Note: Descriptions are shown in the official language in which they were submitted.
~3~
BACXGROUND OF THE INVENTION
The present invention relates to an apparatus for
producing water granulated slag and, more particularly,
to such a slag granulator with associated equipment of
smaller size and simplified construction, in which
a slurry of water granulated slag can be dewatered con-
tinuously and efficiently by a method capable of dewatering
the slurry as it is trans~erled.
Recently, slag which is produced secondarily in blast
furnaces, converters or other metal smelting furnaces is
water-granulated to be utilized as useful materials for
a veriety of applications including a cement material and
fine aggregate of concrete. To obtain such water granulated
slag, molten slag discharged from a furnace is fed intb
a water jet and granulated thereby and recovered as
a slurry of water granulated slag (hereinafter, referred
to as slurry or slag slurry). Thus, it is necessary to
pro~ide a dewatering process for separating the slurry
into granulated slag and water.
Heretofore~ such a dewatering operation has been
accomplished by using a slag granulator as typically
shown in FIG. 1. In the arrangement of FIG. 1, the slag
slurry S discharged from a water blowing unit 1 is first
dxopped into a concentration tank 2 to be precipitated
and concentrated on the botto~ of the tank 2. The con
centrated slurry is then fed by a slurry pump Pl through
a line Ll to a dewatering tank 3, where it is subjected
-- 2 --
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to a predetermined dewatering operation to be re-covered
as a water granulated slag product~ The separated
water is gathered in a collection tank 4. The water
(containing a significant quantity of granulated slag)
overflowing the concentration tank 2 is caught by and
stored in a water reservoir 5 and, then, is fed by
a pump P2 through a line L2 to the collection tank 4, and
thence to a sedimentation tank 6. The granulated slag
slurry precipitated and concentrated in the tank 6 is
fed by a pump P3 through a line L3 to the dewatering
tank 3, where it is subjected to a dewatering operation.
The water separated from the precipitate in the tank
6 is fed by a pump P4 to a cooling tower, where it
is cooled to a predetermined temperature and stored in
a cooled water tank 8. The cooled water is then-fed
through a line L4 to the wa-te-r--bl-owing unit to be recycled
as pressurized blowing jet water. However, the slag
trea~ment processes using the aforementioned water
slag granulator of the prior art have several drawbacks.
In the prior art equipment the slag slurry is transferred
by the action of electrically driven slurry pumps or
the like, and a large amount o~ electrical energy is required.
Also, operational efficiency of the prior art equipment
is significantly limited because dewatering is done in
a batch type dewatering tank needing 12 - 24 hours per one
batch. Since it is often necessary to provide a plurality
of large-sized dewatering tanks, electric energy costs
are high. Further, in the prior art equipment, the cooled
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water tank functioning as a source of the blowing jet
water must necessarily have a large capacity, because
it is necessary to provide a large quantity of pressurlzed
blowing jet water during the startup period and because
the water ratio, namely the ratio of pressurized blowing
jet water versus slag, must be preset to a high level
to adequately meet the variation of the molten slag
quantity fed from the smelting furnace and various troubles
occurring during operation after the startup. Alternatively,
where the cooled water tank capacity is fairly limited,
a rather complicated arrangement would be required to
otherwise supply fresh ~ater.~rom the outside of the water
recycling system. Under these circumstances, the prior
art systems have required large--scale equipment as well
as a high electric energy cost. .In addition, since
...... the dewatering operation is based on a batch-mode~
the dewatering effici.ency and the productivity of granulated
slag have been much rest-ric~ed.
SUMMARY OF THE INVEN~ION
The present invention has been achieved with a view
to overcoming the foregoing drawbacks of the prior art
water slag granulator by providing an improved system
in which a screw conveyor is used as a m~ans for trans-
ferring the granulated slag slurry fed from the water
2S blowing unit and in which said screw conveyor performs
a dual function of transferring and dewatering the water
granulated slag slurry to dispense with the dewatering
tank of the prior art and to permit continuous and
efficient dewatering of the granulated slag slurry.
~3L39~
Accordlngly, an object of the present invention is to
provide an apparatus for producing water granulated slag
comprising a slurry tank for storing a water granulated
slag slurry discharged from a water blowing unit, and
a screw conveyor provided in the slurry tank for transferring
and dewatering the slag slurry, said screw conveyor being
inclined upwardly, as viewed in the direction of slurry
flow, from its near end d-ispo-sed on the bottom of the slurry
tank and immersed in the slurry towards its far end
extended above the liquid suxface of said slurry tank
thereby to permit the slag slurry precipitated on the slurry
tank bottom to be dewatered by the action of gravity
as it is transferred on said screw conveyor from the tank
bottom to the outside of the tank.
