This document discusses methods for removing trace mercury contaminants from natural gas and liquid streams in the liquefied natural gas (LNG) and gas processing industries. It describes how mercury distributes in gas processing plants and ends up in liquid streams. Common methods to remove mercury include sulfur-impregnated carbon beds and molecular sieves, which trap elemental mercury from the vapor phase. Proper mercury detection and low permissible limits are important due to mercury's toxicity and ability to cause equipment corrosion.
Some of our recent solubility work: the behavior of mercury in water alcohols, monoethylene glycol and triethylene glycol - thanks to Dr Gallup and Dr O'Rear for their contributions and effort.
Managing Mercury in Hydrocarbon Processing Plants During TurnaroundsISCT GROUP US LLC
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.
Some of our recent solubility work: the behavior of mercury in water alcohols, monoethylene glycol and triethylene glycol - thanks to Dr Gallup and Dr O'Rear for their contributions and effort.
Managing Mercury in Hydrocarbon Processing Plants During TurnaroundsISCT GROUP US LLC
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.
ALL ABOUT NATURAL GAS : DEFINITION,FORMATION,PROPERTIES,COMPOSITION,PHASE BEHAVIOR ,CONDITIONING"DEHYDRATION ,SWETENING" AND FINAL PROCESSING TO END USER PRODUCTS
The Expander Gas and Ammonia Ratio Influence on the Calcium Cyanamide YieldYogeshIJTSRD
For the first time, thermodynamic calculations based on relatively new physicochemical constants clarified the onset temperature of thermal ammonia decomposition, as well as the side chemical reactions probability between ammonia and carbon dioxide. The influence of the main technological parameters on the calcium cyanamide synthesis is investigated. The exhaust gases composition from the reactor for the calcium cyanamide synthesis was studied depending on the temperature. Kinetic studies of the calcium cyanamide synthesis determined the chemical reaction orders with respect to ammonia and carbon dioxide, and it was proved that the limiting stage of calcium cyanamide synthesis is the initial gas components diffusion through the product layer. O. Kh. Panzhiev | A. Kh. Panzhiev | N. Umarov | O. Azimov "The Expander Gas and Ammonia Ratio Influence on the Calcium Cyanamide Yield" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Special Issue | International Research Development and Scientific Excellence in Academic Life , March 2021, URL: https://www.ijtsrd.com/papers/ijtsrd38440.pdf Paper Url: https://www.ijtsrd.com/engineering/other/38440/the-expander-gas-and-ammonia-ratio-influence-on-the-calcium-cyanamide-yield/o-kh-panzhiev
Processing of Hydrogen Sulfide & Carbon Dioxide From Natural Gas StreamsMohamed Almoalem
This poster was presented in GPA (Gas Processors Association) 23rd technical conference in November 2015. It is the outcome of an individual research that was done voluntarily by me during my internship in Tatweer Petroleum.
Low Temperature Pyrolysis of Graptolite Argillite (Dictyonema Shale) in Autoc...IJERA Editor
The results of the systematic experimental study obtained in this work on the effects of temperature (340–420
°C) and exposure time (0–8h) at nominal temperature on the yield of pyrolysis products from Estonian
graptolite argillite (GA) generated in autoclaves without any solvent are described. The yields of solid residue
(SR), gas, pyrogenetic water (W) and extractable with benzenemix ofthermobitumen and oil (TBO) were
estimated. The compound groups of TBO were assessed. The highest yield of TBO, 2.18% on dry GA basis and
13.2% of organic matter (OM) was obtained at temperature of 420 °C and duration 0.5 h. The main compound
groups in TBO obtained at 400 ᵒC are polar hetero-atomic compounds and polycyclic hydrocarbons surpassing
45% and 30% of TBO. The shares of aliphatic and monocyclic hydrocarbons are below 15% of TBO. The yield
of W from GA is – about 10-15% of OM. The quantity of OM left in SR after pyrolysis is high, about 65% of
OM. The yield of pyrolysis products from GA and the composition of its TBO are compared with those obtained
under similar conditions from different oil shales: Estonian Kukersite, US Utah Green River, and Jordanian
Attarat.
It describes how the Sulfur is removed from the coal and oil. Desulfurisation of coal and oil is very helpful to bring down the sulfur oxide emissions in the air from the industries and power plants.
ALL ABOUT NATURAL GAS : DEFINITION,FORMATION,PROPERTIES,COMPOSITION,PHASE BEHAVIOR ,CONDITIONING"DEHYDRATION ,SWETENING" AND FINAL PROCESSING TO END USER PRODUCTS
The Expander Gas and Ammonia Ratio Influence on the Calcium Cyanamide YieldYogeshIJTSRD
For the first time, thermodynamic calculations based on relatively new physicochemical constants clarified the onset temperature of thermal ammonia decomposition, as well as the side chemical reactions probability between ammonia and carbon dioxide. The influence of the main technological parameters on the calcium cyanamide synthesis is investigated. The exhaust gases composition from the reactor for the calcium cyanamide synthesis was studied depending on the temperature. Kinetic studies of the calcium cyanamide synthesis determined the chemical reaction orders with respect to ammonia and carbon dioxide, and it was proved that the limiting stage of calcium cyanamide synthesis is the initial gas components diffusion through the product layer. O. Kh. Panzhiev | A. Kh. Panzhiev | N. Umarov | O. Azimov "The Expander Gas and Ammonia Ratio Influence on the Calcium Cyanamide Yield" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Special Issue | International Research Development and Scientific Excellence in Academic Life , March 2021, URL: https://www.ijtsrd.com/papers/ijtsrd38440.pdf Paper Url: https://www.ijtsrd.com/engineering/other/38440/the-expander-gas-and-ammonia-ratio-influence-on-the-calcium-cyanamide-yield/o-kh-panzhiev
Processing of Hydrogen Sulfide & Carbon Dioxide From Natural Gas StreamsMohamed Almoalem
This poster was presented in GPA (Gas Processors Association) 23rd technical conference in November 2015. It is the outcome of an individual research that was done voluntarily by me during my internship in Tatweer Petroleum.
Low Temperature Pyrolysis of Graptolite Argillite (Dictyonema Shale) in Autoc...IJERA Editor
The results of the systematic experimental study obtained in this work on the effects of temperature (340–420
°C) and exposure time (0–8h) at nominal temperature on the yield of pyrolysis products from Estonian
graptolite argillite (GA) generated in autoclaves without any solvent are described. The yields of solid residue
(SR), gas, pyrogenetic water (W) and extractable with benzenemix ofthermobitumen and oil (TBO) were
estimated. The compound groups of TBO were assessed. The highest yield of TBO, 2.18% on dry GA basis and
13.2% of organic matter (OM) was obtained at temperature of 420 °C and duration 0.5 h. The main compound
groups in TBO obtained at 400 ᵒC are polar hetero-atomic compounds and polycyclic hydrocarbons surpassing
45% and 30% of TBO. The shares of aliphatic and monocyclic hydrocarbons are below 15% of TBO. The yield
of W from GA is – about 10-15% of OM. The quantity of OM left in SR after pyrolysis is high, about 65% of
OM. The yield of pyrolysis products from GA and the composition of its TBO are compared with those obtained
under similar conditions from different oil shales: Estonian Kukersite, US Utah Green River, and Jordanian
Attarat.
It describes how the Sulfur is removed from the coal and oil. Desulfurisation of coal and oil is very helpful to bring down the sulfur oxide emissions in the air from the industries and power plants.
key lessons learned from mercury mapping of process streams to developing an understanding of the sorption dynamics of mercury in process, accumulation rates, species and mass loading per surface area
OPERATION AND TROUBLE SHOOTING IN LP AND VACUUM SECTION FOR MS SAIPEM PROCESS...PremBaboo4
In Urea Process corrosion/Erosion also observed in LP and vacuum section. The paper indeed how to tackle this type of problem? Root cause of corrosion in LP & vacuum section. Construction of material used in these sections. Operation of LP section with trouble shooting How to balance water in the process, Distillation Tower Versus LP carbonate solution tank with operation of LP decomposer. Water balance in whole plant prilling rout as well as granulation rout. How a small variation of Pressure & temperature makes a drastic change in the process including waste water section? How Distillation tower feed related to LP decomposer pressure & temperature? The detail described in this article. The intensity of corrosion is greatest in the reaction section and the first recycle, where pressures, temperatures and concentrations are higher than downstream. The reactor liner, pumps, decomposers, strippers and condensers are more vulnerable to attack by ammonium carbamate. But the corrosion is also important in LP and vacuum sections. The typical corrosion is observed in 2nd stage of vacuum in some plants of urea.
OPERATION AND TROUBLE SHOOTING IN LP AND VACUUM SECTION FOR MS SAIPEM PROCESS...PremBaboo4
In Urea Process corrosion/Erosion also observed in LP and vacuum section. The paper indeed how to tackle this type of problem? Root cause of corrosion in LP & vacuum section. Construction of material used in these sections. Operation of LP section with trouble shooting How to balance water in the process, Distillation Tower Versus LP carbonate solution tank with operation of LP decomposer. Water balance in whole plant prilling rout as well as granulation rout. How a small variation of Pressure & temperature makes a drastic change in the process including waste water section? How Distillation tower feed related to LP decomposer pressure & temperature? The detail described in this article. The intensity of corrosion is greatest in the reaction section and the first recycle, where pressures, temperatures and concentrations are higher than downstream. The reactor liner, pumps, decomposers, strippers and condensers are more vulnerable to attack by ammonium carbamate. But the corrosion is also important in LP and vacuum sections. The typical corrosion is observed in 2nd stage of vacuum in some plants of urea.
ER Publication,
IJETR, IJMCTR,
Journals,
International Journals,
High Impact Journals,
Monthly Journal,
Good quality Journals,
Research,
Research Papers,
Research Article,
Free Journals, Open access Journals,
erpublication.org,
Engineering Journal,
Science Journals,
Engineering Research Publication
Best International Journals, High Impact Journals,
International Journal of Engineering & Technical Research
ISSN : 2321-0869 (O) 2454-4698 (P)
www.erpublication.org
Inhibitory Effect of Some Carbazides on Corrosion of Aluminium in Hydrochloric Acid and Sodium Hydroxide Solutions
The dissolution of aluminium in hydrochloric acid and sodium hydroxide solutions in the presence of semicarbazide, thiosemicar- bazide and sym.dipheny1carbazide as corrosion inhibitors has been studied using thermometric, weight-loss and polarization methods. The three methods gave consistent results. The higher inhibition efficiency of these compounds in acidic than in alkaline madia may be due to the less negative potential of aluminium in hydrochloric acid solution, favouring adsorption of the additive.The adsorption of these compounds were found to obey Frurnkin adsorption isotherm. Cathodic polarization measurements showed that these com- pounds are cathodic inhibitors and their adsorption in the double layer does not change the mechanism of the hydrogen evolution reaction. The results are analysed in terms of both molecular and cationic adsorption.
