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Carbon monoxide (CO), also called carbonous oxide, is a colorless, odorless, and tasteless gas which is slightly
lighter than air. It is highly toxic to humans and animals in higher quantities. Carbon monoxide consists of one
carbon atom and one oxygen atom, connected by a triple bond which consists of two covalent bonds as well as
one dative covalent bond. It is the simplest oxocarbon. In coordination complexes the carbon monoxide ligand is
Carbon monoxide is produced from the partial oxidation of carbon-containing compounds; it forms when there is
not enough oxygen to produce carbon dioxide (CO2). In the presence of oxygen, carbon monoxide burns with a
blue flame, producing carbon dioxide. Some processes in modern technology, such as iron smelting, still produce
carbon monoxide as a by-product.
Levels normally present in the atmosphere are unlikely to cause ill effects. Inhalation of low levels of carbon
monoxide (200 parts per million for 2-3 hours) can cause headache, dizziness, light-headiness and fatigue.
Exposure to higher concentrations (400 parts per million) of carbon monoxide can cause sleepiness,
hallucinations, convulsions, collapse, loss of consciousness and death. It can also cause personality and memory
changes, mental confusion and loss of vision.
Extremely high exposures to carbon monoxide can cause the formation of carboxyhemoglobin and decrease the
body’s ability to carry oxygen. This can cause a bright red color to the skin and mucous membranes causing
trouble breathing, collapse, convulsions, coma and death.
Long term (chronic) health effects can occur from exposure to low levels of carbon monoxide. These effects may
produce heart disease and damage to the nervous system. Exposure of pregnant women to carbon monoxide
may result in low birth weights and other defects in the offspring.
Generally, industrial plants exhaust carbon monoxide to air from a combustion process. Examples of industrial
plants that produce carbon monoxide include: metals (iron, steel, non-ferrous) manufacturing, electricity supply,
mining (metal ore, coal), food manufacturing, oil and gas extraction, chemical manufacturing, cement lime, plaster
and concrete manufacturing and petroleum refining.
Economical Industrial Prevention
Regenerative Thermal Oxidizers and Catalytic Thermal Oxidizers to include Regenerative Catalytic Oxidizers are
combustion systems that control Volatile Organic Compounds (VOCs), Carbon Monoxide (CO), Hydrogen Sulfide
(H2S) and Hazardous Air Pollutants (HAP’s) emissions by combusting them to carbon dioxide (CO2) and water
with exception of H2S which is reduced to sulfur dioxide (SO2) & Sulfur trioxide (SO3).
The design of the system is dependent on the pollutant concentration in the waste gas stream, type of pollutant,
presence of other gases, level of oxygen, stability of processes vented to the system, and degree of control
required. Important design factors include temperature (a temperature high enough to ignite the organic
constituents in the waste gas stream), residence time (sufficient time for the combustion reaction to occur),
turbulence or mixing of combustion air with the waste gas and in the case of many VOCs and CO the level of O2
Time, temperature, degree of mixing, and sufficient oxygen concentration govern the completeness of the
combustion reaction. Of these, only temperature and oxygen concentration can be significantly controlled after
construction. Residence time and mixing are fixed by thermal oxidizer design, with flow rate being controlled only
over a limited range.
Many state regulatory agencies granting permits are not familiar with CO destruction using a Regenerative
Thermal Oxidizers. Regenerative Thermal Oxidizer’s are capable of combusting between 98.5 and 99.9% of CO
within the combustion chamber using very low levels of fuel. Destruction efficiency depends on the system design
on whether you have a (2) heat recovery system or (3) heat recovery chamber design.
The CO combustion will occur in the upper portion of the ceramic media beds and also in the combustion
chamber, destruction occurs within the operating temperatures of (1,200 - 1,550°F). A typical pressure drop is
across the ceramic media bed is between 4 to 8” inches of water column for each of the operating media beds
and will provide adequate mixing of the CO gas stream resulting in little stratification in the combustion chamber.
Tests were performed with inlet CO gas stream having a high concentration of CO ranging from 1,400 ppmv to
3,800 ppmv. Tests completed indicated that an inlet oxygen concentration as low as 9% may be sufficient for
adequate combustion of CO.
Despite the destruction efficiency observed within the combustion chamber, any leakage across the inlet or outlet
valves may limit the ultimate performance of the systems. Consideration should be given to the required control
efficiency and alternate methods of valve arrangement, such as in series valve arrangement or with a positive air
seal should higher destruction efficiencies be required above 98%. Consideration must also be given to possible
valve performance decline due to the valve seal over their lifetime. Systems should be maintained on a semi-
annual basis during which valve seals should be observed for any possible leaks.
Frequent monitoring or testing of an RTO may be required to assure continued compliance with any permit
conditions. A continuous CO monitor may be effectively used as an indication of CO control. If the permit is based
upon control efficiency rather than allotted mass emission rates based upon historical influent concentrations and
flows, compliance with the permit can be monitored using a continuous CO analyzer on the outlet stream.
One of the most cost effective approaches at present of controlling CO emissions with ppmv ranges between 500
to 5000 ppmv is either a Regenerative Catalytic Oxidizer or the Regenerative Thermal Oxidizer. When controlling
CO or VOC emissions, consideration must be given to the overall control efficiency of the system. While a
regenerative thermal oxidizer with indirect ceramic media heat exchanger's are capable of constantly exceeding
99% control efficiency, a regenerative system may be limited by valve performance. Depending on the desired
control efficiency of the system, appropriate valves or valve configuration must be included in the design.
The use of a continuous CO analyzer to monitor the VOC control efficiency of the RTO system without CO in the
inlet stream may not give an accurate representation of the actual performance of the RTO. After installing any
pollution air control system, continued monitoring will play a valuable role in proper source control and continued
compliance with the permit to operate.
Air Pollution Control Equipment
American Environmental Fabrication & Supply, LLC
Call +1 (918) 708 - 1253
|Controlling Carbon Monoxide Emissions