Hybrid ethylene cracking furnace

Abstract

A cracking furnace for cracking a hydrocarbon feed, the furnace including a firebox having a single radiant zone including, a first plurality of cracking coils each having a first shape arranged within the firebox. The radiant zone includes a second plurality of cracking coils each having a second shape arranged within the radiant zone. A burner section positioned below the first plurality cracking coils and below the second plurality of cracking coils. A convection section is positioned on top of the firebox configured to recover residual heat from the firebox.

1 - 23 . (canceled) 
     
     
         24 . A cracking apparatus for cracking at least two hydrocarbon feeds, the furnace comprising:
 a cracking furnace, including:
 a firebox including having a single radiant zone; 
 a plurality of U-shaped cracking coils having a first diameter arranged within the firebox for feeding a first hydrocarbon feedstock into a single radiant zone following a first path within the firebox; 
 a plurality of M- or W-shaped cracking coils having a second diameter greater than the first diameter arranged within the firebox, separate from the plurality of U-shaped cracking coils, for feeding a second hydrocarbon feedstock into the firebox following a second flow path while feeding the first hydrocarbon feedstock to the single radiant zone; and 
 a heat source positioned within firebox for heating each of the plurality of U-shaped cracking coils and the plurality of M-shaped cracking coils or W-shaped cracking coils to a temperature determined as a function of an outlet temperature of the first hydrocarbon feedstock such that each of the hydrocarbon feedstocks are cracked converted to a unique thermally cracked product; and 
   a downstream section configured to cool the thermally cracked products to recover at least two olefins from the thermally cracked products.   
     
     
         25 . The cracking apparatus of  claim 24 , further comprising a convection section positioned on top of the firebox configured to recover residual heat from the firebox to preheat the first and second hydrocarbon feedstocks before entering the firebox. 
     
     
         26 . The cracking apparatus of  claim 24 , wherein the heat source includes a plurality of burners positioned adjacent the plurality of U-shaped cracking coils and the plurality of M- or W-shaped cracking coils, wherein the plurality of burners comprises a first plurality of burners positioned adjacent the plurality of U-shaped cracking coils and a second plurality of burners positioned adjacent the plurality of M- or W-shaped cracking coils. 
     
     
         27 . The cracking apparatus of  claim 26 , wherein the first plurality of burners are grouped under the plurality of U-shaped cracking coils or on side walls of the firebox directed towards the plurality of U-shaped cracking coils. 
     
     
         28 . The cracking apparatus of  claim 26 , wherein the second plurality of burners are grouped under the plurality of M- or W-shaped cracking coils or on side walls of the firebox directed towards the plurality of M- or W-shaped cracking coils. 
     
     
         29 . The cracking apparatus of  claim 26 , wherein the plurality of U-shaped cracking coils defines a first group, the plurality of M- or W-shaped cracking coils defines a second group, and further comprising a third group defined by a plurality of U-shaped cracking coils or M- or W-shaped cracking coils, wherein the third group is positioned within tine single radiant zone separate from the first group and the second group. 
     
     
         30 . The cracking apparatus of  claim 29 , wherein the heat source includes a plurality of burners positioned adjacent the first group, the second group, and the third group, wherein the plurality of burners comprises a first plurality of burners positioned adjacent first group, a second plurality of burners positioned adjacent the second group, and a third plurality of burners positioned adjacent the third group. 
     
     
         31 . The cracking apparatus of  claim 30 , wherein:
 the first plurality of burners are positioned under the first group or on side walls of the firebox directed towards the first group;   the second plurality of burners are positioned under the second group or on side walls of the firebox directed towards the second group; and   the third plurality of burners are positioned under the third group or on side walls of the firebox directed towards the first third.   
     
     
         32 . The cracking apparatus of  claim 24 , wherein an outlet temperature of the second hydrocarbon feedstock is dependent on a feed rate of the second hydrocarbon feed. 
     
     
         33 . The cracking apparatus of  claim 24 , wherein the first hydrocarbon feedstock is a liquid, wherein the first hydrocarbon feedstock includes vacuum gas oil or naphtha. 
     
     
         34 . The cracking apparatus of  claim 24 , wherein the second hydrocarbon feedstock is a vapor, wherein the second hydrocarbon feedstock includes butane, propane or ethane. 
     
     
         35 . The cracking apparatus of  claim 24 , wherein the at least two olefins recovered include ethylene and propylene. 
     
     
         36 . A system for cracking a plurality of hydrocarbon feeds simultaneously within a single radiant zone of a firebox, the furnace comprising:
 a firebox including having a single radiant zone;   a first plurality of cracking coils of a first shape having a first diameter arranged within the firebox for feeding a first hydrocarbon feedstock into a single radiant zone following a first path within the firebox;   a second plurality of cracking coils of a second shape different from the first shape having a second diameter greater than the first diameter arranged within the firebox, separate from the plurality of U-shaped cracking coils, for feeding a second hydrocarbon feedstock into the firebox following a second flow path shorter than the first flow path;   a heat source positioned within firebox for heating the first and second feedstocks to a temperature determined as a function of an outlet temperature of the first hydrocarbon feedstock such that each of the hydrocarbon feedstocks are cracked and converted to a unique thermally cracked product; and   a downstream section configured to cool the thermally cracked products to recover at least two olefins from the thermally cracked products.   
     
     
         37 . The system of  claim 36 , wherein the shape of the first plurality of cracking coils U-shaped cracking coils, and wherein the shape of the second plurality of cracking coils is M- or W-shaped cracking coils. 
     
     
         38 . The system of  claim 37 , wherein the plurality of U-shaped cracking coils defines a first group, the plurality of M- or W-shaped cracking coils defines a second group, and further comprising a third group defined by a plurality of U-shaped cracking coils or M- or W-shaped cracking coils, wherein the third group is positioned within tine single radiant zone separate from the first group and the second group. 
     
     
         39 . The system of  claim 37 , wherein the first group and second group are positioned on a first side of the fire box and wherein the third group is positioned on a second side of the firebox, across from the first group. 
     
     
         40 . The system of  claim 39 , wherein the heat source includes a plurality of burners positioned adjacent the first group, the second group, and the third group, wherein the plurality of burners comprises a first plurality of burners positioned adjacent first group, a second plurality of burners positioned adjacent the second group, and a third plurality of burners positioned adjacent the third group. 
     
     
         41 . The system of  claim 40 , wherein:
 the first plurality of burners are positioned under the first group or on a first side wall of the firebox directed towards the first group;   the second plurality of burners are positioned under the second group or on the first side wall of the firebox directed towards the second group; and   the third plurality of burners are positioned under the third group or on side walls of the firebox directed towards the first third.   
     
     
         42 . The system of  claim 36 , wherein the first hydrocarbon feedstock is a liquid including vacuum gas oil or naphtha, wherein the second hydrocarbon feedstock is a vapor including butane, propane or ethane, and wherein the at least two olefins recovered include ethylene and propylene. 
     
     
         43 . A method of overhauling an existing cracking furnace to the cracking furnace of claim  1 ,
 providing the existing cracking furnace having a firebox with a single radiant zone and a first plurality of cracking coils having a single distinct first shape for cracking a first hydrocarbon feedstock;   removing a portion of the first plurality of cracking coils from the firebox; and   installing a second plurality of cracking coils having a second shape different from the first shape to replace the portion of the first plurality of cracking coils removed from the firebox, the second plurality of cracking coils configured for cracking a second hydrocarbon feedstock different from the first hydrocarbon feedstock simultaneously with the existing hydrocarbon feedstock, such that that each of the hydrocarbon feedstocks are cracked and converted to a unique thermally cracked products so as to recover at least two olefins from the thermally cracked products cracked in the single radiant zone of the firebox,   whereby the overhauled furnace includes:
 the firebox including having a single radiant zone; 
 the first plurality of cracking coils including a plurality of U-shaped cracking coils having a first diameter arranged within the firebox for feeding the first hydrocarbon feedstock into the single radiant zone following a first path within the firebox; 
 the second plurality of cracking coils including a plurality of M- or W-shaped cracking coils having a second diameter greater than the first diameter arranged within the firebox, separate from the plurality of U-shaped cracking coils, for feeding a second hydrocarbon feedstock into the firebox following a second flow path while feeding the first hydrocarbon feedstock to the single radiant zone; and 
 a heat source positioned within firebox for heating each of the plurality of U-shaped cracking coils and the plurality of M-shaped cracking coils or W-shaped cracking coils to a temperature determined as a function of an outlet temperature of the first hydrocarbon feedstock such that each of the hydrocarbon feedstocks are cracked converted to the unique thermally cracked product.