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Module 2: Characteristics of Gases - Dry Basis Conversions
Concentration Conversions Between Wet and Dry Basis-
Calculator:
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Correction of Concentration (Wet
Dry Basis)
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Practice Problems
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Calculator:
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Gas Flow Rate Converter (Wet Dry Basis)
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Practice Problems
Objectives
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Convert concentrations of gaseous pollutants between a wet and dry basis.
- Convert gas flow rates between a wet and dry basis.
Concentration Conversions Between Wet and Dry Basis
Many air pollution regulations are written on a moisture-free basis since moisture can be a highly variable quantity in some processes. In these cases, it is necessary to convert the gas concentration and pollutant concentration data to a moisture-free (or dry) basis. The concentration data is converted by using Equation 1.
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- Where: Conc. i (Dry) and Conc. i (Wet) can be expressed as any concentration format.
Figure 1 illustrates the difference between wet and dry concentrations.
The expressions in Table 1 will be used to present concentration data in wet and dry formats at actual and standard conditions.
Example Problem 1.
Conversion to Dry Basis Concentration (Volume Percent)
What is the dry basis concentration of oxygen in combustion gas having a concentration of 74% molecular nitrogen, 6% molecular oxygen, 11% carbon dioxide, and 9% water vapor?
Solution:
Example Problem 2.
Conversion to Dry Basis Concentration (PPM)
What is the dry basis concentration of sulfur dioxide using the concentration data given below?
Conc. SO2 (Wet) = 0.15% or 1,500 ppm
Conc. H2O = 8%
Solution:
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#1
- When a gas concentration is corrected to a dry basis, does its concentration increase or decrease?
Correction of Concentration (Wet 
Dry Basis)
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Purpose: This calculator corrects concentration data for moisture content and can convert concentrations from a wet to dry basis and vice versa.
Restrictions on Use: Do not use commas when inputting values. Output is invalid when inputted values for concentration exceed 100% or 106 ppm. |
Notes:
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This Java applet may take a few minutes to load.
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Sometimes calculator output is provided in an exponential format in base ten as shown below.
5.2e003 = 5.2
103
5.2e-003 = 5.2 10-3
- Inputting non-numeric characters such as commas and percent signs will result in erroneous output. (Decimal points are fine to use.)
Practice Problems
Concentration Conversions Between Wet and Dry Basis
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Instructions:
- Complete the Practice Problems before proceeding to the next section. Click on the button below.
Gas Flow Rate Conversions Between Wet and Dry Basis
It is often necessary to convert gas flow rate data to a dry basis to compare gas flow rates with equipment guarantee limits and to calculate emission rates. The use of a dry basis normalizes the gas flow rates to a consistent value despite the variations in the moisture content due to routine changes in process operating conditions.
Units of Measure for Gas Flow Rate
In this Module and the remainder of Basic Concepts in Environmental Sciences, the following units of measure for gas stream flow rates will be used. The author believes that these are the most descriptive and clear terms for the various ways of expressing gas flow rate. However, students should be aware that there are alternative expressions for these units of measure in some technical articles. Furthermore, many technical articles do not use complete and clear descriptions. It is important to confirm the meaning of the terms used to describe a unit of measure.
.gif)
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#2
- When a gas flow rate is corrected to a dry basis, does its value increase or decrease?
Gas Flow Rate Converter (Wet Dry Basis).
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Purpose: This calculator converts gas flow rates between a wet and dry basis.
Restrictions on Use: Do not use commas when inputting values. |
Notes:
-
This Java applet may take a few minutes to load.
-
Sometimes calculator output is provided in an exponential format in base ten as shown below.
5.2e003 = 5.2
103
5.2e-003 = 5.2 10-3
- Inputting non-numeric characters such as commas and percent signs will result in erroneous output. (Decimal points are fine to use.)
Practice Problems
Gas Flow Rate Conversions Between Wet and Dry Basis
-
Instructions:
- Complete the Practice Problems before proceeding to the next lesson. Click on the button below.