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Showing records 176 to 200 of 798. [First] Page: 4 5 6 7 8 9 10 11 12 Last
Stability of Optimal Closed-Loop Cleaning Scheduling and Control with Application to Heat Exchanger Networks under Fouling
Federico Lozano Santamaria, Sandro Macchietto
July 19, 2021 (v1)
Keywords: closed-loop scheduling, fouling, heat exchanger networks, optimal control and scheduling, scheduling stability
Heat exchanger networks subject to fouling are an important example of dynamic systems where performance deteriorates over time. To mitigate fouling and recover performance, cleanings of the exchangers are scheduled and control actions applied. Because of inaccuracy in the models, as well as uncertainty and variability in the operations, both schedule and controls often have to be revised to improve operations or just to ensure feasibility. A closed-loop nonlinear model predictive control (NMPC) approach had been previously developed to simultaneously optimize the cleaning schedule and the flow distribution for refinery preheat trains under fouling, considering their variability. However, the closed-loop scheduling stability of the scheme has not been analyzed. For practical closed-loop (online) scheduling applications, a balance is usually desired between reactivity (ensuring a rapid response to changes in conditions) and stability (avoiding too many large or frequent schedule changes... [more]
Shear-Thinning Effect of the Spinning Disc Mixer on Starch Nanoparticle Precipitation
Sahr Sana, Vladimir Zivkovic, Kamelia Boodhoo
July 19, 2021 (v1)
Subject: Materials
Keywords: Process Intensification, shear rate, solvent–antisolvent precipitation, spinning disc, starch nanoparticles, thin films
Spinning disc technology is capable of achieving intensified micromixing within thin liquid films created through large shear rates, typically of the order of 103 s−1, generated by means of fast disc surface rotation. In this study the effect of the high shear on solvent−antisolvent mixing and starch nanoparticle precipitation is reported. Rheological studies of starch solutions at 2% w/v and 4% w/v have demonstrated their shear-thinning behaviour at the large shear rates experienced on the spinning disc surface. The effect of such high shear rate on starch nanoparticle precipitation is investigated alongside solute concentration and several other operating parameters such as flow rate, disc rotational speed, and solvent/antisolvent ratio. A reduction in nanoparticle size has been observed with an increase in starch concentration, although agglomeration was found to be more prevalent amongst these smaller particles particularly at larger flow rates and disc rotational speeds. Micromixi... [more]
Eulerian Multiphase Simulation of the Particle Dynamics in a Fluidized Bed Opposed Gas Jet Mill
Dyrney Araújo dos Santos, Shivam Baluni, Andreas Bück
July 19, 2021 (v1)
Keywords: comminution, compressible flow, granular temperature, OpenFOAM, particle velocity, turbulent flow
The compressible and turbulent gas−solid multiphase flow inside a fluidized bed opposed jet mill was systematically investigated through numerical simulations using the Euler−Euler approach along with the kinetic theory of granular flow and frictional models. The solid holdup and nozzle inlet air velocity effects on the gas−solid dynamics were assessed through a detailed analysis of the time-averaged volume fraction, the time-averaged velocity, the time-averaged streamlines, and the time-averaged vector field distributions of both phases. The simulated results were compared with the experimental observations available in the literature. The numerical simulations contributed to a better understanding of the particle−flow dynamics in a fluidized bed opposed gas jet mill which are of fundamental importance for the milling process performance.
