EP1336072A1

EP1336072A1 - Method for drying plaster boards, device therefor

Info

Publication number: EP1336072A1
Application number: EP01993804A
Authority: EP
Inventors: Charles Falinower
Original assignee: Lafarge Platres SA
Current assignee: Etex France Building Performance SA
Priority date: 2000-11-08
Filing date: 2001-11-05
Publication date: 2003-08-20
Also published as: NZ525678A; CA2428010A1; US20030217799A1; KR20030062330A; AU2002223741B2; PL360485A1; NO20032044L; NO20032044D0; RU2266818C2; BR0115464A; CN1253689C; AU2374102A; IL155630A0; UA75380C2; EP1205722A1; AR031309A1; IL155630A; JP2004520962A; CN1473259A; ZA200303188B

Abstract

The invention concerns a method for making plaster boards comprising the following steps: (i) forming the board; (ii) hydration hardening of the board; (iii) drying during rotation of the board. The invention also concerns a device for implementing the method.

Description

METHOD FOR DRYING PLASTERBOARDS, DEVICE FOR IMPLEMENTING SAME

The invention relates to a new method of manufacturing plasterboard, as well as a device for its implementation.

Plasterboards are known, which consist of a dense plaster core (density for example 0.6 to 1.0, in general about 0.7) on at least one paper-type support, and preferably between two paper-type supports

(and typically one being called cream paper and the other gray paper). The conventional manufacturing process for such plasterboard comprises the following steps.

Typically, the process comprises the formation of the plate, this step comprising the substeps of unwinding the cream paper, the mixture to obtain a paste composed mainly of plaster (semi-hydrate) and water, to which are added additives for give the plate specific properties of use (in particular starch and possibly a foaming agent is (are) added (s) to form a foam); depositing said paste on cream paper; unrolling then applying gray paper to continuously form the precursor sandwich of the plate; hydration, hardening and cohesion of the paste during hydration with the two papers on supports constituting the forming line. At the end of the forming line, we are in the presence of a semi-finished product capable of being cut by shears, then possibly manipulated in particular with a turning operation to place the cream face on top. Finally this product is introduced into a dryer to remove excess water of the plate (so-called plate drying operation). At the outlet of the dryer, the plate is subjected in the dry state to various conditioning treatments to give it its final presentation.

If each stage presents its own technical problems, certain stages are critical, either in terms of kinetics of chemical reaction, kinematics or process which will influence the characteristics and the quality of the final product, or in term of complexity and size of the apparatus. and difficulty in maintenance, as well as occupying space, or several in combination. The most critical steps, in addition to the initial forming step, are the hydrating-hardening steps; transfer to the wet state and drying in the dryer to remove excess free water. In fact, each major step in the plasterboard manufacturing process is critical to the process and / or the final product. Such a degree of criticality is particular to the process for manufacturing plasterboard.

The stage of beginning hydration up to the shears typically lasts a few minutes, typically around 3 to 4 minutes or more, the following stage of wet transfer and end of hydration until the dryer entry lasts 5 10 minutes. When it is desired to increase the line speed, in order to reach values greater than 150 m / min, with conventional hydration times, it is then necessary to increase the length of the forming line up to values greater 500m, which is very expensive and poses many problems of kinematics of transfer and positioning of the plates on the machines.

The wet transfer stage uses complex devices which must operate in a hot and humid atmosphere. The productivity of the production chain is therefore dependent on the reliability of these devices, the maintenance of which is delicate and expensive. Furthermore, these traditional devices generate by construction, different hydration times in the longitudinal direction of the plate on the one hand and offsets between trains of plates on the other hand before entering the dryer which must be to set free by complicated systems. It is then necessary to make up for these offsets in order to obtain uniform drying over the entire surface of the plates and in particular at the end of the plates. The mechanism must ensure that the plates do not break at their ends and do not overlap. To do this in the prior art, very complex mechanics and speed regulation of many motors are essential.

The drying step requires mechanical devices which must operate in a humid environment which can reach the saturation of the water vapor and which can reach several hundreds of degrees C., which again poses maintenance problems.

Finally, the drying step consumes a lot of energy and it would be advantageous to have a drying method and device which makes it possible to supply only the necessary quantity of calories to the plates.

The other steps of the process also pose other problems, which must also be resolved as best as possible. For example, the shearing step implements a shear in the form of two rollers equipped with blades which must be cleaned regularly. This device is quite destructive and mechanically harsh vis-à-vis the plate (this is also one of the reasons which make it necessary a relatively long hardening time because the hardened wet plate -hydrated- must be able to withstand the stresses generated by the shears and handling in the wet transfer area). The flipping or pinball stage is so far often necessary. The thinned edges of the plate are formed by means of a lower roller with thickened edges or a strip having the counterform; this implies that the cream paper is in the lower position. However, during subsequent drying, it is preferable that this cream side is on top, in order to avoid any soiling coming from the rollers of the dryer. It would be desirable to be able to avoid this restrictive step of the pinball machine (while possibly being able to keep, if desired, the current configuration with the plaster paste which is deposited on the cream paper).

The transfer stage in the dry state certainly poses fewer problems than in the wet state, but it remains complicated and always heavy maintenance.

The object of the invention is to provide a method and a device for its implementation, which make it possible to avoid the above problems and to offer other advantages still in terms of process / quality of the final product, maintenance, operating, investment, and working condition costs. The invention is based in part on the principle that unlike the prior art in which the plates move over great distances in the various equipment, in the invention the plates are practically static; it is the equipment which is mobile and generally in rotation.

