| Summary: | Due to the continued dominance of fossil fuels in global industry, CO2 capture
and geological storage (CCS) is a vital technology in efforts to combat climate
change. Capture technologies are implemented to purify CO2 streams from
industrial sources, and these streams are injected deep underground in specialised
geological storage media. However, impurity gases could still comprise greater
than 5% of the captured stream and be co-stored with the CO2. The presence of
impurities underground could be detrimental or beneficial to CO2 storage; but as
yet, the influence of many impurities is unclear.
Coal seams, which have been classified as ‘unmineable’, are unconventional CO2
storage media that hold importance in areas where saline aquifers are not readily
available. The major storage mechanism in this medium is sorption, which must
be quantified experimentally for storage capacity estimations. An important
impurity in CCS is SO2, which has very strong sorbing properties and the
potential to affect coal storage capacity. In this study, the effect of different
concentrations of SO2 on CO2 sorption in a typical South African coal was
investigated via laboratory-scale volumetric adsorption experiments.
After sorption experiments of binary CO2-SO2 mixtures, with SO2 concentration
from 0% to 6.7%, were run for 48 hours at 85 bar and 40°C, it was clear that SO2
sorbed very strongly to the coal and its sorption is preferential to that of CO2. The
results show that SO2 interacts with CO2, and can potentially enhance or inhibit
CO2 sorption, depending on the model used to describe the density of the CO2-
SO2 mixture. The effect of SO2 is seen to be significant even at low
concentrations (< 2% SO2), and it is recommended that its effect is taken into
account when storage capacity estimations on coal seams are carried out.
|
|---|
