Academic literature on the topic 'Reaction mass-transfer processes'
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Journal articles on the topic "Reaction mass-transfer processes"
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Tripathi, R., S. Sodaye, K. Ramachandran, S. K. Sharma, and P. K. Pujari. "Incomplete mass transfer processes in 28Si +93Nb reaction." International Journal of Modern Physics E 27, no. 02 (February 2018): 1850010. http://dx.doi.org/10.1142/s0218301318500106.
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Cross sections of reaction products were measured in [Formula: see text]Si[Formula: see text]Nb reaction using recoil catcher technique involving by off-line gamma-ray spectrometry at beam energies of 105 and 155[Formula: see text]MeV. At [Formula: see text][Formula: see text]MeV, the contribution from different incomplete mass transfer processes is investigated. Results of the present studies show the contribution from deep inelastic collision (DIC), massive transfer or incomplete fusion (ICF) and quasi-elastic transfer (QET). The contribution from massive transfer reactions was confirmed from the fractional yield of the reaction products in the forward catcher foil. The present results are different from those from the reactions with comparatively higher entrance channel mass asymmetry with lighter projectiles, for which dominant transfer processes are ICF and QET which involve mass transfer predominantly from projectile to target. The [Formula: see text] values of the products close to the target mass were observed to be in a wide range, starting from [Formula: see text] of the target ([Formula: see text]Nb) and extending slightly below the [Formula: see text] of the composite system, consistent with the contribution from DIC and QET reactions. At [Formula: see text][Formula: see text]MeV, a small contribution from QET was observed in addition to complete fusion.
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Prytula, A., V. Fedirko, Y. M. Pohreliuk, and Ya Matychak. "Surface Chemical Reactions in Processes of Diffusion Mass Transfer." Defect and Diffusion Forum 237-240 (April 2005): 1312–0. http://dx.doi.org/10.4028/www.scientific.net/ddf.237-240.1312.
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The phenomenological theory for describing high-temperature interaction between metal and diluted gaseous medium has been developed. The theory is based on the assumption of duplex contact layer existence in the vicinity of interface (with relative thickness 2 d), where chemical reactions and processes of gas component migration occur. The non-stationary conditions of mass transfer at the interface are described involving effective average parameters. These conditions allow considering a wide spectrum of boundary diffusion phenomena (in a short and prolonged time ranges), in order to describe the kinetics of accumulation of diffusing component close to the interface. The description of the kinetic of gaseous saturation of metal (nitriding and borating) in the diluted medium becomes a partial proof of the suggested models. In order to approach the diffusion phenomena, boundary conditions, which contain, besides the coordinate derivative of concentration function, also the time derivative, were suggested. The derived equations describe the time dependence of change of surface concentration of gaseous component, the kinetics of its accumulation owing to chemical reaction, the specimen mass change owing to both, the diffusive addition dissolution in metal and its chemical interaction. The role of temperature is also discussed.
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Gancarczyk, Anna, Katarzyna Sindera, Marzena Iwaniszyn, Marcin Piątek, Wojciech Macek, Przemysław J. Jodłowski, Sebastian Wroński, Maciej Sitarz, Joanna Łojewska, and Andrzej Kołodziej. "Metal Foams as Novel Catalyst Support in Environmental Processes." Catalysts 9, no. 7 (July 5, 2019): 587. http://dx.doi.org/10.3390/catal9070587.
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Metal foams are considered as promising catalyst carriers due to their high porosity, large specific surface area, and satisfactory thermal and mechanical stability. The study presents heat transfer and pressure drop experiments performed for seven foams of different pore densities made from diverse metals. Mass transfer characteristics are derived using the Chilton–Colburn analogy. It was found that the foams display much more intense heat/mass transfer than a monolith, comparable to packed bed. Next, the foams’ efficiencies have been compared, using 1D reactor modeling, in catalytic reactions displaying either slower (selective catalytic reduction of NOx) or faster kinetics (catalytic methane combustion). For the slow kinetics, the influence of carrier specific surface area at which catalyst can be deposited (i.e., catalyst amount) was decisive to achieve high process conversion and short reactor. For this case, monolith appears as the best choice assuming it’s the lowest pressure drop. For the fast reaction, the mass transfer becomes the limiting parameter, thus solid foams are the best solution.
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Nagy, Endre, and Márta Vitai. "Analysis of Mass Transport through Anisotropic, Catalytic/Bio-Catalytic Membrane Reactors." Catalysts 9, no. 4 (April 13, 2019): 358. http://dx.doi.org/10.3390/catal9040358.
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This paper investigated the steady-state mass transport process through anisotropic, composite membrane layers with variable mass transport coefficients, such as the diffusion coefficient, convective velocity, or chemical/biochemical reaction rate constant. The transfer processes can be a solution-diffusion model or diffusive plus convective process. In the theoretical part, the concentration distribution as well as the inlet and outlet mass transfer rates’ expressions are defined for physical transport processes with variable diffusion or solubility coefficients and then that for transport processes accompanied by first- and zero-order reactions, in the presence of diffusive and convective flow, with constant and variable parameters. The variation of the transport parameters as a function of the local coordinate was defined by linear equations. It was shown that the increasing diffusion coefficient or convective flow induces much lower concentrations across the membrane layer than transport processes, with their decreasing values a function of the space coordinate. Accordingly, this can strongly affect the effect of the concentration dependent chemical/biochemical reaction. The inlet mass transfer rate can also be mostly higher when the transport parameter decreases across the anisotropic membrane layer.
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Bhattacharya, S., J. D. Belgrave, D. G. Mallory, R. G. Moore, M. G. Ursenbach, and S. A. Mehta. "Investigation of Thermal Fingerprint in Accelerating-Rate Calorimetry for Air-Injection Enhanced-Oil-Recovery Processes." SPE Journal 22, no. 02 (October 10, 2016): 548–61. http://dx.doi.org/10.2118/178095-pa.
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Summary The accelerating-rate calorimeter (ARC) is unique for its exceptional adiabaticity, its sensitivity, and its sample universality. Accelerating Rate Calorimetry is one of the screening tests used to determine the suitability for air-injection enhanced oil recovery (EOR). These tests show oil reactivity and exothermicity over a broad range of temperatures: low-temperature range (LTR), negative-temperature-gradient region (NTGR), and high-temperature range (HTR). An experimental and simulation study was carried out to expand understanding and interpretation of the data derived from high-pressure closed-ARC tests. Athabasca bitumen was used for the experimental study in a closed ARC at 13.89 MPag (2000 psig) to identify the temperature ranges over which the oil reacts with oxygen in the injected air. Self-heat rate from accelerating-rate calorimetry and mass-loss rates from the differential thermogravimetric analysis show the influence of mass transfer of oxygen within bitumen in the LTR and HTR. A numerical model was developed to integrate the concept of mass transfer with a reaction-kinetic model. The model incorporates solubility of oxygen with partition equilibrium coefficient (K-value) as a medium to introduce oxygen into the bitumen layer, which later transfers throughout oil layer by diffusion. This model considers both low- and high-temperature oxidation (LTO and HTO), and thermal-cracking reactions, as described in traditional reaction-kinetic models of in-situ-combustion (ISC) processes. Results show that formation of an asphaltenes film in the LTR caused by oxidation of maltenes obstructs oxygen (mass-transfer restriction) penetration into the bitumen layer. The simulated result shows that, by integrating mass transfer with the kinetic model, it is possible to predict the NTGR. Viscosity and temperature dependence on the mass transfer of oxygen is linear. As time passes and chemical reaction becomes more important with increasing temperature, the relationship deviates from linearity. With increasing temperature, the influence of chemical interaction on the oxygen distribution becomes greater, and this results in a shorter initial stage of mass transfer of oxygen within the bitumen film at low temperatures. This implies that the ARC can be a useful tool for understanding the effect of mass transfer on the oxidation characteristic for predicting LTR, NTGR, and HTR.