The invention relates, according to a first variant, to a process for manufacturing plasterboard comprising the following steps:

(i) forming the plate;

(ii) hardening by hydration until a hydrated product with a content of less than 80% is obtained;

(iii) continued hydration in at least one rotating barrel; and (iv) drying. According to one embodiment, hydration is continued in said at least one barrel up to the whole. According to one embodiment, hydration is continued in said at least one barrel still partially, and up to the whole in a second barrel.

According to one embodiment, the method comprises, between steps (ii) and (iii), an intermediate shearing step.

According to one embodiment, this shearing step is implemented according to the principle of the wire.

According to one embodiment, the hydration at the end of step (ii) is less than 66%.

According to one embodiment, the hydration at the end of step (ii) is between 33 and 66%, preferably between 33 and 50%.

The invention also provides a device for manufacturing plasterboard comprising a linear zone of partial hardening-hydration and at least one barrel comprising a central axis 9 around which are arranged a plurality of branches 10a, 10b, 10c, 10d.

According to one embodiment, in the barrel each branch is divided into a plurality of arms 11a, 11b, lie, lld, the area occupied by the arms representing from 50 to 99% of the area of the corresponding branch.

According to one embodiment, the barrel comprises from 10 to 150, preferably from 40 to 120, branches. According to one embodiment, the hardening-hydration zone and the barrel are along two parallel axes. According to one embodiment, the hardening zone and the barrel are coupled by means of rollers 8a, 8b and 8c, these rollers interpenetrating the branches 10a, 10b, 10c, 10d.

According to one embodiment, the device comprises a shearing device comprising a wire.

The invention also provides a barrel comprising a central axis 9 around which are arranged a plurality of branches 10a, 10b, 10c, 10d, each branch being divided into a plurality of arms 11a, 11b, lie, lld, the surface occupied by the arm representing from 50 to 99% of the surface of the corresponding branch. According to one embodiment, the barrel comprises from 10 to 150, preferably from 40 to 120, branches.

The invention relates, according to a second variant, to a process for manufacturing plasterboard comprising the following steps:

(i) forming the plate; (ii) hardening of the plate with hydration, - (iii) drying during rotation of the plate. According to one embodiment, the drying is carried out in at least one barrel rotating in an enclosure. According to one embodiment, the drying is carried out in at least one barrel, said at least one barrel comprising a single drying section.

According to one embodiment, the drying is carried out in at least one barrel, said at least one barrel comprising two separate drying sections. According to one embodiment, the drying is carried out in at least one barrel, said at least one barrel comprising three or more separate drying sections.

According to one embodiment, the drying is carried out in at least two barrels. According to one embodiment, the drying is carried out in at least two barrels, with separate drying sections from one barrel to another.

According to one embodiment, each barrel can comprise one, two, three or more separate drying sections.

According to an advantageous embodiment, the drying is carried out in at least one barrel, said at least one barrel having at least two separate drying zones; this embodiment covers the case where two distinct drying zones are present in the same barrel and that where at least two distinct barrels comprise at least two distinct drying zones (at least one zone by at least one barrel). According to one embodiment, the drying is carried out in at least one barrel, with recovery of the latent heat of condensation of the water.

According to one embodiment, the drying is carried out in at least a first barrel without recovery and in at least one barrel with recovery.

According to one embodiment, the method further comprises a step:

(iv) cooling the plate. According to one embodiment, the cooling is partly implemented in a part of the last barrel.

The invention further provides a device for manufacturing plasterboard comprising a hardening and hydration zone and a barrel comprising a central axis 13 around which are arranged a plurality of branches 14a, 14b, 14c, 14d, said barrel being confined in an enclosure 15.

According to one embodiment, each branch is divided into a plurality of comb fingers. According to one embodiment, the enclosure represents a single drying section.

According to one embodiment, the enclosure is divided into two separate drying sections.

According to one embodiment, the enclosure is divided into three or more separate drying sections.

According to one embodiment, the central axis is a barrel and the fingers are hollow, in relation to said barrel.

According to one embodiment, the central axis is a barrel and the fingers are hollow, in relation to said barrel, and pierced with holes along these.

According to one embodiment, the device comprises at least one barrel without recovery and at least one barrel for recovering the latent heat of condensation of water. According to one embodiment, the barrel has a cooling zone.

According to one embodiment, the cooling zone corresponds to a quarter of the barrel located below the median horizontal, the enclosure possibly being positioned at this zone.

According to one embodiment, the cooling zone corresponds to a quarter of the barrel situated above the median horizontal, the enclosure possibly being arranged at this zone.

The invention also provides a barrel comprising a central axis 13 around which a plurality of branches 14a, 14b, 14c, 14d are arranged, each branch being divided into a plurality of comb fingers, said barrel being confined in an enclosure 15.

According to one embodiment, the enclosure represents a single drying section.

According to one embodiment, the central axis is a barrel and the fingers are hollow, in relation to said barrel. According to one embodiment, the central axis is a barrel and the fingers are hollow, in relation to said barrel, and are pierced with holes along these.

According to one embodiment, the barrel has a cooling zone. According to one embodiment, the cooling zone corresponds to a quarter of the barrel situated below the median horizontal, the enclosure possibly being arranged at this zone.

The invention relates, according to a third variant, to a method of cooling plasterboard by rotation in a rotating barrel, this barrel comprising a central axis 13 around which are arranged a plurality of branches 14a, 14b, 14c, 14d. According to one embodiment, the method is implemented in a barrel in contact with the ambient air.

According to one embodiment, the method is implemented in a barrel confined in an enclosure. According to one embodiment, the method is implemented in a quarter of the barrel located below the median horizontal, the enclosure possibly being arranged at this zone.