Optimized Geochemical Modeling of Produced Fluids Provides Important Insight ...Donald Carpenter
Pitzer-based solution equilibria modeling is leveraged to understand the geochemical controls on alkaline earth sulfate-encapsulated radium precipitation during produced fluid handling generating one type of Naturally Occurring Radioactive Material (NORM).
Like all elements, the mercury has also existed on the planet since the Earth was
formed. Mercury moves through the environment as a result of both natural and human
activities. The human activities that are most responsible for causing mercury to enter
the environment are
burning materials (such as batteries), fuels (such as coal) that contain mercury,
and
certain industrial processes. These activities produce air pollution containing
mercury.
The explosion hazard in urea process (1)Prem Baboo
In Urea plant passivation air is used in reactor, stripper and downstream of the all equipments. The reactor liner material used Titanium, Zirconium, SS 316L (urea grade), 2RE-69 and duplex material .except Titanium and Zirconium all stainless steel required more passivation air. In CO2 some quantity of Hydrogen is present about 0.14% to 0.2% . The passivation oxygen and Hydrogen makes explosive mixture. To avoid a fire or explosion in a process vessel is to introduce inert (noncombustible) gases in such a way that there is never a mixture with a combustible concentration in exit of MP vent. Mixtures of fuel, oxygen, and inert gases are not combustible over the entire range of composition. In CO2 stripping process the HP scrubber is the risky vessel and this vessel consisting blanketing sphere, Heat exchanger part and a scrubbing part. With help of triangular diagram that shows the shape of the combustible/noncombustible regions for a typical gaseous mixture of fuel, oxygen, and inert at specified temperature and pressure. Present article how to avoid that combustible rang and how to tackle that gases in CO2 & ammonia stripping process.
HEAP SORT ILLUSTRATED WITH HEAPIFY, BUILD HEAP FOR DYNAMIC ARRAYS.
Heap sort is a comparison-based sorting technique based on Binary Heap data structure. It is similar to the selection sort where we first find the minimum element and place the minimum element at the beginning. Repeat the same process for the remaining elements.
Water billing management system project report.pdfKamal Acharya
Our project entitled “Water Billing Management System” aims is to generate Water bill with all the charges and penalty. Manual system that is employed is extremely laborious and quite inadequate. It only makes the process more difficult and hard.
The aim of our project is to develop a system that is meant to partially computerize the work performed in the Water Board like generating monthly Water bill, record of consuming unit of water, store record of the customer and previous unpaid record.
We used HTML/PHP as front end and MYSQL as back end for developing our project. HTML is primarily a visual design environment. We can create a android application by designing the form and that make up the user interface. Adding android application code to the form and the objects such as buttons and text boxes on them and adding any required support code in additional modular.
MySQL is free open source database that facilitates the effective management of the databases by connecting them to the software. It is a stable ,reliable and the powerful solution with the advanced features and advantages which are as follows: Data Security.MySQL is free open source database that facilitates the effective management of the databases by connecting them to the software.
KuberTENes Birthday Bash Guadalajara - K8sGPT first impressionsVictor Morales
K8sGPT is a tool that analyzes and diagnoses Kubernetes clusters. This presentation was used to share the requirements and dependencies to deploy K8sGPT in a local environment.
Literature Review Basics and Understanding Reference Management.pptxDr Ramhari Poudyal
Three-day training on academic research focuses on analytical tools at United Technical College, supported by the University Grant Commission, Nepal. 24-26 May 2024
NUMERICAL SIMULATIONS OF HEAT AND MASS TRANSFER IN CONDENSING HEAT EXCHANGERS...ssuser7dcef0
Power plants release a large amount of water vapor into the
atmosphere through the stack. The flue gas can be a potential
source for obtaining much needed cooling water for a power
plant. If a power plant could recover and reuse a portion of this
moisture, it could reduce its total cooling water intake
requirement. One of the most practical way to recover water
from flue gas is to use a condensing heat exchanger. The power
plant could also recover latent heat due to condensation as well
as sensible heat due to lowering the flue gas exit temperature.
Additionally, harmful acids released from the stack can be
reduced in a condensing heat exchanger by acid condensation. reduced in a condensing heat exchanger by acid condensation.
Condensation of vapors in flue gas is a complicated
phenomenon since heat and mass transfer of water vapor and
various acids simultaneously occur in the presence of noncondensable
gases such as nitrogen and oxygen. Design of a
condenser depends on the knowledge and understanding of the
heat and mass transfer processes. A computer program for
numerical simulations of water (H2O) and sulfuric acid (H2SO4)
condensation in a flue gas condensing heat exchanger was
developed using MATLAB. Governing equations based on
mass and energy balances for the system were derived to
predict variables such as flue gas exit temperature, cooling
water outlet temperature, mole fraction and condensation rates
of water and sulfuric acid vapors. The equations were solved
using an iterative solution technique with calculations of heat
and mass transfer coefficients and physical properties.
