JP7390860B2 - Hydrocarbon separation method and separation device - Google Patents

Description

The present invention relates to a hydrocarbon separation method and apparatus used for separating and recovering ethane or propane from, for example, natural gas, petroleum-associated gas, or off-gas from an oil refinery or petrochemical plant.

Conventionally, methane and hydrocarbons having two or more carbon atoms have been separated, and ethane and hydrocarbons having three or more carbon atoms have been separated.

For example, as a method for recovering ethane or propane from natural gas, natural gas is cooled and a demethanizer (deethanizer in the case of propane recovery) is used to separate light components from ethane (or propane) and heavy hydrocarbon components. Distillation separation is widely used. This method uses a propane refrigeration system and a turboexpander to cool the natural gas to the temperature required for separation.

Patent Document 1 discloses a method of recovering ethane or propane from a raw material gas such as natural gas using a distillation column. This method has the following steps.
(a) A step of cooling the raw material gas and condensing a part of it to separate gas and liquid;
(b) supplying the liquid obtained in step (a) to the distillation column;
(c) a step of expanding the gas obtained in step (a) using an expander and condensing a part of it to separate gas and liquid;
(d) a step of supplying the liquid obtained in step (c) to a distillation column;
(e) branching the gas obtained in step (c) into a first part and a second part;
(f) feeding the first portion to a distillation column;
(g) compressing and cooling the second portion to condense it and then reduce the pressure and feed it as reflux to the distillation column;
(h) A step of obtaining residual gas from the top of the distillation column and obtaining a heavy fraction from the bottom of the distillation column.

International Publication No. 2005/009930

In the method described in Patent Document 1, the liquid obtained in step (c) is supplied as is to the distillation column. Therefore, there is room for improvement from the perspective of cold recovery, and a relatively large compressor power is required to recover ethane or propane.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a hydrocarbon separation method capable of recovering ethane or propane, the method including improved cold recovery allowing reduction of compressor power. . Another object of the invention is to provide a hydrocarbon separation apparatus suitable for carrying out this method.

According to one aspect of the invention,
A feed gas containing at least methane and a hydrocarbon with lower volatility than methane is combined with a residual gas enriched in methane and thinner in hydrocarbons with lower volatility than methane and a residual gas enriched in methane and thinner in hydrocarbons having lower volatility than methane. In a method for separating hydrocarbons into a heavy fraction enriched with hydrocarbons with lower volatility than methane,
a) a step of cooling and partially condensing the raw material gas using the residual gas and another refrigerant as a refrigerant, and then separating the gas and liquid;
b) a step of reducing the pressure of the liquid obtained in step a and supplying it to the distillation column;
c) a step of expanding part or all of the gas obtained from step a using an expander to partially condense it, and then separating it into gas and liquid;
d) supplying the liquid obtained from step c to the distillation column after using it as the other refrigerant in step a;
e) supplying part or all of the gas obtained from step c to the distillation column; and f) obtaining the residual gas from the top of the distillation column and supplying the heavy distillate from the bottom of the distillation column. Provided is a method for separating hydrocarbons, the method comprising the step of obtaining a hydrocarbon.

According to another aspect of the invention:
A feed gas containing at least ethane and a hydrocarbon less volatile than ethane is separated into a residual gas enriched in ethane and leaner in hydrocarbons less volatile than ethane and a residual gas enriched in ethane and leaner in hydrocarbons less volatile than ethane. In a method for separating hydrocarbons into a heavy fraction enriched with hydrocarbons with lower volatility than ethane,
a) a step of cooling and partially condensing the raw material gas using the residual gas and another refrigerant as a refrigerant, and then separating the gas and liquid;
b) a step of reducing the pressure of the liquid obtained in step a and supplying it to the distillation column;
c) a step of expanding part or all of the gas obtained from step a using an expander to partially condense it, and then separating it into gas and liquid;
d) supplying the liquid obtained from step c to the distillation column after using it as the other refrigerant in step a;
e) supplying part or all of the gas obtained from step c to the distillation column; and f) obtaining the residual gas from the top of the distillation column and supplying the heavy distillate from the bottom of the distillation column. Provided is a method for separating hydrocarbons, the method comprising the step of obtaining a hydrocarbon.

According to yet another aspect of the invention,
A feed gas containing at least methane and a hydrocarbon less volatile than methane is combined with a residual gas enriched in methane and leaner in hydrocarbons less volatile than methane; In a hydrocarbon separation device that separates hydrocarbons into a heavy fraction enriched with
a distillation column that discharges the residual gas from the top of the column and discharges the heavy fraction from the bottom of the column;
A heat exchange means for cooling and partially condensing the raw material gas, the heat exchange means including a refrigerant flow path through which the residual gas flows as a refrigerant, and another refrigerant flow path through which another refrigerant flows;
a first gas-liquid separator that separates the partially condensed raw material gas obtained from the heat exchange means into gas and liquid;
a line that supplies the liquid obtained from the first gas-liquid separator to the distillation column via a pressure reducing valve;
an expander that expands and partially condenses part or all of the gas obtained from the first gas-liquid separator;
a second gas-liquid separator connected to the outlet of the expander;
A line for supplying the liquid obtained from the second gas-liquid separator to the distillation column via the another refrigerant flow path; and a part of the gas obtained from the second gas-liquid separator or A hydrocarbon separation apparatus is provided that includes a line feeding the entire distillation column to the distillation column.

According to yet another aspect of the invention,
A feed gas containing at least ethane and a hydrocarbon less volatile than ethane is combined with a residual gas enriched in ethane and leaner in hydrocarbons less volatile than ethane, and a residual gas enriched in ethane and leaner in hydrocarbons less volatile than ethane; In a hydrocarbon separation device that separates hydrocarbons into a heavy fraction enriched with
a distillation column that discharges the residual gas from the top of the column and discharges the heavy fraction from the bottom of the column;
A heat exchange means for cooling and partially condensing the raw material gas, the heat exchange means including a refrigerant flow path through which the residual gas flows as a refrigerant, and another refrigerant flow path through which another refrigerant flows;
a first gas-liquid separator that separates the partially condensed raw material gas obtained from the heat exchange means into gas and liquid;
a line that supplies the liquid obtained from the first gas-liquid separator to the distillation column via a pressure reduction valve;
an expander that expands and partially condenses part or all of the gas obtained from the first gas-liquid separator;
a second gas-liquid separator connected to the outlet of the expander;
A line for supplying the liquid obtained from the second gas-liquid separator to the distillation column via the another refrigerant flow path; and a part of the gas obtained from the second gas-liquid separator or A hydrocarbon separation apparatus is provided that includes a line feeding the entire distillation column to the distillation column.

According to one aspect of the present invention, there is provided a method for separating hydrocarbons capable of recovering ethane or propane, the method including improved cold recovery that allows for reduced compressor power. Ru. According to another aspect of the invention, a hydrocarbon separation apparatus suitable for carrying out this method is provided.

