The distillation and hydrotreating fuel units will stop simultaneously on Sept. 23, while the remaining areas of the Tarragona complex, such as the chemical plants, will continue to operate normally, Repsol said.

Repsol has dubbed the project "the most important turnaround ever carried out at the refinery".

The work is designed to improve the energy efficiency of the complex's facilities and prevent the emissions of 32,500 tonnes of carbon dioxide each year.

Repsol aims to be a net zero emissions company by 2050.

(Reporting by Rowena Edwards; Editing by Elaine Hardcastle, Kirsten Donovan)

By Rowena Edwards