EP1769851A1 - Electrostatic precipitator - Google Patents

Abstract

An electrostatic filter unit (2) for removing particles from a gaseous fluid sucked into a gas turbine comprises a vertically arranged tube electro-filter (20) and at least one additional textile filter (22) arranged after the electro-filter. Preferably the electro-filter comprises needle-shaped ionizing electrodes that produced overlapping ion beams to ionize the particles. An independent claim is also included for a gas turbine comprising the above filter.

Description

The invention relates to a filter device for separating particles from a gas fluid aspirated by a gas turbine and a gas turbine with such a filter device.

In a gas turbine, a compressor from the surrounding air sucks, compresses and directs them to a combustion chamber of the gas turbine. There, the air is burned together with a supplied fuel, resulting in hot combustion gases. The combustion gases flow at high speed into a turbine which is driven therewith.

When sucking the air from the environment of the gas turbine compressor, it is unavoidable that dirt particles are introduced into the compressor with. The dirt particles can sand grains, insects, pollen, dust of different chemical composition u. Ä. Have. In the compressor, they encounter rotating parts, which can lead to unwanted reactions. These include erosion or corrosion of compressor blades, deposits on the compressor blades and other parts inside the compressor, or agglomerations and chemical reactions of the supplied foreign bodies with each other.

In order to reduce such effects in their effects, usually the sucked air is filtered before entering the compressor with a textile filter. With the currently available textile filters, a very effective filtering can be achieved, so that hardly any dirt particles can penetrate into the interior of a compressor. When using such filters, however, there is the fundamental problem that with increasing filter effect, a pressure loss is accompanied, so that always a compromise between filter efficiency and efficiency of the gas turbine must be concluded. In addition, it has been shown that in humid ambient air, for example, due to fog, the particles of dirt retained in the filter become moist, they clump together, and thus the Air permeability and efficiency of the filter is limited, whereby an additional pressure loss in the compressor is unavoidable. Especially at temperatures below 0 ° C, the operation of a textile filter can be problematic, since forming a wet surface of the filter ice, thus a flow passage is significantly hampered and a gas turbine is only partially operable. To prevent these effects, usually the textile filters used are regularly replaced with new and clean filters, to achieve a long life of the gas turbine, the associated compressor including the compressor blades are cleaned several times a year. Since in this case the gas turbine, which is usually in operation without interruption, must be switched off and power generation by the gas turbine is thus interrupted, such maintenance measures are complex and expensive.

The invention is therefore an object of the invention to provide a filter device of the type mentioned above, which has a low pressure loss between the input and output side of the filter device at a high filter effect, so that a high gas turbine performance is achievable, this being both dry and should be possible in humid ambient air. In addition, a time-consuming maintenance and cleaning of the filter device should no longer be necessary.

This object is achieved in that the filter device for separating particles from a gas fluid aspirated by a gas turbine has a vertically arranged pipe electrostatic filter. In such a filter dirt particles are electrically charged in the gas fluid and transported by the action of electrical forces to an electrode on which they are deposited. Since the gas fluid no longer needs to flow through any meshes of a textile filter, this filtering is coupled with a low pressure loss between the inlet and outlet sides of the filter device, so that even large gas fluid streams can be efficiently filtered. The charging of dirt particles succeeds even with moist gas fluid, so that can be achieved on the output side of the filter, a dry fluid. Thus, the frequency of maintenance operations for cleaning compressor blades and the like will become less frequent. a. significantly reduced, and the erosion and corrosion of compressor blades is reduced. Due to the low pressure loss, a compressor can be sized smaller and a larger gas turbine performance can be achieved.

In a preferred embodiment of the invention, the tubular electrostatic filter of the filter device for ionization of the particles in the gas fluid needle-shaped sputtering electrodes, which generate overlapping ion beams. This can generate a strong turbulence of the ion beams, slowed down by the dirt particles in the gas fluid and effectively to one for the deposition provided electrode can be transported. This makes it possible to achieve a high deposition rate of the dirt particles.

It is advantageous if a voltage of greater than 130 kV is present between a positive and a negative electrode of the tubular electro-filter. Thus, a relatively large distance between the electrodes can be achieved, so that the pressure loss during the passage of the filter is even lower. In addition, larger tolerances for a deposited amount of dust on a collecting electrode can be allowed by the greater distance of the electrodes. This makes it possible to increase a time interval between individual cycles for cleaning such a filter. Furthermore, such a high voltage enables an even higher deposition rate and thus a very efficient filtering effect.

The tube electrostatic precipitator may comprise a filter cell having a honeycomb-shaped precipitation electrode for the deposition of the contaminant particles, wherein the precipitation electrode is arranged around the ejection electrodes. The honeycomb structure allows a self-supporting structure of the filter device, so that a lightweight construction can be achieved. This reduces the manufacturing costs of the filter device according to the invention.

Preferably, the filter device is provided with a tubular electrostatic filter having 1, 3, 4, 7, 10, 16, 25, 36, 45, 55, 65 or 95 filter cells. The filter cells are arranged in parallel, so that can be filtered by such a modular design of the filter device very small to very large volume flows efficiently.

The filter device according to the invention is preferably designed such that a dry or wet cleaning of the electrodes can be carried out in the tubular electrostatic filter. Thus, depending on the availability of cleaning media, a suitable cleaning of the electrodes can be carried out. If a dry cleaning of an electrode is provided, according to the invention, this cleaning is preferably carried out by a mechanically induced vibration of the electrodes. This can be done for example in such a way that the electrodes hit impact tools regularly, whereby the dust is released from the electrode surfaces and drops. If the operating voltage is briefly lowered during knocking, the cleaning can be improved. For wet cleaning, the electrodes are, for example, sprayed with water and the resulting sludge flushed out.

In a further embodiment of the invention, the filter device has at least one additional filter, which is connected downstream of the tube electrostatic precipitator. This may be a plate electrostatic filter with relatively narrow lanes intended for dry gas fluid. The additional filter takes over a "monitoring function", so that there is additional security with regard to a low entry of dirt particles into the compressor in the case of possibly not well filtered gas fluid through the tubular electrostatic filter.

As an additional filter and a textile filter can be provided. This is advantageous because the contamination of the textile filter can be reduced to a minimum by the upstream tubular electrostatic filter, so that the hitherto known difficulties, such as frequent maintenance, no longer occur in a textile filter downstream of the tubular electrostatic precipitator. After passing through the tubular electrostatic precipitator, a moist gas fluid has already been freed from moisture to such an extent that no clumping or clogging of filter meshes occurs in the textile filter. This is also advantageous when operating the filter in winter, because the dirt particles on the textile filter can not freeze and a passage of gas fluid is no longer blocked. The textile filter is also advantageous because it can be operated without the supply of electrical energy, so that sufficient energy can still be obtained for a limited time when the electrical energy that is not present can be reached.

The invention further relates to a gas turbine with a compressor, a combustion chamber and a turbine, wherein the gas turbine has a filter device, as has been previously described.

Figur 1:

eine schematische Darstellung einer ersten Gasturbine mit einer erfindungsgemäßen Filtervorrichtung;

Figur 2:

eine schematische Darstellung einer zweiten Gasturbine mit einer erfindungsgemäßen Filtervorrichtung;

Figur 3:

eine Draufsicht einer ersten Ausführungsform der erfindungsgemäßen Filtervorrichtung mit einem vertikalen Rohrelektrofilter, und

Figur 4:

eine Draufsicht einer zweiten Ausführungsform der erfindungsgemäßen Filtervorrichtung mit mehreren Filterzellen.

The invention will be further described with reference to embodiments shown in the drawings. Show it:

FIG. 1:

a schematic representation of a first gas turbine with a filter device according to the invention;

FIG. 2:

a schematic representation of a second gas turbine with a filter device according to the invention;

FIG. 3:

a plan view of a first embodiment of the filter device according to the invention with a vertical Rohrelektrofilter, and

FIG. 4:

a plan view of a second embodiment of the filter device according to the invention with a plurality of filter cells.

FIG. 1 schematically shows a gas turbine 100. From a compressor 3, air 1 is sucked from the outside and passes through a filter device 2. The filter device 2 has in this embodiment, a tubular electrostatic precipitator 20 and a downstream textile filter 22, which are shown in Figure 1 only schematically. The tubular electrostatic precipitator is intended to provide, in a first stage filter, high filtration, even from a humid gas fluid, e.g. To reach air. The downstream textile filter is thus supplied dried air, so that clogging of dirt particles does not occur and a good air passage is given. The filtered air enters the compressor 3 and is compressed there until it exits at its outlet as compressed air 4 again. There it is passed to a combustion chamber 5, where it is burned together with a supplied fuel 7. This produces combustion gases 8, which are passed to a downstream turbine 9 and drive the turbine. The flow energy of the combustion gas 8 is partially converted to mechanical energy by driving the compressor 3 and a generator 12. For this purpose, the compressor 3 and the turbine 9 as well as the generator 12 are mounted on a common shaft 13. After passing through the turbine 9, the combustion gas 8 finally exits the turbine 9 as hot exhaust gas 10.

