JP2015155689A - Liquefied gas cold utilization system and liquefied gas cold utilization method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquefied gas cold utilization system and liquefied gas cold utilization method capable of reducing installation cost and operation cost, reducing the temperature of combustion air by making effective use of the cold of liquefied gas, and preventing a reduction in output from a gas turbine generator.

SOLUTION: A liquefied gas cold utilization system according to the present invention comprises: a first heat exchanger 1 implementing heat exchange between cold of liquefied gas and intermediate refrigerant; and a second heat exchanger 3 implementing heat exchange between the intermediate refrigerant and a cooling target that needs the cold of the liquefied gas and supplying the cold of the liquefied gas to the cooling target.

COPYRIGHT: (C)2015,JPO&INPIT

Description

  The present invention relates to a liquefied gas cold energy utilization system and a liquefied gas cold energy utilization method, and more particularly to a liquefied gas cold energy utilization system that utilizes the LNG cold energy between an LNG receiving terminal and a gas turbine power plant, and a cold energy utilization method thereof.

  Conventionally, LNG is used for power generation by a gas turbine generator in a LNG (Liquid Natural Gas) receiving base and a gas turbine power plant in the vicinity thereof. In such a gas turbine generator, fuel gas and combustion air are supplied to the combustor, and high-temperature gas obtained by burning the fuel gas is supplied to the turbine to rotate the turbine. The gas turbine generator is rotationally driven by the rotational driving force to generate electric power, and the air compressor is rotationally driven to compress the combustion air. The combustion air (hereinafter also referred to as intake air) decreases in density at high temperatures such as in summer, the mass flow rate decreases, and the output of the gas turbine generator decreases. In order to maintain the output of the gas turbine generator to the rated value, it is necessary to cool the intake air of the air compressor and increase its air density.

  As such an intake air cooling method, a method using latent heat of water mist, a method using a mechanical refrigerator, or a method using cold heat of LNG can be considered. When water mist latent heat is used, only a limited effect can be obtained in areas with high humidity. In the case of using a mechanical refrigerator, the equipment cost and the operating cost are increased, which is not suitable for practical use. When using the cold energy of LNG, the equipment cost and operation cost are comparatively small, so it is practical.

  As such a method for utilizing the cold energy of LNG, a method is known in which the cold heat of LNG is taken out using EGW (Ethylen Glycol-Water: ethylene glycol water), chlorofluorocarbon or the like as an intermediate refrigerant, and further taken out through water. (See Patent Document 1).

JP 2001-81483 A

  In view of the above circumstances, the present invention efficiently utilizes the liquefied gas cold energy to prevent a decrease in the output of the gas turbine generator, and reduces the facility cost and operating cost of the liquefied gas cold heat utilization system and the liquefied gas cold heat. The purpose is to provide usage.

  In order to achieve the above object, the liquefied gas cold energy utilization system according to the present invention requires a first heat exchanger for exchanging heat between the liquefied gas cold energy and the intermediate refrigerant, and the intermediate refrigerant and the liquefied gas cold energy. It is characterized by comprising at least a second heat exchanger for exchanging heat with the object to be cooled and supplying the cooling object with cold heat of the liquefied gas.

  In the liquefied gas cold heat utilization system according to the present invention, the number of heat exchangers in the system equipment is reduced by not using a second refrigerant such as water as the cold heat transfer medium, and the system equipment configuration is simplified. The

  Further, it is preferable that the liquefied gas is LNG, the intermediate refrigerant is nonflammable, and the object to be cooled is combustion air of a gas turbine generator.

  In such a case, it is avoided that the flammable LNG is routed to the vicinity of the gas turbine operating at a high temperature, and the nonflammable intermediate refrigerant can be used for cold heat transfer between the LNG receiving terminal and the gas turbine power plant.

  The intermediate refrigerant is preferably a non-flammable refrigerant made of HFC-23, HFC-134a, HCFC-22, HCFC-124, PFC-14, PFC-116, PFC-218, or a mixture thereof. It is.

  With such an intermediate refrigerant, the latent heat of the intermediate refrigerant is utilized for LNG cooling transfer, the circulation flow rate of the intermediate refrigerant is reduced, and the amount of intermediate refrigerant charged is also reduced. Thereby, the utilization efficiency of the cold of LNG can be improved. Further, cold heat can be efficiently extracted in accordance with the use temperature of an object that requires cold heat (hereinafter also referred to as a cooling object). In other words, when it is necessary to avoid freezing of moisture in the air, it is possible to set the extraction temperature of the cold heat higher by increasing the operating pressure of the intermediate refrigerant, or when you want to extract the cold heat at a lower temperature By lowering the operating pressure, it becomes possible to take out cold heat at a lower temperature regardless of the temperature of the heat medium. Since the freezing point of the refrigerant is sufficiently low, even if the LNG cold extraction temperature is set lower, the intermediate refrigerant in the system or the heat exchanger is not frozen or its viscosity does not increase. Thereby, the handling property of the system can be improved. As a result, the use of cold energy is expanded, and the facility cost and operation cost are reduced. When the intermediate refrigerant is HFC-134a, compared with the case where water or EGW is used, the circulation flow rate of the intermediate refrigerant is reduced to about 1/7, and the charging amount of the refrigerant is reduced to about 1/8. The Thus, the utilization efficiency of the cold heat of the liquefied gas is improved, so that the equipment configuration of the system is simplified, and the equipment cost and operation cost are reduced. That is, the circulation flow rate affects the pump power, and the charging amount of the refrigerant affects the size of the heat exchanger.

  The intermediate refrigerant is preferably a mixture of HFC-134a and HFC-32.

  By using a mixture of HFC-134a and HFC-32, it is possible to apply the cold utilization system even to a low-temperature plant having a temperature range in which HFC-134a cannot be used.

  Further, the present invention is another embodiment in which when the amount of heat for vaporizing the liquefied gas in the first heat exchanger is insufficient, a predetermined amount of liquefied gas is supplied and separately supplied by a heat medium outside the system. A vaporizer attached to the first heat exchanger to be vaporized can be further provided.

  In this embodiment, when the amount of heat for vaporizing the entire amount of the liquefied gas is insufficient in the first heat exchanger, a predetermined amount of the liquefied gas is provided in the vaporizer arranged in parallel to the first heat exchanger. Is vaporized separately by an external heat medium such as seawater. Accordingly, the entire amount of the combustible liquefied gas is used for the gas turbine generator without taking it out.

  In another aspect, the present invention is a method for using cold energy of a liquefied gas. The method for utilizing the cold heat of the liquefied gas according to the present invention includes heat exchange between the cold heat of the liquefied gas and the intermediate refrigerant in the first heat exchanger, and the intermediate refrigerant and the liquefied gas in the second heat exchanger. Heat exchange with an object to be cooled that requires the above-described cold heat, and supplying at least the cold heat of the liquefied gas to the object to be cooled.

  In such a cold gas utilization method of the liquefied gas according to the present invention, the cold heat of the liquefied gas is efficiently utilized to lower the temperature of the object to be cooled, and the quantity of the heat exchanger of the cold energy utilization facility is reduced, The equipment configuration is simplified. As a result, the equipment cost and operation cost are reduced.

  In light of the above-described object, according to the present invention, a system for utilizing cold energy of liquefied gas and liquefaction that efficiently uses the cold energy of the liquefied gas to prevent a reduction in the output of the gas turbine generator and reduce its equipment and operating costs. A method for utilizing cold energy of gas is provided.

FIG. 1 is a conceptual diagram illustrating first and second embodiments of a liquefied gas cold energy utilization system and a liquefied gas cold energy utilization method according to the present invention.

  Hereinafter, a first embodiment of a liquefied gas cooling / heating system according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a conceptual diagram illustrating first and second embodiments of a liquefied gas cooling / heating system according to the present invention. As shown in FIG. 1, the liquefied gas cold heat utilization system of the present embodiment performs first heat exchange in order to exchange heat between LNG and combustion air (hereinafter also referred to as a cooling object). The apparatus 1 and the 2nd heat exchanger 3 are provided. Further, as the combustion air, combustion air of a gas turbine generator can be used from a practical viewpoint.

  The first heat exchanger 1 is a shell-and-tube heat exchanger that exchanges heat between the cold heat of the liquefied gas and the intermediate refrigerant. The first heat exchanger 1 is branched from the LNG supply line 6, a line 7 into which LNG flows, a line 8 through which NG (Natural Gas: natural gas) that vaporizes LNG flows out, and a line 9 through which intermediate refrigerant flows. , And a line 11 through which the intermediate refrigerant that has received the cold heat of LNG flows out. The LNG supply line 6 is branched into a line 7 and a line 18 so that LNG supplied from an LNG storage tank (not shown) flows into the line 7 and a predetermined amount of LNG flows into the line 18 as necessary. It is configured. In these systems, it is preferable that an LNG receiving terminal and a gas turbine power plant are installed in the vicinity.

  The first heat exchanger 1 includes an upstream header that communicates with the line 7, a plurality of heat transfer tubes that communicate with the upstream header and are provided in parallel with each other, and a body of the first heat exchanger 1 that communicates with the line 9. A refrigerant chamber surrounded by (usually having a cylindrical shape) and a downstream header communicating with the line 11. The first heat exchanger 1 is configured so that heat can be exchanged between the LNG flowing in the heat transfer tube and the intermediate refrigerant flowing in the refrigerant chamber. An incombustible intermediate refrigerant is used as a heat source for exchanging heat with LNG. For this reason, in a system having a heat exchanger that directly exchanges heat between LNG and air, or a heat exchanger that directly exchanges heat between flammable intermediate refrigerant such as ethylene glycol and air, flammable LNG due to medium leakage / A situation where a mixed gas of a heat medium and air is generated can be prevented.

