Worked example: a Method 5 test
Methods 1 through 5 and Method 19, three runs from field data to pounds per hour
This is the arithmetic a test report is built on. Change any number on the field data sheet and follow it through moisture, molecular weight, velocity, flow, concentration, emission rate and the isokinetic check.
- Source
- A coal-fired boiler with a 72 in. stack, sampled at 24 points for 96 minutes per run
- Inputs
- One field data sheet per run, plus the lab weight of the particulate catch
- Outputs
- gr/dscf, mg/dscm, lb/hr, lb/MMBtu and the isokinetic rate
- Uses
- Method 1 area, Method 2 velocity and flow, Method 3 molecular weight, Method 4 moisture, Method 5 concentration, Method 19 F-factor
How to use this example
The data sheet on the left holds one run’s averages and totals, the numbers a crew carries off the platform. The column on the right works through the calculation in the order a report does, with every equation shown twice: once in symbols and once with this run’s numbers plugged in.
Switch between runs with the tabs. Edits are kept for each run until you reset them, and the three-run summary below updates as you go. Try nudging the meter volume and watch the isokinetic rate, or raise the stack temperature and see how velocity and flow respond.
Field data to results
Three-run summary
A compliance test is normally the average of three runs, and the average is what gets compared with the limit. Each run still has to stand on its own: a run outside 90–110% isokinetic, or with a failed leak check, is not averaged in. It has to be repeated or the agency has to accept it.
Pounds per million Btu
Boiler limits are often written per unit of heat input rather than per hour, so a large boiler and a small one are held to the same standard. Method 19 converts a dry concentration to lb/MMBtu without measuring fuel flow, using an F-factor: the volume of dry flue gas produced by burning one million Btu of a given fuel with no excess air. The O₂ term scales the result back to zero excess air.
Emission rate in lb/MMBtu from a dry concentration and dry O₂ (Method 19)
- C_d
- pollutant concentration, lb/dscf (gr/dscf ÷ 7,000)
- F_d
- dry F-factor, dscf/MMBtu: natural gas 8,710; bituminous coal 9,780; fuel oil 9,190
- \%O_{2d}
- oxygen on a dry basis, percent, from Method 3 or 3A
Reading a results table
- Check the isokinetic rate first. If a run fails it, nothing else on that run counts.
- Check moisture against the other runs. A run that reads much drier than the rest often had a leak or a warm ice bath.
- Compare flow between runs. At a steady process the dscfm should agree within a few percent.
- Only then compare the average emission rate with the limit, in the limit’s own units.