摘要:

AbstractA model for surface shear in the contact line region of a steady state two‐component evaporating thin film in the shape of a meniscus is developed. A constant vapor pressure boundary condition at the liquid‐vapor interface is combined with experimental meniscus profile data to obtain temperature and composition profiles. The results are used to delineate the relative effects of meniscus shape, temperature, and composition on fluid flow toward the higher temperature in an evaporating meniscus. For the system analyzed, it is found that surface shear due to composition gradients and temperature gradients is the single most important contribution to flow in the evaporating, two‐component capillary meniscus in the film thickness range 10−6m ≤ δ ≤ 10−5m. The effect of concentration on the vapor pressure leads to a maximum evaporation rate at a thickness of approximately 6 μm for the conditions studied. Theoretical results are discussed in the light of experiment

ISSN:0001-1541    

DOI:10.1002/aic.690330102

出版商:American Institute of Chemical Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractHighly concentrated coal‐water mixtures were prepared using two different types of dispersants, anionic and nonionic. Through experimental investigations of the effect of the electrolytes on their rheological properties, the mechanisms of the particle dispersion in both mixtures have been elucidate

ISSN:0001-1541    

DOI:10.1002/aic.690330103

出版商:American Institute of Chemical Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractNumerical calculations of the velocity and temperature fields were conducted for unsteady flows over a single circular cylinder and a bundle of cylinders. Periodic disturbances, natural or externally imposed, were considered. Periodic and averaged heat transfer rates were examined. Results compare favorably with experimental data. Calculations were carried out to predict heat transfer rates in regimes of unsteady flows that have not been tested experimentally.

ISSN:0001-1541    

DOI:10.1002/aic.690330104

出版商:American Institute of Chemical Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractA two‐phase approach to the control and operation of complex chemical processes at their optimum operating conditions is presented. The first phase consists of on‐line parameter identification and state estimation of approximate nonlinear dynamic process models using on‐line and off‐line measurements. In the second phase, the optimum operating strategy is determined by integrating and optimizing this identified process model over a selected time horizon into the future. The method is particularly suited to those processes that exhibit slow dynamic responses and are subject to disturbances that have a significant economic impact. Examples include batch chemical reactors, large distillation towers, and processes with significant holdup times such as large fluidized‐bed

ISSN:0001-1541    

DOI:10.1002/aic.690330105

出版商:American Institute of Chemical Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractIn chemical process control, the application of an optimal control strategy, dictated by the theory of the linear quadratic problem, does not always guarantee the best process performance. The main problem is that the unspecified weighting matrices in the quadratic performance index have a pronounced effect on the optimal control law derived from linear quadratic theory. In the past, values of the weighting matrices have been selected by experimenting with the process in much the same manner as a PID controller is tuned. The objective of the present study is to resolve the inverse problem of optimal regulator control, limiting the performance index in the quadratic form with two independent weighting matrices which are investigated. A new criterion has been developed such that the computation of determining those matrices can be carried out off‐line in advance, and then stored in a computer for real‐time

ISSN:0001-1541    

DOI:10.1002/aic.690330106

出版商:American Institute of Chemical Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractExperimental results for the batch extraction of amines using emulsion liquid membranes with an internal aqueous HCI solution are presented. Four amines and mixtures of one binary pair were studied. Reversibility of the acid‐amine reaction within the internal droplets affected extraction rates. The reversible reaction model presented earlier satisfactorily predicts these experimental result

ISSN:0001-1541    

DOI:10.1002/aic.690330107

出版商:American Institute of Chemical Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractSignificant errors can result in modeling dissolution processes if the polydispersity of the solid particles is ignored and the sample is treated as a collection of monodisperse spheres having the average size of the mixture. Population balance modeling provides an effective analytical means of predicting the effect of polydispersity on a wide variety of heterogeneous reaction systems including dissolution processes.

ISSN:0001-1541    

DOI:10.1002/aic.690330108

出版商:American Institute of Chemical Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractKinetics of the carbochlorination with phosgene of an alumina‐silica material are reported for a temperature range of 723 to 1,023 K and a phosgene partial pressure range of 4 to 90 kPa. The oxides react in a constant ratio over most of the conversion range and the grain model accurately predicts conversion as a function of tim

ISSN:0001-1541    

DOI:10.1002/aic.690330109

出版商:American Institute of Chemical Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractClassification of variables and measurements in multicomponent flow networks is treated in this paper. Classification rules are derived that exploit the relationship between cutsets of the process graph and certain graphs derived from it, and the solvability of the relevant equations. These rules are incorporated in two graph‐oriented algorithms for observability and redundancy classificatio

ISSN:0001-1541    

DOI:10.1002/aic.690330110

出版商:American Institute of Chemical Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractAn experimental evaluation of methods to analyze process resilience based on internal model control (IMC) has been performed. A pilot plant consisting of two coupled distillation columns was instrumented for control studies using an LSI 11/23 microcomputer. Two alternative sets of inputs were chosen and the two full 7 (all outputs) × 4 (all inputs) transfer matrix models of the pilot plant were identified. From these models, a large number of potential 3 × 3 control structures were first screened for different levels of achievable control performance using the newly developed tools for resilience analysis. Without the need for simulation and with minimal computational effort these new techniques allow prediction of the effect of nonminimum phase characteristics, input constraints, and model uncertainty on achievable closed‐loop performance. The resilience analysis results were found to be in agreement with qualitative physical intuition. To more fully investigate the usefulness and precision of the resilience analysis, three control structures for maintaining three product compositions from a distillation system were studied experimentally. The design and performance of IMC for this complex system is demonstrated and compared with single‐loop PID controllers combined with a dynamic deco

ISSN:0001-1541    

DOI:10.1002/aic.690330111

出版商:American Institute of Chemical Engineers    

年代:1987

数据来源: WILEY