The sorbents with stable CO2 capture behavior during cyclic
reactions can be obtained through three different technical routes:
sol–gel combustion, wet mixing combustion using metal nitrate
precursor, and wet mixing combustion using metal oxide precursor.
However, their raw material costs are different. Table 2 shows
that the costs of metal nitrate were approximately 10 times higher
than those of natural carbonate, which can be decomposed into
metal oxide by calcination. Considering a citric acid molar ratio
of 0.5 in the sorbents, the raw material costs of SG CaO/MgO 5:1,
WM(3)CaO/MgO 2:1 and WM(2)CaO/MgO 2:1 were 12,000,
13,000, and 5600 CNY/t (about 2000, 2100 and 900 USD/t), respectively.
These results indicate that wet mixing combustion synthesis
using a metal oxide precursor is more cost effective than the other
two routes. The major cost of the sorbents was due to fuel consumption.
Wet mixing combustion synthesis requires soluble fuels
to obtain a well-dispersed solution. If the cost of soluble fuels can
be lowered further, the costs of wet mixing combustion synthesis
can also be significantly lowered. Given that the cost of
WM(2)CaO/MgO 2:1 was the lowest, further investigation focused
on the sorbent characteristics.