WO2019031300A1

WO2019031300A1 - Liquefied fuel gas vaporization system and temperature control method for same

Info

Publication number: WO2019031300A1
Application number: PCT/JP2018/028588
Authority: WO
Inventors: 尚則木梨; 春名　一生; 和晶加藤; 直毅西田
Original assignee: 住友精化株式会社; サノヤス造船株式会社
Priority date: 2017-08-08
Filing date: 2018-07-31
Publication date: 2019-02-14
Also published as: JP2020186732A

Abstract

This liquefied fuel gas vaporization system (X1) for vaporizing a liquefied fuel gas for the purpose of supplying the liquefied fuel gas to a combustion device (5) is provided with: a vaporizer (2) which vaporizes a liquefied fuel gas by heating the liquefied fuel gas by means of a liquid heat medium; a heat recovery unit (4) which recovers exhaust heat of the combustion device (5) by means of the liquid heat medium; heat medium circulation lines (62, 63) for circulating the liquid heat medium between the heat recovery unit (4) and the vaporizer (2); a mixing unit (71) which is provided in the heat medium circulation lines (62, 63) so as to mix the liquid heat medium which has passed through the heat recovery unit (4) and the liquid heat medium which is discharged from the vaporizer (2) and has not passed through the heat recovery unit (4); and flow rate control units (624, 73) which control the flow rate of the liquid heat medium to be supplied to the vaporizer (2).

Description

Liquefied fuel gas vaporization system and temperature control method therefor

The present invention relates to a liquefied fuel gas vaporization system for heating and vaporizing a liquefied fuel gas such as liquefied natural gas with a liquid heat medium such as water, and supplying the vaporized gas as a fuel gas to a combustion apparatus. The invention also relates to a temperature control method for a liquefied fuel gas vaporization system.

Gas engines are diesel engines and are widely used in generators, automobile engines, marine engines and the like. Gas engines are narrower in stable combustion area between knocking area and misfire area than liquid fuel diesel engines, and are more sensitive to conditions such as excess air ratio, charge air temperature, fuel gas composition, and fuel gas temperature. There is a problem that the combustion state is affected. For this reason, in general, a gas engine uses a governor (speed governor) to prevent a large change in engine rotation speed due to a minute change in engine load.

In a facility that supplies natural gas fuel to a combustion apparatus such as a gas engine, LNG (liquefied natural gas) is stored in a fuel storage tank at a low temperature of -160 ° C. or less, heated by a vaporizer or the like to be vaporized and gasified. As a heat source of the vaporizer, for example, water (liquid heat medium) is used.

In Patent Document 1, in a marine gas engine (dual fuel engine) as a combustion apparatus, in order to supply fuel gas efficiently and safely, engine cooling water (engine cooling water) is directly heated for heating a carburetor. It is used as water. Since there is no such thing as a fuel injection pump in a gas engine, if the gas fuel temperature changes, the amount of gas fuel supplied at standard conditions (0 ° C, atmospheric pressure) changes, the calories supplied change, and the governor adjustment function Will be lost. Therefore, for example, when the fuel gas temperature changes rapidly, there is a problem that the governor can not control. On the other hand, when the natural gas supply system according to the prior art is used as it is, in the case of a marine diesel engine such as a marine diesel engine where load fluctuation largely changes as a gas engine, the amount of fuel gas according to the output of the engine It could not be supplied to the engine at (e.g. ± 5 ° C).

JP, 2015-147508, A

The present invention has been conceived under such circumstances, and using only the exhaust heat of the combustion apparatus without using means for forced heating and cooling, it is discharged from the vaporizer and burned. It is a primary object to provide a liquefied fuel gas vaporization system suitable for supplying a gaseous fuel (e.g., natural gas) supplied to the apparatus in a predetermined temperature range.

According to a first aspect of the present invention, there is provided a liquefied fuel gas vaporization system for vaporizing liquefied fuel gas and supplying it to a combustion apparatus, comprising: a vaporizer for heating and vaporizing liquefied fuel gas with a liquid heat medium; A heat recovery unit that recovers the exhaust heat of the combustion apparatus with the liquid heat medium, a heat medium circulation line for circulating the liquid heat medium between the heat recovery unit and the vaporizer, and the heat medium circulation A mixing unit provided in a line for mixing the liquid heat medium that has passed through the heat recovery unit and the liquid heat medium that has been discharged from the vaporizer and has not passed through the heat recovery unit; And a flow rate control unit for controlling the flow rate of the liquid heat medium supplied to the liquid fuel gas vaporization system.

Preferably, a gas temperature detection unit for detecting the temperature of the fuel gas discharged from the vaporizer is further provided, and the flow rate adjustment unit is configured to perform the vaporization based on the temperature of the fuel gas detected by the gas temperature detection unit. The flow rate of the liquid heat medium supplied to the vessel is adjusted.

Preferably, the heat medium circulation line includes a low temperature side line for sending the liquid heat medium having a relatively low temperature discharged from the vaporizer to the heat recovery unit, and the heat recovery unit passed through the heat recovery unit. A high temperature side line for sending the liquid heat medium which is high temperature to the vaporizer, the mixing unit has one end connected to the low temperature side line and the other end connected to the high temperature side line 1 Includes a bypass line.

Preferably, a heat medium temperature detection unit is provided downstream of the connection point with the first bypass line in the high temperature side line and detects the temperature of the liquid heat medium, and the heat medium temperature detection unit detects the temperature of the liquid heat medium. And a temperature control unit for controlling the flow rate of the liquid heat medium that is mixed with the high temperature side line through the first bypass line so that the temperature of the liquid heat medium falls within a predetermined range.

Preferably, the flow rate adjustment unit is provided in the high temperature side line, and is connected to a flow rate adjustment three-way valve that adjusts the flow rate of the liquid heat medium supplied to the vaporizer, and one end is connected to the flow rate adjustment three-way valve And a second bypass line connected at the other end to the low temperature side line.

Preferably, the high temperature side line further includes a temperature maintaining chamber provided between the mixing unit and the flow rate adjusting unit, and the heat medium temperature detecting unit is provided in the temperature maintaining chamber.

Preferably, the combustion device is a dual fuel engine for ships.

Preferably, the heat recovery unit further includes a heat exchanger provided between the low temperature side line and the high temperature side line, and in the heat exchanger, the cooling water from the combustion device and the low temperature side line Heat exchange between the heat transfer medium and the heat transfer medium.

Preferably, the fuel gas is natural gas and the heat medium is water.

According to a second aspect of the present invention, there is provided a temperature control method in a liquefied fuel gas vaporization system for vaporizing liquefied natural gas and supplying it to a combustion apparatus. According to the method, the liquid heat medium is circulated between the vaporizer which heats and vaporizes the liquefied fuel gas with the liquid heat medium, and the heat recovery unit which recovers the exhaust heat of the combustion apparatus, and The liquid heat medium that has been discharged and has not passed through the heat recovery unit is mixed with the liquid heat medium that has passed through the heat recovery unit so that the temperature of the liquid heat medium after mixing falls within a predetermined range. A control step of controlling the temperature of the liquid heat medium and a flow rate of the liquid heat medium supplied to the vaporizer are controlled to control the temperature of the fuel gas discharged from the vaporizer to be within a predetermined range. And temperature control steps.

Preferably, the fuel gas is natural gas and the heat medium is water.

Preferably, the liquefied fuel gas vaporization system has passed through the low temperature side line for sending the liquid heat medium discharged from the vaporizer at a relatively low temperature to the heat recovery unit, and the heat recovery unit. A heat medium circulation line including a high temperature side line for sending the liquid heat medium having a relatively high temperature to the vaporizer, one end connected to the low temperature side line, and the other end connected to the high temperature side line Adjusting a flow rate of the liquid heat medium supplied to the high temperature side line through the bypass line, a gas temperature detection unit for detecting the temperature of the fuel gas discharged from the vaporizer, and the bypass line; A temperature control unit for maintaining the temperature of the liquid heat medium at a substantially constant temperature within a predetermined range; a flow rate control unit for adjusting the flow rate of the liquid heat medium supplied to the vaporizer via the high temperature side line; Equipped with The flow rate adjusting unit is configured to supply the liquid heat medium to the vaporizer through the high temperature side line so that the temperature of the fuel gas detected by the gas temperature detection unit is maintained within a predetermined range. Adjust the flow rate.

Preferably, the flow rate control unit is configured to control the flow rate of the liquid heat medium supplied to the vaporizer through the high temperature side line so as to fall within the range of 15 to 50 ° C., which is ± 5 ° C. from the target temperature of the fuel gas. Adjust the

Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

It is a schematic block diagram which shows one Embodiment of the liquefied fuel gas vaporization system which concerns on this invention. It is a graph showing the characteristic of gas fuel consumption change to gas engine operation time. It is a graph showing the characteristic of the fuel gas temperature change discharged from the carburetor to gas fuel consumption. It is the schematic which shows the other structural example of a liquid heat-medium flow rate adjustment part. It is the schematic which shows the other structural example of a liquid heat-medium flow rate adjustment part. It is the schematic which shows the other structural example of a liquid heat-medium flow rate adjustment part.

Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings.

FIG. 1 shows an embodiment of a liquefied fuel gas vaporization system according to the present invention. The liquefied fuel gas vaporization system X1 of the present embodiment includes a fuel storage tank 1, a vaporizer 2, a buffer tank 3, a heat recovery unit 4 (heat exchanger), and lines connected thereto. . The liquefied fuel gas vaporization system X1 supplies the fuel gas to the combustion device 5. The combustion device 5 may be, for example, a gas engine for a ship, and is mounted, for example, on a bottom portion of the ship. Also, the fuel gas may be, for example, natural gas. In the following, for the sake of simplicity, the description will be made assuming that the combustion device 5 is a ship engine and the fuel gas is a natural gas.

The fuel storage tank 1 is for storing liquefied natural gas (LNG) to be a fuel. The fuel storage tank 1 has a double surrounding wall, and a heat insulating material is filled between the two surrounding walls and the pressure is reduced to a vacuum to block the heat of entry from the outside air. . In the fuel storage tank 1, LNG is stored at a temperature of −160 ° C. or less. Although the details will be described later, the fuel storage tank 1 receives the natural gas generated by the vaporization of the LNG in the vaporizer 2 through the gas line 67 at a pressure of about 0.7 MPaG (G indicates that it is a gauge pressure). There is.

A fuel supply line 61 is connected to the lower portion of the fuel storage tank 1. The fuel supply line 61 is a flow path for transferring the LNG delivered from the fuel storage tank 1 to the carburetor 2. The fuel supply line 61 is provided with a shutoff valve 611.

A gas extraction line 612 is connected to the upper portion of the fuel storage tank 1. The gas extraction line 612 is for extracting the gas in the space in the fuel storage tank 1 and flowing it to the fuel supply line 61 when the fuel storage tank 1 is refilled with LNG. The gas extraction line 612 is provided with a shutoff valve 613.

The vaporizer 2 is for evaporating and vaporizing LNG using a liquid heat medium (hereinafter, simply referred to as “heat medium”) as a heating source. The vaporizer 2 includes a heat medium container 21 and

heat transfer tubes

22 and 23 disposed inside the heat medium container 21.

The heat medium container 21 is a sealed container for containing a heat medium for heating and vaporizing the LNG in the heat transfer tube 22. The heat medium can be replenished. Examples of the heat medium include water.

In the present embodiment, the heat medium container 21 has a structure in which a substantially bell-shaped container body 212 is mounted on a disc-shaped bottom plate 211, and the container body 212 and the bottom plate 211 sandwich bolts for sealing and bolts. Integrated and fixed. According to such a configuration, when carrying out a periodic inspection required by high pressure gas or the laws and regulations of the ship, if the heat medium is extracted and the bolt is removed, the bell-shaped container body 212 can It is possible to directly inspect the

heat transfer pipes

22 and 23 simply by pulling up the fuel supply line 61) and the heat medium pipe (heat

medium circulation lines

62, 63, etc. described later) (the heat

medium circulation lines

62, 63 and the like).

The heat

medium circulation lines

62 and 63 are connected to the heat medium container 21. The heat

medium circulation lines

62 and 63 circulate the heat medium between the vaporizer 2 and the heat recovery unit 4. The heat medium circulation line 62 is connected to the bottom plate 211 of the heat medium container 21 and is a flow path for sending the heat medium having passed through the heat recovery unit 4 to the heat medium container 21 (vaporizer 2). The heat medium circulation line 63 is connected to the bottom plate 211 of the heat medium container 21 and is connected to the overflow pipe 24 penetrating the bottom plate 211 in a sealed state. The heat medium having passed through the inside of the heat medium container 21 by being sequentially supplied via the heat medium circulation line 62 is discharged to the heat medium circulation line 63 via the overflow pipe 24. Although the details will be described later, the heat medium discharged from the heat medium container 21 is reheated in the heat recovery unit 4 and supplied again to the heat medium container 21 (vaporizer 2) to be circulated and used. The heat medium circulation line 62 is provided with a circulation pump 621.

The heat medium passing through the heat recovery unit 4 and flowing through the heat medium circulation line 62 has a relatively high temperature. The heat medium passing through the heat medium container 21 (vaporizer 2) and flowing through the heat medium circulation line 63 has a relatively low temperature. Therefore, the heat medium circulation line 62 can also be called a high temperature side line, and the heat medium circulation line 63 can also be called a low temperature side line.

In the present embodiment, the heat

medium circulation lines

62 and 63 are connected to the bypass line 71 (first bypass line). One end of the bypass line 71 is connected to the heat medium circulation line 63 (low temperature side line), and the other end is connected to the heat medium circulation line 62 (high temperature side line). The bypass line 71 is a flow path for mixing the heat medium that has passed through the heat recovery unit 4 with the heat medium that has been discharged from the vaporizer 2 and has not passed through the heat recovery unit 4. Here, the temperature of the heat medium flowing through the bypass line 71 is lower than the temperature of the heat medium flowing through the heat medium circulation line 62.

In the present embodiment, a temperature control unit 72 is provided at the connection point of the bypass line 71 to the heat medium circulation line 62. The temperature control unit 72 adjusts the flow rate of the heat medium to be mixed with the heat medium circulation line 62 through the bypass line 71 and includes, for example, a three-way valve.

In the present embodiment, the temperature control unit 72 passes the bypass line 71 so that the temperature of the heat medium detected by the heat medium temperature detection unit 622 falls within a predetermined range, and the heat medium circulation line 62 (high temperature side line) Adjust the flow rate of the heat medium mixed into the In the present embodiment, a temperature maintenance chamber 623 is provided near the downstream side of the connection point of the bypass line 71 in the heat medium circulation line 62. A predetermined amount of heat medium is accommodated in the temperature maintenance chamber 623, and the heat medium temperature detection unit 622 detects the temperature of the heat medium in the temperature maintenance chamber 623.

In the present embodiment, the heat medium circulation line 62 is provided with a flow control valve 624 (flow control unit). The flow control valve 624 is for adjusting the flow rate of the heat medium supplied to the vaporizer 2 and includes a three-way valve. The flow control valve 624 is provided between the circulation pump 621 and the vaporizer 2, and is preferably provided near the vaporizer 2.

In the present embodiment, the flow control valve 624 is connected to the bypass line 73 (second bypass line). One end of the bypass line 73 is connected to the flow rate control valve 624, and the other end is connected to the heat medium circulation line 63 (low temperature side line). The bypass line 73 is provided for mixing a part of the heat medium which is derived from the temperature maintenance chamber 623 and flows in the heat medium circulation line 62 into the heat medium circulation line 63 (low temperature side line) without passing through the vaporizer 2. It is a flow path. The flow rate control valve 624 adjusts the flow rate of the heat medium supplied to the vaporizer 2 based on the temperature of the natural gas detected by the gas temperature detection unit 641 described later. When the flow rate of the heat medium supplied to the vaporizer 2 is reduced by the flow rate adjustment valve 624, the heat medium corresponding to the reduced flow rate passes through the bypass line 73 and is mixed with the heat medium circulation line 63.

