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Chemical Reaction Engineering

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... The process of making struvite was carried out by crystallization at pH 9, molar ratio of 3:1:1, also air rate of 0.4 L/min. The study carried out following the first order with the best conversion was 0.7797 at 8 pembebasan sejumlah amonium terlarut dari limbah [7]. Reaktor kolom bersekat merupakan alat yang menggunakan laju udara sebagai pengganti pengaduk. ...
... Kinetika reaksi mengacu pada penentuan orde reaksi dan tetapan laju reaksi dari material yang ditentukan. Selain menentukan orde reaksi dan tetapan laju reaksi, penelitian ini juga dilakukan untuk menentukan energi aktivasi [8]. Dalam penelitian kali ini, peneliti akan mengkaji kinetika reaksi yang terjadi dalam penyisihan amonium pada limbah urine sapi sebagai mineral struvite. ...
... Waktu tinggal (residence time) adalah waktu yang diperlukan untuk mereaksikan zat reaktan di dalam reaktor alir. Untuk sistem densitas konstan, maka waktu rata-rata sama dengan waktu tinggal, seperti ditunjukkan pada persamaan berikut ini [8]: (5) Studi pengaruh laju alir pada pembentukan struvite telah dilakukan sebelumnya. Laju alir umpan 16-38 mL/menit menghasilkan perolehan fosfat hingga 37,19% [10]. ...
... A calibration curve with tracer concentration was prepared to adjust conductivity. Following the following equation, the age equation (E(t)) was calculated from the shift in tracer volume with time [28 ]: ...
... Two comparison models were compared to the laboratory outcomes acquired in the current work: (1) perfect mixing model [28] and (2) mixing with dead time model [31]. The age feature was calculated according to formula (7) for the model of perfect mixing [28]: ...
... Two comparison models were compared to the laboratory outcomes acquired in the current work: (1) perfect mixing model [28] and (2) mixing with dead time model [31]. The age feature was calculated according to formula (7) for the model of perfect mixing [28]: ...
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Waste cooking oil (WCO) transesterification using a catalyst of Dodecylbenzenesulfonic acid was investigated using a continuous stirred tank reactor. A techniques of surface response plus the design of centered composite were used for the optimizing the factors effecting on the process. The optimum conditions in this research were concluded as (catalyst amount: 1 wt. %; reaction time: 20 min; methanol/oil flow ratio: 4; reactor temperature: 60°C). The biodiesel obtained at the optimum conditions in the process was obtained at yield of 98.5%. The distribution of residence time was found experimentally and a dead zone of (110 cm ³ ) was estimated in the CSTR using the compartment model. The physic-chemical properties for the biodiesel were found in agreement with the ASTM standard (D-6751-2) and the conventional diesel properties. The specific gravity value of biodiesel (0.87) was greater than that one of the diesel fuel (0.834). The calorific value was slightly lower than that one prescribed in the ASTM D-6751 specifications. The kinematic viscosity proved to be within the accepted limits of the. The flash point was found greater than the value specified in the ASTM and that for mineral diesel, which means safer. Acid value of 0.4 mg KOH/g was found accepted according to the biodiesel standard ASTM D-6751-2. Cetane value was found greater than that for mineral diesel.
... The distribution of different lengths of time to pass through different routes in a vessel is called RTD denoted by E(t) function [1]. The ever-increasing amount of literature on this topic since Danckwerts work [2] has generally followed his nomenclature [3]. ...
... The transfer function, G(s), defined as the ratio of the Laplace transform of the response function to the Laplace transform of the input function [6]. Replacing the Laplace transform of the unit impulse function as unity, the RTD can be derived via inversion of Laplace transforms of the transfer function ( )   -1 (1) where can be used for the systems with a defined transfer function, keeping in mind that some systems do not have transfer function, e.g. a pipe in the laminar flow condition. The theoretical RTD of laminar flow is derived using volumetric flowrate forcing function [3]. ...
... It has been shown that at Reynolds number (Re) <3000, a theoretical RTD for laminar flow that assumes no radial mixing provides a good approximation [9]. Levenspiel et al. derived the RTD of laminar flow of liquids in various forms of vessels [1]. ...
Article
The famous definition of RTD is based on the volumetric flow rate but is experimentally defined using the tracer concentration. These different views have erroneously limited the application of the velocity profile for RTD evaluation to the laminar flows. In this work, a more general sense of RTD is introduced and it has been emphasized that regardless of the dispersion behavior, the velocity profile is sufficient in order to obtain the corresponding RTD. A general algorithm for RTD evaluation using axial velocity profile is developed and the relations were derived for different systems. In addition, the corresponding velocity profiles to the famous RTD models were numerically evaluated. It has been shown that the final forms are consistent compared to the previous relations for laminar flows.
... where C A is the FFA concentration, equivalent to the oleic acid concentration (mol.L −1 ), A is the acidity (%) or the FFA content/concentration calculated by dividing the fat acid value (mg KOH/g fat) by 1.99, i.e., acid value (mg KOH/g fat) = 1.99 fat acidity (%), m is fat mass in grams, M OleicAcid is the molecular mass of oleic acid (g·mol −1 ), and V corresponds to the reacting mixture (fat plus alcohol) volume in liters. Therefore, assuming that the reaction volume is constant, the following mass balance equation describes the variation of the fatty acids concentration, C A , in the reaction vessel [46]. ...
... In this work, both simple irreversible and reversible rate laws were considered. In particular: first-and secondorder irreversible reactions, a function only of the oleic acid concentration, and reversible second-order reaction, a function of both the oleic acid and ethanol concentration (with the goal of identifying any potential effect of the ethanol concentration on the fitting of the experimental data to the kinetic data); the Michaelis-Menten rate law; and the second-order reversible reaction of both oleic acid and ethanol [46]. The fitting of the rate law to the experimental results took into consideration the possibility that Equation (2) can be integrated analytically or not, and assumes that for t = 0, the initial concentrations of alcohol and fat are known or can be calculated independently. ...
... The first case occurs for most of the rate laws considered in this work. The analytical expressions presented below are expressed in a form that simplifies the task of identifying which is the most adequate rate law and the calculation of the equation constants, as from the plot of the left side vs. right side of each equation, the kinetic constants and the adequacy of the rate law can be evaluated [46]. ...
Article
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Adding value to agro-industrial residues is becoming increasingly important, satisfying needs to promote resources’ use efficiency and a more sustainable and circular economy. This work performs a parametric and kinetic study of enzymatic esterification of lard and tallow with high acidity, obtained by the rendering of slaughter by-products, allowing their use as a feed ingredient and increasing their market value. After an initial analysis of potential enzyme candidates, a Candida antarctica lipase B was selected as a biocatalyst for converting free fatty acids (FFA) to esters, using excess ethanol as the reagent. Results show that the fat acidity can be reduced by at least 67% in up to 3 h of reaction time at 45 °C, using the mass ratios of 3.25 ethanol/FFA and 0.0060 enzyme/fat. Kinetic modelling shows an irreversible second-order rate law, function of FFA, and ethanol concentration better fitting the experimental results. Activation energy is 54.7 kJ/mol and pre-exponential factor is 4.6 × 106 L mol−1 min−1.
... De manière très générale, une réaction chimique est influencée par la composition chimique des réactifs et par un « facteur énergétique » qui peut être la température, l'intensité lumineuse, etc. (Levenspiel, 1999). Elle se représente par des schémas réactionnels établis de façon théorique ou sous certaines hypothèses validées ou non par des mesures expérimentales (Côme, 1995;Levenspiel, 1999). ...
... De manière très générale, une réaction chimique est influencée par la composition chimique des réactifs et par un « facteur énergétique » qui peut être la température, l'intensité lumineuse, etc. (Levenspiel, 1999). Elle se représente par des schémas réactionnels établis de façon théorique ou sous certaines hypothèses validées ou non par des mesures expérimentales (Côme, 1995;Levenspiel, 1999). À un schéma réactionnel est associé une loi de vitesse empirique qui s'exprime en fonction de grandeurs représentatives de la réaction photochimique (Côme, 1995). ...
