CN1252017A - electric filter - Google Patents

Abstract

The invention relates to an electrostatic filter, especially a wet-type electrostatic filter, for separating liquids and/or solids from gases, with collecting electrodes which are tubular in shape and are interconnected electroconductively. These collecting electrodes are connected to ground individually or as a whole. The invention is characterized in that the tubes which form a support frame for the collecting electrodes consist of plastic and the collecting electrodes consist of cylinders inserted into these plastic tubes. Said cylinders consist of corrosion-resistant metal.

Description

electric filter

The subject of the invention is an electrofilter, in particular a wet electrofilter, for separating liquids and/or solids from gases, wherein the deposition electrodes are of tubular construction and electrically conductively connected to one another, and the electrodes are grounded individually or collectively.

Harmful substances in non-gaseous form are separated from the gas by so-called dedusting methods. In order to remove solid particles, electrostatic precipitators operate with high DC voltages.

For electroseparators or electrofilters, a distinction is made between tubular electroseparators and planar electroseparators. In contrast to planar electrical separators, with tubular electrical separators the cleaning, ie the removal of the filtered particles adhering to the separator walls, is expensive and difficult. Tubular electrical separators have thus until now been mainly used where the particles in the gas are either solid particles wetted by upstream scrubbers or coolers, or small mist droplets which can act as deposits or liquid films be separated. The separated particles then flow down as sediment along the inner wall of the vertical separation tube into a dirt sump. People call this method a tube-type wet electric separator or a tube-type electric filter.

In DE-OS 33 02 851, a wet tube type-the middle part of the electric filter is disclosed, wherein not only the deposition electrode, but also the pipe body into which the deposition electrode is welded, is made of plastics. For structural stability, the space between the deposition electrode and the inside of the housing is filled with foamed plastic.

A construction of this type has the advantage of reduced weight and low investment costs in contrast to conventional electric filters, which are substantially entirely made of metal.

However, the electrical separator can only function if the deposition electrodes on the inside of the tube are sprayed or sprayed with a conductive liquid, or a mist of liquid separated from a gas, becomes conductive.

This method has the following disadvantages. The smooth plastic surface generally has anti-wetting characteristics, so a closed liquid film cannot be formed on the inner surface of the deposition tube and can not be wetted evenly. The liquid forms multiple small streams or individual rivulets which leave islands of unwetted plastic material. This not only weakens the effect of the electrical separator, but also tends to cause high-voltage discharges due to the inconsistent height of the so-called trickles.

In German patent specification DE 2 134 576, a kind of tube type hydroelectric separator is disclosed, and in it, above-mentioned difficulty is avoided by following mode: the inner shell surface of separator tube is formed a uniform liquid film To be roughened by sandblasting. The casing surface thus treated is uniformly wetted with the separating liquid, mist or the like. In CH-PS 683 892, a tubular wet electric separator is described, wherein the tubes are made of plastics doped with graphite. The stability of this material is uncertain under various marginal conditions, and besides this, the price of conductive plastics is relatively high.

The object of the present invention is to provide a tubular electric filter, in particular a tubular electric filter, in which the above-mentioned disadvantages of the state of the art no longer occur. In particular, compared to conventional electric filters, which are essentially made of metal, a weight reduction should be sought and the use of expensive electrically conductive plastics should be avoided, thereby reducing investment costs. The grit blasting of the expensive separator inner housing surfaces should also be eliminated and at the same time the electrofilter according to the invention should be improved in a manner similar to those in which the inner housing surface structure is a flat plastic surface .

This task is achieved by the invention, which is characterized in that the tubes forming the frame of the deposition electrodes consist of plastic and that each deposition electrode is made of a corrosion-resistant metal formed by a sheet pushed into the respective plastic tube, wherein the sheet is slightly longer than the surrounding Plastic tubes of thin sheets having a width slightly less than the inner circumference of the plastic tube surrounding the sheets, and each sheet having a folded edge at the upper end of the outer plastic tube. So that the foil is rolled up along its shorter side before being pushed into the plastic tube, the foil can be unrolled inside the plastic tube and there form the deposition electrode, hereinafter referred to as the cylinder.

The structure of the frame can be produced in a simple manner from standardized tube bundles made of perforated plates and standard tubes. By means of this, a substantial reduction in weight can be achieved compared to electric filters which are essentially made of metallic raw materials.

In a preferred embodiment of the invention, tube bundles made of glass-fiber-reinforced plastic are used. However, depending on the installation area of the electric filter, it is also possible to use other plastics which are not reinforced with glass fibres.

The cylinder constituting the deposition electrode is made of a corrosion-resistant metal, such as a corrosion-resistant iron, titanium or aluminum alloy, wherein the choice of the metal depends on the respective conditions of use and must in any case be such that the metal satisfies expected request. If the material of the cylinder is a corrosion-resistant iron alloy, it has the advantage that the metal used for the cylinder can be stainless steel, for example chromium- and/or nickel- and/or molybdenum-alloyed steel.

According to a modification of the invention, the cylinder is made of Hastelloy 276, an alloy steel with a high nickel content. This material is extremely corrosion-resistant and is also particularly suitable for use with aggressive media.

It is advantageous if the wall thickness of the cylinder is less than 1 mm. It is particularly advantageous if the thickness of the cylinder is less than 0.4 mm. Since the basic mechanical load is taken up by the plastic tube surrounding the cylinder, thin foils can be used, while the wall thickness of the cylinder should be kept as thin as possible for reasons of expense.

According to an improvement of the invention, the thickness of the cylinder is 0.3 mm. The weight of the cylinder and the outlay for precious metals are thus low.

In a rather unexpected manner, it was determined that a long weld seam on the sheet forming the deposition electrode was discarded. This contributes substantially to the structural simplification of the electrofilter according to the invention.

In a preferred solution, the deposition electrodes have a folded edge at the outer upper end of the plastic tube. This avoids possible downward movement of the deposition electrode inside the plastic tube.

It is another advantage if the deposition electrode is at the outer lower end of the plastic tube, with a disclosed funnel-shaped flare. Through this widening, a greater distance can be achieved from the drip edge relative to the discharge electrode, so that discharges are avoided and the operating voltage is increased.

The present invention will now be described in detail with reference to the embodiment depicted in FIG. 1 as follows.

In FIG. 1 , a section through two tubes of an electrofilter according to the invention is shown. Tubes 1 made of plastic, for example glass-fibre-reinforced plastic, are separated by a perforated plate 2 and a laminated plastic 3 . In the pipe 1, a cylinder 4 made of a corrosion-resistant metal, such as Hastelloy 276, is pushed all the way to the flange 7. Every two adjacent cylinders 4 communicate 6 with each other at their lower ends. The cylinder 4 serves as a deposition electrode, in the center of which is arranged a discharge electrode, realized for example as a wire or rod.

Claims (10)

1. An electric filter, especially a wet electric filter, is used to separate liquid and/or solid from gas, wherein the deposition electrode structure is tubular and conductively connected to each other, while the deposition electrodes are individually or jointly grounded, characterized in that , the tube constituting the support for the deposition electrode consists of plastic, and the deposition electrode consists of a cylinder made of corrosion-resistant metal pushed into the tube. 2. Electrofilter according to claim 1, characterized in that each deposition electrode consists of a sheet made of corrosion-resistant metal which is pushed into a plastic tube respectively, wherein the length of the sheet is slightly greater than the length of the plastic tube surrounding the sheet And the width of the sheet is slightly smaller than the inner perimeter of the plastic tube surrounding the sheet. 3. An electrofilter as claimed in any one of claims 1 or 2, characterized in that each deposition electrode has a folded edge at the outer upper end of the plastic tube. 4. The electrofilter as claimed in one of claims 1 to 3, characterized in that the corrosion-resistant metal used for the deposition electrodes is a corrosion-resistant iron, titanium or aluminum alloy. 5. Electrofilter according to one of claims 1 to 4, characterized in that the corrosion-resistant metal used for the deposition electrodes is stainless steel. 6. The electrofilter as claimed in one of claims 1 to 5, characterized in that the stainless steel used for the deposition electrodes is chromium and/or nickel and/or alloy steel. 7. An electrofilter as claimed in any one of claims 1 to 6, characterized in that the thickness of the sheets forming the deposition electrodes is less than 1 mm. 8. An electrofilter as claimed in any one of claims 1 to 7, characterized in that the thickness of the sheets forming the deposition electrodes is less than 0.4 mm. 9. The electrofilter as claimed in one of claims 1 to 8, characterized in that the material of the plastic tube surrounding the deposition electrode is plastic, optionally reinforced with glass fibres. 10. The electric filter according to any one of claims 1 to 9, characterized in that the outer lower end of the plastic tube of the deposition electrode has a conical flaring opening.

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