air quality.pdf

Note: The source of the technical material in this volume is the ProfessionalEngineering Development Program (PEDP) of Engineering Services.

Warning: The material contained in this document was developed for SaudiAramco and is intended for the exclusive use of Saudi Aramcosemployees. Any material contained in this document which is notalready in the public domain may not be copied, reproduced, sold, given,or disclosed to third parties, or otherwise used in whole, or in part,without the written permission of the Vice President, EngineeringServices, Saudi Aramco.

Chapter : Environmental For additional information on this subject, contactFile Reference: ENV10103 K. Hibrawi on 873-0211

Engineering EncyclopediaSaudi Aramco DeskTop Standards

Air Quality

Engineering Encyclopedia Environmental

Air Quality

Saudi Aramco DeskTop Standards

CONTENTS PAGES

SAUDI ARAMCO EMISSIONS, THEIR SOURCES, THEIRIMPACTS, AND THE RELEVANT STANDARDS FOR EMISSIONSOURCES AND AMBIENT AIR QUALITY........................................................1

Saudi Aramco Emissions and Their Sources............................................... 1

Point/Non-Point ............................................................................... 2

Production Related Emissions .........................................................3

Hydrocarbon Processing Related Emissions.................................... 4

Marketing Related Emissions ..........................................................4

Impacting Agents ........................................................................................4

Environments Impacted............................................................................... 6

Air .................................................................................................... 6

Terrestrial.........................................................................................6

Aquatic.............................................................................................6

Marine..............................................................................................6

Areas of Value.............................................................................................6

Health...............................................................................................7

Flora/Fauna ......................................................................................7

Bodies of Water ............................................................................... 7

Potential Impacts .........................................................................................7

Direct ...............................................................................................7

Indirect .............................................................................................7

Duration ...........................................................................................8

Relevant Standards for Emission Sources and Ambient AirQuality......................................................................................................... 8

Saudi Aramco .................................................................................. 8

National..........................................................................................10


Air Quality

Saudi Aramco DeskTop Standards

AIR POLLUTION CONTROL METHODS.........................................................12

Emission Control Technologies and Methods........................................... 12

Measures to Avoid or Mitigate Impacts ....................................................14

Production......................................................................................14

Hydrocarbon Processing ................................................................15

Marketing.......................................................................................15

METHODS USED IN SAUDI ARAMCO TO DETERMINECOMPLIANCE WITH SAUDI ARAMCO AND NATIONAL AIRQUALITY STANDARDS ....................................................................................16

Air Monitoring ..........................................................................................16

Ambient Air Quality ...................................................................... 16

Sources of Emissions ..................................................................... 20

Predictive Modeling .................................................................................. 21

Purpose ..........................................................................................22

Air Dispersion Modeling ...............................................................22

GLOSSARY ......................................................................................................... 24


Air Quality

Saudi Aramco DeskTop Standards 1

SAUDI ARAMCO EMISSIONS, THEIR SOURCES, THEIR IMPACTS, AND THERELEVANT STANDARDS FOR EMISSION SOURCES AND AMBIENT AIRQUALITY

Air quality (AQ) is a function of the level in the ambient outdoor atmosphere of one or morecontaminants that have characteristics that exist long enough to be injurious, or tounreasonably interfere with comfortable enjoyment of life and property. Contaminants in theambient air include dust (particulate matter), mist (fumes and aerosols), gases, odor, andvapor. The contaminants can be injurious to human, plant, animal life, and/or to property.Contaminants that are emitted into the atmosphere are agents that impact the air environment.

Saudi Aramco Emissions and Their Sources

Saudi Aramcos three areas of operation are production, processing and marketing. Theseareas have the potential to emit a wide variety of emissions. The four general types ofemissions are as follows:

Gases Vapors Aerosols Particulates

The types of emissions are discussed below.

Gases are elements or compounds with temperatures that are above their normal boilingpoints (the boiling point at atmospheric pressure). Examples of gases include: nitrogen,oxygen, methane and various non-methane hydrocarbons, nitrogen oxides, hydrogen sulfide,sulfur dioxide, ammonia, carbon monoxide, and carbon dioxide.

A vapor is the gaseous phase of an element or compound that normally exists in a liquid orsolid state at ambient temperature and atmospheric pressure. The space that is located above aliquid or solid will contain some vapor that is generated from the element or compound. Thisvapor has a pressure that is associated with it (i.e., the vapor pressure). The vapor pressure isa function of the temperature. The concentration of the vapor in the space will depend on thetemperature and the total pressure in the space. The concentration increases as temperatureincreases and decreases as total pressure increases. Examples of vapors include those frommercury, mercaptans, phenolic compounds, and gasoline, which is a mixture of chemicalcompounds.

