Method for increasing the temperature homogeneity in a pit furnace

Abstract

A method for increasing temperature homogeneity in a pit furnace wherein at least two ingots to be heated lean against a respective one of first and second opposite inner walls of the pit furnace to form an elongated space having a V-shaped cross-section between them includes arranging at least one lance for an oxidant with an oxygen content of at least 85 percent by weight and at least one lance for fuel in a furnace wall with their orifices opening into the furnace at a distance from each other for supplying the oxidant and fuel to said V-shaped space to be combustible therein, wherein the orifice of the oxidant lance is arranged above the orifice of the fuel lance and is directed for the oxidant to flow obliquely downwards and along a longitudinal direction of said V-shaped space.

1 - 14 . (canceled) 
     
     
         15 . A method for increasing temperature homogeneity in a pit furnace, comprising:
 leaning at least two ingots to be heated against a respective one of first and second opposite inner walls of the pit furnace for forming an elongated space having a V-shaped cross-section between the at least two ingots as viewed along the first and second walls;   arranging at least one lance for an oxidant having an oxygen content of at least 85 percent by weight, and at least one lance for fuel in a furnace wall such that orifices of the at least one oxidant lance and the at least one fuel lance open out into the furnace at a distance from each other;   supplying the oxidant and the fuel to said V-shaped space for being combustible therein;   arranging the orifice of the oxidant lance above the orifice of the fuel lance; and   directing the oxidant flow obliquely downwards and along a longitudinal direction of said V-shaped space.   
     
     
         16 . The method of claim  1 , wherein the orifice of the oxidant lance is arranged above all supply locations for the fuel in the furnace wall where the orifice of the oxidant lance is arranged. 
     
     
         17 . The method of  claim 15 , wherein the supplying the oxidant is at a velocity of at least 100 m/s. 
     
     
         18 . The method of  claim 17 , wherein the supplying the oxidant is at sonic velocity or more. 
     
     
         19 . The method of  claim 15 , further comprising directing streams from the oxidant lance and the fuel lance to meet in the V-shaped space. 
     
     
         20 . The method of  claim 15 , wherein the arranging the at least one oxidant lance comprises mounting said lance for streaming oxidant into the furnace at an angle of between 0 and 20° in relation to a horizontal plane. 
     
     
         21 . The method of  claim 20 , wherein the arranging the at least one oxidant lance comprises mounting said lance for streaming oxidant into the furnace at an angle of between 3 and 5° in relation to the horizontal plane. 
     
     
         22 . The method of  claim 15 , further comprising directing the oxidant lance for controlling an angle of an oxidant stream in both horizontal and vertical planes depending upon operating conditions of the furnace. 
     
     
         23 . The method of  claim 15 , wherein the at least one oxidant lance comprises at least two oxidant lances having respective orifices and being mounted so that the respective orifices are arranged above each other in the furnace for streaming the oxidant from the lances into the furnace at different angles in the horizontal and/or vertical planes. 
     
     
         24 . The method of  claim 23 , wherein some of the at least two oxidant lances have orifices arranged relatively higher for the respective oxidant from said lances to stream into the furnace at an angle in relation to the horizontal plane which is at least equal to the oxidant streams from others of the plurality of the oxidant lances having orifices arranged at lower heights. 
     
     
         25 . The method of  claim 23 , further comprising controlling heating power in the furnace by the at least one or a plurality of the oxidant lances being switched on or off, and controlling an amount of the fuel supplied to stoichiometrically correspond to total oxygen supplied via the oxidant. 
     
     
         26 . The method of  claim 23 , wherein the temperature homogeneity in the furnace is increased during operation by supplying the oxidant through different lances for the oxidant or through at least one constellation of lances for the oxidant. 
     
     
         27 . The method of  claim 15 , further comprising measuring an oxygen level in the furnace with at least one lambda sensor, and controlling the oxygen supplied through the at least one oxidant lance for maintaining an oxygen concentration in the furnace to be substantially constant. 
     
     
         28 . The method of  claim 15 , further comprising:
 providing a first group of lances having at least one oxidant lance with an oxygen content of at least 85 percent by weight and at least one fuel lance;   arranging orifices of said first group at a first short side of the furnace;   providing a second group of lances having at least one oxidant lance with an oxygen content of at least 85 percent by weight and at least one fuel lance;   and arranging orifices of said second group at a second short side of the furnace opposite to the first short side;   wherein the first group are arranged with their orifices at a height between 0.9 and 1.5 meters above a floor of the furnace and the second group is arranged with their orifices at a lower height.