Showing papers in "Chemical Engineering Communications in 1974"
TL;DR: In this paper, the authors present a review of the performance of chemical reactors in the 1970s, focusing on the periODic operation of CHEMICAL REACTORS.
Abstract: (1974). PERIODIC OPERATION OF CHEMICAL REACTORS: A REVIEW. Chemical Engineering Communications: Vol. 1, No. 3, pp. 111-124.
234 citations
TL;DR: The problem of determining the optimal operating conditions for both continuous and batch crystallizers is discussed, and good physical reasons for the existence of unconstrained optimal policies given.
Abstract: The problem of determining the optimal operating conditions for both continuous and batch crystallizers is discussed, and good physical reasons for the existence of unconstrained optimal policies given. Computational methods for determining these optimal policies are outlined and illustrated by analogy with earlier work on polymerization reactors. A specific problem of the optimal temperature program in a batch crystallizer is solved and the results compared with the predictions and experimental data of Mullin and Nyvlt (1971).
40 citations
TL;DR: In this paper, a two dimensional fluidized bed reactor 24 cm wide, 51 cm high and 2.5 cm in thickness was used for visual observation through a wide front window 24 cm × 35 cm covered with a silica glass plate 1 cm thick.
Abstract: Ignition of activated carbon particles were measured in a vertical tube reactor of 4 cm ID, where single particles fell consecutively through a gas mixture containing oxygen. A two dimensional fluidized bed reactor 24 cm wide, 51 cm high and 2.5 cm in thickness was used for visual observation through a wide front window 24 cm × 35 cm covered with a silica glass plate 1 cm thick. Activated carbon particles were fluidized incipientiy by air, and a gas mixture containing oxygen was injected upwards into the bed through a nozzle positioned 5 cm above the distributor, forming single bubbles intermittently. It was observed that carbon particles dispersed in rising bubbles were ignited abruptly at emulsion phase temperatures above 550°C. Experimental findings from the fluidized bed were compared with those from the tube reactor, suggesting that the igniting conditions for particles dispersed in bubbles are nearly the same as for single particles falling in the tube reactor.
24 citations
TL;DR: The underlying theoretical structure of stochastic differential equations requires an extension of the classical calculus, and this is described in this paper, which provides an excellent framework for the design and analysis of control systems for randomly disturbed plants.
Abstract: The underlying theoretical structure of stochastic differential equations requires an extension of the classical calculus, and this is described. These equations provide a convenient method for the construction of Markov processes that have pre-specified statistical properties and that are very useful as models for random disturbances in process plants. The utility as models for random systems is demonstrated by several examples. Itos lemma, the method of moments, and the method of partial moments are demonstrated as methods of solution of these equations. The theory provides an excellent framework for the design and analysis of control systems for randomly disturbed plants. Examples are given to show that classical design techniques can be completely inadequate for plants of this nature, whereas the stochastic theory leads to good design.
12 citations
TL;DR: A numerical solution of the Navier-Stokes equations for Poiseuille flow around an axially placed, fixed sphere in a circular cylinder is presented in this paper, where the wall effects are examined by comparison with results of previous investigations for an unbounded flow around a sphere.
Abstract: A numerical solution of the Navier-Stokes equations is presented for Poiseuille flow around an axially placed, fixed sphere in a circular cylinder. Streamlines and isovorticity lines are calculated from the governing equations for the strearnfunction and the vorticity. Isobars are calculated from a Poisson equation, derived from the Navier-Stokes equations. The pressure and vorticity distribution on the surface of the sphere, the additional pressure drop and the drag coefficients are presented. Solutions are obtained for Reynolds numbers up to 150 (based on cylinder diameter and mean velocity). The wall effects are examined by comparison with results of previous investigations for an unbounded flow around a sphere.
12 citations
TL;DR: An efficient algorithm for the integration of stiff systems of ordinary differential equations based on the boundary value technique is derived and the automatic step-size control procedure can be easily adapted.
Abstract: An efficient algorithm for the integration of stiff systems of ordinary differential equations based on the boundary value technique is derived. The automatic step-size control procedure can be easily adapted. Results for a very stiff problem are compared with those obtained by other methods and the high effectiveness of the method is shown.
9 citations
TL;DR: In this paper, the authors developed a conformal solution theory for the viscosity and thermal conductivity of fluid mixtures, which involves expanding the transport coefficient for the mixture about the value for an ideal solution, using groupings of the potential parameters and molecular mass as expansion coefficients.
Abstract: Conformal solution theory is developed for the viscosity and thermal conductivity of fluid mixtures. The procedure involves expanding the transport coefficient for the mixture about the value for an ideal solution, using groupings of the potential parameters and molecular mass as expansion coefficients. The parameters for the ideal solution are chosen so as to annul the first-order term in this expansion, thus encouraging rapid convergence. This yields mixing rules (similar to those of the van der Waals 1 theory for thermodynamic properties) for the potential parameters and molecular mass of the reference fluid. Reference fluid properties are obtained from pure fluid corresponding states correlations By making calculations for dilute gas mixtures and comparing with Chapman-Enskog theory, it is found that the first-order theory works well for mixtures of quite widely different energy parameters (e) and molecular masses; it is more sensitive to the size difference of the molecular components, howev...
