LNG technology selectionDr Tariq Shukri, Foster Wheeler, UK, discusses availableLNG technologies and the important criteria for selection.Axens Liquefin process

This is a two-mixed refrigerant process, which isbeing proposed for some new LNG base load projectsof train sizes up to 6 million tpy. It is illustratedin Figure 7.

Detailed studies have been made including inputfrom main equipment vendors. All cooling and liquefactionis conducted in PFHE arranged in coldboxes. The refrigerants are made up of componentsfrom methane, ethane, propane, butane and nitrogen.

The first mixed refrigerant is used at three differentpressure levels to precool the process gasand precool and liquefy the second mixed refrigerant.

The second mixed refrigerant is used to liquefyand subcool the process gas.

Using a mixed refrigerant for the precoolingstage allows a lower temperature to be achieved(for example, -60 C) depending on refrigerant composition.

The PFHEs are non-proprietary and can besupplied by independent vendors. Two large driverscan drive the refrigerant compression systems.Frame 7 gas turbines are being proposedfor the large LNG trains.

TPG-4140LNG, fundamentale prinsippBengt Olav Neeraas18/09/2007

Large Capacity LNG Plant Development J.J.B. Pek*, A. van Driel, E.C.J.N. de Jong, R. Klein Nagelvoort

http://www.worldoil.com/magazine/magazine_detail.asp?ART_ID=2272New gas liquefaction process provides increased capacity at reduced cost Pierre Boutelant, Senior Advisor, LNG, Axens, Rueil Malmaison, France Technology from Europe:France/BelgiumVol.225No.4French firm Axens and its parent company, IFP, has developed In the Liquefin process, both mixed refrigerants are used in the a process for liquefaction of natural gas that achieves the best usage same way as pure components. The mixed refrigerant is condensed of large gas turbines and plate-fin heat exchangers. Compared to and vaporized at different pressure levels in each section, without existing technologies, this process provides increased capacity and any phase separation or fractionation. a reduced investment cost, while remaining simple and reliable. Very large capacities (up to 8 million t/year) can be achieved in This way, the exchange line can be kept very simple and compact. one train at a very low LNG unit cost and with minimal space required.

A significant advantage of this new scheme is the opportunity to The Liquefin process operates according to the typical flow scheme adjust the power balance between the two cycles. Thus, it is possible presented in the diagram (this page) on the following. to directly use the full power provided by two identical gas turbines, The pre-refrigeration of gas is achieved by using a mixed without any transfer of power from one cycle to the other. refrigerant instead of propane. In this process, the pre-refrigeration cycle operates at a much lower temperature than when propane is An LNG production between 3 million and 8 million t/year can used, and the temperature is decreased down to about - 60C be achieved on one single train, at quite attractive conditions ( - 75F). At this temperature, the cryogenic mixed refrigerant can be as regards CAPEX and OPEX. completely condensed, so that the quantity of this refrigerant is substantially reduced.

In the Liquefin general scheme, the pre-refrigeration cycle operates at a much lower temperature than when propane is used.

The molar ratio between the cryogenic mixed refrigerant and LNG can, in some cases, be lower than 1:1. The overall, required power is reduced, as a good part of the energy necessary to condense the cryogenic mixed refrigerant is shifted from the cryogenic cycle to the pre-refrigeration cycle. Moreover, this shifting of energy leads to a better distribution of the necessary heat exchange area. The same number of cores in parallel can be used all along the line between the ambient and cryogenic temperatures.

http://www.worldoil.com/Magazine/MAGAZINE_DETAIL.asp?ART_ID=2808&MONTH_YEAR=Feb-2006Global 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-specificvariables and economics be studied. Saeid Mokhatab, University of Wyoming, Laramie, Wyoming, and Michael J. Economides, University of Houston, Houston February 2006LIQUEFIN PROCESS IFP and Axens have developed the Liquefin process that aims to Overall necessary power is decreased, as the quantity of cryogenic 1) increasing the plant capacity; produce LNG cheaper than with any other process. Via Liquefin, mixed refrigerant is lower, and a good part of the energy necessary 2) reducing the heat exchanger costs; very high capacities can be reached with a simple scheme and to condense it is shifted from the cryogenic cycle to the pre-refrigeration cycle. 3) all-over plate-fin heat exchangers; standard compressors. 12 This makes it the choice to be considered Moreover, this shifting of energy allows a better repartition of 4) a compact plot area; and for an LNG project today. exchange loads. The same number of cores in parallel can be 5) multi-sourcing of all equipment, including heat exchangers. 7

used all along between the ambient and the cryogenic temperature, Significant effort has been expended to assure optimal, fool-proof allowing a very compact design for the heat exchange line. A very The Liquefin process has all the positive features of MFCP, with operation of such an assembly. significant advantage of this new scheme is the possibility to adjust much better efficiency and a smaller amount of rotating equipment.