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Altabbakh, Dr Ban A. Ahmed, Sattar J. Hussen, and Saba A. Yosif. "Simultaneous Mass, Heat and Momentum Transfer in an Adiabatic Packed Bed Reactor." Journal of Petroleum Research and Studies 3, no. 1 (May 6, 2021): 1–25. http://dx.doi.org/10.52716/jprs.v3i1.61.
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Process modeling or computer simulation is one of the most important studies which gives the engineer a whole description about certain processes including all the mathematical relationships that are relating the process variables.
Transport phenomena on fixed bed reactor was studied because of their importance and their effects on the catalyst performance in all chemical reactions.
Simultaneous mass , heat and pressure drop were studied and all the process variables such as temperature, rate of reaction , pressure along length of the reactor were calculated and the data obtained from the mathematical package showed that with the increase the reaction temperature the process production , rate of reaction and pressure drop will increase.
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Samant, Ketan D., and Ka M. Ng. "Effect of kinetics and mass transfer on design of extractive reaction processes." AIChE Journal 44, no. 10 (October 1998): 2212–28. http://dx.doi.org/10.1002/aic.690441010.
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Berkemeier, T., A. J. Huisman, M. Ammann, M. Shiraiwa, T. Koop, and U. Pöschl. "Kinetic regimes and limiting cases of gas uptake and heterogeneous reactions in atmospheric aerosols and clouds: a general classification scheme." Atmospheric Chemistry and Physics Discussions 13, no. 1 (January 9, 2013): 983–1044. http://dx.doi.org/10.5194/acpd-13-983-2013.
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Abstract. Heterogeneous reactions are important to atmospheric chemistry and are therefore an area of intense research. In multiphase systems such as aerosols and clouds, chemical reactions are usually strongly coupled to a complex sequence of mass transport processes and results are often not easy to interpret. Here we present a systematic classification scheme for gas uptake by aerosol or cloud particles which distinguishes two major regimes: a reaction-diffusion regime and a mass-transfer regime. Each of these regimes includes four distinct limiting cases, characterized by a dominant reaction location (surface or bulk) and a single rate-limiting process: chemical reaction, bulk diffusion, gas-phase diffusion or mass accommodation. The conceptual framework enables efficient comparison of different studies and reaction systems, going beyond the scope of previous classification schemes by explicitly resolving interfacial transport processes and surface reactions limited by mass transfer from the gas phase. The use of kinetic multi-layer models instead of resistor model approaches increases the flexibility and enables a broader treatment of the subject, including cases which do not fit into the strict limiting cases typical of most resistor model formulations. The relative importance of different kinetic parameters such as diffusion, reaction rate and accommodation coefficients in this system is evaluated by a quantitative global sensitivity analysis. We outline the characteristic features of each limiting case and discuss the potential relevance of different regimes and limiting cases for various reaction systems. In particular, the classification scheme is applied to three different data sets for the benchmark system of oleic acid reacting with ozone. In light of these results, future directions of research needed to elucidate the multiphase chemical kinetics in this and other reaction systems are discussed.
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Berkemeier, T., A. J. Huisman, M. Ammann, M. Shiraiwa, T. Koop, and U. Pöschl. "Kinetic regimes and limiting cases of gas uptake and heterogeneous reactions in atmospheric aerosols and clouds: a general classification scheme." Atmospheric Chemistry and Physics 13, no. 14 (July 15, 2013): 6663–86. http://dx.doi.org/10.5194/acp-13-6663-2013.
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Abstract. Heterogeneous reactions are important to atmospheric chemistry and are therefore an area of intense research. In multiphase systems such as aerosols and clouds, chemical reactions are usually strongly coupled to a complex sequence of mass transport processes and results are often not easy to interpret. Here we present a systematic classification scheme for gas uptake by aerosol or cloud particles which distinguishes two major regimes: a reaction-diffusion regime and a mass transfer regime. Each of these regimes includes four distinct limiting cases, characterised by a dominant reaction location (surface or bulk) and a single rate-limiting process: chemical reaction, bulk diffusion, gas-phase diffusion or mass accommodation. The conceptual framework enables efficient comparison of different studies and reaction systems, going beyond the scope of previous classification schemes by explicitly resolving interfacial transport processes and surface reactions limited by mass transfer from the gas phase. The use of kinetic multi-layer models instead of resistor model approaches increases the flexibility and enables a broader treatment of the subject, including cases which do not fit into the strict limiting cases typical of most resistor model formulations. The relative importance of different kinetic parameters such as diffusion, reaction rate and accommodation coefficients in this system is evaluated by a quantitative global sensitivity analysis. We outline the characteristic features of each limiting case and discuss the potential relevance of different regimes and limiting cases for various reaction systems. In particular, the classification scheme is applied to three different datasets for the benchmark system of oleic acid reacting with ozone in order to demonstrate utility and highlight potential issues. In light of these results, future directions of research needed to elucidate the multiphase chemical kinetics in this and other reaction systems are discussed.
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Cheng, Huanbo, Jie Zhang, Haihong Huang, and Zhifeng Liu. "Mass transfer model of supercritical fluid degradation for carbon fiber composites." Journal of Composite Materials 51, no. 8 (July 17, 2016): 1073–85. http://dx.doi.org/10.1177/0021998316658944.
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It is critical to study the mass transfer of supercritical fluid degradation for carbon fiber composites to investigate their degradation mechanism, design the reactor, and develop recycling processes. The mass transfer process of supercritical fluid degradation was described from two aspects: mass diffusion from outside to inside, and from inside to outside. Mass transfer model of supercritical fluid degradation was established based on a proposed concentric cylindrical representative volume element. The reaction kinetic parameters were incorporated into the mass transfer equation, and the concentration distribution of supercritical fluid, mass transfer rate, reaction order, and reaction rate constant during the carbon fiber composites degradation process were calculated. Relaxation time was incorporated into the mass transfer process, and the supercritical fluid concentration calculation method considering non-Fick effect was proposed. Finally, two pretreatment methods were adopted to speed up the mass transfer process.
Dissertations / Theses on the topic "Reaction mass-transfer processes"
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Xu, Yaodong. "Applications of mass spectrometric techniques to charge-transfer processes and cluster ion reactions." Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/26208.
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Никольский, Валерий Евгеньевич. "Синергетические реакционно-массообменные процессы в газожидкостных аппаратах и топливных агрегатах химической технологии." Thesis, Украинский государственный химико-технологический университет, 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/24524.
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Диссертация на соискание ученой степени доктора технических наук по специальности 05.17.08 – процессы и оборудование химической технологии. – Национальный технический университет "Харьковский политехнический институт" Министерства образования и науки Украины, Харьков, 2016 г.
