JP4917008B2 - Liquefied gas vaporization system - Google Patents

Description

  The present invention relates to a liquefied gas vaporization system that vaporizes liquefied gas while recovering cold energy of low-temperature liquefied gas such as liquefied natural gas as power by a Stirling engine.

  Conventionally, a vaporization system that vaporizes a low-temperature liquefied gas such as LNG (Liquefied Natural Gas) by exchanging heat with hot water, seawater, or a high-temperature heat medium such as outside air in a vaporizer. Generally known.

  On the other hand, a cold energy recovery system that collects cold energy of low-temperature liquefied gas as power by a Stirling engine is also known (see, for example, Patent Documents 1 and 2). This cold heat recovery system cools the cooler (low temperature part) of the Stirling engine with a low temperature liquefied gas and heats the heater (high temperature part) with a heat medium such as combustion heat of vaporized gas or seawater. Power is recovered by operating the Stirling engine according to the temperature difference.

JP-A-11-22550 JP 2006-348872 A

  If the cold recovery system as described in Patent Documents 1 and 2 described above is incorporated into the liquefied gas vaporization system, before the low-temperature liquefied gas is vaporized by the vaporizer, the cold energy of the liquefied gas is reduced. Since the part can be recovered as power by the Stirling engine, the energy efficiency of the entire vaporization system is expected to be improved. However, in practice, the following problems exist.

  When cooling a Stirling engine cooler with low-temperature liquefied gas, there is no problem if the sensible heat (liquid temperature) of the liquefied gas rises due to heat input from the cooler or if the liquefied gas is completely vaporized. When only a part of the liquefied gas is vaporized, the gas is supplied to the subsequent vaporizer in a gas-liquid two-phase flow state in which the vaporized gas and the liquefied gas are mixed.

  The Stirling engine is ideally operated if there is even a temperature difference between the cooler on the low temperature side and the heater on the high temperature side. In reality, however, power loss occurs due to piston sliding resistance and crankshaft rotation resistance. Therefore, in order to operate a Stirling engine, the temperature difference between the cooler and the heater must be maintained at a certain level. must not. For this purpose, although depending on the temperature on the heater side, the temperature of the liquefied gas for cooling the cooler needs to be a certain temperature or lower.

  However, when the liquefied gas used for cooling the cooler is a mixture of a plurality of types of components having different boiling points, such as LNG in which high-boiling components such as propane and butane are mixed in the main component methane, The low-boiling components such as methane are first vaporized by the heat input from the cooler, while the high-boiling components such as propane and butane are not vaporized until they reach their boiling points. I will do it. Even if the high-boiling components still remain in the liquid state, if the temperature of the liquefied gas rises to the minimum necessary temperature for operating the Stirling engine, the liquefied gas will further cool down. Therefore, the gas is inevitably supplied to the vaporizer in a gas-liquid two-phase flow state.

  As described above, supplying gas to the vaporizer in a two-phase flow state in which liquefied gas and vaporized gas are mixed has various adverse effects on the vaporizer. For example, a vaporizer for the purpose of vaporizing a liquefied gas is usually designed to satisfy the required predetermined vaporization performance under the condition of accepting only the liquefied gas. However, when the gas is supplied in a two-phase flow state, heat is transferred to the liquefied gas in the vaporizer pipe as compared with the case where only the liquefied gas is supplied because the gas exists. The rate is reduced. For this reason, the required amount of heat is not given to the liquefied gas and the liquefied gas cannot be completely vaporized, or the temperature of the vaporized gas delivered from the vaporizer cannot be higher than the design temperature. There is a risk that it will not be able to be demonstrated. In addition, when gas is supplied to the vaporizer in a gas-liquid two-phase flow state, pipe vibration is likely to occur in each vaporizer pipe in the vaporizer, which may cause fatigue failure.

  An object of the present invention is to separate a vaporized gas generated when cooling a cooler of a Stirling engine from a liquefied gas and supply the gas to the vaporizer in a two-phase flow state in which the liquefied gas and the vaporized gas are mixed. Is to prevent.

