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GAS DEHYDRATIONThrough the
TRIETHYLENE GLYCOLREGENERATIVE METHOD
A Basic Seminar on the Operation of TEG Systems
SERVICES, INC.
IPRINCIPLES ANDOPERATION OF
GLYCOLDEHYDRATORS
WATER IS PRODUCED WITH NATURAL GAS IN ONE OF THREE
STATES
• Free water
• Water as a mist, or entrained droplets
• Water vapor
THE AMOUNT OF WATER VAPOR THAT CAN BE HELD BY THE GAS
IS DETERMINED BY
• PRESSURE
• TEMPERATURE
DEWPOINT
• The temperature, at a given pressure, at which water vapor condenses into a free liquid, representing a volume of water measured in pounds/MMSCF gas.
• At Dewpoint the gas is 100% Saturated with water vapor.
Water Content of Natural Gas & Hydrate Formation Chart, TEG Systems Manual, Page 90
WHY DO WE DEHYDRATE NATURAL GAS?
• To prevent the formation of hydrates, or “Ice-like” crystals, that when compacted at pipeline pressure, can plug the pipeline
• To insure total pipeline efficiency
• To reduce corrosion damage
• To increase its energy value
• To improve measurement
WHAT ARE HYDRATES?
• A physical combination of water and other small molecules to produce a solid which has an “Ice-like” appearance but possesses a different crystalline structure than ice.
• Hydrate formation in gas or NGL systems can plug pipelines, damage equipment or instruments, and can restrict or interrupt flow.
• Hydrates can form when the gas is at or below its water Dew Point or 100% Saturation condition.
How Do We Dehydrate Natural Gas?
• By mechanically forcing the gas stream to contact a desiccant with greater hygroscopic properties than the gas, thereby absorbing the water from the gas stream
CONTACTORCONTACTOR
DRY GLYCOL
WET GLYCOL
DRY GAS
WET GAS
DRY
GAS
DRY
GLYCOL
INLET
WET
GLYCOL
WET
GAS
OUTLET
Desiccant Selection
• Both liquid and solid desiccants can dehydrate gas
– Liquids: MEG, DEG, TEG, TTEG
– Solid: Mole Sieve, Silica Gels, Deliquescing Salts, Activated Alumina, and others
• Liquid desiccants are economically favored due to their less costly regenerative capabilities
PRINCIPLES of DEHYDRATIONTEG
• ABSORPTION of water vapor by glycol from the gas stream.
• DISTILLATION of the glycol to remove the lower boiling point water.
Process Overview
Absorption Distillation
PRINCIPLES of DEHYDRATIONAbsorption
• The ability of Glycol to Absorb water is known as “Hygroscopicity”.
• The water absorbing ability of Glycol decreases as the Glycol becomes cooler.
• The temperature where Gas will no longer give up its water to the Glycol is the Thermal Equilibrium Temperature.
PRINCIPLES of DEHYDRATIONAbsorption
• Absorption typically takes place in a vessel called an Absorber or Contact Tower.
• In the Contact Tower the Absorption process is improved by several different types of possible tower internals.
• The Absorption process can also take place in other types of equipment such as glycol injection into a static mixer.
PRINCIPLES of DEHYDRATIONAbsorption
• Contact Tower Vessel Diameter Determines flow rate
• Contactor Internals- Random Packing
Ceramic SaddlesPall Style Rings
Structured Packing• Packing height• Packing density
Bubble Cap Trays• Number of trays• Tray spacing
Vapor and Liquid Distributors
Components of a Contact Tower with Bubble Cap Trays
BUBBLE CAPS
RISER CAP
BUBBLE CAPS
DOWNCOMER
WIER
GAS-LEAN GLYCOL HEX
CONTACTOR TOWER
• Structured Packings typically consist of thin corrugated metal plates arranged in a way to force fluid flow to take a complicated flow path through the column, creating a large surface area for contact between phases.
• Structured Packing provides a large amount of surface area for gas/glycol contact in a fixed volume space while reducing restriction to gas flow.
CONTACTOR TOWERStructured Packing Segments
Mist Extractor
Glycol Feed Pipe
Glycol Distributor
Structured Packing
Gas Feed and Distributor
TROUGH GLYCOL DISTRIBUTOR
HIGH EFFICIENCY MIST EXTRACTOR
Still Column
Use of Multiple Packing Styles
Packing may be Random:Pall Style Stainless Steel
Rings,Ceramic Saddles
orStills may be fitted with
High Performance Structured Packing
Glycol/Glycol Hairpin Heat ExchangersFinned (Extended) Surface
HOT DRY GLYCOL
FROM REBOILER390°F
TI
350°F
TI
200°F
HOT WET
GLYCOL
TO STILL
COLUMN
WARM WET
GLYCOL
250°F TI
200°F
WARM WET
GLYCOL
TI
100°F
COOL WET
GLYCOL
FROM
CONTACTOR 150°F
SHELL
TUBE
FINS
WARM DRY GLYCOL TO STORAGE
TI
SECTION A-A
A
A
Typical Vertical Separator2 Phase and 3 Phase
Horizontal Gas-Condensate-Glycol SeparatorSpill-Over Weir & Oil Bucket with Weir
Particulate (Sock) Filter
Dirt Holding Capacity, DHC, is the
quantity of contaminant a filter
can trap and hold before reaching the
MAX Allowable Differential Pressure
PARTICULATE FILTER - SOCK
STRINGWOUND
CARBON ADSORBER HOUSINGS
GAC ELEMENT
ACTIVATED CARBON ADSORPTION PROCESS
• The unique structure of activated carbon produces a very large surface area: 1 lb of granular activated carbon typically provides a surface area of 125 acres (1 Kg =1,000,000 sq. m.) and will adsorb approximately 0.5 lb of hydrocarbon contaminants.
Glycol/Glycol Hairpin Heat ExchangersFinned (Extended) Surface
HOT DRY GLYCOL
FROM REBOILER390°F
TI
350°F
TI
200°F
HOT WET
GLYCOL
TO STILL
COLUMN
WARM WET
GLYCOL
250°F TI
200°F
WARM WET
GLYCOL
TI
100°F
COOL WET
GLYCOL
FROM
CONTACTOR 150°F
SHELL
TUBE
FINS
WARM DRY GLYCOL TO STORAGE
TI
SECTION A-A
A
A
Reboiler with Integral Surge Tank and Gas
Sparger
HEAT SOURCE
WET GLYCOL
DRY GLYCOL
WET GAS
DRY GAS
PACKING
GLYCOL
OUTLET
FILL
CONNSTRIPPING
GAS
FILL
CONN
GLYCOL INLET
VAPOR OUTLET
TC TI HTSDLGLG
GAS DEHYDRATIONThrough the
TRIETHYLENE GLYCOLREGENERATIVE METHOD
A Basic Seminar on the Operation of TEG Systems
SERVICES, INC.