FI120002B - Procedure and arrangement in connection with the press section of a paper or cardboard machine - Google Patents

Description

METHOD AND COMPOSITION IN THE PAPER OR BOARD MACHINE CLAMBING PART

The invention relates to a method and arrangement for a press section of a paper or cardboard machine in which: - the web is passed between fabrics through at least one press nip, and - each web passes through an endless loop supported by rollers, 10 - at least one fabric is restored by nip on the opposite side, - the web is blown dry immediately after the press section.

15 Some paper machine press concepts are known from Finnish patent 112263. The press section usually has one or more nipples, at least one of which is currently a so-called. longip pepper press, or shoe press. Closed press outlets have been used to increase travel speed. On the other hand, the web box heating steam box has been able to increase the dry solids content after the press section. After the press section, it is preferable to use blowing because the first drying cylinders used as an alternative do not achieve full drying capacity due to the reduced vapor pressures. The web would also adhere to the 25 hot roller surfaces if run at full steam pressure.

By using blasting, the solids content can be raised to a level with good runnability. This results in a higher production speed and less interruptions and more efficient drying when higher vapor pressures can be used on post-blast cylinders.

In particular, the problem with the 1-nip press is the uneven moisture profile 35 which has been attempted to be corrected by a profiled steam box and a profiled blow.

Existing press parts are difficult to achieve with sufficient high speed SC quality (supercalendered), dry matter content 2 (KAP) moisture profile, and tissue life. The problem is to develop a concept for high speed SC, which at the same time produces high quality paper.

Generally, the prior art problem can be described as limited runnability and / or paper quality at high speed, limited KAP, moisture profile, and tissue life. In addition, the prior art wet wet drawing of the web at low KAP has the disadvantage of weakening the web and causing breaks later on in the paper machine, after finishing, or printing house, and degrading web quality with increasing porosity. The high need for wet drawing also limits the speed of the paper machine. The low compaction and smoothness of the surface of the web due to the high draw requirement of the prior art and the limited dewatering cause missing spots and dusting in the printing houses.

The object of the invention is to provide a method and an arrangement better than known devices in connection with a press section of a papermaking machine. Characteristic features of the method of the invention 20 are set forth in claim 1 and features of a corresponding arrangement implementing the method are set forth in claim 3.

By heating the fabric to be washed, heat is transferred through the web transmission to the post-press overflow, where "excess" heat is utilized not only to improve the drying efficiency of the press section. If the temperature of the tissue is increased, for example, from 50 ° C to 80 ° C, the blowing will be greatly enhanced.

30

In one embodiment of the invention, the press portion or said tissue cycle is covered with a hood if the temperature rise of the fabric is in the order of 20 ° C or greater. The hood is not required at lower temperatures, i.e., raising the temperature of 10-15 ° C with the fabrics 35 does not yet require covering the press due to the temperature savings.

The invention provides the following advantages: Increase of dry web content (KAP) prior to cylinder drying 3 Improvement of web quality (surface density, smoothness and moisture profile) prolongation of tissue life due to improved tissue repair 5 - Faster start of tissues in a warmer process,

Preferably, one or more of the following are used in the embodiments of the invention: 1) In addition to, or instead of, existing tissue repair, steam roller and vacuum reconstituted fabrics are used to improve dewatering, thereby increasing KAP and improving web quality. In addition, low vacuum and friction reduce tissue abrasion efficiency, prolong tissue life, and save energy (due to reduced frictional power, reduced vacuum efficiency).

2) An increased line load, such as 1000 to 1500 kN / m, is applied in the long nip (s) to provide effective paper surface sealing and KAP lifting.

3) Use extended tissue cycles to increase tissue life. This would advantageously provide additional production time which would otherwise be lost in tissue replacement, especially as speed and line load increase.

4) The hood can be applied to the press section, either to the overflow area or to the entire press section, depending on the temperatures used on the press section. This saves energy 30 when heat is not transferred to the data center.

5) The solution can be implemented with a press section by exporting the web to the upper or lower fabric side. It is advantageous to implement the solution as an upper tissue export if continued with blasting and as a lower tissue export if continued with cylinder drying with a drying section.

The invention is very profitable according to preliminary calculations.

The invention provides the following advantages: 4 1) A very significant additional saving in investment cost as the drying section and the machine hall become shorter. Significant additional yield to the mill as KAP rises, enabling higher speeds and improved paper quality -> more speed, less breaks, better paper sales price.

2) Little downtime compared to many of the solutions presented, as the number of components has been reduced and the switching interval has been increased.

3) Steam is a cheap heating energy.

io 4) More efficient steam conditioning provides longer-lasting tissue lifetimes for tissues.

The dewatering power and surface forming power of the press section are individually adjustable.

15

In the following, the invention will be illustrated by the examples set forth in the accompanying drawings.

Figure 1 shows a papermaking press concept 20 Figure 2 shows a modification of the solution of Figure 1

In the press concept shown in Fig. 1, the web (not shown) runs in a known manner from a pick-up roll 13 on the underside of an upper press felt 10 through a press nip N and thereafter between a press 25 and a felt suction roll 19 to transfer a web to a lower press felt 11. here for special blow drying and further to roll 24, after which the web is transferred to the next cylinder drying.

30

In a known manner, the press nip is formed by a long nip roll 16 and its counter roll 17. A special dryer provided after the lower felt 11 and the transfer wire 31 comprises an inflating unit 20 and a suction box 21 terminating in a turning roll 23 and a suction roll 35 22. These are essential The hood can also be used in the basement as shown in the picture.

Here, fabric loops 12 are provided in connection with the loops of the upper and lower press felts 10, 11, which is one way of introducing heat into the fabric during fabric washing. Preferably, the steam roller / suction cup maker is fitted with a folding roller as here, whereby the sealing surface of the loose seal opens and dirt can be removed more easily.

The tissue repair device 12 of the upper tissue loop 10 is disposed within a rotation of about 180 ° of the tissue loop, i.e., has a coverage area of about 180 °. Correspondingly, the lower tissue repair device 10 has a coverage range of about 150 °. Coverage is important in the context of such a conditioning device in which heat is introduced into the tissue by an internal steam box whose sector depends on the coverage area of the tissue (not shown).

It is essential to the present invention that the fabric conditioners 12 provide heat to each tissue which is partially transferred to the web and improves the dry matter rise in the press nip and the drying conditions, particularly in the overblowing process. The difference can be clearly seen. The fabric conditioner 12 here comprises the Fri-20 shower jets 12.1, the subsequent steam roller 12.2, and an anti-suction box 12.3.

When using a higher temperature rise (20 ° C or more), at least the upper loop of tissue is supported by a protective hood, which prevents heat from escaping.

In addition, the fabric / web may also be heated by the steam box 40 prior to the press nip to provide enhanced interaction.

30

In the variation shown in Fig. 2, the separate transfer wire between the press section and the overblowing section may have been dispensed with. For functionally similar parts, the same reference numerals as above are used. The 10 loops of the upper press felt are slightly extended 35, but otherwise the structure is simplified. The transfer suction roll 19 secures the passage of the web in the upper press felt until the next transfer suction roll 19.1 transfers it to the drying fabric of the blowing unit 20, after which the structure is the same as above.

6

Due to more efficient rehabilitation and heat, new types of fabrics (e.g., semi-permeable fabrics) can be used, which provide faster start-up than conventional felt and better web surface sealing than the transfer belt. These tissues cannot be successfully used with conventional rehabilitators because otherwise the partially permeable tissues become blocked too quickly.

Claims (4)

A method in connection with a press section of a paper or board machine, wherein: 5. the web is passed between the webs (10, 11) through at least one press nip (N), and - each web (10, 11) passes through an endless loop supported by rolls, (10, 11) is rehabilitated with a steam roller (12.2), a suction box (12.3) and washed with washing jets (12.1), - the web is dried by blowing (20) immediately after the press section, characterized in that - the washable fabric (10, 11) heating by said refining to transfer heat to the web, and - heating the tissue to transfer heat to the blast, and - isolating the press portion from the heated region with a hood (30) 20 to prevent uncontrolled escape of heat from said heating and blowing (20). Method according to Claim 1, characterized in that at least one press nip (N) has a line load of 200 to 1500 25 kN / m. An arrangement with a press section of a papermaking machine comprising at least one web-drying long nip (N) and fabric loops (10, 11) above and below the nip and at least one web 30 (12) fabric reconditioner (12) and a web over-blow dryer ( 20), and wherein the fabric conditioner (12) comprises wash jets (12.1), a subsequent steam roller (12.2) and an anti-suction box (12.3), characterized in that said fabric conditioner (12) is adapted to provide heat to the fabric loops (10, 11) and further to enhance drying of the web, and that the assembly includes a press member insulating hood (30) to prevent heat from escaping from the heated fabric. Arrangement according to Claim 3, characterized in that said fabric loop (10) is extended to divide the wear over a greater length. Arrangement according to Claim 4, characterized in that the fabric loop (10) above the nip (N) is arranged to convey the web directly to the fabric loop (20) of the special blow-drying.