EA027518B1 - Method and device for beating an electrofilter - Google Patents

Abstract

The present invention relates to a method for use when beating an electro filter (203) comprising at least one emission electrode (207) and at least one precipitation electrode (206), past which precipitation electrode (206) a first gas to be cleaned from particles is caused to stream in a downstream direction (204) in one or several gas passages (208). The present invention is characterised in that a stream (210) of a second gas temporarily is applied in the or those gas passages (208) for the first gas that pass the said precipitation electrode (206) while the beating of the precipitation electrode (206) is ongoing, and in that the stream (210) of the second gas is applied from a position downstream of the precipitation electrode (206) and so that it streams in an upstream direction, counter-current to the stream of the first gas, and thereby counteracts the stream of the first gas past the precipitation electrode (206).

Description

The present invention relates to a method and apparatus for reducing particle emissions from an electrostatic precipitator. In particular, the present invention relates to a method for reducing re-dispersion of particles during impact cleaning of a precipitation electrode in an electrostatic precipitator.

State of the art

The flue gases generated in many industrial processes contain particulate matter. For example, this is characteristic of various types of combustion. To remove such particles, so-called electrostatic precipitators are usually used, using an electric field created between the emission electrode and the precipitation electrode to direct the particles to the emission electrode, which traps them.

The specified precipitation electrode must be regularly cleaned of accumulating dust, which can be done by so-called impact cleaning. To do this, using a hammer or other similar means, they ensure the vibration of the precipitation electrode and, thereby, cause the release of dust, which, under the action of gravity, falls into the dust receiver located under the electrode for further processing and removal.

One of the problems is that during such an impact cleaning, dust emissions temporarily increase, since the dust released from the precipitation electrode is re-scattered in the passing flue gas stream. In particular, this problem occurs during shock cleaning of the last precipitation electrode in an electrostatic precipitator containing several precipitation electrodes arranged in series, since there is no additional precipitation electrode downstream of the last precipitation electrode, which could catch particles re-scattered during shock cleaning the specified last precipitation electrode. Part of the total dust emissions due to repeated dust dispersal during impact cleaning can reach 15-20% of the total dust emissions.

To solve this problem, it was proposed to separate the precipitation electrode from the flue gas stream during shock cleaning of the specified electrode, for example, by means of shutters installed with the possibility of quick lowering from above on both sides of the electrode. Such a technical solution is complex and increases both capital costs and operating costs for electrostatic precipitator systems. In addition, the specified technical solution assumes the presence of moving parts in the filter itself, which increases the cost of maintenance work.

Disclosure of invention

The present invention allows to solve the above problems.

Thus, the present invention relates to a method used during impact cleaning of an electrostatic precipitator comprising at least one emission electrode and at least one precipitation electrode, wherein the first gas to be cleaned of particles flows past said precipitation electrode in a downstream direction into one or more gas channels. The proposed method is characterized in that in one or more gas channels for the first gas passing through the specified precipitation electrode, during the impact cleaning of the precipitation electrode, a second gas flow is temporarily created. Moreover, said second gas stream is created from a position downstream of the precipitation electrode so that it flows in an upstream direction opposite to the direction of flow of the first gas, and thereby counteracts the flow of the first gas passing by the precipitation electrode.

Brief Description of the Drawings

The following is a detailed description of the present invention based on the exemplary embodiments thereof with reference to the accompanying drawings, in which the following is shown.

In FIG. 1 is a top view, in cross section, of a conventional electrostatic precipitator.

In FIG. 2 is a top view, in cross section, of an electrostatic precipitator to which the method of the present invention can be applied.

In FIG. 3, a top view shows the electrostatic precipitator of FIG. 2.

In FIG. 4 is a side cross-sectional view of the electrostatic precipitator of FIG. 2.

In FIG. 5 is a front view, in cross section, of the electrostatic precipitator of FIG. 2.

In FIG. 6 is a detailed view corresponding to that of FIG. 5, but illustrating an alternative embodiment of the present invention.

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The implementation of the invention

In FIG. 1 shows a source 101 of contaminated flue gases. The specified source 101 can be involved in the production process of burning fossil fuels, chemical process, etc. Flue gases containing solid particles are fed through a pipe 102 to a particle separator made in the form of a conventional electrostatic precipitator 103. An external electric field is applied between a predetermined number of emission electrodes 107 and a predetermined number of precipitation electrodes 106. Particles transported in the main flow direction 104 in the electrostatic precipitator 103 are charged in the indicated electric field, pass to the precipitation electrodes 106, and accumulate on them.

These precipitation electrodes 106 are arranged in the form of parallel, flat sheet metal elements, between which parallel, elongated gas channels 108 are formed, passing through an electrostatic precipitator 103. These emission electrodes 107 are located in these gas channels 108 between the precipitation electrodes 107. FIG. 1 shows five parallel gas channels 108, however, it is understood that their number can vary from one to a very large value, depending on the characteristics of a particular embodiment. In addition, several levels of gas channels can be provided, one above the other, perpendicular to the plane shown in FIG. one.

These precipitation electrodes 106 are cleaned of accumulated dust by shock cleaning, in which a hammer or other similar tool causes the electrode to vibrate for a predetermined period of time so that the dust is released from the electrode and falls down onto a receiving pan or other similar tool located under the specified electrode.

A gas stream passing through a conventional electrostatic precipitator 103 maintains a velocity of about 0.52 m / s. As a result, part of the released dust has time to re-disperse in the flue gas stream before it reaches the specified receiving pan. This problem is especially relevant during the shock cleaning of the most extreme, downstream precipitation electrodes, namely the precipitation electrodes shown in FIG. 1 to the extreme right, since it is not possible to remove the re-scattered dust by means of an additional, applied downstream electric field and the corresponding precipitation electrodes. Instead, said re-dispersed dust leaves the cleaned flue gas through outlet 105.

In FIG. 2 and 3, respectively, in plan views, in cross section, an electrostatic precipitator 203 is shown containing the device of the present invention and designed to reduce re-scattering of particles during impact cleaning of the electrostatic precipitator 203, the same reference numbers being used in these drawings. As with the technical solution illustrated in FIG. 1, a polluted gas source 201 emits flue gases containing particles, said flue gases being directed through a pipe 202 to an electrostatic precipitator 203. Said electrostatic precipitator 203 also contains a predetermined number of emission electrodes 207 and a predetermined number of precipitation electrodes 206, between which parallel gas channels 208 are formed. These flue gases move through the electrostatic precipitator 203 in the main direction 204 of the flow of the electrostatic precipitator 203 and finally exit through the outlet 205.

According to the present invention, said device comprises a control unit 216 and a predetermined number of blowing means 221 for creating an unidirectional gas flow at the collecting electrodes 206.

Said blowing means comprise gas nozzles 209 and a feed pipe 219 for supplying gas to said nozzles 209, which is best shown in FIG. 4 and 5.

Said nozzles 209 are mounted behind an extreme, downstream electrode in an electrostatic precipitator 203, wherein the gas stream 210 exiting from these nozzles moves from a specified position located downstream of the settling electrodes 206 in an upstream direction, said direction being the opposite with respect to the direction 204, in which the flue gases flow through the electrostatic precipitator 203 through the gas channels 208. As a result, the flow of flue gases passing through the precipitation electrode is counteracted.

According to the present invention, said control unit 216 is for temporarily supplying gas to each of said blowing means 221 only for the duration of the impact cleaning of the precipitation electrode, behind which there is a corresponding blowing means. As a result, an antidirectional gas stream from this blowing means is created in one or those gas channels, which or which pass by the precipitation electrode subjected to impact cleaning at the indicated time.

In FIG. 2 that these nozzles 209 are located essentially centrally in each parallel gas channel 208 formed between the respective precipitation electrodes 206, and the antidirectional gas stream 210 acts essentially across the entire width of the gas channel 208. However, it is understood that these nozzles 209 can be arranged differently, moreover, several nozzles can be arranged in a row in each gas channel, provided that it will be possible to create a temporary counter-flow according to the invention during cleaning the precipitation electrodes 206. In addition, these blowing means 221 can be constructed otherwise, without the use of nozzles 209, to direct the gas flow in the gas channels 208, for example, by means of elongated slots or other similar elements, provided that the creation of the specified counter-directed gas flow will be ensured. In more detail, this embodiment is disclosed below.

As can be seen from FIG. 3, illustrating a preferred embodiment of the present invention, a portion of the gas that has already passed through the electrostatic precipitator 203 and, accordingly, is purified, enters the purge means 221. In this case, the gas moves through the supply pipe 217 from the outlet 205, possibly after additional purification or other stages of the flue gas treatment, through the control unit 216, to the purge means 221. The pipe system and the connections between the specified control unit 216 and the purge means 221 can be otherwise implemented, provided that the control unit 216 provides control of the gas stream and its movement from each purge means 221 to the respective gas channels 208.

According to another preferred embodiment of the present invention, filtered atmospheric air is used as the gas supplied through the blowing means 221. In this embodiment, it is advisable to use purified flue gas, since in this case it is possible to prevent an increase in the gas flow and cooling of the gas, which can also lead to sedimentation of water or acid and corrosion. In addition, this option eliminates the use of expensive filtering devices for atmospheric air.

The specified control unit 216 is preferably configured to control the purge means 221 to create an anti-directional gas flow in the gas channels surrounding the specific precipitation electrode, throughout the entire shock cleaning of the electrode. Thus, synchronization is provided between the percussion mechanism and the moment of creation of the anti-directional gas flow, preferably realized in the form of a connection (not shown) between the percussion mechanism (also not shown) and said control unit 216.

By using an antidirectional gas flow around the precipitation electrode subjected to shock cleaning, it is possible to achieve that particles separated from the precipitation electrode are not capable of re-scattering in the flue gas stream and further movement downstream. Instead, a gas cushion formed by an antidirectional gas flow temporarily limits the flow rate of flue gas passing through the precipitation electrode subjected to shock cleaning, with most of the dust leaving the specified electrode falling into the receiving pan under the electrode.

The gas cushion is preferably implemented such that the flue gas flow rate is completely limited in one or those channels that are adjacent to the precipitation electrode subjected to impact cleaning.

According to a preferred embodiment of the present invention, the anti-directional gas flow is maintained for a shorter period of time, preferably from 2 to 10 seconds, after the shock cleaning of the corresponding precipitation electrode is stopped. Thus, even small particles will have time to fall far enough so that they do not re-disperse after the cessation of the antidirectional gas flow.

As shown in FIG. 2, illustrating a preferred embodiment of the present invention, one or more collecting electrodes, in which or in which one or more counter-directed gas flows are generated, are part of the electrostatic precipitator stage 218 shown in FIG. 2 in the form of a closed region, drawn by a dashed line, and this step, in turn, forms the most extreme, downstream stage of the electrostatic precipitator from several stages of the electrostatic precipitator connected in series. As used herein, the term “electrostatic precipitator stage” refers to a series of parallel connected precipitation electrodes in an electrostatic precipitator, between which flue gases flow in a directional direction in parallel flow. Thus, the stage of the electrostatic precipitator may contain only one precipitation electrode or several such precipitation electrodes, in which case they are arranged in a row and / or one above the other.

In the event that several precipitation electrodes are located in parallel in the electrostatic precipitator stage 218, which is subject to shock cleaning and in which an anti-directional gas flow according to the invention should be created during shock cleaning, it is advisable that the precipitation electrodes in the specified electrostatic precipitator stage 218 be subjected to impact in turn, preferably each individually, with corresponding counter-directed gas flows being temporarily created only in one or those gas channels 208, which or which surround each respective precipitation electrode 206 in an electrostatic precipitator stage, being subjected to impact cleaning at a given time. Due to this, the total flue gas stream passing through the electrostatic precipitator 203 has a limited effect, since the antidirectional gas stream flows through only one or more precipitation electrodes, past which the flue gas stream moves. Thus, the operation of the electrostatic precipitator 203 is violated only within the specified limits, as a result of impact cleaning.

According to a preferred embodiment of the present invention, the antidirectional gas stream from the purge means 221 is sufficiently strong and substantially ensures that particles released during the impact cleaning from the precipitation electrode in which the antidirectional gas stream is generated do not flow down flow. This is due to the fact that the gas stream in combination with pressure waves arising from the impact on the precipitation electrode acts against the opposed gas flow during shock cleaning.

