51 research outputs found
Method for Particle Size Control During the Drying and Granulation in Fluidized Bed
The fluidized bed process presented in this paper is suitable for recovery of solids from
solutions in the form of granules. The solution is sprayed into the bed and as solvent
evaporates, solid material is deposited on the surface of fluidizing particles. During this
process, particle growth takes place by surface layering and/or agglomeration. A special
grinder is used in the fluidized bed to control particle growth by causing selective
disintegration of large particles. For steady state operation, the most important task is to
determine the existing particle size distribution in the fluidized bed. A special method
was developed to measure torque and stress fluctuations* in the bed of particles. Using a
correlation between torque and stress fluctuations and particle size, this method and
device can be used for direct control of the rotation speed of the grinder to produce
granules of given size in the fluidized bed. Results of torque and stress measurements
and their correlation to particle size are presented
Particle Size Control by Torque Measurements in Fluidized Beds during Drying and Granulation from Solutions
The fluidized bed process presented in this paper is suitable to recover solids from solution in
form of granules. Solution is sprayed into the bed and, as the solvent evaporates, solid
material is deposited on the surface of fluidizing particles. During this process, particle
growth takes place by surface layering and/or agglomeration. A special grinder is used in the
fluidized bed to control particle growth by causing selective disintegration of large particles.
For steady state operation, the most important task is to determine the existing particle size
distribution in the fluidized bed. A special method was developed to measure torque and
stress fluctuations in the bed of particles. Using a correlation between torque and particle size,
this method and device can be used for direct control of the rotation speed of the grinder to
produce granules of given size in the fluidized bed. In this paper, the results of torque
measurements and their correlation with particle size are presented
Torque Measurements and DEM Simulations in a Couette-type Device with Application to Particle Size Measurements
A continuously operating modified Cuette-type shearing device has been developed for
in-situ measurements to estimate the average particle size during size enlargement
processes in fluidized bed granulator. It was proven by experiments that well-defined
correlation exists between the mean torque and the average particle size being in the
device. DEM simulations revealed interesting aspects of this method
Particle Size Control by Torque and Stress Measurement in Fluidized Bed Drying and Granulation from Solutions
The fluidized bed process presented in this paper is suitable for recovery of solids from
solutions in the form of granules. The solution is sprayed into the bed and as solvent
evaporates, solid material is deposited on the surface of fluidizing particles. During this
process, particle growth takes place by surface layering and/or agglomeration. A special
grinder is used in the fluidized bed to control particle growth by causing selective
disintegration of large particles. For steady state operation, the most important task is to
determine the existing particle size distribution in the fluidized bed. A special method was
developed to measure torque and stress fluctuations* in the bed of particles. Using a
correlation between torque and stress fluctuations and particle size, this method and device
can be used for direct control of the rotation speed of the grinder to produce granules of
given size in the fluidized bed. Results of torque and stress measurements and their
correlation to particle size are presented
Partitioning multi-dimensional sets in a small number of ``uniform'' parts
In this paper we prove that every finite subset of ZxZ
can be partitioned into a small number of subsets so that,
in each part all vertical sections have aproximately the same size and
all horyzontal sections have aproximately the same size. The generalization
of this statement is used to give a combinatorial interpretation to
every information inequality
Particle dynamics in sheared granular matter
The particle dynamics and shear forces of granular matter in a Couette
geometry are determined experimentally. The normalized tangential velocity
declines strongly with distance from the moving wall, independent of
the shear rate and of the shear dynamics. Local RMS velocity fluctuations
scale with the local velocity gradient to the power . These results agree with a locally Newtonian, continuum model, where the
granular medium is assumed to behave as a liquid with a local temperature
and density dependent viscosity
Self-similar shear-thickening behavior in CTAB/NaSal surfactant solutions
The effect of salt concentration Cs on the critical shear rate required for
the onset of shear thickening and apparent relaxation time of the
shear-thickened phase, has been investigated systematically for dilute
CTAB/NaSal solutions. Experimental data suggest a self-similar behavior of the
critical shear rate and relaxation time as functions of Cs. Specifically, the
former ~ Cs^(-6) whereas the latter ~ Cs^(6) such that an effective Weissenberg
number for the onset of the shear thickened phase is only weakly dependent on
Cs. A procedure has been developed to collapse the apparent shear viscosity
versus shear rate data obtained for various values of Cs into a single master
curve. The effect of Cs on the elastic modulus and mesh size of the
shear-induced gel phase for different surfactant concentrations is discussed.
Experiments performed using different flow cells (Couette and cone-and-plate)
show that the critical shear rate, relaxation time and the maximum viscosity
attained are geometry-independent. The elastic modulus of the gel phase
inferred indirectly by employing simplified hydrodynamic instability analysis
of a sheared gel-fluid interface is in qualitative agreement with that
predicted for an entangled phase of living polymers. A qualitative mechanism
that combines the effect of Cs on average micelle length and Debye parameter
with shear-induced configurational changes of rod-like micelles is proposed to
rationalize the self-similarity of SIS formation.Comment: 27 pages, 17 figure
The history of degenerate (bipartite) extremal graph problems
This paper is a survey on Extremal Graph Theory, primarily focusing on the
case when one of the excluded graphs is bipartite. On one hand we give an
introduction to this field and also describe many important results, methods,
problems, and constructions.Comment: 97 pages, 11 figures, many problems. This is the preliminary version
of our survey presented in Erdos 100. In this version 2 only a citation was
complete
Chip-Firing and Rotor-Routing on Directed Graphs
We give a rigorous and self-contained survey of the abelian sandpile model
and rotor-router model on finite directed graphs, highlighting the connections
between them. We present several intriguing open problems.Comment: 34 pages, 11 figures. v2 has additional references, v3 corrects
figure 9, v4 corrects several typo
Granular Flow in Silo Discharge: Discrete Element Method Simulations and Model Assessment
Discharge dynamics of granular particles from a flat-bottomed silo is studied using both continuum modeling and three-dimensional (3D) discrete element method (DEM) simulations. Using DEM, the influence of microscopic parameters (interparticle friction coefficient, particle–wall friction coefficient and particle coefficient of restitution) and system parameters (orifice width) on the discharge rate is quantified. The spatial extent of different regimes (quasi-static, intermediate and inertial) of granular rheology are quantified using a regime map previously established from DEM data of homogeneously sheared granular flow. It is shown that all three regimes of granular rheology coexist during silo discharge, and the intermediate regime plays a significant role in discharge dynamics. A quantitative comparison between results of continuum and DEM simulations is performed by computing discharge rates, solid velocities, and solid stresses for a three-dimensional (3D) flat-bottomed silo. It is found that the three constitutive models investigated in this study overpredict the discharge rate when compared to DEM data. Contour plots of the error in solid stress prediction are compared with the spatial extent of different regimes of granular rheology to deduce that it is inaccurate modeling of the intermediate regime that is responsible for overprediction of the discharge rate
- …