the power balance between the two cycles, making it possible to It is particularly well-adapted to the range of 4 to 8 MTPA, per train, This is a two-mixed refrigerant process that is proposed for some use the full power provided by two identical gas drivers. 13 with many open options for designing and erecting a plant fully new LNG baseload projects of train sizes up to 6 MTPA. responding to the client's needs. 12 The Liquefin process operates according to the basic flow scheme The Liquefin process is very flexible. It offers more than one possibility presented in Fig. 7. All cooling and liquefaction is conducted in a to reach large, highly competitive capacities, either by using very plate-fin heat exchanger (PFHE), 13 arranged in cold boxes. large gas turbines (combined cycle) to produce electricity, and PFHE arrangement is at the heart of the liquefaction technology. large electrical motors (up to 70 MW) in parallel on each cycle,

or by using larger gas turbines. Frame 7 gas turbines are proposed The refrigerants are made up of components from methane, ethane, for large LNG trains. The Frame 9 has very recently been qualified for propane, butane and nitrogen. The first mixed refrigerant is used mechanical drive. With Liquefin, this would allow capacities of 7 to at three different pressure levels to pre-cool the process gas and 8 MTPA with only two main drivers. Although volumetric flowrates pre-cool and liquefy the second mixed refrigerant. are seriously increased, a choice compressor can be found for this The second mixed refrigerant is used to liquefy and sub-cool the case, because the speed of the Frame 9 is lower than the Frame 7 speed. 2 process gas. Using a mixed refrigerant for the pre-cooling stage, the temperature is decreased down to a range of - 50C to - 80C The process represents a real breakthrough - the plant capacity can depending on refrigerant composition. At these temperatures, the be chosen by considering the economics and marketing possibilities cryogenic mixed refrigerant can be completely condensed, no phase without being bothered by technical hindrances. A total cost reduction separation is necessary and, moreover, the quantity of cryogenic per ton of LNG is reported to be 20% when compared to the APCI/MR refrigerant is substantially reduced. The weight ratio between the process. The cost reductions arrive from: cryogenic mixed refrigerant and LNG can be lower than unity.

DRIVER SELECTION FORLNG COMPRESSORSDr Sib Akhtar14th December 2004MSE (Consultants) LtdCarshalton, Surrey SM5 2HWsib.akhtar@mse.co.ukhttp://www.mse.co.uk Tel: 020 8773 4500

Mixed refrigerants for pre-cooling, liquefactionand sub-cooling duties

Liquefin development studies presently orientedtowards increasing capacity to 6 MTPA with:2 x Frame 7 Gas Turbines for main compression2 x Frame 5 Gas Turbines for power generation

Higher capacities possible using:Frame 9 GTsElectric motorsSteam turbines etc.

Similar to APCI with Propane compressorreplaced with Mixed Refrigerant for pre-cooling

Allows more balanced flows, refrigeration loadsand power between the two compressors

Avoids the process design limits associated withPropane compressors

LNG process selection, no easy taskPierre-Yves Martin, Jrome Pigourier, Axens, franceBatrice Fischer, IFP, FranceHydrocarbon engineering May 2004

Liquefin: The Economic Solutionfor LNG TrainsJean SentenacAxens Chairman and CEOIran's Gas Export Vision Conference 25 & 26 April 2004

Efficiency Physical and Financial

For a given power consumption, Liquefinproduces up to 15% LNG more than currentunits. For that given power Liquefin is at least 10 %less expensive. The cost per ton of LNG produced can be upto 25% lower* than established processes.

*Note: For the liquefaction unit alone: for the complete train the difference is around 10% - a major cost reduction.

The attractive cost of a Liquefin Unit ismainly due to:

Reduced number of main equipment items Use of plate-fin heat exchangers Reduced footprint (plot plan size) Limited number of control loops Open competition between primeequipment vendors (compressors, coldboxes)Easy adjustment of pre-cooling temperature,while maintaining optimal efficiency allows:

Optimizing around any driver configuration, Adjustment of LPG extraction within a broadrange, Processing feedstocks containing highconcentrations of mercaptans and benzene, Operating with significant variations in feed gascomposition and pressure.

Response To Todays Market Needs

Liquefin is designed to keep the sameefficiency over a large spectrum ofproduction rates. From 3 MTPA per train to 8 MTPA per train Using Gas Turbines or Electric Motors, Regardless of the configuration, CO2atmospheric emissions remain lower thanwith any other process.

REFERENCES CITED 4. M. Khakoo , B.Fischer, J.C.Raillard - The Next Generation of LNG plants - LNG13, Seoul, Korea, 2001 5. B.Fischer - A New Process To Reduce LNG Cost - AICHE Spring National Meeting, 2002

NATURAL GAS LIQUEFACTION PROCESSES COMPARISONCOMPARAISON ENTRE PROCEDES DE LIQUEFACTIONDE GAZ NATURELPierre-Yves MartinJrme PigourierAxens (France)www.axens.frBatrice FischerIFP (France)Poster PO-39PO-3 9.1

This process (see figure 6) is a dual mixed refrigerant process, with the same power on both mixed refrigerant cycles. Plate-fin heat exchanger are used for the whole exchange line. As for all processes with mixed refrigerant on the first cycle, the main condenser is smaller (see figure 11) and the compressor of the first cycle has a lower mach number (see figure 7). The lower amount of mixed refrigerant on the cold cycle allows to reach much higher LNG capacities with the existing axial compressors.