KR20160067957A - Split feed addition to iso-pressure open refrigeration lpg recovery - Google Patents

Abstract

Forming a first portion of the feed gas stream and a second portion of the feed gas stream wherein the mass ratio of the first portion to the second portion is in the range of 95: 5 to 5:95; Cooling the portion and at least partially condensing the first portion and supplying the second portion and the cooled and at least partially condensed first portion to the distillation column wherein the harder component is the overhead vapor stream The heavier components are removed from the bottom of the distillation column as a product stream and the second portion is fed into the distillation column at one or more vapor-liquid equilibrium points below the first portion, To allow mass transfer of the liquid between the second portion of the liquid and the vapor of the second portion), a method of recovering a natural gas liquid from a feed gas stream It is disclosed in the specification. Corresponding devices are also disclosed.

Description

{SPLIT FEED ADDITION TO ISO-PRESSURE OPEN REFRIGERATION LPG RECOVERY}

Related application

This application claims priority to U.S. Provisional Application No. 61 / 888,901, filed October 9, 2013.

Technical field

The embodiments described herein relate to an improved process for recovery of a natural gas liquid from a gas feed stream containing hydrocarbons, particularly recovery of propane and ethane from a gas feed stream.

Natural gas contains a variety of hydrocarbons including methane, ethane and propane. Natural gas usually has mostly methane and ethane, that is, methane and ethane usually together contain at least 50 mol% of gas. The gas also contains relatively fewer heavier hydrocarbons such as propane, butane, pentane, and the like, and hydrogen, nitrogen, carbon dioxide and other gases. In addition to natural gas, other gas streams containing hydrocarbons may contain mixtures of lighter hydrocarbons and heavier hydrocarbons. For example, the gas stream formed in the purification process may contain a mixture of hydrocarbons to be separated. The separation and recovery of the hydrocarbons can provide valuable products that can be used directly or used as feedstock for other processes. The hydrocarbons are typically recovered as natural gas liquids (NGL).

The embodiments described herein relate generally to the recovery of C ₃ + components in a gas stream containing hydrocarbons, particularly the recovery of propane from this gas stream. Typical natural gas feedstocks that are processed according to the process described below typically contain 92.12% methane, 3.96% ethane and other C ₂ components, 1.05% propane and other C ₃ components, 0.15% Of isobutane, 0.21% of normal butane, 0.11% of pentane or heavier and the balance mainly consists of nitrogen and carbon dioxide. The refinery gas stream may contain less methane and contain a higher amount of heavier hydrocarbons.

The recovery of the natural gas liquid from the gas feed stream is carried out using various processes such as cooling and freezing of the gas, oil absorption, refrigeration oil absorption or through the use of multiple distillation columns. More recently, the cryogenic expansion process using a Joule-Thompson valve or turboexpander is the preferred process for recovering NGL from natural gas.

In a typical cryogenic expansion recovery process, the feed gas stream under pressure is cooled by heat exchange with another stream of the process and / or an external source of refrigeration, such as a propane compression-refrigeration system. As the gas is cooled, the liquid can be condensed and collected in one or more separators as a high-pressure liquid containing the desired components.

High pressure liquids can be expanded and fractionated to lower pressures. The expanded stream, including a mixture of liquid and vapor, is fractionated in a distillation column. In the distillation column, volatile gases and lighter hydrocarbons are removed as overhead vapor and heavier hydrocarbon components are withdrawn from the bottom as liquid product.

The feed gas typically does not condense as a whole and the remaining steam from the partial condensation can pass through lower pressure through the Rhine-Thomson valve or turboexpander, where additional liquid is condensed as a result of further cooling of the stream. The expanded stream is fed as a feed stream to the distillation column.

A portion of the reflux stream, typically a partially condensed feed stream after cooling but prior to expansion, is provided in the distillation column. Various processes use a stream of recycled residual gas supplied under another source, such as pressure, for reflux.

While various improvements have been made to the general cryogenic process described above, this improvement continues to expand the feed stream over the distillation column using a turboexpander or a Row-Thomson valve. It would be desirable to have an improved process for increasing the recovery of NGL from the natural gas feed stream.

The embodiments described herein relate to an improved process for recovery of NGL from a feed gas stream. The process uses an open-loop mixed refrigerant process to achieve the low temperatures needed for high levels of NGL recovery. A single distillation column is used to separate the heavier hydrocarbons from the harder components, such as the sails gas. The overhead stream from the distillation column is cooled to partially liquefy the overhead stream. The partially liquefied overhead stream is separated into a vapor stream comprising lighter hydrocarbons, such as a shale gas, and a liquid component acting as a mixed refrigerant. The mixed refrigerant provides process cooling, and a portion of the mixed refrigerant is used as the reflux stream to make the critical components in the distillation column rich. With the gas rich in the distillation column, the overhead stream of the distillation column condenses at a warmer temperature and the distillation column is typically run at a warmer temperature than that used for the higher NGL recovery. The process achieves a high recovery of the desired NGL component by only a single distillation column, without expanding the gas as in a line-Thomson valve or turboexpander-based plant.

In one embodiment, C ₃ + hydrocarbons, especially propane, are recovered. The temperature and pressure are maintained as required to achieve the desired number of C ₃ + hydrocarbons based on the composition of the incoming feed stream. In this embodiment of the process, the feed gas enters the main heat exchanger and is cooled. The cooled feed gas is fed into a distillation column, which serves as a deethanizer in this embodiment. Cooling of the feed stream can be provided primarily by a warm refrigerant, such as propane. The overhead stream from the distillation column enters the main heat exchanger, is cooled to the temperature required to produce the mixed refrigerant and to provide the desired NGL recovery from the system.

The cooled overhead stream from the distillation column is combined with the overhead stream from the reflux drum and separated in the distillation column overhead drum. The overhead vapor from the distillation column overhead drum is shale gas (i.e., methane, ethane and inert gas) and the liquid residue is a mixed refrigerant. The mixed refrigerant is rich in C ₂ and harder components compared to the feed gas. The sales gas is supplied through the main heat exchanger, where it is warmed up. The temperature of the mixed refrigerant decreases to a cool enough temperature to facilitate the required heat transfer in the main heat exchanger. The temperature of the refrigerant is lowered by decreasing the refrigerant pressure across the control valve. The mixed refrigerant is fed to the main heat exchanger, where it evaporates and overheats as it passes through the main heat exchanger.

After passing through the main heat exchanger, the mixed refrigerant is compressed. Preferably, the compressor discharge pressure is higher than the distillation column pressure since no reflux pump is required. The compressed gas passes through the main heat exchanger, where it is partially condensed. The partially condensed mixed refrigerant is routed to the reflux drum. The bottom liquid from the reflux drum is used as the reflux stream for the distillation column. The vapor from the reflux drum is combined with the distillation column overhead stream to exit the main heat exchanger and the combined stream is routed to the distillation column overhead drum. In this embodiment, the process can achieve more than 99% recovery of propane from the feed gas.

In another embodiment of the process, the feed gas is treated as described above, and a portion of the mixed refrigerant is removed from the plant after compression and cooling. A portion of the mixed refrigerant removed from the plant is fed to the C ₂ recovery unit to recover the ethane from the mixed refrigerant. After the mixed refrigerant stream passes through the main heat exchanger and is compressed and cooled, the removal of a portion thereof has minimal effect on the process, and sufficient C ₂ component remains in the system to provide the necessary refrigeration. In some embodiments, as many as 95% of the combined refrigerant streams can be removed for C ₂ recovery. The stripped stream may be used as a feed stream in an ethylene cracking unit.

In another embodiment of the process, the absorber column is used to separate the distillation column overhead stream. The overhead stream from the absorber is a sluice gas and the residue is a mixed refrigerant.

In yet a further embodiment, only one separator drum is used. In this embodiment, the compressed and cooled mixed refrigerant is returned to the distillation column as a reflux stream.

The process described above may be modified to achieve separation of the hydrocarbons in any desired manner. For example, the plant may be operated such that the distillation column separates C ₄ + hydrocarbons, mainly butane, from C ₃ and harder hydrocarbons. In another embodiment, the plant can be operated to recover both ethane and propane. In this embodiment, the distillation column is used as a demethanizer, and the plant pressure and temperature are adjusted accordingly. In this embodiment, the residue from the distillation column mainly contains the C < ₂ + > component, but the overhead stream mainly contains methane and an inert gas. In this embodiment, recovery of as much as 55% of the C < ₂ + > component in the feed gas can be obtained.

Among the advantages of this process is that the reflux to the distillation column is, for example, ethane rich, thereby reducing the loss of propane from the distillation column. Reflux also increases the molar fraction of harder hydrocarbons, such as ethane, in the distillation column, making it easier to condense the overhead stream. This process uses twice the condensed liquid in the distillation column overhead, once as the low temperature refrigerant and secondarily as the reflux stream to the distillation column. Other advantages of the processes described herein will be apparent to those skilled in the art based on the detailed description of the preferred embodiments provided below.

In yet a further embodiment, forming a first portion of the feed gas stream and a second portion of the feed gas stream wherein the mass ratio of the first portion to the second portion is in the range of 95: 5 to 5:95, ; Cooling the first portion within the heat exchanger and at least partially condensing the first portion; And a second portion and a cooled, at least partially condensed first portion into a distillation column, wherein the harder component is removed from the distillation column as an overhead vapor stream, and the heavier component Is removed from the bottom of the distillation column as a product stream and the second portion is fed into the distillation column at one or more vapor-liquid equilibrium points below the first portion to separate the liquid of the cooled first portion To permit mass-to-mass exchange between the vapor of the feed gas stream. The process comprises feeding a distillation column overhead stream to a heat exchanger, cooling the distillation column overhead stream to at least partially liquefy the distillation column overhead stream, separating the at least partially liquefied distillation column overhead stream into a first separator Separating the vapor and liquid in a first separator to produce a bottoms stream comprising an overhead vapor stream comprising a seth gas and a mixed refrigerant, supplying the combined refrigerant stream to a heat exchanger , Wherein the mixed refrigerant stream is vaporized as it passes through the heat exchanger, compressing the vaporized mixed refrigerant stream and passing the compressed mixed refrigerant stream through the exchanger, Feeding at least a portion thereof as a reflux stream into a distillation column It should. In an embodiment, the energy input is about 5-30% or about 10-20% lower than the energy input for the unpartitioned process, and the entire feed stream passes through the heat exchanger for cooling. Reduced energy input significantly reduces operating costs.

In a further embodiment, there is provided an apparatus for separating a natural gas liquid from a feed gas stream, the apparatus comprising a primary feed gas line configured to deliver a feed gas stream, a line between the feed gas stream and the at least one process stream, A heat exchanger operable to provide heating and cooling necessary for the separation of the natural gas liquid from the feed gas stream by the exchange contact to form a cooled feed gas stream and a feed gas stream containing a feed gas stream, A column overhead stream containing a substantial amount of the harder hydrocarbon component and a distillation column configured to separate into a column residual stream comprising a substantial amount of the heavier hydrocarbon component. The apparatus includes a first separator configured to receive a distillation column overhead stream and separate the column overhead stream into an overhead sour gas stream and a residual stream comprising a mixed refrigerant configured to provide process cooling in a heat exchanger, A compressor configured to compress the mixed refrigerant stream after the stream provides process cooling in a heat exchanger and a feed gas bypass line configured to remove a portion of the feed gas stream prior to being conveyed to the heat exchanger, Wherein the feed gas bypass line is fluidly connected to the distillation column at one or more vapor-liquid equilibrium points below the point where the cooled feed gas stream from the heat exchanger is connected to the fluid to provide a cooled feed from the heat exchanger The vapor of the gas stream and the bypass feed gas stream in the column Allow the mass of the mobile exchange includes also) additionally.

1 is a schematic illustration of a plant for carrying out an embodiment of a method in which a mixed refrigerant stream is compressed and returned to a reflux separator;
2 is a schematic diagram of a plant for performing an embodiment of a method in which a portion of a compressed mixed refrigerant stream is removed from a plant for ethane recovery;
3 is a schematic illustration of a plant for carrying out an embodiment in which an absorber is used to separate a distillation overhead stream;
4 is a schematic view of a plant for carrying out an embodiment in which only one separator drum is used;
Figure 5 is a schematic diagram of a plant for carrying out an embodiment of a process wherein the feed stream for the distillation column is divided and fed to different locations of the column, the mixed refrigerant is compressed and returned to the reflux separator;
Figure 6 is a schematic diagram of a plant for carrying out an embodiment of a method in which a feed stream for a distillation column is split and fed to different locations in the column and a portion of the compressed mixed refrigerant stream is removed from the plant for ethane recovery;
Figure 7 is a schematic illustration of a plant for carrying out an embodiment of a method in which a feed stream for a distillation column is split and fed to different locations in the column and the absorber is used to separate the distillation column overhead stream;
Figure 8 is a schematic view of a plant for carrying out an embodiment of a method in which a feed stream for a distillation column is divided and fed to different locations of the column and only one separator drum is used;
9 is a schematic diagram of a plant for carrying out another method embodiment in which the feed stream for the distillation column is divided and fed to different locations of the column.

The embodiments described herein relate to improved processes for the recovery of natural gas liquids (NGL) from natural gas or gas streams from hydrocarbon feedstock feed streams, such as petroleum processing. In an embodiment, the process is performed at approximately constant pressure without intentional reduction of gas pressure through the plant. The process uses a single distillation column to separate the harder and heavier hydrocarbons. The open-loop mixed refrigerant provides process cooling to achieve the required temperature for high recovery of NGL gas. The mixed refrigerant consists of a mixture of harder and heavier hydrocarbons in the feed gas, and the harder hydrocarbons are generally richer than the feed gas.

The open-loop mixed refrigerant is also used to provide a rich reflux stream to the distillation column, which allows the distillation column to be operated at a higher temperature and increases the recovery of NGL. The overhead stream from the distillation column is cooled to partially liquefy the overhead stream. The partially liquefied overhead stream is separated into a vapor stream containing lighter hydrocarbons, such as a sluice gas, and a liquid component acting as a mixed refrigerant.

In an embodiment, the process can be used to obtain the desired separation of hydrocarbons in the mixed feed gas stream. In one embodiment, the process herein may be used to obtain a high level of propane recovery. Recovery of more than 99% of propane in feed can be recovered in the process. The process may also be operated in a manner that recovers propane with a significant amount of ethane or rejects the sale gas with most of the ethane. Alternatively, the process may be operated to recover the C ₄ + components of the high percentage of the feed stream and discharges the C ₃ and lighter components of more.

In embodiments, a substantial reduction in energy use may be achieved using the split feed configuration described herein. In an embodiment, the compressor duty can be reduced by at least 5%, or at least 10, or 5-20%, compared to a system in which the split feed is not used. In an embodiment, the reboiler duty may be reduced by at least 10%, or at least 20%, or at least 30%, as compared to a system that does not have a split feed. In an embodiment, the size of the distillation column can also be reduced, resulting in lower capital costs. In embodiments, the mass ratio of the first portion of the feed stream (cooled and partially condensed prior to feeding to the distillation column) and the second portion of the feed stream (uncooled and partially condensed) is from 95: 5 to 5 : 95, or in the range of 95: 5 to 65:35, or in the range of 95: 5 to 70:30.

A plant for performing some embodiments is schematically illustrated in Fig. It should be understood that operational parameters for the plant, such as temperature, pressure, flow rate and composition of the various streams, are established to achieve the desired separation and recovery of NGL. The required operating parameters also depend on the composition of the feed gas. The required operating parameters can be readily determined by those skilled in the art using known techniques, including, for example, computer simulations. Accordingly, the description and scope of the various operational parameters provided below are intended to provide a description of specific embodiments, which are not intended to limit the scope of the present disclosure in any way.

The feed gas is supplied to main heat exchanger 10 via line 12. The feed gas may be natural gas, refinery gas or other gas stream requiring separation. The feed gas is typically filtered and dehydrated before being fed to the plant to prevent freezing within the NGL unit. The feed gas is typically fed to the main heat exchanger at a temperature of about 110 ℉ to 130 및 and a pressure of about 100 psia to 450 psia. The feed gas is cooled in the main heat exchanger 10 by heat exchange contact with a coolant that can be supplied to the main heat exchanger via line 15 in an amount necessary to provide additional cooling required for the cooler process stream and process Partially liquefied. A warm refrigerant, such as propane, can be used to provide the necessary cooling of the feed gas. The feed gas is cooled in the main heat exchanger to a temperature of about 0 ℉ to about -40..

The cold feed gas 12 exits the main heat exchanger 10 and enters the distillation column 20 via the feed line 13. The distillation column is typically operated at a pressure slightly below the pressure of the feed gas at a pressure of about 5 psi to 10 psi below the pressure of the feed gas. In the distillation column, heavier hydrocarbons such as propane and other C ₃ + components are separated from harder hydrocarbons such as ethane, methane and other gases. The heavier hydrocarbon components escape from the distillation column through the line 16 through the liquid residues, while the harder components escape through the vapor overhead line 14. Preferably, the retentate stream 16 exits the distillation column at a temperature of about 150 ° F to 300 ° F and the overhead stream 14 exits the distillation column at a temperature of about -10 ° F to -80 ° F.

The retentate stream 16 from the distillation column is split and the product stream 18 and the recycle stream 22 are directed to a reboiler 30 that receives the heat input Q. Optionally, the product stream 18 can be cooled in a cooler to a temperature of about 60 < 0 > F to 130 < 0 > F. The product stream 18 is heavier than the heavier hydrocarbons in the feed gas stream. In the embodiment shown in Figure 1, the product stream can be very rich in propane and heavier components, and the ethane and lighter gases are removed as a sale gas as described below. Alternatively, the plant may be operated such that the product stream is very rich in C ₄ + hydrocarbons and propane is removed from the sale gas with ethane. The recycle stream 22 is heated in the reboiler 30 to provide heat to the distillation column. Any type of reboiler commonly used in distillation columns may be used.

The distillation column overhead stream 14 passes through the main heat exchanger 10, which is cooled by heat exchange contact with the process gas to partially liquefy the stream. The distillation column overhead stream exits the main heat exchanger via line 19 and is sufficiently cooled to produce a mixed refrigerant as described below. Preferably, the distillation column overhead stream is cooled in the main heat exchanger from about -30 내지 to -130..

The cooled and partially liquefied stream 19 is combined with the overhead stream 28 from the reflux separator 40 in the mixer 100 and then fed to the line 32 via the line 32. In the embodiment of the process shown in Figure 1, To the distillation column overhead separator (60). Alternatively, stream 19 may be fed to distillation column overhead separator 60 without being combined with overhead stream 28 from reflux separator 40. The overhead stream 28 may be fed directly to the distillation column overhead separator or in another embodiment of the process the overhead stream 28 from the reflux separator 40 may be combined with the sale gas 42 . Optionally, the overhead stream from the reflux separator 40 can be fed through the control valve 75, before being fed via line 28a, which is mixed with the distillation column overhead stream 19. Depending on the feed gas used and other process parameters, the control valve 75 holds the pressure in the ethane compressor 80 (which may facilitate condensation of this stream) and transfers the liquid to the top of the distillation column Lt; / RTI > Alternatively, the reflux pump may be used to provide the pressure necessary to transfer the liquid to the top of the column.

1, the combined distillation column overhead stream and reflux drum overhead stream 32 are separated into overhead stream 42 and residual stream 34 in a distillation column overhead separator 60 do. The overhead stream 42 from the distillation column overhead separator 60 contains product sales gas (e.g., methane, ethane, and harder components). The residual stream (34) from the distillation column overhead separator is the liquid mixed refrigerant used for cooling in the main heat exchanger (10).

The sales gas flows through line 42 and through main heat exchanger 10 to warm up. In a typical plant, the sale gas exits the deethanizer overhead separator at a temperature of about -40 내지 to -120 및 and a pressure of about 85 psia to about 435 psia and is passed through a main heat exchanger at a temperature of about 100 내지 to 120 져 It comes out. The sales gas is transported for further processing through line 43.

The mixed refrigerant flows through the distillation column overhead separator residual line 34. The temperature of the mixed refrigerant can be lowered by reducing the pressure of the refrigerant over the control valve 65. [ The temperature of the mixed refrigerant decreases to a temperature that is cool enough to provide the required cooling in the main heat exchanger 10. The mixed refrigerant is fed via line (35) to the main heat exchanger. The temperature of the mixed refrigerant entering the main heat exchanger is typically about -60 내지 -175.. When the control valve 65 is used to reduce the temperature of the mixed refrigerant, the temperature is typically reduced by about 20 ℉ to 50 ℉, and the pressure is reduced by about 90 psi to 250 psi. The mixed refrigerant evaporates as it passes through the main heat exchanger (10), is superheated, and exits through the line (35a). The temperature of the mixed refrigerant exiting the main heat exchanger is about 80 < 0 > F to 100 < 0 > F.

After exiting the main heat exchanger, the mixed refrigerant is fed to the ethane compressor (80). The mixed refrigerant is compressed to a pressure of about 15 psi to 25 psi greater than the operating pressure of the distillation column at a temperature of about 230 ℉ to 350.. By compressing the mixed refrigerant at a pressure greater than the distillation column pressure, a reflux pump is not required. The compressed mixed refrigerant flows through line 36 to cooler 90 where it is cooled to a temperature of about 70 내지 to 130.. Optionally, the cooler 90 may be omitted and the compressed mixed refrigerant may flow directly to the main heat exchanger 10 as described below. The compressed mixed refrigerant then flows through the main heat exchanger 10 via line 38, where it is further cooled and partially liquefied. The mixed refrigerant is cooled in the main heat exchanger to a temperature of about 15 내지 to -70.. The partially liquefied mixed refrigerant is introduced into reflux separator 40 via line 39. 1, the overhead 28 from the reflux separator 40 is combined with the overhead 14 from the distillation column and the combined stream 32 is combined with the overhead 14 from the distillation column overhead 14. In the embodiment of FIG. Lt; / RTI > The liquid residue 26 from the reflux separator 40 is again fed as a reflux stream 26 into the distillation column. The control valves 75 and 85 can be used to maintain pressure in the compressor to facilitate condensation.

The open-loop mixed refrigerant used as reflux is rich in distillation columns with gaseous components. With the gas rich in the distillation column, the overhead stream of the column condenses at a warmer temperature and the distillation column is run at a warmer temperature than is normally required for high NGL recovery.

Reflux to the distillation column also reduces the loss of heavier hydrocarbons from the column. For example, in the process for the recovery of propane, reflux increases the molar fraction of ethane in the distillation column, which makes it easier to condense the overhead stream. The process uses twice the condensed liquid in the distillation column overhead drum, once as the low temperature refrigerant and as the reflux stream to the distillation column.

In another embodiment shown in FIG. 2 (the same numbers represent the same components and flow stream described above), the process is used to separate propane and other C ₃ + hydrocarbons from ethane and light components. Tee 110 is provided in line 38 after mixed refrigerant compressor 80 and mixed refrigerant cooler to split the mixed refrigerant into a return line 45 and an ethane recovery line 47. The return line 45 conveys a portion of the mixed refrigerant to the process through the main heat exchanger 10 described above. The ethane recovery line 47 supplies a portion of the mixed refrigerant to a separate ethane recovery unit for the recovery of ethane. The removal of a portion of the mixed refrigerant stream has minimal effect on the process and sufficient C ₂ component remains in the system to provide the necessary refrigeration. In some embodiments, as many as 95% of the combined refrigerant streams can be removed for C ₂ recovery. The stripped stream may be used, for example, as a feed stream in an ethylene cracking unit.

In another embodiment, the NGL recovery unit is capable of recovering a significant amount of ethane with propane. In this embodiment of the process, the distillation column is a demethanizer, and the overhead stream mainly contains methane and inert gas, while the column residue contains ethane, propane and heavier components.

In another embodiment of the process, the deethanizer overhead drum may be replaced by an absorber. In this embodiment, the overhead stream 14 from the distillation column 20 passes through the main heat exchanger 10 (as shown in Figure 3, where the same numbers represent the same components and flow stream described above) , And the cooled stream (19) is fed to the absorber (120). The overhead stream 28 from the reflux separator 40 is also fed to the absorber 120. The overhead stream 42 from the absorber is the sale gas and the residue stream 34 from the absorber is a mixed refrigerant. Other streams and components shown in Figure 3 have the same flow path as described above.

In yet another embodiment, shown in FIG. 4 (the same numbers represent the same components and flow stream described above), the second separator and cooler are not used in the process. In this embodiment, the compressed mixed refrigerant 36 is fed through the main heat exchanger 10 and fed to the distillation column via line 39 to provide a reflux stream.

In the embodiment shown in Figure 5, the gas feed stream 112 is divided to produce a first feed stream 112a and a second feed stream 112b. The first feed stream 112a enters the heat exchanger 110 for cooling and is partially liquefied to form a stream 113 containing a mixture of liquid and vapor from a heat exchanger 110 to a cold feed stream & (113). The second feed stream 112b is a warm gas bypass feed stream that has not been precooled, and typically is entirely vapor-free without liquid. The valve 195 is connected to the second feed stream 112b for process control purposes that includes control of the relative flow rates of the first feed stream 112a and the second feed stream 112b to the distillation column 120. [ / RTI > When the liquid is condensed in the first feed stream 112a, some of the condensed liquid is methane and ethane. Usually methane and ethane are overhead vapor products from the process. The second feed stream 112b has the same overall composition as the first feed stream 112a and the cooled feed stream 113 typically contains no liquid. As a result, there is a higher concentration of propane and butane vapor in the bypass gas of the second feed stream 112b than in the cold feed stream 113. [ Of the second feed stream 112b into one or more, or from one to ten, or from one to seven, or from one to four vapor-liquid equilibrium distillation columns below the cold feed stream 113, The supply of warm bypass gas permits mass transfer to exchange liquid methane and ethane for the propane and butane vapors in the distillation column 120. This vaporizes methane and ethane while condensing propane and butane. By doing so, it substantially increases the overall efficiency of the process by substantially reducing the refrigeration efficiency and reboiler efficiency. In an embodiment, the size of the distillation column may be reduced compared to a system that does not include the second feed stream 112b.

The feed gas 112 may be a natural gas, a refinery gas, or other gas stream that requires separation. The feed gas is typically filtered and dehydrated before being fed to the plant to prevent freezing within the NGL unit. The feed gas in the first feed stream 112a is typically fed to the main heat exchanger at a temperature of about 110 ℉ to 130 및 and a pressure of about 100 psia to 450 psia. The feed gas is cooled in the main heat exchanger 110 by heat exchange contact with a coolant that can be supplied to the main heat exchanger via line 115 in an amount required to provide additional cooling required for the cooler process stream and process Partially liquefied. A warm refrigerant, such as propane, can be used to provide the necessary cooling of the feed gas. The feed gas is cooled in the main heat exchanger to a temperature of about 0 ℉ to about -40..

The cold feed gas 112a exits the main heat exchanger 110 and enters the distillation column 120 through the feed line 113. The distillation column is typically operated at a pressure slightly below the pressure of the feed gas at a pressure of about 5 psi to 10 psi below the pressure of the feed gas. In the distillation column, heavier hydrocarbons such as propane and other C ₃ + components are separated from harder hydrocarbons such as ethane, methane and other gases. The heavier hydrocarbon components escape from the distillation column through the line 116 through the liquid residuum, while the lighter components escape through the vapor overhead line 114. Preferably, the retentate stream 116 exits the distillation column at a temperature of about 150 ℉ to 300 ℉ and the overhead stream 114 exits the distillation column at a temperature of about -10 내지 to -80..

The retentate stream 116 from the distillation column is split and the product stream 118 and recycle stream 122 are directed to a reboiler 130 that receives the heat input Q. Optionally, the product stream 118 can be cooled in a cooler to a temperature of about 60 < 0 > F to 130 < 0 > F. The product stream 118 is heavier than the heavier hydrocarbons in the feed gas stream. In the embodiment shown in FIG. 5, the product stream can be very rich in propane and heavier components, and ethane and lighter gases are removed as a sale gas in the sale gas line 143 as described below. Alternatively, the plant may be operated such that the product stream is very rich in C ₄ + hydrocarbons and propane is removed from the sale gas with ethane. Recycle stream 122 is heated in reboiler 130 to provide heat to the distillation column. Any type of reboiler commonly used in distillation columns may be used.

The distillation column overhead stream 114 passes through the main heat exchanger 110, which is cooled by heat exchange contact with the process gas to partially liquefy the stream. The distillation column overhead stream exits the main heat exchanger via line 119 and is sufficiently cooled to produce a mixed refrigerant as described below. Preferably, the distillation column overhead stream is cooled in the main heat exchanger from about -30 내지 to -130..

5, the cooled and partially liquefied stream 119 is combined with the overhead stream 128 from the reflux separator 140 in the mixer 200, To the distillation column overhead separator 160. The distillation column overhead separator 160, Alternatively, stream 119 may be fed to distillation column overhead separator 160 without being combined with overhead stream 128 from reflux separator 140. The overhead stream 128 may be fed directly to the distillation column overhead separator or in another embodiment of the process the overhead stream 128 from the reflux separator 140 may be combined with the sale gas 142 . Optionally, the overhead stream from reflux separator 140 may be fed via control valve 175, prior to being fed via line 128a, which is mixed with distillation column overhead stream 119. Depending on the feed gas used and other process parameters, the control valve 175 retains pressure in the ethane compressor 180 (which can facilitate condensation of this stream) and transfers the liquid to the top of the distillation column Lt; / RTI > Alternatively, the reflux pump may be used to provide the pressure necessary to transfer the liquid to the top of the column.

5, the combined distillation column overhead stream and reflux drum overhead stream 132 are separated into overhead stream 142 and residual stream 134 in a distillation column overhead separator 160 do. The overhead stream 142 from the distillation column overhead separator 160 contains product sales gas (e.g., methane, ethane and lighter components). The residual stream 134 from the distillation column overhead separator is the liquid mixed refrigerant used for cooling in the main heat exchanger 110.

The sales gas flows through line 142 and through main heat exchanger 110. In a typical plant, the sale gas exits the deethanizer overhead separator at a temperature of about -40 내지 to -120 및 and a pressure of about 85 psia to about 435 psia and is passed through a main heat exchanger at a temperature of about 100 내지 to 120 져 It comes out. The sales gas is conveyed for further processing through line 143.

The mixed refrigerant flows through the distillation column overhead separator residual line 134. The temperature of the mixed refrigerant can be lowered by reducing the pressure of the refrigerant over the control valve 165. [ The temperature of the mixed refrigerant decreases to a temperature that is cool enough to provide the necessary cooling in the main heat exchanger 110. The mixed refrigerant is supplied via line 135 to the main heat exchanger. The temperature of the mixed refrigerant entering the main heat exchanger is typically about -60 내지 -175.. When the control valve 165 is used to reduce the temperature of the mixed refrigerant, the temperature is typically reduced by about 20 ℉ to 50 ℉ and the pressure is reduced by about 90 psi to 250 psi. The mixed refrigerant evaporates and overheats as it passes through the main heat exchanger 110 and exits through line 135a. The temperature of the mixed refrigerant exiting the main heat exchanger is about 80 < 0 > F to 100 < 0 > F.

After exiting the main heat exchanger, the mixed refrigerant is fed to the ethane compressor (180). The mixed refrigerant is compressed to a pressure of about 15 psi to 25 psi greater than the operating pressure of the distillation column at a temperature of about 230 ℉ to 350.. By compressing the mixed refrigerant at a pressure greater than the distillation column pressure, a reflux pump is not required. The compressed mixed refrigerant flows through line 136 to cooler 190 where it is cooled to a temperature of about 70 ℉ to 130.. Optionally, the cooler 190 may be omitted and the compressed mixed refrigerant may flow directly to the main heat exchanger 110 as described below. The compressed mixed refrigerant then flows through line 138 to the main heat exchanger 110 where it is further cooled and partially liquefied. The mixed refrigerant is cooled in the main heat exchanger to a temperature of about 15 내지 to -70.. The partially liquefied mixed refrigerant is introduced via line 139 into reflux separator 140. 5, the overhead 128 from the reflux separator 140 is combined with the overhead 114 from the distillation column and the combined stream 132 is combined with the distillation column overhead < RTI ID = 0.0 >Lt; / RTI > The liquid residue 126 from the reflux separator 140 is again fed to the distillation column as reflux stream 126. The control valves 175, 185 may be used to maintain pressure in the compressor to facilitate condensation.

In the embodiment shown in Figure 6, the gas feed stream 212 is split to produce a first feed stream 212a and a second feed stream 212b. The first feed stream 212a enters the heat exchanger 210 for cooling and forms a cold feed stream 213 from the partially liquefied heat exchanger 210. [ The second feed stream 212b is a warm gas bypass feed stream that has not been precooled, and is typically entirely vapor-free without liquid. A valve 295 is provided in the second feed stream 212b for process control purposes. When the liquid condenses, some of the condensed liquid is methane and ethane. Usually methane and ethane are overhead vapor products from the process. The second feed stream 212b has the same overall composition as the first feed stream 212a, but contains less liquid (and is typically all in the vapor phase). As a result, propane vapor and butane vapor are present at higher concentrations in the bypass gas of the second feed stream 212b than in the cold feed stream 213. [ The warm bypass gas of the second feed stream 212b into one or more, or one to ten, or one to seven, or one to four, vapor-liquid equilibrium stages below the cold feed stream 213, Permits mass transfer to exchange liquid methane and ethane for the propane and butane vapors in the distillation column 220. This vaporizes methane and ethane while condensing propane and butane. By doing so, it substantially increases the overall efficiency of the process by substantially reducing the refrigeration efficiency and reboiler efficiency. In an embodiment, the size of the distillation column may be reduced compared to a system that does not include the second feed stream 212b.

In the embodiment of Figure 6, the process is used to separate propane and other C ₃ + hydrocarbons from ethane and light components. The tee 310 is provided in line 238 after the combined refrigerant compressor 280 and mixed refrigerant cooler to split the mixed refrigerant into a return line 245 and an ethane recovery line 247. The return line 245 conveys a portion of the mixed refrigerant to the process through the main heat exchanger 210 described above. The ethane recovery line 247 supplies a portion of the mixed refrigerant to a separate ethane recovery unit for the recovery of ethane. The removal of a portion of the mixed refrigerant stream has minimal effect on the process and sufficient C ₂ component remains in the system to provide the necessary refrigeration. In some embodiments, as many as 95% of the combined refrigerant streams can be removed for C ₂ recovery. The stripped stream may be used, for example, as a feed stream in an ethylene cracking unit.

7, the gas feed stream 312 enters the heat exchanger 310 for cooling to form a cold feed stream 313 from the partially liquefied heat exchanger 310. In this embodiment, To produce a first feed stream 312a and a second feed stream 312b that is a non-precooled warm gas bypass feed stream. A valve 395 is provided in the second feed stream 312b for process control purposes. As the liquid condenses in the first feed stream 312a, some of the condensed liquid is methane and ethane. Usually methane and ethane are overhead vapor products from the process. The second feed stream 312b has the same overall composition as the first feed stream 312a but contains less liquid. As a result, there is a higher concentration of propane vapor and butane vapor in the bypass gas of the second feed stream 312b than in the cold feed stream 313. The warm bypass gas of the second feed stream 312b to one or more, or one to ten, or one to seven, or one to four, vapor-liquid equilibrium stages below the cold feed stream 313 Permits mass transfer to exchange liquid methane and ethane for the propane and butane vapors in the distillation column 320. This vaporizes methane and ethane while condensing propane and butane. By doing so, it substantially increases the overall efficiency of the process by substantially reducing the refrigeration efficiency and reboiler efficiency. In an embodiment, the size of the distillation column may be reduced compared to a system that does not include stream 312b.

As shown in Figure 7, the deethanizer overhead drum can be replaced by an absorber. In this embodiment, the overhead stream 314 from the distillation column 320 passes through the main heat exchanger 310 and the cooled stream 319 is fed to the absorber 321. The overhead stream 328 from the reflux separator 340 is also fed to the absorber 321 via line 332. The overhead stream 342 from the absorber 321 is a sale gas and the residual stream 334 from the absorber 321 is a mixed refrigerant. Other streams and components shown in Figure 7 have the same flow path as described above.

In yet another embodiment shown in FIG. 8, the second separator and cooler are not used in the process. In this embodiment, the compressed mixed refrigerant 436 is fed through the main heat exchanger 410 and fed to the distillation column 420 via line 439 to provide a reflux stream.

8, the gas feed stream 412 enters the heat exchanger 410 for cooling to form a cold feed stream 413 from the partially liquefied heat exchanger 410. In this embodiment, To produce a first feed stream 412a and a second feed stream 412b which is a non-precooled warm gas bypass feed stream. Valve 495 is provided in second feed stream 412b for process control purposes. When the liquid condenses, some of the condensed liquid is methane and ethane. Usually methane and ethane are overhead vapor products from the process. The second feed stream 412b has the same overall composition as the first feed stream 412a but contains less liquid. As a result, there is a higher concentration of propane vapor and butane vapor in the bypass gas of the second feed stream 412b than in the cold feed stream 413. The warm bypass gas of the second feed stream 412b into one or more, or one to ten, or one to seven, or one to four, vapor-liquid equilibrium stages below the cold feed stream 413 Permits mass transfer to exchange liquid methane and ethane for the propane and butane vapors in the distillation column 420. This vaporizes methane and ethane while condensing propane and butane. By doing so, it substantially increases the overall efficiency of the process by substantially reducing the refrigeration efficiency and reboiler efficiency. In an embodiment, the size of the distillation column may be reduced compared to a system that does not include stream 412b.

In yet another embodiment shown in FIG. 9, the split supply plan is introduced into a system somewhat similar to the process described in U.S. Patent No. 8,627,681, the contents of which are incorporated herein by reference. The advantage of the embodiment of FIG. 9 is the surprisingly unexpected reduction in refrigeration efficiency specifications by a high pressure feed, a reduction in deethanizer reboiler efficiency specifications, a reduction in deethanizer steam and liquid traffic (thereby providing a distillation column size reduction) ), And refrigeration and reboiler efficiency specifications. The overall propane and mixed refrigerant compressor efficiencies are higher than 11% higher than without split feeds. As shown, a significant economic benefit from reduced overall investment costs and operating costs can be achieved as a result of this unexpected improvement.

More specifically, the entire process of Fig. 9 is designated as 502. Fig. The feed stream 512 is divided to produce a first feed stream 512a and a second feed stream 512b. The first feed stream 512a enters the heat exchanger 510 for cooling and forms a cold or high pressure stream 513 from the partially liquefied heat exchanger 510. [ The warm vapor bypass stream 512b is a second stream that is not precooled. Stream 512b is passed through control valve 605 to reduce its pressure and thereafter one or more, or one to ten, or one to seven, or one to seven, Is fed into the middle of the distillation column 520 at four vapor-liquid equilibrium positions.

Although a multi-pass heat exchanger 510 is illustrated, the use of multiple heat exchangers can also be used to achieve similar results, as in the case of the embodiment shown in Figs. 5-8. Feed stream 512 may be a natural gas, a refinery gas, or other gas stream that requires separation. The feed gas is typically filtered and dehydrated before being fed to the plant to prevent freezing within the NGL unit. In an embodiment, the first feed stream 512a is typically fed to the main heat exchanger at a temperature of about 43 DEG C to 54 DEG C (110 DEG F to 130 DEG F) and a pressure of about 7 to 31 bar (100 psia to 450 psia) . The first feed stream 512a is passed through indirect heat exchange with a refrigerant that can be supplied to the main heat exchanger via line 515 in an amount necessary to provide additional cooling required for the cooler process stream and / Cooled and partially liquefied in the main heat exchanger (510). Warm refrigerants, such as propane, can be used, for example, to provide the necessary cooling to the feed gas. The feed gas may be cooled in the main heat exchanger to a temperature of about -18 캜 to -40 캜 (0 ℉ to -40.).

The cold feed gas exits the main heat exchanger 510 and is fed to the distillation column 520 via the feed line 513. Distillation column 520 is operated at a pressure slightly below the pressure of the feed gas, typically at a pressure of about 0.3 to 0.7 bar (5 to 10 psi), which is lower than the pressure of the feed gas. In the distillation column, heavier hydrocarbons such as propane and other C ₃ + components are separated from harder hydrocarbons such as ethane, methane and other gases. The heavier hydrocarbon components escape from the liquid residues through line 516 from the distillation column, while the lighter components escape through the vapor overhead line 514. In an embodiment, the retentate stream 516 exits the distillation column at a temperature of about 65 ° C to 149 ° C (150 ° F to 300 ° F) and the overhead stream 14 exits the distillation column at about -23 ° C to -62 ° C Lt; / RTI > to < RTI ID = 0.0 > -80 F). ≪ / RTI >

The retentate stream 516 from the distillation column is split and the product stream 518 and reboil stream 522 are directed to the reboiler 530. Optionally, the product stream 518 may be cooled in a cooler (not shown) to a temperature of about 515 ° C to 554 ° C (60 ° F to 130 ° F). The product stream 518 is heavier than the heavier hydrocarbons in the feed gas stream. In the embodiment shown in FIG. 9, the product stream can be rich in propane and heavier components, and the ethane and harder gases are further processed as described below. Alternatively, the plant may be operated such that the product stream is very rich in C ₄ + hydrocarbons, and propane is removed from the produced gas with ethane. Reboil stream 522 is heated in reboiler 530 to provide heat to the distillation column. Any type of reboiler commonly used in distillation columns may be used.

Distillation column overhead stream 514 passes through main heat exchanger 510 where it is cooled by indirect heat exchange with process gas to at least partially liquefy or completely (100%) liquefy the stream. The distillation column overhead stream exits the main heat exchanger 510 via line 519 and is sufficiently cooled to produce a mixed refrigerant as described below. In some embodiments, the distillation column overhead stream is cooled to about -34 째 C to -90 째 C (-30 내지 to -130 내) in the main heat exchanger (510).

The cooled and partially liquefied stream 519 and overhead stream 528 (stream 532 after control valve 575) from reflux separator 540 can be fed to distillation column overhead separator 585 .

The components in the distillation column overhead stream 519 and the reflux drum overhead stream 532 are fed to the overhead stream 542, the side draw fraction 551, (534). The overhead stream 542 from the distillation column overhead separator 585 contains methane, ethane, nitrogen, and other harder components and is rich in nitrogen. The side discharge fraction 551 may have an intermediate nitrogen content. The residual stream 534 from the distillation column overhead separator 585 is the liquid mixed refrigerant used for cooling in the main heat exchanger 510 where the nitrogen content may be depleted. The side discharge fraction decreases in pressure across flow valve 595 and may be supplied to heat exchanger 510 for use in an integrated heat exchange system and recovered via flow line 552.

The components in the overhead stream 542 are supplied to the main heat exchanger 510 and warmed up. In a typical plant, the overhead fraction recovered via stream 542 from overhead separator 585 is maintained at a temperature of about -40 째 C to -140 째 C and a temperature of about 5 to 30 bar (85 psia to 435 psia). The overhead fraction recovered from the heat exchanger 510 via stream 543 after heat exchange in the main heat exchanger 510 may be at a temperature of about 37 ° C to 49 ° C (100 ° F to 120 ° F). The overhead fraction can be recovered via stream 543 as a nitrogen-rich, low-btu natural gas stream.

The mixed refrigerant is withdrawn from the distillation column overhead separator 585 via bottom line 534, as mentioned above. The temperature of the mixed refrigerant can be lowered by reducing the pressure of the refrigerant through the control valve 565. [ The temperature of the mixed refrigerant decreases to a temperature cool enough to provide the necessary cooling in the main heat exchanger < RTI ID = 0.0 > 510. < / RTI & The mixed refrigerant is fed via line 535 to the main heat exchanger. The temperature of the mixed refrigerant entering the main heat exchanger is typically from about-51 C to-115 C (-60 F to -175 F).

When using the control valve 565 to reduce the temperature of the mixed refrigerant, the temperature is typically reduced by about 6 ° C to 10 ° C (20 ° F to 50 ° F) and the pressure is reduced to about 6 to 17 bar ). The mixed refrigerant is evaporated and heated as it passes through the main heat exchanger 510 and exits through line 535a.

The temperature of the mixed refrigerant exiting the main heat exchanger is about 26 DEG C and 38 DEG C (80 DEG F to 100 DEG F).

After exiting the main heat exchanger (510), the mixed refrigerant is supplied to the compressor (580). The mixed refrigerant is compressed to a pressure of from 1 psi to 2 psi (15 psi to 25 psi) greater than the operating pressure of the distillation column at a temperature of from about 110 ° C to 177 ° C (230 ° F to 350 ° F). By compressing the mixed refrigerant to a pressure greater than the distillation column pressure, a reflux pump is not required. The compressed mixed refrigerant flows through line 536 to cooler 590 where it is cooled to a temperature of about 21 ° C to 54 ° C (70 ° F to 130 ° F). Optionally, the cooler 590 may be omitted, and the compressed mixed refrigerant may flow directly to the main heat exchanger 510. The compressed mixed refrigerant then flows through main heat exchanger 510 via line 538, where it is further cooled and partially liquefied.

The mixed refrigerant is cooled in the main heat exchanger to a temperature of about -9 째 C to -57 째 C (15 째 F to -70 째 F). The partially liquefied mixed refrigerant is introduced via line 539 into reflux separator 540. The overhead 528 from the reflux separator 540 and the overhead 514 from the distillation column 520 are fed to the distillation column overhead separator 585 as previously described. The liquid residue 526 from the reflux separator 540 is again fed to the distillation column 520 as a reflux stream 526. Control valves 575, 586 can be used to maintain pressure in the compressor to facilitate condensation.

The mixed refrigerant used as reflux (supplied via stream 526) causes the vapor phase component to become enriched in the distillation column 520. With the gas rich in the distillation column, the overhead stream of the column condenses at a warmer temperature and the distillation column is run at a warmer temperature than is normally required for high NGL recovery.

Reflux to the distillation column 520 also reduces the heavier hydrocarbons in the overhead fraction. For example, in the process for the recovery of propane, reflux increases the molar fraction of ethane in the distillation column, which makes it easier to condense the overhead stream. The process uses twice the liquid condensed in the distillation column overhead separator, once as the cold coolant and secondarily as the reflux stream to the distillation column.

At least a portion of the mixed refrigerant in the low nitrogen content stream line 528 may be vented through the stream stream 532ex before the separator 585. In some embodiments, the portion drained through the stream stream 532ex may be used for pipeline sales. In another embodiment, a mixed refrigerant stream (532ex) with less than 1 mole% nitrogen is mixed with a high or intermediate btu natural gas process stream having more than 4% nitrogen to produce a pipeline sales stream having less than 4% Can be generated.

For example, a mixed refrigerant stream (532ex) may be combined with an intermediate btu natural gas stream (551) (side discharge) to produce a natural gas stream suitable for pipeline sales. The flow rates of streams 532ex and 551 may be such that the resulting product stream 548 has a nitrogen (inert) content of less than 4 mole%. In some embodiments, the flow stream 532ex may be supplied to the main heat exchanger 510; After heat transfer, the mixed refrigerant may be withdrawn from heat exchanger 510 via flow line 541 for mixing with intermediate btu stream 551. The other process stream may also be mixed with the mixed refrigerant stream 532ex in another embodiment.

The process according to the embodiment of FIG. 9 allows substantial process flexibility and provides the ability to efficiently process feed gas streams having a wide range of nitrogen content. The embodiment described in connection with Fig. 9 allows recovery of most of the feed gas btu values as a natural gas sales stream. An isostatic open refrigeration process in accordance with the embodiments disclosed herein may additionally include the separation of nitrogen from a high or intermediate nitrogen content stream so that an additional number of btu values in relation to process conditions and feed gas nitrogen content Or additional flexibility.

Examples of specific embodiments of the process are described below. This embodiment is provided to further describe the processes described herein, and they are not intended to limit the full scope of this disclosure in any manner.

Control Example 1

In the following examples, the operation of the process plant shown in FIG. 1, wherein the type and composition of the feed gas are different, was computer simulated using the process of the Apsen HYSYS simulator. In this embodiment, operational parameters for C ₃ + recovery using a relatively lean feed gas are provided. Table 1 shows operating parameters for propane recovery using lean feed gas. The composition of the feed gas, the feed gas stream and the C ₃ + product stream, and the mixed refrigerant stream of the molar fraction are provided in Table 2. The energy input for this embodiment included about 3.717x105 ⁵ Btu / hr (Q) for the reboiler 30 and about 459 horsepower (P) for the ethane compressor 80.

As can be seen in Table 2, the product stream 18 from the bottom of the distillation column contained a very rich C ₃ + component, but the sup- ply gas stream 43 contained almost all C ₂ and harder hydrocarbons and gases . Approximately 99.6% of the propane in the feed gas was recovered in the product stream. The mixed refrigerant mainly consists of methane and ethane, but contains more propane than the sales gas.

Control Example 2

In this embodiment, the operating parameters are provided in the process plant shown in FIG. 1, using purified feed gas for the recovery of the C ₃ + components in the product stream. Table 3 shows operating parameters using purified feed gas. The composition of the feed gas, the feed gas stream and the C ₃ + product stream, and the mixed refrigerant stream of the molar fraction are provided in Table 4. The energy input for this embodiment included about 2.205 x 10 ⁶ Btu / hr (Q) for the reboiler 30 and about 228 hp (P) for the ethane compressor 80.

As can be seen in Table 4, the product stream 18 from the bottom of the distillation column is very rich in C ₃ + components, but the seth gas stream 43 contains almost all of the C ₂ and harder hydrocarbons and gases, Lt; / RTI > This stream was fed to the membrane unit or PSA and used to upgrade the stream to useful hydrogen. Approximately 97.2% of the propane in the feed gas was recovered in the product stream. The mixed refrigerant mainly consists of methane and ethane, but contains more propane than the sales gas.

Control Example 3

In this embodiment, the operating parameters are provided in the process processing plant shown in FIG. 1, using purified feed gas for the recovery of the C ₄ + component in the product stream, and the C ₃ component is removed . Table 5 shows operating parameters for this embodiment of the process. The composition of the feed gas, the feed gas stream and the C ₄ + product stream, and the mixed refrigerant stream of the molar fraction are provided in Table 6. The energy input for this embodiment included about 2.512x10 ⁶ Btu / hr (Q) for reboiler 30 and about 198 horsepower (P) for ethane compressor 80.

As can be seen in Table 6, the product stream 18 from the distillation column bottom is C ₄ + components are very rich, but the sales gas stream (43) was almost all containing C ₃ and more light hydrocarbons and gas . Approximately 99.7% of the C ₄ + component in the feed gas was recovered in the product stream. The mixed refrigerant mainly consists of C ₃ and harder components, but contains more butane than the sales gas.

Control Example 4

In this embodiment, the operating parameters are provided in the process processing plant shown in Figure 2, using purified feed gas for the recovery of the C ₃ + components in the product stream, wherein C ₂ and the harder component Gas stream. In this embodiment, a portion of the mixed refrigerant is removed via line 47 and fed to the ethane recovery unit for further processing. Table 7 shows operating parameters for this embodiment of the process. The composition of the feed gas, the feed gas stream and the C ₃ + product stream, and the mixed refrigerant stream of the molar fraction are provided in Table 8. The energy input for this embodiment included about 2.089x10 ⁶ Btu / hr (Q) for reboiler 30 and about 391 horsepower (P) for ethane compressor 80.

As can be seen in Table 8, in this embodiment, the product stream 18 from the bottom of the distillation column is very rich in C ₃ + components, but the seth gas stream 43 is almost all C ₂ and harder hydrocarbons And gas. The mixed refrigerant mainly consists of C ₂ and harder components, but contains more propane than the sale gas.

Control Example 5

In this embodiment, the operating parameters are provided in the process processing plant shown in Figure 3, using a poor feed gas for the recovery of the C ₃ + components in the product stream, and the C ₂ and harder components Was removed from the sales gas stream. In this embodiment, the absorber 120 is used to separate the distillation column overhead stream and the reflux separator overhead stream to obtain a mixed refrigerant. Table 9 shows operating parameters for this embodiment of the process. The composition of the feed gas, the feed gas stream and the C ₃ + product stream, and the mixed refrigerant stream of the molar fraction are provided in Table 10. The energy input for this embodiment included about 3.734x10 ⁵ Btu / hr (Q) for the reboiler 30 and about 316 horsepower (P) for the ethane compressor 80.

As can be seen in Table 10, in this embodiment, the product stream 18 from the bottom of the distillation column is very rich in C ₃ + components, but the seth gas stream 43 is almost all C ₂ and harder hydrocarbons And gas. The mixed refrigerant mainly consists of C ₂ and harder components, but contains more propane than the sale gas.

Control Example 6

In this embodiment, the operating parameters are provided in the processing plant shown in FIG. 1 using a rich feed gas for the recovery of the C ₃ + component in the product stream, and the C ₂ component is fed to the Removed. Table 11 shows operating parameters for this embodiment of the process. The composition of the feed gas, the feed gas stream and the C ₃ + product stream, and the mixed refrigerant stream of the molar fraction are provided in Table 12. The energy input for this embodiment included about 1.458 x 10 ⁶ Btu / hr (Q) for reboiler 30 and about 226 hp (P) for ethane compressor 80.

As can be seen in Table 12, in this embodiment, the product stream 18 from the bottom of the distillation column is very rich in C ₃ + components, but the seth gas stream 43 is almost all C ₂ and harder hydrocarbons And gas. The mixed refrigerant mainly consists of C ₂ and harder components, but contains more propane than the sale gas.

Example 7

In this embodiment, the operating parameters are provided in the simulated process processing plant shown in Figure 5, using the rich feed gas of Control 6 for the recovery of the C ₃ + components in the product stream, and C ₂ The components were removed from the sales gas stream. The energy input for this embodiment included about 1.117x10 ⁶ Btu / hr (Q) in reboiler 130 and reduced horsepower in ethane compressor 180. In this embodiment, about 15 weight percent of the gas feed stream 112 forms the bypass stream 112b and the remainder of the stream 112 forms the first feed stream 112a.

As in the previous embodiment, in this embodiment, the product stream 118 from the bottom of the distillation column is very rich in C ₃ + components, but the Sewage gas stream 143 contains almost all C ₂ and harder hydrocarbons and gases Lt; / RTI > The mixed refrigerant mainly consists of C ₂ and harder components, but contains more propane than the sale gas. Based on the process simulation data, by inserting the feed stream 112b into the column 120 as shown, unexpectedly surprisingly, the refrigeration efficiency specification is reduced, the deethanizer reboiler efficiency specification is reduced, It has been found that the device steam and liquid flow rates are reduced, providing a reduction in distillation column size and a reduction in refrigeration and reboiler efficiency specifications by high pressure feeds. The overall propane and mixed refrigerant compressor efficiencies were higher by more than 12% without the split feed. This saved both the total invested cost (TIC) and the operating cost in the plant considerably economically. As an example, in the United States, a 200 MMSCFD gas plant is commonplace. Such a plant may have a refrigeration compressor of about 15,000 HP depending on the feed composition. Based on the following calculations, the configuration saved about 12% compressor efficiency. 15,000 HP x 0.12 savings x 0.746 kw / hp x 0.1 $ / kwh = 134 $ / hr (more than millions of dollars of power each year).

For a 200 MMSCFD plant, the reboiler efficiency without split feed is approximately 29.2 MMBTU / HR. In this embodiment, the reboiler efficiency is about 22.2 MMBTU / HR. Assuming a US 5.00 MMBTU energy cost, the annual savings would be around $ 307,000.

Example 8

In this set of embodiments, the operating parameters that are comparable to the preceding embodiment are obtained using the same poor feed gas and product stream composition as used in Control 1 for recovery of the C < ₃ + > component in the product stream, 5, and the C ₂ component was removed from the sales gas stream. The bypass feed stream contained about 10-15 wt% feed gas stream (112). The energy input for this embodiment was about 20-27% lower than the energy input for Control 1. This set of embodiments saved both the total investment cost (TIC) and the operating cost in the plant considerably economically.

