AustraliaProcess Group Pty Ltd

5 Hobbs Court, Rowville, (Melbourne), VIC 3178, Australia.Phone: +61 3 9212 7100 Fax: +61 3 9212 7199

E-mail: sales@processgroup.com.au Web: www.processgroup.com.au

Singapore Process Group Pte Ltd

298 Tiong Bahru Road,#12-02/03 Central Plaza, Singapore 168730Phone: +65 6276 8349 Fax: +65 6274 2005

E-mail: sales@processgroup.com.sg Web: www.processgroup.com.sg

Middle EastProcess Group International Ltd

P.O. Box 46153, Abu Dhabi, UAE.Phone: +971 2 5500 899 Fax: +971 2 5500898

E-mail: sales@processgroupintl.com Web: www.processgroupintl.com

Hydrocarbon Dew Point ControlA.03

Introduction

Hydrocarbon Dew Point Control Units (DPCUs) are designed to inhibit the formation of solid hydrates in gas streams and by default they perform a level of dehydration. This is achieved through the injection of a liquid Hydrate Inhibitor directly into the gas stream. The Hydrate Inhibitor is selected based on low viscosity and low freezing temperature rather than dehydration ability.

There are 2 common types of liquid Hydrate Inhibitor used for Dew Point Depression:

• Mono-EthyleneGlycol(MEG)• Methanol(MeOH)

The type of Hydrate Inhibitor used and the package design dependsonseveralfactors,andtheend-usersspecificrequire-ments and objectives for the gas stream being processed. Eachpackageistypicallydesignedincloseconsultationwiththe client to ensure the best overall design is achieved.

Design Basis

The design of a DPCU follows a basic structure. However, there are a number of approaches to achieve the end means – Hydrocarbon Dew Point Depression.

Eachsystemistypicallydesignedandbuiltasacompleteturn-key package with particular emphasis given to the following issues:

• Dischargegashydrocarbondewpoint,• Dischargegaswaterdewpoint,• Minimuminhibitorlosses,• Minimumpowerconsumption,• Optimumplantefficiency&designintegrity,• CompliancewithHSErequirements,• Environmentallyconscientiousdesign.

The resulting design will be influenced by all of these factors, andtheemphasis&importancegiventoeachparticularissue.

Photograph:MEGDPCU(155TJ/day)package for Blacktip Project, N.T. Australia.

Rev11/2012

Represented by:

Hydrocarbon Dew Point Control

A.03

Process Description

InatypicalMEGInjectionDewPointControlUnit(DPCU),thegasisfirstpassedthroughanInletSeparator(1)whereanyfreeliquidsareremoved.

Justpriortoenteringthegas/gasexchangerpressurisedLeanMEGisinjectedintothegasstream(2).AdditionalMEGisinjectedandtheMEG-gasmixtureisthenfurthercooledthrougheitherExpansion(Joule-ThompsonValve/Orifice)orRefrigeration(3).

Thefurthercoolingcondensesanyresidualwaterand/orhydrocarbons.ALowTemperatureSeparator(LTS)(4) is located downstream to remove any free liquids – now including the condensed water, condensed hy-drocarbonsandinjectedMEG.Thecooledgaswithadepresseddewpointiscirculatedbackintothegas/gasexchangerforpre-coolingoftheinletgas(2).

TheLTSisgenerallya3-PhaseSeparatorwhichallowsthe effective separation of not only the gas from the liquids, but also the aqueous and hydrocarbon liquid phases from one another.

Theaqueousphase,containingthewaterandMEGisroutedtotheMEGRegenerationPackagewherethewa-terisdrivenofftoproduceLeanMEG.Theliquidhydro-carbonphaseisusuallymixedwiththeliquidsfromanyinlet separation and either routed to storage or further processinginaCondensateStabilisationPackage.

© Process Group Pty Ltd, 2008 – 2012.

(OPTIONAL)

CONDENSATE STABILISATION UNIT

Hydrocarbon Dew Point Control Unit

OUTLET GAS

INLET GAS1

MEG REGENERATION PACKAGE

EXPANSION2

6

REFRIGERATION

3

5

4