Patent ES-272068-A1 (ES)
Title: Method and apparatus of continuously obtaining uranium dioxide with predetermined characteristics from uranium trioxide
IPC: B01J19/20
Filed: 1961-11-16
Abstract: UO3 in the form of pastilles or granules is introduced into the furnace by means of hopper 8, provided with a rotatable obturation 9 permitting the supply of UO3 to the furnace, and at the same time preventing the release of powder to the outside, and is heated inside the furnace 1 to a temperature between 600 DEG and 900 DEG C., in the presence of a counter-current of air via inlet 10 and outlet 11. The oxide leaves the furnace 1 for cooler 2, comprising a double envelope 13 with a water inlet at 14 and an outlet at 15. Nitrogen introduced <PICT:0966898/C1/1> at 16 and leaving at 17 circulates in a counter-current to the oxide. Several modifications of the furnace 1 and the cooler 2 can be provided. The oxide flows through throttle 18 in the form of U3O8 or in an intermediate form between UO3 and U3O8 into vertical furnace 3. A reducing mixture of ammonia-nitrogen gas is introduced at 20 and the escaping gases leave at 21. The temperature of the reaction is regulated between 400 DEG and 800 DEG C. Other reducing gases and diluents are specified. The substances flow to the lower part of the furnace 3 through a throttle 22 beneath which there is fed a current of nitrogen 23. Since the pressure of this gas is higher than the pressures prevailing on the downstream and upstream sides of the throttle, the nitrogen thus prevents any possible mixture between the gaseous phase of the horizontal reactor 4 leaving at 26 and the gaseous phase entering the vertical furnace 3 at 20. The nitrogen introduced at 23 leaves again at one and the same time at 21 and 26. A current of cracked ammonia is fed at 25 into reactor 4 and the escaping gases leave at 26. A coil 27 ensures the circulation of the product and allows very efficient mixture to take place with the continuous renewal of the contact surfaces between the solids and the gas and a good homogeneity of the temperature. In the reactor 4, thermal stabilization of UO2 occurs, during which the reduction of the UmOn is to UO2 is completed. The UO2 leaving the reactor 4 flows via a throttle 28 into cooler 5 comprising a double envelope 29 cooled by a circulation of water entering at 30 and leaving at 31. Nitrogen, previously cooled if desired, is introduced at 32 and leaves at 33. A coil 34 ensures the circulation of the product and facilitates the exchange of calories. The horizontal chemical stabilizer 6 comprises a double envelope 35 cooled by a circulation of water entering at 36 and leaving at 37. Stabilizer gas, constituted for example by oxygen or by carbon tetrachloride vapour, circulating in a countercurrent to the powder UO2, enters at 38 and leaves at 39. Between the cooler 5 and the stabilizer 6 is placed a rotary obturation 40 permitting the flow therethrough of UO2 but entirely preventing the mixture of the gaseous phases. The calcination assembly may be separate from the reduction-stabilization assembly and the horizontal cooler may be replaced by two vertical discontinuous coolers, situated parallel to one another, one being filled while the other is emptied.