US 2748888 A
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June 5, 1956 P. HODSON VORTEX-ELECTROSTATIC GAS CLEANER Filed March 2'7, 1952 E w w 5 H S R E H D O Y D N C a M E 4 m m: J y E N 5 u PM K L W L 5 E I 0 5 4 r j 6 m we J n E r m W HE G P H 0 5 H5 H V E m H a E RY G 6 Z Y am B m H 607 Z Z 1 TE 4 5 w 1 2 m 4 J. 0. 8 8%.. ...l. ....H...'.. 8 Y. 0 1 ..u... .m M 1 2 9/ D A L .4 m s 6 5 5n m 1+ f 5 H 5% 3 5C 660. M ii W D 05 ma United h VORTEX-ELECTROSTATI'G GAS CLEAN-ER Peter Hodson, Well'sville, N. Y., assignor, by mesne assignnients, to Apra Precipitator Corporation, New York, N. Y., a corporation of Delaware Application March 27, 1952', Serial No. 278,924
3 Claims. (Cl. 183'-=7) This invention relates to gas cleaning and particularly to the removal of foreign particles entrained in a gas stream by employing a combination of electrostatic and centrifugal actions.
In the art of gas cleaning, it is well known that a vortex type centrifugal cleaner is most effective in the removal of relatively large heavy particles of dust from a gas stream, while an electrostatic cleaner is more highly efficient in the removal of relatively small light particles.
In the common types of electrostatic precipitators, the collecting efficiency of the small particles is high, as contrasted with a lower collecting efliciency for large particles. Moreover, large particles which have been separated from the gas stream by electrostatic action frequently become re-entrained in the gas stream during rapping or cleaning periods so there is little or no actual removal of such particles from the gas.
In centrifugal types of gas cleaners, the removal of relatively large dust particles is efliciently accomplished; however, the removal of small dust particles becomes much less efficient as such particles are affected by Brownian movement or have insufficient mass to be affected strongly by centrifugal force.
Since the size range of the particles most easily handled by the electrostatic and vortex types of mechanical collectors is complementary, it becomes evident that the two' types of cleaner can be effectively used as a combined cleaner whereby one type of cleaner becomes more effective as the efiiciency of the other type of cleaner drops.
It is therefore an object of this invention to provide for a single apparatus of simple construction which will effectively utilize the desirable features of a vortex type mechanical cleaner together with those of an electrostatic cleaner so as to provide for a more effective removal of certain sizes of suspended material than can be obtained by either means alone.
A further object of this invention is to provide for an arrangement whereby collected particles which become re-entrained in the gas stream will be readily discharged to the dirty gas outlet.
In the accompanying drawings which illustrate the invention, Figure 1 is a sectional view showing a preferred form;
Figure 2 schematically illustrates the operation of the device of the invention.
The apparatus of Figure 1 comprises a preferred form of the invention wherein the tubular wall 1 provides a grounded body member and collecting surface for the apparatus having a dirty gas inlet 3 and a dust discharge 4. concentrically within the housing 1 at the discharge end thereof is a tubular member 2 which defines the clean gas outlet 5. Suspended from the housing 1 and adjacent the gas inlet end of the apparatus are located a plurality of vanes 6 which support a ring-like insulator mounting 7. This mounting member rigidly holds a hollow streamline insulator 8 in concentric alignment. Depending from the insulator 8 and in concentric alignment therewith is an electrostatic discharge electrode 9 composed of a thin 2,748,888 Patented June 5, 1956 strip of metal wound in helical form whereby adjacent coils thereof provide a series of louvers permitting fluid flow there-between. Suitable mounting means 10 is used to join the discharge electrode tothe insulator body 8, and aplurality of stiffening rods 11 serves to stabilize the helical discharge electrode 9. Connected to the helical discharge electrode 9 via a lead through the hollow insulator 8 is the high voltage connection 12 which may be connected to a suitable source of high voltage direc current.
