KR20120056416A - Method and apparatus for fractionating natural gas - Google Patents

Abstract

PURPOSE: A method and an apparatus for classifying natural gas are provided to efficiently implement a classifying process and to be adopted for a floating structure by minimizing the influence of pitching on the sea. CONSTITUTION: An apparatus for classifying natural gas classifies specific hydrocarbon components from hydrocarbon components contained in natural gas by flowing liquid natural gas from the upper side of a distillation tower. The distillation tower is divided into a plurality of small-sized columns(11, 12). The small-sized columns are spaced apart in the width direction of the distillation tower. The small-sized columns are connected by a liquid transferring line(13) and a gas transferring line(15). The liquid transferring line is equipped with a transferring pump(14). A natural gas supplying line(16) and a gas discharging line(17) are in connection with the upper side of the first column of the small-sized columns.

Description

Natural gas classification method and apparatus {METHOD AND APPARATUS FOR FRACTIONATING NATURAL GAS}

The present invention relates to a method and apparatus for classifying natural gas, and more particularly, a large distillation tower in the form of a tower installed for classifying natural gas is separated from a plurality of columns so as to be suitable for the marine environment. It relates to a natural gas classification method and apparatus adapted to be mounted on a floating structure to be used.

Natural gas is transported in a gaseous state through onshore or offshore gas piping, or to a distant consumer while stored in an LNG carrier in the form of liquefied liquefied natural gas (LNG). Liquefied natural gas is obtained by cooling natural gas to cryogenic temperature, and its volume is reduced to about 1/600 than that of natural gas in gas state, so it is very suitable for long distance transportation by sea.

In the present specification, natural gas means a mixture containing methane but other hydrocarbon components or nitrogen as a main component, and includes any form (gas phase, liquid phase or mixed phase of gas phase and liquid phase). It is a concept.

In order to store and transport the natural gas in the liquid state, the natural gas must be cooled to about -151 ° C to -163 ° C, where LNG has a pressure of about atmospheric pressure. In the prior art, in a land liquefaction facility, methods such as a cascade process, a mixed refrigerant process, a refrigerant gas expander process, and the like are used for cooling natural gas.

Recently, floating structures such as LNG FPSO (Floating, Production, Storage and Offloading) have been proposed, which can produce and store natural gas directly from natural gas sources extracted from gas wells, not on land. There is a need for a liquefaction and sorting device for natural gas.

Liquefaction and classification of natural gas on land cannot be applied directly to floating structures at sea, and improvements need to be made to suit the marine environment. In the case of LNG FPSO, small and medium sized liquefaction facilities and sorting facilities are highly feasible, and as a suitable liquefaction process, gas refrigerant expansion processes and mixed refrigerant processes are attracting attention.

However, these liquefaction facilities use heat exchangers such as BAHX (Brazed Aluminum Heat Exchanger) or SWHE (Spiral Wound Heat Exchanger). Especially, SWHE is expensive and high (e.g., about 50m). There is a possibility that this will be reduced and safety problems may occur.

In addition, in the design and installation of a fractionation tower used for the classification of natural gas, there is a problem that can cause design problems due to the height that can be installed due to the movement of the hull, or cause problems in design, manufacture, and installation. have.

In order to solve these problems, the present invention, instead of installing one huge distillation column in the floating structure to classify the natural gas is divided into a plurality of columns of relatively small size due to the fluctuations at sea To provide a natural gas classification method and apparatus that can minimize the number and efficiently perform the classification process.

According to the present invention for achieving the above object, as a natural gas fractionation device for classifying a specific hydrocarbon component of the hydrocarbon components contained in the natural gas while flowing down the natural gas in the liquid state from the top of the distillation column, Is divided into a plurality of columns, the plurality of columns are provided with a natural gas fractionation device, characterized in that spaced apart from each other arranged in the width direction.

The plurality of columns are preferably connected to each other by a liquid transfer line and a gas transfer line.

The liquid transfer line is preferably provided with a transfer pump for supplying the liquid natural gas discharged from the lower portion of the upstream column among the plurality of columns to the upper portion of the downstream column.

It is preferable that the natural gas supply line and the gas discharge line are connected to an upper end of the first column in which the liquid natural gas is first supplied among the plurality of columns.

The gas discharge line is preferably provided with a condenser for condensing the natural gas of the gaseous state discharged from the first column.

Preferably, the condenser is connected to the natural gas supply line so that the liquid natural gas condensed in the condenser can be supplied to the initial column again.

It is preferable that the liquid discharge line is connected to the lower end of the last column in which the liquid natural gas is finally supplied among the plurality of columns.

Preferably, the natural gas fractionation apparatus further includes a return line branching from the liquid discharge line to return the liquid natural gas discharged from the last column back to the last column.

The return line is preferably provided with a reboiler for heating liquid natural gas.

The natural gas fractionation device, De-Methanizer, De-Ethanizer, De-Propanizer, De-Butanizer and Glycol Regeneration Tower (Glycol) Regeneration Tower).

According to another aspect of the invention, it is installed on a floating offshore structure which is used to perform a specific purpose while floating on the sea, and in this liquid while flowing down a liquid containing a plurality of components at the top of the distillation column. A classification apparatus for classifying a specific component among the components included, wherein the distillation column is installed divided into a primary column and a secondary column, wherein the primary and secondary columns are characterized in that the separation spaced apart from each other in the width direction An apparatus is provided.

According to another aspect of the present invention, a sorting device for sorting a specific component of the components contained in the liquid while flowing down the liquid containing a plurality of components from the top of the distillation column, floating on the sea A floating offshore structure used for performing a specific purpose, wherein the distillation column is installed divided into a primary column and a secondary column, the primary and secondary columns are each other in the width direction on the upper deck of the floating offshore structure. Floating offshore structures are provided that are spaced apart.

The floating offshore structure may be LNG FPSO.

According to another aspect of the present invention, a natural gas classification method for classifying a specific hydrocarbon component among the hydrocarbon components contained in the natural gas while flowing down the liquid natural gas at the top of the distillation column, the distillation column is wide It consists of a plurality of columns are spaced apart from each other in the direction, the liquid natural gas is discharged from the last column after sequentially passing through the plurality of columns, at least a portion of the discharged liquid natural gas is heated and vaporized After returning to the last column, the natural gas of the gaseous state is passed back through a plurality of the column is discharged from the first column is provided.

According to the present invention as described above, instead of installing one huge distillation column in the floating structure to classify the natural gas can be provided natural gas classification method and apparatus divided into a plurality of relatively small columns installed. have.

Accordingly, according to the present invention, it is possible to minimize the effects of fluctuations at sea and to perform the classification process efficiently, and to provide a natural gas classification method and apparatus suitable for use in a floating structure.

1 is a conceptual diagram illustrating a natural gas fractionation apparatus according to the present invention.

Hereinafter, a natural gas classification method and apparatus according to a preferred embodiment of the present invention will be described in detail with reference to the drawings.

The natural gas fractionation apparatus according to the present invention can be installed and used on an upper deck of an LNG plant installed on land or offshore, a vessel such as an LNG carrier, and an offshore structure such as LNG FPSO (Floating, Production, Storage and Offloading). have. The LNG FPSO is a floating offshore structure used to directly liquefy the produced natural gas at sea and store it in an LNG storage tank, and, if necessary, to transfer LNG stored in the LNG storage tank to an LNG carrier.

The natural gas fractionation apparatus according to the present invention for classifying natural gas extracted from a gas well installed in a floating structure is liquefied after the impurities from water, carbon dioxide, and acid gas are removed through a pretreatment process after being extracted from the gas well. And a secondary column for receiving the natural gas in the liquid state and starting the sorting operation, and a secondary column installed separately from the primary column and capable of continuously performing the sorting operation of the natural gas.

Natural gas fractionation apparatus according to the present invention, De-Methanizer, De-Ethanizer, De-Propanizer, Di-Butizer for classifying specific components from natural gas It can be used in the form of De-Butanizer, Glycol Regeneration Tower, and the like.

As described above, according to the natural gas fractionation apparatus of the present invention, a plurality of columns, that is, primary columns and secondary columns are arranged in series but spaced apart in the width direction rather than in the vertical direction, and thus, a large distillation column, which is widely used in conventional land, Compared to the size, in particular the height can be reduced. As a result, it is possible to minimize the influence of the floating structure movement in the marine environment where the fluctuations inevitably occur and to improve the efficiency of sorting work.

In the present specification, the expression "a plurality of columns are installed so as to be spaced apart from each other in the width direction" is arranged in the vertical direction, the top surface of one column and the bottom surface of the other column is not installed to face each other, one The side of the column and the side of the other column should be considered to be adjacent to each other so that they can at least partially face each other. Furthermore, the plurality of columns spaced apart in the width direction do not have to have the same size, the heights of the places where the plurality of columns are installed may be slightly different, and the plurality of columns must be installed on the same horizontal plane. It is not.

