Process and apparatus for removing dust particles disposed between the lining of a casting ladle and a template

A process for removing dust produced in the lining of casting ladles wherein a slinging mass is slung between the inner walls of the ladle and an opposing template whereby a free space is defined between the ladle wall and the template which free space contains dust which process involves sucking the dust in the free space from a point near the upper edge of the template into a region behind the template; an apparatus for performing such a process comprising a template, a suction conduit inside said template having an inlet and an outlet, the inlet being in fluid communication with particles disposed near the upper edge of said template, the suction conduit including filtering means for filtering out entrained particles from air sucked therethrough, the filtering means including means for collecting filtered particles, the outlet end of the suction conduit includes means for sucking air therethrough.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a process and apparatus for removing dust and 
other particles which are present as a result of slinging a slinging mass 
into the free space between the wall of the casting ladle and an inserted 
template to build up the lining. More especially, this invention relates 
to an apparatus for removing residual dust, dirt and debris, especailly 
fine sand particles and the like, which are whirled up during a slinging 
process wherein a slinging mass is applied to the walls of a casting by 
slinging the mass vertically from above into a free space between the 
inner walls of the casting ladle and a defining template spaced therefrom. 
2. Discussion of the Prior Art 
The preparation of refractory linings for vessels to be employed in metals 
refinery is known. A device for the production of such a refractory ling 
is disclosed in the British Pat. No. 1,326,097, or the U.S. Pat. No. 
3,872,912 which technique is specifically referred to for better 
understanding. According to some of the known processes a template is 
disposed opposite the walls of the vessel to be lined so as to define the 
region is which the liner is to be formed. The slinging mass is slung 
using known slinging apparatuses such as those disclosed in German Pat. 
Nos. 1,235,522 and 2,004,429, corresponding to U.S. Pat. No. 3,872,912. 
Other slinging machines are disclosed in German Pat. Nos. 1,247,561 and 
1,289,963. The slinging machine disclosed in British Pat. No. 1,326,097 
can also be employed as well as the device disclosed in German 
Offenlegungsschrift No. 1,483,584. According to the state of the art the 
lining of casting ladles is carried out wherein the refractory mass is 
slung in quick succession and at high speed by the use of the slinger head 
of the slinging machine into the free space between the wall of the ladle 
and a template inserted therein. 
The mass employed includes a sand composition. Slinging of the slinging 
mass including the slinger sand causes a dust nuisance for operating 
personnel owing to the high proportion of fine grains in the sand and the 
air introduced during the slinging operation which is usually at a high 
velocity. This nuisance is particularly acute in the region surrounding 
the free space between the refractory wall and the template. Because of 
these nuisances it has heretofore been proposed to add moisture or oil to 
the dry masses. Other methods for reducing the dust nuisance have included 
sucking off the collected dust upwards from the free space to decrease the 
dust nuisance. However, to effectively decrease dust nuisance it has been 
necessary to provide a suction hood over the point where the dust forms. 
This known suction procedure is not only expensive and cumbersome but has 
proven to be unsatisfactory even with high suction performance as the 
formation of dust still leads to hinderances and nuisances to operating 
personnel. 
It is therefore an object of this invention to provide a process and 
apparatus which guarantee good and effective dust removal from the region 
surrounding the free space between the walls of the refractory vessel and 
the template. It has become an object of this invention, moreover, to 
provide an apparatus which can be effectively employed which does not 
require the use of a hood disposed over the free space. Moreover, it has 
become desirable to provide a process and apparatus for effective dust 
removal whereby the dust removal can be effective with substantial 
unimpairment to the slinging operation itself. 
SUMMARY OF THE INVENTION 
The objects and longfelt desideratum are realized in accordance with the 
present invention which contemplates a process for removing dust during 
the lining of casting ladles wherein a slinging mass is slung between the 
inner walls of a ladle and an opposing template whereby a free space is 
defined between the ladle wall and the template which process comprises 
sucking said dust in said free space from a point proximate the upper edge 
of the template into a region behind said template. In accordance with the 
present invention the dust and other small particles and debris obtained 
in the free space between the vessel walls and the template are sucked 
from a region near the upper edge of the template to a point behind the 
template by applying a negative pressure to such sand particles and/or 
dust and removing the particles downwardly in entrained sucked air through 
a filter chamber comprising a filter means. The air is withdrawn, 
preferably through a radially disposed portion of a suction tube which is 
in fluid communication with a centrally disposed centering tube which 
includes a means for sucking the air through the suction conduit. 
