TW201920891A - Natural gas production equipment and natural gas production method - Google Patents

Abstract

To provide a natural gas production equipment and supply method capable of supplying NG having a required pressure (for example, a high pressure such as 6 MPa to 10 MPa) while maintaining the recovery rate of NGL, without using an additional expensive heat source such as steam in the reboiler. The natural gas production equipment is provided with a raw material supply section 101 for introducing com-pressed liquefied natural gas (LNG) in a supercooled state as a raw material to the first distillation column 7 through the raw material supply section 101, the first heat exchanger 1, the second heat exchanger 2, the first vaporiser 3, and the first expansion turbine 4, then through the second heat exchanger 2 again. A methane-rich gas component drawn from the head of a first distillation column 7 is delivered as natural gas. A liquid component stored in the bottom of the first distillation column 7 is introduced to a second distillation column 9. A methane-rich gas component drawn 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

   Device for manufacturing natural gas and method for manufacturing natural gas   

The invention relates to a natural gas manufacturing device and a natural gas manufacturing method using liquefied natural gas as raw materials, and in particular, it is a natural gas that can supply natural gas with a required pressure (for example, high pressure of 6 MPa to 10 MPa) while maintaining the recovery rate of the natural gas liquid. Is useful for manufacturing equipment and supply methods.

Natural gas (NG) is stored as liquefied natural gas (LNG) due to the convenience of transportation or storage. After being gasified, it is mainly used for thermal power generation or urban gas. In addition, after the shale gas revolution, cheap LNG can also be obtained on the LNG spot market, and the use of LNG in each country of origin has also increased. In addition, for example, when NG is used as a fuel for power generation, it is more convenient to use 100% methane to increase the amount of power generation in order to increase combustion energy. On the other hand, components with a large carbon number such as ethane (hereinafter sometimes referred to as "components such as ethane") are valuable not only as raw materials for chemical plants, but also by reducing LPG by using them as high-temperature heating of LNG (Liquid propane gas). In view of the above situation, it is required to provide a process with high energy efficiency for separating LNG into methane-rich gas, that is, NG, and ethane and other components at the LNG consumption site (LNG receiving base).

The technology of extracting natural gas liquid (NGL (Natural Gas Liquid)) from LNG to supply NG is a technology mainly for the purpose of adjusting the heat of the fuel gas supplied to a power station or a pipeline. However, for example, in Patent Document 1, it is as follows Way to achieve the purpose of NG supply and heat adjustment: temporarily depressurize the raw material LNG boosted to the NG supply pressure to a pressure capable of distillation operation, and then separate it into NG and NGL by distillation, and use an expansion turbine to recover the pressure The expansion energy at that time will once again boost the NG separated to the NG supply pressure by the compressor driven by its power.

In Patent Document 2, in order to supply high-pressure NG, the methane recovered from the top of the distillation column is fully pressurized by a compressor, and then liquefied, and the pressure is further increased by a pump and evaporated to supply NG.

    [Prior Art Literature]         [Patent Literature]    

[Patent Document 1] Japanese Patent Laid-Open No. 2016-156581

[Patent Document 2] US Patent Application Publication No. 2009/0282865

The components contained in the LNG used as the raw material differ depending on the place where the LNG is produced, and there are also cases in which a large amount of hydrocarbons having a carbon number of 3 or more, that is, propane, butane, and the like. In this case, the boiling point of LNG rises, so the methane recovery rate decreases when the NG rich in methane is taken out. In order 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 decreased.

In order to increase the operating temperature of the distillation column, it is conceivable to supply steam or warm water instead of seawater or industrial water, which is widely used as a reboiler of a distillation column that performs LNG distillation. However, because steam or warm water uses natural gas or electricity as a heat source, it has poor energy efficiency and high operating costs.

On the other hand, in the case where the reboiler uses seawater as usual and the operating pressure of the distillation column is lowered, although a heat source such as natural gas or electricity is not required, there is a concern that the pressure of the NG obtained may not meet the application requirements. Situations requiring pressure.

However, with the increase in the power generation facilities of NG power generation, the pressure on NG supply tends to rise. The effective operating pressure in the distillation operation depends on the LNG composition, so it can be considered to be approximately constant. Therefore, when the device disclosed in Patent Document 1 is used, the difference between the feed pressure of the raw material LNG and the operating pressure of the distillation column becomes large. This pressure difference causes the expansion of the above-mentioned raw material LNG and the expansion and compression ratio related to the recompression of NG. In order to reach the NG supply pressure, there may be a need for an additional compressor.

On the other hand, the method disclosed in Patent Document 2 requires a pump that processes the entire amount of NG to be supplied, and is therefore costly.

In addition, especially when the raw material LNG contains a larger amount of hydrocarbon components having a carbon number of 3 or more such as propane, the operating pressure of the distillation column is determined by the gas-liquid equilibrium based on the liquid composition at the bottom and the temperature of the reboiling heat source. As the operating pressure of the distillation column decreases, the difference between the feed pressure of the raw material LNG and the operating pressure of the distillation column tends to increase.

In view of the above-mentioned actual situation, the present invention provides a natural gas production device and a supply method, which do not use expensive heat sources such as steam in a reboiler due to the use of seawater, for example, and can supply NGL while maintaining the recovery rate of NGL NG with required pressure (for example, 6MPa ~ 10MPa high pressure).

