Drivers for Gas
Compression
A comparison between reciprocating
engines, turbines, and electric motors
Presented by
Wayne Longer
Courtesy of
Compressor station design 73,000 horse-power
42” pipeline
Courtesy of
Courtesy of
Exhaust-Catalyst-Air intake-Engine coolers-Gas coolers-Separators
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Courtesy of
How does the air flow ?
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Working space – overhead bridge crane - ventalation
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Note the insulation on the exhaust systems
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How Does an Engineer Decide?
Factors and Examples
Company
ABC
Project
Factors for Deciding Driver & Compressor
Site information
– environmental issues
– operating conditions
• pressure ratios
• volume of gas
• variability of operation
Owning and operating costs
– initial capital expenditure
– fuel/electricity costs
– maintenance
What driver is familiar
– like to go with what you know
Risk assessment
– driver reliability - storm outage?
– redundancy of units – crank failure?
– mix of driver types
Driver Options
Driver Options
Reciprocating Engines
Major players
– Caterpillar
– Waukesha
– Wärtsilä
CAT G16CM34
Typical engine power
1200 - 8000 bhp
Operate at 750 - 1000 rpm
CAT G3612
Waukesha ATGL16V
Driver Options
Turbines
Major players
Solar Mars 90
– Solar
– Siemens
– Elliot
GE10-2
– GE
– Rolls-Royce
– MAN Turbo
Typical power 1500 - 30,000 bhp
Operate at 11,000 - 23,000 rpm
GE10-1
Driver Options
Electric Motors
Major players
– Toshiba
– Siemens
– Rockwell (formerly Reliance)
– Ideal
– GE
– ABB
Typical power 1300 - 20,000 bhp
Operate typically at 300 - 3600 rpm
Siemens
H-Compact
Siemens
H-Compact PLUS
– high speed motors at 12,000 - 23,000 rpm
Direct Drive Systems
Frame 2 (high speed motor)
Compressor Options
Compressor Options
Reciprocating
Major players
–
–
–
–
Ariel
Dresser-Rand
Cameron Compression
GE
Ariel JGV/6
300 - 1800 rpm input speed
Wide operating range 1 to 10,000 PSI
– Advantage at higher pressure ratios, > 3:1
Dresser-Rand HOS
Cameron Axis
Compressor Options
Centrifugal
Solar C16
Dresser-Rand
Datum
Major players
– Solar
– Dresser-Rand
– Siemens
– Rolls Royce
Operates with higher speed drivers (motors
and turbines)
Sweet spot at low pressure ratios and high
volumes
– < 1.4 pressure ratio is ideal
Operate best at lower discharge pressures
– < 2000 psi
Siemens STC-SV
Package Combinations
Package Combinations
Reciprocating Compressor
Recip Engine
Electric Motor
Package Combinations
Centrifugal Compressor
Turbine
Electric Motor
Emerging Technology
Dual Drive
Engine or Electric motor driver
Flexibility – lowest cost by the hour
Reduced emissions
Performance Characteristics
Fuel and Power*
Compression Efficiency
(Turndown – Flexible operation)
De-ration
Emissions
Noise
* For the following comparison tables, cost of electricity is based solely on cents/kWhr price; demand
charges not included and could substantially increase yearly energy cost
Electricity Source: Energy Information Administration
Engine
Fuel and Power
4700 - 5500 bhp*
($4.00/MMBtu and 6.5 cents/kWhr at 8000 hours/year)
Btu/bhp-hr
$/year
Efficiency
or kW
rpm
bhp
($/hp-hr)
G3616
4735
1000
39%
6736
$1,020,638
(.0269)
Turbines Gas Turbine
Motors
4700
15,000
27.9%
9125
$1,372,400
(.0366)
501 KC-5
5500
13,600
29.6%
8495
$1,495,120
(.0339)
DDS Frame 8
5360
7000
97.5%
4101
Toshiba/
Siemens
5500
1800
96.5%
4252
$2,132,565
(.0497)
$2,211,040
(.0502)
* Ratings based on companies’ published ISO conditions
Demand charges not included and could substantially increase yearly electric costs
Fuel and Power
7700 - 10,400 bhp*
($4.00/MMBtu and 6.5 cents/kWhr at 8000 hours/year)
Btu/bhp-hr
Efficiency
or kW
bhp
rpm
Engines G16CM34
8180
750
42.7%
5959
Wärtsilä
16V34SG
Turbines Gas Turbine
9360
750
44.3%
5793
7700
15,000
32%
7960
Gas Turbine
10,310
15,200
34%
7484
Toshiba/
Siemens
10,000
1800
96.5%
7730kwk
Motor
$/year
($/hp-hr)
$1,559,827
(.0238)
$1,735,119
(.0232)
$1,961,344
(.0318)
$2,469,121
(.02993)
$4,019,896
(.0502)
•Ratings based on companies’ published ISO conditions @ 70F – Turbines de-rate as temp increases
• Demand charges not included and could substantially increase yearly electric costs.
