Department of Mechanical Engineering, RWTH Aachen, Templergraben 55, 52056 Aachen, Germany.
Environ Sci Technol. 2012 Jan 3;46(1):559-65. doi: 10.1021/es2034697. Epub 2011 Dec 20.
The reaction of CaO with CO(2) is a promising approach for separating CO(2) from hot flue gases. The main issue associated with the use of naturally occurring CaCO(3), that is, limestone, is the rapid decay of its CO(2) capture capacity over repeated cycles of carbonation and calcination. Interestingly, dolomite, a naturally occurring equimolar mixture of CaCO(3) and MgCO(3), possesses a CO(2) uptake that remains almost constant with cycle number. However, owing to the large quantity of MgCO(3) in dolomite, the total CO(2) uptake is comparatively small. Here, we report the development of a synthetic Ca-rich dolomite using a coprecipitation technique, which shows both a very high and a stable CO(2) uptake over repeated cycles of calcination and carbonation. To obtain such an excellent CO(2) uptake characteristic it was found to be crucial to mix the Ca(2+) and Mg(2+) on a molecular level, that is, within the crystalline lattice. For sorbents which were composed of mixtures of microscopic crystals of CaCO(3) and MgCO(3), a decay behavior similar to natural limestone was observed. After 15 cycles, the CO(2) uptake of the best sorbent was 0.51 g CO(2)/g sorbent exceeding the CO(2) uptake of limestone by almost 100%.
氧化钙与二氧化碳的反应是一种从热烟道气中分离二氧化碳的有前途的方法。使用天然存在的碳酸钙（即石灰石）的主要问题是，在碳酸化和煅烧的反复循环中，其二氧化碳捕集能力迅速衰减。有趣的是，白云石是碳酸钙和碳酸镁的等摩尔混合物，其二氧化碳吸收量几乎随着循环次数的增加而保持不变。然而，由于白云石中含有大量的碳酸镁，其总二氧化碳吸收量相对较小。在这里，我们报告了一种使用共沉淀技术开发的富钙白云石，它在煅烧和碳酸化的反复循环中表现出非常高且稳定的二氧化碳吸收。为了获得如此优异的二氧化碳吸收特性，发现将 Ca(2+)和 Mg(2+)在分子水平上（即在晶体晶格内）混合是至关重要的。对于由碳酸钙和碳酸镁的微观晶体混合物组成的吸附剂，观察到类似于天然石灰石的衰减行为。经过 15 次循环后，最佳吸附剂的二氧化碳吸收量为 0.51g CO(2)/g 吸附剂，超过石灰石的二氧化碳吸收量近 100%。