... Lorsque c'est la température qui influence la réaction, dans le cas où celle-ci a lieu en phase homogène, la vitesse de réaction (apparition ou disparition) de l'espèce i s'écrit sous la forme (Levenspiel, 1999) : ...
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La présence des micropolluants dans l’environnement est reconnue comme un problème potentiel de santé publique qu’il convient de maitriser afin, d’une part de mettre en place une politique de circularité de l’eau, et d’autre part, de limiter leur dissémination et ainsi leurs effets sur les écosystèmes. Ces substances sont d’origine anthropique et sont pour la plupart bio-récalcitrantes donc partiellement ou non éliminées par les installations de traitement d’eaux usées qui reposent sur l’activité biologique. La photocatalyse hétérogène fait partie des procédés d’oxydation avancée développés spécifiquement pour le traitement des micropolluants. Ce procédé a la particularité de pouvoir utiliser l’énergie solaire comme source énergétique principale ce qui en fait un candidat d’intérêt dans une démarche de développement durable. Les caractéristiques de la ressource solaire, fluctuations/intermittence, impactent directement la capacité de traitement du procédé, et doivent être prises en compte dans sa gestion. Dans la littérature, cette prise en compte pour opérer le procédé porte exclusivement sur les réacteurs dits fermés. Le processus de traitement est alors interrompu la nuit dans les pilotes solaires étudiés. Lors du développement d’un procédé en mode continu, la gestion de l’intermittence s’impose afin de pouvoir assurer un traitement continu de l’effluent. Cette thèse vise à développer un modèle de représentation de la capacité de traitement d’un réacteur fonctionnant sur le principe de la photocatalyse hétérogène. Cette étape est indispensable pour le dimensionnement et pilotage de procédés solaires. Dans une deuxième partie, l’étude se focalise sur la faisabilité d’une technologie de gestion de l’intermittence basée sur un matériau composite adsorbant/photo-catalyseur. L’adsorbant permet de stocker les polluants lorsque la ressource est insuffisante et le photo-catalyseur vise à dégrader les polluants en phase liquide et en phase solide, ce qui revient à régénérer l’adsorbant lors des périodes d’ensoleillement. Ces deux études s’inscrivent dans l’objectif, sur le long terme, de permettre la mise en œuvre d’un procédé de photocatalyse hétérogène solaire en mode continu, capable d’opérer un traitement permanent malgré les fluctuations et l’intermittence solaires. Le premier objectif a consisté à développer un modèle de représentation du transfert radiatif dans les différents milieux hétérogènes réactifs étudiés afin de déterminer la puissance locale absorbée par ces derniers. Dans le cas de particules de photo-catalyseur en suspension, la littérature est relativement fournie, en comparaison des géométries plus complexes, pour lesquelles les études sont moins avancées. Les photo-catalyseurs testés, que sont le dioxyde de titane sous forme particulaire ou déposé sur une mousse alvéolaire macroporeuse inerte, ont ainsi nécessité de développer une approche spécifique. Le second objectif a consisté à déterminer la cinétique de photo-dégradation - dépendant principalement de la concentration en polluant d’étude et de la puissance locale absorbée - à partir d’expérimentations en réacteur fermé. Les vitesses locales des couples polluant, la caféine/photo-catalyseurs, sous forme particulaire ou supportée, ont été déterminées. Connaissant les modèles hydrodynamiques des réacteurs étudiés, un réacteur piston et un réacteur ouvert parfaitement agité, le modèle de représentation de la capacité de traitement, couplant l’ensemble des étapes énoncées (transfert radiatif, cinétique, convection), a été validé et appliqué à des expérimentations de photo-dégradation en réacteur ouvert soumis à des consignes dynamiques représentatives de l’ensoleillement réel. Le dernier objectif, dit exploratoire, a été de tester le matériau composite dans un photo-réacteur ouvert soumis à des cycles sans lumière/avec lumière. La capacité de ce dernier à opérer un traitement photo-catalytique et à s’auto-régénérer au cours des cycles a été montrée.
... The reaction first takes place on the outer surface of low nickel matte. The zone of reaction then enters in the interior of the particle, leaving an inert solid, which is the "ash" [29]. Therefore, there is an unreacted core of solid at any time, which shrinks in size during the reaction (Fig. 5). ...
... Therefore, the experimental data in this study were analyzed based on the SCM model. The leaching reaction controlled by interfacial chemical reaction and internal diffusion are as follows [29]: ...
... From the slope of the fitted equation, the apparent activation energy was 48.7 kJ⋅mol − 1 . It can be seen that the value of the obtained apparent activation energy was unexpectedly high for a pore diffusion process, and it seems that the leaching process of low nickel matte is controlled by chemical reaction [29,35,36]. Some studies have showed that the reactions controlled by diffusion can have high activation energy for the inert layer diffusion-controlled dissolution of minerals. ...
Article
In the previous study of our group, the low nickel matte was leached directly using H2SO4 under atmospheric pressure. As long as the acidity of the solution was high enough, the high-efficiency leaching of iron, cobalt and nickel can be realized. Moreover, the cuprous sulfide and precious metals cannot be decomposed by H2SO4 and were enriched in the leach residue. Due to the high concentration acid used in the leaching process of low nickel matte, the residual acid in leaching solution may need to be neutralized firstly before the subsequent metal separation. However, a lot of alkali will be consumed, resulting in the formation of harmful inorganic salts. In the experiments, we found that sulfate in the leaching solution could reach saturated and continuously crystallized out under the condition of high concentration of sulfuric acid. Based on the above considerations, the crystallization method may be a choice. Upon combination of the leaching and crystallization process, a new way to extract valuable metals and effectively recycle the sulfuric acid was proposed. However, the dissolution of low nickel matte will be also affected when the solution is saturated. Therefore, it is necessary to explore the leaching behavior of low nickel matte in the presence of solutions saturated with sulfate. In this study, the leaching kinetics of low nickel matte in H2SO4 solutions saturated with FeSO4 and NiSO4 was investigated. Kinetic data of the dissolution of nickel for various parameters showed best fit to the kinetic model governed by diffusion in the inert porous media. The results shown that the reaction order of H2SO4 was 3.02 and the activation energy of the system was found to be approximately 48.7 kJ·mol⁻¹. Compared with sulfuric acid leaching, the reaction order of this study increased greatly, which indicated that the influence of acid concentration on leaching process increased. In addition, the decrease of activation energy showed that the oversaturated sulfate solution leaching process was consistent with the internal diffusion control, which may be because the existence of crystal had an effect on the diffusion of H⁺ ions in pores.
... [23][24] Another special property unique to flow is the relationship of space and time in the context of steady state. [25] Batch reaction processes never really achieve steady state; the transformation is constantly changing over time until it either completes or stalls, but it always takes place in the same space. A flowed set-up typically involves separate streams of reactants that are united when they enter the flow channel and travel through the reactor device, i. e., through space, and react prior to exiting and being quenched. ...
... A flowed set-up typically involves separate streams of reactants that are united when they enter the flow channel and travel through the reactor device, i. e., through space, and react prior to exiting and being quenched. [25,26] This is a fundamental difference for flow; not only does it have the elements of both space and time, but these elements are, under the right circumstances, potentially interchangeable in the context of steady state (vide infra) of a chemical process. [25] We can consider a hypothetical continuous flow stream as being comprised of 100 reaction plugs occupying 100 distinct reactor zones in a reaction channel that are necessary to go from 0 to 100 % conversion (ideally) for a given transformation. ...
... [25,26] This is a fundamental difference for flow; not only does it have the elements of both space and time, but these elements are, under the right circumstances, potentially interchangeable in the context of steady state (vide infra) of a chemical process. [25] We can consider a hypothetical continuous flow stream as being comprised of 100 reaction plugs occupying 100 distinct reactor zones in a reaction channel that are necessary to go from 0 to 100 % conversion (ideally) for a given transformation. Plug #1 enters the reactor device at zone #1 and will move progressively through zones 2, 3, 4, and so forth, until passing through zone 100. ...
