KR20230083367A - Ammonia Decomposition System And Method For Ship - Google Patents

Abstract

A system and method for decomposing ammonia of a ship are disclosed. The ammonia decomposition system of the present invention includes a vaporizer for receiving and vaporizing liquid ammonia; A decomposer that receives the vaporized ammonia supplied from the vaporizer and thermally decomposes it to generate a decomposition gas containing hydrogen, nitrogen, and undecomposed ammonia; an undecomposed ammonia removal unit collecting undecomposed ammonia from the decomposed gas; a hydrogen purifier receiving the cracked gas that has passed through the undecomposed ammonia removal unit and purifying it into hydrogen by removing nitrogen; and a selective catalytic reduction unit (SCR) for denitrifying combustion gas generated by thermal decomposition of ammonia in the decomposer, wherein gaseous ammonia vaporized in the vaporizer is supplied as a reducing agent to the selective catalytic reduction unit.

Description

Ammonia Decomposition System And Method For Ship}

The present invention relates to a system and method for decomposing ammonia in a ship, and more particularly, to vaporize liquid ammonia, thermally decompose the vaporized ammonia in a decomposer, and remove undecomposed ammonia and nitrogen to obtain purified hydrogen as fuel for an onboard fuel cell. It relates to a system and method for decomposing ammonia of a ship that supplies combustion gas generated by thermal decomposition of ammonia and sends it to a selective catalytic reduction unit (SCR) together with gaseous ammonia for denitrification.

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.

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.

In addition, since ammonia contains three hydrogen atoms per molecule and is easier to liquefy and store than hydrogen, its value as a hydrogen transport means for using hydrogen, a representative eco-friendly fuel, as a fuel has been recognized and various studies have been conducted.

The present invention proposes a method for producing hydrogen from ammonia in a ship, supplying it as inboard fuel, and reducing nitrogen oxides in the combustion gas generated in the hydrogen production process so that the combustion gas can be discharged in accordance with the overboard emission regulation standard. .

According to one aspect of the present invention for solving the above problems, a vaporizer for receiving and vaporizing liquid ammonia;

A decomposer that receives the vaporized ammonia supplied from the vaporizer and thermally decomposes it to generate a decomposition gas containing hydrogen, nitrogen, and undecomposed ammonia;

an undecomposed ammonia removal unit collecting undecomposed ammonia from the decomposed gas;

a hydrogen purifier receiving the cracked gas that has passed through the undecomposed ammonia removal unit and purifying it into hydrogen by removing nitrogen; and

A selective catalytic reduction unit (SCR) for denitrifying combustion gas generated by thermal decomposition of ammonia in the decomposer;

There is provided an ammonia decomposition system of a ship, characterized in that gaseous ammonia vaporized in the vaporizer is supplied as a reducing agent to the selective catalytic reduction unit.

Preferably, an exhaust discharge line for supplying the combustion gas generated in the decomposer to the selective catalytic reduction unit; a combustion gas cooler provided in the exhaust discharge line to cool the combustion gas to a temperature required by the selective catalytic reduction unit; and a reducing agent supply line connected from the vaporizer to a front end of the combustion gas cooler of the exhaust discharge line.

Preferably, a tail gas supply line for supplying tail gas generated by hydrogen purification in the hydrogen purifier to the cracker further includes, and in the hydrogen purifier, pressure swing adsorption (PSA) Hydrogen can be purified by

Preferably, the undecomposed ammonia removal unit receives the decomposed gas from the decomposer, and includes a water port for dissolving and collecting the undecomposed ammonia in water; and a regeneration line for removing ammonia from the aqueous ammonia solution generated in the water port and circulating water to the water port.

Preferably, the undecomposed ammonia removal unit is provided in the regeneration line and receives the tail gas to be supplied to the cracker from the hydrogen purifier through the tail gas supply line and separates ammonia from the aqueous ammonia solution; a cooler provided in the regeneration line and cooling water from which ammonia has been removed through the membrane separator; and a pump provided in the regeneration line and transporting the water cooled by the cooler to the water port.

Preferably, the undecomposed ammonia removal unit may remove undecomposed ammonia from the decomposed gas by thermal swing adsorption (TSA).

Preferably, the hydrogen purified in the hydrogen purifier may be supplied as fuel to a fuel cell for onboard propulsion or power generation.

According to another aspect of the present invention, liquid ammonia is vaporized, and the vaporized ammonia is thermally decomposed in a decomposer to generate a decomposition gas containing hydrogen, nitrogen, and undecomposed ammonia, and the decomposed ammonia is collected and removed from the decomposition gas. Nitrogen is removed through a hydrogen purifier, and the purified hydrogen is supplied as fuel to the onboard fuel cell, and the combustion gas generated from the thermal decomposition of ammonia in the decomposer is denitrated in the selective catalytic reduction unit (SCR) and discharged overboard, and the liquid ammonia is vaporized There is provided an ammonia decomposition method of a ship, characterized in that for supplying the ammonia to the selective catalytic reduction unit as a reducing agent.

Preferably, the hydrogen purifier purifies hydrogen by pressure swing adsorption (PSA), and tail gas generated by hydrogen purification in the hydrogen purifier may be supplied to the cracker.

Preferably, the decomposed gas generated in the cracker is supplied to a water port to dissolve undecomposed ammonia in water and collected, and the aqueous ammonia solution generated in the water port and the tail gas to be supplied from the hydrogen purifier to the cracker are transferred to the membrane. After being supplied from the separator and separating ammonia from the aqueous ammonia solution, the water from which the ammonia is removed may be cooled and circulated to the water port.

In the present invention, liquid ammonia is vaporized, the vaporized ammonia is pyrolyzed in a decomposer, and hydrogen purified by removing undecomposed ammonia and nitrogen is supplied as fuel to a fuel cell on board, thereby providing a liquid state that is easy to store and transport on board. While storing ammonia, it is possible to effectively generate hydrogen from ammonia to supply hydrogen fuel required for a fuel cell.

In particular, the combustion gas generated during ammonia pyrolysis is sent to the selective catalytic reduction unit (SCR) along with vaporized ammonia from the vaporizer to denitrify, thereby reducing nitrogen oxides (NOx) to meet overboard emission standards and reducing air pollutant emissions. can be minimized.

In addition, instead of urea, which is normally used as a reducing agent when applying SCR, gas ammonia generated during the hydrogen production process is applied as a reducing agent in the selective catalytic reduction unit, thereby reducing carbon dioxide generation and providing devices for storing and supplying urea water. Installation space and installation cost can be reduced.

1 schematically shows an ammonia decomposition system of a ship according to an 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, ships in the present invention refer to all types of ships equipped with fuel cells capable of using hydrogen generated by decomposing ammonia to be described later as fuel, and are representative of LNG carriers, liquid hydrogen carriers, and LNG RVs. It includes ships with self-propelled capabilities such as (Regasification Vessel), as well as offshore structures floating on the sea that do not have propulsion capabilities, such as LNG FPSO (Floating Production Storage Offloading) and LNG FSRU (Floating Storage Regasification Unit). In other words, a fuel cell using hydrogen as fuel may be provided for propulsion or power generation of a ship.

1 schematically shows an ammonia decomposition system of a ship according to an embodiment of the present invention.

As shown in FIG. 1, the ship's ammonia decomposition system of this embodiment includes a vaporizer 100 for receiving liquid ammonia and vaporizing it, receiving vaporized ammonia from the vaporizer and thermally decomposing it to contain hydrogen, nitrogen and undecomposed ammonia. A cracker 200 that generates gas, an undecomposed ammonia removal unit that collects undecomposed ammonia from the cracked gas, and a hydrogen purifier 400 that receives the cracked gas that has passed through the undecomposed ammonia remover and removes nitrogen to purify it into hydrogen. Including, it is a system that stores ammonia in a liquid state, vaporizes it, pyrolyzes it, purifies it, and supplies hydrogen fuel to a fuel cell provided on board.

In particular, in the system of this embodiment, the combustion gas generated while decomposing ammonia in the decomposer passes through the Selective Catalytic Reduction (SCR) 500 to denitrate the nitrogen oxides contained in the combustion gas, but is usually used as a reducing agent in SCR. It is characterized in that it is configured to spray a portion of gas ammonia generated in the vaporizer 100 to the combustion gas instead of urea water to be used as a reducing agent for denitrification.

First, we look at the process of producing hydrogen from ammonia in this system.

Ammonia stored in a liquid state, such as in a storage tank on board, is supplied to the vaporizer 100 and vaporized to produce gaseous ammonia. Ammonia can be stored in a liquid state up to a temperature of about 50 ° C at 20 bar and up to 25.7 ° C at 10 bar, so it can be stored on board in a liquid state with a small volume, transported to a vaporizer, vaporized, and then used for hydrogen generation.

Gaseous ammonia is supplied to the decomposer 200 along the pipe HL and separated into hydrogen and nitrogen as it is thermally decomposed. The decomposed gas includes a part of gaseous ammonia undecomposed in the decomposer. The decomposer may comprise a combustion chamber for pyrolysis of ammonia.

The decomposed gas including hydrogen, nitrogen, and undecomposed ammonia generated in the cracker 200 is supplied to the undecomposed ammonia removal unit.

The undecomposed ammonia removal unit includes a water port 300 that collects undecomposed ammonia by dissolving it in water by receiving decomposition gas from the decomposer, and removing ammonia from an aqueous ammonia solution generated by dissolving undecomposed ammonia in the water port to the water port. It includes a regeneration line (UL) for circulating water.

Ammonia has a very high water solubility of about 89.5, while hydrogen and nitrogen have very low water solubility of 0.0002 and 0.003, respectively. The undecomposed ammonia contained in is dissolved in water and collected, and the decomposed gas passing through the water port is sent to the hydrogen purifier 400 through the upper part of the water port for purification.

The undecomposed ammonia removal unit may collect and remove undecomposed ammonia from cracked gas by a thermal swing adsorption (TSA) method, and then supply the undecomposed ammonia to a hydrogen purifier.

On the other hand, in the hydrogen purifier 400, the decomposed gas is supplied, nitrogen is removed, purified into pure hydrogen, and then supplied as fuel to the onboard fuel cell. The hydrogen purifier 400 may purify hydrogen by removing nitrogen from cracked gas by, for example, a pressure swing adsorption (PSA) method.

Tail gas generated during hydrogen purification in the hydrogen purifier 400 is supplied to the cracker 200 through the tail gas supply line TL and used as a heat source for ammonia decomposition.

On the other hand, in the regeneration line UL of the undecomposed ammonia removal unit, a membrane separator 310 for separating ammonia from an aqueous ammonia solution, a cooler 320 for cooling water from which ammonia has been removed through the membrane separator, and cooling in the cooler A pump 330 is provided to transport the water to the water port, and after removing the ammonia dissolved in the aqueous ammonia solution by membrane separation, the water is cooled and circulated to the water port to be reused for ammonia collection.

In the membrane separator 310, ammonia is removed from the aqueous ammonia solution by membrane separation. To this end, the aqueous ammonia solution generated in the water port 300 and the tail gas generated in the hydrogen purifier 400 are supplied to the membrane separator. The tail gas generated in the hydrogen purifier and supplied to the cracker 200 through the tail gas supply line TL passes through the membrane separator 310, absorbs ammonia from the aqueous ammonia solution by the difference in partial pressure, and then supplies the tail gas to the cracker 200. do. The high-temperature tail gas with high ammonia concentration through the membrane separator is used as a heat source for the cracker, and at the same time, ammonia in the tail gas is used as a raw material for hydrogen generation.

On the other hand, the combustion gas generated from the thermal decomposition of ammonia in the cracker 200 is supplied to the selective catalytic reduction unit (SCR) 500 to denitrate. A significant amount of nitrogen oxides may be included in the combustion gas, which is a representative air pollutant and is a substance regulated by the IMO for overboard emissions.

As the reducing agent in the selective catalytic reduction unit, an aqueous solution of urea ((NH ₂ ) ₂ CO), that is, urea water, is often used. Since it needs to be maintained, there is a problem of installation space and installation cost.

In this embodiment, ammonia is directly used as a reducing agent in the selective catalytic reduction unit instead of urea, and a portion of gaseous ammonia vaporized in the vaporizer is branched to supply the selective catalytic reduction unit as a reducing agent.

To this end, an exhaust discharge line (EL) is provided to discharge the combustion gas generated from the decomposer 200 overboard through the selective catalytic reduction unit, and a combustion gas cooler is provided in the exhaust discharge line to cool the combustion gas to a temperature required by the selective catalytic reduction unit. 510 is provided, and a reducing agent supply line RL is connected from the vaporizer 100 to the front end of the combustion gas cooler of the exhaust discharge line. The reducing agent supply line is provided with a valve (V) capable of opening and closing the pipe and adjusting the supply of gaseous ammonia.

Gaseous ammonia generated in the vaporizer 100 is injected into the combustion gas through the reducing agent supply line RL, and cooled to a temperature suitable for the catalytic reduction reaction through the combustion gas cooler 510, for example, 280 to 500 ° C. After that, it flows into the selective catalytic reduction unit 500. In the selective catalytic reduction unit, ammonia reacts with NOx in the presence of a catalyst inside the reactor to change into N ₂ and H ₂ O, reducing the NOx content in the combustion gas, and the reaction formula is as follows.

Unreacted ammonia included in the combustion gas can also be used as a reducing agent in the selective catalytic reduction unit.

In this way, by denitrifying the combustion gas generated in the decomposer and reducing nitrogen oxides (NOx) in the combustion gas, it is possible to meet the overboard emission standards and minimize the emission of air pollutants.

It is obvious to those skilled in the art that the present invention is not limited to the above embodiments and can be variously modified or modified without departing from the technical gist of the present invention. it did

100: vaporizer
200: decomposer
300: Waterport
310: membrane separator
320: cooler
330: pump
400: hydrogen purifier
500: selective catalytic reduction unit
510: combustion gas cooler
RL: reducing agent supply line
TL: Tail gas supply line

Claims (10)

A vaporizer for receiving and vaporizing liquid ammonia;
A decomposer that receives the vaporized ammonia supplied from the vaporizer and thermally decomposes it to generate a decomposition gas containing hydrogen, nitrogen, and undecomposed ammonia;
an undecomposed ammonia removal unit collecting undecomposed ammonia from the decomposed gas;
a hydrogen purifier receiving the cracked gas that has passed through the undecomposed ammonia removal unit and purifying it into hydrogen by removing nitrogen; and
A selective catalytic reduction unit (SCR) for denitrifying combustion gas generated by thermal decomposition of ammonia in the decomposer;
Ammonia decomposition system of a ship, characterized in that gaseous ammonia vaporized in the vaporizer is supplied as a reducing agent to the selective catalytic reduction unit. According to claim 1,
an exhaust discharge line supplying the combustion gas generated in the decomposer to the selective catalytic reduction unit;
a combustion gas cooler provided in the exhaust discharge line to cool the combustion gas to a temperature required by the selective catalytic reduction unit; and
The ship's ammonia decomposition system further comprising: a reducing agent supply line connected from the vaporizer to the front end of the combustion gas cooler of the exhaust discharge line. According to claim 2,
Further comprising a tail gas supply line for supplying tail gas generated by hydrogen purification in the hydrogen purifier to the cracker,
In the hydrogen purifier, the ship's ammonia decomposition system, characterized in that for purifying hydrogen by pressure swing adsorption (PSA). The method of claim 3, wherein the undecomposed ammonia removal unit
a water port receiving the decomposition gas from the decomposer and dissolving and collecting undecomposed ammonia in water; and
Ammonia decomposition system of a ship comprising: a regeneration line for removing ammonia from the aqueous ammonia solution generated in the water port and circulating water to the water port. The method of claim 4, wherein the undecomposed ammonia removal unit
a membrane separator provided in the regeneration line and configured to separate ammonia from the aqueous ammonia solution by receiving the tail gas to be supplied to the cracker from the hydrogen purifier through the tail gas supply line;
a cooler provided in the regeneration line and cooling water from which ammonia has been removed through the membrane separator; and
Ammonia decomposition system of a ship further comprising: a pump provided in the regeneration line and transporting the water cooled in the cooler to the water port. According to claim 3,
The ammonia decomposition system of a ship, characterized in that the undecomposed ammonia removal unit removes undecomposed ammonia from the decomposition gas by thermal swing adsorption (TSA). According to any one of claims 1 to 6,
Ammonia decomposition system of a ship, characterized in that the hydrogen purified in the hydrogen purifier is supplied as fuel to a fuel cell for onboard propulsion or power generation. The liquid ammonia is vaporized, and the vaporized ammonia is thermally decomposed in a cracker to generate a cracked gas containing hydrogen, nitrogen, and undecomposed ammonia, and after collecting and removing the undecomposed ammonia from the cracked gas, nitrogen is removed through a hydrogen purifier, Purified hydrogen is supplied as fuel to the onboard fuel cell,
The combustion gas generated by the thermal decomposition of ammonia in the decomposer is denitrated in a selective catalytic reduction unit (SCR) and discharged overboard,
Ammonia decomposition method of a ship, characterized in that for supplying ammonia vaporized from liquid ammonia as a reducing agent to the selective catalytic reduction unit. According to claim 8,
In the hydrogen purifier, hydrogen is purified by pressure swing adsorption (PSA),
Ammonia decomposition method of a ship, characterized in that the tail gas generated by hydrogen purification in the hydrogen purifier is supplied to the cracker. According to claim 8,
Supplying the decomposed gas generated in the decomposer to a water port to dissolve and collect undecomposed ammonia in water,
The membrane separator receives the aqueous ammonia solution generated in the water port and the tail gas to be supplied to the cracker from the hydrogen purifier, separates ammonia from the aqueous ammonia solution, and then cools and circulates the water from which the ammonia is removed to the water port. Ammonia decomposition method of a ship, characterized in that.

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