Electrostatic Precipitator and Method for Electrostatic Precipitation of Materials Out of an Exhaust Gas Flow

Abstract

An electrostatic precipitator (1) to precipitate one or more materials (9) out of an exhaust gas flow (5) has a spray electrode (2) having an active part (14) for generating a corona discharge (6) and a flushing liquid supply (21), by means of which flushing liquid (10) is supplied into the precipitator (1) for removing deposits (11), made of the material(s) (9) to be separated, that settle on the spray electrode (2). The precipitator (1) uses less cleaning liquid and the cleaning is carried out more reliably. For this purpose, a flushing device (8) directs the flushing liquid (10) across a head region (12) of the spray electrode (2) onto the active part (14) of the spray electrode (2) as a flushing stream (22).

Claims

1. An electrostatic precipitator (1) for precipitating one or more materials (9) out of an exhaust gas flow (5) comprising: a spray electrode (2) having an active part (14) for generating a corona discharge (6) and having a head region (12); a flushing liquid supply (21), to supply flushing liquid (10) into the precipitator (1) for removing deposits (11) of the material(s) (9) to be separated that settle on the spray electrode (2); and a flushing device (8) configured to direct the flushing liquid (10) across the head region (12) of the spray electrode (2) as a flushing stream (22) onto the active part (14) of the spray electrode (2), said flushing device (8) having means for reducing the flow speed of the flushing stream (22) with respect to the flow speed of an influx (20) of flushing liquid (10) delivered by the flushing liquid supply (21), and having a cup element (23) whose bottom (25) faces the active part (14) and whose opening (24) faces the head region (12) of the spray electrode (2), wherein the bottom (25) of the cup element (23) and/or its peripheral wall (40) has at least one flushing opening (26) for dispensing the flushing stream (22), and wherein at least one flow resistance (43) is provided within the cup element (23) to increase the flow resistance for the flushing liquid (10) and/or to generate and/or reinforce a turbulent current in the flushing liquid (10).

2. The precipitator (1) according to claim 1, wherein at least one projecting discharge point (15) is provided in the active part (14) of the spray electrode (2) and the flushing device (8) comprises devices for guiding the flushing stream (22) over the at least one discharge point (15).

3. The precipitator (1) according to claim 2, wherein at least two discharge points (15) are arranged in the longitudinal direction (19) of the spray electrode (2), and the flushing device (8) is configured so that the flushing stream (22) successively flushes the at least two discharge points (15).

4. The precipitator (1) according to claim 1, wherein the spray electrode (2) is fixed at its head region (12) in the precipitator (1), and the active part (14) extending in its longitudinal direction (19) is arranged suspended in the interior of the precipitator (1), and wherein the flushing stream (22) runs off on the active part (14) assisted by gravity.

5. The precipitator (1) according to claim 1, wherein the spray electrode (2) is configured in sections with at least one plate element (18) or rib element (41) and with at least one discharge point (15) provided thereon.

6. The precipitator (1) according to claim 5, wherein the flushing device (8) is designed substantially concentric to the cross section (45) of the spray electrode (2) for a uniform distribution of the flushing liquid (10) on the spray electrode (2).

7. (canceled)

8. (canceled)

9. The precipitator (1) according to claim 1, wherein the at least one flushing opening (26) for dispensing the flushing stream (22) is a hole or a slot or a like opening.

10. The precipitator (1) according to claim 1, wherein at least one flushing opening (26) is aligned at the at least one discharge point (15) of the spray electrode (2).

11. The precipitator (1) according to claim 1, wherein the least one flow resistance (43) is a deflection device.

12. The precipitator (1) according to claim 1, further comprising an electrical connection (27) in the head region (12) of the spray electrode (2) for connecting the spray electrode (2) to an electrical supply outside of the precipitation chamber (34) of the precipitator (1), wherein the electrical connection (27) and the precipitation chamber (34) are separated from one another by an electrode collar (50).

13. The precipitator (1) according to claim 12, wherein the electrode collar (50) has a wet side (32) and a dry side (33), and wherein the dry side (33) is arranged outside of the precipitation chamber (34) and the wet side (32) is arranged inside of the precipitation chamber (34), and the electrode collar (50) has a chamber (30), to which a purging gas (35) is applied from outside, and through which a part of the spray electrode (2) extends.

14. The precipitator (1) according to claim 13, wherein the electrode collar (50) has a widening (28), due to which a purging gap (31) for the purging gas (35) remains clear on the wet side between the spray electrode (2) and the electrode collar (50).

