US2374715A - Adjustable gas distribution means for multiple tube electrical precipitators - Google Patents

Description

May 1, 1945. H. J. WHITE 2,374,715

ADJUSTABLE GAS DISTRIBUTION MEANS FOR MULTIPLE TUBE ELECTRICAL PRECIPITATORS Filed Jan. 20, 1943 2 Sheets-Sheetl ADJUSTABLE GAS DISTRIBUTION MEANS FOR MULTIPLE TUBE ELECTRICAL PREC TATORS Filed Jan. 20, 3 2 Sheets-Sheet 2 y 1945- H. .1. WHITE 2,374,715

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Hal-r KE/L Patented May 1, 1945 ADJUSTABLE GAS DISTRIBUTION MEANS FOR MULTIPLE TUBE LELECTR'ICAL PRE- CIPITATORS Harry J. White, Cambridge, Mass., assignor to Research Corporation, New York, N. Y., a corporation of New Yorl;

Application January 20, 1943, Serial No. 473,008

3 Claims.

This invention relates generally to apparatus for electrical precipitation of suspended particles from gases, and more particularly to means for controlling the distribution of gas flow in each of the parallel gas tubes of a multiple tube electrical precipitator, a general object of the invention being the provision of conveniently adjustable means for establishing uniformity of gas flow in the tubes of such a precipitator for any total rate of gas flow throughout a relatively wide range. The invention has particular application to and utility in a two-stage precipitator of the water film type, such as shown in my prior Patent N 0. 2,192,249, and is herein described particularly in that connection, though it also has application to and is described in connection with precipitators which do not employ water films.

In multiple tube precipitators of the class to which the invention appertains, either with 'or without water films, the gas is distributed from a header to the inlet ends of a plurality of parallel, cylindric gas conduits, usually and preferably vertically disposed, though not necessarily so. Within each of these conduits is a concentric high-tension electrode, while the conduits provide collecting electrode surfaces opposing the high-tension electrodes, onto which suspended particles charged by the action of the discharging electrode are precipitated. In Water film precipitators, these collecting electrode surfaces are each supplied with a flowing water film, which is designed to collect and carry off the precipitated material.

In the preferred, two-stage type of precipitator, the high-tension electrode includes a discharging section, typically in the'formof a fine wire, and a non-discharging section, of materially increased radius of curvature, the non-discharging section following the discharging section in the direction of gas flow. The expression discharging section or discharging electrode will be understood to designate an electrode that facilitates corona discharge therefrom because it has a configuration that establishes asufficiently high potential gradient at or near its surface to create corona, discharge before there is disruptive discharge or sparkover. The expression nondischarging section or non-discharging electrode will be understood to designate an electrode that minimizes or prevents corona dis-- charge therefrom because it has a configuration that establishes a sufficiently low field concentration at or near the surface to suppress corona discharge at, elevated potentials lower than the voltage required for disruptive discharge or sparkover. For this purpose, a non-discharging electrode is usually one of extended surface area, substantially free from sharp corners or other parts'of sharpsurface curvature at all portions which are located with n the electric field, so as substantially to avoid ionization or corona discharge at that electrode.

Uniformity of action and high efliciency in precipitators of the classes mentioned depend upon the avoidance of excessive turbulence of the gas flowing through the conduits, and upon the establishment of substantially uniform gas distribution in the regioncf the high-tension electrodes. It is particularly important to avoid nonuniformity of gas distribution and excessive turbulence in water film types of apparatus, for the reason that excess; ely turbulent gas flow exerts a disruptive efiect on the water film, breaking loose droplets of Water and causing sparking between the electrodes. ,I have found that excessive turbulence and non-uniformity of distribution of the gas within the conduits frequently arises from non-uniform or unsymmetrical entrance of the gas into the intake ends of the conduits, and are contributed to by gas surges resulting from sudden changes in pressure. A conduit whose inlet end comprises simply the unobstructed end of a round tube, of course, provides uniform distribution of the gas. However, it is usually desirable to provide some form of damper means located at the inlet ends of the conduits for regulating the rates of inflow into the conduits. and such damper means as invariably constructed heretofore have caused unsym metrical gas entry, and consequent non-uniform gas distribution and turbulence in the conduits.

It is, therefore, a primary object of the present invention to provide simple, inexpensive damper means at the inlet ends of the conduits, so formed as to assure symmetrical distribution of the gas at point of entry, and therefore decreased turbulence and increased uniformity of gas distribution within the conduits.

A further object of the invention is the provision of a simple and inexpensive gas control means at the inlet ends of the gas conduits for conveniently adjusting the individual rates of gas flow, and a still further object is the provision of novel and improved gas control means for securing uniform or any other desired adjustment and distribution of gas fiow among the several conduits, as well as enabling the inlet orifice of one or more tubes to be entirely closed.

