SE2330120A1

SE2330120A1 - Screw feeder

Info

Publication number: SE2330120A1
Application number: SE2330120A
Authority: SE
Inventors: Örjan Ahlgren; Johan Carlsson; Patrik Pettersson
Original assignee: Valmet Oy
Priority date: 2023-03-13
Filing date: 2023-03-13
Publication date: 2024-03-05

Abstract

A screw 1; 1' for a screw feeder 3 for transporting biomass material in a system 100 for treatment of biomass material, said screw 1; 1' comprising a central shaft 11 configured to extend along a length, I, of the screw feeder 3 and a helical screw blade 13 provided around the central shaft 11, wherein said screw 1; 1' comprises different sections 1a, 1b, 1c along its length direction whereof a first section la is configured to be positioned inside a screw housing 21 of the screw feeder 3, whereby material is to be fed into the screw feeder 3 via a screw housing inlet 23 of the screw housing 21, from a connected feeding device 31, wherein the screw 1; 1', in its first section la, comprises one or more material distribution devices 15; 15' which are connected to and extending from the central shaft 11 and/or the helical screw blade 13, wherein said material distribution devices 15; 15' are configured for bringing material which is fed into the screw housing 21 via the screw housing inlet 23 towards an opposite side of the screw housing 21 to where the screw housing inlet 23 is provided when the screw 1; 1' is rotated.

Description

Screw feeder TECHNICNAL FIELD OF THE INVENTION The present invention relates to a screw feeder and to a screw for a screw feeder for transporting biomass material in a system for treatment of biomass material.

BACKGROUND I\/|aterial transporting screws are widely used in different technical areas for transporting material inside a vessel by rotating the screw. ln the pulp industry material transporting screws are used for transporting biomass material, such as lignocellulose materials, e.g. wood chips or other raw materials, such as sawdust, bagasse or straw, from one part ofthe pulping process to another. The material transporting screw and the vessel may be called a screw feeder or a plug screw feeder. When used in a pulping process, a plug screw feeder is typically not only used for conveying and feeding material, but is also used for dewatering of the material and to provide a pressure-tight plug to a pressurized zone, such as a digester. A material transporting screw can also be used for transporting material through a pressurized reactor vessel for pretreatment or prehydrolysis of biomass. Such a material transporting screw/plug screw typically comprises a shaft extending along the longitudinal central axis throughout the whole vessel in which it is provided and a screw flight provided around the shaft in the form of a screw helix for transporting the material along the length of the vessel when the shaft is rotated.

There are often problems related to wear in these types of feeding systems. The material which is transported through the system is pressed against the inner wall of the vessel and both the material transport screw and the inner wall of the vessel will be affected and eventually worn out. Hereby feeding abilities are decreased and problems may arise related to blow-back in the system, co-rotation ofthe material, plugging and shearing in the system.

A feeding screw may be used for feeding material into the screw feeder. lf material is unevenly distributed around the screw there may be problems with uneven wear of the screw and the vessel, i.e. the screw and vessel will be more worn at one side compared to the other side, which will decrease working time even more.

SUMMARY lt is an object of the invention to provide an improved screw feeder in which the problems with uneven material distribution and uneven wearing of the screw feeder are decreased.

This is achieved by a screw for a screw feeder, a screw feeder and a material transport arrangement according to the independent claims.

According to one aspect of the invention a screw for a screw feeder for transporting biomass material in a system for treatment of biomass material is provided, said screw comprising a central shaft configured to extend along a length, l, of the screw feeder and a helical screw blade provided around the central shaft, wherein said screw comprises different sections along its length direction whereof a first section is configured to be positioned inside a screw housing ofthe screw feeder, whereby material is to be fed into the screw feeder via a screw housing inlet ofthe screw housing, from a connected feeding device, wherein the screw, in its first section, comprises one or more material distribution devices which are connected to and extending from the central shaft and/or the helical screw blade, wherein said material distribution devices are configured for bringing material which is fed into the screw housing via the screw housing inlet towards an opposite side of the screw housing to where the screw housing inlet is provided when the screw is rotated.

According to another aspect ofthe invention a screw feederfor transporting biomass material in a system for treatment of biomass material is provided, said screw feeder comprising a screw as described above, a screw pipe enclosing a part of said screw and a screw housing enclosing a first section of the screw.

According to another aspect of the invention a material transport arrangement for transporting biomass material in a system for treatment of biomass material is provided, said material transport arrangement comprising a screw feeder as described above and a feeding device connected to the screw housing of the screw feeder for feeding material into the screw housing.

Hereby material which is fed into the screw feeder will be better distributed around the screw and hereby there will be less problem with uneven wearing of the screw feeder. Thanks to the material distribution devices which according to the invention are attached to the screw in the area ofthe screw feeder where a material inlet is provided, the material will be forced by the material distribution devices towards the opposite side of the screw to where the inlet is provided and hereby the material is better distributed around the whole screw. The material distribution devices are formed and positioned such that they will bring the material towards the other side of the screw when the screw is rotated. Thanks to the improved material distribution the problem with uneven wear of the screw and screw feeder will be reduced. Hereby the screw and also the screw pipe which is enclosing a part of the screw can be used for a longer time whereby costs are saved. ln one embodiment of the invention the one or more material distribution devices are plates having a width, w, and a height, h. ln one embodiment of the invention the screw comprises at least three separate material distribution devices which are separated around a circumference ofthe screw. ln one embodiment of the invention at least one of the one or more material distribution devices is positioned on a leeward side of the screw blade. ln one embodiment of the invention at least one of the one or more material distribution devices is positioned on the central shaft. ln one embodiment ofthe invention the one or more material distribution devices each has a height, h, extending essentially in a radial direction from the central shaft and a width, w, extending essentially in a length direction, l, of the screw. ln one embodiment of the invention the height, h, is between 1/50 and 1/1 of a screw blade height, hs, at the position of the material distribution device and the width, w, is between 1/50 and 1/1 of a pitch ofthe screw blade. ln one embodiment of the invention the one or more material distribution devices are distributed over an inlet part of the first section of the screw, which inlet part is the part of the screw which is configured to be positioned within a part of the screw housing where the screw housing inlet is provided. ln one embodiment of the invention the screw is a plug screw for a plug screw feeder. ln one embodiment of the invention the screw feeder is a plug screw feeder.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic, perspective view of a part of a system for treatment of biomass material.

Figure 2 shows schematically in cross section a material transport arrangement comprising a screw feeder.

Figures 3a and 3b show schematically side views of screws for screw feeders according to two different embodiments of the invention.

Figure 4 is a side view of a screw feeder according to one embodiment of the invention.

DETAILED DESCRITPION OF El\/lBODll\/IENTS Figure 1 is a schematic, perspective view of a part of a system 100 for treatment of biomass material. The system comprises a screw feeder 3 according to the invention. The screw feeder 3 according to the invention may be used in different parts of a system 100 for treatment of biomass material. The screw feeder 3 may be used for transporting material in the system. lt may also be used as a plug screw feeder to provide a pressure-tight plug to a pressurized zone in the system, such as a digester. Figure 2 shows schematically in cross section a material transport arrangement 103 comprising a screw feeder 3. The screw feeder 3 in Figure 2 is a plug screw feeder. The invention can however be implemented also in another type of screw feeder. With reference to both Figure 1 and Figure 2 the screw feeder 3 is now described in general terms. Figure 2 shows a screw feeder 3 schematically, without any details which are specific for the invention. The invention specific details are instead shown in Figures 3 and 4 and will be discussed further below. The screw feeder 3 comprises a screw 1; 1' comprising a central shaft 11 configured to extend along a length, l, of the screw feeder 3 and a helical screw blade 13 provided around the central shaft 11. The screw 1; 1' can be divided into different sections along its length, in this example: a first section 1a, a second section 1b and a third section 1c. The screw feeder 3 comprises furthermore a screw housing 21 which is enclosing the first section 1a of the screw 1; 1' and a screw pipe 5 which is enclosing the second section 1b of the screw 1;1'. ln this example it further comprises a plug pipe 6 which is enclosing the third section 1c of the screw 1; 1'. This plug pipe 6 and third section 1c of the screw 1; 1' are specific for a plug screw feeder, but not necessary for the invention. The screw housing 21 of the screw feeder 3 comprises a screw housing inlet 23, whereby material is to be fed into the screw feeder 3 via the screw housing inlet 23 of the screw housing 21, from a connected feeding device 31. The connected feeding device 31 may be a feeding screw, for example a force-feeding screw. The feeding device 31 may however also comprise another feeding mechanism. The specific type of feeding into the screw feeder 3 is not crucial for the invention. Hereby material is fed into the screw housing 21 of the screw feeder 3 from one side. This is schematically shown in Figure 2. ln Figure 1 no feeding device 31 is shown. However, the screw housing inlet 23 to which a feeding device 31 is to be connected can be seen and it can be seen how material will be fed from one side of the screw feeder 3 via the screw housing inlet 23.

The invention will now be described with reference to Figures 1-2, and further with reference to Figures 3-4. Figures 3a and 3b show schematically side views of screws 1; 1' for screw feeders 3 according to two different embodiments of the invention. Figure 4 is a side view of a screw feeder 3 according to one embodiment of the invention. ln Figure 4 the screw housing 21 and the screw housing inlet 23 are shown. The screw 1;1' can be seen through the screw housing inlet 23. Material will be fed into the screw feeder 3 via the screw housing inlet 23. According to the invention the screw 1; 1' comprises, in its first section 1a, one or more material distribution devices 15; 15' which are connected to and extending from the central shaft 11 and/or the helical screw blade 13 of the screw 1; 1'. The one or more material distribution devices 15; 15' are configured for bringing material which is fed into the screw housing 21 via the screw housing inlet 23 towards an opposite side ofthe screw housing 21 to where the screw housing inlet 23 is provided when the screw 1; 1' is rotated for transportation of material. The one or more material distribution devices 15; 15' are suitably designed as plates having for example a rectangular or triangular form. Other forms are also possible. The plates may have a width, w, and a height, h, and they may be welded to the screw 1; 1'. The screw 1; 1' comprises in some embodiments at least three separate material distribution devices 15; 15' which are separated around a circumference of the screw 1; 1'. There may be provided for example 3-20 or 4-12 separate material distribution devices 15; 15' which may be distributed around the circumference ofthe screw 1;1' and possibly also along a length of the screw within the first section 1a of the screw. The material distribution devices 15; 15' are in some embodiments distributed evenly around the circumference ofthe screw. The one or more material distribution devices 15;15' may have a height, h, by which they are extending from the central shaft 11, i.e. substantially in a radial direction ofthe screw 1;1' and they may have a width, w, by which they are extending in a direction along a length direction, l, of the screw 1; 1', i.e. between two ofthe blades of the screw blade 13 of the screw 1; 1'. However, the material distribution devices 15; 15' may also be tilted, for example tilted from the length direction and/or tilted from the radial direction, i.e. the material distribution devices 15;15' may extend along other directions than the length direction and radial direction of the screw. The material distribution devices 15; 15' may have a maximum height, h, which is the same as a screw blade height, hs, from the central axis 11 at the position of the material distribution device 15; 15'. The height, h, of the material distribution devices 15;15' can for example be between 1/50 and 1/1 ofthe screw blade height, hs, at the position ofthe material distribution device 15; 15'. The material distribution devices 15; 15' may further have a maximum width, w, which is the same as a pitch of the screw blade 13, i.e. a distance between the two blades ofthe screw blade 13 between which this material distribution device 15; 15' is provided. The width, w, of the material distribution devices 15; 15' can for example be between 1/50 and 1/1 ofthe pitch ofthe screw blade 13. Two examples of material distribution devices 15; 15' are shown in Figures 3a and 3b. Other number of and sizes of material distribution devices are possible.

One embodiment of a screw 1 for a screw feeder 3 according to the invention is schematically shown in Figure 3a. ln this embodiment the material distribution devices 15 are positioned on a leeward side 13a of the screw blade 13. A number of material distribution devices 15 are distributed around the circumference of the screw 1. ln the view as shown in Figure 3a four material distribution devices 15 are visible distributed over two threads of the screw 1, however, more material distribution devices 15 may be provided on the other side of the screw 1. ln this embodiment the material distribution devices 15 are provided as plates or wings extending from the leeward side 13a of the screw blade 13. As the screw 1 rotates the material distribution devices 15 will hereby help bringing the material towards the opposite side ofthe screw 1.

Another embodiment of a screw 1' for a screw feeder 3 according to the invention is shown schematically in Figure 3b. ln this embodiment the material distribution devices 15' are positioned on the central shaft 11 in between blades of the screw blade 13. Three material distribution devices 15' can be seen distributed around the circumference in this view and there may be more material distribution devices 15' on the backside of the screw 1'. The number of material distribution devices can as described above be varied between for example 3-20. The material distribution devices 15' can also in this embodiment be provided as plates or wings and they have a height, h, by which they are extending from the central shaft 11 and a width, w, extending along a length, l, of the screw 1'.

The two different examples of material distribution devices 15; 15' as illustrated in Figures 3a and 3b may be combined in the same screw. Other designs of material distribution devices 15; 15' are also possible. Any type of plate or wing extending from the central shaft 11 and/or the screw blade 13 of the screw 1; 1' which is designed for bringing material towards the opposite side ofthe screw when the screw is rotated can be used in this invention.

