NO753036L - - Google Patents

Description

Method and facility for manufacture

of plasterboard

The present invention relates to a method for the production of plasterboard, in which a layer of burnt plaster, fibers or other fillers or a mixture of these or several superimposed sub-layers of one or more of these materials is placed on the upper side of a conveyor belt. and where water is also used to set the plaster.

It is known to produce plasterboard by mixing burnt plaster and plenty of water into a slurry which is poured onto a cardboard sheet, after which another sheet of cardboard is guided down towards the slurry from above so that it is contained before it is set. This method requires the use of a lot of so-called surplus water, i.e. the water that is used in excess of the stoichiometrically necessary amount of water in the bound gypsum: CaSO^, 2H^ 0, as otherwise one does not get sufficiently good opportunities to form the gypsum root . The excess water must then be removed by heating the plate, which is quite energy-intensive. The stbchiometric amount of water in the bound gypsum is approx. 19% of the bound plaster's weight, but in many cases the added amount of water will be significantly greater.

There is also a known method for the production of gypsum boards where, in order to reduce the amount of shot water to a mixture of burnt gypsum and fibers, water is added in the form of crushed ice and then the mixture is shaped. However, this method requires that plaster and fibers are cooled to below 0°C and kept at this temperature during the mixing process. The shaping must then be complete by the time the ice melts. The method requires a lot of energy, especially due to the cooling of the burnt gypsum, to which are added expenses for special dressing equipment. It would be better if mixing and shaping could take place at temperatures above 0°C.

The aim of the invention is to provide a method of the type stated above, which allows the mixture of burnt plaster, fibers and other fillers to be formed dry at a relatively high temperature, so that the energy-consuming cooling down is avoided, and which also allows any excess water to to a large extent can be removed in a very energy-saving way: The method according to the invention is characterized by the fact that the burnt plaster has a temperature between 1 and

140°C, and that the layer or sub-layers are laid out dry, i.e. only containing the remaining crystal water that is bound to the burnt gypsum, after which the layer or sub-layers are then possibly shaped and/or pre-compressed, and that water is then added to the layer or the sub-layers in their full width and in an amount that at least allows the plaster to set, and that a pressure difference is created between the outer side of the plate thus formed to distribute the added water and remove as much excess water as possible. Thereby, a strong reduction in the energy required to remove any excess water is achieved, as, among other things, the organs necessary to maintain the pressure difference require relatively little energy; moreover, energy is saved by not

needs to do some cooling down to be able to shape tort. If fibers or other fillers have been added to strengthen the plaster, the expensive cardboard sheets can be completely dispensed with.

According to the invention, the gypsum used can have a temperature between 10 and 100°C, which is appropriate, as the burnt gypsum, depending on the storage conditions and the season, normally has a temperature within this range.

According to the invention, the thickness of the layer or the total thickness of the sub-layers can be between approx. 5 and 100 mm, whereby it is achieved that there is no need to work with very large pressure differences.

Furthermore, according to the invention, the pressure difference can be created by maintaining a vacuum on the outside of the layer or collection of sub-layers which is opposite the outside on which the water is supplied, which vacuum is preferably between lOO and 5000 mm water column, depending on the desired plate thickness and the speed of the conveyor belt. Thereby, the desired pressure difference is achieved in both a simple and relatively cheap way.

According to the invention, the pressure difference can be provided at the same time as the water supply and possibly continue after this, as the water is supplied under pressure, e.g. a pressure below 6 ato. Thereby, relatively large pressure differences can be achieved.

Furthermore, according to the invention, a loosening agent can be added to the water, whereby the distribution of the water in the layer or sub-layers is promoted.

Furthermore, according to the invention, the pre-compression can be carried out using a vacuum between two or more of the places where the materials are laid out on the conveyor belt, which vacuum is preferably of the order of 1000 mm water column. Hereby it is achieved that the burnt plaster will fit tightly into the fillers, so that internal cavities are largely avoided when the water is later supplied.

According to the invention, the partially bound plate, after part of the excess water has been removed, can have its upper and/or lower side shaped an additional time, whereby it or these sides can have a specific desired surface structure.

