Optimized cracker conditions to accept pyrolysis oil

Abstract

Recycle content pyoil is cracked in a cracker furnace to make olefins and the coil outlet temperature of the r-pyoil fed coils can be lowered by adding r-pyoil to the cracker feedstock, or alternatively, the coil outlet temperature of the r-pyoil fed tubes can rise if the mass flow rates of the combined cracker stream containing r-pyoil are kept the same or lowered. Further, increasing the hydrocarbon mass flow rate by addition of r-pyoil can be achieved to also increase the output of ethylene and propylene in the cracker effluent. The cracker furnace can accept ethane and/or propane feedstocks in vapor form along with a liquid and/or vapor feed of r-pyoil.

What is claimed is: 
     
         1 . A method for making one or more olefins, said method comprising:
 (a) cracking a cracker stream in a cracking unit at a first coil outlet temperature;   (b) subsequent to step (a), adding a stream comprising a recycle content pyrolysis oil composition (r-pyoil) to said cracker stream to form a combined cracker stream; and   (c) cracking said combined cracker stream in said cracking unit at a second coil outlet temperature, wherein said second coil outlet temperature is lower than said first coil outlet temperature.   
     
     
         2 . The method of  claim 1 , wherein the hydrocarbon mass flow rate of the combined cracker stream is substantially the same as or higher than the hydrocarbon mass flow rate of the cracker stream in step (a). 
     
     
         3 . The method of  claim 1 , wherein said cracker stream comprises a predominantly C 2 -C 4  hydrocarbon containing stream. 
     
     
         4 . The method of  claim 1 , wherein said r-pyoil has a 50% boiling point that is at least 5 percent higher than the 50% boiling point of said cracker stream. 
     
     
         5 . The method of  claim 2 , wherein said second coil outlet temperature is at least 35° C. lower than said first coil outlet temperature. 
     
     
         6 . The method of  claim 1 , wherein said r-pyoil is obtained from the pyrolysis of waste plastic. 
     
     
         7 . The method of  claim 1 , further comprising, prior to said cracking, making said r-pyoil in a pyrolysis unit located within 4 kilometers of a cracker unit within which said cracking is carried out. 
     
     
         8 . A method for making one or more olefins, comprising:
 (a) cracking a cracker stream in a cracking furnace at a first hydrocarbon mass flow rate (MF1);   (b) subsequent to step (a), adding r-pyoil to said cracker stream to form a combined cracker stream having a second hydrocarbon mass flow rate (MF2) that is higher than MF1; and   (c) cracking said combined cracker stream at MF2 in said cracking unit to obtain an olefin-containing effluent comprising ethylene and propylene, said olefin-containing effluent having a combined output of ethylene and propylene that same as or higher than the output of ethylene and propylene obtained by cracking said cracker stream at MF1.   
     
     
         9 . The method of  claim 8 , wherein the increase in the combined output of ethylene and propylene is accomplished without varying the heat flux in the furnace. 
     
     
         10 . The method of  claim 8 , wherein the increase in the combined output of ethylene and propylene is accomplished without varying the fuel feed rate to the burners assigned to heat at least one of the coils fed with r-pyoil. 
     
     
         11 . The method of  claim 8 , wherein the increase in the combined output of ethylene and propylene is accomplished without varying the fuel feed rate to any of the burners in the furnace. 
     
     
         12 . The method of  claim 8 , wherein the higher hydrocarbon mass flow rate MF2 is in at least one of the r-pyoil fed coils in the furnace. 
     
     
         13 . The method of  claim 8 , wherein the olefin-containing effluent stream has a total output of propylene and ethylene from the combined cracker stream at MF2 that is the same as or higher than the output of propylene and ethylene of an effluent stream obtained by cracking the same cracker feed but without r-pyoil by at least 1%. 
     
     
         14 . The method of  claim 8 , wherein the olefin-containing effluent stream has a total wt. % of propylene and ethylene from the combined cracker stream at MF2 that is the same as or higher than the wt. % of propylene and ethylene of an effluent stream obtained by cracking the same cracker feed but without r-pyoil by at least 1%.