Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to an apparatus
for discharging fine-grained solids.
In particular, the present invention relates
to apparatus for discharging fine-grained solids from
a system which is under a higher pressure into a receiving
space which is under a lower pressure.
It is often necessary to discharge fine-grained
solids from a system in such a manner that reaction gases
cannot escape from the system and that gases cannot enter
the system. If the fine-grained solids have an exactly
defined angle of repose, said solids can substantially
seal the discharge apparatus if the discharge apparatus
always contains a sufficient amount of solids. Flowable
solids may fail to provide a seal even if they are con-
lS tained in the discharge apparatus. In both cases the solids
will not provide a seal if the discharge apparatus contains
no solids or only an inadequate quantity of solids. Flow-
able solids often cannot be discharged in a controlled
quantity or at a controlled rate.
German patent specification 915,199 discloses
a discharge apparatus in which a passage which is rela-
tively small in diameter is provided between two chambers,
which are under different pressures, and the passage is
closed at its outlet end by a weight-biased flap. A feeding
plunger is provided for forcing solids in a compacted
state into the passage so that the flap will be opened
by the solids as they are advanced and a corresponding
quantity of solids will fall out of the outlet end, which
is subsequently closed by the flap.
Germain patent publication 11 21 545 discloses
discharge apparatus in which the sealing means consist
of a lock chamber provided with a star feeder, which
discharges the solids through a supply line to a lifting
tube, in which the solids are pneumatically conveyed.
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U.S. patent 2,833,622 discloses discharge
apparatus which comprises a U-shaped siphon, one leg of
which is connected to a duct for supplying solids from
a cyclone, which is connected to fluidized bed equipment.
The other leg is provided in its top part with an opening
for discharging the solids, which drop into a container.
A line for supplying an entraining gas opens above the
bottom of the U-shaped siphon. The entraining gas entrains
the solids upwardly in the discharge leg and through the
outlet opening out of the siphon. That discharge apparatus
will not provide a seal if no solids are contained in
the siphon and if the higher pressure in the system is
sufficient for a discharge of flowable solids. In the
latter case the discharge rate will highly depend on the
lS pressure in the system.
It is an object of the invention to provide
apparatus for the discharge of fine-grained solids, in-
clusive of flowable solids, from a system that is under
a higher pressure to a receiving space which is under
a lower pressure, which discharge apparatus does not tend
to be clogged and has only a small wear and permits a
simple and accurate control of the discharge rate and
will prevent an escape of gases from the system even when
no solids are contained in the discharge apparatus.
According to the present invention, there is
provided an apparatus for discharging fine-grained solids
from a system which is under a high pressure into a re-
ceiving space which is under a lower pressure, comprising:
means forming a U-shaped siphon having a vertical
entrance leg, a vertical discharge leg, and a connection
at a bottom of the siphon between said legs;
a solid supply line leading from the system
under a higher pressure to said entrance leg of the U-
shaped siphon;
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means forming a solids outlet on said discharge
leg for connecting sald discharge leg of the U-shaped
siphon to said receiving space;
a supply line for supplying entraining gas to
solids contained in a lower portion of the siphon, said
discharge leg being shorter than said entrance
leg; and
a shut-off device for opening and closing said
solids outlet of the discharge leg and biased opposite
to the direction of flow by a force which slightly exceeds
a force which is exerted on said shut-off device in the
direction of flow by pressure in said discharge leg.
The expression "system which is under a higher
pressure" covers any equipment in which fine-grained solids
are treated and which is under a pressure that is higher
than the pressure in the space which receives the treated
solids. Such equipement is used, e.g., in fluidized bed
processes. The expression "receiving space" covers any
equipment which is under a lower pressure than the system,
and includes, e.g., a bin, a belt conveyor, a handling
vessel etc.. The pressure difference between the system
and the receiving space may be very small, e.g., 0.5 mbars,
or may be much higher, e.g., 10 mbars or more. The line
for supplying the entraining gas is so arranged that in
an inoperative condition of the apparatus said line opens
in the bed of solids in the lower portion of the siphon
and that it is directed toward or directly into the dis-
charge leg. The discharge leg is about 10 to 40~ shorter
than the entrance leg. The height of the column of solids
in the entrance leg connected to the solids supply line
should be so large that said column will seal the system
from the receiving space. The magnitude of the force which
biases the shut-off device opposite to the direction of
flow is so selected that it will just seal the solids
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outlet against the action of the pressure in the system.
