Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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ELECTROSTATIC PRECIPITATOR FOR CLEANING DUST-LADEN EXHAUST GASES
The invention relates to an electric filter for cleaning
dust-laden waste gases, comprising a plurality of rows of
grounded collecting electrodes arranged in a housing, and
discharge electrodes arranged between the rows of the collecting
electrodes and being under negative high voltage, wherein
knocking means comprising at least one knocking member for
periodically knocking off the dust from the collecting
electrodes and the discharge electrodes are assigned to the
collecting electrodes and the discharge electrodes, and wherein
the collecting electrode knocking means comprises a drive device
for the at least one knocking member of the collecting electrode
knocking means.
Waste gases loaded with dust and/or aerosol, which usually
originate from combustion processes, are frequently cleaned with
electric filters. In the electric filters, the dust particles
are predominantly ionized negatively by the discharge electrodes
that are under negative high voltage. The negatively charged
dust particles migrate to the positively charged or grounded
collecting electrodes and deposit there in the course of time in
the form of a dust layer. Both the discharge electrodes, where
dust layers also form, and the collecting electrodes are cleaned
periodically, for instance, by knocking, and the dust coming off
is, for instance, collected in a dust collecting funnel and
transported in appropriate containers for further disposal or
recycling.
The cleaning of the collecting electrodes is usually
performed by periodic mechanical blows by means of appropriate
knocking members, in particular hammers or tappets. The
individual collecting electrodes or a plurality of collecting
electrodes are cleaned collectively by a so-called tumble hammer
hitting on an appropriate anvil. The acceleration generated
detaches the adhering dust layers.
Knocking means for an electric filter are, for instance,
known from DE 1 112 499, DE 1 865 538, or DE 101 24 871 Cl.
DE 43 22 162 Cl discloses an electric filter with a specific
drive of a horizontally arranged hammer shaft. DE 28 39 542 Al
describes an electric filter with a mechanically operable
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knocking means, wherein the knocking elements are insulated from
each other by means of disc insulators.
More rarely is the cleaning of the collecting electrodes of
electric filters performed by means of vibration stimulation,
notching devices, vibrators, brushes, or compressed air. Such
systems are, for instance, known from DE 38 37 439 Al,
DE 103 00 549 Al, or DE 197 28 369 Al.
In addition to the collecting electrodes that are subject to
stronger pollution, corresponding dust layers also deposit on
the discharge electrodes, so that the discharge electrodes also
have to be cleaned at appropriate time intervals. Since the
discharge electrodes are under a corresponding negative high
voltage, the components of the cleaning means for the discharge
electrodes correspondingly have to be insulated from the ground
potential. For this purpose, in the case of knocking cleaning
systems, the drive device of the discharge electrode knocking
means which is arranged separately from the collecting electrode
knocking means is insulated by a rotating insulator or bushing
insulator in the shaft supply. The rotating insulator is
arranged externally of the gas flow, if possible, and is
partially impacted with cleaning air so as to avoid pollutions
and the resulting flash-overs up to destruction.
A disadvantage with the known electric filters with
collecting electrode and discharge electrode cleaning means is
the high effort caused by the separate drive devices for the two
electrode systems and the effort for the insulation of the
cleaning means for the discharge electrodes.
Moreover, the necessary components for the cleaning of the
collecting electrodes and of the discharge electrodes increase
the overall size of the electric filter. This disadvantage is
still increased by the fact that the drive device for the
collecting electrode knocking means is arranged at an
appropriate distance from the drive device for the discharge
electrode knocking means so as to safely avoid possible flash-
overs between the systems being of different potentials.
The object of the present invention therefore consists in
providing an above-mentioned electric filter comprising cleaning
means for the collecting and discharge electrodes, which has a
preferably simple, cost-efficient, and space-saving construction
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and enables an efficient cleaning of the collecting electrodes
and of the discharge electrodes.
Disadvantages of known electric filters and their cleaning
methods are intended to be avoided or at least reduced.
The object according to the invention is solved by an above-
mentioned electric filter in which the discharge electrode
knocking means is connected with the drive device of the
collecting electrode knocking means, so that the at least one
knocking member of the discharge electrode knocking means is
adapted to be actuated by the drive device of the collecting
electrode knocking means. In accordance with the invention, the
collecting electrode knocking means is thus coupled with the
discharge electrode knocking means, so that an appropriate drive
device is required only for the collecting electrode knocking
means. The drive device for the discharge electrode knocking
means may be omitted since the actuation of the knocking
members, in particular hammers, of the discharge electrode
knocking means is performed indirectly by the drive device of
the collecting electrode knocking means. Thus, the corresponding
components that would be required for driving the knocking
members of the discharge electrode knocking means may be
omitted, and no measures have been taken for their electric
insulation from the ground, either. Hence, costs and space may
be saved.
