Valve

Abstract

The invention relates to a valve (1) for a refiner or a system for steam pressure digestion, having an inlet (2) oriented along an inlet direction (4) and an outlet (3) oriented along an outlet direction (5), wherein the outlet direction (5) is at an angle (α) of less than 180 degrees to the inlet direction (4), and a piston (6) which can be moved along the inlet direction (4), wherein, as a result of a movement of the piston (6) along the inlet direction (4), a flow cross-section along a flow path between the inlet (2) and the outlet (3) can be changed, wherein the piston (6) can be moved, counter to the inlet direction (4), from a first position in which the valve (1) is open, into a second position in which the valve (1) is closed, wherein the piston (6) has an end face (7) at which a normal vector (8) is at a normal angle (β) to the inlet direction (4). In order to achieve high efficiency during operation and a particularly long service life, the invention proposes that the piston (6) can be moved counter to the inlet direction (4) beyond the second position, in order in particular to be able to compensate for possible wear on the end face (7).

Description

[0001] valve

[0002] The invention relates to a valve for a refiner or a steam pressure digestion system, comprising an inlet oriented along an inlet direction and an outlet oriented along an outlet direction, wherein the outlet direction is at an angle of less than 180 degrees to the inlet direction, and a piston movable along the inlet direction, wherein a flow cross-section along a flow path between inlet and outlet can be changed by moving the piston along the inlet direction, wherein the piston can be moved from a first position in which the valve is open, opposite to the inlet direction, to a second position in which the valve is closed, wherein the piston has an end face in which a normal vector is at a normal angle to the inlet direction.

[0003] Valves of the type mentioned above are known from the prior art for the controlled depressurization of liquids or gases under high pressure, or for venting them from pressure vessels. Such valves are used in particular in steam pressure digestion plants, such as MDF recycling plants or refiners.

[0004] State-of-the-art valves are known, for example, from documents WO 2006 / 070321 A1 and DE 35 15 755 C1.

[0005] A disadvantage of state-of-the-art valves has been found to be a short service life on the one hand and a high pressure loss when the valve is open on the other, which results in low efficiency.

[0006] This is where the invention comes in. The object of the invention is to provide a valve of the type mentioned above which achieves a particularly long service life and particularly high efficiency in operation.

[0007] This problem is solved according to the invention by a valve of the type mentioned at the outset, in which the piston can be moved beyond the second position in the opposite direction to the inlet direction in order to compensate in particular for any wear on the end face.

[0008] Within the scope of the invention, it was recognized that prior art valves achieve only a short service life, particularly because high wear occurs on an end face of the piston, especially when the valve is used in a flow containing a fluid with solids, so that a sealing effect is no longer given in a comparatively short time.

[0009] The invention solves this problem by allowing the piston to move beyond the second position, in which the valve is completely closed, and in the opposite direction to the inlet. This allows the piston to move further towards the inlet in the event of wear on the end face, in order to compensate for the wear. Thus, in a valve according to the invention, there is no valve seat or stop that limits the maximum movement of the piston in a closing direction at a position where the valve is already closed in a new or wear-free state. Instead, the piston can move further beyond this closed position and in the opposite direction to the inlet, thereby allowing it to move freely in or against the inlet direction to compensate for wear.

[0010] In the event of wear, the end positions are redefined by moving the piston against the intake direction, resulting in a new first position and a new second position. In these new positions, the function of the worn valve corresponds to the function of a new valve. This is possible until no further adjustment of the piston against the intake direction is possible, allowing the piston length to influence the adjustment travel and potentially achieve very long service lives.

[0011] It is understood that the valve may have a device for determining wear, allowing for automated readjustment of the end positions. The valve is typically used in such a way that a fluid, which may contain solids, flows from the inlet to the outlet, meaning that the pressure at the inlet is higher than at the outlet. This results in a fluid flow into the valve / towards the piston along the inlet direction and out of the valve / away from the piston along the outlet direction. In this application, the piston is thus moved against the flow direction of the fluid in the inlet during a closing movement.

[0012] However, it is also possible to use the valve in such a way that the pressure at the outlet is higher than at the inlet, resulting in a flow from the outlet to the inlet against the direction of both the inlet and outlet. In this case, the piston is moved from the first position to the second position parallel to the flow at the inlet to close the valve.

