EP0343618A2 - Process and apparatus for drying hollow block preforms - Google Patents

Abstract

A process and apparatus for drying hollow block preforms, in which drying air is blown onto the faces of the preforms (54) which have the hole mouths, in order to bring about a through-flow through the hole channels. To maintain an intensive through-flow of the hole channels, it is envisaged that the preforms (54) are arranged in a single layer, advantageously in a horizontal layer, which is positioned transversely to the through-flow direction. The blowing apparatus (80) for the delivery of the drying air has parts (82) which are provided with air passage openings and which are arranged on both sides of the layer on which the hole channel mouths are exposed. In this connection, drying air is blown through the hole channels in a direction which is always the same, possibly alternating in given regions on account of an appropriate arrangement of deflection shafts (82). <IMAGE>

Description

The invention relates to a method and a device for drying perforated brick blanks with the features according to the preamble of claims 1 and 2 and 13 respectively.

The drying of perforated brick blanks before firing must be carried out in such a way that the moisture is extracted from the blanks without cracking. As has long been recognized, this is only possible if the perforated brick blanks are not only washed around by the drying air on their outer surfaces, but if drying air also penetrates the perforated channels themselves (cf. EP-PS 89 408, DE-OS 25 49 696) . For this reason, methods and devices of the type mentioned are already known, in which care is taken to ensure that the heated drying air is applied to those end faces of the perforated brick blanks in which the perforated channels open, in order to flow through the perforated channels and thus to remove them to cause moisture contained in the perforated channel walls. In a known device of this type (cf. EP-PS 89 408 mentioned), the perforated brick blanks are arranged in rows or layers parallel to one another, these rows or layers being at a transverse distance with respect to the conveying direction, and the blowing device has side parts whose blow-out openings directly opposite the perforated channel mouths on the end faces of the two outer rows of perforated brick blanks. Drying air emerging from the blow openings therefore impacts these end faces and can flow through the perforated channels.

However, it has been shown that the known proposals for drying perforated brick blanks have not yet led to a satisfactory result with regard to the fact that crack-free drying is made possible within the shortest possible periods of time. This is mainly due to the fact that, despite the known measures described, it has not hitherto been possible to let a sufficiently large proportion of the available drying air flow through the perforated channels and to obtain a balanced ratio of the moisture removed from the perforated channels and from the outer surfaces. Because the perforated channels also oppose a relatively large flow resistance with the perforated channel dimensions, which are present, for example, with perforated bricks with cross-sectional areas of 36 x 50 cm, so that the flow velocity within the perforated channels is increasingly throttled and thus the air throughput and thus the drying effect are low . The result of this is that the drying intensity on the outer surfaces of the perforated brick blanks must not be too pronounced, because otherwise there is a risk of cracking. As a consequence, the drying process takes a relatively long time and therefore requires large drying rooms.

The object of the invention is to provide a method and a device for drying perforated brick blanks, by means of which the drying process can be considerably shortened with perfect brick quality, ie without crack formation. According to the invention, this is achieved in terms of the method by the procedure according to the characterizing part of patent claims 1 and 2, and in terms of the device by the features according to the characterizing part of patent claim 13.

The invention is based on the consideration that the desired flow through the perforated channels can only be achieved if the occurrence of a dynamic pressure on the end face of the blanks downstream of the flow is prevented. Because such a dynamic pressure in any case lowers the pressure drop effective between the perforated channel openings on the two end faces and therefore reduces the flow velocity and the flow rate. However, a back pressure on the downstream side cannot be avoided if the blanks are arranged next to one another in several rows or layers. In particular, if more than two rows or layers of blanks run next to each other, of which - as is the case with the known method described at the beginning - drying air is applied to the two outermost rows, there is on the two end faces of the rows between them or layers almost equal pressure, so that there is practically no flow through the perforated channels. The method according to the invention therefore provides for an arrangement of the perforated brick blanks only in a single layer directed transversely to the direction of flow or at most in such a layer in which two or at most three blanks with perforated channels aligned with one another are arranged directly one after the other. In both cases there are uninterrupted flow paths for the drying air, so that the flow velocity necessary for adequate drying can be generated in the perforated channels by a suitable choice of the blow-out pressure.

Depending on the size of the cross-section of the perforated ducts, a sufficient flow through the perforated ducts cannot be achieved simply by selecting the blow-out pressure, because the flow resistance with a small flow cross-section only increases the dynamic pressure in front of the upstream end, due to which there is a strong lateral outflow and flow around the remaining side surfaces of the perforated brick blanks. According to an advantageous embodiment of the method, it is therefore provided that the other side surfaces of the blanks, which have no mouth openings, are shielded by sealing edges or baffles, so that washing of these side surfaces with drying air is largely impeded. This ensures that the dynamic pressure building up on the upstream side is effective in the sense of a flow through the perforated channels.