15. The precipitator (1) according to claim 14, wherein the chamber (30) of the electrode collar (50) for the spray electrode (2) is divided into a central chamber (37) and an outer annular chamber (38) connected to a purging gas supply (29), and wherein the central chamber (37) and the annular chamber (38) are separated from one another by means of a homogenization device (39) for the purging gas flow (51).

16. The precipitator (1) according to claim 1 wherein the flushing liquid supply (21) is configured so that the influx (20) of flushing liquid (10) enters at least partially as a solid stream into the flushing device (8).

17. The precipitator (1) according to claim 13, wherein the flushing liquid supply (21) in in a central chamber (37) of the electrode collar (50).

18. A method for the electrostatic precipitation of materials (9) out of an exhaust gas flow (5), comprising: guiding exhaust gas flow (5) through a corona discharge (6) generated in a precipitator (1) during a precipitation mode, said precipitator (1) comprising: a spray electrode (2) having an active part (14) for generating a corona discharge (6) and having a head region (12); a flushing liquid supply (21) to supply flushing liquid (10) into the precipitator (1) for removing deposits (11) of the material(s) (9) to be separated that settle on the spray electrode (2); and a flushing device (8) configured to direct the flushing liquid (10) across the head region (12) of the spray electrode (2) as a flushing stream (22) onto the active part (14) of the spray electrode (2), said flushing device (8) having means for reducing the flow speed of the flushing stream (22) with respect to the flow speed of an influx (20) of flushing liquid (10) delivered by the flushing liquid supply (21), and having a cup element (23) whose bottom (25) faces the active part (14) and whose opening (24) faces the head region (12) of the spray electrode (2), wherein the bottom (25) of the cup element (23) and/or its peripheral wall (40) has at least one flushing opening (26) for dispensing the flushing stream (22), and wherein at least one flow resistance (43) is provided within the cup element (23) to increase the flow resistance for the flushing liquid (10) and/or to generate and/or reinforce a turbulent current in the flushing liquid (10) wherein said corona discharge is generated between an active part (14) of the at least one spray electrode (2) and a counter electrode (3) of the precipitator (1): and interrupting the exhaust gas flow (5) and the corona discharge (6) during a regeneration mode in order to remove deposits (11), made of the material(s) (9) to be separated, from the spray electrode (2) by means of a flushing liquid (10), and directing the flushing liquid (10) from a flushing device (8) across the head region (12) of the spray electrode (2) as a flushing stream (22) onto the active part (14) of the spray electrode (2) so that the flushing stream (22) runs along the spray electrode (2) under the influence of gravity and thereby at least partially flushes away deposits (11), made of the material(s) (9), present on the spray electrode (2).

19. The method according to claim 18, wherein influx (20) of flushing liquid (10) is initially guided to the head region (12) of the spray electrode (2) and, by means of the flushing device (8), from there over the active part (14) of the spray electrode (2) as a flushing stream (22).

20. The method according to claim 18, wherein the flushing device (8) swirls the flushing liquid (10) during the generation of the flushing stream (22) and/or distributes the flushing liquid across a cross section (45) of the spray electrode (2).

Description

DESCRIPTION OF THE DRAWINGS

[0046] Further goals, advantages, features and applications of the present invention are derived from the subsequent description of embodiments by way of the drawings. All described and/or depicted features per se or in any combination constitute the subject matter of the present invention, regardless of their summary in the claims or their back-reference. As shown in:

[0047] FIG. 1A a schematic depiction of a first embodiment of a tubular electrostatic precipitator for depicting the technical features,

[0048] FIG. 1B a view identical with FIG. 1A in which the effects occurring during the precipitation mode are characterized,

[0049] FIG. 2A an enlarged, schematic view of a part of the tubular precipitator according to FIG. 1A,

[0050] FIG. 2B a view according to FIG. 2A, in which the effects occurring during the regeneration mode are characterized,

[0051] FIG. 3A-3C schematic cross-sectional depictions of differently shaped spray electrodes,

[0052] FIG. 4-6 schematic depictions of the bottom of flushing devices according to the invention with spray openings,

[0053] FIG. 7 a schematic perspective depiction of an example for a flushing device,

[0054] FIGS. 8 and 9 multiple schematic perspective views of flushing devices according to the invention with spray openings in the peripheral wall,

[0055] FIG. 10A a schematic view of a second embodiment for depicting the technical features,

[0056] FIG. 10B a depiction according to FIG. 10A, in which the effects occurring during the regeneration mode are characterized.

