Gas Sweetening and Processing Field Manual (eBook)

Front Cover 1
Gas Sweetening and Processing Field Manual 4
Copyright 5
Contents 6
Part 1: Gas Sweetening 12
Processing natural gas 12
Introduction 12
Natural Gas Processing 13
Oil and Condensate Removal 15
Water Removal 17
Glycol Dehydration 17
Solid-Desiccant Dehydration 19
Separation of NGLs 19
NGL Extraction 20
Absorption Method 20
Cryogenic Expansion Process 21
NGL Fractionation 22
Sulfur and Carbon Dioxide Removal 23
Gas Sweetening Plant 24
Acid gas considerations 25
Acid Gases 25
Sour Gas 25
Sweet Gas 25
Gas Sales Contracts Limit Concentration of Acid Compounds 27
CO2 27
H2S 27
Partial Pressure 27
NACE RP 0186 27
Sweetening processes 28
Solid bed processes 29
General Process Description 29
Iron Sponge Process 30
Application 30
Regeneration 32
Hydrate Considerations 34
Sulfa-Treat Process 35
Application 35
Molecular Sieve Process 36
Regeneration 36
Mechanical Degradation 37
Application 37
Zinc Oxide Process 37
Process 37
Bed Considerations 37
Application 38
Chemical solvent processes 38
General Process Description 38
Regeneration 38
Most Common Chemical Solvents 38
Amine Processes 38
Amine Considerations 38
Process Description 39
Methyldiethanolamine (MDEA) 41
Monoethanolamine (MEA) Systems 41
General Discussion 41
Regeneration 41
Disadvantages 41
Reclaimer 42
Corrosion Considerations 43
Foam Considerations 43
Micro-fiber Filter Separator 43
Blanket Gas System 43
MEA Losses 44
Summary 44
Diethanolamine (DEA) Systems 44
General Discussion 44
Reclaimer 44
Solution Concentration and Solution Loading 44
Amine Losses 45
Diglycolamine (DGA) Systems 45
General Discussion 45
Solution Concentration and Solution Loading 45
Advantages 45
Diisopropanolamine (DIPA) Systems 46
General Discussion 46
Advantages 46
Methyldiethanolamine (MDEA) Systems 46
General Discussion 46
CO2/H2S Ratio 46
Solution Concentration and Solution Loading 47
Advantages 47
Inhibited Amine Systems 47
General Discussion 47
Hot Potassium Carbonate Systems 48
General Discussion 48
Process Description 48
Performance 49
Dead Spot Considerations 50
Corrosion Considerations 50
Proprietary Carbonate Systems 50
Specialty Batch Chemical Solvents 50
General Discussion 50
Process Description 51
Performance 51
Sulfa-Check 51
Concentration Considerations 51
Bubble Flow 52
Disposal of Oxidizing Solution 52
Physical solvent processes 52
General Process Description 52
Fluor Solvent Process 54
Sulfinol Process 55
Acid Gas Loadings 56
Features of the Sulfinol Process Include 56
Design Considerations 56
Foam Considerations 56
Factors to Consider Before Selecting a Treating Process 56
Selexol Process 57
Rectisol Process 57
Direct conversion processes 58
General Process Description 58
Stretford Process 58
General Discussion 58
Process Description 58
IFP Process 60
General Discussion 60
Process Description 61
Ratio of H2S to SO2 61
LO-CAT 61
General Discussion 61
Process Description 62
Operating Considerations 62
Sulferox 62
Claus 62
General Discussion 62
Process Description 64
Tail Gas Treating 66
General Discussion 66
Sulfa-Check 66
General Discussion 66
Distillation process 67
Ryan-Holmes Distillation Process 67
General Discussion 67
Process Description 67
Three-Column System 67
Four-Column System 68
Two-Column System 68
Gas permeation process 68
Membranes 68
Definition 68
Applications 68
Membrane Permeation 69
Asymmetric Membrane Structure 71
Composite Membrane Structure 72
Membrane Elements 74
Flat Sheet 74
Hollow Fiber 75
Spiral Wound Versus Hollow Fiber 77
Major Vendors 77
Membrane Modules 77
Membrane Skids 78
Design Considerations 79
Process Variables Affecting Design 79
Flow Rate 79
Operating Temperature 79
Feed Pressure 79
Permeate Pressure 80
CO2 Removal 82
Other Design Considerations 83
Process Conditions 83
Environmental Regulations 83
Location 84
Fuel Requirements 84
Design Standards 84
Process Flow Schemes 84
Single-Stage Membrane Process (Figure 1-21) 84
