Improved Process for Roasting Ores and Metallic Compounds.
Year: 1890

page_text: Date of Application, 27th Aug., 1890
Complete Specification Left, 4th May, 1891-Accepted, 6th June, 1891
PROVISIONAL SPECIFICATION.
Improved Process for Roasting Ores and Metallic Compounds.
A communication from abroad by LÉON BEMELMANS, a citizen of the United
States of America, residing at Brussels, Belgium.
I, WILLIAM LLOYD WISE, of 46 Lincoln's Inn Fields, in the County of
London, Consulting Engineer and Patent Agent, do hereby declare the nature of
this invention to be as follows:-
-
This invention relates to an improved process of roasting ores and compounds of
metals (containing precious metals or not) such as iron and copper pyrites; blende;
nickel, cobalt, and arsenic sulphurets; antimonious sulphurets and the like, in
which are substances such as sulphur, selenium, tellurium, arsenic or antimony, so
objectionable in most metallurgical processes, so that the sesubstances are driven off
without polluting the atmosphere and are subsequently recovered.
In carrying out this process there are used closed vessels such as retorts of any
suitable shape such as is illustrated in the accompanying drawings in which Fig. 1
is a cross section and Fig. 2 a longitudinal sectional elevation of one retort.
In carrying out this invention the ore or compound (hereinafter referred to as
ore) treated, is converted into
1st. Oxides of the principal metals of the ore such as iron, zinc, lead, cobalt,
nickel, bismuth &c., these oxides being obtained free from sulphur, selenium,
tellurium, arsenic, antimony and the like; if gold and silver be present in the ore,
they become free and fit for amalgamation;
2nd. Pure sulphur, selenium or tellurium or two or all of these if present in
excess in the ore, these substances being recovered as hereinafter described as
well as sulphurets of arsenic and antimony if arsenic and antimony be present in
the ore;
3rd. Hydrogen compounds of sulphur selenium or tellurium which are partially
burnt, so that the hydrogen only of the compounds is burnt, the sulphur, selenium
or tellurium present being condensed.
The ore, in the form of grain or pea ore, is first roasted with a variable amount
of fine ore at a dark red heat in the presence of steam, superheated or not, in closed
retorts, the formula of reduction being as follows:-

page_text: residuum being in a most perfect chemical state for amalgamation; for electrolysis
with acids or alkalies; for the chemical or metallurgical separation of the various
oxides; or for reduction. The gaseous mixture resulting from the roasting
operation is made up of the excess of steam; of compounds of hydrogen with
sulphur, selenium, or tellurium, or with each of these if all of them be present; of
volatilized sulphur if there be more than enough to combine with the hydrogen
present; and of arsenious and antimonious acids if arsenic and antimony be present
and providing there be enough sulphur present in the ore (or added in the shape
of pyrites) to perfect the reaction illustrated by the following formula:
This gaseous mixture is passed from the retort into a condensing flue, wherein
the free sulphur together with arsenious and antimonious acids will settle at once,
the latter at this lower heat and with the sulphuretted hydrogen, being transformed
into sulphides. Further on in the flue, where the temperature is sufficiently low,
the steam will condense while the remaining compounds of hydrogen with sulphur,
selenium, or tellurium, or with each as the case may be, are led into a chamber or
furnace, wherein a high temperature is maintained, and which may have fire brick
work arranged therein, and be in the nature of a regenerative furnace.
Into this chamber or furnace a regulated amount of air is admitted, sufficient.
only to enable the hydrogen to be burnt, while the sulphur, selenium or tellurium
is left free.
11
The sulphur, selenium, or tellurium &c. carried off as vapor from this chamber or
furnace is condensed in a suitable condenser, and the steam together with the
nitrogen of the air admitted to the chamber or furnace is passed off into the
chimney.
When roasting ore rich in sulphur, there is enough heat produced by the burning
hydrogen to heat the retorts and to raise steam in a boiler for use in the said
retorts during the roasting as hereinbefore mentioned. The hydrogen compounds
produced may therefore with advantage be utilized for this purpose by burning
them under the retorts and boilers, the unconsumed sulphur, selenium, tellurium, &c.
being subsequently condensed.
In the drawings a represents a retort of any impervious material for example
cast iron, that will withstand a dark red heat. It is made of any suitable shape or
length with a false floor b, permeable to steam, firmly secured at each end above
the floor of the retort. To the space between the floors is supplied superheated
steam that enters through an opening c. Opposite this opening c is an opening g,
normally closed by a lid h, and through which any sediment which might pass
through the false floor can be blown out. d is an exit branch for carrying off all
gaseous products to the condenser. The mouth of the retort close to the stand pipe is
partially closed by a cast iron plate or curtain e which regulates the thickness of
the stream of ore admitted into the retort. At the opposite end of the retort is a
cast iron plate or curtain that closes also all the upper part of that end of the
retort, leaving over the floor b, only sufficient room for the escape of the roasted
ore, and for the introduction of tools should they be needed in order to disintegrate
material that may have become agglomerated within the retort. which would be
liable to occur if sufficient steam were not used, or the heat employed were too

page_text: great. At the end of the retort near the exit pipe a plate or curtain of about
three inches in depth is sufficient. At the opposite end a space of about two inches
in depth between the false floor and the curtain is quite enough, but these dimensions
although convenient are by no means essential. For convenience of manufacture
the retorts may be made of prismatic form, with rounded corners and slightly bent
sides; the retort shewn is however of rectangular form in cross section but having
rounded corners. These retorts may be made about three yards long, and sixteen
to twenty inches wide and eight to twelve inches high inside. The retorts are set
in any suitable kind of furnace wherein they can be heated to a dark red heat. It
is preferred, though it is not essential, to set them in such an inclined position that
the ore will naturally flow into and partly fill the retort, the ore extending from
under the curtain e to about one foot from the end f of the retort, thus leaving an
approximately wedge shaped space above it through which the gases produced flow
to the exit branch d. By thus inclining the retort and tightly fitting its upper end
outside the furnace to an iron box containing the crushed ore, the retort will be fed
automatically as fast as the roasted ore is raked out at the lower end, thereby
keeping the charge in constant motion, and preventing agglomeration thereof as
well as the formation of direct steam-ways therethrough. By these means also the
gas in the retort cannot escape except by the exit branch d, the lower and upper
ends of the retort being closed by a good thickness of ore; the thickness of ore in
the retort should not be greater than twelve inches at any part so that the steam
can be present in excess at all parts of the charge. A charge of ore of this
thickness can usually be desulphurized in about two hours, but some sulphurets are
more difficult to reduce than others. The pressure of steam employed should not
exceed that of ten inches of water in order that steam ways shall not be formed
through the charge or that slag shall not be carried off.
Steam that is not superheated can be used to act on the heated sulphurets but a
better effect is obtained both as to quantity of steam necessary and as to the time
needed for desulphurizing, if the steam admitted to the retort be first superheated
to about the same temperature as the charge; that is, to a dark red heat. Even
galena can be desulphurized without melting, by this process with superheated
steam, although more slowly than ores of iron, zinc, nickel, cobalt, and other
metals. After roasting the galena, the lead will be in the state of lead oxide, the
precious metal or metals therein being then in a free state. The process is thus
adapted for treating silver-bearing galena, and blende, and gold-bearing pyrites so
that the precious metals can be subsequently recovered by amalgamation and
without loss due to reduction and melting. For the sake of convenience of working
there is placed at the lower end of the inclined retort, a sheet iron casing k to
receive the roasted ore before it is discharged into waggons or the like. This casing
is provided with an adjustable sliding gate k¹ which is so regulated as to allow the
roasted ore to run off as fast as it is properly reduced. The process is thus
rendered a continuous one.
