IMPROVEMENTS IN TREATING WASTELIQUORS FROM THE MANUFACTURE OF TINPLATES
Year: 1885

page_text: I, WILHELM ERDMANN ALBERT HARTMANN of 51 Trafalgar Terrace, Swansea,
in the county of Glamorgan, Engineer do hereby declare the nature of the said
invention for IMPROVEMENTS IN TREATING WASTELIQUORS FROM THE MANUFACTURE
OF TINPLATES to be as follows:-
This Invention relates to the wasteliquor which is produced in the manufacture
of tinplates by pickling the plates of iron in hydrochloric acid, and which chiefly
consists of a mixture of protochloride of iron with more or less free hydrochloric
acid. And the object of these improvements is to manufacture from this liquor free
hydrochloric acid and oxide of iron. For this purpose I mix the wasteliquor
with.caustic magnesia in excess, whereby the chloride of iron is decomposed and
oxichloride of magnesium is formed, which hardens the whole to a solid mass. This
mass is dried to expell a portion of the moisture contained in it, either by exposure
to the air in covered sheds or by artificial heat, and it is then subjected to a low
redheat in any convenient apparatus, such as a retort or an ordinary brickkiln.
At this temperature the mass is decomposed, leaving a mixture of caustic magnesia
and oxide of iron behind, while hydrochloric acid gas, either alone or mixed with
chlorine gas, escape and are conducted to condensing towers, such as are in general
use for the manufacture of hydrochloric acid, where the gases are absorbed by
means of water. Should chlorine be present in the escape from these condensers,
then the gases may be led through another similar condenser where they are
brought in contact with fresh wasteliquor, which absorbs the chlorine and may
be afterwards treated with magnesia as described. Or steam may be passed over
the mass while it is being decomposed, and thus the formation of free chlorine may
be avoided. The mixture of caustic magnesia and oxide of iron, left behind in the
heating apparatus, is crushed by any suitable crushing device and may then
again serve to decompose fresh quantities of wasteliquor until the oxide of iron
predominates too much in the mixture. When this point is reached the mixture,
after having been crushed, is treated with an excess of wasteliquor or with free
hydrochloric acid so that there results an acid solution, while much of the oxide of
iron remains undissolved and can thus be separated by settling or filtration. The

page_text: acid solution, after such separation, is again fit to be treated with an excess of
magnesia as described. The caustic magnesia for the decomposition of the waste-
liquor may be partly replaced by carbonate of magnesia, but enough of the former
must be added at the end of the operation so that the oxichloride above mentioned
may be formed. In order to harden the mixture of caustic magnesia and oxide of
iron, which results from the application of redheat as described, and thus to better
enable it to carry the incumbent weight when piled up in a kiln or similar
apparatus, a small proportion of any indifferent salt may be added to the mixture,
which salt should melt or soften in redheat without being decomposed, such as for
instance would be the case with common salt. If the decomposition of the mixture
by burning is to be performed in an ordinary limekiln, the mixture may be filled
into, casings. of earthenware or cast iron which allow of free exit to the gases
evolved, while protecting the mixture from being crushed into dust during its
descent through the kiln.

page_text: Improvements in Treating Waste Liquors from the Manufacture
of Tin Plates.
I, WILHELM ERDMANN ALBERT HARTMANN, formerly of 51 Trafalgar Terrace,
Swansea, in the County of Glamorgan, but now of Belleville, Illinois, United
States of America, 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 waste liquor which is produced in the manufacture
of tin plates and of other forms of iron such as galvanized sheet iron and galvanized
wire by pickling the iron in hydrochloric acid, and which chiefly consists of a
mixture of protochloride of iron with more or less free hydrochloric acid. The
object of this invention is to manufacture from this liquor free bydrochloric acid
and oxide of iron.
For this purpose I mix the waste liquor with caustic magnesia in excess whereby
the chloride of iron is decomposed and oxychloride of magnesium is formed, which
hardens the whole to a solid mass. This mass is dried to expel a portion of the
moisture contained in it and it is then subjected to a low red heat in any
convenient apparatus which allows the escaping gases to be collected, such as a
retort or an ordinary brick kiln. The drying may be effected either by exposure
to the air in covered sheds or by artificial heat in special drying rooms or it may.
be accomplished in the same apparatus in which the mass is afterwards to be
subjected to red heat, by passing hot air or superheated steam through the same as
is well understood.
When the mass is made red hot it decomposes leaving a mixture of caustic
magnesia and oxide of iron behind, while bydrochloric acid gas, either alone or
mixed with chlorine gas, escapes. These gases are conducted to condensing towers,
such as are in general use for the manufacture of hydrochloric acid, where they are
absorbed by means of water. Should chlorine be present in the gases escaping
from these condensers then such gases may be led through another similar condenser
where they are brought in contact with fresh waste liquor which absorbs the
chlorine and may be afterwards treated with magnesia as described. Or the
formation of free chlorine may be avoided by passing steam over the mass while
it is being decomposed. The mixture of caustic magnesia and oxide of iron left
behind in the heating apparatus is crushed by any suitable crushing device and
may then again serve to decompose fresh quantities of waste liquor until the oxide
of iron predominates too much in the mixture. When this point has been reached
the mixture, after having been crushed is treated with an excess of waste liquor or
with free hydrochloric acid so that there results an acid solution of magnesia while
much of the oxide of iron remains undissolved and can thus be separated by
settling or filtration. The acid solution after such separation is again fit to be
treated with an excess of magnesia as described. The caustic magnesia for the
decomposition of the waste liquor may be partly replaced by carbonate of magnesia,
but enough of the former must be added at the end of the operation so that the
oxychloride abovementioned may be formed. In order to harden the mixture of

page_text: ,
caustic magnesia and oxide of iron which results from the application of red heat
as described, and thus to better enable it to carry the incumbent weight when
piled up in a kiln or similar apparatus, a small proportion of any indifferent salt
may be added to the mixture which salt should melt or soften in redheat without
being decomposed itself, such as for instance would be the case with common salt.
If the decomposition of the mixture is to be performed in an ordinary lime kiln
the mixture may be filled into cases of earthenware or iron which allow of free exit
to the gases evolved while protecting the mixture from admixture of fuel or ashes
as well as from being crushed into dust during its descent through the kiln.
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 use of magnesia for the recovery of hydrochloric acid and oxide of iron
from waste liquors which result from the pickling of iron in hydrochloric acid,
substantially as described.
2. The hereinabove described process for the recovery of hydrochloric acid and
oxide of iron from waste liquors which result from the pickling of iron in
hydrochloric acid.