Ionizer and use thereof in an exhaust gas purifying installation for condensed humid and/or droplet-loaded gases

Translation of description of equivalent WO 2004033104 A1

Ionizer and its use in an emission control system for drip-laden and / or condensing moist gases

The invention relates to an ionizer in an emission control system for drip-laden, condensing moist gases.

The ionizer is used for charging of liquid and solid particles in process gases, is accordingly of a Nasselekt- rofilter or dry electrostatic precipitators talk.

In DE 101 13 582 an apparatus for electrostatic cleaning of gas is described, namely a wet electrostatic precipitator. The system is installed in the gas flow channel, in which the gas to be purified flows from the top of the plant. If the system is turned upside down so that the gas stream flows from bottom to top, it is observed that a film of water is pushed up from the lower nozzle member to the upper nozzle part and narrows the cross-section. This leads to flashovers, even before the high voltage reaches a value such that sufficient Ionisationstrom can flow. This effect occurs especially with condensing and dripping laden gases at speeds from about 3 m / s from the bottom up through the nozzle. In addition, it is observed that in addition, the negatively charged electrode means the virtually weightless at the edge of the floating water film takes bead inwardly and causing flashover.

In US 4,449,159 is a tapered cylindrical nozzle, a so-called Venturi described, which is horizontally oriented and into the electrode is immersed deep to the throat. The electrode pin carries the Ionisationsscheibe, flows on the periphery of the corona current through the gas to the anode. The thicker electrode pin serves as a focusing electrode.

In US 4,247,307, the vertical spray wires of a tube Naßelektrofilters be provided along the direction of flow with switched hintereinanderge- spray discs. These can be divided sawtooth tig circumferentially. Further, in US 5,254,155 a central Lance provided in a hexagonal tube with 6-pointed rings show their tips toward the corners of the hexagon tube. JP 2001198488 describes that alternating discs and 8-pointed stars are drawn to the central spray wire.

The horizontal venturi from US 4,449,159 is not suitable as a film of water is always drawn into the nozzle with or at lower speeds of water in the throat dripped from above onto the lonisatorscheibe and caused rollovers for Droplet denes, wet gas. The disc must be adjusted for uniform current distribution over the periphery closely. This is the harsh operating practically not feasible. Since the electrode pins have to be immersed in the nozzle, the assembly is complicated. The spray discs from US 4,247,307 have the task to enhance the ionization at its periphery, while the ionization along the wire becomes smaller. Through along the flow direction on the wire strung slices particle separation to be improved. The discs, connected to the increased ionization there, however, lead to increased turbulence and renewed transverse mixing, which in particular improves the finest droplets deposition. If the disk is circumferentially divided into many sawtooth ionizing, the additional ionization effect is only slightly, because the short distance in the same direction-charged zones repel each other. Otherwise, the relative to the gas flow direction, a series connection of Ionisationszonen not effective because particles that are already near the wall of the deposition electrode, are newly mixed by the turbulence and the electrical wind and ultimately the likelihood of deposition does not increase. In US 5,254,155 may be used instead of cylindrical tubes Hexagonal tubes and along the gas flow direction one behind the other switched 6-pointed rings so that one is faced with the same problem. For in JP 2001198488 Described the abovementioned arguments apply also, the object only in that 8-pointed stars, are alternately taken with slices differs. Experiments have shown that the gas velocity in the nozzle to

Values ​​below 3 m / s can be reduced while Durchmesservergroßerung and reducing the number of nozzles when the same electrode of a single peak on a multiple tip arrangement, for., 7-star-electrode is changed. If, for example, 1,600 cubic meters per hour, short Bm³/ H, therefrom sent wet gas by 166 conical cylinder nozzle with a diameter of 24 mm, the result is an average Dusen gas velocity of 5.9 m / s and a maximum voltage to the electrode of 9 kV and about 30 uA Ionisatorstrom per nozzle, corresponding to a total current of 5 mA. Pro Bm³/ H gas only about 0,028 watts Ionisatorleistung can thus be introduced. Due to the above-described effect of the ascending water films results from approx. 9 kV to rollover, which interrupt the ionization and charge the high-voltage power supply greatly.

