PETROLEUM REFINING IN NONTECHNICAL LANGUAGE Fourth Edition William L. Leffler Disclaimer: The recommendations, advice, descriptions, and the methods in this book are presented solely for educational purposes. The author and publisher assume no liability whatsoever for any loss or damage that results from the use of any of the material in this book. Use of the material in this book is solely at the risk of the user.
Copyright © 2008 by PennWell Corporation 1421 South Sheridan Road Tulsa, Oklahoma 74112-6600 USA 800.com Marketing Manager: Julie Simmons National Account Executive: Barbara McGee Director: Mary McGee Managing Editor: Marla Patterson Production Manager: Sheila Brock Production Editor: Tony Quinn Book Designer: Susan E. Ormston Cover Designer: Charles Thomas Library of Congress Cataloging-in-Publication Data Leffler, William L. Petroleum Refining in Nontechnical Language — 4th ed.5’3--dc22 2008026094 All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transcribed in any form or by any means, electronic or mechanical, including photocopying and recording, without the prior written permission of the publisher.
Printed in the United States of America 1 2 3 4 5 12 11 10 09 08 PREFACE The secret of a good sermon is to have a good beginning and a good ending, then having the two as close together as possible. —George Burns If you have somehow been charmed by the ads of my publisher or beguiled by the word-of-mouth ravings of a colleague about the inestimable merit of this book, you probably don’t need an introduction to this subject. It’s not likely you would have opened the cover if you didn’t already have at least an uneasy feeling, and maybe a genuine need to know, about petroleum refining. In either event, you have come to the right place.
The layout of the material in this book is designed to satisfy three needs. It can be used as a reference book because there’s a good table of contents in the front, a good index in the back, and a glossary of terms. The book has been used extensively as a text for courses on refinery processes. A combination of lectures, reading, and problem solving should be very reinforcing.
Because most people do not have the luxury of listening to a lecturer like me, the layout is designed primarily for personal study. With that in mind, the dry material has been moistened with as much levity and practicality as I could render. For personal study the following plan might work. Chapters 1 and 2 are pleasant precursors, but chapter 3 on crude oil is the most important part of the book.
For what goes on inside a refinery, chapter 4 has a lot of mechanical detail that’s not fundamentally important. Don’t let it dismay you. The materials on vacuum flashing, cat cracking, alkylation, reforming, hydrocracking, and residue reduction are all important as lead-ins to gasoline and other product blending. Struggle through chapter 6 on chemistry.
xvi Petroleum Refining in Nontechnical Language The chapter on gasoline blending is the most fun (in a cerebral sort of way) because it deals with things familiar yet mysterious—car engines and octane numbers. For anyone in the business part of the business, the chapter on simple and complex refineries will wrap up all the processes into a nice economic package. The other chapters are like lagniappe, a nearly forgotten tradition where a Cajun merchant gives a small gift of appreciation at the time of sale. The information in those chapters, which reflect just as much labor on my part as the rest of the book, is useful but nevertheless not vital to understanding petroleum refining.
So plan to manage your attention span to work through at least the first 15 chapters. Many thanks go to the people who have contributed to this and earlier editions of Petroleum Refining in Nontechnical Language. This fourth edition has had the advantageous insights and inputs of Mike Dossey, longtime refining executive. With his guidance, omissions and commissions of previous editions have been dealt with.
Bob Awe and his authoritative views on lubricants helped me polish the new chapter on that subject to an acceptable patina. Robert Junge graciously filled me in on the nearly impenetrable turmoil in gasoline blending activities and the industry responses. Of course none of these could overcome my final say and massaging, and therefore I carry the ultimate responsibility for getting everything right. And as always, I benefited from my wife allowing me long hours of solitude while I ground away at research and prose.
CONTENTS List of Illustrations. xv 1 The Evolution of Petroleum Refining. 1 2 From the Oil Patch to the Refinery. 7 Oil Patch Operations.
11 3 Crude Oil Characteristics. 13 Crude Oil Composition. 25 The Simple Still. 25 The Distilling Column.
27 Reflux and Reboil. 33 Setting Cut Points. 39 vi Petroleum Refining in Nontechnical Language 5 Vacuum Flashing. 41 The Cracking Phenomenon.
41 Effects of Low Pressure. 45 Adjusting the Distillation Curve. 48 6 The Chemistry of Petroleum. 49 Atoms and Molecules.
52 Olefins and Aromatics. 56 7 Refinery Gas Plants. 57 Sats Gas Plant. 57 Cracked Gas Plant.
81 The Chemical Reaction. 89 The Chemical Reactions. 91 Contents vii The Hardware. 95 Continuous Cat Reforming.
101 The Hardware and the Reactions. 113 Thermal Cracking and Visbreaking. 116 Cat Cracking and Hydrocracking. 136 Petrochemical Blending Components.
138 Combating Smog and Ozone. 142 TOX, NOx, VOCs, and SOx. 142 Gasoline Blending: Impact on Operations. 146 15 Distillate and Residual Fuels.
147 Kerosene and Jet Fuel. 148 Automotive Diesel Fuel. 153 viii Petroleum Refining in Nontechnical Language Review. 155 16 Hydrogen, Hydrotreating, and Sulfur Plants.
167 Asphaltic Crude Oils. 175 Properties and Specifications. 192 20 Simple and Complex Refineries. 199 Same Refinery—Different Modes.
202 What Sets Prices. 205 21 Solvent Recovery of Aromatics. 208 Benzene and Aromatics Recovery. 211 Contents ix 22 Fuel Values—Heating Values.
213 Competitive Fuel Value Nomogram. 216 23 Answers to the Exercises. 249 1 THE EVOLUTION OF PETROLEUM REFINING Until the advent of the gasoline engine in the late 19th century, people used petroleum products for what we now consider basic needs—lighting, heating, cooking, and lubricating. When Colonel Edwin Drake drilled the first well to a depth of 69 feet in 1859 in Titusville, Pennsylvania, and initiated the oil era, his investors were thrilled.
They saw the opportunity to compete with whale oil in the illumination market by providing a similar product, kerosene. Gasoline and naphtha were mostly considered waste products, often allowed to “weather,” a euphemism for evaporating into the atmosphere, before the kerosene was recovered. Sometimes refiners just burned the light material in pits or dumped it into nearby streams to get rid of it. It did not take long for refiners to recognize that the heavier parts of the crude oil could be used as fuel oil for raising steam and heating buildings.
For 30 years after the discovery of crude oil, refining consisted of separating these various products by batch processing, tediously handling one tank of crude at a time. Batch processing operations consisted essentially of a tank where the oil was heated and vaporized and a condenser where the vapors were returned to the liquid state. Starting around 1900, refiners strung these tanks in series and used a so-called continuous batch process, still a capital- and energy-intensive way to do separation (figs. Fractional distillation, using the trayed columns now used worldwide, did not come into widespread use, especially in the United States, for another two decades.
This technique had been used for nearly a decade to distill alcohols. Translation to the refining industry came shortly after the Prohibition Act of 1920 as out-of-work technologists from the spirits industry brought their expertise and enthusiasm to refining research and development. The efficiency of separating crude oil into its constituents increased by 25%. Crude oil separation.
The towers at Shell’s Suez refinery, circa 1912, are of the continuous batch type, separating one fraction per column. Courtesy Royal Dutch Shell. Batch processing unit. Lube oils separation at the London and Thames Haven Refinery, circa 1922.
Courtesy Royal Dutch Shell. The Evolution of Petroleum Refining 3 Early automobiles such as the famous Stanley brothers’ Stanley Steamer were steam-driven, fueled by kerosene. By 1890 inventor-entrepreneurs with the venerable names Karl Benz, Henry Ford, Ransom Olds, and Dave Buick, among others, were marketing their automotive namesakes with internal combustion engines that needed a light fuel, gasoline. That changed the profile and purpose of refining.
By 1910, some 500,000 cars traveled U. roads, and the demand for gasoline exceeded even the formally disposed of volumes. Running more crude oil to satisfy the growing gasoline demand only created surpluses of the nongasoline fractions. Chemical engineers then realized they could convert some of the heavier parts of the crude oil by cooking it until it cracked into lighter fractions.
Vladimir Shukov patented the thermal cracking process in Russia in 1891, but Amoco brought the first American cracker on stream in 1912 in Chicago. Their chief scientist William Burton took a victory lap for one of the most important breakthroughs in refining history, the cracker. The timing was fortuitous because electricity was devastating the illumination market for kerosene and the jet plane had not yet been invented. The chemists of General Motors, led by Charles Kettering, discovered in 1921 that adding small amounts of lead compounds to gasoline significantly improved the octane number.
Thereafter engine efficiency improved, but lead emissions polluted the environment until they were prohibited in the 1970s. Catalysis was still an emerging science when Eugene Houdry introduced in 1936 the grandfather of all catalytic crackers—a fixed bed design that doubled the volume of quality gasoline made from heavy feedstocks, compared to thermal cracking. The first fluidized bed cat cracker followed at Esso’s Baton Rouge refinery in 1942. Meanwhile the auto industry continued to demand better quality gasoline, and in 1949 the first catalytic reformer started up at, of all places, the Old Dutch Refining Company in Muskegon, Michigan, improving the octane number of the naphtha already being blended into gasoline.
Hydroprocessing became increasingly important in the latter half of the 20th century. It includes hydrotreating to remove contaminants, a response to social demands to preserve the environment. Hydrocracking had its origin in concerns about the burgeoning supplies of middle distillates (home heating oil, diesel fuel, and kerosene) manufactured as refiners struggled to meet growing gasoline demands. A technology that could convert one into the other lent quick solution to the imbalance.
Finally, refiners solved the problem of coking in thermal crackers by delaying it until it could take place in a vessel where the coke could be 4 Petroleum Refining in Nontechnical Language harvested—the coke drum in a delayed coker. As environmental regulations and growing crude runs pushed down the relative value of residual fuel, refiners built ever more cokers to eliminate the bottom of the barrel from their product offerings. Why the evolution is important Most of the technological change in the last 20 years has been driven by environmental concern, causing refiners to tweak existing processes, especially with the introduction of new and improved catalysts. Responding to environmental mandates almost always costs money and undermines refining capabilities (otherwise the refiners would already have done it).
Successions of improved and new designer catalysts have enabled most refiners to respond without the albatross of totally debilitating capital expenditure. Holding aside the totally baffling chemistry of catalysis, this slow evolution should be especially good news to you. It is tough enough to understand the basic processes without having to worry about what is becoming obsolete before you have learned it. The basic five refining processes remain the same: t Separation.
Either by distillation or absorption; the molecules remain intact and no chemistry takes place.