Mercury Managementr

Mercury Management White Paper 2012 Minimizing Occupational Exposure to Mercury in Hydrocarbon Processing Plants

Mercury and mercury compounds are found in all geologic hydrocarbons including coal, natural gas, gas condensates and crude oil. Mercury can accumulate in hydrocarbon production, processing and transportation systems. Occupational exposure to mercury and mercury compounds poses serious health risks to maintenance and inspection personnel working on hydrocarbon processing equipment potentially contaminated by process streams and products containing mercury. Mercury exposure risks are often underestimated, underscoring the need for companies engaged in hydrocarbon processing to develop a comprehen-sive mercury management strategy that accurately quantifies risks and minimizes worker exposure.

Introduction 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 analytical methods for detecting and quantifying mercury in various matrices and media have improved. Over the past eight years, PEI’s Mercury and Chemical Services Group have been engaged in occupational mercury exposure studies in hydrocarbon processing facilities worldwide. The main objective of these studies has been to determine worker exposure risks during routine as well as non-routine maintenance and inspection activities associ-ated with turnarounds, shutdowns and inspections. The appropriate approach for assessing mercury exposure risk is based on four components: 1. The development of sampling and analysis plans that are based on each plant’s process design and scheduled maintenance events. 2. The identification and development of plant and process specific Similar Exposure Groups (SEG).3. The use of a combination of exposure measurement techniques including portable field monitoring instruments, and active and passive sorbent trap sampling techniques.4. The identification and use of appropriate analytical methods for the detection and quantification of total mercury and specific mercury compounds (speciation).

Sampling campaigns are designed and focused on the measurement of mercury vapor concentrations in worker breathing zones during specific maintenance events including; pipe pigging, process filter replacement, process vessel inspection and hot-work (cutting, welding and grinding).

This white paper presents an overview of mercury management program compo-nents and occupational exposure monitoring methods in hydrocarbon processing plants, including the evaluation of an emerging passive dosimeter technology.

www.pei-tx.com [email protected]

White Paper 2012 Minimizing Occupational Exposure to Mercury Ron Radford, Roberto Lopez-Garcia2

Contributing Factors for Underestimating Mercury Exposure Risks

Hg in vapor form is colorless and odorless

Hg toxicity is gradual and generally produces no immediate impairment that can be attributed to a specific occupational exposure event

Hg exposure monitoring is not routine or performed at all in some hydrocarbon pro-cessing work environments

Precise Hg concentrations in process streams are often unknown

Concentrations of speciated Hg compounds in process streams and products are rarely known


White Paper 2012 Minimizing Occupational Exposure to Mercury Ron Radford, Roberto Lopez-Garcia 3

Mercury in Hydrocarbons The development of plans to minimize occupational mercury exposure requires an understanding of how mercury is distributed in hydrocarbon processing sys-tems and how mercury reacts with process equipment surfaces. In hydrocarbon liquids, dissolved mercury occurs in its elemental form (Hg0), as organic (dialkyl, monoalkyl) mercury [Hg(CH3)2, Hg(C2H5)2, HgCH3Cl], and as inorganic (HgCl2) forms. In addition, produced liquids and some process streams contain suspend-ed mercury compounds, such as mercuric sulfide (HgS), which can be a significant fraction of the measured total mercury concentration.

In natural gas, mercury exists almost exclusively in its elemental form at con-centrations below saturation suggesting that no liquid mercury phase exists in most reservoirs. However, there are a number of reservoirs which are known to produce gas at saturation (with respect to elemental mercury). Organic mercury compounds in produced gas, under normal operating conditions, will partition to separated hydrocarbon liquids as the gas is cooled. Therefore, if organic mer-cury is present in the reservoir, it would be most likely found in gas 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. Crude oil and gas condensate can contain several chemical forms of mercury, which differ in their chemical and physical properties.

In hydrocarbon processing and petrochemical manufacturing, mercury in process feeds can contaminate equipment and can partition into 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

Chemical and Physical Properties of Mercury in Crude Oil and GasDissolved Elemental Mercury (HgO): Elemental mercury is soluble in crude oil and hydrocarbon liquids up to a few parts per million (ppm).

Dissolved Organic Mercury: This category includes dialkylmercury (i.e., dimethylmercury, diethylmercury) and monomethyl-mercury halides (or other inorganic ions).

Inorganic (ionic) mercury salts (Hg2+X or Hg2+X2, where X is an inorganic ion): Mercury salts are soluble in oil and gas condensate but preferentially partition to the water phase in primary separations. Ionic salts may also be physically suspended in oil or may be absorbed to suspended particles.

Complexed mercury (HgK or HgK2): Where K is a ligand such as an organic acid, porphyrin or thiol.

Suspended mercury compounds: Mercury sulfide (HgS) and selenide (HgSe) are insoluble in water and oil but may be present as suspended solid particles.

Table 1.



contain. In fact, in locations where mercury is known to be present in produced reservoir fluid, rigorous safety precautions are required to detect mercury vapor that emanates from steel vessels and pipe when opened for maintenance or inspections purposes. A mercury-contaminated steel pressure vessel will emit mercury vapor long after it has been ventilated and cleaned to remove sludge and surface hydrocarbons. Under these conditions there is significant potential for workers to be exposed to mercury and its compounds during routine repair, maintenance and inspection activities, and when handling process fluid and waste materials. Occupational Mercury Vapor Exposure Limits Mercury and its compounds are highly reactive toxic agents that can damage the central nervous system, endocrine system, kidneys and other organs. Mercury is highly volatile making vapor inhalation the most common pathway for exposure. Exposure over longer periods of time can result in brain damage and ultimately death. Therefore, companies operating oil and gas production and processing facilities should be aware of the concentrations of mercury in processed trans-

ported fluids and gases in order to quantify the magnitude of contamina-tion and potential for worker exposure.

Health, regulatory and advisory limits have been established for exposure to mercury vapor (Chart 1). Workplace standards are generally based on preventing adverse health effects from exposure over a 40-hour work week and are higher than health/toxicological exposure values. The Occupational Safety and Health Administration (OSHA) has established a legally enforceable ceiling limit for work place exposure of 100 µg/m3. Mercury concentrations cannot exceed this level at any time during the work day. The National Institute for Occupational Safety and Health (NIOSH) has established a recommended exposure limit (REL) for mer-cury vapor of 50 µg/m3 expressed as a time weighted average (TWA) for a 10-hour work day. The American Conference of Governmental Industrial Hygienists (ACGIH) recommends a threshold limit value (TLV) of 25 µg/

m3 mercury vapor as a time weighted average exposure for a normal 8-hour work day.

The OSHA PEL for alkyl mercury compounds is 10 µg/m3 and should be used if the presence of dialkyl mercury is suspected in gas condensates. Samples should be analyzed for organic mercury compounds in process streams and ambient air in closed space equipment atmospheres to quantify alkyl mercury

Exposure Level

Chart 1.

White Paper 2012 Minimizing Occupational Exposure to Mercury Ron Radford, Roberto Lopez-Garcia White Paper 2012 Minimizing Occupational Exposure to Mercury Ron Radford, Roberto Lopez-Garcia 5


concentrations. Dialkyl mercury compounds are many more times toxic than elemental mercury. Temperature, pressure, and chemical changes throughout hydrocarbon processing systems allow mercury to change from one chemical form to another. Knowledge of the amount and type of mercury present is required for the design of effective exposure assessment and management programs. The Environmental Protection Agency (EPA) sets a reference concentration (RfC) of 0.3 µg/m3 for inhalation exposure to mercury. The reference concentration is a screening tool used to help risk assessors determine where to focus their investi-gations into hazardous exposures. Similarly, the Agency for Toxic Substances and Disease Registry (ASTDR) has set a minimal risk level (MRL) for inhalation exposure at 0.2 µg/m3. Mercury Management Program Components Mercury accumulates in hydrocarbon processing system components such as heat exchangers, separators and filters, slug catchers, and other process towers and vessels. Mercury reacts with and chemically modifies steel surfaces such that hydrocarbon and surface layers as well as substrate layers (mercury pen-etrates steel surfaces several millimeters) will emit mercury vapor when equip-ment is opened for inspection and maintenance. Hydrocarbon processing companies can minimize potential worker exposures by the implementation of a mercury management strategy. Some key components of a comprehensive mercury management strategy include the following:1. Risk Assessment2. Worker Health and Safety Protocol3. Exposure Monitoring Plan4. Data Quality Objectives5. Medical Surveillance6. Mercury Awareness Training

1. Risk Assessment Risks associated with producing, transporting and processing petroleum and natural gas containing mercury fall into several categories. Of primary importance is the risk to workers who handle fluids or repair and maintain equipment. As-sessing health risks to workers includes the acquisition of analytical information required to make the correct judgments.



There are clear economic risks associated with mercury in process feeds such as: • Compromise of product quality. • Potential interaction with process equipment.• Detrimental impact on the environment.

Human and economic risks generally are related to the concentration of mercury in process hydrocarbons. They are determined according to the total mercury concentra-tion obtained using analytical procedures and suitable quality assurance measures.

2. Worker Health and Safety Protocol Avoiding exposure to mercury, in most maintenance and inspection activities, can be accomplished if some steps are taken to identify the situations in which exposure is possible. This is commonly achieved by employing the right equipment for worker protection from inhalation and/or dermal absorption. Policies designed to ensure the health and safety of workers should be based on a rigorous chemical analysis of the process streams and ambient air monitoring in work areas. With this information, exposure to mercury can be avoided using conventional personal protective equipment (PPE) and engineering controls.

Threshold Values for Specifying Levels of RiskLOW RISK MEDIUM RISK HIGH RISK

Less than 10 ppb liquid (<5 µg/Sm3 gas)

Between 10 and 100 ppb liquid (5-50 µg/Sm3 gas)

Greater than 100 ppb liquid (>50 µg/Sm3 gas)

Table 2.

PPE Decision Tree

Chart 2.

< 25 µg/m3 25 - 50 µg/m3 50 - 100 µg/m3 > 50-100 µg/m3

•

•

•

•

•

•

•

•

•

•

•

•

•

•

•



3. Exposure Monitoring Plan 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. (Note: One square meter of steel holding 1 gram of elemental mercury can contaminate around

40,000 cubic meters of air to a level that exceeds the TLV of 25 µg/m3.)

Preventative Exposure Controls Controls to reduce or prevent exposure can be accomplished through the following:• Engineering: Eliminate or reduce the risk of exposure through the use or substitution of engineered machinery or equipment.• Administrative: Reducing the risk of exposure through employee training, housekeeping and rotation of personnel.• Personal Protective Equipment: Used when the implementation of engineering and administrative controls do not eliminate the risk of exposure.

Site Controls Performance of some work tasks may require definition of three clearly established work zones: an Exclusion Zone (EZ), a Contamination Reduction Zone (CRZ), and a Clean Zone (CZ). Work zones are established based on the extent of anticipated contamination and projected work activities. Field measurements combined with climatic conditions may, in part, determine the control zone distances.• Exclusion Zone (EZ): The EZ includes any area(s) of potential contamination. All personnel entering the EZ must wear the appropriate PPE for the tasks they are to perform in that area and meet training, and medical surveillance requirements.• Contamination Reduction Zone (CRZ): The CRZ is the area where hazardous substances are removed from site personnel and their protective equipment. Access to the contamination reduction zone from the clean zone is allowed only through established control points.• Clean Zone (CZ): The CZ is a non-contaminated area where support services, non-hazardous materials storage and administrative activities generally occur. The CZ should be equipped with potable water, first aid kits, safety equipment, and supplies of clean PPE. In some cases the CZ is also equipped with hand/face washing facilities.



Personal Exposure Sampling and Analysis The personal exposure sampling and analysis methodology includes the develop-ment of Similar Exposure Groups (SEGs). Prior to completing final design of an exposure monitoring plan interviews should be conducted with plant operations/engineering personnel to identify plant specific exposure profiles. A key goal is to identify exposure profiles that are specific to similar types of plants and/ or processes.

Real-Time Monitoring Ambient air monitoring is conducted to assess airborne concentrations of mercury. Real-time baseline ambient air monitoring is performed just prior to work conditions during which the potential for mercury vapor exposure may occur to assist in deter-mining exposure risk and appropriate PPE selection. Real-time monitoring should also continue throughout work tasks during which the potential for mercury vapor exposure exists. There are a variety of field mercury vapor analyzers available on the market today, each of which has some limitations associated with interference gases and conditions common in hydrocarbon processing. Understanding these limitations is critical when developing occupational exposure monitoring plans. The research and development team at PEI has expanded previous industry research and performed detailed comparative studies using cold vapor atomic florescence spectrometry (CVAFS) and available atomic adsorption (AA) field-portable mercury vapor analyzers. Data from those comparative studies will be presented in a sepa-rate white paper.

Control zones and work areas should be regularly monitored with a portable Mercury Vapor Analyzer (MVA) for accurate detection and measurement of toxic mercury vapor in the air. Frequency of testing is based on multiple conditions, such as, work tasks, process changes, weather conditions, or voluntary testing.

Mercury

Vapor

Analyzer

Example 1.

Portable mercury vapor analyzers used extensively by PEI proven to be accurate, reliable and robust.

MERCURY TRACKER 3000 IP THE OHIO LUMEX RA-915 LIGHT

Mercury Vapor Analyzer (detection limit = 0.1 µg/m3) Mercury Vapor Analyzer (detection limit = .02 µg/m3).



Passive Personnel Sampling Passive personal exposure samples are collected from exposure assessment program participants identified and selected from specific SEGs. Passive personal exposure samples consist of a solid sorbent sample media with an engineered diffusive membrane that allows for a specific air diffusion rate to occur during the sampling period. The sampling takes place as the work activities start and throughout the duration of activities.

During the comparative testing of the SKC and Radiello, FGS, the National Envi-ronmental Laboratory Accreditation Program (NELAP), and ISO 17025 accredited laboratory, provided analytical services. The analytical method used for passive dosimeters during the comparative study consisted of FGS-SOP-136: Analysis of Hg in Air via Capture on Sorbent Trap based on the principles of US EPA 1631 Revision E. The comparative results of the Radiello, and SKC to the standard OSHA ID-140 method (active pump) indicate that the Radiello samplers collect mercury at a higher rate than the SKC samplers.

Passive dosimeter have two notable limitations:1. Particulate bound mercury compounds cannot be collected with the device.2. The dosimeter is sample rate depends on air velocity and should not be used in areas where the air velocity is greater than 229 m/min (750 ft./min). A sampling pump (active sampling method) and collection media are required for this for particulate collection and during those times when air velocity exceeds the recommended limit.

Occupational Exposure

Monitoring Samples

Example 2.

Two types of passive samplers (SKC and Radiello) have been tested for use during recent Occupational Exposure Monitoring Studies.

SKC PASSIVE DOSIMETER RADIELLO DIFFUSIVE SAMPLER

Passive Sampler for Inorganic Mercury (520 Series) which has been validated by the OSHA ID-140 Mercury Vapor in Work Place Atmo-spheres method. The sampling media consists of Anasorb® C300.

Radiello Diffusive Sampler (Code 120 Diffusive Body) and was used with FSTM media provided by Frontier Global Sciences (FGS) is analyzed by the same method employed for the Anasorb media. The Radiello Diffusive Sampler has potential attractive passive sampling dynamics although it is not a validated approach at this time and is considered experimental only.



Active Personnel Sampling Mine Safety Appliances (MSA) Escort LC Pumps (low-flow active sample pumps) calibrated to 0.2 to 0.4 liters per minute are used for active sampling events. Calibration of the sampling pump is a critical aspect of insuring the quality of the sample collection process. A sampling assembly is connected to a calibrated pump using flexible tubing. If a prefilter is used, it should be connected to the sampling tube with a minimum amount of Tygon™ or Teflon™ tubing. The pumps can be placed on employees and also staged around the perimeter of control zones (Table 3). A total air volume in the range of 3 to 100 L is typically employed to collect mercury onto the sorbent media cartridge. The analytical procedure used for the analysis of all three types of personal exposure samples (Illustration 1) during the comparative study is the FGS Standard Operating Procedure FGS 069.4.1 “Determination of Total Mercury in Various Matrices by Cold Vapor Atomic Fluorescence Spectrom-etry (Modified EPA Method 1631E).

Active Personnel Sampling

LOW-FLOW SAMPLE PUMPLow Flow Sample Pump, Sample Tubing and FGS Sample Trap

SAMPLE TUBING FGS SAMPLE TRAP

Personal Sampling

Example 3.

Illustration 1.


4. Data Quality Objectives Data quality objectives (DQOs) are a critical component of any project re-quiring extensive collection of raw and analytical data. This is especially true for occupational exposure monitoring studies due to the extensive field sam-pling campaigns (including the collection of a large number of critical field data parameters) and the importance to the health and safety of a large number of employees involved in oil and gas pro-cessing operations. To support this effort a detailed Quality Assurance Project Plan (QAPP) is developed to inform, and guide the team so that data of desired quality is produced, and a clear protocol for the acceptance/rejection of data is established.

The QAPP should include a QA/QC (quality assurance/quality control) sample collection protocol for the field data collection phase as well as for the laboratory analysis phase. Field data QA/QC samples consists of duplicate samples, field spikes with NIST (National Institute of Standards and Technology) traceable spike standards, field blanks, and breakthrough sections.

5. Medical Surveilance Biological monitoring is the measurement of chemical agents in the blood, urine, or other body tissue of exposed individuals to determine how much of the chemical has been absorbed into the body. Biological monitoring of mercury is necessary if some-one is exposed to mercury, or thinks they might be exposed. It serves as a back-up to environmental exposure measurements, since air measurements cannot take into consideration skin exposure or the effectiveness of protective equipment and work practices. Biological monitoring measures the amount of an agent actually present in the body and is usually better than air monitoring as an estimate of risk for adverse health effects.

Data Quality Objectives

Table 3

QA/QC Samples and Performance

CriteriaPerformance

Criteria

PERSONAL EXPOSURE SAMPLES AMBIENT AIR SAMPLES

Passive - SKC

Passive - Radiello Active Passive -

SKCPassive - Radiello Active

Sampling Method OSHA ID - 140 OSHA ID - 140

Analytical MethodFGS-136: FGS-SOP-136: Analysis

of Hg in Air via Capture on Sorbent Traps (based on the principles

of US EPA 1631).

FGS-136: FGS-SOP-136

Sample Preparation Method OSHA ID - 140 OSHA ID - 140 FGS SOP 009.04

Sample Media Anasorb C300 FSTM FSTM Anasorb

C300 FSTM FSTM

Target Detection Limit* µg/scm 12.5 12.5 12.5 12.5 12.5 12.5

Field DuplicatesFrequency

5%, 1 per 2 days mini-

mum

10%, 1 per 2 days

minimum

10%, 1 per 2 days

minimum

10% 1/day minimum

(% RD) 25 25 25 25 25 25

Field SpikesFrequency NA NA

(% recovery) NA NA

Breakthrough Sections

Frequency NA 100% NA 100%

B Section Mass % NA

5% of A Section Hg Mass

NA5% of A Section Hg Mass

Field BlanksFrequency 1/day 1/day

Performance Criteria ≤ blank mass value ≤ blank mass value



White Paper 2012 Minimizing Occupational Exposure to Mercury Ron Radford, Roberto Lopez-Garcia

Contacts

Ron Radford

Director of Chemical

Cleaning Operations

Portnoy Environmental, Inc.

1414 W. Sam Houston Pkwy. N.

Suite 170

Houston, TX 77043 USA

713-503-6803

www.pei-tx.com

[email protected]

Bob Brunette

Frontier Global Sciences, Inc.

11720 N. Creek Pkwy. N.

Suite 400

Bothell, WA 98011 USA

206-660-7307

www.frontiergeosciences.com/

[email protected]

Roberto Lopez-Garcia

Chief Scientist

Mercury and Chemical

Services Group


London, England

44-7791904-977

www.pei-tx.com

[email protected]

James ‘Vic’ Vickery

Vice President, and

Technical Director of Mercury

and Chemical Services Group


1414 W. Sam Houston Pkwy. N.

Suite 170

Houston, TX 77043 USA

281-536-0899

www.pei-tx.com

[email protected]

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Measurements are taken regularly (several times a year) for chronically exposed workers. Individual results and also group results are evaluated. To effectively interpret the results, baseline levels need to be established before exposure begins for comparison purposes.

Site personnel and subcontract personnel who may be at risk to mercury expo-sure should follow the appropriate medical monitoring requirements in accordance with the United States Department of Labor standard 29 CFR 1910.120(f). Each individual entering a contaminated area should successfully complete an annual surveillance examination and/or an initial baseline examination.

6. Mercury Awareness Training Training is important to ensure worker health and safety and that plant environ-ments are not contaminated by mercury. Workers should be:• Trained to anticipate situations in which they could be exposed.• Provided appropriate PPE, trained in the use of PPE.• Taught to recognize symptoms of exposure.

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