[0057] Identical or identically functioning components are provided with identical reference signs based on multiple embodiments in the subsequently depicted figures in order to improve readability.

DETAILED DESCRIPTION

[0058] FIG. 1A shows a first embodiment of an electrostatic precipitator 1, which is designed as a tubular precipitator in the present example. A spray electrode 2 is applied suspended in the interior of precipitator 1. Spray electrode 2 is surrounded by a counter electrode 3 or lies opposite counter electrode 3, which is formed as a fluid wall 13 on the inner side of the precipitator column 4. Fluid wall 13 is to be understood as a liquid film which is formed by a separating liquid 7 running down the inner side in precipitator column 4.

[0059] To form fluid wall 13, separating liquid 7 emerges from an annular overflow channel 47 and flows downward on the inner side of precipitator column 4 influenced by gravity.

[0060] Spray electrode 2 is fixed with its head region 12 in an electrode collar 50 acting as a fluid barrier and is thus arranged suspended in precipitator column 4.

[0061] Multiple discharge points 15 are arranged on an active part 14 of spray electrode 2 which connects to head region 12 in longitudinal direction 19. Discharge points 15 are arranged uniformly along length 16 of spray electrode 2 in active part 14. Discharge points 15 project laterally from spray electrode 2 and are oriented in the direction of counter electrode 3.

[0062] A lower end region 17 of spray electrode 2 thereby hangs freely in precipitation chamber 34 formed by precipitator column 4.

[0063] As is clear in FIG. 1B, during the precipitation mode of precipitator 1, an exhaust gas flow 5 enters into precipitation chamber 34 from the direction of lower end region 17. Exhaust gas flow 5 rises counter to the force of gravity from lower end region 17 in the direction of head region 12 of the spray electrode and leaves precipitation chamber 34 through an exhaust duct 46 in outflow region 53 of precipitator 1.

[0064] Outflow region 53 connects above active part 14 of spray electrode 2 to a precipitation region 52. The transition from precipitation region 52 into outflow region 53 is carried out approximately along connection line 54 between the transition from active part 14 of the spray electrode and an overflow 48 of overflow channel 47 of precipitator column 4. The flow directions of separating liquid 7 along precipitator column 4 and exhaust gas flow 5 are opposite.

[0065] Fluid wall 13, formed by separating liquid 7 discharging from overflow channel 47 in the direction of exhaust gas flow 5, extends along longitudinal direction 19 of spray electrode 2 up into its head region 12, thus above active part 14.

[0066] A flushing device 8, formed as a cup element 23, is arranged between head region 12 and active part 14 of spray electrode 2, the opening 24 of said cup element is directed toward head region 12. On its bottom 25, flushing device 8 has flushing openings 26 which function to generate a flushing stream 22.

[0067] Figure FIGS. 4-9 show examples of flushing device 8 with differently designed flushing openings 26.

[0068] A flushing liquid supply 21, which in the present case functions as a spray nozzle for generating an inflow 20 of flushing liquid 10, is arranged above active part 14 of spray electrode 2 in outflow region 53 of precipitator 1 close to the transition to exhaust duct 46.

[0069] As is depicted in FIG. 1B, exhaust gas flow 5 is guided upward into precipitation chamber 34 counter to the flow direction of separating liquid 7 during the precipitation mode. Exhaust gas flow 5 contains materials 9, depicted as dots, which are present in the present example as particles or as aerosols with particle sizes in the range of less than 10 m.

[0070] Materials 9 carried along by exhaust gas flow 5 encounter a corona discharge 6 generated between spray electrode 2 and counter electrode 3 so that the materials to be separated are electrically charged with respect to the separating liquid in fluid wall 13 and are drawn into separating liquid 7 under the effect of electrostatic forces. In the present example, separating liquid 7 is situated on an electric ground potential. Upon impact of materials 9 on fluid wall 13, said materials 9 are captured by fluid wall 13 and are swept away to a drain, not depicted.

[0071] Purified exhaust gas flow 5 then enters into exhaust duct 46 in outflow region 53 and is there either emitted to the environment, subjected to a further exhaust gas treatment, or supplied to a downstream process.

[0072] During the precipitation mode of precipitator 1, deposits 11 are deposited over time, in particular on discharge points 15 of spray electrode 2. This hinders the generation of corona discharge 6. The precipitation output of precipitator 1 thus drops.

