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首页> 外文期刊>Crystal growth & design >Growth of nanosized calcite through gas-solid carbonation of nanosized portlandite under anisobaric conditions
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Growth of nanosized calcite through gas-solid carbonation of nanosized portlandite under anisobaric conditions

机译：在异压条件下通过气固碳化纳米晶石生长纳米方解石

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The gas-solid carbonation of nanosized portlandite was experimentally investigated using a static bed reactor under anisobaric conditions. The effects of initial CO_2 pressure (10-40 bar), reaction temperature (30 and 60 °C), and relative humidity were investigated. Three steps of the carbonation process were determined: (1) instantaneous CO_2 mineralization during CO_2 injection period. From 25 to 40 wt % of initial portlandite grains were transformed into calcite during the CO _2 injection period (from 0.9 to 2 min). (2) Fast CO_2 mineralization after gas injection period (<5 h) followed by (3) a slow CO_2 mineralization until an equilibrium state (<24 h). The results revealed high efficiency from portlandite-to-calcite transformation (>95%). For this case, the mineralization of CO_2 does not form a protective carbonate layer around the reacting particles of portlandite as typically observed by other gas-solid carbonation methods. This method could be efficiently performed to produce nanosized calcite. Moreover, the separation of calcite particles from the fluid phase is most simple compared with precipitation methods. A kinetic pseudo-second-order model was satisfactorily used to describe the three CO_2 mineralization steps except for the carbonation reaction initiated at 40 bar. In this latter case, a kinetic pseudo-first-order model was satisfactorily used; indicating that the slow CO_2 mineralization step appears less significant during the carbonation process.
机译：使用静态床反应器在等压条件下，对纳米级辉石的气固碳化进行了实验研究。研究了初始CO_2压力（10-40 bar），反应温度（30和60°C）和相对湿度的影响。确定了碳化过程的三个步骤：（1）在CO_2注入期间瞬时CO_2矿化。在CO _2注入期间（0.9至2分钟），有25至40 wt％的初始硅酸盐晶粒转变为方解石。 （2）气体注入期（<5 h）后快速的CO_2矿化，然后（3）缓慢的CO_2矿化直至平衡状态（<24 h）。结果表明，从钙钛矿到方解石的转化效率很高（> 95％）。对于这种情况，CO_2的矿化不会像其他气固碳化方法通常观察到的那样，在硅酸盐反应颗粒周围形成保护性碳酸盐层。该方法可以有效地进行以生产纳米级方解石。此外，与沉淀方法相比，从液相分离方解石颗粒最简单。一个令人满意的动力学拟二级模型用于描述三个CO_2矿化步骤，除了在40 bar下引发的碳酸化反应。在后一种情况下，可以令人满意地使用动力学伪一阶模型。表明缓慢的CO_2矿化步骤在碳化过程中显得不那么重要。

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