EP1286779B1 - Electrostatic dust separator - Google Patents

Abstract

The invention relates to an electrostatic dust separator (8) for a horizontal gas flow, comprising a housing (2) which is substantially rotationally symmetrical to a central housing axis (3). Said dust separator also comprises an input connection piece (1) which extends the housing diameter (D) by 80 to 95 % in a single cone-shaped section (10). The remaining extension of 5 to 20 % of the housing diameter (D) is carried out in the form of a step (5) which is substantially perpendicular and radially symmetrical to the housing axis (3). Said dust separator also comprises at least two gas distribution perforated plates (6, 6', 6'') which are placed in the cone-shaped section (10) and which are arranged in such a way that they are substantially perpendicular to the housing axis.

Description

The invention relates to an electrostatic dust collector for horizontal gas passage, with a housing substantially rotationally symmetrical to a central housing axis.

Such electrostatic precipitators are known in the art and typically have vertical plate-shaped collecting electrodes arranged equidistant from each other parallel to the main axis of the housing. The collecting electrodes are arranged at equidistant intervals parallel to the main axis of the housing, which extends in accordance with the respective chord line length substantially over the entire available height. Between the collecting electrodes tensioned discharge electrodes are provided in frame. In addition, to remove separated dust from the housing inner wall, scratching devices may be provided, for example around the housing axis via the lower area of the housing wall provided with dust discharge openings, pivotable scraper devices.

Such a dust separator is from the EP 0 252 371 A1 known. This dust collector has an inlet and outlet nozzle, each formed by 3 different conical sections, the conical sections are in certain size and height ratios to the housing diameter of the dust collector. In the middle conical section, three gas distribution perforated plates are arranged.

Dust collectors of this type are used for dry dedusting of industrial useful and exhaust gases, especially when it comes to permanently or temporarily explosive gas mixtures. Thus, for example, top gases from blast furnaces, which operate at an overpressure of 1.5 to 2.5 bar, dedusted in this way to relax without erosion risk for energy recovery in turbines at 40 to 80 mbar, previously the dust content to 5 must be reduced to 20 mg / m ³ . With regard to the highest possible usable pressure gradient, only electrostatic precipitators with a pressure loss of 1 to 2 mbar come into consideration, because in the separation efficiency equivalent high-performance scrubbers have a pressure drop of 200 to 400 mbar.

Another field of application for such dust are coal pulverizers whose exhaust gases are explosive because of the coal dust content within certain limits. Uncontrolled changes in the gas composition due to the build-up of coal dust deposits or the ingress of false air must be avoided in any case.

Particularly critical is the dedusting of exhaust gases from steel converters, because the dust collector is alternately flows through the discontinuous mode of operation of combustible gases and only slightly mixed with dust and gases ambient air. The combustible gases are collected after dedusting in containers or fed into gas supply systems, while the intermittently occurring outside the actual blowing phases of the converter gases are discharged after dedusting through a fireplace in the atmosphere. The purpose of a switching device downstream of the dust collector, which is controlled in time or in dependence on the gas composition. From this switching device, the converter and also by deflagration upstream of the dust collector, pressure surges can be initiated in the gas stream, can be replaced by the dust accumulations in the dust or in the upstream channel system and swirled in the gas stream. Such "dust surges" on the one hand affect the separation efficiency of the dust collector and on the other hand are associated with an increased risk of deflagration.

Due to today's increasingly stringent environmental legislation, however, it is no longer sufficient to use dust collectors in which only the risk of dust impacts and deflagration is minimized. With relevant, from the prior art, in particular from the EP 0 252 371 A1 known electrostatic precipitators, it is hardly possible to meet today's legal requirements regarding the dust content of the clean gas. Another disadvantage of the from the EP 0 252 371 A1 known electrostatic precipitator is that the three conical sections of the input and Ausgangssstzutzens are technically difficult and expensive to implement.

It is therefore the object of the subject invention to propose an electrostatic dust collector, which has a comparison with the prior art improved deposition efficiency and is cheaper to manufacture, but the known from the prior art low tendency to deflagration should be maintained.

This object is achieved according to the invention by the combination of the following features: that the electrostatic dust collector is provided with an expanding into a single conical section to 80 to 95% of the housing diameter inlet nozzle, the remaining extension of 5 to 20% of the housing diameter in Is formed of a step which is carried out substantially perpendicular and radially symmetrical to the housing axis, with at least two arranged in the conical section Gasverteilungslochblechen, which are arranged substantially perpendicular to the housing axis.

Surprisingly, it is possible by this feature combination that the electrostatic precipitator continues to not tend to deflagration, but that the separation efficiency is increased compared to the dust separator known from the prior art. The increase in the separation efficiency is based on a gas velocity profile which is largely uniformized over the cross section of the stucco separator, as a result of which the residence time distribution is likewise uniform. While these factors affect the ongoing operation of the electrostatic precipitator, a simpler and more cost-effective production is possible due to the simple construction of the dust collector according to the invention with only a single cone and a stage. Furthermore, it is also possible to convert existing dust separators into dust collectors according to the invention quickly and with little cost.

