KR20200062234A - Natural gas manufacturing apparatus and natural gas manufacturing method - Google Patents

Abstract

The natural gas production apparatus uses compressed liquefied natural gas (LNG) in a supercooled state as a raw material, a raw material supply unit 101, a first heat exchanger 1, a second heat exchanger 2, a first vaporizer 3, and A raw material supply unit 101 is introduced through the first expansion turbine 4 and then through the second heat exchanger 2 to the first distillation column 7. The methane-rich gas component derived from the head of the first distillation column 7 is delivered as natural gas. The liquid component stored at the bottom of the first distillation column 7 is introduced into the second distillation column 9. The methane-rich gas component derived from the head of the second distillation column 9 is delivered as natural gas. Natural gas liquid is delivered from the bottom of the second distillation column (9).

Description

Natural gas manufacturing apparatus and natural gas manufacturing method

The present invention relates to a filter The present invention relates to a natural gas production apparatus using a liquefied natural gas as a raw material, a natural gas production method, and more specifically, the pressure required while recovering the natural gas liquid (for example , 6 MPa to 10 MPa), and a natural gas manufacturing apparatus capable of supplying natural gas) and a useful supply method.

Natural gas (NG) is stored as liquefied natural gas (LNG) for convenience in transportation and storage, and is primarily vaporized before being used in thermal power generation or city gas. After the shale gas boom, inexpensive LNG has become available in the LNG spot market, and the use of LNG from different countries of origin is increasing. For example, when NG is used as a power generation fuel, 100% methane is quite convenient for increasing power generation by increasing combustion energy. On the other hand, carbon-rich components such as ethane (hereinafter sometimes referred to as'ethane') are used as high-calorie LNG, in addition to being valuable as raw materials in chemical plants, using liquid propane gas (LPG) It has the advantage of saving. Reflecting this situation, it is required at the LNG consumption location (LNG receiving terminal) to provide an energy efficient process for separating LNG into components such as methane-rich NG gas and ethane.

The purpose of the technology of supplying NG by extracting natural gas liquid (NGL) from LNG is mainly to control the calorific value of fuel gas supplied to power plants and pipelines. In Patent Document 1, for example, it is boosted by NG supply pressure. Prior to distillation, the raw material LNG is first decompressed to a pressure that allows distillation to separate it into NG and NGL, the expansion energy associated with the decompression is recovered by an expansion turbine, and the NG separated by a compressor driven by the turbine is again NG. The purpose of controlling the calorific value of the NG supply was achieved by raising the pressure to the supply pressure.

In Patent Document 2, in order to supply high pressure NG, all of the methane recovered from the head of the distillation column is boosted with a compressor, liquefied before distillation, and further boosted with a pump to supply NG.

Japanese Patent Publication No. 2016-156581 United States Patent Application Publication No. 2009/0282865

Ingredients including raw LNG vary depending on where the LNG is produced, and may contain large amounts of C3 or higher hydrocarbons such as propane or butane. This LNG has a higher boiling point, reducing the recovery of methane when extracting methane-rich NG. To maintain the methane recovery rate, the operating temperature of the distillation column must be increased or the operating pressure of the distillation column must be reduced.

In order to increase the operating temperature of the distillation column, a method of supplying steam or hot water instead of seawater, industrial water, and the like, which are frequently used in reboilers of distillation columns for distilling LNG, is considered. However, since steam or hot water uses natural gas or electricity as a heat source, energy efficiency is poor and operation costs are high.

However, conventionally, when seawater is used in a reboiler to reduce the operating pressure of the distillation column, a heat source such as natural gas or electricity is unnecessary, but the resulting NG pressure cannot meet the pressure required according to the intended use. There is a concern.

NG supply pressure tends to increase due to high pressure of power generation equipment used for NG power generation. Since the most effective working pressure during the distillation operation is determined according to the LNG composition and cannot be regarded as fixed, when the equipment disclosed in Patent Document 1 is used, the supply pressure of the raw LNG is significantly different from the working pressure of the distillation column. This pressure difference can lead to expansion of the raw LNG, expansion of the NG associated with recompression, and increase in compression rate, and may require additional compressors to achieve the NG supply pressure.

On the other hand, the method disclosed in Patent Document 2 is expensive because it requires a pump to process the entire amount of NG supplied.

In particular, when the raw material LNG contains more C3 or more hydrocarbon components such as propane, the operating pressure of the distillation column is determined by gas-liquid equilibrium based on the composition of the bottom liquid and the temperature of the reboiler heat source. The difference between the feed pressure and the working pressure of the distillation column tends to be larger.

In view of this situation, the present invention uses the seawater while maintaining the NGL recovery rate, without using additional expensive heat sources such as steam in the reboiler, and the required pressure (for example, 6 MPa). It provides a natural gas manufacturing apparatus and a supply method capable of supplying NG at a high pressure of 10 to 10 MPa.

Natural gas production apparatus according to an aspect of the present invention:

A device for supplying natural gas by extracting a natural gas liquid from liquefied natural gas,

-Compressed liquefied natural gas in supercooled state is introduced as a raw material through a raw material supply unit, a first heat exchanger, a second heat exchanger, a first vaporizer, and a first expansion turbine, and introduced again into a first distillation column through a second heat exchanger. Raw material supply flow path;

A first reboiler for heating the liquid component D at the bottom of the first distillation column;

Branching the methane-rich gas component A derived from the head of the first distillation column, and delivering one gas component B separated from the gas component A as natural gas through a first compressor connected to the first expansion turbine A first natural gas delivery flow path;

A first reflux flow path for introducing another gas component C separated from the gas component A as a first reflux liquid to the top of the first distillation column through a first heat exchanger;

A bottom supply flow path for introducing the liquid component D derived from the bottom of the first distillation column into the second distillation column;

