AN IMPROVED PROCESS OF TREATING MINERAL PYRITES AND SULPIIURETS IN THE PREPARATION THEREFROM OF SULPHURIC ACID, METALS, AND METALLIC COMPOUNDS
Year: 1881

page_text: LETTERS PATENT to John Richardson Francis, of the Firm Richardson & Co.,
of Swanson, in the County of Glamorgan, Merchant, for an Invention of
"AN IMPROVED PROCESS OF TREATING MINERAL PYRITES AND SULPIIURETS
IN THE PREPARATION THEREFROM OF SULPHURIC ACID, METALS, AND
METALLIC COMPOUNDS." A communication from abroad by Henry Wurtz, of
the City, County, and State of New York, United States of America.
PROVISIONAL SPECIFICATION left by the said John Richardson Francis
at the Office of the Commissioners of Patents on the 30th September 1881.
JOHN RICHARDSON FRANCIS, of the Firm Richardson & Co., of Swansea, in the
County of Glamorgan, Morchant. "AN IMPROVED PROCESS OF TREATING MINERAL
PYRITES AND SULPHURETS IN THE PREPARATION THEREFROM OF SULPHURIC
ACID, METALS, AND METALLIC COMPOUNDS." A communication from abroad by
Henry Wurtz, of the City, County, and State of New York, United States of
America.
This Invention is especially and directly applicable to minerals composed of
sulphur combined with iron or copper, or with both these metals together, including
common yellow iron pyrites, yellow copper pyrites, whito iron pyritos or marcasito,
magnetic pyrites or pyrrhotine, or mixtures of any of these, or mixtures of these
with other ininerals or ores when such sulphurets occur in a pulverulent, com-
minuted or granular state, whether found naturally in such granular state, or as
reduced incidentally to such state by handling or transportation, or when pulverized
by artificial means, citber purposely or incidentally, as in the case of concentrated
sulphurets or "tailings" from ore-milling operations.
The Invention consists,-
Firstly. In iningling with such pulverulent or granular sulphurets, inetallic iron,
also in granular or comminuted state, and moistening the inixture with a saline
solution which will cause the iron to rust, and thus cement the granulos together
into a coherent inass.

page_text: Secondly. In aiding and accelerating the rusting of the iron in such mixture,
and thus hastening the consolidation thereof by an alternating application of heat
and moisture.
Thirdly. In incorporating with such mixtures fibrous and foliated inineral
substances, such as asbestus and mica, which add to the cohesion of the inass before
burning and prevent crumbling in the kiln, and in the subsequent handling of the
cinders or residues.
55
Fourthly. In the uso in this process of so called iron-sponge," or iron in the
comminuted form that results from the deoxidation of previously pulverized heated
iron-oxides by heated carbon, or by hot deoxidizing gases.
Fifthly. In crushing the metallic sulphurets to granular condition when required,
and removing the ganguo and impurities by means of a curront of air or water or
otherwise, and then re-cementing tho purified granulos together into masses by the
rusting of comminuted metallic iron mingled therewith.
SPECIFICATION in pursuance of the conditions of tho Lotters Patent filed
by the said John Richardson Francis in the Great Seal Patent Office on
the 14th March 1882.
JOHN RICHARDSON FRANCIS, of the Firm Richardson and Co., of Swansea, in the
"AN IMPROVED PROCESS OF TREATING MINERAL
County of Glamorgan, Merchant.
PYRITES AND SULPHURETS IN THE PREPARATION THERE FROM OF SULPHURIC
ACID, METALS, AND METALLIC COMPOUNDS." A communication from abroad by
Henry Wurtz, of the City, County, and State of New York, United States of
America.
This Invention is especially and directly applicable to minerals composed of
sulphur combined with iron or copper, or with both these metals together, including
cominon yellow iron pyrites, yellow copper pyrites, white iron pyrites or marcasito,
magnetic pyrites or pyrrhotine, or mixtures of any of these, or mixtures of these
with other minerals or ores when such sulphurets occur in a pulverulent, cOID-
minuted, or granular state, whether found naturally in such granular state, or as
reduced incidentally to such state by handling or transportation, or when pulverized
by artificial means, either purposely or incidentally, as in the case of concentrated
sulphurets or "tailings" froin ore-milling operations.
-
This Invention consists,―
Firstly In-mingling with such pulverulent or granular sulphurets, metallic iron,
also in granular or comminuted state, and moistening the mixture with a saline.
solution which will cause the iron to rust, and thus cement the granules together
into a coherent mass.
Secondly. In aiding and accelerating the rusting of the iron in such mixture,
and thus hastening the consolidation thereof by an alternating application of heat
and moisture.

page_text: Thirdly. In incorporating with such mixtures fibrous and foliated mineral
substances, such as asbestus and mica, which add to the cohesion of the mass before
burning, and prevent crumbling both in the kiln and in the subsequent handling of
the cinders or residues.
Fourthly. In the use in this process of so called iron-sponge, or iron in the com-
minuted form that results from the dooxidation of previously pulverized heated iron
oxides by heated carbon, or by hot deoxidizing gases.
Fifthly. In crushing the metallic sulphurets to granular condition when required,
and removing the gangue and impurities by means of a current of air or water or
otherwise, and then re-cementing the purified granules together into masses by the
rusting of comminuted metallic iron mingled therewith.
When sulphurets are to be operated on, which occur in a compact or massive
form, it is necessary in the application thereto of this Invention, to crush thein
previously to a granular or powdery condition. This renders it practicable to apply
before the subsequent re-consolidation of the powder processes of purification for
removal of gangue and other foreign matter, thus increasing the proportional per-
centage of sulphur in the mass, and improving the uniformity, regularity, and
completeness of combustion to form sulphurous-oxide in the pyrites-kiln without
clogging, slagging, or scarring. Such purification also adds greatly to the value of
the residues or cinders left after burning in the kiln, whether these are to be
employed as paint-material or for gas purification, or inade into polishing powder,
or to be reduced to iron-sponge, or smelted into Bessorer-pig, or used for furnace
fottling, or converted into open-hearth steel, or into iron-sulphates or iron-chlorides,
or applied to any other use.
Also in the case of cupriforous sulphurets, the extraction of the copper by solvents
is greatly faciliated by having the cinder in the condition of porous lumps instond
of impalpable dust and mud. The same advantagos rosult also with auriferous and
argentiferous sulphurets in the extraction of the precious metals from the residues
of burning the saine by means of chlorine, hyposulphite of soda, and other solvonts.
of gold and silver.
The crushing of the pyrites or other ore may, for the purposes of this Invention,
bo accomplished by the rudder and more rapid methods, and thus without expensivo
plant, for the reason that it is not essential that such crushing should be uniformly
fine.
The finer and coarser material should, however, for reasons well known to those
skilled in the art of concentrating oros be sorted or separated by screens of diflorent
apertures into fractions or sorts of more uniform sizes of granule respectively,
previous to the operation of removal of the gangue, whether this latter be accom-
plished by dry or wet concentration, or by air currents, such sorting is indeod
especially useful in this caso, for reasons explained below.
Such purification and concentration is applicable in like manner of course to such
pyrites and sulphurets as occur naturally in granular or crumbly forms. For these
also some additional crushing and sorting is always advisable after the process of
concentration has been applied.
.
This is because a certain proportion of powder of a considerable degree of fineness
is. requisite to fill up the interstices between the larger granules, in order to
promote compactness in the mixture to be consolidated.
This-proportion of fine material varies generally from one-half to three-fourths
of the whole, according to the size or degree of coarseness, as well as the shape
also of the coarser particles, the sizo to which it is advisable to reduce the latter
being dependent on the variable degree of crushing needed with different ores to
free the sulphuret from the gangue sufficiently for the concentration process. The
proportion of finely-screened to coarser material with any special orc is therofore
best determined by tentative experiments. When thus: ascertained, such proper
proportion can be uniformly ensured by dint of the sorting and sifting of the
crushed ore previous to concentration, which is recommended above.
