Improvements in the Treatment of Ores containing Sulphur, and in Apparatus for Carrying same out.
Year: 1899

page_text: Date of Application, 18th Apr., 1899-Accepted, 18th Apr., 1900
Improvements in the Treatment of Ores containing Sulphur, and in
Apparatus for Carrying same out.
A communication from abroad by ARTHUR WALLACE CHASE, a Second Lieutenant
in the United States Army, now serving in the Island of Cuba.
I, PHILIP MIDDLETON JUSTICE, of 55 and 56, Chancery Lane, in the County
of Middlesex, Fellow of the Chartered Institute of Patent Agents, do hereby
declare the nature of this invention and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following state-
ment:
-
My invention relates to improvements in processes for the treatment of ores
and by-products containing sulphur and iron and which may or may not contai
other metals such as copper, manganese, phosphorus, cobalt, zinc, lead, etc.
It also relates to the apparatus for carrying out the processes mentioned above
and to one of the products obtained therefrom.
The object of my invention is to recover practically all of the valuable consti-
tuents in said ores. In ordinary ores that are used for sulphuric acid making
the ash is generally of no value and moreover is a source of expense. By my
process I am enabled to convert this hitherto waste material into a valuable
product and especially to save the iron contained therein, which has never been
done up to the present time.
This recovery of the iron in a commerical form, at a comparatively slight expense
constitutes the chief value of my process, although the saving of the by-products,
such as sulphuric acid, copper and gold and silver, if any are present, constitutes
a valuable feature thereof.
The ores intended to be treated by my process contain in general varying per-
centages of sulphur, iron and copper, but this process is also intended to treat
the ash or residuum left over after roasting said ores in the process of making
sulphuric acid.
More specifically stated, therefore, my process has for its object, first, the expul-
sion of sulphur which may be utilised for the manufacture of sulphuric acid, or
otherwise, as desired. Second, the extraction of the copper and other metals,
except iron, and the reduction of the sulphur to a degree which will not be
injurious in the use of the iron residue in a blast furnace.
In the manufacture of sulphuric acid I make use of standard processes well
known in the art, but where the manufacture of acid is not the primary con-
sideration, I roast the ore either to a dead roast or until the sulphur is reduced
to nearly the percentage of the copper, if there is any present. In general atter
roasting with a small percentage of carbonaceous material I mix the residue with
common salt, finely crush the mixture and pass the same through my furnace
again, maintaining the heat at about a dull red and so timing the roasting as to
convert the copper to a chloride, and by lixiviation, as hereafter described, remove

page_text: the copper and other metals that have formed soluble compounds and precipitate
them by standard methods and obtain iron oxides so low in sulphur as to be
available for use in the blast furnace.
In the accompanying drawings,
Fig. 1 is a longitudinal section of the roasting furnace constituting a part of
my apparatus.
Fig. 2 is a central cross section of the same.
Fig. 3 is a cross section on the line 3-3 of Fig. 1.
Fig 4 is a detail view of a modified form of the conveyor, and
Fig. 5 is a side view, partly in section, of my complete apparatus.
In the drawing A, A' represent the end walls of the furnace, B, B₁ the side
walls, C the top, D D D the arched bridge walls, and E the grate bars.
in the top C is a pipe c which leads either into a chimney or into a washer
for removing the gases evolved in the roasting operation which may be utilized
by standard means, well known in the art.
In the top of the wall A is a passage fl which may be closed by a sliding
valve f, and which communicates with the hopper F which is adapted to receive
the charge to be roasted. The lower end of this passage communicates with a
trough G, which is U-shaped in cross section, open at the top and made in sections
dovetailed together, as shewn at g. The trough G is supported at its outer ends
by the walls A, A¹ and at the junction of the sections by the bridge wall D³, and,
if desired, between such supports by the cradle and cross supports glo, gl, the
object being to fully support the trough and its charge while exposing the
maximum surfaces to the action of the heated air and the furnace products of
combustion. The furnace may be of any desired size and the trough G may be
composed of any desired number of sections, but it is desirable that outer ends
of the troughs, the junctions of sections, and where necessary, intermediate points
on the sections, be supported, as shewn.
