One of the first works Dr. Roberto Lopez Garcia (aka one of the biggest brains in this business and good friend) and I collaborate on to bring this issue to light in the US and globally. Since this early publication the complicated issues associated with mercury in processing has increased throughout the US as the shale gas plays have developed and refineries have increased their feeds from these plays. In addition the approval of Keystone which takes crude form the oil sands in Alberta (full of metals including Hg) will only compound the mercury issues at US refineries taking this production. Dilution with Bakken production is not really going to eliminate this problem.

1. © T O U C H B R I E F I N G S 2 0 1 2
Processing
19
Mercury and mercury compounds are found in all geologic hydrocarbons
including coal, natural gas, gas condensates and crude oil. As a result,
mercury can be distributed throughout hydrocarbon production,
processing and transportation systems. Mercury and mercury
compounds present health risks to personnel performing equipment
maintenance and inspection activities, environmental risks from
atmospheric emissions and wastewater effluents and process risks to
cryogenic equipment. Oil and gas producers and processors should
understand the risks and liabilities associated with produced mercury and
develop appropriate mercury management strategies for turnarounds
including mercury mapping, exposure and medical monitoring,
turnaround management and chemical decontamination plans.
The general perception of produced mercury in hydrocarbon processing
systems has changed over the last decade, as its effect on processes has
become better understood and the science and methods of detecting
and measuring mercury in various matrices and media have advanced.
Over the last seven years our understanding of the sorption dynamics of
mercury in steel pipe and effective chemical approaches for the removal
of mercury from steel has also advanced. Since 2005, members of
Portnoy Environmental, Inc. (PEI) Mercury and Chemical Services
Group have been engaged in mercury management programmes in
hydrocarbon processing and petrochemical facilities worldwide. As part
of our ongoing efforts to mitigate the risks associated with mercury
impacted hydrocarbon processing systems, PEI’s research and
development team has focused its efforts on the improvement of
mercury sampling and analysis technologies and the development
of chemical cleaning methods and products that are effective in the
removal of mercury. PEI has deployed these methods to monitor
and remove mercury from impacted process systems including subsea
piping, natural gas processing systems and petroleum refining systems.
Mercury in Hydrocarbons
Mercury is present as a contaminant in virtually all fossil fuels,
including oil and gas. Based on available data, reported levels of
mercury present in oil and gas are extremely variable, both between
and within geographical areas.1 Some of this variability may result
from inconsistent sampling and analytical techniques and some can be
attributed to variance in geological formations. This, however, does
not account for all variations, as there can be significant differences
within a single oil or gas field. In general, average mercury levels are
relatively low, although some reported values have been extremely
high. Recent studies have concluded that mercury emissions from the
oil and gas sector (oil burning boilers in petroleum refining) in the US
represents 7 % (approximately 11 tons) of the national total mercury
emissions (158 tons) most of which (73 tons) are attributed to coal
combustion.2
The large variability in mercury content may lead to a
greater need for controls in some regions in the oil and gas sector
where mercury levels are high in comparison with those areas with
lower mercury levels. Based on available data, the volume of oil and
gas produced, refined and used globally may result in significant
mercury emissions and releases, even though they are significantly
lower than those associated with coal combustion. Mercury emissions
from coal burning power plants will most likely be regulated soon and
it is likely that emissions from hydrocarbon processing will be included.
The concentration of mercury in crude oil, natural gas and associated
liquids varies with geological and reservoir conditions with high
concentrations occurring in Southeast Asia (Thailand and Indonesia),
North Africa (Algeria), Egypt, South America (Venezuela, Bolivia), China
and the Netherlands (see Figure 1).
Partitioning of Mercury in Oil and Gas
Mercury (Hg) is a highly volatile transition metal found in the environment
in trace quantities in both elemental form and as highly toxic
organomercury compounds.3 The speciation of mercury in crude oil has
been comprehensively reviewed elsewhere.4 In brief, the complex variety
of mercury species in oil can be separated into three broad categories:
volatile mercury (including elemental mercury and dialkyl mercury);
insoluble mercury and dissolved forms (including elemental mercury, dialkyl
mercury); and mono-alkyl mercury and loosely complexed ionic mercury.
Whereas crude oil contains a complex array of mercury species, most
of the mercury in natural gas is elemental mercury.5 Trace quantities of
Roberto Lopez-Garcia began his career as a research
assistant at PSAnalytical and currently holds a Senior
Scientist position at Portnoy Environmental, Inc. (PEI)
Mercury and Chemical Services Group. He is responsible
for the development and application of measurement
and monitoring technologies for mercury and toxic
metals in oil and gas processing facilities. Over the last
seven years he has focused on developing and providing
solutions for the management of mercury and toxic
metals in hydrocarbon processing facilities in North America, Europe, the Middle East,
Thailand and South America. Mr Lopez-Garcia received a PhD in Organometallic
Chemistry from the University of Nottingham in 2005.
E: rgarcia@pei-tx.com
Ron Radford co-manages the Mercury and Chemical
Services Group at PEI and is the Chemical Cleaning
Director responsible for managing mercury management
and chemical decontamination programmes in the US and
overseas. He has 18 years of environmental remediation,
consulting and industrial services experience providing
specialised services to the energy sector. He is responsible
for managing projects/programmes including remedial
construction, facility decontamination, regulatory
compliance programmes, chemical cleaning, toxic metals sampling and analysis,
technology evaluations and remediation technology development.
E: rradford@pei-tx.com
a report by
Roberto Lopez-Garcia1 and Ron Radford2
1. Chief Scientist, Portnoy Environmental, Inc. (PEI) Mercury and Chemical Services Group, London, UK; 2. Director of Chemical Cleaning Operations,
Portnoy Environmental, Inc. (PEI) Mercury and Chemical Services Group, Texas, US
Managing Mercury in Hydrocarbon Processing Plants During Turnarounds

2. Managing Mercury in Hydrocarbon Processing Plants During Turnarounds
H Y D R O C A R B O N W O R L D – V O L U M E 7 I S S U E 120
inorganic (including mercury chloride [HgCl2]), organic (including
dimethylmercury [Hg(CH3)2] and diethylmercury [Hg(C2H5)2]) and
organo-ionic compounds have been detected.5
The partitioning of elemental mercury and mercury compounds in gas
and petroleum processing is largely determined by their solubility and
physical properties. Mercury speciation in crude oil is complex with a
variety of species detected. The different species behave differently
during refining, with volatile forms partitioning into low-density fractions
such as liquefied petroleum gas (LPG) and thermally stable species that
resist volatilisation partitioning into high-density residual products such as
petroleum coke and wastewater. In natural gas, the mercury present
is almost always elemental, although trace amounts may be present as
organic complexes. Mercury in natural gas poses similar problems
to those experienced with oil during transport, storage and handling. The
solubility of mercury in petroleum liquids coupled with its volatility mean
that mercury and mercury compounds can contaminate essentially the
entire production, processing and petrochemical manufacturing systems.
Organic mercury compounds in produced gas, under normal operating
conditions, will partition to separated hydrocarbon liquids as the gas is
cooled. Therefore, if organic mercury were present in the reservoir,
it would be found primarily in condensates. Measuring dialkyl mercury
compounds in hydrocarbon liquids is complicated due to several aspects
of mercury chemistry that make it difficult to detect and quantify.
Mercury emissions and releases can occur during all phases of the
production, processing and refining of oil and gas as well as during
the use of the final products. Mercury releases can occur from the
discharge of produced water as well as from process vents and flares.
Mercury Management During Turnarounds
In hydrocarbon processing and petrochemical manufacturing, mercury in
process feeds can contaminate equipment and can segregate to sludge
and other waste streams. Steel piping and pressure vessels that are used
to transport and process produced fluids interact chemically with the
mercury species in the fluids they contain. Carbon steel is an excellent
scavenger of mercury and the appearance of mercury at downstream
processing facilities can be delayed by months or years due to scavenging
of elemental mercury by steel pipeline surfaces. In locations where
mercury is known to be present in produced reservoir fluids, rigorous
safety precautions are needed to detect mercury vapour that emanates
from steel vessels and pipes when opened for maintenance or inspection
purposes. A mercury-contaminated steel pressure vessel will emit
mercury vapour long after it has been ventilated and cleaned to remove
sludge and surface hydrocarbons. Opportunities therefore exist for
workers to be exposed to mercury and its compounds in routine repair,
maintenance and inspection activities and when handling process fluids
and waste materials. This, along with the obvious environmental issues
associated with mercury, underscores the need for comprehensive
mercury management strategies during plant turnarounds.