Numerical Simulation on the Brake Effect of FAC-EMBr and EMBrRuler in the Continuous Casting Mold
Zhuang Li, Lintao Zhang, Yanming Bao, Danzhu Ma
July 19, 2021 (v1)
Keywords: continuous casting, electromagnetic brake, mold
The brake effect of the freestanding adjustable combination electromagnetic brake (FAC-EMBr) and EMBr ruler on the behavior of molten steel flow and the level fluctuation were investigated with the numerical method. The effects of the horizontal magnetic pole position (EMBr ruler), magnetic induction intensity, and casting speed on two types of electromagnetic brakes were studied. The numerical simulation results show that the magnetic field caused by the EMBr ruler is mainly distributed under the submerged entry nozzle (SEN), and it is very weak nearby the meniscus area. After the FAC-EMBr is applied, the magnetic field is mainly distributed in the area below the submerged entry nozzle, the upper roll region, and in the meniscus region. The application of the electromagnetic brake can effectively suppress the impact of the jet and decrease the molten steel velocity in the meniscus area. The brake effect of the EMBr ruler on the behavior of the molten steel flow and the level fluctuati... [more]
Improved Statistical Pattern Analysis Monitoring for Complex Multivariate Processes Using Empirical Likelihood
Jianwen Shao, Xin Zhang, Wenhua Chen, Xiaomin Shen
July 19, 2021 (v1)
Keywords: empirical likelihood, higher-order statistics, moving window, statistical pattern analysis
This article developed an improved statistical pattern analysis (SPA) monitoring strategy for fault detection of complex multivariate processes using empirical likelihood. The technique based on statistical pattern analysis performs fault detection by inspecting change in the statistics of process variables (e.g., mean value, correlation coefficient, variance, kurtosis, etc.). It is capable of monitoring non-Gaussian or even nonlinear processes. However, the original SPA framework explicitly computes all the high-order statistics, which significantly increases the scale and dimensionality of the problem, especially in the case of complex multivariate processes. To alleviate this difficulty, we propose monitoring changes in the statistics with the same order using empirical likelihood, which is a widely used estimation method to construct confidence limits or regions for parameters with similar properties. As a result, changes in statistics of the same order can be translated into a sin... [more]
Numerical Simulation of Performance of an Air−Water Separator with Corrugated Plates for Marine Diesel Engines
Jie Tian, Yan Chen, Zheshu Ma
July 19, 2021 (v1)
Keywords: air–water separator, corrugated plate, discrete phase model, pressure drop, separation efficiency
For low speed diesel engines under severe ocean conditions, high efficiency air−water separators must be equipped to separate excess moisture contained in the air and reduce the corrosion. Optimal design of air−water separator is an indispensable part in the development of marine main engines. In view of the complex gas−liquid two-phase turbulent motion within an air−water separator with corrugated plates, a mathematical model is established and numerical simulations of flow field, droplet trajectory and secondary transport are realized. The separation efficiency and pressure drop of the air−water separator under different structure parameters and different working conditions are studied. The results show that reducing the spacing of corrugated plate is helpful to improve the separation efficiency. The bending and hydrophobic hooks of the corrugated channel are important to improve the separation efficiency. The separation of droplet is mainly concentrated on the first two stages of th... [more]
Multi-Aspect Comparison of Ethyl Acetate Production Pathways: Reactive Distillation Process Integration and Intensification via Mechanical and Chemical Approach
Branislav Šulgan, Juraj Labovský, Zuzana Labovská
July 19, 2021 (v1)
Keywords: auxiliary reaction, energy-economy-safety aspects, ethyl acetate, ethylene oxide, process integration and intensification, Reactive Distillation
This paper provides a multi-aspect comparison of selected methods of ethyl acetate production and shows the possibility of further reactive distillation process integration and sophisticated intensification including process stream regeneration. The production pathways were selected with respect to their practical applicability and sufficient experimental and feasibility studies already published. A total of four case studies were designed and compared: conventional process set-up (ethyl acetate is produced in a chemical reactor) is designed as a base case study; reactive distillation with a separation unit is derived from the conventional process set-up. The mechanical and chemical approach to reactive distillation process intensification and integration were assumed: reactive distillation column with a stripper and reactive distillation column with an auxiliary chemical reaction (ethylene oxide hydration). Process models were compiled in the Aspen Plus software. Complex process flows... [more]