The natural gas manufacturing device of the present invention is a device for extracting natural gas liquid from liquefied natural gas to supply natural gas, and includes a raw material supply flow path, pressurized liquefied natural gas in a supercooled state as a raw material, The exchanger, the second heat exchanger, the first gasifier, and the first expansion turbine are further introduced into the first distillation column after passing through the second heat exchanger; the first reboiler is a tower for the first distillation column. The liquid component D at the bottom is heated; the first natural gas supply and outlet flow path branches from the methane-rich gas component A that is derived from the top of the first distillation tower, and one of the gas components B separated from the gas component A passes through The first compressor connected to the first expansion turbine is supplied as the natural gas; and the first return flow path, another gas component C separated from the gas component A is passed through the first heat exchanger as the first reflux liquid. It is introduced into the upper part of the first distillation column, and the bottom liquid supply flow path introduces the liquid component D from the bottom of the first distillation column to the second Distillation column; second reflux flow path, one of the liquid components separated from the gas component E is branched off after liquefaction of the methane-rich gas component E from the top of the second distillation column F is introduced into the upper part of the second distillation column as a second reflux liquid; and a second natural gas supply flow path, another liquid component G separated from the gas component E, is used as the natural gas through a pressure means and a second gasifier. Is supplied; a second reboiler that heats the liquid component H at the bottom of the second distillation tower; and a natural gas liquid supply flow path, the liquid component H that is derived from the bottom of the second distillation tower is used as the natural gas The liquid is supplied; and in the first heat exchanger, the gas component C is condensed by using at least a portion of the coldness of the liquefied natural gas supplied from the raw material supply unit to produce the first reflux liquid, and the second heat In the exchanger, the liquefied natural gas in the gaseous state derived from the first expansion turbine is cooled by the coldness of the liquefied natural gas derived from the first heat exchanger. Part or all of the gas is cooled and condensed to produce the raw materials introduced into the first distillation column, and at least a portion of the coldness of the liquefied natural gas supplied from the raw material supply unit in the third heat exchanger is produced. , The gas component E is condensed at a low temperature to produce the second reflux liquid and the liquid component G.

In addition, the present invention is a method for producing natural gas by extracting natural gas liquid from liquefied natural gas, which is characterized by: (1) releasing at least a part of the liquefied natural gas supplied from a raw material supply unit and releasing a part of the coldness of the liquefied natural gas, and then introducing it to the first A distillation column; (2) the methane-rich gas component A is derived from the top of the first distillation column; (3) the gas component A is branched, and one of the gas components B separated from the gas component A is pressurized Then, it is supplied as the natural gas; (4) Another gas component C separated from the gas component A is cooled, and then introduced into the upper part of the first distillation column as a first reflux liquid, and (5) is stored in the above. The liquid component D at the bottom of the first distillation column is heated via the first reboiler; (6) at least a part of the liquid component D derived from the bottom of the first distillation column is introduced into the second distillation column; (7) from The methane-rich gas component E derived from the top of the second distillation column is cooled and liquefied and branched, and one of the liquid components F separated from the gas component E is introduced as a second reflux liquid to The upper part of the second distillation column; (8) the other liquid component G separated from the gas component E is supplied as the natural gas after being pressurized and gasified; (9) is stored at the bottom of the second distillation column The liquid component H is heated through a second reboiler; (10) The liquid component H derived from the bottom of the second distillation column is supplied as the natural gas liquid.

After at least a part of the liquefied natural gas supplied from the raw material supply part releases a part of the coldness of the above-mentioned liquefied natural gas, it is introduced into the process of (1) in the first distillation column, and the liquefied natural gas introduced into the first distillation column is due to its composition or temperature The difference is the gas-liquid mixed state or the gas state.

In addition, in the method for producing natural gas according to the present invention, at least a part of the liquefied natural gas supplied from the raw material supply unit passes through a first heat exchanger, a second heat exchanger, a first gasifier, and a first expansion turbine as raw materials. Into the first distillation column; In the first heat exchanger, the gas component C is condensed by introducing at least a portion of the coldness of the liquefied natural gas supplied from the raw material supply unit, and introduced into the upper portion of the first distillation column. The first reflux liquid; in the second heat exchanger, by the coldness of the liquefied natural gas derived from the first heat exchanger, part or all of the liquefied natural gas derived from the first expansion turbine is cooled, and This condensation produces the above-mentioned raw materials; the methane-rich gas component E derived from the top of the second distillation tower is liquefied via a third heat exchanger; and in the third heat exchanger, it is supplied from the above-mentioned raw materials At least a part of the cold of the liquefied natural gas supplied, and the above-mentioned gas component E is condensed at a low temperature to produce the second reflux liquid and the liquid. Ingredient G.

The raw material LNG is introduced into the first distillation column for distillation, and a methane-rich gas component A is obtained at the top of the column, and a liquid component D is stored at the bottom of the column. In the present invention, methane gas can be contained in the liquid component D. Therefore, the reboiler for heating the liquid component D is not charged with natural gas or electricity, and for example, unheated seawater can be used. In addition, since the first distillation column can be operated at a relatively high pressure, it is possible to supply high-pressure NG without using a multi-stage compressor.

When LNG containing a large amount of hydrocarbons having a carbon number of 3 or more is introduced into the first distillation column having a reboiler that does not use natural gas or a heat source such as electricity, if distillation is performed, a methane-rich The gas component A, but the liquid component D stored at the bottom of the column contained a larger amount of methane. This is because the boiling point of the raw material LNG is increased by containing a hydrocarbon having 3 or more carbon atoms.

The liquid component D containing methane is introduced into a second distillation column, and distillation is performed. Here, the methane in the liquid component D is derived from the top of the second distillation column as a methane-rich gas component E, and the components such as ethane in the liquid component D are taken as the liquid component H from the bottom of the second distillation column. It is exported and supplied as a natural gas liquid.

As described above, in the present invention, by setting a second distillation column and further distilling the liquid component containing methane stored in the bottom of the first distillation column, a methane-rich gas component and a natural gas liquid can be obtained. Therefore, when the raw material LNG contains a large amount of hydrocarbons with a carbon number of 3 or more, a heat source is not put into the reboiler, and the natural gas can be supplied while maintaining the recovery rate of NGL.

Furthermore, according to the present invention, when natural gas is supplied and supplied at a high pressure, the operating pressure of the first distillation column can be increased. When the operating pressure of the first distillation column increases, the methane component contained in the liquid component D stored in the bottom of the first distillation column increases. The liquid component D containing methane is further distilled in the second distillation column to obtain a gas component rich in methane and a natural gas liquid, and the recovery rate of NGL is also maintained. Due to the high operating pressure of the first distillation column, the pressure of the methane-rich gas component A obtained from the top of the first distillation column is also high. Therefore, even if the compressor for compressing the gas component A is not multi-staged, natural gas can be supplied and supplied at high pressure.

