{HEAD ~ The H2} is separated and recycled to the alcohol synthesis zone as {TAIL ~ a second source} of H2 
{ HEAD ~ The H2 } is separated and recycled to the alcohol synthesis zone as { TAIL ~ a second source } of H2
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH