Emerging Technology Allows Greater Flexibility for the Design and Operation of FLNG

By

Peter J H Carnell

Matthew Humphrys

Worldwide Higher Heating Value (HHV) Specifications

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• Spot sales complicated by differences in LNG specification• Lean LNG gives more marketing flexibility

– Easier for user to add LPG than N2

Typical LNG Flowsheet

Transportation Study Results for Conventional Floating LNG (FLNG)

• Based on Qmax LNG Vessels– Length 400m, breadth 80m, displacement 550,000Te

• High Plant Utilisation Rate Required• Need Spare Storage Capacity to allow for loading

delays– LNG Storage Capacity 350,000 m3

– LPG Storage Capacity 80,000 m3

– Condensate Storage Capacity 160,000 m3

Condensate Storage LNG StorageLPG Storage

Liquefaction Plant

Machinery Space

Accommodation

Seawater intake reservoir

Fla

re t

ower

Floating LNG Hull Layout

• Comparable to the Worlds Largest Ship– Knock Nevis; Length 458m - Breadth 69m

• Larger than Very Large Crude Carriers– Length 333m - Breadth 58m

Ship to Ship LNG Transfer Time Log

Operation Duration (Hrs)

Preparation 13

Cargo Transfer 25.8

Dismantling 6.2

Total Duration 45.0

• 2 – 3 day window for transfers• Difficult operation for two huge vessels• LPG & condensate needs additional transfer equipment & operations

Issues with Higher Hydrocarbons (C2+) on FLNG

• LPG marketable, but adds complexity and reduces LNG storage (or increases vessel size)

• LPG system increases fire risk by ~30%

• C2 content of LPG limited to 2% (vapour pressure)

• Excess C2 may exceed fuel gas demand

• C2 –rich fuel gas may exceed NOx emission limit on gas turbine

• ‘Slopping’ on FLNG can create variable Boil Off Gas, hence variable Fuel Gas composition & Wobbe Number– Impact on Fuel Gas burners

Catalytic De-Richment

• Catalytic De-Richment (CDR) converts higher hydrocarbons (ethane up to naphtha) to methane

• Well established technology developed for substitute natural gas (SNG)

• Overall reactions:

4C2H6 + 9H2O 7CH4 + 7H2O + CO2

2C3H8 + 7H2O 5CH4 + 5H2O + CO2

4C4H10 + 19H2O 13CH4 + 13H2O + 3CO2

C5H12 + 6H2O 4CH4 + 4H2O +CO2

LNG Plant with Catalytic De-richment

Catalytic De-richment Reactors & reactions

Typical CDR Operating Conditions*

Component Inlet Kmol/h Exit Kmol/h

CH4 - 175

C2H6 100 -

CO2 - 25

H2O 167 116

Temp 275 °C: Press 30 bara: Steam/Carbon 0.833

* Patented catalyst

Potential Increase in LNG from Heavy Gases

Raw Gas Composition Product Gas Composition

C1

(%)

C2

(%)

C3

(%)

C4

(%)

C1

(%)

Increased C1

%+

100 - - - 100 -

95 5 - - - 9

90 5 3 2 113 26

85 10 5 - 115 35

Catalytic De-Richment

• Catalytic De-Richment (CDR) converts higher hydrocarbons to methane– Increased LNG production– Simplified FLNG design

• Well established technology • Reduces flaring where ethane in excess of fuel

gas demand• Generates constant

Wobbe number fuel gas• Lean LNG gives more marketing

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Mercury Distribution

J M C o n f i d e n t i a l

G l o b a l H o t S p o t s f o r M e r c u r y i n O i l a n d G a s R e s e r v e s

Why Must Mercury be Removed?

• Avoid corrosion of equipment using aluminium alloys, copper alloys and some other alloys– LME (liquid metal embrittlement)– Amalgam corrosion

• Process cheaper mercury-distressed crudes

• Avoid emissions to environment• Comply with HSE directives &

protect employees– Feb ’09 UN Environment Programme – World-wide

treaty to limit Hg exposure

LME

2004 Moomba Explosion

Losses:• Caused by LME of aluminium

heat exchanger inlet, by Hg• Leading insurers put the insured

loss at A$320million (USD245 million)

• Energy crisis in NSW & South Australia– Supplies were limited to 30-40%

capacity– Cutbacks by major industrial

customer– Job layoffs

PURASPEC Mercury Removal Technology

• Uses variable valency metal sulphide

Hg + MxSy → MxSy-1 + HgS

• Metal sulphide can be generated in situ from mixed metal oxide (patented co-removal of H2S & Hg)

• Grades for gas and liquid hydrocarbons (LPG, condensate etc)

• Can be used on saturated gas

Full Cradle to Grave Service

• Optimisation of Mercury Removal Unit (MRU) design with customer

• Data sheets and vessel drawings– Low PD radial flow designs possible

• Provision of most suitable absorbent• Supervised loading and discharge• Recycling of spent absorbent

– Absorbents are made from materials compatible with smelters

– Only audited, approved smelters used– Certificate proves environmentally safe disposal

Mercury Distribution – Gas Processing Plant Mercury Survey Results

4%

2%Multiphase

flowSeparation

Cooling/Al Heat

Exchanger

LP Compression

Amine System

Fuel Gas

<10 nanogram / Nm3

inlet specification

Export

Overboard

NGL’s

Separation

ExportRegeneration Medium

Wells

100%

2%

90%

8%

90%

25%

Amine

65%

5%20% 19%

15%

GasOil

NGL’s

WaterGlycol

Amine

Oil Storage/Export

Compression

4%

Waste Water

Molecular Sieve/Glycol Unit

Recommended location of MRU

Typical location of (carbon) MRU

Fit and Forget Technology

• Intervention only required for charging and discharging

• High mercury capacity gives long bed life

• Sharp absorption profile means bed can cope with high excursions in mercury in feed and in the flow rate of feed

FPSO SE ASIA

MRU on FPSO

Oil & Gas Platform Gulf of Thailand

Offshore MRU

Conclusions

• Catalytic De-Richment can be used to increase LNG production – Free up space for LNG storage or reduce size of vessel– Simplifies FLNG design and improves safety– Potentially reduce the need for flaring

• Mercury removal essential– Location upstream of acid gas & water removal

maximises protection of equipment, people and environment