ES2268407T3 - ELECTROSTATIC OPERATING FILTER AND PROCEDURE FOR SEPARATION OF PARTICLES FROM A GAS. - Google Patents

Abstract

The invention relates to an electrostatically operating filter for separating particles from a gas, comprising at least one electrode (4) connected to a high voltage source and at least one earthed or oppositely poled electrode (5) between which the gas charged with particles is guided. In order to improve the cleaning performance of the filter, at least one of the electrodes (4,5) is provided with a space (9) in which the particles can enter and in whose extension essentially no electric potential difference prevails. The invention also relates to a method for separating particles from a gas by means of an electrostatically operating filter.

Description

Electrostatic operating filter and procedure for the separation of particles from a gas.

The invention relates to a filter of electrostatic operation for particle separation from a gas, which has at least one electrode, connected in a high voltage source and at least one grounded electrode and polarized opposite, between which the gas can be conducted loaded with particles. Document DE 28 02 965 A publishes a electrostatic filter of this type.

On the other hand, the invention relates to a procedure for the separation of particles from a gas by means of an electrostatic operating filter.

Electrostatic operating filters of the type described at the beginning are known, for example, from EP 0 847 806 B1. They are used for electrostatic separation of discretionary particles and droplets from different gases in many technical process processes, especially for the removal of dust from gases. In this case, the gas to be purified circulates through a register arranged in the form of steps of precipitation electrodes, each of which is essentially formed as a plate. At the center of each of the passages formed through the precipitation electrodes are spray electrodes. A high continuous voltage is placed between the spray electrodes and the precipitation electrodes, which is above the corona application voltage. In this way it is achieved that the spraying electrodes emit electrons, which are accelerated in the immediate environment of the high voltage spraying electrodes by virtue of the high electric field intensity that predominates there to such an extent that their kinetic energy is sufficient. to emit other electrons from gas atoms and / or neutral gas molecules and thus generate an electron cloud. On the way to the precipitation electrode (grounded), the intensity of the electric field is rapidly reduced, so that the kinetic energy of the electrons does not reach that limit value, in which the electrons are joined again through molecules of has or of gas atoms under the formation of gas ions
negative

These negative gas ions accumulate in the next course of the separation mechanism in a way preferred in dust particles and communicate to them of this way an electric charge, bringing dust particles charged in this way experience in the electric field a Acceleration force acting in the electrode direction of precipitation. There they accumulate in a layer of dust, through from which charge carriers flow to the electrode of grounded precipitation, agglomerate and in a way Preferred are purified through electrode vibrations, for example caused by tapping and are conducted through the gravity force of the dust accumulation device and of dust discharge.

A special type of construction of a filter electrostatic operation is described in DE 3 723 544 A1. Here is a "separation electrode structured "like precipitation electrode, which is placed opposite to the spray electrode. The structuring can be stamp differently. It always serves for mechanical bonding and the accumulation of separate dust particles electrostatically

In this type of construction is not provided dust extraction during filter operation outside of the system. The evacuation of the dust is done through the combustion in the filter or through exchange or purification of the filter out of the filter operation.

If the structure formation elements of the separate electrode are placed in front of a plate closed metal, then it is formed inside the electrode of separation a field-free space that is not described, without However, in its dimensions, since it has no interest for the Separation electrode function. Conditioned by the construction, a Faraday cage is casually formed. For the function of this type of filter are porous elements decisive of structure formation, which must ensure a union and separate dust accumulation.

With the mentioned principle they can be separated into many applications dust particles and droplets of Different types from different gas streams. In this case, separation efficiency is greatly influenced through the particles, but also through the properties of gas The composition of the gas determines in a decisive measure the ionization capacity of gases and, therefore, the number of the gas ions, which is available for charging, that is, for The electrical charge of the dust particles. In the particles of powder is known especially the specific electrical resistance as essential property of the powder, since through this variable the amount of cargo carriers that flow to The precipitation electrode.

In a way independent of the conditions marginal, which occur through the properties of gas and dust, is always tried through proper regulation of the voltage source (HS aggregate), prepare the number of carriers possible and maximum load (current) suitable for a constellation determined. In this case, it is accepted that the flow maximum current also generates a turbulence that inhibits, in general, separation, a so-called electric wind.

For the avoidance of electric wind, the EP 0 847 806 B1 proposes a procedure, in which performs the loading of dust particles and their separation from according to the partial stage procedure technique decoupled In a first charging zone, they are electrically charged dust particles with the highest possible supply of load carriers - also tolerating high turbulence of the gas-. In a second zone connected then the zone of separation, charged dust particles are separated electrically in an electric field, whose voltage is found by below the corona application voltage. In this way, it prevents an excitation of the electric wind.

In filters that work electrostatically mentioned above, which are also designated as filters electrical, a relatively high energy expenditure is necessary to efficient separation of particles or droplets from the gas On the other hand, in general, the problem arises mentioned that the generated electric wind generates turbulence that inhibit separation. With high electrical resistance specific to the dust, the powder layer acts on the electrodes of precipitation increasingly as a limitation for the current and separation efficiency.

Therefore, the invention has the task of eliminate the above mentioned inconveniences and propose a electric filter and a procedure for its operation, which characterized by high separation efficiency with an expense reduced energy In addition, the appearance should be minimized of electric wind and the action to limit the specific electrical resistance of dust.

This task is solved through a filter electrostatic according to claim 1 or through the procedure for the separation of particles according to the claim 14.

Finally, as opposed to document DE 3 723 544 A1, the construction must be carried out in such a way that guarantees continuous or almost continuous extraction of particles separated during the ongoing operation of the filter.

The solution of this task through the invention is characterized in that the electric filter does not contain no spray electrode and electrodes (4, 5) are configured with a space (9) open at least at one end in its longitudinal extension, almost free of field, transformed into grid shape, in which particles can enter through of grille openings and can exit at the end open.

In this case, the employment of a spraying electrode, that is, of an electrode, in which through small radii or other geometric pointed endings extreme peaks of field strength are generated. Since then the electrodes of both polarities act as electrodes of precipitation or separation electrodes, it is necessary to distinguish, by therefore, in terms of the concept only still between electrode High voltage and grounded electrode. High electrode voltage can be in this case the positive electrode or the electrode negative.

According to a configuration, it is proposed in this case that only at least one electrode connected in the high voltage source, preferably all electrodes connected to the high voltage source, contain a space of this type. But it can also be provided that only at least a grounded electrode, in a preferred manner all grounded electrodes, contain such a space. By last, both at least one electrode connected to the high source voltage as well as at least one grounded electrode, with preference all electrodes, contain a space of this kind.

With advantage, this space is limited to less partially by means of a grid, a net or the like and by a separation plate, which are electrically connected each other in a conductive way of electricity, and form the electrode. The grid has entry holes for the particles

In this case, the grid, the net or similar represents a blockage of the projected surface of the electrodes (= surface of the separation plate) of maximum 10%. Of none way has the function of a mechanical separator or an accumulator for separate particles.

The almost field-free space, formed between the grid, net or similar and the separation plate, is configured in such a way that incoming particles are braked to the point that after the impact on the sheet of separation do not adhere over a prolonged period of time, but continually fall down and are unloaded.

The grid, the net or the like can be formed at from a number of bars connected to each other and arranged in parallel to each other, these being conductively connected in electricity with the separation plate configured in the form of license plate. But it can also be provided, for example, that the grid is formed by a number of rings connected to each other and arranged in parallel with each other, these being connected in a electricity conductor with a configured separation plate hollow cylindrical or cylindrical and forming the electrode.

The electrostatic operating filter can be configured as an "electric plate filter", in which a plurality of flat electrodes configured in the form of a cascade They are arranged in parallel with each other. In the same way it is It may be configured as an electric tube filter in the that at least two configured cylindrical or cylindrical electrodes gaps are arranged coaxially with each other.

For the improvement of particle discharge filtered it can be provided that at least one electrode present an exit channel for particles, which is adjacent to the space in large field-free electrically.

The procedure for the separation of particles from a gas by means of an operating filter electrostatic is characterized because the particles are deflected towards one of the two electrodes (4, 5) and because the particles they reach a space (5) transformed into a grid electrode, in whose extension no difference of electrical potential, and are separated there, the filter without a spray electrode.

It belongs to the characteristics of this type of filter that the electrodes that conduct high voltage and the grounded electrodes may be constituted of the same type As for the design. Between the electrodes it is formed, therefore, an electric field almost homogenous perpendicular to the direction of the circulation of charged gas particles - no peak of the field strength, as in the systems known so far with spray electrodes Unlike the types of construction of the electric filters known so far, the Particle separation from the gas can be performed from the same way in the electrodes of the two polarities.

The proposed procedure uses the action of an electric field between two electrodes on dust particles not ionized through technical installation or on particles of ionized dust selectively in a gas stream. The electrodes are in this case in a preferred way under a voltage, which is below the application voltage of crown. In this case, the particles in the electric field are deflected according to the polarity towards one of the two electrodes

The electric filter may be constituted as filter crossed horizontally by the current, in which uses a cascade electrode casing. Every second box-shaped electrode or is connected in this case in the high voltage source or is grounded or polarized in opposite way. In the same way, a type can also be provided construction, which leads to an electric filter of tubes or honeycombs crossed vertically by the current. Of the same way, the proposed principle can be applied to a filter wet electric.

The invention uses the circumstance that in the proposed electrode configuration with almost space field-free electrically dust particles can enter virtue of its kinetic energy in space, but in this space are not exposed to any other electrostatic force performance exterior and, therefore, are separated under the use of the force of gravity and are discharged continuously from the system.

In an advantageous way, the electric filter proposed has a capacity for particle separation and highly efficient droplets from a gas stream discretionary, being necessary only a reduced expense of Energy. The appearance of a wind is largely avoided electric.

In the case of fluid particles, the electrode purification is carried out in a way automatic, as described. Instead, if it's about particles with adherent or adhesive properties, you can perform the purification of the filtered particles from the electric filter walls and / or from the electrodes in a way known in itself through tapping of the electrodes, being made the fall of the particles in a predominant measure in Space largely field-free electrically. Agree with the properties of the particles, it is also possible to wash -that is, a wet filtrate- during operation.

The separation of the particles in the electrodes (between separating plates and grilles / bars / or similar, which form the electrodes) is also essentially a function of field strength, which predominates between the electrode High voltage and grounded electrode. The field line of maximum field strength is found, according to the polarity perpendicularly between the electrodes; this applies in principle also for known filters with separation plates grounded and for spray electrodes that found in high voltage potential. To increase effectiveness of the invention, it is intended to increase the distance between the electrodes of different polarity.

This is achieved because from the electrodes opposite polarity bodies are projected - by example wires - electricity conductors alternately, conductively connected with the corresponding electrodes, in the space between the electrodes. These bodies can be arranged in parallel or perpendicularly or inclined with respect to the direction of the circulation of the gases to be purified.

This results in maximum field strengths firstly between opposite bodies and electrodes and in second place between the bodies of different polarity. The maximum field strengths depend on the layout constructive and therefore can have different values and addresses. The angles between the maximum field strengths (body - electrode or body - body) can adopt all values between 0º and 180º.

The following drawings represent Examples of embodiment of the invention. In this case:

Figure 1 shows a representation in perspective of an electrostatic operating filter, which is configured as a filter that is crossed horizontally by the stream.

Figure 2 shows a representation in perspective of a tube filter crossed vertically by the stream.

Figures 3a, 3b show sections transverse through the filter electrodes; Y

Figure 4 shows a representation in perspective of a filter passage of a crossed filter horizontally by the current, whose electrodes are provided with field-free spaces and with additional bodies (here wire clamps).

An electric filter is shown in figure 1, which is suitable for filtering particles and / or droplets from the gas stream The gas contaminated with particles, which flows into the filter is provided with an arrow with the reference number 1. The gas stream circulates through the filter, being filtered  the particles that are in the gas and being discarded. The Outgoing purified gas stream is illustrated through the arrow with the reference sign 2. The particle current separated 3 leaves from the filter down.

For the purification of a gas stream greater is used a cascade of electrodes. How can you deduct from figure 1, a plurality of electrodes 4 and 5 in the form box are arranged parallel to each other. Between the electrodes 4, 5 steps 8 are present, through which the gas 1 to be purified. Electrodes 4, 5 or are connected to alternating form in a high voltage source (namely, the electrodes 4) or are grounded (namely electrodes 5).

In the exemplary embodiment according to the Figure 1, all electrodes 4, 5 are provided with a space not shown here, in which particles can enter filter, in whose extent there is no predominance, however, electric potential difference; therefore it is designated here as an almost field-free space electrically. This space is create at electrodes 4, 5 because the separation plate 7 is surrounded by a grid 6. The separating plate 7 and the grid 6 They are conductively connected to electricity. Grid 6 It consists of a plurality of parallel arranged bars each.

Gas charged with particles circulates first place between electrodes 4, 5 (see gas stream 1) and arrives there under the action of the almost homogeneous electric field. The particles are deflected in the direction of the electrodes and enter through the holes in the grid. In this way, it they find in the almost field-free space electrically, where they are no longer exposed to any electrostatic force performance Exterior. Due to the force of gravity they fall down and they can be removed continuously - during operation filter current - from the filter. The purified gas leaves the filter in horizontal direction through the output hood (see the gas stream 2).

The electrodes 4, 5 according to figure 1 show as an example the creation of free field space electrically through the grid 6 which is constituted by bars connected to each other, and that is electrically connected with the inner separation plate 7. The electrodes 4, 5 may be Modularly constituted and can be placed superimposed and arranged one after the other, as depicted in figure 1. In this example, the electrodes have a field-free space. on both sides of the separation plate. Marginal electrodes or in a single-pass filter for gas circulation, the electrodes may also be constituted in such a way that they have a free field space only on one side of the separation plate. In any case, the depth of space Field free conforms to extraction needs Continuous particles.

In figure 2 it is represented schematic an alternative configuration of this type of filter electric. In the example, only the grounded electrode 5 it contains the almost free space of field 9, which is delimited here by an annular grid 6 and by the cylindrical separation plate 7. The grid 6 is formed here by a plurality of metal rings arranged parallel to each other and joined together, being connected these conductive metal rings of electricity with the separation plate 7 and together form the electrode 5.

In all cases it is intended that for avoidance of the new entry of dust into the gas stream, it configure the field-free spaces 9 electrically as zones Quiet circulation. This can be achieved through the corresponding geometric arrangement of the grid bars or either of the grid rings and / or of a configuration corresponding of the gas inlet and gas outlet.

Figures 3a and 3b show some details for the configuration of electrodes 4, 5 with the sheet of separation 7, the grid and the spaces 9 almost free of field electrically defined in this way.

According to figure 3aa, the plates of separation 7 are configured in the form of a plate and are surrounded by bar-shaped grid elements, which form the grid 6. Between the separation plates 7 and the grid 6 the space is formed 9 largely field-free electrically at electrodes 4, 5. The filtered particles move in the direction of the arrow 3 (direction of the force of gravity) down and can be Remove from electric filter.

In figure 3b you can see a form of double wall realization of electrodes 4, 5 for the support of the discharge of the particles from the filter. The particles that are found in space 9 largely free of field electrically descend by virtue of the force of gravity down and are led through the guide plates and the Slots of the double wall separating plate 7 to a space protected intermediate arranged inside, namely in a channel download 10. There you can download without being influenced by the circulation of external gas from the electric filter.

The represented structure of the electrodes is you can provide in principle in a crossed electric filter horizontally and vertically by the current, being able to be used straight, curved, edged or round electrodes.

Electrode configuration and height of the tension are adapted to each other in such a way that produces no over-elevation of the electric field intensity, which leads to a crown or partial external discharges.

In figure 4 a fragment is represented as passage of an electric filter crossed horizontally by the stream. In front of the separating plate 7 are inserted the 6 grids, which are formed here by wire clamps. Between the grids 6 the bodies 11 are shown. Here they are formed by wire clamps, which are connected in a way conductive with the respective electrodes (4, 5). In the construction represented, straight wires are arranged perpendicular to the gas stream. The bodies can be also arranged in parallel to the gas stream or in all angles between vertical and parallel to the gas stream. These possible arrangements of the bodies (for example, rings of wire or wire spirals) can also be transferred to tube shaped electrodes.