These objects are accomplished in accordance with the invention by the provision of damper width at the inlet ends of-the several conduits.

For example, I may employ in spaced relation to the inlet end of each conduit a damper element in the form of a disc, cone, cap or the like, mounted coaxially with the end of the conduit, so as to cooperate therewith lar inlet orifice. This disc, cone, cap or the like is arranged for axial adjustment movement whereby the width of the orifice and therefore the rate of gas inflow may be regulated and is preferably movable entirely into engagement with the inlet end of the conduit, whereby the orifice may be entirely closed and the corresponding conduit taken out of action, if desired. The inlet orifice is symmetrical with respect'to the axis of the conduit in all positions of adjustment,

with the result that the inflow of gas is uniform and symmetrical about said axis. The adjustment thus not only permits close control of the rate of gas flow in a simple and inexpensive manner, but the symmetry of the inlet orifice assures uniformity of distribution of the gas in the conduit with respect to its central axis in all positions of adjustment. By then spacing the high-tension electrode a fairly substantial distance from the inlet end of the conduit, the gas is given an opportunity to equalize its distribution radially of the conduit, and is not only uniformly distributed about the axis of the conduit, but is substantially uniformly distributed across it-i. e., radially of the conduit-by the time it reaches the high-tension electrode, and the water film region opposite it, if the apparatus be of the water film type. At the same time, the damper element largely prevents sudden gas surges or eddies fromentering the conduit. The individual gas control means at the inlet ends of the several conduits permit the accomplishment of any desired distribution of the total gas flow among the several conduits, uniform or otherwise, and permit ready compensation for any tendency for any, of the conduits to take in more or less gas than'do the others.

Various additional objects and corresponding accomplishments of the invention will appear and be described in the course of the following detailed description of certain present illustrative embodiments thereof, reference vfor this purpose being had to the accompanying drawings in which:

Fig. 1 is a vertical medial section of the lower portion of a water-film type of precipitator equipped with the improvements of the, present invention, it being understood that the upper portion of the precipitator, not shown herein, may be, for instance, of the type shown in my prior Patent No. 2,192,249; v

Fig, 2 is a perspective showing in some detail the illustrative flow control means of Fig. 1;

Fig. 3 is a detail cross-section on line 33 of Fig.

Fig. 4 is a view similar to Fig. 1 but showing the invention'incorporated in a'screen pocket electrode type of precipitator;

Fig. 5 is a transverse section taken as indicated by line 5-5 of Fig. 4;

Fig. 6 is a bottom view of a modified form of damper cone indicating the optional use of perforations in the damper element;

Fig. 7 is a vertical section showing'the optional perforated type of damper cone, and

Fig. 8 is a vertical medial section of a further modified type of gas control means.

Fig. 1 shows the lower portion of a two-stage in the definition of an annuwet-electrode precipitator comprising a plurality of preferably vertical gas conduits ID, of substantially circular cross-section, arranged in parallel, all the conduits being supplied with gas to be treated from a header II at the bottom of the apparatus; a detailed consideration of the upper portion of the apparatus not being essential to an understanding of the present invention, no illustration thereof is included herein, though reference may be had to my aforesaid Patent No. 2,192,249 for a detailed description of a complete precipitator of the type intended.

The apparatus is encased in a cylindrical housing l2, preferably constructed of sheet metal, a header plate l3 extending across the interior of the housing defining the upper side of the aforementioned header l I. This plate I3 is here shown as slanting, for a purpose which will presently appear, though this arrangement is not essential.

A gas inlet duct l5 opens inside header ll, preferably just below the high side of header plate 13, and a water outlet l6 mounted in the wall of housing 12 just below the lowermost edge of slanting plate vl3 serves as a drain for water descending from above and caught by plate 13.

Each of gas conduits In, in the form of the invention here chosen for illustrative purposes, comprises an upper tubular electrode I8, maintained at ground potential, and a lower gas inlet tube I9 extending through and mounted in plate l3, tube i9 beingof lesser diameter than tubular electrode l8 and its upper end-being received partially within the lower end portion of the latter, with a small annular space 20 being provided therebetween. This space 20 is preserved by spacing lugs 20a welded to the outside of tube I9. As here shown, the tube i9 is mounted on header plate I3 by means of a flange 2| welded to the tube and clamped by means of bolts 22 between a gasket 23, which bears against the header plate, and a clamp ring 24. The lower ends of the inlet tubes :9 depend from header plate 13 to a level preferably well below gas inlet duct l5.

