KR200436336Y1 - Pressure control system for dual fuel engine of a ship for transporting liquefied gas - Google Patents

Abstract

The present invention is installed on a ship carrying LNG (liquefied natural gas) and the heavy oil that is the main fuel of the vessel and the boil-off gas (BOG) and liquefied gas forcibly evaporated from the storage tank of the liquefied gas In dual fuel engine (DDF) engine, which can be used as fuel for engine, the pressure of fuel supplied to DF engine by installing buffer tank on pipe to supply BOG and evaporative gas to DF engine Can be adjusted to within the range of 5.1 ± 0.2 bar, which is most suitable for combustion, to ensure more stable engine operation during operation of gas transport vessels, while at the same time avoiding waste of energy and engine defects caused by engine operation. It relates to a pressure compensation system for dual fuel engines in gas carriers that can be minimized.

To this end, the present invention, the supply pump 4 of the liquefied gas (2) is installed in the storage tank (1) in which LNG (liquefied natural gas) is stored, the supply line (extended from the supply pump 4 ( 5) is connected to the gas heater 15 via the forced evaporator (8), discharge line 12 extending from the BOG (Boil-off gas) tank (3) provided on the upper end of the storage tank (1) The two stage low capacity compressor 13 is connected to the gas heater 15 together with the supply line 5, and the fuel discharged from the gas heater 15 is supplied to the fuel supply line 18 and the fuel distribution line ( In a system configured to be supplied to a dual fuel (DF) engine 22 for a gas carrier via a gas heater 15, a gas heater 15 is disposed between the fuel supply line 18 and the fuel distribution line 24. Buffer tank (19) is installed to adjust the pressure of the discharged fuel within the range of 5.1 ± 0.2 bar constant It is done.

LNG, gas carriers, dual fuel engines, buffer tanks

Description

Pressure control system for dual fuel engine of a ship for transporting liquefied gas}

1 is a piping diagram showing a conventional fuel supply system installed on a gas carrier.

2 is a piping diagram showing a pressure compensation system for a double fuel engine of a gas carrier according to the present invention.

Figure 3 is a side cross-sectional view showing an embodiment of a buffer tank applied to the present invention.

<Explanation of symbols for main parts of drawing>

1: storage tank 2: liquefied gas 3: BOG tank

4: supply pump 5: supply line 5a, 16: return line

5b, 16a: Return valve 6: Supply valve 7: Auxiliary supply line

7a: auxiliary supply valve 8: forced evaporator 9: mixer

10: Demister 11: Temperature sensor 12: Discharge line

13: 2-stage low capacity compressor 14: Main valve 15: Gas heater

17: machine room 18: fuel supply line 19: buffer tank

19a: casing 19b: screen 19c: pressure control plate

19d: Constant pressure chamber 21: Engine chamber 22: DF engine

23: combustor 24: fuel distribution line 25: on-off valve

26 pressure gauge 27 bypass line 27a bypass valve

The present invention is installed on a ship carrying LNG (liquefied natural gas) and the heavy oil that is the main fuel of the vessel and the boil-off gas (BOG) and liquefied gas forcibly evaporated from the storage tank of the liquefied gas In dual fuel engine (DDF) engine, which can be used as fuel for engine, the pressure of fuel supplied to DF engine by installing buffer tank on pipe to supply BOG and evaporative gas to DF engine Can be adjusted to within the range of 5.1 ± 0.2 bar, which is most suitable for combustion, to ensure more stable engine operation during operation of gas transport vessels, while at the same time avoiding waste of energy and engine defects caused by engine operation. It relates to a pressure compensation system for dual fuel engines in gas carriers that can be minimized.

In general, storage tanks provided in gas carriers carrying LNG (liquefied natural gas) generally have an amount of approximately 0.1% to 3% per day regardless of the shape of the storage tank such as Moss type or main brain type. LNG is evaporated as a result of the inflow of external heat through the insulator surrounding the storage tank, and when the amount of LNG boil-off gas (BOG) increases, the pressure inside the storage tank increases, which is dangerous such as an explosion of the tank. Will result.

As described above, in the case of volatile gas generated in the LNG storage tank, it has been used as an auxiliary fuel source for generating power by a boiler or a generator of a ship, but in recent years, the design of an LNG carrier has a turbine according to steam driving. Since diesel engines are being used rather than engines, a reliquefaction system that recovers volatile gas generated in the storage tank, reliquefyes it into LNG, and sends it back to the storage tank, is mainly applied to a gas transportation vessel.

