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1. (WO2017151147) FLARE RECOVERY WITH CARBON CAPTURE
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Flare Recovery with Carbon Capture

CROSS-REFERENCE TO RELATED APPLICATION

[0001] Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

[0003] Not applicable.

BACKGROUND

[0004] An oil production site generates gas while recovering crude oil from a subterranean formation. The gas can include lighter hydrocarbons such as Ci-C8 hydrocarbons, water, nitrogen, carbon dioxide, and other components. The gas is commonly combusted to convert the hydrocarbons in the gas into carbon dioxide and water, which are then released into the environment. The combustion of the gas may be referred to as a flare, and the gas that is combusted may be referred to as flare gas.

SUMMARY

[0005] In one aspect, the disclosure includes a method for flare recovery. A flare gas inlet stream is received, wherein the flare gas inlet stream comprises Ci-C8 hydrocarbons. The flare gas inlet stream is separated in a recovery column to produce a Ci-C2 hydrocarbon stream and a C3-C8 hydrocarbon stream. The C3-C8 hydrocarbon stream is separated in a separation column to produce a C3 hydrocarbon stream and a C4-C8 hydrocarbon stream.

[0006] In another aspect, the disclosure includes a set of process equipment for flare recovery. The set of process equipment includes a first multi-stage distillation column and a second multi-stage distillation column. The first multi-stage distillation column receives a flare gas inlet stream and produces a first overhead stream and a first bottoms stream. The second multi-stage distillation column receives the first bottoms stream and produces a second overhead stream and a second bottoms stream. The second bottoms stream comprises C4+ hydrocarbons, and the first multi-stage distillation column and the second multi-stage distillation column are the only two multi-stage distillation columns in the set of process equipment.

[0007] In yet another aspect, the disclosure includes a set of process equipment comprising a first column, a second column, an expander, and a compressor. The first column receives a Ci-C8 hydrocarbon stream and produces a C1-C2 hydrocarbon stream and a C3-C8 hydrocarbon stream. The second column receives the C3-C8 hydrocarbon stream and produces a C3 hydrocarbon stream and a C4-C8 hydrocarbon stream. The expander expands the C1-C2 hydrocarbon stream to generate energy, and the compressor compresses the Ci-C8 hydrocarbon stream using the energy generated by the expander before the Ci-C8 hydrocarbon stream is fed to the first column.

[0008] These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] For a more complete understanding of the disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts.

[0010] FIG. 1 is a schematic diagram of a system for recovering flare gas in which the flare gas is separated into a C4+ hydrocarbon stream and a Ci-C3 hydrocarbon stream.

[0011] FIG. 2 is a schematic diagram of a system for recovering flare gas in which the flare gas is separated into a C4+ hydrocarbon stream, a C3 hydrocarbon stream, and a C1-C2 hydrocarbon stream.

[0012] FIG. 3 is a detailed diagram of a system of recovering flare gas in which the flare gas is separated into a C4+ hydrocarbon stream and a Ci-C3 hydrocarbon stream.

[0013] FIG. 4 is a detailed diagram of a system of recovering flare gas in which the flare gas is separated into a C4+ hydrocarbon stream, a C3 hydrocarbon stream, and a C1-C2 hydrocarbon stream.

[0014] FIG. 5 is a detailed diagram of a system of recovering flare gas that has additional processing before the inlet stream is fed to the first column.

DETAILED DESCRIPTION

[0015] It should be understood at the outset that although an illustrative implementation of one or more embodiments are provided below, the disclosed systems and/or methods may be implemented using any number of techniques, whether currently known or in existence. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated below, including the exemplary designs and implementations illustrated and described herein, but may be modified within the scope of the appended claims along with their full scope of equivalents.

[0016] Disclosed herein is a flare recovery process that recovers at least a portion of flare gas that would otherwise be combusted in a flare. In one embodiment, flare gas is separated into a C4+ hydrocarbon stream and a Ci-C3 hydrocarbon stream. The C4+ hydrocarbon stream is combined with crude oil to increase the production of crude oil, and the Ci-C3 hydrocarbon stream is used to generate energy or is flared. In another embodiment, the flare gas is separated into a C4+ hydrocarbon stream, a C3 hydrocarbon stream, and a C1-C2 hydrocarbon stream. The C4+ hydrocarbon stream is combined with crude oil, the C3 hydrocarbon stream is transported away by pipe, truck, or rail as saleable product, and the C1-C2 hydrocarbon stream is used to generate energy or is flared. The process reduces carbon emissions because a portion of the flare gas, which would normally be burned and produce carbon dioxide, is used to increase the production of crude oil and optionally to recover a C3 hydrocarbon stream. Specifically, one embodiment of the flare recovery process without C3 hydrocarbon recovery reduces carbon emissions by 27.80 mole %, and another embodiment of the flare recovery process with C3 hydrocarbon recovery reduces carbon emissions by 36.58 mole %, both in comparison to flaring the gas fed to the disclosed process. Furthermore, it should be noted that addition of the C4+ hydrocarbon stream to the crude oil does not cause the crude oil to fail any specifications (e.g., specifications for energy content, vapor pressure, etc.). This is accomplished in part by using two multistage separation columns to remove the C3 hydrocarbon from the C4+ hydrocarbons, where the C3 hydrocarbons would cause the crude oil to fail specifications. Additionally, certain embodiments may provide other benefits such as not requiring any refrigeration, only requiring two columns (e.g., only requiring two multistage separation columns), operating at relatively low pressures (e.g., 200-500 pounds per a square inch gauge (psi)), and having a post separation expansion process that generates energy. These and other features and benefits are described in greater detail below.

[0017] FIG. 1 is a schematic diagram of a system 100 for recovering flare gas in which the flare gas is separated into a C4+ hydrocarbon stream and a Ci-C3 hydrocarbon stream. First, a hydrocarbon stream 104 is recovered from a subterranean formation 102. Subterranean formation 102 may include one oil well or may include many oil wells (e.g., 10-100 oil wells), which may be on land or offshore. The hydrocarbon stream 104 contains heavy hydrocarbons (e.g., C + hydrocarbons), light hydrocarbons (e.g., Ci-C8 hydrocarbons), water, nitrogen, carbon dioxide, and other components. The hydrocarbon stream 104 is passed to a heavy hydrocarbon separator 106 that separates the heavy hydrocarbons from the light hydrocarbons. The heavy hydrocarbon separator 106 produces a light hydrocarbon stream 108 containing the Ci-C8 hydrocarbons, water, nitrogen, carbon dioxide, and other components (i.e., the flare gas) and produces a heavy hydrocarbon stream 110 containing the C + hydrocarbons. The light hydrocarbon stream 108 is then compressed at a compressor 112 to increase the pressure of the light hydrocarbon stream 108. In some embodiments, system 100 is operated at relatively low pressures such as, but not limited to, about 200 to about 500 psi. The compressor 112 produces a compressed light hydrocarbon stream 114 that is optionally fed to a dryer 116. The dryer 116 may include any equipment that can remove water from a hydrocarbon stream (e.g., a molecular sieve, glycol, etc.). The dryer 116 produces a dehydrated light hydrocarbon stream 118 that is fed to a recovery column 120.

[0018] The recovery column 120 is illustratively a distillation column, but can include alternative columns such as scrubbers, strippers, absorbers, adsorbers, packed columns, or a combination of column types. Such columns may employ weirs, downspouts, internal baffles, temperature control elements, and/or pressure control elements. Such columns also may employ some combination of reflux condensers and/or reboilers, including intermediate stage condensers and reboilers. The recovery column 120 generates an overhead recovery column stream 122 and a bottoms recovery column stream 124. The overhead recovery column stream 122 may comprise Ci-C3 hydrocarbons, and the bottoms recovery column stream 124 may comprise C3-C8 hydrocarbons.

