China Nonferrous Metallurgy

In view of the frequent ringing problem in the process of secondary aluminum dross smelting in rotary kiln， this study used low-salt secondary aluminum dross as raw material for sintering experiment. The densification sintering temperature and the composition volatilization temperature were determined by thermogravimetric analysis， high temperature deformation analysis and the relationship between liquid volume and volatile matter and temperature. A two-stage roasting process was proposed and verified. When the rotary kiln roasts the low-salt secondary aluminum ash， the main reason for the ringing phenomenon is the excessive liquid phase generated at the high temperature stage. At 710℃， the secondary aluminum dross emits a lot of heat due to violent combustion， which leads to the rapid heating of the local micro-area to produce liquid phase， which promotes the densification of sintering， and the densification is completed at 850℃. At 939. 5-1 194. 9℃， Cl， F， K， Na and other elements volatilize. With the increase of temperature， the total liquid phase increases first and then decreases， reaching a maximum of 10. 66% at 1 000℃， and the total molten salt liquid phase decreases to 7. 16% at 1 300℃. The twostage roasting process， i. e. low-temperature roasting at 850℃ for 3 h， is used to complete the balling densification and let the nitrogen escape smoothly. The purpose of high temperature roasting at 1 300℃ for 3 h is to concentrate and volatilize Cl， F， K， Na and other salt elements that easily lead to ring formation. The verification test showed that compared with single temperature roasting， the ring quality under two-stage roasting （850℃，3 h；1 300℃， 3 h） is only 0. 41 g， which is 28. 07% lower than that of scheme 1（850℃，3 h） and 14. 58% lower than that of scheme 2（1 300℃，3 h）， and the effect of inhibiting the ring formation is obvious. After two-stage roasting， the content of Na and Cl in the sample decreased to 1. 21% and 0. 03%， respectively， and Al₂O₃ increased to 81. 44%. In addition， the mass fraction of Cl， K₂O， SO₃ and F also decreased significantly， and the roasting effect was better. The results of this study provide theoretical guidance and technical reference for the ringing formation inhibit in roasting of low-salt secondary aluminum dross by rotary kiln.