Showing papers in "Chemical Engineering and Processing in 1997"
TL;DR: In this paper, the feasibility of a large scale application of the lightenhanced Fenton reaction has been investigated for the treatment of highly contaminated industrial waste water containing toxic aromatic amines (dimethyl anilines or xylidines) as the main pollutants.
Abstract: The feasibility of a large scale application of the light-enhanced Fenton reaction has been investigated for the treatment of a highly contaminated industrial waste water containing toxic aromatic amines (dimethyl anilines or xylidines) as the main pollutants. The Fenton reagent, a combination of hydrogen peroxide and a ferrous salt, is a potent oxidizing agent of organic compounds in acidic aqueous solution, and UV/visible irradiation may significantly enhance the degradation rates. Preliminary laboratory tests on the model compounds, 2,4- and 3,4-xylidine have been performed for selecting appropriate experimental conditions. Subsequent experimentation on the industrial waste water at a large scale level (3000 mg C l−1, 500 l) has been carried out using an experimental design methodology for the simulation and the evaluation of the effects of the two critical factors, hydrogen peroxide and ferrous ion concentrations. The results indicate that the light-enhanced Fenton reaction is a most effective treatment process under acidic conditions and is a realistic alternative to adsorption of xylidines on activated carbon as used at present.
169 citations
TL;DR: In this article, the authors present a laboratory scale apparatus in which a single freely suspended particle can be coated under well defined and constant coating and drying conditions, and the particle growth rate and the development of particle morphology were measured and investigated under various experimental conditions.
Abstract: The coating and granulation of solid particles in a fluidized bed is a process which converts pumpable and atomizable liquids (solutions, slurries, melts) into granular solids in one step by means of drying. The solution to be processed is sprayed onto a fluidized bed. Particle growth can take place either via surface layering or agglomeration. In the case of surface layering the atomized droplets deposit a thin layer of liquid onto the seed particles. The solvent is then evaporated by the hot fluidizing, leaving behind the dissolved material on the surface. Although fluidized bed spray granulation and film coating have been applied in industry for several years, there is still a lack of understanding of the physical fundamentals and the mechanisms by which spherical granules are formed. Hence a new method was developed which allows the direct observation of the subsequent particle-forming mechanisms such as droplet deposition, spreading, wetting and drying. The authors present a laboratory scale apparatus in which a single freely suspended particle can be coated under well defined and constant coating and drying conditions. With this device, particle-growth-rate and the development of particle morphology were measured and investigated under various experimental conditions.
137 citations
TL;DR: In this article, a procedure is presented for evaluating the shell side pressure drop in shell-and-tube heat exchangers with segmental baffles based on correlations for calculating the pressure drop, coupled with correction factors, which take into account the influence of leakage and bypass streams.
Abstract: A procedure is presented for evaluating the shell side pressure drop in shell-and-tube heat exchangers with segmental baffles. The procedure is based on correlations for calculating the pressure drop in an ideal tube bank coupled with correction factors, which take into account the influence of leakage and bypass streams, and on equations for calculating the pressure drop in a window section from the Delaware method. The proposed equations were checked by comparing experimental measurements available in the literature with the theoretical predictions. The ranges of the geometrical and operational parameters, for which the deviations between the experimental measurements and the theoretical predictions were within ± 35%, are presented in the paper
77 citations
TL;DR: In this paper, a new mathematical model of evaporative fluid cooling with countercurrent air flow is presented, which consists of four ordinary differential equations with their boundary conditions and some associated algebraic equations.
Abstract: In this paper heat and mass transfer processes in evaporative fluid coolers are discussed. A new mathematical model of evaporative fluid cooling with countercurrent air flow is presented. The model consists of four ordinary differential equations with their boundary conditions and some associated algebraic equations. A method of adjusting the model to geometrical arrangement which is used in bare-tube heat exchangers is proposed. The study presents a comparison of the results computed using an analytical model with the experimental results of the evaporative water cooler test. A good agreement between the calculated and experimental values is achieved. The correction function of mass transfer coefficient introduced into the analytical model improves this agreement.