Hence the task underlying the invention: an ascending at the Duseninnenwand water film to be prevented.

The consequence: is the Dusendurchmesser therefore enlarged, must at the same time the Ionisatorstrom who by now greater distance: needlepoint - becomes smaller Dusenrand are also greater because of the greater to be ionized gas volume.

The object is achieved by a Ionisatoraufbau according to the features of claim 1. Advantageous embodiments are described in the dependent claims 2 to the 7th Claim 8 finally claims the use of the ionizer in a special filter system: The ionizer is constructed so that the Dusenplatte is flown from the bottom and the high voltage electrode with their pins, each with a star at the free end in the gas stream behind it, ie above the Dusenplatte, sitting ; that is with exhaust gas streams from boilers, wash columns, filters etc, before entry into the chimney mostly the case. The incident flow parallel from bottom to top, circular ionization nozzles have a diameter such that the gas velocity under 4 m / s, but preferably less than 3 m / s remains. The height of a Ionisationsdüse is not substantially greater or, for convenience, just the same as the thickness of the nozzle plate. Besides a Randfase or edge rounding up and down, the nozzle in the flow direction on a profile. The electrode is located in the flow direction seen above the nozzle. The deepest part of the E- elec- trode is still above the highest point of the nozzle. The electrode is split in a star shape on the lower end, said pointing in the direction of the nozzle perimeter star points at the end horizontally or even diagonally facing down. The number of peaks is greater than 1, it is preferably uneven. The number of peaks is calculated so that the recoverable at the stable ionization ionization just is so great that per cubic meters per hour of gas flowing through the nozzle, an e lectric power from 0.01 to 0.5, preferably 0 , from 05 to 0.3 watts is consumed. The distance between the tips of the nozzle edge is determined by the stable ionization which results from the type of gas, from the absolute pressure and the absolute temperature (see description of the embodiment, there the distance 15 mm with flue gas with about 50% by volume of water vapor at 75 ° C and 1000 mbar and 13 kV).

To reduce the water deposit on the nozzle plate further, vertical drain tubes are inserted respectively in the imaginary center of gravity of each nozzle 3 in bores of the nozzle plate. The tubes look out below the nozzle plate about 1 to 10 plate thicknesses down. The catchment area of ​​the tube on top of the nozzle plate by about 5 - 30 ° extended funnel-shaped chamfer. The tube is preferably made of a smooth plastic aterial low wall adhesion, for example Polytetraflu- orethylen, PTFE.

With this structure and the Anströ clothes from the bottom up with, seen in flow direction, first the nozzle plate and then the elec- rode, prevents large amounts of water, the so-called

Drops surge, may fall from the top of the ionization and cause short circuits. By gravity opposite flow direction can only smaller drops swarms, which are endorsed by the flow reaching the nozzle plate. Again, the greater part thereof is deposited already on the nozzle plate and drains off downward.

While the flow from top to bottom mm-large droplets may fall on the nozzle plate, achieve the reverse flow case ^' the most present channel speeds from 0.5 to 2 m / s just drop sizes of max. about 0,1 - 0,3 mm, the nozzle plate. Due to the reduced gas velocity in the enlarged nozzle a water film on the inner edge of the nozzle is no longer pushed up, accumulated and drawn inwardly.

So far, each nozzle has been assigned to an electrode having a Ionisationsspitze. Now the die is associated with a central electrode having a plurality of star-shaped towards the edge oriented tips. This allows the nozzle for a higher gas throughput and for heavy ionized gases such. As air-water vapor mixtures, to operate so that nevertheless the required particle charging performance can be introduced.

