FI116404B - Arrangement and method to prevent wear on calender thermo rolls - Google Patents

Description

Arrangement and Method for Preventing Wear of Calender Thermal Rolls 116404

The invention relates, for example, to an arrangement according to the preamble of claim 1 for preventing wear on the calender thermo rolls. The invention also relates, for example, to a method according to claim 6 for preventing wear on the calender thermo rolls.

In pursuit of higher travel speeds in on-line calendars, the temperatures of the used thermo rolls have increased, especially in multi-nip calendars. In order to improve the calendering result, a fine amount of water mist is sprayed onto the surface of the fiber web 10 entering the calender roll nip (s). It has now been found that, due to the improvement in the above calendering technique, problems are often encountered because the fibrous web coming from the drying section of the pulping step adheres to the hot thermal roller. Particularly easily, a filler such as kaolin, talc or calcium carbonate adheres to the surface of the thermal roller. Although the calendars have 15 pattern colors that continually clean the surface of each thermal roll, the loose material still consumes the surface of the thermal roll quickly, roughening it. This, in turn, degrades the calendering result, whereby the drop in quality must be compensated for by changing process parameters, such as raising the temperature of the thermo roll and / or increasing the humidity. However, changing process parameters increases costs and changing them may cause hardware issues if you move beyond the upper limits of process-specific process parameter control.

. The invention is intended to eliminate the disadvantages of the prior art. Thus, biscuit; the main object of the invention is to provide an arrangement as well as a method for preventing the wear of the thermal rollers.

It is a further object of the invention to provide an arrangement and a method of preventing thermal rolls from being worn without altering process parameters such as the amount of heat introduced into the roll nipple or the moisture of the fibrous web entering the roll nip.

''; The third object of the invention is to substantially reduce the adhesion of the fibrous web: to the surface of a hot thermal roll in a roll nip.

! ' The arrangement of claim 1 and the method of claim 6 achieve the above objectives.

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The sequenced calender according to the invention has one or more roll nips between which the fibrous web passes at the same time in profiled form, at least one of which comprises a pair of rolls having a thermal roll opposite the roll. Prior to said pair of rolls, the fibrous web is wetted with a wetting device and, prior to the wetting device 5, there is a dust removal device for cleaning the fibrous web adjacent the fibrous web entering the calender. In the method according to the invention, the fibrous web is cleaned by blowing gas on its surface before moistening the fibrous web.

The invention is based on the basic idea that, after drying the fibrous web, prior to moistening the fibrous web entering the calender, easily disintegrating material is often removed from the fibrous web, which is often a filler which is removed from the fibrous web as dry dust. The fibrous web is made by pulping a wet end of a papermaking machine onto a wire, in which case fillers are added. The pulping is followed by drying the pulp made on the wire into a low moisture content fibrous web. Thus, in this context, drying refers primarily to drying the fiber web formed on the dryer portion of the pulp. Also, the fibrous web coming from the coating of the fibrous web may be dusted after drying on the tumble dryer or similar drying apparatus, and therefore the dust removal arrangement of the invention may also be located immediately after the moistening of the fibrous web entering the calender.

Removal of dust from the fibrous web after drying after coating is described, for example, in US-A-4,019,953 and US-5,878,462 and US-A *! ! No. 5,577,294, but there is no indication of how this would improve the calendering result of a calender having at least one roll nipple in which one of the opposing rolls is a heated thermal roll.

The sequenced and used method of the invention effectively reduces the wear of thermal rolls without changing process parameters, since the amount of loose material such as filler released from the fibrous web to the surface of the thermal roll is substantially reduced by blowing the fibrous web before the calender. It has also been found that * even if the fibrous web is a paper web to which fillers are not normally added: '30 (eg newsprint, wrapping paper), the fibrous web is adhered to the thermo | . reduced by the arrangement according to the invention.

The invention is illustrated in more detail by means of the accompanying drawings.

Figure 1 is a schematic side elevational view of an arrangement according to the invention.

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Figure 2 is a schematic side view of the dust extraction apparatus used in the arrangement of the invention.

In the following, the main features of the arrangement of Fig. 1 and the main structures of the dust removal apparatus of Fig. 2 will be discussed first.

In the arrangement of Figure 1, the fibrous web W passes from left to right. When the W arrives from the dryer of the paper machine wet end dryer 6; 61, through the guide rollers 4 to the dust removal apparatus 3. From the dust removal apparatus, the fibrous web W continues to travel through the guide rollers to the first water box 2; 2 'and another water box 2; 2 ", with water boxes 2 wetting both 10 sides of the fiber web W. From the water boxes, the fiber web W extends to a multi-nip calender 5 having seven roll nips N, of which six pairs of roll nipples having a heatable roll opposite the metal or polymer surface.

The dust removal apparatus 3 of Figure 2 has a blowing device 32 for blowing air onto the fibrous web W and a suction box 31 for collecting dust discharged from the fibrous web.

The invention will now be described in more detail with reference to the accompanying drawings and a general description thereof.

