A nozzle in a burner assembly is configured to produce a flame. The nozzle is configured to include a fuel-discharge outlet and to conduct fuel along a path in the nozzle to the fuel-discharge outlet. Pressurized primary oxygen is provided to mix with fuel discharged by the nozzle to produce a mixture that can be ignited to produce a flame. Staged oxygen is provided to the flame in a region downstream from the nozzle.