| 摘要 |
The flow of air removed from the dryer section (20), the flow of process air and the amount of heat supplied to the process air are varied or kept constant depending on drying performance. A method for drying a web, preferably a paper web (1), comprises passing the web through a dryer installation containing a number of drying levels with upper blowboxes (13) suspended above lower blowboxes (12), the latter blowing out hot air on the top side in order to dry the web and remove the water vapour expelled from the web. At least some of this process air is recirculated and the air which is not recirculated is removed and replaced with warm air having a low moisture content. The flow if air removed from the dryer section, the flow of process air and the supply of heat to the process air are controlled throughout the drying process. For low drying performance, the flow of air removed from the dryer section and the flow of process air are kept substantially constant, whilst the amount of heat supplied to the process air is varied in order to alter drying performance. For medium drying performance, the flow of air removed from the dryer section and the amount of heat supplied to the process air are kept substantially constant, whilst the flow of process air is varied in order to alter drying performance. For high drying performance, the flow of process air and the amount of heat supplied to the process air are kept substantially constant, whilst the flow of air removed from the dryer section is varied in order to alter drying performance. |
