Jordanian-German Winter Academy 2006

Combustions Emissions

ByEng. Samar Jaber

February, 2006

- Combustion of standard fossil fuels results in - Combustion of standard fossil fuels results in nine emissions, carbon dioxide, nitrogen, nine emissions, carbon dioxide, nitrogen, oxygen, water, nitrogen oxide, carbon oxygen, water, nitrogen oxide, carbon monoxide , sulfur oxides, volatile organic monoxide , sulfur oxides, volatile organic compounds (VOCs) , and particulate matter. compounds (VOCs) , and particulate matter.

- We will describe the formation and control of - We will describe the formation and control of each pollutant each pollutant

What is NOWhat is NOxx? ?

- A Nitrogen Oxide, or NO- A Nitrogen Oxide, or NOxx, is the generic , is the generic term for a group of highly reactive gases, term for a group of highly reactive gases, all of which contain nitrogen and oxygen in all of which contain nitrogen and oxygen in varying amountsvarying amounts. . Many of the nitrogen Many of the nitrogen oxides are colorless and odorlessoxides are colorless and odorless. . However, one common pollutant, nitrogen However, one common pollutant, nitrogen dioxide dioxide ((NONO22) ) along with particles in the air along with particles in the air can often be seen as can often be seen as

a reddisha reddish--brown layer brown layer over many urban areasover many urban areas..

Nitrogen oxides form when fuel is burned at Nitrogen oxides form when fuel is burned at high temperatures, as in a combustion processhigh temperatures, as in a combustion process. . In an internal combustion engine, a mixture of In an internal combustion engine, a mixture of air and fuel is burned. When the mixture is air and fuel is burned. When the mixture is tuned so as to consume every molecule oftuned so as to consume every molecule of reactant reactant (in this case fuel and(in this case fuel and oxygen oxygen) it is said ) it is said to be "running atto be "running at stoichiometrystoichiometry". With this burns, ". With this burns, combustion temperatures reach a high enough combustion temperatures reach a high enough level to actually burn some of thelevel to actually burn some of the nitrogen nitrogen in in the air, yielding variousthe air, yielding various oxidesoxides of of nitrogennitrogen, the , the results of which can be seen over major cities results of which can be seen over major cities such assuch as Los Angeles , California Los Angeles , California in the summer in the summer in the form of brown clouds of in the form of brown clouds of smog.smog.

..

Where does NOWhere does NOxx come from? come from?

In general, the contribution of mobile In general, the contribution of mobile sources to the total NOsources to the total NOxx level ranges from level ranges from

60 to 80 percent60 to 80 percent

For stationary sources, it ranges between 20 For stationary sources, it ranges between 20 and 40 percentand 40 percent..

Primary Primary Sources of NOSources of NOxx

Formation in Combustion Formation in Combustion ProcessesProcesses

Thermal NOThermal NOxx: refers to NO: refers to NOxx formed through high formed through high temperature oxidation of the diatomic nitrogen found in temperature oxidation of the diatomic nitrogen found in combustion air. The formation rate is primary function of combustion air. The formation rate is primary function of temperature and thetemperature and the residence time residence time of nitrogen at of nitrogen at temperature. temperature.

NN22 + O → NO + N + O → NO + N N+ ON+ O22 → NO + O → NO + O N + OH → NO + HN + OH → NO + H

Prompt NOPrompt NOxx : : This is a fast reaction between This is a fast reaction between the Nthe N22, , OO22 and hydrocarbon and hydrocarbon ((CHCH) ) fragmentsfragments::

Fuel NOx : The major source of NOFuel NOx : The major source of NOxx production production from burning fuels such as certain coals and oil, from burning fuels such as certain coals and oil, is the conversion of fuel bound nitrogen to NOis the conversion of fuel bound nitrogen to NOxx during combustion. During combustion, the during combustion. During combustion, the nitrogen bound in the fuel is released as a free nitrogen bound in the fuel is released as a free radical and ultimately forms free Nradical and ultimately forms free N22, or NO. , or NO.

Fuel NOFuel NOxx can contribute as much a s 50% of can contribute as much a s 50% of total emissions when combusting oil and as total emissions when combusting oil and as much as 80% when combusting coalmuch as 80% when combusting coal..

The most significant factors affecting NOThe most significant factors affecting NOx x

formation are flame temperature , the formation are flame temperature , the amount of nitrogen in the fuel , excess air amount of nitrogen in the fuel , excess air

level and combustion air temperaturelevel and combustion air temperature..

The Formation of NOThe Formation of NOxx

Carbon monoxide is a pollutant that is readily Carbon monoxide is a pollutant that is readily absorbed in the body and can impair the oxygenabsorbed in the body and can impair the oxygen--carrying capacity of the hemoglobincarrying capacity of the hemoglobin. . Impairment of Impairment of the body's hemoglobin results in less oxygen to the the body's hemoglobin results in less oxygen to the brain, heart, and tissuesbrain, heart, and tissues. . Even shortEven short--term over term over exposure to carbon monoxide can be critical, or fatal, exposure to carbon monoxide can be critical, or fatal, to people with heart and lung diseasesto people with heart and lung diseases. . It may also It may also cause headaches and dizziness in healthy people. cause headaches and dizziness in healthy people.

During combustion, carbon in the fuel oxidizes During combustion, carbon in the fuel oxidizes through a series of reactions to form carbon dioxide through a series of reactions to form carbon dioxide ((COCO22). ). However, 100 percent conversion of carbon to However, 100 percent conversion of carbon to COCO22 is rarely achieved in practice and some carbon is rarely achieved in practice and some carbon only oxidizes to the intermediate step, carbon only oxidizes to the intermediate step, carbon monoxidemonoxide..

Carbon Monoxide EmissionsCarbon Monoxide Emissions

Sulfur Compounds (SoSulfur Compounds (Soxx)) The primary reason sulfur compounds, are The primary reason sulfur compounds, are

classified as a pollutant is because they react with classified as a pollutant is because they react with water vapor (in the flue gas and atmosphere) to water vapor (in the flue gas and atmosphere) to form sulfuric acid mist. Airborne sulfuric acid has form sulfuric acid mist. Airborne sulfuric acid has been found in fog, smog, acid rain, and snow. been found in fog, smog, acid rain, and snow. Sulfuric acid has also been found in lakes, rivers, Sulfuric acid has also been found in lakes, rivers, and soil. and soil.

The acid is extremely corrosive and harmful to the The acid is extremely corrosive and harmful to the environment.environment.

The combustion of fuels containing sulfur (primarily The combustion of fuels containing sulfur (primarily oils and coals) results in pollutants occurring in the oils and coals) results in pollutants occurring in the forms of SOforms of SO22 (sulfur dioxide) and SO (sulfur dioxide) and SO33 (sulfur (sulfur

trioxide), together referred to as SOtrioxide), together referred to as SOxx (sulfur (sulfur

oxides). The level of SOoxides). The level of SOxx emitted depends directly emitted depends directly

on the sulfur content of the fuel. on the sulfur content of the fuel.

Typically, about 95% of the sulfur in the fuel will be Typically, about 95% of the sulfur in the fuel will be emitted as SOemitted as SO22, 1-5% as SO, 1-5% as SO33, and 1-3% as sulfate , and 1-3% as sulfate

particulate. Sulfate particulate is not considered particulate. Sulfate particulate is not considered part of the total SOpart of the total SOxx emissions. emissions.

Volatile Organic CompoundsVolatile Organic Compounds (VOCs)/Hydrocarbons (HC) (VOCs)/Hydrocarbons (HC)

VOCs are compounds containing combinations of VOCs are compounds containing combinations of carbon, hydrogen, and sometimes oxygen. VOCs carbon, hydrogen, and sometimes oxygen. VOCs vaporize easily once emitted into the air and are of vaporize easily once emitted into the air and are of concern because of their role in ground level concern because of their role in ground level ozone formation. ozone formation.

Formation of VOCs result from poor or incomplete Formation of VOCs result from poor or incomplete combustion .combustion .

VOC's are vapors released from gasoline, paints, VOC's are vapors released from gasoline, paints, solvents, pesticides, and other chemicals.solvents, pesticides, and other chemicals.

Formation of VOCs in commercial and industrial Formation of VOCs in commercial and industrial boilers primarily result from poor or incomplete boilers primarily result from poor or incomplete combustion due to improper burner set-up and combustion due to improper burner set-up and adjustment. adjustment.

