(19)
(11)EP 3 392 586 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
29.07.2020 Bulletin 2020/31

(21)Application number: 18176643.7

(22)Date of filing:  05.12.2013
(51)International Patent Classification (IPC): 
F26B 15/12(2006.01)
F26B 21/00(2006.01)

(54)

DRYING SYSTEM

TROCKNUNGSSYSTEM

SYSTÈME DE SÉCHAGE


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 05.12.2012 EP 12290428

(43)Date of publication of application:
24.10.2018 Bulletin 2018/43

(62)Application number of the earlier application in accordance with Art. 76 EPC:
13801575.5 / 2929265

(73)Proprietor: SAINT-GOBAIN PLACO
92400 Courbevoie (FR)

(72)Inventors:
  • MONGROLLE, Jean-Louis
    93410 Vajours B.P.6 (FR)
  • LALANDE, Jérôme
    93410 Vajours B.P.6 (FR)
  • GOODAIRE, Martin
    Coventry, Warwickshire CV3 2TT (GB)
  • SELBY, Stephen
    Coventry, Warwickshire CV3 2TT (GB)

(74)Representative: Murgitroyd & Company 
Murgitroyd House 165-169 Scotland Street
Glasgow G5 8PL
Glasgow G5 8PL (GB)


(56)References cited: : 
WO-A2-2004/101238
US-A- 4 467 537
DE-A1- 4 412 352
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description


    [0001] The present invention relates to drying systems for drying boards, in particular for drying gypsum plasterboards.

    [0002] Gypsum wallboard is well-known for use in the construction industry, e.g. for providing linings for walls, ceilings, lift-shafts and corridors.

    [0003] The term "gypsum", as used herein, refers to calcium sulphate in a stable dihydrate state (CaSO4.2H2O), and includes the naturally occurring mineral, the synthetically derived equivalents, and the dihydrate material formed by the hydration of anhydrite or stucco (calcium sulphate hemihydrate).

    [0004] Gypsum is capable of being dehydrated to form plaster, which can subsequently be rehydrated and cast, moulded or otherwise formed to useful shapes, such as boards.

    [0005] Gypsum is generally prepared for use as plaster by grinding and calcining at relatively low temperature (such as from about 120 to 170°C), generally at atmospheric pressure. This results in partially dehydrated gypsum, typically in the form of the beta crystalline form of the hemihydrate. The partially dehydrated gypsum may be used as a building or construction material by mixing it with water to form an aqueous stucco slurry, paste or dispersion, and then allowing the slurry to set by re-crystallisation from the aqueous medium.

    [0006] In the production of gypsum boards, slurry is typically deposited on a liner e.g. a paper sheet, and is covered with a further liner, such that the slurry is sandwiched between the two liners. This sandwich structure is then passed through a pair of forming plates or rolls that determine the thickness of the board. After this, the structure passes along a conveyor line, to allow time for the stucco slurry to hydrate and harden. The hardened structure is cut to provide multiple boards of the desired length and these are transferred to a drying system to allow excess water to evaporate.

    [0007] It is known to provide drying systems having conduits that direct airflow in a longitudinal direction of the system, that is, in the direction of travel of the gypsum board.

    [0008] It is also known to provide drying systems having conduits that direct airflow towards one of the faces of the board. In such cases, the flow patterns are such that after leaving the conduit, air tends to travel along the surface of the board in a transverse direction of the system. These systems tend to have multiple conduits that are spaced along the length of the system.

    [0009] The drying system is typically made up of a series of drying chambers, each of which provides heated airflow that is directed towards the main faces of the board. Typically, a board travels through each of the drying chambers in turn, supported and conveyed by a roller array. Thus, each board passes along the temperature profile of the drying system.

    [0010] It is desirable for drying systems to be provided that have one or more of the following attributes:
    • they dry the boards more evenly;
    • they have a reduced spatial requirement (that is, a reduced footprint and/or fewer drying chambers);
    • they have reduced energy requirements.