[0013] The front surface typically has a normal vector at at least one position, preferably along the entire front surface, which is at a normal angle of, for example, more than 1 degree, preferably more than 30 degrees, to the inlet direction.

[0014] Preferably, the end face has a normal vector that coincides approximately with an angle bisector of the inlet and outlet. This results in a favorable deflection of the fluid from the inlet to the outlet, such that, for example, if the inlet and outlet are arranged at an angle of 90 degrees relative to each other, a deflection of 45 degrees occurs at the end face. Compared to a 90-degree deflection, this achieves increased efficiency or reduced pressure loss, and avoids or at least minimizes unfavorable turbulence.

[0015] Preferably, the front surface has a normal vector that lies in a plane defined by the inlet and outlet directions. In this way, the front surface deflects the flow entering through the inlet towards the outlet.

[0016] It is advantageous if the normal angle is less than or equal to the angle at which the inlet is positioned relative to the outlet. Preferably, the normal angle is 40% to 60% of the angle at which the inlet is positioned relative to the outlet. To achieve the lowest possible pressure loss and thus high efficiency, while simultaneously reducing wear on the end face, it is preferably provided that the end face is geometrically continuous, in particular planar. For example, the end face can lie in a single plane, which is at a corresponding angle to the inlet direction. In the case of a cylindrical piston, the end face then corresponds to a corresponding cylinder cross-section, resulting, for example, in an elliptical, planar end face.

[0017] Preferably, the piston is cylindrical. In this case, it is preferably provided that the end face projects up to a circumferential surface of the piston.

[0018] To easily accommodate wear in the second position of the piston, in which the valve is closed, it is advantageous for the piston to have a circumferential seal, formed in particular by one or more sealing rings. This eliminates the need for a sealing seat, allowing for easy adjustment of the end positions in the piston's stroke direction or against the inlet direction, and enabling the piston to move freely within the inlet while maintaining a seal. The circumferential seal can be designed as either a line seal or a surface seal. Preferably, the seal is spaced from the end face to ensure a sealing effect even if the end face is worn. For example, the seal can be positioned at least 1 cm, preferably at least 5 cm, away from the end face.

[0019] The seal, which may have one or more sealing rings or piston rings, thus seals the inlet on a circumferential surface, whereby a cross-section of the inlet and a cross-section of the piston are usually constant along the inlet direction or the stroke direction.

[0020] In contrast, prior art valves often feature a sealing surface that is conical or arranged perpendicular to the flow direction, for example, conical to the outlet direction as described in document DE 35 15 755 C1, so that pressure acting on the inlet also acts on the piston and presses it against the sealing surface, thereby increasing the sealing effect. However, such an oriented sealing surface also causes the piston to stop in the corresponding direction, so that wear cannot be compensated for.

[0021] It is therefore preferred that the piston has a constant cross-section, at least in some areas, along the intake direction. This allows for easy adjustment of the end positions, in which the valve is fully open or fully closed, to compensate for wear. The cross-section is usually circular, resulting in a cylindrical piston, although a non-circular cross-section is also possible, for example, a rectangular or elliptical cross-section of the piston and intake.

[0022] The valve can be designed in a variety of ways. Preferably, the angle between the inlet and outlet is between 30 and 150 degrees, preferably between 70 and 110 degrees. Often, the conditions of a system necessitate deflecting a flow by a specific angle, for example, 90 degrees. If the valve has a corresponding angle between the inlet and outlet, it can be used not only to shut off the flow but also to deflect it. For example, with an angle of 90 degrees between the inlet and outlet directions, a front surface inclined at 45 degrees can be advantageous, where the normal vector to the front surface is at an angle of 45 degrees to the inlet direction, preferably across the entire front surface.

[0023] Due to its long service life, achieved even under abrasive operating conditions, the valve can be used, among other things, to control the flow of fluids containing solids, for example, flowing water and wood chips or shredded MDF boards. In many such systems, it is necessary to only partially open the valve to achieve a specific pressure drop and / or a required flow rate for a downstream system. In principle, the valve could be partially opened by moving the piston to an intermediate position between the first and second positions. However, this carries the risk of solids accumulating on the partially opened piston, which cannot be moved through a correspondingly restricted flow cross-section, potentially leading to complete valve blockage.

