Displacement dewatering a web using compressed gas

Abstract

Apparatus, methods, and fabrics for dewatering a nascent paper web, carried in a web sandwich, in a dewatering section of a papermaking machine. Water is driven from the web by a combination of mechanical pressure and compressed air, both typically applied in a nip. The mechanical pressure and air pressure can be applied in the same nip, or in separate nips, where the mechanical pressure is applied upstream, in the papermaking machine, from the air pressure application. The mechanical pressure can be lower than pressures used in conventional press sections of known papermaking machines. Air pressure is that pressure which can be contained in a seal section between the web sandwich and the structure supplying the air. Fabrics supporting the nascent paper web through the air dewatering station have limited lateral air flow under compressed air conditions, whereby air flows generally perpendicularly through the web being dewatered.

Having thus described the invention, what is claimed is: 
     
         1 . A method for removing water from a nascent paper web in a papermaking machine in the process of fabricating a finished paper product, the nascent paper web comprising papermaking fibers and water, and having first and second opposing web surfaces which extend between first and second opposing edges of such nascent paper web, the nascent paper web having a generally continuous length, and a width, a first carrier fabric being disposed on the first surface of the nascent paper web and a second carrier fabric being disposed on the second opposing surface of the nascent paper web, the first and second carrier fabrics and the nascent paper web collectively defining a web sandwich, the web sandwich having first and second opposing sandwich surfaces, and a web machine direction corresponding with a machine direction of the papermaking machine, and a web cross machine direction, the web sandwich moving in the machine direction of the papermaking machine, the method comprising:
 (a) applying mechanical pressure to the web sandwich and thereby driving water from the nascent paper web;   (b) providing a gas pressure source and a gas receptive vent, the gas pressure source having a length extending along the width of the nascent paper web; and   (c) providing a generally constant compressed gaseous pressure along the entire cross direction length of the gas pressure source, the gas pressure source thereby conveying compressed gas to the web sandwich and thereby developing a seal zone at the web sandwich.   
     
     
         2 . A method as in  claim 1 , a gas pressure chamber in gaseous communication with the gas pressure source providing the compressed gaseous pressure, the gas pressure chamber being adapted and configured to constantly provide a generally constant compressed gaseous pressure along the entire length of the gas pressure source. 
     
     
         3 . A method as in  claim 2 , the gas pressure chamber comprising a pressure box disposed inside the gas pressure source. 
     
     
         4 . A method as in  claim 2 , the gas pressure chamber comprising an enclosure having an edge extending along the length of the gas pressure source, the enclosure being open to a surface of the gas pressure source, further comprising a seal extending about the enclosure along the length of the gas pressure source and between the enclosure edge and the respective surface of the gas pressure source, such seal inhibiting leakage of gas between the gas pressure chamber and the gas pressure source, between the first and second edges of the nascent paper web. 
     
     
         5 . A method as in  claim 4 , the gas pressure source comprising a pressure roll having an outer shell, the gas pressure chamber being disposed inside the pressure roll, the seal being disposed at an inner surface of the outer shell. 
     
     
         6 . A method as in  claim 1  comprising providing vacuum at the gas receptive vent to assist in receiving gas and water from the web sandwich, and conveying such received gas and water away from the web sandwich. 
     
     
         7 . A method as in  claim 1 , the gas pressure source and the gas receptive vent defining a nip, the nip comprising first and second loading devices which apply mechanical pressure to the web sandwich in the nip, and further providing a pressure device adapted and configured to apply the compressed gaseous pressure in the nip through one of the first and second loading devices. 
     
     
         8 . A method as in  claim 1  comprising applying the mechanical pressure to the nascent paper web, through the first and second carrier fabrics, at a first dewatering station in the papermaking machine, and applying the compressed gas to the nascent paper web, through the first and second carrier fabrics, in a second dewatering station, separate and distinct from the first dewatering station and downstream in the papermaking machine from the first dewatering station. 
     
     
         9 . A method as in  claim 8  comprising, after applying the mechanical pressure to the nascent paper web at the first dewatering station, and before applying the compressed gas to the nascent paper web at the second dewatering station, replacing at least one of the first and second carrier fabrics in the web sandwich with a third carrier fabric, different from the respective first or second carrier fabric. 
     