61 citations
TL;DR: In this article, a general model of multicomponent pressure swing adsorption (PSA) is presented which describes the operation of multi-column PSA installations, where individual columns can be packed with one or two layers of different adsorbents.
Abstract: A general model of multicomponent pressure swing adsorption (PSA) is presented which describes the operation of multi-column PSA installations. The individual columns can be packed with one or two layers of different adsorbents. All the basic steps of modern PSA cycles are taken into account. The operation of a large-scale PSA installation is analysed using a hydrogen purification plant as a test case
56 citations
TL;DR: In this article, modern statistical techniques were used to compare the traditional linear regression technique with the modern nonlinear regression as applied to the Arrhenius equation, and it was concluded that linear regression, in principle, is in principle not inferior to non-linear regression and if the relative error in the data is distributed normally, it can even be superior.
Abstract: Engineers must often use correlations that were developed before statistical analysis and verification of the correlation became a routine procedure. In this paper, we use modern statistical techniques to compare the traditional linear regression technique with the modern nonlinear regression as applied to the Arrhenius equation. The objective of the comparison is to determine whether there are basic flaws with the technique used in the past and whether these flaws may render the constants published in the literature untrustworthy. It is concluded that linear regression, when applied to the Arrhenius expression, is in principle not inferior to nonlinear regression and if the relative error in the data is distributed normally, it can even be superior. Nevertheless, if insufficient data were used for calculation of the constants and/or the experimental data were interpolated or smoothed, the accuracy of the published correlation is unpredictable.
54 citations
TL;DR: In this paper, the esterification of myristic acid in a reaction column is optimized through simulations and a complex dynamic model for reactive distillation, which includes control systems and the capability of coupling additional columns is derived.
Abstract: A complex dynamic model for reactive distillation, which includes control systems and the capability of coupling additional columns is derived. On this basis, a typical reactive distillation column coupled with a recovery column is investigated and optimized. In this paper, the esterification of myristic acid in a reaction column as a typical example is optimized through simulations. To guarantee an almost complete conversion of the acid and a high purity of the reaction by product water, the reaction column is coupled with a recovery column. Both columns are designed based on steady state simulations. To develop a control structure, the reaction column's steady state and dynamic sensitivity of possible disturbances and manipulated variables are analyzed. It is shown, that in this reaction column there is no direct relationship between temperature and purity as is usual in common distillation columns. The influence of the reaction on the temperature profile within the reaction column has to be known, when the temperature is used as a reference variable for the purity. The recovery does not lead to an instability of the system. With this knowledge an efficient control structure is presented for this strongly non-linear coupled system. The purities of the product streams can be guaranteed
44 citations
TL;DR: In this paper, a pseudo-permanent model is developed for a solid-gas reactor, taking into account the average functioning characteristics of a solid gas reactor during an interval of time, which allows simple calculations to be made concerning the dimensioning and thereby helps in the decision-making process.
Abstract: In the following study, a basis has been developed for a pseudo-permanent model, taking into account the average functioning characteristics of a solid-gas reactor during an interval of time This model is of interest thanks to its analytical form and allows simple calculations to be made concerning the dimensioning, and thereby helps in the decision-making process The industrial development of thermochemical reactors requires the design and construction of demonstration machines and thus calls for dimensioning models The already existing models are based on dynamic simulation linked to the discontinuous and transient functioning mode of such processes Hence, these dynamic models require initially arbitrary choices, which are tested successively to achieve a correct sizing of the machine The comparison of the analytical model developed in this study with a dynamic model, and with the results of experiments, demonstrates the limits of the analytical model, as well as its reliability compared to the dynamic model Elsewhere, the flexibility linked to its analytical form shows the scale of the field of application
36 citations
TL;DR: In this paper, the use of a Reactor with periodic flow reversal for catalytic incineration of the model pollutants carbon monoxide and propane has been experimentally studied and the most important parameters influencing the Reactor operation were found to be catalytic activity, adiabatic temperature rise (reactant concentration) and heat transfer properties of the fixed bed.
