The long-term future for coal looks bleak. The recent UN climate change conference in Paris called for an end to the use of fossil fuels. However, coal remains one of the world’s most important sources of energy, fuelling more than 40% of electricity generation worldwide, with many developing nations relying almost wholly on coal-fuelled electricity.
Coal has been the fastest growing energy source in recent years and is essential for many industrial activities, but the coal industry is hugely damaging for the environment. A major driver in climate change and causing around 40% of the world’s carbon dioxide emissions, coal fuel comes at a high environmental price. Furthermore, mining and air pollution kill thousands each year.
A timely addition to the series, this book critically reviews the role of coal in the 21st century, examining energy needs, usage and health implications. With case studies and an examination of future developments and economics, this text provides an essential update on an environmental topic the world cannot ignore.
The long-term future for coal looks bleak. The recent UN climate change conference in Paris called for an end to the use of fossil fuels. However, coal remains one of the world’s most important sources of energy, fuelling more than 40% of electricity generation worldwide, with many developing nations relying almost wholly on coal-fuelled electricity.
Coal has been the fastest growing energy source in recent years and is essential for many industrial activities, but the coal industry is hugely damaging for the environment. A major driver in climate change and causing around 40% of the world’s carbon dioxide emissions, coal fuel comes at a high environmental price. Furthermore, mining and air pollution kill thousands each year.
A timely addition to the series, this book critically reviews the role of coal in the 21st century, examining energy needs, usage and health implications. With case studies and an examination of future developments and economics, this text provides an essential update on an environmental topic the world cannot ignore.
Coal in the 21st Century: Energy Needs, Chemicals and Environmental Controls
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Coal in the 21st Century: Energy Needs, Chemicals and Environmental Controls
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Overview
The long-term future for coal looks bleak. The recent UN climate change conference in Paris called for an end to the use of fossil fuels. However, coal remains one of the world’s most important sources of energy, fuelling more than 40% of electricity generation worldwide, with many developing nations relying almost wholly on coal-fuelled electricity.
Coal has been the fastest growing energy source in recent years and is essential for many industrial activities, but the coal industry is hugely damaging for the environment. A major driver in climate change and causing around 40% of the world’s carbon dioxide emissions, coal fuel comes at a high environmental price. Furthermore, mining and air pollution kill thousands each year.
A timely addition to the series, this book critically reviews the role of coal in the 21st century, examining energy needs, usage and health implications. With case studies and an examination of future developments and economics, this text provides an essential update on an environmental topic the world cannot ignore.
Product Details
| ISBN-13: | 9781788012515 |
|---|---|
| Publisher: | RSC |
| Publication date: | 10/02/2017 |
| Series: | Issues in Environmental Science and Technology , #45 |
| Sold by: | Barnes & Noble |
| Format: | eBook |
| Pages: | 224 |
| File size: | 2 MB |
About the Author
The series has been edited by Professors Hester and Harrison since it began in 1994.
Professor Roy Harrison OBE is listed by ISI Thomson Scientific (on ISI Web of Knowledge) as a Highly Cited Researcher in the Environmental Science/Ecology category. He has an h-index of 54 (i.e. 54 of his papers have received 54 or more citations in the literature). In 2004 he was appointed OBE for services to environmental science in the New Year Honours List. He was profiled by the Journal of Environmental Monitoring (Vol 5, pp 39N-41N, 2003). Professor Harrison’s research interests lie in the field of environment and human health. His main specialism is in air pollution, from emissions through atmospheric chemical and physical transformations to exposure and effects on human health. Much of this work is designed to inform the development of policy.
Now an emeritus professor, Professor Ron Hester's current activities in chemistry are mainly as an editor and as an external examiner and assessor. He also retains appointments as external examiner and assessor / adviser on courses, individual promotions, and departmental / subject area evaluations both in the UK and abroad.
Read an Excerpt
CHAPTER 1
World Energy Needs: A Role for Coal in the Energy Mix
LIAM McHUGH
ABSTRACT
The last 18 months have been a landmark period for climate, environment and development negotiation processes with the delivery of the Sustainable Development Goals and the Paris Agreement at the 21st Session of the Conference of the Parties (COP21). Energy access and climate goals are not competing priorities. As demonstrated by the Intended Nationally Determined Contributions (INDC) submitted in the lead-up to the Paris summit, each nation will choose an energy mix that best meets its needs. For this reason many countries have identified a continuing role for coal. Coal is a critical enabler in the modern world. It provides 41% of the world's electricity and is an essential raw material in the production of 70% of the world's steel and 90% of the world's cement. This chapter provides an introductory overview of coal, its use in building modern societies and its role in delivering low-cost on-grid electricity while integrating environmental commitments.