According to one embodiment, the method is implemented in a quarter of the barrel situated above the median horizontal, the enclosure possibly being arranged at this zone.

The invention relates, according to a fourth variant, to a method of handling plasterboard by rotation in a rotating barrel, this barrel comprising a central axis 13 around which are arranged a plurality of branches 14a, 14b, 14c, 14d.

According to one embodiment, the method is for the inversion of plates.

According to one embodiment, the method is for the alternating inversion of plates.

According to one embodiment, the method is for the pairing of plates.

The invention relates, according to a fifth variant, to a method of drying / cooking / reacting flat objects during the rotation of said flat object in at least one rotating barrel, this barrel comprising a central axis 13 around which are arranged a plurality of branches 14a, 14b, 14c, 14d, said barrel being confined in an enclosure 15.

According to one embodiment, each branch is divided into a plurality of comb fingers. According to one embodiment, said at least one barrel comprises a single drying section. According to one embodiment, said at least one barrel comprises two separate drying sections, corresponding to two sections of the enclosure.

According to one embodiment, said at least one barrel comprises three or more separate drying sections, corresponding to two sections of the enclosure.

According to one embodiment, the drying is carried out in at least two barrels, with separate drying sections from one barrel to another. According to one embodiment, the drying is carried out with recovery of the latent heat of condensation of the water.

According to one embodiment, the central axis is a barrel and the fingers are hollow, in relation to said barrel. According to one embodiment, the central axis is a barrel and the fingers are hollow, in relation to said barrel, and pierced with holes along these.

According to one embodiment, cooling is implemented in part of the last barrel. According to one embodiment, the cooling zone corresponds to a quarter of the barrel situated below the median horizontal, the enclosure possibly being arranged at this zone.

According to one embodiment, the flat object is a wooden plate, plaster tile, plate or tile of clay, cement, or other.

It is advantageous to combine the variants with one another, particularly the first and second variants with one another, the second and third variants with one another, and the First, second and third variants with each other The invention is now described in more detail in the description which follows and with reference to the accompanying drawings, in which: FIG. 1 represents a schematic view of an installation according to the prior art; FIG. 2 represents a general diagram of a device according to the invention; FIG. 3 represents a rotating hydration barrel according to the invention; Figure 4 shows the previous barrel, but seen from above; FIG. 5 represents a variant of the hydration barrel according to the invention; Figures 6a and 6b show a drying barrel according to the invention; Figures 7a and 7b show a drying barrel according to the invention, exploded and in top view; FIGS. 8a and 8b show a drying barrel according to the invention capable of being used in indirect drying and / or in heat recovery; FIG. 9 represents a cooling barrel according to the invention; FIG. 10 represents a turning barrel according to the invention; FIG. 11 represents a variant of a method for supplying plates with barrels according to the invention.

Referring to Figure 1, a conventional installation for manufacturing plasterboard is described. Zone 1 represents the step of forming the plate, this step comprising the sub-steps of unwinding the cream paper, mixing to obtain the plaster paste, depositing the paste on the cream paper and unwinding the gray paper to form the precursor sandwich of the plate. Zone 2 represents the hardening stage until a substantially hydrated product is obtained. Zone 3 represents the step of shearing in individual plates or by train of plates. Zone 4 represents the wet transfer step (with an inversion operation to place the cream side on top using a device called "flipper" as well as the offset absorption operation between front plate trains entry into the dryer). zone 5 represents the stage of drying in a drier to remove excess water. Zone 6 represents the step of transfer in the dry state (including a possible pairing of the plates face cream against cream, resawn, wrapping and packaging).

With reference to FIG. 2, the general diagram of a device according to the invention is described. This includes, as before, a hardening zone, during which the hydration of the plaster begins. This hydration is not completely continued, but only in general up to less than 80%, preferably at a value for example between 33% and 66%, more preferably less than 50%. The term hydration has the classic meaning, namely the reaction of transformation of CaS0 .0.5H ₂ 0 into CaS0 .2H ₂ 0. The measurement of hydration is done in a conventional manner, namely measurement on a curve, which can be temperature rise, weight gain (or water intake), hardening, etc. All the conventional methods are suitable.

This hardening zone is represented here schematically by the forming strip 7a, the rollers before shears 7b and the shears 7c itself, as well as the zone 7d. This zone 7d is an acceleration zone 7d (in order to create a space between the plate trains in a conventional manner). This zone is coupled to a stop zone 8, which will serve as an introduction device into a rotating barrel equipped with arms. This stop zone includes rollers 8a, 8b, 8c, 8d, 8e, 8f, 8g, etc. These rollers are typically regularly spaced, intended (as in the prior art) to receive the wet plates, to the difference that here the plates are less hydrated therefore less hard. The spacing of the rollers will be determined to avoid creep of the plates between these supports, which a person skilled in the art can easily determine. Once on these rollers 8a, 8b, 8c, etc., the plate is then taken up by the barrel 9, object of the invention.

It should be noted here that the shearing step can be implemented in a conventional device. It can also be implemented in a more suitable device, of the "butter cutting wire" type. This wire can be single or double, for example as on scissors. Since the hydration level is lower during cutting, the shears can be much simpler, and do not need to be "robust". A metal wire, stretched across the line, is sufficient. It can be inclined, relative to the plane of the plate and / or to the axis of the line. Its handling is very simple, and the cutting is sharper. The drawbacks associated with prior art shears are eliminated. Cleaning this wire is very simple; one can for example mount the wire in a loop, and operate a rotation between each cut. During rotations, a very simple brush cleans the wire.

Referring to Figure 3, there is described a rotating barrel according to the invention, interposed with the rollers 8a, 8b, 8c described above. The term carousel can also be used in place of the rotating barrel. The barrel is represented with only one quadrant of the arms, in order to better represent the cooperation with the rollers 8a, 8b, 8c. Barrel 9 includes an axis 10

(generally representing a barrel), on which are fixed branches 10a, 10b, 10c, lOd, 10e, etc. (the connection of the branches on the central axis is not shown for readability of the figure). Each branch comprises several arms 11a, 11b, lie and lld, for example, (of optimized shape) and relatively wide to obtain a hardening of the plate without the appearance of creep. The number of arms per branch is determined by several factors, including mainly the speed of the line, the length of the barrel and the number of branches. This number is for example between 3 and 60. If we consider the surface of a complete branch, the arms can represent, in general, from 50 to 99% of the surface of the corresponding branch. The arms may be full or have holes so as to both support the plate without creep and not slow down the phenomenon of water evaporation which occurs at this stage of the process. The dimensions of the barrel are generally as follows: diameter from 3m to 6m, preferably from 3.5 to 4m. Regarding the length, it is very easily adjustable to production needs. An increase in capacity is achieved by adding additional arms. Typically the length of the barrel can be between 3m and 25m or even more. If we consider a plasterboard P, it arrives on the rollers 8a, 8b, 8c (its stroke is controlled by mechanical and / or electrical and electronic devices). In this case, the barrel is in a position such that the plate P can pass between the branches 10a and 10b. The barrel turns, the arms come into contact with the wet plate P (which has not had time to bend appreciably) and separate the plate P from the rollers, the plate P then resting on the arms 11a, 11b, lie and lld of branch 10b. Then, the rollers become free again, so as to accept a new plate P '. This is this time at the start between the arms 10b and 10c, then after a rotation of the barrel in contact with the arms of the arm 10c. So on, we can "fill" the branches of the barrel. The barrel comprises for example from 10 to 150 branches, preferably from 40 to 120. The speed of rotation of the barrel will be chosen in particular as a function of the speed of the line, the dimensions and the number of branches of the barrel and of the process parameters which must lead to complete hydration and good flatness of the plate at the outlet of the barrel. In general, the barrel rotation speed is between lt / h (revolution / hour) and 6t / h, and preferably between 4 and 6 t / h in the case of an installation with a single hydration barrel.

With reference to FIG. 4, the preceding embodiment seen from above is described (only one branch is represented, the one which will lift the plate P).

With reference to FIG. 5, a variant of the preceding situation is described. This time, the rotating barrel 9 is offset relative to the rollers 8a, 8b and 8c. A transporter 12 ensures the translation of the plates of the rollers 8a, 8b and 8c towards the barrel 9. This transporter ensures the supply of the plates of the train of plates on a branch of the barrel. This ferry is conventionally a set of integral supports which move in a translational movement, then back in position from below, in the manner of a track shoe for example, associated with an up-and-down movement. drop.

One could also provide the barrel directly at the end of the accelerating / stopping zone, but this time with an axis no longer parallel but perpendicular to the direction of movement of the plates. In this case, the axis of the plates is perpendicular to the axis of the barrel; it then has a length of the order of the width of the plate.

The plate then comes, at the end of the stroke, to abut on the barrel hub before being manipulated by the branches of the barrel.

The hydration in the revolving barrel (s) saves considerable space. Indeed, the traditional hardening section can be reduced in length by up to 50%. In addition, the wet transfer area up to the dryer entrance is also considerably reduced. In addition, the residence time of each plate in the barrel is identical, which makes it possible to have a very homogeneous rate of hydration of the plates. This is still more apparent when a drying barrel is used in conjunction with a hydration barrel.

The barrels according to the invention can accommodate plates of various lengths, such as 1.50 m up to the total length of the barrel. Indeed, the arms are of sufficient width to accommodate all the lengths of plates and all types of plate train of all lengths: the plates, whatever their length, will always rest sufficiently (in general) on the arms of the barrel.

To discharge the barrel, systems similar to those used to load it can be used in the variant illustrated in FIG. 5, namely a ferry. The ferry can include rollers; it can also include an endless band, placed between the arms, the axis of the band being perpendicular to the axis of the barrel. In such a case, the plate arriving on the strip is placed on it, the branches naturally emerge. The speed of rotation of the strip is then adapted to that of the barrel in order to be able to empty it. Any other known system will apply to the handling of the plate to transfer it from one barrel to another.

We could also have two or more barrels of hydration, if necessary. The transport of the plates from one barrel to another is done as above, for example.

With reference to FIGS. 6a and 6b, another embodiment of the invention is described, namely a dryer based on this principle of the rotating barrel. It comprises an axis 13, and branches 14a, 14b, 14c, etc., the whole being placed in an enclosure 15. (Only half a part has been shown). This dryer of a new type is supplied from the wet transfer according to the prior art or from a hydration barrel according to the invention described above. The operation of the dryer is very simple. The plates enter the dryer, are placed on the branches, and can then under the effect of heat evacuate the water. The enclosure 15 makes it possible to confine the drying zone or section. This enclosure is in relation to an aeraulic circuit, not shown in the diagram, which comprises, in addition to the conduits, one or more heat generators and fans for circulating the hot gases around the plasterboards to be dried. For example, the enclosure 15 can be divided into two or more sections, with the circulation of air or another gas between these sections; this is described in more detail below. Figure 6a shows the case with a single drying section while Figure 6b shows the case with two separate drying sections (different temperatures from one section to another). The gas circulation in the barrel and the enclosure will be described in more detail in Figure 7.

