Interactions between SO2 and KCl -A comparison between air and oxy-fuel combustion

Drastic cuts in global CO2 emissions are needed to mitigate the global warming. The power generation sector is largely based on fossil fuels and produces a significant share of the global CO2 emissions. Thus, new power generation processes with drastically reduced CO2 emissions are needed. Two alternatives which may be part of the solution is the replacement of coal with biomass or the employment of carbon capture and storage (CCS). In CCS the CO2 is captured and processed on site and thereafter transported to a storage location. Oxy-fuel combustion, which has been studied in this paper, has been demonstrated in large-scale pilot plants (30-60 MW) and is one of the suggested capture technologies. This work investigates the possibilities to co-combust biomass and coal in oxy-fuel combustion for CO2 capture. Biomass combined with CO2 capture has the potential to contribute to negative CO2 emissions. However, the high temperature corrosion (HTC) associated with biomass combustion need to be studied in detail in order to determine the potential consequences for corrosion on heat transfer surfaces in oxy-combustion atmospheres. This work is based on experiments performed in a 100 kW combustion unit and modelling of chemical kinetics. The results from this work show that a high CO2 and SOX concentration is clearly beneficial to achieve a high degree of sulphation of the alkali chlorides. The combined effect of CO2 and SOX causes a significantly higher degree of sulphation in oxy-fuel compared to air-fuel combustion atmospheres