KR101654093B1

KR101654093B1 - The natural gas static-pressure facilities comprising System for liquefied carbon dioxide using cold heat of regenerative power in natural gas

Info

Publication number: KR101654093B1
Application number: KR1020150154103A
Authority: KR
Inventors: 오승재; 김수문
Original assignee: (주)동양환경
Priority date: 2015-11-03
Filing date: 2015-11-03
Publication date: 2016-09-09

Abstract

The present invention relates to a natural gas constant-pressure facility comprising a carbon dioxide liquefaction system using cold energy in natural gas waste-pressure power generation. The purpose of the present invention is to perform the constant pressure control and waste-pressure power generation of natural gas, and use cold energy naturally generated during a waste-pressure power generation process for carbon dioxide liquefaction or the like without balancing the cold energy via a heating process. Accordingly, liquefaction costs of carbon dioxide are reduced, and heating costs of natural gas are reduced due to an increase in the temperature of natural gas. According to the present invention, the natural gas constant-pressure facility comprising a carbon dioxide liquefaction system using cold energy in natural gas waste-pressure power generation comprises: a constant pressure part (20) receiving natural gas whose temperature was increased by a first heater of a natural gas supply part to perform constant pressure control; a turbo-generation part (30) which is connected to the natural gas supply part in parallel with the constant pressure part, receives the natural gas whose temperature was increased by the first heater, and generates electricity using the waste pressure of the natural gas; a cold energy recovery part (40) recovering heat from the natural gas whose temperature was lowered via the turbo-generation part (30), and supplying the heat for carbon dioxide liquefaction; and a second heater (33) increasing the temperature of the natural gas whose temperature was lowered via the cold energy recovery part (40) to the temperature of the natural gas required to supply the natural gas to a place of usage.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a natural gas static pressure facility including a carbon dioxide liquefaction system using natural gas,

The present invention relates to a natural gas static pressure facility, and more particularly, to a natural gas static pressure facility which is capable of generating electricity using a turboexpander in a static pressure process of natural gas, The present invention relates to a natural gas constant-pressure facility including a carbon dioxide liquefaction system using cold energy of power generation.

Natural gas is imported as liquid (LNG), and after passing through facilities such as loading facility, storage tank, compressor and vaporizer of LNG receiving base, high pressure gaseous natural gas (NG) Piping, and is firstly reduced in pressure to a pressure suitable for each receiving destination. More specifically, 70 kg / ㎠ of high pressure NG of primary supplier (KOGAS), which owns LNG acquisition and NG supply facilities from overseas, is supplied at 30 Kg / ㎠ or 8.5 ㎏ / ㎠, and it is sent to the secondary supplier including the city gas company that distributes the NG supplied from the primary supplier to domestic consumers, and the power supplier, industry and 2 Small-scale static pressure facility of the car supplier. At this time, by using a pressure reducing valve (pressure regulator) to lower the pressure, it is possible to supply medium and low pressure natural gas suitable for the use of the receiver.

Through the process of passing through the static pressure facility of the primary supplier supply station and the static pressure of the secondary supplier static pressure facility, the natural gas becomes monotonic expansion while the pressure is lowered, the temperature is lowered by the Joule - Thompson effect, And depending on external conditions, icing on the inside and outside of the pipe may occur. For this reason, the primary supplier is normally sent to 0 ° C or higher when sending to the secondary supplier. In order to maintain the temperature of the natural gas which is reduced during the decompression, it is necessary to heat the upstream of the regulator. Loses. As shown in FIG. 1, in the case of Korea, in particular, the primary supplier supply station operates a gas boiler as a heater (heat source) for temperature maintenance, and the degree of temperature drop is not large in the secondary pressure supplier Generally, no temperature preservation is carried out.

In the meantime, the existing natural gas static pressure system is operated as mentioned above, and a system for generating electricity by utilizing the pressure (waste pressure) that is forcibly discharged from the static pressure device during decompression has been proposed. Korea Gas Corporation is in pilot operation. In FIG. 1, one of the regulators connected in parallel is replaced with a turbo expander (hereinafter referred to as TE) to perform both functions of static pressure (depressurization) and electricity production at the same time. The pressure (waste pressure) that can not be utilized by simply using a regulator can be regenerated as a thermodynamically important energy source, and it produces clean power by recovering waste pressure using TE. A Turbo Expander Generator (hereinafter referred to as TEG) includes a TE for converting the pressure of gas into a mechanical rotational motion and a generator for converting the mechanical rotational force of the TE into electric energy. The operation principle of the TEG in more detail and related contents are omitted here.

