ISSN:0001-1541    

DOI:10.1002/aic.690180303

出版商:American Institute of Chemical Engineers    

年代:1972

数据来源: WILEY

摘要:

AbstractModern control theory for systems with load changes is applied to distillation column control. Both linear and nonlinear distillation models are developed and tested. Excellent control is achieved by using an optimal multi‐variable‐proportional‐integral (MPI) controller for systems with unmeasurable disturbances. When the disturbances are measurable an optimal multi‐variable proportional controller with error coordination (MPE) is desirable. Various structures for distillation control have also been inves

ISSN:0001-1541    

DOI:10.1002/aic.690180304

出版商:American Institute of Chemical Engineers    

年代:1972

数据来源: WILEY

摘要:

AbstractThe rate at which water is extracted from thoria sols was investigated by fluidizing single thoria sol droplets in 2‐ethyl‐1‐hexanol (2EH) and measuring the diameter of a droplet over a period of time until shrinkage no longer occurred. Diameter data from both water and sol drops were obtained at 25°C. The experimental variables were initial drop diameter (0.1 to 0.2 cm), sol molarity\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm (0 to 2}{\rm .5 }\underline M {\rm ThO}_{\rm 2}) $\end{document}, and water concentration in the 2EH (2–12 mg./cc.). The water and sol droplet data were correlated by Equation (5). The single relationship for the fluidized water and sol drops verified that an organic‐phase film surrounding the drop is the rate‐controlling resistance. The sphere Reynolds number was based on the approach velocity and varied from 0.4 to 14. The Schmidt number for the system was fixed at 35,700. During the extraction of water, the mass transfer coefficients for fluidized sol drops were found to depend only on the molarity of the sol. By expressing the mass transfer coefficients as a function of the density difference between the aqueous sol and the organic phase, an equation was derived to predict the gelation time required for any initial sol molarity and drop diameter fluidized in

ISSN:0001-1541    

DOI:10.1002/aic.690180305

出版商:American Institute of Chemical Engineers    

年代:1972

数据来源: WILEY

摘要:

AbstractA fiber optic technique for obtaining multiple, simultaneous, point residence time distributions on operating, commercial scale distillation trays is described. The method has sufficient resolution to yield residence time profiles on the tray and to separate tray and downcomer effects. The results indicate severe flow nonuniformities on the tray, which are not accounted for in present models of distillation.

ISSN:0001-1541    

DOI:10.1002/aic.690180306

出版商:American Institute of Chemical Engineers    

年代:1972

数据来源: WILEY

摘要:

AbstractA fiber optic technique was used to obtain point residence time distributions at several points on an 8 ft. diam. sieve tray in hydrocarbon service. Residence time patterns were obtained over a wide range of vapor and liquid loadings with the isopropyl alcohol–water system and at both ends of the cyclohexane toluene system. The data reveal severe flow nonuniformities on the tray including nonuniform velocity distribution and retrograde flow near the column walls. The reasons for this behavior are discusse

ISSN:0001-1541    

DOI:10.1002/aic.690180307

出版商:American Institute of Chemical Engineers    

年代:1972

数据来源: WILEY

摘要:

AbstractInitial rates were measured for the reduction of single pellets of nickel oxide with carbon monoxide at atmospheric pressure and temperatures from 566 to 796°C. The nickel oxide pellets were porous (ϵ0= 0.032 − 0.35) and intrapellet diffusion retarded the rate so that the shrinking core model was not applicable. Effective diffusivities for the lower porosity pellets were very small, corresponding to tortuosity factors of about 180 forϵ0= 0.032 and 92 forϵ0= 0.062.The reaction appeared to be first order in carbon monoxide. Rate constants, based upon the intraparticle area, indicated an activation energy of 47 kcal/g.‐mole over the temperature range 566 to 682°C. At higher temperatures the rate was constant. These results, while not conclusive, are in agreement with a reaction sequence consisting of formation of nuclei of nickel atoms in the nickel oxide surface, rapid adsorption of carbon monoxide at the nickel‐nickel oxide interface, migration of the adsorbed carbon monoxide to the adjacent lattice, and a slow reaction to extract oxygen from t