Abstract: The use of a reactor with periodic flow reversal for catalytic incineration of the model pollutants carbon monoxide and propane has been experimentally studied. The mean axial temperature profile over one period in cycle steady state is a symmetrical curve which can be linearised and subdivided into three regions. The center of reactor with a constant maximum temperature and two reactor ends with a linear temperature profile. The most important parameters influencing the reactor operation were found to be catalytic activity, adiabatic temperature rise (reactant concentration) and heat transfer properties of the fixed bed. Higher catalytic activity leads to a decrease of the maximum temperature profile. Increasing reactant concentrations cause higher values of maximum temperature, temperature gradient in the reactor ends and mean temperature at reactor inlet/outlet. A higher number of heat transfer units as a measure for the heat transfer characteristics of the catalyst bed give rise to higher maximum temperature and higher temperature gradient in the reactor ends, while the mean temperature at reactor inlet/outlet remains constant. Investigation of the ignition and extinction behavior of the reactor has shown that a fixed bed with a lower number of heat transfer units requires higher reactant concentrations to maintain stable operation in the ignited state.
35 citations
TL;DR: In this article, five empirical correlations for the prediction of heat transfer to liquid-solid fluidized beds with three, four, five, six and seven constants were fitted to experimental data using the database as given in (Haid et al., Chem. Eng. Proc, 33 (1994) 211-225) comprising more than 2500 measured data.
Abstract: Five empirical correlations for the prediction of heat transfer to liquid-solid fluidized beds with three, four, five, six and seven constants were fitted to experimental data using the database as given in (Haid et al., Chem. Eng. Proc, 33 (1994) 211-225) comprising more than 2500 measured data. The average relative error of prediction and the standard deviation for the heat transfer coefficient were calculated. The simplest correlation with three constants and the most complex correlation with seven constants are compared for different liquid and solid properties. The comparison shows that there is no real improvement in the accuracy of predicting the heat transfer coefficient using more than three constants
34 citations
TL;DR: In this paper, the design and operation of reactors for catalytic, hydrogenation in the fine chemical industries are discussed and the requirements for a good multiproduct catalytic hydrogenation unit as well as the choice of the reactor type are considered.
Abstract: The design and operation of reactors for catalytic, hydrogenation in the fine chemical industries are discussed. The requirements for a good multiproduct catalytic hydrogenation unit as well as the choice of the reactor type are considered. Packed bed bubble column reactors operated without hydrogen recycle are recommended as the best choice to obtain a flexible reactor with good selectivities.
The results of an experimental study of the catalytic hydrogenation of 2,4-dinitrotoluene in a miniplant installation are presented to prove that the maximum yield in such a reactor can be achieved without a hydrogen recycle and with a hydrogen supply somewhat higher than the stoichiometric amount. Some characteristic properties of the reactor system and the influence of the reactor pressure and the hydrogen supply ratio are elucidated.
TL;DR: In this article, a model has been derived for a free jet to calculate the particle and gas velocities, the void fraction and the cross-sectional area of the jet.
Abstract: In fluidized bed granulation the liquid is often distributed by means of a two-fluid-nozzle that is positioned inside the bed. Then the wetting process takes place in the jet that is formed by the atomizing air. A model has been derived for a free jet to calculate the particle and gas velocities, the void fraction and the cross-sectional area of the jet. The results are compared with experimental data for the particle circulation time in the fluidized bed. Based on the particle and gas motion the liquid deposition is calculated, resulting in particle moisture distributions. The influence of different parameters on the moisture distribution and possible consequences on the granulation process are discussed.
TL;DR: In this article, aqueous suspensions of china clay using a batch kneader drier at pilot plant scale were measured for aqueously suspended of clay using the penetration model for contact drying.
