Patent ID: 7413648
Filing Date: 2008-08-19
Classification: C10G

Abstract:
1. A process for cracking hydrocarbonaceous feed that comprises: (a) preheating said feed in a first tube bank of a convection zone of a furnace, said feed being introduced to said first tube bank through at least one of (b) mixing the hydrocarbon feedstock with water and steam added to the first tube bank via one or more inlets for introducing water and steam and removing said heated mixture stream through an outlet in said first tube bank, the water and steam being added in respective amounts which control the temperature of said heated mixture stream; (c) further controlling said temperature of said heated mixture stream by: (d) directing said heated mixture stream by a bypass line substantially external to said convection zone for receiving said heated mixture stream from said first tube bank to a fourth tube bank positioned beneath said second tube bank and said third tube bank, which fourth tube bank comprises an inlet connected to said bypass line and an outlet for directing a partially liquid effluent to a vapor/liquid separator, wherein said economizer inlet introducing high pressure boiler feed water to said second tube bank is responsive to the temperature of said effluent entering said vapor/liquid separator; (e) flashing said effluent from said fourth tube bank effluent in said vapor/liquid separator external to said convection zone to provide a liquid bottoms phase and an overhead vapor phase; (f) directing said overhead vapor phase to a fifth tube bank of said convection zone positioned beneath said fourth tube with an inlet for receiving overhead from said vapor/liquid separator and an outlet in order to further heat said overhead vapor phase; (g) cracking said further heated overhead vapor phase in a radiant zone beneath said convection zone, which includes a plurality of burners producing flue gas passing upwards through the radiant zone and convection tube banks, to provide a cracked effluent; and (h) withdrawing said cracked effluent from said radiant zone.