Advanced Power Plant Materials, Design and Technology

Dermot Roddy

• Publisher: Woodhead Publishing
• Year: 2010
• Print ISBN:
  9781845695156
• eBook ISBN:
  9781845699468
• Topic: Technology & Engineering
• Subtopic: Mechanical Engineering
• Index: Technology & Engineering

Fossil-fuel power plants account for the majority of worldwide power generation. Increasing global energy demands, coupled with issues of ageing and inefficient power plants, have led to new power plant construction programmes. As cheaper fossil fuel resources are exhausted and emissions criteria are tightened, utilities are turning to power plants designed with performance in mind to satisfy requirements for improved capacity, efficiency, and environmental characteristics.Advanced power plant materials, design and technology provides a comprehensive reference on the state of the art of gas-fired and coal-fired power plants, their major components and performance improvement options. Part one critically reviews advanced power plant designs which target both higher efficiency and flexible operation, including reviews of combined cycle technology and materials performance issues.Part two reviews major plant components for improved operation, including advanced membrane technology for both hydrogen (H2) and carbon dioxide (CO2) separation, as well as flue gas handling technologies for improved emissions control of sulphur oxides (SOx), nitrogen oxides (NOx), mercury, ash and particulates. The section concludes with coverage of high-temperature sensors, and monitoring and control technology that are essential to power plant operation and performance optimisation.Part three begins with coverage of low-rank coal upgrading and biomass resource utilisation for improved power plant fuel flexibility. Routes to improve the environmental impact are also reviewed, with chapters detailing the integration of underground coal gasification and the application of carbon dioxide (CO2) capture and storage. Finally, improved generation performance is reviewed with coverage of syngas and hydrogen (H2) production from fossil-fuel feedstocks.With its distinguished international team of contributors, Advanced power plant materials, design and technology is a standard reference for all power plant engineers and operators, as well as to academics and researchers in this field. - Provides a comprehensive reference on the state-of-the-art gas-fired and coal-fired power plants, their major components and performance improvement options - Examines major plant components for improved operation as well as flue gas handling technologies for improved emissions control - Routes to improve environmental impact are discussed with chapters detailing the integration of underground coal gasification

Part I

Advanced power plant materials and designs

1

Advanced gas turbine materials, design and technology

J. Fadok, Siemens Energy Inc., USA

Abstract:

This chapter will discuss the technologies and material used in modern industrial gas turbines. Rapid evolution of the gas turbine since its first application to wartime aircraft engines has been made possible through the deployment of advanced materials and technologies. The background of these advancements, their use in the gas turbine, and the drivers for new technologies to achieve higher temperatures and efficiencies will be the main focus. Furthermore, the technologies needed for advanced hydrogen-fuelled gas turbines will be considered.

Key words

gas turbine

advanced materials

turbine

combustion

compressor

IGCC

NGCC

thermal barrier coating

single crystal

hydrogen

Brayton cycle

CO₂ capture

gamma prime phase

1.1 Introduction

The industrial gas turbine is a key element to meeting the world energy demands today and in the future. The flexibility of this technology facilitates deployment in simple cycle peaking applications as well as combined cycle applications. Evolution from the first industrial gas turbines in the 1940s of about 19% thermal efficiency to today’s combined cycle plants at 60% efficiency has been enabled by advancements in materials, design and technology. This chapter will discuss the background of these advancements, their use in the gas turbine, the drivers for new technologies to achieve higher temperatures and efficiencies, and technologies needed for advanced hydrogen-fuelled gas turbines.

In only 50 years, industrial gas turbines have evolved from the early jet engines for airplanes used in the Second World War to one of the most widely deployed power generation technologies in the world today. Early applications to power generation were direct adaptations of the jet engine, but, as industrial use increased, especially in combined cycle systems, technologies necessary to advance land-based gas turbines were developed. The first industrial gas turbines went into service in the early 1950s for application in power generation, transportation and mechanical drives. The 1960s saw the development of the combined cycle power plants. By thermodynamically coupling the gas turbine Brayton cycle to the Rankine cycle, an efficiency of 39% was already possible compared to about 30% simple cycle efficiency available at that time (Scalzo and Bannister, 1994). Figure 1.1 shows schematic representations of a simple cycle and a combined cycle gas turbine power plant configuration.

1.1 Schematic representation of a gas turbine in (a) simple cycle configuration and (b) combined cycle configuration.

In the schematic diagram for a simple cycle, the conditions for temperature T_n and pressure P_n are noted at key thermodynamic points in the gas turbine, where n represents the following:

1. compressor inlet

2. compressor discharge

3. turbine inlet

4. turbine exhaust.

Despite their common heritage, the aero and heavy industrial gas turbines have significant differences in design and technology. Table 1.1 shows the most notable differences between these technologies.

Table 1.1

Key differences in requirements for aero engines and heavy industrial gas turbines

Parameter	Aeroengine	IGT
Weight	Very important	Not significant
Operating time (hours)	25 000	> 100 000
– steady state	< 1000	> 100 000
– peak temperature
Cyclic duty	Severe	Severe
Environment	Non-corrosive	Corrosive
Size	Small	Large

Owing to the weight constraints the most obvious physical differences will be found in the rotor and casing constructions, but other differences are also notable, particularly in the combustor and turbine sections. The key driver for power generation technology is cost of electricity (COE) and the driver for aircraft engines is specific fuel consumption (SFC). Both parameters are driven by efficiency and lead to higher pressures and temperatures, which challenge the gas turbine designer. While the focus of this chapter is heavy industrial gas turbines, frequent reference to the aircraft industry is made to highlight the synergy between these industries.

When evaluating the available power generation technologies, COE is levelized over a specified operating period, usually 20 years. This gives the levelized cost of electricity (LCOE) on a per annum basis, and can be expressed as

[1.1]

Figure 1.2 shows the LCOE breakdown for a modern gas turbine combined cycle power plant. It can be seen that the major portion of the LCOE is fuel cost, while capital cost makes up most of the remainder.

1.2 LOCE for a natural gas combined cycle (NGCC) power plant (source of data US Department of Energy (NETL, 2007)).

With the main contribution to LCOE being fuel cost, natural gas-fired combined cycles must achieve the highest possible cycle efficiency. Over the past decades this increase has been significant, as can be seen in Fig. 1.3. A similar trend for firing temperature (temperature entering the turbine, T₃) and pressure ratio P₂/P₁ could also be derived. As you will see, these advancements have been made possible through improvements in materials and technologies. The second most significant contributor to the COE is capital cost, therefore, an evaluation of total life cycle cost, to compare the efficiency benefit versus additional cost of higher grade materials is necessary. The LCOE distribution shown in Fig. 1.2 is a very simplified view of the total actual operating cost for a gas turbine based power plant, and also assumes a base-load duty cycle, presented later. The importance of availability, reliability and degradation should not be under-stated. Parts replacement costs are high, and frequent maintenance drives up operating cost. Forced outages must be avoided and efficiency has to be maintained at a competitive level over extended operating intervals. Upgraded conditions in the gas turbine tend to increase risk, therefore extensive rig testing and highly instrumented prototypes are manufactured and tested to verify analysis predictions prior to full commercial product release and market acceptance.

1.3 Trends in output and efficiency (used with permission from Siemens Energy, Inc.).

Emissions constraints for natural gas combined cycle (NGCC) plants include strict regulations for nitrogen oxides (NO_x) and carbon monoxide (CO). Advanced lean premix combustion systems, constrained by emissions, must be capable of operating with contradicting requirements for high temperature and low NO_x emissions. Furthermore, the emission of greenhouse gases like carbon dioxide (CO₂) is an increasing concern in the world today and often influences decisions regarding the deployment of new power generation technology. When comparing fossil fuel technologies, NGCC has the lowest emissions of CO₂ (one-half of the emissions compared to a coal-fired steam power plant). However, integrated gasification combined cycle (IGCC) plants fuelled by coal are currently being designed to capture CO₂ and produce hydrogen-rich syngas (or synthesis gas), which can be burned in gas turbine engines yielding CO₂ emissions almost five times lower than those from a NGCC. The challenges of operating on hydrogen-rich fuels resulting from coal-derived syngas (with CO₂ captured) will be discussed in more detail later in this chapter.

1.2 Development of materials and coatings for gas turbines and turbine components

An advanced industrial gas turbine engine is shown in Fig. 1.4. From left to right the major components of the gas turbine are the compressor section, combustor section and turbine section. The engine shown drives a generator from the compressor (cold end), and employs a can-annular combustion system, where individual transition pieces convey the hot combustion gases to the inlet of the turbine. It is a single-shaft (rotor) engine that operates at 3600 r/min (60 Hz) and is optimized for combined cycle application. A (50 Hz) system operates at 3000 r/min and is approximately 1.2 times the size. The casings are designed with a horizontal split line and multiple vertical joints for maintenance of the individual sections of the engine. The materials for the major components of the gas turbine are subjected to differing operating conditions and criteria, both of which influence material selection.

1.4 Advanced SGT6-6000G industrial gas turbine (used with permission from Siemens Energy, Inc.).

1.2.1 Compressor

Blades and vanes ...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributor contact details
• Woodhead Publishing Series in Energy
• Preface
• Part I: Advanced power plant materials and designs
• Part II: Gas separation membranes, emissions handling, and instrumentation and control technology for advanced power plants
• Part III: Improving the fuel flexibility, environmental impact
• Index