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A process for producing liquid hydrocarbon products includes converting a natural gas feedstock to synthesis gas, which is reacted, in a hydrocarbon synthesis stage and by a Fischer-Tropsch reaction, to produce a range of hydrocarbon product. An overheads vapour phase is separated from a liquid phas

A process for producing liquid hydrocarbon products includes converting a natural gas feedstock to synthesis gas, which is reacted, in a hydrocarbon synthesis stage and by a Fischer-Tropsch reaction, to produce a range of hydrocarbon product. An overheads vapour phase is separated from a liquid phase, and fed to a product condensation stage, where condensation of some components thereof takes place. A vapour phase, an aqueous phase, and a condensed product phase are withdrawn. The vapour phase is fed to a vapour phase work-up stage where a gas component comprising increased concentrations of CO and H2, relative to the vapour phase feed to the vapour phase work-up stage, is recovered, with this gas component being recycled to the hydrocarbon synthesis stage.

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1. A process for producing liquid hydrocarbon products, which process includesconverting, in a synthesis gas production stage, a natural gas feedstock comprising mainly CH 4 to synthesis gas comprising CO, H 2 , CO 2 and CH 4 ;feeding the synthesis gas, as a feedstock, to a hydrocarbon synthesis

1. A process for producing liquid hydrocarbon products, which process includesconverting, in a synthesis gas production stage, a natural gas feedstock comprising mainly CH 4 to synthesis gas comprising CO, H 2 , CO 2 and CH 4 ;feeding the synthesis gas, as a feedstock, to a hydrocarbon synthesis stage;in the hydrocarbon synthesis stage, reacting the synthesis gas at elevated temperature and pressure, and in the presence of a Fischer-Tropsch catalyst, to produce a range of hydrocarbon products of differing carbon chain lengths, and separating an overheads vapour phase comprising gaseous hydrocarbon products, unreacted synthesis gas, water, and any soluble organic compounds which form in the hydrocarbon synthesis stage, from a liquid phase comprising heavier liquid hydrocarbon products;withdrawing the liquid phase from the hydrocarbon synthesis stage;withdrawing the overheads vapour phase from the hydrocarbon synthesis stage and feeding it to a product condensation stage, where condensation of at least some components of the overheads vapour phase takes place;withdrawing from the product condensation stage a vapour phase comprising gaseous hydrocarbon products, an aqueous phase comprising water and said any soluble organic compounds which form in the hydrocarbon synthesis stage, and a condensed product phase comprising condensed hydrocarbon products;feeding the vapour phase to a vapour phase work-up stage;in the vapour phase work-up stage, recovering from the vapour phase a first gas component comprising increased concentrations of CO and H 2 , relative to the vapour phase feed to the vapour phase work-up stage; andrecycling the CO and H 2 -containing first gas component to the hydrocarbon synthesis stage, as a feedstock component. 2. A process according to claim 1, wherein the conversion of the natural gas to synthesis gas in the synthesis gas production stage is effected by a reaction mechanism involving reacting hydrocarbonaceous material with steam and/or oxygen, with the reaction mechanism being selected from the group consisting in steam reforming, which does not require the use of oxygen; autothermal reforming, in which the hydrocarbonaceous material reacts with oxygen in a first reaction section, whereafter an endothermic steam reforming reaction takes place adiabatically in a second reaction section; ceramic oxygen transfer membrane reforming, in which oxygen required for the reforming reaction is transported through an oxygen permeable membrane into a reaction zone; plasma reforming in which the reforming reaction is driven by an electrically generated plasma; non-catalytic partial oxidation; catalytic partial oxidation; and two or more of these reaction mechanisms. 3. A process according to claim 1, wherein no CO 2 removal from the synthesis gas is effected, prior to the synthesis gas being fed as the feedstock to the hydrocarbon synthesis stage. 4. A process according to claim 1, wherein the hydrocarbon synthesis stage includes a reactor in which the synthesis gas is catalytically reacted by means of low temperature Fischer-Tropsch synthesis using a Co-based Fischer-Tropsch catalyst, with the reaction temperature being in the range of 200° C. to 280° C., with the main reactants being H 2 and CO, and with the CO 2 in the synthesis gas behaving as an inert gas in the reactor. 5. A process according to claim 4 wherein, in the vapour phase work-up stage, the vapour phase is separated into the first gas component comprising the increased concentrations of CO and H 2 a second gas component enriched in CH 4 , and, optionally, a third gas component comprising mainly CO 2 . 