Modeling and Design of the Automatic Pressure Regulating Valve in the Foam Firefighting System
Zhijun Yang, Hongjun Chen, Lifang He, Xikun Wang
July 19, 2021 (v1)
Keywords: automatic pressure balancing valve, foam firefighting system, in-line balanced pressure (ILBP) proportioner, mathematical model, Simulation
This paper presents a novel design of the automatic pressure balancing valve, used in the in-line balanced pressure (ILBP) proportioner for the foam firefighting system, at a required percentage of solution. Featured in a four-chamber configuration with a double-acting diaphragm actuator, it can automatically maintain the foam concentrate pressure with the pressure in the supply water pipeline, within a precision level of 0.02 MPa (or 1.3%), under the design operating condition. The static characteristics at the equilibrium state have been discussed in terms of poppet displacement with reference to the geometrical dimensions and operating pressures of the valve. The dynamic response of the valve during the startup has been examined through building the mathematical model of the forces on the valve and solving it numerically using MATLAB. The results show that the response time of the valve is always less than 0.01 s, which fully satisfies the stability and hysteresis requirement. The p... [more]
Sulfatide-Rich Liposome Uptake by a Human-Derived Neuroblastoma Cell Line
Daniel Arroyo-Ariza, Elizabeth Suesca, Chad Leidy, John M. Gonzalez
July 19, 2021 (v1)
Subject: Biosystems
Keywords: drug delivery system, LDL receptor, liposomes, neuroblastoma, sulfoglycosphingolipids
Liposomes are bilayer membrane vesicles that can serve as vehicles for drug delivery. They are a good alternative to free drug administration that provides cell-targeted delivery into tumors, limiting the systemic toxicity of chemotherapeutic agents. Previous results from our group showed that an astrocytoma cell line exhibits selective uptake of sulfatide-rich (SCB) liposomes, mediated by the low-density lipoprotein receptor (LDL-R). The goal of this study was to assess the uptake of liposomes in a neuroblastoma cell line. For this purpose, we used two types of liposomes, one representing a regular cell membrane (DOPC) and another rich in myelin components (SCB). An astrocytoma cell line was used as a control. Characterization of liposome uptake and distribution was conducted by flow cytometry and fluorescence microscopy. Similar levels of LDL-R expression were found in both cell lines. The uptake of SCB liposomes was higher than that of DOPC liposomes. No alterations in cell viabilit... [more]
Rapid Two Stage Anaerobic Digestion of Nejayote through Microaeration and Direct Interspecies Electron Transfer
David Valero, Carlos Rico, Raul Tapia-Tussell, Liliana Alzate-Gaviria
July 19, 2021 (v1)
Keywords: anaerobic digestion, direct interspecies electron transfer, granular activated carbon, microaeration, nejayote, Peptoclostridium
Corn is one of the main food products in Mexico. The elaboration of corn-derived products generates wastewater with a high organic load (nejayote). Anaerobic digestion is an indicated treatment for wastewater with high organic loads. The results of this study show that the application of microaeration in the hydrolysis-fermentative reactor increased the percentage of volatile fatty acids (VFA) available in the medium by 62%. The addition of a conductive material, such as granulated activated carbon (GAC), promotes DIET (Direct interspecies electrons transfer) in the methanogenic UASB reactor increasing the methane yield by 55%. Likewise, a great diversity of exoelectrogenic bacteria, with the ability to donate electrons DIET mechanisms, were developed in the GAC biofilm, though interestingly, Peptoclostridium and Clostridium (17.3% and 12.75%, respectively) were detected with a great abundance in the GAC biofilm. Peptoclostridium has not been previously reported as a participant in DIE... [more]
Functionality of Special Beer Processes and Potential Health Benefits
Liana Claudia Salanță, Teodora Emilia Coldea, Maria Valentina Ignat, Carmen Rodica Pop, Maria Tofană, Elena Mudura, Andrei Borșa, Antonella Pasqualone, Ofélia Anjos, Haifeng Zhao
July 19, 2021 (v1)
Keywords: beer, craft beer, functional, low-alcohol beers, nonalcoholic beer, process
Consumers’ demand for functional fermented food that can fulfill nutritional needs and help maintain a balanced diet while also having a positive impact on one’s health status is increasing all over the world. Thus, healthy choices could include beverages with nutrients and bioactive compounds which can be used as an effective disease-prevention strategy. Regular beer has certain health benefits which inspire further research with the prospect of obtaining special functional beers with little or no alcohol content. As observed, the special beer market remains highly dynamic and is predicted to expand even further. Therefore, brewers need to keep up with the consumers’ interests and needs while designing special beers, namely nonalcoholic beers (NABs), low-alcohol beers (LABs), and craft beers (CBs). Thus, understanding the potential uses of bioactive compounds in special beer, the wide range of therapeutic effects, and the possible mechanisms of action is essential for developing healt... [more]
