Parallel flow burner

In a furnace having a furnace wall defining at least one burner throat defined by the wall and extending through the wall from an exterior thereof into a combustion chamber of the furnace, a burner including a liquid fuel atomizing nozzle mounted concentrically with respect to the burner throat, first duct means for flowing combustion air past the nozzle towards the throat, and second duct means disposed about the first duct means for flowing a second combustion airflow substantially concentrically to the first flow past the nozzle towards the throat, the improvement to the burner comprising in combination:

• means for flowing an enveloping, third combustion airflow from between the wall and the second duct means at a point downstream of the nozzle about the second airflow to thereby restrict the radial extent of the flame generated by the burner and protect walls of the burner throat from the flame;
• a plurality of gas spuds defined by generally radially oriented tubular members extending into the second airflow, each tubular member terminating in a slanted cap facing in the direction of the second airflow, each cap having a plurality of gas discharge openings of a relatively large diameter and an orientation so that vectorial momentums of the gas streams issuing from the holes and contacted by the second airflow carries the gas streams in a downstream direction from the spuds and cause, in cross-section a substantially complete coverage by all gas streams of the space occupied by the second airstream downstream of the spuds and upstream of the chamber, and of at least a portion of the space occupied by the first gas stream;
• and means for supplying to the spuds gas of a pressure no more than abut 10 psi.

A burner for a furnace comprising a centrally located nozzle for the discharge of fuel in a downstream direction towards a combustion chamber of the furnace, the nozzle including a housing defining a chamber, an aperture and a spaced apart conduit both in fluid communication with the chamber, the aperture and the conduit extending generally in an axial direction, the conduit extending to an exterior of the housing and comprising first, second and third aligned conduit sections of successively larger diameters from the chamber to the exterior of the housing, the housing also defining a compartment separate of the chamber;

• means for connecting the chamber to a supply of steam;
• means defining a first passage communicating the compartment with an upstream end of the second conduit section, the first passage being arranged and dimensioned so as to extend in a radial direction about the conduit;
• and means defining a second passage communicating the aperture with an upstream end of the third conduit section, the second passage being dimensioned and arranged so as to extend in a radial direction about the second hole;
• whereby a steam-atomized liquid fuel flow exits from a downstream end of the third conduit section upon the application of steam to the chamber and the application of pressurized liquid fuel to the compartment, the flow comprising a steam core flow, an annular liquid fuel flow surrounding the core flow, and an annular steam flow enveloping the liquid fuel flow so that the annular steam flow prevents contact between the liquid fuel and walls of the third conduit section;
• means for forming a first, combustion airflow substantially co-axially about the nozzle;
• means for flowing a second combustion airstream co-axially about the first airstream past the nozzle and towards the furnace chamber;
• and means for flowing a third airstream generally co-axially about the second airstream at a point downstream of the nozzle, the last mentioned means being formed to substantially fully envelop the second airstream with the third airstream;
• whereby the third airstream limits the diameter of a flame produced by the nozzle and thereby prevents substantial contact between the flame and a burner throat defined by the furnace;
• a plurality of spaced apart gas spuds arranged in the second airflow, each spud including a cap generally facing in the direction of the airflow, each cap including a plurality of relatively large diameter gas discharge openings so that a gas stream issues from each such opening and enters the second gas stream, the cap having a thickness at least about equal to 0.75 the diameter of one of the openings, the openings being further arranged so that the gas stream discharged by each follows a trajectory which prevents an interference of such stream with the streams discharged by the other openings, so that all gas streams together, at points downstream of the spuds, substantially fully penetrate the space occupied by the second airflow while no more than a minor portion of all gas streams impinges on the first airstream and further so that substantially no portion of the gas streams discharged by the openings flows radially beyond the second airstream.