US3907525A - Ventilating system washer cleaning apparatus - Google Patents

Abstract

An apparatus for clearing ventilating systems of grease vapors, odors, smoke and the like which comprises a housing having inlet and outlet passages and enclosing between these passages, sequentially in the direction of air flow, a centrifugal extractor thereby substantially reversing the airstream flow, a continuous cold water spray intersecting and directed counter to the airstream flow and a group of electrostatic precipitators. The combined action of the extractor, water spray and precipitators remove variously sized grease, vapor and smoke particles from the ventilating airstream.

Description

United States Patent King Sept. 23, 1975 [5 1 VENTILATING SYSTEM WASHER 3,260,189 7/1966 Jensen 126/299 R NI APPARATUS 3,618,659 11/1971 Rawal 165/1 3,628,311 12/1971 Costarella..... /228 X lnventorl Donald King, Luwsvflle. y- 3,660,045 5/1972 Gladu 23 277 c 3,672,126 6/1972 Goettle 261/116 X [73] Assgnee' a" Kmg 3,702,756 11/1972 Bowman .1 /119 x 3,731,462 5/1973 Costarella et a1... 98/115 K X 22] il d; July 12 1973 3,744,217 7/1973 Ebert 55/387 X 3,747,301 7/1973 Glover et al.. 55/104 X [21] App1.l 1o.:378,566 3,785,124 1/1974 Gaylord 55/118 3,788,041 1/1974 Gaylord 55/129 [52] US. Cl. 55/122; 55/126; 55/139; O G TEN S OR A PLIC TION 55/242; 55/260; SS/ G. 36; 913/ 15 K 1,019,617 2/1966 United Kingdom 55/126 [51] Int. C1. B03C 13/01 1,071,680 3/1954 France 55/122 [58] Field of Search 126/299 R, 299 A, 299 B, 354,917 7/1961 Switzerland 98/115 K 126/299 C, 300', 301; 98/115 R, K; 55/108, 110, 111, 118, 122, 126, DIG. 36, Primary Examiner-Bernard Nozick 220, 239, 257, 259, 260, 242, 481, 139; Attorney, Agent, or Firm-Woodard, Weikart,

261/126,115,116,1l7,l18 Emhardt& Naughton [56] References Cited [57] ABSTRACT UNITED STATES PATENTS An apparatus for clearing ventilating systems of grease 1,078,927 11/1913 Keltner 261/126 UX vapors, dors, smoke and the like which comprises a 111021996 7/1914 30116115161" 261/126 UX housing having inlet and outlet passages and enclosing gerhold 1 between these passages, sequentially in the direction egg 2,245,516 6/1941 Wintermute 55/122 x $5,?" a i frii 222; gzgfi gzg zi 2,273,194 2/1942 Hedberg et a1. v.55/13 y reversllg e ea 2,347,709 5/1944 Penney 55/118 Water Spray ""ersectmg and dlrected i F 2,387,345 10/1945 Peary v I I 261/126 airstream flow and a group of electrostatlc prec1p1ta- 2,392,038 1/1946 Gaylord 55 010. 36 ms The m n d a ti n f th extra tor, water 2,555,216 5/1951 Wintermute 55/1 18 spray and precipitators remove variously sized grease, 2,643,105 6/1953 Lipowitz 261/126 X vapor and smoke particles from the ventilating air- 2,709,580 5/1955 Kameya..... 261/111 Stream, 2,862,354 12/1958 Barnhart.... 55/122 3,156,547 11/1964 Fleck 55/118 x 2 CIaImS, 6 Drawlng Flgures $54 2%54 51 43 34 34 W47 a l 1' |5\ ','"7""" M 13 33 1 32 111/ we xxnwmen 24 2s \I, 17 E 27b I 22 l 1 l Z1 US Patent Sept. 23,1975 Sheet 10M 3,907,525

US Patent Sept. 23,1975 Sheet 2 of4 3,907,525

Fig.3

US Patent Sept. 23,1975 Sheet 3 of4 3,907,525

VENTILATING SYSTEM WASHER CLEANING APPARATUS BACKGROUND OF THE INVENTION The ventilation of enclosures in which a smoke and grease laden atmosphere is generated (for example, commercial and institutional kitchens) is beset with problems. More generally, industrial installations also have difficulty with respect to, for example, removal of oil mist from the area adjacent to lathes and screw machines, removal of welding dust from in-plant welding shops, and removal of dust lint and vapors from various industrial processes. Difficulties in disposing of grease vapor, odors and smoke, time consuming clean-up and maintenance of the equipment and ventilating apparams, the fire hazard resulting if such periodic clean-up is not rigorous are some of the difficulties involved. Airpollution ordinances have foreclosed the possibility of meeting these difficulties by merely dumping the contaminated ventilating airstream to atmosphere exte rior of the building or enclosure.

