Apparatus for dewatering slag sand

Provided below the funnel-shaped outlet opening of a receptacle filled with wet slag sand is an outlet funnel which is closed to begin with and forms a conical annular gap around the receptacle. This gap fills with slag sand, as a result of which dewatering occurs according to the principle of the siphon effect.

TECHNICAL FIELD 
The invention relates to an apparatus for dewatering slag sand, in 
particular blast furnace slag sand located in a receptacle. 
BACKGROUND OF THE INVENTION 
In the prior art, the slag flowing out of a shaft furnace, e.g. 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 known as the slag mash, which results from 
the said spraying must as far as possible be 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 surfaces permeable to water. To this end, the vertical side 
walls, for example of 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 be designed to be relatively 
large, but the portion of slag sand located in the bottom, e.g. 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 mentioned 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 constructions (or a combination 
of the two) consists in the fact that the said filter surfaces become 
clogged by slag sludge after relatively short use and thus become 
ineffective. To remove the sludge from the filter surfaces, injection of 
water, for example by means of nozzles, from outside through the filter 
surfaces toward the interior of the receptacle is known in the prior art. 
SUMMARY OF THE PRESENT INVENTION 
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 not need 
any filter surfaces while maintaining a maximum dewatering effect. 
This object is achieved by an apparatus which is characterized 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 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.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 shows the bottom part of a, for example cylindrical, receptacle 8 
for the slag sand to be dewatered, 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 according to the invention is 
based on the principle of communicating 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 dewatering over the top 
edge 18 of the outlet funnel 14. 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. Accordingly, the slag sand itself acts as a filter mass. 
In said first stage of the dewatering, the water is allowed to flow of 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 12 and this top edge 18, in 
particular because substantial 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 drawn off via a discharge 21. 
For the purpose of further providing the separating effect between water 
and 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 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 receptacle 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 dewatering process is shortened. During 
the dewatering operation, the flow of slag sand is blocked by the 
cylindrical run-off connection piece 30, e.g. by means of a squeezing 
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 receptacle 8 is 
completely emptied at any time between two dewatering operations. 
FIG. 2 shows an embodiment variant of the invention in 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 
according to the invention between slag sand and water improved even 
further, but the portions of slag sand otherwise not participating in the 
separation operation, e.g. in FIG. 1, the quantities of slag sand located 
below the outlet opening 12, are also reduced to a minimum. The bottom 
funnel 36 is used for this purpose by opening its water outlet 37 when the 
top funnel 34 has performed its function. 
FIG. 3 shows a constructional example having a pivotal 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 arrangement according to FIG. 2 and not dewatered. 
FIG. 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, e.g. in FIG. 1, but its top part 44 has essentially cylindrical 
forms. To make this possible, the outlet of the receptacle 8 has a 
corresponding cylindrical connection piece 46. This configuration ensures 
that small quantities of slag sand cannot possibly be floated off to the 
top along a continuously sloping funnel wall (see 14 in FIG. 1) but are 
retained in the bottom part of the funnel 42 on account of their density. 
In FIG. 5, in an extended construction of FIG. 4, an outlet connection 
piece 48 of the receptacle 8 is provided at the bottom with a conical 
skirt 50 widening toward 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 FIG. 6 puts into concrete form an extension 
of the idea of the separation effect by means of water-velocity gradient 
in the 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 gap 58 
and the deceleration in the water velocity accompanying this reduction, 
the said separation effect is substantially assisted by decantation. 
FIG. 7 shows an extension of the inventive alternative shown in FIG. 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 moment of the sytem, 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 optimizing 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 
the 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. 
While preferred embodiments have been shown and described, various 
modifications and substitutions may be made thereto without departing from 
the spirit and scope of the invention. Accordingly, it is to be understood 
that the present invention has been described by way of illustrations and 
not limitations.