Continuous on-line measurement of fluid or slurry rheology

Measuring and testing – Liquid analysis or analysis of the suspension of solids in a... – Viscosity

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G01N 1102

Patent

active

053158636

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to the continuous measurement of the rheological properties, such as viscosity and yield stress, of fliuds or slurries, especially fluids or slurries which exist in rugged industrial environments such as are found in the mining and mineral processing industries. More particularly the invention relates to the rheology measurements of fluids or slurries having significant quantities of entrained air or gases present and/or coarse (usually up to about 10 mm diameter) solid particles, varying ambient temperature and/or varying fluid or slurry temperature and pressure.


BACKGROUND ART

On-line viscometers are known for determining the yield stress and plastic viscosity of non-Newtonian or Bingham type fluids, calculated from formulae for laminar flow. However, in general, such known on-line viscometers are not capable of handling the extremes or demands which exist in the mining and mineral processing environments. For example, rotational types often suffer from reliability problems especially when applied to slurries. They also have difficulty in handling coarse solid particles and high process pressures. The static force measurement type viscometers are not suited to coarse particle slurries and will give erroneous readings when entrained air is present. Similar comments apply to vibrating element type viscometers.
The general technique of measuring the pressure differential between two points in a laminar fluid flowing through a tube of known diameter at a known rate is well known. This is shown, for example, in U.S. Pat. Nos. 3468158, 4680957 and 4384792. A technique using a vertical tube to measure slurry viscosity is shown in Australian Patent Application No. 31949/77. U.S. Pat. No. 3520179 discloses a rheometer or viscometer for non-Newtonian fluids using a capillary U-tube type apparatus, however this apparatus does not use differential pressure measurements, and further does not appear to be suitable for on-line measurements. U.S. Pat. No. 3465573 also discloses a U-tube type arrangement, but uses a comparison between two different paths, rather than the mere U-tube, to produce a measurement.
U.S. Pat. No. 4680957 (Dodd) would appear to be the most relevant reference to the present invention in that it discloses a viscosity level conduit to measure viscosity. However one of the main problems with this type of viscometer is the tendency for solids to settle out of solution along the conduit thus adversely affecting the accuracy of readings from the viscometer. There is no suggestion of the use of a U-tube in this specification.


DISCLOSURE OF INVENTION

It is an object of the present invention to overcome the above and other disadvantages by the provision of a method and apparatus for the measure of a fluid or slurry rheology or viscosity.
This object may be achieved, in accordance with the present invention, by the provision of a rheometer comprising an inlet for a sample of a non-Newtonian fluid to be measured, a vertically disposed inverted U-tube conduit connected to said inlet at one end and to an outlet at its other end, pressure differential measurement means operatively mounted across the said U-tube and flow meter and control valve means disposed between said outlet and said other end of the U-tube.
The present invention further provides a method for measuring and monitoring the rheological properties of a fluid or slurry flowing through a vertically disposed inverted U-tube conduit, comprising the steps of
(a) providing a stream of fluid or slurry through said U-tube conduit in non-turbulent laminar flow;
(b) determining the pressure differential across the U-tube; and
(c) further determining the rheology or viscosity therefrom.
The invention provides a basis for on-line adjustment of slurry consistency and rheology by more efficient usage of chemical reagents and modifiers, resulting in substantial modifiers, resulting in substantial cost reductions.


BRIEF DESCRIPTION OF THE DRAWINGS

In order that the reader may gain a better understanding of the p

REFERENCES:
patent: 2716337 (1955-08-01), Heerlen
patent: 3465573 (1969-09-01), Shoemaker
patent: 3520179 (1970-07-01), Reed
patent: 3554010 (1969-04-01), van der Veen et al.
patent: 3839901 (1974-10-01), Finkle et al.
patent: 3839914 (1974-10-01), Modisette et al.
patent: 3926050 (1975-12-01), Turner et al.
patent: 4024753 (1977-05-01), Ouvrard
patent: 4384792 (1983-05-01), Sommers et al.
patent: 4680957 (1987-07-01), Dodd
patent: 4735227 (1988-04-01), Royse et al.
patent: 4890482 (1990-01-01), Maini

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