Means for Solving the Problems and Effects of the Invention

  A liquefied gas vaporization system according to a first aspect of the present invention includes a Stirling engine that obtains power by using the cold heat of the liquefied gas, and a vaporized gas that is generated when a part of the liquefied gas is vaporized by heat from the cooler of the Stirling engine. Are separated from the liquefied gas, and a vaporizer for vaporizing the remaining liquefied gas after the vaporized gas is separated in the gas-liquid separator. .

  According to this configuration, when the cooler of the Stirling engine is cooled, the vaporized gas generated by vaporizing a part of the liquefied gas by the heat from the cooler is separated from the liquefied gas in the gas-liquid separator. For this reason, only the liquid (liquefied gas) is supplied to the vaporizer, and various adverse effects on the vaporizer caused by supplying the vaporized gas in a gas-liquid two-phase flow state mixed with the vaporized gas. Is prevented.

  In the liquefied gas vaporization system according to a second invention, in the first invention, the gas-liquid separator includes a container for storing the supplied liquefied gas in a lower portion thereof, and the liquefied gas at a lower end portion of the container. The cooler of the Stirling engine is disposed at a position where the gas is buried, a gas outlet for deriving the vaporized gas is provided at the upper end of the container, and the liquefied gas is introduced into the side or bottom of the container. A liquid outlet for leading out is provided.

  According to this configuration, the liquefied gas layer exists in the lower part of the container, while the vaporized gas layer exists in the upper part of the container. Moreover, the cooler of the Stirling engine is arrange | positioned at the lower end part of the container so that it may be buried in the stored liquefied gas. Therefore, the vaporized gas generated by the heat from the cooler at the lower end of the container moves upward in the liquefied gas and is separated from the liquefied gas, and further, from the gas outlet provided at the upper end of the container to the outside of the container. Derived. On the other hand, the liquefied gas remaining without being vaporized is led out from the liquid outlet provided at the side or bottom of the container and supplied to the vaporizer at the subsequent stage.

  In addition, by arranging the cooler at the lower end of the container in which the liquefied gas is stored, pool nucleate boiling occurs in the lower end of the container, which significantly increases the heat transfer coefficient between the cooler and the liquefied gas. Cooling of the cooler by gas can be performed efficiently. Further, since the vaporized gas generated around the cooler disposed at the lower end of the container rises quickly so as to leave the cooler, heat transfer between the cooler and the liquefied gas is not hindered by the vaporized gas. .

  The liquefied gas vaporization system according to a third aspect of the present invention is the liquefied gas vaporization system according to the second aspect, wherein the flow rate adjusting means for adjusting the supply flow rate of the liquefied gas to the container, and the liquid level level detecting means And a control means for controlling the flow rate adjusting means so that the liquid level of the liquefied gas is always located above the liquid outlet based on the detection result of the liquid level detecting means. It is a feature.

  According to this configuration, since the liquid level of the liquefied gas is always maintained above the liquid outlet from which the liquefied gas is led out from the container, the vaporized gas existing above the liquid level is liquefied gas. At the same time, it is prevented from flowing from the liquid outlet to the vaporizer.

  In the liquefied gas vaporization system according to a fourth aspect of the present invention, in the second or third aspect of the invention, the horizontal cross-sectional area at the upper part of the container where the vaporized gas is present is the horizontal of the lower part of the container where the liquefied gas is stored. It is characterized by being larger than the cross-sectional area.

  Thus, when the horizontal cross-sectional area of the upper part of the container where the vaporized gas is present is larger than the horizontal cross-sectional area of the lower part of the container where the liquefied gas is stored, it is separated from the liquefied gas and is discharged to the gas outlet at the upper end of the container. The flow rate of the vaporized gas when flowing in the direction decreases. Therefore, it can suppress that a part of liquefied gas of a container lower end part is discharged | emitted from a gas exit with the flow of vaporized gas.

  In the liquefied gas vaporization system according to a fifth invention, in any one of the second to fourth inventions, a cylindrical member extending from the position of the cooler to a position above the liquid outlet is disposed in the container. It is characterized by that.