While use of electrostatic precipitators has, in the past, been attempted in dust, oil and grease vapor laden enclosure ventilation, the results have not been satisfactory because accumulation of grease on and adjacent the cells progressively inhibited their functioning. The appratus of the present invention succeeds in meeting the ventilation problem discussed above because it combines a cold water spray and a watercooled centrifugal extractor with the use of the electrostatic precipitators. The centrifugal extractor and cold water curtain, directed generally counter to the flow of the ventilating airstream, serve to remove and wash away heavier grease vapors and the larger of the smoke particles. Since these are removed prior to entry of the airstream into the precipitator cell area, the cells can perform, without pregressive inhibition of their function, removal of the final smaller particles remaining in the airstream.

BRIEF DESCRIPTION OF THE DRAWINGS nozzles and their manifold.

FIG. 5 is a schematic view of the piping arrangement for the continuous cold water spray nozzle array shown in FIG. 4.

FIG. 6 is a schematic illustration of the piping arrangement for the wash-down nozzle array.

FIG. 7 is a schematic showing of the electrical circuit for the apparatus of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring initially to FIG. 1 the apparatus of the present invention is shown generally at 10 and is formed by a tubular housing, the upper end of which is formed to provide an outlet collar 1 l on which is mounted a motor drivenfan 12 enclosed in a suitable housing 13. The fan 12 and the housing protecting it maybe of any suitable type drawing air through the housing 10 and discharging it in any suitable fashion either peripherally around the housing 13 or over the open upper end of the housing. It will be understood that the fan structure and the housing 13 form no part of the present invention but merely illustrate the environment in which the apparatus of the present invention, enclosed by the housing 14, is utilized. The fan 12 merely serves to initiate the flow of ventilating air through the housing 14 which is shown in detail in FIGS. 2 and 3.

Referring particularly to FIG. 2, the housing 14 is shown as generally rectangular and tubular in configuration, one sidewall of the housing being formed by an access door 16. The access door is removable by moving the door latch member 17 out of overlying relation to the upper edge of the access door and then sliding the access door upwardly out of itss peripheral retaining members 17 formed integrally with the housing sidewall indicated at 18.

At its lower end the housing 14 carries an inlet collar 21 which is adapted to be installed on, for example, an existing roof-top duct exit, the apparatus and housing 14 thus being interposed between the roof-top duct exit and the conventional roof-top fan assembly which may be accommodated on the outlet collar 11. The housing, adjacent the collar 21, is provided with an inwardly turned flange 22 which thus forms an inlet passage for the airstram entering through the collar 21 as indicated by the air flow arrows in FIG. 2. The upper margin of the collar 22 carries brackets 23 which support a baffle or plate 24 having a depending skirt 26 which extends toward the collar and to a point generally aligned with the upper margin of the inlet passage formed by the collar 22. The inlet passage formed by collar 22 is smaller in cross section than the housing which extends outwardly to its sidewalls and thus forms a peripheral trough within the housing indicated at 27 as will be evident from the flow arrows of FIG. 2. The direction of flow of the airstream is substantially reversed by the skirt 26 of the baffle 24 and the airstream moves toward the base of the trough 27 but is again directed upwardly, by the trough, toward the outelet at the top of the housing 14.

Above the baffle 24, the housing carries a support frame 31 which has a depending portion 31a forming an entry to the flat filter member 32 which is supported on the frame 31. The filter 32 serves as a mist, or moisture droplet barrier, and removes droplets from the airstream which progresses upwardly through the filter.

Supported on appropriate mounting members 33 is an array of electrostatic precipitator cells indicated generally at 34. These electrostatic precipitator cells are well known in the prior art and are formed by collector plates 34a and include an ionizing section provided with a relatively high DC voltage. Any particles remaining in the airstream as it passes upwardly through the cells move through the ionizing section and are there given a positive charge. As these charged particles pass up into the collecting plate sections, they are attracted and held to the ground potential plates by a strong electrostatic field. As indicated by the arrows in FIG. 2 the airstream, after moving through the precipitator cells continues upwardly to exit through the outlet collar 1 1.

As may be seen in FIGS. 2 and 3, suitable brackets 36 carried on the exterior surface of the skirt 26 sup port a continuous, rectangular header pipe 37 which is shown in detail in FIG. 4. A connecting tee 37a provides for supply of cold water to the manifold 37. As may best be seen in FIG. 3, the tee 37a is connected to a supply pipe 38 which has a branch 40 extending to the exterior of the housing and to the extending end of which a controlled, cold water supply pipe may be connected, the piping connections being shown in detail in FIG. to be described subsequently. A capped alternate cold water inlet connection 39a is provided for use as an alternate cold water inlet connection where the piping must be brought to the assembly through the duct work on which the assembly is mounted. It will be understood that when the alternate supply connection 39a is utilized, the supply connection 40 would be capped. Spaced around the length of the header 37 are continuous water wash nozzles 39 which are of a conventional type and provide a spray pattern generally in the form illustrated in broken lines in FIG. 2. It will be noted that this cold water spray issuing from the nozzles 39 is directed generally counter to the flow of ventilating air as it moves from the trough 27. Supported on the skirt 26 somewhat below the nozzles 39 is generally rectangular configurated wash-down water manifold 41. Brackets 42 support the manifold and spaced along its length are outwardly directed wash-down nozzles 43 which are of conventional construction but which differ in spray pattern from the nozzles 39 in that they direct peripherally outwardly a conical water spray of approximately 120 degrees. This wash-down water, supplied at intervals as will subsequently be described, moves down the inner surface of the housing sidewalls and into the trough 27 from whence it, together with the water resulting from the spray issuing from the nozzles 39, drains from the trough 27 through the drain connection 27a (FIG. 3). The grease and particle laden drain water may be passed through a suitable grease removal unit (not shown) before discharge into the conventional drainage system. As may best be seen in FIG. 2, the wash-down water to the header 41 is supplied by a pipe 46 and a portion 46a of this pipe extends to the exterior of the housing and permits connection of a controlled supply of hot water to be described in detail with reference to FIG. 6. The capped extension 46b of the pipe permits an alternate supply connection through the duct work.

As may best be seen in FIGS. 2 and 3 an array of hot water, wash-down nozzles 51 is supported in overlying relation to the precipitator cells, the nozzles being supplied by the header 52 which is connected to the downwardly extending pipe 53 (FIG. 2) which joins the pipe 46 at the tee-connection 54. Adjacent the nozzles 51 are nozzles 54, adapted for dispensing a detergent solution into the area above the precipitator cells for bathing the cells in the detergent solution at controlled intervals. Nozzles 54 are supplied by a separate header pipe adjacent the header pipe supplying the nozzles 51 and this detergent supply header is connected to the pipe 56 (FIG. 3) which has a portion 56a extending to the exterior of the housing and which is adapted to be supplied with a detergent solution. An extending portion 56b, shown capped in FIG. 3, provides an alternate connection for supplying detergent to the pipe 56 and the nozzles 54. An alternate connection for the trough 27, to be used where the drain piping must be brought through the duct work on which the apparatus is installed, is indicated at 27b in FIG. 3, this drain being capped when the drain connection 27a is utilized.

Referring to FIG. 5, the control connections for the continuous spray nozzles 39 will now be described. The union 62 is connected to the cold water supply source and a manual stop valve 63, together with a vacuum breaker 64 are provided. The solenoid valve 66 controls the flow of cold water (a by-pass line 67 controlled by a manual valve 68 is also provided) the manual valve 68 normally being closed during operation. The cold water supply line includes a line strainer 69, a pressure regulator 71 and a pressure gage 72. The downstream end 73 of the cold water line is connected to the cold water nozzle line 39 (FIG. 3) which supplies water through the pipe 38 to the nozzles 37a. A branch line 74 to the drain may be suppled and is controlled by the normally open solenoid valve 76. The line 74 and the solenoid valve 76, when present in the system, provide a means for automatically bleeding the supply and nozzle lines when the system is shut-off, thus preventing these lines from freezing in climates where this precaution is necessary.

Referring to FIG. 6, the piping arrangement for supplying hot water to the nozzles 43 and 51, and detergent solution to the nozzles 54, will now be described. The piping system for supplying hot water to the line 77 which is connected to the line 46a (FIG. 3) includes a union 78 which is connected to a source of hot water supply, a stop valve 79, a vacuum breaker 81 and a normally closed solenoid valve 82. A by-pass including the manual stop valve 83 is provided around the solenoid valve, the valve 83 being closed during normal operation of the apparatus. A normally open solenoid valve 84 in the line 86 to the drain provides an arrangement for bleeding the line where temperatures require precaution against freezing. The detergent supply line 87 is connected to the line 56a (FIG. 3) and extends to a detergent solution container 88, flow from which through the line 87 is established by the electrically energized detergent pump 89. The control system for the apparatus is shown schematically in FIG. 7. It includes the power line members 101 and 102 and a start-stop, push-button switch 103 which has normally open stop contacts 103a and normally closed stop contacts 1031; connected in series with the control relay CR-l Series connected contacts 103C and 103d are connected in series with a pair of contacts identified at T-2A and to the control relay identified at CR-2. Contacts T-2A are controlled by the timer motor T-2. Once timer motor T-2 has been energized, the contacts T-2A are not reclosed until a time delay subsequent to de-energization of the timer T-2. The timer T-l is energized with relay control CR-2 and the detergent pump 89 is connected to this circuit through the normally closed timer actuated switch T-IA. The contacts T-lA are opened by the timer T-l after a short time period of the order of 15 seconds so that detergent solution is supplied to the nozzles 54 only for this short period during the washdown cycle. The start-stop switch 103 is provided with holding contacts CR-lA and CR-2A which are closed by the energization of the relay coils CR-l and CR-Z, respectively. Connected between the upper one of the contacts CR-2A and the supply line 102 is a control relay identified as CR-3 which has in series with it a the airstream. The thermostat 106 is not shown in FIGS. 2 and 3, however, it will be understood that it functions as a reverse-acting high temperature limit control and is appropriately located in the duct work through which the ventilating airstream passes as it moves to the apparatus of the present invention. The timer T-2 is connected across the lines 101 and 102 through the parallel connected control relay switch identified at CR'2B and timer controlled switch T-2B, energization of the control relay CR-2 closing the switch CR-ZB and the switch T-2B being closed by the timer T-2. A wash cycle indicator light may be provided in parallel with the timer T-2.

The hot water solenoid valve 82, mentioned previously, is connected across the power lines 101 and 102 by means of the parallel connected switches CR-3B and T-2D. The switch CR-3B is closed upon energization of the relay CR-3 and the switch T-2D is closed by the timer switch T-2 after a delay period of approximately 5 minutes subsequent to energization of the timer T-2.

A normally closed relay switch identified as CR-3C, and opened upon energization of the control relay CR-3, is connected in series with a normally open pair of contacts identified as CR-lB, these contacts being closed upon energization of control relay CR-l. These series connected relay switches have connected to them a circuit branch identified at 108 which connects to the parallel connected members 12a, 12b and cold water solenoid valve 66. The exhaust fan control coil is identified by 12a, and, it will be understood, that energization of the member 12a causes closing or comple tion of the electrical power circuit to the driving motor of the ventilating fan 12 (FIG. 3). The control member 12b represents the energizing coil for a control switch which energizes the electrical motor driving a make-up air fan which, in some applications, is located in the duct leading to the enclosure (kitchen) from the outside. The makeup air fan is not shown (other than its controller 121; of FIG. 7) since its presence is optional and is not included in all installations. The solenoid valve 66 is, of course, the cold water solenoid valve shown in FIG. 5, and controls the flow of cold water to the nozzles 39 (FIG. 2).

Connected in parallel to the circuit branch 108 is a wire 109 which serves to connect the power pack 110 to the power input. In series with the power pack 110 are normally closed timer switch T-2C and the normally closed door switch 111. The door switch 111 is shown in FIG. 2 and is mechanically closed by the presence of the access door 15. When the access door 16 is opened or removed from the bracket 17, the door switch 111 is opened, the switch thus functioning as a safety switch permitting energization of the power pack 110 only when the door 16 is in place. The power pack 110 is primarily a step-up transformer and a rectifier which supply the elevated, DC voltage necessary to provide the ionizing charge to the precipitator plates 34a. The switch T-2C is opened upon starting of the wash cycle, that is, when the timer T-2 is energized and is returned to closed position only after a time interval of the order of 30 minutes has elapsed subsequent to the termination of the wash cycle to provide against the precipitator cells being energized before they have dryed subsequent to the wash cycle.

