METHOD AND ASSEMBLY FOR PRODUCING COATED PRILLS OR GRANULATES, PRILLS OBTAINED THEREWITH, AND USE THEREOF

Abstract

A process for producing prills, in particular fertilizer prills, coated with at least one biologically degradable polymer layer, in particular a PLA layer, may involve applying a degradable polymer layer to a carrier material of the respective prill in a drum coating step, in particular in a drum coater at relative negative pressure, and then coating the prills with a second degradable polymer layer on top of the first degradable polymer layer in a fluidized bed coating step, in particular in a fluidized bed coater at a relative positive pressure. Coating the prills with the second degradable polymer layer may involve introducing the prills into a fluidized bed coater after the drum coating step, and the fluidized bed coating step may be performed spatially adjacent alongside the drum coating step.

Claims

1.-14. (canceled)

15. A process for producing prills or granules, the process comprising: coating a carrier material of respective prills with a first degradable polymer layer in a drum coating step; and coating the prills with a second degradable polymer layer on top of the first degradable polymer layer in a fluidized bed coating step.

16. The process of claim 15 wherein coating the prills with the second degradable polymer layer comprises introducing the prills into a fluidized bed coater after the drum coating step, and/or wherein the fluidized bed coating step is performed spatially adjacent alongside the drum coating step.

17. The process of claim 15 wherein a rest phase or a drying phase of between 1 to 3 minutes occurs after coating the carrier material of the respective prills and before coating the prills with the second degradable polymer layer.

18. The process of claim 15 wherein at least one of: a proportion by weight of the degradable polymer layers is in a range from 0.05% to 20% of a mass of each prill; a proportion by weight of the first degradable polymer layer is in a range from 0.05% to 15% of a mass of each prill; a proportion by weight of the second degradable polymer layer is in a range from 0.05% to 5% of a mass of each prill; a layer thickness of the degradable polymer layers in absolute terms is in a range from 1 to 500 m; the first degradable polymer layer is at least as thick as the second degradable polymer layer; or a ratio of layer thicknesses or proportions by weight of the first degradable polymer layer compared to the second degradable polymer layer is in a range from 20:1 to 1:1.

19. The process of claim 15 wherein at least one of: in the drum coating step, setting a temperature in a range from 0 to 130 C.; or in the fluidized bed coating step, setting a temperature in a range from 0 to 90 C.

20. The process of claim 15 wherein at least one of: in the drum coating step, setting a pressure in a range from 1 to 0 bara; or in the fluidized bed coating step, setting a pressure in a range from 1 to 10 000 mbar.

21. The process of claim 15 wherein at least one of: the first and second degradable polymer layers each comprises a layer of biologically degradable PLA; or the first degradable polymer layer has a clew-like, pore-rich structure and the second degradable polymer layer has a plaster-like, dense, low-pore structure

22. The process of claim 15 wherein in at least one of the coating steps a chlorine-free solvent is used, and/or wherein in the fluidized bed coating step chlorine-free solvent comprising CO2 is used.

23. A processing assembly for production of prills or granules, the processing assembly comprising: a drum coater as a first process stage; a fluidized bed coater as a second process stage that is downstream of the first process stage, wherein each of the drum coater and the fluidized bed is configured for coating the prills with a biologically degradable polymer layer; and a device for generating a negative pressure or a positive pressure and for generating a pressure difference between the first and second process stages.

24. The processing assembly of claim 23 comprising: a device for receiving the prills that have been coated in the drum coater, the device for receiving being configured for transferring the prills to the fluidized bed coater and having an outlet or a coupling corresponding to an inlet of the fluidized bed coater; and a device having a drying function interposed between the drum coater and the fluidized bed coater.

25. Prills having at least two layers produced by at least two-stage coating of a carrier material of the prills, with a first degradable polymer layer applied by drum coating and with a second degradable polymer layer applied by fluidized bed coating, the prills produced by a process comprising: coating a carrier material of respective prills with the first degradable polymer layer in a drum coating step; and coating the prills with the second degradable polymer layer on top of the first degradable polymer layer in a fluidized bed coating step.

26. A mixture of prills comprising at least one of: the prills of claim 25 mixed with a second type of prills with an at least one mechanically-stabilizing layer; or the prills of claim 25 mixed with a second type of prills without any coating.

Description

[0068] Further features and advantages of the invention are apparent from the description of at least one exemplary embodiment with reference to drawings, and from the drawings themselves. These show, in each case in schematic representation,

[0069] FIG. 1 a sectional view of a single prill produced according to embodiments;

[0070] FIG. 2 a side view of a processing assembly according to an exemplary embodiment;

[0071] FIG. 3 a prill mixture with prills at least comprising prills produced according to embodiments;

[0072] FIG. 4 a process diagram relating to individual process steps according to embodiments.

