Method and device for disinfecting pourable products, preferably seeds, with accelerated electrons

Abstract

The subject matter of the present invention is a method for treating pourable products made of particles which can be separated, preferably seeds (2), with accelerated electrons. During the method, a transparent product flow is guided, using gravity, in a product guiding channel (1) through the electron field generated by at least one electron accelerator (12) under low pressure or excess pressure. The product flow is guided by means of an accelerated gas flow (5) in such a way that the movement thereof corresponds in magnitude and direction to the accelerated movement, which the falling particles execute in said gas flow due to gravitational acceleration. In addition, a device is disclosed which realizes the acceleration of the gas flow (5) in the required way through the shaping of the product guiding channel (1).

Claims

1. A method for treating pourable products made of particles which can be separated, preferably seeds, with accelerated electrons, during which a transparent product flow is guided, using gravity, in a product guiding channel through the electron field generated by at least one electron accelerator under low pressure or excess pressure, characterized in that the product guiding channel has a decreasing cross section in the movement direction of the particles, and the product flow is guided by means of an accelerated gas flow, the movement thereof corresponding in magnitude and direction to the accelerated movement, which the falling particles execute in said gas flow due to gravitational acceleration.

2. The method according to claim 1, characterized in that the acceleration of the gas flow takes place through suction at the outlet and/or through injection at the inlet of the product guiding channel, which narrows in the transport direction.

3. The method according to claim 1, characterized in that the particles are imparted with a rotational movement prior to or at the entrance into the product guiding channel.

4. The method according to claim 3, characterized in that the imparting of the rotational movement of the particles takes place by rolling off of a slanted surface.

5. The method according to claim 3, characterized in that the imparting of the rotational movement of the particles takes place via short-term simultaneous contact with at least one fixed and one rotating component.

6. The method according to claim 3, characterized in that the initiation of the rotational movement of the particles takes place via simultaneous contact with components rotating at different speeds.

7. The method according to claim 1, characterized in that to reduce friction at least in partial areas of the product guiding channel, a gas flow with a movement component directed 45° to 90° to the movement direction of the product flow is introduced into the product flow.

8. The method according to claim 1, characterized in that a process gas is supplied during the treatment of the pourable product using accelerated electrons.

9. The method according to claim 8, characterized in that air or nitrogen or carbon dioxide is used as the process gas.

10. The method according to claim 1, characterized in that the process gas is guided in a circuit.

11. Method The method according to claim 10, characterized in that the process gas is subjected to dedusting.

12. The method according to claim 1, characterized in that the product guiding channel has a narrowing, rectangular cross section according to the correlation $s=k*\frac{1}{\sqrt{h}},$ where s is the gap width between two opposing sides of the product guiding channel, h is the drop path traveled by the particle, and k is a constant that preferably has a value between 170 mm.sup.3/2 and 250 mm.sup.3/2.

13. A device for disinfecting a product flow of pourable particles, preferably seed, with accelerated electrons, having: a process chamber filled with gas with a vertical product guiding channel for guiding the product flow, means for airlock-free, isolating guiding of pourable particles to the upper end of the product guiding channel, at least one electron accelerator with an electron exit window and the associated high voltage and control systems, which is arranged laterally on the product guiding channel, the electron beams of which hit the product flow guided through the product guiding channel and thus form a treatment zone, wherein the emission width of the electron accelerator corresponds at least to the width of the product flow, means for airlock-free exhaust of the product flow, means for generating a low pressure or excess pressure in the process chamber, characterized in that the product channel has a cross section constantly narrowing in the movement direction of the particles, the means for generating a low pressure or excess pressure in the process chamber, and the design of the particle guiding channel induce a constant volume flow of gas in the product guiding channel, which generates an accelerated movement of the gas identical to the movement of the particles in magnitude and direction.

14. The device according to claim 13, characterized in that the product guiding channel has a rectangular cross section and is curved over the course thereof on at least one of the two longer opposing sides such that the cross section thereof decreases in the transport direction.

15. The device according to claim 13, characterized in that a device for generating a rotational movement of the particles of the product flow is arranged prior to or across the treatment zone.

16. The device according to claim 14, characterized in that the gap width s between the two longer opposing sides of the product guiding channel follows the correlation $s=k*\frac{1}{\sqrt{h}}$ in relation to the drop height h of the particles, where s is the gap width between two opposing sides of the product guiding channel, h is the drop path traveled by the particle, and k is a constant that preferably has a value between 170 mm.sup.3/2 and 250 mm.sup.3/2.

17. The device according to claim 13, characterized in that the electron accelerator is a flat beam generator with a hermetically-sealed, evacuated acceleration chamber, for which operation no vacuum pumps are necessary.

18. The device according to claim 13, characterized in that the product guiding channel has a perforation in the area of the electron exit window, which perforation enables a gas flow in the direction of the product flow to keep dust clear as well as for the entry of the electrons into the product guiding channel and the influence thereof on the product.

19. The device according to claim 13, characterized in that the means for generating the low pressure or excess pressure are gas conveying devices.

20. The device according to claim 19, characterized in that the means for generating the low pressure or excess pressure convey the gas of the treatment chamber in a circuit.

21. The device according to claim 20, characterized in that a dedusting device is arranged in the conveying circuit.

22. The device according to claim 13, characterized in that a measuring device for detecting the electron beam density is arranged between the product guiding channel and the electron exit window, and/or in the product guiding channel.

23. The device according to claim 22, characterized in that the measuring device comprises at least two metal segments arranged electrically insulated, which segments are coupled to the ground potential via electrical conductors, and a measuring device for detecting the outgoing electron flow is interconnected to the electrical conductor in order to generate a signal depending on the electron flow density.

24. The device according to claim 13, characterized in that a measuring device for detecting the product status is arranged at the passage area of the electrons in the product guiding channel.

25. The device according to claim 24, characterized in that the measuring device comprises at least two metal segments electrically insulated from each other and from the walls of the product guiding channel, which segments deliver a signal depending on the particle flow density by means of a test voltage prevailing between the segments.

26. The device according to claim 24, characterized in that the measuring device is an optical system, which delivers a signal depending on the particle flow density.

27. The device according to claim 13, characterized in that a vibration conveying device equipped with an X-ray protection device is arranged for supplying the product.

28. The device according to claim 13, characterized in that a conveying device equipped with an X-ray protection device is arranged for supplying the product.

29. The device according to claim 13, characterized in that an ozone catalytic converter is connected upstream of the gas flow guided outward into the environment by the exhaust.

Description

(1) FIG. 1: A section through a device for disinfection of seeds using a fluidically optimized shape for the product guiding channel and gas blower, a hermetically encapsulated electron accelerator with electron exit window and protective grid, as well as product supply using a vibration conveying device, rotational device for the particles, product discharge, and an integrated X-ray protection device,

(2) FIG. 2: A section through a part of the device according to FIG. 1 in the area of the product guiding channel with gas guidance and bypass flow to keep the grid in the product guiding channel clear and for cooling the electron exit window,

(3) FIG. 3: A section through a part of the device according to FIG. 1 in the area of the rotational device for the particles,

(4) FIG. 4: A section through a part of the device according to FIG. 1 in the area of the measuring device for determining the electron flow density.

(5) FIG. 1 represents the basic structure of the exemplary device with product guiding channel 1, which has a constantly decreasing gap width in the direction of drop of the seed particles 2a. In the lower area, the product channel 1 is connected to a gas blower 4 via a suction line 3, which blower constantly supplies a gas flow 5 toward the outside. Due to this constant exhaust, a low pressure is generated in the inside of the treatment chamber. To protect against the exhaust of seed particles 2a, a grid 6 is arranged at the inlet to the suction line 3. An inflow nozzle 7 for supplying the gas flow 5 is located in the upper area of the product guiding channel 1. Air, carbon dioxide, or nitrogen is used as the process gas. The defined decreasing gap width of the product guiding channel 1 in the direction of drop causes a constant acceleration of the gas 5a within the product guiding channel 1 in the same measure as the acceleration due to gravity affecting the seed particle 2a.

(6) The bulk seed 2 is supplied to the process via a buffer container 8. A metering device (not depicted) is located at the outlet of the buffer container 8, which metering device limits the volume flow of the seed 2 to a defined level. The bulk seed 2 arrives at a vibration conveying device 9, which induces a constant feed and pre-separation. The vibration device 9 has, within the product guiding channel 1, an angled segment 10 with a roughened surface to increase friction. A rotating brush roller 11 forms an adjustable gap with the segment 10, the diameter of said gap corresponds to the bulk seed particle 2a. Due to the rotational movement of the brush roller 11, the particles of seed 2 rolling off the segment 10 receive a rotational pulse before they transition into the drop at constant acceleration due to gravity.

