EP-4741711-A1 - GAS COMBUSTION SYSTEM FOR AMMONIA

Abstract

A gas combustion arrangement (100) and method for combusting ammonia originating from an ammonia handling system of a marine vessel is provided. The arrangement comprises a combustion chamber (110) comprising a combustion zone (112) and a dilution zone (114), a primary burner (120) configured to combust a primary fuel feed, comprising the ammonia, in the combustion zone, an air supply system (130) configured to provide a combustion air flow to the primary burner and a dilution air flow to the dilution zone, and a secondary burner (140) configured to combust a secondary fuel feed to provide a support flame supporting the combustion of the primary fuel feed.

Inventors

• MØLGAARD, Søren
• MADSEN, Max

Assignees

• Alfa Laval Corporate AB

Dates

Publication Date

20260513

Application Date

20241111

Claims (17)

1. A gas combustion arrangement (100) for combusting ammonia originating from an ammonia handling system of a marine vessel, comprising: a combustion chamber (110) comprising a combustion zone (112) and a dilution zone (114); a primary burner (120) configured to combust a primary fuel feed, comprising the ammonia, in the combustion zone; an air supply system (130) configured to provide a combustion air flow to the primary burner and a dilution air flow to the dilution zone; and a secondary burner (140) configured to combust a secondary fuel feed to provide a support flame supporting the combustion of the primary fuel feed.
2. The gas combustion arrangement according to claim 1, wherein the secondary fuel feed comprises an ammonia-based fuel.
3. The gas combustion arrangement according to claim 1 or 2, wherein the secondary fuel feed comprises a fuel based on at least one of methane, methanol, liquid hydrocarbons, or hydrogen.
4. The gas combustion arrangement according to any of the preceding claims, wherein the air supply system is configured to draw air for the combustion air flow and the dilution air flow from a common air source.
5. The gas combustion arrangement according to any of claims 1-3, wherein the air supply system is configured to draw air for the combustion air flow and air for the dilution air flow from separate air sources.
6. The gas combustion arrangement according to any of the preceding claims, wherein the air supply system is configured to control the combustion air flow and the dilution air flow independently of each other.
7. The gas combustion arrangement according to any of the preceding claims, further comprising an oxidation catalyst (160) configured to remove residual ammonia from combustion gases generated by the combustion of the primary fuel feed.
8. The gas combustion arrangement according to claim 9, wherein the air supply system is configured to introduce the dilution air flow into the combustion chamber at a position located between the combustion zone and the oxidation catalyst.
9. The gas combustion arrangement according to any of the preceding claims, further comprising a reduction catalyst (150) configured to remove nitrogen oxides from the combustion gases generated by the combustion of the primary fuel feed.
10. The gas combustion arrangement according to claim 9, further comprising a reduction agent supply system (152) configured to provide a reduction agent to the reduction catalyst.
11. A method (200) for combusting ammonia, originating from an ammonia handling system of a marine vessel, in a combustion zone of a combustion chamber, the method comprising: providing (202) a primary fuel feed, comprising the ammonia, to a primary burner; providing (204) a combustion air flow to the primary burner; combusting (206), by the primary burner, the primary fuel feed; providing (208) a dilution air flow to a dilution zone of the combustion chamber; and operating a support flame system in at least one of an active mode (212) and an inactive mode (214), wherein the support flame system in the active mode combusts a secondary fuel feed to generate a support flame supporting the combustion of the primary fuel feed.
12. The method according to claim 11, comprising: determining a temperature in the combustion chamber; operating the support flame system in the inactive mode based on the temperature exceeding a predetermined temperature threshold; and operating the support flame system in the active mode based on the temperature being at or below the predetermined temperature threshold.
13. The method according to claim 11, comprising: operating the support flame system in the active mode during an ignition phase of the primary burner.
14. The method according to claim 11, comprising: determining an ammonia concentration in the primary fuel feed; operating the support flame system in the inactive mode based on the ammonia concentration exceeding a predetermined concentration threshold; and operating the support flame system in the active mode based on the ammonia concentration being at or below the predetermined concentration threshold.
15. The method according to claim 11, comprising: determining a concentration of residual ammonia in exhaust gases generated by the combustion of the primary fuel feed; operating the support flame system in the inactive mode based on the concentration of residual ammonia being at or below a predetermined concentration threshold; and operating the support flame system in the active mode based on the concentration of residual ammonia exceeding the predetermined concentration threshold.
16. The method according to any of claims 11-13, comprising: controlling the dilution air flow based on a concentration of residual ammonia in exhaust gases generated by the combustion of the primary fuel feed.
17. The method according to any of claims 11-13, comprising: passing exhaust gases, generated by the combustion of the primary fuel feed, through an oxidation catalyst to remove residual ammonia from the exhaust gases; and controlling the dilution air flow based on a temperature of the exhaust gases passing through the oxidation catalyst.

