Removal of Inclusions from Aluminum Through Filtration
Removal of Inclusions from Aluminum Through Filtration
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DOI：
10.1007/s11663-010-9367-3
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发表时间：
2010-08-01
影响因子：
3
通讯作者：
Zhang, Lifeng
中科院分区：
文献类型：
--
作者：
Damoah, Lucas Nana Wiredu;Zhang, Lifeng
使用涂覆有AlF₃浆料的和未涂覆的Al₂O₃泡沫陶瓷过滤器进行了过滤实验，以研究非金属夹杂物和杂质元素的去除。结果表明，30孔/英寸的泡沫陶瓷过滤器可从铝中去除高达85%的夹杂物。还展示了非金属和金属间化合物夹杂物的二维和三维形态的若干图片。提出了在深层过滤模式下去除非金属夹杂物的以下作用机制：（1）与壁面碰撞和拦截效应；（2）过滤过程中金属间化合物和非金属夹杂物桥的形成。夹杂物附着在过滤器壁面上的流体动力学模型表明，大多数夹杂物，尤其是尺寸较大的夹杂物，被困在过滤器的上部，而较小的夹杂物则在整个过滤器中均匀分散。对30孔/英寸过滤器计算得到的夹杂物去除分数表明，几乎所有大于125μm的夹杂物都被去除，尺寸约为5μm的夹杂物去除率高达85%。计算了两个相同尺寸碰撞夹杂物之间的界面能，表明在过滤器窗口内可能会导致夹杂物强烈聚集。通过涂覆AlF₃浆料的过滤器，镁杂质的去除率高达86%。除了溶解的[Mg]的空气氧化作用（经计算为13%）外，过滤器还以主动过滤模式起作用。溶解的[Mg]到反应界面的总传质系数经计算为1.15×10⁻⁶m/s。
Filtration experiments were carried out using both an AlF3 slurry-coated and an uncoated Al2O3 ceramic foam filter to study the removal of nonmetallic inclusions and impurity elements. The results showed that the 30-ppi ceramic foam filter removed up to 85 pct inclusions from aluminum. Several pictures of two- and three-dimensional morphologies of both nonmetallic and intermetallics inclusions also have been presented. The following contributing mechanisms for the removal of nonmetallic inclusions in the deep-bed filtration mode are proposed: (1) collision with walls and interception effect and (2) the formation of both intermetallic and nonmetallic inclusion bridges during filtration. Fluid dynamics modeling of inclusion attachment to the filter walls showed that most inclusions, especially those with larger sizes, are entrapped at the upper part of the filter, whereas smaller inclusions are dispersed well throughout the filter. The calculated inclusions removal fractions for the 30-ppi filter showed that almost all inclusions > 125 mu m are removed, and inclusions similar to 5 mu m in size are removed up to 85 pct. The interfacial energy between two collided same-size inclusions was calculated, indicating that a strong clustering of inclusions may result within the filter window. Magnesium impurities were removed up to 86 pct by the AlF3 slurry-coated filter. The filter acted in active filtration mode in addition to the contribution of the air oxidation of dissolved [Mg], which was calculated to be 13 pct. The total mass transfer coefficient of dissolved [Mg] to the reaction interface was calculated to be 1.15 x 10(-6) m/s.