1. Mercury Monitoring in the Oil and Gas Processing Industry
Dr Warren T Corns
R&D Manager
P S Analytical

2. Bio and Company Background
P S Analytical specialises in the ultra-low level detection of mercury, arsenic, selenium, antimony, tellurium and bismuth in all sample types.
Founded by Prof Peter B Stockwell in Dr Warren Corns joined in 1988 as PSA PhD student and became R&D Manager in Focus on R&D sponsoring eight PhD students and several postdocs over last 25 years
Main Office is located in Orpington, Kent, UK . 40 staff involved in production, design, service, R&D, sales, technical support, consultancy and administration.
US Offices are located in Deerfield Beech and New Jersey. SE Asia office in Queensland. Other countries supported by distributers
Main focus of our business is Hg analysis with laboratory and online measurement equipment. The oil, gas and petrochemical industry is just one of our market areas. Huge focus on environmental applications.

3. Oil, Gas & Water Atmospheric Emissions Gas Oil/Condensate Solid Waste
Flaring, vents & exhausts
Gas
0.05 – 5000 µg Nm-3
Oil/Condensate
0.1 – µg kg-1
Solid Waste
e.g. drilling muds /sludge
Water
µg L-1
Gas
Oil
Water
Naturally Occurring Hg in all phases

4. A typical Gas Processing Plant

5. Amalgam Corrosion
Amalgam corrosion occurs when Hg and Al create amalgam in humidity.
Hg + Al  Hg(Al) (amalgamation)…………………….1
Hg(Al) + 6 H2O  Al2O3.3H2O + 3 H2 + Hg…………..2
Hg + Al  Hg(Al) (amalgamation)…………………...1
Due to Hg regenerating itself, the reaction is self propagating while water exist . The amalgam corrosion will accelerate in presence of oxygen, creating a corrosion of Al2O3 feathers

6. Liquid Metal Embrittlement
LME is the most important of the failure mechanisms that attack aluminium in gas plants. Amalgamation occurs in a grain boundary followed by an inter-granular stress cracking activated by stress and or residual stress.
No water is required, however if water is present the corrosion is accelerated. In case of aluminium alloys this attack has been observed where magnesium precipitates in grain boundary during equipment manufacturing process or welding process.
4Hg + Al3Mg2 = 2MgHg2 + 3Al
For effective LME attack, the Hg needs to be in liquid phase above the freezing point of Hg (-38.9C) and also exist as a crack in the aluminium protective oxidized film.

7. Liquid Metal Embrittlement

8. LNG Plant in Algiers. Explosion by mercury induced heat exchanger failure.

9. Santos LNG Moomba Plant
1st Jan 2004, Santos LNG plant in Moomba, Australia explode.
Cause of loss, failure of a nozzle on a heat exchanger from Liquid Metal Embrittlement
Fatalities :
Resulted in the interruption to gas supplies in South Australia and the Eastern Seaboard
No Injuries
Damage to Plant substantial and loss of revenue
7 months of gas interruption supply
On the 23 December 2005 the claim was settled for A$231 Million
(From : “What happens when the catastrophe occurs” Chris McMichael, Presentation on behalf of Santos Ltd)

10. Official Methods for Mercury in Natural Gas
ISO 6978, part 1 and 2. Part 2 is based on two heated gold traps in series to collect Hg. Measurement is based on dual amalgamation – AAS or AFS.
ASTM Based on two gold traps in series to collect Hg. Measurement is based on dual amalgamation – AFS.
PSA online and offline equipment complies to both methods. Detection limits are less than 1ng/m3.

11. Pressure Let down System for Offline Sampling

12. Stainless Steel IP66 Enclosure for 10.547 – Version for heated lines

13. Hg in Gas Analyser - Sir Galahad II

14. TGM Manual Measurements of Remote Tubes

15. Optical Configuration for AFS Plan View
Mercury
Lamp
Lens
Collimator + Filter
Introduction Chimney
Sample in
Sheath
Argon
Reference cell
Photo-
multiplier
tube

