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Mercury managementin petroleum refiningAn IPIECA Good Practice Guide

OperationsGood PracticeSeries2014

www.ipieca.org

The global oil and gas industry association for environmental and social issues

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Mercury management in petroleum refiningAn IPIECA Good Practice Guide

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MERCURY MANAGEMENT IN PETROLEUM REFINING

Contents

Executive summary 1

Introduction and background 3

Forms of mercury 6Elemental mercury (Hg0) 6

Mecury sulphide (HgS) 6

Mercury sulphate (HgSO4) 7

Mercury mercaptides (RS-Hg-SR) 7

Organic mercury (R-Hg-R or R-Hg-X) 7

Mercury salts, such as mercury chloride (Cl-Hg-Cl) 8

Summary of mercury types 8

Analytical methods and challenges 8

Mercury concentrations in crude oils andcondensates 9

Mercury fate in refining 12Tracking mercury input to a refinery 13

Potential accumulation of mercury in process equipment 14

Worker health and safety 15Potential health effects on humans 15

Examples of occupational exposure limits for mercury 15

Potential exposure routes in refineries 16

Exposure control measures 17

Personal protective equipment 17

General approach to the health impacts of mercury 19

Exposure monitoring and sampling 19

Hazard communication and worker training 20

Safe work practices 20

Process safety 21

Environmental considerations 23Waste water treatment 23

Solid waste 24

Product stewardship 25

Mercury removal technologies 26Mercury removal from waste water 26

Conclusion 27

IPIECA fact sheet on mercury 28

References 30

This Guide provides an overview of mercurymanagement in petroleum refining, describinggood practices and strategies related toenvironmental controls, worker health andsafety, process safety, product safety and wastemanagement.

Mercury occurs naturally in soil and rock and isalso released into the environment by volcaniceruptions. For the past 150 years, increasedhuman industrial activity has also generatedsignificant environmental releases of mercury. Arecognized toxin, exposure to mercury can resultin adverse human health effects ranging fromacute to chronic. Mercury has a range of formswith varying levels of toxicity.

In 2009, the United Nations EnvironmentProgramme (UNEP) promoted a global initiativeto limit and mitigate anthropogenic mercuryemissions in order to protect human health andthe environment, which in 2013 culminated inthe Minimata Convention.

As part of the UNEP initiative, the oil and gassector assisted in the generation of data onmercury releases from its activities. In 2012,IPIECA published the largest publicly availabledataset on mercury levels covering 446 crude oilsand condensates. IPIECA data indicates therefining sector’s contribution to global mercuryemissions is 0.07% of the total global mercuryreleases to air, and less than 0.01% to water.Although mercury releases from refining aresmall, they should be managed appropriately andin accordance with local laws and regulations.

This Guide provides a brief review of the varyingforms of mercury and the chemical reactions thatcan cause them to interchange, with particularreference to mercury in the refining process. Itreviews studies into the fate of mercury once itenters a refinery as well as it examines thehuman exposure to mercury and the potentialhealth impacts, providing examples of exposurelimits and exploring potential specific exposureroutes in refineries. Exposure control measures;

1


Executive summary

personal protective equipment; a generalapproach to the health impacts of mercury;exposure monitoring and sampling; hazardcommunication and worker training; and safework practices are briefly described.

Any workplaces handling mercury shouldimplement appropriate procedures for wastemeasurement, analysis, treatment and disposal,which should be incorporated into a specificMercury Waste Management Procedure orincluded in existing waste management plansor procedures. If mercury-containing waste isto be transferred to a third party for handlingand disposal, the refinery should confirm thatthe third party is appropriately qualified forthese tasks.

Refineries sell many products, and this Guideemphasizes the importance of stewardshipacross the supply chain. In assessing product-related risks, each refinery should consider thestewardship issues for both their finishedproducts and the intermediates sold to othermanufacturers. For intermediates, refineryproduct safety becomes process safety inanother plant.

There is currently only one proven technology toremove mercury from crude oil and condensates,and accordingly most mercury removal occurs inrefinery processes or in treating refineryproducts and effluents. The Guide offers a briefdiscussion of treatment options, with an addedfocus on mercury removal from wastewater.

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Introduction

This IPIECA Guide describes good practices andstrategies used to manage mercury in thepetroleum refining industry. The Guideaddresses practices concerning environmentalcontrols, worker health and safety, processsafety, product safety and waste management.

Although mercury concentrations are less than2 parts per billion (ppb) in most crudes, mercuryhas the potential to accumulate and causeoperational issues in refining facilities. The industryhas developed a range of technologies andsolutions to manage this challenge effectively.

In this report, IPIECA recommends goodpractices such as:l knowing the mercury content of the crude oil

entering refining facilities; l monitoring to assure a safe workplace for

workers;l taking appropriate precautions during

operations and maintenance work;l the use of mercury removal units (MRUs),

when appropriate; andl following proper waste management

procedures.

These good practices are a collection ofoperational, equipment and procedural actionsrelated to mercury management in petroleumrefining. Since each refinery is uniquelyconfigured, some of these practices may or maynot be applicable at each specific refinery.

Background

Mercury is a natural component of the Earth.The average concentration of mercury in theEarth’s crust is approximately 0.05 mg/kg(50 wt ppb), but there are significant localvariations (UNEP, 2002).

Mercury sulphide, HgS, is the most common formof mercury in nature (USGS, 2003). Mercurysulphide is among the least mobile and moststable forms of mercury. However, it decomposesat high temperatures, releasing elemental mercury.It is also converted biologically under anaerobicconditions into organic mercury species.

Once mercury enters the biosphere, it becomespart of a mercury cycle, as illustrated in Figure 1.Mercury, in its various forms, can cycle betweenthe atmosphere, water bodies and sediments. Itcan be carried over long distances from itssource, mainly via air and/or water.

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Introduction and background

Figure 1 Mercury cycle in the biosphere

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ce: U

SGS,

200

3

The variation of mercury in the biosphere overtime has been discussed in multiple literaturestudies. One specific study is highlighted here inFigure 2, from the U.S. Geological Survey (USGS).This graph illustrates the variation in mercuryconcentrations within a glacier in the westernUSA, which is indicative of the variation ofmercury in the local atmosphere.

In Figure 2, time is shown on the y-axis, whilemercury levels within the glacier core areexpressed on the x-axis. The units of measure arenanograms per litre, which is equivalent to partsper trillion by weight for a liquid with a specificgravity of 1.

As illustrated, mercury levels in the biosphereundergo significant changes from year to year.For example, there are three spikes due tovolcanic activity, which are shown in blue. Therewere two distant Indonesian eruptions in the1800s (Tambora and Krakatau) plus a smallereruption in 1980 (Mt. St. Helens). This illustratesthe important point that volcanic activity is akey source of mercury in the biosphere.

Also of interest is the period highlighted in thegold colour, which represents the gold rush inthe western USA. Mercury was widely usedduring the gold rush because of its ability toreact with trace quantities of gold, and torelease the gold when heated. The USGS hascited estimates that more than 10,000,000pounds of mercury were released to theenvironment in California during the gold rush(USGS, 2005). Artisanal gold mining in somecountries has been unregulated and is a majorfocus of the UN mercury treaty signed inOctober 2013.

The red portion in Figure 2 is attributed togeneral releases of mercury due toindustrialization. The impact of industrializationis a key driver behind the current focus onhuman activities related to mercury.

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The growth ofindustrializationsince the 1900s is akey driver behindthe current focus onanthropogenicmercury emissions.

Figure 2 Mercury data from glacier samples

Sour

ces:

USG

S, 2

002

and

Shus

ter,

2002

The United Nations Environmental Programme(UNEP) recently updated its estimates ofcontributions from human activities to annualglobal emissions to air (see Figure 3). The figureshows that artisanal and small-scale gold miningrepresents the largest contributor to mercuryemissions. The burning of coal represents thesecond largest contributor.

UNEP’s estimates include two emissions relatedto oil and gas: direct combustion of oil andnatural gas, and oil refining. Each represents lessthan 1% of total anthropogenic emissions.

