KR101387946B1 - Control system of plant for liquified of natural - Google Patents

Control system of plant for liquified of natural Download PDF

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KR101387946B1
KR101387946B1 KR1020110137897A KR20110137897A KR101387946B1 KR 101387946 B1 KR101387946 B1 KR 101387946B1 KR 1020110137897 A KR1020110137897 A KR 1020110137897A KR 20110137897 A KR20110137897 A KR 20110137897A KR 101387946 B1 KR101387946 B1 KR 101387946B1
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South Korea
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mixed refrigerant
natural gas
flow
temperature
display controller
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KR1020110137897A
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Korean (ko)
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KR20130070736A (en
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장현
최광호
이철재
최낙기
김학성
조웅호
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지에스건설 주식회사
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0244—Operation; Control and regulation; Instrumentation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/0002—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the fluid to be liquefied
    • F25J1/0022—Hydrocarbons, e.g. natural gas
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/003—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production
    • F25J1/0047—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle
    • F25J1/0052—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle by vaporising a liquid refrigerant stream
    • F25J1/0055—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle by vaporising a liquid refrigerant stream originating from an incorporated cascade
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0211—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a multi-component refrigerant [MCR] fluid in a closed vapor compression cycle
    • F25J1/0212—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a multi-component refrigerant [MCR] fluid in a closed vapor compression cycle as a single flow MCR cycle

Abstract

The present invention relates to a control system of a natural gas liquefaction apparatus, and is for liquefying natural gas that has undergone a purification process by performing heat exchange, each of which includes a first heat exchange area including a first heat exchanger and a second heat exchanger. A heat exchange area, wherein the first heat exchanger includes a pipe of natural gas, a pipe of a liquid mixed refrigerant, and a pipe of a gaseous mixed refrigerant, and the liquid mixed refrigerant is mixed with the gaseous natural gas by gas phase by heat exchange. The refrigerant is liquefied by heat exchange, and the second heat exchanger passes through a gaseous natural gas pipe and a gaseous mixed refrigerant pipe, whereby the gaseous mixed refrigerant liquefied at low temperature through the first heat exchanger is liquefied by heat exchange. Characterized in that it is configured to cool the natural gas to a lower temperature, thereby supplying two heat By being made to pass through the vent in order, there is provided an effect that the efficiency of gas liquefaction is improved.

Figure R1020110137897

Description

Control system of natural gas liquefaction equipment {Control system of plant for liquified of natural}

The present invention relates to a control system of a natural gas liquefaction apparatus, and more particularly, to a control system of a natural gas liquefaction apparatus for converting natural gas into liquefied natural gas more efficiently using a mixed refrigerant.

In general, natural gas is a flammable gas produced in nature, and means a gas mainly composed of hydrocarbons.

Natural gas extracted from the basement contains moisture, polymers, hydrocarbons, nitrogen, helium, carbon dioxide and hydrogen sulfide as well as methane, ethane, propane and butane which are main components.

Here, if these materials are used without separating and removing them, the calorific value and the physicochemical properties are different, so that such materials are separated from natural gas to improve natural gas quality as fuel, and the separated materials are also used as other resources. In order to remove water, remove sulfides, remove carbon dioxide, and remove dust and oil.

The natural gas is also transported in the gas state through a gas pipeline on land or sea, which is converted into a liquid state through a liquefaction process for the purpose of storing a large amount of natural gas in a long distance transportation and a small storage space.

Liquefied natural gas (LNG) is called liquefied natural gas, and its volume is reduced to 1/600 more than gaseous natural gas, which facilitates transportation and storage.

The main component of natural gas is methane, and the liquefaction temperature of the methane is very low, so it is very difficult to liquefy in the usual way. Natural gas is liquefied through methods such as turbo expander cycle, cascade cycle, or multi-component refrigerant cycle.

Here, in the mixed refrigerant method mainly used to liquefy natural gas, there is a problem that the gas liquefaction efficiency is lowered due to an increase in enthalpy during heat exchange using the mixed refrigerant in the heat exchanger.

The present invention has been made in view of the above problems, and provides a control system of a natural gas liquefaction apparatus to improve the liquefaction efficiency of the gas by sequentially passing two heat exchangers having different temperature differences. There is a purpose.