In operation a generally slightly conical template is disposed opposed with 
space parallel to the walls of a reactor or other vessel employed for 
metal refinering, e.g., ladle. This defines a free space in which a 
slinging mass is to be slung. The slinging mass is slung by the slinger 
machines into the free space whereby a portion of the same is disposed 
against the walls of the cylindrical vessel. Dust and other small 
particles are removed by sucking the same proximate the upper edge of the 
facing template. The dust is withdrawn downwardly in filter tubes which 
allow the sucked air to pass (for instance made of fabric). The filters 
allow egress of the air while retaining the dust particles. The filter 
tubes are generally vertically disposed in a filter chamber behind the 
template and serve to feed a collection means. Disposed in facing 
relationship to a lateral side of the filter tubes is a portion of the 
suction tube which is generally horizontally disposed and proceeds 
radially from a centrally disposed hollow centering tube. In operation a 
single centrally disposed hollow centering tube is employed to which are 
connected a plurality of suction conduits which radiate radially 
therefrom. Each of these suction conduits passes through an elastic seal 
and is in facing relationship to at least one filter tube of the type 
described supra. The filter tube lies in a generally vertically disposed 
filter chamber an upper portion of which is in fluid communication with a 
region above the upper edge of the template. The common centrally disposed 
hollow centering tube is disposed centrally of the walls of the template 
and includes a means for sucking air through the various conduits. When 
air is sucked all of the dust in the free space encounters a negative 
pressure whereby it is withdrawn from over the upper edge of the template, 
and descends into the filter chamber within the filter tubes. Air is 
withdrawn through the small perforations of the filter tubes into the 
radial portion of the suction conduits where it passes into the centrally 
disposed common centering tube including the means for sucking air 
therethrough. The filtered dust is maintained within the filtering tubes 
and descends by gravity into a collection means. 
Thus in operation the dust forming at about the upper edge of the template 
is preferably directed upwards into an inner area of the template wherein 
it is thereafter deflected downwardly behind the template into a further 
inner area. The upward suction and the subsequent deflection offer the 
advantage that direct suction of the slinging refractory mass is prevented 
while at the same time the dust which is whirled up from below can be 
sucked off without hindrance to the slinging operation. 
According to a preferred embodiment of the process the suction capacity, 
considering the suction cross-section leading from the free space between 
the ladle wall and the template to the inner area of the template, is 
dimensioned in such a way that the pressure difference between the free 
space and the inner area of the ladle that is exposed to the effect of 
suction amounts to at least 200 kg/m.sup.2. With such a pressure 
differential the speed of the dust entering through the cross section 
amounts to no more than 15 meters per second and consequently satisfactory 
removal of dust from the free space is guaranteed. 
A device which is particularly suitable for carrying out the process is one 
comprising a template having a circumferential suction slot as a suction 
cross-section in the area of its upper edge. A filter chamber is disposed 
behind the walls of the template and inwardly of the cylindrical template. 
The filter chamber extends generally in the same direction as the template 
in the inner area of the template and is in fluid communication with the 
suction slot functioning as the inlet to the suction conduit. The filter 
chambers are in turn connected with a centrally disposed hollow centering 
tube through a radial portion thereof. The centering tube includes a means 
functioning as a suction aggregate. 
In the apparatus of the invention it is important that the template and 
centering tube are carriers of the elements employed for dust removal. 
Thus a suction hood which is necessary in conventional dust removing units 
and which necessarily had to be disposed over the point where the dust 
collects, can be completely discarded. 
The means for filtering the entrained air to leave behind the dust for 
collection can comprise any number of the separation systems. Preferably, 
the vertically disposed filter chamber comprises a plurality of filter 
hoses which extend collectively annularly along the inner wall of the 
template and are fed into dust collection funnels at their lower ends. 
Such an apparatus is particularly advantageous. 
According to a preferred construction four dust collection funnels are 
provided so that each dust collection funnel covers a quadrant of the 
template (90.degree.). In such an instance eight to 12 filter hoses, for 
example, can be provided in each quadrant. 
