Environmental and Nano Sciences Group, Department of Chemistry, University of the Western Cape, Private Bag X17, Bellville, 7535, Cape Town, South Africa.
J Environ Manage. 2011 Mar;92(3):655-64. doi: 10.1016/j.jenvman.2010.10.008.
Coal combustion by-products such as fly ash (FA), brine and CO(2) from coal fired power plants have the potential to impact negatively on the environment. FA and brine can contaminate the soil, surface and ground water through leaching of toxic elements present in their matrices while CO(2) has been identified as a green house gas that contributes significantly towards the global warming effect. Reaction of CO(2) with FA/brine slurry can potentially provide a viable route for CO(2) sequestration via formation of mineral carbonates. Fractionated FA has varying amounts of CaO which not only increases the brine pH but can also be converted into an environmentally benign calcite. Carbonation efficiency of fractionated and brine impacted FA was investigated in this study. Controlled carbonation reactions were carried out in a reactor set-up to evaluate the effect of fractionation on the carbonation efficiency of FA. Chemical and mineralogical characteristics of fresh and carbonated ash were evaluated using XRF, SEM, and XRD. Brine effluents were characterized using ICP-MS and IC. A factorial experimental approach was employed in testing the variables. The 20-150 μm size fraction was observed to have the highest CO(2) sequestration potential of 71.84 kg of CO(2) per ton of FA while the >150 μm particles had the lowest potential of 36.47 kg of CO(2) per ton of FA. Carbonation using brine resulted in higher degree of calcite formation compared to the ultra-pure water carbonated residues.
燃煤电厂产生的煤灰（FA）、盐水和 CO2 等煤燃烧副产品有可能对环境产生负面影响。FA 和盐水可以通过浸出其基质中存在的有毒元素来污染土壤、地表水和地下水，而 CO2 已被确定为一种温室气体，对全球变暖效应有很大贡献。CO2 与 FA/盐水浆液的反应可能为通过形成矿物碳酸盐来实现 CO2 封存提供可行的途径。分级 FA 含有不同量的 CaO，这不仅增加了盐水的 pH 值，而且还可以转化为环境友好的方解石。本研究考察了分级和受盐水影响的 FA 的碳酸化效率。在反应器装置中进行了受控碳酸化反应，以评估分级对 FA 碳酸化效率的影响。使用 XRF、SEM 和 XRD 评估了新鲜和碳酸化灰的化学和矿物特性。使用 ICP-MS 和 IC 对盐水废水进行了表征。采用析因实验方法测试了变量。观察到 20-150μm 粒径的分级 FA 具有最高的 CO2 封存潜力，为 71.84kg CO2/吨 FA，而粒径>150μm 的颗粒的封存潜力最低，为 36.47kg CO2/吨 FA。与超纯水碳酸化残渣相比，盐水碳酸化导致更高程度的方解石形成。