However, such a reliquefaction system has not only had an unreasonable problem that the expense of the equipment and operation of the reliquefaction system including the nitrogen cooling device is much greater than the advantage of the reliquefaction of the LNG volatile gas, as well as this point of view In recent years, DF engines have been able to alternately use boil-off gas, which has been forcibly evaporated from liquefied gas and liquefied gas from LNG storage tanks, as fuel for engines along with heavy oil as the main fuel of diesel ships. With the development of fuel engines, the fueling of LNG volatile gas and its boil-off gas is emerging again.

As described above, a conventional fuel supply system for using LNG volatile gas and its boil-off gas as fuel of a ship engine is provided on the upper side of the LNG cargo tank 20 to store volatile gas as shown in FIG. 1. The pipe extending from the gas dome 30 to be driven by the constant speed motor 40 passes through the first and / or second low duty compressors 50 and 180 and the gas heater 60. It is connected to the boiler 90 of the chamber 80, a check valve 170 for preventing the backflow of the boil-off gas is installed between the first low capacity compressor 50 and the gas heater 60.

At the same time, the pipe which is mounted at the bottom of the cargo tank 20 and extends from the strip spray pump 100 for supplying LNG passes through a forced vaporizer as a vaporizer 150 and the gas heater ( Connected to the pipe extending from the 60 and then connected to the boiler 90 of the engine compartment 80, and thus, each pipe extending from the gas heater 60 and the vaporizer 150 is connected to one pipe The main valve 70 is provided in the portion extending to the engine chamber 80.

In addition, on the pipe extending from the strip spray pump 100, the recovery line for recovering the remaining LNG passing through the flow control valve 120 of the pumped LNG to the cargo tank 20 via the pressure control valve 110. 130 is installed, and after the vaporizer 150, another pipe extending from the flow control valve 120 with the temperature control valve 140 is connected to mix the liquid LNG with its boil-off gas. Mixer 160 is configured for the configuration (see Korean Patent Publication No. 2003-73975).

However, when the conventional fuel supply system having the above configuration is applied to the fuel supply system for the DF engine, the compressors 50 and 180 of the volatile gas and the vaporizer 150 as the forced evaporator are parallel to supply the fuel. Under conditions of operation of the LNG carrier, unstable low load operation of the compressors 50 and 180 and the vaporizer 150, or evaporation from the vaporizer 150 and the volatile gas supplied from the compressors 50 and 180. Due to various factors such as the pressure of the gas causing irregular interference, it is difficult to keep the pressure of the fuel supplied to the DF engine at a constant level.

In other words, in the case of supplying heavy oil, which is an incompressible fluid having a relatively high viscosity through a DF engine, the pressure of the fuel injected into the cylinder can be easily maintained within the most suitable range for combustion, but LNG volatile gas or its In the case of injecting a compressive fluid such as boil-off gas into the fuel, various conditions such as unstable low load operation of the compressors 50, 180 and the vaporizer 150, or supply pressures of volatile gas and boil-off gas may interfere with each other. Because of the factors, it is often the case that the pressure of the fuel injected into the cylinder is momentarily out of the range of 5.1 ± 0.2 bar, which is best suited for combustion.

As described above, when the pressure of the fuel injected into the cylinder of the DF engine is greatly out of the range of 5.1 ± 0.2 bar, and the deviation according to the supply pressure of the fuel is large, the fuel injected into the cylinder does not combust properly in the combustion chamber. According to the present invention, there was a problem that caused the normal operation of the engine and stable operation of the ship, and irregularities in various fuel injection systems, fuel injection systems, and fuel ignition systems provided in the DF engine due to the large variation in the supply pressure of the fuel. There was a problem that the engine load is easily generated while the phosphorus load is applied.

In addition, due to the incombustible combustion of fuel or incomplete combustion due to over-injection of fuel frequently inside the cylinder, LNG volatilization and its boil-off gas are more efficiently fueled to prevent waste of energy. This caused a problem, and thus, there was a problem in that the practicality and economical efficiency were deteriorated even when compared with a conventional reliquefaction system which recovers LNG volatile gas and reliquefies it into LNG.

The present invention was devised to solve the above conventional problems, the pressure compensation system for a double fuel engine of the gas carrier ship according to the present invention by installing a buffer tank on the pipe for supplying BOG and boil-off gas to the DF engine By adjusting the pressure of the fuel supplied to the DF engine within the range of 5.1 ± 0.2 bar, which is most suitable for combustion, it is possible to ensure more stable engine operation during operation of the gas carrier ship and to maintain the engine operation. The technical challenge is to minimize the waste of energy and engine failure.

