Selective Catalytic Reduction (SCR) by NH 3 in a Fixed-Bed Reactor HEE JE SEONG The Department of Energy and Geo-Environmental Engineering The Pennsylvania State University

Introduction NOx emissions are a major pollutant from engines, incinerators and power plants - unavoidable at conditions where air is involved at high combusting temperature Selective catalytic reduction with NH 3 has been successfully used to remove NOx 4NO + 4NH 3 + O 2  4N 2 + 6H 2 O Kinetic parameters depend much on a catalyst - V 2 O 5 -WO 3 /TiO 2, CuHM and etc

Governing Equations Mass equation - Convection and diffusion where R : -r NO, -r NH3 Momentum equation - Navier-Stokes equation (Brinkman eqn. involved) Energy equation - Assumed as an isothermal state due to a small amount of heat evolved

Boundary Conditions Inlet - Velocity : 1, 2, 4m/s - C NO = 8.16x10 -3 mol/m 3 C NH3 = 8.16x10 -3 mol/m 3 C NH3 = 6.94x10 -3 mol/m 3 C NH3 = 9.38x10 -3 mol/m 3 - P in : x10 5 Pa Outlet - P : P in – Δ P (according to Ergun eqn.) Inlet Wall/ Insulation Outlet Wall/ Insulation 0.1(m) 0.076(m)

Formulation Mass conservation - Convection and diffusion - Chemical reaction E NO : Enthalpy of NO reduction E NH3 : Enthalpy of NH 3 oxidation H NH3 : Heat of NH 3 adsorption k NO : Reaction rate constant of NO reduction k NH3 : Reaction rate constant of NH 3 oxidation K NH3 : Adsorption equilibrium constant for NH 3

Formulation Air is assumed as the fluid flowing through the reactor - small amounts of NO and NH 3 - ρ and η are temperature- dependent - pressure drop is calculated using Ergun eqn. - Permeability is calculated using Darcy’s law

Solution - Much portion of reactants is converted in the inlet of the reactor - NH 3 slip should be considered when NH 3 is injected

Validation SV = 100,000 h -1 SV = 200,000 h -1 - Detailed information in Chae et al’s model is missing - This COMSOL model simulates similar trends of results to those of Chae et al.’s model for both conditions

Parametric Study Temperature ( o C) Porosity = 0.5Porosity = 0.7 ΔP (Pa)K (m 2 )ΔP (Pa)K (m 2 ) x x x x x x x x x x x x x x10 -9

Parametric Study Kinetic parameter DryWet E a,NO E a,NH3 Δ H NH3 k o,NO k o,NH3 K o,NH x x x x Conversion of NO is higher at a dry condition than at a wet condition due to the competition between H 2 O and NH 3 -This COMSOL model also reflects a general phenomenon of SCR when water is involved in the reaction

Conclusion SCR model using COMSOL well describes a general trend of NO removal performance - Valid result compared to the reference - Water effect is predictable The model also indicates that NH 3 /NO should be controlled considering NH 3 slip and performance at operating temperatures