DE1239277B - Process for the separation of mists and solids from gases by means of wet pipe dust collectors - Google Patents

Description

GERMAN ^ / »W PATENT OFFICE

EDITORIAL

German KL: 12 e - 5

Number: 1239 277

File number: M 52608III / 12 e

1 239 27T filing date: April 21, 1962

Open date: April 27, 1967

When cleaning gases containing fine dust, which usually contain condensate in the form of mists, the electrical space charge phenomena have a detrimental effect on the degree of separation of the electrostatic Dust extractor off. If cleaning takes place in electrostatic tubular wet dust extractors, then it does the space charge is particularly noticeable.

The tubular wet dust extractors used in practice have spray distances of, for example 115 mm with tube diameters of about 240 to 250 mm. The spray electrodes are, for example Rods with a triangular cross-section (see British Patent 499 576), assembled Strip elements in saw blade form (see. British Patent 428 471) or rods with star-shaped Cross-sectional area used by screwed-on longitudinal strips (see US Pat. No. 1333 790). The round wires or rods that were frequently used in the past do not guarantee a good charge of the fine ones Dusts. By placing spray tips on these round wires (see US Pat. No. 2,505,907) one tries to improve the spray effect. All of these measures do have an improvement in the Particle charging causes, at the same time, considerable space charge formation in wet tube dust extractors increased, whereby the separation efficiency of these filters are worsened.

If a dust or condensate-containing, preferably mist-containing gas flows z. B. from bottom to top through the tubes of a single-stage wet dust extractor described above, strong space charges arise in the lower part of the tubes due to the high concentration of mist or meshed fine dust particles, which significantly disrupt the separation process. These space charges have the effect, for example, that the current-voltage characteristic, based on a tube element, is different for the lower part than for the upper part. With regard to the electrical conditions, the voltage supply of such a separator will then have to be selected in such a way that one section of the separator (for example the upper half) is at a disadvantage compared to the other (lower half). Optimal separation cannot be achieved with such an arrangement. In normal operating cases, electrostatic tubular wet dust extractors of the type described above are operated with direct voltages of at least 40 kilovolts. In practice, the gas velocities are preferably 0.3 m per second because of the special type of electrode fastenings and because of the strong space charge phenomena. Higher gas velocities, as in the case of mist separation processes
and solids from gases by means of
Tube wet dedusters

Applicant:

Metallgesellschaft Aktiengesellschaft,
Frankfurt / M., Reuterweg 14

Named as inventor:
Heinrich Möbus,

Dipl.-Ing. Otto Güpner, Offenbach / M .;
Josef Müller, Frankfurt / M .;
Dr.-Ing. Kurt Ruckeishausen, Offenbach / M .;
Dr.-Ing. Dietrich Ertl, Koenigstein (Taunus);
Dipl.-Ing.Werner Möbus, Kronberg (Taunus) -

For example, with electrostatic dry dust extractors to avoid flashovers (see US Pat 1 941 861) have been found to be unsuitable. To the electric To give the field time to break down the space charges, the speeds were much slower proposed, however, because of the given gas flow rates and the required large Filters are difficult to implement.

According to the invention, a method for the separation of mists, preferably acidic Mists, and solids from gases by means of electrostatic tube wet dedusters proposed. This inventive method is characterized in that the gases to be cleaned with high Speed, preferably 5 to 15 m per second, through the acting as collecting electrodes Tubes with pipe diameters of, for example, 100 to 120 mm are passed through, the are equipped with appropriately rigidly attached spray electrodes that the distance between the spray electrode to the collecting electrode is 20 mm.

As a further development of the invention, the spray electrodes consisting of tubes are applied to their circumference preferably with rectangular spray tabs arranged vertically offset in a helical manner equipped and by means of the lower guide devices over water-repellent insulators on the housing carried. The arrangement is expedient in such a way that the individual spray flaps are below them and neighbors above are offset by an angle of 60 °. In this way

709 577/309

it is achieved that only every sixth spray rag has the same position and direction (with a Height difference) like the first one.

The device according to the invention for carrying out the method comprises a tubular wet dust extractor, in which a bottom is arranged under the tubes, the holes of a diameter equal to the tube diameter, which is centered on crater-like elevations in the ground a few millimeters below the tube openings.

It is also within the scope of the invention to expand the tubes at their lower end in a funnel shape, the funnel-shaped, in cross-section square parts at the corners of their lower Opening with right-angled, triangular-shaped drainage surfaces pointing vertically downwards are provided.

