Importance

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Abstract

A method and device effect controlled uniform temperature drying of a wet web, such as a paper web substantially immediately after formation in a paper machine, without damaging the supporting fabric carrying the web. The web has a central region and first and second border regions. The wet web to be dried is conveyed on a conventional supporting fabric/wire in a first direction generally parallel to the web border regions, and in a hood drying air is blown against the web from the opposite side thereof as the supporting fabric so that the drying air picks up moisture and becomes moistened air. The moistened air is discharged from the volume adjacent the hood, for example is discharged from at least one hood positioned at and encompassing an impingement surface over which the web and supporting fabric pass. Air supplied for blowing against the web is heated to raise its ability to retain moisture. Drying air with a first temperature and first velocity is directed against a central region of the web, and drying air with a second temperature, lower than the first temperature, and second velocity, higher than the first velocity, is directed against the web in the border regions. The hood may be divided into at least one central block and first and second border blocks, corresponding to the central region and first and second border regions of the web. A first plurality of air nozzles may be disposed within the hood central block, and second and third plurality of air nozzles disposed in the hood first and second border blocks, with a different fan and heater supplying air to each of the plurality of air nozzles.

First Claim