Canadian refining practice in the production of uranium trioxide by solvent extraction with tributyl phosphate
The recovery of high-purity uranium trioxide from uranium-bearing concentrates by solvent extraction with tributyl phosphate is described. Gravity and chemical concentrates, containing 10 to 80% U{sub 3}O{sub 8}, are blended and digested continuously with 55% nitric acid in cascade dissolvers to give a slurry containing about 300 g U/liter, 3N in free nitric acid. Uranium is extracted from the slurry in pulsed columns using 25 vol. % tributyl phosphate in an inert kerosene diluent. Extraction of thorium and other impurities is minimized by maintaining the uranium content at a high saturation density. Residual impurities and free nitric acid are removed from the solvent using a de-ionized water scrub. Uranium is re-extracted from the solvent with de-ionized water to give an aqueous solution containing 100 g U/liter. The stripped solvent is treated with aqueous sodium carbonate (7 wt. %) to remove residual uranium and any mono- or dibutyl- phosphate, and it is then stored for reuse. The uranyl-nitrate solution (100 g U/liter) is concentrated in two thermo-syphon evaporators and is then denitrated batch-wise in stainless steel kettles to give uranium trioxide. This is carried by a vacuum system to storage hoppers, pulverized, and packed in drums for shipment. Sulfuric acid is added to the aqueous raffinate from the initial extraction to convent combined nitric acid into free nitric acid, which is recovered by distillation in a forced-circulation evaporator. The nitric oxide gases from digestion and denitration are converted to dilute nitric acid (30%) in an absorption power. This dilute acid together with the acid recovered from the raffinate is concentrated to 55 to 60% nitric acid in a bubble-cap column. The bottoms from the raffinate evaporator are neutralized to a pH between 5 and 6 with hydrated-lime slurry to precipitate iron, arsenic, and other elements. The solid residue is separated on a rotating-drum filter and trucked to a disposal area. The filtrate, which satisfies the requirements of the International Commission for the Control of Boundary Waters for waste disposal, is pumped into Lake Ontario. (auth)
- Research Organization:
- Eldorado Mining and Refining Ltd., Port Hope, Ontario (Canada)
- NSA Number:
- NSA-13-007301
- OSTI ID:
- 4281999
- Report Number(s):
- A/CONF.15/P/228; AECL-638
- Resource Relation:
- Conference: 2. United Nations International Conference on the Peaceful Uses of Atomic Energy, Geneva (Switzerland), Jun 1958
- Country of Publication:
- Canada
- Language:
- English
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Related Subjects
ACIDITY
ADSORPTION
ARSENIC
BUTYL RADICALS
CALCIUM OXIDES
CHEMICAL REACTIONS
DENSITY
DISTILLATION
EVAPORATION
EXTRACTION COLUMNS
FILTERS
GASES
HYDROCARBONS
IMPURITIES
IONS
IRON
KEROSENE
LIME
MIXING
NITRIC ACID
NITROGEN OXIDES
ORGANIC FLUORINE COMPOUNDS
PHOSPHATES
PLANNING
PRECIPITATION
PRODUCTION
QUALITATIVE ANALYSIS
RECOVERY
REFINING
RESIDUES
ROTATION
SEPARATION PROCESSES
SLURRIES
SODIUM CARBONATES
SOLIDS
SOLUTIONS
SOLVENT EXTRACTION
SOLVENTS
STAINLESS STEELS
SULFURIC ACID
THORIUM
U3O8
URANIUM
URANIUM TRIOXIDE
URANYL NITRATES
USES
VACUUM
VESSELS
WASTE DISPOSAL
WATER