FI20195684A1

FI20195684A1 - Cellulose pulp dryer

Info

Publication number: FI20195684A1
Application number: FI20195684A
Authority: FI
Inventors: Jan Evertsson; Cristian Bohman
Original assignee: Andritz Tech & Asset Man Gmbh
Priority date: 2017-02-17
Filing date: 2018-02-14
Publication date: 2019-08-16
Also published as: BR112019016875A2; CN211713516U; FI130392B; SE1750164A1; WO2018149867A1; BR112019016875B1

Abstract

The present invention relates to a cellulose pulp dryer (1) being operative for drying a web (14) of cellulose pulp by means of gas supplied through gas openings (24) of blow boxes (22, 26) of a first drying section (5), the cellulose pulp dryer (1) comprises at least one light emitting device (41, 43) arranged to illuminate at least a portion of said drying section (5). The light emitting device (41, 43) comprises a light emitting diode (59), a heat transfer member (69) and a housing (53) accommodating said light emitting diode (59) and said heat transfer member (69), wherein said heat transfer member (69) is arranged to transfer heat away from said light emitting diode (59).

Description

CELLULOSE PULP DRYER

20195684 prh 16 -08- 2019

Technical Field of the Invention

The present invention relates to a cellulose pulp dryer being operative for drying a web of cellulose pulp by means of gas supplied through gas openings of blow boxes of a first drying section.

Background Art

Cellulose pulp is often dried in a dryer having several superposed horizontal drying decks. Large dryers may have more than 50 drying decks 10 and each drying deck may be about 60 meters in length and 10 meters in width. Turning rolls are arranged at the ends of the drying decks. Cellulose pulp having about 50% water content is fed into the upper drying deck. A web of cellulose pulp is conveyed across the drying decks and the turning rolls convey the web to the next, lower, drying deck. Dry cellulose pulp, having 15 about 10% water content, is outputted at the end of the lowest drying deck.

An example of a cellulose pulp dryer is illustrated in WO 2012/074462 A1. Hot gas in the form of hot air is blown onto a web of cellulose pulp by means of upper blow boxes and lower blow boxes. The air blown by the blow boxes transfer heat to the web to dry it. In addition, the air blown by the lower 20 blow boxes keeps the web floating above the lower blow boxes. Hot air is supplied to the blow boxes by means of a circulation air system comprising fans and steam radiators heating the drying air.

At unexpected shutdown of such cellulose pulp dryer, or if the web is ripped, a web tail must be threaded through the drying decks. Threading is 25 time-consuming, in particular for large dryers, and in the mean time no dry pulp is produced, which is cost-ineffective. Hence, there is a need for avoiding frequent threading procedures and/or making threading as efficient as possible when it is still necessary.

Summary of the Invention

20195684 prh 16 -08- 2019

It is an object of the present invention to provide an improved cellulose pulp dryer.

These and other objects that will be apparent from the following summary and description are achieved by a cellulose pulp dryer according to 5 the appended claims.

According to one aspect of the present disclosure there is provided a cellulose pulp dryer being operative for drying a web of cellulose pulp by means of gas supplied through gas openings of blow boxes of a first drying section, the cellulose pulp dryer comprises at least one light emitting device 10 arranged to illuminate at least a portion of said drying section, wherein said light emitting device comprises a light emitting diode, a heat transfer member and a housing accommodating said light emitting diode and said heat transfer member, wherein said heat transfer member is arranged to transfer heat away from said light emitting diode.

The light emitting device enables web residues to be easily detected. The light emitting device enables the drying section to be illuminated with low power consumption. Furthermore, since light emitting diodes are more energy efficient than e.g. halogen lamps, thinner cables can be used. Also, shorter cables and less components may be needed, which facilitates installation of 20 the light emitting device.

Hence, a light emitting device of the dryer of the present disclosure, i.e. a light emitting system comprising a light emitting diode, and especially a light emitting system comprising several such light emitting devices, is easier to install compared to light emitting devices comprising e.g. halogen lamps.

Furthermore, the light emitting diode enables higher brightness and/or better colour quality, which provides for a safer working environment for operators working at the dryer and makes it easy to detect web residues during a stoppage in production. Also, the risk of fire may be reduced, since the light emitting diode generates significantly less heat. Furthermore, a light emitting 30 device with increased lifespan may be provided, since a light emitting diode may be designed to be very durable. Also, the design of the housing may allow the beam angle of the light emitting diode to be adapted to the width of the dryer.

