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Articolo pubblicato nel fascicolo di Ottobre 2023 di Carta & Cartiere TECHNOLOGY IN PAPER MILL

MAXIMUM DEWATERING AND ENERGY SAVING

Because of heavily rising energy costs, paper manufacturers are facing more than ever the task of keeping production costs as low as possible. Less energy and more productivity are the guiding principles. This means again pushing paper machines to their performance limits: the focus is on highest machine productivity, best runnability and maximum speed. One of the top priorities is the maximum dry content after the press. Press felts must support this important requirement. Atromaxx and Atromaxx.Connect - felts from the Heimbach NewTech family - fulfil this requirement.

di: Heimbach GmbH

The Atromaxx concept is based on multiaxially arranged base modules providing a highly incompressible structure. Firstly, this maintains the sufficient void volume over the entire running time and secondly a huge amount of water is handled through open drainage channels.

The result: an outstanding dry content! Due to its structure based on modules Atromaxx is versatile in terms of paper produced, production speeds and, combined with suitable batt modules, qualified for all machines and press nips.

Turn off the UHLE box

At higher speeds (>500 m/min) nip dewatering is often desired, which makes it possible to reduce or even completely avoid uhle box vacuum. Considerable energy savings can be achieved.

However, this requires a precisely matched press felts such as Atromaxx, which makes it possible to obtain high dry contents, better runnability and good start-up performance. Numerous references confirm that.

MULTIAXIAL FELT ATROMAXX

  • Modular system. Combination of totally different base properties possible within one felt.
  • Outstanding compaction resistance due to multiaxial structure.
  • Brilliant void volume retention.
  • Uptake of huge amount of water.
  • Excellent dewatering during complete running time.
  • High stability.
  • Operation modes for nip and uhle-box dewatering.
  • Applicable for all paper grades.

Unrivalled flexibility

The efficient dewatering behaviour is significantly influenced by the production speed, the pressure impulse and the degree of felt saturation. At low speeds (< 500 m/min) the dewatering in the nip is hardly possible, but even in these conditions high dry content values can be achieved with Atromaxx. This multitalented felt is convincing on machines where, depending on the paper grade, there are big speed variations and thus changes in dewatering behaviour between nip and uhle box.

Safe and fast

The outstanding characteristics of Atromaxx felt can, of course, also be found in the seam felt version. Atromaxx.Connect can be installed safely and quickly with few personnel and it scores with dewatering values which conventional seam felts can’t match. The seam and seam zone are designed also to high speeds guaranteeing the freedom of marking and problem free runnability. Important: please only use selected felt designs that are custom-made for nip dewatering.

PRINCIPLE – BENEFITS – REQUIREMENTS FOR EFFICIENT NIP DEWATERING

Principle

  • The amount of water being pressed from the sheet should be taken up directly in
    the nip – as completely as possible – by the storage volume of the roll; water should
    not be transported with the felt to the UHLE box.

Benefits

  • With a high level of nip dewatering overall dewatering increases as a rule and
    the dry content after the press rises. As a result runnability improves significantly
    (e.g. fewer sheet breaks, reduction in edge problems); moreover, steam is saved in
    the dryer section and production is increased.
  • This type of dewatering is the most effective method to keep press felts clean
    and open.
  • In addition, UHLE boxes can be operated with a low vacuum – or even shut off,
    resulting in enormous energy savings.

Requirements

  • Sufficient storage volume in the press roll covers and shoe press belts so that
    water exiting into the nip can be absorbed.
  • Save-alls with sufficient capacity to collect accumulated water.
  • Efficient doctoring to avoid water rings.
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