Диссертационная работа посвящена решению актуальной инжиниринговой научно-технической проблемы: разработать современные энергоэффективные экологически чистые технологии, средства генерирования и потребления тепловой энергии с применением систем рекуперации теплоты на основе синергетического единства аппаратурно-технологического оформления процессов и системного подхода. В работе разработаны научно-методологические основы и практические способы повышения эффективности использования топлива в газожидкостных аппаратах и топливных агрегатах химической технологии за счет интенсификации тепловых процессов в их рабочем пространстве. С позиции совершенствования топливо– и материалосберегающих техники и технологий созданы новые конструкции газожидкостных аппаратов и топливных агрегатов. На их основе синтезированы экологически чистые энергоэффективные технологические системы (ЭТС), приемлемые для химической технологии и других сфер промышленности, коммунального, сельского хозяйства, отвечающие современным энергетическим и экологическим требованиям. Систематизированы методы интенсификации гетерогенных процессов в теплотехнологических аппаратах; предложены новые перспективные РТ и АК методы интенсификации и обоснована целесообразность их практического использования при синтезе новых ЭТС на базе синергетически совмещенных реакционно-разделительных процессов (обеспечение неоднофазности, наложение электрических и магнитных полей на контактирующие фазы, оптимизация параметров пульсаций в гетерогенных системах, одно- и многотипное комбинирование теплогенерирующих аппаратов, обеспечение многократных входных и концевых эффектов, соударения, закручивания, взаимной эжекции контактирующих фаз и их осциллирования, циклический подвод энергии). Разработанные и приведенные в диссертации аппараты, технологические процессы и оборудование широко внедрены на предприятиях Минхимпрома, Минметаллургии, Минавтопрома, Минкоммунхоза Украины и стран СНГ.A thesis for Doctor of Technical degree, specialty 05.17.08 – process and equipments of chemical technology. – National Technical University "Kharkiv Polytechnic Institute" Ministry of Education and Science of Ukraine, Kharkiv, 2016. The thesis deals with the improvement of actual engineering science-technical problem: the development of the modern energy effective ecological technologies, the means of energy generation and consumption using the heat recuperation systems on the base of synergetic unity of hardware implementation of the processes and system approach. For that the methodological fundamentals and practical methods of increasing of fuel utilization efficiency in the gas-liquid apparatuses and in the fuel combustion units of chemical technology at the expense of heat processes intensification were developed. Looking for improvements in fuel efficiency and materials saving the new constructions of gas-liquid apparatuses and fuel combustion units were created. On this base the ecological and energy efficiency technological systems were synthesized. They confirm to the requirements of modern power engineering and they are acceptable for the chemical technology and the other industries, as well as for communal services and agriculture. The high-effective contact-module system was developed. It was equipped with the immersion combustion apparatuses with multiple phase inversion and oscillation modulating of contacted phases. The system can be used for heat supply of industrial and agricultural buildings, apartment houses without using boilers with heat utilization of combustion products, when heat rating of 200, 400, 600, 1000, 2000 kWt is assumed, depending a need for generated heat. The expenses for complex structures and buildings’ heating using the development are decreased by 2,5 – 2,8 times in comparison with the traditional means. Contact-module system has stood the government heat-ecological test, which confirmed its high efficiency, ecological compatibility, serviceability. Construction standard specifications for serial production in the different branches of economy were obtained. The developed and presented in the thesis apparatuses, technological processes and equipments were applied in chemistry, metallurgy, motor-car industries and in communal services in Ukraine and CIS countries.
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Нікольський, Валерій Євгенович. "Синергетичні реакційно-масообмінні процеси в газорідинних апаратах і паливних агрегатах хімічної технології." Thesis, НТУ "ХПІ", 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/24517.
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Дисертація на здобуття наукового ступеня доктора технічних наук за спеціальністю 05.17.08 – процеси та обладнання хімічної технології. – Національний технічний університет "Харківський політехнічний інститут" Міністерства освіти і науки України, Харків, 2016 р.
Дисертаційна робота присвячена вирішенню актуальної інжинірингової науково-технічної проблеми: розробити сучасні енергоефективні екологічно чисті технології, засоби генерування та споживання теплової енергії із застосуванням систем рекуперації теплоти на основі синергетичної єдності апаратурно-технологічного оформлення процесів і системного підходу. У роботі розроблено науково-методологічні основи та практичні способи підвищення ефективності використання палива в газорідинних апаратах і паливних агрегатах хімічної технології за рахунок інтенсифікації теплових процесів в їх робочому просторі. З позиції вдосконалення паливо- і матеріалозберігаючих техніки і технологій створено нові конструкції газорідинних апаратів і паливних агрегатів. На їх основі синтезовано екологічно чисті енергоефективні технологічні системи (ЕТС), прийнятні для хімічної технології та інших сфер промисловості, комунального, сільського господарства, які відповідають сучасним енергетичним та екологічним вимогам. Розроблено високоефективну контактно-модульну систему (КМС), обладнану апаратами зануреного горіння (АЗГ) з багатократною інверсією і модуляцією коливань контактуючих фаз для потреб теплопостачання промислових будівель і споруд, житлових і сільськогосподарських комплексів, яка виключає використання котельних і бойлерних установок з утилізацією теплоти продуктів згоряння, тепловою потужністю 200, 400, 600, 1000, 2000 кВт і вище залежно від потреби в генерованій теплоті. Витрати на обігрівання будівель і споруд при використанні пристрою знижуються в 2,5-2,8 рази в порівнянні з традиційними способами обігрівання. КМС пройшла державні тепло-екологічні випробування, які підтвердили її високу енергоефективність, екологічність, надійність в роботі. Отримано технічні умови на серійне її виготовлення і експлуатацію в різних галузях народного господарства. Розроблені і наведені в дисертації апарати, технологічні процеси і устаткування широко впроваджені на підприємствах Мінхімпрому, Мінметалургіі, Мінавтопрому, Мінкомунгоспу України та країн СНД.A thesis for Doctor of Technical degree, specialty 05.17.08 – process and equipments of chemical technology. – National Technical University "Kharkiv Polytechnic Institute" Ministry of Education and Science of Ukraine, Kharkiv, 2016. The thesis deals with the improvement of actual engineering science-technical problem: the development of the modern energy effective ecological technologies, the means of energy generation and consumption using the heat recuperation systems on the base of synergetic unity of hardware implementation of the processes and system approach. For that the methodological fundamentals and practical methods of increasing of fuel utilization efficiency in the gas-liquid apparatuses and in the fuel combustion units of chemical technology at the expense of heat processes intensification were developed. Looking for improvements in fuel efficiency and materials saving the new constructions of gas-liquid apparatuses and fuel combustion units were created. On this base the ecological and energy efficiency technological systems were synthesized. They confirm to the requirements of modern power engineering and they are acceptable for the chemical technology and the other industries, as well as for communal services and agriculture. The high-effective contact-module system was developed. It was equipped with the immersion combustion apparatuses with multiple phase inversion and oscillation modulating of contacted phases. The system can be used for heat supply of industrial and agricultural buildings, apartment houses without using boilers with heat utilization of combustion products, when heat rating of 200, 400, 600, 1000, 2000 kWt is assumed, depending a need for generated heat. The expenses for complex structures and buildings’ heating using the development are decreased by 2,5 – 2,8 times in comparison with the traditional means. Contact-module system has stood the government heat-ecological test, which confirmed its high efficiency, ecological compatibility, serviceability. Construction standard specifications for serial production in the different branches of economy were obtained. The developed and presented in the thesis apparatuses, technological processes and equipments were applied in chemistry, metallurgy, motor-car industries and in communal services in Ukraine and CIS countries.
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Bhatelia, Tejas Jagdish. "Novel reactors for multiphase processes." Curtin University of Technology, Science and Engineering, Department of Chemical Engineering, 2009. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=129027.
