US2847158A - Centrifugal separator - Google Patents

Description

1958 H. w. THYLEFORS 2,847,158

CENTRIFUGAL SEPARATOR Filed Sept. 12, 1956 2 Sheets-Sheet 2 7 25 l2 l4 2/ l9 IN V EN TOR. 7ferzrz'c Wilhelm q/zy/e or:

ATTORNE Y5 United States Patent 2,847,158 CENTRIFUGAL SEPARATOR Henric Wilhelm Thylefors, Stockholm, Sweden, assignor to Aktiebolaget Separator, Stockholm, Sweden, a corporation of Sweden Application September 12, 1956, Serial No. 609,475 Claims priority, application Sweden September 22, 1955 7. Claims. (Cl. 233-29) The present invention relates to centrifugal separators of the type having two sets of conical discs located in the centrifugal bowl for increasing the separating efficiency, these sets being arranged substantially as mir-.

ror images of each other symmetrically on either side of a plane at right angles to the rotation axis of the separator, 'the liquid to be separated being fed into the space between the itwo sets of discs.

In a centrifugal separator having a single disc set in the bowl, where the liquid to be separated is introduced into the disc set from below, the upper part of the disc set is utilized less efiiciently than the lower part. For this reason, the separator design first mentioned above has been proposed, wherein the feed of liquid is arranged between the two disc sets so that. the latter are equally loaded with the liquid to be separated, and the disc sets, considered as a whole, are thus better utilized than in previous designshaving a single disc set. However, in separators having double sets of discs, as constructed heretofore, the discharge of the separated liquid takes place either from one end of the separator bowl (reckoned axially) whereby part of the discharging liquid must flow axially'throughout the separation chamber and thereby pass both the 'disc sets, or from both ends of the separator (reckoned axially) whereby the'liquid from 'each disc set is discharged through a respective outlet. In the first case (one outlet), the liquid from the disc se't more remote from the outlet is forced to overcome a greater flow resistance than is the case. with the liquid from the disc set closer to the outlet. Consequently, the liquid fed into theseparator is distributed differently to the two disc sets. In the latter case (two outlets), it has been impossible in practice to place the two outlets at sufliciently equal distances from the rotation axisof the separator. Thus, owing to the high speed of rotation in centrifugal separation, a ditferencein distance of only ,4 mm. causes a pressure difference of many hundred millimeters of water column at the outlets. The result has been that not even in separators of this type is there a satisfactorily even distribution of the liquid feed among the two disc sets, but one disc set may become clogged by sludge while the other set still functions.

The principal object of the present invention is to avoid the risk of such a deterioration of the separating efliciency, and to provide greater assurance of maintaining through both the disc sets an equal distribution of the liquid (such as a starch suspension) fed into the separator.

A separator made according to the invention is provided with channels leading from the inner edges of the two disc sets (reckoned radially) to a chamber situated substantially in that plane on the two sides of which the disc sets are arranged symmetrically as mirror images of each other, and with an outlet leading from such chamber out of the centrifugal rotor or bowl. As this outlet is a common outlet for the liquids leaving the two disc sets, the flow resistance remains the same regardless 2,847,158 Patented Aug. 12, 1958 of which disc set is passed by the liquid fed into the separator.

The outlet may be arranged in various ways. For instance, it may consist of a paring device in the chamber; or it may consist of an overflow outlet arranged in the wall of the chamber, with a discharge channel leading from this outlet. V

In centrifugal separators having nozzles arranged in the rotor wall for discharge of separated slude, sludge can be returned or flushing liquid can be led in certain cases to the vicinity of the nozzles at the inside of the rotor by means of tubes located in the rotor and which often have bends. For this reason, each time the centrifuge is taken apart and re-assembled, these tubes must always be placed in the rotor in one and the same position. This means that the tubes are exposed to particularly heavy wear at certain points inside the tubes because of the bends, and that the wear becomes concentrated at a certain side of each tube and not distributed along the entire periphery of the inside. According to the present invention, it is possible to provide straight tubes in the rotor for supply of a fluid (sludge or flushing liquid) to the discharge nozzles arranged in the rotor wall, these nozzles as well as the tubes lying substantially in the plane of symmetry between the two disc sets. In addition to avoiding the above-mentioned wear concentration in bent tubes, the advantage of the straight tubes is that a further distribution of the wear is obtained along the entire periphery of the inside of the tubes, because the tubes, each time they are re-inserted in the rotor, take a turned position in relation to the preceding position.

According to another feature of the invention, the previously described chamber is formed. of an upper and a lower half of material arranged in the interior of the rotor with the joint substantially in the afore-mentioned plane of symmetry or a plane parallel therewith, and these halves are kept pressed against each other from the rotor bottom at one side and from the rotor cover at the other side. Thus, no additional locking means are needed for holding these halves together, as they are automatically held together by the usual locking ring when it is screwed tightly againstthe rotor cover.

The invention is explained more in detail below, reference beingmade to the accompanying drawings, in which:

Fig. l is a vertical sectional view of one form of the centrifugal separaton'showing the afore-mentioned chamber provided with an overflow outlet;

Fig. 2 is a similar view of a modified form, showing a paring device arranged in the chamber, and

Fig. 3 is a similanview of still another embodiment provided with straight tubes for leading a fluid to discharge nozzles arranged in the rotor wall.