    [0011] DE4412352A1 discloses tunnel dryers for drying ceramic moldings, in particular brick or roof tile blanks. The tunnel dryers comprise countercurrently-ventilated drying channels through which transport supports are movable, on which the moldings to be dried are arranged in a direction transverse to the transport direction.

    [0012] US 4467537 discloses heat-treating equipment for flat, band-like lengths of materials, using a gaseous flowing drying medium. The equipment being composed of a thermally insulated housing with transmission slots at both ends for a length of material and nozzle conduits arranged in sequential spacing above and below the length of material and directed transversely to the direction of motion of the material.

    [0013] WO 2004/101238 discloses a veneer dryer including at least one drying chamber that includes conveyor for conveying product to be dried between an input end and an output end. The veneer dryer further includes a plurality of upper and lower nozzles are arranged above and below the conveyor and are operative to direct heated air into an impinging contact with material being conveyed on the conveyor. The nozzles are arranged in pairs wherein one nozzle of a pair includes a plurality of discharge ports that are offset with respect to a plurality of discharge ports forming part of the other nozzle of the pair.

    [0014] A vertical side plate defines one common lateral side of the drying chambers and features squared apertures matching the inlets of the nozzles.

    [0015] Therefore, at its most general, the present invention may provide a drier for drying boards, the drier comprising at least one conduit for directing airflow towards one of the faces of the board, the drier being configured such that at least a portion of the airflow travels across the face of the board along the longitudinal axis of the drier (in either direction along this axis). In the present specification, the longitudinal axis of the drier denotes the axis along which the board travels as it is dried. Preferably, airflow occurs predominantly along this axis.

    [0016] By promoting longitudinal airflow across the face of the board, it may be possible to dry the board more evenly, since the variation in the distance travelled by the airflow over different portions of the board face is reduced. Furthermore, by aligning airflow with the longitudinal axis of the drier, it may be possible to increase the contact time between the air and the underlying boards, thus increasing drying rates.

    [0017] Typically, a plurality of conduits are provided at intervals along the longitudinal direction of the drier. The drier is configured such that air exiting the conduit is drawn into the space between adjacent conduits, thus promoting longitudinal flow over the surfaces of the boards.

    [0018] A first aspect of the invention is defined by claim 1.

    [0019] Preferably, the cross-sectional area of the conduit decreases in a downstream direction of the conduit.

    [0020] A second aspect of the present invention is defined by claim 3.

    [0021] The invention will now be described by way of example with reference to the following Figures in which:

    Fig. 1 is a schematic plan view of a drying system according to the invention;

    Fig. 2 is a schematic section view of part of a drier according to the invention; and

    Fig. 3 is a schematic section view taken along the line A-A of Fig. 2 and including multiple drier levels.



    [0022] Referring to Fig. 1, a drying system 10 has multiple drying chambers 12 arranged in sequence. Gypsum boards to be dried pass along this sequence in turn, starting in a pre-drying region 14, before passing through a main drying region 16 and finally a finishing zone 18.

    [0023] The main drying region 16 is heated using gas burners, while the chambers in the pre-drying and finishing regions 14,18 are heated through heat exchangers. The heat exchangers use heat that is recovered from the exhaust of the main drying region 16. Thermal energy may be recovered from the exhaust of the main drying region 16 using a heat pump 22.

    [0024] Referring to Figs. 2 and 3, a drier has rollers 30a,30b that support a gypsum board and cause it to move through the drier (e.g. from left to right in Fig. 2). The rollers are provided in multiple sets 30, each set of rollers defining a different plane for supporting a respective board. A group of four rollers 30a, 30b, 30c, and 30d defines a unit area against which the cross-sectional area of the nozzle boxes is compared.