[0073] FIG. 2 shows an enlarged view of a part of precipitator 1 shown in FIG. 1A and FIG. 1B. Counter electrode 3 present as fluid wall 13 and also the upper wall of precipitation chamber 34 are present, yet not shown.

[0074] In addition to bottom 25, flushing device 8 also has a peripheral wall 40 belonging to cup element 23 which extends from bottom 25 in the direction of head region 12 into outflow region 53.

[0075] Spray electrode 2 in head region 12 is also provided with a rod element 42 designed as a retaining rod, which is provided in its exposed region with an insulating sheath 49 made from electrically insulating material. Insulating sheath 49 protrudes up into electrode collar 50 and opens out in a central chamber 37 of electrode collar 50.

[0076] Electrode collar 50 functions to separate an electrical connection 27 of spray electrode 2 from the moist atmosphere prevailing in precipitation chamber 34. Electrical connection 27 functions to connect spray electrode 2 to an electrical supply, not shown, by means of which a high voltage is applied to spray electrode 2. In the context of the present invention, high voltage is understood to be voltages, in particular direct voltages, in the range from 6 kilovolts to 25 kilovolts.

[0077] A purging gas 35, which is applied to central chamber 37, emerges into precipitation chamber 34 during the precipitation mode, or also continuously through a purging gap 31 formed between rod element 42 and a collar wall 44. Electrode collar 50 has a widening 28 in the region of collar wall 44 so that purging gap 31 between spray electrode 2 and collar wall 44 remains clear. Purging gap 31 and the magnitude of the application of purging gas 35 in central chamber 37 may thereby be designed in such a way that purging gas 35, located in central chamber 37, flows out through purging gap 31 into precipitation chamber 34 at 1.4 times the speed in comparison to the speed of exhaust gas flow 5 in precipitator column 4.

[0078] Purging gas 35 is preferably dry compressed air. Purging gas 35 surrounds a penetration segment 36 of spray electrode 2 enclosed in electrode collar 50 which is actively dried by purging gas 35 located in central chamber 37 and kept free from incoming liquid.

[0079] Central chamber 37 is separated from an outer annular chamber 38 by means of a homogenization device 39 in the form of an annular sponge element. Outer annular chamber 38 and central chamber 37 form a chamber 30, to which purging gas 35 is applied, which in turn is connected to a purging gas supply 29. To guarantee a uniform overflow of purging gas 25 from outer annular chamber 38 into central chamber 37, the homogenization device forms a flow resistance for purging gas 35 so that a pressure difference forms between outer annular chamber 38 and central chamber 37 to ensure a uniform pass through of purging gas through homogenization device 39 into central chamber 37. In this way it is guaranteed that practically no moisture may cross from a wet side 32 of electrode collar 50 to its dry side 33, by which means the presence of leakage currents may be practically prevented between electrical connection 27 and the interior of precipitator column 4. In addition, purging gap 31 at least largely prevents the formation of a continuous conductive film between spray electrode 2 and counter electrode 3 along the wet side 32 of electrode collar 50.

[0080] Flushing liquid supply 21, through which flushing liquid 10 may be guided into flushing device 8 as influx 20 in the form of a solid stream, is arranged to the side of electrode collar 50. This is depicted in FIG. 2B. It is thereby clear that influx 20 of flushing liquid 10 entering into flushing device 8 as a solid stream may be additionally swirled in the interior of flushing device 8 by means of a flow resistance 43 so that flushing liquid 10 is initially distributed uniformly within flushing device 8. Starting from flushing device 8, flushing liquid 10 then emerges as rinsing stream 22 via rinsing openings 26, depicted in FIGS. 4 through 9, onto active part 14 of the spray electrode in order to successively rinse discharge points 15 and to reduce deposits 11 present there.

[0081] At the same time, purging gas flow 51 of purging gas 35 is shown in FIG. 2B, which flows through purging gas supply 29 initially into outer annular chamber 38, further through homogenization device 39 into central chamber 37 and then through purging gap 31 into precipitation chamber 34.

[0082] FIGS. 3A through 3C show three different possible cross-sectional shapes of spray electrode 2 in the region of its active part 14. The cross-sectional shape may thereby be designed as cross-shaped according to FIG. 3A, as star-shaped according to FIG. 3B, or as having multiple arms according to FIG. 3C. Rod element 42 may also extend, as is shown in FIG. 3A and FIG. 3B, up into active part 14. Spray electrode 2 may be designed as plate-like or rib-like, wherein multiple individual ribs or plates may be stamped at the edge to form discharge points 15 in order to then be joined into the respective cross-sectional shape. Discharge points 15 are formed at the edge on the respective plate elements 18 or rib elements 41. Cross sections 45, shown in FIGS. 3A through 3C, are merely examples and may also be shaped differently.