The natural gas manufacturing device of the present invention is located in the raw material supply flow path, and a second expansion turbine is provided downstream of the first gasifier, and at least a part of the liquefied natural gas supplied from the first gasifier passes through the second The expansion turbine is introduced into the first distillation column, and a fourth heat exchanger and a second compressor are provided in the first natural gas supply and output flow path after the first compressor, and the first compressor is supplied from the first compressor. The gas component B is supplied from the first natural gas supply flow path as the natural gas through the fourth heat exchanger and the second compressor, and in the second heat exchanger, the first heat is supplied from the first heat The coldness of the liquefied natural gas derived from the exchanger, part or all of the liquefied natural gas derived from the above-mentioned first expansion turbine and the liquefied natural gas derived from the above-mentioned second expansion turbine is cooled, thereby condensing, and the above raw materials can be produced.

According to the present invention, natural gas can be supplied at a higher pressure by compressing the methane-rich gas component A compressed by the first compressor and then compressing it by the second compressor. In addition, the gas component A compressed by the first compressor is cooled by the fourth heat exchanger, and is further efficiently compressed by the second compressor.

Although it is also considered that the pressure required for the supplied natural gas may change, it can also be controlled as follows: When the required pressure is low, the natural gas derived from the first compressor is directly supplied and the required pressure is In the high case, the natural gas derived from the second compressor is supplied.

In this way, according to the present invention, it is possible to supply natural gas in a wide pressure range while maintaining the recovery rate of NGL without putting a heat source in the reboiler.

In addition, the natural gas manufacturing device of the present invention is provided with a branch bypass line downstream of the first compressor and upstream of the fourth heat exchanger, and a first shut-off valve is provided on the branch bypass line. In addition, the first shut-off valve may be controlled according to a pressure value measured by a first pressure gauge disposed in the first natural gas supply and output flow path.

According to the present invention, when the natural gas supply pressure fluctuates, when the natural gas supply pressure is lower than a predetermined pressure, the second compressor provided in the subsequent stage is stopped and the downstream side of the first compressor is provided. The first shut-off valve of the branch bypass line is opened, and only the first compressor can be used to boost the natural gas. On the other hand, when the natural gas supply pressure is higher than a predetermined pressure, by starting the second compressor provided at the rear stage and closing the first shut-off valve, the second compressor can be used after the first compressor. Boosting natural gas.

The supply pressure of natural gas can be measured by a first pressure gauge arranged in the first natural gas supply and output channel. Depending on the measured pressure, you can choose to use only the first compressor or use both the first and second compressors to optimize the power used by the compressor.

In addition, in the natural gas production device of the present invention, a first generator may be connected to the second compressor.

When the pressure of the natural gas supplied from the first natural gas supply and output flow path is lower than a predetermined value, as described above, the second compressor is stopped. 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 by using a gear. Therefore, it is possible to ensure the function of the optimal conditions corresponding to the fluctuation of the natural gas supply pressure, and to ensure the power generation amount corresponding to the operation of the second expansion turbine alone.

(Invention 5)

In addition, the natural gas manufacturing device of the present invention may include a third expansion turbine arranged in parallel with the second expansion turbine downstream of the first gasifier, and a second generator connected to the third expansion turbine.

When the pressure of the natural gas supplied from the first natural gas supply and output flow path is lower than a predetermined value, as described above, the second compressor is stopped. In this case, the second expansion turbine is also stopped, and the liquefied natural gas supplied from the first gasifier 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 is connected to the second generator. Therefore, in the present invention, it is possible to ensure the function of the optimal conditions corresponding to the fluctuation of the natural gas supply pressure, and to ensure the power generation amount corresponding to the operation of the third expansion turbine alone.

In the method for producing natural gas of the present invention, the temperature of the first reboiler may be 0 ° C or higher and 30 ° C or lower, and the temperature of the second reboiler may be 0 ° C or higher and 30 ° C or lower.

According to the present invention, it is possible to supply natural gas in a wide pressure range while maintaining the recovery rate of NGL without putting a heat source in the first reboiler and the second reboiler. The temperature range of the first reboiler and the second reboiler is preferably 0 ° C or higher and 30 ° C or lower, and more preferably 5 ° C or higher and 10 ° C or lower.

Within the above temperature range, for example, unheated seawater can be used in the reboiler, and it is not necessary to use steam or warm water obtained by burning natural gas or performing electric heating. That is, there is no need to use additional heat sources such as combustion of natural gas or electricity.

From the viewpoint of the operation of the heat exchanger, if the lower limit of the temperature of the first reboiler and the second reboiler is about 5 ° C, it can also be used when the heat load of the heat exchanger fluctuates greatly. Run while suppressing the solidification of water. In addition, if 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 or industrial water temperature of about 15 ° C can be used.

In the constitution of the present invention, since the temperature of the reboiler is low, the liquid component D stored in the bottom of the first distillation column contains a larger amount of methane. The liquid component D containing methane is introduced into a second distillation column, and distillation is performed. Here, the methane in liquid component D is derived from the top of the second distillation column as a methane-rich gas component E, and the components such as ethane in liquid component D are extracted from the second distillation column as liquid component H. The bottom of the tower is led out and supplied as natural gas liquid.

In this way, in the present invention, by providing a second distillation column, the liquid component containing methane stored in the bottom of the first distillation column can be further distilled, thereby obtaining a gas component E and a natural gas liquid rich in methane. Therefore, without putting a heat source in the reboiler, natural gas can be supplied while maintaining the recovery rate of NGL.

In the method for supplying natural gas according to the present invention, the temperature at the time of the introduction of the third heat exchanger of the liquefied natural gas introduced into the third heat exchanger may be -180 ° C or higher and -125 ° C or lower.

