
97Beneficiation Technology
much aluminum to be classied as ferrous scrap but too much iron to be remelted by
secondary smelters.
Figure 5.26 shows a traditional solution to this problem (EnviroAir Inc., 2005;
Nijkerk and Dalmijn, 1998), a sweat furnace. Sweat furnaces can be either the
rotary type shown here or a less sophisticated stationary dry-hearth design. In
either case, the principle is simple. High-irony scrap fed to the furnace is heated
to a temperature just above the melting point of aluminum (660°C). At this tem-
perature, the aluminum slowly melts away (hence the term, sweating), leaving the
higher-melting point iron behind. The liquid ...