Table Of ContentMechanical Engineering
Steam Generators and Waste Heat Boilers
For Process and Plant Engineers
"This book is an ideal reference for anyone involved in the heat transfer field. It is practical for use as a
reference by plant personnel who need an answer ‘right now’ but it is detailed enough to allow consulting
S
engineers, process engineers, manufacturing engineers, designers, and even students to get a compre-
t
hensive understanding of how the equipment works and how to make sure what they have designed is e
really in the best interest of the plant." a
—Bob Stemen, Applied Heat Recovery, USA m
Incorporates Worked-Out Real-World Problems G
Steam Generators and Waste Heat Boilers: For Process and Plant Engineers focuses on the e
thermal design and performance aspects of steam generators, HRSGs and fire tubes, water tube n
waste heat boilers including air heaters, and condensing economizers. Over 120 real-life problems e Steam Generators
are fully worked out, which will help plant engineers evaluate new boilers or make modifications to r
existing boiler components without assistance from boiler suppliers. The book examines recent a
trends and developments in boiler design and technology and presents novel ideas for improving t
boiler efficiency and lowering gas pressure drop. It helps plant engineers understand and evaluate o
the performance of steam generators and waste heat boilers at any load. r
s Waste Heat Boilers
Learn How to Independently Evaluate the Thermal Performance of Boilers
and Their Components a
and
n
This book begins with basic combustion and boiler efficiency calculations. It then moves on to
d
estimation of furnace exit gas temperature (FEGT), furnace duty, view factors, heat flux, and boiler
circulation calculations. It also describes trends in large steam generator designs such as multi-
W
For Process and Plant Engineers
ple-module; elevated drum design types of boilers such as D, O, and A; and forced circulation steam
generators. It illustrates various options to improve boiler efficiency and lower operating costs. The a
author addresses the importance of flue gas analysis, fire tube versus water tube boilers used in s
chemical plants, and refineries. In addition, he describes cogeneration systems; heat recovery in t
sulfur plants, hydrogen plants, and cement plants; and the effect of fouling factor on performance. e
The book also explains HRSG simulation process and illustrates calculations for complete perfor-
mance evaluation of boilers and their components. H
e
• Helps plant engineers make independent evaluations of thermal performance of a
boilers before purchasing them t
• Provides numerous examples on boiler thermal performance calculations that help
B
plant engineers develop programming codes with ease
• Follows the metric and SI system, and British units are shown in parentheses o
wherever possible i
l
• Includes calculation procedures for the basic sizing and performance evaluation of
e
a complete steam generator or waste heat boiler system and their components with
r
appendices outlining simplified procedures for estimation of heat transfer coefficients s
Steam Generators and Waste Heat Boilers: For Process and Plant Engineers serves as a
source book for plant engineers, consultants, and boiler designers.
K23620
Steam Generators
Waste Heat Boilers
and
For Process and Plant Engineers
MECHANICAL ENGINEERING
A Series of Textbooks and Reference Books
Founding Editor
L. L. Faulkner
Columbus Division, Battelle Memorial Institute
and Department of Mechanical Engineering
The Ohio State University
Columbus, Ohio
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Steam Generators
Waste Heat Boilers
and
For Process and Plant Engineers
Boca Raton London New York
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Dedicated to plant and process engineers who henceforth will be able to evaluate
boiler and HRSG performance without assistance from boiler suppliers!
