AU683162B2

AU683162B2 - Method and device for drying perforated bricks and similar articles

Info

Publication number: AU683162B2
Application number: AU23438/95A
Authority: AU
Inventors: Stefan Honcamp; Ralf Koper
Original assignee: Keller GmbH
Current assignee: Keller GmbH
Priority date: 1994-04-11
Filing date: 1995-04-11
Publication date: 1997-10-30
Anticipated expiration: 2015-04-11
Also published as: WO1995027880A1; CZ297896A3; HU9602788D0; EP0754285B1; CZ285340B6; DE59505208D1; HU218769B; AU2343895A; PL316945A1; EP0754285A1; ES2132660T3; ATE177194T1; HUT76701A

Abstract

The invention concerns a method and device for drying green bricks (perforated bricks) (4) disposed in a single layer on air-permeable carriers (3) and in wide rows with the perforation axes (5) oriented in the direction of motion (T), the drying air being supplied through wide-jet nozzles (11) extending across the rows so that it is blown into the gaps (6) between consecutive rows of bricks down to the support (2) used for conveying the bricks, and the air passes round and through each green brick (4), thus drying it uniformly inside and outside.

Description

PROCESS AND DEVICE FOR DRYING PERFORATED BRICKS OR SIMILAR The present invention relates to a process and device for drying ceramic green bricks in the manufacture of honeycomb bricks, so-called perforated bricks, wherein drying air is blown into gaps between adjacent bricks and passes through brick channels.

This type of process and corresponding device are already known from DE-AS 21 09 S 071. In this process the green bricks are fed continuously past nozzles which are arranged offset to one another altemrnatively on both sides and/or above and below the conveyor belt in the direction of motion of the green bricks and at a distance to one another, which corresponds to at least twice the distance of successive bricks. The green bricks are arranged on cables in such a way that their channels (holes) run with the longitudinal axis in the direction of conveying, as in Figure 1. Conveying of the green bricks is regulated in such a way that the bricks are blown on directly for around 0.5 seconds by nozzles of approximately 20 mm in width and that a pause of around 5 seconds follows in which warm air flows past and also through the green bricks as a result of the suction effect. Since the air current impacting the green bricks has to brush along the brick, there is not an even flow over the edging width. In addition, on account of the air being blown into a free space it is not possible for the air to pass intensively and evenly measured through the green bricks, resulting in uneven drying on the upper surface and in the channels. This uncontrolled blowing into the gaps between adjacent green bricks is also a considerable waste of energy. Horizontal blowing in of air can be carried out only in a drying plant with minimal working width. Vertical blowing in of air on one side causes a wind shelter and accordingly requires nozzles to be arranged on both sides of the green brick conveyor path, as is evident also from Figure 2 of DE-AS 21 09 071.

The object of the present invention is to create an improved process and an improved device for rapid drying of honeycomb-type ceramic green bricks, in particular so-called perforated green bricks, in which air can be passed evenly and intensively round and through the green bricks with minimal appliance and energy expenditure and the air can flow through at relatively high velocity.

This is solved by means of a process in accordance with Claim 1 or by means of a device in accordance with ClaimA,1. Advantageous developments of the invention are disclosed in the sub-claims.

In a simple manner the invention enables air to be passed around and through all green bricks to be dried. The position of each green brick within the edging, or lagging, has no negative effect on the drying, that is, there are no delays occurring in the drying progress on account of the position of the individual green bricks in the edging/lagging.

Here it is especially an advantage for the rows of single-layer green bricks to be blown across the entire lagging width both directly and evenly the bricks of one row are treated identically and for a dynamic pressure to build up in the gaps between two rows of green bricks as a result of the rebounding surface opposing the blown-in air which is formed by the conveyor support closed-off and hole-free in this vicinity, whereby finally the air is effectively and to advantage passed under the green bricks and is deflected for improved through-flow. Optimum drying results are guaranteed by completely identical treatment of each and every green brick as it passes through drying.

Direct blowing or blowing in at least one green brick row as well as the formation of dynamic pressure in front of there in a blowing station enable desired through-flow of air of all green bricks at a speed of over 1.0 m/sec, in particular around 2.0 mn/sec not previously achieved with tunnel driers and cause extensive gentle rapid drying with relatively minimal energy expenditure. Here it is noticeably an advantage that there is only a short section for air to pass through, for the expelled dry air stream has to flow through only a single green brick length through the edging (lagging) for completion of the total aeration operation.

This 'achieved' blowing-in renders superfluous any additional guidance apparatus for generating air currents in opposite directions.

The transverse arrangement of the nozzle housings and their wide-jet nozzle(s) enables a simple tunnel drying construction, economic utilisation of space and a green brick arrangement with channels/hole axes running in the conveying direction.

Because of the longitudinally directed brick channels there is also additional use of the 'longitudinal flow' of the air flowing through the drying channel, as well as good aeration of the green bricks during the conveying phase.

I~

In an embodiment involving blowing of the front side of a row of green bricks and simultaneous blowing of the rear side of another row of green bricks, the result is a strong air current in different directions from the blowing station alone caused by its directed air stream or by its directed air streams, that is, without the use of a reversing device. In the process the drying air is propelled in both directions with considerable Etart-up speed through the green brick channels of the directly impacted rows of green bricks.

The especially. eferred blowing of the green bricks from 'in front' and with interposition of a blow-free rest position from 'behind' allows both rapid and gentle drying.

The arrangement of the abovementioned green brick blowing system is of particular advantage when there is alternating cut edge blowing-in with interposition of a blow-free position/rest period in a blowing station operating by way of at least three successive rows of green bricks by means of two downwards diverging air streams which extend over the entire width of the lagging and which blow out the drying air at the same flow rate over the entire width also. The following two advantages are combined in a particularly beneficial way: a. front and back blowing-in with air correspondingly passing around and through the green bricks now from one end and now from the other end, and b. drying air blowing in opposite directions without a reversing device. The invention is schematically represented in the diagrams. In cross-sectional representation of a tunnel dryer for drying ceramic green bricks, in particular so-called perforated bricks, the area of a blowing station for the green bricks to be dried is illustrated in the following figures, in which: Figure 1 shows a blowing station with perpendicular blowing of the dry air between two rows of green bricks running transversely to the conveying direction or tunnel drier longitudinal axis, Figure 2 shows a blowing station with two oblique air streams, and Figure 3 shows a blowing station with two diverging air streams.

The process according to the present invention is realised in a tunnel drier.

4 This tunnel drier has a drying channel/tunnel generally designated by reference numeral 1, through which conveyor supports 2 are moved in cycles. The conveyor supports may be designed as trolleys or otherwise displaceable platforms. Their width can be over 5 m. The arrow T identifies the preferred direction of conveying which runs in particular opposite to the air stream through the tunnel, the so-called 'longitudinal flow', Provided on conveyor supports 2 closed off at the bottom are green brick carriers 3 running transversely to the conveying direction T, which take up green bricks 4 arranged in single layers.

Green bricks 4 placed in oblique rows are arranged at a distance to each adjacent brick and accordingly can be aerated from all sides. Their channels 5 extend with the channel axis in the longitudinal direction of the tunnel drier, that is, in the conveying direction T and consequently enable advantageous aeration on account of the 'ventilation' effect of the 'longitudinal flow'.

Green brick carriers 3, and also green bricks 4 of each transverse row, are arranged by formation of a transverse interstice 6 with space behind. These interstices 6 each form a gap for targeted blowing of convected dry air corresponding to respective requirements.

Green bricks 4 have within a row of bricks an essentially smaller distance to adjacent green brick 4 than the distance between successive rows of green bricks. The small lateral gap between neighbouring green bricks 4 ensures space-saving sequencing and advantageous passage of air.

Green brick carriers 3 are designed to be air-permeable. In each blowing station 7 the dry air blown from a nozzle housing 8, 9 or 10 by means of wide-jet nozzle 11 in a wide air stream (wide-jet) 12 (as in Figure 1) or 13, 14 (as in Figure 2) or 15, 16 (as in Figure 3) extending over the entire edging width and blown against conveyor support 2 acting as impact surface can flow blow aerated green brick 4 and brush over or flow around same underneath partially with dry air.

Each green brick carrier 3 has a braced or stabilised carrier profile made of sheet steel, whose profile or cross-section is designed in the shape of an upside down The length of the U-member corresponds to the brick length in this dimension, as in Figures 1 to 3. This helps to ensure large-surface and good support of 'green' bricks 4. For beneficial stability the U-cross-section widens downwards. In a preferred manner the side legs lie in a symmetrical trapeze.

The U-member and both U-legs of green brick carriers 3 are perforated, whereby the hole portion on each surface is around 35 to 65%. The hole portion of the U-member is of the largest possible size, yet designed independently of the material of green bricks 4 to be dried such that there is adequate support for green brick 4 to be dried and any unfavourable mould impressions are avoided. Perforation in the side walls of each green brick carrier 3 functioning as mounting elements or spacers is carried out such that a dynamic pressure of preferably 20 to 100 Pa can be built up in front thereof; here, in a particularly preferred and advantageous manner the hole portion is approximately In the tunnel drier according to the present invention arranged in drying channel 1 are several successively arranged blowing stations 7 which operate according to Figures 1, 2 or 3. Conveyor supports 2 are supplied to each blowing station 7 and stopped in place in such a way that air stream 12 or air streams 13 to 16 can be blown accurately into a gap 6 between two transverse rows of green bricks. In a preferred manner the bricks are conveyed at intervals of one row so that green bricks 4 are blown 'row by row'.

Each air stream 12 to 16 is blown at the same flow rate onto the entire edging width.

Insofar as a blowing station is operating with two air streams, these lie one behind another and the corresponding slot nozzles run parallel in the transverse direction of the tunnel drier.

Provided in the embodiment according to Figure 1 in drying channel 1 for each blowing station 7 is at least one transverse nozzle housing 8 having at least one wide-jet nozzle 11 perpendicular to conveyor support 2.

Figure 2 illustrates in general the arrangement of two parallel wide-jet nozzles 11 on a nozzle housing 9.

Air streams 13, 14 in Figure 2 are preferably directed obliquely towards the perforated front faces (cut surfaces) of all green bricks 4 of a transverse row of green bricks (transverse row). Obliquely positioned air streams 13, 14 are therefore directed at the green brick or its cross-section such that the entire surface or front surface of green brick 4 is blown; the vertical central axis (vertical bisector) of green bricks 4 and each air stream 13, 14, and in Figure 3 15, 16, coincide.

In the embodiment in Figure 3 nozzle housing 10 is provided with two wide-jet nozzles 11 at an angle to one another, which blow downwards diverging air streams 15, 16 onto two rows of green bricks, whereby on one side the front side is blown and on the other side the rear side of a row of green bricks is blown.

In the embodiments according to Figures 2 and 3 wide-jet nozzles 11 are arranged such that when conveyor supports 2 are stationary at least one row of green bricks hardens unblown between two blown rows of green bricks. This type of aeration of rows of green bricks enables in a blowing station 7 between two blowing points an advantageous rest position for green bricks 4 which are not blown directly, in which the same are dried only through the 'longitudinal flow' which has an essentially lesser flow rate.

Since there is at least one unblown row of green bricks between two other rows of bricks, it is guaranteed that air can flow uninterrupted through the green brick channels of both blown rows of bricks.

Both wide-jet nozzles 11 of nozzle housing 10 are arranged symmetrically to the vertical centre of the nozzle housing. The nozzle stream central plane encloses with itself an angle of 15 to 250 opening out downwards, preferably around 200.

With oblique air streams 13 to 16 the distance between nozzle housings 9, 10 and green bricks 4 on the one hand and between adjacent rows of green bricks on the other hand is measured such that each air stream 13, 14, 15, 16 does not blow the top brick corner of green bricks 4 of a neighbouring, and thus in this position 'unblown', row of bricks. On account of such desired brick aeration the edges are protected from undesired drying and chinks in the edges are prevented as far as possible.

As is apparent from Figure 3, blowing station 7 operates with diverging air streams 16 preferably over a total of four rows of green bricks and in such a way that there are two unblown rows II, III between each of blown rows I, IV. In this blowing station 7 with nozzle housing 10 each row of green bricks stops for four cycles and accordingly undergoes the following operational steps: a. 1 cycle of blowing of the first front surface, b. 2 cycles of rest, and c. 1 cycle of blowing of the second front surface, that is, opposite to a..

One cycle lasts at least 0.5 minutes and preferably 1 minute.

The air streams are shown in the illustration and require no further explanation.

The invention is distinguished by a process as well as a device for drying green bricks (perforated bricks) 4 arranged in single layers on air-permeable green brick carriers 3 as well as in wide transverse rows, with perforation axes 5 oriented in the conveying direction T, whereby the drying air is blown intensively through transverse wide-jet nozzle(s) 11 into gaps 6 between successive rows of green bricks down to conveyor support 2 and over the entire edging width and this air flows around and through each green brick 4, drying it uniformly inside and outside.

In an especially preferred embodiment with green brick aeration by oblique air stream, to enable precise blowing even with different green brick formats, each slot nozzle is designed adjustably and displaceably in the gap width and/or slot. In this case each nozzle slot of a wide-jet nozzle designated by reference numeral 11 designed and/or arranged telescopically, not illustrated here, can have lips.

i rr i Legend 1 drying channel tunnel (general) 2 conveyor support 3 green brick carrier 4 green bricks green brick channels 6 gap between transverse rows of green bricks 7 blowing-station (general) 8 nozzle housing (Figure 1) 9 nozzle housing (Figure 2) nozzle housing (Figure 3) 11 wide-jet nozzle 12 air stream (Figure 1) 13 air stream (Figure 2) 14 air stream (Figure 2) air stream (Figure 3) 16 air stream (Figure 3) I first green brick in vicinity of 7 II second green brick in vicinity of 7 III third green brick in vicinity of 7 IV fourth green brick in vicinity of 7 T conveyor direction

Claims

2. Process as claimed in Claim 1, characterised in that the drying air is blown vertically into the gap(s) .i
3. Process as claimed in Claim 1, characterised in that the drying air is blown obliquely SRAinto a gap or simultaneously into two gaps
4. Process as claimed in at least any one of Claims 1 to 3, characterised in that the drying air builds a dynamic pressure of 20 to 100 Pa in front of the green bricks to be blown or already blown by means of a wide air stream (12 to 16). Process as claimed in Claim 1, characterised in that the green bricks are blown alternately on the front and rear sides on their perforated front surfaces (cut edges) with interposition of a blow-free rest period, whereby the blowing air passes through the green brick from the respective blowing side, that is, the front side or rear side, and evenly flows around tne outside.
6. Process as claimed in Claim 5, characterised in that each green brick stops in a/each blowing station for four cycles and undergoes the following operational steps: a. 1 cycle of blowing of the first front surface, b. 2 cycles of rest, and c. 1 cycle of blowing of die second front surface, that is, opposite to a.. 90 o
7. Process as claimed in Claim 5 or 6, characterised in that in the case of an oblique air stream the drying air is blown towards the perforated cut edge of a green bricks of a transverse row of green bricks and the stream progress of the air stream (13 to 16) runs such that the top corners of the adjacent rows of green bricks are not blown. S8. :to 7, a. b. 30 o o *o «A A device for carrying into effect the process as claimed in at least one of Claims 1 having the following characteristics: this device is designed as a drying channel operated with drying air whose operatinc, floor is designed from conveyor supports such as trolleys or platforms, closed at the bottom and conveying the green bricks to be dried, the conveyor supports assigned functionally to the drying channel exhibit green brick carriers running transversely to the conveying direction which are arranged in the direction of conveying at a distance from one another and each of which carries several green bricks in particular a whole row of green bricks, c. the green brick carriers are air-permeable and are arranged with their top side carrying the green bricks at a vertical distance to each conveyor support such that each green brick can be aerated underneath also by the drying air impacting it, that is, it can be aerated below as well as have air passed around it partially on the support surface, and d. in the drying channel above the brick travel path there are several blowing stations provided consecutively in the direction of conveying, each of which blows on the lagging through at least one wide-jet nozzle (11) extending transversely to the direction of conveying and which blows (propels) the drying air during brick idle periods through at least one gap between successive rows of green bricks.
9. Device as claimed in Claim 8, characterised in that in the drying channel for each blowing station a transverse nozzle housing having at least one wide-jet nozzle (11) vertical to the conveyor support and blowing towards the same is provided. Device as claimed in Claim 8, characterised in that in the drying channel for each blowing station a transverse nozzle housing is provided having at least one wide-jet :2 nozzle (11) blowing obliquely towards the green brick surfaces, in particular perforateJd ick cut edges, adjacent to a gap which forms a blow-in gap for the drying air, in thL ow of green bricks.
11. Device as claimed in Claim 10, characterised in that each nozzle housing (10) has two wide-jet nozzles (11) which blow downwards diverging air streams (15, 16) onto two non-adjacent rows of green bricks. o" 12. Device as claimed in Claim 8, characterised in that two wide-jet nozzles are arranged on a nozzle housing 10) and there is a control (device) for the conveyance of green 30 bricks, such that during every idle phase at least one row of green bricks, in particular two rows of green bricks, hardens without direct blowing. 1-A J\ iv t fW tr2C
13. Device as claimed in Claim 8, characterised in that green brick carriers have a braced carrier profile made of steel plate, which in the profile (cross-section) is designed in the form of an upside down whose U-member and U-legs are perforated, whereby the perforation portion on each surface is 35 to
14. Device as claimed in at least any one of Claims 1 to 13, characterised in that the perforation in the walls of the green brick carriers functioning as mounting elements is designed such that a dynamic pressure is built up in front thereof during air flow through o0 the carrier profile. Device as claimed in Claim 8, characterised in that the blowing station with oblique air stream (12; 13, 14) can have two lips adjustable in the gap width and/or slot for aeration of a row of green bricks in the vicinity of the aeration at position 11. DATED this 13th day of January 1997 KELLER GMBH By their Patent Attorneys CULLEN CO. *a