Process and system for enhancing petrochemical feedstock

Abstract

The present disclosure provides a process scheme for enhancing the petrochemical feedstock through the routing of oligomer products obtained after C4 oligomerization to fluid catalytic cracking unit. More particularly, the present disclosure relates to a process and a system for integrating oligomerization of C 4 hydrocarbon components and fluid catalytic cracking for enhancing the recovery of C 3+ hydrocarbon components from FCC off-gases.

We claim: 
     
         1 . A process for integrating oligomerization of C 4  hydrocarbon components and fluid catalytic cracking (FCC) for enhancing the recovery of C 3+  hydrocarbon components from FCC off-gases, the process comprising:
 introducing a hydrocarbon feed stream ( 210 ) to a riser reactor ( 100 ) of a fluid catalytic cracking unit and catalytic cracking of the hydrocarbon feed stream in the presence of a regenerated catalyst to obtain a cracked product stream ( 211 ); 
 routing the cracked product stream ( 211 ) to a main fractionator ( 102 ) and fractionating the cracked product stream ( 211 ) to obtain fractions of a top stream ( 212 ) comprising a lighter cut, an intermediate stream ( 215 ) comprising a middle distillate cut, and a bottom stream ( 221 ) comprising heavier hydrocarbon components; 
 cooling the top stream ( 212 ) and subjecting the cooled top stream to a reflux drum ( 112 ) for separating the cooled top stream into a vapor stream ( 222 ), an aqueous stream ( 242 ), and a liquid stream ( 246 ) comprising unstabilized gasoline, wherein the unstabilized gasoline comprises majorly C 5+  to C 12  hydrocarbon components and C 5 -hydrocarbons components; 
 subjecting the vapor stream ( 222 ) in a compressor ( 113 ) to compress the vapor stream ( 222 ) and cooling to obtain a cooled compressed stream ( 223 ), and further subjecting the cooled compressed stream ( 223 ) to a high pressure separator ( 114 ) for separating a liquid hydrocarbon stream ( 230 ) from an off-gases stream ( 232 ), wherein the off-gases stream ( 232 ) comprises lighter components, C 2  hydrocarbon components and C 3+  hydrocarbon components; 
 routing a first part of the un-stabilized gasoline stream ( 213 ) to the main fractionator ( 102 ), and routing the off-gases stream ( 232 ) to a primary absorber ( 103 ); 
 routing a second part of the unstabilized gasoline stream ( 214 ) and a part of a stabilized gasoline stream ( 224 ) from a stabilizer column ( 107 ) to the primary absorber ( 103 ) and contacting with the off-gases stream ( 232 ) for recovering the C 3+  hydrocarbon components to obtain a bottom liquid stream ( 225 ) and a top off-gases stream ( 226 ) or alternatively routing a second part of the unstabilized gasoline stream ( 214 ), a part of a stabilized gasoline stream ( 224 ) from a stabilizer column ( 107 ), and a bottom oligomer product stream ( 241 ) from a separation column ( 110 ) to the primary absorber ( 103 ) and contacting with the off-gases stream ( 232 ) for recovering the C 3+  hydrocarbon components to obtain the bottom liquid stream ( 225 ) and the top off-gases stream ( 226 ); 
 feeding the bottom liquid stream ( 225 ) to the high pressure separator ( 114 ) to obtain a liquid hydrocarbon stream ( 230 ), feeding the liquid hydrocarbon stream ( 230 ) to a C 2  stripper ( 106 ) for stripping off H 2 S, C 2  hydrocarbon components, and lighter components, and further feeding a bottom stream ( 233 ) obtained from the C 2  stripper ( 106 ) to a stabilizer column ( 107 ) to obtain a bottom stabilized gasoline stream ( 235 ) and a top liquefied petroleum gas stream ( 234 ), wherein the top liquefied petroleum gas stream ( 234 ) comprises C 3  and C 4  hydrocarbon components; 
 routing the top liquefied petroleum gas stream ( 234 ) to a C 3 /C 4  splitter column ( 108 ) for separating C 3  and C 4  hydrocarbon components to obtain an overhead stream ( 237 ) comprising C 3  hydrocarbon components and a bottom stream ( 238 ) comprising C 4  hydrocarbon components; 
 subjecting the bottom stream ( 238 ) to an oligomerization reactor ( 109 ) and oligomerizing the C 4  hydrocarbon components present in the bottom stream ( 238 ) to obtain a reactor product ( 239 ) comprising C 8+  hydrocarbon components and unconverted C4 hydrocarbon components; 
 feeding the reactor product ( 239 ) to a separation column ( 110 ) and separating the unconverted C 4  hydrocarbon components and C 8+  hydrocarbon components to obtain a top stream ( 240 ) comprising unconverted C 4  hydrocarbon components and the bottom oligomer product stream ( 241 ) comprising C 8+  hydrocarbon components, and routing the bottom oligomer product stream ( 241 ) to a third absorber column ( 105 ) or alternatively routing the bottom oligomer product stream ( 241 ) to the primary absorber column ( 103 ); and 
 routing the top off-gases stream ( 226 ) or alternatively routing a second part of the top off-gases stream ( 244 ) from the primary absorber ( 103 ) to a second absorber column ( 104 ) and contacting with a first stream ( 219 ) for recovering C 3+  hydrocarbon components present in the top off-gases stream ( 226 ) or the second part of the top off-gases stream ( 244 ). 
 
