Wet End Steam Boxes

On a paper machine, the sheet dryness after pressing is important because it is more economical to remove water by mechanical means at the wet end than by evaporation in the dryer section. One way to increase after-press dryness is to increase the temperature of the sheet when it is pressed. Increasing the sheet temperature reduces the viscosity and surface tension of the water contained in the sheet. This reduced viscosity makes it easier for the water to travel out of the sheet, which increases the dewatering capacity of the press. A common way to raise the sheet temperature is to apply steam with a steam box on the wet end of the paper machine.