Method in contact-free air-drying of a material web as well as a nozzle-blow-box and a pulp dryer that make use of the method

A nozzle-blow-box of an air dryer for directing air blowings to a material web to be dried, the air blowings producing a transfer of heat from the drying air to the web and contact-free air support and stabilization of a run of the web through the air dryer, said nozzle-blow-box comprising

• a box part having a nozzle-carrier face arranged to face the web,
• a substantially V-section groove arranged in a middle portion of said nozzle-carrier face and extending in a direction transverse to a running direction of the web, said groove being open toward the web and having a series of nozzle holes arranged in opposite walls for directing support and stabilization air blowings to the web, said support and stabilization air blowings being directed crosswise and in opposite directions in relation to each other,
• said nozzle-carrier face comprising planar nozzle-carrier faces arranged on both sides of said groove and in the same plane with each other, said planar nozzle-carrier faces having extensions comprising lateral carrier face portions arranged further apart from the web, the velocity of said support and stabilization air blowings being lower in proximity to said lateral carrier-face portions as compared with the velocity of said support and stabilization air blowings prevailing in proximity to said planar nozzle-carrier-face portions,
• said nozzle-carrier face further comprising nozzle perforations through which additional air blowings are directed from said nozzle-blow-box in a direction substantially perpendicular to the plane of the web.

A pulp dryer for drying material webs, comprising

• nozzle-blow-boxes arranged at horizontal distances from one another to form spaces therebetween, said nozzle-blow boxes being placed at a distance from a material web to form treatment gaps, a first set of said nozzle-blow-boxes comprising means for directing air through a nozzle carrier face of said nozzle-blow-boxes in both a perpendicular direction to the web and in a parallel direction to the web to support, dry and stabilize the web, said means comprising a groove arranged in said nozzle carrier face and extending in a direction transverse to a running direction of the web, said groove being open toward the web and having a series of nozzle holes arranged in opposite walls for directing air in the direction parallel to the web crosswise and in opposite directions in relation to each other, said means further comprising nozzle means for directing air in the direction perpendicular to the web, the air being removed from said treatment gaps via said spaces, said nozzle-blow-boxes being arranged in the running direction of the web one after another in a horizontal plane such that rows of said nozzle-blow-boxes are formed in the dryer,
• a hood through which the web to be dried runs through the dryer supported by air, the web being arranged to run over said rows of said first set of said nozzle-blow-boxes in horizontal backward and forward runs arranged in a vertical orientation in the dryer, and
• reversing rolls for reversing the running direction of the web between said horizontal runs.