Competence Centre for Energy and Environmental Engineering, THM University of Applied Sciences, Wiesenstr. 14, 35390 Gießen, Germany.
Federal Institute for Geosciences and Natural Resources, Technical Mineralogy and Clay Mineralogy, 30655 Hannover, Germany.
Waste Manag. 2019 Nov;99:135-145. doi: 10.1016/j.wasman.2019.08.026. Epub 2019 Aug 30.
Carbonation is a key process in the aging of waste incinerator bottom ash (BA). The reaction with CO decreases the BA alkalinity and lowers the leachability of amphoteric trace metals. Passive ageing over several months is usually performed in intermittently mixed BA heaps. Here we aimed at accelerating the process in a rotating drum reactor continuously fed with the BA and the reactant gas (10 vol-% CO, volumetric flow rate 60 L/min). In one test, the gas was heated and humidified. Since carbonation depends on the specific CO-supply, experiments were conducted at varied BA residence time (60, 80, and 100 min). Residence time was calculated by mass balancing and confirmed by the breakthrough time of two tracers. Leachates and solid phase properties of the treated BA served to evaluate the carbonation performance. The residence time of BA could be adequately controlled by the reactor loading and feed rate. A residence time of 80 min was sufficient to reduce the BA leachability such as to comply with the German regulatory standards for non-hazardous waste, whereas the untreated BA was hazardous waste. Decreased alkalinity was indicated by lower leachate pH and Ca(OH) contents of the BA as compared to the input. Leachate concentrations of amphoteric trace metals (Pb, Zn, Cu) decreased by at least one order of magnitude while oxyanions became slightly more mobile upon carbonation. In view of relatively short residence times and stable process performance, the rotating drum reactor seems promising for a full-scale implementation of BA carbonation.
碳酸化是垃圾焚烧厂底灰（BA）老化的关键过程。与 CO 的反应降低了 BA 的碱度，并降低了两性痕量金属的浸出率。通常在间歇性混合的 BA 堆中进行数月的被动老化。在这里，我们旨在通过连续向 BA 和反应物气体（10vol-%CO，体积流速 60L/min）进料的旋转鼓式反应器来加速该过程。在一项测试中，气体被加热和加湿。由于碳酸化取决于特定的 CO 供应，因此在不同的 BA 停留时间（60、80 和 100min）下进行了实验。停留时间通过质量平衡计算，并通过两个示踪剂的突破时间确认。处理后的 BA 的浸出液和固相性质用于评估碳酸化性能。通过反应器装料和进料速率可以充分控制 BA 的停留时间。80min 的停留时间足以降低 BA 的浸出率，使其符合德国对非危险废物的监管标准，而未经处理的 BA 则为危险废物。与输入相比，BA 浸出液 pH 值和 Ca(OH)2 含量降低表明碱度降低。两性痕量金属（Pb、Zn、Cu）的浸出液浓度至少降低了一个数量级，而碳酸化后氧阴离子的迁移性略有增加。鉴于相对较短的停留时间和稳定的工艺性能，旋转鼓式反应器似乎有望在 BA 碳酸化的大规模实施中得到应用。