The present invention for achieving the above technical problem, the supply pump of liquefied gas is installed in the storage tank in which the LNG is stored, the supply line extending from the supply pump is connected to the gas heater via a forced evaporator, A discharge line extending from the BOG (Boil-off gas) tank provided in the upper end of the storage tank is connected to the gas heater with the supply line through a two-stage low capacity compressor, the fuel discharged from the gas heater is supplied with fuel In a system configured to supply a dual fuel (DF) engine for a gas carrier via a line and a fuel distribution line, the pressure of the fuel discharged from the gas heater is 5.1 ± 0.2 between the fuel supply line and the fuel distribution line. It is characterized in that a buffer tank (Buffer tank) for constant adjustment within the range of the bar, the buffer tank is connected to the fuel supply line A screen for removing foreign matter from one side of the casing, and a plurality of pressure adjusting plates arranged in a zigzag form at regular intervals are sequentially inserted along the inner space of the casing.

Hereinafter, with reference to the accompanying drawings, the present invention for achieving the above object will be described in detail.

2 is a piping diagram showing a pressure compensation system for a double fuel engine of a gas carrier according to the present invention, Figure 3 is a side cross-sectional view showing an embodiment of a buffer tank applied to the present invention.

In the pressure compensation system for a dual fuel engine of a gas carrier according to the present invention, as shown in FIG. 2, a supply pump 4 of liquefied gas 2 is installed inside a storage tank 1 in which LNG is stored. The supply line 5 extending from the supply pump 4 is connected to the gas heater 15 via the forced evaporator 8, and is provided with an BOG (Boil-off gas) provided at an upper end of the storage tank 1. A discharge line 12 extending from the tank 3 is connected to the gas heater 15 together with the supply line 5 via a two-stage low capacity compressor 13.

Then, on the supply line (5) extending from the supply pump (4) is supplied to the forced evaporator (8) via a supply valve (6) as a flow control valve to return the remaining LNG to the storage tank (1) A return line 5a provided with a valve 5b is installed, and a mixer 9 and a boil-off gas for mixing LNG boil-off gas with liquid LNG on a supply line 5 extending through the forced evaporator 8. Demisters 10 for removing the liquid droplets contained therein are respectively provided.

As described above, in order to reduce the load on the forced evaporator 8 by mixing the LNG boil-off gas with the liquid LNG in the mixer 9 to further evaporate the liquid LNG, the supply line corresponding to the transfer of the supply valve 6. Auxiliary supply line (7) is branched from (5) and connected to the mixer (9), and is input from the temperature sensor 11 of the boil-off gas supplied through the demister (10) on the auxiliary supply line (7) An auxiliary supply valve 7a for controlling the opening and closing of the auxiliary supply line 7 by a signal is provided.

In addition, on the discharge line 12 extending from the BOG tank 3, a mixer 9 for mixing LNG volatile gas with liquid LNG and a demister for removing liquid particles contained in the volatile gas ( 10 are respectively installed, and the auxiliary supply line 7 branched from the supply line 5 corresponding to the transfer of the supply valve 6 is connected to the mixer 9 installed on the discharge line 12. The auxiliary supply valve 7a controls the opening and closing of the auxiliary supply line 7 by a signal input from the temperature sensor 11 of the volatile gas supplied through the demister 10 on the auxiliary supply line 7. Is installed.

In addition, from the discharge line 12 extending through the two-stage low capacity compressor 13 to the gas heater 15 side, the gas passes through the main valve 14 serving as a flow control valve installed immediately before the gas heater 15. Bypass line 27 having a bypass valve 27a for discharging the remaining volatile gas supplied to the heater 15 to the discharge line 12 corresponding to the BOG tank 3 and the mixer 9. ) Is branched and the gas fuel return line 16 having a return valve 16a from the fuel supply line 18 extending from the machine chamber 17 to the engine chamber 21 via the gas heater 15. This branch is connected to the front pipe line of the main valve 14.

The overall fuel supply system having the above configuration is almost the same in context as the conventional fuel supply system shown in FIG. 1, and the only difference is that the fuel supply system according to the present invention has a two-stage low capacity compressor 13. The discharge line 12 extending from) is not connected to the supply line 5 after passing through the gas heater 15, but the discharge line 12 through the two-stage low capacity compressor 13 is connected to the forced evaporator 8. Firstly connected to the coarse supply line (5), and then connected to the pipe line is connected to the gas heater (15).

As described above, the discharge line 12 through the two-stage low capacity compressor 13 and the supply line 5 through the forced evaporator 8 are first connected to the gas heater 15 before the DF engine 22. Control the temperature of the gas fuel to be supplied to the combustion chamber of the) and at the same time, the gas heater 15 performs a function of adjusting the supply pressure of the fuel together with the buffer tank 19 forming the main part of the present invention. In order to be able to control the temperature and supply pressure of the gas fuel more effectively.

