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Natural Gas DehydrationNatural Gas Dehydration
Lessons LearnedLessons Learnedfrom Natural Gas STARfrom Natural Gas STAR
Producers Technology Transfer WorkshopProducers Technology Transfer Workshop
Devon Energy andDevon Energy andEPA’s Natural Gas STAR ProgramEPA’s Natural Gas STAR Program
Casper, WyomingCasper, WyomingAugust 30, 2005August 30, 2005
Slide 2Reducing Emissions, Increasing Efficiency, Maximizing Profits
Natural Gas Dehydration: AgendaNatural Gas Dehydration: Agenda
Methane LossesMethane Losses Methane RecoveryMethane Recovery Is Recovery Profitable?Is Recovery Profitable? Industry ExperienceIndustry Experience Discussion QuestionsDiscussion Questions
Slide 3Reducing Emissions, Increasing Efficiency, Maximizing Profits
Methane Losses from ProductionMethane Losses from Production
1990-2004 Partners reported saving ~ 12.5 1990-2004 Partners reported saving ~ 12.5 Bcf (Billion cubic feet) from dehydratorsBcf (Billion cubic feet) from dehydrators
Pneumatic Pneumatic DevicesDevices61 Bcf61 Bcf
Storage Tank Storage Tank VentingVenting9 Bcf9 Bcf
Other Sources Other Sources 21 Bcf21 Bcf
Inventory of U.S. Greenhouse Inventory of U.S. Greenhouse Gas Emissions and Sinks Gas Emissions and Sinks 1990 - 2003 1990 - 2003
Meters andMeters andPipeline LeaksPipeline Leaks10 Bcf10 Bcf
Gas EngineGas EngineExhaustExhaust12 Bcf12 Bcf
Dehydrators andDehydrators andPumpsPumps17 Bcf17 Bcf
Well Venting Well Venting and Flaringand Flaring18 Bcf18 Bcf
Slide 4Reducing Emissions, Increasing Efficiency, Maximizing Profits
What is the Problem?What is the Problem?
Produced gas is saturated with water, which Produced gas is saturated with water, which must be removed for gas transmissionmust be removed for gas transmission
Glycol dehydrators are the most-common Glycol dehydrators are the most-common equipment to remove water from gasequipment to remove water from gas 38,000 dehydration systems in the natural gas 38,000 dehydration systems in the natural gas
production sectorproduction sector Most use triethylene glycol (TEG)Most use triethylene glycol (TEG)
Glycol dehydrators create emissionsGlycol dehydrators create emissions Methane, VOCs, HAPs from reboiler ventMethane, VOCs, HAPs from reboiler vent Methane from pneumatic controllersMethane from pneumatic controllers
Source: www.prideofthehill.com
Slide 5Reducing Emissions, Increasing Efficiency, Maximizing Profits
Basic Glycol Dehydrator System Basic Glycol Dehydrator System Process DiagramProcess Diagram
Glycol Contactor
Dry Sales Gas
Inlet Wet Gas
Lean TEGPump
Driver
Water/Methane/VOCs/HAPsTo Atmosphere
Rich TEG
Fuel Gas
Glycol Reboiler/ Regenerator
Gas Bypass Glycol
Energy Exchange Pump
Slide 6Reducing Emissions, Increasing Efficiency, Maximizing Profits
Methane Recovery: Four OptionsMethane Recovery: Four Options
Optimized glycol circulation ratesOptimized glycol circulation rates Flash tank separator (FTS) installationFlash tank separator (FTS) installation Electric pump installationElectric pump installation Replace glycol unit with desiccant Replace glycol unit with desiccant
dehydratordehydrator
Slide 7Reducing Emissions, Increasing Efficiency, Maximizing Profits
Optimizing Glycol Circulation RateOptimizing Glycol Circulation Rate
Gas well’s initial production rate decreases Gas well’s initial production rate decreases over its lifespanover its lifespan Glycol circulation rates designed for initial, Glycol circulation rates designed for initial,
highest production ratehighest production rate Operators tend to “set it and forget it”Operators tend to “set it and forget it”
