An average residence time of {HEAD ~ between 5 and 500 milliseconds} of {TAIL ~ the hydrocarbons} during thermal cracking has proven to be effective 
of
An average residence time of { HEAD ~ between 5 and 500 milliseconds } of { TAIL ~ the hydrocarbons } during thermal cracking has proven to be effective
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH