Air hood for a Yankee roll and system comprising a Yankee roll and said air hood
09783927 · 2017-10-10
Assignee
Inventors
Cpc classification
International classification
Abstract
The air hood (3) for Yankee rolls (1) comprises at least one supply circuit (5, 6, 7) to supply dry hot air towards outlets (7A) to a working area, and at least one suction circuit (11) to suck wet air from the working area. The hood comprises a thermal insulation insulating at least partially the supply circuit from the suction circuit.
Claims
1. An air hood for Yankee rolls, comprising: at least one supply circuit to supply dry hot air towards outlets to a working area, wherein the at least one supply circuit comprises at least a supply duct, dry hot air distribution boxes in fluid communication with the supply duct, and inflate channels for supplying dry hot air in the working area of the air hood, said inflate channels being in fluid communication with the distribution boxes and said inflate channels being provided with said outlets; and at least one suction circuit to suck wet air from the working area, wherein the suction circuit comprises an inner space inside the air hood and at least a suction duct in fluid communication with the inner space, wherein the distribution boxes and at least a portion of the supply duct are arranged in the inner space, the distribution boxes having side walls separating an interior of the distribution boxes from the inner space and the distribution boxes being provided with a thermal insulation arranged on the side walls for at least partially insulating the inner space from the interior of the distribution boxes.
2. An air hood according to claim 1, wherein the inflate channels are arranged according to a substantially cylindrical surface, delimiting the inner space of the air hood along the working area which is to face the cylindrical surface of a Yankee cylinder, the inflate channels being spaced from one another to define passages therebetween, through which wet air is sucked from the working area, where a cellulose ply passes, towards the inner space of the air hood and from said inner space of the air hood towards the suction duct.
3. An air hood according to claim 2, wherein the suction circuit comprises openings between the inflate channels in fluid communication with the inner space of the air hood, wherein a heat exchange between the interior of the distribution boxes and the suction circuit is reduced via the thermal insulation.
4. An air hood according to claim 3, wherein the supply duct is provided with said thermal insulation, wherein an outer wall defines the supply duct, the thermal insulation surrounding the outer wall, the outer wall being thermally insulated from at least the at least one suction circuit via the thermal insulation.
5. An air hood according to claim 2, wherein the supply duct is provided with said thermal insulation, wherein an outer wall defines the supply duct, the thermal insulation surrounding the outer wall, the outer wall being thermally insulated from at least the at least one suction circuit via the thermal insulation.
6. An air hood according to claim 2, further comprising a first semi-hood and a second semi-hood, each of said first semi-hood and said second semi-hood comprising a respective supply circuit for supplying said dry hot air and a respective suction circuit for sucking said wet air.
7. An air hood according to claim 1, wherein the suction circuit comprises openings between the inflate channels in fluid communication with the inner space of the air hood, wherein a heat exchange between the interior of the distribution boxes and the suction circuit is reduced via the thermal insulation.
8. An air hood according to claim 7, wherein the supply duct is provided with said thermal insulation, wherein an outer wall defines the supply duct, the thermal insulation surrounding the outer wall, the outer wall being thermally insulated from at least the at least one suction circuit via the thermal insulation, wherein a transfer of heat is reduced between the supply duct and at least an interior of the at least one suction circuit via the thermal insulation.
9. An air hood according to claim 1, wherein the supply duct is provided with said thermal insulation, wherein an outer wall defines the supply duct, the thermal insulation engaging the outer wall, the outer wall being thermally insulated from at least the at least one suction circuit via the thermal insulation.
10. An air hood according to claim 1, further comprising a first semi-hood and a second semi-hood, each of said first semi-hood and said second semi-hood comprising a respective supply circuit for supplying said dry hot air and a respective suction circuit for sucking said wet air.
11. An air hood according to claim 10, wherein each supply circuit comprises a dry hot air supply duct in fluid communication with a plurality of respective dry hot air distribution boxes provided with said thermal insulation, wherein the distribution boxes of each of said first semi-hood and said second semi-hood are in fluid communication with a plurality of respective inflate channels that supply air towards the working area and said plurality of respective inflate channels are provided with outlets for the dry hot air towards the working area of the air hood.
