Dust filter with filter sleeve, emission electrode and collecting electrode

DUST FILTER AND FILTER HOSE, SPRUHELEKTRODE AND PRECIPITATION ELECTRODE

The invention relates to a dust filter according to the preamble of claim 1.

Staubhaitige gases occur in many areas of industry, for example in wood processing, in the particleboard and fibreboard industry, metallurgical industry, in foundries, the construction industry or in metal production on.

To clean the dust-laden waste gases is the use of various filters, such as fabric filters or electrostatic precipitators, common. The fabric filters are usually made ​​of filter bags with a closed end of the tube, which are usually the outside surface of the raw gas and in which the clean gas escapes at the open end of the hose. The filter bags are made ​​of a suitable tissue, remain on the stick the impurities. The dedusting. such filter bags is done by compressed air pulses of short duration. During the cleaning of the gas flow in the filter cloth is reversed and the adhering dust cake is cleaned off by the swelling of the hose and the resulting acceleration and by the flushing action of the compressed air stream. Depending on the nature of the impurities and the bag filter used, the cleaning also gently with low pressure purge air, which is blown into the interior of the filter, take place. The during the cleaning slung from the filter hose particles slide between filter hose in the filter housing downward and are for example collected in a dust collection hopper and transported via a discharge screw in a container for disposal or recycling. In addition to the cleaning of bag filters with scavenging air or compressed air, a cleaning by a shaking of the filter bags is common.

Once in fabric filters a plurality of filter tubes is arranged vertically side by side, slung from dedusted bag filter dust particles are often reabsorbed by adjacent filter hose. Moreover it can not be thrown far enough from the filter hose especially fine dust in the cleaning phase and therefore deposited immediately on the tissue. This is reinforced by the transition from the cleaning phase for filtering phase happens very quickly. This places the of the filter bags thrown off dust directly, but ^'only indirectly down, for example, in the dust collection hopper. This results in a relatively high resistance of the fabric filter, which must be compensated by a low filter surface load.

In addition to fabric filters and electrostatic precipitators for separating particles from exhaust gases are common. With electrostatic precipitators also organic substances and odorous substances can be deposited with good effect in addition to solids. In electrostatic precipitator the dust particles are negatively ionized by charged with negative DC voltage discharge electrodes for the major part. The negatively charged dust particles migrate to the positively charged or grounded collecting electrodes and are deposited there over time in the form of a dust layer. Both the discharge electrodes, to which also form layers of dust, and the collecting electrodes are periodically cleaned off, for example by knocking and the falling dust, well fed as in the fabric filters, for example collected in a dust collection hopper and in containers of other disposal or recycling. In wet ESP, the cleaning by liquids which are directed to the electrodes on top of the filter arranged injectors and thus dissipate the impurities with the washing liquid takes place. In electric filters, the cleaning, as opposed to fabric filters is faster, since the problem of the accumulation of dust particles after cleaning the bag filter is not present here. In contrast, fabric filters have a higher degree of separation.

Filters are known which combine the advantages of electrostatic precipitators with the high separation efficiency of fabric filters. Such combinations of bag filters and electrostatic precipitators of tissue are called hybrid filter. For example, while the high-voltage electrodes of an electrostatic precipitator between the bag filters are arranged. However, this did not resolve satisfactorily the problem of .. Wiederanlagerns the dust to the bag filters after the dedusting

In order to improve is described in US 5 938 818 A proposes a hybrid filter, which are arranged a plurality of bag filters in a filter housing and moreover between individual arranged filter bag rows grounded electrode in plate form and high-voltage electrodes between the filter bag rows, having so an electrostatic field is built up on each side of each tube row. Dust particles passing through this zone will be collected on the grounded sheet-like electrode. Thereafter, the pre-cleaned gas flows through the fabric of the filter tubes into the interior, where it is further led to the pure gas outlet. By the electrostatic field and the corresponding distances between the filter tube, high-voltage electrode and collecting electrode, most particles are deposited on the collecting electrode. Only a small proportion of impurities is deposited on the outside of the filter clever marriage. By thus slowly growing filter cake on the fabric filter cleaning intervals can be made longer. When cleaning the filter bags, the particles are thrown into the zone between the Hochspannungseiektrode and the collecting electrode and thus transported to the collecting electrode and mostly not dressed again from the outside of the fabric filter. To improve the cleaning of the bag filter dedusting a two-stage pressure air pulse is used in addition, consisting of a first short pulse of compressed air of high pressure and a subsequent second longer pulse of compressed air of lower pressure. The collecting electrodes are accomplished by reversing the direction of the electric field between the electrodes. In addition, the cleaning of the collecting electrode by shaking or tapping can be improved. A disadvantage of this design is that the region between the emission electrodes and the filter hose is provided no crude gas flow and is covered by baffles in the inflow. The reason for this is that between the emission electrodes and the filter bags prevails no electric field and dust particles would reach from this area with no electric charge on the filter clever marriage. Said range is therefore not effective for the dust deposition.