Contents
Preface ...........................................................................................................................................xiii
Author .........................................................................................................................................xxxi
1. Combustion Calculations .....................................................................................................1
Introduction ..............................................................................................................................1
Moisture in Air .........................................................................................................................1
Combustion Calculations .......................................................................................................2
Excess Air from Flue Gas Analysis ..................................................................................8
Simplified Combustion Calculations .............................................................................10
Estimation of Heating Values ...............................................................................................12
Burner Selection .....................................................................................................................13
Combustion Temperatures ...................................................................................................14
Simplified Procedure for Estimating Combustion Temperatures ..................................15
Effect of FGR on Combustion Temperature ..................................................................15
Relating FGR and Oxygen in Windbox .........................................................................16
Gas Turbine Exhaust Combustion Calculations ...............................................................17
Relating Oxygen and Energy Input in Turbine Exhaust Gases .................................17
Evaluating Fuel Quantity Required to Raise Turbine Exhaust Gas Temperature ......19
Firing Temperature versus Oxygen, Burner Duty, and Water Vapor ........................21
Boiler Efficiency .....................................................................................................................21
Heat Loss Method .............................................................................................................22
Simplified Formulae for Boiler Efficiency .....................................................................23
Simplified Procedure for Obtaining Major Boiler Parameters ...................................26
Excess Air versus Efficiency ............................................................................................26
Firing Fuels with Low Heating Values ...............................................................................27
Firing of Multiple Fuels .........................................................................................................29
Emission Conversion Calculations: Steam Generators ....................................................29
Converting ppmvd of NO to mg/Nm3 ..............................................................................32
x
Converting Turbine Exhaust Emissions .............................................................................34
Low-Temperature Corrosion in Boilers ..............................................................................35
Condensation of Acid Vapors in Low-Temperature Heat Sinks .....................................38
Acid Dew Point Temperature T ....................................................................................38
dp
References ...............................................................................................................................40
2. Steam Generator Furnace Design ......................................................................................41
Advantages of Water-Cooled Furnaces ..............................................................................43
Ring Header Design .........................................................................................................44
Heat Release Rates .................................................................................................................46
Steam Pressure ..................................................................................................................47
Circulation Systems ..........................................................................................................52
Furnace Exit Gas Temperature Evaluation .........................................................................53
Empirical Formula for Furnace Duty Estimation .............................................................57
vii
viii Contents
Furnace Duty with Combination Firing .............................................................................60
Distribution of Heat Flux around Tubes and Fins ............................................................61
Distribution of Radiation to Tube Banks ............................................................................61
Relating Heat Flux from Furnace to inside Tubes .............................................................64
External Radiation to Heat Transfer Surfaces at Furnace Exit ........................................65
Direct Radiation to Superheater at Part Load ...............................................................66
Terms Frequently Used in Furnace Performance..............................................................67
Estimating Boiling Heat Transfer Coefficient ....................................................................67
Estimating Fin Tip Temperature ..........................................................................................68
Boiling Process .......................................................................................................................69
Boiler Circulation ...................................................................................................................70
Thom’s Method for Estimating Losses ...............................................................................75
Circulation Calculations .......................................................................................................77
Circulation Flow versus Load .........................................................................................81
Flow Stratification in Horizontal Tubes ..............................................................................82
Correlations for CHF (Critical Heat Flux) and Allowable Steam Quality .....................82
Circulation Problems .............................................................................................................85
Guidelines for Good Circulation System Design ..............................................................85
References ...............................................................................................................................86
3. Steam Generators ..................................................................................................................87
Introduction ............................................................................................................................87
Large Package Boilers ............................................................................................................87
Water-Cooled Furnaces .........................................................................................................90
Major Changes in Boiler Design ..........................................................................................90
Absence of Air Heater ...........................................................................................................90
Emissions Affect Steam Generator Designs ......................................................................92
Custom-Designed Boilers .....................................................................................................97
Novel Ideas .............................................................................................................................97
O-Type Package Boiler ......................................................................................................98
Dual-Pressure Design .......................................................................................................99
Small Changes, Big Benefits ............................................................................................99
Boiler Classification .............................................................................................................103
Improving Boiler Efficiency ...............................................................................................108
Adding Condensate Heater to Improve Boiler Plant Efficiency ...............................109
Understanding Boiler Performance ..............................................................................111
Why Economizer Does Not Steam in Steam Generators ..........................................112
Understanding Boiler Surface Areas ............................................................................113
Steam Generators for Oil Sands Application ...................................................................115
Superheaters .........................................................................................................................118
Radiant versus Convective Superheaters ....................................................................121
How Emissions Impact Radiant and Convective Superheaters ...............................124
Arrangement of Superheaters .......................................................................................124
Steam Temperature Control ..........................................................................................125
Steam Generators with Import and Export Steam ..........................................................129
Flow in Parallel Paths ..........................................................................................................129
Steam Inlet and Exit Nozzle Location ...............................................................................130
Off-Design Performance of Superheater ...........................................................................131
