KR101280216B1 - Fuel gas supply system of the direct heat exchange form using boiler steam - Google Patents

Abstract

The present invention relates to a fuel gas supply apparatus of a direct heat exchange method using a boiler steam. The fuel gas supply device of the present invention, the fuel gas supply line (L1) connected from the LNG tank 20 to the engine 10; A feed pump 22 installed in the middle of the fuel gas supply line L1 and pumping LNG from the LNG tank 20 to the engine 10; A vaporizer 23 installed on the fuel gas supply line L1 between the feed pump 22 and the engine 10 to vaporize LNG; A boiler 30 producing steam for heating or power generation; Steam circulating line 31 is installed so that the steam generated in the boiler 30 circulates the vaporizer 23, and heat exchange with LNG in the vaporizer 23 to vaporize the LNG; And a fuel gas cooling heat exchanger 40 installed on the fuel gas supply line L1 between the vaporizer 23 and the engine 10 to cool the fuel gas supplied to the engine 10. The present invention is to obtain a heat source for vaporizing LNG to be supplied to the engine from the steam produced in the boiler instead of supplying through a separate heating device, it is possible to reduce the system maintenance cost and improve energy efficiency, vaporization gas According to forced cooling of the boiler, the vaporization of the vaporizer is improved by supplying boiler steam at the maximum temperature.

Description

FUEL GAS SUPPLY SYSTEM OF THE DIRECT HEAT EXCHANGE FORM USING BOILER STEAM}

The present invention relates to a fuel gas supply apparatus for a ship, a marine floating structure, or an onshore power generation facility using LNG as a fuel of an engine, and more particularly, a heat source for vaporizing LNG to be supplied to an engine through a separate heating device. The present invention relates to a direct heat exchange fuel gas supply apparatus using boiler steam, which can be obtained from steam produced in a boiler instead of supplying, thereby reducing system maintenance costs and greatly improving energy efficiency.

Vessels handling (storing, transporting) LNG (Liquefied Natural Gas) (e.g., LNG carriers), offshore floating structures (e.g., Floating Storage Regasification Units (FSRUs)), or onshore power generation The facility is equipped with a series of vaporization equipment to vaporize the LNG stored in the LNG tank to maximize utilization as an engine power.

Recently, LNG carriers are using diesel engines rather than turbine engines due to steam driving. Therefore, a reliquefaction device that recovers vaporized gas generated in the LNG tank, reliquefyes it into LNG, and sends it back to the LNG tank. It is applied to LNG carriers.

However, such a reliquefaction apparatus has an unreasonable problem in that the expenditure of the expenses associated with the installation and operation of the reliquefaction apparatus is much greater than that of the reliquefaction of the gas.

In this situation, recently, a dual (or heterogeneous) fuel engine has been used in which LNG can be alternately used as an auxiliary fuel of an engine together with heavy oil that is a main fuel of a diesel engine. This dual fuel engine has two combustion modes. As an example of two combustion modes, the secondary fuel (eg Marine Diesel Oil, Marine Gas Oil) is injected before the main fuel (eg, Heavy Fuel Oil, Marine Diesel Oil) is injected in the diesel fuel mode to control the combustion environment of the combustion chamber. To improve soot, NOx and combustion performance. In addition, in the gas fuel mode, only the auxiliary fuel is injected by adjusting the fuel injection amount control device (governor) to achieve stable ignition of the gas fuel introduced through the gas admission valve.

In addition, the development of an engine (for example, MAN Diesel & Turbo's ME-GI engine) that burns and burns LNG gas fuel as a main fuel under high pressure injection and uses it as a propulsion engine or a main engine, fueling LNG again. have.

1 is a system diagram showing a configuration of an engine and a vaporization gas supply apparatus using a conventional LNG gas as a fuel.

The conventional vaporization gas supply apparatus includes the LNG tank 2, the pump 3 for LNG supply, the vaporizer 4, the heating apparatus 5, and the pump 7 for heat exchange medium supply.

Specifically, the fuel gas supply line between the LNG tank 2 and the engine 1 vaporizes a supply pump 3 for pumping LNG stored in the LNG tank 2 and fuel supplied from the supply pump 4. The vaporizer | carburetor 4 sent to the engine 1 is provided. In addition, a separate heat exchange medium circulation line 6 is provided in the vaporizer 4, and a heating device 5 and a heat exchange medium supply pump 7 are installed on the heat exchange medium circulation line 6. The heat exchange medium heated to a constant temperature in the heating device (5) enters the vaporizer (4) by the supply pump (7), heat exchanges with LNG passing through the vaporizer (4), and then circulates back to the heating device (5). . As a result, in the vaporizer | carburetor 4, LNG is vaporized through the heat exchange between a heat exchange medium and LNG, and this vaporized LNG is supplied as a fuel of the engine 1.

However, such a conventional vaporized gas supply device has the following problems.

First, since a heating device 5 which is a heating source of the heat exchange medium is additionally required to vaporize LNG, a part of the power energy generated from the engine 1 is consumed by the heating device 5 which heats the heat exchange medium again. Thus, considering the energy aspect of the overall power system, it is impossible to expect great efficiency.

In addition, in order to satisfy the requirements of the heating apparatus 5 and the vaporizer 4 for vaporizing LNG, facilities such as the vaporizer 4, the heating apparatus 5, and the engine 1 equipment need to be enlarged. This results in increased maintenance costs.

In addition, ethylene glycol (Ethylene Glycol), which is a kind of antifreeze called glycol water, is mainly used as the heat exchange medium for circulating the heat exchange medium circulation line 6 to provide vaporization heat to LNG. This ethylene glycol is a highly viscous colorless liquid having a molecular weight of 62.07, melting point −12.6 ° C., boiling point 197.7 ° C., and specific gravity 1.1131. Freezing may occur during the process. In particular, if a failure occurs in the heating device 5, the low temperature of LNG may cause a great risk of freezing of the piping of the heat exchange medium circulation line 6, as well as the surrounding vaporization equipment, or being damaged by freezing. There is.

The present invention has been invented to solve the conventional problems as described above, the object of the present invention, LNG, the thermal energy of the steam produced in the boiler installed for heating or turbine generator drive in ships, offshore structures or power plants, etc. By directly utilizing as a heat source to vaporize, to prevent the loss of power generated in the engine, to eliminate the additional installation of a heating device for heating the heat exchange medium, thereby improving the efficiency of the overall power system boiler steam It is to provide a fuel gas supply apparatus of a direct heat exchange method using.

Another object of the present invention is to improve the engine performance by allowing the LNG vaporized gas to be adjusted to the optimum temperature required for combustion by cooling the LNG vaporized gas to a temperature suitable for combustion before entering the engine.

In order to achieve the above object, the fuel gas supply apparatus of the direct heat exchange method using the boiler steam according to the present invention,

Further, on the fuel gas supply line between the LNG tank and the feed pump, it is more preferable to provide a buffer tank for temporarily storing LNG and discharging the stored LNG by its internal pressure.

According to the fuel gas supply apparatus of the direct heat exchange method using the boiler steam of the present invention, the carburetor is circulated by a part of steam produced in a boiler installed for heating or driving a turbine generator in a ship, offshore floating structure or power plant, etc. By evaporating by heat exchange with LNG passing through, there is no need to install a separate heating device for vaporizing LNG. Therefore, according to the present invention, the power loss of the engine is reduced, and the efficiency of the entire system is improved.

In addition, according to the fuel gas supply apparatus of the direct heat exchange method using the boiler steam of the present invention, the LNG vaporized gas is cooled to a temperature suitable for combustion before the LNG vaporized gas is introduced into the engine so that the LNG vaporized gas can be adjusted to the optimum temperature required for combustion. By improving the engine performance, the vaporized gas can be used by supplying the boiler steam at the maximum temperature according to the forced cooling of the vaporized gas improves the efficiency of the vaporizer.

1 is a system diagram of a conventional vaporization gas supply apparatus.
2 is a system diagram of a fuel gas supply apparatus of a direct heat exchange method using boiler steam according to the present invention.

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

2 is a schematic diagram of a fuel gas supply apparatus of a direct heat exchange method using boiler steam according to the present invention.

2, in the fuel gas supply apparatus of the liquefied natural gas direct vaporization method using the boiler steam according to the present invention, the boiler is installed and operated for heating or driving a turbine generator in a ship, offshore floating structure or power plant Use steam. That is, by branching the steam line of the boiler 30 that is already installed and operated to form a heat exchanger in the vaporizer 23, by utilizing the high temperature heat of the boiler steam as a heat source for vaporizing LNG, without a separate heating device While allowing LNG to be vaporized, the temperature of the fuel gas exiting the vaporizer 23 and entering the engine 10 is cooled to a temperature suitable for combustion by using the fuel gas cooling heat exchanger 40.

Specifically, the fuel gas supply apparatus of the liquefied natural gas direct vaporization method using the boiler steam according to the present invention, the fuel gas supply line (L1) connected from the LNG tank 20 to the engine 10, and the fuel gas supply line ( It is installed in the middle of L1 and pumps LNG from the LNG tank 20 and sends it to the engine 10 side, on the fuel gas supply line L1 between the feed pump 22 and the engine 10. A vaporizer 23 installed to vaporize LNG, a steam circulation line 31 for vaporizing LNG by heat exchange with LNG in the vaporizer 23, and fuel gas supply between the vaporizer 23 and the engine 10; A fuel gas cooling heat exchanger 40 is installed on the line L1 to cool the fuel gas supplied to the engine 10.

In addition, the cooling heat exchanger 40 is introduced with a cooling water circulation line 51 drawn from the cooling medium circuit 50 provided in the ship, offshore floating structure or power plant. The cooling medium circuit is a cooling circuit for cooling the lubricating oil or the engine cooling water, and cooling water (temperature of about 36 ° C as the antifreeze liquid or water) is used as the cooling medium.

According to the present invention, the steam is flowed through the steam circulation line 31 drawn from the boiler 30 to the heat exchanger 23, and the LNG is vaporized by heat exchange with LNG passing through the vaporizer 23.

Steam heat-exchanged with LNG via the vaporizer 23 is subsequently returned to the boiler 30 along the steam circulation line (L1).

The fuel gas that is vaporized in the vaporizer 23 and then enters the engine along the fuel gas supply line L1 is cooled to a temperature suitable for combustion in the fuel gas cooling heat exchanger 40.

In short, the LNG vaporized gas from the vaporizer 23 is required to always maintain a constant temperature (eg 45 ° C ± 10 ° C) when entering the engine 10. Therefore, since the vaporized fuel gas is maintained at a high temperature by removing heat from the boiler steam in the vaporizer 23, it is forced to cool by the cooling medium to adjust the temperature of the LNG vaporized gas to the optimum state for combustion, This can help to improve engine performance.

In addition, according to the configuration in which the fuel gas entering the engine 10 is forcedly cooled by the fuel gas cooling heat exchanger 40, steam of the maximum temperature from the boiler 30 can be utilized as a heat exchange heat source of the vaporizer 23. The vaporization efficiency in the vaporizer | carburetor 23 can be improved. That is, even if the temperature of the fuel gas vaporized by heat-exchanging with LNG in the vaporizer 23 is high, the fuel gas cooling heat exchanger 40 is cooled to a temperature of 45 ° C ± 10 ° C by about 36 ° C cooling water, The boiler steam close to the temperature or the maximum temperature may be supplied to the steam circulation line 31. Since the maximum temperature of the steam generated in the boiler 30 is about 80 ° C., the steam circulation line 31 may be withdrawn from a position close to the outlet of the steam generator of the boiler to circulate the steam at the maximum temperature.

In addition, on the fuel gas supply line L1 between the LNG tank 20 and the feed pump 22, a buffer tank 21 for temporarily storing LNG and discharging the stored LNG by internal pressure is provided.

The buffer tank 21 is also referred to as a so-called 'suction drum', and the LNG is temporarily pumped from the LNG tank 20 to the supply pump 22 instead of being temporarily pumped to the buffer tank 21. After storage, the LNG can be supplied to feed pump 22 at a stable (constant) pressure.

If LNG, which is compressed at low temperature (-163 ° C.) in the LNG tank 20, is directly supplied to the supply pump 22, LNG is not easily controlled. Therefore, LNG having an appropriate pressure and capacity is supplied to the vaporizer 23. It is not easy to supply.

For this reason, the buffer tank 21 is provided between the LNG tank 20 and the feed pump 22 so that LNG of a stable pressure and capacity can always be supplied to the feed pump 102.

Although not shown in FIG. 2, the buffer tank 21 includes means for adjusting a storage pressure and a storage capacity of the LNG flowing into the LNG tank 21, so that the LNG having a constant pressure and capacity is always provided toward the LNG supply pump 102. Can be supplied stably.

For example, the storage pressure regulating means in the buffer tank 21 may include a pressure controller, a pressure regulating valve and a pressure sensor. The pressure controller receives pressure information from the pressure sensor located in the buffer tank 21, opens and closes the pressure control valve, and returns the natural vaporized gas located above the LNG level in the buffer tank 21 to the LNG tank 20. Accordingly, the pressure inside the buffer tank 21 can be kept constant at a predetermined pressure.

The storage capacity adjusting means of the buffer tank 21 may include a capacity controller, a capacity sensor, and a capacity control valve. The capacity controller receives the capacity (level) information of the LNG from the capacity sensor in the buffer tank 21 to open and close the capacity control valve to keep the level of LNG constant.

Thus, in the present invention, since the existing boiler is used as a heat source for vaporizing LNG, it is necessary to worry about the failure of the heating apparatus as in the conventional case of using a separate heating apparatus and the problem of freezing such as piping. none.

In addition, since boiler steam is used as a heat source for vaporizing LNG, it is not necessary to have a separate heat exchange medium such as a conventional antifreeze.

In addition, since the LNG vaporized gas entering the engine can be forcibly cooled by the coolant in the fuel gas cooling heat exchanger to be optimally matched to engine combustion, the engine performance can be improved.

In addition, according to the configuration forcibly cooling the fuel gas entering the engine, it is possible to utilize the steam of the maximum temperature as the heat exchange heat source of the vaporizer can improve the vaporization efficiency.

The foregoing is a description of certain preferred embodiments of the present invention. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein, but may be modified and altered without departing from the spirit and scope of the invention as defined in the appended claims.

10: Engine
20: LNG tank
21: buffer tank
22: feed pump
23: carburetor
30: boiler
31: steam circulation line
40: heat exchanger for fuel gas cooling
50: cooling medium circuit
51: cooling water circulation line

Claims (3)

A fuel gas supply line L1 connected to the engine 10 from the LNG tank 20;
A feed pump 22 installed in the middle of the fuel gas supply line L1 and pumping LNG from the LNG tank 20 to the engine 10;
A vaporizer 23 installed on the fuel gas supply line L1 between the feed pump 22 and the engine 10 to vaporize LNG;
A boiler 30 producing steam for heating or power generation;
Steam circulating line 31 is installed so that the steam generated in the boiler 30 circulates the vaporizer 23, and heat exchange with LNG in the vaporizer 23 to vaporize the LNG;
Fuel gas cooling for cooling the high-temperature LNG vaporized gas from the vaporizer 23 is installed on the fuel gas supply line (L1) between the vaporizer 23 and the engine 10 before being supplied to the engine 10. A heat exchanger (40),
The cooling heat exchanger 40 introduces a cooling water circulation line 51 drawn from the cooling medium circuit 50 for cooling the lubricant or engine coolant, thereby cooling the fuel gas by the cooling medium for cooling the lubricant or engine cooling water. ,
On the fuel gas supply line L1 between the LNG tank 20 and the feed pump 22, a buffer tank 21 for temporarily storing LNG and discharging the stored LNG by internal pressure is installed. Fuel gas supply system of liquefied natural gas direct vaporization using boiler steam. delete delete

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