After liquefying the methane-rich gas component E derived from the head of the second distillation column, it is branched through a third heat exchanger, and one liquid component F separated from the gas component E is the second reflux liquid, and the top of the second distillation column A second reflux flow path introduced into the;

A second natural gas supply flow path for supplying another liquid component G separated from the gas component E as natural gas through a compression means and a second vaporizer;

A second reboiler for heating the liquid component H at the bottom of the second distillation column; And

A natural gas liquid delivery channel for delivering the liquid component H derived from the bottom of the second distillation column as a natural gas liquid,

In the first heat exchanger, the gas component C is condensed by at least a portion of the cold of the liquefied natural gas supplied from the raw material supply unit, so that a first reflux liquid is prepared;

In the second heat exchanger, some or all of the gaseous liquefied natural gas derived from the first expansion turbine is cooled and condensed by cold cooling of the liquefied natural gas derived from the first heat exchanger, and introduced into the first distillation column Raw materials to be prepared are prepared;

In the third heat exchanger, the gas component E is condensed at a low temperature by at least a portion of the cold of the liquefied natural gas supplied from the raw material supply unit, so that the second reflux liquid and the liquid component G are prepared.

Another aspect of the present invention is a method for producing natural gas by extracting a natural gas liquid from liquefied natural gas,

(1) introducing at least a portion of the liquefied natural gas supplied from the raw material supply unit into the first distillation column after discharging a portion of the cold of the liquefied natural gas;

(2) introducing methane-rich gas component A from the head of the first distillation column;

(3) branching the gas component A and boosting one gas component B separated from the gas component A before delivery as natural gas;

(4) cooling the other gas component C separated from the gas component A as a first reflux liquid before introducing it to the top of the first distillation column;

(5) heating the liquid component D stored at the bottom of the first distillation column through a first reboiler;

(6) introducing at least a portion of the liquid component D derived from the bottom of the first distillation column into the second distillation column;

(7) cooling the methane-rich gas component E derived from the head of the second distillation column;

(8) One liquid component F separated from the liquefied and branched liquid component E is introduced as the second reflux liquid to the top of the second distillation column, and the other liquid component G separated from the gas component E is supplied as natural gas. Boosting and vaporizing;

(9) heating the liquid component H stored at the bottom of the second distillation column through a second reboiler; And

(10) A method comprising delivering the liquid component H derived from the bottom of the second distillation column as a natural gas liquid.

In the step (1) of introducing at least a portion of the liquefied natural gas supplied to the first distillation column from the raw material supply unit after discharging a portion of the cold liquefied natural gas, the liquefied natural gas introduced into the first distillation column has a different composition and temperature. It is either a gas-liquid mixed state or a gaseous state.

In a method for producing natural gas according to aspects of the present invention:

-At least a part of the liquefied natural gas supplied from the raw material supply section can be introduced into the first distillation column as a raw material through a first heat exchanger, a second heat exchanger, a first vaporizer and a first expansion turbine;

In the first heat exchanger, the gas component C is condensed by at least a portion of the cold of the liquefied natural gas supplied from the raw material supply unit, so that a first reflux liquid to be introduced to the top of the first distillation column can be prepared;

In the second heat exchanger, some or all of the gaseous liquefied natural gas derived from the first expansion turbine is cooled and condensed by the cold of the liquefied natural gas derived from the first heat exchanger to prepare the raw materials There is;

The methane-rich gas component E derived from the head of the second distillation column can be liquefied through a third heat exchanger;

In the third heat exchanger, the gas component E is condensed at a low temperature by at least a portion of the cold of the liquefied natural gas supplied from the raw material supply unit, so that the second reflux liquid and the liquid component G can be prepared.

The raw material LNG is introduced into the first distillation column, and methane-rich gas component A is obtained at the head by distillation, and liquid component D is stored at the bottom. In the present invention, since methane gas may be contained in the liquid component D, a natural gas or an electric heat source is not added to the reboiler for heating the liquid component D. For example, non-heated seawater may be used. Since the first distillation column can be operated at a relatively high pressure, high pressure NG can be supplied without using a multistage compressor.

When the raw material LNG containing a large amount of C3 or more hydrocarbons is introduced into a first distillation column having a reboiler that does not use natural gas or an electric heat source, methane-rich gas component A is obtained at the head by distillation, but the liquid component stored at the bottom D contains more methane. This is because the boiling point of raw material LNG increases by containing hydrocarbons of C3 or higher.

The liquid component D containing methane is introduced into a second distillation column and distilled. Methane in liquid component D is derived from the head of the second distillation column as methane-rich gas component E, and components such as ethane in liquid component D are derived from the bottom of the second distillation column as liquid component H and delivered as a natural gas liquid.

Therefore, in this aspect of the present invention, the liquid component containing methane stored at the bottom of the first distillation column can be further distilled to obtain a methane-rich gas component and a natural gas liquid. Therefore, even when the raw material LNG contains a large amount of hydrocarbons of C3 or more, natural gas can be supplied without maintaining a recovery rate of NGL without inputting a heat source to the reboiler.

According to this aspect of the present invention, when delivering natural gas at high pressure, the operating pressure of the first distillation column can be increased. As the operating pressure of the first distillation column increases, the methane component contained in the liquid component D stored at the bottom of the first distillation column increases. However, the liquid component D containing methane can be further distilled in the second distillation column to obtain the methane-rich gas component and natural gas liquid, and also maintain the recovery rate of NGL. Since the operating pressure of the first distillation column is high, the pressure of the methane-rich gas component A obtained from the head of the first distillation column is also high. Thus, natural gas can be delivered at high pressure without a multistage compressor compressing the gas component A.

In the natural gas production apparatus according to an aspect of the present invention:

A second expansion turbine can be arranged downstream of the first vaporizer in the feedstock flow path;

• at least a portion of the liquefied natural gas supplied from the first vaporizer can be introduced into the first distillation column through a second expansion turbine;

In the first natural gas delivery flow path, a fourth heat exchanger and a second compressor can be arranged downstream of the first compressor;

The gas component B supplied from the first compressor can be delivered as natural gas from the first natural gas delivery flow path through the fourth heat exchanger and the second compressor;

In the second heat exchanger, some or all of the liquefied natural gas derived from the first expansion turbine and the liquefied natural gas derived from the second expansion turbine are cooled by the cold of the liquefied natural gas derived from the first heat exchanger Condensation, the raw material can be prepared.

According to this aspect of the invention, the methane-rich gas component A can be further compressed by the second compressor to deliver natural gas at higher pressures. The gas component A compressed by the first compressor is also cooled by the fourth heat exchanger, and more effectively compressed by the second compressor.

The case in which the pressure required for the natural gas to be delivered fluctuates may also be considered, in which case, when the required pressure is low, natural gas derived from the first compressor is directly delivered, and when the required pressure is high, from the second compressor. Delivery can be controlled such that the derived natural gas is delivered.

Therefore, according to this aspect of the present invention, natural gas can be supplied in a wide pressure range while maintaining a recovery rate of NGL without introducing a heat source to the reboiler.

In the natural gas production apparatus according to an aspect of the present invention:

A branch bypass line can be arranged downstream of the first compressor and upstream of the fourth heat exchanger;

A first shut-off valve can be arranged in the branch bypass line;

The first shut-off valve can be controlled based on the pressure value measured by the first pressure gauge disposed in the first natural gas delivery flow path.

According to this aspect of the present invention, when the natural gas supply pressure fluctuates, when the natural gas supply pressure is lower than the preset pressure, the second compressor disposed at the rear stage is stopped, and downstream of the first compressor at the first stage. The first shut-off valve on the branch bypass line to be opened is opened, so that only the first compressor can be used to boost natural gas. If the natural gas supply pressure is higher than the preset pressure, the second compressor disposed at the rear end is operated, and the first shut-off valve is closed, so that the natural gas can be further boosted by the compressor following the first compressor.

The natural gas supply pressure can be measured by a first pressure gauge disposed in the first natural gas delivery flow path. Even if only the first compressor is used based on the measured pressure, the use of both the first compressor and the second compressor can be selected, thereby optimizing the power used in the compressor.

In a natural gas production apparatus according to another aspect of the present invention, the first generator may be arranged to be connected to the second compressor.

When the pressure of the natural gas supplied from the first natural gas supply flow path is less than a preset pressure value, the second compressor is stopped as described above. In this case, the power recovered by the expansion turbine connected to the second compressor can be recovered as electrical energy by the first generator connected to the second compressor. This can ensure power generation in accordance with the operation of the second expansion turbine alone, while ensuring the function at the optimum condition corresponding to the fluctuation of the natural gas supply pressure.

In a natural gas production apparatus according to another aspect of the present invention, a third expansion turbine can be arranged parallel to the second expansion turbine, and a second generator can be arranged to be connected to the third expansion turbine.

When the pressure of the natural gas supplied from the first natural gas supply flow path is less than a preset pressure value, the second compressor is stopped as described above. In this case, the second expansion turbine is also stopped, and the liquefied natural gas supplied from the first vaporizer is not supplied to the second expansion turbine, but is supplied to the third expansion turbine. The third expansion turbine is not connected to the compressor but to the second generator. This can secure the function in the optimum condition corresponding to the fluctuation of the natural gas supply pressure, and ensure the power generation according to the operation of only the third expansion turbine.

In the natural gas manufacturing method according to the aspect of the present invention, the temperature of the first reboiler may be 0°C to 30°C, and the temperature of the second reboiler may be 0°C to 30°C.

Therefore, according to this aspect of the present invention, natural gas can be supplied in a wide pressure range while maintaining the recovery rate of NGL without inputting a heat source to the first and second reboilers. The temperature range of the first reboiler and the second reboiler is preferably 0°C to 30°C, more preferably 5°C to 10°C.

In this temperature range, for example, non-heated seawater can be used for the reboiler, and there is no need to use steam or hot water obtained through heating by using electricity or burning natural gas. That is, it does not require a heat source for heating, for example, by combustion of electricity or natural gas.

From the viewpoint of heat exchanger operation, when the lower limit of the temperature of the first reboiler and the second reboiler is about 5° C., the heat exchanger will operate while suppressing solidification of water even if there is a significant fluctuation in the heat load of the heat exchanger. Can be. When the upper limit of the temperature of the first reboiler and the second reboiler is about 10°C, seawater or industrial water having a seawater temperature of about 15°C or an industrial water temperature may be used.

In the construction of this aspect of the invention, due to the low temperature of the reboiler, the liquid component D stored at the bottom of the first distillation column contains more methane. The liquid component D containing methane is introduced into a second distillation column and distilled. Methane in liquid component D is derived from the head of the second distillation column as methane-rich gas component E, and components such as ethane in liquid component D are derived from the bottom of the second distillation column as liquid component H and delivered as a natural gas liquid.

Therefore, in this aspect of the present invention, the liquid component containing methane stored at the bottom of the first distillation column can be further distilled to obtain the methane-rich gas component E and natural gas liquid. Therefore, natural gas can be supplied without inputting a heat source into the reboiler and maintaining the recovery rate of NGL.

In the method for supplying natural gas according to this aspect of the present invention, the temperature at the time of introducing the liquefied natural gas introduced into the third heat exchanger into the third heat exchanger may be -180°C to -125°C.

In this aspect of the present invention, the methane-rich gas component E derived from the head of the second distillation column is cooled by introducing a portion of the raw material LNG at -180°C to -125°C directly into the third heat exchanger It is condensed and transferred as natural gas after the pressure is boosted by the pump. When the temperature is -180°C to -125°C, since methane is cooled and condensed, methane gas can be effectively recovered from the top of the second distillation column.