Glycol overcirculation results in more Glycol overcirculation results in more methane emissions without significant methane emissions without significant reduction in gas moisture contentreduction in gas moisture content Partners found circulation rates two to three Partners found circulation rates two to three
times higher than necessarytimes higher than necessary Methane emissions are directly proportional Methane emissions are directly proportional
to circulation rateto circulation rate
Slide 8Reducing Emissions, Increasing Efficiency, Maximizing Profits
Installing Flash Tank SeparatorInstalling Flash Tank Separator
Flashed methane can be captured using an Flashed methane can be captured using an FTSFTS
Many units are Many units are notnot using an FTS using an FTS
0
20
40
60
80
100
Per
cen
t
<1 1-5 >5
MMcfd processed
With FTS
WithoutFTS
Slide 9Reducing Emissions, Increasing Efficiency, Maximizing Profits
Methane RecoveryMethane Recovery
Recovers ~ 90% of methane emissionsRecovers ~ 90% of methane emissions Reduces VOCs by 10 to 90% Reduces VOCs by 10 to 90% Must have an outlet for low pressure gasMust have an outlet for low pressure gas
Flash Tank
Gas Recovery
Reduced Emissions
Low Capital Cost/Quick Payback
Slide 10Reducing Emissions, Increasing Efficiency, Maximizing Profits
Flash Tank CostsFlash Tank Costs
Lessons Learned study provides guidelines Lessons Learned study provides guidelines for scoping costs, savings and economicsfor scoping costs, savings and economics
Capital and installation costs:Capital and installation costs: Capital costs range from $5,000 to $10,000 Capital costs range from $5,000 to $10,000
per flash tankper flash tank Installation costs range from $2,400 to $4,300 Installation costs range from $2,400 to $4,300
per flash tankper flash tank Negligible O&M costsNegligible O&M costs
Slide 11Reducing Emissions, Increasing Efficiency, Maximizing Profits
Installing Electric PumpInstalling Electric Pump
Glycol Contactor
Dry Sales Gas
Inlet Wet Gas
Lean TEGPump
Driver
Water/Methane/VOCs/HAPsTo Atmosphere
Rich TEG
Fuel Gas
Glycol Reboiler/ Regenerator
Electric MotorDrivenPump
Slide 12Reducing Emissions, Increasing Efficiency, Maximizing Profits
Overall BenefitsOverall Benefits
Financial return on investment through gas Financial return on investment through gas savingssavings
Increased operational efficiencyIncreased operational efficiency Reduced O&M costsReduced O&M costs Reduced compliance costs (HAPs, BTEX)Reduced compliance costs (HAPs, BTEX) Similar footprint as gas assist pumpSimilar footprint as gas assist pump
Slide 13Reducing Emissions, Increasing Efficiency, Maximizing Profits
Is Recovery Profitable?Is Recovery Profitable?
Three Options for Minimizing Glycol Dehydrator EmissionsThree Options for Minimizing Glycol Dehydrator Emissions
OptionOption Capital Capital CostsCosts
Annual O&M Annual O&M CostsCosts
Emissions Emissions SavingsSavings
Payback Payback PeriodPeriod
Optimize Optimize Circulation Circulation RateRate
NegligibleNegligible NegligibleNegligible 130 – 13,133 130 – 13,133 Mcf/yearMcf/year ImmediateImmediate
Install Flash Install Flash TankTank
$5,000 - $5,000 - $10,000$10,000 NegligibleNegligible 236 – 7,098 236 – 7,098
Mcf/yearMcf/year
5 months 5 months – 17 – 17 monthsmonths
Install Install Electric Electric PumpPump
$4,200 - $4,200 - $23,400$23,400 $3,600$3,600 360 – 36,000 360 – 36,000
Mcf/yearMcf/year
< 2 < 2 months – months – several several yearsyears
Slide 14Reducing Emissions, Increasing Efficiency, Maximizing Profits
Replace Glycol Unit with Desiccant Replace Glycol Unit with Desiccant DehydratorDehydrator
Desiccant DehydratorDesiccant Dehydrator Wet gasses pass through drying bed of Wet gasses pass through drying bed of
desiccant tabletsdesiccant tablets Tablets absorb moisture from gas and Tablets absorb moisture from gas and
dissolvedissolve Moisture removal depends on:Moisture removal depends on:
