Patent ID: 7977524

Claim:
A process for decoking a convection section of a furnace for cracking a hydrocarbon feed, the furnace comprising a radiant section having burners that generate radiant heat and hot flue gas, and the convection section having at least one heat exchange tube for conveying the hydrocarbon feed, said process comprising the step of: interrupting the flow of hydrocarbon feed to the at least one convection section heat exchange tube; passing an air/steam decoking feed mixture having a first air/steam ratio through the at least one convection section heat exchange tube; and increasing the air/steam decoking feed mixture temperature within the tube entering the convection section to decoke; establishing a flue gas temperature within the convection section of the furnace immediately adjacent the at least one convection section heat exchange tube so as to effect a film surface temperature of less than about 540° C. within at least one convection section heat exchange tube, wherein said flue gas temperature establishing step is effective to decoke the at least one convection section heat exchange tube; and wherein the furnace further comprises a steam superheater disposed below the at least one convection section heat exchange tube in the furnace and capable of being supplied with a stream of desuperheater water, and wherein said step of increasing the air/steam decoking feed mixture temperature entering the convection section includes the step of reducing the supply of desuperheater water to the steam superheater during the decoking of the upper convection section of the furnace.