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UNEP’s estimates ofemissions to air fromhuman activitiesshow that artisanaland small-scale goldmining is the largestsingle contributor tomercury emissions,while oil and gasindustry emissionsfrom refining andthe combustion ofoil and natural gasconstitute less than1% of totalanthropogenicemissions.

Figure 3 Relative contributions to estimated emissions to air from anthropogenic sources in 2010

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ce: U

NEP

, 201

3

Mercury-cell chlor-alkali industry

Disposal of waste frommercury-containing products

Cremation

Coal combustion

Primary ferrousmetal production

Oil and naturalgas combustion

Primarynon-ferrousmetal(Ai, Cu, Pb, Zn)

Large-scalegold production

Hg productionCementproduction

Oilrefining

Contaminatedsites

Artisanal andsmall-scale

gold production

Although mercury’s vapour pressure is highrelative to other heavy metals, it is actually lowerthan most liquids. For example, elementalmercury has a much lower vapour pressure thanliquid water; laboratory studies have shown thatdroplets of mercury do not evaporate quicklyinto air (Winter, 2003). This is an important factorwhen responding to mercury spills. In general,droplets should be left undisturbed until they canbe dealt with by appropriately trained personnelusing appropriate procedures and equipment.

Elemental mercury exhibits different behaviourwhen it is mixed with hydrocarbons. This isdiscussed later.

Mercury sulphide (HgS)

Mercury sulphide is the predominant form ofmercury in nature. This is due to the strongaffinity of mercury and sulphur.

At room temperature, mercury sulphide is asolid. It has very low solubility in either water orhydrocarbon. The solubility has been estimatedto be less than one part per quadrillion. Theaffinity of mercury for sulphur is so high, and thesolubility of mercury sulphide in water is so low,that samples of pure mercury sulphide createdby simple mixing of mercury with sulphur havepassed EPA leachability tests (Lopez, 2010). Thisstrong affinity may be important in determiningmercury’s behaviour in the sulphur-richenvironment that exists within many refineryprocesses.

Mercury occurs naturally in soil and rockthroughout the earth’s crust, including theformations that comprise oil and gas reservoirs.Mercury occurs at varying concentrations, and invarious forms. A brief review of the forms ofmercury, as well as the reactions of each form, isgiven below. These reactions are importantbecause of the potential for mercury to changeforms during the refining process.

Elemental mercury (Hg0)

Elemental mercury is the shiny silver-colouredliquid that most people think of when they hearthe word ‘mercury’ (Figure 4). However, it is notthe most common form of mercury, and isunstable in the presence of sulphur and somesulphur compounds. When exposed to thesecompounds, elemental mercury will formmercury sulphide.

Elemental mercury has some properties that areunusual for a heavy metal. For example, it isliquid at room temperature. Another unusualproperty of elemental mercury is its vapourpressure: unlike most heavy metals, mercury hasa measurable vapour pressure at roomtemperature (Table 1).

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Forms of mercury

Figure 4 A droplet of elemental mercury

Table 1 Vapour pressure of elemental mercury

Temperature Vapour pressure°C

0°

20°

40°

60°

°F

32°

68°

104°

140°

Pa

0.027

0.17

0.86

3.5

psi

0.00004

0.0002

0.001

0.005

Sour

ce: U

NEP

, 200

2

Sour

ce: U

.S. N

IST

(Hub

er, 2

006)

However, when heated with a torch, such asduring hot work1, mercury sulphide will begin todecompose, liberating elemental mercury.

Mercury sulphide has lower toxicity than mostother forms of mercury. Due to its low solubilityin water, exposures are very low. In fact mercurysulphide was often used to make jewellery andornamental plates.

As described later in this report, mercurysulphide may be the predominant form ofmercury leaving most refineries.

Mercury sulphate (HgSO4)

Mercury sulphate is considered to be animportant part of the mercury cycle in thebiosphere. In open water bodies such as lakesand rivers, sulphate-reducing bacteria may playa role in the creation of organic mercury species.

However, the chemistry of refining does nottypically involve the oxidation conditions thatwould lead to sulphate formation. For example,many key processes within refineries are carriedout in the presence of hydrogen, and convertsulphur-containing molecules to sulphides.Sulphates are not stable in these refineryprocesses. There are no available data to indicatethat mercury sulphates exist in refineries.Sulphates are not discussed further in this report.

Mercury mercaptides (RS–Hg–SR)

Mercury mercaptides are formed whenmercaptans2 (thiols) react with mercury. Themost commonly cited way to make mercurymercaptides is the reaction of ionic mercury(Hg2+) with light mercaptans. For example, a

1961 paper discusses an analytical method fordetermining mercaptan concentrations bytitrating with an aqueous solution containingHg2+ (Fritz and Palmer, 1961).

The prevalence of mercaptans, plus the relativeinstability of mercury mercaptides, mayinfluence the behaviour of mercury within arefinery. However, mercury mercaptides aremuch less stable than mercury sulphide. Whenthe mercaptides decompose, the end productsmay be elemental mercury and disulphides.Mercury mercaptides may be too unstable to bepresent in refinery products or waste streams.

Organic mercury (R–Hg–R orR–Hg–X)3

Light organic mercury species, such as dimethylmercury, are liquids that are somewhat soluble inboth water and oil. In the environment, methylmercury appears to be the most common form,as dimethyl mercury is relatively unstable.Methyl mercury is an ion, soluble in water.

Light organic mercury species are believed to beamong the most toxic forms of mercury.Literature papers suggest that the toxicity ofthese forms of mercury is due to their ability todissolve in, and ultimately pass through, cellmembranes and tissue.

Species such as methyl mercury and dimethylmercury are the result of organic processes, suchas those that exist within the tissue of algae andfish. The tendency of biological processes tomethylate mercury is one key reason whyregulators want to limit total mercury in thebiosphere. There are limits on the organicmercury concentrations in fish and seafoodintended for human consumption. These limits

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1 Hot work is any activity that creates heat, flame, sparks or smoke.2 Mercaptan: from the Latin mercurium captans, meaning ‘seize mercury’ (CDC.gov)3 X is indicative of non-organic matter, e.g. Cl- (chloride) and R indicative of organic matter, e.g. CH3.

are typically on the order of 0.5 to 1 part permillion (500 to 1000 ppb).

IPIECA members have never observed light organicmercury species being a product of refiningprocesses. In fact, the nature of refinery processeswould tend to destroy, rather than create, lightorganic mercury species. However, good wastemanagement practices are directed towardsavoiding biologic conversion in the environment.

Mercury chloride (Cl–Hg–Cl)

Mercury can also exist in the form of mercurychloride, HgCl2. Pure mercury chloride is a whitecrystalline material.

Mercury chloride and mercury sulphide are bothexamples of inorganic mercury. Some literaturestudies lump them together under the label ofinorganic mercury, but this may overlook thesubstantial differences between the propertiesof the chloride vs. the sulphide.

Mercury chloride is quite soluble in water (morethan 1% by weight), and can form a number ofspecies depending on the other ions present. Itis also somewhat soluble in hydrocarbon, andsomewhat volatile.

It is not clear how much mercury chloride couldpersist within a refinery. Mercury chloride is veryreactive with sulphur, including mercaptans andH2S, which are common components in manyintermediate refinery streams.

The instability of mercury chloride wasdemonstrated, for example, by a hygienist inQuebec (Pare, 1966). IPIECA is not aware of anydata showing that mercury chloride iscommon in refineries.

Summary of mercury types

This section has presented a brief summary ofsome of the types of mercury that may exist innature or within a refinery. The discussionincluded brief mention of some of the chemicalreactions that can cause mercury types tointerchange.

The two species of mercury that are believed tobe prevalent in refineries are elemental mercuryand mercury sulphide.

This will serve as background for the goodpractices discussed later.

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For example, one common test method can bedescribed as a four-step process: (1) convertingall forms of mercury to elemental mercury;(2) capturing the elemental mercury via areaction with a gold film; (3) releasing themercury from the gold film via heating; and(4) measuring the total mercury that is emitted.This method is useful but does not provideinformation about which species of mercury mayhave existed in the original sample. This is one ofthe drivers behind ongoing research onimproved analytical methods.

