Simulation study on coal and ammonia co-firing in a tangential firing boiler under different ammonia injection methods

As a new zero-carbon fuel, ammonia co-firing in coal-fired boilers is one of the feasible technologies for reducing carbon emission. This study validated an ammonia-coal co-firing simulation model using experimental data from a 300 MW unit tangential firing boiler, and investigated the impacts of different ammonia injection methods (uniform injection, lower layer concentrated injection and upper layer concentrated injection) at 20% ammonia co-firing ratio on boiler performance. Key findings include flow fields characteristics: uniform injection enhanced the tangential flow pattern, while pure ammonia burners in concentrated injection modes exhibited weaker tangential momentum compared to coal burners; combustion and temperature fields: all the three injection methods reduced peak furnace temperatures but increased flue gas temperature at furnace outlet; coal burnout performance: uniform injection and lower layer concentrated injection inhibited coal burnout, whereas upper layer concentrated injection promoted it; NO_x emissions: both uniform injection and lower layer injection reduced NO_x emissions, while upper layer injection significantly increased them. These conclusions provide critical guidance for retrofitting power plant boilers for ammonia co-firing.