Optimization of steam cracking furnaces for light feedstocks containing high boiling components

Abstract

A system and a method for steam cracking hydrocarbons are disclosed. The system includes a steam cracking system comprising a first steam cracking furnace and a second steam cracking furnace. A hydrocarbon feed stream is fed into a convection section of a first steam cracking furnace. The preheated feed stream is mixed with steam and then separated into a light vapor stream and a heavy stream in a vapor-liquid separation unit. The light vapor stream is further steam cracked in a radiant section of the first steam cracking furnace. The heavy stream is further heated and steam cracked in the second steam cracking furnace.

1 . A method of steam cracking hydrocarbons, the method comprising:
 (a) heating a hydrocarbon feed stream in a first convection section of a first steam cracking furnace to a temperature sufficient to vaporize at least a portion of the hydrocarbon feed stream and form a heated hydrocarbon feed stream;   (b) mixing dilution steam with the heated hydrocarbon feed stream to produce a mixed feed stream;   (c) separating the mixed feed stream to form (i) a light vapor stream comprising steam and hydrocarbons in vapor phase and (ii) a heavy stream comprising liquid hydrocarbons; and   (d) heating the light vapor stream in the first steam cracking furnace under first steam cracking conditions sufficient to crack the hydrocarbons of the light vapor stream.   
     
     
         2 . The method of  claim 1 , further comprising:
 (e) heating the heavy stream in a second convection section of a second steam cracking furnace to produce a heated heavy stream, wherein at least a portion of the heated heavy stream is in vapor phase;   (f) mixing the heated heavy stream with dilute steam to form a mixed heavy stream; and   (g) heating at least a portion of the mixed heavy stream in one or more radiant coils of the second steam cracking furnace under second steam cracking conditions sufficient to crack the hydrocarbons of the mixed heavy stream.   
     
     
         3 . The method of  claim 2 , further comprising:
 prior to step (e), pretreating the heavy stream in a pretreatment unit.   
     
     
         4 . The method of  claim 3 , wherein the pretreatment unit includes a filtration unit, a cyclone based solid removal unit, a sulfur removal unit, or combinations thereof. 
     
     
         5 . The method of  claim 2 , further comprising:
 prior to step (g), separating the mixed heavy stream to form (I) a heavy vapor stream comprising steam and vaporized hydrocarbons, and (II) a heavy liquid stream comprising liquid hydrocarbons.   
     
     
         6 . The method of  claim 2 , wherein the second steam cracking conditions include a reaction temperature in a range of 750 to 900° C. 
     
     
         7 . The method of  claim 2 , wherein the second steam cracking conditions include a residence time of the second steam cracking furnace in a range of 100 to 1000 ms. 
     
     
         8 . The method of  claim 2 , wherein, in step (e), the heavy stream is heated to a temperature of 150 to 500° C. 
     
     
         9 . The method of  claim 2 , further comprising:
 prior to step (g), heating at least a portion of heavy mixed stream to a temperature of 500 to 700° C.   
     
     
         10 . The method of  claim 1 , wherein the first steam cracking conditions include a reaction temperature in a range of 750 to 900° C. 
     
     
         11 . The method of  claim 1 , wherein the first steam cracking conditions include a residence time of the first steam cracking furnace in a range of 100 to 1000 ms. 
     
     
         12 . The method of  claim 1 , wherein the dilute steam is at a temperature of 180 to 600° C. 
     
     
         13 . The method of  claim 1 , wherein, in step (a), the hydrocarbon feed stream is heated to a temperature of 100 to 400° C. 
     
     
         14 . The method of  claim 1 , further comprising:
 prior to step (d), heating at least a portion of light vapor stream to a temperature of 500 to 700° C.   
     
     
         15 . The method of  claim 2 , further comprising:
 prior to step (d), heating at least a portion of light vapor stream to a temperature of 500 to 700° C.   
     
     
         16 . The method of  claim 3 , further comprising:
 prior to step (d), heating at least a portion of light vapor stream to a temperature of 500 to 700° C.   
     
     
         17 . The method of  claim 4 , further comprising:
 prior to step (d), heating at least a portion of light vapor stream to a temperature of 500 to 700° C.   
     
     
         18 . The method of  claim 5 , further comprising:
 prior to step (d), heating at least a portion of light vapor stream to a temperature of 500 to 700° C.   
     
     
         19 . The method of  claim 6 , further comprising:
 prior to step (d), heating at least a portion of light vapor stream to a temperature of 500 to 700° C.   
     
     
         20 . The method of  claim 7 , further comprising:
 prior to step (d), heating at least a portion of light vapor stream to a temperature of 500 to 700° C.