Upload
chiviya-viya-fariku
View
54
Download
0
Tags:
Embed Size (px)
DESCRIPTION
Natural Gas Processing Slides
Citation preview
4/16/2013
1
NNPC FSTP Engineers
Natural Gas Processing and Transmission
Course Code:
Lesson 4
NGPT Assessment Plan
4/16/2013
2
Lesson 4
Introduction to
Natural Gas Processing
Lesson 4 Contents
Introduction to Natural Gas Processing
Heat Transfer Process
Refrigeration Processes and Plants
LNG and GTL Processes
Natural Gas Water Content and Hydrate Formation
Dehydration
Sweetening
Gas-to-Liquid Process (GTL)
Natural Gas
Co
urs
e W
ork
30
%
Pro
ject
20
%
Form
al E
xam
45
%
ATC
5%
Tota
l 10
0%
5-A
pr
12
-Ap
r
19
-Ap
r
4/16/2013
3
Introduction to Natural Gas Processing
Natural Gas Processing Processing of reservoir natural gas involving its separation into its component phases and
the subsequent treatment of the phases into either merchantable or disposable qualities.
Processes include: Separation Heat Transfer Refrigeration Dehydration Sweetening Factional Distillation LPG and, NGL recovery LNG production GTL production Compression and Transmission
Basic Components of Natural Gas
Name Chemical Formula Boiling point(oC) State at atm. PressureMethane CH4 -165.5 Gaseous at normalEthane C2H6 -88.6 atmospheric temp.Propane C3H8 -42.1 and pressureIs Butane C4H10 -11.7 Normal Butane C4H10 -0.5 Extremely Volatile
Is Pentane C5H12 27.9 Liquid at normalNormal Pentane C5H12 36.1 atmosphericNormal Hexane C6H14 68.7 temperature andNormal Heptane C7H16 98.4 PressureNormal Octane C8H18 125.7
Introduction to Natural Gas Processing
4/16/2013
4
Version
Why do we process gas ?
To add value
To make it dry
To meet customers specifications
To manage toxicity and corrosion concerns
To allow for delivery conditions
To account for availability requirements
Introduction to Natural Gas Processing
Version
Undesirables in Natural Gas
Water (Corrosion / Hydrates)
H2S (Corrosion / Toxic)
CO2 (Corrosion)
Mercury (Aluminum Corrosion)
Heavy Hydrocarbons (2 Phase Flow)
Natural Gas Standard Conditions
Standard Cubic Metre15oC (288.15 K) @ 101.325 Pa (1.01325 bar)Normal Cubic Metre0oC (273.15 K) @ 101.325 Pa (1.01325 bar)Standard Cubic Foot60oF @ 14.696 psi
(1 scf = 0.0283 scm)
Introduction to Natural Gas Processing
4/16/2013
5
Version
HC States Phase Diagrams
Temperature
Pressure
Dry GasGas Condensate
Light Oil
Heavy Oil
Introduction to Natural Gas Processing
VersionTemperature
Pressure Gas OutFeed Liquid
Liquid Out
Separator Conditions (P,T)
Bubble Point (Liquid Out)Dew Point (Gas Out)
Introduction to Natural Gas Processing
Changing Phase Diagram with Separation
4/16/2013
6
SLIDE 11
Introduction to Natural Gas Processing
SWEETENING
SpecificationsPTWater Dew PointHC Liquid Dew Point
HC LIQUID REMOVAL
DEHYRATION
Basic Natural Gas Processing Train
Introduction to Natural Gas Processing
Dehydration
Sweetening
LNG
Regasification
GTLFractionation
Expansion
Separation
Cooling
NGL Sales
Compression
NG Sales
Gas Well
Oil Well
Crude Oil
Condensate
Gas
Propane
Butane
Pentane+
Separation
4/16/2013
7
SLIDE 13
Introduction to Natural Gas Processing
NG Ex-Well Mol.% Field Treated mol.% LNG Mol. %
Methane CH4 70-90% 89.26 88-96
Ethane C2H6
0-20%
4.63 5.0
Propane C3H8 2.65 1.63 - 4
Butane C4H10 - IC4 0.495 0.2 -1
C4H10 - nC4 0.785 0.3 -1.5
Pentane+ C5H12+ 0.681 0.12
Carbon Dioxide CO2 0-8% 1.5 0.1
Avg Mol.Wt = 18.77 g/mol Gross heating value = 42.7 Mj/std m3
Oxygen O2 0-0.2%Water Content 150 ppm Gross heating value =
42.7 Mj/std m3
Nitrogen N2 0-5% - -
Hydrogen
sulphideH2S 0-5%
- 5 mg/m3
Rare gases A, He, Ne, Xe trace 0.2%
SLIDE 14
Escravos-Lagos Pipeline System (ELPS)
Nominal capacity of 270 MMscf
HC dew point spec of 15 C at 76 barg
Water dew point spec of 7 C at 76 barg
West African Gas Pipeline (WAGP)
620 km pipiline from Nigeria to Ghana
Nominal capacity of 360 MMscfd
HC dew point spec of 100C at 26 barg
Water dew point spec of 7 lb/MMSCF
Introduction to Natural Gas Processing
4/16/2013
8
Lesson 4-1
Heat Transfer Processes
Treatment Processes
Heat Transfer Processes
Processes involving the Transfer of Heat From a Hotter (Higher Temperature) Medium to a Cooler or Less Hot(Low Temperature) Medium
Treatment Operations Requiring Heat Transfer
Fluids Out of Process Equipment Requiring Specific Temperature Status
Fluids Going into Process Equipment Requiring Specific Temperature Status
Use of Waste Energy for Efficient Processing and Economic Purposes
Fluids Out of Well Requiring different Temperature Processing Conditions
Storage Conditions Requiring Different Temperature From Processing Conditions.
4/16/2013
9
Treatment Processes
Heat Transfer Processes
Heat Transfer Benefits
Process Efficiency
Energy Conservation
Reduces Maintenance
Types of Heat Transfer Processes
Refrigeration
Liquefaction
Factors Affecting Heat Transfer
Type of Material.Only Materials That Conduct Heat
Thickness of Material.The Thicker the Material the Less Its Ability to Conduct.
Conductivity.The More Conductive the Material The More Efficient.
Surface Area.The Larger the Exposed Area the More Efficient.
Rate of TransferThe Higher the Rate the More Efficient.
Flow RateThe Higher, the More Heat Transferred.
4/16/2013
10
Factors Affecting Heat Transfer
TurbulenceThe Greater the Heat Transfer.
The Two Exchanging Media Temperature Difference T the Greater, the Better.
Corrosion and ContaminantsReduces the Rate of Heat Transfer.
Fluid API Gravity.Generally the Lesser the Better.
The Flow PathCounter and Cross Flow Patterns Provide More Heat Transfer
Tube ArrangementTriangular Arrangement Provides More Heat Transfer.
Types of Heat Exchangers
Shell and Tube Heat ExchangerMajor Components
ShellTubes and Tube SheetHeadBaffles
Tubes ContentCorrosive and Fouling FluidsHigh Pressure FluidHigh Viscosity FluidLow Flow Rate FluidDirty Fluid
Internal of Heat Exchanger
Tubes Baffle
4/16/2013
11
SLIDE 21
Double Tube Heat Exchanger
Shell and Tube Sections are Both Tubes
One Fluid Passes Through Outer Tube While the Other Passes through the Inside Tube(s)
Tubes and Shell Configuration
U-Tubed
Manifolded in Parallel and Series
Finned
Types of Heat Exchangers
Manifolded in Parallel
Cut-out Tube area
SLIDE 22
Double Tube Heat Exchanger Tubes and Shell Configuration
Fins Configuration
Single Finned Tube Multiple Finned Tube
Fins Types
Types of Heat Exchangers
4/16/2013
12
SLIDE 23
Double Tube Heat Exchanger
Tubes and Shell Configuration
Types of Shell
One or Several Pass Shell
Cross Flow Shell
Kettle Type Shell
Types of Heat Exchangers
1-Pass Shell, 2-Pass Tube Exchanger
Kettle Reboiler
Floating Tube Sheet
Fixed Tube Sheet
Flow Passes and Pattern
Heat Exchanger Flow Passes.This is the number of times the fluid upon entering the heat exchanger passes the length of the heat exchanger before it exitsOne-Pass Flow
Two-Passes Flow
Multi-passes Flow
1-1 pass flow
2-2 pass flow
4/16/2013
13
Flow Passes and Pattern
Heat Exchanger Flow Patterns This is the direction with which the fluids flowing and exchanging heat inside the heat exchanger cross one another.
Parallel Flow Pattern
Cross Flow Pattern
Counter Flow Pattern
SLIDE 26
Plate-Type Heat ExchangerMajor Components Carrying Bars Fixed Frame/Plate Pressure Plate End Plate with Open Ports End Plate with Blind Ports Channel Plates with Open Ports
Plates are Corrugated or Embossed
Ports Serving One Side of a Plate are Connected to the Side Carrying Same Fluid on the Alternative Plate
They are: Less Expensive LighterMore Compact High in Performance
Types of Heat Exchangers
4/16/2013
14
SLIDE 27
Plate and Frame Heat Exchanger
SLIDE 28
Plate and Frame Heat Exchanger
Corrugated Plates with Ports
4/16/2013
15
SLIDE 29
Plate-Fin Heat Exchanger Basic Construction
Alternating Aluminium Layers of Corrugated Fins
Brazed Together and Separated with Flat Aluminium Plates (Parting Sheets)
Stack of Parting Sheets and Core is Called the CORE
Can Handle Many Fluids at Once
Fluid Flow Configuration can be:
Counter Flow
Cross Flow
Cross-Counter Flow
Can Operate in Very Low Temperature (-2690C or -4520F)
SLIDE 30
Plate-Fin Heat Exchanger Basic Construction
4/16/2013
16
SLIDE 31
Brazed Aluminium Plate-Fin and Tube Combination Heat Exchanger
Tube Fin-Plate Tube Combination Heat Exchanger
SLIDE 32
Combination Heat Exchanger
4/16/2013
17
SLIDE 33
Cryogenic Heat Exchangers
Mostly Consists of Plate Fins
Aluminum Core Tubes
Mostly Applicable in
Very Cold Operations
High Heat Transfer Operation
They Have: Less Weight.
Maximum Surface Area per Unit Volume and weight
Minimum Resistance to Flow
Low Heat Capacity
Examples of Cryogenic Exchanger
Joy-Collins
Trane
Hampson Ramens Lamella
SLIDE 34
Aerial Coolers
Forced Draft Aerial Coolers Induced Draft Aerial Coolers
4/16/2013
18
SLIDE 35
Fired Heaters
Direct Fired Heaters
Applications
Direct Heating of Process Fluid
Direct Boiling of Process Fluid
Direct Heating of Circulating Fluid(Oil) Which Then Heats or Boils Process Fluid
Direct Heating of Regeneration Gas in Solid Desiccant Dehydration Plants
Major Components
Burners
Radiant Tubes
Convection Coils
SLIDE 36
Fired Heaters
Direct Fired Heaters
Types of Direct Fired Heaters
Vertical-Tube Cylindrical Heaters
Horizontal-Tube box-Type Heater
Radiant Tubes
Convection Tubes
4/16/2013
19
OnoSLIDE 37
Fired Heaters
Indirect Fired tube Heater
Heating Process
Flame and Combustion Gas Heat a Pool of Intermediate Fluid
Intermediate Fluid Transfers Heat to Process Fluid in Coils or Series of Tubes
Transfer of Heat is by Both Radiation and Convection
SLIDE 38
Fired Heaters
Indirect Fired tube Heater
Heating Process Flame and Combustion Gas Heat a Pool of Intermediate Fluid
Intermediate Fluid Transfers Heat to Process Fluid in Coils or Series of Tubes
Transfer of Heat is by Both Radiation and Convection
4/16/2013
20
OnoSLIDE 39
Flow Diagram Symbols
SLIDE 40
Heat Exchangers Classification by Service Types
Coolers.Cools /Reduces Temperature by the use of Water/Air.
Air Cool
Water Cool
Heater Raises Temperature by Direct Heat Addition (Application).
4/16/2013
21
SLIDE 41
Heat Exchangers Classification by Service Types
Phase-change heat exchangersCondenser .Removes Heat while Changing gas to Liquid.
Vaporizer.Adds Heat while Changing Liquid to Gas.
Reboiler.Adds Heat.
Chiller or Evaporator.Process fluid in tubes is Cooled through heat removal by a Flowing Pool Refrigerant.
Water Condenser
Evaporator
NNPC FSTP Engineers
Natural Gas Processing and Transmission
Course Code:
Lesson 4
4/16/2013
22
Lesson 4-2
Refrigeration
Processes & Plants
Lesson 4-2 Contents
Refrigeration
Compression Refrigeration
Expansion Refrigeration
Cascade Refrigeration
Cryogenic Refrigeration
4/16/2013
23
SLIDE 45
REFRIGERATIONRefrigeration is the cooling of air or liquids to lower(chilled) temperature Level
The lower temperature is used to preserve food, cool beverages, make ice, etc, at out homes, the medical and food/beverage industry.
In Natural Gas processing, the lower temperature provided by refrigeration is employed to condense liquid hydrocarbon and water from the gaseous well stream and also liquefy the natural gas for storage and transportation
Methods of Refrigeration.Cooling by Evaporation of a Refrigerant in an Evaporator(Chiller).Cooling by Expansion of Process Fluid.Combination of the Above Processes.
Refrigeration Systems. Compression Refrigeration. Expansion Refrigeration. Absorption Refrigeration
SLIDE 46
NGL Liquefaction
NGL
Natural Gas Liquid
Liquefied Portion (Fraction ) of Gaseous Reservoir Fluid
Includes Ethane, Propane, Butane, Pentane, Natural Gasoline, and Condensate.
Liquefaction Processes
Compression.
Cooling by Expander.
Absorption.
Combination of Any Two or Three of Above.
Cascade Refrigeration
Cryogenic Refrigeration
4/16/2013
24
SLIDE 47
NGL Liquefaction
NGL Extraction Schematic
SLIDE 48
Mechanical Refrigeration (Vapour Compression Refrigeration).
Cooling by Evaporation of Compressed Liquid Refrigerant in aChiller or Evaporator.
Principle of Operation:Liquid Refrigerant Takes Latent Heat of Evaporation to Vaporize.
Heat is Exchanged With the Process Fluid in the Tubes.
Process Fluid Supplies the Needed Heat and Gets Cooled inthe Process.
REFRIGERATION
4/16/2013
25
SLIDE 49
Mechanical Compression Refrigeration System
Basic ComponentsRefrigerant Evaporator/Chiller CompressorCondenserReceiverThermostatic
Expansion Valve (TXV)
SLIDE 50
Mechanical Compression Refrigeration System
Vapour Compression Refrigeration Process Cycle
4/16/2013
26
SLIDE 51
Mechanical Compression Refrigeration System
Vapour Compression Refrigeration Process Description1. Evaporator - point 4 to point 1Cold liquid from the expansion valve boils
inside evaporator, absorbing latent heat Reversible heat addition at Pe = const. Isobaric boiling (horizontal line on
PV diagram) Results in evaporation to saturated vapor Latent heat of vaporization Q (cold)
used
2. Compressor - point 1 to point 2 Cold saturated vapor from the
evaporator is compressed to the condensing pressure Pc ,
Temperature is raised
SLIDE 52
Mechanical Compression Refrigeration System
Vapour Compression Refrigeration Process Description3. Condenser - point 2 to point 3 Hot vapor from the compressor condenses
releasing latent heat.
Isobaric condensation (horizontal line on PV diagram) High Temperature Latent heat of vaporization Q (hot) released Reversible heat rejection at Pc = const. Results in condensation to saturated liquid.
4. Expansion Valve - point 3 to point 4 Liquid from the condenser is depressurized, lowering its pressure and
boiling point temperature.
Process is adiabatic expansion (vertical line on PV diagram) No work done W = 0 Throttling (irreversible process) from high pressure Pc to lower
pressurePe
4/16/2013
27
SLIDE 53
Refrigeration Load
Refrigeration Load Depends on:Process Fluid Composition.
Pressure.
Temperature.
Heat Required for Process Fluid Reduction to Chiller Temperature.
Latent Heat Required to Condense Liquefiable Hydrocarbons.
Richer Fluids Require More Refrigeration Load.
SLIDE 54
Refrigerant
Refrigerants.Properties of Refrigerants:Non-toxic.Non-corrosive.High Latent Heat of Vaporization.Compatible With System Needs.
Types of Refrigerants.At Chiller Temperature -25 0CPropane.Ammonia.
At Chiller Temperature -25 0C (Cryogenic) Methane.Ethane. Ethylene
4/16/2013
28
SLIDE 55
.
Table 4-1
Properties of Common Refrigerants
No. Refrigerant Boiling Point Chiller
Temp.
Remark
1 Propane - 44 0F (- 42
0C) -25 0C Good for 13
0F (-25
0C)
Poor Quality Impairs Compressor
Performance
2 Ammonia - 28 0F - 25 0C Problem of Odor.
Odor Helps to Prevent Large
Accumulation or Spillage without
Notice.
Requires Lower Refrigeration
Circulation than C 3 Requires Higher
hp.
Easier to Handle with Ordinary Steel.
3 Freon 12 -21.6 0F(-29.8
0C) - 25 0C Safe to Use.
Requires More Hp per Ton of
Refrigeration than C3 and NH4
Requires Low Vapor Pressure and
Low Compression Ratio.
It is Difficult to Store.
Must Avoid the Use of Water with
Freon 12.
Cryogenic Refrigerants1 Methane -259
0F( -161
0C) - 25 0C
2 Ethane -128 0F( -89
0C) - 25 0C Quantity above 22% will increase
Compressor Discharge Pressure.
3 Ethylene - 154 0F - 25 0C
Table 4-1
Properties of Common Refrigerants
No. Refrigerant Boiling Point Chiller
Temp.
Remark
1 Propane - 44 0F (- 42
0C) -25 0C Good for 13
0F (-25
0C)
Poor Quality Impairs Compressor
Performance
2 Ammonia - 28 0F - 25 0C Problem of Odor.
Odor Helps to Prevent Large
Accumulation or Spillage without
Notice.
Requires Lower Refrigeration
Circulation than C3 Requires Higher
hp.
Easier to Handle with Ordinary Steel.
3 Freon 12 -21.6 0F(-29.8
0C) - 25 0C Safe to Use.
Requires More Hp per Ton of
Refrigeration than C3 and NH4
Requires Low Vapor Pressure and
Low Compression Ratio.
It is Difficult to Store.
Must Avoid the Use of Water with
Freon 12.
Cryogenic Refrigerants1 Methane -259
0F( -161
0C) - 25 0C
2 Ethane -128 0F( -89
0C) - 25 0C Quantity above 22% will increase
Compressor Discharge Pressure.
3 Ethylene - 154 0F - 25 0C
Refrigerant
SLIDE 56
Mechanical Compression Refrigeration System
Refrigerant
Sales Gas
Liquid to Stabilization
Chiller
Separator
Gas-Gas Heat Exchanger
Inlet Gas
Applications.NGL extractionNatural Gas Pre-cooling in LNG Processes
Basic Compression Refrigeration NG Processing Schematic
4/16/2013
29
SLIDE 57
Pressure Expansion Refrigeration Systems
Refrigeration or Temperature Reduction Due to Expansion of the Process Fluid on Passing Through Valve/Choke or Turbine
Two Possible CausesJoule-Thompson EffectWithout Work Done or Heat Transfer
Turbine ExpansionWith Removal of Work from the Gas Stream
Types of Expansion Refrigeration Systems.Valve or Choke Expander Cooling System
Turbine Expander Cooling System
Pressure Expander(Reducing) Cooling System
SLIDE 58
Joule-Thompson Valve/chokeMajor FeaturesExpansion (Joule-Thompson) Valve. Choke Valve.
Self-refrigeration Process
Process Flow and Principle of Operation.Process Fluid Gets Expanded Going Through Pressure Reducing Valve/Choke.
Temperature Reduction is Achieved by Joule-Thompson Effect of Stream Expansion
Constant Enthalpy.No Heat TransferNo Work Done
Pressure Drops.
Temperature Drops Due to Non-ideal Behaviour of Fluid.
Pressure Expansion Refrigeration Systems
4/16/2013
30
SLIDE 59
Joule-Thompson Valve or Choke Refrigeration System
Temperature Change is Proportional to Pressure Drop.
Process Fluid Vapour Condenses.
Condensed Fluid May Be Fractionated to Meet Vapour Pressure and Composition Specification.
J-T Valveor Choke
Sales Gas
Liquid to Stabilization
Separator
Gas-Gas Heat Exchanger
Inlet Gas
Basic J-T Expansion Refrigeration NG Processing Schematic
SLIDE 60
Joule-Thompson Valve or Choke Refrigeration System
Cooling Associated with Constant Enthalpy is Estimated from Correlation Chart
Temp Drop Vs Press Drop @ Given Press
4/16/2013
31
SLIDE 61
Low Temperature Separation (LTS) Refrigeration Plants
Factors Affecting Constant Expansion SystemsChoke Up-Stream TemperatureShould be as Low as Possible
Determines Amount of Liquid Formed
Pressure Differential Across ChokeConstant and Property of Choke Design
Determines and Proportional to Temperature Drop
Amount of Liquid FormedDetermined by the Choke Up-stream Temperature and Pressure Drop Across Choke
Types of Low Temperature Separation PlantsLTS Plant Without Hydrate FormationLTX Plant With Hydrate Formation
SLIDE 62
LTS Expansion Refrigeration Plant Without Hydrate Formation
4/16/2013
32
Typical LTS Schematic
SLIDE 64
Typical LTX Expansion Refrigeration With Hydrate Formation
4/16/2013
33
SLIDE 65
Typical LTX Expansion Refrigeration With Hydrate Formation
SLIDE 66
Cryogenic Refrigeration
Cryogenic Refrigeration
Any refrigeration system that reduces temperature Extremely Low level -150 0F
Cryogenics Study that Deals with Effects and Production of Extremely Low Temperature -
150 0F.
Used in Liquefaction of Natural Gas.
Methane (and Ethane Sometimes) is Removed in the Process.
The Rest Ethane Propane, Butane and Natural Gasoline is Liquefied.
4/16/2013
34
SLIDE 67
Turbine Expansion Refrigeration System
Expansion Turbine
Sales Gas
Liquid to Stabilization
Separator
Gas-Gas Heat Exchanger
Inlet Gas
SLIDE 68
Demethanizer
Separator
Separator
Exchangers
Compressor
Expander
Turbine Expansion Refrigeration System
4/16/2013
35
SLIDE 69
Major Features.
Expansion Turbine Replaces the Joule-Thompson or Choke Valve.
Direct-Connected Compressor Makes Use of Work Made Available fromGas Expansion at Turbine.
Cooling associated with Turbine Expansion is Modelled Along Lines ofCompression Calculation
Turbine Expansion Refrigeration System
SLIDE 70
Process Flow and Principle of Operation. Process Fluid Gets Treated for Water and Contaminants.
Process Fluid is Split into Two Parts; One Goes Through 1st Gas/Gas Heat Exchanger.
The Other Goes Through Demethanizer Side Heat Exchanger.
Two Flows Meet to Enter 2nd Gas/Gas Heat Exchanger.
Cold Residue Gas is Used in Both 1st and 2nd Heat Exchangers.
Liquid Condensed at the Heat Exchangers is Separated at the Cold Separator and Enters the Demathanizer at an Intermediate Point.
Turbine Expansion Refrigeration System
4/16/2013
36
SLIDE 71
Process Flow and Principle of Operation.
Process Vapour Gets Expanded on Going Through the Turbine.
Work is Removed from the Process Fluid and It gets Cooled.
Turbine is Designed to Handle Condensate Formed During this Expansion.
Process Fluid Expansion Supplies Work to Turbine Shaft.
Direct-Connected Compressor Extract Work from Turbine Shaft to Compress Out-Let Sales Gas.
Turbine Expansion Refrigeration System
SLIDE 72
Process Flow and Principle of Operation.
Expansion and Work Supply Reduces Process Fluid Enthalpy.
Decrease in Enthalpy Causes Larger Temperature Drop and Process Fluid Condensation.
Mixture of Gas and Liquid from the Expander Enters Demathanizer through a Top Separator where Residue Gas is Separated Out.
Inlet-Gas Temperature to Demethanizer Should be Low (-130 to 150 0F) to Liquefy a Lot of Ethane.
Demethanizer Stabilizes Liquid by Reducing Methane Content to the
Lowest.
Turbine Expansion Refrigeration System
4/16/2013
37
SLIDE 73
Process Flow and Principle of Operation.Bottom Product Temperature is Below Ambient so it is Used to Cool Feed
Gas for Better Refrigeration.
Bottom Product Methane/Ethane Molar Ratio 0.02 to 0.03.
Residue Gas Used for Cooling Inlet Gas in the Gas/Gas Exchangers.
Gets Compressed to Sale Gas Pressure at the Expander Compressor and Another Regular Compressor.
Gets Heated up at the Reboiler and Leaves for Sales Line.
Condensed Liquid Gets Stabilized by Demathanizer or De-ethanizer
Turbine Expansion Refrigeration System
SLIDE 74
Major Considerations For Turbo-Expander. Materials.
Carbon Steel -20 0F
Charpy-Impact-Tested Carbon Steel -50 0F
3.5% Nichel Steel - 50 0F to 150 0F
Stainless Steel -150 0F
Water Content of Process Fluid. Very Low To Prevent Hydrate Formation.
Dehydrator Unit Should be Installed Upstream.
CO2 Content of Process Fluid. Should be Below 0.5 % Mole.
Higher than 0.5% Mole. Solid CO2 Forms on Expander Out-let Gas.
Must Be Removed.
Turbine Expansion Refrigeration System
4/16/2013
38
SLIDE 75
Major Considerations For Turbo-Expander.
Operating Conditions.Must Not be severe and Liquid Should not Formed inside Turbine
Will Impair Performance and Result in Plant Shut down.
Operated at Lowest Possible Temperature.
Gas Final Temp. Depends on:Amount of Liquid Recovered
Pressure Expansion Ratio
Amount of Work Removed
CO2 Content
SLIDE 76
Cryogenic Refrigeration.
Mostly on Methane and Ethane Recovery from Natural Gas.
Used in Recovery of Power From Expanding Streams.
Used in Helium, CO2 and Hydrogen Recovery Processing.
Very Low Temperature Separators.
Refrigeration or Cooling Up To 150 0F.
Processes Requiring Pressure Drop Up to or Greater than 500 psia
Turbo-Expander Applications
4/16/2013
39
SLIDE 77
NGL, Helium and Hydrogen Liquefaction.
Easy and Simple to Operate.
Require Relatively Low Investment Cost.
Range of Horse-Power Available 250 10,000 hp.
Efficiency is Higher (85%) than Mechanical Refrigeration (65 %) ForProcesses below 75 0F.
Turbo-Expander Must be located at the Lowest Possible TemperaturePoint in view of Above.
Typical Recovery is Between 8 to 12 % of Feed Gas.
Turbo-Expander Applications
SLIDE 78
Special Considerations in Cryogenic Process.
Contaminants
Gases
CO2H2S.
Nitrogen.
Liquids
Water.
Liquid Hydrocarbons(C5+)
Solids
Dirt
Wax
Iron Sulfide
4/16/2013
40
SLIDE 79
Special Considerations in Cryogenic Process.
Effects of Contaminants
Reduce Quality.
Plug Fine Passages
Foul Cryogenic Heat Exchangers.
Contaminants Removal by:
Dehydration ( Molecular Sieve).
Separation (Separators, Filters, etc.)
Sweetening.
Filtration.
Condensation
SLIDE 80
Cryogenic Heat Exchangers.
As Treated Earlier.
Cryogenic Pumps
Should Have Extended Shaft Between the Motor and the Pump Body.
Pump is Inside Insulation Box and Motor Outside.
Cold Box
Cryogenic Devices are Always Located in a Cold Box to Provide Insulation.
Instrument and Control Valves
Require Extended Shaft.
Special Considerations in Cryogenic Process.
4/16/2013
41
SLIDE 81
Cryogenic Refrigeration Methods
Basic Cryogenic Refrigeration Methods
Expander-Compression. Combination Method(As Treated Earlier)
Cascade Refrigeration Method.
Mixed Refrigerant Method
Multi-Component
Propane-MRC Method
SLIDE 82
Cryogenic Refrigeration Methods
Cascade Refrigeration Method.
Consists of Two or More Separate but Interlocked Refrigeration Systems.
Cascade Component Systems Mostly Differ in Refrigerants Only.
System Provides Low Power Consumption.
Has High Cost of Installation.
Has Large Number of Equipment.
Requires Controlling and Monitoring of Many Streams.
Grades of Refrigerants Used are Normally Expensive.
4/16/2013
42
Ono SLIDE 83
Propane- Ethane Cascade Refrigeration System
Propane Refrigeration System Carries out the First Refrigeration of the Process Fluid to 40 0F.
Ethane refrigeration System then Chills the Propane Vapor to Liquid and Process Fluid to 120* 0F
.
Residue Gas For Sale
Treated Inlet GasC
3C
om
p
C2 Surge Tank
C3 Surge Tank
C2 Chiller -120 0F
C3 Chiller -40 0F
De-methanizer
C2
Co
mp
Liquid Gas
Ono SLIDE 84
Propane-Ethylene- Methane Cascade Refrigeration System
-250 0F
ChillerChiller Chiller
EthyleneEvaporator
WaterCondenser
PropaneEvaporator
-30 0F -150 0F
Second Refrigeration is Done by Ethylene to 150 0F.
Third refrigeration is Done by Methane
to 250* 0F .
First Refrigeration is Done by Propane to 30 0F.
.
4/16/2013
43
SITP / O & G OnoSLIDE 85
Liquid Stabilization
SLIDE 86
Liquid Stabilization
Stabilization.Removal of Liquefiable Gaseous Components of Liquefied ProcessFluid.
Done by Stripping or Heating.
Produces Stable LiquidTo Satisfy Gas Line Transport Specification
To Meet Storage Temperature Requirement
To Obtain Additional Revenue.
Its Vapour Pressure Must NOT be Greater than the Storage Pressure atthe Maximum Storage Temperature
Liquid TVP = C RVPTVD is a Function of Composition so Below is Approximation
4/16/2013
44
SLIDE 87
Fractionation
Recovery of Max. HC Liquid Stable Under Storage Condition with MinimumVol. of Soln Vapour Removed
This is Achieved by Fractionation
Separation of Raw HC Liquid into its Components in Series of Columns or Towers.
Bottom Component is C5+ (Natural Gasoline)
SLIDE 88
Fractionation
Stabilizer
4/16/2013
45
SLIDE 89
Liquid Stabilization Unit with LTS
SLIDE 90
Refrigeration Applications
Refrigeration Applications.Propane Liquefaction.
NGL.
LNG.
Recovery of Liquid from Oil Treaters.
Recovery of Liquid from Stock Tank Vapour.
Low-Temperature Separation.
Well Stream Must be Rich of Hydrocarbons.
Note that a Btu of Heat Subtracted From a System by RefrigerationRequires More Work to Achieve than a Btu Supplied To System by Heating.
Refrigeration Systems Must be Totally and Carefully Insulated.
4/16/2013
46
SLIDE 91
Basic FeaturesGas Expansion By Gas Flow Velocity Increase To Supersonic Level
Supersonic gas Velocity Results In Astronomical Pressure Drop
Pressure Drop Attended With Subsequent Temperature Drop
Liquid Hydrocarbon and Water Condenses out of Gas Stream
Twister Supersonic Separator
SLIDE 92
Basic ComponentsMultiple Inlet Guide Vanes Generate A High Vorticity, Concentric Swirl of gas
Laval Nozzle Expands Saturated Feed Gas Thereby Transforming Pressure Drop To Kinetic Energy (i.e Supersonic Velocity).
Pressure Drop Results In A Low Temperature.
Mist of Water and Hydrocarbon Condensation Droplets Form.
Cyclic Separator High Vorticity Swirl Centrifuges Droplets to Equipment Wall While Gas Travels in Middle
Diffuser Slows Down gas Stream Velocity Gaining Back About 70 - 75% Of The Initial Pressure.
