introducing alumina into {TAIL ~ the tank} at a slow rate CL which is from {HEAD ~ 15 to 50%} below the normal rate of alumina consumption CN 
introducing alumina into { TAIL ~ the tank } at a slow rate CL which is from { HEAD ~ 15 to 50 % } below the normal rate of alumina consumption CN
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH