Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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sAcRGRO~ND OF TEIE ID~vE~7TION
Water throughput in a steam generation device for
industrial purposes is considerable. If, for instance, an
apparatus with an output of 15 liters per hour i5 operated in the
course of 10 hours a day, 150 liters of water per day and, in a
hundred days (~0 working weeks), 15,000~1iters are converted into
steam .
Depending upon the hardness of the water, greater or
lesser amounts of solid residues remain irl the tank of the steam
generator. The quantity of the residuals contained in 15, 000
liters of water amounts, at an average hardness of 17 dH,
approximately to 0.3 grams per liter. Thus, for 15,000 liters,
this amounts to 4 . 5 kilograms . The water hardness can amount up
to ~0 dH which entails a proportional increase in mineral
res idue .
A portion of the residue (approximately 309~) is removed
from the tank in powder form, together with the waste water in
the course of the automatic draw-down operations of the steam
producing apparatus . The L~ i n,l~r, mostly in the form of small
beads or platelets, is however left behind. These platelets are
formed by sheet-like deposits at the cylinder wall, which drop
off due to extension and vorticity of the water. These deposits
are fragmented into platelets which drop upon ~he base of ~he
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cylinders and produce sediments there and constitu~es a basis ~or
the growth (seeding) of limestones. The platelets are not
carried away with the waste water because, on the one hand, the
waste water cross-sections are too small due to the existing
screens and other constrictions and, on the other hand, because
the water f low is too small due to the short elutrition or
desludging. ~urthermore the waste water :~quantity is often too
small and solid blocks are formed during the stoppages. The tank
must therefore either be cleaned or replaced at regular
intervals, depending upon the water hardness.
Two types of tanks are on the market today: so called
replacement or throw away cylinders and cylinders which can be
opened to pe~lr.it cleaning. ~eplacement cylinders contain
electrodes and consist of economical plastics material which are
easy to install and remove are still used, at the present time,
although the electrode costs have risen. On the other hand,
their disposal generates expenses which cannot be neglected.
These days however, cylinders which can be opened and cleaned are
increasingly used. Due to the cleaning, the time for maintenance
has increased. Furthermore, experience has demonstrated that a
cylinder can only be closed in a sealed manner if the closing
contact region is provided with a new seal. In addition, the
mineral deposits on the electrodes cannot be removed since the
scale deposits are very pronounced, so that the electrodes must
be changed from time to time, even in cylinders which ca~. be
cleaned, thus causing additional expense
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Although the electrode type air moisturizers presently
obtainable and fed with drinking water is based on developed
technology and operate reliably, they do not satisfy two
requirements of the user to a sufficient extent: they are not
free of maintenance~as explained above and they are not very
ecological in that not yet used and ~contaminated" parts cannot
be cleaned and must be replaced. Additionally, when the quantity
of the minerals accumulating at the base of the water tank is so
large, they can touch and shortcircuit the electrodes These
accumulations must therefore be removed by work- intensive
cleaning. This, however, still permits increasing the useful
life by at least 509~. Electrodes with crustations however can
hardly be cleaned; rather they must be replaced.
It is therefore an object of the invention to provide a
method and apparatus for preventing the development of scale
deposits in a water tank.
Another object of the invention is a device for
removing the dust from the contaminated air.
SU~RY OF l~E INVENTION
These and other objects of the invention, which become
apparent hereinafter, are achieved, accordi~g to the presen~
invention, by method and apparatus which prevent the development
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of scale deposits accumulated in steaming installa~tions where
drinking water is used and which provide for removing the
minerals accumulating at the tank base by the usual waste water
drawn-down operations. The inventive method can be used not only
in steam generators, but also in other apparatuses in which water
has been enriched by minerals and other precipitated materials.
According to the invention, a tark provided at the top
with a steam-or air outlet and containing water and air, can be
prevented from accumulating scale consisting of limestone and
other materials by turbulence of the water~ produced at least
periodically by air supplied from the bottom.
The. inventive apparatus also comprises a steam
generator with a water feed line, a heating arrangement, an open
steam outlet and a sludge drain, wherein the water tank has an
air feed device discharging into the base to prevent formation of
scale deposits by producing turbulence at least periodically in
the water by air fed from the bottom.
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21 63932
sRIEF DESC~IP~ION QF TEIE DP~AwINGs
The invention will be better understood by the Detailed
Description of the Preferred Embodiments with reference to the
drawings, of which:
Figure 1 is a cross-sectional a1ld schematic view of a
steam generator heated by electrodes; and
Figure 2 is a cross-sectional schematic view of an air
cleaning or scrubbing installation.
DETAI3iED DESCRIPTIO~ OF T~ ~ ~El~ EM30DIMENTS
The steam generator shown in Figure 1 has an
essentially cylindrically shaped housing 1 of plastic material,
in which two electrodes 2 and 3 are disposed ~or heating the
water ~. Electric li~es 2a and 3a connec~ the electrodes to a
current source through a control device (not shown). The
cylinder 1 has a steam outlet la at the top, through which the
generated steam can exit from the cylinder 1 and be directed to
where it is re~uired The water supply line 5 discharges into
the cylinder at the base lb or in its vicinity. This base lb, is
configured to be somewhat funnel-shaped and discharges into a
sludge drain '~7, which can be closed by an electric valve 5.
Steam generating tanks designed and built in this way are known
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~owe~er, in the invention, the air supply arrangement feeding
into the base itself, or into the vicinity of the base lb,
consists of an air line 8 and air pump 9, preferably electrically
actuated, as well as a control device 9a for the pump.
A diaphragm pump, with an output of approximately 30
watts can be used as an air pump. The control device 9a can be
configured either as a :component of the electronics controlling
the steam generator or as an independent construction element.
The control device is designed in such a way that it switches the
pump on periodically ~or 30 seconds - thus, for instance, at
intervals of 5 minutes. The selection o$ l~he minimum duration oL
the pump operation and the maximum length of the interruptions
depends upon how the air flows into the cylinder and is
distributed there as it rises to the top. Tests have shown that
mineral scale or the development of larger mineral formations is
prevented by inducing thorough turbulence from time to time in
all areas of the cylinder. In such cases, the separated minerals
form only a very fine powder, which does not stick to the
electrodes; rather, it appears as a sediment upon the base lb.
From there, the sediment is again swirled up by the turbulence
prior to any scale deposit being able to occur. If the sludge
drain 7 is opened by actuating the electric valve 6, the entire
quantity of the powder consisting of limestone and other minerals
is floated away. In this way, the development of the scale can
be prevented so that the steam generator, equipped in this way,
is free from. such maintenance.
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The method described is prevented i~ a tank containing
water by periodically swirling the water by air supplied from the
bottom. The method can be utilized not only in steam generator5,
but also in other tanks as, for instance, a tank in which air is
scrubbed. Such a tank is designated by the numeral lo in Figure
2. In this tank, which is, for the most part, filled with
flushing or scrubb~ng water 11, a distribution arrangement 12 is
located in the vicinity of the tank base o:r bottom lOa. The
distributor is connected to the air feed line 13, supplying air
to be scrubbed in the water. The top part of the tank 10
discharges into the air outlet 14. At the bottom, it is
connected to the desludging line 16 through a valve 15. The
water line 17 serves for adding water.
If the air supply is interrupted for a longer ~ime,
since no air has to be scrubbed, a portion of the ingredients
separated from the already scrubbed air will i~orm scale deposits
so that complete elutrition or desludging is no longer possible.
In order to eliminate this shortcoming ~i . e ., to prevent
crustation), air is periodically blown in by the air pump 19
through the auxiliary line 18. The air causes turbulence in the
water and thereby prevents scale deposits. The distributor
J~2
arrangement ~ can be used for distributi~g this auxiliary air,
as shown. It is however also possible to use an additional
distributor i~nstallation for the auxiliary air.
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While the pre~erred embodimen~s o~ the invention have
been described in dçtail, modifications_and adap~aEions may be
made thereto, without depa7~ting from he spirit and scope of the
invention, ad delineated in the following claims:
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