16. Vapour Injection Calibration Procedure
Capillary Tube
Thermometer
Gas Tight Syringe
Elemental Hg B C A

17. Typical results using Hg removal beds Outlet Specification < 10ng/Nm3
Sample Description
Bed Volume m3
Inlet Conc.
ng/Nm3
Outlet Conc.
Sales Gas 31
279 ± 12
370 ± 53
735 ± 130
522 ± 72
3.2 ±0.9 Dec 11
2.6 ±1.1 Aug 11
7.1±0.9 Dec 10
5.9 ± 2.6 July 10 10
1268 ±197
1.2±0.7
Regeneration Gas 3
370 ± 139
1.1 ± 0.1

18. Amasil Trap Cleaner

19. How do you know if your results are good?
Sampling system is well designed so that no adsorption losses or contamination is experienced. Check blank on sampler using purified air/nitrogen. Check reference gas through sampling arrangement
Sampling system and sample point is flushed with sample prior to use
Bypasses are used to ensure a representative sample is obtained
Sample traps are regularly checked by spiking known masses of Hg before use
Ensure calibrated and certified components are used throughout
Ensure that no condensation is experienced during sampling. Use phase diagram.
Traps must be used in series so that breakthrough can be monitored (<10%)
Traps are heated (circa 100oC)to ensure no condensation on gold
Test different sample volumes to ensure result is independent on volume collected
Dynamic spike additions in the field to check collection and efficiency in presence of sample
Participate in inter-laboratory collaborative and proficiency exercises

20. How about Wet Gas? More challenging for a number of reasons
Gas saturated with water at process conditions
High potential of liquid hydrocarbon (BTEX) and water condensation because of JT cooling at sampling arrangement
High concentration of Hg – small sample volumes difficult to collect in practice
Adjustment of primary bypass flow control can be problematic.

21. Arrangement for Wet Gas
Deliver sample at line pressure via a short Teflon braided hose
Control primary bypass flows using calibrated armoured flowmeters at process conditions
High flow bypass upstream of primary pressure reduction. Condensation is only in vent line so does not affect measurement
Primary pressure reduction with a heated regulator to overcome JT cooling prevent condensation – Dropping the pressure in stages is standard practice to avoid condensation
Entire sampling system is coated with SilcoNert to avoid losses of Hg and minimize carryover

22. Sampling arrangement for wet raw gas

23. Experiences with Wet Gas Sampling arrangement
All lines in sample pathway run warm well above the dew-point of sample even with multiple sampling systems connected.
Results for wet gas look very good showing stable results with good repeatability. Short term precision typically below 5%RSD
No breakthrough on traps
Results were independent of volume
Gas Analysis
Location
Time
Volume Collected (L)
Result (ug/Nm3)
% Breakthrough
22/10/2016
Train 1 Outlet
13: :45 10
149.1
1.2
16: :39 2
148.3
0.8
17: :16 3
151.7
0.9

24. LPG Accessory

25. Manual Sampling onto Remote Traps

26. European Mercury Removal Plant Yearly Average in RED

27. Mixed LPG Plant Case Study Reported Hg Issues for C4

28. Mercury Contribution from Offshore facility in Indonesia
Site produces at maximum capacity 1 Billion Cubic Feet of Mixed LPG/day equivalent to 28,000,000,000 litres/day
At Average Concentration of 1.2mg Hg/m3 this equates to a Hg loading of 33.6Kg Hg/day (12.3 tonnes Hg per year)
Low Hg in LPG due to storage at low temperature (freezing point Hg = - 39oC)
Stabilized condensate 38 ± 3 ppbw

29. Hg Condensation Model

30. Cold Box and Chiller trains

31. Hg in Produced Water
It is estimated that more than 50% of the Hg released from the oil and gas industry is from produced water.
Environment and Regulation bodies enforce different permitted discharge concentrations mostly between 0.1 to 10 µg/L. Not strictly enforced in all areas.
To achieve this concentration some sites require Hg removal.

