Coal Combustion Products (CCPs)

Characteristics, Utilization and Beneficiation

Tom Robl, Anne Oberlink, Rod Jones

• Publisher: Woodhead Publishing
• Year: 2017
• Print ISBN: 9780081009451
• eBook ISBN: 9780081010471
• Topic: Business
• Subtopic: Energy Industry
• Index: Business

Coal Combustion Products (CCPs): Their Nature, Utilization and Beneficiation is a valuable resource for engineers and scientists from the coal, cement, concrete, and construction industries seeking an in-depth guide to the characteristics, utilization, beneficiation, and environmental impacts of coal combustion by-products. Researchers in universities working in this area will also find much to expand their knowledge.The book provides a detailed overview of the different waste materials produced during power generation from coal, exploring their nature, beneficiation techniques, applications, and environmental impacts. Strong focus is placed on coal fly ash, bottom ash, and flue gas desulfurization materials, and their employment in cement, concrete, gypsum products, aggregates, road construction, geotechnics, and agriculture, among other products and industries.Part 1 focuses on the nature of coal ashes, with chapters on their origin, generation, and storage, both in ponds and landfill. The coal combustion by-products produced as a result of clean coal technologies are the focus of the final chapter in the section. The next group of chapters in Part 2 considers the utilization of different waste materials, including the key products coal fly ash, bottom ash, and flue gas desulfurization materials. This is followed by a contribution reviewing the latest research into innovative and advanced uses for coal ash.After an introduction to ash quality problems and quality monitoring, Part 3 concentrates on the essential area of by-product beneficiation techniques, in other words how to maximize the quality of materials for the end user. Topics covered include separation methods, thermal processing, and chemical passivation. The final section of the book addresses environmental issues, including the use of coal combustion by-products in green construction materials and the essential health and safety considerations associated with their use.- An essential reference on the nature, reactivity, beneficiation, potential and environmental risks of coal-combustion by-products- Contains an in-depth review of the origin and geochemistry of coal ash- Explores the utilization of coal combustion by-products as supplementary cementitious materials to reduce the anthropomorphic greenhouse gas emissions associated with the use of ordinary Portland cement concrete- Describes the essential area of the toxicology of coal combustion by-products

Part One

Nature of coal combustion products

1

An introduction to the nature of coal

J. Groppo University of Kentucky, Lexington, KY, United States

Abstract

To comprehend the varied composition, properties and uses coal ash, it is important to begin with an understanding of the coal from which it is derived. Coal is essentially an assemblage of organic and inorganic material that transforms over geologic time into a relatively high energy density fuel through the process of coalification. Energy density, or rank, increases as coalification proceeds, which accounts for the wide ranges in coal quality that exist in the world today. Wherever practical, mined coal is cleaned using physical beneficiation techniques to reduce the amount of inorganic material present in order to increase energy density and reduce fuel impurities, a practice that is limited to higher rank coals. The most common practice for electricity generation is to pulverize coal prior to combustion. Combustion consumes organic phases, while remaining inorganic components, such as minerals and trace elements, transform into coal ash. The composition, properties and use of the residual ash is dependent upon both the inorganic material present in the fuel and the combustion conditions. Clean coal technologies (CCT) are practices developed to reduce emissions of SO_x and NO_x produced by coal combustion. Since CCTs are quite different from pulverized coal combustion, the composition and properties of the ash they produce are also quite different.

Keywords

coal rank; minerals; trace elements; beneficiation; clean coal technologies

1.1 Coal formation and rank

Coal is a heterogeneous material essentially comprised of fossilized carbon that originates from organic material accumulated in low-lying areas or sediment basins. The parent organic material was typically vegetative in origin, consisting of trees, plants, leaves, roots, branches, pollen, and spores. As these materials accumulated in a saturated environment, partially decayed vegetation would settle to the bottom of the swamp or bog and transform into peat, provided suitable acidity and anaerobic conditions existed to prevent full decay. This process, termed humification, refers to the decomposition of plant matter as it is transformed into organic residue (Fuchsman, 1980). Over time, massive amounts of vegetative matter cyclically accumulated. As long as the water table continued to rise and prevent the swamp from drying out, more peat formed.

Several different systems are used to classify peat, using characteristics such as geology, botanical content, or physiochemical properties (Fuchsman, 1980; Boron, Evans, & Peterson, 1987). Table 1.1 shows an increase in carbon content and a decrease in oxygen content as the level of humification increases. As decomposition proceeds, readily degraded components, such as cellulose and hemicellulose, are the first to be attacked by microorganisms, while more resistant lignin remains (Boron et al., 1987). In addition the amount of bitumen and humic acids also increase, with humic acids comprising up to 60% of the organic material present (Table 1.2). The organic matter composition of peat is important because it comprises the parent material that will eventually be transformed with time and pressure into coal.

Table 1.1

Elemental composition of peat as a function of humification (Fuchsman, 1980)

Element (dry basis)	H1 to H3	H4 to H7	H8 to H10
Carbon (%)	43–53	56–58	59–63
Hydrogen (%)	5.0–6.1	5.5–6.1	5.1–6.1
Oxygen (%)	40–46	34–39	31–34
Nitrogen (%)	0.5–1.0	0.8–1.1	0.9–1.9
Sulfur (%)	0.1–0.2	0.1–0.3	0.2–0.5

Table 1.2

Organic matter components in peat as a function of humification (Boron et al., 1987)

Organic material	H1 to H2	H5 to H6	H9 to H10
Cellulose (%)	15–20	5–15	–
Hemicellulose (%)	15–30	10–30	0–1
Lignin (%)	5–40	5–30	5–20
Humic Acids (%)	0–5	20–30	50–60
Bitumens (%)	1–10	5–15	5–20
Nitrogen Compounds (%)	3–14	5–20	5–25

Infiltration of sediments via flooding events or erosion resulted in the burial of the peat. The burial depth increased with a continued deposition of sediment layers, eventually progressing to depths where tempe...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of contributors
• Editors biography
• Preface
• Acknowledgments
• Part One: Nature of coal combustion products
• Part Two: Utilization of coal combustion products
• Part Three: The beneficiation of coal combustion materials
• Part Four: Coal products and the environment
• Index