     
     
         2 . The process as claimed in  claim 1 , wherein the intermediate stream ( 215 ) obtained from the main fractionator ( 102 ) comprising the middle distillate cut is routed to a stripper column ( 111 ) and contacted with steam to strip off lighter components and a heavier stream, wherein the lighter components are routed back to the main fractionator ( 102 ), and the heavier stream comprising stabilized cycle oil after cooling is partially routed to the second absorber column ( 104 ) via the first stream ( 219 ) and partially withdrawn as a product via a second stream ( 220 ). 
     
     
         3 . The process as claimed in  claim 1 , wherein the process further comprising:
 routing a first part of the top off-gases stream ( 243 ) from the primary absorber ( 103 ) comprising C 3+  hydrocarbon components to the third absorber column ( 105 ) and contacting with the bottom oligomer product stream ( 241 ) for recovering C 3+  hydrocarbon components present in the first part of the top off-gases stream ( 243 ) to obtain a liquid bottom stream ( 228 ) and a top gaseous stream ( 227 ), and feeding the liquid bottom stream ( 228 ) to the riser reactor ( 100 ) of the fluid catalytic cracking unit, wherein the liquid bottom stream ( 228 ) comprises recovered C 3+  hydrocarbon components and C 8+  hydrocarbon components.   
     
     
         4 . The process as claimed in  claim 1 , wherein the catalyst is supplied from a regenerator ( 101 ) of the fluid catalytic cracking unit, and the catalytic cracking is performed in a continuous fluidized bed reactor at a riser top temperature in a range of 530° C. to 600° C., a catalyst to oil ratio of 10:1 to 25:1, and a catalyst contact time in a range of 1-10 seconds. 
     
     
         5 . The process as claimed in  claim 1 , wherein the fractionation is performed at a bottom pressure in a range of 1 to 5 bar, a top temperature in a range of 100° C. to 135° C., and a bottom temperature in a range of 300° C. to 400° C. 
     
     
         6 . The process as claimed in  claim 1 , wherein the recovery in the primary absorber ( 103 ), the second absorber column ( 104 ), and the third absorber column ( 105 ) is performed at a top pressure in a range of 10 to 17 bar, a top temperature in a range of 30° C. to 60° C., and a liquid to gas actual volume ratio in a range of 0.05:1 to 0.25:1. 
     
     
         7 . The process as claimed in  claim 1 , wherein the hydrocarbon feed stream ( 210 ) comprises vacuum gas oil, resid oil fraction, or a combination thereof. 
     