32. Millennium Merlin – Cold Vapour AFS System
Elemental, inorganic and organic mercury forms present in sample . Chemical digestion with acidic oxidants required before CV-AFS. Stannous chloride reduction of Hg2+ to Hgo
Detection Limits less than 1 part per trillion. Linearity 5 orders of magnitude
2 minute measurement time

33. Typical Results for Hg in Seawater and Produced Water
Sample Reference
Concentration (ug/l)
% Spike Recovery
Water CRM (ORMS-1) ±
( ±0.0013)
Formation Water – North Sea
14.7 ± 0.5
Produced Water - Canada
0.57 ± 0.02 96
11.66 ± 0.01 98
Produced Water – SE Asia
2098 ± 136
92-103
Produced Water – North Sea
3.24 ± 0.01 94

34. Hg in Crude Oil and Condensates
Very wide Hg concentration range from low ppb to ppm
Raw crude and condensates requires processing. Desalting and caustic wash treatment both remove Hg
During stabilisation of raw crude, elemental mercury is released to overheads.
During processing Hg has a tendency to pre-concentrate in lighter fractions producing Hg concentrations in excess of raw feedstock.
Hg becomes distributed to all refined products. Mass balances are difficult because of plant losses.

35. Relative Weight Distribution of Hg in Condensate Cuts – Data from IFP

36. Mercury Removal for Liquid Hydrocarbons
Liquid feed-stocks (propane, butane, naphtha, condensates) used by the petrochemical industry are typically treated to remove Hg to below 1ppbw.
Other heavier streams such as diesel, kerosene, fuel oil and residuals are not treated or tested for Hg. Typically used as fuels.
Mercury is known to cause problems in the petrochemical industry due to poisoning of expensive precious metal hydrogenation catalysts and Hg attack on heat exchangers
Removal technologies are similar to gas applications (e.g sulphided metal oxides).

37. Commonly used Measurement Techniques for Hg in Liquid Hydrocarbons
Chemical Digestion/Extraction with CVAFS
Volatilization – Amalgamation -AFS (Suitable for Online Measurements)

38. Typical Results for HgTotal by Aqua Regia
Sample
Prep
Mercury (ng/ml)
Mean Result
(ng/ml)
Conostan CRM 1 2
35.3 ± 0.3
33.7 ± 0.3
34.5 ± 0.3
(100%)*
North Sea Crude Oil 1
97.1 ± 0.2
103.6 ± 0.5
100.4 ± 0.5
(97.2%)*
North Sea Crude Oil 2
78.5 ± 0.1
74.3 ± 0.3
76.4 ± 0.3
(102.1%)*
Thai Crude Oil
2896 ± 15
2991 ± 8
2944 ± 17
(96.4)*
Venezuelan Crude Oil
3852 ± 18
3926 ± 10
3889 ± 21
(95.1)*
Algerian Condensate
733 ± 14
741 ± 15
737 ± 21
(98.2)*
* Spike Recovery Data, MDL=0.2ng/ml

39. Schematic for Automated Mercury Measurement for Liquid Hydrocarbons

40. Comparison of Data between Digestion CV-AFS and Volatilization - AFS
Sample Reference
Hg ppbw using
Hg ppbw using CV-AFS
NWS Condensate
36.8 +/- 1.3
35.1 +/- 0.5
Saudi Aramco Condensate
15.7 +/- 0.7
16.9 +/- 1.0
Malaysian Condensate
56.9 +/- 2.8
59.4 +/- 0.1
Condensate Outlet MRU
0.14 +/- 0.03
>0.2
Naphtha (UK)
5.65 +/- 0.12
6.21 +/- 0.23
Naphtha (Hawaii)
265 +/- 12
260 +/- 2.5
Norwegian Condensate
2.51 +/- 0.07
2.20 +/- 0.13
Australian Condensate
35.6 +/- 2.4 (pyrolysis =38)
South African Condensate
1.81+/- 0.12
2.01 +/- 0.25

41. Hg Species in Liquid Hydrocarbons?
Mercury Classification
Forms of Mercury
Elemental Hg
Hgo(gas), Hgo (dissolved) , Hgo (solids)
Particulate Hg
HgS, Hg (solid associated), Hg (insoluble)
Inorganic Hg
Hg2+, Hg22+
Organometallic Hg
R-Hg+ ,R-Hg-R, Hg thiolates - Unknowns??
Complexity of sample matrix and number of potential species of Hg inhibits the use of a single approach for determining all Hg species
Fractionation Methods are therefore used

42. The Fractionation Method
Hg Total
CV-AFS
Particulate Hg
HgS
Aqua Regia
Other Particulate Hg
Nitric Acid
Volatile Hg
Purge & Trap
Dissolved Hg
KCl extraction
Ionic Hg
Aqueous Phase
Unknown Hg
Organic Phase
Organic Hg
GC-AFS

43. Hg Fractionation in Condensates Example data
Sample A
Sample B
Sample C
Sample D
Sample E
Sample F
Sample G
Sample H
Sample I
Total Hg
1.00
1.24
780.80
8.17
420.74
73.73
168.30
925.30
Dissolved Hg
0.73
0.66
552.70
0.00
19.82
0.44
0.50
14.00
2.30
Ionic Hg, KCl
0.57
0.36
13.60
3.95
18.59
0.18
0.23
0.25
Unknown Hg, non - KCl NA
539.10
Organic Hg
Particulate Hg
0.27
0.58
226.20
4.06
400.92
73.29
167.80
923.00
Volatile Hg
0.10
0.07
1.90
0.01
0.06
0.84
0.05
0.24
0.35
Fraction Sum
0.94
(94%)
(100%)
8.02
(98%)
419.57
74.31
(101%)
168.03
(99%)
923.60
NA = Not Analysed - Only analysed if summation of fractions is poor
ND = Not detected, MDL= 1ng/g
All results in ng/g (ppbw)
Fraction Sum = summation of columns in yellow
Results have higher confidence if total Hg and Fraction Sum are in good agreement

44. Hg Fractionation in Crude Oil Example DataB1 B2 B3 B4 B5 B6 B7 B8
Total Hg
538.24
98.79
60.80
37.04
62.56
46.79
42.38
84.83
96.00
Dissolved Hg
43.44
7.72
9.12
4.25
11.82
7.79
6.69
13.13
4.99
Ionic Hg, KCl
19.06
4.73
7.59
3.43
6.08
4.46
3.82
6.60
0.74
Unknown Hg non-KCl NA
Organic Hg ND
Particulate Hg
494.80
91.07
51.68
32.79
50.74
39.00
35.69
71.70
91.01
Volatile Hg
24.25
0.20
0.10
0.08
0.12
0.33
0.25
0.37
Fraction Sum
538.11
(100%)
(97%)
59.37
(98%)
36.30
57.02
(91%)
39.12
(84%)
39.84
(94%)
78.55
(93%)
92.12
(96%)
NA = Not Analysed - Only analysed if summation of fractions is poor
ND = Not detected. MDL = 1ng/g
All results in ng/g (ppbw)
Fraction Sum = summation of columns in yellow
Results have higher confidence if total Hg and Fraction Sum are in good agreement
Sample B – Same plant sampled at different periods

45. Sampling Uncertainties for Liquid Hydrocarbons
Depressurization and stabilization might release volatile Hg compounds such as elemental mercury vapour.
Potential Loss of Mercury on sampling components. Materials and speed loop should be carefully considered.
Losses of Mercury from association with particulates and aqueous phase. Sample filtration devices and sample point selection should be carefully considered.
Losses and species conversion of Mercury during storage and shipping of samples. Sample containers and storage conditions are critical.
Sample homogenization is required prior to measurement.
Shipping regulations often require metal containers!

46. PSA 20.610 Auto injection of liquid hydrocarbons to 10.515

47. What type of Samples? High pressure samples collected in Bombs
– 10barg
20.610H – 100barg
Samples that are compatible with the Hg pre-concentration unit
Samples that are 100% liquid at process conditions. This information is obtained using a Phase Diagram. Un-stabilized condensates, un-stabilized crude, depropanizer bottoms and debutanizer bottoms, LPG, propane, NGL, butane, naphtha, etc.
Collecting samples in open vessels will allow gases to vent off and causes losses of elemental Hg.
There may be cases where higher temperature cause gasification in the sample bomb

48. Phase Diagram @1bar, 5°C, sample is 50.6% gas.
@20°C, >3.5 bar g needed to keep sample in liquid phase.

49. Auto injection system

50. Mass Balance Ethylene Plant
PS Analytical are an instrument manufacturer specializing in the measurements of Hg and Hydride forming elements using AFS. We also provide consultancy onsite and offsite measurement services.
PSA were approached by a Olefin plant to independently test for Hg across the plant because they were experiencing poisoning of Palladium based acetylene reactor catalysts.
The spent catalyst was tested for Hg (40-60ppmw) which confirmed Hg was the issue.
The site added a UOP Hg removal control to the Mol Sieve gas and liquid dryers and replaced the acetylene catalyst.
PSA visited site to perform Hg testing of the feedstock streams and also to test the performance of the newly installed mercury removal units. Other streams were tested to gain better understanding of the fate of Hg across the plant.