[0019] The bottoms recovery column stream 124 is fed to a separation column 126. Like the recovery column 120, the separation column 126 may also be a distillation column, a scrubber, a stripper, an absorber, an adsorber, a packed column, or a combination of column types. The separation column 126 generates an overhead separation column stream 128 and a bottoms separation column stream 130. The overhead separation column stream 128 may comprise C3 hydrocarbons, and the bottoms separation column stream 130 may comprise C4+ hydrocarbons (e.g., C4-C8 hydrocarbons). The bottoms separation column stream 130 is then optionally combined with the heavy hydrocarbon stream 110 in a mixer 132 to increase the amount of crude oil 134 produced. The mixer 132 may be a dynamic mixer, which contains moving parts to mix the constituent streams, or a static mixer, which may include internal baffles or may simply be a junction that combines the two constituent streams. It should be noted that the bottoms separation column stream 130 can be mixed with the heavy hydrocarbon stream 110 without causing the resulting crude oil 134 to fail any needed specifications such as, but not limited to, vapor pressure or energy content requirements.

[0020] Returning to the recovery column 120, the overhead recovery column stream 122 is fed to an expander 136. The expander 136 expands the overhead recovery column stream 122 to produce a cooled stream 138 that is at a lower pressure. The expansion optionally generates an energy stream 140 that can be used in other parts of the system 100. For instance, the energy stream 140 may be used to power the compressor 112. Then, the cooled stream 138 is mixed with the overhead separation column stream 128 in a mixer 142 to produce a residue stream 144. The mixer may be similar to mixer 132. The residue stream 144 may comprise Ci-C3 hydrocarbons and may be used for energy recovery in an energy recovery unit 146. For instance, the residue stream 144 can be combusted in the energy recovery unit 146 to generate energy for the compressor 112 (e.g. residue stream 144 fay be a fuel for the compressor 112), the dryer 116 (e.g. for the regeneration gas heater for the molecular sieve unit), or the reboilers for columns 120 and 126. Finally, any remaining gas 148 from the energy recovery unit 146 may be flared in flare 150 as needed.

[0021] FIG. 2 is a schematic diagram of a system 200 of recovering flare gas in which the flare gas is separated into a C4+ hydrocarbon stream, a C3 hydrocarbon stream, and a C1-C2 hydrocarbon stream. System 200 may be beneficial over system 100 described above in that a C3 hydrocarbon stream is produced. The C3 hydrocarbon stream is a saleable product that meets the specifications for (e.g., energy content and vapor pressure) and can be transported away by truck, rail, pipeline, or by any other means. However, if no means are available to transport the C3 hydrocarbon stream away (e.g., the system 200 is in an isolated location with no truck or pipeline access), then system 100 that does not produce the C3 hydrocarbon stream may be beneficial.

[0022] In system 200, components 202, 204, 206, 208, 210, 212, 214, 216, 218, 220, 222, 224, 226, 228, 230, 232, 234, 238, 246, 248, and 250 are the same as or are similar to components 102, 104, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124, 126, 128, 130, 132, 134, 138, 146, 148, and 150 in system 100 and need not be described again. System 200 differs from system 100 in that the overhead separation column stream 228 containing C3 hydrocarbons is not mixed with the cooled stream 238. Instead, the overhead separation column stream 228 (i.e., the C3 hydrocarbon stream) is recovered by itself. The overhead separation column stream 228 is then used for energy recovery and/or is used as a saleable product and is transported away by truck, rail, pipeline, or by any other means. Additionally, the system 200 may optionally include a hydrogen sulfide removal unit 296 to remove hydrogen sulfide if necessary. For instance, the system 200 may use iron sponge, sulfanol, or iron chelate processing to remove hydrogen sulfide. The hydrogen sulfide removal unit 296 generates a sweetened propane product stream 298.

[0023] FIG. 3 is a detailed diagram of a system 300 of recovering flare gas in which the flare gas is separated into a C4+ hydrocarbon stream and a Ci-C3 hydrocarbon stream. The system 300 corresponds to system 100 in FIG. 1, but the system 300 is shown in greater detail. The system 300 begins with an inlet stream 302 being fed to a first compressor 304. The inlet stream 302 may comprise Ci-C8 hydrocarbons, carbon dioxide, nitrogen, water, and other components included in flare gas. For instance, the inlet stream 302 may comprise about 96 -about 100 mole % Ci-C8 hydrocarbons, about 0 - about 2 mole % carbon dioxide, and about 0 -about 2 mole % nitrogen. The first compressor 304 increases the pressure of the inlet stream 302 to generate a first compressed stream 306. The first compressor 304 may include compressors and/or pumps, which may be driven by electrical, mechanical, hydraulic, or pneumatic means. Specific examples of a first compressor 304 include centrifugal, axial, positive displacement, turbine, rotary, and reciprocating compressors and pumps.

[0024] The first compressed stream 306 is fed to a second compressor 308 to generate a second compressed stream 310. The second compressor 308 may include any of the types of compressors listed for first compressor 304. Additionally, a second compressor energy stream 312 is supplied to the second compressor 308 to power the second compressor 308.

[0025] The second compressed stream 310 is fed to a first cooler 314 (e.g., an air cooler) that generates a first cooled stream 316. The first cooled stream 316 may then optionally be processed through a dehydrator 318 (e.g., a molecular sieve, etc.) to remove any water from the stream if needed. Following the first cooler 314 and/or the dehydrator 318, the first cooled stream 316 is processed through a first heat exchanger 320 to produce a cooled recovery column inlet stream 322. The recovery column inlet stream 322 is fed to a recovery column 324. Recovery column 324 may include any of the types of columns listed for recovery column 104 in FIG. 1. Additionally, recovery column 324 may include a reboiler and/or a reflux. In the example shown in FIG. 3, recovery column 324 has a recovery column reboiler 326 that receives a recovery column reboiler energy stream 328 to power the recovery column reboiler 326. The reflux for the recovery column includes heat exchanger 354 and reflux separator 358.

[0026] The recovery column 324 generates a recovery column overhead stream 330 and a recovery column bottoms stream 332. The recovery column overhead stream 330 may comprise C1-C2 hydrocarbons, C3 hydrocarbons, trace amounts of C4-C8 hydrocarbons, trace amounts of carbon dioxide, and trace amounts of nitrogen. For instance, the recovery column overhead stream 330 may comprise about 80 - about 90 mole % C1-C2 hydrocarbons, about 10 -about 20 mole % C3 hydrocarbons, about 0 - about 2 mole % C4-C8 hydrocarbons, about 0 -about 2 mole % carbon dioxide, and about 0 - about 2 mole % nitrogen. The recovery column bottoms stream 332 may comprise small amounts of C1-C2 hydrocarbons, C3-C8 hydrocarbons, trace amounts of carbon dioxide, and no nitrogen. For instance, the recovery column bottoms stream 332 may comprise about 5 - about 15 mole % C1-C2 hydrocarbons, about 85 - about 95 mole % C3-C8 hydrocarbons, about 0 - about 2 mole % carbon dioxide, and 0 mole % nitrogen.

However, the precise compositions of streams 330 and 332 may vary, and they may contain other components in various amounts.

[0027] The recovery column bottoms stream 332 is then cooled through a second cooler 334 (e.g., an air cooler) to produce a separation column inlet stream 336. The separation column inlet stream 336 is fed to the separation column 338. Separation column 338 may include any of the types of columns listed for recovery column 120 in FIG. 1. Additionally, separation column 338 may include a reboiler and/or a compressor. In the example shown in FIG. 3, separation column 338 has a separation column reboiler 340 and a separation column reflux condenser 342. The separation column reboiler 340 receives a separation column reboiler energy stream 344 to power the separation column reboiler 340, and the separation column reflux condenser 342 generates a separation column condenser energy stream 346.