20195684 prh 16 -08- 2019

The heat transfer member is configured to transfer heat away from the light emitting diode, which enables light emitting diodes, and especially 24 V light emitting diodes, to withstand continuous operation, although the environment where the light emitting device is installed is humid and warm.

Since the light emitting device comprises a heat transfer member, no external cooling is required, which enables a cost efficient solution that is easy to install and service.

According to one embodiment the heat transfer member comprises at least one heat sink fin.

According to one embodiment the heat transfer member comprises a heat sink base and several heat sink fins.

According to one embodiment the heat transfer member is a separate part of the light emitting device. This embodiment has the advantage that installation and/or replacement of a light emitting diode attached to the heat transfer member can be carried out in a very easy and fast manner.

According to one embodiment the light emitting diode and the heat transfer member together form a lamp unit being connectable to a connection unit of the light emitting device, which further facilitates installation and/or replacement of a light emitting diode.

According to one embodiment the light emitting diode is fixedly attached to said heat transfer member.

According to one embodiment the light emitting diode is a DC light emitting diode.

The light emitting diode may be configured to be driven by a voltage of 25 12V, or a voltage of 24V, or a voltage of 48V, or a voltage of 60V.

According to one embodiment the light emitting diode is configured to be driven by a voltage of 12V or more.

According to one embodiment the light emitting diode is configured to be driven by a voltage of 60V or less.

According to one embodiment the light emitting diode is configured to be driven by a voltage in the range of 24V to 48V.

According to one embodiment said light emitting device (LED) comprises a 24V DC LED power supply.

20195684 prh 16 -08- 2019

According to one embodiment said light emitting device (LED) comprises a 48V DC LED power supply.

The housing of the light emitting device is configured for accommodating the light emitting diode. According to one embodiment said heat transfer member is a separate part of the housing, which provides for a solution with few parts and that is easy to installl and service.

According to one embodiment said light emitting device comprises a clamping device configured to secure a first housing part and a second housing part to each other.

According to one embodiment said clamping device comprises a first clamping member, which is connected to one of said housing parts and a second clamping member which is connected to the other one of said housing parts, said clamping members being configured to, in an assembled state of the housing, engage each other.

According to one embodiment said first clamping members is pivotally arranged to one of said housing parts.

According to one embodiment the dryer comprises several light emitting devices arranged at different levels of the dryer, as seen in a direction perpendicular to a direction of travel of said web.

According to one embodiment said housing is formed from metal, such as Aluminium.

According to one embodiment said dryer comprises a drying hood that encloses drying sections of the dryer.

According to one embodiment said heat transfer member comprises a 25 thermoelectric element, such as a Peltier element.

These and other aspects of the invention will be apparent from and elucidated with reference to the claims and the embodiments described hereinafter.

Brief Description of the Drawings

The invention will now be described in more detail with reference to the appended drawings in which:

Fig. 1 is a schematic side view, and illustrates a dryer for drying cellulose pulp according to an embodiment of the present disclosure.

20195684 prh 16 -08- 2019

Fig. 2 is a perspective view and illustrates drying decks and two light emitting devices of the dryer shown in Fig. 1.

Fig. 3 is a perspective view and illustrates a light emitting device of the dryer shown in Fig. 1.

Figs. 4a-4b are perspective views and illustrate a light emitting device of the dryer shown in Fig. 1.

Detailed Description of Preferred Embodiments of the Invention

Fig. 1 illustrates a cellulose pulp dryer 1 for drying cellulose pulp in accordance with the air borne web principle where cellulose pulp is dried by means of hot air while travelling along horizontal drying sections 5. The drying sections 5 will, in reference to the embodiment of Fig. 1, be referred to as drying decks 2. Typically, a dryer 1 would comprise 4-40 drying decks 2. Large dryers may even comprise 50 drying decks or more, but for clarity purposes a smaller number of drying decks 2 are illustrated in Fig. 1. The dryer 1 illustrated in Fig. 1 comprises 23 superposed drying decks 2 arranged in a housing 3. At a first end 4 of the housing 3 a first column of rotatable turning rolls 6 is arranged, and at a second end 8 of the housing 3 a second column of rotatable turning rolls 10 is arranged. Each drying deck 2 may typically be between 15 and 80 meters in length and between 1 and 15 meters in width, why the turning roll side walls 12 of the housing 3 normally constitute the short sides of the housing 3. For clarity purposes, only the end portions of the dryer 1, i.e. the portions of the dryer 1 which are close to the turning roll side walls 12 are illustrated in Fig. 1. The middle section of the dryer 1 is cut away, which is illustrated by vertical dotted lines in Fig. 1.

