A discharge valve

Abstract

A discharge valve (1) comprising a valve housing (2) connectable to a process element (10) having a pressurized interior process volume, said discharge valve (1) comprising a flow channel (3) having a longitudinal centre axis (A) and extending from an inlet (5) of the flow channel to an outlet (6) thereof, and being arranged to be in fluid communication with a pressurized interior process volume of said process element (10); and a first valve member (4) being arranged to protrude into the flow channel (3), and a second valve member (7) being arranged to protrude into the flow channel from a different direction than the first valve member.

Description

[0001] A discharge valve

[0002] Technical field

[0003] The present disclosure relates to a discharge valve, in particular a discharge valve for use in a manufacturing process involving processing of lignocellulosic material, such as a pulp manufacturing processes or a process for manufacturing bio-fuel.

[0004] Background art

[0005] In the process industry and, in particular, in the biomass process industry such as in pulp manufacturing and in the manufacturing of bio-fuels, discharge valves are used to control the pressure and / or process flow in process elements such as boilers, reactors and refiners which have inner pressurized process chambers.

[0006] Shutter valves, gate valves and ball sector valves are the most commonly used types of discharge valves in the pulp manufacturing industry. Process flows in processes involving processing of lignocellulosic materials are generally corrosive, high temperature and containing abrasive particulate material such as cellulose fibers and fragments and impurities following with the processed material. A discharge valve being continuously exposed to such harsh material will wear over time and will eventually have to be replaced by a new valve, which is costly and may involve lengthy stop-times in the process. In to mitigate this, a replaceable inner lining can be arranged in the flow channel. An example of this is shown in document WO16171604A1. However, it has been found that problems with wear of the inner surfaces of the discharge valve may still arise, in particular in applications where the pressure difference over the discharge valve is very high and the process flow has a high content of abrasive particles, and there is a desire to find solutions to this.

[0007] Summary

[0008] The present invention aims at providing a way of reducing the wear of the inner surface of a discharge valve, to allow discharging a highly abrasive process flow with less risk of damaging the discharge valve, thus leading to a discharge valve having a more robust construction and longer service life. The discharge valve as disclosed herein may be a discharge valve adapted for connection to an outlet of a pressurized process element in any biomass processing system involving evacuation of material from pressurized processing voids, such as found in refiners, boilers and reactors or may be a discharge valve connected to an outlet of a pressurized process element in any biomass processing system involving evacuation of material from pressurized processing voids, such as found in refiners, boilers and reactors. Biomass processing systems may be found, e.g. in cellulose pulp manufacturing processes and in bioplants for the production of biofuels such as ethanol and biodiesel. Such processes involve processing of lignocellulosic raw materials derived from perennial plants such as trees as well as annual plants such as sugar cane, straw, hemp, etc. thus, the process flow may typically be a wood or plant fibre mix, i.e. a mix of wood or plant fibers, steam, chemicals and abrasive particles, or the like.

[0009] In a mechanical pulping process for example, wood chips are generally washed, and subjected to heat and / or a chemical pre-treatment and refined to pulp by being fed between two disks in a refiner wherein the wood chips are ground to pulp, which is discharged through a discharge valve connected to an outlet of the refiner. During processing in the refiner, pressure and heat are built up, putting the discharge valve under a lot of strain and wear as the discharge valve is opened and pressurized pulp is discharged through the discharge valve.

[0010] In prior art solutions, such as the one disclosed in W02016171604A1, a valve member may be arranged to be inserted into the flow channel. In such a discharge valve, the valve geometry with a valve member inserted into the flow channel from one direction, in combination with increased pressure difference over the valve and more abrasive particles in the raw material, may cause the flow direction of the process flow to change when it collides with the inserted part of the valve member. The solid materials of the process flow will hit the inserted part and then change direction so that they bounce down on the surface of flow channel, or the wear lining inserted therein, before they move forward out from the discharge valve and into a discharge tubing and further onward to a tank, dryer or the like. When a small valve opening is used, the abrasive solid materials of the process flow may also bounce back toward the opposite side of the valve and cause abrasion on the flow channel surface also on the upper side of the valve, and possibly also in the discharge tubing following the discharge valve.

[0011] According to the present invention, there is provided a discharge valve, or blow valve, comprising a valve housing connectable to a process element having a pressurized interior process volume. The discharge valve comprises a flow channel having a longitudinal centre axis, A, and extending from an inlet of the flow channel to an outlet thereof, and being arranged to be in fluid communication with a pressurized interior process volume of the process element. The discharge valve comprises two valve members. A first valve member is arranged to protrude into the flow channel and a second valve member is arranged to protrude into the flow channel from different direction that the first valve member.

[0012] Due to the presence of the two valve members protruding from different directions, the process flow will collide with two obstacles in the flow channel, which will cause the abrasive solid particles of the process flow to collide with themselves in the centre of the flow channel of the discharge valve, and this will decrease the wear of the surface of the flow channel or of a wear lining arranged therein. The two valve members may be retractable as discussed in more detail below. The first and second valve members may preferably have the shape of a cylindrical body, as discussed in more detail below.

[0013] The first valve member may be arranged to protrude from a first location, and the second valve member may be arranged to protrude from a second location, said first and second locations being situated at different positions in a circumferential direction of the flow channel. The second location in the circumferential direction is preferably situated 160°-200°, from the first location in the circumferential direction of the flow channel, more preferably, 175°-185°, and most preferably 180°. The more opposite to one another the protruding valve members are, the more effective the breakup of the passing process flow will be, and the more decreased the wear of the flow channel surface.

[0014] Further, the first valve member may be arranged at a first length position along said longitudinal centre axis of the flow channel, and the second valve member may be arranged at a second length position in said length direction, which at least partially overlaps with said first position, such that the process flow is forced to pass a narrow passage and hit the protruding valve members. Preferably, these first and second length positions along the longitudinal centre axis fully overlap.

[0015] Thus in a most preferred embodiment, the first and second protruding valve members are arranged at substantially the same length position along the longitudinal centre axis and circumferentially substantially opposite each other.

[0016] The first valve member may be arranged to protrude into said flow channel at a first angle to said longitudinal centre axis of the flow channel, and said second valve member protrudes into said flow channel at a second angle to said longitudinal centre axis of the flow channel, said first and second angles being the same or different, and being 30- 150°, preferably from 45-135°, more preferably from 80-100°, most preferably substantially 90°. Most preferably, the valve members protrude radially into the flow channel. The forward ends of the valve members can then meet at the centre of the flow channel and partially or fully close the flow channel in a fully inserted position.

[0017] The valve member may have the form of a cylindrical body, such as a cylindrical piston, rod or tube, wherein the cylindrical body preferably has a rounded cross section, preferably circular or elliptic cross section. The rounded shape of the cylindrical body reduces the risk of folid material getting stuck on the leeward side of the cylindrical body. A cylindrically shaped valve member may also be preferred as it provides better sealing of the flow channel than other types of valve members. The valve member is preferably solid to provide better wear resistance.

[0018] The housing discharge valve suitably comprises a first containment portion connected to the flow channel and from which the first valve member is arranged to protrude into the flow channel and a second containment portion connected to the flow channel and from which the second valve member is arranged to protrude into the flow channel. Arranging the valve members in containment portions provides improved stability to the valve members, which is beneficial in a valve exposed to the high forces that is the case in blow valves in processing of lignocellulosic material. Further, the presence of the containment portions allows the possibility to provide sealing arrangements, which is important to reduce the risk of leakage of the hot and pressurized flow through the valve, which is important for operating staff safety. The containment portion suitably has a similar shape as the valve member and is preferably shaped as a tubular housing portion enclosing the valve member leaving a gap, which is large enough to allow movement of the valve member in and out of the flow channel of the discharge valve, and small enough to allow sealing of the outer surface of the valve member to the inner surface of the containment portion.

[0019] The discharge valve may thus further comprise sealing elements on the one or both valve members, such that a first sealing element is arranged between the first valve member and the first containment portion of the housing and a second sealing element is arranged between the second valve member and the second containment portion of the housing. The sealing element(s) are suitably in the form of a continuous ring arranged around the circumference of the valve member(s). The sealing element is preferably comprised of a flexible and elastic material, such as elastic rubber, e.g. polyurethane.

[0020] Moreover, the discharge valve may further comprise one or more inlets for steam or compressed air arranged in the containment portion of one or both valve members. The inlets are suitably configured to be connected to a source of pressurized steam or compressed air. This allows the gap between the valve member and the containment portion to be filled with pressurized clean steam or compressed air, which should suitably have higher pressure than the flow of steam and fibres from the process element. The pressure in the flow channel upstream the valve members may typically be 2-25 bar, and the sealing steam or compressed air may suitably have a pressure that is at least 1-3 bar higher than the flow from the process element. Thereby the steam or compressed air forms a pressure barrier additionally preventing leakage from the flow channel of the valve, and also protects the sealing element mention above from damage, and thereby improves operation of the blow valve and extends the life time of the valve.

