Optics: measuring and testing – For size of particles
Patent
1994-10-24
1996-10-01
Rosenberger, Richard A.
Optics: measuring and testing
For size of particles
73 6171, 356 36, G01N 1502
Patent
active
055615201
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to apparatus and a method for measuring one or more properties, especially related to floc strength, of a slurry.
2. Discussion of Prior Art
The lack of appropriate on-line and in-situ instrumentation for monitoring the size distribution of particulate matter in concentrated particulate (e.g. mineral) slurries has been a long standing and limiting constraint in the modelling and control of processing plants. Numerous on-line sizing instruments are available from commercial suppliers but, with few exceptions, these require sampling and/or dilution of the slurry prior to analysis. Such instruments utilise a variety of individual or hybrid sensing principles including ultrasonics, laser-diffraction, x-ray absorption and electrical properties. Alternative approaches have been suggested, such as centrifugal differentiation of particles according to their size in a spiral tube and detection of the resulting solids concentration variation across the tube using penetrating radiation. However, in all of these known categories of instrumentation the particulates are analysed in an environment that bears little resemblance to that encountered within the process stream or vessel to be used in a practical working system. Indeed, the solids concentration and the shear conditions often differ by several orders of magnitude, Consequently, the interpretation of results derived from such measuring devices has to be undertaken with some care, especially if the particulates are fine (<50 .mu.m) and prone to aggregation.
SUMMARY OF THE INVENTION
According to the present invention in a first aspect there is provided an apparatus for measuring properties of a slurry which comprises a slurry transporting section, means for measuring at a first inspection site the particle size distribution of a slurry entering the transporting section, means for measuring at a second inspection site the particle size distribution of slurry leaving the transporting section and means for calculating from the particle size distribution measured at the first and second inspection sites a parameter related to the floc strength of the slurry which has passed between the first and second inspection sites.
According to the present invention in a second aspect there is provided a method of measuring one or more properties of a slurry using the apparatus of the first aspect which comprises introducing a slurry to be investigated to the said first inspection site, measuring the particle size distribution at the first inspection site, passing the slurry through the transporting section, measuring the particle size distribution at the second inspection site and calculating from signals representing the said particle size distributions a parameter related to the floc strength of the slurry.
The transporting section may comprise a pipe which may optionally include a flow constriction. Desirably, the transporting section is a removable section fitted between a slurry inlet means, e.g. an inlet reservoir, and an outlet means, e.g. an outlet reservoir. Desirably, different transporting sections, e.g. having different internal diameters and lengths and containing different flow constrictions (such as diameter reducing orifices or in-line mixer elements) may be fitted between the same positions between the inlet means and outlet means.
The said parameter which is calculated may be calculated using one of two methods.
In the first method one or more of the regression coefficients which for a given set of flow conditions define the solution to the floc mass size equation, Equation 1 given below are obtained. The regression coefficients K, .alpha., .mu..sub.J and .sigma..sub.J, which are explained further below, can be calculated by fitting experimental particle size distribution data to an analytical solution of Equation 1. Thus, the regression coefficients describe the floc breakage under the shear conditions within the transporting section.
In the second method, a breakage rat
REFERENCES:
patent: 5135662 (1992-08-01), Ho
British Nuclear Fuels PLC
Rosenberger Richard A.
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