US2008153042A1PendingUtilityA1

Integrated oxy-fuel combustion and nox control

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Assignee: LAUX STEFAN E FPriority: Dec 20, 2006Filed: Nov 27, 2007Published: Jun 26, 2008
Est. expiryDec 20, 2026(~0.4 yrs left)· nominal 20-yr term from priority
Inventors:Stefan LauxLawrence E. Bool, IiiHisashi Kobayashi
F23J 15/003F27D 2019/004C03B 5/2353Y02P40/50Y02E20/34F27D 99/0033F23J 2219/20C03B 5/237
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Claims

Abstract

The efficiency of selective non-catalytic reduction reactions for converting NOx in a flue gas to molecular nitrogen is improved by producing the flue gas from combustion of fuel with oxidant having an oxygen concentration above that of air.

Claims

exact text as granted — not AI-modified
1 . A method of modifying a combustion process, comprising
 (a) providing a combustion apparatus in which fuel and gaseous oxidant, preferably air, are combusted, wherein the combustion produces flue gas containing NOx and containing carbon monoxide in a concentration higher than 200 ppm and having a temperature at which adding the nitrogen-containing reducing reagent added in step(d) to the flue gas would oxidize the reagent to form NOx,   (b) increasing the aggregate oxygen concentration of the gaseous oxidant fed to said combustion apparatus to a level at which combustion of said fuel with said gaseous oxidant decreases the carbon monoxide concentration of said flue gas to less than 200 ppm, and decreases the temperature of said flue gas to a temperature within the range within which the reaction of the reducing reagent added in step (d) with NOx proceeds to at least 90% of stoichiometric completion under ideal mixing conditions and said reducing reagent is not oxidized to form NOx in the flue gas, and   (c) combusting said fuel with said gaseous oxidant having said increased oxygen concentration to form flue gas that contains carbon monoxide at a concentration higher than 200 ppm, contains NOx, and has a temperature in a said range, and   (d) feeding into said flue gas produced in step (c) a nitrogen-containing reducing reagent and reacting it with NOx in said flue gas to form N 2  at a temperature within said range within which the reaction of the reducing reagent added in step (d) with NOx proceeds to at least 90% of stoichiometric completion under ideal mixing conditions and said reducing reagent is not oxidized to form NOx in the flue gas.   
   
   
       2 . A method according to  claim 1  wherein the fuel that is combusted in said combustion apparatus is gaseous. 
   
   
       3 . A method according to  claim 1  wherein the fuel that is combusted in said combustion apparatus is liquid. 
   
   
       4 . A method according to  claim 1  wherein the fuel that is combusted in said combustion apparatus is solid. 
   
   
       5 . A method according to  claim 1  wherein the aggregate oxygen concentration of the gaseous oxidant is increased in step (b) to at least 30 vol. %. 
   
   
       6 . A method according to  claim 1  wherein the aggregate oxygen concentration of the gaseous oxidant is increased in step (b) to at least 90 vol. %. 
   
   
       7 . A method according to  claim 1  wherein the combustion apparatus is a kiln. 
   
   
       8 . A method according to  claim 7  wherein the fuel that is combusted in said combustion apparatus is gaseous. 
   
   
       9 . A method according to  claim 7  wherein the fuel that is combusted in said combustion apparatus is liquid. 
   
   
       10 . A method according to  claim 7  wherein the fuel that is combusted in said combustion apparatus is solid. 
   
   
       11 . A method according to  claim 7  wherein the aggregate oxygen concentration of the gaseous oxidant is increased in step (b) to at least 30 vol. %. 
   
   
       12 . A method according to  claim 7  wherein the aggregate oxygen concentration of the gaseous oxidant is increased in step (b) to at least 90 vol. %. 
   
   
       13 . A method of operating a combustion process, comprising
 (a) combusting fuel and gaseous oxidant having an oxygen concentration higher than that of air in a combustion apparatus to produce flue gas containing NOx and containing carbon monoxide under conditions under which, if the gaseous oxidant were air, the carbon monoxide concentration of the flue gas would be greater than 200 ppm, except that the oxygen concentration of said gaseous oxidant is at a level at which the flue gas produced by said combustion of said fuel with said gaseous oxidant contains carbon monoxide at a concentration below 200 ppm, and the temperature of said flue gas is in a range within which the reaction of the reducing reagent added in step (b) with NOx proceeds to at least 90% of stoichiometric completion under ideal mixing conditions and said reducing reagent is not oxidized to form NOx in the flue gas, and   (b) feeding into said flue gas produced in step (a) a nitrogen-containing reducing reagent which and reacting it with NOx in said flue gas to form N 2  wherein the temperature of said flue gas is within said range.   
   
