BRIEF CONTENTS

BOOK 2- ENERGY EFFICIENCY IN THERMAL UTILITIES

Chapter 1 Fuels and Combustion

Chapter 2 Boilers

Chapter 3 Steam System

Chapter 4 Furnaces

Chapter 5 Insulation and Refractories

Chapter 6 FBC Boilers

Chapter 7 Cogeneration

Chapter 8 Waste heat recovery

Chapter 9 Heat Exchanger

Annexure

BOOK 2 - ENERGY EFFICIENCY IN THERMAL

UTILITIES

Table of Contents

Chapter

1 FUELS AND COMBUSTION

1.1 Introduction to Fuels

1.2 Properties of Liquid Fuels

1.3 Properties of Coal

1.4 Properties of Gaseous Fuels

1.5 Properties of Agro Residues

1.6 Combustion

1.7 Combustion of Oil

1.8 Combustion of Coal

1.9 Combustion of Gas

1.10 Combustion of Biomass

1.11 Draft System

1.12 Combustion Controls

2 BOILERS

2.1 Introduction

2.2 Boiler Systems

2.3 Boiler Types and Classifications

2.4 Performance Evaluation of Boilers

2.5 Boiler Water Treatment

2.6 Boiler Blow Down

2.7 Improving Boiler Availability

2.8 Thermic Fluid Heaters

2.9 Energy Conservation Opportunities

3 STEAM SYSTEM

3.1 Introduction

3.2 Properties of Steam

3.3 Steam Distribution

3.4 Efficient Steam Utilisation

3.5 Proper Selection, Operation and Maintenance of Steam Traps

3.6 Performance Assessment Methods for Steam Traps

3.7 Efficient Steam Utilisation and Energy Saving Opportunities

4 FURNACES

4.1 Types and Classification of Different Furnaces

4.2 Performance Evaluation of a Typical Fuel Fired Furnace

4.3 General Fuel Economy Measures in Furnaces

5 INSULATION AND REFRACTORIES

5.1 Purpose of Insulation

5.2 Types and Application

5.3 Calculation of Insulation Thickness

5.4 Economic Thickness of Insulation (ETI)

5.5 Simplified Formula for Heat Loss Calculation

5.6 Cold Insulation

5.7 Refractories

5.8 Properties of Refractories

5.9 Classification of Refractories

5.10 Typical Refractories in Industrial Use

5.11 Selection of Refractories

5.12 Heat Losses from Furnace Walls

6 FBC BOILERS

6.1 Introduction

6.2 Mechanism of Fluidised Bed Combustion

6.3 Types of Fluidised Bed Combustion Boilers

6.4 Retrofitting of FBC Systems to Conventional Boilers

6.5 Advantages of Fluidised Bed Combustion Boilers

6.6 Application Considerations with Biomass FBC Boilers

7 COGENERATION

7.1 Need for Cogeneration

7.2 Principle of Cogeneration

7.3 Technical Options for Cogeneration

7.4 Classification of Cogeneration Systems

7.5 Factors Influencing Cogeneration Choice

7.6 Important Technical Parameters for Cogeneration

7.7 Prime Movers for Cogeneration

7.8 Typical Cogeneration Performance Parameters

7.9 Relative Merits of Cogeneration Systems

7.10 Steam Turbine Efficiency

7.11 Cogeneration Heat Rate and Efficiency Assessment -Illustrative

Case

7.12 Trigeneration

7.13 Microturbine

8 WASTE HEAT RECOVERY

8.1 Introduction

8.2 Classification and Application

8.3 Benefits of Waste Heat Recovery

8.4 Development of a Waste Heat Recovery System

8.5 Commercial Waste Heat Recovery Devices

9 HEAT EXCHANERGS

9.1 Heat Transfer Basics

9.2 Concept of Heat Exchanger

9.3 Heat Exchanger Types (by Flow Design)

9.4 Heat Exchanger Types (by Construction)

9.5 Heat Exchanger Types (by Application)

9.6 Pinch Analysis and Pinch technology Application for Process and

Energy Efficiency Improvements

Fuels & Combustion

Learning Objectives

BoilersLearning Objectives

Steam System Learning Objectives

FurnacesLearning Objectives

Insulation & Refractories

Learning Objectives

FBC BoilersLearning Objectives

CogenerationLearning Objectives

Waste Heat Recovery

Learning Objectives

Heat ExchangerLearning Objectives

Figure 1.1 Duplex Arrangement of Strainers in a Pipeline

Air/Fuel ratio, 3 3m of air to m of Fuel

Figure 1.3 Relation between Residual Oxygen and Excess Air

Residual Oxygen (%)

Carbon dioxide (%)

Figure

Figure

Figure 1.9 Biomass Combustion in a Boiler

Types, Combustion, Performance Evaluation, Feed Water Treatment, Blow Down, Improving Availability (Reducing Tube Failure, Soot Blowing and Reducing Soot Deposition, Preservation, Start-up and Shutdown procedure), Thermic Fluid Heaters, Energy Conservation Opportunities.

Figure 2.1 Boiler System Schematic

Packaged Boiler: The packaged boiler is so called because it comes as a complete package.Once delivered to site, it requires only the steam, water pipe work, fuel supply and electricalconnections to be made for it to become operational. Package boilers are generally of shelltype with fire tube design so as to achieve high heat transfer rates by both radiation andconvection (Refer Figure 2.4).

The pulverized coal is blown with part of thecombustion air into the boiler plant through a seriesof burner nozzles. Secondary and tertiary air mayalso be added. Combustion takes place attemperatures from 1300-1700C, dependinglargely on coal grade. Particle residence time in theboiler is typically 2 to 5 seconds, and the particlesmust be small enough for complete combustion tohave taken place during this time.

This system has many advantages such as ability tofire varying quality of coal, quick responses tochanges in load, use of high pre-heat airtemperatures etc.

Water/steam is used as heat carrier in many heating applications. However, at high temperatures, steam requires a corresponding high operating pressure. Industrial heating systems, a high temperature level is often a great advantage, and establishing this with steam can be very cumbersome and expensive in some cases.

In thermic fluid heaters, a special type of oil-synthetic / mineral -is used as heat carrier. This ofluid can be heated up to 300 C at atmospheric pressure. In comparison steam would

require a pressure of 85 bars to obtain this temperature.

There are several advantages in using thermic fluids compared to steam systems. The most obvious advantages are as follows.

The Table 2.5 gives the theoretical amount of air required for combustion of various types of fuel. Excess air is required in all practical cases to ensure complete combustion, to allow for the normal variations in combustion and to ensure satisfactory stack conditions for some fuels. The optimum excess air level for maximum boiler efficiency occurs when the sum of the losses due to incomplete combustion and loss due to heat in flue gases is minimum. This level varies with furnace design, type of burner, fuel and process variables. It can be determined by conducting tests with different air fuel ratios.

Short Type Questions

Long Type Questions

The heat required to change the temperature of a substance is called its

oIf 1 kg of water in a vessel at 25 C i.e. containing heat value of 25 kCal is heated by adding 75 kCal,

othe water is brought to boiling point of 100 C.

sensible heat.

To change the water to steam, an additional 540 kCal would be required. This quantity of heat required to change a chemical from the liquid to the gaseous state is called latent heat.

2For a boiler is operating at a pressure of 8 kg/cm , osteam saturation temperature is 170 C and steam

enthalpy or total heat of dry saturated steam is given by:h + h = 171.35 + 489.46 = 660.81 kCal/kg.f fg

If the same steam contains 4% moisture, the total heat of steam is given by:171.35 + 0.96 x 489.46 = 641.23 kCal/kg.