摘要:

AbstractPlasma processing has emerged as an important technology for the deposition and etching of thin solid films in the manufacture of microelectronic devices. In fact, much of the progress achieved to date in device miniaturization would have been much more difficult without the unique characteristics of plasma processes. It is anticipated that future progress will continue to rely heavily on plasma technology. Although plasma chemical reactors are widely used, a lack of fundamental understanding has resulted in heavy reliance on empiricism in process design and control. The complexities inherent in any chemical reactor are compounded in plasma processing by the presence and active participation of the discharge in both gas phase and surface chemical processes. This has resulted in a technology that is sensitive to many design and operating parameters. A large parameter space gives process engineers flexibility in tailoring process conditions to meet objectives. However, without fundamental insight into the key physical and chemical processes, reactor design and control cannot be based on systematic, rational procedures. The purposes of this review are to introduce chemical engineers to plasma processing practice and phenomenology; to outline the progress made to date in fundamental studies of discharge physics and chemistry; to indicate areas in which chemical engineers must expand their traditional training to participate in plasma processing research; and finally to suggest how established chemical engineering methodology can be applied to plasma chemical reactors.

ISSN:0001-1541    

DOI:10.1002/aic.690350102

出版商:American Institute of Chemical Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractA simple one‐dimensional mathematical model validated with high‐temperature entrained‐flow reactor data successfully explained dispersed calcium hydroxide particle surface area evolution resulting from concomitant calcination and sintering. An integrated first‐order calcination rate expression and a second‐order sintering rate form accurately predicted time‐resolved surface area generation and degradation. The effects of water vapor and gaseous carbon dioxide concentration on asymptotic specific surface areas and sintering rates were noted. This methodology for predicting sorbent surface area evolution will enable more accurate sulfation modeling efforts in furnace sorbent injection (FSI) applications, where calcination, sintering, and sulfation can all occur on the same

ISSN:0001-1541    

DOI:10.1002/aic.690350103

出版商:American Institute of Chemical Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractExperimental data on sulfation rates of CaO particles derived from CaCO3are compared to those derived from Ca(OH)2using a product layer diffusion control model differing only in the shape of the CaO grain. Both the model and the experimental data indicate slightly higher reactivity for the Ca(OH)2‐derived oxide due to the observed difference in grain shape. This effect is considered as a contributor to the greater performance of Ca(OH)2in pilot‐scale SO2removal stud

ISSN:0001-1541    

DOI:10.1002/aic.690350104

出版商:American Institute of Chemical Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractMonte Carlo simulation is used to calculate partition coefficients for rigid, axisymmetric, nonspherical molecules in various pore geometries. Novel quantitative results are presented for a variety of molecule and pore shapes, including pores of nonuniform cross‐section such as the interstitial space within granular and fibrous materials.Quick estimation methods for obtaining partition coefficients are discussed, and the effects of molecule and pore wall curvature are described in detail. A boundary perturbation analysis is used to derive easy‐to‐use formulas for a variety of molecule shapes in circular

ISSN:0001-1541    

DOI:10.1002/aic.690350105

出版商:American Institute of Chemical Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractThe equilibrium and rate of uptake of the amino acids phenylalanine and tyrosine by Amberlite 252, a strongly acidic, cation‐exchange resin, have been investigated. Uptake of the amino acids by the hydrogen form of the resin occurs primarily by the stoichiometric exchange of hydrogen ions and amino acid cations. The amount of amino acid taken up by the resin can be calculated as a function of solution pH and amino acid concentration from a model that takes into account both solution and ion‐exchange equilibria. The rates of uptake of the two amino acids have been determined experimentally for a closed batch system. The results of experiments in which the resin particle size, the flow rate, and the concentration were varied show that intraparticle transport is dominated by the slow diffusion of amino acid cations through the macroreticular polymer structure of the resin, with some contribution from macropore transport of amino acid cations and zwitterions. An intraparticle diffusion model has been developed to describe these results and predict the performance of fixed‐bed opera

