The Japanese manufacturer IHI Corporation announced on March 28 that it had successfully demonstrated the co-firing of ammonia and coal in a fuel mix composed of 20% ammonia. (All references to fuel composition herein are based on contribution to energy content.) Ammonia-coal co-firing had previously been demonstrated by Chugoku Electric in a fuel mix composed of just 0.6-0.8% ammonia.
The idea of ammonia co-firing entered the public discourse in Japan in January 2017 when the Central Research Institute of the Electric Power Industry (CRIEPI) “disclosed technical data of co-firing experiments,” according to a video provided by the Cross-Ministerial Strategic Innovation Promotion Program – Energy Carriers (SIP). The video continued, “In these experiments the feeding condition of ammonia to minimize NOx concentration was studied by using the same type of pulverized coal burner used in major coals plants in Japan.”
A Nikkei Asian Review story in March 2017 reported that Kansai Electric and five other utilities intended to enter the ammonia-coal co-firing arena. In July, Chugoku Electric conducted the electric industry’s first at-scale co-firing demonstration (reported here in Ammonia Energy). Chugoku subsequently reported that the boiler’s energy conversion efficiency was maintained even as a decrease in carbon dioxide emissions was observed. In addition, when plant output was throttled back to 120 MW from its typical output of 155 MW, the rate of nitrogen oxide (NOx) generation was reduced. According to a Chugoku official, these results added up to “encouraging” economic prospects for the technology.
In September Chugoku announced that it had filed a patent application for a “clean-power technology that involves co-firing ammonia with coal.” The announcement also mentioned the company’s intention to develop the co-firing method so that mixtures of up to 20% ammonia could be applied.
In the meantime investigators associated with at least two research institutions were studying pertinent aspects of co-firing combustion. Some of this work was described in detail by a team from Osaka University at the NH3 Energy + Conference in November in a paper entitled “Detailed Observation of Coal-Ammonia Co-Combustion Processes.” (Click here for the team’s abstract.) The SIP video stated that Hideaki Kobayashi of Tohoku University has also been studying the topic, but did not provide details of his work. (Kobayashi’s research on ammonia combustion in gas turbines has been described previously by Ammonia Energy.) The video makes it clear that how “ammonia is supplied inside the pulverized coal flow path” is a key determinant of whether there is an “increase [of] NOx and N2O in the exhaust gas.”
In December the Nikkei Sangyo Shimbun reported that IHI was interested in ammonia-coal technology and also intended to achieve a 20% co-firing rate. IHI’s demonstration was started that month at its “large-capacity combustion facility” in Aioi City. The company developed its own system for delivering ammonia to the combustion zone (including “the shape of the piping”) that was optimized “to suppress emission of NOx.” The March 28 announcement revealed that the company had been able to reach the 20% goal – and had done so in time to claim “world-first” status.
As had been the case when Chugoku co-fired at 0.6-0.8%, IHI was able to maintain NOx emissions at the rate exhibited by coal-only firing. In the future IHI says it will “consider the possibility of further lowering NOx by evaluating the impact on boiler performance and selection of operating conditions.” IHI too plans to seek patent protection for its technology. Its stated goal is to bring the system to the commercial market in 2020.
The IHI press release states that coal-fired plants generate approximately 30% of Japan’s electricity, while the Nikkei Sangyo article refers to the “head winds” blowing globally against coal-fueled power generation. IHI sees ammonia co-firing as an important way to fight these head winds. The press release notes that the company’s technology can be retrofitted into existing coal-fired boilers. Given this widespread applicability, the technology’s impact could be substantial. According to the Nikkei Sangyo article, “if the domestic coal-fired power plants are upgraded with the co-firing method developed by IHI, there is also an estimate that it is possible to reduce the CO2 emissions of the whole country by 4%.”
IHI says its ultimate goal is to “construct a value chain that connects the production and use of ammonia, using combustion technology of gas turbines and coal-fired boilers, using ammonia as fuel, and solid oxide fuel cells.”
Note: The original version of this post was edited on April 16, 2018 to rectify a Japanese-to-English translation problem.