摘要:

AbstractA hydrodynamic model of fluidization was developed that computes void fractions, pressure and solid and gas velocities in cylindrical fluidized beds. Cmputed time‐averaged gas velocity distributions of a jet compared well with Westinghouse experimental data without the use of any fitted parameters. The main empirical input was a drag correlation from the literatur

ISSN:0001-1541    

DOI:10.1002/aic.690300402

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractThe transient combustion of porous char particles is modelled. The model takes into account the reactions of carbon with CO2and O2and the oxidation of CO in the gas phase. It reveals strong effects of the intraparticle thermal gradients and of the pore structure evolution scheme on the burning time and predicts an optimum particle size that gives minimum burning time.

ISSN:0001-1541    

DOI:10.1002/aic.690300403

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractThe diffusion and reaction model developed in a previous paper is extended allowing for shrinkage of the char particles. It is shown that possible shrinkage, arising from disintegration of the solid structure at a certain conversion level, modifies severely the extinction behavior of the reacting particles. Specifically, the region of ambient temperature and particle radius in which the predictions of the nonisothermal and of the isothermal versions of the model differ significantly becomes smaller. However, the particle shrinkage does not affect the ignition phenomena observed since a particle usually ignites at low conversion levels where the radius change is still negligible.

ISSN:0001-1541    

DOI:10.1002/aic.690300404

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractA mechanism is proposed for the dehydration‐rehydration process in solid inorganic salts, and model rate equations are derived and applied to the observed behavior of potassium carbonate. Quantitative expressions for the effect of pressure on the reaction rates are derived using basic principles from nucleation and heterogeneous phase transformation theory. Model equation predictions agree with experimental dehydration and rehydration rate data at all but extreme pressures. The basic rate equation is also used to interpret the data of Eckhardt and Flanagan (1964) for the effect of pressure on the dehydration of manganous formate dihydrate. The mechanism on which the model equations are based is also consistent with the observed effects of cycling and of high temperature pretreatment on the K2CO3rehydration rat

ISSN:0001-1541    

DOI:10.1002/aic.690300405

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractA capillary rise technique was developed for measuring the effect of the surface viscosities upon the displacement of air by liquids in glass capillaries. Measurements were made in two tubes with optically measured radii of 37.5 and 48.6 μm.No surface viscous effects were observed with doubly distilled water or with octane, in good agreement with the Washburn equation. The behavior of a dilute aqueous solution of dodecyl sodium sulfate was easily distinguished from that corresponding to zero surface viscosities. The surface dilatational viscosity was found to be two orders of magnitude greater than the surface shear viscosity. Previous qualitative (Slattery, 1974, 1979) and quantitative (Giordano and Slattery, 1983) theories for the effect of the interfacial viscosities upon displacement are fully supported by this experimental study

ISSN:0001-1541    

DOI:10.1002/aic.690300406

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractHuman blood is sheared in cone‐and‐plate and parallel‐plate rotational viscometers, the latter with variable plate spacingsh. Plasma is analyzed for hemoglobin and LDH content before and after shearing to determine the extent of shear‐induced blood damage within the low‐stress regime (stress ⩽ 13 Pa). Geometrical variations in the test apparatus can be accommodated by correlating blood damage with the radially‐averaged shear rate. Data on expired blood are shown to imply that much of the damage arises in the bulk fluid, with a smaller contribution from surface effects. Models are proposed to explain these results, obtained over a shear rate range to 5,000 s−1; parallel‐plate platen separation is 0.25

ISSN:0001-1541    

DOI:10.1002/aic.690300407

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractWe have successfully used cross‐linked, partially‐hydrolyzed, polyacrylamide gels to concentrate solutions of high molecular weight solutes. The gels are sizeselective, concentrating solutes whose diameter exceeds 3 nm. They can be easily regenerated by means of pH‐induced changes in gel swelling; this regeneration is consistent with that inferred from existing theories of gel swelling. The resulting separation process is a good alternative to ultrafiltr

ISSN:0001-1541    

DOI:10.1002/aic.690300408

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractA simple particle model is used to interpret differential thermogravimetric data taken on the gasification of coal/char with CO2, H2and H2O. The model takes into account the major physical factors which influence the gasification rate,viz., the changing magnitudes of surface area, porosity, activation energy and effective diffusivity during gasification. Specific reaction rate constants based on surface area and activation energies are extracted from the data. Practical criteria for regimes of reaction rate and diffusion control and for particle isothermality are developed. For isothermal particles at low classical Thiele moduli, the data can be correlated with only one parameter, which has a simple physical interpretation.

ISSN:0001-1541    

DOI:10.1002/aic.690300409

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractThe adsorption and effective diffusivity of pyridine dissolved in heptane were measured in silica‐alumina pellets using a specially developed single‐pellet continous‐flow diffusion cell. The measured diffusivities varied between 0.43 × 10−9and 3.25 × 10−9m2·s−1; the temperature dependence of the diffusivities indicated that both pore volume diffusion and surface diffusion play a role in the

ISSN:0001-1541    

DOI:10.1002/aic.690300410

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractThe characteristics of a new heterogeneous reactor of the “two impinging streams” type, suitable for gas‐solid heat and mass‐transfer operations, were investigated.The operating limits of the reactor, with respect to gas and solid particles mass flow rate and pressure drop, were determined; scale‐up criteria with respect to the hydrodynamics of the reactor were also established. It has been found that, under certain conditions, the introduction of solid particles into the gas stream lowers the pressure drop on the reactor. In addition, the maximal pumping energy per kg of solids transported through the reactor by the air is much lower than in a fluidized‐bed‐type reactor.A stochastic model based on Markov processes was developed which closely describes the behavior of the solid particles in the reactor. A technique based on this model was employed for determining the residence time distribution of the particles i

ISSN:0001-1541    

DOI:10.1002/aic.690300411

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY