摘要:

AbstractProcess synthesis is the step in design where the chemical engineer selects the component parts and how to interconnect them to create his flowsheet. This paper reviews the rapidly growing process synthesis literature of over 190 articles, almost all of which have been produced in the last decade.The paper first introduces the nature of the synthesis problem and outlines the variety of approaches which have appeared to solve aspects of it. The problems include developing a representation, a means to evaluate alternatives, and a strategy to search the almost infinitely large space of possible alternatives. As the article demonstrates, effective solutions are very dependent on the nature of the synthesis problem being addressed.The article covers in detail the following five synthesis topics: chemical reaction paths, separation systems, heat exchanger networks, complete flowsheets, and control systems. Readily apparent are the development of industrially significant insights to aid in the design of heat exchanger networks. Reasonable progress exists in the synthesis of separation systems based on nearly ideal distillation technology and in the development of computer aids by chemists for reaction path synthesis leading to desired complex organic molecules. More work is needed for the remaining areas to become industrially significant.

ISSN:0001-1541    

DOI:10.1002/aic.690270302

出版商:American Institute of Chemical Engineers    

年代:1981

数据来源: WILEY

摘要:

AbstractThe external forces imparted by the bed material on tubes in a fluidized bed contribute to failure of the tubes and their support systems. The objective of this investigation was to provide data on tube forces to be used in structural design. Forces on tubes of various lengths were measured in fluidized beds operating at room temperature. The parameters varied in the experiments were superficial gas velocity and tube array height above the gas distributor. The force‐time histories consisted of a series of pulses, whose magnitudes were approximately linearly proportional to tube length. Spectral analyses of the time series indicated that the primary frequency composition of the load was below 25 H

ISSN:0001-1541    

DOI:10.1002/aic.690270303

出版商:American Institute of Chemical Engineers    

年代:1981

数据来源: WILEY

摘要:

AbstractLaser Doppler Anemometry (LDA) was used for the simultaneous measurement of the gas and particle velocities in a gas‐solid, two‐phase flow. The flow configuration consists of an air jet at ambient temperature in which a spherical glass powder of a mean particle diameter of 97.0 or 13.7 μm was injected from one side using a secondary air jet. Both principal and secondary jets were also seeded with talcum powder with a mean particle diameter of about 1 μm which served as a tracer.The probability density distribution function (PDF) of the LDA output showed two distinct peaks corresponding to the particle and gas velocities. As the particles were accelerated by the flow, the slip velocity between the gas and the particles decreased causing the gap between these two peaks to narrow. The measured mean particle velocity profiles were in agreement with the predictions of a theoretical model.The objectives of the present investigation was to obtain experimental data on the dependence of the particle trajectories and their mean velocities on the injection conditions in a free jet stream. The principal question, however, was whether such data could be obtained using Laser Doppler Anemometry (LDA). In other words, whether LDA could be effectively used in two‐phase flow systems for the simultaneous measurement of the gas and particle velocities? Obviously, the answer to this last question can affect far beyond this particular study and more than justified the effort for this detailed investigation. It should be pointed out that, while LDA has been known for sometime, and the necessary equipments for an LDA system are available on a commercial bases, relatively little attention has been given to its application to other than single‐phase, fluid‐flow m

ISSN:0001-1541    

DOI:10.1002/aic.690270304

出版商:American Institute of Chemical Engineers    

年代:1981

数据来源: WILEY

摘要:

AbstractThe hydrodynamic drag force in a uniform flow field acting on a spherical body with small particles attached to its surface was determined experimentally. The experimental data are used to substantiate the approximate force expressions derived from available theories for several types of collector‐particle geometries. Procedures for applying these results to the prediction of the pressure drop across a filter bed with various degrees of particle deposition are also develope

ISSN:0001-1541    

DOI:10.1002/aic.690270305

出版商:American Institute of Chemical Engineers    

年代:1981

数据来源: WILEY

摘要:

AbstractThis paper presents numerical solutions to the nonlinear, coupled boundary‐layer equations governing laminar condensation heat and mass transfer in the vicinity of the forward stagnation point of a spherical cold water droplet translating in a saturated mixture of three components. The environment surrounding the droplet is composed of a condensable (steam), a noncondensable and nonabsorbable (air), and a third component which is noncondensable but absorbable (Elemental Iodine, for example). The dispersed and the continuous phases have been treated simultaneously. Results obtained here show excellent agreement with experimental results where available. An important conclusion is that for laminar condensation on a freely falling droplet, for a given thermal driving force and noncondensable gas concentration in the bulk, the dimensionless heat transfer decreases with increasing saturation temperature of the outside mediu

