The Chemical Engineering Journal最新文献

Multicomponent film model equations in the framework of generalized Maxwell-Stefan model were solved for non-ideal fluid mixtures for any given composition dependence of concentration, diffusivities and thermodynamic non-idealities. The solution is valid for planar, cylindrical and spherical film geometries. This proposed solution was used to evaluate the available approximate solutions and to examine the conditions under which they perform well. On the basis of calculations for the system acetone-benzene-carbon tetrachloride, it was observed that approximate methods generally give rise to greater errors in calculating small fluxes, i.e. when components transfer under small values of driving force. A parameter α was defined for each component to assess the influence of varying physical properties on the error associated with approximate methods. When α⩽ 15% the error is about 6% and, when α$\text{̆}$ 25%, the corresponding errors are greater than 18%. Whenever the approximate methods may be used for calculation, their performances are similar, but the method based on effective diffusivities has the advantage of being simple.

Kinematic viscosities have been measured for 1,2-ethanediol, 2-methoxyethanol and nine binary mixtures thereof over the entire composition range and at 19 temperatures ranging from −10 to 80°C. Several empirical relations (e.g. McAllister, Heric, Lobe, Grunberg-Nissan and polynomial equations) have been used in order to fit the experimental data and to correlate the binary mixture results with the kinematic viscosities of the pure components. All these approaches correlate the kinematic viscosity data well, while the adjustable parameters provide some useful information about the specific interactions between different molecules.

This paper deals with the experimental study of the axial dispersion phenomenon during flow through and by fixed beds packed with sheets of nickel foams. Its purpose is to characterize the hydrodynamic behaviour of a liquid flowing through different nickel foams according to configurations corresponding to the two working modes of volumic electrodes. A comparison of axial dispersion in liquid flow through various porous media determined by using the same procedure is presented. The axial dispersion is very low for flow through reticulated nickel foams, while tightly packed beds of very anisotropic flat plates show a very dispersive behaviour. For all other media a single correlation equation based on dimensionless numbers taking structural parameters into account is proposed.

The intermittent initial period of crossflow microfiltration has been studied, and the nature of foulinglayer deposits ascertained by simple physical inspection. At low crossflow velocity, a visible solid deposit was formed on the inside of the tubular membrane, but at high velocities no such layer could be detected. In this regime, fouling was controlled by the concentration polarisation phenomenon. The initial flux in these cases was restored by stopping the apparatus for a few seconds. Cyclical stop-start operation as a way of increasing permeate production is discussed.

A method is proposed for predicting vapor pressures, liquid densities and vaporization enthalpies of pure compounds in a wide temperature range between the triple point and the critical point. The method relies on the application of a previously proposed multicomponent equation of state which is based on well known properties of pure components and universal behavior of fluids. Simple rules are given for the calculation of all eight constants of the chosen equation of state which requires as input data the critical point and the normal boiling temperature only. The reliability of the new procedure is discussed on the basis of results obtained by predicting the properties of several well studied compounds belonging to the following classes: hydrocarbons, alcohols, acids and polar compounds not strongly associated. The method compares favorably with the Riedel equation for predicting the vapor pressures and with the Rackett equation for predicting the orthobaric densities. However, it only gives semi-quantitative results for the vaporization enthalpies of the C₅₊ compounds. The method appears less sensitive to the inaccuracies of the critical values than literature methods.

Methods for the prediction of bed height and pressure drop in tapered air-fluidized beds are proposed. A comparison was made with measurements in slugging fluidized beds in the slow bubble regime over a wide range of apex angle from 0° (rectangular) to 45°. The bed height and pressure drop are well predicted by each of the proposed methods using the same constant values of bubble rise velocity and fluctuation ratio as for the rectangular fluidized bed with the same distributor geometry.

The hydrogenation of soybean oil was studied using aqueous sodium formate solution and a palladium on carbon catalyst. All the hydrogenation reactions

Monosized spherical zirconia particles were synthesized by controlled hydrolysis of zirconium tetrabutoxide (Zr(OBu)₄) in 1-propanol. The zirconia

Solid motion in liquid fluidized beds has been analysed using a radioactive particle and two detection devices partly superimposed, dividing the be

Particle velocity was determined by two different estimations, using the net flux across a zone frontier and the residence time between two successive

Particle dispersion coefficients, determined from residence time distribution, were also strongly increasing with increasing liquid velocity. It was co