KR102664944B1 - Ammonia Decomposition System And Method For Ship - Google Patents

Abstract

A marine ammonia decomposition system and method are disclosed. The ammonia decomposition system of the present invention includes a vaporizer that receives liquid ammonia and vaporizes it; A decomposition unit that receives the ammonia vaporized in the vaporizer and thermally decomposes it to produce decomposition gas containing hydrogen, nitrogen, and undecomposed ammonia; An undecomposed ammonia removal unit that collects undecomposed ammonia from the decomposed gas; A hydrogen purifier that receives the decomposed gas that has passed through the undecomposed ammonia removal unit, removes nitrogen, and purifies it into hydrogen; and a selective catalytic reduction unit (SCR) for denitrifying combustion gas generated by thermal decomposition of ammonia in the decomposition unit, wherein gaseous ammonia vaporized in the vaporizer is supplied to the selective catalytic reduction unit as a reducing agent.

Description

Ammonia Decomposition System And Method For Ship}

The present invention relates to a system and method for ammonia decomposition on ships, and more specifically, to vaporize liquid ammonia, thermally decompose the vaporized ammonia in a decomposer, remove undecomposed ammonia and nitrogen, and use purified hydrogen as fuel for fuel cells onboard ships. It relates to a ship's ammonia decomposition system and method that supplies and denitrifies combustion gas generated from ammonia thermal decomposition along with gaseous ammonia to a selective catalytic reduction unit (SCR).

As the global warming phenomenon intensifies, efforts are being made to reduce greenhouse gas emissions around the world, and as the 1997 Kyoto Protocol, which included obligations for developed countries to reduce greenhouse gases, expires in 2020, the event held in Paris, France in December 2015 The 195 parties participating in the Paris Climate Change Accord, which was adopted at the 21st United Nations Framework Convention on Climate Change and came into effect in November 2016, are making various efforts with the goal of reducing greenhouse gases.

Along with this global trend, interest in renewable energy (or renewable energy) such as wind, solar energy, solar power, bioenergy, tidal power, and geothermal heat as a pollution-free energy that can replace fossil fuels and nuclear power is increasing, and various technologies are being developed. I'm losing.

Liquefied gases, including liquefied natural gas, can remove or reduce air pollutants during the liquefaction process, so they can be viewed as eco-friendly fuels that emit fewer air pollutants during combustion. Accordingly, the consumption of liquefied gases such as Liquefied Natural Gas (LNG) and LPG (Liquefied Petroleum Gas) has recently been rapidly increasing worldwide. Liquefied gas, which is made by liquefying gas at low temperature, has a much smaller volume than gas, so it has the advantage of increasing storage and transportation 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 of that of natural gas. Therefore, when natural gas is liquefied and transported, it can be transported very efficiently.

Liquefied petroleum gas (LPG) has different liquefaction temperatures depending on its composition, but in the case of petroleum gas mainly containing propane, it is liquefied at a low temperature of about -42℃ at normal pressure, up to a temperature of about 45℃ at 18 bar, and 20℃ at 7 bar. It can be stored in liquid state up to ℃.

Meanwhile, conventional LPG carriers, etc., adopt a fuel supply system that uses relatively inexpensive heavy oil such as bunker C oil as propulsion fuel for ships. This heavy oil fuel supply system has the international exhaust gas emissions associated with the use of heavy oil fuel. Due to strengthened regulations, a separate low-sulfur heavy fuel fuel tank (LSHFO tank) had to be installed, and the demand for an eco-friendly fuel supply system that meets international environmental regulation standards has increased.

Recently, the application of fuel supply systems that use LPG or LNG and boil-off gas generated therefrom as propulsion fuel has been increasing in LPG or LNG carriers, and in accordance with the strengthening of international exhaust gas emission regulations, in addition to LPG or LNG carriers, general ships also use LNG. The number of ships using propulsion fuel is increasing.

However, although LNG and LPG are considered eco-friendly fuels compared to other fossil fuels previously used as ship fuels, they still produce carbon dioxide when burned, and ships that use them as fuel still emit carbon dioxide during operation.

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

According to EEDI (Energy Efficiency Design Index), a mandatory carbon dioxide reduction regulation applied by IMO to new ships, the initial EEDI announcement called for a 10% reduction in carbon dioxide emissions in 2015 based on carbon dioxide emissions from 2013 to 2015. EEDI Phase 1 was applied, and it was planned to apply Phase 3 in 2025 by strengthening and applying one step every five years. However, for LPG carriers, EEDI Phase 3 will be applied early from 2022, two years after the application of EEDI Phase 2. It is being done. As regulations on carbon dioxide emissions from ships are rapidly being strengthened, it may be difficult to achieve carbon dioxide emissions regulations in the future by using only LNG or LPG as fuel.

