A method for achieving low NOx combustion of fuel gas in heated pelletizing process air, comprising: conveying pelletized material through an indurating furnace, having a heating station and a passage that directs heated process air to the heating station; driving heated process air through the passage toward the heating station; and operating a premix burner having a reaction zone with an outlet to the passage, including the steps of: injecting a premix of primary fuel gas and combustion air into the reaction zone; combusting the premix to provide combustion products including vitiated combustion air in the reaction zone; injecting staged fuel gas into the reaction zone separately from the premix; discharging the staged fuel gas and vitiated combustion air from the reaction zone through the outlet to the passage; and combusting the staged fuel gas and vitiated combustion air in the heated process air in the passage, whereby low NOx combustion in the heated process air is achieved as a result of interacting the staged fuel gas with the vitiated combustion air in the reaction zone, characterized in that the reaction zone has a central axis, and staged fuel gas is injected into the reaction zone as a jet centered on the axis, or that the premix is injected into the reaction zone from a mixer tube, and the staged fuel gas is injected into the reaction zone from a staged fuel injector, located within the mixer tube. conveying pelletized material through an indurating furnace, having a heating station and a passage that directs heated process air to the heating station; driving heated process air through the passage toward the heating station; and operating a premix burner having a reaction zone with an outlet to the passage, including the steps of: injecting a premix of primary fuel gas and combustion air into the reaction zone; combusting the premix to provide combustion products including vitiated combustion air in the reaction zone; injecting staged fuel gas into the reaction zone separately from the premix; discharging the staged fuel gas and vitiated combustion air from the reaction zone through the outlet to the passage; and combusting the staged fuel gas and vitiated combustion air in the heated process air in the passage, whereby low NOx combustion in the heated process air is achieved as a result of interacting the staged fuel gas with the vitiated combustion air in the reaction zone, injecting a premix of primary fuel gas and combustion air into the reaction zone; combusting the premix to provide combustion products including vitiated combustion air in the reaction zone; injecting staged fuel gas into the reaction zone separately from the premix; discharging the staged fuel gas and vitiated combustion air from the reaction zone through the outlet to the passage; and combusting the staged fuel gas and vitiated combustion air in the heated process air in the passage, whereby low NOx combustion in the heated process air is achieved as a result of interacting the staged fuel gas with the vitiated combustion air in the reaction zone, characterized in that the reaction zone has a central axis, and staged fuel gas is injected into the reaction zone as a jet centered on the axis, or that the premix is injected into the reaction zone from a mixer tube, and the staged fuel gas is injected into the reaction zone from a staged fuel injector, located within the mixer tube.