Another object of the present invention is to provide
apparatus for producing water granuIated slag comprising
a slurry tank for storing a water granulated slag slurry
discharged from a water blowing unit, a sedimentation tank
for precipitating and concentrating said slag slurry on
the bottom thereof while permitt.ing at its one peripheral
end an inflow of the liquid overflowing said slurry tank and
an outflow of the supernatant liquid from other peripheral
end at an upper part thereof, and a water xeservoir for
storing said supernatant liquid flowing out of the
sedimentation tank, the slurry tank and the sedimentation
tank each being provided with a screw conveyor for trans-
ferring and dewatering the slag slurry, each screw conveyor
being inclined upwardly, as viewed in the direction
~3~9~
of slurry ~low, from its near end disposed on the bottom
of its associated tank and immersed in the slurry towards
its far end extended above the liquid surface of each
associated tank thereby to permit the granulated slag
slurry precipitated on said slurry tank and sedimentation
tank bottoms to be dewatered by the action of gravity as
the precipitated slurry is transferred on each screw
conveyor from its associated tank bottom to the outside
thereof.
Still another object of the present invention is to
provide the aforementioned apparatus which further
comprises a cooling tower and in which said water reservoir
is composed of an intercommunicated hot water tank and
cold water tank, said supernatant liquid flowing out of
the sedimentation tank being stored in the hot water
tank and then cooled to a predetermined temperature in
a cooling tower to be stored in the cold wate~ tank for
recycled use as the blowing jet water.
These and other objects and features of the present
invention will become obvious ~rom the detailed description
of the invention when read with the accompanying drawings.
BRIEF DESCRIPTION OF T~E DRAWINGS
FIG. 1 is a schematic sectional view of a typical
water slag granulator according to the prior art;
FIG. 2(I) is a schematic sectional view of a preerred
embodiment of the water slag granulator according to
the present invention, and FIG. 2(II) is a section taken
on the line A - A of FIG. 2(I); and
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FIG. 3 (I) is a schematic sectional view of another
preferred embodiment of the water slag granulator according
to the present invention; and FIG. 3(II) is a section taken
on the line B - B and C - C.
DETAIL~D DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings, especially to FIG. 2,
showing one preferred arrangement of the present invention,
the reference numeral 1 ~enerally represents a water
blowing unit, to which is connected a slurry tank 9
provided therein with a screw conveyor 10. The water
blowing unit l is composed of a molten slag trough l.l,
a cooling blower 1O2, a ~lowing bo~es 1.3 and 1.4
producing cold water jets C, and an exhaust duct 1.5.
The water jets produced under pressure by the blowing
boxes 1.3 and 1.4 have a predetermined flow rate-and
vPlocity, and act to fine the molten sla~ and then to
coagulate the resultant fine parti~les into larger particles
which are then formed into a slag slurry in the presence
of water. This process is called a water slag granulation.
The resultant slurry S of the water granulated slag is
fed through a slurry trough l n6 into the slurry tank 9,
where it is precipitated, and the slag slurry separates
into a concentrated slurry at the lower part of the tank 9
and clear supernatant water on the upper part. As shown
in FIG. 2(II), the slurry tank 9 is provided therein
with a screw conveyor 10 which is inclined upwardly from
its near end towards its far end as viewed in the direction
of slurry flow. As the screw conveyor 10 is rotated by
~L3~9~ `
~ suitable drive means M at a predetermined speed about
its longitudinal axis, the concentrated slurry predipitated
on the bottom of the tank 9 is transferred at a predetermined
rate from the near end of the conveyor 10 to its far end
extended above the liquid surface (f) of the tank 9.
Further, as the screw conveyor 10 is rotated, the slag
slurry reaching the liquid surface (f) is then subjected
to a dewatering action called "hydro-extractlon" by
gravity. The separated water may be caught and returned
to the slurry tank 9 by a suitable means, e.g. a chute 13.
Upon reaching the far end of the screw conveyor 10,
the thus dewatered slurry, namely granulated slag, is dropped
through a duct 11 onto a belt conveyor 12 provided immediately
below the duct 11, thence it is continuously carried on
the belt conveyor 12 to a predetermined yard (not shown).
Thus, the screw conveyor lO functions not only as a carrying
means for transferring the ~re-cipitated slurry S from
the bottom of the tank 9 to the outside thereof, but also as
a dewatering means for hydro-extracting the slurry as
it is moved from the surface level of the tank 9 to the far
end of the belt conveyor. It has ~een experimentally
shown that the moisture content of the granulated slag
fed out to the yard is reduced to about 15 - 20% or less.
In the meantime, transfer of a fluidic substance
on a screw conveyor generally requires a trough~like guide
member to be provided longitudinally along the underside
of the screw conveyor. According to the present invention,
3g~
however, since as the screw conveyor i5 rotated the slag
granules are deposited below the screw conveyor to such
an extent that the gra~ulated slag deposition itself
provides a function of a "material guide" for the slurry
under being transferred, as indicated at S' in FIG. 2 (II),
the screw conveyor according to the present invention
can transfer the slurry smoothly without otherwise providing
such a guide member.
If a metal screen conveyor of a suitable mesh size
is used as the belt conveyor 12 for transferring
the granulated slag taken out of the slurry tank to the yard,
an added hydro-extracting effect is obtained during
the course of transfer to the yard which will improve
the dewatering effect.
Although the foregoing FIG. 2 shows only the water
blowing unit, sluEry tank and screw-conveyor provi-ded~
therein, it is to be noted that the water slag granulator
is provided, as re~uired, with other associated equipment
including those for feeding the blowing jet water or for
draining the slurry tank. Further, there may be provided,
as required, a sedimentation tank for precipitating and
separating the granulated slag entrained by water over-
flowing the slurry tank, or various equipment required to
recycle the separated water as the blowing jet water.
Referring now to FIG. 3 ~I), showing another preferred
arrangement of the water slag granulator according to
the present invention, the slurry tank 9 for storing the slag
slurry discharged from the water blowing unit l is further
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provided with a sedimentation tank 14 and a cooling tower
19 which promotes separation of the granulates slag from
the slurry in the sedimentation tank 14 and which cools
clean supernatant water from the tank 14 for recycling
the same to the blowing jet water.
In this preferred equipment, a part of the slag slurry
in the slurry tank 9 overflows into the sedimentation tank
14 from its one peripheral end. ~he slag slurry fed from
the water blowing unit into the slurry tank 9 is treated
therein in the same manner as in the slurry tank shown in
FIG. 2, to be transferred and dewatered as a concentrated
slurry by a screw conveyor 10.1 for recovery in the form
of dewatered slurry, namely, granulated slag. The slag
slurry overflowing the slurry tank 9 into the sedi-
mentation tank 14 is further subjected therein to slag-
water separation. Preferably, the sedimentation tank 14
may be provided with a slag mud collector 15. As shown
in FIG. 3(II), the slag mud collector :L5 has a tray-like
shape in its vertical section containing its center axis. As
it is rotated about the center axis, the slag mud collector
15 acts on the slurry to collect the same into the slag
mud collecting chamher 16 at the bottom of the sedimentation
tank 14. Although the slag mud collector is provided
singly in the example illustrated in FIG. 3(II), there may
be a plurality of slag mud collectors so as to distribute
among them any large load imposed by an input of
a large quantity OL slurry. However, it is to be noted
that use of a large plurality of slag mud collectors
~ 10 -
.
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unduly adds to the size of the sedimentation tank.
Normally, two slag mud collectors as shown in FIG. 3(I)
are sufficient for achieving satisfiable results.
Alternatively, the sedimentation tank may dispense with
the slag mud collector, leaving the slag granules to
naturally precipitate under gravity onto the tank bottom.
Further, screw conveyors 10.2 and 10.3 are provided
at the bottom of the sedimentation tank 14. Each of
these conveyors is inclined upwardly, as viewed in
the direction of slurry flow, from its near end disposed
in the slag mud collecting chamber 16 where the precipitated
sluxry is collected towards its far end extended above
the liquid surface of the sedimentation tank.
The granulated slag slurry flowing in the sedimentation
tank 14 undergoes precipitation and concentration to be
ef~iciently collected in the slag mud collecting chamber
16 by the slag mud collectors I5.1 and lS.a. Like
the slurry precipitated on th-e b~ttom of the slurry tank 9,
the concentrated slurry thus collected is dewatered as
it is transferred on the rotating screw conveyor from
the liquid surface to the outside of the tank and, upon
reaching the far end of the screw conveyor, the dewatered
slurry or granulated slag is passed through the duct
11' onto the belt conveyor 12, which in turn carries
the granulated slag to the yard. The clear supernatant
liquid separated from the slurry in the sedimentation
tank 14 is then fed through a passage 17 to a water reservoir
-- 11 --
In the conventional equipment, sedimentation tanks
have almost a circular shape in plan view with their slurry
feed port located at the center and their supernatant liquid
discharge ports at the periphery. Thexefore, since they
must have a diameter at least twice the natural precipitation
distance of slag granules and since a plurality of sedi-
mentation tanks must be provided when large loads are to
be treated, large eqipme~t coats are incurred. To
the contrary, in the preferred equipment of the present inven-
tion, for example as shown in FIG. 3(I), since the wateroverflowing the slurry tank is fed into the sedimentation
tank from its one peripheral end, the water flow or liquid
flow cased thereby permits a use of slag mud collectors
of smaller diameter. Further, the sedimentation tank can
be of compact design by adopting a rectangular configura-
- tion with a due consideration paid to its effecti~e area------
and by distributing a large load capacity to two slag mud
collectors.