List of reference signs

one

Gas tributary contaminated with particles

2

Gas purified outgoing

3

Current out of the particles separated

4

Electrode that is in connection with a high voltage source

5

Grounded electrode

6

Grating

7

Lock from separation

8

Steps between the electrodes

9

Largely free field space electrically

10

Channel download

eleven

Electrode body

Claims (15)

1. Electrostatic operating filter for the separation of particles from a gas (1), which has at least one electrode (4) connected to a high voltage source and at least one electrode (5) grounded or polarized opposite, between which can carry the gas charged with particles, characterized in that the electric filter does not contain any spray electrode and the electrodes (4, 5) are configured with a space (9) transformed into a grid, almost free of field, open in its longitudinal extension at least at one end, in whose space the particles can enter through the holes of the grids and can exit through the open end. 2. Electrostatic operating filter according to claim 1, characterized in that the grounded electrodes may be constituted as to the design of the same type as the electrodes that conduct high voltage. 3. Electrostatic operating filter according to claim 1, characterized in that the particles are continuously discharged from the electrode free spaces. 4. Electrostatic operating filter according to claim 1, characterized in that only at least one electrode (4) connected to the high voltage source, preferably all electrodes (4) connected to the high voltage source contains (n) a space (9) almost free of field. 5. Electrostatic operating filter according to one of claims 1 to 3, characterized in that only at least one electrode grounded or polarized opposite, in a preferred manner all electrodes (5) contain (n) a space (9) of this type. 6. Electrostatic operating filter according to one of claims 1 to 3, characterized in that at least one electrode (4) connected to the high voltage source as well as at least one electrode (5) grounded or polarized opposite, with Preference All electrodes (4, 5) contain such a space (9). 7. Electrostatic operating filter according to one of claims 1 to 6, characterized in that the space (9) is partially delimited through a grid (6), a network or similar structure, which is open for the passage of the particles, presenting only a narrowed narrowing of the cross section and which is conductively connected to the separation plate (7) and forms the electrode (4, 5) with it. 8. Electrostatic operating filter according to claim 7, characterized in that the grid (6) is constituted by a number of bars connected to each other, arranged in parallel, these bars being conductively connected with a separation plate (7) configured in the form of a plate and forming with it the electrode (4, 5). 9. Electrostatic operating filter according to claim 7, characterized in that the grid (6) is constituted by a number of rings arranged in parallel with each other, connected to each other, these being conductively connected with an electric plate separation (7) configured cylindrical or hollow cylindrical and form with it the electrode (4, 5). 10. Electrostatic operating filter according to one of claims 1 to 8, characterized in that it is configured as an electric plate filter, in which a plurality of electrodes (4, 5) configured in the form of a plate are arranged parallel to each other. 11. Electrostatic operating filter according to one of claims 1 to 7 or 9, characterized in that it is configured as an electric tube filter, wherein at least two electrodes (4, 5) configured hollow cylindrical or cylindrical are arranged coaxial between yes. 12. Electrostatic operating filter according to one of claims 1 to 11, characterized in that at least one electrode (4, 5) has a discharge channel (10) for particles, which is adjacent to the space (9). 13. Electrostatic operating filter according to one of claims 1 to 12, characterized in that bodies (13) are arranged with alternating polarity in the space between the electrodes, which are conductively connected to electricity in accordance with their respective polarity with one of the two adjacent electrodes (4, 5). In this case, the bodies are at all angles between 0 ° and 90 ° with respect to the direction of gas circulation. 14. Procedure for the separation of particles from a gas (1) by means of an electrostatic operating filter, which has at least one electrode (4) connected to the high voltage source and at least one grounded electrode (5) or opposite polarized, between which the gas charged with particles is conducted, characterized in that the particles are diverted to one of the two electrodes (4, 5), and because the particles reach a space (5) of the transformed electrode in the form of grid, in whose extension no difference in electrical potential predominates, and they are separated there, the filter being operated without a spray electrode. 15. Method according to claim 14, characterized in that at least one electrode (4) connected to the high voltage source is supplied with a voltage, which is below the corona application voltage.