Process for heating the column for distillation of the C3 fraction from an FCC unit by means of a circuit of water heated by streams belonging to units placed upstream and/or downstream of the FCC unit

A process for heating a reboiler of a propane/propylene separation column system which is fed with a C3 cut from a fluid catalytic cracking unit, said process comprising:

• heating water in a water circuit heat exchange with one or more process fluids originating from units positioned upstream and/or downstream of said fluid catalytic cracking, and then using the heated water in the water circuit to heat said reboiler of the propane/propylene separation column system, wherein said one or more process fluids are:
• an overhead vapor stream from a fractionation column of a mild hydrocracking unit positioned upstream of said fluid catalytic cracking,
• an overhead vapor stream from a stripper of a mild hydrocracking unit positioned upstream of said fluid catalytic cracking unit, and/or
• effluent from a hydrodesulphurization reactor of a fluid catalytic cracking gasoline hydrotreatment positioned downstream of said fluid catalytic cracking unit, after said effluent undergoes heat exchange with a feedstock of the hydrodesulphurization reactor and with a feedstock of a selective hydrogenation reactor.