Yankee drying hood arrangement, a Yankee drying cylinder fitted with a Yankee drying hood arrangement and a method of drying a fibrous web

Patent metadata

Field	Value
Publication number	US-11268240-B2
Application number	US-202017423005-A
Country	US
Kind code	B2
Filing date	Jan 15, 2020
Priority date	Jan 15, 2019
Publication date	Mar 8, 2022
Grant date	Mar 8, 2022

Abstract

The invention relates to a Yankee drying hood arrangement (1) which has a first temperature main supply conduit (9, 9′) for a fluid such as hot air, or hot air and steam and/or water vapour, at a first temperature T1 and a second temperature main supply conduits (10, 10′) for a fluid such as hot air, or hot air and steam and/or water vapour, at a second temperature T2 which is not the same as T1, the first temperature and second temperature main supply conduits (9, 9′, 10, 10′) being in communication with the distributor conduits (8) such that a fluid such as hot air can stream from the first temperature and second temperature main supply conduits (9, 9′, 10, 10′) to the distributor conduits (8), wherein at least one distributor conduit (8) is provided with damper means (31) for changing the ratio between amount of fluid at temperature T1 from the first temperature main conduit and the amount of fluid at temperature T2 from the second temperature main conduit that streams into the distributor conduit.

First claim

The invention claimed is:

1. A Yankee drying hood arrangement ( 1 ) which is shaped to be fitted over a rotatable Yankee drying cylinder ( 2 ) having an axial extension (A) and a circular cylindrical surface ( 3 ) such that the Yankee drying hood arrangement ( 1 ) covers a part ( 4 ) of the circular cylindrical surface ( 3 ) of the Yankee drying cylinder ( 2 ), the Yankee drying hood arrangement ( 1 ) comprising:
a plurality of nozzle boxes ( 5 ) distributed around an imaginary axis (X) which is coincident, or substantially coincident, to the axis of rotation of the Yankee cylinder, such that, when the Yankee drying hood arrangement ( 1 ) is fitted over a Yankee drying cylinder ( 2 ), the nozzle boxes ( 5 ) are spaced from the circular cylindrical surface ( 3 ) of the Yankee drying cylinder ( 2 ) and form a curved structure ( 6 ) that follows the outer contour of the circular cylindrical surface ( 3 ) of the Yankee drying cylinder ( 2 ), each nozzle box ( 5 ) having a longitudinal extension in a direction parallel to the axial extension (A) of the Yankee drying cylinder ( 2 ) and each nozzle box ( 5 ) having a plurality of openings ( 7 ) distributed along the longitudinal extension of the nozzle box ( 5 ) through which openings ( 7 ) a fluid such as hot air can exit the nozzle boxes ( 5 ) and stream towards the circular cylindrical surface ( 3 ) of the Yankee drying cylinder ( 2 ) at different points along the longitudinal extension of each nozzle box ( 5 ) such that the fluid streaming from the openings ( 7 ) reaches the circular cylindrical surface ( 3 ) of the Yankee drying cylinder ( 2 ) at different points along the axial extension of the Yankee drying cylinder ( 2 );
a plurality of distributor conduits ( 8 ) for a fluid such as hot air, the distributor conduits ( 8 ) extending in the circumferential direction around the curved structure ( 6 ) formed by the nozzle boxes ( 5 ) and each distributor conduit ( 8 ) being in communication with one or more nozzle boxes ( 5 ) such that a fluid such as hot air streams from each distributor conduit ( 8 ) to said one or more nozzle boxes ( 5 );
at least one first temperature main supply conduit ( 9 ) for a fluid including one or more of hot air, hot air and steam, or water vapor, at a first temperature T 1 , and at least one second temperature main supply conduit ( 10 ) for a fluid including one or more of hot air, hot air and steam, or water vapor, at a second temperature T 2 which is not the same as T 1 , said first temperature and second temperature main supply conduits ( 9 , 10 ) being in communication with the distributor conduits ( 8 ) such that fluids from the first temperature and second temperature main supply conduits ( 9 , 10 ) flow into the distributor conduits ( 8 ) and be mixed,
wherein at least one distributor conduit ( 8 ) is provided with damper means ( 31 ) for changing the ratio between the flow rate of fluid at temperature T 1 from the first temperature main conduit and the flow rate of fluid at temperature T 2 from the second temperature main conduit into said at least one distributor conduit ( 8 ).