I In o eration of the centrifugal cleaner, dirty gas enters the apparatusat inlet 3 and passes the vanes 7 which irn part to it a rotary motion. This rotary motion tends to move the dust particles to the outer wall 1 by centrifugal force where said particles may be removed through the dust discharge 4 with a small portion of the gas to be further treated in a high efficiency secondary collector. The larger portion of clean gas is removed through the cylinder 2 which is in concentric relation with the outer cylinder 1.
The centrifugal collector described above has the disadvantage of being unable to collect extremely fine particles which have insufiicient mass to be affected appreciably by centrifugal force. Therefore, such fine particles would pass out with the clean gas but for the simultaneous action of the electrostatic precipitator.
In the present device when the incoming dirty gas passes vanes 6 and is thereby given a rotary motion, said gas is also subjected to electrostatic or corona discharge emanating from the electrode 9. The corona discharge ionizes the dust entrained in the gas stream and tends to agglomerate said particles and move them toward the grounded collecting surface 1. It is therefore apparent that both centrifugal and the electrostatic forces act concurrently to move the supended particles toward the outer surface 1. Some of the fine particles will tend to deposit upon the surface 1 but this deposit will not build up to any appreciable extent before being blown off in the form of large flakes and carried out of the outlet 4 by the velocity of the gas stream.
As before mentioned, the electrostatic force more readily affects the comparatively small entrained dust particles while the centrifugal force tends to more readily affect the larger entrained particles. Those particles which range in size between large and small are acted upon effectively by both centrifugal and electrostatic actions. It is therefore seen that nearly all dust particles entrained in the gas stream are acted upon simultaneously by electrostatic and centrifugal actions, and that an efficient removal of such dust particles is thereby achieved.
Figure 2 illustrates the combined action of the centrifugal and electrostatic forces within the device of the invention. The larger dust particles are moved toward the outer housing 1 by the centrifugal force of the whirling gas stream, while the electrostatic discharge from the electrode 9 ionizes the smaller dust particles and moves them toward also the grounded housing 1. The dust particles agglomerate to form larger particles which are moved along collectively toward the outer housing and to the outlet 4. As shown, the overlapping helical electrode 9 also tends to separate the dust from the gas by utilizing the force of inertia of the dust particles, since the clean gas at 23 must make two right angle bends to reach the outlet 5, while the dust 24 can continue its straight line motion to the outlet 4.
From the foregoing description, it is apparent that the various elements of the invention may be subject to a variation in form without departing from the scope of the invention.
What I claim is:
1. Apparatus for separating suspended particles from a gas stream comprising; a housing having an inlet and a plurality of concentric outlets, said inlet being adapted to receive gas carrying suspended dust particles while one of said outlets is adapted to discharge clean gas and another is adapted to discharge collected dust particles therefrom; means fixed to said housing and imposed in the gas inlet for imparting a whirling motion to the gas stream; a discharge electrode depending from said means and insulated therefrom, said discharge electrode comprising a helical conductor whose adjacent coils form louvers permitting clean gas to pass radially inward through spaces between coils of said helical conductor to the clean gas outlet in opposition to normal outward movement of the suspended dust particles.
2. Apparatus as defined in claim 1 wherein said helical discharge electrode tapers outwardly from the inlet to the outlet so as to afford an increasing degree of ionization to gas passing therethrough.
3. Apparatus as defined in claim 1 wherein said helical discharge electrode comprises a thin metallic strip wound into a tapered coil in concentric alignment with said housing and having the end coil thereof substantially superimposed over the clean gas outlet.
References Cited in the file of this patent UNITED STATES PATENTS 1,357,201 Nesbit Oct. 26, 1920 1,371,995 Nesbit Mar. 15, 1921 1,372,710 McGee et al. Mar. 29, 1921 1,381,719 McGee et al. June 14, 1921 1,440,887 Nesbit et al. Jan. 2, 1923