Density/Percent Solids Gauge for Slurries

Offshore Scientific P/L has completed a preliminary study of an acoustic based percent solids / density gauge to be used in coal preparation circuit pipes. This low cost scoping study forms a basis for possible future development of a density gauge that would be low cost, and an alternative to nuclear-based gauges currently in use for measuring the material properties of slurries flowing in pipes.

This project was performed in co-operation with the CSIRO QCAT facility and staff in Pinjarra Hills, Qld, with the CSIRO acting in a sub-contract role with testing, advisement and reporting responsibilities. A separate (independent) report compiled by CSIRO staff can be found appended to this document.

The goals of this project included:

1. To measure the effect of an enclosed pipe environment upon underwater acoustic sensors and gauge system proven to be successful in "open water" environments.
2. To measure the effect of fluid mix flow upon these sensors and system.
   
3. To obtain an indication of inherent, or potential accuracy of this system.
4. To obtain estimates of cost and technical effort required to bring the system up to operational performance levels.

Two series of tests were carried out. The first test series was an initial "quick look" series of data acquisition at the CSIRO facility to obtain estimates of the electronic, acoustic and data acquisition requirements needed for a more complete second test series. The second test series was completed in October 2000.

This final test used improved electronics, sensors and data acquisition techniques. Three mixes were used for the flowing slurries in the 6 inch diameter pipe:

a) Thickener feed/rejects
b) Flotation feed ROM coal
c) Dense Medium cyclone/magnetite

Overall, the results of this preliminary study were promising. With respect to the objectives listed above, it was found that the enclosed pipe environment did not affect the performance of this technology. Next, the effect of fluid flow upon this technology was significant. This effect includes turbulence, bubbles and other sources of flow noise. It was found that reasonable results could be obtained at lower flow velocities (typically less than 1.5 metres per second). Testing at higher velocities offset the gauge data, and at high velocities (greater than 2 m/s) the gauge had difficulties obtaining quality measurements. The accuracy of the system was good (as judged by CSIRO staff) for two out of the three mixes at lower flow velocities. Finally, it is estimated that further work involved with the development of this system in order to bring it up to operational levels would be at least several multiples of the cost and effort used for this project.