ISSN:0001-1541    

DOI:10.1002/aic.690270306

出版商:American Institute of Chemical Engineers    

年代:1981

数据来源: WILEY

摘要:

AbstractMeasurements of local hold‐up and liquid recirculation rate in an air‐lift reactor were performed with two types of gas spargers using a manometric technique. A simple exponential function correlated properly the liquid velocity measured to the gas flow rate. The local hold‐up varied appreciably along the column and showed a maximum in most of the cases. A simple linear relationship correlated the local gas velocity with the total flow rate of the mi

ISSN:0001-1541    

DOI:10.1002/aic.690270307

出版商:American Institute of Chemical Engineers    

年代:1981

数据来源: WILEY

摘要:

AbstractAn on‐line statistical study of the pressure fluctuations in fluidized beds was conducted by using pressure transducers, a correlation and probability analyzer and a Fourier transform analyzer. The causes of the fluctuations were explored, and the effects of the gas velocity, bed height, particle size and distributor design on the major frequency and amplitude of the fluctuations were investigated. The results indicate that the motion of bubbles appears to be the major cause of the pressure fluctuations in the upper portion of a fluidized bed. In the lower portion, the combined effects of the formation of large bubbles in the middle portion of the bed, the formation of small bubbles near the distributor, and the jet flow immediately above the distributor appear to be the major causes of pressure fluctuation

ISSN:0001-1541    

DOI:10.1002/aic.690270308

出版商:American Institute of Chemical Engineers    

年代:1981

数据来源: WILEY

摘要:

AbstractSimultaneous biological and activated‐carbon treatment of organic wastewaters appears promising. The effects of bacterial film growth on adsorbent particles is investigated by laboratory work and mathematical modelling. Regeneration of the adsorbent due to film growth does occur, but faster than predicted. The discrepancy reflects uncertainty about the structure of bacterial film

ISSN:0001-1541    

DOI:10.1002/aic.690270309

出版商:American Institute of Chemical Engineers    

年代:1981

数据来源: WILEY

摘要:

AbstractAerosol formation in reacting gases is treated in terms of the gas‐phase reaction, homogeneous nucleation of the reaction product, and particle growth by parallel mechanisms. In the absence of foreign nuclei, nucleation of the gas‐phase reaction product is described by classical homogeneous theory with a nonequilibrium correction factor included; particle growth by diffusion, surface reaction, and cluster scavenging are examined. The predicted contribution of the latter mechanism increases with increasing supersaturation ratio due to a shift in the distribution of cluster sizes in accordance with a Boltzmann‐type steady‐state distribution. Illustrative results predict a nucleation burst during which the formation of nucleating monomer by chemical reaction competes with the loss of monomer due to diffusion to the surface of the freshly formed particles. In addition, conditions under which cluster scavenging can dominate are shown.The particle‐size spectra predicted using the theory are compared with experimentally measured size spectra of NH4Cl particles formed by the gas‐phase reaction of NH3and HCl. The size spectra were measured using an electrical aerosol size analyzer and an optical counter at the outlet of a continuous flow reactor after residence times ranging from 2 to 50 seconds. Reactant concentrations of 2.1 × 10−5to 4.1 × 10−4mol/m3(0.5 to 10 ppm) were studied at 23 to 26°C and near atmospheric pressure. The predicted size spectra showed good agreement with the experimental results. At reactant concentrations below 4.1 × 10−4mol/m3, the predominant particle growth was apparently by diffusion of the monomer in the noncontinuum range. Based on analysis of other data, cluster scavenging became more significant at reactant concentrations greater than about 8 × 10−4mol/m3, and coagulation was not significantly important. Furthermore, these studies implied a microscopic surface free energy for NH4Cl of

ISSN:0001-1541    

DOI:10.1002/aic.690270310

出版商:American Institute of Chemical Engineers    

年代:1981

数据来源: WILEY

摘要:

AbstractMolecular thermodynamics is used to develop a new model for the prediction of the thermodynamic properties of liquid metal mixtures. It combines corresponding states theory with a perturbed hard sphere model to predict successfully, without adjustable parameters, a variety of mixture properties from pure component properties for simple eutectic mixtures.

ISSN:0001-1541    

DOI:10.1002/aic.690270311

出版商:American Institute of Chemical Engineers    

年代:1981

数据来源: WILEY