According to an advantageous embodiment, which contributes to the further optimization of the gas velocity distribution, a cylindrical section is provided between the conical section and the step-shaped extension, wherein the height (h ₁ ) of the cylindrical section is 5 to 15%, preferably about 10% of the housing diameter D. ,

In order to ensure optimum gas distribution, it is expedient that the height h _{2 of} the conical section is in a certain size ratio to the housing diameter. A height h _{2 of} the conical section of 20 to 40% of the housing diameter has proven to be particularly advantageous.

It has also proved to be advantageous if at least three, preferably exactly three gas distribution perforated plates are provided in the conical section of the inlet nozzle, wherein the gas permeability of the gas distribution perforated plates in the gas flow direction of 51-47% to 48-44% and then to 45- 41% / off-takes.

wobei $${\mathrm{\xi }}_{\mathrm{1}}\mathrm{=}\mathrm{0}\mathrm{,}\mathrm{18}\mathrm{bis}\mathrm{0}\mathrm{,}\mathrm{28}$$

$${\mathrm{\xi }}_2\mathrm{=}\mathrm{0}\mathrm{,}\mathrm{45}\mathrm{bis}\mathrm{0}\mathrm{,}\mathrm{60}$$

$${\mathrm{\xi }}_3\mathrm{=}\mathrm{0}\mathrm{,}\mathrm{76}\mathrm{bis}\mathrm{0}\mathrm{,}\mathrm{92}$$

bedeutet.In addition, the post-ion x ₁ obey to x ₃ of the gas distribution perforated plates the following relationship, wherein x ₁ is measured to x ₃ along the housing axis, from the cross sectional plane of the stepped recess that is, from the transition stage / cone or step / cylindrical portion, opposite to the gas flow direction: $${\mathrm{<figure-callout\; id="1"\; label="X"\; filenames="imgf0001.png"\; state="\{\{state\}\}">X</figure-callout>}}_{\mathrm{1}\mathrm{.}\mathrm{2}\mathrm{.}\mathrm{3}}\mathrm{=}{\mathrm{<figure-callout\; id="1"\; label="\xi "\; filenames="imgf0001.png"\; state="\{\{state\}\}">\xi </figure-callout>}}_{\mathrm{1}\mathrm{.}\mathrm{2}\mathrm{.}\mathrm{3}}\mathrm{\times }{\mathrm{H}}_{\mathrm{2}}\mathrm{+}{\mathrm{H}}_{\mathrm{1}}$$

in which $${\mathrm{<figure-callout\; id="1"\; label="\xi "\; filenames="imgf0001.png"\; state="\{\{state\}\}">\xi </figure-callout>}}_{\mathrm{1}}\mathrm{=}\mathrm{0}\mathrm{.}\mathrm{18}\mathrm{to}\mathrm{0}\mathrm{.}\mathrm{28}$$

$${\mathrm{\xi }}_2\mathrm{=}\mathrm{0}\mathrm{.}\mathrm{45}\mathrm{to}\mathrm{0}\mathrm{.}\mathrm{60}$$

$${\mathrm{\xi }}_3\mathrm{=}\mathrm{0}\mathrm{.}\mathrm{76}\mathrm{to}\mathrm{0}\mathrm{.}\mathrm{92}$$

means.

According to a further advantageous embodiment, the gas outlet side of the housing includes a stepped taper to 80 to 95% of the housing diameter, which taper is executed substantially perpendicular and radially symmetrical to the housing axis.

It is also useful if the step-shaped taper adjoins a conically tapering section in a single section, with at least one arranged in the conical section Gasverteilungslochblech, which are arranged substantially perpendicular to the housing axis and wherein the height ( h ₄ ) of the conical section 20 to 40% of the housing diameter D.

Conical section and stepped taper together form an outlet nozzle of the dust collector according to the invention.

Advantageously, a cylindrical section is arranged between step-shaped taper and outlet connection, the height ( h ₃ ) of the cylindrical section being 5 to 15% of the housing diameter D.

Preferably, three gas distribution hole plates are provided in the conical section of the outlet nozzle, wherein the gas permeability of the gas distribution hole plates in the gas flow direction of 41-45% to 44- 48% and then to 47 51% increases / decreases.

In a preferred embodiment of the dust separator according to the invention, the inlet and outlet nozzles are the same, but symmetrically symmetrical.

Particular preference is given for inlet and outlet nozzles each arranged between the conical section and step-shaped extension cylindrical portion and three each in the respective conical part arranged gas distribution hole plates.

The fact itself, to perform input and output nozzle similar and mirrored is known from the prior art, but not the inventive combination of cone, jump-shaped extension and Gasverteilungslochblechen.

While previously the separation efficiency of an electrostatic precipitator on the last distance before the outlet nozzle decreases sharply, also achieved in this area through the cross section uniformized gas velocity distribution and thus over the entire length of the dust separator constant separation efficiency.

• Fig. 1: Eingangsstutzen mit Gasverteilungslochblechen
• Fig. 2: erfindungsgemäßer Staubabscheider

Subsequently, the dust collector according to the invention with reference to the in the drawings Fig. 1 and Fig. 2 illustrated embodiments explained in more detail.

• Fig. 1 : Inlet with gas distribution perforated sheets
• Fig. 2 : dust collector according to the invention

In Fig. 1 schematically an inlet nozzle 1 for a dust collector according to the invention with a substantially cylindrical housing 2 and a central housing axis 3 is shown. The inlet port 1 expands in a single conical section 10 to about 90% of the diameter D of the housing 2 of the dust collector and the height h _{2 of} the conical section 10 is about 35% of the housing diameter D. At the conical portion 10 includes a cylindrical section. 4 whose height h _{1 is} about 5% of the housing diameter D. The remaining 10% of the diameter extension of the housing diameter D are formed in the form of a stepped, radially symmetrical recess 5. In the conical portion 10 Gasverteilungslochbleche 6,6 ', 6 "arranged at the intervals x ₁ to x ₃ , wherein the Distances x ₁ to x ₃ are measured from the plane of the step-like recess 5. With the arrow 7, the gas flow direction is indicated.

In Fig. 2 schematically, an inventive dust collector 8 is shown with an inlet nozzle 1, a housing 2 and an outlet nozzle 9, wherein the arrow 7 again illustrates the gas flow direction.

The existing in the housing 2 internals, such as precipitation and discharge electrodes, scrapers, etc., are - because erfindungsunwesentlich - not shown in the drawing.

The inlet connection 1 and the outlet connection 9 are in Fig. 2 constructed identically, so that h ₁ = h ₃ and h ₂ = h ₄ . Furthermore, the respective dimensions x ₁ to x _{3 of} the input and output nozzle are the same size.

Claims (10)

1. Electrostatic dust separator (8) for horizontal gas throughflow, with a housing (2) having a conical tubular inlet port (1) which is substantially rotationally symmetrical in relation to a central housing axis (3) and with at least two perforated gas-distributing plates (6, 6', 6") arranged in the tubular inlet port (1) and substantially perpendicularly in relation to the housing axis (3), characterized by the combination of the following features: with a tubular inlet port (1) flaring in a single conical section (10) up to 80 to 95% of the housing diameter (D), the remaining widening of 5 to 20% of the housing diameter (D) taking the form of a step (5) which is configured substantially perpendicularly and radially symmetrically in relation to the housing axis (3).
2. Electrostatic dust separator (8) according to Claim 1, characterized in that a cylindrical section (4) is provided between the conical section (10) and the step-shaped widening (5).
3. Electrostatic dust separator (8) according to Claim 2, characterized in that the height (h₁) of the cylindrical section (4) is 5 to 15%, preferably approximately 10%, of the housing diameter (D).
4. Electrostatic dust separator (8) according to one of Claims 1 to 3, characterized in that the height (h₂) of the conical section (10) is 20 to 40% of the housing diameter (D).
5. Electrostatic dust separator (8) according to one of Claims 1 to 4, characterized in that at least three perforated gas-distributing plates (6, 6' 6'') are provided in the conical section (10).
6. Electrostatic dust separator (8) according to one of Claims 1 to 5, characterized in that three perforated gas-distributing plates (6, 6' 6'') are provided in the conical section (10) of the tubular inlet port (1), the gas permeability of the perforated gas-distributing plates (6, 6' 6") being configured to increase/decrease in the direction of gas flow (7) from 51 - 47% to 48 -44% and then to 45 - 41%.
7. Electrostatic dust separator (8) according to one of Claims 1 to 6, characterized in that there follows on the gas outlet side of the housing (2) a step-shaped narrowing of the housing (2) to 80 to 95% of the housing diameter, which narrowing is configured substantially perpendicularly and radially symmetrically in relation to the housing axis (3).
8. Electrostatic dust separator (8) according to Claim 7, characterized in that the step-shaped narrowing is followed by a section tapering conically in a single section, with at least two perforated gas-distributing plates arranged in the conical section and substantially perpendicularly in relation to the housing axis, and the height (h₄) of the conical section being 20 to 40% of the housing diameter D.
9. Electrostatic dust separator (8) according to Claim 8, characterized in that a cylindrical section is arranged between the step-shaped narrowing and the tubular outlet port, the height (h₃) of the cylindrical section being 5 to 15% of the housing diameter D.
10. Electrostatic dust separator (8) according to one of Claims 7 to 9, characterized in that three perforated gas-distributing plates are provided in the conical section of the tubular outlet port, the gas permeability of the perforated gas-distributing plates being configured to increase/decrease in the direction of gas flow from 41 - 45% to 44 - 48% and then to 47 - 51%.

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