EP1358984A1 - Method and apparatus for manufacturing gypsum boards - Google Patents

Abstract

The procedure consists of forming the board from plaster and layers of paper, hardening by hydration to give a hydrated product with a water content of under 80 per cent and preferably 33 - 50 per cent, cutting into sheets (10a - 10e; 11a - 11d) and drying. Following hydration and during the drying stage the sheets are moved by vertical or oblique conveyors (9). The conveyor used in the drying stage passes through two separate zones.

Description

The subject of the invention is a new process for manufacture of plasterboard, as well as a device for its implementation.

We know the plasterboards, which are made a dense plaster core (density for example 0.6 to 1.0, generally about 0.7) on at least one type of support paper, 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 drywall includes the following steps. Typically, the process includes forming the plate, this step including the sub-steps of the process cream paper, the mixture to obtain a compound paste mainly plaster (semi-hydrate) and water, to which additives are added to give the plate specific use properties (especially starch and possibly a foaming agent is (are) added (s) to form a foam); depositing said paste on paper cream; the course then the application of gray paper to continuously form the precursor sandwich of the plate; hydration, hardening and cohesion of the current dough of hydration with the two papers on supports constituting the forming line. At the end of the line forming we are in the presence of a semi-finished product can be cut with shears and then handled possibly in particular with a turning operation to place the cream side on top. Finally this product is introduced into a dryer to remove excess water of the plate (so-called plate drying operation). To the leaving the dryer, the plate is subjected in the dry state to different conditioning treatments to give it his final presentation.

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

The hydration start step up to the shears typically lasts a few minutes, typically about 3 at 4 minutes or more, the next step of wet transfer and end of hydration until the entry dryer 5 hard 10 minutes. When you want to increase the speed of line, 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 over 500m, which is very expensive and poses many kinematic problems of transfer and positioning of the plates on the machines.

The wet transfer stage implements complex devices to operate in an atmosphere hot and humid. The productivity of the chain production is therefore dependent on the reliability of these devices whose maintenance 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 plate trains on the other hand before the entry into the dryer which must be freed by complicated systems. It is then necessary to catch up these offsets 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, a very complex mechanics and a speed control of many motors are found indispensable.

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

Finally, the drying step is very consuming of energy and it would be advantageous to have a process and a drying device which allows only the necessary amount of calories to the plates.

The other process steps also pose other problems, which must also be resolved as best as possible. Through example the shearing step implements a shear in the form of two rollers equipped with necessary blades clean regularly. This device is quite destructive and mechanically rough towards the plate (it is also one of the reasons that makes time for relatively long hardening as the wet plate hardens -hydrated- must be able to withstand the stresses caused by shears and handling in the area wet transfer).

The flipping or pinball stage is up to present often necessary. The thinned edges of the plate are formed by a lower roller with thickened edges or a strip having the counterform; this implies that the cream paper is in the lower position. Now, when of the subsequent drying, it is preferable that this face cream either on top, to avoid any soiling from the dryer rolls. It would be desirable to be able to avoid this restrictive pinball stage (all possibly being able to keep if desired current configuration with plaster paste which is deposited on cream paper).

The transfer stage in the dry state certainly poses less than problems only in the wet 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 provide other benefits in terms of process / quality of the final product, maintenance, operating cost, investment, and of working condition. The invention is based in part on the principle that unlike the prior art in which the plates move over great distances in various equipment and along a longitudinal axis, in the invention the plates move along an axis perpendicular to their plane.

(i) formage de la plaque;

(ii) durcissement par hydratation jusqu'à obtention d'un produit hydraté à une teneur inférieure à 80%;

(iii) cisaillement en plaques;

(iv) poursuite de l'hydratation au cours de la translation de la plaque selon un axe perpendiculaire ou oblique par rapport au plan de la plaque; et/ou

(v) séchage au cours de la translation de la plaque selon un axe perpendiculaire ou oblique par rapport au plan de la plaque.

The invention therefore provides a method of 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) plate shear;

(iv) continued hydration during translation of the plate along an axis perpendicular or oblique to the plane of the plate; and or

(V) drying during the translation of the plate along an axis perpendicular or oblique with respect to the plane of the plate.

According to one embodiment, steps (iv) and / or (v) are implemented in at least one noria.

According to one embodiment, the hydration is pursued in said at least one noria until the screen.