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Process intensification tools, such as the capillary reactor, offer several benefits to the chemical process industries due to the well-defined high specific interfacial area available for heat and mass transfer, which increases the transfer rates, and due to low inventories, they also enhance the safety of the process. This has provided motivation to investigate three such tools, namely the capillary microreactor, spinning disc and rotating tube reactors, in this study.The gas-liquid slug flow capillary microreactor intensifies reactor performance through internal circulation caused by the shear between the continuous phase/wall surface and the slug axis, which enhances the diffusivity and consequently increases the reaction rates. However, integrating the complex hydrodynamics of this reactor with its chemical kinetics is a mathematically challenging task. Therefore, in this study, a simple-to-complex approach, using a set of state-of-the-art computational fluid dynamic tools, has been used. Firstly, simulations were performed without any chemical reaction to ascertain the extent of slug flow regime. The model also clearly captured the slug flow generation mechanism which can be used to structurally optimize the angle of entry in these reactors. Finally, the hydrodynamic model was also capable of estimating the pressure drop and slug lengths. After successfully simulating the hydrodynamics of the system, a reaction model was incorporated to study the chemical reaction kinetics. The results were compared with the published experimental work and were found to be in good agreement.
The spinning disc reactor utilizes the centrifugal and shear forces to generate thin liquid films characterized with intense interfering waves. This enables a very high heat transfer coefficients to be realized between the disc and liquid, as well as very high mass transfer between the liquid and the bulk gas phase. The waves formed also produce an intense local mixing with very little back mixing. This makes a spinning disc reactor an ideal contactor for multiphase processes. The focus of this study has been to elucidate the hydrodynamic behaviour of the liquid film flow over the horizontal spinning disc. Investigations were also performed to elaborate the local and overall hydrodynamic characteristics of a fully developed spinning disc reactor. Simulation results showed a continuous linear liquid film on the horizontal spinning disc and intense mixing performance in the annulus of the reactor around the disc surface. Finally, the film thickness data from the simulations were compared with the limited amount of data available for this novel process.
Rotating tube reactor also uses centrifugal forces to generate the liquid film and a high degree of mixing along with an improved control over the reactant retention times. In this work we have conducted a CFD analysis to understand the hydrodynamics of this new technology for future developments.
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Gallager, Kevin A. "Mass transfer and biosorption processes with Rhizopus oryzae as an absorbent of reactive dye and metal ions from aqueous effluent." Thesis, Queen's University Belfast, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364591.
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Du, Preez Louis Jacobus. "Reactive absorption kinetics of CO2 in alcoholic solutions of MEA: fundamental knowledge for determining effective interfacial mass transfer area." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86656.
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Thesis (PhD)--Stellenbosch University, 2014.ENGLISH ABSTRACT: The reactive absorption rate of CO2 into non-aqueous solvents containing the primary amine, mono-ethanolamine (MEA) is recognised as a suitable method for measuring the effective interfacial mass transfer area of separation column internals such as random and structured packing. Currently, this method is used under conditions where the concentration of MEA in the liquid film is unaffected by the reaction and the liquid phase reaction is, therefore, assumed to obey pseudo first order kinetics with respect to CO2. Under pseudo first order conditions, the effect of surface depletion and renewal rates are not accounted for. Previous research indicated that the effective area available for mass transfer is also dependent upon the rate of surface renewal achieved within the liquid film. In order to study the effect of surface depletion and renewal rates on the effective area, a method utilising a fast reaction with appreciable depletion of the liquid phase reagent is required. The homogeneous liquid phase reaction kinetics of CO2 with MEA n-Propanol as alcoholic solvent was investigated in this study. A novel, in-situ Fourier Transform Infra-Red (FTIR) method of analysis was developed to collect real time concentration data from reaction initiation to equilibrium. The reaction was studied in a semi-batch reactor set-up at ambient conditions (T = 25°C, 30°C and 35°C, P = 1 atm (abs)). The concentration ranges investigated were [MEA]:[CO2] = 5:1 and 10:1. The concentration range investigated represents conditions of significant MEA conversion. The reaction kinetic study confirmed the findings of previous research that the reaction of CO2 with MEA is best described by the zwitterion reactive intermediate reaction mechanism. Power rate law and pseudo steady state hypothesis kinetic models (proposed in literature) were found to be insufficient at describing the reaction kinetics accurately. Two fundamentally derived rate expressions (based on the zwitterion reaction mechanism) provided a good quality model fit of the experimental data for the conditions investigated. The rate constants of the full fundamental model were independent of concentration and showed an Arrhenius temperature dependence. The shortened fundamental model rate constants showed a possible concentration dependence, which raises doubt about its applicability. The specific absorption rates (mol/m2.s) of CO2 into solutions of MEA/n-Propanol (0.2 M and 0.08 M, T = 25°C and 30°C, P = ±103 kPa) were investigated on a wetted wall experimental setup. The experimental conditions were designed for a fast reaction in the liquid film to occur with a degree of depletion of MEA in the liquid film. Both interfacial depletion and renewal of MEA may be considered to occur. The gas phase resistance to mass transfer was determined to be negligible. An increase in liquid turbulence caused an increase in the specific absorption rate of CO2 which indicated that an increase in liquid turbulence causes an increase in effective mass transfer area. Image analysis of the wetted wall gas-liquid interface confirmed the increase in wave motion on the surface with an increase in liquid turbulence. The increase in wave motion causes an increase in both interfacial and effective area. A numerical solution strategy based on a concentration diffusion equation incorporating the fundamentally derived rate expressions of this study is proposed for calculating the effective area under conditions where surface depletion and renewal rates are significant. It is recommended that the reaction kinetics of CO2 with MEA in solvents of varying liquid properties is determined and the numerical technique proposed in this study used to calculate effective area from absorption rates into these liquids. From the absorption data an effective area correlation as a function of liquid properties may be derived in future.
AFRIKAANSE OPSOMMING: Die reaktiewe absorpsie van CO2 in nie-waterige oplossings van die primêre amien, monoetanolamien (MEA) word erken as ‘n geskikte metode om die effektiewe massaoordragsarea van gepakte skeidingskolomme te bepaal. Tans word die metode gebruik onder vinnige pseudo eerste orde reaksietoestande met betrekking tot CO2. Die pseudo eersteorde aanname beteken dat die konsentrasie van MEA in die vloeistoffilm onbeduidend beïnvloed word deur die reaksie en effektief konstant bly. Onder pseudo eerste orde toestande word oppervlakverarming- en oppervlakvernuwingseffekte nie in ag geneem nie, juis as gevolg van die konstante konsentrasie van MEA in die vloeistoffilm. Daar is voorheen bevind dat oppervlakverarming en oppervlakvernuwing ‘n beduidende invloed het op die beskikbare effektiewe massaoordragsarea. Hierdie invloed kan slegs bestudeer word met ‘n vinnige reaksie in die vloeistoffilm wat gepaard gaan met beduidende oppervlakverarming van die vloeistoffase reagens. Die homogene vloeistoffase reaksiekinetika van CO2 met MEA in die alkohol oplosmiddel, n- Propanol, is in hierdie studie ondersoek. ‘n Nuwe, in-situ Fourier Transform Infra-Rooi (FTIR) metode van analiese is ontwikkel in hierdie ondersoek. Die reaksie is ondersoek in ‘n semienkelladings reaktor met MEA wat gevoer is tot die reaktor om met die opgeloste CO2 te reageer. Die FTIR metode meet spesiekonsentrasie as ‘n funksie van tyd sodat die konsentrasieprofiele van CO2, MEA en een van die soutprodukte van die reaksie gebruik kan word om verskillende reaksiesnelheidsvergelykings te modelleer. Die reaksie is ondersoek onder matige toestande (T = 25°C, 30°C and 35°C, P = 1 atm (abs)). Die konsentrasiebereik van die ondersoek was [MEA]:[CO2] = 5:1 en 10:1. Hierdie bereik is spesifiek gebruik sodat daar beduidende omsetting van MEA kon plaasvind. Die reaksiekinetieka studie het, ter ondersteuning van bestaande teorie, bevind dat die reaksie van CO2 met MEA in nie-waterige oplosmiddels soos alkohole, beskyf word deur ‘n zwitterioon reaksiemeganisme. Die bestaande reaksiesnelheids modelle (eksponensiële wet en pseudo gestadigde toestand hipotese) kon nie die eksperimentele data met genoegsame akuraatheid beskryf nie. Twee nuwe reaksiesnelheidsvergelykings, afgelei vanaf eerste beginsels en gebaseer op die zwitterioon meganisme, word voorgestel. Hierdie volle fundamentele model het goeie passings op die eksperimentele data getoon oor die volledige temperatuur en konsentrasiebereik van hierdie studie. Die reaksiekonstantes van die fundamentele model was onafhanklik van konsentrasie en tipe oplosmiddel en het ‘n Arrhenius temperatuurafhanklikheid. Die verkorte fundamentele model se reaksiekonstantes het ‘n moontlike konsentrasieafhanlikheid gewys. Dit plaas onsekerheid op die fundamentele basis van hierdie model en kan dus slegs as ‘n eerste benadering beskou word. Die spesifieke absorpsietempos (mol/m2.s) van CO2 in MEA/n-Propanol oplossings (0.2 M en 0.08 M MEA, T = 25°C and 30°C, P = ±103 kPa) is ondersoek met ‘n benatte wand (‘wetted wall’) eksperimentele opstelling. Die eksperimentele toestande is gekies sodat daar ‘n vinnige reaksie in die vloeistoffilm plaasgevind het, met beide beduidende en nie-beduidende MEA omsetting. Die doel met hierdie eksperimentele ontwerp was om die invloed van intervlakverarming en intervlakvernuwing op die spesifieke absorpsietempo te ondersoek. Gas fase weerstand was nie-beduidend onder die eksperimentele toestande nie. Beide intervlakverarming en intervlakvernuwing gebeur gelyktydig en is waargeneem vanuit die eksperimentele data. ‘n Beeldverwerkingstudie van die gas-vloeistof intervlak van die benatte wand het bevind dat daar ‘n toename in golfaksie op die vloeistof oppervlak is vir ‘n toename in vloeistof turbulensie. Hierdie golfaksie dra by tot oppervlakvernuwing en ‘n toename in effektiewe massaoordragsarea. ‘n Numeriese metode word voorgestel om die effektiewe area van beide die benatte wand en gepakte kolomme te bepaal vanaf reaktiewe absorpsietempos. Die metode gebruik die fundamentele reaksiesnelheidsvergelykings, bepaal in hierdie studie, in a konsentrasie diffusievergelyking sodat oppervlakverarming en vernuwing in ag geneem kan word. Daar word voorgestel dat die reaksiekinetika van CO2 met MEA in oplossings met verskillende fisiese eienskappe (digtheid, oppervlakspanning en viskositeit) bepaal word sodat die numeriese metode gebruik kan word om ‘n effektiewe area korrelasie as ‘n funksie van hierdie eienskappe te bepaal.
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Nourgaliev, Robert R. "Modeling and analysis of heat and mass transfer processes during in-vessel melt progression stage of light water reactor (LWR) severe accidents /." Stockholm : Tekniska högsk, 1998. http://www.lib.kth.se/abs98/nour0427.pdf.
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Duespohl, Dale W. "Modeling and optimization of a cross-flow, moving-bed, flue gas desulfurization reactor." Ohio : Ohio University, 1995. http://www.ohiolink.edu/etd/view.cgi?ohiou1179511746.
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Tokode, Oluwatosin. "Photocatalytic destruction of volatile organic compounds from the oil and gas industry." Thesis, Robert Gordon University, 2014. http://hdl.handle.net/10059/1134.
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Heterogeneous photocatalysis is an advanced oxidation technology widely applied in environmental remediation processes. It is a relatively safe and affordable technology with a low impact on the environment and has found applications in a number of fields from chemical engineering, construction and microbiology to medicine. It is not catalysis in the real sense of the word as the photons which initiate the desired photocatalytic reaction are consumed in the process. The cost of these photons is by far the limiting economic factor in its application. From a technical standpoint, the inefficient use of the aforementioned photons during the photocatalytic reaction is responsible for the limited adoption of its application in industry. This inefficiency is characterised by low quantum yields or photonic efficiencies during its application. The mechanism of the technique of controlled periodic illumination which was previously proposed as a way of enhancing the low photonic efficiency of TiO2 photocatalysis has been investigated using a novel controlled experimental approach; the results showed no advantage of periodic illumination over continuous illumination at equivalent photon flux. When the technique of controlled periodic illumination is applied in a photocatalytic reaction where attraction between substrate molecules and catalyst surface is maximum and photo-oxidation by surface-trapped holes, {TiIVOH•}+ ads is predominant, photonic efficiency is significantly improved. For immobilized reactors which usually have a lower illuminated surface area per unit volume compared to suspended catalyst and mass transfer limitations, the photonic efficiency is even lower. A novel photocatalytic impeller reactor was designed to investigate photonic efficiency in gas–solid photocatalysis of aromatic volatile organic compounds. The results indicate photonic efficiency is a function of mass transfer and catalyst deactivation rate. The development of future reactors which can optimise the use of photons and maximize photonic efficiency is important for the widespread adoption of heterogeneous photocatalysis by industry.
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Braga, Maria. "Étude des phénomènes de transfert et de l'hydrodynamique dans des réacteurs agités à panier catalytique." Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10011/document.
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Parmi les différents outils de laboratoire, les réacteurs agités triphasiques à panier catalytique sont souvent utilisés pour l'acquisition de données cinétiques avec des catalyseurs mis en forme. Malgré sa large utilisation, très peu d'auteurs se sont intéressés à la caractérisation de l'hydrodynamique et des transferts de matière de ces outils. Or, dans les cas de réactions rapides, des limitations hydrodynamiques et/ou au transfert peuvent conduire à des difficultés à discriminer les catalyseurs ou à obtenir des paramètres cinétiques. L'objectif de cette étude était de connaître le domaine d'applicabilité de ces outils et présenter des pistes d'optimisation. Une méthodologie de caractérisation qui couple une étude hydrodynamique et une étude de transfert de matière a été mise en place. L'étude hydrodynamique a permis d'établir une cartographie des régimes d'écoulement gaz/liquide selon les conditions opératoires et les configurations géométriques. Cette étude a permis d'expliquer les résultats obtenus au niveau du transfert de matière, notamment, l'influence de la présence du panier et des bulles de gaz. Dans la configuration actuelle, cet outil semble être limité par le transfert liquide/solide. Ainsi, avec ce système, des études cinétiques pour des réactions avec une constante cinétique cin k pouvant aller jusqu'à 0,02 s-1 pourront être réalisées. Au-delà, l'outil sera inadapté. Pour améliorer cet outil de test, il faut optimiser le réacteur en modifiant le design du panier et de la turbine, et le diamètre de la cuve de manière à maximiser la vitesse radiale à travers du milieu poreux. Il faut aussi éviter la présence d'un régime de contournement du panier par le liquideStationary catalytic basket stirred reactors are often used among the various three-phase laboratory reactors for primary screening of commercial shaped catalysts. Until today, hydrodynamics and mass transfer studies concerning the impact of the presence of the basket in the flow are scarce which can be an obstacle to catalyst screening mainly in the case of fast reactions. The aim of this study is to know the range of applicability of these devices and optimize them if necessary. A characterization methodology that couples hydrodynamics and mass transfer was developed. The hydrodynamic studies allowed establishing a flow regime map of the gas/liquid flow for different reactor designs and operational conditions. This study has allowed as well understanding the influence of the basket and gas bubbles on gas/liquid and solid/liquid mass transfer. For the studied reactor, the liquid/solid mass transfer is the limiting phenomena. This system can however be used for catalyst screening for reaction rate constants smaller than 0.02 s-1. For faster reactions, these devices must be improved by changing the design of basket and impeller and the tank diameter. The optimized configuration should improve de radial flow through the porous medium and avoid the flow bypassing around the basket
Books on the topic "Reaction mass-transfer processes"
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Transport processes in chemically reacting flow systems. Mineola, N.Y: Dover Publications, 2000.
