Methods of Treating Metallic Ores.
Year: 1899

page_text: Date of Application, 17th Jan., 1899-Accepted, 11th Mar., 1899
COMPLETE SPECIFICATION.
Methods of Treating Metallic Ores.
A communication from abroad by THE ILLINOIS REDUCTION Co., a corporation
organized and existing under the laws of the State of Illinois, and having its
principal place of business at Room No. 904, No. 115, Monroe Street, Chicago,
Illinois, U.S.A., Manufacturers.
I, WILLIAM LLOYD WISE, of No. 46, Lincoln's Inn Fields, in the County of
London, Consulting Engineer and Chartered 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 any by the following statement:- -
The invention is directed more particularly to the treatment of copper ores and
is equally applicable whether a minor per centage of silver be present in the ore
or not. In the preferred form, the improvement designs to convert the metals
into sulphates by digesting the ores under heat and pressure, with a suitable
oxidizing agent in presence of free sulphuric acid, and after precipitating the
silver if any by means of copper filings, subjecting the solution to electrolysis.
Under such action, the copper and the oxidizing agent are for the most part
recovered; the copper depositing on the cathodes while the oxidizing agent is
regenerated at the insoluble anodes and--in proper state for re-use-precipitates
from the electrolyte. The residue of the metallic salts with free sulphuric acid,
constituting the bulk of the spent electrolyte, is later evaporated, the salts
crystallized out and calcined or otherwise treated to restore the contained oxidizing
agent to active condition for re-use while the sulphuric acid, after crystallization
of the salts, remains as a mother liquor, in readiness to be employed anew at the
digestor. The method proceeds in cycle, that is, the oxidizing agent and sulphuric
acid which effect the solution of the metallic elements of the ore at the leaching
stage, are both ultimately recovered-at marked saving-to be employed over
again in digesting fresh batches of ore.
The nature of the invention will appear in detail from the description following
and be more distinctly pointed out by claim at the conclusion thereof.
In the drawings which accompany: Fig. 1 is a diagrammatic elevation view of
various sorts of apparatus employed for practice of the invention. Fig. 2 is a
like view of the same, in plan. Fig. 3 a graphic table of the chemical changes
which ensue during progress of the treatment. Fig. 4, a view of the rotary
digestor in longitudinal section; Fig. 4, an end view thereof: Fig. 4", detail
section view of one of the stuffing boxes for the digestor. Fig. 5, elevation view
of a series of evaporating vats or tanks; Fig. 5, plan view of one of said vats
with pipe coil therein.
As shown by the drawings, the ore will be delivered in usual manner to the
bins A from which it passes into a suitable crusher B and thence through the
screens C into storage bin D. From bin D the classified ore discharges by chute e
and hopper E into digestor F.
Digestor F consists of a revoluble cylinder made of boiler plate or the like

page_text: having an acid-proof lining of lead, brick or similar material. Digestor F i
mounted upon supporting rolls f and at its opposite ends carries the stuffing
boxes fitted with lead pipes g for entry of air or steam. Man-holes m afford
access to the interior of the vessel. In practice, the digestor may contain
from 10-20 tons of ore when half full, in readiness for action.
Within the closed cylinder F the ore charge is treated with manganese oxide
(or similar oxidizing agent) to which some free sulphuric acid, preferably, is
added. While the digestor revolves slowly, hot air at 40-80 lbs., pressure is
injected through the hollow trunnions. The proportions of oxidizing agent and
acid used will depend upon the per centage of metallic elements present in the
ore under treatment. Ordinarily from 10-15% of manganese oxide will suffice
for each 100.0% of ore. The sulphuric acid should be in quantity slightly in
excess of what is necessary to convert the metals into sulphates.
The digestor being properly charged is caused to revolve slowly while hot air
forces itself into the interior through pipes g leading from furnace G or other
convenient source. The batch of material within the digestor is subjected simul
taneously to the action of the oxidizing agent and of the heated air and in presence
of the free acid, the copper and part of the silver are taken up in solution. The
duration of the treatment at the digestor must depend upon the character of the
ore and in measure upon the size to which it had been previously ground. The
time varies ordinarily from 4-16 hours per charge. At the end it will be found
that the digestor contains copper (perhaps silver), manganese and iron sulphates,
sulphuric acid and insoluble tailings. This condition of the charge is indicated
by the graphic table at Fig. 3. The iron sulphate is to be traced in large measure
to the manganese oxide with which the iron is generally associated.
At the close of the digestor treatment, the solution is drained off from the
tailings and discharges from the extractor by suitable troughs h into a settling
tank H. Only one settling tank is shown although any number may be used
if requisite to obtain a perfectly clear solution. After the tailings are washed
and the liquor added to the main_solution, the solid residues find exit through
trap door h¹ into the tailing flume I.
The solution remains in the settling tank or tanks until it is thoroughly clarified
which must depend in measure upon the character of the ores taken and the
tendency to form slime. When sedimentation is effected the clear solution is
drawn off and if silver be present it may be run over copper or other metallic
filings within a suitable precipitating tank K. The filings serve to throw down
the silver in metallic form, to be subsequently cast into bars, while the copper
takes its place in solution.
Thus prepared, the finished bath or solution serves as an electrolyte and can
at once be admitted from tank K into the refinery vats M. Said refinery vats
contain insoluble anodes either of carbon or lead."
By action of the electric current the copper in solution is deposited on the
cathodes as usual while the manganese oxide constituting the oxidizing agent at
the digestor is for the most part regenerated at the anodes and separates from
the solution. When the spent electrolyte is drawn off from the rats, the regene-
rated oxidizing agent remains and can be cleaned out and taken back for re-use,
at the digestor.
The electrolyte solution is kept flowing from vat to vat of the refinery M;
eventually, all of the copper present is deposited from solution. Aside from the
free acid, the spent or lean electrolyte contains a minor part of the oxidizing
agent and as well the associated iron in form of sulphates. The spent bath is
run into a tank or tanks where it may be repeatedly evaporated and then cooled
to crystallize out the salts of iron and manganese; the free sulphuric acid left
as the
"mother liquor" remains in proper state for re-use at the digestor. To
effect evaporation, the tanks ( may be arranged in series, one tier above another,
as seen at Fig. 5. The tanks at one part of the plant can be out of action, to
allow for crystallization and removal, while at another part evaporation proceeds.

