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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