Influence of NOx and SO2 on Li4SiO4 based carbon capture

” NOx and SO2 are common gas contaminants which have done great harm to the environment and people’s health. Thus, the effects of NOx and SO2 in the flue gas on the CO2 absorption by Li4SiO4 material should be considered. The effects of NOx and SO2 on the CO2 absorption performance of Li4SiO4 material could be great despite of their minor contents [82].

Puccini et al. [82] performed CO2 absorption tests in an atmosphere of 4 vol.% CO2 and various concentrations of NO, and the results showed that NO in the absorption atmosphere does not show a harmful effect on the CO2 absorption capacity of Li4SiO4 material. Furthermore, when the concentration of SO2 in the absorption atmosphere increased from 0 to 2000 ppm, the weight change of Li4SiO4 material increased with the increase of SO2 concentration, but the regeneration performance of Li4SiO4 material in the presence of SO2 was worse compared with that in the absence of SO2. Additionally, the cyclic CO2 absorption performance of Li4SiO4 material was negatively influenced in the presence of SO2 under absorption and regeneration atmospheres [71]. The authors ascribed this phenomenon to the nonreversible reaction between SO2 and Li4SiO4, as shown in Equations (12) and (13):

Li4SiO4+SO2Li2SO3+Li2SiO3 (12)
Li2SiO3+SO2Li2SO4+SiO (13)
The formation of Li2SO3 and Li2SO4 prevented the regeneration of the materials, indicating that the presence of SO2 in the absorption atmosphere has an adverse effect on the absorption performance of Li4SiO4 material [82]. In general, NO had no negative impact on the CO2 absorption property of Li4SiO4 materials, while SO2 had an adverse effect due to the formation of the irreversible Li2SO3 and Li2SO4, so SO2 must be scrubbed prior to the trapping of CO2. However, the exact joint role and acting mechanism of NO and SO2 in the process of CO2 capture are still unknown, and the effects of other contaminants, like HCl or H2S, on the CO2 absorption by Li4SiO4 material are not clear, thus further research is necessary. “

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