Sequestration of CO2 after reaction with alkaline earth metal oxides CaO and MgO
Sequestration of CO2 after reaction with alkaline earth metal oxides CaO and MgO
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DOI：
10.1016/j.apgeochem.2011.03.125
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发表时间：
2011-07-01
影响因子：
3.4
通讯作者：
Peiffer, Stefan
中科院分区：
文献类型：
--
作者：
Back, Martin;Bauer, Markus;Peiffer, Stefan
在不同温度（15 ~ 75℃）、搅拌速率（300 ~ 600 rpm）和固液比（0.0125 ~ 0.125 mol L-1）条件下，对CaO和MgO在水溶液中的吸附CO2进行了批量实验研究，以确定动力学控制和限制。这两种矿物都是许多燃烧残留物的成分，它们的碳化被认为是二氧化碳封存的一种选择。一般来说，由于更好的气/水交换和矿物溶解和碳酸盐沉淀速率的提高，湍流加剧，金属（水合）氧化物悬浮液对二氧化碳的吸收增加。溶液中CaO和MgO与CO2的反应发生在不同的pH值下。在CaO体系中，pH值介于12.8 （0.1 mol L-1）和11.7 （0.0125 mol L-1）之间，而MgO悬浮液的最大pH值仅接近10.3，尽管这些实验中矿物表面积更大(MgO为140 m（2) L-1，而CaO为7.5 m(2) L-1）。这种反应pH值的差异影响了二氧化碳从气体到液相的转移以及矿物本身的溶解速率。在pH为12.8的条件下，含CaO实验的CO2吸收率最高为0.027 mmol L-1 s（-1）。在所有测试温度和浓度下，CaO的溶解速度很快，方解石的沉淀瞬间发生。因此，CO2溶解步骤限制了整个碳酸化反应。在其他类似条件下，MgO系统的最大CO2吸收率较低。碳酸镁的析出比方解石的析出慢，且与不同的边界条件密切相关，尤其是温度和过饱和程度。为了使碳酸镁以氢菱镁矿(Mg-5(CO3)(4)(OH)（2)中心点4H(2)O）的形式析出，在低溶解Mg2+和CO32-浓度的实验中，温度必须大于50℃。在50℃以下，必须使用高浓度的Mg和C来初始化碳酸镁沉淀为nesquehonite （MgCO3中心点3H(2)O）。这对矿物碳酸化作为碳捕获和储存手段在水系统中的应用具有启示意义。如果提供最佳的二氧化碳供应，富钙材料可以有效地利用，并且几乎独立于反应制度。相比之下，使用碱性镁矿物的CO2结合势需要特定的条件，因为碳酸镁的沉淀需要50 ~ 50℃或高浓度。(C) 2011 Elsevier Ltd.版权所有。
The uptake of CO2 by CaO and MgO in aqueous solution has been studied in batch experiments at different temperatures (15-75 degrees C), stirring rates (300-600 rpm) and solid liquid ratios (0.0125-0.125 mol L-1) in order to identify the kinetic controls and limitations. Both minerals are constituents in many combustion residues and their carbonation is considered as an option for CO2 sequestration. Generally the uptake of CO2 by metal (hydr)oxide suspension increased with higher turbulence due to better gas/water exchange and higher temperature due to enhanced rates of mineral dissolution and carbonate precipitation. The reaction of CaO and MgO with CO2 in solution occurred at distinctly different pH values. While in the CaO systems a pH between 12.8 (0.1 mol L-1) and 11.7 (0.0125 mol L-1) was established, suspensions with MgO only reached maximum pH values of similar to 10.3 even though the mineral surface area was larger in these assays (140 m(2) L-1 for MgO compared to 7.5 m(2) L-1 for CaO). This difference in reaction pH affected the transfer of CO2 from the gas into the liquid phase as well as dissolution rates of the minerals themselves.Maximum CO2 uptake rates were 0.027 mmol L-1 s(-1) for the CaO containing experiments at pH 12.8. Dissolution of CaO was fast and calcite precipitation occurred instantaneously at all tested temperatures and concentrations. Thus, the CO2 dissolution step was limiting the overall carbonation reaction. Under otherwise similar conditions maximum CO2 uptake rates were lower for the MgO system. Magnesium carbonate precipitation was slower than calcite precipitation and depended strongly on the different boundary conditions, in particular temperature and the degree of supersaturation. Temperatures greater than 50 degrees C were required for assays with low dissolved Mg2+ and CO32- concentrations in order to precipitate Mg carbonate in the form of hydromagnesite (Mg-5(CO3)(4)(OH)(2)center dot 4H(2)O). Below 50 degrees C the use of high concentrations of Mg and C species were necessary to initialise precipitation of Mg carbonate as nesquehonite (MgCO3 center dot 3H(2)O). This has implications for the application of mineral carbonation in an aqueous system as a means of C capture and storage. Calcium-rich materials can be utilized efficiently and almost independently of reaction regime if an optimum supply of CO2 is provided. In contrast specific conditions are required to use the CO2 binding potential of alkaline Mg minerals, as T > 50 degrees C or high concentrations are required for Mg carbonate precipitation. (C) 2011 Elsevier Ltd. All rights reserved.