In the different figures, corresponding details have identical reference numerals.

In the separator illustrated in Fig. 1, a sludge-containing liquid to be separated is fed downward through a stationary pipe 1, from which it flows downward and outward as indicated by the arrows to a space 2 situated between two sets 3 and 4 of conical discs. The two disc sets 3 and 4 are arranged as mirror images of each other symmetrically on opposite sides of a plane which passes through nozzle openings 6 arranged in the Wall of the centrifugal bowl or rotor 5, this plane being normal to the rotation axis of rotor 5. From the space 2, the liquid continues radially outward into a chamber 7 and then flows inward into the disc sets 3 and 4. The sludge separated from the liquid moves outward toward the nozzles 6. The separated liquid flows radially inward from the inner edges of the disc sets 3 and 4 into channels 8 and 9 from which it flows via channels 10 and 11 to a chamber 12 defined by two half- sections 13 and 14. As shown, the two halves 13 and 14 as well as the disc sets 3 and 4 are held in position in the rotor through the pressure which the rotor cover 15 exerts upon them when the cover is locked to the rotor body by means of a threaded looking ring 16. From the chamber 12, the separated liquid is discharged over an overflow outlet 17 which is arranged in the wall of this chamber and from which a channel 18 leads upward to discharge the liquid from the rotor. When the separator is stopped, it is emptied of residual liquid through bottom discharge channels 19. The rotor 5 is supported and driven by a spindle 20.

The embodiment illustrated in Fig. 2 differs from that shown in Fig. 1 in that the chamber 12 is provided with a stationary paring device 21 instead of the overflow outlet 17 and channel 18. The paring device 21 has a discharge passage formed by a tube 22 extending upward through the top half-section 13 and feed pipe 1. In order to prevent the liquid fed into the separator from directly entering the paring chamber (the space 12), a splash shield 23 is threaded on the paring device above the opening in section 13 through which this device extends.

The embodiment of Fig. 3 is similar to that of Fig. 2 but is arranged for supply of a flushing liquid to the regions of the inlets of the nozzles 6 for washing out the sludge, or for recirculation of sludge already withdrawn from the separator so that the concentration of this sludge can be kept at the desired value despite comparatively wide nozzle openings. Both of these measures are known per se in the art of centrifugal separation. As shown in Fig. 3, however, the supply of flushing liquid or sludge to the nozzles is eflected by means of straight tubes 26 located substantially in the above-mentioned plane of symmetry between the disc sets 3 and 4, and'these straight tubes give an even distribution of wear on the inside of the tubes, whereby the life of the tubes is increased. More particularly, the flushing liquid 'or the recirculated sludge is fed into the rotor through a central channel 24 in the rotor spindle 20. This channel opens upward into a chamber 25 in the interior of the rotor, this chamber being directly below the two sections 1311-1411 forming the chamber 12. From chamber 25, the liquid or sludge flows outward through the above-mentioned straight tubes 26, which open into the outer part of the bowl near the nozzles 6. h

It will be understood that in all three of the illustrated embodiments of the invention, the two sections 1314 (or 13a14a) constitute meansin the rotor forming the chamber 12 common to the two disc sets 34 and located substantially in the plane of symmetry between the disc sets. These sections also form the channels 11, and the upper section 13 in Fig. 1 also forms the overflow outlet 17 anddischarge channel 18.

4 I claim: 1. A centrifugal separator having a hollow rotor, two

' sets of conical discs in said rotor for increasing the separating efficiency, said disc sets being arranged substantially as mirror images of each other symmetrically on opposite sides of a plane at right angles to the rotation axis of the rotor, there being a feed space located between the two disc sets and through which the liquid to be separated is fed to the disc sets, means in the rotor forming a discharge chamber separated from said feed space and located substantially in said plane, the rotor having an outlet for a separated lighter component leading from said chamber, and channels leading to said chamber from the inner edges of the two disc sets.

2. A centrifugal separator according to claim 1, in which said rotor outlet includes an overflow outlet in a wall of said chamber, and a discharge channel leading from the overflow outlet.

3. A centrifugal separator according to claim 1, comprising also a paring device located in said chamber and forming said rotor outlet.

4. A centrifugal separator according to claim 1, comprising also discharge nozzles in the rotor wall, and tubes in the rotor for supplying a fluid to the regions of said nozzles, said nozzles and tubes lying substantially in said plane.

5. A centrifugal separator according to claim 1, comprising also discharge nozzles in the rotor wall, and straight tubes in the rotor for supplying a fluid to the regions of said nozzles, said nozzles and tubes lying substantially in said plane, said means also forming a second chamber through which said fluid is fed to the tubes.

6. A centrifugal separator according to claim 1, in which said means include upper and lower half-sections which engage each other substantially in a plane at right angles to said axis, the rotor having a cover pressing said sections together against the rotor bottom.

7. A centrifugal separator according to claim 1, comprising also discharge nozzles in the rotor wall, said means including upper and lower sections forming said chamber and also forming a second chamber for receiving a fluid, and tubes extending from said second chamber to the regions of said nozzles, the nozzles and tubes lying substantially in said plane.

References Cited in the file of this patent UNITED STATES PATENTS 499,347 Peck June 13, 1893 555,893 Andersson Mar.'3, 1896 2,209,043 Strezynski July 23, 1940 2,403,089 Lars July 2, 1946

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