Gas Dehydration Field Manual


  • Maurice Stewart, President, Stewart Training Company
  • Ken Arnold, Ken Arnold Consulting Inc.

Gas Dehydration Field Manual presents different methods of gas dehydration, focusing on the differences between adsorption and absorption. It discusses the various designs and operations in a gas processing facility. As an introduction, the book provides different concepts and theories that describe the gas processing industry. It then discusses the processes involved in the gas processing industry, which include absorption, adsorption, glycol regeneration, glycol filtration, and carbon purification. The book is divided into three parts. The first part discusses some of the basic terms and concepts of gas dehydration. The second part focuses on the factors involved in the different gas-dehydration methods. It also describes the difference between absorption and adsorption, as well as the process involved in glycol dehydration. The last part of the book discusses the proper care, maintenance, and troubleshooting methods of glycol dehydration process. This book is mainly designed for engineers, technologists, and operating personnel in the gas processing industry. Aside from engineers and process designers, readers who are interested in the different processes involved in gas dehydration will find this book a useful guide and reference.
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Production Engineers, Reservoir Engineer ,Chemical Engineers, Petroleum Engineers, Pipeline Engineers, Any engineers working with the production, transportation, or drilling of natural gas


Book information

  • Published: August 2011
  • ISBN: 978-1-85617-980-5

Table of Contents

Part 1 Hydrate Prediction and Prevention



         Dew Point

         Dew Point Depression

         Why Dehydrate?

    Water Content of Gas


         Partial Pressure and Fugacity

         Empirical Plots

         Sour Gas Correlations

         Effect of Nitrogen and Heavy Ends

         Example 1-1: Calculation of Water Content in a Sour Gas Stream


         Amount of Water Condensed

    Gas Hydrates

         What Are Gas Hydrates?

         Why Is Hydrate Control Necessary?

         What Conditions Are Necessary to Promote Hydrate Formation?

         How Do We Prevent or Control Hydrates?

    Prediction of Operating Temperature and Pressure

         Wellhead Conditions

         Flowline Conditions

         Calculation of Temperature and Pressure at the Wellhead

         Calculation of Flowline Downstream Temperature

    Temperature Drop Determination


         Temperature Drop Correlation

         Example 1-2: Determine the Temperature Drop across a Choke

    Hydrate Prediction Correlations


         Vapor-Solid Equilibrium Constants

         Pressure-Temperature Curves

         Equations of State Calculations

         Vapor-Solid Equilibrium Constants

         Example 1-3: Determination of Hydrate Formation Temperature Using Vapor-Solid Constants

         Pressure-Temperature Curves

         Example 1-4: Determine the Hydrate Formation Temperature Using Pressure-Temperature Correlations

    Hydrate Prevention


         Adding Heat

         Temperature Control

         Chemical Injection

         Comparison of Hydrate Prevention Methods

         Summary of Hydrate Prevention Methods

    Hydrate Inhibition

         Hammerschmidt Equation

         Determination of Total Inhibitor Required

         Procedure for Determining Inhibitor Requirements

         Example 1-5: Determining the Amount of Methanol Required in a Wet Gas Stream


Part 2 Dehydration Considerations



         Process Overview

         Principles of Adsorption

         Process Reversal

         Mass Transfer Zone (MTZ)

         Principles of Operation

         Effect of Process Variables

         Example 2-1: Determination of Pressure Drop through a Dry Bed Desiccant Dehydration Tower


         Inlet Gas Cleaning Equipment

         Adsorber Tower

         Insufficient Gas Distribution

         Inadequate Insulation

         Improper Bed Supports


         Regeneration Gas Exchangers, Heaters, and Coolers

         Regeneration Gas Separator

         Control Valves

         Expander Plant Molecular Sieve Applications

    Desiccant Performance

         General Conditions

         Moisture Analyzer

         Effect of Contaminants in Inlet Feed Stream

         Effect of Regeneration Gases Rich in Heavy Hydrocarbons

         Effect of Methanol in the Inlet Gas Stream

         Useful Life

         Effect of Insufficient Reactivation

         Effect of High Reactivation Temperature

         Areas Requiring Engineering Attention

         Example 2-2: Preliminary Solid Bed Desiccant Design


         Process Overview

         Principles of Absorption

    Glycol Dehydration

         Principles of Operation

         Gas System

         Glycol System

         Effect of Operating Variables

    System Design

         Sizing Considerations

         Inlet Microfiber Filter Separator

         Glycol Gas Contactor

         Contactor Diameter

         Tray Design

         Tray Spacing

         Glycol Circulation Rate

         Lean Glycol Concentration

         Glycol-Glycol Preheater

         Glycol-Gas Cooler

         Glycol-Glycol Heat Exchanger

         Gas-Glycol-Condensate Separator


         Heat Duty

         Fire Tube Sizing

         Reflux Condenser

         Stripping Still Column

         Diameter Size


         Amount of Stripping Gas


         Glycol Pumps

         Still Emissions

    Mercury Considerations



    Special Glycol Dehydration Systems

         General Considerations

         Drizo (wt.-2) Process

         Cold Finger Condenser Process

    Systems Utilizing Glycol-Gas Powered Pumps

    Systems Utilizing Electric Driven Pumps

         Example 2-3: Glycol Dehydration

    Nonregenerable Dehydrator

    Nonregenerable Dehydrator


         Calcium Chloride Unit

    Physical Properties of Common Glycols

Part 3 Glycol Maintenance, Care, and Troubleshooting

    Preventive Maintenance

         Scheduled Preventive Maintenance

         Five Steps to a Successful Preventive Maintenance Program


         Mechanical Maintenance

         Glycol Care

         Corrosion Control


         General Considerations


         Thermal Decomposition

         pH Control

         Salt Contamination




    Analysis and Control of Glycol

         General Considerations

         Visual Inspection

         Chemical Analysis

         Chemical Analysis Interpretation


         General Considerations

         High Dew Points

         Glycol Loss from the Contactor

         Glycol Loss from the Reconcentrator

         Glycol Loss-Glycol Hydrocarbon Separator

         Glycol Loss-Miscellaneous

         Three-Step Approach to Troubleshooting

         Glycol System Cleaning

    Eliminating Operating Problems

         General Considerations

         Inlet Scrubber/Microfiber Filter Separator


         Glycol-Gas Heat Exchanger

         Lean Glycol Storage Tank or Accumulator

         Stripper or Still Column

    Improving Glycol Filtration

         General Considerations

    Use of Carbon Purification

         General Considerations