[0083] Flushing device 8 may be aligned preferably concentric to the respective cross section 45 of spray electrode 2 in its active part 14. Flushing device 8 in the form of a cup element 23 may be attached on rod element 42 and come to rest contacting active part 14.

[0084] Differently shaped and arranged rinsing openings 26, depicted in FIGS. 4 through 9, are preferably aligned with discharge points 15 of spray electrode 2 to rinse discharge points 15 in a most targeted way.

[0085] Rinsing openings 26 may, for example, be arranged cross shaped as slots, as are present in FIGS. 4 and 5, or also as holes. Alternatively, the rinsing openings may be provided as lateral slots or notches in a peripheral wall 40 of cup element 23, so that a rinsing flow 22 emerges via these rinsing openings 26 when flushing liquid 10 overflows in cup element 23. According to the depiction in FIG. 7, rinsing openings 26 may also be provided as cross-shaped slots, which at least partially protrude into lateral peripheral wall 40 starting from cup element bottom 25.

[0086] A second embodiment of the present invention is depicted in FIGS. 10A and 10B. In contrast to the first embodiment according to FIGS. 1A through 2B, this embodiment differs in that flushing liquid supply 21 is not designed as a separate nozzle next to electrode collar 50, but instead as an additional connection in electrode collar 50 via which flushing liquid may be guided into central chamber 37. While this does make the design of electrode collar 50 somewhat more complex, the provision of a flushing liquid supply 21 in precipitator column 4 may be omitted. As shown in FIG. 10B, an influx 20 no longer occurs as a solid stream and flushing liquid 10 may be guided more directly and in a targeted way through purging gap 31 along widening 28 into flushing device 8. After ending the supply of flushing liquid 10 into flushing liquid 8, purging gas flow 51 dries the region of penetration section 36 wetted by the flushing liquid so that the precipitation mode and the high voltage necessary for this may be switched on again at spray electrode 2. In any case, the complete draining of rinsing flow 22 out of flushing device 8 must be waited out, so that no chronological disadvantage is generated.

[0087] Overall, the present invention, according to the embodiments depicted here, allows a significantly more efficient and economical operation of the electrostatic precipitator, compared to the previously known functioning principles.

[0088] The precipitator shown here may be combined together with additional precipitators 1 into a precipitator system, which enables continuous operation through alternating and overlapping operation of individual precipitator columns 4.

REFERENCE NUMERALS

[0089] 1 Electrostatic precipitator [0090] 2 Spray electrode [0091] 3 Counter electrode [0092] 4 Precipitator column [0093] 5 Exhaust gas flow [0094] 6 Corona discharge [0095] 7 Separating liquid [0096] 8 Flushing device [0097] 9 Material [0098] 10 Flushing liquid [0099] 11 Deposit [0100] 12 Head region [0101] 13 Fluid wall [0102] 14 Active part [0103] 15 Discharge point [0104] 16 Length [0105] 17 Lower end region [0106] 18 Plate element [0107] 19 Longitudinal direction [0108] 20 Influx [0109] 21 Flushing liquid supply [0110] 22 Flushing stream [0111] 23 Cup element [0112] 24 Opening [0113] 25 Bottom [0114] 26 Flushing opening [0115] 27 Electrical connection [0116] 28 Widening [0117] 29 Purging gas supply [0118] 30 Chamber [0119] 31 Purging gap [0120] 32 Wet side [0121] 33 Dry side [0122] 34 Precipitation chamber [0123] 35 Purging gas [0124] 36 Penetration segment [0125] 37 Central chamber [0126] 38 Annular chamber [0127] 39 Homogenization device [0128] 40 Peripheral wall [0129] 41 Rib element [0130] 42 Rod element [0131] 43 Flow resistance [0132] 44 Collar wall [0133] 45 Cross-section [0134] 46 Exhaust duct [0135] 47 Overflow channel [0136] 48 Overflow [0137] 49 Insulating sheath [0138] 50 Electrode collar [0139] 51 Purging gas flow [0140] 52 Precipitation region [0141] 53 Outflow region [0142] 54 Connection line