Experimental Measurements and Mass Transfer/Reaction Modeling for an Industrial NOx Absorption Process

An industrial reactive separation process for NO x absorption into water and nitric acid in a world-scale mononitrobenzene (MNB) plant in Redcar, U.K., was investigated. Gas- and liquid-phase concentrations were measured in situ, while operating conditions such as temperature, pressure, and absorbent flow were varied. Furthermore, a comprehensive mass transfer/reaction model was developed in the process simulator Aspen Plus to simulate the absorption process, with the field process data used for validation. The model accurately predicted NO x removal from the gas (i.e., typically within 3.5% of the plant data). Other key findings are that the model successfully predicted changes in performance when key parameters such as temperature and pressure were varied. Furthermore, addition of a bleaching section was investigated, resulting in a significant improvement in NO x removal. Currently, the completed model is used to simulate existing and proposed NO x absorption systems and to develop new and innovative designs for NO x capture.