Research On Formation Mechanism And Prevention Measure Of Integral Solidification Of Electric Furnace Slag

High-temperature cleaning and flotation are new technologies used widely to recover valuable metals from smelting slag in many copper smelting enterprises, of which the most important process is the slow-cooling process of electric furnace slag. During slow-cooling process, the slag often solidificate so integrally that it cannot be broken when the salg drops down from slag ladle, which will affect seriously the operation of subsequent flotation process. Therefore, to research the formation mechanism and prevention measure of integral solidification of electric furnace slag has theoretical value and practical significance for the comprehensive utilization of copper smelting slag.Based on consulting pertinent literature, for this study, the physicochemical properties of normal electric furnace slag and integral-solidificating slag were studied experimentally at first, then the formation mechanism of integral solidification of electric furnace slag was analyzed. The prevention measures were proposed by synthesizing each technology of flash smelting process, slag cleaning process and slow-cooling process.The major research contents are as follows:(1) The phases and chemical composition of normal slag and integral-solidificating slag were researched experimentally. Results show that, compared with normal slag, the integral-solidificating slag has higher viscosity, three layers(dark full-density outer shell, layered hard middle layer, and polyporous core layer), higher sulfur content and alkalinity(Ca O/Si O2) but lower copper content and Fe/Si O2, higher Fe3O4 content in outer shell and middle layer, and some Zn S with high melting point in middle layer.(2) The melting points and viscosities of normal slags and integral-solidificating slags were measured, and the effects of Fe3O4 content(43OFew), Cu2 O content(OCu2w), ratio of iron to silicon(2FSi Oe/ mm) and alkalinity(2CSi Oa O/ mm) on the melting point and viscosity were studied. Results show that, compared with normal slag, the integral-solidificating slag has higher melting point which decreases from outer shell to core layer and increases linearly with increasing 43 OFew but decreases with the increase of 2FSi Oe/ mm, 2CSi Oa O/ mm andOCu2w; the integral-solidificating slag has higher viscosity in outer shell and middle layer, which increases slow at first then fast with decreasing temperature, and increases fast with the increase of 43 OFew but slow with the increase of 2FSi Oe/ mm, 2CSi Oa O/ mm andOCu2 w.(3) The formation mechanism of integral solidification of electric furnace slag was analyzed. Results show that the viscosity of electric furnace slag with high Fe3O4 content and some other high melting point materials(such as Zn S) increases rapidly during slow-cooling process, resulting in a thick full-density outer shell which makes the slag solidificate so integrally that it cannot be broken when dropping down from slag ladle. This is the reason why the integral solidification phenomenon happens. The thick full-density outer shell also can prevent the normal heat transmission between internal parts of electric furnace slag and external air or cooling water, which can easily lead to red ladle or explosion phenomenon.(4) By synthesizing each technology of flash smelting process, slag cleaning process and slow-cooling process, some prevention measures were proposed from the point of view of the operating control of flash smelting process, the operation optimization of electric furnace cleaning process and improvement of slag slow-cooling process.