CN117071316A

CN117071316A - Method for use in a pulp dryer and cutting device for a pulp dryer

Info

Publication number: CN117071316A
Application number: CN202310552951.9A
Authority: CN
Inventors: M·基乌鲁; V·科尔皮尼蒂
Original assignee: Valmet Technologies Oy
Current assignee: Valmet Technologies Oy
Priority date: 2022-05-17
Filing date: 2023-05-16
Publication date: 2023-11-17
Also published as: AT526181A2; DE102023112845A1; AT526181B1; FI20225431A1; AT526181A3; FI130563B

Abstract

The present invention relates to a method for use in a pulp dryer and a cutting device for a pulp dryer. The method comprises forming (10) a pulp web (14), and pressing (11), drying (12). The method then includes slicing the formed pulp web (14) into sheets (24), and stacking the sheets (24) into packs (32). The method further comprises monitoring the production of the pulp web (14). According to the method any discontinuity in production is detected by monitoring, but slicing (13) of the remaining pulp web (14) is continued until slicing (13) is stopped.

Description

Method for use in a pulp dryer and cutting device for a pulp dryer

Technical Field

The present invention relates to a method for use in a pulp dryer, comprising forming a pulp web, and pressing, drying, then slicing the formed pulp web into sheets, stacking the sheets into bales, and monitoring the production of the pulp web. The invention also relates to a cutting device for a pulp dryer.

Background

The formation of a pulp web is a lengthy process comprising different successive stages. In each stage and between stages, the pulp web may break or for some other reason the production has to be stopped suddenly. During web breakage, the pulp travels to the breakage treatment in the wet and dry parts, the breakage is cleared, and production begins again. There is an operator monitoring the production.

Web breakage occurs more easily in the production stage before the drying box than in the drying box. In other words, the pulp web is still wet at the time of forming and pressing. The drying box is also large and it accommodates hundreds of meters of pulp web. However, information about web breaks during forming or pressing is passed in a delayed manner to the slicer after the pulp dryer or not at all to the slicer after the pulp dryer. After breakage, the pulp web proceeds to the pulper after the drying box and the slicer is stopped. Problems may also occur in microtomes if the delay time is long. Moreover, a large amount of pulp web must travel into the pulper to empty the pulp dryer before production begins again.

Disclosure of Invention

The object of the present invention is to provide a new method for use in a pulp dryer which is more economical, safer than previous methods and which is easy to implement in pulp dryers. Another object of the present invention is to provide a new cutting device for pulp dryers that can cut narrow pulp strips stably and quickly. According to the present invention, there is provided a method for use in a pulp dryer, comprising: forming a pulp web, and pressing, drying, then slicing the formed pulp web into sheets, stacking the sheets into bags, and monitoring the production of the pulp web, the slicing of the remaining pulp web continuing until the slicing is stopped, even if any discontinuity in the production is detected by the monitoring. According to the invention there is also provided a cutting device for a pulp dryer, the cutting device comprising a frame supporting a pinch roller and a blade operated by an actuator for cutting off a narrow strip separated from a full width pulp web. By this method, the amount of breakage can be significantly reduced. This increases the yield of pulp and thus profits. At the same time, the downtime of the pulp dryer is reduced and the stopping and restarting of production can be achieved with low labor. Moreover, the stop can be controlled completely. This further shortens the downtime and prevents damage to the device. The cutting device is strong and also easy to install to the pulp dryer.

Drawings

The invention will now be described in detail with reference to the accompanying drawings, which illustrate some embodiments of the invention, wherein:

figure 1 shows a main side view of a pulp dryer,

fig. 2 shows an enlarged view of a part of fig. 1, which shows a microtome for a pulp web,

figure 3a shows the start of the stop of the microtome according to the invention,

figure 3b shows the separation of the strips of pulp web,

figure 3c shows the introduction of a cutting device on top of the strip,

figure 3d shows the beginning of the deployment of the strip,

figure 3e shows the unfolded end of the strip,

figure 4 shows the slicer of figure 2 during a stop,

figure 5a shows a cutting device according to the invention during normal production,

figure 5b shows the cutting device of figure 5a before breaking,

fig. 5c shows the cutting device of fig. 5a just after disconnection.