Prophetic Example 9

In this example, the operating parameters comparable to the preceding embodiment are obtained using the same poor feed gas and product stream composition as used in Control 4 for recovery of the C < ₃ + > component in the product stream, Is provided in the illustrated simulated process plant, and the C ₂ component has been removed from the sales gas stream. The bypass feed stream contained about 10-15 wt% feed gas stream 212. The energy input for this embodiment was lower than the energy input for Control 4. This embodiment saved both the total investment cost (TIC) and the operating cost in the plant considerably economically.

Prophetic Example 10

In this embodiment, the operation parameter that is comparable to the prior embodiment, with the same poor feed gas and the product stream composition to that used in Control Example 5 for recovery of C ₃ + components in the product stream, in Figure 7 Is provided in the illustrated simulated process plant, and the C ₂ component has been removed from the sales gas stream. The bypass feed stream contained about 10-15 wt% feed gas stream 312. The energy input for this embodiment was lower than the energy input for Control 5. This embodiment saved both the total investment cost (TIC) and the operating cost in the plant considerably economically.

Although specific embodiments have been described above, those skilled in the art will recognize that many modifications or variations can be made to the processes described above without departing from the scope of the claims. Accordingly, the above description of the preferred embodiments is intended to describe the embodiments in an illustrative rather than a restrictive sense.

Claims (25)

A method of recovering a natural gas liquid from a feed gas stream,
(a) forming a first portion of the feed gas stream and a second portion of the feed gas stream, wherein the mass ratio of the first portion to the second portion is in the range of 95: 5 to 5:95; and ;
(b) cooling the first portion within the heat exchanger and at least partially condensing the first portion;
(c) feeding the second portion and the cooled, at least partially condensed first portion into a distillation column, wherein the lighter component is removed from the distillation column as an overhead vapor stream, The heavier components are removed from the bottom of the distillation column as a product stream and the second portion is introduced into the distillation column at one or more vapor-liquid equilibrium points below the first portion, Permitting a mass transfer of the liquid between the first portion of the liquid and the vapor of the second portion;
(d) feeding the distillation column overhead stream to the heat exchanger, and cooling the distillation column overhead stream to at least partially liquefy the distillation column overhead stream;
(e) feeding the at least partially liquefied distillation column overhead stream to a first separator;
(f) separating the vapor and liquid in the first separator to produce a bottoms stream comprising an overhead vapor stream comprising the sale gas and a mixed refrigerant;
(g) feeding the mixed refrigerant stream to the heat exchanger to provide refrigeration, wherein the mixed refrigerant stream is vaporized while passing through the heat exchanger;
(h) compressing the vaporized mixed refrigerant stream and passing the compressed mixed refrigerant stream through the heat exchanger; And
(i) feeding at least a portion of said compressed mixed refrigerant stream as said reflux stream into said distillation column. The method of claim 1, further comprising: (i) feeding the compressed mixed refrigerant stream to a second separator prior to (i) and feeding the residue from the second separator to the distillation column as the reflux stream And recovering the natural gas liquid from the feed gas stream. 2. The method of claim 1 further comprising reducing the temperature of the mixed refrigerant stream before the mixed refrigerant stream enters the heat exchanger by reducing the pressure of the mixed refrigerant using a control valve, To recover the natural gas liquid. 2. The method of claim 1 further comprising combining an overhead stream from the second separator with an overhead stream from the distillation column and feeding the combined stream to the first separator, A method for recovering a natural gas liquid from a stream. The method of claim 1, further comprising cooling the compressed mixed refrigerant in a cooler before passing the compressed mixed refrigerant stream through the heat exchanger, a method of recovering a natural gas liquid from a feed gas stream . The method of claim 1, wherein the first separator is an absorber. The method of claim 1, wherein the feed gas stream is one of a natural gas or a refinery gas. 2. The method of claim 1, wherein the distillation column is operated at a pressure of about 100 psia to 450 psia. The method of claim 1, wherein the first portion and the second portion of the feed gas stream have the same composition. The method of claim 1, wherein the first and second portions of the feed gas stream have a mass ratio in the range of 95: 5 to 65:35. The method of claim 1, wherein the first and second portions of the feed gas stream have a mass ratio in the range of 95: 5 to 70:30. The method of claim 1, wherein a portion of the compressed mixed refrigerant stream is removed as a supplemental product stream. The method of claim 1, wherein separating the vapor and liquid in the separator further comprises generating a side draw fraction. 14. The process of claim 13, wherein the overhead vapor stream is rich in nitrogen and depleted in propane, the residual fraction being nitrogen depleted and propane rich, the side effluent fraction having a medium propane and nitrogen content, To recover the natural gas liquid. The method of claim 1, further comprising the step of reboiling a portion of the distillation column reboiler in a distillation column reboiler, wherein the energy input to the distillation column reboiler is selected such that the feed gas stream, At least 5% lower than the energy input for the process having the same volume and composition of the stream and no second portion is formed from the feed gas stream. The method of claim 1, further comprising the step of reboiling a portion of the distillation column reboiler in a distillation column reboiler, wherein the energy input to the distillation column reboiler is selected such that the feed gas stream, Wherein at least 10% lower than the energy input for the process having the same volume and composition of the stream and no second portion is formed from the feed gas stream. The method of claim 1, wherein the overall compressor duty of the process is at least 5% lower than the compressor efficiency for the process having the same volume and composition of the feed gas stream, product stream and the sales gas stream, Wherein no second portion is formed from the feed gas stream. 2. The method of claim 1 wherein the overall compressor efficiency of the process is at least 10% lower than the compressor efficiency for the process having the same volume and composition of the feed gas stream, product stream and the sales gas stream, Is not formed in the feed gas stream. An apparatus for separating a natural gas liquid from a feed gas stream,
(a) a primary feed gas line configured to deliver a feed gas stream;
(b) a heat exchanger operable to provide heating and cooling necessary for separation of the natural gas liquid from the feed gas stream by heat exchange contact between the feed gas stream and the at least one process stream to form a cooled feed gas stream; ;
(c) receiving the feed gas stream, wherein the feed gas stream comprises a column overhead stream comprising a substantial amount of a harder hydrocarbon component of the feed gas stream and a column overhead stream comprising a substantial amount of a heavier hydrocarbon component A distillation column configured to separate into streams;
(d) a first separator configured to receive the distillation column overhead stream and separate the column overhead stream into a residual stream comprising a mixed refrigerant configured to provide an overhead sales gas stream and process cooling in the heat exchanger, ;
(e) a compressor configured to compress the mixed refrigerant stream after the mixed refrigerant stream provides process cooling in the heat exchanger; And
(f) a feed gas bypass line configured to remove a portion of the stream before the feed gas stream is conveyed to the heat exchanger, the feed gas bypass line comprising a cooled feed gas stream from the heat exchanger Fluidly connected to the distillation column at one or more vapor-liquid equilibrium points below the point at which the stream is connected to the fluid, such that the liquid of the cooled feed gas stream from the heat exchanger and the bypass feed gas stream Wherein said feed gas bypass line permits mass transfer of the gas between the steam and the vapor. 20. The method of claim 19, further comprising a second separator configured to receive the compressed mixed refrigerant stream and separate the compressed mixed refrigerant into an overhead stream and a reflux stream, An apparatus for separating a natural gas liquid from a feed gas stream. 20. The method of claim 19, further comprising a splitter configured to provide a stream entering the feed gas bypass line with the same composition as a portion of the feed gas stream delivered to the heat exchanger, Apparatus for separating gas liquid. 20. The method of claim 19, wherein the splitter is configured to provide the bypass line to receive from about 5 wt% to about 35 wt% of the feed gas from the primary feed gas line, Device. 20. The apparatus of claim 19, further comprising a splitter configured to remove a portion of the compressed mixed refrigerant as a product stream. 20. The apparatus of claim 19, wherein the first separator is an absorber. 25. The apparatus of claim 24, wherein the absorber has a side discharge line configured to remove a side discharge stream.

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