Compared to the prior art, this type of dryer allows better homogeneity in drying. Indeed, in the prior art the plates were introduced in the longitudinal direction and slowly, which caused a shift between train of plates, therefore a potential risk of calcination said end of plates. On the other hand, the plates in a train of plates having a different hydration rate, drying was affected by this heterogeneity. In the new process, the plates are introduced in the transverse direction and quickly, which avoids the above drawbacks.

Each branch preferably (but not necessarily) includes comb fingers rather than arms

(as opposed to the hydration barrel), since there is no longer any serious risk of creep and to further allow better heat exchange. It is however possible to use arms, in particular pierced with a multitude of holes. The comb finger has a section in contact with the plate of., For example, 0.5 to 10 cm, in particular 1 to 8cm. The barrel comprises, for example, from 20 to 150 branches, preferably from 60 to 120. The dimensions of the barrel are generally as follows: diameter from 3 to 6 m, preferably from 3.5 to 4.5 m and length from 3 to 25 m , or even more, preferably from 6 to 15m. In general, two or more drying barrels are used. These barrels preferably have separate drying sections (to optimize the drying process by precise control of the drying curve - weight loss as a function of time -).

The speed of rotation of the barrel will be chosen according to the number of branches of the barrel, the flow rate of the line, etc. In general, the speed of rotation of the barrel is between lt / h and 6t / h, preferably between 2 and 4t / h.

The barrel can be partially or as a whole disposed in the heated enclosure, with a substantially homogeneous atmosphere in the barrel. It will however be preferred that the plates form the gas transport conduits, in order to obtain circulation

"intelligent" of these gases in the enclosure. This makes it possible to have several drying sections with different profiles, and therefore to optimize drying. To obtain good drying uniformity along the length of the plates, in each drying section thus defined, the flow of hot gases will be alternately reversed. This operation is carried out simply for example by reversing the direction of operation of the fans or by installing appropriate deflectors at the ends of the enclosure. With this solution, each section has an even number of conduits. Burners can also be installed, for example, at both ends of the enclosure. The circulation circuit can in particular be obtained by an appropriate casing, the enclosure 15 being divided at the ends of the barrel into as many sections as desired. With reference to FIG. 7a, the barrel is described and the hot gas circuit is represented by arrows. The enclosure is such that the plates act as deflectors and guides for the hot gases, parallel to the plates. It is thus possible, by modifying the operating conditions, two or more drying sections with distinct conditions. In fact, there can be as many drying sections as there are cells formed by two consecutive plates. More specifically, the enclosure comprises at its two ends a cover 16 and 16 ', which is divided into as many sections as there are drying sections. In the example shown in Figure 7, there are two drying sections, and therefore two compartments at the end covers (16a and 16b, and 16'a and 16'b, respectively). The arrows indicate the direction of circulation of the hot gases.

For example, there may be two drying sections, one with an inlet temperature of about 250 ° C and an outlet temperature of about 230 ° C, and another section with an inlet temperature of about 220 ° C and an outlet temperature of about 180 ° C. We can then apply a greater amount of heat, being sure not to "burn" or calcine the plates. It is also possible and advantageous to have a baffle at the cowlings; in this case, the cowling 16 ′ would include a baffle which makes it possible to use the gases leaving the first section at around 230 ° C as the gas entering the other section at around 220 ° C (or even at the same temperature). This is more apparent in FIG. 7b, a top view in section, in which the cowling 16 ′ comprises a baffle 17 ′, around which the hot gases circulate. The gas circulation is represented by the arrows.

The invention therefore makes it possible to optimize the drying zones, which is very difficult, if not impossible, with the prior art. At this point, it is worth remembering that the art of drying generally recognizes three zones, zone 1, zone 2 and zone 3. Zones 1 and 2 comprise a drying at high temperature of the gases (strong drying) to ensure the efficient migration of the starch towards the paper and evacuate approx. 80% of the water. . Zone 3 is a zone in which the drying is gentler, in order to avoid exceeding the calcination temperature of the plates. In this zone, the drying speed is limited by the diffusion of steam in the heart of the plate. In general, zones 1 and 2 have a cumulative duration of 15 to 30 min (in general therefore less than 45 min) while zone 3 has a duration equivalent to that of zones 1 and 2 cumulated. The temperatures in these zones are typically those indicated above. It should also be noted that the invention makes it possible to obtain, as is sought in the prior art, drying against the current or co-current. The invention therefore makes it possible to obtain a particularly suitable and homogeneous drying profile.

It is possible to imagine a central barrel, this being divided into zones (in the manner of orange wedges), each zone being supplied with hot gas independently, which makes it possible to recreate separate heating zones. The heating of the plates is then done radially, from the central barrel, the hot gases being distributed by orifices arranged on the central barrel or by the fingers of the barrel (see for example FIG. 8a infra to which this embodiment is applicable ).

It is possible and advantageous to place several barrels in series. The devices for transporting from one barrel to another have been described above with reference to the hydration barrel. For example, one can have a first barrel, for example of the type described above with two drying sections, and a second barrel with a third drying section. The third drying section, for example, has an inlet temperature about 150 ° C and an outlet temperature of about 100 ° C. The barrels in series can very easily be synchronized.

The design of this dryer allows great flexibility as to the type of drying process. The dryer described above is of the direct dryer type (hot gases in direct contact with the plates, with a gas velocity vector parallel to the plates).

A direct drying variant is also possible with this type of dryer. Instead of circulating the hot gases between the plates as indicated in the description, the gases are introduced through the central barrel and then into the pierced fingers (the fingers are generally such that the contact surface with the plate is minimal while the gases escape through holes arranged along the fingers). The shape of the fingers is suitable for this type of drying, which is rounded in shape to prevent the plates from obstructing the holes and the passage of gases. This jet drying type method has the advantage of having better exchange coefficients, therefore a higher energy yield.

The plasterboard can also be dried using the indirect steam drying process, for example with minor modifications to the barrel. The choice of indirect drying makes it possible to use other cheaper fuels than gas or light fuel oil, such as coal, heavy fuel oil, wood chips or all kinds of waste likely to be burned in a boiler.

In this configuration, the steam is introduced into the central axis and then is distributed in the fingers. The steam condensed by heat exchange with the plates is recovered in the barrel or the crown and then returned to the boiler. The barrel adapted to this type of indirect steam drying is relatively similar to that described with reference to FIGS. 8a and 8b below. With reference to FIGS. 8a and 8b, another embodiment is described. The central axis 13 becomes a barrel in which the hot gases charged with water vapor are reintroduced, in particular from the first sections of the dryer or from the preceding barrels. The branches 14a, 14b, 14c, consist of hollow comb fingers connected to the central shaft. The hot gases charged with water vapor then circulate in these comb fingers from the center to the outside, and possibly from the outside to the center.

In the variant illustrated in FIG. 8a, the gases are collected by the external enclosure through a calibrated orifice, several orifices 17a, 17b, 17c, 17d, being (equi) distributed over the periphery. The external enclosure in this case consists of a double wall (15, 15 ') connected to a fan. When the barrel turns, the ends of the fingers being hollow, they come regularly opposite the orifices (equi) distributed. A gas flow can then be established.

In the variant illustrated in FIG. 8b, the gases go back and forth in the fingers, these being provided with an internal baffle. They are then collected in a crown 13 'around the central barrel. These gases are indirectly in contact with the plates placed on the branches. Under these conditions, the steam water will condense and give in contact with its latent heat of condensation. The condensed water flows along the comb fingers and is collected in the compartmentalized barrel or the crown, from where it is preferably removed by gravity or by means of a pump. Similarly, the water condensed on the double wall of the enclosure will be evacuated by gravity. One could also plan to collect the condensed water in the barrel and then drain it by the comb fingers in the low position. This technique can also be implemented according to the teaching of document DE-A-4326877. It is thus possible to recover the hot water vapors produced elsewhere during drying. In In fact, the barrels can accommodate all conventional energy recovery systems, thus operating as true internal heat exchangers.

Figures 8a and 8b therefore represent a barrel capable of being used in indirect drying and / or heat recovery, the main difference between these two modes being the amount of heat provided by one or more burner (s).

Referring to Figure 9, a dryer barrel is described which further includes a plate cooling function, always with an insertion zone (E) of the plates, in particular horizontally, and an outlet. The hatched area here represents the drying section. The barrel then presents, at the level of the enclosure for example, an additional quarter. For example, the exit (S) in the form of a day on the outside is not arranged horizontally, but downwards. In this additional quarter, the plate can cool down naturally or not, in order to avoid possible thermal shocks. A better quality plate is thus obtained than with a traditional dryer. In addition, the day being shifted, the plate slides naturally on a conveyor belt located below.

We could also have this quarter above the horizontal, the cooled plate then leaving horizontally, for example on a conveyor belt.

One could also provide one (or more) complete barrel for cooling purposes if necessary.

There is thus obtained at the outlet of the last barrel a cooled plate which it is possible to send directly to the final conditioning zone, without passing through the series of heavy and noisy equipment which is usually found at the dryer outlet, namely cascade of grouping of plates from the different stages, acceleration and stopping zones, transfer tables etc.

The drying barrels can, as for the hydration barrel, accept different lengths of plates. For the drying barrel to obtain an even better flow of gases in the cells, it is for example possible to arrange the plates alternately, that is to say an edge-to-edge plate on one side of the barrel and the other edge-to-edge on the other side. It is also possible and preferably to use branches having at their ends (at the level of the lateral disks of the barrel) segments having a sufficient surface for each plate to rest on this segment, whatever its length, and / or having a suitable shape ( for example in the form of a deflector) to avoid calcination at the end of the plate, which may take place due to the hot ventilated gases.

The use of barrels, in particular at the level of drying, makes it possible to put outside the enclosure all the drive members, and therefore to protect them from a hot and humid environment which is aggressive.

Note that it is particularly advantageous to couple at least one hydration barrel with at least one drying barrel. In particular, two or three drying barrels will be used in this case, preferably the first (and the second) with one or two separate drying sections and the last preferably with heat recovery. One can also in the present case use an indirect type of drying.

Incidentally, the barrel is also useful for handling the plate under mild conditions. * Figure 10 shows a barrel used for a plate inversion, always in mild conditions, thus freeing itself from the traditionally used inversion pinball machine. The inversion can be applied to all the plates, and can be alternated; one plate can be removed just below the horizontal and another about 180 ° later, still below the horizontal. We can therefore have an alternating inversion of the plates, which can be useful for packaging plates face cream against face cream.

In the embodiment represented in FIG. 10, there is an input (E) as for FIG. 9, and two outputs

(SI) and (S2). It is possible to extract all the plates at the output (SI), but also alternately at the level of (SI) and (S2), which leads to already alternated plates (which facilitates for example the dry transfer for 1 pairing cream side / cream side). When the plates are handled in the upper part of the barrels, they rest partly on the hub or central barrel. When the plates are handled in the lower part of the barrels (especially between the outlets

(SI) and (S2)), they can slide on the enclosure or any other suitable railing or even be accompanied in their movement by a band whose linear speed corresponds to the speed of the plate considered at the level of the circumference of the barrel. (the bands will preferably have a trajectory along this circumference).