page_text: The tanks should be lined with lead or like resistant and, as shown at Fig. 5*,
may be heated by submerged lead-pipe coils o through which live steam can pass.
On removal from the tanks O, the sulphate crystals may be decomposed in an
ordinary calciner to form resultant oxides in which condition the manganese
stands regenerated and in readiness to be used again at the digestor. The fumes
of sulphuric acid evolved during calcination may be condensed by water and saved.
Instead of calcining the sulphate crystals derived from evaporating tanks O,
said crystals can be dissolved in water and then treated hot with slack lime
sufficient to unite with the free and combined acids, hot air being blown in during
the treatment. The manganate of lime thence resulting can be used as
oxidizing agent at the digestor.
an
Having removed the copper-and also the silver if present-by primary diges-
tion or leaching, in manner already detailed, it becomes feasible to retreat the
tailings for recovery of the gold should the ore values justify.
To such end, the refuse tailings are to be restored to the digestor. Leaching
proceeds anew, hydrochloric in lieu of sulphuric acid being now employed along
with the oxidizing agent, e.g., manganese oxide. The soluble salts of gold thence
derived, on removal from the digestor, may be treated with ferrous sulphate or
metallic zinc for precipitation of the gold, as well understood. The chlorides of
iron and manganese yet held in solution would thereupon be evaporated, crystal-
lized out, and calcined for re-generation of the oxidizing agent, in manner already
detailed.
Should zinc or nickel be present in paying quantities, these can be leached out
as soluble salts by the digestor treatment and be ultimately recovered under
suitable conditions, although the acid electiblyte already detailet could only
serve at the refinery for the separation of the copper alone.
Manifestly the details can be varied according to the mechanic's skill without
departing from the essentials of the improvement.
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed, I declare that what
I claim is:-
1. The method of leaching metallic ores which consists in digesting the wet
pulverized ore, under heat and pressure, by means of a suitable oxidizing agent
in presence of a free acid and thereafter separating the soluble salts from the
refuse gangue, substantially as described.
2. In extracting copper from its ores, the method of preparing the electrolyte
which consists in digesting the wet pulverized ore, under heat and pressure, with
manganese oxide in presence of free sulphuric acid, substantially as described.
3. In extracting copper from its ores, the method of preparing the electrolyte
which consists in injecting hot air into the wet pulverized ore while digesting the
same with a suitable oxidizing agent in presence of a free acid, substantially as
described.
4. In extracting copper from its ores, the method of preparing the electrolyte
which consists in injecting hot air into the wet pulverized ore while digesting the
same with manganese oxide in presence of free sulphuric acid, substantially as
described.
5. In extracting copper from its ores, the method of preparing the electrolyte
which consists in injecting hot air into the wet pulverized ore while digesting
the same with a suitable oxidizing agent, such as manganese oxide, in presence
of a free acid, e.g., sulphuric acid, and separately precipitating the silver from
solution by metallic copper or the like, preliminary to electro-deposition of the
copper salts, substantially as described.
6. The electrolytic method of extracting copper ores which consists in digest-
ing the wet pulverized ore under heat and pressure, with aid of a suitable
oxidizing agent, c.g., manganese oxide, in presence of free acid (e.g. sulphuric
acid), eliminating the silver if any be in solution, by metallic precipitation, and

page_text: then electrolysing with help of insoluble anode-the bath thus prepared, to
effect deposition of the copper at the cathode and simultaneously to eliminate
in the regenerated state, the oxidising agent from the electrolyte solution, sub-
stantially as described.
7. The method of extracting copper ores which consists in digesting the wet
pulverized ore under heat and pressure by means of a suitable oxidizing agent,
e.g. manganese oxide, in presence of free acid, e.g., sulphuric acid, electrolysing
the dissolved sulphates thence derived to deposit the copper and precipitate a part
of the oxidizing agent in regenerated state, then evaporating the spent electrolyte,
crystallizing out the metallic sulphates for subsequent re-generation of the
oxidizing agent, e.g., by calcination, and saving the mother liquor, i.e., the con-
centrated free acid, for digesting fresh charges of ore, substantially as described.
8. The wet process of extracting copper from its ores having precious metal
therein, which consists in digesting the pulverized ore under action of heat and
an oxidizing agent, in presence of sulphuric acid, exposing the dissolved sulphates
to metallic copper for precipitation of the silver, treating the filtrate electro-
lytically to deposit the copper, evaporating the lean electrolyte to concentrate the
free acid, and crystallize the metallic sulphates, and finally calcining such
crystallized sulphates to properly regenerate them as oxidizing agents for re-use,
substantially as described.
D
1511
1
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.