Search Results for Flue gases

Coal-based thermal power plants play a major role in the welfare of many nations and the overall global economy. This chapter describes the basic equipment requirements and operating principles of thermal power plants, particularly subcritical, supercritical, and ultra-supercritical types.

Combustion byproducts such as soot, ash, and abrasive particulates can inflict significant damage to boiler tubes through the cumulative effect of erosion. This chapter examines the types of erosion that occur on the fire side of boiler components and the associated causes. It discusses the erosive effect of blowing soot, steam, and fly ash as well as coal particle impingement and falling slag. It also includes several case studies.

Fossil fuels produce many byproducts that, if not fully combusted, put boiler tubes at risk. Fuel ash, chemical residues, and process heat pose the greatest threat and are the primary contributors to fireside corrosion. This chapter covers various types of fireside corrosion such as waterwall, fuel ash, and hot corrosion, acid dew-point or cold-end corrosion, and polythionic acid corrosion. It also addresses stress corrosion cracking and includes relevant case studies.

Boilers are engineered systems designed to convert the chemical energy in fuel into heat to generate hot water or steam. This chapter describes boiler applications and types, including firetube boilers, watertube boilers, electric boilers, packaged boilers, fluidized bed combustion boilers, oil- and gas-fired boilers, waste heat boilers, and black liquor recovery boilers. It also describes the operation and working principle of utility or power plant boilers, covering conventional subcritical and advanced supercritical types.

Boiler tubes operating at high temperatures under significant pressure are vulnerable to stress rupture failures. This chapter examines the cause, effect, and appearance of such failures. It discusses the conditions and mechanisms that either lead to or are associated with stress rupture, including overheating, high-temperature creep, graphitization, and dissimilar metal welds. It explains how to determine which mechanisms are in play by interpreting fracture patterns and microstructural details. It also describes the investigation of several carbon and low-alloy steel tubes that failed due to stress rupture.

This chapter provides a brief overview of iron and steel manufacturing and the major equipment involved in the process as well as identifying where casting fits into the overall process. In addition, it provides an overview of cast iron manufacturing, including the processes involved in converting pig iron into cast iron and steel.

Boiler tubes subjected to cyclic or fluctuating loads over extended periods of time are prone to fatigue failure. Fatigue can occur at relatively low stresses and is implicated in almost 80% of the tube failures in firetube boilers. This chapter covers the most common forms of boiler tube fatigue, including mechanical or vibrational fatigue, corrosion fatigue, thermal fatigue, and creep-fatigue interaction. It discusses the causes, characteristics, and impacts of each type and provides several case studies.

This chapter details the types of heat treating furnaces. It discusses energy sources and modes of heat transmission. The chapter’s focus is on the different types of batch furnaces and continuous furnaces, including box furnaces, integral-quench batch furnaces, pit furnaces, furnaces for heat treating with fluidized beds, and straight chamber continuous furnaces.

The melting furnace is a critically important piece of equipment in a foundry; it influences the balance between the metal required by molding machines and the melting capacity. This chapter presents the features, types, advantages, and applications of furnaces suitable for iron and steels such as cupolas, induction furnaces, and arc furnaces.

Stainless steels and nickel-base alloys are recognized for their resistance to general corrosion and other categories of corrosion. This chapter examines the effects of specific alloying elements, metallurgical structure, and mechanical conditioning on the corrosion resistance of these alloys. Some categories of corrosion covered are pitting, crevice, intergranular, stress-corrosion cracking, general, and high-temperature corrosion.

This chapter provides a detailed discussion on the definitions, alloy classification, alloy selection, mechanical properties, hot gas corrosion resistance, and formability of heat-resistant high alloy steels. In addition, the applications of cast heat-resistant alloys are also discussed.

Managing corrosion continues to be a challenge for operators of modern boilers worldwide. This chapter addresses the corrosion-related problems that can occur in boilers burning municipal solid waste (MSW). It describes corrosion mechanisms associated with different environments and alloys. It also discusses corrosion protection methods for furnace waterwalls and superheater tubes in waste-to-energy boilers.

Boiler tube failures associated with material defects are often the result of poor quality control, whether in primary production, on-site fabrication, storage and handling, or installation. This chapter examines quality-related failures stemming from compositional and structural defects, forming and welding defects, design defects, improper cleaning methods, and ineffective maintenance. It also includes case studies and illustrations.

Boilers are often classified based on the maximum operating temperature and pressure for which they are designed. Classifications, in ascending order, are subcritical, supercritical, ultra-supercritical, and to advanced ultra-supercritical. At each higher operating point comes greater efficiency, as well as greater demand on construction materials. This chapter discusses the primary requirements for boiler tube materials, including oxidation and corrosion resistance, fatigue strength, thermal conductivity, and the ability to resist creep and rupture. It also provides information on various steels and alloys, covering cost, engineering specifications, and ease of use.

This chapter discusses the effects of corrosion on boiler tube surfaces exposed to water and steam. It describes the process of corrosion, the formation of scale, and the oxides of iron from which it forms. It addresses the primary types of corrosion found in boiler environments, including general corrosion, under-deposit corrosion, microbially induced corrosion, flow-accelerated corrosion, stress-assisted corrosion, erosion-corrosion, cavitation, oxygen pitting, stress-corrosion cracking, and caustic embrittlement. The discussion is supported by several illustrations and relevant case studies.

This chapter focuses on various factors to be considered at design stage to minimize corrosion. It begins by providing information on design considerations and general corrosion awareness. This is followed by a description of several factors influencing materials-component failure. Details on design and materials selection, which assist in controlling corrosion, are then provided. The chapter ends with a discussion on the design factors that influence corrosion.

This chapter discusses material-related problems associated with coal-fired burners. It explains how high temperatures affect heat-absorbing surfaces in furnace combustion areas and in the convection pass of superheaters and reheaters. It describes how low-NOx combustion technology, intended to reduce NOx emissions, accelerates tube wall wastage. It also covers circumferential cracking in furnace waterwalls, thermal fatigue cracking induced by waterlances and water cannons, superheater-reheater corrosion, and erosion in fluidized-bed boilers.

Black liquor recovery boilers are an integral part of the kraft pulping process used in paper mills. Besides recovering chemicals for reuse, they also produce process steam. High operating temperatures and exposure to process chemicals and combustion byproducts make recovery boilers susceptible to corrosion. This chapter describes some of the problems that the pulp and paper industry has solved as well as ongoing issues and concerns. It includes an in-depth review of 304L cladding failures involving coextruded composite tubes used as floor tunes in the lower furnace, as superheater tubes, and for other purposes such as smelt openings. It provides detailed images showing cracks on the outer surfaces of the tubes and explains where the tubes were used and how they were operated.