All Natural Gas Slides

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


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


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


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)


4/16/2013

5

Version

HC States Phase Diagrams

Temperature

Pressure

Dry GasGas Condensate

Light Oil

Heavy Oil


VersionTemperature

Pressure Gas OutFeed Liquid

Liquid Out

Separator Conditions (P,T)

Bubble Point (Liquid Out)Dew Point (Gas Out)


Changing Phase Diagram with Separation

4/16/2013

6

SLIDE 11


SWEETENING

SpecificationsPTWater Dew PointHC Liquid Dew Point

HC LIQUID REMOVAL

DEHYRATION

Basic Natural Gas Processing Train


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


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


4/16/2013

8

Lesson 4-1

Heat Transfer Processes

Treatment 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 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


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


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


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


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


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


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


Vapour Compression Refrigeration Process Cycle

4/16/2013

26

SLIDE 51


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


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


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


Separator


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



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


Separator


Inlet Gas

SLIDE 68

Demethanizer

Separator

Separator

Exchangers

Compressor

Expander


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


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.


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.


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.


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


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.


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


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.


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


4/16/2013

47

SLIDE 93


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 .


4/16/2013

48

NNPC FSTP Engineers


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


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


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 Structures.

.

4/16/2013

55

Ono SLIDE 109


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


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


.

62

3

Correlation Lines

4/16/2013

62

SLIDE 123


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


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


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)


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


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


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.


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


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 Sieve Structure Diameter.

4/16/2013

72

SLIDE 143

..


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


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


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


NATURAL GAS

Rich Glycol

NG

WaterMolecules

SLIDE 152


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


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


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


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


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


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


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


Gasflow

Liquidflow

VALVE PLATE

Valve open(Gas flows)

Valve close(No Gas flow)

Liquid inlet

Liquid outlet

Gas inlet

Gas outlet


4/16/2013

83

SLIDE 165

Packed Columns.

.

Packed ElementsIntalox Packing

SLIDE 166


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


SLIDE 168


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


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


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


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


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)


Dehydration

Cooling CoolingCoolingCondensate Extraction


Compression(70 bar)

Compression(30 bar)

Sales Gas

InletGas

4/16/2013

89

Typical Compression Station

NNPC FSTP Engineers


Course Code:

Lesson 4

4/16/2013

90

Lesson 4-4

Dehydration

SLIDE 180


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


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


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


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


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


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


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


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


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


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


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


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


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


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


Sivalls Number of Trays/Packing Chart

4/16/2013

99

SLIDE 197


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


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


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


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


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


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


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


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


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


SLIDE 208


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


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


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


McCabe-Thiele Diagram

4/16/2013

108

NNPC FSTP Engineers


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


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


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


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


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


Liquefaction Process

SLIDE 228


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


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


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

Date post:	13-Oct-2015
Category:	Documents
Upload:	chiviya-viya-fariku
View:	54 times
Download:	0 times

All Natural Gas Slides

Documents