SOLID BOWL SCREW CENTRIFUGE

Abstract

A solid bowl centrifuge includes a rotatable drum having a cylindrical portion with length L.sub.1 and a conical portion with length L.sub.2, which, when added, give the length L.sub.T of the drum. A screw is arranged in the drum and is rotatable relative to the rotatable drum with a differential speed. At least two drum bearings for supporting the drum in the housing are spaced apart with a spacing L.sub.L. A spacing L.sub.L of the drum bearings for supporting the drum relative to one another is less than the length L.sub.T of the drum.

Claims

1-14. (canceled)

15. A solid bowl screw centrifuge, comprising: a housing; a rotatable drum having an axis of rotation, wherein the rotatable drum comprises a cylindrical portion having a length L.sub.1 and a conical portion having a length L.sub.2, and wherein a sum of lengths L.sub.1 and L.sub.2 is equal to a length L.sub.T of the rotatable drum; a screw arranged in the rotatable drum, wherein the screw is rotatable relative to the rotatable drum at a differential speed; a rotor rotatably mounted in the housing, wherein the rotor is formed by the rotatable drum and the screw; a liquid discharge arranged in the cylindrical portion of the rotatable drum; a solids discharge arranged in the conical portion of the rotatable drum; at least two drum bearings arranged to support the rotatable drum in the housing, wherein the at least two drum bearings are spaced at a distance L.sub.L; and at least one screw bearing arranged to support the screw in the drum, wherein the distance L.sub.L between the at least two drum bearings is less than the length L.sub.T of the rotatable drum, and wherein one of the at least two drum bearings is positioned radially outside on the conical portion of the rotatable drum.

16. The solid bowl screw centrifuge of claim 15, wherein either one or both of the at least two drum bearings are arranged within an axial region laying between the solids discharge and the liquid discharge of the rotatable drum.

17. The solid bowl screw centrifuge of claim 15, wherein the at least two drum bearings are arranged between the rotatable drum and the housing or a part connected to the housing, or the at least one screw bearing is arranged between the screw and the rotatable drum.

18. The solid bowl screw centrifuge of claim 15, wherein either one or both of the at least two drum bearings or the at least one screw bearing directly adjoin(s) a region of the liquid discharge or the solids discharge of the rotatable drum.

19. The solid bowl screw centrifuge of claim 15, wherein a distance A.sub.1 or A.sub.2 between a respective axial end of the rotatable drum and a respective axial position of one or both of the at least two drum bearings is 0 to 25% of the length L.sub.T of the rotatable drum.

20. The solid bowl screw centrifuge of claim 15, wherein the at least two drum bearings are positioned radially outside on the rotatable drum or outside directly on a drum cover of the rotatable drum.

21. The solid bowl screw centrifuge of claim 15, wherein one of the at least two drum bearings is positioned radially outwardly on the cylindrical portion of the rotatable drum.

22. The solid bowl screw centrifuge of claim 21, wherein the one of the at least two drum bearings is positioned radially outwardly on the conical portion of the rotatable drum on a portion of the conical portion having a smaller inner diameter than the cylindrical portion of the rotatable drum.

23. The solid bowl screw centrifuge of claim 15, wherein one of the at least two drum bearings is positioned axially outside directly on a drum cover of the rotatable drum.

24. The solid bowl screw centrifuge of claim 15, wherein one or both of the at least two drum bearings are magnetic bearings.

25. The solid bowl screw centrifuge of claim 15, wherein one or both of the at least two drum bearings are roller bearings.

26. The solid bowl screw centrifuge of claim 25, wherein one or both of the at least two drum bearings are ceramic bearings or hybrid ceramic bearings.

27. The solid bowl screw centrifuge of claim 15, wherein a ratio between a diameter of the drum, at a point where the solids discharge is arranged, and a maximum diameter of the drum is between 0.4 and 0.3.

28. The solid bowl screw centrifuged of claim 15, wherein the axis of rotation of the rotatable drum is aligned horizontally or vertically.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0024] In the following, the invention is described in more detail with reference to the drawing using exemplary embodiments, wherein:

[0025] FIGS. 1 to 3 show side views of three different solid bowl screw centrifuges according to the invention, each of which is shown schematically; and

[0026] FIG. 4 shows a side view of a fourth schematic diagram of a solid bowl screw centrifuge according to the prior art.

DETAILED DESCRIPTION

[0027] FIG. 1 shows a solid bowl screw centrifuge having a frame, which is not rotatable or does not rotate in operation, and preferably housing 100 and a rotor 200, which is rotatable or rotating in operation.