In the present invention, by introducing a part of the raw material LNG above -180 ° C and below -125 ° C directly into the third heat exchanger, the methane-rich gas component E which is derived from the top of the second distillation tower is removed. The methane contained is cooled, condensed, and pumped up to be supplied as natural gas. If the temperature is -180 ° C or higher and -125 ° C or lower, methane is cooled and condensed, and thus methane gas can be efficiently recovered from the upper part of the second distillation column.

It can also be boosted by pressurizing means, and then evaporated by a heater to supply. According to the present invention, the methane component introduced into the second distillation column can be recovered and supplied as natural gas, so that the recovery rate of methane in the raw material LNG can be further increased.

1‧‧‧The first heat exchanger

2‧‧‧Second heat exchanger

3‧‧‧ the first gasifier

4‧‧‧ the first expansion turbine

5‧‧‧The first compressor

6‧‧‧ warmer

7‧‧‧The first distillation column

8‧‧‧ third heat exchanger

9‧‧‧Second distillation column

10‧‧‧Pressure means

11‧‧‧Second Gasifier

13‧‧‧second expansion turbine

14‧‧‧Second Compressor

30‧‧‧ branch bypass pipeline

31‧‧‧The first shut-off valve

32‧‧‧ pressure gauge

33‧‧‧The first generator

34‧‧‧ Third expansion turbine

35‧‧‧Second generator

100‧‧‧ Natural Gas Manufacturing Plant

101‧‧‧ Raw material supply department

102‧‧‧ Raw material supply channel

103‧‧‧The first natural gas supply and output channel

104‧‧‧first return flow path

105‧‧‧ tower bottom liquid supply flow path

111‧‧‧second return flow path

112‧‧‧Second natural gas supply channel

113‧‧‧ Natural gas liquid supply and outlet

201‧‧‧The first reboiler

FIG. 1 is a diagram showing a configuration example of a natural gas production apparatus according to the first embodiment.

FIG. 2 is a diagram illustrating an empirical result in a configuration example of a natural gas manufacturing apparatus according to the first embodiment.

Fig. 3 is a diagram showing a configuration example of a natural gas production apparatus according to a second embodiment.

FIG. 4 is a diagram illustrating an empirical result in a configuration example of a natural gas manufacturing apparatus according to the second embodiment.

Fig. 5 is a diagram showing another configuration example of the natural gas production apparatus according to the second embodiment.

FIG. 6 is a diagram showing another configuration example of the natural gas production apparatus according to the second embodiment.

Fig. 7 is a diagram showing another configuration example of the natural gas production apparatus of the second embodiment.

Hereinafter, some embodiments of the present invention will be described. The embodiment described below describes an example of the present invention. The present invention is not limited to the following embodiments, and includes various modifications that can be implemented within a range that does not change the gist of the present invention. In addition, all the structures explained below are not necessarily essential structures of the present invention.

(The natural gas production device of the present invention)

The natural gas manufacturing device of the present invention uses liquefied natural gas (LNG) as a raw material to be introduced into a first distillation column, and a gas component derived from the top of the first distillation column is used to produce methane-rich natural gas (NG). The liquid component derived from the bottom is further introduced into the second distillation column. The gas component derived from the top of the second distillation column is used to produce methane-rich natural gas (NG), and the liquid component derived from the bottom of the column is used to produce a natural gas liquid. (NGL).

Equipped with: a raw material supply flow path, pressurized liquefied natural gas in a supercooled state as a raw material, passed through a raw material supply unit, a first heat exchanger, a second heat exchanger, a first gasifier, and a first expansion turbine, and then passes through The second heat exchanger is introduced into the first distillation column; the first reboiler heats the liquid component D at the bottom of the first distillation column; the first natural gas supply and outlet flow path is from the first distillation column. Methane-rich gas component A branching out from the top of the tower, one of the gas components B is supplied as the natural gas through the first compressor connected to the first expansion turbine; the first return flow path, and the other gas component C is passed through The first heat exchanger is introduced into the upper part of the first distillation column as a first reflux liquid; the bottom liquid supply flow path introduces the liquid component D, which is led out from the bottom of the first distillation column, into the second distillation. Column; second reflux flow path, the methane-rich gas component E, which is derived from the top of the second distillation column, is liquefied through a third heat exchanger, and is branched, one of which is a liquid component F It is introduced into the upper part of the second distillation column for a second reflux liquid; a second natural gas supply flow path, and another liquid component G is supplied as the natural gas through a pressure means and a second gasifier; a second reboiler, The liquid component H at the bottom of the second distillation tower is heated; and the natural gas liquid supply flow path, the liquid component H derived from the bottom of the second distillation tower is supplied as the natural gas liquid.

In the first heat exchanger, at least a part of the coldness of the liquefied natural gas supplied from the raw material supply unit, the gas component C is condensed to prepare the first reflux liquid, and in the second heat exchanger, From the coldness of the liquefied natural gas derived from the first heat exchanger, a part or all of the liquefied natural gas derived from the first expansion turbine is cooled, thereby condensing, and the above raw materials are produced. In the third heat exchanger, The gas component E is condensed at a low temperature by at least a part of the coldness of the liquefied natural gas supplied from the raw material supply unit to produce the second reflux liquid and the liquid component G. Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)

The natural gas production apparatus according to the first embodiment will be described with reference to FIG. 1. The natural gas supply device 100 according to the first embodiment is configured to introduce liquefied natural gas (LNG) as a raw material from the raw material supply unit 101 to the first distillation column 7 and prepare a rich component from a gas component derived from the top of the first distillation column 7 Natural gas (NG) of methane, the liquid component derived from the bottom of the column is further introduced into the second distillation column 9, and the gas component derived from the top of the second distillation column 9 is used to produce methane-rich natural gas (NG). The liquid component derived from the bottom of the tower is used to make natural gas liquid (NGL).

