Computation of plate columns for NOx absorption by a new stage‐to‐stage method

A new stage-to-stage method has been developed for the calculation of NXx absorption columns. Each stage of the absorption column is simulated as a combination of a bubble column reactor (absorption) and an adiabatic plug for reactor (oxidation). The bubble column reactor is modelled as two single stirred tank reactors, one as a gas-phase and one as a liquid-phase reactor, both coupled by mass and heat transfer. In this hydrodynamic model, a dynamic approach is adopted, in which the gas-phase transport of N2O4 is the limiting step for the absorption. A gas-phasepseudo-enhancement for factor for N2O4 is therefore introduced. The balance equations for a single phase of the bubble column are solved with a Newton-Raphson algorithm. The entire column calculation is divided into a gas and a liquid side. On both sides, the stage-to-stage method is applied in such way that the overall calculation is performed as a loop process. The direction of the loop calculation follows that of the flow: gas-side upwards and liquid-side downwards.