Boilers constitute a vast, mature, and interesting subject that attracts a sizable number of engineers and keeps them fascinated for most of their lives. This book is meant to help those who have been initiated into the field and who desire to clarify their fundamentals, delve deeper into the design and engineering aspects, and learn more about the various types of boilers popularly employed in the industries and utilities.

The readers are urged to spend a few minutes reading this introductory note to under­stand the structure of this book, which can facilitate in selecting and reading the main text. The process of assimilation can be easier and faster.

This book is essentially divided into three sections that address three different aspects of boilers, namely, the

1. Scientific body of knowledge behind all steam generation

2. Study of parts and auxiliaries common to all boilers

3. Combustion systems and boilers built around them—some popular designs

Although it is a good idea to read all chapters in sequence, it is not strictly required. As a matter of fact, a reader can choose the sequence he likes best. A practicing and seasoned engineer may, in fact, prefer to read chapters in Section III first, whereas the designers and younger readers may prefer chapters in Sections I and II dealing with the basics.

In all, there are 14 chapters covering the essence of the subject of boilers in reasonable detail, with modules covering boiler calculations and a glossary of boiler terms at the end.

Section I

The first section is devoted to the fundamentals. It deals with the science of boilers. Essentially a boiler burns a given fuel to release its heat, which is then used to convert water into steam.

The first chapter titled "Boiler Fundamentals" is a primer on the basics of a boiler, starting from the definition of what a boiler is. Boiler classification, scope, efficiency, testing, performance evaluation and enhancement, design codes, and data capture are the main topics examined. The fundamentals relating to heat, fuel, water, and materials are examined in the subsequent four chapters. Boiler technology is built on a large number of engineering subjects such as fuels, combustion, heat transfer, fluid flow, high — temperature materials, water chemistry, and metallurgy. Each of these is a full-fledged discipline but only areas applicable to boilers are captured here.

The two chapters on "Heat and Flow" (Chapter 2) and "Fuels and Ash" (Chapter 3) are the most essential and core chapters for thermal design. No doubt, a boiler designer would need a larger body of knowledge and data than what can be presented in any book to be able to actually perform design. However, the bare essentials provided here along with the calculations in appendices help a reader not only as a welcome refresher course on core fundamentals but also to perform the basic process calculations. This should be of

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Great benefit to consulting and operating engineers. Moreover, in these days of extensive dependence on software programs, it is not unusual for designers to lose touch with the core formulae and graphs, hidden away in the programs somewhere. A brief summary as provided here is of great help in refreshing and staying in touch with the fundamentals. Chapter 2 starts with the properties of steam and water and covers the elements of heat transfer, fluid flow, combustion, and circulation before concluding with the utilization of steam in various power plant cycles. Chapter 3 deals with the properties of prime waste and biofuels and their combustion in boilers, along with the effects on boiler design in adequate detail. Ash characteristics and effects on boiler design form the second part of the chapter.

Chapter 4, "Water Conditioning," restricts itself to the effects of water on boilers, deaera­tion, conditioning, and carryover. It does not deal with water treatment. Also, water as a subject is not considered here but only the aspects of interfaces with boilers are covered.

Chapter 5, "Boiler Materials," dealing with structural steels, high-temperature boiler quality steels, and refractory materials, should be of use for pressure part (PP) and mechanical design of boilers. Boiler steels (plates, tubes, pipes, castings, and forgings of PP quality) are briefly explained with the help of tables giving their composition, strength, and equivalent specifications from other codes. Likewise, the structural steels and refrac­tory and insulation materials are also tabulated and briefly explained. Concise writeups on properties and classification of steel, heat treatment processes, corrosion, and erosion are provided as main refresher topics of metallurgy. Erosion of PPs and refractories is a serious problem, and erosion protection along with wear-resistant ceramics is briefly described.

These five chapters contain equations, graphs, and tables packed with a lot of practical and theoretical data that is proven in practice. A reader can use the data presented in this book reliably.

