Liquid application system

Abstract

It is provided in a liquid application system for applying liquid to a material cake transported on a conveyor device having a liquid application device, that the conveyor device comprises a porous section on which the material cake lies or which the material cake contacts and which is permeable for a liquid to be applied, that the liquid application device comprises an application device via which the liquid to be applied can be applied to the side of the porous section of the conveyor device facing away from the material cake, and that the liquid application device comprises an overpressure chamber having a first overpressure relative to the environment by which the porous section of the conveyor device passes, wherein the applied liquid can be transported via the first overpressure through the porous section of the conveyor device or held via the first overpressure to the porous section.

Claims

1. A liquid application system for the application of liquid to a material cake transported on a conveyor device, the liquid application system comprising a conveyor device comprising a liquid application device, wherein the conveyor device further comprises a porous section on which the material cake lies or which the material cake contacts and which is permeable to a liquid to be applied, the liquid application device comprises an application device via which the liquid to be applied can be applied to the side of the porous section of the conveyor device facing away from the material cake, and the liquid application device comprises an overpressure chamber with a first overpressure relative to the environment by which the porous section of the conveyor device passes, wherein the applied liquid can be transported via the first overpressure through the porous section of the conveyor device or be retained via the first overpressure to the porous section.

2. The liquid application system of claim 1, wherein the application device is arranged in the overpressure chamber.

3. The liquid application system of claim 1, wherein the overpressure chamber comprises an opening directed towards the porous section, the porous section of the conveyor device sealingly surrounding the opening.

4. The liquid application system of claim 1, wherein the liquid application device comprises a high-pressure chamber with a second overpressure relative to the environment, the high-pressure chamber being arranged downstream of the overpressure chamber, seen in the conveying direction of the material cake.

5. The liquid application system of claim 4, wherein the high-pressure chamber comprises a cover with a plurality of openings, the porous section of the conveyor device sealingly contacting the cover.

6. The liquid application system of claim 1, further comprising a cleaning system for cleaning the conveyor device and/or the overpressure chamber.

7. The liquid application system of claim 6, wherein the cleaning system comprises cleaning nozzles for ejecting air or a cleaning fluid.

8. The liquid application system of claim 1, wherein the conveyor device is designed as a porous conveyor belt which forms the porous section.

9. The liquid application system of claim 1, wherein the porous section has a pore width between 0.05 mm and 2 mm.

10. The liquid application system of claim 1, wherein the porous section comprises a surface, wherein the percentage of the surface area formed by the material of the conveyor device is between 50% and 95%.

11. The liquid application system of claim 1, further comprising a roll configured for pressing the material cake against the conveying device, the roll being arranged directly opposite the liquid application device or being situated immediately upstream of the liquid application device, seen in the conveying direction of the material cake.

12. The liquid application system of claim 1, further comprising a pressing band configured for pressing the material cake against the conveying device, wherein the pressing band is arranged directly opposite the liquid application device, is situated immediately upstream of the liquid application device, seen in the conveying direction of the material cake, or spans the liquid application device.

13. A method for the application of liquid onto a material cake, in which comprising the following steps: applying a liquid onto a porous section of a conveyor device that transports the material cake, applying a first overpressure onto the porous section, wherein the first overpressure transports the liquid through the porous section or retains the liquid on the porous section.

14. The method of claim 13, further comprising the following step: subsequently applying a second overpressure onto the porous section, the second overpressure being higher than the first overpressure.

15. The method of claim 14 wherein the second overpressure is controllable.

16. The method of claim 14 wherein the second overpressure is 5 bar at most.

17. The method of claim 13, wherein the first overpressure is controllable.

18. The method of claim 17 further comprising the following step: subsequently applying a second overpressure onto the porous section, the second overpressure being higher than the first overpressure, wherein the second overpressure is controllable. is 5 bar at most.

19. The method of claim 18 wherein the first overpressure is 0.3 bar at most and wherein the second overpressure is 5 bar at most.

20. The method of claim 13, wherein the first overpressure is 0.3 bar at most.

Description

(1) The following is a detailed description of the invention with reference to the accompanying drawings.

(2) In the Figures:

(3) FIG. 1 is a schematic sectional view of a liquid application system according to the present invention, and

(4) FIG. 2 is a detail of the cover of the high-pressure chamber.

(5) FIG. 1 schematically illustrates a section through a liquid application system 1 of the present invention.

(6) In FIG. 1 a liquid application system 1 of the present invention for the application of liquid onto a material cake 100 is schematically shown in sectional view. The liquid application system comprises a conveyor device 3 which in the embodiment illustrated is configured as a porous conveyor belt 5. The material cake 100 lies on the porous conveyor belt 5 and is transported in the direction of transport indicated by an arrow in FIG. 1.

(7) The liquid application system 1 comprises a liquid application device 7 by which a liquid to be applied can be applied in liquid state onto the material cake 100.

(8) The porous conveyor belt 5 of the conveyor device 3 forms a porous section 9 above the liquid application device 7, wherein the porous conveyor belt 5 is permeable to the liquid at least in the porous section 9.

(9) The liquid application device 7 comprises an application device 11 which in the embodiment illustrated is designed as a spraying nozzle. Using the application device 11, the liquid is sprayed in liquid state onto the side of the porous section 9 of the conveyor belt 5 that faces away from the material cake 100.

