Combustion of Ammonia for Reduced CO2 in Heating and Power Generation Systems

Grant # 08F-03
Principal Investigator: Terrence Meyer
Organization: Iowa State University
Technical Area: Renewable Energy

Public Abstract

Ammonia has been utilized as an alternative fuel to power internal combustion (IC) engines since the 1940’s, and interest in ammonia as an alternative fuel for military applications led to successful demonstrations of ammonia combustion in gas-turbine engines in the 1960’s. Recently, this interest has been renewed by concern over greenhouse gas emissions. Like hydrogen, the products of ammonia combustion with air are potentially composed of only nitrogen and water. Unlike hydrogen, however, there is a well-established infrastructure for mass storage and worldwide distribution of ammonia. The proposed work is concerned primarily with a class of stationary combustors that are common in furnaces for home/ industrial heating, as well as in gas turbines for power generation. In fact, gas turbines are one of the fastest growing devices for power generation due to their relative efficiency and scalability. There is a growing interest in using micro-turbines, for example, to achieve a more secure, distributed power grid with flexible fuels.

However, combustion of ammonia is not as straightforward as combustion with conventional fuels because it is more difficult to ignite, requires more time to burn, and does not release as much energy. The goal of the proposed work, therefore, is to develop advanced combustion control strategies that allow the utilization of ammonia for use in homes and small-scale, industrial combined heating/power systems.

Initial work will involve facility set-up and combustor design to achieve reliable ignition and flame stability. Strategies for ammonia injection, combustion staging, heat recirculation, and proper combustor sizing will play important roles in the design process. During this effort, combustion chamber and exhaust gas concentrations of critical species such as nitric oxide, water, and temperature will be measured to characterize the effects of mixing and preheating on ammonia combustion and emissions. This work will take place in close collaboration and consultation with Goodrich Turbine Fuel Technologies (TFT), an industry partner headquartered in Des Moines, Iowa that specializes in the production of gas-turbine combustion nozzles and control systems.

Based on this effort, it is fully expected that a new combustor design will be pursued in a second generation burner with controlled recirculation for optimizing combustion efficiency. This will allow for the design of a tailored temperature distribution for increasing flame speed and improving flammability limits. However, it will be critical to ensure that stable combustion can be achieved without an increase in unwanted NO emissions. In addition, control of temperature through proper staging of chemical reactions and appropriate combustor sizing will be required in the final design to avoid excessive unburned ammonia in the exhaust. The collaboration with Goodrich TFT will be critical in this phase as the fuel system delivery components will be used to optimize the fuel-air mixture.

The outcome of this work will include a facility for studying and optimizing ammonia utilization in home and industrial heating and power systems, a first generation burner to study ignition and flame stability, and a second generation burner optimized for efficiency and reduced emissions. A preliminary product design and commercialization strategy for an opportune target application is also anticipated based on close collaboration with industry.