Economic and Environmental Assessment of Catalytic and Thermal Pyrolysis Routes for Fuel Production from Lignocellulosic Biomass
Akshay D. Patel, Masoud Zabeti, K. Seshan, Martin K. Patel
July 19, 2021 (v1)
Keywords: abatement cost, biofuel, Catalysis, economics, lifecycle environmental impacts, lignocellulosic biomass, pyrolysis, Renewable and Sustainable Energy
Meeting the transport needs of a growing world population makes it imperative to develop renewable and sustainable routes to production of liquid fuels. With a market-driven economic structure and pressing environmental issues, it is essential that these new routes provide environmental benefits while being economically viable. Conversion of second-generation lignocellulosic biomass resources to fuels via pyrolysis represents an important technological route. In this article, we report comparative assessment of the economic and lifecycle environmental aspects for catalytic and thermal pyrolysis. The goal of this assessment is two-fold: one is to understand the potential of this conversion route via the catalytic and thermal processes and second is to provide feedback for further development of catalysts for various stages of this conversion. The complete assessment is interdisciplinary in nature and connects the laboratory experiments with contextual sustainability assessment. Three ca... [more]
Numerical and Experimental Study on Waviness Mechanical Seal of Reactor Coolant Pump
Xiaodong Feng, Wentao Su, Yu Ma, Lei Wang, Heping Tan
July 19, 2021 (v1)
Keywords: leakage rate, liquid film, mechanical seal, reactor coolant pump (RCP), waviness
Based on the fluid hydrodynamic lubrication theory, a mathematical model of liquid film lubrication was established for the waviness hydrodynamic mechanical seal of a reactor coolant pump. The influences of the waviness amplitude and pressure on the sealing performance were investigated by the numerical simulation. The numerical results showed that the leakage rate increases linearly as the pressure and waviness amplitude increase under the force balance condition. The minimum liquid film thickness decreases first and then increase as the pressure increases. Stationary slide rings with three different waviness amplitudes were processed using the pre-deformation method and tested at different pressure and temperature. The experiments showed that all the three kinds of seal have good stability under different pressure conditions. The experimental results showed that the leakage rate is influenced by the pressure, waviness amplitude, and temperature, and the leakage rate increases as the... [more]
Renewable Energy Sources in Transport on the Example of Methyl Esters and Bioethanol
Adam Kupczyk, Joanna Mączyńska-Sęczek, Ewa Golisz, Piotr F. Borowski
July 19, 2021 (v1)
Subject: Energy Policy
Keywords: CO2 emission reduction, mechanical engineering, eco-mobility, esters, processes, renewable energy sources
The aim of this article is to show how the situation of domestic biofuels in Poland and the alternative fuels sector is changing. On the basis of our own research and the available literature, changes in the production potential of Poland in the field of alternative fuels/biofuels are examined. Moreover, the reasons for changes in the production structure are analyzed. The flexibility of production potential to changes in legal conditions is assessed, and the value of sectors and their future are determined. This paper discusses legal and market aspects related to selected renewable energy sources used in Polish transport. Based on a review of literature and statistical data, the production and use of methyl esters and bioethanol are characterized in detail. Analysis of legal regulations enables the presentation of targets regarding renewable energy source (RES) use in transport by 2030. The results of studies conducted in 2020 are discussed with regard to the value (attractiveness) of... [more]
Methanol in Grape Derived, Fruit and Honey Spirits: A Critical Review on Source, Quality Control, and Legal Limits
Goreti Botelho, Ofélia Anjos, Letícia M. Estevinho, Ilda Caldeira
July 19, 2021 (v1)
Keywords: human health, legal limits, manufacturing processes, Methanol, quality control, spirits, volatile composition
Spirits are alcoholic beverages commonly consumed in European countries. Their raw materials are diverse and include fruits, cereals, honey, sugar cane, or grape pomace. The main aim of this work is to present and discuss the source, quality control, and legal limits of methanol in spirits produced using fruit and honey spirits. The impact of the raw material, alcoholic fermentation, and the distillation process and aging process on the characteristics and quality of the final distilled beverage are discussed. In addition, a critical view of the legal aspects related to the volatile composition of these distillates, the origin and presence of methanol, and the techniques used for quantification are also described. The methanol levels found in the different types of spirits are those expected based on the specific raw materials of each and, almost in all studies, respect the legal limits.