Article
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The manufacturers of fine chemicals and pharmaceuticals are beginning to accept flow chemistry as a production alternative following the lead of commodity chemical manufacturers, who have been producing goods in continuous format for decades. The ability to trace time backwards by retracting the spatial length of a flow reactor is perhaps one of the biggest advantages of flowed synthesis. However, in the absence of an appropriate tool that would allow scientists to sample throughout the entire space of a production line, the theory is not possible to put into practice. A step in this direction has been taken with the invention of a unique, multi‐port valve/flow reactor that allows the chemist to simultaneously sample multiple timepoints of a chemical transformation with one single valve actuation, thereby capturing instantaneously the entire reaction course of the flowed chemical process. A hybrid continuous flow reactor/sampling device has been invented that allows multiple samples to be taken from a flowing stream simultaneously to create a complete set of kinetic data for any process, of any duration (hours, days, weeks) with the simple rotation of the novel valve, which sits at the heart of the device.
... Mathematical modelling of a chemical process that includes flow depends on the details of the flow pattern of its elements and the distribution of the residence times [11][12][13][14]. This distribution obeys statistical laws and can be determined as a test signal passing through the system. ...
... where M is the amount of tracer injected. For an inert tracer, [12]. ...
... It can be defined according to the column length (PeL) or particle diameter (PeP). If the Pe number is high, that is, the axial dispersion coefficient is low, it shows that we have approached plug flow (PF); however, if the Pe coefficient is low, it shows that we have approached the conditions in a continuous stirred tank reactor (CSTR) because the axial dispersion coefficient is high [12]. Peclet numbers calculated with the help of Eq (11) and their change with the ratio of column L/D are shown in Fig 2a. ...
... Leaching kinetics rate of a metal-bearing mineral in the presence of a solution is mainly demonstrated by the shrinking core model (SCM) (Eq.1). It has been proven that the SCM model represents a realistic estimation of kinetic reactions in comparison with other models (Levenspiel, 1999;Astuti et al., 2015;Safari et al., 2009;Erdem and Yurten, 2015). Thus, the SCM kinetic modeling concept was employed for identifying the kinetic mechanism of the copper leaching process. ...
... 2) and chemical reaction (Eq. 4) controlling models were fitted to the experimental data obtained from the leaching kinetics experiments (Levenspiel, 1999). The kinetic parameters i.e. nominal kinetic rate and coefficient of rate controlling step were estimated through the copper dissolution. ...
Article
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Although the operating properties of Galvanox TM leaching have been widely studied in the literature, several factors concerning chalcopyrite passivation during the process remain unknown so far. The present work hence aims at investigating the significant effect of externally added pyrite features with a particular focus on its particle size (d80 of 0.52, 20, 45 and 2000 µm) through a series of experiments performed in a 2-L stirred-tank electro-reactor. To this end, the role of pyrite: chalcopyrite ratio (0.49:1, 2:1 and 4:1) and presence of electrical current were examined while the rest of the parameters kept constant (80 °C temperature, 400-500 mV (Ag/AgCl) redox potential, pulp density of 10% (w/v), and stirring rate of 1200 rpm). Plus, kinetic models of the leaching tests were studied based on the diffusion and chemical controlling concepts. It was found that the coarser the pyrite particles, the more favorable the copper extraction from the concentrate due to acceleration of reactions in the cathodic electrode and high mass transfers. However, this was in contradiction with the existing reports in the literature. Moreover, galvanic interactions became intensive in the presence of pyrite meaning extensive chalcopyrite dissolution with significantly reduced passivation. Ultimate copper extraction values of 24.17±1.25%, 55.79±0.91% and 57.26±1.59% were resulted at Py:Cp ratios of 0.49:1 (natural), 2:1 and 4:1, respectively. The results showed that maximum copper recovery of 67.32±2.34% was obtained at an optimum condition of pyrite grain size=2000 µm, Py:Cp=4:1, current application=500 mA, 8 h and 80 °C. Finally, detailed kinetic modeling indicated that the chemical control mechanism was dominant in the early reaction stages (t<3.5 h) concerning the availability of fresh surface for chemical agents; however, the second half of the process (8.0 h>t>3.5 h) was controlled by the diffusion control.
... For axial dispersion; the backmixing criteria is also fulfilled by conducting the experiment at a ratio between bed length and catalyst particle diameter higher than one hundred as quoted by [21,22]. Details on the relationships between a chemical reaction in a porous catalyst and reactants diffusion were addressed in (Levenspiel, 1999) [23] and (Carberry, 1971) [24]. It is well established that always there is competition between hot a chemical reactions are progressing and how rapid reactants are diffusing inside the pores of a given catalyst. ...
... For axial dispersion; the backmixing criteria is also fulfilled by conducting the experiment at a ratio between bed length and catalyst particle diameter higher than one hundred as quoted by [21,22]. Details on the relationships between a chemical reaction in a porous catalyst and reactants diffusion were addressed in (Levenspiel, 1999) [23] and (Carberry, 1971) [24]. It is well established that always there is competition between hot a chemical reactions are progressing and how rapid reactants are diffusing inside the pores of a given catalyst. ...
Article
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Due to the presence of refractory sulphur (S) compounds in the gasoil, the achievement of Ultra-low-Sulphur Diesel (ULSD) using the conventional bimetallic catalyst in the Hydrodesulphurization (HDS) process in order to bring sulphur down to less than 10 ppmwt is considered as a tough task/challenge and gain major attention due to the EPA regulations on the transportation fuel industry. In this work, a catalytic testing of four commercial alumina-supported cobalt–molybdenum (CoMo) catalysts were conducted using fixed bed pilot plant reactor using a complex real mixture of straight run gasoil fraction (C12-C20) in order to determine the operating conditions at industrial unit particularly by focusing on the refractory (S) compounds and determining their reaction kinetics parameters. A limited pilot plant real data and a simplified kinetic model were employed to estimate the kinetic parameters for the four tested CA, CB, CC and CD catalysts. A parameter estimation technique with explicit models was also used to determine their highest posterior density intervals. The technique is based on minimization of the sum of the square errors (SSE) between the experimental and predicted data of the residual sulphur concentrations in the product distributions. The results revealed that each catalyst showed, expectedly, different results translated into how longer a commercial run length can be extended.
... Considering the above, for no catalytic reaction of mineral particles with a surrounding fluid, Levenspiel [59] mainly presents two simple idealized models, the progressive conversion model (PCM) and the shrinking core model (SCM). In the SCM the reactions first occur in the outer skin of the particle. ...
... Sheikhzadeh et al. [86] model in aggregate form the unsaturated liquid flow in the bed uniform spherical mineral particles, developing an unsteady two dimensional model based on mass conservation equations in both the liquid phase in the bed and in the particles. The mass conservation equation of the unsaturated liquid flow through the porous bed is presented in Equation (58), while the diffusion of the liquid into the particle is presented in Equation (59). Fluctuations in the degree of saturation depend not only on the period, but also vary with the intrinsic permeability; the depth of the bed decreases as the intrinsic permeability or depth increases. ...
Article
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Mineral leaching is the key unit operation in metallurgical processes and corresponds to the dissolution of metals. The study of leaching is carried out in many areas, such as geology, agriculture and metallurgy. This paper provides an introduction to the theoretical background regarding the mathematical modelling of the leaching process of copper minerals, establishing an overall picture of the scientific literature on technological developments and the generation of representative mathematical and theoretical models, and indicating the challenges and potential contributions of comprehensive models representing the dynamics of copper mineral leaching.
... The generalized kinetic formula for nth order reaction 10 can be written as where t F is time for F fractional disappearance of the reactant, k is reaction rate constant, C Ao is initial concentration of reactant A. In this case A is CV. Therefore we have; ...
... The rate constant value is independent of the NaOH concentration as the value at a particular temperature remain constant irrespective of the concentration. This is consistent with literature information about such reaction 10 . Solutions of Eq. (20) using values of the variables in Table 2 gives Equation (21) is the thermodynamic relation for the enthalpy of the reaction and the activation energy 12 where H a is the enthalpy at activation. ...
