenomenon was solved by pH‐controlled operation and high yields in both glucose (83–93%) and xylose (75–80%) were simultaneously obtained. The final ethanol yield from cellulose to ethanol reached as high as 84–93%. © 2018 American Institute of Chemical Engineers AIChE J, 2018
A decomposition algorithm for simultaneous scheduling and control of CSP systems AlChE J. (IF 2.836) Pub Date : 2018-02-08 Alexander W. Dowling; Tian Zheng; Victor M. Zavala
We present a decomposition algorithm to perform simultaneous scheduling and control decisions in concentrated solar power (CSP) systems. Our algorithm is motivated by the need to determine optimal market participation strategies at multiple timescales. The decomposition scheme uses physical insights to create surrogate linear models that are embedded within a mixed‐integer linear scheduling layer to perform discrete (operational mode) decisions. The schedules are then validated for physical feasibility in a dynamic optimization layer that uses a continuous full‐resolution CSP model. The dynamic optimization layer updates the physical variables of the surrogate models to refine schedules. We demonstrate that performing this procedure recursively provides high‐quality solutions of the simultaneous scheduling and control problem. We exploit these capabilities to analyze different market participation strategies and to explore the influence of key design variables on revenue. Our results also indicate that using scheduling algorithms that neglect detailed dynamics significantly decreases market revenues. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Scalar mixing in anisotropic turbulent flow AlChE J. (IF 2.836) Pub Date : 2018-02-08 Quoc Nguyen; Dimitrios V. Papavassiliou
While turbulent mixing has been studied extensively in homogeneous turbulence, chemical engineering processes where mixing is important are anisotropic. In anisotropic turbulence, the interplay between convection and diffusion is critical. Flow in an infinite channel is utilized here with clouds of scalars released instantaneously at different distances from the wall and at Schmidt numbers between 0.7 and 2400. Qualitative and quantitative measures of mixing efficiency and intensity are defined and the dynamics of mixing are explored. It is found that molecular diffusivity can even hinder mixing in some instances, because it affects the development of the cloud of the released scalars from regions within the viscous wall layer. Another finding is that while one would expect mixing to occur mostly in the space between two points of release, considerable amount of mixing could take place outside of this region and closer to the wall. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Optimal design of batch‐storage network considering ownership AlChE J. (IF 2.836) Pub Date : 2018-02-09 Gyeongbeom Yi; Gintaras V. Reklaitis
This article develops a model of multi‐national supply chain activities, which incorporates currency storage units to manage currency flows associated with activities such as raw material procurement, processing, inventory control, transportation, and finished product sales. The core contribution of this model is that it facilitates the quantitative investigation of the influence of macroscopic economic factors such as ownership on supply chain operational decisions. The supply chain system is modeled as a batch‐storage network with recycle streams. The supply chain optimization problem is posed with the objective of minimizing the opportunity costs of annualized capital investments and currency/material inventories, while taking into account the benefit to stockholders in the numeraire currency. The major constraints on the optimization are that the material and currency storage units must not be depleted. A production and inventory analysis formulation (the periodic square wave model) provides useful expressions for the upper and lower bounds and for the average levels of the currency and material inventory holdings. The expressions for the Kuhn‐Tucker conditions of the optimization problem are reduced to a subproblem that allows development of analytical lot‐sizing equations. The lot sizes of procurement, production, transportation, and financial transactions can be determined in closed form once the average flow rates are known. The key result we obtain is that optimal value of the economic order quantity changes substantially with variation in ownership, thus showing quantitatively that ownership structure does impact plant operation. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Removal of yield‐stress fluids from pipework using water AlChE J. (IF 2.836) Pub Date : 2018-02-10 Ibrahim Palabiyik; Estefania Lopez‐Quiroga; Phillip T. Robbins; Kylee R. Goode; Peter J. Fryer
The emptying of product from process plant is a significant multiphase flow problem in food and personal care industries, controlling both product recovery, and cleaning time. Product and operational losses can be significant, especially with viscous products. It is necessary to maximize product recovery while minimizing cleaning time and effluent volume. The removal of a range of products from fully filled pipework using water has been characterized and monitored by weighing pipes at intervals and by inline turbidity probe. Data is presented for a range of products (toothpaste, hand cream, apple sauce, yoghurt, and shower gel) that have been cleaned from two pipe systems. The data can be fitted by a linear relationship between a dimensionless cleaning time, and the ratio of the product yield stress to the surface shear stress. The effect of pipe fittings is to reduce cleaning times, reflecting increased shear/energy dissipation in the pipe. © 2018 The Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers AIChE J, 2018
An evaluation of the impact of SG1 disproportionation and the addition of styrene in NMP of methyl methacrylate AlChE J. (IF 2.836) Pub Date : 2018-02-12 Stijn K. Fierens; Paul H. M. Van Steenberge; Florence Vermeire; Marie‐Françoise Reyniers; Guy B. Marin; Dagmar R. D'hooge
A kinetic modeling study is presented for batch nitroxide mediated polymerization (NMP) of methyl methacrylate (MMA; nitroxide: N‐tert‐butyl‐N‐[1‐diethylphosphono‐(2,2‐dimethylpropyl)] (SG1)). Arrhenius parameters for SG1 disproportionation (A = 1.4 107 L mol−1 s−1; Ea = 23 kJ mol−1) are reported, based on homopolymerization data accounting for unavoidable temperature variations with increasing time, that is, nonisothermicity. For low targeted chain lengths (TCLs ≤ 300), this nonisothermicity is also relevant for NMP of MMA with a small amount of styrene. Parameter tuning to copolymerization data confirms a penultimate monomer unit effect for activation (sa2 = ka12/ka22=6.7; 363 K; 1: MMA; 2: styrene). To obtain, for a broad TCL range (up to 800), a dispersity well below 1.3 an initial styrene mass fraction of ca. 10% is required. An interpretation of the comonomer incorporation is performed by calculating the fractions of activation‐growth‐deactivation cycles with a given amount of monomer units and the copolymer composition distribution. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Characterization of PVC‐soy protein nonwoven mats prepared by electrospinning AlChE J. (IF 2.836) Pub Date : 2018-02-12 HeeRan Hong; Zachary C. Tronstad; Yi Yang; Matthew D. Green
Poly(vinyl chloride) (PVC) is one of the most common polymers used in the water treatment industry due to outstanding hydrophobicity and mechanical strength. Generating eco‐friendly membranes derived from natural polymers has gained attention, particularly for water purification and producing potable water. In this study, nonwoven mats were prepared by electrospinning polymer solutions. Mats with a tailorable hydrophilicity were prepared by electrospinning solution mixtures containing PVC and an eco‐friendly, hydrophilic natural polymer: soy protein. As the viscosity of the solution decreased, the average fiber diameter, and average pore surface area reduced. However, when the PVC concentration remained constant and the soy protein concentration increased, the viscosity decreased and average fiber diameter became reduced, while the average pore diameter remained relatively constant. The mats with volumetric ratios of PVC:soy protein of 85:15 and 80:20 displayed optimal characteristics suitable for mat fabrication based on the fiber diameter and average pore surface area. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Universal correlation for gas hydrates suppression temperature of inhibited systems: II. Mixed salts and structure type AlChE J. (IF 2.836) Pub Date : 2018-02-12 Yue Hu; Bo Ram Lee; Amadeu K. Sum
The first paper of this study discussed the development of the Hu‐Lee‐Sum (HLS) correlation and demonstrated the generality and universality of the correlation to predict structure I hydrates suppression temperature for any single salt system. However, natural gas commonly forms structure II hydrates, and mixed salts naturally occur in oil and gas production. Therefore, reliable prediction of structure II hydrates suppression temperature in presence of mixed salts over a wide range of pressure is considerably important. The contribution for each salt in salt mixtures is accounted for in the effective mole fraction to extend the HLS correlation for mixed salts systems. Moreover, a parameter (α) is introduced to account for the effect of hydrate structure on the hydrate suppression temperature. Herein, the HLS correlation is further shown to be universal and reliable to predict the hydrate suppression temperature for more complicated systems for mixed gases and mixed salts. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Predicting NRTL binary interaction parameters from molecular simulations AlChE J. (IF 2.836) Pub Date : 2018-02-14 Ashwin Ravichandran; Rajesh Khare; Chau‐Chyun Chen
A predictive approach for calculating the binary interaction parameters ( ) of the nonrandom two liquid (NRTL) local composition model is developed, combining molecular simulations with the two‐fluid theory. The binary interaction parameters are determined for the following three sets of model binary mixtures: water + methanol, methanol + methyl acrylate, and water + methyl acrylate. For each binary mixture, the interaction parameters are expressed in terms of molecular size and strength of interactions, which are in turn, calculated from molecular simulations. We show that the binary interaction parameters determined from simulations are in qualitative agreement with those estimated from regressing experimental data. The major factors that determine the binary interaction parameters are outlined based on simple thermodynamic arguments for each mixture. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Supra‐monolayer coverages on small metal clusters and their effects on H2 chemisorption particle size estimates AlChE J. (IF 2.836) Pub Date : 2018-02-14 Abdulrahman S. Almithn; David D. Hibbitts
H2 chemisorption measurements are used to estimate the size of supported metal particles, often using a hydrogen‐to‐surface‐metal stoichiometry of unity. This technique is most useful for small particles whose sizes are difficult to estimate through electron microscopy or X‐ray diffraction. Undercoordinated metal atoms at the edges and corners of particles, however, make up large fractions of small metal clusters, and can accommodate multiple hydrogen atoms leading to coverages which exceed 1 ML (supra‐monolayer). Density functional theory was used to calculate hydrogen adsorption energies on Pt and Ir particles (38–586 atoms, 0.8–2.4 nm) at high coverages (≤3.63 ML). Calculated differential binding energies confirm that Pt and Ir (111) single‐crystal surfaces saturate at 1 ML; however, Pt and Ir clusters saturate at supra‐monolayer coverages as large as 2.9 ML. Correlations between particle size and saturation coverage are provided that improve particle size estimates from H2 chemisorption for Pt‐group metals. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Dynamics of pristine graphite and graphene at an air‐water interface AlChE J. (IF 2.836) Pub Date : 2018-02-16 David M. Goggin; Joseph R. Samaniuk
We examine the dynamics and morphology of graphitic films at an air‐water interface in a Langmuir trough by varying interfacial surface coverage, by observing in situ interfacial structure, and by characterizing interfacial structure of depositions on mica substrates. In situ interfacial structure is visualized with Brewster angle microscopy and depositions of the interface are characterized with atomic force microscopy and field‐emission scanning electron microscopy. Compression/expansion curves exhibit a monotonically decreasing surface pressure between consecutive compressions, but demonstrate a “rebound” of hysteretic behavior when the interface is allowed to relax between consecutive compressions. This dynamic results from a competition between consolidation of the interface via agglomeration of particles or the stacking of graphene sheets, and a thermally‐driven relaxation where nanometer‐thick particles are able to overcome capillary interactions. These results are especially relevant to applications where functional films with controlled conductivity and transparency may be produced via liquid‐phase deposition methods. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Microfluidic synthesis of elastomeric microparticles: A case study in catalysis of palladium‐mediated cross‐coupling AlChE J. (IF 2.836) Pub Date : 2018-02-17 Jeffrey A. Bennett; Andrew J. Kristof; Vishal Vasudevan; Jan Genzer; Jiri Srogl; Milad Abolhasani