1 Introduction
There is little doubt that the 'Paris Agreement' delivered at the 2015 Climate Change Conference represented a landmark accomplishment. Equally, the rapid endorsement by national governments and the private sector to implement the deal is a welcome development.
Looking ahead, as the deal becomes a reality it is vitally important that its delivery integrates environmental imperatives with the aims of universal access to energy, energy security and social and economic development. Only by balancing these elements can the agreement produce emissions reductions consistent with its vision while maintaining legitimate economic development and poverty alleviation efforts.
Energy is vital to development. Access to affordable and reliable electricity is the foundation of prosperity in the modern world. The Paris Agreement, however, has given countries an added impetus to ensure that improving energy access is balanced with action on reducing emissions.
Energy access and climate goals are not competing priorities. This understanding formed the basis of national climate pledges that were submitted in the months prior to the Paris climate negotiations and ultimately provided the foundation for the Agreement. Known as the Nationally Determined Contributions (NDCs), these pledges will act as strategic roadmaps for countries' climate, energy and development priorities.
Twenty four countries, representing over 50% of the world's emissions, submitted Intended Nationally Determined Contribution (INDCs) that identified a continuing role for coal. No doubt as the INDC process is formalised this figure will rise.
Coal is a critical enabler in the modern world. It provides 41% of the world's electricity and is an essential raw material in the production of 70% of the world's steel and 90% of the world's cement. Fossil fuels today provide over 80% of the world's primary energy, a percentage not forecast to change significantly for decades to come. With the use of coal projected to continue to grow over the coming decades, a low-emission technology pathway for coal is required to meet emissions targets.
This pathway begins with deployment of high-efficiency, low-emissions (HELE) power stations using technology that is available today. These facilities are being built rapidly and emit 25–33% less CO2 and eliminate other emissions, such as oxides of sulfur and nitrogen and particulates. Moreover, HELE technology represents significant progress on the pathway towards carbon capture, use and storage (CCUS), which will be vital to achieving global climate objectives.
This chapter provides a comprehensive overview of coal and the role it plays in supporting sustainable development. It covers how coal is formed, how it is mined, through to its use and the impact it has on our societies and natural environments. It describes coal's role as an energy source and how coal – along with other sources of energy – will be vital in meeting the world's rapidly growing development needs along a sustainable pathway.
2 What Is Coal?
2.1 Coal Formation
Coal is a combustible, black or brownish-black sedimentary, organic rock, which is composed mainly of carbon, hydrogen and oxygen.
At its most basic level, coal is the altered remains of prehistoric vegetation that was originally located in swamps and peat bogs. Like all living organisms, these plants stored energy from the sun through a process known as photosynthesis. Generally, as plants die this energy is released during decay. At times, however, interruption of the decay process through the build-up of silt and other sediments, combined with tectonic movements, buried vegetation to great depths. In turn, buried vegetation underwent chemical and physical changes as a result of millions of years of pressure and heat transforming it into coal.
The process of coal formation began 360 to 290 million years ago during the Carboniferous Period – also known as the first coal age.
Several factors, including temperature, pressure and age, determined the quality of each coal deposit. Peat, in the first instance, was converted into lignite or 'brown coal'. Over millennia, pressure and temperature combined to transform lignite coal to more energy-intensive 'sub-bituminous' coal. Further chemical and physical changes occurred until these coals became harder and blacker, forming the 'bituminous' or 'hard' coals. Under the right conditions, the progressive increase in the organic maturity continued, finally forming anthracite.
2.2 Coal Classification
The degree of change that coal undergoes as it matures from lignite to anthracite is known as 'coalification'. The process has an important bearing on the physical and chemical properties of coal and is referred to as the 'rank' of the coal. Ranking is determined by the degree of transformation of the original plant material to carbon and is illustrated in Figure 1.
Low-rank coals–lignite and sub-bituminous–are low in carbon but high in hydrogen and oxygen content, and therefore lower in energy content. Low-rank coals are typically softer, friable materials with a dull, earthy appearance.
High-rank coals are high in carbon and therefore in heat value, with conversely lower levels of hydrogen and oxygen. Generally, high-rank coal is harder, stronger and often has a black, vitreous lustre. At the top of the rank scale, anthracite has the highest carbon and energy content, with the lowest levels of moisture.
2.3 Where Is Coal Found?
According to the International Energy Agency (IEA), there are over 985 billion tonnes of proven coal reserves worldwide. At the current rate of production there are enough coal reserves to last around 128 years.
Moreover, while it is estimated that current coal reserves could sustain demand well into next century, this could extend still further through a number of developments, including:
• The discovery of new reserves through ongoing and improved exploration activities
• Advances in mining techniques, which will allow previously inaccessible reserves to be reached.
As seen in Figure 2, coal reserves are available in almost every region, with recoverable reserves in almost 70 countries. Although the largest reserves are in the USA, Russia, China and India, coal is actively mined in more than 70 countries. By contrast, Russia, Iran and Qatar control over half of the world's gas reserves and close to 50% of the world's oil reserves are located in the Middle East.
Most coal is consumed domestically and only 17% is traded internationally. In a number of countries coal is also the only domestically available energy fuel and its use is motivated by both economic and energy security considerations. This is the case in countries and regions such as Europe, China and India, where coal reserves are much higher than oil or gas reserves. Most of the world's coal exports originate from countries that are considered to be politically stable – a characteristic which reduces the risks of supply interruptions.
2.4 Coal Exploration
Coal reserves are discovered through exploration activities. The process usually involves creating a geological map of the area, then carrying out geochemical and geophysical surveys, followed by exploration drilling. This allows an accurate picture of the area to be developed.
The area will only ever become a coal mine if it is large enough and of sufficient quality that the coal can be economically recovered. Once this has been confirmed, mining operations can begin.
2.5 Coal Mining
Coal is mined by two methods – surface (opencast) or underground (deep mining).
The choice of mining method is largely determined by the geology of the coal deposit. Underground mining currently accounts for about 60% of world coal production, although in several important coal-producing countries surface mining is more common. Surface mining accounts for around 80% of production in Australia, while in the USA it is used for about 67% of production.
2.5.1 Underground Mining. There are two main methods of underground mining: room and pillar and longwall mining.
In room and pillar mining, coal deposits are mined by cutting a network of 'rooms' into the coal seam and leaving behind 'pillars' of coal to support the roof of the mine. These pillars can be up to 40% of the total coal in the seam, although this coal can sometimes be recovered at a later stage. This can be achieved in what is known as 'retreat mining', where coal is mined from the pillars as workers retreat. The roof is then allowed to collapse and the mine is abandoned.
Longwall mining involves the full extraction of coal from a section of the seam or 'face' using mechanical shearers. A longwall face requires careful planning to ensure favourable geology exists throughout the section before development work begins. The coal 'face' can vary in length from 100–350 m. Self-advancing, hydraulically-powered supports temporarily hold up the roof while coal is extracted. When coal has been extracted from the area, the roof is allowed to collapse. Over 75% of the coal in the deposit can be extracted from panels of coal that can extend 3 km through the coal seam.
The main advantage of room and pillar mining over longwall mining is that it allows coal production to start much more quickly, using mobile machinery that costs under $5 million (longwall mining machinery can cost $50 million).
The choice of mining technique is site-specific but always based on economic considerations; differences even within a single mine can lead to both methods being used.
2.5.2 Surface Mining. Surface mining – also known as opencast or open cut mining – is only economic when the coal seam is near the surface. This method recovers a higher proportion of the coal deposit than underground mining as all coal seams are exploited – 90% or more of the coal can be recovered. Large opencast mines can cover an area of many square kilometres and use very large pieces of equipment, including: draglines which remove the overburden; power shovels; large trucks which transport overburden and coal; bucket wheel excavators; and conveyors.
The overburden of soil and rock is first broken up by explosives; it is then removed by draglines or by shovel and truck. Once the coal seam is exposed, it is drilled, fractured and systematically mined in strips. The coal is then loaded on to large trucks or conveyors for transport to either the coal preparation plant or direct to where it will be used.
2.6 Coal Preparation
Coal straight from the ground, known as run-of-mine (ROM) coal, often contains unwanted impurities such as rock and dirt and comes in a mixture of different-sized fragments. However, coal users need coal of a consistent quality. Coal preparation – also known as coal beneficiation or coal washing – refers to the treatment of ROM coal to ensure a consistent quality and to enhance its suitability for particular end-uses.
The treatment depends on the properties of the coal and its intended use. It may require only simple crushing or it may need to go through a complex treatment process to reduce impurities. To remove impurities, the raw run-of-mine coal is crushed and then separated into various size fractions. Larger material is usually treated using 'dense medium separation'. In this process, the coal is separated from other impurities by being floated in a tank containing a liquid of high specific gravity, usually a suspension of finely ground magnetite. As the coal is lighter, it floats and can be separated off, while heavier rock and other impurities sink and are removed as waste.
The smaller size fractions are treated in a number of ways, usually based on differences in mass, such as in centrifuges. A centrifuge is a machine which turns a container around very quickly, causing solids and liquids inside it to separate. Alternative methods use the different surface properties of coal and waste. In 'froth flotation', coal particles are removed in a froth produced by blowing air into a water bath containing chemical reagents. The bubbles attract the coal but not the waste and are skimmed off to recover the coal fines. Recent technological developments have helped increase the recovery of ultra-fine coal material.
2.7 Coal Transportation
The way that coal is transported to where it will be used depends on the distance to be covered. Coal is generally transported by conveyor or truck over short distances. Trains and barges are used for longer distances within domestic markets, or alternatively coal can be mixed with water to form a coal slurry and transported through a pipeline.
Ships are commonly used for international transportation, in sizes ranging from Handymax (40–60 000 deadweight tonnage or DWT), Panamax (approximately 60–80 000 DWT) to large Capesize vessels (>80 000 DWT). Around 1311 million tonnes (Mt) of coal was traded internationally in 2015 and around 90% of this was seaborne trade. Coal transportation can be very expensive – in some instances it accounts for up to 70% of the delivered cost of coal.
2.8 Coal Mining and the Environment
Measures are taken at every stage of coal transportation and storage to minimise environmental impacts.
Coal mining – particularly surface mining – requires large areas of land to be temporarily disturbed. This raises a number of environmental challenges, including soil erosion, dust, noise and water pollution, and impacts on local biodiversity. Steps are taken in modern mining operations to minimise these impacts. Good planning and environmental management minimises the impact of mining on the environment and helps to preserve biodiversity.
2.8.1 Land Disturbance. In best practice, studies of the immediate environment are carried out several years before a coal mine opens in order to define the existing conditions and to identify sensitivities and potential problems. The studies look at the impact of mining on surface and ground water, soils, local land use, and native vegetation and wildlife populations. Computer simulations can be undertaken to model impacts on the local environment. The findings are then reviewed as part of the process leading to the award of a mining permit by the relevant government authorities.
2.8.2 Mine Subsidence. A problem that can be associated with underground coal mining is subsidence, whereby the ground level lowers as a result of coal having been mined beneath. Any land use activity that could place public or private property or valuable landscapes at risk is clearly a concern. A thorough understanding of subsistence patterns in a particular region allows the effects of underground mining on the surface to be quantified. This ensures the safe, maximum recovery of a coal resource, while providing protection to other land uses.
2.8.3 Water Pollution. Acid mine drainage (AMD) is metal-rich water formed from the chemical reaction between water and rocks containing sulfur-bearing minerals. The runoff formed is usually acidic and frequently comes from areas where ore- or coal-mining activities have exposed rocks containing pyrite, a sulfur-bearing mineral. However, metal-rich drainage can also occur in mineralised areas that have not been mined. AMD is formed when the pyrite reacts with air and water to form sulfuric acid and dissolved iron. This acid runoff dissolves heavy metals such as copper, lead and mercury into ground and surface water. There are mine management methods that can minimise the problem of AMD, and effective mine design can keep water away from acid-generating materials and help prevent AMD occurring. AMD can be treated actively or passively. Active treatment involves installing a water treatment plant, where the AMD is first dosed with lime to neutralise the acid and then passed through settling tanks to remove the sediment and particulate metals. Passive treatment aims to develop a self-operating system that can treat the effluent without constant human intervention.
(Continues…)
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Table of Contents
World Energy Needs;
Coal-fired Power Stations;
The Life Cycle of Coal and Associated Health Impacts;
The State of Coal Regulation Around the World;
Liquid Fuels and Chemical Feedstocks;
Carbon Capture, Use and Storage.