reducing emissions from compressor seals
DESCRIPTION
Reducing Emissions from Compressor Seals. Lessons Learned from Natural Gas STAR Transmission Technology Transfer Workshop Duke Energy Gas Transmission Interstate Natural Gas Association of America (INGAA) and EPA’s Natural Gas STAR Program September 22, 2004. Compressor Seals: Agenda. - PowerPoint PPT PresentationTRANSCRIPT
Reducing Emissions from Reducing Emissions from Compressor SealsCompressor Seals
Lessons LearnedLessons Learnedfrom Natural Gas STARfrom Natural Gas STAR
Transmission Technology Transfer WorkshopTransmission Technology Transfer Workshop
Duke Energy Gas TransmissionDuke Energy Gas Transmission
Interstate Natural Gas Association of America (INGAA) andInterstate Natural Gas Association of America (INGAA) and
EPA’s Natural Gas STAR ProgramEPA’s Natural Gas STAR Program
September 22, 2004September 22, 2004
Page 2Reducing Emissions, Increasing Efficiency, Maximizing Profits
Compressor Seals: AgendaCompressor Seals: Agenda
Methane LossesMethane Losses
Methane RecoveryMethane Recovery
Is Recovery Profitable?Is Recovery Profitable?
Industry ExperienceIndustry Experience
Discussion QuestionsDiscussion Questions
Page 3Reducing Emissions, Increasing Efficiency, Maximizing Profits
Methane Losses from Transmission Methane Losses from Transmission and Storageand Storage
Transmission and storage sector responsible for 96 Transmission and storage sector responsible for 96 billion cubic feet (Bcf) in methane emissionsbillion cubic feet (Bcf) in methane emissions
EmissionsEmissionsReductionsReductions
Trans & Storage Trans & Storage 96 Bcf 96 Bcf
Production Production 149 Bcf149 Bcf
Processing Processing 36 Bcf 36 Bcf
Distribution Distribution 77 Bcf77 Bcf
26 Bcf26 Bcf
5 Bcf5 Bcf
20 Bcf20 Bcf
1 Bcf1 BcfOil Downstream Oil Downstream 2 Bcf 2 Bcf
Inventory of U.S. Inventory of U.S. Greenhouse Gas Greenhouse Gas Emissions and Emissions and Sinks 1990 - 2002Sinks 1990 - 2002
Page 4Reducing Emissions, Increasing Efficiency, Maximizing Profits
Methane Losses from Methane Losses from Compressor SealsCompressor Seals
Compressor seals contribute 50% of transmission Compressor seals contribute 50% of transmission and storage emissionsand storage emissions 40 Bcf from reciprocating compressors40 Bcf from reciprocating compressors 8 Bcf from centrifugal compressors8 Bcf from centrifugal compressors
Pneumatic DevicesPneumatic Devices11 Bcf11 Bcf
Centrifugal CompressorsCentrifugal Compressors8 Bcf8 Bcf
Pipeline LeaksPipeline Leaks7 Bcf 7 Bcf
Gas Engine ExhaustGas Engine Exhaust11 Bcf11 Bcf
ReciprocatingReciprocatingCompressors Compressors 40 Bcf40 Bcf
Station VentingStation Venting7 Bcf7 Bcf
Other Sources Other Sources 5 Bcf5 Bcf
Station FugitivesStation Fugitives7 Bcf7 Bcf
Inventory of U.S. Inventory of U.S. Greenhouse Gas Greenhouse Gas Emissions and Emissions and Sinks 1990 - 2002Sinks 1990 - 2002
Page 5Reducing Emissions, Increasing Efficiency, Maximizing Profits
Compressor SealsCompressor SealsWhat is the problem?What is the problem?
