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© 2012 Valerus. Confidential and proprietary. All rights reserved. © 2012 Valerus. Confidential and proprietary. All rights reserved.
Compression Split – Technical Seminar
September 26, 2013
Tom Birney, Director of Business Development
© 2012 Valerus. Confidential and proprietary. All rights reserved. © 2012 Valerus. Confidential and proprietary. All rights reserved.
OVERVIEW
© 2012 Valerus. Confidential and proprietary. All rights reserved.
OUTLINE
1. Selection Of A Reciprocating Or Centrifugal Compressor a. Parameters b. Drivers c. Centrifugal Compressors d. Reciprocating Compressors d. Recip. vs. Centrifugal Comparison - Examples e. Conclusion
© 2012 Valerus. Confidential and proprietary. All rights reserved.
OUTLINE
2. High/Medium Speed Vs. Slow Speed Comparison of API 11P (ISO-13631): High/medium speed compressors and API 618 slow speed compressors
3. Sizing, Selection and Applications
4. Packaging Considerations
© 2012 Valerus. Confidential and proprietary. All rights reserved. © 2012 Valerus. Confidential and proprietary. All rights reserved.
COMPRESSION 1. Selection of a Reciprocating or Centrifugal Compressor
© 2012 Valerus. Confidential and proprietary. All rights reserved.
COMPRESSOR TYPES
Rolling Lobe (Roots)
Reciprocating
Single Screw
Axial
Liquid Ring
Screw
Vane
Radial
Positive Displacement Dynamic
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HISTORY
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DEFINE THE QUESTION
• Plant or Site Parameters
• Project Parameters
• Process Parameters
• Machinery Parameters
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PLANT OR SITE PARAMETERS
• Onshore / Offshore
• Elevation/Barometric Pressure
• Ambient Temperature - design/range
• Fuel Available - type, pressure, cost
• Soil/Foundation conditions
• Enclosure Required - open, partial, full
• Manpower/Staffing Plans
• Utilities - water, power, air
• Environment - noise, air, effluents
© 2012 Valerus. Confidential and proprietary. All rights reserved.
PROJECT PARAMETERS
• Anticipated life
• Required start up date & equipment deliveries
• Economic evaluation criteria
© 2012 Valerus. Confidential and proprietary. All rights reserved.
PROCESS PARAMETERS
• Gas analysis
• Suction pressure - design/range
• Discharge pressure - design/range
• Suction temperature - design/range
• Flow rate - design/range
• Extra process heat requirement
• Operating flexibility required
• Operating reliability required
© 2012 Valerus. Confidential and proprietary. All rights reserved.
MACHINERY PARAMETERS
• Initial cost
• Transportation/installation cost & time
• Compressor efficiency - kw/m3
• Specific fuel consumption over range
• Power avail/power required match
• Actual emissions/emissions allowed
• Operation & maintenance cost
• Flexibility to handle range of conditions
© 2012 Valerus. Confidential and proprietary. All rights reserved.
ELECTRIC OR GAS DRIVER
• Fuel gas availability & quality
• Electricity availability
• Speed control
• Fuel gas vs electric cost
• Maintenance vs initial cost
• Emissions
• Lead time
© 2012 Valerus. Confidential and proprietary. All rights reserved.
• Fuel gas availability & quality – Not Required
• Electricity availability - Required
• Speed control – Additional VFD and Torsional Analysis
• Fuel gas vs electric cost – varies
• Maintenance vs initial cost – Maintenance Low / (high failure cost)
Initial cost comparable
• Emissions - None
• Lead time – Long, built to order
ELECTRIC DRIVER
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• Two types of gas turbines – Industrial
• steam turbine technology • in-situ repair
– Aero-derivative • replace - don’t repair
COMBUSTION GAS TURBINE
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• Fuel gas availability & quality –Required / high quality
• Electricity availability - No
• Speed control – Usually ran at constant speed
• Fuel gas vs electric cost – varies
• Maintenance vs initial cost – Maintenance Low / (high failure cost)
Higher Initial cost
• Emissions - High
• Lead time – Long
TURBINE DRIVER
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• Complex start-up/stop sequencing • Complex controls required for fuel scheduling and emissions
controls • Many critical monitoring points for gas turbine • Complicated surge control
GAS TURBINE CONTROLS
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• Fuel gas availability & quality –Required / low quality
• Electricity availability - No
• Speed control – Included
• Fuel gas vs electric cost – varies
• Maintenance vs initial cost – Maintenance medium / Low Initial cost
• Emissions - medium
• Lead time – short
RECIPROCATING ENGINE DRIVER
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• Industry did not have a large industrial gas engine until 1995. – Caterpillar G3616 in 1995 (4500 HP) – Caterpillar G16CM34 in 2001 (7670 HP) – Waukesha 16V-AT27 in 2000 (4500 HP) – Wartsila 18V34SG in 1997 (8000 HP) – Wartsila 20V34SG in 1998 (10600 HP)
RECIPROCATING DRIVERS
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Turbine Engine
Available HP >30,000 >10,000
Temp. 22°C 37.8°C
Altitude Sea Level 1500m
Intake Loss None allowed 1500mm WC
Exhaust Loss None allowed 300mm WC
Degradation Allow up to 10% 0%
Weight / Footprint Low High
RECIPROCATING ENGINE VS. GAS TURBINES DRIVERS
© 2012 Valerus. Confidential and proprietary. All rights reserved.
CENTRIFUGAL COMPRESSORS
WHY Centrifugal? • Mature Technology – Since 1940’s • Handles large capacities • High Horsepower • Small footprint • 99% Availability • Minimal Maintenance
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CENTRIFUGAL CHARACTERISTICS
• Dynamic compressor Achieves pressure increase by controlling gas velocities
• Narrow operating range Precise matching to design point
• Minimal degree of capacity control\ • Large Volumetric flow rates
© 2012 Valerus. Confidential and proprietary. All rights reserved.
Flow: Minimum flow is approx. 3 m3/min (100 acfm) into any impeller. As flow decreases toward this limit efficiency falls off dramatically.
CENTRIFUGAL COMPRESSOR APPLICATION LIMITATIONS
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CENTRIFUGAL COMPRESSOR APPLICATION LIMITATIONS
Pressure: • Lower limit, none with proper seals. • Upper limit, high discharge pressure not itself a limiting factor, just
thicker components. This may reduce number of stages possible. • Most applications are below 350 bar. • Higher suction pressure are more difficult to seal. Most applications
below 200 bar.
© 2012 Valerus. Confidential and proprietary. All rights reserved.
Temperature: • Low temps. down to -75°C handled using higher cost materials of
sufficient ductility. Special seals required. Upper limit set by shaft seals.
• Temps. of 195°C are common & can be increased to 230°C with cool buffer gas.
CENTRIFUGAL COMPRESSOR APPLICATION LIMITATIONS
© 2012 Valerus. Confidential and proprietary. All rights reserved.
CENTRIFUGAL COMPRESSOR APPLICATION LIMITATIONS
Compression Ratio or Head: • Determines the number of stages required. For dynamic compressors this is a function of pressure ratio, MW, temperature, compressibility and ratio of specific heats. Due to rotor stability 10 impellers is normal max. At 4,600 m kg/kg polytropic head per impeller this limits methane to 7.92 ratios in one casing and propane to 200 ratios. Correct MW is critical to proper selection.
© 2012 Valerus. Confidential and proprietary. All rights reserved.
CENTRIFUGAL COMPRESSOR APPLICATION LIMITATIONS
Horsepower: • Applications less than 750 kw (~1000 hp) usually have some other
limiting factor such as low flow or poor efficiency.
• Upper limits are typically set by available drivers.
• Centrifugal compressors can handle high powers.
© 2012 Valerus. Confidential and proprietary. All rights reserved.
CENTRIFUGAL COMPRESSOR APPLICATION LIMITATIONS
Rotative Speed: • With dynamic compressors higher speed results in improved
performance. Work per stage and flow increases with speed. Mechanical considerations limit tip speeds to 335 m/sec for open impellers and 425 m/sec for closed impellers.
© 2012 Valerus. Confidential and proprietary. All rights reserved.
CENTRIFUGAL COMPRESSOR APPLICATION LIMITATIONS
Efficiency: • Polytropic efficiency per stage of 85% is normal for quantity constant
of 100 to 300 and declines to 70% as quantity constant drops to 35. Quantity Constant = ICFM X 1000 X 1728 RPM X IMP. DIA. (in)
© 2012 Valerus. Confidential and proprietary. All rights reserved.
RECIPROCATING COMPRESSORS
WHY Reciprocating? • Large, operating range / flow / pressure / variations in gas • +95% Availability • Portability • Ease of Start – Stop • Re-Application • Cost
© 2012 Valerus. Confidential and proprietary. All rights reserved.
RECIPROCATING CHARACTERISTICS
• Positive Displacement compressor Achieves pressure by reducing the volume
• Wide operating range • Infinite capacity control • Efficiency improves with decreasing flow
© 2012 Valerus. Confidential and proprietary. All rights reserved.
RECIPROCATING COMPRESSOR APPLICATION LIMITATIONS
Flow: • No minimum flow. Maximum flow limited by piston displacement of
available cylinders.
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Pressure: • No minimum limit, can attain high vacuums. Maximum pressures
can be ultra high for special processes. Separable applications are normally limited to 415 bar (6000 psi), at reduced rotative speeds.
RECIPROCATING COMPRESSOR APPLICATION LIMITATIONS
© 2012 Valerus. Confidential and proprietary. All rights reserved.
RECIPROCATING COMPRESSOR APPLICATION LIMITATIONS
Temperature: Minimum limit is -30°C with standard material and -40°C with special alloys. Maximum limit is normally 175°C and preferably below 150°C.
© 2012 Valerus. Confidential and proprietary. All rights reserved.
RECIPROCATING COMPRESSOR APPLICATION LIMITATIONS
Compression Ratio: • Normally limited by one of following;
Max. discharge temp. Allowable rod load Low cylinder volumetric efficiency
• Practical limits on natural gas are 4 - 5 on first stage and 3.5 - 4.5 on succeeding stages.
© 2012 Valerus. Confidential and proprietary. All rights reserved.
RECIPROCATING COMPRESSOR APPLICATION LIMITATIONS
Horsepower: • Limited by frame ratings or driver ratings. Reciprocating (aka Separable)
frames of 7500kw and gas engines of 6100 kw (8000 Bhp) are available.
© 2012 Valerus. Confidential and proprietary. All rights reserved.
RECIPROCATING COMPRESSOR APPLICATION LIMITATIONS
Rotative Speed: • Smaller compressors operate at speeds up to 1800 rpm with larger units in
the 750 - 1200 rpm range. Speed is normally determined by available driver speed.
© 2012 Valerus. Confidential and proprietary. All rights reserved.
SEPARABLE / CENTRIFUGAL COMPARISION
Comparing the most abundant combination in the upstream gas field. • Reciprocating Compressor driven by a Gas Engine : Separable
• Radial Compressor driven by a Gas Turbine : Centrifugal
© 2012 Valerus. Confidential and proprietary. All rights reserved.
SEPARABLE / CENTRIFUGAL COMPARISION
Coverage:
© 2012 Valerus. Confidential and proprietary. All rights reserved.
SEPARABLE / CENTRIFUGAL COMPARISION
Separable vs. Centrifugal Coverage:
© 2012 Valerus. Confidential and proprietary. All rights reserved.
SEPARABLE / CENTRIFUGAL COMPARISION
POWER COMPARISON:
3
2 1
Point Separable Centrifugal
1 5182kW 5660kW 2 5138kW 6129kW 3 4016kW 4685kW
© 2012 Valerus. Confidential and proprietary. All rights reserved.
SEPARABLE / CENTRIFUGAL COMPARISION
POWER COMPARISON:
Point Separable Centrifugal
1 5182kW 5660kW 2 5138kW 6129kW 3 4016kW 4685kW
DRIVER RATINGS: Derate
Temperature 37C 18% Altitude 260m 4%
GT intake losses 100mm 0.7% GT exhaust losses 100mm
• Gas Turbine Derate: 22% + 10% degradation • Gas Engine Derate: 0%
© 2012 Valerus. Confidential and proprietary. All rights reserved.
SEPARABLE / CENTRIFUGAL COMPARISON
POWER COMPARISION: Required Driver Rating (from Point 1): • Gas Engine rating required: 5182 kw
• ISO Gas Turbine rating required: 5660 ÷0.68 = 8323 kw
• Turbine rating needs to be 60%
more than gas engine rating to meet design flows
Solar Titan 130
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SEPARABLE / CENTRIFUGAL COMPARISON
OPERATING COSTS: Fuel: • Cost of fuel is the single largest operating cost.
• Reciprocating uses 23% less fuel than the Gas Turbine.
Reciprocating Turbine
Site Rating 8.44 Mj/Kwh 10.09 Mj/Kwh Total 43736 Mj/hr 57109 Mj/jr
© 2012 Valerus. Confidential and proprietary. All rights reserved.
EFFICIENCY COMPARISON
Turbine / Centrifugal Engine / Reciprocating
Driver Heat Rate Btu / (hp-hr)
8239 6400 29%
Compressor Hp / MMSCFD
26.5 24.7 +7%
Decreasing Driver
Speed Increased Fuel Rate No Change or Decrease
Total Difference +36%
© 2012 Valerus. Confidential and proprietary. All rights reserved.
Reciprocating Compressor: – piston rings and wear bands 16000 hr – valve overhaul 8000 hr – packings 16000 hr – complete 70000 hr
• Engine – spark plugs 2000 hr – top end 30000 hr – complete 60000 hr
• Estimated cost $7.2/MWh
MAINTENANCE COMPARISON
Centrifugal Compressor: – minimal with high quality gas
• Gas Turbine – major overhaul 32000 hr
• Estimated Cost $6.4/MWh
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AVAILABILITY
100%Downtime)dUnschedulefromLossesProduction(Actual
ProductionActualyReliabilit
100%scheduled) LossesdUnscheduleLossesProduction(Actual
ProductionActualtyAvailabili
© 2012 Valerus. Confidential and proprietary. All rights reserved.
AVAILABILITY
• Reciprocating Rental fleet operators guarantee 97 - 99% availability for separable units
• Rotating 99% expected for gas turbine / centrifugal
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PIPELINE APPLICATION EXAMPLE ASSUMPTIONS
• 7500 Bhp installed • Heat rates (btu / (hp-hr))
– CAT 3616TA: 6810 – Wartsila 34SG: 6400 – Solar Taurus: 8239
• Fuel Cost: $2.5 / MM btu • Interest rate: 10% • Project life: 18 years
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PIPELINE APPLICATION EXAMPLE
SOLAR CAT Wartsilla
Installed Cost $6,091,000 $5,642,000 $5,834,000
O&M ($/hp) 25 40 45
Yearly O&M ($) $200,000 $320,000 $360,000
Yearly Fuel ($) $1,160,000 $841,000 $909,000
NPV - O&M ($) $1,640,000 $2,624,000 $2,952,000
NPV - Fuel ($) $9,511,000 $6,896,000 $7,454,000
Life Cycle Cost ($) $17,242,000 $15,162,000 $16,240,000
% Difference 14% 0% 7%
© 2012 Valerus. Confidential and proprietary. All rights reserved.
PIPELINE APPLICATION EXAMPLE
0
50
100
150
200
250
300
350
Flo
w (
MM
SC
FD
)
Jan Mar May July Sept Nov
During Engineering / Design:
© 2012 Valerus. Confidential and proprietary. All rights reserved.
PIPELINE APPLICATION EXAMPLE
FlowMMSCFD
Suction PressurePSIA
Discharge PressurePSIA
305 550 900
300 564 900
290 590 900
280 615 900
250 678 900
225 722 900
During Engineering / Design:
© 2012 Valerus. Confidential and proprietary. All rights reserved.
PIPELINE APPLICATION EXAMPLE
Reciprocating
Centrifugal
Percent Flow0 20 40 60 80 100 120 140
Co
mp
res
sio
n R
ati
o
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.1
2.2
2.3
2.4
2.5
During Engineering / Design:
© 2012 Valerus. Confidential and proprietary. All rights reserved.
PIPELINE APPLICATION EXAMPLE
ACTUAL Operating Conditions:
© 2012 Valerus. Confidential and proprietary. All rights reserved.
PIPELINE APPLICATION EXAMPLE
Reciprocating
Centrifugal
Percent Flow 0 20 40 60 80 100 120 140
Co
mp
ressio
n R
ati
o
1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5
Design vs Actual:
© 2012 Valerus. Confidential and proprietary. All rights reserved.
PIPELINE APPLICATION EXAMPLE
Percent Flow
0 20 40 60 80 100 120 140
Co
mp
ressio
n R
ati
o
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.1
2.2
2.3
2.4
2.52 Reciprocating
Units Reciprocating
1 Reciprocating Unit
Centrifugal
Design vs Actual:
© 2012 Valerus. Confidential and proprietary. All rights reserved.
OTHER CONSIDERATIONS
gas turbine driven
centrifugal compressor
gas engine driven reciprocating
compressor
operating pressure
not flexible, has very limited pressure ratio
very flexible, can be designed to cover broad range of pressures
flow capacity typical 100%-60% with variable guide vanes Large Capacity
typically 100% - 50% with clearance control
100%-0% with recycle 100%-0% with recycle
gas gravity pressure ratio is sensitive to the gas gravity
pressure ratio is not affected by the gas gravity
modification not practical to modify for changing gas conditions
can be modified for # stages and changing gas types and flows
cannot readily change pressure ratio can be designed as 1 stage / 2 stage or 2 stage/3 stage, etc
size, weight small and compact larger and heavier than centrifugal available in large powers but similarly sized standby needed if the service is critical
Above about 4700 hp would require multiple units but costs and flexibility are improved
© 2012 Valerus. Confidential and proprietary. All rights reserved.
OTHER CONSIDERATIONS
gas turbine driven centrifugal
compressor
gas engine driven reciprocating
compressor
cost usually higher capital cost usually lower capital cost
fuel consumption 3 - 4 times higher than gas engine as low as 6800 - 8000 btu/bhp/hr usually requires fuel conditioning for field gases tolerant of field gases
reliability typically 99 - 99.8% typically 95-98.5% needs sophisticated controls and instrumentation
off the shelf control and instrumentation
maintenance requires special shop repair and skilled technicians
common tools and oil-field mechanics
usually requires special synthetic lubricants
Uses locally available engine crankcase lubricants
requires special tools and assembly fixtures
common tools and assembly techniques
parts low usage, high cost predictable usage, low cost special parts, expensive insurance spares common parts, no insurance spares
© 2012 Valerus. Confidential and proprietary. All rights reserved.
OTHER CONSIDERATIONS
gas turbine driven centrifugal
compressor
gas engine driven reciprocating
compressor
failure modes can be unexpected and catastrophic usually with early symptoms and limited to replaceable components
delivery Can be very long 9 - 18 months Can be very short 14 - 36 weeks
installation small footprint and close centerlines larger footprint
unbalance and vibration are nil unbalanced forces and moments are low
typically 4 - 8 weeks typically a few days to a week
portability usually not portable since the compressor is designed for a specific set of conditions and gas
below about 2,000 hp can operate without foundation
site rating turbines lose power generally above 500 ft
turbocharged gas engines maintain power up to about 5,000 ft
© 2012 Valerus. Confidential and proprietary. All rights reserved.
RECIPROCATING / CENTRIFUGAL COMPARISON
Compressor Type Separable Centrifugal kw/m3 1 3 Installed cost 1 2 Lead time 1 3 Fuel consumption 1 2 Waste heat avail. 3 1 Availability 2 1 O & M cost 2 1 Low emissions 2 2 Operating flexibility 1 3
Compare a natural gas engine driven separable compressor to a gas turbine driven centrifugal compressor.
1 = best 2 = not quite as good 3 = worst
© 2012 Valerus. Confidential and proprietary. All rights reserved.
CONCLUSIONS
• Best compressor choice depends on:
– Plant or site parameters
– Project parameters
– Process parameters
– Machinery parameters
© 2012 Valerus. Confidential and proprietary. All rights reserved.
CONCLUSIONS
Gas Turbine driven Centrifugal compressors are best when:
• Large horsepower is required
• Waste heat is required
• Limited range of process conditions
• Minimal foundation is required
• Light weight is desired
• Low fuel gas cost
• Long lead time is possible
© 2012 Valerus. Confidential and proprietary. All rights reserved.
CONCLUSIONS
Separable compressors are best when:
• High fuel cost
• No waste heat required
• Minimum initial cost required
• 6000 kw or less increments required
• Medium project life is required
• Relocation or conversion may be required
• Minimum shipping/construction schedule
• Maximum operating flexibility