[0028] The rotor 200 comprises a rotating drum 210 having a horizontal axis of rotation D. The axis of rotation D can also be oriented differently, especially vertically, in space. The rotor 200 also includes a screw 230 arranged in the drum 210, whose axis of rotation coincides with that of drum 210. The screw 230 can be rotated at a different speed to drum 210 during operation.

[0029] Drum 210 has a cylindrical portion 211 with a length L.sub.1 and an axially adjacent conical portion 212 with a length L.sub.2. The cylindrical portion 211 is closed by a drum cover 213, which extends essentially radially. In the conical portion 212 with a length L.sub.2, the drum is conical inside and outside (in relation to the drum shell).

[0030] The screw 230 here also has a cylindrical portion 231 and an axially adjacent conical portion 232. It is arranged inside the drum 210.

[0031] A feed pipe 214, which here extends concentrically to the axis of rotation, projects into drum 210 and opens into a distributor 215, through which a suspension Su to be processed can be radially fed into a centrifuging chamber 216 of drum 210. The feed pipe 214 can either be guided into drum 210 from the side of the cylindrical drum portion 211 or it can be guided into drum 210 from the side of the conical drum portion 212.

[0032] One or more liquid discharges 217 can be formed in or on the drum cover 213. These can be formed in different ways, for example as openings in the drum cover 213, which have a kind of overflow weir, or in other ways, for example as a peeling disc. At the end of the conical portion 212 at least one solids discharge 218 is formed.

[0033] As a rule, drum 210 is designed as a solid-bowl drum. At least one liquid phase Fl is then clarified from solids Fe in the rotating drum 210. The at least one liquid phase emerges from the liquid discharge 217 at the drum cover 213. The solids, on the other hand, are transported by screw 230 in the direction of the solids discharge 218, where they are ejected from drum 210.

[0034] FIG. 4 shows a solid bowl screw centrifuge in which a first drum shaft section 220 is axially connected to the drum cover 213 or the actual drum 210, which is non-rotatably connected to drum 210, and a second drum shaft section 219 axially adjoins the conical drum section 212, which is also non-rotatably connected to drum 210.

[0035] A first screw shaft section 234 axially adjoins the cylindrical portion 231 of the screw 230, which is non-rotatably connected to the screw 230, and a second screw shaft section 233 axially adjoins the conical drum section 232, which is also non-rotatably connected to the screw 230.

[0036] The rotor 200 is driven by a drive unit having one or two motors (not shown here). The drive device 300 is followed by at least one gear unit 310, on which two pulleys 320, 330 are schematically shown here, indicating that the gear unit 310 has at least two interfaces for feeding a respective torque of the motor or motors into the gear unit 310 to drive the drum and the screw. Alternatively (not shown here), the rotor can also be driven by hydraulic motors, so that no gear is required. It is also possible to drive the rotor by a combination of electric motor(s) and hydraulic motor(s), using different gear boxes and eliminating the pulleys completely or partially.

[0037] The gear unit 300 rotates the drum 210 on the one hand and the screw 230 on the other. For this purpose, the gear unit 300 has two output shafts. The first output shaft is non-rotatably coupled to the first drum shaft section 220 or directly coupled to drum 210 and the second output shaft is directly or indirectly non-rotatably coupled to the first screw shaft section 234 or directly coupled to screw 230.

[0038] The drum and the shaft are each rotatably supported by two drum bearings 221, 222 arranged axially in the direction of the axis of rotation. The term “bearing” should not be too narrowly defined in this respect. Each of the bearings 221, 222 can consist of one or more single bearings, which are arranged axially directly next to each other, so that they can be considered functionally in each case as one single bearing. The bearings 221, 222 can also be designed as bearings of various types, such as roller bearings—especially ceramic bearings, hybrid ceramic bearings, magnetic bearings or plain bearings.

[0039] The drum bearings 221, 222 are arranged between drum 210 and frame 100 or a part connected to the frame, so that drum 210 can be rotated relative to frame 100. This also applies to all variants described below and covered by the claims. The drum bearings 221, 222 are preferably arranged radially between drum 210 and frame 100 or a part connected to the frame.

[0040] The screw bearings 235, 236, on the other hand, are arranged radially between the screw 230 and the drum 210, so that the screw 230 can rotate relative to the drum 210. The screw bearings 235, 236 are preferably arranged radially between the drum 210 and the screw 230.

