2015 Honeywell Users Group
Europe, Middle East and Africa
Retrofitting of the natural gas liquid (NGL) fractionation trains using a
modified self-heat recuperative (MSHR) process to improve the overall
energy efficiency of gas processing plant (GPP)
Students: Ren Jie Lee, Shih Chiang Lim, Tze Mun Sam, Ying Ting Loo
Curtin University, Sarawak Malaysia
Supervisor: Dr Mesfin Getu Woldetensay
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• Background
• Problem Statement
• Objectives & Scopes
• Methodology
• Results & Discussion
• Conclusion
• References
Content
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• Natural gas is the major source of liquid
hydrocarbons product primarily used in
petrochemical industry and transportation sector.
• The composition of natural gas varies substantially
depending on its source.
• High quality natural gas and natural gas liquids (NGL)
possess clean fuel characteristic and it is the major
source of income among gas processors [1].
• The growing interest has allowed the energy market to
keep up with the accelerating trend where 64% growth
in demand is forecasted by 2030 [2].
Background
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Background (cont.)
Natural gas and NGL shows promising production trend
Global Primary Energy Sources Comparison [1]
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Background (cont.)
Demand for clean fuel is expected to rise over time
Natural Gas Production/Consumption Share of 2014 [3]
28%
5% 29%
17%
6% 15%
Production
28%
5% 30%
14%
3% 20%
Consumption
North America South and Central America Europe and Eurasia Middle East Africa
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• The Gas Processing Plant separates natural gas liquid
(NGL) components, acid gases, and water from a gas-
producing well and it conditions these fluids for sale
or disposal [4].
• The purpose for further removing C2+ hydrocarbons: ‒ NGL fractions have higher economical value separately.
‒ Safety specification for delivery and combustion.
• The fractionation train consists of 3 main distillation
column namely Deethanizer, Depropanizer and
Debutanizer in PRU.
Background (cont.)
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pretreatment unit (PTU)
acid gas removal unit
(AGRU)
condensate treatment unit
(CTU)
dehydration unit (DHU)
low temperature separation unit
(LTSU)
sales gas compression unit (SGCU)
propane refrigeration unit
(PRU)
propane recovery unit
(C3RU)
Background (cont.)
Natural Gas Processing Plant
product recovery
unit (PRU)
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Product of GPP
Sales Gas
Ethane
Propane Butane
Condensate
Background (cont.)
Fuel for
vehicles
Plastic
pellets
Cooking
gas, LPG
Industries
application
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There was less effort made in trying to improve
the energy efficiency of the product recovery unit
(PRU) of gas processing plant (GPP). The PRU which
consists of Deethanizer, Depropanizer and Debutanizer
fractionation train consumes a significant amount of
energy due to the large amount of utilities applied
during operation. Hence, there is a need to reduce the
energy consumption of these fractionation trains using
promising alternative retrofit design.
Problem Statement
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Objectives
• To improve the PRU energy efficiency of gas processing
plant
• To explore different options of single column distillation to
achieve higher energy efficiency of gas processing plant
• To assess the economical feasibility of the gas processing
plant and thereby optimize the whole process.
Scope
• The project focuses on enhancement of GPP energy
efficiency and product recovery from each distillation
columns.
Objectives and Scope
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Methodology
Base Case Stimulation
Base Case Optimization
Retrofit MSHR Simulation
Retrofit MSHR Optimization
Energy Integration
Economic Analysis
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• According to Long and Lee [5], up to 73.43 − 83.48% of
the condenser and reboiler energy were saved with
the self-heat recuperation technology.
• It is also theoretically proven that MSHR provides the
highest annual operating cost saving, up to 67.19%
per annum amongst the others.
MSHR (Modified self-heat recuperative)
52.03%
53.49%
62.17%
67.19%
0 10 20 30 40 50 60 70
Annual Operating Cost Saving [5]
MSHR
(Heat exchangers
in parallel)
MSHR
(Heat exchangers
in series)
Self- heat
recuperative
column
Heat Pump
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MSHR Concept
• To maximize heat recovery duty, feed stream is divided into two parallel stream.
• Vapor is compressed and condensed in column's reboiler.
• Top outlet stream exchanges heat with the feed stream and cooled further before divided into two stream. 1. recycled back into the column as reflux 2. another is the final top product
• As a result, all heat is recirculated in the process
without the need for external heat.
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UniSim® – Conventional Gas Processing Plant
Base Case with fractionation train Deethanizer
Depropanizer
Debutanizer
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UniSim® – Pre-Treatment Unit (PTU)
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UniSim® – Condensate Treatment Unit (CTU)
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UniSim® – Low Temperature Separation Unit (LTSU)
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UniSim® – C3RU and SGCU
Propane Refrigeration Unit (C3RU)
Sales Gas Compression Unit (SGCU)
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Retrofit – GPP with MSHR
Overall PFD of retrofits in UniSim® sub-flowsheets
39.7% energy saving
29.5% total energy saving
34.9% energy saving
15.4% energy saving
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Retrofit I – Deethanizer
39.7% energy saving
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Retrofit II – Depropanizer
15.4% energy saving
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Retrofit III – Debutanizer
34.9% energy saving
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Results and Discussion- Energy Saving
39.7% energy saving compared to base case
Base Case kW
Condenser 5607
Reboiler 7264
Total energy consumed 12871
MSHR kW
Compressor 4244
Cooler 3514
Total energy consumed 7758
Total Savings 5113
Deethanizer
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Results and Discussion- Energy Saving (cont.)
15.4% energy saving compared to base case
Base Case kW
Condenser 6436
Reboiler 5348
Total energy consumed 11784
MSHR kW
Compressor 4665
Cooler 5305
Total energy consumed 9970
Total Savings 1814
Depropanizer
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34.9% energy saving compared to base case
Base Case kW
Condenser 3660
Reboiler 2506
Total energy consumed 6166
MSHR kW
Compressor 1331
Cooler 2682
Total energy consumed 4013
Total Savings 2153
Debutanizer
Results and Discussion- Energy Saving (cont.)
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Energy Saving Analysis With MSHR
Total energy saved worth 30% from base case
Depropanizer Debutanizer Deethanizer
39.7% 34.9% 15.4%
Retrofit I Retrofit II Retrofit III
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Sensitivity Analysis
$0,00
$200.000,00
$400.000,00
$600.000,00
$800.000,00
$1.000.000,00
$1.200.000,00
$1.400.000,00
$1.600.000,00
$1.800.000,00
$2.000.000,00
80 90 100 110 120
To
tal O
pe
rati
ng
Co
st,
$/y
r
Electricity price factor, $/(kW.a)
TOC vs Electricity price factor
Retrofit I
Retrofit II
Retrofit III
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Optimization Result
Increase in profit after optimization
Optimization Base Case ($/yr) MSHR ($/yr)
Before 203,912,158 207,029,971
After 326,104,913 328,009,054
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Economic Analysis
Analysis shows improved profit profile
Base Case ($/yr) MSHR ($/yr)
Total Operating Cost (TOC) 7,629,122.87 3,108,628.67
Total Capital Cost (TCC) 4,255,896.80 12,201,082.65
Total Annualized Cost (TAC) 11,885,019.67 15,309,711.31
Gross Profit 435,000,000 437,900,000
Net Profit 326,104,913 328,009,054
Payback Period (yr) 0.04 0.05
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• The energy savings of Deethanizer, Depropanizer
and Debutanizer columns are 39.72 %, 15.39 %,
and 34.92 %
• Total annualized cost (TAC) for the base case and
MSHR retrofit are 12×106 $/year and 15×106
$/year.
• Payback periods for the MSHR retrofit is 0.05 year
Conclusion
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1. Kidnay, A. J., W. R. Parrish, and D. G. McCartney. 2011. Fundamentals
of Natural Gas Processing. 2 ed. 0 vols: CRC Press.
2. BP Energy Outlook 2030. 2013. BP. Accessed on June 17,
http://www.bp.com/content/dam/bp/pdf/Energy-economics/Energy-
Outlook/BP_Energy_Outlook_Booklet_2013.pdf.
3. BP statistical Review of world energy June 2015. 2015. Accessed June
26, http://www.bp.com/en/global/corporate/about-bp/energy-
economics/statistical-review-of-world-energy.html.
4. Mokhatab, Saeid, and William A. Poe. 2012. "Chapter 4 Basic Concepts
of Natural Gas Recovery Plant." In Handbook of Natural Gas
Transmission and Processing (Second Edition), ed. Saeid
MokhatabWilliam A. Poe, 353-391. Boston: Gulf Professional
Publishing.
5. Long, Nguyen Van Duc and Moonyong Lee. 2013. A novel NGL (natural
gas liquid) recovery process based on self- heat recuperation. Energy,
57. 663-670.
References
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