As shown in FIG. 3(I), it is pxeferable that
the water reservoir 18 for storing the clear supernatant
water from the sedimentation tank is composed of a hot
water tank 18.1 and a cold wa~er tank 18.2 which are
combined with a cooling tower l9. In this arrangement
the cleaE supernatant water naturally flowing from
the sedimentation tank 14 is first stored in the hot water
tank 18.1 to be fed by a feed pump Pa into the cooling
tower, where it is cooled to a predetermined temperature
to be stored in the cold water tank 18.2. The cold water
- 12 -
.
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is fed, from time to time, through a line L to the water
blowing unit 1 by a feed pump Pb to be used as a recycled
blowing jet water.
Further, the hot water tank 18.1 of the water reservoir
18 has the same water level as that of -the seaimentation
tank 14 and is communlcated with the cold water tank 18.2,
so that unbalanced water supply or flow rate may be prevented
when starting or stopping the water slag granulator
or in case of any emergency and so that a required
quantity of the pressurized jet water may always be secured.
In this connection, the molten slag quantity fed into
the water blowing unit 1 generally varies with the slag
production in the associated blast ~urnace or other
smelting furnace, and its maximum variation reaches
a level higher than or equal to twofold or three fold its
average level. To maintain an adequate water ratio under
such changeable circumstances, a sufficient quantity of
cooling water must be secured for feeding the pressurized
jet water responsive to the variation. For accomplishing
this, the prior art has preset a considerably high water
ratio by always feeding a large ~uantity of pressurized
jet water for accommodating an expected maximum variation
of the molten slag ~eed, without controlling the water
feed responsively to the variation at all. Thus, according
2S to the prior art, a large sized cold water tank must
necessarily be provided together with its associated
equipment of correspondingly larger size. According
to the present invention, the water feed is controlled
- 13 -
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responsively to the mol.ten slag feed variation and the hot
water tank 18~1 is communicated with the cold water tank
18.2 for maintaining the latter to a required water
level, so that an a~uate quantity of the pressurized
jet water can always be fed responsively to the molten
slag feed variation. Further, even if the water level
of ~he cold water tank drops during the startup time,
water naturally flowing therein from the hot water tank
can compensate the level decrease, and feed pump water supply
problems are avoided.
As a means for determining the variation of the molten
slag feed, an amrneter may be connected to the power circuit
of the slag mud collector 15 provided in the sedimentation
tank 14, so that it can detect the various loads on
the slag mud collector 15. Alternatively, a variation of
the indication of an armme-te-r--connected to the slurry pump
circuit, a water temperature variation in the slurry tank
or water level variation in the sedimentation tank may
be utilized to detect the rnolten slag feed variation.
20 In the preferred equipment illustrated in FIG~ 3,
the slurry tank 9, sedimentation tank 14 and water reservoir
18 may be provided in one integral outer wall structure
with common partition walls. If the water reservoir is
to be provided adjacent to the sedimentation tank,
the latter may be cornmunicated with the hot water tank of
the water reservoir directly through the partition wall.
In such an arrangement, if any trouble occurs, for example,
in the water feed system to cause a water level decrease
- 14 -
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in the sedimentation ~ank and water reservoir, the blowing
water feed can be secured by causing the water to flow
directly from the sedimentation tank into the water
reservoir as an emergency measure.
As described herein according to the present
invention, the slag slurry can be dewatered continuously
and efficiently in a shorter time, because a screw
conveyor for transferring the slurry is used also for
the dewatering purpose, as compared with the batch
type processing using a dewatering tan~ according to
the prior art. In the p-rior art system using the dewatering
tank, since a plurality of dewatering tanks and equipment
must be providedl a large cost is incurred. Also, the prior
art equipment was extremely inefficient, in that a long time
was needed to achieve a required dewatering level.
- - According to the---present invention, an improved apparatus ~ - --~--
is pro~ided in which all such problems of the prior art
can be solved. For example, while the prior art system
using a dewatering tank consumed about l,000 KW of
electric power per one ton of slag slurry the power con-
sumption of the equipment according to the present invention
is reduced to about 400 KW under the same conditions.
The moisture content of the water granulated slag processed
by the equipment of the present invention is in the range
of about 15 - 20% or less, showing that the present
equipment equals or imp~oves the dewatering effect of
the prior art equipment.
_ 15 _
~3L3~
Finally, an organic combination of the slurry tank,
sedlmentation tank and water reservoir according to
the present invention provides an lmproved processing capacity
and permits an automatic control over the water feed
responsive to the molten slag feed variation as well as
a reduction of the equipment size.
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