Method for in-furnace regulation of SO
View Patent ↗A method of controlling SO 3 flue gas concentration in a combustion process utilizing a SCR using a sulfurous fuel, the method steps including: providing a combustion system with low NOx burners and SCR; partially combusting the fuel in a first stage to create a reducing environment; maintaining the reducing environment for a sufficient time period such that SO 3 is reduced to SO 2 to achieve a desirable level of SO 3 ; combusting the remainder of the fuel and combustion intermediates in a second stage with oxidizing environment; reducing the remaining NOx with the SCR; thereby reducing emissions NOx.
1. A method of controlling SO 3 flue gas concentration in a combustion process utilizing a SCR using a sulfurous fuel, comprising the steps of:
a) providing a combustion system with low NOx burners and SCR
b) partially combusting the fuel in a first stage to create a reducing environment;
c) maintaining the reducing environment for a sufficient time period such that SO 3 is reduced to SO 2 to achieve a desirable level of SO 3 ;
d) combusting the remainder of the fuel and combustion intermediates in a second stage with oxidizing environment;
e) reducing the remaining NOx with the SCR;
thereby reducing emissions NOx.
2. The method of claim 1 , further including the step of micro-staging the first stage fuel combustion.
3. The method of claim 2 , wherein the micro-staging includes the use of low-NOx burners.
4. The method of claim 1 , further including the step of macro-staging the first stage of fuel combustion.
5. The method of claim 4 , wherein the macro-staging is provided through the use of over-fired air.
6. The method of claim 1 , further including a combination of micro-staging and macro-staging.
7. The method of claim 6 , wherein the micro-staging includes the use of low-NOx burners and the macro-staging is provided by over-fired air.
8. The method of claim 1 , wherein the fuel is coal.
9. A method of controlling SO 3 flue gas concentration in a combustion process utilizing a SCR using a sulfurous fuel, comprising the steps of:
a) providing a combustion furnace with low NOx burners and SCR
b) partially combusting the fuel in a first stage to create a reducing environment;
c) combusting the remainder of the fuel and combustion intermediates in a second stage with oxidizing environment;
d) measuring the acid dewpoint of the flue gas;
e) adjusting the reducing environment in the first stage such that the flue gas acid dewpoint is lowered to a desirable level;
thereby controlling the SO 3 concentration of the flue gas.
10. The method of claim 9 , wherein the step of adjusting the reducing environment includes adjusting the first stage residence time.
11. The method of claim 9 , further including the step of micro-staging the first stage fuel combustion.
12. The method of claim 11 , wherein the micro-staging is provided through the use of low-NOx burners.
13. The method of claim 9 , further including the step of macro-staging the first stage of fuel combustion.
14. The method of claim 13 , wherein the macro-staging is provided through the use of over-fired air.
15. The method of claim 9 , further including a combination of micro-staging and macro-staging.
16. The method of claim 15 , wherein the micro-staging is provided by low-NOx burners and the macro-staging is provided by over-fired air.
17. The method of claim 9 , wherein the fuel is coal.