According to a further advantageous embodiment of the method according to the invention, it is also ensured that a suction effect is generated on the downstream end face of the blanks in order to keep the previously observed dynamic pressure as low as possible there, to directly suck off the drying air flowing around the outer surfaces of the blanks and that between the Hole channel mouths to enlarge existing pressure drops. This suction effect can be generated according to the device in that a suction fan is provided in addition to the pressure fan that promotes the drying air.

A particularly advantageous further embodiment of the invention is specified in claims 7 and 21.

Since the blanks are then dried lying in a horizontal layer, with their hole sides facing up and down, they can be used in a mutual manner with different brick formats

A distance from each other can be arranged, which can always be adjusted under practical conditions so that a flow around the outside of the brick only takes place to the desired extent, which does not disadvantage the flow through the perforated channels. Unlike in the case of vertical stacking, in which after the change from one brick format to another, the height difference only comes into play at the top edge of the stack, the corresponding difference in horizontal layering is divided between the distances to be set between the individual bricks. Another advantage of horizontal layering is that the width of the layer is not limited by the load capacity of the bottom perforated brick, which is just permissible.

To carry out the method according to the invention in the form proposed here, the device is adapted in such a way that the transport support of its conveyor device for receiving the blanks is designed in the form of a horizontal layer and is permeable to the drying air flow. This means that this transport pad represents a grate formed from bars or rolls or also by means of a grid, on which the perforated brick blanks rest with one side of the hole and to which the parts of the blowing device connect so tightly from below that the drying air passing through the air passage openings initially Rust and then penetrated the perforated channels of the blanks. It goes without saying that in this case too, as with the previously described method and the associated device, care is taken to prevent the drying air from escaping laterally around the outer edge of the transport support by appropriate measures.

According to a particularly advantageous development of the invention, which is basically applicable not only to the arrangement of the blanks in a horizontal layer, but also to their vertical stacking, and for which further protection is therefore claimed, it is provided that the outflow-side holes the drying air exiting the blanks in a section of the blank layer is diverted and fed to the upstream hole openings of the blanks in a subsequent section of the blank layer. As a result, the drying air which has already flowed through the perforated channels in a section of the blank layer and is not yet "used up", ie up to Saturation is loaded with moisture, again used to dry the brick blanks in a subsequent section of the blank layer. This procedure is particularly advantageous if the deflection process and the renewed supply of the drying air are repeated one or more times on successive sections of the blank layer, with intermediate heating of the drying process, if necessary air can take place, and the deflection takes place so that the resulting main flow direction of the drying air runs counter to the conveying direction of the conveyor in the event that the blanks or the like in a continuous process through a drying tunnel. be driven. This countercurrent drying largely reduces the risk of cracking even with very short drying times because drying air comes into contact with the pre-dried and therefore still very moist blanks, which has already absorbed moisture from the previous flows through the blank layer and therefore to the blanks freshly entering the drying tunnel result in a gentle drying which takes their shape into account and which is necessary for the respective mass offset. In order to take into account the shrinkage that occurs during drying in the case of the brick blanks lying in a horizontal layer, the transport support of the conveying device, which is designed as a grate, is designed in such a way that it also permits the movement of the brick blanks caused by the shrinkage. There are various options for this: In the simplest case, the contact surface of the bars or rollers forming the grate can be designed with low friction with regard to the material of the blanks. This includes a smooth surface, possibly with a plastic coating that further reduces friction. Furthermore, the bars forming the grate can also be suspended in an oscillating manner, so that the blanks lying thereon do not perform any relative movement with respect to the bars during the shrinkage, but the bars move closer to one another. Furthermore, the bearing surface of the rods can have a flat curvature, thereby avoiding that the edge of the rods is locally in the underside of the blanks press in and prevent them from slipping. It is understood that the measures described can also be used in combination with one another.

Further procedural and device-specific embodiments of the invention result from the subclaims

• Fig. 1 bis 3 in sehr schematischer Darstellung eine erste Ausführungsform einer erfindungs­gemässen Trocknungsvorrichtung in Seiten­ansicht, Stirnansicht und Draufsicht;
• Fig. 4, 5 eine zweite Ausführungsform der Trocknungs­vorrichtung in Stirnansicht und Draufsicht;
• Fig. 6 rein schematisch nach Art eines Blockdiagrammes den Verfahrensablauf vom Abschneiden der Rohlinge von dem Strang bis zur Bildung einer Horizontalschicht nach einer modifizierten Ausführungsform;
• Fig. 7, 8 eine schematische Längsschnitt-Ansicht bzw. eine Draufsicht auf eine Trocknungsein­richtung nach einer dritten Ausführungsform;
• Fig. 9 einen schematischen Querschnitt durch die Trocknungseinrichtung gemäß den Fig. 7 und 8, und
• Fig. 10, 11 Stirnansicht bzw. Längsschnitt in ver­grössertem Maßstab der Transportauflage der Fördereinrichtung, die in der Trocknungs­einrichtung gemäß den Fig. 7 bis 9 zur Anwendung kommt.