The invention also relates to a facility for carrying out the method according to the invention, and which comprises a conveyor belt at the top of which there are units for laying out a layer of burnt gypsum, fibers or other fillers or a mixture thereof, or several superimposed sub-layers of one or several of these materials, and this facility is characterized by the fact that the conveyor belt is perforated, and that a filter belt is placed in contact with it, and that above and at a distance from the filter belt, devices for shaping the upper side of the layer or sub-layers are possibly mounted, which forming devices are preferably placed between two or more of the laying units, and that there are also pre-compression devices between two or more of the laying units, and that above the filter belt devices are mounted for the supply and uniform distribution of water over the layer or the assembly of sub-layers, and that there moreover above the filter band at a distance from this and/or below r the conveyor belt is fitted with devices for maintaining a pressure difference between the outer sides which is formed on the belt, preferably devices for maintaining a vacuum under the conveyor belt. In practice, this facility has proven to be particularly effective for rolling out the method according to the invention.

According to the invention, the vacuum devices can consist of one or more boxes placed under the conveyor belt which extend the full width of the layer or sub-layers, as well as a blowing device connected to the box or boxes. This results in very rapid removal of any excess water. The water is collected in the box or boxes and diverted away from there.

Furthermore, according to the invention, the vacuum devices can lie mainly below the water supply devices, which is practical if the forward speed of the conveyor belt is relatively small, and there is a relatively large pressure difference.

According to the invention, the vacuum means - seen in the conveyor belt's production direction - can extend further than the water supply devices, whereby the plasterboard formed on the belt has its excess water removed particularly effectively.

According to the invention, it is also possible for the vacuum devices, with a view to a more even distribution of the water, to be placed in a place which - seen in the forward direction of the conveyor belt - lies behind the water supply devices. This design is particularly appropriate if the conveyor belt's forward speed is high and the layer or layers relatively thick.

Furthermore, according to the invention, the individual vacuum box can be divided into several compartments sealed in relation to each other, where each compartment is connected to its own separate blowing device. This ensures that any holes or cavities in the plaster or fillers (at which holes or cavities the air resistance is relatively small) will not cause difficulties in maintaining the vacuum in neighboring areas. When a possible hole in the plaster or the fillers comes to lie outside a certain box section, the pressure difference will only fall at the latter. In the neighboring departments, on the other hand, the pressure difference will be maintained to its full extent.

According to the invention, the pre-compression devices can be made of one or more vacuum units, preferably vacuum auxiliary boxes which serve to get the dry plaster to fill the cavity between the fillers. In this way, a particularly effective filling of the aforementioned cavities is achieved.

In order to ensure that the thickness of the individual sub-layers will lie within certain desired limits, the forming devices can be made of a profile roller or a mainly plough-shaped device. Namely, the forming devices will distribute the laid material, possibly leading away some of it.

According to the invention, side shaping devices can be mounted next to the conveyor belt, preferably in the form of endless belts and/or rollers, whereby a certain shaping of the sides of the layer or sub-layers on the conveyor is enabled.

Furthermore, according to the invention, after the devices maintain a pressure difference - seen in the forward direction of the conveyor belt - auxiliary forming devices can be mounted, e.g. a profile roller or an old overband. This makes it possible to add a specific monster to the top and/or bottom of the finished plate.

A final embodiment of the plant according to the invention is characterized by the fact that the filter belt is relatively thin and on part of its path is free from the conveyor belt, and that the auxiliary shaping devices are made up of one or more profile rollers which are placed under the filter belt in contact with it for shaping the underside of the partially bonded plate, e.g. formation of a monster on the underside of the plate, as well as a smooth counter-pressure wave Ise that is placed above the plate. In this way, it is achieved in a particularly simple way that the underside of the plate gets a certain structure.

The invention is explained in the following with reference to the drawing where

Fig. 1 schematically shows an embodiment of the plant according to the invention seen from the side, clearly seeing that the devices for maintaining a pressure difference are made up of a vacuum box and the precompression devices are made up of vacuum auxiliary boxes, while the forming devices are made up of a roller which is placed between two of the layout units, Fig. 2 same view in section along the line II - II in fig. 1, Fig. 3 a cross-section corresponding to fig. 2 in another embodiment of the plant according to the invention, which embodiment is provided with an auxiliary forming device in the form of a pro-filing roller, Fig. 4 schematically yet another embodiment of the plant according to the invention in which the auxiliary forming device consists of an upper band which is placed behind. the vacuum box, Fig. 5 schematically yet another embodiment of the plant according to the invention, where the filter belt on part of its path is free from the conveyor belt, and where the auxiliary forming devices are made up of a lower profile roll and an upper smooth counter pressure roll, and Fig. 6 a vacuum box which is constructed of a number of departments which are sealed - in relation to each other - seen in perspective obliquely from above.

