KR102566451B1 - Ammonia Boil-Off Gas Reliquefaction System And Method For Ship - Google Patents

Abstract

A system and method for re-liquefying ammonia boil-off gas of a ship are disclosed. The ammonia boil-off gas re-liquefaction system of the ship of the present invention is provided in the ship and includes an ammonia storage tank for storing ammonia to be supplied as fuel for an engine in the ship; a fuel supply line connected to the engine from the ammonia storage tank to supply ammonia; a heater provided in the fuel supply line to heat ammonia to be supplied to the engine through heat exchange with a heat medium; a compressor for receiving and compressing the boil-off gas generated from the ammonia storage tank; and a cooler for cooling the boil-off gas compressed by the compressor. The cooler heats ammonia to be supplied as engine fuel from the heater and cools the boil-off gas by receiving the cooled heat medium.

Description

Ammonia Boil-Off Gas Reliquefaction System And Method For Ship}

The present invention relates to a system and method for re-liquefying ammonia boil-off gas of a ship, and more particularly, in a ship using ammonia as a fuel for an onboard engine, compresses boil-off gas generated from an ammonia storage tank and heats the ammonia to be supplied to the engine. It relates to a system and method for re-liquefying ammonia boil-off gas of a ship that re-liquefies by cooling by a cooling heat medium while doing so.

Efforts are being made to reduce greenhouse gas emissions worldwide as the global warming phenomenon intensifies, and as the Kyoto Protocol in 1997, which contained the obligations of developed countries to reduce greenhouse gases, expired in 2020, the conference was held in Paris, France in December 2015. According to the Paris Climate Change Accord, which was adopted in the 21st United Nations Framework Convention on Climate Change and entered into force in November 2016, the 195 Parties participating in the agreement are making various efforts to reduce greenhouse gases.

Along with this global trend, interest in renewable energy (or renewable energy) such as wind power, solar power, solar heat, bioenergy, tidal power, and geothermal heat has increased and various technologies have been developed as pollution-free energy that can replace fossil fuels and nuclear power. are losing

Liquefied gas, including liquefied natural gas, can remove or reduce air pollutants during the liquefaction process, so it can be seen as an eco-friendly fuel with less air pollutant emissions during combustion. Accordingly, consumption of liquefied natural gas such as liquefied natural gas (LNG) or liquefied petroleum gas (LPG) is rapidly increasing worldwide. Since liquefied gas obtained by liquefying gas at a low temperature has a very small volume compared to gas, it has the advantage of increasing storage and transfer efficiency.

Liquefied natural gas (LNG) is a colorless and transparent liquid obtained by liquefying natural gas containing methane as a main component by cooling it to about -162 ° C., and has a volume of about 1/600 compared to natural gas. Therefore, when the natural gas is liquefied and transported, it can be transported very efficiently.

Liquefied petroleum gas (LPG) has a difference in liquefaction temperature depending on its composition, but in the case of petroleum gas whose main component is propane, it is liquefied at a low temperature of about -42 ℃ at atmospheric pressure, up to about 45 ℃ at 18 bar, and 20 ℃ at 7 bar. It can be stored in liquid state up to °C.

On the other hand, conventional LPG carriers adopt a fuel supply system using heavy oil such as bunker C oil, which is relatively inexpensive as a propulsion fuel for ships. Due to stricter regulations, a separate heavy fuel oil fuel tank (LSHFO tank) with low sulfur content had to be installed, and the demand for an eco-friendly fuel supply system that meets international environmental regulatory standards has increased.

In recent years, the application of fuel supply systems that use LPG or LNG and boil-off gas generated from them as propulsion fuel in LPG or LNG carriers is increasing, and in accordance with the strengthening of international exhaust gas emission regulations, general ships in addition to LPG or LNG carriers are also using LNG. Ships using it as a propulsion fuel are increasing.

Representative marine engines that can use LNG as fuel include gas fueled engines such as DFDE, X-DF engines, and ME-GI engines.

DFDE is composed of 4 strokes, and adopts an Otto Cycle in which natural gas having a relatively low pressure of about 5.5 barg is injected into the combustion air inlet and compressed while the piston rises.

The X-DF engine is composed of two strokes, uses about 15 barg of natural gas as fuel, and adopts an Otto cycle.