     
         10 . A method as in  claim 8  comprising, after applying the mechanical pressure to the nascent paper web at the first dewatering station, and before applying the compressed gas to the nascent paper web at the second dewatering station, replacing the first carrier fabric in the web sandwich with a third carrier fabric and replacing the second carrier fabric in the web sandwich with a fourth carrier fabric. 
     
     
         11 . A method as in  claim 7  including providing, as the first loading device, a roll comprising a shell, the shell having a length and extending about a circumference of the roll, apertures being arrayed about the circumference and along the length of the shell, and extending through the shell, the roll being equipped with a pressure box supplying the compressed gas, through the apertures and to the web sandwich. 
     
     
         12 . A method as in  claim 7  including providing, as the first loading device, a pressure roll or a pressure shoe. 
     
     
         13 . A method as in  claim 7  including providing, as the second loading device, a vent receptive structure, optionally a vent receptive belt, a vent receptive sleeve, or a vent receptive roll. 
     
     
         14 . A method as in  claim 8  including providing the mechanical pressure at a first nip, at an average nip pressure of up to about 400 pounds per square inch, optionally up to about 600 pounds per square inch, optionally up to about 800 pounds per square inch, optionally up to about 1000 pounds per square inch of nip pressure provided by mechanical force between the first and second loading devices at the first dewatering station. 
     
     
         15 . A method as in  claim 8 , the gas pressure source and the gas pressure receptive vent defining a first nip, the method including providing, at the second dewatering station, a second nip providing an average mechanical loading of the web sandwich at a nominal amount of pressure and optionally an average pressure of up to about 2 pounds per square inch, optionally an average pressure of up to about 5 pounds per square inch, optionally an average pressure of up to about 100 pounds per square inch, optionally an average pressure of up to less than about 300 pounds per square inch, optionally an average pressure of up to 500 pounds per square inch, optionally an average pressure of up to less than about 800 pounds per square inch, and optionally a seal, optionally a self-loading seal, optionally a self-loading ganged seal. 
     
     
         16 . A method as in  claim 8  including providing, at the second dewatering station, a gas pressure shoe providing the compressed gas to the web sandwich. 
     
     
         17 . A method as in  claim 16  including providing, at the second dewatering station, a porous sleeve or belt at a surface of the web sandwich opposite the pressure shoe, the porous sleeve or belt receiving and venting water and gas passing through the web sandwich. 
     
     
         18 . A method as in  claim 1 , the first carrier fabric comprising a layer having at least one property selected from the group consisting of
 (i) a basis weight of up to about 1200 grams per square meter   (ii) no more than about 40 percent void space,   (iii) a moisture ratio of no more than 0.4, optionally no more than 0.25, optionally no more than 0.15,   all prior to applying the compressed gaseous pressure to the web sandwich.   
     
     
         19 . A method as in  claim 1  optionally including providing the first carrier fabric on the web sandwich surface to which the gas is applied, an amount of water removed from the first carrier fabric, as the compressed gaseous pressure is applied to the web sandwich, being less than two times the amount of water removed from the nascent paper web. 
     
     
         20 . A method as in  claim 1  including providing the second carrier fabric on the web sandwich surface which is away from the compressed gaseous pressure being applied to the web sandwich, the second carrier fabric being adapted and configured to readily convey flow of water, which is pushed from the nascent paper web by the compressed gas, and to inhibit movement of water back into the nascent paper web under relatively lower ambient or reduced gaseous pressure. 
     
     
         21 . A method as in  claim 1  including providing at least one of the first and second carrier fabrics comprising a perforated membrane. 
     
     
         22 . A method as in  claim 21  including providing the respective carrier fabric wherein the perforated membrane is a first layer or sub-layer, and the respective carrier fabric further comprises a second layer or sub-layer. 
     
     
         23 . A method as in  claim 21 , a respective layer or sub-layer adjacent the perforated membrane facilitating development of relative uniformity of gas flow through the nascent paper web in the seal zone. 
     
     
         24 . A method as in  claim 1  including providing, in the first carrier fabric, on the web sandwich surface to which the compressed gaseous pressure is applied, a layer or sub-layer having low voids, optionally compacted or filled, optionally thermoplastic yarns, optionally mono mesh fabrics and/or monofilament fabrics, and optionally less than 40 percent void volume. 
     
     
         25 . A method as in  claim 1  including providing a multifilament or batt structure or other structure in contact with the nascent paper web and thereby limiting in-plane gas leakage in the nascent paper web. 
     
