Abstract

Process Economics Program Report 135A NATURAL GAS LIQUIDS (December 2001)

Natural gas liquids (NGLs) are the C2+ liquefied hydrocarbons that are recovered above ground in natural gas field facilities or in gas processing plants. The principle products are ethane, propane, isobutane, n-butane, and C5+ natural gasoline. Besides the growing demand for these NGLs, some natural gas is also extracted to obtain marketability of the gas by reducing its dew point to below pipeline specification. Some natural gases contain impurities that are removed in treaters. Worldwide production of NGLs totaled over 246 million gallons daily in 2000. Due to increasing demand for environmentally clean burning fuels and increasing demand for petrochemicals such as ethylene and propylene, the demand for liquefied petroleum gas (propane and butane mixtures) is forecast to continue to grow at a faster rate than the demand for petroleum. Developments in the turboexpansion process and new technology, acid gas re-injection for example, are reducing costs of NGL recovery from natural gas. This report reviews the technology of gas treating and NGL recovery. Two of the most widely used recovery processes are evaluated: cryogenic turboexpansion, the leading process, and the refrigerated absorption process, an older process that ranks second in the U.S. and third worldwide in the production of NGLs. We have also evaluated a generic fractionator that produces ethane, propane, isobutane, n-butane and C5+ natural gasoline from mixed NGLs produced by extraction plants. This report should provide a useful overview of the natural gas liquids extraction industry and process developments within the industry for people involved in the energy industry, professionals who research, development or plan investments in the natural gas industry as well as those professionals who manage, plan, operate or do design work of existing plants.

PEP’ 135A RHN TABLE OF CONTENTS

TABLE OF CONTENTS ...... i TABLE OF TABLES ...... v TABLE OF FIGURES ...... x INTRODUCTION ...... 1-1 CONCLUSIONS ...... 2-1 SUMMARY ...... 3-1 COMMERCIAL ASPECTS...... 3-1 TECHNICAL ASPECTS...... 3-2 ECONOMIC ASPECTS ...... 3-3 INDUSTRY STATUS...... 4-1 NGL USES...... 4-2 NGL DEMAND AND SUPPLY ...... 4-2 NGL Demand ...... 4-3 Ethane Demand...... 4-4 Propane Demand...... 4-4 LPG Demand ...... 4-5 Butane Demand...... 4-4 NGL Supply ...... 4-7 Plant Capacity...... 4-9 Ethane Supply ...... 4-24 Propane Supply ...... 4-24 LPG Supply...... 4-25 Butanes Supply...... 4-25 Natural Gasoline...... 4-26 NGL Storage and Transportation ...... 4-26 NATURAL GAS DEMAND AND SUPPLY...... 4-27 Natural Gas Demand...... 4-28

iii Natural Gas Supply ...... 4-30 PRICING OF NATURAL GAS AND NGLs...... 4-30 Natural Gas Pricing ...... 4-31 NGL Pricing ...... 4-33 U.S. NGL Plant Gas Pricing ...... 4-37 RESERVES...... 4-38 Natural Gas Reserves...... 4-38 NGL Reserves...... 4-41 NATURAL GAS TREATING PROCESS REVIEW...... 5-1 WELLHEAD GAS COMPOSITION...... 5-3 NATURAL GAS SPECIFICATIONS ...... 5-4 NGL SPECIFICATIONS...... 5-5 NGL CONTAMINANTS AND IMPURITIES ...... 5-10 ACID GAS REMOVAL PROCESSES...... 5-16 Desulfurization...... 5-17 Physical Absorption ...... 5-20 Chemical Absorption...... 5-22

CO2 Removal...... 5-25 Selected Commercial Acid Gas Removal Processes ...... 5-28 Amine Processes...... 5-28 Sulfinol Process ...... 5-30 IFPEXOL Acid Gas Re-injection...... 5-33 Selected Developmental Processes ...... 5-34 Morphysorb Process...... 5-35 HCI Coastal Acid Gas Removal Process ...... 5-36 Hybrisol Process...... 5-36 Elf Activated MDEA Process for Acid Gas Re-injection ...... 5-37 Ultralean™ Amine Process ...... 5-38 CrystaSulf(sm) Liquid Redox Process ...... 5-38 SULFINT HP Process...... 5-39 SULFUR RECOVERY ...... 5-40 Claus Process ...... 5-40 TDA Direct Oxidation Process ...... 5-42 Tail Gas Treating...... 5-42

iv Clauspol II Process...... 5-44 DEHYDRATION...... 5-45 Twister™ Supersonic Separator ...... 5-46

N2 REMOVAL...... 5-47 MERCURY REMOVAL ...... 5-48 ENVIRONMENTAL EMISSIONS...... 5-50 NGL RECOVERY AND FRACTIONATION PROCESS REVIEW...... 6-1 TYPES OF PROCESSES...... 6-1 TURBOEXPANSION ...... 6-6 Thermodynamics...... 6-6 Vapor-Liquid Equilibrium ...... 6-7 Hydrate Formation...... 6-9 Equations of State ...... 6-9 Expander Processes ...... 6-10 Residue Gas Recycle-Reflux Process ...... 6-10 Gas Subcooled Process ...... 6-12 Delpro™ Process...... 6-13 Dephlexol Process...... 6-14 Case Studies ...... 6-15 REFRIGERATION ...... 6-17 Conventional Refrigeration...... 6-18 Mixed Refrigerants ...... 6-18 Ryan Holmes Process...... 6-21 Stothers Deep Cut Process...... 6-22 Case Studies ...... 6-23 REFRIGERATED ABSORPTION ...... 6-23 JOULE-THOMSON EXPANSION...... 6-23 ABSORPTION ...... 6-23 Mehra Process ...... 6-24 Case Studies ...... 6-25 ADSORPTION ...... 6-25 COMPRESSION ...... 6-26 MEMBRANE PROCESS...... 6-26 FRACTIONATION...... 6-26

v Case Studies ...... 6-27 ECONOMICS OF NGL EXTRACTION AND FRACTIONATION ...... 7-1 TURBOEXPANSION PROCESS...... 7-1 Process Description ...... 7-2 Section 100 – Feed Gas Guard Dryer...... 7-2 Section 200 – Extraction...... 7-3 Process Discussion...... 7-3 Capital Costs ...... 7-12 Production Costs ...... 7-18 Profitability ...... 7-19 REFRIGERATED ABSORPTION PROCESS ...... 7-23 PROCESS DESCRIPTION...... 7-24 PROCESS DISCUSSION...... 7-36 Capital Costs ...... 7-36 Production Costs ...... 7-40 Profitability ...... 7-40 NGL FRACTIONATION ...... 7-43 Process Description ...... 7-43 Process Discussion...... 7-44 Cost Estimates ...... 7-50 Capital Costs ...... 7-50 Production Costs ...... 7-50 Profitability ...... 7-51 APPENDIX A: PATENT SUMMARY TABLES...... A-1 APPENDIX B: DESIGN AND COST BASES ...... B-1 APPENDIX C: CITED REFERENCES...... C-1 APPENDIX D: CITED PATENTS...... D-1 APPENDIX E: PROCESS FLOW DIAGRAMS...... E-1