Numerical Study on Bubble Rising in Complex Channels Saturated with Liquid Using a Phase-Field Lattice-Boltzmann Method
Kang Yu, Yumei Yong, Chao Yang
July 19, 2021 (v1)
Keywords: bubble evolution, complex channel, flow pattern, multiphase system, packed bed reactor, phase-field LB model
Packed bed reactors have been widely applied in industrial production, such as for catalytic hydrogenation. Numerical simulations are essential for the design and scale-up of packed beds, especially direct numerical simulation (DNS) methods, such as the lattice-Boltzmann method (LBM), which are the focus of future researches. However, the large density difference between gas and liquid in packed beds often leads to numerical instability near phase interface when using LBM. In this paper, a lattice-Boltzmann (LB) model based on diffuse-interface phase-field is employed to simulate bubble rising in complex channels saturated with liquid, while the numerical problems caused by large liquid-to-gas density ratio are solved. Among them, the channel boundaries are constructed with regularly arranged circles and semicircles, and the bubbles pass through the channels accompanied by deformation, breakup, and coalescence behaviors. The phase-field LB model is found to exhibit good numerical stabi... [more]
Study of Dynamics of Heat Transfer in the Flat-Plate Solar Collector
Joanna Aleksiejuk-Gawron, Andrzej Chochowski
July 19, 2021 (v1)
Keywords: heat exchanger, heat transfer, solar collector, step response, thermoelectric analogy
Flat plate solar collector has been presented as an example of a heat-exchanger with two input signals, solar radiation intensity and temperature of working medium on the input, and one output signal, the temperature of a working medium on the output. The dynamics of heat exchange were analyzed for two models of a solar collector—an analog one using a thermoelectric analogy, and a digital one—determined experimentally in on-line mode using the parametric identification method. The characteristics of both models were compared in terms of their step and frequency response for selected construction and operational parameters. Tests of step responses determined for the analog model indicate that the dynamics of heat exchange in the solar collector depending on two input signals is varied. For step-forcing of input signals of the analog model, in both cases, a stable steady state is achieved, but while the first of the signals is inertial, the second one is oscillatory. The phenomenon of te... [more]
Global Internal Recirculation Alternative Operation to Reduce Nitrogen and Ammonia Limit Violations and Pumping Energy Costs in Wastewater Treatment Plants
Ignacio Santín, Ramon Vilanova, Carles Pedret, Marian Barbu
July 19, 2021 (v1)
Keywords: benchmark simulation model no. 2, control strategies, fuzzy control, wastewater treatment plant
The internal recirculation plays an important role in different areas of the biological treatment of wastewater treatment plants because it has a great influence on the concentration of pollutants, especially nutrients. A usual manipulation of the internal recirculation flow rate is based on the target of controlling the nitrate concentration in the last anoxic tank. This work proposes an alternative for the manipulation of the internal recirculation flow rate instead of nitrate control, with the objective of avoiding limit violations of nitrogen and ammonia concentrations and reducing operational costs. A fuzzy controller is proposed to achieve it based on the effects of the internal recirculation flow rate in different areas of the biological treatment. The proposed manipulation of the internal recirculation flow rate is compared to the application of the usual nitrate control in an already established and published operation strategy by using the internationally known benchmark simu... [more]
