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Mass Balance Equations (mass + balance_equation)
Selected AbstractsSimulation of a slurry-bubble column reactor for Fischer-Tropsch synthesis using single-event microkineticsAICHE JOURNAL, Issue 8 2009Gisela Lozano-Blanco Abstract A single-event microkinetic model for Fischer-Tropsch synthesis including the water-gas shift reaction has been implemented in a one-dimensional, two-bubble class, heterogeneous model with axial effective diffusion to study the performance of a commercial slurry bubble column reactor. Mass balance equations are solved for every species in the reaction network in the large bubbles, small bubbles, and slurry phase, whereas the energy balance is applied to the slurry phase. The catalyst concentration profile is described by a sedimentation-dispersion model. The combination of microkinetics that generate net production rates for the individual reaction products and hydrodynamics allows describing detailed concentration profiles along the reactor axis as a function of operating conditions and design parameters. As example, the effects of catalyst loading, syngas feed flow rate, inlet temperature, or hydrogen to carbon monoxide inlet ratio on the individual hydrocarbons are investigated. To our knowledge, no reactor model in literature is able to describe detailed compositions at the level described by the reactor model developed in this work. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Behavior of interacting species in vacancy affinity capillary electrophoresis described by mass balance equationELECTROPHORESIS, Issue 16 2008Ying Sun Abstract Vacancy ACE (VACE) is one of the ACE methods, and has been used to study binding interactions between different biomolecules. Thermodynamic binding constants can be estimated with nonlinear regression methods. With a highly efficient computer simulation program (SimDCCE), it is possible to demonstrate the detailed behaviors of each species during the interaction process under different conditions. In this work, thirteen scenarios in four different combinations of migration orders of the free protein, free drug, and complex formed are studied. The detailed interaction process between protein and ligand is discussed and illustrated based on the mass balance equation, also called mass transfer equation. By properly setting the parameters in the simulation model, the influence of different factors during the interaction process can be well understood. [source] Fast liquid composite molding simulation of unsaturated flow in dual-scale fiber mats using the imbibition characteristics of a fabric-based unit cellPOLYMER COMPOSITES, Issue 10 2010Hua Tan The use of the dual-scale fiber mats in liquid composite molding (LCM) process for making composites parts gives rise to the unsaturated flow during the mold-filling process. The usual approaches for modeling such flows involve using a sink term in the mass balance equation along with the Darcy's law. Sink functions involving complex microflows inside tows with realistic tow geometries have not been attempted in the past because of the problem of high computational costs arising from the coupling of the macroscopic gap flows with the microscopic tow flows. In this study, a new "lumped" sink function is proposed for the isothermal flow simulation, which is a function of the gap pressure, capillary pressure, and tow saturation, and which is estimated without solving for the microscopic tow simulations at each node of the FE mesh in the finite element/control volume algorithm. The sink function is calibrated with the help of the tow microflow simulation in a stand-alone unit cell of the dual-scale fiber mat. This new approach, which does not use any fitting parameters, achieved a good validation against a previous published result on the 1D unsaturated flow in a biaxial stitched mat,satisfactory comparisons of the inlet-pressure history as well as the saturation distributions were achieved. Finally, the unsaturated flow is studied in a car hood-type LCM mold geometry using the code PORE-FLOW© based on the proposed algorithm. POLYM. COMPOS., 31:1790,1807, 2010. © 2010 Society of Plastics Engineers. [source] Determination of the stable carbon isotopic compositions of 2-methyltetrols in ambient aerosols from the Changbai MountainsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2010Li Li Isoprene is one of the most important non-methane hydrocarbons (NMHCs) in the troposphere: it is a significant precursor of O3 and it affects the oxidative state of the atmosphere. The diastereoisomeric 2-methyltetrols, 2-methylthreitol and 2-methylerythritol, are marker compounds of the photooxidation products of atmospheric isoprene. In order to obtain valuable information on the ,13C value of isoprene in the atmosphere, the stable carbon isotopic compositions of the 2-methyltetrols in ambient aerosols were investigated. The 2-methyltetrols were extracted from filter samples and derivatized with methylboronic acid, and the ,13C values of the methylboronate derivatives were determined by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). The ,13C values of the 2-methyltetrols were then calculated through a simple mass balance equation between the 2-methyltetrols, methylboronic acid and the methylboronates. The ,13C values of the 2-methyltetrols in aerosol samples collected at the Changbai Mountain Nature Reserves in eastern China were found to be ,24.66,±,0.90, and ,24.53,±,1.08, for 2-methylerythritol and 2-methylthreitol, respectively. Based on the measured isotopic composition of the 2-methyltetrols, the average ,13C value of atmospheric isoprene is inferred to be close to or slightly heavier than ,24.66, at the collection site during the sampling period. Copyright © 2010 John Wiley & Sons, Ltd. [source] Groutability of cement-based grout with consideration of viscosity and filtration phenomenonINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 16 2009Jong-Sun Kim Abstract The groutability depends on the properties of the grout, its injection processes, and on the mechanical properties of the soil formation. During the process of pouring cement-based grouting into a porous medium, a variation with time occurs in the viscosity of grout suspension. In addition, the particle filtration phenomenon will limit the expansion of the grouted zone because cement particles are progressively stagnant within the soil matrix. In this paper, a closed-form solution was derived by implementing the mass balance equations and the generalized phenomenological filtration law, which can be used to evaluate the deposition of cement-based grout in the soil matrix. The closed-form solution relevant to a particular spherical flow was modified by a step-wise numerical calculation, considering the variable viscosity caused by a chemical reaction, and the decrease in porosity resulting from grout particle deposition in the soil pores. A series of pilot-scale chamber injection tests was performed to verify that the developed step-wise numerical calculation is able to evaluate the injectable volume of grout and the deposition of grout particles. The results of the chamber injection tests concurred well with that of the step-wise numerical calculation. Based on the filtration phenomenon, a viable approach for estimating the groutability of cement-based grout in a porous medium was also suggested, which might facilitate a new insight in the design of the grouting process. Copyright © 2009 John Wiley & Sons, Ltd. [source] Studies on pyrolysis of vegetable market wastes in presence of heat transfer resistance and deactivationINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2005Ruby Ray Abstract In the present investigation, the pyrolysis of predried vegetable market waste (dp=5.03 mm) has been studied using a cylindrical pyrolyser having diameter of 250 mm under both isothermal and non-isothermal conditions within the temperature range of 523,923 K with an intention to investigate the effective contribution of different heat transfer controlling regime namely intra-particle, external along with kinetically control regime on the overall global rate of pyrolysis. Thermogravimetric method of analysis was utilized to obtain experimental data for both isothermal and non-isothermal cases by coupling a digital balance with the pyrolyser. The pyrolysis of vegetable market waste has been observed to exhibit deactivated concentration independent pyrolysis kinetics, analogous to catalytic poisoning, throughout the entire range of study. The deactivation is of 1st order up to 723 K and follows the 3rd order in the temperature range of 723 Mass Balances in Porous Foods ImpregnationJOURNAL OF FOOD SCIENCE, Issue 9 2001V. Roa ABSTRACT: A simple model based on mass balance equations is proposed for prediction of the final mass and composition of products subjected to vacuum impregnation. It was applied to some tropical fruits in a fruit-sucrose solution system. The phenomenon can be described in terms of volumetric fraction of impregnating solution as the basic modeling parameter, instead of effective porosity. To use the equations of the model, only routine laboratory equipment and simple experiments are required. Prediction of the final weight of impregnated fruit was accomplished with an average absolute error of 2 to 3%, while in final composition of the fruit (total solids), it was 5.7 %. [source] Matrix Representation of Polymer Chain Size Distributions, 2,MACROMOLECULAR THEORY AND SIMULATIONS, Issue 2 2007Fundamental Analysis of Linear Polymerization Mechanisms at Transient Conditions Abstract Analysis of the mass balance equations that describe a reaction system may be useful to provide information about its dynamics, such as the restricted set of compositions that can be achieved from a given set of initial compositions and the effect of feeding reactants to the reaction environment along the reaction course. Since these results may be important for the formulation of reaction policies, this work presents the properties of a matrix polymerization model previously developed and extended to describe transient conditions. This model is based on the definitions of two matrices: the consumption matrix (A,,,Kt), which contains information about chemical transformations among the many active polymer species in the system, and the propagation matrix Kp, which contains information about chain growth. It is shown that the set of mass balance equations that describes the dynamics of active chemical species in polymerization reactions has a stable and unique solution, which is bounded if feed rates are also bounded. It is also shown that the set of compositions that may be reached through manipulation of the feed rates is restricted and may not include all possible chemical compositions. Finally, it is shown that the obtained molecular weight distributions are special multiple time convolutions of the initiation rates. [source] Modeling and simulation approaches in the resin transfer molding process: A reviewPOLYMER COMPOSITES, Issue 4 2003A. Shojaei A review of current approaches in modeling and simulation of the resin transfer molding (RTM) process is presented. The processing technology of RTM is discussed and some available experimental techniques to monitor the process cycle are presented. A master model is proposed for the entire process cycle consisting of mold filling and curing stages. This master model contains the fundamental and constitutive sub-models for both stages. The key elements of the master model discussed in this study are: flow, heat and mass balance equations for fundamental sub-models, permeability, cure kinetics, resin viscosity and void formation for constitutive sub-models. At the end, numerical methods widely used to simulate the filling process are presented and published simulation results of mold filling and process cycle are reviewed. [source] Modelling air flow and ambient temperature effects on the biological self-heating of compost pilesASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2010T. Luangwilai Abstract We formulate and investigate a one-dimensional model for self-heating in compost piles. The self-heating occurs through a combination of biological and chemical mechanisms. Biological heat generation is known to be present in most industrial processes handling large volumes of bulk organic materials. The heat release rate due to biological activity is modelled by a function which at sufficiently low temperatures is a monotonic increasing function of temperature. At higher temperatures, it is a monotonic decreasing function of temperature. This functionality represents the fact that micro-organisms die or become dormant at high temperature. The heat release due to oxidation reaction is modelled by Arrhenius kinetics. The model consists of mass balance equations for oxygen and energy. Steady-state temperature diagrams are determined as a function of the size of the compost pile and the flow rate of air through the pile. We show that there is a range of flow rates for which elevated temperatures, including the possibility of spontaneous ignition, occur within the pile. We also investigate the effects of variations in the ambient temperature. Copyright © 2010 Curtin University of Technology and John Wiley & Sons, Ltd. [source] A Procedure for High-Yield Spore Production by Bacillus s ubtilisBIOTECHNOLOGY PROGRESS, Issue 4 2005Sandra M. Monteiro Bacillus subtilis spores have a number of potential applications, which include their use as probiotics and competitive exclusion agents to control zoonotic pathogens in animal production. The effect of cultivation conditions on Bacillus subtilis growth and sporulation was investigated in batch bioreactions performed at a 2-L scale. Studies of the cultivation conditions (pH, dissolved oxygen concentration, and media composition) led to an increase of the maximum concentration of vegetative cell from 2.6 × 109 to 2.2 × 1010 cells mL - 1 and the spore concentration from 4.2 × 108 to 5.6 × 109 spores mL - 1. A fed-batch bioprocess was developed with the addition of a nutrient feeding solution using an exponential feeding profile obtained from the mass balance equations. Using the developed feeding profile, starting at the middle of the exponential growth phase and finishing in the late exponential phase, an increase of the maximum vegetative cell concentration and spore concentration up to 3.6 × 1010 cells mL - 1 and 7.4 × 109 spores mL - 1, respectively, was obtained. Using the developed fed-batch bioreaction a 14-fold increase in the concentration of the vegetative cells was achieved. Moreover, the efficiency of sporulation under fed-batch bioreaction was 21%, which permitted a 19-fold increase in the final spore concentration, to a final value of 7.4 × 109 spores mL - 1. This represents a 3-fold increase relative to the highest reported value for Bacillus subtilis spore production. [source]
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