Low pressure olefin recovery process
First Claim
1. A process for recovering olefins from a feed stream, comprising:
- supplying the feed stream at a primary distillation pressure, including if required compressing the feed stream in a primary compression stage;
distilling the feed stream at the primary distillation pressure in a primary distillation zone to obtain a primary overhead vapor stream enriched in ethylene and one or more ethylene-lean bottoms streams;
chilling the primary overhead vapor stream at a pressure less than 30 kg/cm2 (430 psia) in a first cooling stage to recover a first partial condensate stream and a first-stage vapor effluent;
refluxing the primary distillation zone with at least a portion of the first partial condensate stream;
further chilling the first-stage vapor effluent to recover at least a second partial condensate stream and a second-stage vapor effluent;
feeding the at least second partial condensate stream and any remaining portion of the first partial condensate stream to a demethanizer to recover a methane-rich overhead stream and a bottoms stream essentially free of methane and lighter components;
fractionating the bottoms streams from the primary distillation zone and the demethanizer into respective streams consisting essentially of hydrocarbons selected from the group consisting of ethylene, ethane, propylene, propane, C4'"'"'s, C5+ and combinations thereof;
further chilling the second-stage vapor effluent in a cold section and phase-separating the resulting mixed vapor-liquid stream in one or more stages to obtain additional condensate and a vapor tail gas stream essentially free of ethylene, wherein the additional condensate is vaporized to a relatively lower pressure to provide refrigeration for the condensation and to form a low pressure recycle vapor stream.
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Accused Products
Abstract
A low-pressure olefins recovery process and plant are described. The feed gas 300 is compressed 302, 304 and distilled 310 at a primary distillation pressure. The overhead stream 312 is chilled 318 at a pressure less than 30 kg/cm2 (430 psia) to partially condense the overheads. The primary distillation tower 310 is refluxed with at least a portion of the condensate 320. The overhead vapor is further chilled 318 and partially condensed and the condensate 322 is fed to a demethanizer 324. The remaining vapor 326 is cooled in a cold section 328 and the resultant liquid is phase-separated 330 and expanded 331, 334 to provide refrigeration for the cold ssection. The expanded vapor 332 from the cold section is recycled to the process gas compressor. The bottoms streams 338, 342 from the primary distillation zone and the demethanizer are fractionated into respective streams consisting essentially of ethylene 356, ethane 358, propylene 364, propane 366, C4'"'"'s 346, and C5+ 348.
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Citations
24 Claims
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1. A process for recovering olefins from a feed stream, comprising:
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supplying the feed stream at a primary distillation pressure, including if required compressing the feed stream in a primary compression stage;
distilling the feed stream at the primary distillation pressure in a primary distillation zone to obtain a primary overhead vapor stream enriched in ethylene and one or more ethylene-lean bottoms streams;
chilling the primary overhead vapor stream at a pressure less than 30 kg/cm2 (430 psia) in a first cooling stage to recover a first partial condensate stream and a first-stage vapor effluent;
refluxing the primary distillation zone with at least a portion of the first partial condensate stream;
further chilling the first-stage vapor effluent to recover at least a second partial condensate stream and a second-stage vapor effluent;
feeding the at least second partial condensate stream and any remaining portion of the first partial condensate stream to a demethanizer to recover a methane-rich overhead stream and a bottoms stream essentially free of methane and lighter components;
fractionating the bottoms streams from the primary distillation zone and the demethanizer into respective streams consisting essentially of hydrocarbons selected from the group consisting of ethylene, ethane, propylene, propane, C4'"'"'s, C5+ and combinations thereof;
further chilling the second-stage vapor effluent in a cold section and phase-separating the resulting mixed vapor-liquid stream in one or more stages to obtain additional condensate and a vapor tail gas stream essentially free of ethylene, wherein the additional condensate is vaporized to a relatively lower pressure to provide refrigeration for the condensation and to form a low pressure recycle vapor stream. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. An olefin recovery plant for recovering olefins from a feed stream, comprising:
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means for supplying the feed stream at a primary distillation pressure, including if required a primary compression stage;
means for distilling the feed stream at the primary distillation pressure in a primary distillation zone to obtain a primary overhead vapor stream enriched in ethylene and one or more ethylene-lean bottoms streams;
means for chilling the primary overhead vapor stream at a pressure less than 28 kg/cm2 (400 psia) in a first cooling stage to recover a first partial condensate stream and a first-stage vapor effluent;
means for refluxing the primary distillation zone with at least a portion of the first partial condensate stream;
means for further chilling the first-stage vapor effluent to recover at least a second partial condensate stream and a second-stage vapor effluent;
means for feeding the at least second and any remaining portion of the first partial condensate stream to a demethanizer to recover a methane-rich overhead stream and a bottoms stream essentially free of methane and lighter components;
means for fractionating the bottoms streams from the primary distillation zone and the demethanizer into respective streams consisting essentially of hydrocarbons selected from the group consisting of ethylene, ethane, propylene, propane, C4'"'"'s, C5+ and combinations thereof;
means for further chilling the second-stage vapor effluent in a cold box and phase-separating the resulting mixed vapor-liquid stream in one or more stages to obtain additional condensate and a vapor tail gas stream essentially free of ethylene, wherein the additional condensate is expanded to a relatively lower pressure to provide refrigeration for the condensation and to form a low pressure recycle vapor stream. - View Dependent Claims (22, 23, 24)
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Specification