A process is described for synthesising hydrocarbons comprising the steps of: (a) feeding a gas mixture comprising
hydrogen and
carbon dioxide to a reverse water-gas shift unit to form a crude synthesis gas comprising
hydrogen,
carbon monoxide carbon dioxide and steam, (b) cooling the crude synthesis gas to condense water and removing water, and optionally
carbon dioxide, from the crude synthesis gas to produce a feed
stream comprising
hydrogen and
carbon monoxide, (c) passing the feed
stream though a
hydrocarbon synthesis unit comprising a reactor containing a Fischer-Tropsch catalyst to form a product
stream comprising a mixture of
liquid hydrocarbons, a co-
produced water stream, and a
tail gas stream containing hydrogen,
carbon monoxide and gaseous hydrocarbons, and (d) upgrading the product stream in an upgrading unit to produce an upgraded product stream, wherein a
naphtha stream is separated from the product stream or the upgraded product stream, at least a portion of the
tail gas stream is fed with steam to a first derichment vessel containing a derichment catalyst to form a first gas mixture containing
methane, at least a portion of the
naphtha stream is fed with hydrogen and steam to a second derichment vessel containing a derichment catalyst to form a second gas mixture containing
methane, and the first and second gas mixtures containing
methane are fed to the reverse
water gas shift unit. A
system for performing the process is also provided.