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Module 6: Air Pollutants and Control Techniques - Incompletely Oxidized Compounds - Practice Problems
- Instructions:
- Answer these questions on a sheet of paper and check your responses against those provided below.
-
#1
- What are some examples of partially oxidized organic compounds?
- Answer: Some examples of partially oxidized organic compounds are polycyclic aromatic compounds, unsaturated compounds, aldehydes, and organic acids.
-
#2
- Under what circumstances are partially oxidized organic compounds and carbon monoxide formed?
-
- Answer: Partially oxidized organic compounds and carbon monoxide are formed when combustion conditions are unfavorable and organic compounds cannot be completely oxidized to carbon dioxide and water. Incomplete combustion occurs when gas temperatures and/or oxygen concentrations are insufficient.
-
#3
- What temperature is necessary to oxidize carbon monoxide to carbon
dioxide?
- 800°F
- 1000°F
- 1500°F
- 1800°F
- 800°F
-
- Answer: d. 1800°F
Practice Problems
Formation Mechanisms
- Instructions:
- Answer these questions on a sheet of paper and check your responses against those provided below.
-
#1
- The conditions that favor ____________ generation are the opposite
of those that contribute to the formation of partially oxidized organic
compounds.
- Nitrogen oxides
- VOC
- Sulfur dioxide
- Carbon monoxide
- Nitrogen oxides
-
- Answer: a. Nitrogen oxides
- The conditions that favor nitrogen oxides generation (high temperatures and low oxygen concentrations) are the opposite of those that contribute to the formation of partially oxidized organic compounds.
-
#2
- What conditions in a fossil-fuel-fired boiler can contribute to the incomplete destruction of carbon monoxide and partially oxidized organic compounds?
-
- Answer: The following conditions in a fossil-fuel-fired boiler can contribute to the incomplete destruction of carbon monoxide and partially oxidized organic compounds.
- Poor fuel-air distribution in the boiler or incinerator
- Cold air infiltration into portions of the boiler or incinerator
- Insufficient excess air levels
- Excessive moisture levels in the fuel or waste being fired
- Overly aggressive NOx combustion modifications
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#3
- Why is carbon monoxide used as a surrogate indicator for the emission of partially oxidized organic compounds from combustion sources?
-
- Answer: Carbon monoxide is used as a surrogate indicator for the emission of partially oxidized organic compounds from combustion sources for the following reasons.
- It is easy to measure.
- There are too many partially oxidized organic compounds to measure
easily.
- Carbon monoxide begins to form before the concentration of the partially oxidized organic compounds increases.
-
#4
- Use the Figure below to explain the following observations.
- Explain the reason that carbon monoxide (and partially oxidized
organic compounds) concentrations fall in section A of the graph.
- Explain the reason that carbon monoxide (and partially oxidized organic compounds) concentrations start to rise in section C of the graph.
- Explain the reason that carbon monoxide (and partially oxidized
organic compounds) concentrations fall in section A of the graph.
-
- Answer: i.
- In section A of the graph, the air-to-fuel ratio is low. As the concentration
of oxygen increases, the air-to-fuel ratio increases and the concentration
of incomplete combustion products such as carbon monoxide decreases.
- Answer: ii.
- In section C of the graph, oxygen concentrations are higher than needed for optimal combustion (stoichiometric conditions). Temperatures in combustion zones decrease under these circumstances because heat is transferred to the excess air entering the combustion gas stream.
-
#5
- Explain how a combustion facility could form condensable particulate matter if there is incomplete combustion in the process.
-
- Answer: With incomplete combustion of organic compounds, some volatile organic compounds remain in the vapor state throughout the air pollution control system and are released in the plume. When the gas stream mixes with the ambient air and cools, these organic vapors cool and condense to form condensable particulate matter in the plume.
Practice Problems
Control Techniques
- Instructions:
- Answer these questions on a sheet of paper and check your responses against those provided below..
-
#1
- What is the primary method for controlling the emissions of carbon monoxide and partially oxidized organic compounds from combustion sources?
-
- Answer: Good combustion practices are the primary way to control these emissions. It is important to maintain sufficient oxygen levels in the burner flames and throughout the combustion chamber where oxidation reactions go to completion. Leaks of ambient air into the combustion chamber should be avoided as much as possible because these leaks chill localized areas within the chamber. Combustion temperatures must be maintained for oxidation reactions to go to completion. NOx combustion modifications must be limited as well because they can create conditions in the burner flames and the combustion chamber that interfere with the complete oxidation of carbon dioxide and partially oxidized organic compounds.
-
#2
- When is it appropriate to use add-on controls for carbon monoxide and partially oxidized organic compounds?
-
- Answer: Add-on controls such as thermal or catalytic oxidizer systems can be used for sources that generate a relatively small gas stream. Add-on control devices are not economically feasible for the very large utility and industrial-sized boilers or for large waste incinerators because the fuel costs would be prohibitive. Furthermore, the combustion of additional fuel in the incinerator would increase the overall nitrogen oxides emissions.