Process Engineering for a Small Planet

Methods for more planet-friendly process engineering

Our earth is just one big, complex Process Facility with limited air, water, and mineral resources. It responds to a number of process variables—among them, humanity and the environmental effects of our carbon consumption. What can professionals in the Hydrocarbon Process Industry do to retard environmental degradation? Rather than looking to exotic technology for solutions, Process Engineering for a Small Planet details ready-at-hand methods that the process engineer can employ to help combat the environmental crisis.

Drawing from the author's professional experience working with petroleum refineries petroleum refineries, petrochemical plants, and natural gas wells, this handbook explains how to operate and retrofit process facilities to:

• Reuse existing process equipment
• Save energy
• Reduce greenhouse gas emissions
• Expand plant capacity without installing new equipment
• Reduce corrosion and equipment failures

Covering topics from expanding fractionator and compressor capacity and vacuum tower heater expansion to minimizing process water consumption and increasing centrifugal pump capacity, Process Engineering for a Small Planet offers big ideas for saving our small planet.

Foreword xv

Preface xvii

Introduction: Turning of the Tide 1

1. Expanding Fractionator and Compressor Capacity 3

Reuse of Existing Fractionator

Changing Tray Deck Panels

Alternates to New Compressor

Keeping Compressor Rotor Clean

Calculating Liquid Injection Rates to Compressor

2. Vacuum Tower Heater Expansion 17

Entrainment Velocity Limitations

Missing Tray Deck Manways

Heater Draft Limitation

Improving Ejector Performance

Velocity Steam in Heater Passes

3. Natural-Draft-Fired Heaters 27

Control Excess Air

O₂ and Combustible Analyzers

Improving Air–Fuel Mixing

Convective Section Air Leaks

Air Preheater Leaks

Indirect Air Preheat

4. Crude Pre-Flash Towers 37

Pre-Flash Tower Flooding

Energy Saving with Pre-Flash Towers

Capacity Benefits

Pre-Flash Tower External Reflux

5. Amine Regeneration and Sulfur Recovery 47

Amine Capacity Expansion

Sulfur Plant Capacity Expansion

Rich Amine Flash Drum Design

Cascaded Seal Legs

Sulfur Recovery from Sour Water Stripper Off-Gas

Acid Gas of High CO₂ Content

Sulfur Plant Oxygen Enrichment

6. Treating and Drying Hydrocarbons 59

Jet Fuel Treating

Salt Dryer Operation

Water-Washing Sodium Naphthanates from Jet Fuel

Pipe Distributor Design

Treating Sour Naphtha

Converting Mercaptans to Disulfides

7. Minimizing Process Water Consumption 71

Two-Stage Wastewater Stripper

Steam Condensate Recovery

Condensate Drum Balance Line Location

Water Hammer

Measuring Condensate Recovery

Cooling Tower Cycles of Concentration

8. Incremental Expansion Design Concept: Reprocessing Waste Lube Oil 79

Reprocessing Waste Lube Oil

Vacuum Tower Design

Wash Oil Grid Coking

Vapor Horn Design in Vacuum Towers

Stripping Tray Efficiency

Precondenser Fouling

Pump NPSH Limit in Vacuum Service

Exchanger Fouling in Waste Oil Service

Transfer-Line Sonic Velocity

9. Improving Fractionation Efficiency in Complex Fractionators 91

Pre-Flash Tower Concept

Intermediate Reflux

Stripping Tray Efficiency

Maximizing Diesel Recovery from Crude

Picket Weirs

Adjusting Pump-arounds

Pressure Optimization

10. Increasing Centrifugal Pump Capacity and Efficiency 103

Hydraulic Limitations

Worn Impeller-to-Case Clearances

Impeller Wear Ring

Upgrading Impeller Size

Marginal Cavitation

Viscosity Effects on Efficiency

NPSH Limited Condition

11. Eliminating Process Control Valves Using Variable-Speed Drivers 113

Frequency Control of Motors

Eliminating Control Valves on Pump Discharge

Direct Speed Control of Steam Turbine

Variable-Speed Compressors

Spill-backs Waste Energy

Calculating Incentive for Variable-Speed Drivers

Floating Tower Pressure Control

12. Expanding Refrigeration Capacity 123

Centrifugal Compressor Head vs. Flow Curve

Calculating Compression Work

Horsepower vs. Suction Pressure Limited

Effect of Increasing Suction Pressure

Reducing Refrigerant Condenser Fouling

Effect of Noncondensibles

Condensate Backup in Condenser

13. Oversizing Equipment Pitfalls 135

Amine H₂ S Scrubber

Optimizing Number of Trays in Absorbers

Consequences of Overdesign

Use of Demister in Knockout Drum

Low Demister Velocity Promotes Mist Entrainment

14. Optimizing Use of Steam Pressure to Minimize Consumption of Energy 145

Preserving the Potential of Steam to Do Work

Power Recovery from Steam to a Reboiler

Use of the Mollier Diagram

Cogeneration Plants

Extracting Work from Reboiler Steam Using

Existing Equipment

Understanding Thermodynamics of Flowing Steam

Steam Turbine Efficiency Checklist

15. Expanding Compressor Capacity and Efficiency 157

Reciprocating Compressors

Pulsation Dampener Plates

Adjustable Head-End Unloaders

Natural Gas Engines

Axial Compressor

Rotor Fouling of Axial Air Compressor

Centrifugal Compressors

Cleaning Centrifugal Compressor Rotor

16. Vapor–Liquid Separator Entrainment Problems 171

Effect of Foam on Indicated Liquid Levels

Hydrogen-Heavy Gas Oil Separtors

Foam Induced Carry-Over

Enhancing De-Entrainment Rates

Vapor Distribution Aids De-Entrainment

17. Retrofitting Shell-and-Tube Heat Exchangers for Greater Efficiency 179

Running Slops Without Fouling

Floating Suction in Charge Tanks

Exchanger Online Spalling

Effect of Feed Interruptions

Tube Velocity and Surface Roughness

Shell-Side Seal Strips

Cooling High-Viscosity Fluids

Expanding Water Cooler Capacity

Hydrocarbon Losses to Cooling Towers

18. Reducing Sulfur and Hydrocarbon Emissions 189

Sulfur Plant Waste Heat Boiler Modifications

Hydrocarbon Leaks in Seawater Cooling Systems

Incinerator Back-Fire in Sulfur Plant Main

Reaction Furnace

Loss of Draft Due to Air Leaks

Global Emissions in Perspective

19. Hydrocarbon Leaks to the Environment 201

Measuring Leaks Through Valves

Fixing Leaking Valves On-Stream

Detecting Leaking Relief Valves

On-Stream Repair of Leaking Relief Valves

Measuring Flows in Flare Lines

Leaks into Cooling Water

Air Cooler Leaks

Valve Stem Packing

Leaking Pump Mechanical Seal and Improper Use of Seal Flush

Fixing Weld Leaks On-Stream

20. Composition-Induced Flooding in Packed Towers: FCU Fractionator Expansion 209

Fluid Cracking Unit Fractionator Expansion

Flooding of Slurry Oil P/A Sections

FCU Fractionator Vapor Line Quench

Multipump Piping Stress Analysis

Perception vs. Reality in Process Design

21. Maintenance for Longer Run Lengths 219

Sulfuric Acid Regeneration

Importance of Reactor Insulation

On-Stream Piping Repairs

Preserving Pump Mechanical Seals

Concept of Avoiding Unit Shutdowns

22. Instrument Malfunctions 229

Control Valve Loss Due to Instrument Air Pressure Signal

Stuck Flow Control Valve Stem

Mislocated Liquid-Level Tap

Reducing Load to Vacuum System by Correcting False Level Indication

23. Summary Checklist for Reuse of Process Equipment 237

Fired Heaters

Heat Exchangers

Fin-Fan Air Coolers

Distillation Tower Trays

Vapor–Liquid Separators

Centrifugal Pumps

Fixed-Bed Reactors

Electric Motors

Gas and Steam Turbines

Reciprocating and Centrifugal Compressors

Air Blowers

Water–Hydrocarbon Separators

Overcoming Utility System Limits

24. Water–Hydrocarbon Separation: Corrosive Effects of Water 245

Water–Oil Separators

Corrosive Elements from Cracking Plants

Water Traps in Strippers

Current CO₂ Levels

Environmental Overview

Appendix: Solar Power Potential 257

Index 259

NORMAN P. LIEBERMAN is an independent process design engineer and field troubleshooter. His clients are refineries and petrochemical plants. He is well known in the process industry for his seminar "Troubleshooting Process Operations," which has been presented to over 16,000 engineers and plant operators.