A process for oxidizing a sulfur stream includes supplying at least one sulfur stream into a furnace; supplying oxygen-enriched combustion air into the furnace; separately supplying pure oxygen into the furnace; and at least partially oxidizing the at least one sulfur stream in the furnace. A related apparatus is also provided and includes a furnace; an inlet for supplying at least one sulfur stream into the furnace; an inlet for supplying a stream of an oxygen-enriched combustion air into the furnace; and an inlet for supplying a pure oxygen stream into the furnace separately from the supplying of the oxygen-enriched combustion air.