The invention relates to a CLC plant for the combustion of solid hydrocarbon feedstocks generating particles of unburnt residues, comprising a solid/solid separator above the combustion reactor in order to efficiently separate the particles of the oxygen-carrying solid from the particles of unburnt residues contained in the gas/solid mixture (14) exiting from the combustion reactor. The chamber (1) of the solid/solid separator, the combustion reactor and the inlet (2) for the gas/solid mixture (14) of the chamber have a parallelepiped shape. The inlet (2) is equipped at its top with means (3) for distribution of said gas/solid mixture in the chamber which extend over the entire length of the inlet, improving the solid/solid separation.