The circumferential suction slot at the upper edge of the template which 
serves as an inlet to the respective suction conduits is positioned for 
expedience at a short distance below the upper edge of the template itself 
and is substantially vertically coplanar thereof. Generally speaking, the 
slot is between 10 and 40 cm, preferably between 20 and 30 cm below the 
upper edge of the template. Preferably the circumferential slot is 
provided with stabilizing bars which are equally distributed along the 
periphery of the template. Particularly advantageous construction is one 
in which the lower edge of the suction slot is drawn somewhat within the 
inner area of the suction conduit so as to be disposed within the 
cylindrical area of the cylindrical template. This can be achieved simply 
by bending the lower edge of the conduit towards the inner area of the 
template. The bending is coordinated for expedience with the desired 
acceptance cross-section. Bending at an angle with which the space from 
the upper edge to the bend lower edge amounts to 30-80 mm., preferably 
50-70 mm., has proven particularly advantageous. 
According to the invention the upper edge of the template can be undercut 
by means of the lower edge of the suction slot which is disposed inwardly 
of the cylindrical template. Direct penetration of the refractory mass 
slung by the slinging machines is prevented by this undercut while at the 
same time the dust which is whirled up is readily sucked off upwards in 
the direction in which it is moving into the inner area of the template. 
Here it is deflected within the suction conduit downwardly toward the 
filter means and the radial portion of the suction conduit leading to the 
centering tube. 
The latter construction enables the lining of the ladle or other vessel to 
be slung with a slinger mass on the underside of the suction slot or even 
beyond the same whereby the suction slot locks in the final phase of the 
slinging operation to form an annular mass edge on the inner side of the 
lining being formed. This annular mass edge, however, can readily be 
removed by the use of a door on the template which when opened allows the 
template to be constricted thereby assuming a smaller diameter. Suction on 
the dust in the free zone withdraws the dust readily through the suction 
conduit and the dust is collected in the collecting means provided. In 
this operation the annular mass edge is removed by shearing and the 
constricting action on the template. The device of the present invention 
preferably comprises a plurality of the suction tubes each of which is 
securely connected to a common vertical centering tube. A portion of the 
suction tubes or conduits extends radially from the respective filter 
chambers thereby joining the filter chambers with the common vertical 
centering tubes. The portion of the suction tube disposed radially from 
the vertical centering tube to the filter chamber is preferably 
displaceable in the radial direction. In order to achieve this radial 
displaceability in the filter chamber the free end of the portion of the 
suction chamber is preferably guided through an elastic seal into the 
filter chamber. This construction enables the template to be contracted on 
opening the template door. The suction can be provided by a suction 
aggregate preferably disposed on the lower end of the centering tube. This 
means can comprise a ventilator, for example, whereby the suction 
aggregate feeds into an air duct for drawing off the dust-free spent air. 
One embodiment of the invention includes the use of divided templates. The 
divided templates are both in the form of a cylinder and one of the 
template portions is disposed over the other. Each of the divided 
templates includes at least one suction slot with its respective filter 
chamber and centering tube. The centering tubes of the respective 
individual templates can be connected by a guide tube so as to be coaxial 
with one another and in fluid communication. Thereby a single suction 
device can be employed for the individual templates. Preferably, the 
suction device is arranged on the lower end of the centering tube. A 
suction slot is provided whose lower edge is drawn inwardly, as described 
above, in the case of the dividing template. The entire suction capacity 
of the suction device is arranged on the lower centering tube, after 
locking of the suction slot of the lower template, for the suction slot of 
the upper individual template. 
By the device of the invention, are more fully described below, good dust 
removal is provided with the limited capacity of the suction device by 
sucking off the collecting dust into the inner area of the template and 
collecting off within the area of the template the separated dust. Using 
the device of the invention one can sling refractory masses which have a 
relatively high proportion of dust. This can be done without creating a 
dust nuisance and hence the problems in dust nuisances are no longer 
crucial and no longer limit the composition of the refractory mass to be 
employed. Furthermore the removal of the dust is carried out without the 
use of excessive infiltrative air. The type of dust removal provides a 
constructive solution to the problems of dust presence by a compact 
arrangement involving minimum interference with the slinging operation 
itself. The template itself and/or the centering tubes of the template 
furthermore act as carriers for the construction elements employed for the 
dust removal. Moreover, the solution to the problem is effected using a 
device which consumes little space and provides a good suction effect.