51. Olefin Production

52. Sample Types Gases and Liquified Gases (e.g. C1-C4) – Sir Galahad
Liquid Hydrocarbons (e.g. C5+) – Hg preconcentrator
Aqueous Phase (e.g. caustic wash/wastewater)- CVAFS
Gas – Liquid Mixtures (e.g. DeC3 bottoms) – Combined

53. Multiphase Samples
Gas Analysis
Liquid Analysis

54. Mass Balance Model
All samples measured and collected over a 7 day period at steady state conditions. 3 gas samples strategically positioned so that each section of the plant could be studied. Liquid samples collected every day am and pm.
Main source of mercury to the plant was from the butane feed.
Gas phase measurements generated results in ng/Nm3 so results must be converted to ppbw (µg/Kg = mg Hg/Tonne).
Process flows recorded in Tonne/Hour. Mean flow over sampling times was used for calculations
Mass Balance calculations were based on mg Hg/Hour
All measurements done on site on samples collected within 24 hours if possible.

55. Results

56. Mercury Removal Unit

57. Mercury Removal Results
Gas Dryer MRU efficiency = 99.7% Liquid Dryer MRU efficiency = 94.2%

58. Acetylene Reactor Beds
Acetylene Reactor Inlet should ideally be less than 10ng/m3
Mercury Removal Units only recently installed so quite possible that Hg result
is elevated from pipework contamination
Testing several months later gave results less than 10ng/m3

60. Mass Balance Summary
A mercury mass balance was successfully performed on Olefin plant producing ethylene and propylene using atomic fluorescence spectrometry for gas and liquid phase samples
Hg was found in the butane feedstock at 18.3ppbw (46350ng/m3)
15% of this Hg was removed at gasoline stripper bottoms 4% and spent caustic 11%
The remaining 85% of this Hg was split between gas (93%) and liquids (7%)
A mass balance close to 100% was found between feed and gas/liquid dryers.
Mercury removal beds installed at the gas and liquid dryers removed 99.7 and 94% respectively
Downstream acetylene reactor and cold boxes considered low risk although not quite operating at ideal specification of less than 10ng/m3
A model estimating distribution of Hg downstream was produced which suggested low levels of mercury across fractionation trains and splitters

61. Online Mercury Analyser

63. Block Diagram of Online Natural Gas System

64. Gas Stream Sampling

65. Hg Measurement Amalgamation AFS

66. Online Determination of Mercury in LNG

67. Online Liquid Stream Analysis

69. Liquid Stream Sampling

70. Online Hg in Naphtha Results from MRU with Zero and 10ppbw Conostan Span Checks

71. Combined Online Gas and Liquids

72. Performance Specifications

73. Development of Hg Removal Adsorbents

74. Development of Hg Removal Adsorbents

75. Development of Adsorbents for Liquid Hydrocarbons
Cycling feed of liquid hydrocarbon dosed with elemental Hg
Metering pumps to log flow across beds
4 test beds
Direct measurement of inlet 1ppm and outlet streams (<1ppb)
Auto-calibration

76. Occupational Hg Exposures
The oil, gas and petrochemical industry have a various Hg occupational exposures to consider.
Condensation of Liquid Mercury. This can equate to several tons of Hg being drained from the process.
Hg contamination on pipework and vessels
Hg in various exhausts and re-boiler vents
Hg in spent adsorbents, catalysts
Hg in waste products such as sludge, caustic wash, spent amines, spent glycol and wastewater
Hg on PIG receivers
Hg in various refined product streams and also vapours.
Exposure Management by air monitoring, staff urine and blood tests, education HSE training.

77. CONCLUSIONS
This presentation has hopefully provided an overview of monitoring techniques for Hg in the Oil and Gas Industry.
Additional research needs to be done to study the behaviour of Hg during the extraction and processing oil and gas.
Mercury removal approaches are very effective but they are focused on mercury removal on specific product streams to meet specifications and to protect downstream components.
Offline and online Hg measurement technologies are available from PS Analytical for all types of samples for the oil, gas and petrochemical industry.

78. Thank you for attention. Any Questions?