[0021] Accordingly, a first inlet for steam or compressed air may be located in the first containment portion, and likewise a second inlet for steam or compressed air may be located in the second containment portion to allow applying a gap between the first valve member and the first containment portion can be filled with pressurized steam or compressed air.

[0022] By reducing the risk of fibrous material being caught behind the valve members as described above, and by sealing the valve members to the housing, the risk that solids enter the gap between the valve member and the housing is reduced, which in turn reduces the risk that the valve member and the housing seize against each other when the valve member is to be moved in or out of the flow channel. In contrast, plate or disc-shaped valve members that cannot be sealed to the valve housing may have a considerable risk of seizing to the housing due to solid material caught between the valve member and the housing. The discharge valve may also comprise guide bands arranged between the valve member and the containment portion, in order to improve and stabilize the movement of the valve members. For example, guide bands can be arranged on each side of the sealing element. In that case inlets for steam or compressed air can be arranged on each side of the guide band located closest to the flow channel of the discharge valve, to further improve sealing protecting the sealing element and preventing leakage.

[0023] Preferably, the first and second valve members are arranged to protrude into the flow channel to such an extent that a forward end of said first valve member and a forward end of said second valve member are on substantially the same distance from the longitudinal centre axis of the flow channel.

[0024] A detachable inner lining is preferably arranged in said flow channel and at least partly forms the flow channel. The detachable inner lining may have a generally tubular shape with an inner envelope wall surface defining the shape of the flow channel in the discharge wall and an outer envelope wall surface which is arranged to face the valve housing and which is adapted to cooperate with the valve housing when attaching the detachable inner lining in the valve housing. The tubular shape of the inner lining may have any cross-sectional shape, such as square, rectangular, circular, which may vary along the length of the discharge valve. The detachable inner lining may suitably be arranged to be removed from the valve housing and may be arranged to be reattached to the valve housing and / or to be replaced by another detachable inner lining. By providing the discharge valve with a detachable inner lining, the useful life of the discharge valve may be considerably extended by merely replacing a worn- down detachable inner lining with a new detachable inner lining without having to replace the whole discharge valve.

[0025] The first valve member and second valve member are advantageously arranged to be retractable, so as to be able to move between a protruding state and a retracted state. Thereby, the first and second valve members may be arranged such that they can be displaced out of the flow channel, to a position in which it is clear from flow channel. This means that the valve members may be moved in a displacement direction until it is completely retracted from the flow channel and also moved away from the flow channel in the displacement direction at least a further distance corresponding to the thickness of the envelope wall of the detachable inner lining. By positioning the valve member in the fully retracted service position, where it is clear from the detachable inner lining, the detachable inner lining can be removed from the valve housing without needing to completely disassemble the discharge valve.

[0026] The discharge valve may typically be a throttle valve and the first and second valve members, or throttles, may be plungers which are inserted into the flow channel to fully or partly close the flow channel. When the valve members are fully inserted into the flow channel, the flow in the flow channel will be completely blocked, while partly inserted valve members will only serve as throttles and restrict the flow in the flow channel.

[0027] The present disclosure also relates to a process element in a manufacturing process involving processing of lignocellulosic material, which comprises the discharge valve described above. The described discharge valve may be particularly useful when discharging from pressurized interior spaces, such as pressurized chambers, such as during a steam explosion pulp manufacturing process.

[0028] The present disclosure will become apparent from the detailed description given below. The detailed description and specific examples disclose preferred embodiments of the disclosure by way of illustration only. Those skilled in the art understand from guidance in the detailed description that changes and modifications may be made within the scope of the disclosure.

[0029] Brief of the

[0030] The present invention will be further explained hereinafter by means of non-limiting examples and with reference to the accompanying drawings.

[0031] Figure 1 shows a refiner and a discharge valve;

[0032] Figure 2 shows a cross sectional view of a discharge valve of the present invention;

[0033] Figure 3 shows a cross sectional view of a discharge valve of the present invention, transverse to the view of Figure 2.

[0034] Figure 4 shows a cross sectional view transverse the longitudinal direction of a discharge valve of the present invention;

[0035] Figure 5 shows a cross sectional view in the longitudinal direction of a discharge valve of the present invention;

[0036] Figure 6 shows a cross sectional view transverse the longitudinal direction of another discharge valve of the present invention; and

[0037] Figure 7 shows a cross sectional view in the longitudinal direction of another discharge valve of the present invention.

[0038] Detailed

[0039] The present disclosure will now be described with reference to the accompanying drawings, in which preferred example embodiments of the disclosure are shown. The disclosure may, however, be embodied in otherforms and should not be construed as limited to the herein disclosed embodiments. The disclosed embodiments are provided to fully convey the scope of the disclosure to the skilled person.