Detailed Description

Fig. 1 schematically shows a side view of a pulp dryer with a method and a cutting device according to the invention. The pulp dryer comprises in succession: the forming section 10, the press section 11 and the drying box 12, and finally a slicer 13 for the freshly produced pulp web 14. In the forming section 10, an aqueous slurry (aqueousslurry) is fed onto the wire section 15 through a headbox 16. A pulp web 14 is formed on the forming section 10 by removing water. The pulp web is then pressed several times in the press section 11, whereby more water is removed. After the press section 11, the pulp web 14 is led by an open draw section to a drying box 12. Later, the forming section is equivalent to forming, the pressing section is equivalent to pressing, the drying oven is equivalent to drying, and the slicer is equivalent to slicing. The same reference numerals are used accordingly.

The drying box 12 has an enclosure 17 comprising superimposed drying decks. Only a small portion of the oven 12 is shown in fig. 1. Each drying plate has a rotating roller at both ends and a blow box therebetween. In an air-cushion (airbed) drying oven, the pulp web travels horizontally in a zigzag manner via a drying plate. Between the turning rolls, the air blown out of the blow box supports and dries the pulp web. The pulp web moves over the air layer. Typically, the pulp web enters from the top of the hood 17 and exits at the bottom of the opposite end. The height of the dryer plate is mainly dependent on the amount of air required and the width of the pulp web. The wider the pulp web, the higher the blow box and the higher the drying plate. In practice, the height of the drying plates is 250mm-800mm, and there are typically 10-30 drying plates in one drying box.

In a microtome, a uniform and full width pulp web is first cut into sheets in the machine direction and then in the cross direction, after which it is piled up into packets. Fig. 1 and in particular fig. 2 show the slicer 13 in operation. Microtomes are used for pulp webs produced by pulp dryers as previously described. Between the drying oven 12 and the slicer 13 there is a draw press 18 and a pulper 19. The draw press pulls the entire pulp web out of the oven. Here, the traction press 18 is preceded by a scanner 20 for determining properties of the pulp web 14 (FIG. 1). If the pulp web breaks somewhere, it proceeds down to the pulper 19 and the remaining pulp web is drawn out of the drying box by a traction press. During the emptying of the drying cabinet, the microtome is stopped and cleaned, if necessary. There is also another pulper 19' for handling the breaks from the press section 11 and the drying box 12.

The slicer 13 successively includes: a slitter (slit) 21, a cross cutter (cross cutter) 22, and a tabbed (layboy) conveyor belt 23 for stacking cut sheets 24 prior to a bagging station 25. The slitter 21 comprises several parallel blades 26 arranged against a bottom slitter 27. As the pulp web 14 travels through the slitter 21, several strips are formed. From there, the strips are pulled by a feed press 28 and pushed further to the crosscutter 22. In other words, slitter 21 longitudinally cuts the pulp web 14 into parallel strips that are then transected into sheets 24 by a rotating cutting roll 29 with transecting blades 30 and stationary counter-blades 31. These sheets are then stacked by a knock-up belt 23 and sent in packets to a packing station 25. The bagging table descends little by little until the bagging is completed.

The method is carried out in a pulp dryer and comprises forming 10 a pulp web 14, then pressing 11 and drying 12 the pulp web, and finally slicing 13 the formed pulp web 14 into sheets 24 and stacking into bales 32. Slicing occurs in the slicer 13. Moreover, the method includes monitoring the production of the pulp web 14. According to the invention, slicing 13 of the remaining pulp web 14 is continued until slicing 13 is stopped, even if any discontinuity in production is detected by monitoring. In other words, the cut sheet continues and the sheet is baled despite the production discontinuity. In this way, more bags are produced, reducing breakage. Moreover, less pulp remains in the drying cabinet, which saves cleaning time of the pulp dryer in the event of breakage. In practice, the breakage detector at the wet end initiates a stop sequence comprising said continuation and stop of the slice.

The method further comprises monitoring the forming 10 and the pressing 11 of the pulp web 14. In other words, the forming section and press section are monitored, as these stages are the most vulnerable. When web breakage occurs, a trigger for stopping the microtome is detected. Also, the slice continues despite the trigger. But now triggered information is known without delay so production and stopping of the microtome can be done in a controlled manner.

