Kinetic model of SCR catalyst-based de-NOx reactions including surface oxidation by NO2 for natural gas-fired combined cycle power plants

As intermittent renewable energy is introduced into the power grid, Natural Gas-fired Gas Turbine Combined Cycle (NGCC) is expected to increase rapid start-up, rapid shut-down, and partial-load operation time to stabilize the frequency of the power grid. These transient operations of the NGCC significantly change the ratio of NO2/NOx in the exhaust gas. Therefore, it is necessary to develop an efficient de-NOx system applicable across the range of potential NO2/NOx ratios. In addition to Eley-Rideal reaction mechanisms between adsorbed NH3 and gas-phase NOx, this study considers temporal changes between V⁵⁺=O and V⁴⁺-OH. A two-dimensional, unsteady state numerical simulation code was developed and fitted using experimental results obtained under simplified gas compositions with a honeycomb-shaped SCR catalyst commonly employed in the flue gas duct of actual NGCC power plants. The numerical simulation accurately predicts transient changes and equilibrium concentrations of NOx and NH3 in each experimental condition using a honeycomb catalyst under the gas conditions including NO2.