When the siphon contains no solids or only a small amount
of solids, the valve will seal the solids outlet so that
no gas can escape from the system. In that case the valve
will be closed even when entraining gas is being supplied
because this will virtually result in no increase of the
pressure. If the entrance leg of the siphon is filled
with solids, the solids outlet will be closed too as long
as no entraining gas is supplied. When entraining gas
is being supplied, the valve will be opened by the pressure
in the discharge leg and solids will be entrained by the
entraining gas through the solids outlet. The force which
biases the valve opposite to the direction of flow may
be exerted pneumatically, mechanically or electrically.
The solids outlet may be provided at the top or on the
side.
Preferably, the shut-off device consists of
a plate, which closes the solids outlet and which is se-
cured to a movable piston rod. The plate may constitute
a planar surface or may have the shape of a cone having
an apex facing opposite to the direction of flow. The
conical shape will be particularly desirable if the solids
outlet faces vertically upwardly. That end of the discharge
leg where the solids outlet is provided is preferably
formed with a bead because this will improve the seal.
The provision of the shut-off device comprising a plate
and a piston rod will ensure a good guidance of the shut-
off device.
Preferably, the piston rod is secured to a dia-
phragm, which is accomodated in a pressure vessel, anda fluid is supplied to the outer chamber of the pressure
vessel. The fluid may consist of a gas or a liquid. In
this manner the required force can easily be exerted on
the plate.
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Preferably, a supply line Eor a gaseous fluid
and a discharge line for a gaseous fluid open in the outer
chamber of the pressure vessel. In that case the required
force can be exerted on the plate in a particularly simple
manner.
Preferably, the discharge line for the gaseous
fluid leads from the outer chamber of the pressure vessel
to the system. A flow of gas at a low rate from the pres-
sure vessel through the discharge line into the system
will ensure that the force by which the plate is biased
opposite to the direction of flow will exceed the pressure
acting from the system on the plate in the direction of
flow. The area of the diaphragm must slightly exceed that
area of the plate which can be subjected to the pressure
in the system. In that case the required backpressure
force can be produced and controlled in a very simple
manner.
Preferably, the solids outlet of the discharge
leg communicates with a coaxial tube which has an aperture,
the piston rod extends through said aperture, and the
aperture is sealed by a sealing element which surrounds
the piston rod. The coaxial tube extends somewhat above
the solids outlet of the discharge leg and is sealed at
that end by a diaphragm. The solids entrained by the
entraining gas are entrained downwardly through the annular
gap which is defined between the discharge leg and the
coaxial tube. This design results in a particularly simple
and reliable structure.
A preferred embodiment of the invention will
now be explained in more detail as example without limita-
tive manner with reference to the drawings, wherein:
Figure 1 is a transverse sectional view showing
discharge apparatus in which the solids outlet faces up-
wardly; the connection to the system and the receiving
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space are not shown.
Figure 2 is a diagrammatic view showing discharge
apparatus which is provided with a lateral solids outlet
and is connected to the system and the receiving space.
The dischar~e apparatus comprises a U-shaped
siphon 1, which has an entrance leg 3. The latter is con-
nected to a system 17 (figure 2) by a solids supply line
2 (which is indicated only by an arrow in figure 1). The
discharge leg 5 is provided with a solids outlet 4, which
faces upwardly in figure 1 and laterally in figure 2.
In accordance with figure 1 the solids are entrained by
the entraining gas into the annular gap between the dis-
charge leg 5 and the coaxial tube 15. In accordance with
figure 2 the solids are entrained by the entraining gas
into the laterally disposed space 18. Thereafter the solids
enter the receiving space l9, which is provided in ac-
cordance with figure 2 by a belt conveyor and which is
under a lower pressure than the system 17. A nozzle pro-
vided in the bottom of the siphon constitutes a supply
line 6 for entraining gas. The shut-off device 7 associated
with the solids outlet 4 consilsts of a plate 8, which
is secured to a movable piston rod 9. The piston rod 9
is secured to a diaphragm 10, which is contained in a
pressure vessel 11. A supply line 13 and a discharge line
14 for a gaseous fluid open in the outer chamber 12 of
the pressure vessel 11.
In accordance with figure 1 the top opening
of the coaxial tube 15 is sealed by a diaphragm seal 16,
which surrounds the piston rod 9 in gastight contact there-
with. The piston rod 9 extends through the bearing 20.
The solids outlet 4 is closed by the plate 8. When en-
training air is supplied through the nozzle 6, as is
indicated by a dotted line, the plate 8 will be lifted
so that solids are entrained by the entraining air through
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the solids outlet 4 into the annular gap between the dis-
charge leg S and the coaxial tube 15 (dotted line arrows).
In accordance with figure 2, the rate at which
air is supplied through the supply line 13 into the outer
part 12 of the pressure vessel 11 is sufficient to result
in a flow of air at a low rate through the discharge line
14 into the system.
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