Lean LNG Plants Heavy Ends Removal and Optimum Recovery of ...
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17th INTERNATIONAL CONFERENCE & EXHIBITION
ON LIQUEFIED NATURAL GAS (LNG 17)
Lean LNG Plants – Heavy Ends Removal
and Optimum Recovery of Liquid
Hydrocarbons for Refrigerant Make-up By: Laurent Brussol & Dominique Gadelle, Technip France
April 17, 2013
17th INTERNATIONAL CONFERENCE & EXHIBITION ON
LIQUEFIED NATURAL GAS (LNG 17)
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LNG 17 – Lean Gas Liquefaction Processes – Laurent Brussol & Dominique Gadelle 2
Summary
1. The trends towards liquefaction of lean gas
2. Scrub column or turbo-expander based NGL recovery
3. Technico-economic comparison
4. Conclusions
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Lean gas feed – high methane content.
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The trends towards liquefaction of lean gas
LNG 17 – Lean Gas Liquefaction Processes – Laurent Brussol & Dominique Gadelle
New LNG provinces – pipeline gas
New LNG provinces – lean gas reserves
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C3/MR Liquefaction process requires continuous make-up
Nitrogen
From utility generation
Methane
From feed gas
Ethane
Extracted from feed gas
Propane
Extracted from feed gas
Extraction of C2 and C3 is desirable and is a challenge for
lean gas
Refrigerant make-up requirements
NG
LNG 17 – Lean Gas Liquefaction Processes – Laurent Brussol & Dominique Gadelle
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Pipeline gas liquefaction
High cost feed stock
No revenue from condensate or LPG
Lean gas from “non associated gas” fields
Challenging separation of traces of heavy HC
No revenue from condensate or LPG
Penalized economics need to be compensated by best
efficiency through high pressure liquefaction
Economics of Lean gas liquefaction
LNG 17 – Lean Gas Liquefaction Processes – Laurent Brussol & Dominique Gadelle
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Scrub column or turbo-expander based NGL recovery
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Scrub Column
The most commonly used method with long history
Scrub column operation at liquefaction pressure
Reflux generated by the main refrigeration cycles
Works well with rich gas
More difficult with lean gas
• Low NGL extraction rates
• Low density difference between L&V
• Uncertain heavy ends removal
LNG 17 – Lean Gas Liquefaction Processes – Laurent Brussol & Dominique Gadelle
NG
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NGL Recovery : Single or Dual Reflux
Used in several recent LNG plants and FLNG
T1 operates at low pressure
No integration with refrig. Cycles
No risk of C5+ / Benzene carry-over
High NGL extraction rates
Opportunity to use a d/s booster
compressor & High pressure liquefaction
LNG 17 – Lean Gas Liquefaction Processes – Laurent Brussol & Dominique Gadelle
Dual reflux selected for comparison study
Single Reflux Dual Reflux
T1
M
NG
To Fractionation
Unit
Treated
Gas
Ethane
T1
M
NG
To Fractionation
Unit
Treated
Gas
Ethane
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Technico-economic Comparison
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• Main assumptions
• Equipment count
• Production / Efficiency
• CapEx
• Operability
LNG 17 – Lean Gas Liquefaction Processes – Laurent Brussol & Dominique Gadelle
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Main assumptions
Representative of many lean gas liquefaction plants
Lean Feed Gas Composition
C3/MR Liquefaction Process
Fixed 4.8 MTPA LNG Production
Heavy Duty Gas Turbines + Helpers
No LPG production
Air-cooling
Component Mol. %
CO2 50 ppm
Nitrogen 0.30
Methane 97.27
Ethane 1.60
Propane 0.35
i-Butane 0.20
n-Butane 0.20
i-Pentane 0.02
n-Pentane 0.02
C6+ incl. Benzene 0.04
LNG 17 – Lean Gas Liquefaction Processes – Laurent Brussol & Dominique Gadelle
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NG
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More equipment in an NGL Recovery unit compared to a the Scrub Column…
Yet the return on investment is improved
LNG 17 – Lean Gas Liquefaction Processes – Laurent Brussol & Dominique Gadelle
M
NG
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....compensated by OPEX savings
NGL Recovery means lower auto-consumption
Higher liquefaction pressure requires less energy consumption
for a given quantity of LNG
NGL Recovery
vs
Scrub column
Refrigeration Power (C3+MR Compressors) -16%
Liquefaction pressure +30 bar
Total power (C3+MR+Booster Compressors) -4%
Specific power (C3+MR Compressors) -16%
Specific power (C3+MR+Booster Compressors) -4%
Fuel Gas consumption -4%
LNG 17 – Lean Gas Liquefaction Processes – Laurent Brussol & Dominique Gadelle
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... without increasing overall CapEx …
Liquefaction CapEx is reduced when an NGL Recovery Unit is used
Cost Comparison /
Method
NGL recovery
vs
Scrub Column
Remark
NGL Extraction Unit +300% Additional equipment
Liquefaction Unit
(including refrigeration) -10% Smaller equipment
Fractionation Unit Similar
Overall Installed Cost Similar
Liquefaction > 90% of
investment cost in both
cases
LNG 17 – Lean Gas Liquefaction Processes – Laurent Brussol & Dominique Gadelle
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… and with improved operability
The NGL recovery unit is a happy combination of operating
flexibility and reduced energy consumption
Criteria Scrub Column NGL recovery
Sensitivity to feed gas
composition variations
Cannot handle
> 97% methane
Robust reflux
Refrigerant make-up
production when
liquefaction shutdown
Relies on main
refrigeration
Independent of
liquefaction
Availability Simplicity With JT mode
and sparing
LNG 17 – Lean Gas Liquefaction Processes – Laurent Brussol & Dominique Gadelle
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Summary of main advantages and disadvantages
Scrub column NGL recovery
CapEx = = Robustness to composition
variation - + + Refrigeration drivers duty - + + Refrigerant make-up
production - + + Efficiency - + + Availability + -
NGL Recovery is more attractive overall
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Main conclusions
Turbo-expander based NGL Recovery should always be
considered for plants liquefying lean gas
Consider savings in the liquefaction unit when selecting the NGL
Recovery method
Overall efficiency is better when a NGL Recovery is considered
NGL Recovery offers better operability and flexibility as it is
decoupled from refrigeration cycles
Overall layout is similar for both options
For a given installed refrigeration power the LNG production can be increased by installing an upfront NGL Recovery unit
LNG 17 – Lean Gas Liquefaction Processes – Laurent Brussol & Dominique Gadelle
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www.technip.com
Thank you
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Visit us at Technip booth #545