Nitric oxide recovery from hydrogen combustion streams. A clean pathway for the sustainable production of nitrogen compounds

This work proves that nitric oxide (NO) can be successfully recovered from hydrogen flue gas streams in nitric acid, opening new pathways for NO control in combustion streams. Recovering NO from hydrogen combustion streams allows for increasing the combustion temperature in the turbine, reducing the fuel consumption per kWh, while obtaining a building block for nitric acid production. The solubility of nitric oxide is determined in amines, ethanol, and nitric acid solutions at a laboratory scale, suitable candidates for nitric oxide absorption. The solubility of nitric oxide in amines and ethanol is very low (0.009 mol/L/bar & 0.018 mol/L/bar respectively) compared with nitric acid (0.23 mol/L/bar), which is in the same range as the solubility of CO₂ in amines solutions. Nitric acid, in addition to having good NO solubility, also presents high selectivity towards nitric oxide and easy recovery of nitric oxide by simply raising the temperature. Finally, a fugacity-activity coefficient model combining the Peng-Robinson (PR) equation of state with the Non-Random Two-Liquid (NRTL) activity coefficient model is proposed as a thermodynamic model to represent the NO-HNO₃-H₂O equilibrium, giving as a result an average absolute deviation between the experimental results and the model predictions of only 5%.