Although one preferred embodiment of the present invention is illustrated in FIG. 1, it is illustrated that two columns are used, that is, primary and secondary columns, but may be divided into two or more columns as necessary.

Subsequently, a natural gas classification method and apparatus according to an embodiment of the present invention will be described in more detail with reference to FIG. 1.

Referring to FIG. 1, as described above, the natural gas fractionation apparatus of the present invention is spaced apart from the primary column 11, which receives a natural gas in a liquid state and starts the sorting operation. And a secondary column 12 capable of being installed and continuously performing a sorting operation of natural gas.

The primary column 11 and the secondary column 12 are connected to each other by the liquid transfer line 13 and the gas transfer line 15. The conveying pump 14 may be installed in the liquid conveying line 13.

The upper end of the primary column 11 is connected to the natural gas supply line 16 to which the natural gas in the liquid state is supplied and the gas discharge line 17 to which the natural gas in the gas state is discharged. The condenser 18 is installed in the gas discharge line 17 so as to cool and liquefy gaseous natural gas from which specific hydrocarbon components have been removed while passing through the primary and secondary columns 11 and 12. The condenser 18 may be a heat exchanger that condenses gaseous natural gas by a refrigerant.

The natural gas condensed in the condenser 18 may be supplied to the primary column 11 again as needed, may be supplied to a storage tank (not shown), or may be supplied to a post process or the like.

At the lower end of the secondary column 12, a liquid discharge line 19 through which natural gas in a liquid state is discharged is connected. Specific hydrocarbon components in the liquid state classified while passing through the primary and secondary columns 11 and 12 are discharged through the liquid discharge line 19 to be stored in a storage tank (not shown) or supplied to a post process or the like. Can be.

In addition, in order to increase the proportion of the specific hydrocarbon component in the liquid component to be discharged, a return line 20 may be installed which can be supplied to the lower end of the secondary column 12 after heating the liquid component. The return line 20 is provided with a reboiler 21 for heating and at least partially vaporizing liquid natural gas. The reboiler 21 may be a heat exchanger for heating the natural gas of the liquid component by steam.

The classification process of natural gas can be carried out as follows.

Natural gas extracted from a gas well and subjected to pretreatment such as removing impurities contains various hydrocarbon components such as ethane, propane and butane, in addition to methane, which is a main component of liquefied natural gas. Since these hydrocarbon components have different liquefaction temperatures, it is possible to classify specific hydrocarbon components from natural gas using the difference in liquefaction temperature.

According to the natural gas classification method and apparatus of the present invention, the natural gas of the liquid state in the liquefied state in advance through the liquefaction process is supplied to the upper end of the primary column (11). Although not shown, a distribution means may be installed at the upper end of the primary column 11 so that the supplied liquid natural gas flows down evenly distributed within the column. Distributing means may be installed at the top and bottom of the primary and secondary columns (11, 12), respectively.

The liquid natural gas supplied to the primary column 11 exchanges heat with the gaseous natural gas flowing upward while flowing downward. Since liquid natural gas is relatively cold compared to gaseous natural gas, the temperature of liquid natural gas gradually increases as it flows down by heat exchange, and thus hydrocarbon components having a relatively high liquefaction temperature are preferentially preferred. Is vaporized.

The natural gas in the liquid state flowing down to the lower end of the primary column 11 is transferred to the upper end of the secondary column 12 by the transfer pump 14. The natural gas in the liquid state supplied to the upper end of the secondary column 12 flows down as in the primary column 11, and heat exchange is performed.

Liquid natural gas at the bottom of the secondary column 12 is discharged through the liquid discharge line 19, the liquid natural gas discharged from the secondary column 12 to be supplied to the primary column (11). Compared to the case, hydrocarbons such as methane have low carbon components, and the proportion of hydrocarbon components having a high carbon number is high.

The natural gas in the liquid state discharged from the liquid discharge line 19 may be supplied to the storage tank as it is, or may be supplied to a later process for classifying other hydrocarbon components.

Meanwhile, the liquid natural gas discharged from the liquid discharge line 19 may return to the lower end of the second column 12 through the return line 20 branching from the liquid discharge line 19. It is heated by the boiler 21 and returns to the second column 12 in at least partially evaporated state, preferably in a fully evaporated state.

The natural gas in the gaseous state is gradually cooled by heat exchange with the natural gas in the liquid state flowing down from the second column 12. At this time, the heavy hydrocarbon components having a relatively high liquefaction temperature are liquefied and flow down to the lower end of the second column 12, and the hydrocarbon components having a relatively low liquefaction temperature continue to rise.

Natural gas in a gaseous state at the upper end of the second column 12 is transferred to the lower end of the first column 11 by the gas transfer line 15. The gaseous natural gas supplied to the lower end of the first column 11 is heat-exchanged with the liquid natural gas flowing down as in the second column 12, whereby the gaseous natural gas is gradually cooled while rising. . At this time, the heavy hydrocarbon components having a relatively high liquefaction temperature are liquefied to flow down to the lower end of the first column 11, and the hydrocarbon components having a relatively low liquefaction temperature continue to rise.

Natural gas in the gaseous state at the top of the first column 11 is discharged through the gas discharge line 17 and then condensed in the liquid state in the condenser 18. The condensed natural gas is classified as most of the heavy hydrocarbon components are removed and stored in the storage tank or supplied to the first column 11 to increase the proportion of specific hydrocarbon components by repeating the sorting operation as necessary. Can be.

As described above, the natural gas classification method and apparatus according to the present invention have been described with reference to the illustrated drawings, but the present invention is not limited to the above-described embodiments and drawings, and the present invention belongs to the claims. Of course, various modifications and variations can be made by those skilled in the art.

11: primary column, 12: secondary column, 13: liquid transfer line, 14: transfer pump, 15: gas transfer line, 16: natural gas supply line, 17: gas discharge line, 18: condenser, 19: liquid discharge Line, 20: return line, 21: reboiler.

Claims (14)

Natural gas fractionation apparatus for classifying specific hydrocarbon components among the hydrocarbon components contained in the natural gas while flowing down the liquid natural gas from the top of the distillation column,
The distillation column is installed divided into a plurality of columns, the plurality of columns are natural gas fractionation apparatus, characterized in that spaced apart from each other arranged in the width direction. The method according to claim 1,
And a plurality of the columns are connected to each other by a liquid transfer line and a gas transfer line. The method according to claim 2,
And a transfer pump for supplying the liquid natural gas discharged from the lower portion of the upstream column among the plurality of columns to the upper portion of the downstream column. The method according to claim 1,
Natural gas fractionation apparatus characterized in that the natural gas supply line and the gas discharge line is connected to the upper end of the first column in which the liquid natural gas of the plurality of columns is supplied for the first time. The method of claim 4,
And a condenser for condensing the natural gas of the gaseous state discharged from the first column in the gas discharge line. The method according to claim 5,
And the condenser is connected to the natural gas supply line to supply the liquid natural gas condensed in the condenser back to the first column. The method according to claim 1,
Natural gas fractionation apparatus characterized in that the liquid discharge line is connected to the lower end of the last column is the last supply of the liquid natural gas of the plurality of columns. The method of claim 7,
And a return line branching from the liquid discharge line to return the liquid natural gas discharged from the last column back to the last column. The method according to claim 8,
And a reboiler for heating the natural gas in the liquid state in the return line. The method according to claim 1,
The natural gas fractionation device, De-Methanizer, De-Ethanizer, De-Propanizer, De-Butanizer and Glycol Regeneration Tower (Glycol) Natural gas fractionation device, characterized in that any one of the (Regeneration Tower). It is installed on a floating offshore structure which is used to perform a specific purpose while floating in the sea, and it flows down the liquid containing a plurality of components from the top of the distillation column to remove certain components contained in the liquid. As a sorting device to classify,
The distillation column is installed divided into a primary column and a secondary column, wherein the primary and secondary columns are separated from each other in the width direction arranged. A sorting device for sorting a specific component among the components contained in the liquid while flowing down a liquid containing a plurality of components from the top of the distillation column, and used to perform a specific purpose while floating at sea. As an offshore structure,
The distillation tower is installed divided into a primary column and a secondary column, the primary and secondary columns are floating offshore structure, characterized in that spaced apart from each other in the width direction on the upper deck of the floating offshore structure. The method of claim 12,
The floating offshore structure is a floating offshore structure, characterized in that the LNG FPSO. Natural gas classification method for classifying specific hydrocarbon components among the hydrocarbon components contained in the natural gas while flowing down the liquid natural gas from the top of the distillation column,
The distillation column is composed of a plurality of columns are spaced apart from each other in the width direction, the liquid natural gas is discharged from the last column after sequentially passing through the plurality of columns, at least a portion of the discharged liquid natural gas Is heated and vaporized and then returned to the last column, and the returned natural gas is passed from a plurality of columns in a reverse direction and discharged from the first column.

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