Lng Plant Process Useful

(1)

DRIVER SELECTION FOR

LNG COMPRESSORS

14

thth

_{December 2004}

Dr Sib Akhtar

MSE (Consultants) Ltd MSE (Consultants) Ltd Carshalton, Surrey SM5 2HW Carshalton, Surrey SM5 2HW [email protected] [email protected] http://www.mse.co.uk Tel: 020 8773 4500 http://www.mse.co.uk Tel: 020 8773 4500

(2)

Driver Selection for LNG Compressors

Introduction

Drivers Used in Past & Present Projects

Factors Influencing Driver Selection

Potential Future Applications

Pros & Cons of:

Steam Turbines

Industrial Gas Turbines

Aero-derivative Gas Turbines Electric Motors

(3)

Introduction

History

Early LNG Trains Steam Driven

Development of Gas Turbines

The LNG Growth Pause

US & UK became self sufficient in Gas

Japan and later Korea needed secure energy-LNG Japan remains the biggest importer of LNG

Re-emergence of LNG Demand New Markets

Gas Shortages in US Re-opening of LNG terminals Expansion of LNG in Europe

(4)

Common LNG Process Systems

Phillips Cascade Process

Three Pure Components

Propane

Ethylene

Methane

APCI (Air Products)

Two Components

Propane

(5)

New Emerging LNG Process Systems

Linde Process

Three Mixed Refrigerants

Axens Liquefin Process

Dual Mixed Refrigerant

Shell Process

(6)

Factors Influencing

Compressor Driver Selection

Factors Influencing

Compressor Driver Selection

Plant Capacity

Process Used – Choice and Number of

Refrigerant Streams

Compressor Configuration

Plant Location; Ambient Conditions

Plant Availability

Operational Flexibility

(7)

Gas Trade Flows

(8)

LNG Import Capacity

(9)

LNG Export Capacity

(10)

LNG Processes

Phillips Optimised Cascade and Air Products

(APCI) processes dominate the LNG plants

currently under design, construction & operation

New processes include:

Axens (DMR)

Linde (Statoil)

(11)

Phillips Cascade Process

Many plant still being designed and built using

the cascade process – simple and reliable

Three pure components used for refrigeration:

Propane pre-cooling

Ethylene

(12)

Phillips Cascade Process

Propane pre-cooling

Centrifugal compressors

Typically 2 x ~30 MW Gas Turbines (e.g. Frame 5)

Ethylene and Methane cycles

Centrifugal compressors

Typically 2 x ~30 MW Gas Turbines (e.g. Frame 5)

for each cycle

(13)

Phillips Cascade Process

ALNG – Trinidad

Phillips Cascade Process

ALNG

–

Trinidad

Propane pre-cooling

Centrifugal compressors

2 x Frame 5 C – upgraded to D

Ethylene and Methane cycles

Centrifugal compressors

2 x Frame 5 C upgraded to D for each cycle

Plant Capacity 3 MTPA – Raised to 3.3 MTPA

High Availability 95-96%

(14)

Phillips Cascade Process

ALNG – Optimised Design

Phillips Cascade Process

ALNG

–

Optimised Design

(15)

Phillips Cascade Process

Simple to design and operate

Simple cycle Frame 5 gas turbines mechanical drive

No helper turbine or large motor needed for start-up

Increased size with two gas turbine trains for each

refrigerant process

Parallel compressor trains avoids capacity limits

Increased CAPEX due to more (six) trains offset by

increased availability 95-96% with parallel train operation

Loss of one train does not cause plant shut down

Production carries on with reduced capacity

Refrigerant and exchangers temperature not affected by

one train trip enabling quick restart

(16)

APCI Process

Most of existing plant are using the APCI process

with 3 – 3.3 MTPA Fr 6 / Fr 7 combination

Train capacities up to 4.7 MTPA built or under

construction using Fr 7 / Fr 7 combination

Higher Capacities to 7.9 MTPA being announced

with Frame 9 GT

Two main refrigeration cycles:

Propane pre-cooling

(17)

APCI Process

Propane pre-cooling

Centrifugal compressor (to 15 – 25 bar)

Side-streams at 3 pressure levels

Typically requires a ~40 MW Gas Turbine (e.g.

