DE102008049211B4 - Electrostatic separator for the purification of flue gases - Google Patents

Abstract

Electrostatic separator for cleaning flue gases from wood-burning stoves or stationary diesel engines, consisting of: - a housing (1) with at least one flue gas inlet (2) and at least one clean gas outlet (3), - one that follows the flue gas inlet in the direction of flow and leads vertically downwards, tubular first flow channel section (5) with a non-corona agglomerator, followed by a unipolar corona discharger, the radial gap width between the unipolar corona discharger and the inner wall of the flow channel section (5) being smaller than the radial gap width between the non- Corona / agglomerator and the inner wall of the flow channel section (5) and where the flow channel opens out to collect the precipitated soot particles, - a tubular second flow channel section (11) which follows in the direction of flow and leads vertically upwards from the covered shaft (16) and which exits in a clean gas (3) opens out as a collector (10) is equipped with a rotatable, helical brush (14) and has at least one scraper bar (15) attached along its inner wall, the shaft (16) being part of ...

Description

The invention relates to an electrostatic precipitator for the purification of flue gases. In this case, the flue gas to be processed can come from wood combustion processes or stationary diesel engines. In particular, it is intended to wood burning stoves diverse nature and use.

Electrostatic precipitators have a wide range of applications for cleaning aerosols. For example, in one in the CH 694645 A5 described electrostatic precipitator, the particles of a combustion gas sent through an ionizer in which they are charged in a corona discharge, which is generated at the sharp corners of a high voltage electrode. The collector pipe of the separator is earthed. Charged particles are collected on the inner surface of the collector tube, mainly downstream of the ionizer.

Out DE 10 2004 039 118 B3 it can be seen that particles can be charged and deposited in a first ionization field. Charged particles are deposited under the influence of an aerosol space charge on the inner surface of the walls of the deposition chamber through which the flue gases pass, and then exit the separator in a cleaned state.

In the US 3,924,547 A An electrostatic precipitator is described which has an ionizer structure in the form of negatively charged, vertically juxtaposed pins and a collector assembly in the form of a corresponding number of positively charged tubes surrounding the pins ( 1 in this). Each tube is centered on the corresponding pin forming a gap. The positive DC voltage is applied to the conductive pins of the collector assembly and the negative voltage to the ionizer assembly. In the electrostatic precipitator, the ionizer, the collector cell assembly and the high voltage supply are housed in the separator housing. The housing is internally thermally insulated, as well as the high voltage power supply is thermally isolated from the ionizer and the collector cell assembly. The ionizer and collector cell assembly can be removed for cleaning.

A method and apparatus for particle collection is disclosed in U.S. Patent No. 5,376,854 US 6,238,459 B1 described. An electrostatic agglomerator is used to agglomerate smaller particles. The actual agglomeration occurs on the collector surface as submicron particles come into mechanical contact with each other. A high voltage electrode is positioned along a central axis. This electrode is isolated from the grounded surface via an insulator. The insulator is protected from dirt and condensation by the use of radiant heaters and by the inlet of purge gas. The insulators are housed in a housing that is flooded with nitrogen slightly above the operating pressure. A transformer rectifier is connected to the electrode. The collector surface and the high voltage electrode must be tapped regularly for cleaning.

A laminar flow electrostatic precipitator ( US 5,707,428 A ) has a vertically oriented housing in which the gas to be processed flows downwardly therein to an exit port. The gas enters the laminar flow separator through the inlet and passes through an ionization stage. The charging step imposes a charge on the particles carried by the flue gas. The flue gas with the charged particles then flows to a collector stage downstream of the ionization stage. The collector stage consists of a number of tubular collector passages in it. Each collector tube is electrically connected to a potential opposite that of the particle charge, so that the charged particles are attracted to the inner surface. The separated particles are collected in a container or re-flowed into the gas stream for subsequent filtering. The gas stream is then directed to a shaft from where it flows as clean gas into the environment. The filter may be a conventional electrostatic precipitator. In the device, which is not particularly designed for particle re-flow, the filter is optionally designed to collect any agglomerated particles that have been accidentally re-flowed into the gas stream. The device essentially has a vertically downwardly directed gas flow in combination with a two-stage electrostatic precipitator assembly having separate ionization and collector stages to have a laminar particle flow electrostatic precipitator.

It has always been customary to burn wood for heating without any exhaust / flue gas cleaning. The problem of flue gas cleaning has arisen in recent years due to pollution of the environment and health hazards due to particulate matter. Fine dust particles can be collected and processed before they escape into the environment through effective flue gas cleaning. An electrostatic precipitator is one such effective gas purifier.

• – geringer Druckabfall in ihm; damit ein Ofen zur Holzverbrennung effektiv arbeitet, muss er entsprechend ziehen, d. h. eine entsprechend starke Rauchgasströmung zum Kamin haben;
• – der Abscheider muss einfach, sicher, robust sein, darf keine hohen Investierungskosten und nur geringe Betriebskosten haben, muss leicht gereinigt und ausgetauscht werden können;
• – das Rauchgas von einem Holzverbrennungsofen muss auf kurzem Wege in einem Ofenrohr dem Partikelreinigungsprozess zugeführt werden.

In addition to efficient flue gas cleaning, several requirements are made on the electrostatic precipitator, such as:

• - low pressure drop in it; for a wood burning stove to work effectively, it must draw accordingly, ie have a correspondingly strong flue gas flow to the chimney;
• - The separator must be simple, safe, robust, must not have high investment costs and low operating costs, must be easily cleaned and replaced;
• - The flue gas from a wood burning stove must be supplied to the particle cleaning process in a short stoke in a stovepipe.

Thus, the objects are set, which are the basis of the invention.

The object is achieved by the electrostatic precipitator according to the characterizing features of claim 1 and thus meets the requirements of an efficient flue gas cleaning. The requirements are realized in the electrostatic precipitator. The electrostatic precipitator for preferably quantitatively smaller wood combustion processes such as in private households consists of a housing with Rauchgaseinstritt and clean gas outlet, a tubular non-corona agglomerator and unipolar corona discharger, a tubular collector with a built-in wire brush for cleaning and a shaft / container for collecting segregating / deposited particles. Both tubular assemblies, the agglomerator with corona discharger and the collector stand vertically on this shaft, which connects both as part of the flow channel. The flow channel for the flue gas to be processed in the electrostatic precipitator is, thermally insulated, packaged in a housing.

The electrostatic precipitator, suitable both for the purification of flue gases from wood combustion stoves and for the purification of exhaust gases from stationary diesel engines, according to claim 1 the following features:
The separator has at least one flue gas inlet and at least one clean gas outlet in its housing.

The flow channel leads vertically downwardly as a tubular first flow channel section with a non-corona agglomerator, followed by a unipolar corona discharger which opens into a covered well / vessel as a flow channel component for trapping excreted particulate matter.

From this covered shaft leads downstream, but vertically upward, the second tubular flow channel section, which opens into a clean gas outlet. This second tubular flow channel section is the collector for the exiting from the gas stream particles, it is equipped with a rotatable, helical brush, with which the particles deposited on the pipe inner wall can be brushed off constantly or periodically or as needed by turning down. To clean this brush during the brushing process, there is at least one scraper rail along the inner wall, over which the brush rubs in the pipe during axial rotation and is thereby shaken off or spun onto the particles that are stored thereon.

The non-corona agglomerator with its corona discharger downstream of the gas consists of one of heirs of an out of the flow path insulator housing in the first flow channel section centrally projecting, rod-shaped high voltage electrode, which is coated in its middle exposed in the flow channel region of a deflection electrode and Downstream of the gas, a thin corona discharge electrode has been centrally exposed in its free end region.

The helical brush sits according to claim 2 on a centrally exposed drive shaft, which is clamped at one end up outside the flow path in a drive device and centrally rotatably supported at its other end. The drive device may be a hand crank or a rotary motor.

According to claim 3, the shaft, the particle container, part of the flow channel in the separator. He sits at the lowest point of the flow channel in the separator. The tubular non-corona agglomerator with a downstream corona discharger discharges vertically from above. From it rises vertically upwards the tubular collector with built-in spiral brush. In its deepest part of the shaft has an access, can be removed by the deposited and accumulated particles (claim 4).

The entire flow channel in the separator, the tube of the non-corona agglomerator and corona discharger, the shaft and the tube of the collector are according to claim 5 to an electrical reference potential, usually ground potential. In the latter case, deposited and still charged particles are electrically neutralized on the inner wall of the flow channel.

According to claim 6, it may be expedient that the agglomerator and corona discharger fluidly opens into a first shaft section, from which it then goes down to a bridging, second shaft area, the actual shaft, from which it then to the other, third shaft area goes. The third shaft area is similar to the first one. From the third shaft area it goes vertically up into the collector. Overall, the shaft, the Container for separated, separated and collected particles, an inlet area and an exit area of the process gas flow.

The electrostatic precipitator effectively removes and separates fine particles from combustion exhaust gases.

The electrostatic precipitator has a low pressure drop along its flow path and low operating costs. Its technical structure is simple and robust. He is easy to maintain and clean.

The size of the electrostatic precipitator is limited and takes up little space. The investment costs for installation in a heating system or stationary diesel engine plant or the cost of retrofitting such are low.

In the following two exemplary embodiments of the electrostatic precipitator are presented and the construction described with reference to the drawing.

1 shows the structure of the electrostatic precipitator;

2 shows the separator after 1 with removable non-corona agglomerator with corona discharger and removable collector;

3 shows three construction variants in plan view;

4 shows the separator with removable particle catcher on the shaft;

5 shows the top view of a two-channel electrostatic precipitator;

6 shows the section through a two-channel separator with a divided shaft.

The construction principle, the structure of the electrostatic precipitator is in section in 1 shown. The process to be processed flue gas from here z. B. a wood burning stove is a stove pipe to the housing 1 of the separator introduced and passes through the flue gas inlet 2 one. The aerosol flow bends down and enters the vertically oriented tube 5 from the side at the top, in which the non-corona agglomerator and the gas downstream following corona discharger are installed. In the tube 5 projects from above centrally axially the rod-shaped high voltage electrode 7 in which the pipe 5 covering pot 6 clamped on a high voltage insulator (not highlighted) and connected there to a high voltage power supply. The pot 6 is to the interior of the pipe 5 open, but is not in the flow path. It can be rinsed with pure air or clean gas in such a way that there is always a slight overpressure which places a process gas flow branch in the pot 6 suppressed.

The high voltage electrode 7 is in the flow path in the central area of the pipe 5 from the deflection electrode 8th encased, which is not sharp-edged in their exposed areas. The area of the exposed deflection electrode 8th forms with the inner wall of the pipe 5 a coaxial cylindrical gap and thus the non-corona agglomerator.

• – die frei exponierte Hochspannungselektrode 7 bildet mit der radial gegenüber liegenden Innenwand des Rohres 7 Spaltbereiche mit der größten Spaltweite und damit niedrigen elektrischen Feld im Falle angelegter Hochspannung;
• – die an ihren exponierten Bereichen nicht scharfkantige Ablenkungselektrode 8 bildet mit der radial gegenüber liegenden Innenwand des Rohres 7 einen Spaltbereich mit mittlerer, noch nicht eine Korona erzeugender elektrischer Feldstärke;
• – die Korona-Entladungs-Elektrode 9 bildet mit der radial gegenüber liegenden Innenwand des Rohres 7 einen Spaltbereich mit hoher, koronaerzeugender elektrischer Feldstärke.

Gas downstream in the lower free end of the high voltage electrode 7 sits at least on its circumference thin sharp-edged, possibly provided with equal-length tips corona discharge electrode 9 connected to the inner wall of the pipe 7 forms a coaxial gap whose gap width is smaller than that of the non-corona agglomerator. The sharp-edged corona discharge electrode 9 forms with the radially located inner wall portion of the tube 5 the unipolar corona discharger. In the pipe 7 of the non-corona agglomerator with corona discharger 4 exist different gap areas:

• - The exposed high voltage electrode 7 forms with the radially opposite inner wall of the tube 7 Gap areas with the largest gap width and thus low electric field in the case of applied high voltage;
• - The non-sharp deflection electrode at their exposed areas 8th forms with the radially opposite inner wall of the tube 7 a gap region with mean, not yet a corona generating electric field strength;
• - the corona discharge electrode 9 forms with the radially opposite inner wall of the tube 7 a gap region with high, corona-generating electric field strength.

