Improvements in or appertaining to the Extraction of Zinc from Substances or Compounds containing the same.
Year: 1899

page_text: Improvements in or appertaining to the Extraction of Zinc from
Substances or Compounds containing the same.
We, THOMAS RYAN, Junior. of Castle Hill House, Flint, in the County of
Flint, and NEWTON HUGHES, F.I.C., of Bedol, Bagillt, in the County of Flint,
Chemical Engineer and Analytical Chemist respectively, do hereby declare the
mature of this invention to be as follows:--
This invention has for its principal object an improved process for the extraction
of zine from substances or compounds containing the same. According to our
process the zine is isolated in the form of zinc oxide or zine hydroxide and the
future treatment or utilization thereof may vary according to requirements.
Among the substances or compounds that may be treated by our improved
process we mention the following though we do not intend the list to be taken
as exhaustive riz. zinc fume, furnace gases of flue dust containing zinc, zine
dust, zinc seconds," calcined blend, zine waste, galvanised scrap or waste, battery
liquors containing zinc, zine ores.
The zine or substance containing zine is first treated with a caustic alkali such
as caustic soda or caustic potash, in solution, by lixibiation, agitation or digestion,
either with or without artificial heat, and in some cases the comingling may be
assisted mechanically, for instance by grinding. The liquid resulting from the
above treatment (and which is hereafter termed the zincate liquor) is separated
from the insoluble residue by filtration or decantation. The zincate liquor is
treated to separate the lead, if such be present, by being passed into or through
a vessel or plant where a zine and iron couple is caused to act upon it, and so to
throw down the lead. This deplumbating may be effected early on in the process
herein described, or at any other subsequent stage prior to the final precipitation
of the zine hydroxide. Scrap iron, scrap zine, or scrap galvanised iron or a
combination of two or more of these may be used to throw down the lead.
Either before or after the lead has been eliminated the zincate liquor is prefer-
ably clarified by treatment with lime and injection of air, or super-oxidised in
any other suitable way.
..
The liquor is then fined." for instance by adding bleaching powder, and the
resulting insoluble matters separated. The clarified zincate liquor is finally
treated with carbonic acid, which causes a precipitation of zine oxide, or zine
hydroxide. This may be effected by passing the zincate liquor down or into a
tower or other suitable vessel, in which the de-caustifying or carbonating process
is partly or wholly completed. Or the final and complete saturation with carbonie
acid may be effected in a separate vessel, after a preliminary treatment with
carbonic acid, as above described. The carbonic acid may be generated for the
purpose, or waste furnace gases, or blast furnace gases, or those from lime kilus
may be utilised.
The zine hydroxide is finally separated by filtration or decantation, or in other
suitable way.
The residual carbonated liquors may be crystallised, or may by causticised with
lime and used again for a fresh operation. Or they may be agitated and heated

page_text: with the substance to be treated, with the addition of caustic lime or milk of lime.
The various bye-products may be utilised as seems best, and according to circum-
stances.
1
1000
CHARLES COVENTRY,
Agent for the Applicants,
Improvements in or appertaining to the Extraction of Zinc from
Substances or Compounds containing the same.
We, THOMAS RYAN, Junior, of Castle Hill House, Flint, in the County of
Flint, and NEWTON HUGHES, F.I.C., of Bedol, Bagillt. in the County of Flint,
Chemical Engineer and Analytical Chemist respectively, 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:--
Our invention has for its principal object an improved process for extracting
zinc from substances or compounds containing the same. According to our
process the zine is finally isolated in the form of zinc oxide or zine hydroxide, and
the further treatment or utilization of this product may vary according to circum-
stances. An important result in the carrying out of our process lies in the fact
that nearly all the reagents employed may be recovered in a valuable commercial
form. Among the substances or compounds which contain zine, and which may
be treated economically by our process we mention the following as examples:--
zine fume, furnace gases or flue dust containing zine, zine dust or scrap, zine
seconds," calcined blend, galvanized scrap or waste, battery liquors containing
zine, zine ores.
The substance is first washed, leached or lixiviated, with a solution of a caustic
alkali. We prefer to use caustic soda in practice. This treatment is preferably
carried out in a series of vessels or vats and the liquid enters the series in rotation,
a fresh supply following on step by step. The liquid is commingled with the
substance being treated, and agitation and artificial heat may be employed to
make the dissolving action rapid and thorough, and in some cases it may be
assisted mechanically as by grinding. It will be seen from the foregoing that the
liquid in its passage through the vats encounters a fresh supply of raw material
at each vat, while the partly denuded raw material is as often attacked by fresh
liquid.
The number of vats and the time during which the treatment is continued will
vary according to the raw material. For instance, we find in practice that for the
treatment of Spiegel-Eisen flue dust, five vats are sufficient to remove all but a
very small trace of zine, while the caustic liquor is practically saturated with
zinc. We term this the zincate liquor.
The zincate liquor which is separated from the insoluble residue by decantation
or filtration is now treated to separate from it any lead that is held in solution
by running it through a vessel containing scrap zine and scrap iron, or scrap
galvanized iron may be employed, or a combination of them. A galvanic action
is set up and the lead is thereby thrown down as a metallic precipitate. In some
cases an independent supply of electric current from external sources may be
employed, arranged in well known manner, the object in either case being to
throw down the lead.
After being deplumbated the liquor is heated and agitated with caustic lime
which has the effect of clarifying or fining it, and this action may be aided by
blowing through it atmospheric air. If a very pure product is desired the liquor

page_text: may be still further fined by the addition of bleaching powder. The treatment
with lime and with bleaching powder causes an insoluble precipitate composed
partly of organic matters and partly of oxides of iron, manganese, or silicon.
should such bases be present in the raw material. This deposit is removed by
decantation or filtration and the clarified zincate liquor is finally treated with
carbonic acid with the result that the zine is precipitated in the form of zinc
oxide or zine hydroxide. The liquor remaining contains carbonate of soda in
solution and the oxide or hydroxide of zine is separated from it by well known
or a filter press or centrifugal machine
means such as decantation:
employed. Washing with water to remove adhering soluble matters, and drying,
complete the product.
may
be
After the zine is removed the carbonate of soda may be recovered by crystallisa-
tion in well known manner, or the liquor may be treated with caustic lime and he
again employed to treat a fresh lot of raw.material. Or the liquor may be agitated
and heated with the raw material, with the addition of caustic lime or milk of
lime, thus at one operation dissolving the zine and fixing some of the extraneous
matters such as silicates. We wish to point out that the treatment of the zincate
liquor to throw down the lead may take place at any stage of our process, prior
to the final throwing down of the zinc oxide or hydroxide, but we prefer it to
take place as above described. It is obvious that other acids, acetic for instance,
may be used instead of carbonic acid.
The various bye-products accruing during the carrying out of our invention may
be utilized as seems best.
We wish to point out that one very great advantage accompanying the employ-
ment of our process is that most of the reagents used are recoverable in forms
whose value equals or excells their initial worth.
The zinc oxide or hydroxide is in a state of very high commercial purity.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed we declare that what
we claim is: --
1st. The process of extracting zine from substances containing the same con-
sisting in subjecting the raw material to the action of a solution of a caustic
alkali, precipitating any lead present by galvanic action, securing the removal
of organic matters, and iron, manganese, and silicon, by the addition of caustic
lime and bleaching powder, and finally precipitating the dissolved zine in the
form of zinc oxide or zinc hydroxide by decaustifying the solution by the addition
of carbonic acid, substantially as described.
2nd. The process of extracting zine from substances containing the same con-
sisting in subjecting the substances to the action of a caustic alkali the various
steps of the dissolving being so carried out that the solution of caustic alkali is
several
with
contact
brought in
material
raw
of
portions
successive
cach successively treated
precipitating any
material
are
solution,
caustic
lead
and the various portions of raw
with different portions of
present by galvanic action, securing the removal of organic matters and
extraneous metals present by the addition of caustic lime and bleaching powder.
and finally precipitating the zine in the form of zinc oxide or zine hydroxide, by
the addition of carbonic acid, substantially as described.