At the end of the central electrode of the electrode star may be interchangeably mounted. If for changed operating conditions, z. B. Other temperatures,

Gaszusa pressures and compositions, the number of tips has to be adjusted, it is sufficient to replace only the electrodes star. With only one electrode tip, it would have been necessary before, to change the number of nozzles.

The nozzle must not be cut out of a thicker plate or composed by cylindrical, separately manufactured parts, but the slightly broader or rounded edge of a normal drilled or waterjet-cut metal plate is sufficient. The fact that the nozzle does not have a bead on the edge, can liquid which accumulates on top of the nozzle plate, simply drain through the nozzle downwards.

The central electrode is connected to the star electrode projects with the lowest point for about 3 - 6 mm above the upper edge of the nozzle plate addition. Therefore, the nozzle plate can be horizontally under the grid plate that holds the electrodes removed, which facilitates the installation and removal considerably.

The central adjustment tolerance of the central electrode is enlarged by the nozzle diameter correspondingly larger, so that arise particularly practical advantages in large-scale nozzle plates. Deposits at the nozzle edge effect, in relative terms due to the now larger nozzle diameter, a smaller distortion of the current-voltage characteristic.

By centrally between each 3 nozzle inserted into a bore of the nozzle plate flow tube ensures that liquid which accumulates on the plate surface, can also occur here. The inner diameter of the tube is chosen so that on the one hand flow through any significant amount of gas in the short circuit, but on the other hand, the accumulating water can drain freely. On the bottom of the nozzle plate from which I watch the tube, there is the advantage that preferentially accumulate here drooping drop on the tube, so the outside can drip down the tubes.

The ionizer is used in the flow channel of a filter system with a tube bundle separator, in such a manner as it is preceded by this in the flow direction. The / The ionizer in electrically charged, gas to be cleaned / air flows through the conical indented or lobed Anströmstirn of Rohrbündelabscheiders. The Rohrbündelabscheider is spatially so above the ionizer and has the conical concave or convex Anströmstirn therefore, so that the down-running in the separator water runs out at the end face towards the wall or toward the middle and is led away from there and does not drip on the ionizer, otherwise its electrical properties would be operational harmful impaired or eliminated.

The ionizer does besides cleaning of moist air / gas from drying processes and exhaust gases from combustion processes beyond the purification of course- or zwangsversetztem with droplet swarms wet gas, ie the gas to be purified is treated before entering the treatment plant already with droplet swarms due to the previous use process or is compulsorily so by spraying about projecting into the flow channel nozzle. A filter system constructed in this way cleans / washes thus even gas / air, / the gaseous pollutants, such as HC1, S0₂, S0₃, NOX, is offset.

An exemplary embodiment is described below with reference to the drawing. The drawing consists of the figures 1-3, which show in detail:

Figure 1 is a plan view of three immediately adjacent nozzles. FIG. 2 is a side view thereof, Fig. 3 shows the seat of the ionizer in the flow channel.

The installation of the ionizer is mechanically and in terms of insulation in the structure of the same illustrated and described 101 32 582, in DE.

The material for the electrode is determined by the gas to be processed and the therein constituents and their chemical reaction property. The material can, for example, copper or brass, each also coated with a protective metal, or stainless steel or titanium or alloyed titanium.