Accordingly, various studies are being conducted on eco-friendly marine fuels that can reduce carbon dioxide emissions, and recently, technologies for marine engines that can use ammonia as fuel along with fuels such as LNG or LPG are being researched and developed.

Ammonia (NH ₃ ) is a substance in which three hydrogens are bonded to one nitrogen. It can form strong hydrogen bonds between molecules, making it easy to liquefy. It has a boiling point of -33.34°C and a melting point of -77.73°C at 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 any carbon dioxide, so it is attracting attention as an eco-friendly marine fuel that can respond to the trend of strengthening international greenhouse gas emission standards.

In addition, ammonia contains three hydrogen atoms per molecule and is easier to liquefy and store than hydrogen, so its value as a means of transporting hydrogen to use hydrogen, a representative eco-friendly fuel, as a fuel has been recognized, and various studies are being conducted.

The present invention seeks to propose a method of producing hydrogen from ammonia on a ship and supplying it as onboard fuel, and reducing nitrogen oxides in combustion gas generated during the hydrogen production process so that combustion gas can be discharged in compliance with overboard emission regulation standards. .

According to one aspect of the present invention for solving the above-described problem, a vaporizer that receives liquid ammonia and vaporizes it;

A decomposition unit that receives ammonia vaporized from the vaporizer and thermally decomposes it to produce decomposed gas containing hydrogen, nitrogen, and undecomposed ammonia;

An undecomposed ammonia removal unit that collects undecomposed ammonia from the decomposed gas;

A hydrogen purifier that receives the decomposed gas that has passed through the undecomposed ammonia removal unit, removes nitrogen, and purifies it into hydrogen; and

It includes a selective catalytic reduction unit (SCR) that denitrifies combustion gas generated by thermal decomposition of ammonia in the decomposition unit,

An ammonia decomposition system for ships is provided, wherein gaseous ammonia vaporized in the vaporizer is supplied as a reducing agent to the selective catalytic reduction unit.

Preferably, an exhaust discharge line supplies combustion gas generated from the decomposition unit 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 carburetor to the front end of the combustion gas cooler of the exhaust discharge line.

Preferably, the hydrogen purifier further includes a tail gas supply line that supplies tail gas generated from hydrogen purification to the decomposition unit, and in the hydrogen purifier, pressure swing adsorption (PSA) is used. Hydrogen can be purified by

Preferably, the undigested ammonia removal unit receives the decomposed gas from the decomposer and collects the undecomposed ammonia by dissolving it in water; and a regeneration line that removes ammonia from the ammonia aqueous solution generated in the water port and circulates water to the water port.

Preferably, the undecomposed ammonia removal unit is provided in the regeneration line and receives tail gas to be supplied to the decomposition unit from the hydrogen purifier through the tail gas supply line, and includes a membrane separator that separates ammonia from the aqueous ammonia solution. A cooler provided in the regeneration line to cool the water from which ammonia has been removed through the membrane separator; and a pump provided in the regeneration line and transporting water cooled in 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 can be supplied as fuel to a fuel cell for propulsion or power generation on board the ship.

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

Preferably, in the hydrogen purifier, hydrogen is purified by pressure swing adsorption (PSA), and tail gas generated from hydrogen purification in the hydrogen purifier can be supplied to the decomposer.

Preferably, the decomposition gas generated in the decomposer is supplied to a water port to collect the undecomposed ammonia by dissolving it in water, and the ammonia aqueous solution generated in the water port and the tail gas to be supplied to the decomposer from the hydrogen purifier are separated into a membrane. After ammonia is separated from the ammonia aqueous solution supplied from a separator, the water from which ammonia has been removed can be cooled and circulated to the water port.

In the present invention, liquid ammonia is vaporized, the vaporized ammonia is thermally decomposed in a decomposer, and the undecomposed ammonia and nitrogen are removed and the purified hydrogen is supplied as fuel to the ship's fuel cell, thereby producing a liquid form that is easy to store and transport on board. While storing ammonia, hydrogen can be effectively generated from ammonia to supply the hydrogen fuel needed for a fuel cell.

In particular, by sending the combustion gas generated during ammonia thermal decomposition to the Selective Catalytic Reduction (SCR) along with the ammonia vaporized in the vaporizer for denitrification, nitrogen oxides (NOx) can be reduced to meet overboard emission standards and air pollutant emissions can be reduced. It can be minimized.

In addition, instead of urea, which is usually used as a reducing agent when applying SCR, gaseous 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 installing devices for storing and supplying urea water. Installation space and installation costs can be reduced.

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

In order to fully understand the operational advantages of the present invention and the objectives achieved by practicing 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 structure and operation of a preferred embodiment of the present invention will be described in detail with reference to the attached drawings. Here, in adding reference numerals to components in each drawing, it should be noted that identical components are indicated with the same reference numerals as much as possible, even if they are shown in different drawings.

Hereinafter, the ship in the present invention refers to all types of ships equipped with a fuel cell that can use hydrogen generated by decomposing ammonia, which will be described later, as fuel. Representative examples include LNG Carrier, Liquid Hydrogen Carrier, and LNG RV. It includes ships with self-propulsion capabilities such as (Regasification Vessel), as well as offshore structures that do not have propulsion capabilities but are floating at sea, such as LNG FPSO (Floating Production Storage Offloading) and LNG FSRU (Floating Storage Regasification Unit). , a fuel cell using hydrogen as fuel may be provided for ship propulsion or power generation.

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

As shown in FIG. 1, the ammonia decomposition system of the ship of this embodiment includes a vaporizer 100 that receives liquid ammonia and vaporizes it, and receives ammonia vaporized in the vaporizer and thermally decomposes it to include hydrogen, nitrogen, and undecomposed ammonia. A decomposer 200 that generates gas, an undigested ammonia removal unit that collects undigested ammonia from the decomposed gas, and a hydrogen purifier 400 that receives the decomposed gas that has passed through the undecomposed ammonia removal unit, removes nitrogen, and purifies 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 installed on board the ship.

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 denitrify nitrogen oxides contained in the combustion gas, but is usually used as a reducing agent in SCR. It is characterized by being configured to spray some of the gaseous ammonia generated in the vaporizer 100 into the combustion gas and use it as a reducing agent for denitrification instead of urea water.

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

Ammonia stored in a liquid state in a storage tank onboard the ship is supplied to the vaporizer 100 and vaporized to generate 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, transferred to a vaporizer, vaporized, and used to generate hydrogen.

Ammonia in a gaseous state is supplied to the decomposer 200 along the pipe HL and is thermally decomposed and separated into hydrogen and nitrogen. The decomposition gas contains some gaseous ammonia that has not been decomposed in the decomposition unit. The decomposer may be configured to include a combustion chamber for thermally decomposing ammonia.

The decomposition gas containing hydrogen, nitrogen, and undecomposed ammonia generated in the decomposer 200 is supplied to the undecomposed ammonia removal unit.

The undecomposed ammonia removal unit includes a water port (300) that receives decomposed gas from the decomposer and collects the undecomposed ammonia by dissolving it in water, and removes ammonia from the ammonia aqueous solution produced by dissolving the undecomposed ammonia in the water port and transfers it to the water port. Includes a regeneration line (UL) that circulates 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. Therefore, the decomposed gas generated in the decomposer is transferred to the water port 300, and the decomposed gas is The undecomposed ammonia contained in is collected by dissolving in water, and the decomposed gas that has passed 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 the decomposed gas using Thermal Swing Adsorption (TSA) method and then supply it to the hydrogen purifier.

Meanwhile, the hydrogen purifier 400 receives decomposed gas, removes nitrogen, purifies it into pure hydrogen, and supplies it as fuel to the fuel cell onboard the ship. The hydrogen purifier 400 can purify hydrogen by removing nitrogen in decomposed gas by, for example, pressure swing adsorption (PSA).

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

Meanwhile, in the regeneration line (UL) of the undecomposed ammonia removal unit, there is a membrane separator 310 that separates ammonia from the aqueous ammonia solution, a cooler 320 that cools the water from which ammonia has been removed through the membrane separator, and cooling in the cooler. A pump 330 is provided to transfer the water to the water port, and the ammonia dissolved in the ammonia solution is removed by membrane separation, and then 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 ammonia aqueous solution through membrane separation. For this purpose, the ammonia aqueous 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 to be supplied to the decomposer 200 through the tail gas supply line (TL) passes through the membrane separator 310, absorbs ammonia from the aqueous ammonia solution by a partial pressure difference, and then supplies it to the decomposer 200. do. The high-temperature tail gas, whose ammonia concentration has increased through the membrane separator, is used as a heat source for the decomposer, and at the same time, the ammonia in the tail gas is used as a raw material for hydrogen production.

Meanwhile, the combustion gas generated by thermal decomposition of ammonia in the decomposer 200 is supplied to the selective catalytic reduction (SCR) 500 and denitrified. Combustion gases may contain significant amounts of nitrogen oxides, which are representative air pollutants and are regulated by the IMO for overboard emissions.

As a reducing agent in the selective catalytic reduction unit, an aqueous solution of urea ((NH ₂ ) ₂ CO), that is, urea water, is often used. When urea is stored in an aqueous solution, its service life decreases over time and the temperature is maintained at a constant temperature. Since it has to be maintained, there are issues with installation space and installation costs.

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

For this purpose, an exhaust discharge line (EL) is provided that discharges the combustion gas generated from the decomposer 200 overboard through the selective catalytic reduction unit, and a combustion gas cooler is installed in the exhaust discharge line to cool the combustion gas to the required temperature in the selective catalytic reduction unit. (510) is provided, and a reducing agent supply line (RL) is connected from the carburetor 100 to the front end of the combustion gas cooler of the exhaust discharge line. The reducing agent supply line is equipped with a valve (V) that opens and closes the pipe and controls the supply amount of gaseous ammonia.

Gaseous ammonia generated in the vaporizer 100 is injected as combustion gas through the reducing agent supply line (RL), and cooled to a temperature suitable for the catalytic reduction reaction, for example, around 280 to 500 ° C. through the combustion gas cooler 510. Afterwards, 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 and changes into N ₂ and H ₂ O, thereby reducing the NOx content in the combustion gas. The reaction formula is as follows.

Unreacted ammonia contained in 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, overboard emission standards can be met and air pollutant emissions can be minimized.

It is obvious to those skilled in the art that the present invention is not limited to the above-mentioned embodiments, and that it can be implemented with various modifications or variations without departing from the technical gist of the present invention. It was done.

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 that receives liquid ammonia and vaporizes it;
A decomposition unit that receives ammonia vaporized from the vaporizer and thermally decomposes it to produce decomposed gas containing hydrogen, nitrogen, and undecomposed ammonia;
An undecomposed ammonia removal unit that collects undecomposed ammonia from the decomposed gas;
A hydrogen purifier that receives the decomposed gas that has passed through the undecomposed ammonia removal unit, removes nitrogen, and purifies it into hydrogen;
A selective catalytic reduction unit (SCR) that denitrifies combustion gas generated by thermal decomposition of ammonia in the decomposition unit; and
It includes a tail gas supply line that supplies tail gas generated from hydrogen purification in the hydrogen purifier to the decomposer,
The undigested ammonia removal unit includes a water port that receives the decomposed gas from the decomposition unit and collects the undecomposed ammonia by dissolving it in water; A regeneration line that removes ammonia from the ammonia aqueous solution generated in the water port and circulates water to the water port; A membrane separator provided in the regeneration line, receives tail gas to be supplied from the hydrogen purifier to the decomposition unit through the tail gas supply line, and separates ammonia from the aqueous ammonia solution; A cooler provided in the regeneration line to cool the water from which ammonia has been removed through the membrane separator; And a pump provided in the regeneration line and transporting water cooled in the cooler to the water port,
Ammonia decomposition system for ships, characterized in that gaseous ammonia vaporized in the vaporizer is supplied as a reducing agent to the selective catalytic reduction unit. According to clause 1,
An exhaust discharge line that supplies combustion gas generated from the decomposition unit 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 the front end of the combustion gas cooler of the exhaust discharge line. According to clause 2,
A ship's ammonia decomposition system, characterized in that hydrogen is purified by pressure swing adsorption (PSA) in the hydrogen purifier. delete delete According to clause 3,
A ship's ammonia decomposition system, characterized in that the undecomposed ammonia removal unit removes undecomposed ammonia from the decomposed gas by thermal swing adsorption (TSA). According to any one of claims 1 to 3 or 6,
A ship's ammonia decomposition system, wherein the hydrogen purified in the hydrogen purifier is supplied as fuel to a fuel cell for propulsion or power generation on board the ship. Liquid ammonia is vaporized, the vaporized ammonia is thermally decomposed in a decomposition device to generate decomposed gas containing hydrogen, nitrogen, and undecomposed ammonia, and the decomposed gas is supplied to a water port to collect and remove the undecomposed ammonia from the decomposed gas. Nitrogen is removed through a hydrogen purifier and the purified hydrogen is supplied as fuel to the ship's fuel cells.
The ammonia aqueous solution generated in the water port and the tail gas to be supplied from the hydrogen purifier to the decomposition unit are supplied from a membrane separator, and ammonia is separated from the ammonia aqueous solution. The water from which ammonia has been removed is cooled and circulated to the water port. ,
The combustion gas generated by thermal decomposition of ammonia in the decomposition unit is denitrified in the selective catalytic reduction unit (SCR) and discharged overboard,
A method of decomposing ammonia on a ship, characterized in that ammonia vaporized from liquid ammonia is supplied as a reducing agent to the selective catalytic reduction unit. According to clause 8,
In the hydrogen purifier, hydrogen is purified by pressure swing adsorption (PSA),
A method of decomposing ammonia on a ship, characterized in that tail gas generated from hydrogen purification in the hydrogen purifier is supplied to the decomposition unit. delete

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