Abstract: The drying of paste-like products is a common industrial task Usually a batch vacuum contact drying process is used and the process is carried out in a kneader dryer with a low stirrer speed due to very high torques appearing during the drying process The process can be divided into two parts, the paste and the particulate regime Both regimes are separated by a sharp maximum in the torque curve The position of the maximum depends on the type of product In the paste regime the drying rate decreases with decreasing moisture content of the product, while torque increases and the product temperature remains nearly constant In the particulate regime the drying rate decreases further with decreasing product moisture content At the same time product comminution takes place, the torque decreases and the product temperature rises Drying rate curves are measured for aqueous suspensions of china clay using a batch kneader drier at pilot plant scale The influence of the main drying parameters on the drying process is investigated experimentally and theoretically The measured drying rate curves are compared to calculations based on the penetration model for contact drying Neglecting mass transfer effects and assuming that the particle size distribution of the product remains constant, the penetration model is able to describe both the paste regime and the particulate regime of the drying process over the whole moisture range Measured and calculated drying rate curves are in good agreement for a variety of drying parameters
TL;DR: In this paper, the removal and recovery of an amine from waste air of a foundry by adsorption is discussed on the basis of experiments and simulation studies, and the results show that activated carbons as well as a hydrophobic Y-zeolite are well suited for the purification.
Abstract: The removal and recovery of an amine from waste air of a foundry by adsorption is discussed on the basis of experiments and simulation studies. The results show that activated carbons as well as a hydrophobic Y-zeolite are well suited for the purification. Since parts of the amine are chemically bound to the adsorbents, a decrease in adsorption capacity is found for both adsorbents after the first cycles. For the desorption and recovery, a combined vacuum and temperature swing (VTSA) technique is used. To achieve a sufficient degree of regeneration without using too low pressures, a small amount of purge gas is added during the vacuum desorption. This allows the condensation to be performed at an ambient temperature (10–20°C). In experiments with a single adsorption column as well as in cyclic experiments with a three column setup it was shown that more than 95% of the continuously fed amine can be removed and recovered from the waste air. The further purification down to the required clean gas concentration has to be done in a second purification step, e.g. a bio-filter.
TL;DR: In this paper, the influence of the gas velocity and particle diameter on the interfacial areas, pressure drops and liquid holdups has been investigated by means of chemically enhanced absorption of CO2 into DEA in a packed bed bubble column reactor.
Abstract: Gas?liquid interfacial areas have been determined by means of chemically enhanced absorption of CO2 into DEA in a packed bed bubble column reactor with an inner diameter of 156 mm. The influence of the gas velocity and particle diameter on the interfacial areas, pressure drops and liquid holdups has been investigated. For both packings the limiting values of the gas velocities have been determined above which the interfacial areas and liquid holdups stabilize. In particular gas channelling has been found, which is less pronounced in the bed of larger particles.
TL;DR: In this paper, some dimensioning nomograms have been developed in order to simplify the dimensioning of a fixed-bed solid-gas thermochemical transformers and facilitate decision-making at early stages of a project.
Abstract: The development of solid-gas thermochemical transformers requires the design and the construction of demonstration machines which could not exist without simulation models, allowing the dimensioning of fixed-bed solid-gas reactors. All of the models developed so far are based on a dynamic modelling of the process describing the temporal evolution of the principal elements of which the machine consists. This approach to dimensioning is certainly better adapted to the discontinuous and unstationary working mode of these machines. However, the dimensioning of the machine becomes a very complex and time consuming operation. With the aim of simplifying this procedure, some dimensioning nomograms have been developed in this study. They will enable any designer to draft a rapid dimensioning of a fixed-bed solid-gas reactor, thus facilitating decision making at the early stages of a project. These nomograms have been set up from a simplified analytical model which considers the average functional characteristics of a thermochemical reactor over a given time step. Finally, several applied examples are given to demonstrate the various possibilities, as well as the simple usage of these dimensioning nomograms.
TL;DR: In this article, a study was conducted on the use of a Moving Bed Heat Exchanger-Filter (MHEF) for removing fine dust particles from gases, and a stable numerical model for filtration and heat exchange was developed that predicts the two dimensional transient response of both solid and fluid phases.
