Device and method for sealing an overpressure zone

Abstract

The invention relates to a method for conveying a material to be conveyed into or out of an overpressure zone (1), wherein the material to be conveyed is conveyed into and / or out of an overpressure zone (1) by means of a stuffing screw (2) and compressed to form an airtight and liquidtight plug, which seals the overpressure zone (1). The invention is characterized in that the sealing of the plug is controlled by the relative positioning of the screw (6) and the plug tube (8). The invention relates to a device for carrying out the method and enabling optimal control of the sealing of the overpressure zone (1).

Description

Technical Field

[0001] The present invention relates to a method for conveying a material to be conveyed, such as wood chips, to or from an overpressure zone, wherein the material to be conveyed is conveyed into the overpressure zone and / or is discharged from the overpressure zone by a stuffing screw according to the present invention, the stuffing screw receives the material to be conveyed in an inlet zone, and a screw rotating around a rotation axis in a housing conveys the material to be conveyed to a discharge zone, wherein the material to be conveyed is compressed into an airtight and liquidtight plug between a plug tube and the screw, and the plug is conveyed into the overpressure zone in order to convey the material to be conveyed into the overpressure zone, and / or the material to be conveyed compressed into a plug is discharged from the overpressure zone in order to convey the material to be conveyed out of the overpressure zone, wherein the plug seals the overpressure zone relative to the stuffing screw. The present invention also relates to a device for conveying a material to be conveyed into or out of an overpressure zone. Background Art

[0002] Stuffing screws are used to dehydrate the conveyed material by compression, in particular to obtain a pressure seal between two process steps that are carried out at different pressure levels. To form the pressure seal, one process step comprises conveying the conveyed material in the stuffing screw from the inlet zone to the outlet zone, during which the conveyed material forms a gas-tight and liquid-tight plug. Here, when the material is conveyed into the overpressure zone, the outlet zone of the stuffing screw is connected to the overpressure zone, or, when the material is conveyed out of the overpressure zone, the inlet zone of the stuffing screw is connected to the overpressure zone. In this way, the conveyed material itself forms a pressure seal between process steps, one of which includes an overpressure zone, which is designed, for example, as a pressure vessel, reactor or digester. Typical applications in this regard are in the field of papermaking and fiber materials, or generally in the processing of fiber materials (for example wood fibers) and in the production of fiberboards (for example medium-density fiberboards, etc.). Another application is the production of biofuels, for example, bioethanol can be produced from biomass including corn, corn or sugar beets.

[0003] A stuffing screw generally comprises a housing and a screw mounted therein in a rotatable manner about an axis of rotation, wherein the screw at least partially has a helix and wherein the material to be conveyed is continuously compressed in the tapering region between the housing and the screw. In the discharge region of the stuffing screw, the screw is at least partially designed without a helix in order to form a plug. The housing may have openings in the region of the screw in order to dehydrate the conveyed material by compression. Conventional stuffing screws can be formed by combining a cylindrical housing with a screw having a cylindrical outer contour, or other housing shapes, for example with a conical outer contour, can also be used.

[0004] In EP 2 817 449 B1, a system for processing wood-free plant matter is described. It is further outlined that a plugging screw is used to feed sawdust into a digester, wherein the plugging screw comprises a plug tube having a constant inner diameter at the end of the plugging screw. Furthermore, the object of EP 2 817 449 B1 is primarily to disclose a plugging screw arrangement which minimizes the risk of steam backflow from the overpressure zone, thereby optimizing the pressure seal. This is achieved by the interaction of a plugging screw conveyor and a forced feed screw.

[0005] In WO 2016 / 036300 A1, a packing screw for processing lignocellulosic material is described. It is recognized that when lignocellulosic material is fed into a digester operating at high pressure, uniform and reliable compression is required to form a seal. WO 2016 / 036300 A1 provides a special design of the spiral.

[0006] DE 102008012156 A1 describes a screw conveyor for conveying biomass into a pressure vessel, wherein the size of the compression zone is produced by an adjustable counterpressure device comprising a conical pipe section, a pressure cylinder and a regulating device.

[0007] DE 35 45 339 A1 discloses a screw conveyor for conveying fine-grained solids, wherein a spiral tube is lined with a sleeve made of a flexible material, against which the spiral threads abut, wherein the spiral tube and / or the threaded screw shaft are axially movable.

