Process for synthesising hydrocarbons

A process for synthesising hydrocarbons comprising the steps of (a) making a synthesis gas comprising hydrogen, carbon monoxide and carbon dioxide from a feedstock in a synthesis gas generation unit, (b) removing carbon dioxide from the synthesis gas in a carbon dioxide removal unit to produce a carbon dioxide stream and purified synthesis gas comprising hydrogen and carbon monoxide, and (c) synthesising a mixture of hydrocarbons from the purified synthesis gas in a Fischer-Tropsch (FT) hydrocarbon synthesis unit, with co-production of a FT water stream, wherein (i) at least a portion of the FT water stream is fed to an electrolysis unit to provide an oxygen stream, which is fed to the synthesis gas generation unit, and a hydrogen stream, (ii) at least a portion of the carbon dioxide stream recovered from the carbon dioxide removal unit and a portion of the hydrogen stream produced by the electrolysis unit are fed to a reverse water-gas shift unit to produce a carbon monoxide stream, and (iii) at least a portion of the carbon monoxide stream from the reverse water-gas shift unit is fed to the Fischer-Tropsch hydrocarbon synthesis unit;

• wherein the FT water stream is treated upstream of the electrolysis unit to remove contaminants.