1. Simultaneous Production of LNG and NGL
Good morning ladies and gentlemen, before I start my presentation I would like to express my thanks to the co-authors of this paper : my colleagues at Technip Henri Paradowski and Dominique Gadelle and from Total, Madame Pascale Morin and Jean-Claude Garcel.
This is a presentation of a means of realizing synergy between on the one hand the UK which needs lean LNG and on the other Qatar which apart from its ambitions as a major LNG producer also has a rapidly expanding petrochemical sector capable of adding value to extracted ethane.
The presentation is in four parts and centres on a case study of a large base load LNG plant fitted with Technip’s Cryomax turbo-expander process adapted to C2+ NGL recovery.

2. Why NGL with LNG is of increasing interest NGL recovery processes
Case study Cryomax process
 0% - 65% ethane recovery
 Three configurations in LNG train
Operability and reliability considerations
So why is NGL recovery of interest?

3. NGL recovery in LNG plants
Existing LNG plants
Next step C4
Sometimes
100% C3
Sometimes % C2
Once %
Scheme
Scrub column
Turbo-Expander
Refrigerated propane and butane are already produced at many LNG facilities but, with a few exceptions, only at moderate extraction rates.
There is only one reference in the world for producing ethane for ethylene production.
The vast majority of existing plants use a simple scrub column process at liquefaction pressure
While turbo-expander based processes can improve the recovery of propane to increase revenue, the key factor for moving away from the simple scrub column process is ethane.

4. Ethane New markets require lean revaporised NG
UK Wobbe Index 51.4 MJ/Sm3 (max)
~ 50.8 MJ/Sm3 in Qatar
Met with 36% ethane extraction
Ethylene from ethane in Qatar
Qatar 2.5 Mtpa in 2008
UK Mtpa (all feed stocks)
France 3.4 Mtpa (all feed stocks)
Ethane extraction at the LNG production site is an excellent way of meeting the requirements of new markets such as in the UK. Even after weathering during the sea voyage and offloading, the low Wobbe Index of the UK gas market can still be met with around 36% ethane extraction in Qatar.
At the same time, a large amount of ethane based ethylene capacity is in operation and a lot more is planned so its not just the LNG industry which is booming. Ethylene production in Qatar will soon be on a par with large European economies and this offers a local market for ethane extracted from LNG.

5. Why NGL with LNG is of increasing interest NGL recovery processes
Case study Cryomax process
 0% - 65% ethane recovery
 Three configurations in LNG train
Operability and reliability considerations
What are we looking for in the NGL recovery process?

6. NGL recovery processes
Efficient ethane and propane plus extraction
Flexibility in ethane recovery
Good selectivity - minimal methane in NGL
Entrainment tolerant – no heavy ends, ever
Resistance to equipment failure
Lean gas at high pressure to favour liquefaction
Well, the process must be able to remove efficiently more than 35% ethane and substantially all propane and heavier components.
To fit with the market, simple adjustments to operating conditions must allow the amount of ethane recovery to be adjusted to match changes in feedstock and market conditions
It needs to be highly selective. In particular we are interested in recovering an NGL which has a low methane content
It has to be entrainment tolerant. We don’t want any heavy ends going to the liquefier at any time not even during start up or during equipment failure.
There is an increase in the amount of rotating machinery and ideally we would like to be able to continue operation following a failure
And because we have an objective of high train capacity we would like to send the gas to the liquefier at high pressure.

7. Conventional scrub columnNG
54 bar
-35°C NG
55 bar
-16°C
NGL
LNG
C3R
SCRUB
COLUMN
REFLUX
LIQUEFACTION
MCHE
PRECOOLING
The conventional scrub column process is attractive because it is very simple to operate. Liquid reflux is produced using low level propane to extract small amounts of ethane and propane for use as refrigerant make up.
LEAN GAS
C3R MR
DRY NG
NGL

8. Scrub column (high recovery)
MCHE NG
52 bar
-65°C NG
55 bar
-35°C
LNG
NGL
REFLUX
LIQUEFACTION
MCHE
PRECOOLING
SCRUB
COLUMN
OVERHEAD
When the gas is lean or higher recovery is required the temperature in the reflux drum can be reduced by inserting a third bundle in the main cryogenic exchanger.
However, as we approach the critical temperature of the gas, there’s a limit to how far NGL recovery can be taken.
LEAN GAS
C3R MR
NGL
DRY NG

9. Cryomax LIQUEFACTION PRECOOLING MCHE LNG C3R MR DRY NG NGL CRYOMAX
DUAL
COLUMN NGL RECOVERY
LEAN
GAS
The Cryomax process, which replaces the scrub column, uses the expansion of the gas to low pressures and temperatures so that the fractionation of the gas and liquid produced can be performed in much more favourable conditions.
C3R MR
DRY NG
NGL

10. Cryomax - LNG LEAN GAS TO MCHE PRECOOLED GAS 36 bar -80°C 29 barRT
DC1
The origins of the dual column Cryomax process are in C3+ NGL recovery in gas plants not related to LNG.
The principal feature of the process as applied in these plants is the use of two columns, the second producing a purified ethane rich reflux to the main recovery tower. Typically 95 to 99% propane recovery is possible with this scheme which has operating references in NGL recovery plants including in Qatar.
In the patented application of the Cryomax process to LNG as shown on this slide, a few specific features have been introduced.
To maintain the highest possible natural gas pressure for liquefaction, the recovery tower is operated at a pressure above that of the Demethanizer in order to maximize the pressure of the gas going to the liquefier.
The purified reflux is split into two qualities so that the recovery tower reflux is now richer in methane. This helps meet the objective of ethane (as opposed to propane) recovery.
The quality of the reflux, obtained by distillation, means butane and heavier hydrocarbons are completely absent from the top stage of the recovery tower so its very resistant to entrainment. There is, for example, significantly less than 1ppm butane in the lean gas sent to liquefaction.
Recovery Tower Reflux
NGL
Demethaniser Reflux
US Patent 5,291,736

11. Why NGL with LNG is of increasing interest NGL recovery processes
Case study Cryomax process
 0% - 65% ethane recovery
 Three configurations in LNG train
Operability and reliability considerations
So now we’ll move on to the case study

12. Cryomax Case Study Qatar: North Field gas; climate APCI C3/MCR process
High LNG capacity (approximately 5 Mtpa)
High natural gas pressures
Two GE Frame 7 gas turbines
MCHE outlet temperature –148°C
Hydraulic turbines for MCR and LNG
Four ethane extraction rates (0-65%) in three configurations
The study considered a prospective large capacity LNG train in Qatar using the APCI C3/ MCR liquefaction process.
Because this study was performed in the context of a large capacity LNG train, the study adopted features consistent with this such as high natural gas pressure, large gas turbines, a high MCHE outlet temperature (with additional power put in the final nitrogen rejection section of the train) and hydraulic turbines for the dynamic expansion of MCR and LNG
A total of twelve cases were developed covering ethane extraction rates of between 0 and 65% and three configurations of the NGL recovery process within the train.

13. Cryomax Unit Location “Front End” Warm natural gas feed
No propane refrigeration
Driven by lean gas compression
Inlet = Outlet (P; T) NG
NGL
NRU OFF GAS
“FRONT END”
NGL
RECOVERY
LEAN GAS
COMPRESSION C3
PRECOOLING NG
LIQUEFACTION
NITROGEN
REMOVAL
LNG
“Straddle”
Pre-cooled feed
Inlet = Outlet (P; T)
NGL NG
“STRADDLE”
NRU OFF GAS C3
PRECOOLING
NGL
RECOVERY
LEAN GAS
COMPRESSION NG
LIQUEFACTION
“Mid train”
Pre-cooled feed
P2 < P1
Simpler
Less power
Less capacity
NITROGEN
REMOVAL
LNG
The NGL recovery unit is located in all cases upstream of the liquefaction section. NGL recovery requires no contribution from the liquefaction refrigerant so there is no requirement for a third bundle in the MCHE.
Integration can mean that the NGL unit is located upstream or downstream of the propane based precooling section.
When located downstream, there is an additional option in which no recompression of the lean natural gas is provided.
This leads us to the three configurations named for study
Front end
Straddle type
Mid train
In the Front End configuration, the NGL recovery unit is fed with dry but warm natural gas. None of the refrigeration for NGL recovery is provided by propane. The driving force for refrigeration is a lean gas compressor which at sends the lean gas to the precooling section at high pressure.
The so-called straddle configuration is a reference to the fact that the lean natural gas can be returned to the natural gas circuit at the similar conditions of pressure and temperature as at the withdrawal point. It is an ideal scheme for debottlenecking.
The mid-train configuration is the multicoloured scheme that we saw in previously. It differs from the straddle scheme in that it is simpler. Lean gas is sent to liquefaction at reduced pressure. There is no lean gas compressor so less power and less capacity. NG
NGL
NRU OFF GAS
“MID TRAIN” C3
PRECOOLING
NGL
RECOVERY NG
LIQUEFACTION
NITROGEN
REMOVAL
LNG

14. Why NGL with LNG is of increasing interest NGL recovery processes
Case study Cryomax process
 0% - 65% ethane recovery
 Three configurations in LNG train
Operability and reliability considerations
More detail of the case study results are given in the paper.

15. NGL recovery rates Ethane 1% 16% 36% 65% Propane 99.0% 95.8% 94.5%
97.7%
Butane +
100%
100%
100%
100%
HHV * Btu/scf
1046.6
1042.0
1033.8
1019.0
NGL recovery rates are high right across the range of ethane recovery rates as studied
This table gives results for all three schemes as we can effectively achieve very similar operating conditions in the recovery tower whichever location is used.
Propane recovery is high in all cases and there is complete recovery of all butane plus.
The table shows the variation of heating value and Wobbe Index in the LNG tanks in Qatar as ethane is removed. The value of 50.8 corresponds to 51.4 for revaporised LNG in the UK.
Wobbe *
MJ/Sm3
51.1
51.0
50.8
50.5
* In LNG tanks in Qatar

16. Specific power Target C2 Recovery Front end Straddle Mid-train
Specific power means the amount of refrigerant and other compressor power per ton of liquid produced.
This is the main parameter for comparing the cases as it translates the notion of process efficiency. In the context of an LNG train it is production capacity and revenue that depends on the efficient and full use of the installed compression power.
There are three main conclusions which can be drawn from this large study
The first one is that the Cryomax process is well adapted at the targeted ethane extraction level of around 36% which corresponds to matching the Wobbe Index specification of the UK market, in Qatar. Specific power is at a minimum at this level of extraction. When we reach 64%, we see that specific power is at levels equivalent to zero extraction. While this performance can be acceptable at 64%, we should consider another type of process for ethane recovery levels higher than this.
The second conclusion is that the efficiency of the process expressed in terms of specific power is quite insensitive to location. The difference is as little as 2% at the target ethane recovery level. This is an interesting result as it means that the decision about location can be based on operability considerations alone.
Finally we can make the observation that the straddle type unit is the most efficient by a small margin.

17. Why NGL with LNG is of increasing interest NGL recovery processes
Case study Cryomax process
 0% - 65% ethane recovery
 Three configurations in LNG train
Operability and reliability considerations
So now we’ll look at operability and reliability which are particularly important considerations in base load LNG.

18. “Straddle” - Lean gas compressor failure
Same as “mid-train” scheme
LNG quality unchanged
10% to 15% reduction in throughput
We’ve selected the straddle scheme because it’s the best. It benefits from the presence of both propane pre-cooling upstream and the lean gas compressor downstream.
If the lean gas compressor fails, the straddle scheme becomes equivalent to the mid-train scheme, so that provided this case is taken into account in the design, the only effect would be a slight loss of LNG production roughly equivalent to the loss in overall compression power.

19. “Straddle” - Joule-Thomson Mode
C3 precooling & lean gas compressor OK
Specifications OK except Wobbe
5%-10% reduction in throughput
During start up and in the unlikely event of a turbo-expander failure, the straddle unit would operate in Joule-Thomson mode in which the natural gas is expanded across a control valve in parallel with the expander.
Thanks to the presence of the lean gas compressor and propane precooling, straddle scheme operation in JT mode is very good, considering these are upset conditions.

20. “Straddle” - Joule-Thomson Mode
C3 precooling & lean gas compressor OK
Specifications OK except Wobbe
5%-10% reduction in throughput
Expander
JT mode
Expander power MW
5.4 -
Ethane recovery % 36 1
Propane recovery % 93 76
All specifications continue to be met with the exception of the LNG Wobbe Index
LNG can continue to be produced, albeit at a reduced rate.
In this mode no ethane recovery is possible and propane recovery levels are reduced, but the quality of the reflux is such that the absence of heavies on the top tray of the recovery tower, a main feature of this process, is maintained.
Wobbe Index MJ/Sm3
50.8
51.2
Sp consumption MW.h/t
0.267
0.287

21. Conclusions
Ethane and C3/C4 LPG extraction in Qatar meets lean gas specifications directly
The Cryomax process can be adapted to a wide range of ethane recovery requirements
Process efficiency insensitive to extraction rate or location
Cryomax “Straddle” – Efficient and reliable
New or existing trains
So these are the conclusions
Ethane and C3/C4 LPG extraction from natural gas prior to liquefaction is a good way to meet UK type specifications for lean gas directly in Qatar.
Technip’s Cryomax process can be adapted to a wide range of ethane recovery requirements including those of the new markets for lean LNG.
Process efficiency is almost constant whatever the extraction rate and varies little with location of the NGL unit within the train.
The Cryomax process in straddle configuration is both the most efficient and the most reliable, the latter being a prerequisite of the LNG industry.
The process can be used in new or existing LNG trains.

22. Technip and Total thank you for your attention
Technip and Total thank you for your attention and I look forward to your questions.