[0008] WO 2016139000 A1 describes a device and a method for conveying bulk material into a pressure chamber, wherein an outlet opening is provided in the circumferential direction at the lower part of the housing, which outlet opening can be closed or its size can be changed by a sleeve arranged in the region of the outlet opening of the housing.

[0009] US 2 428 995 describes a device for conveying particulate material to a high pressure zone, comprising a feed neck with a resilient liner and valve means for closing the outlet of the feed neck, the valve means having a lip extending from the proximal end of the resilient liner.

[0010] WO2015081443A1 describes a device and method for controlling the back pressure in a screw conveyor using a deformable control device.

[0011] WO2016036300A1 discloses a stuffing screw conveyor with improved feeding conditions for the material to be conveyed, wherein the spiral line has a tooth shape in the inlet area. Summary of the invention

[0012] The technical problem to be solved by the present invention is to improve the possibilities for controlling the tightness between two process steps, in particular the tightness of the overpressure zone into which the conveyed material is fed and / or the tightness of the overpressure zone from which the conveyed material is discharged. The technical problem to be solved is also to achieve an optimal dewatering while maintaining the required tightness, or to correct the influence of uneven conveyed material, which is, for example, fed unevenly into the stuffing screw or has widely varying material properties. The technical problem to be solved is also to be able to adjust the tightness between process steps even if the screw or the stuffing tube is worn, or to minimize the power consumption of the stuffing screw while maintaining the required tightness between process steps.

[0013] According to the invention, this is achieved by controlling the tightness of the plug by the relative positioning of the screw and the plug pipe. The plug pipe is arranged in the discharge area of ​​the plug screw in the housing and has an at least partially annular and / or at least partially truncated cone-shaped structure. The screw extends into the plug pipe, wherein the screw is arranged rotatably around the rotation axis and, in order to form the plug, the screw has a helix-free area in the plug pipe. The plug pipe is usually replaceable because it can be easily replaced if worn and because different geometries can be formed by replacing the plug pipe. The area between the plug pipe and the screw can be influenced by the positioning of the screw relative to the plug pipe. Thus, the area between the plug pipe and the screw, in particular the gap at the end of the screw towards the plug pipe, can be reduced or enlarged. By reducing this area or gap, the sealing effect of the plug is increased, and by enlarging this area or gap, the sealing effect is reduced. The screw moves axially along the rotation axis in the housing to control the tightness. Here, the housing and the plug tube are fixed in position, and the screw is moved axially, thereby reducing or expanding the area between the plug tube and the screw, in particular the gap between the screw end and the plug tube. The movement of the screw can be achieved in that the bearing unit of the screw is designed to be movable, wherein the bearing unit accommodates the shaft of the screw and is arranged opposite the discharge area. Here, the screw is driven by a fixed drive, wherein a coupling (Kupplung) is designed between the bearing unit of the screw and the drive to receive the axial movement of the screw. In addition, the material to be conveyed is compressed between the housing and the at least partially helical screw between the inlet area and the discharge area, wherein a material plug is formed in the discharge area between the plug tube and the area of ​​the screw without helical threads. In the area of ​​the plug tube, the screw can partially have an area with a helical thread, wherein the area of ​​the screw with a helical thread follows the area of ​​the screw without a helical thread in the conveying direction.

[0014] Another advantageous embodiment of the invention is characterized in that the plug passes through an annular zone in the discharge zone, wherein the annular zone is formed by a region of the plug tube with a constant inner diameter and a region of the screw with a constant outer diameter without a helix. In particular, the plug is formed in this annular zone, wherein in this zone the properties of the plug or the sealing effect of the plug have not yet been adjusted. Advantageously, the plug first passes through the annular zone to form a sealed plug and then passes through a calibration zone to adjust the properties of the plug.

[0015] Furthermore, the invention is characterized in that in the discharge zone, the plug passes through a calibration zone after the annular zone, wherein the calibration zone is formed by a region of the plug tube with a decreasing inner diameter in the conveying direction and by a helix-free region of the screw with a constant or decreasing outer diameter, or the calibration zone is formed by a region of the plug tube with a constant or increasing inner diameter in the conveying direction and by a helix-free region of the screw with an increasing outer diameter. If the calibration zone is formed by a region of the plug tube with a constant inner diameter in the conveying direction and by a helix-free region of the screw with an increasing outer diameter, then a region with a diameter greater than the constant inner diameter of the plug tube is adjacent to the plug tube. Here, the helix-free region of the screw with an increasing outer diameter can be positioned inside the plug tube or in a region with a diameter greater than the constant inner diameter of the plug tube, wherein, of course, positioning between these positions is also possible. Due to the relative positioning of the plug tube and the screw, a specific spacing is provided between the plug tube and the screw in the calibration zone, in particular a specific gap is provided between the end of the screw and the plug tube. The calibration zone can be reduced or enlarged by the relative positioning of the plug tube and the screw. The area of ​​the plug tube with a decreasing inner diameter can be realized with a conical plug tube shape, wherein the imaginary cone tip points to the discharge zone. Then, the helix-free area of ​​the screw with a constant diameter or a decreasing outer diameter is formed conically, wherein the imaginary cone tip also points to the discharge zone. By the relative displacement between the conical surfaces that overlap each other, the spacing between each other and the properties of the plug can be directly influenced, and thus the sealing effect brought about by the plug can also be directly controlled. The area of ​​the plug tube with an increasing inner diameter can be realized with a conical plug tube, wherein the imaginary cone tip points to the inlet zone. Then, the helix-free area of ​​the screw with an increasing outer diameter is designed to be conical, wherein the imaginary cone tip also points to the inlet zone. Advantageously, the sealing effect of the plug can then be increased by reducing the calibration zone or reduced by expanding the calibration zone by axial displacement of the screw.

[0016] The subject matter of the invention also includes a stuffing screw for conveying material to be conveyed, such as wood chips, to or from an overpressure zone. In this case, the screw is movable along an axis of rotation and axially relative to a housing, the screw at least partially comprising a helix, wherein in the region of the stuffing tube the screw is at least partially designed as a helix-free region. Furthermore, an annular region is advantageously formed between the stuffing tube and the screw, wherein the annular region comprises a region of the stuffing tube having a constant inner diameter and a helix-free region of the screw having a constant outer diameter.

[0017] An equally advantageous design of the stuffing screw is characterized in that a calibration zone is formed between the plug tube and the screw, wherein the calibration zone comprises a region of the plug tube with an inner diameter which tapers in the conveying direction and a helix-free region of the screw with a constant or decreasing outer diameter, or the calibration zone comprises a region of the plug tube with an inner diameter which tapers in the conveying direction and a helix-free region of the screw with an increasing outer diameter. If the calibration zone is formed by a region of the plug tube with an inner diameter which is constant in the conveying direction and a helix-free region of the screw with an increasing outer diameter, a region whose diameter is greater than the constant inner diameter of the plug tube adjoins the plug tube. The tapering or increasing region of the screw or plug tube can be formed by a conical configuration of the plug tube or screw. According to these embodiments, the axial positioning of the screw relative to the plug tube can reduce or increase the calibration zone. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will now be described exemplarily with reference to the accompanying drawings.

[0019] Figure 1 A stuffing screw according to the prior art is shown for feeding an overpressure zone.

[0020] Figure 2 The design of the stuffing screw according to the invention is shown, wherein the screw and the stuffing tube are in a first relative position.

[0021] Figure 3 The design of the stuffing screw according to the invention is shown, wherein the screw and the stuffing tube are in a second relative position.

[0022] Figure 4 A further design of a stuffing screw according to the invention is shown. DETAILED DESCRIPTION

[0023] Figure 1 A stuffing screw for feeding an overpressure zone according to the prior art is shown. Here, the material to be conveyed is fed into the overpressure zone 1 via an inlet region 3 of a stuffing screw 2, which has a housing 4, a screw 6 which at least partially has a helix 9 and can rotate about an axis of rotation 5, a discharge region 7 and a plug tube 8. The screw 6 has a region without a helix 10 in the region of the plug tube 8.

[0024] A stuffing screw for conveying the material to be conveyed out of the overpressure zone is not shown here, but it is also within the scope of the invention. In this case, the inlet zone is arranged in the overpressure zone or connected to the overpressure zone, wherein the material to be conveyed is conveyed from the overpressure zone to the discharge zone of the stuffing screw, while forming a plug.