In the present invention, the two heat exchangers are mixed with a gaseous mixed refrigerant and a liquid mixed refrigerant to form a heat exchange with a supply natural gas, and then are separated by a gas-liquid separator at low temperature and low pressure by an expansion valve. It is also an object of the present invention to provide a control system of a natural gas liquefaction device to increase the utilization of the refrigerant to pass through the air to improve the liquefaction efficiency of the gas.

In addition, the present invention analyzes and controls in real time the state of the natural gas is liquefied natural gas liquefied by heat exchange, and the mixed refrigerant used to liquefy the natural gas, so that more efficient natural gas liquefaction is achieved as well as the desired amount of production It is also an object of the present invention to provide a control system of a natural gas liquefaction apparatus capable of producing liquefied natural gas.

The natural gas liquefaction apparatus according to the present invention for achieving the above object is to be liquefied by the heat exchange of the natural gas through the refining process, each of the first heat exchange zone and the second heat exchanger is provided with a first heat exchanger And a second heat exchange area provided, wherein the first heat exchanger passes through a pipe of natural gas, a pipe of a liquid mixed refrigerant, and a pipe of a gaseous mixed refrigerant so that the liquid mixed refrigerant exchanges the natural gas in the gas phase by heat exchange. The gas and the gaseous mixed refrigerant are liquefied by heat exchange, and the second heat exchanger passes through the gaseous natural gas pipe and the gaseous mixed refrigerant pipe, so that the gaseous mixed refrigerant liquefied to a low temperature through the first heat exchanger. It is characterized in that it is configured to cool the natural gas liquefied by heat exchange to a lower temperature.

Here, the first heat exchange region, the first expansion valve for lowering and cooling the pressure of the liquid mixed refrigerant passed through the first heat exchanger, and the gas-liquid separation of the mixed refrigerant consisting of two-phase refrigerant while passing through the first expansion valve Further comprising a first gas-liquid separator to pass through the first heat exchanger,

The second heat exchange zone may include a second expansion valve for lowering and cooling the pressure of the liquefied gaseous mixed refrigerant passing through the second heat exchanger, and gas-liquid separation of the mixed refrigerant consisting of the two-phase refrigerant while passing through the second expansion valve. It is preferable to further include a second gas-liquid separator to pass through the second heat exchanger.

Furthermore, the liquefied gaseous mixed refrigerant passing through the second gas-liquid separator and passing through the second heat exchanger is preferably passed through the first heat-exchanger via the first gas-liquid separator.

On the other hand, the present invention, in order to produce a desired amount of liquefied natural gas discharged through the rear end of the natural gas pipe, the flow rate and temperature of the liquefied natural gas heat exchanged by the first heat exchange region and the second heat exchange region, the gas phase It characterized in that it further comprises a control system for controlling the flow rate and temperature of the mixed refrigerant and the liquid mixed refrigerant, respectively, to control the optimum mixed refrigerant flow rate.

Here, the control system receives the flow rate and temperature of the liquefied natural gas, and the flow rate and temperature of the gaseous mixed refrigerant and liquid mixed refrigerant to display various complex calculations, variables, control points, and control output signals on a display device such as a monitor. Can be implemented with DCS.

In addition, the control system is installed in the gas pipe, and the refrigerant pipes to which the gaseous mixed refrigerant and the liquid mixed refrigerant are respectively transferred to measure the flow rates of the liquefied natural gas, the gaseous mixed refrigerant and the liquid mixed refrigerant, and the value is measured. It includes a flow measuring transmitter for transmitting to any one of the first, second flow rate display controller and the first, second flow rate display controller of the DCS,

Installed in the gas pipe and the refrigerant pipe further comprises a temperature measuring transmitter for measuring the temperature of the liquefied natural gas, gas phase mixed refrigerant and liquid mixed refrigerant and transmits the value to the temperature display controller or the temperature difference display controller of the DCS It is preferable.

The flow rate measuring transmitter may include: a first flow rate measuring transmitter installed at a rear end of the gas pipe and measuring a flow rate of the liquefied natural gas heat-exchanged, and transmitting the value to the first flow indicating controller; A second flow rate measuring transmitter installed in the liquid mixed refrigerant pipe to measure a flow rate of the liquid mixed refrigerant, and transmitting the value to the second flow indicator controller; And a third flow rate measuring transmitter installed in the gas phase mixed refrigerant pipe to measure the flow rate of the liquefied gas phase mixed refrigerant and transmitting the value to the first flow ratio display controller.

