Cat cracker gas plant process for increased olefins recovery

A process for recovering olefins from hydrocarbons produced in a fluid catalytic cracking unit, the process comprising:

• a. providing a fluid catalytic cracking reactor effluent stream to a Main Fractionator distillation tower, said reactor effluent stream comprising hydrogen, methane, ethylene, ethane, propylene, propane, butylene, butane, and C5 and heavier components;
• b. operating said Main Fractionator tower to produce therefrom (i) a wet gas stream comprising hydrogen, methane, ethylene, ethane, propylene, propane, butylene, and butane, and (ii) a Main Fractionator overhead liquid stream comprising predominantly C5 and heavier components;
• c. pressurizing the chemical components of said wet gas stream to a pressure in the range of approximately 120-300 psig;
• d. pressuring the chemical components of said Main Fractionator overhead liquid stream to a pressure in the range of approximately 120-300 psig;
• e. cooling the chemical components of said wet gas stream to a temperature in the range of approximately 80-120 degrees F.;
• f. cooling the chemical components of said Main Fractionator overhead liquid stream to a temperature in the range of approximately 80-120 degrees F.;
• g. feeding the chemical components of said wet gas stream and said Main Fractionator overhead liquid steam to a separator vessel operated at a pressure of approximately 120-270 psig;
• h. yielding from said separator vessel (i) a first stream comprising a major portion of said propylene and propane from said reactor effluent and substantially all of said ethane, ethylene, methane, and hydrogen from said reactor effluent, and (ii) a second stream comprising C5 and heavier compounds;
• and wherein the second stream further comprises a portion of the propylene and propane from said reactor effluent;
• i. feeding said second stream from said separator vessel to a stripper tower;
• j. operating said stripper tower to remove as a stripper overhead stream a major portion of the propane and propylene from said second stream fed to said stripper tower;
• k. feeding said stripper overhead stream into the hydrocarbons entering said separator vessel;
• and
• l. yielding from said stripper tower bottom a de-propanized liquid stream.

A process for recovering olefins from hydrocarbons produced in a fluid catalytic cracking unit, the process comprising:

• a. providing a fluid catalytic cracking reactor effluent stream to a Main Fractionator distillation tower, said reactor effluent stream comprising hydrogen, methane, ethylene, ethane, propylene, propane, butylene, butane, and C5 and heavier components;
• b. operating said Main Fractionator tower to produce, therefrom (i) a wet gas stream comprising hydrogen, methane, ethylene, ethane, propylene, propane, butylene, and butane, and (ii) a Main Fractionator overhead liquid stream comprising predominantly C5 and heavier components;
• c. pressurizing the chemical components of said wet gas stream to pressure in the range of approximately 120-300 psig;
• d. pressuring the chemical components of said Main Fractionator overhead liquid stream to pressure in the range of approximately 120-300 psig;
• e. cooling the chemical components of said wet gas stream to a temperature in the range of approximately 80-120 degrees F.;
• f. cooling the chemical components of said Main Fractionator overhead liquid stream to a temperature in the range of approximately 80-120 degrees F.;
• g. feeding the chemical components of said wet gas stream and said Main Fractionator overhead liquid steam to a separator vessel operated at a pressure of approximately 120-270 psig;
• h. yielding from said separator vessel (i) a first stream comprising a major portion of said propylene and propane from said reactor effluent and substantially all of said ethane, ethylene, methane, and hydrogen from said reactor effluent, and (ii) a second stream comprising propane and heavier compounds;
• i. processing said first stream from said separator to separate therefrom substantially all of said methane and hydrogen thereby producing an ethylene and heavier stream comprising a major portion of said ethylene, ethane, propylene and propane from said reactor effluent stream;
• j. feeding said ethylene and heavier stream to a deethanizer tower;
• k. producing from said deethanizer tower a deethanizer overhead stream comprising a major portion of said ethylene and ethane from said reactor effluent stream and a deethanizer bottoms stream comprising a major portion of said propylene and propane from said reactor effluent stream;
• l. feeding said deethanizer bottoms stream to a depropanizer tower;
• m. producing from said depropanizer tower a depropanizer overhead stream comprising propylene and propane and a depropanizer bottoms stream comprising butylene and heavier components;
• n. feeding said second stream from said separator vessel to a stripper tower;
• o. operating said stripper tower to remove as a stripper overhead stream a major portion of the propane from said second stream fed to said stripper tower;
• p. feeding said stripper overhead stream into the hydrocarbons entering said separator vessel;
• and
• q. yielding from said stripper tower bottom a de-propanized liquid stream.

A process for recovering olefins from a mixture of hydrocarbons from a fluid catalytic cracking unit comprising the steps of:

• a. providing a fluid catalytic cracking reactor effluent stream to a Main Fractionator distillation tower, said reactor effluent stream comprising hydrogen, methane, ethylene, ethane, propylene, propane, butylene, butane, naptha, and water;
• b. operating said Main Fractionator to produce (i) a wet gas stream comprising hydrogen, methane, ethylene, propylene, propane, butylene, butane, naptha, and water, and (ii) a Main Fractionator overhead liquid stream including predominantly naptha;
• c. feeding said wet gas stream and said Main Fractionator overhead liquid stream to a separator vessel operated at a pressure of 120-270 psig and a temperature in the range of 80-120 degrees F.;
• d. yielding from said separator vessel (i) a first stream containing a major portion of said propane and propylene and substantially all of said ethane, ethylene, methane, and hydrogen and a portion of said water, and (ii) a second stream comprising butylene and heavier components;
• e. removing water from said first stream;
• f. chilling said first stream, thereby condensing a portion thereof and forming a liquid hydrogen-lean stream and a gaseous hydrogen-rich stream;
• g. feeding said liquid hydrogen-lean stream to a Deethanizer tower;
• h. operating said Deethanizer tower at a pressure of approximately 225-450 psig and a bottoms temperature of approximately 120-200 degrees F.;
• i. producing from said Deethanizer tower (i) a Deethanizer tower overhead stream comprising a major portion of the methane, ethylene, and ethane from said wet gas and Main Fractionator overhead liquid streams, and (ii) a Deethanizer bottoms stream comprising a major portion of the propane and propylene from the wet gas and Main Fractionator overhead liquid streams;
• j. stripping propane and propylene from said second stream from said separator vessel to form a stripped butylene and heavier stream;
• and
• k. recycling the propane and propylene stripped from said second stream such that said stripped propane and propylene are processed in said separator.