Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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P-PWU-221
APPARATUS FOR DEWATERING SI4~1G SAND
The invention relates to an apparatus for dewa-
tering slag sand, in particular blast-furnace slag sand
located in a receptacle.
In the prior art, the slag flowing out of a shaft
furnace, for example a blast furnace, is quenched by
means of water jets emerging from nozzles in such a way
that the liquid slag turns into a more or less fine slag
sand. So that this slag sand can be used further in a
profitable manner, the mixture of slag sand and water,
the slag mash, which results from the said spraying must
as far as possible be largely dewatered.
According to the prior art, this dewatering takes
place without exception by wall sections of a receptacle
for the wet slag sand being designed as filtering sur
faces permeable to water. To this end, the vertical side
walls, for example 4f a cylindrical receptacle, can be
designed entirely or partly as filter surfaces, or even
only the conical outlet area of such a receptacle.
In the first case, the filtering surfaces can
certainly be designed to be relatively large, but the
portion of slag sand located in the bottom, ~or example
conical, outlet is left without being dewatered; whereas
in the second case, dewatering of this portion certainly
takes place, but the filtering surface remains relatively
small. In both cases, but especially in the last men-
tioned case, the filter surfaces are exposed to high
mechanical compressive stress from the contents of the
receptacle so that these filter wall sections must be of
appropriately resistant, that is expensive, construction.
A particularly serious disadvantage of both
constructians (or a combination of the two) consists in
the fact that the said filter surfaces become clogged lay
slag sludge after relatively short use and thus become
ineffective. To remove the sludge from the filter sur-
faces, inje:c.tion o~ water, for example by means of
nozzles, from outside through the filter surfaces towards
the interior of the receptacle .is known in 'the prior art.
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To avoid these disadvantages of the prior art, it
is therefore the object of the invention to propose an
apparatus of the generic category mentioned at the
beginning for dewatering slag sand, which apparatus does
riot need any filter surfaces 'while maintaining a maximum
dewatering effect.
This object is achieved by an apparatus of the
generic category mentioned at the beginning which is
characterised in that the bottom outlet opening of the
receptacle leads into an outlet funnel which is arranged
downstream of the receptacle and whose diameter in the
area of the said bottom outlet opening is greater than
the diameter of this outlet opening of the receptacle and
whose top edge runs in such a way above the bottom outlet
edge of the receptacle that a free, annular passage for
rising extracted water flowing off over the said top edge
is formed between the said outlet opening and the said
top edge.
Exemplary embodiments of the invention are shown
in the drawings and will be described in greater detail
below.
In the drawingss
Figure 1 shows a schematic longitudinal section
through a first exemplary embodiment of the invention
having an essentially conical outlet funnel;
Figure 2 shows a schematic longitudinal section
through a second exemplary Pmbodiment of the invention
similar to that in Figure 1 but having a double outlet
funnel in tandem arrangement;
Figure 3 shows a schematic longitudinal section
through a third exemplary embodiment similar to that in
Figure 1 but additionally having a pivotable shutter for
the receptacle outlet;
Figure 4 shows a schematic longitudinal section
3S through a fourth exemplary embodiment of the invention
having a cylindrical-conical profile of the outlet
funnel;
Figure 5 shows a schematic longitudinal section
through a fifth exemplary embodiment of the invention
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similar to that in Figure 4 but having a conical widening
of the receptacle outlet;
Figure 6 shows a schematic longitudinal section
through a sixth exemplary embodiment of the invention,
essentially consisting of a combination of the exemplary
embodiments according to Figures 1 and 5;
Figure 7 shows a schematic longitudinal section
through a sixth exemplary embodiment of the invention
having a vertically adjustable outlet funnel.
Figure 1 shows the bottom part of a, for example
cylindrical, receptacle 8 for the slag sand to be de-
watered, having a preferably conical bottom outlet 10
(the slag-sand charge of the receptacle 8 is not shown
further in the Figure). The outlet opening 12 of the
outlet 10 is surrounded by an outlet funnel 14 arranged
downstream, likewise of an essentially conical shape. The
diameters of the outlet 10 in its bottom part and of the
outlet funnel 14 are appropriately selected in order to
create between the two a conical annular gap 16, the top
edge 18 of the outlet funnel 14 being higher than the
bottom edge of the outlet opening 12.
The functional principle of the apparatus accord-
ing to the invention is based on the principle of com-
municating vessels. On the basis of this principle, the
water contained in the slag sand rises in the annular
channel 16 and runs off in a first stage of the dewater-
i~ng over the top edge 18 of the outlet funnel 1~. On
account of its density and internal friction, the slag-
sand portion of the slag mash does not participate in
this rising of the water in the annular space 16, which
results in the separation between sand and water, and
with astonishing efficiency, as tests have shown. Accord-
ingly, the slag sand itself acts as a filter mass.