[0024] To easily prevent such valve blockage, especially when only partially open, a drive is preferably provided which is configured for the cyclical movement of the piston, particularly with a frequency of 0.01 mHz to 10 Hz, preferably 0.01 Hz to 1 Hz. Thus, a de facto only partial opening of the valve or a reduced volume flow through the valve can be achieved, for example, by regularly fully opening and partially or fully closing the valve. This is accomplished by varying the times during which the valve is fully open or closed, thereby achieving a stepless change in the volume flow through the valve in the sense of pulse duration modulation, thus avoiding the risk of blockage by coarse solids.This allows, for example, the regular discharge of coarse materials with low steam consumption when used in an MDF recycling plant. Due to the inclined face, this periodic movement of the piston, or the cyclical opening and closing of the valve, is associated with only minimal turbulence within the valve, thus maintaining high efficiency.

[0025] The valve can be used in a wide variety of systems. In a system with a valve for releasing steam at a pressure greater than 2 bar, preferably greater than 10 bar, and particularly greater than 15 bar, via the valve, especially in a steam pressure digestion system, it is particularly preferred that the valve be designed according to the invention. In this way, the advantages of such a design can be utilized to their fullest potential. The valve is preferably used in a system in which the steam to be released contains solids, for example, fibers. The components of the valve, in particular the piston and the valve body, can be made of any material suitable for the respective application, for example, a metal such as steel or stainless steel. Preferably, the material is wear-resistant and suitable for a temperature of at least 200 °C.

[0026] A steam explosion plant with such a valve can be used, for example, to produce biofuels, such as second-generation bioethanol or black pellets, from various lignocellulose biomass using steam explosion or steam explosion.

[0027] Furthermore, in a system with a valve arranged on a pressure vessel for discharging a mixture of water and fibers from the pressure vessel via the valve, particularly in a system for recycling MDF boards, it is preferably provided that the valve is designed according to the invention. The mixture can, of course, contain water in both liquid and gaseous form. A pressure vessel is understood to be any container in which an overpressure prevails relative to the surrounding environment, so that the pressure vessel can, for example, also be the housing of a refiner.

[0028] Especially in such systems, wear often occurs in the valve due to solids or plate residues, so that by using a valve according to the invention in such a system, the service life can be significantly increased, thereby reducing downtime of the system.

[0029] Preferably, such a system is equipped with a drive for the cyclical reciprocating movement of the piston to cyclically discharge large contaminants while simultaneously minimizing water and / or steam consumption. This effectively prevents blockages in the valve area caused by large contaminants, which could occur if the piston were only partially open. To achieve these cyclical movements, a control system can be provided, for example, that acts on the piston drive and ensures the valve is fully opened regularly by periodically moving the piston to its initial position.

[0030] To easily prevent the accumulation of contaminants in the pressure vessel of such a system, particularly in the area of ​​an opening through which a medium can be discharged from the pressure vessel, it is preferably provided that the valve inlet is connected to an opening in the inner wall of the pressure vessel. The end face of the piston is designed such that, in a closed position, the piston seals the opening, with the inner wall preferably transitioning seamlessly into the end face. This results in a smooth transition from the inner wall of the pressure vessel to the end face, thus easily preventing solids from becoming trapped or accumulating in the area of ​​the opening and ensuring that flow within the pressure vessel is not impaired when the valve is closed.The pressure vessel can be, for example, a container of a steam pressure digestion plant or a housing of a refiner.

[0031] It is understood that the position in which the piston's end face closes the opening, preventing solids from accumulating in the opening and in front of the piston when the valve is closed, can be a position in which the piston has moved beyond the second position in the opposite direction to the inlet. Thus, for example, when moving the piston in the opposite direction to the inlet, starting from an open valve position, the valve can first be closed by the piston completely interrupting the flow path between the inlet and outlet at the second position. Afterward, the piston is moved even further in the opposite direction to the inlet until it reaches a third position in which it closes the opening. Preferably, the piston closes the opening flush in the third position, so that the inner wall of the pressure vessel transitions smoothly into the piston's end face.It may also be provided that the piston can be moved beyond the third position into the pressure vessel in order to push any solids located on the end face of the piston into the pressure vessel.

[0032] Such pressure vessels often have a cylindrical shape with optionally flat end faces. The opening can be located at the end face or around the circumference of the pressure vessel. It is understood that the end face of the piston is then correspondingly flat or curved.