Prior to performing equipment maintenance and inspection on mercury
impacted process equipment during a turnaround or shutdown, it is
necessary to understand the type and distribution of mercury throughout
the plant. This is not always the case though; sometimes mercury is
discovered during a turnaround without the benefit of this understanding.
In these instances turnaround management teams can decide to: proceed
with the turnaround using high levels of personal protective equipment
(PPE), extensive exposure monitoring and reactive waste management
planning or postpone the turnaround until an understanding of the type
and distribution of mercury can be obtained. The latter option is preferred
but not always feasible. The required mercury management strategies in
both instances are similar and discussed in this article.
Mercury Mass Flow Assessments
It is helpful to have an understanding of how mercury can be
distributed in hydrocarbon processing systems, which also includes
an understanding of mercury chemistry and how mercury reacts with
steel surfaces. In hydrocarbon liquids, dissolved mercury occurs in its
elemental form (Hg°), as organic (dialkyl, monoalkyl) mercury – Hg(CH3)2,
Hg(C2H5)2, methylmercury chloride (HgCH3Cl) – and as inorganic
(HgCl2) forms. In addition, produced liquids and some process streams
contain suspended mercury compounds, such as mercury sulphide
(HgS), which can be a significant fraction of the measured total
mercury concentration. Temperature, pressure and chemical changes
13.3 μg/kgAlgeria
Thailand
Vietnam
Asia
Canada
Norway
Europe
Argentina
Columbia
South America
Alaska
California
Texas
Louisiana
GOM
593 μg/kg
66.5 μg/kg
220.1 μg/kg
2.1 μg/kg
19.5 μg/kg
8.7 μg/kg
16.1 μg/kg
3.4 μg/kg
5.3 μg/kg
3.7 μg/kg
11.3 μg/kg
3.4 μg/kg
9.9 μg/kg
2.1 μg/kg
GOM deep shelf gas
US Mid-Continent
Western sedimentary basin
500 μg/Sm3
5 μg/Sm3
1 μg/Sm3 (additional data pending)
Global Crude Oil Mercury Concentrations
Known mercury belts and hot spots Recently discovered mercury hot spots
Recently Discovered Mercury Hot Spots and Natural Gas Mercury Concentrations
Figure 1: Global Mercury Belts and Hot Spots
GOM = Gulf of Mexico.

3. Managing Mercury in Hydrocarbon Processing Plants During Turnarounds
H Y D R O C A R B O N W O R L D – V O L U M E 7 I S S U E 1 21
throughout hydrocarbon processing systems allow mercury to change
from one chemical form to another.
Mercury mass flow assessments are used to quantify the gain or loss of
mercury across a plant or an entire process unit and each individual
process vessel. Analytical results from gas and fluid streams can identify
process vessels and groups of process vessels with process streams that
have elevated mercury concentrations and increased mercury mass gain or
loss, either accumulating mercury or adding mercury to the process fluids.
In some cases surrogate sample data may need to be used to complete
the mercury mass flow balance. Mercury mass flow assessments help
guide the turnaround team by providing mercury speciation and
distribution data that are used to develop mercury management plans,
exposure monitoring plans, chemical decontamination plans and waste
minimisation plans (solids, liquids and vapours). The photograph (see
Figure 2) depicts a process unit at a refinery where the mercury mass and
distribution were determined before the turnaround, providing valuable
data needed to complete the turnaround safely and on schedule.
Mercury Exposure Monitoring
Oil and gas processing equipment and appurtenances contaminated
with mercury require stringent safety precautions and exposure
monitoring procedures to mitigate risks to personnel during inspection
and maintenance activities. For example, one square metre of steel
holding 1 gram (g) of mercury can potentially contaminate 40,000
cubic metres (m3) of air to a concentration >25 µg/m3 of mercury.6 It is
easy to underestimate mercury exposure risks before and during
turnarounds for several reasons:
• Precise mercury concentrations in process streams are often unknown.