FIG. 1 is a process flow diagram showing an ethane recovery method according to a first embodiment of the present invention. FIG. 2 is a process flow diagram showing the ethane recovery method of Comparative Example 1. FIG. 3 is a process flow diagram showing an ethane recovery method according to a second embodiment of the present invention. FIG. 4 is a process flow diagram showing the ethane recovery method of Comparative Example 2. FIG. 5 is a process flow diagram showing an ethane recovery method according to a third embodiment of the present invention. FIG. 6 is a process flow diagram showing the ethane recovery method of Comparative Example 3.

The following description and drawings are merely for illustrating preferred forms of the invention, and the invention is not limited thereto. In a narrow sense, "reflux" means a liquid that condenses the gas at the top of a distillation column and returns it to the distillation column, but in a broader sense, "reflux" refers to a liquid that is added to the top of a distillation column for the purpose of rectification. Also includes the liquid to be supplied. In this specification, "reflux" is used in a broad sense, and includes a liquid having a rectifying effect that is supplied to a distillation column.

[Embodiment 1]
The present invention relates to an ethane recovery process and a propane recovery process. Regarding the first embodiment of the present invention, an example of an ethane recovery process will be described using the process flow diagram shown in FIG. The ethane recovery process referred to herein is a process in which hydrocarbon components contained in raw material gas are separated into methane, ethane, and heavy components by distillation. The ethane recovery process includes a distillation column (demethanizer) and equipment that cools the raw material gas to the temperature required for distillation.

The process combines a feed gas containing at least methane and a hydrocarbon less volatile than methane with a residual gas enriched in methane and leaner in hydrocarbons less volatile than methane, and a residual gas enriched in methane and leaner in hydrocarbons less volatile than methane; Separation into a heavy fraction enriched in hydrocarbons of low volatility. For this purpose, a demethanizer tower 11 is used as a distillation column which discharges residual gas from the top of the tower and discharges a heavy fraction from the bottom of the tower. In this process, steps a to f are performed.

a) Step of partially condensing the raw material gas by cooling it using residual gas as a refrigerant and another refrigerant, and then separating it into gas and liquid.In this step, the raw material gas is cooled and partially condensed. , a heat exchange means including a refrigerant flow path through which residual gas flows as a refrigerant and another refrigerant flow path through which another refrigerant flows is used. Further, a first gas-liquid separator is used that separates the partially condensed raw material gas obtained from the heat exchange means into gas and liquid. The heat exchange means may include one or more heat exchangers. When the heat exchange means includes two or more heat exchangers, the refrigerant flow path through which the residual gas flows and another refrigerant flow path may be provided in the same heat exchanger, or may be provided in different heat exchangers. They may be provided separately. Further, each of the plurality of heat exchangers may have a refrigerant flow path through which residual gas flows. Each of the plurality of heat exchangers may have a separate refrigerant flow path. A plurality of types of refrigerants can be used as the other refrigerant, and for example, one heat exchanger may have a plurality of "another refrigerant channels" through which multiple types of refrigerants flow, respectively.

A raw material gas, such as natural gas, is cooled by the heat exchange means and partially condensed. The partially condensed raw material gas is separated into gas and liquid by a first gas-liquid separator 4, also called a low-temperature separator. In order to increase the recovery rate of ethane, it is preferable that the temperature of the low-temperature separator 4 is as low as possible. Further, the rate at which natural gas is condensed varies depending on the composition of the natural gas (the proportion of hydrocarbons having 2 or more carbon atoms), and is approximately 5 mol% or more and 20 mol% or less. As the heat exchanger used to cool the raw material gas, a known heat exchanger such as a plate-fin heat exchanger or a shell-and-tube heat exchanger can be used as appropriate. In addition, a vertical or horizontal vessel (a cylindrical container with mirror plates at both ends) can be used as the low-temperature separator 4, and a mist separator can be provided inside the vessel in order to increase the gas-liquid separation efficiency. .

In the example of FIG. 1, a first raw material gas cooler 1, a raw material gas chiller 2, and a second raw material gas cooler 3 are used as heat exchangers used in step a. The raw material gas is cooled in the first raw material gas cooler 1 by heat exchange with the residual gas and the side stream F1 of the demethanizer, then cooled by propane refrigeration in the raw gas chiller 2, and then the residual gas is cooled again in the second raw material gas cooler 3. , the side stream F3 of the demethanizer, and the condensate (line 104) condensed in the turbo expander outlet separator 7 (second gas-liquid separator). Partially condensed raw material gas (gas-liquid two-phase flow) is obtained from the second raw material gas cooler 3. Note that the side streams F1 and F3 are each returned to the demethanizer tower 11 after the above-mentioned heat exchange (the returned streams are indicated as F2 and F4, respectively). That is, as "another refrigerant" in step a, the condensate 104 condensed in the turbo expander outlet separator 7 (liquid obtained in step c), the side streams F1 and F3 of the demethanizer, and propane in the propane refrigeration system are used. used.

The first raw material gas cooler 1 has a refrigerant flow path through which the residual gas flows, and has a refrigerant flow path through which the side stream F1 flows as the "another refrigerant flow path." The second raw material gas cooler 3 has a refrigerant flow path through which residual gas flows as a refrigerant, and as the "another refrigerant flow path", a refrigerant through which the liquid obtained from the second gas-liquid separator (line 104) flows. It has a flow path and a refrigerant flow path through which the side stream F3 flows. The raw material gas chiller 2 has a refrigerant flow path through which propane of the propane refrigeration system flows.

b) Step of reducing the pressure of the liquid obtained in step a and supplying it to the distillation column In this step, a line is used to supply the condensed liquid obtained from the low temperature separator (first gas-liquid separator) 4 to the demethanizer column 11. 101 is used. A pressure reducing valve 14 can be provided in this line. Typically, the condensate is depressurized by the pressure reduction valve 14 to a pressure equal to the operating pressure of the supply stage of the demethanizer (deethanizer in the case of propane recovery) plus the pressure loss during liquid feeding, A part of it vaporizes and becomes a gas-liquid two-phase flow. Further, the temperature decreases with this vaporization (in the case of Example 1 corresponding to Embodiment 1, the temperature decreases to -84.6° C.).

c) A step in which part or all of the gas obtained from step a is expanded by an expander to partially condense it, and then separated into gas and liquid. In this step, the gas obtained from the low temperature separator (first gas-liquid separator) 4 is An expander, particularly a turbo expander 5, is used to expand and partially condense part or all of the gas. Further, a turbo expander outlet separator 7 connected to the outlet of the turbo expander 5 is used as a second gas-liquid separator.

In this example, all of the low temperature separator 4 outlet gas (line 110) is sent to the turbo expander 5, and typically the pressure at the turbo expander 5 outlet is the same as the pressure at the outlet of the demethanizer (or deethanizer in the case of propane recovery). The pressure is reduced to the operating pressure of the stage plus the pressure loss during liquid transfer. At this time, due to the effect of isentropic expansion, the outlet gas of the turbo expander 5 becomes extremely low temperature (-85.2°C in the case of Example 1), and is partially condensed (in the case of Example 1, 27.9 mol% liquefy). Furthermore, the energy lost by the gas during expansion can be recovered as power for the compressor 6.

The gas partially condensed at the outlet of the turbo expander 5 is separated into gas and liquid by the turbo expander outlet separator 7 (second gas-liquid separator).

A vertical or horizontal vessel (a cylindrical container with end plates at both ends) can be used for the turbo expander outlet separator 7, and it may also have a mist separator inside to increase the gas-liquid separation efficiency. can.

d) Step of supplying the liquid obtained from step c to the distillation column after using it as the above-mentioned "another refrigerant" in step a In this step, the liquid obtained from the turbo expander outlet separator 7 is A line is used which supplies the demethanizer (distillation column) 11 via "another refrigerant flow path" (lines 104 and 102). In this example, the "another refrigerant flow path" through which the liquid obtained from the turbo expander outlet separator 7 flows is the one located most downstream with respect to the flow direction of the raw material gas among the heat exchangers used for cooling in step a. This is one of the refrigerant channels provided in the two-source gas cooler 3. In the case of Example 1, the liquid in line 104 is used as "another refrigerant" and is heated to -39.0° C., resulting in a gas-liquid two-phase flow.

e) Step of supplying part or all of the gas obtained from step c to the distillation column In this step, part or all of the gas obtained from the turbo expander outlet separator (second gas-liquid separator) 7 is supplied to the distillation column. A line feeding the demethanizer tower (distillation tower) 11 is used.

In this example, all of the gas obtained from the turbo expander outlet separator (second gas-liquid separator) 7 is supplied to the demethanizer 11 (line 103).

The demethanizer tower 11 has, for example, a tray or packing inside the tower, and separates high-volatile components and low-volatile components by a distillation operation. In order to reduce the power required to compress the residual gas downstream, the pressure of the demethanizer is preferably as high as possible within a range that can achieve a predetermined ethane recovery rate, and from this point of view, it is 1.5 MPa or more and 3.5 MPa or less. is preferable, and more preferably 2.5 MPa or more and 3.5 MPa or less.

In this example, three types of fluids are fed to the demethanizer 11. The condensate separated by the low-temperature separator 4 is fed to the top of the column as reflux via the pressure reducing valve 14 (line 101), and the outlet gas of the turbo expander outlet separator 7 is fed below it (line 103). Further below, the liquid separated by the turbo expander outlet separator 7 is fed after exchanging heat with the raw material gas in the second raw material gas cooler 3 (line 102). In Figure 1, the liquid separated by the low temperature separator 4 is fed as reflux (line 101), but the liquid separated by the turbo expander outlet separator 7 is used as reflux after exchanging heat with the raw material gas. You can. The detailed position of the feed to the demethanizer can be determined as appropriate depending on the temperature and methane concentration of each feed.

A reboiler 12 is installed at the bottom of the demethanizer tower, and heat is applied to volatilize the methane in the bottom liquid and keep the methane concentration in the bottom liquid below a predetermined value.

f) Process of obtaining residual gas from the top of the distillation column and obtaining a heavy fraction from the bottom of the distillation column From the top of the demethanization column, methane from which components such as ethane and propane have been removed is the main component. The residual gas is separated and used for heat exchange with the raw material gas. Thereafter, if necessary, the gas is compressed to a predetermined pressure by a compressor 6 driven by a turbo expander and a compressor (residual gas compressor) 13 driven by a motor or the like. From the bottom of the demethanizer 11, ethane, propane, and heavy components are separated as NGL (Natural Gas Liquid). The obtained NGL is separated into each component, for example, in an NGL separation step provided further downstream.

As the raw material gas, methane and natural gas containing hydrocarbons with lower volatility than methane are preferable. The feed gas may be petroleum-associated gas or off-gas from a refinery or petrochemical plant.

The greater the concentration of hydrocarbons that are less volatile than methane in the raw material gas, the greater the difference between the methane concentration in the turbo expander 5 inlet gas and the methane concentration in the turbo expander outlet gas separator 7 outlet gas, and the reflux Improvement effects are likely to occur. Therefore, the effects of the present invention are particularly remarkable when the concentration of hydrocarbons that are less volatile than methane in the raw material gas is 5 mol% or more and 50 mol% or less, furthermore 10 mol% or more and 50 mol% or less.

Furthermore, since a lower ethane concentration in the residual gas means a higher ethane recovery rate, the ethane concentration in the residual gas is preferably as low as possible, preferably 5 mol% or less, and more preferably 1 mol% or less.

NGL is composed of hydrocarbons that are less volatile than liquefied and recovered methane, and is sent, for example, to an NGL fractionation facility provided further downstream, where it is separated into products such as ethane, propane, and butane. In such a case, the methane content in the NGL is preferably low enough to satisfy the standards for ethane products, preferably 2 mol% or less, and more preferably 1 mol% or less.

In the case of the propane recovery process, the principle is the same as in the above example, and a deethanizer is used instead of the demethanizer 11, and residual gas containing methane and ethane as main components is released from the top of the deethanizer. Propane and heavy components are separated as NGL from the bottom of the deethanizer tower.

[Embodiment 2]
Regarding the second embodiment of the present invention, an example of an ethane recovery process will be described using the process flow diagram shown in FIG. Descriptions of the same points as in Embodiment 1 will be omitted.

In Embodiment 1, in step c, the entire amount of gas (line 110) obtained from step a, that is, from the low temperature separator 4, is supplied to the turbo expander 5. In the second embodiment, the line 110 is branched and only a part of the gas in the line 110 (line 110a) is sent to the turbo expander 5 to be subjected to step c. The branching ratio of line 110 is determined in consideration of the required ethane recovery rate (in the case of Example 2 corresponding to Embodiment 2, line 110a:line 110b=70:30 (molar ratio)). The pressure at the outlet of the turbo expander 5 is reduced to the operating pressure of the supply stage of the demethanizer (deethanizer in the case of propane recovery) plus the pressure loss during liquid feeding. At this time, due to the effect of isentropic expansion, the outlet gas of the turbo expander 5 becomes extremely low temperature (-86.4°C in Example 2) and partially condenses (24.7% liquefies in Example 2). . Furthermore, the energy lost by the gas during expansion can be recovered as power for the compressor 6.

The remainder of the gas in line 110 (line 110b) is cooled in the condenser 10 by heat exchange with the residual gas obtained from the top of the demethanizer to completely condense it (-90.8 ℃), and the entire condensed liquid is reduced in pressure by a pressure reduction valve 15 and supplied to a demethanizer (distillation column) 11 (line 105). The pressure of the entire condensed liquid is reduced by the pressure reduction valve 15 to a pressure equal to the operating pressure of the supply stage of the demethanizer (distillation column) 11 plus the pressure loss during liquid feeding. Further, a part of the completely condensed liquid is vaporized by the reduced pressure, resulting in a gas-liquid two-phase flow, and the temperature decreases as the vaporization occurs (-94.2° C. in the case of Example 2).

For this purpose, use the following:
A line 110a that sends a part of the gas obtained from the low temperature separator (first gas-liquid separator) 4 to the turbo expander 5;
A condenser 10 that cools and completely condenses the remainder of the gas (line 110b) obtained from the low-temperature separator (first gas-liquid separator) 4 by heat exchange with the residual gas;
A pressure reduction valve 15 that reduces the pressure of the liquid completely condensed in the condenser 10; and a line 105 that connects the outlet of the pressure reduction valve 15 to the demethanizer (distillation column) 11.

As the condenser 10, a heat exchanger that exchanges heat between the gas in the line 110b and the residual gas can be used. The condenser 10 can be disposed upstream of the raw material gas coolers 1 and 3 and the raw material gas chiller 2 with respect to the flow direction of residual gas.

In this example, four types of fluids are fed to the demethanizer tower 11. The liquid from line 105 is fed to the top of the column as reflux, below which the outlet gas of turbo expander outlet separator 7 is fed (line 103), and below that the liquid from low temperature separator 4 is fed to the pressure reducing valve. The liquid from the turbo expander outlet separator 7 is fed after being depressurized at 14 (line 101), and the liquid from the turbo expander outlet separator 7 is fed after exchanging heat with the raw material gas (line 102).

Regarding the process flow, the second embodiment may be the same as the first embodiment except for the above points. However, conditions such as temperature and pressure can be changed as appropriate depending on the difference in process flow.

[Embodiment 3]
Regarding the third embodiment of the present invention, an example of an ethane recovery process will be described using the process flow diagram shown in FIG. Descriptions of the same points as in Embodiment 1 will be omitted.

In Embodiment 1, in step e, the entire amount of the gas (line 103) obtained from step c, that is, from the turbo expander outlet separator 7, is supplied to the demethanizer 11. In the third embodiment, the line 103 is branched and only a part of the gas in the line 103 (line 103a) is subjected to step e, that is, fed to the demethanizer 11. The branching ratio of line 103 is determined in consideration of the required ethane recovery rate (in the case of Example 3 corresponding to Embodiment 3, line 103a:line 103b=63:37 (molar ratio)). The remainder of the gas in line 103 (line 103b) is compressed (to 6.00 MPa in the case of Example 3), cooled by heat exchange with the residual gas obtained from the top of the demethanizer tower, and completely condensed ( -94.2° C. in the case of Example 3), and the completely condensed liquid is further depressurized and supplied to the demethanizer 11 (line 105). The pressure of the entire condensed liquid is reduced by the pressure reduction valve 15 to a pressure equal to the operating pressure of the supply stage of the demethanizer (distillation column) 11 plus the pressure loss during liquid feeding. In addition, part of the completely condensed liquid is vaporized by the reduced pressure, resulting in a gas-liquid two-phase flow, and the temperature decreases (-97.2° C. in the case of Example 3) as the liquid vaporizes.

For this purpose, use the following:
A line 103a that supplies a portion of the gas obtained from the turbo expander outlet separator 7 (second gas-liquid separator) to the demethanizer tower (distillation tower) 11;
a compressor 8 that compresses the remainder of the gas (line 103b) obtained from the turbo expander outlet separator 7 (second gas-liquid separator);
A condenser (reflux condenser) 10 that cools and completely condenses the gas compressed by the compressor 8 through heat exchange with residual gas;
A pressure reduction valve 15 that reduces the pressure of the liquid completely condensed in the condenser 10; and a line 105 that connects the outlet of the pressure reduction valve 15 to the demethanizer (distillation column) 11.

As the condenser 10, a heat exchanger that exchanges heat between the gas in the line 103b and the residual gas can be used. The condenser 10 can be disposed upstream of the raw material gas coolers 1 and 3 and the raw material gas chiller 2 with respect to the flow direction of residual gas. In this example, the gas compressed by the compressor 8 is cooled by a heat exchanger (reflux cooler) 9 using propane refrigeration, and then cooled by heat exchange with the residual gas in a reflux condenser 10 to completely condense it. There is. The reflux cooler 9 can be provided as needed, and is not necessary if cooling by the reflux condenser 10 is sufficient.

In this example, four types of fluids are fed to the demethanizer tower 11. The liquid from line 105 is fed to the top of the tower as reflux, below which a part of the outlet gas of turbo expander outlet separator 7 is fed (line 103a), and below that the liquid from low temperature separator 4 is fed. is fed after being depressurized by the pressure reducing valve 14 (line 101), and below that, the liquid from the turbo expander outlet separator 7 is fed after exchanging heat with the raw material gas (line 102).

Regarding the process flow, the third embodiment may be the same as the first embodiment except for the above points. However, conditions such as temperature and pressure can be changed as appropriate depending on the difference in process flow.

Hereinafter, the present invention will be explained in more detail based on Examples, but the present invention is not limited thereto.

[Example 1]
A process simulation was conducted for an example of ethane recovery using a hydrocarbon separation apparatus having the configuration shown in FIG. High-pressure raw material natural gas from which water has been removed in advance is introduced into a hydrocarbon separation device under conditions of 6.24 MPa and 17.1°C. The composition of the raw material gas at this time is as shown in Table 1. The flow rate is 13,700 kg-mol/hr (10 ³ mol/hr). Note that Cn (n is a natural number) represents a hydrocarbon having n carbon atoms. C5+ represents a hydrocarbon having 5 or more carbon atoms.

The raw material gas exchanges heat with the residual gas at -39.0°C and the side stream F1 of the demethanizer 11 at -33.5°C in the first raw material gas cooler 1, and is cooled to -24.6°C. Thereafter, the raw material gas chiller 2 cools the gas to -37.0°C by propane freezing, and the second raw material gas cooler 3 cools the residual gas at -84.6°C, the side stream F3 of the demethanizer 11 at -76.1°C, and It is cooled to -62.9°C by heat exchange with the condensate (line 104) of the turbo expander outlet separator 7 at -85.2°C. Here, the first raw material gas cooler 1 and the second raw material gas cooler 3 are plate fin heat exchangers, and the raw material gas chiller 2 is a kettle-type multi-tubular heat exchanger.

Next, the raw material gas is separated into gas and liquid by a low temperature separator 4. The low-temperature separator 4 is a vertical vessel (a cylindrical vessel with mirror plates at both ends) having a mist separator inside.

The entire amount of the low temperature separator 4 outlet gas is sent to the turbo expander 5, and the pressure is reduced to 3.47 MPa. The outlet gas is cooled to −85.2° C. by the effect of isentropic expansion and provides 529 kW of power to the compressor 6 driven by the expander. The gas at the outlet of the turbo expander 5 is separated into gas and liquid by the turbo expander outlet separator 7. The turbo expander outlet separator 7 is a vertical vessel (a cylindrical vessel with mirror plates at both ends) having a mist separator inside.

The -85.2°C condensate (line 104) separated by the turbo expander outlet separator 7 is heated to -39.0°C by applying cold heat to the raw material gas in the second raw material gas cooler 3, and then desorbed. It is fed to the methane tower 11 (line 102).

The demethanizer tower 11 has 40 trays installed therein, and the gas at the outlet of the turbo expander outlet separator 7 is fed to the third tray from the top of the tower (line 103). Further, the liquid separated by the turbo expander outlet separator 7 passes through the second raw material gas cooler 3 and is fed to the 10th stage from the top of the column (line 102). Further, the liquid separated by the low-temperature separator 4 is reduced in pressure to 3.29 MPa by the pressure reducing valve 14, and then fed to the first stage from the top of the column as reflux (line 101).

The demethanizer tower 11 is operated at a temperature of 3.27 MPa and -84.6°C at the top of the tower, and at a temperature of 3.32 MPa and 39.8°C at the bottom of the tower. The temperature at the bottom of the column is determined by the equilibrium temperature at which the methane concentration in the NGL is 1 mol % or less, and in order to operate at that temperature, 3.60 MW of heat is added from the reboiler 12. The compositions of the residual gas separated from the top of the demethanizer 11 and the NGL separated from the bottom of the tower are as shown in Table 2. The flow rates are 12,553 kg-mol/hr (10 ³ mol/hr) for residual gas and 1,147 kg-mol/hr (10 ³ mol/hr) for NGL. In addition, "NC4" represents normal butane, and "IC4" represents isobutane.

Of the ethane in the raw material gas, 76.7% is recovered as NGL.

The residual gas exiting the top of the demethanizer 11 exchanges heat with the raw material gas, and reaches a temperature of 15.1° C. at the outlet of the first raw material gas cooler 1. Thereafter, the compressor 6 driven by the turbo expander compresses the gas to 3.25 MPa, and the residual gas compressor 13 compresses it to 3.77 MPa. At this time, the required power of the residual gas compressor 13 is 1,031 kW.

[Comparative example 1]
A process simulation was conducted for an example of ethane recovery using a hydrocarbon separation apparatus having the configuration shown in FIG. The results are summarized in Table 3 together with the results of Example 1.

In the case of Example 1, the condensed liquid (line 104) separated into gas and liquid by the turbo expander outlet separator 7 recovers cold heat in the second raw material gas cooler 3 and becomes a gas-liquid two-phase flow (line 102). At this time, since the methane fraction, which is a low boiling point component, is mainly vaporized, the methane concentration in the gas-liquid two-phase flow in line 102 decreases. The higher the methane concentration in the reflux liquid in the demethanizer tower 11, the higher the reflux effect. It is fed to the first stage of the demethanizer as a flux liquid.

On the other hand, in the configuration shown in FIG. 2, the cold energy of the condensate (line 102) separated by the turbo expander outlet separator 7 is not recovered by the second source gas cooler 3, and the methane concentration is lower than that of the low temperature separator 4. Since the methane concentration is higher than that of the condensate, it is supplied as reflux to the first stage of the demethanizer 11 (line 102).

In the demethanizer tower 11, the gas at the outlet of the turbo expander outlet separator 7 is fed to the fourth tray from the top of the tower (line 103). The liquid separated by the low temperature separator 4 is reduced in pressure to 2.82 MPa by the pressure reducing valve 14, and then fed to the 14th stage from the top of the column (line 101).

Regarding the process flow, Comparative Example 1 is the same as Example 1 except for the above points.

In Table 3, "refrigeration load" is the heat load of the propane refrigeration system in the raw gas chiller 2. A reduction in the refrigeration load means a reduction in the capacity of the propane refrigeration equipment, which has the effect of reducing the energy consumed by the propane refrigeration equipment and the cost of propane refrigeration equipment.

"Reboiler heat load" is the heat load of the bottom reboiler 12 of the demethanizer tower. This reduction means a reduction in the energy required for distillation, which has the effect of reducing the cost of externally supplied utilities. "Refrigerating compressor power" is the power consumed by the compressor in a propane refrigeration system. “Residual gas compressor” is the power consumed by the residual gas compressor 13.

As is clear from Table 3, although the ethane recovery rate of Example 1 is about the same as that of the case where ethane recovery is performed using the configuration of Comparative Example 1, the total compressor power and reboiler heat load are It is possible to reduce the

[Example 2]
A process simulation was conducted for an example of ethane recovery using a hydrocarbon separation apparatus having the configuration shown in FIG. The raw material gas is the same as in Example 1.

The raw material gas exchanges heat with the residual gas at -39.0°C and the side stream F1 of the demethanizer 11 at -39.3°C in the first raw material gas cooler 1, and is cooled to -23.7°C. Thereafter, the raw material gas chiller 2 cools the gas to -37.0°C by propane freezing, and the second raw material gas cooler 3 cools the remaining gas at -76.6°C, the side stream F3 of the demethanizer 11 at -77.7°C, and It is cooled to -60.4°C by heat exchange with the condensate (line 104) of the turboexpander outlet separator 7 at -86.4°C. Here, the first raw material gas cooler 1 and the second raw material gas cooler 3 are plate fin heat exchangers, and the raw material gas chiller 2 is a kettle-type multi-tubular heat exchanger.

Next, the raw material gas is separated into gas and liquid by a low temperature separator 4. The low-temperature separator 4 is a vertical vessel (a cylindrical vessel with mirror plates at both ends) having a mist separator inside.

Of the gas at the outlet of the low temperature separator 4, 70 mol% is sent to the turbo expander 5 (line 110a), where the pressure is reduced to 3.20 MPa. The outlet gas is cooled to -86.4° C. by the effect of isentropic expansion, and a portion of it is condensed to form a gas-liquid two-phase flow, which provides 723 kW of power to the compressor 6 driven by the expander. The gas (partially condensed) at the outlet of the turbo expander 5 is separated into gas and liquid by the turbo expander outlet separator 7. The turbo expander outlet separator 7 is a vertical vessel (a cylindrical vessel with mirror plates at both ends) having a mist separator inside.

The remaining 30 mol% of the gas at the outlet of the low-temperature separator 4 is sent to the condenser (reflux condenser) 10 (line 110b), where it exchanges heat with the residual gas at the top of the demethanizer tower 11, resulting in a temperature of -90.8°C. It is completely condensed. The pressure of the condensed liquid is reduced to 3.00 MPa by the pressure reducing valve 15, and a portion of it is vaporized to form a gas-liquid two-phase flow, and the temperature drops to -94.2°C as it vaporizes. Thereafter, it is supplied to the first stage from the top of the column as a reflux liquid (line 105). Here, the reflux condenser 10 is a plate-fin heat exchanger.

The demethanizer tower 11 has 40 trays installed therein, and the gas at the outlet of the turbo expander outlet separator 7 is fed to the fourth tray from the top of the tower (line 103). In addition, the -86.4°C condensate (line 104) separated at the turbo expander outlet separator 7 is heated to -39.0°C by cold heat recovery in the second raw material gas cooler 3, and a part of it is vaporized. After it becomes a gas-liquid two-phase flow, it is fed to the 20th stage from the top of the column (line 102). Furthermore, the pressure of the liquid separated by the low-temperature separator 4 is reduced to 3.20 MPa by the pressure reducing valve 14, and a portion of the liquid is vaporized to become a gas-liquid two-phase flow, and the temperature is reduced to -84.2°C as the liquid is vaporized. Thereafter, it is fed to the 14th stage from the top of the tower (line 101).

The demethanizer tower 11 is operated at a temperature of 3.00 MPa and -92.8°C at the top of the tower, and at a temperature of 3.05 MPa and 31.5°C at the bottom of the tower. The temperature at the bottom of the column is determined by the equilibrium temperature at which the methane concentration in the NGL is 1 mol % or less, and in order to operate at that temperature, 3.65 MW of heat is added from the reboiler 12. The compositions of the residual gas separated from the top of the demethanizer 11 and the NGL separated from the bottom of the tower are as shown in Table 4. The flow rates are 12,444 kg-mol/hr (10 ³ mol/hr) for residual gas and 1,256 kg-mol/hr (10 ³ mol/hr) for NGL.

