APPARATUS FOR AGGLOMERATING POWDERS

Abstract: A powder spheroidiser has a housing in which is rotatable a paddle blade having two concave surfaces (8,) (9) defining chambers (40,) (41) with a surrounding surface (33.) Powder admitted through closable inlet (51) is agglomerated into granules by rotating the paddle, the powder rolling over curved surfaces (8,) (9,) (33.) The granules may be removed through closable outlet (52.)

Description: This invention relates to apparatus for agglomerating powders. The US-A 3554263 describes an agglomerating device comprising a cylindrical casing a rotor provided at its circumference with radially extending blades and a treating zone formed between the rotor and the arcuate wall of the casing. According to this invention the apparatus for agglomerating powders comprises a blade rotatable in a housing, the housing having end walls and a peripheral wall, the blade defining a chamber with an inner surface of the peripheral cylindrical wall, the blade having a concave surface confronting the chamber, and means for admitting powder to the chamber. The concave surface may have the same radius as the inner surface of the peripheral wall. The blade may be shaped to provide two such chambers, angularly spaced. The two chambers may be diametrically opposed. The blade may have an arcuate outer surface close to the inner surface of the peripheral wall. There may be a closable inlet and a closable outlet in the peripheral wall. The invention may be performed in various ways and one specific embodiment with possible modifications will now be described by way of example with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a side view of a spheroidiser; Figure 2 is a perspective view of part of Figure 1; and Figure 3 is an end view of another arrangement. In the present case powder is agglomerated into granules. Referring to Figures 1 and 2, a spheroidising device has a housing 10 having front and rear walls 11, 12 and a peripheral wall 13 having an inlet/outlet port 14 closable by a removable plug 15. A paddle 16 in the housing 10 is rotatable by an electric motor 17 having a control unit 18 and a driving shaft 19 supported in bearings 20 and sealingly extending through walls 11, 12. The paddle 16 may for example be rotatable at a selected speed within the range 4 to 100 rpm. The front wall 11 can be transparent eg glass or perspex. The paddle 16 has blade means in the form of blades 30, 31 on opposite sides of the shaft 19. Each blade 30, 31 has an outer arcuate surface 32 close to the inner surface 33 of the wall 13 to resist build-up of material. The sides 34, 35 of the blades merge to give two smooth part-circular curved surfaces 8, 9 of a radius equal to the radius of the surface 33 (eg 100 mm). Powder 65 is fed through the port 14 into one or both of the chambers 40, 41 respectively provided by the concave sides 34, 35 (8, 9) and the surface 33, the plug 15 closes the port 14, the paddle 16 is rotated at a speed and for a time found appropriate for the particular powder eg 20 rpm for 15 minutes for ceria powder. Higher speeds may cause the powder to be thrown rather than rolled. The extent of agglomeration can be assessed in tests using for example angle of slip and standard flowrate tests. When the powder has been spheroidised, the plug 15 is removed and the device inverted to discharge the granules through the port 14. The granules may not be spheres and the team spheroidiser is not restricted to spherical granules. The device may be located in a glove box and may discharge into a container. A preferred loading may be obtained by tests. Thus a 35% by volume loading of chamber 40 and/or chamber 41 is preferred for ceria powder CeO₂. In a preferred arrangement of Figure 3, the housing has a top inlet port 50 and associated plug 51, and a bottom discharge outlet 52 and associated plug 53 so there is no need to invert the housing. The housing 10 is normally stationary. The body 10 is fixed, allowing permanent connections during filling and emptying. The inlet and outlet ports 50, 51 are simply plugged but the plugs can be replaced by valves. Motion is imparted to the powder inside the spheroidiser by the action of the rotor or paddle; the curved surfaces 34, 35 of which are of the same radius as the internal surface 33 of the spheroidiser housing. Thus, by the action of the rotor, powder is continually rolled on surfaces of this radius. UO₂ and PuO₂ ― UO₂ powders can be granulated. In a modification the trailing ends 60 Figure 2 of the outer arcuate surfaces of the paddle 16 are further from the inner surface 33 of the wall than the leading ends 61 to resist build-up of material as a result of compression of the material against the surface 33. The concave surfaces 8, 9 need not have the same radius as the surface 33. Preferably surfaces 8, 9, 33 are polished to a mirror finish. The device converts the fine powder into a free-flowing granular material. The plugs could be replaced by valves.

Claims: 1. Apparatus for agglomerating powders comprising a blade (19) rotatable in a housing (10), the housing (10) having end walls (11, 12) and a peripheral cylindrical wall (13), the blade (19) defining a chamber (40 or 41) with an inner surface (33) of the peripheral wall (13), the blade (19) having a concave surface (34, or 35) confronting the chamber (40 or 41), and means (50, 51) for admitting powder to the chamber (40 or 41). 2. Apparatus as claimed in Claim 1, characterised in that the inner surface (33) has a radius and the concave surface (34 or 35) has a radius equal to the radius of the inner surface. 3. Apparatus as claimed in Claim 1 or Claim 2, characterised in that the blade (19) is shaped to provide two said chambers (40, 41), angularly spaced. 4. Apparatus as claimed in Claim 3, characterised in that the two chambers (40, 41) are diametrically opposed. 5. Apparatus as claimed in any preceding claim, characterised in that the blade (19) has an arcuate outer surface close to the inner surface (33) of the peripheral wall. 6. Apparatus as claimed in Claim 5, characterised in that a trailing end (60) of the arcuate surface is further from the inner surface (33) than a leading end (61). 7. Apparatus as claimed in any preceding claim, characterised by a closable inlet (50) and a closable outlet (52) in the peripheral wall (13).

Inventors: BAXTER, WARREN, MARSHALL, ALAN
Applicants: BRITISH NUCLEAR FUELS PLC
Application year: 1989
Main classification: B01J2
IPC codes: B01J2