Conduit for conveying a fiber stream

Abstract

A conduit (1) for conveying a stream comprising fibers, - said conduit being provided with solely two openings (2, 3) for connecting the conduit to one or more additional conduits and / or to one or more apparatuses for providing and / or treating said stream; - said conduit comprising a curved portion (4); - said conduit being provided with a releasably connected wall portion (5) along at least a portion of said curved portion (4), said wall portion being at least partly provided at an outer radius of the curved portion, said wall portion forming at least part of an inner surface of the curved portion, said wall portion (5) being curved solely along a lengthwise direction of said curved portion (4), wherein said wall portion (5) comprises a wear-resistant coating, such as a ceramic coating, at an inner surface thereof.

Description

[0001] CONDUIT FOR CONVEYING A FIBER STREAM

[0002] TECHNICAL FIELD

[0003] The invention relates to the field of conduits / blow lines for conveying a stream comprising fibers and steam or air, which conduit or blow line comprises at least one curved portion.

[0004] BACKGROUND

[0005] Conduits or blow lines for conveying a stream comprising fibers, such as a stream comprising fibers and steam resulting from steam explosion discharge of biomass treated in a pressurized reactor, are known in the art Such conduits or blow lines normally comprises at least one curved portion. One problem with such conduits or blow lines is that the fiber content of the stream is concentrated to radially outermost trajectories in the curved portion and thus causes wear on the (inside of the) radially outermost portion of the curved portion, eventually causing the conduit or blow line to break. Repairing such a conduit or blow line on-site by means of welding is time-consuming and costly since a certified welder is required due the pressure vessel directive. A less time-consuming but even more costly option is to replace the conduit or blow line part comprising the curved portion when worn out

[0006] SUMMARY

[0007] An object of the invention is to provide a conduit or blow line which at least partly solves or improves on the problems identified in the above background section.

[0008] These and other objects are achieved by the present invention by means of a conduit according to the independent claim.

[0009] According to a first aspect of the invention, there is provided a conduit for conveying a stream comprising fibers. The conduit is provided with two openings (preferably at its opposite ends) for connecting the conduit to one or more additional conduits and / or to one or more apparatuses for providing and / or treating said stream. The conduit comprises a curved portion. The conduit is provided with a releasably connected wall portion along at least a portion of said curved portion, the wall portion being provided along at least part of the outer periphery of the curved portion.

[0010] It is understood that the releasably connected wall portion is a wall portion in the sense that it forms part of the wall of the curved portion (along at least part of the outer periphery thereof) which would otherwise be formed by a fixed portion of the wall of the curved portion. Thus, the wall portion forms at least part of an inner surface of the curved portion, i.e. the wall portion is in direct contact with the stream of fibers conveyed through the conduit. The wall portion may also be described as (having an inner surface) facing towards the interior of the conduit.

[0011] In other words, a conduit or blow line part is provided which comprises a curved portion. The conduit is suitable for conveying a stream comprising air and / or steam and fibers (such as biomass or cellulosic fibers) in the sense that it is (partly or wholly) made from a wear resistant material, and / or (partly or wholly) comprises a wear resistant coating or the like, which can withstand the abrasive action of the fibers. The stream may also be referred to as an airstream or steam stream comprising / conveying fibers. The conduit is provided with two openings (inlet and outlet), which may be at its opposite ends. Between the two openings, the conduit is preferably not provided with any openings / connections for discharging or supplementing the stream or parts thereof, i.e. preferably there are solely two openings, i.e. the conduit comprises solely one inlet and solely one outlet. Since openings are provided solely at two positions (such as at the opposite ends), the conduit is for conveying the stream, not for other purposes such as separating away (part of) the air or steam content of the stream. The conduit is preferably provided with a connecting portion at the respective opening. The connecting portions, which may be in the form of flanges, are adapted to connect the conduit to one or more additional conduits and / or to one or more apparatuses for providing and / or treating said stream. The conduit comprises a curved portion, i.e. at least part of the conduit (but not necessarily the whole) is curved. The curved portion may also be referred to as a bend. The conduit is provided with a releasably connected wall portion along at least a portion of the curved portion (or along the whole curved portion, or a wall portion which extends beyond the curved portion). At least part of the wall portion is provided at an outer radius or periphery of the curved portion, i.e. forms (part of) the radially outermost (peripheral) wall of the conduit. The curved portion or bend may be described in that the center line formed by the curved portion of the conduit forms a curve in plane, i.e. the curved portion is curved only in one direction / plane.

[0012] The curved portion may have an angular extension of 30 to 120 degrees, such as 90 degrees. The curved portion may be curved with a radius of at least 500 mm, or at least 1000 mm, or at least 1500 mm, the radius being the radius of the center line of the conduit

[0013] The invention is based on the insight that by making the part of the conduit which is most subjected to wear (the radially outermost wall portion) releasably connectable, a conduit is achieved which can quickly be repaired simply by replacing the wall portion. In embodiments, the wall portion is curved solely in a direction of curvature of said curved portion. It is understood that the curvature of the curved portion refers to the (overall) curvature of the curved portion which causes the flow therethrough to change direction. In other words, the wall portion is curved only along the lengthwise direction / flow direction of the curved portion, i.e. not curved in a lateral direction (the lateral direction being perpendicular to the lengthwise direction / flow direction of the curved portion). The wall portion may also be described as substantially straight as seen in said lateral direction. For example, the wall portion may be curved with solely one radius relative one center axis. The wall portion may also be described in that the wall portion is curved only in one direction / plane. Such embodiments are advantageous since the wall portion can be easily manufactured by means of bending plane material to form the curved wall portion. Further, an inner surface being only curved in one direction can be conveniently and accurately coated with a wear-resistant layer.

[0014] In embodiments, the conduit (or the curved portion) is formed by two parts; the releasably connected wall portion and a main part. At least part of, or the whole, main part may have a substantially u-shaped cross section (as seen perpendicular to the lengthwise direction / flow direction of the conduit). Such a u-shaped part may be provided with (laterally outwardly directed) flanges at its open end, the wall portion being attached to the flanges, for instance by means of screw connections extending through the flanges and the wall portion. The flanges may be provided with grooves in which one or more seals are arranged to seal the connection between the wall portion and the flanges. Having the seals arranged in the flanges of the main part is advantageous since no machining of the replaceable wall portion is needed for seals. The (substantially u-shaped) main part may be formed by casting or by means of welding.

[0015] In embodiments, the wall portion is formed from a material which has greater wear resistance than the rest of the curved portion, or than the rest of the conduit (such as the main part). For example, the wall portion may be made from a high yield steel material. The wall portion may be made from a duplex stainless steel such as EN 1.4462 or a super-duplex stainless steel such as EN 1.4410.

[0016] In embodiments, the wall portion comprises a wear-resistant coating at an inner surface thereof. The wear-resistant coating may be a ceramic coating. Alternatively, the coating may be a weld coating such as Stellite 6, Stellite 12 or MeltolitX 700.

[0017] In embodiments, the wall portion is formed by, or comprises, an inner layer facing towards the interior of the conduit and an outer layer, wherein the inner layer is formed from a material which has greater wear resistance than the outer layer. The inner layer may be described as sandwiched between the outer layer and the above-described main part (or more specifically the flanges thereof). Such embodiments may be advantageous since the outer layer (acting as a pressure bearing layer) can be made from a cheaper and less wear resistant layer than the inner layer.

[0018] In embodiments, the wall portion is releasably connected by means of a plurality of screw connections. If the wall portion comprises inner and outer layers as described above, the wall portion may be releasably connected by means of screw connections which do not extend through the inner layer. This may be advantageous since drilling holes through the (harder) inner layer is avoided, thus resulting in a conduit which is easier to manufacture.

[0019] In embodiments, the curved portion has a substantially square or rectangular cross section as seen perpendicular to a lengthwise direction / flow direction of the conduit. The cross section is substantially square or rectangular in the sense that the circumference of the conduit comprises four straight portions, which straight portions together constitute at least 80 % or 90 % of the circumference.

[0020] In embodiments, an effective flow area of the curved portion is greater than a flow area of the conduit at its openings (which may be at the opposite ends). This may be advantageous since the speed of the stream is reduced through the curved portion, thus causing less wear.

[0021] According to a second aspect of the embodiment, an arrangement for treating biomass material is provided. The arrangement comprises a reactor for treating the biomass material at elevated pressure and temperature by means of steam addition, a steam explosion discharge device configured to carry out steam explosion discharge of the biomass material from the reactor, and at least one conduit according to the first aspect of the invention or embodiments thereof. The conduit is connected directly or indirectly to the steam explosion discharge device for conveying a stream comprising steam exploded biomass material and steam from the steam explosion discharge device. The reactor may be configured to carry out hydrolysis or pre-hydrolysis of the biomass material. As is well-known in the art, pre-hydrolysis is carried out at milder conditions compared to a hydrolysis process and is used for hydrolyzing the hemicellulose content of the biomass. Optionally, a catalyst such as acid may be added to, or prior to, the reactor. The steam explosion discharge device may be described as comprising (or consisting of) a blow valve. According to a third aspect of the invention, an arrangement for producing fibers for fiberboard production from biomass material is provided. The arrangement comprises a refining device arranged to refine or grind the biomass material into fibers, and at least one conduit according to the first aspect of the invention or embodiments thereof. The conduit is connected directly or indirectly to said refining device for conveying a stream comprising fibers from the refining device. The refining device may also be referred to as a defibrator.

[0022] The features of the embodiments described above are combinable in any practically realizable way to form embodiments having combinations of these features. Further, all features and advantages of embodiments described above with reference to the first aspect of the invention may be applied in corresponding embodiments of the arrangements according to the second and third aspects of the invention.

[0023] BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Above discussed and other aspects of the present invention will now be described in more detail using the appended drawings, which show presently preferred embodiments of the invention, wherein: fig. 1 shows a perspective view of an embodiment of a conduit according to the first aspect of the invention; fig. 2a shows a cut-away view of a portion of the conduit in fig. 1; fig. 2b shows a cut-away view of an alternative embodiment of a conduit according to the first aspect of the invention; fig. 3 shows a side view of the conduit in fig. 1; fig. 4 shows a top view of the conduit in fig. 1; fig. 5 shows a partial cross-section view of the conduit in fig. 1 taken along line A-A shown in fig. 3; fig. 6 shows a partial cross-section view of the conduit in fig. 1 taken along line B-B shown in fig. 4; fig. 7 shows a schematic view of an embodiment of an arrangement according to the second aspect of the invention, and fig. 8 shows a schematic view of an embodiment of an arrangement according to the third aspect of the invention.

[0025] DETAILED DESCRIPTION Fig. 1 shows a perspective view of an embodiment of a conduit 1 according to the first aspect of the invention. The conduit is configured for conveying a stream comprising fibers from a first opening 2 to the second opening 3 or in the opposite direction.

[0026] The openings 2, 3 are provided at the opposite ends of the conduit, the conduit being provided with connecting portions 2 a, 3 a in the form of flanges at the openings for connecting the conduit to one or more additional conduits and / or to one or more apparatuses for providing and / or treating said stream.

[0027] The conduit comprises a curved portion 4 having an angular extension of 90 degree and a radius rc(see fig. 3) of 1000 mm and shorter straight portions 2b, 3b at the respective end of the curved portion, the straight portions connecting the curved portion to flanges 2a, 3a.

[0028] The conduit is provided with a releasably connected wall portion 5 along the outer periphery of the whole curved portion 4. The wall portion 5 is curved solely in a direction of curvature of said curved portion 4. As can be seen in fig. 1, the wall portion 5 is releasably connected by means of a plurality of screw connections.

[0029] Fig. 2a shows a cut-away view of a portion of the conduit in fig. 1. As can be seen in fig. 2a, the wall portion 5 is straight as seen in a lateral direction, i.e. the wall portion 5 is curved only in the direction of curvature of the curved portion 4, i.e. curved only along the lengthwise direction / flow direction of the curved portion.

