摘要:

AbstractAn expanded liquid molecular thermodynamic model is developed to predict the solubilities of pure solids in a liquid expanded with a gaseous antisolvent. Experimental data are presented for systems containing naphthalene, phenanthrene, and a mixture of both in toluene expanded with a gas antisolvent, CO2. The pressure range is 1 to 64 bar and the temperature is 25°C. The data are predicted accurately with regular solution theory up to moderate pressures, but not at the higher pressures where the liquid phase is nearly pure CO2. In contrast, the new expanded liquid equation of state model describes the wide range of behavior from the nearly ideal liquid solution at ambient pressure to the highly nonideal compressible fluid at elevated pressures. As a result, it predicts solubilities accurately over three orders of magnitude by using only binary interaction parameters. The implications of the phase behavior on fractional crystallization with a gas antisolvent are discussed

ISSN:0001-1541    

DOI:10.1002/aic.690371002

出版商:American Institute of Chemical Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractLongitudinal solids mixing was studied experimentally in circulating fluidized bed risers of internal diameter 0.152 m and 0.305 m. Superficial gas velocity and mean solids flux used were 2.8–5.0 m/s and 5.0–80 kg/m2·s, respectively, and the bed solids had a surface volume mean diameter of 71 μm and a particle density of 2,456 kg/m3. A sodium chloride tracer was used in impulse injection experiments. A simple, one‐dimensional dispersion model describes measured solids mixing satisfactorily. Peclet numbers (UoL/Dz) found, in the range 1.0–9.0, were correlated with the riser diameter and mean solids flux. The modeling approach described here permits residence time distribution curves to be calculated directly from the knowledge of superficial gas velocity, mean solids flux, and riser diameter. Longitudinal solids mixing in the riser decreased with increasing riser diameter. The results are consistent with recent hydrodynami

ISSN:0001-1541    

DOI:10.1002/aic.690371003

出版商:American Institute of Chemical Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractA direct numerical simulation (DNS) code has been modified to investigate chemically reacting flows in a stationary, homogeneous turbulence. Single and multispecies reactions as well as complicated reaction schemes such as parallel/consecutive reactions are studied. The effects of some parameters are discussed. The numerical data are used to test a simple first‐order closure model, proposed by Dutta and Tarbell (1989), for turbulent reacting flows. It is shown that the DNS technique provides us with an effective tool to isolate the effects of different parameters and is likely to be useful for proposing and testing closure model

ISSN:0001-1541    

DOI:10.1002/aic.690371004

出版商:American Institute of Chemical Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractA model for the photochlorination of methyl chloride in the liquid phase was developed, with numerical solution and experimental verification. The reaction was carried out under pressure, using carbon tetrachloride as a solvent with polychromatic radiation in a nonisothermal tubular reactor. Momentum, thermal energy, mass and photon balances were established rigorously and solved numerically. Reaction constants were taken from the known reaction mechanistic kinetics in the gas phase. Theoretical results agreed well with bench‐scale experiments performed inside an elliptical reflector in the prediction of both reactant conversion and product selectivities. The validated model was used to show the existence of significant temperature and concentration gradients inside the reactor, both in the radial and in the axial direction

ISSN:0001-1541    

DOI:10.1002/aic.690371005

出版商:American Institute of Chemical Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractThe simultaneous deposition of particles and material from the vapor phase gives rise to surface deposits having characteristic structure. A mathematical model of the particle‐vapor codeposition process is developed that predicts the structure and properties of these deposits as well as their growth rate over a wide range of conditions. A random sphere formulation is developed that provides the framework for a unified treatment of both subprocesses: ballistic particle deposition and porous media densification through vapor deposition. The model is applied to particleenhanced chemical vapor deposition (PECVD) processes for the production of ceramic materials. In PECVD, particles are introduced into a CVD process, either in the form of an aerosol created in situ by a controlled amount of gas‐to‐particle conversion or in the form of independently charged powder. The model identifies PECVD conditions that produce deposition rates substantially higher than those achievable by conventiona

