An Improved Method of Treating Flue Dust obtained from Sulphide Ores.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
An Improved Method of Treating Flue Dust obtained from Sulphide
Ores.
RICHARD THRELFALL, of Hollowforth, near Preston, Lancashire, Professor of
Physics in the University of Sydney, N.S.W., Australia, do hereby declare the
nature of this invention to be as follows;-
The flue dust to which this invention refers is mainly produced during the
smelting of ores containing sulphides of lead and zinc. It is also produced to
some extent in the process of roasting these ores and particularly in the process
of Ellershausen (British Patent 16808 of 1897). In many cases it is found neces-
sary to separate the zine from the lead and silver constituents of the flue dust before
the latter can be prepared for smelting. My invention consists in effecting the
desired separation by means of a solution of sodium (or potassium) hydrogen
sulphate. Such a solution dissolves the zinc constituents leaving the compounds
of lead and silver. The most convenient source of sodium hydrogen sulphate for
my purpose is the so called " nitre cake a residue, obtained from the vessels in
which nitric acid is produced by the action of sulphuric acid upon sodium nitrate.
The solution of sodium or potassium hydrogen sulphate which is employed to
leach the flue dust may be of any convenient strength provided that it is not so
strong as to lead to a premature crystallising out of the salts which it contains
after the leaching is accomplished. The zinc may be recovered from the solution
by any suitable process but this invention is particularly applicable to a process
of zinc extraction in which the zinc as sulphide is precipitated from the solution
by sulphide of sodium. In this case the sulphide of zinc is separated from the
solution which then contains a mixture of sodium sulphate with other salts whose
amount and nature depends upon the special circumstances of the original leach-
ing. The solution is evaporated down to a convenient point so as to allow of the
recovery of the neutral sodium sulphate and of such other sodium salts as may
be conveniently converted into sodium sulphide by known processes.
The sodium hydrogen sulphate thus acts not only as a leaching agent but also
as a source of sodium sulphide; and in this manner makes up more or less for the
losses of sodium which necessarily occur in the cycle of operations.
Dated this 25th day of May 1898.
RICHARD THRELFALL.
An Improved Method of Treating Flue Dust obtained from Sulphide
Ores.
I, RICHARD THRELFALL, of Hollowforth, near Preston, Lancashire, Professor of
Physics in the University of Sydney, N.S.W., Australia, do hereby declare the
[Price 8d-1

page_text: 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 flue dust and fume to which this invention refers is mainly produced during
the smelting of ores containing sulphides of lead and zinc. It is also produced to
some extent in the process of roasting these ores and particularly in the process
of Ellershausen (British Patent No. 16808 of 1897). In many cases it is found
necessary to separate the zinc more or less from the lead and silver constituents
of the flue dust by leaching hefore the latter can be prepared for smelting, and
the leaching itself may he performed with suitable agitation in any suitable vessel
or vessels and at any desired temperature. My invention consists in effecting
the desired separation by means of a solution of sodium (or potassium) hydrogen
sulphate. Such a solution dissolves the zinc constituents leaving the compounds
of lead and silver. The most convenient source of sodium hydrogen sulphate for
my purpose is the so called "nitre cake" a residue obtained from the vessels in
which nitric acid is produced by the action of sulphuric acid upon sodium nitrate:
The solution of sodium or potassium hydrogen sulphate which is employed to leach
the flue dust may be of any convenient strength provided that it is not so strong
as to lead to a premature crystallising out of the salts which it contains after the
leaching is accomplished. The zine may he recovered from the solution by any
suitable process but this invention is particularly applicable to a process of zine
extraction in which the zinc as sulphide is precipitated from the solution by a
solution of sulphide (or mixtures of sulphides) of sodium. In this case the
sulphide of zinc is separated in any suitable manner, such as filter pressing, from
the solution which then contains a mixture of sodium sulphate with other salts
whose amount and nature depends upon the special circumstances of the original
leaching. The solution is evaporated down to a convenient point so as to allow
of the recovery of the neutral sodium sulphate and of such other sodium salts as
may be present and may be conveniently reconverted into sodium sulphide by
known processes.
The sodium hydrogen sulphate thus acts not only as a leaching agent but also
as a source of sodium sulphide; and in this manner makes up more or less for the
losses of sodium which necessarily occur in the cycle of operations.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:
In the treatment of flue dust and fume from sulphide ores, the separation of
the zinc from the lead constituents by leaching out the former by. means of a
solution of sodium or potassium hydrogen sulphate, substantially as herein
described.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.