Below the trough G are similar troughs G1, G2, supported by the outer walls,
the bridge walls D¹, D; and the intermediate cradles and supports. Removable
braces F are used to hold the troughs firmly in position.
It is understood that I do not limit myself to three troughs but may use any
number.
A passage g³ in the wall A¹ connects the troughs G, G¹ and a similar passage g³
in the wall A connects the troughs G¹, G³. Connected with one end of the
trough G is a discharge passage in the wall A', which is adapted to be closed
by a sliding valve 95.
Suitable standards I, I' are located outside of the furnace and journaled in these
standards are hollow shafts H, H', H³, one being located in each trough. These
shafts are square in cross-section within the furnace and round outside of the
furnace, and to the square portions of the same are fastened screw conveyor
flights h¹, h, h³, made in sections and secured by bolts h or by set screws as
shown in Figure 4. The flights h¹, h, are pitched in one direction and the
flights in the opposite direction.
h, ha, ha, h7, ho, ho, are removable doors or closures bolted directly to plates P P¹
which are provided with openings and removably attached to the furnace walls A A¹.
Each closure is made in two parts which fit around the corresponding shaft. By
this construction the interior parts of the furnace are made easily accessible.
The
These plates P, P₁ are provided with vertical slots of somewhat greater width
than the bolts of the closures , h³, etc., engaging therein, for the purpose of
allowing for the displacement of the troughs G, G1, G2 under the furnace heat
or for general alignment of the conveyors and troughs when necessary.
journal boxes on the standards I I¹ are also capable of being lowered or shifted
by suitable means (not shewn) for the purpose of accommodating the axial position
of the conveyor flights to any variations or changes in the position of the
troughs GG, G due to heat or other causes.
The conveyor flights h¹ ª³ are made either in two parts fitting around the

page_text: shaft, or in suitable sections of complete pitches of the conveyor, or otherwise,
secured in place on the shaft by the set screws.
On the shaft H¹ are mounted spur wheels J J' meshing respectively with similar
gear wheels i, j, on the shafts H, H. This gearing is so proportioned that the
shaft H travels faster than the shaft H and the shaft H faster than the shaft H'.
This provision removes the material fed into the troughs G¹ G at a faster rate
of travel and lesser stream than exists in the overlying trough. This not only
obviates the possibility of clogging in the passages, g, but provides that as
the charge approaches the exit g, the furnace heat increasing as the charge is
fed into lower troughs, the charge stream is of smaller cross-section, thus more
largely exposing the particles of the same to the action of the heated air and
products of combustion in the furnace.
On the shaft H is mounted the bevel gear wheel, which is driven by any
suitable means (not shewn). Besides the standards I, I other standards K, K
are provided, which aid in supporting the gearing and the stuffing boxes k, k', kº,
into which the pipes, 12 deliver a cooling fluid from the main L.
The shafts H, HH pass through journal boxes in the standard I' and into
stuffing boxes R, R1, R2 secured to said standard by brackets ³. r, which are bolted
to the standard and to the stuffing boxes. Pipes r, rare connected to the
stuffing boxes R, R¹, R³ and serve to discharge the water or other fluid which
passes through the shafts H, H¹, H².
The complete apparatus for carrying out my process is represented in Fig. 5
in which s represents a hopper which delivers into a crusher S of any approved
type. This crusher delivers to a chute s', which in turn delivers into a revolving
screen S. The ore that does not pass through the screen falls into a chute sa,
from whence it is returned by an elevator S into the hopper s.
The ore that passes
through the screen is delivered by means of a chute and hopper into a
roaster S³, of any approved type. A pipe connects the gases evolved during the
roasting operation into a sulphuric acid chamber St. The ore, after the roasting
operation, which removes a large percentage of the sulphur present, passes through
the chutes into a hopper and thence between crushing rolls So, falling into
a chute S6, from whence it is delivered by an elevator Sinto a chute S³, provided
with a valve 8, from whence it is delivered to a mixer S⁹.
Ahopper So, provided with a valve sto is arranged to deliver any carbonaceous
matter, preferably coke dust, into the mixer S⁹ which is provided with a shaft
having a pulley s³.
The mixed ore and carbon pass through the chute s into the hopper S¹ of a
roasting furnace S1, constructed as shewn in Figures 1-4.
After passing through the roasting furnace S, the ore falls into a chute 12,
from whence it is conveyed by an elevator SB into a chute from whence it
passes into a hopper and the mixer S". A hopper S5, provided with a cut-
off 15 is adapted to deliver common salt to the mixer S, which is similar in
construction to the mixer S9 already described. From the mixer the ore is
delivered through the chute 16 into the hopper s7 of the roasting furnace S17
of the construction shewn in Figures 1-4. From this furnace the ore is delivered
to the washer S18 where it is subjected to the action of steam under pressure and
hot water, the water escaping through the tube 18 into the vessel $10 while the
ore escapes through the chute into the receptacle S. The vessel S acts as
a precipitative tank and into this vessel will be discharged practically all copper,
gold and silver and other soluble salts contained in the roasted mixture. The
clean ore is taken from the receptacle S20, and after subjection to the action of
a magnetic separater, if desired, the ore is suitable for use in a blast furnace or
in other ways. Practically all of the iron contained in the ore will be discharged
into the receptacle S2, and it will contain nothing but this iron ore with the
exception of mechanical impurities, such as silica and the other insoluble gangue
of the ore.
In carrying out my process, the ore or ash is finely crushed and mixed with

page_text: a percentage of coal dust, coke, or other carbonaceous matter, but preferably coke
dust a percentage calculated for the reduction of the sulphur until it is reduced
so that it is slightly in excess of the copper present in the ore or ash. This
percentage, of course, varies with the percentage of sulphur in the ore or ash
and the presence or absence of alkalies, alkaline earths, etc.; but as much of the
sulphur is expelled in roasting as vapor of sulphur, sulphurous and sulphuric
oxides, the percentage of carbon needed will usually be much less than the per-
centage of sulphur, and in the ordinary run of ash will be about 3%. This
mixture is roasted in the furnace shewn in Figures 1-4. In this furnace the
mixture is given a continuous and regular stirring, so that fresh surfaces of the
ore are continually exposed to heated air or to fire clay or iron at a red heat.
The temperature is maintained at or slightly above a full red heat and the time
of passing of the ore or ash through the furnace is that needed for the reduction
of the sulphur to the desired point. As the percentage of carbon used, the furnace
heat and the time of roasting are all under control, the roasting can be regulated
exactly as desired. The residue after this roasting is generally sufficiently fine
and without "scars"; if not, it is then crushed and mixed with a percentage
of common salt, varying from one and one-half to two times that of the sulphur
now present and again passed through my furnace. The heat is now kept at about
a dull red and the time of passing through the furnace is so regulated that the
copper is completely converted into a chloride.
The residue from this roasting is lixiviated as in the well known Henderson
process, and the copper, together with the silver and gold present, if any, recovered
by standard methods. When I find the ash from the sulphuric acid furnaces
properly roasted, that is, when the percentages of sulphur and copper therein are
nearly equal, the step of preliminary roasting with carbon may be omitted, and
the ore may be ground, mixed with common salt and roasted, as above set forth
I do not claim the roasting with salt and subsequent lixiviation, as broadly
new, but I do claim the process as above outlined, as applied to raw sulphuret
ores and as applied to ash obtained from the roasters in sulphuric acid making,
where, as is generally the case, the sulphur is relatively much higher in per-
centage than the copper and the amount of salt needed in the Henderson process
is relatively much greater than by my process. The preliminary roasting of ash
and sulphuret ores with an admixture of carbonaceous material reduces the amount
of salt necessary in the subsequent roasting operation usually by one-half.
In applying my process to sulphuret ores or ash which do not contain any
appreciable amount of copper, I am able to roast the ore or ash with an admixture
of carbonaceous material and obtain good iron, practically free from sulphur,
without resorting to the secondary roasting with salt. The operation is the same
as has already been described as carried out in the furnace S¹2
By this method I have found in practice that I can reduce the sulphur present
to a small fraction of 1%, at times only a trace remaining. The iron oxides are
then ready for treatment in a magnetic separator, if necessary, to separate them
from silica and other insoluble impurities.
The advantages of my process are that it is quick, inexpensive and that it
utilizes practically all the valuable constituents of the ore or ash, a thing which
has never been done before up to the present time. The iron contained in the
ash obtained in the process of making sulphuric acid has never been recovered,
except as a by-product in the Henderson process. And in the case of ores which
do not contain copper (pyrite ores, for example) or in which the copper percentage
is too low for profitable extraction by the Henderson process, the iron has never
been recovered.
Looking at the process as a whole it is seen that under a red heat soune sulphur
passes off as S02, some as vapor of sulphur (S), some from the continued formation
of sulphates from sulphides and the subsequent reduction of the sulphates to
sulphides and oxides with evolution of vapor of sulphur, SO, and SO, The sulphur
is thus gradually reduced and as my process involves the continual turning over of

page_text: the ore, the latter being in a fine state of division, the cycle of changes from
sulphides to sulphates, or oxides, and the evolution of sulphur in various forms
is regularly continued at about the constant temperature of a full red heat, until
the percentage of the sulphur is as low as is desired, such sulphur being almost
entirely in a soluble form. Further, that by mutual decomposition due to the
temperature and the presence of carbon, the percentages of cobalt and manganese
are materially reduced or changed to soluble forms; that arsenic and phosphorus
are volatilized at this high heat. It is also seen that zinc salts, in the presence
of carbon at a high temperature, are reduced and that the zinc is vaporized.
The process as whole therefore has a constant tendency to remove the volatile
constituents of the ore or ash," either in vapor or as oxides, reducing the iron
to the stable oxides, placing the residual sulphur in a soluble state, and leaving
the copper, silver, and gold ready for a subsequent roasting with a minimum
quantity of common salt for their recovery by a modification of "Henderson's
process.
**
"3
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed as communicated to
me by my foreign correspondent, I declare that what I claim is:-
1. The apparatus for treating ores or by-products containing sulphur and iron,
whether mixed with ores of other metals or not, as herein described and set forth
in Figure 5 of the drawings.
2. The roasting furnace as herein described and shewn in Figures 1-4 of the
drawings.
3. The herein described process of treating ores and by-products containing
sulphur and iron, whether said ores and by-products contain other metals or not,
which consists in crushing them, subjecting them to a roasting operation while
mixed with carbonaceous material and then separating out the various valuable
constituents of the material under treatment in any well known manner.
4. The herein described process for the treatment of ores and by-products con-
taining sulphur, iron and copper and which may or may not contain other metals
which consists in crushing them, subjecting them repeatedly to the roasting
operations described, lixiviating the product and treating the liquid and solid orc
obtained by said lixiviation in any well known way to extract therefrom the
valuable constituents.
5. The herein described process of treating sulphuret ores, which consists in
crushing them, roasting them with the admission of a suitable quantity of air
for the production of sulphuric acid, crushing the ash thus obtained, mixing said
crushed product with a small percentage of finely divided carbonaceous material,
roasting the mixture at a full red heat with free access of air, mechanically stirring
said mixture during said roasting operation, mixing the roasted material with
a quantity of common salt chemically equivalent to the copper present, roasting
the mixture at a dull red heat with free access of air, mechanically stirring said
mixture during the roasting operation, subjecting the product to the action of
hot water and steam under pressure, thereby forming a solution of all the soluble
salts present, and treating the solution and the residue by any well known methods
to obtain the valuable constituents thereof.
6. The herein described roasting furnace consisting of end walls, having passages
therein and openings there-through, sliding valves for some of said passages, sido
walls, bridge walls, U-shaped troughs composed of fire-clay sections, conveyors,
each composed of a hollow shaft and sectional flights secured thereto located in
said troughs, means for driving said conveyors at different rates of speed, and
removable doors or closures for the openings in the end walls.
Dated this 18th day of April 1899.
PHILIP M. JUSTICE.