[0025] Figure 2 and Figure 3 A design of a stuffing screw according to the invention is shown, in which: Figure 2 shows the first relative position of the screw and the plug tube, Figure 3 A second relative position of the screw and the plug tube is shown. Here, a rotatable screw 6 at least partially provided with a helix 9 is arranged in a housing 4 and can be rotated about an axis of rotation 5. In the discharge zone 7, the screw 6 has a helix-free region 10 in the plug tube 8, the plug tube 8 and the helix-free screw 10 forming an annular zone 11, and in the conveying direction of the material to be conveyed, a calibration zone 12 follows the annular zone 11. In addition, the helix-free region 16 of the screw with a gradually increasing outer diameter is designed to be conical, wherein the imaginary cone tip points to the inlet zone and the plug tube 8 has a constant inner diameter in the conveying direction. The calibration zone is formed by the helix-free region 16 of the plug tube with a constant inner diameter and the helix-free region 16 of the screw with a gradually increasing outer diameter, wherein a region 15 having a diameter greater than the constant inner diameter of the plug tube is adjacent to the plug tube. Here, in Figure 2 In the embodiment, the helix-free region 16 of the screw with a gradually increasing outer diameter is located in a region 15 with a diameter greater than the constant inner diameter of the plug tube, while in Figure 3 In the embodiment, the helix-free region 16 of the screw with a gradually increasing outer diameter is located in the plug tube 8. Advantageously, by axial movement of the screw 6, the sealing effect of the plug can be increased by reducing the calibration region 12 or reduced by enlarging the calibration region 12. Here, Figure 2 The filling screw 2 is shown, the relative position of its screw 6 is further in the conveying direction of the material to be conveyed, that is, closer to the discharge zone 7. Figure 3 A stuffing screw 2 is shown, the relative position of the screw 6 of which is opposite to the conveying direction of the material to be conveyed, i.e. closer to the inlet zone 3. Figure 3 The calibration area 12 is Figure 2 The small one in Figure 3 The positioning of the screw 6 in the Figure 2 The positioning of the screw 6 in the sealing plug results in a lower sealing effect.

[0026] Figure 4A further design of a stuffing screw according to the invention is shown, in which a screw 6 is rotatably arranged in a housing 4 and at least partially has a helix 9. In the discharge region 7, the screw 6 has a helix-free region 10 in the stuffing tube 8, wherein the stuffing tube 8 and the helix-free screw 10 form an annular region 11, which is followed by a calibration region 12 in the conveying direction of the material to be conveyed. Furthermore, the helix-free region 14 of the screw with an outer diameter that decreases in the conveying direction is designed to be conical, wherein the imaginary cone tip points to the discharge region 7, and the stuffing tube 8 has a region 13 of decreasing inner diameter. Arrow A here illustrates the possibility of positioning the screw 6 relative to the stuffing tube 8.

[0027] The invention thus offers numerous advantages: the tightness between two process steps can be effectively controlled, in particular the tightness of the overpressure zone into which the conveyed material is conveyed or from which it is discharged. In this way, the risk of, for example, steam backflow or leakage from the overpressure zone is effectively minimized. Moreover, the dewatering performance can be optimized while maintaining a controllable tightness. It is also possible to select a mode in which the required tightness can be set with minimal power consumption of the stuffing screw. In this way, the wear of the stuffing screw, the stuffing tube, etc. can be minimized, or conversely, after the stuffing screw, the stuffing tube, etc. has been worn, the required tightness can still be set, making longer use possible, because the worn parts can be replaced at a later stage. Likewise, the influence of uneven conveyed material (because these materials, for example, are unevenly fed into the stuffing screw, have widely varying material properties or a variable composition) can also be compensated, wherein the required tightness can be set accordingly. In addition, the solution according to the invention enables a fast start-up of the stuffing screw with low power consumption, while being able to control or quickly set to a suitable tightness.

[0028] Reference numerals list

[0029] 1 Overpressure zone

[0030] 2 Stuffing screw

[0031] 3 Entrance Area

[0032] 4 Housing

[0033] 5 Axis of rotation

[0034] 6 Screw

[0035] 7 Discharge area

[0036] 8 Plug tube

[0037] 9 Helix

[0038] 10 Helix-free area of ​​the screw

[0039] 11 Ring Area

[0040] 12 Calibration Area

[0041] 13 The area of ​​the plug tube with a gradually decreasing inner diameter

[0042] 14 The helix-free region of the screw with a decreasing outer diameter

[0043] 15 The area with a diameter greater than the constant inner diameter of the plug tube

[0044] 16 The helix-free region of the screw with a gradually increasing outer diameter