The concentration, or rather the elimination of the less dense components of the

page_text: crushed ore, which include the gangue and other impurities, may likewiso be
conducted without refined methods, and thence with plant of minimum cost and
with maximum rapidity. The methods of accomplishing this are several in number,
simple and familiar to those skilled in the art of concentration; it is therefore
unnecessary to describe them all. One which I have found satisfactory is that in
which a current of water carrying a mixture of ore and gangue of oven granulation
is caused to flow over openings communicating below with receptacles or boxes
filled with water, into which the heavy sulphurots settle.
In another that I use, water carrying similar evenly-granulated mixtures flows
into circular tanks which contain slowly revolving stirrers, the latter boing adjust-
able in height so as to avoid reagitation of the already deposited layer of sulphurots
below while the overflow over the rim carries out the gangue.
The mixing of the fine and coarse sorts of concentrated sulphuret in proper
proportions with each other, and with the granular iron and the salino solution,
together with asbostus or mica, if employed, may be effected by hand-tools or by
any kind of common rotary mixing machine, but it has been found important
that the saline solution should be heated nearly to its point of ebullition, and that
the granulated ore with the granular iron, etc., be also previously and uniformly
heated to or near the temperature of boiling water, which is rapidly accomplished
by passing hot air through the mass whether the latter be dry or moist. The air
driven by a small rotary blower or otherwise passes first through a coil immersed
in boiling-hot water, and then into a chamber forming the lower part of a receptacle.
containing the fine and coarse sorts together with the granular iron, etc., the
components having been roughly mixed by fractional shovelling in the operation of
filling of the receptacle.
This partial-mixture rests on a diaphragın of fine wire gauze supported_by_a
coarser iron grating, this diaphragm-forming the ceiling of the inforior chamber
aforesaid, from which chamber the hot air percolatos upward through the diaphragin
and its superposed mass.
Whon it is desirable to operate directly on wot granulated pyrites, as theso come
from the concentrated apparatus, without draining or drying for the sake of saving
time or other reasons, and if the mass be too much clogged with moisture to allow
of the percolation of the heated air, the above apparatus may, by the employment
of a reversible blower, be used for first oxtracting the excess of moisture by creating
first a diminished pressure in the inferior chamber.
The blower being after this reversed and the hot air turned on the hoating
operation ensues. After becoming heated throughout, the granular mass is then
introduced by means of olevating buckets into the mixing box or vat together
with a properly proportioned streain of the boiling hot saline solution.
The completed mixture, which should have about the consistence of thick
mortar, is spread in a thin layer of from half an inch to an inch, proferably about
three-fourths of an inch, upon square thin sheets of lead, which are supported and
transported on light and thin movable iron gratings or hurdles.
A square wooden framework or rim is temporarily applied to the sheet of lead to
confine the mixture. When the lattor has been spread uniformly this frame may
be removed and the hardening process then proceeded with, the largo cako thus
obtained being broken subsequently by hand into fraginents of suitabla sizo for the
⚫ kiln.
The following plan however is preferable:-An inverted mould is provided,
composed of cast iron tinned superficially to prevent rusting, which mould is so
constructed with knife edged sopta as when brought down over the cake of
mixture and applied thereto with adequate pressure to cut down into and divide
the sheet or cake uniformly nearly through its whole thickness into squaro,
triangular, or preferably hexagonal segments or discs, each or about three or four
square inches superficial area, in a manner similar to that of the handling of dough
by a biscuit-cutting or moulding machine.
The sheet of lead with its charge of composition supported by its iron grating is

page_text: •
then laid side by side with others on a metallic table having an enclosed space
below, which may be heated by hot air or steam to a temperaturo of from 120 to
150 degrees Fahrenheit.