     
         26 . A method as in  claim 1  including providing the first carrier fabric on the web sandwich surface to which the compressed gas is being applied, the first carrier fabric inhibiting web machine direction flow of such compressed gas. 
     
     
         27 . A method as in  claim 1 , the gas pressure source and the gas pressure receptive vent defining a nip, the first carrier fabric being disposed on the web sandwich surface to which the compressed gaseous pressure is being applied, the nip comprising first and second loading devices which apply sufficient mechanical pressure to the web sandwich to cause a reduction in thickness of the web sandwich, to a minimum thickness, in the nip, as the compressed gas is being passed through the web sandwich, the web sandwich rebounding from the minimum thickness as the web sandwich exits the nip, the method comprising optionally continuing to provide compressed gaseous pressure to at least the first carrier fabric and the nascent paper web after the web sandwich exits the nip. 
     
     
         28 . A method as in  claim 27  comprising providing a third carrier fabric as part of the web sandwich, the third carrier fabric being disposed on a surface of the second carrier fabric remote from the nascent paper web and remote from the compressed gaseous pressure source, the method comprising separating the third carrier fabric from the web sandwich when the web sandwich exits the nip while optionally continuing to provide compressed gaseous pressure to the first carrier fabric, the nascent paper web, and the second carrier fabric after the first carrier fabric, the second carrier fabric, and the nascent paper web have exited the nip. 
     
     
         29 . A method as in  claim 28 , the third carrier fabric expanding as the web sandwich moves toward a nip exit, and thereby drawing water from the web sandwich and into expanding voids in the third carrier fabric. 
     
     
         30 . A method as in  claim 1  including providing the first carrier fabric on the web sandwich surface to which the compressed gaseous pressure is being applied, the first carrier fabric being designed and configured to selectively inhibit lateral web machine direction flow of water in the first carrier fabric. 
     
     
         31 . A method as in  claim 1  including providing the second carrier fabric on the web sandwich surface remote from the surface to which the compressed gaseous pressure is being applied, the second carrier fabric having a greater affinity for water removed from the nascent paper web than a web affinity for water extant in the nascent paper web. 
     
     
         32 . A method as in  claim 1  including applying and adjusting intensity of compressed gaseous pressure, and optionally heat, being applied to the nascent paper web, independent of intensity of any mechanical pressure being applied to the nascent paper web. 
     
     
         33 . A method as in  claim 7  comprising applying and adjusting intensity of compressed gaseous pressure, and optionally heat, being applied to the nascent paper web, independent of intensity of any mechanical pressure being applied to the nascent fibrous web. 
     
     
         34 . A method as in  claim 1  comprising specifying compressed gaseous pressure and mechanical pressure according to properties to be provided in the finished paper product. 
     
     
         35 . A method as in  claim 1 , the method further comprising extending a seal from a body of the pressure device to the web sandwich, the seal extending about the seal zone, the seal limiting lateral gas leakage in the web machine direction and the web cross machine direction from the seal zone. 
     
     
         36 . A method as in  claim 1  comprising providing the compressed gas at pressures, measured at the gas pressure chamber, of about 5 pounds per square inch to about 125 pounds per square inch, optionally about 5 pounds per square inch to about 75 pounds per square inch, optionally about 10 pounds per square inch to about 60 pounds per square inch. 
     
     
         37 . A method as in  claim 1 , a gas pressure chamber in gaseous communication with the gas pressure source providing the compressed gaseous pressure, the gas pressure chamber comprising a first gas pressure chamber providing a first compressed gaseous pressure of a first magnitude to the web sandwich, the method further comprising providing a second gas pressure chamber downstream in the web machine direction from the first gas pressure chamber, and proximate the first gas pressure chamber, the second gas pressure chamber being in gaseous communication with the gas pressure source, the second gas pressure chamber providing a generally constant compressed gaseous pressure of a second magnitude, optionally less than the first magnitude of the compressed gaseous pressure provided by the first gas pressure chamber, the gas pressure source conveying the compressed gaseous pressure of the second gas pressure chamber to the web sandwich. 
     
     
         38 . A method as in  claim 37 , the gas pressure source conveying the compressed gaseous pressure of the second gas pressure chamber to the web sandwich along the entire length of the gas pressure source. 
     
