FI69410C - CYCLONSEPARATOR MED ICKE-CIRKULAERT REJEKTUTLOPP - Google Patents

Description

1 69410

Cyclone separator with non-circular waste port

The present invention relates to a cyclone separator comprising means for forming a separation chamber having a generally circular cross-section at its first end and including a tangential inlet to the separation chamber through which the liquid suspension of substance enters and a central outlet through which the acceptor portion of the liquid suspension exits the separation chamber an outlet having a smaller flow area than said chamber, through which the reject part of the liquid suspension leaves the separation chamber.

It is now well known to use vortex cleaners to separate sand, gravel, bark particles and fiber bundles from cellulosic fibers in a pulp slurry. Generally, such purifiers include an elongate chamber of circular cross-section that is either cylindrical or somewhat conical. The pulp slurry to be cleaned is introduced under pressure to one end of the chamber through a limited tangential inlet so that a very rapid vortex develops along the length of the chamber. The velocity of the vortex is typically high enough to form an axial gas core centrally located in the chamber. The end of the chamber opposite the inlet is tapered and forms a relatively small diameter tip outlet for the wreck portion formed by the denser and larger particles of the slurry. Acceptable fibers with a relatively lower density, located near the interior of the vortex, change their flow direction near the tapered end of the chamber and flow upward to be pulled out through the axial outlet at the larger-diameter icy end of the chamber.

Generally, a cyclone separator system includes a plurality of stages connected in series, each of which includes a plurality of parallel-connected separators having common inlet and outlet chambers. The second stage treats the first stage scrap, the third stage treats the second stage scrap, etc., with the intention of minimizing the amount of good fiber discarded while concentrating the impurities. Such a system is used for 2 69410 ______ - to initially divide a highly contaminated pulp suspension into a usable papermaking fibrous part (the lower density part of the approved materials) and the thickened, larger and denser impurities part (scrap). An increase in the waste stream from the cyclone separator system may result in a more complete removal of contaminants and impurities from the pulp suspension. However, as a result of the increased waste material flow, there is a greater need for power in the system to handle and transport larger amounts of material. In addition, the increased waste material flow increases the amount of good fiber that is discarded from the system.

However, the smaller the diameter of the separator orifice, the more sensitive it becomes to blockages caused by contaminants. Many attempts have been made to eliminate the problems associated with fiber loss control and outlet obstructions. Some companies have fed pressure water to dilute the heavy scrap fraction and wash away good papermaking fibers. Other companies have used special valve arrangements to control the flow of scrap through the outlet. Attempts of this type include those disclosed in U.S. Patents 3,696,927 and 3,277,926. Others use grooves, moldings, and guide rods located in a tapered portion of the cyclone chambers to control the flow of scrap. Examples of solutions of this type include U.S. Patents 3,971,718, 4,153,558, 4,156,485 and 4,224,145.

At best, these attempts have been only partially successful in solving clogging problems and reducing fiber losses. Accordingly, there is still a need in the art for a cyclone separation device that is efficient, has no clogging problems, and minimizes losses of good papermaking fiber through a waste outlet.

3,69410

The present invention satisfies the above need by providing a cyclone separation device in which the separator comprises wall members comprising a plurality of tapered wall portions extending along the longitudinal axis of the separator and defining an outlet having a non-circular cross-section and continuously open during separator operation. Other preferred embodiments of the invention will become apparent from the appended subclaims.

It has been found that by changing the shape of the wreck opening of the cyclone separator, it is also possible to vary the amount of scrap, the thickening factor and the feed pressure of the device while maintaining substantially the same cleaning efficiency without clogging problems. The waste port of the present invention may be included or may form an integral part of a conventional cyclone separation device, or it may be made as a replaceable tip. In addition, the present invention can be used both in simple separation devices and in groups of such devices. The modified waste port of the present invention can also be used in inverted centrifugal cleaning devices, such as the device disclosed in U.S. Patent 4,155,839. Finally, the present invention can also be used to separate solids from gases.

