Thermal Power Plant Control and Instrumentation: The control of boilers and HRSGs.
Thermal Power Plant Control and Instrumentation describes the systems and equipment used for measuring and controlling boilers and heat-recovery steam-generators used in land and marine power plant and in process industries. It provides a practical guide to the design, installation, operation and maintenance of these systems. Starting with descriptions of how each area of the plant operates, it shows how the relevant control systems have evolved, how they are implemented in modern systems and how to evaluate the merits of alternative approaches. The rise of renewable power in the generation mix, and of biomass in the fuel, has demanded greater flexibility from combustion plants, requiring more sophisticated and robust control. In parallel, thermal power plants have been developed with overfire air systems to reduce NOx, once-through supercritical boilers to increase efficiency and model-based control schemes to optimise response. These developments have brought opportunities in terms of flexibility, energy efficiency and safety, but also the risk of a comprehension gap between control specialists and power plant engineers, a gap this new edition aims to bridge.
Other keywords: Lo-NOx burners; instrumentation systems; thermal power plant control; recycling; control technology; plant design; boiler control; HRSGs; carbon-capture
- Book DOI: 10.1049/PBPO119E
- Chapter DOI: 10.1049/PBPO119E
- ISBN: 9781785614194
- e-ISBN: 9781785614200
- Page count: 330
- Format: PDF
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Front Matter
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1 The basics of steam generation and use
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This chapter outlined the change of state of water to steam, followed by an overview of the basic principles of steam generation and use. This seemingly simple subject is extremely complex. This will necessarily be an overview: it does not pretend to be a detailed treatise and at times it will simplify matters and gloss over some details which may even cause the thermodynamicist or combustion physicist to shudder, but it should be understood that the aim is to provide the C&I engineer with enough understanding of the subject to deal safely with practical control system design, operational and maintenance problems.
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2 The steam and water circuits
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In a conventional thermal power plant, the heat used for steam generation may be obtained by burning a fossil fuel, or, in the case of a heat-recovery steam generator (HRSG), may be derived from the exhaust of a gas turbine. In a nuclear plant, the heat may be derived from the radioactive decay of a nuclear fuel. In this chapter we shall be examining the water and steam circuits of boilers and HRSGs, as well as the steam turbines and the plant that returns the condensed steam to the boiler.
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3 The fuel, air and flue–gas circuits
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In this chapter, we shall examine not only the burners or other equipment used to burn the fuel but also the fans and air heaters. Finally, we shall briefly examine how gas turbines are used in combined-cycle plant.
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4 Setting the demand for the steam generator
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In this chapter we have seen how a `master demand' signal is generated with respect to the nature of the duties that the plant is designed to undertake. This signal is responsible for ensuring that the boiler reacts to changes in demand, and it must also coordinate the operation of each of the subsidiary systems. The main areas involved in this process are the combustion and draught systems in conventional boilers, the feedwater and the steam temperature control systems in both conventional boilers and HRSGs.
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5 Combustion and draught control
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In this chapter, we shall see how the combustion process is controlled to meet the two objectives defined in the previous paragraph. We shall also examine the subsidiary systems that maintain the correct operational conditions in the fuel-handling plant of coal-fired boilers.
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6 Feedwater control and instrumentation
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Once the combustion process has occurred, the water has boiled and the steam has been generated, the next requirement is to ensure that the temperature of the steam that is delivered to the turbine or heat load is maintained at the correct value. In the next chapter we shall look at the control and instrumentation systems that are employed for this purpose.
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7 Steam temperature control and measurement
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This ends our system-by-system survey of boiler and HRSG C&I systems, and we return in Chapter 11 to look in more detail how the dynamics of these systems are taken into account by the boiler and turbine master controls to match the unit load demand, particularly for units that are required to change load frequently in response to the grid's requirement for power.
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8 Control equipment practice
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On an operational plant, the control systems that have so far been examined may be implemented in any of a variety of ways, ranging from pneumatics to advanced computer-based systems, but in all cases, it should be possible to identify the various loops within the relevant configuration. These days, most control functions are implemented by means of a computer-based system, so we shall now briefly look at a typical configuration. After that, we shall examine some of the other hardware used in the systems and then consider the environmental factors that influence the selection of control and instrumentation equipment.
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9 Requirements definition and equipment nomenclature
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In this chapter we have considered some of the documentation systems that may be used to define and manage the wide range of requirements to be met by a C&I system. In the next two chapters we will delve into some of the processes used for designing modern boiler protection systems and the structures of advanced modulating and sequence controls employed to enhance the operational flexibility of power plant.
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10 Functional safety and associated reviews for boiler protection and control systems
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This chapter gives an outline of the functional safety processes and associated boiler-related reviews. Real examples from boiler reviews are included. It is an introduction to the processes. It is not intended as a formal guide. In all cases guidance should be sought from a competent engineer.
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11 Improving plant automation and operational flexibility
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In this chapter we shall describe modern practices to improve the operational flexibility of conventional power plant, including characteristics of highly automated systems designed to improve start-up times and reduce the operator's role in direct plant control, in both normal and abnormal situations. We shall also examine the design outlines of modern boiler/turbine coordinated controls to provide fast ramping capability and wider, more stable frequency regulation performance.
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12 Upgrading and refurbishing systems
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We have now reached the end of this overview of a wide and complex subject. We hope that we have been able to throw some light on the technology and that the explanations may have lifted some of the veils of mystery that sometimes seem to obscure it. The fact remains that it is a complex matter and it is unwise to entrust the safety of a plant to people who do not understand either the control aspects or the plant operations. It has been the privilege of the three of us to have worked with power plant throughout our careers, and we hope that some of what we have put down here will be useful and that it may encourage others to take up a very interesting and important subject.
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Back Matter
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Supplementary material
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Errata Sheet for 'Thermal Power Plant Control and Instrumentation: The control of boilers and HRSGs. 2nd Edition'
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There is an errata sheet available for this title.
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