Article
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Hydrolysis reaction was carried out at varying NaOH concentrations of 0.008, 0.016 and 0.024 M, variable temperature of 6 and 21 °C, and constant initial crystal violet (CV) concentration of 2.6 × 10–5 M. Kinetic data of the reaction were generated using UV–Vis Spectrophotometer. Analysis of the reaction kinetics shows that the overall rate order of the hydrolysis reaction was 1st order. The individual rate order of the reaction with respect to NaOH and CV was temperature dependent. At 21 °C the rate order with respect to NaOH and CV were 0.24th and 0.76th, respectively. While at 6 °C the individual rate order were 0.38th and 0.62th with respect to NaOH and CV, respectively. Values of the reaction rate constant (k) at 21 and 6 °C were 7.2 and 1.9 molL-0.9min-1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\left( {\frac{{{\text{mol}}}}{{\text{L}}}} \right)^{{ - 0.9}} min^{-1}$$\end{document}, respectively. The activation energy of the reaction was determined as 60.57 kJ/mol. The reaction was an endothermic reaction having enthalpy values of 58.13 and 58.29 kJ/mol at 21 and 6 °C, respectively. The entropy and Gibbs free energy of the hydrolysis reaction at ambient temperature of 21 °C were − 64.72 J/mol K and 77.15 kJ/K, respectively. At 6 °C the entropy and Gibbs free energy of the reaction were − 64.29 J/mol K and 76.19 kJ/K, respectively.
... Activation energy (Ea) is expressed as the energy barrier reactants have to prevail over in order to react [30] and this was determined using Arrhenius equation. Arrhenius equation relates how temperature influences a reaction at equilibrium state represented as: ...
... The calculated activation energy is in agreement with the conversion results. The activation energy result shows the amount of energy barrier that the reactants have to surmount inorder to react [30] with the aid of the optimized sulfonated glucose catalyst in the esterification. The catalyst influences the reaction rate enabling the formation of the product, thus leading to lower activation energy than the uncatalyzed reaction [29]. ...
... According to the reaction between C and Ti (Ti + C = TiC), in an ideal state, 1 mol CB as reactant generates 1 mol TiC as a product. Therefore, the equation between CB and TiC as follows [43]: ...
... The rate of conversion (ν) of CB to TiC can be expressed as the rate of TiC formation or CB disappearance. Therefore, in a homogeneous and dilute system with constant volume, it can be represented as the change in the number of moles of CB [43]: ...
Article
In the present investigation, nanocrystalline TiC with 20 nm average size was synthesized through molten LiCl-KCl using elemental Ti and carbon black (CB) powders as starting materials. The molar ratio of CB to Ti and the weight ratio of salt to reactants were selected 2:1 and 9:1, respectively. The mixture of salt and reactants was blended for 45 minutes by agate mortar and then dried at 110oC for 60 minutes. To better understanding the effect of heating time, four samples were synthesized from 1 to 4 hours at 970oC, and the results obtained from X-ray diffraction (XRD) analysis patterns showed that the purity of samples was improved with increasing the heating time. The crystallite size of TiC powders from 1 to 4 hours at 970oC was calculated using the modified Scherrer equation and Rietveld refinement methods. Rietveld refinement showed that the crystallite size of TiC from 1 to 3 hours is <10 nm, but with increasing the heating time to 4 hours, it reached 20 nm. Modified Scherrer equation results were in good agreement to Rietveld refinement. The transmission electron microscopy (TEM) image of synthesized TiC confirmed that kinetics of TiC formation could be modeled using a shrinking core model (SCM). The results of SCM indicated that the transfer of Ti atoms from bulk to the surface of an individual CB through the liquid boundary controlled the synthesis path.
... Or, it could be written in simple way with, (2) The kinetic model of a single-substrate enzymatic reaction was well known as Michaelis -Menten kinetic equation [12] [13]. This kinetic equation was expressed by, ...
... The kinetic rate of (-r A ) was obtained from the slope of -dC A /dt using the same differential technique for batch kinetic data [12]. Then, (-r A ) vs (-r A )/C A was plotted resulting a linear regression with slope -K M and V M as y-axis intercept. ...
Article
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In many years, bioethanol research has been an outstanding topic because of renewable energy issue. The aim of this research is focused on utilization of cocoa pod husk as a feedstock for bioethanol production through fermentation using Z. mobilis . Moreover, the kinetic model of cocoa pod husk fermentation using Z. mobilis as a microorganism was also preformed in this study. Fermentation of cocoa pod husk was carried out at room temperature for 0, 2, 4, 6, and 8 days of reaction. The bacteria were also varied with 8%, 10%, 12%, 14%, and 16% (v/v) of concentration towards the substrate mixture. The kinetic model was conducted by Michaelis – Menten equation followed by Eadie-Hofstee plot and batch kinetic data plot for its fitting parameter technique. The result of this study indicates that the slow reaction has occurred regarding the low value of conversion and small value of maximum reaction velocity. The highest conversion was achieved on the 8 th day with 14% (v/v) of bacteria concentration that is 10.65%. The maximum velocity of reaction for 16% (v/v) of bacteria addition was obtained at approximately 0.0017 mol/L.hour.
... Heterogeneous fluid-solid reaction may be used in leaching processes. The reaction progress can be controlled by the following steps: (1) the mass transfer of reactants and products between the fluid molecules and the external surface of the solid particle, (2) the diffusion of reactants and products within the pores of the solid, (3) chemical reaction between the reactants in the fluid and in the solid [60,61]. One or more of these factors might control the rate of the reaction according to the slowest link step. ...
... (determined from RTD tests) to define recovery as function of the degree of axial mixing (Levenspiel, 1998 As shown and described in Figure 1, the mineral kinetic coefficients for pulp phase are determined from the laboratory kinetic test data. Additionally, the pulp recovery model employs laboratory data to predict full-scale flotation performance using the changes in the bubble surface area flux between laboratory and full-scale flotation systems. ...
Article
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The detailed modelling and simulation of flotation circuits can effectively reduce risks associated with the process scale—up and plant modifications, improve the accuracy of performance estimate, and assist operators in improving the performance of flotation circuits through detailed evaluations of different design scenarios. Over the last century, various modelling strategies have been developed; however, kinetic-based sub-process models have largely prevailed as the industry standard for the adequate prediction of ultimate flotation circuit performance. In the current study, a multi-compartment flotation model was developed to incorporate the rate-based pulp recovery, non-selective froth recovery, partition-based entrainment recovery, and physical carrying capacity limitations. The proposed modelling paradigm is capable of predicting the performance of flotation circuits while integrating kinetic coefficients, feed characteristics, equipment specifications, and operational parameters as the primary inputs. The capabilities of this multi-compartment model have been validated through a systematic batch laboratory- and continuous pilot-scale experimental program using FLSMidth nextSTEP and Wemco flotation cells.
... Water-rock reactions are heterogeneous surface reactions and most surface reactions have a sequential process that involves the following steps (Fogler, 1992;Lasaga, 1998;Levenspiel, 1999): ...
Article
Fault zones significantly influence the migration of fluids in the subsurface and can be important controls on the local as well as regional hydrogeology. Hence, understanding the evolution of fault porosity/permeability is critical for many engineering applications (like geologic carbon sequestration, enhanced geothermal systems, groundwater remediation, etc.), as well as geological studies (like sediment diagenesis, seismic activities, hydrothermal ore deposition, etc.). The highly heterogeneous pore structure of fault zones along with the wide range of hydrogeochemical heterogeneity that a fault zone can cut through make conduit fault zones a dynamic reactive transport environment that can be highly complex to accurately model. In this article, we present a critical review of the possible ways of modeling reactive fluid flow through fault zones, particularly from the perspective of chemically driven “self-sealing” or “self-enhancing” of fault zones. Along with an in-depth review of the literature, we consider key issues related to different conceptual models (e.g., fault zone as a network of fractures or as a combination of damaged zone and fault core), modeling approaches (e.g., multiple continua, discrete fracture networks, pore-scale models), and kinetics of water/rock interactions. Inherent modeling aspects related to dimensionality (e.g., one-dimensional vs. two-dimensional) and the dimensionless Damköhler number are explored. Moreover, we use a case study of the Little Grand Wash Fault zone from central Utah as an example in the review. Finally, critical aspects of reactive transport modeling like multiscale approaches and chemomechanical coupling are also addressed in the context of fault zones.
... The sample weight seemed to be constant after the temperature reaches 850°C. It indicates that the process was already completed, and the sample left is recognized as 'ash' (Levienspiel, 1999). The TGA analyses of the mortar samples give good indication that the cement material that has been used in the JMUP was a blind of hydraulic lime and gypsum while in the JMLP was only hydraulic lime. ...
Article
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The purpose of this study was to investigate the mineral composition of the historical mortars of Qasr Tuba and to re-produce them for the restoration process. The mortar samples were collected from the foundation and walls of Qasr Tuba. The chemical and mineral composition of the mortar was determined using several techniques. In addition, the quantitative minerals content was recalculated for the mortar samples utilizing the material balances equation. Moreover, 12 mixtures of mortar were prepared and tested for fresh and hardened properties, according to their respective national and international standards. The results revealed that two types of mortar were used: (i) the lime-based mortar was used for the foundation and joint mortars in the lower parts of the building walls with a gypsum-hydrated lime ratio of 1:3; and (ii) the gypsum-based mortar was used as joint mortar in the upper parts of the building walls for baked bricks at a gypsum-hydrated lime ratio of 4:1. A pozzolanic reaction in the Qasr Tuba mortar produced a new formation of Xonotlite, Stratlingite, and calcium aluminium hydrate as a secondary cementing mineral. In conclusion, the use of hydraulic lime mortar was considered for building an environment for capturing the CO2 gas.J. Ecol. Eng. 2021; 22(3):121–134
... The measured residence time Here axial dispersion model is used to characterize non-ideal mixing in the microchannel. The correlation between the RTD curve and the Peclet number is given by (Levenspiel 1999) ...
Article
Microfluidics plays an essential role in process intensification, carrying out reactions safely and enhancing mass and heat transfer coefficients. In this work, hydrodynamics, mixing and reaction in the microchannel are investigated numerically and experimentally. To predict the flow field, three dimensional transient CFD simulations are performed. The irreversibility induced by the flow is used to quantify the liquid circulation. To improve the flow field, the geometry of the microchannel is modified by placing obstacles. It is found that geometric modifications have a significant effect on the hydrodynamics and hence mixing and reaction. The axial and lateral mixing are analyzed for various obstacles using Residence Time Distribution (RTD). The mixing index is calculated to characterize lateral mixing and to find an optimum configuration that supports flow field and mixing. Further, the implications of these obstacles on a fast neutralization reaction in the microchannel are studied.
... This parameter describes the internal flow rates and the level of mixing inside the reactor, with ∈ [0 , ∞] . So, when the recycle ratio tends to infinity, the behavior of the reactor approaches the behavior of a perfect mixing reactor [28] . ...
Article
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In the present paper a new two-phase multi-scale mathematical model of a tubular loop reactor is presented to describe the bulk polymerization of propylene. The model comprises transient mass and energy balances for the liquid and solid phases and population balance equations to describe the spatio-temporal evolution of the particles size distributions. Particularly, the mathematical modeling approach presented here also takes into account inter-phase transport phenomena for the first time for this class of reactors. As shown through computational simulations, inter-phase mass and energy transport constraints can exert significant influence on the properties of the final product and should not be neglected a priori.
... according to a mode of operation for either endothermic or exothermic reaction chemical vessel equipment's classified into a batch and flow type. Unsteady state mode of operation and it holds homogenous or heterogonous reactant components for a specific time of the reaction inside the batch reactor [1]. Whereas the flow type reactors operated in steady-state and open system mode of reaction conditions [2].Among them,continuously stirred tank reactorsare used for homogenous reaction systems and operating at the steadystate condition. ...
Article
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Investigation study of three-stage continuous stirred tank reactor for ethyl acetate hydrolysis reaction has been accompanied. Sodium hydroxide and Ethyl acetate were selected for reaction evaluation.The parameters evaluated for saponification reaction were flowrate (40ml/min,70 ml/min, and 100 ml/min), agitation rate (minimum, medium, and maximum), and temperature of non-isothermal conditions.Nine experimental performances were investigated and for all the experiments initial concentration of ethyl acetate and sodium hydroxide were constant. The NaOH(4%)and CH3COONA (6%) were used for the data recorded. The minimum conductivity values, the maximum temperatures, and conversion values of the reaction were 45.2%,66.34% at a temperature of 24.9 °C for R1,41.1%, 69.53%at a temperature of 24.5 for R2, and 40.7%, 69.76 % at the temperature of 24 ºC for R3 for 40 ml/min flowrate and minimum agitation rate individually. Based on the medium agitation rate and medium flow rate (70ml/min)the minimum value of conductivity and maximum value of conversion was 38.3% and 71.59% obtained at a temperature of 27.1 °C of R1,30.5%, and 77.53% at a temperature of 27.5 °C of R2, 27.8% and 79.59% at a temperature of 26.8 °C of R3 respectively.Compared to others the reactions operated at a maximum flow rate (100ml/min) and maximum agitation rate of the conductivity and conversion values were 43.1% and 67.94% of R1 at the temperature of 27.8 ºC,34.4 % and 74.56% R2, 34.1% and 74.79 % of R3 at the temperature of 28.3 °C. The three-stage CSTRs connected in series value of conductivity decreased accelerable, but the value of conversion increased progressively. The results gained in this evaluation may help optimize the production of desired products at a large level and predict the advantage of multiple-stage reactors connected in series extra appropriate for the saponification reaction of ethyl acetate
... The rate of dissolution was found to be described by the shrinkingparticle model with reaction control. This model accounts for the change in available surface area as the particle gets smaller (Levenspiel, 1999). For this model, a plot of 1 − (1 − X) 1/3 against time elapsed, where X is the conversion, in the batch test is a straight line. ...
Article
The effect of UV light on the rate of dissolution of sphalerite, (Zn,Fe)S, has been investigated for samples from different sources. These different samples had different amounts of substitutional iron, ranging between 0.55 and 8.62%. It was found that the rate of dissolution of sphalerite is proportional to the content of substitutional iron, and that the rate of dissolution increased in the presence of UV light. Analysis of the data indicated that the effect of light was more pronounced for samples with lower iron content. A mechanism is described for the dissolution reaction that envisages that the oxidant preferentially accepts electrons from (or injects holes into) the d-band orbitals arising from the iron in substitutional positions in the lattice. The resulting hole in the d-band reacts with the surface causing the removal of the dissolution products from the surface. The effect of light was proposed to be due to the excitation of a valence band electron to the conduction band to create electron-hole pairs. The holes react with the surface, resulting in dissolution products, while the excited electrons are captured by the oxidant. Rate equations are derived that describe these mechanisms. These rate equations are shown to agree with the experimental data.
... according to a mode of operation for either endothermic or exothermic reaction chemical vessel equipment's classified into a batch and flow type. Unsteady state mode of operation and it holds homogenous or heterogonous reactant components for a specific time of the reaction inside the batch reactor [1]. Whereas the flow type reactors operated in steady-state and open system mode of reaction conditions [2].Among them,continuously stirred tank reactorsare used for homogenous reaction systems and operating at the steadystate condition. ...
... (27)) [68]. The value of M T was determined to be 4.81 × 10 -5 , which was less than the critical value (< 0.4) required to obtain an effectiveness factor close to unity, suggesting that the reaction was not internally mass transfer limited [69]. ...
Article
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Reaction kinetics for heterogeneous catalysis of styrene carbonate (SC) synthesis via CO2 cycloaddition to styrene oxide (SO) using silica-supported pyrrolidinopyridinium iodide (SiO2-PPI) catalyst has been investigated. The results obtained from the mixing study and theoretical analysis based on Thiele modulus (< 0.4) and effectiveness factor (∼1.0) revealed no external and internal mass transfer limitations. The experimental results were compared with pseudo-homogeneous (PH) and Langmuir-Hinshelwood (LH), Eley-Rideal (ER) heterogeneous kinetic model. The experimental data was found to be the best fit with the ER model among the three kinetic models. Moreover, the Arrhenius and Eyring equations were used to determining the activation energy (i.e. 64.9 kJ mol–1) and thermodynamic activation parameters such as enthalpy of activation (ΔH‡= 60.6 kJ mol–1), the entropy of activation (ΔS‡ = –148.3 J mol–1 K–1) and Gibb’s free energy (ΔG‡ = 115.9 kJ mol–1 at 373 K). The SiO2-PPI heterogeneous catalyst exhibited excellent reusability: up to five cycles without any substantial decrease in activity and selectivity towards SC formation.