The trigger may be a visual observation by the operator when web breakage occurs. The operator then initiates the necessary actions to reduce production. Additionally or alternatively, the method comprises selecting as a trigger a signal from a control system 33 comprised in the pulp dryer. One or more sensors, probes, etc. may be used to detect web breaks.

In practice, the method still includes continuing with the slice 13 until the next set of unfinished packets 32 is ready. In other words, at least the unfinished packet is completed. Thus, a suitable set of packages is obtained and they can be shipped to the market at full price. When the pack is ready, the slicer is stopped and production is started again later, if necessary.

On the other hand, the method comprises determining the amount of pulp web 14 remaining and continuing slicing 13 until the group of packs 32 based on the determined amount is ready, or as long as the pulp web remains tensioned so that it does not travel sideways. For slicing, the pulp web should have a certain tension. In practice, here the performance of the pulp dryer is known in advance. In other words, it is possible to determine how much pulp web is in the drying box when the web breaks. The slicing and bagging of the groups of packets then continues until the drying box is almost empty. In practice, up to three or four groups may even be accomplished depending on the pulp dryer in question.

As previously described, the operator may initiate a stop of production. Advantageously, the stop is arranged as an automatic sequence. In practice, all or at least most of the necessary actions are automatically performed when the control system detects a web break. At the end of the pulp dryer, i.e. after the drying cabinet, the steps are as follows.

The method includes, during a stop, first separating the narrow strip 34 from the full width pulp web 14. Typically, the width of the separated strips 34 is 50-300mm. In practice, the method includes separating the strips 34 by water jet cutting or mechanical cutting. The position of the water cutter is indicated by an arrow in fig. 1. In fig. 3a, the water jet cutter 35 is moved to the edge of the pulp web 14. The water jet cutter 35 then begins cutting and separates the narrow strip 34 (fig. 3 b). Both the strip and the rest of the pulp web are still pulled to the cutter. Slicing and packaging may still continue. However, before the actual stop, the method includes opening the waste door 36 arranged after the slice 13. This is shown in fig. 4, where the cut sheet 24 is directed downwards towards the pulper 19. Here the strip 34 is truncated and it falls down towards the pulper 19.

Next, the method includes breaking the strip 34 prior to slicing 13 and fully deploying the strip 34 again while pulling down prior to slicing 13. The strip 34 breaks between the traction press 18 arranged before the slice 13 and the feed press 28 contained in the slice 13. Here, the method comprises breaking the strip 34 on a feed roll 37 arranged between the traction press 18 and the feed press 28. In this position both the bar and the pulp web are under tension, which promotes breaking. Before the actual breaking, the method comprises pressing a movable pinch roller 38 against the feed roller 37, said movable pinch roller having a width corresponding to the strip 34. In fig. 3c, pinch roller 38 is pressed against feed roller 37. The strip thus travels through the nip formed by the pinch roller and the feed roller. In this way, the strip travels steadily before breaking.

Finally, the method includes striking the strip 34 prior to the feed roll 37. In other words, the strip is broken by striking, here by striking the strip 34 with an actuator operated blade 39. In fig. 3d the strip travels down to the pulper 19, while the remaining pulp web 14 still travels to the slicer 13. The water jet cutter 35 is then moved towards the other edge of the pulp web (here left to right). Thus, the strips become wider and the rest of the pulp web becomes narrower. During widening the strip travels down to the pulper. In fig. 3e the strip is almost completely widened. When the water cutter reaches the edge of the pulp web, the whole pulp web travels down to the pulper and nothing enters the slicer, so that the slicer can be stopped or at least cleaned before production is started again.

