Year: 1886

page_text: I, JOHN WESLEY HALL, of Broadmead, Bristol, in the County of Gloucester,
Merchant 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 the treatment of lead ore, antimony ore, complex or
mixed lead and zinc ore, and refractory ores containing precious metals, i.e. such as
ores bearing silver and gold and containing zinc, arsenic, antimony, tellurium and
other base metals and metalloids that prevent smelting of the ore even with fluxes,
as causing a too great loss in the precious metals with the slag and fumes; And
my invention consists essentially in roasting the ore (when necessary), and collecting
the fumes by means of strainers made of a suitable textile fabric, and then treating
the roasted mass or slag and waste fumes, either for the manufacture of a white
pigment or for the manufacture of the metals in a smelting furnace connected with
the fume-catching apparatus. The treatment of the ore necessarily depends on the
character of the latter. If the ore contains but little or no sulphur, the roasting
process will not be necessary, but if it should contain any considerable amount of
sulphur then roasting will be required.
Apparatus suitable for carrying my invention into practice is shown in the
accompanying drawing in which,
Figure 1 represents a longitudinal vertical section of the said apparatus.
Figure 2 represents a plan view of the same.
A represents a roasting furnace, connected with a series of pipes a, and the
suction-fan B. Below the pipes a are secured hoppers or bins b for the reception
of any deposits of the metallic fumes which may accumulate, or be deposited, in
the pipes. The bulk of the fumes will be drawn by the fan B, and driven through
the pipe C into the bags c made of any suitable textile fabric, preferably woollen
material,

page_text: The fumes from these bags are collected by shaking the bags and causing any
condensation in them to fall into the hoppers or bins d provided at their lower ends
with an opening and a damper D, for discharging the accumulation onto the
hearth E, where the fumes are subjected to a final roasting and this concludes the
first step in my new process.
The furnace I use for roasting the ore is similar to the American Scotch hearth,
only I prefer a hot blast produced either by heating the blast outside of the
furnace, or, as represented in the drawing, by passing the air through the pipe F
(as shewn in Figure 2) and thence through the hollow back and sides of the
furnace before entering the tuyeres.
The lead-well G in the Scotch hearth furnace, is not absolutely necessary, but it
is always preferable, as, even if the ore contains no lead, or not enough to produce
metallic lead, the well will be filled with molten slag that serves the same purpose
in allowing the workmen to manipulate the charge with greater ease; I also prefer
using a wider furnace with a series of tuyeres, instead of a single tuyere.
I carry out my process by first building a fire on the hearth and then feeding it
with ore, fluxes (if necessary), and soft coal, or any other kind of fuel, solid, liquid,
or gaseous. The fuel mostly serves to keep up the necessary temperature. This
roasting differs from the ordinary roasting in that, while in ordinary roasting
furnaces, as the heat and air strike over the charge, the latter must be constantly
turned to come in contact with the air, and the process is both slow and expensive;
while in the manner herein set forth according to my invention, the blast enters
into the charge, is very effective in a short time, and requires very little fuel or
labor.
By my process a large amount of metallic fumes is formed and collected. If the
ore is a galena ore, or contains much lead, part of the lead smelts down, and carries
down the bulk of silver and gold; but if little or no lead is present, none smelts
down; thus in the case of Galena ore, the roasting furnace acts partly as a smelting
furnace.
The fan B draws the fumes from the furnace through the cooling pipes a (which
I prefer to make of sheet iron) and drives them into the bags c and thence into the
sheet-iron hoppers d to which the lower ends of the bags are properly secured, the
gases and products of combustion being forced through the interstices of the textile
fabrics, while the metallic fumes are most thoroughly condensed, and being
condensed, gradually fall into the hoppers d, the bags being shaken from time
to time.
When the hoppers & contain sufficient material, it is let out, through the
openings D, onto the floor E for further treatment. As the fumes are bulky and
easily lost while being handled, I prefer to expose them to a preparatory roasting,
which is easily done as by the use of bitumunous coal in the roasting furnace, the
fumes will contain a little soot and some finely divided sulphides, so that by simply
setting fire to the mass on the hearth E with a lighted taper or glowing coal, the
mass will gradually come to a glow and cinder together.
The next step in my new process consists in treating the slaggy mass and the
waste fumes. The treatment of this depends upon whether I, desire to manufacture
a white pigment, or (in view of the character of the ore I am treating) to manu-
facture as much metal as possible. If the slag and fumes be rich in lead, or in
lead and zinc I prefer where local circumstances do not forbid, to manufacture a
white pigment; but in either case the apparent difference in the two modes of
proceeding has reference only to the height of the furnace and the arrangement of
the blasts. If a white pigment is not desired the waste fumes from the smelting
furnace may be collected in the same bags in which the waste fumes from the
.roasting furnace are collected. The fluxes to be added depend entirely upon the
character of the ore.
Where it is desirable to manufacture a white pigment, I employ a low cupola
furnace with tuyeres with cast or wrought iron water boxes; I prefer to have the
furnace resting on a lead-well, but an ordinary low lead slag hearth works equally

page_text: as well, only the constant flow of slag and lead makes it more difficult to handle
than when the alag is topped in the case of a lead well.
1
Instead of a single tuyere, as in the ordinary slag hearth, I prefer to use two
tuyeres on each side of the furnace; and besides this, I provide the furnace with a
blast (preferably hot) from another set of tuyeres, near the top of the charge, say.
four or eight inches below the top. I then feed the slags and fumes on-top with a
clean non-bitumous fuel, such for instance as well burnt coke. Parts of the lead
will smelt down as in the ordinary slag hearth but a large amount of fumes of
sulphate and oxide of lead as also the oxide of zinc (if zinc be present) will rise from:
the fire and will be carried off by the exhaust fan, through the cooling pipes into the
textile receptacles, where the metallic fumes are collected, and are then ready for
the market, as a superior white pigment.
I prefer to feed some raw galena ore in with the slag and fumes, the amount of
the pigment being thus increased, and the combustion of the sulphur in the galena
ore raises the heat so that less fuel need be used. I also prefer to construct a brick
flue some 25 feet in length, rather flat and broad, over the furnace so that if any
black particles happen to pass the fire they will suffer complete combustion in this
flue, and by having a gas flame in this flue, I can feed the furnace much heavier,
without discolouring the pigment.
If the character of the ore prevents the manufacture of a pigment, I treat the
roasted slaggy mass and fumes in a "Rachette" furnace or any similar high cupola
furnace with only one set of tuyeres near the bottom, and collect the fumes in my
textile receptacles. By adding proper fluxes amongst these lead ores or granulated
ores, when necessary to save all the silver and gold, I am enabled to save practically
all the lead, and with it, all the precious metals, while all the other metals enter
the slag, and fumes, except such as form the matt which is collected with the
glassy slag, and is treated in the ordinary manner. By collecting the fumes they
may be worked over and over again with the fumes from the roasting furnace.
In the case of antimony ore the fumes from the roasting furnaces may be
manufactured directly into antimony preparations or they may be worked up
into metallic antimony, in the ordinary antimony reduction furnace, and the fumes
from this may be worked into antimony preparations.
my said
Having now particularly described and ascertained the nature of
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 :-
First. The process herein described for treating sulphuretted ore, the same
consisting essentially in roasting the ore (mixed with proper fluxes and fuel)
in a furnace which has connected therewith an apparatus for collecting and
condensing the metallic fumes, the said apparatus having receptacles of textile
fabric (preferably flannel), and then exposing the mixture to a current of air
(preferably hot) permeating the mass in a furnace similar to the American Scotch
Hearth, substantially as herein set forth, and for the purpose described.
Second. The process herein described for the treatment of lead and antimony ore,
or lead and zinc ore, or any other refractory ore, the same consisting essentially
in roasting such ore in a furnace, in which a blast of air passes through the mass
of ore and fuel; and in condensing the fumes in receptacles of textile fabric, then
treating the roasted slaggy mass and waste fumes in a furnace suited to the
character of the ore; and finally condensing the metallic fumes in the receptacles
of textile fabric substantially as herein before set forth and for the purpose
described.
Third. The process herein described for the manufacture of a white pigment
suitable for painters' use, the same consisting in treating lead ore, or lead and zinc
ore, either with or without the precious metals in a roasting furnace in which air
is blown into the mass of ore and fuel, and condensing the waste from this mass
into receptacles of textile fabric, then treating the roasted slaggy mass and waste
fumes in a low cupola furnace with a clean non-bituminous fuel and condensing

page_text: the white pigment resulting from this treatment in receptacles of textile fabric,
substantially as herein described.
Fourth. The process of working antimony ore, the same consisting essentially in
roasting the ore in a furnace, in which blasts of air pass through the mass of ore
and fuel; condensing the fumes in receptacles of textile fabric; and then working
the waste fumes into antimony preparations, or smelting these, together with the
roasted mass, in an ordinary antimony reduction furnace to which are attached
receptacles of textile fabric, and using these waste fumes for antimony preparations,
substantially as herein described.