Emission and transformation of various pollutants during coal-ammonia combustion in fluidized bed: CO/CO2/CxHy/NH3/NOx/SO2/Hg

Coal-ammonia combustion is a hot coal combustion technology for achieving carbon emission reduction, which lacks systematic studies on the combustion in fluidized beds. In this work, the effects of combustion temperature, ammonia doping amount, and excess air ratio on the emission and transformation of various pollutants (CO, CO 2 , C x H y , NH 3 , NOx, SO 2 , Hg) of Guizhou anthracite with ammonia combustion were studied on a bubbling fluidized bed. It shows 850 °C is the optimal combustion temperature for the Guizhou anthracite, which achieving the complete combustion of carbon in coal and combustible carbon compounds in flue gas with the highest CO 2 concentration. Increasing the ammonia doping amount benefits for reducing the concentrations of CO 2 , C x H y , SO 2 , NOx in flue gas and mercury content in fly ash, but increasing that of NH 3 , H 2 O, Hg 0 in the flue gas. 20 % is the optimal ammonia doping amount. Increasing the excess air ratio is beneficial to the co-combustion of coal and ammonia, where the concentrations of CO, C x H y , H 2 O, SO 2 , and NO 2 in the flue gas gradually decrease with opposite pattern to CO 2 . The concentrations of NOx, NO, Hg 0 in flue gas and the mercury content in the fly ash firstly increase and then decrease. The 1.2 is the optimal excess air ratio. Combustion temperature, ammonia doping amount, and excess air ratio affect the migration and transformation of various pollutants in the flue gas mainly through influencing the combustion state of coal and ammonia, the carbon content on fly ash surface, and the redox atmosphere of gas-gas/gas-solid reactions. Combustion temperature of 850 °C, ammonia doping content of 20 %, and excess air ratio of 1.2 are the optimal combustion conditions for coal-ammonia in a bubbling fluidized bed. • Guizhou anthracite and ammonia co-combustion was studied to fill the gap in the fluidized bed. • 850 °C is the optimal temperature to achieve the anthracite complete combustion and highest CO 2 . • Increasing ammonia doping benefits for reducing CO 2 , C x H y , SO 2 , NO x and fly ash mercury. • Enhancing excess air coefficient is good for coal ammonia co-combustion with 1.2 optimal value. • 850 °C, 20 % ammonia doping, and an1.2 excess air coefficient are the optimal combustion conditions.