A wet pulp web 14 enters the dryer 1 via an inlet 16 arranged in a turning roll side wall 12 of the housing 3. In the embodiment of Fig. 1, the inlet 16 is arranged in the upper portion of a turning roll side wall 12, but the inlet may, in an alternative embodiment, be arranged in the lower portion of a turning roll side wall 12. The web 14 is forwarded horizontally, towards the right as illustrated in Fig. 1, in the dryer 1 until the web 14 reaches a turning roll. In the dryer 1 illustrated in Fig. 1, the web 14 will first reach a turning roll 10 of the second column of turning rolls. The web 14 is turned around the

20195684 prh 16 -08- 2019 turning roll 10, and then travels horizontally towards the left as illustrated in Fig. 1, in the dryer 1 until the web 14 reaches a turning roll 6 of the first column of turning rolls, at which the web 14 is turned again. In this manner the web 14 is fed through the housing 3 from the inlet 16 and travels, in a zigzag manner, from the top to the bottom of the dryer 1, as illustrated by arrows P. The web 14 leaves the dryer 1 via an outlet 18 arranged in one of the turning roll side walls 12 of the housing 2. In the embodiment of Fig. 1, the outlet 18 is arranged in the lower portion of the turning roll side wall 12, but the outlet 18 may, in an alternative embodiment, be arranged in the upper portion of the turning roll side wall 12.

Blow boxes 22, 26 are arranged in each of the drying decks 2. Each drying deck 2 is defined by a row of juxtaposed lower blow boxes 22, which at their upper side discharge heated air, through lower air openings 24, for drying the web 14. Each row of lower blow boxes 22 is associated with a row of juxtaposed upper blow boxes 26, which at their underside discharge heated air, through upper air openings 28, for drying the web 14. The air is blown through air openings 24, 28, which may have any suitable shape, such as circular perforations or so called “eyelid perforations”, which may have a similar design as the openings referred to as “eyelid perforations” in

WO 97/16594. The air openings 24, 28 are designed to keep the web 14 in a floating manner slightly above the lower blow boxes 22 in accordance with the air borne web principle. Typically, each drying deck 2 comprises 20-300 lower blow boxes 22 and the same number of upper blow boxes 26, although in Fig.

only the portions of the drying decks 2 close to a turning roll side wall 12 are shown, why only 16 lower blow boxes 22 and 16 upper blow boxes 26 are illustrated in each drying deck 2.

A wet forming station 39, only schematically illustrated in Fig. 1, is arranged upstream of the dryer housing 3 and forms, from a suspension of cellulose pulp, the wet web 14 entering the dryer housing 3.

One or several guiding rolls 40 are arranged at the outlet 18 of the dryer 1 and the web 14 is transported past the guiding roll 40.

Typically air of a temperature of 80 to 250°C is utilized for the drying process. The cellulose pulp entering the dryer 1, from a wet forming station

20195684 prh 16 -08- 2019

39, only schematically illustrated in Fig. 1, typically has a dry solids content of 40-60% by weight, and the cellulose pulp web 14 leaving the dryer 1 has a dry solids content of typically 85-95% by weight. The cellulose pulp web 14 leaving the dryer 1 typically has a basis weight of 800 to 1500 g/m², when measured at a moisture content of 0.11 kg water per kg dry substance, and a thickness of 0.8 to 3 mm.

As described above, the web 14 is fed in a floating manner between the lower blow boxes 22 and the upper blow boxes 26. The vertical height of a drying deck 2, i.e. the vertical distance between the upper side of the lower 10 blow boxes 22 and the lower side of the upper blow boxes 26 of a drying deck 2, is relatively small, for instance between 5 and 50 millimetres, whereas the width and length of a drying deck 2 is relatively large, for instance between 1 to 15 meters in width and between 15 and 80 meters in length.

The dryer 1 comprises several light emitting devices, two of which are illustrated in Fig. 2, arranged at different levels of the dryer 1, as seen in a direction perpendicular to the direction of travel of the web through the dryer 1.

Now referring to Fig. 2, which schematically illustrates portions of drying decks 2 of the dryer 1 without a web, two light emitting devices of the 20 dryer 1 will now be further described. A first light emitting device 41 is arranged to emit light at a first drying deck 2a and a second light emitting device 43 is arranged to emit light at a second drying deck 2b. The first and second light emitting devices 41,43 are identical to each other. As illustrated in Fig. 2, each of the first and second light emitting devices 41,43 is arranged 25 at a long side of the drying decks 2a, 2b by means of a respective mounting bracket 45, 47. Each of the first and the second light emitting devices 41,43 is connected to a 24V DC power supply (not shown) by means of cables 49, 51, respectively. In Fig 2, only one light emitting device is illustrated at each drying deck 2. It is however appreciated that each drying deck of the dryer 1 30 may comprise several light emitting devices arranged at the same vertical level that together emit light to the actual drying deck.

The light emitting devices 41,43 of the dryer 1 facilitate inspection of the drying decks 2. Especially, the light emitting devices 41,43 facilitate to

20195684 prh 16 -08- 2019 detect if any web residues are present at the drying decks 2. During a stoppage of production, the web is removed from the dryer 1. When the web is removed from the dryer 1 web residues might get stuck in one of the drying decks 2. The light emitting devices 41, 43 are then activated and emit light into the interior of the drying decks 2.

Typically, the light emitted by the light emitting devices 41,43 is a scattered light, which is spread widely in the interior of the drying decks 2. Light emitted by the light emitting devices 41,43 is obstructed by web residues present at the drying deck 2. As an effect of such obstruction, light 10 emitted by the light emitting devices 41,43 is reflected on the residues. The reflected light may be detected by an operator working at the dryer 1 or by an image sensor of a camera device. If such a camera device is used, the respective image sensor sends image information to an image processor included in an inspection device control system (not shown). An image processor of the control system analyses the image information provided by the image sensor and may, based on such analysis, determine the existence and position of a web residue. The coordinates of the detected web residue may e.g. be displayed on a monitor by the control system. Thus, an operator working at the dryer 1 can be informed that web residues are present at a particular drying deck 2, and the operator will also get the exact location of each web residue at the drying deck 2. The actual image of the detected web residue may also be displayed on the monitor controlled by the system, such that an operator may view the web residue.

Now referring to Fig. 3, the first light emitting device 41 will be further 25 described. The first light emitting device 41 comprises a housing 53. The housing 53 comprises a first part, in the form of a cover member 55, and a second part, in the form of a base member 57. Each of the cover member 55 and the base member 57 is made by metal.

The cover member 55, which is hollow, defines a light source compartment, in which a 24V light emitting diode (LED) is accommodated.

The light emitting diode 59, illustrated in Fig.4b, is connected to the 24V DC power supply by means of cables 49.

20195684 prh 16 -08- 2019

A clamping clip, in the form of an U-shaped metal wire 61, is pivotally connected to the cover member 55. The clamping clip 61 is configured to, in an assembled state of the housing 53, engage a clamping clip retaining portion 63 of the base member 57. In this embodiment, the clamping clip retaining portion 63 comprises several recesses 65a, 65b. A first group of recesses 65a is formed in a first protruding retainer 66 and a second group of recesses 65b is formed in a second protruding retainer 68. The clamping clip 61 and the clamping clip retaining portion 63 together form a clamping device 67. The clamping device 67 allows the housing 53 to be easily asssembled. In 10 the assembled state the clamping clip 61 maintains the members 55, 57 of the housing 53 secured to each other in a robust manner by engagement with the clamping clip receiving portion 63. Also, the clamping device 67 allows the cover member 55 to be easily removed from the base member 57 and thus facilitatates replacement of a LED during a stoppage in production, e.g.

during service and/or maintenance of the dryer 1. A sealing device may be used to seal the housing 53.

Now referring to Figs. 4a and 4b, which illustrate the interior of the light emitting device 41, the light emitting device 41 comprises a heat transfer member 69 and the light emitting diode 59, which is attached to a base plate 20 71 of the heat transfer member 69. The light emitting diode 59 may thus be attached to the base plate 71. In this embodiment, the light emitting diode 59 is fixedly attached to the base plate 71 by means of a thin mounting element 73 and screws (not shown). The base plate 71 of the heat transfer member 69 has a central opening (not shown) for power supply connections (not 25 shown) to the light emitting diode 59. If, as in this case, a mounting element 73 is used to attach the light emitting diode 59 to the base plate 71, also the mounting element 73 has a central opening for power supply connections to the light emitting diode 59. The power supply connections of the light emitting diode 59 are connected to a connection unit 75, which is connected to the 30 power supply of the light emitting device 41 by means of cables 49 for driving the light emitting diode 59. The connection unit 75 is secured to a support plate 77, which is secured to the base member 57 of the housing 53, e.g. by means of screws.

20195684 prh 16 -08- 2019

The heat transfer member 69 is configured to transfer heat away from the light emitting diode 59. To this end the heat transfer member 69 comprises several cooling fins 79 protruding from the base plate 71. The base plate 71 and the cooling fins 79 together from a heat sink, i.e. the base plate

71 forms a heat sink base and the cooling fins 79 form heat sink fins.

The heat transfer member 69 is attached to the support plate 77 by means of mounting elements, in this case by screws 81.

The heat transfer member 69, the light emitting diode 59 and connections, which are connected to the light emitting diode 59 and configured to be connected to the connection unit 75, together form a detachable lamp unit 83.

With reference to Figs. 4a and 4b, replacement of a light emitting diode 59 of the light emitting device 41 will now be described.

Firstly, the cover member 55 of the housing 53 is removed, as illustrated by arrow A in Fig. 3a. Then, the lamp unit 83 is disconnected from the connection unit 75 and removed from the support plate 77. In order to allow the lamp unit 83 to be removed from the support plate 77 after disconnecting the lamp unit 83 from the connection unit 75, the screws 81 are untightened. Then, a replacement lamp unit is fastened to the support plate

77 by means of the screws 81. Finally, the cover member 55 is attached to the base member 57, by means of the clamping device 67, to dose the housing 53, as schematically illustrated by arrow B in Fig. 4a. Replacement of a light emitting diode 59 thus involves replacement of an entire lamp unit, which provides for an easy and fast replacement.

The person skilled in the art realizes that the present invention by no means is limited to the embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.

Claims

1. Use of a light emitting device (41,43) to illuminate a portion of a first drying

5 section (5) of a cellulose pulp dryer (1), the cellulose pulp dryer (1) being operative for drying a web (14) of cellulose pulp by means of gas supplied through gas openings (24) of blow boxes (22, 26) of the first drying section (5), wherein said light emitting device (41,43) comprises a light emitting diode (59),

10 a heat transfer member (69) and a housing (53) accommodating said light emitting diode (59) and said heat transfer member (69), wherein said heat transfer member (69) is arranged to transfer heat away from said light emitting diode (59).

15

2. Use of a light emitting device (41,43) according to claim 1, wherein said heat transfer member (69) comprises at least one heat sink fin (79).

3. Use of a light emitting device (41,43) according to any of the preceding claims, wherein said heat transfer member (69) comprises a heat sink base

20 (71) and several heat sink fins (79).

4. Use of a light emitting device (41,43) according to any of the preceding claims, wherein said heat transfer member (69) is a separate part of said light emitting device (41,43).

5. Use of a light emitting device (41,43) according to any of the preceding claims, wherein said light emitting diode (59) and said heat transfer member (69) together form a lamp unit (83) being connectable to a connection unit (75) of said light emitting device (41, 43).

6. Use of a light emitting device (41,43) according to any of the preceding claims, wherein said light emitting diode (59) is fixedly attached to said heat transfer member (69).

20195684 prh 16 -08- 2019

7. Use of a light emitting device (41,43) according to any of the preceding claims, wherein said light emitting diode (59) is a DC light emitting diode.

5

8. Use of a light emitting device (41,43) according to any of the preceding claims, wherein said light emitting diode (59) is a 24V light emitting diode.

9. Use of a light emitting device (41,43) according to any of the preceding claims, wherein said light emitting device (41, 43) comprises a 24V DC power

10 supply configured to drive said light emitting diode (59).

10. Use of a light emitting device (41,43) according to any of the preceding claims, wherein said light emitting device (41,43) comprises a clamping device (67) configured to secure a first part (55) of said housing (53) and a

15 second part (57) of said housing (53) to each other.

11. Use of a light emitting device (41,43) according to claim 10, wherein said clamping device (67) comprises a first clamping member (61), which is connected to one (55) of said housing parts (55, 57) and a second clamping

20 member (63, 65a, 65b) which is connected to the other one (57) of said housing parts (55, 57), said clamping members (61,63, 65a, 65b) being configured to, in an assembled state of said housing (53), engage each other.

12. Use of a light emitting device (41,43) according to any of the preceding 25 claims, wherein the dryer (1) comprises several light emitting devices (41, 43) arranged at different levels of the dryer (1), as seen in a direction perpendicular to a direction of travel of said web (14).

13. Use of a light emitting device (41,43) according to any of the preceding 30 claims, wherein said heat transfer member (69) is formed from metal, such as

Aluminium.

14. Use of a light emitting device (41, 43) according to any of the preceding claims, wherein said dryer (1) comprises a drying hood that encloses drying sections (5) of the dryer (1).

5 15. Use of a light emitting device (41, 43) according to any of the preceding claims, wherein said heat transfer member (69) comprises a thermoelectric element, such as a Peltier element.