Palladium (Pd)‐loaded poly‐hydromethylsiloxane (PHMS) microparticles of tunable size and elasticity are prepared in a capillary‐based coaxial flow‐focusing microfluidic device constructed using off‐the‐shelf components. Simultaneous droplet formation and chemical cross‐linking processes are performed by tuning the dilution of the cross‐linking catalyst in the annular flow of the microreactor, resulting in PHMS microparticles synthesized in a single step. The size of the elastomeric microparticles can be tuned by adjusting the flow rate ratio of the polymer and cross‐linker mixture to water, while the elasticity can be tuned by the polymer to cross‐linker ratio as well as the flow rate ratio of the polymer mixture to cross‐linking catalyst mixture. Microparticle elasticity is characterized by the degree of solvent uptake. Application of the synthesized PHMS microparticles in organic synthesis is demonstrated by producing monodispersed Pd‐loaded microparticles and utilizing them as microreaction vessels for continuous Suzuki‐Miyaura cross‐coupling in a Pd‐loaded microparticle‐packed bed reactor. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Hydrothermal pretreatment for deconstruction of plant cell wall: Part I. Effect on lignin‐carbohydrate complex AlChE J. (IF 2.836) Pub Date : 2018-02-17 Kun Yao; Qinfeng Wu; Ran An; Wei Meng; Mingzhu Ding; Bingzhi Li; Yingjin Yuan
Hydrothermal pretreatment with characteristic of green chemistry is considered as promising technology in the biorefineries. Using material balance and multiscale characterization techniques, the effects of process severity factor and pH on chemical behaviors of lignin‐carbohydrate complex (LCC) were systematically studied. During pretreatment, spatial relocation of lignin with covalently linked xylan facilitated local cell wall collapse. A kinetic model was established to describe the behaviors of LCC components changing with severity factor. It was found that cleavage of LCC linkage was strongly pH‐dependent. Low pH dominated cleavage of coumarate/ferulate esters which cross‐linking lignin with xylan and repolymerization of aromatics either from furfural or lignin into polymers such as pseudo lignin, while high pH which allowed the existence of soluble LCC dominated the aldol condensations from xylose to aromatics and depolymerizaton of lignin to phenols. Detailed reaction pathways concerned with LCC were finally established to elucidate the underlying mechanism. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Reduction in greenhouse water usage through inlet CO2 enrichment AlChE J. (IF 2.836) Pub Date : 2018-02-20 Neil Stacey; James Fox; Diane Hildebrandt
Agriculture is mankind's single largest usage of water, comprising 70% of all water usage. Optimizing water usage in agriculture is therefore crucial to ensuring global water security. A greenhouse is quantitatively modeled as a bioreactor and it is shown that the bulk of the water supplied to a conventionally aspirated greenhouse is lost in the form of humidity. This implies that evaporative losses in agriculture comprise a clear majority of mankind's total water consumption. Inlet CO2 enrichment using existing membrane materials can minimize the air feed rate required to supply adequate CO2 for photosynthesis, thereby mitigating evaporative losses. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Heat/mass transfer from a neutrally buoyant sphere by mixed natural and forced convection in a simple shear flow AlChE J. (IF 2.836) Pub Date : 2018-02-20 Bing Yuan; Chao Yang; Zai‐Sha Mao; Xiaolong Yin; Donald L. Koch
Building on the work of Yang et al. in 2011, the finite difference method and the Boussinesq approximation were applied to solve the time‐dependent Navier‐Stokes, convection diffusion and continuity equations in spherical coordinates. An idealized condition, the mass transfer from a neutrally buoyant sphere in a horizontal simple shear flow with natural convection was numerically simulated for the first time in this work. In the hybrid transfer case, the outwardly spiraling streamlines enhanced the transfer process, but the counter‐gravity spiraling streamlines near the sphere hindered the natural convection and the spatial dilution action weakened the natural convection transfer process. These competing effects led to nonmonotonic behavior of the Nusselt number with Reynolds number. Results from these previously undocumented cases were summarized into correlations for predicting Nusselt numbers at finite Reynolds numbers for various Grashof and Prandtl numbers. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Hydrodynamics in a pilot‐scale cocurrent trickle‐bed reactor at low gas velocities AlChE J. (IF 2.836) Pub Date : 2018-02-22 Puneet Kawatra; Srikanth Panyaram; Benjamin A. Wilhite
Hydrodynamic data obtained from laboratory‐scale trickle‐beds often fail to accurately represent industrial‐scale systems with high packing aspect ratios and column‐to‐particle diameter ratios. In this study, pressure drop, liquid holdup, and flow regime transition were investigated in a pilot‐scale trickle‐bed column of 33 cm ID and 2.45 m bed height packed with 1.6 mm × 8.4 ± 1.4 mm cylindrical extrudates for air‐water mass superficial velocities of 0.0023 – 0.094 kg/m2s and 4.5 – 45 kg/m2s, respectively, at atmospheric pressure. Significant deviation was observed from pressure drop and liquid holdup correlations at low liquid flows rates, corresponding to gravity‐driven flow limit. Likewise, liquid saturation is overestimated by correlations at high liquid flow rates, owing to significantly reduced wall effects. Lastly, trickle‐to‐dispersed bubble flow and trickle‐to‐pulsing flow regime transitions are reported using a combination of visual observations and analysis of the magnitude of local pressure fluctuations within the column. © 2018 American Institute of Chemical Engineers AIChE J, 2018
A Numerical model of exchange chromatography through 3‐D lattice structures AlChE J. (IF 2.836) Pub Date : 2018-02-22 Maher Salloum; David B. Robinson
Rapid progress in the development of additive manufacturing technologies is opening new opportunities to fabricate structures that control mass transport in three dimensions across a broad range of length scales. We describe a structure that can be fabricated by newly available commercial 3‐D printers. It contains an array of regular three‐dimensional flow paths that are in intimate contact with a solid phase, and thoroughly shuffle material among the paths. We implement a chemically reacting flow model to study its behavior as an exchange chromatography column, and compare it to an array of 1‐D flow paths that resemble more traditional honeycomb monoliths. A reaction front moves through the columns and then elutes. The front is sharper at all flow rates for the structure with three‐dimensional flow paths, and this structure is more robust to channel width defects than the 1‐D array. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Bilevel and parallel programing‐based operability approaches for process intensification and modularity AlChE J. (IF 2.836) Pub Date : 2018-02-22 Juan C. Carrasco; Fernando V. Lima
