Optimization of an Urea Decomposition Chamber Using CFD and VR

Selective Catalytic Reduction (SCR) is an important air pollution control process that consists of injecting ammonia (NH₃) into the boiler flue gas and passing the flue gas through a catalyst bed where the NO_x and NH₃ react to form nitrogen gas (N₂) and water vapor (H₂O). [1] At a coal-fired power station, a decomposition chamber uses combustion air and a natural gas burner to provide the necessary temperature, air flow and pressure to convert the injected urea solution into ammonia gas. The inspections of this decomposition chamber indicate debris formations occurring at the burner/roof block the chamber from achieving proper temperature for conversion and redirect the burner flame/flow, which can potentially shift the flow pattern in the chamber. In order to identify the cause of this debris formation, Computational Fluid Dynamics (CFD) and Virtual reality fVR have been employed to simulate and visualize the flow distribution and species concentration inside this decomposition chamber. By analyzing the simulation data, excessive ammonia recirculation had been identified as the cause of the debris formation at the top of the chamber. Parametric studies have also been conducted to optimize the existing chamber design by introducing multiple turning vanes to eliminate the excessive recirculation, thus minimizing debris formation.