Practical Guide to Industrial Boiler System by Ralph L. Vandagriff PDF

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Information contained in this work has been obtained from sources believed to be reliable. However, neither Marcel Dekker, Inc., nor its authors guarantees the accuracy or complete- ness of any information published herein and neither Marcel Dekker, Inc., nor its authors shall be responsible for an...

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Information contained in this work has been obtained from sources believed to be reliable. However, neither Marcel Dekker, Inc., nor its authors guarantees the accuracy or completeness of any information published herein and neither Marcel Dekker, Inc., nor its authors shall be responsible for any errors, omissions, or damages arising out of use of this information. This work is published with the understanding that Marcel Dekker, Inc., and its authors are supplying information but are not attempting to render engineering or other professional services. If such services are required, the assistance of an appropriate professional should be sought. ISBN: 0-8247-0532-7 This book is printed on acid-free paper. Headquarters Marcel Dekker, Inc. 270 Madison Avenue, New York, NY 10016 tel: 212-696-9000; fax: 212-685-4540 Eastern Hemisphere Distribution Marcel Dekker AG Hutgasse 4, Postfach 812, CH-4001 Basel, Switzerland tel: 41-61-261-8482; fax: 41-61-261-8896 World Wide Web http:/ /www.dekker.com The publisher offers discounts on this book when ordered in bulk quantities. For more information, write to Special Sales/Professional Marketing at the headquarters address above. Copyright  2001 by Marcel Dekker, Inc. All Rights Reserved. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming, and recording, or by any information storage and retrieval system, without permission in writing from the publisher. Current printing (last digit): 10 9 8 7 6 5 4 3 2 1 PRINTED IN THE UNITED STATES OF AMERICA

To My mother, Martha Louise Lunday Vandagriff, Native American of the Delaware Nation My father, Ralph B. Vandagriff, a true gentleman My wife, Sue Chapman Vandagriff, who has put up with me for over 45 years Thank you for your love, help, and guidance. Thank you for teaching me about God and how to trust in Him.

Preface

Much time was spent in researching data in the 35-plus years of my involvement in boiler house work. This text is a compilation of most of that data and information. The purpose of this book is to make the day-to-day boiler house work easier for the power engineer, the operators, and the maintenance people, by supplying a single source for hard-to-find information. Nontechnical people with an interest in boiler house operation include plant management personnel, safety personnel, and supervisory personnel in government and industry. The technical material in this book, including the spreadsheet calculations and formulas, should be of interest to the boiler engineer, boiler designer, boiler operator, and the power engineering student. Ralph L. Vandagriff North Little Rock, Arkansas

v

Contents

Preface Requirements of a Perfect Steam Boiler Tables and Spreadsheets 1 Experience

v ix xi 1

2 General Data

29

3 Gas and Oil Fuels

81

4 Solid Fuels

101

5 Steam Boiler Feedwater

145

6 Boiler Feedwater Pumps

161

7 Stack Gases

181

8 Flows

205

9 Boiler Energy Conservation

267

10 Electricity Generation and Cogeneration

293

Appendix References Index

327 347 351 vii

Requirements of a Perfect Steam Boiler 1.

2. 3. 4. 5. 6.

7.

8.

9.

10. 11. 12.

Proper workmanship and simple construction, using materials which experience has shown to be the best, thus avoiding the necessity of early repairs. A mud drum to receive all impurities deposited from the water, and so placed as to be removed from the action of the fire. A steam and water capacity sufficient to prevent any fluctuation in steam pressure or water level. A water surface for the disengagement of the steam from the water, of sufficient extent to prevent foaming. A constant and thorough circulation of water throughout the boiler, so as to maintain all parts at the same temperature. The water space divided into sections so arranged that, should any section fail, no general explosion can occur and the destructive effects will be confined to the escape of the contents. Large and free passages between the different sections to equalize the water line and pressure in all. A great excess of strength over any legitimate strain, the boiler being so constructed as to be free from strains due to unequal expansion, and, if possible, to avoid joints exposed to the direct action of the fire. A combustion chamber so arranged that the combustion of the gases started in the furnace may be completed before the gases escape to the chimney. The heating surface as nearly as possible at right angles to the currents of heated gases, so as to break up the currents and extract the entire available heat from the gases. All parts readily accessible for cleaning and repairs. This is a point of the greatest importance as regards safety and economy. Proportioned for the work to be done, and capable of working to its full rated capacity with the highest economy. Equipped with the very best gauges, safety valves, and other fixtures.