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

According to one embodiment, the drying is set in works in at least one noria, said at least one noria comprising at least two separate drying zones.

According to one embodiment, the method comprises in in addition to a cooling step (vi).

According to one embodiment, cooling is implemented in part of the noria.

According to one embodiment, the method is implemented works in a single noria.

The invention also relates to a noria comprising an endless drive mechanism on which are fixed a plurality of trays, each tray being divided into a plurality of arms, and further comprising an enclosure.

According to one embodiment, the enclosure is divided in at least two separate drying zones.

According to one embodiment, the noria comprises a hydration zone in the ascending part.

According to one embodiment, the noria comprises of plus a cooling zone.

The invention finally relates to a device for manufacture of plasterboard comprising an area hardening-hydration line and at least one noria according to the invention.

According to one embodiment, the hardening zone and the noria are coupled via rollers, these rollers interpenetrating the plates.

• la figure 1 représente une vue schématique d'une installation selon l'art antérieur;
• la figure 2 représente un schéma général d'un dispositif selon l'invention;
• la figure 3 représente une noria d'hydratation selon l'invention;
• la figure 4 représente la noria précédente, mais vue de dessus;
• la figure 5 représente une variante de la noria d'hydratation selon l'invention;
• la figure 6 représente une noria de séchage selon l'invention.

The invention is now described in more detail in the description which follows and with reference to the accompanying drawings, in which:

• Figure 1 shows 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 hydration noria according to the invention;
• FIG. 4 represents the preceding noria, but seen from above;
• FIG. 5 represents a variant of the hydration noria according to the invention;
• FIG. 6 represents a drying noria according to the invention.

Referring to Figure 1, an installation is described classic plasterboard manufacturing. Zone 1 represents the plate forming step, this step including the substeps of unwinding the cream paper, mixture to obtain the plaster paste, depositing the paste on the cream paper and unwinding of the gray paper for form the precursor sandwich of the plate. Zone 2 represents the hardening stage until a substantially hydrated product. Zone 3 represents the stage shear in individual plates or by train plates. Zone 4 represents the wet transfer stage (with a flipping operation to place the face cream on top using a device called "flipper" as well as the offset absorption operation between plate train before entering the dryer). the zone 5 represents the drying step in a dryer to remove excess water. Zone 6 represents the step of transfer in the dry state (including pairing of plates face cream against cream, resection, wrapping and conditioning).

With reference to FIG. 2, the diagram is described general of a device according to the invention. This one as before includes a hardening zone, at the during which the hydration of the plaster. This hydration is not also pursued completely as in the prior art, but only up to a value for example between 33% and 66%, preferably less than 50%. This hardening area is represented here schematically by the strip of forming 7a, the rollers before shears 7b and the shears 7c itself. Following this is an area 7d acceleration (to create space between trains of plates in a conventional manner). This area is mated to a stop zone 8, which will serve as a device of introduction into a noria. This stop zone includes rollers 8a, 8b, 8c, etc. These rolls are typically regularly spaced, intended (as in art previous) to receive the wet plates, unlike that here the plates are less hydrated therefore less hard. Roll spacing will be determined to avoid creep of the plates between these supports, what the man of art can easily determine. Once on these rollers 8a, 8b, 8c, etc., the plate is then taken up by the noria or the perambulator, according to the invention.

With reference to FIG. 3, a noria is described according to the invention, interposed with the rollers 8a, 8b, 8c described above. This noria includes, around a endless drive mechanism, endless chain type 9, a multiplicity of plates 10a, 10b, 10c, 10d, etc. The endless chain is shown connected to the plate 10a (arm 11d), but it is clear that each tray is directly or indirectly connected to mechanism 9. Each tray includes several arms 11a, 11b, 11c and 11d, (for example optimized) and relatively wide to obtain a hardening of the plate without the appearance of creep. The number of arms is determined by the speed of the line, the length of the noria and the number of trays. If we consider the surface of a complete tray, the arms can represent, in general, from 50 to 99% of the surface of the corresponding tray. The arms can be full or present holes so as to provide both support of the plate without creep and do not slow down the phenomenon evaporation of water that occurs at this stage of the process. If we consider a plasterboard P, this one arrives on the rollers 8a, 8b, 8c (its race is controlled by mechanical and / or electrical devices and e). In this case, the noria is in a position such that the plate P can pass between the plates 10a and 10b. The noria turns, the arms come into contact with the wet plate P (which did not have time to substantially flex) and separates the plate P from the rollers, the plate P then resting on the arms 11a, 11b, 11c and 11d of tray 10b. Then the rollers become free again, from so accept a new plate P '. This is found this time at the start between plates 10b and 10c, then after an advance of the noria in contact with the arms of branch 10c. So on, we can "fill" the barrel trays. The noria includes a variable number tray, for example from 10 to 200 trays, preferably from 30 to 100. The scroll speed of the noria will be chosen in particular according to the speed of the line, the dimensions and the number of trays of noria and process parameters which must lead to hydration complete and good flatness of the outlet plate. In general, the speed of the noria is such that the residence time of the plates in the hydration zone complete is 5 to 30 min, preferably between 5 and 15 min. The dimensions of the noria are generally the following: the depth corresponds to a plate (but there would be possible to put two or more) and the width corresponds to the plate or train of plates.