vi TABLE OF TABLES

3.1 SUMMARY OF COST ESTIMATES FOR NGL EXTRACTION ...... 3-5 4.1 NGL MARKETS...... 4-4 4.2 U.S. MARKET SHARE DEMAND FOR NGLS...... 4-4 4.3 RECENT WORLD LPG GROWTH AND FORECAST, %/YR...... 4-6 4.4 TOP 10 NGL PRODUCING COUNTRIES, 2000 ...... 4-8 4.5 DISTRIBUTION OF WORLD NGL PRODUCTION...... 4-8 4.6 WORLD NATURAL GAS PLANT LIQUIDS PRODUCTION, 1980-2000...... 4-10 4.7 WORLD NGLS PRODUCTION—2000 ...... 4-13 4.8 U.S. NGLS PRODUCTION—2000...... 4-16 4.9 NON-U.S. FRACTIONATOR PLANT CAPACITY—2000 ...... 4-17 4.10 U.S. FRACTIONATOR PLANT CAPACITY—2000...... 4-18 4.11 NEW PLANT CONSTRUCTION IN NORTH AMERICA ...... 4-12 4.12 NEW PLANT CONSTRUCTION OUTSIDE NORTH AMERICA...... 4-22 4.13 NATURAL GAS CONSUMPTION FORECAST FOR SELECTED REGIONS, TCF/YR.... 4-29 4.14 WORLD’S TOP 20 NATURAL GAS PRODUCING COUNTRIES, 2000 ...... 4-30 4.15 TYPICAL ASSOCIATED AND NONASSOCIATED NATURAL GAS COMPOSITIONS ... 4-31 4.16 WORLD NATURAL GAS RESOURCES...... 4-39 4.17 NATURAL GAS RESERVES AND PRODUCTION OF TOP 20 COUNTRIES ...... 4-40 4.18 NATURAL GAS RESOURCES, LOWER 48 STATES...... 4-41 4.19 ASSOCIATED GAS AND NGLS FROM ASSOCIATED GAS RESERVES BY REGION.. 4-42 4.20 U.S. NGL RESERVES AND PRODUCTION ...... 4-43 4.21 NATURAL GAS AVERAGE NGL CONTENT BY STATE ...... 4-44 5.1 NATURAL GAS WELLHEAD COMPOSITIONS ...... 5-4 5.2 U.S. PIPELINE NATURAL GAS SPECIFICATIONS...... 5-5 5.3 ONE SET OF Y-GRADE NGL SPECIFICATIONS...... 5-6 5.4 QUALITY OF COMMON ETHANE AND ETHANE-PROPANE MIXTURES...... 5-8 5.5 LPG PRODUCT SPECIFICATIONSA ...... 5-9 5.6 GPA NATURAL GASOLINE SPECIFICATIONS ...... 5-9

vii 5.7 GPA NATURAL GASOLINE GRADES ...... 5-10 5.8 POSSIBLE NGL CONTAMINANTS ...... 5-11 5.9 NGL CONTAMINENT SURVEY RESULTS ...... 5-13 5.10 CONCENTRATIONS OF NATURAL GAS CONDENSATE CONTAMINANTS...... 5-14 5.11 REGIONAL AVERAGE MERCURY LEVELS IN NATURAL GAS ...... 5-15 5.12 DISTRIBUTION OF MERCURY IN STEAM CRACKER EFFLUENT ...... 5-15 5.13 TYPES OF SULFUR REMOVAL PROCESSES ...... 5-17 5.14 ADSORBENT PROCESSES FOR ACID GAS REMOVAL...... 5-19 5.15 AMINE SOLVENT CHARACTERISTICS FOR ACID GAS REMOVAL ...... 5-23 5.16 TYPICAL SULFINOL PROCESS OPERATING DATA ...... 5-31 5.17 RANGES OF SULFINOL PROCESS FEEDSTOCK COMPOSITION AND CONDITIONS5- 32 5.18 MORPHYSORB PROCESS VS. MDEA ABSORPTION...... 5-36 5.19 MOLE SIEVE SELECTION GUIDE FOR NATURAL GAS DRYING ...... 5-46 5.20 DISTRIBUTION OF SOURCE OF LOSSES FROM FOUR OLDER PLANTS ...... 5-50 5.21 HYDROCARBON EMISSIONS FROM FUGITIVE EQUIPMENT LEAKS ...... 5-51 5.22 NATURAL GAS EMISSIONS FROM GAS PROCESSING INDUSTRY...... 5-51 6.1 DISTRIBUTION OF NGL PROCESSES - SUMMARY ...... 6-3 6.2 RECOVERY RATE OF NGLS FROM NATURAL GAS HEATING VALUE...... 6-4 6.3 RECOVERY OF NGL BY PROCESS ...... 6-4 6.4 MULTILEVEL MIXED REFRIGERATION VS. CONVENTIONAL REFRIGERATION ...... 6-21 7.1 FEED GAS COMPOSITIONS ...... 7-5 7.2 NGLS BY TURBOEXPANSION - DESIGN BASIS AND ASSUMPTIONS ...... 7-6 7.3 NGLS BY TURBOEXPANSION - PRODUCT YIELD AND PROPERTIES...... 7-7 7.4 NGLS BY TURBOEXPANSION - STREAM FLOWS (RICH GAS) ...... 7-8 7.5 NGLS BY TURBOEXPANSION - STREAM FLOWS (LEAN GAS)...... 7-9 7.6 NGLS BY TURBOEXPANSION - MAJOR EQUIPMENT (RICH GAS)...... 7-10 7.7 NGLS BY TURBOEXPANSION - MAJOR EQUIPMENT (LEAN GAS) ...... 7-11 7.8 NGLS BY TURBOEXPANSION - UTILITIES SUMMARY (RICH GAS)...... 7-12 7.9 NGLS BY TURBOEXPANSION - UTILITIES SUMMARY (LEAN GAS) ...... 7-12 7.10 NGLS BY TURBOEXPANSION - TOTAL CAPITAL INVESTMENT (RICH GAS)...... 7-14 7.11 NGLS BY TURBOEXPANSION - TOTAL CAPITAL INVESTMENT (LEAN GAS) ...... 7-15 7.12 NGLS BY TURBOEXPANSION - CAPITAL INVESTMENT BY SECTION (RICH GAS).. 7-16 7.13 NGLS BY TURBOEXPANSION - CAPITAL INVESTMENT BY SECTION (LEAN GAS) .. 7-17 7.14 NGLS BY TURBOEXPANSION - PRODUCTION COSTS (RICH GAS) ...... 7-19

viii 7. 15 NGLS BY TURBOEXPANSION - PRODUCTION COSTS (LEAN GAS)...... 7-21 7.16 NGLS BY REFRIGERATED ABSORPTION - DESIGN BASES...... 7-25 7.17 NGLS BY REFRIGERATED ABSORPTION - PRODUCT YIELDS AND PROPERTIES. 7-25 7.18 NGLS BY REFRIGERATED ABSORPTION - MAJOR STREAM FLOWS...... 7-28 7.19 NGLS BY REFRIGERATED ABSORPTION - MAJOR EQUIPMENT ...... 7-33 7.20 NGLS BY REFRIGERATED ABSORPTION - UTILITIES SUMMARY ...... 7-35 7.21 NGLS BY REFRIGERATED ABSORPTION - TOTAL CAPITAL INVESTMENT...... 7-38 7.22 NGLS BY REFRIGERATED ABSORPTION - CAPITAL INVESTMENT BY SECTION ... 7-39 7.23 NGLS BY REFRIGERATED ABSORPTION - PRODUCTION COSTS...... 7-41 7.24 NATURAL GAS LIQUIDS FRACTIONATION - PRODUCT YIELDS AND PROPERTIES 7-44 7.25 NATURAL GAS LIQUIDS FRACTIONATION - STREAM FLOWS...... 7-45 7.26 NATURAL GAS LIQUIDS FRACTIONATION - MAJOR EQUIPMENT...... 7-46 7.27 NATURAL GAS LIQUIDS FRACTIONATION - UTILITIES SUMMARY ...... 7-48 7.28 NATURAL GAS LIQUIDS FRACTIONATION -TOTAL CAPITAL INVESTMENT...... 7-49 7.29 NATURAL GAS LIQUIDS FRACTIONATION - PRODUCTION COSTS...... 7-52 A.1 NATURAL GAS LIQUIDS - PATENT SUMMARY ...... A-1

ix TABLE OF FIGURES

4.1 DISTRIBUTION OF FEEDSTOCK CAPACITY OF NGL PLANTS OUTSIDE THE U.S.... 4-20 4.2 DISTRIBUTION OF FEEDSTOCK CAPCITY OF NGL PLANTS IN THE U.S...... 4-20 4.3 QUARTERLY AVERAGE U.S. SPOT MARKET PRICES OF ETHANE AND PROPANE 4-34 4.4 QUARTERLY AVERAGE U.S. SPOT MARKET PRICES OF ISOBUTANE, NORMAL BUTANE AND NATURAL GASOLINE ...... 4-35 4.5 U.S. PRODUCER PRICE INDICES FOR NGLS AND CRUDE OIL ...... 4-36 4.6 NET ETHANE VALUE ABOVE FUEL VALUE SINCE 1995 ...... 4-36 4.7 RECENT TRENDS IN LOUISIANA/GULF OF MEXICO GAS LIQUIDS PRODUCTION AND NATURAL GAS PRICE ...... 4-37 5.1 INTEGRATED AMINE, MERCAPTAN REMOVAL AND SCOT TAIL GAS SYSTEMS ...... 5-2

5.2 N2 REJECTION AND THE RECOVERY AND PURIFICATION INTEGRATED WITH NGL EXTRACTION ...... 5-2 5.3 TYPICAL ACID GAS ABSORPTION USING PHYSICAL SOLVENTS...... 5-21 5.4 TYPICAL ACID GAS ABSORPTION USING CHEMICAL SOLVENTS ...... 5-22

5.5 CO2 REMOVAL PROCESS SELECTION CHART...... 5-26 5.6 SULFINOL PROCESS ...... 5-30 5.7 ADVANCED IFPEXOL RE-INJECTION SCHEME ...... 5-34 5.8 BASIC CLAUS PROCESS SCHEMATIC...... 5-41 5.9 SOUR GAS PROCESSING TRAIN WITH LIQUID REDOX TAIL GAS TREATER ...... 5-43 5.10 SCOT TAIL GAS SULFUR RECOVERY PROCESS...... 5-44 5.11 PSA REMOVAL OF NITROGEN BY THE MOLECULAR GATE PROCESS ...... 5-48 6.1 NGL RECOVERY VAPOR-LIQUID EQUILIBRIUM FOR A MULTICOMPONENT MIXTURE ...... 6-8 6.2 NGL RECOVERY THE EFFECT OF CRITICAL POINT LOCATION ON LIQUID-GAS RATIO...... 6-9 6.3 RESIDUE GAS RECYCLE-REFLUX PROCESS...... 6-12 6.4 GAS SUBCOOLED PROCESS...... 6-13 6.5 DELPHLEXOL PROCESS ...... 6-15

x 6.6 HEATING AND COOLING CURVES FOR CONVENTIONAL REFRIGERATION PROCESS ...... 6-18 6.7 HEATING AND COOLING CURVES FOR A MULTILEVEL MIXED REFRIGERATION PROCESS ...... 6-20 6.8 STOTHERS DEEP CUT PROCESS ...... 6-22 6.9 MEHRA PROCESS INTEGRATED WITH A REFRIGERATION PROCESS ...... 6-25 7.1 NGL BY RECYCLE REFLUX TURBOEXPANDER (RICH GAS) ...... E-3 7.2 NGL BY RECYCLE REFLUX TURBOEXPANDER (LEAN GAS)...... E-5 7.3 NGL BY REFRIGERATED ABSORPTION ...... E-7 7.4 NGL FRACTIONATION...... E-9

xi