Multistage Membrane Process 84
Two-Step Membrane Process 85
Two-Stage Membrane Process (Figure 1-22) 85
Multistage Membrane Process 85
Membrane Pretreatment 88
General Considerations 88
Pretreatment System Considerations 88
Traditional Pretreatment 89
Additions to Traditional Pretreatment 90
Chiller 90
Turbo-Expander 90
Glycol Unit 90
Enhanced Pretreatment 91
Need for Enhanced Pretreatment 91
Advantages of Membrane Systems 94
Lower Capital Cost (CAPEX) 94
Lower Operating Costs (OPEX) 94
Deferred Capital Investment 94
High Turndown 95
Operational Simplicity and High Reliability 95
Single-Stage Membrane Systems 95
Multistage Membrane Systems 95
Good Weight and Space Efficiency 96
Adaptability 96
Environmental Friendly 97
Design Efficiency 97
Power Generation 97
Ideal for De-bottlenecking 97
Ideal for Remote Locations 98
Process selection 98
Inlet Gas Stream Analysis 98
General Considerations 99
Removal of H2S to Meet Pipeline Qualities (4ppm) 99
Feeds with Small Acid Gas Loadings 99
Feeds with Moderate to High Acid Gas Loadings 99
Process Must Be Added Downstream of the Amine System 100
Normally Accomplished with 100
Amine-Based System 100
Gas Permeation 100
General Considerations 100
Feeds with Low Concentrations of CO2 100
Feeds with Increasing Concentrations of CO2 100
Selection Charts 101
Selection Procedure 103
Design procedure 104
Iron Sponge 104
General Considerations 104
Design Considerations 105
The Amine System 108
General Considerations 108
Amine Absorbers 108
Amine Circulation Rates 109
Heat of Reaction 112
Flash Vessel 114
Amine Reboiler 114
Amine Stripper 115
Overhead Condenser and Reflux Accumulator 119
Rich/Lean Amine Exchangers 122
Amine Cooler 123
Amine Solution Purification 124
Amine Solution Pumps 124
Procedure for Sizing an Amine System 125
Design examples (oilfield units) 126
Example Problem 1: Iron Sponge Unit 126
Example Problem 2: Amine Processing Unit (DEA) 129
Design examples (SI units) 139
Example Problem 1: Iron Sponge Unit 139
Example Problem 2: Amine Processing Unit (DEA) 142
Nomenclature 150
Part 2: Gas Processing 152
NGL recovery considerations 152
"Gas Processing" Is Used to Refer to the Removal of 152
Liquids May Be 152
Processing Objectives 152
Producing Transportable Gas 153
Condensation Has Two Drawbacks 153
Two Alternatives Exist 153
Meeting Sales-Gas Specifications 153
Most Gas Specifications Contain 153
If HC Is More Valuable as a Liquid 153
If HC Is More Valuable as a Gas 153
Maximizing Liquid Recovery 153
Value of NGL components 154
Ethane and Heavier HC Components (C2+) Can Be Liquefied 154
"Crude Spiking" 155
Gas processing terminology 156
Definitions of LPG and NGL 156
Liquid recovery processes 157
Any Cooling Will Induce Condensation and Yield NGL 157
Absorption/Lean Oil Process 158
General Considerations 158
In Most Lean Oil Plants 159
Liquid Recovery Levels 159
Disadvantages 160
Mechanical Refrigeration 160
Joule-Thomson (J-T) Expansions 162
Cryogenic (Expansion Turbine) Plants 162
Advantages 164
Process selection 164
If the NGL Content of the Feed Gas Is Low 165
For Gases Very Rich in NGL 165
If the Inlet Gas Pressure Is Very High 165
Low Inlet Gas Pressure 165
Very Low Gas Rates 165
Large Flow Rates 165
Remote Wells 165
Fractionation 165
Design considerations 166
Appendix A: Membrane/Amine Hybrid... 168
Introduction 168
Process overview 168
Background 168
General Considerations 168
First Commissioning 169
TSA design and performance 170
General Design Considerations 170
TSA Process Description 171
Reasons for Four Towers 172
Cycle Times and Breakthrough 172
Heat Recovery Between Cooling and Heating 172
Air liquide-medal membrane 174
General Considerations 174
Membrane Performance 176
Permeate/Acid Gas Utilization 177
Amine System 178
Appendix B: Judge Digby Gas Plant Hikes... 180
Judge digby plant 180
Debottlenecking 182
Preparing for the conversion 182
The turnaround 184
Plant operations 185
Betex emissions 186
Index 188