Akihabara News (Tokyo) — Japan’s commitment to a carbon neutral society by 2050 may be aided by the development of ammonia co-firing. As an energy-efficient carrier of hydrogen, and with successful co-firing tests already completed, the technology appears promising.
In 2017, the world’s first test of coal power generation with ammonia co-firing was conducted at the Chugoku Electric Power Company’s Mizushima Power Station.
The issue with coal-fired power generation is its production of carbon dioxide. Mixing carbon-free fuel with pulverized coal at already existing coal-fired boilers is a cost-effective means to reduce carbon emissions while maintaining stable power generation.
A subsequent test at the IHI Aioi Works in Hyogo Prefecture demonstrated stable combustion of ammonia and pulverized coal at a 20% co-firing rate. This was found to create a corresponding 20% reduction in carbon dioxide emissions.
JERA is also investigating the possibility of utilizing a 50% ammonia mix.
The main drawback of this technology is the possibility for an increased concentration of nitrous oxides (NOx) in the flue gas. NOx is the main constituent in the formation of ground-level ozone, which may result in respiratory problems. Moreover, NOx in combination with sulfur oxides contributes to acid rain, and it can also create a greenhouse gas under certain conditions.
Fortunately, the tests performed at the IHI Aioi Works showed no increase in the output of NOx at a 20% ammonia co-firing rate when using two-staged combustion.
The results of these tests appear to indicate that existing coal-fired generators in Japan can be modified to use ammonia as a combustible fuel without having to install additional facilities.
The use of ammonia as a fuel would also take advantage of existing ammonia transportation and storage infrastructure at power plants.
Globally, ammonia is already a mass produced inorganic chemical due to the role it serves as a fertilizer for agriculture. Utilizing ammonia as a fuel would therefore involve only the expansion of an already robust supply chain.
As Prakash Sharma, vice president of multi-commodity research at Wood Mackenzie, puts it, ammonia “can leverage existing infrastructure and can be used directly in power generation and as a shipping fuel.”
On the other hand, ammonia production itself can be a stumbling block towards carbon neutrality goals.
Large-scale ammonia production usually employs the Haber-Bosch process, which requires the use of large amounts of natural gas. Consequently, ammonia production of this kind releases significant quantities of carbon dioxide into the atmosphere, and it is therefore known as “brown ammonia.”
But if the carbon dioxide is later returned to the ground through carbon capture and storage, then it becomes known as “blue ammonia.”
Japan is currently seeking to invest in companies that may be able to provide blue ammonia, but is also developing a third technology of this kind–green ammonia.
Green ammonia does not rely on natural gas as a feedstock for hydrogen. In this process, hydrogen is obtained through electrolysis of water, powered entirely by renewable energy sources.
In 2018, at its pilot plant in Koriyama city, Fukushima Prefecture, JCG Holdings demonstrated both the production of green ammonia as well as the generation of electricity using gas turbines fueled only by synthesized ammonia.
Ammonia fuel could become a cost-effective means to advance Japan towards its carbon neutrality objectives. As an early step, the Japanese government is seeking to phase out inefficient coal plants and looking to co-fire ammonia at a 20% rate in its remaining plants.
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