In the combustion chamber the unburned In the combustion chamber the unburned hydrocarbon emissions have several different hydrocarbon emissions have several different sources :sources :

1. During compression and combustion, the 1. During compression and combustion, the increasing cylinder pressure forces some of the increasing cylinder pressure forces some of the gas in the cylinder into crevices, or narrow gas in the cylinder into crevices, or narrow volumes connected to the combustion volumes connected to the combustion chamber: The volumes between the piston, chamber: The volumes between the piston, rings and cylinder wall are the largest of these.rings and cylinder wall are the largest of these.

2. Most of this gas 2. Most of this gas is unburned fuel-is unburned fuel-air mixture much air mixture much of it escapes the of it escapes the primary primary combustion combustion process because process because the entrance to the entrance to these crevices is these crevices is too narrow for the too narrow for the flame to enter.flame to enter.

3. This gas which 3. This gas which leaves these leaves these crevices in the crevices in the expansion and expansion and exhaust exhaust processes, is one processes, is one of the unburned of the unburned hydro carbon hydro carbon emissions.emissions.

Particulate Matter (PM)Particulate Matter (PM) Emissions of PM from combustion sources consist Emissions of PM from combustion sources consist

of many different types of compounds, including of many different types of compounds, including nitrates, sulfates, carbons, oxides, and any nitrates, sulfates, carbons, oxides, and any uncombusted elements in the fuel. uncombusted elements in the fuel.

Particulate pollutants can be corrosive, toxic to Particulate pollutants can be corrosive, toxic to plants and animals, and harmful to humans.plants and animals, and harmful to humans.

PM emissions are primarily dependent on the PM emissions are primarily dependent on the grade of fuel fired in the boiler. Generally, PM grade of fuel fired in the boiler. Generally, PM levels from natural gas are significantly lower than levels from natural gas are significantly lower than those of oils.those of oils.

PM emissions generally are classified into two PM emissions generally are classified into two categories, PM and PM10. PM10 is a particulate categories, PM and PM10. PM10 is a particulate matter with a diameter less than 10 microns. All matter with a diameter less than 10 microns. All PM can pose a health problem. However, the PM can pose a health problem. However, the greatest concern is with PM10, because of its greatest concern is with PM10, because of its ability to bypass the body's natural filtering system. ability to bypass the body's natural filtering system.

When burning heavy oils, particulate levels mainly When burning heavy oils, particulate levels mainly depend on four fuel constituents: sulfur, ash, depend on four fuel constituents: sulfur, ash, carbon residue, and asphalenes. These carbon residue, and asphalenes. These constituents exist in fuel oils, particularly residual constituents exist in fuel oils, particularly residual oils, and have a major effect on particulate oils, and have a major effect on particulate emissions. By knowing the fuel constituent levels, emissions. By knowing the fuel constituent levels, the particulate emissions for the oil can be the particulate emissions for the oil can be estimated. estimated.

Health and Environmental ImpactsHealth and Environmental Impacts

The main reason that NOx is considered an The main reason that NOx is considered an environmental problem is because it initiates environmental problem is because it initiates reactions that result in the production of ozone reactions that result in the production of ozone and acid rain. Ozone and acid rain can damage and acid rain. Ozone and acid rain can damage fabric, cause rubber to crack, reduce visibility, fabric, cause rubber to crack, reduce visibility, damage buildings, harm forests and lakes, and damage buildings, harm forests and lakes, and cause health problems.cause health problems.

By controlling NOBy controlling NOxx levels, along with the other levels, along with the other pollutants, the levels of acid rain and ozone can pollutants, the levels of acid rain and ozone can be reducedbe reduced..

SmogSmog SmogSmog is a kind of air pollution, originally named for is a kind of air pollution, originally named for

the mixture of smoke and fog in the air. Classic the mixture of smoke and fog in the air. Classic smog results from large amounts of coal burning in smog results from large amounts of coal burning in an area and is caused by a mixture of smoke and an area and is caused by a mixture of smoke and sulfur dioxide. sulfur dioxide.

In the 1950s a new type of smog, known as In the 1950s a new type of smog, known as Photochemical Smog, was first described. This is a Photochemical Smog, was first described. This is a noxious mixture of air pollutants including:Nitrogennoxious mixture of air pollutants including:Nitrogen Oxides, Tropospheric Ozone and Volatile Organic Oxides, Tropospheric Ozone and Volatile Organic Compounds (VOCs) Compounds (VOCs)

All of these chemicals are usually highly reactive All of these chemicals are usually highly reactive and oxidizing. Due to this fact, photochemical and oxidizing. Due to this fact, photochemical smog is considered to be a problem of modern smog is considered to be a problem of modern industrialization.industrialization.