Type of desiccant (salt)Type of desiccant (salt) Gas temperature and pressureGas temperature and pressure
Hygroscopic Hygroscopic SaltsSalts
Typical T and P Typical T and P for Pipeline Specfor Pipeline Spec
Cost Cost
Calcium chlorideCalcium chloride 4747ooF 440 psigF 440 psig Least expensiveLeast expensive
Lithium chlorideLithium chloride 6060ooF 250 psigF 250 psig More expensiveMore expensive
Slide 15Reducing Emissions, Increasing Efficiency, Maximizing Profits
Desiccant PerformanceDesiccant Performance
Desiccant Performance Curves at Maximum Desiccant Performance Curves at Maximum Pipeline Moisture Spec (7 pounds water / MMcf)Pipeline Moisture Spec (7 pounds water / MMcf)
Max Spec Line Max Spec Line for CaClfor CaCl22
Max Spec Line Max Spec Line forfor LiClLiCl22
Slide 16Reducing Emissions, Increasing Efficiency, Maximizing Profits
Filler Hatch
Drain Valve
Support Grid
Minimum Desiccant Level
Maximum Desiccant Level
Brine
Desiccant Tablets
Desiccant Dehydrator Schematic Desiccant Dehydrator Schematic
Drying Bed
Inlet Wet Gas
Dry Sales Gas
Slide 17Reducing Emissions, Increasing Efficiency, Maximizing Profits
Estimate Capital CostsEstimate Capital Costs
Determine amount of desiccant needed to Determine amount of desiccant needed to remove waterremove water
Determine inside diameter of vesselDetermine inside diameter of vessel Costs for single vessel desiccant dehydratorCosts for single vessel desiccant dehydrator
Capital cost varies between $3,000 and Capital cost varies between $3,000 and $17,000$17,000
Gas flow rates from 1 to 20 MMcf/dayGas flow rates from 1 to 20 MMcf/day Capital cost for 20-inch vessel with 1 MMcf/day gas Capital cost for 20-inch vessel with 1 MMcf/day gas
flow is $6,500flow is $6,500 Installation cost assumed to be 75% of capital costInstallation cost assumed to be 75% of capital cost
Note:Note:MMcf = Million Cubic FeetMMcf = Million Cubic Feet
Slide 18Reducing Emissions, Increasing Efficiency, Maximizing Profits
How Much Desiccant Is Needed?How Much Desiccant Is Needed?
Example:Example: Where: Where:D = ?D = ? D = Amount of desiccant needed (pounds/day) D = Amount of desiccant needed (pounds/day)F = 1 MMcf/day F = 1 MMcf/day F = Gas flow rate (MMcf/day) F = Gas flow rate (MMcf/day)I = 21 pounds/MMcf I = Inlet water content (pounds/MMcf) I = 21 pounds/MMcf I = Inlet water content (pounds/MMcf) O = 7 pounds/MMcf O = Outlet water content (pounds/MMcf)O = 7 pounds/MMcf O = Outlet water content (pounds/MMcf)B = 1/3 B = 1/3 B = Desiccant/water ratio vendor rule B = Desiccant/water ratio vendor rule of thumb of thumb
Calculate:Calculate:D = F * (I - O) * BD = F * (I - O) * BD = 1 *(21 - 7) * 1/3D = 1 *(21 - 7) * 1/3D = 4.7 pounds desiccant/dayD = 4.7 pounds desiccant/day
Source: Van AirNote:Note:MMcf = Million Cubic FeetMMcf = Million Cubic Feet
Slide 19Reducing Emissions, Increasing Efficiency, Maximizing Profits
Example:Example: Where: Where:ID = ?ID = ? ID = Inside diameter of the vessel (inch) ID = Inside diameter of the vessel (inch)D = 4.7 pounds/day D = 4.7 pounds/day D = Amount of desiccant needed D = Amount of desiccant needed (pounds/day)(pounds/day)T = 7 days T = 7 days T = Assumed refilling frequency (days) T = Assumed refilling frequency (days)B = 55 pounds/cf B = 55 pounds/cf B = Desiccant density (pounds/cf) B = Desiccant density (pounds/cf)H = 5 inchH = 5 inch H = Height between minimum and H = Height between minimum and
maximum bed maximum bed level (inch)level (inch)
Calculate:Calculate:
ID = 12* ID = 12* 4*D*T*124*D*T*12 = 16.2 inch = 16.2 inch H*B*H*B*ππ
Commercially ID available = 20 inchCommercially ID available = 20 inch
Calculate Vessel Inside DiameterCalculate Vessel Inside Diameter
Source: Van AirNote:Note:cf = Cubic Feetcf = Cubic Feet
Slide 20Reducing Emissions, Increasing Efficiency, Maximizing Profits
Operating CostsOperating Costs
Operating costsOperating costs Desiccant: $2,059/year for 1 MMcf/day Desiccant: $2,059/year for 1 MMcf/day
exampleexample $1.20/pound desiccant cost$1.20/pound desiccant cost
Brine Disposal: NegligibleBrine Disposal: Negligible $1/bbl brine or $14/year$1/bbl brine or $14/year
Labor: $1,560/year for 1 MMcf/day exampleLabor: $1,560/year for 1 MMcf/day example $30/hour$30/hour
Total: ~$3,633/yearTotal: ~$3,633/year
Slide 21Reducing Emissions, Increasing Efficiency, Maximizing Profits
SavingsSavings
Gas savings Gas savings Gas vented from glycol dehydratorGas vented from glycol dehydrator Gas vented from pneumatic controllersGas vented from pneumatic controllers Gas burner for fuel in glycol reboilerGas burner for fuel in glycol reboiler Gas burner for fuel in gas heaterGas burner for fuel in gas heater
Less gas vented from desiccant dehydratorLess gas vented from desiccant dehydrator Methane emission savings calculationMethane emission savings calculation
Glycol vent + Pneumatics vents – Desiccant ventsGlycol vent + Pneumatics vents – Desiccant vents Operation and maintenance savingsOperation and maintenance savings
Glycol O&M + Glycol fuel – Desiccant O&MGlycol O&M + Glycol fuel – Desiccant O&M
Slide 22Reducing Emissions, Increasing Efficiency, Maximizing Profits
Gas Vented from Glycol DehydratorGas Vented from Glycol Dehydrator
Example:Example: Where:Where:GV = ?GV = ? GV= Gas vented annually (Mcf/year)GV= Gas vented annually (Mcf/year)F = 1 MMcf/day F = 1 MMcf/day F = Gas flow rate (MMcf/day)F = Gas flow rate (MMcf/day)
W = 21-7 pounds HW = 21-7 pounds H22O/MMcfO/MMcf W = Inlet-outlet HW = Inlet-outlet H22O content (pounds/MMcf)O content (pounds/MMcf)R = 3 gallons/poundR = 3 gallons/pound R = Glycol/water ratio (rule of thumb)R = Glycol/water ratio (rule of thumb)OC = 150%OC = 150% OC = Percent over-circulationOC = Percent over-circulationG = 3 cf/gallon G = 3 cf/gallon G = Methane entrainment (rule of thumb)G = Methane entrainment (rule of thumb)
Calculate:Calculate:
GV = GV = (F * W * R * OC * G * 365 days/year)(F * W * R * OC * G * 365 days/year) 1,000 cf/Mcf1,000 cf/Mcf
GV = 69 Mcf/yearGV = 69 Mcf/year
Glycol Dehydrator Unit Glycol Dehydrator Unit Source: GasTechSource: GasTech
Slide 23Reducing Emissions, Increasing Efficiency, Maximizing Profits
Gas Vented from Pneumatic ControllersGas Vented from Pneumatic Controllers
Example:Example: Where:Where:GE= ?GE= ? GE = Annual gas emissions (Mcf/year)GE = Annual gas emissions (Mcf/year)PD= 4 PD= 4 PD = Number of pneumatic devices per PD = Number of pneumatic devices per
dehydrator dehydratorEF = 126 Mcf/device/year EF = 126 Mcf/device/year EF = Emission factor EF = Emission factor
(Mcf natural gas leakage/(Mcf natural gas leakage/ pneumatic devices per year)pneumatic devices per year)
Calculate:Calculate:GE = EF * PDGE = EF * PDGE= 504 Mcf/yearGE= 504 Mcf/year
Source: norriseal.comSource: norriseal.com
Norriseal Norriseal Pneumatic Liquid Pneumatic Liquid Level ControllerLevel Controller
Slide 24Reducing Emissions, Increasing Efficiency, Maximizing Profits
Example:Example: Where: Where:GLD = ?GLD = ? GLD = Desiccant dehydrator gas loss GLD = Desiccant dehydrator gas loss (Mcf/year)(Mcf/year)ID = 20 inch (1.7 feet)ID = 20 inch (1.7 feet) ID = Inside Diameter (feet) ID = Inside Diameter (feet)H = 76.75 inch (6.4 feet) H = Vessel height by vendor specification (feet) H = 76.75 inch (6.4 feet) H = Vessel height by vendor specification (feet) %G = 45%%G = 45% %G = Percentage of gas volume in the vessel %G = Percentage of gas volume in the vessel
PP11= 15 Psia= 15 Psia P P11 = Atmospheric pressure (Psia) = Atmospheric pressure (Psia)
PP2 2 = 450 Psig = 450 Psig P P2 2 = Gas pressure (Psig)= Gas pressure (Psig)T = 7 daysT = 7 days T = Time between refilling (days) T = Time between refilling (days)
Calculate:Calculate:
GLD = GLD = H * IDH * ID22 * * ππ * P * P22 * %G * 365 days/year * %G * 365 days/year
4 * P4 * P11 * T * 1,000 cf/Mcf * T * 1,000 cf/Mcf
GLD = 10 Mcf/yearGLD = 10 Mcf/year
Gas Lost from Desiccant DehydratorGas Lost from Desiccant Dehydrator
Desiccant Dehydrator Unit Desiccant Dehydrator Unit Source: usedcompressors.comSource: usedcompressors.com
Slide 25Reducing Emissions, Increasing Efficiency, Maximizing Profits
Desiccant Dehydrator and Glycol Desiccant Dehydrator and Glycol Dehydrator Cost ComparisonDehydrator Cost Comparison
•Based on 1 MMcfd natural gas operating at 450 psig and 47Based on 1 MMcfd natural gas operating at 450 psig and 47°F°F•Installation costs assumed at 75% of the equipment costInstallation costs assumed at 75% of the equipment cost
Desiccant ($/yr)
Glycol ($/yr)
Implementation Costs
Capital Costs
Desiccant (includes the initial fill) 13,000Glycol 20,000Other costs (installation and engineering) 9,750 15,000
Total Implementation Costs: 22,750 35,000
Annual Operating and Maintenance Costs
Desiccant
Cost of desiccant refill ($1.20/pound) 2,059Cost of brine disposal 14Labor cost 1,560
Glycol
Cost of glycol refill ($4.50/gallon) 167Material and labor cost 4,680
Total Annual Operation and Maintenance Costs: 3,633 4,847
Type of Costs and Savings
Slide 26Reducing Emissions, Increasing Efficiency, Maximizing Profits
Partner Reported ExperiencePartner Reported Experience
Partners report cumulative methane Partners report cumulative methane reduction of 12.5 Bcf since 1990reduction of 12.5 Bcf since 1990
Past emission reduction estimates for U.S Past emission reduction estimates for U.S offshore is 500 MMcf/year or $1.5 offshore is 500 MMcf/year or $1.5 million/yearmillion/year
Slide 27Reducing Emissions, Increasing Efficiency, Maximizing Profits
Case StudyCase Study
One partner routes glycol gas from FTS to One partner routes glycol gas from FTS to fuel gas system, saving 24 Mcf/day (8,760 fuel gas system, saving 24 Mcf/day (8,760 Mcf/year) at each dehydrator unitMcf/year) at each dehydrator unit
Texaco has installed FTSTexaco has installed FTS Recovers 98% of methane from the glycolRecovers 98% of methane from the glycol Reduced emissions from 1,232 - 1,706 Reduced emissions from 1,232 - 1,706
Mcf/year to <47 Mcf/yearMcf/year to <47 Mcf/year
Slide 28Reducing Emissions, Increasing Efficiency, Maximizing Profits
Lessons LearnedLessons Learned
Optimizing glycol circulation rates increase gas Optimizing glycol circulation rates increase gas savings, reduce emissionssavings, reduce emissions Negligible cost and effortNegligible cost and effort
FTS reduces methane emissions by ~ 90 percentFTS reduces methane emissions by ~ 90 percent Require a gas sink and platform spaceRequire a gas sink and platform space
Electric pumps reduce O&M costs, reduce Electric pumps reduce O&M costs, reduce emissions, increase efficiencyemissions, increase efficiency Require electrical power sourceRequire electrical power source
Desiccant dehydrator reduce O&M costs and reduce Desiccant dehydrator reduce O&M costs and reduce emissions compared to glycolemissions compared to glycol Best for cold gasBest for cold gas
Slide 29Reducing Emissions, Increasing Efficiency, Maximizing Profits
Discussion QuestionsDiscussion Questions
To what extent are you implementing these To what extent are you implementing these technologies?technologies?
How can the Lessons Learned studies be How can the Lessons Learned studies 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, focus, manpower, etc.) that are preventing focus, manpower, etc.) that are preventing you from implementing this technology?you from implementing this technology?