FI118972B - Process and assembly to wash and recondition a dewatering belt web used in paper manufacture has water inlet gap in close proximity to rotating drum - Google Patents

Abstract

Claimed is a process to clean an recondition a dewatering web (10) employed in a papermaking process in which the web passes around a rotating drum (121) mantle (129) where it is exposed to water jets and/or steam and a suction zone (25). An inlet gap (128) is located on or in close proximity to the drum, through which washing water impinges on the web at high pressure. The inlet gap is located between the web and a roller (121). The web is washed both sides before entering the gap. Further claimed is a commensurate washing and reconditioning assembly.

Description

118972 METHOD and device for the repair of endless tissue

The present invention relates to a method and apparatus for endless water-permeable fabric rehabilitation of a paperboard machine, wherein the fabric rotates a perforated rotating roll as this jacket is carried out of the coverage area and is applied to the fabric with at least a portion of and, respectively, a suction area is provided outside.

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During the manufacturing process, fibers and other materials adhere to paper machine tissues. The press fabrics are worn, soiled, compacted and their ability to remove water in the press nip is impaired. The press section utilizes felt suction box, high pressure jets, low pressure jets, counter scraping, steam box against conventional felt suction box, and compressed air conditioning through the tissue for continuous repair of the press fabrics. Known rehabilitation methods using a felt vacuum cleaner consume tissue because the tissue rubs against the lid 20 of the felt vacuum cleaner. Compressed air conditioning is expensive and inefficient compared to water purification, which, in turn, often results in degradation of the dewatering properties of the fabric. In addition, high-pressure jets of water consume and even damage the tissue with targeted jets, causing uneven distribution of water into the fabric, and hence a change in the moisture profile.

«• · · • · · · ·: 3; The disadvantage of the steam box is that, against a conventional felt vacuum cleaner, the steam pressure and the vacuum can only be used on the crane. This is due to sealing and abrasion problems (the fabric dries up as the vapor pressure / vacuum increases as • · 1 'also leaks). Rehabilitation power and tissue dehydration power are • ·: 1 ·· inadequate in the prior art.

2 · · · 1 · · 3 35 of U.S. Patent Nos. 2,352,991 and 4,116,762 are known in the art. rabbit where the loop of tissue is guided around the hole roll. The holes · ·· * 1 provide a differential pressure across the fabric that drains the wash water 2 118972. 991 employs a traverse suction device inside a roll. In '762, air or gas is introduced into the coverage area from the internal pressure chamber of the roll through a perforated diaper through the tissue and sucked in an external suction box, respectively, to remove water from the tissue. Here, the overpressure and suction areas extend over the entire tissue coverage area.

The object of the invention is to provide a method and apparatus for tissue repair that is better than known devices 10. Characteristic features of the present invention will be apparent from the appended claims, the internal chambers of the perforated roll may be limited to different pressure ranges, providing a more economical roll design and the ability to use increased roll internal pressure with the following advantages: Because of the scrubbing, better control of the final moisture after tissue repair and greater heat transfer to the tissue (higher dry solids content, KAP).

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Some of the water in the tissue is easily released by ... ... frictional pressure, centrifugal force, and gravity, and by utilizing * * * this phenomenon, the suction means can be reduced by shortening the suction box • · · '· * *.

·· ♦ ...: 25 • · · In one embodiment, water jets are used before the sting,:.,, Σ, where most of the wash water is easily removed by a simple arrangement of the invention: **, which saves the suction system. Suction box and. . ·. 30 less water is added to the entire system. Compared to • # · ··· .···. the conventional scrubber / vacuum cleaner combination of the invention may use more washing water and thus: *** regenerate the tissue with better washing.

»··• · t« · * · 35 The internal overpressure of the roller is also advantageous for the said initial part, ·]. la, whereby the flow of medium through the diaper drives the wash water out of the tissue. In another preferred embodiment, the 118972 3 talaroma overpressure zone at the beginning and the higher overpressure zone are used thereafter.

In embodiments of the invention, the press fabric is cleaned and heated using one or more of the following: 1) The fabric is first washed with warm water from the inside and / or outside. The use of warm water is advantageous in terms of washing performance, moisture profile and KAP. io 2) The roll shell holes, fabric and roll boundary layers then carry air into the roll and fabric sealing kite, which creates an overpressure that can be adjusted by adjusting the pressure of at least one of the roll chamber's steam chamber -> water exits and cleans the tissue. Also, if the web is adhered to the tissue, it will come off at this point. The idea for energy saving is as follows: Because the air layer is between the steam and the water leaving the tissue, the heat energy of the steam is not transferred to the water leaving the tissue so that the heat energy of the steam is minimized to heat the water leaving the tissue.

... 3) Then a low vacuum zone begins, which S * * removes from the tissue the water created when the steam condenses into · · · * · '* water. This will warm and clean the tissue. • • .i * 25 pressure zone slot width depends on roll overpressure zone • ·:. · ·, Narrower at high overpressure to prevent: pj *: fabric bending towards the box.