Disposed within and co-axially of each of the tubular electrode members I8 is a complementary central or high-tension electrode assembly 30, the lower part of which comprises a fine wire discharge electrode 3! adapted, in cooperation with the surrounding tubular electrodes, to create an ionizing field, and the upper part of which comprises an extended surface electrode 32 of relal tively large diameter adapted, in cooperation with from the lower ends of the electrodes l8 via anthat part of tubular electrode I8 which surrounds it, to provide a static electric precipitating field free from corona discharge. The lower end of the central high-tension electrode assembly terminates somewhat above the lower end of the tubular electrode member I8, as shown.

It will be understood that the inner surfaces of the several tubular electrodes i 8 are supplied from above with water films, which discharge nular spaces 20, and are caught by sloping header plate .13, to be discharged finally by way of water outlet l6.

Each of gas inlet tubes l9 comprises two pipe sections 35 and 36 having flanges 31 and 38, respectively, on their adjacent ends. The annular rim 39a of a spider 39 is received between flanges 31 and 8, and the assembly is clampedtogether by means of bolts 40. Bolted to and depending from the hub 4| of each of spiders 39 is a vertical damper supporting rod 42, which is thus co-axial with the gas inlet tube [9. perforated damper disc 43, of approximately the A centrally diameter of the gas inlet tube, is mounted on each of rods 42 and supported by a nut 44 which is screwed onto the threaded lower section 45 of the rod. This disc 43, in cooperation with the annular lower end of tube section 35, defines an annular gas inlet orifice, whose width, or height, is determined by the position of nut 44 on supporting rod 42.

The annular inlet orifice provided by the damper disc is entirely symmetrical in all positions of adjustment, and assures uniform and symmetrical entry of the'gas into the gas inlet tube with respect to the central axis of the latter. The distribution of the gas at point of entry is thus uniform. with respect to the axis of the inlet tube. As the gas rises in the tube, its distribution across the section of the tube tends to become equalized, and by the time it has reached the region of the tubular electrode l8 and high-tension wire 3! its distribution across the conduit is substantially uniform. The consequent reduction in swirling and turbulence reduces to a minimum the tendency for the gas flow to. disrupt the water films on the insides of the tubular electrodes. Surges of gas into the lower ends of the gas inlet tubes, and consequent eddies and turbulence from that cause, are also minimized by the presence of the damper disc, which acts as a shield to guard against unrestricted entry of such gas surges. Very close control of the rates of flow through the individual tubes, as well as of the distribution among the several tubes, is secured by individual adjustment of the vertical positions of the damper discs 43 by means of the adjusting nuts 44. And,

if desired, the discs 43 may be set up against the ends of any inlet tubes which it may be desired to take out of action. Attention is directed'to the preferred location of the gas inlet duct 15 well above the lower inlet ends of the tubes l8, this arrangement preventing the lateral gas current entering via duct I5 from disturbing the uniform flow of the gas into the annular inlet orifices.

Figs. 4 and 5 show the invention applied to a multiple gas conduit precipitator which is of the screen pocket electrodetype, and also show the damper means in a modified form. In this embodiment, the header I la formed in the bottom of housing l2a is defined at the top by a hopper shaped structure 50 comprising walls 5i sloping downwardly from the side wall of housing In to a central discharge outlet 52 leading to discharge screw conveyor 53. Gas inlet duct l5a opens inside header I I a, as indicated.

Vertical gas conduits la comprise upper ,tubular electrode members I8a, similar to the tubular electrodes l8 of the precipitator of Fig. 1, and lower gas inlet tubes 190. which extend through and are mounted in the walls tubes [9a being of lesser diameter than tubular electrodes l8a and their upper ends being received partially, and with annular clearance, within lower end portions of electrodes I8a, and being joined at their upper ends to tubular screen members l4 which are spaced from electrode members l8a and form therewith annular pockets for the collection of precipitated material. The tubular electrodes 18a contain co-axially positioned hightension electrodes a. The annular clearance spaces between the gas inlet tubes Na and the tubular electrodes l8a are designed to pass the collected dust as it. falls from the inside surfaces of electrodes l8a, this dust being caught by hopper 58, and removed by conveyor 53. Any material which may fall from screen members I4 down through the inside of inlet tubes 19a may be removed from header Ila through door 49.

. Each of gas inlet tubes Isa is supported by a flange 55 welded to it near its lowerend, this flange being clamped, by means of bolts 55, between clamp ring 51 and the annular-flange 58 on the lower end of a supporting sleeve 58 which depends from and is welded to wall 5|, a gasket 50 being here shown as placed between flange 55 and the flange 58 on sleeve 58.