[0041] In a possible embodiment variant (not shown), one of the screw bearings 235 in the area of the solids discharge 218 can be omitted. In this case, the rotating screw centers itself automatically, which is known e.g., from a vertical arrangement of the decanter.

[0042] According to the prior art, as shown in FIG. 4, the drum bearings 221, 222 are arranged axially outside the axial region L.sub.T of drum 210, which lies between the solids discharge 218 and the liquid discharge 217 of drum 210. In FIG. 4, for example, they are located between the solids discharge 218 and an axial end of the housing 100 adjacent thereto and the liquid discharge 217 and an axial end of the housing adjacent thereto. Accordingly, a distance L.sub.L of the drum bearings 221, 222 is greater than a length L.sub.T of the drum 210, which is the sum of the length L.sub.1 of the cylindrical portion 211 of drum 210 and the length L.sub.2 of the conical portion 212 of drum 210.

[0043] This means that the two drum bearings 221, 222 are arranged at a relatively large axial distance from each other in relation to the length L.sub.T of drum 210. And according to the prior art, as shown in FIG. 4, the screw bearings 235, 236 are also arranged axially outside the axial region of drum 210, which lies between the solids discharge 218 and the liquid discharge 217 of drum 210. This means that the two screw bearings 235, 236 are also arranged at a relatively large axial distance from each other in relation to the length L.sub.T of drum 210 and screw 230.

[0044] Here the invention takes a different path. Either one or both drum bearings 221, 222 are arranged within an axial region, which lies between the solids discharge 218 and the liquid discharge 217 of drum 210 or directly adjoins an area of the liquid discharge 217 and/or the solids discharge 218 of drum 210. The drum bearings 221, 222 are then positioned radially outside on the drum 210 or radially or axially outside on the drum cover 213.

[0045] If one of the drum bearings 221, 222 is arranged within the axial region laying between the solids discharge 218 and the liquid discharge 217 of drum 210, the respective other of these bearings—the other of the drum bearings 221, 222—can be arranged outside of this axial region. However, it may also be provided in the context of the invention to provide both of the respective bearings—both drum bearings 221, 222—there or in the area described above (FIG. 3).

[0046] It has been shown that in this way, and with an otherwise unchanged geometry of the rotor, the first resonance frequency of the rotor is raised and thus the drum speed could be further increased.

[0047] Different variants of this technical teaching are shown in FIGS. 1 to 3. In FIGS. 1 to 3 the length of drum 210 is marked L.sub.T and the distance between drum bearings 221 and 222 is marked L.sub.L. In FIG. 4, and thus for prior-art solid bowl screw centrifuges, L.sub.T<L.sub.L

[0048] FIG. 1 shows an embodiment of the invention in which the first drum bearing 221 is assigned to the conical portion 212 of drum 210. It is axially spaced from the solids discharge 218 in the direction of the cylindrical portion 211 of drum 210. The other of the drum bearings 222 “at the other end of the drum” is outside this axial section.

[0049] The first drum bearing 221 is thus located between the solids discharge 218 and the liquid discharge 217 in the area of the conical portion 212 of drum 210 on the conical portion. The drum shaft section 219 in the area of the conical portion 212 of drum 210 can thus also be dispensed with. The length of drum 210 is greater here than the distance between the drum bearings 221 and 222, therefore L.sub.T>L.sub.L.

[0050] It is possible to design the conical portion to be axially very long and the diameter of the drum where the solids discharge is located to be relatively small. The ratio between the diameter of the drum where the solids discharge is located and the maximum inner diameter of the drum can be between 0.4 and 0.3. This can be advantageous in keeping low or reducing the energy loss caused by the solids discharge. Furthermore (see definition above), a relatively high value “λ” can be achieved.

[0051] FIG. 2 shows an embodiment variant of the invention in which the first drum bearing 221 is assigned to the conical portion 212 of drum 210 (analogous to the embodiment variant according to FIG. 1), wherein it is axially spaced from the solids discharge 218 in the direction of the cylindrical portion 211 of drum 210. The drum bearing 221 is thus located between the solids discharge 218 and the liquid discharge 217 in the area of the conical portion 212 of drum 210.

[0052] The other drum bearing 222 is here assigned to the cylindrical portion 211 of drum 210 or arranged outside on it. It is directly axially adjacent to an area of the liquid discharge 217 of drum 210. Therefore, the drum shaft section 219 in the area of the conical portion 212 of drum 210 and the drum shaft section 220 in the area of the cylindrical portion 211 of drum 210 can be omitted here. The length of drum 210 is also greater here than the distance between the drum bearings 221 and 222, therefore here too L.sub.T>L.sub.L.

