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Historical Metallurgy Interests
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The following is adapted from Wadsley (2001)
Contents
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During the seventeenth century, the ability of steam under
pressure to do useful work was recognised by Giambattista
in 1604, by Salomon de Caus in 1615, by Giovanni Branca
in 1629, by the Marquis of Worcester in 1663 and by
Isaac Newton in 1680. During the eighteenth century,
industrial steam engines were widely employed and the
mechanical age had begun. An early use of steam power
was in pumps used in mines.
In the late eighteenth century electricity,
Alessandro Volta generated direct-current electricity
through a pile consisting of alternating zinc and silver
metal discs. In 1807 Humphrey Davy used a similar devise
to electrolyse potash and form metallic potassium.
Michael Faraday demonstrated rotary electromagnetic
motion in 1820. In 1833, Faraday produced metallic
aluminium by electrolysis. An alternate metallurgical
reductant to carbon was available.
H. St.-C. Deville commenced the commercial production
of aluminium by reduction of aluminium chloride with
sodium metal in 1854. The sodium metal was produced by
reduction of sodium carbonate with carbon. The aluminium
chloride was produced by carbo-chlorination of alumina.
This is an early example of achieving a desired result
by multiple steps where the direct process (here the
carbon reduction of alumina) is not feasible.
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Smelting may produce condensed phase metals as
either solids or liquids. The advantages of
producing metal in the molten state and casting
directly into useful shapes from the molten state
were well known to the older metallurgists.
Ancient copper smelting furnaces were able to
attain temperatures in the range 1180 to 1350 C,
the melting point of copper being 1085 C.
However the advantages of bronze, the copper-tin
alloy, which with a composition of 10 % wt tin
melts at about 950 C, which could be more readily
cast (and which is harder than pure copper) were
well known to the older metallurgists.
Although copper ores existed in many locations,
tin ores were rare and tin oxide concentrates
were an important traded commodity.
Iron was first smelted in ancient times in the
solid state. The maximum temperature obtained in
old metallurgy was apparently less than that
required to melt pure iron, that is 1536 C.
Slag was removed from the iron and it was shaped
both by hammering. Steel was manufactured by
carburising the iron with charcoal.
It was learned that iron-carbon alloys could be
melted and cast, the eutectic temperature being
about 1153 C. China was the first region to
obtain liquid iron-carbon alloys by direct
smelting around 2000 years ago. Steel was
manufactured by oxidising carbon from the melt.
This technology was being introduced into
Europe during the sixteenth century.
In pyrometallurgy, heat energy is required
under reducing conditions both to heat the
reactants to the desired reaction temperature
and to supply the endothermic heat of reaction
for most metals. In practice this usually
means combustion in the presence of an excess
of carbon. The combustion chemistry of
carbon under these conditions is concerned
both with the relative stability and the heat
of formation from the elements of carbon
monoxide and carbon dioxide. The
thermodynamic stability of carbon monoxide
relative to that of carbon dioxide increases
with increasing temperature. The heat of
formation from the elements of carbon dioxide
(-197 kJ/g-atom O at 25 C) is significantly
greater than that of carbon monoxide
(-111 kJ/g-atom O at 25 C). Consequently as
it is attempted to attain higher temperatures,
the proportion of carbon monoxide in the gas
phase increases but the heat generated by
oxidation of a unit mass of carbon decreases.
In addition, more heat is required to raise
the temperature of the air, with its high
concentration of inert nitrogen, to the
reaction temperature. Smelting temperatures
were thus quite limited in the simple
charcoal-air system.
Modern smelting utilises air preheating and
oxygen enrichment to attain higher temperatures
but, with these methods, the limitations
imposed by natural carbon-oxygen chemistry are
still present. Electric heating is used to
overcome these limitations.
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Those involved in the computer simulation of
processes will be aware that many aspects of
many unit operations have yet to be described
in detail in terms of mathematical functions.
The physical and chemical properties of many
complex materials, in particular of
metallurgical solutions, are still the subject
of active mathematical modelling research.
Many mathematical models for both operations
and properties are based mainly on empirical
relationships rather than fundamental properties.
