Method and apparatus for zonal injection of chemicals into a furnace convective pass to reduce pollutants from flue gases

Abstract

Zonal injection of varying compositions of chemicals, particularly an ammonia-based reagent and hydrocarbon, through injection lances arranged in a grid formation to define planar zones in a furnace convective pass of a furnace. The supply of chemicals is controlled so as to be individually determined for each discrete zone of the grid depending on conditions in that zone.

1 . A method of reducing pollutants in flue gases from a furnace having a convection pass comprising the steps of 
 installing an injector grid arrangement in the convective pass to define a plurality of planar zones formed of lances having apertures for injecting reagents into the flue gases;    providing chemicals for reducing pollutants in the flue gas;    supplying the chemicals to the injector grid arrangement;    controlling the chemicals supplied to the injector grid arrangement to cause each of the zones to receive a controlled amount of the chemicals depending upon conditions in that zone to reduce pollutants in the flue gases.    
     
     
         2 . A method as recited in  claim 1  wherein said injector grid installing step includes defining a plurality of “n” planar zones extending horizontally in a side-by-side arrangement across the convection pass.  
     
     
         3 . A method as recited in  claim 1  wherein said injector grid installing step includes defining a plurality of “m” planar zones extending vertically in a top-to-bottom arrangement from the top to the bottom of the convection pass.  
     
     
         4 . A method as recited in  claim 1  wherein said injector grid installing step includes defining a plurality of “n” planar zones extending horizontally in a side-by-side arrangement across the convection pass and defining a plurality of “m” planar zones extending vertically in a top-to-bottom arrangement from the top to the bottom of the convection pass whereby the injector grid forms an “n” by “m” zonal matrix.  
     
     
         5 . A method as recited in  claim 4  wherein said installing step includes disposing the zonal matrix in a plane orthogonal to the flow of flue gases.  
     
     
         6 . A method as recited in  claim 1  wherein said chemicals providing step includes providing an ammonia-based reagent and a hydrocarbon.  
     
     
         7 . A method as recited in  claim 6  wherein said chemicals supplying step includes supplying a mixture of ammonia-based reagent and hydrocarbon to the injector grid arrangement.  
     
     
         8 . A method as recited in  claim 6  wherein said chemicals supplying step includes supplying the ammonia-based reagent and the hydrocarbon separately to the injector grid arrangement and mixing the ammonia-based reagent and the hydrocarbon in the injector grid arrangement.  
     
     
         9 . A method as recited in  claim 6  wherein said chemicals supplying step includes using steam as a carrier for the ammonia-based reagent and the hydrocarbon.  
     
     
         10 . A method as recited in  claim 1  wherein said injector grid installing step includes installing a plurality of injection grids in the convective pass in substantially parallel, spaced planes.  
     
     
         11 . Apparatus for zonal injection of chemicals into a furnace convective pass to reduce pollutants in flue gases comprising 
 a grid arrangement of injection lances defining a plurality of planar injection zones from side to side in the convective pass and a plurality of planar zones extending from the top to bottom in the convective pass to define a zonal matrix grid, said injection lances having apertures therealong in each of said zones for injecting chemicals into the flue gases in the convection pass;    a supply manifold arrangement supplying the chemicals to said injection lances; and    a valve arrangement controlling the flow of chemicals to said injection lances to control the amount of chemicals injected into the flue gases in each of said zones whereby injection of chemicals into each planar zone can be controlled in accordance with flue gas properties in said planar zone.    
     
     
         12 . Apparatus for zonal injection of chemicals as recited in  claim 11  wherein the chemicals include an ammonia-based reagent and a hydrocarbon and said supply manifold arrangement mixes said ammonia-based reagent and said hydrocarbon and supplies the mixture to said injection lances.  
     
     
         13 . Apparatus for zonal injection of chemicals as recited in  claim 12  wherein each of said injection lances extends through a plurality of said planar injection zones and is formed by concentric tubes defining a central passage and an annular passage surrounding said central passage, said central and annular passages distributing the mixture in selected amounts to each of said planar zones.  
     
     
         14 . Apparatus for zonal injection of chemicals as recited in  claim 11  wherein the chemicals include an ammonia-based reagent and a hydrocarbon and said supply manifold arrangement supplies said ammonia-based reagent and said hydrocarbon separately to said injection lances and said apertures include nozzles mixing said ammonia-based reagent and said hydrocarbon.  
     
     
         15 . An apparatus for zonal injection of chemicals as recited in  claim 14  wherein each of said injection lances extends through a plurality of said planar injection zones and is formed by a body having a first set of tubes extending through an inner portion thereof and a second set of tubes surrounding said first set of tubes, said first and second sets of tubes each carrying one of said ammonia-based reagent or said hydrocarbon for distributing said ammonia-based reagent and said hydrocarbon separately to said aperture.  
     
     
         16 . An apparatus for zonal injection of chemicals as recited in  claim 11  wherein each of said injection lances passes through a plurality of said planar zones.  
     
     
         17 . Apparatus for zonal injection of chemicals as recited in  claim 11  wherein each of said injection lances is disposed in only a single planar zone.  
     
     
         18 . Apparatus for zonal injection of chemicals as recited in  claim 11  wherein said grid arrangement includes a second zonal matrix grid spaced from said first-mentioned zonal matrix grid.