In vthe said first stage of the dewatering, the
water is allowed to flow off over the top edge 18, since
a good separating action between water and any entrained
sludgy sand constituents takes place over the relatively
. large distance thereby provided between outlet x2 and ,.
this top edge 18, in particular because substantial
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slowing-down of the water velocity takes place when the
water rises in the widening annular gap 16.
The water flowing over the edge 18 is caught in
an encircling annular space 20 and dxawn off via a
discharge 21.
For the purpose of further improving the separa-
ting effect between water and any entrained slag sludge,
a separating and steadying wall 22 having an additional
separator action can facultatively be provided in the
annular space 20, in which case accumulating sludge can
settle in the bottom part of the annular space 20 and,
after dewatering is complete, can be drawn off through a
discharge 28.
It has been found in the said tests that, in the
further course of dewatering, the cleanliness of the
accumulating water increases on account of the increasing
filtering effect of the slag sand drying in the recep
tacle 8, and the accumulating water quantities naturally
decrease. The invention therefore facultatively makes
provision for the water, as water purity increases and
water quantity decreases, to be allowed to flow off first
of all through a valve 24 and later through a valve 26 in
an even lower position, as a result of which the dewater-
ing process is shortened. During the dewateri.ng opexa-
Lion, the flow of slag sand is blocked by the cylindrical
run-off connection piece 30, for example by means of a
sgueezing valve (not shown) which is known per se and is
attached below the connection piece 30 in the adjoining
discharge pipe (not shown).
Finally, the invention facultatively provides
water. injection nozzles 32 in any number which are
arranged all around at the top part of the annular space
20 and serve to clean the outlet funnel 14 if the recep
tacle 8 is completely emptied at any ti.ane between two de
watering operations.
Figure 2 shows an embodiment variant of the
invention i.n which two outlet funnels 34, 36 connected
one behind the other in tandem arrangement are provided.
In this way, not only is the intended separating effect
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according to the invention between slay sand and water
improved even further, but the portions of slag sand
otherwise not participating in the separation operation
(that is, for example in Fig. l, the quantities of slag
sand located below the outlet opening 12) are also
reduced to a minimum. The boiaom funnel 36 is used for
this purpose by opening its welter outlet 37 when the top
funnel 34 has performed its function.
Figure 3 shows a constructional example having a
pivotable shutter 38 at the outlet 40 of the receptacle
8. The squeezing valve (not shown) is relieved of the
weight of the receptacle charge by this shutter 38. But
the shutter also helps to reduce to a minimum the bottom
quantity of slag sand already reduced with the arrange=
ment according to Figure 2 and not dewatered.
Figure 4 shows a construction in which an outlet
funnel 42 according to the invention is not designed so
as to run continuously in a conical manner to the top
(as, for example, in Figure 1), but its top part 44 has
essentially cylindrical forms. To make this possible, the
outlet of the receptacle 8 has a corresponding cylindri-
cal connection piece 46. This configuration ensures that
small quantities of slag sand cannot possibly be floated
off to the top along a continuously slaping funnel wall
(see 14 in Fig. 1) but are retained in the bottom part of
the funnel 42 on account of their density.
In Figure 5, in an extended construction of
Figure 4, an outlet connection piece 48 of the receptacle
8 is provided at the bottom with a conical skirt 50
widening towards the bottom. This configuration creates
a relatively narrow annular gap 54 between the skirt 50
and the outlet funnel 52, with the effect that not only
is slag sand restrained in a purely mechanical manner
from floating up, but in addition a further separation
effect also results due to the water-velocity gradient in
the gap 54 and the annular space 56 located above it.
The construction according to Figure 6 puts into
concrete farm an extension of the idea of the separation
effect by means of a water-velocity gradient in the
CA 02031702 1999-11-22
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annular gap 58, widening to the top, between the outlet skirt 62 of the
receptacle 8 and the
funnel wall 66, which is again of conical design. Due to the considerable
cross-sectional
increase in this annular ga.p 58, which reaches a maximum at the top edge 64
of the funnel
66, and the deceleration in the water velocity accompanying this reduction,
the said
separation effect is substantially assisted by decantation.
Figure 7 shows an extension of the inventive alternative shown in Figure 6 by
the
outlet funnel 68 according; to the invention being designed to be vertically
adjustable with
accessories. Encircling bellows 70 permit a corresponding vertical movement of
the system,
this vertical displacement being brought about with the aid of means (not
shown) known per
se.
If the funnel 68 is displaced upwards, the gap 72 narrows while at the same
time the
water volume located above it increases and the end edge 74 is lifted higher,
which, as
follows from the above explanations, results in optimum cleaning effects. This
vertical
adjustment enables the apparatus to be optimally adapted to various grades of
sand.
For the purpose of further optimising the cleaning effect, the invention
facultatively
provides an annular encircling filter element 78 between the outlet connection
piece 76 of
the receptacle 8 and the outlet funnel 68. In contrast to the filter elements
mentioned at the
beginning according to floe prior art, this filter element 78, which
preferably acts as a
retaining screen, is not exposed to any great mechanical stress together with
corresponding
wear and in particular does not have to bear the weight of the receptacle
contents.
