METHOD AND DEVICE FOR DRYING BULK MATERIAL

Abstract

The invention relates to a method for convective drying of bulk material in a container (1), wherein in a drying step a gas mixture flows around the bulk material to be dried in the container (1), which gas mixture absorbs water contained in the bulk material to be dried and is then discharged from the container (1), wherein a cooling step is carried out before the drying step, in which the bulk material is brought to a temperature lower than the ambient temperature, and both the cooling step and the drying step take place in the same gas-tight container (1).

Claims

1. A method for convective drying of bulk material in a container, wherein in a drying step a gas mixture flows around the bulk material to be dried in the container, which gas mixture takes up water contained in the bulk material to be dried and is then discharged from the container, wherein before the drying step a cooling step is carried out in which the bulk material is brought to a temperature lower than the ambient temperature, wherein both the cooling step and the drying step take place in the same gas-tight container, wherein the drying step takes place in an inert atmosphere, the inert atmosphere is produced by introducing an inert gas mixture into the container, the inert gas mixture consists of nitrogen, carbon dioxide and at least one noble gas, preferably argon, in the drying step the gas mixture is heated via a first heat exchanger, which is connected to a hot-water storage tank, the cooling air is cooled by a second heat exchanger, which is connected to a cold water storage tank, and process heat is recovered by means of a heat pump from water which originates from the cold water storage tank and has been heated by heat exchange in the second heat exchanger, and which water is supplied to the hot water storage tank, via the heat pump by means of an inlet.

2. The method according to claim 1, wherein the inert gas mixture consists of 70-95% nitrogen, 5-10% argon, and 2-4% carbon dioxide.

3. The method according to claim 1, wherein, in a final phase of the drying step for sterilizing the bulk material, the dosage of the carbon dioxide in the inert gas mixture is increased to 5-20%.

4. The method according to claim 1, wherein a shifting of the bulk material takes place in the drying step.

5. The method according to claim 1, wherein in the drying step the gas mixture saturated with moisture is condensed out before renewed heating.

6. The method according to claim 1, wherein the hot water storage tank is additionally fed from at least one of the following sources: geothermal energy, process heat or solar collectors.

7. The method according to claim 1, wherein the energy for the heat pump is additionally taken from a well or another heat source with heat recovery.

8. The method according to claim 1, wherein the cooling step is implemented by means of cooling air.

9. The method according to claim 8, wherein ambient air is used as cooling air.

10. The method according to claim 1, wherein the temperature in the container is lowered to 5 to 13° C. during the cooling step.

11. The method according to claim 10, wherein the cold water storage tank is additionally fed by a well.

12. The method according to claim 1, wherein additional bulk material is introduced into the container during the cooling step.

13. The method according to claim 1, wherein the gas mixture is circulated in a gas-tight closed system.

14. A drying device for convective drying of bulk material in a container, comprising means for introducing bulk material into a gas-tight container and means for discharging bulk material from the container, a gas supply line and a gas discharge line, wherein a first and a second heat exchanger are connected to the container, wherein the second heat exchanger can be used for cooling and the first heat exchanger can be used for heating a gas mixture which can be supplied to the gas-tight container via the gas supply line, wherein an inert gas storage tank is connected to the container, in particular via the gas supply line, for supplying inert gas into the container, the first heat exchanger is connected to a hot water storage tank, the hot water storage tank is connected to at least one heat pump as the source, the heat pump is connected to at least one cold water storage tank as the source, and the second heat exchanger is connected to a cold water storage tank, and that process heat can be recovered by means of a heat pump from water which originates from the cold water storage tank and has been heated by heat exchange in the second heat exchanger, and which water can be supplied to the hot water storage tank via the heat pump by means of an inlet.

15. The drying device according to claim 14, wherein at least one inert gas source can be connected to a supply line to the inert gas storage tank.

16. The drying device according to claim 14, wherein at least one means for shifting the bulk material is present in the container. cm 17. The drying device according to claim 16, wherein the hot water storage tank is connected to at least one of the following sources: geothermal energy, process heat, solar collectors.

