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