• Speciated forms of mercury in process streams and products are
rarely known.
• Mercury toxicity is gradual and generally produces no immediate
impairment that can be attributed to a specific occupational
exposure event.
• Mercury in vapour form is colourless and odourless and often not
included in monitoring programmes if it is not observed visually in
liquid elemental form.
• Available field mercury vapour analysers are subject to
environmental and chemical interferences found in hydrocarbon
processing environments and can generate false or under-reported
mercury concentrations.
Plant Environmental, Health and Safety (EHS) personnel should
understand the limitations of field portable mercury vapour analysers
and develop policies designed to ensure the health and safety of
workers based on rigorous chemical analysis of the process streams and
ambient air monitoring in work areas. With this information, exposure
to mercury can be managed using conventional PPE, engineering
controls and chemical decontamination. Data generated during
mercury mass flow assessments is invaluable when developing facility
and turnaround management plans. Organic mercury is significantly
more toxic than inorganic mercury and having this information before
a turnaround allows EHS personnel to design appropriate exposure
monitoring plans. Mercury exposure monitoring plans during
turnarounds should include detailed personnel/area sampling plans,
data quality objectives, selection of similar exposure groups, medical
surveillance for at-risk personnel and mercury awareness training.
Mercury Chemical Decontamination of Process Equipment
The incorporation of mercury into steel surfaces, its accumulation in
sludge and other deposits along with the condensation of mercury
in equipment can lead to situations during turnarounds, which require
special procedures and precautions. In these situations, removal of
mercury from equipment may be necessary to protect workers, to protect
equipment integrity and to ensure environmental compliance. There is
some debate regarding the potential for mercury to diffuse into the steel
matrix through some mechanism other than adsorption and
chemisorption.7 Thermal desorption tests show a substantial amount of
mercury is desorbed at 200 °C indicating mercury strongly adsorbs or
chemisorbs to steel surfaces.7 Generally speaking, for in-service process
equipment going back into service in a mercury contaminated system, it
is not practical or necessary to remove adsorbed or chemisorbed mercury
from all interfacial steel surfaces.8 Mercury chemical decontamination
objectives must be decided during turnaround planning so the
appropriate chemistry, decontamination methods and verification
analyses are selected. For example, if the goal is for limited entry into a
vessel for a short duration then removal of residual surface hydrocarbon,
hydrocarbon soluble mercury and surface oxide scale followed by venting
may be sufficient to meet objectives. If the goal includes extended entry
into vessels contaminated with mercury then more concentrated
oxidising agents and chelants can be used to remove a higher mercury
mass per area such that work can be performed in modified level D or C
PPE. Equipment scheduled for decommissioning and metals recycling
may require a more aggressive approach. Chemical cleaning results
based on sequential digestions of representative test coupons, removed
by cold cutting sections ofcontaminated pipe, indicate that 50 % or more
of the measured mercury mass in the steel can be removed by employing
inhibited acids/chelants. Thermal desorption testing of steel coupons can
also be used to determine baseline and post-verification mercury mass
concentrations. Determining the removal mass depends on local
environmental regulations, waste disposal regulations, selected metals
recycling vendor permits and final disposition of the equipment.
Successful mercury chemical decontamination of process equipment
depends on accurate analytical data to design chemistries and chemical
application phases appropriately to meet a range of project objectives.
The chemical process flow diagram (see Figure 3) depicts vapour phase
Figure 2: Refinery Solvent Extraction Unit

4. Managing Mercury in Hydrocarbon Processing Plants During Turnarounds
H Y D R O C A R B O N W O R L D – V O L U M E 7 I S S U E 122
and cascade phase chemical flow paths using surfactant and chelant
based chemistries to decontaminate a process tower during a
turnaround to allow extended entry in lower levels of PPE. A critical
component of chemical decontamination is monitoring progress in the
treatment process so that decisions can be made to increase chemical
concentrations, temperatures and residence times. A field analytical
method to measure total mercury concentrations in the applied
chemistries provides a means of monitoring the reaction efficiency and
overall required residence times. Chemical treatment sequence as well
as the verification methods should be determined during turnaround
planning and should consider:
• the safety of the personnel implementing the chemical
cleaning/inspection programme;
• safety and effectiveness of selected chemical phases;
• data quality objectives; and
• waste minimisation after the chemical cleaning programme.
