Fcc dual elevation riser feed distributors for gasoline and light olefin modes of operation

Abstract

A fluid catalytic cracking process includes feeding hydrocarbon into a riser in the presence of a catalyst, cracking the hydrocarbon in the riser in the presence of the catalyst to form a cracked stream, and separating the catalyst from the cracked stream. When in a gasoline mode, the hydrocarbon is fed through a first distributor into the riser, and when in a light olefin mode, the hydrocarbon is fed through a second distributor into the riser. The second distributor is positioned at a higher elevation than the first distributor.

1 . A fluid catalytic cracking process, comprising:
 feeding hydrocarbon into a riser in the presence of a catalyst;   cracking said hydrocarbon in said riser in the presence of said catalyst to form a cracked stream, and   separating said catalyst from said cracked stream,   
     wherein, when in a gasoline mode, said hydrocarbon is fed through a first distributor into said riser, and when in a light olefin mode, said hydrocarbon is fed through a second distributor into said riser, wherein said second distributor is positioned at a higher elevation than said first distributor. 
   
   
       2 . The process of  claim 1 , wherein each one of said distributors comprises a plurality of nozzles having substantially the same elevation and being spaced radially around said riser. 
   
   
       3 . The process of  claim 1 , wherein said separation of catalyst from said cracked stream is performed in a swirl arm arrangement. 
   
   
       4 . The process of  claim 1 , wherein the light olefin mode has residence time of between about 0.5 second and about 2 seconds in said riser. 
   
   
       5 . The process of  claim 1 , wherein propylene-preferential mode has residence time of about 1 to about 2 seconds in said riser. 
   
   
       6 . The process of  claim 1 , wherein gasoline-making mode has residence time of between about 2 seconds and about 5 seconds. 
   
   
       7 . The process of  claim 1 , wherein said FCC process is changeable from one mode to another without shutting the process down. 
   
   
       8 . The process of  claim 1 , wherein said hydrocarbon and steam are fed through same distributor nozzle. 
   
   
       9 . The process of  claim 1 , wherein when in said gasoline mode, said process produces a cracked stream having gasoline vol-% between about 50 and about 70. 
   
   
       10 . The process of  claim 1 , wherein, when in said light olefin mode, said process produces a cracked stream having vol-% of propylene between about 20 and about 40. 
   
   
       11 . The process of  claim 1 , wherein said temperature at the outlet of said riser is between about 490° and about 630° C. 
   
   
       12 . The process of  claim 1 , wherein said catalyst is about 2 to about 20 wt-% medium or smaller pore zeolite while operating in said light olefin mode and less than 0.5 wt-% medium or smaller pore zeolite while operating in said gasoline mode. 
   
   
       13 . The process of  claim 1 , wherein said temperature in said reactor in said light olefin mode is between about 550° and about 590° C. 
   
   
       14 . The process of  claim 1 , wherein said temperature in said reactor in said gasoline-preferential mode is between about 500° and about 550° C. 
   
   
       15 . The process of  claim 1 , wherein more steam is added to the riser when operating in the light olefin mode than when operating in the gasoline mode. 
   
   
       16 . The process of  claim 1 , wherein a greater catalyst to feed ratio is used when operating in the light olefin mode than when operating in the gasoline mode. 
   
   
       17 . The process of  claim 1  further comprising the step of quenching said cracked stream with a liquid after exiting said riser. 
   
   
       18 . A fluid catalytic cracking process, comprising:
 feeding hydrocarbon into a first region having a first predetermined elevation in a riser in the presence of a catalyst, wherein said thirst region and said first predetermined elevation are selected to provide a greater yield of light olefins in a light olefin mode;   cracking said hydrocarbon in said riser in the presence of said catalyst to form a cracked stream;   separating said catalyst from said cracked stream; and   changing from said light olefin mode to a gasoline mode by changing the location of the feed of said hydrocarbon to a second region having a second predetermined elevation lower than that of said first predetermined elevation to produce a smaller yield of light olefins than when operated in the light olefin mode.   
   
   
       19 . A fluid catalytic cracking process, comprising:
 feeding hydrocarbon into a riser in the presence of a catalyst;   cracking said hydrocarbon in said riser in the presence of said catalyst to form a cracked stream; and   separating said catalyst from said cracked stream,   
     wherein, when in a recracking mode, said hydrocarbon is fed through a first distributor into a mixing chamber below said riser. 
   
   
       20 . The process of  claim 19  further comprising the step of introducing C 8 -feed into said mixing chamber below said riser.