August 04, 2020, 04:02:36 PM
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### Topic: Conversion from NO2 to NO from a stack emission  (Read 235 times)

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#### Miskin

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• Mole Snacks: +0/-0 ##### Conversion from NO2 to NO from a stack emission
« on: April 11, 2020, 03:58:37 PM »
Hello. I have encountered the same calculation in various emission calculation reports used by the environmental agencies in my country. I have a sense that these calculations are wrong but I can't prove they are and also I can't prove that they are true The legislation says "For nitrogen monoxide emissions, a transformation rate of 60 per cent to nitrogen dioxide shall be taken as a basis; this implies that the emission mass flow of nitrogen monoxide must be multiplied by factor 0.92 and used in the nomogram as the emission mass flow Q of nitrogen dioxide"

The same legislation limits NO2 emissions as "Emissions of nitrogen monoxide and nitrogen dioxide in waste gas from cement kilns shall not exceed a mass concentration of 0.50 g/m³, to be indicated as nitrogen dioxide."

In my opinion, for a stack with 100,000 m³/hr flowrate, the calculations should be as followed since we exactly know the allowed emission concentration as NO2:

Mass flow of NO2 = 100000 × 0.5 × 10^-3 = 50 kg/hr

However, most people follow the calculations below:
NO2 Concentration = 0.5 g/m³
MW(NO) / MW(NO2) × 0.5 = (30/46) x 0.5 ≈ 0.326 mg/m³ as NO
Mass flow of NO = 100000 × 0.326 × 10^-3 = 32.6 kg/hr
32.6 kg/hr NO x 0.92 = 300 kg/hr as NO2

I am not even sure if the molecular weight conversion is correct or not. I am really confused. I don't think so many people could be wrong but can't prove it.

Thank you very much

#### chenbeier

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• Gender:  ##### Re: Conversion from NO2 to NO from a stack emission
« Reply #1 on: April 11, 2020, 05:17:05 PM »
Quote
The legislation says "For nitrogen monoxide emissions, a transformation rate of 60 per cent to nitrogen dioxide shall be taken as a basis; this implies that the emission mass flow of nitrogen monoxide must be multiplied by factor 0.92 and used in the nomogram as the emission mass flow Q of nitrogen dioxide"

Questionable

Quote
In my opinion, for a stack with 100,000 m³/hr flowrate, the calculations should be as followed since we exactly know the allowed emission concentration as NO2:

Mass flow of NO2 = 100000 × 0.5 × 10^-3 = 50 kg/hr

However, most people follow the calculations below:
NO2 Concentration = 0.5 g/m³
MW(NO) / MW(NO2) × 0.5 = (30/46) x 0.5 ≈ 0.326 mg/m³ as NO
Mass flow of NO = 100000 × 0.326 × 10^-3 = 32.6 kg/hr

Correct calculation, but based on 100% conversion.

Quote
32.6 kg/hr NO x 0.92 = 300 kg/hr as NO2

See above questionable

#### Miskin

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• Mole Snacks: +0/-0 ##### Re: Conversion from NO2 to NO from a stack emission
« Reply #2 on: April 11, 2020, 06:24:51 PM »

Correct calculation, but based on 100% conversion.

Thank you for your answer. But for which calculation did you say correct since you quoted both of them? Did you mean first calculation and second calculation up to last part with factor of 0.92?

#### chenbeier

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• Gender:  ##### Re: Conversion from NO2 to NO from a stack emission
« Reply #3 on: April 12, 2020, 07:25:39 AM »
The first quote is questionable and mathematically wrong.
The second one is correct, if 100%  is calculated.
The third one uses the numbers of first quote. So it cannot be right.