[0040] Figure 1 shows a refiner 10 and a discharge valve. Figure 2 shows a cross sectional view of a preferred embodiment of the discharge valve of the present invention. Figure 3 shows a partial cross sectional view of a discharge valve of the present invention, transverse to the view of Figure 2 along the line B-B in Figure 2. Only one valve member is shown in Figure 3, but both valve members are suitably arranged in the same way in the valve. The discharge valve 1 comprises a valve housing 2 connectable to a process element 10 (such as a refiner as shown in Figure 1) having a pressurized interior process volume, and comprises a flow channel 3 having a longitudinal centre axis A. The flow channel extends from an inlet 5 of the flow channel to an outlet 6 thereof, and is arranged to be in fluid communication with a pressurized interior process volume of the process element 10. A first valve member 4 is arranged to protrude into the flow channel 3, and a second valve member 7 is arranged to protrude into the flow channel from different direction that the first valve member. A detachable inner lining 8 is arranged in said flow channel 3 and at least partly forms the flow channel. Figure 2 illustrates how the process flow will collide with two obstacles in the flow channel, causing the abrasive solid particles of the process flow to collide with themselves in the centre of the flow channel of the discharge valve instead of the wall surfaces of the flow channel. Thereby, the wear of the surface of the flow channel or of a wear lining arranged therein is decreased. As shown in Figures 2 and 3, the first and second valve members have the shape of a cylindrical body.

[0041] In the embodiment shown in Figure 2 and 3, the housing 2 comprises a first containment portion 20 connected to the flow channel 3 and from which the first valve member is arranged to protrude into the flow channel 3 and a second containment portion 21 connected to the flow channel 3 and from which the second valve member is arranged to protrude into the flow channel 3. A first sealing element 11 is arranged between the first valve member 4 and the first containment portion 20 of the housing 2 and a second sealing element 12 is arranged between the second valve member 7 and the second containment portion 20 of the housing 2.

[0042] Further, a first steam or compressed air inlet 13 is located in the first containment portion 20, a second inlet (not shown in the drawings) for steam or compressed air is located in the second containment portion to allow application steam or compressed air to the gap between the valve member and the containment portion. Guide bands 15, 16, 17, 18 can be arranged between the valve members 4, 7, and the containment portions 20, 21 of the housing 2. Inlets 13, 14 for steam or compressed air may preferably be arranged on each side of a lower guide band, i.e. the guide band located closest to the flow channel.

[0043] Figures 4 and 6 illustrate how the first valve member 4 is arranged to protrude from a first location and the second valve member 7 is arranged to protrude from a second location, where the first and second locations being situated at different positions in a circumferential direction of the flow channel 3, preferably on opposite sides of a centre line C, transverse to the longitudinal centre axis A, dividing the flow channel in substantially equal halves. As shown in Figures 4 and 6, the second location is situated 160°-200°, preferably 175°-185°, more preferably 180°, from the first location in a circumferential direction of the flow channel 3. Figure 4 shows a preferred embodiment where the first and second valve members are arranged substantially opposite each other. Figures 5 and 7 illustrate how the first valve member 4 is arranged at a first length position 101 along said longitudinal centre axis A of the flow channel 3 the second valve member is arranged at a second length position 102 in said length direction, which at least partially overlaps with said first position 101. Figure 5 shows a preferred embodiment where the first and second length positions 101, 102 along the longitudinal centre axis A fully overlap.

[0044] As shown in Figure 5, the first valve member 4 may protrude into said flow channel 3 at a first angle al to said longitudinal centre axis A of the flow channel, and the second valve member may protrude into the flow channel 3 at a second angle a2 to said longitudinal centre axis A of the flow channel. In the preferred embodiment illustrated in Figure 5, the first and second angles al, a2 are same and are substantially 90°. However, first and second angles al, a2 may also be same or different, and be 30- 150°, preferably from 45-135°, more preferably from 80-100°.

[0045] As shown in Figures 2-7, the first and second valve members may protrude into the flow channel 3 to such an extent that a forward end 4a of said first valve member 4 and a forward end 7a of said second valve member 7 are on the same distance from said longitudinal centre axis A of the flow channel. The first valve member 4 and second valve member 4 may be retractable so as to be able to move between a protruding state and a retracted state as illustrated by arrows in Figures 4 and 6.

