Reporting pollutant releases: example calculations, chapter 6


Example 1 - Converting CAC Releases from ppm (volume) to tonnes

If you have had your stack tested for NOx (expressed as NO2), Carbon Monoxide (CO), or Sulphur Dioxide (SO2) you will notice that the results from the laboratory are usually in the units of parts per million volume or ppm (volume). Before you can use these number to estimate your releases of these substances for the NPRI you need to Convert from ppm (volume) to a mass release in tonnes.

This example will walk you through the process of converting from ppm (volume) to an annual mass release in tonnes for NOx. This same method can be used for CO and SO2.

1. The first step is to calculate the stack's volumetric gas flow rate () using the formula below:

V

(m3/min) = (gas velocity, m/s) * [π * (internal stack diameter, m)2 /4] * 60 s/min

V

where π = 3.1416

2. Then you need to correct the stack gas flow rate for the moisture content and standard conditions using the formula below:

Dry V(m3/min) = (V, m3/min) * (273.15K/T actual) * (P actual/1atm) * (1-fraction water vapour)

Example: If the stack gas volumetric flow is 1330 m3/min at 80°C and 1 atm pressure with a moisture content of 10%, the dry volumetric stack flow rate is:

Dry V (m3/min) = (1330 m3/min) * (273.15K/(273.15+80)K) * (1atm/1atm) * (1-0.1)

= 925.84 m3/min

3. The next step is to Convert from ppm (volume) to mass emission rate (kg/h) as follows:

kg/h = ppm * density of air at standard conditions * Dry V * 60min/h * (MW substance/MW air)

Example: NOx is emitted from a stack that is 2.1 ppm by volume. The dry volumetric stack flow rate is 925.84 m3/min. Density of air at standard conditions is 1.29 kg/m3

kg/h = (2.1/1 000 000) * 1.29 kg/m3 * 925.84 m3/min * 60min/h * (46/28.97)

= 0.239 kg/h

4. Use the mass emission rate to calculate the yearly NOx release.

Yearly Release = Mass Emission Rate * (hours/year)

=0.239kg/hr*8760h/yr

= 2093.64 kg

= 2.09 tonnes NOx released for the year

Molecular Weights (MW) for Air and CAC Substances

Molecular Weights (MW) for Air and CAC Substances
CAC Substance Molecular Weight (grams/mole)
Air 28.97
NOx (expressed as NO2) 46.00
Carbon Monoxide (CO) 28.00
Sulphur Dioxide (SO2) 64.06

 

Example 2 - Converting CAC Releases from ppm (mass) to tonnes

If you have had your stack tested for total particulate matter (TPM), PM10 or PM2.5 you will notice that the results from the laboratory are usually in the units of parts per million mass or ppm (mass). Before you can use these number to estimate your releases of these substances for the NPRI you need to convert from ppm (mass) to a mass release in tonnes.

This example will walk you through the process of converting from ppm (mass) to an annual mass release in tonnes for TPM. This same method can be used for PM10 and PM2.5 as well.

  1. The first step is to convert from ppm (mass) to the mass emission rate as follows:
    1. Convert ppm to grams / tonne
    2. Use the stack mass flow rate (kg/min) to Convert to mass emission rate.

Example: The TPM emission rate from the stack is 250 ppm (mass). The dry mass flow rate is 10.54 kg/min. The stack is operational 24 hours a day, 365 days a year.

(i.e.525 600 minute per year).

a) Convert from ppm to g/tonne by using the conversion of:

1 ppm(mass) = (1 gram/1 tonne)

=250 ppm (mass) = (250g TPM/1 t emissions)

b) Using stack dry mass flow rate, calculate the mass emission rate:

(250g TPM/1tonne of emissions) * (10.54 kg emissions/min) * (1 tonne/1000 kg) = (2.635 g TPM/min)

2. Then use the mass emission rate to calculate the yearly TPM release.

(2.635 g TPM/min) * (525 600min/year) * (1 t/1 000 000 g) = (1.384 tTPM/year)

The TPM release for this particular stack is 1.384 tonnes.

