When copper converter slag is used as a raw material for iron smelting, copper in the slag must be removed as much as possible, because copper may bring out the hot-brittleness of steel. It is reported that most copper in the slag is found as sulphide.
In this experiment, the various conditions of chloridized volatilization and roasting methods had been investigated by using copper sulphides, copper oxides and converter slag.Chlorine was obtained by decomposition of CaCl₂·2H₂O.
The summary of those experimental results is shown below.
(1) Copper sulphides were chloridized easily more than copper oxides, expecially CuS was converted by roasting at 900°C and 30 minutes.Copper content of its calcine was less than 0.1% and removing coefficient of copper was over 98%.
(2) When Cu₂S was roasted at 1, 100°C after holding at 600°C (it may be named “the two stages roasting” ), copper was chloridized rapidly during the temperature increase (600-4, 100°C).
(3) On the roasting at 1, 000°C, if 17% of. CaCl₂·2H₂O was added, copper in the slag was removed above 95%, but removing coefficient of zinc was below 80%.
However, on the two stages roasting added 30% of CaCl₂·2H₂O, copper and zinc were both removed above 95%. By this method, CaCl₂·2H₂O was decomposed slowly in comparison with 1, 000°C roasting.
From the results described above, the two stages roasting may be considered as one of the useful methods for removal of copper and zinc in copper converter slag.