Incineration of Ammonia Wastewater and The Effect to The Environment

Abstract

Wastewater containing ammonia is normally sent to the wastewater treatment system in a chemical plant for the removal of ammonia compound. Alternatively, it is proposed to remove the ammonia compound by incinerating the wastewater using the existing incinerator system. However, it is essential to ensure that the gaseous and aqueous emission produced by the incinerator system do not exceed the Clean Air Regulations (CAR) 2014 and Industrial Effluent Regulations (IER) 2009 limits, especially the nitrogen oxides (NOx) content and unburnt ammonia compound. A process simulation model of the incinerator system was developed using a Gibbs energy minimization reactor approach coupled with Gasification property package to predict the products of the incineration process. Two case study runs were conducted to evaluate the impact of incinerator operating temperature and ammonia concentration in the wastewater feed. Theoretically, there are two causes of NOx production; from thermal NOx (oxidation of nitrogen at high temperature) and fuel NOx (oxidation of liberated nitrogen from ammonia). The study showed that the thermal NOx effect is significantly higher than fuel NOx effect through this study. This is because the total liberated nitrogen molecules from the intended concentration of ammonia in the aqueous water is comparatively small when compared with the amount of nitrogen molecules in the combustion air. Based on the case study results, there is very minimal impact of ammonia injection on total NOx production as the incinerator temperature is commonly controlled on a fixed set point. There is also opportunity to reduce fuel gas requirement because the heating value of the waste streams increases through the combustion of hydrogen molecules in ammonia.