PROCESS FOR PRODUCING HYDROGEN
A process for producing hydrogen comprising the steps of reforming a hydrocarbon feedstock to form a synthesis gas; subjecting the synthesis gas to one or more stages of water gas shift to convert carbon monoxide to carbon dioxide and form a hydrogen-enriched synthesis gas; and treating the hydrogen-enriched synthesis gas to form a purified hydrogen product and tail gas stream containing methane, wherein at least a portion of the tail gas stream is treated by subjecting it to partial oxidation or autothermal reforming to form a partially-oxidised or reformed tail gas, followed by of water gas shift of the partially-oxidised or reformed tail gas to form a hydrogen-enriched tail gas, and a step of carbon dioxide removal from the hydrogen-enriched tail gas to form a hydrogen stream and a carbon dioxide stream, wherein the carbon dioxide stream is recovered and a portion of the hydrogen stream is a fuel.
1 . A method for retrofitting a hydrogen production unit comprising:
a hydrocarbon reforming unit comprising a fired steam reformer arranged to be fed with a hydrocarbon feedstock;
a synthesis gas water gas shift unit arranged to be fed with a synthesis gas from the hydrocarbon reforming unit to produce a hydrogen-enriched synthesis gas; and
a purification unit arranged to be fed with a hydrogen-enriched synthesis gas from the synthesis gas water gas shift unit to generate a hydrogen product and a tail gas stream:
wherein in the hydrogen production unit there is no step of recovering carbon dioxide from the hydrogen-enriched synthesis gas stream upstream of the purification unit;
the method comprising installing a tail gas treatment unit comprising:
a partial oxidation reactor or a tail gas reforming unit arranged to accept at least a portion of the tail gas stream from the purification unit and produce a partially-oxidised or reformed tail gas stream;
a tail gas water-gas shift unit arranged to accept a partially-oxidised or reformed tail gas stream from the partial oxidation reactor or a tail gas reforming unit and produce to form a hydrogen-enriched tail gas stream;
a tail gas carbon dioxide removal unit arranged to accept a hydrogen-enriched tail gas stream from the tail gas water-gas shift unit and produce a hydrogen stream,
wherein the tail gas treatment unit is arranged to feed the hydrogen stream to the fired steam reformer as a fuel.
2 . The method according to claim 1 , wherein the method includes installing an autothermal reformer within the hydrocarbon reforming unit, wherein the autothermal reformer is arranged to be fed with a reformed gas from the fired steam reformer and an oxygen containing gas to generate the synthesis gas.
3 . The method according to claim 1 , wherein the method includes installing a fired heater to heat one or more feeds to the tail gas treatment unit using a portion of the hydrogen stream.
4 - 5 . (canceled)
6 . A process for producing hydrogen comprising the steps of:
(i) reforming a hydrocarbon feedstock in a hydrocarbon reforming unit comprising a fired steam reformer to form a synthesis gas containing hydrogen, carbon monoxide and carbon dioxide;
(ii) subjecting the synthesis gas to one or more stages of water gas shift in a synthesis gas water gas shift unit to convert carbon monoxide to carbon dioxide and form a hydrogen-enriched synthesis gas; and
(iii) treating the hydrogen-enriched synthesis gas in a purification unit to form a purified hydrogen product and tail gas stream containing methane,
wherein there is no step of recovering carbon dioxide from the hydrogen-enriched synthesis gas stream upstream of the purification unit;
wherein at least a portion of the tail gas stream is treated in a tail gas treatment unit by subjecting it to:
partial oxidation in a partial oxidation reactor or autothermal reforming in a tail gas reforming unit to form a partially-oxidised or reformed tail gas, followed by
one or more stages of water gas shift of the partially-oxidised or reformed tail gas in a tail gas water-gas shift unit to form a hydrogen-enriched tail gas, and
a step of carbon dioxide removal from the hydrogen-enriched tail gas in a tail gas carbon dioxide removal unit to form a hydrogen stream and a carbon dioxide stream,
wherein the carbon dioxide stream is recovered and a portion of the hydrogen stream is fed to the fired steam reformer as a fuel.
7 . The process according to claim 6 , wherein the hydrocarbon reforming unit comprises a fired steam reformer and an autothermal reformer and the process comprises feeding an oxygen containing gas and a reformed gas from the fired steam reformer to the autothermal reformer to generate the synthesis gas.
8 . The process according to claim 7 , wherein the reformed gas from the fired steam reformer is mixed with a portion of the hydrocarbon feedstock.
9 . The process according to claim 6 , wherein the hydrogen-enriched synthesis gas is cooled to below the dew point and condensate separated from it upstream of the purification unit.
10 - 11 . (canceled)
12 . The process according to claim 6 , wherein the tail gas fed to the tail gas treatment unit is supplemented with a portion of the hydrocarbon feed and/or another hydrocarbon-containing gas stream.
13 . The process according to claim 6 , wherein one or more feeds to the tail gas treatment unit are heated using a fired heater that is fired by a portion of the hydrogen stream.
14 . The process according to claim 6 , wherein a portion of the hydrogen gas stream is fed to the purification unit or is blended with the purified hydrogen product.
15 . The process according to claim 6 , wherein the feed to the partial oxidation reactor or a tail gas reforming unit is supplied at a pressure of 10-30 barg.