APPAREIL DESTINE AU RAFFINAGE A VIDE CONTINU DES METAUX

APPARATUS FOR CONTINUOUS VACUUM-REFINING OF METALS

Abrégé anglais

Abstract of the Disclosure

The present invention relates to apparatus for continuous
purifying of tin from impurities - lead and bismuth, by refining.
The apparatus comprises a vacuum chamber accommodating a
range of trays arranged in succession and fitted each with an
overflow conduit disposed in its side wall at a certain distance
from its upper end face, with the overflow conduit communicating
with the tray space and being positioned parallel to the tray
axis and with an overflow conduit outlet being connected to the
underlying tray and a tray column being encompassed by an induc-
tion is spinning climbing to the level of the overflow conduit.

Revendications

The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:-

1. An apparatus for continuous vacuum-refining of metal,
comprising a cylindrical vacuum chamber; a range of trays,
having each a central hole and side walls, said trays being
accommodated in said vacuum chamber, disposed in succession one
above another in a vertical plane, forming a column and adap-
ted to receive preliminary melted impure metal; a vapor pipe
formed by the holes of said trays; a heater set up inside said
vacuum chamber, encompassing the column of said trays and provi-
ded with a current lead to feed electric energy thereto for
heating the metal accommodated in the trays and evaporating
low-boiling impurities therefrom, said impurities being removed
along said vapor pipe; a condenser located under the column of
said trays and adapted to receive the impurities emerging from
said vapor pipe; each of said trays has an overflow conduit
located in its side wall at a certain distance from its upper
end face, said overflow conduit communicating with the tray
space, being disposed parallel to the tray axis, with the out-
let of this overflow conduit being in communication with the
underlying tray, an induction coil encompassing the column of
said trays and establishing a magnetic field under whose effect
the molten metal accommodated in the tray rotates climbing to
the level of said overflow conduit; a cooler set up under said
vacuum chamber and communicating with said outlet of said over-
flow conduit of the lower tray to supply metal therein.



2. An apparatus, as set forth in Claim 1, wherein said
induction coil is disposed outside the heater and encompasses it.

Description

~0~8~9
APPARATU~ FOR CONTINUOUS V~CUUM-REFINING OF MET~LS
The present invention relates to metal processing equip-
ment and more particularly to apparatus for continuous vacuum-
refining of metals.
The invention may prove to be most advantageous in produc~
ing tin with a minimum lead and bismuth content.
The now-existing apparatus for continuous vacuum-refining
of metals comprises a cylindrical vacuum chamber accommodating
a range of graphite trays arranged in succession one above ano-

~her in a vertical plane, adapted to receive preliminary melted ' `
impure metal and forming a column~ and an induction heater en~
com~assing the graphite tray column and provided ~ith a current
l~ad to feed electric energy thereto. The induction heater'
warms up the metal acc,o~modated in the trays to a volatiliza~
tion temperature of low-boiling imp~rities and evaporates them.
~ach tray has in its bottom an internal cylindrical collar with
a central hole into which a tapered branch pipe is introduced~
In this case the collar central holes and tapered branch
plpes are,aligned axially. ~ ,
The internal cylindrical collar precludes the draining
of metal being refined through its central hole. The collar
height is so selected that a clearance for the passage of im-
purity vapors, referred to hereinafter as volatilized impuri-
ties~ is formed between ~he bottom of the overlging tray and

the collar end face. -
'~



.


,



. , - . , .. . ~:

~1~41!~;~69
The coaxial centr~l holes of all the trays and tapered
branch plpes form a vapor pipe for removing volatllized impuri-
ties. ~le length oE the tapered brancb pipe wouLd be such that
its lower end face would be spaced at a minimum distance fro~
the central hole of the `underlying tray. This would rule out
the ingress of the volatilized impurities from the underlying
tray into the space of the over-lying tray and would provide
for the ejection of vapors from the underlyin~ trays~
In the zone of molten metal the bottom of each tray has
an outlet ensuring a gradual overf~w of the molten metal from
the overly~ng into the underlying trayO The lower tray communi-

cates via a pipeline with a cooler located outsids the vacuum ~-
chamber. The refined metal flows from the lower tray into the

cooler where the metal temperature decreases and the metal is `
drained into a receiving tank.
A disadvantage of thi~s present-art apparatus resides in
a small open metal surface in the tray9 the area of this sur-

,:
face determining the intensity of impurity evaporation. As itis known, dipped impurities are not able to volatilize and can
ireach the metal surface only due to diffusion. The process of
transfer of such dipped impurities to the metal surface can be ~-
intj~e~si~ed by stirring. However~ the known apparatus are not
provided with such stirring means. This disadvantage can be
partly offset by increasing the number of trays. But it will
lead to a considerable lncrease in the overall dimensions of


'',..
_2, ~ ~ ~




-':
: . -.: - '

8;269
the apparatus.
Moreover, the now-e~isting apparatus suffars from another
disadvantage which lies in the arrangement of the metal over-
flow conduit in the tray bottom. ~ith the above arrange~ent
the batches of metal, that have not yet been sub~ected to refl-
ning, oan overflow through this outlet illtO the next tray,
diminishing thereby the degree of metal refining.
The principal ob~ect of the invention ls the provision
oE an apparatus for continuous refining of metals, wherein,
owing to a modified design of trsys and the use of means increa~
sing an open metal surfaceg the apparatus output and the degree
of purifying the metal from impurities by refining are enhanced
and overall dimensions of the apparatus are reduced.
Said object is achieved by p~oviding an apparatus for
continuous refining of metal, comprising a cylindrical vacuum
chamber accommodating a range of trays with central holes arran-
ged in succession one above another in a vertical plane, for-
ming a column and adapted to receive preliminary melted impure
metal, and a heater encompassing the column and provided with
a current lead to feed electric energy th~reto for heating
the metal accommodated in the trays and evaporatlng low~boiling
impurities therefrom~ with the volâtilized impurities being
removed via a vapor pipe formed by said tray holes into a con-
denser disposed in the vacuum chamber under the tray column,
wherein, according to the invention, each tray is fitted with ;

i~04~2~;~
an overflow condult located in its slde wall at a certain dis-
~anc~ from its upper end face~ sald overflow conduit communi~
cating with the tray space and being disposed parallel to the
tray axis, with the overflow conduit outlet being in communi-
cation with the underlying tray~ and the tray column is encompas-
sed by an induction coil establishing a magnetic field under
whose effece the molten metal accommodated in the tray rotates
climbing to the level of the overflow conduit~ wlth the over-
flow conduit outlet of the lower tray com~unicating with a re-
fined metal cooler set up under the vacuum chamber.
Owing to the magnetic field established by the coil the -~
metal being refined commences to rotate i~tensively and is in~
ter-mixed. Centrifugal forces urge the spinnlng metal to tlimb
along the vertical tray wall with the open metal surface being
substantially enlarged as a result. Hence~ the surface firom
which volatilization of impurities occurs is considerably in- -
creased. Owing to an intense s~irring the dipped batches of me-
tal comprising a larger amount of impurities, as compared with
the metal disposed on the open surface, move to the volatiliza-
tion surface.
Thig intensifies substantially the metal refining rate.
Since the rotating open surface of the metal assumes the
shape of a heavily concaved meniscus, the thickness of metal in
the upper part of the meniscus is rather small, with the deg-
ree of metal refining in thls zone being a maximum one for a




~4- ~



:'



....

~O~Z6~ :
given tray, and as the overElow conduit is located in the upper
part of the ~eniscus, the metal dralned f~om that tray will
feature a highest rcfining degree.
Thus, metal spinnining ensures a higher rate and a maxlmum
degree of removing impurities from a single tray, this result-
ing in a higher output of the apparatus and in a better refining
degree. The higher degree of refining achievable owing to in~
tense rotation, which contribu~es to a substantial increase in
the open metal surface, does not call for a larger number of
trays, the apparatus enabling the above outlined effect to be
obtained with a minimum number of the trays. This diminishes
the overall dimensions of the apparatus as a whole.
me nature of the invention will be clear Erom the follow~
ing detailed description of the particular embodiment of an ap-
paratus for purifying tin~rGmaleàd~ànd bismuth by refining, to
be had in conjunction with the accompanying drawings, in which:
Fig. 1 is a longitudlnal sectional view of an apparatus
for continuous refining of metal, according to the inv~ntion; `
Fig. 2 is a longitudinal sectional view (scaled up) of
trays shown in Fig. 1.