The ME-GI engine consists of two strokes and adopts a diesel cycle in which high-pressure natural gas of around 300 barg is directly injected into the combustion chamber near the top dead center of the piston.

However, although LNG or LPG is evaluated as an eco-friendly fuel compared to other fossil fuels previously used as ship fuel, carbon dioxide is still generated during combustion, and ships that use it as fuel still emit carbon dioxide during operation.

IMO (International Maritime Organization), a UN specialized organization established to internationally unify ship routes, traffic rules, port facilities, etc., also reduced greenhouse gas emissions by 50% in 2050 compared to 2008 and 100% in 2100. % reduction (GHG Zero Emission) is presented as a goal, and regulations in each country and region are expected to be strengthened accordingly.

According to EEDI (Energy Efficiency Design Index), a compulsory carbon dioxide reduction regulation applied by IMO to new ships, in the initial EEDI announcement, CO2 emissions in 2015 were reduced by 10% based on the CO2 emissions from 2013 to 2015 EEDI Phase 1 was applied, and it was scheduled to apply Phase 3 in 2025 by strengthening and applying one step every 5 years. are making it As such, since regulations on carbon dioxide emission from ships are being rapidly strengthened, it may be difficult to achieve carbon dioxide emission regulations by using only LNG or LPG as fuel in the future.

Accordingly, various studies on eco-friendly ship fuels that can reduce carbon dioxide emissions have been conducted, and recently, research and development have been conducted on technologies related to ship engines that can use ammonia as a fuel along with fuels such as LNG or LPG.

Ammonia (NH ₃ ) is a substance in which three hydrogens are bonded to one nitrogen, and it is easy to liquefy because it can form a strong hydrogen bond between molecules, and has a boiling point of -33.34 ° C and a melting point of -77.73 ° C under normal pressure.

This ammonia is easier to store than LNG, and although it is slightly lower in SPECIFIC ENERGY and ENERGY DENSITY compared to existing HFO, it does not emit carbon dioxide at all, so it is attracting attention as an eco-friendly ship fuel that can respond to the strengthening trend of international greenhouse gas emission standards.

Ammonia has a higher boiling point than LNG, but is also higher than room temperature, so boil-off gas is generated in a storage tank storing ammonia to be supplied as fuel on board.

The present invention intends to propose a method for effectively re-liquefying boil-off gas generated from ammonia to be supplied as fuel in this way to prevent fuel waste and safely maintain the storage tank pressure.

According to one aspect of the present invention for solving the above problems, an ammonia storage tank provided on a ship and storing ammonia to be supplied as fuel for an inboard engine;

a fuel supply line connected to the engine from the ammonia storage tank to supply ammonia;

a heater provided in the fuel supply line to heat ammonia to be supplied to the engine through heat exchange with a heat medium;

a compressor for receiving and compressing the boil-off gas generated from the ammonia storage tank; and

A cooler for cooling the boil-off gas compressed by the compressor: Including,

In the cooler, there is provided a system for re-liquefying ammonia boil-off gas of a ship, characterized in that for heating ammonia to be supplied as engine fuel from the heater and receiving a cooled heat medium to cool the boil-off gas.

Preferably, the compressor and the cooler are provided and the re-liquefying line for re-liquefying the boil-off gas generated in the ammonia storage tank and recovering it to the ammonia storage tank; and a pressure reducing valve provided in the reliquefaction line and reducing the boil-off gas cooled in the cooler.

Preferably, a cold heat recovery cooler further cools the boil-off gas cooled in the cooler by heat exchange with uncompressed boil-off gas to be supplied from the ammonia storage tank to the compressor; may be supplied to the pressure reducing valve.

Preferably, the uncompressed evaporation gas to be supplied from the ammonia storage tank to the compressor is supplied to the compressor via the cooler, so that the evaporation gas compressed in the compressor passes through the heater and is supplied to the compressor from the heat medium and the ammonia storage tank. can be cooled by uncompressed boil-off gas.

Preferably, a fuel recovery line for recovering and recycling non-consumed ammonia among ammonia supplied to the engine; and a catch tank provided in the fuel recovery line to accommodate ammonia recovered from the engine, wherein the ammonia recovered through the fuel recovery line may be supplied to a front end of the heater of the fuel supply line via the catch tank. there is.

Preferably, a supply pump provided in the ammonia storage tank and transferring ammonia to the fuel supply line; A compression pump provided downstream of the heater of the fuel supply line and compressing ammonia to be supplied to the engine according to the fuel supply pressure of the engine may be further included.

Preferably, the boil-off gas re-liquefied in the re-liquefaction line through the compressor and the cooler may be supplied to a front end of the heater of the fuel supply line and supplied to the engine.

According to another aspect of the present invention, supplying ammonia to the engine from an ammonia storage tank for storing ammonia to be supplied as fuel for the onboard engine,

The boil-off gas generated from the ammonia storage tank is compressed, cooled in a cooler, re-liquefied, and then returned to the ammonia storage tank,

In the cooler, there is provided a method of re-liquefying ammonia boil-off gas of a ship, characterized in that for heating the ammonia to be supplied to the engine and receiving a cooled heat medium to cool the boil-off gas.

In the present invention, ammonia, which is an eco-friendly fuel, is supplied as fuel for a ship engine to reduce greenhouse gas emissions during ship operation and to meet regulatory standards set by international agreements.

In particular, by compressing the boil-off gas generated in the ammonia storage tank in which ammonia to be supplied as engine fuel is stored, re-liquefying it by heating the ammonia fuel to be supplied to the engine, cooling it with the cold heat of the cooled heat medium, and then recovering or supplying it as fuel, It can effectively utilize the cold heat of ammonia to be supplied as fuel and increase the re-liquefaction efficiency.

In addition, the pressure of the ammonia storage tank can be safely maintained through re-liquefaction of boil-off gas, and waste of ammonia fuel can be prevented.

1 schematically shows an ammonia boil-off gas re-liquefaction system of a ship according to a first embodiment of the present invention.
2 schematically shows a system for re-liquefying ammonia boil-off gas of a ship according to a second embodiment of the present invention.
3 schematically shows a system for re-liquefying ammonia boil-off gas of a ship according to a third embodiment of the present invention.

In order to fully understand the operational advantages of the present invention and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings illustrating preferred embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, the configuration and operation of a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. In adding reference numerals to the components of each drawing, it should be noted that the same components are marked with the same numerals as much as possible, even if they are displayed on different drawings.

Hereinafter, the ship in the present invention refers to all types of ships in which an engine capable of using ammonia as a fuel for an inboard engine is installed, and is representative of an LPG carrier, an LNG carrier, a liquid hydrogen carrier, and a liquid hydrogen carrier. Carriers, ammonia carriers, container carriers, crude oil carriers, bulk carriers such as minerals or grains, special vessels such as wind turbine installation vessels, and self-propelled capabilities such as Ro-Ro (Roll on/Roll off) vessels It may also include ships with propulsion, but offshore structures floating on the sea that do not have propulsion capability.

An engine supplied with ammonia as a fuel of an engine means that it is supplied as a fuel together with other marine fuel such as LNG, LPG, HFO, MGO, and Diesel Oil, and ammonia is supplied as a single fuel. Includes both engines for propulsion and engines for power generation. The engine for propulsion and the engine for power generation may be provided in a plurality of two or more units as needed.

1 to 3 schematically show the ammonia boil-off gas re-liquefaction system of the ship according to the first to third embodiments of the present invention, respectively.

As shown in FIGS. 1 to 3, the ammonia boil-off gas re-liquefaction system of the present embodiments is provided on a ship and supplies ammonia from an ammonia storage tank (AT) to an engine (not shown) for storing ammonia to be supplied as fuel for an engine on board. While supplying, the evaporation gas generated from ammonia stored in the ammonia storage tank is re-liquefied and recovered to the tank or supplied as engine fuel.

To this end, a fuel supply line (FSL) connected to the engine from the ammonia storage tank (AT) and supplying ammonia, and a re-liquefaction line (GL) that re-liquefies the boil-off gas generated in the ammonia storage tank and recovers it to the ammonia storage tank provided

In particular, the re-liquefaction system of the present embodiments is characterized in that it is configured to use the cooling heat of the cooled heat medium while heating the ammonia fuel to be supplied to the engine to re-liquefy the ammonia boil-off gas.

In the ammonia storage tank (AT), a supply pump (P) is provided to transfer ammonia to the fuel supply line (FSL), and a heater 200 for heating the ammonia to be supplied to the engine along the fuel supply line by heat exchange with the heat medium, and the engine A compression pump 220 for compressing ammonia according to the fuel supply pressure of is provided. A booster pump 210 may be additionally provided upstream of the heater to pump ammonia transported from the supply pump and supply it to the heater.

Depending on the design pressure of the ammonia storage tank (AT), the temperature of ammonia in the storage tank can vary. If provided, it can be stored at room temperature around 25 ° C.

Liquid ammonia transferred from the ammonia storage tank (AT) through the supply pump (P) is supplied to the engine in a high-pressure liquid state according to the temperature and pressure required by the engine through the heater 200 and the compression pump 220.

When an incompressible fluid having little or no change in volume even when pressure is applied, that is, fuel in a liquid state is supplied to the engine, excess fuel is supplied to the engine to respond to engine load fluctuations and prevent cavitation. Among the fuel supplied to the engine, the remaining fuel after being consumed as fuel is recovered upstream of the engine.

To this end, in the systems of the present embodiments, a fuel recovery line (RL) for recovering and recirculating ammonia that is not consumed by the engine among fuel that is excessively supplied to the engine is provided, and a catch tank for accommodating ammonia recovered from the engine is provided in the fuel recovery line. 300 is provided.

Ammonia recovered through the fuel recovery line RL is supplied to the front end of the heater 110 of the fuel supply line SL via the catch tank 300 and recycled.

In this fuel supply system, the heater 200 controls the temperature of ammonia through heat exchange with the heat medium. .

In the present embodiments, the heat medium discharged after being cooled through heat exchange with ammonia fuel in the heater is utilized for re-liquefying ammonia boil-off gas.

To this end, in the re-liquefaction line GL through which boil-off gas is discharged from the ammonia storage tank AT, a compressor 100 for receiving and compressing ammonia boil-off gas, and coolers 110A, 110B for cooling the boil-off gas compressed by the compressor, 110C) is provided, and the cooler cools the ammonia boil-off gas by receiving the heat medium discharged from the heater. The heat medium cooled by the heater is supplied to the cooler through the heat medium branch line HBL connected to the cooler at the downstream of the heater of the heat medium line HL.

The boil-off gas cooled in the coolers 110A, 110B, and 110C is expanded and cooled through a pressure reducing valve to be re-liquefied and returned to the ammonia storage tank AT. For example, ammonia evaporation gas is pressurized to around 18 bar in a compressor, cooled to room temperature through a cooler, and then expanded and cooled through a pressure reducing valve to have a dryness of 0.2 or less, so that it can be re-liquefied without a separate additional device.

The systems of the first to third embodiments differ in the cooling method of the boil-off gas compressed by the compressor. First, in the first embodiment system shown in FIG. 1, the boil-off gas compressed by the compressor is cooled by the cooler 110A is supplied to, cooled through heat exchange with the heat medium passing through the heater, and then reduced in pressure by the pressure reducing valve 130.

In the system of the second embodiment shown in FIG. 2, a cold heat recovery cooler 140 is additionally provided at the rear end of the cooler to utilize the cooling heat of ammonia evaporation gas generated in the ammonia storage tank. As shown in FIG. 2, the ammonia evaporation gas generated in the ammonia storage tank is introduced into the compressor 100 and compressed after recovering cold heat in the cold heat recovery cooler 140. The compressed evaporation gas is cooled through heat exchange with a heating medium in the cooler 110B, further cooled by the uncompressed evaporation gas in the cold heat recovery cooler 140, and then expanded and cooled through the pressure reducing valve 130 to be recovered to the ammonia storage tank. do. As such, the present embodiment can increase re-liquefaction efficiency by additionally cooling the gas to be re-liquefied using the cooling heat of the uncompressed boil-off gas itself to be re-liquefied without a separate additional refrigerant.

In the system of the third embodiment shown in FIG. 3, the cooling heat of the uncompressed boil-off gas is utilized like the system of the second embodiment, but a separate cold-heat recovery cooler is not installed, and the heat medium and the uncompressed boil-off gas are cooled and cooled in the cooler 110C. It is designed to be used as a circle. Accordingly, as shown in FIG. 3, the ammonia evaporation gas generated in the ammonia storage tank (AT) is compressed in the compressor 100 through the cooler 110C, and the compressed evaporation gas is cooled in the cooler 110C. In the cooler 110C, three streams of compressed boil-off gas, heat medium supplied from the heater, and uncompressed boil-off gas are heat-exchanged. The compressed gas cooled through the cooler is returned to the ammonia storage tank (AT) through the pressure reducing valve 130. As in the second embodiment described above, the re-liquefaction efficiency can be increased by utilizing the cooling heat of the uncompressed boil-off gas. By not installing an additional heat exchanger, it can reduce installation costs and contribute to securing space in the ship.

In each embodiment, the ammonia re-liquefied from the ammonia storage tank along the re-liquefaction line through the compressor and the cooler may be recovered to the storage tank, and may be sent to the front end of the heater of the fuel supply line and directly supplied as engine fuel.

As described above, in the present embodiments, by utilizing the cooling heat of ammonia to be supplied as fuel and re-liquefying boil-off gas generated in the ammonia storage tank, it is possible to prevent waste of ammonia and maintain the storage tank pressure.

The present invention is not limited to the above embodiments, and it can be practiced with various modifications or variations within a range that does not deviate from the technical gist of the present invention to those skilled in the art to which the present invention belongs. It is self-evident.

AT: Ammonia storage tank
P: feed pump
FSL: fuel supply line
RL: fuel return line
GL: reliquefaction line
100: compressor
110A, 110B, 110C: Cooler
130: pressure reducing valve
140: cold heat recovery cooler
200: heater
210: booster pump
220: compression pump

Claims (8)

An ammonia storage tank provided in the ship and storing ammonia to be supplied as fuel for the ship's engine;
a fuel supply line connected to the engine from the ammonia storage tank to supply ammonia;
a heater provided in the fuel supply line to heat ammonia to be supplied to the engine through heat exchange with a heat medium;
a compressor for receiving and compressing the boil-off gas generated from the ammonia storage tank;
a cooler for cooling the boil-off gas compressed by the compressor;
a fuel recovery line for recovering and recirculating ammonia that is not consumed among the ammonia supplied to the engine; and
A catch tank provided in the fuel recovery line and accommodating ammonia recovered from the engine;
The ammonia recovered through the fuel recovery line is supplied to the front end of the heater of the fuel supply line through the catch tank,
The cooler heats ammonia to be supplied as engine fuel from the heater and receives a cooled heat medium to cool the boil-off gas. According to claim 1,
a re-liquefaction line provided with the compressor and the cooler and re-liquefying boil-off gas generated in the ammonia storage tank and returning it to the ammonia storage tank; and
The vessel's ammonia boil-off gas re-liquefaction system further comprising: a pressure-reducing valve provided in the re-liquefaction line and reducing the boil-off gas cooled in the cooler. According to claim 2,
A cold heat recovery cooler for additionally cooling the evaporation gas cooled in the cooler by heat exchange with uncompressed evaporation gas to be supplied from the ammonia storage tank to the compressor;
Ammonia boil-off gas re-liquefaction system of a ship, characterized in that the boil-off gas additionally cooled in the cold heat recovery cooler is supplied to the pressure reducing valve. According to claim 2,
The uncompressed boil-off gas to be supplied from the ammonia storage tank to the compressor is supplied to the compressor through the cooler,
In the cooler, the evaporation gas compressed in the compressor is cooled by the heat medium passing through the heater and the uncompressed evaporation gas from the ammonia storage tank. delete According to any one of claims 2 to 4,
a supply pump provided in the ammonia storage tank and transferring ammonia to the fuel supply line;
Ship's ammonia boil-off gas re-liquefaction system further comprising: a compression pump provided downstream of the heater of the fuel supply line and compressing ammonia to be supplied to the engine according to the fuel supply pressure of the engine. According to claim 6,
Ammonia boil-off gas re-liquefaction system of a ship, characterized in that the boil-off gas re-liquefied in the re-liquefaction line through the compressor and the cooler is supplied to the front end of the heater of the fuel supply line and supplied to the engine. delete

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