(7) Electron accelerators 12 are arranged on two sides of the product guiding channel 1. The flat electron beam 14 generated by the electron accelerators 12 enters through the electron exit window 13 into the product guiding channel 1 and moves in the direction of the seed particle 2a while forming a Gauss-shaped intensity profile 15 in the plane of representation, which profile has a half-power width of approximately 30 mm. In the Z-axis, perpendicular to the plane of representation, the electron beam 14 has a dimension of approximately 1000 mm. The electron beam 14 is further scattered during the propagation thereof in the air and affects the falling and rotating seed particle 2a, supplied to the gas flow 5a, diffusely and from all sides. After exposure to the electron beam 14, the bulk seed exits the product guiding channel 1 via a high-speed belt 16 arranged directly thereunder within less than one second, by which means the exposure to X-ray radiation is reduced to a minimum.

(8) The electron accelerators 12 are arranged rotated around the longitudinal axes (Z-axis) thereof, such that the primary movement direction of the electron beam 14 is not at a right angle to the movement direction of the seed particle 2a. By this means, the respectively opposing electron accelerator 12 is not hit, and also high electron energies and electron flows cannot damage the opposing electron exit window. Measuring devices 17 in the form of molybdenum plates for recording a measuring signal depending on the electron flow distribution are arranged on the product guiding channel 1 next to the electron exit windows 13.

(9) An optical measuring system 18 enables the measurement of the density of the seed particle 2a and the determination of the product state.

(10) The entire system is equipped with an X-ray protective housing 19, which prevents the emission of X-ray radiation into the environment. Due to the design with the integration of the vibration conveying device 9, the high-speed belt 16, and the interior barriers 19, the exposure time of the seed particle 2a in the area of the X-ray radiation is reduced to a minimum.

(11) FIG. 2 is a section through a part of the device according to FIG. 1, with the right side of the product guiding channel 1 and an electron accelerator 12 represented as enlarged, but only schematically. This area is the effective zone of the electron beam, in which the actual disinfection takes place. The electron beam 14 is guided using the Gauss-shaped intensity distributor 15 through the perforated region 1a into the product guiding channel 1 and affects the rotating seed particle 2a on all sides. The static low pressure generated by the gas flow 5a causes a gas flow 20, which is directed from outside through the perforated area 1a into the product guiding channel 1 and keeps said perforated area clear of contamination and particles. A flow channel 21 induces the targeted inflow of air with a selected direction distinctly parallel to the electron exit window 13 and cooling the same through convection.

(12) FIG. 3 shows an enlarged schematic section through a part of the device according to FIG. 1 with the rotational device for the seed particle 2a. The rotating brush roller 11 captures the seed particle 2a and transfers it to the rough surface of the segment 10 of the vibration conveying device 9 in a rotational movement. Kernel size differences are compensated for by the elastic bristles 11a, such that after leaving the rotational device, all seed particles 2a rotate.

(13) In the device, which is schematically represented in FIG. 4, a measuring device 17 is arranged on the side of the electron exit window 13, which measuring device determines the electron flow distribution 22 present in the Z-axis of the plane of representation. Said device comprises several temperature resistant molybdenum plates 23 positioned in the area of the edge electrons of the electron beam. The molybdenum plates are coupled to the potential of the housing of the electron accelerator 12 via electrical conductors. A measuring device 24 connected in series serves to detect the outgoing electron flow.

LIST OF REFERENCES

(14) 1 Product guiding channel

(15) 1a Perforated area of the product guiding channel

(16) 2 Bulk seed, seed (product)

(17) 2a Seed particle

(18) 3 Suction line

(19) 4 Gas blower

(20) 5 Gas flow

(21) 5a Gas flow in the direction of drop

(22) 6 Grid

(23) 7 Inflow nozzle

(24) 8 Buffer container

(25) 9 Vibration conveying device

(26) 10 Angled segment

(27) 11 Brush roller

(28) 11a Elastic bristles of the brush roller

(29) 12 Electron accelerator

(30) 13 Electron exit window

(31) 14 Electron beam

(32) 15 Intensity distribution of the electron beam

(33) 16 High speed belt

(34) 17 Measuring device for electron flow distribution

(35) 18 Optical measuring system

(36) 19 X-ray protective housing

(37) 20 Incoming gas flow

(38) 20a Incoming gas flow for cooling the electron exit window

(39) 21 Flow channel

(40) 22 Electron flow density distribution

(41) 23 Molybdenum plate

(42) 24 Measuring device