And, the buffer tank (19) forming the main portion of the pressure compensation system according to the present invention is the fuel discharged from the gas heater 15 through the fuel supply line 18 and the fuel distribution line 24 gas carrier ship In order to be supplied to the dual fuel (DF) engine 22 or the combustor 23 of a boiler, it is installed between the fuel supply line 18 and the fuel distribution line 24, and the gas heater 15 The pressure of the fuel discharged from) is adjusted to be constant within the range of 5.1 ± 0.2 bar, and each of the volatile gas discharge line 12, the boil-off gas supply line 5 and the fuel distribution line 24 The pressure gauge 26 is provided so that the pressure of the gas passing through the line can be displayed to the outside.

That is, the low load operation of the two-stage low capacity compressor 13 or the forced evaporator 8 under the condition that the two-stage low capacity compressor 13 and the forced evaporator 8 are operated in parallel to set the supply pressure of the fuel first. Situations such as the supply pressures of the volatile gas and the boil-off gas flowing through the discharge line 12 extending from the two-stage low capacity compressor 13 and the supply line 5 extending from the forced evaporator 8 are different from each other. Due to the factor, when the pressure of the gas fuel discharged from the gas heater 15 is momentarily largely out of the range of 5.1 ± 0.2 bar which is most suitable for combustion, this pressure deviation is alleviated inside the buffer tank 19 to distribute the fuel. The pressure of the fuel supplied to line 24 will be adjusted to a range of 5.1 ± 0.2 bar that is most suitable for combustion.

If it is possible to achieve the above function, the buffer tank 19 can be used in a variety of structures, but a representative example thereof, as shown in Figure 3, the casing (19a) to which the fuel supply line 18 is connected. Screen 19b for removing foreign matter from one side (left side in the drawing) and a plurality of pressure adjusting plates 19c arranged in a zigzag form at regular intervals are sequentially inserted along the inner space of the casing 19a. The inner space on the other side (right side in the drawing) of the casing 19a to which the fuel distribution line 24 is connected is to form a static pressure chamber 19d.

The combustor 23 installed together with the DF engine 22 is installed in a boiler for supplying steam for the operation of the forced evaporator 8 or for heating or supplying hot water for the life of the crew aboard the ship. It is connected in parallel with the DF engine 22 by the fuel distribution line 24, the fuel distribution line 24 on the combustor 23 side is provided with an on-off valve 25 for the selective supply of gas fuel, The on-off valve 25 may be installed in the fuel distribution line 24 on the DF engine 22 side.

Hereinafter, the working relationship of the present invention having the above-described configuration will be described in detail with reference to FIG. 2, and the supply of volatile gas through the forced evaporator 8 and the supply of volatile gas through the two-stage low capacity compressor 13 will be described. As the system is also known in the prior art, it is a matter generally applied to use LNG loaded on a gas transportation vessel as a fuel, so the following description of the working relationship will be described based on the main points of the present invention. .

First, LNG is liquefied and loaded into the storage tank 1 in a state where the gas transportation vessel is docked at the port, and then the ship in which the loading of the liquefied gas 2 is completed is departed from the port. Since a relatively large amount of power is required at the initial point of departure from the port, at this point, the DF engine 22 is operated by using heavy oil loaded on the vessel as fuel.

When the DF engine 22 is operated using heavy oil loaded on the vessel as described above, the operation of the fuel supply system using LNG is not performed. When the constant speed operation of the gas is possible and the LNG volatilized gas is generated from the liquefied gas 2 stored in the storage tank 1 in an amount sufficient to use the fuel, the fuel supply using heavy oil is cut off and the LNG is To operate the fuel supply system.

When operating the fuel supply system using the LNG as described above, the liquefied gas (2) is supplied to the forced evaporator (8) through the supply line (5) from the supply pump (4) installed inside the storage tank (1) Due to this, the liquefied gas (2) is evaporated inside the forced evaporator (8) and then supplied to the gas heater (15) along the supply line (5), and at the same time, the volatile gas discharged from the BOG tank (3) It is supplied to the low capacity compressor 13, pressurized, and then supplied to the gas heater 15 along with the evaporation gas along the discharge line 12.

Thus, the pressure rise of the fuel supplied to the DF engine 22 is primarily achieved by the forced evaporator 8 and the two stage low capacity compressor 13, but the forced evaporator 8 and the two stage low capacity compressor 13 The discharge line 12 and the forced evaporator extending from the low load operating situation of the forced evaporator 8 or the two-stage low capacity compressor 13 or the two-stage low capacity compressor 13 due to the characteristics of the gas which is a compressive fluid under the conditions operating in parallel. Due to various factors such as supply pressures of the volatile gas and the boil-off gas flowing through the supply line 5 extending from 8) are different from each other, pressures of the volatile gas and the boil-off gas flowing into the gas heater 15 are often Will fluctuate.

As described above, when the pressures of the volatile gas and the boil-off gas flowing into the gas heater 15 are momentarily largely out of the range of 5.1 ± 0.2 bar, which is most suitable for combustion, the pressure deviation within the gas heater 15 is adjusted. Although it may be made primarily, since the main function of the gas heater 15 is to raise the temperature of the volatile gas and the boil-off gas to be suitable for combustion, the pressure deviation of the gas fuel discharged from the gas heater 15 is It is substantially adjusted by the buffer tank 19.

That is, even if the pressure of the gas fuel discharged from the gas heater 15 greatly exceeds the up and down range of 5.1 ± 0.2 bar which is most suitable for combustion, the gas fuel is introduced into the casing 19a of the buffer tank 19 After passing through the screen 19b, the pressure deviation of the gaseous fuel is stably adjusted in the course of turning the pressure adjusting plate 19c in a zigzag form, and thus the gas stored in the constant pressure chamber 19d of the buffer tank 19 is stabilized. The fuel will be able to maintain a constant pressure of 5.1 6 0.2 bar.

Therefore, as the fuel discharged to the fuel distribution line 24 connected to the buffer tank 19 is maintained at the pressure most suitable for combustion without large deviation, stable combustion of fuel is continuously made in the cylinder of the DF engine 22. This enables normal operation of the DF engine 22 and stable operation of the ship, and the irregular loads applied to various fuel injection systems, fuel injection systems, and fuel ignition systems provided in the DF engine 22. Minimization also prevents engine failures that may occur during the operation of the vessel.

In addition, since incombustibility of fuel or incomplete combustion due to over-injection of fuel hardly occurs in the cylinder of the DF engine 22, LNG volatilization and its evaporation gas are fueled more efficiently to prevent waste of energy. It is possible to greatly contribute to the aspect, which can greatly improve the practicality and economic feasibility even when compared to the conventional reliquefaction system to recover the LNG volatilized gas to LNG.

As described above, the pressure compensation system for the dual fuel engine of the gas carrier according to the present invention is installed with a buffer tank on the pipe for supplying BOG and boil-off gas to the DF engine, and 5.1 is most suitable for combustion of the pressure of the fuel supplied to the DF engine. By allowing constant adjustment within the range of ± 0.2 bar, it is effective to ensure stable combustion of fuel inside the cylinder of the DF engine, thereby enabling normal operation of the DF engine and stable operation of the ship. At the same time, it minimizes irregular loads on various fuel injection systems, fuel injection systems, and fuel ignition systems provided in the DF engine, thereby preventing engine defects that may occur during operation of the ship.

In addition, since incombustibility of fuel or incomplete combustion due to over-injection of fuel hardly occurs in the cylinder of the DF engine, LNG volatilization gas and its boil-off gas are fueled more efficiently to prevent waste of energy. There is an effect that can greatly contribute to this, because of this, even compared with the conventional reliquefaction system to recover the LNG volatile gas to LNG, it has the effect of greatly improving the practicality and economics.

Claims (2)

A supply pump 4 of liquefied gas 2 is installed inside the storage tank 1 in which LNG (liquefied natural gas) is stored, and a supply line 5 extending from the supply pump 4 is a forced evaporator ( 8 is connected to the gas heater 15 via a discharge line 12 extending from the BOG (Boil-off gas) tank (3) provided at the upper end of the storage tank 1 is a two-stage low capacity compressor ( 13 is connected to the gas heater 15 together with the supply line 5, and the fuel discharged from the gas heater 15 passes through the fuel supply line 18 and the fuel distribution line 24. In a system adapted to be supplied to a dual fuel (DF) engine 22, Between the fuel supply line 18 and the fuel distribution line 24, a buffer tank (19) for constantly adjusting the pressure of the fuel discharged from the gas heater 15 in the range of 5.1 ± 0.2 bar Pressure compensation system for a double fuel engine of the gas carrier, characterized in that the installation. The method of claim 1, wherein the buffer tank 19 is arranged in a zigzag form at regular intervals with a screen 19b for removing foreign matter from one side of the casing 19a to which the fuel supply line 18 is connected. A pressure compensation system for a dual fuel engine of a gas carrier, characterized in that a plurality of pressure adjusting plate (19c) is inserted into the casing (19a) in order to be installed sequentially.

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