Exemplary embodiments of the invention are explained in more detail below with reference to the accompanying drawings, in which:

• Figures 1 to 3 in a very schematic representation of a first embodiment of a drying device according to the invention in side view, front view and top view;
• 4, 5 a second embodiment of the drying device in front view and top view;
• 6 shows, purely schematically in the manner of a block diagram, the process sequence from cutting the blanks from the strand to forming a horizontal layer according to a modified embodiment;
• 7, 8 are a schematic longitudinal sectional view and a plan view of a drying device according to a third embodiment;
• 9 shows a schematic cross section through the drying device according to FIGS. 7 and 8, and
• 10, 11 front view or longitudinal section on an enlarged scale of the transport support of the conveyor, which is used in the drying device according to FIGS. 7 to 9.

1 to 3, the first embodiment of the device according to the invention comprises a drying room 1, which is only indicated, which can be a drying tunnel or a drying chamber to be charged on one side and is delimited by walls 2 and a ceiling 3. In the drying room 1 there is a conveyor in the form of a driven roller conveyor 4, of which only a few rollers are schematically indicated in FIG. 1 and on which pallets 5 with perforated brick blanks 6 stacked thereon can be conveyed. As can be seen from FIGS. 2 and 3, the perforated brick blanks 6 are arranged on the correspondingly dimensioned pallets 5 in such a way that only two blanks lie directly next to each other transversely to the conveying direction, ie without any space. The perforated channels run transversely to the conveying direction and open, as can be seen from Fig. 1, in the lateral end faces 6 'of the blanks. Especially in the case of brick blanks, which are manufactured in the extrusion process, the position and size of the perforated channels in the individual blanks are relatively precise, so that the perforated channels in the individual blanks are flush with one another and one uninterrupted due to the direct juxtaposition of two blanks Form flow channel for drying air to be blown through. In addition, since the cross section of the perforated channels generally corresponds to the size of the Perforated brick is in a certain relation, ie with larger dimensions of the perforated brick, the length of the flow channels created in this way is still sufficiently small in relation to their cross-section to maintain a flow even against the flow resistance that occurs.

Arranged in the drying room 1 is a blowing device, designated as a whole by 8, which in the exemplary embodiment shown consists of a housing 9, preferably made of sheet metal, with side parts 10, 11 adjoining it on both sides. The housing side parts 10, 11 close to form corresponding air guide shafts directly to the housing 9 extending transversely over the blanks 6, extend downward and have vertically standing opening surfaces 10 'and 11'. In these opening areas 10 '11' air passage openings, not shown, are provided. Instead of these opening surfaces with the perforation provided therein, only a single opening can be provided, which makes up the entire cross section of the housing side part at its mouth towards the blanks 6. As can be seen from Fig. 2, the blowing device 8 overlaps with the two side parts 10, 11 of the stack of blanks on both sides, said opening surfaces 10 ', 11' being at a distance from one another which is only slightly greater than the distance of both sides of the blank stack. The opening surfaces 10 ', 11' run largely parallel to the side surfaces of the blank stack, i.e. to the end faces of the blanks 6 having the hole openings.

At the front and rear end faces of the housing 9 in the conveying direction there are an air inlet opening 12 and an air inlet opening 12, respectively Air outlet opening 13 is provided, in which a pressure blower 14 or a suction blower 15 are arranged. The air inlet opening 12 leads to an inflow shaft 16 which is delimited in the region of the housing 9 by a partition 9 'and continues in the side part 11. In an analogous manner, an outflow shaft 17 is formed in the side part 10, which lies on the other side of the partition 9 'and opens into the outlet opening 13.

As indicated in dashed lines in Fig. 1, the inlet opening 12 and the outlet opening 13 can be connected by air shafts with corresponding openings, not shown, in the ceiling 3 of the drying room 1, as a result of which drying air is supplied from the outside via the inlet opening 12 to the blower 5, which is heated by a heater, not shown. Correspondingly, moisture-enriched air is discharged to the outside via the air shaft connected to the outlet opening 13. In this construction, the blowing device 8 is expediently arranged stationary in the drying room 1, so that the pallets 5 are moved relative to it by the conveyor device 4. Instead of the one blowing device 8 shown, several of them can also be arranged in a row one behind the other. If the air ducts mentioned in dashed lines in FIG. 1 are not present, then it is also possible to arrange the blowing device 8 (or several of them) in a known manner so as to be movable parallel to the conveying direction of the pallets 5. In this case, heated drying air is fed into the drying room 1 from the outside through an opening (not shown), so that the drying air is sucked in from the right-hand part of the drying room in FIG. 1 and expelled into the left part thereof. From there, the air enriched with moisture is then through again an opening, not shown, is led outside.

As can be seen from FIG. 2, the side parts 10, 11 are rounded in a flow-favorable manner in order to ensure a largely loss-free flow in the supply air shaft 16 and the exhaust air shaft 17. This streamlined design requires that the underside of the transverse housing 9 runs at a certain distance above the top of the blank stack. To ensure that, despite the short distance from the side surfaces of the blank stack, opening surfaces 10 ', 11' on the pressure side cannot escape too large amounts of air into the space formed thereby, the side parts 10, 11 are by a baffle 15 (Fig. 2nd ) connected to each other, which runs only a short distance above the top of the blank stack and parallel to it.