The heat transfer tube 22 is a flow path through which the LNG introduced into the heat medium container 21 flows, and is wound, for example, in a coil shape. The upstream end of the heat transfer tube 22 penetrates the bottom plate 211 of the heat medium container 21 and is connected to the fuel supply line 61. A gas line 64 is also connected to the bottom plate 211 of the heat medium container 21. The downstream end of the heat transfer tube 22 penetrates the bottom plate 211 and is connected to the gas line 64.

The LNG in the heat transfer tube 22 is heated by the heat medium present in the surrounding area to be vaporized and vaporized, and the vaporized natural gas is discharged to the gas line 64 leading to the outside of the heat medium container 21. The downstream end of the gas line 64 is connected to the buffer tank 3. Natural gas vaporized in the heat transfer tube 22 is fed to the buffer tank 3 via the gas line 64.

Here, when water is used as the heat medium, water flows in a temperature range of, for example, 20 to 60 ° C. in the heat medium container 21 (vaporizer 2). The fuel gas vaporized in the heat transfer tube 22 is heated, for example, to a temperature range of 15 to 50 ° C., preferably 20 to 45 ° C., and discharged to the gas line 64 at a pressure of about 0.70 MPaG.

In the present embodiment, a gas temperature detection unit 641 is provided at a portion near the heat medium container 21 (vaporizer 2) in the gas line 64. The gas temperature detection unit 641 detects the temperature of the fuel gas discharged from the vaporizer 2.

The heat transfer tube 23 is a flow path through which the LNG introduced into the heat medium container 21 flows, and is wound, for example, in a coil shape. The heat transfer tube 23 raises the pressure in the space portion inside the fuel storage tank 1 by the vaporized natural gas. The upstream end of the heat transfer tube 23 penetrates the lower portion (bottom plate 211) of the heat medium container 21 and is connected to the LNG supply line 66. The LNG supply line 66 is connected in the middle of the LNG supply line 61 in a branched manner. The LNG supply line 66 is provided with a shutoff valve 661. A gas line 67 is also connected to the lower portion (bottom plate 211) of the heat medium container 21. The downstream end of the heat transfer tube 23 penetrates the bottom plate 211 and is connected to the gas line 67. The gas line 67 is provided with a pressure control valve 671.

The fuel gas vaporized in the heat transfer pipe 23 is sent to the fuel storage tank 1 through the gas line 67. In the gas line 67, the gas pressure is pressurized, for example, to 0.75 MPaG. This pressurized pressure is the pressure for supplying LNG from the fuel storage tank 1 and is a gas fuel supply pressure source necessary for the marine gas engine 5 (diesel engine) which is an internal combustion engine.

The buffer tank 3 is a sealed container for containing the vaporized natural gas. The buffer tank 3 is used to absorb load fluctuation of the consumption gas amount of the combustion apparatus 5 (gas engine 5 for ships) of the latter stage with respect to the natural gas fed in through the gas line 64. For example, when the combustion apparatus is an internal combustion engine, the configuration in which natural gas is stored by the buffer tank 3 is effective in absorbing load fluctuations. A gas line 65 is connected to the buffer tank 3. The gas line 65 is provided with a pressure control valve 651. In the pressure control valve 651, the natural gas flowing through the gas line 65 is depressurized to a pressure suitable for consumption by the ship gas engine 5 in the subsequent stage.

The natural gas passed through the gas line 65 is supplied to the marine gas engine 5. The marine vessel gas engine 5 is, for example, a dual fuel engine (a dual fuel diesel engine), and is switched on from liquid fuel mode to gas fuel mode after being activated by liquid fuel such as heavy oil, and gas fuel is supplied. . The gas fuel supplied to the marine vessel gas engine 5 is burned through the governor 51 (speed governor) with a consumption amount corresponding to the output of the marine vessel gas engine 5.

The marine vessel gas engine 5 is cooled while circulating engine cooling water by the cooling water pump 681 or the engine driven pump 682 (driven by the engine 5) all the time during operation. The engine cooling water circulates in a temperature range of 55 to 90 ° C. while repeating exhaust heat recovery and cooling in a steady operation state. The engine cooling water leaving the marine vessel gas engine 5 is introduced into the heat recovery unit 4 while the temperature is detected by the cooling water temperature detection unit 683 through the cooling water circulation line 68.

The heat recovery unit 4 is for recovering the exhaust heat of the marine gas engine 5 with water (liquid heat medium). In the present embodiment, the heat recovery unit 4 is configured by an indirect heat exchanger. In the heat recovery unit 4, the water (liquid heat medium) discharged from the vaporizer 2 and flowing through the heat medium circulation line 63 and the engine cooling water flowing through the cooling water circulation line 68 are subjected to heat exchange. Exhaust heat is recovered to water (liquid heat carrier).

The engine cooling water removed by the heat recovery unit 4 is further cooled by seawater by the cooler 684 and mixed with part of the engine cooling water flowing through the cooling water bypass line 686 while being controlled by the cooling temperature control valve 685. Then, the pressure is raised again by the cooling water pump 681 or the engine driven pump 682 and supplied to the marine gas engine 5.