12. An air hood according to claim 11, wherein each suction circuit comprises a semi-hood inner space and a suction duct.
13. An air hood according to claim 1, further comprising two front walls substantially orthogonal to an axis of a Yankee roll when the air hood is associated with the Yankee roll, at least one of said front walls being provided with passages for one or more of the supply duct and the suction duct.
14. An air hood according to claim 13, wherein the front walls are provided with said thermal insulation.
15. An air hood according to claim 14, wherein the thermal insulation of the front walls comprises sheets or plates of thermal insulating material fastened to support flanks.
16. An air hood according to claim 15, wherein one or more of the sheets or plates of thermal insulating material comprises a thermal insulating material with a polymeric matrix, where one or more of the following components are dispersed: glass particles, rock wool, clay particles, montmorillonite particles.
17. An air hood according to claim 16, wherein a hollow space inside the thermal insulating material is lower than 10%, preferably lower than 3% and more preferably lower than 2% of a whole volume thereof.
18. An air hood according to claim 15, wherein at least one side wall is provided between the two front walls, the at least one side wall being provided with said thermal insulation.
19. An air hood according to claim 14, wherein at least one side wall is provided between the two front walls, the at least one side wall being provided with said thermal insulation.
20. An air hood according to claim 13, wherein at least one side wall is provided between the two front walls, the at least one side wall being provided with said thermal insulation.
21. An air hood according to claim 20, wherein the at least one side wall comprises a plurality of insulation panels forming the thermal insulation.
22. An air hood according to claim 21, wherein each of said insulation panels comprises two outer covers, between which at least one sheet or plate of thermal insulating material is arranged.
23. An air hood according to claim 22, wherein a sealed space is provided between the two outer covers, inside which said at least one sheet or plate of thermal insulating material is housed.
24. An air hood according to claim 22, wherein reciprocal fastening members are arranged between consecutive insulation panels to join said insulation panels together.
25. An air hood according to claim 24, wherein said insulation panels are mounted with a reciprocal clearance to allow heat expansion.
26. An air hood according to claim 24, wherein said insulation panels are fastened to the two front walls so as to allow the heat expansion of said insulation panels.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The present invention will be better understood by means of the description below and the attached drawing, which shows a non-restrictive practical embodiment of the invention. More particularly, in the drawing:
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
DETAILED DESCRIPTION OF EMBODIMENTS
(10) The detailed description below of example embodiments is made with reference to the attached drawings. The same reference numbers in different drawings identify the equal or similar elements. Furthermore, the drawings are not necessarily to scale. The detailed description below does not limit the invention. The protective scope of the present invention is defined by the attached claims.
(11) In the description, the reference to “an embodiment” or “the embodiment” or “some embodiments” means that a particular feature, structure or element described with reference to an embodiment is comprised in at least one embodiment of the described object. The sentences “in an embodiment” or “in the embodiment” or “in some embodiments” in the description do not therefore necessarily refer to the same embodiment or embodiments. The particular features, structures or elements can be furthermore combined in any adequate way in one or more embodiments.
(12) In
(13) In some embodiments, the air hood 3 is subdivided into two semi-hoods or semi-bodies 3A and 3B adjacent to each other in correspondence of a vertical median plane P1-P1 containing the axis of rotation A-A of the Yankee roll 1.
(14) The two semi-hoods 3A and 3B move towards and away from each other according to the double arrow f3, so as to allow accessing the Yankee roll 1 below for inspection, maintenance, and cleaning. This movement may be controlled by means of actuators 2 arranged at the sides of the air hoods 3.
(15) Each semi-hood 3A, 3B has a dry hot air supply duct, indicated with number 5 for both the semi-hoods 3A, 3B. The supply ducts 5 are into fluid communication with a plurality of dry hot air distribution boxes 6. Each box 6 is in fluid communication with a plurality of inflate channels 7 supplying dry hot air towards the working area of the air hood 3. The inflate channels 7 are arranged around the cylindrical surface of the Yankee roll 1. The inflate channels 7 extend longitudinally nearly parallel to the axis A-A of the Yankee roll 1. They are substantially arranged according to a nearly cylindrical pattern partially following the extension of the cylindrical wall of the Yankee roll 1.