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Transport processes in chemically reacting flow systems. Boston: Butterworths, 1986.
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T, Rogers J., and Seminar on Fission Product Transport Processes in Reactor Accidents (1989 : Dubrovnik, Yugoslavia), eds. Fission product transport processes in reactor accidents. New York: Hemisphere Pub. Corp., 1990.
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Rogers, J. T. Fission Product Processes In Reactor Accidents (Proceedings of the International Centre for Heat and Mass Transfer, No. 30). CRC, 1990.
Find full textBook chapters on the topic "Reaction mass-transfer processes"
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Reutt-Robey, Janice E., and Woei-Wu Pai. "Mass Transfer in Surface Chemical Processes: Adsorption, Faceting and Reaction on Ag(110)." In Surface Diffusion, 475–87. Boston, MA: Springer US, 1997. http://dx.doi.org/10.1007/978-1-4899-0262-7_42.
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Nagy, Endre. "Diffusion mass transfer in enzyme membrane reactor." In Integration of Membrane Processes into Bioconversions, 211–21. Boston, MA: Springer US, 2000. http://dx.doi.org/10.1007/978-1-4615-4269-8_16.
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"More about Diffusion: Transient Diffusion and Diffusion with Reaction." In Mass Transfer and Separation Processes, 167–218. CRC Press, 2007. http://dx.doi.org/10.1201/9781420051605-9.
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Doraiswamy, L. K. "Gas-Liquid Reactions." In Organic Synthesis Engineering. Oxford University Press, 2001. http://dx.doi.org/10.1093/oso/9780195096897.003.0022.
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The general physical picture characterizing fluid-fluid reactions is sketched in Figure 14.1. A is the solute in phase 1 (gas or liquid) and is slightly soluble in phase 2, which is always a liquid. Upon entering phase 2, A reacts with B present in that phase. When phase 1 is a gas, the reaction is almost always restricted to phase 2 (except in the rare case of a desorbing product reacting in the gas phase), but when phase 1 is a liquid or a solid, reaction can occur in both phases. In this chapter we consider the case where reaction is confined to phase 2, gas-liquid reactions. Because two phases are present, mass transfer across the interface is clearly an important consideration. Therefore, the basis of the analysis is interaction between mass transfer and reaction, leading to the formulation of conditions and rate expressions for reactions with varying roles in the two processes (i.e., with different controlling regimes). Consider a reaction of the general form . . . vAA(g) + vBB(I) → R [14.1] . . .where vA = 1. Our objective is to examine the effect of chemical reaction on mass transfer.
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Doraiswamy, L. K. "Phase-Transfer Reaction Engineering." In Organic Synthesis Engineering. Oxford University Press, 2001. http://dx.doi.org/10.1093/oso/9780195096897.003.0028.
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There are many situations in organic synthesis where it is desirable to bring about reaction between reactants present in two (or more) immiscible phases. Agents known as phase-transfer catalysts are used for this purpose. Their role in initiating or accelerating such reactions has been proven extensively since the early seventies, and the principles of their operation are being increasingly understood [see Weber and Gokel, 1977; Reuben and Sjoberg, 1981; Frechet, 1984; Freedman, 1986; Goldberg, 1992 (English translation); Dehmlow and Dehmlow, 1993; Starks et al., 1994; Yufit, 1995; Sasson and Neumann, 1997; Naik and Doraiswamy, 1998]. To date, an estimated 500 different commercial chemical processes (mostly for small volume chemicals) using about 5-25 million pounds per annum of phase-transfer catalysts have been reported (Starks et al., 1994), and well over 6,500 compounds have been synthesized in the laboratory using PTC (Keller, 1979, 1986). A large number of industrial applications of phase-transfer catalysis are found in the pharmaceutical, agrochemical, and fine chemicals industries. Additionally, it is now being increasingly used in processes related to the environment, in process modifications for eliminating the use of solvents, and in reactions related to the treatment of poisonous effluents. Not surprisingly, then, there has been a constant stream of publications and patents every year. Phase-transfer catalysis (PTC) is an area that has largely been the province of the preparatory organic chemist (defined broadly to include organometallic and polymer chemists). It is only since the early eighties that the engineering aspects of phase-transfer catalysis are being explored, including such traditional features as mass and heat transfer and reactor design. Our main objective is to present a brief but coherent engineering analysis of PTC, following an introduction to its basic principles. When two reactants are present in two different, immiscible liquid phases (usually one aqueous and the other organic), they can often be brought together by addition of a solvent that is both water-like and organic-like (e.g., ethanol, which derives its hydrophilic nature from its hydroxyl group and its lipophilicity from the ethyl group). However, the rate enhancement tends to be limited due to excessive solvation of the nucleophile.
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Zhao, Fang, Kai Wang, and Guangsheng Luo. "A Review of Mass-Transfer and Reaction-Kinetics Studies in Microfluidic Solvent Extraction Processes." In Ion Exchange and Solvent Extraction: Volume 23, 219–52. CRC Press, 2019. http://dx.doi.org/10.1201/9781315114378-6.
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Bokstein, Boris S., Mikhail I. Mendelev, and David J. Srolovitz. "Kinetics of homogeneous chemical reactions." In Thermodynamics and Kinetics in Materials Science. Oxford University Press, 2005. http://dx.doi.org/10.1093/oso/9780198528036.003.0010.
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Kinetics considers the rates of different processes. Chemical kinetics refers to the rates and mechanisms of chemical reactions and mass transfer (diffusion). Recall that since thermodynamic equilibrium implies that the rates of all processes are zero, time is not a thermodynamic variable. Rather, time is the new parameter introduced by the consideration of kinetic processes. The rate of a kinetic process and how it depends on time is determined, in part, by the degree of the deviation from equilibrium. If the deviation from equilibrium is small, the rate decreases (without changing sign) as the system approaches equilibrium. If the deviation from equilibrium is large, the situation is more complicated. For example, non-monotonic (including oscillatory) processes are possible. The sign of the rate can change during such processes; that is, the reaction can proceed in one direction and then the other. Additionally, if the deviation from equilibrium is large, small changes to the system can produce very large changes in the rate of the kinetic process (i.e. chaos). Non-equilibrium, yet nearly stationary states of the system can arise (i.e. states that exist for a very long time). Finally, if the deviation from equilibrium is very large, the system can explode (i.e. the process continues to accelerate with time). In this chapter, we develop a formal description of the kinetics of rather simple chemical reactions. Consecutive and parallel reactions will also be considered here. A more general approach (irreversible thermodynamics) will be considered in Chapter 9. In Chapter 10, we examine diffusive processes. Then, in Chapter 11, we consider the kinetics of heterogeneous processes. In order to start the study of chemical reaction kinetics, we must first define what we mean by the rate of reaction. Consider the following homogeneous reaction: . . . Cl2 + 2NO → 2NOCl. (8.1) . . .