   
       14 . A method according to  claim 13  wherein the fuel that is combusted in said combustion apparatus is gaseous. 
   
   
       15 . A method according to  claim 13  wherein the fuel that is combusted in said combustion apparatus is liquid. 
   
   
       16 . A method according to  claim 13  wherein the fuel that is combusted in said combustion apparatus is solid. 
   
   
       17 . A method according to  claim 13  wherein the aggregate oxygen concentration of the gaseous oxidant combusted in step (a) is at least 30 vol. %. 
   
   
       18 . A method according to  claim 13  wherein the aggregate oxygen concentration of the gaseous oxidant combusted in step (a) is at least 90 vol. %. 
   
   
       19 . A method according to  claim 13  wherein the combustion apparatus is a kiln. 
   
   
       20 . A method according to  claim 19  wherein the fuel that is combusted in said combustion apparatus is gaseous. 
   
   
       21 . A method according to  claim 19  wherein the fuel that is combusted in said combustion apparatus is liquid. 
   
   
       22 . A method according to  claim 19  wherein the fuel that is combusted in said combustion apparatus is solid. 
   
   
       23 . A method according to  claim 19  wherein the aggregate oxygen concentration of the gaseous oxidant combusted in step (a) is at least 30 vol. %. 
   
   
       24 . A method according to  claim 19  wherein the aggregate oxygen concentration of the gaseous oxidant combusted in step (a) is at least 90 vol. %. 
   
   
       25 . A method of improving the efficiency of a process that lowers the amount of NOx in a gaseous stream of flue gas by reacting a nitrogen-containing reducing reagent with said NOx to convert said NOx to N 2 , comprising
 (a) combusting fuel and gaseous oxidant that has an oxygen concentration higher than that of air in a combustion apparatus to produce flue gas containing NOx and carbon monoxide, while maintaining the oxygen concentration of said gaseous oxidant at a level at which (i) the flue gas produced by said combustion of said fuel with said gaseous oxidant contains carbon monoxide at a concentration below 200 ppm, and (ii) the temperature of said flue gas is in a range within which the reaction of the reducing reagent added in step (b) with NOx proceeds to at least 90% of stoichiometric completion under ideal mixing conditions and said reducing reagent is not oxidized to form NOx in the flue gas, and   (b) combining flue gas produced in step (a) with nitrogen-containing reducing reagent and reacting it with NOx in said flue gas at a temperature within the range set forth in step (a)(ii) to form N 2  while controlling the concentration of carbon monoxide in said flue gas and the temperature of said flue gas by controlling the concentration of oxygen in the gaseous oxidant that is combusted in step (a).   
   
   
       26 . A method according to  claim 25  wherein the fuel that is combusted in said combustion apparatus is gaseous. 
   
   
       27 . A method according to  claim 25  wherein the fuel that is combusted in said combustion apparatus is liquid. 
   
   
       28 . A method according to  claim 25  wherein the fuel that is combusted in said combustion apparatus is solid. 
   
   
       29 . A method according to  claim 25  wherein the aggregate oxygen concentration of the gaseous oxidant combusted in step (a) is at least 30 vol. %. 
   
   
       30 . A method according to  claim 25  wherein the aggregate oxygen concentration of the gaseous oxidant is combusted in step (a) is at least 90 vol. %. 
   
   
       31 . A method according to  claim 25  wherein the combustion apparatus is a kiln. 
   
   
       32 . A method according to  claim 31  wherein the fuel that is combusted in said combustion apparatus is gaseous. 
   
   
       33 . A method according to  claim 31  wherein the fuel that is combusted in said combustion apparatus is liquid. 
   
   
       34 . A method according to  claim 31  wherein the fuel that is combusted in said combustion apparatus is solid. 
   
   
       35 . A method according to  claim 31  wherein the aggregate oxygen concentration of the gaseous oxidant is combusted in step (a) is at least 30 vol. %. 
   
   
       36 . A method according to  claim 31  wherein the aggregate oxygen concentration of the gaseous oxidant is combusted in step (a) is at least 90 vol. %.

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