The smallest gas pressure necessary to achieve this effect varies depending on the particular embodiment of the present invention, however, this pressure can be established empirically. The gas source supplied by said blowing means 221 is preferably under pressure, which is provided, for example, by a conventional fan or compressor (not shown). An advantage of the present invention is that the pressure of the gas source can be increased by conventional, reliable and economically efficient fans, since the pressure necessary to provide the gas cushions described herein is generally relatively low.

In FIG. 4 schematically in side view shows a precipitation electrode 206 located between the upper part 211 and the bottom 212 of the electrostatic precipitator 203.

According to a preferred embodiment of the present invention, most clearly illustrated in FIG. 3 and 4, the control unit 216 supplies gas to the purge means 221 through the supply pipe 215 and the distribution pipe 214. Said distribution pipe 214 distributes gas to various distribution pipes 219, each of which supplies gas to the nozzles 209 into respective parallel gas channels 208 To direct gas to various purge means 221, as described above, control means (not shown) controlled by said control unit 216 can be installed in a distribution pipe 214 supplying ubah 219 or at the nozzle 209 or alternatively several distribution pipes 214 can be connected to said control unit 216 with separate control. Alternatively, each feed pipe 219 may also be individually connected to said control unit 216.

Nozzles 209 are located along the entire or substantially all part of the precipitation electrode 206, past which the flue gas stream flows in the gas channel 208, the wall of which forms the specified precipitation electrode 206, the nozzles being perpendicular to the direction 204 of the flue gas stream. In other words, these nozzles 209 are distributed along the supply pipe 219 so that the gas flow provided by the nozzles covers substantially the entire vertical, downstream side edge of the precipitation electrode 206, so that the resulting air bag limits the flow rate of the flue gases along the entire bottom along the flow of the final part of the precipitation electrode 206. It is advisable that an antidirectional gas flow be created along the entire height of one or those gas channels 208, which or which surround the precipitation electrode. In addition, it is preferable that said nozzles 209 are spaced at equal intervals and so close to allow the formation of a combined or substantially combined air cushion along the entire downstream end portion of the precipitation electrode 206.

A corresponding option occurs if the blowing means 221 is made differently without using a sequence of nozzles 209. For example, an elongated slot may be provided in the supply pipe 219, which leads to the formation of a corresponding combined vertical air cushion.

This design allows you to effectively prevent re-scattering of the released particles in the flue gas stream along the entire length of the precipitation electrode 206.

According to a preferred embodiment of the present invention illustrated in FIG. 4 and 5, at least one of the purge means 221, preferably all of the purge means 221, is connected to the distribution pipe 114 by means of a flexible connection 220. The connection between the purge means 221 and the distribution pipe 214 in this case is extended through the bushing 213 in the cover of the electrostatic precipitator 203 preferably through its upper part 211. Thus, an advantage of the device according to the invention lies in the fact that parts of the device located inside the electrostatic precipitator 203, namely the supply pipe 219 and c pla 209 in the embodiment illustrated in FIG. 4 move independently of the parts of the proposed device that are located outside the lid of the electrostatic precipitator 203, in particular in FIG. 4 is a system of pipes 214, 215, 216, a control unit 216, and other elements.

In other words, several purge means 221 are connected through such flexible connections 220 to a main switchgear comprising a distribution pipe 214 located outside the cover of the electrostatic precipitator 203. The main switchgear, in turn, is connected via a control unit 216 to a central source of gas supplied through the purge means 221. Due to this, a cheap and reliable design is achieved, not subject to the negative effects of relative displacements arising in There are changes in operating temperatures inside the electrostatic precipitator 203.

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In addition, in this case, at least all the active or moving parts of the control system for supplying an anti-directional gas stream to the appropriate gas channels 208 (see Fig. 4), namely, the control unit 216, as well as at least part of the remaining pipes 215, 217 containing controls, controlled valves or the like, and also preferably active components such as compressors, fans, etc. for receiving compressed gas, etc., are located outside the cover of the electrostatic precipitator 203, preferably in the upper part 211 of the electrostatic precipitator 203. It is most preferable that the parts of the anti-directional gas flow supply system located inside the electrostatic precipitator 203 are completely made in the form of passive components without moving parts . This arrangement allows for simple and cheap maintenance of the system, since the parts that usually require maintenance are located so that to gain access to them there is no need to open or remove the cover of the electrostatic precipitator 203.

According to a preferred embodiment of the present invention, the collection electrodes 206 are in the form of vertical sheet metal elements, and the supply pipes 219 extend vertically along the collection electrodes 206. This arrangement allows a simple but effective structure to be realized. In FIG. 5 illustrates a first preferred embodiment of the present invention, according to which the purge means 221 for generating an anti-directional gas flow are parallel to the precipitation electrodes 206 and centered in each respective gas channel 208 between the precipitation electrodes 206. Thus, each purge means 221 forms an anti-directional gas flow, creating a gas cushion along two respective sides of the collecting electrodes 206 surrounding each respective AZOV channel 208. Accordingly, in a specific time the shock purification precipitation electrode is necessary to use two purged means disposed on each side of said precipitation electrode.

An alternative or additional embodiment of the present invention is illustrated in FIG. 6, wherein said embodiment is similar to that shown in FIG. 5. Position number 304 indicates the main flow direction of the flue gas. In contrast to the embodiment of FIG. 5, in FIG. 6, the purge means 321 for generating countercurrent gas flows are located in the protruding portion of the respective precipitation electrode 306 each in a direction 304. Thus, the countercurrent gas stream provided by each purge means 321 will be present on both sides of the corresponding precipitation electrode 306, resulting in during shock cleaning of a specific precipitation electrode is necessary to use only one blowing means 321.

Thus, the present invention allows to create a reliable system for reducing emissions of particulate matter from electrostatic precipitators, and simple and cheap means are used in this system. In addition, the available electrostatic precipitator can easily be supplemented with the proposed device to reduce re-dispersion and thereby achieve the indicated emission reduction without the need to replace or reconstruct large parts of the electrostatic precipitator, which often requires significant capital investments in additional electrical systems.

Preferred embodiments of the present invention are disclosed above. However, it will be apparent to those skilled in the art that various changes may be made to the disclosed embodiments without departing from the basic idea of the present invention.

For example, the specified anti-directional gas stream can be obtained in other ways, without the use of nozzles or slots, provided that the anti-directional gas stream is obtained around the precipitation electrode to be impacted, so that re-scattering of the released particles is reduced or completely prevented.

In addition, the blowing means can be equipped with nozzles, slots, etc., configured to create an opposed gas stream of different strengths at different heights along the downstream end section of the precipitation electrode subjected to impact cleaning. For example, a more powerful gas cushion can be created further down along the precipitation electrode, which will improve protection against re-scattering near the bottom of the precipitation electrode, where the density of released particles is greater than that of the upper parts of the precipitation electrode.

If appropriate, the anti-directional gas flow can be maintained for a longer period of time further downstream along the shock-cleaning sedimentation electrode, compared with positions further upstream along the specified precipitation electrode, so that re-scattering of smaller particles at the same time is prevented. the time when the flue gas stream again passes in the upper part along the precipitation electrode, where the density of the released particles is less.

In addition, other precipitation electrodes can also be exposed to the opposed gas flow, except for the most extreme, downstream precipitation electrodes, during impact cleaning of such precipitation electrodes.

Thus, the present invention is not limited to the disclosed embodiments, but may vary within the scope of the appended claims.

Claims (13)

CLAIM 1. A method of reducing particle emissions used during impact cleaning of an electrostatic precipitator (203) containing at least one emission electrode (207) and at least one precipitation electrode (206), the first gas to be cleaned from the particles flowing past the precipitation electrode , in the direction (204) downstream into one or more gas channels (208), moreover, in one or those gas channels (208) for the first gas passing through the specified precipitation electrode (206) during impact cleaning of the precipitation electrode (206) ) temporarily created a second gas stream (210) is generated, said second gas stream (210) being created from a position downstream of the precipitation electrode (206), while it flows in an upstream direction opposite to the direction of flow of the first gas and, thereby, counteracts the flow of the first gas passing by the precipitation electrode (206), and the flow of the second gas is created by at least one blowing means (221) located centrally in the corresponding gas channel (208) between the precipitation electrodes (206), distinguishing the fact that the specified stream (210) of the second gas is created by blowing means (221) connected by means of a flexible connection (220) with the main switchgear (214) located outside the specified electrostatic precipitator (203), moreover, the control of the specified stream of the second gas (210) carried out by a control unit (216), all moving parts of which are located outside the electrostatic filter cover (203). 2. The method according to claim 1, characterized in that said second gas is formed by a part of the first gas that has already passed through the electrostatic precipitator (203). 3. The method according to any one of claims 1, 2, characterized in that the precipitation electrode (206) is part of the electrostatic precipitator stage (218), which, in turn, forms the most extreme, downstream stage of several electrostatic precipitator stages connected in series. 4. The method according to any one of claims 1 to 3, characterized in that the precipitation electrode (206) is part of the electrostatic precipitator stage (218), comprising several precipitation electrodes arranged in parallel and subjected to shock cleaning in turn, the corresponding stream or several corresponding flows ( 210) a second gas is created for temporary exposure in one or another of the gas channels (208), which or which surround each respective precipitation electrode to be shock cleaned at a given time. 5. The method according to any one of claims 1 to 4, characterized in that the electrostatic precipitator (203) is an available electrostatic precipitator, which is supplemented by a control unit (216) and blowing means (221) to provide said second gas stream (210). 6. A device for implementing a method of reducing particle emissions according to claim 1 during impact cleaning of an electrostatic precipitator (203) containing at least one emission electrode (207) and at least one precipitation electrode (206), next to the precipitation electrode (206) ) one or more gas channels (208) are provided for guiding the first gas to be cleaned of particles, said device comprising a control unit (216) and at least one blowing means (221) for creating a second gas stream (210) from a position lower on out of the precipitation electrode (206) into one or those gas channels (208) for the first gas passing through the specified precipitation electrode (206), and these blowing means (221) are configured to create a stream (210) of the second gas so that it flows in an upstream direction opposite to the direction of flow of the first gas stream, wherein said control unit (216) is configured to control said blowing means (221) to temporarily create said second gas stream (210) during impact cleaning a precipitation electrode (206), said blowing means (221) being centrally located in the corresponding gas channel (208) between the settling electrodes (206), characterized in that said blowing means (221) are connected via a flexible connection (220) to the main distribution a device (214) located outside the specified electrostatic precipitator (203), and all the moving parts of the control unit (216) are located outside the electrostatic filter cover (203). 7. The device according to claim 6, characterized in that the precipitation electrode (206) is part of the electrostatic precipitator stage (218), which, in turn, forms the most extreme, downstream stage from several electrostatic precipitator stages connected in series. 8. The device according to claim 6 or 7, characterized in that the precipitation electrode (206) is part of the electrostatic precipitator stage (218) containing several precipitation electrodes arranged in parallel and with the possibility of performing shock cleaning alternately, said control unit (216) being made with the ability to control one or more appropriate blowing means from said blowing means (221) to temporarily create a corresponding flow or corresponding flows in one or another of the gas channels (208), which are ok each respective precipitation electrode (206) to be impact cleaned at a given time is blasted. 9. A device according to any one of claims 6 to 8, characterized in that at least one of said blowing means (221) is configured to create a second gas stream (210) perpendicular to the direction (204) of the first gas stream, essentially along the entire portion of the precipitation electrode (206), past which the first gas passes into the gas channel (208). 10. The device according to claim 9, characterized in that said precipitation electrodes (206) are made in the form of vertical elements from sheet metal, and at least one of these blowing means (221) extends vertically parallel to the precipitation electrodes (206) and between indicated precipitation electrodes (206). 11. A device according to any one of claims 6 to 10, characterized in that at least one of said blowing means (221) comprises a plurality of nozzles (209) arranged one after the other and intended to distribute the second gas stream (210). 12. A device according to any one of claims 6 to 10, characterized in that at least one of said blowing means (221) comprises an elongated slot for distributing a second gas stream (210). 13. A filtering device for separating solid particles from gas, characterized in that said filtering device comprises an electrostatic precipitator (203), as well as a device according to any one of claims 6-12 for limiting re-scattering of solid particles captured by said electrostatic precipitator (203), shock cleaning time of at least one precipitation electrode (206) in the electrostatic precipitator (203).