Natural Gas Dehydration

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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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)


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


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


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)


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


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


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


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


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


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?

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Natural Gas Dehydration

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