The ancestry of many metallurgical processes,
particularly those involving the blast furnace,
may be directly traced back to ancient technology.
In the lead, zinc and copper blast furnaces,
sulfide minerals from beneath the earth's surface
are converted to oxides before being smelted with
carbon. The continued use of carbon in extractive
metallurgy is partly based on its useful natural
properties and partly on over six thousand years
of history.
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"Bergwerk und Probierbuchlein", A translation from
the German of the "Bergbuchlein", a sixteenth century
book on mining geology by Anneliese Grunhaldt Sisco and of the
"Probierbuchlein", a sixteenth century work on assaying,
by Anneliese Grunhaldt Sisco and Cyril Stanley Smith. Published by
The American Institute of Mining and Metallurgical Engineers,
New York, 1949
Georgius Agricola, "De Re Metallica", translated
into English from the first Latin edition of 1556 by
Herbert Clark Hoover and Lou Henry Hoover.
Published by the Mining Magazine, London, 1912
Reprint published by Dover Publications, New York, 1950.
Georgius Agricola, "De Natura Fossilium", translated
into English from the first Latin edition of 1546 by M.C.Bandy and
J.A.Bandy in Geological Society of America. Special Paper 63,
New York, 1995
Vannoccio Biringuccio, "The Pirotechnia",
translated from the first Italian edition of 1540
by Cyril Stanley Smith and Martha Teach Gnudi.
Published by The American Institute of Mining and
Metallurgical Engineers, New York,1942
Lazarus Erckerr, "Treatise on Ores and Assaying",
translated from thr German Edition of 1580 by
Anneliese Grunhaldt Sisco and Cyril Stanley Smith.
Published by the University of Chicago Press,
Chicago Illinois. 1951
Barba,A.A. "Arte De Los Metales", Coleccion de la
Cultura Bolivia. A 1967 "Potosi"
reprint of the original Madrid edition of 1640.
Bern Dibner, "Agricola on Metals",
Burndy Library, Norwalk, 1958
Kuhner,D. and Rizzo,T. (1980). "The Herbert Hoover
Collection", Claremont
Healy,J.F., (1978). "Mining and Metallurgy in the Greek
and Roman World"", Thames and Hudson
Checkland,S.G., (1967). "The Mines of Tharsis",
Allen & Unwin, London
Avery,D. (1974). "Not on Queen Victoria's Birthday:
the Story of the Rio Tinto Mines", Collins, London
Rothenberg,B. and Blanco-Freijeiro,A., (1981). "Studies
in Ancient Mining and Metallurgy in South-West Spain",
Institute for Archeo-Metallurgical Studies, London
Robert Raymond "Out of the Fiery Furnace",
MacMillan, South Melbourne, 1984
Bryan Bunch and Alexander Hellemans, "The Timetables
of Technology", Touchstone, New York, 1993
J.R.Partington, "A Short History of Chemistry",
3rd Ed., Dover, New York, 1989
P. J. Golas, "Science and Civilisation in China
", Cambridge University Press, Cambridge, 1999
D. P. Agrawal, "Ancient Metal Technology and Archaeology
of South Asia: a Pan-Asian Perspective", Aryan; India,
1999
Wadsley,M.W., (1979). "Metals and Energy Options",
pp.167-169 in M.Diesendorf Ed., "Energy and
People", SSRS, Canberra, 1979
Wadsley,M.W., (2001). "Greenhouse
Gases and Extractive Metallurgy" pp.1-14 in Pickles,C.A. Ed.
" Greenhouse Gases in the Metallurgical Industries: Policies,
Abatement and Treatment " , Aug. 2001, CIM., Montreal,
ISBN: 1-894475-15-1
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All rights reserved
Beginnings of Metallurgy
Carbon has been the metallurgist's reductant of choice since
the Stone Age. Carbon, in the form of charcoal, is readily
derived from wood by pyrolysis, or partial combustion.
The naturally occurring minerals of most metals, when outcropping
at the earth's surface, are their oxides. Some of these oxide
minerals, such as some of those of copper and iron, are brightly
coloured and hence attract the eye. Probably by chance,
over six thousand years ago, humans learned that these oxide
minerals could be converted to metals by their interaction
with charcoal at the high temperature found in fires, possibly
in the kilns used to fire pottery. Those persons also learned of
the beneficial properties of the metals. By observation and
by trial and error people improved their ability to recognise
the various minerals of metals and improved their ability to
convert those minerals into metals.
Sixteenth Century Metallurgy
A fortunate combination of events has given us a record of
the production of metals and chemicals towards the end of
the era when metals were produced only by the renewable or
sustainable resources of water, wind, animal and human energy
plus carbon, mainly as wood charcoal. These events were the
invention and development of the moveable type printing press
by Johann Gutenburg and Laurens Koster about the year 1445
and the commitment of their metallurgical knowledge to paper
by the authors of "Bergbuchlein", and
"Probierbuchlein", by Vannoccio Biringuccio in 1540,
by Georgius Agricola in 1556 and by Lazarus Erckerr in 1580.
Soon after this time, an acute shortage of wood in Europe in
general, and in Britain in particular, caused this region to
substitute coal for wood in the production of heat and in the
smelting of metals.
Biringuccio recognised that coal could replace charcoal in the
smelting of metals but indicated that its use was restricted
to certain localities and was not general.
Further Developments
In England iron makers began in 1589 to patent methods for
using coal at different stages of the manufacturing process
although none of these early methods seemed to have replaced
charcoal in the actual smelting. Hugo Platt, in 1603
discovered coke produced by heating coal. Simon Sturtevant
obtained in 1611 the first British patent for a process in
which coal was used instead of charcoal for smelting iron.
The significant use of fossil fuels as reductants in
extractive metallurgy had begun.
Thermochemistry
It is instructive to note the metals produced prior to
1580 and those produced in modern times. Biringuccio,
Agricola and Erckerr describe in detail the production
of the metals gold, silver, copper, tin, lead, iron,
arsenic, antimony, bismuth and mercury and of the
alloys bronze, steel and brass. Zinc metal was known
and small quantities were produced in Europe as a
by-product in some lead smelters but it was not
considered to be useful. Some other metals were
probably produced in near pure or in alloy form but
were not recognised because of their chemical and
physical similarity with the known metals.
Modern metals include aluminium, magnesium, titanium,
zirconium, silicon, manganese and chromium. It is
apparent from an examination of physical properties,
such as melting point and boiling point, that these
were not the reason why modern metals were not known
to the older metallurgists. The reason lies in the
relative thermochemical stability of the oxides of
carbon and of the oxides of the metals.
At the temperatures generated by the combustion of
charcoal with air supplied at ambient temperatures,
the oxides of the older metals are less stable and
the oxides of the modern metals are more stable
than the oxides of carbon. This information is
often expressed as the oxide free energy diagram
or Ellingham diagram.
Heat Production at High
Temperature
Evolution of Metallurgy
Before the time of Antoine Lavoisier's
combustion experiments, around 1780, the
concepts of quantitative mass and energy
balances were not recognised, yet these
principles form the basis of modern process
design and analysis. The concept of
assaying was well known to the older
metallurgists who used standard procedures
to determine whether the metal content of
an ore was worth the effort to extract it or
whether the metal product or coins were of
the desired purity. In general,
advancement in the ancient process
industries was made predominantly by
observation and experience. Much of
modern industry has a similar basis.
It is rare for a new plant to be designed
from first principles. In many cases, the
design of a new plant is based on the
designs of older plants, with minor
modifications being made for the different
location and recent experience.
Austherm's Courses
Austherm has collected a number of publications concerning
ancient mineralogy, metallurgy and applied chemistry. Some of
these are listed below. Austherm personnel have visited sites
of ancient mining and metallurgy in Mediterranean Europe.
Austherm are able to use their interest, resources, experiences
and teaching expertise to provide tailored courses at
under-graduate, graduate and community level in aspects
of ancient mineralogy, metallurgy and applied chemistry.
Reprint published as Dover Phoenix Edition, New York, 2004