Data on NO/NO2 levels 2

[GarethJones]

I am searching for publications or data that gives information in the relative levels of NO and NO2 in flue gases from coal fired boilers. Does anyone have any ideas where this might be found?

 

[25362]

There various websites that can be of help.For example:

http://www.geocities.com/koturn/noxtechnologiestext.htm

 

[yulinios]

Hi
¨Cobustion Fossil Power¨ was very useful to our coal power plant.
Bye

 

[JEB66]

Unstaged coal cyclone units ~900 ppm corrected to 3% O2 dry
PC fired coal units w/ LNB's ~300 ppm to `500 ppm
OFA units ~ 150 ppm to `400 ppm
SCR units ~60 ppm

 

[athomas236]

25362 - the site you quote seems to be inactive

JEB66 - any suggestions for PC fired coal units without LNB's

athomas236

 

[25362]

To athomas, you are right. Reasons unknown. As an alternative, I can recommend Noel de Nevers' Air Pollution Control Engineering 1995, McGraw-Hill, ISBN 0-07-061397-4, as a good source of information on nitrogen oxides formed by combustion.

 

[JEB66]

It all comes down to balance.

Calibrate you Primary air flow and coal flow. Then, tune the furnace so that the difference between the highest and lowest %o2 reading is 1. Use a grid in the back pass and do not relay solely on the CR in-situ probes until after your check on the back pass, The CR probes can calibrate just fine but a plugged snubber or diffuser will cause the to read low.

I have improved nox by up to 60% by just balance alone. The furnace was way out.

Once the furnace is tuned youi can start lowering excess air until your CO & LOI go past your desired value. I personally like to keep the overall average below 100 ppm CO. But people have different values thast they want to use.

If LOI is an issue increasee fineness. As the fineness increases, LOI will go done. Increased fineness will also help if slagging is an issue.

Do not forget about low load excess air. Those values were always set high in the past. That way they new things would be safe and they would not have to check them. Again watch CO and LOI, Burner diff ( 3 to 5 iwc), flue gas velocity (> 40 fps) and make sure that your SSH and RH inlet temps do not approach saturation.

A pipe to pipe coal flow balance would help the overall process of balancing.

 

[davefitz]

try reading the proceedings from the following annual conferences:
Pittsburgh coal conference
Clearwater coal conference
American Power conference ( prior to 2002)
IJPGC ( prior to 2004)
ECOS
and of course POWERGEN

 

[25362]

To athomas, the site is back.

 

[rmw]

I believe that the B&W "Steam, Its generation and uses" discussed in other threads on this site would be a great help as well.

rmw

 

[athomas236]

25362

Thanks or letting me know, have printed off the report.

athomas236

 

[davefitz]

As an aside, see the recently published papers by G.S. Madia on the topic of NO to NO2 ratio in flue gases.

There are 3 separate reactions that can occur on the surface of the SCR, depending on whether it is (a) NO + NH3, (b) No + NO2 + NH3 ,or (c) NO2 + NO3.

The SCR catalyst "space velocity" is sized for reaction (a), and this reaction proceeds at a moderate rate. If there also exists NO2 and the amount of NO2 is less than the amount of NO, then the equimolar reaction (b) proceeds very quickly, and tha apparent effectiveness of the SCR improves by about 30% at 650F. However, if there is more NO2 than NO, the reaction (c) for the reduction of the residual amoujnt of NO2 preoceeds very slowly ( about 10 times slower at 650 F than reaction (a) ), and this excess NO2 will slip past the SCR and increase stack NOx.

 

[JEB66]

All of the data I have taken at the furnace exit has showed NO to be 90+% of the NOx.

So I expect what Davefitz is describing is how things proceede through each layer of catalysts. 1st layer knows down the NO then the % of N2O increases as the gas enters the next layer...