A novel process concept for the capture of CO₂ and SO₂ using a single solvent and column

The presence of SO₂ in flue gas has a negative impact on typical CO₂ capture processes utilising aqueous amines. For countries like Australia, that do not have flue gas desulfurisation, retrofitting such equipment to existing coal fired power stations is of the order of 100's of millions of dollars. In this work a new process configuration is described in which SO₂ is absorbed into a fraction of the absorbent used for CO₂ capture. SO₂ absorption is carried out in the bottom of the absorber column into a bleed stream from the bulk solvent, and a recycle flow allows the absorbent to be near saturation in SO₂. This high concentration allows a number of low cost options for sulfur removal from the absorbent such as chemical treatment and precipitation. The principles underlying the concept, have been studied in the laboratory, and a rate based model of an absorber column has been used to model the SO₂ removal column section. The laboratory and modelling results support both the feasibility and utility of the process concept.