With reference to FIG. 4, the mode of previous realization seen from above (we represent only one tray, the one who will come and lift the plate P).

With reference to FIG. 5, a variant of the previous situation. This time, the noria is shifted relative to the rollers 8a, 8b and 8c. A ferry 12 translates the plates of the rollers 8a, 8b and 8c towards the noria. This ferry ensures the supply of plates of the train of plates on a plate of the noria. This ferry is conventionally a set of supports joined together that move in a movement of translation, then back to position below, at the like a skid of a caterpillar for example.

We could also plan the noria directly at the end accelerator / stop zone, but this time with an axis no longer parallel but perpendicular to the sense of displacement of the plates. In this case, the axis of the plates is perpendicular to the axis of the noria; this one presents then a width of the order of the width of the plate. The plate then comes, at the end of the race, abut on inside the noria before being manipulated by noria trays.

Depending on the embodiment chosen, waste disposal from the curing line can be done from the side (first case, for example with a ferry of the type described under reference 12 and third case) or from above or in the axis (second case).

Hydration in the noria saves space considerable. Indeed, the traditional section of hardening can be reduced in length by up to 50%. In addition, the wet transfer area up to the entrance of the dryer is also considerably reduced. In addition, the residence time of each plate in the noria is identical, which allows to have a hydration rate of very homogeneous plates. This is even more apparent when another drying noria is used together with a hydration noria; in fact he it is generally the same noria which has several separate areas (which discussed below).

The norias according to the invention can accommodate plates of various lengths, such as 1.50 m up to the full width of the noria. Indeed, the arms are wide enough to accommodate all plate lengths and all types of plate train of all lengths: the plates, whatever their length, always rest enough (usually mostly) on the arms of the noria plateau.

To discharge the noria, we can use systems similar to those used to charge it, namely a ferry. The ferry can include rollers; it can also include an endless band, placed between the arms, the axis of the strip being perpendicular to the axis of the barrel. In such a case, the plate arriving on the band rests on it, the branches are released naturally. The speed of rotation of the strip is then adapted to that of the noria to be able to empty it. Any other known system will apply to the plate handling to transfer it from a noria outwards or to another noria.

We could also have two or more norias hydration, if necessary. Transport of plates from one noria to another is done as above for example.

With reference to FIG. 6, another mode of description is described. embodiment of the invention, namely a dryer based on this principle of the noria. The noria is substantially identical to that described above, with the difference that it is placed at least partially in an enclosure 13 arranged around this noria. This new type of dryer is fed from the wet transfer according to the prior art or from a hydration noria according to the invention described above.

The operation of the dryer is very simple. The plaques enter the dryer, are placed on the trays, and can then under the effect of heat evacuate the water. The enclosure 13 makes it possible to confine the drying zone. This enclosure is related to an air circuit, not represented on the diagram, which includes in addition to the conduits, one or more heat generators and fans to circulate the gases around the drywall to dry. For example, enclosure 13 can be divided into two or more zones (usually multiple of two), with circulation of air or other gas between these areas; this is described in more detail below.

Compared to the prior art, this type of dryer allows better homogeneity in drying. Indeed, in the prior art it took a certain time to load all the stages of the traditional dryer, this which caused a delay, because on the one hand we could not be sure that every plate that came in had been hydrated to 100% and secondly the plates introduced first (as well as the one extracted last) had a time of stay different from the plate inserted / extracted in the middle of the device. By perfect homogeneity, we improve the yield and quality of the plates.

