A new aproach to characterize suspensions in stirred vessels based on computational fluid dynamics

Abstract

-Fluid dynamics simulations were applied for evaluating the suspension of particles in stirred vessels. The spatial distribution of particles throughout the vessel was characterized by a single parameter, here called the suspension quality (σ). Based on simulation results, a semi-empirical correlation was developed that correlated the suspension quality with the vessel geometry and solid and fluid properties, including a large variety of conditions, such as vessel and impeller diameters, impeller clearances, rotational speeds, particle densities and sizes. Comparison of the model with experimental data from the literature (Bohnet and Niesmak, 1980) suggests that the model can be extended to systems with different impeller geometries by adjustment of one single empirical parameter. The model can be used in the design of stirred vessels for the identification of the rotation speeds necessary to promote a specified suspension quality.

The interplay of suspended sediment concentration, particle size and fluid velocity on the rapid deposition of suspended iron oxide particles in PVC drinking water pipes

“…Therefore, initial SSC in the pipes was estimated on the basis of a stable particle suspension in the CSIOP established after the stabilization period of 5 minutes during the short injection periods, given the constant mixing intensity and small variation in the water level in the tank. It is also reasonable to assume that the grab sample had an equivalent SSC to the CSIOP fraction injected in the pipe since the sample was collected from an equivalent location in the mixing tank, which is expected to have a flow symmetry around the vertical rotation axis, which produces similar particle suspension in both water intake regions ( Cekinski et al., 2010 ). The average of the SSC difference between CSIOP samples collected before and after the injection was 3% which suggests that no changes occurred during the injection period.…”

Particle Responses to Flow Field Oscillations in Heterogeneous Polymerizations Performed in Tank Reactors

“…Available studies concentrate the analyses on numerical aspects of CFD (Computational Fluid Dynamics) simulations, on characterization of operational failures and on the formation of turbulent and velocity fields in other processes. [6][7][8][9][10][11][12] Although several studies have explored the use of CFD tools to investigate the particular characteristics of polymerization reactions performed in different conditions and reaction systems, [13][14][15][16][17][18][19][20][21][22] the published studies are focused upon the details of heat and mass transfer of a particular process or proposed geometrical configuration and on the computation of particle size distributions for uniform temperature and concentration flow fields. Based on these studies, it is difficult to understand whether temperature and concentration gradients inside the vessel would be important to explain the obtained results and to devise a general simulation scenario for the commonest simulation and reactor design problems faced by the analyst in the polymerization field.…”

“…However, very little has been reported in the literature about the formation of spatial temperature and concentration gradients inside heterogeneous polymerization reactors at real operation conditions. Available studies concentrate the analyses on numerical aspects of CFD (Computational Fluid Dynamics) simulations, on characterization of operational failures and on the formation of turbulent and velocity fields in other processes …”