18. The drying device according to claim 17, wherein the heat pump is connected to at least one of the following sources: geothermal energy, solar collectors or other heat sources with heat recovery.

19. The drying device according to claim 14, wherein the cold water storage tank is connected to a well.

20. The drying device according to claim 14, wherein an air inlet for ambient air is provided, which is connected to the second heat exchanger for cooling the ambient air, and the cooled ambient air can be conducted via a bypass line, by excluding the first heat exchanger, through the gas supply line into the container.

21. The drying device according to claim 14, wherein the container is connected via the gas discharge line to the second heat exchanger for the purpose of condensing water from the gas mixture, which communicates via a gas line with the first heat exchanger, which is connected via the gas supply line to the container in a closed circuit for the gas mixture.

22-25. (canceled)

26. The method of claim 1 wherein the 70-95% nitrogen comprises 90% nitrogen.

27. The method of claim 1 wherein the 5-10% argon comprises 7% argon.

28. The method of claim 1 wherein the 2-4% carbon dioxide comprises 3% carbon dioxide.

29. The method of claim 10 wherein the 5 to 13° C. comprises 6 to 12° C.

30. The drying device of claim 14 wherein the inert gas storage tank is connected to the container via the gas supply line.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The invention is now explained in more detail by reference to an embodiment example. The drawings are exemplary and are intended to illustrate the idea of invention but in no way to restrict it or even to reflect it conclusively.

[0040] The drawings show as follows:

[0041] FIG. 1 shows a schematic representation of the cooling process of the method according to the invention;

[0042] FIG. 2 shows a schematic representation of the inerting process of the method according to the invention;

[0043] FIG. 3 shows a schematic representation of the drying process of the method according to the invention;

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] FIG. 1 shows a schematic representation of the cooling step of the method according to the invention. During the entire filling process, the bulk material, preferably harvested material, is fed via a bulk material feeder 9, preferably a lift, into a container 1, preferably a silo. The bulk material, preferably harvested material, is immediately cooled to a temperature lower than the ambient temperature, preferably 5 to 11° C. or 7 to 13° C., by means of cooling air when it is introduced. The cooling air is obtained from the ambient air and is sucked in via an air inlet 11 through a filter 12 by means of at least one fan 10, preferably a radial fan, via the line 38 to at least one second heat exchanger 5, where it is cooled by means of this heat exchanger, which is in contact with at least one cold water storage tank 6, which is supplied via a cold source, preferably a well 7 and/or a heat pump 4 (see FIG. 3). Water that has been heated by the heat exchange with the cooling air in the second heat exchanger 5 is discharged into a return seepage well 37 or fed to the heat pump 4 (see FIG. 3).

[0045] From the heat exchanger 5, the cooling air is guided via a gas line 44, the fan 10, a bypass line 13, controlled by a valve 14 and introduced via the gas supply line 21 into a preferably horizontal, round or cuboidal base of the container 1, which is provided with passage openings 16, preferably with perforated plates or slotted screens, and distributed uniformly in the interior of the container 1 preferably silos, by means of these passage openings 16. The cooling air rises upwards and thus flows through the bulk material or crop in container 1 and cools it down to a temperature of 5 to 11° C., preferably 6 to 10° C. or 7 to 13° C., preferably 8 to 12° C. By means of outlet 17, the cooling air heated by the bulk material or harvested crop is led outside via an upper valve 18. An embodiment variant in which a flap or a similar opening or closing mechanism is used instead of an upper valve 18 is conceivable.

[0046] During cooling and filling of container 1 an inert gas supply line 19 (see FIG. 2) remains closed in order to avoid unnecessary consumption of inert gas. When a preferred filling level is reached, a gas-tight closable filling flap 20 or a gas-tight closable inlet slide and the gay-tight closable air inlet 11 are closed and inerting of container 1 begins.

[0047] FIG. 2 shows a schematic representation of the inerting process of the method according to the invention. First of all, an inert gas mixture, which preferably consists of nitrogen, carbon dioxide and at least one noble gas (helium, neon, argon, krypton, xenon, radon), is provided in an inert gas storage tank 8 for rapid charging <f the container 1 and for post-gassing, wherein nitrogen is preferably supplied by means of a PSA (Pressure Swing Adsorption) system 15 in combination with a compressed air system 23, which consists of compressor 32, compressed air tank 33 with condensate drain 34, dryer 36 with condensate drain 35. In a preferred embodiment variant of the method according to the invention, a cylinder storage system 24 is connected to the inert gas storage tank 8 via a dosing station 25, a solenoid valve 26 and a compressor 27. In a preferred embodiment variant, the inert gas mixture is brought to a pressure of 30-40 bar by means of compressor 27.

[0048] The inert gas mixture is passed on via a solenoid valve 28 and the gas pressure is reduced to preferably 0.1 to 0.2 bar or 0.2 to 1.0 bar by means of a pressure reducer and the gas mixture is passed into the container 1 by means of an inert gas supply line 19 and a gas supply line 21, where it is distributed uniformly inside the container 1, preferably silos, through the passage openings 16, preferably slotted screens or perforated plates. After complete filling of container 1 with the inert gas mixture, i.e. after displacement of the atmospheric oxygen, the upper valve 16 is closed.

[0049] FIG. 3 shows a schematic representation of the drying step of the method according to the invention. A gas-tight closable product outlet opening 29 is arranged at the bottom of container 1, which can be closed by means of an outlet slide or similar. A discharge screw is preferably used as the product discharge mechanism 30. When the upper valve 18 is closed, the inert gas mixture saturated with moisture is conducted via the gas discharge line 22 to the second heat exchanger 5, where water is condensed out of the gas preferably at 9 to 21° C. or 4 to 19° C. and discharged to the environment via a condensate outlet 31. The dewatered inert gas mixture is fed by fan 10 to the first heat exchanger 2, where it is brought to the desired temperature and returned via the gas supply line 21 to the interior of container 1.

[0050] Water heated by the second heat exchanger 5 can be discharged from the cold water storage tank 6 to the return seepage well 37 or fed to the heat pump 4 for cooling and supplied in a cooled down manner back to the cold water storage tank 6 again. Via heat pump 4 (consisting of evaporator 39, compressor 40 and condenser 41), hot water can be supplied to the hot water storage tank 3 via inlet 42. From another heat source 46, heat can be supplied directly to the DHW cylinder 3 via the inlet 42. Hot water can be recirculated from the hot water storage tank 3 via a return 43 to the heat pump 4 for heating or decoupled from the process.

LIST OF REFERENCE NUMERALS

[0051] 1 Container

[0052] 2 First heat exchanger

[0053] 3 Hot water storage tank

[0054] 4 Heat pump

[0055] 5 Second heat exchanger

[0056] 6 Cold water storage tank

[0057] 7 Well

[0058] 8 Inert gas storage tank

[0059] 9 Bulk material feeder

[0060] 10 Fan

[0061] 11 Aft inlet

[0062] 12 Filter

[0063] 13 Bypass line

[0064] 14 Valve

[0065] 15 PSA system

[0066] 16 Passage openings

[0067] 17 Outlet

[0068] 18 Upper valve

[0069] 19 Inert gas supply line

[0070] 20 Filling flap

[0071] 21 Gas supply line

[0072] 22 Gas discharge line

[0073] 23 Compressed air system

[0074] 24 Cylinder storage system

[0075] 25 Dosing station

[0076] 26 Solenoid valve

[0077] 27 Compressor

[0078] 28 Solenoid valve

[0079] 29 Product outlet opening

[0080] 30 Product discharge

[0081] 31 Condensate outlet 3

[0082] 32 Compressor

[0083] 33 Compressed air tank

[0084] 34 Condensate drain

[0085] 35 Condensate drain

[0086] 36 Dryer

[0087] 37 Return seepage well

[0088] 38 Line

[0089] 39 Evaporator

[0090] 40 Compressor

[0091] 41 Condenser

[0092] 42 Inlet

[0093] 43 Return

[0094] 44 Gas line

[0095] 45 Sensors

[0096] 46 Other heat source