  The upstream header causes the LNG flowing from the line 7 to flow out to the heat transfer tube, the heat transfer tube causes the LNG flowing from the upstream header to exchange heat and flow to the downstream header, and the downstream header causes the NG vaporized LNG to the line 8 It is configured to flow out. Further, the refrigerant chamber is configured to exchange heat with the intermediate refrigerant flowing in from the line 9 and to flow out to the line 11. Inside the heat transfer tube, LNG is vaporized into NG by heat exchange with the intermediate refrigerant. On the other hand, inside the refrigerant chamber, the gaseous intermediate refrigerant that has received the cold heat of LNG is liquefied at a reduced temperature. Note that the flow direction of the LNG and the intermediate refrigerant at the time of heat exchange may be countercurrent or parallel flow.

  Further, the refrigerant flow rate is monitored by the pressure sensor, and by adjusting the opening of the control valve, a predetermined amount of the refrigerant flowing through the line 13 so that the internal pressure of the heat exchanger 1 is maintained within a predetermined range. Is supplied to the second heat exchanger 3 via the line 13. The intermediate refrigerant determined to be in excess amount flows into the line 14 and is returned to the heat exchanger 1. Since only the nonflammable intermediate refrigerant is stored in the heat exchanger 1 and its internal pressure is maintained within a predetermined range, the heat exchanger 1 is maintained in a stable state.

  The second heat exchanger 3 is a heat exchanger that exchanges heat between the intermediate refrigerant and combustion air that requires cooling of the liquefied gas, and supplies the cooling air of the liquefied gas to the combustion air. The second heat exchanger 3 is connected to a line 13 through which the intermediate refrigerant flows, a line 9 through which the intermediate refrigerant flows out, a line 15 through which combustion air flows in, and a line 16 through which the combustion air flows out. ing. The second heat exchanger 3 is configured to exchange heat between the intermediate refrigerant flowing in from the line 13 and the intermediate refrigerant and combustion air from the line 15. In addition, a finned tube heat exchanger can be used as the second heat exchanger 3.

  The line 15 branches to a line 17 at a predetermined position up to the second heat exchanger 3, and the line 17 merges with the line 16 to become a line 22. The line 22 is provided with a temperature sensor and a flow sensor (not shown) for monitoring the internal temperature and flow rate, and the line 17 is provided with a control valve (not shown). The sensor and the control valve are configured to adjust the amount of combustion air flowing from the line 15 to the line 17 and maintain the temperature of the combustion air supplied from the line 22 to the gas turbine at a predetermined temperature. Yes. The intermediate refrigerant is used for both cold recovery of LNG by the first heat exchanger 1 and heat exchange for intake air cooling by the second heat exchanger 3.

  The refrigerant cooling device 4 includes a first heat exchanger 1, a second heat exchanger 3, and a line interposed therebetween. The refrigerant cooling device 4 functions to take out the necessary amount of cold heat from the LNG and cool the combustion air of the gas turbine generator via the intermediate refrigerant.

  In the present embodiment, an open rack type vaporizer (ORV: Open-Rack-type Vaporizer) 5 is provided in parallel to the first heat exchanger 1. “Parallel arrangement” means that they are provided in parallel with each other when viewed in the flow direction of the LNG.

  The vaporizer 5 includes a plurality of heat transfer tubes arranged in a panel shape. When the amount of heat is insufficient in the first heat exchanger 1, a predetermined amount of liquefied gas is supplied, and a heat medium outside the system is used. Vaporize separately. The vaporizer 5 branches from the line 6 and is connected to a line 18 through which LNG flows in and a line 19 through which NG vaporized by LNG flows out. The vaporizer 5 uses, for example, seawater as a heat source, and is configured to vaporize LNG therein by spraying seawater on the outer surfaces of the plurality of heat transfer tubes in the atmosphere. That is, the vaporizer 5 is a heat exchanger for exchanging the residual cooling heat of the LNG, and can supplement the amount of heat for vaporizing the entire amount of LNG from an external heat source, and can pass NG to the combustor of the gas turbine. It is comprised so that it may function as an apparatus which sends in.

  The line 19 joins with the line 8 and is configured to flow NG flowing out of the vaporizer 5 to the line 20. Line 20 is connected to a gas turbine combustor (not shown). The line 8 can be provided with a heater 23. The NG in the line 20 sent to the combustor of the gas turbine is adjusted by the heater 23 so that its temperature does not drop too much. Thereby, it is possible to cope with various operating states of the gas turbine generator.

As the intermediate refrigerant, a refrigerant that is incombustible with respect to the heat medium is used, and functions as a refrigerant that collects cold heat from LNG and a refrigerant that cools the intake air of the gas turbine. Intermediate refrigerants include hydrofluorocarbons (HFCs) such as HFC-23 (CHF ₃ ) and HFC-134a (CH ₂ FCF ₃ ), hydrochlorocarbons such as HCFC-22 (CHClF ₂ ) and HCFC-124 (CHClCF ₃ ). Perfluorocarbons (PFC) such as fluorocarbons (HCFCs), PFC-14 (CF ₄ ), PFC-116 (C ₂ F ₆ ), PFC-218 (C ₃ F ₈ ), carbon dioxide (CO ₂ ), dioxide An inorganic compound such as sulfur (SO ₂ ) and a mixture thereof can be used as long as the use condition as the intermediate refrigerant is satisfied.

  The intermediate refrigerant is preferably a refrigerant composed of non-flammable HFC-23, HFC-134a, HCFC-22, HCFC-124, PFC-14, PFC-116, PFC-218, or a mixture thereof. More preferably, it is a mixture of 134a and HFC-32. In this case, the intermediate refrigerant is not frozen during the operation of the cold LNG, and the handling property on the system can be improved. Further, even if the LNG cold heat extraction temperature is set lower, the intermediate refrigerant does not freeze, so that efficient heat utilization utilizing the latent heat is possible while ensuring the handling of the system. As a result, the system configuration is simplified and the equipment cost and operation cost are reduced. Furthermore, when the intermediate refrigerant is HFC-134a, for example, compared with the case where EGW is used, the circulation flow rate can be reduced to about 1/7, and the charging amount of the refrigerant can be reduced to about 1/8. Can do.

  According to the present embodiment, the temperature of combustion air can be lowered by efficiently utilizing the cold energy of LNG, and the number of system equipment, particularly the number of heat exchangers, can be reduced. For example, in an intake air cooling system for a gas turbine in which LNG cold moves with LNG, intermediate refrigerant, water, and air, three heat exchangers are required. In the present embodiment, the two heat exchangers of the first heat exchanger 1 and the second heat exchanger 3 enable the intake turbine cooling of the gas turbine. As a result, the equipment configuration of the system can be simplified and the equipment cost and operation cost can be reduced.

  When a refrigerant that can use only the sensible heat, for example, EGW, is used as an intermediate refrigerant, the utilization efficiency of cold heat is low, and it is necessary to pump a large amount of intermediate refrigerant from the LNG receiving terminal to the gas turbine power plant. Thereby, the installation cost and the operating cost increase. According to the present embodiment, the latent heat of the intermediate refrigerant can be used for the LNG cold transfer, and the intermediate refrigerant circulation flow rate, the charging amount of the refrigerant, and the intermediate refrigerant are pumped from the LNG receiving base to the gas turbine power plant. Pump power to be reduced can also be reduced. As a result, the system configuration can be simplified and the equipment cost and operation cost can be reduced.

  Since the temperature of LNG is relatively low, there is a risk of freezing in all of the intermediate refrigerant, water, and air, and there is a problem in handling properties on the system. In particular, if the LNG cold extraction temperature is set low in order to maintain the power generation output of the gas turbine, the intermediate refrigerant in the heat exchanger may freeze or increase in viscosity, and the range of the cold extraction temperature is limited. End up. Therefore, the handling property on the system is deteriorated, and the utilization efficiency of the cold heat of LNG is also lowered. According to the present embodiment, even if the LNG cold extraction temperature is set lower during the operation of LNG cold, the intermediate refrigerant in the system or heat exchanger freezes or its viscosity increases. Can also prevent. Thereby, while improving the utilization efficiency of the cold of LNG, the handling property of a system can be improved. Therefore, it is possible to prevent the moisture of the combustion air from freezing during system operation. As a result, the system configuration can be simplified and the equipment cost and operation cost can be reduced.

  For example, compared with the case where EGW is used as an intermediate refrigerant, the freezing point of EGW is relatively high (−13 ° C. to 0 ° C.), and heat exchange is performed with low-temperature LNG in a low flow rate region or dead space in the heat exchanger. The freezing at the time may cause damage to the apparatus in the system or line clogging due to the fall of the intermediate refrigerant solidified material. However, according to the present embodiment, an intermediate refrigerant having a relatively low freezing point can be used ( For example, the freezing point of HFC-134a is about −101 ° C.). Moreover, there exists a fault that the viscosity of EGW increases in the low temperature range, and handling property worsens by the viscosity of EGW. According to the present embodiment, it is possible to improve the handling properties of the system and avoid the possibility that the intermediate refrigerant is solidified.

  As the circulation flow rate of the intermediate refrigerant that can be reduced, for example, HFC-134a (latent heat: 217 kJ / kg) is used as the intermediate refrigerant and compared with EGW (60.0 wt%, specific heat: 2.90 kJ / kg / ° C.) When the EGW input temperature is 10.0 ° C and the output temperature is 20.0 ° C, the ratio of the circulation amount (mass) between HFC-134a and EGW is the difference between the latent heat of HFC-134a and the sensible heat of EGW. Since it corresponds to the ratio, 2.90 × 10.0 / 217 = 0.134 (approximately 1/7).

  As the refrigerant charge amount of the intermediate refrigerant that can be reduced, for example, in the present embodiment, EGW (60.0 wt%, liquid specific gravity: 1.08) using HFC-134a (liquid specific gravity: 1.19) as the intermediate refrigerant. ), When the inlet temperature is 10.0 ° C and the outlet temperature is 20.0 ° C, the ratio of refrigerant volume (volume) between HFC-134a and EGW is multiplied by the ratio of liquid specific gravity. Since they are calculated together, 0.134 × 1.08 / 1.19 = 0.122 (approximately 1/8).

  Furthermore, when the amount of heat for vaporizing the entire amount of the liquefied gas is insufficient, a predetermined amount of the liquefied gas can be separately vaporized by a heat medium outside the system and used for the gas turbine. Therefore, the whole quantity can be utilized for a gas turbine generator, without taking out combustible liquefied gas outside.

  A second embodiment of the liquefied gas cold energy utilization system according to the present invention will be described in detail with reference to FIG. There is a difference in the intermediate refrigerant between the present embodiment and the first embodiment, and the description of the same configuration as the first embodiment is omitted.

As the intermediate refrigerant, a mixture composed of HFC-134a and HFC-32 (CH ₂ F ₂ ) is used. The mixing amount of HFC-134a is preferably 35 mol% to 70 mol%, and the mixing amount of HFC-32 is preferably 30 mol% to 65 mol%. If it is within the range of the mixing amount, an intermediate refrigerant having a sufficiently low freezing point of −150 ° C. can be obtained.

  According to the present embodiment, since an intermediate refrigerant having a lower freezing point and higher vapor pressure than HFC-134a can be used, the operating temperature range in which HFC-134a could not be used, for example, −40 ° C. to 27 ° C. It is possible to apply the liquefied gas cold energy utilization system according to the present invention to a low temperature plant having the operating temperature range.

  Moreover, the freezing point and vapor pressure of the mixture used as an intermediate refrigerant can be adjusted by the mixing ratio of HFC-134a and HFC-32. Therefore, by using an intermediate refrigerant having a mixing ratio suitable for a plant having a different operating temperature range, the liquefied gas cooling / heating system according to the present invention can be selectively applied to a plant having a different operating temperature range. It becomes.

  Next, the operation mode of the liquefied gas cold heat utilization system (first embodiment) described above will be described to explain the first embodiment of the liquefied gas cold heat utilization method according to the present invention. .

  LNG is fed from the LNG supply line 6 to the first heat exchanger 1 via the line 7. LNG flows into the upstream header of the first heat exchanger 1 and flows out into a plurality of heat transfer tubes provided in parallel in the first heat exchanger 1. On the other hand, the intermediate refrigerant is sent from the line 9 into the refrigerant chamber of the first heat exchanger 1.

  Heat exchange is performed between the LNG flowing into the heat transfer tube and the intermediate refrigerant flowing into the refrigerant chamber. When LNG receives the latent heat of the intermediate refrigerant, its temperature rises and vaporizes to become NG. On the other hand, the intermediate refrigerant receives the cold heat of LNG, and its temperature decreases and liquefies. NG flows from the downstream header of the first heat exchanger 1 to the line 8. On the other hand, the intermediate refrigerant flows out from the refrigerant chamber to the line 11 and flows into the second heat exchanger 3. When a nonflammable intermediate refrigerant is used as a heat source for heat exchange with LNG, compared with a method in which heat is directly exchanged between LNG and air, a mixed gas of flammable LNG and air is caused by medium leakage. The situation that occurs can be prevented.

  The flow rate in the line 11 of the intermediate refrigerant is monitored by a flow rate sensor (not shown). When it is determined that the amount exceeds the predetermined amount flowing into the line 13, the excess intermediate refrigerant flows into the line 14 via the delivery pump 12 by adjusting the opening of a control valve (not shown). Return to the heat exchanger 1. The internal pressure in the heat exchanger 1 is maintained within a predetermined range by adjusting the opening degree of the control valve installed in the line 21. Since only the intermediate refrigerant is stored in the heat exchanger 1 and the internal pressure is maintained within a predetermined range, a stable state is maintained.

  In the second heat exchanger 3, heat exchange is performed between the intermediate refrigerant flowing from the line 13 and the combustion air flowing from the line 15 so as to counter-flow with the intermediate refrigerant. The temperature of the intermediate refrigerant rises due to heat exchange with the combustion air, and vaporizes. On the other hand, the combustion air is cooled by intake air when the temperature of the combustion air decreases due to heat exchange with the intermediate refrigerant. The vaporized intermediate refrigerant flows out from the second heat exchanger 3 to the line 9. On the other hand, the cooled combustion air flows out from the second heat exchanger 3 to the line 16. When a nonflammable intermediate refrigerant is used as a heat source for exchanging heat with LNG, combustible LNG due to medium leakage compared to a method using a heat exchanger that directly exchanges heat between LNG and air. A situation where a mixed gas with air is generated can be prevented.

  Part of the combustion air flows from line 15 to line 17. The combustion air in the line 17 merges with the combustion air in the line 16 and flows into the line 22. The temperature in the line 22 is monitored by a temperature sensor (not shown). When the temperature of the combustion air in the line 22 is outside the predetermined temperature range, the amount of the combustion air flowing into the line 17 from the line 15 by adjusting the opening of a control valve (not shown) provided in the line 17 Thus, the temperature of the combustion air supplied from the line 22 to the gas turbine can be maintained within a predetermined temperature range.

As the intermediate refrigerant, a refrigerant that is incombustible with respect to the heat medium is used, and functions as a refrigerant that collects cold heat from LNG and a refrigerant that cools the intake air of the gas turbine. Examples of the intermediate refrigerant include hydrofluorocarbons (HFC) such as HFC-23 (CHF ₃ ) and HFC-134a (CH ₂ FCF ₃ ), and hydrochlorocarbons such as HCFC-22 (CHClF ₂ ) and HCFC-124 (CHClCF ₃ ). Perfluorocarbons (PFC) such as fluorocarbons (HCFCs), PFC-14 (CF ₄ ), PFC-116 (C ₂ F ₆ ), PFC-218 (C ₃ F ₈ ), carbon dioxide (CO ₂ ), dioxide An inorganic compound such as sulfur (SO ₂ ) and a mixture thereof can be used as long as the use condition as the intermediate refrigerant is satisfied.

  As the intermediate refrigerant, HFC-23, HFC-134a, HCFC-22, HCFC-124, PFC-14, PFC-116, PFC-218 or a mixture thereof is preferably used, and HFC-134a or a mixture thereof is used. It is more preferable. In this case, the intermediate refrigerant is not frozen during the operation of the cold LNG, and the handling property on the system can be improved. Further, even if the LNG cold heat extraction temperature is set lower, the intermediate refrigerant does not freeze, so that efficient heat utilization utilizing the latent heat is possible while ensuring the handling of the system. As a result, the system configuration is simplified and the equipment cost and operation cost are reduced. Further, when the intermediate refrigerant is HFC-134a, for example, compared with the case where EGW is used, the circulation flow rate can be reduced to about 1/7, and the refrigerant charge amount can be reduced to 1/8. .

  When the amount of LNG to be supplied is large, it is necessary to avoid taking LNG out of the system as much as possible. In such a case, LNG is supplied from the line 6 to the line 18 and supplied to the vaporizer 5. In the vaporizer 5, LNG is vaporized by taking latent heat from a heat source (for example, seawater). Thereby, the residual cooling heat of LNG is heat-exchanged, and the whole amount of LNG supplied can be vaporized. Further, when the temperature of the combustion air supplied to the second heat exchanger 3 varies depending on the season, the amount of LNG in the line 7 flowing into the first heat exchanger 1 is increased or decreased to supply the gas turbine. The temperature of the combustion air to be performed can be set within a predetermined range.

  The NG from the first heat exchanger 1 and the NG from the vaporizer 5 merge at the line 20 via the line 8 and the line 19 and then sent to the combustor of the gas turbine. The line 8 can be provided with an LNG heater 23 as shown. When the LNG heater 23 is provided, the temperature of the NG supplied to the combustor of the gas turbine can be controlled so as not to decrease too much.

  The temperature relationship in each line is shown as an example. When the temperature of the LNG is −157 ° C., the LNG having substantially the same temperature flows through the line 6 and the lines 7 and 18 branched from the line 6. In the first heat exchanger 1, LNG at −157 ° C. supplied from the line 7 flows into the heat transfer tube, and an intermediate refrigerant at 9 ° C. and HFC-134a supplied from the line 9 flow into the refrigerant chamber. . The boiling point (condensation point) of HFC-134a is 9 ° C. under a pressure of 0.4 MPa. In the heat transfer tube and the refrigerant chamber, the heat exchange between the LNG and the intermediate refrigerant removes the latent heat of the intermediate refrigerant, and the LNG vaporizes to become NG at 5 ° C. In line 8, NG at 5 ° C. from which LNG is vaporized flows, and in line 11, an intermediate refrigerant at 9 ° C. flows. In addition, NG of 5 degreeC or more heated by the LNG heater 23 flows through the line 8 as needed.

  In the second heat exchanger 3, the 9 ° C. intermediate refrigerant supplied from the line 13 flows into the heat transfer tube, and the 30 ° C. combustion air supplied from the line 15 flows in. In the second heat exchanger 3, the latent heat of the intermediate refrigerant is taken away by heat exchange between the intermediate refrigerant and the combustion air, and the temperature of the combustion air is reduced from 30 ° C to 24 ° C. An intermediate refrigerant at 9 ° C. flows through the line 9, and combustion air at 24 ° C. flows through the line 16. In the line 22, combustion air of 24 ° C. supplied to the gas turbine flows.

  In the vaporizer 5, LNG at −157 ° C. supplied from the line 18 flows into the heat transfer tube, and seawater supplied from a line (not shown) flows in. The LNG in the vaporizer 5 takes latent heat from the seawater, whereby the LNG is vaporized to become NG at 5 ° C. and is discharged to the line 19. The gas turbine is supplied with 5 ° C. NG in the line 20 where the line 19 merges with the line 8.

  Thus, even if the temperature of the intermediate refrigerant that cools the combustion air of the gas turbine is low, it is about 9 ° C. Even if the latent heat is lost due to the cold heat of LNG, the temperature of the intermediate refrigerant and the combustion air Water does not freeze and the viscosity of the intermediate refrigerant does not increase.

  According to the present embodiment, the temperature of combustion air can be lowered by efficiently utilizing the cold energy of LNG, and the number of system equipment, particularly the number of heat exchangers, can be reduced. For example, in a gas turbine intake air cooling method in which LNG cold moves with LNG, intermediate refrigerant, water, and air, three heat exchangers are required. In the present embodiment, the two heat exchangers of the first heat exchanger 1 and the second heat exchanger 3 enable the intake turbine cooling of the gas turbine. As a result, the configuration of the cold energy utilization facility can be simplified and the facility cost and operation cost can be reduced.

  When a refrigerant that can use only the sensible heat, for example, EGW, is used as an intermediate refrigerant, the utilization efficiency of cold heat is low, and it is necessary to pump a large amount of intermediate refrigerant from the LNG receiving terminal to the gas turbine power plant. Thereby, the installation cost and the operating cost increase. According to the present embodiment, the latent heat of the intermediate refrigerant can be used for the LNG cold transfer, and the intermediate refrigerant circulation flow rate, the charging amount of the refrigerant, and the intermediate refrigerant are pumped from the LNG receiving base to the gas turbine power plant. Pump power to be reduced can also be reduced. As a result, the configuration of the cold energy utilization facility can be simplified and the facility cost and operation cost can be reduced.

  Since the temperature of LNG is relatively low, there is a risk of freezing in all of the intermediate refrigerant, water, and air, and there is a problem in handling properties when using cold energy. In particular, if the LNG cold extraction temperature is set low in order to maintain the power generation output of the gas turbine, the intermediate refrigerant in the heat exchanger may freeze or increase in viscosity, and the range of the cold extraction temperature is limited. End up. Therefore, the handling property in the utilization of cold heat is deteriorated, and the utilization efficiency of cold heat of LNG is also lowered. According to the present embodiment, even when the LNG cold heat extraction temperature is set lower during the operation of LNG cold heat, the intermediate refrigerant in the cold energy utilization facility or the heat exchanger freezes or its viscosity increases. Can also be prevented. Thereby, while improving the utilization efficiency of the cold of LNG, the handling property in utilization of cold can be improved. Therefore, it is possible to prevent the moisture of the combustion air from freezing during the cold operation. As a result, the configuration of the cold energy utilization facility can be simplified, and the facility cost and operation cost can be reduced.

  For example, compared with the case where EGW is used as an intermediate refrigerant, the freezing point of EGW is relatively high (−13 ° C. to 0 ° C.), and heat exchange is performed with low-temperature LNG in a low flow rate region or dead space in the heat exchanger. There is a risk that the freezing at the time may cause damage to the equipment in the cold energy utilization facility or the line clogging due to the fall of the intermediate refrigerant solidified material, but according to the present embodiment, it is necessary to use an intermediate refrigerant with a relatively low freezing point. (For example, the freezing point of HFC-134a is about -101 ° C.). Moreover, there exists a fault that the viscosity of EGW increases in the low temperature range, and handling property worsens by the viscosity of EGW. According to the present embodiment, it is possible to improve the handling property in using cold energy and to avoid the risk of solidifying the intermediate refrigerant.

  As the circulation flow rate of the intermediate refrigerant that can be reduced, for example, HFC-134a (latent heat: 217 kJ / kg) is used as the intermediate refrigerant and compared with EGW (60.0 wt%, specific heat: 2.90 kJ / kg / ° C.) When the EGW input temperature is 10.0 ° C and the output temperature is 20.0 ° C, the ratio of the circulation amount (mass) between HFC-134a and EGW is the difference between the latent heat of HFC-134a and the sensible heat of EGW. Since it corresponds to the ratio, 2.90 × 10.0 / 217 = 0.134 (approximately 1/7).

  As the refrigerant charge amount of the intermediate refrigerant that can be reduced, for example, in the present embodiment, EGW (60.0 wt%, liquid specific gravity: 1.08) using HFC-134a (liquid specific gravity: 1.19) as the intermediate refrigerant. ), When the inlet temperature is 10.0 ° C and the outlet temperature is 20.0 ° C, the ratio of refrigerant volume (volume) between HFC-134a and EGW is multiplied by the ratio of liquid specific gravity. Since they are calculated together, 0.134 × 1.08 / 1.19 = 0.122 (approximately 1/8).

  Furthermore, according to the present embodiment, when the amount of heat for vaporizing the entire amount of the liquefied gas is insufficient in the first heat exchanger 1, the first heat exchanger 1 is arranged in parallel with the first heat exchanger 1. In the carburetor, a predetermined amount of liquefied gas can be separately vaporized by an external heat medium such as seawater and used for a gas turbine. Therefore, the whole quantity can be utilized for a gas turbine generator, without taking out combustible liquefied gas outside.

