Heat Recovery Steam Generator Technology

Vernon L. Eriksen

• Publisher: Woodhead Publishing
• Year: 2017
• Print ISBN: 9780081019405
• eBook ISBN: 9780081019412
• Topic: Technology & Engineering
• Subtopic: Renewable Power Resources
• Index: Technology & Engineering

Heat Recovery Steam Generator Technology is the first fully comprehensive resource to provide readers with the fundamental information needed to understand HRSGs. The book's highly experienced editor has selected a number of key technical personnel to contribute to the book, also including burner and emission control device suppliers and qualified practicing engineers.In the introduction, various types of HRSGs are identified and discussed, along with their market share. The fundamental principles of the technology are covered, along with the various components and design specifics that should be considered. Its simple organization makes finding answers quick and easy.The text is fully supported by examples and case studies, and is illustrated by photographs of components and completed power plants to further increase knowledge and understanding of HRSG technology.- Presents the fundamental principles and theories behind HRSG technology that is supported by practical design examples and illustrations- Includes practical applications of combined cycle power plants and waste recovery that are both fully covered and supported by optimization throughout the book- Helps readers do a better job of specifying, procuring, installing, operating, and maintaining HRSGs

1

Introduction

Vernon L. Eriksen, Nooter/Eriksen, Inc., Fenton, MO, United States

Abstract

Combined cycle and cogeneration power plants have been popular for a number of years due to their high efficiency, low emissions, and a number of other reasons. Due to its ability to start up quickly and respond to demand changes rapidly, the combined cycle power plant’s popularity has increased even more in recent years, to complement variable energy sources such as wind energy and solar energy.

The role of the heat recovery steam generator (HRSG) in combined cycle and cogeneration power plants is discussed in this chapter. Characteristics of HRSGs are presented and types of HRSGs are listed.

Finally, the focus and structure of the book are outlined.

Keywords

Heat recovery steam generator; steam turbine; gas turbine; combined cycle; heat recovery boiler; firetube heat recovery boiler; watertube heat recovery boilers; cogeneration; natural circulation; forced circulation; assisted circulation; once through design; Benson design

Chapter outline

1.1 Gas turbine–based power plants 1

1.1.1 Advantages 1

1.1.2 History 2

1.1.3 Outlook 3

1.2 Heat recovery steam generator (HRSG) 4

1.2.1 Role of the HRSG in the power plant 4

1.2.2 Characteristics 5

1.2.3 Types of HRSGs 6

1.3 Focus and structure of book 14

References 15

1.1 Gas turbine–based power plants

A number of different power plants use the gas turbine engine as their primary driver. Among them are the simple cycle, the combined cycle, many (but not all) cogeneration facilities, and the recuperative cycle to name a few. Heat recovery steam generators (HRSGs) are used in combined cycle plants and in cogeneration plants that utilize the gas turbine as their primary driver, so the expression gas turbine–based power plants will be used to refer to these two types of plants for the purposes of this book. Furthermore, there is very little difference between the HRSG used in a combined cycle plant and the HRSG used in a cogeneration facility, so one often finds the expressions used interchangeably in the industry. We will try to distinguish between the two when necessary in this book.

1.1.1 Advantages

Combined cycle power plants and cogeneration power plants that use the gas turbine engine as their primary driver have been popular for a number of years for a number of reasons.

Efficiencies of over 60% based on lower heating of the fuel have been achieved by these facilities. Other fossil fuel power plants, such as plants with conventional boilers, have efficiency in the range 40–42% for supercritical technology and 45–47% for ultrasupercritical technology based on lower heating value of the fuel.

Gaseous emissions from gas turbine–based power plants are very low. Oxidizing catalysts can be used to convert carbon monoxide to carbon dioxide, and NO_x reduction catalysts that utilize ammonia can be used to convert oxides of nitrogen to nitrogen and water vapor and reduce these two types of emissions to 2 ppm. Due to their high efficiency and the fact that they usually burn natural gas fuel, gas turbine–based power plants also emit far less carbon dioxide than other types of fossil fuel power plants.

Capital cost is lower than other power plants.

Reasonably priced natural gas (primarily due to the development of shale gas) is available at least in the US market.

They have a small footprint and do not require much space when compared to other modes of power generation.

A small operating and maintenance staff is all that is required.

It is relatively easy to permit them.

Construction time is short compared to other types of power plants.

Lastly, due to its ability to start up quickly and respond to demand changes rapidly, the combined cycle power plant has become the ideal companion for renewable power generation sources such as wind energy and solar energy, whose output is variable.

1.1.2 History

Although recent markets for combined cycle power plants have been strong and there has been rapid development of the technology since the mid-1990s, the basic technology has existed for a considerable length of time. References to systems being installed as early as the late 1940s exist in the literature. Development continued into the 1960s, when systems up to 35 MW in size were being built. The 1970s brought about demand for larger amounts of power, especially for intermediate load (run primarily during the workday), and turbine manufacturers responded with larger gas turbines and larger combined cycle plants. General Electric referred to their combined cycle plants as STAG (steam and gas) while Westinghouse called theirs PACE (Power at Combined Efficiency). Plants of this era utilizing a single gas turbine could be as large as approximately 100 MW. Both the STAG and PACE plants utilized vertical gas flow, horizontal tube, forced circulation HRSGs manufactured by both General Electric and Westinghouse at this time.

The oil embargo of the 1970s slowed the market in the United States; however, a brisk market in Saudi Arabia developed. Both General Electric and Westinghouse stopped manufacturing HRSGs at this time; however, their partners in Europe and Asia continued.

Federal legislation (i.e., the Public Utility Regulatory Policies Act or PURPA) in the United States stimulated a market in the late 1970s and early 1980s for cycles that only needed to export a small amount of energy to qualify for tax incentives. This legislation led to the formation of independent power producers (IPPs), who developed projects to take advantage of the situation. Opportunities increased and an entire industry developed. HRSGs at this time were designed to work with standard gas turbines and meet the various export energy requirements of each individual application. Due to wide range of steam flows and conditions encountered along with the operational flexibility required by the different sites, the vertical tube, natural circulation HRSG became the technology of choice.

In the late 1990s and early 2000s an extremely large market developed in the United States and a significant market developed in many other areas for shorter periods of time for both IPPs and conventional utilities. Development of larger and more efficient gas turbines continued at an escalating pace and HRSG development continued in parallel. The very large and efficient HRSGs that we see today are a result of this development. Fig. 1.1 shows a photograph of a modern combined cycle facility. Refs. [1–3] were used in the preparation of this section.

Figure 1.1 Modern large combined cycle power plant with nine gas turbines and HRSGs. Source: Photo courtesy of Nooter/Eriksen.

1.1.3 Outlook

Looking forward, a strong market for gas turbine–based power generation systems should continue due to the high efficiency and low emissions achieved by these systems along with their ability to support intermittent energy sources such as wind and solar energy. An abundance of reasonably priced natural gas in many areas will only increase opportunities for them.

Most projections available show growth in power generation from natural gas. The US Energy Information Administration projects growth of 40% in power generated from natural gas between 2013 and 2040 for their reference case with the natural gas share of the power generation market growing from 27% to 31% over that period of time.

1.2 Heat recovery steam generator (HRSG)

The HRSG is a special boiler within the broader category heat recovery boilers. The expression heat recovery boiler covers a wide range of boilers and boiler systems that recover energy from a variety of different heat sources. The gas flows from these sources vary widely in flow rate, pressure, temperature, composition, and cleanliness of the gas. Most heat recovery boilers, other than the HRSG, utilize one, or two at the most, levels of steam pressure. The gas flow in a heat recovery boiler can be either on the inside or outside of the tubes. When the gas flow is inside of the tubes, the heat recovery boiler is referred to as a firetube heat recovery boiler. When the gas flow is outside of the tubes, the heat recovery boiler is referred to as a watertube heat recovery boiler. Firetube heat recovery boilers have been used in the process industries for many years and have proven to be especially useful when the gas being cooled is pressurized. They are often referred to as waste heat boilers for these pressurized applications. HRSGs, whi...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of contributors
• 1. Introduction
• 2. The combined cycle and variations that use HRSGs
• 3. Fundamentals
• 4. Vertical tube natural circulation evaporators
• 5. Economizers and feedwater heaters
• 6. Superheaters and reheaters
• 7. Duct burners
• 8. Selective catalytic reduction for reduced NOx emissions
• 9. Carbon monoxide oxidizers
• 10. Mechanical design
• 11. Fast-start and transient operation
• 12. Miscellaneous ancillary equipment
• 13. HRSG construction
• 14. Operation and controls
• 15. Developing the optimum cycle chemistry provides the key to reliability for combined cycle/HRSG plants
• 16. HRSG inspection, maintenance and repair
• 17. Other/unique HRSGs
• Index