Experimental study and mechanism analysis of the NOx emissions in the NH3 MILD combustion by a novel burner

NH3 can be used as an H-2 energy carrier or an alternative carbon-free fuel because of its high volumetric energy density and easy liquefaction, which leads to convenient and economic transportation and storage within the global energy network. However, the combustion of NH3 is associated with some practical challenges, such as weak reactivity and high NOx emission. In this study, Moderate & Intense Low Oxygen Dilution (MILD) combustion of NH3 was conducted experimentally in a novel burner. The heated and diluted air was produced by burning a premixed lean CH4 mixture using a metal fiber burner installed at the bottom of the combustion chamber and NH3 was injected into the furnace by 20 nozzles oppositely installed on the sidewalls of the combustion chamber at 40 mm above its bottom. A total of 20 cases were investigated in the present work, including premixed combustion of CH4 and CH4/NH3, and MILD combustion of NH3, under various conditions. The Chemical reactor network (CRN) in the ANSYS Chemkin 17.0 and the HUST mechanism were used to simulate and analyze the NO formation mechanism under several experimental conditions. The experimental results showed that the NH3 MILD combustion significantly reduces the NOx emissions. The NOx reduction kinetics and the impact of NH3 flow rate and the equivalence ratio on NO emission in NH3 MILD combustion were analyzed in detail.