IMPROVEMENTS IN OBTAINING SULPHATE OF ZINC AND OXIDE OF ZINC FROM CUPREOUS ORES, AND IN FURNACES FOR SMELTING SUCH ORES, AND FOR OTHER LIKE PURPOSES
Year: 1880

page_text: PROVISIONAL SPECIFICATION left by Edward Andrew Parnell and Andrew
French at the Office of the Commissioners of Patents on the 3rd December
1880.
EDWARD ANDREW PARNELL, of Swansea, in the County of Glamorgan, Chemical
Manufacturer, and ANDREW FRENCH, of Llansamlet, in the same County,
Metallurgist. "IMPROVEMENTS IN OBTAINING SULPHATE OF ZINC AND OXIDE OF
ZINC FROM CUPREOUS ORES, AND IN FURNACES FOR SMELTING SUCH ORES, AND
FOR OTHER LIKE PURPOSES."
This Invention relates to the treatment of cupreous ores containing a considerable
proportion of zinc, the copper and zinc being wholly or partially in the form of
sulphides; and one of the objects is to recover the zinc in the form of sulphate and
oxide in a more complete manner than has been hitherto effected. The Invention
also comprises an improved furnace for smelting the cupreous ores, and applicable
for other like purposes.
In the ordinary modes of smelting such ores for the extraction of copper, the
zinc is volatilised and allowed to escape into the air, being thereby lost. By the
present Invention the smelting is conducted in a cupola furnace, and the gases and
fumes therefrom, and containing metallic zinc and light oxide of zinc in suspension,
and sulphurous acid derived from the ore, are mixed with excess of air and are
brought into contact with water in any suitable condensing or absorbing apparatus.
The condensing apparatus preferred is of the kind described in the Specification of
Letters Patent, granted to Henry Joseph Wilson, John Wycliffe Wilson, and
Andrew French, and dated 21 December 1878 (No. 5239). In the presence of
moisture the light oxide of zinc combines with sulphurous acid, forming sulphite
of zinc, which is converted by the excess of oxygen present into sulphate. By
lixiviation the sulphate of zinc thus formed is separated from any oxide of zinc
which may still be present in an uncombined state, and the liquor may then be
evaporated to obtain crystallised sulphate, or it may be otherwise employed, as, for
example, for the preparation of oxide of zinc and sulphuric acid by the process
described in the Specification of Letters Patent granted to Edward Andrew Parnell,
and dated 28 February 1877 (820).

page_text: The small proportion of lead sometimes contained in the ore is almost wholly
volatilised and condensed along with the zinc, and when it is present in quantity
to be worth separating, the fume is mixed or treated with dilute sulphuric acid,
which dissolves out zinc oxide and leaves lead sulphate undissolved. When the
ore contains silver, a part of this is also volatilised, and is recovered from the fume
along with the lead.
The improved cupola furnace employed in carrying out the Invention is provided
with a hot blast: Inside the cupola above the charge and round the sides are
placed a series of cast iron pipes, about 7 inches in diameter. These pipes, where
exposed to the fire, are preferably of oval section, being in diameter 9 inches
vertically, and 3 inches horizontally. They form one continuous pipe, the upper
and inlet end being connected with the blast fan or blower, and the lower end
with tuyeres discharging into the cupola. For ores of the kind herein before referred
to the height of the cupola from the tuyeres to the bottom of the charging door
should be not more than 2 feet, otherwise inconvenience will be caused by
accretions on the walls. The smelting operation is conducted in the same manner
as when smelting copper ores in a blast furnace to obtain copper regulus. The
copper and the greater part of the silver and gold contained in the ore are found
in the regulus, which is tapped off from time to time from the hearth. By this
process the copper is more perfectly freed than heretofore from injurious metals,
such as zinc, arsenic, and antimony.