Improvements relating to the Treatment of Ores containing Lead, Zinc, and other Metals.
Year: 1889

page_text: Date of Application, 2nd Aug., 1889-Accepted, 19th Oct., 1889
COMPLETE SPECIFICATION.
Improvements relating to the Treatment of Ores containing
Lead, Zinc, and other Metals.
I, FRANK LESLIE BARTLETT, of Portland, in the County of Cumberland and State
of Maine, United States of America, Metallurgist, 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:-
..
ores, more
This Invention relates to the treatment of the so called sulphuret
particularly such ores as contain large quantities of zine in the form of zinc sulphuret,
together with more or less silver, lead, copper, etc.
ore
According to the methods hitherto in common use, these ores have been carefully
roasted to expel the sulphur and then smelted with an excess of some other
containing no zine. When the zinc was volatilized under these conditions without
the presence of sulphur, it carried off with it large quantities of silver which was
A further
not only lost, but if pigment was made, greatly injured the quality of it.
difficulty was occasioned by the action of the zine on the slag, which was made
thick and pasty by its presence, making it difficult to separate out the precious metals,
and thus causing further losses.
When the ore was treated in a raw or unroasted state, large quantities of sul-
phuric acid, which is very destructive, was given off.
Many attempts have been made to expel the zine without undue loss of silver, but so
far as I am aware, without success, for the reasons above stated.
The object of the present invention is to devise a method of treatment whereby
the zinc may be carried off in the form of fume without taking with it any
appreciable amount of silver and the silver is left behind in the slag to be again
smelted by the usual methods.
The invention is based on the fact believed to be hitherto unknown, that when ores
containing silver and zinc are burned in the presence of an excess of sulphur, the zinc
escapes without taking with it any of the silver.
of
The process consists broadly of mixing the ore with a hydrocarbon fuel, adding an
excess of sulphur in some suitable form, if the ore does not contain an excess
sulphur, burning it in the presence of an air blast and admitting air above the burning
ore to destroy the sulphuric acid which would otherwise be given off.
The amount of sulphur to he used varies greatly according to the nature of the
ore to be treated but there must be at least as much sulphur in the charge as there is
zinc.
In carrying out the process f prefer to proceed as follows viz. —
The
I take the raw ore and if it does not contain an excess of sulphur in the form of
sulphurets, I mix with it sulphuret of iron or copper and then crush it to a fine state
of division and mix it with two-thirds by weight of finely divided petroleum oils or
residues, bituminous coal, saw dust or other flaming fuel. I then charge it into a
furnace having a perforated hearth, in a shallow layer about four inches deep.
Wetherell hearth, so called, is well suited to my process. The ore is burned in
presence of an air blastwhich is forced upthrough the perforated hearth and a sufficient
quantity of air is also forced in through openings in the sides of the furnace above
the layer of ore.
The zinc and lead, if any is present, are given off in the form of fume and may be
collected in a bag room or by other suitable means. The sulphur fuses with the
copper, iron, silver and gold and forms a slag or scorice which retains all the non-
volatile metals and which may be drawn off to be subsequently treated in the ordinary
manner by smelting.
The sulphuric acid which would otherwise be formed is destroyed by the action of
the hydrocarbon flame and the air which is admitted for this purpose above the

page_text: burning ore. The combustion of the sulphur takes the place of a considerabl
portion of fuel and furnishes a large proportion of the heat necessary to carry on th
process.
The advantages of the process, it will thus be seen are, that by it raw ores can b
worked, the zinc is completely separated from the silver in the form of fume, the
slag is kept free from zinc, so that the non-volatile metals may be readily smelted ou
by the ordinary process, and a cheap class of fuel, as saw dust, chips, waste fine coal
may be used.
In the accompanying drawing I illustrate a furnace suitable for carry my process
into effect.
In the drawing
Fig. 1. is a central vertical section on a of Fig. 2.
Fig. 2. is a plan view of the furnace.
A represents the walls of the furnace, B is the hearth having numerous perforations b.
Beneath the hearth is an air supply pipe C through which air under pressure is intro-
duced. is the outlet connected with any suitable cooling or collecting apparatus.
ee are openings for charging in the ore and e¹ el are covers for the same.
dd are a
set of air supply pipes passing through the walls of the furnace and entering the
combustion chamber at a comparatively small distance above the hearth. These pipes
are supplied with air from the pipe D. The ore and fuel are charged in through the
openings e c forming a shallow layer on the hearth or bottom B. Air is forced up
through the perforated bottom B and through the layer of ore. Air is also blown in
or allowed to enter through the pipes d d for the purpose already pointed out.
It should be stated that unless a fuel is used containing much hydrocarbon, sulphuric
acid will be formed. Coke and anthracite coals alone cannot be used, since the
necessary reaction upon the sulphur fumes will not take place except in the presence of
a hydrocarbon flame. It is not absolutely necessary that the air blast should be forced
upward through a perforated hearth but it may be blown through the mass from the
sides by using suitable apparatus.
Having now particularly described and ascertained the nature of my 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 treating ores containing zine and silver which
consists in mixing the ore with hydrocarbon fuel, supplying sufficient sulphur to
produce an excess of the same and burning in the presence of an air blast forced
through the mass of ore, substantially as shown.
(2) The herein described process of treating ores containing zinc and silver which
consists in mixing the ore with hydrocarbon fuel, supplying sufficient sulphur to
produce an excess of the same, burning in the presence of an air blast forced
through the mass of ore and supplying air to unite with the products of combustion
above said mass, substantially as shown.
Dated this 2nd day of August LSSO
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.