11th October 2002, 15:39
measure compatability of powders
I want to mix two powders together, ship them, then process them. How can I predict whether the particles will segregate. Or, rather measure their potential to segregate?
I can think now only of measuring their particle size distributions before mixing and if they are close in distribution, they would not be inclined to segregate. I suppose that the bulk densities might also play a role.
What are other factors? Can I predict behaviour without actually testing the materials by simulating the agitation of transport and measuring the concentration distribution of the materials before and after?
Thanks for any help.
5th December 2002, 13:44
Testing for segregation
Probably the best approach is to replicate, on a small scale, the mechanism that is likely to be present in the preparation of the material for transit. The most common feature is that of forming a repose pile in the loading of containers. Pouring the material through a funnel onto a pile, and comparing a sample scraped from the periphery with one taken from the centre will quickly indicate the extent to which segregation may occur. A more quantitative tets is to rotate a sample in an inclined drum, say length equals diameter at 15 degrees axial inclination. Fill with sufficient material to reach near the rim when rotating. After about 30 rotations a sample should be taken of that quanitiy filling half way down the cylinder and comparing its particles size distribution with the remaining quantity.
the 'User Guide to Segregation', published by the British Materials Handling Board, gives much background and useful tips for dealing with this form of problem. Soe technical publications from www.ajax.co.uk are also available.
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