Controlling Nitrogen Oxide (NOx) Emissions from Exothermic Nitrogen Generation Systems for Application in Subsea Environments

A highly exothermic nitrogen generation system (NGS) can be achieved by mixing solutions of sodium nitrite and ammonium chloride, a process used by the oil and gas industry to dissolve paraffin wax and gas hydrates. Although its main products are nitrogen gas and a sodium chloride brine, the NGS has a side reaction that produces nitrogen oxides. To optimize this process to ensure the greatest and fastest heat generation with the lowest oxide production, this reaction was checked by infrared spectroscopy and calorimetry. The factors temperature, pH, and initial concentration of nitrite and ammonium were evaluated, and the optimal conditions of the NGS were determined by the constructed models to predict heat and NOx generation. These conditions were a ratio of ammonium/nitrite equal to 1 and a catalyst concentration of 0.07 mol·L–1 (for a case in which the temperature is 5 °C).