6. A process according to claim 5, wherein the third gas component is present, with the vapour phase work-up stage including a CO 2 removal step in which the third gas component is removed from the vapour phase, and a subsequent cryogenic separation step to which the residual vapour phase is subjected and in which the first gas comp onent is cryogenically separated from the second gas component. 7. A process according to claim 5, wherein the third gas component is present, with the vapour phase work-up stage including a heavy ends recovery step in which hydrocarbon products having 3 or more carbon atoms, and which are present in the vapour phase, are removed from the vapour phase, and with the residual vapour phase then passing to a subsequent pressure swing adsorption step where it is separated into the first, second and third gas components, with the third gas component thus comprising mainly CO 2 and some light hydrocarbon products. 8. A process according to claim 7, wherein the second gas component is fed into a hydrogen production stage in which hydrogen is produced from the CH 4 . 9. A process according to claim 8, wherein hydrogen produced in the hydrogen production stage is added to the synthesis gas feedstock to the hydrocarbon synthesis stage, thereby to increase the synthesis gas hydrogen content. 10. A process according to claim 7, which includes, in a liquid product upgrading stage, upgrading the liquid hydrocarbon products in the liquid phase withdrawn from the hydrocarbon synthesis stage as well as the hydrocarbon products in the condensed product phase from the product condensation stage, by hydroprocessing the hydrocarbon products using hydrogen from the hydrogen production stage. 11. A process for producing liquid hydrocarbon products, which process includesconverting, in a synthesis gas production stage, a natural gas feedstock comprising mainly CH 4 to synthesis gas comprising CO, H 2 , CO 2 and CH 4 ;without removal of CO 2 , feeding the synthesis gas, as a feedstock, to a hydrocarbon synthesis stage;in the hydrocarbon synthesis stage, reacting the synthesis gas at elevated temperature and pressure, and in the presence of a Co-based Fischer-Tropsch catalyst, to produce a range of hydrocarbon products of differing carbon chain lengths, and separating an overheads vapour phase comprising gaseous hydrocarbon products, unreacted synthesis gas, water, and any soluble organic compounds which form in the hydrocarbon synthesis stage, from a liquid phase comprising heavier liquid hydrocarbon products;withdrawing the liquid phase from the hydrocarbon synthesis stage;withdrawing the overheads vapour phase from the hydrocarbon synthesis stage and feeding it to a product condensation stage, where condensation of at least some components of the vapour phase takes place;withdrawing from the product condensation stage a vapour phase comprising gaseous hydrocarbon products, an aqueous phase comprising water and said any soluble organic compounds which form in the hydrocarbon synthesis stage, and a condensed product phase comprising condensed hydrocarbon products;feeding the vapour phase to a heavy ends recovery stage;in the heavy ends recovery stage, separating hydrocarbon products having 3 or more carbon atoms, from the vapour phase; andrecycling at least a portion of the vapour phase from the heavy ends recovery stage to the synthesis gas production stage, as a feedstock component. 12. A process according to claim 11, wherein the conversion of the natural gas to synthesis gas in the synthesis gas production stage is effected by a reaction mechanism involving reacting hydrocarbonaceous material with steam and/or oxygen, with the reaction mechanism being selected from the group consisting in steam reforming, which does not require the use of oxygen; autothermal reforming, in which the hydrocarbonaceous material reacts with oxygen in a first reaction section, whereafter an endothermic steam reforming reaction takes place adiabatically in a second reaction section; ceramic oxygen transfer membrane reforming, in which oxygen required for the reforming reaction is transported through an oxygen permeable membrane into a reaction zone; plasma reforming in which the reforming reaction is driven by an electrically generated plasma; non-catalytic partia l oxidation; catalytic partial oxidation; and two or more of these reaction mechanisms. 13. A process according to claim 11, wherein the hydrocarbon synthesis stage includes a reactor in which the synthesis gas is catalytically reacted by means of low temperature Fischer-Tropsch synthesis using the Co-based Fischer-Tropsch catalyst, with the reaction temperature being in the range of 200° C. to 280° C., with the main reactants being H 2 and CO, and with the CO 2 in the synthesis gas behaving as an inert gas in the reactor.