Of the ethane in the raw material gas, 88.7% is recovered as NGL.

The residual gas exiting the top of the demethanizer 11 exchanges heat with the raw material gas, and reaches a temperature of 15.1° C. at the outlet of the first raw material gas cooler 1. Thereafter, the compressor 6 driven by the turbo expander compresses the gas to 3.17 MPa, and the residual gas compressor 13 compresses it to 3.77 MPa. At this time, the required power of the residual gas compressor 13 is 1,859 kW.

[Comparative example 2]
A process simulation was performed for an example of ethane recovery using a hydrocarbon separation apparatus having the configuration shown in FIG. The results are summarized in Table 5 together with the results of Example 2.

In the configuration shown in FIG. 4, the condensate (line 102) separated by the turbo expander outlet separator 7 is supplied to the demethanizer 11 as it is without the cold heat being recovered by the second raw material gas cooler 3.

In Comparative Example 2, cold recovery using the condensate of the turbo expander outlet separator 7 is not performed, so the temperature of the stream flowing into the low temperature separator 4 is -52.0°C, which is 8.4°C when compared with Example 2. ℃ becomes higher. Therefore, the methane concentration in the gas (line 110) separated by the low-temperature separator 4 is lower than in Example 2, which ultimately leads to a decrease in the reflux effect in the distillation column.

In the demethanizer tower 11, the liquid from the line 105 is supplied from the top of the tower to the first stage as a reflux liquid. The gas at the outlet of the turbo expander outlet separator 7 is fed to the fourth tray from the top of the column (line 103). The liquid separated by the turbo expander outlet separator 7 is fed from the top of the column to the 14th stage (line 102). Further, the liquid separated by the low temperature separator 4 is reduced in pressure to 2.83 MPa by the pressure reducing valve 14, and then fed to the 20th stage from the top of the column (line 101).

Regarding the process flow, Comparative Example 2 is the same as Example 2 except for the above points.

As is clear from Table 5, Example 2 achieved a higher ethane recovery rate than the case where ethane recovery was performed using the configuration of Comparative Example 2, and furthermore, the total compressor power and reboiler heat load were reduced. is possible.

[Example 3]
A process simulation was conducted for an example of ethane recovery using a hydrocarbon separation apparatus having the configuration shown in FIG. The raw material gas is the same as in Example 1.

The raw material gas exchanges heat with the residual gas at -39.0°C and the side stream F1 of the demethanizer 11 at -35.3°C in the first raw gas cooler 1, and is cooled to -22.6°C. Thereafter, the raw material gas chiller 2 cools the gas to -37.0°C by propane freezing, and the second raw material gas cooler 3 cools the residual gas at -68.0°C, the side stream F3 of the demethanizer 11 at -74.3°C, and It is cooled to -59.0°C by heat exchange with the condensate (line 104) of the turboexpander outlet separator 7 at -86.8°C. Here, the first raw material gas cooler 1 and the second raw material gas cooler 3 are plate fin heat exchangers, and the raw material gas chiller 2 is a kettle-type multi-tubular heat exchanger.

Next, the raw material gas is separated into gas and liquid by a low temperature separator 4. The low-temperature separator 4 is a vertical vessel (a cylindrical vessel with mirror plates at both ends) having a mist separator inside.

The entire amount of gas at the outlet of the low temperature separator 4 is sent to the turbo expander 5, and the pressure is reduced to 3.07 MPa. The outlet gas is cooled to −86.8° C. by the effect of isentropic expansion and provides a power of 1,259 kW to the compressor 6 driven by the expander. The gas at the outlet of the turbo expander 5 is separated into gas and liquid by the turbo expander outlet separator 7. The turbo expander outlet separator 7 is a vertical vessel (a cylindrical vessel with mirror plates at both ends) having a mist separator inside.

37 mol% of the outlet gas (line 103) of the turbo expander outlet separator 7 is pressurized to 6.00 MPa by a compressor (low-temperature compressor) 8, and then transferred to a heat exchanger (reflux cooler) 9 using propane refrigeration and demethanization. The column 11 is cooled to -94.2° C. by a condenser (reflux condenser) 10 that exchanges heat with the residual gas at the top of the column, and is completely condensed. The pressure of the obtained condensate is reduced to 2.87 MPa by the pressure reducing valve 15, and a portion of it is vaporized to form a gas-liquid two-phase flow, and the temperature drops to -97.2° C. as it vaporizes. Thereafter, it is supplied to the first stage from the top of the column as a reflux liquid (line 105). Here, the reflux cooler 9 is a kettle-type multi-tube heat exchanger, and the reflux condenser 10 is a plate fin heat exchanger. Note that if the outlet temperature of the reflux condenser 10 can be lowered to a temperature at which a predetermined ethane recovery rate can be achieved only by heat exchange with residual gas, reflux condenser 10 can be used to reduce the load on propane refrigeration. It is not necessary to install the cooler 9.

The demethanizer tower 11 has 40 trays installed therein, and a portion of the gas at the outlet of the turbo expander outlet separator 7 is fed to the ninth tray from the top of the tower (line 103a). In addition, the -86.8°C condensate (line 104) separated by the turbo expander outlet separator 7 is heated to -39.0°C by cold heat recovery in the second raw material gas cooler 3, and a part of it is vaporized. After it becomes a gas-liquid two-phase flow, it is fed from the top of the column to the 18th stage (line 102). Further, the pressure of the liquid separated by the low-temperature separator 4 is reduced to 2.89 MPa by the pressure reducing valve 14, and a portion of it is vaporized to become a gas-liquid two-phase flow, and the temperature drops to -83.7° C. as it vaporizes. Thereafter, it is fed to the 15th stage from the top of the column (line 101).

The demethanizer tower 11 is operated at a temperature of 2.87 MPa and -96.2°C at the top of the tower, and at a temperature of 2.92 MPa and 27.5°C at the bottom of the tower. The temperature at the bottom of the column is determined by the equilibrium temperature at which the methane concentration in the NGL is 1 mol % or less, and in order to operate at that temperature, 3.35 MW of heat is added from the reboiler 12. The compositions of the residual gas separated from the top of the demethanizer 11 and the NGL separated from the bottom are shown in Table 6. The flow rates are 12,388 kg-mol/hr (10 ³ mol/hr) for residual gas and 1,312 kg-mol/hr (10 ³ mol/hr) for NGL.

95.5% of the ethane in the raw material gas is recovered as NGL.

The residual gas exiting the top of the demethanizer 11 exchanges heat with the raw material gas, and reaches a temperature of 15.1° C. at the outlet of the first raw material gas cooler 1. Thereafter, the compressor 6 driven by the turbo expander compresses the gas to 3.19 MPa, and the residual gas compressor 13 compresses it to 3.77 MPa. At this time, the required power of the residual gas compressor 13 is 1,824 kW.