ISSN:0001-1541    

DOI:10.1002/aic.690180308

出版商:American Institute of Chemical Engineers    

年代:1972

数据来源: WILEY

摘要:

AbstractA technique for direct measurement of the differential diffusion coefficients in a ternary system of water, sugar, and a dilute organic species is described. The individual sugars were d‐fructose, d‐glucose, and sucrose; and ethyl alcohol, ethyl acetate,n‐butyl acetate, andn‐hexanal individually constituted the dilute organic species. The four ternary diffusivities were obtained over a range of sugar concentrations by the use of horizontal diaphragm cells, a differential interferometer, a flame‐ionization gas‐liquid chromatograph and postulation of the validity of the Onsager reciprocal relations. The equilibrium partial pressures of the dilute organic species over these solutions have also been measured, using a vapor head space chromatographi

ISSN:0001-1541    

DOI:10.1002/aic.690180309

出版商:American Institute of Chemical Engineers    

年代:1972

数据来源: WILEY

摘要:

AbstractThe retention of trace volatile components in food liquids during low temperature drying processes is analyzed through a ternary diffusion model. Flux equations for both water and trace organic components are solved numerically for typical drying situations. Several effects are found with the ternary analysis which are not evident from a simpler binary model. The sugar‐water composition gradient which develops during drying causes an appreciable transport of the trace volatile species. This transport can occur in the same direction as the transport resulting from the concentration gradient of the volatile species, or in the opposite direction, and can result in a local accumulation of the volatile species. Concentration profiles for both water and dilute volatile components were experimentally measured during nearly isothermal drying of gelled slabs of synthetic sugar solutions and natural fruit juice concentrates. The predicted internal maximum in volatiles concentration is borne out by the experiment, and a satisfactory agreement of observed with predicted volatiles retention is found, within the limits of the experimen

ISSN:0001-1541    

DOI:10.1002/aic.690180310

出版商:American Institute of Chemical Engineers    

年代:1972

数据来源: WILEY

摘要:

AbstractThe problem of developed turbulent heat or mass transfer in a duct is considered for the limit of large σ (Prandtl or Schmidt number). The limiting results depend on the behavior of the eddy diffusivity near the solid surface. Since there is a question about whether this variation begins with ϵ ∝ y+3+ … or ϵ ∝ y+4+ … for y+near zero, both possibilities are considered. In each case the first three terms of the asymptotic expansion for σ → ∞ are obtained. The first term of the asymptotic expansion agrees with limiting results derived earlier, while the correction terms indicate the errors associated with earlier simplifying assumptions.By proper scalling, it is demonstrated that in the limit of σ → ∞ the results are independent of geometry and boundary conditions for situations involving parallel plates, circular tubes and concentric annuli with either constant surface heat flux or temperature. The correction terms to the σ → ∞ asymptote can be significant, although the effect of Reynolds number on the correction terms is very small.A comparison between a typical numerical integration and the asymptotic formula shows excellent agreement. The asymptotic formulae are used to correlate large Schmidt

ISSN:0001-1541    

DOI:10.1002/aic.690180311

出版商:American Institute of Chemical Engineers    

年代:1972

数据来源: WILEY

摘要:

AbstractA method is developed for decomposition of a recycle process so as to minimize the summation of weighting factors for variables torn. This procedure is based on application of dynamic programming to a state space representing combinations of cycles opened. The resulting algorithm is well suited to machine implementation and is more efficient for large problems than alternative procedures that also guarantee decomposition.

ISSN:0001-1541    

DOI:10.1002/aic.690180312

出版商:American Institute of Chemical Engineers    

年代:1972

数据来源: WILEY