In carrying out the process herein before described it is to be understood that I
do not limit myself to the apparatus herein described but may use any suitable form
of retort of any impervious material able to withstand a dark red heat, having a
false bottom permeable to steam such as perforated plates, lamina disposed shingle,
fashioned, split, or perforated pipes, or any other arrangement that will evenly
distribute the steam under the heated ore, and over which the ore can naturally
slide or be made to slide while it is permeated at a dark red heat with steam that
may be superheated or not.
am aware that it is known that steam will desulphurize metallic sulphurets at a
dark red heat, producing metallic oxides of the common metals, free precious
metals, and sulphuretted hydrogen; also, that sulphuretted hydrogen can be burnt
with a limited supply of air so as to produce only water and sulphur. But these
reactions have not, to my knowledge, been combined into a process for treating
sulphurets selenurets, tellurets, with or without arsenic and antimony.

page_text: When treating copper pyrites sufficient sulphur can if desired be left in the ore
to form sulphate of copper from which the copper may then be extracted by
solution and cementation or by electrolysis.
When the sulphur, selenium &c. present in the ore is not in excess, the first
condensation hereinbefore referred to may be dispensed with, and the compounds of
hydrogen may be led direct into the second furnace and burnt in the presence of
air, the sulphur, selenium, &c. set free being afterwards condensed.
Dated this 27th day of August 1890.
W. LLOYD WISE.
COMPLETE SPECIFICATION.
Improved Process for Roasting Ores and Metallic Compounds.
A communication from abroad by LEON BEMELMANS, a citizen of the United
States of America, residing at Brussels, Belgium.
I, WILLIAM LLOYD WISE, of 46 Lincoln's Inn Fields, in the County of London,
Consulting Engineer and Patent Agent, do hereby declare the nature of this
invention 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 an improved process of roasting ores and compounds
of metals (containing precious metals or not) such as iron and copper pyrites;
blende; nickel, cobalt, and arsenic sulphurets; antimonious sulphurets, and the
like, in which are substances such as sulphur, selenium, tellurium, arsenic or
antimony, so objectionable in most metallurgical processes, whereby these sub-
stances are driven off without polluting the atmosphere and are subsequently
recovered.
In carrying out this process there are used closed vessels such as retorts of any
suitable shape such as illustrated in the drawings left with my Provisional
Specification and in which
Fig. 1 is a cross section and Fig. 2 a longitudinal sectional elevation of one
retort.
In carrying out this invention the ore or compound (hereinafter referred to as
ore) treated is converted into
1st. Oxides of the principal metals of the ore such as iron, zinc, lead, cobalt,
nickel, bismuth &c. these oxides being obtained free from sulphur, selenium,
tellurium, arsenic, antimony and the like; if gold and silver be present in the ore,
they become free and fit for amalgamation;
2nd. Pure sulphur, selenium or tellurium, or two or all of these, if present in
excess in the ore, these substances being recovered as hereinafter described, as
well as sulphurets of arsenic and antimony if arsenic and antimony be present in
the ore;
3rd. Hydrogen compounds of sulphur selenium or tellurium which are partially
burnt, so that the hydrogen only of the compounds is burnt, the sulphur, selenium
or tellurium present being condensed.
The ore, in the form of grain or pea ore, is first roasted with a variable amount
of fine ore at a dark red heat in the presence of steam, superheated or not, in closed
retorts, the formula of reduction being as follows:-

page_text: This gaseous mixture is passed from the retort into a condensing flue, wherein the
free sulphur together with arsenious and antimonious acids will settle at once, the
latter, at this lower heat and with the sulphuretted hydrogen, being transformed
into sulphides. Further on in the flue, where the temperature is sufficiently low,
the steam will condense, while the remaining compounds of hydrogen with sulphur,
selenium, or tellurium, or with each, as the case may be, are led into a chamber or
furnace wherein a temperature say about 100° C. or less is maintained, and which
may have fire-brick work arranged therein, and be in the nature of a regenerative
furnace.
