New Trends in Coal Conversion

Combustion, Gasification, Emissions, and Coking

Isabel Suarez-Ruiz, Fernando Rubiera, Maria Antonia Diez, Isabel Suarez-Ruiz, Fernando Rubiera, Maria Antonia Diez

• Publisher: Woodhead Publishing
• Year: 2018
• ISBN:
  9780081022023
• Topic: Technology & Engineering
• Subtopic: Fossil Fuels
• Index: Technology & Engineering

New Trends in Coal Conversion: Combustion, Gasification, Emissions, and Coking covers the latest advancements in coal utilization, including coal conversion processes and mitigation of environmental impacts, providing an up-to-date source of information for a cleaner and more environmentally friendly use of coal, with a particular emphasis on the two biggest users of coal—utilities and the steel industry. Coverage includes recent advances in combustion co-firing, gasification, and on the minimization of trace element and CO 2 emissions that is ideal for plant engineers, researchers, and quality control engineers in electric utilities and steelmaking.

Other sections cover new advances in clean coal technologies for the steel industry, technological advances in conventional by-products, the heat-recovery/non-recovering cokemaking process, and the increasing use of low-quality coals in coking blends. Readers will learn how to make more effective use of coal resources, deliver higher productivity, save energy and reduce the environmental impact of their coal utilization.

• Provides the current state-of-the-art and ongoing activities within coal conversion processes, with an emphasis on emerging technologies for the reduction of CO2 and trace elements
• Discusses innovations in cokemaking for improved efficiency, energy savings and reduced environmental impact
• Include case studies and examples throughout the book

1

Coal

Isabel Suárez-Ruiz, María Antonia Diez, and Fernando Rubiera Instituto Nacional del Carbón, INCAR-CSIC, Oviedo, Spain

Abstract

Coal as a fossil fuel has long been used for a variety of industrial and domestic purposes. The worldwide distribution and widespread availability of coal resources have been a major contributor to the economic growth of many countries, either directly through their own resources or indirectly through access to the international coal trade. Alhough coal usage has continued to increase, environmental concerns and changes in the political climate have begun to give coal an unfavorable public image. Increasing concerns about coal utilization as a contributor to greenhouse gas emissions, particularly CO₂, have led to more intense questioning of the role of coal and a renewed search for alternative energy sources. Despite this coal will remain the second largest energy source worldwide in the next years and a key feedstock for other industrial usages.

Coal has been thoroughly researched over the years to the point where all its characteristics and properties that make it such a versatile product are known. This chapter describes and summarizes the general knowledge acquired about coal in relation to its formation, worldwide resources and reserves, composition and properties, and all the characteristics relevant for describing the quality of a coal when it is used in the main conversion processes: combustion, gasification, and cokemaking.

Keywords

Classification of coals; Coal; Coal composition; Coal distribution; Coal quality; Coal utilization; Coal weathering; Cokemaking; Combustion; Gasification; Rank; Type of coals

Chapter Outline

1. 1.1 Introduction
2. 1.2 General concepts about coal
   1. 1.2.1 Coal definition
   2. 1.2.2 Coal formation
3. 1.3 Coal resources
   1. 1.3.1 Geographical distribution of coal
   2. 1.3.2 Distribution of coal by geological age
4. 1.4 Coal reserves, production, and consumption
5. 1.5 Coal quality
   1. 1.5.1 Fundamental characteristics of coal
      1. 1.5.1.1 Coal composition
      1. 1.5.1.2 Coal rank, determination, and classification of coals
   1. 1.5.2 Characterization of coal for industrial use
      1. 1.5.2.1 Coal utilization
      1. 1.5.2.2 Coal characterization: analysis and test
      1. 1.5.2.3 Coal weathering and coal oxidation
6. 1.6 Environmental issues related to coal
   1. 1.6.1 Coal mining
   1. 1.6.2 Coal utilization
      1. 1.6.2.1 Coal combustion for power generation
      1. 1.6.2.2 Utilization of coal at coking plants
      1. 1.6.2.3 Other uses of coal sources of pollution
7. 1.7 The coal in the future
8. 1.8 Concluding remarks
9. Acknowledgments
10. References

1.1. Introduction

Coal is an organic sedimentary rock that belongs to the category of fossil fuels together with oil and natural gas. It is considered a nonrenewable natural resource because it requires millions of years to form and therefore it cannot be replenished within the human time frame. Although coal may have been used for ornamental purposes in prehistoric times, its properties as a fuel seem to have been known since some 1000 years ago. In fact, the use of coal as a fuel probably dates back from its first use in China, 1000 years BC (Finkelman and Greb, 2008). The National Coal Council (2015) reported that during the second and third centuries, AC coal was used in Rome basically as an energy source (heating source). By the 18th century coal had replaced wood charcoal mainly because coal burned cleaner and gave off more heat. At that time coal also contributed to the industrial revolution. More recently, in most industrialized countries, coal has been a key source of energy and a major contributor to their economic growth.

Coal is the world's cheapest, most abundant, and widely distributed fossil fuel, and today it is still a primary energy source for electric power, accounting for 41% of energy generation in the world (National Coal Council, 2015). According to recent estimates, and despite its slight decline in recent years, coal is expected to remain the second largest energy source worldwide until 2030–40 (U.S. Energy Information Administration, 2016, 2017).

In addition to electric power generation, the main uses of coal are for steel industry as well as for the production of cement and chemicals. In the steel industry, coal is used to produce coke which is used in blast furnaces for smelting iron ore to produce molten iron, which is a primary component of steel. Seventy percent of the steel produced in the world is made using coal (National Coal Council, 2015). Coal is also used in the manufacturing process of cement, ferroalloys, nonferrous metals such as aluminum, lime, and bricks. Cement is produced in kilns that use coal as fuel to heat the raw materials to produce the clinker, which is one of the components in the manufacture of cement. Moreover, coal is an important feedstock in the production of carbon materials such as coal-based activated carbon with a high surface area for air and water treatments and chemical-derived products such as oils, tar, and pitches for a wide range of chemical products such as fertilizers and primary chemicals among others.

However, at the same time, coal is also an intensive source of pollutant emissions, mainly carbon emissions which are directly related to the global warming and climate change. Despite recent environmental policies in some developed countries against the use of coal, the world continues to be heavily dependent on this fossil fuel. The future of coal utilization in a sustainable development scenario will be conditioned by the capacity of reducing associated emissions through the construction of advanced coal power plants in case of power generation and to make industrial processes using coal so efficient that they reduce pollutant emissions to the point of near-zero emissions.

Because of the importance of coal in the economic development of many countries, this natural resource has been thoroughly researched over the years, particularly during the last century to the point where all its characteristics and properties that make it such a versatile product are known. This chapter describes and summarizes the general knowledge acquired about coal in relation to its formation, worldwide resources and reserves, coal composition and properties, and all the characteristics relevant for describing the quality of a coal when it is used in the main conversion processes: combustion, gasification, and cokemaking.

1.2. General concepts about coal

1.2.1. Coal definition

Coal is an organic and combustible sedimentary rock of black or brownish-black color with a high carbon content and varied physical, chemical, and technological properties depending on the rank (degree of evolution) reached throughout its geological history. Whereas the majority of rocks are inorganic, coal consists predominantly of organic matter, largely derived from a variety of plant remains (higher plants, ferns, fungi, and algae) and different tissues (leaves, stalks, woody trunks, bark, pol...