Regeneration of sulfate‐rich postcombustion capture amines through reactive crystallisation

Flue gas desulfurisation is a prerequisite for successful CO2 capture in coal‐fired power stations utilising aqueous amine absorbents. For nations like Australia, where there is nonexistence of mandatory flue gas desulfurisation, this increases the cost for power plants retrofitting CO2 capture. The CSIRO's CS‐Cap process, a potentially low cost method for combined CO2 and SO2 capture, provides an alternate sulfur management solution to such plants. The CS‐Cap process, however, results in high sulfur‐loaded amines that require continuous regeneration to retain cost benefits. Reactive crystallisation by KOH addition is shown to be successful in removing the bulk of the sulfate from aqueous amines without any additional heating or cooling requirements. Increasing initial sulfate loading by amine recycling initially improves sulfate removal efficiency, up to the postsaturation level where the systems ionic strength determines further sulfate solubility. Oxidative amine degradation had no significant effect on the precipitation efficiency or purity of K2SO4 crystals apart from their slight discoloration. The behaviour of the residual potassium in these regenerated aqueous amines needs further investigation as it could lead to unwanted precipitation inside the absorber column and other parts of the process.