Nitrogen oxides are one of the most significant pollution sources during coal combustion. This experimental study was conducted in a 15 kW(th) lab-scale pressurized fluidized bed (inner diameter = 81-100 mm, H = 2100 mm) firing with bituminous coals. The effects of operating parameters, including bed temperature (800 degrees C-900 degrees C), operating pressure (0.1-0.4 MPa), excess air level (16%-30%) and flow pattern on NOx and N2O emissions were systematically studied during the tests. During each test the interaction effects of all the operating parameters were properly controlled. The results show that most operating parameters have an opposite effect on NOx and N2O emissions, and the N2O emissions mainly depend on the bed temperature. Increasing the operating pressure can significantly suppress the fuel-N conversion to NOx but enhance its conversion to N2O. With the rise of the excess air level and fluidization number, NOx emissions grow distinctly while N2O emissions remain almost unchanged. Total nitrogen oxide emissions increase with the bed temperature while decrease with the operating pressure. (C) 2018 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.