SERVICES, INC. GAS DEHYDRATION Through the TRIETHYLENE GLYCOL REGENERATIVE METHOD A Basic Seminar on the Operation of TEG Systems
I PRINCIPLES AND OPERATION OF GLYCOL DEHYDRATORS
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 Icelike 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? CONTACTOR DRY GAS DRY GLYCOL INLET DRY GLYCOL WET GLYCOL DRY GAS WET 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 WET GAS WET GLYCOL 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 DEHYDRATION TEG 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 DEHYDRATION Absorption 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 DEHYDRATION Absorption 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 DEHYDRATION Contact Tower Vessel Diameter Determines flow rate Contactor Internals - Random Packing Ceramic Saddles Pall Style Rings Structured Packing Packing height Packing density Bubble Cap Trays Number of trays Tray spacing Vapor and Liquid Distributors Absorption
Components of a Contact Tower with Bubble Cap Trays
BUBBLE CAPS RISER CAP
BUBBLE CAPS
WIER DOWNCOMER
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 TOWER Structured 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 or Stills may be fitted with High Performance Structured Packing
Glycol/Glycol Hairpin Heat Exchangers Finned (Extended) Surface HOT DRY GLYCOL FROM REBOILER 390 F TI TI 350 F HOT WET GLYCOL TO STILL COLUMN A A 200 F WARM WET GLYCOL SHELL FINS TI 250 F TI TUBE SECTION A-A 200 F WARM WET GLYCOL TI 100 F 150 F COOL WET GLYCOL FROM CONTACTOR WARM DRY GLYCOL TO STORAGE
Typical Vertical Separator 2 Phase and 3 Phase
Horizontal Gas-Condensate-Glycol Separator Spill-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 Exchangers Finned (Extended) Surface HOT DRY GLYCOL FROM REBOILER 390 F TI TI 350 F HOT WET GLYCOL TO STILL COLUMN A A 200 F WARM WET GLYCOL SHELL FINS TI 250 F TI TUBE SECTION A-A 200 F WARM WET GLYCOL TI 100 F 150 F COOL WET GLYCOL FROM CONTACTOR WARM DRY GLYCOL TO STORAGE
VAPOR OUTLET Reboiler with Integral Surge Tank and Gas Sparger GLYCOL INLET FILL CONN STRIPPING GAS FILL CONN LG TC TI HTSD GLYCOL OUTLET HEAT SOURCE WET GLYCOL DRY GLYCOL WET GAS DRY GAS PACKING
SERVICES, INC. GAS DEHYDRATION Through the TRIETHYLENE GLYCOL REGENERATIVE METHOD A Basic Seminar on the Operation of TEG Systems