Many MindedA small hydrogen dose may be enough to light ammonia in ship engines
Researchers at Norway's NTNU, led by David Emberson of the Department of Marine Technology, have studied hydrogen as an ignition fuel for ammonia engines. Ph.D. candidate Duc Duy Nguyen co-authored the paper, published in Energy & Fuels. Their results suggest only about 7%–8% hydrogen is needed to ignite ammonia, provided it is delivered in the right way. This is research, not a product.
Ammonia burns without producing carbon dioxide and can be made with renewable energy, but it ignites poorly on its own. Ammonia engines therefore usually run dual-fuel, with a pilot fuel such as coal gas, biofuel or diesel, and those fuels bring carbon emissions back. In World War II, Belgian buses converted to ammonia needed a mix with up to 40% coal gas to burn stably. The NTNU work injects fuel directly into the combustion chamber, rather than mixing at the intake as other labs and existing dual-fuel engines do.
Why it matters: shipping accounts for 11%–12% of global transport emissions, and the International Maritime Organisation targets a 50% cut from 2008 levels by 2050. Ammonia is easier to handle than hydrogen. It can be stored at moderate pressure, is not explosive and holds more energy per liter. Emberson calls 700-bar hydrogen storage, as in a Toyota Mirai, infeasible for ships. If a small hydrogen share can replace carbon-based pilot fuels, ammonia becomes a more fully carbon-free marine fuel.
Caveats: the 7%–8% figure depends on how the hydrogen is delivered. Using hydrogen requires extra storage or onboard cracking of ammonia into hydrogen and nitrogen, which costs energy. Hydrogen combustion can also produce nitrogen oxides. Emberson believes some engines could be retrofitted, but that has not been demonstrated. For now, Equinor's supply vessel Viking Energy is being converted to an ammonia dual-fuel engine that still uses marine gas oil as its pilot fuel. Our source text was cut off, so later findings are not covered here.
Source: Phys.org