Hello enzyme76,
I do not have the exact information that you are looking at achieving, but I may have some information that can point you in the right direction.
In the oilfield, Rasching Rings (
http://en.wikipedia.org/wiki/Raschig_ring) are commonly used, and you may be able to determine the porosity of structured packing (spherical media -
http://en.wikipedia.org/wiki/Porosity). By performing a quick test with media in a laboratory, you can determine the displaced space inbetween each media by filling the pore spaces with water.
This could help you determine the spacing requirements.
This may also help you identify the reasons why the structured packing may have collapsed.
I hope this helps.
Sincerely,
Eugene