Compressor seals account for 13% of natural gas Compressor seals account for 13% of natural gas industry emissionsindustry emissions Over 45,000 compressors in the natural gas industryOver 45,000 compressors in the natural gas industry Over 8,500 compressors in gas transmission sectorOver 8,500 compressors in gas transmission sector
CompressorStation
CompressorStation
Production
32,000 Compressors
Processing
5,000 Compressors
Transmission & Storage
8,500 Compressors
Distribution
0 Compressors
CompressorStation
Page 6Reducing Emissions, Increasing Efficiency, Maximizing Profits
Methane Losses from Methane Losses from Reciprocating CompressorsReciprocating Compressors
Reciprocating compressor rod packing leaks Reciprocating compressor rod packing leaks some gas by designsome gas by design Newly installed packing may leak 60 cubic feet per Newly installed packing may leak 60 cubic feet per
hour (cf/h)hour (cf/h) Worn packing has been reported to leak up to 900 Worn packing has been reported to leak up to 900
cf/hcf/h
Distance PieceDistance Piece
Piston RodPiston Rod
(Side View, Cut in Half)(Side View, Cut in Half)
OILOIL
CylinderCylinder
SuctionSuction
DischargeDischarge
PistonPiston
Rod Packing CaseRod Packing Case
Page 7Reducing Emissions, Increasing Efficiency, Maximizing Profits
Reciprocating Compressor Reciprocating Compressor Rod PackingRod Packing
A series of flexible rings fit around the shaft A series of flexible rings fit around the shaft to prevent leakageto prevent leakage
Leakage still occurs through nose gasket, Leakage still occurs through nose gasket, between packing cups, around the rings and between packing cups, around the rings and between rings and shaftbetween rings and shaft
LubricationLubrication
FlangeFlange
GasGasLeakageLeakage
(Side View, Cut in Half)(Side View, Cut in Half)
Cylinder WallCylinder Wall
High Pressure High Pressure
Gas Inside Gas Inside
CylinderCylinder
Two RingsTwo Rings(In Three Segments)(In Three Segments)
SpringsSprings
Packing CupPacking Cup
Piston RodPiston Rod
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Gas STAR Partners Reduce Emission with Gas STAR Partners Reduce Emission with Economic Rod Packing ReplacementEconomic Rod Packing Replacement
Compare current leak rate to initial leak rateCompare current leak rate to initial leak rateto determine leak reduction expectedto determine leak reduction expected
Monitor and record baseline packing Monitor and record baseline packing leakage and piston rod wearleakage and piston rod wear
Assess costs of replacementsAssess costs of replacements
Determine economic replacement thresholdDetermine economic replacement threshold
Replace packing and rods where cost-effectiveReplace packing and rods where cost-effective
Decision ProcessDecision Process
Page 9Reducing Emissions, Increasing Efficiency, Maximizing Profits
Methane Recovery Through Economic Methane Recovery Through Economic Rod Packing ReplacementRod Packing Replacement
Step 1: Monitor and record baseline leakage and rod Step 1: Monitor and record baseline leakage and rod wearwear Establishing baseline leak rates and monitoring rod wear Establishing baseline leak rates and monitoring rod wear
can help to track leakage and evaluate economicscan help to track leakage and evaluate economics
Step 2: Compare current leak rate to initial leak rate to Step 2: Compare current leak rate to initial leak rate to determine leak reduction expecteddetermine leak reduction expected Leak Reduction Expected (LRE) = Current Leak Rate (CL) Leak Reduction Expected (LRE) = Current Leak Rate (CL)
– Initial Leak Rate (IL)– Initial Leak Rate (IL) Example: The current leak rate is measured as 100 cf/h, Example: The current leak rate is measured as 100 cf/h,
the same component leaked 11.5 cf/h when first installedthe same component leaked 11.5 cf/h when first installed
LRE = 100 cf/h – 11.5 cf/hLRE = 100 cf/h – 11.5 cf/hLRE = 88.5 cf/hLRE = 88.5 cf/h
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Methane Recovery Through Economic Methane Recovery Through Economic Rod Packing ReplacementRod Packing Replacement
Step 3: Assess costs of replacementsStep 3: Assess costs of replacements A set of rings:A set of rings: $ 500$ 500 to to $ 800$ 800
(with cups and case)(with cups and case) $1500$1500 to to $2500$2500
Rods:Rods: $1800$1800 to to $3500$3500 Step 4: Determine economic replacement Step 4: Determine economic replacement
thresholdthreshold Partners can determine economic threshold Partners can determine economic threshold
for all replacementsfor all replacements
@ interest i
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Is Recovery Profitable?Is Recovery Profitable?
Step 5: Replace packing and rods when Step 5: Replace packing and rods when cost-effectivecost-effective Example:Example: Rod and RingsRod and Rings
Rings:Rings: $1,200$1,200Rod:Rod: $7,000$7,000Gas:Gas: $3/Mcf$3/McfOperating:Operating: 8,000 hrs/yr8,000 hrs/yr
Rings OnlyRings OnlyRings:Rings: $1,200$1,200Rod:Rod: $0$0Gas:Gas: $3/Mcf$3/McfOperating:Operating: 8,000 hrs/yr8,000 hrs/yr
Based on 10% interest rateMcf = thousand cubic feet, scfh = standard cubic feet per hour
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Industry ExperienceIndustry Experience
One partner reported replacing worn rod One partner reported replacing worn rod packing rings on 15 compressor unitspacking rings on 15 compressor units
Estimated gas savings of 7,000 Mcf or $21,000 Estimated gas savings of 7,000 Mcf or $21,000 @ $3/Mcf@ $3/Mcf
Cost including materials and labor of $17,000Cost including materials and labor of $17,000
Payback period of less than one yearPayback period of less than one year
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Methane Losses from Methane Losses from Centrifugal CompressorsCentrifugal Compressors
Centrifugal compressor wet seals leak little gas at Centrifugal compressor wet seals leak little gas at the seal facethe seal face Seal oil degassing may vent 40 to 200 cubic feet per Seal oil degassing may vent 40 to 200 cubic feet per
minute (cf/m) to the atmosphereminute (cf/m) to the atmosphere A Natural Gas STAR partner reported wet seal A Natural Gas STAR partner reported wet seal
emissions of 75 Mcf/day (52 cf/m)emissions of 75 Mcf/day (52 cf/m)
ShaftSeal
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Centrifugal Compressor Wet SealsCentrifugal Compressor Wet Seals
High pressure seal oil is circulates between rings High pressure seal oil is circulates between rings around the compressor shaft around the compressor shaft
Gas absorbs in the oil on the inboard side Gas absorbs in the oil on the inboard side Little gas leaks through the oil sealLittle gas leaks through the oil seal Seal oil degassingSeal oil degassing
vents methane to vents methane to the atmospherethe atmosphere
Page 15Reducing Emissions, Increasing Efficiency, Maximizing Profits
Gas STAR Partners Reduce Emissions Gas STAR Partners Reduce Emissions with Dry Sealswith Dry Seals
Dry seal springs press the stationary ring in the seal Dry seal springs press the stationary ring in the seal housing against the rotating ring when the housing against the rotating ring when the compressor is not rotatingcompressor is not rotating
At high rotation speed, gas is pumped between the At high rotation speed, gas is pumped between the seal rings creating a high pressure barrier to leakageseal rings creating a high pressure barrier to leakage
Only a very smallOnly a very smallamount of gas amount of gas escapes through escapes through the gap the gap
2 seals are often 2 seals are often used in tandemused in tandem
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Methane Recovery with Dry SealsMethane Recovery with Dry Seals
Dry seals typically leak at a rate of only Dry seals typically leak at a rate of only 0.5 to 3 cf/m0.5 to 3 cf/m Significantly less than the 40 to 200 cf/m Significantly less than the 40 to 200 cf/m
emissions from wet sealsemissions from wet seals These savings translate to approximately These savings translate to approximately
$48,960 to $48,960 to $279,360 $279,360 in annual gas in annual gas valuevalue
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Other Benefits with Dry SealsOther Benefits with Dry Seals
Aside from gas savings and reduced emissions, dry Aside from gas savings and reduced emissions, dry seals also:seals also: Lower operating costLower operating cost
Dry seals do not require seal oil make-upDry seals do not require seal oil make-up Reduced power consumptionReduced power consumption
Wet seals require 50 to 100 kiloWatt hours (kW/hr) for Wet seals require 50 to 100 kiloWatt hours (kW/hr) for ancillary equipment while dry seals need only 5 kW/hrancillary equipment while dry seals need only 5 kW/hr
Improve reliabilityImprove reliability More compressor downtime is due to wet sealsMore compressor downtime is due to wet seals
Eliminate seal oil leakage into the pipelinesEliminate seal oil leakage into the pipelines Dry seals lower drag in pipelines (and horsepower to Dry seals lower drag in pipelines (and horsepower to
overcome)overcome)
Page 18Reducing Emissions, Increasing Efficiency, Maximizing Profits
Gas STAR Partners Reduce Emissions Gas STAR Partners Reduce Emissions with Dry Seal Replacementwith Dry Seal Replacement
Estimate savings of dry seal retrofitEstimate savings of dry seal retrofit
Identify candidates for wet seal replacementIdentify candidates for wet seal replacement
Determine costs for conversion to dry sealsDetermine costs for conversion to dry seals
Compare costs to savingsCompare costs to savings
Decision ProcessDecision Process
Page 19Reducing Emissions, Increasing Efficiency, Maximizing Profits
Decision Process to Replace SealsDecision Process to Replace Seals
Step 1: Identify candidates for replacementStep 1: Identify candidates for replacement Dry seals are routinely used for compressors Dry seals are routinely used for compressors
operating up to 1,500 pounds per square inch operating up to 1,500 pounds per square inch (psi), up to 400º Fahrenheit(psi), up to 400º Fahrenheit
Step 2: Estimate savings from a dry sealStep 2: Estimate savings from a dry seal Gas savings between 34 to 196 cf/mGas savings between 34 to 196 cf/m Other dry seal benefits ≈ $63,000/yrOther dry seal benefits ≈ $63,000/yr
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Decision Process to Replace SealsDecision Process to Replace Seals
Step 3: Determine dry seal conversion costsStep 3: Determine dry seal conversion costs Dry seals cost $5,000 to $6,000 per inch of Dry seals cost $5,000 to $6,000 per inch of
shaft diameter or $8,000 to $10,000 for shaft diameter or $8,000 to $10,000 for tandem sealstandem seals
Beam compressors require two seals, one at Beam compressors require two seals, one at each endeach end
Overhung compressors require one seal at Overhung compressors require one seal at the inboard endthe inboard end
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Decision Process to Replace SealsDecision Process to Replace Seals
Step 4: Compare costs and savings for a Step 4: Compare costs and savings for a 6-inch shaft beam compressor6-inch shaft beam compressor
Flowserve CorporationFlowserve Corporation
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Is Recovery Profitable?Is Recovery Profitable?
Replacing wet seals in a 6 inch shaft beam Replacing wet seals in a 6 inch shaft beam compressor operating 8,000 hr/yrcompressor operating 8,000 hr/yr Net Present Value = $531,940Net Present Value = $531,940
Assuming a 10% discount over 5 yearsAssuming a 10% discount over 5 years Internal Rate of Return = 86%Internal Rate of Return = 86% Payback Period = 14 monthsPayback Period = 14 months
Ranges from 8 to 24 months based on wet seal Ranges from 8 to 24 months based on wet seal leakage rateleakage rate
Economics are better for new installationsEconomics are better for new installations Vendors report that 90% of compressors sold Vendors report that 90% of compressors sold
to the natural gas industry are centrifugal with to the natural gas industry are centrifugal with dry sealsdry seals
Page 23Reducing Emissions, Increasing Efficiency, Maximizing Profits
Industry ExperienceIndustry Experience
One Gas STAR partner replaced a wet seal One Gas STAR partner replaced a wet seal with a dry seal and reduced emissions by with a dry seal and reduced emissions by 97%97%
Dry seal leaked 2 Mcf/d versus wet seal Dry seal leaked 2 Mcf/d versus wet seal emissions of 75 Mcf/demissions of 75 Mcf/d
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Discussion QuestionsDiscussion Questions
To what extent have you replaced rod To what extent have you replaced rod packing or seals in your reciprocating and packing or seals in your reciprocating and centrifugal compressors?centrifugal compressors?
How can the Lessons Learned study be How can the Lessons Learned study be improved upon or altered for use in your improved upon or altered for use in your operation(s)?operation(s)?
What are the barriers (technological, What are the barriers (technological, economic, lack of information, regulatory, economic, lack of information, regulatory, etc.) that are preventing you from etc.) that are preventing you from implementing this technology?implementing this technology?