ISSN:0001-1541    

DOI:10.1002/aic.690371006

出版商:American Institute of Chemical Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractExperimental data are obtained for bovine serum albumin transport through asymmetric polyethersulfone ultrafiltration membranes of differing molecular weight cutoff in a stirred ultrafiltration device. The actual membrane sieving coefficient is determined from filtrate concentration measurements using a stagnant film model to account for bulk mass transport effects. These sieving coefficients are then used to evaluate the relative contributions of diffusive and convective transport to the overall protein flux. The results are in good agreement with available hydrodynamic models for the hindrance factors for convective and diffusive transport of spherical solutes through well‐defined pores, with the effective solute to pore size ratio evaluated from a partitioning model that explicitly accounts for the ellipsoidal shape of the protein and the membrane pore size distribution. The implications of these results to the analysis of experimental data for membrane sieving and to the design of effective protein fractionation devices are also discusse

ISSN:0001-1541    

DOI:10.1002/aic.690371007

出版商:American Institute of Chemical Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractComputer simulations have been used to examine the approximations upon which the van der Waals‐Platteeuw theory of hydrate stability is based, and in particular, the extent to which the water lattice relaxes about the guest molecules. It is found that the behavior of the water lattice depends significantly on both the nature and number of guest molecules present—an effect that is neglected in the van der Waals‐Platteeuw theory. The simulations also indicate an important role for the repulsive guest‐host interactions in generating the mechanical stability of gas hydrates in the bulk. On the basis of these simulations, it is conjectured that surface interactions (particularly at a water/guest interface) are fundamental to the phase behavior of gas h

ISSN:0001-1541    

DOI:10.1002/aic.690371008

出版商:American Institute of Chemical Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractIt is well known that separation efficiency and solute rejection change when two or more proteins are ultrafiltered. This phenomenon is primarily due to membrane fouling and is not significantly influenced by concentration polarization. If membrane fouling is the dominant resistance, then negative transmembrane pressure pulsing might significantly reduce this barrier.A study was performed to determine the effect of negative transmembrane pressure pulsing on solute rejection for an albumin and gamma‐globulin mixture in ultrafiltration. Pulsing improved solute flux for all cross‐flow rates investigated including turbulent conditions by as much as two orders of magnitude. Under certain pulsing conditions, substantially higher solute flux was obtained for operations involving increased concentration polarization. This study reveals that negative transmembrane pressure pulsing can be effective in lowering the solute flux resistance that is observed in binary protein mixture ultrafiltrat

ISSN:0001-1541    

DOI:10.1002/aic.690371009

出版商:American Institute of Chemical Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractStudies of the motion of a dilute suspension of 100‐micron glass and stainless steel spheres in water flowing turbulently down a pipe revealed that they could be trapped in necklace formations that move slowly at a distance of less than one particle diameter from the wall. The tendency toward trapping increases with particle density and decreases with flow rate. The phenomenon is interpreted as occurring when the Saffman lift force toward the wall overcomes the ability of fluid turbulence to mix the particles. The location of the particles is dictated by a balance between the Saffman lift force and a wall‐induced force associated with the displacement of fluid as a particle moves parallel to the w

ISSN:0001-1541    

DOI:10.1002/aic.690371010

出版商:American Institute of Chemical Engineers    

年代:1991

数据来源: WILEY

摘要:

AbstractElectrophoresis is a useful analytic technique for the separation of proteins and other large molecules, but has proven resistant to scale‐up to production levels. In this article we describe a new technique that permits the use of much greater feed rates than possible in a conventional electrophoresis unit. The technique, in its simplest form similar to the cyclical field‐flow fractionation technique developed by Giddings (1986) and extended by Shmidt and Cheh (1990), relies on the application of an oscillatory electric field across the narrow gap of the electrophoretic cell. The motion of the solute species induced by this field interacts with an oscillatory cross‐flow to cause a separation based on the electrophoretic mobility of the species. This horizontal separation is combined further with a gradient in the strength of the oscillating electric field and oscillations in the vertical downflow to lead to different steady streamlines for species with different mobil

ISSN:0001-1541    

DOI:10.1002/aic.690371011

出版商:American Institute of Chemical Engineers    

年代:1991

数据来源: WILEY