Patent ID: 7488459

Claim:
An apparatus for cracking a variety of hydrocarbonaceous feed, which comprises: (I) a convection zone containing: (a) a first tube bank comprising (i) an upper hydrocarbon feed inlet, (ii) an optional lower hydrocarbon feed inlet, (iii) one or more inlets for introducing water and steam, and (iv) an outlet for a heated mixture stream; (b) a vapor/liquid separator receiving the heated mixture stream from a fourth tube bank; (c) a second tube bank positioned beneath said first tube bank comprising an economizer inlet for introducing high pressure boiler feed water and an economizer outlet for withdrawing boiler feed water of greater heat content, including means for controlling high pressure boiler feed water through said economizer inlet, responsive to the temperature of the heated mixture stream entering the vapor/liquid separator over a wide range by regulating the temperature of said second tube bank; (d) a third tube bank positioned beneath said first tube bank comprising an inlet for high pressure steam which is heated in a section of said third tube bank, an inlet for mixing desuperheater water with said high pressure steam to cool the high pressure steam, a section for reheating said high pressure steam, and an outlet for withdrawing superheated high pressure steam; (e) a bypass line for receiving said heated mixture stream from said first tube bank; (f) a fourth tube bank positioned beneath said second tube bank and said third tube bank which comprises an inlet connected to said bypass line and an outlet for directing effluent to said vapor/liquid separator; and (g) a fifth tube bank positioned beneath said fourth tube bank with an inlet for receiving overhead from said vapor/liquid separator and an outlet; and (II) 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, which radiant zone receives effluent from said fifth tube bank and further comprises an outlet for removing cracked effluent.