In operation, to start the system, the start button of the switch 103 is depressed therby energizing control relay CR-l. This causes energization, through the switch CR-lB and wire 108, of the exhaust fan 12, the make-up air fan 12b, if such is used, and energizes the cold water solenoid valve 66 providing a cold water spray from the nozzles 39 (FIG. 2). Assuming the accessdoor 16 is in place, the power pack and the precipitator cells are also energized through the relay contacts CR-lB. Operation may now continue as desired and when the apparatus is to be de-energized, the stop button of the switch 103 is depressed. Deenergization of control relay CR-l, through opening of the relay contacts CR-lB thereupon de-energizes the fan controls 12a and 12b and closes the cold water solenoid valve 66 and de-energizes the power pack 110. Depression of the stop-button of the switch 103 causes control relay CR-2 to be energized through the contacts 103: and contacts 103!) of the switch 103. Energization of relay CR-2 closes relay contacts CR-2B and energizes timer T-2. Timer T-l is also energized as is the detergent solution pump 89 so that detergent solution is sprayed from the nozzles 54 (FIG. 2) for a timer interval until time T-1 opens the contacts T-lA, the time interval being of the order of 15 seconds. Be cause the timer T-2 closes the contacts T-2D only after a time delay, subsequent to its energization, of approximately 5 minutes, the detergent solution sprayed from the nozzles 54 onto the precipitator cells is permitted to soak until the 5 minute delay interval timed by the timer T-2 has been completed and switch T-2D is closed, thereby opening the hot water solenoid valve 82 which supplies rinsing hot water spray to the nozzles 5 1 and the nozzles 43 (FIG. 2). This rinse or wash-down cycle is completed at the end of the predetermined time interval by opening of the timer contacts T-2D by the timer T-2. The timer motor T-2 retains the timer contacts T-2C open for the 30 to 40 minute interval necessary to assure that the precipitator cells have dryed. After this time period passes, the timer T2 opens the contacts T-2A, de-energizing the timer and the wash cycle light. Operation of the apparatus may then be restarted by again depressing the start button of the switch 103. It should also be noted that operation of the exhaust fan 12 (energized by controller 12a) and the continuous water wash controlled by solenoid valve 66, and issuing from nozzles 39, can be reinstituted without waiting for the lapse of the time interval necessary for reclosure of timer switch T-2C and reenergization electrostatic precipitator power pack 110. Depressing the start button of switch 103 immediately after release of the stop button deenergizes relay CR-3, closing switch Cr-3C, and energizes relay CR-l, closing switch CR'IB. The exhaust fan 12 and the cold water spray (controlled by solenoid valve 66) are thus restarted immediately. This mode of operation is utilized where the process being ventilated cannot be shut down for any extended period of time. As the circuit of FIG. 7 indicates, the system can be stopped without automatically going into the wash-down cycle by depres sion of both the start and stop buttons of the switch 103 simultaneously.

When both buttons are depressed simultaneously control relay CR-2 is not energized and timer T-2 is not started and the wash-down cycle does not occur.

It should be noted that a safety feature is provided in that the duct thermostat 106 overrides all other controls in the circuit to start water flow from the washdown nozzles 43 and 51 upon the existance of an abnormally high temperature in the air flow duct. With the system in operation and the switch 103 in released or quiescent condition, closure of duct thermostat 106 energizes control relay CR-3, which closes relay switch CR-3B energizing solenoid valve 82 and causing washmight also be installed in horizontal position with the plate 20 lowermost.

I claim:

1. Apparatus for clearing grease vapors, odors,

down nozzles to spray water until the start button of smoke and the like from enclosure ventilating systems switch 103 is manually depressed. lf thermostat 106 remains closed, indicating the abnormal duct temperature persists, the flow of wash-down water will immediately start again when the start button is released, and the system cannot be reset by the start button until after the duct thermostat 106 has opened its contacts.

Referring again to FIG. 3, it will be noted that one side of the housing 14 is provided with a drain panel to permit water from the prccipitator cell area to drain back to the drainage area provided by drain connection 27a when the apparatus is installed horizontally, rather than vertically as shown in FlGS. 2 and 3.

From the foregoing it will be evident that the apparatus of the present invention combines three elements to clean grease vapors, odors and smoke from ventilating systems. These combined elements are the water cooled centrifugal extractor formed by the trough 27 and baffle skirt 26 which causes a reversal in the airstream flow depositing the heavier particles entrained in the airstream at the base of the trough 27. The continuous water washing of the airstream, flowing counter to the water spray, provided by the nozzles 39 tends to remove remaining grease vapors and larger greasy smoke particles from the airstream. The electrostatic precipitator component takes out the remaining small particles in the airstream. Since the larger particles are eliminated from the airstream before it reaches the precipitator cells, these operate with maximum efficiency.