9 citations
TL;DR: In this paper, the Liapunov design approach for model reference adaptive control (MRAC) is extended to include adaptive integral and setpoint control modes, and a multi-variable MRAC system based on a fifth-order state space model of a pilot scale, double-effect evaporator is presented.
Abstract: The Liapunov design approach for model reference adaptive control (MRAC) is extended to include adaptive integral and setpoint control modes. The feasibility of the Liapunov approach is illustrated by designing a multi-variable MRAC system based on a fifth-order state space model of a pilot scale, double-effect evaporator. Simulation results are presented to demonstrate that the MRAC approach gives satisfactory control for a wide range of adaptive loop gains and despite very poor initial control policies.
7 citations
TL;DR: The applicability of modified Stefan-Maxwell equations to multicomponent diffusion in the transition diffusion region has been investigated in this paper, where conditions for determining the key component and composition of the diffusion stoichiometric mixture were developed.
Abstract: The applicability of modified Stefan-Maxwell equations (1) to multicomponent diffusion in the transition diffusion region has been investigated. It appears that ratios of diffusion fluxes imposed by the reaction stoichiometry and the necessity of a momentum balance of molecules cause a total pressure gradient to be formed. Assuming a negligible effect of these gradients, Eqs. (1) were numerically integrated for cyclopropane hydrogenolysis: the resulting mutual concentration dependences were virtually linear. Using this linearity, conditions for determining the key component and composition of the diffusion stoichiometric mixture were developed. A simplified diffusion equation (18), together with the definition of the appropriate diffusion coefficient 𝒟I was suggested for the description of multi-component diffusion with a catalytic reaction in the transition diffusion region.
6 citations
TL;DR: In this paper, a Model Reference Adaptive Control (MRAC) system is evaluated via hybrid computer simulation and experimental application to a computer-controlled, pilot plant evaporator, which performed well and was insensitive to unmeasured process disturbances, to the choice of the initial control policy and to changes in plant operating conditions.
Abstract: A Model Reference Adaptive Control (MRAC) system is evaluated via hybrid computer simulation and experimental application to a computer-controlled, pilot plant evaporator. In both the simulation and experimental studies, the MRAC system performed well and was insensitive to unmeasured process disturbances, to the choice of the initial control policy and to changes in plant operating conditions. In addition to providing an algorithm for adapting control systems to accommodate changing process parameters, MRAC also provides a systematic approach for tuning or developing multivariable control systems for time-invariant processes.
5 citations
TL;DR: In this paper, the authors investigated the behavior of a plug-flow tubular reactor with recycle under feedback control of the RCGutalor type, and showed that the presence of any time delay, regardless of its magnitude, in the controller response prevents stabilization of a naturally unstable state by means of control strategics.
Abstract: The topic of interest in this paper is the behavior of a plug-flow tubular reactor with recycle under feedback control of the rcgutalor type. Attention is devoted mainly to the problem of stabilizing those sicady-slatc profiles which are unstable in the absence of control, but the investigation also includes the controlled behavior of those steady states which arc naturally liable. The study reported in this paper is theoretical; it invokes methods of linear stability analysis and computer simulations in considering two separate cases involving different controlled and manipulated variables. The class of controller functions considered includes the conventional proporIionaI-integraderivative controller. The principal discovery is that the presence of any time delay, regardless of its magnitude, in the controller response prevents stabilization of a naturally unstable state by means of control Strategics of this type. In one of the cases considered, It Is shown that if time delay in the control action is t...
TL;DR: In this article, the rates of photochlorination of liquid solutions of Cl2 and n-heptane were measured at 25°C in a tubular-flow reactor.
Abstract: The rates of photochlorination of liquid solutions of Cl2 and n-heptane were measured at 25°C in a tubular-flow reactor. By using educed light intensities and short illuminated reactor lengths it was possible to obtain low conversions of chlorine (approach differential-reactor operation) for this fast reaction. The rate of morochloride production was first order in chlorine concentration and first order in light intensity. An overall quantum yield of 0.8 × 108 g mole/Einstein was obtained At the low chlorine concentrations (> 1.5 mole 7percnt;) employed no dichlorides were found in the product. The monochlorides contained a little more of the primary isomer than has been observed in other photochemical studies.
TL;DR: In this article, it was found that the optimal design is quite sensitive to small changes in some of the feed components, but not to others, and a lower-order model frequently adopted to simplify the calculations, may not be completely adequate.
Abstract: Singular perturbation methods, developed originally by Levin and Levinson (1954) and Vasil'eva (1963), can be viewed as an alternative technique for decomposition of large-scale systems with widely-varying time constants. An example is a chemical reactor in which a multiplicity of fast and slow chemical reactions simultaneously occur. A lower-order model frequently adopted to simplify the calculations, may not be completely adequate, and a singular perturbation attack offers an efficient correction procedure. It is found that the optimal design is quite sensitive to small changes in some of the feed components, but not to others.