    [0025] Lower nozzle boxes 34 provide airflow conduits for supplying heated air to the underside of a respective gypsum board 32 via apertures 36,38. Upper nozzle boxes 40 provide airflow conduits for supplying heated air to the upper side of a respective board 32 via apertures 42,44. The apertures are provided in the surface of the respective nozzle box that faces the board to be dried. The upper and lower nozzle boxes are aligned with the rollers 30a,30b, such that they extend in a transverse direction of the drier (that is, into the plane of Fig. 2).

    [0026] The terms "lower nozzle box" and "upper nozzle box" denote the position of the nozzle box relative to the board that experiences airflow from that nozzle box.

    [0027] The upper and lower nozzle boxes 34,40 are each provided with a set of multiple apertures, the set of multiple apertures extending along the length of the respective nozzle box. The apertures are provided in the face of the nozzle box that is opposed to the respective board. The nozzle box further has sides that extend away from the respective board, towards the back face of the nozzle box.

    [0028] At least 90% of the apertures provided on the lower nozzle box 34 are located within 30mm of the sides of the nozzle box. Thus, at least 90% of the apertures are located within two bands extending adjacent to the sides of the nozzle box, and each band having a width that is about 18% of the total width of the nozzle box. This arrangement helps to ensure that air exiting the apertures 36,38 flows towards the rollers and down the sides of the nozzle box. That is, air exiting the apertures of the lower nozzle box 34 initially flows in a generally longitudinal direction of the drier, rather than along the length of the nozzle boxes.

    [0029] The upper nozzle boxes are about 40% wider than the lower nozzle boxes, and thus extend over a greater area of the respective gypsum board 32. This arrangement helps to ensure that air exiting the apertures 42,44 flows towards the closest edge of the upper nozzle and up the sides of the nozzle. That is, air exiting the apertures of the upper nozzle initially flows in a generally longitudinal direction of the drier, rather than along the length of the nozzle boxes.

    [0030] The width of the lower nozzle boxes 34 is such they each fit between an adjacent pair of rollers 30,30b.

    [0031] The height of the upper nozzle boxes 40 is less than that of the lower nozzle boxes 34, with the result that the cross-sectional area of the upper and lower nozzle boxes is the same. This helps to ensure a homogenous air distribution to both the upper and lower faces of the board.

    [0032] Referring to Fig. 3, the upper and lower nozzle boxes 40,34 are aligned with the rollers 30, and hence extend transversely to the direction of travel of the gypsum boards 32. Air enters the nozzle boxes at an air inlet 50, travels along the nozzle boxes and is directed towards the gypsum boards 32 by a plurality of apertures located on the face of the nozzle that is opposed to the respective gypsum board. The upper and lower nozzle boxes taper in a direction away from the air inlet 50, that is, in a downstream direction. However, the face of the nozzle box that is opposed to the respective gypsum board remains aligned with the gypsum board.

    [0033] The taper of the upper and lower nozzle boxes 34,40 helps to reduce the pressure differential along the length of the nozzle boxes, so as to reduce the extent to which air exiting the nozzle apertures tends to flow along the external length of the nozzle box. By reducing this effect, the configuration promotes airflow in a generally longitudinal direction of the drier.

    [0034] A mask 54 extends in the direction of travel of the gypsum board, that is, into the plane of Fig. 3 and transversely to the nozzle boxes 34,40, and is provided at the downstream end of the nozzle boxes. The mask 54 helps to prevent air leaving the drier in the longitudinal direction of the rollers 30. Thus, the presence of the mask helps to reduce airflow along the length of the nozzle boxes and increase airflow in a generally longitudinal direction of the drier.