The tubular collector 10 consists of the tube 11 , the engine 12 , the support staff 13 , the brush 14 and the scraper rail 15 to clean the brush 14 of particles deposited on it. The tubular non-corona agglomerator / corona discharger 4 and the collector 10 are vertical in the housing 1 built of the electrostatic precipitator. From the flow, the agglomerator / corona discharger ends / ends 4 in the one opening 17 above and begins the collector 10 in the other opening 18 at the top of the shaft 16 , The shaft 16 is a part of the flow channel, it connects the agglomerator / corona discharger 4 fluidically with the collector 10 , Down the shaft is the access 19 to empty the shaft 16 and disposal of the manhole 16 accumulated particles. Between the flow channel 5 . 11 . 16 and the housing 1 the separator is the thermal insulation material 20 filled. Both pipes 5 and 11 are on the housing via detachable flanges 21 and 22 fixed and have the high voltage power supply and the high voltage insulator in the housing 6 and the motor drive 12 for the brush 14 on top of the case 1 placed.

This arrangement allows easy access to each covered pipe 6 respectively. 11 which makes repairs and maintenance easy. From the agglomerator / corona discharger 4 and the collector 10 the particles fall down through the respective opening 17 respectively. 18 in the shaft 16 and are in the deepest area 19 of the shaft 16 started. The two pipes 5 and 11 below bridging shaft 16 is a simple design that allows easy access to the separator 1 also allows from below. By filling the gaps in the separator 1 with thermal insulation material there is no heat flow to the environment, at most a minimal, so that heat losses through the electrostatic precipitator 1 are minimal to the outside and a stable chimney effect for the gas outlet from the oven remains.

The agglomerator / corona discharger 4 and the collector 10 can be rotated either up to 90 ° both individually or individually, so that the flue gas enters 2 and the clean gas outlet 3 are frontal or one side and one frontal. The pipes 5 and 11 are over the flanges 21 and 22 ( 2 ) Solder, and thus rotatable, and again detectable. The variants shows 3 with the top views. The assembly of the separator is thus arbitrarily adaptable to the local situation. Are the two pipes 5 and 11 in addition equal, can be swapped under Umflanschung the high voltage supply HV and the motor drive M both.

For cleaning purposes, the shaft 16 be varied at its bottom. An example is a downwardly directed outlet of the duct 16 rotatably mounted pot 23 with lever 24 and handle 25 , which can be attached by axial rotation in one direction and removed in the other direction (see 4 ). About rotary and rotary actuators this intention could also be made possible by remote handling.

If larger accumulating flue gas volumes are also to be processed, the simple electrostatic precipitator can be used according to the 1 to 4 possibly be expanded in a modular manner in its arrangement of the flow channel. 5 and 6 show two exemplary, two-channel situations. 5 shows in top plan view of the compact arrangement of the two agglomerator / corona discharger 4 and 41 opposite the two collectors 10 and 101 in this situation, from the separator housing 1 are encased roughly square. 6 shows the lateral or planar arrangement of the two agglomerator / corona dischargers 4 and 41 as well as the two collectors 10 and 101 , 5 but could also for 6 be unfolded in the plane. In both cases, it is expedient to design the shaft in a multi-chamber system, here for example a three-chamber system. Thus, both agglomerator / corona dischargers discharge fluidly 4 in the entrance fore chamber 161 of the shaft 16 merging into the main shaft 16 empties. From the shaft 16 from the gas flow occurs again in the outlet prechamber 162 one from where he joins the two collectors 10 and 101 fan out. From both process areas 4 . 41 and 10 . 101 falling particles trickle downwards through the respective prechamber 161 and 162 and finally collect sight in the shaft 16 at. It is also possible for groups on the agglomerator / corona discharger and / or collectors to open into different inlet pre-chambers or outlet pre-chambers, which are then bridged together by the shaft. The system, since it is modular, can be numerically increased in terms of the number of process areas if technically justified by the volume to be processed.

