Carbon capture and storage (CCS) is considered a key
process to
reach net-zero emission by the 2050 aim of limiting global warming.
Coal bed methane (CBM) is considered potential geological reservoirs
for underground CCS due to the CO2–CH4 exchange feasibility by adsorptive phenomena. Global implementation
has been focused only on deep reservoirs to provide methane recovery.
Thus, this work proposes a modified CCS process based on silica nanoparticle
inclusion for shallow CBM reservoirs (<300 m). The nanomaterials
were evaluated at high pressure in two main stages including i) CO2 sorption on a single CO2 stream
and ii) CO2 selectivity on a flue gas
stream (N2–CO2 mixture). This work includes
silica nanomaterial synthesized from rice husk as agro-waste sources
with better technical-economic feasibility framed in a circular economy
to reduce costs and maximize the use of available resources. Rice
husk silica (RSi) nanoparticles were doped with 1.0, 3.0, and 5.0
wt % of urea (Si–U), diethylamine (Si-DE), triethylamine (Si-TE),
and ethylenediamine (Si-EM) to enhance the CO2 sorption.
First, CO2 sorption was evaluated at 30 °C and between
0.084 and 3 MPa using a CO2 stream to determine the best-doped
amount of each N-source. Then, the best nanoparticles were used to
impregnate CBM at 10 and 20 wt %, and the subsequent CO2 storage on the flue gas stream (70% v/v N2 and 30% v/v
CO2) was done. The results showed that CO2 sorption
on RSi increases with the N-group coating in the order RSi-DE <
RSi-TE < RSi-U < RSi-EM. Also, the best-doped amount for each
N-source was 3 wt %. For CBM impregnation, the nanofluid containing
20 wt % of RSi-EM3 presented the best yield increasing the CO2 sorption from 0.05 to 0.75 mmol g–1, meaning
an increase of more than 1000% in the sorption capacity.