Mounted in each of gas inlet tubes l8a is a spider 55, .to the hub 55 of which is bolted the upper end of damper supporting rod 61, the latter depending to a point somewhat below the lower end of tube l9a, as illustrated. While the supporting rod 61 might carry a disc-type damper element, of the kind illustrated in Fig. 1, I here show a modified cone-shaped damper element 58. This cone-shaped damper element 58 has a central sleeve 59 slidably mounted on supporting rod 51, a downwardly diverging conical wall I0 connected with the upper end of sleeve 69, and

radial webs H joining sleeve 59 with wall 10. The lower end 'of sleeve 69 is shown provided with a collar 12 in which is mounted a clamp screw 13 adapted to be set up against supporting rod 51 to secure the damper element in any position of vertical adjustment on rod 81.

This form of the invention operates in a mannor substantially similar to that of the form previously described, the cone-shaped damper element again defining a symmetrical annular inlet or'fice of adjustable height, which in all positions of adjustment assures symmetrical and uniform flow of the gas from the header into inlet tubes ISa, and therefore uniform distribution of the gas with reference to the central axis of the gas conduits, as well as substantially uniform distribution of the gas across the conduits bythe time it reaches the region of the hightension electrodes.

Figs. 6 and 7 show a modified form of conical damper element, in which the conical wall 10 is provided with a plurality of perforations I5.

. These perforations 15 are distributed uniformly about the axis of the cone so that the gas entering inlet pipe l9a through them will have a uniform distribution about the axis of the inlet pipe, and thus serve to provide additional or increased symmetrically distributed gas inflow. Such perforations may be, of course incorporated in other forms of the damper element than the conical form illustrated in these figures.

Fig. 8 shows a further modification, in which the damper element is in the form of a cup 88,

the bottom wall 8| of which is spacedfrom and cooperated with the lower 'end of gas inlet tube |9a in the definition of an annular gas inlet ori. fice, and the side wall 82 of which extends upwardly above the lower end of tube 19a. The bottom 8| of cup is centrally perforated to pass supporting rod 61, and is provided with a collar 83 carrying a clamp screw 84 adapted to vbe set up against suporting rod 61 to secure the cup in any position of vertical adjustment on rod 51. The gas enters by way of the annular space provided between the side wall '82 of the cup and the lower end portion of tube I911, thence passing inwardly through the annular orifice between the lower end of tube I91; and the bottom 8| of the cup, and then upwardly within the tube I5a, all as indicated by the arrows in Fig. 8. It will be evident that the damper of Fig. 8 is similar to the damper 43 of Fig. 1, with the exception of the addition of side wall 82. This added side wall 82 i has the advantage that it acts as a shield against any lateral gas currents which may prevail inside header Ila, thus preventing such ciu'rents from interfering with the uniform and symmetrical inflow of gas into the lower ends of tubes [9a. It will, of course, be understood that the damper element shown in Fig. 8, as well as any of the modiiied forms of damper element, disclosed. may be employed in connection with any of the forms of precipitator illustratively disclosed herein, or any other to which the invention is broadly applicable.

It will be understood that the drawings and 3 description are merely illustrative of and not restrictive 'of the invention, and that various changes in design, structure and-arrangement may be made without departing from the spirit and scope of the invention or of the appended claims.

I claim:

1. In an electrical precipitator having a vertical gas conduit embodying an upper tubular electrode surrounding a co-axially positioned i high-tension electrode, and a co-axially positioned lower gas inlet tube of lesser diameter than said tubular electrode 'and annularly spaced therewithin to provide an annular opening for discharge of precipitated material from the upper tubular-electrodes: a damper member spaced below the lower end of said gas inlet tube, and means adjustably supporting said damper member for movement toward and from the inlet end of said inlet tube along the vertical longitudinal axis of saidv tube, said damper member being shaped to define with said inlet end 01' said inlet tube a symmetrical annular inlet orifice.

- 2. In an electrica1 preclpitator having a vertical gas conduit embodying an upper tubular electrode surounding a co-axially positioned hightension electrode, and a co-axially positioned lower gas inlet, tube of lesser diameter than said tubular electrode and annularly spaced therewithin to provide an annular opening for discharge of precipitated materialfrom the upper tubular electrodes: a damper disc spaced below the lower end of said gas inlet tube, and supporting means for said damper disc embodying upper tubular electrodes: a damper cone spaced belowrthe lower end of said gas inlet tube, and supporting means for said damper cone comprising a rod mounted co-axially of said gas inlet tube and projecting from the inlet end thereof, said cone having a central perforation adapted to receive said rod, and being supportable in various positions of longitudinal adjustment on said rod.

HARRY. J. WHITE.

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