A consortium led by Mitsui Chemicals has achieved an 85% ammonia co-firing rate across an entire naphtha cracking furnace, marking a major step toward replacing fossil fuels with ammonia in one of the petrochemical industry's biggest sources of carbon emissions.
The breakthrough was achieved in a test furnace equipped with newly developed ammonia-fired burners under a Green Innovation Fund project backed by Japan's New Energy and Industrial Technology Development Organization (NEDO).
Mitsui Chemicals, NEDO, Maruzen Petrochemical, Toyo Engineering and Sojitz Machinery said the 85% co-firing rate was achieved on a heat-input basis while keeping nitrogen oxide (NOx) emissions at levels comparable with existing commercial furnaces.
The result clears a significant technical hurdle in the push to decarbonize naphtha cracking, a process that uses high temperatures to break down naphtha into key petrochemical building blocks such as ethylene and propylene.
Naphtha cracking furnaces traditionally burn off-gas, including methane produced as a by-product. Switching to ammonia could substantially cut combustion-related CO2 emissions because ammonia does not produce CO2 during combustion.
But ammonia presents its own engineering challenges. It burns more slowly than conventional fuels and can generate fuel-derived NOx. Any viable replacement therefore has to maintain stable combustion, deliver sufficient heat to cracking tubes and control NOx emissions simultaneously.
The consortium tackled those challenges by developing two ammonia burner designs: hearth burners, which provide the furnace's primary heat input, and wall burners, which help control flame shape and temperature distribution.
During the demonstration, the hearth burners operated on 100% ammonia, while the wall burners continued to use 100% off-gas methane.
That configuration delivered an overall ammonia co-firing rate of 85% across the furnace on a heat-input basis — described by the consortium as a world-class level for test-furnace operation using ammonia fuel in naphtha cracking.
The achievement also demonstrated that the high ammonia firing rate could be reached without a significant increase in NOx emissions compared with existing commercial furnaces.
The project, which began in fiscal 2021, is scheduled to run through fiscal 2030. Its ultimate target is considerably more ambitious: 100% ammonia firing across the entire naphtha cracking furnace.
The next phase will focus on applying ammonia firing to the wall burners, which currently rely on off-gas methane. The consortium also plans to advance the technology toward commercial-scale naphtha cracking furnaces.
If successfully commercialized, the technology could help cut emissions from petrochemical complexes while maintaining production of basic chemical feedstocks used in plastics, synthetic fibres and synthetic rubber.
Mitsui Chemicals and its partners said the work is aimed at accelerating both the decarbonization of the petrochemical industry and the stable supply of basic chemical products.