[0033] In such pressure vessels, the outlet is preferably arranged such that the outlet direction is oriented in a plane perpendicular to the axis of rotation of the pressure vessel. This ensures that the end face of the piston, on the one hand, provides a smooth closure of the opening inside the vessel and, on the other hand, a favorable flow deflection towards the outlet. Further features, advantages, and effects of the invention will become apparent from the exemplary embodiments shown below. The drawings, to which reference is made, show:

[0034] Figs. 1a and 1b show a section through a valve in different states;

[0035] Fig. 2 shows a flow diagram of a system with a valve according to the invention;

[0036] Figs. 3a and 3b show a detail of a plant in different views;

[0037] Figs. 4a and 4b show a detail of another plant in different views;

[0038] Figs. 5a and 5b show a detail of another plant in different views;

[0039] Figs. 6a and 6b show a detail of another plant in different views.

[0040] Figures 1a and 1b show a valve 1 according to the invention in sectional view. The valve housing 13 is visible, with an inlet 2 connected to an outlet 3, the inlet 2 being at an angle α of approximately 90 degrees to the outlet 3. A piston 6 is movably arranged in the valve housing 13, and the flow cross-section between the inlet 2 and outlet 3 can be changed by moving the piston 6 from a first position to a second position. A drive mechanism (not shown) is provided for moving the piston 6.

[0041] Fig. 1a shows the valve 1 in an open position, in which the piston 6 is in the first position, so that a flow between inlet 2 and outlet 3 is possible.

[0042] With the position of the piston 6 shown in Fig. 1a and an overpressure at the inlet 2, a flow through the valve 1 along an inlet direction 4 to the piston 6 results, at which the flow is deflected, so that subsequently a flow along an outlet direction 5 through the outlet 3 results.

[0043] As can be seen, the piston 6 has a constant cross-section, here a circular cross-section, along the inlet direction 4, so that the piston 6 can also be moved beyond the second position. In this second position, the piston 6 completely closes the outlet 3, preventing any flow between inlet 2 and outlet 3. Such a closed state of the valve 1, in which the piston 6 is in the second position and thus closes the outlet 3, is shown in Fig. 1b.

[0044] The end face 7 of the piston 6 is flat, as shown, and inclined at approximately 45 degrees to the inlet direction, such that a normal vector 8 to the end face 7 lies approximately at an angle perpendicular between inlet 2 (inlet direction 4) and outlet 3. The normal vector 8 is therefore at a normal angle β to the inlet direction 4 of approximately 45 degrees.

[0045] The inlet direction 4 and outlet direction 5, as well as the normal vector 8, lie in one plane, so that the inclined frontal surface 7 deflects the flow, which enters the valve 1 via the inlet 2, towards the outlet 3. This minimizes turbulence in the area of ​​the piston 6 and thus pressure loss, enabling particularly high efficiency.

[0046] Wear occurs on the end face 7 of this valve 1, particularly when used in a system where high-pressure steam and solids flow through the inlet 2. To compensate for wear, the piston 6 is movable beyond the second position, allowing it to be adjusted. A seal is achieved by circumferential sealing rings, sealing lips, scrapers, O-rings, or the like (not shown), which are preferably spaced from the end face 7 such that the seal is maintained even if the end face 7 is worn.

[0047] Piston 6 and valve housing 13 can be made of any material suitable for the respective application, for example of steel, in particular a wear-resistant stainless steel, wherein a pressure of 10 bar to 22 bar and a temperature of 200 °C can prevail in a corresponding pressure vessel 10, for example.

[0048] Fig. 2 shows a schematic diagram of a steam pressure digestion system with a valve 1 according to the invention. As shown, the system includes a silo 14 through which raw material, for example wood chips, can be supplied. These wood chips are then digested with steam in a pressure vessel 10, after which a volumetric flow of steam and digested material from the pressure vessel 10 is fed to a cyclone 15 to separate solids. As can be seen, the valve 1 is arranged at a position where the flow is deflected by 90 degrees. As can be seen in the detail shown in Fig. 2, a piston 6 with an end face 7 is also provided here, in which a normal vector 8 lies approximately midway between the inlet direction 4 and the outlet direction 5, so that the inclined end face 7 results in an advantageous deflection of the flow.Here, valve 1 is positioned such that the pressure at inlet 2 is higher than at outlet 3, resulting in a flow at inlet 2 in the inlet direction 4.

