IMPROVEMENTS IN THE TREATMENT AND UTILISATION OF TIN AND LEAD DROSS AND OF THE SLAG RESULTING THEREFROM
Year: 1883

page_text: LETTERS PATENT to Thomas Lloyd of Aberdylais in the County of Glamorgan
for an Invention of IMPROVEMENTS IN THE TREATMENT AND UTILISATION OF
TIN AND LEAD DROSS AND OF THE SLAG RESULTING THEREFROM
.
PROVISIONAL SPECIFICATION left by the said Thomas Lloyd at the Office
of the Commissioners of Patents on the 6th July 1883.
THOMAS LLOYD of Aberdylais in the County of Glamorgan
"IMPROVEMENTS
IN THE TREATMENT AND UTILISATION OF TIN AND LEAD DROSS AND OF THE SLAG
RESULTING THEREFROM
"
Hitherto the scruff or oxide formed on the surface of molten tin or lead or a
mixture of both has been sold as waste without further treatment or has been
melted and rabbled in order to mechanically separate the metal therefrom after
which the residuum has been sold as dross-Occasionally however such residuum
has been remelted and reduced to a cinder but in all cases unassisted heat only has
been employed which has resulted in a considerable waste of metal owing to the
imperfect action thereof
Now the object of my invention is to avoid all such waste by an improved
method of treating such scruff or oxide and the slag resulting therefrom which is
as follows-Having taken the dross out of the furnace I mix a little water there-
with in order to increase the gravity of the minuter particles and so prevent their
escaping up the flue-I then intimately mix therewith Carbon-Carbon and lime
and alkali which substances I obtain by utilising certain waste or by products
such as soot or powdered Coke, impure chalk and the by products from nitric acid
works I use the same in about the following proportions videlicet-To one ton of
damp dross I add of alkali compound about 1 cwt;-of powdered coke or soot
about / cwt and of waste or impure chalk about 1/, cwt Having well blended
such ingredients with the dross by stirring or otherwise I replace such dross in
the furnace when the ingredients so mixed therewith in combination with the heat
act thereon as powerful fluxes and effectually separate the metallic residue there-
from the Carbon materially assisting deoxydisation while the alkali acts as a

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Thomas Lloyd in the Patent Office on the 5th January 1884.
1
*
'
THOMAS LLOYD of Aberdylais in the County of Glamorgan IMPROVEMENTS IN
THE TREATMENT AND UTILISATION OF TIN AND LEAD DROSS, AND OF THE SLAG.
RESULTING THEREFROM
;
Hitherto the scruff or oxide formed on the surface of molten tin or lead or a
mixture of both has been sold as waste without further treatment or has been
melted and rabbled in order to mechanically separate the metal therefrom after
which the residuum has been sold as dross
Occasionally however such residuum has been remelted and reduced to a cinder,'
but in so doing unassisted heat only has been employed which has resulted in a
considerable waste of metal owing to the imperfect action thereof
Now the object of my invention is to avoid all such waste by an improved
method of treating such scruff oxide, or dross and the slag resulting therefrom
which is as follows.
1
The cakes of scruff are placed in the furnace and exposed to a degree of heat
a little above the melting point, then stirred or rabbled until the 'residuum has
assumed the form or state of powder which is termed dross.
Having taken the dross out of the furnace I mix a little water therewith in
order to increase the gravity of the minuter particles, and so prevent their escaping,
up the flue
I then intimately mix therewith Carbon, carbon and lime, and alkali which
substances I obtain by utilising certain waste or bye products such as soot or
powdered coke, impure chalk, and the bye products from Nitric Acid Works.
I use the same in about the following proportions, videlicet;-To one ton of
damp dross I add of alkali compound powdered about 1 cwt;-of powdered coke
or soot about 1/2 cwt:-and of waste or impure chalk about 1/2 cwt, also in a'
powdered state
I now bring up the furnace to a high degree of heat, and with damper down I
replace such dross in the furnace, when the ingredients so mixed therewith,-in
combination with the heat act thereon as powerful fluxes, and effectually separate
the metallic residue therefrom:-the carbon materially assisting deoxidation,
while the alkali acts as a reducing agent, and the lime operates on the slag or
cinder
The heat of the furnace is then raised so that the flame impinges on the charge,
soon melting down the fluxes which in their fluid state bring with them the
metal in bright globules of various sizes
A small hole is pricked in the clay tamping of the tap hole allowing the metal
to come out in a comparatively pure state, and when apparently the whole of the
metal is extracted the cinder is then well mixed with a small quantity of lime,-
(say, about a shovel full,)-and thoroughly stirred; and after allowing it to rest
for about twenty minutes to allow of any further metallic deposit being made the
hole is pricked for metal and then the whole charge is rabbled or otherwise caused
to flow into water thus rendering it extremely friable and so facilitating both the
careful examination thereof and the separation and removal therefrom of any
metallic residuum
Should it be found that the depth of the molten charge in the furnace is too
great to allow the heat to penetrate therethrough so as to completely extract the
metal therefrom, I provide a hole above the tap hole about four inches in size to
allow the upper and lighter stratum to flow out thus exposing the lower stratum
to the full heat of the furnace

page_text: With the aid of a good furnace having a chimney from 30 to 35 feet high and
a proper manipulation of the fluxes together with care in tapping, almost every
particle of metal may be extracted by my improved method of treatment
The metal obtained by this means is not only purer and softer, but when
refined yields less oxide and other impurities than when treated with unassisted
beat.
I would here observe that my improved fluxes can be mixed with the dross
without removing it from the furnace in the manner before described, but less
satisfactory results are obtained..
'#
To extract the metal from old slag I grind or otherwise reduce such slag into a
fine dust I then mix such dust with one fifth of its weight of my improved fluxes
used respectively in the before mentioned proportions after which I subject the
same to a white heat in a cupola furnace
I would here observe that whether my improved process be carried out in a
cupola or other furnace I, prefer to make the bottom of one entire brick corre
sponding in shape to the form of the bottom of the furnace employed
The advantages of my improved method of treatment may be summarised as
follows videlicet
1° Utilisation of the waste scruff or oxide
2° Considerable economy of time, labour and fuel
3° Great purity of metal
4° Extraction of the entire.metallic residuum
5° A considerable saving of interest on capital as by this process the metal is
speedily reclaimed for use
Having thus particularly described and ascertained the nature and operation of
my said invention and the manner of carrying the same into effect I would have
it understood that I claim as novel and of my invention
1
The improved method of treating tin and lead dross and the slag resulting there-
from with the fluxes and otherwise substantially in the manner and for the
purposes herein before specified In. witness whereof I the said Thomas Lloyd
have hereunto set my hand and seal this fifth day of January One thousand
eight hundred and eighty four
"