Sonic injection furnace

Abstract

A low-NOx end-fired furnace for melting glass equipped with an overhead burner includes an inlet duct for oxidizer, including 15% to 30% of oxygen, in its upstream wall, a duct for receiving the combustion flue gases in its upstream wall, and a sonic injection system including at least one injector for injecting a jet of a gas at a speed at least equal to 80% of the speed of sound, referred to as a sonic injector, opening into the upstream wall or opening into the duct for receiving the combustion flue gases, the sonic injector injecting its gas counter-current to the stream of the combustion flue gases that are heading toward the duct for receiving the combustion flue gases.

1 . An end-fired furnace for melting glass comprising:
 an overhead burner;   an oxidizer inlet duct in an upstream wall of the end-fired furnace, the inlet duct being in fluid communication with a source of oxidizer comprising 15% to 30% of oxygen;   a combustion flue gas duct constructed and arranged to, in operation, receive combustion flue gases, the duct opening into the upstream wall of the end-fired furnace; and   a sonic injection system comprising at least one sonic injector opening into the upstream wall or opening into the combustion flue gas duct and constructed and arranged to inject a jet of a gas at a speed at least equal to 80% of the speed of sound, said sonic injector being further configured and arranged to, in operation, inject its gas counter-current to a stream of the combustion flue gases that are heading toward the combustion flue gas duct.   
     
     
         2 . The furnace as claimed in  claim 1 , wherein the sonic injector is configured and arranged to inject its gas at a speed that is at least 95% of the speed of sound. 
     
     
         3 . The furnace as claimed in  claim 2 , wherein an impulse component of the sonic injection system perpendicular to the wall comprising the combustion flue gas duct is greater than 5 newtons. 
     
     
         4 . The furnace as claimed in  claim 2 , wherein an impulse component of the sonic injection system perpendicular to the wall comprising the combustion flue gas duct is greater than 10 newtons. 
     
     
         5 . The furnace as claimed in  claim 1 , wherein a cross-sectional area of the oxidizer inlet duct in the upstream wall is within the range extending from 0.5 to 3 square meters and wherein a cross-sectional area of the combustion flue gas duct is within the range extending from 0.5 to 3 square meters. 
     
     
         6 . The furnace as claimed in  claim 1 , wherein a discharge area of the sonic injection system is within the range extending from 0.2 to 4 square centimeters. 
     
     
         7 . The furnace as claimed in  claim 1 , wherein an impulse component of the sonic injection system perpendicular to the wall comprising the combustion flue gas duct is greater than 5 newtons. 
     
     
         8 . The furnace as claimed in  claim 1 , wherein an impulse component of the sonic injection system perpendicular to the wall comprising the combustion flue gas duct is greater than 10 newtons. 
     
     
         9 . The furnace as claimed in  claim 1 , wherein each sonic injector of the sonic injection system opens into the combustion flue gas duct or into the upstream wall at a point closer to the combustion flue gas duct than to the oxidizer inlet duct. 
     
     
         10 . The furnace as claimed in  claim 1 , wherein each sonic injector of the sonic injection system opens at a position that is less than 1 meter from an edge of the combustion flue gas duct. 
     
     
         11 . The furnace as claimed in  claim 10 , wherein each sonic injector opens at a position that is less than 0.5 meter from the edge of the combustion flue gas duct. 
     
     
         12 . The furnace as claimed in  claim 1 , wherein the jet of gas comprises air. 
     
     
         13 . The furnace as claimed in  claim 1 , wherein the sonic injection system is in fluid communication with a source of air, and wherein the jet of the gas comprises a jet of air. 
     
     
         14 . The furnace as claimed in  claim 1 , wherein the sonic injection system comprises a plurality of sonic injectors. 
     
     
         15 . The furnace as claimed in  claim 1 , wherein the sonic injection system is controllable to deliver the jet of gas of from 0.2% to 5% of a volume of oxidizer introduced by the oxidizer inlet duct.