    Claims

    1. A drier for drying a board (32), the board (32) having two principal surfaces that are opposed to each other, the drier comprising:

    conveying means for conveying the board (32) along a longitudinal direction of the drier, the conveying means further being for supporting the board (32) in a support plane (33) containing the longitudinal direction of the drier;

    air inflow means for directing airflow towards at least one of the principal surfaces of the board (32); and

    airflow control means comprising a panel within the drier that is aligned with the longitudinal direction of the drier and intersects the support plane (33), the panel being for enhancing airflow in the longitudinal direction of the drier, and wherein the air inflow means comprises a conduit (40, 34) extending transversely to the longitudinal direction of the board (32), the conduit (40, 34) comprising a plurality of apertures (42, 44, 36, 38) for directing airflow towards the board (32), and characterised in that the panel is located at the downstream end of the conduit (40, 34), relative to the direction of airflow along the conduit.


     
    2. A drier according to claim 1,
    wherein the cross-sectional area of the conduit decreases in a downstream direction of the conduit.
     
    3. A drier for drying a board (32), the board (32) having two principal surfaces that are opposed to each other, the drier comprising:

    conveying means for conveying the board (32) along a longitudinal direction of the drier, the conveying means further being for supporting the board (32) in a support plane (33) containing the longitudinal direction of the drier; and

    air inflow means for directing airflow towards at least an underside of the board (32), the air inflow means comprising a conduit (40, 34) extending transversely to the longitudinal direction of the board (32), the conduit (40, 34) comprising a plurality of apertures (36, 38, 42, 44) for directing airflow towards the underside of the board (32);

    wherein at least 90% of the apertures (36, 38, 42, 44) are distributed within two bands extending along the length of the conduit (40, 34), the bands being provided in the lateral portions of the conduit (40, 34) and being separated by a central strip comprising at least 55% of the width of the conduit (40, 34), and further wherein a plurality of apertures (36, 38, 42, 44) is located within each band; and

    wherein the cross-sectional area of the conduit decreases in a transverse direction of the drier.


     


    Ansprüche

    1. Ein Trockner zum Trocknen einer Platte (32), wobei die Platte (32) zwei Hauptoberflächen aufweist, die einander gegenüberliegen, wobei der Trockner Folgendes beinhaltet:

    ein Fördermittel zum Fördern der Platte (32) entlang einer Längsrichtung des Trockners, wobei das Fördermittel ferner zum Stützen der Platte (32) auf einer Stützebene (33), die die Längsrichtung des Trockners enthält, ist;

    ein Luftzuströmungsmittel zum Leiten von Luftstrom zu mindestens einer der Hauptoberflächen der Platte (32); und

    ein Luftstromsteuermittel, das ein Panel innerhalb des Trockners beinhaltet, das nach der Längsrichtung des Trockners ausgerichtet ist und sich mit der Stützebene (33) überschneidet, wobei das Panel zum Verbessern des Luftstroms in der Längsrichtung des Trockners ist, und wobei das Luftzuströmungsmittel einen Leitkanal (40, 34) beinhaltet, der sich quer zu der Längsrichtung der Platte (32) erstreckt, wobei der Leitkanal (40, 34) eine Vielzahl von Öffnungen (42, 44, 36, 38) zum Leiten von Luftstrom zu der Platte (32) beinhaltet, und

    dadurch gekennzeichnet, dass sich das Panel am stromabwärtigen Ende des Leitkanals (40, 34) relativ zu der Richtung des Luftstroms entlang des Leitkanals befindet.


     
    2. Trockner gemäß Anspruch 1,
    wobei die Querschnittsfläche des Leitkanals in einer stromabwärtigen Richtung des Leitkanals abnimmt.
     
    3. Ein Trockner zum Trocknen einer Platte (32), wobei die Platte (32) zwei Hauptoberflächen aufweist, die einander gegenüberliegen, wobei der Trockner Folgendes beinhaltet:

    ein Fördermittel zum Fördern der Platte (32) entlang einer Längsrichtung des Trockners, wobei das Fördermittel ferner zum Stützen der Platte (32) auf einer Stützebene (33), die die Längsrichtung des Trockners enthält, ist; und

    ein Luftzuströmungsmittel zum Leiten von Luftstrom zu mindestens einer Unterseite der Platte (32), wobei das Luftzuströmungsmittel einen Leitkanal (40, 34) beinhaltet, der sich quer zu der Längsrichtung der Platte (32) erstreckt, wobei der Leitkanal (40, 34) eine Vielzahl von Öffnungen (36, 38, 42, 44) zum Leiten von Luftstrom zu der Unterseite der Platte (32) beinhaltet;

    wobei mindestens 90 % der Öffnungen (36, 38, 42, 44) innerhalb von zwei Bändern verteilt sind, die sich entlang der Länge des Leitkanals (40, 34) erstrecken, wobei die Bänder in den Seitenabschnitten des Leitkanals (40, 34) bereitgestellt sind und durch einen Mittelstreifen getrennt sind, der mindestens 55 % der Breite des Leitkanals (40, 34) beinhaltet, und wobei sich ferner eine Vielzahl von Öffnungen (36, 38, 42, 44) innerhalb jedes Bandes befindet; und

    wobei die Querschnittsfläche des Leitkanals in einer Querrichtung des Trockners abnimmt.


     


    Revendications

    1. Un séchoir servant à sécher une plaque (32), la plaque (32) ayant deux surfaces principales qui sont opposées l'une à l'autre, le séchoir comprenant :

    un moyen de transport servant à transporter la plaque (32) le long d'une direction longitudinale du séchoir, le moyen de transport étant en outre destiné à supporter la plaque (32) dans un plan de support (33) contenant la direction longitudinale du séchoir ;

    un moyen d'arrivée d'air servant à diriger le flux d'air vers au moins une des surfaces principales de la plaque (32) ; et

    un moyen de régulation de flux d'air comprenant un panneau à l'intérieur du séchoir qui est aligné sur la direction longitudinale du séchoir et coupe le plan de support (33), le panneau étant destiné à augmenter le flux d'air dans la direction longitudinale du séchoir, et

    dans lequel le moyen d'arrivée d'air comprend un conduit (40, 34) s'étendant de manière transversale par rapport à la direction longitudinale de la plaque (32), le conduit (40, 34) comprenant une pluralité d'ouvertures (42, 44, 36, 38) servant à diriger le flux d'air vers la plaque (32), et

    caractérisé en ce que le panneau est prévu au niveau de l'extrémité aval du conduit (40, 34), par rapport à la direction du flux d'air le long du conduit.


     
    2. Un séchoir selon la revendication 1,
    dans lequel l'aire en section transversale du conduit diminue dans un sens vers l'aval du conduit.
     
    3. Un séchoir servant à sécher une plaque (32), la plaque (32) ayant deux surfaces principales qui sont opposées l'une à l'autre, le séchoir comprenant :

    un moyen de transport servant à transporter la plaque (32) le long d'une direction longitudinale du séchoir, le moyen de transport étant en outre destiné à supporter la plaque (32) dans un plan de support (33) contenant la direction longitudinale du séchoir ; et

    un moyen d'arrivée d'air servant à diriger le flux d'air vers au moins un côté inférieur de la plaque (32), le moyen d'arrivée d'air comprenant un conduit (40, 34) s'étendant de manière transversale par rapport à la direction longitudinale de la plaque (32), le conduit (40, 34) comprenant une pluralité d'ouvertures (36, 38, 42, 44) servant à diriger le flux d'air vers le côté inférieur de la plaque (32) ;

    dans lequel au moins 90 % des ouvertures (36, 38, 42, 44) sont distribuées à l'intérieur de deux bandes s'étendant le long de la longueur du conduit (40, 34), les bandes étant prévues dans les portions latérales du conduit (40, 34) et étant séparées par un ruban central comprenant au moins 55 % de la largeur du conduit (40, 34), et en outre dans lequel une pluralité d'ouvertures (36, 38, 42, 44) est située à l'intérieur de chaque bande ; et

    dans lequel l'aire en section transversale du conduit diminue dans une direction transversale du séchoir.


     




    Drawing











    Cited references

    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description