Process for removing water from fibrous web using oscillatory flow-reversing air or gas

A process for removing water from a fibrous web, which process comprises the following steps:

• (a) providing a fibrous web having a moisture content from about 10% to about 90% and supported by a web support having a machine direction and a cross-machine direction perpendicular to the machine direction, the web support further having a web-contacting surface associated with the fibrous web and a backside surface opposite to the web-contacting surface;
• (b) providing a means for moving the web support having the web thereon in the machine direction;
• (c) providing a pulse generator designed to produce and discharge oscillatory flow-reversing gas having a frequency from about 15 Hz to about 1500 Hz;
• (d) providing a gas-distributing system in fluid communication with the pulse generator and terminating with a plurality of discharge outlets, each of the discharge outlets having an equivalent diameter D and an open area through which the oscillatory flow-reversing impingement gas is discharged, the plurality of the discharge outlets having a resulting open area;
• (e) disposing the web support having the web thereon at a predetermined impingement distance Z from the plurality of the discharge outlets, thereby defining an impingement region between the discharge outlets and the web support, a pattern of the discharge outlets further defining an impingement area of the web, corresponding thereto, the resulting open area of the plurality of the discharge outlets comprising from about 0.5% to about 20% of the impingement area, and a ratio Z/D comprising from 1 to 10;
• (f) moving the web support having the web thereon in the machine direction at a velocity from 100 feet per minute to 10,000 feet per minute;
• and
• (g) operating the pulse generator and impinging the oscillatory flow-reversing gas through the discharge outlets onto the web, thereby removing the moisture therefrom.
• 12.The process according to claim 11, wherein in the step (a) the web support comprises a fluid-permeable endless belt or band.

A process for removing water from a differential-density fibrous web, which process comprises the following steps:

• (a) providing a structured fibrous web comprising a plurality of low-density micro-regions and a plurality of high-density micro-regions, and having a moisture content from about 10% to about 90%, the web being supported by a fluid-pervious web support having a machine direction and a cross-machine direction perpendicular to the machine direction, and comprising a reinforcing structure joined to a substantially continuous framework, the framework forming a web-contacting surface associated with the web, a backside surface opposite to the web-contacting surface, and a plurality of fluid-permeable conduits encompassed by the framework and extending from the web-contacting surface to the backside surface;
• (b) providing a means for moving the web support having the web thereon in the machine direction;
• (c) providing a pulse generator designed to produce and discharge oscillatory flow-reversing impingement gas having a frequency from about 15 Hz to about 1500 Hz;
• (d) providing a gas-distributing system in fluid communication with the pulse generator and terminating with a plurality of discharge outlets comprising a predetermined pattern designed to provide a substantially even distribution of the oscillatory flow-reversing impingement gas in the cross-machine direction;
• (e) disposing the web support having the web thereon at a predetermined impingement distance from the plurality of the discharge outlets, thereby defining an impingement region between the discharge outlets and the web-contacting surface of the web support, the pattern of the discharge outlets defining an impingement area of the web corresponding thereto;
• (f) moving the web support having the web thereon in the machine direction;
• and
• (g) operating the pulse generator and impinging the oscillatory flow-reversing impingement gas through the discharge outlets onto the web, thereby removing the moisture from the web.
• 22.The process according to claim 21, further comprising steps of providing a vacuum apparatus and juxtaposing the vacuum apparatus with the backside of the web support in the area at least partially corresponding to the impingement area of the web, the vacuum apparatus being designed to apply a vacuum pressure to the web through the conduits of the web support, and a step of applying the vacuum pressure to the web, thereby removing the moisture therefrom.