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

The absorption of NO X gases in water and alkalies [NaOH, NH 4 OH, 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 = N 2 O 3 , N 2 O 4 . However, the reported value of H√(kD) for N 2 O 3 absorption in strong alkaline solution was 50 times its value in water. For the intermediate case of NO X absorption in weak alkali Ca(OH) 2 , it was necessary to have a mathematical model which incorporated the HNO 2 decomposition, as well as neutralization by alkali. This led to a unified model for NO X absorption, which can be used for predicting point rates of NO X 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(NO 2 ) 2 manufacture has been made to test the model validity.