Low nox emission burner and operating method for reducing nox formation applied to iron ore pellet sintering and/or enduring method

Abstract

A burner (12) using the oxygen present in the descending flow (18) of gases, composed by a mixture of air with combustion products that circulates through the iron ore pelletizing furnace zones. The burner set (12) includes a fuel collector ring (24) equipped with fins (26) mounted on the inner part of the collector and further counts on a plurality of openings (30) for discharge of fuel gas. Said openings (30) make up a sequence of groups (32) aligned with each fin (26). The burner set (12) is inserted through the special window (16) and installed where the descending flow (18) needs to be heated, for example, from 850 to 1350° C. The fins (26) deflect part of the descending flow (18) and create the rotating effect in the gases in the furnace downcomer. The fuel gas jets discharged from the collector ring (24) are mixed with the flow of gases and burn in the descending flow current in a swirl. The even distribution of the fuel gas around the perimeter of the descending passage together with the descending flow swirling effect allows the quick mixing of the fuel gas with the descending oxygen flow and for this reason significantly reduces the NOx formation in the combustion zone.

1 . A LOW NOX EMISSION BURNER, comprising a burner for applying to heating process in iron ore pelletizing furnaces (FO) with low NOx emission comprising a collector ring with openings for mixing fuel gas with an oxidant and formation of flames for direct heating of a circulating gaseous medium; wherein the fuel gas discharge is executed through a collector ring provided with multiple openings for mixing the fuel gas with oxidant and flame formation; the collector ring being equipped with at least one input for fuel gas supply; said ring being, additionally, equipped with fins installed on the inner part of said collector in (α) angulation relative to a horizontal plane of the collector ring deflecting part of a descending flow of circulating hot air diluted with combustion gases originating from burning the fuel gas in a vertical direction to the horizontal resulting in a speed vector obtaining a tangential component and which in the cylindrical profile of a descending channel generates a rotation or a swirling effect. 
     
     
         2 . The LOW NOX EMISSION BURNER, according to  claim 1 , wherein fuel gas collector comprises a ring shape, manufactured with a circular or rectangular section, the outer diameter (D) of the collector ring being reduced relative to the inner diameter (D′) of a descending passage. 
     
     
         3 . The LOW NOX EMISSION BURNER, according to  claim 1 , wherein the deflection angle (α) of the fin being between 30° to 60° relative to the horizontal transversal plane of the fuel gas collector ring. 
     
     
         4 . The LOW NOX EMISSION BURNER, according to  claim 1 , wherein each fin is modelled in ‘L’ profile with a flap in 90° (β) angle. 
     
     
         5 . The LOW NOX EMISSION BURNER, according to  claim 4  wherein the angle (β) varies from about 45° to 90°. 
     
     
         6 . The LOW NOX EMISSION BURNER, according to  claim 4 , wherein the dimension (N) of the fin is related to the diameter (D′) and the area of the descending channel, wherein the burner is installed. 
     
     
         7 . The LOW NOX EMISSION BURNER, according to  claim 4 , wherein the relation of the dimensions (M)/(N) of each fin are between 0.25 and 0.5. 
     
     
         8 . The LOW NOX EMISSION BURNER, according to  claim 4 , wherein the distance (K) between the fins, the length (L) of each fin is determined to create an intensity of a descending swirling flow without significantly increasing the loss of charge through the burner installed in the descending channel; the determination of three parameters (K), (L) and number of fins depending on the diameter (D′) and descending channel area, wherein the burner is installed; the larger the diameter (D′) of the channel, the greater the diameter (D) of the ring of the burner and greater the number of fins. 
     
     
         9 . The LOW NOX EMISSION BURNER, according to  claim 4 , wherein the shape of each fin is capable of being plane, curved, tubular or any other shape suitable for a better mixture of the fuel gas with the oxidant flow. 
     
     
         10 . The LOW NOX EMISSION BURNER, according to  claim 4 , wherein the discharge of the fuel gas is positioned through the plurality of openings formed in groups, aligned, and with the discharges thereof pointed in the direction of the wall of each fin; each group of openings discharges the fuel jets in the direction of a single fin; there is a group of openings for each fin; part of the total descending flow runs along the passage of the fin mixing with the five fuel jets and all together are deflected so as to create a rotational flow downstream of the burner; each group having at least one opening, depending on the diameter of the collector ring, transversal section of the ring and number of fins installed. 
     
     
         11 . The LOW NOX EMISSION BURNER, according to  claim 1 , wherein the cylindrical descending channel forms part of the burner; wherein part of the descending flow, is deflected by the fins, is pre-mixed with the fuel gas and acquires rotational movement along a cylindrical surface of the descending channel; wherein this region, has a length (L) equal to approximately a diameter (D′) of the channel, the fuel is burned; and wherein the fuel gas is evenly distributed around the circumference of this channel, the mixing occurs quickly with oxygen diluted in the inert gases, and, temperature peaks are reduced. 
     
     
         12 . An OPERATING METHOD FOR REDUCING NOX FORMATION APPLIED TO IRON ORE PELLET SINTERING AND/OR ENDURING METHOD, according to  claim 1 , wherein said method comprising the steps:
 the fuel gas jets are discharged from the plurality of openings to be mixed with an oxidant flow which can be predominantly a flow of low or high temperature gases, which circulates, in the iron ore pellet furnace (FO) for heating the pellets during the sintering or hardening process;   the fuel jets mixed with oxidant form a jet or jets of flame, which are mixing and directly heating a circulating process flow; and   circulating process flow, which is the descending flow in iron ore pelletizing furnace (FO), containing nitrogen, oxygen, carbon dioxide and water vapor are heated until the temperatures required by the process, continuing through the iron ore pellet bed, transferring the required heat for the occurrence of the necessary chemical reactions and physical transformations in the pellets.   
     
     
         13 . The OPERATING METHOD FOR REDUCING NOX FORMATION APPLIED TO IRON ORE PELLET SINTERING AND/OR ENDURING METHOD, according to  claim 11 , wherein part of the descending flow is deflected, and runs through and between the passages of the fins, from vertical direction to horizontal direction, creating a swirling movement along the circumference of the cylindrical descending channel downstream of the burner ring. 
     
     
         14 . The OPERATING METHOD FOR REDUCING NOX FORMATION APPLIED TO IRON ORE PELLET SINTERING AND/OR ENDURING METHOD, according to  claim 11 , wherein fuel gas is discharged from the openings of the collector ring in the form of multiple jets and directed to each deflection surface of the fin. 
     
     
         15 . The OPERATING METHOD FOR REDUCING NOX FORMATION APPLIED TO IRON ORE PELLET SINTERING AND/OR ENDURING METHOD, according to  claim 11 , wherein fuel gas jets mix with the descending oxidant flow on the surface of the fin. 
     
     
         16 . The OPERATING METHOD FOR REDUCING NOX FORMATION APPLIED TO IRON ORE PELLET SINTERING AND/OR ENDURING METHOD, according to  claim 11 , wherein the descending flow of oxidant pre-mixed with the fuel gas on the surface of the fin is discharged to the descending furnace channel (FO); wherein the rotational current is self-inflamed from the temperature of the process and the flames with rotational components are stabilized on the inner surface of the descending channel. 
     
     
         17 . The OPERATING METHOD FOR REDUCING NOX FORMATION APPLIED TO IRON ORE PELLET SINTERING AND/OR ENDURING METHOD, according to  claim 11 , wherein fuel gas evenly distributed around the circumference of the descending channel is quickly mixed with the oxygen diluted in the inert gases, and obtains a significant reduction of the temperature peaks and consequent reduction in the NOX formation in the combustion process.