The process in the electrostatic precipitator is as follows:
The particulate laden exhaust gas from a combustion application enters the electrostatic precipitator 1 through the smoke gas inlet 2 , The particles in the exhaust are mainly positive and negatively charged. The particles are originally given their electric charge by thermal ionization in the flame. The positively and negatively charged particles flow through the annular gap between the deflection electrode 8th and the opposite inner wall of the tube 5 , the non-corona agglomerator. Is a high voltage to the rod-shaped high voltage electrode 7 on, forms from the deflection electrode 8th to the inner wall of the pipe 5 an electric field of comparatively moderate strength without corona discharge. At negative high voltage, the negatively charged particles drift to the mostly grounded pipe wall, which is at reference potential, and the positively charged particles to the deflection electrode 8th , This radial drift of the positively and negatively charged particles increases the likelihood of particle electrostatic coagulation and enhances the growth of large agglomerates. According to the coagulation of oppositely charged particles, the agglomerates are electrically more or less charge-compensated to electrically neutral. According to the coagulation and particle agglomeration, the concentration of fine particles in the flow decreases, but the size of the particles increases. The large particles are transported by the gas flow in the gas downstream unipolar corona discharger, where they unipolar in the electric field of the highest strength in the therefore existing corona discharge at the sharp-edged corona discharge electrode 9 be charged, provided the high voltage electrode 7 is at high voltage. The particles are there in the ion current between the corona electrode 9 and the inner wall of the pipe 5 electrically charged unipolar. Some of the particles are stored downstream of the corona discharge electrode 9 on the grounded inner wall of the pipe 5 from. The particles deposited there form into large flakes that fall down and in the shaft below 16 accumulate. The flow goes through the connecting shaft 16 and enters the collector 10 one. Under the influence of the space charge caused by the remaining particles, the charged particles collect on the inner wall of the collector tube 11 and on the wires / wire tufts of the helical wire brush 14 at. The helical wire brush 14 rotates in such a way that a brushing on the inner wall of the collector tube 11 down. During the rotary movement of the brush 14 strikes the same over the on the inner wall longitudinally mounted scraper rail 15 , whereby on the wires or on the tufts of the brush deposited particles are shaken / thrown away / away and against the gas flow down to the brush coil and on into the shaft 16 fall to be finally caught up in it. The shaft 16 is emptied regularly or when a level is reached.

The particle-liberated gas, the clean gas, flows in the collector 10 further up and enters the gas downstream clean gas outlet 3 from the separator 1 out.

During operation of the electrostatic precipitator may be on the inner walls of the two tubes 5 and 11 form smaller amounts of condensate down into the shaft 16 flow. The condensate does not affect the process stability of the separator, because it evaporates again during prolonged operation by the hot gas.

Claims (6)

Electrostatic separator for the purification of flue gases from wood burning stoves or stationary diesel engines, comprising: - a housing ( 1 ) with at least one flue gas inlet ( 2 ) and at least one clean gas outlet ( 3 ), - the flue gas inlet in the flow direction following, vertically downwardly leading, tubular first flow channel section ( 5 ) with a non-corona agglomerator, followed by a unipolar corona discharger, wherein the radial gap width between the unipolar corona discharger and the inner wall of the flow channel section (FIG. 5 ) is smaller than the radial gap width between the non-corona / agglomerator and the inner wall of the flow channel section (FIG. 5 ) and wherein the flow channel section ( 5 ) in a covered shaft ( 16 ) discharges discharged soot particles, - one from the covered shaft ( 16 ) in the flow direction, vertically upwardly leading, tubular second flow channel section ( 11 ) leaving in a clean gas ( 3 ), which acts as a collector ( 10 ) with a rotatable, helical brush ( 14 ) and along its inner wall at least one scraper rail ( 15 ), the shaft ( 16 ) Part of the existing flow channel of the electrostatic precipitator ( 1 ) and wherein the non-corona agglomerator with its gas downstream corona discharger consists of a top of an insulator housing (not in the flow path) ( 6 ) in the first flow channel section centrally projecting rod-shaped high-voltage electrode ( 7 ), which in its middle flow channel exposed area of a deflection electrode ( 8th ) and gas downstream in their free Endbe rich a star disk-shaped corona discharge electrode ( 9 ) has been exposed centrally. Electrostatic separator according to claim 1, characterized in that the helical brush ( 14 ) on a centrally exposed drive shaft ( 13 ) is seated with one end up out of the flow path in a drive device ( 12 ) is clamped and stored centrally with its other end. Electrostatic separator according to claims 1 to 2, characterized in that the flow channel in the housing ( 1 ) in a thermal insulation material ( 20 ) is packed. Electrostatic separator according to claims 1 to 3, characterized in that the shaft ( 16 ) in its lowest lying area an outlet device ( 19 ) for the precipitated and trapped particles. Electrostatic separator according to claims 1 to 4, characterized in that the flow channel is at an electrical reference potential. Electrostatic separator according to claims 1 to 5, characterized in that the shaft is in one or more parts, wherein the multi-part shaft from at least one flow inlet region ( 161 ), at least one flow outlet area ( 162 ) and these two areas ( 161 ) and ( 162 ) main shaft ( 16 ) consists.

Images