 

Example 3 - Converting CAC Releases from mass per volume to tonnes

If you have had your stack tested for volatile organic compounds (VOCs) you will notice that the results from the laboratory are usually in the units of mass per volume. Typically the result of the VOC stack testing is expressed in the units of m g/m3. Before you can use these numbers to estimate the release of these substances for the NPRI you need to Convert from the mass per volume values to an annual mass release in tonnes.

This example will walk you through the process of converting from a mass per volume value to an annual mass release in tonnes for VOCs.

1. The first step is to calculate the stack's volumetric gas flow rate (V) using the formula below:

V(m3/min) = (gas velocity, m/s) * [π * (internal stack diameter, m)2 /4] * 60 s/min

where π = 3.1416

2. Then you need to correct the stack gas flow rate for the moisture content and standard conditions using the formula below:

Dry V (m3/min) = (V, m3/min) * (273.15K/T actual) * (P actual/1atm) * (1-fraction water vapour)

Example: If the stack gas volumetric flow is 1330 m3/min at 80°C and 1 atm pressure with a moisture content of 10%, the dry volumetric stack flow rate is:

Dry V (m3/min) = (1330 m3/min) * (273.15K/(273.15+80)K) * (1atm/1atm) * (1-0.1)

= 925.84 m3/min

3. The next step is to use the stack flow rate (m3/min) to Convert to a mass emission rate as follows:

Example: VOCs are emitted from a stack that at a rate of 60 m g/m3. The dry volumetric stack flow rate is 925.84 m3/min.

Mass Emission Rate = 925.84 m3/min * 60 m g /m3 * 60 minute / hour

= 3 333 024 m g/hour

4. Use the mass emission rate to calculate the yearly VOCs release.

Yearly Release = Mass Emission Rate * (8760 hours/year)

= (3 333 024 U g/hour) * (8760 hours/year)

= (29 197 290 2240 U g/year) * (tonnes/1 000 000 000 000 U g)

= 0.029 tonnes VOC

ASIDE:

The following two examples use the duration of the stack test to calculate an emission factor for the process. To simplify the calculation a test duration of one hour was used. If the duration of your stack testing was different you will first need to Convert it to a one hour basis before following the methods outlined in Examples 4 and 5.

Example: Stack duration is 2 hours and a TPM release value of 316.2 g during the test period.

Stack TPM release = (316.2g/2 hours) = (158.1g/hour)

Example: Stack testing was based on a total volume sampled instead of time. A total of 107 000 m3 of emissions needed to be tested. The dry volumetric stack flow rate was 1197 m3 per minute. The total release of VOCs during the testing period was 6.42g.

Stack test duration = (107 000m3/(1197m3/min)) * (1 hour/60 min) = 1.49 hours

Stack VOC release = (6.42g/1.49 hours) = (4.309g/hours)

 

Example 4 - Calculating CAC Releases from Source Testing and Fuel Consumption Data

Many facilities participating in a stack testing program will have information on the fuel feed rate during the test period and total annual fuel consumption. This data can be used to more accurately estimate CAC releases taking into account the process variations and production rates. For example, you may choose to use this method if the equipment is only operation for part of the year or the fuel feed rate fluctuates based on the facility's production rate.

To illustrate this method the data in Example 2 was assigned to a boiler burning bituminous coal.

From Example 2:

1. The first step is to convert from ppm (mass) to the mass emission rate as follows:

  1. Convert ppm to grams / tonne
  2. Use the stack mass flow rate (kg/min) to Convert to mass emission rate.

Example: The TPM emission rate from the stack is 250 ppm (mass). The dry mass flow rate is 10.54 kg/min. The stack is operational 24 hours a day, 365 days a year.

(i.e.525 600 minute per year).

a) Convert from ppm to g/tonne by using the conversion of:

1 ppm (mass) = (1 gram/1 tonne)

250 ppm (mass) = (250g TPM/1 t emissions

b) Using stack dry mass flow rate, calculate the mass emission rate:

(250g TPM/1 tonne of emissions) * (10.54 kg emissions/min) * (1 tonne/1000 kg) = (2.635 g TPM/min)

converting to grams per hour:

(2.635 g TPM/min) * (60 min/hour) = (158.1 g TPM/hour)

2. Use the mass emission rate and the boiler fuel feed rate to Create CAC production rate to fuel consumption to Create an emission factor.

a) Use the general formula below to Create the emission factor:

CAC substance release (g/hour) / Fuel feed rate during testing (kg/hour)

Example: The TPM emissions being released from the stack are the result of combustion in a bituminous coal fired boiler. The stack testing results were based on a one hour test period. The fuel feed rate of the boiler during the test was 25 kg bituminous coal per hour.

((158.1g TPM released/hour)/(25kg bituminous coal burned/hour)) = (6.324 TPM released/kg bitumous coal burned)

(6.324g TPM released/kg bitumous coal burned) = (6.324kg TPM released/tonne bitumous coal burned)

3. Use the emission factor calculated above along with the boiler's specific total annual consumption of bituminous coal.

Example: The boiler in question burned 218.85 tonnes of bituminous coal in the reporting year. The calculated emission factor for TPM for this boiler was 6.324 kg per tonne bituminous coal burned.

TPM released (tonnes) = (6.324kg TPM released/tonne bitumous coal burned) * 218.85 tonnes bituminous coal burned

= 1384 kg TPM released

= 1.384 tonnes TPM released

The TPM release for this particular stack is 1.384 tonnes.

 

Example 5 - Calculating CAC Releases from Source Testing and Total Production Data

Another method that can be used to estimate your CAC releases is to correlate your stack testing data with the facility's production data. Most facilities participating in a stack testing program will have information on the production rate during the test period and total annual production. This data can be used to more accurately estimate CAC releases taking into account the process variations and production rates. For example, you may choose to use this method if the process line is only operation for part of the year or the production rate fluctuates with demand for the product.

To illustrate this method the data in Example 3 was assigned to the fluidized bed prilling process used in urea production.

From Example 3:

1. The first step is to calculate the stack's volumetric gas flow rate (V) using the formula below:

V(m3/min) = (gas velocity, m/s) * [π * (internal stack diameter, m)2 /4] * 60 s/min

where π = 3.1416

2. Then you need to correct the stack gas flow rate for the moisture content and standard conditions using the formula below:

Dry V (m3/min) = (V, m3/min) * (273.15K/T actual) * (P actual/1atm) * (1-fraction water vapour)

Example: If the stack gas volumetric flow is 1330 m3/min at 80°C and 1 atm pressure with a moisture content of 10%, the dry volumetric stack flow rate is:

Dry V (m3/min) = (1330 m3/min) * (273.15K/(273.15+80)K) * (1atm/1atm) * (1-0.1)

= 925.84 m3/min

3. The next step is to use the stack flow rate (m3/min) to Convert to a mass emission rate as follows:

Example: VOCs are emitted from a stack that at a rate of 60 m g/m3. The dry volumetric stack flow rate is 925.84 m3/min.

Mass Emission Rate = 925.84 m3/min * 60 m g /m3 * 60 minute / hour

= 3 333 024 m g/hour

= 3.33 g/hour

Use the mass emission rate and the facility's production rate to Create CAC release to total production emission factor.

a) Use the general formula below to Create the emission factor:

(CAC substance release (g/hour)/Facility production rate during testing (tonnes product produced/hour))

NOTE: The facility's production rate can be in tonnes product produced, number of unit produced or any other applicable measure of production. Likewise, the CAC substance release could be in any units of mass. This example will use tonnes product produced and grams of substance released to illustrate the process.

Example: The VOC emissions being released from the stack are the result of the fluidized bed prilling processes used in urea production. The stack testing results were based on a one hour test period. The production rate of the facility during the test was 23 tonnes of urea per hour.

((3.337 g VOC released/hour)/(23 tonnes urea produced/hour)) = (0.145 g VOC released/tonnes urea produced)

3. Use the emission factor calculated above along with the facility's total annual production of urea.

Example: The facility in question produces a total of 203 210 tonnes of urea in the reporting year. The emission factor calculated in, part 2 above, for VOCs from the fluidized bed prilling process, was 0.145g per tonne urea produced.

VOC released (tonnes) = (0.145 g VOC released/tonne urea produced) * 203 210 tonnes urea produced

= 29 465.45g VOC released

= 0.029 tonnes VOC released

The VOC release for this particular stack is 0.029 tonnes.

 

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