Each tray can include (but not necessarily) comb fingers rather than arms (as opposed to the noria of hydration), since there more serious risk of creep and to allow further better heat exchange. However, this is not necessary; when drying and hydration are set work in the same noria arms have the same shape. The dimensions of the noria used for drying are from same order of magnitude as those for noria hydration (taking into account the relative residence times for both operations). The frame rate is also suitable; in general, this speed is of the same order of size than for the hydration noria.

The noria can be partially or as a whole disposed in the heated enclosure 13, with an atmosphere substantially homogeneous in noria. We will however prefer that the plates form the routing conduits of gases, to obtain an "intelligent" circulation of these gases inside the enclosure. This allows to have several zones of drying with different profiles, and therefore optimizing drying. To obtain good drying uniformity lengthwise of the plates, in each zone drying thus defined the flow of hot gases will alternately reversed. This operation is carried out simply for example by reversing the direction of travel of fans or by installing appropriate deflectors at the ends of the enclosure. With this solution, each zone has an even number of conduits. Can also install burners for example at both ends of the enclosure. The circulation circuit can in particular be obtained by an appropriate cover, the enclosure 13 being divided at the sides of the noria into as many areas as desired.

According to one embodiment, the enclosure 13 is such that the plates act as deflectors and guides for hot gases. We can thus obtain, by modifying operating conditions, two or more areas of drying with separate conditions. In fact, we can have as many drying zones as there are cells formed by two consecutive plates. More specificly, in the example of figure 6, there are two drying zones (zone 1 and zone 2), and therefore two compartments at the level of the rollover. The zones are separated by baffles 14a and 14b.

For example, we can have two drying zones, one with an inlet temperature of around 250 ° C and a outlet temperature of approximately 220 ° C, and another with an inlet temperature of approximately 220 ° C and a temperature 180 ° C outlet temperature. We can then apply a more heat being sure not to "burn" or calcine the plates.

In the previous case, the baffles can be used to return hot exhaust gases from the first zone to the second zone.

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

The design of this dryer allows great flexibility in the type of drying process. Dryer described above is of the direct dryer type. (hot gases in direct contact with the plates). It is also possible to provide for indirect drying. Similarly, the norias can receive all conventional recovery systems energy.

It is possible to place several norias (drying for example) in series. Transport devices of a noria to another have been described above.

It is however preferred, in one embodiment particular, to use a single noria for all hydration and drying operations. In this mode of realization, we can have hydration on the way vertical and drying from the top and in the area down. The enclosure can be present on the whole or not noria.

According to one embodiment, the noria dryer further includes a cooling function of the plates. This device then presents a free zone which is not included in the enclosure. In this area additional, the plate can cool down naturally or not, to avoid possible thermal shock. We thus obtains a plate of better quality than with a traditional dryer.

The mechanism for extracting the plate is similar to the one to introduce it, except that it is operated in the other meaning.

One could also provide a complete noria for the purposes cooling if necessary.

We thus obtain at the end of the last noria a cooled plate that can be sent directly to the final conditioning area, without going through the series heavy and noisy equipment found usually at the dryer outlet, i.e. waterfall grouping of plates from the different floors, acceleration and stopping zones, transfer tables etc.

The drying waterweeds can, as for the waterweed hydration, accept different lengths of plates. For drying noria to get better still gas flow in the alveoli we can by example arrange the plates alternately, i.e. an edge-to-edge plate on one side of the noria and the other edge-to-edge on the other side. We can also preferably use trays with their ends (at the sides of the noria) of the segments having sufficient area for each plate to rest on this segment, whatever its length.

At the level of the passage of the trays at the "angles" of the noria, it is possible to provide several solutions. We can have an angle with a radius of curvature sufficiently important so that the plates do not touch each other. It is also possible to provide a release mechanism and acceleration (similarly, for example, to that that can be encountered with cabin cable cars multiple or the so-called declutching chairlifts).

Generally the norias or perambulators used in the invention may be of the type of those described in documents DE-A-2950661 and EP-A-0999152.