Aerosols are finely divided liquid particles of microscopic size that are suspended in the air orin a gas. Examples of aerosols include: fumes, mists, and fog. Fog consists of tiny dropletsof water that are suspended in the air.


Air Quality


Particulates are any solids that are dispersed in the air and the individual aggregates are largerthan a molecule, about 0.002 microns, but smaller than 100 microns. Particulates includesolid particles that are blown into the air by the wind. Particulates can be generated bymechanical processes, such as crushing or grinding, or they can be generated by combustion.Examples of particulates include smoke and dust.

Contaminants that affect air quality are emitted from both point and non-point sources. Thefour basic types of contaminants that result from Saudi Aramco's areas of operation are asfollows:

Volatile organic compounds (VOCs) that include hydrocarbons

Inorganic gases and compounds that include chlorine, ammonia, and hydrogensulfide

Man-made gases that are artificially produced and added to the naturalatmosphere. Examples of man-made gases are chlorofluorocarbons (CFCs)and HCFCs

Combustion products that include carbon dioxide, carbon monoxide, nitrogenoxides, sulfur dioxide, and particulates

Point/Non-Point

Air emission sources are classified as point and non-point. Point sources release emissions aspart of their normal operations from a readily identifiable location such as the tip of a flare.Because they are readily identifiable, point sources can often be economically collected.Non-point sources are small releases from multiple similar points, or emissions that are from abroad area. Emissions from non-point sources are also called fugitive or secondaryemissions. Because non-point sources are from multiple points, or from a broad area, non-point sources are more difficult and costly to collect through control or exhaust systems.


Air Quality


Figure 1 lists some sources of point and non-point emissions.

CLASS SOURCE

Point Process stacks/vents

Utilities stacks/vents

Flares

Non-Point

(Fugitive)

Valves (including pressure relief valves) seals, flanges, andopen-ended lines

Tanks (fixed and floating roofs)

Loading/Unloading (products/feedstocks)

Incidents, e.g. pressure relief

Wastewater treatment

Cooling towers

Incidents, e.g. spills

Mobile Automobiles, Trucks, Ships, Trains, Aircraft

Examples of Emission SourcesFigure 1

All three of Saudi Aramcos areas of operation can potentially emit contaminants to theatmosphere. Examples of emissions from Saudi Aramcos three areas of operations arepresented next.

Production Related Emissions

Malodorous sulfur compounds, NOx, SOx, and volatile organics are the primary impactingagents that can be generated during production. The malodorous sulfur compounds are theresult of drilling operations and the movement of crude oil and natural gas to storage andshipping facilities and to hydrocarbon processing facilities. These impacting agents or aircontaminants can negatively affect air quality.


Air Quality


Hydrocarbon Processing Related Emissions

Hydrocarbon processing has more potential for negatively affecting air quality than doesproduction or marketing. The greater potential to negatively impact air quality is due to:

Complex process equipment that consists of many valves, flanges, etc.

Extensive handling and storage

Conversion of environmentally benign compounds to toxic ones

Use of catalysts to make desirable products

Major consumption of energy through chemical and combustion processes

This module will focus on hydrocarbon processing area of operation because hydrocarbonprocessing has more potential sources of impacting agents than the marketing or productionareas of operation.

Marketing Related Emissions

Saudi Aramcos marketing operation is concerned with the movement, storage, and sale ofrefined products, hydrocarbon gases, NGLs, and crude. Consequently, marketing is primarilyconcerned with tankage and loading/unloading facilities, valves, seals, and flanges as non-point sources of emissions.

Impacting Agents

Contaminants emitted are impacting agents to the air environment . Figure 2 providesexamples of the contaminants and their sources that can be emitted during Saudi Aramcooperations.


Air Quality


AIR CONTAMINANT SOURCES

Malodorous sulfur compounds Hydrogen sulfide

Mercaptans

Evaporation, leaks, spills during all operations

Irritant compounds Sulfur oxides

Ozone

Combustion gases from furnaces, Claus sulfur plants,catalyst regeneration, and other treating processes

Photochemical reaction of NOx, VOCs, and UVradiation

Nitrogen oxides Nitric acid, nitrogen dioxide

Nitrous oxide

Combustion furnaces and internal combustionengines

Volatile organic compounds (VOCs)

Methane, butane, gasoline, benzene, toluene,xylene

Evaporation, process leaks, spills during all processand maintenance operations

Asphyxiant gases Carbon dioxide, nitrogen Equipment that has been purged with inert gas

Toxic Gases Carbon monoxide, hydrogen cyanide, nickel

carbonyl, hydrogen sulfideCatalyst regeneration

Inorganic acids Hydrofluoric acid, hydrochloric acid, sulfuric

acidProcess catalysts, equipment cleaning

Odors Phenols, sulfides, mercaptans, hydrocarbons, and

VOCsEvaporation, leaks, spills during all processoperations

Particulate Matter Smoke, process dust Flares, furnaces and boilers, catalyst regenerators

Mists, aerosols, and fog Cooling towers; steam leaks and vents

CFCs Cooling and refrigeration units

Examples of Contaminants and SourcesFigure 2


Air Quality


Environments Impacted

In addition to impacting the air environment, emissions can also impact the terrestrial, aquatic,and marine environments. A discussion of the environments that are impacted by emissionsto the atmosphere follows. Information about the impacting agents is discussed below in thesection on Potential Impacts.

Air

The air is the primary environment that is impacted when the type of impacting agents listedin Figure 2 are emitted.

Terrestrial

The terrestrial environment can also be adversely affected by impacting agents that areemitted into the atmosphere and that can kill foliage, leave deposits on the ground, and foulbuildings, structures, and works of art.

Aquatic

The aquatic environment can also be impacted by emissions to the air environment. Theprimary impact to the aquatic environment is from acid rain. Acid rain is rain water thatcontains acidic chemicals such as sulfuric acid, nitric acid, and hydrochloric acid. Acid rain,when it accumulates in ponds and lakes, can stunt or kill desirable fish species. Acid rain canalso leach through ground deposits, and, as a result, it can contaminate the aquifers. Itshould be noted that Saudi Aramco has no bodies of water that could be impacted.

Marine

The marine environment is impacted less than the aquatic environment by emissions to the airbecause the large volume of sea water neutralizes or equilibrates the contaminants.

Areas of Value

The air that we breath is the primary area of value that is affected by impacting agents emittedto the atmosphere. The health of flora and fauna, including man, is the most importantspecific value that can be affected by impacting agents to the air environment. Other specificvalues that can be affected are architectural and historic values. For example, works of art,monuments, and buildings can become discolored and eroded by contaminants in the airenvironment.

The potential impacts will be discussed in detail in the next section.


Air Quality


Health

The health of man and animals is the most important specific value that can be impacted bythe quality of the air environment. The impact of poor air quality can range from short-termdiscomfort, such as the odor from mercaptan leaks or releases from refineries, to long-termchronic and fatal illnesses, such as emphysema, asthma, and lung cancer.

Flora/Fauna

The flora can be stunted or killed by the presence of certain chemicals in the atmosphere.Stunted or dead flora are direct impacts of the chemicals in the atmosphere. An indirectimpact of the chemicals in the atmosphere is loss of aesthetic value because the appearance ofthe vegetation is damaged. Another indirect impact from contaminants in the atmosphere isloss of economic value. An example of loss of economic value is reduced quality andquantity of agricultural products.

Bodies of Water

Although of limited concern in Saudi Arabia, bodies of fresh water are areas of value that canbe impacted by poor air quality. The water quality can be degraded by acid rain and thedeposit of toxic chemicals from the air.

Potential Impacts

Poor air quality has many potential impacts. The following are some of the most importantimpacts:

Direct

The most important direct impacts of poor air quality are the health and comfort of man andanimals, reduced visibility, increased soiling from exposure to the air, and the viability ofplant life. Examples of direct impacts are odors that make an area unpleasant to inhabit andillnesses that can kill people.

Indirect

Examples of indirect impacts of poor air quality include the loss of aesthetic value due tochanges in the appearance of vegetation and structures; harm to historic and archaeologicalvalues due to the erosion and discoloration of buildings, monuments, and art treasures;the loss of recreational values, such as the extinction of sport fish; the loss of economic value,such as structures that require increased maintenance; and the decreased productivity ofworkers due to respiratory and other similar illnesses.


Air Quality


Duration

The duration of the impact varies from short-term to long-term. An example of a short-termimpact is the release of a toxic chemical such as hydrogen sulfide gas (H2S) that quicklydissipates. An example of a medium-term impact is the contamination of fresh water bodiesfrom acid rain. The contamination can take several years to reverse after the source of theemission that causes the acid rain is controlled to an acceptable level or eliminated. Anotherimpact example for long-term potential environment change due to the release of airpollutants that cause climate change (i.e., CFCs, Halon, N2O, CO2, SO2, etc.) is calledgreenhouse gases (GHGs).

Impacts to the air quality can be short-term when there is only one source in a wide area andwhen the release from that one source can be eliminated. Most impacts to the air quality arenot short-term because the sources of air emissions are so numerous that the reduction orelimination of one source of emissions is not sufficient to minimize impacts to the air qualityA majority of the sources must be reduced or eliminated to improve the quality of the air.Examples of contaminants with many sources are nitrogen and sulfur oxides.

Relevant Standards for Emission Sources and Ambient Air Quality

Because contaminants are easily transported in the air, and because the impact of thecontaminants can be severe and widespread, there is a need for standards to control emissionsand thereby maintain or improve the ambient air quality. The following discussion presentsthe relevant Saudi Aramco and national standards for ambient air quality, and also presentsthe use of the standards.

Saudi Aramco

Saudi Aramcos primary standard for ambient air quality is SAES-A-102. The followingsection provides information about contaminates and sources specified in SAES-A-102. Theexact specifications and limits can be found in SAES-A-102.

SAES-A-102-Saudi Aramco Engineering Standard, SAES-A-102 provides Ambient AirQuality Standards (AAQSs) and standards for the maximum allowable amount of emissionsfrom specific sources.

Figure 3 presents a list of contaminants controlled by the Ambient Air Quality Standards(AAQSs).


Air Quality


Sulfur dioxide (SO2)

Inhalable particulate matter (PM10)

Photochemical oxidants

Ozone (O3)

Nitrogen dioxide (NO2)

Carbon monoxide (CO)

Hydrogen sulfide (H2S)

Fluorides

Contaminants Controlled by Ambient Air Quality StandardsFigure 3

SAES-A-102 specifies the AAQSs for each of the contaminants that are listed in Figure 3.The AAQSs specify the maximum allowable ground level concentrations of the contaminants.In addition to the national standards, three jurisdictions have standards that slightly differfrom the national standards. These three jurisdictions are: MEPA, the Jubail RoyalCommission, and Yanbu

Royal Commission. The specifications for each of these jurisdictions is contained in SAES-A-102. Note that the Jubail Royal Commission, and Yanbu Royal Commission are under thesame administrative umbrella, so their standards are the same.

In addition to the AAQSs, there are Source Emission Standards (SESs) for new or modifiedfacilities. SESs set the quantitative limits for the maximum amount of the contaminant thatcan be emitted from a facility. In some cases, the SESs specify the method for controllingemissions from a facility. It should be emphasized that SESs are directed at the amount of aparticular contaminant that is emitted, regardless of its ground level concentration.

Figure 4 lists the types of facilities and contaminants that are identified in SAES-A-102.


Air Quality


TYPE OF FACILITY CONTAMINANT

Combustion facilities (boilers/furnaces) Particulate matter, sulfur dioxide, nitrogenoxides

Petroleum/petrochemical facilitiestankage over 1000 barrels capacity

Crude oil, VOC vapor pressure

Fuel gas combustion Hydrogen sulfide, nitrogen oxides

FCC unit regenerators Carbon monoxide, particulate matter

Sulfur recovery plants Sulfur

Fugitive emissions Volatile organic compounds

Visible emissions Opacity (water vapor excluded)

Asphaltic concrete Particulate matter

Sources and Contaminants Specified in SAES-A-102Figure 4

It is important to note that toxic substances may not be discharged from new or modifiedfacilities in quantities that are considered harmful to public health, whether or not they arespecifically covered in SAES-A-102.

National

The following documents provide information that supports SAES-A-102.

MEPA is the Saudi Arabian Government's Meteorology and Environmental ProtectionAdministration. MEPAs standards for air quality are contained in the following document:

MEPA Document No. 1409-01, Environmental Protection Standards, Articles10 and 11

The Environmental Protection Standards consist of Ambient Air Quality Standards and AirPollution Source Standards.


Air Quality


The Ambient Air Quality Standards specify the following:

The quantitative levels for specific contaminants

The methods and procedures to determine the level of the contaminants

The requirements for reports

The Air Pollution Source Standards specify the following:

Emission source according to type

Emissions that are associated with the type of source

Quantities to which emissions are limited in order to prevent a harmful impacton air quality

In some cases, the control methodology that is used to limit emissions topermitted quantities and thereby to prevent a harmful impact on air quality

Royal Commissions of Yanbu and Jubail-The Royal Commissions of Yanbu and Jubail arejurisdictional authorities that administer activities within the Madinat Jubail Al-Sinaiyah andMadinat Yanbu Al-Sinaiyah areas. The Royal Commission standards for Yanbu and Jubailair quality are contained in the following documents:

Environmental Design Guidelines

Interim Environmental Protection Manual

The Environmental Design Guidelines and the Interim Environmental ProtectionManual specify the quantitative levels for specific contaminants. The two documents alsoprovide guidelines for the methods and procedures for measuring the contaminant level and,in some cases, the acceptable methods for controlling the level of the contaminants in the airenvironment.


Air Quality


AIR POLLUTION CONTROL METHODS

Many technologies or methods are used to control the level of impacting agents that areemitted to the atmosphere from industrial facilities. The selection of the best control methoddepends on the volume and type of emission, the desired emission level for the particularcontaminant, and the cost effectiveness. There are two general types of control strategies.The first type of control strategy is source control. In source control, the volume of aparticular contaminant is minimized by operational or process modifications. The secondtype, which is non-source control, reduces the contaminant that is generated by the source toan acceptable level before the contaminant is allowed to enter the atmosphere. Non-sourcecontrol is also called end-of-pipe or stack control. Source control is the preferred strategybecause it addresses the cause and not the effect. An example of source control is the use ofnatural gas instead of fuel oil in furnaces and boilers. Natural gas burns cleaner than fuel oil,and, therefore, it reduces the emissions from the boilers and furnaces. An example of non-source control is the use of a scrubber to remove SOx that is generated by the use of fuel oilin a furnace. In this example of non-source control, the SOx is removed from the stack gasleaving the furnace.

Emission Control Technologies and Methods

There are many technologies and methods that are available to control emissions. Some ofthe more common technologies and methods that are utilized by Saudi Aramco are as follows:

Use of natural gas in the combustion process

Low-NOx burners

Leak detection and repair program (LDAR Program)

Flue gas desulfurization and scrubbing

Thermal oxidizers

Electrostatic precipitators

Tail gas treatment

Flaring

Vapor recovery systems

Storage tank secondary seals and boots


Air Quality


The following section provides brief descriptions of the emission control technologies andmethods that are listed above.

Use of natural gas in the combustion process-The sulfur content of fuel oil is much higher than thatof either natural gas or refinery gas after the gas is treated to remove sulfur compounds.Therefore, the use of natural gas in the combustion process of furnaces and utility boilerssignificantly reduces the amount of generated sulfur oxides.

Low-NOx burners are a modification to standard burners. Low NOx burners modify themethod of the introduction of air and fuel so that the air and fuel are mixed in stages. Theintroduction of air and fuel in stages reduces the concentration of oxygen, and, thus, it reducesthe peak flame temperature in the furnace, which subsequently reduces the amount of oxidesof nitrogen that are formed. Low-NOx burners can reduce the NOx output by up to 50%, andthey can be retrofitted to furnaces that currently exist.

Leak detection and repair (LDAR) program-Flanges, valve stems, pump and compressor shafts,pressure-relief devices, and sampling connections are emission sources of gaseoushydrocarbons and volatile organic compounds (VOCs). Proper operation and preventivemaintenance should be performed routinely to reduce emissions.

Flue gas desulfurization and scrubbing-A number of technologies have been developed to removeSOx from flue gas. The technologies involve the absorption of SOx into a solution in a gasscrubber or absorption column. One can distinguish between the various technologies bytheir use of a regenerable or a non-regenerable solution. In the regenerable processes, SOx isstripped from the solution, and it is recovered as SO2 or SO3, or, in most cases, it is convertedto elemental sulfur in a Claus unit. In the non-regenerable processes, SOx is converted tosolid sodium, calcium, or ammonia sulfites and sulfates. The solids must be separated fromthe solution and sent to a landfill.

Thermal oxidizers use high combustion temperatures to convert gases, vapors, and, to a limitedextent, particulates to carbon dioxide and water. Supplemental fuel is added to increase thecombustion temperatures. Heat recovery, and in some cases, further treatment of the flue gas,follows the thermal oxidizers. The primary application for thermal oxidizers is for thedisposal of small volumes of toxic and odorous compounds.

Electrostatic precipitators use electrical energy to charge particulate matter in a gas stream andto collect the particulates on a collector plate. Electrostatic precipitators do not removegases or vapors. A typical application of an electrostatic precipitator is the removal ofparticulates from the flue gas that leaves the regenerator in a catalytic cracking unit.

Tail gas treatment removes low concentrations of SO2 from process off-gases, such as the off-gas from the catalyst regenerator in a catalytic cracker. Examples of the treatment processesthat are used are scrubbing and the conversion of SO2 to sulfuric acid.


Air Quality


Flaring-Flares are used to burn waste gases that are not economical to recover or gases that arethe result of intermittent, unusual, or emergency operations. Flares are needed to destroyorganics that are heavier than methane. The goal in flaring is to burn 98% or more of theorganics that enter the flue stack. Smokeless flares typically inject steam at the burner tip toimprove the way the fuel and air are mixed. This improvement in the way fuel and air aremixed results in a more complete combustion of the waste gases and reduced opacity.

Vapor recovery systems recover valuable hydrocarbons and/or remove toxic compounds from agas stream before the gas stream goes to a flare or to the atmosphere. Vapor recovery systemscollect vapors or displaced air and then remove the hydrocarbons by condensation,adsorption, or combustion. When combustion is used, the hydrocarbons are burned in aspecially designed incinerator or flare. One application of a vapor recovery system is theloading of motor gasoline, aromatics, and other products onto barges, tankers, tank cars, andtrucks. In this application, the air, that is displaced from the vessel as a product is loaded, iscollected, and is sent to a vapor recovery system. Another application of vapor recoverysystems is the collection of vapors that are expelled from fixed-roof storage tanks.

Storage tank secondary seals are used on floating roof tanks. Floating roof tanks have a primaryseal between the floating roof and the shell of the tank. However, as the roof moves up anddown as the tank is filled and emptied, hydrocarbon vapors are emitted, primarily by theevaporation of hydrocarbon, from the shell of the tank. By adding a secondary seal, thevapors are contained and the emissions are significantly reduced.

Measures to Avoid or Mitigate Impacts

Saudi Aramco takes every effort to maintain the quality of the air in the Kingdom. Towardsthis end, Saudi Aramco takes all reasonable measures to avoid or mitigate any impacts to theair environment.

Production

The major effort to avoid or mitigate impacts in the production area of operation is tominimize the amount of hydrocarbon gases and VOCs emitted to the atmosphere when crudeoil is withdrawn from wells. Generally, the gases withdrawn with the crude oil arecompressed and re-injected into the oil formation, or the gases are transferred to a treatmentfacility for NGL recovery and sulfur removal.

The measures to avoid or mitigate emissions in the treatment facilities are similar to thosemeasures used in a refinery or chemical plant, some of which have been discussed above.Leak detection and repair programs are also important activities in the production area ofoperation.


Air Quality


Hydrocarbon Processing

Great emphasis is placed on source control (avoidance) in modern hydrocarbon processingoperations. Technologies that reduce the level of pollutants downstream of the source(mitigation) are expensive, and they usually result in the destruction or the consumption ofvaluable hydrocarbon compounds. One exception, where the hydrocarbons are not destroyed,is vapor recovery. In vapor recovery, recovered materials can be recycled back to theprocessing operation, or they can be used as fuel. An example is vapor recovery in flaresystems, where valuable hydrocarbons that were once burned in the flare are now recycled.All of the ten types of control technologies or methods described above are pertinent tohydrocarbon processing.

Marketing

In general, marketing is concerned with emissions that result from storing, handling, andtransporting products. Therefore, the primary control technologies used in marketing caninclude the use of storage tank seals, vapor recovery systems, and leak detection programs.

When marketing is discussed, it is appropriate to note that the quality of the product can alsoaffect air quality. As an example, the reduction of the vapor pressure of motor gasolinereduces the emissions of VOCs at gasoline stations and from automobile gas tanks. A secondexample is that the reduction of the sulfur and nitrogen levels in diesel fuel will reduce theSOx and NOx in the exhausts of automobiles and trucks.


Air Quality


METHODS USED IN SAUDI ARAMCO TO DETERMINE COMPLIANCE WITHSAUDI ARAMCO AND NATIONAL AIR QUALITY STANDARDS

Air Monitoring

Monitoring of air quality has two principal purposes. The first purpose of monitoring is tomonitor ambient air quality for specific pollutants to ensure compliance with applicablestandards and operating permits. Saudi Aramco is subject to comply with the standardsspecified in SAES-A-102, which include the regulations of MEPA and the RoyalCommissions. If the Saudi Aramco facility is located in either the Yanbu or the Jubail area,the Royal Commission regulations apply. The second purpose of monitoring is to provideweather data and information on levels and trends in air quality. The weather data are used inidentifying the source of any exceedance of a standard, and they are used for developing thedesign criteria that are used in Saudi Aramco projects.

Ambient Air Quality

Saudi Aramco has established an Air Quality Monitoring and Meteorology Network, which iscalled AMMNET, to measure ambient air quality levels and to collect weather data at SaudiAramco facilities in Saudi Arabia.

Air Quality Monitoring and Meteorology Network (AMMNET)-AMMNET consists of nine airquality monitoring stations and five weather stations. All of the air quality monitoringstations monitor weather parameters as well as air quality.

The locations of the air quality monitoring sites except for the one at East-West PipelineStation #6 are shown in Figure 5.


Air Quality


AMMNET LocationsFigure 5


Air Quality


The capabilities of the nine air quality monitoring sites are shown in Figure 6.

IMPACTING AGENTS

Location CO SO2 OZONE NOX H2S CH4Non-meth-ane hydro-carbons

Inhalableparticulates

Abqaiq AlHamra X X X X X X X X

Dhahran X X X X X X X X

Tanajib X X X X X X X X

Udhailiyah X X X X X X X

Ju'aymah X

RahimahTown X X X X X X

Tarut Island X X X X X

Shedgum X X X X

East-Westpipelinestation #6 X

AMMNET, Air Quality Monitoring CapabilityFigure 6


Air Quality


All AMMNET stations are equipped with dedicated real-time data-logging systems. Real-time monitoring implies the ability to access up-to-the-minute readings.

These data loggers are designed to collect data from the individual analyzers, to process andstore data, and, on command, to report the data in various formats.