After being boosted by the compression means, methane can be distilled off by a warmer and delivered. According to this aspect of the present invention, since the methane component introduced into the second distillation column can be recovered and delivered as natural gas, the recovery rate of methane in the raw material LNG can be further increased.

1 is a diagram showing a configuration example of a natural gas production apparatus according to the first embodiment.
2 is a diagram showing verification results in a configuration example of a natural gas production apparatus according to the first embodiment.
3 is a diagram showing a configuration example of a natural gas production device according to the second embodiment.
4 is a diagram showing verification results in a configuration example of a natural gas production apparatus according to the second embodiment.
5 is a diagram showing another configuration example of the natural gas production apparatus according to the second embodiment.
6 is a diagram showing another configuration example of the natural gas production apparatus of the second embodiment.
7 is a diagram showing another configuration example of the natural gas production apparatus according to the second embodiment.

Now, some embodiments of the present invention will be described below. The embodiments described below illustrate examples of the present invention. The present invention is not limited to the following embodiments in any way, and includes various modifications implemented within the scope of not altering the essence of the present invention. The configurations described below are not necessarily all of the essential configurations of the present invention.

According to the invention Natural gas  Manufacturing device

In the natural gas production apparatus according to the present invention, liquefied natural gas (LNG) is introduced as a raw material into a first distillation column, and methane-rich natural gas (NG) is prepared from gas components derived from the top of the first distillation column, Liquid components derived from the bottom are introduced into the second distillation column, methane-rich natural gas (NG) is prepared from gas components derived from the top of the second distillation column, and natural gas liquids (NGL) from the liquid components derived from the bottom Is ready.

The manufacturing apparatus introduces the compressed liquefied natural gas in the supercooled state through a raw material supply unit, a first heat exchanger, a second heat exchanger, a first vaporizer, and a first expansion turbine, and then again through the second heat exchanger. A raw material supply channel introduced into the first distillation column;

A first reboiler for heating the liquid component D at the bottom of the first distillation column;

A first natural gas delivery flow path for branching the methane-rich gas component A derived from the head of the first distillation column, and delivering one gas component B as natural gas through a first compressor connected to the first expansion turbine;

A first reflux passage for introducing another gas component C as a first reflux liquid to the top of the first distillation column through a first heat exchanger;

A bottom supply flow path for introducing the liquid component D derived from the bottom of the first distillation column into the second distillation column;

A second reflux flow path that liquefies the methane-rich gas component E derived from the head of the second distillation column and then branches through a third heat exchanger and introduces one liquid component F as a second reflux liquid to the top of the second distillation column. ;

A second natural gas supply flow path for supplying another liquid component G as natural gas through a compression means and a second vaporizer;

A second reboiler for heating the liquid component H at the bottom of the second distillation column; And

And a natural gas liquid delivery channel for delivering the liquid component H derived from the bottom of the second distillation column as a natural gas liquid.

In the first heat exchanger, the gas component C is condensed by at least a portion of the cold of the liquefied natural gas supplied from the raw material supply unit, so that a first reflux liquid is prepared;

In the second heat exchanger, part or all of the gaseous liquefied natural gas derived from the first expansion turbine is cooled and condensed by cold cooling of the liquefied natural gas derived from the first heat exchanger, whereby raw materials can be prepared. ;

In the third heat exchanger, the gas component E is condensed at a low temperature by at least a portion of the cold of the liquefied natural gas supplied from the raw material supply unit, so that the second reflux liquid and the liquid component G are prepared. Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

Embodiment 1

The natural gas manufacturing apparatus of Embodiment 1 will be described with reference to FIG. 1. In the natural gas production apparatus 100 of Embodiment 1:

Liquefied natural gas (LNG) is introduced as a raw material from the raw material supply unit 101 to the first distillation column 7, and methane-rich natural gas (NG) is prepared from gas components derived from the top of the first distillation column 7 , Liquid components derived from the bottom are introduced into the second distillation column 9, and methane-rich natural gas (NG) is prepared from gas components derived from the top of the second distillation column 9, and the liquid components derived from the bottom The natural gas liquid (NGL) is prepared from.

A portion of the compressed LNG supplied from the raw material supply unit 101 includes a first heat exchanger (1), a second heat exchanger (2), a first vaporizer (3) and a cold expansion process including a first expansion turbine (4) The vaporized through, the vaporized LNG passes through the second heat exchanger 2 to form a gas-liquid mixture, and the gas-liquid mixture is introduced into the first distillation column 7 as a raw material. In the second heat exchanger (2), the U-turned LNG heat exchanges with the counter-current LNG itself, thereby cooling the cold of the LNG in the emission process and the temporarily vaporized LNG itself. Used to cool and condense. That is, during the flow of LNG in the raw material preparation process introduced into the distillation column, the cold of LNG is discharged, but a portion of the cooled cold is stored to reuse the cold more effectively.

Specifically, the natural gas production apparatus, the raw material supply unit 101, the first heat exchanger (1), the second heat exchanger (2), the first vaporizer (3) and the first expansion as the compressed LNG in the supercooled state as a raw material A raw material supply flow path 102 is introduced through the turbine 4 and then through the second heat exchanger 2 again into the first distillation column 7. Low temperature and high pressure (for example, about -135°C and about 10 MPa) LNG is supplied as a liquid from the raw material supply unit 101, and the first heat exchanger 1 before LNG is vaporized by the first vaporizer 3 And cold is continuously discharged through the second heat exchanger 2. The vaporized LNG is vaporized by the first expansion turbine 4, cooled to a low temperature, and then compressed to a predetermined optimum pressure (for example, 3.2 MPa) for the raw material to become low temperature and low pressure gas LNG. The gas LNG is cooled again by the second heat exchanger 2 to the optimum temperature preset for the raw materials. The preset temperature refers to a temperature at which LNG of a predetermined composition condenses at an optimum pressure to form a gas-liquid state; For example, for LNG with the composition shown in Table 1 below, the optimum temperature at about 3.2 MPa is about -80 °C. The condensed LNG is introduced into the first distillation column (7).

