Improvements in the Extraction of Tin and other Products from the Refuse Slags and Debris of Tin-smelting Furnaces.
Year: 1889

page_text: Date of Application, 27th Sept., 1889
Complete Specification Left, 28th July, 1890-Accepted, 27th Sept., 1890
PROVISIONAL SPECIFICATION.
Improvements in the Extraction of Tin and other Products from the
Refuse Slags and Debris of Tin-smelting Furnaces.
I, ALFRED JOHN CAMPION of No. 11 Buckingham Street, Strand, London
Financial Agent do hereby declare the nature of this invention to be as follows:-
By my invention, the tin slags or debris are reduced to a state of fine powder
and fused with sulphate or bi-sulphate of soda or potash in excess on the floor of a
reverberatory furnace but under certain circumstances the mixture can be fused
in an ordinary cupola furnace. The resulting fused mass is lixiviated in boiling
water and allowed to settle. The clear liquor will be a solution of soluble
silicate of soda or potash with stannate of soda, or potash and possibly tungstate
of soda or potash.
The insoluble residue in the settling tank will consist of peroxide of iron;
sulphate of lead should that metal have been present-together with insoluble
residue, and undecomposed nickel and cobalt, should these metals have been
present, which is frequently the case. The tin can be separated from the
stannate of alkali in the solution by the introduction of zinc or zinced irou,
connecting the same by the means of a conductor with the iron pan in which
the fluid is contained, and heating the same to the boiling point.
The tin will be thrown down on the inner side of the pan, and is collected and
melted into ingots.
The zinc, which will be dissolved in the solution replacing the tin as the latter
is thrown down, can be precipitated by cautiously adding a solution of sulphide
of sodium which will throw down the zinc as sulphide of zinc in the form of
white powder, useful for many purposes and as a source of white oxide of zine
largely used as a paint.
"
The silicate of alkali remaining can be evaporated and sold as
water glass
largely used as an ingredient in artificial stone and for coating buildings; or by
the addition of lime mixed with water, silicate of lime is formed and precipitated,
and the alkali is recovered in the caustic form. The tungstate of alkali, if any
is present, crystalizes out during the concentration of the caustic alkali.
The alternative or second process of this my invention is by boiling the finely
owdered slags with a strong solution of caustic soda or other alkalies, preferably
n closed vessels and under pressure. By this treatment the silica is dissolved
s silicate of alkali; the tin oxides are converted into stannate of alkali; the
ungsten, if any be present, is converted into tungstate of alkali, and these salts
fre separated and treated as in the first process.
Dated this 27th day of September 1889.
Improvements in the Extraction of Tin and other Products from the
Refuse Slags and Debris, of Tin-smelting Furnaces.
1, ALFRED JOHN CAMPION of High Cliff Hotel Cliftonville Margate, Kent,
Financial Agent do hereby declare the nature of this invention and in what
Brive Su

