Session: 1.1.1 - Fuels, Combustion & Material Handling

Paper Number: 107257

107257 - Opportunities and Challenges for Co-Firing Ammonia in Coal-Fired Boilers 

Ammonia is being evaluated worldwide as an alternate energy carrier (AEC) for hydrogen in future low-carbon energy scenarios. Ammonia is presently the second most produced chemical in the world. This global experience with ammonia has resulted in development of mature technologies for its production, handling, transport, and storage. The global supply chain already exists, and distribution infrastructure is well established locally in many countries.  Additionally, safety regulations concerning the handling, transport, and storage of ammonia are well established.  Ammonia could form the basis of an integrated energy storage and distribution decarbonization solution for multiple industries beyond its historic use in the production of fertilizers and other chemicals.

The properties of ammonia also make it an attractive option for use as an energy storage medium and as a fuel in power generation.  Ammonia is a hydrogen AEC and is anticipated to be a near-term future consideration for direct co-firing in fossil power plants. Ammonia co-firing in commercial power generation plants offers several near-term attributes including established transport and storage capabilities, existing plant infrastructure, and minimal required plant modifications for those facilities already using ammonia in selective catalytic reduction (SCR) systems or feedwater control.

The thermal properties and combustion characteristics of ammonia warrant investigation as a combustion fuel (co-firing or direct) when compared to gaseous (e.g., natural gas, hydrogen) and liquid (e.g., gasoline, diesel) hydrocarbon fuels. Ammonia has a relatively low energy content (lower heating value) and reactivity that lead to lower heat of combustion and flame velocity compared to typical hydrocarbon fuels.  Additionally, ammonia exhibits a narrow flammability limit and higher ignition energy/temperature. In direct firing applications, the ammonia/air flame temperature and radiation heat transfer rate are lower compared to combustion of other hydrocarbon fuels due primarily to the absence of CO2 in the combustion products. Finally, ammonia’s high heat of vaporization can result in significant temperature drop when evaporated from liquid to gas that can lead to lowering in-cylinder temperatures and freezing of injection nozzles.

The combustion behavior of pulverized coal and ammonia in various co-firing ratios has received significant research attention in the international community, especially by multiple organizations in Japan. Studies suggest ammonia can be burned with pulverized coal in certain co-firing ratios with a reduction in CO2 emissions, reduced flyash production, and comparable NOx emissions.  New burner designs demonstrated at laboratory scale have shown to be effective in achieving stable combustion. Co-firing ammonia with coal appears to be a relatively low-cost CO2 reduction technology since major system modifications, including SCR systems may be minimized.  Ammonia co-firing/firing may provide a pathway forward for coal assets that are to be prematurely closed. Multiple full-scale ammonia co-firing demonstration activities are underway.

EPRI is evaluating the opportunities for coal/ammonia co-firing to understand the potential benefits in avoiding premature shutdown of valuable coal assets and the technical challenges that may occur regarding degradation of boiler components (e.g., waterwalls, headers, piping) due to the changing combustion profile from ammonia co-firing.  This paper will summarize ongoing research in ammonia co-firing and discuss future applications.

Presenting Author: Stan Rosinski EPRI

Presenting Author Biography: Stan Rosinski is a Technical Executive in the Generation Sector at the Electric Power Research Institute (EPRI). He currently supports the resolution of age-related degradation issues in major fossil power generation components. Previously, Rosinski led EPRI’s Renewable Generation area and its corporate-wide Technology Innovation Program. He also managed reactor pressure vessel integrity and fatigue activities in the Nuclear Materials Reliability Program. Before joining EPRI in 1995, Rosinski was a Senior Member of Technical Staff at Sandia National Laboratories, where he was responsible for the resolution of light water reactor (LWR) materials-related issues. Rosinski received a bachelor’s degree in mechanical engineering and a master’s degree in metallurgy from the University of Nebraska-Lincoln. Mr. Rosinski is active in ASME Boiler & Pressure Vessel Code and in B31.1 Piping committees.