[0049] Figures 3a and 3b show a pressure vessel 10 of a system with a horizontal screw conveyor, for example, a discharge screw conveyor. Figure 3a shows the pressure vessel 10 in a view along the axial direction of the screw conveyor, while Figure 3b shows the pressure vessel 10 in a side view. As shown, a medium can be withdrawn from the pressure vessel 10 via two valves 1 designed according to the invention, which are positioned at openings 12 on an inner wall 11. The valves 1 are positioned such that the inlet direction 4 is tangentially adjacent to the circumference of the pressure vessel 10.

[0050] As can be seen, the pistons 6 are movable along the inlet direction 4 beyond the second position up to a third position shown, such that the pistons 6 completely and smoothly close the openings 12. For this purpose, the pistons 6 have a curvature corresponding to the inner wall 11 of the pressure vessel 10. This effectively prevents the accumulation of solids in the inlet 2 in front of the piston 6, which could lead to a blockage of this opening 12.

[0051] The outlet direction 5 lies in a plane normal to the axis of rotation 16 and is positioned relative to the inlet direction 4 such that the end face 7 of the piston 6, defined here by the piston 6's ability to smoothly seal the inner wall 11, again results in a fluid-mechanically advantageous deflection of the flow towards the outlet direction 5. The inclined end face of the piston thus ensures, on the one hand, a tight seal of the opening when the valve is closed, and on the other hand, a favorable deflection of the flow within the valve when the valve is open. Figures 4a and 4b show another pressure vessel 10 with a horizontal screw conveyor, with Figure 4a showing the pressure vessel 10 in the axial direction and Figure 4b showing a side view. In contrast to the one in Figure 4a, the pressure vessel 10 is not designed for a specific application.In the pressure vessels 10 shown in Figures 3a and 3b, the openings 12 through which a medium can exit the pressure vessel 10 are not located on a circumferential surface 9, but rather on the end face. Accordingly, the end faces 7 of the pistons 6 are designed to be flat for a smooth closure of the openings 12. Furthermore, the end faces 7 are inclined relative to the inlet direction 4, resulting in a favorable deflection of the flow in the valve 1 towards the outlet direction 5, which here also lies in a plane perpendicular to the axis of rotation 16 of the screw conveyor.

[0052] Figures 5a and 5b show another pressure vessel 10 with a screw conveyor and valves 1 designed according to the invention, which can, for example, be a constant-speed conveyor. In contrast to the pressure vessel 10 shown in Figures 4a and 4b, this one has a vertical screw conveyor and the

[0053] Openings 12 and valves 1 are positioned at the bottom. Analogous to the pressure vessel 10 shown in Figs. 4a and 4b, the pistons 6 of the valves 1 are also designed with an inclined end face 7 in order to be able to close the openings 12 smoothly and to achieve favorable flow deflection in the valve 1, and here too the outlet direction 5 lies in a plane which is normal to the axis of rotation 16 of the screw conveyor.

[0054] Figures 6a and 6b show a refiner with two valves 1, where Figure 6a shows an axial section and Figure 6b a section in a plane normal to the refiner's axis of rotation. As can be seen, one of the valves 1 opens tangentially and the other radially into the pressure vessel 10. The valve 1 opening tangentially into the pressure vessel 10 has an end face 7 that transitions smoothly into the inner wall 11 to prevent blockages in the area of ​​the inlet 2 upstream of the piston 6. The radially opening valve 1 has a piston 6 with an end face 7 that is favorable for flow deflection within the valve 1, but does not completely seal the inner wall 11.To prevent the opening 12 on this radial valve 1 from becoming clogged, it can be provided that the piston 6 is moved so far into the pressure vessel 10 of the refinder that no volume remains in the inlet 2 in front of the piston 6 and thus any solids that could accumulate in the inlet 2 of the valve 1 are pushed back into the pressure vessel 10.

[0055] The valves 1 shown in Figures 3a to 6b can be mounted vertically and horizontally as shown and, if necessary, integrated directly into the pressure vessel 10 or the refiner housing on its circumference or end face, or mounted on the pressure vessel 10 or the housing, thus minimizing welding effort. Depending on the orientation of the valves 1, a radial, tangential, or axial flow into the inlet 2 or through the valve 1 results.

[0056] The individual valves 1 shown in Figures 2 to 6b can be operated by moving the piston 6 cyclically. This prevents the valve 1 from becoming clogged with solids and minimizes steam loss, resulting in particularly efficient operation. Alternatively, operation with the valve fully or partially open, with the piston positioned between the first and second positions, is also possible to achieve a continuous flow of volume through the valve.

[0057] A valve 1 according to the invention enables a particularly long service life, especially when used in fluids containing impurities, for example in MDF recycling plants, as well as a particularly efficient operation, since flow losses are minimized when the flow is deflected in the valve 1.

Claims

Patent claims 1. Valve (1) for a refiner or a steam pressure digestion plant, comprising an inlet (2) oriented along an inlet direction (4) and an outlet (3) oriented along an outlet direction (5), wherein the outlet direction (5) is at an angle (a) of less than 180 degrees to the inlet direction (4), and a piston (6) movable along the inlet direction (4), wherein a flow cross-section along a flow path between inlet (2) and outlet (3) can be changed by moving the piston (6) along the inlet direction (4), wherein the piston (6) can be moved from a first position in which the valve (1) is open, opposite to the inlet direction (4), to a second position in which the valve (1) is closed, wherein the piston (6) has an end face (7) in which a normal vector (8) is at a normal angle (β) to the inlet direction (4), characterized in thatthat the piston (6) can be moved beyond the second position in the opposite direction to the intake direction (4) in order to compensate for any wear on the end face (7).

2. Valve (1) according to claim 1 , characterized in that the end face (7) has a normal vector (8) which lies in a plane defined by the inlet direction (4) and the outlet direction (5).

3. Valve (1) according to claim 1 or 2, characterized in that the normal angle (β) is less than or equal to the angle (a) at which the inlet (2) is relative to the outlet (3).

4. Valve (1) according to one of claims 1 to 3, characterized in that the normal angle (β) is 40% to 60% of the angle (a) at which the inlet (2) is to the outlet (3).

5. Valve (1) according to one of claims 1 to 4, characterized in that the end face (7) is geometrically continuous, in particular planar.

6. Valve (1) according to one of claims 1 to 5, characterized in that the end face (7) projects to a circumferential surface (9) of the piston (6).

7. Valve (1) according to one of claims 1 to 6, characterized in that the piston (6) has a seal on its circumferential side, in particular one or more sealing rings.

8. Valve (1) according to one of claims 1 to 7, characterized in that the piston (6) has a constant cross-section at least in certain areas along the inlet direction (4).

9. Valve (1) according to one of claims 1 to 8, characterized in that the angle (a) between inlet (2) and outlet (3) is 30 degrees to 150 degrees, preferably 70 degrees to 110 degrees.

10. Valve (1) according to one of claims 1 to 9, characterized in that a drive is provided which is configured for the cyclic movement of the piston (6), in particular with a frequency of 0.01 Hz to 1 Hz.

11. System with a valve (1) for releasing steam at a pressure of more than 2 bar, preferably more than 10 bar, in particular more than 15 bar, via the valve (1), in particular system for steam pressure release, characterized in that the valve (1) is designed according to one of claims 1 to 10.

12. System with a valve (1) arranged on a pressure vessel (10) for discharging a mixture of water and fibers from the pressure vessel (10) via the valve (1), in particular a system for recycling MDF boards, characterized in that the valve (1) is designed according to one of claims 1 to 10.

13. Plant according to claim 11 or 12, characterized in that a drive is provided for the cyclical back-and-forth movement of the piston (6) in order to cyclically remove large impurities and at the same time minimize water and / or steam consumption.

14. System according to one of claims 11 to 13, characterized in that the inlet (2) of the valve (1) is connected to an opening (12) in an inner wall (11) of a pressure vessel (10), wherein the end face (7) of the piston (6) is such that The system is designed such that the piston (6), in a position where the valve (1) is closed, closes the opening (12), the inner wall (11) preferably transitioning into the end face (7), in particular without edges.

15. System according to one of claims 11 to 14, characterized in that the opening (12) is arranged on the end face or circumferential side of the pressure vessel (10).

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