Plastic and nonmetallic article shaping or treating: processes – Formation of solid particulate material directly from molten... – By vibration or agitation
Patent
1994-05-13
1996-03-19
Theisen, Mary Lynn
Plastic and nonmetallic article shaping or treating: processes
Formation of solid particulate material directly from molten...
By vibration or agitation
264 14, 425 6, 425 10, B29B 910
Patent
active
055001629
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention refers to a method for producing microspheres by means of vibration-stimulated dripping of liquid through a plurality of openings of a nozzle plate, the droplets taking on a spherical shape while falling through a first free-fall section and then, in a second free-fall section, being exposed to a reaction gas to produce gelling, thereafter falling into a reaction liquid which may possess a foam layer.
The invention further refers to an apparatus for producing microspheres, comprising a nozzle plate which has a plurality of openings for dripping a liquid and can be caused to vibrate; a reaction free-fall section in which the droplets falling from the nozzle plate react with a reaction gas; and a reaction liquid, present below the free-fall section in a vessel, which may be covered with a foam.
2. Description of the Prior Art
A corresponding method and apparatus are disclosed by DE 28 16 059 C3, referring to the production of a pelletized nuclear fuel; the resulting uranium oxide pellets have a diameter of approximately 80 um. It has been found in practice that larger spheres, in the range up to approximately 5 mm, cannot be produced with a corresponding method or apparatus, especially not in industrial-scale facilities.
Also known in addition to vibration-stimulated dripping is the gravity drip technique, although with this only small dripping rates of approximately 1 to 10 droplets per nozzle per second can be achieved.
SUMMARY OF THE INVENTION
The underlying problem of the present invention is to develop a method and an apparatus of the aforesaid type in such a way that spheres of sufficiently uniform geometry can be produced with diameters in the range up to 5 mm, allowing the possibility of scale-up to industrial-scale facilities.
In terms of the method, the problem is substantially solved by the fact that the same quantity of liquid passes through each opening in the nozzle plate per unit time; that the falling droplets form an envelope around which the reaction gas flows on all sides; and that reaction gas is introduced peripherally inside or outside the envelope, and is extracted outside or inside the envelope.
According to the invention the liquid, for example a dispersion, emerges through a plurality of openings, for example nozzle orifices, arranged in one or more circles arranged concentrically with one another, at identical volumetric flows, and is turned into droplets as the nozzle plate is caused to vibrate periodically. The result is to form a "droplet wall" referred to as an envelope, which may for example have the geometrical form of a hollow cylinder.
In the first free-fall section, the droplets emerging from the openings are then given the opportunity to take on a spherical shape before they reach the second freefall section, in which the spherical shape is stabilized by the fact that the droplets are stimulated to a sol-gel reaction by exposure to a reaction gas. The droplets, in a stable spherical shape, then reach the reaction liquid; before this, either they are decelerated in a foam present on the liquid, or reaction liquid is directed onto the falling droplets tangentially (or substantially tangentially) to and in the same direction as the direction in which the droplets are falling. The two features ensure that the droplets are not deformed, for example flattened, when they strike the reaction liquid present in a vessel.
In particular, the droplets are enveloped by and exposed on all sides to a reaction gas which is delivered from inside the envelope and extracted outside the envelope, extraction occurring between the gas inlet and the nozzles.
In terms of the apparatus, the problem is solved by the fact that a gas delivery device delivering the reaction gas is arranged inside the reaction free-fall section, inside or outside an envelope formed by apparent attachment of the falling droplets; that an extraction device extracting reaction gas is arranged outside or inside the envelope; and that a device generatin
REFERENCES:
patent: 3380894 (1968-04-01), Flack
patent: 3845179 (1970-04-01), Wace
patent: 3886086 (1975-05-01), Simpson
patent: 3957933 (1976-05-01), Egli et al.
patent: 4043507 (1977-08-01), Wace
patent: 4063856 (1977-12-01), Dziedzic
patent: 4285645 (1981-08-01), Bezzi et al.
patent: 4347200 (1982-08-01), Bezzi et al.
patent: 4692284 (1987-09-01), Braden
patent: 5223185 (1993-06-01), Takei et al.
European Search Report.
Brauneis Edwin
Pirstadt Bernd
Theisen Wolfgang
Nukem GmbH
Theisen Mary Lynn
LandOfFree
Process and device for producing microspheres does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process and device for producing microspheres, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process and device for producing microspheres will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1957595