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Hagelberg, P., V. Alopaeus, K. Lipiäinen, J. Aittamaa, and A. O. I. Krause. "Mass and heat transfer effects in the kinetic modelling of catalytic cracking." In Reaction Kinetics and the Development and Operation of Catalytic Processes, Proceedings of the 3rd International Symposium, 165–71. Elsevier, 2001. http://dx.doi.org/10.1016/s0167-2991(01)81959-5.
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Bethke, Craig M. "Sediment Diagenesis." In Geochemical Reaction Modeling. Oxford University Press, 1996. http://dx.doi.org/10.1093/oso/9780195094756.003.0023.
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Diagenesis is the set of processes by which sediments evolve after they are deposited and begin to be buried. Diagenesis includes physical effects such as compaction and the deformation of grains in the sediment (or sedimentary rock), as well as chemical reactions such as the dissolution of grains and the precipitation of minerals to form cements in the sediment's pore space. The chemical aspects of diagenesis are of special interest here. Formerly, geologists considered chemical diagenesis to be a process by which the minerals and pore fluid in a sediment reacted with each other in response to changes in temperature, pressure, and stress. As early as the 1960s and especially since the 1970s, however, geologists have recognized that many diagenetic reactions occur in systems open to groundwater flow and mass transfer. The reactions proceed in response to a supply of reactants introduced into the sediments by flowing groundwater, which also serves to remove reaction products. Hay (1963, 1966), in studies of the origin of diagenetic zeolite, was perhaps the first to emphasize the effects of mass transport on sediment diagenesis. He showed that sediments open to groundwater flow followed reaction pathways different from those observed in sediments through which flow was restricted. Sibley and Blatt (1976) used cathodoluminescence microscopy to observe the Tuscarora orthoquartzite of the Appalachian basin. The almost nonporous Tuscarora had previously been taken as a classic example of pressure welding, but the microscopy demonstrated that the rock is not especially well compacted but, instead, tightly cemented. The rock consists of as much as 40% quartz (SiO2) cement that was apparently deposited by advecting groundwater. By the end of the decade, Hayes (1979) and Surdam and Boles (1979) argued forcefully that the extent to which diagenesis has altered sediments in sedimentary basins can be explained only by recognition of the role of groundwater flow in transporting dissolved mass. This view has become largely accepted among geoscientists, although it is clear that the scale of groundwater flow might range from the regional (e.g., Bethke and Marshak, 1990) to circulation cells perhaps as small as tens of meters (e.g., Bjorlykke and Egeberg, 1993; Aplin and Warren, 1994).
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Pisu, M., A. Cincotti, G. Cao, and F. Pepe. "Simulation of the effect of mass transfer limitations in complex gas-liquid reactions." In Reaction Kinetics and the Development and Operation of Catalytic Processes, Proceedings of the 3rd International Symposium, 471–76. Elsevier, 2001. http://dx.doi.org/10.1016/s0167-2991(01)81997-2.
Full textConference papers on the topic "Reaction mass-transfer processes"
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Hedayat Mofidi, Seyyed Ali, and Kent S. Udell. "Study of Heat and Mass Transfer in MgCl2/NH3 Thermo-Chemical Batteries." In ASME 2016 10th International Conference on Energy Sustainability collocated with the ASME 2016 Power Conference and the ASME 2016 14th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/es2016-59099.
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Intermittency of sustainable energy or waste heat availability calls for energy storage systems such as thermal batteries. Thermo-chemical batteries are particularly appealing for energy storage applications due to their high energy densities and ability to store thermal energy as chemical energy for long periods of time without any energy loss. Thermo-chemical batteries based on a reversible solid-gas (MgCl2 - NH3) reactions and NH3 liquid-gas phase change are of specific interest since the kinetics of absorption are fast and the heat transfer rates for liquid — vapor phase change are high. Thus, a thermo-chemical battery based on reversible reaction between magnesium chloride and ammonia was studied. Experimental studies were conducted on a reactor in which temperature profiles within the solid matrix and pressure and flow rates of gas were obtained during charging processes. A numerical model based on heat and mass transfer within the salt and salt-gas reactions was developed to simulate the absorption processes within the solid matrix and the results were compared with experimental data. The studies were used to determine dominant heat and mass transfer processes within the salt. It is shown that for high permeability materials, heat transfer is the dominant factor in determining reaction rates. However increasing thermal conductivity might decrease permeability and reduce reaction rates. The effect of constraining mass flow rate on the temperature and reaction propagation is also studied. These results show that optimized heat and mass transfer within the solid-gas reactor will lead to improved performance for heating and air conditioning applications.
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Yang, Guogang, Wei Wei, Jinliang Yuan, Danting Yue, and Xinrong Lv. "Analysis of Transport Processes and Chemical Reaction in Combustion Duct of Compact Methane Reformer." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22420.
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A composite combustion duct in compact methane reformers consists of a gas flow channel, porous layer and solid plates. There are various transport processes appeared, such as gas flow in the channel, multi-component species convection/diffusion in the porous layer, and heat transfer. They are further coupled by methane catalytic combustion in the porous layer, which affects the reformer overall performance and reliability. By three dimensional CFD approach, the reacting gas flow and heat transfer processes were numerically studied. The reformer conditions such as mass balances associated with the chemical reaction and gas permeation to/from the porous layer are implemented in the calculation. The results reveal that the catalytic combustion reaction is confined in a thin porous catalyst area close to fuel gas flow duct. Transport processes of the fuel gas species and temperature distribution are significantly affected by the reactions.
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Dreher, Simon, Matthias Kronsbein, and Peter Woias. "Heat and Mass Transfer and Wall Contact for Laminar Vortices in Microreactors." In ASME 2008 6th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2008. http://dx.doi.org/10.1115/icnmm2008-62310.
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In microreactors, interactions between fluid and channel wall affect many chemical reactions. Due to a good heat and momentum transfer, highly exothermic reactions can be quenched and so combustion is inhibited. On the other hand, reactions on catalyst-coated walls call for a high mass transport to and from the walls which is one of the parameters determining the reaction rate for fast reactions. In this contribution, heat and mass transfer towards the walls are investigated in bent microchannels. Laminar flow in the Reynolds number range of 100 < Re < 1000 is studied, where Dean vortices are induced by bends. Optimized geometries of the bends are found with numerical fluid simulations and compared experimentally using chemical reactions. As characteristic parameter, the contact time distribution is calculated which is defined by the distribution of the residence time in regions near the wall. For the characterization of the reactors, also simulations of heat flux are performed. Various optimized reactors are fabricated and experimentally compared by a luminol reaction catalyzed at the copper-plated walls. In other experiments, heat transfer into the fluid is measured. The experimental results are compared to the simulated transport processes.
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Peng, Shi-Wen, Robert W. Besant, and Graeme Strathdee. "Heat and Mass Transfer in Granular Potash Fertilizer With a Surface Dissolution Reaction." In ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-1023.
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Abstract Potash is a widely used granular fertilizer and when exposed to high humidities it readily adsorbs water forming a liquid electrolyte solution on each particle. Heat and mass transfer due to air flow through granular potash beds is studied experimentally and numerically. A one dimensional experimental set-up is used to measure the temperature and air humidity response and mass gain of a potash bed subject to a step change in air flow. A porous media mathematical model is developed to predict the transient temperature and moisture content distributions. The transport processes are modelled as non-equilibrium heat and mass transfer between the porous solid and air flow gaseous phases. The state of the surface electrolyte solution is modelled by the thermodynamics of electrolyte solutions. Experimental and numerical results shows that when there is a strong surface heat source due to phase change, especially near the entrance region, non-equilibrium internal moisture and heat transfer processes exist. The temperature difference between potash granules and the air flowing through the potash bed is significant.
