Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Organic polymerization
Patent
1995-01-20
1997-03-04
Warden, Robert J.
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Organic polymerization
422159, 422229, 422239, 423613, B01J 400
Patent
active
056076487
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to rotary kilns in which gaseous reactions are carried out to form a solid product. The invention has particular relevance, although not exclusively, to rotary kilns used to manufacture uranium dioxide powder suitable for subsequent conversion to nuclear fuel pellets.
2. Discussion of Prior Art
In one known type of rotary kiln uranium hexafluoride vapour is fed with steam into an inlet end of the kiln. Reaction between the uranium hexafluoride and steam produces a solid intermediate product in the form of uranyl fluoride which passes into a heated rotating barrel by the aid of a scroll feed device. As the uranyl fluoride progresses along the barrel it reacts with a counterflowing stream of hydrogen and steam. This reduces the uranyl fluoride to a uranium dioxide powder which is discharged from the outlet end of the kiln.
Off gases produced by reactions in the kiln flow towards the inlet end and pass into a filter hopper arranged above the scroll feed device. Mounted on the top of the hopper are several filter assemblies which are used to extract solid particles from the reaction gases.
In use, a major portion of the uranyl fluoride particles circulate within the inlet region for a period of time during which particle can grow and agglomorate in a dendritic manner. Eventually, the particles become disentrained from the reaction gases and fall into the scroll feed device which transfers them into the kiln barrel.
SUMMARY OF THE INVENTION
We have found that the filter hopper can be reduced in height by use of the construction hereinafter described without adverse effect on the product quality and reaction in the inlet region. It is an object of this invention to provide a rotary kiln having an improved inlet region.
According to one aspect of the invention there is provided a rotary kiln for producing a solid material from gaseous reactants, said kiln having an inlet arrangement, an outlet arrangement and a rotatable barrel extending between the inlet and outlet arrangements, means for introducing gaseous reactants into said inlet arrangement, said reactants reacting together to form a solid product, wherein the inlet arrangement includes a rotatable scroll feed device for feeding the solid product into the barrel, and a filter for separating particles from gases produced in the kiln, the filter being arranged so as to at least partially encircle the scroll feed device and located adjacent thereto.
Preferably, the scroll feed device comprises a number of helical blades which effect a cleaning action on the filter.
The filter may comprise a porous metal or ceramic body in the form of an annular sleeve which surrounds the filter. Gases leaving the kiln through the filter may be extracted from a chamber externally surrounding the filter through pipes communicating with the chamber.
In a preferred embodiment the solid material produced by the kiln is uranium dioxide powder.
The gaseous reactants introduced into said inlet arrangement are preferably uranium hexafluoride and steam which in use react together to form a solid uranyl fluoride intermediate product, wherein means are provided for introducing steam and hydrogen at said outlet arrangement so as to flow along the barrel towards said inlet arrangement, the steam and hydrogen reacting with the uranyl fluoride product to produce said uranium dioxide powder.
The uranium hexafluoride and steam reactants may be introduced into the inlet arrangement through a nozzle having an inner tube surrounded by an annular passage, one reactant being supplied through the inner tube and the other reactant being conveyed through the annular passage. Uranium hexafluoride is preferably supplied through the inner tube while steam is conveyed through the annular passage.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:
FIG. 1 is a diagrammatic view of a rotary kiln assembly,
F
REFERENCES:
patent: 3057702 (1962-10-01), Pierce et al.
patent: 3111394 (1963-11-01), Weber et al.
patent: 3518062 (1970-06-01), Delange et al.
patent: 3698697 (1972-10-01), Gillies et al.
patent: 4112055 (1978-09-01), Artuad
patent: 4397824 (1983-08-01), Butler et al.
patent: 4574078 (1986-03-01), Cortesi et al.
Carter Robert
Semeraz John T.
British Nuclear Fuels PLC
Snider Theresa T.
Warden Robert J.
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