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Module 2: Characteristics of Gases: Dry Basis Conversions - Practice Problems

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Concentration Conversions Between Wet and Dry Basis

Instructions:: Work these problems on a sheet of paper and check your answers against those provided below.
Helpful Calculators:: The following calculator may be useful in solving these problems. You can access it either from the "Calculators" button on the screen or from the link below.; Correction of Concentration (Wet Dry Basis)

#1: A gas stream has a nitrogen oxides concentration of 584 ppm and a moisture content of 7% by volume. Will the concentration value expressed on a dry basis by higher or lower than 584?

: Answer: Higher; The definition of ppm is the number of moles of the pollutant divided by the total number of moles.; When the concentration data is converted to a dry basis, the denominator is reduced because the moles of water vapor are subtracted from the denominator. This conversion increases the ppm value.

#2

Concentration data expressed on a dry basis are always _____ than the wet basis concentration value.

Higher
Lower

: Answer: a. Higher; Dry basis concentration values are always higher than the corresponding wet basis concentration values.

#3: A gas mixture has a hydrogen chloride concentration of 100 ppm. Convert this value to a dry basis using the measured moisture content of 14%.

: Answer: 116.3 ppmvd; Solution:

#4: The concentration data in an emission test report has been provided in a dry basis. The carbon monoxide concentration was 790 ppmvd. What is the concentration in the stack (wet basis) if the moisture content is 63% by volume?

: Answer: 292.3 ppm CO; Solution:; In this problem, the concentration must be corrected back to a wet basis. The available data is substituted into Equation 1. The dry basis value and the moisture volume percent values are known and the wet basis value must be calculated.

#5: What is the dry basis concentration of oxygen in a combustion gas having a concentration of 75% molecular nitrogen, 7% molecular oxygen, 10% carbon dioxide, and 8% water vapor?

: Answer: 7.6% O₂, dry basis; Solution:

#6: The concentration of lead (Pb) has been measured as 1.5 mg/m³. What is the dry basis concentration if the moisture concentration is 12% by volume?

: Answer: 1.70 ppm; Solution:

Instructions:: Read the next section in the lesson before working the next set of practice problems.

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Dry Basis Conversions

Practice Problems

Gas Flow Rate Conversions Between Wet and Dry Basis

Instructions:: Work these problems on a sheet of paper and check your answers against those provided below.
Helpful Calculators:: The following calculator may be useful in solving these problems. You can access it either from the "Calculators" button on the screen or from the link below.

#1: The gas flow rate from a wet process cement kiln has been measured at 83,000 SCFM. What is the gas flow rate expressed on a dry basis if the moisture content of the gas stream is 32% by volume?

: Answer: 56,440 DSCFM; Solution:; Apply the standard equation for expressing gas flow rate in a dry basis.

#2: A gas stream exiting a stack has a measured gas flow rate of 200 m³/min. What is the gas flow rate expressed on a dry basis if the moisture content is 25%?

: Answer: 150 Dm³/min; Solution:

#3: The gas flow rate reported in an emission test report is 1,000 Dm³/min. What is the gas flow rate on a wet basis if the moisture content is 11%?

: Answer: 1,123.6 m³/min; Solution:

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Dry Basis Conversions

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Oxygen Basis Conversions

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