EP0732559B1 - Dryer for earthenware products - Google Patents

Abstract

The procedure for ventilation drying of terracotta products which are baked in an oven consists in placing the products (6) on small width racks (3). The racks are stacked to form a long narrow rows (2). These rows are then placed in a drying area (1) so that each row is enclosed by two spaces (A,B), one pressurised and the other under vacuum in order that the drying air passes through the rows. For better control of air circulation casings (4) with openings (5) are located in the spaces. The air stream is temperature and humidity adjusted and partially recycled. Periodically the air flow circulation is reversed during the same drying cycle. The racks have a width of the order of 40 cm, corresponding to the dimensions of a brick or tile. In this way each row constitutes a wall whose thickness is determined by the width of the rack. Its length is determined by the length of the drying area. The terracotta products all receive the same quantity of drying air at the same temperature and humidity.

Description

The present invention relates to a dryer such as those used in the terracotta industry.

The manufacturing of this type of product involves essentially three phases: in a first phase the earth is shaped either by molding or by spinning by extrusion which requires it to be in a semi-pasty state that is to say having a high percentage of humidity; then in a second phase the shaped products but raw are dried so as to contain practically no more water; and finally they are cooked at high temperature in a baking oven.

The present invention relates to a dryer for the implementation of the second phase.

In the dryers currently in use, the raw and moist products are placed on racks; the racks are arranged in superimposed layers on wagons which are introduced into an enclosure. This the enclosure is then crossed by a current of air which causes drying of raw products.

It is known to act on the volume, the rate humidity and the temperature of the air passing over them raw products to dry them.

There are a large number of dryers with breakdowns of various types: longitudinal, transverse, with rotation of the air circuits or others, but we have never been able to achieve fully satisfactory homogeneity drying of the products nor a faithful reproducibility of drying cycles. The degree of drying varies according to the position of the product in relation to the air source, the nearest products dry faster than more distant products and the air arriving at the products being more moisture laden and cooler than the air arriving on the nearest products.

The drying method according to the present invention consists of depositing the products on low racks width that can accommodate one or two on this width products to dry, stack these racks so as to constitute alignments of small width and large length then to have these alignments in an enclosure so that each alignment is framed by two spaces one of which is under pressure and the other under depression so that the drying air crosses said alignment with a practically constant speed, this after which it is regulated in temperature and humidity then recycled so that the products receive all practically the same amount of air, at the same temperature and at the same humidity level.

According to this process we can also reverse periodically air circulation from space to the other in the same drying cycle.

The invention also relates to an installation for the implementation of this method according to claim 3.

• les espaces dans lesquels arrive l'air de séchage sont occupés par des caissons allongés munis d'ouvertures par lesquelles l'air est insufflé à travers l'alignement faisant face audit caisson,
• les espaces par lesquels l'air arrive et ceux par lesquels il est évacué sont occupés par des caissons allongés, de sorte que chaque alignement est encadré de caissons sur ses deux côtés les uns en pression et les autres en dépression, l'enceinte de séchage comportant n alignements de claies et n + 1 caissons de ventilation.

The installation according to the invention can also include the following arrangements:

• the spaces in which the drying air arrives are occupied by elongated boxes provided with openings through which the air is blown through the alignment facing said box,
• the spaces by which the air arrives and those by which it is evacuated are occupied by elongated boxes, so that each alignment is framed by boxes on its two sides, some under pressure and others under depression, the drying enclosure with n rows of racks and n + 1 ventilation boxes.

The present invention on the other hand the advantage of being usable as well for dryers so-called "chamber" only for "tunnel" type dryers.

Figure 1, une vue schématique d'un séchoir à un alignement mettant en oeuvre le procédé selon l'invention,

Figure 2, une variante de réalisation du dispositif à la figure 1,

Figure 3 une vue de face d'un séchoir à chambre selon l'invention, avec un détail agrandi,

Figure 4 une vue de dessus du séchoir de la figure 3,

Figure 5 une vue en coupe selon I-I de la figure 3,

Figure 6 une vue en élévation latérale en coupe selon II-II du séchoir de la figure 4,

Figure 7 une vue de face d'un séchoir tunnel de grandes dimensions avec un détail agrandi,

Figure 8 une vue d'une variante de réalisation de la disposition des éléments constitutifs du séchoir de la figure 7,

Figure 9 une vue en plan des figures 7 et 8,

Figure 10 une vue en élévation latérale et en coupe du séchoir des figures 7 à 9.