The first distillation column (7) has a first reboiler (201) for heating the liquid component D stored at the bottom of the first distillation column (7). The first reboiler 201 heats the liquid component D by heat exchange between the liquid component D and the heat transfer medium in the first reboiler 201. The temperature of the first reboiler 201 may be any temperature that can be maintained by seawater or industrial water, specifically, in the range of 0°C to 30°C. Thus, specifically, unheated seawater can be used, and there is no need to arrange heating means for heating the heat transfer medium in the first reboiler 201.

The liquid component D heated in the first reboiler 201 is re-introduced to the bottom of the first distillation column 7, and after distillation in the first distillation column 7, the methane-rich gas component A is the first distillation column ( It is introduced from the head of 7) and liquid component D is drawn from the bottom of the first distillation column 7.

Methane-rich gas component A derived from the head of the first distillation column 7 is branched, and one gas component B separated from the gas component A is passed through a first compressor 5 connected to the first expansion turbine 4 It is delivered as natural gas.

Specifically, the gas component A derived from the head of the first distillation column 7 is low temperature and low pressure (eg, about -95°C and about 3.2 MPa) methane-rich NG. In this embodiment, the gas component A is heated and boosted without introducing additional energy by adiabatic compression by the first compressor 5 connected to the first expansion turbine 4 used to prepare the raw materials. Can be processed.

The gas component A derived from the first compressor 5 may be supplied as NG as it is, but the first compressor to extract as product NG having a preset temperature and pressure (for example, 15° C. and about 10.6 MPa) It may be heated by a heater 6 disposed at the rear end of 5).

The other gas component C separated from the gas component A derived from the head of the first distillation column 7 is cooled and condensed through the first heat exchanger 1, and as the first reflux liquid to the top of the first distillation column 7 Is introduced.

Specifically, the first reflux flow path 104 is provided to introduce another gas component C as the first reflux liquid to the top of the first distillation column 7 through the first heat exchanger 1. In the first heat exchanger 1, the low and low pressure gas components A (eg, about 95° C. and about 3.2 MPa) are cooled and condensed by heat exchange with supercooled LNG before being introduced into the first distillation column 7 do.

The liquid component D stored at the bottom of the first distillation column 7 is introduced from the bottom liquid supply passage 105 to the second distillation column 9. Liquid component D contains a preset amount of methane. Thus, methane-rich component E from the head of the second distillation column 9 and liquid component H from the bottom of the second distillation column 9 are obtained by distillation in the distillation column 9.

Since the second distillation column 9 is operated at a lower pressure (for example, 1.8 MPa) than the first distillation column 7, the reboiler disposed at the bottom of the second distillation column 9 to overheat the liquid component H It does not need to be high temperature, and may be, for example, a temperature of 0°C to 30°C. Thus, specifically, unheated seawater can be used, and there is no need to arrange heating means for heating the heat transfer medium in the first reboiler 201.

The methane-rich gas component E derived from the head of the second distillation column 9 is cooled in the third heat exchanger 8 by heat exchange with supercooled LNG. The raw material LNG is branched from the rear end of the raw material supply unit 101, a part of which is supplied to the third heat exchanger 8, and the rest is supplied to the first heat exchanger 1.

The gas component E heat-exchanged in the third heat exchanger 8 is cooled and condensed, for example, to -110°C, and the liquid component F comprising a portion separated from the gas component E is the second reflux liquid. It is introduced from the reflux flow path 111 to the top of the second distillation column (9).

After passing through the third heat exchanger 8, another liquid component G separated from the gas component E is boosted by the compression means 10 and vaporized and heated in the second vaporizer 11 to set a predetermined temperature and pressure. Product NG with (for example, 15° C. and about 10 MPa) is prepared.

The liquid component H derived from the bottom of the second distillation column 9 is a liquid containing a number of components such as ethane, and is delivered as a natural gas liquid.

Therefore, in the natural gas production apparatus of this embodiment, the raw material LNG is distilled by the first distillation column 7 to obtain the methane-rich gas component A, and contains the methane component from the bottom of the first distillation column 7 Liquid component D is obtained. The liquid component D containing the methane component is further distilled in the second distillation column 9, and NG can be supplied while maintaining the recovery rate of NGL.

According to this embodiment, since the recovery rate of LNG can be maintained even when the liquid component D stored at the bottom of the first distillation column 7 contains a methane component, the first distillation column 7 can be operated at high pressure, Accordingly, high pressure NG can be supplied.

Since the first distillation column 7 can be operated at a low temperature, the present embodiment can provide a natural gas production apparatus having high energy efficiency without requiring a heat source to be introduced into the reboiler.

LNG supplied from this device has a composition as shown in Table 1 below, for example, the components fluctuate depending on the origin, and the temperature and pressure conditions for storage in a high-pressure tank are changed.

Specifically, LNG is stored under temperature conditions of about -120°C to -160°C and pressure conditions of about 5 to 10 MPa. In addition to what is conventionally called LNG, the LNG according to the present invention includes shale gas as described above, and refined LNG as well as unrefined LNG.

[Table 1]

The first heat exchanger 1, the second heat exchanger 2 and the third heat exchanger 8 are not specifically limited, and may be, for example, plate-fin heat exchangers or shell and tube heat exchangers. have.

The compression means 10 is not specifically limited, and may be, for example, a liquid delivery pump.

