CA1249529A - Apparatus for the removal of particulates from industrial gases - Google Patents
Apparatus for the removal of particulates from industrial gasesInfo
- Publication number
- CA1249529A CA1249529A CA000461218A CA461218A CA1249529A CA 1249529 A CA1249529 A CA 1249529A CA 000461218 A CA000461218 A CA 000461218A CA 461218 A CA461218 A CA 461218A CA 1249529 A CA1249529 A CA 1249529A
- Authority
- CA
- Canada
- Prior art keywords
- gas
- electrodes
- corona
- assembly
- scrubbing
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
- B03C3/02—Plant or installations having external electricity supply
- B03C3/16—Plant or installations having external electricity supply wet type
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D47/00—Separating dispersed particles from gases, air or vapours by liquid as separating agent
- B01D47/06—Spray cleaning
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
- B03C3/34—Constructional details or accessories or operation thereof
- B03C3/38—Particle charging or ionising stations, e.g. using electric discharge, radioactive radiation or flames
Abstract
ABSTRACT OF THE DISCLOSURE
A wet scrubber for scrubbing particles from an industrial gas is provided with a discharge electrode assembly to charge the particle before they meet an atomizing spray. The column is dimensioned for a gas velocity of 5 to 30 m/sec., the effective length of the discharge electrode is 15 to 40 cm, and the applied voltge is 20,000 to 70,000 V and a venturi scrubber may be provided downstream of the atomizing nozzle arrangement.
A wet scrubber for scrubbing particles from an industrial gas is provided with a discharge electrode assembly to charge the particle before they meet an atomizing spray. The column is dimensioned for a gas velocity of 5 to 30 m/sec., the effective length of the discharge electrode is 15 to 40 cm, and the applied voltge is 20,000 to 70,000 V and a venturi scrubber may be provided downstream of the atomizing nozzle arrangement.
Description
4746 ~2 ~ 529 APPARATUS FOR THE REMOVAL OF PARTICULATES
FROM INDUSTRIAL GAS~S
SPECIFICATION
Field of the Invention our present invention relates to an apparatus ~or the removal of dust from indu~trial gases and, more particularly, to a ~crubber operating with an aqueous scrubbing liquid, l.e.
a scrubber in which the ~crubbing solu~ion 1~ predominantly water, and which can be u~ed for the scrubbing o~ du~t and other particles fro~ industrlal gases and especlally industrial wa~te qa~es such as flue ga~e~ (e.g. gases from combustion cha~ber~ of boilers or the llke), metallurglcal plant gases, che~ical plant g~se~, incinerators and the like.
Background _ the Invantion Applicants and their assignee have fil0d numerou3 U.S. patent applications and obtain~d va~ious Letters Patent~
ln the United States inventing scrubbers ~or, inter aiia, cleaning industrlal ga-~e~ and removlng particulates therefeom and the following li~t of repre~entative patent~ is con~idered to be of ~i~nificance for information purpo~e~ 801ely and as r2presentative of the earl~er work in this fiQlB by appli~ant~ and/or their assignee:
~z~c~9 U.S. Patent 4,503,020 and u.S. patent 4,093,434.
Karl-Rudolf HEGEMANN: ~.S. patent~ 3,631,656, 3,726,065, 3,799,520 3,820,307, 3,844,744,- 3,844,745, 3,854,968, 3,976,454, ~,007,02~, ~,052,042, ~,055,331, 4,081,914, 4,145~193, 4,218,241, 4,23~,335, 4,316,727, 4,375,439, 4,427,183, 4,415l142.
From the above-mentioned will be apparent that it 18 known to provide a ~crubbing column for the scrubblng of an industrial ga~ with water wherein at least one atomlzing nozzle is provlded for spraying the scrubbing liquid and a sump or collectlon facility is provided at the ba~e of the column for collectlng the scrubbing liquid which may entrain lnto this ~ump or b~sin the particulates which are washed from the gas, It is also known in the scrubbing of indu~trlal gases to provlde such a column ln conjunction with an electro~tatic separator havlng a corona-discharge electrode assembly which is maintained at an electrlcal potential ~uch that a corona or glow discharge is generated at surfaces of the electrode3 for charging the particle~.
The term ~scrubbing column~ i8 u~ed herein to refer to a predominantly upright flow pas~a~e for the gas and the scrubbing liquid and along the axis of which column a plurality of individual atomizlng nozzles can be d~sposed along the axis of th~s tower or column; al~srnatlvely the nozzle assemblle6 can be spaced along the axis of the flow passage, each compris$ng a multipllcity of nozzles.
The wet scrubblng which 1B e~fa~tlYe in the nozzle . region is a wet ~eparation of dust which 18 e~ected by adhes~on of du3t partlcles to water dropl~ts; collection o~
water droplet~ or du~t particles, adhesion o~ multlple du~t partlcles to a water droplet, etc., whereby ~h~ partlcles are removed from the ga~ stream to collect in the step o~ the scrubbing column.
It is ~el~-evldent that the ~crubbing water will al~o remove soluble (absorpt~vely removed) and ~d~orbtively collected gase3 and al90 thu8 ~ay ~crub one or more gaseous components from the raw ga3, The scrubblng column can also lnclude one vr more annular gap or venturi wash~r3 (see the earlier patents mentioned)~
The corona electrodes which are ut~llzed can operate under the electrofilter principles described ln Lueger_Lexikon der Verfahren6technik~ Vol. 16, 1970, p. 119.
. . , _ i;2~
The principle of the electrofilter is similar to that of a cylinder or plate condensor in which between the field electrodes a direct potential i~ appl~ed of 20,000 - 70,000 V and more, l.e. the potential across the gap is closed at the breakdown S voltage, Thi~ potential i5 derived from an alternating or three-phaRe network, a high voltage transformer connected to the supply network and a rectifier connected to the ~ransformer. The negative side of the rectifier output is connected to the corona--discharge electrodes wh~ch pr~ferably have a minimum radius of curvature and can even be relatively thln wir~s of a rectangular cro~s section and in many ca6e~ can be provided wlth barb~ or points. The positive pole of the direct current source is generally grounded a~ are the dust-collecting electrodes, ~owever, the reverRe polarization of the two sets of electrodes is 15 al30 pos~ible. Within ~he present inventlon as well, the corona--di~charge ~lectrodes will be negative and thu~ generally be connected to the ne~ative side of the rectlfier output while the electrode~ flanking the corona electrodes will generally be grounded together with the positive terminal o~ the rectifier.
Within the pre~ent invention as well, the reverse polar$zation of the electrode~ is pos~ible.
The raw gas ~tream carryiny partlculates i~ conducted between the electrodes, the du~t particles and/or fine dropletq of a liquid entrained in the gas stream, being charged by the corona--di~charge electrode~ predominantly negatively are attracted to the du6t-collectlng electrodes. From the latter the agglomerates of du~t are readily swept into a collecting bin.
~2~
In prlor art sy~tems such an electrofilter can be follow~d by the qcrubber and ba~ically the appara~us represents an aggrega~e o~ two du~t-removal device~, namely, the electrofllter and a scrubber. In such 6ystems the path of the gas through the aggrega~e i8 relatively long~ e~peci311y since the sy~tem endeavors to allow sufficient time for the particle~ to charge be~ore the dust is collected or the collecting electroder4 surrounding the ~orona electrodes. Compact assemblies utillzing wet Rcrubbing and electro~tatic principle~ have not, there~or~, been used in pra~tice.
Ob~_cts of _ Invention It ~, therefore, the prlncipal object of the present invention to provide an improved du t-removal apparatus for 1ndustrial ga~es which merges an electrostatie and wet-scrubbing op~ration in such clo~e symbiotic relationship a~ to allow the entire system to be mo~e compact.
Another ob~ect of the invention is to provide an apparatus with improved dust-removal capabilities, both with respect to the dust-removal efficiency (i,e, the degree of removal of the dust) as well as wlth respect to the li~iting particle size, i.e. ~he particle size above which all du~t i3 collected from an en~raine~ qas.
~b~
We have now di~covered/ guite surpri~ingly, ~hat it is possible to provide a ~elatively compact ~crubbing column which 18 ~raversed by a gas and which includeR at least one atomizing nozzle for spraying the ~crubbing liquid, generally water or a water-ba~ed scrubbing solution into the ga~ passing vertically through the column, and an electrosta~ic charging ~ystem so that the electrostatic charge imparted to ~he particles is greatly improves the wet scrbbing ~o that both the particle size and the degree of particle removal will be greatly lmproved over earlier scrubbing ~ystem~ and aggre~ate~. The invention is ba~ed upon our discovery of an essential rel~tlonship between the charging system and the noz~le arrangement and the con~truction of the column which bring about this unique result and appe~rs to be due to the fact that the electrostatic action no longer need depend upon sufficlent time for the partlcles to collect on a dust-collecting electrode. Indeed, lt appear~ that ~he water dropl~t~ function as discrete electrostatic dust-collecting surfaces even though they may not be independently charg~d under the conditions which will be described, Speci~ically we have found that it i8 e~ential ~or the column cross section to be dimensioned so that the gas ~low velocity i8 5 to 30 m/~ec., preferably 5 to 15 m/~ec. (the cross section taking into con~lderation any objects within the pa~h of the flow) while the corona-di~charge electrode assembly in the flow dlrec~ion of th~ raw ga~ manife^qt~ a corona-discharge electrode length o~ 15 to 40 cm, preferably 15 to ~0 cm and the ..... . _ . . , . . . . -1 476 ~2~ 9 corona di~charge el~ctrod~3 are surrounded by polarlzaklon ~lectrode~, and th~ column in the region of the atomizing nozzle or nozzles and the region lmmediately the~ebelow 1~ free from p~cking or baf~le~, i.e. ~orms ~ ~ree space in which the S ~paratlon o~ the du~t from the gas i8 effected.
In a pr~ferred embodiment of the inventlon, ~he flow cros~ section of ~he column and, of cour3e, the meanR for inducing the flow of the raw gas ~o and the di~charge o~ the ~crubbed gas from the column ar~ con~tructed and arranged ~o that the gas velocity i8 about 10 m/sec. while th~ length of the corona-discharge electrod~ i~ about 15 cm and the and the corona digcharge i8 effected with a potential of 20,000 to 70,000 V and preferably 45,000 V.
~e have found that, under ~hese conditions, the lS polarization electrode~ surroundlng th~ corona~dl~charge electrodes do not collect ~ignificant quantitie~ of dust and they readily release the dust thu3 co~lected in the ~luid traversing the polarization el~ctrode a~Yembliy, while the agglomeriza~lon o~
dust or li~uid partlcle~ below the ~praying head or head~ is slgnl~lcantly grea~er than that of other wet-~cxubbing By~ems 80 that th~ degree of 3eparation o~ the d~st i3 greatly ~mproved over earller scrubblng aggregate~.
Th~ polarization a~embly can c0n8t8t 0~ a multipl$city of tube sections ~oin~d together in lateral contact with one another, the tub~ sectlons being, ~or example, hexagonal cross section tube sections to form a honeyco~b construction through which th~ corona discharge electrode~ pa88, baing locat~d along 14746 :~Z~Z9 the axes of these tub~ ~ectlons. The tu~e section~ can be composed of metal and can also serve as dust-collecting electrode~
i de~ired, althou~h it should be noted that the eP~iciency of the present inventlon does not require the tube ~ection~ to act as du~t-collecting electrode~. .
The atomizing nozzle may be provided as a pre~Mure atomizer, i,e. a nozzle which di~per~e~ the droplet~ in the mic~on particle slze range 801ely by forcing the liquid at high ~elocity through ~mall orifices, or a 3pin atomizer which impart~ a twist to the spray. Best r~sults are obtained when each atomizing head include~ a ~o-called twi~t-cup nozzle from which the spray i~
discharged tangentially from a cylindrical bed through appropriate Or11Ce8 30 that the atomlzation 18 generated by the twist e~fect.
The washing column of the lnvention can al80 be provid~d . 15 with an annular gap ~crubber and in thi~ cdse ~he corona electrode assembly is provlded upstr~am o~ the annular gap scrubber in the directlon of flow o the gas.
According to a preferred embodiment o ~he lnvention the corona-di~charge ~lectrode a~sembly i8 provided down~tream of at least one atomizing no~zle arrangement 80 that the gas reaching the electrode a~sembly i3 saturated with water ~apor as i3 the gas reaching the annular gap wa~her. The corona-discharge electrode as~embly can be ad~u~table with respRct to the annular gap washerO
Summarizing the unique char~cteristics of the instant invention, we can observe that while the invention utllize~
corona-disch~rge electrod~s to charg~ the dust particles, th~
~tatic collection of these dust par~icle~ on fixed-surface " .
14746 ~f~
precipi~at~on electrode~ is not neces~ary and i~ replaced by the collection of the du~t partlcles or droplets which function as collection surfaces. ~he pola~ization electrodes indeed can func~ion as du t collection or pre~ipitation electrode~ although their main purpo~e is to enable a high potential gradient to be established to facilitate charging of the dust particles.
rief_Description of the Drawing The above and other objects, features and advantages o~
the pre~ent inventlon will be more readily apparent from the following de~cription, reference being made to the accompanying drawing in which:
FIG. 1 is an axial section through a scrubber according to a first embodiment of the ~nvention~
~ G. 2 ls a detall view drawn to a larger scale of the region of FIG. ls FIG, 3 i~ a ~ection taken along the llnes III - III of FIG. 27 and FIG. 4 is an el~vational vlew, partly broken away, of a ~crubber according to another embodiment o the inventlon.
Specific De~crl tion In FIG. 1 we have Rhown a scrubbing column 1 having a gas inlet 5 at its upper end, a gas outlet 6 a~ its lower end and, below ~his gas outlet, a sump 20 in which the scrubbing llquid can collect, the ~crubbing liquid being di~charged via a line 21 along with partlculates which have been R~parated from the ~ndu~rial waste gas and which orm a suspens~on or a ~lurry in the liquld~
_g_ , . .
- --~ .
~Z~Z9 A manifold 22 i8 connected to a reclrculatlng pump or other source of scrubblng liquid and communicates with a Rcrubber of vertically ~paced atomizlng nozzle heads 2 which spray dropletY
whlch can be in the micron particle size range, into the ga~
stream passing through the column. According to ~he invention, upQtream of the atomlzing nozzle arrangement gQnerally represented at 23, 1~ a corona-di~charge electrode ass~mbly which ha been represented at 4. The ax~s of the column haR been represented at 3. The column and any ob~truction~ along the path of the ga3 i dimen~ioned 50 that the gas ~low velocity i8 a preferred value of S to 15 m/sec. and most advantageou~ly is abou~ 10 m/sec.
A~ can be 3een ~rom FIG. 2, the corona dl~charge electrode arrangement 4 can compri$e a plurality of vertical di~charge electrQdes 7 which can depend from a bu~ bax 24 lS supported in t~e housing of the ~crubber by suitable insulators which have been represented diagrammatically at 25 and 26 and which are surrounded by polarizing electrodes 8, The polarization electrode~ 8 are ha%agonal tube ~ection~ as ~hown ln PIG. 3 with theie walls 8a and 8b, for example, abu~ting one another to ~orm a honeycomb. A high voltage direct cur~ent ~ource 27 has it8 negatlve terminal connected at 9 to the electrode 7 while iS~
po itive terminal 1~ groundad. The honey comb i~ l~kewise grounded as repre~ented at 10. The corona di~charge elec~rodes 7 are energized with 20,000 to 70,000 V, preerably 45,000 V a~
mea~ured across the gap beSween ~h~se electrode~ and the con~ronting sur~aces o ~he hon~ycomb.
. _ ..... .. . . . .. ... . ... .
147~6 ~he tube ~e~tlons 8 are oriented in the flow direction of the ga~ and the electrode 7 can be barbed electrode~ which lle along the axes of the respective tube sections 8. The tube ~ections 8 can be compri~ed of metal or a metallic material and can act as dust-collecting electrode~. The effective length of the corona-dlscharge electrode has been repre~ented at L and corresponds of cour~e to ~he length o the polarlzation electrode tubes 8 and is pre~er~bly 15 to 20 cm.
In this embodiment, the solld part~cle~ or droplets in lU the raw ga~ stream are negatively charg~d and are, as a result, attracted to the more positively charged water droplet~ from the twi~t spray ~rom the atomizing nozzles 2 and thus collect on the~e water dropl~t~ particularly e~ficiently. The du~t-laden gas encountering the corona discharge as~embly 7 can have previou~ly been saturated wlth wat~r.
In the embodiment of PIG. 4 the sa~ura~ion o~ the du~t with water is ensur~d by a palr o~ atomizlng nozzles 102 wh~ch spray the scrubbing liquld into the ga~ stream admitted via an inlet 105 to a scrubb~ng column 101. The latter ha~ a pair o~
housings 130 and 131 recelving the insulators 125 which Yupport~
the bus bar 127, the latter being connected to the direct current source 1~7. The corona electrodes io7 are su~pended from the t)ar 124 and are disposed within a honeycomb of hexagonal tube sections 108 ~or the ~lectrode assembly 104 as previously de~cribed.
Ano~her at~mizing nozzle arrangement represented at 113 i~ provided below the corona dlscharge assembly and generates the droplets at which the charged dust part1cles are attracted, the ,.~, . .
.
14746 ~Z~ 9 qeparation being intensiied by an annular gap or venturi scrubber 111 disposed downstream of the no2zle arrangemen~ 113. ~he annular gap scrubber 111 comprises a vertically displaceable fru~toconical body 112 dl~po~ed with a shell 132 forming a venturi throat 133. The vertical adjustability of thi~ body, e.g, via a ~notor o~ other drive as~embly repre~ented at 134, allows the gap width to be ad~u~ted in ~he annular gap wa~her and hence permits the pressure drop across ~he annul~r gap washer to be varied.
This allows the control of the back pressure at the ~ource of the ga~, e.g, a press~riæed blas~ furnace. ~ blower 135 or an expansion ~urbine for release of ~he gas energy can be prvvi~ed downstream o~ the venturi ~crubber and can op~n into a stack 136 di~charging th~ ~crubbed gas into ~he atmosph~re. It will be appreciated that the embodiment of FIG. 4, apart ~rom differences already de~cribed, operates slmilarly to the embodimen~ of FIG. 1 with re3pect to the collection o~ the charged particle~. The as~embly 104 can be ral~ed and lowered rela~ive to the annular gap washer 111 by hand wheel3 140 rota~ing insulating tubes threaded over spindles 141 by which the as~embly is su~pended in the insulator 125.
.
FROM INDUSTRIAL GAS~S
SPECIFICATION
Field of the Invention our present invention relates to an apparatus ~or the removal of dust from indu~trial gases and, more particularly, to a ~crubber operating with an aqueous scrubbing liquid, l.e.
a scrubber in which the ~crubbing solu~ion 1~ predominantly water, and which can be u~ed for the scrubbing o~ du~t and other particles fro~ industrlal gases and especlally industrial wa~te qa~es such as flue ga~e~ (e.g. gases from combustion cha~ber~ of boilers or the llke), metallurglcal plant gases, che~ical plant g~se~, incinerators and the like.
Background _ the Invantion Applicants and their assignee have fil0d numerou3 U.S. patent applications and obtain~d va~ious Letters Patent~
ln the United States inventing scrubbers ~or, inter aiia, cleaning industrlal ga-~e~ and removlng particulates therefeom and the following li~t of repre~entative patent~ is con~idered to be of ~i~nificance for information purpo~e~ 801ely and as r2presentative of the earl~er work in this fiQlB by appli~ant~ and/or their assignee:
~z~c~9 U.S. Patent 4,503,020 and u.S. patent 4,093,434.
Karl-Rudolf HEGEMANN: ~.S. patent~ 3,631,656, 3,726,065, 3,799,520 3,820,307, 3,844,744,- 3,844,745, 3,854,968, 3,976,454, ~,007,02~, ~,052,042, ~,055,331, 4,081,914, 4,145~193, 4,218,241, 4,23~,335, 4,316,727, 4,375,439, 4,427,183, 4,415l142.
From the above-mentioned will be apparent that it 18 known to provide a ~crubbing column for the scrubblng of an industrial ga~ with water wherein at least one atomlzing nozzle is provlded for spraying the scrubbing liquid and a sump or collectlon facility is provided at the ba~e of the column for collectlng the scrubbing liquid which may entrain lnto this ~ump or b~sin the particulates which are washed from the gas, It is also known in the scrubbing of indu~trlal gases to provlde such a column ln conjunction with an electro~tatic separator havlng a corona-discharge electrode assembly which is maintained at an electrlcal potential ~uch that a corona or glow discharge is generated at surfaces of the electrode3 for charging the particle~.
The term ~scrubbing column~ i8 u~ed herein to refer to a predominantly upright flow pas~a~e for the gas and the scrubbing liquid and along the axis of which column a plurality of individual atomizlng nozzles can be d~sposed along the axis of th~s tower or column; al~srnatlvely the nozzle assemblle6 can be spaced along the axis of the flow passage, each compris$ng a multipllcity of nozzles.
The wet scrubblng which 1B e~fa~tlYe in the nozzle . region is a wet ~eparation of dust which 18 e~ected by adhes~on of du3t partlcles to water dropl~ts; collection o~
water droplet~ or du~t particles, adhesion o~ multlple du~t partlcles to a water droplet, etc., whereby ~h~ partlcles are removed from the ga~ stream to collect in the step o~ the scrubbing column.
It is ~el~-evldent that the ~crubbing water will al~o remove soluble (absorpt~vely removed) and ~d~orbtively collected gase3 and al90 thu8 ~ay ~crub one or more gaseous components from the raw ga3, The scrubblng column can also lnclude one vr more annular gap or venturi wash~r3 (see the earlier patents mentioned)~
The corona electrodes which are ut~llzed can operate under the electrofilter principles described ln Lueger_Lexikon der Verfahren6technik~ Vol. 16, 1970, p. 119.
. . , _ i;2~
The principle of the electrofilter is similar to that of a cylinder or plate condensor in which between the field electrodes a direct potential i~ appl~ed of 20,000 - 70,000 V and more, l.e. the potential across the gap is closed at the breakdown S voltage, Thi~ potential i5 derived from an alternating or three-phaRe network, a high voltage transformer connected to the supply network and a rectifier connected to the ~ransformer. The negative side of the rectifier output is connected to the corona--discharge electrodes wh~ch pr~ferably have a minimum radius of curvature and can even be relatively thln wir~s of a rectangular cro~s section and in many ca6e~ can be provided wlth barb~ or points. The positive pole of the direct current source is generally grounded a~ are the dust-collecting electrodes, ~owever, the reverRe polarization of the two sets of electrodes is 15 al30 pos~ible. Within ~he present inventlon as well, the corona--di~charge ~lectrodes will be negative and thu~ generally be connected to the ne~ative side of the rectlfier output while the electrode~ flanking the corona electrodes will generally be grounded together with the positive terminal o~ the rectifier.
Within the pre~ent invention as well, the reverse polar$zation of the electrode~ is pos~ible.
The raw gas ~tream carryiny partlculates i~ conducted between the electrodes, the du~t particles and/or fine dropletq of a liquid entrained in the gas stream, being charged by the corona--di~charge electrode~ predominantly negatively are attracted to the du6t-collectlng electrodes. From the latter the agglomerates of du~t are readily swept into a collecting bin.
~2~
In prlor art sy~tems such an electrofilter can be follow~d by the qcrubber and ba~ically the appara~us represents an aggrega~e o~ two du~t-removal device~, namely, the electrofllter and a scrubber. In such 6ystems the path of the gas through the aggrega~e i8 relatively long~ e~peci311y since the sy~tem endeavors to allow sufficient time for the particle~ to charge be~ore the dust is collected or the collecting electroder4 surrounding the ~orona electrodes. Compact assemblies utillzing wet Rcrubbing and electro~tatic principle~ have not, there~or~, been used in pra~tice.
Ob~_cts of _ Invention It ~, therefore, the prlncipal object of the present invention to provide an improved du t-removal apparatus for 1ndustrial ga~es which merges an electrostatie and wet-scrubbing op~ration in such clo~e symbiotic relationship a~ to allow the entire system to be mo~e compact.
Another ob~ect of the invention is to provide an apparatus with improved dust-removal capabilities, both with respect to the dust-removal efficiency (i,e, the degree of removal of the dust) as well as wlth respect to the li~iting particle size, i.e. ~he particle size above which all du~t i3 collected from an en~raine~ qas.
~b~
We have now di~covered/ guite surpri~ingly, ~hat it is possible to provide a ~elatively compact ~crubbing column which 18 ~raversed by a gas and which includeR at least one atomizing nozzle for spraying the ~crubbing liquid, generally water or a water-ba~ed scrubbing solution into the ga~ passing vertically through the column, and an electrosta~ic charging ~ystem so that the electrostatic charge imparted to ~he particles is greatly improves the wet scrbbing ~o that both the particle size and the degree of particle removal will be greatly lmproved over earlier scrubbing ~ystem~ and aggre~ate~. The invention is ba~ed upon our discovery of an essential rel~tlonship between the charging system and the noz~le arrangement and the con~truction of the column which bring about this unique result and appe~rs to be due to the fact that the electrostatic action no longer need depend upon sufficlent time for the partlcles to collect on a dust-collecting electrode. Indeed, lt appear~ that ~he water dropl~t~ function as discrete electrostatic dust-collecting surfaces even though they may not be independently charg~d under the conditions which will be described, Speci~ically we have found that it i8 e~ential ~or the column cross section to be dimensioned so that the gas ~low velocity i8 5 to 30 m/~ec., preferably 5 to 15 m/~ec. (the cross section taking into con~lderation any objects within the pa~h of the flow) while the corona-di~charge electrode assembly in the flow dlrec~ion of th~ raw ga~ manife^qt~ a corona-discharge electrode length o~ 15 to 40 cm, preferably 15 to ~0 cm and the ..... . _ . . , . . . . -1 476 ~2~ 9 corona di~charge el~ctrod~3 are surrounded by polarlzaklon ~lectrode~, and th~ column in the region of the atomizing nozzle or nozzles and the region lmmediately the~ebelow 1~ free from p~cking or baf~le~, i.e. ~orms ~ ~ree space in which the S ~paratlon o~ the du~t from the gas i8 effected.
In a pr~ferred embodiment of the inventlon, ~he flow cros~ section of ~he column and, of cour3e, the meanR for inducing the flow of the raw gas ~o and the di~charge o~ the ~crubbed gas from the column ar~ con~tructed and arranged ~o that the gas velocity i8 about 10 m/sec. while th~ length of the corona-discharge electrod~ i~ about 15 cm and the and the corona digcharge i8 effected with a potential of 20,000 to 70,000 V and preferably 45,000 V.
~e have found that, under ~hese conditions, the lS polarization electrode~ surroundlng th~ corona~dl~charge electrodes do not collect ~ignificant quantitie~ of dust and they readily release the dust thu3 co~lected in the ~luid traversing the polarization el~ctrode a~Yembliy, while the agglomeriza~lon o~
dust or li~uid partlcle~ below the ~praying head or head~ is slgnl~lcantly grea~er than that of other wet-~cxubbing By~ems 80 that th~ degree of 3eparation o~ the d~st i3 greatly ~mproved over earller scrubblng aggregate~.
Th~ polarization a~embly can c0n8t8t 0~ a multipl$city of tube sections ~oin~d together in lateral contact with one another, the tub~ sectlons being, ~or example, hexagonal cross section tube sections to form a honeyco~b construction through which th~ corona discharge electrode~ pa88, baing locat~d along 14746 :~Z~Z9 the axes of these tub~ ~ectlons. The tu~e section~ can be composed of metal and can also serve as dust-collecting electrode~
i de~ired, althou~h it should be noted that the eP~iciency of the present inventlon does not require the tube ~ection~ to act as du~t-collecting electrode~. .
The atomizing nozzle may be provided as a pre~Mure atomizer, i,e. a nozzle which di~per~e~ the droplet~ in the mic~on particle slze range 801ely by forcing the liquid at high ~elocity through ~mall orifices, or a 3pin atomizer which impart~ a twist to the spray. Best r~sults are obtained when each atomizing head include~ a ~o-called twi~t-cup nozzle from which the spray i~
discharged tangentially from a cylindrical bed through appropriate Or11Ce8 30 that the atomlzation 18 generated by the twist e~fect.
The washing column of the lnvention can al80 be provid~d . 15 with an annular gap ~crubber and in thi~ cdse ~he corona electrode assembly is provlded upstr~am o~ the annular gap scrubber in the directlon of flow o the gas.
According to a preferred embodiment o ~he lnvention the corona-di~charge ~lectrode a~sembly i8 provided down~tream of at least one atomizing no~zle arrangement 80 that the gas reaching the electrode a~sembly i3 saturated with water ~apor as i3 the gas reaching the annular gap wa~her. The corona-discharge electrode as~embly can be ad~u~table with respRct to the annular gap washerO
Summarizing the unique char~cteristics of the instant invention, we can observe that while the invention utllize~
corona-disch~rge electrod~s to charg~ the dust particles, th~
~tatic collection of these dust par~icle~ on fixed-surface " .
14746 ~f~
precipi~at~on electrode~ is not neces~ary and i~ replaced by the collection of the du~t partlcles or droplets which function as collection surfaces. ~he pola~ization electrodes indeed can func~ion as du t collection or pre~ipitation electrode~ although their main purpo~e is to enable a high potential gradient to be established to facilitate charging of the dust particles.
rief_Description of the Drawing The above and other objects, features and advantages o~
the pre~ent inventlon will be more readily apparent from the following de~cription, reference being made to the accompanying drawing in which:
FIG. 1 is an axial section through a scrubber according to a first embodiment of the ~nvention~
~ G. 2 ls a detall view drawn to a larger scale of the region of FIG. ls FIG, 3 i~ a ~ection taken along the llnes III - III of FIG. 27 and FIG. 4 is an el~vational vlew, partly broken away, of a ~crubber according to another embodiment o the inventlon.
Specific De~crl tion In FIG. 1 we have Rhown a scrubbing column 1 having a gas inlet 5 at its upper end, a gas outlet 6 a~ its lower end and, below ~his gas outlet, a sump 20 in which the scrubbing llquid can collect, the ~crubbing liquid being di~charged via a line 21 along with partlculates which have been R~parated from the ~ndu~rial waste gas and which orm a suspens~on or a ~lurry in the liquld~
_g_ , . .
- --~ .
~Z~Z9 A manifold 22 i8 connected to a reclrculatlng pump or other source of scrubblng liquid and communicates with a Rcrubber of vertically ~paced atomizlng nozzle heads 2 which spray dropletY
whlch can be in the micron particle size range, into the ga~
stream passing through the column. According to ~he invention, upQtream of the atomlzing nozzle arrangement gQnerally represented at 23, 1~ a corona-di~charge electrode ass~mbly which ha been represented at 4. The ax~s of the column haR been represented at 3. The column and any ob~truction~ along the path of the ga3 i dimen~ioned 50 that the gas ~low velocity i8 a preferred value of S to 15 m/sec. and most advantageou~ly is abou~ 10 m/sec.
A~ can be 3een ~rom FIG. 2, the corona dl~charge electrode arrangement 4 can compri$e a plurality of vertical di~charge electrQdes 7 which can depend from a bu~ bax 24 lS supported in t~e housing of the ~crubber by suitable insulators which have been represented diagrammatically at 25 and 26 and which are surrounded by polarizing electrodes 8, The polarization electrode~ 8 are ha%agonal tube ~ection~ as ~hown ln PIG. 3 with theie walls 8a and 8b, for example, abu~ting one another to ~orm a honeycomb. A high voltage direct cur~ent ~ource 27 has it8 negatlve terminal connected at 9 to the electrode 7 while iS~
po itive terminal 1~ groundad. The honey comb i~ l~kewise grounded as repre~ented at 10. The corona di~charge elec~rodes 7 are energized with 20,000 to 70,000 V, preerably 45,000 V a~
mea~ured across the gap beSween ~h~se electrode~ and the con~ronting sur~aces o ~he hon~ycomb.
. _ ..... .. . . . .. ... . ... .
147~6 ~he tube ~e~tlons 8 are oriented in the flow direction of the ga~ and the electrode 7 can be barbed electrode~ which lle along the axes of the respective tube sections 8. The tube ~ections 8 can be compri~ed of metal or a metallic material and can act as dust-collecting electrode~. The effective length of the corona-dlscharge electrode has been repre~ented at L and corresponds of cour~e to ~he length o the polarlzation electrode tubes 8 and is pre~er~bly 15 to 20 cm.
In this embodiment, the solld part~cle~ or droplets in lU the raw ga~ stream are negatively charg~d and are, as a result, attracted to the more positively charged water droplet~ from the twi~t spray ~rom the atomizing nozzles 2 and thus collect on the~e water dropl~t~ particularly e~ficiently. The du~t-laden gas encountering the corona discharge as~embly 7 can have previou~ly been saturated wlth wat~r.
In the embodiment of PIG. 4 the sa~ura~ion o~ the du~t with water is ensur~d by a palr o~ atomizlng nozzles 102 wh~ch spray the scrubbing liquld into the ga~ stream admitted via an inlet 105 to a scrubb~ng column 101. The latter ha~ a pair o~
housings 130 and 131 recelving the insulators 125 which Yupport~
the bus bar 127, the latter being connected to the direct current source 1~7. The corona electrodes io7 are su~pended from the t)ar 124 and are disposed within a honeycomb of hexagonal tube sections 108 ~or the ~lectrode assembly 104 as previously de~cribed.
Ano~her at~mizing nozzle arrangement represented at 113 i~ provided below the corona dlscharge assembly and generates the droplets at which the charged dust part1cles are attracted, the ,.~, . .
.
14746 ~Z~ 9 qeparation being intensiied by an annular gap or venturi scrubber 111 disposed downstream of the no2zle arrangemen~ 113. ~he annular gap scrubber 111 comprises a vertically displaceable fru~toconical body 112 dl~po~ed with a shell 132 forming a venturi throat 133. The vertical adjustability of thi~ body, e.g, via a ~notor o~ other drive as~embly repre~ented at 134, allows the gap width to be ad~u~ted in ~he annular gap wa~her and hence permits the pressure drop across ~he annul~r gap washer to be varied.