Arrangements are also provided by means of which water as a shower of very
finely divided "atomized" spray may be sprinkled uniformly over the surface of
the mixture when so desired.
The further process consists then in alternately sprinkling the porous mixture
very uniformly and gradually with water till permeated and moistened throughout,
and allowing it to dry slowly either by spontaneous evaporation or under the
influence of a very gentle heat applied, from below, as already explained, from four
to six altornations of the wetting and drying operations, occupying according to
the proportion and fineness of division of the granular iron in the mixture as well
as to the temperature applied from 24 to 48 hours, effects the complete consolidation
of the mass. The sheet of lead is then by bonding readily separable from the
consolidated cake, and the latter by virtue of the segmental divisions made while
soft, as above described, is readily divisible into discs of uniforın size ready for
burning in the pyrites kiln.
Tho granular iron used in this process may be of any commercial variety of
granulated metal, either borings, turnings, planings, or filings, either of foundry
pig or other pig, wrought-iron, low steel, Bessemer, or other ingot-iron. It is
usually dosirable that it be free from such impurities as would contaminate the
cinders for any special usos to which the latter are to be applied. Thus for exempli-
fication, if the cinders or residues in the kiln are to be used in making Bessemer-pig
or open-hearth steel by a pig-and-ore or a pig-and-sponge or other process, or if
again amalgamation or chlorination is to be applied to them for extraction of gold,
the granular iron used ought in the first case to be tolerably low in phosphorus,
and in both the first and second cases it ought to be previously put through a
magnotic soparator to eliminate all incidental lead, zinc, copper, and brass with
rags, sawdust, sand, and other non-metallic impuritios.
If grease bo present in the granular iron it should be lixiviated previous to use
with diluto caustic soda or with potroleum-naphtha. If the sulphurets operated
on are cupriferous and copper is to be extracted froin the cinders, of course the
presence of copper and brass in the granular iron may be neglected.
If it be necessary to use granular iron as prosented in commerce it should he
procured, if practicable, solely from operations or establishments where soft
foundry pig or castings thereof are bored or finished, for the reason that fineness
of division of the iron is conducive to much economy of time in operating this
Invention, and such soft borings or planings are easily reducible to very fine
division, at least in great part, by first pounding under chilled-iron stamps
and then grinding in mills having bearing surfaces of hard chilled-iron or
spiegel-iron.
Pig-iron may also be very finely granulated for the purposes of this Invention
by the centrifugal method of the "Baron De Rostning" by passing molted pig in
a small streain through a funnel placed over the centre of a horizontally whirling
cast-iron table making 2,000 revolutions per minute.
But the form of comminuted iron which I have found preferable for the purposes
of this Invention is that known commercially. as "iron-sponge" produced by tho
deoxidation of proviously pulverized iron-oxido at temperatures too low to weld
or agglomerato together the granules of reduced metal. If, however, iron-sponge.-
be purchased for the uses of this Invention assurance should be obtained by
analysis that it has been prepared from an ore previously freed from gangue and
not contaminated with impurities, such as phosphorus; etc., which will detract
from the value of the residues for metallurgical or other purposes... Above all, such
sponge must have been deoxidized with at least approximate completeness, that is,
must-bo-nearly free from intermixed unreduced oxides of iron, which lattor are
wholly inert for the purposes of this Invention...
It is to be pointed out that the cinder or residue resulting from the burning-of-

page_text: purified iron pyrites that has been prepared or caked by this Invention is highly
and especially suitable for the preparation of iron-sponge to be used in carrying
out the Invention itself. It is to be noted likewise that all the metallic iron
employed for the purpose of consolidation according to this Invention boing
recovered again in the form of oxide, which adds itself to the cinders; the cost
of such iron used in carrying out this process is thus reduced to a much lower
figure.
The salino material employed in carrying out this process for causing rapid
rusting of the granular iron under atmospheric influences must,―
Firstly, he neutral or free from sufficient acidity to give rise to any evolution
of hydrogen from action on the iron, as I have found such gaseous evolution in
the mass to be highly objectionable by producing porosity and then diminishing
cohesion.
