Reducing agent can be conveyed back from {HEAD ~ the delivery device} to {TAIL ~ the reservoir} via a return line 
Reducing agent can be conveyed back from { HEAD ~ the delivery device } to { TAIL ~ the reservoir } via a return line
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH