Continuous rheometry for industrial slurries

Mineral solids are usually processed, produced or handled in the form of two-phase slurries. Examples may be found in all aspects of mining and mineral processing. The ability to handle and process mineral slurries depends on the flow behaviour of the slurries. A good knowledge of the flow characteristics of these slurries is very important in the design and optimisation of mining and extractive processes. It is essential that the rheological properties of these slurries be determined as accurately as possible. This however, is not an easy task when dealing with heterogeneous suspensions where there are large and high-density solid particles. Accurate and reliable measurements of the rheological properties of these slurries using conventional viscometric instruments can be difficult, if not impossible, since the solid particles settle rapidly under the influence of gravity. We report on the development of an on-line helical flow rheometer for characterising the rheological behaviour of settling mineral slurries. The instrument design is based on the principles of helical flow, which is the combination of tangential Couette and axial annular flows. The data reduction procedure developed is firmly based on the theory of helical flow and has been extensively tested and validated with model fluids of different rheological behaviour. Testing of the helical flow rheometer and the data reduction method with various solutions, including Newtonian and pseudo-plastic fluids have produced good results.T.J. Akroyd & Q.D. Nguye