Source: List prepared by George H. Babcock and Stephen Wilcox, in 1875 [31].

ix

Tables and Spreadsheets

Table number 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.1 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 4.11 4.12

Title Boiler Horsepower Horizontal Return Tube Boiler Ratings Theoretical Air Required for Various Fuels Cost of Energy Steam Boiler Tubing and Drum Materials U.S. Sieve Series and Tyler Equivalents Horsepower Worth: Present Worth Analysis Surface Emittances of Metals and their Oxides Normal Emissivities for Various Surfaces Properties of Rubber Scotch Marine Boiler Tube Data Fuels: Oil and Gas Analysis Combustion Constants Minimum Auto-Ignition Temperatures Natural Gas Combustion Natural Gas Combustion—Formulas Fuel Oil Combustion Fuel Oil Combustion—Formulas Biomass Fuel Combustion Biomass Fuel Combustion—Formulas Typical Biomass fired Boiler Performance Municipal Solid Waste Combustion Btu in Wet Biomass Fuel Table of Moisture Content Types of Pulverizers for Various Materials Thermochemical Properties of Biomass Fuels Data: Southern Hardwoods Thermochemical Analysis: Miscellaneous Fuels Thermochemical Analysis of Rubber Tires Stages: Vegetal Matter in Coal

Page number 40 41 44 45 53 74 77 78 78 80 87, 88, 89 93 94 95 96 97 98 99 113 114 115 116, 117 120 121 134 135, 136, 137 138 139 140 141

xi

xii 4.13 5.1 5.2 7.1 7.2 7.3 7.4 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 8.9 8.10 8.11 8.12 8.13 8.14 8.15 8.16 8.17 8.18 8.19 8.20 8.21 8.22 9.1 9.2 9.3 9.4 9.5 9.6 10.1 10.2 10.3 10.4 10.5a 10.5b 10.6 10.7

Tables and Spreadsheets Properties: U.S. Coals & Low-Rank World Coals Properties of Water Boiler Feedwater Btu Characteristics of Air & Gas Cleaning Devices Gas Particles Gas Property: Cp Heat Content of Combustion Gases: Btu/lb. Viscosities of Miscellaneous Fluids Losses in Equivalent Feet of Pipe—Valves, etc. Losses in Equivalent Feet of Pipe—Sch. 80/0.5″ wall Estimated Piping Heat Loss Estimated Piping Heat Loss Thermal Conductivity of Pipe Insulation Linear Thermal Expansion—Metals Saturated Steam Properties w/Piping Loss Saturated Steam Properties w/piping Loss—Formulas Superheated Steam Properties w/Piping Loss Superheated Steam Properties w/Piping Loss—Formulas Steam Desuperheater Water Requirements Pneumatic Conveying of Materials Compressed Air Flow—Orifice or Leak Theoretical Adiabatic Discharge Temperature for Air Compression Boiler Tubing Properties Boiler Tubing Properties—2″ od and larger Properties of Pipe Pipe Fitting Dimensions Pipe Flange Dimensions Length of Alloy Steel Stud Bolts Pipe Flange Facings Economizer Extended Surface Effect Various Economizer Designs Excess Air Requirements Natural Gas Combustion Losses Fuel Oil Combustion Losses Boiler Steam Energy Cost Estimated Steam Turbine/Generator Output Theoretical Turbine Steam Rates Steam Turbine—Generator Sets: Actual Prices Gas Turbines—Partial Current List Gas Turbine Data Gas Turbine Data Gas Engines Cogeneration in Texas—Results

142 151 152 199 200, 201 202 203 210 212 215 217 219 220 221 227 229 232 234 236 239 242 249 250 251 252 258 259 261 263 273 276 280 282 282 292 315 316 317 318 319 320 321 324

1 Experience Design Notes; Boiler Operation and Maintenance; Experience.

I.