We have compiled the most important slides from each speaker's presentation. This year’s compilation, available for free, captures the key insights and contributions shared during the DfMAy 2024 conference.
1. 1
Session No. 43, Paper No. 43c
Removal of Trace Mercury Contaminants from
Gas and Liquid Streams
in the LNG and Gas Processing Industry
by
Julio A. Rios, MEChE
Process Manager, LNG
David A. Coyle, BSChE
Chief Technology Engineer, LNG
Charles A. Durr, MSChE
Technology VP, LNG & Gas Processing
Felix F. De la Vega, P.E., MSChE
Brian M. Frankie, MEChE
The M. W. Kellogg Company
Houston, Texas, USA
Prepared for presentation at the
AIChE 1998 Spring National Meeting
New Orleans, Louisiana, USA
Tuesday, March 9, 1998
Session: Cryogenic Gas Processing II
UNPUBLISHED
2. 2
AIChE shall not be responsible for statements or opinions contained in papers or printed
in its publications
ABSTRACT
Mercury, present as a contaminant innaturalgas and its associated condensates, has to be removed
to prevent corrosion in aluminumequipment as wellas to avoid downstreamcatalyst poisoning. Elemental
mercury present in the gas phase has traditionally been removed by adsorption on sulfur impregnated
carbon or on an alumina carrier. Currently there are other options including the use of special types of
molecular sieves which are regenerated, and by other fixed bed adsorbents.
Similarly, mercury is removed from natural gas condensates used as steam cracking feedstock to
avoid downstream poisoning of selective hydrogenation catalyst. Some environmental concerns on the
disposal of the spent adsorbent containing mercury or of the mercury released from the molecular sieve
regenerating medium are briefly discussed.
Also presented is how mercury in the feed gas to an LNG plant distributes itself to the different
products and internal streams.
3. 3
INTRODUCTION
Althoughrelativelyhighlevels ofelementalmercurywere discovered inthe Groningen(Holland) field
as early as 1969, the first recorded cold box failure attributed to mercury corrosion was in the aluminum
spiral wound heat exchanger of the LNG plant at Skikda, Algeria1,2
in 1974. Since this time, mercury in
natural gas has become a major concernincryogenic gas processingindustries. These industries, including
liquefied natural gas (LNG), liquefied petroleum gases (LPG), and olefins, often use aluminum heat
exchangers in their cold boxes. Mercury corrosion of aluminum exchangers has led to several additional
failures since the problems at Skikda. Inaddition, mercuryaccumulationcanlead to poisoningofcatalysts
used in olefin processes, personnel safety hazards, and waste disposal difficulties. This paper describes
different forms of mercury found in natural gas, the distribution of mercury in process plants, methods of
mercuryattack, the latest options for treatment ofmercurycontaminated process streams, and the treatment
and disposal of mercury contaminated wastes.
SOURCES AND DISTRIBUTION OF MERCURY
Mercury Forms: Mercury is present in natural gas and natural gas associated condensates, as
organometallic and inorganic compounds, and inthe elemental(metallic) formdependingonthe originofthe
gas. The elemental form can be found in either the vapor or liquid phase. The organometallic (typically
dimethylmercury, methylethylmercury, or diethylmercury) and inorganic (suchas HgCl2) compoundsdrop
into the liquid phase in any fractionation of the natural gas streams. Vapor phase elemental mercury is a
primary culprit in corrosion of aluminum exchangers inside cryogenic cold boxes.
4. 4
Elementalmercurythat leaves the plant inthe liquid phase naturalgas condensate streams is a primary
source ofcorrosioninaluminumequipment inolefinplants that crack liquids and LPG (propane and butane)
recovered from the natural gas plants. Mercury also poisons the selective hydrogenationcatalysts inolefin
plants, and can pose inhalation hazards to workers.
Organometallic and inorganic mercury usually end up in the condensate stream fromthe naturalgas
plant. These compounds are important environmentaltoxins that are easilyabsorbed and accumulated by
biological organisms. The presence of these compounds innaturalgas condensate streams leads to waste
disposal problems and safety hazards to workers.
Mercury Sources: Elemental mercury is a natural contaminant present at the wellhead in various
concentrations at different geographic locations. The concentrationofelementalmercuryinthe gas streamis
often expressed in g/Nm3
, which is a very small number. Table 1 is a comparisonbetween g/Nm3
with
more conventional expressions (such as ppm, ppb and ppt). Generallyspeaking, elementalmercurylevels
have been found to be the highest in Southeast Asian gases (up to 400 g/Nm3
in the vapor phase) and
lowest in United States Gulf Coast gases (as low as 0.02 g/Nm3
)3
, although wide variation is known to
occur even within local regions. However, evenat the verylowest naturalconcentrations it is stilldesirable
to reduce the amount ofmercurybefore anycryogenic processing, where mercurycanaccumulate to higher
concentrations.