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Berezikov, Nikolay I., Alexander S. Gorshkov, Andrey V. Zenkov, and Kirill B. Larionov. "Intensification of ignition and combustion processes of low-reaction solid fuels by liquid hydrocarbons." In HEAT AND MASS TRANSFER IN THE THERMAL CONTROL SYSTEM OF TECHNICAL AND TECHNOLOGICAL ENERGY EQUIPMENT (HMTTSC 2021). AIP Publishing, 2021. http://dx.doi.org/10.1063/5.0067944.
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Mewes, Dieter, and Dierk Wiemann. "Numerical Calculation of Mass Transfer With Heterogeneous Chemical Reactions in Three-Phase Bubble Columns." In ASME/JSME 2007 5th Joint Fluids Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/fedsm2007-37031.
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Bubble column reactors are used for several processes in the chemical industry, e.g. hydrogenation or oxidation reactions. At the bottom of the reactor a gaseous phase is dispersed into a continuous liquid phase with suspended particles. The resulting bubble swarm induces three-dimensional, time-dependent velocity and concentration fields, which are predicted numerically. All phases are described by an Eulerian approach. The numerical calculations of the local interfacial area density and the interphase transfer terms for mass and momentum are based on a population balance equation approach which enables an effective way to couple population balance and computational fluid dynamics. In three-phase gas-liquid-solid flow particles with diameters of 100 μm are considered as catalyst for a heterogeneous chemical reaction. The influence of particles on bubble coalescence has been investigated in order to extend an existing model for the kernel functions in the population balance equation describing bubble coalescence and dispersion. The resulting three-dimensional, time-dependent velocity and concentration fields are described and graphically presented for the hydrogenation of anthra-chinone.
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Paradis, Hedvig, Martin Andersson, Jinliang Yuan, and Bengt Sunde´n. "The Kinetics Effect in SOFCs on Heat and Mass Transfer Limitations: Interparticle, Interphase and Intraparticle Transport." In ASME 2011 9th International Conference on Fuel Cell Science, Engineering and Technology collocated with ASME 2011 5th International Conference on Energy Sustainability. ASMEDC, 2011. http://dx.doi.org/10.1115/fuelcell2011-54015.
Full textAbstract:
The transport processes in the porous, micro-structured electrodes are one of the least understood areas of research of the solid oxide fuel cell (SOFC). To enhance the knowledge of the transport process’ impact on the performance in the electrodes, the micro-structure needs to be modeled in detail. But at these smaller scales, it can be both cost and time saving to first conclude at which scales, the limiting action on the transport processes occurs. This study investigates the limiting effect of the kinetic parameters’ on the heat and mass transfer at interparticle, interphase and intraparticle transport level. The internal reaction and the electrochemical reaction rates are studied at three levels in the microscopic range or even smaller. At the intraparticle level the effect of temperature distribution, i.e., heat transfer, within a catalyst particle is often less limiting than the internal mass diffusion process, while at the interphase level the former is more limiting. In this study, no severe risk for transport limitations for the anode and the cathode of the SOFC was found with the chosen kinetic parameters. It was found that the reaction rates constitute the largest risk. A parameter study was conducted by increasing the steam reforming and the electrochemical reaction rates by a factor of 100 without any transport limitations for the same kinetic parameters. The result of this study provides one type of control of the kinetic parameters which in turn have an impact on the reforming reaction rates and the cell performance.
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Renken, Albert. "Micro-Structured Reactors and Catalysts for the Intensification of Chemical Processes." In ASME 2009 7th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2009. http://dx.doi.org/10.1115/icnmm2009-82147.
Full textAbstract:
Process intensification is the term which describes an innovative design approach in chemical engineering aiming on a significant increase of the specific performance of chemical reactors and plants miniaturization, of at least an order of magnitude. In addition, the running costs should be reduced and the process should be more efficient, safer, and less polluting than the existing ones. Micro process technology is considered as means of process intensification leading to better use of raw materials and energy. Chemical micro-structured reactors (MSR) are devices containing open paths for fluids with dimensions in the sub-millimeter range. Mostly they consist of multiple parallel channels with diameters between ten and several hundred micrometers where the chemical transformations occur. This results in a high specific surface area in the range of 10,000 to 50,000 m2m−3 and allows a more efficient mass and heat transfer compared to traditional chemical reactors having usually ∼100 m2m−3. Another important feature of micro-structured reactors is that the heat exchange and the reaction are mostly performed in the same gadget. Intensification of heterogeneous catalytic processes involves besides of innovative engineering of micro-structured reactors, the proper design of the catalyst. This requires the simultaneous development of the catalyst and the reactor. The catalyst design should be closely integrated with the reactor design taking into consideration the reaction mechanism, mass/heat transfer and the energy supply / evacuation resulting in high selectivity and yield of the target products. Besides general criteria for the choice and proper design of micro-structured reactors for process intensification, particular needs for homogeneous and multiphase reactions will be discussed.
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Hathaway, Brandon J., Jane H. Davidson, and David B. Kittelson. "Solar Gasification of Biomass: Kinetics of Pyrolysis and Steam Gasification in Molten Salt." In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-39829.
Full textAbstract:
The use of concentrated solar energy for pyrolysis and gasification of biomass is an efficient means for production of hydrogen rich synthesis gas. Utilizing molten alkali-carbonate salts as a reaction and heat transfer media offers enhanced stability and higher reaction rates to these solar processes. To establish the reaction kinetics, experiments were carried out in an electrically heated molten salt reactor. Cellulose or activated charcoal were pyrolyzed or gasified with steam from 1124 K to 1235 K with and without salt. Arrhenius rate expressions are derived from the data supported by a numerical model of heat and mass transfer. The average rate of the reactions in molten salt, as measured by their reactivity index, is increased by 70% for pyrolysis and by an order of magnitude for steam gasification.
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Xiang, Rong, Erik Einarsson, Junichiro Shiomi, and Shigeo Maruyama. "Feedstock Diffusion and Decomposition in Aligned Carbon Nanotube Arrays." In ASME 2009 Second International Conference on Micro/Nanoscale Heat and Mass Transfer. ASMEDC, 2009. http://dx.doi.org/10.1115/mnhmt2009-18479.
Full textAbstract:
Feedstock diffusion and decomposition in the root growth of aligned carbon nanotube (CNT) arrays is discussed. A non-dimensional modulus is proposed to differentiate catalyst-poisoning controlled growth deceleration from one which is diffusion controlled. It is found that, at current stage, aligned multi-walled carbon nanotube (MWNT) arrays are usually free of feedstock diffusion resistance. However, for single-walled carbon nanotube (SWNT) arrays, since the inter-tube distance is much smaller than the mean free path of carbon source (ethanol here), high diffusion resistance is significantly limiting the growth rate. The method presented here is also able to predict the critical lengths in different chemical vapor deposition (CVD) processes from which CNT arrays begin to meet this diffusion limit, as well as the possible solutions to this diffusion caused growth deceleration. The diffusion of carbon source inside of an array becomes more important when we found ethanol undergoes severe thermal decomposition at the reaction temperature. This means, in a typical alochol CVD, hydrocarbons and radicals decomposed from ethanol may collide and react with the outer walls of SWNTs before reaching catalyst particles. We found when flow rate is low and ethanol is thoroughly decomposed, the produced SWNTs contain more soot structures than the SWNTs obtained at higher ethanol flow rate. Understanding the mass transport and reaction inside a SWNT array is helpful to synthesize longer and cleaner SWNTs.