As described in the previous section, mercurycan exist in several forms, such as elementalmercury or mercury sulphide.

Analytical techniques for detecting mercuryhave improved in recent years, but it isimportant to note that the most commonanalytical tests report the total concentration ofmercury, not the concentration of individualspecies. This is particularly true for the tracemercury concentrations that exist within thehydrocarbon streams in a refinery.

Analytical methods and challenges

In 2009, UNEP’s Governing Council agreed tobegin negotiations on a legally bindinginstrument on mercury. The Council asked itsExecutive Director to convene anintergovernmental negotiating committee (INC)with the mandate to prepare that instrument.The INC process included five sessions (INC 1through INC 5) over the time period from June2010 to January 2013.

At the INC 2 session in January, 2011, the INCrequested that the UNEP Secretariat prepare adocument on the releases of mercury from theoil and gas sector. After preparing a draft report,the UNEP Secretariat invited IPIECA and othersto comment. IPIECA provided comments anddata to the UNEP Secretariat, and IPIECArepresentatives were invited to presentcomments and data at the Technical BriefingSession of the INC 3 meeting in Nairobi, Kenya,in October 2011.

In support of the INC process, IPIECA requestedthat its members provide data on the mercury

levels in crude oil. The purpose in assemblingthis data was to document the amount ofmercury in crudes, and to help resolveuncertainties around the mercury levels in crudeoils and condensates.

The IPIECA data set, which included a total of446 crude oils and condensates, is summarizedbelow. For each crude oil, the mercurymeasurement in the IPIECA database is the bestassessment of the typical mercury content,according to the IPIECA member who providedthe value for that crude. The majority of theIPIECA data were generated during the2007–2011 timeframe. The analytical methodsused in generating the data were deemedcomparable to an older UOP4 method,UOP 938-00 (UOP, 2000), or a newer ASTM5

standard method, D7623-10 (ASTM, 2010).

More details about the data can be found on theIPIECA website and in Doll et al., 2012. Theoverall distribution of mercury in crude oil fromthe IPIECA data set is summarized in Figure 5.

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Mercury concentrations in crude oils and condensates

Figure 5 Range of mercury levels in global crude grades (summarized from the IPIECA dataset, which includes 446 crude assays)

4 Formerly known as Universal Oil Products llp, UOP is a leading international supplier and licensor for the oil and gas industry.5 ASTM International (formerly known as the American Society for Testing and Materials) is a globally recognized leader in the development and delivery of

international voluntary consensus standards.

Statistics

Range (ppb) Count %

!2 284 64

2–5 68 15

5–15 42 10

15–50 33 7

50–100 6 1

>100 13 3

446 100%

! 2 ppb

2–5

5–15

15–50

50–100

> 100 ppb

This chart and the corresponding statistics havenot been adjusted for the production volumes ofthe various crudes. For example, many of thecrudes that are below 2 ppb of mercury arehigh-volume crudes from large fields in theMiddle East, while some of the crudes above100 ppb are from small fields in other parts ofthe world. Considering the production volumes,IPIECA data suggests that the 13 crudes thatcontain more than 100 ppb of mercury make upless than 1% of the global volume of crude oilproduction.

There are regional differences in the range ofmercury concentrations within the IPIECA dataset, as illustrated in Table 2.

The Middle East shows the lowest mercurylevels, with 79% of crudes from this regionshowing less than or equal to 2 ppb of mercury.No Middle East crude in this dataset is above15 ppb of mercury.

Countries in the Pacific and Indian Ocean regionrepresent the highest mercury levels, with 30%above 15 ppb, and 8% above 100 ppb.

In order to estimate the global average mercuryconcentration in crude, IPIECA has updated acalculation that was first done by Mark Wilhelmand co-authors (Wilhelm et. al., 2007).

The study by Wilhelm estimated the totalmercury in crude oil refined within the UnitedStates. This was done by first calculating thesimple arithmetic mean mercury level of knowncrudes from individual countries. This wasmultiplied by the volume of crude imported intothe USA from that country. The sum of thesevalues was calculated, and divided by the totalestimated refinery input.

For example, the numeric average mercury levelin crudes coming from Saudi Arabia wasestimated by Wilhelm to be 0.9 parts per billion,and the volume of crudes imported to the USAfrom Saudi Arabia was estimated to be547,000,000 barrels in 2004. Wilhelm did thiscalculation for each country, but limited hisscope to the crudes and crude volumes importedinto the USA. Using this methodology, Wilhelmestimated that crude oils refined in the USA hada mean mercury concentration of 3.5 wt ppb.

IPIECA has extended Wilhelm’s methodology inorder to calculate a global estimate. Thisinvolved using the more extensive IPIECA dataset for mercury concentrations in crude oil (Dollet al., 2012), and the total production of crude oilby country (as assembled by the PetroleumAssociation of Japan) as opposed to Wilhelm’sfocus on only the crude imported into theUnited States.

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Table 2 Regional breakdown of mercury in crude

Cruderegion

Count Median Hg level(ppb)

!2 ppb 2–5 ppb 5–15 ppb 15–50 ppb 50–100 ppb >100 ppb

Africa 90 1.0 72% 15% 9% 3% 1% -

Eurasia 95 1.2 74% 10% 6% 4% 1% 5%

Middle East 34 1.0 79% 18% 3% - - -

North America 95 1.2 64% 21% 9% 6% - -

Pacific and Indian Ocean

93 3.0 41% 13% 16% 18% 4% 8%

South America 39 1.4 69% 12% 8% 8% - 3%

Percentage of crudes and condensates containing specific ranges of mercury (ppb of mercury)

The IPIECA calculation was:

‘condensate’ as opposed to calling it a ‘crude’. Insome cases materials called ‘condensates’ maynot fit the typical engineering definition of theword, which involves something that hascondensed from the vapour phase to form aliquid. Because of the inconsistent use of theword ‘condensate’, caution must be used inassuming that ‘condensates’ share any particulartrait, such as containing specific levels of mercury.

In the IPIECA data set, self-identified‘condensates’ show only slightly elevated levelsof mercury compared to non-’condensates’. Forexample, 52% of the ‘condensates’ are above2 ppb of mercury, compared to 35% of thenon-‘condensates’. However, even for‘condensates’, the majority are below 5 ppb ofmercury (Table 3).

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Table 3 Mercury in ‘condensate’ vs. non-’condensates’

Percentage of crudes and condensates containing specific ranges of mercury (ppb of mercury)

Count Median Hg level(ppb)

!2 ppb 2–5 ppb 5–15 ppb 15–50 ppb 50–100 ppb >100 ppb

‘Condensates’ 51 2.4 48% 14% 14% 12% 8% 4%

Non-’condensates’ 395 1.3 65% 15% 9% 7% 1% 3%

where GWA is the global weighted averagemercury concentration, MassC is the mass ofcrude produced by an individual country ‘C’, andHg—C is the simple arithmetic mean of themercury concentration in crudes produced in agiven country.

According to this methodology, the weightedaverage mercury content of the global crudesupply is 7.5 wt ppb. This is higher than the3.5 ppb value estimated by Wilhelm et al. forcrudes processed in the USA. The difference islargely driven by the fact that refineries in theUnited States process large quantities of crudesfrom the USA, Canada, Mexico and the MiddleEast, where average mercury levels are low. Theglobal refining industry processes additionalcrudes that are higher in mercury content.

The IPIECA estimate for global crudes,7.5 wt ppb, is much lower than the 55 ppboriginally estimated by UNEP as part of their2011 ‘Mercury Toolkit’ methodology.

It is important to note that, in the above analysis,both crude oil and ‘condensate’ are included. The‘condensate’ label is used here in the same waythat it is used in the commercial crude oilmarket. Different crude suppliers may havedifferent criteria for labeling their product as a

Waste

Refined products

Air emissions

Petroleum coke

Water discharges

A number of studies have been published whichexamine the fate of mercury once it enters arefinery. One example is the Western StatesPetroleum Association (WSPA) study of mercuryin five refineries in the San Francisco, USA region(WSPA, 2009).

In the WSPA study, multiple samples of the feedto each of seven refinery crude units wereanalysed. The mercury levels in the feeds werefound to range from 1.5 ppb to 19 ppb. Thestudy attempted to determine the mercury massbalances at the five San Francisco refineries. Theresults are shown in Figure 6 which indicatesthat the majority of the mercury left therefineries in waste streams. Small amounts ofmercury were found in refined products or wereemitted to the air, and smaller amounts werefound in petroleum coke and waste water.

The WSPA study relied in part on literature data.Several literature studies are available, including:l ‘Ft. McHenry Tunnel Study: Source profiles

and mercury emissions from diesel andgasoline powered vehicles’ (Landis, 2007);

l ‘Estimate of mercury emission from gasolineand diesel fuel consumption, San FranciscoBay area, California’ (Conaway, 2005); and

l ‘Mercury emissions from automobilesusing gasoline, diesel, and LPG’ (Won, 2007).

The studies agree that only trace levels ofmercury, typically less than 1 ppb, are found ingasoline and diesel fuel.

While the WSPA study is useful, it might notapply to all refineries, and further study may bejustified. Any future study should consider notonly the amount of mercury entering a refinery,but also the amount of sulphur.

Some refineries process crudes that contain verylittle sulphur. As already described, several formsof sulphur have a strong affinity for mercury.Low-sulphur refineries may have a tendency toaccumulate deposits of elemental mercury. Onthe other hand, refineries that process high-sulphur crudes may have a tendency toaccumulate mercury sulphide, which has lowvolatility and solubility.

Some refineries process crudes which containhigher levels of mercury (for example 50 wt ppbor more). IPIECA members have noted that suchrefineries may see increased levels of elementalmercury, as opposed to mercury sulphide. Whenmixed with hydrocarbons, elemental mercurybehaves very differently from how it does in air.In particular, elemental mercury tends to showan apparent vapour pressure similar to that oflight hydrocarbons such as propane and butane.Hence, crudes that are high in elementalmercury may cause elevated levels of mercury inthe overheads of crude distillation units, and inlight streams such as LPG.

Mercury’s behaviour is affected when refineriesrun mixtures of crudes and at least some of thecrudes are high in sulphur (for example, >1 wt %sulphur). This sulphur has at times causedmercury to appear in streams such asatmospheric residuum, as well as the light ends.

In these cases, secondary conversion units likecokers or other resid crackers might re-convertthe mercury to more volatile species. Suchvolatile species would again tend to migrate

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Mercury fate in refining

Figure 6 Example of a mercury mass balance for five refineries in theSan Francisco region

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ce: W

SPA

, 200

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Process water

LPG

WSR

LGO

HGO

AGO

VGO

Crude

FCC feed

Wastewatertreatment

Vac Resid

ATMresid

Non-volatileHg

Desalterwater

VolatileHg

AtmO/H

VacO/H

VAC

Desalter ATM

STA

B

towards the overhead sections of fractionationtowers, and into light product streams.

IPIECA members’ experience is that the mercuryfound in streams such as LPG is amenable totreatment using commercially available mercuryremoval units.

Mercury can also show up in refinery sulphur andsulphur-derived products such as sulphuric acid.

Tracking mercury input to a refinery

The data summarized above show that mercuryexists in varying concentrations in crude oils andcondensates from all regions of the world.

The amount of mercury within the variousstreams and products in a specific refinerydepend strongly on the mercury content of therefinery’s feed streams. Hence, each refineryshould be aware of the mercury level of itsincoming feedstocks.

As discussed later in this report, refineries needto protect workers, equipment and customersfrom the potential impacts of mercury. Oneapproach to minimize potential mercuryaccumulation is to have an approved ‘mercuryoperating envelope’ where refineries can applyacceptance criteria to limit the intake of mercuryinto their processes. A simple example of amercury envelope could be:

‘the mercury content of incoming crudesto refinery X will be less than 10 wt ppb, ona month-average basis, and no individualcrude should exceed 100 wt ppb’.

Maintaining operations within an approvedoperating envelope may help to assure propercontrol of mercury impacts. The envelope shouldbe subject to a management-of-change process,so that deviations outside of the envelope aremade only after considering the potentialimpact on workers, equipment, customers, etc.

Mercury, like other trace elements present incrude, may accumulate slowly over time inprocess equipment, and may be present invarious waste streams or internal metal surfacesin selected equipment as the result of years ofaccumulation. This is especially true for areas ofthe process that may experience poorcirculation. Figure 7 provides a simplifiedexample of where mercury may distribute/accumulate in a refinery.

A refiner could track the mercury in its feeds inmultiple ways. A multi-tiered approach might beconsidered, such as:1. Assuring that the crude assays used for

purchasing decisions include mercury as oneof the crude properties. These assaymeasurements might be updated on aninfrequent basis, for example when majorchanges in production occur, but they areessential to establish a baseline for a mercuryoperating envelope.

13


Figure 7 The most common mercury distribution paths in hydrocarbons and water

6 Total accumulations may be higher assuming the average time between turnarounds is between 3–4 years. Typical crudes are1–10 µg/kg mercury; API gravity assumed was 32°. Crudes with elevated mercury tend to be lighter; API gravity assumed was 45°.Accumulation estimate is based on the assumption that 20% of the mercury in the incoming crude accumulates in the processequipment or associated wastes. In addition, plants need to consider that units have been in place for many years, and may havepre-existing accumulation of mercury, including equipment downstream of MRUs.

2. Performing additional, periodicmeasurements on crudes known to containmercury, or that are relevant for confirmingthat the refinery is within its operatingenvelope. These measurements might bedone on a scheduled basis, such as multipletimes per year.

3. Performing frequent measurements on anycrude known to contain an elevated level ofmercury, for example if the crude is known tocontain more than 100 ppb of mercury.(IPIECA member experience shows that suchcrudes can show significant variation fromcargo to cargo.)

The specific method used by a refinery must befit for purpose, and should be based on thatrefinery’s specific circumstances.

Potential accumulation of mercuryin process equipment

It is important to note that mercury canaccumulate in refining equipment even whengood operating practices and feed stock controlsare implemented. Table 4, illustrates thepotential accumulation of liquid mercury in a‘small’ or ‘large’ refinery. Figure 8 is an exampleof the logic that could be used to monitor andmitigate the potential for accumulation.

IPIECA

14

Table 4 Comparison of annual mercury accumulation for range of concentrations in a ‘small’ and ‘large’ refinery6

Potential annual accumulation

Mercury in crude, µg/kg (ppb) 1 µg/kg 10 µg/kg 200 µg/kg

50,000 bbls/day — ‘small’ refinery 0.5 kg/year 5 kg/year 90 kg/year

250,000 bbls/day — ’large’ refinery 2.5 kg/year 25 kg/year 450 kg/year

Figure 8 Logic for selecting focus areas during turnarounds

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Potential health effects on humans

The different forms of mercury are toxic, tovarying extents. Exposure to humans canhappen via inhalation, via contact with skin andeyes, or via ingestion. Depending on theduration of the exposure, different toxic effectsare distinguished, ranging from acute to chronic.The toxic effects have been described in detailby the World Health Organization (WHO, 2007),among others.

High short-term exposures to metallic mercurymay cause lung damage, nausea, vomiting,diarrhoea, increases in blood pressure or heartrate, skin rashes and eye irritation. Whilefrequent repeated exposures to lowconcentrations mostly target the nervous systemaffecting the brain, this type of exposure mayalso affect the kidneys and developing fetus. In

general, it should be noted that mercury’s half-life in adults is long, i.e. months, thus even lowexposures repeated monthly could result in theaccumulation of mercury in the body atpotentially toxic levels.

Examples of occupational exposurelimits for mercury

Due to the toxic effect of mercury, somecountries and authoritative bodies haveestablished occupational exposure limit values.These values vary by country and agency, asillustrated by the examples in Table 5.Companies generally adopt appropriatestandards for their medical surveillanceprogrammes. Additionally, companies complywith national, regional or local regulatoryrequirements, whichever is more stringent.

15


Worker health and safety

Table 5 Examples of occupational exposure limits for mercury

UK WEL(Workplace

Exposure Limits)

DFG MAK (German Research

Foundation)The Netherlands

US ACGIH (AmericanConference of Governmental

Industrial Hygienists)

US OSHA (OccupationalSafety and Health

Administration

Elemental andinorganic mercury0.02 mg/m3

(8 hours)


(8 hours)


(8 hours)

Alkyl mercury1.1 mg/m3

(8 hours)

1.2 mg/m3

(15 minutes)

Methyl mercury0.01 mg/m3

(8 hours)

0.1 mg/m3

(15 minutes)

Organic mercury forms0.01 mg/m3

(8 hours)

0.03 mg/m3

(15 minutes)


(8 hours)


(8 hours)

0.03 mg/m3

(15 minutes)

Aryl Mercury0.1 mg/m3

(8 hours)


(8 hours)


(8 hours)

0.04 mg/m3

(Ceiling)

Aryl Mercury0.1 mg/m3

(8 hours)

Potential exposure routes inrefineries

The most probable exposure risk for refineryworkers will be via inhalation of elementalmercury vapour. Because of the low vapourpressure of mercury compounds, airborneexposures will most likely be highest duringconfined space entry or when thecontaminated equipment is heated, forexample during welding.

Moreover, workers could have skin contact withelemental mercury and mercury salts duringopening or entry of equipment or handlingcontaminated parts. Potentially, workers inmercury adsorption process units could have anelevated risk of skin exposures during adsorberchange-out, draining equipment in preparationfor opening, draining low points in vessels orpiping, and other tasks involving opening. In allcases, it is unlikely that workers will absorbtoxicologically significant quantities of mercurysalts via intact skin as these workers should bewearing suitable personal protective equipment(PPE—see below under Exposure controlmeasures) to prevent not only contact withmercury but also with other substances such ashydrocarbons, caustics or acids.

As activities that involve potential exposure tomercury are typically related to process unitshutdowns and openings, the ordinary workerexposures are typically infrequent. Most refineryoperators and craftworkers working in non-mercury units will have infrequent, i.e. annual,exposures associated with unit shutdown andmaintenance. It is therefore unlikely that non-mercury unit workers would suffer the diseasesassociated with chronic, low-concentrationexposures. Nevertheless, it is prudent to ensurethat workers in plants with mercury in theprocess fluids are not exposed to chronic (oracute) concentrations, by providing medicalsurveillance examinations (see page 18).

IPIECA member experience shows a number ofareas where mercury might be detected within arefinery. Examples include:l desalter sludge/desalter tank bottoms;l crude units, crude distiller, crude unit gas

stabilizer, crude unit overhead gas splitters,crude oil tank bottoms;

l bundle cleaning sludge;l petroleum coke burning, petroleum coke;l waste polymerization catalyst;l waste adsorbent;l heavier residue fractions associated with

asphaltenes and mercuric sulphides;l lighter product streams such as gases, LPG or

naphtha;l amine and sulphur systems;l filters;l waste water treatment plant sludges and

sediments; andl decommissioned process equipment and

pipelines.

In addition to these specific areas where mercurymight be found, there are also specific activitiesthat could liberate mercury. Some examples ofrefinery activities that can create mercuryvapours are provided in a paper published by theNational Petrochemical & Refiners Association(Grice and Alvarez, 2011). One specific example,related to hot work, is shown in Box 1.

There can also be other sources of mercurywithin a refinery, where the mercury does notoriginate in the feedstock. Examples include:l instrumentation containing mercury,

including flow meters and barometers;l fluorescent lamps and high-intensity

discharge lamps;l electrical devices, including switches, relays,

batteries and thermostats; andl medical devices, including thermometers and

blood pressure gauges.

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16

Exposure control measures

As shown in Table 5 (page 15), variousoccupational exposure limits exist which aredesigned to protect workers from exposure tomercury. Mercury hazard control programmestypically apply a hierarchy of controls to prevent,reduce and maintain mercury and othercontaminant exposure at or below theapplicable exposure limit. Examples include:l Acceptance criteria for crude oil intake:

refineries can apply acceptance criteria for thecrude oil to limit the intake of mercury intotheir processes and subsequently reducepotential exposure of their workers to mercury.

l Design and engineering controls: forexample preventing bends in equipment andavoiding temperature drops; implementingflushing facilities for cleaning the internalcomponents of installations; utilizing exhaustsystems or ventilation to capture or dispersemercury vapour.

l Procedural control: identification of suspectedlocations of mercury; designating safe workareas; application of the permit-to-work(PTW) system; flushing; monitoring and

sampling to detect mercury and measure itsconcentration; employee training and hazardcommunication; shift work.

l Worker protection: if the above measures areconsidered insufficient, PPE and medicalsurveillance examinations can be provided tomaintain exposures below the exposure limitand to monitor potential actual exposures,respectively.

l Decontamination of equipment in case ofexposure.

A general approach is described below, togetherwith more information on some of the availablecontrol measures.

Personal protective equipment

The potential for mercury exposure, and thevarying exposure limits, result in the need for atiered approach to the use of PPE. An example isshown in Figure 9 (overleaf ). This example wasdeveloped by the Oil Companies InternationalMarine Forum (OCIMF) and applies to theshipboard handling of crude oil; however, it can

17


Box 1 Example of specific activities that can generate mercury vapours

Hot work, grinding and blasting on mercury impacted metals requiresspecial attention:

• Initial surface reading with vapour monitor may be zero—but onceheated, the vapour level may exceed >50 µg/m3.

• Adjacent impacted metals may be the exposure source on a largerpiece of equipment.

• Engineering controls such as a simple fan can help to control openair exposures—other techniques such as local exhaust ventilation,underwater welding, wet grinding/blasting and wet cutting mayoffer other control options.

• Air emissions may be a factor on downwind work areas.

Source: Grice and Alvarez, 2011

also be used as a guide for protection againstmercury exposure in refineries.

The OCIMF matrix involves, as a first step, themonitoring of mercury levels using a directreading instrument. OCIMF provides examples ofsuch devices, which include the ‘EMP 1-AMercury Gas Monitor’ (Nippon InstrumentsCorporation) and the ‘Jerome® J405 MercuryVapor Analyzer’ (Arizona Instrument LLC). Otheranalysers may also be suitable.

OCIMF’s recommendations for PPE depend onthe readings obtained from the analyser, andstate the following:

‘Personal protective equipment:The following respiratory protection andPersonal Protective Equipment (PPE) actionlevels are provided as an example of how risksof workforce exposure may be controlled whenwork is being undertaken in close proximity to

mercury vapour or when handling mercury-containing materials. It is recommended thatcompanies develop their own procedures toprotect personnel against exposure.’

Medical surveillance examinations

Medical surveillance examinations may cover thefollowing aspects:l Programme participation: pre-placement,

periodic, and end-of-duty examinations.l Biological monitoring considerations: urine

and/or blood sampling, timing, exposurehistory information, diet history, frequency oftesting, entrance and exit criteria.

l Medical removal provisions: handling ofbackground/dietary mercury, handlinghourly/daily variation in results,repeat/follow-up testing, including physicalexamination including signs/symptomsinformation.

l Emergency exposure provisions.

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18

This action-levelmatrix for PPE wasdeveloped by OCIMFfor the shipboardhandling of crudeoil, but can also beused as a guide forprotection againstmercury exposure inrefineries.

Figure 9 Example of an action-level matrix for PPE

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Personnel contaminated with mercury metal orother mercury compounds should seek medicalattention. Medical personnel might recommendsteps such as washing the eyes (if they wereaffected), removing contaminated clothing (ifclothing was affected), and appropriate testing toquantify the exposure (blood tests, urine tests, etc.).

General approach to the healthimpacts of mercury

A general approach to dealing with the potentialimpacts of mercury is given in the reportentitled, Guidelines on Mercury Management in theOil and Gas Industry, published in 2011 by theDepartment of Occupational Safety and Health(DOSH), Ministry of Human Resources, Malaysia.

The DOSH approach begins with a high-level riskassessment, as shown in Figure 10.

The risk assessments for mercury shouldconsider the locations where mercury might bedetected in a refinery. Once the risks have beenidentified, and PPE strategies have beenestablished, a health monitoring programmemay also be put into place. The DOSHrecommendations for a risk-based monitoringapproach is illustrated in Figure 11.

Exposure monitoring and sampling

Instantaneous elemental mercury readings inµg/m3 concentrations may be measured withinstruments such as the Lumex RA-915+,NICEMP 1A or Jerome® 431. Other analysers mayalso be suitable. Time-weighted averagepersonnel exposures may be collected usingadsorbent tubes, diffusion badges or filters(inorganic mercury) followed by laboratory

19


Figure 10 Example of a risk-based approach to dealing with mercury

Figure 11 Example of a risk-based monitoring approach 7

7 Acronyms are defined as follows: PEL = Permissible Exposure Limit; BEI = Biological Exposure Indices (the ‘BEI’ acronym is copyright ACGIH®); ALARP = As Low As Reasonably Practicable.

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analysis methods. Surface wipe sampling can bedone to assess contamination.

Precautions for identifying and testing forpotential contamination typically includesampling at selected locations such as gascompressors, the distillation column andoverhead coolers/exchangers.

Hazard communication and workertraining

Any workers who might potentially be exposedto mercury should receive appropriateinstructions and training. This should be part oftheir workplace hazard training, and should bestructured to enable them to prevent workplaceexposure and to respond appropriately tocircumstances within the specific refinery.

Examples of topics that might be covered duringtraining sessions include:l Material Safety Data Sheets (MSDS) for

mercury or mercury-containing materials, toprovide an understanding of the physicalproperties of mercury and the potentialhealth effects, such as the symptoms ofmercury exposure;

l exposure guidelines/limits;l locations where exposure to mercury may

occur in the workplace;l how to identify mercury contamination;l origin and consequence of mercury in plant

feeds;l measures used to control and/or monitor

potential mercury exposures;l description of mercury vapour monitoring

techniques;l signs used to identify areas where there is a

potential for exposure to mercury or itsassociated compounds, and the appropriateuse of warning labels;

l proper PPE selection and use;l basic chemistry of mercury;

l proper personal hygiene procedures (e.g.proper hand washing/decontaminationbefore eating, etc.);

l special precautions to minimize exposure,techniques for spill prevention, properprocedures for spill clean-up; and

l toxicity of mercury exposures.

Safe work practices

During refinery maintenance activities and otheroperations, situations may arise where thepresence of mercury is anticipated, or isindicated by measurement or visual inspection.During such events, specific areas should bedesignated for the application of dedicatedcontrols. A designated area might be as small asthe walkway near a specific manway, and placedunder appropriate controls until such time thatdirect measurements show the manway to befree of mercury vapours. At the other extreme,the designated area might be large, for examplebefore opening a low point drain that issuspected to contain elemental mercury.

It is advisable to be prepared with writtenprocedures, training and appropriate equipment,including procedures and capabilities to:l restrict and control access to a designated

area;l implement spill prevention and containment

procedures;l provide awareness training to personnel;l assure the availability of appropriate

instruments, tools and protective equipment;l implement decontamination procedures for

personnel and tools to prevent migration ofmercury out of the designated area; and

l implement spill clean-up procedures, ifneeded.

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20

In addition to personnel safety, there are alsoprocess safety aspects related to mercury.

A phenomenon known as liquid metalembrittlement (LME) can occur when someequipment is exposed to liquid elementalmercury. Equipment made of aluminium isespecially susceptible to LME.

LME has been the cause of multiple equipmentfailures within the oil and gas industry. Oneexample took place at the Moomba gas plant inAustralia, where a piece of cryogenic aluminiumequipment was unknowingly exposed to liquidmercury, leading to a metallurgical failure; asignificant rupture occurred (Figure 12) which ledto a loss of containment resulting in a fire.

21


Process safety

Figure 12 Metallurgical failure caused by liquid mercury Figure 13 Example of a decision tree for equipment risk minimization

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The following are examples of questions to beconsidered when dealing with potentialequipment issues:l How much mercury is (or was) present in the

feed to the plant?l What is (or was) the concentration of mercury

in the streams entering the aluminiumequipment?

l Is there an upstream dehydration system anddoes it perform to specification?

l Is there an upstream MRU and does it performto specification?

l Is the pressure drop across the equipmentconstant or increasing?

l Can mercury condense to a liquid or solidphase due to cooling, for example in a heatexchanger?

The potential for LME has led to a risk-basedprocess to minimize the risk to equipment, asdescribed in Wilhelm, 2009. Figure 13 shows anexample of this process.

Other metals besides aluminium are, to varyingextents, also susceptible to LME. These includebrass and copper alloys, which can often befound in water-cooled heat exchangers in crudeunit overhead systems.

l Are mercury deposits known to be present inthe heat exchanger?

l What is the amount and distribution of thecontamination?

l Do welds have backing rings?l Is liquid mercury in contact with aluminium

welds having a susceptible metallurgicalmicrostructure?

l At the locations of mercury deposits, arestresses present that have sufficientmagnitude to allow LME?

l What is the frequency of strain events (trips,shutdowns, upsets)? Are strains dynamic?

l How old is the equipment? Who made it andwhat are the construction details?

l What unusual operating procedures areemployed, for example methanol injection,derime (defrost) procedures, particulateintrusion, upstream chemical usage, etc.?

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Mercury is released into the environment bynatural processes such as volcanic activity. It isalso released from human activities such asmining and coal combustion.

Mercury is also released into the environmentduring the refining process, and from thecombustion of refinery products such asgasoline and diesel fuel. Direct contributionsfrom refining activities are small. IPIECA’s datasetindicates that the refining sector’s contributionto global mercury emissions is 0.07% of the totalglobal mercury releases to air, and less than0.01% to water. These estimates of mercuryemissions are lower than the estimatescontained in the 2013 UNEP global mercuryassessment. There are two reasons for this:1. The amount of mercury entering refineries is

lower than assumed by UNEP. The IPIECAdataset shows that the global averagemercury concentration in crude oil is 7.5 ppb.(The IPIECA calculations are discussed onpage 10.) This is substantially lower than the55 ppb assumed in the earlier UNEP work.

2. The amount of mercury leaving refineries viaair and water is lower than assumed by UNEP.This was demonstrated by the WSPA studydiscussed on page 12 (WSPA, 2009).

Additional details can be found in the IPIECA factsheet, Mercury in crude oil and contribution toglobal mercury emissions, which is reproduced onpages 28–29 of this Guide.

Although mercury releases from refining aresmall, it is still important to ensure that mercuryreleases are properly monitored and controlled.Some of these considerations are discussedbelow.

Waste water treatment

Refinery water effluents typically show very lowmercury concentrations, as long as the solidshave already been removed from the water.

Most of the mercury entering a refinery wastewater treatment facility will end up in the solidfraction (i.e. waste water treatment sludge). Thisis due to the chemistry and behaviour ofmercury. Most mercury in refinery water tends toassociate with particles rather than remaining insolution in the water. One IPIECA member hastested the particulates in waste water, andreports that the mercury was in the form ofmercury sulphide particulates.

23


Environmental considerations

The primary variable affecting mercury ineffluent water appears to be the amount ofsuspended solids. High levels of suspendedsolids in water streams can lead to an apparenthigh level of mercury in those same streams.This can be resolved by removing the solids.

The wastewater from a specific US refinery is thesubject of a detailed study by the ArgonneNational Laboratory. Initial results have beenpublished in Negri et al., 2011.

Solid waste

The following are some general principles thatapply to all refinery solid wastes:l Solid wastes from refineries need to be

identified, properly labelled, stored inappropriate waste containers, and disposed ofin an appropriate manner.

l If a particular waste stream has uniqueproperties and disposal issues, it should besegregated from other waste streams.

l If third parties are involved in handling anddisposing of waste, they must beappropriately qualified.

Mercurial solid waste originates from processunits dedicated to mercury removal, such asspent catalysts, rags and contaminated PPE. In arefinery running elevated-mercury crudes, otherwastes may also contain mercury. Mercurialwastes should be classified, disposed of andmanaged according to country regulations, e.g.in accordance with EU Directives (EU membercountries classify mercury as a hazardous waste,which is to be disposed of and managedresponsibly in specific plant facilities).

The potential presence of mercury is anothervariable in a refinery’s waste management system,but also fits within these general principles.

Waste streams should be analysed to determinewhether they contain mercury. If the waste doescontain mercury, the waste stream might requireclassification as mercury-contaminated waste,and hence might need to be collected anddisposed of appropriately. For example, somethird parties might use incineration as a meansto destroy refinery waste; this may not beappropriate for certain mercury-contaminatedwaste if the third-party facility doesn’t controlmercury in its waste gases.

Workplaces handling mercury waste shoulddevelop a Mercury Waste ManagementProcedure or integrate mercury waste into theirexisting Waste Management Procedure. Someexamples of essential considerations can befound in DOSH, 2011.

In few cases, the ‘waste’ may be a piece ofequipment, such as a length of pipe. Three waysto sample and determine whether material iscontaminated with mercury are:l non-destructive, in-situ, online measuring

using handheld X-ray fluorescence analysis(XRF, HXRF) that provides measuring resultsimmediately;

l ‘conventional’ sampling and sample analysisin a laboratory—a technique that is generallydestructive (e.g. it involves drilling a hole) andcannot be executed while equipment is still inoperation; and

l non-destructive assays for determiningmercury per area (quantity per area unity), forexample by using cotton swabs or viamercury check surface sampling.

If mercury-containing waste is to be transferredto a third party for handling and disposal, therefinery should confirm that the third party isappropriately qualified for such tasks.

IPIECA

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Refineries sell many products. Some products,such as gasoline, are sold directly to consumers.Other products are sold to other manufacturers,for example when propane is sold to a chemicalcompany as an intermediate product for use inthe manufacture of propylene and polypropylene.

The amount of mercury that might be found inthese products varies, as does the species ofmercury. In the case of lighter products such aspropane, the mercury might be in the form ofelemental mercury. In the case of heavyproducts such as petroleum coke, the mercurymay be in the form of mercury sulphide.

It is important to emphasize that when a refineryproduct is sold to be processed in anothermanufacturing process, the product safety issuebecomes a process safety issue in another plant.See page 21 for a discussion on process safetyand the potential effect of liquid mercury onsome equipment.

The mercury limits on feeds to some chemicalplants may be as low as 1–5 parts per billion.This is because some chemical plants containcryogenic aluminium equipment which could beaffected by liquid elemental mercury. For

example, olefin plants that generate propylenefrom propane often contain ‘cold boxes’ withlarge amounts of aluminium equipment. Someolefin plants have MRUs. However, some havealuminium equipment but lack MRUs, and couldtherefore be subject to process safety issues.

Thus, in assessing product-related risks, eachrefinery should consider not only the finishedproducts, but also the intermediates that aresold to other manufacturers. In some cases theseintermediates will be subject to stringentconstraints on mercury levels. A good practice isto have fit-for-purpose, agreed-upon constraintson mercury in these intermediate streams.

25


Product stewardship

Mercury removal technologies can be applied inrefineries. However, they are most applicable torefinery products and effluents; there is only oneproven technology for the removal of mercurydirectly from crude oil and condensates. Thistechnology is in use by one IPIECA member insouthern Argentina.

Mercury removal from hydrocarbon productstypically consists of a mercury removal unit, orMRU. MRU technology is available from severalvendors; an example is shown in thephotograph below.

MRUs typically consist of beds that are filled withan adsorbent. The words ‘adsorbent’ and‘absorbent’ are sometimes used loosely. In thecase of MRUs, there may be either a surfaceadsorption, or a chemical reaction, involvingmercury in the feed and sulphur in the adsorbent.

In some cases the beds might be arranged in alead-lag configuration, where the lead bed is theone that is actively removing mercury, while the

lagging bed is on standby, ready to be utilizedfor when the lead bed is spent.

Once a bed becomes spent (i.e. once it hasexhausted its capacity to remove mercury), thebed is taken out of service, and the adsorbentmaterial is removed and disposed ofappropriately. Some companies (e.g. JohnsonMatthey) offer a cradle-to-grave service, and willboth supply the material and handle the disposal.

Mercury removal from waste water

Mercury removal from waste water is discussedbriefly in the section on Environmentalconsiderations on page 23. The primary issuewhen treating waste water is the removal of anysolids from the water, because the mercury willtypically be associated with those solids. Ingeneral, conventional waste water treatmentsystems used by refineries have demonstratedan excellent capacity to remove solids andtherefore also remove the associated mercury.

Vendors offer water treating additives to assist inthe process of controlling mercury levels inwaste water. For example, Nalco offers a productcalled NalMet™, and G. E. Betz offers a productcalled MetClear™. In each case the vendor statesthat small amounts of the additive will help toensure that the mercury will be bound to solids,which can then be removed via settling orfiltration.

Solids from waste water treatment typicallycontain a variety of contaminants, as well astrace levels of mercury. These solids should bemanaged appropriately and in accordance withlocal laws and regulations.

IPIECA

26

Mercury removal technologies

Example of amercury removalunit (MRU)

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Mercury is present in trace levels in crude oil andcondensates. IPIECA data show that the majorityof the world’s crudes are low in mercury. Forexample, 64% of the crudes in the IPIECAdatabase show mercury levels of 2 wt ppb orless, although a small fraction of crudes (3%)contain over 100 wt ppb of mercury. On a globalbasis, IPIECA estimates that the weightedaverage mercury content of the global crudesupply is 7.5 wt ppb of mercury.

Mercury exists in several forms in nature, but thetwo species of mercury that are believed to beprevalent in refineries are elemental mercuryand mercury sulphide.

This Guide has highlighted some importantgood practices for managing mercury in therefining industry. Examples include trackingmercury in refinery input, assuring workerprotection via proper training and appropriateuse of personal protective equipment, havingfit-for-purpose constraints on mercury inproducts and intermediates, and assuringprocess safety via awareness of mercury’spotential impact on equipment.

27


Conclusion

Mercury in crude oil and contribution to global mercury emissions Mercury has become a focus of global scrutiny with the United Nations leading the negotiations to develop a legally binding global treaty on the control of mercury releases. In 2012 IPIECA published the largest publicly available dataset on mercury levels covering 446 Crude Oils and Condensates. UNEP has estimated global mercury emissions from many sources. As illustrated in the pie chart1, UNEP currently estimates the petroleum refining sector is responsible for 0.8% of the total anthropogenic emissions to air (this was revised downward from their earlier estimate of 2.4%)-this data does not incorporate IPIECA dataset.

Figure 1: 'Relative contributions to estimated emissions to air from anthropogenic sources in 2010', UNEP Draft Global Mercury Report 2012

IPIECA dataset indicates that Mercury concentrations in crude oil are lower than determined by UNEP. The is 0.07% of the total global mercury releases to air

estimate) and less than 0.01% to water . In a study of a number of refineries in California, U.S, the data showed that most of the mercury that enters petroleum refineries is removed as solid waste (87%).This proportion is representative of most refinery operations. The waste is then disposed of in accordance with local regulations.

(See reverse side for calculations and additional references.)

1 UNEP, Global Mercury Report 2013, DRAFT 13 November 2012

Disposal of waste from mercury-containing products

Contaminated Sites

Coal combustion

Artisanal Scale Gold Mining

Large scale gold mining

Mercury-cell chlor-alkali

Mercury production

Cement Production

Oil Refining 0.8%

Oil & gas combustion

UNEP Estimates: Sources of Mercury Air Emissions (emphasis has been added for the oil related contributions)

Metals Production Al, Cu, Pb, Zn Ferrous

IPIECA is the global oil and gas industry association for environmental and social issues. It develops shares and promotes good practices

communication with the United Nations. For information, please visit www.ipieca.org

IPIECA

28

IPIECA fact sheet on mercuryPrepared for UNEP's INC-5, Geneva, January 2013

(See next page for calculations and additional references.)