In accordance with one feature of the invention, the drive
device of the collecting electrode knocking means is coupled
with the at least one knocking member of the discharge electrode
knocking means by at least one insulated actuator. Such a
construction is relatively easy to implement and comprises the
safety and robustness required for operation. If the drive
device of the collecting electrode knocking means is actuated to
have the appropriate knocking members, in particular hammers,
act on the collecting electrodes, the knocking members for the
discharge electrodes can be actuated via the insulated actuator,
so that they also act on the discharge electrodes and hence the
dust layer is flung away.
Usually, the drive device of the collecting electrode
knocking means comprises a drive shaft connected with a drive
motor and a pertinent gear mechanism. The at least one knocking
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member of the collecting electrode knocking means is arranged on
this drive shaft. An appropriate control means activates the
drive motor at certain times, so that the at least one knocking
member is actuated at these times and the collecting electrodes
are thus cleaned.
With this construction it is of advantage if each insulated
actuator is also arranged on the drive shaft of the collecting
electrode knocking means and is adapted to be taken along by the
movement of the drive shaft of the collecting electrode knocking
means, and the at least one knocking member of the discharge
electrode knocking means is adapted to be actuated by the
actuator. If the drive shaft of the collecting electrode
knocking means is thus actuated, every insulated actuator that
is arranged thereon will also be actuated and hence acts on the
respective knocking member for the discharge electrodes. Thus,
an actuation of the knocking members of the discharge electrode
knocking means is performed automatically whenever the
collecting electrode knocking means is actuated. An extra drive
device for the discharge electrode knocking means is not
necessary, and hence their electric insulation is not necessary,
either.
Advantageously, a position generator is arranged at the
drive shaft of the collecting electrode knocking means, so that
the drive shaft and each actuator arranged thereon is adapted to
be taken to a defined starting position after the completion of
a cleaning process. After the cleaning process, a predetermined
position of the drive shaft is hence achieved. It is of
particular advantage if each actuator points substantially
perpendicularly downward once it is not needed, so that the
actuator offers a preferably small contact surface for dust and
need not assume a permanent insulating function. Apart from the
undesired pollution of the actuator, the insulating effect of
the actuator might be hindered by dust adhering thereto, so that
flash-overs might take place in the case of cleaning.
In accordance with a further feature of the invention, an
entrainment device, for instance, a rotatably mounted roller, is
arranged at the free end of each actuator, which is adapted to
be rotated on contact with the at lest one knocking member of
the discharge electrode knocking means. The provision of such
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entrainment device avoids frictions between the insulated
actuator and the knocking member of the discharge electrode
knocking means. The entrainment device, in particular the
rotatably mounted roller, thus rolls off at the knocking member
of the discharge electrode knocking means and actuates same
without causing disturbance or destruction by friction.
Advantageously, a plurality of collecting electrodes are
connected with each other, for instance, via a connector bar,
wherein an anvil is arranged at the combination of a plurality
of collecting electrodes for each knocking member of the
collecting electrode knocking member. By the knocking of the
knocking member on the anvil, the entire combination of the
collecting electrodes is hence supplied with an appropriate
impulse, so that the dust layer of the entire combination of
collecting electrodes is flung away therefrom. By combining a
plurality of collecting electrodes it is possible to have a
correspondingly small and space-saving design of the knocking
means. This is of particular advantage for smaller electric
filters.
Likewise, a plurality of discharge electrodes may be
connected by at least one frame, and a plurality of discharge
electrode frames by at least one connector bar if need be,
wherein an anvil for each knocking member of the discharge
electrode knocking means is arranged on at least one discharge
electrode frame or at least one connector bar. Here, too, it is
possible to knock on a combination of discharge electrodes with
one blow of each knocking member on a pertinent anvil.
A space-saving design variant may be achieved in that each
discharge electrode frame comprises an appropriate indentation
in the region of the discharge electrode knocking means. The
knocking members for the discharge electrodes are thus arranged
next to the indentation of the discharge electrode frame, so
that the outer dimensions of an electric filter having the
design of the invention do not deviate substantially from the
dimensions of an electric filter without cleaning means.