As a further feature of the invention it is proposed that for the deposition of arsenic Fog and solids the gases in the tubular wet dust extractor according to the invention are indirectly cooled will. This cooling can take place in cocurrent, countercurrent or crosscurrent.

As a result of the high gas velocity in the process according to the invention and the very low Spray distances as well as the special spray electrode devices according to the invention occur A number of advantages over the conventional, prior art method. The high gas velocities cause strong turbulence in the individual tubes in turn, experience has shown that it promotes good, uniform ionization of the gas. With a gas flow direction in a tubular wet dust extractor, for example, from top to bottom is due to the high gas velocity an additional conveying effect on the precipitated on the tube walls draining condensate achieved, which increases the cleaning effect for the tubes with respect to adhering Dust caused by the rapidly draining condensate.

Furthermore, when using the tubular wet dust extractor as an indirect heat exchanger through the high speed increases the heat transfer on the gas side. Because of the low Spray distances, which are preferred in the method according to the invention, can be used in place of of the high-voltage units used up to now with secondary voltages of 40 kilovolts and above Aggregates are chosen with only 16 to 18 kilovolts. With the same current density, considerably cheaper units are used than those for arrangements according to the prior art necessary. In addition, at (assumed for comparison) initially the same space charge as at conventional tubular wet dust extractors because of the small distance from the tube wall to the spray electrode their influence is significantly less than with the usual constructions. Due to the considerably higher Spray effect - sharp edge on high voltage a few millimeters in front of a smooth surface - and that is considerable higher field strength, the space charge influence is largely reduced, or the space charge is largely eliminated by instant knockdown.

Especially when cleaning acidic gases, for example for the production of contact

sulfuric acid, the problem was to remove acid mist and, above all, often in the finest form arsenic compounds, which are contact poisons, should be separated as much as possible.

As tests have shown, this succeeds with good success in the method according to the invention and using the arrangement according to the invention.

While with the earlier design only the desired freedom from arsenic can be achieved, if there is already freedom from fog, whereby this freedom from fog can only be achieved by connecting two in series Electrostatic precipitator is achieved according to the new method and with the invention The device achieves this desired cleaning with one stage of the tubular wet deduster. This fact represents a significant technical simplification.

The production of the spray electrodes, for example in the extrusion process, is expediently done by that tubes with continuously arranged longitudinal ribs, preferably six at equal intervals distributed over the circumference, extruded. After that, the longitudinal ribs are down to the desired Spray rag removed by cutting. The helical arrangement of the spray tabs has the advantage that the spray effect does not directly affect the edges and corners of a spray rag any spray rag above or below it is disturbed, but becomes full with each spray rag can unfold.

A b b. Fig. 1 shows a section through a single field electrostatic tube wet dust extractor;

A b b. Figure 2 shows a single spray electrode that

A b b. 3 shows a cross section through the spray electrode of A b b. 2 along the section line II-II;

A b b. 4 shows a view of the lower intermediate floor necessary to collect the condensate, which is shown in Fig. 1 in section; finally shows

A b b. 5 a tube with a drain device at the lower end and

Fig. 6 shows an oblique plan view of this.

In A b b. 1, the gas to be cleaned enters the tubular wet dust extractor, the housing of which is denoted by 2 , at 1. The tubes 4 are embedded in the intermediate floor 3, 3 '. The spaces 5 between the precipitation tubes 4 serve to receive the cooling liquid can wash around both in cocurrent, countercurrent or cross-current tubes. 4 To increase the flow rate and the heat transfer, the spaces 5 can be filled with fillers 6, such as balls, coarse-grained material, Raschig rings and the like. The spray electrodes 7 according to the invention with the spray tabs 8 attached are carried at their upper end on guides 9 via rods 10 on insulators 11 . At their lower end are the spray electrodes? guided in a guide device 12 and spaced from the housing wall via an insulator 13. The spacing device is preferably made of water-repellent plastic or is coated with such a material. The withdrawal of the clean gas and the supply device for cooling liquid are not shown for the sake of simplicity.

