Feeding pyoil and steam at cracker furnace crossover

Abstract

Olefins are made by passing a cracker stream through a convection section of a cracker furnace; introducing steam and a stream comprising a recycle content pyrolysis oil into the cracker stream to form a combined stream, and the steam, r-pyoil stream, or both are introduced downstream of the inlet to the convection section, such as between the inlet to the coils and the radiant zone, or at the cross-over. Additionally, dilution steam can be added to a stream of r-pyrolysis to form a steam-diluted r-pyoil stream which is then introduced into a cracker furnace at any location, such as downstream of the inlets to the convection box or at a cross-over.

What is claimed is: 
     
         1 . A method for making olefins, said method comprising:
 (a) passing a cracker stream through a convection section of a cracker furnace;   (b) introducing steam and a stream comprising a recycle content pyrolysis oil composition (r-pyoil) into said cracker stream to form a combined stream, wherein at least one of said steam and the r-pyoil stream are introduced downstream of the inlet to said convection section; and   (c) cracking said combined stream in said cracker furnace to form an olefin-containing effluent stream.   
     
     
         2 . The method of  claim 1 , wherein r-pyoil is co-fed with steam at the location where steam is introduced into the convection zone. 
     
     
         3 . The method of  claim 1 , wherein said r-pyoil is present in said combined stream in an amount of at least 5 weight percent, based on the total weight of the combined stream. 
     
     
         4 . The method of  claim 1 , wherein said combined stream has a steam-to-hydrocarbon ratio of at least 0.2:1. 
     
     
         5 . The method of  claim 1 , wherein the residence time of the cracker feed in the radiant section is not more than 2 seconds. 
     
     
         6 . The method of  claim 1 , wherein said r-pyoil stream is introduced downstream of the inlet to said convection section. 
     
     
         7 . The method of  claim 1 , wherein said r-pyoil stream is introduced at a cross-over zone between said convection section and said radiant section. 
     
     
         8 . The method of  claim 1 , wherein said steam is introduced downstream of the inlet to said convection section. 
     
     
         9 . The method of  claim 1 , wherein said steam is introduced at a cross-over zone between said convection section and said radiant section. 
     
     
         10 . The method of  claim 1 , wherein said r-pyoil stream and said steam are combined and the combined stream is introduced at a cross-over zone between said convection section and a radiant section of said furnace. 
     
     
         11 . The method of  claim 1 , wherein said cracker stream comprises predominantly propane or predominantly ethane. 
     
     
         12 . The method of  claim 1 , wherein said cracker stream comprises at least 55 weight percent of non-recycled C 2  to C 4  components, based on the total weight of said cracker stream. 
     
     
         13 . A method for making olefins, said method comprising:
 (a) adding dilution steam to a stream comprising a recycle content pyrolysis oil composition (r-pyoil) to form a steam-diluted r-pyoil stream;   (b) introducing said steam-diluted r-pyoil stream into a cracker stream in a cracker furnace; and   (c) cracking the combined stream in a radiant section of said furnace to form an olefin-containing effluent stream,   
       wherein said pyrolysis oil and dilution steam are introduced into said cracker stream upstream of the entrance to said radiant section. 
     
     
         14 . The method of  claim 13 , wherein said adding of step (a) occurs upstream of an inlet to a convection section of said furnace. 
     
     
         15 . The method of  claim 13 , wherein said adding of step (a) occurs in the cross-over zone of said furnace. 
     
     
         16 . The method of  claim 13 , wherein said steam-diluted r-pyoil stream is atomized prior to said introducing. 
     
     
         17 . The method of  claim 13 , wherein said introducing of step (b) occurs upstream of the inlet to a convection section of said furnace. 
     
     
         18 . A method for making olefins, said method comprising:
 (a) passing a cracker stream through convection tubes in a cracker furnace;   (b) combining a stream comprising a recycle content pyrolysis oil composition (r-pyoil) with steam to form a steam-diluted r-pyoil stream;   (c) combining said steam-diluted r-pyoil stream with said cracker stream in a cross-over zone of said cracker furnace to provide a combined cracker stream; and   (d) cracking said combined cracker stream in a radiant section of said cracker furnace to form an olefin-containing effluent stream.   
     
     
         19 . The method of  claim 18 , further comprising, prior to said combining of step (b), heating a feed stream comprising r-pyoil to form a heated r-pyoil stream and wherein step (b) comprises combining said heated r-pyoil stream with said steam to form said steam-diluted r-pyoil stream. 
     
     
         20 . The method of  claim 19 , wherein said steam-diluted r-pyoil stream has a vapor fraction of at least 0.75. 
     
     
         21 . The method of  claim 20 , wherein said r-pyoil is present in said combined cracker stream in an amount of at least 5 weight percent, based on the total weight of the combined stream. 
     
     
         22 . The method of  claim 21 , wherein the residence time of the combined cracker stream in the radiant section is not more than 1.1 seconds.