1.6 Differences between solid–liquid and solid–gas separation
References
2. Fundamentals of separation science
Abstract Chapter Outline
2.1 Introduction
2.2 Liquid/gas systems
2.3 Liquid/liquid systems
References
Further reading
3. Industrial contaminants
Abstract Chapter Outline
3.1 Introduction
3.2 Origins and types
3.3 Characterizing contaminants
References
Further reading
4. Industrial filtration technologies
Abstract
Chapter Outline
4.1 Introduction
4.2 Gravity separators
4.3 Basket strainers
4.4 Filter press
4.5 Cyclonic separators and cyclo-filters
4.6 Disposable cartridge filters
4.7 Regenerable filters
4.8 Other filtration technologies
4.9 Filtration summary
References
Further reading
5. Industrial separation technologies
Abstract
Chapter Outline
5.1 Introduction
5.2 Liquid/liquid separation
5.3 Liquid-gas separations
5.4 Three-phase separations
References
6. Role of chemical additives
Abstract
Chapter Outline
6.1 Introduction
6.2 Surfactants
6.3 Typical chemical additives
6.4 Process applications
6.5 Effect on filtration/separation
References
Further reading
7. Effect of contamination on processes in the natural gas industry
Abstract
Chapter Outline
7.1 Introduction
7.2 Natural gas supply chain
7.3 Gas production at well head
7.4 Gas processing plant
7.5 Pipeline
7.6 Underground storage
7.7 Liquefied natural gas production
References
Further reading
8. Diagnostics and troubleshooting methods
Abstract
Chapter Outline
8.1 Introduction
8.2 Strategic approach
8.3 Field methods
8.4 Lab methods
8.5 Applications/case studies
References
9. Filtration and separation rating
Abstract
Chapter Outline
9.1 Introduction
9.2 Solid/liquid filter rating standards
9.3 Liquid/liquid separation rating standards
9.4 Solid/gas separation rating standards
9.5 Liquid/gas separation rating standards
9.6 Filter and coalescer characterization methods
References
Appendix 1. Conversion factors
Appendix 2. Cartridge diameter factors
Appendix 3. Carbon steel pressure vessel and nozzle diameters
Index
Copyright
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Dedication
This book is dedicated to my family which in these times has become even more significant than ever and especially to my wife, Donna, and children, Daniel and Shannon, for their pandemic support and patience with this project over the last 2½ years.
Thomas H. Wines
I wish to dedicate this book to my wife, Maryam, and my son, Sam, whose patience, understanding, and encouragement were essential to completion of this book. They contributed to this effort in ways that I probably will never know or understand.
Saeid Mokhatab
About the authors
Thomas H. Wines is currently a Director of Applications Development for Pall Corporation's Fluid Technologies and Asset Protection (FTAP) Group in Port Washington, NY, United States. Prior to assuming the above role, he was a Director of Product Management, Senior Marketing Manager, and Senior Staff Engineer for the Scientific and Laboratory Services Division at Pall. He has 33 years of experience in filtration, separation, and purification serving the refinery, gas processing, and chemical industries, and is a specialist in the fields of liquid–gas and liquid–liquid coalescing. He has authored over 50 technical publications and given numerous presentations in this field at professional societies. He holds a PhD in Chemical Engineering from Columbia University, and is a member of AIChE.
Saeid Mokhatab is recognized globally as a process technology expert in the fields of natural gas processing and liquefied natural gas (LNG). For over two decades, he has been actively involved in different aspects of several large-scale gas processing and LNG projects, from conceptual design through plant startup and operations support. He has contributed to the understanding of gas processing and LNG knowledge, practices, and technologies through 300 technical papers and three reference books (published by Elsevier in the US), which are widely read and highly respected. He founded the Elsevier peer-reviewed Journal of Natural Gas Science and Engineering and has served on the editorial/advisory boards of leading professional publications pertaining to gas processing and LNG. He has also been an active member of several professional societies, including the Society of Petroleum Engineers (SPE) and Gas Processors Association (GPA) Europe, and has served on the
technical program/advisory commi ee of many acclaimed gas processing conferences worldwide. As a result of his outstanding work in the natural gas industry, he has received a number of international awards and medals and has been listed in highly prestigious biographical directories.