     
         39 . A method as in  claim 1 , at least one of the first and second carrier fabrics having sufficiently low permeability to pressure of the compressed gas that the respective carrier fabric provides functional mechanical loading to the web sandwich, thereby aiding in release of water from the nascent paper web. 
     
     
         40 . A papermaking machine employing a method of  claim 1 . 
     
     
         41 . Apparatus for removing water from a nascent paper web in a papermaking machine in the process of fabricating a finished paper product, the nascent paper web comprising papermaking fibers and water, and having first and second opposing web surfaces which extend between first and second opposing edges of such nascent paper web, the nascent paper web having a generally continuous length, and a width, a first carrier fabric being disposed on the first surface of the nascent paper web and a second carrier fabric being disposed on the second opposing surface of the nascent paper web, a web sandwich comprising said first and second carrier fabrics and said nascent paper web, said web sandwich having first and second opposing sandwich surfaces, and a web machine direction corresponding with a machine direction of the papermaking machine, and a web cross machine direction, the web sandwich moving in the machine direction of the papermaking machine, said apparatus comprising:
 (a) apparatus applying mechanical pressure to the opposing web sandwich surfaces and thereby driving water from the nascent paper web;   (b) a gas pressure source and a gas receptive vent, said gas pressure source having a length extending along the width of the nascent paper web; and   (c) a gas pressure chamber providing a generally constant compressed gaseous pressure along the entire cross direction length of said gas pressure source, said gas pressure source thereby conveying compressed gas to the web sandwich and thereby developing a seal zone at the web sandwich.   
     
     
         42 . Apparatus as in  claim 41 , said gas pressure chamber being adapted and configured to constantly provide a generally constant compressed gaseous pressure along the entire length of said gas pressure source. 
     
     
         43 . Apparatus as in  claim 41 , said gas pressure chamber comprising a pressure box disposed inside said gas pressure source. 
     
     
         44 . Apparatus as in  claim 41 , said gas pressure chamber comprising an enclosure having an edge extending along the length of said gas pressure source, the enclosure being open to a surface of said gas pressure source, further comprising a seal extending about the enclosure along the length of said gas pressure source and between the enclosure edge and the respective surface of said gas pressure source, said seal inhibiting leakage of gas between said gas pressure chamber and said gas pressure source, between the first and second edges of the nascent paper web. 
     
     
         45 . Apparatus as in  claim 44 , said gas pressure source comprising a pressure roll having an outer shell, said gas pressure chamber being disposed inside said pressure roll, said seal being disposed at an inner surface of said outer shell. 
     
     
         46 . Apparatus as in  claim 41  comprising a vacuum source providing vacuum at said gas receptive vent to assist in receiving gas and water from the web sandwich, and conveying such received gas and water away from the web sandwich. 
     
     
         47 . Apparatus as in  claim 41  first and second loading devices, loaded against each other and thereby defining a nip therebetween, said first and second loading devices applying mechanical pressure to the web sandwich in the nip, further comprising a pressure device adapted and configured to apply the compressed gaseous pressure in the nip through one of said first and second loading devices. 
     
     
         48 . Apparatus as in  claim 41  comprising a first dewatering station in the papermaking machine, said first dewatering station applying the mechanical pressure to the nascent paper web, through said first and second carrier fabrics, further comprising a second dewatering station, separate and distinct from the first dewatering station and downstream in said papermaking machine from said first dewatering station, the compressed gaseous pressure being applied to the nascent paper web, through said first and second carrier fabrics, at said second dewatering station. 
     
     
         49 . Apparatus as in  claim 48  comprising, after applying the mechanical pressure to the nascent paper web at said first dewatering station, and downstream of said first dewatering station and before applying the compressed gaseous pressure to the nascent paper web at said second dewatering station, the web sandwich comprising a third carrier fabric, different from said first and second carrier fabrics, on one of the first and second surfaces of the nascent paper web. 
     
     
         50 . Apparatus as in  claim 48  comprising, after applying the mechanical pressure to the nascent paper web at said first dewatering station, and downstream of said first dewatering station and before applying the compressed gaseous pressure to the nascent paper web at said second dewatering station, the web sandwich comprising third and fourth carrier fabrics, different from the first and second carrier fabrics, on the first and second surfaces of the nascent paper web. 
     
     
         51 . Apparatus as in  claim 49 , said third and fourth carrier fabrics having replaced said first and second carrier fabrics. 
     