2, the conventional natural gas static pressure facility includes a first heater 2 for raising the temperature of the natural gas supplied through the natural gas supply pipe 1 and the natural gas supply pipe 1 (for example, 20 ° C) A static pressure regulator 3 for regulating the static pressure of the natural gas heated through the first heater 2 and a TEG 4 connected in parallel with the natural gas supply pipe 1 for generating electricity through the waste pressure, The second heater 5 is further provided in front of the TEG 4 to raise the temperature of the natural gas heated by the first heater 2 to 60 ° C due to the operation of the TEG.

It is a very novel system that operates the TEG that replaces the regulator but produces the effect of power generation by using the positive pressure as well as the main process of supplying natural gas, which is the main process of supplying natural gas. However, more temperature drop occurs than when the regulator is used. This is due to the temperature drop due to the Joule - Thompson effect of the constant pressure process and the energy conversion in the process of producing electricity (day production as a physical quantity). Therefore, additional heating is required as shown in FIG. 2 in case of TEG operation (decompression power generation), and a second heat source is installed at the front side of the TEG so that the temperature of the rear end of the TEG is 0 ° C. At this time, it is common to use gas boiler as the second heat source, but when the waste heat is used, the heating cost is reduced and the economical efficiency is further increased. It is in operation in Canada to use the array of fuel cell power generation as the second heat source of the TEG.

On the other hand, as the use of fossil fuels increases, carbon dioxide emitted in large quantities is designated as one of greenhouse gas (GHG) that causes global warming phenomenon. Although the global warming index of carbon dioxide is lower than other greenhouse gases, it is classified as a very important greenhouse gas in that it accounts for about 80% of total greenhouse gas emissions and can regulate its emissions. Therefore, it is regulated to reduce greenhouse gas emissions from various countries through various international agreements. One of the technologies derived from this is the recovery of carbon dioxide from various industrial sites and isolation and storage in a separate place, so that the amount of carbon dioxide Carbon dioxide treatment technology that reduces carbon dioxide emissions.

The treatment steps to reduce carbon dioxide emissions are largely carried out through four steps of recovery, separation, concentration, transportation and storage of carbon dioxide. The exhaust gas containing carbon dioxide generated at the industrial site is recovered and stored by concentrating and transporting only carbon dioxide at a high concentration. The separation and concentration technique of carbon dioxide is performed through an absorption process, an adsorption process, or a membrane separation process.

In recent years, CCS (Carbon Capture and Storage) technology, in which carbon dioxide separated from the exhaust gas is injected into an underground place such as the ocean, the underground, and an indicator, and the technology for transporting it is emerging.

In this way, it is essential to liquefy carbon dioxide in storing and transporting the carbon dioxide captured at the power plant. Normally, the pressure is about 21 kg / ㎠ and the temperature is stored and transported at about -18 ℃. However, in the conventional method, carbon dioxide of about 20 kg / ㎠ is liquefied through a cooling process through a condenser. In the cooling process, electricity is required to operate the refrigerator, so cooling costs are required.

Patent Document 10 (Publication No. 10-2011-0047905) discloses a gas supply system including a gas inlet connected to a gas supply source including a high-pressure gas to receive a high-pressure gas; A gas outlet for withdrawing the decompressed gas; A conduit fluidly connecting the gas inlet and the gas outlet; A TEG connected to the conduit between the gas inlet and the gas outlet to convert the pressure of the gas flowing in the conduit into electrical energy; A heat source for increasing the temperature of the gas flowing through the conduit between the gas inlet and the TEG to cancel the temperature drop due to the expansion of the gas, And a battery heat exchanger. Only the static pressure and the power generation of the natural gas are possible. The cold heat generated when the TEG waste pressure is generated is regarded as energy to be overcome through heating.

Published patent application No. 10-2011-0047905

The present invention is not the heating (preheating) through the second heat source at the TEG front end, which is the current TEG operating concept as described above, but the concept of heating at the rear end of the TEG, that is, post heat. It is possible to reduce the cost of liquefaction of carbon dioxide by using it for liquefying carbon dioxide without disposing the cold heat generated immediately after the TEG, and to improve the economical efficiency of heating by reducing the heating cost of natural gas by raising the temperature of natural gas due to liquefaction. The present invention has been made to provide a natural gas hydrostatic facility including a carbon dioxide liquefaction system using cold energy of a natural gas nuclear power generation which can be expected.

The natural gas static pressure facility including the carbon dioxide liquefaction system using the cold heat of the natural gas waste power generation plant according to the present invention includes a static pressure unit that receives natural gas whose temperature has been raised through the first heater of the natural gas supply unit and regulates the static pressure; A turbo generator connected to the natural gas supply unit in parallel with the static pressure unit and supplied with natural gas having a high temperature through the first heater and generating electric power using waste pressure of the natural gas; A cold / hot water recovering unit for recovering heat of the natural gas having passed through the turbogenerating unit and having a lowered temperature and supplying it to liquefied carbon dioxide; And a second heater for increasing the temperature of the natural gas having passed through the cold / hot water recovering unit to a temperature for supplying the natural gas to the user.

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According to the natural gas static pressure facility including the carbon dioxide liquefaction system using the cold heat of the natural gas waste power generation power generation system according to the present invention, it is possible to utilize the natural gas cold power and the carbon dioxide liquefaction It is possible to simplify the facility by replacing the refrigerator which is driven for the liquefaction of carbon dioxide and to reduce the liquefaction cost of carbon dioxide. In terms of natural gas, natural gas discharged from TEG consumes cold heat for liquefaction of carbon dioxide, and since natural gas temperature rises as cold heat is used for liquefaction, the operation of heater for heating natural gas is significantly reduced and heating fuel cost is also reduced The economic effect is doubled.

FIG. 1 is a general natural gas pressure-pressure process diagram. FIG.
Fig. 2 is a view showing a general natural gas static pressure and waste pressure power generation TEG process. Fig.
3 is a systematic diagram of a carbon dioxide liquefaction system using cold heat of a natural gas nuclear power generation plant according to the present invention.
4 is a view illustrating an example of a cold heat recovery unit applied to a carbon dioxide liquefaction system using cold energy of a natural gas waste power generation plant according to the present invention.
5 is a phase change graph showing the liquid phase change condition of carbon dioxide.

As shown in FIG. 3, the carbon dioxide liquefaction system using cold heat of the natural gas waste pressure power generation plant according to the present invention is composed of a turbo generator 30 for generating electricity using natural gas waste pressure, The second heaters 33 and the static pressure part 20 together with the natural gas and the natural gas, The power generation unit 30 and the cold / hot water recovery unit 40 are connected to the static pressure unit 20 in a parallel manner.

Natural gas is supplied through the natural gas supply unit 10 and the natural gas supply unit 10 supplies the natural gas supplied through the natural gas supply pipe 11 and the natural gas supply pipe 11 to a temperature And a first heater 22 for raising the temperature to a predetermined temperature.

The static pressure section 20 is constituted by a first branch pipe 21 branched from the natural gas supply pipe 11 and a static pressure regulator 22 for controlling the static pressure of the natural gas supplied through the first branch pipe 21 do.

The power generation unit 30 includes a second branch pipe 31 branched from the natural gas supply pipe 11 and a turbo generator 32 for generating electricity through the waste pressure of the natural gas supplied through the second branch pipe 31 .

The turbo generator 32 comprises a turboexpander for converting the pressure of the gas into a mechanical rotational motion and a generator for converting the mechanical rotational force of the turboexpander into electric energy.

The cold / hot water recovering unit 40 recovers the cold heat (-40 to -30 ° C) of the natural gas discharged from the turbo generator 32 and supplies it to the liquefied carbon dioxide. The turbo generator 32 and the second heater 33, And a heat exchanger tube connected to the second heater 33 for supplying the natural gas discharged from the turbo generator 32 and recovering the cold heat of the natural gas flowing in the connection tube 34 .

As shown in FIG. 4, the cold / hot water recovering unit 40 collects carbon dioxide from a carbon dioxide generating source (a facility storing all the facilities generating carbon dioxide as a power plant, a factory, and the like, A compressor 42 for regulating and feeding carbon dioxide collected through the tube 41 and the collecting tube 41 to a liquefying pressure and an inner tube 34 for connecting the turbo generator 32 and the second heater 33 A heat exchange pipe 43 connected to the compressor 42 to allow the heat exchange between the carbon dioxide collected through the carbon dioxide collecting pipe 41 and the natural gas flowing through the connecting pipe 34, And a transfer pipe (44) connected to the discharge end for transferring the liquid carbon dioxide to the storage part.

The collecting pipe 41 collects carbon dioxide generated from the carbon dioxide generating source and supplies the collected carbon dioxide to the heat exchange pipe 43.

The compressor 42 regulates the pressure of carbon dioxide to 20 bar, which is the liquefying pressure of carbon dioxide, and sends it to the heat exchange pipe 43. That is, as shown in the phase change graph (see FIG. 5) It is characterized by the liquefaction of carbon dioxide without additional facilities.

The heat exchange pipe 43 is installed in the path of the natural gas so that the heat exchange between the carbon dioxide and the natural gas flowing in the interior of the natural gas is performed. The connection pipe 34 connects the turbo generator 22 and the second heater 33, It is preferable to use a coil shape in order to increase the heat exchange efficiency between the carbon dioxide and the natural gas.

In the cold / hot water recovering unit 40 having such a structure, the heat exchange pipe 43 is installed in the transfer path of the natural gas, and direct heat exchange is performed between the carbon dioxide and the natural gas without using a separate heat exchange medium. As a result, The liquefaction ratio also improves. For example, a heat exchange medium circulation pipe is piped through a connection pipe 34 and a storage portion of a carbon dioxide liquefying portion (a liquefied carbon dioxide storage portion, a separate carbon dioxide liquefied portion, etc., which may be a carbon dioxide generating source) The heat of the natural gas flowing through the connection pipe 34 is recovered while circulating by the pump or the compressor along the media circulation pipe and the carbon dioxide stored in the carbon dioxide liquefaction unit is liquefied through the heat.

Since it is difficult to install the heat exchange pipe 43 in the connection pipe 34, it is preferable to use a tubular socket having the heat exchange pipe 43 installed therein. The openings of both sides of the socket are connected to the connection pipe 34 so as to provide liquefaction of carbon dioxide while providing a path of natural gas.

On the other hand, in the process of liquefying the gaseous carbon dioxide into the liquid phase carbon dioxide through the heat exchange pipe 43, some of the gaseous carbon dioxide may remain, and a separate liquefier is constituted to liquefy the gaseous carbon dioxide passing through the heat exchange pipe 43 And a gas-liquid separator 45 is preferably applied.

The gas-liquid separator 45 is connected to the transfer pipe 44 to gas-liquid separate the carbon dioxide transferred through the transfer pipe 44.

Liquid phase carbon dioxide is separated from the gaseous carbon dioxide in the gas-liquid separator 45. The liquid carbon dioxide is transferred to the carbon dioxide storing unit through the transfer pipe 44 and the gaseous carbon dioxide is supplied to the collecting pipe 41 through the return pipe 46 . In other words, the return pipe 46 is connected to the front of the inlet of the compressor 42 so that the bypassed carbon dioxide passes through the compressor 42.

The return pipe 46 is opened and closed by a valve and can be used if necessary.

It is also possible to constitute a bypass flow path for transferring carbon dioxide to the carbon dioxide storage section without passing through the gas-liquid separator 45 so as to use the gas-liquid separator 45 only when necessary.

The cold / hot water recovering unit 40 is not limited thereto, and various examples in which the heat exchange between the natural gas and the heat exchange medium can be performed are also possible.

The power generation unit 30 may include a thermometer for measuring the temperature of the heat exchange medium.

The compressor 42 can be on / off controlled manually by an administrator or can be automatically controlled by the controller. In the latter case, after the reference temperature is set in the memory, the controller compares the temperature measured in real time with the thermometer through the thermometer and the reference temperature. If the current temperature deviates from the reference temperature range, for example, And controls the compressor 42 to be operated only under the condition that the present temperature satisfies the reference temperature range.

The second heater 33 is characterized in that the temperature of the natural gas heat exchanged with the carbon dioxide of the cold / hot water recovering unit 40 is adjusted to an appropriate temperature (0 ° C) for use.

The operation of the carbon dioxide liquefaction system using the cold heat of the natural gas nuclear power plant according to the present invention and the operation of the natural gas static pressure facility including the system will be described as follows.

1. Static pressure.

The natural gas is supplied through the natural gas supply pipe 11 and is heated to, for example, 20 캜 while passing through the first heater 12.

The natural gas is supplied through the first branch pipe (21) to the regulator (22) and regulated in static pressure.

The natural gas passed through the regulator 22 is supplied at 0 캜. Since the static pressure process is the same as that of the conventional art, a detailed description thereof will be omitted.

2. Development.

The natural gas is passed through the first heater 12 to be heated, and then supplied to the turbo generator 32 through the second branch pipe 31.

The turbo generator 32 converts the natural gas pressure into a mechanical rotational motion through a turboexpander, and converts the mechanical rotational force of the turboexpander into electrical energy through a generator.

3. Cold heat recovery.

The natural gas is further lowered to a low temperature and discharged from the turbo generator 32. The cold and hot water recovering unit 40 collects carbon dioxide from the carbon dioxide generating source and controls the carbon dioxide to 20 bar through the compressor 42. [ And then supplied to the heat exchange pipe 43. The carbon dioxide flowing in the heat exchange pipe 43 is heat-exchanged with the natural gas of low temperature that flows inside the connection pipe 34 and outside the heat exchange pipe 43 to be liquefied.

The liquid carbon dioxide discharged from the heat exchange pipe (43) is transferred and stored to a liquid carbon dioxide storage unit through a transfer pipe (44).

On the other hand, when the gas-liquid separator 45 is applied, it is separated into liquid-phase carbon dioxide and gaseous carbon dioxide through the gas-liquid separator 45, the liquid-phase carbon dioxide is transferred to and stored in the carbon dioxide storage unit and the gaseous carbon dioxide is collected through the recovery pipe 46 (41) and then passes through the compressor (42).

The natural gas is heated while passing through the cold / hot water recovering unit 40 and heated to the proper temperature (0 ° C) through the second heater 33 and then supplied.

10: natural gas supply unit, 11: natural gas supply pipe
12: first heater, 20: static pressure section
21: 1 st branch, 22: regulator
30: power generation section, 31: second branch engine
32: turbo generator, 33: second heater
34: conduit, 40: cold /
41: collection tube, 42: compressor
43: Heat exchange tube, 44: Transfer tube
45: gas-liquid separator, 46: recovery pipe

Claims

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A static pressure unit 20 which receives natural gas whose temperature has been raised through the first heater of the natural gas supply unit and regulates the static pressure;
A turbo generator 30 connected to the natural gas supply unit in parallel with the static pressure unit and supplied with natural gas having a high temperature through the first heater and generating electric power using the natural pressure of the natural gas;
A cold / hot water recovering unit (40) for recovering heat of the natural gas having passed through the turbogenerating unit and having a lowered temperature and supplying it to liquefied carbon dioxide;
And a second heater for increasing the temperature of the natural gas having passed through the cold / hot water recovering unit to a temperature for supplying the natural gas to the user, wherein the second heater comprises a carbon dioxide liquefaction system using cold energy. .

[5] The apparatus of claim 5, wherein the cold / hot water recovering unit comprises: a collecting pipe for collecting carbon dioxide from a carbon dioxide generating source; a compressor for regulating carbon dioxide collected through the collecting pipe to a liquefying pressure; And a heat exchanging tube connected to the compressor to perform heat exchange between the carbon dioxide collected through the collecting tube and the natural gas flowing through the connecting tube. The liquid phase carbon dioxide is connected to the discharging end of the heat exchanging tube, Wherein the natural gas gas pressure regulating system includes a carbon dioxide liquefaction system using cold heat of a natural gas nuclear power generation plant.