In fig. 5a, the pulp web 14 travels normally via the feed roll 37. The cutting device here comprises a pinch roller 38 with a blade 39. This unit is supported by an articulated arm 40 to a bracket 41. The upper part of the unit is connected to a bracket 41 by means of an air cylinder 42. Therefore, pinch roller 38 can be easily pressed against feed roller 37 by using air cylinder 42 (FIG. 5 b). The blade 39 is then pushed into the strip 34 by means of the actuator 43 (fig. 5 c), the strip being truncated. In other words, the cutting device comprises a support 41 supporting the pinch roller 38 and a blade 39 operated by an actuator for cutting off the narrow strip 34 separated from the full width pulp web 14. In addition, puck 38 is supported to a frame 41 by an articulating arm 40 and an air cylinder 42. The unit further comprises a guard 49, which in this respect protects the cutting device and the user from the blade. The cutting device shown is compact and robust. It can be easily automated and the narrow strip is cut stably. The action of the device is rapid, so that the stopping of the microtome can be rapid, but still controlled. After stopping, the puck is lifted. The blades are preferably serrated impact blades extending transversely across the separated strips. Furthermore, the cutting device is even easy to install on older pulp dryers.

The knock-up belt 23 includes a plurality of independent sets 44 of support rollers 45 disposed opposite pinch rollers 46. There is a set of pinch rollers for each feed roller. In this way, a nip is formed between the backup roll and the pinch roll. When the backup roller is driven, the sheet moves forward. As shown in fig. 2, at the first set 44, the sheets 24 have been partially stacked. For the next few groups, the sheets are further stacked and finally, at the packing station 25, the sheets are stacked on top of each other to form a package. After the baling station, the bale is wrapped and also typically bundled and transported forward.

There is also a waste gate 36 positioned below the code conveyor 23. At a stop, the sheet will fall down to the waste gate 36 and thus to the broken slide 47. With the method according to the invention, the stopping of the microtome is newly arranged, and the slitter 21 and the crosscutter 22 can be arranged in a safety barrier 48. This improves occupational safety and reduces waste. Meanwhile, the transverse cutting machine can be reversible. In normal production, the speed of the sheets decreases after the stacking step, and therefore, the leading edge of each sheet is placed on the trailing edge of the preceding sheet, resulting in the sheets being partially stacked on each other.

Claims

1. A method for use in a pulp dryer, comprising: forming (10) a pulp web (14), and pressing (11), drying (12), then slicing (13) the formed pulp web (14) into sheets (24), stacking the sheets (24) into packs (32), and monitoring the production of the pulp web (14), characterized in that the slicing (13) of the remaining pulp web (14) is continued even if any discontinuity in the production is detected by the monitoring, until the slicing (13) is stopped.

2. A method according to claim 1, characterized in that the forming (10) and the pressing (11) of the pulp web (14) are monitored.

3. A method according to claim 1 or 2, characterized in that a signal from a control system (33) comprised in the pulp dryer is selected as a trigger.

4. A method according to any one of claims 1 to 3, characterized in that slicing (13) is continued until the next set of unfinished packages (32) is ready.

5. A method according to any one of claims 1-3, characterized in that the amount of the remaining pulp web (14) is determined and slicing (13) is continued until a group of packs (32) based on the determined amount is ready.

6. A method according to any one of claims 1 to 5, characterized in that the stopping is arranged as an automatic sequence.

7. A method according to any one of claims 1-6, characterized in that during the stopping a narrow strip (34) is separated from the full-width pulp web (14) and the strip (34) is broken before the slicing (13) and the strip (34) is fully unwound again while being pulled down before the slicing (13).

8. A method according to claim 7, characterized in that the strip (34) is broken between a traction press (18) arranged before the slice (13) and a feed press (28) comprised in the slice (13).

9. A method according to claim 8, characterized in that the strip (34) is broken off on a feed roll (37) arranged between the traction press (18) and the feed press (28).

10. Method according to claim 9, characterized in that before the breaking, a movable pinch roller (38) is pressed against the feed roller (37), the movable pinch roller having a width corresponding to the strip (34).

11. A method according to claim 9 or 10, characterized in that the strip (34) is impacted before the feed roller (37).

12. The method according to any one of claims 7 to 11, wherein the separated strips (34) have a width of 50mm-300 mm.

13. Method according to any one of claims 1 to 12, characterized in that before the stopping, a waste door (36) arranged after the slice (13) is opened.

14. Cutting device for a pulp dryer, characterized in that the cutting device comprises a frame (41) supporting a pinch roller (38) and a blade (39) operated by an actuator for cutting off a narrow strip (34) separated from a full-width pulp web (14).

15. Cutting device according to claim 14, characterized in that the pinch roller (38) is supported to the support (41) by means of an articulated arm (40) and an air cylinder (42).