The C3MR APCl process

www.lngplants.com/

TPG-4140

LNG, fundamentale prinsipp

Bengt Olav Neeraas

18/09/2007

Large Capacity LNG Plant Development

J.J.B. Pek*, A. van Driel, E.C.J.N. de Jong, R. Klein Nagelvoort

LNG technology selection

Dr Tariq Shukri, Foster Wheeler, UK, discusses available

LNG technologies and the important criteria for selection. The process gas passes through all the bundles to emerge

APCI propane pre-cooled mixed refrigerant process (MCR) liquefied at the top. The liquid MR stream is extracted after the

warm or middle bundle and is flashed across a Joule Thomson

This process accounts for a very significant proportion valve or hydraulic expander onto the shell side. It flows downwards

of the worlds baseload LNG production and evaporates, providing the bulk of cooling for the

capacity. Train capacities of up to 4.7 million tpy lower bundles. The vapour MR stream passes to the top (cold

were built or are under construction. It is illustrated in Figure 3 bundle) and is liquefied and sub-cooled, and is flashed across

as part of an overall LNG plant flow scheme. a JT valve into the shell side over the top of the cold bundle. It

flows downwards to provide the cooling duty for the top bundle

There are two main refrigerant cycles. The precooling and, after mixing with liquid MR, part of the duty for the

cycle uses a pure component, propane. The liquefaction lower bundles.

and sub-cooling cycle uses a mixed refrigerant (MR)

made up of nitrogen, methane, ethane and propane. The overall vaporised MR stream from the bottom of the

The precooling cycle uses propane at three or four pressure MCHE is recovered and compressed by the MR compressor

levels and can cool the process gas down to -40 C. It is to 45 - 48 bara. It is cooled and partially liquefied first by water

also used to cool and partially liquefy the MR. The cooling is or air and then by the propane refrigerant, and recycled to the

achieved in kettle-type exchangers with propane refrigerant MCHE. In earlier plants all stages of the MR compression

boiling and evaporating in a pool on the shell side, and with the were normally centrifugal, however, in some recent plants

process streams flowing in immersed tube passes. axial compressors have been used for the LP stage and centrifugal

for the HP stage. Recent plants use Frame 6 and/or

A centrifugal compressor with side streams recovers Frame 7 gas turbine drivers. Earlier plants used steam turbine

the evaporated C3 streams and compresses the vapour to drivers.

15 - 25 bara to be condensed against water or air and

recycled to the propane kettles. A recent modification of the process, which is being considered

In the MR cycle, the partially liquefied refrigerant is separated for large LNG capacity plants (> 6 million tpy), is the

into vapour and liquid streams that are used to liquefy APX-process, which adds a third refrigerant cycle (nitrogen

and sub-cool the process stream from typically -35 C to expander) to conduct LNG subcooling duties outside the

between -150 C - -160 C. This is carried out in a proprietary MCHE.

spiral wound exchanger, the main cryogenic heat exchanger

(MCHE).

The MCHE consists of two or three tube bundles

arranged in a vertical shell, with the process gas and

refrigerants entering the tubes at the bottom which then

flow upward under pressure.

Single mixed refrigerant process has appeal for growing offshore market

Tariq Shukri and Michael Barclay, LNG Consultants, Foster Wheeler Energy

The enhanced single mixed refrigerant process is suitable for medium-scale

(0.5-1.5 million tonnes per annum) and offshore natural gas liquefaction.

http://www.worldoil.com/Magazine/MAGAZINE_DETAIL.asp?ART_ID=2808&MONTH_YEAR=Feb-2006

Global LNG Report

Process selection is critical to onshore LNG economics

Despite evolving and diversifying, no one liquefaction process is

substantially better than others, mandating that project-specific

variables and economics be studied.

Saeid Mokhatab, University of Wyoming, Laramie, Wyoming, and

Michael J. Economides, University of Houston, Houston

February 2006

PROPANE PRE-COOLED MIXED REFRIGERANT PROCESS

The Propane Pre-cooled Mixed Refrigerant (PPMR) process, developed A recent modification of the process, which is being considered for large

by Air Products & Chemicals Int. (APCI), began to dominate the LNG capacity plants (>6 million t/year), is the APX process, which

industry from the late 1970s on. This process accounts for a very adds a third refrigerant cycle (nitrogen expander) to conduct LNG

significant proportion of the world's baseload LNG production capacity. sub-cooling duties outside the MCHE. 6

Train capacities of up to 4.7 MTPA have been built or are under construction.

2 BP is partnered in plants using this process at Das Island, Abu Dhabi; 6 Rentler, R.J., P. Macungie and D. D. Sproul, "Combined cascade and

Bontang, Indonesia; and North West Shelf, Australia. multi-component refrigeration method with refrigerant intercooling,"

US Patent 4,404,008, Sept. 13, 1983.

The PPMR process, Fig. 3, utilizes a mixed refrigerant (MR) that has a

lower molecular weight and is composed of nitrogen, methane, ethane

and propane. The natural gas feed is initially cooled by a separate

propane chiller package to an intermediate temperature, about - 35C

( - 31F), at which the heavier components in the feed gas condense

out and are sent to fractionation. The natural gas is then sent to the

main heat exchanger, which is composed of a large number of

small-diameter, spiral-wound tube bundles. These permit very close

temperature approaches between the condensing and boiling streams.

The MR refrigerant is partially condensed by the propane chiller before

entering the cold box. The separate liquid and vapor streams are then

chilled further before being flashed across Joule-Thompson valves

that provide the cooling for the final gas liquefaction.

In earlier plants, all stages of MR compression were normally centrifugal.

However, in some recent plants, axial compressors have been used for

the low-pressure stage and centrifugal for the high-pressure stage.

Recent plants have used Frame 6 and/or Frame 7 gas turbine drivers.

Earlier plants used steam turbine drivers.

COMMERCIAL AND TECHNICAL CONSIDERATIONS IN THE

DEVELOPMENTS OF OFFSHORE LIQUEFACTION PLANT

COMMERCIAL AND TECHNICAL CONSIDERATIONS IN THE

DEVELOPMENTS OF OFFSHORE LIQUEFACTION PLANT

23rd World Gas Conference, Amsterdam 2006.

Chen-Hwa Chiu

Senior Technology Advisor

Chevron Energy Technology Company

1500 Louisiana Street

Houston, TX 77002

DRIVER SELECTION FOR

LNG COMPRESSORS

Dr Sib Akhtar Mixed refrigerant liquefaction and sub-cooling

MSE (Consultants) Ltd

Carshalton, Surrey SM5 2HW Axial LP for Shell Advised Plant

sib.akhtar@mse.co.uk

14th December 2004 Centrifugal HP compressor (45 48 bar)

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

Frame 7) plus Helper Motor or Steam Turbine

Most of existing plant are using the APCI process

with 3 3.3 MTPA Fr 6 / Fr 7 combination Large volumetric flows

Train capacities up to 4.7 MTPA built or under Two casing arrangements (LP and an HP)

construction using Fr 7 / Fr 7 combination Axial LP / centrifugal HP compressor (45 48 bar)

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

Higher Capacities to 7.9 MTPA being announced Frame 7) plus Helper Motor or Steam Turbine

with Frame 9 GT LP and HP compressor speeds compromised

LP axial compressor (higher efficiency)

Two main refrigeration cycles: HP centrifugal compressor

Propane pre-cooling

Mixed refrigerant liquefaction and sub-cooling

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)

NATURAL GAS LIQUEFACTION PROCESSES COMPARISON

COMPARAISON ENTRE PROCEDES DE LIQUEFACTION

DE GAZ NATUREL

Pierre-Yves Martin

Jrme Pigourier

Axens (France)

www.axens.fr

Batrice Fischer

IFP (France)

Poster PO-39

PO-3 9.1

All the natural gas liquefaction baseload plants built during the last

twenty years or so are C3/MR units, to the exception of Trinidad. The

C3/MR process is well known (see figure 1): the MR and natural gas

are pre-cooled with propane, at 3 or now 4 levels of pressure. The mixed

refrigerant is only partially condensed, and separated before entering

the large spiralwound exchanger.