Waste Minimisation During Plant Turnarounds
When feasible, the most effective approach for managing mercury is
to remove mercury from process feeds. Mercury removal units are
available for naphtha feeds, condensates and natural gas but the
technology to remove mercury from crude oil is not commercially
available at this time. Waste minimisation strategies should be a part
of pre-turnaround planning so waste minimisation systems can be
designed to meet project objectives and applicable environmental
regulations. Mercury can be removed from spent chemical cleaning
liquids and turnaround condensates such that they are rendered
non-hazardous and suitable for routine disposal at plant wastewater
facilities. There are a variety of technologies to choose from and
selection depends on project goals, costs, and treatment schedule.
Sorbent media used in these processes will remain a hazardous waste
stream and should be sampled and characterised per applicable
regulations. Also, filtration and adsorption units used in the waste
minimisation process should be chemically decontaminated before
demobilisation to the companies that provided them. Mercury and
hydrocarbons can also be removed from vapour streams and waste
gases generated during turnarounds preventing release to the
atmosphere. Chemically impregnated sorbents are used successfully in
this application and treatment units can be monitored for
breakthrough. As with fluid treatment systems this equipment
should be chemically decontaminated before leaving the site. When
monitoring breakthrough on these systems careful consideration
should be given to the instruments used since most of the field mercury
vapour analysers are subject to interferences from gases contained in
these vapour streams.
Conclusion
Mercury management during turnarounds requires some forward
thinking to determine the type and distribution of mercury
throughout hydrocarbon processing plants, process units and
pipeline systems to minimise worker exposure, and develop
appropriate turnaround management, chemical decontamination
and waste minimisation strategies. n
Cascade Chem
Inlet 165 F
SP 01
Top 2 Inch Valve <1 μg/m3
8”8”
SP 02
TR 20 MW
<1 μg/m3
TCV 6,650 Gal
V 4305 6’ ID x 66’6”T/T
Operating Temp.
260º F
Operating Temp.
277º F
SP 03
TR 10 MW
<1 μg/m3
SP 04
TR 1 MW
<1 μg/m3
20”
20”
6”
V-04309
E-04308A
E-04308B
E-04308C
E-04308D
E-04308E
E-04308F
E-04400A
E-04400B
Steam/Chem
Injection 225 F
Steam/Chem
Injection 225 F
E-04305
Steam/Chem
Injection 225 F
Figure 3: Naptha 2 Extract Stripper Chemical Process Flow Diagram
1. Wilhelm SM, Bloom N, Mercury in petroleum,
Fuel Processing Technology, 2000;63(1):1–27.
2. Wilhelm SM, Avoiding exposure to mercury during inspection
and maintenance operations in oil and gas processing,
Process Safety Progress, 1999;18(3):178–88.
3. Carnell PJH, Mercury Matters, Hydrocarbon Engineering,
2005;10:37–40.
4. Wilhelm SM, Liang L, Kirchgessner D, Identification and
Properties of Mercury Species in Crude Oil, Energy Fuels,
2005;20:180–6.
5. Wilhelm SM, Mercury in petroleum and natural gas:
Estimation of emissions from production, processing, and
combustion, US EPA, 2001. Available at: http://purl.access.
gpo.gov/GPO/LPS34680 (accessed 7 June 2012).
6. Zettlitzer M, Kleinitz W, Mercury in steel equipment used for
natural gas production - amounts, speciation and penetration
depth, Oil Gas European Magazine, 1997;23:25–30.
7. Wilhelm SM, Nelson SM, Interaction of Elemental Mercury
with Steel Surfaces, JCSE 2010;13 (preprint 38).
8. Hase B, Radford R, Vickery V, Mercury in Hydrocarbon Process
Streams: Sampling/Analysis Methods, Exposure Monitoring,
Equipment Decontamination and Waste Minimization,
Presented at: 110th American Fuel & Petrochemical
Manufacturers Annual Meeting, California US, 12 March 2012.