Into this chamber or furnace a regulated amount of air is admitted, sufficient only
to enable the hydrogen to be burnt, so that the sulphur, selenium or tellurium shall
be left in the free state.
The formula illustrating this reaction is as follows:-
At the high temperature present in the combustion chamber, the sulphur,
(selenium, tellurium,) thus produced, in the presence of steam gives a second
reaction thus
The SO is immediately decomposed by the heat into sulphur and S O², the
sulphur being again taken up by steam so that finally there remains only H2S
and S O² with steam in excess as if the reaction had taken place according to the
following reaction,

page_text: The sulphur, selenium, or tellurium, &c. carried off as vapor from the chamber
or furnace above referred to is condensed in a suitable condenser, and the steam,
together with the nitrogen of the air admitted to the chamber or furnace, is
passed off into the chimney, or it is driven through purifiers such as are used in
gas works.
Instead of leading the sulphuretted hydrogen into the combustion chamber or
furnace and before the steam in excess, coming from the retorts is condensed, I may
also bring said mixture of steam and sulphuretted hydrogen into a lead room or
other convenient chamber into which is also admitted a proper proportion of
sulphurous acid produced by a pyrite burner, the resulting reaction being expressed
by the formula
if the proper proportions are maintained between the gases.
When roasting ore rich in sulphur, there is enough heat produced by the burning
hydrogen to heat the retorts and to raise steam in a boiler for use in the said
retorts during the roasting as herein before mentioned. The hydrogen compounds
produced may therefore with advantage be utilised for this purpose by burning them
under the retorts and boilers, the unconsumed sulphur, selenium, tellurium, &c.
being subsequently condensed.
In the drawings a represents a retort of any impervious material for example cast
iron, that will withstand a dark red heat. It is made of any suitable shape or
length with a false floor b, permeable to steam, and firmly secured at each end
above the floor of the retort. To the space between the floors is supplied super-
heated steam that enters through an opening c. Opposite this opening c is an
opening g, normally closed by a lid h, and through which any sediment which might
pass through the false floor b can be blown out. d is an exit branch for carrying
off all gaseous products to the condenser. The mouth of the retort close to the
stand or exit pipe, is partially closed by a cast iron plate or curtain e which
regulates the thickness of the stream of ore admitted into the retort. At the
opposite end of the retort is a cast iron plate or curtain that closes also all the
upper part of that end of the retort, leaving over the floor b, only sufficient
room for the escape of the roasted ore, and for the introduction of tools should
they be needed in order to disintegrate material that may have become agglome-
rated within the retort, which would be liable to occur if sufficient steam were not
used, or the heat employed were too great. At the end of the retort near
the exit pipe a plate or curtain of about three inches in depth is sufficient. At the
opposite end a space of about two inches in depth between the false floor and the
curtain is quite enough, but these dimensions although convenient are by no means
essential. For convenience of manufacture the retorts may be made of prismatic
form, with rounded corners and slightly bent sides; the retort shewn is however of
rectangular form in cross section but having rounded corners. These retorts may
be made about three yards long, and sixteen to twenty inches wide and eight to
twelve inches high inside. The retorts are set in any suitable kind of furnace
wherein they can be heated to a dark red heat. It is preferred, though it is not
essential, to set them in such an inclined position that the ore will naturally flow
into and partly fill the retort, the ore extending from under the curtain e to about
one foot from the end of the retort, thus leaving an approximately wedge shaped
space above it through which the gases produced flow to the exit branch d. By
thus inclining the retort and tightly fitting its upper end outside the furnace to an
iron box containing the crushed ore, the retort will be fed automatically as fast as
the roasted ore is raked out at the lower end, thereby keeping the charge in
constant motion, and preventing agglomeration thereof as well as the formation of
direct steam-ways therethrough. By these means also the gas in the retort cannot
escape except by the exit branch d, the lower and upper end of the retort being
closed by a good thickness of ore. The thickness of ore in the retort should not
be greater than twelve in ches at any part so that the steam can be present in

page_text: excess at all parts of the charge. A charge of ore of this thickness can usually
be desulphurized in about two hours, but some sulphurets are more difficult to
reduce than others. The pressure of steam employed should not exceed that of len
inches of water in order that steam ways shall not be formed through the charge or
slag carried off.
Steam that is not superheated can be used to act on the heated sulphurets, but a
better effect is obtained both as to quantity of steam necessary, and as to the time
needed for desulphurizing, if the steam admitted to the retort be first superheated
to about the same temperature as the charge; that is, to a dark red heat. Even
galena can be desulphurized without melting by this process with superheated
steam, although more slowly than ores of iron, zinc, nickel, cobalt, and other metals.
After roasting the galena, the lead will be in the state of lead oxide, the precious
metal or metals therein being then in a free state. The process is thus adapted
for treating silver-bearing galena, and blende, and gold-bearing pyrites, so that the
precious metals can be subsequently recovered by amalgamation and without loss
due to reduction and melting. For the sake of convenience of working there is
placed at the lower end of the inclined retort, a sheet iron casing k to receive the
roasted ore before it is discharged into waggons or the like. This casing is provided
with an adjustable sliding gate k¹ which is so regulated as to allow the roasted
ore to run off as fast as it is properly reduced. The process is thus rendered a
continuous one.
In carrying out the process hereinbefore described it is to be understood that
I do not limit myself to the apparatus herein described, but may use a retort of
any suitable form and of any impervious material able to withstand a dark red heat,
and having a false bottom permeable to steam such as perforated plates; lamina
disposed shingle; fashioned, split, or perforated pipes, or any other arrangement
that will evenly distribute the steam under the heated ore, and over which the ore
can naturally slide or be made to slide while it is permeated at a dark red heat with
steam that may be superheated or not.
I am aware that it is known that steam will desulphurize metallic sulphurets at a
dark red heat, producing metallic oxides of the common metals, free precious
metals, and sulphuretted hydrogen; also, that sulphuretted hydrogen can be burnt
with a limited supply of air so as to produce only water and sulphur. But these
reactions have not, to my knowledge, been combined into a process for treating
sulphurets, selenurets, tellurets, with or without arsenic and antimony.
When treating copper pyrites, sufficient sulphur can if desired be left in the ore
to form sulphate of copper from which the copper may then be extracted by solution
and cementation or by electrolysis.
When the sulphur, selenium &c. present in the ore is not in excess, the first
condensation hereinbefore referred to may be dispensed with, and the compounds
of hydrogen may be led direct into the second furnace and burnt in the presence of
air, the sulphur, selenium, &c. set free being afterwards condensed.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. The herein described process of roasting ores or metallic compounds and
recovering the products of such roasting operation, which consists in subjecting the
ores or compounds whilst at a dark red heat to the action of steam in a closed
retort; condensing the easily condensible products such as sulphur, selenium,
tellurium, arsenic, antimony, and the excess of steam, subsequently burning the
hydrogen compounds at a high temperature in a separate chamber with a regulated
supply of air so that the hydrogen only in the said compounds shall be burnt, and
condensing the vapours of sulphur, selenium, or tellurium therefrom, substantially
as hereinbefore described.
2. The herein described process of roasting ores or metallic compounds and
recovering the products of such roasting operation, which consists in subjecting the

page_text: said ores or compounds while at a dark red heat, to the action of steam in a closed
retort, subsequently burning the hydrogen compounds at a high temperature in a
separate chamber (which may be under the retorts and steam boilers) with a
regulated supply of air so that the hydrogen only in the said compounds shall be
burnt, and condensing the vapours of sulphur, selenium, or tellurium therefrom as
set forth..
W. LLOYD WISE,
Per F. J. Brougham.