2.4%

0.8%

0.07%0

1

2

UNEP 2011 UNEP 2012 IPIECA 2012

Contribution of oil refining to global mercury releases to air (%)

UNEP 2011 & 2012 and IPIECA 2012 data

2011 Toolkit Methodology for total mercury input to the petroleum refining sector was as follows:

Assumed average mercury content of crude oil 55 parts per billion (by weight)2 Multiply by total crude production x 3.6 billion tonnes / year of crude _ Total mercury input to petroleum refining sector = 200 tonnes / year of mercury (UNEP, 2011)

IPIECA data and calculation of total mercury input to the petroleum refining sector shows a much lower number:

IPIECA average mercury content of crude oil 7.5 parts per billion (by weight)3 Multiply by total crude production x 3.6 billion tonnes / year of crude _ Total mercury input to petroleum refining sector = 27 tonnes / year of mercury (IPIECA, 2012)

For mercury emissions to air: o UNEP estimated that the refining sector contributed

0.8% (16 t/y)1 of total global air emissions (revised downward from their previous estimate of 2.4%).

o The corresponding IPIECA calculation indicates that emission levels are 12 times lower (0.07% of the total air emissions):

(27 tonnes total mercury input3) x (5% emission to air4) = 1.35 tonnes / year to air (IPIECA)

mercury emissions to water:

o UNEP estimated the refining sector contributed 0.1% (2t/yr) 1: (200 tonnes total input) x (1% to water) = 2 tonnes / year to water (UNEP)

o IPIECA estimated the refining sector contributed less than 0.01% which is 37 time less than the UNEP estimate:

(27 tonnes total input3)x (0.2% emission to water4) = 0.054 tonnes / year to water (IPIECA)

waste: o Most of the mercury that enters the refinery ends up as solid waste (87.4%)4. This waste is being

disposed of and managed according to country regulations (e.g. EU Directive, EU member countries classify mercury as hazardous waste, which is disposed of and managed responsibly in specific plant facilities). This will be discussed as part of an IPIECA good practice guide on waste management to be released in mid-2013.

o The mercury that is not contained in waste (12.6% of the total) is accounted for in refined products (6.7%), refinery air emissions (4.9%), water discharges (0.2%) and petroleum coke (0.8%)4.

___________________ 2 quantification of Mercury Releases, Reference Report- -14, 2011. 3 Weighted average based on SPE/APPEA International Conference on Health, Safety and Environment in Oil and Gas Exploration and Production,

Perth, A IPIECA Dataset for Mercury in Crudes and Condensates, 2012.

4 Resource Management, 2009.

29


ASTM (2010). D7623-10: Standard Test Method for Total Mercury in Crude Oil Using Combustion-GoldAmalgamation and Cold Vapor Atomic Absorption Method. ASTM International, West Conshohocken,Pennsylvania, USA.

CDC (1998). Criteria for a Recommended Standard: Occupational Exposure to n-Alkane Mono Thiols,Cyclohexanethiol, and Benzenethiol, Chapter III: ‘Biologic Effects of Exposure’. U.S. Centers for Disease Controland Prevention. cdc.gov/niosh/pdfs/78-213b.pdf

Conaway, C. H., Mason, R. P, Steding, D. J. and Flegal, A. R. (2005). Estimate of mercury emission from gasolineand diesel fuel consumption, San Francisco Bay area, California. In Atmospheric Environment, Vol. 39, Issue 1,pp 101-105.

Doll, B. E., Knickerbocker, B. M. and Nucci, E. (2012). Industry Input to the UN Global Mercury Treaty NegotiationsFocus on Oil and Gas. Society of Petroleum Engineers Paper SPE-157572-PP, presented at the SPE/APPEAInternational Conference on Health, Safety and Environment in Oil and Gas Exploration and Production, 2012.

DOSH (2011). Guidelines on Mercury Management in Oil and Gas Industry. Department of Occupational Safetyand Health, Ministry of Human Resources, Malaysia.

Fritz, J. S. and Palmer, T. A. (1961). Determination of Mercaptans by Titration with Mercury(II). In AnalyticalChemistry, Vol. 33, No. 1, pp 98-100.

Grice, K. J. and Alvarez, J. (2011). Refinery Turnaround Planning Lessons Learned. NPRA, Fort Worth, Texas, May, 2011.

Ho, Y. S. and Uben, P. C. (1994). Determination of inorganic Hg(II) and organic mercury compounds by ion-pairhigh-performance liquid chromatography. In Journal of Chromatography A, Vol. 688, Issues 1-2, pp 107-116.

Huber, M. L., Laesecke, A. and Friend, D. G. (2006). The Vapor Pressure of Mercury. National Institute of Standardsand Technology, US Department of Commerce. NISTIR 6643, April 2006.

Humphrys, M. (2009). Welcome to the Johnson Matthey Mercury Seminar, April 2009. Johnson MattheyCatalysts, 2009.

IPIECA (2013). Mercury in crude oil and contribution to global mercury releases. IPIECA fact sheet, January 2013.

Johnson Matthey (2009). ‘Mercury Removal Technology’. Johnson Matthey Catalyst Mercury Seminar, April, 2009.

Landis, M. S., Lewis, C. W., Stevens, R. K., Keeler, G. J., Dvonch, J. T. and Tremblay, R. T. (2007). Ft. McHenry tunnelstudy: Source profiles and mercury emissions from diesel and gasoline powered vehicles. In AtmosphericEnvironment, Vol. 41, Issue 38, pp 8711-8724.

Lopez, F. A., Lopez-Delgado, A., Padilla, I., Tayibi, H. and Alguacil, F. J. (2010). Formation of metacinnabar bymilling of liquid mercury and elemental sulfur for long-term mercury storage. In Science of the TotalEnvironment, Vol. 408, Issue 20, pp 4341-4345.

Negri, M. C., Gillenwater, P. and Demitras, M. U. (2011). Emerging Technologies and Approaches to MinimizeDischarges into Lake Michigan, Phase 2, Module 3 Report. Argonne National Laboratory.

OCIMF (2011). Safety, Health, Environmental Issues and Recommendations for Shipboard Handling of ElevatedMercury Crude Cargoes. Oil Companies International Marine Forum, August 2011.

Pare, Jean P. (1966). Journal of the Air Pollution Control Association, Volume 16, No. 6, June 1966.

IPIECA

30

References

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IPIECA is the global oil and gas industry association for environmental and social issues. It develops,

shares and promotes good practices and knowledge to help the industry improve its environmental and

social performance, and is the industry’s principal channel of communication with the United Nations.

Through its member-led working groups and executive leadership, IPIECA brings together the collective

expertise of oil and gas companies and associations. Its unique position within the industry enables its

members to respond effectively to key environmental and social issues.

Company members

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Bashneft

BG Group

BP

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EDF

eni

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Hess

Hunt Oil

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INPEX

KPC

Mærsk

Marathon

Nexen

Noble Energy

NOC Libya

OMV

Petrobras

Petronas

Petrotrin

PTT EP

Qatargas

RasGas

Repsol

Saudi Aramco

Shell

SNH

Statoil

Talisman

Total

Tullow Oil

Woodside Energy

African Refiners Association (ARA)

American Petroleum Institute (API)

Australian Institute of Petroleum (AIP)

Australian Petroleum Production & Exploration Association (APPEA)

Canadian Association of Petroleum Producers (CAPP)

Canadian Fuels Association

European Petroleum Industry Association (EUROPIA)

Instituto Brasiliero de Petróleo, Gás e Biocombustíveis (IBP)

International Association of Oil & Gas Producers (OGP)

Japan Petroleum Energy Center (JPEC)

Petroleum Association of Japan (PAJ)

Regional Association of Oil and Natural Gas Companies in LatinAmerica and the Caribbean (ARPEL)

South African Petroleum Industry Association (SAPIA)

The Oil Companies’ European Association for Environment, Healthand Safety in Refining and Distribution (CONCAWE)

UK Petroleum Industry Association (UKPIA)

World Petroleum Council (WPC)

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