     
         52 . Apparatus as in  claim 47 , said first loading device comprising a roll, said roll comprising a shell, said shell having a length and extending about a circumference of said roll, apertures being arrayed about the circumference and along the length of said shell, and extending through said shell, said roll being equipped with a pressure box supplying the compressed gaseous pressure, through the apertures and to the web sandwich. 
     
     
         53 . Apparatus as in  claim 47 , said first loading device comprising a pressure roll or a pressure shoe. 
     
     
         54 . Apparatus as in  claim 52 , said second loading device being selected from the group consisting of a vent receptive belt, a vent receptive sleeve, or a vent receptive roll. 
     
     
         55 . Apparatus as in  claim 47 , average mechanical nip pressure between said first and second loading devices at said first dewatering station comprising up to about 400 pounds per square inch, optionally up to about 600 pounds per square inch, optionally up to about 800 pounds per square inch, optionally up to about 1000 pounds per square inch. 
     
     
         56 . Apparatus as in  claim 47 , said gas pressure source and said gas receptive vent defining a second nip therebetween at said second dewatering station, and applying mechanical loading to the web sandwich at a nominal amount of pressure and optionally an average pressure up to about 2 pounds per square inch, optionally an average pressure of up to about 5 pounds per square inch, optionally an average pressure of up to about 100 pounds per square inch, optionally an average pressure of up to about 300 pounds per square inch, optionally an average pressure of up to about 500 pounds per square inch, optionally an average pressure of up to about 800 pounds per square inch, optionally a seal, optionally a self-loading seal, optionally a self-loading ganged seal. 
     
     
         57 . Apparatus as in  claim 41 , further comprising, at the second dewatering station, said gas pressure source comprising a gas pressure shoe providing the compressed gas to the web sandwich. 
     
     
         58 . Apparatus as in  claim 57 , said gas receptive vent, at said second dewatering station, comprising a porous sleeve or belt at a surface of the web sandwich opposite said pressure shoe, said porous sleeve or belt receiving and venting water and gas passing through the web sandwich. 
     
     
         59 . Apparatus as in  claim 41 , said first carrier fabric comprising a layer having at least one property selected from the group consisting of
 (i) a basis weight of up to about 1200 grams per square meter,   (ii) up to about 40 percent void space,   (iii) a moisture ratio less than 0.4, optionally less than 0.25, optionally less than 0.15 prior to applying the compressed gas to said web sandwich.   
     
     
         60 . Apparatus as in  claim 41  said first carrier fabric being disposed on the web sandwich surface to which the compressed gaseous pressure is applied, and wherein an amount of water removed from the first carrier fabric, as the compressed gaseous pressure is applied to said web sandwich, is less than two times the amount of water removed from the nascent paper web. 
     
     
         61 . Apparatus as in  claim 41  said second carrier fabric being disposed on the web sandwich surface which is away from said gas pressure chamber, said second carrier fabric being adapted and configured to readily convey flow of water, which is pushed from the nascent paper web by the compressed gas, and to inhibit movement of water back into the nascent paper web under relatively lower ambient or reduced gaseous pressure. 
     
     
         62 . Apparatus as in  claim 41 , at least one of said first and second carrier fabrics comprising a perforated membrane. 
     
     
         63 . Apparatus as in  claim 63  wherein said perforated membrane is a first layer or sub-layer, and the respective said carrier fabric further comprises a second layer or sub-layer. 
     
     
         64 . Apparatus as in  claim 62 , a respective layer or sub-layer adjacent said perforated membrane facilitating development of relative uniformity of gas flow through the nascent paper web in said seal zone. 
     
     
         65 . Apparatus as in  claim 41 , said first carrier fabric being disposed on the web sandwich surface to which the compressed gas is applied, said first carrier fabric comprising a layer having low voids, optionally compacted or filled, optionally thermoplastic yarns, optionally mono mesh fabrics and/or monofilament fabrics, and optionally less than 40 percent void volume. 
     
     
         66 . Apparatus as in  claim 41 , a multifilament or batt structure or other structure in contact with the nascent paper web and thereby limiting in-plane gas leakage in the nascent paper web. 
     
     
         67 . Apparatus as in  claim 41 , said first carrier fabric being disposed on the web sandwich surface to which the compressed gas is being applied, said first carrier fabric inhibiting web machine direction flow of compressed gas. 
     
     
         68 . Apparatus as in  claim 41 , said first carrier fabric being disposed on the web sandwich surface to which the compressed gaseous pressure is being applied, first and second loading devices defining a nip therebetween, and applying sufficient mechanical pressure to said web sandwich in the nip to cause a reduction in thickness of said web sandwich, to a minimum thickness as the compressed gas is being passed through said web sandwich, said web sandwich rebounding from the minimum thickness as said web sandwich exits the nip, said gas pressure chamber continuing to provide compressed gaseous pressure to at least said first carrier fabric and the nascent paper web after said web sandwich exits the nip. 
     
     
         69 . Apparatus as in  claim 68 , further comprising a third carrier fabric as part of the web sandwich, said third carrier fabric being disposed on a surface of said second carrier fabric remote from the nascent paper web and remote from said compressed gaseous pressure source, further comprising said third carrier fabric being separated from said web sandwich when said web sandwich has exited the nip while optionally continuing to provide compressed gaseous pressure to said first carrier fabric, the nascent paper web, and said second carrier fabric after said first carrier fabric, said second carrier fabric, and the nascent paper web have exited the nip. 
     
     
         70 . Apparatus as in  claim 69 , said third carrier fabric expanding as said web sandwich moves toward a nip exit, and thereby drawing water from said web sandwich and into expanding voids in said third carrier fabric. 
     
     
         71 . Apparatus as in  claim 41 , said first carrier fabric being disposed on the web sandwich surface to which the compressed gaseous pressure is being applied, said first carrier fabric being designed and configured to selectively inhibit lateral web machine direction flow of water in said first carrier fabric. 
     
     
         72 . Apparatus as in  claim 41 , said second carrier fabric being disposed on the web sandwich surface remote from the surface to which the compressed gaseous pressure is being applied, said second carrier fabric having a greater affinity for water removed from the nascent paper web than a web affinity for water extant in the nascent paper web. 
     
     
         73 . Apparatus as in  claim 41 , said gas pressure source and said gas receptive vent collectively defining a nip therebetween, further comprising a gas pressure generator adapted and configured for applying and adjusting intensity of compressed gaseous pressure, and optionally heat, being applied to the nascent paper web in the nip, independent of intensity of any mechanical pressure being applied to the nascent paper web in the nip. 
     
     
         74 . Apparatus as in  claim 47 , further comprising a gas pressure generator adapted and configured for applying and adjusting intensity of compressed gaseous pressure, and optionally heat, being applied to the nascent paper web independent of intensity of any mechanical pressure being applied to the nascent paper web in the nip. 
     
     
         75 . Apparatus as in  claim 41 , further comprising first and second controllers adapted and configured for specifying compressed gaseous pressure and mechanical pressure according to properties to be provided in the finished paper product. 
     
     
         76 . Apparatus as in  claim 41 , further comprising a seal extending from a body of said pressure device to said web sandwich, said seal extending about the seal zone, said seal limiting lateral gas leakage in the web machine direction and the web cross machine direction from said seal zone. 
     
     
         77 . Apparatus as in  claim 41 , said pressure chamber being adapted and configured to provide compressed gas at pressures, measured at the gas pressure chamber, of about 5 pounds per square inch to about 125 pounds per square inch. 
     
     
         78 . Apparatus as in  claim 41 , said gas pressure chamber comprising a first gas pressure chamber providing a first compressed gaseous pressure of a first magnitude to said web sandwich, further comprising a second gas pressure chamber downstream in the web machine direction from said first gas pressure chamber, and proximate said first gas pressure chamber, said second gas pressure chamber being in gaseous communication with said gas pressure source, said second gas pressure chamber providing a generally constant compressed gaseous pressure of a second magnitude, optionally less than the first magnitude of the compressed gaseous pressure provided by said first gas pressure chamber, said gas pressure source conveying the compressed gaseous pressure of said second gas pressure chamber to said web sandwich. 
     
     
         79 . Apparatus as in  claim 78 , said gas pressure source conveying the compressed gaseous pressure of said second gas pressure chamber to said web sandwich along the entire length of said gas pressure source. 
     
     
         80 . Apparatus as in  claim 41 , at least one of said first and second carrier fabrics having sufficiently low permeability to the compressed gas that the respective carrier fabric provides functional mechanical loading to said web sandwich, thereby aiding in release of water from the nascent paper web. 
     
     
         81 . Apparatus as in  claim 41 , said gas pressure source, said gas receptive vent, and said gas pressure chamber collectively defining a first dewatering station adapted and configured to pass compressed gas through the web sandwich in a first direction, further comprising a second dewatering station, separate and distinct from the first dewatering station, said second dewatering station comprising a second gas pressure source, a second gas receptive vent, and a second gas pressure chamber, collectively adapted and configured to pass compressed gas through the web sandwich in a second opposing direction. 
     
     
         82 . Apparatus as in  claim 41 , further comprising a controller controlling and adjusting mechanical pressure applied to the web sandwich and air pressure and heat applied to the web sandwich, thereby to adjust and control properties of a paper product produced from the nascent paper web. 
     
     
         83 . Apparatus as in  claim 81 , further comprising a controller controlling and adjusting mechanical pressure applied to the web sandwich and air pressure and heat applied to the web sandwich and thereby to adjust and control properties of a paper product produced from the nascent paper web. 
     
     
         84 . Apparatus as in  claim 41 , said gas pressure source comprising a pressure roll having an outer shell, further comprising an air permeable layer disposed on an outer surface of said outer shell, said air permeable layer diffusing compressed air passing therethrough, said and being in direct contact with the nascent paper web. 
     
     
         85 . Apparatus as in  claim 45 , said first carrier fabric comprising an outer layer extending about a circumference of an outer surface of said shell, said outer layer being adapted and configured to receive gas passing through the apertures and to assist in diffusing such gas so as to provide for increased uniformity of gas flow across the width and length of the nascent paper web, whereby said first carrier fabric comprises a temporary element of said web sandwich. 
     
     
         86 . Apparatus as in  claim 85 , wherein said first carrier fabric is made using materials selected from the group consisting of sintered polymer, sintered metal, a shrunken sleeve, and a nonwoven fabric. 
     
     
         87 . Apparatus as in  claim 76 , said first carrier fabric further comprising first and second impermeable seal strips ( 758 ) extending along edges of said first carrier fabric, said first and second seal strips inhibiting leakage of compressed air from the seal zone, both laterally in said first carrier fabric and through a thickness of said first carrier fabric. 
     
     
         88 . A papermaking machine comprising apparatus of  claim 44 . 
     
     
         89 . A method as in  claim 1 , the gas pressure source, the gas receptive vent, and the gas pressure chamber collectively defining a first dewatering station and passing compressed gas through the web sandwich in a first direction, further comprising a second gas pressure source, a second gas receptive vent, and a second gas pressure chamber defining a second dewatering station, separate and distinct from the first dewatering station, the second gas pressure source, the second gas receptive vent, and the second gas pressure chamber collectively passing compressed gas through the web sandwich in a second opposing direction. 
     
     
         90 . A method as in  claim 1 , further comprising controlling and adjusting mechanical pressure applied to the web sandwich and air pressure applied to the web sandwich and thereby adjusting and controlling properties of a paper product produced from the nascent paper web. 
     
     
         91 . A method as in  claim 88 , further comprising controlling and adjusting mechanical pressure applied to the web sandwich and air pressure applied to the web sandwich and thereby adjusting and controlling properties of a paper product produced from the nascent paper web. 
     
     
         92 . A method as in  claim 1 , the gas pressure source comprising a pressure roll having an outer shell, further comprising an air permeable layer disposed on an outer surface of the outer shell, the air permeable layer being in direct contact with the nascent paper web, the method further comprising diffusing compressed air through the air permeable layer. 
     
     
         93 . A papermaking fabric having lateral leakage, using the “DB Lateral Air Flow Test”, of no more than 8 cubic feet per minute, optionally no more than 6 cubic feet per minute, optionally no more than 3 cubic feet per minute, optionally no more than 2 cubic feet per minute. 
     
     
         94 . A papermaking fabric as in  claim 92 , said papermaking fabric having a basis weight less than 1200 grams per square meter. 
     
     
         95 . A papermaking fabric as in  claim 92  and having voids less than 40 percent of the volume of said papermaking fabric. 
     
     
         96 . A papermaking fabric as in  claim 92 , containing a perforated layer. 
     
     
         97 . A papermaking fabric as in  claim 92  made using one or more materials selected from the group consisting of polyamide, polyester, polyolefin, and mixtures thereof.