Abstract: A method and device for controlling a process gas (10) during drying of a product in a drying chamber, in which the process gas is brought into contact with the product so that a substance, for instance water, is taken up by the process gas and transported out from the drying chamber and makes use of a control paradigm for controlling process variables of the process gas (10). In the process, and by the device, a first group of process variables including the process gas content (x) of the substance removed from the product and the pressure conditions (z) inside the dryer hood are monitored and controlled.

Abstract: A blowbox for use in a plant for drying a material web includes an essentially horizontal box wall having formed therein circular orifices and eyelid perforations each of which includes a slit extending in parallel with the center line of the upper box wall. A depression is formed m the upper box wall adjacent one side of the slit. The eyelid perforations are arranged in two rows and parallel with the center line and together they form a zigzag pattern about the center line that intersects the depressions of the eyelid perforations in both rows. The orifices are disposed in a first and second pair of rows with both rows in each pair positioned on either side of and spaced equally from the center line. The upper box wall has a shallow continuous arcuate shape across its entire width.