Process operability emerged in the last decades as a powerful tool for the design and control of chemical processes. Recent efforts in operability have been focused on the calculation of the desired input set for process design and intensification of natural gas utilization applications described by nonlinear models. However, there is still a gap in terms of problem dimensionality that nonlinear operability methods can handle. To fill this gap, in this article, the incorporation of bilevel and parallel programing approaches into classical process operability concepts is discussed. Results on the implementation of the proposed method show a reduction in computational time up to two orders of magnitude, when compared to the original results without parallelization. These results could be extrapolated for use in a supercomputer as presented in the computational time analysis performed. In terms of intensification, the proposed approach can produce a natural gas combined cycle plant modular design with a dramatic reduction in size, from the original 400 to 0.11 MW, while still keeping the high net plant efficiency. This approach thus provides a computationally efficient framework for process intensification of high‐dimensional nonlinear energy systems toward modularity. The proposed approach also enables the verification of a modular design and conditions that can be obtained according to economic and physical constraints associated with a specific natural gas well production. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Concentrated slurry formation via drawdown and incorporation of wettable solids in a mechanically agitated vessel AlChE J. (IF 2.836) Pub Date : 2018-02-23 Thomas Wood; Mark J. H. Simmons; Richard W. Greenwood; E. Hugh Stitt
This article describes the effect of vessel configurations on the drawdown and incorporation of floating solids to prepare concentrated alumina slurries in stirred tanks. The impeller speed and power draw required to incorporate all dry powder within four seconds, NJI and PJI, are used to evaluate incorporation performance. The effect of impeller type is assessed, with pitched blade impellers proving to be the most effective across the full range of solid contents considered. At higher solids content the energy demand is shown to increase dramatically, with a 100‐fold increase in energy required to add 1% w/w more solid at 50% by weight compared to 1% by weight. Analysis of impeller power numbers show this coincides with a transition from constant power number to a region where power number increases linearly with decreasing Reynolds number. Contrary to studies at low solids content, the presence of baffles is shown to inhibit drawdown. © 2018 The Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers AIChE J, 2018
Experimental and numerical investigation of structure and hydrodynamics in packed beds of spherical particles AlChE J. (IF 2.836) Pub Date : 2018-02-23 P. Lovreglio; S. Das; K. A. Buist; E. A. J. F. Peters; L. Pel; J. A. M. Kuipers
In chemical industry, flows often occur in nontransparent equipment, for example in steel pipelines and vessels. Magnetic resonance imaging is a suitable approach to visualize the flow, which cannot be performed with classical optical techniques, and obtain quantitative data in such cases. It is therefore a unique tool to noninvasively study whole‐field porosity and velocity distributions in opaque single‐phase porous media flow. In this article, experimental results obtained with this technique, applied to the study of structure and hydrodynamics in packed beds of spherical particles, are shown and compared with detailed computational fluid dynamics simulations performed with an in‐house numerical code based on an immersed boundary method‐direct numerical simulation approach. Pressure drop and the radial profiles of porosity and axial velocity of the fluid for three packed beds of spheres with different sizes were evaluated, both experimentally and numerically, in order to compare the two approaches. © 2018 The Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers AIChE J, 2018
Experimental data for code validation: Horizontal air jets in a semicircular fluidized bed of Geldart Group D particles AlChE J. (IF 2.836) Pub Date : 2018-02-23 William D. Fullmer; Casey Q. LaMarche; Allan Issangya; Peiyuan Liu; Ray Cocco; Christine M. Hrenya
Experiments were conducted with 6 mm plastic beads (Geldart Group D) in a semi‐circular, gas‐fluidized bed with side jets. Attention was paid to particle characterization and bed measurements, making the resulting dataset ideal for CFD‐DEM validation and uncertainty quantification. The bed was operated slightly above and below the minimum fluidization velocity, with additional fluidization provided by one of two pairs of opposing jets located above the distributor near the flat, front face of the unit. Care is taken to report material properties and bed conditions with either measured distribution functions or uncertainty bounds. High‐speed video imaging and particle tracking velocimetry are used to extract bin‐averaged velocity profiles, which are used to extract jet penetration depths. The time‐averaged mean and standard deviation of the bed pressure drop is also reported. Finally, the lower jets are also inserted into the bed until the opposing jets merge to form a spout‐like pattern. © 2018 American Institute of Chemical Engineers AIChE J, 2018
The effect of particle rotation on the motion and rejection of capsular particles in slit pores AlChE J. (IF 2.836) Pub Date : 2018-02-26 Armin Delavari; Basavaraju Agasanapura; Ruth E. Baltus
The results from a two‐dimensional computational model describing the motion of capsule‐shaped particles in a slit pore under small Re conditions are reported. Average particle velocities and particle rejection coefficients were determined for capsules with aspect ratios of 2 and 4. Two different approaches were used to characterize particle rotation and hydrodynamic particle‐pore wall interactions. In one approach, all sterically allowed particle orientation angles had equal probability, i.e., infinite rotational diffusion was assumed. In the second approach, particles were allowed to freely rotate in the pore; particle orientations were dictated by hydrodynamic forces acting on the particle surface and rotational particle diffusion was neglected. Minimal lateral migration across the pore was observed for the freely rotating particles. Although particle alignment was observed for the freely rotating particles, rejections predicted from the two approaches were found to be in close agreement. © 2018 American Institute of Chemical Engineers AIChE J, 2018
An experimental and modeling study of vacuum residue upgrading in supercritical water AlChE J. (IF 2.836) Pub Date : 2018-02-27 Soumya Gudiyella; Lawrence Lai; Isaiah H. Borne; Geoffrey A. Tompsett; Michael T. Timko; Ki‐Hyouk Choi; Mohnnad H. Alabsi; William H. Green
Arabian Heavy crude oil was fractionated into distillate and vacuum residue fractions. The vacuum residue fraction was treated with supercritical water (SCW) at 450°C in a batch reactor for 15–90 min. The main products were gas, coke, and upgraded vacuum residue; the upgraded residue consisted of gasoline, diesel, and vacuum gas oil range components. The molecular composition of gas and upgraded vacuum residue was analyzed using gas chromatography (GC, GC × GC). SCW treatment converted higher carbon number aliphatics (≥C21) and long‐chain (≥C5) alkyl aromatic compounds into C1C20 aliphatics, C1C10 alkylaromatics, and multiringed species. The concentrations of gasoline and diesel range compounds were greater in the upgraded product, compared to the feed. A first‐order, five lump reaction network was developed to fit the yields of gas, coke, diesel, and gasoline range components obtained from SCW upgrading of vacuum residue. Distillation of crude oil followed by SCW treatment of the heavy fraction approximately doubled the yield of chemicals, gasoline, and diesel, while forming significantly less coke than conventional upgrading methods. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Relative time‐averaged gain array (RTAGA) for distributed control‐oriented network decomposition AlChE J. (IF 2.836) Pub Date : 2018-02-28 Wentao Tang; Davood Babaei Pourkargar; Prodromos Daoutidis
Input‐output partitioning for decentralized control has been studied extensively using various methods, including those based on relative gains and those based on relative degrees and sensitivities. These two concepts are characterizations of long‐time and short‐time input‐output response, respectively. A unifying new input‐output interaction measure, called relative time‐averaged gain, which characterizes the input‐output interactions during a time scale of interest for linear time‐invariant systems is proposed. This measure is used as a basis for community detection in the input‐output bipartite graph of a process network to produce subnetworks whose responses are weakly coupled in the time scale of interest. As such, the resulting decomposition accounts for both response characteristics and the network topology, and can be used efficiently for distributed control architecture design. In a case study, the proposed decomposition is applied to the distributed model predictive control of a reactor‐separator benchmark process. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Bubble‐separation dynamics in a planar cyclone: Experiments and CFD simulations AlChE J. (IF 2.836) Pub Date : 2018-03-01 Xiao Xu; Xiao‐Ling Ge; Yun‐Dong Qian; Hua‐Lin Wang; Qiang Yang
A planar cyclone is designed for visualizing bubbles in the cross‐section of a degassing hydrocyclone. The pressure distribution is studied through a series of experiments and Reynolds stress model simulations. The velocity distribution of the planar cyclone mostly exhibits the quasi‐forced vortex zone and boundary layer zone. The bubble dynamics are simulated using both Euler‐Euler and Euler‐Lagrange approaches, and the output is compared with the imaging results. The Euler‐Euler simulation provides more accurate predictions of the bubble trajectory. The histograms of residence time and traveling distance given by the Euler‐Lagrange approach exhibit a reasonably regular pattern. With higher values of the inlet Reynolds number, stronger forces acting on the bubbles lead to a decreased but more uniform residence time. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Carbon dioxide chemical absorption by solvents based on diamine and amines blend AlChE J. (IF 2.836) Pub Date : 2018-03-01 Alberto Cachaza; Diego Gómez‐Díaz; Adrián Montáns; José M. Navaza; Antonio Rumbo
Present work includes research about the influence of the type of amino group using one or two amine molecules on carbon dioxide chemical absorption using aqueous solutions of alkanolamines and diamines. A comparison of chemical absorption processes using aqueous solutions of two individual diamines (3‐(dimethylamino)propan‐1‐amine and 1,3‐diaminopropane) and a mixture of amines (3‐amino‐1‐propanol and 3‐(dimethylamino)propan‐1‐ol) is reported including absorption rate curves, carbon dioxide loading, reaction mechanism or solvent regeneration to obtain useful information about the quality of each solvent for carbon dioxide separation. In general, amines blend of 3‐amino‐1‐propanol and 3‐dimethylamino‐1‐propanol, have shown a better behavior than their individual amines. Diamines and mainly 3‐dimethylamino propylamine that presents primary and tertiary amine groups in its structure, have led similar results. After these studies, 3‐dimethylamino propylamine, can be considered an appropriated amine to industrial carbon dioxide absorption process. © 2018 American Institute of Chemical Engineers AIChE J, 2018
The role of wettability of nonideal nozzle plate: From drop‐on‐demand droplet jetting to impact on solid substrate AlChE J. (IF 2.836) Pub Date : 2018-03-03 Lei Zhang; Tao Ku; Jingsong Jia; Xiaoding Cheng
The dynamics of drop‐on‐demand (DoD) droplet formation and subsequently impact on the solid substrate are investigated using a three‐dimensional (3‐D) multirelaxation‐time (MRT) pseudopotential lattice Boltzmann (LB) model. The wettability of nonideal nozzle plate and solid substrate is modeled by a geometric scheme within the LB framework. The dynamics of droplet formation are explored in a range of the inverse of Ohnesorge number , , and , and the Reynolds number , , and . For , no satellite droplet is observed and the wettability of nozzle plate greatly influences the velocity and length of jetting fluids. For , the filament breakup and recombination are observed. The moment of filament breakup is delayed with advancing contact angle increasing. For with , the primary and satellite droplets could not be recombined with and which agree with the literature. Whereas with , the recombination occurs. The dynamics of subsequent oscillating droplet impact on the substrate are similar to that of equilibrium droplet which could obtain high‐resolution printed features. Consequently, considering with large and numbers, the printable range could be extended which could help increase the printing frequency and boost the production outputs of inkjet printing. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Continuous manufacturing: Is the process mean stationary? AlChE J. (IF 2.836) Pub Date : 2018-03-03 Levente L. Simon
The statistical framework to systematically detect mean stationarity in the context of continuous manufacturing is described in this article. The methods presented in this article use econometric and financial time‐series analysis concepts in the form of unit‐root and stationarity hypothesis tests. The tests under discussion are the augmented Dickey‐Fuller, Philips‐Perron, Leybourne‐McCabe, and Kwiatkowski‐Phillips‐Schmidt‐Shin. These hypothesis tests are evaluated on data generated by a focused‐beam reflectance measurement sensor implemented on‐line in a continuous plug‐flow crystallizer. This contribution has shown that the hypothesis tests can be used to detect steady‐state conditions on‐line in a plug‐flow crystallizer. Furthermore, this econometric framework can be used as a mean stationarity “certificate” of collected samples to document that the process was mean stationary during the sampling. The statistical framework described in this article can be applied to any continuously operated unit operation or sensor measurement.
Theoretical and computational comparison of continuous‐time process scheduling models for adjustable robust optimization AlChE J. (IF 2.836) Pub Date : 2018-03-07 Nikolaos H. Lappas; Chrysanthos E. Gounaris
Coping with uncertainty in system parameters is a prominent hurdle when scheduling multi‐purpose batch plants. In this context, our previously introduced multi‐stage adjustable robust optimization (ARO) framework has been shown to obtain more profitable solutions, while maintaining the same level of immunity against risk, as compared to traditional robust optimization approaches. This paper investigates the amenability of existing deterministic continuous‐time scheduling models to serve as the basis of this ARO framework. A comprehensive computational study is conducted that compares the numerical tractability of various models across a suite of literature benchmark instances and a wide range of uncertainty sets. This study also provides, for the first time in the open literature, robust optimal solutions to process scheduling instances that involve uncertainty in production yields. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Probabilistic Design space determination in pharmaceutical product development: A Bayesian/latent variable approach AlChE J. (IF 2.836) Pub Date : 2018-03-07 Gabriele Bano; Pierantonio Facco; Fabrizio Bezzo; Massimiliano Barolo
To find the design space (DS) of a pharmaceutical process, quantification of the “assurance of quality” for the product under development is required. In this study, latent‐variable modeling is combined with multivariate Bayesian regression to identify a subset of input combinations (process operating conditions and raw materials properties) within which the DS of the product will lie at a probability equal to, or greater than, an assigned threshold. Partial least‐squares regression is used to obtain a linear transformation between the original multidimensional input space and a low‐dimensional latent space. The input domain is then discretized on its lower dimensional representation and a Bayesian posterior predictive approach is used to quantify the probability that the critical quality attributes of the product will meet their specifications for each discretization point. The methodology is tested on two case studies taken from the literature, one of which involving experimental data. The ability of the proposed approach to obtain a probabilistic identification of the DS, while simultaneously reducing the computational burden for the discretization of the input domain and providing a simple graphical representation of the DS, is shown. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Acid hydrolysis of glycosidic bonds in oat β‐glucan and development of a structured kinetic model AlChE J. (IF 2.836) Pub Date : 2018-03-08 Hoang S. H. Nguyen; Jari Heinonen; Tuomo Sainio
Homogeneous acid‐catalyzed hydrolysis of oat β‐glucan, which contains β‐(1,4) and β‐(1,3) glycosidic bonds in a nonrandom order, was studied at 353 K using HCl and H2SO4. A new structured kinetic model was developed that takes into account the difference in the reactivity of β‐(1,4) and β‐(1,3) glycosidic bonds as well as their positions in the polysaccharide chain. To minimize the correlation of adjustable parameters in the new model, the reactivities of these bonds were studied independently (T = 313…363 K; cH+ = 0.1…2 mol/L) using cellobiose and laminaribiose. The difference in kinetic parameters (e.g., T = 338 K: kβ‐(1,4) = 0.693 × 10−3 L/mol/min, kβ‐(1,3) = 1.027 × 10−3 L/mol/min) was found to be statistically significant (P < 0.0001), which emphasizes the need for the structured model for oat β‐glucan hydrolysis. The simulation of β‐glucan hydrolysis with the new model was in good agreement with the experimental data and shows improvement over existing nonstructured models. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Measurements of horizontal three‐phase solid‐liquid‐gas slug flow: Influence of hydrate‐like particles on hydrodynamics AlChE J. (IF 2.836) Pub Date : 2018-03-08 Luis M. M. Rosas; Carlos L. Bassani; Rafael F. Alves; Fábio A. Schneider; Moisés A. Marcelino Neto; Rigoberto E. M. Morales; Amadeu K. Sum
Gas hydrate formation is a main flow assurance concern in oil and gas production. Understanding the effects of the introduction of solid particles in the slug flow is essential to improve the efficiency and safety of multiphase production. The purpose of the present work is the experimental characterization of solid‐liquid‐gas slug flow with the presence of dispersed hydrate‐like particles. Experimental tests were carried out with inert polyethylene particles of 0.5‐mm diameter with density similar to gas hydrates (938 kg/m3). The test section comprised a 26‐mm ID, 9‐m length horizontal duct of transparent Plexiglas. High Speed Imaging and resistivity sensors was used to analyze the slug flow unit cell behavior due to the introduction of the solid particles and to measure the unit cell translational velocity, the slug flow frequency, the bubble and slug lengths, and the phase fractions. Two distinct concentrations of solid particles were tested (6 and 8 g/dm3). © 2018 American Institute of Chemical Engineers AIChE J, 2018
Multiactor multicriteria decision making for life cycle sustainability assessment under uncertainties AlChE J. (IF 2.836) Pub Date : 2018-03-08 Jingzheng Ren; Xusheng Ren; Lichun Dong; Alessandro Manzardo; Chang He; Ming Pan
This article aims at developing a generic multiactor multicriteria decision making (MAMCDM) method for life cycle sustainability assessment (LCSA) of industrial systems under uncertainties, which can help multiple stakeholders/decision‐makers to prioritize the alternative industrial systems in a group decision‐making approach. The interval best–worst method, which can address the ambiguity, vagueness and hesitations existing in human's judgments, was developed for determining the weight of the criteria in LCSA. The consensus convergence model was developed for aggregating the relative importance of each criterion determined by different stakeholders/decision‐makers into an interval weight. Afterward, a novel multicriteria decision‐making method which can address the decision‐making matrix with interval numbers was developed to prioritize industrial systems under data uncertainties. An illustrative case has been studied by the developed model, and it reveals that the developed model allows multiple stakeholders/decision‐makers to participate in the decision‐making processes and prioritize industrial systems accurately by using interval numbers. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Velocity variation effect in fixed bed columns: A case study of CO2 capture using porous solid adsorbents AlChE J. (IF 2.836) Pub Date : 2018-03-08 Nadeen Al‐Janabi; Reza Vakili; Patthadon Kalumpasut; Patricia Gorgojo; Flor R. Siperstein; Xiaolei Fan; Paschal McCloskey
This study shows that for a reliable evaluation of porous adsorbents for carbon capture based on the fixed bed adsorption analysis, one must consider the effect of velocity variation due to adsorption to make a fair judgment on predicting the performance of materials under flow conditions. A combined experimental and numerical study of CO2/N2 adsorption in fixed beds using three forms of adsorbents of amorphous powder (bulk activated carbon, AC), crystalline powder (bulk CuBTC metal‐organic framework, MOF) and crystalline pellets (pelleted CuBTC) was carried out to show the effect of velocity variation on CO2 breakthrough curves. Significant deviations are observed in the estimated amount adsorbed calculated from fixed bed experiments when models used for interpretation the measured data consider constant gas velocity because the stoichiometric time is underestimated. We show that the difference in breakthrough times estimated in models that consider constant and variable gas velocity grows exponentially with the feed gas concentration. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Fully resolved simulations of single char particle combustion using a ghost‐cell immersed boundary method AlChE J. (IF 2.836) Pub Date : 2018-03-08 Kun Luo; Chaoli Mao; Jianren Fan; Zhenya Zhuang; Nils Erland L. Haugen
A novel ghost‐cell immersed boundary method for fully resolved simulation of char particle combustion has been developed. The boundary conditions at the solid particle surface, such as velocity, temperature, density, and chemical species concentration, are well enforced through the present method. Two semiglobal heterogeneous reactions and one homogeneous reaction are used to describe the chemical reactions in the domain, and the Stefan flow caused by the heterogeneous reactions is considered. A satisfactory agreement can be found between the present simulation results and experimental data in the literature. The method is then used to investigate the combustion property of a char particle and the interaction between CO2 gasification and O2 oxidation. Furthermore, combustion effect on the exchange of mass, momentum and energy between gas‐ and solid‐ phase is explored. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Recombinantly expressed gas vesicles as nanoscale contrast agents for ultrasound and hyperpolarized MRI AlChE J. (IF 2.836) Pub Date : 2018-03-08 Arash Farhadi; Gabrielle Ho; Martin Kunth; Bill Ling; Anupama Lakshmanan; George J Lu; Raymond W. Bourdeau; Leif Schröder; Mikhail G. Shapiro
Ultrasound and hyperpolarized magnetic resonance imaging enable the visualization of biological processes in deep tissues. However, few molecular contrast agents are available to connect these modalities to specific aspects of biological function. We recently discovered that a unique class of gas‐filled protein nanostructures known as gas vesicles could serve as nanoscale molecular reporters for these modalities. However, the need to produce these nanostructures via expression in specialized cultures of cyanobacteria or haloarchaea limits their broader adoption by other laboratories and hinders genetic engineering of their properties. Here, we describe recombinant expression and purification of Bacillus megaterium gas vesicles using a common laboratory strain of Escherichia coli, and characterize the physical, acoustic, and magnetic resonance properties of these nanostructures. Recombinantly expressed gas vesicles produce ultrasound and hyperpolarized 129Xe MRI contrast at subnanomolar concentrations, thus validating a simple platform for their production and engineering. © 2018 American Institute of Chemical Engineers AIChE J, 2018
The impact of hydrodynamics on viscosity evolution in colloidal dispersions: Transient, nonlinear microrheology AlChE J. (IF 2.836) Pub Date : 2018-03-08 Ritesh P. Mohanty; Roseanna N. Zia
Evolution of microstructure and rheology during flow startup, and its connection to microscopic transport processes, is studied theoretically via active microrheology. At steady state, the balance between entropic, hydrodynamic, and other forces changes with flow strength, producing sustained microstructural asymmetry and non‐Newtonian rheology. However, the transition from equilibrium to steady flow is sometimes marked by overshoots in viscosity that suggests a temporally evolving competition between these rate processes. Here, we formulate and solve a Smoluchowski equation for the time‐dependent evolution of particle microstructure induced by the motion of a colloidal probe driven through a bath of colloidal spheres. The structure is then utilized to compute the time‐dependent microviscosity. Brownian diffusion always sets short‐time particle dynamics, which hinders maturation of the boundary layer. The disparity in Brownian and advective transport rates produces a reversal from flow thinning to flow thickening during startup, revealing that non‐Newtonian flow phenomenology is not instantaneously established. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Validation study on spatially averaged two‐fluid model for gas‐solid flows: II. Application to risers and fluidized beds AlChE J. (IF 2.836) Pub Date : 2018-03-10 Simon Schneiderbauer
In our prior study (Schneiderbauer, AIChE J. 2017;63(8):3544–3562), a spatially averaged two‐fluid model (SA‐TFM) was presented, where closure models for the unresolved terms were derived. These closures require constitutive relations for the turbulent kinetic energies of the gas and solids phase as well as for the subfilter variance of the solids volume fraction. We had ascertained that the filtered model do yield nearly the same time‐averaged macroscale flow behavior in bubbling fluidized beds as the underlying kinetic‐theory‐based two‐fluid model, thus verifying the SA‐TFM model approach. In the present study, a set of 3D computational simulations for validation of the SA‐TFM against the experimental data on riser flow and bubbling fluidized beds is performed. Finally, the SA‐TFM predictions are in fairly good agreement with experimental data in the case of Geldart A and B particles even though using very coarse grids. © 2018 The Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers AIChE J, 2018
Modeling of hydrogen separation through porous YSZ hollow fiber‐supported graphene oxide membrane AlChE J. (IF 2.836) Pub Date : 2018-03-10 Yun Jin; Xiuxia Meng; Naitao Yang; Bo Meng; Jaka Sunarso; Shaomin Liu
In this work, hydrogen (H2) permeation fluxes through 230 nm‐thick graphene oxide (GO) membrane deposited on porous YSZ hollow fiber were measured and correlated to an explicit H2 permeation model. H2 fluxes through such GO‐YSZ hollow fiber membrane increased from 4.83 × 10−8 mol cm−2 s−1 to 2.11 × 10−7 mol cm−2 s−1 with temperature rise from 20 to 100 °C. The activation energy of H2 permeation was determined by the linear regression of the experimental data and was applied in the theoretical calculations. The model predictions fit well the temperature dependent and the argon sweep gas flow rate dependent H2 fluxes data. Using the derived permeation model, the effects of vacuum pressure at lumen side and H2 partial pressure at shell side, membrane area, and GO membrane film thickness on the membrane performance were simulated and discussed to provide insights for practical applications. © 2018 American Institute of Chemical Engineers AIChE J, 2018
How the catalyst circulates and works in organocatalyzed atom transfer radical polymerization AlChE J. (IF 2.836) Pub Date : 2018-03-10 Jun‐Kang Guo; Zheng‐Hong Luo
The catalyst plays a vital role in organocatalyzed atom transfer radical polymerization (O‐ATRP). Catalysts in the ground‐state, excited‐state, and oxidized‐state are in competitive equilibrium and mutually transforming status. However, the catalyst circulation process remains unclear in some respects. In this work, for the first time, a novel kinetic model is successfully developed to illustrate the exact circulation process and working mechanism of catalyst. For a broad range of conditions, the reported model presents excellent descriptions of kinetic behaviors of O‐ATRP. In the polymerization process, the photolysis effect contributes to a small proportion of radical generation. Sufficient deactivation effect is crucial for controlled polymerization at the early stage of polymerization. And increased light intensity, halide ion concentration, catalyst loading and initiator concentration accelerate the establishment of catalyst dynamic equilibrium. Additionally, the excited‐state catalyst quenches with an extremely high rate, leading to an immediate dormant period in “on–off” light switching regulation. The formulated results shed light on the catalyst circulation process and provide insights into the polymerization kinetics. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Application of inline imaging for monitoring crystallization process in a continuous oscillatory baffled crystallizer AlChE J. (IF 2.836) Pub Date : 2018-03-12 Rohit Kacker; Sebastian Maaß; Jörn Emmerich; Herman Kramer
In this study, an in situ imaging system has been analysed to characterize the crystal size, the shape and the number of particles during a continuous crystallization process in a Continuous Oscillatory Baffled Crystallizer (COBC). Two image analysis approaches were examined for particle characterization in the suspension containing both small nuclei and larger grown crystals (nonspherical and irregular in shape). The pattern matching approach, in which the particles are approximated to be spherical, did result in an overestimation of the size. Alternatively, a segmentation‐based algorithm resulted in reliable crystal size and shape characteristics. The laser diffraction analysis in comparison to the image analysis overestimated the particle sizes due to the agglomeration of particles upon filtration and drying. The trend in the particle counts during the start of crystallization process, including nucleation, determined by the image analysis probe was comparable with the one measured by FBRM, highlighting the potential of in situ imaging for process monitoring. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Quantified mass transfer and superior antiflooding performance of ordered macro‐mesoporous electrocatalysts AlChE J. (IF 2.836) Pub Date : 2018-03-12 Min Jie Wang; Tao Zhao; Wei Luo; Zhan Xin Mao; Siguo Chen; Wei Ding; Yonghui Deng; Wei Li; Jing Li; Zidong Wei
For oxygen reduction reaction (ORR), constructing porous catalysts are highly important for mass transfer inside. However, the various porous structures usually possess significantly different water buffer efficiency, that is, the antiflooding capability, for which one is still difficult to give a quantitative evaluation. In this work, we designed a special “rattle‐drum” like working electrode, by which an exactly quantitative assessment on the mass transfer efficiencies can be conducted. Particularly, ordered macro‐mesoporous Pt/C shows quantified mass transfer and antiflooding efficiency to be four times high as that of the commercial one. This observation should be attributed to their different pore characteristics, as the dual‐porosity Pt/C has 3.4 times the pore volume of the commercial one, together with regular pore arrangement. Simultaneously, it also demonstrated excellent durability, indicating that the macro‐mesoporous Pt/C indeed owns high stability in both antiflooding and durability. © 2018 American Institute of Chemical Engineers AIChE J, 2018
A hybrid thermo‐kinetic model for high temperature plasma gasification AlChE J. (IF 2.836) Pub Date : 2018-03-13 Babita K. Verma; E. Rajeshkannan; T. Renganathan; S. Pushpavanam
Plasma gasification is a process intensification technique in which the prevailing high temperatures accelerate the reactions resulting in a significant size reduction of the gasifier. Conventionally, a gasifier is modeled using either a thermodynamic or a kinetic approach. Present work proposes a novel method of modeling the plasma gasification process which combines these two approaches. The process is modeled as a combination of two regions: a Plasma Gasifier Zone (PGZ) and a Quenching Zone (QZ). PGZ, where gasification of feedstock takes place at high temperatures is modeled by thermodynamic equilibrium. QZ, where the syngas produced in the PGZ cools down, is modeled by kinetic approach. The hybrid approach captures the behavior more accurately and requires less computational effort. The proposed hybrid model is validated with experimental data from literature. The model is used to analyze the influence of radicals in plasma gasification and the performance for different operating conditions. © 2018 American Institute of Chemical Engineers AIChE J, 2018
Framework for Work‐Heat Exchange Network Synthesis (WHENS) AlChE J. (IF 2.836) Pub Date : 2018-02-14 Sajitha K Nair; Harsha Nagesh Rao; I A Karimi
Work and heat are the two predominant forms of energy in the process industry. Considerable savings can be achieved by synergizing the work and heat requirements of process streams. In this work, a generalized framework for integrating heat and work simultaneously is proposed based on a mixed‐integer nonlinear programming (MINLP) model for work‐heat exchange network synthesis (WHENS). Starting with a set of streams with known flows, temperatures, and pressures, a network of single‐shaft‐turbine‐compressors (SSTCs) with motors/generators, valves, heat exchangers, and utility heaters/coolers is synthesized for minimized total annualized cost. In contrast to existing works, we (1) do not pre‐classify streams as hot/cold or high/low‐pressure, (2) allow pressure changes for streams with no net pressure change, (3) allow liquid‐vapor phase changes, and (4) use phase‐based property correlations. Successful application of our approach to C3 splitting yields a non‐intuitive configuration. We also study another application of an offshore natural gas liquefaction process. This article is protected by copyright. All rights reserved.
New Algorithm for the Flexibility Index Problem of Quadratic Systems AlChE J. (IF 2.836) Pub Date : 2018-02-24 Hao Jiang; Bingzhen Chen; Ignacio E. Grossmann
A new flexibility index algorithm for systems under uncertainty and represented by quadratic inequalities is presented. Inspired by the outer‐approximation algorithm for convex mixed‐integer nonlinear programming, a similar iterative strategy is developed. The subproblem, which is a nonlinear program, is constructed by fixing the vertex directions since this class of systems is proved to have a vertex solution if the entries on the diagonal of the Hessian matrix are non‐negative. By overestimating the nonlinear constraints, a linear min‐max problem is formulated. By dualizing the inner maximization problem, and introducing new variables and constraints, the master problem is reformulated as a mixed‐integer linear program. By iteratively solving the subproblem and master problem, the algorithm can be guaranteed to converge to the flexibility index. Numerical examples including a heat exchanger network, a process network, and a unit commitment problem are presented to illustrate the computational efficiency of the algorithm. This article is protected by copyright. All rights reserved.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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