[0053] FIG. 3 shows an embodiment variant of the invention in which the first drum bearing 221 is again arranged radially outside on the conical portion 212 of drum 210. It is again axially spaced from the solids discharge 218 in the direction of the cylindrical portion 211 of drum 210, analogous to the embodiment variant according to FIG. 1. The first drum bearing 221 is thus again located between the solids discharge 218 and the liquid discharge 217 in the area of the conical portion 212 of drum 210, while the second drum bearing 222 is then located on the cylindrical portion 211 of drum 210. It is axially spaced here from the liquid discharge 218 in the direction of the conical portion 212 of drum 210. The drum shaft section 220 in the area of the cylindrical portion 211 of drum 210 and the drum shaft section 218 in the area of the conical portion 212 of drum 210 can thus be dispensed with. The length of drum 210 is greater here than the distance between the drum bearings 221 and 222, therefore L.sub.T>L.sub.L.

[0054] In the exemplary embodiments shown in FIG. 1 to FIG. 3, there is a distance A.sub.1 and/or A.sub.2 between the respective end of drum 210 and the respective position of drum bearing 221 and/or 222. The respective distance A.sub.1 and/or A.sub.2, by which the respective drum bearing 221, 222 is spaced from the liquid discharge 217 and/or or the solids discharge 218 in the axial direction so that it is positioned between the liquid discharge 217 and the solids discharge 218, is preferably 0 to 35% and especially preferably 0 to 25% of the length of the drum 210 L.sub.T.

[0055] By positioning the drum bearings 221, 222 each at a position within the axial region between the solids discharge 218 and the liquid discharge 217, the distance L.sub.L between the drum bearings 221, 222 is advantageously reduced in such a way that the first natural resonance of drum 210 only occurs at a higher speed than with a bearing arrangement according to the prior art (see FIG. 4). Due to the higher operating speed now possible, the achievable separation efficiency of the solid bowl screw centrifuge according to the invention is advantageously increased compared to a solid bowl screw centrifuge of the same volume according to the prior art.

[0056] The explanations regarding the arrangements of the drum bearings 221, 222 according to FIG. 1 to FIG. 3 are by no means to be understood conclusively. Rather, other advantageous arrangements of the drum bearings 221, 222 are also conceivable within the scope of the claims. However, the axial distance L.sub.L between the drum bearings 221, 222 should be shorter than the length L.sub.T of drum 210.

[0057] Although the invention has been illustrated and described in detail by way of preferred embodiments, the invention is not limited by the examples disclosed, and other variations can be derived from these by the person skilled in the art without leaving the scope of the invention. It is therefore clear that there is a plurality of possible variations. It is also clear that embodiments stated by way of example are only really examples that are not to be seen as limiting the scope, application possibilities or configuration of the invention in any way. In fact, the preceding description and the description of the figures enable the person skilled in the art to implement the exemplary embodiments in concrete manner, wherein, with the knowledge of the disclosed inventive concept, the person skilled in the art is able to undertake various changes, for example, with regard to the functioning or arrangement of individual elements stated in an exemplary embodiment without leaving the scope of the invention, which is defined by the claims and their legal equivalents, such as further explanations in the description.

LIST OF REFERENCE NUMERALS

[0058] 100 Housing [0059] 200 Rotor [0060] 210 Drum [0061] 211 Cylindrical portion [0062] 212 Conical portion [0063] 213 Drum cover [0064] 214 Feed pipe [0065] 215 Distributor [0066] 216 Centrifuging chamber [0067] 217 Liquid discharge [0068] 218 Solids discharge [0069] 219 Drum shaft section [0070] 220 Drum shaft section [0071] 221 Drum bearing [0072] 222 Drum bearing [0073] 230 Screw [0074] 231 Cylindrical portion [0075] 232 Conical portion [0076] 233 Screw shaft section [0077] 234 Screw shaft section [0078] 235 Screw bearing [0079] 236 Screw bearing [0080] 300 Drive device [0081] 310 Gear unit [0082] 320 Pulley [0083] 330 Pulley [0084] A.sub.1 Distance [0085] A.sub.2 Distance [0086] D Axis of rotation [0087] L.sub.1 Length [0088] L.sub.2 Length [0089] L.sub.L Distance drum bearing [0090] L.sub.T Length drum [0091] Su Suspension [0092] Fe Solids [0093] Fl Liquid phase