The Liquid Stream Typically Contains Slip-gas, Which Is Degassed at Compact Liquid De-gassing Vessel and Then Recombined With The Dry Gas Stream.
Separated Liquids Get Discharged at About 7 0C. At
Twister Supersonic Separator
4/16/2013
47
SLIDE 93
Twister Supersonic Separator
SLIDE 94
Applications:Condense and separate water and heavy hydrocarbons from natural gas
Water Dewpointing (Dehydration)
Hydrocarbon Dewpointing
Natural Gas Liquids extraction (NGL/LPG)
Heating Value Reduction
Fuel gas treatment
Other New Applications such as;Offshore fuel gas treatment for large aero-derivative gas turbines, Pre-treatment upstream CO2 membranes and Bulk H2S removal upstream sweetening plants .
Twister Supersonic Separator
4/16/2013
48
NNPC FSTP Engineers
Natural Gas Processing and Transmission
Course Code:
Lesson 4
Lesson 4-3
Natural Gas Water Content
and Hydrate Formation
4/16/2013
49
Lesson 4-3 Contents
Natural gas Water content
Hydrates and Hydrates Formation
SLIDE 98
Natural Gas Water Content
NG Contains Some Degree of Water at ALL Conditions
Water Content of Natural Gas is expressed in
lb(water)/MM SCF(NG) for Gas
Obtained from McKetta and Wehe Correlation Chart
Solubility of Water in Gas
Increases with Increasing Temperature
Decreases with Increasing Pressure
Dissolved Salt in Water Reduces Solubility of Water in Gas
4/16/2013
50
SLIDE 99
Natural Gas Water Content
Water Dew PointTemperature and pressure at which natural gas is saturated with water.
Temperature at Which Natural Gas is Saturated with Water Vapour at a Given Pressure
Water Vapour is in Equilibrium at Dew Point.
Reduction of Temperature OR Increase of Pressure Will Result Water Condensation
Water Dew Point DepressionDifference in Dew Point Temperature of Water Saturated Natural Gas
Before Dehydration and After DehydrationWDPD = DP(Before) - DP(After)
SLIDE 100
McKetta and Wehe Correlation Chart
.
0F
5
10
30
60
40
85
4/16/2013
51
SLIDE 101
The Use of McKetta and Wehe Correlation ChartThe chart is good for 0.7 SG natural gas at 600F with zero Salt content.Corrections are obtained from chartWater is in lb.water per mm/scf of NG
Example;What is the water content of 0.9 SG natural gas operating at 85 0F and 1000 psia with 2% salt content.
1. Correction for salt content = 0.9542. S.G correction = 0.983. Water content 85 0F and1000 psia from chart = 40 lb.water/mmscfNG
1. Corrected water content = 40 x 0.954 x 0.98 = 37.4 lb.water/mmscf NG
McKetta and Wehe Correlation Chart
SLIDE 102
Exercise
Exercise
A 0.85 SG Natural gas flowing at 67 mm scf/day contains 55 lb.water/mm
scf with 2% salt content . How many pounds of water will be required
removed by a dehydration plant per day if the pipeline water dew point
require is 20 0F ? The natural gas feed line operates at 87 0F and 75 bar.
Does this stream contain any free water?
Solution
Qsc = 67 mm.scf/day, salt = 2%, SG = 0.85, P = 75 x 14.7 = 1100psi,
T = 870F., Water Content = 55 lb.h2o/mm.scf. Required Dew point 20 0F
From Chart:
At , P = 1100psi, & T = 870F
Salt correction = 0.95, SG corr = 0.98, Water content = 45 lb.H2O/mm.scf
Corr. WC = 0.95x098x45 = 41.9 lb.H20/mm.scf.
Free Water = 55 41.9 = 13.1 lb.H2O/mm.scf.
At T = 200F , P = 1100psi, - from chart
Water content at required Dew Point = 4 lb.H2O/mm.scf
Corrected WC = 0.95x0.98x4 = 3.724
Water removed per day (41.9 3.724)x67 = 2557.79 lb.H20/day
4/16/2013
52
SLIDE 103
Hydrates
HYDRATES
Definition.
Hydrates Are Crystalline(ice-like) Compounds Formed by Combination of Water and Hydrocarbons Under Pressure at Considerable Higher Temperature Than Water Freezing Point.
Hydrates Occurrence
In Pipeline.
In Equipment
Valves.
Regulators.
Chokes
In Formations As Hydrate Rock.
Burning Snow
140
120
100
80
60
40
20
00 5 10 15 20 25
TEMPERATURE
PRESSURE
CONDITIONS IN WHICHHYDRATES ARE LIKELYTO BE FORMED
HYDRATE CURVE
4/16/2013
53
SLIDE 105
Hydrates Crystal
Hydrocarbons in Hydrates.Methane CH4 . 7H2O
Ethane C2H6 . 8H2O
Propane C3H8 . 18H2O
Butane C4H10 . 24H2O
CO2 CO2 . 7H2O
H2S H2S .6H2O
SLIDE 106
Hydrates Crystal
The Hydrate Crystal
The Water or Host Molecules Are Linked Together by Hydrogen Bonds Into Cage-like Structures Called Clathrates.
The Water Framework Though is Ice-like, but
it Has Void Space and It is Weak.
The Hydrocarbon or Guest Molecules are held together by Weak Bonds within the Void of the Crystalline Network or Structure of the Water to Stabilize Water Structure.
The Water Framework Holds the Hydrocarbon Molecules in a Void Space or Network.
Hydrate Clathrate
Hydrate Clathrate
4/16/2013
54
SLIDE 107
Hydrate Crystalline Structure
Two Basic Structures:
Structure II Diamond
Structure I Cubic or Body-Centered
Smaller Hydrocarbon Molecules (C1,C2,CO2, & H2S) Form More Stable and Cubic Structures.
Larger Hydrocarbon Molecules (C3 & iC4 ) Form Less-stable and Diamond Structures.
Molecules Larger Than C4 Cannot Form Hydrates Because They Cannot Fit Into the Cavity in the Water Molecule Structure.
Ono SLIDE 108
Hydrate Crystalline Structure
Hydrate Crystalline Structures.
.
4/16/2013
55
Ono SLIDE 109
Hydrate Crystalline Structure
Hydrate Crystalline Structures.
.
SLIDE 110
Properties of Hydrates
STRUCTURE I STRUCTURE IILattice Shape Body- Cubic Centered Diamond
Stability More Stable Less Stable
Water Molecules per Unit Cell 46 136
Cavities per Unit CellSmall 2 16Large 6 8
Typical Gases That Methane* Propane**Form in Each Cavity Ethane* I-Butane**of this Structure H2S n-Butane**
CO2 neo-Pentane*** Small**Large
4/16/2013
56
SLIDE 111
Properties of Hydrates
They Have Fixed Chemical Composition BUT No Chemical Bond
They Behave Like Chemical Compounds.
They are Physically Like Ice or Wet Snow Crystals but Do Not Have Solid Structure of Ice.
They Have Less Density Than Ice.(SG 0.96 0.98)
They Sink in Liquid Hydrocarbons and Float in Water.
They Contain 90% Water by Weight
SLIDE 112
Conditions for Hydrates Formation
Presence of High Concentration of Hydrate forming Gases
Presence of Free Water.
Natural Gas at or Below its Water Dew Point.
Operating Temperature Below Hydrate Formation Temperature for That Pressure and Fluid Composition.
Hydrate Formation Temperature Temperature Below Which Hydrates Will Form at a Particular Pressure.
They Form at Hydrate Temperature of the Gas and NOT That of the Component Gases.
The Hydrates Formed are Mixtures of the Hydrates of the Component Gases Rather than Hydrate of the Natural Gas.
4/16/2013
57
SLIDE 113
Presence of Small Hydrate Crystal.
Operating at High Velocity or Agitation Through Equipment and Pipe Network.
Turbulence Encourages Hydrate Formation; Hence Their Presence Mostly Downstream of Valves, Regulators, Orifice Plates, Chokes, Sharp Bends, Pipe Elbows, etc. and Upstream of these Devices if Flow is Turbulent and Temperature is Low.
Hydrates Form at Gas-water Boundary With the Forming Molecules Coming From the Solution.
Parameters Such as High Temperature That Encourages High Solubility Enhances Hydrate Formation.
Contaminants Such as H2S and CO2 are More Soluble in Water Than Hydrocarbon and as Such, More Conducive for Hydrate Formation.
Very High Solution GOR Encourages Hydrates Formation Due to High Gas Molecules Presence
Conditions for Hydrates Formation
SLIDE 114
Hydrates Formation
4/16/2013
58
SLIDE 115
Effect of GOR on Hydrates Formation
SLIDE 116
Hydrates Formation Prediction
Parameters PredictedTemperature
ORPressure
at Which Hydrates Will Form.
Katz Gas Gravity Method.Uses Gas Gravity, Pressure and Temperature.
It is Simple but Only an Approximation.
Values Excellent for Methane and 0.7 or Less SG Natural Gas.
Not Good for Pipeline Gases.
Less Accurate for Natural Gas With SG Between 0.9&1.0 Useless for Streams With Sulfur Compounds and/or Larger Molecules.
4/16/2013
59
SLIDE 117
Hydrates Formation Prediction
Katz Hydrate Formation Temperature Determination Procedure Given Gas Gravity and Temperature or Pressure
Hydrate Formation Pressure or Temperature is Got From Katz Graph
If Gas Composition Fractions are Given, Gas SG is then Calculated B4 Going to Graph
SLIDE 118
Katz Pressure-Temperature Curves for Hydrates Formation Prediction
4/16/2013
60
SLIDE 119
Katz Hydrate Formation Condition Estimation Method
Example 4-3
Estimate Hydrate Formation Temperature of Natural Gas With the Composition Shown Below at 1000 Psia.
Component Mole %
N 10.1
C1 77.7
C2 6.1
C3 3.5
i-C4 0.7
n-C4 1.1
C5+ 0.8 (Assume C6)
Step 1
Compute the Specific GravityComponent Mole % MW Z.MW
N 10.1 28 2.83
C1 77.716 12.43
C2 6.1 30 1.83
C3 3.5 44 1.54
i-C4 0.7 58 0.41
n-C4 1.1 58 0.64
C5+ 0.8 86 0.69
100.0 20.38
SG = 20.38/28.9625 = 0.7 .
Step 2
Read Hydrate Formation Temperature From Katz CurveHydrate Formation Temperature = 65 0F
SLIDE 120
Baillie and Wichert Method.
Method Used Mostly to Predict Hydrate Formation Temperature of Acid Gases
Range of Application
Total Acid Gas Content: 170%
H2S Content 1 50%
H2S/CO2 Ratio 1:3 10:1
Correction Has to Be Made for C3 Content.
Chart Good for C3 Content Up to 10%
4/16/2013
61
SLIDE 121
Baillie and Wichert Method.
Estimation Procedure
For the Above Gas at 1000 psia
Compute SG As in Example 4-3 Above.(SG = 0.7)
Enter Fig. 4-35 at 1000 psia
Move Horizontally to 0% H2S
Descend Vertically to the Horizontal (SG = 0.7)
Follow Sloping Lines to the Horizontal Bottom Temperature Scale.
Read off the Hydrate Temperature = 62 0F
Ono SLIDE 122
Baillie and Wichert Method.
.
62
3
Correlation Lines
4/16/2013
62
SLIDE 123
Baillie and Wichert Method.
Determine Correction for C3.
Interpolate For C3 = 3.5 Position on C3 Adjustment Chart.
Enter Chart at H2S = 0%
Descend Vertically to 1 X 103 psia Line
Move Horizontally to Read the Correction. = +3 0F
Add Correction.
Hydrate Temperature = 62 + 3
= 65 0F
SLIDE 124
Baillie and Wichert Method.
Other Methods of Hydrates Formation Temperature Estimation
Pressure -Temperature Curves
by Gas Processors Suppliers Ass.
Hydrates Formation Curves for Gases Undergoing Expansion
by Gas Processors Suppliers Ass.
4/16/2013
63
SLIDE 125
Hydrates Control and Prevention
High Stream Flow Rate (Helps to destroyed week formed hydrates).
Reduction of H2S and CO2 Content.
Keep Lines and Equipment Dry of Liquid Water.
If Water Must Be Present, Stream Must Flow at Above Hydrate Formation Temperature.
Application of Heat.
Dehydration
If Stream Must Have Water and Must Flow at Low Temperatures, Then Inhibitors Must Be Injected.
SLIDE 126
Hydrates Control and Prevention
Inhibitors .
Materials Added to Water to Depress its Freezing and Hydrate Forming Temperature.
Inhibitor Temperature Range
Methanol Any
Di-Ethylene Glycol (DEG). -10 0F
Ethylene Glycol (EG) -10 0F
Tri-ethylene Glycol (TEG) -10 0F
4/16/2013
64
SLIDE 127
.
Inhibitor Concentration in Water Phase
W = D. M 100
Ki + D . M
W = Weight % Inhibitor in the Water Base
M = Mol. Weight of Inhibitor
D = 0C (0F) Depression of Hydrate Point.
Ki = Constant
Inhibitor KiMethanol, 1297 (0C) or 2335 (0F)
Glycols 2220 (0C) or 4000(0F)
Hydrates Control and Prevention
SLIDE 128
Effect of DEG on Hydrate Formation
Freezing Point of DEG Glycol
4/16/2013
65
SLIDE 129
.
Problems Caused by Hydrates
Hydrates in Flow Line Reduces Well Head Pressure.
Hydrates Can Block Flow Line and Equipment.
Hydrates Can Constrict Equipment Surface Lines and Flow Strings.
Fouling of Heat Exchangers.
Problems Caused by Hydrates
SLIDE 130
In-Class Exercise
A natural gas is to be compressed to flow 150 mm scf/day at 95.24 barg from Lagos to Syracuse in Italy in the new Nigeria-European transcontinental line. Yearly average temperature of Lagos is 30 0C while Syracuse lowest temperature in Winter is 5 0C. Frictional losses on this journey have been estimated at about 7.14% by the Crypto Inc. the pipeline designers. In Lagos, Tolu Laboratories Ltd using equilibrium calculation method estimated this gas hydrate formation temperature to be 46.4 0F at 1283 psi.
MW = (150 gm/mol), density = 9.35 ppg
Questions:
1. Does this gas journey require any hydrate formation prevention intervention?
1. If so, how many gallons of glycol would you recommend to prevent hydrate formation?
4/16/2013
66
NNPC FSTP Engineers
Natural Gas Processing and Transmission
Course Code:
Lesson 4
Lesson 4-4
Dehydration
4/16/2013
67
Lesson 4-4 Contents
Dehydration
Batch Dehydration Process
Continuous Dehydration process
SLIDE 134
Dehydration
Dehydration
Removal of water and/or water vapour
Reasons for Water Removal
Water reduces natural gas heating value
Water and Natural gas form solid, ice-like hydrate that plugs equipment.
Natural gas with water and CO2/ H2S is corrosive.
Condensed water from natural gas causes slugging flow condition.
Water increases natural gas volume and the natural gas line capacity.
4/16/2013
68
SLIDE 135
Dehydration Equipment
Equipment
Free Water Knock-out.
3 Phase Separators.
Emulsion Treaters.
Heater Treaters.
Chemical Treatment.
SLIDE 136
Dehydration Processes
Processes
Director Cooling.
Cooling Gas Stream for Dehydration Purpose
Mechanical Refrigeration
Expansion Through Choke
LTS
Compression followed by Cooling.
These Two Methods Do not Reduces Gas Dew Point.
Absorption.
Adsorption.
4/16/2013
69
SLIDE 137
Adsorption Dehydration
Removal of Water by Solid Materials Called Desiccants
Desiccants.
Solids That Have Affinity For Or Ability To Hold Water To Their Surfaces.
Adsorption.
The Process Whereby Solids Take In And Hold Water or Gas Molecules To Themselves.
Process Whereby Solids Are Used To Remove Water.
SLIDE 138
Adsorption Dehydration
Characteristics of Solid Desiccants They Have Large Surface Area Per Unit Weight. - 500 to 800 m2/gm
The Surface Area Consists of Small Pores With Capillary Openings.
Liquid Vapor is Held and Concentrated at the Surface by Forces Presumably Caused by Residual Valency, Capillary, Chemical Reaction or Intermolecular Forces.
They Have Capability to Remove Almost All Water Content of Gas to the Tune of 1.0 lb/MM SCF;
Has Higher Efficiency than Other Dehydration Agents.
4/16/2013
70
SLIDE 139
Characteristics of Desiccants
They are Applicable to High Temperature Operation to the Tune of 125 0F.
Lower Dew Points can be Achieved Over a Wide Range Conditions of Operation with Solid Desiccants.
Their Efficiency Reduces with Each Regeneration and Material Deteriorate due to Surface Attrition or Abrasion.
They Produce Dry Gas.
Cheap and Easily/Economically Regenerated.
Non-Corrosive, Non-Toxic and Chemically Inert.
Adsorption Dehydration
SLIDE 140
Types of Desiccants .
Silica Gel.
Silica-Based Beads
Activated Alumina
Activated Bauxite
Membranes
Carbon(Charcoal) -Not for Water
Molecules Sieves.
Crystalline or Metal Alumino-Silicates Zeolite) Which Have Great Affinity for Water.
They are Synthetic Crystals Manufactured to Contain Uniform Cavities
They are also used for CO2 and H2S Sweetening
Adsorption Dehydration
4/16/2013
71
SLIDE 141
Molecular Sieves Characteristics
Cavities Have Electric Charges that Attract Polar Molecules
Polar Molecules are Adsorbed in Preference to Non-Polar Molecules
Unsaturated Hydrocarbons are Also Adsorbed in Preference to Saturated Hydrocarbons.
Cavities are interconnected by pores
Adsorption Takes Place in the Crystalline Cavities
Diameter of Cavity Determines Size of Molecules that can be Adsorbed.
SLIDE 142
Molecular Sieves Characteristics
Molecular Sieve Structure Diameter.
4/16/2013
72
SLIDE 143
..
Molecular Sieves Characteristics
SLIDE 144
Solid Desiccant Dehydration Plant
Components Contractor (Absorber or Sorber)
Has beds of Granular Desiccants Where Adsorption Occurs.
Fluid Inlet and Outlet Connections.
Flow is Down the Column; Reduces Disturbances.
Filter Separator Removes all Solids and Contaminants.
Regeneration Gas Heater. Produces Hot Regeneration Gas
Regeneration Gas Cooler Cools the Rich Regeneration Gas.
Regeneration Gas Scrubber. Removes the Water from the Regeneration Gas.
Produces the Cool Gas for Contractor Beds Cooling.
4/16/2013
73
SLIDE 145
Solid Desiccant Dehydration Plant
Process Plant Lay-Out
Ono SLIDE 146
Inlet Gas Dehydration Cycle
.
Rich Inlet Gas Stream Goes Through Filter For Contaminant Removal.
Inlet gas Flows Contactor From Top, Goes Through Desiccant Beds and Got its Water Removed.
4/16/2013
74
SLIDE 147
Desiccant Beds Regeneration Cycle
Desiccant Beds Regeneration
Hot Regeneration Gas From Heater is Released at the End of Dehydration Cycle to Remove All Water From Beds Flowing from Bottom to Top.
.
Boiling and Evaporation Starts at 240 0F and Continues Till 350-375 0F for 4 Hours.
While One Adsorber is Dehydrating, The Other is Being Regenerated.
.
SLIDE 148
Desiccant Beds Cooling Cycle
Hot Regenerated Desiccant Beds are Cooled by Shutting off or Bypassing the Heater.
Cool Regeneration Gas from Scrubber then Flows From Top Downwards to Cool Beds. Cooling Terminate at 125 0F..
The Cool and Hot Regeneration Gas Finally Goes Through the Regeneration Cooler and Scrubber for All Adsorbed Water to Condense Out.
Power Operated Valves, Activated by a Timing Device, Switch the Adsorber Between Dehydration, Regeneration and Cooling Steps
.
4/16/2013
75
SLIDE 149
Solid Desiccant Dehydration Plant
Major Points of Consideration.
Efficiency Decreases With Each Regeneration.
Plant is Always Put in Operation More Quickly after Shut Down.
Plant can be Adopted For Hydrocarbon Liquid Recovery.
Removal of all Contaminants Must be Ensured.
Operating Life of Desiccants is Between 1- 4 Years.
Sudden Pressure Surges Should be Avoided.
SLIDE 150
Absorption Dehydration Process.
DefinitionAbsorption is a Process Whereby Water or Water Vapor is Attracted or Removed by a Liquid Agent.
Liquid Desiccant Liquid that absorbs water.
Types of Liquid Desiccants.Ethylene Glycol - EG
Di-ethylene Glycol DEG
Tri-ethylene Glycol TEG
Tetra-ethylene Glycol T4EG
4/16/2013
76
NATURAL GAS
WATER
GLYCOL
Absorption Process
GLYCOL
Absorption Dehydration Process.
NATURAL GAS
Rich Glycol
NG
WaterMolecules
SLIDE 152
Absorption Dehydration Process.
Advantages of Tri-ethylene Glycol (TEG)
Lower Capital and Operating Cost.
Decomposition Temperature is Very High (404 0F)
DEG is 328 0F
Low Viscosity (Above 70 0F)
Lower Vaporization Loss than EG or DEG
More Easily Regenerated to Concentration of 98- 99.95% due to its High Boiling and Decomposition Temperature.
4/16/2013
77
SLIDE 153
Tri-Ethylene Glycol(TEG) Dehydration
Requirements for TEG Dehydration Inlet Gas Stream Must Be Free of:
Free Liquid Water
Liquid Hydrocarbon
Wax
Sand
Mud
Other Solid Contaminants
Dew Point Depression Achieved Depends on:
The Contact Temperature With TEG
Dew Point /Temperature of TEG.
SLIDE 154
Tri-Ethylene Glycol(TEG) Dehydration
TEG Dehydration Plant
Components
Inlet Scrubber
Removes Entrained or Free Water Which:
Increases Fuel Cost
Increases Reboiler Heat Load.
Increases Glycol Re-circulation Rate.
Causes System Over Load Resulting in Glycol Carry-over From Contactor or Still.
4/16/2013
78
SLIDE 155
Tri-Ethylene Glycol(TEG) Dehydration
Removes Oils or Dissolved Hydrocarbons Which:
Reduces Drying Capacity of Glycol
Combined With Water to Cause Foaming.
Undissolved Oils Can Plug Absorber Trays.
Undissolved Oil Also Increases Glycol Viscosity and Cokes on Heat Transfer Surfaces of the Reboiler
Removes Entrained Brine Which
Dissolves on Glycol and Becomes Corrosive.
Deposit on Boiler Fire Tubes
Cause Hot Spots
SLIDE 156
Tri-Ethylene Glycol(TEG) Dehydration
Removes Down-Hole Additives Such as:
Corrosion Inhibition Materials
Acidizing Materials
Fracturing Materials
These Can Cause
Foaming
Corrosion
Hot Spots
Removes Solids(Sand, Rust, Fe, etc)
Promote Foaming
Erode Valves
Erode Pumps
Plug Trays and Packing
4/16/2013
79
SLIDE 157
TEG Dehydration Plant.
Aerial Cooler
SLIDE 158
Contactor Absorber.
4/16/2013
80
SLIDE 159
Tri-Ethylene Glycol(TEG) Dehydration
Contactor (Absorber). Scrubber Section.
Centrifugal Separator
Mist Extractor
Removes Remaining Entrained Liquid Droplets.
Minimize Contamination of Glycol.
Prevent Presence of Free Water
Absorber Section
Cooling Coils
Drying Section
Bubble Cap
Downcomers
Mist Extractor
TRAY COLUMNS:Bubble cap tray, Sieve tray, Valve tray and Baffle tray.Internals and Operations of Contactor, Distillation and Stabilization Columns.Advantages of Tray Columns.
SLIDE 160
Typical Commercial Trays.
.
Bubble-Cap TraySieve Tray
Standard Flexitray Valve
Flexitray Valve Tray
4/16/2013
81
SLIDE 161
Tri-Ethylene Glycol(TEG) Dehydration
Drying Section
Mechanism of Operation
Bubble Cap Trays
Divides Gas into Small Bubbles in Continuous Liquid Phase
Spray Chambers (Sieve or Valve Trays):
Forming the Liquid into Small Droplets in a Continuous Gas Phase
Packed Columns
Spreading the Liquid into Thin Films that Flow through a Continuous Gas Phase
SLIDE 162
Tri-Ethylene Glycol(TEG) Dehydration
Drying Section
Gas Gets in Contact on Moving Up With Glycol in Bubble Cap or Valve Trays.
Trays Spacing Should 18 to 24-30 to Prevent Foaming.
Circulation Rate of TEG Per lb. of Water Removed is Inversely Proportional to the No. of Trays.
3-6 Trays 3 gal TEG/lb. Water
8 Trays 2 gal TEG/lb. H2O
.
Operation of the Bubble Cap
4/16/2013
82
Gasflow
Liquidflow
Holes drilled 1/8to 1/2 in.dia
Sieve plate
Sieve Tray Column
Liquid inlet
Liquid outletGas inlet
Gas outlet
Gas bubble
Tri-Ethylene Glycol(TEG) Dehydration
Gasflow
Liquidflow
VALVE PLATE
Valve open(Gas flows)
Valve close(No Gas flow)
Liquid inlet
Liquid outlet
Gas inlet
Gas outlet
Tri-Ethylene Glycol(TEG) Dehydration
4/16/2013
83
SLIDE 165
Packed Columns.
.
Packed ElementsIntalox Packing
SLIDE 166
Tri-Ethylene Glycol(TEG) Dehydration
Glycol Cooler.
Inlet Lean Glycol Got Cooled by Exchanging Heat with the Out Going Dehydrated Gas.
Shell & plate type
Shell : rich glycol
Plate : lean glycol
Mist Extractor
Extracts all Entrained Glycol Droplets From Out Going Dehydrated Gas.
Glycol Pump
4/16/2013
84
Mist Extractor GAS OUTLET
MISTEXTRACTOR
TOP TRAYLIQUIDSTREAM
ENTRAINEDLIQUIDS
Tri-Ethylene Glycol(TEG) Dehydration
SLIDE 168
Tri-Ethylene Glycol(TEG) Dehydration
Glycol Strainer
Removes Solid Content From Lean Glycol.
Solid Should be Kept to 0.0I Weight % to Prevent
Heat Exchanger Plugging
Fouling of Contactor Trays.
Foaming.
Pump Wear, etc
4/16/2013
85
SLIDE 169
Tri-Ethylene Glycol(TEG) Dehydration
Heat Exchangers Surge Tank.
Cold Wet Glycol from the Flash Separator Gets Heated Up by the Hot Lean Glycol From Reboiler
It Also Serves as Surge Tank for the Lean Glycol
Reboiler with Stripping Still.
Regeneration of glycol by heating/boiling: rich lean
Heat source: natural draught burner
Operating @ 118 C and 100 mbarg
To achieve required purity of glycol
To minimize glycol decomposition
Normally Boils Glycol to Re-concentrate it to 98.7 %
Gets to 99.6% with Stripping Gas.
Mostly Heated by Direct Fire Tube(Box) Using NG as Fuel or
Hot Heated Coil Fire Box or
SLIDE 170
Re-Boiler and Stripping Still
Typical Direct Fired Reboiler Temp. Profile
Operating @ 118 C and 100 mbarg To achieve required purity of glycolTo minimize glycol decomposition
4/16/2013
86
SLIDE 171
Re-Boiler and Stripping Still
Stripping Still
Distillation of glycol and water
To minimize glycol losses via overhead vapour
Stripping Still Strips water from Glycol
Internals:
Random packing: Pall rings
Inlet device: half open pipe
Reflux condenser
To minimize glycol losses via overhead vapour
Rich glycol is cooling medium
Shell (overhead vapour) and Coil (glycol) design
Globe valve to set reflux ratio; normally closed
Rich Glycol IN
Rich GlycolOUT
Reflux Condenser
SLIDE 172
Tri-Ethylene Glycol(TEG) Dehydration
Stripping Gas
Any Gas that is Insoluble in Water and Can Withstand 400 0F
Natural Gas is Commonly Used.
Sometimes Taken From the Fuel Gas Line by a Valve and Injected Into the Reboiler.
It Rolls the Glycol to Release Any Pockets of Water Vapor.
It Also Sweeps All the Water Vapor From the Reboiler and the Still Column.
Raising TEG Concentration Beyond (to 99.96%)
Vacuum Pump
Installed in the Reboiler or the Still Column Can Also Achieve the Same Feat
4/16/2013
87
SLIDE 173
Tri-Ethylene Glycol(TEG) Dehydration
Factors for Consideration in TEG Plant Operations.
Water, Hydrocarbon Liquids and Lubricating Oils in Gas Require That an Efficient Separator Be Installed Upstream of Absorption Tower.
Water With High Concentration of Minerals in Gas May Crystallize Over a Long Period and Fill the Reboiler With Solid Salts.
Highly Concentrated Glycol May Be Difficult to Pump at Low Temperature Because of Their High Viscosity.
SLIDE 174
Tri-Ethylene Glycol(TEG) Dehydration
Factors for Consideration in TEG Plant Operations.
In Cold Weather Regions, Glycol Lines Have Tendency to Solidify If Not in Use, Therefore Continuous Circulation is Required.
Sudden Surges Should Be Avoided in Starting and Shutting Down the Plant to Avoid Occurrence of Large Carry-over Losses of Glycol.
Foreign Matter Such As Dirt, Iron Oxide, etc. Can Contaminate Glycol.
Decomposition of Glycol May Occur If Overheated.
The Presence of Oxygen and Hydrogen Sulphide May Cause Corrosion.
4/16/2013
88
Typical TEG Dehydration Plant Process Flow Diagram
SLIDE 176
AGG Plant Major Processes.Compression
Cooling
Condensate Extraction
Dehydration
Compression(12.3 bar)
Condensate Extraction
Dehydration
Cooling CoolingCoolingCondensate Extraction
Condensate Extraction
Compression(70 bar)
Compression(30 bar)
Sales Gas
InletGas
4/16/2013
89
Typical Compression Station
NNPC FSTP Engineers
Natural Gas Processing and Transmission
Course Code:
Lesson 4
4/16/2013
90
Lesson 4-4
Dehydration
SLIDE 180
Tri-Ethylene Glycol(TEG) Dehydration
Disadvantages Of TEG Plants.
Water, Hydrocarbon Liquids and Lubricating Oils in Gas Require That an Efficient Separator Be Installed Upstream of Absorption Tower.
Water With High Concentration of Minerals in Gas May Crystallize Over a long Period and Fill the Reboiler With Solid Salts.
Highly Concentrated Glycol May Be Difficult to Pump at Low Temperature Because of Their High Viscosity.
In Cold Weather Regions, Glycol Lines Have Tendency to Solidify If Not in Use, Therefore Continuous Circulation Is Required.
4/16/2013
91
SLIDE 181
Tri-Ethylene Glycol(TEG) Dehydration
Disadvantages Of TEG Plants.
Sudden Surges Should Be Avoided in Starting and Shutting Down the Plant to Avoid Occurrence of Large Carry-over Losses of Glycol.
Foreign Matter Such As Dirt, Iron Oxide, etc. Can Contaminate Glycol.
Decomposition of Glycol May Occur If Overheated.
The Presence of Oxygen and Hydrogen Sulphide May Cause Corrosion.
SLIDE 182
Comparison of Solid Desiccant and Glycol Dehydration Systems
4/16/2013
92
SLIDE 183
TEG Dehydration Design
Basic Information
Inlet Gas Water Content (lb/mm Scf)
Dehydrated(outlet) Gas Water Content. (lb/mm Scf)
Inlet Gas Flow Rate. (mm Scf/day)
Inlet Gas Temperature(0F)
Inlet Gas Pressure.(psig.)
Inlet Gas Specific Gravity.
Contactor Working Pressure. (psig)
SLIDE 184
TEG Dehydration Design
Major Factors For Consideration
TEG Circulation Rate(LW).
Gal/lb. H2O Removed
2-6 Gal/lb.H2O(Normal Ops.)
2.5 4 Gal/lb.H2O(Field Ops)
TEG Concentration
99.9% Possible
99.5% Adequate
Sivalls Charts and Tables
Scrubber Design
Determine Type of Scrubber
Guided by Gas Stream Composition
Either 2-phase or 3-phase
4/16/2013
93
SLIDE 185
TEG Dehydration Design
Calculate Gas Flow Rate
Operating Pressure.
Operating Temperature.
Gas Compressibility.
Determine Scrubber Diameter.
Gas Capacity
Operating Pressure.
Scrubber Capacity(mm scf/day)
Note that Fig. is 0.7 SG and 100 0F. Gas Charts for Other Conditions are Available.
Determine Other Scrubber Specs. From Tables 4-6 and 4-7.
Gas Capacity of Vertical Gas Scrubber.
SLIDE 186
Vertical Scrubbers SpecificationsGas Capacity of Vertical Gas Scrubber.
4/16/2013
94
SLIDE 187
TEG Dehydration Design
Glycol Contactor (Asorber)
Select a Contactor Diameter.
Fig. For Trayed Column
Fig. For Packed Column
Using;
Operating Pressure
Concentrator Inlet Gas Flow Rate.
Approx. Contactor Required Gas Capacity
Obtained Gas Capacity has to be Corrected for Gas Gravity(0.7) and Operating(100 0F) Temp.
Gas Capacity for Tray Glycol Contactors
SLIDE 188
TEG Dehydration Design
Gas Capacity for Packed Column Contactors
4/16/2013
95
Ono SLIDE 189
TEG Contactors Specifications
SLIDE 190
TEG Contactors Specifications
4/16/2013
96
SLIDE 191
TEG Dehydration Design
Correct Approx. Capacity to Actual Contactor Gas Capacity qopqop = qs . Ct. Cg
qop = Contactor Gas Capacity at Operating Condition(mmscf/day)
qs = Contactor Gas Capacity at Standard Conditions of 100 0F with 0.7 SG and
From Fig 4-50.
= Contator Inlet Gas Flow Rate(mm Scf/day)
Ct = Operating Temperature Correction Factor0F(Table 4-6A)
Cg = SG Correction Factor(Table 4-6C)
SLIDE 192
TEG Dehydration Design
Correction Factors for Temperature and Specific Gra vity
Operating Temperature,
OF
40 50 60 70 80 90
100 110 120
Source: After Sivalls.
Correction Factor Ct
1.071.06 1.05 1.04 1.02 1.01 1.00 099 098
50 50 70 80 90
100 110 120
Source: After Sivalls.
0.93 0.94 0.96 0.97 0.99 1.00 1.01 1.02
C
Gas Capacity Correction F actors for
Trayed Glycol -Gas Contactors
Specific Gravity Correction Fac tors, Cg
Gas Specific Correction Factor,
Gravity C g
D Gas Capacity Correction Factors for
Packed Glycol -Gas Contactors
Specific Gravity Correction Factors, C g
Gas Specific Correction Factors
Gravity Cg
0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90
Source: After Sivalls.
1.14 1.08 1.04 1.00 0.97 0.93 0.90 0.88
0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90
Source: After Sivalls.
1.13 1.08 1.04 1.00 0.97 0.94 0.91 0.88
A
Gas Capacity Correction Factors for
Trayed Glycol -Gas Contactors
Temperature Correction Factors, C t
B
Gas Capacity Correction Factors
for Packed Glycol -Gas Contactors
Temperature Correction Factors, Ct.
Operating Correction
Temperature, Factor, OF Ct
Operating
Temperature 0F
Correction
Factor
Ct
Table 4-6Gas Capacity Correction Factors
4/16/2013
97
SLIDE 193
TEG Dehydration Design
Determine Required Dew Point Depression.
Determine Outlet Gas Dew Point From Fig. 4-53 Using
Operating Pressure.
Required Outlet Gas Water Content.
Inlet Gas Assumed Saturated With Vapor and is at Its Dew Point Temp. and Pressure.
Dew Point Depression = Inlet Gas Temp.- Outlet Gas Dew
Point Temp.
0F
5
10
30
60
SLIDE 194
TEG Dehydration Design
Rate of Water Removal (Wr).
= lb.(H2O) Removed
hr
= (Inlet Gas - Outlet Gas) Water Content x (Gas Flow)
24
Wr = (Wi - Wo) qo24
Wr = Rate of Water Removed(lb/hr)
Wi = Inlet Gas Water Content (lb.H2O/mm cf Gas)
Wo = Outlet Gas Water Content (lb.H2O/mm cf Gas)
qo = Gas Flow Rate (mm scf/day)
4/16/2013
98
SLIDE 195
TEG Dehydration Design
Correct Water Content for H2S and CO2 if Present
Tray Contactor Special Consideration
Number of Trays Selection.
Sivalls Tray Chart
Determines Trays Number Using
Dew Point Depression From Above.
Selected Glycol(gal) to Water(lb) Circulation Rate(Lw).
Gives Approx. No. Required for Field Dehydrators
SLIDE 196
TEG Dehydration Design
Sivalls Number of Trays/Packing Chart
4/16/2013
99
SLIDE 197
TEG Dehydration Design
Modified McCabe-Thiele Diagram.
Gives More Detailed Consideration For Required number for Economic Sizing.
Gives Theoretical Number of Trays.
Above Converted to Actual Tray Number by Tray Efficiency Factor
TNactual = TNtheor X Ect
Ect = Tray Efficiency Factor
SLIDE 198
TEG Dehydration Design
Construction of Modified McCabe-Thiele Diagram
Determine Rich TEG Conc. Leaving Contactor.
Rich TEG Conc. =
= Density of Lean TEG - lb/gal
= 8.33 x SG
SG = Specific Gravity of Lean Glycol at Contactor Operating Temperature.
= TEG to Water Circ. Rate Gal.Teg/lb.H2O
Rich TEG Conc. Conc. of TEG From Contactor(%)
Lean TEG Conc. Conc. of TEG Entering Contactor(%)
w
i
i
L
ConcTEGLean
1
.)(
i
wL
4/16/2013
100
SLIDE 199
TEG Dehydration Design
The Diagram Construction
McCabe-Thiele Diagram Operating Line.
Determine Gas Water Content and TEG Conc. at Column Top.
Point of Gas Outlet With Given H2O Content and Lean TEG Entry With Given Conc.
lb(H2O)/mm scf(gas) and % Conc. Lean TEG
Determine Gas Water Content and TEG Conc. at Column Bottom
Point of Gas Inlet With H2O Content As Determined by Operating Press. and Temp. and Rich TEG Outlet With Conc. as Calculated.
lb(H2O)/mm scf (Gas) and % Conc. Rich TEG.
Plot These Points and Draw the Operating Line as Shown Between the Two Points.
SLIDE 200
TEG Dehydration Design
McCabe-Thiele Diagram McCabe-Thiele Diagram Equilibrium Line.
Represents Water Content of Gas That Will Be in Equilibrium With Various TEG Conc.
With the Operating Temp, Choose Various Conc. Fig 4-56
Determine Equilibrium Dew Points at Contactor Operating Temp.
Determine Gas Water Content for Each Conc. From Fig. 4-53
Construct the Equilibrium Line With the Above Points
4/16/2013
101
SLIDE 201
Dew Point of Aqueous TEG Vs Temperature
TEG Dehydration Design
Fig 4-56
SLIDE 202
Table 4-6
Determine Theoretical Trays Number
Step off by Triangulation on the Two McCable-Thiele Diagram Lines.
Actual Tray Number = No. Of Theoretical Trays
Tray Efficiency
Contactor Bubble Cap Tray Efficiency = 25%Valve Tray Efficiency = 33.5%Tray Spacing = 24
* Always Round Up Trays Number.
4/16/2013
102
SLIDE 203
TEG Dehydration Design
Packed Contactor Special Consideration. Fig 4-53
Depth of Packing = No. of Theoretical Trays.
Depth Footage is Normally Rounded up to Whole Number
Glycol Reconcentrator
Glycol Circulation Rate(L).
gal/hr
Lw Teg/H2O Conc. Ratio
gal(Teg)/lb (H2O)
Wi Inlet Gas Water Content.
lbH2O/mm Scf (Gas)
qo Gas Flow Rate at Operating
Conditions(mm Scf/day)
24
oiw qWLL
SLIDE 204
TEG Dehydration Design
Reboiler
Total Heat Load(Ht)
By Estimation
Ht = 2000 L
Normally Enough for HP Requirement of Glycol Dehydrator Sizing.
Detail Determination
Ht = HL + Hw + Hr + HhHL = TEG Heat Requirement(Btu/hr)
=
i = TEG Density at Reboiler Average Temp. lb/gal
C = TEG Specific Heat at Reboiler Avg. Temp. btu/lb/0F
T2 = TEG Outlet Temp. 0F
T1 = TEG Inlet Temp. 0F
= 1200 for High Pressure TEG Dehydrator
12 TTCL i
12 TTCi
4/16/2013
103
SLIDE 205
TEG Dehydration Design
Hw = Water Heat of Vaporization Btu/hr
= 970.3 (Wi - Wo) qo24
970.3 = Water Heat of Vaporization at 212 0Fand 14.7 psia in btu/lbm
HR = Heat Needed to Vaporize Reflux Water in the Still
= 0.25 Hw Btu/hr
HH = Heat Losses From Reboiler and Stripping Still Surfaces(Btu/hr)
HH By Estimation
HH = 5000 to 20,000 Btu/hr Depending on Size.
HH By Detail Determination
HH = 0.24 As (T2 - T1); As Total Reboiler and Still Exposed Surface Area Ft2
T2 Vessel Fluid Temp. 0F
T1 Min. Ambient Temp. 0F
0.24 Heat Load Constant For Large Insulated Surfaces btu/hr/ft2. 0F
SLIDE 206
TEG Dehydration Design
Fire Box Surface Area
Required Info.
Heat Flux of About 7000 Btu/ 0F
AF = Ht = Total Surface Area of Fire Box (ft2)
7000
= Fire Box Diameter x Overall U-tube Length
= DF X LF
Table 4-7 Consists of Specs of Glycol Concentrator Components.
4/16/2013
104
SLIDE 207
TEG Dehydration Design
SLIDE 208
TEG Dehydration Design
Types of Pumps
Glycol Pumps
Uses Rich Glycol to Pump Lean Glycol.(Table 4-8 for Selection)
Positive Displacement and Centrifugal Pumps
Glycol Flash SeparatorSized by Retention Time
Flash Separator Retention = 5 mins.
VL = LT Settling Vol.(gals)
60
VL = Settling Volume gal
T = Retention time - 5 mins
L = Glycol Circulation Rate- Gal/hr
4/16/2013
105
SLIDE 209
Sivalls Stripping Still Chart
SLIDE 210
TEG Reconcentrator Specifications
.
4/16/2013
106
SLIDE 211
TEG Dehydration Design Example
ExampleSize a TEG Dehydrator System for a Gas Stream to be dehydrated to meet the following requirements.
Gas flow Rate 10.0 mm sfc/day
Gas specific Gravity 0.70
Operating Line Pressure 1000. 0 psig
Contactor Max. Working Pressure 1440.0 psig
Gas Inlet Temperature 100 0F
Outlet Gas Water Content 7.0 lb H2O/mm scf
Selected Design Criteria:
TEG to Water Circulation Rate 3.0 galTEG/lb H2O
Lean TEG Concentration 99.5 % TEG
Use Trayed-Type Contactor With Valve Trays
Contactor Sizinga. With Gas Flow Rate of 10.0 mm scf/day and 1000 psig Operating Pressure, From Fig 4-51a Select 24 Diameter.
b. Approx. Gas Capacity at 24 Diameter and 000 psig = 11.3 mm scf/day
c. From Table 4- 6, Ct = 1 and Cg = 1
qo = qs . Ct . Cg = 11.3 x 1.0 x 1.0 = 11.3 mm scf/day
SLIDE 212
TEG Dehydration Design Example
Dew point Depression and Water Removed.
From Fig. 4-53
Dew Point Temp. Water Co lb. H2O/mm cf ntent
Inlet 100 0F 61
Outlet 33 0F 7
67 0F 50 lb. H2O/mm cf
3. Required Number of Trays
1. Using Sivalls Chart Fig 4-54
With Dew Point Depression - 67 0F
TEG to Water Circulation Rate(Lw) - 3.0 gal. TEG/lb. H2O
No. of Trays = 4.5
.2. Using McCabe-Thiele
i. Lean TEG Density = 1.11 x 8.34 = 9.266 lbm/gal.
ii. Rich TEG Conc. =
= 0.995 x 9.266 = 0.96 = 96%
9.266 + 1/3 w
i
i
L
ConcTEGLean
1
.)(
4/16/2013
107
SLIDE 213
TEG Dehydration Design Example
iii. Operating Line Points.
Column Top 7.0 lb. H2O/mm cf and 99.5 % TEG
Column Bottom 61 lb H2O/mm cf and 96.0 % TEG
iv. Equilibrium Line Points
Percentage TEG Equilibrium dew Point Water Content of Gas
Temperature at 100 0F at Dew Point Temperature
And 1000 psig
______________ _________________ ___________________
99 12 3.2 lb. H2O/mm cf
98 30 6.3
97 40 9.0
96 47 11.7
95 51 13.3
v. Construct McCabe-Thiele Diagram See Fig 4-55
Number of Theoretical trays = 1.48
Number of Actual trays = 1.48 = 4.44 = 5
0.33
SLIDE 214
TEG Dehydration Design Example
McCabe-Thiele Diagram
4/16/2013
108
NNPC FSTP Engineers
Natural Gas Processing and Transmission
Course Code:
Lesson 5
Lesson 5
LNG and GTL Processes
4/16/2013
109
Lesson 5 Contents
LNG Process
GTL Process
Lesson 5
LNG Process
4/16/2013
110
SLIDE 219
Liquefied Natural Gas (LNG)
Definition of LNGNatural gas is cooled through cryogenic refrigeration to - 260 0F (-162 0C) to form Liquefied Natural Gas.
The LNG is 1/600th the volume the natural gas, which makes it feasible to transport it over long distances.
It is Flammable in 5-15% concentration
It is a Cleaner burning gas
Special LNG vessels load LNG at the liquefaction facility and transport it to regasify at import terminals in remote demand and offshore locations
At these import terminals, LNG is warmed back to natural gas, and nally pumped into pipelines and sent to market.
LNG Process
Customers
Shipping RegasificationProduction Liquefaction
4/16/2013
111
SLIDE 221
Liquefied Natural Gas Process
Basic LGN Train
Vaporization
Industry Users
ResidentialCommercial& Industry
Vaporization Storage
ShippingRoad Transport
Storage at PlantLNG Processing PlantGas Supply from Field
Loading LNG Containers
Supply Station
SLIDE 222
Liquefied Natural Gas Process
Basic Processes involved in LNG
Transportation
Pressure Equalization
Condensate Removal
CO2, H2S and Mercury Removal
Dehydration
Refrigeration
Liquefaction
Storage and Loading
Transportation and Marketing
4/16/2013
112
SLIDE 223
Liquefied Natural Gas Process
Raw material to LNG
SLIDE 224
Nigerian Liquefied Natural Gas
NLNG Natural Gas Liquefaction Process Bonny LNG Simplified Process Flow Diagram
4/16/2013
113
SLIDE 225
Nigerian Liquefied Natural Gas
Gas Inlet Facilities Natural gas received from suppliers is scrubbed for hydrocarbon liquids (C5 +) and undergoes pressure control at the Pressure Control Station which ensures plant has stable supply pressure of 70-90b(g) reduced to 54b(g).
Further resultant condensate generated from this process is separated out. Other facilities include pigging of transmission lines from suppliers.
Acid Gas Removal ProcessThis removes acid gasses of CO2 & H2S by absorption using circulating amine solution to prevent corrosion & freezing at low temperatures
Dehydration ProcessDrying of the gas is ensured by using molecular sieve beds to adsorb water to prevent ice & hydrate formation at low temperatures
SLIDE 226
Nigerian Liquefied Natural Gas
Mercury Removal ProcessIn the NLNG, Gas from Soku contains traces of mercury. Activated carbon bed process is employed to remove trace quantities of mercury to prevent attack on aluminium tubing found in the Main Cryogenic Heat Exchangerof a combined cycle power plant.
Liquefaction Process The refrigeration system employed in the cooling of the gas to liquid state is Propane Pre-cooled Mixed Refrigerant System.
The gas is pre-cooled by propane mechanical compression refrigeration system to -17oC to remove C5, aromatics & some LPG is routed to the fractionation section.
The sweet natural gas (C1,C2,C3 & C4 ) is now liquefied in 2 stages involving initial cooling with propane refrigeration to -38oC followed by further cooling against mixed refrigerant in the MCHE to -161oC.
The mixed refrigerant comprises of Nitrogen, Methane, Ethane & Propane
4/16/2013
114
SLIDE 227
Nigerian Liquefied Natural Gas
Liquefaction Process
SLIDE 228
Nigerian Liquefied Natural Gas
Fractionation ProcessDistillation columns are used to separate LPG into fractions to be used for make up propane & mixed refrigerants or re-injection into LNG.
The functions of the Fractionation Unit are:
To produce an acceptable ethane and propane make-up to the refrigerant
cycles.
To reject methane into the HP Fuel Gas system.
To recover LPG for re-injection into the LNG product.
To produce a condensate product with a specified vapor pressure.
Fractionation (Liquid Handling Unit)
LPG from all trains, separates Propane & Butane for storage & exportof a
combined cycle power plant.
4/16/2013
115
SLIDE 229
LNG Storage & LoadingThe LNG from the main heat exchanger is stored in three 84,000m3 full containment above ground cryogenic storage tanks. Each tank is fitted with 3 loading pumps capable of a combined loading rate of 10,000m3/hr through 2 loading arms, a third arm is provided for vapour return during loading. The returned vapour is compressed and routed to the plant fuel gas system. LNG Carriers are of both membrane and spherical tank type and have a capacity of 122,000 - 132,000m3
LPG Storage & LoadingPropane and butane from the fractionating tower are stored separately in two refrigerated tanks each with a capacity of 65,000m3 . Propane being stored at -45oC and Butane at -5oC. Each tank is provided with three pumps designed to load refrigerated LPG ships a a rate of 3000m3 /hr. Chilling of the Propane & Butane as well as re-liquefaction of tank boil off is done in a propane refrigeration unit.
LNG Loading & Transportation
SLIDE 230
LNG Loading & Transportation
Condensate Storage & Loading Condensate from the inlet gas processing plant is stored in two 36,000m3 floating roof tanks. Five loading pumps (+ 1 spare) rated at 800m3 provide the ability to load a typical 60,000m cargo in approximately 16 hours through two loading arms.
The sphere tank The membrane tank
Shipping Tank Configurations
4/16/2013
116
Land-based Terminal Platform Terminal
Floating Storage & Regasification Unit
LNG Loading & Transportation
SLIDE 232
Regasification is the physical process whereby liquefied natural gas (LNG) is heated to its gaseous state.
The regasification process entails pumping the LNG, under high pressurethrough various receiving terminal piping components where it is heated by direct-fired in a controlled environment.
The re-vaporized natural gas is regulated for pressure and enters the sales pipeline system for delivery to consumers
LNG import (regasication) terminals can be onshore-terminal or oshore-onboard.
At an onshore terminal, a conventional LNG carrier (LNGC) unloads its LNG cargo to the storage tanks and the LNG in then regasied at the regasication unit and pumped into the local natural gas pipeline.
At an oshore terminal, LNG is regasied onboard specialized transport vessels that connect directly to pipeline.
LNG Regasification
4/16/2013
117
SLIDE 233
LNG Regasification
Lesson 5
GTL Process
4/16/2013
118
Gas to Liquids describes Technology that carries out a chemical transformation process which converts natural gas(CH4) into products such as fertilizers, methanol or liquid hydrocarbons such as diesel, kerosene and waxes, which are readily transported to any location.
It is a chemical process involving the polymerization of methane molecule to form chain and cyclic hydrocarbons
Basic Process of GTL Technology
Gas to Liquid Process
Basic Process Blocks of GTL TechnologyThree Basic Steps are involved in the GTL Technology converting natural gas to GTL
Gas to Liquid Process
Step 1
Step 3
Step 2
4/16/2013
119
Process Block 1Steam Reforming of natural gas into synthesis gas (a mixture of hydrogen and carbon monoxide) also called syngas for short
It can be produced from other sources than natural gas: biomass, coal or even heavy oil residue are all possible.
Natural gas is particularly convenient for several reasons
Synthesis Gas need to undergo sweetening to remove contaminants before FT process
Process Block 1Two processes may be used to convert methane into syngas: Natural gas autothermal reforming (ATR). CH4 may be converted into syngas via a reaction with water (steam) and oxygen O2 :
2CH4 + O2 + H2O 5H2 + 2COOR
with water (steam) and carbon dioxide CO2: 2CH4 + O2 + CO2 3H2 + 3CO + H2O
Both reactions are exothermic (they produce heat), and the temperature of the syngas produced is around 1000 OC.
Steam methane reforming (SMR).CH4 may also be converted to syngas using only water. It requires a high temperature
(700-1000 OC) and occurs in presence of a Nickel based catalyst. CH4 + H2O CO + 3 H2
This method is most used produce syngas (also used to produce ammonia-based fertilizers).
4/16/2013
120
Process Block 2 - Fisher-Tropsh SynthesisIt uses a catalyst(mostly iron or cobalt base) to convert hydrogen (H2) and carbon monoxide (CO) into higher hydrocarbons, mostly normal paraffins (alkanes CnH2n+2)
The chosen catalyst and process conditions will determine the composition of products, ranging from
gasoline to diesel and waxes.
The Main reaction at Fischer Tropsch Reactor1