(10) The liquid application device 7 further comprises an overpressure chamber 13 in which a first overpressure prevails relative to the environment. The overpressure may be 0.003 bar, for example. The overpressure chamber 13 comprises an opening 15 directed towards the porous section 9 of the conveyor belt 5, with the porous section 9 of the conveyor belt 5 sealingly surrounding the opening 15. The overpressure prevailing in the overpressure chamber 13 thus acts against the side of the porous section 9 that faces away from the material cake 100. An airflow is thereby created, so that the liquid sprayed onto this side is transported through the pores of the porous section 9. The overpressure thus overcomes the capillary resistance prevailing in the pores of the porous section 9, the gravity acting on the liquid, as well as the flow resistance, so that the liquid reaches the material cake 100. In this manner, the liquid can be applied onto the material cake 100 in an advantageous manner, in particular on the lower side of the material cake.

(11) In the embodiment illustrated in FIG. 1, the application device 11 is arranged within the overpressure chamber 13. Of course, it is also possible that the same is arranged upstream of the overpressure chamber 13, when seen in the conveying direction, and thus outside the overpressure chamber 13.

(12) The application device 11 may be configured to be pivotable. Further, a cleaning system 17 may be arranged in the overpressure chamber 13, which system is merely indicated in FIG. 1. The cleaning system 17 comprises pivotable cleaning nozzles 19 for ejecting air or a cleaning fluid. During maintenance, the cleaning nozzles 19 can be used to clean the porous section 9 of the conveyor belt 5 from residual material of the material cake and liquid residues. In addition, the cleaning nozzles 19 can be used to clean the overpressure chamber 13 from liquid residues.

(13) The overpressure chamber 13 may further comprise a drain device 21 via which residual liquid or cleaning fluid can be drained during operation or maintenance. If the drain device 21 is used in operation, a counter-pressure must prevail at the same, in order to prevent that the overpressure built in the overpressure chamber 13 is affected by the drain device 21.

(14) Downstream of the first overpressure chamber 13, seen in the conveying direction, the liquid application device 7 further comprises a high-pressure chamber 23 in which a second overpressure prevails relative to the environment. Preferably, the second overpressure in the high-pressure chamber 23 is higher than the first overpressure in the overpressure chamber 13. Preferably, the second overpressure is between 0.2 bar and 5 bar. The porous section 9 of the porous conveyor belt 5 sealingly contacts a cover 25 of the overpressure chamber 23. The cover 25 has a plurality of openings 27 which, as is best seen in FIG. 2 which is a schematic top plan view on the cover 25, are arranged in a pattern. In the embodiment illustrated in FIG. 2, the openings 27 are arranged in a zigzag pattern. The arrangement of the openings 27 as well as the size of the openings 27 is chosen such that the airflow generated by the second overpressure is prevented from causing the material cake 100 to be lifted off the porous section 9 or from causing the conveyor device 5 from being lifted off the cover 25.

(15) The second overpressure prevailing in the high-pressure chamber 23 has the effect that liquid possibly still adhering to or in the porous section 9 of the porous conveyor belt 5 are pressed through the pores of the porous section towards the material cake. In addition, the airflow caused by the second overpressure has the effect that gaps possibly existing between the material cake 100 and the porous section 9 of the conveying belt 5 are overcome, so that the liquid clings to the material cake 100. Further, it is possible due to the second overpressure that liquid in the edge portion of the material cake 100 can be pressed deeper into the material cake, if so desired.

(16) The overpressures prevailing in the overpressure chamber 13 and in the high-pressure chamber 23 can be controlled via control devices not illustrated herein. Thereby, it is possible to adjust the amounts of liquid to be pressed through the porous section 9 and whether the liquid is to be transported farther into the inside of the material cake 100.

(17) A roll, not illustrated herein, or a pressing band, not illustrated herein, may be arranged opposite the liquid application device 7. The material cake 100 is compressed thereby, by making the distance between the porous section 9 and the roll, not illustrated herein, or the pressing band, not illustrated herein, smaller than the normal height of the material cake 100. Downstream of the roll or downstream of the pressing band, seen in the conveying direction, the material cake 100 can relax again, whereby a vacuum is generated inside the material cake and, grace to this sponge effect, the liquid is advantageously retained on the material cake 100 or transported into the inside of the material cake 100.

(18) The pore width of the porous section 9 may for example be between 0.05 mm and 2 mm. The porous conveyor belt 5 may for example be designed as a textile or be made from a mesh structure. Here, the porous section 9 may have a surface, wherein the percentage of the surface area formed by the material of the conveyor device is between 50% and 95%.

(19) The liquid application system 1 of the present invention is advantageous in that for example a humidifying agent can be applied in liquid state in a particularly advantageous manner onto a material cake 100. This allows for a very accurate dosing of the humidifying agent. The liquid application system 1 may be used in particular in presses for the production of material panels.

(20) The liquid application system 1 may further comprise a second liquid application device which is arranged at the upper side of the material cake 100, the device being of a structure similar or identical to the liquid application device 7. Of course, the liquid application system 1 may also comprise a second liquid application device that applies the liquid onto the material cake 100 in another manner, e.g. via rolls.