Abstract: A study was conducted on the use of a Moving Bed Heat Exchanger-Filter (MHEF) for removing fine dust particles from gases. The influence of a number of variables was examined, including gas velocities, solid velocities, gas temperatures and dust sizes. The collection efficiency was found to decrease with increasing temperature; the total collection efficiency decreases strongly when the solid velocity increases. A stable numerical model for filtration and heat exchange was developed that predicts the two dimensional transient response of both solid and fluid phases. The numerical model incorporates variation in void fraction, velocities and transport coefficient due to combined processes of filtration and heat exchange.
TL;DR: A simplified stage-wise hydrodynamic model for simulation of a pulsed sieve-plate extraction column has been presented in this paper, which is based on a drop population balance which takes into account drop breakage and coalescence in each stage.
Abstract: A simplified stage-wise hydrodynamic model for simulation of a pulsed sieve-plate extraction column has been presented. The model is based on a drop population balance which takes into account drop breakage and coalescence in each stage. Each stage is represented by the actual column compartment between two sieve plates. Although experimental break-up parameters have been used in the model, the coalescence coefficients have been taken as the fitting parameters and the values which gave the best fit with the experimental data have been used. The predicted values have been compared with data from two different diameter pilot plant columns and the agreement is found to be quite satisfactory for the system butylacetate-water. The model can be used for coalescence parameter estimation of different drop sizes, which will be taken up as part of the extension of the present work.
TL;DR: In this paper, a simple steady-state countercurrent reactor model that is capable of describing the influence of adiabatic temperature rise and heat transfer properties of the fixed bed of catalyst on mean reactant conversion and temperature profile in cycle steady state is proposed.
Abstract: Analysis of the reverse-flow reactor and comparison to a conventional adiabatic fixed bed reactor with external heat exchanger has shown that both systems are closely related. The required additional system parameter is the center of gravity of energy release caused by exothermic chemical reaction, which can also be rationalized as the mean fraction of the reverse-flow reactor acting as a regenerative heat exchanger. A simple steady-state countercurrent reactor model that is capable of describing the influence of adiabatic temperature rise and heat transfer properties of the fixed bed of catalyst on mean reactant conversion and temperature profile in cycle steady state is proposed. Generally, the agreement between calculated and experimentally determined parameters is satisfying. While discrepancies occur in the case of carbon monoxide oxidation, reactant conversion and maximum temperature as well as the minimum concentration for stable operation in cycle steady state are accurately predicted for the oxidation of propane.
TL;DR: In this article, a model has been developed to predict the spectral emittance (directional, normal, hemispherical) of semi-transparent and opaque particulate deposits without considering dependent effects.
Abstract: This paper presents the results of an experimental and theoretical investigation on the importance of dependent effects in determining the emittance of ash deposits. A model has been developed to predict the spectral emittance (directional, normal, hemispherical) of semi-transparent and opaque particulate deposits without considering dependent effects. Predictions from this model have been presented to illustrate the effects of particle size and composition. Hemispherical transmission and reflection measurements have been performed on semi-transparent and opaque particular deposits over a wavelength range typical of pf fired furnances and spectral emittance has been deduced therefrom. Well characterised slag particles, with composition and size similar to ash deposits formed in pf fired furnances, have been used in the measurements. For the opaque deposit, difference between the model predictions and measurements, in terms of emittance, have been found to be significant at wavelengths up to 7 μm. This difference is believed to be largely due to dependent effects. Such measurements and comparisons appear to be the first of its kind and more experiments are recommended to quantify the effects.
TL;DR: In this paper, a simple model based on the theory of liquid emulsions is proposed to develop correlations suitable for estimating gas-liquid interfacial areas for the bubble flow regime in three-phase fixed bed reactors operated with gas and liquid flowing cocurrently upflow.
Abstract: A simple model, based on the theory of liquid emulsions, is proposed to develop correlations suitable for estimating gas–liquid interfacial areas for the bubble flow regime in three-phase fixed bed reactors operated with gas and liquid flowing cocurrently upflow. The model is also employed for trickle-bed reactors for estimating the increase in gas–liquid interfacial areas when these reactors are operated under high pressure conditions. It is found that developed correlations account satisfactorily for most of the data of gas–liquid interfacial areas available in the literature for cocurrent upflow three-phase fixed bed reactors and for trickle-bed reactors operated at high pressure conditions.
TL;DR: The theory of multicomponent isotope separation cascade with losses is developed in this paper, where the losses from each stage of a cascade are set proportional to the flow entering the stage, the fraction of flow lost per stage being constant.
Abstract: The theory of multicomponent isotope separation cascade with losses is developed. The losses from each stage of a cascade are set proportional to the flow entering the stage, the fraction of flow lost per stage being constant. The interstage flows of each component are expressed as simultaneous linear equations and solved explicitly in the case where the separation factors do not vary from stage to stage. An illustrative example dealing with the separation of the 5-component tungsten isotope mixture in the matched abundance ratio cascade composed of gas centrifuges is included.
TL;DR: In this article, the effects of agitation level on the mass transport coefficient in a new electrochemical reactor equipped with reciprocating sieve-plate electrodes were analyzed and the results of experimental investigations carried out on laboratory apparatus and in a pilot plant using stainless steel electrodes and an aqueous solution of potassium iodide.
Abstract: This paper analyses the effects of agitation level on the mass transport coefficient in a new electrochemical reactor equipped with reciprocating sieve-plate electrodes. It also presents the results of experimental investigations carried out on laboratory apparatus and in a pilot plant using stainless steel electrodes and an aqueous solution of potassium iodide in the presence of an excess of supporting electrolyte (sodium sulphate). The mass transport coefficient was evaluated from limiting current measurements and current polarisation curves, and correlated with vibrational variables by a controlling dimensionless numbers relationship.
TL;DR: In this article, the effects of the electrodes morphology on the slit flow of an electrorheological (ER) fluid via laser-Doppler-anemometry (LDA) were studied via two types of grooved electrodes.
Abstract: In this study the rheological properties of two electrorheological (ER) fluids (experimental samples) under the influence of an AC as well as under DC conditions are investigated using a rotational viscometer. Plastic-fluid behavior quite well describes the flow curves with a yield stress which depends upon the applied electric field. The results show that the behavior of an ER-fluid depends on its composition. Comparison between the shear-type (rotational viscometer) and flowtype (slit flow) measurements leads to the hypothesis that the inhomogenous electric field (in viscometer) may be the cause for an increase of the measured ER-effect relative to that measured in a homogeneous field (channel with smooth electrodes). Based on this hypothesis, the ER-effect in slit flow should increase by altering the electrode morphology. For that purpose, the effects of the electrodes morphology on the slit flow of an ER-fluid are studied via laser-Doppler-anemometry (LDA). Two types of grooved electrodes were used. In the presence of an AC-field, the ER-effect with grooved electrodes is greater in comparison to the case of smooth electrodes at the same field strength and pressure drop. An average factor of 2.5 describes this increase. This increase in the ER-effect is accompanied by a decrease in electric current. Under a DC-field the ER-effect with grooved electrodes is somewhat better than the smooth electrodes but only at very low field strength. Increasing the field strength leads to a decreased ER-effect in comparison to the smooth electrodes.
TL;DR: In this article, the results of investigations of tubular and plate settlers constituted a basis for the determination of sedimentation effectiveness being a function of dimensionless groups, which served to verify models and calculational methods, quoted in the literature.
Abstract: This paper deals with packed-type (multicurrent) settlers, which — compared to conventional ones — display a number of advantages. Two experimental stands, viz. with tubular elements and plate packing, have been constructed. Eight kinds of suspensions were tested. The results of investigations of tubular and plate settlers constituted a basis for the determination of sedimentation effectiveness being a function of dimensionless groups. Moreover, the experimental results have served to verify models and calculational methods, quoted in the literature.
