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SUN ET AL .
in 1-10 nm, it is easily to be blocked during carbonation pro- cess of the sorbent, because of which much of the surface is coated in the product layer and cannot be effectively utilized for carbonation reaction. Therefore, the LM shows much poorer carbonation performance compared with the lime- stone during the chemical reaction controlled stage. The pre- wash treatment obviously improves the microstructure of the LM. The surface area and V 1-100 nm of the calcined PLM are increased by 74% and 56% compared with those of the cal- cined LM. Especially, the value of V 10-100 nm of the calcined PLM is 4.5 times that of the calcined LM. The prolonged carbonation treatment further enhances the microstructure of the calcined PLM. Though the surface area is decreased, the value of V 10-100 nm for the PLM is increased by 3.4 times through prolonged carbonation process. The microstructure of the PLM after prolonged carbonation process is much more beneficial to CO 2 capture compared with the LM, with
FIGURE 12 Fitting results of the carbonation conversions of the PLM after prolonged carbonation treatment during chemical reaction controlled stage
TABLE 4 Effect of prewash and prolonged carbonation treatment on pore distribution parameters of the calcined sorbents
Surface area (m 2 /g)
V 1-100 nm (cm 3 /g)
V 1-10 nm (cm 3 /g)
V 10-100 nm (cm 3 /g)
Sample
Cycle
LM
1
6.2
0.016
0.014
0.002
P LM
1
10.8
0.025
0.016
0.009
PLM after prolonged carbonation
1
5.6
0.051
0.011
0.040
Limestone
1
4.25
0.047
0.002
0.045
(b)
(a)
FIGURE 13
Pore volume distributions of the calcined limestone, LM, PLM before and after prolonged carbonation treatment in the 1st cycle.
A, Pore volume distribution and B, cumulative pore volume
CO 2 capture of calcium-based sorbent, 26 is only 4.4% that of the calcined limestone. The diffusion resistance of CO 2 in the calcined LM is larger than that in the calcined lime- stone. Since most of the pores of the calcined LM distributes
smaller diffusion resistance of CO 2 in the sorbent and higher utilization efficiency of the surface area. As is shown in Table 4, the values of surface area for the calcined PLM after prolonged carbonation treatment is a
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