Natural Silicate and Carbonate Minerals (Ores)
Natural silicate-type (e.g., wollastonite) and carbonate-type (e.g., limestone) ores containing alkaline earth metal are suitable for mineral carbonation reaction due to their excellent theoretical sequestration potential. Over geologic time, the natural
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Natural Silicate and Carbonate Minerals (Ores)
Abstract Natural silicate-type (e.g., wollastonite) and carbonate-type (e.g., limestone) ores containing alkaline earth metal are suitable for mineral carbonation reaction due to their excellent theoretical sequestration potential. Over geologic time, the natural weathering of carbonate-type ores captures and sequesters atmospheric CO2. On the other hand, vast quantities of silicate-type minerals are required to sequester a significant fraction of emitted CO2. In this chapter, the physico-chemical properties of various types of natural ores and/or minerals are illustrated. Two promising processes utilizing natural ores to capture CO2 from the flue gas, (1) accelerated mineral carbonation and (2) accelerated carbonate weathering, are discussed in detail in terms of theoretical process chemistry and practical applications, including challenges and barriers.
10.1
Types of Natural Minerals/Ores
Natural silicate minerals are suitable feedstock for natural carbonation (i.e., weathering) because they are rich in calcium or magnesium content. They are abundant but generally difficult to access. Based on their chemical properties, they can be categorized into two types: (1) silicate ores and (2) carbonate ores. The majority of previous researches have focused on the aqueous carbonation of naturally existing silicate minerals, for example, wollastonite [1–3], serpentine [4–6], and olivine [7, 8]. According to Lackner [9], although there are natural ores on earth to sequester CO2 emissions from all fossil fuels, cost-effective methods for accelerating carbonation (for silicate-type ores or alkaline solid wastes) or accelerating weathering (for carbonate-type ores) should be developed. Different types of natural ores are involved with different reaction with CO2. Table 10.1 presents the physico-chemical properties of these natural ores. Natural silicate ores, suitable materials subject to accelerated mineral carbonation (see details in Sect. 10.2 in this chapter), include wollastonite (CaSiO3), serpentine
© Springer Nature Singapore Pte Ltd. 2017 P.-C. Chiang and S.-Y. Pan, Carbon Dioxide Mineralization and Utilization, DOI 10.1007/978-981-10-3268-4_10
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Natural Silicate and Carbonate Minerals (Ores)
Table 10.1 Physico-chemical properties of natural silicate-type and carbonate-type ores Properties Physical Chemical
Items
Unit
Silicate-type
Carbonate-type
Serpentine
Wollastonite
Olivine
Talc
Dolomite
Limestone
Density
g/cm3
2.5–2.6
2.5–2.6
3.3–4.3
2.5–2.8
2.8–2.9
2.71
Hardness
–
3–5
5–5.5
6.5–7.0
1.0
3.5–4.0
3.0
CaO
%
–
45.53
0–18
30.41
56.0
MgO
%
43.0
0.03
9–32
21.87
–
SiO2
%
44.1
52.91
42–61
–
–
Al2O3
%
–
0.07
0–11
–
–
FeO
%
–
0.38
3–20
–
–
MnO
%
–
0.56
–
–
–
CO2
%
–
–
–
47.72
44.0
H2O
%
12.9
–
–
–
–
(Mg3Si2O5(OH)4), olivine ((Mg,Fe)2SiO4), talcum (Mg3Si4O10(OH)2), pyroxene ((Ca,Na,Fe,Mg)2(Si,Al)2O6), and amphibole. On the other hand, natural carbonate ores, such as limestone (CaC
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