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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exceed the defined gray box.

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


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)


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 8 8

MEG Reclamation – Slip Stream – Nature of the

aqueous streams


MEG Reclamation – Full Reclaimer – Nature of

the aqueous streams






What Next?


• 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






Example – Physical Properties

What Next?


• 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


• 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


• 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


• 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)


• 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.


• 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






Example – Reclaimer VLE

What Next?


Stream Analyzer™ Applications

Rich MEG

Water

Lean MEG

NaCl

MEG-water vapour


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






Example – NaCl solubility mapping

What Next?


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.






Example – Reclaimer Solubilities

What Next?


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






Example – Calcium Removal

What Next?


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



• 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



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






What Next?


• 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


OLI Stream Analyzer™ in the Design of

MonoEthyleneGlycol (MEG) Reclamation Units

Thank You…

Any questions ?

Brian Messenger

Cameron Limited , Sunbury-on-Thames , Middlesex , UK

[email protected]

www.c-a-m.com

mailto:[email protected]





http://www.c-a-m.com/





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