Photochemical smog is a concern in most major Photochemical smog is a concern in most major urban centres but, because it travels with the wind, urban centres but, because it travels with the wind, it can affect sparsely populated areas as well. it can affect sparsely populated areas as well.

Smog is caused by a reaction between sunlight Smog is caused by a reaction between sunlight and emissions mainly from human activity. and emissions mainly from human activity.

Acid Rain Acid Rain

NOx and sulfur dioxide react with other substances NOx and sulfur dioxide react with other substances in the air to form acids which fall to earth as rain, fog, in the air to form acids which fall to earth as rain, fog, snow or dry particles. Some may be carried by wind snow or dry particles. Some may be carried by wind for hundreds of miles.for hundreds of miles.

Acid rain damages; causes deterioration of Acid rain damages; causes deterioration of cars, buildings and historical monuments; cars, buildings and historical monuments; and causes lakes and streams to become and causes lakes and streams to become acidic and unsuitable for many fish. Acid acidic and unsuitable for many fish. Acid rain also reduces how far and how clearly rain also reduces how far and how clearly we can see through the air, an effect we can see through the air, an effect called visibility reduction. called visibility reduction.

ParticlesParticles

NONOxx reacts with ammonia, moisture, and other reacts with ammonia, moisture, and other

compounds to form nitric acid and related particlescompounds to form nitric acid and related particles. . Human health concerns include effects on Human health concerns include effects on breathing and the respiratory system, damage to breathing and the respiratory system, damage to lung tissue, and premature deathlung tissue, and premature death. . Small particles Small particles penetrate deeply into sensitive parts of the lungs penetrate deeply into sensitive parts of the lungs and can cause or worsen respiratory disease such and can cause or worsen respiratory disease such as emphysema and bronchitis, and aggravate as emphysema and bronchitis, and aggravate existing heart diseaseexisting heart disease..

Water Quality DeteriorationWater Quality Deterioration

Increased nitrogen loading in water bodies, Increased nitrogen loading in water bodies, particularly coastal estuaries, upsets the particularly coastal estuaries, upsets the chemical balance of nutrients used by aquatic chemical balance of nutrients used by aquatic plants and animalsplants and animals. . Additional nitrogen Additional nitrogen accelerates accelerates ""eutrophication,eutrophication," " which leads to which leads to oxygen depletion and reduces fish and shellfish oxygen depletion and reduces fish and shellfish populationspopulations. .

Global WarmingGlobal Warming

One member of the NOOne member of the NOxx is a greenhouse is a greenhouse

gasgas. . It accumulates in the atmosphere with It accumulates in the atmosphere with other greenhouse gasses causing a other greenhouse gasses causing a gradual rise in the earth's temperaturegradual rise in the earth's temperature. . This will lead to increased risks to human This will lead to increased risks to human health, a rise in the sea level, and other health, a rise in the sea level, and other adverse changes to plant and animal adverse changes to plant and animal habitathabitat..

Toxic ChemicalsToxic Chemicals

In the air, NOIn the air, NOxx reacts readily with common reacts readily with common

organic chemicals and even ozone, to organic chemicals and even ozone, to form a wide variety of toxic products, some form a wide variety of toxic products, some of which may cause biological mutationsof which may cause biological mutations..

Visibility ImpairmentVisibility Impairment

Nitrate particles and nitrogen dioxide can Nitrate particles and nitrogen dioxide can block the transmission of light, reducing block the transmission of light, reducing visibility in urban areas and on a regional visibility in urban areas and on a regional scale in our national parksscale in our national parks..

Post combustion methods address Post combustion methods address NONOx x emissions after formationemissions after formation

Combustion control techniques Combustion control techniques prevent the formation of NOprevent the formation of NOxx

during the combustion processduring the combustion process . .

Post combustion methods tend to Post combustion methods tend to be more expensive than be more expensive than combustion control techniquescombustion control techniques

NONOxx Control Technologies Control Technologies

Post combustion control methodsPost combustion control methods

Selective Non-catalytic ReductionSelective Non-catalytic Reduction

Selective non-catalytic reduction involves the Selective non-catalytic reduction involves the injection of a NOinjection of a NOxx reducing agent, such as reducing agent, such as

ammonia or urea. The ammonia or urea breaks ammonia or urea. The ammonia or urea breaks down the NOdown the NOxx in the exhaust gases into water in the exhaust gases into water

and atmospheric nitrogen. Selective non-and atmospheric nitrogen. Selective non-catalytic reduction reduces NOcatalytic reduction reduces NOxx up to 70%. up to 70%.

Selective Catalytic ReductionSelective Catalytic Reduction - Selective catalytic reduction involves the injection of - Selective catalytic reduction involves the injection of

ammonia in the boiler exhaust gases in the presence of ammonia in the boiler exhaust gases in the presence of a catalyst.a catalyst.

- The catalyst allows the ammonia to reduce NO- The catalyst allows the ammonia to reduce NOxx levels levels

at lower exhaust temperatures than selective non-at lower exhaust temperatures than selective non-catalytic reduction. Unlike selective non-catalytic catalytic reduction. Unlike selective non-catalytic reduction, where the exhaust gases must be reduction, where the exhaust gases must be approximately 1400-1600 °F, selective catalytic approximately 1400-1600 °F, selective catalytic reduction can be utilized where exhaust gasses are reduction can be utilized where exhaust gasses are between 500 °F and 1200 °F, depending on the catalyst between 500 °F and 1200 °F, depending on the catalyst used. used.

- Selective catalytic reduction can result in NO- Selective catalytic reduction can result in NOxx

reductions up to 90%. reductions up to 90%.

Combustion Control TechniquesCombustion Control Techniques

Low Excess Air (LEA) FiringLow Excess Air (LEA) Firing

One of the factors influencing NOOne of the factors influencing NOxx formation is formation is

the excess air levels. High excess air levels the excess air levels. High excess air levels (>45%) may result in increased NO(>45%) may result in increased NOxx formation formation

because the excess nitrogen and oxygen in the because the excess nitrogen and oxygen in the combustion air entering the flame will combine combustion air entering the flame will combine to form thermal NOto form thermal NOxx. .

Low excess air firing can be used on most Low excess air firing can be used on most boilers and generally results in overall NOboilers and generally results in overall NOxx

reductions of 5-10% when firing natural gasreductions of 5-10% when firing natural gas..

Low Nitrogen Fuel OilLow Nitrogen Fuel Oil

When firing fuel oils, NOWhen firing fuel oils, NOxx formed by fuel-bound formed by fuel-bound

nitrogen can account for 20-50% of the total nitrogen can account for 20-50% of the total NONOxx level. level.

One method to reduce NOOne method to reduce NOx x levels from boilers levels from boilers

firing distillate oils is through firing distillate oils is through

the use of low nitrogen fuel oil the use of low nitrogen fuel oil

ReburningReburning Reburning is a method of NOReburning is a method of NOxx control that uses control that uses

hydrocarbon radicals to convert nitrogen oxide hydrocarbon radicals to convert nitrogen oxide ((NONO) ) to nitrogen to nitrogen ((NN22) ) and carbon dioxide and carbon dioxide ((COCO22). ).

Reburning can be applied to boilers that cannot Reburning can be applied to boilers that cannot use standard low NOuse standard low NOxx combustion modification combustion modification techniques due to the need to maintain high techniques due to the need to maintain high furnace temperatures, such as wet bottom boilersfurnace temperatures, such as wet bottom boilers. .

In many cases, reburning can be more economical In many cases, reburning can be more economical than post combustion NOthan post combustion NOxx controls that would controls that would otherwise be used in these instancesotherwise be used in these instances..

Reburning is accomplished by Reburning is accomplished by diverting a portion of a boiler's diverting a portion of a boiler's fuel, typically 10-20%, to a fuel, typically 10-20%, to a point above the primary point above the primary combustion zone where it is combustion zone where it is injected to create a fuel rich injected to create a fuel rich ""reburn zonereburn zone." ." The remaining The remaining combustion air is then injected combustion air is then injected above the reburn zone to above the reburn zone to provide the necessary burnout provide the necessary burnout airair..

Water/Steam InjectionWater/Steam Injection By injecting water or steam into the flame, flame By injecting water or steam into the flame, flame

temperatures are reduced, thereby lowering temperatures are reduced, thereby lowering thermal NOthermal NOxx formation and overall NO formation and overall NOxx levels. levels.