En termes de procédé et qualité conférée à la plaque :

• un temps d'hydratation pratiquement identique pour toutes les plaques à l'entrée du séchoir;
• plus d'écart entre trains de plaques à l'entrée du séchoir;
• plus d'écart entre plaques dans le séchoir.
• possibilité de multiplier le nombre de zones de séchage pour se rapprocher du profil de séchage idéal;
• possibilité d'intégrer une zone de refroidissement dans le dispositif;
• possibilité de manutentionner les plaques humides à des échéances plus courtes que dans les lignes classiques;

En termes d'investissement:

• réduction du coût de transfert humide et partiellement du transfert sec qui sont intégrés dans l'équipement;
• réduction du coût de ligne de formage, car plus courte et/ou avec une cisaille de conception de plus simple;
• moins de terrain et de bâtiments.

En termes de maintenance:

• réduction des coûts de maintenance sur les transferts humide et sec;

En termes de coût d'exploitation :

• réduction de la consommation d'énergie électrique (la puissance installée pour la motorisation des entraínements est divisée par 3 à 4).
• réduction de la consommation d'air comprimé (sur les tables de transfert) et la maintenance associée.
• amélioration des taux d'utilisation des équipements.

En termes de sécurité et condition de travail :

• réduction du bruit en particulier sur les 2 transferts et par la suppression de la cascade à la sortie séchoir. Plus de bruit lié à l'utilisation de l'air comprimé sur les tables de transfert.
• Sécurité : moins de pièces en mouvement rapide.

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;
• more gap between train of plates at the entrance to the dryer;
• more gap between plates in the dryer.
• possibility of increasing the number of drying zones to get closer to the ideal drying profile;
• possibility of integrating a cooling zone in the device;
• possibility of handling wet plates at shorter times than in conventional lines;

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;
• less land and buildings.

In terms of maintenance:

• reduction of maintenance costs on wet and dry transfers;

In terms of operating cost:

• reduction in the consumption of electrical energy (the power installed for the motorization of the drives is divided by 3 to 4).
• reduction of compressed air consumption (on transfer tables) and associated maintenance.
• improvement in equipment utilization rates.

In terms of safety and working conditions:

• noise reduction in particular on the 2 transfers and by eliminating the cascade at the dryer outlet. No more noise related to the use of compressed air on transfer tables.
• Safety: fewer fast moving parts.

It should be noted that the invention applies to generic way to individual plates as well as to plate trains. The terms forming, shearing, hydration, drying, etc. "from the plate" aim as well heard "plates from the plate train".

It should also be noted that the term "plate plaster "used in the invention covers the base plates plaster, and in particular but not limited to the plates with one or more paper or cardboard siding (called in English "wall-board", "plaster-board"), but also in other materials such as a fiber mat glass (so-called "fire" plates), fiber plates (called in English "fiber-board), etc. The invention preferably applies to plates with siding cardboard ("plaster-board").

The invention is not limited to the embodiments described but is susceptible to numerous variations readily accessible to those skilled in the art.

Claims (15)

A method of 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) plate shear; (iv) continued hydration during translation of the plate along an axis perpendicular or oblique to the plane of the plate; and or (V) drying during the translation of the plate along an axis perpendicular or oblique with respect to the plane of the plate. The method of claim 1, wherein the steps (iv) and / or (v) are implemented in at minus a noria. The method of claim 2, wherein hydration is continued in said at least a noria up to the totality. Method according to one of claims 1 to 3, in which the hydration at the end of the step (ii) is less than 66%, preferably included between 33 and 66%, more preferably between 33 and 50%. Method according to one of claims 2 to 4, in which the drying is carried out in at minus one noria, said at least one noria comprising at least two drying zones distinct. Method according to one of claims 1 to 5, further comprising a step (vi) of cooling. The method of claim 6, wherein a cooling is implemented in a part of the noria. Method according to one of claims 1 to 7, set in one noria. Noria including a drive mechanism without end 9 on which are fixed a plurality of plates 10a, 10b, 10c, 10d, each plate being divided into a plurality of arms 11a, 11b, 11c, 11d, and further comprising an enclosure 13. Noria according to claim 9, wherein the enclosure is divided into at least two zones of separate drying. Noria according to claim 9 or 10, comprising a hydration zone in the ascending part. Noria according to one of claims 9 to 11, further comprising a cooling zone. Device for manufacturing plasterboard including a linear hardening-hydration zone and at least one noria according to one of claims 9 to 12. The device of claim 13, wherein the hardening zone and the noria are mated by means of rollers 8a, 8b and 8c, these rollers interpenetrating the plates 10a, 10b, 10c, 10d. Device according to claim 13 or 14, for the implementation of the method according to one of claims 1 to 8.

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