A LITERATURE REVIEW OF NOX EMISSIONS IN CURRENT AND FUTURE STATE-OF-THEART GAS TURBINES

Current U.S. government policy seeks to achieve a completely carbon- free economy by 2050, with a carbon-free electricity sector by 2035 (per executive orders #14008 and #14057). To address these goals, the U.S. Department of Energy is evaluating strategies and technologies that support the production, utilization, transport, and storage of hydrogen (via initiatives such as DOE's Energy Earthshot - Hydrogen and various DOE funding opportunity announcements). A carbonfree fuel such as hydrogen cannot be overvalued in a dynamic electric energy sector seeking to decarbonize. One of the most important technologies needed to achieve the goal of a carbon-free electricity sector is a 100% hydrogen-fueled gas turbine. Accommodating hydrogen-based fuels has been a key goal for various original engine manufacturers (OEMs) for many years, but much more research and development (R&D) is needed. The purpose of this paper is to highlight the current state-of-the-art of hydrogen turbine technology, especially regarding nitrogen oxide (NOX) emissions compared to natural gas-fueled turbines. NOX is the primary criteria pollutant from thermally-driven combustion turbines and should be controlled to levels that are equivalent to or below existing standards (as reported "existing standards" for hydrogen-fueled gas turbines may need to be re-baselined). This paper will provide an overview of hydrogen as a fuel and various NOX emissions control techniques that are relevant for hydrogen-based fuels. A conclusion from this overview is that, with some level of R&D, NOX emissions from hydrogen-fueled gas turbines can be controlled to levels similar to those produced by state-of-the-art natural gas-fueled combustion turbines while remaining competitive in terms of performance and efficiency.