Decarbonisation of a chemical plant

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) an autothermal reformer, arranged to accept a hydrocarbon-containing fuel stream comprising hydrocarbons and steam and produce a reformed gas stream;
• (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;
• 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;
• with the proviso that the hydrocarbon-containing off-gas stream is not a purge gas stream from a methanol loop;
• and
• with the proviso that if the hydrocarbon-containing off-gas stream is a tail-gas stream from the purification unit of a hydrocarbon reforming section comprising a fired steam reformer, water-gas shift and purification unit, then the decarbonised fuel stream from the off-gas treatment unit is not sent to the fired steam reformer of the hydrocarbon reforming section as a fuel.