Ammonia is gaining momentum as technology matures

Demand for ammonia is changing due to the energy transition. Until recently used as a feedstock for fertilizers and chemicals, new markets are emerging for green and blue ammonia to replace coal in power generation, green steel production, and marine fuels.

Currently, around 200 million tons are produced annually worldwide, of which 20 million tons are transported by LPG ships. These numbers will rise due to new demand and the size of the potential demand. How quickly this can be achieved will determine acceptance within the transport.

Interest in ammonia stems both from its zero emissions when used as a fuel and because ammonia production does not rely on biogenic carbon sources. As the global economy transitions away from fossil-based fuels, biogenic carbon from captured CO2, electrolysis, and even waste sources will be exposed to increased competition from a variety of industries.

Fossil carbon is now increasingly being replaced by biogenic carbon in many products used in industrial and consumer goods. Competition from the energy and aviation sectors will inevitably lead to higher prices, but production capacity will have to come from industrial sources rather than from biomass harvested for this purpose.

The increase in ammonia also opens up the possibility of green hydrogen as a fuel. However, because ammonia is much cheaper to transport over long distances, and given the energy loss when hydrogen is converted to ammonia by the Haber-Bosch process, most of the hydrogen is transferred to green ammonia at the location. It seems likely that it is manufactured by disassembling the . Hydrogen will be consumed.

Ammonia production

Achieving large-scale production of green ammonia for new markets will require a significant expansion of production capacity in conjunction with renewable electricity and green hydrogen. The installed capacity of the wind and solar power plants currently installed around the world, especially the electrolyzers needed to produce the green hydrogen needed to produce ammonia, appears small compared to the capacity needed.

Renewable electricity for electrolysis needs to be produced in locations around the world where conditions are favorable and large areas of land are available for wind and solar energy generation. These locations are often in remote areas. Regions such as Western Australia, Chile, West Africa, Oman and Saudi Arabia are expected to be the main centers of production. Ammonia must be transported from these locations to demand centers, firstly North/East Asia and Europe.

Current projections for global production growth indicate that by 2040 there will be enough renewable electricity to produce the required amount of green ammonia by shipping fleet alone. But the shipping industry will also be competing with many other industries for both renewable and green power. Supply constraints are expected not only for the hydrogen needed for ammonia production, but also for other sectors that rely on green ammonia consumption, such as agriculture and coal-fired power plants.

Propulsion technology

Initial tests were conducted by several major engine manufacturers using ammonia as a fuel in combustion engines. This test is very promising and has not found any significant problems when using ammonia as a combustion fuel in internal combustion engines.

Although pilot fuel volumes and NOx, NH3 slip, and N2O emissions for commercial marine engines have not yet been quantified, marine engine manufacturers generally agree that the diesel cycle is optimal for ammonia combustion. I am.

Research is ongoing on both diesel and Otto cycle combustion concepts. Optimizing emissions reductions is expected to be a challenge, with high temperature combustion required to control N2O and ammonia slip, which also produces high levels of NOx. Tests on two-stroke engines have shown that NOx is less of a problem when using diesel cycle combustion principles when burning ammonia. When ammonia is injected into the combustion chamber, it expands and creates a cooling effect, eliminating the high peak temperatures in the combustion zone that produce high NOx.

Pilot fuel is needed to ignite the ammonia and is also needed to stabilize combustion. For small 4-stroke engines, he requires 10% pilot fuel after engine optimization is completed and the engine is running. Large two-stroke engines using the diesel cycle require only 5% pilot fuel, and some engine manufacturers expect to be able to reduce this amount even further.

Evaluation of emissions

Therefore, although the actual emissions of NH3 and N2O have not yet been accurately evaluated, emissions are expected to be low, especially in the diesel combustion cycle. Still, according to the IPCC 2013-ARS, the 20-year global warming potential (GWP) for N2O is 264 and the 100-year GWP is 265, so depending on the emission level, the benefits of using ammonia as a fuel over CO2 much of it may be canceled out. This remains a potentially significant barrier to adoption.

However, designers of marine two-stroke engines have found that N2O levels are low in tests, in the same range as observed with other fuels such as marine diesel, LNG, and methanol. Overall, the diesel combustion principle is ideal for the use of ammonia because the temperature inside the combustion chamber reaches a “sweet spot” where the slip levels of NOX, N2O, and ammonia are recorded at very low levels. It's possible. It is therefore expected that these engines will be able to operate according to IMO NOx Tier II standards without the need for mitigation systems.

As of Q1 2024, major marine engine manufacturers have the following development plans and lead times for ammonia-fueled engines:

• Two-stroke ammonia dual-fuel engine covering a power range from 5 MW to 31 MW. These engines will be available for delivery from Q4 2024/Q1 2025.
• Four-stroke ammonia engines are also becoming available as dual-fuel generator engines. Two engine manufacturers are expected to launch engines of this type at the end of 2024 or early 2025.

Safety and exhaust treatment

Most engine designers anticipate that exhaust gas aftertreatment will be required to comply with the IMO NOx Tier III standard, and all agree that the preferred means of cleaning exhaust gases after they have been expelled is We expect to specify selective catalytic reduction (SCR) as It uses a combustion chamber rather than exhaust gas recirculation (EGR), which alters combustion conditions and limits NOX production. EGR reduces the amount of oxygen in the intake air, and there are concerns that this will have a very negative impact on ammonia combustion performance, but this is still subject to further investigation.

In addition to ammonia-powered main engines and generators, auxiliary engine designs are also emerging that are necessary to complete the transition to ammonia-powered vessels. Boiler manufacturers are preparing dual-fuel boilers that use ammonia as fuel so that steam and heat can be produced by combustion of ammonia.

Routine handling of ammonia onboard ships requires a solution to collect ammonia vapor in a safe manner. This vapor is released during normal engine shutdowns when the piping system needs to be purged or when a failure occurs somewhere in the fuel supply system.

Various solutions for vapor treatment are under development from multiple manufacturers, including water scrubber designs that can remove ammonia vapor from purge air. In this solution, ammonia vapor is stored in a dedicated tank as a water-ammonia solution. However, this approach requires dedicated infrastructure at the port to receive and store data.

All of the above systems are being prepared for newbuild projects of various vessel types, and it is expected that these systems will be operational by the end of 2025 or the beginning of 2026. It is estimated that approximately 50 to 70 vessels are currently on order. April 2024.

René Sejer Laursen is Director of Fuels and Technology at the American Bureau of Shipping (ABS).