[0028] Separation column 338 generates an overhead separation column stream 348 and a bottoms separation column stream 350. The overhead separation column stream 348 may comprise C1-C2 hydrocarbons, C3 hydrocarbons, trace amounts of C4-C8 hydrocarbons, and trace amounts of carbon dioxide. For instance, the overhead separation column stream 348 may comprise about 30 - about 40 mole % C1-C2 hydrocarbons, about 60 - about 70 mole % C3 hydrocarbons, about 0 - about 2 mole % C4-C8 hydrocarbons, and about 0 - about 2 mole % carbon dioxide. The bottoms separation column stream 350 may comprise no C1-C2 hydrocarbons, trace amounts of C3 hydrocarbons, C4+ hydrocarbons (e.g., C4-C8 hydrocarbons), and no carbon dioxide. For instance, the bottoms separation column stream 350 may comprise about 0 mole % Ci-C2 hydrocarbons, about 0 - about 2 mole % C3 hydrocarbons, about 98 -about 100 mole % C4+ hydrocarbons, and about 0 mole % carbon dioxide. The bottoms separation column stream 350 may then be combined with crude oil (e.g., C9+ hydrocarbons) to increase the amount of oil produced, and the overhead separation column stream 348 is fed to a mixer 352.

[0029] Returning to the recovery column 324, the recovery column overhead stream 330 is cooled through second heat exchanger 354 to produce a separator inlet stream 356 that is fed to a reflux separator 358. Reflux separator 358 may be a phase separator, which is a vessel that separates an inlet stream into a substantially vapor stream and a substantially liquid stream, such as a knock-out drum, flash drum, reboiler, condenser, or other heat exchanger. Such vessels also may have some internal baffles, temperature control elements, and/or pressure control elements, but generally lack any trays or other type of complex internal structure commonly found in columns.

[0030] Reflux separator 358 produces a reflux separator bottoms stream 360 and a reflux separator overhead stream 366. Reflux separator bottoms stream 360 comprises C hydrocarbons, C2-C3 hydrocarbons, trace amounts of C4-C8 hydrocarbons, trace amounts of carbon dioxide, and trace amounts of nitrogen. For instance, reflux separator bottoms stream 360 may comprise about 20 - about 30 mole % Ci hydrocarbons, about 70 - about 80 mole % C2-C3 hydrocarbons, about 0 - about 1 mole % C4-C8 hydrocarbons, about 0 - about 2 mole % carbon dioxide, and about 0 - about 1 mole % nitrogen. Reflux separator overhead stream 366 comprises Ci hydrocarbons, C2-C3 hydrocarbons, trace amounts of C4-C8 hydrocarbons, trace amounts of carbon dioxide, and trace amounts of nitrogen. For instance, reflux separator overhead stream 366 may comprise about 80 - about 90 mole % Ci hydrocarbons, about 10 -about 20 mole % C2-C3 hydrocarbons, about 0 - about 1 mole % C4-C8 hydrocarbons, about 0 -about 2 mole % carbon dioxide, and about 0 - about 5 mole % nitrogen. Reflux separator bottom stream 360 is processed through a reflux pump 362 to produce a recovery column reflux stream 364 that is fed back to the recovery column 324. Reflux pump 362 receives energy through a reflux pump energy stream 363.

[0031] Reflux separator overhead stream 366 is then fed to an expander 368. Expander 368 may be an expansion turbine, which reduces the temperature and/or pressure of expander outlet stream 372 and produces an expander energy stream 370 (e.g. mechanical or electrical

energy). The expander 368 may be coupled to the first compressor 304 such that the expander energy stream 370 created by the expansion process is used to run the first compressor 304.

[0032] From the expander 368, the expander outlet stream 372 is passed through the second heat exchanger 354 to cool the recovery column overhead stream 330 and to produce a heated expander outlet stream 374. Heated expander outlet stream 374 is then combined with overhead separation column stream 348 in mixer 352 to produce a mixer outlet stream 376. Mixer outlet stream 376 comprises Ci hydrocarbons, C2-C3 hydrocarbons, trace amounts of C4-C8 hydrocarbons, trace amounts of carbon dioxide, and trace amounts of nitrogen. For instance, mixer outlet stream 376 may comprise about 75 - about 85 mole % Ci hydrocarbons, about 10 - about 20 mole % C2-C3 hydrocarbons, about 0 - about 1 mole % C4-C8 hydrocarbons, about 0 - about 1 mole % carbon dioxide, and about 0 - about 5 mole % nitrogen. Mixer outlet stream 376 is passed through first heat exchanger 320 to cool the first cooled stream 316 and to produce a cold residue stream 378. The cold residue stream 378 may be used to generate energy and/or the cold residue stream 378 may be combusted as flare gas. It should be noted that no compressors are included in system 300 after the mixer 352 to increase the pressure and/or the temperature of the cold residue stream 378 as may be required in other systems.

[0033] FIG. 4 is a detailed diagram of a system 400 of recovering flare gas in which the flare gas is separated into a C4+ hydrocarbon stream, a C3 hydrocarbon stream, and a C1-C2 hydrocarbon stream. The system 400 corresponds to system 200 in FIG. 2, but the system 400 is shown in greater detail. The system 400 begins with an inlet stream 402 being fed to a first compressor 404. The inlet stream 402 may comprise Ci-C8 hydrocarbons, carbon dioxide, nitrogen, water, and other components included in flare gas. For instance, the inlet stream 402 may comprise about 96 - about 100 mole % Ci-C8 hydrocarbons, about 0 - about 2 mole % carbon dioxide, and about 0 - about 2 mole % nitrogen. The first compressor 404 increases the pressure of the inlet stream 402 to generate a first compressed stream 406. The first compressor 404 may include compressors and/or pumps, which may be driven by electrical, mechanical,

hydraulic, or pneumatic means. Specific examples of a first compressor 404 include centrifugal, axial, positive displacement, turbine, rotary, and reciprocating compressors and pumps.

[0034] The first compressed stream 406 is fed to a second compressor 408 to generate a second compressed stream 410. The second compressor 408 may include any of the types of compressors listed for first compressor 404. Additionally, a second compressor energy stream 412 is supplied to the second compressor 408 to power the second compressor 408.

[0035] The second compressed stream 410 is fed to a first cooler 414 (e.g., an air cooler) that generates a first cooled stream 416. The first cooled stream 416 may then optionally be processed through a dehydrator 418 (e.g., a molecular sieve, etc.) to remove any water from the stream if needed. Following the first cooler 414 and/or the dehydrator 418, the first cooled stream 416 is processed through a first heat exchanger 420 to produce a cooled recovery column inlet stream 422. The recovery column inlet stream 422 is fed to a recovery column 424. Recovery column 424 may include any of the types of columns listed for recovery column 120 in FIG. 1. Additionally, recovery column 424 may include a reboiler and/or a reflux. In the example shown in FIG. 4, recovery column 424 has a recovery column reboiler 426 that receives a recovery column reboiler energy stream 428 to power the recovery column reboiler 426.

[0036] The recovery column 424 generates a recovery column overhead stream 430 and a recovery column bottoms stream 432. The recovery column overhead stream 430 may comprise C1-C2 hydrocarbons, C3 hydrocarbons, trace amounts of carbon dioxide, trace amounts of nitrogen, and no C4-C8 hydrocarbons. For instance, the recovery column overhead stream 430 may comprise about 80 - about 90 mole % C1-C2 hydrocarbons, about 10 - about 20 mole % C3 hydrocarbons, about 0 - about 2 mole % carbon dioxide, about 0 - about 2 mole % nitrogen, and about 0 mole % C4-C8 hydrocarbons. The recovery column bottoms stream 432 may comprise C3-C8 hydrocarbons, trace amounts of C1-C2 hydrocarbons, no carbon dioxide, and no nitrogen. For instance, the recovery column bottoms stream 432 may comprise about 90 -about 100 mole % C3-C8 hydrocarbons, about 0 - about 10 mole % C1-C2 hydrocarbons, about 0 mole % carbon dioxide, and about 0 mole % nitrogen. However, the precise compositions of streams 430 and 432 may vary, and they may contain other components in various amounts.

[0037] The recovery column bottoms stream 432 is then cooled through a second cooler 434 (e.g., an air cooler) to produce a separation column inlet stream 436. The separation column inlet stream 436 is fed to the separation column 438. Separation column 438 may include any of the types of columns listed for recovery column 120 in FIG. 1. Additionally, separation column 438 may include a reboiler and/or a compressor. In the example shown in FIG. 4, separation column 438 has a separation column reboiler 440 and a separation column reflux condenser 442. The separation column reboiler 440 receives a separation column reboiler energy stream 444 to power the separation column reboiler 440, and the separation column reflux condenser 442 generates a separation column condenser energy stream 446.

[0038] Separation column 438 generates a vapor stream 447, a propane product stream 448, and a bottoms separation column stream 450. The vapor stream 447 may comprise Ci-C3 hydrocarbons, trace amounts of C4-C8 hydrocarbons, trace amounts of carbon dioxide, and no nitrogen. For instance, the vapor stream 447 may comprise about 90 - about 100 mole % Q-C3 hydrocarbons, about 0 - about 10 mole % C4-C8 hydrocarbons, about 0 - about 2 mole % carbon dioxide, and about 0 mole % nitrogen. The propane product stream 448 may comprise small amounts of Ci-C2 hydrocarbons, C3 hydrocarbons, small amounts of C4-C8 hydrocarbons, trace amounts of carbon dioxide, and no nitrogen. For instance, the propane product stream 448 may comprise about 10 - about 20 mole % C1-C2 hydrocarbons, about 70 - about 90 mole % C3 hydrocarbons, about 0 - about 10 mole % C4-C8 hydrocarbons, about 0 - about 1 mole % carbon dioxide, and about 0 mole % nitrogen. The bottoms separation column stream 450 may comprise trace amounts of Ci-C3 hydrocarbons, C4+ hydrocarbons (e.g., C4-C8 hydrocarbons), no carbon dioxide, and no nitrogen. For instance, the bottoms separation column stream 450 may comprise about 0 - about 5 mole % Ci-C3 hydrocarbons, about 95 - about 100 mole % C4+ hydrocarbons, about 0 mole % carbon dioxide, and about 0 mole % nitrogen. The bottoms

separation column stream 450 may then be combined with crude oil to increase the amount of oil produced, and the propane product stream 448 may be recovered as saleable C3 product. Additionally, the system 400 may optionally include a hydrogen sulfide removal unit 496 to remove hydrogen sulfide if necessary For instance, the system 400 may use iron sponge, sulfanol, or iron chelate processing to remove hydrogen sulfide. The hydrogen sulfide removal unit 496 generates a sweetened propane product stream 498.

[0039] Returning to the recovery column 424, the recovery column overhead stream 430 is cooled through second heat exchanger 454 to produce a separator inlet stream 456 that is fed to a reflux separator 458. Reflux separator 458 may be a phase separator, which is a vessel that separates an inlet stream into a substantially vapor stream and a substantially liquid stream, such as a knock-out drum, flash drum, reboiler, condenser, or other heat exchanger. Such vessels also may have some internal baffles, temperature control elements, and/or pressure control elements, but generally lack any trays or other type of complex internal structure commonly found in columns.

[0040] Reflux separator 458 produces a reflux separator bottoms stream 460 and a reflux separator overhead stream 466. The reflux separator bottoms stream 460 comprises Ci hydrocarbons, C2-C3 hydrocarbons, trace amounts of C4-C8 hydrocarbons, trace amounts of carbon dioxide, and trace amounts of nitrogen. For instance, the reflux separator bottoms stream 460 may comprise about 25 - about 35 mole % Ci hydrocarbons, about 65 - about 75 mole % C3 hydrocarbons, about 0 - about 2 mole % C4-C8 hydrocarbons, about 0 - about 2 mole % carbon dioxide, and about 0 - about 2 mole % nitrogen. The reflux separator overhead stream 466 comprises Ci hydrocarbons, C2-C3 hydrocarbons, about 0 mole % C4-C8 hydrocarbons, trace amounts of carbon dioxide, and trace amounts of nitrogen. For instance, the reflux separator overhead stream may comprise about 80 - about 90 mole % C hydrocarbons, about 10 - about 20 mole % C2-C3 hydrocarbons, about 0 mole % C4-C8 hydrocarbons, about 0 - about 2 mole % carbon dioxide, and about 0 - about 2 mole % nitrogen. The reflux separator bottom stream 460 is processed through a reflux pump 462 to produce a recovery column reflux stream 464 that is fed back to the recovery column 424. Reflux pump 462 receives energy through a reflux pump energy stream 463.

[0041] Reflux separator overhead stream 466 is then fed to an expander 468. Expander 468 may be an expansion turbine, which reduces the temperature and/or pressure of expander outlet stream 472 and produces an expander energy stream 470 (e.g. mechanical or electrical energy). The expander 468 may be coupled to the first compressor 404 such that the expander energy stream 470 created by the expansion process is used to run the first compressor 404.

[0042] From the expander 468, the expander outlet stream 472 is passed through the second heat exchanger 454 to cool the recovery column overhead stream 430 and to produce a heated expander outlet stream 474. Heated expander outlet stream 474 is then passed through first heat exchanger 420 to cool the first cooled stream 416 and to produce a cold residue stream 478. The cold residue stream 478 may be used to generate energy and/or the cold residue stream 478 may be combusted as flare gas. It should be noted that no compressors are included in system 400 after the reflux separator 458 to increase the pressure and/or the temperature of the cold residue stream 478 as may be required in other systems.

[0043] FIG. 5 is a detailed diagram of a system 500 of recovering flare gas in which the flare gas is separated into a C4+ hydrocarbon stream, a C3 hydrocarbon stream, and a C1-C2 hydrocarbon stream. The system 500 is similar to the system 200 in FIG. 2 and the system 400 in FIG. 4, but the system 500 has additional processing before the inlet gas (e.g., the flare gas) is fed to the first column for separation. This additional processing may be beneficial in improving the recovery rates of the C4+ hydrocarbon stream and the C3 hydrocarbon stream. Also, the additional processing may be easier, less expensive, or more practical to implement. Furthermore, it should be noted that the additional processing shown in FIG. 5 can be added to any of the other systems (e.g., system 100 in FIG. 1, system 200 in FIG. 2, system 300 in FIG. 3, and system 400 in FIG. 4).

[0044] The system 500 begins with an inlet stream 502 being fed to a first compressor 504. The inlet stream 502 may comprise Ci-C8 hydrocarbons, carbon dioxide, nitrogen, water, and other components included in flare gas. For instance, the inlet stream 502 may comprise about 96 - about 100 mole % Ci-C8 hydrocarbons, about 0 - about 2 mole % carbon dioxide, and about 0 - about 2 mole % nitrogen. The first compressor 504 increases the pressure of the inlet stream 502 to generate a first compressed stream 506. The first compressor 504, as well as any of the other compressors in system 500, may include compressors and/or pumps, which may be driven by electrical, mechanical, hydraulic, or pneumatic means. Specific examples of a first compressor 504 include centrifugal, axial, positive displacement, turbine, rotary, and reciprocating compressors and pumps. Additionally, a first compressor energy stream 508 is supplied to the first compressor 504 to power the first compressor 504.

[0045] The first compressed stream 506 is fed to a second compressor 510. The second compressor 510 generates a second compressed stream 512 and is supplied with a second compressor energy stream 514. The second compressed stream 512 is fed to a first cooler 516 that generates a first cooled stream 518. The first cooler 516, as well as any of the other coolers in system 500, may comprise a cooler such as an air cooler or may comprise any other type of heat exchanger.

[0046] The first cooled stream 518 is fed to a first separator 520. In one embodiment, the first separator 520, as well as other separators in system 500, comprise a two-phase scrubber. However, embodiments of separators in system 500 are not limited to any particular kind of separator and can include any separator such as, but not limited to, a phase separator, a knock-out drum, a flash drum, a reboiler, a condenser, or a heat exchanger. The first separator 520 generates a first separator top stream 522.

[0047] The first separator top stream 522 is fed to a third compressor 524. The third compressor 524 generates a third compressed stream 526 and is supplied with a third compressor energy stream 528. The third compressed stream 526 is fed to a second cooler 530 that

generates a second cooled stream 532. The second cooled stream 532 is fed to a second separator 534. The second separator 534 generates a second separator top stream 536 and a second separator bottom stream 538.

[0048] The second separator top stream 536 is fed to a fourth compressor 540. The fourth compressor 540 generates a fourth compressed stream 542 and is supplied with a fourth compressor energy stream 544. The fourth compressed stream 542 is fed to a third cooler 546 that generates a third cooled stream 548. The third cooled stream 548 is fed to a third separator 550 that generates a third separator top stream 552 and a third separator bottom stream 554. The third separator top stream 552 is cooled through a first heat exchanger 555 to generate a cooled recovery column inlet stream 556 that is fed to the recovery column 558. Returning to the second separator bottom stream 538, the second separator bottom stream 538 is transferred from the second separator 534 by a material transfer device 560 such as, but not limited to, a pump. The material transfer device 560 receives a material transfer device energy stream 562 and generates a material transfer device stream 564. The material transfer device stream 564 and the third separator bottom stream 554 are mixed together in a mixer 566 to generate a mixed recovery column inlet stream 568 that is fed to the recovery column 558.

[0049] The recovery column 558 may include any of the types of columns listed for recovery column 120 in FIG. 1. Additionally, recovery column 558 may include a reboiler and/or a reflux. In the example shown in FIG. 5, recovery column 558 has a recovery column reboiler 570 that receives a recovery column reboiler energy stream 572 to power the recovery column reboiler 570.

[0050] The recovery column 558 generates a recovery column overhead stream 574 and a recovery column bottoms stream 576. The recovery column overhead stream 574 may comprise C1-C2 hydrocarbons, C3 hydrocarbons, trace amounts of carbon dioxide, trace amounts of nitrogen, and no C4-C8 hydrocarbons. For instance, the recovery column overhead stream 574 may comprise about 75 - about 85 mole % C1-C2 hydrocarbons, about 15 - about 25 mole %

C3 hydrocarbons, about 0- about 3 mole % carbon dioxide, about 0 - about 1 mole % nitrogen, and about 0 - about 1 mole % C4-C8 hydrocarbons. The recovery column bottoms stream 576 may comprise C3-C8 hydrocarbons, trace amounts of C1-C2 hydrocarbons, no carbon dioxide, and no nitrogen. For instance, the recovery column bottoms stream 576 may comprise about 90 - about 100 mole % C3-C8 hydrocarbons, about 0 - about 10 mole % C1-C2 hydrocarbons, about 0 mole % carbon dioxide, and about 0 mole % nitrogen. However, the precise compositions of streams 574 and 576 may vary, and they may contain other components in various amounts.

[0051] The recovery column bottoms stream 576 is then cooled through a fourth cooler 578 (e.g., an air cooler) to produce a separation column inlet stream 580. The separation column inlet stream 580 is fed to the separation column 582. The separation column 582 may include any of the types of columns listed for recovery column 120 in FIG. 1. Additionally, the separation column 582 may include a reboiler and/or a reflux. In the example shown in FIG. 5, the separation column 582 has a separation column reboiler 584 and a separation column reflux condenser 586. The separation column reboiler 584 receives a separation column reboiler energy stream 588 to power the separation column reboiler 584, and the separation column reflux condenser 586 generates a separation column condenser energy stream 590.

[0052] The separation column 582 generates a propane product stream 592 and a bottoms separation column stream 594. The propane product stream 592 may comprise small amounts of C1-C2 hydrocarbons, C3 hydrocarbons, small amounts of C4-C8 hydrocarbons, trace amounts of carbon dioxide, and no nitrogen. For instance, the propane product stream 592 may comprise about 10 - about 20 mole % C1-C2 hydrocarbons, about 70 - about 90 mole % C3 hydrocarbons, about 0 - about 10 mole % C4-C8 hydrocarbons, about 0 - about 1 mole % carbon dioxide, and about 0 mole % nitrogen. The bottoms separation column stream 594 may comprise trace amounts of C1-C3 hydrocarbons, C4+ hydrocarbons (e.g., C4-C8 hydrocarbons), no carbon dioxide, and no nitrogen. For instance, the bottoms separation column stream 594 may comprise about 0 - about 5 mole % C1-C3 hydrocarbons, about 95 - about 100 mole % C4+

hydrocarbons, about 0 mole % carbon dioxide, and about 0 mole % nitrogen. The bottoms separation column stream 594 may then be combined with crude oil to increase the amount of oil produced, and the propane product stream 592 may be recovered as saleable C3 product. Additionally, the system 500 may optionally include a hydrogen sulfide removal unit 596 to remove hydrogen sulfide if necessary. For instance, the system 500 may use iron sponge, sulfanol, or iron chelate processing to remove hydrogen sulfide. The hydrogen sulfide removal unit 596 generates a sweetened propane product stream 598.

[0053] Returning to the recovery column 558, the recovery column overhead stream 574 is cooled through a second heat exchanger 600 to produce a separator inlet stream 602 that is fed to a reflux separator 604. The reflux separator 604 may be a phase separator, which is a vessel that separates an inlet stream into a substantially vapor stream and a substantially liquid stream, such as a knock-out drum, flash drum, reboiler, condenser, or other heat exchanger. Such vessels also may have some internal baffles, temperature control elements, and/or pressure control elements, but generally lack any trays or other type of complex internal structure commonly found in columns.

[0054] The reflux separator 604 produces a reflux separator bottoms stream 606 and a reflux separator overhead stream 608. The reflux separator bottoms stream 606 comprises Ci hydrocarbons, C2-C3 hydrocarbons, trace amounts of C4-C8 hydrocarbons, trace amounts of carbon dioxide, and trace amounts of nitrogen. For instance, the reflux separator bottoms stream 606 may comprise about 15 - about 20 mole % Ci hydrocarbons, about 75 - about 80 mole % C2-C3 hydrocarbons, about 3 - about 5 mole % C4-C8 hydrocarbons, about 0 - about 2 mole % carbon dioxide, and about 0 - about 2 mole % nitrogen. The reflux separator overhead stream 608 comprises Ci hydrocarbons, C2-C3 hydrocarbons, about 0 mole % C4-C8 hydrocarbons, trace amounts of carbon dioxide, and trace amounts of nitrogen. For instance, the reflux separator overhead stream may comprise about 60 - about 70 mole % Ci hydrocarbons, about 30 - about 40 mole % C2-C3 hydrocarbons, about 0 mole % C4-C8 hydrocarbons, about 0 -

about 2 mole % carbon dioxide, and about 0 - about 2 mole % nitrogen. The reflux separator bottom stream 606 is processed through a reflux pump 610 to produce a recovery column reflux stream 612 that is fed back to the recovery column 558. The reflux pump 610 receives energy through a reflux pump energy stream 614.

[0055] The reflux separator overhead stream 608 is then fed to an expander 615. The expander 615 may be an expansion turbine, which reduces the temperature and/or pressure of expander outlet stream 616 and produces an expander energy stream 618 (e.g. mechanical or electrical energy). The expander 615 may be coupled to the first compressor 504 such that the expander energy stream 618 created by the expansion process is used to run the first compressor 504.

[0056] From the expander 615, the expander outlet stream 616 is passed through the second heat exchanger 600 to cool the recovery column overhead stream 574 and to produce a heated expander outlet stream 620. The heated expander outlet stream 620 is then passed through first heat exchanger 555 to cool the third separator top stream 552 and to produce a cold residue stream 622. The cold residue stream 622 may be used to generate energy and/or the cold residue stream 622 may be combusted as flare gas. It should be noted that no compressors are included in system 500 after the reflux separator 604 to increase the pressure and/or the temperature of the cold residue stream 622 as may be required in other systems.

[0057] Furthermore, it should be noted that the systems 100, 200, 300, 400, and 500 shown in FIGS. 1-5 reduce carbon emissions by recovering hydrocarbons that would otherwise be combusted in a flare and enable those hydrocarbons to be used in energy recovery or for sale. For instance, in simulations, systems 100 and 300 were able to recover more than about 99 mole % of the C4-C8 hydrocarbons that enter the systems 100 and 300, and systems 200, 400, and 500 that include propane product recovery were able to recover more than about 97 mole % of the C4-C8 hydrocarbons and more than about 45 mole % of the C3 hydrocarbons that enter the systems 200, 400, and 500. These hydrocarbon recoveries result in a reduction of carbon

emissions by about 27.80 mole % in systems 100 and 300, and result in a reduction of carbon emissions by about 36.58 mole % in systems 200 and 400, as compared to flaring the gas that is fed to systems 100, 200, 300, 400, and 500.

EXAMPLE 1

[0058] In one example, a process simulation was performed using the flare recovery system 300 shown in FIG. 3. The simulation was performed using Aspen Technology Inc.'s HYSYS version 8.8 software package. The specified values are indicated by an asterisk (*). The physical properties are provided in degrees Fahrenheit (F), pounds per a square inch gauge (psig), million standard cubic feet per day (MMSCFD), pounds per hour (lb/hr), barrels per a day (barrel/day), and British thermal units per hour (Btu/hr). The material streams, their compositions, and the associated energy streams produced by the simulation are provided in Tables 1 , 2, and 3 below, respectively.


Table 1A: Material Streams

Heated Reflux Reflux

Expander Recovery

Expander Separator Separator

Name Outlet Stream Column Reflux

Outlet Stream Overhead Bottoms

372 Stream 364

374 Stream 366 Stream 360

Vapor Fraction 0.9321 1.0000 1.0000 0.0000 0.0000

Temperature

(F) - 165.4 -5.13 -46.0 -46.0 -44.95

Pressure

(psig) 25.00* 20.0 355.0 355.0 455.0

Molar Flow

(MMSCFD) 8.715 8.715 8.715 2.019 2.019

Mass Flow

(lb/hr) 1.794E+04 1.794E+04 1.794E+04 7617 7.62E+03

Liquid Volume Flow

(barrel/day) 3752 3752 3752 1 189 1 189

Heat Flow

(Btu/hr) -3.421E+07 -3.241E+07 -3.310E+07 - 1.069E+07 - 1.068E+07

Table IB: Material Streams


Table 1C: Material Streams

Overhead Bottoms

Separation

Mixer Outlet Separation Separation

Name Column Inlet

Stream 376 Column Column Stream 336

Stream 348 Stream 350

Vapor Fraction 0.0000 1.0000 1.0000 0.0000

Temperature

(F) 120.0* -0.991 109.1 288.6

Pressure

(psig) 355.0 20.0 325.0 325.0

Molar Flow

(MMSCFD) 1.303 9.1 17 0.402 0.901

Mass Flow

(lb/hr) 8.40E+03 1.96E+04 1644 6.758E+03

Liquid Volume Flow

(barrel/day) 1003 3998 246.8 756.4

Heat Flow

(Btu/hr) -9.049E+06 -3.426E+07 1.859E+06 -6.224E+06

Table ID: Material Streams


Table 2A: Stream Compositions

Expander Heated Reflux Reflux Recovery

Outlet Expander Separator Separator Column

Name

Stream Outlet Stream Overhead Bottoms Reflux 372 374 Stream 366 Stream 360 Stream 364

Comp Mole Frac (Methane) 0.8504 0.8504 0.8504 0.241 1 0.241 1

Comp Mole Frac (Ethane) 0.0851 0.0851 0.0851 0.2186 0.2186

Comp Mole Frac (Propane) 0.0412 0.0412 0.0412 0.5270 0.5270

Comp Mole Frac (i-Butane) 0.0002 0.0002 0.0002 0.0069 0.0069

Comp Mole Frac (n- Butane) 0.0000 0.0000 0.0000 0.001 1 0.001 1

Comp Mole Frac (i-Pentane) 0.0000 0.0000 0.0000 0.0000 0.0000

Comp Mole Frac (n-Pentane) 0.0000 0.0000 0.0000 0.0000 0.0000

Comp Mole Frac (C02) 0.0045 0.0045 0.0045 0.0040 0.0040

Comp Mole Frac (n-Hexane) 0.0000 0.0000 0.0000 0.0000 0.0000

Comp Mole Frac (n- Heptane) 0.0000 0.0000 0.0000 0.0000 0.0000

Comp Mole Frac (n-Octane) 0.0000 0.0000 0.0000 0.0000 0.0000

Comp Mole Frac (Nitrogen) 0.0186 0.0186 0.0186 0.0013 0.0013

Table 2B: Stream Compositions


Table 2C: Stream Compositions

Separation

Overhead Bottoms

Column

Mixer Outlet Separation Separation

Name Inlet

Stream 376 Column Column

Stream

Stream 348 Stream 350

336

Comp Mole Frac (Methane) 0.0444 0.8193 0.1442 0.0000

Comp Mole Frac (Ethane) 0.0644 0.0905 0.2089 0.0000

Comp Mole Frac (Propane) 0.1986 0.0672 0.6316 0.0057

Comp Mole Frac (i- Butane) 0.1426 0.0006 0.0104 0.2015

Comp Mole Frac (n- Butane) 0.2157 0.0001 0.0012 0.31 13

Comp Mole Frac (i-Pentane) 0.1 151 0.0000 0.0000 0.1664

Comp Mole Frac (n-Pentane) 0.1297 0.0000 0.0000 0.1875

Comp Mole Frac (C02) 0.0012 0.0045 0.0037 0.0000

Comp Mole Frac (n-Hexane) 0.0384 0.0000 0.0000 0.0555

Comp Mole Frac (n- Heptane) 0.0161 0.0000 0.0000 0.0233

Comp Mole Frac (n- Octane) 0.0338 0.0000 0.0000 0.0488

Comp Mole Frac (Nitrogen) 0.0000 0.0178 0.0000 0.0000

Table 2D: Stream Compositions


Table 3: Energy Streams

EXAMPLE 2

[0059] In another example, a process simulation was performed using the flare recovery system 400 shown in FIG. 4. The material streams, their compositions, and the associated energy streams produced by the simulation are provided in Tables 4, 5, and 6 below, respectively.

Recovery Recovery

Recovery

Inlet Stream Column Column Separator Inlet

Name Column Inlet

402 Overhead Bottoms Stream 456

Stream 422

Stream 430 Stream 432

Vapor Fraction 1.0000 0.9334 1.0000 0.0000 0.81 19

Temperature

(F) 100.0* 72.44 6.955 252.8 -46.00*

Pressure

(psig) 15.00* 440.0 425.0 425.0 355.0

Molar Flow

(MMSCFD) 10.00* 10.0 10.990 1.291 10.730

Mass Flow

(lb/hr) 2.63E+04 2.63E+04 2.58E+04 8548 2.56E+04

Liquid Volume Flow

(barrel/day) 4744 4744 5045 1011 4941

Heat Flow

(Btu hr) -3.93E+07 -4.07E+07 -4.29E+07 -8.29E+06 -4.48E+07

Table 4A: Material Streams


Table 4B: Material Streams

Second First Separation

Cold Residue First Cooled

Name Compressed Compressed Column Inlet

Stream 478 Stream 416

Stream 410 Stream 406 Stream 436

Vapor Fraction 1.0000 1.0000 0.9732 1.0000 0.0000

Temperature

(F) 90.0* 587.4 1 10.0* 186.6 120.0*

Pressure

(psig) 15.0 450.0* 445.0 28.8 420.0

Molar Flow

(MMSCFD) 8.69 10.00 10.00 10.00 1.291

Mass Flow

(lb/hr) 1.767E+04 2.628E+04 2.628E+04 2.628E+04 8.55E+03

Liquid Volume Flow

(barrel/day) 3722 4744 4744 4744 101 1

Heat Flow

(Btu/hr) -3.139E+07 -3.185E+07 -3.987E+07 -3.818E+07 -9.097E+06

Table 4C: Material Streams


Table 4D: Material Streams

Recovery Recovery

Inlet Recovery Separator

Column Column

Name Stream Column Inlet Inlet Stream

Overhead Bottoms

402 Stream 422 456

Stream 430 Stream 432

Comp Mole Frac (Methane) 0.7465* 0.7465 0.7402 0.0000 0.7407

Comp Mole Frac (Ethane) 0.0822* 0.0822 0.1202 0.0539 0.1198

Comp Mole Frac (Propane) 0.0608* 0.0608 0.1197 0.2475 0.1196

Comp Mole Frac (i-Butane) 0.0187* 0.0187 0.0000 0.1448 0.0000

Comp Mole Frac (n-Butane) 0.0281* 0.0281 0.0000 0.2176 0.0000

Comp Mole Frac (i-Pentane) 0.0150* 0.0150 0.0000 0.1162 0.0000

Comp Mole Frac (n-Pentane) 0.0169* 0.0169 0.0000 0.1309 0.0000

Comp Mole Frac (C02) 0.0041* 0.0041 0.0047 0.0000 0.0047

Comp Mole Frac (n-Hexane) 0.0050* 0.0050 0.0000 0.0387 0.0000

Comp Mole Frac (n- Heptane) 0.0021* 0.0021 0.0000 0.0163 0.0000

Comp Mole Frac (n-Octane) 0.0044* 0.0044 0.0000 0.0341 0.0000

Comp Mole Frac (Nitrogen) 0.0162* 0.0162 0.0151 0.0000 0.0151

Table 5A: Stream Compositions


Table 5B: Stream Compositions

Cold

Second First Separation Residue First Cooled

Name Compressed Compressed Column Inlet

Stream Stream 416

Stream 410 Stream 406 Stream 436

478

Comp Mole Frac (Methane) 0.8581 0.7465 0.7465 0.7465 0.0000

Comp Mole Frac (Ethane) 0.0858 0.0822 0.0822 0.0822 0.0539

Comp Mole Frac (Propane) 0.0327 0.0608 0.0608 0.0608 0.2475

Comp Mole Frac (i- Butane) 0.0000 0.0187 0.0187 0.0187 0.1448

Comp Mole Frac (n- Butane) 0.0000 0.0281 0.0281 0.0281 0.2176

Comp Mole Frac (i-Pentane) 0.0000 0.0150 0.0150 0.0150 0.1 162

Comp Mole Frac (n-Pentane) 0.0000 0.0169 0.0169 0.0169 0.1309

Comp Mole Frac (C02) 0.0047 0.0041 0.0041 0.0041 0.0000

Comp Mole Frac (n-Hexane) 0.0000 0.0050 0.0050 0.0050 0.0387

Comp Mole Frac (n- Heptane) 0.0000 0.0021 0.0021 0.0021 0.0163

Comp Mole Frac (n-Octane) 0.0000 0.0044 0.0044 0.0044 0.0341

Comp Mole Frac (Nitrogen) 0.0186 0.0162 0.0162 0.0162 0.0000

Table 5C: Stream Compositions


Table 5D: Stream Compositions

Name Heat Flow (Btu/hr)

Recovery Column Reboiler Energy Stream 428 1.212E+06

Reflux Pump Energy Stream 463 6.516E+03

Expander Energy Stream 470 1.1 19E+06

Second Compressor Energy Stream 412 6.326E+06

Separation Column Condenser Energy Stream 446 1.036E+06

Separation Column Reboiler Energy Stream 444 1.852E+06

Table 6: Energy Streams

EXAMPLE 3

[0060] In another example, a process simulation was performed using the flare recovery system 500 shown in FIG. 5. The material streams, their compositions, and the associated energy streams produced by the simulation are provided in Tables 7, 8, and 9 below, respectively.