Various methodologies are employed to measure the level of air impacting agents. Themethodology that is used depends on the impacting agent that is present. The methodologiescan be continuous or non-continuous.

Continuous, or real-time, monitoring is the recommended method because it continuouslymeasures the air for various impacting agents.

Examples used by Saudi Aramco include the following:

Pulsed-Fluorescent Analyzer for SO2

UV Photometric Analyzer for O3

Chemiluminescent Analyzer for Oxides and Nitrogen

Non-Dispersive Infrared Analyzer for CO

Instrument analysis is the most precise and most useful measurement technique because theaverage concentration over any period of time, or the concentration for any single point intime, can be determined. Saudi Aramco uses instrument analysis at all AMMNET stations.

The measurement of the concentration of particulates is performed over a fixed period oftime, usually from several hours up to several days. A calibrated, fixed volume of air iswithdrawn from the air with a vacuum pump. The sampling device knocks out large particles,and, then, a series of screens and filters remove particles of various sizes down to those ofparticles in the inhalable range. The change of weight of the screens and filters is used tocalculate the amount of particulates in the air.

The United States Environment Protection Agency (USEPA) has published methods to obtainand analyze air samples. The USEPA methods provide details of the recommendedprocedures to be followed and the type of equipment to be used. The USEPA methodincludes appropriate references. Saudi Aramco follows the USEPA recommendations.


Air Quality


The following meteorological data are collected at each of the 14 Saudi Aramco stations:

Wind velocity and direction

Ambient Temperature

Barometric pressure

Precipitation (Rainfall)

Dewpoint

Solar Radiation

Wind velocity is measured with an anemometer or pitot tube. Wind direction is measuredwith a sophisticated type of weather vane that dampens small oscillations. Temperature ismeasured with a thermometer at one or more heights above ground level. Barometricpressure is measured with a barometer. Rainfall is measured with a rain gauge.

Sources of Emissions

Because monitoring of ambient air quality is conducted at locations that are often distant fromindustrial plants, data obtained from these distant locations does not accurately indicate theprecise sources of emissions. Monitoring of emissions at their sources permits accurate,ongoing determinations of the amounts of emissions that are being released anddeterminations of precisely when emissions from specific sources are exceeding regulatorylimits.

Stack Testing-Emissions from furnace/boiler stacks are measured in the stack at appropriatelocations in order to determine the levels of the following:

Carbon monoxide

Carbon dioxide

Hydrogen sulfide

Nitrogen oxide

Sulfur oxide

Particulates


Air Quality


The furnace/boiler stacks have as follows:

Sampling ports

Stack gas velocity instruments

Moisture content instruments

Sample withdrawal devices

Analytical instruments

The data obtained from these measurements can be used to adjust burner operations, such asthe amount of excess air, to reduce emissions.

Continuous Emission Monitoring (CEM) involves the monitoring of stack gas parameters on acontinuous basis. CEM is performed on process units where there is a specific impactingagent of concern to alert the operators that an undesirable situation is occurring that couldendanger the neighborhood. Based on the data that is obtained from CEM, the operators canalleviate or remedy the situation.

Process Control Monitoring-If a specific process can or does emit a specific impacting agent ofconcern, continuous analysis of a particular stream can be used to adjust the process variablesthrough the computerized process control system. Examples of process variables that mightbe adjusted with process control monitoring are the feed rate, the treating-agent-to-feed ratio,the reactor conditions, the furnace air, and the flue gas recycle rate. Process controlmonitoring has become an integral part of the design of new and expanded facilities, as it isan important method of emission control.

Predictive Modeling

Predictive modeling involves the use of a mathematical model to predict the dispersion of airimpacting agents from facilities and operations. Predictive modeling enables the dispersion ofair impacting agents, and consequently the ground level concentrations at various distancesfrom the potential emission source, to be estimated before a facility is built or modified. Theestimates from predictive modeling can be used to determine the nature and extent of thecontrols that are needed in the facility to reduce emissions to a level that will meet standards.

This section describes the computer models used by Saudi Aramco to predict air quality. AirQuality Modeling is typically called "air dispersion modeling."


Air Quality


Purpose

Predictive, or air dispersion modeling, has the following purposes:

To ensure that workers and the community are safe from the emission ofcontaminants at existing and new facilities for planned and unplanned releases,including both continuous and intermittent releases

To comply with regulatory requirements (MEPA AAQSs)

To obtain construction and/or operating permits

To provide data for developing cost-effective and appropriate projectdesigns

To assist in the development of site emergency response plans for the release oftoxins and/or flammables

Air Dispersion Modeling

Three computer programs recommended by the USEPA are used by Saudi Aramco to modelor predict the dispersion of air impacting agents, and subsequent ground level concentrationsof the modeled impacting agents can be estimated. The concentrations are estimated atvarious distances or locations (called receptors) from the emission sources. These threecomputer programs are discussed next.