Next, a method of controlling the temperature of the heat medium circulating between the vaporizer 2 and the heat recovery unit 4 when the liquefied fuel gas vaporization system X1 is in operation will be described.

The heat medium discharged from the vaporizer 2 and flowing through the heat medium circulation line 63 has a relatively low temperature due to heat exchange with the LNG or vaporized natural gas in the heat transfer tube 22 in the vaporizer 2. The heat medium flowing through the heat medium circulation line 63 recovers the exhaust heat of the marine gas engine 5 by passing through the heat recovery unit 4 and is temporarily stored in the temperature maintenance chamber 623 after the heat medium temperature rises. Ru. Here, the heat medium temperature in the temperature maintenance chamber 623 is detected by the heat medium temperature detection unit 622, and a part of the heat medium flowing through the heat medium circulation line 63 is a bypass line so that the heat medium temperature becomes a constant temperature. The flow rate is adjusted by the temperature control unit 72 via the point 71 and mixed with the heat medium in the heat medium circulation line 62. In this way, a heat medium having a substantially constant temperature (hereinafter referred to as "basic temperature heat medium" as appropriate) is produced. In the present embodiment, the heat medium stored in the temperature maintenance chamber 623 is the basic temperature heat medium. The temperature of the basic temperature heat transfer medium is set to a predetermined temperature, for example, in a temperature range of 25 to 60.degree.

The basic temperature heat transfer medium that has reached a constant temperature using the temperature control unit 72 is pressurized by the circulation pump 621 and flows toward the vaporizer 2. In the vicinity of the inlet of the vaporizer 2, the basic temperature heat transfer medium flowing at a constant temperature is divided into two flow paths by the flow rate control valve 624, one flows into the vaporizer 2, and the other passes the vaporizer 2. Instead, it flows to the bypass line 73 to adjust the heating amount of the vaporizer 2. The distribution of the basic temperature heat medium is adjusted so that the temperature of the fuel gas discharged from the vaporizer 2 becomes a predetermined target temperature (for example, 30 ° C., 32 ° C., or 35 ° C.). For example, in the case of a carburetor 2 having an output of 1,200 kw for the marine gas engine 5 and a vaporization capacity of about 400 kg / h for the supply of natural gas, the engine load is at least 15 m ³ / h when the engine load is 100%. It is appropriate to flow the basic temperature heat transfer medium to the vaporizer 2.

On the other hand, the flow rate of the LNG flowing from the fuel storage tank 1 to the carburetor 2 (heat transfer pipe 22) is determined by the consumption of the gas fuel in the marine gas engine 5. When there is a load fluctuation of the marine gas engine 5, the gas fuel consumption also fluctuates correspondingly.

In the heat transfer tube 22, for example, when the pressure is 0.7 MPaG, about -130 ° C. of LNG is vaporized and then heated to a temperature range of 15 to 50 ° C., preferably 20 to 45 ° C. . In the present embodiment, the temperature of the natural gas discharged from the vaporizer 2 is detected by the gas temperature detection unit 641 in the vicinity of the vaporizer 2. Then, the detected temperature of the natural gas discharged from the vaporizer 2 becomes the target temperature within the temperature range of the fuel gas (for example, 25 ± 5 ° C. to 40 ± 5 ° C.) suitable to be supplied to the marine gas engine 5 Thus, the flow rate of the heat medium supplied to the vaporizer 2 via the heat medium circulation line 62 is controlled.

Next, with reference to FIG. 2, the change characteristic of the gas fuel consumption with respect to the operation time of the gas engine 5 for ships will be described. First, after the ship gas engine 5 (two-fueled diesel engine) is started and operated in the liquid fuel mode, the liquid fuel mode is changed to the gas fuel mode to shift to the operation of the gas engine. At that time, the gas fuel consumption switches from 0 to 100% in about 30 seconds as shown by the rising line at the left end of FIG. By this switching, the engine cooling water is already circulated in the cooling water circulation line 68 in the liquid fuel mode, and from the state cooled by the seawater by the cooler 684, the heat recovery unit 4 changes to a state where the heat medium recovers the exhaust heat. . The function of exhaust heat recovery by the heat recovery unit 4 is that the heat medium corresponding to the heat of vaporization of the liquefied natural gas is deprived of more heat from the heat medium as the gas fuel consumption increases, and the heat medium returned from the vaporizer 2 As the temperature starts to fall, it automatically changes to the state of recovering more exhaust heat from the engine coolant.

Here, in order to keep the temperature of the heat medium whose exhaust heat has been recovered by the heat recovery unit 4 constant, the temperature of the heat medium is measured in the temperature maintenance chamber 623, and the first bypass line is adjusted by the temperature control unit 72. The heat medium temperature is set to 25 ° C. by increasing or decreasing the amount of the heat medium mixed with the heat medium heated by the heat recovery unit 4 among the cooled heat medium returned from the vaporizer 2 through 72. Maintain at any set temperature in the temperature range of -60 ° C.

In addition, when the gas fuel consumption increases, the temperature of the natural gas discharged from the vaporizer 2 is detected by the gas temperature detection unit 641, and the flow control valve 624 controls the flow rate of the heat medium supplied to the vaporizer 2. Operate to increase.

Contrary to the above-mentioned operation in which the gas fuel consumption (engine load) rises to 100%, when the engine load decreases and the gas fuel consumption of the gas engine decreases, 100% gas fuel consumption as shown in FIG. 2 The amount may drop to a minimum of 19% gas fuel consumption (equivalent to 15% for engine load) as engine load decreases. At this time, in the liquefied fuel gas vaporization system X1, since the temperature control unit 72 always operates to make the basic temperature heat medium, the temperature of the basic temperature heat medium is reduced even if the amount of consumption of vaporization heat of LNG decreases. There is no change. Therefore, even if the gas fuel consumption decreases, the temperature of the natural gas discharged from the vaporizer 2 does not become higher than the temperature of the basic temperature heat medium, so even if the control of the flow control valve 624 becomes faulty. It is safe. The same control is performed even when the gas engine (gas engine for ships 5) switches from the gas fuel mode to the liquid fuel mode and the ship enters a halted state. As described above, when the liquefied fuel gas vaporization system X1 is operated, an operation to keep the temperature of the natural gas discharged from the vaporizer 2 always at the target temperature required by the gas engine is executed.

The vaporizer 2 has a structure in which a heat transfer tube 22 in the form of a coil is immersed in a heat medium container 21 accommodating a heat medium. The heat medium flowing from the lower part of the heat medium container 21 ascends while circulating along the inner wall of the heat medium container 21 and passes through the overflow pipe 24 penetrating the center from the upper part of the heat medium container 21 to circulate the external heat medium. Flow into line 63. Since the size of the vaporizer 2 is fixed no matter how the load of the gas fuel consumption, ie, the amount of vaporized gas, fluctuates, the total heat transfer area formed by the heat transfer tubes 22 in the heat medium container 21 is constant. It is. Therefore, when the gas fuel consumption decreases, the amount of vaporized natural gas delivered from the heat transfer pipe 22 to the engine 5 decreases (that is, the amount of vaporized natural gas remaining in the heat transfer pipe 22 increases). The heat transfer area of (the region where LNG and vaporized natural gas are mixed) decreases, and the heat transfer area of the gas heating portion (region where only the vaporized natural gas is present) increases. On the other hand, the temperature (basic heat medium temperature) of the heat medium supplied to the vaporizer 2 (heat medium container 21) is constant regardless of the gas fuel consumption. Therefore, when the load of gas fuel consumption decreases, the degree of temperature drop of the heat medium due to cooling in the vaporizer 2 becomes smaller, and the temperature difference between the heat medium and the fuel gas through the heat transfer tube 22 becomes large. The heat advances and the temperature of the fuel gas discharged from the carburetor 2 rises. On the other hand, when the gas fuel consumption increases, the heat transfer area of the evaporation unit increases and the heat transfer area of the gas heating unit decreases. At the same time, the degree of temperature drop of the heat medium is increased, the temperature difference between the heat medium and the natural gas through the heat transfer tube 22 is reduced, the heat transfer is delayed, and the temperature of the natural gas discharged from the vaporizer 2 is decreased. Do. The present invention has been made by focusing on such characteristics of the carburetor 2 of a fixed capacity when the gas fuel consumption fluctuates.

Next, with reference to FIG. 3, the change characteristic of the temperature of the natural gas discharged from the vaporizer 2 with respect to the gas fuel consumption will be described. FIG. 3 shows that the gasification capacity of LNG in the vaporizer 2 is about 400 kg / h, and the temperature of the basic temperature heat medium supplied to the vaporizer 2 can be adapted to the marine gas engine 5 with an output of 1,200 kw. In the case of 40 ° C., it represents the temperature change of the natural gas discharged from the vaporizer 2 with respect to the gas fuel consumption. FIG. 3 shows four examples in the case where the circulation flow rate of the basic temperature heat medium supplied to the vaporizer 2 is different, and each curve shows that the flow rate control valve 624 vaporizes the basic temperature heat medium having a constant flow rate. When supplied to 2, it represents how the temperature of the natural gas discharged from the vaporizer 2 changes with respect to the gas fuel consumption which changes with the load fluctuation of the gas engine. In FIG. 3, the four curves show that the basic temperature heat medium to the vaporizer 2 has a circulation flow rate of 20 m ³ / h, 10 m ³ / h, 5 m ³ / h and 3 m ³ / h. Respectively. The load of the gas engine is usually 15% when the maximum load factor is 100%, and the corresponding load factor of the gas fuel consumption is 19% when the maximum load factor is 100%. Therefore, if the maximum gas fuel consumption is about 400 kg / h, the minimum is about 76 kg / h.

First, when the basic temperature heat medium having a temperature of 40 ° C. is flowed to the vaporizer 2 at a flow rate of 20 m ³ / h as one example shown in FIG. The temperature of the fuel gas discharged from the carburetor 2 approaches 40 ° C., which is almost the same as the water temperature. However, when the amount of gas fuel consumption increases and the amount of vaporized gas increases, the temperature of the natural gas discharged from the vaporizer 2 falls to 27 ° C. at the maximum fuel load ratio of 100%. As another example, when the basic temperature heat medium having a temperature of 40 ° C. is flowed to the vaporizer 2 at a flow rate of ³ m ³ / h, the gas fuel consumption is the smallest (fuel load rate 19%, engine load rate 15% ), The temperature of the natural gas discharged from the vaporizer 2 is 37.degree. However, as the amount of gas fuel consumption increases, the temperature of the natural gas discharged from the vaporizer 2 drops rapidly.

Therefore, when it is desired to set the target value of the gas fuel temperature of the gas engine to 32 ° C., first, the temperature control unit 72 adjusts the temperature of the base temperature heat medium to 40 ° C. and supplies the base temperature heat medium to the vaporizer 2. Thereafter, as the gas fuel consumption increases as the gas engine load increases, the temperature of the natural gas discharged from the carburetor 2 falls. Then, the gas temperature detection unit 641 detects the temperature drop of the natural gas, and the flow rate control valve 624 increases the flow rate of the basic temperature heat medium supplied to the vaporizer 2. For example, when the basic temperature heat medium is flowed to the vaporizer 2 at a flow rate of 20 m ³ / h, the flow rate of the heat medium in the vaporizer 2 (heat medium container 21) rises immediately, and the natural gas discharged from the vaporizer 2 The temperature is 27.degree. As described above, the temperature change of the natural gas fuel produced by changing the flow rate of the heat medium supplied to the vaporizer 2 is excellent in responsiveness.

In addition, when the gas fuel consumption decreases, the temperature of the natural gas discharged from the vaporizer 2 rises, but does not exceed 40 ° C. Then, when the fuel load rate decreases to 19% and the heat medium flow rate reaches 3 m ³ / h, the temperature of the natural gas discharged from the vaporizer 2 settles at 37 ° C. As a result, the target value 32 ° C. ± 5 ° C. of the gas fuel temperature is achieved.

Although the embodiment of the present invention has been described above, the scope of the present invention is not limited to the above-described embodiment, and all modifications within the scope described in each claim are all included in the scope of the present invention. Be done.

The structure of the vaporizer is not limited to the water tank type vaporizer described in FIG. 1, and any structure can be adopted as long as the vaporizer can circulate the heat medium to vaporize the liquefied fuel gas. You may

Further, the mounting position and the configuration of the flow control valve for controlling the flow rate of the heat medium supplied to the vaporizer 2 are not limited to the configuration and the mounting position of the flow control valve 624 shown in FIG. If the flow rate of the heat medium supplied to the vaporizer 2 is adjusted in the vicinity of the vaporizer 2, even if it is performed on the upstream side (heat medium circulation line 62 side) of the vaporizer 2, the downstream side (heat medium circulation line) 63).

4 to 6 illustrate variations of attachment of the flow control valve for adjusting the flow rate of the heat medium supplied to the vaporizer 2. In FIG. 4, a flow control valve 625 is provided on the downstream side of the vaporizer 2. The flow control valve 625 is provided in the heat medium circulation line 63 (low temperature side line) and includes a three-way valve. The flow control valve 625 is connected to a bypass line 74 branched from the heat medium circulation line 62 (high temperature side line). The bypass line 74 is drawn from the temperature maintenance chamber 623 and mixes a part of the heat medium flowing in the heat medium circulation line 62 with the heat medium circulation line 63 (low temperature side line) without passing through the vaporizer 2. It is a flow path. The flow rate adjustment valve 625 adjusts the flow rate of the heat medium supplied to the vaporizer 2 based on the temperature of the natural gas detected by the gas temperature detection unit 641.

In FIG. 5, a flow control valve 626 is provided in the heat medium circulation line 62 (high temperature side line). In the example shown in FIG. 5, the flow control valve 626 includes a two-way valve instead of the three-way valve. Although a pressure loss can be reduced by using a three-way valve, the flow rate of water supplied to the vaporizer 2 may be adjusted by changing the opening degree directly by using a flow control valve 626 which is a two-way valve.

In FIG. 6, a flow control valve 627 which is a two-way valve is provided in a bypass line 75 branched from the heat medium circulation line 62. One end of the bypass line 75 is connected to the heat medium circulation line 62, and the other end is connected to the heat medium circulation line 63. The bypass line 75 is a flow path for mixing a part of the heat medium flowing in the heat medium circulation line 62 with the heat medium circulation line 63 (low temperature side line) without passing through the vaporizer 2. In the configuration shown in FIG. 6, the flow rate of the heat medium supplied to the vaporizer 2 is adjusted by changing the opening degree of the flow rate control valve 627 (two-way valve) provided in the bypass line 75.

X1 liquefied fuel gas vaporization system 1 fuel storage tank 2 vaporizer 21 heat medium container 211 bottom plate 212 container body 22 heat transfer tube 23 heat transfer tube 24 overflow tube 3 buffer tank 4 heat recovery unit 5 marine gas engine 51 governor 61 fuel supply line 611 shut off Valve 612 Gas extraction line 613 Shut-off valve 62 Heat medium circulation line (high temperature side line)
621 Circulation pump 622 Heat medium temperature detection unit 623 Temperature maintenance chamber 624 Flow control valve (Flow control unit, flow control three-way valve)
625 Flow control valve (flow control unit)
626 Flow control valve (flow control unit)
627 Flow control valve (flow control unit)
63 Heat medium circulation line (low temperature side line)
64 gas line 641 gas temperature detection unit 65 gas line 651 pressure control valve 66 fuel supply line 66 shutoff valve 67 gas line 671 pressure control valve 68 cooling water circulation line 681 cooling water pump 682 engine driven pump 683 cooling water temperature detection unit 684 cooler 685 Cooling control valve 686 Cooling water bypass line 71 Bypass line (1st bypass line)
72 Temperature control unit 73 bypass line (second bypass line)
74 Bypass line (second bypass line)
75 bypass line (second bypass line)

Claims

A liquefied fuel gas vaporization system for vaporizing liquefied fuel gas and supplying it to a combustion device, comprising:
A vaporizer that vaporizes liquefied fuel gas by heating it with a liquid heat medium;
A heat recovery unit that recovers the exhaust heat of the combustion apparatus with the liquid heat medium;
A heat medium circulation line for circulating the liquid heat medium between the heat recovery unit and the vaporizer;
A mixing unit provided in the heat medium circulation line for mixing the liquid heat medium that has passed through the heat recovery unit and the liquid heat medium that has been discharged from the vaporizer and has not passed through the heat recovery unit ,
A liquefied fuel gas vaporization system comprising: a flow rate control unit which controls the flow rate of the liquid heat medium supplied to the vaporizer.
And a gas temperature detection unit for detecting the temperature of the fuel gas discharged from the vaporizer.
The liquefied fuel gas vaporization according to claim 1, wherein the flow rate adjustment unit adjusts the flow rate of the liquid heat medium supplied to the vaporizer based on the temperature of the fuel gas detected by the gas temperature detection unit. system.
The heat medium circulation line is a relatively high temperature which has passed through the heat recovery unit, a low temperature side line for sending the liquid heat medium which is relatively low temperature discharged from the vaporizer to the heat recovery unit, and the heat recovery unit. A high temperature side line for sending the above liquid heat medium to the above vaporizer;
The liquefied fuel gas vaporization system according to claim 1 or 2, wherein the mixing unit includes a first bypass line having one end connected to the low temperature side line and the other end connected to the high temperature side line.
A heat medium temperature detection unit provided downstream of the connection point with the first bypass line in the high temperature side line and detecting the temperature of the liquid heat medium;
The flow rate of the liquid heat medium, which passes through the first bypass line and is mixed with the high temperature side line, is adjusted so that the temperature of the liquid heat medium detected by the heat medium temperature detection unit falls within a predetermined range. The liquefied fuel gas vaporization system according to claim 3, further comprising: a temperature control unit.
The flow rate adjusting unit is provided in the high temperature side line, and a flow rate adjusting three-way valve that adjusts the flow rate of the liquid heat medium supplied to the vaporizer;
The liquefied fuel gas vaporization system according to claim 3 or 4 including the 2nd bypass line by which one end was connected to said flow control three way valve, and the other end was connected to said low temperature side line.
And a temperature maintaining chamber provided between the mixing unit and the flow rate control unit in the high temperature side line,
The liquefied fuel gas vaporization system according to any one of claims 3 to 5, wherein the heat medium temperature detection unit is provided in the temperature maintenance chamber.
The liquefied fuel gas vaporization system according to any one of claims 1 to 6, wherein the combustion device is a dual fuel engine for ships.
The heat recovery unit further includes a heat exchanger provided between the low temperature side line and the high temperature side line, and in the heat exchanger, the cooling water from the combustion device and the heat flowing through the low temperature side line The liquefied fuel gas vaporization system according to any one of claims 3 to 7, which is configured to perform heat exchange with the medium.
The liquefied fuel gas vaporization system according to any one of claims 1 to 8, wherein the fuel gas is natural gas.
The liquefied fuel gas vaporization system according to any one of claims 1 to 9, wherein the heat medium is water.
In a liquefied fuel gas vaporization system for vaporizing liquefied fuel gas and supplying it to a combustion device,
The liquid heat medium is circulated between a vaporizer that heats and vaporizes liquefied fuel gas with a liquid heat medium, and a heat recovery unit that recovers the exhaust heat of the combustion apparatus,
The liquid heat medium discharged from the vaporizer and not passing through the heat recovery unit is mixed with the liquid heat medium passed through the heat recovery unit, and the temperature of the liquid heat medium after mixing is predetermined A liquid heat medium temperature control step of controlling to be within the range;
A fuel gas temperature control step of adjusting the flow rate of the liquid heat medium supplied to the vaporizer and controlling the temperature of the fuel gas discharged from the vaporizer to be within a predetermined range; Method of temperature control of gas vaporization system.
The liquid heat medium temperature control method according to claim 11, wherein the fuel gas is a natural gas, and the heat medium is water.
The above liquefied fuel gas vaporization system
The liquid heat medium having a relatively high temperature which has passed through the heat recovery unit and the low temperature side line for sending the liquid heat medium having a relatively low temperature discharged from the vaporizer to the heat recovery unit A heat medium circulation line including a high temperature side line for sending to the vaporizer;
A bypass line having one end connected to the low temperature side line and the other end connected to the high temperature side line;
A gas temperature detection unit that detects the temperature of the fuel gas discharged from the vaporizer;
A temperature control unit which maintains the temperature of the liquid heat medium at a substantially constant temperature within a predetermined range by adjusting the flow rate of the liquid heat medium supplied to the high temperature side line through the bypass line;
A flow rate control unit for controlling the flow rate of the liquid heat medium supplied to the vaporizer through the high temperature side line;
The flow rate adjustment unit is configured to supply the liquid heat medium to the vaporizer through the high temperature side line such that the temperature of the fuel gas detected by the gas temperature detection unit is maintained within a predetermined range. The liquid heat medium temperature control method according to claim 11, wherein the flow rate is adjusted.
The flow rate adjusting unit adjusts the flow rate of the liquid heat medium supplied to the vaporizer through the high temperature side line so as to be within 15 to 50 ° C., which is ± 5 ° C. from the target temperature of the fuel gas. The liquid heat medium temperature control method according to claim 13.