DESIGN NOTES

A. Industrial Power Plant Design* It is not the intent to go into the matter of steam power plant design in any detail, but merely to indicate a few points that come up during the course of the study, to give a little flavor of the kinds of practical considerations that must be taken into account. 1. Steam Piping High process steam pressures are costly in terms of by-product power generation. Failure to increase steam pipe sizes as loads increase results in greater pressure drops, which can lead to demands for higher pressures than are really needed. This reduces the economy of power generation and can introduce serious temperature-control problems as well. 2. Plant Location If a new steam and power installation is being put in, careful consideration should be given to its location in relation to the largest steam loads. Long steam lines are very expensive and can result in pressure and temperature losses that penalize power production.

* Extract from Seminar Presentation, 1982. Courtesy of W. B. Butler, retired Chief Power Plant Superintendent and Chief Power Engineer for Dow Chemical Co., Midland, Michigan. (Deceased)

1

2

3.

Chapter 1

Boiler Steam Drum

Although many field-erected boilers are custom designed, considerable engineering is required, and experienced personnel are scarce. A known and proven design can be offered for much less than a corresponding special design. A boilermaker might be asked, for example, for a 200,000-lb/hr boiler of 600 psi working steam pressure. He may have a proven design for a 300,000-lb/hr boiler of 700 psi working steam pressure that would fill the requirements, so he might build according to that design and stamp the drum according to the customer’s order. If so, the customer is losing an opportunity for additional economical power generation, so he should explore this possibility before the drum is stamped and the data sheets submitted to the national board. Also, the proper size safety valve nozzles must be installed before the drum is stress relieved. 4.

Steam Turbine Sizing

The ratio of steam pressure entering the turbine to that leaving should be at least 4: 1 for reasonable turbine efficiency, and as much higher as feasible on other grounds. For example, assume our usual boiler conditions of 900 psi and 825°F, and a process steam requirement of 400,000 lb/hr. If the process steam pressure is 150 psi, about 21.2 MW of gross by-product power generation is possible. If the process steam pressure is 300 psi, this drops to near 14.4 MW. 5.

Turbine Manufacturers

Turbine manufacturers may use the same frame for several sizes and capacities, especially in the smaller sizes, which will be sufficiently designed to withstand the highest pressure for which it will be used. Many turbine frames have extraction nozzles for feedwater heating, which are merely blanked off if not required. Knowing the practices of the selected turbine manufacturer, here, can help obtain the most for the money. 6.

Stand-Alone Generation

If self-generation is installed in an industrial plant with the idea of becoming independent of the local utility, some thought should be given to auxiliary drives in event of a power failure, momentary or longer. If the auxiliaries are electrically driven, they should have mechanically ‘‘latched in’’ or permanent magnet starters to prevent many false trip-outs. 7.

Auxiliary Steam Turbine Drives

Steam turbine drives for auxiliaries have a number of advantages besides alleviating some problems during shutdowns and start-ups. They do require special maintenance, however. The advantages of turbine drives elsewhere throughout the plant should also be explored once it is planned to have higher-pressure steam available.

Experience

3

8. Deaerating Feedwater Heater Many small steam plants have become extinct owing to boiler and condensate system corrosion problems that could have been prevented with a good deaerating heater. 9. Synchronous Generators and Motors Synchronous generators and synchronous motors have the capability of feeding as much as ten times their rated maximum currents into a fault or short circuit. The impact is capable of breaking foundation bolts, shearing generator shaft coupling keys, tearing out windings, and exploding oil circuit breakers. Precautions include installing breakers of adequate interrupting capacity, installing currentlimiting reactors in the armature circuit, using a transformer to change the generator voltage and limit short-circuit fault currents with its impedance, and using separate breakers and external circuits for the separate windings of the generator. 10. Unbalanced Loads Electric loads leading to unbalanced circuits should be avoided or, at most, be a small fraction of the total load. As much as 10% unbalance between phases can be troublesome. A large unbalanced load on a small generator will usually cause serious damage to the field coil insulation by pounding it from one side of the slot to the other. A small industrial power plant should never attempt to serve such a load as a large single-phase arc furnace, no matter how economically attractive it might appear. 11. Cogeneration Problem Areas Many of the problems that will need to be considered will be specific to the individual case, and only some of the more general ones will be mentioned. The listing is illustrative rather than comprehensive. a. Management Philosophy. The attitude and policies of the management of the industrial concern involved can be a key factor. Those with policies and experience favoring backward integration into raw materials would not have much trouble with the idea of generating their own power. On the other hand, a management (perhaps even in the same industry) whose policy has been not to make anything they can buy, short of their finished products for sale, might well say, ‘‘We’re not in the power business and we’re not going into the power business as long as we can buy from the utility.’’ In such a case, return on investment is of little consequence. Examples can be found in the automotive industry, the chemical industry, and doubtless others. The influence of management philosophy can also extend into the operation and maintenance of the steam and power plant, which has its own characteristics and needs. The steam and power plant should be considered a key and integral

4

Chapter 1

part of the manufacturing system and not just a necessary evil. Failure to do this can lead to injudicious decisions or demands that accommodate manufacturing at the price of serious or even disastrous trouble later on. b. Return on Investment. Standards for acceptable return on investment (ROI) will differ, and the 20% ROI used in this study is intended only as a typical average figure. A rapidly growing company having trouble raising capital for expanding its primary business, for example, could well set its sights higher. c. Difference in Useful Plant Life. A difference in time scales needs to be realized and reconciled. Many manufacturing processes or major equipment installations become obsolete and are replaced or changed after perhaps 10 or 12 years. The useful life of a power plant is probably closer to 30 years, and this must be considered in making the investment commitment. Along the same vein, any substantial shift toward coal as a boiler fuel (which seems almost inevitable at this time) will require opening new mines, as it is quite evident that this will necessitate commitment to long-term purchase contracts. Many products have shorter lifetimes than the periods just mentioned. d. Outage. A workable, economic solution to many total-energy problems may seem easy until the question is asked, ‘‘What do we do when this generator is out of service?’’ Two weeks of outage in a year is a reasonable estimate for a well-maintained steam-powered system. Under favorable conditions, this maintenance period can be scheduled; many industries also require such periodic maintenance. Some industries can easily be shut down as needed, but others, however, would sustain significant losses if forced to shut down. Stand-by power can be very expensive, whether generated in spare equipment or contracted for from the local utility. Consideration should also be given to a similar problem on a shorter time scale. Small power plants using gas, oil, or pulverized coal firing are subject to codes such as National Fire Protection Association (NFPA) and others to prevent explosive fuel–air mixtures in boiler furnaces. One measure usually required is a prolonged purge cycle through which the draft fans must be operated before any fuel can be introduced into the furnace. A 5-min purge can be tolerated in a heating or process steam boiler. A flameout, and the required purge in a power boiler serving a loaded turbine–generator, will usually result in a loss of the electrical load. Whether or not this can be tolerated for the type of manufacturing involved should be studied before undertaking power generation. e. Selling Power to the Utility. If power is to be generated for sale, the attitude of the utility’s management also becomes an important factor. Most utilities have strongly discouraged the private generation of power in the past, and old habits and policies sometimes die hard in any industrial organization. Wheeling of

Experience

5

power through utility transmission lines has been acceptable to some, although usually only on behalf of another investor-owned utility, and unacceptable to others. Where policies have discouraged these practices in the past, there will have been little experience to shape relationships in the future, and it would be natural for many utilities to begin with a tighter control over industrial power generation than might be necessary in the long run. Each industrial concern must consider the effect on and compatibility with their own patterns of operation, production schedules, load curves, and similar items. B. Wood-Fired Cogeneration* 1. Fuel Preparation and Handling Initially, remove all tramp iron from the fuel material before entering the hammer mill or pulverizer by use of a properly placed electromagnet. This is considerably more expensive than use of a metal detector to trip the feed conveyor system; however, a detector alone requires an operator to search for the piece of metal and to restart the conveyor system. In general, design the conveyor system for free-flowing drop chutes and storage bins. Almost any necked-down storage bins or silos are certain to bridge or hang-up. Wood chips and bark, when left in place, will generate heat (owing to moisture content) and will set up to an almost immovable solid mass. 2. Boiler Unit Make sure that the furnace and boiler heat-exchange surfaces are designed for the fuel being fired and in accordance with standard boiler design criteria. Provide excess capacity so that the boiler does...