That in fig. 1 shown plant consists of an endelo.st perfo- . connected conveyor belt 1 on top of which a filter belt 2. Above

the conveyor belt is fitted with three layout units in the form of dosing containers 3, 4 and 5 with an adjustable opening where the container 3 e.g. may contain burnt plaster plus reinforcing fibres, while the container 4 may contain burnt plaster plus a suitable filler, e.g. light clay bricks or plastic bodies and finally the container 5 can have the same contents as the container 3. Each container lays out its dry sub-layer 6, 7 and 8. By "dry" here it is understood that the layer only contains the crystal water which is connected to the burnt gypsum. By laying out layers 6, 7 and 8 tort, they can be placed more noy-like in relation to each other. If the lightweight clinkers were laid together with a gypsum wall, they would quickly shift. The reinforcing fibers used can be either natural or synthetic. Instead of sub-layers 6, 7 and 8, one can of course make do with laying out just one layer. Optionally, you can insert paths or mats of reinforcing material between the individual sub-layers. Between the containers 3 and 4, as shown, a shaping device 13 can be mounted in the form of a profile roller or a plough-shaped part, whereby the upper side of the sub-layer 6 can be shaped so that parts of the sub-layer 7 can penetrate below the upper limit of the sub-lid 6, and can thus achieve a better distribution of the reinforcing material. A pre-forming device can also be placed between the containers 4 and 5. Under the conveyor belt and between the containers 3, 4 and 5, precompression devices 14 in the form of vacuum auxiliary boxes can be mounted, as shown, which are each connected to a blowing device, not shown, so that suitable suction can be maintained in the individual box. Optionally, there can also be an auxiliary vacuum box just after the container 5 as indicated at 14a. The vacuum in the auxiliary vacuum boxes is of the order of 100 mm water level. The pre-compression means serve to make the dry gypsum effective

tive to fill the voids between fibers and fillers before water is added. A little further from the containers 3, 4 and 5, there are organs 9 for the supply and uniform distribution of water over

■layer 8 upper side. The devices 9 can e.g. made up of water-pressure nozzles. The plant also has devices for maintaining a pressure difference between the upper side of the partial layer 8 and the lower side of the partial layer 6, which pressure difference serves to remove a large part of the water that has been added to the plaster via the water pressure nozzles. These pressure difference-creating devices can e.g. is made up of one or more vacuum boxes of which only one box 10 is shown in fig.

1. One end of the box is connected to the suction side of a blowing device not shown. Between the upper edges of the box and the underside of the conveyor belt 1 there are inserted sealing strips 11 which cooperate with sealing rollers 12 which themselves run on the underside of the conveyor belt. With the help of the vacuum box, when a suitable negative pressure is maintained in it, it can be ensured that almost all excess water is removed. Relatively little energy is thus used. The box 10 normally extends over the entire width of the sub-layers 6, 7 and 8. If many boxes are used, they can be relatively narrow, but they must still together cover the entire width of the sub-layers. As shown in fig. 6, the individual vacuum box can be divided into a number of compartments 10a, 10b, 10c, 10d, etc., where each compartment is then connected to its not shown blowing device so that the vacuum in an area below the conveyor belt does not significantly affect the vacuum in the neighboring areas. This is of particular importance if there are holes in the laid out layers which reduce air resistance when suction is applied through the layers. It is noted that both the box 10 and the auxiliary boxes 14 can be divided into compartments. Between the upper edge of the partition walls and the lower side of the conveyor belt, there must of course be suitable sealing devices, which are not shown, however. '

As shown in fig. 1, the vacuum box - or boxes - viewed in the direction of the conveyor belt (indicated by arrow A) - can extend further than the water nozzles 9, whereby there are particularly good opportunities to remove large parts of the excess water, even if the parts 6, 7 and 8 together should have a relatively large thickness.

If the sub-layers 6, 7 and 8 are very thick, it may be appropriate to place the water pressure nozzles for the vacuum box, seen in the production direction of the belt 1, which situation is indicated by the dashed water pressure nozzle 9'.

In fig. 2 shows how side shaping devices can be mounted at each of the conveyor belt 1's sides in the form of long steel bands 15 and 16 which ensure that the manufactured plasterboard has nicely shaped surfaces in a direction perpendicular to the conveyor belt. This avoids material loss, as there is no need to cut off the edges of the plate. The side forming devices can optionally also be made of rollers not shown.

In order for the partially bonded plasterboard, after part of the excess water has been removed, to have its upper and/or lower side shaped an additional time, (i.e. to be assigned a specific monster or a specific profile), the plant as shown in fig. 3 be provided with an upper profile roller 18. To ensure a sufficiently large clamping pressure, a counter-pressure valve 19 can be mounted under the conveyor belt 1, as shown.

In fig. 5 shows how the profile roller and the counter-pressure roller can be changed, provided that care is taken to ensure that the filter belt 2 is released from the conveyor belt 1 on a certain part of its upper horizontal loop. The profile roller is in this case indicated at 18', while the counter-pressure roller is indicated at 19'. However, the auxiliary shaping devices can also be made of an upper band 21, as shown in fig. 4, which upper band is located behind the vacuum box 10. The band 21 serves to give the plasterboard a certain profile or a certain surface structure during possible compression.

There is nothing in the way of the container 3 being able to add burnt plaster, the container 4 adding fibers and/or lightweight clinker and the container 5 'adding burnt plaster. Optionally, the fibers can be added in an area close to the plate's grooves, i.e. where the plate is most vulnerable and therefore needs bracing.

When the plant is in operation, the added burnt gypsum that comes directly from the calcination process can be approx. 140°C, and this gypsum can easily be led to containers 3, 4 and 5, so that it can be laid out relatively quickly on the filter belt. Normally, the total thickness of the sub-layers 6, 7 and 8 will be between 5 and 100 mm. The vacuum box IO (or the corresponding boxes) can e.g. work with a pressure of between 100 and 5,000 mm water column, depending on the desired slab thickness, as it applies that the stronger the suction, the denser the finished slab will be 30. A very high suction leads to a stronger collapse of the sub-layers.. The water supplied via the nozzles 9 will normally have a pressure below 6 ato.

To promote the water's passage through layers 6, 7 and 8, a relaxing agent such as sulphosoap can be added to the water. Optionally, an accelerator can also be added, e.g. potassium sulfate, to shorten the setting time.

With respect to the conveyor belt 1 in fig. 1, 3 and. 4 is considered to be endless, since it runs around two drums 22 and 23, while the filter belt 2 runs around both the drums 22 and 23 as well as auxiliary rollers 24 and 25. In fig. "5, however, the conveyor belt 1 wraps around its own drum 23', while the filter belt runs around an additional drum 29. The upper belt 21 in Fig. 4 wraps around drums 27 and 28. In the vicinity of the filter belt and the upper belt, washing units can be mounted at their return which, however, is not shown.

The conveyor belt and the filter belt can optionally be combined into one belt. This is then fed around two drums and passes over a table in which the vacuum box or boxes and possibly also the vacuum auxiliary box or boxes are built-in. The band is supported by the tabletop, which is perforated. The suction from the boxes can thus easily act on the plaster that is fed forward on the belt.

After the stiffened plasterboard 30 has left the facility, it is brought to be cut into suitable lengths and to final drying. Optionally, the drying can take place before the cutting.

The invention can be changed in many ways without deviating from its idea. thus one can e.g. use colored plaster or you can add the dye via the water through the water pressure nozzles 9.

It is noted that the method according to the invention is continuous in contrast to many of the known methods which are carried out in batches.

Claims (20)

1. Procedure for the production of gypsum boards (30) in which a layer of burnt gypsum, fibers or other fillers or a mixture thereof, or several superimposed partial layers (6, 7, 8) is laid out on the upper side of a conveyor belt (1) of one or more of these materials, and where water is also used to set the plaster, characterized in that the burnt plaster has a temperature between 1 and 140°C during laying, and that the layer or sub-layers (6, 7, 8) are laid dry, i.e. only containing the remaining crystal water that is bound to the burnt gypsum, after which the layer or sub-layers (6, 7, 8) are possibly formed and/or clay is pre-compacted, that water is then added to the layer or sub-layers in their full width and in an amount that at least allows the plaster to set, and that a pressure difference is created between the outer side of the sheet formed thereby to distribute the added water and remove it of as much excess water as possible. 2. Method according to claim 1, characterized in that the gypsum used has a temperature between 10 and 100°C. 3.. Method according to claim 1 or 2, characterized in that the thickness of the layer or the total thickness of the partial layers (6, 7, 8) is between 5 and 100 mm. 4. Method according to claim 1, 2 or 3, characterized in that the pressure difference is created by maintaining a vacuum on the outer side of the layer or collection of sub-layers (6, 7, 8) which is opposite the outer side on which the water is supplied, which vacuum preferably lies between 100 and 5000 mm water column, depending on the desired plate thickness and the speed of the conveyor belt (1). 5. Method according to claim 1, 2, 3 or 4, characterized in that the pressure difference is provided at the same time as the water supply and possibly continues after this, as the water is supplied under pressure, e.g. a pressure below 6 ato. 6. Method according to claim 1, 2, 3, 4 or 5, characterized in that a relaxing agent is added to the water to promote the distribution of the water in the layer or sub-layers (6, 7, 8). 7. Method according to claim 1, 2, 3, 4, 5 or 6, characterized in that the pre-compression is carried out using a vacuum between two or more of the places (3, 4, 5) where the material is laid out on the conveyor belt (1) , which vacuum is preferably of the order of 1000 mm water column. 8. Method according to one or more of claims 1-7, characterized in that the partially bonded plate, after part of the excess water has been removed, has its upper and/or lower side shaped an additional time. 9. Installation for carrying out the method according to one or more of claims 1 - 8, and which comprises a conveyor belt (1) at the top of which there are units (3, 4, 5) for laying out a layer of burnt gypsum, fibers or other fillers or a mixture thereof, or several superimposed partial layers (6, 7, 8) of one or more of these materials, characterized in that the conveyor belt (1) is perforated, and that a filter belt (2) is placed in contact with it , and that devices (13) for shaping the upper side of the layer or sub-layers (6, 7, 8) are possibly mounted above and at a distance from the filter belt (2), which shaping devices (13) are preferably placed between two or more of the layout units (3, 4, 5), and that, in addition, between two or more of the layout units (3, 4, 5) there may be pre-compression devices (14), and that above the filter belt (2) devices (9) are mounted for feeding and uniform distribution of water over the layer or collection of sub-layers (6, 7, 8), and that in addition above the filter belt (2) at a distance from this and/or below the conveyor belt (1) devices are mounted for maintaining a pressure difference between the outer sides of the plate (30) which is formed on the belt (1) preferably devices (10) for maintaining a vacuum under the conveyor belt (1) 10. Plant according to claim 9, characterized in that the vacuum devices are made up of one or more boxes (10) placed under the conveyor belt (1), which extend across the full width of the layer or sub-layers (6, 7, 8), as well as one for the box or the boxes connected to a blowing device. 11. Plant according to claim 9 or 10, characterized in that the vacuum devices (10) are located mainly below the water transfer devices (9). 12. Plant according to claim 9 or 10, characterized in that the vacuum devices (10) - seen in the conveying direction A - extend further than the water supply devices (9). 13. Installation according to claim 9 or 10, characterized in that the vacuum devices (10) with a view to a more even distribution of the water are placed in a place which - seen in the forward direction A of the conveyor belt - lies behind the water supply devices (9'). 14. Installation according to one or more of claims 9 - 13, characterized in that the individual vacuum box is divided into several compartments sealed in relation to each other (10a, 10b, 10c, 10d) where each compartment is connected to its separate blowing device. 15. Plant according to one or more of claims 9 - 14, characterized in that the pre-compression devices are made up of one or more vacuum units, preferably vacuum auxiliary boxes (14) which serve to cause the dry plaster to fill the voids between the fillers. 16.. Plant according to one or more of claims 9 - 15, characterized in that the forming devices are made up of a profile roller (13) or a mainly plough-shaped device. 17. Plant according to one or more of claims 9 - 16, characterized in that side shaping devices are mounted next to the conveyor belt (1), preferably in the form of end belts (15, 16) and/or rollers. 18. Installation according to one or more of claims 9 - 17, characterized in that after the devices (10) for maintaining a pressure difference, seen in the conveyor belt's forward direction A, auxiliary shaping devices are mounted, e.g. a profile roller (18) or an upper belt (21). 19. Plant according to one or more of claims 9 - 18, characterized in that the filter belt (2) is relatively thin and on part of its path is free of the conveyor belt (1), and that the auxiliary forming devices are made up of one or more profile rollers (18' ) which is placed under the filter band (2) in contact with it for shaping the underside of the partially bonded plate, e.g. forward bringing a monster on the underside of the plate, as well as a smooth counter pressure roller (19') which is placed above the plate. 20. Installation according to one or more of claims 9 - 19, characterized in that the conveyor belt and the filter belt are worked together into a belt that can slide across a table, in which the vacuum box or boxes or the vacuum auxiliary boxes are built-in, which table has a perforated table top.