Embodiment 2

The LNG storage system of Embodiment 2 is demonstrated with reference to FIG. Elements marked with the same reference numerals as the natural gas production apparatus 100 of Embodiment 1 have the same function and are not described again.

In the natural gas production apparatus 100 of the second embodiment, the second expansion turbine 13 in the raw material supply flow path 102 is disposed downstream of the first vaporizer 3. LNG vaporized in the first vaporizer 3 is branched, a part of which is introduced into the first expansion turbine 4, and the rest of which is introduced into the second expansion turbine 13. The gas LNG decompressed by the first expansion turbine 4 and the gas LNG decompressed by the second expansion turbine 13 are joined and introduced into the second heat exchanger 2. LNG is cooled by heat exchange in the second heat exchanger 2, and condensed LNG is introduced into the first distillation column 7.

In the first natural gas delivery flow path 103, the fourth heat exchanger 15 is arranged at the rear end of the first compressor 5, and the second compressor 14 is arranged to be connected to the second expansion turbine 13. .

The gas component B supplied from the first compressor 5 is cooled in the fourth heat exchanger 15 by LNG supplied from the raw material supply unit 101. LNG cooled in the fourth heat exchanger 15 is, for example, -54°C, and is introduced into the second compressor 14. Cooling in the fourth heat exchanger 15 contributes to an improvement in compression efficiency in the second compressor 14. The gas component B boosted to the predetermined pressure (for example, 11.2 MPa) in the second compressor 14 is delivered from the first natural gas delivery flow path 103 as product NG. Since the product NG is at a predetermined temperature (for example, 15°C), the heater 6 can be disposed at the rear end of the second compressor 14 to heat the gas component B.

Other embodiments

As another embodiment, as shown in FIG. 5, a branch bypass line 30 may be disposed downstream of the first vaporizer 3, and a first shut-off valve 31 may be used as the branch bypass line 30. Can be placed on. The first shutoff valve 31 is controlled based on the pressure value measured by the pressure gauge 32 disposed in the first natural gas delivery flow path 103. Specifically, when the natural gas supply pressure is low and the pressure measured by the pressure gauge 32 is less than a preset value (for example, 6 MPa), the first shut-off valve 31 is opened and the second compressor 14 at the same time ) Can be stopped to increase the natural gas supply pressure, and when the pressure measured by the pressure gauge 32 is greater than or equal to a preset value (for example, 6 MPa), the first shut-off valve 31 is closed at the same time The second compressor 14 can be controlled to operate.

When the first shut-off valve 31 is opened toward the branch bypass line 30, the valve (not shown) on the inlet side of the fourth heat exchanger 15 is controlled to close.

When the first shut-off valve 31 is closed toward the branch bypass line 30, the valve (not shown) on the inlet side of the fourth heat exchanger 15 is controlled to open.

Based on the compression ratio of the first compressor 5 to the second compressor 14, the pressure of the natural gas before being introduced into the first compressor 5, and the pressure of the natural gas delivered from the natural gas delivery passage 103 The preset value can be determined.

For example, if the pressure of the natural gas before introduction to the first compressor 5 is 3 MPa and the compression ratio of the first compressor 5 is 2, the first compressor 5 will increase the natural gas to 6 MPa. It may, accordingly, a preset value for the pressure measured by the pressure gauge 32 may be 6 MPa.

When the pressure measured by the pressure gauge 32 is less than a preset value of 6 MPa, the first shut-off valve is controlled to open, and when the measured pressure is 6 MPa or more, the first shut-off valve is controlled to close.

When the first shut-off valve 31 is opened, the second compressor 14 is stopped, and when the first shut-off valve 31 is closed, the second compressor 14 is operated to compress natural gas.

By controlling in this way, when the natural gas should be supplied at a pressure of 6 MPa or more, the natural gas is brought to the required pressure by being boosted by the first compressor 5 before being compressed by the second compressor 14. Can be boosted.

However, when the natural gas is supplied at a pressure of less than 6 MPa, the apparatus can be operated under optimum conditions without using the second compressor 14 and only using the first compressor 5 to boost the pressure. have.

Other embodiments

As another embodiment, as shown in FIG. 6, the first generator 33 may be arranged to be connected to the second compressor 14.

Even when the natural gas supply pressure is low and the second compressor 14 is stopped, the second expansion turbine 13 connected to the second compressor 14 is operated.

Therefore, the first generator 33 connected to the second compressor 14 secures the power required to operate the second expansion turbine 13 when the second compressor 14 is stopped.

Other embodiments

As another embodiment, as shown in FIG. 7, a third expansion turbine 34 disposed in parallel with the second expansion turbine 13 is disposed downstream from the first carburetor 3, and the second generator ( 35) is arranged to be connected to the third expansion turbine (34).

The liquefied natural gas delivered from the first vaporizer 3 is switched to a new flow path by the second shut-off valve 36 or the third shut-off valve and supplied to the second expansion turbine 13 or the third expansion turbine 34. .

More specifically, when the natural gas supply pressure is low and the first shutoff valve 31 is opened and the second compressor 14 is stopped, the second shutoff valve 36 is closed and the third shutoff valve 37 is Is open.

Accordingly, natural gas delivered from the first vaporizer 3 is bypassed through the third shut-off valve 37 and introduced into the third expansion turbine 34. The second generator 35 connected to the third expansion turbine 34 secures the power required to operate the third expansion turbine 34.

However, when the natural gas supply pressure is high and the first shut-off valve 31 is closed and the second compressor 14 is operated, the second shut-off valve 36 is opened and the third shut-off valve 37 is closed.

Accordingly, natural gas delivered from the first vaporizer 3 is bypassed through the second shut-off valve 36 and introduced into the second expansion turbine 13.

Therefore, even when the natural gas supply pressure is low and the second compressor 14 is stopped, the third expansion turbine 34 operates, so that the second generator 35 connected to the third expansion turbine 34 is the third expansion turbine. Power required to operate (34) can be secured.

