Burner configurations for staged combustion

A burner configuration adapted to be positioned in a furnace for carrying out staged combustion in order to decrease nitrogen oxides (NOx) during the combustion of hydrocarbon fuel with air, comprising:

• (a) a combustion chamber and means for supplying into one end of said combustion chamber a mixture of hydrocarbon fuel and air in an amount less than 70% of the stoichiometric amount;
• (b) flow path means surrounding and extending along said combustion chamber for flowing secondary air around and along said combustion chamber;
• (c) a flame holding means in said one end of said combustion chamber for stabilizing the substoichiometric combustion, said flame holding means being a nozzle for said mixture of hydrocarbon fuel and air, and a foraminate plate in front of and spaced from said nozzle, and having a size smaller than the cross-sectional area of said combustion chamber, whereby partial combustion gas containing mainly H.sub.2 and CO as combustible components and substantially no hydrocarbon is obtained;
• (d) said combustion chamber having an exit at the other end thereof;
• (e) said flow path means having an exit adjacent said exit of said combustion chamber;
• (f) a partial combustion gas discharging means at said exit of said combustion chamber for varying the pattern of the flow of said partial combustion gas during its discharge from said combustion chamber exit by converting the enthalpy of said partial combustion gas into kinetic energy;
• (g) a secondary air discharging means at said exit of said flow path means for varying the pattern of the flow of said secondary air;
• and
• (h) at least one of said discharging means varying the flow of the gas flowing therethrough to mix burned gas from the space around said exit of said combustion chamber into the partial combustion gas and secondary air.