oli stream analyzer in the design of monoethyleneglycol...
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OLI Simulation Conference, Whippany, NJ
16-17 October 2012
OLI Stream Analyzer in the Design of
MonoEthyleneGlycol (MEG) Reclamation Units
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Process & Compression Systems 2
MEG Reclamation – Overview
Where is Stream Analyzer™ Used
What Next?
MEG Reclamation
• MEG (Monoethylene Glycol) is injected into gas production pipelines to protect
against hydrate formation
Process & Compression Systems 3
Hydrates form at high pressures
and low temperatures associated with
long sub-sea gas pipelines
Hydrate Engineering E. Dendy Sloan Jr. – SPE Monograph Vol 21
Increasing
MEG
Well
Head
Process
Facility
Process & Compression Systems 4 4
MEG Reclamation – What is it?
Subsea Development
(Tied Back to
Host Facility)
Compliant
Tower
Tension
Leg Platform SPAR
Concept
Floating
Production
Unit
Tension Leg
Platform (TLP) Floating Production
Storage Offloading
Unit (FPSO)
Deep
Water
Platform
Cameron design & fabricate
MEG Recovery Packages
employing proprietary
technology to minimise MEG
losses
Longer sub-sea tie-backs
require mitigation against
hydrate formation.
MEG injection is one option
MEG Reclamation
• MEG Plant unit operations
Removal of free hydrocarbon – PRE-TREATMENT
Removal of Produced Water -REGENERATION
Removal of Dissolved Salts – [NaCl] – RECLAMATION
Removal of Divalent Cations (Ca2+, Mg2+, Fe2+) – CALCIUM REMOVAL
• By convention…
Inlet RICH MEG ‘Rich’ in water
Product LEAN MEG ‘Lean’ in Water
• By convention…
MEG wt% salt-free basis MEG / (MEG + H2O)
salt wt% mass basis TDS / (MEG + H2O + TDS)
Process & Compression Systems 6
MEG Reclamation
• The selected configuration of MEG Reclamation / Regeneration Packages is
project dependent.
A number of factors are considered:
On-Shore v. Off-Shore
MEG Feed Rate
Salt content
Lean MEG Specification
• Slip-Stream Reclaimer–
• Some salt returns with Lean MEG to MEG Injection Valve
• Full Reclaimer –
• Salt-free MEG returned to Lean MEG Injection Valve
• Generally smaller footprint / fewer equipment items– Preferred for Off-Shore
applications
Process & Compression Systems 7
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Process & Compression Systems 10
MEG Reclamation – Overview
Where is Stream Analyzer™ Used
What Next?
Process & Compression Systems 11
• Some Examples
Equipment sizing - Physical properties of aqueous streams
Chemistry - Solubility limits – Sodium Chloride / Calcium Chloride
Chemistry - Calcium Removal - precipitation from MEG-water solutions
Stream Analyzer™ Applications
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Process & Compression Systems 12
MEG Reclamation – Overview
Where is Stream Analyzer™ Used
Example – Physical Properties
What Next?
Process & Compression Systems 13
• Equipment Sizing – Physical Properties of MEG-water-salt solutions
Dissolved salts change physical properties of MEG-water mixtures.
Equipment sizing requires correct physical property data
Simulation software [Hysys / ProMax] do not include ‘salt’
OLI can generate density, specific heat, viscosity and thermal conductivity
values
Stream Analyzer™ Applications – Physical Property Data
Process & Compression Systems 14
• Physical Properties of Salt-Free MEG-water streams
Hysys v MEGlobal Brochure v OLI v Cameron curve fits
Density –
50% MEG, 50% water
Specific Heat
90% MEG, 10% water
Viscosity
50% MEG, 50% water
Thermal Conductivity
90% MEG, 10% water
Viscosity –
95-99% MEG, 1-5% water
Process & Compression Systems 15
• Solubility of Sodium Chloride in MEG water
Stream Analyzer™ provides solubility limits for NaCl in MEG-water streams throughout the MEG Package.
Normally operate at <50% of solubility limit
Rich MEG:
30-60%MEG
5-80oC
Lean MEG:
80-90%MEG
40-145oC
Recycle MEG:
95-99%MEG
120-150oC
NaCl Brine
0%MEG
40oC
Process & Compression Systems 16
• Physical Properties of Saline MEG-water streams
We use OLI to quantify deviations in selected physical properties as a function of dissolved NaCl
NaCl is the predominant dissolved salt in most cases – salt = NaCl.
Density at 25oC
δρ = 6.6 kg/m3 per wt% NaCl
Specific Heat
Capacity at 25oC
Δ(sp.ht) = f(NaCl,MEG)
Process & Compression Systems 17
• Physical Properties of Saline MEG-water streams
OLI – Predicted Viscosity at 80oC 0-10% salt
Added salt has little effect on
calculated viscosity. Viscosity at 80oC from experimental results
Viscosity = f(NaCl)
Cameron employs correlations from
experimental data for viscosity
calculations.
Process & Compression Systems 18
• OLI Stream Analyzer™ is
one of a suite of tools
used to determine physical
properties in MEG
Regeneration &
Reclamation Packages.
• Cameron has a MEG Pilot
Plant operating at The
University of Manchester
in UK plus bench-scale
test equipment
• Cameron plans to
generate additional
physical property data for
correlation with OLI /
Hysys / Promax.
Stream Analyzer™ Applications – Physical Property Data
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Process & Compression Systems 19
MEG Reclamation – Overview
Where is Stream Analyzer™ Used
Example – Reclaimer VLE
What Next?
Process & Compression Systems 20
Stream Analyzer™ Applications
Rich MEG
Water
Lean MEG
NaCl
MEG-water vapour
Process & Compression Systems 21
Stream Analyzer™ Applications – Reclaimer VLE
NaCl
Rich MEG
The Reclaimer Vessel is operated at 0.1-0.3bara to reduce
temperature and minimise MEG degradation
A large recycle stream is used to vapourise the incoming MEG-
water.. OLI can be used to predict vapour liquid equilibrium
1bara / 50%MEG / 160oC
VAP LIQ
0.2bara / 50%MEG / 120oC
VAP LIQ
MEG-water vapour
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Process & Compression Systems 22
MEG Reclamation – Overview
Where is Stream Analyzer™ Used
Example – NaCl solubility mapping
What Next?
Process & Compression Systems 23
Stream Analyzer™ Applications – Salt Solubility
High salt levels in the Regenerator
Reboiler can lead to scaling by NaCl.
This may direct the project to Full
Reclaimer mode.
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Process & Compression Systems 24
MEG Reclamation – Overview
Where is Stream Analyzer™ Used
Example – Reclaimer Solubilities
What Next?
Process & Compression Systems 25
Stream Analyzer™ Applications – Salt Solubility in Reclaimer
NaCl
Rich MEG
Rich MEG feed contains
dissolved salts
NaCl, KCl,
MgCl2, CaCl2, MCl2
NaHCO3
Na2SO4
MEG and Water are vapourised
Salt accumulates in MEG
Recycle Pool
95-99% MEG
0.1-0.3bara
120-150oC
OLI is used to predict precipitation from Recycle MEG
1. Solids accumulate in MEG pool
2. NaCl precipitates at 7wt%
2
3. Mixed salt KCl.CaCl2 is predicted at 24% dissolved salts
3
4. BaCl2 is predicted at 26% dissolved salts
4
5. CaCl2 is predicted at 32% dissolved salts
5
6. Solution density (and viscosity) rise as salts accumulate
6
In practice, only sodium chloride precipitates
Calcium accumulates as complex CaCl2.(MEG)x
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Process & Compression Systems 26
MEG Reclamation – Overview
Where is Stream Analyzer™ Used
Example – Calcium Removal
What Next?
Process & Compression Systems 27
Stream Analyzer™ Applications – Calcium Removal
• Calcium in the MEG-Water is removed by elevating pH
CaCl2 + Na2CO3 CaCO3 (s) + 2 NaCl
• Magnesium is more soluble in alkaline solutions than Ca2+ and other M2+ species.
• Elevated pH is required for precipitation of magnesium (pH >9.0)
MgCl2 + 2 NaOH Mg(OH)2 (s) + 2NaCl
• Bicarbonate in Formation Water is a source of carbonate for Ca precipitation
HCO3- + OH- CO3
2- + H2O
Process & Compression Systems 28
Stream Analyzer™ Applications – Calcium Removal
• Stream Analyzer™ is used to help predict the extent of M2+ precipitation
‘Typical’ Rich MEG feed
stream to MEG Package
Need to
remove M2+ as
MCO3 &
M(OH)2
CaCO3
pH
BaSO4
pH = 8
SrCO3 pH = 8.2
BaCO3
pH = 9
FeCO3
No magnesium precipitation is predicted on addition
of carbonate – pH too low
ADD Na2CO3 solution
This is
achieved by
raising pH
Stoichiometry
indicates:
Need 70kg of
Na2CO3
plus
10kg NaOH
ADD NaOH to 70kg Na2CO3
solution
Process & Compression Systems 29
Stream Analyzer™ Applications – Calcium Removal
CaCO3
pH
SrCO3
BaCO3
Magnesium precipitates as
Mg(OH)2 at pH > 9.1
FeCO3
pH > 9.2
OLI model output is reflected in
experimental results..
Mg is more difficult to precipitate than Ca
Experimental data show that precipitation of
magnesium occurs on addition of Na2CO3 alone…
Ideally, all of the divalent cations would be removed
100% efficiency is never achieved -
Breakthrough of Ca2+ / Mg2+ is managed by blowdown.
Some uncontrolled precipitation (scaling ) of CaCO3 / Mg(OH)2 / … will
occur. Managed by Clean-In-Place – ADD ACID
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Process & Compression Systems 30
MEG Reclamation – Overview
Where is Stream Analyzer™ Used
What Next?
Process & Compression Systems 31
• Future application of OLI software to MEG Recovery Units:
• OLI review physical property correlations at high MEG / high temp / high salt
• Cameron will generate experimental data -
• Physical Properties – high temperature , high MEG, high salt
• Calcium Chemistry
• Oxygen Chemistry
• Metallurgy – RedOx Chemistry /Corrosion
• Develop MEG Loop Chemistry – Subsea – Scaling & Corrosion
MEG Reclamation – Stream Analyzer™ - Future Work
Process & Compression Systems 32
OLI Stream Analyzer™ in the Design of
MonoEthyleneGlycol (MEG) Reclamation Units
Thank You…
Any questions ?
Brian Messenger
Cameron Limited , Sunbury-on-Thames , Middlesex , UK
brian.messenger@c-a-m.com
www.c-a-m.com
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