Yankee dryer cylinder operating without steam

Abstract

A Yankee dryer cylinder comprising a fixed hollow shaft provided with an inlet mouth through which a flow of hot air is fed into the cavity, and an outlet mouth through which the flow of hot air exits the dryer cylinder. The Yankee dryer cylinder provides, furthermore, a cylindrical shell having an internal surface and rotatably mounted about the fixed hollow shaft. Into the cavity a partition wall is provided which divides the fixed hollow shaft in a feeding portion and in a discharging portion.

1 . A Yankee dryer cylinder comprising:
 a fixed hollow shaft having a cavity and a lateral surface provided with a plurality of holes arranged to connect said cavity with the external environment, said fixed hollow shaft being provided with:
 an inlet mouth through which a flow of hot gas having a predetermined temperature, in particular a temperature higher than 100° C., is arranged to be fed into said cavity; 
 an outlet mouth through which said flow of hot gas is arranged to exit said dryer cylinder; 
   a cylindrical shell provided with an internal surface and rotatably mounted about said fixed hollow shaft, between the internal surface of said cylindrical shell and said lateral surface of said hollow shaft, an internal chamber being defined;   said Yankee dryer cylinder further comprising:   a partition wall mounted within said cavity in such a way to divide said fixed hollow shaft in a feeding portion and in a discharging portion, said feeding portion provided with at least one feeding hole arranged to feed said flow of hot gas from said cavity to said internal chamber, in such a way to hit said internal surface, said discharging portion provided with at least one discharging hole pneumatically connected to said outlet mouth, said flow of hot gas, after having hit said internal surface of said shell, being arranged to pass through said, or each, discharging hole, from said internal chamber to said cavity, in such a way to flow outside said Yankee dryer cylinder through said outlet mouth.   
     
     
         2 . The yankee dryer cylinder, according to  claim 1 , wherein a plurality of distributor members is provided that are housed within said internal chamber, each distributor member of said plurality arranged to distribute a share of said flow of hot gas, fed into said cavity of said fixed hollow shaft, on a respective determined portion of said internal surface of said shell. 
     
     
         3 . The yankee dryer cylinder, according to  claim 2 , wherein each distributor member of said plurality is tubular-shaped and is provided with at least one inlet aperture facing towards at least one feeding hole, and at least one distribution aperture facing towards said internal surface of said cylindrical shell. 
     
     
         4 . The yankee dryer cylinder, according to  claim 3 , wherein said, or each, distribution aperture is associated to a distribution plate provided with a plurality of distribution holes, in such a way to uniformly distribute the respective share of flow of hot gas on the respective portion of the internal surface of said cylindrical shell. 
     
     
         5 . The yankee dryer cylinder, according to  claim 2 , wherein said distributor members are arranged a at predetermined distance from each other, and said distribution apertures are arranged at a predetermined distance from said internal surface of said shell, in such a way that the lateral surfaces facing each other, of two next distributor members, are arranged to delimit a space, which, in use, is passed through by a flow of hot exiting gas directed towards said discharging holes. 
     
     
         6 . The yankee dryer cylinder, according to  claim 1 , wherein said feeding portion provides a plurality of feeding holes and said discharging portion provides a plurality of discharging holes, said feeding holes and said discharging holes being positioned on said fixed hollow shaft at different longitudinal rows. 
     
     
         7 . The yankee dryer cylinder, according to  claim 1 , wherein each distributor member of said plurality is oriented radially to said cylindrical shell, and extends longitudinally along said Yankee cylinder. 
     
     
         8 . The yankee dryer cylinder, according to  claim 1 , wherein said inlet mouth and said outlet mouth are provided at a same side of said fixed hollow shaft. 
     
     
         9 . The yankee dryer cylinder, according to  claim 8 , wherein, at the end of said fixed hollow shaft opposite to said inlet mouth and to said outlet mouth, a closing wall is provided. 
     
     
         10 . The yankee dryer cylinder, according to  claim 1 , wherein said partition wall is selected from the group consisting of:
 a partition wall arranged substantially orthogonal to the longitudinal axis of said fixed hollow shaft;   a partition wall arranged longitudinal to said fixed hollow shaft;   a partition wall, which extends longitudinally along said fixed hollow shaft ( 20 ), said partition wall comprising a first portion and a second portion inclined by a predetermined angle (α).   
     
     
         11 . The yankee dryer cylinder, according to  claim 1 , wherein said flow of hot gas is a flow of a mixture of gases. 
     
     
         12 . The yankee dryer cylinder, according to  claim 1 , wherein said flow of hot gas is a flow of hot air. 
     
     
         13 . The yankee dryer cylinder, according to  claim 1 , wherein said temperature of said flow of hot gas is set between 250° C. and 700° C., preferably set between 300° C. and 600° C. 
     
     
         14 . The yankee dryer cylinder, according to  claim 1 , wherein a suction device is provided connected to said outlet mouth of said fixed hollow shaft, said suction device arranged to suck said flow of hot gas fed into said cavity of said fixed hollow shaft through said inlet mouth. 
     
     
         15 . A plant for drying a humid web of paper, or similar product, comprising:
 the Yankee dryer cylinder, according to  claim 1 , said Yankee dryer cylinder provided with an external surface, on which, in use, said humid web to be dried is laid;   a drying hood arranged, in use, at the opposite side of said Yankee dryer cylinder with respect to said humid web, said drying hood arranged to cause the drying of said humid web operating in combination with said Yankee dryer cylinder;   a duct arranged to pneumatically connect said drying hood and said cavity of said fixed hollow shaft, said duct being arranged to feed a flow of hot gas circulating within said drying hood within said cavity.   
     
     
         16 . A method for drying a humid web of paper, or similar product comprising:
 disposing of a fixed hollow shaft having a cavity and a lateral surface provided with a plurality of holes arranged to connect said cavity with the external environment, said fixed hollow shaft provided with:
 an inlet mouth through which a flow of hot air is arranged to be fed into said cavity; 
 an outlet mouth through which said flow of hot air is arranged to flow outside said dryer cylinder; 
   disposing of a cylindrical shell provided with an internal surface and rotatably mounted about a said fixed hollow shaft, between the internal surface of said cylindrical shell and said lateral surface of said hollow shaft an internal chamber being defined;   disposing of a partition wall mounted within said cavity in such a way to divide said fixed hollow shaft into a feeding portion and into a discharging portion,   feeding a flow of hot air in said feeding portion, said flow of hot air passing from said cavity to said internal chamber through at least one feeding hole provided in said feeding portion, then, hitting said internal surface, and, then, passing in said discharging portion of said fixed hollow shaft through at least one discharging hole provided in said discharging portion, and, then, passing from said cylinder through said outlet mouth, said flow of hot air, after having hit said internal surface of said shell, being arranged to pass through said, or each, discharging hole from said internal chamber to said cavity, in such a way to flow outside said Yankee dryer cylinder through said outlet mouth.