With reference to FIG. 11, this describes an embodiment in which the plates are supplied in the barrels (hydration, drying, cooling, handling). According to this embodiment, the plates are supplied along the axis of the barrels, the direction of advance being made along the same line (unlike the previous embodiments, in which the supply was effected by translation once the plate brought to the side of the barrels. Schematically, the sequence is as follows. description is made with a plate, for convenience, but the embodiment is applicable to a train of plates in the same way; the description is made in section, the plates arriving in the direction perpendicular to the sheet. At time t = 0, the barrel is in the initial position; the plate n is placed on an arm or a branch of the barrel. At t = tl, a mechanism formed by a set of rollers (for example) moves under the plate n (for example by translation) - there is only one roller shown in the figure, the others being in fact hidden taking into account the mode of representation chosen. At t = t2, this mechanism lifts, the rollers being inserted between the arms or branches of the barrel, which has the effect that the plate n no longer rests on the arms or branches of the barrel. At t = t3, the plate n + 1 coming along the axis of the barrel replaces the plate n by pushing it or by means of the motorized rollers, the plates n and n + 1 moving on the rollers. At t = t4, the mechanism is lowered, which has the effect that the plate n + 1 rests on the arms or branches of the barrel. At t = t5, the mechanism retracts on the side of the barrel, thus allowing the latter to rotate by the desired angle to bring the plate n-1 to the starting position of the method according to the specific embodiment. In this way (as in other embodiments), it is possible to use the entire barrel, namely 360 ° C., to carry out the required operations (hydration, drying, cooling, handling). During the part of the rotation in the lower part of the barrel, the plates can for example be maintained by returns at the level of the arms or branches, or simply be guided by an external casing or even be guided on a caterpillar arranged on the part lower, this track accompanying the movement of the plates. In this so-called "360 °" embodiment, the data previously indicated relative to the residence time, rotation speed, etc. must be adapted (for example for an identical residence time, the speed of rotation can be halved since we actually use the 360 ° of the barrel and no longer only 180 ° C). Likewise, for drying, zones 1, 2 and 3 can be combined in a single barrel, if desired.

Finally, it should be noted that the invention is intended to apply generally: in the case of plasterboard to any operation of handling the plate, including turning. in the case of drying, any type of flat object, in particular but not limited to plaster tile, tile (for example in cement or clay), etc. or object for which there is a reaction of a hydraulic binder. In the latter case, "drying" should in fact be understood as covering any reaction liable to lead in particular to hardening, such as cooking. There is not necessarily evacuation of water, but there may be another type of reaction with the release of other gaseous effluents, or not. For example, one aims at steaming in the case of cement plates. It should be noted that in these cases of steaming, there is always the concern of having in most cases at least two periods or phases of "drying". Indeed, it is recognized that for the hardening of these plates several stages are used, among which: stage (1): a rest stage to allow the start of setting before application of heat; step (2): a heating step with a relatively gentle slope up to the maximum temperature with possible addition of humidity; stage (3): a stage stage in order to ensure the homogeneity of the heating and the temperature of the parts in the room; step (4): ventilation with warm air then ambient to dehumidify the chamber before unloading. The invention makes it possible to obtain a specific profile during steaming. The invention also makes it possible to obtain so-called "FIFO" (First In, First Out) chambers which are safe and do not present a risk of process interruption.

The invention also relates to all combinations between one or more hydration barrels, and one or more drying barrels (with one or more drying sections, with or without heat recovery), one or more cooling barrels, one or several handling barrels are possible. The number of barrels and / or the number of sections are in no way limitative of the present invention. For example, you can have only one hydration barrel, as you can have two or more. One can have one (or more) hydration barrel (s) associated with one (or more) barrel (s) for drying, and / or cooling and / or handling; you can also only have drying barrels; they can also be combined with cooling and / or handling barrels. We can have only one drying barrel, as we can have two, three or more. Each barrel may include only one drying section, but it may also include two, three or more. Each barrel can be heated directly or indirectly. One or more barrels can be of the heat recovery type. We can combine all these types (function / constitution) of barrels together; all combinations are permitted. The invention applies in particular to the case of the combination of hydration barrel (s) followed by drying barrel (s), all of the embodiments as recalled above being capable of being combined.

The advantages provided by the invention are therefore in particular:

In terms of process and quality conferred on the plate: a practically identical hydration time for all the plates at the entrance to the dryer; elimination of the gap between plates at the entrance to the dryer, - elimination of calcination at the end of the plate; possibility of increasing the number of drying sections to get closer to the ideal drying profile; possibility of integrating a cooling zone in the device; possibility of easily recovering the latent heat of condensation in the last dryer; flexibility in the choice of drying process

(direct or indirect or both combined) depending on the cost of energy; possibility of handling wet plates at shorter times than in conventional lines; there is no longer any breakage or deterioration of the plate by rapid or rough handling or by impacts on the stops.

In terms of investment: reduction of the cost of wet transfer and partially of dry transfer which are integrated in the equipment; reduction of the cost of forming line, because shorter and / or with a simpler design shears; - simpler dryer (no moving part), and smaller; flexible installation in capacity by varying the length, the number of barrels or the number of branches per barrel; this makes it possible to carry out capacity extensions through reduced investments and rapid installation; Reduction of land and building surfaces; The addition of the device for recovering the latent heat of condensation of water vapor much less expensive than with a conventional dryer (practically integrated in principle).