Here, a part of the pressurized LNG in the supercooled state supplied from the raw material supply unit 101 passes through the first heat exchanger 1 to the second heat exchanger 2 to the first gasifier 3 and the first expansion turbine 4. It is gasified during the cold release process, and the gasified LNG is further passed through the second heat exchanger 2 to form a gas-liquid mixture, which is introduced into the first distillation column 7 as a raw material. In the second heat exchanger 2, the rotating LNG performs heat exchange with the LNG itself countercurrently, and the coldness of the LNG during the release process is used for the cooling and condensation of the temporarily vaporized LNG itself. That is, during the flow of LNG during the production of the raw materials introduced into the distillation column, not only the cold of the LNG is released, but a part of the released cold is contained, whereby the cold can be effectively utilized.

Specifically, the natural gas manufacturing apparatus includes a raw material supply flow path 102 in which the pressurized LNG in a supercooled state is used as a raw material and passes through the raw material supply unit 101, the first heat exchanger 1, the second heat exchanger 2, and the first A gasifier 3 and a first expansion turbine 4 are introduced into the first distillation column 7 after passing through the second heat exchanger 2. The low-temperature and high-pressure LNG (for example, about -135 ° C, about 10 MPa) is supplied in liquid form from the raw material supply unit 101, and the cold is released through the first heat exchanger 1 and the second heat exchanger 2 in sequence. The gasifier 3 is gasified. The gasified LNG is gasified and reduced in temperature by the first expansion turbine 4, and decompressed to a predetermined pressure (for example, about 3.2 MPa) that is optimal as a raw material, and becomes a low-temperature and low-pressure gas-like LNG. The gaseous LNG is again cooled by the second heat exchanger 2 to a predetermined temperature optimal as a raw material. The so-called predetermined temperature at this time refers to the temperature at which the LNG of a predetermined composition condenses under the optimal pressure to form a coexisting state of gas and liquid. For example, in the case of the LNG of the composition illustrated in Table 1 below, it is preferably at about 3.2MPa. -80 ° C. The condensed LNG is introduced into the first distillation column 7.

The first distillation column 7 includes a first reboiler 201 that heats the liquid component D stored in the bottom of the first distillation column 7. In the first reboiler 201, the liquid component D and the heat medium of the first reboiler 201 undergo heat exchange, and the liquid component D is heated. The temperature of the first reboiler 201 may be a temperature that can be maintained by seawater or industrial water, and is specifically in a range of 0 ° C to 30 ° C. Therefore, in particular, unheated seawater can be used, and there is no need to provide heating means for heating the heat medium of the first reboiler 201.

The heated liquid component D in the first reboiler 201 is re-introduced to the bottom of the first distillation column 7, and is distilled in the first distillation column 7, and the gas component rich in methane is led out from the top of the first distillation column 7. A, and the liquid component D is derived from the bottom of the first distillation column 7.

The methane-rich gas component A branching out from the top of the first distillation column 7 is branched, and one of the gas components B separated from the gas component A passes through the first compressor 5 connected to the first expansion turbine 4 as The above-mentioned natural gas is supplied. Specifically, the gas component A derived from the top of the first distillation column 7 is a low-temperature and low-pressure (for example, about -95 ° C, about 3.2 MPa) methane-rich NG. In the present embodiment, the gas component A is subjected to adiabatic compression by the first compressor 5 connected to the first expansion turbine 4 used in the production of the raw materials, and the heating and boosting processes can be performed without introducing additional energy. . The gas component A derived from the first compressor 5 can also be directly supplied as NG. However, in order to take it out as a product NG of a predetermined temperature and pressure (for example, 15 ° C, about 10.6 MPa), it can also be arranged in the first compression The heater 6 in the latter stage of the machine 5 performs heating.

In the gas component A which is led out from the top of the first distillation column 7, the separated gas component C is cooled and condensed through the first heat exchanger 1, and is introduced into the first distillation column 7 as a first reflux liquid. Upper part.

Specifically, another gas component C is provided as a first reflux liquid to the first reflux flow path 104 above the first distillation column 7 through the first heat exchanger 1. In the first heat exchanger 1, a low-temperature and low-pressure gas component A (for example, about 95 ° C. and about 3.2 MPa) is cooled and condensed by heat exchange with supercooled LNG, and is introduced into the first distillation column 7.

The liquid component D stored in the bottom of the first distillation column 7 is introduced into the second distillation column 9 from the column bottom liquid supply flow path 105. Liquid component D contains a predetermined amount of methane. Therefore, as the second distillation column 9 performs distillation, a methane-rich component E is obtained from the top of the second distillation column 9 and a liquid component H is obtained from the bottom of the second distillation column 9.

Since the second distillation column 9 operates 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 and heating the liquid component H need not be at a high temperature, for example, Temperatures above 0 ° C and below 30 ° C are sufficient. Therefore, specifically, unheated seawater can be used, and there is no need to provide a heating means for heating the heat medium of the first reboiler 201.

The methane-rich gas component E, which is led out from the top of the second distillation column 9, is cooled by heat exchange with the supercooled LNG in the third heat exchanger 8. The raw material LNG is branched at the rear stage of the raw material supply unit 101, and a part of the raw material LNG is supplied to the third heat exchanger 8 and the other part is supplied to the first heat exchanger 1. By the heat exchange in the third heat exchanger 8, the gas component E is cooled to, for example, -110 ° C, and is condensed, and a part of the gas component E, that is, the liquid component F, is used as the second reflux liquid, and the second reflux liquid The flow path 111 is introduced into the upper part of the second distillation column 9.

After passing through the third heat exchanger 8, the other component separated from the gas component E, that is, the liquid component G, is boosted by the pressurizing means 10, and gasified and heated in the second gasifier 11 as a predetermined The temperature and pressure (for example, 15 ° C, about 10 MPa) of the product NG are taken out.

