摘要:

AbstractExisting methods for synthesizing thermally‐integrated distillation sequences fail frequently when applied to nonideal and azeotropic systems, because increasing the column pressures often introduces new azeotropes and distillation boundaries into the mixture, which make some separation tasks infeasible. A new thermal integration procedure is presented that combines a bifurcation and residue‐curve map analysis with the methods of Andrecovich and Westerberg. The procedure is demonstrated with two commercially important separations: ethanol‐water‐ethylene glycol and methanol‐acetone‐water. Energy savings of 65% and 40%, respectively, over the optimized nonintegrated sequences a

ISSN:0001-1541    

DOI:10.1002/aic.690360702

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractFor systems described by algebraic or differential equation models where all variables are subject to error, the error‐in‐variables method (EVM) for parameter estimation has been shown to be superior to standard least‐squares techniques. Previous EVM algorithms were developed assuming linear (or linearized) model equations. Unfortunately, many chemical engineering processes operate in strongly nonlinear regions where linear approximations may be inaccurate. In this paper, new algorithms using nonlinear programming techniques for the error‐in‐variables methods are proposed. In addition, a method for discerning when these methods are necessary is discussed. The proposed algorithms are compared to the least‐squares method and traditional error‐in‐variable approaches. Improved parameter estimates for several steady‐state nonlinear processes

ISSN:0001-1541    

DOI:10.1002/aic.690360703

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractInterpenetrating polymer networks (IPNs) of poly(ethylene oxide) (PEO) and a polyether substituted polysiloxane were synthesized containing variations of PEO content (35 and 65% dry network weight) and PEO systematically varied from low to high molecular weight (2,000, 8,000, and 20,000). Biocompatibility was assessed by measureing111In platelet deposition in a baboon femoralex vivoshunt. Mass transfer analysis revealed that platelet transport to PEO/polysiloxane surfaces was kinetically limited and correlated with both PEO content and molecular weight. Differences in material performance were noted particularly after the initial 30 min blood contact period. In mid and high PEO molecular weight networks (8,000 and 20,000), reduced platelet deposition was noted with increased PEO content. In materials of high PEO content (65%), mid and high PEO molecular weight samples had significantly lower levels of platelet adsorption than PDMS (60 min;p<0.05) or networks of low PEO molecular weight, coded 2K‐65 (30 and 60 min;p<0.05). The lowest level of platelet deposition was noted on 20K‐65 networks, less than one platelet per 1,000

ISSN:0001-1541    

DOI:10.1002/aic.690360704

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractA new fludized bed which is divided in a looplike shape by a partition wall has been developed for recovering trace elements from a large quantity of industrial water. The bed, a circulating fluidized bed applicable to a liquid‐solid two‐phase flow, is called a circulating fluidized bed absorber (CFBA). Adsorbent particles are mixed and carried along with water in the CFBA. At the upper part of the bed, the absorbent particles are separated from the water flow and recycled in the bed; the depleted water flows out of a water outlet. The CFBA is operated at two to three times higher velocity than conventional liquid‐solid contacting systems. The pressure drop in the CFBA is in proportion to the amount of adsorbent suspended in the contacting section. Characteristics of the CFBA, including design considerations, are desc

ISSN:0001-1541    

DOI:10.1002/aic.690360705

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractSolvent diffusion from spheres at constant mass‐transfer Fourier number,FoM, in a single continuous‐flow stirred tank (CFST) and in a series of CFSTs is simulated. A transfer efficiency is defined and transfer efficiency curves are constructed as a function ofFoMand the residence time distribution of the spheres in the system. The fraction of solvent removed from the spheres in a series of CFSTs can be approximated using the transfer efficiency curves and knowledge of the operating conditions in each tank. The usefulness of the curves to predict solvent removal from polymer spheres under pilot‐plant conditions is exa

ISSN:0001-1541    

DOI:10.1002/aic.690360706

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractUtilizing a modified form of the Flory‐Huggins theory of polymer solution thermodynamics, a generalized expression has been obtained for correlating protein partitioning in the polyethylene glycol (PEG)/dextran aqueous two‐phase systems. The expression relates the natural logarithm of the partition coefficient of the protein to the polymer concentration difference between the phases. The parameters of the relationship are a function of protein and phase forming polymer molecular weight, protein‐water, protein‐polymer and polymer‐water interaction parameters, and the electrostatic potential difference between the phases. The relationship was verified by partitioning 17 proteins covering a wide range of molecular weight in the tie lines of the above systems, along with data from the literature. This correlation will facilitate the selection and engineering scale‐up of aqueous two‐phase systems for biomolecule

ISSN:0001-1541    

DOI:10.1002/aic.690360707

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractA compensator that approximates the inverse of dead time at low frequencies in a modified Smith predictor (MSP) control system is proposed, and the design of an MSP control system for it is given. The performance of the MSP with compensator, using a first‐order element as a low‐pass filter, is described. Analysis and simulation results show that the compensator improves performance in the disturbance rejection of the original Smith predic

ISSN:0001-1541    

DOI:10.1002/aic.690360708

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThe method of self‐propagating high‐temperature synthesis (SHS) can be utilized to synthesize certain advanced ceramic materials, such as metal carbides, borides and silicides, directly from the elements in powder form. The method involves mixing the powders, preparing pellets from the mixture, and igniting one end of the pellet. Owing to high exothermicity of the reactions, a combustion wave can propagate through the pellet. The influence of processing conditions on propagation of the combustion wave is investigated extensively in this modeling study for pellets of finite length. It is shown that unlike infinitely long systems, the combustion wave for a finite pellet does not propagate in constant pattern. It is also shown that radiative heat losses play a major role in SHS, while convective heat losses are not relatively import

ISSN:0001-1541    

DOI:10.1002/aic.690360709

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThe paper reports on experimental and analytic studies on translational motions of liquid drops in an immiscible, dielectric liquid confined by a pair of tilted parallel‐plate electrodes, across which a steady electric field is being applied. With an increase of the strength of the field, drops begin to bounce back and forth between the electrodes while falling down along the axis of tilt of the electrodes. The bouncing motions are found to be predictable with a reasonable accuracy by using a simple model constructed within the framework of conventional fluid mechanics and electrostatic

ISSN:0001-1541    

DOI:10.1002/aic.690360710

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThe development phase of the optical photolithography process has long been considered the most crucial, as it is the final image‐forming step. Process monitoring methods have focused primarily on end point detection and have not used other inferable on‐line information. This paper examines the use of mathematical models in conjunction with on‐line development penetration data to determine process changes. An on‐line sequential parameter identification scheme is used to calculate a current rate parameter value for the development model, and a Kalman filter is used to reduce erroneous observations caused by measurement noise. A powerful development monitor system results from the combination of real‐time data, and on‐line parameter and state estima

ISSN:0001-1541    

DOI:10.1002/aic.690360711

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY