During bessemerization of copper, the reaction taking place in the Bessemer converter is

The sulfide ore of copper is heated in the air until a part is converted to oxide and then further heated in the absence of air to let the oxide react with unchanged sulfide.

Self-reduction of CuS to Cu can be carried out by a Bessemer converter as

$2{\mathrm{Cu}}_2\mathrm{O}+{\mathrm{Cu}}_2 \mathrm{S}\to 6\mathrm{Cu}+{\mathrm{SO}}_2$