[Comparative example 3]
A process simulation was conducted for an example of ethane recovery using a hydrocarbon separation apparatus having the configuration shown in FIG. This process corresponds to the process disclosed in Patent Document 1. The results are summarized in Table 7 together with the results of Example 3.

In the configuration shown in FIG. 6, the condensate (line 102) separated by the turbo expander outlet separator 7 is supplied as it is to the demethanizer 11 without recovering cold heat in the second raw material gas cooler 3.

In Comparative Example 3, cold recovery using the condensate of the turbo expander outlet separator 7 is not performed, so the temperature of the stream flowing into the low temperature separator 4 is -44.1°C, which is 14.9°C when compared with Example 3. ℃ becomes higher. Therefore, the methane concentration in the gas (line 110) separated by the low-temperature separator 4 is lower than in Example 3, which ultimately leads to a decrease in the reflux effect in the distillation column.

In the demethanizer tower 11, the liquid from the line 105 is fed from the top of the tower to the first stage as reflux. A part of the gas at the outlet of the turbo expander outlet separator 7 is fed from the top of the tower to the ninth tray (line 103a). Further, the liquid separated by the turbo expander outlet separator 7 is fed to the 12th stage from the top of the column (line 102). Furthermore, the pressure of the liquid separated by the low-temperature separator 4 is reduced to 2.82 MPa by the pressure-reducing valve 14, and a portion of it is vaporized to become a gas-liquid two-phase flow, and the temperature drops to -64.0°C as it vaporizes. Thereafter, it is fed to the 15th stage from the top of the column (line 101).

Regarding the process flow, Comparative Example 3 is the same as Example 3 except for the above points.

As is clear from Table 7, Example 3 achieved a higher ethane recovery rate than the case where ethane recovery was performed using the configuration of Comparative Example 3, and furthermore, the total compressor power and reboiler heat load were reduced. is possible.

1: First raw material gas cooler 2: Raw material gas chiller 3: Second raw material gas cooler 4: Low temperature separator 5: Turbo expander 6: Compressor driven by turbo expander 7: Turbo expander outlet separator 8: Low temperature compressor 9: Reflux cooler 10 : Reflux condenser 11: Demethanizer (deethanizer in the case of a propane recovery plant)
12: Reboiler 13: Residual gas compressor 14: Pressure reducing valve 15: Pressure reducing valve F1: Demethanizer side stream F2: Return of side stream F1 F3: Demethanizer side stream F4: Return of side stream F3

Claims (12)

