The Coal Handbook: Towards Cleaner Production

Volume 1: Coal Production

Dave Osborne

• Publisher: Woodhead Publishing
• Year: 2013
• ISBN:
  9780857097309
• Topic: Technology & Engineering
• Subtopic: Fossil Fuels
• Index: Technology & Engineering

Coal is an important fossil fuel resource for many nations due to its large remaining resources, relatively low production and processing cost and potential high energy intensity. Certain issues surround its utilisation, however, including emissions of pollutants and growing concern about climate change. The coal handbook: Towards cleaner production Volume 1 reviews the coal production supply chain from analysis to extraction and distribution.Part one explores coal characterisation and introduces the industrial use of coal as well as coal formation, petrography, reserves, sampling and analysis. Part two moves on to review coal extraction and preparation. Chapters highlight advances in coal mining technology, underground coal gas extraction, coal sizing, comminution and cleaning, and solid-liquid separation technologies for coal. Further chapters focus on economic factors affecting coal preparation, post-treatment of coal, coal tailings treatment, and the optimisation, simulation and control of coal preparation plants. Finally, part three considers aspects of the coal supply chain including the management approach and individual functions such as coal blending and homogenisation, transportation and handling along the entire supply chain.With its distinguished editor and international team of expert contributors, The coal handbook Volumes 1 and 2 is a comprehensive and invaluable resource for professionals in the coal mining, preparation, and utilisation industry, those in the power sector, including plant operators and engineers, and researchers and academics interested in this field.

• Reviews the coal production supply chain from analysis to extraction and distribution
• Explores coal characterisation, formation, petrography, reserves, sampling and analysis
• Examines coal extraction and preparation and highlights advances in coal mining technology, underground coal gas extraction, coal sizing, comminution and cleaning, and solid-liquid separation technologies

Part I

Introduction and coal characterization

1

Industrial uses of coal

D.G. Osborne, XstrataTechnology, Australia and

S.K. Gupta, University of New South Wales, Australia

Abstract:

This chapter provides an overview of the current status of coal usage. Existing and emerging technologies for power generation, metal processing and coal conversion are discussed, together with other industrial uses of coal. The current ‘state-of-play’ and the implications of suggested trends towards emerging, cleaner manufacturing industries on sustainable coal utilization in the short to mid-term are also discussed, together with the likely impacts of increasing environmental pressures.

Key words

coal

power

iron and steel

coal-to-liquids (CTL)

cement and carbon (climate change) management

1.1 Introduction

Coal-based industries have played a critical role in the development of the modern world and are expected to play a dominant role for a long time to come particularly in the developing countries. Coal is still the world’s most prevalent and widely distributed fossil fuel, accounting for 64% of globally recoverable fossil resources compared to 19% for oil and 17% for natural gas.

The coal industry has two principal markets, namely thermal coal (for energy use, including power generation and other applications such as the cement manufacturing sector), and metallurgical coal (principally for steel making); but there are also other coal uses, including conversion into gas or other energy or chemical products, and in situ forms whereby indigenous coal deposits are gasified and the gases then utilized after some treatment. Coal provides just over a quarter of the world’s primary energy needs, with thermal coal generating about 40% of the world’s electricity, whilst almost 70% of the world’s steel industry is dependent on coal for either coke production or for coal injection, either via what is known as the integrated route, or as the energy/reductant source in direct reduction processes.

Coal demand is forecast to rise by over 50% between now and 2030, driven mainly by economic growth in the so-called BRIC countries (Brazil, Russia, India and China), particularly the latter two, and during this period increased utilization will continue to be dominated by the conventional pulverized coal-fired boilers and blast furnace applications. China is already the world’s largest steel producer, at over 500 Mtpa, and accounts for 40% of global production compared to 15% in 2000, and usage is expected to continue to grow by over 3% annually over the next 5 years or so. Indian steel production had an average annual growth of 9.4% from 2000 to 2008 and is also expected to continue to grow by more than 4.5% per annum over the next 5-year period.

Early developments in the industrial use of coal occurred via four main avenues, namely steam-raising, iron and steelmaking, gasification, and conversion to transport fuels and/or chemicals. Figure 1.1 provides an indication as to how these applications progressed, and also serves to illustrate how each of these avenues has tended to become linked over time. In steam-raising the early developments were stationary engines, progressing over a 50-year period into various modes of transportation via trains, ships, etc., and steam-generating boilers for power generation. The first-ever commercial steam engine was designed by Thomas Newcomen and commissioned three hundred years ago in 1712. Since then, steam power transportation has peaked and all but disappeared in the space of only 250 years, and applications such as driving machinery in mills and factories, pumping water, raising men and minerals from deep mines, etc., have risen and fallen, but steam still provides the bulk of our heating and electrical power and, perhaps surprisingly, the most commonly used fuel is still coal.

1.1 Milestones in coal utilization.

In the first century after Newcomen’s engine, the reciprocating steam engine was refined and steadily improved till it reached its zenith in the early twentieth century. James Watt came up with the idea of the separate condenser in about 1763. He observed that if steam was condensed in a separate vessel from the cylinder, it would be possible to keep the condensing vessel cool and the cylinder hot at the same time. He built a prototype and found that the concept worked, and later added other improvements before building his now famous improved steam engine. After one or two disastrous business experiences, James Watt associated himself with a venture capitalist, Matthew Boulton, the owner of the Soho Engineering Works, near Birmingham, England. The firm of Boulton and Watt became famous, and James Watt’s steam engine probably emerged as the greatest single factor in the upcoming new industrial era in the UK. Matthew Boulton and James Watt, though they were pioneers, were not the only ones working on the development of the steam engine. They had serious rivals: one was Richard Trevithick in England, another was Oliver Evans of Philadelphia. Independently, both Trevithick and Evans invented a high-pressure engine which, in contrast to Watt’s steam engine, involved an arrangement whereby the steam entered the cylinder at slightly above atmospheric pressure.

The options for steam-raising boilers rapidly expanded from the mid-nineteenth century well into the next, as did the development of various firing appliances and auxiliaries. Numerous boiler types emerged, and emphasis began to be laid on thermal efficiency, which was extraordinarily low in the earliest units. Higher efficiencies were achieved via higher temperatures and pressures and by the incorporation of air heaters, economizers, super heaters, etc. With increased knowledge of boiler conditions, designers were able to adapt designs for coals of a very wide range, in terms of both quality and grade (Carney, 2012).

Emerging boiler types included vertical boilers, locomotive-type boilers, internal flue horizontal shell type (Lancashire and Cornish boilers are examples), multi-tubular horizontal shell type (e.g., the Economic boiler) and water-tube boilers. Marine boilers were either modified Economic or water-tube type. Firing types ranged from hand firing, as for locomotive boilers, to a variety of mechanical types for stoker-type boilers. Many of the early boilers used lump coal, which was burnt on a grate and could not cope with fines. But as boiler designs became larger, pulverized fuel firing was introduced with specially designed burner systems, which further improved efficiency by ensuring that very effective combustion conditions prevailed without smoke and with minimal excess air requirement. From then on boiler designs progressed to larger and larger unit capacities, and steady improvement in efficiency continued. Sub-critical units were able to deliver efficiencies up to the low to mid-1930s. Driven by the increasing demand for electricity, pulverized coal combustion (PCC) systems become the predominant option for electrical...