In terms of maintenance: reduction of maintenance costs on wet and dry transfers; - Reduction of costs on the dryer, since the motorization and drive system can be outside the hot and humid part of the dryer; there are fewer moving parts; elimination of the use of compressed air in this equipment.

In terms of operating cost: reduction of the drying energy by the system for recovering the latent heat of condensation of water vapor; reduction in electrical energy consumption (the power installed for motorizing the drives is divided by 3 to 4); reduction of compressed air consumption (on transfer tables) and associated maintenance; reduction in the cost of drying by using cheaper fuel, in the case of indirect drying; - improvement in equipment utilization rates.

In terms of safety and working conditions: noise reduction, especially on the 2 transfers and by eliminating the cascade at the dryer outlet. No more noise linked to the use of compressed air on transfer tables; Safety: fewer parts in rapid movement either in rotation (rollers) or in translation (table rises and falls).

It should be noted that the invention applies generically to individual plates as well as to trains of plates. The terms forming, shearing, hydration, drying, etc. "of the plate" also refer of course to "plates of the train of plates".

It should also be noted that the term "plasterboard" used in the invention covers plaster-based plates, and in particular but not limited to plates with one or more facings made of paper or cardboard (known in English as "wall- board "," plaster-board "), but also in other materials such as a glass fiber mat (so-called" fire "plates), fiber plates

(called in English "fiber-board", etc.) The invention preferably applies to plates with cardboard facing ("plaster-board").

The invention is not limited to the embodiments described but is capable of numerous variants easily accessible to those skilled in the art.

Claims

A method of manufacturing plasterboard comprising the following steps:

(i) forming the plate;

(ii) hardening of the plate with hydration; (iii) drying during rotation of the plate.

The method of claim 1, wherein the drying is carried out in at least one barrel rotating in an enclosure.

3. Method according to claim 1 or 2, wherein the drying is carried out in at least one barrel, said at least one barrel comprising a single drying section.

4. The method of claim 1 or 2, wherein the drying is carried out in at least one barrel, said at least one barrel comprising two separate drying sections.

5. The method of claim 1 or 2, wherein the drying is carried out in at least one barrel, said at least one barrel comprising three or more separate drying sections.

6. Method according to one of claims 1 to 5, wherein the drying is carried out in at least two barrels.

V. The method of claim 6, wherein the drying is carried out in at least two barrels, with separate drying sections from one barrel to another.

8. The method of claim 6 or 7, wherein each barrel may comprise one, two, three or more separate drying sections.

9. Method according to one of claims 1 to 8, wherein the drying is carried out in at least one barrel, with recovery of the latent heat of condensation of water.

10. The method of claim 9, wherein the drying is carried out in at least a first barrel without recovery and in at least one barrel with recovery.

11. Method according to one of claims 1 to 5 further comprising a step:

(iv) cooling the plate.

12. The method of claim 11 wherein the cooling is partly implemented in a part of the last barrel.

13. Device for manufacturing plasterboard comprising a hardening and hydration zone and a barrel comprising a central axis 13 around which are a plurality of branches 14a, 14b, 14c, 14d, said barrel being confined in an enclosure 15 .

14. Device according to claim 13, in which each branch is divided into a plurality of comb fingers.

15. Device according to claim 13 or 14, wherein the enclosure represents a single drying section.

16. Device according to claim 13 or 14, wherein the enclosure is divided into two separate drying sections.

17. Device according to claim 13 or 14, in which the enclosure is divided into three or more separate drying sections.

18. Device according to one of claims 13 to 17, wherein the central axis is a barrel and the fingers are hollow, in relation to said barrel.

19. Device according to one of claims 13 to 17, wherein the central axis is a barrel and the fingers are hollow, in relation to said barrel, and pierced with holes along these.

20. Device according to one of claims 13 to

19, comprising at least one barrel without recovery and at least one barrel for recovering the latent heat of condensation of water.

21. Device according to one of claims 13 to

20, in which the barrel has a cooling zone.

22. Device according to claim 20, in which the cooling zone corresponds to a quarter of the barrel situated below the median horizontal, the enclosure possibly being arranged at this zone.

23. Device according to claim 20, in which the cooling zone corresponds to a quarter of the barrel situated above the median horizontal, the enclosure possibly being disposed at this zone.

24. Device according to one of claims 13 to 23, for implementing the method according to one of claims 1 to 12.

25. Barrel comprising a central axis 13 around which are arranged a plurality of branches 14a, 14b, 14c, 14d, each branch being divided into a plurality of comb fingers, said barrel being confined in an enclosure 15.

26. Barrel according to claim 25, in which the enclosure represents a single drying section.

27. Barrel according to claim 25, in which the enclosure is divided into two separate drying sections.

28. The barrel of claim 25, wherein the enclosure is divided into three or more separate drying sections.

29. Barrel according to one of claims 25 to 28, wherein the central axis is a barrel and the fingers are hollow, in relation to said barrel.

30. Barrel according to one of claims 25 to 28, wherein the central axis is a barrel and the fingers are hollow, in relation to said barrel, and are pierced with holes along these.

31. Barrel according to one of claims 25 to 30, having a cooling zone.

32. Barrel according to claim 31, in which the cooling zone corresponds to a quarter of the barrel situated below the horizontal. median, the enclosure possibly being arranged at this zone.

33. Barrel according to claim 31, in which the cooling zone corresponds to a quarter of the barrel situated above the median horizontal, the enclosure possibly being arranged at this zone.