John Courtenay will be presenting a paper on behalf of MQP and Trimet. Here is a synopsis:

Results of trials with a multi stage filtration system employing a cyclone

by John Courtenay², Marcel Rosefort¹, and Phil Jankowski¹.

1Trimet Aluminium SE, Aluminium Allee, 1, 45356 Essen, Germany

2 MQP Limited, 6 Hallcroft Way, Knowle, Solihull, B93 9EW United Kingdom



Optifilter is a multi-stage filter system comprising a ceramic foam filter in a first chamber, a grain refiner added in a second chamber and a cyclone deployed in a final chamber. The ceramic foam filter is intended to operate in cake mode and the cyclone ensures removal of oxides and agglomerates arising from the grain refiner addition.

Evaluation of the Optifilter multi stage filtration system has continued at Trimet and provided interesting insights into in-line filtration mechanisms. An industrial prototype Optifilter unit has successfully operated on a Research Casting Pit and metal cleanliness measured by Podfa, before and after passing through the filter, together with microstructural analysis of spent ceramic foam filter sections.

The results are reported in this paper and showed that the filtration efficiency was like that achieved with a standard CFF when a known amount of inclusions was deliberately added in the form of Mikro 100 rod to a 99.85% aluminium clean melt. However micro examination of the spent CFF filter from the first chamber revealed that no bridges had been formed and that the filter had operated in standard depth mode and not cake mode.

Investigation of the nature of the Mikro 100 inclusion source showed that particles ofɤ-alumina in the size range 6-8µm are released. This means that with a CFF filter pore size of more than 1000µm the condition for the formation of bridges, that is a pore size to particle size ratio of less than 10 to 12 times greater, was not met. Furthermore, the effective particle size operating range for the cyclone chamber is from 20-80µm and therefore it had no effect on particle removal under the test conditions.

More trials will be conducted under industrial conditions closer to the design parameters used in the original Optifilter computer flow modelling program.