Secondly. Deliquescent salts like the earthy chlorides are also highly objection-
able as interfering with the nethod set forth of accelerating oxidation by
alternations of drying and moistening. Such chlorides as common salt and
sal-ammoniac, even though not themselves deliquescent, are likewise inadmissible,
as they lead to the formation of the highly deliquescent sesquichloride of iron in
the mass.
Thirdly. Another conclusive objection to all chlorides is that if applicable they
would have to be washed out of the mass again after consolidation or otherwise,
the sulphurous oxido proceeding from the pyrites kiln and the oil of vitriol
resulting thorofrom in the acid chambers would be contaminated with muriatic
acid.
==
Fourthly. Highly efflorescent salts, as, for instance, sulphato of soda, cannot be
used, efflorescence proving almost as much in the way of the alternating method of
oxidation as the opposito quality of deliquoscence.
As salino agents-1-have-for-the-abovo-reasons_found_it_necessary to employ
certain sulphates, and of these cominon sulphate of iron, green vitriol, or copperas.
presents with great cheapness and convenience the highest adaptability on the
whole, though the sulphates of magnesia and zinc have been found to possess
superior consolidating power, and sulphate of alumina has also been found applicable.
Sulphates of potash and ammonia, though found effective. are too expensive for
ordinary use; where magnesian minerals soluble in sulphuric acid like serpentine
and magnesite are cheaply obtainable a solution of crude sulphate of magnesia
may be prepared and applied to advantage for those purposes. Sulphate of zinc is
liable to the important objection that it is not readily decomposed by the heat of
burning pyrites and its sulphuric acid remains accordingly to contaminate the
cinder. Sulphates of magnesia and alumina are decomposible by the heat of the
kiln. Sulphate of iron is also completely decomposed in the kiln, and as the
products of such decomposition are solely iron-oxide with sulphurous and sulphuric
oxidos, all of which are utilized in the process, it may be said that sulphate of
iron is for the purposes of this Invention virtually without cost, except for labour
in handling, etc.
Asbestus, which I mingle when desirable with the sulphurets to be consolidated
for the purpose of divesting the resulting cinders of all tendency to crumble, either
in the kiln or in subsequent handling, may be of coarsest and cheapest quality, and
of short fibre, one half inch being sufficiently long, though somewhat fonger fibre
is sometimes preferable, up to one inch, beyond which little or no advantage can
arise, and if the staple bo longer than this it may be ent down. Dark or rusty
-color is of course no objection for these purposes. The fibre should not be carded
or separated too completely or finely so as to diminish the average strength
of the single fibres too much, a mean fineness being gonerally preferable in this
case.
Mica, which I also sometimes use for the same purpose for adding cohesion to
the mass during and after the action of the kiln, may be very cheaply obtained,
for the purposes of this Invention, by disintegrating mechanically many abundant

page_text: mica-schists with or without subsequent washing to separate the mica scales
from quartzose or other impurities. Such mica may be cut if preferred into
narrow elongated ribbons, which need not be inore than half an inch in length.
The proportions of the agents and materials used for consolidation of granular
sulphurets by this method admit of a certain amount of variation.
When the metallic iron used is clean and very finely comminuted, as in the form
of fine filings, fine siftings from ground borings of cast iron or well reduced iron
sponge, five per cent of the weight of the sulphurets to be consolidated yields
results as good as any, and there is usually little or no advantage in the use of
a larger proportion. If the iron however is deficient in fineness of granulation, or
in purity or cloanuess, it may be advantageous to increase the proportion up to
7, 8, or oven in extremo cases 10
por cont. The amount of protosulphate of iron
admissible, taking it as commercial crystallized green vitriol with seven equivalents
of water of crystallization, is generally five per cent. of the weight of tho
sulphurous.
This is the maximum that is admissible without detriment to the process, such
detriment arising mainly from crystallization of the groon-vitriol in the superficial
pores of the cake undergoing consolidation, which diminishos the coherence of the
suporficial granules.
With good manipulation threo por cont. of green-vitriol gives good results, but
bocause, as before stated, the constituents of the groon vitriol are recovered in
forms even moro valuablo than itself there is probably no important advantage in
using less than four or five per cent.
The amount of asbestus that I have used to effect good results thorowith has
been one per cent. of the weight of the sulphurots, but twice this proportion may
be used to advantage if cheaply obtainable.
Mica in thin scales may be used to the extent of two or three por cont., or even
moro, being very cheaply obtainable.
Great advantages and economies in the manufacture of sulphuric acid from
sulphurets arise out of this mode of previous proparation of the ore. The porous
solid material thus obtained kindles much more readily and propagates its own
combustion, such combustion being much more rapid, complete, and uniform than
with compact lump pyrites, so that less than one per cent of sulphur is left in the
cindors, the kilns requiring also much less attendanco and less of expensive skilled
labour than in the usual way. The cinders or residues will also be found much
more available for all purposes to which they are applicable.
I am aware that granular pyrites has been ceinented with clay into blocks,
which could be imperfectly burned in kilns; and also that by a method in use of
late in Europe" pyrites-smalls" has been finely ground with water in pug-mills to
a mud, which in the case of some varieties of pyrites whon moulded into cakes
hardens by drying or slight baking, sufficiently to be handled and burned in
kilns.
In my method however the consolidation does not arise from any cohesion sot
up by oxidation or otherwise, or from any other change of the sulphurots them-
selves, but is effected by the agency and through changes of other materials added
thereto which act independently of the special character of the sulphurets thom-
selves, and on all varieties alike.
I have now particularly described the nature of the said Invention, and in
what manner the same is to be carried into effect, as it has been communicated to
me, and wish it to be understood that I do not claim broadly as a novel Invention
the agglomeration of granulated sulphurets, but what I do claim is,—
Firstly. The consolidation of all varieties of granular sulphurets into cakes,
lumps, or blocks by mixing therewith metallic iron in comminuted or divided
form, and causing this iron to rust and form hydrated oxide or a basic salt in the
interstices of the inass by admixture with a saline solution.
Secondly. The combined process of preparing metallic sulphurets for the operation
of desulpurization and burning out of the sulphur therefrom, by crushing to

page_text: granular condition, removing the gangue and impurities by means of a current of
air or water, or otherwise, and then re-cernenting the purified granules together
into masses by the rusting of comminuted metallic iron mingled therewith.
Thirdly. Accelerating and intensifying the rusting and cementing action of
motallic iron when mingled with other materials by the process of alternately
moistening the mixture with water, and drying either spontaneously or by a gentle
hoat, as herein specified.
Fourthly. As an article of manufacture or new composition of matter, a con-
solidated product made by mingling together granulated metallic sulphurets with
granulated metallic iron, and causing the latter to rust by the action of a saline
solution, either with or without the addition thereto of asbestus or of mica.
Fifthly. Increasing the cohesion and infrangibility of caked masses of granulated
sulphurets, and of the cinders or residues left after burning the same, by mingling
therewith asbestus or other fibrous refractory minoral substance.
Sixthly. Increasing the cohesion and infrangibility of caked masses of granu-
lated sulphurets, and of the cinders or residues left after burning the saine, by
mingling therewith common mica or other refractory foliated or micaceous mineral
substance in thin scales.
Seventhly. The use of metallic iron in the form of iron-sponge produced by
roducing to metallic form granulated or powdered iron-oxide or ore, or pyrites-
cindors, by exposure to heat in-admixture with carbon or a combustible gas, for
cementing together granular materials by the rusting action thercon of a saline
SONITION.
----
SONILION.
In-witness-whereof, I, the said John Richardson Francis, havo horeunto, set
my hand and seal, this Eleventh day of March, in the year of our-Lord-
One thousand eight hundred-and-eighty-two.