The operation of the device is as follows: through the pressure blower 14 heated drying air is sucked in through the inlet opening 12, conveyed through the supply air shaft 16 and blown out with a certain pressure from the openings or the opening of the opening surface 11 '. Due to the small distance of the opening surface 11 'from the side surface of the blank stack, which is formed by the end faces lying in one plane with the hole mouths, the heated drying air is blown into the hole channels. As a result of the flow resistance in the perforated channels, a dynamic pressure builds up in the area of the opening surface 11 and in front of the aforementioned end surfaces of the blanks 6, by means of which the drying air is forced into the perforated channels. As a result of the baffle plate 15 and the top side of the blank stack being formed only a relatively limited flow cross section, the gap between the edge of the opening area and the gap can 11 'and the stack side surface leak drying air only to a limited extent and flow along the top of the stack. Due to the action of the suction fan, the drying air emerging on the left side of the blank stack in FIG. 2 after it has flowed through the perforated channels is sucked in through the air passage openings of the opening surface 10 'into the exhaust duct 17 and conveyed away via the outlet opening 13. It is provided that the pressure blower 14 and the suction blower 15 maintain their running direction during the drying process, ie there is no reversal of the flow through the perforated channels in the blanks 6. This prevents air that has already been enriched with moisture from being exposed to areas of the perforated channels that have already dried and to deposit moisture there.

The embodiment according to FIGS. 4 and 5 is basically the same in structure and operation as the previously described embodiment. However, the conveying device for the blanks 6 is formed here by a series of stacking carriages 20 traveling in series, which pass through the drying room 1. These settling wagons 20 are so wide that two stacks of blanks 6 can be formed thereon, each of which contains only one blank in the direction transverse to the conveying direction. The blanks 6 are also arranged in these stacked layers in such a way that their end faces provided with perforated openings face to the side.

A, for example, stationary blowing device 21 has two side parts 22, 23 which, in the same way as in the exemplary embodiment according to FIGS. 1 and 2, the outer side surfaces of the blank stack are assigned and each have an opening wall 22 'or 23', in which only indicated air passage openings are formed. In addition, a suction shaft 24, which is essentially box-shaped, extends centrally from the transverse housing of the blowing device 21 into the intermediate space formed by the two blank layers from top to bottom. The suction shaft 24 likewise has two opposing opening surfaces in the form of perforated walls and has an air outlet opening 25 at its lower end, in which a suction fan 26 is arranged. In an air inlet opening 27 of the housing of the blowing device 21, a pressure blower 28 is arranged, through which air can be conveyed into the side parts 22 and 23.

On the underside of the transverse housing of the blowing device 21 are guide rails 30 or the like. provided, in which upwardly projecting fingers are guided by holding frames, not shown, in which the blanks are supported. In this way, it is possible to stack a larger number of blanks 6 one above the other, as shown in FIG. 4, without the risk of lateral tilting, and yet maintain a small distance between the blank faces and the opening surfaces. When the device is in operation, the drying blower in turn heats heated drying air through the inlet opening 27 and conveys it to the side parts 22, 23 on both sides via the transverse housing. The air is then blown through the openings of the opening surfaces 22 ', 23' and enters the perforated channels of the blanks 6. The top of the blank layers or stacks are each covered by a cover plate 31, so that, analogously to the mode of operation of the guide plate 15 according to FIG. 2, a relatively limited flow cross section flows around this top side Drying air is available. Due to the operation of the suction blower 26, a negative pressure is generated in the suction shaft 24, through which moisture-enriched drying air emerging on the mutually facing end faces of the blanks 6 is sucked into the suction shaft 24 and discharged through the outlet opening 25. It is understood that the suction shaft 24 is connected to the housing of the blowing device 21 for structural reasons and is supported by it, but there is no flow connection to it.

Within the scope of the invention, the exemplary embodiments described above can be further developed. Thus, it can be considered to provide air guiding devices in the side parts 10, 11 or 22, 23, in particular if these are given correspondingly larger dimensions due to the greater height of the blank stack. These air guiding devices ensure that a uniform distribution of the inflowing air takes place over the entire opening area 10 ', 11' and 22 ', 23', in order thereby to ensure even application of drying air to the blank end faces. Furthermore, the heating device which heats the drying air can also be arranged in the housing of the blowing device itself. It is also possible to integrate the blowing device into the walls or ceiling of the drying room 1 so that its side walls themselves represent the opening areas for the inflow of the heated drying air. It is understood that in this case the conveying device for the blanks is dimensioned correspondingly wide, so that the end faces of the blanks having the hole openings are guided closely along the hole walls.

In order to adapt the drying room or the blowing device to different stocking heights of the pallets 5 or the depositing carriage 20, the air passage openings can furthermore be designed so that they can be closed, at least on the outlet side. This makes it possible to adapt the opening area largely exactly to the size of the stack side area with the hole openings. In order to largely hinder or prevent a lateral outflow of the drying air around the outer surfaces of the blanks which are not provided with hole openings, it can be considered to make the guide plate or the corresponding cover plates 31 adjustable in height.