It is of advantage if the discharge electrode knocking means
is arranged in the lower region of the discharge electrode frame
and the discharge electrode frame is designed to converge in
this lower region. Without the necessity of modifying the
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housing of such an electric filter, the knocking means for the
discharge electrodes finds its place next to the converging
lower region of the discharge electrode frame.
The present invention will be explained in detail by means
of the enclosed drawings.
There show:
Fig. 1 a schematic view of an electric filter;
Fig. 2 a schematic embodiment of the internal structures of
an electric filter according to the invention;
Fig. 3 a detailed view of an embodiment of the coupling
between the drive of the collecting electrode knocking means and
the discharge electrode knocking means in enlarged scale; and
Fig. 4 a frame for combining a plurality of discharge
electrodes, in a schematic view.
Fig. 1 illustrates an electric filter 1 for cleaning dust-
laden waste gases A that are supplied from one side of the
electric filter 1. Usually, the components of the electric
filter 1 are accommodated in a housing G. The electric filter 1
consists of rows of collecting electrodes 2 which are usually
designed in the form of plates. Discharge electrodes 3 being on
a negative high voltage potential are arranged between the rows
of the collecting electrodes 2. Appropriate knocking means 4, 5
are assigned to the collecting electrodes 2 and the discharge
electrodes 3. The knocking means for the collecting electrodes
and the discharge electrodes comprise appropriate knocking
members 6 and 7 knocking on appropriate anvils 8 and 9 of the
collecting electrodes 2 or the discharge electrodes 3,
respectively, and effecting a flinging away of the adhering dust
layer.
The controlling of the knocking members 6, 7 of the
collecting electrodes 2 or the discharge electrodes 3,
respectively, is performed by appropriate drive devices.
Depending on the dust load, the cleaning is repeated at
different time intervals. In prior art, appropriate components
and drives are necessary both for the collecting electrode
knocking means 5 and for the discharge electrode knocking means
4, which increase the effort, the costs, and the overall size of
the electric filter.
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Fig. 2 illustrates a schematic view of the internal
structures of an embodiment of an electric filter 1 according to
the invention, wherein the drive device of the collecting
electrode knocking means 5 is formed by an appropriate drive
motor 11, a gear mechanism 12, and an appropriate drive shaft
13. At least one knocking member 6, in particular at least one
tumble hammer, is mounted on the drive shaft 13, and is rotated
appropriately on actuation of the drive shaft 13 and is forced
to knock on an anvil at the collecting electrodes 2, wherein a
plurality of collecting electrodes 2 may also be combined via a
connector bar 18 and may be cleaned jointly. In accordance with
the invention, the drive device of the collecting electrode
knocking means 5 is now coupled with the knocking member 7 of
the discharge electrode knocking means 4, so that the knocking
member 7 is adapted to be actuated via the drive shaft 13 of the
collecting electrode knocking means S.
The detail pursuant to Fig. 3 renders this coupling clearer.
Accordingly, the drive shaft 13 of the drive device of the
collecting electrode knocking means 5 is actuated during
cleaning, and the pertinent knocking member 6 for the collecting
electrodes 2 is rotated and dashed on the pertinent anvil 8 for
the collecting electrodes 2. An insulated actuator 14 is
arranged at the drive shaft 13 and actuates the knocking member
7 for the discharge electrode knocking means 4. A roller 15
rolling off at the appropriately designed knocking member 7 may
be arranged at the insulated actuator 14. Thus, the knocking
member 7 of the discharge electrode knocking means 4 is actuated
and dashed against an appropriate anvil 9 at a connector bar
combining a plurality of discharge electrode frames 19.
In accordance with the invention, an extra drive for the
discharge electrode knocking means 4 is hence not required. The
knocking member 7 of the discharge electrode knocking means 4 is
actuated through the insulated actuator 4 arranged at the drive
shaft of the collecting electrode knocking means 5.
Fig. 4 illustrates an embodiment of a frame 16 combining a
plurality of discharge electrodes 3. The frame 16 is provided in
the lower region with an indentation 19 in which the appropriate
drive device for the collecting electrode knocking means 5 may
be arranged. The result is an electric filter 1 having outer
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dimensions that are smaller than those of electric filters with
conventional cleaning.
The present invention is of advantage in particular with
smaller electric filters for biomass combustion in the output
range of 0.3-3MW.