The Concept of Sustainable Development of Modern Dentistry
Leszek A. Dobrzański, Lech B. Dobrzański, Anna D. Dobrzańska-Danikiewicz, Joanna Dobrzańska
July 19, 2021 (v1)
Subject: Other
Keywords: caries, dental implantology, dental interventionistic treatment, dental prophylaxis, dental prosthetics, dentist ethics, dentist safety, Dentistry 4.0, dentistry sustainable development, endodontics, periodontology, toothlessness
This paper concerns the assessment of the current state of dentistry in the world and the prospects of its sustainable development. A traditional Chinese censer was adopted as the pattern, with a strong and stable support on three legs. The dominant diseases of the oral cavity are caries and periodontal diseases, with the inevitable consequence of toothlessness. From the caries 3.5−5 billion people suffer. Moreover, each of these diseases has a wide influence on the development of systemic complications. The territorial range of these diseases and their significant differentiation in severity in different countries and their impact on disability-adjusted life years index are presented (DALY). Edentulousness has a significant impact on the oral health-related quality of life (OHRQoL). The etiology of these diseases is presented, as well as the preventive and therapeutic strategies undertaken as a result of modifying the Deming circle through the fives’ rules idea. The state of developme... [more]
Economic Analysis of a New Business for Liposome Manufacturing Using a High-Pressure System
Paolo Trucillo, Roberta Campardelli, Silvia Iuorio, Paolo De Stefanis, Ernesto Reverchon
July 19, 2021 (v1)
Keywords: economic indexes, liposomes, market analysis, processes, supercritical fluids
Supercritical assisted Liposome formation (SuperLip) is a lab-scale process for the production of liposomes. SuperLip was recognized as being a versatile supercritical assisted technique for the encapsulation of molecules for different industrial applications, such as pharmaceutic, cosmetic, textile, and nutraceutic purposes. The aim of this work was to perform an economic analysis to assess the profitability of the SuperLip process. The liposomes market was analyzed and the SuperLip process was compared to other techniques in terms of manufacturing advantages using the Canvas and Strengths, Weaknesses, Opportunities, and Treats (S.W.O.T.) models. SuperLip Plant Capital Expenditures (CAPEX) were estimated, and plant Operating Expenditures (OPEX) were also evaluated and integrated with personnel cost and other plant goods and services. A profit and loss statement was generated, together with a cash flow analysis. According to the market average selling price, liposome price is 1.8 €/mL;... [more]
Synthesis of 2-(4-hydroxyphenyl)ethyl 3,4,5-Trihydroxybenzoate and Its Inhibitory Effect on Sucrase and Maltase
Wen-Tai Li, Yu-Hsuan Chuang, Jiahn-Haur Liao, Jung-Feng Hsieh
July 19, 2021 (v1)
Keywords: hyperglycemia, inhibitor, kinetics assay, maltase, sucrase
We report on the synthesis of an active component, 2-(4-hydroxyphenyl)ethyl 3,4,5-trihydroxybenzoate (HETB), from Rhodiola crenulata. Subsequent analysis revealed that HETB exhibits α-glucosidase inhibitory activities on maltase and sucrase, with potency exceeding that of the known α-glucosidase inhibitors (voglibose and acarbose). An inhibition kinetics study revealed that HETB, acarbose, and voglibose bind to maltase and sucrase, and HETB was shown to be a strong competitive inhibitor of maltase and sucrase. In a molecular docking study based on the crystal structure of α-glucosidase from Saccharomyces cerevisiae, we revealed the HETB binding in the active site of maltase via hydrogen-bond interactions with five amino acid residues: Ser 240, Asp 242, Glu 277, Arg 315, and Asn 350. For HETB docked to the sucrase active site, seven hydrogen bonds (with Asn 114, Glu 148, Gln 201, Asn 228, Gln 381, Ile 383, and Ser 412) were shown.