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

As described above, in the natural gas manufacturing apparatus of this embodiment, the raw material LNG is distilled in the first distillation column 7 to obtain a gas component A rich in methane, and obtained from the bottom of the first distillation column 7 Liquid component D containing a methane component. By distilling the liquid component D containing a methane component in the second distillation column 2, NG can be supplied while maintaining the recovery rate of NGL. According to this embodiment, even if the liquid component D stored in the bottom of the first distillation column 7 contains a methane component, the LNG recovery rate can be maintained as in the past. Therefore, the first distillation column 7 can be operated at a high pressure. As a result, It can supply high pressure NG. In addition, according to this embodiment, since the first distillation column 7 can be operated at a low temperature, it is not necessary to input a heat source into the reboiler, and a device for producing natural gas with high energy efficiency can be provided.

The LNG supplied in this device has, for example, the composition exemplified in Table 1 below. Depending on the origin, the composition varies, and the temperature or pressure conditions stored in the high-pressure tank are also different. Specifically, it is stored under a temperature condition of about -120 to -160 ° C and a pressure condition of about 5 to 10 MPa. In addition, the LNG of the present invention includes, in addition to the conventional LNG, shale gas as described above, or not only refined LNG but also unrefined LNG.

The first heat exchanger 1, the second heat exchanger 2, and the third heat exchanger 8 are not particularly limited, and for example, a plate-fin heat exchanger or a shell and tube heat exchanger can be used.

The pressurizing means 6 is not particularly limited, and for example, a liquid pump can be used.

(Embodiment 2)

The LNG storage system according to the second embodiment will be described with reference to FIG. 3. Elements having the same reference numerals as those of the natural gas production apparatus 100 according to the first embodiment have the same functions, and therefore descriptions thereof will be omitted.

The natural gas manufacturing apparatus 100 according to the second embodiment is provided with a second expansion turbine 13 in the raw material supply flow path 102 downstream of the first gasifier 3. Part of the gasified LNG branch in the first gasifier 3 is introduced into the first expansion turbine 4 and the other is introduced into the second expansion turbine 13. The decompressed gas-like LNG in the first expansion turbine 4 and the decompressed gas-like LNG in the second expansion turbine 13 are combined and introduced into the second heat exchanger 2. The LNG cooled and condensed by heat exchange in the second heat exchanger 2 is introduced into the first distillation column 7.

In the first natural gas supply / exit flow path 103, a fourth heat exchanger 15 and a second compressor 14 connected to the second expansion turbine 13 are provided behind the first compressor 5. The gas component B supplied from the first compressor 5 is cooled by heat exchange with the LNG supplied from the raw material supply unit 101 in the fourth heat exchanger 15. The cooled LNG in the fourth heat exchanger 15 is, for example, about -54 ° C, and is introduced into the second compressor 14. The cooling in the fourth heat exchanger 15 helps to improve the compression efficiency in the second compressor 14. The gas component B boosted to a predetermined pressure (for example, 11.2 MPa) in the second compressor 14 is supplied from the first natural gas supply flow path 103 as a product NG. In order to set the temperature of the product NG to a predetermined temperature (for example, 15 ° C.), the heater 6 may be disposed at the rear stage 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 provided on the downstream side of the first gasifier 3, and a first shut-off valve 31 may be provided on the branch bypass line 30. The first shut-off valve 31 is controlled based on a pressure value measured by a pressure gauge 32 arranged on the first natural gas supply and output flow path 103. Specifically, the following control can be performed: when the supply pressure of natural gas is low and the pressure measured by the pressure gauge 32 is lower than a predetermined value (for example, 6 MPa), the first shut-off valve 31 can be opened at the same time When the second compressor 14 is stopped, when the supply pressure of natural gas is high, and the pressure measured by the pressure gauge 32 is a predetermined value (for example, 6 MPa) or more, the first shut-off valve 31 may be closed at the same time , The second compressor 14 is operated.

When the first shut-off valve 31 on the side of the bypass line 30 is opened, the valve opening and closing control of closing the valve (not shown) on the inlet side of the fourth heat exchanger 15 is performed.

When the first shutoff valve 31 on the side of the bypass line 30 is closed, the valve opening and closing control for opening a valve (not shown) on the inlet side of the fourth heat exchanger 15 is performed.

The predetermined value can be determined based on the compression ratios of the first compressor 5 and the second compressor 14, the pressure of the natural gas before the first compressor 5 is introduced, and the pressure of the natural gas supplied from the natural gas supply / exit flow path 103. For example, when the pressure of the natural gas before the introduction of the first compressor 5 is 3 MPa, and the compression ratio of the first compressor 5 is 2, the natural gas can be boosted to 6 MPa by the first compressor 5, so from The predetermined value of the pressure measured by the pressure gauge 32 can be set to 6 MPa. The following control can be performed: if the predetermined value of the pressure measured by the pressure gauge 32 is less than 6 MPa, the first shut-off valve is opened, and if it is 6 MPa or more, the first shut-off valve is closed.

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 the manner described above, when natural gas must be supplied at a pressure of 6 MPa or more, the natural gas can be boosted by the first compressor 5 and then boosted by the second compressor 14. As a result, Natural gas is boosted to the necessary pressure.

On the other hand, when natural gas is supplied at less than 6 MPa, operation under optimal conditions can be performed, that is, only the first compressor 5 is used for boosting pressure, and the second compressor 14 is not used.

(Another embodiment)

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

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 also operates. Therefore, when the second compressor 14 is stopped, the first generator 33 connected to the second compressor 14 can secure an electric power corresponding to the operation of the second expansion turbine 13.

(Another embodiment)

As still another embodiment, as shown in FIG. 7, a third expansion turbine 34 arranged in parallel with the second expansion turbine 13 may be provided downstream of the first gasifier 3 and connected to the third expansion turbine 34. Second generator 35.

The liquefied natural gas supplied from the first gasifier 3 is switched to the second expansion valve 13 or the third expansion turbine 34 through the second shutoff valve 36 and the third shutoff valve.

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 opened. As a result, the natural gas supplied from the first gasifier 3 is introduced into the third expansion turbine 34 through the third shutoff valve 37. The second generator 35 connected to the third expansion turbine 34 ensures electric power corresponding to the operation of the third expansion turbine 34.

On the other hand, when the natural gas supply pressure is high, the first shutoff valve 31 is closed, and the second compressor 14 is operated, the second shutoff valve 36 is opened, and the third shutoff valve 37 is closed. As a result, the natural gas supplied from the first gasifier 3 is introduced into the second expansion turbine 13 through the second shutoff valve 36.

Therefore, when the natural gas supply pressure is low and the second compressor 14 is stopped, the third expansion turbine 34 can be operated, and the second generator 35 connected to the third expansion turbine 34 can be used to ensure the third expansion. Electricity corresponding to the operation of the turbine 34.

(Example 1)

Using the natural gas manufacturing apparatus of Embodiment 1, LNG with the composition exemplified in Table 1 was supplied as a raw material, and the pressure (MPaA), temperature (° C), flow rate (kg / h), and composition (weight) of each part were verified by simulation. %).

(Result)

If LNG (-135 ° C, 9.96MPa) is supplied at 572,373 kg / h, the pressure (MPaA), temperature (° C), flow rate (kg / h), and composition (wt%) of each part A to R in FIG. 2 are obtained The results are illustrated in Table 2 below.

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

The position of A is the exit of the raw material supply section 101.

The position of B is downstream of the raw material supply section 101 and is near the entrance of the first heat exchanger 1.

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

The position of D is downstream of the raw material supply section 101 and is near the entrance of the third heat exchanger 8.

The position of E is downstream of the third heat exchanger 8 and immediately before the flow merges from the first heat exchanger 1 to the second heat exchanger 2.

The position of F is downstream of the second heat exchanger 2 and upstream of the first gasifier 3.

The position of G is downstream of the first gasifier 3 and upstream of the first expansion turbine 4.

The position of H is the downstream-side outlet of the first expansion turbine.

The position I is when the first distillation column 7 in the raw material supply flow path 102 is introduced.

The position of J is the gas component B obtained from the top of the first distillation column 7 immediately before being introduced into the first compressor 5 and upstream of the first compressor 5.

The position of K is downstream of the first compressor 5 and upstream of the warmer 6.

The position of L is located on the first natural gas supply and outlet flow path 103 and is downstream of the warmer 6.

The position of M is in the bottom liquid supply flow path 105 extending from the bottom of the first distillation column 7, and is the outlet portion of the bottom of the first distillation column 7.

The position of N is in the bottom liquid supply flow path 105 and is a position to be introduced into the second distillation column 9.

The position of O is downstream of the third heat exchanger 8 and upstream of the pressurizing means 10.

The position of P is downstream of the pressurizing means 10 and upstream of the second gasifier 11.

The position of Q is downstream of the second gasifier 11 and immediately before the confluence in the first natural gas supply and outlet flow path 103.

The position of R is in the natural gas liquid supply and outlet flow path 113 and is downstream of the second distillation column 9.

(Comparative example 1)

Then, the comparison between the recovery rate and the NG supply pressure of Example 1 and Comparative Example 1 (a natural gas supply device without a second distillation column) was verified. In Comparative Example 1, a conventional natural gas supply device is used, which is not provided with a second distillation column, and NG rich in methane is supplied from the top of the first distillation column, and natural gas liquid is supplied from the bottom of the first distillation column. A comparison between Example 1 and Comparative Example 1 is shown in Table 3 below.

The reboiler temperatures in Example 1 and Comparative Example 1 when the methane recovery rate, ethane recovery rate, and propane recovery rate were set to 99.9% or more were used as raw materials LNG having the same temperature and pressure.

In Example 1, the unreheated seawater (temperature: 10 ° C) was used in the first reboiler and the second reboiler to obtain an NG supply pressure of 10.57 MPa.

In contrast, in Comparative Example 1, it was found that in order to obtain the same NG supply pressure (10.46 MPa), the temperatures of the first reboiler and the second reboiler must be set to 45 ° C. Therefore, the first reboiler and the second reboiler must use steam.

Compared to Example 1, no additional heat source is required for the reboiler. In Comparative Example 1, since the reboiler uses steam, an additional heat source is required.

(Example 2)

Using the natural gas manufacturing device of Embodiment 2, LNG with the composition exemplified in Table 1 was supplied as a raw material, and the pressure (MPaA), temperature (° C), flow rate (kg / h), and composition (weight) of each part were verified by simulation. %).

(Result)

If LNG is supplied at 572,373 kg / h (-135 ° C, 9.96MPa), the pressure (MPaA), temperature (° C), flow rate (kg / h), composition (weight) of each part A to R, D2 to K2 in Figure 4 %) The results exemplified in Table 4 below were obtained.

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

The position of D2 is downstream of the raw material supply section 101 and is near the entrance of the fourth heat exchanger 15.

The position of E2 is the outlet of the fourth heat exchanger 15.

The position of G1 is directly behind the branch point after the downstream branch of the first gasifier 3 and upstream of the first expansion turbine 4.

The position of G2 is directly behind the branch point after the downstream branch of the first gasifier 3 and upstream of the second expansion turbine 13.

The position of H1 is the exit portion of the first expansion turbine 4.

The position of H2 is the inlet portion of the second expansion turbine 13 after branching downstream of the first gasifier 3.

