Chi Tien

Sedimentation and liquid fluidization of solid particles of different sizes and densities

Abstract The sedimentation and fluidization of particles of mixed sizes and different densities were studied. A new concept—the apparent porosity of suspensions—was introduced, on the basis of which equations have been developed that are capable of predicting the settling velocities of individual types of particles in a suspension containing mixtures of particles. The validity of these equations was tested against experimental data in both sedimentation and fluidization.

Cake formation and growth in cake filtration

Abstract Equations describing the formation and growth of cakes in cake filtration taking into account of cake compression and the moving-boundary nature of the growth process are derived and methods for their solutions developed. The numerical solutions provide detailed information about cake growth including the cake thickness and its structure as functions of time. Comparisons between the present analysis and conventional cake filtration theories are presented.

Calculation of single fiber efficiencies for interception and impaction with superposed brownian motion

Abstract The single fiber efficiency of fibrous filters was studied by using a Brownian dynamics simulation technique. This simulation technique permits a rigorous and simultaneous consideration of all the important mechanisms of particle capture including interception, inertial impaction and Brownian motion. Simulation results obtained for a variety of situations indicate that diffusion tends to act synergistically with particle inertia leading to an increase in the collection efficiency as compared to when the mechanisms are considered individually. In particular, significant increases in collection efficiency are found in the critical range of the minimum single fiber efficiency.

Hydrosol deposition in granular media under unfavorable surface conditions

Abstract Hydrosol deposition in granular media under unfavorable surface conditions was studied. The theoretical part of the study examined the interaction of a particle with patch-like charged regions on the surface of a sphere. Expressions were derived for the double layer interaction between particle and patched surface and for the extent of particle deposition onto such a surface. Deposition experiments were performed under a range of conditions and their results compared with predictions based on the above model. A procedure to quantify the blocking effect of deposited particles on further deposition was also developed and the results compared with experimental data on transient deposition behavior.

Hydrosol deposition in granular beds

Abstract Hydrosol deposition in granular beds was studied analytically using trajectory calculations incorporating a surface adhesion model, and the assumption that the surface potentials of hydrosols and filter grains were not uniform. Results of the analysis were compared with available experimental data.

Kinetics of Metal Ion Adsorption from Aqueous Solutions

Preface. 1. Introduction. 2. Adsorption of Ionic Solutes at Solid-Solution Interfaces. 3. Adsorption of Metal Ions from Aqueous Solutions: Model Development. 4. Adsorption of Metal Ions from Aqueous Solutions: Algorithm Development. 5. Adsorption of Metal Ions from Aqueous Solutions: Model Application. 6. Summary and Future Development. Computer Programs. Index.

Approximations of uptake rate of spherical adsorbent pellets and their application to batch adsorption calculations

Abstract Two approximate expressions of sorbate uptake rate of spherical adsorbent pellets (referred to as model I and model II) were derived and applied to batch adsorption calculations. The derivations were made by assuming that the significant part of the concentration profile within a pellet may be represented by a parabolic expression over a spatial domain which expands with time. Both models I and II have expressions similar to that of the linear driving force (LDF) model but give much better accuracy, especially for small time. In particular, the results obtained from using model I were found to be nearly the same as those of the exact solutions.

Adsorption of gas mixtures on adsorbents with heterogeneous surfaces

Abstract A method is presented for estimating the adsorption equilibrium of gas mixtures. This method is based on the hypothesis of energetic heterogeneity of adsorbents and assumes that the ideal adsorbed solution (IAS) theory is valid for describing gas mixture adsorption locally. An empirical procedure based on adsorption data of binary gas mixtures is developed for matching the energetic states of a given adsorbate with those of the other adsorbates. Predictions derived from this method were found to agree closely with the experimental data on systems which are known to be highly nonideal and cannot be dealt with adequately with existing theories.

Deposition of Brownian particles in packed beds

Abstract An analysis is presented to describe the deposition of Brownian particles from suspensions flowing through granular media. The constricted tube porous media model recently proposed by Payatakes et al .[8] was used to characterize the media and the deposition process was assumed to be controlled by convective diffusion as well as the nature of the surface interaction between the media grains and the Brownian particles. Three different tube configurations were considered and the differences among the results were found to be relatively unimportant. Agreement between the analysis and available experimental data was found to be reasonably good for the limiting case when the surface effect is favorable.

Simultaneous development of velocity and concentration profiles in reverse osmosis systems

Abstract A mathematical analysis for the simultaneous development of the velocity and concentration profiles in a reverse osmosis system consisting of two parallel flat membranes is presented. This analysis, based on boundary layer theory, takes into account the nonlinear effects created by the fact that the water flux produced varies in the longitudinal direction. The initial velocity and concentration profiles are assumed to be uniform and the analysis is resctricted to two dimensional, steady state laminar flows with constant physical properties. The momentum and diffusion equations, coupled through both the boundary conditions and the convective terms in the differential equations, are solved simultaneously using the approximate integral method. The analysis is applicable to both the entrance region and the fully developed region at large distances from the conduit inlet. Data are presented on the concentration build-up at the wall for a wide range of parameters and typical results for the water flux produced and productive capacity are given. Since the concentration profile at any value of x + is given as a simple polynomial, the results can be used conveniently to study the relaxation or attenuation, of concentration polarization as a Graetz type problem. Reasonable agreement is observed between the results of the present work and the limited experimental results available in the literature. However, it is shown that some of the reported experimental data were probably significantly influenced by natural convection. It is shown that the extent of concentration polarization may be significantly different depending on whether the velocity profile in the stream entering the membrane section is parabolic or flat. An explanation is offered for the somewhat surprising fact that the water flux is greater and the polarization is less in fully developed flow than when the velocity profile is flat at the system entrance . This effect will be most pronounced in the highly productive membranes which probably will be developed in the future.