Korean researchers develop next-generation exhaust purification technology for eco-friendly ships

South Korean researchers have successfully developed a technology that can dramatically reduce nitrogen oxide emissions from eco-friendly vessels.

LNG and ammonia have drawn growing attention as alternative fuels for eco-friendly ships as the shipping industry works to cut greenhouse gas emissions. However, both fuels carry their own environmental drawbacks, producing harmful substances and greenhouse gases including methane (CH₄), nitrous oxide (N₂O) and toxic ammonia.

A research team led by Senior Researcher Im Dong-ha at the Korea Institute of Industrial Technology's Ulsan Technology Commercialization Division developed a high-efficiency exhaust purification technology that overcomes the shortcomings of existing systems.

In an exhaust purification device, the catalyst chemically breaks down harmful substances while the substrate serves as the structural framework that holds the catalyst securely in place.

Although catalysts perform effectively at optimal temperatures, real operating conditions on vessels cause the temperature and composition of exhaust gases to fluctuate constantly, making it difficult to maintain stable purification performance.

Existing ceramic-substrate purification systems are particularly problematic — they are bulky and heavy, and their slow heat transfer limits how quickly temperature can be adjusted.

To address these issues, the research team replaced the substrate with a thin metallic material. The substrate is a structure that fixes the catalyst to the surface of the channels through which exhaust gases pass, and using metal allows it to be made far thinner than ceramic.

Thinner walls increase the catalyst's reactive surface area within the same overall size, reduce pressure loss that would otherwise impede exhaust gas flow, and accelerate heat transfer to the catalyst.

The research team evenly coated the metal substrate with catalysts designed to purify exhaust gases — including unreacted methane, ammonia, nitrogen oxides and nitrous oxide — to produce a complete catalyst module.

In a land-based demonstration applying the metal-substrate catalyst module to a 1 MW-class marine engine, nitrogen oxide (NOx) emissions fell by 98.8% and nitrous oxide emissions by 72.1% at 75 percent engine output.

The test marks the first domestic demonstration conducted under 1 MW-class marine engine operating conditions. Compared with conventional ceramic-substrate systems, the new module also reduced catalyst usage by about 55 percent, the number of modules by 24 percent and reactor volume by 30 percent, cutting both production costs and installation space at the same time.

The research team also built a bench-scale catalytic reaction system that heats the metal-substrate catalyst module directly using high-frequency induction heating, and secured design technology to scale the system up to pilot size.

"The key achievement is combining a metal-substrate coated catalyst with high-frequency induction heating to miniaturize the catalytic reactor and realize an electrically driven direct-heating catalyst platform," Im said. "Building on these results, we are working to automate part of the process for coating catalysts onto metal substrates and to develop an AI model capable of predicting pollutant reduction performance according to catalyst type and reaction conditions."