  According to this structure, the flow of the liquefied gas which goes upwards arises in the inside of a cylindrical member as the vaporized gas vaporized with the heat from a cooler rises. Furthermore, when the liquefied gas overflows at the upper end of the cylindrical member, a downward flow of the liquefied gas is generated outside the cylindrical member. Thereby, since a circulating flow is generated in the liquefied gas in the container, the uneven temperature distribution of the liquefied gas caused by heat input from the cooler is eliminated. Further, the cylindrical member prevents the vaporized gas generated around the cooler from flowing out from the liquid outlet to the vaporizer together with the liquefied gas.

  Next, an embodiment of the present invention will be described. FIG. 1 is a schematic configuration diagram of a liquefied gas vaporization system of the present embodiment. The liquefied gas vaporization system 1 of the present embodiment vaporizes a low-temperature liquefied gas such as LNG (liquefied natural gas) and sends the vaporized gas having a predetermined temperature and a predetermined pressure to downstream equipment.

  As shown in FIG. 1, a liquefied gas vaporization system 1 according to the present embodiment includes a liquefied gas tank 2 that stores liquefied gas, and a Stirling engine that obtains power by using cold heat of a low-temperature liquefied gas supplied from the liquefied gas tank 2. 3, a gas-liquid separator 4 connected to the liquefied gas tank 2, a vaporizer 5 for vaporizing the liquefied gas derived from the gas-liquid separator 4, and a vaporized gas separated from the liquefied gas by the gas-liquid separator 4 And a control device 7 (control means) for controlling the entire vaporization system 1 and the like.

  A flow rate adjusting device 9 for adjusting the flow rate of the liquefied gas to the gas-liquid separator 4 is provided in the middle of the liquefied gas supply pipe 8 extending from the liquefied gas tank 2 to the gas-liquid separator 4. The flow rate adjusting device 9 has a general configuration including a known flow rate adjusting valve, and receives a signal from the control device 7 to set the flow rate of the liquefied gas supplied to the gas-liquid separator 4 to a predetermined amount. adjust.

  The Stirling engine 3 has two cylinders (a first cylinder 10 on the high temperature side and a second cylinder 11 on the low temperature side) and two powers arranged so as to be reciprocally movable up and down in the two cylinders 10 and 11, respectively. Pistons 12 and 13, a heater 14 for heating the first cylinder 10, and a cooler 15 for cooling the second cylinder 11 are provided.

  A working fluid such as helium is sealed in the two cylinders 10 and 11. The two cylinders 10 and 11 communicate with each other via the regenerator 16 so that the working fluid can move between the cylinders 10 and 11.

  The heater 14 receives heat from a high-temperature heat medium such as warm water or seawater supplied from the heat source 17 by the pump 18 and heats the working fluid in the first cylinder 10. On the other hand, the cooler 15 receives cold from the low-temperature liquefied gas stored in the lower end portion of the gas-liquid separator 4 described later (heat is dissipated into the liquefied gas), and cools the working fluid in the second cylinder 11.

  The lower end portions of the two power pistons 12 and 13 are respectively connected to the crankshaft 19, and the pistons 12 and 13 reciprocate up and down while maintaining a predetermined phase difference (for example, about 90 °), Power is transmitted to the crankshaft 19. The crankshaft 19 is provided with a flywheel 20 that rotates integrally with the crankshaft 19. A power recovery device 21 (for example, a generator) that recovers power is attached to the end of the crankshaft 19.

  Then, the expansion of the working fluid in the first cylinder 10 and the contraction of the working fluid in the second cylinder 11 cause the two power pistons 12 and 13 to reciprocate up and down, thereby rotating the crankshaft 19. Power is recovered by a power recovery device 21 attached to the crankshaft 19.

  When the cooler 15 of the Stirling engine 3 is cooled by the cold heat of the liquefied gas, the gas-liquid separator 4 separates the vaporized gas generated by the vaporization of a part of the liquefied gas from the heat of the cooler 15 from the liquefied gas. To do. The specific structure of the gas-liquid separator 4 will be described later.

  From the gas-liquid separator 4, liquefied gas is sent to the vaporizer 5, and the liquefied gas is vaporized by the vaporizer 5 and is heated to a predetermined temperature. Here, since the vaporized gas is separated from the liquefied gas in the gas-liquid separator 4 located in the preceding stage of the vaporizer 5, only the liquid (liquefied gas) is supplied to the vaporizer 5, and the liquefied gas and The gas is not supplied in a two-phase flow state where vaporized gas is mixed. The vaporizer 5 is not limited to a specific heat source type, and various types such as an air type, a seawater type, a hot water type, or an intermediate heat medium type can be used.

  On the other hand, the vaporized gas separated from the liquefied gas by the gas-liquid separator 4 is still in a vaporized state, but is still in a considerably low temperature, and is therefore sent to the vaporized gas temperature riser 6 to rise to a predetermined temperature. Be warmed. Also, in the vaporized gas temperature riser 6, various types such as an air type and a hot water type can be used as in the vaporizer 5.

  Here, when the Stirling engine 3 is operated, heat is supplied from the cooler 15 to the liquefied gas (part of the chilled heat of the liquefied gas is used in the cooler 15), so that compared with the case where the Stirling engine 3 is not provided. Thus, in the vaporizer 5 and the vaporized gas temperature riser 6, less heat energy is required to convert the same amount of liquefied gas into vaporized gas at the same temperature. Furthermore, in the Stirling engine 3, part of the cold energy of the liquefied gas is recovered as power by the power recovery device 21, so that the energy efficiency of the entire vaporization system 1 is further improved.

  The vaporized gas delivered from the vaporizer 5 and the vaporized gas delivered from the vaporized gas temperature riser 6 are mixed by the mixer 22. Further, a pressure detector 23 for detecting the pressure of the mixed vaporized gas and a temperature detector 24 for detecting the temperature of the vaporized gas are provided at the subsequent stage of the mixer 22.

  Both the pressure detection signal from the pressure detector 23 and the temperature detection signal from the temperature detector 24 are input to the control device 7. Then, the control device 7 outputs a control signal to the flow rate adjusting device 9 based on the detected pressure and temperature of the vaporized gas, and liquefaction is performed so that the pressure and temperature of the vaporized gas have predetermined values, respectively. The supply flow rate of the liquefied gas from the gas tank 2 is controlled.

  Next, the gas-liquid separator 4 will be described in detail. FIG. 2 is a longitudinal sectional view of the gas-liquid separator 4. As shown in FIG. 2, the gas-liquid separator 4 includes a container 30 that stores the liquefied gas supplied from the liquefied gas tank 2 through the liquefied gas supply pipe 8 in the lower part thereof.

  The container 30 has an elongated shape in the vertical direction. A liquefied gas supply pipe 8 is connected to the side surface of the lower end portion of the container 30, and the liquefied gas supplied from the liquefied gas supply pipe 8 is stored in the lower part of the container 30. Further, a liquid outlet 30a is provided at a position slightly below the center in the vertical direction on the side portion of the container 30, and this liquid outlet 30a is connected to the vaporizer 5 via the liquefied gas pipe 25. Yes. The liquid outlet 30 a may be provided at the bottom of the container 30. On the other hand, a gas outlet 30 b is provided at the upper end portion of the container 30, and the gas outlet 30 b is connected to the vaporized gas heater 6 through the vaporized gas pipe 26.

  The cooler 15 of the Stirling engine 3 described above is disposed at the lower end of the container 30, and the container 30 and the cooler 15 are integrated. The cooler 15 is always buried in the liquefied gas supplied from the liquefied gas supply pipe 8 and stored in the lower portion of the container 30, and heat exchange is continuously performed between the liquefied gas and the cooler 15. .

  The heat from the cooler 15 is consumed as sensible heat and latent heat of vaporization of the liquefied gas, and the temperature of the liquefied gas rises and part of the liquefied gas is vaporized. Then, the vaporized gas (indicated by a large number of bubbles 40 in FIG. 2) generated by the vaporization of a part of the liquefied gas moves upward in the liquefied gas and reaches the liquid surface, and from the liquefied gas. To separate. This vaporized gas is sent to the vaporized gas temperature elevator 6 from a gas outlet 30b provided at the upper end of the container 30. On the other hand, the liquefied gas after the vaporized gas is separated is sent to the vaporizer 5 from the liquid outlet 30 a provided at the side of the container 30.

  Note that when the liquefied gas is vaporized to become a vaporized gas, the volume rapidly increases, and thus the flow rate of the vaporized gas toward the gas outlet 30b becomes considerably large. Therefore, when the vaporized gas is separated from the liquefied gas, the liquefied gas is blown up, and a part thereof may flow out from the gas outlet 30b together with the vaporized gas. Therefore, it is preferable that the height (length) of the container 30 is sufficiently large so that the liquefied gas blown up can fall before reaching the gas outlet 30b.

  Further, the cooler 15 is disposed at the lower end portion of the container 30 so as to be buried in the liquefied gas, so that pool nucleate boiling occurs in the lower end portion of the container 30 and the heat transfer coefficient between the cooler 15 and the liquefied gas is remarkably increased. Get higher. Therefore, the cooler 15 can be efficiently cooled with the liquefied gas. Furthermore, since the vaporized gas generated around the cooler 15 rises rapidly away from the cooler 15, the heat transfer coefficient is reduced as much as possible due to the vaporized gas intervening between the cooler 15 and the liquefied gas. Is prevented.

As shown in FIG. 2, a cylindrical member 31 extending from the position of the cooler 15 to a position above the liquid outlet 30 a is installed inside the lower end portion of the container 30. Therefore, as indicated by an arrow in FIG. 2, an upward flow of the liquefied gas occurs in the cylindrical member 31 as the vaporized gas evaporated by the heat from the cooler 15 rises. Furthermore, when the liquefied gas overflows at the upper end of the cylindrical member 31, a downward flow of the liquefied gas is generated outside the cylindrical member 31. Thereby, since a circulation flow is generated in the liquefied gas in the container 30, the uneven temperature distribution of the liquefied gas caused by heat input from the cooler 15 is eliminated. Further, the tubular member 31 prevents the vaporized gas generated around the cooler 15 from flowing out from the liquid outlet 30a to the vaporizer 5 together with the liquefied gas.

  Further, the container 30 is provided with a liquid level detector 32 (liquid level detecting means) for detecting the liquid level of the liquefied gas. As shown in FIG. 1, the liquid level from the liquid level detector 32 is provided. The level detection signal is sent to the control device 7. In addition to the control based on the detection results of the pressure detector 23 and the temperature detector 24 described above, the control device 7 further controls the liquid level from the liquid outlet 30a based on the detection result of the liquid level by the liquid level detector 32. Also, the flow rate adjusting device 9 is controlled so that the liquid level A of the liquefied gas is always positioned above. According to this configuration, since the state in which the liquid level A of the liquefied gas is positioned above the liquid outlet 30a is always maintained, the vaporized gas present above the liquid level A is vaporized from the liquid outlet 30a together with the liquefied gas. It is prevented that it flows into the vessel 5.

  However, if the liquid level A of the liquefied gas in the container 30 is positioned too high, the liquefied gas droplets blown up to the vaporized gas may flow out to the gas outlet 30b. The liquid level A is preferably maintained at a position above the liquid outlet 30 a and below the center position in the vertical direction of the container 30.

  As described above, in the liquefied gas vaporization system 1 of the present embodiment, when the cooler 15 of the Stirling engine 3 is cooled, the vaporized gas generated by the vaporization of a part of the liquefied gas by the heat from the cooler 15. Is separated from the liquefied gas in the gas-liquid separator 4. For this reason, only the liquid (liquefied gas) is supplied to the vaporizer 5, and various kinds of vaporization to the vaporizer 5 caused by being supplied in a gas-liquid two-phase flow state in which the vaporized gas is mixed are provided. Adverse effects are prevented.

