Integrated hydrocarbon cracking and product olefin cracking

Abstract

Processing scheme and arrangement for increasing the relative yield of light olefins involves integration of the cracking a heavy hydrocarbon feedstock to produce an effluent comprising a range of hydrocarbon products including C 4 -C 7 olefins and the subsequent cracking at least a portion of the C 4 -C 7 olefins to produce additional light olefins.

1 . An integrated process for cracking a heavy hydrocarbon feedstock to produce an effluent comprising a range of hydrocarbon products including C 4 -C 7  olefins and for subsequently cracking at least a portion of the C 4 -C 7  olefins to produce additional C 2  and C 3  olefins, said integrated process comprising: 
 contacting the heavy hydrocarbon feedstock with a hydrocarbon cracking catalyst in a primary fluidized bed reactor to produce a hydrocarbon effluent comprising a range of hydrocarbon products comprising C 4 -C 7  olefins;    separating the hydrocarbon effluent in a hydrocarbon separation system to recover selected hydrocarbon fractions including a first hydrocarbon fraction comprising C 4 -C 7  olefins;    cracking at least a portion of the first hydrocarbon fraction to form a cracked olefin effluent comprising C 2  and C 3  olefins; and    treating the cracked olefin effluent in the hydrocarbon separation system to recover at least the C 2  and C 3  olefins.    
     
     
         2 . The integrated process of  claim 1  additionally comprising separating the cracked olefin effluent to form a first stream comprising primarily C 3  hydrocarbons and a second stream comprising primarily C 4  hydrocarbons.  
     
     
         3 . The integrated process of  claim 1  wherein the separation of the hydrocarbon effluent in the hydrocarbon separation system results in the formation of a wet gas stream comprising C 5  and lighter hydrocarbons.  
     
     
         4 . The integrated process of  claim 3  additionally comprising: 
 compressing the wet gas stream via a first compressor; and    treating the compressed wet gas stream in a gas concentration system to at least separately concentrate and remove C 2  hydrocarbon products, concentrate and recover C 3  and C 4  hydrocarbon products and separate C 5  olefin hydrocarbon products;    wherein the cracking of at least a portion of the first hydrocarbon fraction comprises cracking the separated C 5  olefin hydrocarbon products to form a cracked olefin effluent comprising C 2 -C 4  hydrocarbons including C 2  and C 3  olefins.    
     
     
         5 . The integrated process of  claim 4  additionally comprising separating the cracked olefin effluent to form a first stream comprising primarily C 3  hydrocarbons and a second stream comprising primarily C 4  hydrocarbons.  
     
     
         6 . The integrated process of  claim 5  wherein the first stream is compressed via the first compressor prior to being treated in the gas concentration system.  
     
     
         7 . The integrated process of  claim 1  wherein the first hydrocarbon fraction consists essentially of C 5  olefins.  
     
     
         8 . The integrated process of  claim 7  wherein the C 5  olefins consist essentially of n-C 5  olefins.  
     
     
         9 . The integrated process of  claim 1  wherein the hydrocarbon separation system additionally results in the recovery of a separated stream consisting essentially of a material selected from the group consisting of C 2  hydrocarbons, C 3  hydrocarbons and C 4  hydrocarbons.  
     
     
         10 . An integrated process for cracking a heavy hydrocarbon feedstock to produce an effluent comprising a range of hydrocarbon products including C 5  olefins and for cracking C 5  olefin hydrocarbon products to produce C 2  and C 3  olefins, said integrated process comprising: 
 contacting the heavy hydrocarbon feedstock with a hydrocarbon cracking catalyst in a primary fluidized bed reactor to produce a hydrocarbon effluent comprising a range of hydrocarbon products including C 5  olefins;    separating the hydrocarbon effluent to form a wet gas stream comprising C 5  and lighter hydrocarbons;    compressing the wet gas stream via a first compressor;    treating the compressed wet gas stream in a gas concentration system to at least separately concentrate and remove C 2  hydrocarbon products, concentrate and recover C 3  and C 4  hydrocarbon products and separate C 5  olefin hydrocarbon products;    cracking the separated C 5  olefin hydrocarbon products to form a cracked olefin effluent comprising C 2 -C 4  hydrocarbons including C 2  and C 3  olefins; and    treating the cracked olefin effluent in the gas concentration system to recover the C 2  and C 3  olefins.    
     
     
         11 . The integrated process of  claim 10  additionally comprising separating the cracked olefin effluent to form a first stream comprising primarily C 3  hydrocarbons and a second stream comprising primarily C 4  hydrocarbons.  
     
     
         12 . The integrated process of  claim 11  wherein the first stream is compressed via the first compressor prior to being treated in the gas concentration system.  
     
     
         13 . The integrated process of  claim 10  wherein the separated C 5  olefin hydrocarbon products consist essentially of n-C 5  olefin hydrocarbon products.  
     
     
         14 . The integrated process of  claim 13  wherein the separated C 5  olefin hydrocarbon products consist of n-C 5  olefin hydrocarbon products.  
     
     
         15 . An integrated system for cracking a heavy hydrocarbon feedstock to produce an effluent comprising a range of hydrocarbon products including C 5  olefins and for cracking C 5  olefin hydrocarbon products to produce C 2  and C 3  olefins, said integrated system comprising: 
 a fluidized catalytic cracking reactor wherein the heavy hydrocarbon feedstock contacts a hydrocarbon cracking catalyst at hydrocarbon cracking reaction conditions to produce a hydrocarbon effluent comprising a range of hydrocarbon products including C 5  olefins;    a separator to separate the hydrocarbon effluent to form a wet gas stream comprising C 5  and lighter hydrocarbons;    a first compressor to compress the wet gas stream;    a gas concentration system wherein the compressed wet gas stream is processed to at least separately concentrate and remove C 2  paraffinic hydrocarbon products, concentrate and recover C 3  and C 4  hydrocarbon products and separate C 5  olefin hydrocarbon products;    an olefin cracking reactor wherein at least a portion of the C 5  olefin hydrocarbon products are cracked to form a cracked olefin effluent comprising C 2 -C 4  hydrocarbons including C 2  and C 3  olefins; and    a first return line wherein at least a portion of the cracked olefin effluent is introduced into the first compressor and subsequently processed through the gas concentration system.    
     
     
         16 . The system of  claim 15  additionally comprising a cracked olefin effluent separation system effective to separate the cracked olefin effluent into a vapor stream comprising C 2  and C 3  olefins, a liquid stream comprising C 4  hydrocarbons and a third stream comprising C 5  hydrocarbons.  
     
     
         17 . The system of  claim 16  wherein at least a portion of the vapor stream is introduced into the first compressor via the first return line.  
     
     
         18 . The system of  claim 16  additionally comprising a second return line wherein at least a portion of the liquid stream is introduced into the gas concentration system at a point subsequent to the first compressor.  
     
     
         19 . The system of  claim 16  additionally comprising an olefin cracking reactor return line wherein at least a portion of the third stream C 5  hydrocarbons are returned to the olefin cracking reactor.  
     
     
         20 . The system of  claim 15  wherein the C 5  olefin hydrocarbon products cracked in the olefin cracking reactor consist essentially of n-C 5  olefin hydrocarbon products.