A method is disclosed a method for recovering olefins and for producing hydrogen
from a refinery off-gas stream in which such stream is conventionally pretreated
and separated to obtain a light ends stream that contains nitrogen, hydrogen and
carbon monoxide and a heavy ends stream that contains the olefins. The light ends
stream is subjected to reforming and a water gas shift reactions after addition
of a natural gas stream. The addition of the natural gas increases the hydrogen
recovery from the light ends and also stabilizes the hydrocarbon content in the
stream to be subjected to the reforming and water gas shift reactions. The heavy
ends can be further treated to recover olefins such as ethylene and propylene.
The rate of natural gas addition is controlled so that the concentration of the
nitrogen in a stream exiting the water gas shift reactor is less than about 5 percent
by volume so that hydrogen separation from such stream becomes practical.