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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.