DESCRIPTION OF SPECIFIC EMBODIMENTS 
Referring to FIGS. 1 to 3 there is shown a casting ladle 10 having a 
built-in template 1. The ladle 10 has the usual cylindrical, but slightly 
conical form and the template corresponds to this thereby forming a free 
space 11 between ladle 10 and template. For lining the ladle 10 the free 
space 11 is filled by slinging a refractory slinging mass by a slinger 
head of a slinger machine. The operation of the slinger machine including 
repeated circuits around the space 11 is known to the specialist by U.S. 
Pat. No. 3,872,942. 
According to FIG. 1 the template 1 is formed of individual divided 
templates comprising an upper template 1a and a lower template 1b. A 
centering tube 7 is formed for the entire assembly comprising an upper 
centering tube 7a and a lower centering tube 7b, belonging to template 1. 
A suction device having a drive 8a and a ventilator element 8 is provided 
on the lowering centering tube 7b which leads from the lower centering 
tube 7b to the air duct 9. The suction device is positioned at the lower 
end of the centering tube 7, i.e., the lower end of the lower centering 
tube 7b as shown in the drawings and is securely connected to the 
centering tube 7. 
Removal of dust from the free space 11 between the ladle 10 and the 
template 1 is achieved by the device which sucks air through the suction 
slot 2 disposed in short distance below the upper edge of the template 1. 
The air containing entrained free sand dust is therefore sucked through 
the slot 2 of the template 1 to an area within the cylindrical template 
and behind the same. The entrained dust is separated off within a filter 
chamber 3. The filter chamber 3 constitutes a portion of the overall 
suction conduit. A portion of that suction conduit is tube 6 which is 
radially disposed in facing relationship to a lateral side of a filter and 
extends towards centering tube 7 and from there to the air duct 9 via the 
ventilator element 8. 
In the case of a devided template 1 comprising an upper template 1a and a 
lower template 1b each of the templates has its own slot 2, filter chamber 
3, suction tube 6 and centering tube 7, whereby the upper part 7a and the 
lower part 7b of the centering tube 7 can be connected as explained later 
(FIG. 4). 
The air duct 9 is guided for expedience against the inner side of the 
filter chamber 3. In this way stabilization is achieved. According to one 
embodiment the air duct 9 is guided directly along the filter chamber, 
whereby a relatively high proportion of spent air can be received, 
deflected and distributed. 
Referring to FIG. 3 a suction slot 2 is provided having a cross-section a 
short distance below the upper edge of the template 1. The suction slot 2 
is formed by the drawing inwardly of the lower edge 12 into the inner area 
of the template, i.e., within the cylinder of the template itself. As 
shown in FIG. 3, the lower edge 12 is drawn so far into the inner area of 
the template that the distance from the upper side of the undercut 12 
amounts to about 60 mm. 
The slot 2 being on the entire portion of the template can be provided with 
stabilizing bars (not shown) so that the slots 2 are equally distributed 
about the periphery of the template. The filter chamber 3 extends 
downwardly parallel to the template 1 and comprises a plurality of filter 
hoses 4, wherein several filter hoses at a time feed into a conical dust 
collection funnel 5 which can be emptied by means of a manual slide damper 
5a. The number of dust collection funnels 5 is governed by the diameter of 
the template 1 and amounts to four in the shown example. 
FIG. 2 shows the suction tubes 6, which are securely connected with the 
centering tube 7 and feed into the filter chamber 3. Four suction tubes 6 
in all, each desplaced at 90.degree., are provided in the shown example. 
The suction tube 6 terminates in the filter chamber with its free end 6a 
through the elastic seal 3a so that a relative radial movement is possible 
between the filter chamber 3 and the suction tube 6. This is desirable 
when the template 1 is removed in order to facilitate a contraction of 
said template 1 on opening the door 14 of the template. 
FIG. 4 shows that, in the case of a template 1 of several parts having a 
respective centering tube 7 of several parts, the upper centering tube 7a 
can be connected with the lower centering tube 7b by a guide tube 15 
whereby a rubber ring 16 provided in the upper centering tube 7a to effect 
the sealing. 
FIG. 5 shows the location of the slinging device 20 when slinging the lower 
section of the ladle lining in the case of a two-section slinger operation 
having individual devided templates. The casting ladle 10 having built in 
the lower template 1b which has its own slot 2, filter chamber 3, suction 
tube 6 and the lower centering tube 7b to which the drive 8a, the 
ventilator element 8 and the air duct 9 are connected. The slinger device 
20 mounts the lower centering tube 7b thereby locking the open upper end 
of the lower centering tube 7b. The slinger head 19 of the slinger device 
20 is directed vertically from above into the free space 11 between the 
ladle 10 and the lower centering tube 1b. The mass stream 21 slung by the 
slinger head 19 builds up the lining 17. 
The operation of a two-section slinger having two individual divided 
templates is explained as follows: 
A suction device 8, 8a operates through the use of a centering tube 7. 
Initially, the lower centering tube 7b and lower template 1b with the 
respective suction slot 2, filter chamber 3 and suction tube 6, only is 
employed. The lower centering tube 7b is, however, locked by the slinger 
device 20 placed thereon during the slinging of the lower portion of the 
ladle 10. Shortly before the locking of the suction slot 2 of the lower 
template 1b the slinger device 20 is raised by a crane. Then the upper 
assembly comprising the upper template 1a with its own slot 2 below the 
upper end and with the respective filter chamber 3, suction tube 6 
connected to the respective upper centering tube 7a are put in place. The 
upper centering tube 7a is disposed upon the lower centering tube 7b, 
which is now open to the top as the slinging device 20 has been removed. 
Upper centering tube 7a and lower centering tube 1b are connected by using 
guide tube 15 shown in FIG. 4. Then the slinging device 20 is placed on 
the upper centering tube 1a and slinging of the upper half of the lining 
is conducted. At the beginning of this part of operation both the slot 2 
of the lower template 1b and the slot 2 of the upper template 1a are 
connected to the suction device 8 via the respective filter chamber 3, 
suction tubes 6 and the connected centering tubes 7a and 7b. The slinging 
is conducted over the suction slot 2 of the lower template 1b whereby an 
annular mass edge 18 is formed on the inner side of the lining 17 as shown 
in FIG. 3. The vertical slinging operation is not disturbed by sucking off 
the dust through the slot 2 of the lower template 1b, as the dust is 
sucked off inwards and upwards, i.e. in a different direction to the 
vertically slung refractory mass. After this closing the slot 2 of the 
lower template 1b the full suction capacity acts on the slot 2 of the 
upper template 1a. 
The annular mass edge 18 which forms during slinging past the slot (FIG. 3) 
is readily sheared without difficulty on opening the template door 14 and 
on drawing the template 1b. In case of one part-template only one suction 
slot 2 with respective filter chamber 3, suction tube 6 and centering tube 
7 is provided. To guarantee a good suction up to the end of the slinging 
operation in this case according to one alternative, the template 1 
extends beyond the height of the ladle wall so that the lower edge 12 of 
the suction slot 2 is in the height of the upper end of the ladle 10. 
According to the more preferred alternative, the template 1 does not 
extend beyond the upper end of the ladle 10 but ends substantially at the 
same height as that of the upper end of the ladle 10 so that the lower 
edge 12 of the suction slot 2 is situated about 250 mm below the upper end 
of the ladle 10. In this case it is preferred to stop the slinging 
operation at the height of the lower edge 12. The removing part of the 
lining of about 250 mm is finished by bricks in the usual manner. 
Certainly one can also sling over the slot as described in connection with 
FIG. 3 in the case of the lower template, but it has to be recognized that 
in this case there is no possibility for dust removal. 
The device of the present invention enables excellent dust removal with 
minimum suction capacity of the apparatus and minimum component parts. For 
instance, adequate dust removal has been achieved for a template having a 
diameter of 3750 mm and a thickness of walls to be slung of 180 mm when 
the suction slot was about 60 mm wide (the distance from the upper side to 
the drawn-in lower edge) and the suction aggregate sucked off amounted to 
about 5 m.sup.3 /sec. The pressure difference between the free space 11 
and the inner area of the template 13 amounted in this case to about 300 
kg/m.sup.2, the speed of entrance of the sucked off dust being slightly 
above 20 m/sec.