  Next, the operation mode of the liquefied gas cold heat utilization system (second embodiment) will be described in detail to describe the second embodiment of the liquefied gas cold heat utilization method according to the present invention. . There is a difference in the intermediate refrigerant between the present embodiment and the first embodiment, and the description of the same configuration as the first embodiment is omitted.

As the intermediate refrigerant, a mixture composed of HFC-134a and HFC-32 (CH ₂ F ₂ ) is used. The mixing amount of HFC-134a is preferably 35 mol% to 70 mol%, and the mixing amount of HFC-32 is preferably 30 mol% to 65 mol%. If it is within the range of the mixing amount, an intermediate refrigerant having a sufficiently low freezing point of −150 ° C. can be obtained.

  According to the present embodiment, since an intermediate refrigerant having a lower freezing point and higher vapor pressure than HFC-134a can be used, the operating temperature range in which HFC-134a could not be used, for example, −40 ° C. to 27 ° C. It becomes possible to apply the cold heat utilization method of the liquefied gas according to the present invention also to a low temperature plant having the operating temperature range of

  Moreover, the freezing point and vapor pressure of the mixture used as an intermediate refrigerant can be adjusted by the mixing ratio of HFC-134a and HFC-32. Therefore, by using an intermediate refrigerant having a mixing ratio suitable for a plant having a different operating temperature range, the method for utilizing the cold energy of the liquefied gas according to the present invention can be selectively applied to a plant having a different operating temperature range. It becomes.

  In the above-described embodiment, an open rack type vaporizer is employed as the vaporizer 5. However, it is also possible to employ a shell and tube type heat exchanger. If the vaporizer 5 is a shell-and-tube type heat exchanger, it is easier to reduce the size, and the LNG can be re-used by an offshore floating body such as FSRU (Floating Storage and REGWification Unit) or FPSO (Floating Production, Storage and Offloading), or an LNG ship. This is advantageous when gasifying.

  According to the cold gas utilization system and the cold gas utilization method according to the present invention, it is possible to efficiently utilize the cold energy of the liquefied gas, to prevent a reduction in the output of the gas turbine generator, and to reduce the equipment cost and The operating cost can be reduced.

DESCRIPTION OF SYMBOLS 1 1st heat exchanger 3 2nd heat exchanger 4 Refrigerant cooling device 5 Vaporizer 6 LNG supply line 12 Delivery pump 23 LNG heater

Claims (10)

A first heat exchanger for exchanging heat between the cold heat of the liquefied gas and the intermediate refrigerant;
A heat exchanger that exchanges heat between the intermediate refrigerant and a cooling target that requires cooling of the liquefied gas, and that supplies the cooling heat of the liquefied gas to the cooling target. Liquefied gas cooling system.   The liquefied gas cold energy utilization system according to claim 1, wherein the liquefied gas is LNG, the intermediate refrigerant is nonflammable, and the object to be cooled is combustion air of a gas turbine generator.   The intermediate refrigerant is a refrigerant composed of non-combustible HFC-23, HFC-134a, HCFC-22, HCFC-124, PFC-14, PFC-116, PFC-218 or a mixture thereof. The system for utilizing cold energy of liquefied gas described in 1.   The liquefied gas cold utilization system according to claim 1 or 2, wherein the intermediate refrigerant is a mixture of HFC-134a and HFC-32.   When the amount of heat for vaporizing the liquefied gas in the first heat exchanger is insufficient, a predetermined amount of the liquefied gas is supplied, and the first heat exchanger is separately vaporized by a heat medium outside the system. The cold energy utilization system of liquefied gas as described in any one of Claims 1-4 further equipped with the vaporizer provided side by side. Heat exchange between the cold of the liquefied gas and the intermediate refrigerant in the first heat exchanger;
Heat exchange between the intermediate refrigerant and a cooling target requiring cooling of the liquefied gas in a second heat exchanger, and supply the cooling heat of the liquefied gas to the cooling target. How to use cold energy.   The method for using cold energy of liquefied gas according to claim 6, wherein the liquefied gas is LNG, the intermediate refrigerant is nonflammable, and the object to be cooled is combustion air of a gas turbine generator.   The intermediate refrigerant is a refrigerant composed of non-flammable HFC-23, HFC-134a, HCFC-22, HCFC-124, PFC-14, PFC-116, PFC-218 or a mixture thereof. The method for using cold energy of the liquefied gas described in 1.   The method for cold utilization of liquefied gas according to claim 6 or 7, wherein the intermediate refrigerant is a mixture of HFC-134a and HFC-32.   When the amount of heat for vaporizing the liquefied gas in the first heat exchanger is insufficient, a predetermined amount of liquefied gas is supplied, and the heat exchanger outside the system is attached to the first heat exchanger. 10. The method for utilizing cold energy of a liquefied gas according to any one of claims 6 to 9, wherein the vaporization is performed separately by a separate vaporizer.

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