(16) The inflate channels 7 have dry hot air outlets, schematically indicated with 7A, allowing the dry hot air, supplied by means of the supply ducts 5 and the boxes 6 into the inflate channels 7, to exit towards the cylindrical surface of the Yankee roll 1, and more precisely against the cellulose ply (not shown) driven around the Yankee roll 1. In some embodiments, the inflate channels 7 are spaced from one another so as to leave, between pairs of adjacent inflate channels 7, respective openings or hollow spaces 9, through which wet air is sucked from the cylindrical surface of the Yankee roll 1 and the web material N. The wet air is sucked by means of suction ducts 11 and, dragging therewith humidity removed from the cellulose ply, is conveyed towards a system for removing humidity and heating air. The air, dried and heated again, returns towards the air hood through the supply ducts 5.
(17) In the illustrated embodiment, each semi-hood or semi-body 3A, 3B has only one suction duct 11 in fluid communication with the inner space of the respective semi-hood 3A, 3B, defined between the outer walls of the air hood and the series of inflate channels 7 partially closing the inner space towards the Yankee roll 1.
(18) The air hood 3 contributes to the drying of the cellulose ply driven around the Yankee roll, as described below. The cellulose ply is into contact with the surface of the Yankee roll and the water contained therein evaporates due to the effect of the absorption of heat emitted from the Yankee roll 1. The emitted water vapor is removed by means of dry hot air inflated in the space between the air hood 3 and the cylindrical surface of the Yankee roll 1 through the outlets 7A of the inflate channels 7 and sucked through the hollow spaces or openings 9 and the suction duct 11.
(19) The supply duct 5, the boxes 6 and the inflate channels 7 define a dry hot air supply circuit for each semi-hood 3A, 3B. The spaces or openings 9 between inflate channels 7, the hollow inner space of the semi-hoods 3A, 3B and the suction duct 11 define together a wet air suction circuit.
(20) The temperature of the dry hot air supplied through each supply duct 5 is higher than the temperature of the wet air sucked through the openings or hollow spaces 9. As it will be better described below, to reduce the heat exchange between the air circulating in the supply ducts 5 and in the boxes 6 and the air sucked in the inner space of each semi-hood 3A, 3B through the spaces or opening 9, in some embodiments insulation coatings may be provided, covering at least partially the surfaces dividing the volumes where the dry hot air circulates from the volumes where the colder wet air circulates. This allows advantages in terms of energy savings and, on the other hands, in terms of greater uniformity in the temperature of the air inflated towards the Yankee roll 1, i.e. a reduced temperature gradient along the axial extension of said Yankee roll 1.
(21) The inner space of each semi-hood 3A, 3B may be closed towards the outside by means of panels of thermal insulating material to form a thermal insulation indicated as a whole with 25, that can surround the whole surface, or a part, of each semi-hood 3A, 3B, leaving the area towards the Yankee roll 1 free of panels, i.e. the area where the inflate channels 7 and the hollow spaces 9 are located. Also in the area, where the two semi-bodies or semi-hoods 3A, 3B are adjacent to each other, there are no insulation panels. The thermal insulation 25 may be also provided for the front walls 3X of the two semi-hoods 3A, 3B, i.e. the walls orthogonal to the axis A-A of the Yankee roll 1 and to the channels 9.
(22) In some embodiments, the thermal insulation is comprised of a plurality of adjacent insulation panels 31, fastened to a frame 13 and/or self-supporting, as better described below.
(23) Each insulation panel may be made with a sheet or a plurality of plates of thermal insulating material, housed in a case formed by walls ad covers made for instance of sheet metal. The construction details of the insulation panels used for the outer insulation of the air hood will be detailed below.
(24) Also a part of the walls delimiting the supply duct 5 and the boxes 6 may be provided with a thermal insulation to limit the heat losses towards the environment (in the segment of the supply duct 5 between the heat exchanger downstream, not shown, and the inside of the air hood 3) and towards the sucked wet air flow exiting the air hood (inside the air hood 3).
(25)
(26) Similarly, the outer wall of each supply duct 5 may be thermally insulated.
(27) The supply duct 5 may comprise a substantially cylindrical wall 41 surrounded by an outer wall or casing 43. A space is defined between the two walls 41, 43, that can be filled with a thermal insulating material. In this case again, sintered carbon foam with cell structure may be used as thermal insulating material.
(28) Advantageously, the front wall 3C of the air hood has a through hole 47, through which the supply duct 5 extends. To allow radial heat expansion of the supply duct 5 with respect to the front wall 3X, the hole 47 has a diameter greater than the outer diameter of the wall 43 protecting the insulation of the supply duct 5. A gasket 49 may be provided between the front wall 3X and the outer surface of the wall 43. In this way it is possible to avoid that, through the suction duct 11, environment air is sucked, penetrating in the inner volume of the hood 3 through the space between wall 43 and wall 3X.
(29) To allow their axial expansion, on each supply duct 5 there is provided an expansion joint 51, shown in
(30) Similar insulation systems and expansion joints may be provided on the suction ducts 11.
(31) As schematically indicated in
(32) The described arrangement allows mounting one or more covers 63 onto the flank 59 of each front wall 3X, holding one or more sheets of thermal insulating material 61 inside the space between covers 63 and flank 59. The sheets or plates 61 of thermal insulating material may be provided with through holes for the fasteners 65, and the holes may be formed during manufacturing of the sheets or plates 61.
(33) A curved side wall 3Y extends between the two front walls 3X that define the flank and the cover of each semi-hood 3A, 3B. The curved side wall 3Y may be formed by a plurality of insulation panels 31 aligned together. Each insulation panel 31 may flat and the whole curvature of the wall 3Y may be achieved by arranging the insulation panels 31 inclined with respect to one another, as shown in
(34) The insulation panels 31 may be connected to the front walls 3X of each semi-hood 3A, 3B as shown in
(35)
(36) With reference to
(37) On the opposite side, illustrated in
(38) In some embodiments, a sheet 85 of thermal insulating material may be provided inside the insulation panel 31. This sheet may be made of the same insulating material of which are made the sheets or plates 61 surrounding the front walls 3X. Some examples of materials and production methods will be described below.
(39) The sheets or plates of thermal insulating material 85 may be contained in a case, shell or housing space, delimited on the main faces by covering sheet metals 87 and 89 that are respectively outside and inside the air hood 3. The covering sheet metals 87 and 89 of each insulation panel 31 may be made of steel and form the case or shell for housing the sheets or plates of thermal insulating material 85 together with the side seal 75 and with longitudinal banks or edges 91, 93.
(40) In some embodiments, pads or strips 95 of a different material, for instance with higher elasticity and compressibility, may be arranged between the inner cover 89 and the sheet of thermal insulating material 85. The pads or strips 95 may be for instance made of sintered carbon foam.
(41) As shown in
(42) The angular profile 103 of each insulation panel 31 acts as a support for the adjacent insulation panel 31 and the angular profile 101 defines, together with the angular profile 103, a channel for reciprocal joining of the two adjacent insulation panels 31. Practically, the angular profiles 101 and 103 define reciprocal fastening members to join consecutive insulation panels 31 together. In this way it is possible to join together the insulation panels 31, one following the other, to form the insulation of the wall 3Y.
(43) The seals 75 may extend between the bent edges 87A, 89A; in this way these seals may surround the whole sheet or plate of thermal insulating material 85.
(44) Strips 107, 109 of a different thermal insulating material, for instance a more compressible material, may be inserted between the bent edges 87A, 89A and the sheets or plates of thermal insulating material 85. Typically, the strips 107, 109 may be made for instance of sintered carbon foam, to allow differential heat expansions between the sheets of thermal insulating material 85 and the covers 87, 89.
(45) Adjacent and consecutive insulation panels 31 may be mounted keeping a space 110 therebetween, thus allowing heat expansion.
(46) The sheets or plates of thermal insulating material 61, 85 forming the thermal insulating coatings of the front walls 3X and filling the insulation panels 31 may be formed separately and then applied to the flank 59 and to one of the covers 87, 89 of the panel 31 respectively. In other embodiments, the plates of thermal insulating material 61, 85 may be produced by pouring a liquid onto the flank 59 or onto one of the covers 87, 89 and then hardening the thermal insulating material.
(47) In some embodiments, the thermal insulating material forming the sheets or plates 61 and 85 may be comprised of a polymeric matrix comprising one or more of the following fillers: glass spheres, rock wool fibers and clay particles, montmorillonite particles.
(48) Advantageously, in some embodiments the glass spheres have a dimension comprised between 5 micrometers and 100 micrometers, for instance between 5 and 60 micrometers, based upon the percent composition of the material.
(49) In some embodiments, the rock wool fibers may have a cross dimension—intended as the maximum dimension of the cross-section—comprised between 2 and 6 micrometers. In case the fibers have round cross-section, this dimension refers to the diameter. The length of the rock wool fibers may be comprised between 5 and 70 micrometers, depending upon the percent composition of the material.
(50) The numbers mentioned above have been given just by way of example and, even if they may be preferred in some embodiments, however they do not limit the scope of the invention.
(51) Generally, the rock wool is an amorphous silicate in the form of thin filaments obtained from siliceous rocks.
(52) The polymeric matrix may contain or be substantially constituted by an acrylic polymer, for instance an acrylic polymer with polar functional groups, to have adhesive features. In some embodiments the acrylic polymer may be an acrylic acid copolymer with acililates and methacrylates with different alkyl chain lengths.
(53) In some embodiments the polymer may be a thermoplastic polymer of long hydrocarbon chain with polar functional groups.
(54) In some embodiments, phosphor compounds and/or nanostructured clays may be added to the polymeric matrix. The phosphor compound may be chosen among the flame-retardant compounds, for instance an alkyl or aromatic phosphonate.
(55) Clay particles and/or montmorillonite particles may have nanoscale sizes, in particular comprised between 5 and 100 nanometers, preferably between 5 and 50 nanometers and more preferably between 5 and 20 nanometers, based upon the percent chemical composition.
(56) In some embodiments the insulating material may be produced starting from a composition having a dry percent composition by weight comprising:
(57) glass spheres 5-40% by weight;
(58) rock wool 5-40% by weight;
(59) clay and/or montmorillonite 0.5-5% by weight
(60) polymer, for instance acrylic polymer, 10-40% by weight.
(61) A liquid dispersing agent may be added to this composition, such as water or another dispersor that can be easily vaporized and has low environmental impact. The function of the dispersing liquid is to adjust the viscosity of the material before distributing it on adequate structures or equipment, to form a layer of material that is then heated and solidified.
(62) The sheets or plates of thermal insulating material may be formed starting from a suspension, in water or other dispersing liquid, of the polymer and the inorganic components indicated above. The suspension is applied onto a support of adequate shape, according to the final use of the sheet or plate. The layer is then solidified and hardened in a furnace. Once ready, the sheets or plates may be cut or shaped, if necessary, and then applied onto the sides 59 and/or the cover 87 or 89 of the single insulation panel 31. Alternatively, the sheet or plate may be produced by pouring the material directly onto the plate 59 for the insulation of the front walls 3X, or on one of the covers 87, 89 forming the shell surrounding the thermal insulating material 85 for the insulation panels 31.
(63) In some embodiments, the thickness of the thermal insulating material forming the plates 61 and 85 may be advantageously comprised between 20 and 60 mm.
(64) While the disclosed embodiments of the subject matter described herein have been shown in the drawings and fully described above with particularity and detail in connection with several exemplary embodiments, it will be apparent to those of ordinary skill in the art that many modifications, changes, and omissions are possible without materially departing from the novel teachings, the principles and concepts set forth herein, and advantages of the subject matter recited in the appended claims. Hence, the proper scope of the disclosed innovations should be determined only by the broadest interpretation of the appended claims so as to encompass all such modifications, changes, and omissions. In addition, the order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments.