Sub Topic: Coal, Biomass, and New Devices Spring Technical Meeting Eastern States Section of the Combustion Institute March 4–7, 2018 State College, Pennsylvania Nitrogen Oxide Evolution in Oxy-Coal Combustion Sai Krishna Sirumalla 1 , Aidin Panahi 2 , Abhir Purohit 1 , Andrew Baugher 1 , Yiannis A. Levendis 2 , and Richard H. West 1,* 1 Department of Chemical Engineering, Northeastern University, Boston, MA, USA 2 Department of Mechanical & Industrial Engineering, Northeastern University, Boston, MA, USA * Corresponding author: r.west@northeastern.edu Abstract: This paper investigates emissions of NO x from pulverized coal burning in O 2 /CO 2 en- vironments. Such environments are pertinent to oxy-coal combustion, a promising “clean-coal” technology. The replacement of the inert nitrogen gas in air with carbon dioxide, which has differ- ent physical properties, alters the combustion conditions in the furnace. Hence, the purpose of this work is to theoretically examine the effects of (a) the oxygen concentration in the O 2 /CO 2 gases, and (b) the resulting combustion temperatures, on the evolution of NO x . To achieve these goals a previously published kinetic model was used, which assumes that fuel-bound nitrogen is released along with the tars during coal devolatilization and converts mostly to hydrogen cyanide. A sizable fraction of hydrogen cyanide is then converted to NO. Flame simulations were performed using Can- tera to investigate the relative impacts of temperature and oxygen mole fraction, and to understand the causes of the observed trends. Keywords: Coal, NOx, Fuel-Nitrogen, Hydrogen Cyanide, Oxy-Combustion. 1. Introduction Combustion-generated pollutants, such as acid gases, particulates, and air toxics, as well as green- house gases such as carbon dioxide, are a serious concern. Technologies to capture the pollutants, with various degrees of efficiency, have been developed and implemented [1]. One promising approach is carbon capture and sequestration (CCS) or carbon capture and utilization (eg. for un- derground oil recovery)[2]. Oxy-coal combustion, where coal combustion occurs in neat oxygen provided by an air separation plant, can greatly facilitate CCS as, upon drying, flue gases consist mainly of carbon dioxide. To reduce temperatures, flue gases are recycled, so the oxidizer stream is essentially a mixture of O 2 and CO 2 . In addition to facilitating carbon dioxide capture, oxy-coal combustion can drastically reduce the generation of nitrogen oxides, NO x , which consist of mostly NO and little NO 2 [3]. Since com- bustion takes place in the absence of atmospheric N 2 no thermal NO x is generated; the detected amount of NO x originates from fuel nitrogen. It has been shown that increasing the concentration of O 2 increases the NO x generation during coal oxy-combustion, but it remains unclear whether this is driven by the increased temperature, increased oxygen concentration, or both. This study aims to separate the effects of temperature and oxygen partial pressure. This separation was in- vestigated by first assuming that fuel-bound nitrogen is released along with the tars during coal devolatilization and converts mostly to hydrogen cyanide, HCN. Then to assess the conversion 1