NOx formation of swirl burner under air-staged combustion with flue gas recycle Jinyan Yuan, Mingming Wang, Jihua Li, Yuyu Lin, Xiangyong Huang and Mingyan Gu E3S Web Conf., 194 (2020) 01042 Published online: 15 October 2020 DOI: 10.1051/e3sconf/202019401042