Under the tubes 4, at a distance of a few millimeters, an intermediate floor 14 is arranged, the holes 15 of the same diameter as the raw

Claims (5)

having diameter. These holes are located on crater-like elevations 16 (see FIG. 4 in particular), which are attached centrally under the openings of the tubes so that the gas flow can pass through the intermediate floor 14 without interference. It is also possible to have the edges of the holes 15 protrude into the tubes 4 by a few millimeters. The condensate flowing down the tube walls, which follows the slightly outwardly curved edge surface of the tubes at the end thereof, is collected on the bottom 14 in the depressions between the crater-shaped elevations and discharged through openings 17 via drainage channels 18 into the bunker 19. At 20, the resulting sludge can be removed from the electric gas cleaner. It is also possible, instead of the intermediate floor 14, to design the lower opening of the tubes 4 in such a way that the tubes are widened in a funnel shape at their lower end in such a way that the funnel-shaped part 21, which is square in cross section, has right-angled corners at its corners is provided in the view triangular drainage surfaces 22. See Figures 5 and 6. The condensate that flows down the tube walls follows the sloping surfaces of the funnel-shaped part 21 and is thereby led away from the area of influence of the spray electrodes. It can drip down at the drains 22 without disturbing the electric field, or it can be collected in gutters. This device and the inclusion of an intermediate floor 14 have the common advantage that the disruptive effect that often occurs with electrostatic tube wet dedusters, namely that the draining condensate at the lower end is drawn to the spray electrodes as a result of the electric field, is excluded . To carry out the method, the tubes 4 can preferably have a length of approximately 4 m. By reducing the diameter of the tubes, greater stability is achieved with the same wall thickness as the conventional ones. FIG. 2 shows a piece of a spray electrode 7 with spray tabs 8 attached. With a material thickness of the spray flaps of about 2 mm, their heights are, for example, 20 mm and their lengths are preferably 25 mm with a distance from one another of about 5 mm. With the electrode according to the invention it should be noted that each spray rag reaches its full spray strength undisturbed at a given voltage applied, since, as mentioned, its two neighbors are preferably each 5 mm away from it in height and at an angle of with it horizontally each preferably form 60 °. If you cut the electrode in Fig. 2 along the section line in II-II, you get the picture as shown in A b b. 3 is shown. With tube diameters of approximately 100 mm and with diameters of the actual spray electrode 7 of approximately 10 mm, a spray distance of approximately 20 mm is achieved with the specified lengths of the spray tabs. To increase the stability of the collecting electrodes, it is within the scope of the invention to make the core of the lead pipe from steel. The described advantages, which the method according to the invention and the device according to the invention have, consist mainly in the considerably higher cleaning effect compared with methods and arrangements according to the prior art. Tests have shown that with the same degree of purification, the total precipitation area can be roughly halved compared to the known arrangements, i.e. that the cost of materials according to the invention is about half less. Patent claims: 1. A method for separating mists, preferably acidic mists, and solids from gases by means of electrostatic tube wet dedusters and optionally indirect cooling of these gases, characterized in that the gases to be cleaned at high speed, preferably 5 to 15 m per second, through the Acting as collecting electrodes tubes with pipe diameters of 100 to 120 mm, for example, are passed through, which are equipped with appropriately rigidly attached spray electrodes that the voltage distance spray electrode to collecting electrode is about 20 mm. 2. Apparatus for performing the method according to claim 1, characterized in that the spray electrodes (7) consisting of tubes are preferably equipped on their circumference with rectangular, vertically helically offset spray tabs (8) and by means of the lower guide devices (12) via water-repellent insulators (13) on the housing (2). 3. Apparatus according to claim 2, characterized in that under the tubes (4) a base (14) is arranged in the electrostatic tube wet dust extractor, the holes (15) having a diameter equal to the tube diameter, which on crater-like elevations (16) are arranged centrally in the floor a few millimeters below the tube openings. 4. Apparatus according to claim 2, characterized in that the tubes (4) are funnel-shaped widened at their lower end in such a way that the funnel-shaped, square in cross-section parts (21) at the corners of their lower opening with perpendicular downward-pointing right-angled, in Triangular drainage surfaces (22) are provided in the view. 5. Operation of electric tubular wet dust extractors, preferably for the separation of arsenic-containing mists and solids from gases according to claims 1 to 4, characterized in that the gases in the wet dust extractors are cooled indirectly, the cooling being carried out by means of cooling liquid. Documents considered: German Auslegeschrift No. 1013 626; U.S. Patent Nos. 1941861, 2,505,907, 790; British Patent Nos. 499 576, 428 471. 1 sheet of drawings 709 577/309 4.67 © Bundesdruckerei Berlin