     
         8 . The process as claimed in  claim 1 , wherein the cooling is carried out through a condenser. 
     
     
         9 . A system for integrating oligomerization of C 4  hydrocarbon components and fluid catalytic cracking (FCC) for enhancing the recovery of C 3+  hydrocarbon components from FCC off gases, the system comprising:
 a riser reactor ( 100 ) of a fluid catalytic cracking unit is configured to receive a hydrocarbon feed stream ( 210 ) and a regenerated catalyst and conduct a catalytic cracking reaction to obtain a cracked product stream ( 211 ); 
 a main fractionator ( 102 ) is configured to receive the cracked product stream ( 211 ) from the riser reactor ( 100 ) and perform fractionation to obtain fractions of a top stream ( 212 ) comprising a lighter cut, an intermediate stream ( 215 ) comprising a middle distillate cut, and a bottom stream ( 221 ) comprising heavier hydrocarbon components; 
 a reflux drum ( 112 ) is configured to receive the top stream ( 212 ) from the main fractionator ( 102 ) after cooling in a condenser to obtain a vapor stream ( 222 ), an aqueous stream ( 242 ), and a liquid stream ( 246 ) comprising unstabilized gasoline, wherein the unstabilized gasoline comprises majorly C 5+  to C 12  hydrocarbon components and C 5 -hydrocarbons components; 
 a compressor ( 113 ) is configured to receive the vapor stream ( 222 ) from the reflux drum ( 112 ) and compress the vapor stream ( 222 ) followed by cooling to obtain a cooled compressed stream ( 223 ); 
 a high pressure separator ( 114 ) is configured to receive the cooled compressed stream ( 223 ) from the compressor ( 113 ) and perform separation of a liquid hydrocarbon stream ( 230 ) from an off-gases stream ( 232 ), wherein the off-gases stream ( 232 ) comprises lighter components, C 2  hydrocarbon components and C 3+  hydrocarbon components; 
 a primary absorber ( 103 ) is configured to receive a second part of the unstabilized gasoline stream ( 214 ) from the reflux drum ( 112 ), a part of a stabilized gasoline stream ( 224 ) from a stabilizer column ( 107 ), and the off-gases stream ( 232 ) from the high pressure separator ( 114 ) and perform recovery of the C 3+  hydrocarbon components present in the off-gases stream ( 232 ) to obtain a bottom liquid stream ( 225 ) and a top off-gases stream ( 226 ) or alternatively configured to receive the second part of the unstabilized gasoline stream ( 214 ) from the reflux drum ( 112 ), the part of the stabilized gasoline stream ( 224 ) from the stabilizer column ( 107 ), and a bottom oligomer product stream ( 241 ) from a separation column ( 110 ) and perform recovery of the C 3+  hydrocarbon components present in the off-gas stream ( 232 ) from HP separator ( 114 ) to obtain the bottom liquid stream ( 225 ) and the top off-gases stream ( 226 ), further the primary absorber ( 103 ) is configured to send the bottom liquid stream ( 225 ) to the high pressure separator ( 114 ); 
 a C 2  stripper ( 106 ) is configured to receive the liquid hydrocarbon stream ( 230 ) from the high pressure separator ( 114 ) and perform stripping off H 2 S, C 2  hydrocarbon components, and lighter components present in the liquid hydrocarbon stream ( 230 ) to obtain a bottom stream ( 233 ); 
 a stabilizer column ( 107 ) is configured to receive the bottom stream ( 233 ) from the C 2  stripper ( 106 ) and to separate a bottom stabilized gasoline stream ( 235 ) and a liquefied petroleum gas stream ( 234 ) from the bottom stream ( 233 ), wherein the top liquefied petroleum gas stream ( 234 ) comprises C 3  and C 4  hydrocarbon components; 
 a C 3 /C 4  splitter column ( 108 ) is configured to receive the top liquefied petroleum gas stream ( 234 ) from the stabilizer column ( 107 ) and perform separation of C 3  and C 4  hydrocarbon components present in the liquefied petroleum gas stream ( 234 ) to obtain an overhead stream ( 237 ) comprising C 3  hydrocarbon components and a bottom stream ( 238 ) comprising C 4  hydrocarbon components; 
 an oligomerization reactor ( 109 ) is configured to receive the bottom stream ( 238 ) from the C 3 /C 4  splitter column ( 108 ) and perform oligomerization of the C 4  hydrocarbon components present in the bottom stream ( 238 ) to obtain a reactor product ( 239 ) comprising C 8+  hydrocarbon components and unconverted C 4  hydrocarbon components; 
 a separation column ( 110 ) is configured to receive the reactor product ( 239 ) from the oligomerization reactor ( 109 ) and perform separation of C 8+  hydrocarbon components and unconverted C 4  hydrocarbon components to obtain a bottom oligomer product stream ( 241 ) comprising C 8+  hydrocarbon components and a top stream ( 240 ) comprising unconverted C 4  hydrocarbon components, further configured to release the top stream ( 240 ) comprising unconverted C 4  hydrocarbon components; and 
 a second absorber column ( 104 ) is configured to receive the top off-gases stream ( 226 ) or alternatively configured to receive a second part of the top off-gases stream ( 244 ) from the primary absorber ( 103 ) and a first stream ( 219 ) from a stripper column ( 111 ) and perform recovery of the C 3+  hydrocarbon components present in the top off-gases stream ( 226 ) or the second part of the top off-gases stream ( 244 ). 
 