[0030] Further as can be seen in fig. 2a, the curved portion 4 of the conduit comprises a portion 4a having substantially u-shaped cross section, the portion 4a being provided with (laterally outwardly directed) flanges 4b, 4c at its open end. The wall portion 5 is arranged in abutment with and attached to the flanges 4b, 4c by means of screw connections 6 extending through the flanges 4b, 4c and the wall portion 5. The flanges 4b, 4c are provided with a respective groove 4b’, 4c’ in which seals 7a, 7b are arranged to seal the connection between the wall portion 5 and the flanges 4b, 4c.

[0031] In this embodiment, the u-shaped portion of the curved portion is formed integrally with the straight portions 2b, 3b and flanges 2a, 3a by casting. 2a, 2b, 3a, 3b and 4a may together be described as a main part of the conduit, which forms the conduit together with the wall portion The wall portion 5 is formed from a duplex stainless steel according to EN 1.4462 which has greater wear resistance than the rest of the conduit. Optionally, the wall portion 5 comprises a wear-resistant ceramic coating 5’ at an inner surface thereof. In such embodiments having a wear-resistant coating, the wall portion 5 may of a less wear-resistant material such as a lower- grade stainless steel.

[0032] Fig. 2b shows a cut-away view of an alternative embodiment of a conduit according to the first aspect of the invention. This embodiment corresponds to the embodiment in fig. 1 and 2a with the only difference being that the releasably connected wall portion comprises an inner layer 5b facing towards the interior of the conduit and an outer layer 5a, wherein the inner layer is formed from a material such as EN 1.4462, while the outer layer 5a is formed from a material having less wear resistance. The wall portion is releasably connected by means of screw connections which extend through the outer layer 5a but not through the inner layer 4b.

[0033] Fig. 3 shows a side view of the conduit in fig. 1 and 2a. Fig. 4 shows a top view of the conduit in fig. 1, 2a and 3. As can be seen in fig. 3-4, the curved portion is curved only in one direction, i.e. with its center line forming a curve in one plane. A radius of the (center line of the) curved portion is indicated in fig. 3 as rc. Further as can be seen in fig. 3, the wall portion 5 is curved with a radius rwp relative a center axis common with the radius rcof the curved portion 4. As described above, the wall portion 5 is straight as seen in a lateral direction and is thus curved only with radius rwpas indicated in fig. 3. Further, it can be seen in fig. 3 that the openings 2, 3 have a round cross-section.

[0034] Fig. 5 shows a partial cross-section view of the conduit in fig. 1 taken along line A-A shown in fig.

[0035] 3. In fig. 5 it can be seen that the curved portion has a substantially square cross section (of height / width H) as seen perpendicular to a lengthwise direction / flow direction of the conduit The cross section is substantially square or rectangular in the sense that the circumference of the conduit comprises four straight portions, which straight portions together constitute at least 90 % of the circumference.

[0036] Fig. 6 shows a partial cross-section view of the conduit in fig. 1 taken along line B-B shown in fig.

[0037] 4. Fig. 5-6 together illustrate how the straight portion 2b transitions from a round cross-section at opening 2 to a square cross section at the curved portion formed by 4a, 5. The height / width H of the substantially square cross section at the curved portion is only slightly smaller than the diameter D at the opening 2 which means that the effective flow area of the curved portion 4 is greater than a flow area of the conduit at its opening 2. The same description applies to the other end with straight portion 3b and opening 3. As can be seen in fig. 6, a seal 7c is provided in a laterally directed groove to seal the connection between the wall portion 5 and the straight portion 2b.

[0038] Fig. 7 shows a schematic view of an embodiment of an arrangement according to the second aspect of the invention. The arrangement 100 comprises a substantially vertically arranged reactor 102 for treating the biomass material at elevated pressure and temperature by means of steam addition through steam inlet 104. Biomass is fed to the reactor using feeding screw 105. A discharge screw 104 (for example a pressure sealing screw) is arranged at the bottom of the reactor 102 and is arranged to feed the treated biomass to a blow valve (steam explosion discharge device) 103 over which the pressure drops to a substantially lower pressure, preferably to substantially atmospheric pressure, such that the treated biomass material is subjected to steam explosion. A conduit 101 of the same type as in fig. 1 is connected to the blow valve for receiving a stream comprising steam exploded biomass material and steam. The stream is conveyed via additional (not shown) conduits / blow line parts to for example a cyclone / steam separator.

[0039] Fig. 8 shows a schematic view of an embodiment of an arrangement 200 according to the third aspect of the invention. The arrangement is for producing fibers for fiberboard production from biomass material. The arrangement comprises a refining device 202 comprising two discs arranged to refine or grind the biomass material therebetween into fibers. The biomass material is received via an axial inlet 203 and is discharged via a tangential outlet 204. Such refining devices (also known as defibrators) are well-known in the art and will not be described in further detail here. One example is the Valmet Evolution Defibrator. A conduit 201 of the same type as in fig. 1 is connected to outlet 204 to receive a stream comprising air and fibers from the refining device.

[0040] The description above and the appended drawings are to be considered as non-limiting examples of the invention. The person skilled in the art realizes that several changes and modifications may be made within the scope of the invention. For example, the curved portions can have a different angular extension than 90 degrees, such as 45 degrees. Further, the cross section of the curved portion does not necessarily need to have a substantially square cross section. Further, the conduit may be used in other arrangements than shown in fig. 7-8.

Claims

CLAIMS1. A conduit (1) for conveying a stream comprising fibers, said conduit being provided with solely two openings (2, 3) for connecting the conduit to one or more additional conduits and / or to one or more apparatuses for providing and / or treating said stream; said conduit comprising a curved portion (4); said conduit being provided with a releasably connected wall portion (5) along at least a portion of said curved portion (4), said wall portion being at least partly provided at an outer radius of the curved portion, said wall portion forming at least part of an inner surface of the curved portion, said wall portion (5) being curved solely along a lengthwise direction of said curved portion (4), wherein said wall portion (5) comprises a wear-resistant coating (5’), such as a ceramic coating, at an inner surface thereof.

2. Conduit according to claim 1, wherein said wall portion (5) is formed from a material which has greater wear resistance than the rest of the conduit3. Conduit according to any of the preceding claims, wherein said wall portion is formed by an inner layer (5a) facing towards the interior of the conduit and an outer layer (5b), wherein the inner layer is formed from a material which has greater wear resistance than the outer layer.

4. Conduit according to any of the preceding claims, wherein said wall portion (5) is releasably connected by means of screw connections (6).

5. Conduit according to claim 4 as dependent on claim 3, wherein said wall portion (5) is releasably connected by means of screw connections which do not extend through the inner layer (5a).

6. Conduit according to any of the preceding claims, wherein said curved portion (4) has a substantially square or rectangular cross section as seen perpendicular to a flow direction of said conduit7. Conduit according to any of the preceding claims, wherein an effective flow area of the curved portion (4) is greater than a flow area of the conduit at its openings (2, 3).

8. Conduit according to any of the preceding claims, wherein said curved portion (4) has an angular extension of 30 to 120 degrees, such as 90 degrees.

9. Conduit according to any of the preceding claims, wherein said curved portion (4) is curved with a radius (rc) of atleast 500 mm, or atleast 1000 mm, or at least 1500 mm.

10. An arrangement (100) for treating biomass material comprising: a reactor (102) for treating the biomass material at elevated pressure and temperature by means of steam addition;a steam explosion discharge device (103) configured to carry out steam explosion discharge of the biomass material from the reactor, and at least one conduit (101) according to any of the preceding claims, said conduit being connected directly or indirectly to said steam explosion discharge device (103) for conveying a stream comprising steam exploded biomass material and steam from the steam explosion discharge device.

11. An arrangement (200) for producing fibers for fiberboard production from biomass material, said arrangement comprising: a refining device (202) arranged to refine or grind the biomass material into fibers, and at least one conduit (201) according to any claims 1-9, said conduit being connected directly or indirectly to said refining device (202) for conveying a stream comprising fibers from the refining device.

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