Frame 6) plus Helper Motor or Steam Turbine

Compressor sizes reaching maximum capacity

limits

Added aerodynamic constraint; high blade Mach

numbers due to high mole weight of propane (44)

Prevents utilisation of full power from larger gas

turbines (Frame 7)

(18)

APCI Process

Mixed refrigerant liquefaction and sub-cooling

Axial LP for Shell Advised Plant

Centrifugal HP compressor (45 – 48 bar)

Typically requires ~70 MW Gas Turbine (e.g.

Frame 7) plus Helper Motor or Steam Turbine

(19)

(20)

ELLIOTT IN LNG

A HISTORY OF FIRSTS

World’s first large-scale liquefaction plant (CAMEL – Arzew, Algeria)

World’s first baseload refrigeration plant (Phillips - Kenai, Alaska)

World’s first gas turbine driven LNG compressors (Phillips, Alaska)

World’s first single-mixed refrigerant (APCI) process compression (Esso (Exxon) – Marsa el-Brega, Libya)

World’s first dual-shaft (GE Frame 5) gas turbine driven compressor strings (P.T. Arun (Mobil) – Indonesia)

World’s first C3-MR (APCI) process compression (P.T.Arun – Indonesia)

World’s first GE Frame 7 driven Propane MR compressor (Ras Gas 1&2 – Ras Laffan, Qatar)

World’s largest four-section Propane MR compressor (Ras Gas 3 – Ras Laffan, Qatar -UNDER CONSTRUCTION)

(21)

Partial List - ELLIOTT LNG Plants

End User Process Capacity MM T/Yr # of Units Service

C.A.M.E.L.

Arzew, Algeria Cascade 1.3 3 3 3 3 3 Propane Ethylene Methane 1 Methane 2 Vapor Phillips Petroleum Kenai, Alaska Cascade 1.1 2 2 1 Propane Methane 1 Methane 2 Esso Libya Marsa El Brega, Libya Mixed Refrigerant 3.2 4 4 MR-1 MR-2 Sonatrach

Arzew, Algeria Mixed Refrigerant & Propane 16.4 6 6 6 MR-1 MR-2 Propane Abu Dhabi Liquefaction Co. Das Island, Abu Dhabi Mixed Refrigerant & Propane 3.0 2 2 2 2 Feed Gas Feed Gas Feed Gas Propane P. T. Arun Liquefaction Co. Lhokseumawe, Indonesia Mixed Refrigerant & Propane 9.0 6 6 6 MR-1 MR-2 Propane Ras Laffan Liquefaction Co. Qatar Mixed Refrigerant & Propane 6.0 2 2 2 MR-1 MR-2 Propane

(22)

APCI Process

Mixed refrigerant liquefaction and sub-cooling

Large volumetric flows

Two casing arrangements (LP and an HP)

Axial LP / centrifugal HP compressor (45 – 48 bar)

Typically requires ~70 MW Gas Turbine (e.g.

Frame 7) plus Helper Motor or Steam Turbine

LP and HP compressor speeds compromised

LP axial compressor (higher efficiency)

(23)

APCI Process

(24)

Example of APCI Process Evolution

Petronas MLNG, located in Bintulu, Sarawak

First trains designed in the ’70s:

3 x Centrifugal compressors

(25)

Example of APCI Process Evolution

Extension trains designed in the ’90s:

Propane pre-cooling:

Centrifugal compressor

30 MW Gas Turbine & 7 MW Steam Turbine

Mixed component refrigeration (MCR):

LP axial compressor & HP centrifugal compressor

64 MW Gas Turbine & 7 MW Steam Turbine

(26)

RAS GAS I & II – RAS LAFFAN, QATAR

RAS GAS I & II

(27)

RAS GAS III (&IV), RAS LAFFAN, QATAR

UNDER CONSTRUCTION

RAS GAS III (&IV), RAS LAFFAN, QATAR

UNDER CONSTRUCTION

(28)

Axens Liquefin Process

Axens

Liquefin

Process

Mixed refrigerants for pre-cooling, liquefaction

and sub-cooling duties

Liquefin development studies presently oriented

towards increasing capacity to 6 MTPA with:

2 x Frame 7 Gas Turbines for main compression

2 x Frame 5 Gas Turbines for power generation

Higher capacities possible using:

Frame 9 GTs

Electric motors

(29)

Axens Liquefin Process

Axens

Liquefin

Process

Similar to APCI with Propane compressor

replaced with Mixed Refrigerant for pre-cooling

Allows more balanced flows, refrigeration loads

and power between the two compressors

Avoids the process design limits associated with

Propane compressors

(30)

Axens Liquefin Process

Axens

Liquefin

Process

(31)

Shell DMR Process

Ref O G J July 16 2001

Shell DMR Process

Ref O G J July 16 2001 Ref O G J July 16 2001

Similar to Axens but with twin parallel

compressor trains for each process stream

Use of aero-derivative or VSD motors

(32)

Linde Process

Mixed refrigerants for pre-cooling, liquefaction

and sub-cooling duties

Minimum of Three Gas Turbine or electric motors

needed for compressor driver

4.3 MTPA plant under construction with VSD

motor drivers and onsite power generation with

aero-derivative gas turbines

(33)

Linde Process

(34)

Process Design, Driver Ratings

& Compressor Configuration

Process Design, Driver Ratings

& Compressor Configuration

APCI process uses larger and larger gas turbines

to reduce CAPEX in a single train configuration;

bigger gas turbine have lower $/kW

Frame 7EA used for Mixed Refrigerant

Frame 6 being replaced by Frame 7 for Propane

for larger plants

The plants are “single train” i.e. each machine is

designed for 100% capacity and arranged in

(35)

Process Design, Driver Ratings

& Compressor Configuration

Process Design, Driver Ratings

& Compressor Configuration

Phillips Optimised Cascade process have used

2x50% compressor configuration and achieved

cost savings and high availability

Shell DMR process appears to favour twin train

configuration and achieves 4.5 - 5.5 MTPA with

larger aero-derivative

(36)

Gas Turbines Used in LNG Plant

Heavy Duty Gas Turbines:

Mechanical drive shown in blue

Power generation shown in yellow

(37)

Aero-Derivative Gas Turbines

for LNG Plant – Potential

Aero

-

Derivative Gas Turbines

for LNG Plant

–

Potential

(38)

Combined Cycles and LNG

Plant – Potential

Combined Cycles and LNG

Plant

–

Potential

Combined Cycles:

ISO Power (kW ) Heat Rate (kJ/kWh) Efficiency (%)

LM1600PE 18591 7605 45 LM2500PE 31048 7186 50 LM2500+ 6STG 40912 6981 52 LM6000PC 55007 6764 53 LM6000PD Sprint 59142 6876 52 RB211-24GT RT62 39760 7005 51.4 Trent 50 64458 6780 53.1 Trent 60 72268 7189 50.1

(39)

Economies of Scale

(40)

Economies of Scale

(41)

Steam Turbines - Pros

Steam Turbines

-

Pros

Several established Vendors

Size; may be built to exact process specification Mechanical drive up to 130 MW not a problem Constant speed power generation 600–1100 MW High reliability; 30 years life is achievable

High availability; compressors & steam turbines may both achieve 3 years non-stop operation, no need for inspection Steam is often required elsewhere in process

Mixed fuel; boilers can utilise varying fuel mix whereas gas turbines require fuel specification to be maintained

Higher thermodynamic efficiency than simple cycle GT (but lower efficiency than GT-steam combined cycle)

(42)

Steam Turbines - Cons

Steam Turbines

-

Cons

Perceived as old “Victorian” technology

Physically very large; boilers, condensers, desalination

plant (for make-up water), water polishing plant etc.

CAPEX of steam turbine plant is higher than simple cycle

GT (but similar cost to combined cycle)

Overhaul of steam turbine similar to large frame GT (but

interval between overhauls is twice as long!)

Added complexity in steam auxiliaries, including feed

heating, boiler feed pumps etc.

(43)

Industrial Gas Turbines - Pros

Industrial Gas Turbines

-

Pros

Simple cycle GT is uncomplicated in its design Low CAPEX

Economies of scale when using large frame GTs

Extensive operational experience with mechanical drive applications

Large population; perceived as low risk technology Skid mounted; easier to install than a steam system Smaller plant footprint; less extensive civil works Lower NO_X than Aero-derivative GT

Range of sizes available:

~ 110 MW Frame 9 ~ 75 MW Frame 7 ~ 40 MW Frame 6 ~ 30 MW Frame 5

(44)

Industrial Gas Turbines - Cons

Industrial Gas Turbines

-

Cons

Paucity of Vendors!

Low thermal efficiency, high CO

₂

emissions

Maintenance is intensive, involving prolonged on-site work

which reduces plant availability

Fixed sizes and fixed optimal speeds

Process and compressors must be designed around the

GT (unlike steam turbines)

Process may not make full use of the GT power

Power output highly sensitive to ambient conditions e.g.

typical large GT:

At 30 °C ~88% power At 20 °C ~95% power At 15 °C 100% power

(45)

Aero-Derivative Gas Turbines - Pros

Aero

-

Derivative Gas Turbines

-

Pros

Higher thermal efficiency than Industrial GT; 38-42% compared to 28-32% for similar size Industrial GTs in simple cycle

Smaller footprint area than Industrial GT because of aero design Shorter maintenance period; modular design allows gas engine and power turbine sections to be swapped out

Off-site maintenance (in factory) Thus, higher plant availability

Most engines have free power turbines for variable speed operation (within a range)

Large helper motors or steam turbines may not be needed for start-up

Range of sizes available:

~ 55 MW Trent ~ 40 MW LM6000 ~ 30 MW RB211

(46)

Aero-Derivative Gas Turbines - Cons

Aero

-

Derivative Gas Turbines

-

Cons

Paucity of Vendors (essentially only 2)! Higher NO_X than Industrial GTs

Engines need more care and maintenance due to higher operating pressures and temperatures and design complexity

Fixed sizes and fixed optimal speeds

Process and compressors must be designed around the GT (unlike steam turbines)

Process may not make full use of the GT power Power output highly sensitive to ambient conditions Fuel quality is critical – even more than in Industrials!

Limited operating experience for LNG, although extensive for offshore mechanical drive and power generation

Powers greater than 60 MW not available in simple cycle Dry Low Emissions (NO_X) technology adds complexity Higher risk technology than Industrial GTs

(47)

Combined Cycles - Pros

Combined Cycles

-

Pros

Mitigates some of the cons of Industrial GTs

Adds some of the pros of Steam Turbines

Essentially, 50% extra power / 50% extra thermal

efficiency / 50% lower CO

₂

emissions

Allows optimisation of process and compressors

Steam turbine can be used for start-up and additional

power

(48)

Combined Cycles - Cons

Combined Cycles

-

Cons

High CAPEX, increased complexity, more extensive

civil works… same as for Steam Turbine

Combined cycles are not presently favoured by LNG

plant designers, but may be considered when CO

₂

is

(49)

Variable Speed Electric Motors - Pros

Variable Speed Electric Motors

-

Pros

Can be made to suit, allowing optimisation of process

and compressors

Higher availability of LNG plant than if using GTs or

Steam Turbines

Reduced manning levels

May avoid gearboxes for 3000-3600 rpm compressor

speeds (large flow capacity compressors)

Power generation may be off-site

Lower CAPEX if power is bought from the grid

Simple layout, reduced civil works

(50)

Variable Speed Electric Motors - Cons

Variable Speed Electric Motors

-

Cons

Most LNG plant are in remote locations; off-site power generation of 400-500 MW not available!

Very high CAPEX if power generation is built alongside LNG High OPEX (although savings may be possible)

Limited experience with high power VSDs; 45-55 MW is achievable, 65 MW is the maximum

Electrical issues at compressor start-up; grid peak current and fault levels

Power generation using GTs must happen somewhere; CO₂, NO_X and sensitivity to ambient conditions is similar to a GT (unless power generation is using a combined cycle)

(51)

Conclusions and Observations

LNG drivers are predominately Industrial Heavy Duty Gas Turbines e.g. GE Frames 5, 6, 7 … even 9!

Frame 5s generally used on older LNG plant, although ALNG in Trinidad was recently fitted with Frame 5Ds; these are

demonstrating high overall availability at low CAPEX… 3.3 MTPA with 6 x Fr 5

Fr 6 / Fr 7 combinations replaced Steam Turbines at MLNG Now Fr 6 / Fr 7 commonly used at NLNG, Oman LNG, Qatar LNG… 3.3 – 3.5 MTPA

Fr 7 / Fr 7 combinations used at Qatar LNG, but with poor use of GT power because of non-optimal process, process had to be redesigned… ~4 MTPA

Larger and larger trains are pushing the limits of compressor technology i.e. Axials for Mixed Refrigerant and largest