CO2 REACTIVE ABSORPTION FROM FLUE GASES INTO AQUEOUS AMMONIA SOLUTIONS: THE NH3 SLIPPAGE EFFECT

Future deployment of NH3-based CO2 capture technology into coal-fired power plants will shift unwanted emissions from those currently comprising SO2, NOx and particulate matter towards those comprising NH3. This is due to volatility of ammonia. Therefore, the current paper aims at understanding of NH3 slippage to flue gases from the NH3-based CO2 capture process and at identifying the opportunities to limit this unwanted slippage. The paper presents experimental and 2D modelling-based analysis of CO2 reactive absorption from flue gases into aqueous ammonia solutions in a falling film reactor. The results enable one to characterise hydrodynamics of the falling film reactor, to analyse the effect of pH, pressure and temperature on CO2 absorption and NH3 slippage and to explain the role of migrative transport of ionic species in total mass transport. It was found that NH3 slippage to the gaseous phase can be limited by alleviated operating temperatures, optimised pH, increased pressure and large CO2 absorption fluxes which force negative enhancement of NH3 mass transfer [16]. The NH3 slippage under CO2 capture conditions and under air stripping conditions is illustrated by experimental and simulation data. Finally, main approaches used for the integration of CCS systems into power plants are expounded.