Treatment of Tin Oxide, in the Form of Powder, Sludge, or Paste, for the Smelting thereof.
Year: 1897

page_text: Date of Application, 10th May, 1897-Accepted, 12th June, 1897
COMPLETE SPECIFICATION.
Treatment of Tin Oxide, in the Form of Powder, Sludge, or Paste,
for the Smelting thereof.
I, EMIL ERNST VON DER LINDE, of Uerdingerstrasse No. 114, Crefeld, Germany,
Manufacturer, 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 :-
Hitherto finely divided tin oxide, obtained in the form of powder, sludge or paste,.
as by-product of other technical processes, or the like, could only be smelted in blast.
furnaces under the action of blast, with great difficulty and loss.
According to my invention I avoid these difficulties and losses by first converting
the finely divided tin oxide into cohering masses before subjecting it to reduction.
For this purpose I form the tin oxide into lumps, pieces, or briquettes of any desired
form by means of binding materials which cause the particles to cohere without.
interfering with the reduction thereof and without rendering the metal impure.
: Such binding materials are: caustic alkalies, lime and tin slag, which are mixed.
together with the tin oxide to be reduced.
The incorporation of these materials with the tin oxide is preferably effected in such
manner that the tin oxide is first mixed with the caustic alkalies, (potassium hydroxide
or sodium hydroxide) after which the tin slag is added, and then the caustic lime.
These additions can be effected either dry, or stirred up with water and dissolved.
After the addition of water the mixture is ground fine so as to produce a tough stiff
pasty mass, which is of a sufficiently plastic nature to be moulded.
The production of lumps or briquettes from this mass is effected either by hand or
in suitable presses of known form. The moulded pieces are dried either in the open
air or in drying rooms, if necessary, with the application of heat. The mode of
carrying out such drying is optional with the operator, and depends upon the special
conditions of the works, as also whether the drying is to be effected rapidly or slowly.
In drying, the lumps harden and become sufficiently durable not to crumble in the
blast furnace, but to allow of the ready smelting thereof.
It is not possible to produce the lumps of tin oxide or to effect a good reduction
thereof in the blast furnace when using only one of the above binding materials as
addition to the tin oxide; it is necessary to employ the caustic alkali, tin slag and
caustic lime in combination with each other. The influence of these additions and their
action is probably as follows:-
The slag serves in particular to produce in the furnace, as quickly as possible, a
iquid slag mass, which surrounds the reduced tin and protects
oxidation.
from renewed
The additions of the caustic alkalies and lime have mainly for their object to.
naintain the melt in an alkaline condition.
The dried lumps or pieces are smelted in the usual manner in the blast furnace, in:
which process the said additions separate in the form of a slag.
The tin slag employed in the production of the tin oxide lumps can also be replaced.
y its constituents: silicic acid, lime, soda and potass.
In place of caustic lime and caustic alkalies (sodium hydroxide and potassium.
ydroxide) may also be used the carbonate salts thereof.
It is optional with the operator whether, of the above named compounds, the alkal

page_text: hydroxides and caustic lime, or the carbonate salts of the alkalies and of the calcium
should be used. The choice would depend upon the relative cost of the materials.
The proportions of the quantities of the ingredients employed will vary according
to the nature of the tin oxide to be reduced, that is to say, according to the quantity
of the acid compounds contained therein..
The additions must be so chosen, that the mass is of alkaline nature, so that the
acid constituents are bound with bases. Also, the several constituents of the addition-
compound can vary relatively to each other. The choice of the proportions depends
upon whether it is desired to have lumps or briquettes that will dry rapidly or slowly,
or whether slags are desired that will melt easily or with difficulty.
. By way example the following proportions may be given for an advantageous
composition of the moulded lumps or briquettes :
ABEL & IMRAY,
Agents for the Applicant.