Methods and apparatus for dewatering paper webs

摘要

A wet paper web or other wet porous web exiting a web former is supported on a vented press roll and sequentially subjected to a relatively high pressure mechanical nip pressing force and a relatively low pressure water displacement-pressing force. The combination of the two diverse pressing forces applied in sequence to the web is very effective in efficient and economical de-watering of the web and at the same time provides a de-watered web having high bulk, high solids content and high mechanical strength. The low pressure fluid displacement pressing force is applied immediately contiguous to the high pressure mechanical nip pressing force and may be applied upstream or downstream or both upstream and downstream of the mechanical nip pressing force.