废旧高铝砖在LF精炼渣中的溶解行为研究

Dissolution behavior of waste high-alumina bricks in LF refining slag

LF精炼渣中Al_(2)O_(3)通常来源于铝矾土,其成分与废旧高铝砖相近,因此可用废旧高铝砖替代铝矾土作为LF精炼炉的造渣剂。将废旧高铝砖切割为∅17.3 mm×12.0 mm的试样与精炼渣分别在1600℃反应5、10、15和25 min,分析了废旧高铝砖试样在精炼渣中反应不同时间后的溶解率、显微形貌及溶解后精炼渣成分,探讨了废旧高铝砖在精炼渣中的溶解机制。结果表明:高铝砖溶解后与精炼渣存在明显的边界层,精炼渣中MgO会优先扩散至边界层与试样溶解的Al_(2)O_(3)形成Al_(2)O_(3)-MgO固溶体,随着反应时间的增加,Al_(2)O_(3)-MgO固溶体逐渐增多,反应后期在试样表面形成Al_(2)O_(3)-MgO固溶层,抑制了溶解产物铝酸钙相向精炼渣中扩散;反应25 min后,高铝砖试样溶解率达35%,且与反应5 min后的精炼渣相比,精炼渣中Al_(2)O_(3)含量(w)由27.1%提升至30.9%。

The Al_(2)O_(3) in LF slag usually originates from bauxite,and LF slag has similar composition with waste high-alumina bricks.Hence,it is possible to substitute for bauxite with waste high-alumina bricks.Waste high-alumina bricks were cut into cylindrical specimens(∅17.3 mm×12.0 mm)and put into the refining slag of 1600℃for different durations(5,10,15,and 25 min).The dissolution rate and microstructure of the waste high-alumina specimens as well as the composition of the refining slag after reaction were analyzed,and the dissolution mechanism of waste high-alumina bricks in the refining slag was explored.The results show that after dissolution,there is an obvious boundary layer between the high-alumina specimen and the refining slag,and MgO in the refining slag preferentially diffuses to the boundary layer to form Al_(2)O_(3)-MgO solid solution with the dissolved Al_(2)O_(3) in the specimen;with the increasing reaction time,the Al_(2)O_(3)-MgO solid solution gradually increases,forming an Al_(2)O_(3)-MgO solid solution layer on the specimen surface at the later stage of reaction,which prevents the diffusion of dissolved calcium aluminate into the refining slag;after 25 min of reaction,the dissolution rate of the specimen reaches 35%;by comparing the slag reacted for 25 min with that reacted for 5 min,the Al_(2)O_(3) content increases to 30.9 mass%from 27.1 mass%.