Table 7A: Material Streams

Second

Third Second Second Fourth

Separator

Name Compressed Cooled Separator Top Compressed

Bottom

Stream 526 Stream 532 Stream 536 Stream 542

Stream 538

Vapor Fraction 1 0.98614507 1 0 1

Temperature

(F) 260.233317 120 120 120 202.1 16522

Pressure

(psia) 240 235 235 235 450

Molar Flow

(MMSCFD) 257 257 253.4392818 3.56071821 253.439282

Mass Flow

(lb hr) 810900.77 810900.77 782550.9724 28349.7976 782550.972

Liquid Volume Flow

(barrel/day) 135413.561 135413.561 132285.9716 3127.58906 132285.972

Heat Flow

(Btu/hr) - 1.077E+09 - 1.14E+09 - 1 1 10838106 -28779233 - 1.084E+09

Table 7B: Material Streams


Table 7C: Material Streams

Mixed Recovery Recovery

Separation Propane Recovery Column Column

Name Column Inlet Product

Column Inlet Overhead Bottoms

Stream 580 Stream 592 Stream 568 Stream 574 Stream 576

Vapor Fraction 0 1 8.92809E-06 0 1

Temperature

(F) 120.890255 52.9001769 252.4654246 120 135.954766

Pressure

(psia) 445 435 435 430 325

Molar Flow

(MMSCFD) 1 1.3478879 285.709613 42.54406644 42.5440664 14.0505052

Mass Flow

(lb hr) 77564.2872 816821.106 2761 17.3047 2761 17.305 65601.9814

Liquid Volume Flow

(barrel/day) 9056.84161 145970.174 32797.56012 32797.5601 9180.64315

Heat Flow

(Btu hr) -82306221 - 1.246E+09 -267882455 -2941 13010 -67725992

Table 7D: Material Streams


Table 7E: Material Streams


Table 7F: Material Streams

Table 8A: Stream Compositions Second Second

Third Second Fourth

Separator Separator

Name Compressed Cooled Compressed

Top Stream Bottom

Stream 526 Stream 532 Stream 542

536 Stream 538

Comp Mole Frac (Methane) 0.5507 0.5507 0.5578 0.0451 0.5578

Comp Mole Frac (Ethane) 0.1777 0.1777 0.1794 0.0597 0.1794

Comp Mole Frac (Propane) 0.1397 0.1397 0.1398 0.1336 0.1398

Comp Mole Frac (i-Butane) 0.0170 0.0170 0.0168 0.0345 0.0168

Comp Mole Frac (n-Butane) 0.0492 0.0492 0.0480 0.1306 0.0480

Comp Mole Frac (i-Pentane) 0.0120 0.0120 0.01 13 0.0658 0.01 13

Comp Mole Frac (n-Pentane) 0.0170 0.0170 0.0157 0.1 148 0.0157

Comp Mole Frac (C02) 0.0191 0.0191 0.0193 0.0031 0.0193

Comp Mole Frac (n-Hexane) 0.0080 0.0080 0.0064 0.1214 0.0064

Comp Mole Frac (n- Heptane) 0.0059 0.0059 0.0036 0.1716 0.0036

Comp Mole Frac (n-Octane) 0.0027 0.0027 0.0010 0.1 197 0.0010

Comp Mole Frac (Nitrogen) 0.0010 0.0010 0.0010 0.0000 0.0010

Table 8B: Stream Compositions


Table 8C: Stream Compositions

Mixed Recovery Recovery Separation

Propane Recovery Column Column Column

Name Product

Column Inlet Overhead Bottoms Inlet

Stream 592 Stream 568 Stream 574 Stream 576 Stream 580

Comp Mole Frac (Methane) 0.0790 0.5372 0.0000 0.0000 0.0000

Comp Mole Frac (Ethane) 0.0921 0.2239 0.0410 0.0410 0.1242

Comp Mole Frac (Propane) 0.1846 0.2057 0.2910 0.2910 0.8637

Comp Mole Frac (i-Butane) 0.0432 0.0086 0.0939 0.0939 0.0093

Comp Mole Frac (n-Butane) 0.1574 0.0033 0.2985 0.2985 0.0026

Comp Mole Frac (i-Pentane) 0.0694 0.0000 0.0727 0.0727 0.0000

Comp Mole Frac (n-Pentane) 0.1155 0.0000 0.1029 0.1029 0.0000

Comp Mole Frac (C02) 0.0051 0.0204 0.0000 0.0000 0.0001

Comp Mole Frac (n-Hexane) 0.0960 0.0000 0.0481 0.0481 0.0000

Comp Mole Frac (n- Heptane) 0.1026 0.0000 0.0357 0.0357 0.0000

Comp Mole Frac (n-Octane) 0.0550 0.0000 0.0160 0.0160 0.0000

Comp Mole Frac (Nitrogen) 0.0001 0.0009 0.0000 0.0000 0.0000

Table 8D: Stream Compositions


Table 8E: Stream Compositions

Heated

Expander

Expander Cold Residue

Name Outlet

Outlet Stream Stream 622

Stream 616

620

Comp Mole Frac (Methane) 0.6553 0.6553 0.6553

Comp Mole Frac (Ethane) 0.2087 0.2087 0.2087

Comp Mole Frac (Propane) 0.1082 0.1082 0.1082

Comp Mole Frac (i- Butane) 0.0027 0.0027 0.0027

Comp Mole Frac (n- Butane) 0.0009 0.0009 0.0009

Comp Mole Frac (i-Pentane) 0.0000 0.0000 0.0000

Comp Mole Frac (n-Pentane) 0.0000 0.0000 0.0000

Comp Mole Frac (C02) 0.0230 0.0230 0.0230

Comp Mole Frac (n-Hexane) 0.0000 0.0000 0.0000

Comp Mole Frac (n-Heptane) 0.0000 0.0000 0.0000

Comp Mole Frac (n- Octane) 0.0000 0.0000 0.0000

Comp Mole Frac (Nitrogen) 0.0012 0.0012 0.0012

Table 8F: Stream Compositions

Table 9: Energy Streams

EXAMPLE 4

1] In another example, calculations were performed to determine the carbon reduction flare recovery process without C3 recovery and with C3 recovery. Table 10 shows the composition of a 10 MMSCFD inlet flow stream used for the calculations. Table 11 shows the composition of a resulting 9.1 MMSCFD residue flow stream without C3 recovery, and Table 12 shows the composition of a resulting 8.55 MMSCFD residue flow stream with C3 recovery. Based on the calculations, it was determined that the flare recovery process without C3 recovery reduces carbon emissions by about 27.80 mole %. The flare recovery process with C3 recovery reduces carbon emissions by about 36.58 mole %. Both processes recovery 750 barrels per a day of C4+ hydrocarbons that are blended with crude oil. Additionally, the flare recovery process with C3 recovery recovers about 54 mole % of the C3 hydrocarbons and produces 240 barrels per a day of C3 hydrocarbons.


Table 10: Inlet Flow

Volume

Mole % (MMSCFD) Moles/day Carbon # Carbon %

Nitrogen 1.78 0.16198 427.3879 0 0

C02 0.45 0.04095 108.0475 108.0475 0.003721

Methane 81.93 7.45563 19671.85 19671.85 0.677555

Ethane 9.05 0.82355 2172.955 4345.91 0.149686

Propane 6.72 0.61 152 1613.509 4840.528 0.166722

I- Butane 0.06 0.00546 14.40633 57.62533 0.001985

N- Butane 0.01 0.00091 2.401055 9.604222 0.000331

I-Pentane 0 0 0 0 0

N-Pentane 0 0 0 0 0

Hexanes 0 0 0 0 0

Heptanes 0 0 0 0 0

Octanes 0 0 0 0 0

Totals 100 9.1 24010.55 ; 29033.56

Table 11 : Residue Flow with No C3 Recovery


Table 12: Residue Flow with C3 Recovery EXAMPLE 5

[0062] In another example, actual inlet stream compositions for a flare recovery process were determined. Table 13 shows the composition of four different inlet streams that can be used in a flare recovery process.


Table 13: Flare Recovery Process Inlet Streams

[0063] At least one embodiment is disclosed and variations, combinations, and/or modifications of the embodiment(s) and/or features of the embodiment(s) made by a person having ordinary skill in the art are within the scope of the disclosure. Alternative embodiments that result from combining, integrating, and/or omitting features of the embodiment(s) are also within the scope of the disclosure. Where numerical ranges or limitations are expressly stated, such express ranges or limitations should be understood to include iterative ranges or limitations of like magnitude falling within the expressly stated ranges or limitations (e.g., from 1 to 10 includes, 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). For example, whenever a numerical range with a lower limit, Rj, and an upper limit, Ru, is disclosed, any number falling within the range is specifically disclosed. In particular, the following numbers within the range are specifically disclosed: R = Rj + k * (Ru - Ri), wherein k is a variable ranging from 1 percent to 100 percent with a 1 percent increment, e.g., k is 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, 50 percent, 51 percent, 52 percent, 95 percent, 96 percent, 97 percent, 98 percent, 99 percent, or 100 percent. Moreover, any numerical range defined by two R numbers as defined in the above is also specifically disclosed. The use of the term "about" means + 10% of the subsequent number, with the exception that about 0% means < 0.1 %. Use of the term "optionally" with respect to any element of a claim means that the element is required, or alternatively, the element is not required, both alternatives being within the scope of the claim. Use of broader terms such as comprises, includes, and having should be understood to provide support for narrower terms such as consisting of, consisting essentially of, and comprised substantially of. Accordingly, the scope of protection is not limited by the description set out above but is defined by the claims that follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated as further disclosure into the specification and the claims are embodiment s) of the present disclosure. The discussion of a reference in the disclosure is not an admission that it is prior art, especially any reference that has a publication date after the priority date of this application. The disclosure of all patents, patent applications, and publications cited in the disclosure are hereby incorporated by reference, to the extent that they provide exemplary, procedural, or other details supplementary to the disclosure.

[0064] While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and methods might be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be

combined or integrated in another system or certain features may be omitted, or not implemented.

[0065] In addition, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items shown or discussed as coupled or directly coupled or communicating with each other may be indirectly coupled or communicating through some interface, device, or intermediate component whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the spirit and scope disclosed herein.