[0046] The person skilled in the art realizes that the present disclosure is not limited to the preferred embodiments described above. The person skilled in the art further realizes that modifications and variations are possible within the scope of the appended claims. For example, although described as implemented in connection to a refiner in a pulping process, the teachings of the current disclosure are equally applicable to other systems (hot or cold) in which abrasive material is evacuated from a pressurized process chamber into a pipe, open air or into another process chamber. As the abrasiveness of a material depends on both the material itself as well as the surrounding environment, the term abrasive is used to describe the processing of a material in which process the material can be regarded as abrasive. As an example, at a low temperature a material might not be viewed as being abrasive whereas at a highertemperature, the abrasive wear of the material is clearly increased. A general system in which the present disclosure can be beneficially implemented may include a pressurized process space such as a process chamber or container into which material is introduced at one end and subjected to e.g. boiling, steaming or other hot or cold process. The material is transported within the processing chamber and evacuated at an outlet in another end of the chamber. The evacuated material is then transported through a system of pipes to subsequent processing arrangements. The teachings of the current disclosure are beneficially implemented at the outlet of the pressurized processing chamber. Examples of such a pressurized processing container include a boiler, steamer, refiner for pulp, impregnator, vertical or horizontal reactors, etc.

Claims

CLAIMS1. A discharge valve (1) comprising a valve housing (2) connectable to a process element (10) having a pressurized interior process volume, said discharge valve (1) comprising a flow channel (3) having a longitudinal centre axis (A) and extending from an inlet (5) of the flow channel to an outlet (6) thereof, and being arranged to be in fluid communication with a pressurized interior process volume of said process element (10); and a first valve member (4) being arranged to protrude into the flow channel (3), characterized in that a second valve member (7) is arranged to protrude into the flow channel from different direction that the first valve member.

2. The discharge valve of claim 1, wherein said first and second valve members have the shape of a cylindrical body.

3. The discharge valve of claim 2, wherein the housing (2) comprises a first containment portion (20) connected to the flow channel (3) and from which the first valve member is arranged to protrude into the flow channel (3) and a second containment portion (21) connected to the flow channel (3) and from which the second valve member is arranged to protrude into the flow channel (3).

4. The discharge valve of claim 3, further comprising a first sealing element (11) arranged between the first valve member (4) and the first containment portion (20) of the housing (2) and a second sealing element (12) arranged between the second valve member (7) and the second containment portion (20) of the housing (2).

5. The discharge valve of claim 3 or 4, further comprising a first steam or compressed air inlet (13) located in the first containment portion (20), such that a gap between the first valve member (4) and the first containment portion (20) can be filled with pressurized steam or compressed air.

6. The discharge valve of any one of the preceding claims, wherein said first valve member (4) is arranged to protrude from a first location (Pl), and said second valve member (7) is arranged to protrude from a second location (P2), said first and second locations being situated at different positions in a circumferential direction of the flow channel (3).

7. The discharge valve of claim 6, wherein said second location is situated 160°-200°, from said first location in a circumferential direction of the flow channel (3), preferably 175°- 185°, more preferably 180°.

8. The discharge valve of any one of the preceding claims, wherein the first valve member (4) is arranged at a first length position (101) along said longitudinal centre axis (A) of the flow channel (3) the second valve member is arranged at a second length position (102) in said length direction, which at least partially overlaps with said first position (101).

9. The discharge valve of any one of the preceding claims, wherein said first and second length positions along said longitudinal centre axis (A) fully overlap.

10. The discharge valve of any one of the preceding claims, wherein said first valve member (4) protrudes into said flow channel (3) at a first angle (al) to said longitudinal centre axis (A) of the flow channel, and said second valve member protrudes into said flow channel (3) at a second angle (a2) to said longitudinal centre axis (A) of the flow channel, said first and second angles (al,a2) being the same or different, and being 30- 150°, preferably from 45-135°, more preferably from 80-100°, most preferably substantially 90°.

11. The discharge valve of any one of the preceding claims, wherein said first and second valve members protrude into the flow channel (3) to such an extent that a forward end (4a) of said first valve member (4) and a forward end (7a) of said second valve member (7) are on the same distance from said longitudinal centre axis (A) of the flow channel.

12. The discharge valve of any one of the preceding claims, wherein said first valve member (4) and second valve member (4) are retractable so as to be able to move between a protruding state and a retracted state.

13. The discharge valve of any one of the preceding claims, wherein a detachable inner lining (8) is arranged in said flow channel (3) and at least partly forms the flow channel.

14. A process element (10) in a manufacturing process involving processing of lignocellulosic material, wherein a discharge valve (1) according to any one of the preceding claims is connected to a pressurized interior process volume of the process element.

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