; ::
An apparatus for continuous vacuum-refining of tin compri-
ses a c~lindrical vacuum chamber 1 (Fig. 1).
The chamber 1 accommodates a range of trays disposed in

succession in a vertical plane~ with the tray 2 being adapted to
receive preliminary melted impure metal and trays 3 and 4 - to

~:
'~ .
, ~ .,:,.



~"`:,




... .. . .

~ 8Z69
refine tin. The tin supply into the tray 2 is shown in the
drawing by arrow A. Y
The trays 3 and 4 in their bottoms haYe central holes 5
into which tapered branch pipes 6 are introduced. The holes S
and br~nch pipes 6 are aligned axially and form a vapor pipe
for removing lo~-boiling impurities liberated during the tin
refining process. The length of the tapered branch pipe 6 in
the tray 3 would be such that their lower end face 7 wouid
be spaced at a minimum distance fr~m the central hole 5 of the
tray 4. This would preclude the ingress of volatilized impuri-
ties from the tray 4 into the space of the tray 3 and would
provide for vapor ejection~ The branch pipe 6 of the ~ray 4
is connected to a condenser 9 through an additional branch pipe
4~ In the condenser 9 the volatillzed impurities are condensed
and cooled to a temperature of 400C~ whereupon they flow ~in
, .
a fluid stste) along a pipeline 10 into a condensate tank 11.
The trays 2, 3 and 4 from in conjunction a column encompas-
sed by a heater 12 which is an inductor. The inductor has a cur-
rent lead to eed electric energy needed for heating the trays
2,3 and 4 together with the tin accommodated therein to an im-
purity volatili~ation temperature. The volatilizing impurities
are removed, as it has been stated above, via a vapor pipe.
Each of the trays 3 and 4 (Fig. 2) has an overflow conduit
15 located in a tray side wall 13 at a certain distance from
its end face 14~ with the inle~ 16 of the overflow~conduit 15 ' ~


-6- ; -
'
~:

8Z69
communicating with a space oE the corresponding tray.
The overflow conduit 15 i9 d~sposed parallel to the tray
axis and the outlet 17 of this condult 15 communicates with
the underlying tray 4. The outlet 17 oE the overflow conduit 15
of the tr~y 4 is connected via a pipeline 18 (Fig. l) to a re-
fined tin cooler 19 disposed outside the vacuum chamber 1. Upon
cooling~ the refined tin runs off along a p~peline 20 from the
cooler 19 into a refined tin tank 21.
The heater 12 is encompassed from the outside by an induc-


tion coil 2~ establishing a magnetic fieldO Under the effectof this field the metaloaccommodated in the trays 3 and 4 ro~
tates climbing to the inlet 16 of the overflow conduit 15 in
the side wall 13 of the trays 3 and 4.
The herein proposed apparatus functions as follows.
Prellminary melted impure tin is supplied into the intake
, : .
tray 2 along a pipeline 23 in the direction shown by arrow A.
~ ~Passlng through a bottom hole 24 in this tray 2 the tin over-
~: flows into the upper tray 3 ~here it is heated to an impurity
~i volatilization temperature owing to the energy generated by
the heater 12. The induction coil 22 brings the molten metal
contained in the trays 3~and 4 into rotation. Stirring and a
larger volatilization surface result in an intense evolution
of volatilized impurities`from the metal, with these volatili-
: zed impurities being passed Yia the vapor plpe into the conden-
ser 9 where they are condensed, cooled and discharged along


. : : ,

-7~
~ ~-

1041~
the pipeline 10 into the condensate tank 11~ The metal revolving
in the trays a~sumes the shape of a meniscus, reaches the inlet
16 of the overflow conduit 15 and gets into the space of the
tray 4.

In the tray 4 the tin is refined to a still higher degree,
and then the refined tln flows through the overflow conduit 15
of the tray 4 into the pipeline 1~ Upon passing via the pipeli-
ne 18~ it runs off into the cooler 1~ and then to the refined
tin tanlc 21.
The tin and condensate from ~he tanks 11 and 21 are cast
into pigs.
' :
~,' .
~' ':




,~
., ''' '~ .


'~


-8- ::



:
~;