TL;DR: In this paper, the authors report on studies on the augmentation of ionic mass transfer rates due to the presence of insert promoters (coaxially placed helical tapes on a rod) in a forced convection flow of electrolyte.
Abstract: This paper reports on studies on the augmentation of ionic mass transfer rates due to the presence of insert promoters—coaxially placed helical tapes on a rod—in a forced convection flow of electrolyte. The experimental limiting current data were obtained at various flow rates using promoters of varying central rod diameter width and pitch of the helical tape. Altogether, 1200 experimental limiting current measurements were obtained covering a wide range of variables. The data are analysed and results are discussed in detail. The developed correlations based on experimental data are presented.
TL;DR: In this paper, various solution methods were studied for the solution of a general isothermal dynamic bubble column reactor model, which can be used to describe various degrees of backmixing in co-and countercurrent bubble columns.
Abstract: Various solution methods were studied for the solution of a general isothermal dynamic bubble column reactor model. The general dynamic reactor model can be used to describe various degrees of backmixing in co- and countercurrent bubble columns. The solution methods were all based on discretization of the transient film-penetration model in the film dimension and on discretization of the column axial dimension. The resulting ODE-system was then integrated with a stiff integration algorithm applying sparse matrix techniques. The solution methods were tested using a single first order irreversible reaction and its autocatalytic modification. Furthermore, more complicated reaction kinetics of two competitive-consecutive second order reactions referring to the chlorination of para -cresol was simulated. The results show that methods based on orthogonal collocation perform extremely well in the film dimension, but suffer from serious stability problems in the column dimension. The discretization methods based on a finite difference approach are robust and reliable, but numerous grid points must be applied in order to obtain an acceptable accuracy. The multipoint finite difference formulae can be used to enhance the accuracy considerably. Also, a dynamic formulation of a semi-empirical outlet boundary condition for the axial dispersion model was tested. The proposed formulation is numerically superior to the traditional Danckwerts' outlet boundary condition in dynamic column simulation with all tested kinetics.
TL;DR: The thermodynamics and kinetics of transalkylation of diethylbenzene and benzene were studied in liquid phase over faujasite Y in a batch reactor as mentioned in this paper.
Abstract: The thermodynamics and kinetics of the diethylbenzene-benzene transalkylation have been studied in liquid phase over faujasite Y in a batch reactor. The reactions were conducted at several temperatures between 423 and 513 K. The main product of the reaction was ethylbenzene. When the molar ratio of benzene over diethylbenzene was greater than five, a selectivity in ethylbenzene greater than 90% was found. The initial rates showed that the transalkylation reaction followed a first order mechanism. A kinetic model is proposed. (C) 1997 Elsevier Science S.A.
TL;DR: In this paper, the individual and synergic effects of vibration and rotation on mass transfer for spheres were experimentally obtained and the limiting current data were measured at the surface of the sphere using an electrochemical method.
Abstract: The individual and synergic effects of vibration and rotation on mass transfer for spheres were experimentally obtained. The limiting current data were measured at the surface of the sphere using an electrochemical method. The investigations covered the following variables: amplitude of vibration, frequency of vibration, rotational speed and diameter of the sphere. The limiting current data were found to increase with an increase in frequency, amplitude and rotational speed. The mass transfer data were correlated in terms of dimensionless groups.
TL;DR: In this paper, the authors reviewed the main transport mechanisms, measurement techniques, experimental results and prediction methods for unsaturated moist packed beds containing a volatile liquid and focused on the description of the heat transfer by effective thermal conductivities at low temperature gradients without free or forced convection.
Abstract: The heat transfer in unsaturated moist packed beds containing a volatile liquid is reviewed by discussing the main transport mechanisms, measurement techniques, experimental results and prediction methods. Attention is focused on the description of the heat transfer by effective thermal conductivities at low temperature gradients without free or forced convection. Possible sources of error in interpretation of experimental results are discussed. Several estimation methods are tested with experimental results of different authors and fitted values for the model parameters are presented. A comparison of the estimation methods reveals that Okazaki's model is the most reliable.