Methods and apparatus for the rapid consolidation of moist porous webs

Claim 2

In a method for consolidating and drying a moist, porous web, the steps of running the web through the nip between a pair of rotatable rolls with one side in contact with one roll and its other side facing a permeable surface pressing the rolls together to develop a high pressure linear load in the press nip sufficient to produce good thermal contact between said one roll and the web at least in areas subjected to said high pressure linear load and to overcome any steam pressure developed between the web and said one roll, supplying heat to the outer surface of said roll as it approaches said nip at a rate such that the roll arrives at said nip with a temperature and heat content high enough to cause moisture in the web to be converted rapidly and violently into steam as the web passes through said nip, and heat is transferred rapidly from the surface of the roll directly to the web under high pressure, the steam thus formed tending to pass straight through the web, carrying with it any free water remaining in the cavities between the fibers of the web, whereby the steam is cooled and practically all of its heat energy is transferred to the web and the water remaining therein.

Claim 3

A method as defined in claim 1 in which the web is run through the nip between a rotable roll having a permeable surface and the heated surface of said one roll.

Claim 4

A method as defined in claim 1 in which the web is run through the nip between said rolls on a permeable belt with one side of the web in contact with said heated roll.

Claim 5

A method as defined in claim 2 in which the web is run through the nip between a roll having a grooved surface and a second roll, the surface of which is heated as it approaches said nip.

Claim 7

A method as defined in claim 1 in which the web is consolidated and dried on the heated roll and is then removed therefrom by doctoring.

Claim 8

A method as defined in claim 1 in which said one roll is heated by combustion of a fuel in close proximity to the surface thereof.

Claim 9

A method as defined in claim 7 in which hot gases produced by combustion of said fuel are flowed against the surface of said heated roll as it approaches said nip.

Claim 10

A method as defined in claim 8 in which part of the hot gases produced by combustion of said fuel are flowed through the web, thereby supplying heat to the latter.

Claim 11

A method as defined in claim 1 in which said one roll is heated by exposing part of the surface thereof to a liquid heating medium.

Claim 12

A method as defined in claim 10 in which the liquid medium is a heat resistant oil.

Claim 13

A method as defined in claim 10 in which the liquid medium is a molten metal.

Claim 14

A method as defined in claim 10 in which the liquid medium is a molten salt.

Claim 15

A method as defined in claim 10 in which the liquid medium is flowed against the surface of the heated roll.

Claim 16

A method as defined in claim 14 in which the principal direction of flow of the liquid is opposite the direction of travel of the roll surface.

Claim 17

A method as defined in claim 1 in which the pressure in the press nip lies in the range of 0.1-5 MN/m 2 .

Claim 18

Apparatus for consolidating and drying a moist, porous web of material comprising: a pair of rotatable rolls defining a nip; means for running the web through said nip with one side in contact with the surface of one of said rolls and with the other side facing a permeable surface; heating means disposed externally of said one roll for supplying heat to a portion of the outer surface thereof as it approaches said nip so that said surface portion is brought to a temperature and heat content high enough to cause the moisture in the web to be converted suddenly and violently into steam as the web passes through said nip, said heating means including conduit means having outlet means generally conforming to the shape of part of said one roll in closely adjacent relation to the surface thereof and disposed upstream of said nip, and means for supplying a liquid heating medium to said conduit means; and means for pressing said rolls together so that a load is created which is sufficient to overcome any steam pressure developed between the web and said one roll in the nip area and sufficient to produce good thermal contact between the web and said one roll in said nip area, whereby heat is transferred rapidly from the surface of the roll directly to the web under high pressure, at least in said nip area.

Claim 19

Apparatus for consolidating and drying a moist, porous web of material comprising: a pair of rotatable rolls defining a nip; means for running the web through said nip with one side in contact with the surface of one of said rolls and with the other side facing a permeable surface; heating means disposed externally of said one roll for supplying heat to a portion of the outer surface thereof as it approaches said nip so that said surface portion is brought to a temperature and heat content high enough to cause the moisture in the web to be converted suddenly and violently into steam as the web passes through said nip, said heating means including conduit means having outlet means generally conforming to the shape of part of said one roll in closely adjacent relation to the surface thereof and disposed upstream of said nip, and means for supplying a liquid heating medium to said conduit means; and means for pressing said rolls together so that a load is created which is sufficient to overcome any steam pressure developed between the web and said one roll in the nip area and sufficient to produce good thermal contact between the web and said one roll in said nip area, whereby heat is transferred rapidly from the surface of the roll directly to the web under high pressure, at least in said nip area.

Claim 20

Apparatus as defined in claim 17 together with means providing clearance between said outlet means and the adjacent surface of said one roll on the upstream side of said outlet means for flowing liquid therethrough in a direction opposite the direction of motion of said one roll.