Claims

1. A plugging screw for squeezing a material to be conveyed into an airtight and liquidtight plug and for conveying the material to be conveyed to an overpressure zone (1) or discharging the material from the overpressure zone (1), comprising an inlet zone (3) for receiving the material to be conveyed, a screw (6) rotatable about a rotation axis (5) in a housing (4), and a discharge zone (7), wherein: In the discharge zone (7), the screw (6) is rotatably arranged in a plug tube (8) and the discharge zone (7) is designed for discharging the material to be conveyed in the direction of the rotation axis (5), characterized in that the plug tube (8) is designed as a tube for the material plug and has an at least partially annular and / or at least partially truncated cone structure, the screw (6) and the plug tube (8) can be moved and positioned relative to each other, wherein the screw (6) can be moved axially along the rotation axis (5) and relative to the housing (4) and the screw (6) at least partially includes a helical line (9), wherein , in the region of the plug tube (8), the screw (6) is at least partially designed as a helix-free region (10), and a calibration zone (12) is formed between the plug tube (8) and the screw (6), wherein the calibration zone (12) comprises a region (13) of the plug tube with a gradually decreasing inner diameter and a helix-free region (14) of the screw with a constant outer diameter or a helix-free region (16) of the screw with a gradually decreasing outer diameter, or the calibration zone (12) comprises a region of the plug tube with a constant or gradually increasing inner diameter and a helix-free region (16) of the screw with a gradually increasing outer diameter.

2. The stuffing screw according to claim 1, characterized in that: The material to be transported is wood chips.

3. The stuffing screw according to claim 1 or 2, characterized in that: An annular zone (11) is formed between the plug tube (8) and the screw (6), wherein the annular zone (11) includes a region of the plug tube (8) with a constant inner diameter and a helix-free region (10) of the screw (6) with a constant outer diameter.

4. The stuffing screw according to claim 1 or 2, characterized in that: By axially positioning the screw (6) relative to the plug tube (8), a reduction in the calibration zone (12) or an increase in the calibration zone (12) can be achieved.

5. A method for conveying material to be conveyed to or from an overpressure zone (1), wherein: The material to be conveyed is fed into the overpressure zone (1) and / or discharged from the overpressure zone (1) by the stuffing screw (2) according to any one of claims 1 to 4, the stuffing screw (2) receives the material to be conveyed in the inlet zone (3), and the screw (6) rotating around the rotation axis (5) in the housing (4) conveys the material to be conveyed to the discharge zone (7), wherein the material to be conveyed is compressed into an airtight and liquid-tight material plug between the plug tube (8) and the screw (6), and the material plug is fed into the overpressure zone (1) so as to convey the material to be conveyed into the overpressure zone (1) and / or the material to be conveyed compressed into the material plug is discharged from the overpressure zone (1). The zone (1) is discharged in order to convey the material to be conveyed out of the overpressure zone (1), wherein the material plug seals the overpressure zone (1) relative to the filling screw (2), characterized in that the sealing of the material plug is controlled by the relative position of the screw (6) and the plug tube (8), wherein the screw (6) is axially moved along the rotation axis (5) in the housing (4), and the material to be conveyed is compressed between the inlet zone (3) and the discharge zone (7), between the housing (4) and the screw (6) at least partially carrying a helix (9), wherein the material plug is formed in the discharge zone (7), between the plug tube (8) and the helix-free area (10) of the screw (6).

6. The method according to claim 5, characterized in that The material to be transported is wood chips.

7. The method according to claim 5 or 6, characterized in that: The plug first passes through the annular zone (11) and then through the calibration zone (12).

8. The method according to claim 5 or 6, characterized in that: The plug passes through an annular zone (11) in the discharge zone (7), wherein the annular zone (11) is formed by a region of the plug tube (8) with a constant inner diameter and a helix-free region (10) of the screw (6) with a constant outer diameter.

9. The method according to claim 5 or 6, characterized in that: The plug passes through a calibration zone (12) after the annular zone (11) in the discharge zone (7), wherein the calibration zone (12) is formed by a region (13) of the plug tube with a decreasing inner diameter and a helix-free region (13) of the screw with a constant outer diameter or a helix-free region (14) of the screw with a decreasing outer diameter, or the calibration zone (12) is formed by a region of the plug tube with a constant or increasing inner diameter and a helix-free region (16) of the screw with an increasing outer diameter.

10. The method according to claim 7, characterized in that By means of an axial displacement of the screw (6), the sealing effect of the plug can be increased by reducing the calibration zone (12) or reduced by enlarging the calibration zone (12).

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