As pointed out above, to facilitate cleaning and maintenance of the apparatus, a wash-down program is incorporated in the apparatus to automatically wash the electrostatic cells and the spray chamber or trough with hot water and detergent when the unit is shut-down. The baffle 24 with its depending skirt 26, forming a part of the centrifugal extractor, can be removed for periodic complete cleaning and access to the nozzles. Access to the filter 32 and the precipitator cells can be obtained, as previously mentioned, through the access door. While the unit has been shown installed vertically on a roof-top for example, it will be understood that it having a power induced ventilating airstream discharged through an outlet mouth exterior of the enclosure, said apparatus comprising a generally tubular housing having one end providing an inlet passage and adapted to overlie and register with the outlet mouth of the ventilating system, the opposite end of said housing providing an outlet passage through which the cleansed ventilating airstream exits, said inlet and outlet passages being substantially in axial alignment, said housing having an inwardly turned flange at said inlet end completely encircling said inlet passage in the housing, said inlet passage being substantially smaller in cross section than the housing interior so that the housing sidewall and flange form a trough surrounding said inlet passage, a baffle plate overlying but spaced from said inwardly turned flange and having a peripheral skirt extending toward said trough whereby the direction of flow of said airstream is reversed and then redirected again toward the housing outlet as it flows around said skirt and out of said trough, electrostatic precipitator cells supported within said housing and disposed in said airstream downstream of said trough, and an array of nozzles supported on the downstream side of said baffle plate, said nozzles being positioned in spaced relation around the margin of the baffle plate and protruding slightly beyond said plate margin to deliver an axially directed spray of cold water in the annular space between the peripheral wall of the housing and said baffle skirt which intersects and flows substantially counter to the airstream as it flows between said skirt and said housing peripheral wall and prior to its movement past said precipitator cells.

2. Apparatus as claimed in claim 1 in which a further array of nozzles (43) encircles said baffle plate and is supported on said peripheral skirt of the baffle plate, said further nozzle array being disposed closer to the base of said trough than said first mentioned array of nozzles and adapted to deliver wash-down water to said trough.

Claims (2)

1. APPARATUS FOR CLEARING GREAS VAPORS, ODORS, SMOKE AND THE LIKE FROM ENCLOSURE VENTILATING SYSTEMS HAVING A POWER INDUCED VENTILATING AIRSTREAM DISCHARGED THROUGH AN OUTLET MOUTH EXTERIOR OF THE ENCLOSURE, SAID APPARATUS COMPRISING A GENERALLY TUBULAR HOUSING HAVING ONE END PROVIDING AN INLET PASSAGE AND ADAPTED TO OVERTILE AND REGISTER WITH THE OUTLET MOUTH OF THE VENTILATING SYSTEM, THE OPPOSITE END OF SAID HOUSING PROVIDING AN OUTLET PASSAGE THROUGH WHICH THE CLEANSED VENTILATING AIRSTREAM EXITS, SAID INLET AND OUTLET PASSAGES BEING SUBSTANTIALLY IN AXIAL ALIGMENT, SAID HOUSING HAVING AN INWARDLY TURNED FLANGE AT SAID INLET END COMPLETELY ENCIRCULING SAID INLET PASSAGE IN THE HOUSING, SAID INLET PASSAGE BEING SUBSTANTIALLY SMALLER IN CROSS SECTION THAN THE HOUSING INTERIOR SO THAT THE HOUSING SIDEWALL AND FLANGE FROM A TROUGH SURROUNDING SAID INLET PASSAGE, A BAFFLE PLATE OVERYLING BUT SPACED FROM SAID INWARDLY TURNED FLANGE AND HAVING A PERIPHERAL SKIRT EXTENDING TOWARD SAID TROUGH WHEREBY THE DIRECTION OF FLOW OF SAID AIRSTREAM IN REVERSED AND THEN REDIRECTED AGAIN TOWARD THE HOUSING OUTLET AS IT FLOWS AROUND SAID SKIRT AND OUT OF SAID TROUGH, ELECTROSTATIC PRECIPTATOR CELLS SUPPORTED WITHIN SAID HOUSING AND DISPOSED IN SAID AIRSTREAM DOWNSTREAM OF SAID TROUGH, AND AN ARRAY OF NOZZLES SUPPORTED ON THE DOWN-

2. Apparatus as claimed in claim 1 in which a further array of nozzles (43) encircles said baffle plate and is supported on said peripheral skirt of the baffle plate, said further nozzle array being disposed closer to the base of said trough than said first mentioned array of nozzles and adapted to deliver wash-down water to said trough.

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