In this case, the first flow display controller is required for the production flow rate of the liquefied natural gas stored in the controller in the DCS by using the flow rate value of the liquefied natural gas transmitted from the first flow measurement transmitter as a variable. It is preferable to calculate the flow rate of the liquid mixed refrigerant to be transmitted, and transmit the calculated value to the second flow indicator controller.

In addition, the second flow display controller,

The flow rate of the liquid mixed refrigerant finally required by using the flow rate measured value of the liquid mixed refrigerant received from the second flow measuring transmitter as a variable and the calculated value of the liquid mixed refrigerant received from the first flow indicator controller as a control point. It is preferable to adjust the opening amount of the first expansion valve so as to obtain.

The temperature measuring transmitter may include: a first temperature measuring transmitter installed at a rear end of the gas pipe and measuring a temperature of the liquefied natural gas heat-exchanged, and transmitting the value to the first temperature display controller; A second temperature measurement transmitter and a third temperature measurement installed at the front end of the gas phase mixed refrigerant pipe and the rear end of the liquid mixed refrigerant outlet pipe to transmit the temperature measured values of the gas phase mixed refrigerant and the temperature of the liquid mixed refrigerant to the temperature difference display controller; It is preferable to include a transmitter.

Herein, the first temperature display controller is configured to obtain a final proper temperature of the liquefied natural gas stored in the controller of the DCS by using the temperature value of the liquefied natural gas transmitted from the first temperature measuring transmitter as a variable. It is preferable to calculate the flow rates of the gaseous mixed refrigerant and the liquid mixed refrigerant required, and transmit the calculated value to the first flow ratio display controller.

In addition, the temperature difference display controller calculates a temperature difference by using the temperatures of the gaseous mixed refrigerant and the liquid mixed refrigerant as variables, and produces the flow rate of the liquefied natural gas stored in the controller in the DCS by the temperature difference. It is preferable to calculate the flow rate of the liquefied natural gas / liquid mixed refrigerant required in order to transmit the calculated value to the second flow ratio display controller.

The second flow ratio display controller may be configured to transmit a flow rate value of a current liquefied natural gas input to the first flow rate display controller and a flow rate value of a current liquid mixed refrigerant input to the second flow rate display controller. It is preferable.

In this case, the second flow display controller uses the current liquefied natural gas flow rate value input to the first flow display controller as a variable, and uses the liquefied natural gas / liquid mixed refrigerant value calculated by the temperature difference display controller as a control point. It is preferable to adjust the opening amount of the liquefied natural gas production valve which is installed at the rear end of the gas pipe so as to obtain the finally required liquefied natural gas flow rate.

As described above, according to the control system of the natural gas liquefaction apparatus according to the present invention, the supply natural gas is sequentially passed through two heat exchangers having a different temperature difference, thereby providing an effect of greatly improving the liquefaction efficiency of the gas.

In the present invention, the two heat exchangers are mixed with a gaseous mixed refrigerant and a liquid mixed refrigerant to form a heat exchange with a supply natural gas, and then are separated by a gas-liquid separator at low temperature and low pressure by an expansion valve. By passing through the group, the utility of the mixed refrigerant is increased, thereby providing the effect of improving the liquefaction efficiency of the gas.

In addition, the present invention analyzes and controls in real time the state of the natural gas is liquefied natural gas liquefied by heat exchange, and the mixed refrigerant used to liquefy the natural gas, making the liquefaction of natural gas more efficient to meet the desired production The effect of producing liquefied natural gas is also provided.

1 is a block diagram showing a natural gas liquefaction apparatus and a control system according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The natural gas liquefaction apparatus according to the present invention includes two heat exchange zones for liquefying the natural gas of the gaseous phase subjected to the purification process by heat exchange.

Of the two heat exchange zones, a first heat exchanger 20 is provided in the first heat exchange zone and a second heat exchanger 30 is provided in the second heat exchange zone.

Among the two heat exchangers 20 and 30, the first heat exchanger 20 provided in the first heat exchange area through which natural gas passes first includes a liquid mixed refrigerant (MRV) and a gas phase mixed refrigerant (MRL). : Mixed Refrigerant Liquid) passes at the same time, and the low temperature liquid mixed refrigerant liquefies the supply natural gas by heat exchange, and at the same time, the gaseous mixed refrigerant is also liquefied by heat exchange.

On the other hand, the natural gas liquefied through the first heat exchanger 20 is continuously passed through the second heat exchanger 30 provided in the second heat exchange area so as to be heat-exchanged to a lower temperature to achieve efficient liquefaction. The liquefied gaseous mixed refrigerant liquefied to low temperature through the first heat exchanger passes through the second heat exchanger (30), wherein the low temperature liquefied gaseous mixed refrigerant cools the natural gas liquefied by heat exchange to a lower temperature.

On the other hand, the first heat exchange zone, the first heat exchanger 20 in the first heat exchanger 20 to give a liquid mixed refrigerant with an increased enthalpy due to heat exchange between the gaseous mixed refrigerant to give a pressure by the Joul Thomson's effect As the pressure is lowered and cooled while passing through the first expansion valve 22 and the first expansion valve 22 to lower and cool the gas, the two-phase refrigerant, that is, the mixed refrigerant of the gaseous phase and the liquid phase is separated by gas-liquid separation. The first gas-liquid separator 24 to pass through the first heat exchanger 20 in the state of gaseous mixed refrigerant and liquid mixed refrigerant.

As such, after the liquid mixed refrigerant heat-exchanged with the supplied natural gas and the gaseous mixed refrigerant is gas-liquid separated in a low pressure and cooled state, the first heat exchanger 20 passes through the first heat exchanger 20 again. By performing heat exchange again with the supply natural gas and the gaseous mixed refrigerant, the efficiency of the mixed refrigerant is increased, thereby increasing the liquefaction efficiency of the supplied natural gas.

In addition, the second heat exchange zone is a second expansion valve for lowering and cooling the pressure by the Joule-Thomson effect of the liquefied gaseous mixed refrigerant whose enthalpy is increased by heat exchange with natural gas liquefied in the second heat exchanger (30). (32), and as the pressure is lowered and cooled while passing through the second expansion valve (32), gas-phase mixed refrigerant and liquid mixed refrigerant are respectively separated by gas-liquid separation of a two-phase refrigerant, that is, a mixed refrigerant composed of a gaseous phase and a liquid phase. And a second gas-liquid separator 34 to pass through the second heat exchanger 30 again.

As described above, the liquefied gaseous mixed refrigerant, which has undergone heat exchange with the liquefied natural gas, is gas-liquid separated in a low pressure and cooled state, and then liquefied natural gas while passing through the second heat exchanger 34 again. By the heat exchange again, the efficiency of the mixed refrigerant is increased, thereby increasing the liquefaction efficiency of the supplied natural gas.

Here, the mixed refrigerant passing through the second expansion valve 32 and the second gas-liquid separator 34 and passing through the second heat exchanger 30 is again subjected to the first expansion valve 22 and the first gas liquid in the first heat exchange area. As the pressure is lowered through the separator 24 and passed through the first heat exchanger 20 in the state of gas-liquid separation, the efficiency of the mixed refrigerant is further increased.

On the other hand, for the control of the natural gas liquefaction apparatus according to the present invention, after setting the amount of liquefied natural gas to be liquefied, the flow rate of the gaseous mixed refrigerant and liquid mixed refrigerant is adjusted accordingly, the first expansion valve and the second expansion A control system is configured to adjust the opening amount of the expansion valve.

The control system performs a variety of complex calculations from the distributed control unit, i.e. each set position, and finalizes the control output signal so that the variable (current measured value, PV: Process Variable), control point (variable) reaches this control point. Distributed control system (DCS) that displays to control device (SP), SP: Set Point} and control output signal (signal to control final control element, CO: Control Output) on display device such as monitor ( Not shown).

Here, the DCS used to control the liquefaction apparatus includes a flow indicating controller (FIC), a temperature indicating controller (TIC), and a flow ratio indicating controller existing as a program implemented in the controller. (FRIC: Flow Ratio Indicating Controller) and Temperature Defferential Indicating Controller (TDIC), which will be described later.

In addition, the control system is connected to a variety of pipes, that is, the gas pipe 10 to which the supply natural gas and liquefied natural gas is transferred, and the refrigerant pipes 12, 14 and 16 to which the gaseous mixed refrigerant and the liquid mixed refrigerant are respectively transferred. A flow measurement transmitter (FT) installed to measure the flow rates of the liquefied natural gas, the gaseous mixed refrigerant and the liquid mixed refrigerant and transmit the values to the flow display controller and the flow ratio display controller of the DCS; Installed in the gas pipe 10 and the refrigerant pipes 12, 14, and 16 to measure the temperature of the liquefied natural gas, gaseous mixed refrigerant and liquid mixed refrigerant, the value of the temperature display controller and temperature difference display controller of the DCS It includes a temperature transmitter (TT: Temperature Transmitter) to transmit to.

Hereinafter, the installation relationship and the control relationship of the control system will be described.

First, the first flow rate measuring transmitter 100 is installed at the rear end of the gas pipe 10 through which the natural gas is supplied into the liquefied natural gas through the first heat exchange zone and the second heat exchange zone. The 1 flow measurement transmitter 100 measures the flow rate of the liquefied natural gas and transmits the value to the first flow display controller 200 in the DCS.

The first flow display controller 200 sets the flow rate of the liquid mixed refrigerant required for the production flow rate of the liquefied natural gas stored and preset in the controller in the DCS using the flow rate of the liquefied natural gas as the variable PV. The calculated value is transmitted to the second flow indicator controller 210.

In addition, after the liquid mixed refrigerant passes through the first heat exchange zone and the first expansion valve 22 to become a two-phase refrigerant, the liquid mixed refrigerant pipe 14 positioned before entering the first gas-liquid separator 24 is formed. A second flow measurement transmitter 110 is installed, and the second flow measurement transmitter 110 measures the flow rate of the liquid mixed refrigerant and transmits the value to the second flow indicator controller 210 in the DCS.

Accordingly, the second flow display controller 210 sets the flow rate measurement value of the liquid mixed refrigerant received from the second flow rate measurement transmitter 110 as a variable PV, and transmits the liquid phase received from the first flow display controller 200. Using the calculated value of the mixed refrigerant as the control point SP, the opening amount of the first expansion valve 22 is adjusted to obtain the flow rate of the finally required liquid mixed refrigerant.

On the other hand, the first temperature measuring transmitter 300 is installed at the rear end of the gas pipe 10 through which the supply natural gas passes through the first heat exchange zone and the second heat exchange zone to be converted into liquefied natural gas and discharged. 1 The temperature measuring transmitter 300 measures the temperature of the liquefied natural gas and transmits the value to the temperature display controller 400 in the DCS.

The temperature display controller 400 uses the temperature value of the liquefied natural gas as a variable (PV), and the gaseous mixed refrigerant and the liquid mixed refrigerant required to obtain the final proper temperature of the liquefied natural gas stored and preset in the controller of the DCS. The flow rate is calculated, and the calculated value is transmitted to the first flow ratio display controller 500.

In addition, a third flow rate measurement transmitter 120 is provided in the liquefied gas phase mixed refrigerant pipe 12 positioned before the gas phase mixed refrigerant passes through the first heat exchange zone and the second heat exchange zone and enters the second expansion valve 32. The third flow rate measuring transmitter 120 measures the flow rate of the liquefied gaseous mixed refrigerant and transmits the value to the first flow ratio display controller 500.

In addition, the first flow ratio display controller 500 receives the flow rate measurement value of the liquid mixed refrigerant from the second flow display controller 210 as a variable.

Accordingly, the first flow ratio display controller 500 sets the measured flow rate value of the gaseous mixed refrigerant and the liquid mixed refrigerant as a variable PV, and compares the gaseous mixed refrigerant and the liquid mixed refrigerant received from the temperature display controller 400. The second expansion valve 32 is used as a control point SP, and the second expansion valve 32 is configured to obtain the required flow rate of the gas phase mixed refrigerant from the second flow indicator controller 210 as the variable measured flow rate of the liquid mixture refrigerant. Adjust the opening amount of).

On the other hand, a second temperature measuring transmitter 310 and a third temperature measuring transmitter 320 are respectively installed at the front end of the pipe 14 of the liquid mixed refrigerant and the rear end of the pipe 16 of the liquid mixed refrigerant. The temperature value of the gaseous phase mixed refrigerant and the liquid phase mixed refrigerant temperature measured by the two temperature measuring transmitter 310 and the third temperature measuring transmitter 320 are respectively transmitted to the temperature difference display controller 600 in the DCS.

The temperature difference display controller 600 calculates the temperature difference by using the temperatures of the gaseous mixed refrigerant and the liquid mixed refrigerant as variables (PV), and based on this temperature difference, the temperature difference is displayed on the production flow rate of the liquefied natural gas stored in the controller in the DCS. The flow rate of the liquefied natural gas / liquid mixed refrigerant required for the calculation is calculated, and the calculated value is transmitted to the second flow ratio display controller 510.

Here, the second flow ratio display controller 510 has a flow rate value of the current liquefied natural gas input to the first flow display controller 200 and the current liquid mixed refrigerant input to the second flow display controller 210. The flow rate value is also transmitted.

Accordingly, the second flow display controller 510 sets the flow rate value of the liquefied natural gas as the variable PV and sets the value of the liquefied natural gas / liquid mixed refrigerant calculated by the temperature difference display controller 600 as the control point SP. By adjusting the opening amount of the liquefied natural gas production valve 18 installed at the rear end of the gas pipe 10 so as to obtain the required liquefied natural gas flow rate.

Therefore, in the natural gas liquefaction apparatus according to the present invention, when the amount of liquefied natural gas to be produced in the DCS is set, each element of the control system is the flow rate and temperature of the liquefied natural gas, the flow rate of the gaseous mixed refrigerant and the liquid mixed refrigerant By controlling the temperature and the optimum mixed refrigerant flow rate to produce the liquefied natural gas by the amount set in the DCS.

The technical ideas described in the embodiments of the present invention as described above may be performed independently of each other, or may be implemented in combination with each other. While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. It is possible. Accordingly, the technical scope of the present invention should be determined by the appended claims.

10: gas piping 12,14,16: refrigerant piping
18: liquefied natural gas production valve 20: the first heat exchanger
22: first expansion valve 24: first gas liquid separator
30: second heat exchanger 32: second expansion valve
34: second gas-liquid separator 100: first flow measurement transmitter
110: second flow measurement transmitter 120: third flow measurement transmitter
200: first flow display controller 210: second flow display controller
300: first temperature measurement transmitter 310: second temperature measurement transmitter
320: third temperature measurement transmitter 400: temperature display controller
500: first flow ratio display controller 510: second flow ratio display controller
600: temperature difference display controller

Claims (15)

Natural gas that has undergone refining process is liquefied by heat exchange, and each includes a first heat exchange zone provided with a first heat exchanger and a second heat exchange zone provided with a second heat exchanger,
The first heat exchanger passes through a pipe of natural gas, a pipe of a liquid mixed refrigerant, and a pipe of a gaseous mixed refrigerant. Let's
The second heat exchanger passes through a gaseous natural gas pipe and a gaseous mixed refrigerant pipe, and thus, the gaseous mixed refrigerant liquefied at a low temperature through the first heat exchanger is liquefied by heat exchange to a lower temperature. A system for controlling a natural gas liquefaction device configured to cool,
The natural gas pipes and the refrigerant pipes through which the gaseous mixed refrigerant and the liquid mixed refrigerant are respectively transferred are measured to measure the flow rates of the liquefied natural gas, the gaseous mixed refrigerant and the liquid mixed refrigerant, and the values of the first and second DCSs are measured. A flow measurement transmitter and a flow rate measuring transmitter for transmitting to one of the first and second flow ratio display controllers,
Installed in the natural gas pipe and the refrigerant pipe further comprises a temperature measuring transmitter for measuring the temperature of the liquefied natural gas, gaseous mixed refrigerant and liquid mixed refrigerant and transmits the value to the temperature display controller or the temperature difference display controller of the DCS Natural gas liquefaction apparatus control system, characterized in that.
The method of claim 1,
The first heat exchange zone may include a first expansion valve for lowering and cooling the pressure of the liquid mixed refrigerant passing through the first heat exchanger, and gas-liquid separation of the mixed refrigerant consisting of a two-phase refrigerant while passing through the first expansion valve. And a first gas-liquid separator for passing through the first heat exchanger.
3. The method of claim 2,
The second heat exchange zone may include a second expansion valve for lowering and cooling the pressure of the liquefied gaseous mixed refrigerant passing through the second heat exchanger, and gas-liquid separation of the mixed refrigerant consisting of the two-phase refrigerant while passing through the second expansion valve. And a second gas-liquid separator allowing the second heat exchanger to pass therethrough.
The method of claim 3,
The liquefied gas phase mixed refrigerant passing through the second gas-liquid separator and passing through the second heat exchanger passes through the first heat-exchanger and passes through the first heat exchanger.
delete delete delete The method of claim 1,
The flow measurement transmitter,
A first flow rate measuring transmitter installed at a rear end of the gas pipe to measure a flow rate of the liquefied natural gas heat-exchanged, and then transmit the value to the first flow display controller;
A second flow rate measuring transmitter installed in the liquid mixed refrigerant pipe to measure a flow rate of the liquid mixed refrigerant, and transmitting the value to the second flow indicator controller;
And a third flow rate measuring transmitter installed in the gas phase mixed refrigerant pipe to measure the flow rate of the liquefied gas phase mixed refrigerant and transmitting the value to the first flow ratio display controller. Control system.
The method of claim 8,
The first flow display controller is a liquid phase mixing required for the production flow rate of the liquefied natural gas stored in the controller in the DCS by using the flow rate value of the liquefied natural gas transmitted from the first flow measurement transmitter as a variable. And calculating the flow rate of the refrigerant and transmitting the calculated value to the second flow controller.
The method of claim 8,
The second flow display controller,
The flow rate measured value of the liquid mixed refrigerant received from the second flow rate measurement transmitter is used as a variable, and the calculated value of the liquid mixed refrigerant received from the first flow indicator controller is used as a control point. A control system of a natural gas liquefaction apparatus, characterized in that for adjusting the opening amount of the first expansion valve to obtain a flow rate.
The method of claim 1,
The temperature measuring transmitter,
A first temperature measuring transmitter installed at a rear end of the gas pipe to measure a temperature of the liquefied natural gas heat-exchanged, and then transmitting the value to the first temperature display controller;
A second temperature measurement transmitter and a third temperature measurement installed at the front end of the gas phase mixed refrigerant pipe and the rear end of the liquid mixed refrigerant outlet pipe to transmit the temperature measured values of the gas phase mixed refrigerant and the temperature of the liquid mixed refrigerant to the temperature difference display controller; Control system of a natural gas liquefaction apparatus comprising a transmitter.
12. The method of claim 11,
The first temperature display controller is required to obtain the final proper temperature of the liquefied natural gas stored in the controller of the DCS by using the temperature value of the liquefied natural gas transmitted from the first temperature measuring transmitter as a variable. And calculating the flow rates of the gaseous mixed refrigerant and the liquid mixed refrigerant, and transmitting the calculated value to the first flow ratio display controller.
13. The method of claim 12,
The temperature difference display controller is required to calculate the temperature difference using the temperatures of the gaseous mixed refrigerant and the liquid mixed refrigerant as variables, and to produce a flow rate of the liquefied natural gas stored in the controller in the DCS by the temperature difference. And calculating the flow rate of the liquefied natural gas / liquid mixed refrigerant to be transmitted to the second flow ratio display controller.
The method of claim 1,
The second flow ratio display controller transmits a flow value of the current liquefied natural gas input to the first flow display controller, and a flow value of the current liquid mixed refrigerant input to the second flow display controller. Control system of natural gas liquefaction equipment.
15. The method of claim 14,
The second flow display controller uses the current liquefied natural gas flow rate value input to the first flow display controller as a variable, and finally uses the liquefied natural gas / liquid mixed refrigerant value calculated by the temperature difference display controller as a control point. A control system of a natural gas liquefaction apparatus, characterized in that for adjusting the opening amount of the liquefied natural gas production valve is installed at the rear end of the gas pipe so as to obtain the required liquefied natural gas flow rate.
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Citations (3)

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Publication number Priority date Publication date Assignee Title
KR19990014147A (en) * 1997-07-24 1999-02-25 마쉬 윌리엄 에프. Method and apparatus for controlling yield and temperature in mixed refrigerant liquefied natural gas plant
KR100490106B1 (en) 2003-03-08 2005-05-17 두산중공업 주식회사 Water level control apparatus and method in degassifier system
KR20110114917A (en) * 2010-04-14 2011-10-20 지에스건설 주식회사 Liquefaction of natural gas

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR19990014147A (en) * 1997-07-24 1999-02-25 마쉬 윌리엄 에프. Method and apparatus for controlling yield and temperature in mixed refrigerant liquefied natural gas plant
JPH1192770A (en) * 1997-07-24 1999-04-06 Air Prod And Chem Inc Method for controlling production and temperature in liquefied natural gas facilities using mixed refrigerant and apparatus therefor
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