Mono Ethylene Glycol (MEG)The Most Complex Simple
Utility on Your SiteSteven Cooper
Hydrocarbons Sector ManagerAPAC Safety Consulting Focal point
Process Safety Professional
November 2016
Ethylene Glycols - utility products
• MEG, DEG, TEG and TETRAEG are versatile chemical intermediates
• Primary use is as a utility• MEG commonly used for plant and pipeline
integrity management• Used for corrosion inhibition, hydrate
management and keeping high pH in production systems
• DEG, TEG and TETRAEG have excellent hygroscopicity and low volatility
Operating withMono Ethylene Glycol
Other name(s): Ethylene glycol | MEG | 1,2-Ethanediol | 1,2-Dihydroxyethane
Physical propertiesPhysical State: Slightly viscous liquidColour: ColourlessOdour: OdourlessMolecular Formula: CH2OH CH2OHSolubility: Miscible in waterVapour Pressure (20 °C): 0.01 kPaFlash Point (°C): 110 (CC)Flammability Limits (%): 3.2-12.8 (vapour in air)Auto ignition Temperature (°C): 412Boiling Point/Range (°C): 197Viscosity: 21 cP @20°CFreezing Point/Range (°C): -13
Operating with MEG provides…
Corrosion Protection• Pipelines vulnerable to
corrosion• Water reacts with
contaminants to acidise water
• MEG in the aqueous phase absorbs water in the gas
• Offshore pipelines subject to low temperatures and high pressures are vulnerable to hydrate formation
• Hydrates formed from free water and gas, reducing flow
• MEG suppresses hydrate formation
Hydrate Protection
However there are always contaminants…Hydrocarbon contaminants can:• Cause the MEG regenerator to operate
erratically• Cause irregular vapour and liquid loads
across packed beds often resulting in column “burping”
• Promote glycol carryover into downstream systems
• Generate excessive back pressures on the MEG regenerator
• Swing lean glycol concentration
Operating with MEG• Condensate must be separated from the
MEG phase prior to recovery to reduce product losses…
• Emulsions form between condensates and MEG, seeing contaminants transported around production facilities
• Factors that need to be controlled include:• Presence of fines• Interfacial tension • Pressure and/or temperature• Foaming
Effect of temperature on emulsion separation
0 Min 5 Min3 Min2 Min1 Min
24ºC
50ºC
The emulsion separates out hydrocarbons contaminants/liquid at lower temperatures
Operating with MEG
• The extent of fouling depends on composition of the production stream
• Equipment items for concern are MEG reboilers, heat exchangers, distillation columns and pipes and pipelines (essentially ALL equipment)
“integral parameter for contaminant precipitation is temperature“
Fouling
An Alternate “Solution”
Use of Ultra Pure MEG™ contains dissolved oxygen levels of less than 20 parts per billion and NAS class 6 cleanliness levels
Minimises generation of contaminants
• Operating facility with existing fouling and blockages • New reservoir conditions require large MEG demand• Predicted increase in fouling and iron sulphide/oxides
MEG Operating Case StudyPotential for increased fines & increase in H2S concentration• Historical start ups saw MEG filter interventions increase
1 to 11 in the first year then reduce to five/six for the next few years
• Introduction of the new field was likely to be similar• Plant made provisions of stocks of replacement filter
elements on site for the start-up period• Prepared to manage the manual removal of
contaminants
Iron Sulphides are pyrophoric materials
Operating withPyrophoric Materials
What is a Pyrophoric Material?A Pyrophoric Material is a liquid or solid
that, even in small quantities and without an external ignition source, can ignite
after coming in contact with air.
How do you manage Pyrophorics? Traditional Methods
Chemical neutralisatio
n before opening
equipment
Keep wet until
removed to a remote
area
Maintain constant air ventilation to ensure
any reaction completes
Replace chemical
components that contain
sulphur compounds
Use nitrogen or inert gases
to keep oxygen out
Be quick - move scale
and potential
pyrophorics to remote
area
Pyrophoric case study
Fire at Hickson & Welch Ltd• 2nd largest manufacturer of nitrotoluenes• Continuous nitration plant• Different materials separated by repeated
distillation & crystallisation• End of system was 60 Stillbase
Conclusions
• Complex reaction chemistry provides a conduit for contaminants
• MEG will deposit particulates where you least expect it• Presence of sulphides = build-up of iron sulphides • You need to understand the potential process equipment
inefficiencies and where exposure to materials could occur• Not considering these facets usually results in unreliable and
difficult to operate facilities
Use of Ultra Pure MEG™ - Chemical Management Simplified
An unidentified hazard is an accident waiting to happen
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