By converting the outlet to a non-circular shape, a number of functional advantages can be achieved. These include: 1. Significantly reduced scrap volumes, i.e. reduced relative proportion of fiber in the scrap compared to the feed mass, without clogging, which minimizes the loss of good fiber from the purifier; 2. a higher content of approved materials compared to a standard round hole when using a square shape; 3. higher coefficient of thickening, i.e. the ratio of the concentration of discarded materials to the concentration of the feed when using an oval or elongate aperture shape; 4. satisfactory operation at lower feed heads than when using a standard round orifice; 5. Ability to handle more volumetric feed flow; and 6. the ability to use substantially wider outlets that are less likely to clog and still retain substantially the same amount of scrap as conventional circular scraps.

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4

Surprisingly, the cleaning efficiency of cyclone separators using the present invention is substantially unchanged even when non-circular waste outlets are used. This allows flexibility in the design of cyclone separator systems so that one or more of the functional advantages listed above can be achieved without any loss in cleaning efficiency.

Accordingly, it is an object of the present invention to provide a cyclone separator device having a modified wreck opening that is efficient, free of clogging problems, and that minimizes losses of good papermaking fiber from the scrap outlet. This and other objects, objects and advantages of the invention will become apparent from the following description and claims taken in conjunction with the accompanying drawings.

Figure 1 is a sectional view of a typical cyclone separator with a wreck opening; Figures 2, 3, 4 and 5 are top views illustrating the waste ports of the cyclone separator; Figures 2a, 3a, 4a and 5a are sectional side views of the wreck openings; and Fig. 2b illustrates a section along the line 2b-2b in Fig. 2a.

Figure 1 illustrates a typical cyclone separation device. The invention is, of course, not limited to simple devices, including inverted centrifugal cleaning devices, but is equally applicable to group arrangements. The device includes a hollow cyclone member 10 forming a separation chamber having a cylindrical portion 12, a tapered portion 14 and a hollow tip cone or tip portion 16 having an outlet 17. The cylindrical and tapered portion of the cyclone body may be formed of a polymeric resin material such as polypropylene, polypropylene such like. The tip portion 16 is preferably formed of a ceramic material that is resistant to abrasion, although it may also be formed as a unitary structure with the cyclone body of the same material as the body.

5,69410

The cylindrical portion 12 of the cyclone has a tangential, slit-like inlet 18 through which a fluid suspension of material, such as paper pulp, enters the device. The end of the cylindrical part 12 of the cyclone body is provided with a closure cover 20, which may be made of the same polymeric resin material as the other parts of the cyclone member 10. The closure cap 20 and the end of the cylindrical portion 12 may be threaded for tight engagement. The closure lid 20 is also provided with a central vortex finder, i.e. an overflow nozzle tube 22, through which an approved part of the suspension flows and which extends inwards into the center of the cylindrical part 12.

The cyclone member 10 includes a tip portion 16, which is preferably formed of an abrasion resistant cast ceramic material. The tapered tip portion 16 forms an extension of the tapered portion 14 and may be formed with an outwardly projecting threaded portion 26 as its original portion receiving an annular, internally threaded coupling nut 28 which seals the tip portion 16 to the tapered portion 14. Alternatively, the threaded portion may be glued to the tapered portion 16. in a known manner.

Figures 2, 2a and 2b illustrate an embodiment of the invention in which the tip portion 116 has an outlet opening 117 having a square cross section. As shown in the figures, the tip body 116 is formed as a replaceable element that can be connected to the cyclone separator using threads 126.

As shown in Figures 2, 2a and 2b, the hollow tapered body portion of the tip body 116 changes gradually from a circular cross-section to a square portion along the length of the tip body. The tapered wall portions 102, 104, 106 and 108, which together form a tapered channel with a square cross-section, may be integrally molded into a tip 116 during its manufacture (as shown in the figures) or the tip may be secured in place after its formation.

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It has now been found that tip performance improved by using an outlet with a non-circular cross-section is further improved as at least a portion of the inner wall of the tip leading to the outlet gradually adopts the same cross-sectional shape as the outlet, as best seen in Figure 2b, has begun to adopt a square cross-sectional shape. The exact amount of taper and the taper angle depend on many factors, including the initial size and diameter of the cyclone separator and the desired cross-sectional area of the outlet.

It will be appreciated, of course, that different portions of the inner wall 101 have different taper angles. This means that the cross-section of the separator gradually changes from round to non-circular, certain wall parts forming smaller angles with the longitudinal axis of the separator than other wall parts. For example, as illustrated in Figures 2, 2a and 2b, the tapered wall portions 102, 104, 106 and 108 form smaller angles with the longitudinal axis of the separator than the wall portions 103, 105, 107 and 109 located between the tapered wall portions.

On the other hand, if a different manufacturing process is used and certain parts of the separator inner wall are removed, for example to form an 80 mm square outlet from a circular opening of the same diameter, with other wall parts because parts of the inner wall are removed.

When it is mentioned in this application that the inner wall of the separator gradually changes from a round to a non-circular shape, this term is intended to cover both situations described above.

In another embodiment of the invention illustrated in Figures 3 and 3a, the tip portion 216 has an outlet portion 217 having a triangular cross-section. As shown, the tip 216 is formed to be connected to the cyclone body using threads 226. Tip 216

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7, the inner wall 201 changes from a circular to a triangular cross-section over a portion of the length of the tip. The tapered wall portions 202, 204 and 206 are formed together by a tapered duct having a triangular cross-section.

The embodiment of the invention shown in Figures 4 and 4a illustrates the use of an elongate or elliptical outlet 317 in the tip portion 316. The elliptical outlet results from the fact that the end of the tip 316 is formed at an angle α to the normal of the longitudinal axis of the tip. The angle α can be varied between 1 and 89 ° to vary the amount by which the outlet portion 317 deviates from the circular cross section. Alternatively, an elliptical outlet may be formed at the tip 316, the end of which is perpendicular to the longitudinal axis of the tip. As in the previous embodiments, the tip 316 may include threads for attachment to the cyclone body.

The embodiment of the invention shown in Figures 5 and 5a illustrates the use of a polygonal or sawtooth outlet 417 in a tip 416 designed to be connected to a cyclone body using threads 426. The inner wall 401 of the tip 416 changes from a circular cross-section to a polygonal cross-sectional shape over a portion of the length of the tip. The tapered wall portions 402, 403, 404, 405, 406, 407, 408, 409, 410, 411, 412, 413, 414, 415, 419 and 420 together form a tapered channel with a polygonal cross section and provide a sawtooth effect on the outlet 417 .

For a better understanding of the invention, reference is made to the following non-limiting examples.

Example 1

Several tests were run using deinked pulp from the third stage of the cyclone separator system as the feed pulp. A 76 mm diameter Cellu-Clone cyclone cleaner available from The Black Clawson Company, Middletown, Ohio was used in these tests.

8 69410

Four different wreck tips were tested as follows: 1. Standard tip, round cross-section, diameter 9.1 mm 2 (open area 66 mm) 2. Tip A - round cross-section, diameter 6.4 mm (open 2 area 32 mm), 3. Tip B - square cross section, side length 6.4 mm (open area 41 mm ^) 4. Tip C - oblong (rectangular) cross section 2, 0.173 x 9.3 mm (open area 41 mm).

The results are given in Table I below. In times 1-4, the flow of the wreckage was controlled by a wreck valve such as that in the cyclone separator. Run 5-8 was performed with the scrap valve fully open in order to eliminate the possibility of the valve clogging. The arrangement for free removal was arranged so that the wreckage was removed from the device into an open tube located approximately 245 cm above the device. With this arrangement 2 a back pressure of about 0.25 kg / cm was provided in its scrap mass.

2

The pressure drop measured in the device was 1.4 kg / cm at all times.

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As can be seen from the table, times 3 and 7 performed on square tip B resulted in significantly lower rejection rates and thickening factors than the standard round tip (runs 1 and 5) or tip Λ (runs 2 and 6). Visual observations showed that the cleaning efficiency was essentially the same at all tips. No blockage occurred at any tip. The elongated tip C (runs 4 and 8) showed a significantly higher coefficient of thickening, indicating its usefulness in situations where a higher consistency waste stream is desired.

Example 2

The same arrangement as in Example 1 was used to test the tips with the exception that the feed mass used was a mixture of corrugated kraft paper raw material, cutting waste and pieces. The results are reported in Table II below. Also in this example, the pressure drop in the device was measured to be 1.4 kg / cm at all times.

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Also in this case, tip B (run 10) operated at a significantly lower scrap rate than the round standard tip (run 9). No clogging occurred and the cleaning efficiencies at all tips appeared to be the same. As in the previous case, the elongated tip C (run 11) had a significantly higher coefficient of thickening than the standard circular tip.

Example 3

Additional tests were performed using the feed mass of Example 1 at a higher consistency (i.e., consistency of approximately 1.0%).

The results are reported in Table III below. The pressure drop measured in the device 2 was 1.4 kg / cm at all times.

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Also in this case, even at higher feed concentrations, square tip B (run 12) had a significantly lower scrap rate as well as a lower thickening factor. Again, no blockage was observed.

Example 4

Additional test runs were performed using the feed mass of Example 1.

The following new tip was also tested: Tip D - square cross section, side length 6.4 mm, no 2 tapers (open area 41 mm).

The phrase no tapering means that the walls of the tip were parallel and not tapering inwards.

At later times (runs 19 and 22), tip D was modified by giving it tapered walls much like tip B.

The test results are reported in Table IV below.

2

The measured pressure drop in the device was 1.4 kg / cm at all times.

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Tests show improved performance when using tapered sides at the square tip (runs 17, 18, 19, 20 and 21) compared to non-tapered sides (run 16) - However, operate the non-tapered tip D (16) with an ever lower number of scraps than the round standard tip ( ajo 21). The thickening coefficients were again lower at the square tips than at the round tips. No blockage occurred.

Thus, by using a non-circular cross-section waste port in the cyclone separator of the present invention, the amount of waste, the coefficient of thickening and the feed pressure of the device can also be varied to give the device improved performance while maintaining substantially the same cleaning efficiency and without clogging problems. For example, a lower rejection rate can be achieved by using the same open area at the square tip instead of the previously known round tip. If clogging is a problem, square tips with a larger open area can be used with substantially the same amount of scrap as previously known round tips. Other modifications to the tip geometry will be apparent to one skilled in the art to achieve optimal performance under varying feed conditions, pressure conditions, consistency conditions, and the like.

Although the devices described herein constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these particular devices and that modifications may be made without departing from the scope of the invention as defined in the appended claims.

Claims (8)

A cyclone separator, comprising means for forming a separating chamber, the first end of which has a generally circular cross-section and comprising a tangential entrance (18) to the separating chamber through which the fluid-suspension of the material enters, and a central exit (17, 117, 217, 317, 417. through which the acceptor portion of the fluid suspension is removed from the separation chamber, the opposite end of the separation chamber tapered to the output exhibiting less flow area than said chamber, and through which the reject portion of the fluid suspension separates from the separation chamber, comprises wall means which comprise a plurality of tapered wall portions extending along the longitudinal axis of the separator defining an output (17, 117, 217, 317, 417) of non-circular cross-section, and the output being continuously open during the operation of the separator. Cyclone separator according to claim 1, characterized in that the output (217) has a triangular cross section. Cyclone separator according to claim 1, characterized in that the output (417) has a polygonal cross-section. Cyclone separator according to claim 1, characterized in that alternately tapered wall portions (102, 104, 106, 108) form smaller angles with the longitudinal axis of the separator than tapered wall portions (103, 105, 107, 109).