Modelling and parametric investigation of NO x reduction by oxidation precatalyst-assisted ammonia-selective catalytic reduction

Abstract

Abstract

Nitrogen oxide (NO _x ) reduction by the selective catalytic reduction (SCR) system assisted by an oxidation precatalyst is modelled and analytically investigated. The Langmuir—Hinshelwood SCR kinetic scheme with vanadium-based catalyst and ammonia (NH₃) reductant in conjunction with the NO—NO₂ conversion reaction over a platinum-based catalyst is used. The effects of the ratio of the oxidation precatalyst to the SCR monolith volume, the gas temperature, the space velocity, and the NH₃-to-NO _x concentration ratio on the de-NO _x performance are parametrically examined. The oxidation precatalyst promotes NO _x conversion at low temperatures. At intermediate temperatures, the NO _x reduction is either activated or deactivated with increase in the space velocity. A higher oxidation precatalyst-to-SCR monolith volume ratio tends to promote the NO _x reduction of higher space velocities. At high temperatures, the de-NO _x efficiency is very high and insensitive to the space velocity. The NO _x conversion efficiency depends on the NH₃-to-NO _x ratio at low temperatures.