ISCST2-Industrial Source Complex Model, Short Term, Version 2 (ISCST2), predicts theshort term exposure to impacting agents of concern that are emitted by a facility. ISCST2uses hourly meteorological and background ambient air quality data to estimate ground levelconcentrations for periods ranging from 1 to 24 hours.

ISCLT2-Industrial Source Complex Model, Long Term, Version 2 (ISCLT2), predicts, basedon annualized amounts of emissions in tons/year, the annual exposure to impacting agents.ISCLT2 uses statistical data on the frequencies of weather conditions, such as wind direction,velocity, and air temperature, to estimate average ground level concentrations of thecontaminants.

SCREEN2 is a simplified model used in the early development of a new project. SCREEN2 isused to predict if the facility, as proposed, might create a problem so that the cost of anyneeded mitigation facilities can be recognized early in the project development phase.


Air Quality


The three computer models are complex, and they require considerable input data. Examplesof the input data that the models require are as follows:

Characteristics of emissions: Temperature and pressure of stream at the discharge point Volumetric flow rate and composition, including the contaminants of

interest Velocity at discharge point Height and configuration of discharge point

Meteorological/air quality information: Seasonal data on the air temperature at various heights above ground

level Seasonal data on the wind velocity and distribution of prevailing wind

direction Seasonal data on the average level of contaminants in the air at various

locations in the vicinity of the discharge Data on atmospheric stability, for example, the frequency of

temperature inversions

As can be seen, the data on meteorological conditions and the background levels of impactingagents that are collected at the AMMNET stations establish a valid base-point, and the dataare vital to the three models.


Air Quality


GLOSSARY

AAQS Ambient Air Quality Standard

aerosols Finely divided liquid particles of microscopic size that aresuspended in the air or in a gas.

AMMNET Air Quality Monitoring and Meteorology Network

CEM Continuous Emission Monitoring

electrostatic An emission control technology that uses electrical energy toprecipitators charge particulate matter in a gas stream and collect the

particulates on a collector plate.

flaring An emission control technology in which waste gases areburned.

gases Elements or compounds that are far above their normal boilingpoints.

Inhalable Solid or liquid particles of such size (less than one micron) thatthey

Particulates (PM10) can pass through the oral and/or nasal passages into the lungs.

ISCLT2 Industrial Source Complex Model, Long Term, Version 2(ISCLT2), predicts, based on annualized amounts of emissions intons/year, the annual exposures to impacting agents.

ISCST2 Industrial Source Complex Model, Short Term, Version 2(ISCST2), predicts the short term exposure to impacting agentsof concern that are emitted by a facility.

low-NOx burner A type of burner that is a modification to a standard burner. LowNOx burners modify the method of the introduction of air andfuel to mix the air and fuel in stages.

non-point sources Known as fugitive or secondary emissions that are not, andcannot be, economically collected through control or exhaustsystems.

normal boiling point The temperature at which an element or compound boils atatmospheric pressure.


Air Quality


particulates Any dispersed solid in which individual aggregates are largerthan single molecules but smaller than 100 microns.


Air Quality


point sources Emissions released as part of normal operations from a readilyidentifiable location.

predictive modeling The use of a mathematical model to predict the dispersion, andsubsequent ground level concentration of air impacting agentsfrom facilities and operations.

process control If a specific process can or does emit a specific impacting agentof

monitoring concern, continuous analysis of a particular stream can be usedto adjust the process variables through the computerized processcontrol system.

SCREEN2 SCREEN2 is a simplified predictive model that is used in theearly development of a new project.

SES Source Emission Standards

smokeless flaring An emission control technology in which steam is injected into aflare to reduce visisble emissions.

storage tank An emission control technology that is used on floating rooftanks.

secondary seals Floating roof tanks have a primary seal between the floating roofand the shell of the tank. By adding a secondary seal, the vaporsare contained and the emissions are significantly reduced.

tail gas treatment An emission control technology that removes low concentrationsof SO2 from process off-gases such as the off-gas from thecatalytic regenerator in a catalytic cracker.

thermal oxidizers An emission control technology that uses high combustiontemperatures to convert gases, vapors, and, to a limited extent,particulates to carbon dioxide and water.

vapor recovery An emission control technology that recovers valuablesystems hydrocarbons and/or removes toxic compounds from a gas

stream before the gas stream goes to a flare or to the atmosphere.

vapors The gaseous phase of elements or compounds that normally existin a liquid or solid state at ambient temperature and atmosphericpressure.

air quality.pdf

Documents

production related emissions

marketing related emissions

emission sources

technical material

ambient air quality

relevant standards

ambient airquality

additional information