Combined cycle
True Carbon foot print ???
Additional Electric Power Costs
Demand charges
– based on total at site power
– no charge if electricity is not used
• even 1 kW of usage triggers total kW demand charge
– can be firm or interruptible
• firm is more expensive
– usually between $5 - $8 per kW in one month
– some companies charge per kW-hr
• $.009/kW-hr is common
Electric
Motor Power
5000 bhp =
3731 kW
Demand
Charge
($/kW-Mo)
$6.50
Yearly
Demand
Charge
$291,000
Compression Efficiency
Reciprocating compressor
– typically run at 70% - 85% efficiency
– suited for higher pressure ratios >1.4:1 ratios
Centrifugal
– typically run at 70% - 85% efficiency
– highest efficiencies at lower pressure ratios 1.2:1
•high pressure ratios favor reciprocating compressors
•low pressure ratios favor centrifugal compressors
Horsepower De-rate
Ambient Temperature
Altitude
Fuel gas
Site specific ???
Turbine60
G16CM34 and Taurus
Available Power
9000
8500
Power, bhp
8000
7500
G16CM34
G16CM34
Turbine - 60
Sea(ISO)
level
Taurus
Taurus
Turbine - 60
500(500
ft
ft)
7000
Taurus
ft)
Turbine - 60
1500(1500
ft
6500
6000
5500
0
10
20
30
40
50
60
Temp, degF
70
80
90
100
Fuel Consumption (btu/bhp-hr)
Fuel Consumption at Sea Level
10000
9500
9000
8500
8000
7500
7000
6500
6000
10
20
30
40
50
60
70
Ambient Temp (deg F)
G3616
Recip
Centaur
Turbine 50
80
90
100
De-rate - Electric Motor
Ambient Temperature
Insulation usually enough to avoid de-ration
Altitude
Typical motor will not de-rate until 3500 ft.
Above 3500 ft. requires special insulation - cooler
– possible derating (though not as severe as engines and turbines)
Load change
Turndown does not affect motor efficiency much .
Emissions
(g/bhp-hr) w/o after treatment
(Oxidation Catalyst 90% reduction)
NOx
CO
THC
G3600
0.5 - 0.7
2.5
6.0
GCM34
0.5 – 0.7
2.0
6.0 - 7.0
0.9
2.0
6.0
0.2 - 0.6
0.6
0.2
Wärtsilä
16V34SG
Turbine
Electric Motor
At site only from packaging leaks (valves, vents…)
Transfers emissions to power plant
- Carbon foot print??
Noise Comparison
Reciprocating Engine
128 dBA
noise dampening required in some areas
Turbine
82 dBA
high frequency noise
– dissipates quickly with distance
Electric Motor
70 dBA
considered noiseless if inside building
–
Exception - air flow for cooling and gas flow in pipe
Packaging and
Installation Comparison
Packaging and Installation
G3600
Air inlet system
Exhaust system
Cooling system
Package
controls/electronics
Recip compressor
Scrubbers
Pulsation bottles
Gas cooler
Packaging and Installation
G3616
Package approx
weight: 95,000 lbs
– G3616:
65,900 lbs
– Compressor:
28,600 lbs
Package approx
length:
29 feet
116”
223”
Package approx
width:
Package approx height: 137 inches
178 inches
Note: does not include auxiliary modules, additional piping
Packaging and
Installation - GCM34
Air inlet system
Exhaust system
Fuel Module
Combined Module
Unit Control Panel
Recip compressor
Scrubbers
Pulsation bottles
Gas cooler
Packaging and
Installation - G16CM34
Package approx weight:
300,000 lbs
– G16CM34: 179,080 lbs
– Compressor: 120,000 lbs
Package approx length:
42 feet
Package approx width:
220 inches
Package approx height:
137 inches
Note: does not include auxiliary modules,
building/infrastructure or additional piping
319”
185”
Packaging and Installation
Turbine
Air inlet system
Exhaust system
Cooling system
Package controls
Rotating compressor
Scrubbers
Gas cooler
Packaging and Installation
Turbine (6000 hp)
CENTRIFUGAL
COMPRESSOR
COOLING SYSTEM
(off skid)
Packaging and Installation
Electric Motor with Reciprocating Compressor
Air ducting
Cooling System
Package controls
Recip compressor
Scrubbers
Pulsation bottles
Gas cooler
Typical motor weight: 20,000 lbs +/- 5000
Typical motor length: 75” +/- 25”
4 throw compressor 116”
Packaging and Installation
Electric Motor with Centrifugal Compressor
Air ducting
Cooling System
Package controls/electronics
Couplings
Gear box or transmission
Centrifugal compressor
Packaging and Installation
Electric Motor with Centrifugal Compressor
Typical motor weight: 20,000 lbs +/- 5000
Typical motor length: 75” +/- 25”
Other package dimensions similar to turbine
– addition of gear box or transmission could greatly increase length
Packaging and Installation
Additional Requirements
Reciprocating Engines and Turbines
Usually need enclosure
Possible noise suppression and exhaust
after treatment
Similar installation for both drivers
Packaging and Installation
Additional Requirements
Electric Motor
Building / enclosure needed
Sub-station
– includes switchgear, breaker, transformers, drives
Need VFD or transmission for variable speed
Need transmission lines
– Could take a years or more to get power to
compression station (Eagleford shale)
– Right-away procurement
Lifetime Maintenance Compared
(includes labor at $100/hour and oil at $7.40/gallon)
Gas turbines
Average ~ $0.0035/bhp-hr Downtime over
15 years 280 hours
Reciprocating engines
G3600 avg. ~ $0.0036/bhp-hr
GCM ~ $0.0037/bhp-hr
Downtime over 15 years
Electric motors
Less than $10,000/year or
$.0004/bhp-hr
Downtime over 15 years 240 hours
G3600 800 hours CM 730 hours
How Does an Engineer Decide?
Factors and Examples
Company
ABC
Project
Factors for Deciding Driver & Compressor
Site information
– environmental issues
– operating conditions
• pressure ratios
• volume of gas
• variability of operation
Owning and operating costs
– initial capital expenditure
– fuel/electricity costs
– maintenance
What power is familiar
– like to go with what know
Risk assessment
– power reliability storm outage?
– redundancy of units
– mix of driver types
Example 1
Project Specifics
4,500 bhp required
Not in non-attainment area
– emissions not a major issue
Site rated at sea level and 100 degrees (F) ambient temperature
Average operating pressure ratio of 1.3 and discharge pressure of 1100 psi
– centrifugal and reciprocating compressors both options
No horsepower in place
– no customer preference
2 miles from electricity power source
Example 1
Compression Options
G3616 (4735 bhp, 6736 Btu/bhp-hr)
Gas Turbine (4700 bhp, 9050 Btu/bhp-hr)
5000 bhp electric motor with reciprocating compressor
5000 bhp electric motor with centrifugal compressor
Example 1
Initial Capital Expenditures
Driver
Driver Cost Package Cost Other Install
Costs
$4,000,000*
Total
($MM)
$7.20
Total
($/bhp)
$1521
G3616
$1,360,000
$3,200,000
Gas Turbine
$1,950,000
$3,750,000
$4,000,000*
$7.75
$1550
Electric Motor
(5000 bhp w/
reciprocating)
Electric Motor
(5000 bhp w/
centrifugal)
$225,000
$900,000
$6,505,000
$7.51
$1501
$225,000
$1,000,000
$6,605,000
$7.61
$1521
* Includes facility and additional piping and controls
Example 1
Electric Motor Installation Breakdown
Package
$900,000
(reciprocating
compressor)
$1,000,000
(centrifugal
compressor)
Total
VFD
Substation with Transmission
($150/bhp)
everything
Lines
included
($1 mill/mi)
Facility,
controls
and piping
$750,000
$855,000
$2,000,000
$3,000,000 $6,505,000
$750,000
$855,000
$2,000,000
$3,000,000 $6,605,000
Example 1
Driver and Compressor Owning and
Operating Costs* 15 year outlook (15 years covers one major overhaul)
Driver
Maintenance
Lifecycle Cost
15 Year
Fuel/Electricity 15 Year Fuel
Maintenance
bhp-hr
Cost
Cost
G3616
(4735)
Gas Turbine
(4700 hp)
Electric Motor
(5000 bhp)
$.0044/bhp-hr
=$2,471,700 $.0269/bhp-hr =$15,284,580
$.0038/bhp-hr
=$2,250,000 $.0366/bhp-hr =$20,642,400
$.0012/bhp-hr
=$690,000
8000 hours/year, $4.00/MMBtu, 6.5 cents/kWhr
$.048/bhp-hr
=$29,820,000
Example 1 Driver and Compressor Owning
and Operating total Costs*
15 year outlook
Driver
Initial Capital
Expenditures
Maintenance
Fuel/
Electricity
Total
(in millions)
Total
($/bhp)
G3616
$7,200,000
$2,471,700
$15,284,580
$24,956,280
$5270
Gas Turbine
$7,750,000
$2,250,000
$20,642,000
$30,642,000
$6519
Electric
Motor
$7,605,000
$690,000
$29,820,000
$38,115,000
$7623
* 8000 hours/year, $4.00/MMBtu, 6.5 cents/kWhr
Advantages/Disadvantages
Reciprocating Engine
Advantages
Fuel efficiency
Operation under variable loads and pressure ratios
Well known technology
Disadvantages
Emissions
High maintenance intervals and costs
Complex package
Lower compressor efficiency at lower pressure ratios
Advantages/Disadvantages
Turbine
Advantages
Long maintenance intervals
Low emissions
Lower first cost for high horsepower applications due to larger
horsepower blocks
Higher efficiencies at lower pressure ratios 1.2
Disadvantages
Fuel consumption
High maintenance costs
Minimal turndown / load reduction
Starting and stopping takes hours off life cycle
Altitude and ambient temperature quickly affect power and heat rate
Advantages/Disadvantages
Electric Motor
Advantages
Low maintenance costs and intervals
No emissions at site
Turndown does not affect motor efficiency much
Can be used with centrifugal or reciprocating compressor
Disadvantages
Dependency on power company (interruptions in service)
If high power source not within 2 - 3 miles, installation cost are high
(14.7 KV)
Complex controls required (VFD or variable speed gear box)
Sources
Manufacturers
Ariel Corporation
Caterpillar
Solar Turbines
Pipeline Companies
Kinder Morgan
El Paso Pipeline
Spectra Energy
Others
Alliance Engineering
Miratech Emissions
Solutions
Shermco Industries
Packagers
Compressor Systems
Inc.
Exterran
References
Ariel Corporation
Ariel Performance Software
Arielcorp.com
Caterpillar Gas Engines
Gas Engine Rating Pro software
catoilandgas.cat.com
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