Grey-Taguchi-Based Optimization of Wire-Sawing for a Slicing Ceramic
Yao-Yang Tsai, Jihng-Kuo Ho, Wen-Hao Wang, Chia-Chin Hsieh, Chung-Chen Tsao, Chun-Yao Hsu
July 19, 2021 (v1)
Subject: Other
Keywords: Grey-Taguchi method, material removal rate, slurry concentration, surface roughness, wire-sawing
Slicing ceramic (SC) is well-known as difficult-to-cut material. It is a hard and brittle material. The Grey-Taguchi method, which converts multiple response problems into a single response, is used to determine the effect of the process parameters for wire-sawing on multiple quality characteristics. The wire-sawing parameters include the wire tension (T), the slurry concentration (C), mixed grains mesh size (G), the wire speed (S), and the working load (P). The machining quality characteristics include a material removal rate (MRR), machined surface roughness (SR) of SC, kerf width (KW), wire wear (WW), and flatness (FT). An analysis of variance (ANOVA) is used to identify the mixed grains and slurry concentration that have a significant effect on multiple quality characteristics. The results of the ANOVA using the Grey-Taguchi method show that the optimum conditions are T2C1G1S2P1 (wire tension of 24 N, slurry concentration of 10% wt., mixed grains of #600 + #1000 mesh size, wire spe... [more]
Numerical Investigation of an Open-Design Vortex Pump with Different Blade Wrap Angles of Impeller
Xiongfa Gao, Ting Zhao, Weidong Shi, Desheng Zhang, Ya Shi, Ling Zhou, Hao Chang
July 19, 2021 (v1)
Keywords: lateral cavity, numerical simulation, open-design, spiral flow, vortex pump
The blade wrap angle of impeller is an important structural parameter in the hydraulic design of open-design vortex pump. In this paper, taking a vortex pump with a cylindrical blade structure as the research object, two kinds of different blade wrap angle of vortex pump impellers are designed. The experiment and numerical simulation research is carried out, and the results of external characteristics and internal flow field are obtained under different flow rate. The results show that when ensuring that other main structural parameters remain unchanged, the efficiency and head of open-design vortex pump increase with the blade wrap angle decreases. In the case of blade wrap angle increasing, the length of rotating reflux back from lateral cavity to inlet is longer. For the same type of vortex pump, the length of rotating reflux to inlet decreases with the increase of flow rate. At the inlet area of impeller front face, there is an area where liquid flows back to the lateral cavity. Th... [more]
Comparative Technical Process and Product Assessment of Catalytic and Thermal Pyrolysis of Lignocellulosic Biomass
Akshay D. Patel, Masoud Zabeti, K. Seshan, Martin K. Patel
July 19, 2021 (v1)
Keywords: Biofuels, catalysts, lignocellulosic biomass, process and product simulation, pyrolysis
Availability of sustainable transportation fuels in future hinges on the use of lignocellulosic resources for production of biofuels. The process of biomass pyrolysis can be used to convert solid biomass resources into liquid fuels. In this study, laboratory experiments and process simulations were combined to gain insight into the technical performance of catalytic and thermal pyrolysis processes. Waste pinewood was used as a feedstock for the processes. The pyrolysis took place at 500 °C and employs three different catalysts, in the case of the catalytic processes. A process model was developed with Aspen Plus and a wide range of representative components of bio-oil were used to model the properties of the bio-oil blend. The results of the process model calculations show that catalytic pyrolysis process produces bio-oil of superior quality. Different technical process scenarios were explored based on the properties of the bio-oil after separation of water-soluble components, with the... [more]
Revisiting the Role of Mass and Heat Transfer in Gas−Solid Catalytic Reactions
Riccardo Tesser, Elio Santacesaria
July 13, 2021 (v1)
Keywords: chemical kinetics, gas–solid catalytic reactions, heat and mass transfer
The tremendous progress in the computing power of modern computers has in the last 20 years favored the use of numerical methods for solving complex problems in the field of chemical kinetics and of reactor simulations considering also the effect of mass and heat transfer. Many classical textbooks dealing with the topic have, therefore, become quite obsolete. The present work is a review of the role that heat and mass transfer have in the kinetic studies of gas−solid catalytic reactions. The scope was to collect in a relatively short document the necessary knowledge for a correct simulation of gas−solid catalytic reactors. The first part of the review deals with the most reliable approach to the description of the heat and mass transfer outside and inside a single catalytic particle. Some different examples of calculations allow for an easier understanding of the described methods. The second part of the review is related to the heat and mass transfer in packed bed reactors, considerin... [more]
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