This allows the control of the back pressure at the ~ource of the ga~, e.g, a press~riæed blas~ furnace. ~ blower 135 or an expansion ~urbine for release of ~he gas energy can be prvvi~ed downstream o~ the venturi ~crubber and can op~n into a stack 136 di~charging th~ ~crubbed gas into ~he atmosph~re. It will be appreciated that the embodiment of FIG. 4, apart ~rom differences already de~cribed, operates slmilarly to the embodimen~ of FIG. 1 with re3pect to the collection o~ the charged particle~. The as~embly 104 can be ral~ed and lowered rela~ive to the annular gap washer 111 by hand wheel3 140 rota~ing insulating tubes threaded over spindles 141 by which the as~embly is su~pended in the insulator 125.
.
Claims (14)
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An apparatus for the removal of particulates from an industrial gas entraining same, said apparatus comprising:
a grounded scrubbing tower dimensioned to and provided with means for generating a downward velocity of a gas to be scrubbed therein of substantially 5 to 30 m/sec;
atomizing nozzle means in said scrubber for spraying an aqueous scrubbing liquid into said gas within said scrubber;
a corona-dischacge electrode assembly connected to a direct current source for applying a potential of 20,000 to 70,000 V
to said assembly, and said assembly disposed in said scrubber to have the complete assembly upstream of said nozzle means with respect to of said gas, said nozzle means situated below said assembly, said assembly comprising a plurality of discharge electrodes having effective lengths of substantially 15 to 40 cm and surrounded by respective polarization electrodes, said polarization electrodes being tube lengths axially traversed by said discharge electrodes, said tube lengths being oriented to extend in said direction and being mutually parallel with lateral surfaces of each tube length in sealing contact with lateral surfaces of a plurality of adjoining tube lengths, a region immediately around and below said nozzle means in said scrubber being free from baffling surfaces to enable particles charged at said assembly to collect on droplets of said scrubbing liquid from said nozzle means in said region and thereby separate from said gas.
a grounded scrubbing tower dimensioned to and provided with means for generating a downward velocity of a gas to be scrubbed therein of substantially 5 to 30 m/sec;
atomizing nozzle means in said scrubber for spraying an aqueous scrubbing liquid into said gas within said scrubber;
a corona-dischacge electrode assembly connected to a direct current source for applying a potential of 20,000 to 70,000 V
to said assembly, and said assembly disposed in said scrubber to have the complete assembly upstream of said nozzle means with respect to of said gas, said nozzle means situated below said assembly, said assembly comprising a plurality of discharge electrodes having effective lengths of substantially 15 to 40 cm and surrounded by respective polarization electrodes, said polarization electrodes being tube lengths axially traversed by said discharge electrodes, said tube lengths being oriented to extend in said direction and being mutually parallel with lateral surfaces of each tube length in sealing contact with lateral surfaces of a plurality of adjoining tube lengths, a region immediately around and below said nozzle means in said scrubber being free from baffling surfaces to enable particles charged at said assembly to collect on droplets of said scrubbing liquid from said nozzle means in said region and thereby separate from said gas.
2. The apparatus defined in claim 1 wherein said discharge electrodes have effective lengths of 15 to 20 cm.
3. The apparatus defined in claim 2 wherein said discharge electrodes of said asgembly have effective lengths of about 15 cm.
4. The apparatus defined in claim 1 wherein said potential is about 45,000 V.
5. The apparatus defined in claim 1 wherein said polarization electrodes are hexagonal tube sections axially surrounding the respective discharge electrodes.
6. The apparatus defined in claim 5 wherein said tube sections are composed of a metallic material and form dust-collection electrodes.
7. The apparatus defined in claim 1 wherein said nozzle arrangement includes at least one twist-cup nozzle.
8. The apparatus defined in claim 1, further comprising an annular gap washer in said column downstream of said arrangement, said annular gap washer including a gap adjustment member for controlling the gap of said washer.
9 . The apparatus defined in claim 8, further comprising spray means upstream of said assembly for saturating said gas with water before it reaches said assembly.
10. The apparatus defined in claim 8, further comprising means for adjusting the assembly with respect to said washer.
11. In an apparatus for the removal of dust-free industrial gas which comprises:
a scrubbing column formed with an upper gas inlet, a lower gas outlet and means for passing said gas through said column downwardly from said inlet to said outlet;
means in said column for scrubbing said gas with scrubbing water and including atomizing nozzles disposed one above another;
and an electrical ionizing device comprising corona electrodes and non-corona electrodes connected to a direct current source for applying a voltage gradient of 20,000 to 70,000 V
across said electrodes, the scrubbing column being grounded and the atomized scrubbing water connecting a wall of the scrubbing column, the improvement wherein;
said ionizing device is constituted of a multiplicity of mutually parallel tube lengths forming said non-corona electrodes and extending generally in direction of flow of said gas with lateral surfaces of each tube length sealingly in contact with lateral surfaces of adjacent tube lengths;
said corona-discharge electrodes each extend axially through a respective one of said tube lengths; and each of said corona-discharge electrodes has an electrode length of substantially 15 to 40 cm.
a scrubbing column formed with an upper gas inlet, a lower gas outlet and means for passing said gas through said column downwardly from said inlet to said outlet;
means in said column for scrubbing said gas with scrubbing water and including atomizing nozzles disposed one above another;
and an electrical ionizing device comprising corona electrodes and non-corona electrodes connected to a direct current source for applying a voltage gradient of 20,000 to 70,000 V
across said electrodes, the scrubbing column being grounded and the atomized scrubbing water connecting a wall of the scrubbing column, the improvement wherein;
said ionizing device is constituted of a multiplicity of mutually parallel tube lengths forming said non-corona electrodes and extending generally in direction of flow of said gas with lateral surfaces of each tube length sealingly in contact with lateral surfaces of adjacent tube lengths;
said corona-discharge electrodes each extend axially through a respective one of said tube lengths; and each of said corona-discharge electrodes has an electrode length of substantially 15 to 40 cm.