  In the gas-liquid separator 4, the cooler 15 is disposed at the lower end of the container 30 in which the liquefied gas is stored. Therefore, pool nucleate boiling occurs in the lower end of the container 30, and the cooler 15 and the liquefied gas are Since the heat transfer coefficient between them becomes much higher, the cooler 15 can be efficiently cooled with the liquefied gas. Further, since the vaporized gas generated around the cooler 15 rises rapidly away from the cooler 15, heat transfer between the cooler 15 and the liquefied gas is not hindered by the vaporized gas.

  In addition, the form which can apply this invention is not restricted to embodiment mentioned above, A various change can be added in the range which does not deviate from the meaning of this invention.

  For example, as shown in FIG. 3, in the gas-liquid separator 4A, the upper part of the container 30A in which the vaporized gas exists is larger than the lower part, and the horizontal cross-sectional area at the upper part is larger than the horizontal cross-sectional area at the lower part. It may be. Thus, when the horizontal sectional area of the upper part of the container 30A is larger than the horizontal sectional area of the lower part of the container 30A, the vaporized gas is separated from the liquefied gas and flows toward the gas outlet 30b at the upper end of the container 30A. The average flow rate of the vaporized gas decreases. Therefore, it can suppress that a part of liquefied gas is discharged | emitted from the gas outlet 30b with the upward flow of vaporized gas.

  Moreover, in the said embodiment, although the container 30 of the gas-liquid separator 4 which stores liquefied gas, and the cooler 15 of the Stirling engine 3 cooled by liquefied gas were integrated, gas separate from the cooler 15 was integrated. A liquid separator may be disposed at a position between the cooler 15 and the vaporizer 5. In this case, a fluid in a two-phase flow state in which liquefied gas and vaporized gas are mixed after heat exchange with the cooler 15 is supplied to the gas-liquid separator, and the vaporized gas is liquefied in the gas-liquid separator. After being separated from the gas, the liquefied gas is supplied to the vaporizer 5.

It is a schematic block diagram of the liquefied gas vaporization system which concerns on embodiment of this invention. It is a longitudinal cross-sectional view of a gas-liquid separator. It is a longitudinal cross-sectional view of the gas-liquid separator which concerns on a modified form.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquefied gas vaporization system 3 Stirling engine 4,4A Gas-liquid separator 5 Vaporizer 7 Control apparatus 9 Flow control apparatus 15 Cooler 30, 30A Container 30a Liquid outlet 30b Gas outlet 31 Cylindrical member 32 Liquid level detector

Claims (3)

A Stirling engine that uses the cold energy of liquefied gas to obtain power,
A gas-liquid separator that separates from the liquefied gas the vaporized gas generated when a part of the liquefied gas is vaporized by heat from the cooler of the Stirling engine;
A vaporizer that vaporizes the remaining liquefied gas after the vaporized gas is separated in the gas-liquid separator;
Equipped with a,
The gas-liquid separator includes a container that stores the supplied liquefied gas in a lower portion thereof,
The Stirling engine cooler is disposed at a position buried in the liquefied gas at the lower end of the container,
A gas outlet for deriving the vaporized gas is provided at the upper end of the container, and a liquid outlet for deriving the liquefied gas is provided at the side or bottom of the container,
A vaporized gas vaporized by heat from the cooler is disposed in the container so as to rise inside, and has a cylindrical member extending from the position of the cooler to a position above the liquid outlet;
A liquefied gas vaporization system characterized in that gaps are provided between the cylindrical member and the container and between the cylindrical member and the cooler, respectively . A flow rate adjusting means for adjusting a supply flow rate of the liquefied gas to the container;
A liquid level detecting means for detecting a liquid level of the liquefied gas in the container;
Control means for controlling the flow rate adjusting means so that the liquid level of the liquefied gas is always located above the liquid outlet based on the detection result of the liquid level detecting means;
The liquefied gas vaporization system according to claim 1 , comprising: Horizontal cross-sectional area at the top of the container in which the vaporized gas is present, according to claim 1 or 2 wherein the liquefied gas is characterized in that is larger than the horizontal cross-sectional area of the lower portion of the container to be stored Liquefied gas vaporization system.

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