The part of the overall plant for the production of perforated bricks shown in FIG. 6 includes an extrusion press 51 with a mouthpiece 52, an adjoining conveyor track 53 for conveying the perforated brick blanks 54 and a cutting device 55, only indicated schematically, for separating the blanks 54 from it continuously from the mouthpiece 52 emerging strand 56. This structure is conventional and requires no further explanation.

Furthermore, this part of the overall system includes, following the cutting device 55, a swivel device, indicated only by an arrow 57, for swiveling the blanks 54 about an axis (which is perpendicular to the plane of the drawing) by 90 °, a pre-dryer 58 connected downstream of the swivel device 57, and one at the end of the Conveyor path 53 located tilting device 59, to which a platform or pallet 60 is assigned to form a horizontal layer of perforated brick blanks 54.

The actual drying device according to FIGS. 7 to 9 comprises an elongated drying tunnel 71 with side walls 72 and a ceiling wall 73, through which a conveyor device 74, which will be discussed in more detail below, runs in the form of an endless conveyor chain in the direction of the arrow (FIG. 7).

The drying tunnel 71 contains a blowing device, designated as a whole by 80, which essentially consists of a drying air inlet duct 81 at the outlet end of the drying tunnel 71, a number of deflection shafts 82 arranged above and below the conveying plane of the conveying device 74, and a drying air outlet duct 83 on the inlet side End of the drying tunnel 71 and a pressure blower 84 arranged in the supply air duct 81 and a suction blower 85 arranged in the exhaust air duct 83. In addition, a burner 86 is arranged in the supply air shaft 81, subsequent to the pressure blower 84, by means of which the drying air is heated to a temperature of approximately 120 ° C. at the outlet from the supply air shaft 81, and in the exhaust air shaft 83, the suction fan 85 is a heat exchanger 87 upstream, which also forms the inlet for the pressure blower 84 and is connected to the supply air duct 81 via a connecting duct 88.

The air passage opening of the supply air shaft 81 - in its place a large number of air passage openings can be provided in a perforated plate or the like - lies in a plane parallel to the conveying plane of the conveying device 74 directly above the hole side of the brick blanks lying on the conveying device of the conveying device 54. In the exemplary embodiment shown, five deflection shafts 82 are formed below this conveying plane, each of which is closed off from one another by partition walls 89 and contains baffles 90. The deflecting shafts 82 also have air passage openings, the plane of which is parallel to the conveying plane and which are arranged at such a small distance from the underside of the transport support of the conveying device 74 that the drying air entering and exiting the deflecting shafts 82 practically exclusively the rust-like conveying support of the conveying device 74 enforced. The air passage openings of the deflecting shafts 82 or the like can be provided by perforated plates, perforated plates. be educated. The upper deflecting shafts 82 arranged above the conveying device 74 are offset with their air passage openings in relation to the lower deflecting shafts 82 by the width or the diameter of the supply air shaft 81 against the conveying direction, but are otherwise constructed in the same way. In some of the deflection shafts 82, additional burners 91 are arranged, which serve to raise the temperature of the already moist and also already cooled drying air again and thereby make the drying air more receptive to further moisture. In order to ensure that the supply air duct and the exhaust air duct for the drying air can be led upwards from the drying tunnel 71, the number of the deflection shafts 82 located at the top is 1 less than that of the deflection shafts 82 located below.

The conveying device 74 essentially consists of two endless chains 95 which run parallel to one another and are guided via chain wheels 96. The chains 95 lie in a horizontal plane, the conveyor plane, and carry pendulum-suspended cross bars 97 on their individual chain links, which in their entirety represent the transport support for the brick blanks 54. The cross bars 97 run parallel to one another and are welded to their ends by tabs 98, which are pivotably mounted on the chain bolts 99 in a manner not specified in any more detail. 11, the cross bars 97 have a flat, elliptical cross-sectional shape, as a result of which their contact surface for the blanks 54 is curved flat upwards.

Depending on the length of the tabs 98 in relation to the distance of these tabs from one another in the conveying direction, the tabs 98 can either swing freely downward when the chains 95 rotate around the sprockets 96 and hang down on the lower run of the conveyor chains 95 or the crossbars If the length of the tabs does not permit swinging through, they stack up like a stack and return to their desired starting position for transport at the entrance of the drying tunnel 71. As an alternative to the solution shown in the exemplary embodiment, instead of the direct attachment to the chain bolts 99, the tabs 98 can also be suspended in a pendulum manner in pallet-like frames, which in turn can be detachably attached to the conveyor chains 95. In this case, the pallet frames are lifted from the conveyor chains 95 together with the blanks located thereon at the exit end of the drying tunnel 71 and the latter are only removed therefrom afterwards. In the exemplary embodiment shown, on the other hand, the conveyor 74 is immediately after passing the exit end of the Unload drying tunnel 71 from blanks 54.

The procedure for this embodiment is as follows using the device described above:

Perforated brick blanks 54 are intermittently separated from the strand 56 emerging from the mouthpiece 52 by the cutting device 55 and then reach the gripping area of the swiveling device 57 on the conveyor track 53. By means of this swiveling device, the brick blanks 54 are swiveled about their vertical axis by 90 ° and then reach or at the same time in the area of the pre-dryer 58. This has blowing nozzles from which heated drying air is blown onto the facing hole side of the brick blanks 54. The heated air and vigorous blowing result in a sharp predrying, so that a leather-hard condition limited to the hole side is achieved within a very short time (a few minutes). This hole side forms the bearing surface of the brick blanks 54 in the further course of the drying process and is more resistant to indentations or markings due to the predrying. After predrying, the brick blanks 54 arrive on a roller conveyor of the tilting device 59, which is formed by cantilevered rollers 100 which are only fastened on one side. Rods 101, which are fastened at one end and which are fastened to a common rotary shaft 102, also protrude between the rollers 100. A supporting plate or the like directed perpendicular to the bars 101 (and perpendicular to the plane of the drawing in FIG. 6) is also fastened to this rotary shaft. The brick blanks 54 running one after the other onto the roller conveyor 100 of the tilting device 59 are jammed there and form a row Roller conveyor 100 completely filled with brick blanks 54, the rotary shaft 102 pivots in the direction of the arrow the rods 101 upwards, so that the brick blanks 54 located thereon are tilted by 90 ° about their longitudinal axis and come to rest on the rotary shaft 102 with the hole side which has previously been dried in the hard leather on the support plate mentioned. This is then located above the pallet or platform 60, so that the brick blanks can be placed thereon by means of a stacking device (not shown). By means of grippers, also not shown, the brick blanks 54 can then be placed on the transport support of the conveyor 74 at the entrance to the drying tunnel 71, if necessary after a specific pulling apart to set the desired distances.

In the blowing device 80, preheated drying air from the burner 86 is further heated by the heat exchanger 87 (to approximately 120 ° C.) and is blown from above through the air passage opening of the supply air duct 81 onto the upwardly facing hole side of the horizontal layer of brick blanks 54. Under the action of the suction fan 85, there is a pressure drop between the upper and the lower hole side of the brick blanks, so that the drying air inflated flows through the perforated channels of the brick blanks and, after passing through the rust-like transport pad, reaches the first deflecting shaft 82. This directs the drying air flow through 180 ° and counter to the conveying direction and now sends it from below through the brick blanks in the section of the horizontal layer of brick blanks 54, which adjoins the wall of the supply air shaft 81 against the conveying direction. In an analogous manner, the drying air flow is redirected several times until the exhaust duct 83 is reached and thus passes through the horizontal layer of brick blanks 54 passing through the drying tunnel 71 several times in zigzag form from above and from below. The drying air is increasingly enriched with moisture.

The state of the drying air can be controlled by the burners 91 provided in the deflection shafts 82, which can be put into operation in a targeted manner. At the entrance end of the drying tunnel 71, the drying air has already been heavily enriched with moisture, so that even at a relatively high temperature it does not cause excessively sharp drying on the brick blanks 54 entering the drying tunnel, which could lead to the formation of cracks. The temperature at the entrance to the exhaust duct is expediently about 100 ° C. Since the brick blanks 54 come into contact with increasingly drier air as they are conveyed through the drying tunnel 71, but their drying state also progresses, there is no danger of the drying tunnel drying out too quickly and thus forming cracks at any point.

With increasing drying, the brick blanks also shrink in the longitudinal and transverse directions. This shrinkage is not hindered by the described design of the transport pad, ie the brick blanks 54 are not held by the cross bars 97, so that tensile stresses occurring in the brick blanks could produce cracks due to the obstruction. Because due to the low-friction design of the straight bars 97 in the transverse direction, the surfaces of the brick blanks which are subject to the shrinkage and therefore move can slide on the bars 97 in their longitudinal direction. Even if the relative mobility transversely to the longitudinal direction of the rods 97 should be hindered or even prevented by the fact that the transverse rods have pressed themselves slightly into the lower side of the hole and therefore fix the corresponding surfaces in a "form-fitting" manner, this does not lead to the formation of cracks because the pendulum suspension of the Rods 97 allow the reduction in size by moving.

As is apparent from FIG. 9, the width of the drying tunnel 71 exceeds that of the conveying device 74 for the purpose of creating a walk-in space on both sides thereof, which is used for maintenance and control purposes.

Various modifications of this exemplary embodiment are conceivable within the scope of the invention. For example, As already explained, pallet-like frames can be provided for the conveyor device, but they are not suspended on conveyor chains, but instead carry rollers on the outside or underside of the frame, which are guided in longitudinal guideways instead of conveyor chains 95. These pallet-like frames are then moved through the drying tunnel by a pusher or the like.

Furthermore, it goes without saying that the condition of the drying air must be adapted to the type of mass offset and the geometrical shape of the brick blanks by a corresponding regulation in each individual case and may well deviate upwards or downwards from the values given in the above exemplary embodiment. For example, the temperature value of 100 ° C at the inlet end in the drying air exhaust duct is only an average value, which in individual cases, however, can vary considerably upwards or downwards. It is also necessary to adjust the air throughput through the perforated channels of the brick blanks according to the flow cross-sections from case to case. Such an adjustment is made by regulating the speed of the pressure blower and / or the suction blower, which results in a corresponding adjustment of the pressure gradient between the upstream and downstream ends of the perforated channels. It is to be expected that the flow cross-section of the perforated channels (number and cross-section of the perforated channels) varies very greatly, so that at low Flow cross sections a strong throttling and resulting in a low flow speed, then it can be considered from the outset to arrange an additional fan in one or more of the deflection shafts, which supports the promotion of the drying air.

It has been shown that by using the method according to the invention, the drying time of perforated bricks, which has hitherto been several hours to ensure freedom from cracks, can be reduced to a drying time of one hour without any loss of quality and freedom from cracks in the bricks . A further reduction in the drying time can be achieved if the brick blanks or moldings are subjected to a precisely conditioned drying air, the condition of which is adapted to the respective requirements in the course of the drying process, ie in particular the drying state of the blanks that has already been achieved. For this purpose, the device according to the invention is equipped with a corresponding heating or tempering device and with a control which makes it possible to specifically change the values for temperature, humidity and the flow rate of the drying air in and around the brick blanks during the drying process. Possibly. these values can also be controlled using a program that is precisely tailored to the brick blanks and sets the values as a function of time. The control The humidity of the drying air is used to influence the removal of moisture from the brick material at a certain flow rate, in order to avoid that the moisture transport from the interior of the blanks to their surfaces does not dry out the surfaces and thus to the drying air swept cracks occur over painted surfaces. Possibly. an additional moistening device can be provided in the device to control the moisture of the drying air.

In particular, if a specific, but very limited flow around the outer surfaces of the blanks is maintained by the guide plates 15 and 31 mentioned in the embodiment according to FIGS. 1-5, it has been shown that suction of the drying air at the downstream ends of the Perforated channels of the blanks, through which an increase in the pressure gradient between the upstream and downstream sides is achieved, is superior to a corresponding increase in the upstream pressure without suction. This can be due to the fact that the flow resistance in the perforated channels rises non-linearly with the pressure on the upstream side and / or that an increase in the upstream pressure of the drying air also results in a stronger flow around the outer surfaces of the blank, which creates pressure-increasing vortices on the downstream side. which result in an increase in the dynamic pressure on the outflow side.

The term "drying air" used in the present context includes both heated or conditioned drying air in the above sense, but can also include untreated air from the environment, for example at room temperature.

Claims (29)

1. Method for drying perforated brick blanks, in which drying air is blown onto the end faces of the blanks with the perforated openings in order to cause a flow through the perforated channels,
characterized,
that the blanks (6) are arranged in a single layer directed transversely to the direction of flow. 2. Method for drying perforated brick blanks, in which drying air is blown onto the end faces of the blanks with the perforated openings in order to cause a flow through the perforated channels.
characterized in that a maximum of two blanks (6) are arranged one after the other in the flow direction, the perforated channels of the blanks (6) lying one behind the other being aligned. 3. The method according to claim 1 or 2,
characterized,
that the blanks are stacked one above the other in the layer or the layers arranged one behind the other. 4. The method according to any one of claims 1 to 3,
characterized in that the drying air is largely prevented from flowing around these side surfaces by a shield (15, 31) of the other side surfaces of the blanks which have no mouth openings. 5. The method according to any one of claims 1 to 4,
characterized in that a suction effect is generated on the end face of the blanks, in which the ends of the perforated channels downstream in the flow direction open. 6. The method according to any one of claims 1 to 5,
characterized in that the flow direction is maintained unchanged during the drying period of the blanks. 7. The method according to claim 1,
characterized in that the blanks are dried lying in a horizontal layer in which their hole sides point up and down. 8. The method according to claim 7
characterized,
that the hole side of the blanks forming the bearing surface is pre-dried to a leather-hard state before the horizontal layer is formed. 9. The method in particular according to one of claims 1, 2 or 7,
characterized,
that the drying air emerging from the outflow-side openings of the blanks in a section of the blank layer is deflected and fed to the upstream-side openings of the blanks in a subsequent section of the blank layer. 10. The method according to claim 9,
characterized,
that the deflection process and the renewed supply of the drying air are repeated one or more times on successive sections of the blank layer. 11. The method according to claim 9 or 10,
characterized,
that the drying air is heated before at least one new supply of the drying air to a subsequent section. 12. The method according to any one of claims 9 to 11, wherein the layer of blanks is moved relative to a blowing device for drying air in a constant direction of movement,
characterized,
that the drying air emerging in each case from the outflow-side hole openings is deflected against the direction of movement mentioned and is fed to a section of the blank layer which is adjacent to the direction of movement. 13. Device for drying perforated brick blanks (6), with a drying room (1), a conveying device (4, 20) for feeding in or conveying the blanks through the drying room (1) and with a blowing device (8, 21) for drying air, whose side parts (10, 11; 22, 23) provided with air passage openings extend approximately parallel to and close to the end faces of the blanks arranged on the conveying device and having the perforated channel openings,
characterized,
that the blanks (6) are arranged or stacked on the conveyor (4, 20) in a layer or layer in which there is only one blank transversely to the direction of conveyance or at most two blanks directly adjacent to one another and lying next to one another with aligned perforated channels , and that the side parts (10, 11; 22, 23) of the blowing device (8, 21) provided with air passage openings are assigned to the two sides of the layer on which the perforated channel openings are exposed, only the air passage openings on one side being designed as blow-out openings . 14. Device according to claim 13,
characterized in that the air passage openings are formed on the other side as suction openings. 15. Device according to claim 13 or 14,
characterized in that the side parts (10, 11; 22, 23) which have the air passage openings have sealing edges which run at a short distance from the end faces of the blanks (6) which have the perforated channel openings. 16. Device according to one of claims 13 to 15,
characterized in that guide or cover surfaces (15, 31) adjoin the side parts (10, 11; 22, 23) which have the air passage openings and hinder the flow of drying air around the side surfaces of the blanks which are not provided with perforated channel openings. 17. Device according to one of claims 13 to 16,
characterized in that the conveying device (20) is designed to receive a plurality of layers or layers of blanks (6) lying parallel to one another, which are arranged at a distance from one another, and in that the blowing device (21) corresponds to a plurality of side parts (22, 23, 24). 18. Device according to one of claims 14 to 17,
characterized in that the blowing device (8, 21) comprises one or more housings (9) which can be moved in the drying chamber (1) along the conveyor device (4, 20) and on which the side parts (10, 11; 22, 23) are arranged and each contain a pressure blower (14, 28) which acts on the blow-out openings and a suction blower (15, 26) which acts on the suction openings. 19. Device according to one of claims 13 to 17,
characterized in that the side parts of the blowing device are formed by the side walls of the drying chamber equipped with air passage openings. 20. Device according to one of claims 13 to 19,
characterized in that the blowing device is associated with a device for producing conditioned drying air, which contains a controllable temperature control device and possibly a humidifying device, and in that the pressure generated by the blowing device or the flow rate of the drying air is variable. 21. Device for drying perforated brick blanks (54), with a drying room (71), a conveyor (74) for feeding into or through the blanks through the drying room and with a blowing device (80) for drying air, the parts provided with air passage openings are approximately extend parallel to and close to the hole sides of the blanks arranged on the conveyor,
characterized,
that the transport pad (97, 98) of the conveying device (74) for receiving the blanks (54) is designed in the form of a horizontal layer with the hole sides of the blanks pointing up and down and is permeable to the drying air flow. 22. Device according to claim 21,
characterized in that the transport support is formed by rollers or rods (97) which extend transversely or parallel to the conveying direction and are spaced apart and parallel to one another. 23.The device according to claim 22,
characterized,
that the rollers or rods (97) have a smooth, low-friction bearing surface and are each suspended in an oscillating manner about an axis parallel to their longitudinal axis. 24. Device, in particular according to one of claims 21 to 23,
characterized,
that the blowing device (80) has a dry air supply duct (81) and a dry air exhaust duct (83) which are in flow connection with one another via at least one deflecting duct (82) which extends in the longitudinal direction of the conveying device (74) and deflects the drying air flow by 180 ° stand, and that the transport support (97, 98) runs between the parts of the supply air duct (81) of the deflection duct (82) and the exhaust duct (83) which have the air passage openings. 25. Device according to claim 24,
characterized,
that the supply air shaft (81) and the exhaust air shaft (83) are in flow connection with one another via an odd number of deflection shafts and are arranged on the same side of the conveying device (74). 26. Device according to claim 24 or 25,
characterized,
that the drying chamber is a drying tunnel (71) passed through by the conveyor (74) in the same conveying direction, and that the supply air shaft (81) at the outlet end and the exhaust air shaft (83) are arranged at the inlet end of the drying tunnel (71). 27. Device according to one of claims 24 to 26,
characterized,
that a heating device (91) for heating the drying air is arranged in one or more of the deflection shafts (82). 28. Device according to one of claims 21 to 27,
characterized,
that a cutting device (55) for separating the brick blanks (54) from the continuous horizontal strand (56) has a swivel device (57) which rotates or swivels the blanks by 90 ° about their vertical axis, and a pre-dryer (58) is arranged downstream, which at least one of the after rotating or pivoting of the blanks pre-dried exposed hole sides. 29. Device according to claim 28,
characterized,
that the pre-dryer (58) is followed by a tilting device (59) for turning the blanks onto the pre-dried hole side and a device for forming the horizontal position of blanks, which is linked to the conveyor (74).

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