[0073] For reference numerals not described explicitly in respect of a single figure reference is made to the other figures.

[0074] FIG. 1 shows a single prill 1, having a core or carrier 1.1, having an optional layer of micronutrient additions 1.2 applied to the carrier 1.1 (for example micronutrient additions such as selenium Se, copper Cu, zinc Zn, applied by means of a drum coating device from a melt, from a solution in water (H2O) or from a solution in other solvents), having at least one first layer 1.3 (applied by means of a drum coating device from a solution in particular in acetone), in particular embodied as a PLA layer, having an optional layer of micronutrient additions 1.4 (for example micronutrient additions such as selenium Se, copper Cu, zinc Zn, applied by means of a drum coating device in particular from a solution in acetone), and having at least one second layer 1.5 (applied by means of a fluidized bed device from a solution in particular in acetone), in particular embodied as a PLA layer. Owing to the drum coating process, the first layer 1.3 can be imparted with a clew-like structure with a relatively high strength. Owing to the fluidized bed process, an outer skin or outer shell surface 1.51 of the second layer 1.5 can be imparted with a very dense surface structure. Instead of PLA, an alternative, biologically degradable polymer or a mixture of such polymers can also be applied for the respective first and/or second layer.

[0075] The following remarks can be made with respect to the individual layer thicknesses: The thickness d3 of the first layer 1.3 (possibly comprising one or more additional layers 1.2) is for example in the range from 10 m to 300 m, in particular is approx. 100 m or 200 m, and the thickness d5 of the second layer 1.5 (possibly comprising one or more additional layers 1.4) is for example in the range from 1 to 50 m, with the absolute coating thickness being given here by summation and for example being in the range from 150 to 350 m. The layers 1.3 and 1.5 can surround the additional layers 1.2, 1.4 here.

[0076] FIG. 2 shows a processing assembly 10 comprising a drum coating device 13 (drum coater) having a first drum coating unit 13.1 and a second drum coating unit 13.2, in particular designed as or comprising a drying unit, and further comprising a fluidized bed coating device 15 (fluidized bed coater) having at least one fluidized bed coating unit 15.1. Further, redundant fluidized bed coating units can optionally be provided. The assembly 10 can optionally also comprise a tower 11 for prill production (untreated prills or prills with conventional granulating aids, in particular UF solution).

[0077] The drum coating device 13 can be provided as a single apparatus or optionally can also consist of a grouping or assembly of a plurality of plant components. In particular, an optional drying can be effected separately.

[0078] By means of a negative pressure/positive pressure device 17, the desired operating pressure can be set in the respective coater 13, 15.

[0079] By means of a device 19 for receiving the prills that have been coated in the drum coater, the prills can be received or subjected to interim storage and can be transferred via the outlet 19.1 to the fluidized bed coater 15. Drying can optionally be effected in the device 19. The device 19 can be designed as a separate drying unit.

[0080] With a first material stream M1, in particular of untreated prills, prills are conveyed from the prilling tower 11 to the drum coating device 13 as first process stage. A supply of polymer and solvent L2 is effected in the drum coating device 13.

[0081] A material stream M1.1 (portion of M1) can optionally be directed to the storage facility. Downstream of the first drum coating unit 13.1, a material stream M2.1 (portion of M2) can optionally be directed to the storage facility. The percentage proportion of the portion can be adjusted depending on requirements, in particular by means of a control unit 20. The coupling of the control unit 20 to the respective devices and units is illustrated by the respective dash-dotted line.

[0082] With a further material stream M2 of prills coated with at least one first layer, the drum-coated prills are conveyed onwards from the corresponding drum coating unit, either to a further drum coating unit or to a drying unit, or as a further material stream M3 from the drum coating device 13 directly to the fluidized bed coating device 15 as second process stage. It is advantageous for the prills to remain warm along the material stream path M3, and so a temperature control device which surrounds the material stream path M3 at least in sections can be provided.

[0083] Optionally, an additional layer consisting of additives can be applied along each of the material stream paths M1, M2, M3, in particular in each case on a conveyor belt and/or during the transport. To this end, the respective material stream path M1, M2, M3, can be hermetically sealed off or surrounded at least in sections by a further coating device. This comparatively thin additional layer is configured to improve the physical properties of the prills (in particular abrasion resistance, compressive strength, resistance with respect to clumping), in particular in connection with the first material stream path M1. The coating with at least one additional layer on the carrier and/or on the first degradable layer can optionally also be effected in a separate (parallel, continuous or discontinuous) process.

[0084] A supply of polymer and solvent L3 is effected in the fluidized bed coating device 15, in particular with acetone or CO2 in the supercritical state, in particular in conjunction with atomizing fluid and/or air.

[0085] The respective supply of polymer and solvent L2, L3 can also include the supply of different polymer material and different solvents.

[0086] By means of a further media stream M4, the respective media can be discharged, with the media stream M4 comprising in particular the discharge, recycling (recovery) and/or disposal of solvents.

[0087] A solvent separation system (e.g. a cold trap, scrubbing) can be connected between drum coater 13 and fluidized bed coater 15. For the case where the intention is to use only a single type of solvent, the solvent is preferably collectively centrally fed to a separation system.

[0088] A separate dryer does not necessarily need to be provided. A drying function can also be fulfilled by the corresponding coater 13, 15.

[0089] In one embodiment, approx. 1% to 20% by weight of the first layer(s) is applied by the drum coating step(s) (first process stage according to the invention), and/or approx. 1% to 15% by weight of the second layer(s) is applied by the fluidized bed coating step(s) (second process stage according to the invention).

[0090] In a preferred embodiment, approx. 4% by weight of the first layer(s) is applied by the drum coating step(s), and/or approx. 1% by weight of the second layer(s) is applied by the fluidized bed coating step(s).

[0091] In a further (fourth) material stream M5, the two-stage coated end product can be provided, in particular in the form of a prill mixture consisting of two-layer coated prills (first type) and prills of at least one further type (second and/or third type, untreated or treated for the purposes of improving the physical properties). The proportions by weight of the mixture can be set individually, in particular by means of the control device 20, by regulation of the individual material streams.

[0092] Owing to the two-stage process, variations both to the process and to the layer structure and/or in relation to the material composition and/or in relation to the solvent selection can be made in a simple manner.

[0093] FIG. 4 shows a process diagram in which individual steps of the process according to the invention are elucidated. A first step S1 comprises supplying prills from a prilling tower. A second step S2 comprises one or more first coating steps, in particular a first drum coating step S2.1 and a second drum coating step S2.2 and optionally also a drying step S2.3 after the first and/or second coating step. In a third step S3 comprising one or more second coating steps, the at least one second layer 1.5 is applied, in particular in a first fluidized bed coating step S3.1 optionally followed by a second fluidized bed coating step S3.2 and optionally also followed by a drying step S3.3 after the first and/or second coating step. A fourth step S4 comprises the discharge or recycling of solvent, in particular CO2, and a fifth step S5 comprises the provision of prills or a prill mixture 5. Step S5 can also comprise the mixing, in particular according to predefined percentages, optionally specified by the control device.

LIST OF REFERENCE NUMERALS

[0094] 1 prill, in particular of the first type [0095] 1.1 core or carrier or carrier material [0096] 1.2 optional layer of micronutrient addition [0097] 1.3 first layer, in particular PLA layer [0098] 1.4 optional layer of micronutrient addition [0099] 1.5 second layer, in particular PLA layer [0100] 1.51 outer skin or outer shell surface [0101] 2 further prill, in particular of the second type [0102] 3 further prill, in particular of the third type [0103] 5 prill mixture [0104] 10 processing assembly [0105] 11 tower for prill production (untreated, unmodified prills) [0106] 13 drum coating device (drum coater) [0107] 13.1 first drum coating unit [0108] 13.2 second drum coating unit, in particular drying unit [0109] 15 fluidized bed coating device (fluidized bed coater) [0110] 15.1 fluidized bed coating unit [0111] 17 negative pressure/positive pressure device [0112] 19 device for receiving the prills that have been coated in the drum coater [0113] 19.1 outlet [0114] 20 control unit [0115] d3 thickness of the first layer [0116] d5 thickness of the second layer [0117] da absolute coating thickness [0118] M1 first material stream, in particular untreated prills [0119] M1.1 material stream (portion) to the storage facility [0120] L2 polymer and solvent supply [0121] M2 further (second) material stream, in particular within the drum coating device [0122] M2.1 material stream (portion) to the storage facility [0123] L3 polymer and solvent supply [0124] M3 further (third) material stream, in particular from the drum coating device to the fluidized bed coating device [0125] M4 further media stream, in particular discharge of solvents [0126] M5 further (fourth) material stream, in particular for providing a prill mixture [0127] S1 first step, in particular supplying of prills from a prilling tower [0128] S2 second step, in particular first coating step [0129] 52.1 first drum coating step [0130] S2.2 second drum coating step [0131] S2.3 drying step [0132] S3 third step, in particular second coating step [0133] 53.1 first fluidized bed coating step [0134] S3.2 second fluidized bed coating step [0135] S3.3 drying step [0136] S4 fourth step, in particular discharge or recycling of solvent [0137] S5 fifth step, in particular provision of prills or a prill mixture