The object of the present invention is to improve the filtering effect further by the dust separation is increased. The disadvantages of known systems are to be avoided or at least reduced.

the object of the invention is achieved in that the Seen filter bag, the one emission behind the at least one collecting electrode is arranged at least. The term "behind" means that the spray at a greater distance from the filter bag as the collecting electrode by the filter hose. The electrodes need not aligned, but can also be offset against each other. The electric field in the ionized between the discharge electrodes and collecting electrodes dust particles migrate to the collecting surface and accumulate there in large part from. Those dust particles do not accumulate on the collecting electrodes, reach the filter bags and form on the tissue surface a dust cake. The deposited on the filter hose dust particles are ionized, however, which is supported in the cleaning of the filter hoses by compressed air pulses, the addition to the grounded Niederschlagselektrodeh. It is thereby avoided that especially the fine dust particles arrive immediately after the cleaning pulse back to the filter surface, thereby increasing the filter resistance. Giving a higher filter loads are possible, with a high dust removal. This affects especially with expensive filter media is positive, since the 'fabric filter can be kept much smaller. In contrast to known dust filters of this type, the effective area for dust collection of the dust filter according to the invention is greater, whereby the dust removal can be increased for the same or dust deposition, the filter can be built smaller.

Advantageously, the at least one filter bag, together with any arranged in the filter bag support basket are electrically isolated so that adhering to the filter bag fabric, not lose electrically charged dust particles their charge. The charge of the dust particles helps cleaning the filter bags, the movement of the same earthed towards precipitation electrode.

According to another feature of the invention provides that the at least one collecting electrode is tubular. This is the surface of precipitation electrode over known constructions^' substantially increased, whereby the frequency of cleaning of the collecting electrode can be reduced and a lower Dust filter bags follows.

According to another feature of the invention that several tubular collecting electrodes are adjacent to each other in a row and spaced from each other. Thus, the precipitation area is further enlarged. A sufficient distance between the collecting electrodes ensures a sufficient flow of gas in the filter.

Advantageously, in each case several filter tubes forming at least one filter bag row. Characterized the filter surface and thus the separation efficiency of the filter is increased.

If at least an electrostatic filter is arranged according to the invention on one side of each filter bag row, it is achieved that always have to go through the ionization zone formed by the electrostatic filter to clean gases before they reach the filter bags.

Advantageously, at least one Sprühelektode and between the at least one Sprüheletrode and each filter bag row at least one collecting electrode is arranged between two filter bag rows. Thereby, the cleaning of Schadstoffbeiasteten gases is substantially increased.

When disposed on the outer side of at least one of the outermost filter bag row at least one collecting electrode, which is effective for the dust removal of the filter can be further increased, whereby the filter effect is further increased. Advantageously, at least one collecting electrode is naturally arranged on the outer sides in outermost filter bag rows. Thus, the filter bag row between this or these collecting electrodes outside and the nearest discharge electrode located within an ionization zone, whereby the negatively charged particles mostly deposit in the cleaning of filter bags on the collecting electrodes.

According to another feature of the invention provides that the at least one collecting electrode is electrically grounded and is at least one discharge electrode on a negative DC voltage potential.

Advantageously, the at least one filter bag and or or at least arranged a collecting electrode substantially vertically. Thereby, the cleaning supported.

Advantage adhesive enough, the dusty gas flows essentially in the direction of the filter bag rows. However, it is convenient and advantageous to arrange before the outermost filter bag of each filter bag row in the inflow of the dust-containing gas a substantially vertical baffle. This baffle covers the filter bags and the surrounding collecting electrodes, so that the dust-prone gases is immediately forced into the established between the discharge electrodes and the collecting electrodes ionization and after passing through the ionization, the ionized dust particles which are not deposited on -the collecting electrodes to the filter Hoses move on. The number and configuration of the baffles can be made arbitrarily according to the desired flow conditions.

The present invention is explained in more detail with reference to the accompanying drawings. Therein:

Fig.l is a plan view of a portion of a dust filter according to an embodiment of the present invention, during the filtering phase;

2 shows a plan view of the part of the filter according to Fig.l during the cleaning phase;

3 shows a multi-stage dust filter according to the present invention in plan view; and

4 is a partially sectioned side view of the dust filter according to Figure 3.

In Fig.l a three filter tubes 1 filter bag row 6 is shown. In addition to the filter bag row 6 an electrostatic precipitator or a electrostatic filter lane 3 is arranged consisting of the discharge electrodes 2 and precipitation electrode. 4 Advantageously 6 precipitation electrodes 4 are arranged on the other side of the discharge electrodes 2 and also on the other side of the filter bag row. The filter bags 1 and any disposed therein supporting baskets 7 are preferably electrically isolated. The

Collecting electrodes 4 are preferably made of vertically arranged and spaced tubes which are electrically grounded. The discharge electrodes 2 are connected to negative DC voltage level, whereby 4, an electric field is established between these and the collecting electrodes, in which the dust particles are ionized 5. The electric charge of the respective components of the dust filter is through the characters "+" and "-". The dust-containing gas is preferably flowed toward the filter bag row 6 to the dust filter. The direction of flow is indicated by arrows X. An upstream of the filter bag row substantially vertically disposed baffle 8, which has a horizontal extent on both sides of the filter bag row 6 arranged collecting electrode 4, the raw gas is forced into the present between the discharge electrodes 2 and the collecting electrodes 4 ionization where the dust particles are negatively charged , Most of the ionized dust particles 5 are deposited on the surface of the precipitation electrodes. 4 Only a small portion passes between the collecting electrodes 4 through it and is passed through the gas flow to the filter bags 1, where they are deposited on the outside of the filter bags. 1 The electric field between the emission electrodes 2 and the collecting electrodes 4 causes movement of the dust particles 5 in the direction of arrows A. Usually, there are a dust filter several filter bag rows arranged parallel to each other. In this case, a respective electric filter lane 3 is arranged between two filter bag rows 6, which consists of each of discharge electrode 2 and arranged on both sides of precipitation electrodes. 4

During the cleaning of filter bags 1 according to Figure 2 1 compressed air pulses are emitted into the open end of the filter bags, thereby increasing the filter bags 1 bloat and adhering thereto dust particles 5 B are moved in the direction of arrows. As the dust particles are ionized and 5, the filter bags 1 and any possible support cages are 7 electrically insulated, the dust particles are attracted by the collecting electrodes surrounding the filter bag rows 6 and stay on this stick. The electrical isolation of the filter bags 1 and of the cost cages 7 may also be no rollovers of the discharge electrodes 2 to the wires of the cages 7, whereby the fabric of the filter hoses 1 may be damaged. Due to the inventive arrangement of collecting electrodes 4 between the discharge electrodes 2 and the filter bags 1, the distance be significantly lower between the discharge electrodes 2 and the filter bags 1 as in known arrangements where no precipitation electrode is disposed between the emission electrodes and the filter hose. In this case, the distance of the discharge electrodes 2 must be to the filter hose 1 substantially larger than the distance of the discharge electrodes 2 to the collecting electrodes 4, otherwise come in too close together to flashovers of the discharge electrodes 2 to the wires of the cages 7 of the filter bags 1 would whereby -the fabric of the filter bags would 1 punctured. The fact that the filter bags are 1 subject to a lesser degree with dust particles 5, they must be cleaned only in larger "time intervals. The cleaning of the collecting electrodes 4 is preferably carried out by tapping and can also occur less frequently due to the opposite of a plate-shaped electrode increased surface . Compared to conventional hybrid filters, the present inventive filter arrangement has the advantage that a considerably higher filter load with a high dust removal is possible. the separation efficiency of electrostatic precipitators Gasse 3 can be substantially improved, since the flow rate in the electrostatic precipitator is low. Compared with the prior art, the present invention has the advantage that when cleaning the bag filter of the particulate matter not again have to go through the ionization zone to reach the precipitation surfaces, but passes directly from the filter hose to the collecting electrodes.

Figures 3 and 4 show a top view and a 'partially sectioned side view of an inventively constructed multistage dust filter in which two filter bag rows are shown 6, wherein the filter bag row left shown 6 in the filtering phase and the right filter bag row 6 is in the cleaning phase. As can be seen from Figure 4, located above the filter bags, the nozzles to deliver the pulses of compressed air for cleaning of the filter hoses 1. The compressed air is via respective compressed air lines 10, of which only a part is shown, respectively. During the cleaning, such as in the right part illustrates the pictures, an air pressure pulse is delivered through the nozzle 9, which is blown into the basket 7 is equipped with a supporting filter bag first This the bottomed tubular filter 1 inflated and the thereon dust particles 5 are B moves against the collecting electrode 4 in the direction of arrows. During the filtering phase, as shown in the left part of the image, the cleaned gas flows in accordance with arrows Y through the open end of the filter bags into the clean gas chamber of the filter. The distance between two filter bag rows 6 can be made smaller in the present arrangement, because a larger area of ​​the filter for dust separation is effective.

The arrangement of the present invention constructed electric filter between the filter bag rows, depending on the number of filter stages and size of the treatment plant, be repeated as often.