     
     
         10 . The system as claimed in  claim 9 , wherein the system further comprises:
 a regenerator ( 101 ) is configured to receive a spent catalyst from the riser reactor ( 100 ) and regenerate the catalyst by burning coke in the presence of air or oxygen containing gases to obtain the regenerated catalyst, and further, the regenerator ( 101 ) is configured to send the regenerated catalyst to the riser reactor ( 100 ).   
     
     
         11 . The system as claimed in  claim 9 , wherein the system further comprises:
 a stripper column ( 111 ) that is configured to receive the intermediate stream ( 215 ) from the main fractionator ( 102 ) and steam and perform stripping off lighter components and a heavier stream, wherein the lighter components are routed back to the main fractionator ( 102 ), and the heavier stream comprising stabilized cycle oil after cooling is partially routed to the second absorber column ( 104 ) via the first stream ( 219 ) and partially withdrawn as a product via a second stream ( 220 ).   
     
     
         12 . The system as claimed in  claim 9 , wherein the system further comprises:
 a third absorber column ( 105 ) is configured to receive the bottom oligomer product stream ( 241 ) from the separation column ( 110 ) and a first part of the top off-gases stream ( 243 ) from the primary absorber ( 103 ) comprising C 3+  hydrocarbon components and perform recovery of C 3+  hydrocarbon components present in the first part of the top off-gases stream ( 243 ) to obtain a liquid bottom stream ( 228 ) and a top gaseous stream ( 227 ), further the third absorber column ( 105 ) is configured to send the bottom stream ( 228 ) to the riser reactor ( 100 ) of the fluid catalytic cracking unit, wherein the liquid bottom stream ( 228 ) comprises recovered C 3+  hydrocarbon components and C 8+  hydrocarbon components.   
     
     
         13 . The system as claimed in  claim 9 , wherein the main fractionator ( 102 ) is a distillation column, wherein the distillation column is employed with a plurality of trays, random packing, structured packing or a combination thereof, and wherein the distillation column is employed with one or more pump-arounds. 
     
     
         14 . The system as claimed in  claim 9 , wherein the fluid catalytic cracking unit is located upstream of the main fractionator ( 102 ), wherein the primary absorber ( 103 ), the second absorber column ( 104 ), and the third absorber column ( 105 ) are located downstream of the main fractionator ( 104 ), and wherein the oligomerization reactor ( 109 ) is located upstream of the third absorber column ( 105 ).