Improvements in and relating to the Production of Zinc Oxide.
Year: 1899

page_text: Date of Application, 16th Feb., 1899
Complete Specification Left, 16th Nov., 1899-Accepted, 16th Dec., 1899
Improvements in and relating to the Production of Zinc Oxide.
I, GUY DE BECHI, of 17, Boulevard de la Madeleine, Paris, France, Chemical
Engineer, do hereby declare the nature of this invention to be as follows:-
This invention relates to the production of zinc oxide for reduction to
metallic zinc.
In the treatment of zinc bearing ores by wet processes, the zinc oxide obtained
by precipitation from solutions of salts of zinc is always hydrated; and in cases
where this hydrated oxide of zinc or zinc hydrate is precipitated from a solution
of zinc chloride by lime, the said hydrate is rendered very impure by the
presence of certain insoluble oxychlorides such as the oxychlorides of zinc or
of lime or both. It is practically impossible to eliminate the oxychlorides by
washing. By moderately heating the hydrate the combined water is driven off
and a more or less impure zinc oxide is produced. This oxide is however very
light, or of a low density, and is therefore incapable of being economically
reduced in retorts to metallic zinc. Moreover when oxychlorides are present,
fumes are liberated during the reducing process, which fumes are not only very
deleterious to the workmen employed but also cause the loss of some of the
zinc.
Now the chief object of my invention is to overcome these disadvantages and
to prepare from the said impure hydrated oxides of zinc, a practically or com-
mercially pure zinc oxide of sufficient density to render it capable of being
economically reduced on a large scale.
According to my invention I heat the said inipure zinc hydrate obtained by
precipitation from a solution of a zinc salt, after washing and drying the same,
to a bright red heat in a suitable furnace, such as a muffle furnace. The com-
bined water is first given off, then the oxychlorides present are decomposed
liberating fumes of zinc and zinc compounds. The fumes are conducted to a
condensin tower wherein the zinc is dissolved in a weak solution of hydro-
chloric acid, from which it is subsequently recovered in any suitable manner.
The completion of this part of the process may be recognized by the cessa-
tion of the liberation of fumes or by testing for chlorine a portion of the con-
tents of the furnace. I sometimes pass a current of air and steam through the
furnace, to accelerate the process.
The calcined residue consists of nearly pure zinc oxide.
I then subject this residue to pressure in a suitable device, so as to greatly
increase its density. The compressed product is broken or pulverized before
being inserted into the retorts together with the reducing agent.
I prefer however to first mix the necessary proportion of reducing agent, say
carbon in the form of anthracite, with the calcined zinc oxide, and then to
compress the mixture. A more intimate mixture of the oxide with the reducing
agent can thus be obtained, and moreover it is thereby possible to reduce a
much greater quantity of zinc oxide in one charge.
Leil
Tohmi 1809
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.

page_text: Improvements in and relating to the Production of Zinc Oxide.
I, GUY DE BECHI, of 17, Boulevard de la Madeleine, Paris, in the Republic
of France, Chemical Engineer, 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 production of zinc oxide for reduction to
metallic zinc.
In the treatment of zinc bearing ores by wet processes, the zinc oxide obtained
by precipitation from solutions of salts of zinc is always hydrated; and in cases
where this hydrated oxide of zinc or zinc hydrate is precipitated from a solution
of zinc chloride by lime, the said hydrate is rendered very impure by the
presence of certain insoluble oxychlorides such as the oxychlorides of zinc or
of lime or both. It is practically impossible to eliminate the whole of the oxy-
chlorides by washing. By moderately heating the hydrate the combined water
is driven off and a more or less impure zinc oxide is produced. This oxide is
however very light, or of a low density, and is therefore incapable of being econo-
mically reduced in retorts to metallic zinc. Moreover when oxychlorides are
present, fumes are liberated during the reducing process, which fumes are not
only very deleterious to the workmen employed but also cause the loss of some
of the zinc.
Now the chief object of my invention is to overcome these disadvantages and
to prepare from the said impure hydrated oxides of zinc, a practically or com-
mercially pure zinc oxide of sufficient density to render it capable of being
economically reduced on a large scale.
According to my invention I first wash and dry the said hydrate, and then
heat the same in a suitable furnace, such as a muffle furnace, gradually increas-
ing the temperature until the substance is brought to a bright red heat. The
combined water is first driven off, and when the oxide is heated to a bright
redness the oxychlorides are decomposed, liberating the combined chlorine and
fumes of zinc and zinc compounds. The fumes are conducted to a condensing
tower wherein the zinc is dissolved in a weak solution of hydrochloric acid,
from which it is subsequently recovered in any suitable manner. From 7%
to 10% of the zinc contained in the hydrate will be carried off by these fumes,
and practically the whole of this is recovered in the condensing tower.
The completion of this part of the process may be recognized by the cessa-
tion of the liberation of fumes, or by testing a portion of the contents of the
furnace for chlorine. I sometimes pass a current of air and steam through the
furnace, to accelerate the process.
I then subject the calcined residue, which consists of nearly pure zinc oxide,
to pressure in a suitable device, with or without a suitable binding agent, 80
as to greatly increase its density. The compressed product is broken or pul-
verized before being inserted into the retorts together with the reducing agent,
and it will preserve its increased density when so broken.
I prefer however to first mix the necessary proportion of reducing agent, say
carbon in the form of anthracite, with the calcined zinc oxide and then to
compress the mixture. A more intimate mixture of the oxide with the reducing
agent can thus be obtained, and moreover it is thereby possible to reduce a
much greater quantity of zinc oxide with one charge of the furnace or retorts.

page_text: 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:-
1. The method of treating precipitated hydrated oxide of zinc, consisting in
heating it to a bright red heat and then compressing the calcined residue with
or without the previous addition to the said residue of carbon and a binding
agent substantially as and for the purposes specified.
2. The method of treating hydrated oxide of zinc substantially as described
for the purposes specified.
Dated this 16th day of November 1899
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.