The mechanismfor formationoforganometallic mercuryis not known. Current postulates suggestthat
elemental mercury may react withthe walls ofreboilers and catalytic furnaces to formactive species which
can then react with methane, ethane, the products of a catalytic cracker, and other organic compounds4
.
5. 5
TABLE 114
VAPOR PHASE ELEMENTAL MERCURY IN NATURAL GAS
COMPARISON OF CONCENTRATION EXPRESSIONS
g/Nm3
8,500
850
85
8.5
0.85
0.085
0.0085
MOL%
0.000,1
0.000,01
0.000,001
0.000,000,1
0.000,000,01
0.000,000,001
0.000,000,000,1
PPM
1
0.1
0.01
0.001
0.000,1
0.000,01
0.000,001
PPB
1,000
100
10
1
0.1
0.01
0.001
PPT
1,000,000
100,000
10,000
1,000
100
10
1
Mercury Distribution5
: Vapor phase elementalmercurydistributioninliquefied naturalgas (LNG)
plants has been studied to determine the areas most in danger of mercuryattack, and whichstreams have
the highest concentration. Three primary areas have been identified.
First, when fractionating natural gas (e.g. scrub column followed by deethanizer, depropanizer and
debutanizer), the majority of the mercury ends up in the butane and some in the propane. Most of the
mercury condenses in the scrub column because of its very low vapor pressure, and because this column
operates at low temperatures (below -30 C), and highpressures (above 50 bar). The mainpurpose ofthe
scrub column is to remove the bulk of the heavy components from the natural gas which can freeze inthe
main cryogenic exchanger. Table 2 shows mercury vapor pressure as a function of temperature.
The remainingcolumns inthe fractionationsectionrecover the C4 and lighter components containedin
the scrub column bottom. LNG plant configurations vary, but both the propane and butane streams are
often reinjected back into the naturalgas enteringthe aluminummaincryogenic exchanger. Inthis case, the
6. 6
mercury in these streams can freeze and accumulate in the tubesheets and tubes of the natural gas circuit.
Mercury freezing will occur at temperatures below -39 C, and where the mercuryconcentrationis greater
than the mercury solubility in the liquid stream.
Secondly, in addition to the above reinjectionstreams into the mainexchanger, some ofthe mercury
also escapes in the overhead of the naturalgas scrub column. This streamis sent directlyto the naturalgas
tube circuit in the main exchanger where it freezes and accumulates. Figure 1 shows the mercury
distributionthrougha typicalLNG process withreinjectionofpropane and butane. Figure 1 was developed
at M. W. Kellogg using interactionparameters and k-values for mercuryinhydrocarbons developed from
proprietary data.
The fractions bythe different streams show the amount ofmercurythat streamcontains based onone
unit of mercury in the feed. These fractions were calculated using vapor-liquid equilibria only; in actual
operation, the 0.99 mercuryfractionshownexitinginthe LNG would freeze and accumulate inthe aluminum
tube circuits of the main exchanger.
Finally, a small amount ofthe elementalmercurygoes inthe overhead streams ofthe deethanizer and
depropanizer. These streams provide makeup mixed refrigerant for the process and willallow mercuryto
accumulate in the mixed refrigerant loop. The refrigerant flows up throughone or more separate aluminum
tube circuits in the main exchanger, is expanded, and flows down the shell side of the exchanger. This
mercury is most likely to freeze in the refrigerant tube circuits.
TABLE 2
VAPOR PRESSURE OF ELEMENTAL MERCURY15
TEMPERATURE(deg.C) PRESSURE(mmHg)
-38.9 2.19x10E-6
-20 23.36x10E-6
7. 7
0 199.6x10E-6
25 1.93x10E-3
40 6.34x10E-3
100 0.277
Mercury Concentrations: Since awareness ofthe problems withmercurycorrosionhas increased,
many cryogenic gas processing facilities have installed guard beds to scavenge elementalmercuryfromthe
vapor phase. Specifications of the outlet gas from these beds are generally about 10 nanograms per
standard cubic meter (0.01 g/Nm3
) ofgas, and are based more onmercurymeasurement limitations rather
than removal limitations. At a large LNG plant producing 8,000 tonnes of LNG product per day, 0.01
g/Nm3
translates to about 36 grams of mercury per year remaininginthe gas stream, whichcanstilldrop
out and freeze in the maincryogenic exchanger. Based onthe distributionanalysis inFigure 1, almost allof
this mercury will freeze to solid mercury in the main exchanger (pure mercury freezes below - 39C).
Much less work has beendone onthe presence oforganometallic and inorganic (as salts) mercuryin
process plants. One source6
reports typicalcondensate concentrations oforganometallic mercuryinthe10
to 1000 ppb(weight) range. A second source7
reports a typical concentrationof30 to 60 ppb(weight) in
AlgerianHR720 condensate feedstock for ethylene plants. Another naturalgas condensate has beenfound
to contain 5% elemental, 21%inorganic, and 74% organometallic mercury16
.
Mercury Detection: Problems with mercury detection mean that operators will often have no
indication of impending trouble until failure of an equipment item due to mercury induced corrosion.
Detection of very low levels of mercury in natural gas streams has been verydifficult indeterminingwhich
streams are contaminated, and the degree of contamination.
