Unified model for NOX absorption in aqueous alkaline and dilute acidic solutions

The absorption of NOX gases in water and alkalies [NaOH, NH4OH, Ca(OH)2] provides commercially important products nitric acid and salts (nitrates and nitrites), respectively. This complex phenomena of mass transfer with chemical reactions is described quantitatively in terms of [H√(kD)]J values for J = N2O3, N2O4. However, the reported value of H√(kD) for N2O3 absorption in strong alkaline solution was 50 times its value in water. For the intermediate case of NOX absorption in weak alkali Ca(OH)2, it was necessary to have a mathematical model which incorporated the HNO2 decomposition, as well as neutralization by alkali. This led to a unified model for NOX absorption, which can be used for predicting point rates of NOX absorption as well as selectivity, for various gas compositions and liquid‐phase pH. Parametric sensitivity has been reported. A comparison of the model predictions with data from patent on Ca(NO2)2 manufacture has been made to test the model validity.