Thermochemical principles of the production of lightweight aggregates from waste coal bottom ash
Thermochemical principles of the production of lightweight aggregates from waste coal bottom ash
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DOI：
10.1111/jace.17458
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发表时间：
2020
影响因子：
3.9
通讯作者：
Mohammad Balapour;Rathin Rao;E. Garboczi;S. Spatari;Y. Hsuan;P. Billen;Y. Farnam
中科院分区：
文献类型：
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作者：
Mohammad Balapour;Rathin Rao;E. Garboczi;S. Spatari;Y. Hsuan;P. Billen;Y. Farnam
通过烧结技术制造轻质骨料（LWA）（即多孔陶瓷）需要三个条件之间的微妙平衡：（a）在烧结过程中形成足够量的熔融液相，（B）达到固液悬浮的适当粘度，以及（c）排放足够量的气体可以被液相捕获以形成孔隙。本研究评估了由两种类型的废煤底灰（低钙和高钙）制成的LWA生产中的这三个条件，并将它们与LWA孔结构的形成联系起来。热化学分析方法，包括热力学建模和布朗宁粘度模型，被用来量化的液相的程度，并计算其粘度。结合热化学分析，还使用了实验方法，包括定量X射线衍射法、热重分析和X射线计算机断层扫描，以确定烧结过程中导致气体排放的候选化合物，并评估LWA孔结构。结果表明，液相的质量分数至少为50%，需要在烧结过程中发射的气相的成功捕获。与用低钙底灰制成的LWA样品相比，在用高钙底灰制成的LWA样品的微观结构中观察到更大的孔。这一观察结果主要归因于高钙样品在烧结过程中形成具有较低粘度的液相，并且比低钙样品排放更多量的气相。结果表明，反应过程中赤铁矿还原和硬石膏分解生成气相，导致O2和SO2的释放。
Manufacturing lightweight aggregate (LWA) (ie, porous ceramics) by means of a sintering technique requires a delicate balance among three conditions: (a) forming a sufficient amount of molten liquid phase during sintering, (b) reaching an appropriate viscosity for solid‐liquid suspension, and (c) emitting a sufficient amount of gas that can be entrapped by the liquid phase to form pores. This study evaluates these three conditions in the production of LWAs made from two types of waste coal bottom ash (low‐calcium and high‐calcium), and relates them to the formation of LWA pore structure. A thermochemical analytical approach, including thermodynamic modeling and the Browning viscosity model, was used to quantify the extent of the liquid phase and calculate its viscosity. In conjunction with thermochemical analysis, an experimental approach including quantitative x‐ray diffractometry, thermogravimetric analysis, and x‐ray computed tomography was also used to identify the candidate chemical compounds that contribute to gas emission during sintering and to evaluate the LWA pore structure. The results indicated that a mass fraction of at least 50% for the liquid phase is required for a successful entrapment of emitted gaseous phases during sintering. Larger pores were observed in the microstructure of LWA samples made using high‐calcium bottom ash in comparison to those made with low‐calcium bottom ash. This observation was mainly attributed to the high‐calcium samples forming liquid phases with lower viscosities and emitting higher amounts of gaseous phase during sintering than did the low‐calcium samples. It was found that the gaseous phase was generated by hematite reduction and anhydrite decomposition, which led to the release of O2and SO2.