In vertically extending gas channel the electrically conductive plate 4 is horizontally installed. The holes 3, the nozzles are regularly arranged, in this case such that three directly adjacent bores having their midpoints, the corners of an equilateral forming the triangle, by the triangle's center of gravity axis of the waste goes running tube 6, 8 opposed from the plate projects the current and on the current side facing away from the nozzle plate 4, a funnel-shaped bevel 7 of here 30 ° has (see Figure 2). The gas stream 8 flows through these nozzle plate 4 from below and passes through the nozzle 3 passes. The holes have advantageously mutually uniform distance and are arranged in a uniform pattern of division. In the direction of flow downstream and above the plate 4 is located at a distance, which is about einhalb- to five times the bore diameter, the electrode grid 5, here a gas-permeable and conductive electrode support structure 5. The electrode holder plate 5 is mounted via insulators horizontally in the gas duct and connected to a relative to the plate 4 negative high voltage (see DE 101 32 582). In projection exactly centered to the holes of the plate 4 carrying the electrode holder plate 5, the central electrodes or electrode pins 1, are directed to the center of the associated nozzle 3 down and opposite to the flow direction. The lower end of the central electrode 1 ends approximately with the 0.05 to 0.2 times the nozzle bore diameter above the plate 4. The lower end of each central electrode 1 is tapered or is spread in a star shape, the individual ends in angle of 60 - 90 ° protrude from the longitudinal axis of the associated electrode pin first The circle diameter, the describe the split ends as a star, is about 0.1 to 0.9 times the nozzle bore diameter. The number of peaks is about Bohrungsum- fang in mm divided by 10 to 50 mm, so that moves up or rounded forms an integer. odd numbers are preferred. The connection technology for the high-voltage electrode 1, 2, 5 here is a detachable, the electrode pin 1 is at its one end screwed to the electrode plate and the Star 2 on the other free. The dimensions are here by way of example the following:

Bore diameter 48 mm thickness of 5 mm

Star diameter 20 mm Spacer plate Star 3 mm

Number 7 tips

Gasgeschwindigk ince 2.9 m / s

Temperature 75 ° C

Gas humidity 50 vol%

High voltage 13 kV

Current 120 uA

Service 1, 6 Watt spec. Performance o, 085 Wh / m³

If, pursuant to the above example, 1600 Bm³/ Sent h wet gas by 85 flat nozzle with a diameter of 48 mm, so this results in an average nozzle gas velocity of 2.9 m / s and at a 7 rating electrode with 20 mm tip diameter a maximum voltage of 13 kV and about 120 microamps lonisatorstrom per nozzle, corresponding to a total current of 10 mA. Pro Bm³/ H gas can be introduced now 0.81 watts. The lower gas velocity no water film is pushed up on the nozzle rim and the high voltage can be increased to the value required for ionization without causing arcing.

Because now larger droplets concentrations in the gas to about 2000 mg / m³ with a maximum droplet diameter to about 0.3 millimeters, the ionization can happen from the bottom up, without causing premature to flashovers, a Tropfenabscheidestufe of FIG. 3 is followed.

Fig. 3 shows the accommodated in the vertical duct portion 18 ionization of FIG. 1 u. 2. In flow direction downstream from and located above the ionization of the channel section 19 is disposed, the one inwardly indented tetes, conical or pyramidal support grid (12 in section 13 shown in plan view) that are on the summary to a tube bundle Abscheiderohre 16th The lower, near-wall circumference of the supporting grid 12, 13 is taken by a with a slight slope (right here) gutter 14 single. This collects the down from the pipes running drip water, which is collected from the support grid and is derived as a result of the effect of gravity to the channel wall 19th From channel 14 the dropping water runs into a drain port 15, where it loaded with solid particles and absorbed gases and vapors may be removed. The pyramid or cone angle is α preferably less than 90 °. The grating pitch of the supporting grid 12, 13 is preferably square o the rectangular, the individual mesh struts is not level, but preferably at an angle of 45 ° to the horizontal and vertical plane extend.

With 8.1 the still heavily loaded with partially electrically charged droplets gas is in after passing the ionization stage. With 8.2 the largely freed from the droplets and pollutant gases pure gas is indicated.

The electrically and insulated from the gas to be processed of the fastening fixed to the hanging device 10 electrode grid 5 is denoted by 11 and described elsewhere. The high drop concentration in the gas can be achieved in addition to the naturally occurring by pure water supply upstream of the lonisatorstufe. The pure water is physically absorb capable of harmful gases and vapors, as in the case of, for. Example, HCl or NOx. If the clean water mixed with a soluble or insoluble base reagent many other acidic pollutant gases z. B. S0 can be chemisorbed,₂,