page_text: manner the same is to be performed, to be particularly described and ascertained
in and by the following statement:-
In smelting the tin slags and other products from the refuse slags and debris
of tin smelting furnaces I find that it is desirable under certain circumstances
where all the contained metals in the refuse slags and other furnace debris have
to be recovered readily and then separated by subsequent treatment that the
material to be operated upon should be smelted in a cupola or other suitable
furnace with coke coal culm or other carbonaceous substances with a proportion
according to the nature of the metallic contents of the material to be treated
of fluor spar lime or limestone granite or granite products such as feldspar
quartz mica and other analogous substances with or without the addition of
rock salt or sulphate of soda, or bi-sulphate of soda either together or separately
in the proportion of from 20 lbs. to 50 lbs. by weight of the whole to each 100 lbs.
of slags, furnace debris or material to be treated according to the proportion
of iron oxides and silicates present. The objects of these additions being to
form a double or multiple silicate of the ingredients contained in the slag or
other products so as to decompose the silicate of tin and other metals present
and allow their oxides to be reduced in the furnace to the metallic form.
As an instance in carrying my invention into practice when treating ordinary
average Cornish tin slags or furnace debris I break the material into manageable
pieces of a few pounds weight each and mix them on the charging stage of the
furnace with one fifth of its weight of a mixture of granite or other fusible
natural rocks such as serpentine with limestone fluor spar or sulphate of soda or any
of these together or separately, as for instance in smelting ordinary Cornish tin
slags and furnace debris the individual proportions of the one fifth of fluxes
to be added would generally be two fifths granite or other fusible natural rock
such as trachyte or serpentine, two fifths lime or limestone and one fifth sulphate
of soda or alternatively one fifth of fluor spar and such proportions of the fluxes
are in practice found sufficient.
When the cupola furnace is sufficiently heated the slag and fluxes are added in
layers of about six inches deep and about one fifth of the weight of the charge of
some suitable fuel such as coal coke or culm which is spread on the top. As
the charge melts and sinks down fresh layers of slags and fluxes and fuel are
added continuously until the well or lower part of the cupola furnace is full
of melted material. The lower stratum of the melted mass will consist of
nearly all the tin originally contained in the slag or debris mixed with nickel
cobalt arsenic and any other metal which may be present-except iron-and
this mixed mass is drawn off into moulds from the lowest tapholes. The upper
stratum of the melted mass consists of a very highly fusible multiple silicate
of soda, lime, and oxides of iron suitable for any purpose to which rough glass
is adapted. This is periodically drawn off from an upper taphole into moulds.
The above proportions of the before mentioned ingredients must necessarily
be modified by the amount of silica and iron contained in the slag and debris
which varies in the slag and debris resulting from the smelting of tin ores in
different localities.
Cornish slags and debris are rich in tin and iron and poor in silica and may be
treated by the addition of a second equivalent of the before mentioned ingre
dients to the quantity of silica or oxide of iron present so as to form double
silicates and release the tin for reduction. The slags from foreign ores arc
frequently very difficult of fusion owing to being poor from continued resmelting
but containing much silica and oxides and arsenides of nickel and cobalt.
These require the addition of fluor spar and limestone or alkali makers tank
waste" either together or separately in the proportion of 20 lbs. to 50 lbs. weight
of the whole to each 100 lbs. of slag, furnace debris, or material to be treated
according to the proportion of oxides, arsenides and silica present to effect the
reduction by heat in a cupola or other furnace in sufficient proportions to form
double or multiple silicates of the vitrious matrix of the combined metallic

page_text: oxides so as to set the latter free which are released as mixed metals. The
metals are melted in suitable fire resisting vessels or in the well of a reverberatory
or other furnace and nitrate of soda or potash preferably the former on account
of cost added little by little with frequent stirring of from 10 to 25 per cent. of
the quantity of metallic mass under treatment; the nitrate by its decomposition
oxidizes the iron and arsenic and antimony if this metal be present and the
alkaline base of the nitrate of soda partly combines with the arsenic and oxide
of iron and other oxides forming a slag and liberating the tin and nickel and
cobalt. The two latter metals sink to the bottom of the receptacle in which
the operation is carried on in combination with some of the arsenic as "spiess"
which being less fusible thin tin solidifies leaving the tin floating on the top
which can be ladled or poured off into moulds.
The mixed metals can also be separated by a second process which is carried
out by melting the mixed metals as above in suitable fire resisting receptacles
or well of a furnace and blowing a current of air through a fire clay or graphite
tube inserted to the bottom of the melted mixed metals. This treatment also
burus or oxidizes the iron, arsenic, or antimony allowing the nickel and cobalt
as above to settle at the bottom as spiess" and leaving the tin floating on
the top in a nearly pure condition.
$
This process can be applied to the purification of "tin plate maker's waste"
or scruff" a refuse metal from the tinning pots or baths. This is an alloy
of iron and tin and by melting it in suitable vessels and treating the mass with
from 10 to 25 per cent. of nitrate of soda according to the quantity of iron in
the alloy, or by blowing air as above through the melted materials the iron
is oxidized and the tin purified and set free and may be cast into moulds.
In practically working this process on various kinds of slags and furnace
debris I assay samples of the parcels to be treated and use an equal weight
of sulphate of soda to the quantity of tin oxide present and or an equal weight
of the above mentioned fluxes together or separately to the oxide of iron or
silicate of iron or bases present
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 smelting of tin slags and furnace debris from tin smelting furnaces in
cupola and other furnaces with the addition of sulphate of soda or rock salt with
or without a certain proportion (preferably about from 20 to 50 per cent. of the
weight of the charge) of fluor spar, feldspar, lime or limestone granite or granite
products serpentine or other fusible rock of igneous origin or alkali manu-
facturer's tank waste" with the object of forming double and multiple silicates
of iron and earthy impurities of the material to be treated, thus setting the tin
and other valuable metals present free as mixed metals.
Total 1 15th day of January 1890
ALFRED JOHN CAMPION.