Example 1

Using the natural gas production apparatus according to Embodiment 1, in order to confirm the supply of LNG having the composition shown in Table 1, pressure (MPaA), temperature (° C.), flow rate (kg/h) and composition in each part (wt%) was simulated.

result

When LNG (-135°C and 9.96 MPa) is supplied at 572 and 373 kg/h, the pressure (MPaA), temperature (°C), flow rate (kg/h) and composition (wt%) of parts A to R of Figure 2 For the results as shown in Table 2 below.

The positions of parts A to R in FIG. 2 are as follows.

A is located at the outlet of the raw material supply unit 101.

B is downstream of the raw material supply unit 101 and is located just in front of the inlet of the first heat exchanger 1.

C is downstream of the first heat exchanger 1 and is located upstream of the second heat exchanger 2.

D is downstream of the raw material supply section 101 and is located upstream of the third heat exchanger 8.

E is downstream of the third heat exchanger 8 and is located just before where the flow path from the first heat exchanger 1 joins the flow path to the second heat exchanger 2.

F is downstream of the second heat exchanger 2 and is located upstream of the first vaporizer 3.

G is downstream of the first vaporizer 3 and is located upstream of the first expansion turbine 4.

H is located at the outlet downstream of the first expansion turbine.

I is located in the raw material supply flow path 102 immediately before where natural gas is introduced into the first distillation column 7.

J is the gas component B obtained from the head of the first distillation column 7 and is just before where the first compressor 5 is introduced and is located upstream of the first compressor 5.

K is downstream of the first compressor 5 and is located upstream of the heater 6.

L is located downstream of the heater 6 on the first natural gas delivery passage 103.

M is located at the outlet portion of the bottom of the first distillation column 7 inside the bottom liquid supply passage 105 extending from the bottom of the first distillation column 7.

N is located in the bottom liquid supply passage 105 just before the liquid is introduced into the second distillation column 9.

O is downstream of the third heat exchanger 8 and is located upstream of the compression means 10.

P is downstream of the compression means 10 and is located upstream of the second vaporizer 11.

Q is in front of where the flow path joins the first natural gas delivery flow path 103 and is located downstream of the second vaporizer 11.

R is located in the natural gas liquid delivery passage 113 downstream of the second distillation column 9.

[Table 2]

Comparative Example 1

Next, a correlation between the NG supply pressure and the recovery rate was confirmed for Example 1 and Comparative Example 1 (a natural gas supply device without a second distillation column). In Comparative Example 1, a conventional natural gas supply device was used in which methane-rich NG was delivered from the head of the first distillation column, natural gas liquid was delivered from the bottom of the first distillation column, and no second distillation column was present. Table 3 shows the comparison between Example 1 and Comparative Example 1.

Reboiler temperatures of Example 1 and Comparative Example 1 were confirmed when raw material LNG having the same temperature and pressure was used and the methane recovery rate, ethane recovery rate, and propane recovery rate were all 99.9% or more.

In Example 1, the NG feed pressure of 10.57 MPa was obtained using unheated seawater (temperature 10° C.) in the first and second reboilers.

On the other hand, in Comparative Example 1, in order to obtain a similar NG supply pressure (10.46 MPa), a temperature of 45° C. was required in the first and second reboilers. Therefore, steam had to be used in the first and second reboilers.

In Example 1, no additional heat source was required, but in Comparative Example 1, an additional heat source was required to use steam in the reboiler.

[Table 3]

Example 2

Using the natural gas production apparatus according to Embodiment 2, in order to confirm the supply of LNG having the composition shown in Table 1, pressure (MPaA), temperature (°C), flow rate (kg/h), and composition in each part (wt%) was simulated.

result

LNG (-135°C and 9.96 MPa) was supplied at 572 and 373 kg/h to provide pressure (MPaA), temperature (°C), flow rate (kg/h) and composition of parts A to R and D2 to K2 in FIG. 4 The results as illustrated in Table 4 below for (wt%) were obtained.

The positions of parts A to R in FIG. 4 are the same as those of parts A to R in FIG. 2. The positions of parts D2 to K2 in FIG. 4 are as follows.

D2 is downstream of the raw material supply unit 101 and is located just before the inlet to the fourth heat exchanger 15.

E2 is located at the outlet of the fourth heat exchanger (15).

G1 is located upstream of the first expansion turbine 4, immediately after the branching point after branching downstream of the first vaporizer 3.

G2 is located upstream of the second expansion turbine 13, immediately after the branching point after branching downstream of the first vaporizer 3.

H1 is located at the outlet portion of the first expansion turbine 4.

H2 is located at the inlet portion of the second expansion turbine 13, after branching downstream of the first vaporizer 3.

K1 is downstream of the fourth heat exchanger 15 and is located upstream of the second compressor 14.

K2 is downstream of the second compressor 14 and is located upstream of the heater 6.

[Table 4]

1 first heat exchanger
2 second heat exchanger
3 First carburetor
4 first expansion turbine
5 first compressor
6 Warmer
7 First distillation column
8 Third heat exchanger
9 Second distillation column
10 Compression means
11 Second carburetor
13 2nd expansion turbine
14 Second compressor
30 quarter bypass line
31 1st shut-off valve
32 pressure gauge
33 first generator
34 third expansion turbine
35 second generator
100 natural gas manufacturing equipment
101 Raw material supply
102 Raw Material Supply Euro
103 1st natural gas delivery channel
104 1st Reflux Euro
105 floor liquid supply flow path
111 Second Reflux Euro
112 Second natural gas supply flow path
113 Natural gas liquid delivery flow path

Claims (9)

A device for supplying natural gas by extracting a natural gas liquid from liquefied natural gas,
The compressed liquefied natural gas in the supercooled state is introduced as a raw material through a raw material supply unit, a first heat exchanger, a second heat exchanger, a first vaporizer, and a first expansion turbine, and then again through the second heat exchanger to the first distillation column. A raw material supply flow path introduced into the;
A first reboiler for heating the liquid component D at the bottom of the first distillation column;
Branching the methane-rich gas component A derived from the head of the first distillation column, and one gas component B separated from the gas component A, through a first compressor connected to the first expansion turbine, natural gas A first natural gas delivery flow path delivered as;
A first reflux flow path for introducing another gas component C separated from the gas component A as a first reflux liquid to the top of the first distillation column through the first heat exchanger;
A bottom supply flow path for introducing the liquid component D derived from the bottom of the first distillation column into the second distillation column;
After liquefying the methane-rich gas component E derived from the head of the second distillation column, it branches through a third heat exchanger, and one liquid component F separated from the gas component E is the second distillation column. A second reflux flow path introduced into the upper portion of the;
A second natural gas supply flow path for supplying another liquid component G separated from the gas component E as natural gas through a compression means and a second vaporizer;
A second reboiler for heating the liquid component H at the bottom of the second distillation column; And
A natural gas liquid delivery channel for delivering the liquid component H derived from the bottom of the second distillation column as a natural gas liquid,
In the first heat exchanger, the gas component C is condensed by at least a portion of the cold of the liquefied natural gas supplied from the raw material supply unit to prepare a first reflux liquid;
In the second heat exchanger, part or all of the gaseous liquefied natural gas derived from the first expansion turbine is cooled and condensed by cooling of the liquefied natural gas derived from the first heat exchanger, so that the 1 The raw material introduced into the distillation column is prepared;
In the third heat exchanger, the gas component E is condensed at a low temperature by at least a portion of the cold of the liquefied natural gas supplied from the raw material supply unit, so that a second reflux liquid and a liquid component G are prepared. According to claim 1,
A second expansion turbine is arranged downstream of the first vaporizer in the raw material supply flow path;
-At least a portion of the liquefied natural gas supplied from the first vaporizer is introduced into the first distillation column through the second expansion turbine;
A fourth heat exchanger and a second compressor connected to the second expansion turbine are arranged downstream of the first compressor in the first natural gas delivery flow path;
-The gas component B supplied from the first compressor is natural gas, and is transmitted from the first natural gas delivery channel through the fourth heat exchanger and the second compressor;
In the second heat exchanger, some or all of the liquefied natural gas derived from the first expansion turbine and the liquefied natural gas derived from the second expansion turbine are cold of the liquefied natural gas derived from the first heat exchanger Cooling and condensing by, the natural gas production apparatus characterized in that the raw material is prepared. According to claim 2,
A branch bypass line is downstream of the first compressor and arranged upstream of the fourth heat exchanger;
A first shut-off valve is arranged in the branch bypass line;
A device for producing natural gas, characterized in that the first shut-off valve is controlled based on a pressure value measured by a first pressure gauge disposed in the first natural gas delivery channel. According to claim 3,
Natural gas production apparatus characterized in that the first generator is arranged to be connected to the second compressor. According to claim 3,
And a third expansion turbine is disposed in parallel with the second expansion turbine, and a second generator is arranged to be connected to the third expansion turbine. A method for producing a natural gas liquid, which is a method for producing natural gas by extracting a natural gas liquid from liquefied natural gas,
(1) introducing at least a portion of the liquefied natural gas supplied from the raw material supply unit into the first distillation column after discharging a portion of the cold of the liquefied natural gas;
(2) introducing methane-rich gas component A from the head of the first distillation column;
(3) branching the gas component A, and boosting one gas component B separated from the gas component A before delivery as natural gas;
(4) cooling the other gas component C separated as gas component A as a first reflux liquid before introducing it to the top of the first distillation column;
(5) heating the liquid component D stored at the bottom of the first distillation column through a first reboiler;
(6) introducing at least a portion of the liquid component D derived from the bottom of the first distillation column into a second distillation column;
(7) Cooling the methane-rich gas component E derived from the head of the second distillation column, branching after liquefaction, and one liquid component F separated from the gas component E as a second reflux liquid, the top of the second distillation column Introducing into;
(8) boosting the other liquid component G separated from the gas component E and vaporizing it before feeding it as natural gas;
(9) heating the liquid component H stored at the bottom of the second distillation column through a second reboiler; And
(10) A method comprising delivering the liquid component H derived from the bottom of the second distillation column as a natural gas liquid. According to claim 3,
-At least a part of the liquefied natural gas supplied from the raw material supply section is introduced into the first distillation column as a raw material through a first heat exchanger, a second heat exchanger, a first vaporizer and a first expansion turbine;
In the first heat exchanger, the gas component C is condensed by at least a portion of the cold of the liquefied natural gas supplied from the raw material supply unit, and a first reflux liquid to be introduced to the top of the first distillation column is prepared. ;
In the second heat exchanger, a part or all of the liquefied natural gas in the gaseous state derived from the first expansion turbine is cooled and condensed by the cooling of the liquefied natural gas derived from the first heat exchanger, Raw materials are prepared;
The methane-rich gas component E derived from the head of the second distillation column is liquefied through a third heat exchanger;
In the third heat exchanger, the gas component E is low-temperature condensed by at least a portion of the cold of the liquefied natural gas supplied from the raw material supply unit, so that the second reflux liquid and the liquid component G are prepared. Gas manufacturing equipment. The method of claim 3 or 4,
The temperature of the first reboiler is 0 ℃ to 30 ℃, the temperature of the second reboiler is 0 ℃ to 30 ℃, natural gas production method. The method according to any one of claims 3 to 5,
The temperature of the liquefied natural gas introduced into the third heat exchanger is -180 °C to -125 °C when introduced into the third heat exchanger.

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