TL;DR: In this paper, the authors presented the parameterer estimation by curve-fitting technologies and the method of moments. But they did not consider the effect of the weather on the estimation.
Abstract: (1974). PARAMETER ESTIMATION BY CURVE-FITTING TECHNIQUES AND THE METHOD OF MOMENTS. Chemical Engineering Communications: Vol. 1, No. 4, pp. 187-189.
TL;DR: In this article, the profile of a liquid film flowing along an inclined cylindrical surface, that is not completely wetted, is presented, and a general solution, represented by a set of elliptical integrals, is given in dimensionless form.
Abstract: The calculation of the profile of a liquid film flowing along an inclined cylindrical surface, that is not completely wetted, is presented. Surface tension and contact angle are taken into consideration, and wave motion is neglected. The situation is described by a second order non-linear differential equation. A general solution, represented by a set of elliptical integrals, is given in dimensionless form The case of liquid film hanging from and flowing along a wire of circular cross-section is discussed in detail. For selected values of wire diameter and contact angle a set of profiles was obtained numerically. The liquid hold-up as well as the corresponding interfacial area of gas-liquid contact were obtained. Further, the method enables us to calculate the gas-liquid interfacial area from the liquid hold-up. In the case of a laminar flow, it is possible to carry out a complete analysis of the problem, including no empirical parameter, on solving the Navier-Stokes equation.
TL;DR: In this article, a statistical technique based on a Monte Carlo calculation is applied to modeling the catalytic hydrogenolysis of thiophene on cobalt molybdate, and the model tested by application to the experimental results of Lipsch and Schuit on this system.
Abstract: A statistical technique based on a Monte Carlo calculation is applied to modeling the catalytic hydrogenolysis of thiophene on cobalt molybdate. The computational method is described, and the model tested by application to the experimental results of Lipsch and Schuit on this system. Surface activation, reversible and irreversible poisoning, competitive adsorption of reactants and products based on a Langmuir isotherm, and crystallite size and defect structure are considered. It is also shown that some gross distinction between mechanistic proposals may be possible if the proper experimental information on poisoning behavior is available.
TL;DR: In this paper, a multi-component distillation column design problem is solved by the combined use of estimation and quasilinearization, where the only variable within the designer's control is the reflux ratio, and the design problem can be stated as follows: obtain a specified purity of certain products from a given feed mixture by the use of an existing column.
Abstract: A multicomponent distillation column design problem is solved by the combined use of estimation and quasilinearization. The design problem can be stated as follows: obtain a specified purity of certain products from a given feed mixture by the use of an existing column. The only variable within the designer's control is the reflux ratio. Several different formulations are solved by the quasilinearization approach. It is shown that the concept of treating multi-component distillation as nonlinear boundary value problems forms a powerful and versatile computational tool. Furthermore, this approach can be extended easily to problems with over-specified conditions with the help of some minimization criterion. The technique is also ideally suited for the dynamic control of a distillation column where a constant purity of certain products over time is desired.
TL;DR: The theory of magnetothermal convection of gases in homogeneous magnetic fields is developed from magnetogas-dynamic theory in this article, where the authors show that the magnetothermal contribution to the total heat transfer is proportional to p 3 H 2(ΔT)2 /ηT 5 where p is the gas pressure, H is the magnetic field strength, ΔT is the temperature difference between plates, η is the viscosity coefficient and T is the absolute temperature.
Abstract: The theory of magnetothermal convection of gases in homogeneous magnetic fields is developed from magnetogas-dynamic theory. Application is made to nonionized paramagnetic and diamagnetic gases between parallel vertical plates. An additive contribution to the natural thermal convection heat transfer results from the temperature dependence of the magnetic permeability of the gas. The result may be expressed parametrically in a dimensionless magnctoconvection number, which characterizes the magnetothermal contribution to the total heat transfer just as the Grashof number characterizes the natural thermal contribution. For oxygen gas at low pressure the magnetothermal contribution is shown to be proportional to p 3 H 2(ΔT)2 /ηT 5 where p is the gas pressure, H is the magnetic field strength, ΔT is the temperature difference between plates, η is the viscosity coefficient and T is the absolute temperature.
TL;DR: In this paper, an experimental study was carried out to check the condensate quality when an azeotropic vapor of ethanol-water was passed over a cooled porous boiling tube.
Abstract: An experimental study was carried out to check the condensate quality when an azeotropic vapor of ethanol-water was passed over a cooled porous boiling tube. The ethanol composition was different from the azeotropic composition at some places on the tube. Overall, there was a net depletion of ethanol in the condensate. When the same azeotropic mixture was pool-boiled on a porous boiling surface, there was a net enrichment of ethanol in the vapor phase. A heteroazeotrope. butanol-water, on condensation, did not show any difference in composition between the vapor and liquid phases. An explanation based on surface capillarity is given for these effects.