Description

Technical field The present disclosure relates to gas combustion arrangements and methods for combusting ammonia. More particularly, the disclosure pertains to systems and techniques for combusting ammonia originating from ammonia handling systems of marine vessels, including fuel tanks. Background Marine vessels have traditionally relied on fossil fuels for propulsion and power generation. However, growing environmental concerns and regulatory pressures have led to increased interest in alternative fuel sources. Among these alternatives, ammonia is particularly promising due to its carbon-free composition, which helps eliminating carbon dioxide emissions. However, the storage and handling of ammonia present challenges, such as handling boil-off gas produced as ammonia evaporates due to ambient heat absorption. Additionally, ammonia poses significant safety risks, as exposure to high concentrations can be life threatening. Therefore, it is crucial to ensure proper handling of the boil-off gas as well as a complete evacuation of ammonia from the ammonia handling systems during planned shutdowns, inspections, and maintenance. One approach would be to combust the released ammonia using a gas combustion system. However, it is challenging to design combustion systems that are capable of handling varying concentrations and flow rates of ammonia, particularly during evacuation and purging in preparation for planned maintenance. There is therefore a need for improved gas combustion arrangements and methods for safely and efficiently combusting ammonia originating from the handling systems of marine vessels. Summary It is an object of the present disclosure to provide a technology that addresses at least some of the above concerns. According to a first aspect, there is provided a gas combustion arrangement for combusting ammonia from a marine vessel's ammonia handling system. The gas combustion arrangement comprises a combustion chamber with a combustion zone and a dilution zone, a primary burner configured to combust a primary fuel feed, comprising the ammonia, in the combustion zone, and an air supply system configured to provide a combustion air flow to the primary burner and a dilution air flow to the dilution zone. Additionally, the gas combustion arrangement comprises a secondary burner configured to combust a secondary fuel feed to provide a support flame supporting the combustion of the primary fuel feed. According to a second aspect, there is provided a method for combusting ammonia, which originates an ammonia handling system of a marine vessel, in a combustion zone of a combustion chamber. The method comprises providing a primary fuel feed, comprising the ammonia, to a primary burner, providing a combustion air flow to the primary burner, and combusting, by the primary burner, the primary fuel feed. Additionally, the method comprises providing a dilution air flow to a dilution zone of the combustion chamber and operating a support flame system in at least one of an active mode and an inactive mode, wherein the support flame system in the active mode combusts secondary fuel feed to generate a support flame supporting the combustion of the primary fuel feed. Ammonia is typically stored in liquefied form at -33°C or lower, and as it absorbs ambient heat, boil-off gas is produced. To avoid excessive pressure buildup in the storage tank, the boil-off gas may be directed to the gas combustion arrangement for combustion. The gas combustion arrangement may also be configured to combust ammonia released during a so-called tank warming process, in which a fuel tank is evacuated from ammonia in preparation for inspection, or service. This process typically includes emptying the tanks of liquid ammonia and injecting a purge gas to force out remaining ammonia vapours while gradually heating the tank. The gas mixture released during this process may be challenging to combust due to its fluctuating ammonia concentrations. Initially, the escaping gas may consist of nearly 100% ammonia, but as the process continues, the concentration drops towards 0%, with the gas eventually consisting entirely of purge gas. Ammonia may be difficult to combust at low concentrations due to its relatively narrow flammability range, typically between 15% and 28%. When ammonia concentrations fall below 15%, combustion may be unsustainable as the mixture becomes too diluted to ignite. To address this issue, the gas combustion arrangement features a secondary burner, which is configured to combust a secondary fuel feed. This secondary burner provides a support flame that sustains the combustion of ammonia and serves as an ignition source. The system can be operated in different modes, with the secondary burner either active, producing a support flame, or inactive. This flexible operation allows the support flame to be deployed as needed, such as during low ammonia concentrations, or continuously if required. Beneficially, the present gas combus