The material distribution devices 15; 15' are in some embodiments of the invention distributed over an inlet part 2 (marked in Figure 2) of the first section 1a of the screw 1;1', which inlet part 2 is the part of the screw 1;1' which is configured to be positioned within a part ofthe screw housing 21 where the screw housing inlet 23 is provided. Herbey the material distribution devices 15; 15' are positioned where the material is fed into the screw feeder whereby they can guide the material to be better distributed around the screw. ln some embodiments ofthe invention the screw 1; 1' is a plug screw for a plug screw feeder.

According to the invention a screw feeder 3 for transporting biomass material in a system 100 for treatment of biomass material is also provided. The screw feeder 3 comprises a screw 1; 1' according to the invention as described above, a screw pipe 5 enclosing a part of said screw 1; 1' and a screw housing 21 enclosing a first section 1a of the screw 1; 1'. ln some embodiments of the invention said screw feeder 3 is a plug screw feeder and said screw 1; 1' is a plug screw.

According to the invention a material transport arrangement 103 for transporting biomass material in a system 100 for treatment of biomass material is also provided. The material transport arrangement 103 comprises a screw feeder 3 according to the invention as defined above and a feeding device 31 connected to the screw housing 21 of the screw feeder 3 for feeding material into the screw housing.

Claims

1. A screw (1; 1') for a screw feeder (3) for transporting biomass material in a system (100) for treatment of biomass material, said screw (1; 1') comprising: - a central shaft (11) configured to extend along a length, l, of the screw feeder (3); and - a helical screw blade (13) provided around the central shaft (11), wherein said screw (1; 1') comprises different sections (1a, 1b, 1c) along its length direction whereof a first section (1a) is configured to be positioned inside a screw housing (21) of the screw feeder (3), whereby material is to be fed into the screw feeder (3) via a screw housing inlet (23) of the screw housing (21), from a connected feeding device (31), wherein the screw (1; 1'), in its first section (1a), comprises one or more material distribution devices (15; 15') which are connected to and extending from the central shaft (11) and/or the helical screw blade (13), wherein said material distribution devices (15; 15') are configured for bringing material which is fed into the screw housing (21) via the screw housing inlet (23) towards an opposite side of the screw housing (21) to where the screw housing inlet (23) is provided when the screw (1; 1') is rotated. Screw according to claim 1, wherein the one or more material distribution devices (15; 15') are plates having a width (w) and a height (h). Screw according to claim 1 or 2, wherein the screw (1; 1') comprises at least three separate material distribution devices (15; 15') which are separated around a circumference of the screw (1; 1'). Screw according to any one of the preceding claims, wherein at least one of the one or more material distribution devices (15) is positioned on a leeward side (13a) of the screw blade (13). Screw according to any one of the preceding claims, wherein at least one of the one or more material distribution devices (15) is positioned on the central shaft (11). Screw according to any one of the preceding claims, wherein the one or more material distribution devices (15) each has a height (h) extending essentially in a radial direction from the central shaft (11) and a width (w) extending essentially in a length direction (l) of the screw (1; 1'). Screw according to claim 6, wherein the height (h) is between 1/50 and 1/1 of a screw blade height (hs) at the position of the material distribution device and the width (w) is between 1/50 and 1/1 of a pitch of the screw blade (13). Screw according to any one of the preceding claims, wherein the one or more material distribution devices (15; 15') are distributed over an inlet part (2) of the first section (1a) of the screw (1; 1'), which inlet part (2) is the part of the screw (1; 1') which is configured to be positioned within a part of the screw housing (21) where the screw housing inlet (23) is provided. Screw according to any one ofthe preceding claims, wherein the screw (1; 1') is a plug screw for a plug screw feeder. A screw feeder (3) for transporting biomass material in a system (100) for treatment of biomass material, said screw feeder (3) comprising a screw (1; 1') according to any one of the preceding claims, a screw pipe (5) enclosing a part of said screw (1; 1') and a screw housing (21) enclosing a first section (1a) of the screw (1; 1'). Screw feeder according to claim 10, wherein said screw feeder (3) is a plug screw feeder and said screw (1; 1') is a plug screw. A material transport arrangement (103) for transporting biomass material in a system (100) for treatment of biomass material, said material transport arrangement (103) comprising a screw feeder (3) according to claim 10 or 11 and a feeding device (31) connected to the screw housing (21) of the screw feeder (3) for feeding material into the screw housing.