2. The Yankee drying hood arrangement ( 1 ) according to claim 1 , wherein temperature T 1 is equal to or greater than 250° C. and less than or equal to 700° C.

3. The Yankee drying hood arrangement ( 1 ) according to claim 1 , wherein, temperature T 2 is equal to or greater than 200° C. and less than or equal to 650° C.

4. The Yankee drying hood arrangement ( 1 ) according to claim 1 , wherein the temperature difference between T 1 and T 2 is equal to or greater than 100° C.

5. The Yankee drying hood arrangement ( 1 ) according to claim 1 , wherein the temperature difference between T 1 and T 2 is equal to or greater than 500° C.

6. The Yankee drying hood arrangement ( 1 ) according to claim 1 , wherein the nozzle boxes ( 5 ) are spaced apart from each other in the circumferential direction of the curved structure ( 6 ) formed by the nozzle boxes ( 5 ) such that a fluid such as air or a mixture of air and steam pass between the nozzle boxes ( 5 ).

7. The Yankee drying hood arrangement ( 1 ) according to claim 6 , wherein an evacuation conduit ( 19 ) is arranged to evacuate exhaust fluid, such as air or a mixture of air and steam and/or water vapor, from the Yankee drying hood arrangement and wherein the evacuation conduit ( 19 ) is in fluid connection with an inlet to a second temperature main supply conduit ( 10 ).

8. The Yankee drying hood arrangement ( 1 ) according to claim 7 , wherein the evacuation conduit ( 19 ) is in fluid connection with an inlet to the first temperature main supply conduit or conduits.

9. The Yankee drying hood arrangement ( 1 ) according to claim 7 , wherein the evacuation conduit is in fluid connection with an exhaust conduit leading to one or more of an atmosphere or a heat recover system.

10. The Yankee drying hood arrangement ( 1 ) according to claim 7 , wherein the evacuation conduit is provided with flow regulating means for regulation the proportion of exhaust fluid which is inputted into each conduit.

11. The Yankee drying hood arrangement according to claim 6 , wherein the nozzle boxes ( 5 ) are spaced from each other by a distance of 30 mm-70 mm in the circumferential direction of the curved structure ( 6 ) formed by the nozzle boxes ( 5 ).

12. The Yankee drying hood arrangement according to claim 1 , wherein said damper means is a flap or plate configured to change the ratio between the flow rate of fluid at temperature T 1 from the first temperature main conduit and the flow rate of fluid at temperature T 2 from the second temperature main conduit that streams into the distributor conduit.

13. The Yankee drying hood arrangement according to claim 12 , wherein said damper means is configured to change the ratio between the flow rate of fluid at temperature T 1 from the first temperature main conduit and the flow rate of fluid at temperature T 2 from the second temperature main conduit that streams into the distributor conduit without changing the total flow rate though the distributor channel.

14. The Yankee drying hood arrangement according to claim 1 , wherein the nozzle boxes ( 5 ) are equidistantly distributed around the imaginary axis (X).

15. A Yankee drying cylinder comprising a Yankee drying hood according to claim 1 .

16. A method of drying a fibrous web (W) on a Yankee drying cylinder comprising a Yankee drying hood in accordance to claim 1 , the method comprising the steps of:
measuring the moisture content of a fibrous web at at least one position,
determining the moisture content for a measured position relative to a predetermined acceptable value and, when the moisture content for a measured position is below the predetermined acceptable value, reducing the flow rate of fluid at temperature T 1 and increasing by a corresponding amount the flow rate of fluid at temperature T 2 entering the distribution conduit in fluid connection with a nozzle box corresponding to that measured position; and
when the moisture content for a measured position is above the predetermined acceptable value, increasing the flow rate of fluid at temperature T 1 and decreasing by a corresponding amount the flow of fluid at temperature T 2 entering the distribution conduit in fluid connection with a nozzle corresponding to that measured position.

Assignees

• Valmet Oy

Inventors

• Saikkonen Olli
• Moscatelli Luca
• Lasic Klavdij
• Malutta Raffaele
• Durisotti Michele
• Simeoni Lorenzo

Classifications

• D21F5/044

  using air hoods over the cylinders · CPC title

• D21F5/181 Primary

  on Yankee cylinder · CPC title

• D21F5/021

  Construction of the cylinders · CPC title