... Our previous studies have demonstrated the value of a layered gas-diffusion electrode (l-GDE) structure, in which a CO-selective catalyst layer (CL) is placed on top of a C 2+ -selective Cu CL 29,30 . The l-GDE was inspired by the higher reactant conversion in a plug-flow reactor (PFR) compared to that in a continuous-stirred-tank reactor (CSTR) for reactions with a positive reaction order 31 . In a PFR, this enhancement in conversion results from increased residence time within the reactor. ...
Article
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Electrochemical CO2 reduction provides a promising route to the sustainable generation of valuable chemicals and fuels. Tandem catalysts enable sequential CO2-to-CO and CO-to-multicarbon (C2+) product conversions on complementary active sites, to produce high C2+ Faradaic efficiency (FE). Unfortunately, previous tandem catalysts exhibit poor management of CO intermediates, which diminishes C2+ FE. Here, we design segmented gas-diffusion electrodes (s-GDEs) in which a CO-selective catalyst layer (CL) segment at the inlet prolongs CO residence time in the subsequent C2+-selective segment, enhancing conversion. This phenomenon enables increases in both the CO utilization and C2+ current density for a Cu/Ag s-GDE compared to pure Cu, by increasing the *CO coverage within the Cu CL. Lastly, we develop a Cu/Fe-N-C s-GDE with 90% C2+ FE at C2+ partial current density (jC2+) exceeding 1 A cm−2. These results prove the importance of transport and establish design principles to improve C2+ FE and jC2+ in tandem CO2 reduction. Poor management of gas flow limits efficiency in tandem (two-catalyst) electrocatalytic CO2 reduction. Here, the authors develop a segmented gas-diffusion electrode architecture that prolongs the residence time of CO (produced by the first catalyst) at the second catalyst, resulting in high production of further reduced yields.
... Then calculated particle distributions (Fig. 3) were compared with visual data. The RTD function E(t) in eq. 1, the cumulative RTD function F(t) in eq.2, the mean residence time  t in eq. 3 were calculated (Fig. 4) using the experimental data 15 . ...
Article
Full-text available
Extrusion is an inexpensive process in terms of production costs used to produce continuous shapes of plastic materials. The mixture design method and regression analysis have been applied to evaluate the performance of the single screw extruder. The performance values of the single-screw extruder system with a glass barrel are calculated by the residence time distribution results of the tracers. Then calculated particle distributions are compared with visual data. Ethylene-vinyl acetate (EVA 210W) is used as the polymeric material. In the study, the EVA 210W is studied with various screw configurations and also process conditions. Optimization is fulfilled using the response optimizer to determine the optimum screw configuration. This method is aimed at feeding and metering zones in screw design and focuses on the search for a solution for optimum screw selection. In addition, the robustness of solutions in process conditions has been redefined.
... [22].Mineralogical investigations of Gabal AbuHadeida microgranite revealed that the main mineral associations were represented by uranium, thorium and REEs-minerals (thorite, uranothorite, zircon, xenotime and monazite), REE-bearing minerals (cerianite), Nb-Ta minerals © 2021 NSP Natural Sciences Publishing Cor. (columbite, ferrocolumbite and yttro-columbite) and base metals included (pyrite, chalcopyrite, arsenopyrite and sphalerite) in addition to apatite, titanite, cassiterite, epidote, garnet and iron oxides. ...
Article
Full-text available
Egypt needs to provide large quantities of nuclear fuel, after its decision to build a number of nuclear plants that will run on nuclear fuel. Uranium is the most important nuclear fuel and has been utilized for producing electrical energy without the threat of global warming. South Eastern Part of Wadi Baroud is located in the Northern Eastern Desert of Egypt at about 20 km westward Safaga City. The purpose of this study was to investigate the mineralogical content of South Eastern part of Wadi Baroud microgranite which revealed that the main mineral associations were represented by uranium, thorium and rare earth elements (REEs)-minerals. Also to investigate the process of sulphuric acid leaching of a representative samples from a new ore of uranium occurrence in South Eastern Part of Wadi Baroud. From the acidic atmospheric agitation leaching study upon the dissolution of U, Th and REEs from the study ore material, it can be concluded that this leaching method is satisfactory in dissolving 97.6 %, 98.8 % and 54.9 % of Th, U and REEs respectively, contents by using the following optimum leaching conditions; Ore grain size-200 mesh; H2SO4 Concentration 20 %; agitation time 4h; Leaching temperature 75 ºC; Solid/liquid ratio (S/L) 1/2.
... Mixing two homogenous miscible fluids is a complex phenomenon, which includes two overlapping aspects: first, mixing on a microscopic level and second, mixing on a macroscopic level. At a macroscopic level, aggregates of fluids are dissipated to the point where further division of aggregates cannot be achieved by mixing but through molecular diffusion which is considered as micromixing (Danckwerts, 1952;Levenspiel, 1999). The transition from macromixing to micromixing is considered as mesomixing (Baldyga and Bourne, 1992). ...
Article
The incorporation model is a widely applied micromixing model for the interpretation of micromixing experiments conducted by the Villermaux–Dushman test reaction. In this work, a deeper look into the model is taken and a modified incorporation model is proposed which leads to more reasonable results regarding the time to equalize concentration gradients, which corresponds to a micromixed state. The original definition of the micromixing time, tm, is revised and two characteristic times are introduced which can be deduced from the modified incorporation model. First, the time in which the acid–base and Dushman reaction are completed, tR, and the time until a complete equalization of concentration gradients is reached, tE, which corresponds to the actual micromixing time. In addition, an instruction to easily revise historical micromixing time calculations from the original incorporation model is given. From the incorporation model, concentration ranges for the kinetic investigation of the Dushman reaction relevant to mixing studies were extracted and are proposed for future kinetic studies of the Dushman reaction. The MatLab codes for implementing the incorporation model are published in GitHub for further scientific exchange. https://github.com/EliasArian/Incorporation-model
... The structure of the cell residence time distribution model (Equation (5)) used to describe the mixing regime in the flotation cells used for modeling of this work is a float cell model reported in [46][47][48], considering a single flotation cell and a perfect mixer with dead time [50,51]. ...
Article
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Due to the increase in the amount of copper sulphide minerals processed through concentration processes and the need to improve the efficiency of these production processes, the development of theoretical models is making an important contribution to generating a better understanding of their dynamics, making it possible to identify the optimal conditions for the recovery of minerals, the impact of the independent variables in the responses, and the sensitivity of the recovery to variations in both the input variables and the operational parameters. This paper proposes a method for modeling, sensitizing, and optimizing the mineral recovery in rougher cells using a discrete event simulation (DES) framework and the fitting of analytical models on the basis of operational data from a concentration pilot plant. A sensitivity analysis was performed for low, medium, and high levels of the operative variables and/or parameters. The outcomes of the modeling indicate that the optimum mineral recovery is reached at medium levels of the flow rate of gas, bubble size, turbulence dissipation rate, surface tension, Reynolds number of bubble, bubble–particle contact angle, superficial gas velocity and gas hold-up in the froth zone. Additionally, the optimal response is reached at maximum levels of particle size and density and at minimum levels of bubble speed, fluid kinematic viscosity and fluid density in the sampled range. Finally, the recovery has an asymptotic behavior over time; however, the optimum recovery depends on an economic analysis, examining the marginalization of the response over time in an operational context.