Preface
Thomas H. Wines and Saeid Mokhatab
Natural gas revolutionized the global energy market over the last 20 years with the development of horizontal fracking of shale formations starting in the United States. This led to a boom in production that was so successful that it reduced the price of natural gas significantly and caused its own downfall with the crash of the gas production market. A second wave of production grew out of the need for chemical feedstocks from “wet” natural gas wells that contained significant natural gas liquids. A third wave is expected for the increase in liquefied natural gas (LNG) production to feed an energy hungry world.
The overall natural gas industry encompasses production from the wellhead sites, purification of the gas in processing plants, extensive transmission pipeline networks and ultimately liquefaction to make LNG. A multitude of process operations have been developed to accomplish these steps and the need for contaminant control is evident throughout these processes. In fact, a commerce sector has flourished due to contaminant control providing vital separation equipment, consulting, and application troubleshooting services. The subject of contaminant control, however, is usually overlooked in University courses and is mostly learned on the job and in many cases only after painful lessons by natural gas engineers.
Much of the information related to contaminant control is sca ered across various journal articles and may not be readily accessible. It was the authors’ intent to consolidate this information into one source for both convenience and continuity so that various aspects of this subject area could be compared, to consider their
benefits and potential limitations. In writing this work, the authors strived to provide practical and useful information for both the novice and the more experienced, providing more scientific depth in certain areas and sufficient technical references if the reader is so inclined to dive in deeper. One of the most difficult aspects of preparing this book was on how to balance the content between the overview of many topics and when and how far to delve into the scientific details.
A passion shared by both authors is the ability to diagnose, troubleshoot, and provide solutions to problems that arise in the natural gas industry. It is our hope that the information provided in this book on contamination control will provide the information needed to assist the reader for these purposes. The authors will be well served if this is accomplished and grateful if the readers find the materials interesting and of practical use.
Acknowledgments
An invaluable contribution to this book is the insight by experts in their specialties and applications. Special thanks are due to friends and colleagues, who encouraged, assessed, and made this book possible. Dr. Thomas H. Wines also expresses his sincere gratitude to some people at Pall Corporation that were invaluable in completing this work. Among them are Sean Meenan, Senior Vice PresidentFTAP Group, for his encouragement and allowing him the space to pursue this project in a demanding work environment; Michael Forzano, Chief IP Consul, for expediting the legal contract that preceded this project’s initiation; Suzanne Hennings, LibrarianResource Service, who provided excellent support in helping him navigate the research search engines and obtain permissions for use of figures and tables; Paul Jones, Director-Quality Assurance and Regulatory, for his quality and assurance reviews; and a special thanks to Dr. Ali Arshad, Senior Director-FTAP Group, for his time consuming, meticulous technical review and comments on the manuscript.
We deeply acknowledge the greatest help of Mr. Cris Heijckers and Mr. Guy Hellinx of Kranji Solutions Pte Ltd., Singapore, who prepared two sections on “Strategic Approach” and “Case Histories” in Chapter 8 (Diagnostics and Troubleshooting Methods). We also appreciate the editorial staff members of Elsevier who have been an excellent source of strong support during the preparation and publication of this book.
Disclaimer
This book is intended to be a learning tool. The materials discussed in this book are presented solely for educational purposes and are not intended to constitute design specifications or operating procedures. While every effort has been made to present current and accurate information, the authors assume no liability whatsoever for any loss or damage resulting from using them.
All rights reserved. This book is sold subject to the condition that it shall not by way of trade or otherwise be resold, lent, hired out, stored in a retrieval system, reproduced or translated into a machine language, or otherwise circulated in any form of binding or cover, other than that in which it is published, without the prior wri en permission of the authors and without a similar requirement including these conditions being imposed on the subsequent purchaser.
Fundamentals of filtration science
Abstract
Many factors go into deciding the type of separation equipment that should be used for a given application Having a basic understanding of how the separation is accomplished and what options are available are important to make the best choices to optimize plant operation. The objectives of this chapter are to introduce the most commonly found filtration and separation technology options used in the oil and gas industry and provide insights into the fundamental governing theory on how they work to lay a framework for further discussion.
1.2.1 Major types of separation equipment used to treat gas streams 2
1.2.2 Major types of separation equipment used to treat liquid streams 7
1 3 Darcy’s law 10
1 4 Capture mechanisms 13
1 4 1 Direct interception (sieving) 13
1.4.2 Inertial impaction 14
1.4.3 Diffusive capture 15
1 5 Filter life 16
1 5 1 Filter type 18
1 5 2 Void volume 18
1.5.3 Flux 19
1.6 Differences between solid–liquid and solid–gas separation 20 References 21
1.1 Introduction
Many factors go into deciding the type of separation equipment that should be used for a given application Having a basic understanding of how the separation is accomplished and what options are available are important to make the best choices to optimize plant operation. The objectives of this chapter are to introduce the most commonly found filtration technology options used in the oil and gas industry and provide insights into the fundamental governing theory on how they work to lay a framework for further discussion
1.2 Overview
The removal of contaminants in the oil and gas industry will generally fall into four categories: solids from liquid, solids from gas, liquids from gas, and liquids from liquids Filtration, separation and many of the terms used in the industry such as coalescer can have different meanings which can often time lead to confusion. The following conventions will be used for this book for the sake of clarity and to provide the reader with an overview of the various technologies available. The separations here are purely mechanical and removal of contaminants that are dissolved by any type of adsorption or by reaction are not covered. The major types of separation equipment used to treat gas and liquid streams along with commentary on the type of separation, separation mechanism, size removal, benefits, and drawbacks are described below. A brief overview of the separation equipment including the relative expenses are also given in Tables 1.1 and 1.2 for gas and liquid streams, respectively. In
many cases, an industrial application may use more than one of these technologies to achieve a desired separation and to meet cost goals.
Table 1.1
Overview of separation equipment used to treat gas streams.
Technology
Knock out Liquid–gas
Solid–gas Gravity >300 µm Non fouling, no expendab les, good for high concentra tion
Cyclone Liquid–gas
Solid–gas Centrifugal >10 µm Non fouling, no expendab les
Low efficiency $
Gas particle filter (disposa ble)
Blowback gas filter (regenerabl e)
Solid–gas Diffusive capture, inertial impacti on, direct intercep tion 1100 µm High efficiency, can select level of filtration
Solid–gas Diffusive capture, inertial impacti on, direct intercep tion
1-20 µm No expendab les, can handle high solids
Vane pack Liquid–gas Inertial impacti on >10 µm Non fouling, no expendab les, good for high concentra tion
Mesh pad Liquid–gas Inertial impacti on >10 µm Non fouling, no expendab les, good for high
Medium efficiency $$
Consumables/not economic at high solids $$
System–more complex, more difficult to operate, waste stream
Medium efficiency, performance affected by turndown $
Medium efficiency, performance affected by turndown $
Technology Separation type
Separation mechanism
Filter-sep Liquid–gas Solid–gas Inertial impacti on, direct intercep tion
Approx. size removal rating Benefits
concentra tion
>10 µm Improvement over mesh pad or vane pack for total liquid removal, has solid removal capabilitie s
Drawbacks Relative expense
Liquid–gas coalesce r (disposa ble cartridg e)
Liquid–gas Diffusive capture, inertial impacti on, direct intercep tion
>0.3 µm High efficiency, can select level of filtration
Medium efficiency, performance affected by turndown, not equipped to handle slugs $
Consumables/not economic at high solids $$
Table 1.2
Overview
Technology Separation type
Decanter Liquid–liquid Gravity >150 µm Non fouling, no expendab les, good for high concentra tion
Plate separato r Liquid–liquid Inertial impactio n >50 µm Non fouling, no expendab les, good for high concentra tion
Mesh pad Liquid–liquid Inertial impactio n >100 µm Non fouling, no expendab les, good for high concentra tion
Media bed Solid–liquid liquid–Liquid Inertial impactio n, direct intercept ion >10 µm Regenerable , low cost
Centrifugal separato r Solid–liquid liquid–liquid
Centrifugal force >5 µm Can handle high solids
Electrostatic coalesce r Liquid–liquid Electric field >10 µm Can handle high solids, no expendab les
Low efficiency, large footprint $$
Low efficiency, poor turndown efficiency $
Low efficiency, poor turndown efficiency $
Medium efficiency, potential channeling $
Equipment maintenance, Not economic for large flow rates
Poor performance with fine drops, electrodes can short out, $$S
Technology Separation type Separation mechanism Approx. size removal rating Benefits
Crossflow
filter Solid–liquid liquid–liquid Direct intercept ion
0.11 µm High efficiency, can handle high solids
Filter press Solid–liquid Direct intercept ion >5 µm No expendab les, can handle high solids
Liquid particle
filter (disposa ble)
Backwash
Solid–gas Direct intercept ion 1100 µm High efficiency, can select level of filtration
filter (regenerabl e) Solid–liquid Direct intercept ion 1-20 µm No expendab les, can handle high solids
Liquid–liquid coalesce r (disposa ble) Liquid–liquid Direct intercept ion, a ractiv e forces between the drops and coalescer medium fibers >1 µm High efficiency, can select level of filtration, 1–2 years’ life when protected by prefilter
Drawbacks Relative expense large footprint
System–more complex, more difficult to operate, waste stream $$$
Labor intensive, may bleed filter aid material $$
Consumables/not economic at high solids $$
System–more complex, more difficult to operate, waste stream $$$
Consumables/not economic at high solids $$
1.2.1 Major types of separation equipment used to treat gas streams
Knock out: Consists of a vessel with no internals that induces an expansion and resultant reduction in the velocity of the gas allowing for liquids to disengage from the flow and be collected at the bo om of the vessel. Knock outs are designed to catch slugs of liquids typically
with drops 300 µm and larger They are often used as a first stage separator followed by more efficient devices. Generally, knock outs are not affected by high solids and the separation mechanism is gravity. At reduced flow rates, they will exhibit improved separation.
Cyclone: A device that directs the gas flow in a circular motion to cause liquids to impact on the walls of a tube by centrifugal force. The liquids then drain downward by gravity to be removed. Cyclones can be made up of one single unit (vessel) or multiple smaller tubes that fit inside a vessel Typically, cyclones will have good removal efficiency for drops 10 µm and larger with multiple tubes Cyclones are used for liquid removal from gas and not affected by high solids levels. As the velocity of the gas swirling in the tubes increases, the separation efficiency and pressure drop will correspondingly increase, and the converse is true so that at reduced flow rates, cyclonic separators will lose efficiency
Gas particle filter (disposable): Consists of a disposable cartridge type filter that can have a number of configurations including: a pleated filter media wrapped around a metal core (out-toin flow), a melt blown depth media wrapped around a metal core (out to in-flow), and a pleated media coreless pack that fits into a permanent porous metal basket for support (in-to-out flow) Filter media can be different type of polymers including polyester, polypropylene, nylon, polyphenylene sulfide or can be made of other materials such as glass fiber or cellulose.
The gas flows through the filter media and solids are removed until the pressure drop increases to the point where the filter cartridge is changed Gas particle filters come in different efficiency ratings based on the type of media used and will span the range of 1-100 µm offering very high removal efficiencies for the rated micron size and above. Generally, they are used when solid contaminants are mid-to-low level concentrations as high solids can cause short service life and excessive change outs leading to poor economics. The separation mechanism is direct interception and diffusive capture. It is not affected by flow reduction and will either maintain or increase separation efficiency because of lowered flowrate
Blowback gas filter (re-generable): Consists of a permanent cartridge type filter that is either constructed of metal or ceramic media. The gas flows through the filter media from the out to the in direction and solids form a porous cake on the outside of the filter. At a set differential pressure, a pulse of pressurized gas is directed in the reverse flow direction to dislodge the collected solids that are then collected in a bo om chamber. The normal gas flow is then established, and the solids start to form another cake layer and the process is repeated. Blowback filters can last for multiple years before requiring a chemical cleaning They may last for decades before requiring replacement
Blowback filters will use filter medium that is in the few micron range in gas service. The filter media should not be exceedingly coarse as this would lead to plugging by the solids and a finer pore structure will allow these solids to form a cake and stay on the exterior of the media for long service life. Blowback applications are limited to processes that have solids that will form a cake (gasification/catalyst recovery) and usually where there are no sticky materials or liquids present Typically used for applications at high temperatures Blowback filters require a more complex system that includes gas nozzles and automated valve sequencing to create the back pulses and also will require a separate vessel or accumulator for the high-pressure gas.
The Blowback system will be inherently costlier for capital expenditure than disposable gas particle filters but will operate in harsher environments and economically at higher solids challenges to the filters. The separation mechanisms are direct interception, inertial impaction, and diffusive capture. It is not affected by flow reduction and will either maintain or increase separation efficiency as a consequence of lowered flowrate
Vane pack: Contains a series of parallel solid sheets with frequent bends that cause the gas flow to change direction repeatedly. Mostly constructed from metals but can also be made of plastics for compatibility reasons. Designed for liquid separation from gas and as the gas changes direction, any liquid drops with sufficient inertia will impact the vane walls and be separated
