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INVENTION
Patent of the Russian Federation RU2246550
METHOD FOR PROCESSING OF THORIUM-CONTAINING RADIOACTIVE WASTES
The name of the inventor: Kudryavsky Yu.P. (RU); Ryaposov Yu.A. (RU); Rakhimova O.V. (RU); Zhulanov N.K. (RU); Dernov A.Yu. (RU); Eremin I.Yu. (RU); Polejaev N.I. (RU); Medvedev A.N. (RU); Koryukov V.N. (RU); Martynov NM
The name of the patent holder: LLC Scientific and industrial environmental firm "ECO-technology"
Address for correspondence: 618400, Perm Region, Berezniki, ul. Деменева, 7, кв.3, Ю.П. Kudryavsky
Date of commencement of the patent: 2003.06.24
The invention relates to the field of metallurgy of rare, dispersed and radioactive metals, in particular to hydrometallurgical methods for reworking polymetallic, multicomponent, thorium-containing radioactive waste generated during processing of various mineral materials containing REE, Nb, Ta, Ti, V, Zr, Hf, W, U, etc. The technical result is to reduce the radioactivity of the filtrates after separation of radioactive fallout due to an increase in the degree of co-precipitation of natural radionuclides of the Th-232 series, in particular Ra-224 and Ra-228 with radioactive fallout. The method comprises treating the solutions and / or pulp with an alkaline reagent, introducing solutions of a sulfate-containing inorganic compound and barium chloride, treating the hydrate-sulphate pulp with a solution containing iron chloride, and separating the radioactive sediment from the solution by filtration. As an alkaline reagent, magnesium milk is used with an MgO concentration of 50-200 g / dm 3 , the treatment is conducted to a pH of 8-10, a solution of sodium sulfate in an amount of 6-9 g of Na 2 SO 4 / dm 3 is introduced as a solution of the sulfate-containing inorganic compound, Then a solution of barium chloride in the amount of 1.5-3 g BaCl 2 / dm 3 is introduced into the pulp, the hydrate-sulphate pulp is treated with a solution containing iron chloride in an amount of 0.8-16 g Fe 3+ / dm 3 of the initial solution and / or Pulps, treated with a high-molecular flocculant and kept without stirring for 0.5-2 hours, the radioactive precipitate is separated from the mother liquor, washed first with 0.5-2 volumes of water per 1 volume of the precipitate, then with a solution and / or suspension containing magnesium chloride in an amount of 1-2 volumes per 1 volume of sediment, the radioactive sediment from the filter is discharged and mixed with magnesium-containing oxide mineral materials taken in an amount of 0.5-0.8 kg MgO per 1 kg of precipitate. The resulting pasty composite composition is placed in molds and / or molds and pressed while heating to 80-120 ° C.
DESCRIPTION OF THE INVENTION
The present invention relates to the field of metallurgy of rare, dispersed and radioactive metals, in particular hydrometallurgical methods for processing polymetallic, multicomponent, thorium-containing radioactive waste generated during processing of various mineral materials containing REE, Nb, Ta, Ti, V, Zr, Hf, W , U, etc. The invention can be used in the processing, neutralization and deactivation of salt waste processes of chlorination of loparate, and / or zirconium, and / or titanium concentrates.
Known is a method for processing thorium-containing radioactive waste - waste from the process of chlorination of loparite concentrates (Non-Ferrous Metals, 1993, No.12, p.30-31; See: Journal of Applied Chemistry, 1990, vol.63, p.946., VINITI 10.10. 1989, No. 6183-B 89). The known method consists in the sorption recovery of thorium by macroporous phosphoric acid cationites of the KFP type, followed by desorption of thorium from the cationite with carbonate-containing solutions, precipitation of the thorium compounds from the eluate to give, after drying and calcining, concentrates containing 90-98% ThO 2 for deactivation of solutions from the daughter products Ra- 228 and Ra-224 - the operation of processing the initial pulp H 2 SO 4 (Na 2 SO 4 ) and BaCl 2 is provided (Journal of Applied Chemistry, 1990, vol. 63, p. 946). However, as the results of special studies and tests have shown, the introduction of this operation in the "head" of the process does not ensure the required degree of decontamination of solutions, and therefore additional deactivation of the filtrate solutions is required after the sorption columns. In the end, this leads to the formation of a large volume of secondary radioactive waste (RW) to be disposed of in a special waste storage facility.
Known ("The method of extracting thorium from solutions" Application No. 9302707/26 with the priority from 11.05.1993 MKI C 01 F 15/00 .Publ .: Bulletin No. 18. 1995, p.27) method of processing thorium-containing radioactive waste ( See also: Radiochemistry, 1996, vol.38, issue 1, pp. 60-65, Non-ferrous metallurgy, 1995, No. 7-8, p.30-33, RZhMet 1996, PG128), consisting in the selective extraction of thorium Coprecipitation with precipitation of Ba (Ca) SO 4 from solutions containing rare-earth elements, rare, dispersed, non-ferrous metals. The method involves treating the stock solution with an alkali metal chloride and / or ammonium chloride and / or hydrochloric acid to obtain a solution saturated with respect to the total amount of metal chlorides, introducing a water-soluble sulfate-containing inorganic compound into the solution, then a water-soluble barium salt in amounts providing the establishment of molar SO 4 / Wa ratios 
1.1 and BaSO 4 / Th thirty; Separation of radioactive sediment from the solution.
The known method allows, with a high selectivity, to extract thorium from solutions containing 0.01-0.1 g / dm 3 of thorium and other metals. However, at a thorium concentration of more than 0.1 g / dm 3, a very high consumption of barium salts and sulfate-containing inorganic compounds (Na 2 SO 4 ) is required, which leads to the formation of a large amount of precipitation - secondary radwaste to be buried, with the required deactivation of solutions from Ra-228 and Ra-224 is not achieved due to adsorption and coprecipitation of thorium with BaSO 4 precipitate and blocking of the surface of barium sulphate by Th 4+ ions .
Among the known analogues, the closest to the set of essential features is the method for processing thorium-containing radioactive waste, which includes treatment of solutions and / or pulp with an alkaline reagent, administration of solutions of the sulfate-containing inorganic compound and barium chloride, treatment of hydrate-sulphate pulp with a solution containing iron chloride and separation of the radioactive sediment From the solution by filtration (RU 2205461 C2, IPC G 21 F 9/30, published on 27.05.2003, page 1 column 1, page 5, example 3, variant 3, example 4, variant 2).
The disadvantage of the known prototype method is the unsatisfactory degree of purification and deactivation of solutions from daughter radionuclides of the thorium-232 series, in particular from Ra-224 and Ra-228, which is due to the incomplete co-precipitation of radium with the deposits of barium, calcium and oxyhydrate sulphates of metals. Another drawback of the known method - the prototype is associated with the need for the export of radioactive fallout into the storage of special waste (CHS), the construction and operation of which requires large capital expenditures.
The claimed technical solution is aimed at solving the problem of increasing environmental and radiation safety.
The technical result that can be obtained by carrying out the claimed invention is to reduce the radioactivity of the filtrates after separation of radioactive fallout due to an increase in the degree of co-precipitation of natural radionuclides of the Th-232 series, in particular Ra-224 and Ra-228 with radioactive fallout, and in localization Radioactive metals (thorium and its decomposition products) and their transfer to a radiation-safe form - a non-dusting, water-insoluble cured state that is resistant to the effects of atmospheric precipitation, groundwater and subsoil water, which does not adversely affect public health and maintenance personnel and is suitable for further storage without Environmental damage to the environment.
Said technical result in the implementation of the claimed method is achieved in that in the known method for processing thorium-containing radioactive waste, which includes treatment of solutions and / or pulp with an alkaline reagent, administration of solutions of sulfate-containing inorganic compound and barium chloride, treatment of hydrate-sulphate pulp with a solution containing iron chloride, and Separation of the radioactive sediment from the solution by filtration, magnesia milk with an MgO concentration of 50-200 g / dm 3 is used as an alkaline reagent, the treatment is conducted to a pH of 8-10; as a solution of the sulfate-containing inorganic compound, a solution of sodium sulfate in an amount of 6-9 g Na 2 SO 4 / dm 3 , then a solution of barium chloride in the amount of 1.5-3 g of BaCl 2 / dm 3 is introduced into the pulp, the hydrate-sulphate pulp is treated with a solution containing 0.8 to 16 g of Fe 3+ / Dm 3 of the initial solution and / or pulp, treated with a high-molecular flocculant and kept without stirring for 0.5-2 hours, the radioactive precipitate is separated from the mother liquor, washed first with 0.5-2 volumes of water per 1 volume of the precipitate, then with a solution and / or A suspension containing magnesium chloride in an amount of 1-2 volumes per 1 volume of precipitate, the radioactive precipitate from the filter is discharged and mixed with magnesium-containing oxide mineral materials taken in an amount of 0.5-0.8 kg of MgO per kg of precipitate, the resulting paste-like composite mixture Are placed in molds and / or molds and pressed with simultaneous heating to 80-120 ° C.
The peculiarity is that as a magnesium milk, a suspension prepared on the basis of magnesium-containing oxide mineral materials, for example asbestos production waste, is used.
The peculiarity is that magnesium-containing oxide mineral materials use previously heat-treated natural mineral materials, industrial products and / or wastes of asbestos production with particle size less than 100 microns.
A peculiarity is that a solution of Na 2 SO 4 with a concentration of 50-200 g / dm 3 is used as a sulfate-containing inorganic compound.
The peculiarity is that a solution with a concentration of 50-200 g of BaCl 2 / dm 3 is used as the solution of barium chloride.
The peculiarity is that as a solution and / or a suspension of magnesium chloride, a suspension obtained by the interaction of magnesium-containing oxide mineral materials, for example asbestos production waste, with a solution of hydrochloric acid is used.
The peculiarity is that as a solution and / or a suspension of magnesium chloride, a slurry is used, which is formed during the purification of waste gases from Cl 2 and / or HCl by magnesia milk.