Detection methods continue to improve, however. A number of available analyzers now claim
capability at the parts per trillion by volume (pptv) level. All of these methods rely on passing a sample
8. 8
stream through a mercury trap (dosimeter) over a long collection period, and then desorbingthe mercury
from the trap as a concentrated pulse into the detector17
.
Primary methods for elemental mercury detection in the gas include gold filament analyzers, cold
vapor atomic fluorescence (CVAF), peroxide scrubbing, and ICP/mass spec8
. CVAF is the preferred
method for laboratorywork, as it is verysensitive. One companyreported theygot accurate and consistent
results measuring mercury levels inthe feed and treated gas usingthe Jerome Model431 mercuryanalyzer
to less than0.001 g/Nm3
usingthe gold wire trap, provided that the sample lines are kept ultra-cleanover
the required long collectionperiod17
. Another companyinstalled a continuous online samplingsystemthat
could accuratelymeasure mercurydownto the 0.001 g/Nm3
level, and found that the Sir Galahad system
by P S Analytical Ltd.10.523 (atomic fluorescence spectrometry) unit could be adapted18
.
All of the methods mentioned above are gradually being improved to more accurately detect ppbv
levels inthe feed gas, and the pptvrequired inthe treated gas. However, theystillhave some problems. For
example, gold filament analyzers, which are the most frequently used detection instrument, have trouble
measuringorganometallic mercury, are sensitive to temperature changes, moisture, H2S, and mercaptans in
the gas, and cannot measure the gas at operating pressures.
For liquid analysis there are two known models: Nippon Instrument Corp. Model SP-3D (uses an
atomic absorption detector), and the PS AnalyticalLtd Merlinmodel(whichuses anelectronfluorescence
detector). One company had the analytical capability to analyze liquid samples including naphthas and
naturalgas condensates, and had developed a method to differentiate betweenthe various species20
.Levels
as low as 0.1 ppb wt. can be quantified.
The most accurate measurements should be done at operating conditions and over a prolonged
collection period8
. As a further complication to the situation, mercury levels in natural gas have been
reported to fluctuate bya factor offive over periods longer thaneight hours8
. Inaddition, whensamplesare
9. 9
collected in the field and brought to the lab, some of the mercury is adsorbed on the container walls,
resulting in lower readings.
MERCURY ATTACK ON EQUIPMENT
A large amount oflaboratorywork onmercurycorrosionis described inthe literature9,10
. Four major
methods of mercuryattack onaluminumand other structuralmetals have beendetermined. Amalgamation
occurs whenelementalmercurymakes a liquid metalsolutionwiththe base metal. Amalgamcorrosionuses
mercuryas a catalyst inthe presence ofwater to forma crystalline hydrated oxide ofthe base metal. Liquid
metalembrittlement (LME) involves the liquid diffusionofmercuryalonggrainboundaries inthe base metal
and can lead to rapid propagationofcracks. Mercuric galvanic corrosionaccelerates acid/base reactions
for a base metal in a corrosive service.
Amalgamcorrosionand LMEhave beenthe primarymeans ofmercuryattack inaluminumequipment
items that have failed. Both of these methods ofattack maybe prevented bykeepingthe temperature too
low for the reactions to proceed, or byanoxide coatingonthe surface ofthe base metal. However, frozen
mercurytends to accumulate incracks and crannies where the metalhas either not formed anoxide layer or
the oxide has cracked due to system temperature changes during a shutdown.
Areas of particular susceptibility are behind backing rings and along welds where the weld heat has
damaged the oxide and/or formed an aluminum/magnesium solution (Aluminum alloy 5083 is 4.5%
magnesium by weight) which is especially vulnerable to mercury attack. Uponlongshutdownperiods, or
during deriming operations, the mercury will melt and attack the base metal.
REMOVAL OF MERCURY FROM NATURAL GAS
10. 10
Many methods for preventing mercury attack have been tried. Measures have included surface
treatment of aluminum, making all aluminum equipment free draining for removal of liquid mercury, and
adding refrigeration units to ensure that the cold boxes stay cold and mercury remains frozen evenduring
sustained periods of plant shutdown. Work is inprogress10
onmethods ofremediationfor equipment that
has already been contaminated by using a chelating agent to remove concentrations ofelementalmercury.
However, operators have arrived at a consensus that it is best to remove the mercuryfromthe naturalgas
rather than preventing or remediating attack once the equipment has been contaminated.
Scavenging Elemental Mercury From The Vapor Phase: Scavenging elemental mercury and
organometallic compounds from the feedstock(s) of gas plants is a maturing technology for mercury
removal. Elemental mercury can be readily trapped by contact with sulfur based trapping agents. The
principle commercial trapping agents include sulfur, metal sulfides, silver and gold. The types of support
materials or carrier agents include activated carbon, alumina and other zeolite materials. Operating
temperatures range from ambient to 100 C, and at pressures up to 100 bar.
Elemental mercury in the gas phase is readilytrapped bysulfur based trappingmaterials whichfixes
the volatile mercuryinthe formofnon-volatile mercurysulfide (HgS). Most commonly, anactivated carbon
is chemically treated or impregnated with a mercury-fixing compound such as sulfur. The mercury is
chemisorbed onto the non-regenerative carbon which must be periodically replaced (typically every 3-4
years).
Activated carbonperforms best ongas streams that are 10-20 C above their hydrocarbondewpoint,
are not saturated withwater (relative humidityofthe gas is 70% or less), and whenthere is verylittle liquid
entrainment. Condensation of hydrocarbons and water would adversely affect the mercury removal
efficiency of the activated carbon and frequency of its change out.
11. 11
The mercury loading capacity of the activated carbon is 10-30wt% of the weight of the carbon,
dependingonthe manufacturer. The mercuryremovalefficiencyis greater than99%, below 0.01 g/Nm3
in
the treated gas. There are several activated carbon manufacturers/suppliers that offer a product for
elemental mercury removal including the following:
ALCOA Mersorb: Sulfur impregnated pelletized activated carbon.
Barneby & Sutcliffe Type CBII: Sulfur impregnated activated carbon.
Calgon Carbon Type HGRR
: Sulfur impregnated granular activated carbon.
CarboTech GmbH Type D47/4: Sulfur impregnated activated carbon.
Lurgi Type Desorex HGD.
Norit Type RBGH 3: Sulfur impregnated activated carbon.
Manufacturers/suppliers of the alumina carrier type include the following:
Procatalyse, CMG 273/275: Sulfur impregnated alumina molecular sieve. CMG 273 is used where the
natural gas is wet and there is liquid entrainment. CMG 275 is used for treatment ofnaturalgas where there
is little to no risk of liquid entrainment16
. Mercury content inthe treated gas is below 0.01 g/Nm3
. These
are not regenerable.
JGC Corp., MR-3: Metal sulfides supported on the surface of alumina. The manufacturer reports19
the
mercury content inthe treated gas is reduced to less than0.001 g/Nm3
, and mercuryadsorptionis as high
as 10 wt%. Mercuryis captured inthe formofmercurysulfide bycontact withthe metalsulfides adsorbent.
The captured mercury can be released and recovered at high temperatures with hydrogen.
ICI Katalco is marketingMERESPECTM
1157:a fixed bed chemicalabsorbent - mixed metaloxides with
cementitious binder. They report it to be a highly effective absorbent for both hydrogen sulfide and
elementalmercuryremoval, and it canbe used bothongaseous and liquid streams. ICI Katalco also reports
12. 12
this adsorbent reduces the mercurycontent below 0.01 g/Nm3
inthe treated gas. The spent adsorbentcan
be sent to a metal refiner/smelter for metals recovery, including the mercury.
UOP HgSIVTM
:Regenerative dualpurpose molecular sieve containingsome silver. The elementalmercury
(either in the gas or hydrocarbon liquid) amalgamates with the silver, and the rest of the HgSIV absorbs
water. Both the mercury and water are regenerated from the HgSIV adsorbent using conventional dryer
regeneration techniques. UOP reports this adsorbent to reduce the mercury content in the treated gas to
below 0.01 g/Nm3
. UOP also reports that the disposalrequirements for spent HgSIV are the same as for
conventional molecular sieves20
.
Removing organometallic mercury from the liquid phase. Less work has been done on the
problem of removal of organometallic mercury from liquid streams than that of the vapor phase removal.
The current leading approaches involve adsorption onto a carbon or molecular sieve, and the use of ion
exchange resins, such as:
ALCOA Mersorb LH: Impregnated pelletized activated carbon.
Calgon Type HGR-LH: Potassium iodide impregnated granular activated carbon.
Stamicarbon Ion Exchange Process6
: Ion exchange resin with thiol groups.
ICI Katalco MERESPECTM
1157:a fixed bed chemicalabsorbent - mixed metaloxides withcementitious
binder.
UOP HgSIVTM
: Silver containing regenerative molecular sieve.
Another method for organometallic mercuryremovalis the IFP/Procatalyse process12
which, through
hydrogenolysis of the organometallic compounds at moderate conditions on a catalyst bed reactor, yields
metallic mercury. The elementalmercurythus produced is thentrapped at a lower temperature ina second
reactor on a bed of the Procatalyse CMG-273 catalyst.
DISPOSAL ISSUES OF MERCURY CONTAMINATED WASTE
13. 13
Mercury contaminated waste from natural gas processing sites can include used catalysts (such as
spent activated carbon, alumina and molecular sieves) contaminated equipment, and contaminated soilfrom
spills and equipment leakage. The mercurycontaminated waste is classified as a D009 characteristic waste
and remediationis covered by40 CFR300 (Superfund). The spent carbonmercurycontent inthe formof
mercury sulfide varies anywhere from 4 wt% to as high as 30 wt%.
Some of the activated carbon suppliers will take the spent carbon back and a) reactivate it and
recover the mercury or b) dispose of it in an environmentally safe manner. They would also take care of
emptying, and rechargingthe adsorber. Other plant operators store the spent materialonsite for examplein
concrete bunkers where they can monitor mercury leakage.
Currently, the onlyapproved Best Demonstrated Available Technology(BDAT) bythe U.S.EPAfor
treatment of mercury contaminated waste is thermal roasting and vacuum retort13
. This treatment is
energy-intensive, costly, and time-consuming. In addition, the treatment usuallyrequires transportationof
the contaminated material or equipment to a central processing site, as mobile treatment units are not
designed to process large quantities of waste.
With the exception of the Stamicarbonionexchange resinprocess, UOP HgSIV, and JGCs MR-3,
the other commercialmercuryscavenger catalysts are nonregenerable. After a typicaloperatingperiod of
three to ten years, the entire mass of adsorbent, often more than5000 kg, withup to 20-30% mercuryby
mass, must be properly disposed.
WithUOPs HgSIV, most ofthe mercuryends up inthe regenerationgas. The mercuryconcentration
in the regeneration gas varies, depending on the regeneration time and temperature. It can peak above
4,000 g/Nm3
for a short period. Normally, the regeneration gas is cooled near ambient, and mixed with
14. 14
other gases. A small activated carbon bed can be added to remove the bulk of the mercury from the
regeneration gas.
Depending on the final cooling temperature, some of the mercury could condense with the water.
UOP reports this to be less than 0.5% of the inlet mercury20
, and that the solubilityofmercuryinwater is
about 25 ppbw. Anyadditionalamount above this would formits ownlayer whichcanbe readilyremoved
and sold. The last fugitive mercury can also be removed from the condensed water.
Disposalinvolves shippingto the processingsite, thermaltreatment, and sanitarylandfillingtheresidue.
Since LNG and many LPG production plants are overseas and mercury treatment facilities are in the
United States or Europe, transportation is expensive and faces a large number oflegalrequirements. The
thermal treating itself is expensive because it must be done in an inert atmosphere or under a vacuum, but
part of the cost can usually be recovered through purification and resale of liquid mercury.
Disposal of the residue must be in a sanitary lined landfill. Existingthermaltreatment processes can
treat up to 150 tonnes of waste per day with over 99.9% recovery of elemental mercury at an estimated
cost of $125 to $225 per ton of material, such as mercury scavenger catalyst or contaminated soil.
New Treatments. A number of new treatments show promise for helping meet mercury waste
specifications. Physical separation technologies based on the high density of mercury are used to treat
contaminated soils and have some effectiveness at bulk removal. However, physical separation cannot
remove the mercury that sorbs onto soil, or mercurychemicallybonded to scavenger catalysts. Biological
treatments use bacteria to concentrate organic mercurycompounds. Immobilizationtechnologiesreducethe
leachability of mercury into groundwater from contaminated soils. Chemicaltreatments show the greatest
promise of providing an alternative to thermal treatment. These technologies typicallyuse anacid to leach
the mercuryfromthe contaminated material. New approaches suggest usingan organic chelatingagentfrom
which the mercury can be recovered. None of the technologies described in this paragraph have yet
demonstrated the ability to achieve U.S. EPA standards.
15. 15
CONCLUSIONS
The presence of elemental and organometallic mercury in natural gas can lead to destruction of
cryogenic process equipment, contaminationofvessels, tanks, and soil, and hazards to operatingpersonnel.
Detection and prevention of mercury contamination is critical to the safe and reliable operation ofanygas
processing plant, particularly those in cryogenic gas processing.
Remediation of mercury contaminated soils and equipment is a costly and complicated procedure.
The current BDAT is thermal roasting or vacuum retort, whichis veryexpensive, time consuming, and not
as flexible as is necessary for treatment of contaminated equipment. However, new processes are under
development which show promise of solving some of the shortcomings of thermal treatment.
16. 16
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72, Jan., 1976, p.39.
2. Leeper, J. E., "Mercury - LNG's Problem," Hydrocarbon Processing, Nov., 1980.
3. Wilhelm, S. M., and A. McArthur, "Removal and Treatment of Mercury Contamination at Gas
Processing Facilities," SPE 29721.
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Arsenic and Mercury Removal from Liquid Hydrocarbon Feedstocks"
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Antonio, Texas, U.S., March, 1995.
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Annual Convention, New Orleans, Louisiana, U.S., March, 1994.
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AnnualConvention, New Orleans, Louisiana, U.S., March,
1994.
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International
Conference on Liquefied Natural Gas, Nice, France, 17-20 Oct., 1989.
17. 17
13. Energy and Environmental Research Center, UND, "A Review of Remediation Technologies
Applicable to Mercury Contamination at Natural Gas Industry Sites," GRI Report 93/0099,
September, 1993.
14. UOP, E.S.Holmes, D.J.Kubek, J.Markovs, and E.P. Zbacnik, Process Improvements InAcid Gas
and Mercury Removal, AIChE 1994 Spring National Meeting, April 17-21, 1994.
15. IUPAC, Solubility Data Series, Vol. 29, Mercury In Liquids, Compressed Gases, Molten
Salts and Other Elements, Appendice IV, p. 240, 1987.
16. C.J. Cameron, Y. Barthel, and P. Sarrazin, Mercury Removal from Wet Natural Gas, GPA,73rd
Annual Convention, March 7-9, 1994, New Orleans LA.
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Gas Conditioning Conference, March 4, 1996, Norman Oklahoma.
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Aluminum Coldboxes, GPA, 75th Annual Convention, March 13, 1996, Denver, Colorado.
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Gas LiquefactionPlant, 10thInternationalConference onLiquefied NaturalGas, 23-28 May, 1992,
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