Shepherd, I.C., LaFontaine, R.F., Hooper, J., Davy, J.L., Burton, D.R., Beeby, C. and White, R.

Measurement of the flow of particles and gas in calcining circuits is of particular interest to the alumina industry. However, there appears to be no satisfactory probe which can provide reliable information on the movement of gas and particles in the high temperature, abrasive environment of calciner circuits. A CSIRO project to develop such a probe was commissioned by the Australian Mineral Industries Research Association (AMIRA) on behalf of five companies related to the alumina industry. The objective was to develop a robust probe which could provide information on the movement anld distribution of particles and gas in alumina calcining circuits where the temperature could be as high as 1100oC and the particles extremely abrasive.

A review of the literature revealed few methods which could be expected to operate reliably in such hostile environments. Three robust sensing techniques were chosen for further research. These involved the measurement of drag on a body, the measurement of the sound generated by particle impacts on a body and the measurement of pressure differences generated around the surface of a body immersed in the flow. A single probe incorporating two or three sensors was envisaged. It was anticipated that the drag sensor would provide information on the total momentum flux of the gas and particulate streams, the impact sensor information on the solids momentum and the pressure sensor information on the momentum of both phases.

Although problems were encountered in designing, fabricating, calibrating and testing the sensors and probes, the drag and impact sensors performed as expected. Impact momenta of particles and the mean momentum flux of the solid stream could be detected with the impact sensor, and the total momentum flux of gas and particles could be detected with the drag sensor. Data extracted from the pressure sensor provided reliable information on the momentum flux of the aggregate stream of fluid and particles but did not distinguish between solids and fluid.

A probe incorporating drag and impact sensors was tested in cold and hot plant which were representative of industrial situations.