Water or steam injection can reduce NOWater or steam injection can reduce NOxx up to up to 80% (when firing natural gas) and can result in 80% (when firing natural gas) and can result in lower reductions when firing oils. lower reductions when firing oils.

Many times water or steam injection is used in Many times water or steam injection is used in

conjunction with other NOconjunction with other NOxx control methods such control methods such as burner modifications or flue gas recirculation.as burner modifications or flue gas recirculation.

Flue Gas RecirculationFlue Gas Recirculation FGR entails recalculating a portion of relatively FGR entails recalculating a portion of relatively

cool exhaust gases back into the combustion cool exhaust gases back into the combustion process in order to lower the flame temperature process in order to lower the flame temperature and reduce NOand reduce NOxx formation. It is currently the formation. It is currently the most effective and popular low NOmost effective and popular low NOxx technology technology for fire tube and water tube boilers. for fire tube and water tube boilers.

In many applications, it does not require any In many applications, it does not require any additional reduction equipment to comply with additional reduction equipment to comply with regulations.regulations.

FGR technology can be classified into two types; FGR technology can be classified into two types;    External FGR utilizes an external fan to recirculate External FGR utilizes an external fan to recirculate

the flue gases back into the flame. External piping the flue gases back into the flame. External piping routes the exhaust gases from the stack to the routes the exhaust gases from the stack to the burner. A valve controls the recirculation rate, burner. A valve controls the recirculation rate, based on boiler input. based on boiler input.

Induced FGR utilizes the combustion air fan to Induced FGR utilizes the combustion air fan to recirculate the flue gases back into the flame. A recirculate the flue gases back into the flame. A portion of the flue gases are routed by duct work or portion of the flue gases are routed by duct work or internally to the combustion air fan, where they are internally to the combustion air fan, where they are premixed with the combustion air and introduced premixed with the combustion air and introduced into the flame through the burner. into the flame through the burner.

Dilution with cold inertsDilution with cold inerts

ExampleExample::

Consider the Nitric Oxide formation in the post Consider the Nitric Oxide formation in the post flame gases of a stoichiometric propane-air flame gases of a stoichiometric propane-air mixture at atmospheric pressure. Assuming mixture at atmospheric pressure. Assuming adiabatic conditions, how does the initial rate of adiabatic conditions, how does the initial rate of NO formation (ppm/s) from the Zoldivich NO formation (ppm/s) from the Zoldivich mechanism compare for no dilution and 25% mechanism compare for no dilution and 25% dilution by Ndilution by N22 (moles of N (moles of N2 2 added equals 0.25 added equals 0.25

the number of moles of air). The reactants and the number of moles of air). The reactants and NN22 diluents are initially at 298 K. diluents are initially at 298 K.

Solution:Solution:

For the case of No Dilution:

With 25% N2 Dilution:

Each method results in a differentEach method results in a different

degree of NOdegree of NOx x controlcontrol..

For example, when firing natural gas, low excess airFor example, when firing natural gas, low excess air

firing typically reduces NOfiring typically reduces NOxx by 10%, FGR by 75% by 10%, FGR by 75% , ,

and selective catalytic reduction by 90%and selective catalytic reduction by 90%..

Selecting the best low NOSelecting the best low NOxx control package should control package should

be made with total boiler performance in mindbe made with total boiler performance in mind

Some NOSome NOxx control technologies used to reduce NO control technologies used to reduce NOxx levels by lowering flame temperatures by modifying levels by lowering flame temperatures by modifying air/fuel mixing patterns. The lower flame air/fuel mixing patterns. The lower flame temperature and decreased mixing intensity can temperature and decreased mixing intensity can result in higher CO levels.result in higher CO levels.

An induced FGR package can lower NOAn induced FGR package can lower NOxx levels by levels by reducing flame temperature without increasing CO reducing flame temperature without increasing CO levels. CO levels remain constant or are lowered levels. CO levels remain constant or are lowered because the flue gas is introduced into the flame in because the flue gas is introduced into the flame in early stages of combustion and the air fuel mixing early stages of combustion and the air fuel mixing is intensified. Intensified mixing offsets the is intensified. Intensified mixing offsets the decrease in flame temperature and results in CO decrease in flame temperature and results in CO levels that are lower than achieved without FGR. levels that are lower than achieved without FGR.

