Flocculation analysis and control system by laser diffractometry at industrial scale

Abstract

International audienceThe flocculant injection control system efficiency was evaluated on-site in an aggregate quarry, by means of laser diffraction and analysis of the size and texture of flocs. The configuration of the feed tank and the laser particle size measurement cell installed at the facility (280,000 t/year of aggregates) allowed characterization of flocs with particle size between 4.2 and 3473 μm under hydrodynamic conditions that were highly favorable for the examination of large and very fragile flocs. Two days of analysis of the floc formation process along the path followed by the slurry showed that flocculation was optimal during standard operation of the facility when the flow rate of waste fines and concentrations of solids were close to those used to calibrate the flocculant injection control system. Conversely, when the concentration of solids in the flocculator feed slurry dropped by 57.3%, the flocculant dosing fluctuated during stabilization of the mechanism, the kinetics of flocculation slowed, the mean size of flocs arriving at the settling tank dropped by 69%, and the mode of smaller flocs shifted from 77.8 to 10.4 μm in relation to normal operation. On-site analyses confirmed that the measurements made with laser diffraction (using a methodology developed in the laboratory) allow determination of the effects of conditioning on the characteristics of flocs in terms of particle size, porosity, density, and volume fraction in the slurry. Evolution of these characteristics according to the local parameters of conditioning (mean detention time, mean slurry velocity, and mean velocity gradient) provides a significant part of basic information necessary to a diagnosis of the operation of an industrial circuit of flocculation. © 2007 American Institute of Chemical Engineers AIChE J, 200

Stability and flocculation of nanosilica by conventional organic polymer

“…Coagulation and flocculation were done in the 1-liter reactor described above. The performance of this reactor is similar to those of industrial flocculation containers [27]. Moreover, this one-dimensional reactor is energy efficient.…”

Filtration characteristics of a mineral mud with regard to turbulent shearing

“…So as to be close to the data and observations made on certain industrial circuits, we used an experimental methodology adapted for characterizing the flocs and a conditioning system validated by on-site tests [8] to respond to the fixed objectives.…”

A Semi-Empirical Model to Estimate Maximum Floc Size in a Turbulent Flow

“…Based on the analysis of light scattering by the flocs in suspension, it is possible to determine the size distribution, the diameter of gyration and fractal dimension [ 2 , 4 , 9 , 14 ]. For the fractal aggregates (flocs) and in the range of validity of the Rayleigh-Gans-Debye approximation, it has been shown that the total scattered intensity I(q) presents power– law dependence in relation to the amplitude of the scattering wave vector q [ 15 , 16 , 17 ]: where R g is the radius of gyration of floc, r P is the primary particle radius and D f is the mass fractal dimension of floc.…”

“…Flocculation is a conventional physico-chemical technique used in many industries, particularly in the industrial ore and mineral processing industry, the food, paper and pharmaceutical industries, and, more prevalently, in water treatment (drinking water and wastewater) [ 1 , 2 , 3 , 4 ]. It is a process through which solid or microbial elementary particles dispersed in a fluid agglomerate in the form of “flocs” under the influence of a chemical reactant.…”