Browse
Subjects
Records with Subject: Modelling and Simulations
Showing records 101 to 125 of 5392. [First] Page: 1 2 3 4 5 6 7 8 9 Last
Is Regulatory Approval without Autonomous Operation for Natural Extract Manufacturing under Economic Competitiveness and Climate-Neutrality Demands Still Permissible?
Alexander Uhl, Larissa Knierim, Martin Tegtmeier, Axel Schmidt, Jochen Strube
July 7, 2023 (v1)
Keywords: autonomous operation, digital twins, digitalization, green technology, natural extraction, natural remedies, regulatory approval
Natural extracts are broadly utilized as remedies, nutrition additives, cosmetics or flavors as well as natural pesticides, fungicides or herbicides. Green manufacturing technologies are of added market value and are sustainable towards the climate neutrality politically demanded for 2045. The concept of digital twins involves experimentally distinct validated process models combined with process analytical technology that is to be adapted to the existing operations. This is a key technology for the autonomous operations in industry 4.0. This paper exemplifies this approach and evaluates the results of the application and implementation efforts of regulated industries. A conductivity sensor for the measurement of the dry residue content and/or Fourier-transformed infrared spectroscopy for marker/lead or reference substance concentration determination are the most feasible and straight forward solutions. Different process control concepts from simple PID controllers (proportional, integ... [more]
Synthetic Minority Oversampling Enhanced FEM for Tool Wear Condition Monitoring
Yuqing Zhou, Canyang Ye, Deqiang Huang, Bihui Peng, Bintao Sun, Huan Zhang
July 7, 2023 (v1)
Keywords: finite-element modeling, sample missing and insufficiency, synthetic minority oversampling technique, tool wear condition
Recent advances in artificial intelligence (AI) technology have led to increasing interest in the development of AI-based tool wear condition monitoring methods, heavily relying on large training samples. However, the high cost of tool wear experiment and the uncertainty of tool wear change in the machining process lead to the problems of sample missing and insufficiency in the model training stage, which seriously affects the identification accuracy of many AI models. In this paper, a novel identification method based on finite-element modeling (FEM) and the synthetic minority oversampling technique (SMOTE) is proposed to overcome the problem of sample missing and sample insufficiency. Firstly, a few tool wear monitoring experiments are carried out to obtain experimental samples with low cost. Then, a FEM model based on the Johnson−Cook constitutive model was established and verified according to the experimental samples. Based on the verified FEM model, the simulated missing sample i... [more]
Mathematical Modelling and CFD Simulation for Oxygen Removal in a Multi-Function Gas-Liquid Contactor
Mengdie Wang, Qianqian Nie, Guangyuan Xie, Zhongchao Tan, Hesheng Yu
July 7, 2023 (v1)
Keywords: Computational Fluid Dynamics, degassing, gas-liquid contactor, mass transfer, reactor modelling
This paper presents and compares the mathematical models and computational fluid dynamics (CFD) models for degassing of oxygen from water in a laboratory-scale multi-function gas-liquid contactor under various operating conditions. The optimum correlations of the overall volumetric liquid-phase mass transfer coefficient (kLa) are determined by the mathematical models of specific contactors. Both the continuous-reactor model and semi-batch model can evaluate the degassing efficiency with relative errors within ±13%. Similarly, CFD models agree with experimental data with relative errors of ±10% or less. Overall, the mathematical models are deemed easy to use in engineering practice to assist the selection of efficient contactors and determine their optimum operation parameters. The CFD models have a wider applicability, and directly provide the local mass transfer details, making it appropriate for harsh industrial scenarios where empirical correlations for important quantities are unav... [more]
Application of Life Cycle of Aeroengine Mainshaft Bearing Based on Digital Twin
Yunfeng Li, Ming Li, Zhong Yan, Ruoxuan Li, Ao Tian, Xinming Xu, Hang Zhang
July 7, 2023 (v1)
Keywords: aeroengine mainshaft bearing, digital twin, fault diagnosis, grinding process, heat treatment process, life prediction, metallurgical process
Aeroengine mainshaft bearings are key components in modern aeroengines, and their main functions are to support the rotation of the main shaft of the aeroengine in harsh environments, such as high temperature, heavy load, high speed and oil break; reduce the friction coefficient during the high-speed rotation of the main shaft; and reliably ensure the rotation accuracy and power transmission of the aeroengine’s main shaft during operation. The manufacture of aeroengine mainshaft bearings requires complex processes and precise machining to ensure high performance and reliability, and how to intelligently complete the production and manufacture of mainshaft bearings and ensure the strength and accuracy of the bearings, quickly distinguish the fault types of the bearings and efficiently calculate, analyze and predict the life of the bearings are the current research hotspots. Therefore, building a high-fidelity and computationally efficient digital twin life cycle of aeroengine mainshaft... [more]
Coupled Thermal-Hydraulic-Mechanical Modeling of Near-Well Stress Evolution in Naturally Fractured Formations during Drilling
Yong Song, Zhenlin Wang, Wei Wang, Peirong Yu, Gang Chen, Jiaying Lin, Bolong Zhu, Xuyang Guo
July 7, 2023 (v1)
Keywords: failure criterion, formation rock, natural fractures, Simulation, wellbore collapse
Naturally fractured formations usually have strong heterogeneities. Drilling and production operations in such formations can involve unwanted formation failure risks such as wellbore collapse and wellbore fracturing. This study presents a coupled thermal-hydraulic-mechanical numerical model for near-well stress evolutions during drilling in naturally fractured formations. The evolution of pressure, temperature, and geo-mechanical responses on the wellbore wall and in the near-well region is simulated. The effects of wellbore pressure, internal friction angle, and natural fracture length on formation rock risks are discussed. A failure index is used to quantify the formation rock failure risks. The existence of natural fractures magnifies the heterogeneous system response induced by drilling. Increasing the wellbore pressure from a relatively low value can improve the support for the wellbore wall, which reduces the failure risks caused by shearing. In mechanically weak formations, the... [more]
Effect of Crude Oil Quality on Properties of Hydrocracked Vacuum Residue and Its Blends with Cutter Stocks to Produce Fuel Oil
Iliyan Kolev, Dicho Stratiev, Ivelina Shishkova, Krassimir Atanassov, Simeon Ribagin, Sotir Sotirov, Evdokia Sotirova, Danail D. Stratiev
July 7, 2023 (v1)
Keywords: blending, hydrocracking, intercriteria analysis, Petroleum, sedimentation, vacuum residue, viscosity modeling
The production of heavy fuel oil from hydrocracked vacuum residue requires dilution of the residue with cutter stocks to reduce viscosity. The hydrocracked residue obtained from different vacuum residue blends originating from diverse crude oils may have divergent properties and interact with the variant cutter stocks in a dissimilar way leading to changeable values of density, sediment content, and viscosity of the obtained fuel oil. H-Oil hydrocracked vacuum residues (VTBs) obtained from different crude blends (Urals, Siberian Light (LSCO), and Basrah Heavy) were diluted with the high aromatic fluid catalytic cracking (FCC) light cycle, heavy cycle, and slurry oil, and the low aromatic fluid catalytic cracking feed hydrotreater diesel cutter stocks and their densities, sediment content, and viscosity of the mixtures were investigated. Intercriteria analysis evaluation of the data generated in this study was performed. It was found that the densities of the blends H-Oil VTB/cutter sto... [more]
Simulation of Unsafe Behavior in Mine Operation Based on the SMAPP Model
Xidi Jiang, Shuheng Zhong, Jialu Liang
July 7, 2023 (v1)
Keywords: fuzzy rules, simulation framework, SMAPP model, unsafe behavior
Mine accidents are mostly caused by human unsafe behavior. To reduce the unsafe behavior of mine operation and reduce the accident of mine operation, the main body of unsafe behavior ‘people’ is analyzed, and 24 attribute factors are selected from five aspects of people’s emotions, motivation, ability, personality, and pressure to construct the comprehensive model of human behavior SMAPP (sentiment−motivation−ability−personality−pressure). The program tool for recording, saving, and executing the mutual and interactive influence relationship of 24 attribute factors under different state values and the simulation process framework of SMAPP was constructed by using 1071 rule statements written in Python language. The fuzzy rules are used to simulate different scenarios. The simulation results are consistent with the actual research results, which shows the reliability and scientificity of the model. In addition, additional events are added to the simulation process to make the model more... [more]
Performance of a Nanofluid-Cooled Segmented Thermoelectric Generator: Hollow/Filled Leg Structures and Segmentation Effects
Cristian Francisco Ramos-Castañeda, Miguel Angel Olivares-Robles, Ana Elisabeth Olivares-Hernandez, Leobardo Hernandez-Gonzalez
July 7, 2023 (v1)
Keywords: Exergy, leg structure variation, nanofluids, numerical simulation, segmentation, thermoelectric generator (TEG)
A thermoelectric generator (TEG) is studied by considering different leg structures of hollow/filled legs, using new cooling nanofluids, and analyzing the segmentation effect. TEG performance is characterized by power output, conversion efficiency, and exergy efficiency. This study shows the impact of different cooling nanofluids (TiO2, graphene, and Al2O3) on the performance of the thermoelectric generator. Furthermore, in the comparative analysis of nanofluid cooling enhancement for TEG, different hollow/filled thermoelectric legs recently proposed in the literature are considered. Likewise, three segmentation types are used, 2n-2p, 1n-2p, and 2n-1p, thus will be compared with the results of the unsegmented legs. This study calculates the performance of thermoelectric leg structures through a validated numerical simulation on the ANSYS Workbench (modeling, design, and simulation). In addition, the optimal working conditions are evaluated. This study found that quenching of nanofluids... [more]
Production of Kojic Acid by Aspergillus niger M4 with Different Concentrations of Yeast Extract as a Nitrogen Source
Tomasa Quiterio-Gutiérrez, Susana González-Morales, José Antonio González-Fuentes, Adalberto Benavides-Mendoza, Fabián Fernández-Luqueño, Julia Medrano-Macías, Armando Robledo-Olivo
July 7, 2023 (v1)
Keywords: Aspergillus niger, kinetic modeling, kojic acid, liquid fermentation
In agro-industrial processes, microorganisms that are not pathogenic and that generate molecules are generally recognized as safe (GRAS). The Aspergillus niger fungus has different industrial applications, being used to produce citric acid and 166 other secondary metabolites. The objective of this research was to optimize a culture medium to induce the production of kojic acid (KA) by the Aspergillus niger M4 strain in a liquid fermentation process. Four fermentative kinetics were developed in flasks, using different levels of yeast extract in (1) 0.05 g/L, (2) 0.10 g/L, (3) 2.5 g/L, and (4) 2.5 g/L + Zinc sulfate. The culture medium conditions influenced the formation and speed of biomass and the synthesis and yield of KA. The optimum production points were from 72 h and 96 h with 0.552 g/L and 0.510 g/L of KA using 2.5 g/L of yeast extract and with a pH of 5.5. The Aspergillus niger M4 strain had the ability to produce kojic acid, which was induced by the concentration of the nitroge... [more]
Machine Learning Algorithms and Fundamentals as Emerging Safety Tools in Preservation of Fruits and Vegetables: A Review
Vinay Kumar Pandey, Shivangi Srivastava, Kshirod Kumar Dash, Rahul Singh, Shaikh Ayaz Mukarram, Béla Kovács, Endre Harsányi
July 7, 2023 (v1)
Keywords: Artificial Intelligence, fruit preservation, Machine Learning, nanotechnology
Machine learning assists with food process optimization techniques by developing a model to predict the optimal solution for given input data. Machine learning includes unsupervised and supervised learning, data pre-processing, feature engineering, model selection, assessment, and optimization methods. Various problems with food processing optimization could be resolved using these techniques. Machine learning is increasingly being used in the food industry to improve production efficiency, reduce waste, and create personalized customer experiences. Machine learning may be used to improve ingredient utilization and save costs, automate operations such as packing and labeling, and even forecast consumer preferences to develop personalized products. Machine learning is also being used to identify food safety hazards before they reach the consumer, such as contaminants or spoiled food. The usage of machine learning in the food sector is predicted to rise in the near future as more busines... [more]
Formulation of Nucleic Acids by Encapsulation in Lipid Nanoparticles for Continuous Production of mRNA
Alina Hengelbrock, Axel Schmidt, Jochen Strube
July 7, 2023 (v1)
Keywords: autonomous operation, continuous biomanufacturing, digital twins, in vitro transcription, lipid nanoparticles, Machine Learning, mRNA vaccine manufacturing
The development and optimization of lipid nanoparticle (LNP) formulations through hydrodynamic mixing is critical for ensuring the efficient and cost-effective supply of vaccines. Continuous LNP formation through microfluidic mixing can overcome manufacturing bottlenecks and enable the production of nucleic acid vaccines and therapeutics. Predictive process models developed within a QbD Biopharma 4.0 approach can ensure the quality and consistency of the manufacturing process. This study highlights the importance of continuous LNP formation through microfluidic mixing in ensuring high-quality, in-specification production. Both empty and nucleic acid-loaded LNPs are characterized, followed by a TFF/buffer exchange to obtain process parameters for the envisioned continuous SPTFF. It is shown that LNP generation by pipetting leads to a less preferable product when compared to continuous mixing due to the heterogeneity and large particle size of the resulting LNPs (86−104 nm). Particle siz... [more]
Digital Twin Implementation for Manufacturing of Adjuvants
Poonam Phalak, Emanuele Tomba, Philippe Jehoulet, André Kapitan-Gnimdu, Pablo Martin Soladana, Loredana Vagaggini, Maxime Brochier, Ben Stevens, Thomas Peel, Laurent Strodiot, Sandrine Dessoy
July 7, 2023 (v1)
Keywords: adjuvant particles, digital twins, Machine Learning, process analytical technology, process modeling, quality by design
Pharmaceutical manufacturing processes are moving towards automation and real-time process monitoring with the help of process analytical technologies (PATs) and predictive process models representing the real system. In this paper, we present a digital twin developed for an adjuvant manufacturing process involving a microfluidic formation of lipid particles. The twin uses a hybrid model for estimating the current state of the process and predicting system behavior in real time. The twin is used to control the adjuvant particle size, a critical quality attribute, by varying process parameters such as the temperature and inlet flow rates. We describe steps in the design and implementation of the twin, starting from the conception of the mechanistic model, up to the generation of its surrogate model used as state estimator, PATs and the setup of the information technology—Operational technology architecture. We demonstrate the performance of the twin by introducing different disturbances... [more]
Numerical Simulation of the Effect of Heat Conductivity on Proton Exchange Membrane Fuel Cell Performance in Different Axis Directions
Longsheng Zhao, Kang Shang, Jiyao Wang, Zhenqian Chen
July 7, 2023 (v1)
Keywords: heat conductivity, heat transfer, mass transfer, porous electrodes, proton exchange membrane fuel cell
In this paper, the effect of changes in the thermal conductivity of porous electrodes in three coordinate directions on the capability of proton exchange membrane fuel cells is investigated on the basis of current density versus voltammetry curves, and the temperature distribution and water-carrying capacity distribution of the membrane. The results show that when the cell discharge voltage of the PEMFC is 0.3 V, the thermal conductivity in the Z-direction of the porous electrode has a greater effect on the performance of the PEMFC than in the other directions, with the thermal conductivity in the X- and Y-directions of the porous electrode having less than a 5% effect on the performance of the PEMFC, which can therefore be neglected. When the thermal conductivity of the porous electrode in the Z-direction of the PEMFC is 500 W/(m·K) and 1000 W/(m·K), the performance of the PEMFC is improved by 5.78% and 5.87%, respectively, and when the thermal conductivity of the porous electrode in... [more]
Molecular Dynamics Simulation of Femtosecond Laser Ablation of Cu50Zr50 Metallic Glass Based on Two-Temperature Model
Jingxiang Xu, Dengke Xue, Oleg Gaidai, Yang Wang, Shaolin Xu
July 7, 2023 (v1)
Keywords: ablation, femtosecond laser, metallic glass, molecular dynamics, two-temperature model
Femtosecond laser machining, characterized by a small heat-affected zone, high precision, and non-contact operation, is ideal for processing metallic glasses. In this study, we employed a simulation method that combines the two-temperature model with molecular dynamics to investigate the effects of fluence and pulse duration on the femtosecond laser ablation of Cu50Zr50 metallic glass. Our results showed that the ablation threshold of the target material was 84 mJ/cm2 at a pulse duration of 100 fs. As the pulse durations increased, the maximum electron temperature at the same position on the target surface decreased, while the electron−lattice temperature coupling time showed no significant difference. As the absorbed fluence increased, the maximum electron temperature at the same position on the target surface increased, while the electron−lattice temperature coupling time became shorter. The surface ablation of the target material was mainly induced by phenomena such as melting, spal... [more]
Digital Twinning of a Magnetic Forging Holder to Enhance Productivity for Industry 4.0 and Metaverse
Omid Khalaj, Mohammad (Behdad) Jamshidi, Parsa Hassas, Bohuslav Mašek, Ctibor Štadler, Jiří Svoboda
July 7, 2023 (v1)
Keywords: cyber-physical systems, digital twin, forging process, Industry 4.0, magnetic forging holder, Metaverse, smart manufacturing
The concept of digital twinning is essential for smart manufacturing and cyber-physical systems to be connected to the Metaverse. These digital representations of physical objects can be used for real-time analysis, simulations, and predictive maintenance. A combination of smart manufacturing, Industry 4.0, and the Metaverse can lead to sustainable productivity in industries. This paper presents a practical approach to implementing digital twins of a magnetic forging holder that was designed and manufactured in this project. Thus, this paper makes two important contributions: the first contribution is the manufacturing of the holder, and the second significant contribution is the creation of its digital twin. The holder benefits from a special design and implementation, making it a user-friendly and powerful tool in materials research. More specifically, it can be employed for the thermomechanical influencing of the structure and, hence, the final properties of the materials under deve... [more]
Numerical Simulation of Dynamic Variation Characteristics of Particles in a Rolling Fluidized Bed
Jiale Huang, Ruojin Wang, Rongsheng Xu, Banghua Wu, Dewu Wang, Yan Liu, Shaofeng Zhang
July 7, 2023 (v1)
Keywords: dynamic characteristics, gas–solid fluidized bed, numerical simulation, rolling condition, solid flow
When transplanting the gas−solid fluidized bed technology to the offshore floating platform, the gas−solid flow characteristics in the bed will be affected by the rolling of the platform. In this paper, the flow field, especially the dynamic variation characteristics of the particles, in a two-dimensional rolling fluidized bed, is investigated using the numerical simulation method. The results show that when the bed is in an inclined position, the gas/particle phases gather in the upper/lower wall region of the inclined bed. During the rolling process of the bed, this behavior results in a periodic change in the gas−solid flow state near the wall region, forming an overall particle internal circulation flow mode of ‘upward flow rate in the upper wall region and downward flow rate in the lower wall region’. The solid holdup in the lower wall region fluctuates at a low amplitude around high values, with a corresponding downward solid flow rate. Meanwhile, the upper wall region has a high... [more]
A Mathematical Model for Force Prediction in Single Point Incremental Sheet Forming with Validation by Experiments and Simulation
Ravi Prakash Singh, Santosh Kumar, Pankaj Kumar Singh, Md. Meraz, Ashutosh Kumar Srivastwa, Sachin Salunkhe, H. M. A. Hussein, Emad S. Abouel Nasr, Ali Kamrani
July 7, 2023 (v1)
Keywords: contact area, finite element model, forming forces, forming limit diagram, incremental sheet forming
Incremental sheet forming (ISF) is an emerging technology that has shown great potential in forming customized three-dimensional (3D) parts without the use of product-specific dies. The forming force is reduced in ISF due to the localized nature of deformation and successive forming. Forming force plays an important role in modeling the process accurately, so it needs to be evaluated accurately. Some attempts have been made earlier to calculate the forming force; however, they are mostly limited to empirical formulae for evaluating the average forming force and its different components. The current work presents a mathematical model for force prediction during ISF in a 3D polar coordinate system. The model can be used to predict forces for axis-symmetric cones of different wall angles and also for incremental hole flanging. Axial force component, resultant force in the r-θ plane, and total force have been calculated using the developed mathematical model appearing at different forming... [more]
Modification and Validation of a Dynamic Thermal Resistance Model for Wet-State Fabrics
Zijiang Wu, Yunlong Shi, Ruiliang Yang, Xiaoming Qian, Shuting Fang
July 7, 2023 (v1)
Keywords: empirical model, thermal comfort, thermal resistance, ultradry state, wet state
To investigate the dynamic thermal resistance of woven fabrics in different wetting states, ten commonly used clothing fabrics were selected and tested for fabric thermal resistance under different levels of water saturation in accordance with Chinese national standards. Based on Mangat’s eight thermal resistance prediction models, the study improved the models by replacing the original moisture content with water content saturation. The suitability of the eight models in predicting the thermal resistance of woven fabrics in wet states was compared using the sum of squared deviations (SSD), sum of absolute deviations (SAD), and correlation coefficient (R2). The results showed that during the process from initial wetting to complete immersion, the measured thermal resistance values of the ten fabric samples were consistent with the predicted values from Model 5 in the theoretical model of thermal resistance (R2 > 0.955). The characteristic of Model 5 is that the air thermal resistance a... [more]
CFD Predictions for Mixing Times in an Elliptical Ladle Using Single- and Dual-Plug Configurations
Rohit Tiwari, Bruno Girard, Chantal Labrecque, Mihaiela M. Isac, Roderick I. L. Guthrie
July 4, 2023 (v1)
Keywords: gas stirring, ladle metallurgy, mathematical modeling, mixing time, porous plug
Argon bottom stirring is commonly practiced in secondary steelmaking processes due to its positive effects on achieving uniform temperatures and chemical compositions throughout a steel melt. It can also be used to facilitate slag metal refining reactions. The inter-mixing phenomena associated with argon gas injection through porous plugs set in the bottom and its stirring efficiency can be summarized by evaluations of 95% mixing times. This study focuses on investigating the impact of different plug positions and ratios of argon flow rates from two plugs on mixing behavior within a 110-tonne, elliptical-shaped industrial ladle. A quasi-single-phase modeling technique was employed for this purpose. The CFD findings revealed that the optimal position of the second plug is to be placed diametrically opposite the existing one at an equal mid-radius distance (R/2). An equal distribution of argon flow rates yielded the best results in terms of refractory erosion. A comparative study was con... [more]
Numerical Simulation Study on the Influence of Twist Tape Parameters on Hydrate Particle Deposition
Shuli Wang, Yongchao Rao, Chengming Hao, Jing Yao, Shidong Zhou
July 4, 2023 (v1)
Keywords: deposition, numerical simulation, swirl flow, twist tape
Numerical simulation is used to carry out research on the swirl flow transportation of a hydrate in the pipeline under the condition of the whole rotation of the twist tape using DPM (discrete phase modeling) and RNG (renormalization group) k-ε. The influence of different twist tape parameters on the swirl number and concentration distribution of hydrate particles is analyzed. The structure parameters of the twist tape are optimized, based on the swirl efficiency evaluation parameters of a gas-solid two-phase pipeline. Finally, the twist tape is compared with different working conditions: the local rotation of twist tape and an ordinary pipeline. The results show that the areas of a high concentration of particles are near the twist tapes, and the concentration of particles on the leeward side of the twist tapes is higher than that on the windward side. The minimum concentration area at the axial position gradually increases with the increase of the flow distance, and the hydrate parti... [more]
Influence of Sputtering Pressure on the Micro-Topography of Sputtered Cu/Si Films: Integrated Multiscale Simulation
Guo Zhu, Mengxin Han, Baijun Xiao, Zhiyin Gan
July 4, 2023 (v1)
Keywords: Cu/Si film deposition, magnetron sputtering epitaxy, multiscale simulation, sputtered particle transport, surface topography
In this work, an integrated multiscale simulation of magnetron sputtering epitaxy was conducted to study the effect of sputtering pressure on the surface micro-topography of sputtered Cu/Si films. Simulation results indicated that, as the sputtering pressure increased from 0.15 to 2 Pa, the peak energy of the incident energy distribution gradually decreased from 2 to 0.2 eV, which might be mainly due to the gradual decrease in the proportion of deposited Cu atoms whose energy ranged from 2 to 30 eV; the peak angle of the incident polar angle distribution increased from 25° to 35°, which might be attributed to the gradual thermalization of deposited Cu atoms; the growth mode of Cu film transformed from the two-dimensional layered mode to the Volmer-Weber mode. The transformation mechanism of growth mode was analyzed in detail. A comprehensive analysis of the simulation results indicated that incident energy ranging from 2 to 30 eV and incident angle between 10° and 35° might be conduciv... [more]
Improvements in the Modeling and Kinetics Processes of the Enzymatic Synthesis of Pentyl Acetate
Beatriz Lorenzo, Luis Fernández, Juan Ortega, Leandro Domínguez
July 4, 2023 (v1)
Keywords: esterification, kinetics modeling, Lipozyme®435, pentyl acetate, solvent-free system
In this work, the enzymatic synthesis of pentyl acetate obtained from acetic acid and pentan-1-ol using the commercial immobilized lipase Lipozyme®435 was studied. Specifically, the effects of several variables of the process on the kinetics were shown, such as the initial concentration of the acetic acid, the alcohol/acid molar ratio, and the possible reuse of the enzyme, while other variables, such as temperature, agitation, and the enzyme/acid ratio were held constant. The kinetics were determined by assessing the acetic acid concentration throughout the reactive process. Experimental data were correlated with the rate equation consisting of a modified version of the Bi−Bi Ping-Pong mechanism. The results showed that when no hydrophobic solvents were used with the reagents in stoichiometric proportion, a high molar fraction of acetic acid (x0,acid ≈ 0.50) caused the loss of enzymatic activity, achieving a conversion of only 5%. However, when there was an excess of pentan-1-ol, the r... [more]
Residence Time Section Evaluation and Feasibility Studies for One-Column Simulated Moving Bed Processes (1-SMB)
Steffen Zobel-Roos, Florian Vetter, Jochen Strube
July 4, 2023 (v1)
Keywords: 1-SMB, simulated moving bed
The simulated moving bed (SMB) is a well-established, fully continuous process for chromatographic separation of difficult tasks with overlapping peaks, but it is relatively complex. The 1-SMB, which uses only one column but includes residence time zones to preserve concentration profiles, is a simpler semi-continuous alternative. This work examines the possible design of these residence time zones. Simulation studies were conducted to investigate the dependence of process metrics, such as purity, yield, productivity, and eluent consumption, on fluid dynamics. No deterioration in purity was observed, and the other variables remained constant over a wide range of axial dispersion before decreasing sharply. Pilot-scale experiments were conducted with various devices, including coiled flow inverters, eluate recycling devices, packed columns, and tank arrangements, to validate possible apparatus implementations with fluid dynamic measurements. It was demonstrated that the 1-SMB offers simi... [more]
Mathematical and Physical Modelling of Transient Multi-Phase Flows in a Ladle Shroud during Start-Up
Daniel R. Gonzalez-Morales, Bruno Girard, Chantal Labrecque, Mihaiela M. Isac, Roderick I. L. Guthrie
July 4, 2023 (v1)
Keywords: CFD modelling, Ladle Shroud, multi-phase flow
The Ladle Shroud has become an important part of secondary steelmaking, with its role in reducing liquid steel contamination and process improvements. Due to the inherent negative pressure at the lower nozzle−Ladle Shroud joint, it is well known that Ladle Shrouds, protecting steel flows between a Ladle and a tundish below, can suffer from inadvertent ingress of air. Therefore, there is a need to apply inert gas injection at the joint. In the present paper, 3D transient multi-phase simulations of flows occurring for a Reverse Tapered Ladle Shroud during start-up were studied using CFD software ANSYS Fluent 19.1. This allowed us to study the initial multi-phase flow developed during the start-up and potential steel reoxidation, based on a first principles approach. Time-dependent phase fields as well as attendant velocity and turbulence fields were obtained, resulting in the prediction of a turbulent multi-phase flow during start-up and filling. Additionally, some transient phenomena li... [more]
Migration Behavior of NH4+ and Na+ in a Bentonite-Clay Mixed Soil Column and Numerical Simulation
Wenjing Sun, Qiantong Tang, Gang Xu, Yunzhi Tan
July 4, 2023 (v1)
Keywords: bentonite, column test, landfill barrier, migration, Simulation
The landfill barriers effectively prevented the migration of high-concentration pollutants, such as NH4+ and Na+, from the landfills to the surrounding environment. However, due to the high hydraulic head inside the landfill compared to the surrounding environment, NH4+ and Na+ can migrate towards the outside of the landfill barrier with the infiltrating solution, potentially causing harm to the surrounding environment. To address this, saturated mixed soil column samples made of bentonite and Shanghai clay, with bentonite contents of 3% and 10%, were used in this study. Permeability coefficients of the column samples in solutions are obtained by using permeation tests, and using NaCl and NH4Cl solutions with concentrations of 37.4 mmol/L and 74.8 mmol/L, respectively. The concentration-depth result of the column samples after permeation tests was determined using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) and Ion Chromatography (ICS-1100). Numerical simulations... [more]
Showing records 101 to 125 of 5392. [First] Page: 1 2 3 4 5 6 7 8 9 Last
[Show All Subjects]