The packed tower includes {HEAD ~ a packing arrangement} including a lower bed of mobile packing elements, and {TAIL ~ an adjacent upper bed} of fixed packing elements 
The packed tower includes { HEAD ~ a packing arrangement } including a lower bed of mobile packing elements , and { TAIL ~ an adjacent upper bed } of fixed packing elements
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH