Improvements in the Method of Desulphurising Zinc Ores.
Year: 1892

page_text: Date of Application. 8th Aug., 1892-Accepted, 10th Sept., 1892
COMPLETE SPECIFICATION.
Improvements in the Method of Desulphurising Zinc Ores.
1, PETER HART, of "Gransmoor " Fairfield, near Manchester, in the County
of Lancaster. Manager of Chemical Works, 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 :-
The most frequently occurring ore of zinc is the native sulphide, commonly known
as blende. Before this ore can be smelted, or the zine therein be reduced to the
metallic state, it is necessary to remove the sulphur. This is at present usually
effected by a prolonged roasting in a suitable furnace. The result of this roasting
is that the sulphur is driven off as sulphurous acid, but this gaseous acid is so diluted
and mixed with other inert gases that it is commercially impracticable to utilise
it in the manufacture of sulphuric acid in the ordinary manner.
The object of this invention is to desulphurise blende and similar sulphur com-
pounds of zinc in such a manner and by such means that the sulphur may be readily
converted into sulphuric acid by the ordinary processes of manufacture of that
acid, and the resulting zinc salt or compound may be at once smelted, reduced
or otherwise utilised. My improved process has the advantages also that the
roasting is effected in a much shorter time, with a less expenditure for fuel, and
that the sulphuric acid required is produced in the process of the desulphurisation
of the ore.
In proceeding according to my invention, I reduce the blende or other sulphur
ore or compound of zinc to a moderately fine powder, such for example as would
pass through a sieve having about forty meshes to the inch. This powder is mixed
with sulphuric acid of about 1750 S. G. in the proportions of about one equivalent
of monohydrated sulphuric acid to one equivalent of the metallic zinc present.
I do not however limit myself strictly to these proportions as they may be varied
with the composition of the powder and the ease with which it is acted on.
The mixed powder and acid is heated in an iron or other suitable vessel or
chamber to a temperature of about 300 to 400 degrees Fahr. By the action of the
heat, gases consisting chiefly of sulphurous acid are given off, and these gases are
collected and conveyed to a vitriol chamber for conversion into sulphuric acid in
the ordinary well known manner.
After the beat has been applied for a short time, the mixture stiffens, when it
may be pushed or transferred into a close or blind furnace, or such a furnace as
that described in the Specification of Letters Patent granted to Peter Spence,
No. 1695 dated the 3rd July 1861. In this furnace any excess of sulphuric acid
will be driven off, and the temperature being raised to a low red heat, all the
sulphur is finally expelled, and the metal or metals is or are left in a state of simple
oxidation or nearly so, and in a fit condition to be dealt with by the smelter in the
ordinary manner or to be otherwise dealt with or utilised.
It will be understood that the sulphurous acid driven off in the furnace is
collected and led to a vitriol chamber for conversion into sulphuric acid, as described
with reference to the preliminary heating process.
I am aware that sulphate of zinc, and a mixture of sulphate of zinc with
blende, have been calcined for the production of sulphuric acid and oxide of zinc,
but according to this process, the raw material is first calcined producing highly
diluted sulphurous acid, and the product of the calcination is converted into sulphate
by means of dilute sulphuric acid, and this sulphate is dried and is again calcined.
By such a process, the water with which the sulphuric acid is diluted has to be
expelled, and the desulphurisation of the ore is divided into three distinct stages
instead of being continuous as hereinbefore described.

page_text: 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 process for the desulphurisation of blende and sulphur compounds of zinc,
substantially as and by the means herein before described.
2. In a process for or method of desulphurising blende and sulphur compounds of
zinc, mixing sulphuric acid with the powdered blende, or sulphur compound of
zinc, heating the mixture to 300 or 400 degrees Fahr. and thereafter transferring it
to and roasting it in a suitable furnace, the gases given off during the heating and
roasting stages being collected and led to a vitriol chamber and converted into
sulphuric acid by the ordinary method, substantially as hereinbefore described.
Dated this 4th day of August A.D. 1892.
WILLIAM E. HEYS,
Agent for the Applicant.