The peculiarity is that as a solution of ferric chloride use a solution with a concentration of 10-100 g FeCl 3 / dm 3 .
The peculiarity is that as a solution of iron chloride use shop sewage, formed during washing of production sites and equipment, with an iron content of 5-2 g / dm 3 .
The peculiarity is that a solution of polyacrylamide with a concentration of 0.01-0.2% is used as the solution of the high-molecular flocculant.
Other things being equal, the proposed method, characterized by new methods of performing actions and a new order of performing actions, using certain substances without which it is impossible to implement the method itself, with new regimes and parameters of the process implementation, ensures the achievement of technical results in the implementation of the claimed invention.
The patentability test of the claimed invention shows that it corresponds to the inventive step, since it should not be for the experts explicitly.
The analysis of the state of the art shows that in the book, journal and patent literature there is no information on the processing of thorium-containing radioactive waste by sequential treatment of the initial solutions (pulp) first with an alkaline reagent, then with solutions of sodium sulfate, barium chloride, and then introducing into the pulp a solution containing Iron chloride, pulp filtration, washing the sediment first with 0.5-2 volumes of water per 1 volume of sediment, then with a solution and / or suspension containing magnesium chloride in an amount of 1-2 volumes per 1 volume of precipitate, mixing the radioactive sediment with magnesium-containing oxide mineral materials , Pressing, heating and block production.
An analysis of the totality of features of the claimed invention and the technical result achieved thereby shows that there is a definite causal relationship between them, expressed in the fact that the process of processing thorium-containing radioactive waste under the strictly defined above conditions, regimes and process parameters: sequence of operations, availability New actions, the introduction of certain substances, determined by the ratio of reagents, and a strictly defined order of introduction of reagents provide an increase in the degree of deactivation and a decrease in the radioactivity of filtrates after separation of radioactive fallout due to an increase in the degree of coprecipitation of natural radionuclides of the Th-232 series, in particular Ra-228 and Ra-224 With hydrated, sulfate and oxysulfate precipitates, localization of radioactive metals and their transfer to an environmentally safe form - a non-dusting, water-insoluble cured state that is resistant to the effects of atmospheric precipitation, groundwater and subsoil waters that do not adversely affect the health of the population and maintenance personnel and is suitable for further storage Without causing environmental and radiation damage to the environment.
If the above ratios of reagents are violated, strictly defined order of introduction of reagents, mixing regimes, process conditions, sequence of actions, etc., the above technical result is not achieved.
It should be noted that the established causal relationship clearly does not follow for specialists and does not follow from the literature data on chemistry and technology of rare and rare-earth metals.
The data supporting the implementation of the invention according to the invention of the above technical result are given in the example.
Example
As solutions containing natural radionuclides for experiments, the following were used: spent melts of the salt irrigation filter of the process of chlorination of loparite concentrates.
Solutions containing, 2.5% by weight of ThCl 4 , 20 AlCl 3 , 7 LnCl 3 , and impurities TiCl 4 , NbCl 3 , TaCl 5 , NaCl, KCl, MgCl 2 , CaCl 2 , water-insoluble residue (5%), - dissolved in water at M: T = 4: 1. 1 dm 3 pulp was treated with magnesia milk to pH 9.0 ± 0.5, then treated with a 40 dm 3 solution containing 100 g / dm 3 of sodium sulfate, 25 dm 3 of a solution containing 100 g / dm 3 of barium chloride, Pulp was injected with 0.8 dm 3 solution containing 5 g / dm 3 Fe 3+ . The pulp was then treated with a 0.1% solution of polyacrylamide, the pulp was kept without stirring for 1 hour and filtered, the radioactive precipitate was separated from the mother liquor, washed first with 1.5 volumes of water per 1 volume of the precipitate, then with a solution containing magnesium chloride in an amount of 1, 5 volumes per 1 volume of precipitate, the precipitate was mixed with magnesium-containing oxide mineral materials taken in an amount of 600 g of MgO per kg of sludge, the resulting paste-like composite mixture was put into molds and pressed while heating to 100 ° C.
Studies and tests showed that the process of decontamination of solutions from natural radionuclides according to the proposed method makes it possible to deactivate RW to the established standards, and the transfer of radioactive fallout into a hardened state ensures their environmentally safe storage without causing damage to the environment, public health and maintenance personnel: According to the proposed method, "blocks" are resistant to fluctuations in ambient temperature (-50 to +50 ° C), they do not dust, water-insoluble and are resistant to atmospheric precipitation, ground and subsoil waters.
CLAIM
A method for processing thorium-containing radioactive waste, comprising treating solutions and / or pulp with an alkaline reagent, introducing solutions of a sulfate-containing inorganic compound and barium chloride, treating the hydrate-sulphate pulp with a solution containing iron chloride, and separating the radioactive sediment from the solution by filtration, characterized in that As an alkaline reagent, magnesium milk is used with an MgO concentration of 50-200 g / dm 3 , the treatment is conducted to a pH of 8-10, a solution of sodium sulfate in an amount of 6-9 g of Na 2 SO 4 / dm 3 is introduced as a solution of the sulfate-containing inorganic compound, