Self-reduction of ${\mathrm{Cu}}_2\mathrm{S}$ to Cu can be carried out in

Matte is obtained in blast furnace and that contains mostly ${\mathrm{Cu}}_2\mathrm{S}$ and FeS. It is transferred to Bessemer converter where self-reduction takes place according to the following reactions. 

$\begin{array}{l}2{\mathrm{Cu}}_2\mathrm{S}+3{\mathrm{O}}_2\to 2{\mathrm{Cu}}_2\mathrm{O}+2{\mathrm{SO}}_2;\\ 2{\mathrm{Cu}}_2\mathrm{O}+{\mathrm{Cu}}_2\mathrm{S}\to 6\mathrm{Cu}+{\mathrm{SO}}_2\end{array}$