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In the arrangement according to the invention, the fibrous web W is a paper web manufactured

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the paper machine at the wet end of the conveyor wire (not shown in the figure) in itself feels »* · 20 in which talc, kaolin calcium carbonate or •: ''! other fillers known per se depending on the type of paper. In the arrangement according to the invention, the fibrous web W arrives on a conveyor wire supported by the drying of the fibrous web 6. The figure shows the last dryer 61 of the drying apparatus 6 The fibrous web W arrives from the drying apparatus to the dust removal apparatus 3; , 25 with the conveyor wire still supported from below. A force is applied to the surface of the fiber web opposite to the supporting side of the fiber web W; 'Fresh air blasting with a blasting device 32 of a dust extraction device 3, which extends, preferably end to end, in the width direction of the fibrous web. Strong air blast; '; removing loose dust from the fibrous web W, which is mostly incomplete fibrous, '; 30 fillers bonded to the fibers of the web for pulp production, such as calcium carbonate! carbonate. The dust blown from the fibrous web W is recovered by the suction box 31 of the dust removal apparatus 3 located below the blasting device 32, on the same side as the blasting device and at a distance from said blasting device so that dust In the figure, the suction box 31 is schematically depicted without a vacuum pump providing the suction box suction function or the like. After the suction box 31, both sides of the paper web W are moistened with water boxes 2; 2'and 2; 2 ". The water boxes 2 are located near the surface of the fibrous web and have 5 nozzles extending transversely to the direction of travel of the fibrous web from which to spray water onto the surface of the fibrous web.

The fiber web 2 may be supported or unstretched upon arrival at the water boxes 2. From the water board 10, the fiber web W is transferred by guide rolls to the multi-nip calender 5.

The multi-nip calender of Fig. 1 has seven nip roller nip rollers. The N line of the Mo nip nip calender passing through the centerline of the rolls is located in an approximately vertical position. In a multi-nip calender, the top roll 51 and the bottom roll 52 are deflection compensated rolls of metal or polymer surface, for example provided with internal loading means of the roll. The top and bottom rollers may be moved in the direction of the track line P of the track by suitable hydraulic means coupled to the bearing housings of said rolls. The intermediate rolls 501 to 506 are either metal or polymer surface rolls, with the intermediate rolls 501 and 504 and 506 being heatable thermal rolls, the other intermediate rolls 502, 503, and 505 being unheated polymer rolls. In addition, the multi-nip calender has a load arm connected to the bearing housing of each intermediate roll. , ·. retractors capable of compensating, as desired, for the self-gravity of the intermediate rolls and for auxiliary means at the ends of the intermediate rolls, such as take-out rolls and thermal rollers; the weight of the scraps.

• «•» ':': The roll nipples N1, N2, N4, N5, N6 and N7 thus have the second roll of the roll pair heated; 25-color metal-coated thermo roll, opposite to which is a roll or roll of metal or polymer -: surface. Roll nipple N3 is a so-called pivot nipple having two unheated polymer-faced intermediate rolls facing each other. The desired nip-v is created on the roll nipples N, e.g. by moving the upper and / or lower roll 51, 52 relative to the track P

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and / or using internal loading means of the upper and lower rollers. The turning nipple is tar '; "30 peen fibrous web W on each side of profiling. For a more detailed structure of multi-nip calendars, reference is made to prior art in the art.

In the multi-nip calender, the fiber web W is guided from the roll nip to the other roll out end rolls connected to the end rolls of the intermediate rolls, whereby the fiber web travels between the roll nips: ... supporting the same heat and pressure in the roll web. Normally, the roll nipples in the thermal rollers (here 1 1 6 4 U 4 5 501 and 504 and 501) would have a considerable amount of filler and other loose material loosened from the fibrous web and this loosened material would have to be removed by scrapers. Due to surface wear, calendering control parameters such as water content and / or thermo roll temperature should be changed to achieve the same fiber web surface profiling.

In the arrangement shown in Figure 1, instead, much less material is adhered to the surface of the thermo rolls 501 and 504 and 501, since the surface of the fibrous web has been cleaned by blowing off the bulk prior to moistening the fiber web. In this case, the calendering result remains constant for the hel-10 bomb without changing the control parameters.

The foregoing or one embodiment of the thermal roller wear arrangement 1 and the dust extraction apparatus 3 used therein are apparent to one skilled in the art that the invention may be practiced in many other ways within the scope of the inventive idea set forth in the claims. Thus, the multi-15 nip calender may have more or less roll nipples. The dust extraction debris treatment of the invention can also be used in calendars with a single roll nip, where the second roll is a thermal roll. The wetting device used for wetting the fiber web may also be other types of device used for wetting the web, such as steam boosting or roller application equipment.

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Claims (6)

An arrangement for preventing calender thermal roller wear, wherein (1) is a calender having one or more roll nipples (N) between which a fiber web (W) passes at the same time and at least one of the roll nipples (N) is formed by a pair of rolls is a thermo roll and its counter roll, wherein before said pair of rolls, the fibrous web is wetted by a humidifying device (2), characterized in that before the fibrous web (W) entering the fibrous web (W) entering the roll roll (s) (s) (2), however, after the fibrous web drying apparatus (6), there is a dust removal apparatus (3) adjacent to the calendering fibrous web to clean the fibrous web. 1 1 ό 4 u 4 Arrangement (1) according to Claim 2, characterized in that the drying apparatus (6) is used to dry the fibrous web coming from the pulp manufacture. Arrangement (1) according to one of the preceding claims, characterized. \ that the fiber web to be cleaned (W) is a paper web containing filler,. of calcium carbonate. Arrangement (1) according to one of the preceding claims, characterized in that the calender (5) is a multi-nip calender with a lower roll (52), an upper roll (51) and · '*' two or more intermediate rolls (50), (50, 51, 52) at least one is a ter- * ... 'motel. ., ;; A method of preventing wear on the thermal rollers of the calender (5), wherein the fish blades have one or more roll nipples (N) between which the fibrous web (W) passes. at the same time, at least one of the roll nipples consists of a pair of rolls having a thermal roll opposite the roll, wherein before said pair of rolls the fiber web is wetted, characterized in that the fiber web (W) is cleaned to blow telanip; *: 30 wetting of the fibrous web (W) entering the silicon / roll nipples (N), but still after the fiber drying apparatus (6). The method according to claim 1 to 5, characterized in that the gas such as air is blown onto the surface of fiber web of the second side of the fibrous web being supported. 1 1 6 4 ϋ 4