12. The improvement defined in claim 11 wherein said tube lengths form a honeycomb array and are constituted of hexagonal-section tube lengths.
13. The improvement defined in claim 12 wherein each of said corona-discharge electrodes has an electrode length of substantially 15 cm.
14. The improvement defined in claim 13 wherein each of said atomizing nozzles is a twist-cup nozzle.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19833329638 DE3329638A1 (en) | 1983-08-17 | 1983-08-17 | DEVICE FOR THE DEDUSTING OF INDUSTRIAL GASES |
| DEP3329638.3-23 | 1983-08-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1249529A true CA1249529A (en) | 1989-01-31 |
Family
ID=6206721
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000461218A Expired CA1249529A (en) | 1983-08-17 | 1984-08-16 | Apparatus for the removal of particulates from industrial gases |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS60106552A (en) |
| CA (1) | CA1249529A (en) |
| DE (1) | DE3329638A1 (en) |
| ES (1) | ES8504490A1 (en) |
| GB (1) | GB2147525B (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2607680B2 (en) * | 1989-05-09 | 1997-05-07 | 三菱重工業株式会社 | Electric precipitator and operating method thereof |
| US5427608A (en) * | 1991-06-28 | 1995-06-27 | Voest Alpine Industrieanlagenges, M.B.H. | Method of separating solid and/or liquid particles and/or polluting gas from a gas stream, and apparatus for carrying out the method |
| DK0545943T3 (en) * | 1991-06-28 | 1997-10-27 | Voest Alpine Ind Anlagen | Process for separating solid and / or liquid and / or gaseous particles from a gas stream as well as plant for carrying out the process |
| ES2059233B1 (en) * | 1992-04-22 | 1997-07-16 | Mendez Fernandez Manuel Ismael | INSTALLATION OF FILTER FOR DEPURATION OF GASES EMITTED TO THE ATMOSPHERE BY INDUSTRIAL OPERATIONS. |
| WO1996004977A1 (en) * | 1993-02-16 | 1996-02-22 | Götaverken Miljö AB | A method and apparatus for removing particulate matter from flue dust |
| FR2750616B1 (en) * | 1996-07-05 | 1998-10-16 | F Tec Indus | PROCESS FOR THE TREATMENT OF GASEOUS EFFLUENTS ELECTROCHEMICALLY |
| ATA62197A (en) * | 1997-04-11 | 2000-07-15 | Voest Alpine Ind Anlagen | METHOD FOR PURIFYING DUST-LOADED PROCESS EXHAUST GASES |
Family Cites Families (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2357354A (en) * | 1941-05-13 | 1944-09-05 | Westinghouse Electric & Mfg Co | Electrified liquid spray dust precipitator |
| GB556939A (en) * | 1941-05-13 | 1943-10-28 | Westinghouse Electric Int Co | Improved method of and apparatus for removing dust or other foreign particles from gas or air |
| US2864458A (en) * | 1955-08-02 | 1958-12-16 | Masch Fabriek Kiekens N V | Liquid-electrostatic precipitation |
| DE2024423A1 (en) * | 1970-05-20 | 1971-12-09 | Schmid O | Method and device for separating solid, liquid and / or gaseous particles from gases or vapors |
| CA1070622A (en) * | 1974-08-19 | 1980-01-29 | James J. Schwab | Process and apparatus for electrostatic cleaning of gases |
| GB1526111A (en) * | 1975-06-19 | 1978-09-27 | Dart Ind Inc | Electrostatic precipitator |
| JPS5286783U (en) * | 1975-12-24 | 1977-06-28 | ||
| GB1542522A (en) * | 1976-02-04 | 1979-03-21 | Air Pollution Syst Inc | Method of and apparatus for charging particles dispersed in a gas stream |
| JPS531517A (en) * | 1976-06-25 | 1978-01-09 | Kenzou Inoue | Dynamic speaker and method of producing same |
| JPS5314788A (en) * | 1976-07-28 | 1978-02-09 | Toagosei Chem Ind Co Ltd | Preparation of polyvinyl chloride |
| DE2636526B1 (en) * | 1976-08-13 | 1977-10-06 | Bischoff Gasreinigung | Wash tower for acidic stack gases - with duplicate spray system to allow separate irrigation of the tower inside wall |
| DE2914340A1 (en) * | 1978-04-10 | 1979-10-25 | Monsanto Co | METHOD AND EQUIPMENT FOR REMOVING PARTICLES FROM A GAS STREAM |
| JPS613408Y2 (en) * | 1978-08-21 | 1986-02-03 |
-
1983
- 1983-08-17 DE DE19833329638 patent/DE3329638A1/en active Granted
-
1984
- 1984-08-06 JP JP59163919A patent/JPS60106552A/en active Granted
- 1984-08-15 GB GB08420768A patent/GB2147525B/en not_active Expired
- 1984-08-16 CA CA000461218A patent/CA1249529A/en not_active Expired
- 1984-08-17 ES ES535238A patent/ES8504490A1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS60106552A (en) | 1985-06-12 |
| GB8420768D0 (en) | 1984-09-19 |
| GB2147525B (en) | 1987-09-03 |
| ES535238A0 (en) | 1985-05-16 |
| ES8504490A1 (en) | 1985-05-16 |
| GB2147525A (en) | 1985-05-15 |
| DE3329638A1 (en) | 1985-03-07 |
| DE3329638C2 (en) | 1988-05-11 |
| JPH0317547B2 (en) | 1991-03-08 |
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