Plant for the production of web-like paper material

Abstract

Herein described is a plant for the production of web-like paper material comprising a forming equipment, which dispenses a paper material slurry on a support canvas, and a desiccating equipment, which is designed to desiccate the paper material slurry to form the web-like paper material. The desiccating equipment comprises at least one first rotary perforated cylinder and at least one second rotary perforated cylinder, on whose surface the paper material slurry conveyed by the support canvas dynamically adheres, and a heating system, which is designed to generate and deliver hot process air to at least one of the first rotary perforated cylinder and the second rotary perforated cylinder. The first rotary perforated cylinder is a cylinder operating under relative pressure conditions, wherein the hot process air is blown from inside the first rotary perforated cylinder towards the web-like paper material conveyed by the support canvas. The second perforated cylinder is a cylinder operating under relative vacuum conditions, wherein the hot process air is suctioned, through the second rotary perforated cylinder, from web-like paper material conveyed by the support canvas. A recovery circuit is designed for the recovery of the hot process air suctioned from the second rotary perforated cylinder and to deliver such hot process air to the first rotary perforated cylinder.

1 . Plant ( 10 ) for the production of web-like paper material ( 200 ), the plant ( 10 ) comprising:
 at least one continuous support belt ( 14 ,  16 ), which is movable through a plurality of rollers ( 18 ,  20 );   at least one forming equipment ( 12 ) for forming said web-like paper material ( 200 ), the forming equipment ( 12 ) comprising at least one device ( 22 ) for dispensing a paper material slurry ( 100 ), which is designed to deposit said paper material slurry ( 100 ) onto said at least one support belt ( 14 ,  16 );   at least one desiccating equipment ( 24 ), which is arranged downstream of said at least one forming equipment ( 12 ) and which is designed to at least partially dry said paper material slurry ( 100 ) conveyed by said at least one support belt ( 14 ,  16 ), so as to form said web-like paper material ( 200 ), the desiccating equipment ( 24 ) comprising:
 at least one first drying device consisting of a first rotary perforated cylinder ( 26 ), on whose surface said paper material slurry ( 100 ) conveyed by said at least one support belt ( 14 ,  16 ) adheres dynamically, said first rotary perforated cylinder ( 26 ) being a circular cylinder with predefined diameter (D 1 ), 
 at least one second drying device consisting of a second rotary perforated cylinder ( 28 ), on whose surface of said paper material slurry ( 100 ) conveyed by said at least one support belt ( 14 ,  16 ) adheres dynamically, said second rotary perforated cylinder ( 28 ) being a circular cylinder with predefined diameter (D 2 ) and being arranged downstream of said first rotary perforated cylinder ( 26 ), and 
 a heating system ( 30 ,  32 ,  34 ,  36 ,  38 ,  40 ), which is designed to generate hot process air and to deliver said hot process air to at least one of said first rotary perforated cylinder ( 26 ) and said second rotary perforated cylinder ( 28 ), 
   
       wherein said first rotary perforated cylinder ( 26 ) is a cylinder operating under relative pressure conditions, and wherein said hot process air is blown from inside said first rotary perforated cylinder ( 26 ) toward said paper material slurry ( 100 ) conveyed by said at least one support belt ( 14 ,  16 ), the plant ( 10 ) being characterized in that said second rotary perforated cylinder ( 28 ) is a cylinder operating under relative vacuum conditions, wherein said hot process air is suctioned, through said second rotary perforated cylinder ( 28 ), from said paper material slurry ( 100 ) conveyed by said at least one support belt ( 14 ,  16 ), and in that said desiccating equipment ( 24 ) comprises at least one recovery circuit ( 42 ), which is designed to recover the hot process air suctioned from said second rotary perforated cylinder ( 28 ) and to deliver said hot process air to said first rotary perforated cylinder ( 26 ), so that said hot process air can be blown on said paper material slurry ( 100 ) additionally to the hot process air generated directly by the components ( 30 ,  34 ,  40 ) of the heating system which are connected to said first rotary perforated cylinder ( 26 ). 
     
     
         2 . Plant ( 10 ) according to  claim 1 , characterized in that the diameter (D 1 ) of said first rotary perforated cylinder ( 26 ) is smaller than or equal to the diameter (D 2 ) of said second rotary perforated cylinder ( 28 ). 
     
     
         3 . Plant ( 10 ) according to  claim 2 , characterized in that the diameter (D 1 ) of said first rotary perforated cylinder ( 26 ) is comprised between about 2 m and about 2.2 m. 
     
     
         4 . Plant ( 10 ) according to  claim 2 , characterized in that the diameter (D 2 ) of said second rotary perforated cylinder ( 28 ) is comprised between about 2 m and about 7.5 m. 
     
     
         5 . Plant ( 10 ) according to  claim 1 , characterized in that said heating system ( 30 ,  34 ,  40 ) is designed to generate and deliver hot process air to said first rotary perforated cylinder ( 26 ) from the bottom upwards, through at least one first conveyor ( 44 ) arranged below said first rotary perforated cylinder ( 26 ). 
     
     
         6 . Plant ( 10 ) according to  claim 1 , characterized in that said recovery circuit ( 42 ), which recovers the hot process air suctioned by said second rotary perforated cylinder ( 28 ), is designed to deliver said hot process air to said first rotary perforated cylinder ( 26 ) from the bottom upwards, through said first conveyor ( 44 ). 
     
     
         7 . Plant ( 10 ) according to  claim 1 , characterized in that said heating system ( 32 ,  36 ,  38 ) is designed to generate and deliver hot process air to said second rotary perforated cylinder ( 28 ) from the bottom upwards, through at least one second conveyor ( 48 ) arranged below said second rotary perforated cylinder ( 28 ). 
     
     
         8 . Plant ( 10 ) according to  claim 1 , characterized in that said support belt ( 14 ,  16 ) consists of a fabric with plain weave, made of material resistant to temperatures up to 200-250° C. 
     
     
         9 . Plant ( 10 ) according to  claim 1 , characterized in that said first rotary perforated cylinder ( 26 ) is designed to blow said hot process air at a temperature comprised between about 80° C. and about 250° C., while said second rotary perforated cylinder ( 28 ) is designed to suction said hot process air at a temperature comprised between about 100° C. and about 230° C.