Improvements in the Treatment of Sulphide Ores of Lead preparatory to Smelting the same, and incidentally in obtaining Sulphurous Acid..
Year: 1897

page_text: Date of Application, 12th Feb., 1897-Accepted, 3rd July, 1897
:
Improvements in the Treatment of Sulphide Ores of Lead preparatory
to Smelting the same, and incidentally in obtaining Sulphurous
Acid..
I, GEORGE GATTON MELHUISH HARDINGHAM, of 191, Fleet Street, in the City of
London, Civil Engineer and Chartered Patent Agent, do hereby declare the nature of
this invention (a communication to me from THOMAS HUNTINGTON and FERDINAND
HEBERLEIN, both of Pertusola, near Spezzia, in the Kingdom of Italy, Metallurgical
Engineers,) and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement:-
This invention relates to the treatment of galena or lead sulphide, with the object
of removing the sulphur, or the greater portion thereof, prior to subjecting the ore to
smelting or other reduction process; the excess of sulphur eliminated being collected
as sulphurous acid and utilised in the manufacture of sulphuric acid or otherwise. fi
In treating sulphide of lead ores or galena with a view to the recovery of the metal
contained therein, it has been found that by steadily raising an intimate mixture of
calcium oxide and galena to a bright red heat (say 700° C.), and then allowing the
mixture to cool slowly to a dull red heat (say 500° C.), decomposition takes place and
oxygen is given off. This nascent oxygen appears to attack the sulphide of lead
energetically, to oxidise it, and to convert part of it into oxide of lead (Pb.0) and
sulphate of lead (Pb SO.), considerable heat being generated. At this point, by
forcing a strong current of air (which may have been previously heated) through
the said mixture, the operation of conversion becomes continuous, and the heat is
maintained at such a point that reaction takes place between the sulphides and
sulphates; the oxygen acting upon the galena so long as any sulphur remains in the
mixture. Concentrated fumes of sulphurous acid are given off, and the mixture
gradually fuses to a mass of lead oxide in conjunction with the gangue matter of the
ore treated. The product thus obtained may be treated in any known manner for the
reduction of the metal.
It is believed that when the temperature of the mixture of calcium oxide and galena
is raised to a bright red heat, the monoxide (Ca O) absorbs oxygen and forms calcium
dioxide (Ca O₂); and that, on the reduction of the temperature to a dull red heat,
decomposition takes place, the dioxide being reduced to monoxide. This appears to
be the most probable rationale, although further investigation may possibly shew this
theory to be erroneous.
Assuming the reactions which take place to be such as suggested, the above
mentioned phases of the process are represented by the following formulæ :-

page_text: sulphur present in the ore, the mixture being then subjected in a reverberatory or other
suitable furnace to the action of a bright red heat (say, 700° C.). The mixture is then
allowed to cool to a dull red heat (say, 500° C.) when the above mentioned reaction of
calcium dioxide upon the galena and the formation of sulphate of lead commences.
At this stage, the mixture is removed to a receptacle, wherein it is exposed to the
action of a current of atmospheric air, which may have been previously heated and
which may be forced or drawn through the mass by means of a blower or equivalent
apparatus; the sulphur present in the ore combines with the oxygen conveyed by the
air, combustion takes place, and, without any additional fuel, an intense heat is
generated, and a large volume of concentrated sulphurous acid gas is given off, the
mixture fusing and gradually settling down to a mass of oxide of lead with the
gangue matters of the ore. It is then ready for further treatment in a blast furnace
or otherwise for the reduction of the metal. The sulphurous acid may be collected
and applied in the manufacture of sulphuric acid or otherwise utilised.
In place of calcium oxide, or other oxide of an alkaline earth metal, ferrous oxide
(Fe 0) or manganous oxide (Mn O) may be mixed with the ore.
It will be seen that, as the result of this method of treatment, the sulphide of lead
originally present in the ore is converted into oxide of lead; which, with its gangue
matter and calcium sulphate, may then be transferred to a blast or other furnace for
the reduction of the metallic lead.
Having now particularly described and ascertained the nature of this invention and
in what manner the same is to be performed, I claim :-
1. The herein described method of treating sulphide ores of lead preparatory to
reduction to metal, which consists in mixing with the ore to be treated the oxide of
an alkaline earth metal (or ferrous or manganous oxide), subjecting the mixture to
heat in the presence of air, then reducing the temperature, and finally passing air
through the mass to complete the oxidation of the metal, substantially as and for the
purpose set forth.
2. The herein described methods of treating sulphide ores of lead preparatory to
réduction to metal, which consists in mixing an oxide of an alkaline earth metal-
such as calcium oxide-with the ore to be treated, subjecting the mixture in the
presence of air to a bright red heat (about 700° C.), then cooling down the mixture
to a dull red heat (about 500° C.), and finally forcing air through the mass until the
ore, reduced to an oxide, fuses, substantially as set forth.
3. The herein described method of treating sulphide ores of lead preparatory to
"réduction to metal, which consists in mixing ferrous oxide or manganous oxide with the
ore to be treated, subjecting the mixture in the presence of air to a bright red heat
(about 700° C.), then cooling down the mixture to a dull red heat (about 500° C.), and
finally forcing air through the mass until the ore, reduced to an oxide, fuses,
substantially as set forth.
4. The herein described method of reducing sulphide ores of lead to sulphate, in
the preparation thereof for reduction to metal, which consists in subjecting the
sulphide to a high temperature in the presence of an oxide of an alkaline earth metal
(or of ferrous or mauganous oxide) and oxygen, whereby the oxide, taking up oxygen,
is converted into dioxide, and then lowering the temperature until the latter yields
the portion of its oxygen taken up to combine with the sulphur in the ore,
substantially as set forth.
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