Chapter
Für die Lösung reaktionstechnischer Aufgabenstellungen sind neben der stöchiometrischen Bilanz der Reaktionsabläufe auch die Kenntnisse von thermodynamischen und kinetischen Gesetzmäßigkeiten chemischer Umsetzungen unabdingbar. Beim Auftreten eines chemischen Gleichgewichts wird der Reaktionsfortschritt durch die Thermodynamik limitiert. Die Kinetik chemischer Reaktionen erfasst den Reaktionsfortschritt als Funktion der Zeit. Das Erstellen eines Reaktionsmodells ist insbesondere bei komplexen Reaktionen, wie beispielsweise in der heterogenen Katalyse, unumgänglich. Dabei ist nicht selten die Kinetik der molekularen Transportvorgänge zu berücksichtigen. Deshalb zählen die Beschreibung der Filmdiffusion, der Diffusion in porösen Katalysatoren sowie der Wärmeleitung und des-übergangs zu den Grundlagen der Chemischen Reaktionstechnik.
Article
This study was focused to reveal the physico-chemical characteristics and the presence of heavy metals in groundwater samples. This research was done at the site of the tanneries, Ambur taluk in Vellore district Tamil Nadu, estimates the pollution indices and risk assessment to assess the rightness of groundwater for human consumption. The knowledge focused physico-chemical parameter and heavy metals, like lead, chromium, copper and zinc contamination on groundwater samples. Flame atomic absorption spectrometer (AAS) technique was used to assess the heavy metals concentration. The analytical results showed that chromium concentration is significantly higher in groundwater samples at the site of the tannery locality. Also lead (Pb), copper (Cu) and zinc (Zn) metals strength was found to be slightly high in groundwater at the site of the tannery areas. The calculated pollution indices, namely contamination index (CI) and index of environmental risk (IER) for the heavy metals propose that majority of the studied groundwater samples are in the highly contaminated zone. All physical and chemical parameters within the limits and metals contamination in groundwater is answerable for the maintenance of harmfulness in farming crops and domestic uses.
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In this study, the selective dissolution of copper and iron from the molybdenite (MoS2) concentrate consisting of chalcopyrite and pyrite by acidic sodium nitrate leaching has been investigated to improve the quality of molybdenite. The influence of various leaching parameters, namely sodium nitrate (NaNO3) and sulfuric acid (H2SO4) concentration, temperature, contact time, and solid: liquid phase ratio, was examined on the dissolution of copper (Cu) and iron (Fe) from the concentrate. Under the optimized conditions, the extraction of Cu and Fe can achieve 81.4% and 74.1%, respectively, along with a minor amount of molybdenum (Mo) loss in the solution from the concentrate in 240 min leaching. The kinetic study indicated that the impurities removal process was controlled by a mixed mechanism with a corresponding activation energy of 35.77 kJ/mol at the temperature range of 70–97 °C. The XRD and SEM-EDS analysis of the solid residues from the leaching revealed the insolubility of molybdenite in the leaching media. As a result, the molybdenite grade reached 90.73 wt% from an initial value of 81.33 wt%.
Article
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A novel oxygen scavenger based on natural rubber latex (NRL), photocatalytic system (PCS) comprising acetophenone and manganese chloride was developed and evaluated for its oxygen scavenging capacity and rate for the first time. The oxygen content (20.9%) in glass vials was reduced to 0% after 60 days and 20 days using NRL mixed with 3 wt% of PCS at 25 ℃ and 45 ℃ respectively. Colorimetry and Fourier transform infrared spectroscopy (FTIR) was performed before and after oxygen scavenging. The rheology along with particle size (399.6 nm) and zeta (−23.30 mV) was done to know viscosity and stability for the viability of NRL/PCS3 as active coatings in packaging applications. The prepared oxygen scavenging system showed an oxygen absorption capacity of 1045 mL O2/g (at 25 ℃) and a rate of 17.42, 52.25 mL O2/g.day at 25 ℃ and 45 ℃ respectively. The rate constant value was increased to 0.4761 h⁻¹ from 0.2119 h⁻¹ when the temperature was raised from 25 ℃ to 45 ℃. Hence, results proved that the NRL-based oxygen scavenging system with UV activation could be an effective alternative for iron-based commercial oxygen scavengers for foods that are moderate to highly susceptible to oxidation.
Chapter
The need for a change in the global energy matrix from a fossil fuel based to a renewable energy one is critical for sustainable development. In this context, biofuels from anaerobic digestion of agro-industrial waste and wastewater, i.e., biohydrogen and biomethane, represent an attractive option. The dark fermentation process for biohydrogen production involves several possible microbial pathways that are dynamics and need to be understood to overcome limitations and process optimization. Methanogenesis for biomethane production occurs close to thermodynamic limitations. Thus, the system needs to be balanced to achieve stability and satisfactory biofuel production. Several operational parameters interfere with the process, and the knowledge about them allows to maximize the methane yield. Besides problems with gas supersaturation, the role of micronutrients and adequate removal of toxic compounds released during the biomass decay represent themes that still must be solved to achieve the full potential of biofuels generation. This chapter provides fundamental knowledge to overcome the technological limitation and advance towards a wide production of biofuels from organic waste using anaerobic digestion.
Article
Translucent structured reactors have proven to be an effective design to scale up microreactors. By generating surface area, this flexible reactor design allows to increase the catalyst loading without increasing the catalyst layer thickness, which is beneficial in tackling diffusion limitations in single-channel reactors. However, adding more depth to such a structure by replicating the channels increases the number of scattering boundaries which leads to energy losses. As a result, there is a design problem which seeks to define the optimal catalyst layer thickness and optimal number of repeating boundaries on a light path. Most of the models are numerically solved and very specific to the reactor type being modeled. In this work, a catalyst layer mass balance model is used to construct a model of a translucent structured reactor which takes into account internal mass transfer effects and which can be used to design an optimal structure. The model is simplified to obtain a graphical tool and an analytical model which is validated to estimate the overall reactor kinetics as a function of dimensionless groups. For a conventional range of parameters, the optimal catalyst layer thickness and optimal number of structural layers was equal to 2 µm and 4, respectively. The presented tools in this work are a step forward in the fabrication of design methods for photocatalytic reactor structures. This way, the designer can easily estimate the design outcome without any complex calculations.
Article
Synthesis of methyl palmitate (MP) has not been considered in the past using a reactive distillation process (continuous or batch) due to the challenge of keeping the reactants palmitic acid (PA) and methanol (MeOH) together in the reactive zone. MeOH, being the lightest in the reaction mixture, travels up the distillation column as distillation proceeds and will be removed from the system via the distillate in a conventional batch reactive distillation (CBRD) column and thus will limit the conversion of PA. Therefore, in this work semi-batch reactive distillation (SBRD) column is proposed where additional methanol will be fed at the bottom of the column in a continuous mode allowing the chemical reaction to continue. However, as water (H2O) is one of the reaction products and is the second lightest component in the mixture, it will travel up the column next and will be removed in the distillate tank. Also due to wide difference in the boiling points of the reaction products and due to the diminishing amount of water in the reboiler, the backward reaction will not be a dominating factor and therefore ignored in this work. With this backdrop, optimal performance of the SBRD column is evaluated in terms of conversion of PA to MP and energy consumption via minimization of the operating batch time for a wide range on MP purity.
Book
Limbah cair domestik meski ‘hanya’ mengandung zat pencemar organik, tetapi jika tidak diolah dengan baik, akan berdampak besar mencemari lingkungan, khususnya pada badan air di sekitar kita. Salah satu penghasil limbah cair domestik adalah apartemen, limbah yang dihasilkannya sangat kompleks karena selain limbah dari buangan manusia, juga berasal dari unit usaha lain seperti restaurant, laundry dan lain-lain yang umumnya ada pada sebuah apartemen. Di dalam buku ini, dibahas tentang bagaimana mengolah limbah domestik tersebut dengan memanfaatkan teknologi Sequencing Batch Reactor yang pengoperasiannya tidak membutuhkan lahan luas. Hal ini sesuai dengan lahan yang tersedia di kota besar sangat terbatas dan mahal. Buku ini ditulis bertujuan untuk mempublikasikan hasil riset yang dilakukan oleh penulis bersama tim peneliti yang terdiri dari mahasiswa dan rekan sejawat. Semoga buku ini bisa menjadi referensi bagi para praktisi dan akademisi teknik lingkungan, kimia, biologi yang berkecimpung di bidang rekayasa pengolahan limbah (sebatik)
Chapter
Fußend auf den Grundlagen der Stöchiometrie, der Thermodynamik, der Reaktionskinetik sowie den Gesetzen des Stoff- und Wärmetransports stellt die Chemische Reaktionstechnik die experimentellen und theoretischen Daten sowie das mathematische Instrumentarium zur Auslegung chemischer Reaktoren bereit. Den Ausgangspunkt einer jeden Reaktorauslegung bilden die Stoff- und Wärmebilanzen im vorgegebenen Bilanzraum. Der Reaktorberechnung liegen Differenzialgleichungen zugrunde, die auf Erhaltungssätzen für Masse, Energie und Impuls basieren. Daraus abgeleitet können Auslegungsgleichungen für ideale oder reale Reaktoren aufgestellt werden.
Article
The reaction of isopropyl alcohol with acetic acid was carried out in an isothermal batch reactor in presence of solid resin catalyst to produce isopropyl acetate and water. A novel solid resin catalyst Indion 140 was used in the present study. The temperature of reaction mixture was maintained in the range of 333.15 – 363.15 K. The effects of reaction temperature, catalyst loading, mole ratio, size of catalyst, agitation speed were investigated on acetic acid conversion. Further, pseudo-homogeneous kinetic model was developed for the catalyzed reaction. The forward reaction rate constants and activation energies were determined from the Arrhenius plot. The forward and backward activation energies are found to 53,459 J/mol and 54,748 J/mol, respectively. The heat of reaction is −1.289 kJ/mol with Indion 140 catalyst. The mathematical equation was developed for frequency factor as function of the catalyst loading and found that it follows a linear relationship between frequency factor and catalyst loading. The simulations were performed for pseudo homogeneous kinetic model and found that the model is able to predict the experimental data very well. The developed kinetic equation is useful for the simulation of a reactive distillation column for the synthesis of isopropyl acetate.
Chapter
Polyreaktionen weisen eine Reihe von Besonderheiten auf, deren reaktionstechnische Implikationen in diesem Kapitel behandelt werden. Zunächst werden Berechnungsmethoden für Produktverteilungen vorgestellt, die für die Eigenschaften der entstehenden Polymere wesentlich sind. Anschließend wird qualitativ die Rheologie von Reaktionsmischungen diskutiert, die bei Polyreaktionen oft durch einen erheblichen Anstieg der Viskosität mit dem Umsatz gekennzeichnet ist. Danach werden Kriterien für die Reaktorauswahl, nichtideales Strömungsverhalten sowie Selektivitätseffekte und Wärmeabfuhr bei Polymerisationsreaktoren behandelt. Abschließend werden wichtige Polymerisationsverfahren und die dort eingesetzten Reaktortypen kurz vorgestellt.
Chapter
Rührreaktoren sind die am häufigsten anzutreffenden chemischen Reaktoren. Die Modellvorstellung des idealen Rührkessels trifft allerdings wenn überhaupt nur auf Apparate im Labormaßstab zu. Technische Reaktoren zeigen dagegen Konzentrations- und Temperaturunterschiede, die wiederum für die chemischen Reaktionen von Bedeutung sein können. Diese Tatsache führt bei der Maßstabsübertragung vielfach zu geringeren Ausbeuten und Selektivitäten im Produktionsreaktor. Für das Zusammenspiel von chemischer Reaktion und Mischvorgängen sind neben der Reaktionskinetik Charakteristika des Mischers wie Homogenisieren, Wärme- und Stofftransport sowie die Spezifika eines mehrphasigen Reaktorbetriebs essenziell.
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Vinasse is an agroindustrial wastewater obtained at large amounts in countries such as Brazil, which is one of the world greatest sugar and ethanol producers from sugarcane. Despite its most common use is as nutrient for fertirrigation in sugarcane crops nowadays, alternative processing has been intensely sought in last decades for vinasse aiming primarily the production of energy carriers and high-added value chemicals. One of these alternatives is the anaerobic digestion promoted by bacteria, which results in several products of economic importance. In view of these information, this work presents an investigation of acidogenic fermentation by C. acetobutylicum ATCC 824 and C. beijerinckii ATCC 25752 was conducted in batch reactors by using synthetic vinasse and aqueous glucose solution as substrates. Evaluation of effects of microorganism and carbon source was focused mainly on the production of short chain organic acids (SCOAs), although other metabolites, such as ethanol, were also detected. Carbohydrates were effectively consumed by bacteria, so remaining concentrations of sucrose and glucose (Suc and Glu) in both substrates were considerably low at the end of tests. Lactic acid (HLa) was the prevailing metabolite in all experiments, determining the trends observed for total SCOAs content as a function of incubation time, while other acids were generated in much lesser amounts. Moreover, ethanol (EtOH) attained notably higher concentrations in batch reactors containing glucose as substrate, which showed more relevant production of this chemical. Maximum of 14.1 g HLa L ⁻¹ was quantified for lactic acid at incubation time 96 h in reactor using synthetic vinasse and C. beijerinckii (VB), linked to a productivity P=146.46 mg HLa L ⁻¹ h ⁻¹ and a yield Y=1108.03 mg HLa g Suc ⁻¹ . For ethanol, maximum was 1.6 g EtOH L-1, occurring in reactor containing glucose and C. acetobutylicum (GA) also at incubation time 90 h, resulting in P=13.60 mg EtOH L ⁻¹ h ⁻¹ and Y=73.04 mg EtOH g Glu ⁻¹ . Finally, kinetic models were adjusted to experimental data of carbohydrate content, lactate concentration and optical density (indicative of microorganism growth), showing good prediction capability as suggested by values of fit quality parameters such as Residual Sum of Squares (RSS) and R ² .
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Herein, the feasibility of water-induced deactivation of cobalt-based Fischer-Tropsch catalysts by oxidation is summarized and discussed with the help of thermodynamic predictions. Furthermore, identified mechanisms for hydrothermal sintering and recent findings on water-induced oxidation of metallic cobalt to CoO are discussed. However, the main emphasis of the review concerns the formation of metal-support compounds and the applicability of various in situ and ex situ characterization techniques on their identification. The current literature only provides limited information on the formation and morphology of metal-support compounds in cobalt-based Fischer-Tropsch synthesis due to the challenging (direct) characterization of these phases in spent catalysts. However, X-ray absorption spectroscopy and other advanced techniques have recently provided significant insights into the formation of metal-support compounds in a (simulated) high-conversion Fischer-Tropsch environment, while high-resolution microscopy was successfully applied to elucidate corresponding catalyst morphologies.
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This study presents a unique concept of fixed-bed in-situ once-through reactor approaching plug flow (PFR) employed for the disinfection of E. coli. This study discusses the potential applications of a low-cost composite composed of Foundry Sand (FS) and fly ash (FA) for combining hybrid effects. This composite has the intrinsic characteristic of containing iron, which lixiviates in acidic conditions (resulting in photo-Fenton), as well as surface-coated TiO2, which results in photocatalysis, demonstrating a hybrid effect. The surface characteristic analysis of the catalyst (SEM/EDS, XRD, DRS, and FTIR) confirmed the presence of iron (acting as natural dopant) and TiO2 making it visibly active. Therefore showed a significant reduction in the treatment time under solar irradiation with 10% synergy of in-situ hybrid-process over individual processes. The implementation of the in-situ hybrid effect in cascade reactor with three reactors in series helped the reactor approaching PFR with 45 min of retention time (Ʈ) and 100% inactivation of E. coli cell count was observed with optimized operational parameters. The cell wall damage was confirmed by the increase in the K⁺ concentration at regular intervals. No regrowth of cells after 24 and 48 h of treatment in the dark and sunlight was observed, in completely inactivated samples. Besides this, the Fe-TiO2 composite portrayed an exceptional durability/recyclability efficacy (>100 recycles) under continuous flow conditions. To visualize the practical viability of the proposed high-performance once-through reactor system, the total cost of the treatment process was analyzed in detail.
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Cobalt–manganese composite catalysts in a reverse-flow fixed-bed reactor showed excellent activity and selectivity for reduction of residual O2 for CO2 purification from pressurized oxy-combustion flue gases.
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