ISSN:0001-1541    

DOI:10.1002/aic.690350106

出版商:American Institute of Chemical Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractCertain nonfunctional macroreticular polymeric adsorbents are nonwet by suffciently dilute aqueous solutions and enable separations not achievable with adsorbents in the prewet state. Fixed‐bed adsorption data were obtained for a multisolute aqueous solution containing acetic acid, 1,3‐butanediol, and succinic acid, with Porapak Q and Amberlite XAD‐4 as adsorbents in both the prewet and nonwet states. The prewet breakthrough data agree with a model allowing for axial dispersion and a linear rate law, using independently estimated parameters. Break‐through curves for the nonwet case depend strongly upon solute volatility since mass transport within the particles appears to occur by Knudsen diffusion, and is rate limiting. Data for Porapak Q reflect an effective particle diffusivity about ten times lower than for Amberlit

ISSN:0001-1541    

DOI:10.1002/aic.690350107

出版商:American Institute of Chemical Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractThe concepts of coherence and composition paths, originally developed for multicomponent chromatography, are used to establish a simple theory of transport in systems with precipitation and dissolution in the course of multicomponent, single‐phase flow in permeable media. Composition route construction in phase diagrams in combination with distance‐time diagrams yields concentration profiles without recourse to trial‐and‐error procedurs. Detailed results are given for systems with three ionsA,B, andXand up to two precipitatesAXandBX. The extension to systems with additional, nonprecipitating species is described. The new approach confirms most conclusions of Bryant's earlier theory, removes assumptions stipulated in the latter, and is simpler to

ISSN:0001-1541    

DOI:10.1002/aic.690350108

出版商:American Institute of Chemical Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractIntrinsic rate equations were derived for the steam reforming of methane, accompanied by water‐gas shift on a Ni/MgAl2O4catalyst. A large number of detailed reaction mechanisms were considered. Thermodynamic analysis helped in reducing the number of possible mechanisms. Twenty one sets of three rate equations were retained and subjected to model discrimination and parameter estimation. The parameter estimates in the best model are statistically significant and thermodynamically consisten

ISSN:0001-1541    

DOI:10.1002/aic.690350109

出版商:American Institute of Chemical Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractGiven the intrinsic kinetics, the tortuosity factor of a Ni/MgAl2O4catalyst was determined under reaction conditions by minimizing the sum of squares of residuals of the experimental and the simulated conversions. The parallel cross‐linked pore model with uncorrelated pore size distribution and orientation was used in the calculation of the effective diffusivities. A modified collocation method was used to obtain the partial pressure profiles of the reacting components in the catalyst pellet. The simulation of the experimental reactor during the optimization of the tortuosity factor also yielded the effectiveness factors of the reactions. The results of the simulation of an industrial steam reformer are also discusse

ISSN:0001-1541    

DOI:10.1002/aic.690350110

出版商:American Institute of Chemical Engineers    

年代:1989

数据来源: WILEY

摘要:

AbstractParticle to gas heat transfer studies were carried out for the exothermic benzene hydrogenation and endothermic cyclohexane dehydrogenation reactions on the same catalyst bed. A recirculation type reactor and eggshell type commercial platinum on alumina catalyst were used. When the thermodynamic value for the heat of reaction is used for both reactions in the steady‐state energy balance, localJHfactors for the exothermic reaction were found to be, in general, higher than those for the endothermic reaction. This was attributed to product molecules leaving the catalyst surface with excess vibrational energy, which implies that the actual heat of reaction would be different than the thermodynamic value used in theJHfactor calculations. The study also indicated significant variations in the localJHfactors; these were attributed to variations in the linear velocity in the radial directio

ISSN:0001-1541    

DOI:10.1002/aic.690350111

出版商:American Institute of Chemical Engineers    

年代:1989

数据来源: WILEY