DECARBONISATION OF A CHEMICAL PLANT
A chemical plant initially arranged such that a hydrocarbon-containing off-gas stream is combusted to provide at least some of the heating duty on the chemical plant, the method comprising the step of: installing an off-gas treatment unit arranged to accept said hydrocarbon-containing off-gas stream, the off-gas treatment unit comprising sequentially: (i) a gas-heated reformer and an autothermal reformer, arranged to accept a hydrocarbon-containing fuel stream comprising hydrocarbons and produce a reformed gas stream, and arranged such that gases from the outlet of the autothermal reformer are used to provide heat required for steam reforming in the gas-heated reformer; (ii) a water-gas shift section arranged to accept said reformed gas stream and produce a shifted gas stream; and (iii) a CO2 removal unit arranged to accept said shifted gas stream and produce a CO2 rich stream and a decarbonised fuel stream.
1 . A method for retrofitting a chemical plant which is initially arranged such that a hydrocarbon-containing off-gas stream is combusted to provide at least some of the heating duty on the chemical plant, the method comprising the step of:
installing an off-gas treatment unit arranged to accept said hydrocarbon-containing off-gas stream, the off-gas treatment unit comprising sequentially:
(i) a gas-heated reformer and an autothermal reformer, arranged to accept a hydrocarbon-containing fuel stream comprising hydrocarbons and produce a reformed gas stream, and arranged such that gases from the outlet of the autothermal reformer are used to provide heat required for steam reforming in the gas-heated reformer;
(ii) a water-gas shift section arranged to accept said reformed gas stream and produce a shifted gas stream; and
(iii) a CO 2 removal unit arranged to accept said shifted gas stream and produce a CO 2 rich stream and a decarbonised fuel stream;
wherein said hydrocarbon-containing fuel stream is derived from said hydrocarbon-containing off-gas stream, steam and any supplemental fuel;
wherein said off-gas treatment unit is arranged such that the decarbonised fuel stream, optionally having first undergone further purification, is combusted instead of the hydrocarbon-containing off-gas stream.
2 . The method according to claim 1 , wherein the off-gas treatment unit is arranged to accept off-gases from two or more different hydrocarbon-containing off-gas streams from the chemical plant.
3 . The method according to claim 1 , wherein the hydrocarbon-containing off-gas stream is a purge stream.
4 . The method according to claim 1 , wherein the hydrocarbon-containing off-gas stream is a hydrocarbon-containing stream from a purification unit.
5 . The method according to claim 4 , wherein the purification unit is part of a steam reforming section.
6 . The method according to claim 1 , wherein the method includes installation of H 2 fuel burners for the decarbonised fuel stream.
7 . The process of treating a hydrocarbon-containing off-gas stream from a chemical plant by converting said hydrocarbon-containing off-gas stream in an off-gas treatment unit to produce a decarbonised fuel stream and combusting said decarbonised fuel stream to provide at least some of the heating duty on said chemical plant, wherein the chemical plant comprises an off-gas treatment unit arranged to accept a hydrocarbon-containing off-gas stream, the off-gas treatment unit comprising sequentially:
(i) a gas-heated reformer and an autothermal reformer, arranged to accept a hydrocarbon-containing fuel stream comprising hydrocarbons and steam and produce a reformed gas stream, and arranged such that gases from the outlet of the autothermal reformer are used to provide heat required for steam reforming in the gas-heated reformer;
(ii) a water-gas shift section arranged to accept said reformed gas stream and produce a shifted gas stream; and
(iii) a CO 2 removal unit arranged to accept said shifted gas stream and produce a CO 2 rich stream and a decarbonised fuel stream;
wherein said hydrocarbon-containing fuel stream is derived from said hydrocarbon-containing off-gas stream, steam and any supplemental fuel; and
wherein said decarbonised fuel stream comprises 50-98 vol % H 2 .
8 . The process according to claim 7 , wherein the chemical plant is an oil refinery.
9 . The process according to claim 7 , wherein the off-gas treatment unit is arranged to accept off-gases from two or more different hydrocarbon-containing off-gas streams from the chemical plant.
10 . The process according to claim 7 , wherein the hydrocarbon-containing off-gas stream is a purge stream.
11 . The process according to claim 7 , wherein the hydrocarbon-containing off-gas stream is a hydrocarbon-containing stream from a purification unit.
12 . The process according to claim 11 , wherein the purification unit is part of a steam reforming section.
13 . The process according to claim 7 , wherein the steam to carbon ratio at the inlet to the gas-heated reformer is from 1.5:1 to 3.5:1.