CO Control TechnologiesCO Control Technologies

High flame temperatures and intimate air/fuel High flame temperatures and intimate air/fuel mixing are essential for low CO emissions. mixing are essential for low CO emissions.

Some NOx control technologies reduce NOSome NOx control technologies reduce NOxx

levels by lowering flame temperatures by levels by lowering flame temperatures by modifying air/fuel mixing patterns. The lower modifying air/fuel mixing patterns. The lower flame temperature and decreased mixing flame temperature and decreased mixing intensity can result in higher CO levels.intensity can result in higher CO levels.

An induced flue gas recirculation package can An induced flue gas recirculation package can lower NOx levels by reducing flame temperature lower NOx levels by reducing flame temperature without increasing CO levels. CO levels remain without increasing CO levels. CO levels remain constant or are lowered because the flue gas is constant or are lowered because the flue gas is introduced into the flame in early stages of introduced into the flame in early stages of combustion and the air fuel mixing is intensified. combustion and the air fuel mixing is intensified.

Intensified mixing offsets the decrease in flame Intensified mixing offsets the decrease in flame temperature and results in CO levels that are lower temperature and results in CO levels that are lower than achieved without FGR. But, the level of CO than achieved without FGR. But, the level of CO depends on the burner design. Not all flue gas depends on the burner design. Not all flue gas recirculation applications result in lower CO levels.recirculation applications result in lower CO levels.

SOSOxx Control Technologies Control Technologies

Methods of SOMethods of SOxx reduction include switching reduction include switching

to low sulfur fuel, desulfurizing the fuel, and to low sulfur fuel, desulfurizing the fuel, and utilizing a flue gas desulfurization (FGD) utilizing a flue gas desulfurization (FGD) system. system.

Fuel desulfurization, which primarily applies Fuel desulfurization, which primarily applies to coal, involves removing sulfur from the fuel to coal, involves removing sulfur from the fuel prior to burning. Flue gas desulfurization prior to burning. Flue gas desulfurization involves the utilization of scrubbers to involves the utilization of scrubbers to remove SOremove SOxx emissions from the flue gases. emissions from the flue gases.

For users of industrial boilers, utilizing low For users of industrial boilers, utilizing low sulfur fuels is the most cost effective method of sulfur fuels is the most cost effective method of SOSOxx reduction. Because SO reduction. Because SOxx emissions emissions

primarily depend on the sulfur content of the primarily depend on the sulfur content of the fuel, burning fuels containing a minimal amount fuel, burning fuels containing a minimal amount of sulfur (distillate oil) can achieve SOof sulfur (distillate oil) can achieve SOxx

reductions, without the need to install and reductions, without the need to install and maintain expensive equipment. maintain expensive equipment.

To control VOC emissions from commercial and To control VOC emissions from commercial and industrial boilers, no auxiliary equipment is industrial boilers, no auxiliary equipment is needed; properly maintaining the burner/boiler needed; properly maintaining the burner/boiler package will keep VOC emissions at a minimum. package will keep VOC emissions at a minimum. Proper maintenance includes keeping the air/fuel Proper maintenance includes keeping the air/fuel ratio at the manufacturer's specified setting, having ratio at the manufacturer's specified setting, having the proper air and fuel pressures at the burner, and the proper air and fuel pressures at the burner, and maintaining the atomizing air pressure on oil maintaining the atomizing air pressure on oil burners at the correct levels. An improperly burners at the correct levels. An improperly maintained boiler/burner package can result in maintained boiler/burner package can result in VOC levels over 100 times the normal levelsVOC levels over 100 times the normal levels

VOCs Control TechnologiesVOCs Control Technologies

The emission levels of particulate matter can be The emission levels of particulate matter can be lowered by switching from a residual to a lowered by switching from a residual to a distillate oil or by switching from a distillate oil to distillate oil or by switching from a distillate oil to a natural gas. Additionally, through proper a natural gas. Additionally, through proper burner set-up, adjustment and maintenance, burner set-up, adjustment and maintenance, particulate emissions can be minimized, but not particulate emissions can be minimized, but not to the extent accomplished by switching fuelsto the extent accomplished by switching fuels

PM Control TechnologiesPM Control Technologies

Thank youThank you