By way of nonlimiting examples and to facilitate understanding of the invention, the accompanying drawings show:

FIG. 1, a schematic view of a drier with an alignment implementing the method according to the invention,

FIG. 2, an alternative embodiment of the device in FIG. 1,

FIG. 3 a front view of a chamber dryer according to the invention, with an enlarged detail,

Figure 4 a top view of the dryer of Figure 3,

FIG. 5 a sectional view along II of FIG. 3,

FIG. 6 a side elevation view in section on II-II of the dryer of FIG. 4,

Figure 7 a front view of a large tunnel dryer with an enlarged detail,

FIG. 8 a view of an alternative embodiment of the arrangement of the constituent elements of the dryer of FIG. 7,

FIG. 9 a plan view of FIGS. 7 and 8,

Figure 10 a side elevational view in section of the dryer of Figures 7 to 9.

FIG. 1 represents an enclosure 1, in the middle of which one has arranged an alignment 2 of racks 3 bearing 6 products to dry.

The racks 3 are provided with means which allow stack them on top of each other while sparing enough space for air to circulate between each product 6 and the bottom of the rack 3 which is above. These means are known in themselves. As is shown by way of example in FIGS. 5 and 10, the racks can have a section in H.

According to the invention, as shown, these racks have a small width and carry only one or possibly two products 6. Thus, by narrow width, we mean a dimension corresponding to the dimensions of a brick or tile, like mechanical tile, that is to say about 40 cm.

These racks 3 are arranged in stacks, aligned the one behind the other in order to achieve what we will hereinafter call an "alignment", that is to say a kind of wall having a thickness of the order of 50 cm determined by the width of the racks 3, a height of the order of 1.5 m to 2 m, and a length corresponding to the length of the drying chamber.

The racks can be square or be rectangular as shown in the figures. In all cases, their width must be small, of of the order of 50 cm and their length is adapted to the means of handling available: what matters is that the width of the alignments 2 is small, that is to say around 50 cm.

As seen in Figure 1, alignment 2 is placed in the middle of enclosure 1, which has the effect that it is framed by two volumes A and B.

The drying air is brought to the enclosure by a line 7 and then brought to volume A via line 8; this air passes from A to B crossing alignment 2; then is evacuated via line 10.

It should be noted that the drying air going from space A (under pressure) towards space B (under depression) does not crosses only one alignment 2. It is then regulated in temperature and humidity before being re-breathed into A and to cross again the alignment 2.

The means of regulation are known per se: the return line 10 has an outlet bypass 10a provided with a valve 10b; distribution line 7 comprises a fan 11 a heating means 12 and a fresh air supply line 13. When there is too much air charged with humidity, it is evacuated in 10a and air outside is introduced at 13, pulsed by the fan 11 and reheated in 12.

To simplify the explanations, circuit 7, 13, 11, 12, 8, 10 will hereinafter be called the recycling circuit, even if the air is only partially recycled, some being evacuated in 10a and part being newly admitted in 13.

It is possible to reverse the direction of traffic air and its flow can be adjusted by means of the valve 9.

The method according to the invention therefore consists in making cross only one narrow alignment at a time by drying air. This width being small and the air circulation can be reversed, this results that all 6 products receive practically the same amount of air at the same temperature and to the same degree hygrometric, which it is not possible to obtain with known devices.

To better control this air circulation, it it is better to have 4 boxes fitted openings 5 in spaces A and / or B.

In the embodiment illustrated in FIG. 1, there is a box 4 in space A only, space B simply being depressed by the action of fan 11.

In the embodiment illustrated in Figures 2 at 10, there are boxes 4 in all spaces A and B (spaces A being under pressure and spaces B being depression).

Figures 3 to 6 show a third example production of a drying device using the method according to the invention.

The dryer consists of an enclosure 1 parallelepiped inside which are arranged parallel to each other two alignments 2a and 2b of stacked screens.

Each alignment 2a or 2b consists of a succession of stacks of racks 3. In the example shown in FIG. 6, the alignments 2 are made by aligning end to end six stacks of racks 3.

In FIG. 3, the two alignments 2a and 2b are arranged so that they are parallel to each other and parallel to the side walls of enclosure 1 so to provide between the two alignments 2a, 2b a space A and outside these two alignments, two spaces B, one spaces B being between the alignment 2a and the side wall of the enclosure 1 which is close to it and the other space B being between the alignment 2b and the other side wall of enclosure 1.

The method according to the invention consists in making circulate the ventilation air either from A to both spaces B crossing the alignments 2a, 2b or vice versa from outdoor spaces B to space interior A.

As the width of the racks 3 is small and does not leaves room for only one or two products, so that all 6 products receive almost the same amount air, at the same temperature and to the same degree humidity, which is not possible with known devices.

Each box 4 is pierced with a plurality orifices 5. However, the caissons 4 occupying the volumes B will only be provided with orifices 5 on the side facing a alignment, 2a or 2b.

In other words, the left outer box 4 in Figure 2 will be provided with holes 5 only on its side right, the right exterior box 4 will not be provided with orifices 5 only on its left side and the inner box 4 will be provided with orifices 5 on its two sides.

Preferably, the orifices 5 will be disposed of so as to be each above a rack 3; But it is not compulsory because you have to be able to use 3 heights in the same dryer "h" varied.

The drying air circulation is ensured by a distribution pipe 7, disposed above the alignments 2, which by means of several pipes vertical 8 feeds the central box 4 (corresponding inside volume A); while the air entering the side boxes 4 (corresponding to volumes B), after be passed on the products 6 through the alignments 2 (2a, 2b), is brought back by two lines 10 to the line of distribution 7.

As described above, this conduct of distribution 7 includes a fan 11 and a means of heating (or heat exchanger) 12; lines 8 are provided with valves 9 and the lines 10, with outputs 10a controlled by l0b valves.

Means such as fan 11 and valves 9 allow the air flow in the different caissons and even in different zones of the same set of boxes since there are several lines 8 each provided with a valve 9.

The heating means 12 makes it possible to adjust the temperature.

The drying air is constantly recycled in the circuit consisting of line 7, lines 8, boxes 4 and pipes 10, with, as was explained above evacuation or not of air having loaded humidity on products 6 and introduction or no fresh air through the opening (s) 13.

As shown in Figure 6, the stacks 2 are brought inside the enclosure 1 by conveyors 14 and the enclosure is closed by a door 15, which, as in the example shown, can be a rolling shutter.

It is possible to reverse the direction of rotation of the fan 11 and therefore reverse the direction of circulation of the drying air which then, instead of arriving in the central box to go into the external boxes, will arrive in the external boxes to go into the central box; and during the same drying cycle we can reverse the circulation direction of the air.

The device intended for the implementation of the drying process according to the invention in relation to Figures 1 to 6 is a dryer of the type called "chamber" that is to say inside which the products remain motionless inside the enclosure throughout the drying operation.

But this process can also be implemented in a "tunnel" type dryer which is consisting of an enclosure crossed from end to end by the products to be dried. Figures 7 to 10 illustrate a device of this type for implementing the method according to the invention, in which the same elements are designated by the same references.

In this exemplary embodiment the enclosure 1 has much larger dimensions so that one will have a plurality of alignments, that is to say n, so that these n alignments will be framed by n + 1 volumes of circulation (A or B), in which there will be n + 1 boxes 4.

Alignments 2 are made identically of what has been described above, as well as the boxes 4.

Referring to Figure 7, we see that we have six alignments 2 and seven boxes 4; there are two boxes 4 exteriors and five casings 4 interiors, i.e. between two alignments 2. As described previously, the external boxes 4 are not provided of openings 5 only on one side, that facing towards a alignment; while the interior 4 boxes have holes 5 on both sides.

By comparing Figures 3 and 7-8, we see that the arrangement of Figures 7 and 8 is obtained by multiplying the arrangement of Figure 3 as many times as there are pairs of alignments 2, i.e. three times. The return lines 10 located side by side are then gathered into one.

We can, as in the case of the example of realization of the previous figures, reverse to several air circulation to have more drying homogeneous, but we can also obtain this inversion of circulation by reversing the position of lines 7, 8 and 10 from one zone to another of the dryer.

If we compare Figures 7 and 8 showing two dryer areas, we see that in Figure 7 the pipes feed 7-8 are arranged in the center of the pairs of alignments 2, while in figure 8, these are the discharge lines 10 which occupy this position. There is therefore reversing the positions of the air supply lines and evacuation, which has the effect of reversing the meaning of the drying air circulation through the alignments 2 as they progress in the tunnel dryer; this progression of alignments 2 is parallel to the boxes 4 and therefore also parallel to themselves.

The present invention has been described in connection with the problem of drying raw products in the ground before their baking in an oven, in the earth industry cooked; but it is obvious that it is not limited to this particular application and can be used to any drying of any products.

Claims (17)

1. A process for ventilation-drying of products, such as in particular raw products intended to be baked in an oven, consisting in laying the products (6) to be dried on grates (3) of low width which can receive one or two products to be dried across this width; stacking these grates (3) so as to form at least one alignment (2) of low width and of great length; then placing this or these alignment(s) (2) in a drying enclosure (1) such that each alignment is framed by two spaces (A, B), one of which is under pressure and the other of which is under partial vacuum, such that the drying air passes through said alignment (2) at a practically constant speed, after which it is regulated in terms of temperature and humidity and recycled at least in part; such that the products (6) to be dried receive practically the same quantity of air, at the same temperature and at the same relative humidity.
2. A process according to Claim 1, in which the air circulation is periodically reversed during one and the same drying cycle.
3. An apparatus for performing the process according to Claim 1 or 2, characterised by the fact that it is formed by an enclosure (1) receiving at least one alignment (2) of grates (3) stacked one upon the other, these grates (3) being of low width; said enclosure (1) comprising spaces (A or B) arranged so as to frame each alignment (2), one of which is under pressure and the other of which is under partial vacuum, said spaces being connected by pipes (7, 8, 10) to air circulation means (11) in which the air is regulated in terms of the temperature and humidity, and is recycled at least in part.
4. An apparatus according to Claim 3, in which box structures (4) provided with openings (5) are arranged in the spaces (A) which are under pressure.
5. An apparatus according to Claim 3, in which box structures (4) provided with openings (5) are arranged in all the spaces (A or B).
6. An apparatus according to Claim 5, characterised by the fact that n alignments (2) and n+1 box structures (4) are arranged on the inside of the enclosure (1).
7. An apparatus according to any one of Claims 3 to 6, in which the grates (3) have a width of the order of 40 cm, corresponding to the dimensions of a brick or a gutter tile, such that each alignment (2) forms a sort of wall, the thickness of which is determined by the width of the grate (3), its length being determined according to the length of the enclosure (1).
8. An apparatus according to any one of Claims 3 to 7, in which the lateral walls of the box structures (4) are provided with lateral openings (5).
9. An apparatus according to Claim 8, in which the box structures (4) which are located between two alignments (2) are provided with openings (5) on their two lateral walls, whilst the two outer box structures (4) are provided with openings (5) only on the side facing towards the alignments.
10. An apparatus according to Claim 9, comprising: an air distribution pipe (7) arranged above the alignments (2) which, by means of certain vertical pipes (8), feeds the box structures (4); at least one return pipe (10) which brings the air which has passed through the alignments (2) back to said distribution piping (7); at least one outlet pipe (10a) and a fresh-air intake (13); so that the drying air is permanently circulated, being partially or completely recycled.
11. An apparatus according to Claim 10, comprising two alignments (2) framed by three box structures (4) and also a pipe (7) connected to the central box structure (4) by means of a plurality of vertical pipes (8), and two pipes (10) connected to the outer box structures (4).
12. An apparatus according to Claim 10, comprising a number n of alignments (2) framed by n+1 box structures (4) in which the circulation of drying air is effected by a plurality of distribution piping systems (8) and a plurality of return piping systems (10).
13. An apparatus according to Claim 12, in which the direction of circulation of the air in the pipes (7) and (10) can be reversed.
14. An apparatus according to any one of Claims 10 to 13, in which the air circulation pipes are provided with a fan (11), heating means (12) and additional air intakes (13).
15. An apparatus according to any one of Claims 3 to 14, in which the drying installation is of the chamber type.
16. An apparatus according to any one of Claims 3 to 14, in which the drying installation is of the tunnel type.
17. An apparatus according to Claim 16, in which the respective positions of the distribution pipes (7) and the evacuation pipes (10) relative to the box structures (4) can be reversed, the result of which is inversion of the direction of air circulation over the products (6) as they advance in a direction parallel to the box structures (4).

Images