The efficiency of a gas turbine can be increased by using the heat of the hot exhaust gas 10. This is done, for example, in that the hot exhaust gas 10 is supplied to a recuperator 5 (heat exchanger), which preheats the compressed air 4 before it enters the combustion chamber 8, see Fig. 2. Thus, the amount of fuel supplied. 7 reduce, so that less energy is required to operate the gas turbine. Less hot exhaust gas 11 then exits the recuperator 5.

FIG. 3 shows a top view of a tubular electro-filter 20 which is used in the filter device according to the invention. The tubular electrostatic precipitator 20 has discharge electrodes 21 which project in a needle-shaped manner in the direction of the precipitation electrode 23 surrounding it. The sputtering electrodes are cathodically poled, so that when a voltage is applied by the sputtering electrode, electrons are emitted. They experience such a strong acceleration that, starting from a certain voltage, an ionization of the gasfluid surrounding and to be filtered by the discharge electrodes occurs. This ionization occurs well below the breakdown voltage.

On the way from the spray electrode to the precipitation electrode, the free electrons strike neutral gas molecules, so that gas ions and other electrons are formed by impact ionization. This forms an electron avalanche, which moves towards the collecting electrode. If the spray electrodes are close enough to each other, the gas ion beams 22 overlap, as shown in FIG. On the one hand, the gas ions strike the collecting electrode and release more electrons on impact. On the other hand, the gas ions deposit on dust particles and load them with it. Under the influence of the electric field between the electrodes, the charged dust particles are transported transversely to the flow direction of the fluid to the collecting electrode where they release their charges and deposit on their surface due to adhesive forces, so that a deposited dust layer 24 is formed (in Fig. 3 is only part of the collecting electrode surface is shown with a deposited layer 24). The entire flow moving from the spray electrode to the precipitation electrode is called an electric wind, which wind consists of negatively charged particles, neutral particles, electrons and ions. The achievable amperage depends inter alia on the dust content of the gas to be cleaned and the already existing dust deposits on the electrodes.

The deposition electrode should be designed such that to achieve a nearly constant electric field between a spray electrode and an associated deposition electrode, the distance between the electrodes is approximately equal.

In the embodiment of the tubular electro-filter shown in FIG. 3, the collecting electrode is honeycombed or formed as a hexagonal tube. This is advantageous in particular with regard to the joining together of a plurality of filter cells 25, see FIG. 4. This makes it possible to achieve a self-supporting structure of the filter device without a gap between the individual cells, which requires relatively little material and is nevertheless stable. The honeycomb structure makes it possible to achieve a larger or smaller passage area for the fluid to be filtered by combining a desired number of filter cells.

Claims (11)

Filter device (2) for separating particles from a gas fluid aspirated by a gas turbine,
characterized,
that the filter device (2) comprises a vertically disposed tubular electric filter (20). Filter device (2) according to claim 1,
characterized,
in that the tubular electrostatic precipitator (20) for the ionization of the particles in the gas fluid has needle-shaped spray electrodes (21) which generate ion beams which overlap one another. Filter device (2) according to one of claims 1 or 2,
characterized,
in that a voltage of greater than 130 kV is applied between a positive and a negative electrode of the tubular electrostatic precipitator (20). Filter device (2) according to one of claims 2 or 3,
characterized,
in that the tubular electrostatic filter (20) has a filter cell (25) with a honeycomb-shaped precipitation electrode (23) which is arranged around the spray electrodes (21). Filter device (2) according to claim 4,
characterized,
in that the tubular electrostatic filter (20) has 1, 3, 4, 7, 10, 16, 25, 36, 45, 55, 65 or 95 filter cells (25). Filter device (2) according to one of claims 4 or 5,
characterized,
in that a dry or wet cleaning of the electrodes can be carried out in the tubular electrostatic filter (20). Filter device (2) according to claim 6,
characterized,
that a dry cleaning of the electrodes by mechanically induced vibration of the electrodes is feasible. Filter device (2) according to one of claims 1 to 7,
characterized,
in that the filter device (2) has at least one additional filter which is connected downstream of the tubular electrostatic filter (20). Filter device (2) according to claim 8,
characterized,
that a plate electrostatic filter is provided as an additional filter. Filter device (2) according to one of claims 8 or 9,
characterized,
in that a textile filter (22) is provided as an additional filter. Gas turbine (9) with a compressor (3), a combustion chamber (5) and a turbine (9),
characterized,
in that the gas turbine (9) has a filter device (2) according to one of claims 1 to 10.

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