4) Finally, the low vacuum zone may extend slightly beyond the steam zone to allow condensation water to flow. . ·. 30 better to suck out tissue even at high tissue speeds ···. • and provide an appropriate level of moisture in the fabric for the • · T nipple drainage.

··· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · There are the following optional solutions: 35 * ·· Τ '. 1) Additional nozzles may be used to enhance the edge wash.

118972 4 2) Easy-to-replace wash pipes can be used to facilitate changing of nozzles.

3) Joint oscillation with wash showers can be used to save costs.

4) If necessary, scrape the web side of the tissue with a scraper or suction box front seal to remove dirt and water from the surface.

5) The seals may, for example, be spring-loaded.

Other advantages and embodiments of the invention will be apparent from the Examples.

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

Fig. 1 shows a press section of a papermaking machine with fabric conditioners according to the invention and the beginning of a drying section

Figure 2 shows a cross section of a tissue fabricator 20 Figure 3 shows another tissue fabricator

Figure 4 shows the suction box slot system of Figure 2 • · ·: In the press concept shown in Figure 1, the web (not shown): * · *: passes in a known manner from a pick-up roll 13 on the lower face of the upper presser

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:. ·, Between the crochet blankets 10 and 11 for a felt suction roll 19, from which ··· *. ·. with the aid of a suction device, first passes through a vertical overflow dryer 20 and then through a horizontal overlay dryer 21 to a first drying cylinder 22.

The press nip N is formed in a known manner by a long nip roll • · 16 and its counter roll 17. These, as well as the blow dryers, are not essential to the present invention, as is the possible hood 30 at least partially surrounding the press member.

This prevents the heat from escaping if the press is raised to a significantly higher temperature than the machine room temperature. The hood may also extend into the basement as shown.

For the purposes of the present invention, fabric repair devices 12 arranged in the loops of the upper and lower press-5 felts 10, 11 are essential.

One preferred embodiment of the fabric conditioners of the invention is a single nip two-felt press followed by blow-drying prior to cylinder drying. In this case, the increased temperature of the press fabrics will assist in the rehabilitation and further enhance the operation of the press nip with clean, temperature-controlled fabric. Further, in this way, the temperature of the web can be raised, which is advantageous in the subsequent over-drying of the press as evaporation enhancement.

The fabric conditioning device 12 of Fig. 2 is disposed about 180 ° with a pivotable loop of fabric, the fabric covering area of the roll being about 180 °. The web 10 rotates a roll 121 having a 20 perforated jacket 129 and separate chambers 122 and 123 within it, close to the closing cam 128, the jets 125 and 126 that form the wash jet are on both sides of the fabric. Optionally high pressure washer nozzles 124 · * · *; (dashed lines). The bulk water is designed to drain into the bottom 25 outlet trays 127. In the center of the coverage area, the roller 121 has a suction box 25. It is essential that the suction box

"Point V is located at an interval L from the beginning of the coverage area

I "is about 30 ° (generally 20 ° to 45 °) on the circumference of roll 121. The steam * · * · * 1a / suction box conditioner is preferably provided with a folding roll such as 30 here to open a dense surface and remove dirt: ** easier Because of the shower jets, the fabric becomes damp just before the coverage area. A slight overpressure of either air or steam is supplied to chamber 123. 35 rye. The main water-driving force of the fabric 10 is created by the fact that the fabric 10 and the roller 121 supply air to the sealing seal, where the fabric and air are compressed into contact with the roller. This causes an overpressure that pushes water out of the tissue with the help of gravity and centrifugal forces. A slight overpressure in chamber 123 assists in the removal of water from the tissue.

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A considerable amount of dewatering already takes place along the length L of the initial coverage area. Thus, the vacuum in the suction box 25 can be reduced to a lesser degree by leaving only a portion of the tissue wash water to be removed. The chamber 122 has a vapor pressure 10 greater than the chamber 123, which provides a large thrust for pushing water through the tissue 10. The suction chamber 25 extends a sector D further in the coverage area than the chamber 122 to suck condensed water out of the tissue and achieve the desired final tissue moisture for the next nip dewatering. For example, in a single nip press, all water removed from the tissue releases a limited amount of water in the tissue, whereby the water removed by extrusion from the web is transported away from the web to the dewatering of the rehabilitation.

The suction surface 251 of the suction chamber 25 comprises a slit system according to Figure 4. At high pressure chamber (sector C) ... the slit width (e.g. about 10 mm) is smaller than other * · ·; 1 / sectors (sectors B and D, e.g. 15 mm). This prevents the felt from being punctured or generally bent, which would result in an increase in operating efficiency and premature wear of the tissue. Slit strips provide pressure pulses, ί Ϊ1: for efficient removal of dirt.

··· m · 7 11S S-7 2 A larger roller, eg 1000 - 1250 mm in diameter, must be used with a blower / steam box size similar to a nessector and similar pressures (or wide and fast machines). In addition, this "1/4 box" application can be divided into at least 5 sectors of different sizes, with a higher pressure in the subsequent and smaller sectors. The diameter of the roll is thus between 600 and 1250 mm, depending on the speed, width, tissue position of the machine, since the contamination of the tissues, the amount of water, the permeability, and the desired ice-10 moisture content still depend on them.

The fabric can be tightly sealed against the curved suction box and steam roller. In this case, the amount of energy lost in leaks can be minimized. The fabric is also supported against the roll so that the fabric does not undergo abrasive abrasion against the seals as the differential pressure increases, as with a conventional felt suction box. Therefore, a high vacuum under the curved suction box may be used if necessary and a steam roller pressure and / or heat applied to the tissue roller for cleaning and heating the tissue.

··· Centrifugal force also contributes to the removal of water from the tissue.

»* •• · ϊ 25 It is very advantageous to use low pressure steam (0 - 1.5 bar), • ϊ.ϊ: then it is possible to use the advantageous residual steam for higher pressure applications (eg drying section) (where comes only the cost of irreversible condensation), or runs more electricity on the turbine when the pressure difference is greater. 30 turbines. In addition, vacuum capacity and electricity save ···. ···. using a low vacuum in the • · * ”pressure chamber.

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The invention is very profitable according to preliminary calculations.

.,, 35 The invention allows for a larger KAP press section) "*. And longer tissue life, and lower tissue scrubbing power, resulting in energy savings. In addition, 118972 8 additional heat of the web warms the track and positively affects the web. It is also possible that the heat of the fabric will have a positive effect on the smoothness of the paper, and it is also possible to use a smaller nipple load for a cleaner and warmer fabric, which reduces the fabric's compactness and increases its life.

The washing and heating power are adjustable by adjusting the steam pressure and temperature, as well as by adjusting the vacuum and the pressure and temperature of the kaa-10 Reva felt suction box on a case-by-case basis.

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Claims (13)

A method for reconditioning an endless, water-permeable fabric (10, 11) of a paper or board machine, wherein the fabric 5 wraps around a perforated rotating roll (121) as it is carried by the covering area, and wherein the fabric is subjected to washing jets. providing at least a portion of the coverage area of the tissue (10, 11) with media overpressure and an exterior suction region, characterized in that the circulation of the fabric (10) is arranged such that sector D at the end of the coverage area A method according to claim 1, characterized in that the total tissue coverage area of the swivel roll is 120 ° to 190 °, most preferably 160 ° to 185 °. A method according to claim 1 or 2, characterized in that said vacuum is outside the swivel roll and the overpressure medium supply is positioned inside the swivel roll (10, 11). • m A method according to any one of claims 1 to 3, characterized in that the water jet is arranged immediately prior to the closure formed by the press fabric and the swivel roll (10,11). A frictional friction (128), wherein the overpressure formed in the spout (128) pushes the washing water through the fabric (10, 11). ··· ··· • · · ··· A method according to any one of claims 1 to 4,. 30 characterized in that the pressurized medium is at least partially • · «!!! steam. • * • «t ·· • 1 ·· The method according to any one of claims 1 to 5,: ***: characterized in that the maximum total tissue affecting *. The 35 differential pressure is 30 to 120 kPa. «··« «· 1 • · • · · A method according to any one of claims 1 to 6, characterized in that a free length (L) is provided at the beginning of the coverage area prior to the suction area for collecting bulk water at this length by means of overpressure, centrifugal force and gravity. 5 A device (12) for reconstructing an endless fabric (10, 11), comprising: a rotatable roll (121) having a perforated jacket to support the fabric within a selected coverage area and in a rotational direction prior to the roll, washing means (125, 10 126) comprising fabric-directed jets; wherein: - the roller (121) includes at least one pressure chamber (122, 123) for introducing pressurized medium through the holes in the diaper to the fabric (10, 11) to expel the washing water therefrom, - on the opposite side of the fabric (10, 11) ) for sucking the washing water out of the fabric, characterized in that, in the direction of rotation, the fabric coverage area of the suction box (25) of the covering area 20 includes the sector (D) after the overpressure chamber (122). Apparatus according to claim 8, characterized in that the fabric covering area 25 has at least • · inside the pivoting roll (121). :, · · One overpressure chamber (122) and outside against the tissue is: suction box (25). · ♦ · ··· ♦ • · ♦ ♦ »·· 9 118972 Device according to claim 9, characterized in that The suction means consist essentially of a suction box (25) covering the fabric covering area (25) and the overpressure means (122, 123) • · at least one overpressure chamber fitted inside the roll together with the perforated roll cover. * ·· • 9 • 1 ··· Apparatus according to any one of claims 8 to 10, characterized in that the fabric (10,11) has a coverage area of the rotating roller · · · - 1 (121) of 120 ° to 190 °, most preferably 160 ° to 185 °. 118972 Device according to one of Claims 8 to 11, characterized in that the device comprises washing jets (125, 126) disposed at a distance from the stopcock (128). 5 Device according to one of Claims 8 to 12, characterized in that at the beginning of the coverage area a suction-free length (L) is provided upstream of the suction area for collecting bulk water at this length by means of overpressure, centrifugal force and gravity. 15