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

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

Claims (10)

    A natural gas manufacturing device is a device for extracting natural gas liquid from liquefied natural gas to supply natural gas. The device is provided with a raw material supply flow path, pressurized liquefied natural gas in a supercooled state as a raw material, The exchanger, the second heat exchanger, the first gasifier, and the first expansion turbine are further introduced into the first distillation column after passing through the second heat exchanger; the first reboiler is a tower for the first distillation column. The liquid component D at the bottom is heated; the first natural gas supply and outlet flow path branches from the methane-rich gas component A that is derived from the top of the first distillation tower, and one of the gas components B separated from the gas component A passes through The first compressor connected to the first expansion turbine is supplied as the natural gas; and the first return flow path, another gas component C separated from the gas component A is passed through the first heat exchanger as the first reflux liquid. And is introduced into the upper part of the first distillation column; the bottom liquid supply flow path, the liquid component D led out from the bottom of the first distillation column is introduced into the second distillation column; Distillation column; second reflux flow path, one of the liquid components separated from the gas component E is branched off after liquefaction of the methane-rich gas component E from the top of the second distillation column F is introduced into the upper part of the second distillation column as a second reflux liquid; and a second natural gas supply flow path, another liquid component G separated from the gas component E, is used as the natural gas through a pressure means and a second gasifier. Is supplied; a second reboiler that heats the liquid component H at the bottom of the second distillation tower; and a natural gas liquid supply flow path, the liquid component H that is derived from the bottom of the second distillation tower is used as the natural gas The liquid is supplied; and in the first heat exchanger, the gas component C is condensed by using at least a portion of the coldness of the liquefied natural gas supplied from the raw material supply unit to produce the first reflux liquid, and the second heat In the exchanger, the liquefied natural gas in the gaseous state derived from the first expansion turbine is cooled by the coldness of the liquefied natural gas derived from the first heat exchanger. Part or all of the gas is cooled and condensed to produce the raw materials introduced into the first distillation column, and at least a portion of the coldness of the liquefied natural gas supplied from the raw material supply unit in the third heat exchanger is produced. , The gas component E is condensed at a low temperature to produce the second reflux liquid and the liquid component G.         For example, in the natural gas production device of the scope of application for a patent, in the raw material supply flow path, a second expansion turbine is provided downstream of the first gasifier, and the liquefied natural gas supplied from the first gasifier At least a part of it is introduced into the first distillation column through the second expansion turbine, and a fourth heat exchanger and a second expansion unit are provided in the first natural gas supply and output flow path after the first compressor. The second compressor connected to the turbine, the gas component B supplied from the first compressor is supplied through the fourth heat exchanger and the second compressor as the natural gas from the first natural gas supply and output channel, and In the second heat exchanger, a portion of the liquefied natural gas derived from the first expansion turbine and the liquefied natural gas derived from the second expansion turbine are derived from the coldness of the liquefied natural gas derived from the first heat exchanger. Or the whole is cooled and condensed to produce the above-mentioned raw materials.         For example, in the natural gas manufacturing device for which the scope of patent application is item 2, a branch bypass line is provided downstream of the first compressor and upstream of the fourth heat exchanger, and a first bypass line is provided on the branch bypass line. A shut-off valve, and the first shut-off valve is controlled according to a pressure value measured by a first pressure gauge arranged in the first natural gas supply and output flow path.         For example, in the natural gas manufacturing device of claim 3, a first generator is connected to the second compressor.         For example, in the natural gas manufacturing device of the third scope of the patent application, a third expansion turbine arranged in parallel with the second expansion turbine is provided downstream of the first gasifier, and is connected to the third expansion turbine. The second generator.         A method for producing natural gas, which is a method for producing natural gas by extracting natural gas liquid from liquefied natural gas. (1) At least a part of the liquefied natural gas supplied from a raw material supply unit is released as a part of the coldness of the liquefied natural gas, and then introduced to the first Distillation column; (2) the methane-rich gas component A is derived from the top of the first distillation column; (3) the gas component A is branched, and one of the gas components B separated from the gas component A is pressurized Is supplied as the natural gas; (4) another gas component C separated from the gas component A is cooled and then introduced as a first reflux liquid to the upper part of the first distillation column; (5) stored in the first The liquid component D at the bottom of a distillation column is heated via a first reboiler; (6) at least a part of the liquid component D derived from the bottom of the first distillation column is introduced into a second distillation column; (7) from the above The methane-rich gas component E, which is derived from the top of the second distillation column, is cooled and liquefied and branched. One of the liquid components F separated from the gas component E is introduced as a second reflux liquid to The upper part of the second distillation column; (8) the other liquid component G separated from the gas component E is supplied as the natural gas after being pressurized and gasified; (9) is stored at the bottom of the second distillation column The liquid component H is heated through a second reboiler; (10) The liquid component H derived from the bottom of the second distillation column is supplied as the natural gas liquid.         For example, the method for manufacturing natural gas according to claim 6 in which at least a part of the liquefied natural gas supplied from the raw material supply unit passes through a first heat exchanger, a second heat exchanger, a first gasifier, and a first expansion turbine. It is introduced into the first distillation column as a raw material. In the first heat exchanger, the gas component C is condensed by introducing at least a portion of the coldness of the liquefied natural gas supplied from the raw material supply unit, and is introduced into the first The first reflux liquid in the upper part of the distillation column; in the second heat exchanger, a part or all of the liquefied natural gas derived from the first expansion turbine is taken from the coldness of the liquefied natural gas derived from the first heat exchanger. After cooling, thereby condensing, the above-mentioned raw materials are produced; the methane-rich gas component E derived from the top of the second distillation tower is liquefied via a third heat exchanger; and in the third heat exchanger, by At least a part of the coldness of the liquefied natural gas supplied from the raw material supply unit, the gas component E is condensed at a low temperature to produce the second reflux liquid and The aforementioned liquid component G.         For example, the method for manufacturing natural gas according to item 6 of the patent application range, wherein the temperature of the first reboiler is 0 ° C to 30 ° C, and the temperature of the second reboiler is 0 ° C to 30 ° C.         For example, the method for manufacturing natural gas according to item 7 of the application, wherein the temperature of the first reboiler is 0 ° C or higher and 30 ° C or lower, and the temperature of the second reboiler is 0 ° C or higher and 30 ° C or lower.         For example, the method for producing natural gas according to any one of claims 6 to 9, wherein the temperature at the time of introduction of the third heat exchanger of the liquefied natural gas introduced into the third heat exchanger is -180 ° C or higher, -125 ° C or lower.