Section II

The second section deals with the design and engineering aspects of a boiler. Any fired boiler consists of

• Firing equipment to burn the fuel

• Heating surfaces (HSs) to capture the heat released

• Auxiliary equipment to move the water and steam in a safe and desired manner

All systems are appropriately connected by pipes and ducts and supported by structures. In terms of a bill of material, therefore, a boiler is an assemblage of

• PPs and airheater (AH)

• Nonpressure parts (NPPs)

• Auxiliaries and firing equipment

This is a classical way of dividing the boiler even for equipment estimation purposes. This section is also divided on similar lines into three chapters.

However, the different firing devices are discussed in relation to in various types of boilers in Section III, which are classified as per the firing method. Section II deals with the boiler engineering. A lot of design information, gas velocity limits, and constructional features are presented to bring the description into a sharper focus.

Chapter 6, "Heating Surfaces," deals with the design and construction of all heat exchangers (HXs) in a boiler, namely the furnace, evaporator (EVAP), superheater (SH), reheater (RH), economizer (ECON), and airheater (AH). Chapter 7, "Fabricated Parts," covers the unheated PPs (drums and integral piping), draft plant, and structure. In Chapter 8, "Boiler Auxiliaries," only the essential boiler auxiliaries are covered, namely, the fans, dust collectors, soot blowers (SBs), level gauge valves, and safety valves. Construc­tion and performance aspects along with selection considerations for a boiler application are discussed here with an eye on their effect on total boiler performance and reliability.

Section III

The last section deals with various types of boilers based on the type of firing. This section discusses various types of combustion processes and the boilers built around them.

It should be of interest to all practicing engineers as the practical issues of design, sizing, construction, and some operational points are discussed. These chapters are light on the­ory and heavy on design and practice. They are directly useful for practicing engineers.

Chapter 9, "Industrial and Utility Boilers," starts with the essential differences between the two (reheating considered as the dividing line) and goes on to describe the several types and their design features. Various industrial boilers are categorized, briefly touched upon (as they are elaborated in subsequent chapters) with pile and semipile burning taken up for a detailed discussion. Likewise, the utility boilers are also classified appropriately and concepts of supercritical boilers are briefly explained.

Chapter 10, titled "Burner Firing," is dedicated to burners and boilers for oil and gas firing, covering both the prime and the lean fuels. With the surge in fuel prices and com­bined cycles (cc) gaining ground, the oil — and gas-fired boilers are confined to process applications. Package (bidrum A, O, and D types) and field — erected (single and bidrum) boilers are the two categories in the industry and both are explained in this chapter. The discussion on burners includes types, parts, igniters, and scanners. Engineering aspects of burners and parts, limits of various boiler configurations, design principles of oil- and gas-fired boilers are some of the salient issues in this chapter.

Chapter 11 deals with "Stoker Firing," which is restricted to burning biofuels today Various grates and mass and spreader stoker (SS) firing are described in detail followed by descriptions of various stoker-fired boilers. Design and construction aspects of different stokers and principles of stoker-fired boiler design are elaborated in this chapter.

Chapter 12, "Fluidized Bed Combustion," encompasses both BFBC and CFBC combus­tors and boilers. Starting with the process of FBC, its characteristics, advantages, and limi­tations, this chapter covers both BFBC and CFBC boilers in much detail. In BFBC, the process, design variables, components are explained before we take up the principles of BFBC boiler design. A similar pattern is followed for CFBC. In case of CFBC, there are many designs with differing principles. Four popular designs are elaborated, compared, and contrasted to bring out finer points of difference. After describing the CFBC boilers for utility application, the chapter is ended with a short description on Ignifluid boilers, the earliest CFBC. The chapter contains many useful design tables such as the process parameters of BFBC and CFBC, besides several comparisons, for example, BFBC versus CFBC, CFBC versus PF, and so on.

Chapter 13 explains "Pulverized Fuel Firing." After a brief overview covering the advantages and limitations, direct and indirect firing, milling plant, burners, and boilers

Are covered in detail. Various types of feeders (volumetric and gravimetric) and mills (ball, beater, and vertical) are detailed. Different parts and configurations of burners are explained. Tangential, circular, down-shot burners in front wall, opposed, and corner firing modes are elaborated. This chapter also covers brown coal firing before describing the various types of PF-fired boilers. There is a section on design principles of PF boilers.

Chapter 14, on "Waste Gas Firing (Heat Recovery System Generators)," deals with HRSG behind GT, the only waste heat boiler of the utility sector and the latest genera­tion utility boiler that comes in the size of an industrial boiler. After elucidating the dif­ferences between WHRB and HRSG, there is a fairly detailed account on GTs explaining their basics, cycles, types, manufacturers, models, and performance before starting on the HRSGs. Scope, thermal and mechanical design aspects, components, types (verti­cal and horizontal), and performance testing are explained. A short note on OTSGs is added. There are several useful tables and graphs.

Appendices and Glossary

A set of boiler process calculations appears in Appendix A, which will be very useful for boiler engineers and students alike. Likewise, a carefully prepared glossary of boiler words with crisp definitions, provided at the end of this book, will be very valuable.

Description

This book stresses brevity of description so that a wider area can be covered without taxing the reader. It also aims to clarify fundamentals at every stage so that a deeper understanding is created. Accordingly, appropriate tables, charts, and illustrations are copiously added to supplement the text, which is kept purposely brief. Many tables are very carefully and painstakingly prepared to compare and contrast important data.

The description is divided into several small paragraphs, which are titled and num­bered, to make the reading and remembering as effortless as possible.

Abbreviations

To shorten the description and simplify reading, a set of standard abbreviations for vari­ous boiler terms are used, a list of which appears at the end of this book. The reader is urged to become familiar with these first.

Units, Standards, and Conversions

Every advanced nation has its own material standards and boiler codes. But American standards are more extensively used world over and hence it was decided to follow them

When explaining the materials, design practices, and testing and equipment codes. This raises the question of what units to be followed. The SI units have not fully gained cur­rency in many places and the MKS is not altogether superseded. The FPS that continues to be popular is built on that platform.

At many places where equivalent units are mentioned, the figures in brackets are appro­priately rounded off the reading and remembering more easy.

A list of applicable conversions of units is given at the beginning for a ready reference.

List of Reference Data Tables and Graphs

As mentioned earlier, the description in this book has been supplemented with numerous charts and tables. Many of them are standard and need to be referred to repeatedly in the course of work. All tables and graphs are therefore separately listed to draw the attention of readers so that they can refer them frequently. Many times a reader may not remember all data and these lists can be helpful. These are classified as

• List of Tables

• List of Calculations

• Design Guidelines

• Fuel and Ash Data

• Technology Comparisons

• Some Important Descriptions

Further Readings

References used in preparing the various chapters and study material useful for further understanding are provided at the end of each chapter. Many are in the form of technical articles from magazines and institutions.

Finally, this book has been compiled not for reading once and storing away but to be used repeatedly as a desktop reference material of long-term value.

Conversion	Of Units
Length
1 in. (")	2.54 cm or 25.4 mm
1 ft (‘)	12 in.
	30.48 cm
1 cm	0.3937 in.
1 mm	0.03937 in.
	1000 ]um
1 m	3.281 ft
	39.37 in.
1 mil (»’) or thousandth 1/1000 in.
	0.0254 mm
	25.4 |jm
1 |jm or micron	10-6 m
	10-3 mm
Area
1 in.2	6.45 cm2
	645 mm2
1 ft2	144 in.2
	929 cm2
	0.0929 m2
1 cm2	100 mm2
	0.155 in.2
1 m2	10,000 cm2
	10.76 ft2
Volume
1 in.3	16.39 cm3/ml
1 cc/1 ml	0.061 in.3
1 ft3	1728 in.3
	28.32 l
	0.0283 m3
1 l/1 dm3	61 in.3
	1000 cc/ml
	0.22 Imperial gallon
	0.2642 U. S. gallon
1 m3	1000 l/dm3
	35.31 ft3
	264.2 U. S. gallons
	220 Imperial gallons

Lv

1 Imperial gallon 277.4 in.3

4.55 l

1.2 U. S. gallons 1 U. S. gallon 231 in.3

3.785 l

0.833 Imperial gallon 1 fluid ounce 28.13 cc

Weight
1 (U. S. long) ton (t)	2240 lb
	1016 kg
	1.016 te
1 metric ton or	2205 lb
1 tonne (te)	1000 kg
	0.984 long tons
	1.102 short tons
1 short ton	2000 t
	907 kg
1 lb	16 oz
	7000 gr
	0.454 kg
1 kg	2.205 lb
1 g	15.43 gr
1 oz	28.35 g
1 gr	64.8 mg
1 stone	14 lb
	6.35 kg

Force 1 lbf 4.45 N 1 kgf 9.807 N 1 N 0.248 lbf 0.102 kgf 1 tonf 9.964 kN 1 tef 9.807 kN

Pressure

1 atmosphere (atm)

(physical) 760 mmHg

10 m of water head

14.7 psi

1.33 kg/cm2 1013 mbar

1.13 bar

1 atmosphere (metric) or 1 kg/cm2

1 bar

1 mbar 1 Pa

1 MPa or 1 N/mm2 1 lb/ft2 1 ton/in.2 1 te/in.2 1 psi

1 kg/m2

1 kg/mm2 1 in. w. g. head

1 ft water head

1 mm water

1 m water head 1 in. Hg head

736 mmHg 9.684 m of water

14.22 psi 981 mbar 1000 mbar

105 Pa

106 dynes/cm2 750 mmHg

1.2 kg/cm2

14.5 psi 0.4 in. w. g.

10.2 mm w. g. 100 Pa

1 N/m2 1 kg/m s2 0.01 mbar 145 psi

10.2 kg/cm2

10 bar

0.1922 in. w. g.

4.88 kg/m2

47.88 Pa 1.575 kg/mm2

157.5 kg/cm2

15.44 MPa 1.551 kg/mm2

155.1kg/cm2

15.20 MPa

2.36 in. Hg 2.307 ft water 0.0703 kg/cm2 703 mm w. g. 0.0695 bar 68.947 mbar

1 mm w. g.

9.81 Pa 0.2048 lb/ft2 0.635 ton/in.2 0.645 te/m2

5.2 lb/ft2 0.036 psi 249 Pa

2.49 mbar 0.434 psi

29.89 mbar

98.7 Pa 0.98 mbar 0.1 kg/cm2

0.491 psi

3386.4 Pa 33.864 mbar

1 mHg head 1.36 kg/cm2

1333 mbar

Velocity
1 fps	0.3048 m/s
1 fpm	0.0051 m/s
	0.3048 m/m
	18.29 m/h
1 mps	3.28 fps
	196.8 fpm
1 m/min	0.0547 fps
	3.28 fpm

Mass Velocity 1 lb/ft2 h 4.8824 kg/m2 h 1.355 X 10-3 kg/m2 s 1 kg/m2 h 0.2048 lb/ft2 h

Volume Flow 1 ft3 /s 0.0283 m3/s 1 ft3/min 0.472 X 10-3 m3/s 0.0283 m3/min 1.699 m3/h 1 m3/h 0.589 ft3/min 3.675 Imperial gpm 4.41 U. S. gpm

Density and Specific Volume 1 lb/ft3 16.02 kg/m3 1 gr/ft3 2.288 g/m3 1 kg/m3 0.0624 lb/ft3 1 ft3/lb 0.0624 m3/kg 1 m3/kg 16.02 ft3/lb

Concentration

1 g/ft3 1 g/m3

2.288 g/m3 0.437 g/ft3

0. 0703 g/Imperial gpm

1 g/Imperial gallon 1426 g/m3

14.26mg/L

1 g/L 70.2 g/Imperial gallon

Power and Heat

1 therm 1 kW h

(energy/work)

1 J

1 Btu 1 kcal

1 W

(power/heat flow) 1 kW

(power/heat flow)

1 Btu/h

1 horse power (hp)

1 metric hp 1 pferdestarke (PS)

1 Btu/lb (calorific value)

1 kcal/kg

1 kJ/kg

10.0 Btu 3413 Btu 860 kcal

3.6 MJ

107 Erg

0. 7375 ft lb

0. 000948 Btu 1 W s

1 kg m2/s2 778 ft lb

107.6 kg m

0. 2520 kcal

1.55 kJ 3088 ft lb 427 kg m 3.968 Btu

4.1868 kJ

1 J/s 1 N m/s 1 kg m2/s2 738 ft lb/s 102 kg m/s 1.341 hp

1.360 metric hp (PS) 3413 Btu/h 860 kcal/h

0. 293 W

33.0 ft lb/min 550 ft lb/s

76 kg m/s

1.14 PS

0. 746 kW 32,550 ft lb/min 542 ft lb/s

0. 986 hp

0. 735 kW

0. 556 kcal/kg 2.326 kJ/kg

1.8 Btu/lb

4.1868 kJ/kg

0. 423 Btu/lb

1 Btu/ft3/h	8.90 kcal/m3/h
(volumetric release)	10.3497 W/m3
1 kcal/m3	0.1124 Btu/ft3
1 Btu/ft2	2.712 kcal/m2
(heat flux)	3.154 W/m2
1 kcal/m2	0.3687 Btu/ft2
	0.2846 kcal/m2
	4.1868 kJ/m2
1 MW/m2	317,193 Btu/ft2
	860,000 kcal/m2/h
1 Btu/lb°F	4.1868 kJ/kg K
(specific entropy)
1 kJ/kg K	0.2388 Btu/lb°F
1 Btu/ft2°F	4.88 kcal/m2°C
(heat transfer	5.678 W/m2 K
Coefficient)
1 kcal/m2°C	0.2048 Btu/ft2°F
	1.163 W/m2 K
1 W/m2 K	0.1761 Btu/ft2°F
	0.860 kcal/m2°C
1 Btu/ft2°F/ft	1.488 kcal/m2°C/m
(thermal
Conductivity)	1.731 W/m K
1 kcal/m2°C/m	0.672 Btu/ft2°F/ft
	8.06 Btu/ft2°F/in.
1 Btu/ft2°F/in.	0.124 kcal/m2°C/m
	0.144 W/m K
1 kJ/kWh	0.948 Btu/kWh
(heat rate)	0.239 kcal/kWh

Water at 16.7°C (62°F)

1 ft3 62.3 lb

1 lb 0.01604 ft3

1 Imperial gallon 10 lb

Water at 4°C (39.2°F) (Maximum Density)

1 ft3 62.4 lb

1 lb 0.01602 ft3

1 m3 1000 kg

1 L 1 kg

1 kg/m3 1 part/1000 or 1 g/L

1 g/m3 1 ppm or 1 mg/L

Viscosity-Dynamic
1 poise (P)	0.1 N-s/m2
	0.1 kg/m-s
	0.1 Pa-s
	0.00209 lb-s/ft2
1 centi poise (cP)	0.01 P
	1 m Pa-s

Viscosity-Absolute/Kinematic 1 stoke (st) 1 cm2/sec 100 mm2/sec 10.76 X 10-4 ft2/sec 1 centistoke (cst) 1 mm2/sec 10.76 X 10-6 ft2/sec 1 ft2/sec 92903 mm2/sec

Emission: NO^ 1 ppm dv (dry volume) 1.912 mg/DSCM 2.05 mg/N m3 1/1196 gr/DSCF 1 mg/Nm3 0.932 mg/DSCM 0.487 ppm 1/2455 gr/DSCF 1 lb/MBtu on 760 on natural gas NCV at 3% O2 800 on refined gas (± 2% accuracy) 725 on fuel oil

Emission: SO2 1 ppm dv 2.66 mg/DSCM (dry volume) 2.857 mg/N m3 1/860 gr/DSCF 1 mg/N m3 0.932 mg/DSCM 0.35 ppm 1/2455 gr/DSCF

Emission: CO

1 ppm dv (dry volume)	1.164 mg/DSCM 1.25 mg/N m3 1/1965 gr/DSCF

0.

1 mg/N m3

932 mg/DSCM 1.250 ppm 1/2455 gr/DSCF

Emission: VOC

1 ppm dv (dry volume)

1 mg/N m3

0. 666 mg/DSCM

0. 714 mg/N m3 1/3440 gr/DSCF

0. 932 mg/DSCM 1.40 ppm 1/2455 gr/DSCF