A feed gas containing at least methane and a hydrocarbon with lower volatility than methane is combined with a residual gas enriched in methane and thinner in hydrocarbons with lower volatility than methane and a residual gas enriched in methane and thinner in hydrocarbons having lower volatility than methane. In a method for separating hydrocarbons into a heavy fraction enriched with hydrocarbons with lower volatility than methane,
a) a step of cooling and partially condensing the raw material gas using the residual gas and another refrigerant as a refrigerant, and then separating the gas and liquid;
b) a step of reducing the pressure of the liquid obtained in step a and supplying it to the distillation column;
c) a step of expanding part or all of the gas obtained from step a using an expander to partially condense it, and then separating it into gas and liquid;
d) supplying the liquid obtained from step c to the distillation column after using it as the other refrigerant in step a;
e) supplying part or all of the gas obtained from step c to the distillation column; and f) obtaining the residual gas from the top of the distillation column and supplying the heavy distillate from the bottom of the distillation column. having a step of obtaining a minute amount;
Part of the gas obtained from step a is subjected to step c,
A method for separating hydrocarbons, characterized in that the remainder of the gas obtained in step a is cooled and completely condensed by heat exchange with the residual gas, and the fully condensed liquid is reduced in pressure and supplied to the distillation column . A feed gas containing at least ethane and a hydrocarbon less volatile than ethane is separated into a residual gas enriched in ethane and leaner in hydrocarbons less volatile than ethane and a residual gas enriched in ethane and leaner in hydrocarbons less volatile than ethane. In a method for separating hydrocarbons into a heavy fraction enriched with hydrocarbons with lower volatility than ethane,
a) a step of cooling and partially condensing the raw material gas using the residual gas and another refrigerant as a refrigerant, and then separating the gas and liquid;
b) a step of reducing the pressure of the liquid obtained in step a and supplying it to the distillation column;
c) a step of expanding part or all of the gas obtained from step a using an expander to partially condense it, and then separating it into gas and liquid;
d) supplying the liquid obtained from step c to the distillation column after using it as the other refrigerant in step a;
e) supplying part or all of the gas obtained from step c to the distillation column; and f) obtaining the residual gas from the top of the distillation column and supplying the heavy distillate from the bottom of the distillation column. having a step of obtaining a minute amount;
Part of the gas obtained from step a is subjected to step c.
A method for separating hydrocarbons, characterized in that the remainder of the gas obtained in step a is cooled and completely condensed by heat exchange with the residual gas, and the fully condensed liquid is reduced in pressure and supplied to the distillation column . A feed gas containing at least methane and a hydrocarbon with lower volatility than methane is combined with a residual gas enriched in methane and thinner in hydrocarbons with lower volatility than methane and a residual gas enriched in methane and thinner in hydrocarbons having lower volatility than methane. In a method for separating hydrocarbons into a heavy fraction enriched with hydrocarbons with lower volatility than methane,
a) a step of cooling and partially condensing the raw material gas using the residual gas and another refrigerant as a refrigerant, and then separating the gas and liquid;
b) a step of reducing the pressure of the liquid obtained in step a and supplying it to the distillation column;
c) a step of expanding part or all of the gas obtained from step a using an expander to partially condense it, and then separating it into gas and liquid;
d) supplying the liquid obtained from step c to the distillation column after using it as the other refrigerant in step a;
e) supplying part or all of the gas obtained from step c to the distillation column; and
f) Obtaining the residual gas from the top of the distillation column and obtaining the heavy fraction from the bottom of the distillation column.
has
Part of the gas obtained from step c is subjected to step e,
The remainder of the gas obtained in step c is compressed, cooled and completely condensed by heat exchange with the residual gas, and the fully condensed liquid is reduced in pressure and supplied to the distillation column. Separation method. A feed gas containing at least ethane and a hydrocarbon less volatile than ethane is separated into a residual gas enriched in ethane and leaner in hydrocarbons less volatile than ethane and a residual gas enriched in ethane and leaner in hydrocarbons less volatile than ethane. In a method for separating hydrocarbons into a heavy fraction enriched with hydrocarbons with lower volatility than ethane,
a) a step of cooling and partially condensing the raw material gas using the residual gas and another refrigerant as a refrigerant, and then separating the gas and liquid;
b) a step of reducing the pressure of the liquid obtained in step a and supplying it to the distillation column;
c) a step of expanding part or all of the gas obtained from step a with an expander to partially condense it, and then separating it into gas and liquid;
d) supplying the liquid obtained from step c to the distillation column after using it as the other refrigerant in step a;
e) supplying part or all of the gas obtained from step c to the distillation column; and
f) Obtaining the residual gas from the top of the distillation column and obtaining the heavy fraction from the bottom of the distillation column.
has
Part of the gas obtained from step c is subjected to step e,
The remainder of the gas obtained in step c is compressed, cooled and completely condensed by heat exchange with the residual gas, and the fully condensed liquid is reduced in pressure and supplied to the distillation column. Separation method. 3. The method according to claim 1 or 2, wherein all of the gas obtained from step c is subjected to step e. 5. The method according to claim 3 or 4, wherein all of the gas obtained from step a is subjected to step c. A feed gas containing at least methane and a hydrocarbon less volatile than methane is combined with a residual gas enriched in methane and leaner in hydrocarbons less volatile than methane; In a hydrocarbon separation device that separates hydrocarbons into a heavy fraction enriched with
a distillation column that discharges the residual gas from the top of the column and discharges the heavy fraction from the bottom of the column;
A heat exchange means for cooling and partially condensing the raw material gas, the heat exchange means including a refrigerant flow path through which the residual gas flows as a refrigerant, and another refrigerant flow path through which another refrigerant flows;
a first gas-liquid separator that separates the partially condensed raw material gas obtained from the heat exchange means into gas and liquid;
a line that supplies the liquid obtained from the first gas-liquid separator to the distillation column via a pressure reducing valve;
an expander that expands and partially condenses part or all of the gas obtained from the first gas-liquid separator;
a second gas-liquid separator connected to the outlet of the expander;
A line for supplying the liquid obtained from the second gas-liquid separator to the distillation column via the another refrigerant flow path; and a part of the gas obtained from the second gas-liquid separator or a line that supplies the entire distillation column to the distillation column ;
a line that sends a portion of the gas obtained from the first gas-liquid separator to the expander;
a condenser that completely condenses the remainder of the gas obtained from the first gas-liquid separator by cooling it by heat exchange with the residual gas;
a pressure reducing valve that reduces the pressure of the liquid completely condensed in the condenser; and
A line connecting the outlet of a pressure reducing valve that reduces the pressure of the liquid completely condensed in the condenser to the distillation column.
Separation equipment for hydrocarbons, including : A feed gas containing at least ethane and a hydrocarbon less volatile than ethane is combined with a residual gas enriched in ethane and leaner in hydrocarbons less volatile than ethane, and a residual gas enriched in ethane and leaner in hydrocarbons less volatile than ethane; In a hydrocarbon separation device that separates hydrocarbons into a heavy fraction enriched with
a distillation column that discharges the residual gas from the top of the column and discharges the heavy fraction from the bottom of the column;
A heat exchange means for cooling and partially condensing the raw material gas, the heat exchange means including a refrigerant flow path through which the residual gas flows as a refrigerant, and another refrigerant flow path through which another refrigerant flows;
a first gas-liquid separator that separates the partially condensed raw material gas obtained from the heat exchange means into gas and liquid;
a line that supplies the liquid obtained from the first gas-liquid separator to the distillation column via a pressure reduction valve;
an expander that expands and partially condenses part or all of the gas obtained from the first gas-liquid separator;
a second gas-liquid separator connected to the outlet of the expander;
A line for supplying the liquid obtained from the second gas-liquid separator to the distillation column via the another refrigerant flow path; and a part of the gas obtained from the second gas-liquid separator or a line that supplies the entire distillation column to the distillation column ;
a line that sends a portion of the gas obtained from the first gas-liquid separator to the expander;
a condenser that completely condenses the remainder of the gas obtained from the first gas-liquid separator by cooling it by heat exchange with the residual gas;
a pressure reducing valve that reduces the pressure of the liquid completely condensed in the condenser; and
A line connecting the outlet of a pressure reducing valve that reduces the pressure of the liquid completely condensed in the condenser to the distillation column.
Separation equipment for hydrocarbons, including : A feed gas containing at least methane and a hydrocarbon less volatile than methane is combined with a residual gas enriched in methane and leaner in hydrocarbons less volatile than methane; In a hydrocarbon separation device that separates hydrocarbons into a heavy fraction enriched with
a distillation column that discharges the residual gas from the top of the column and discharges the heavy fraction from the bottom of the column;
A heat exchange means for cooling and partially condensing the raw material gas, the heat exchange means including a refrigerant flow path through which the residual gas flows as a refrigerant, and another refrigerant flow path through which another refrigerant flows;
a first gas-liquid separator that separates the partially condensed raw material gas obtained from the heat exchange means into gas and liquid;
a line that supplies the liquid obtained from the first gas-liquid separator to the distillation column via a pressure reduction valve;
an expander that expands and partially condenses part or all of the gas obtained from the first gas-liquid separator;
a second gas-liquid separator connected to the outlet of the expander;
a line that supplies the liquid obtained from the second gas-liquid separator to the distillation column via the other refrigerant flow path; and
A line that supplies part or all of the gas obtained from the second gas-liquid separator to the distillation column.
including;
A line that supplies a portion of the gas obtained from the second gas-liquid separator to the distillation column;
a compressor that compresses the remainder of the gas obtained from the second gas-liquid separator;
a condenser that cools and completely condenses the gas compressed by the compressor through heat exchange with the residual gas;
a pressure reducing valve that reduces the pressure of the liquid completely condensed in the condenser; and
A line connecting the outlet of a pressure reducing valve that reduces the pressure of the liquid completely condensed in the condenser to the distillation column.
Separation equipment for hydrocarbons, including : A feed gas containing at least ethane and a hydrocarbon less volatile than ethane is combined with a residual gas enriched in ethane and leaner in hydrocarbons less volatile than ethane, and a residual gas enriched in ethane and leaner in hydrocarbons less volatile than ethane; In a hydrocarbon separation device that separates hydrocarbons into a heavy fraction enriched with
a distillation column that discharges the residual gas from the top of the column and discharges the heavy fraction from the bottom of the column;
A heat exchange means for cooling and partially condensing the raw material gas, the heat exchange means including a refrigerant flow path through which the residual gas flows as a refrigerant, and another refrigerant flow path through which another refrigerant flows;
a first gas-liquid separator that separates the partially condensed raw material gas obtained from the heat exchange means into gas and liquid;
a line that supplies the liquid obtained from the first gas-liquid separator to the distillation column via a pressure reduction valve;
an expander that expands and partially condenses part or all of the gas obtained from the first gas-liquid separator;
a second gas-liquid separator connected to the outlet of the expander;
a line that supplies the liquid obtained from the second gas-liquid separator to the distillation column via the other refrigerant flow path; and
A line that supplies part or all of the gas obtained from the second gas-liquid separator to the distillation column.
including;
A line that supplies a portion of the gas obtained from the second gas-liquid separator to the distillation column;
a compressor that compresses the remainder of the gas obtained from the second gas-liquid separator;
a condenser that cools and completely condenses the gas compressed by the compressor through heat exchange with the residual gas;
a pressure reducing valve that reduces the pressure of the liquid completely condensed in the condenser; and
A line connecting the outlet of a pressure reducing valve that reduces the pressure of the liquid completely condensed in the condenser to the distillation column.
Separation equipment for hydrocarbons, including : The apparatus according to claim 7 or 8 , comprising a line for supplying all of the gas obtained from the second gas-liquid separator to the distillation column. 11. Apparatus according to claim 9 or 10, comprising a line conveying all of the gas obtained from the first gas-liquid separator to the expander.

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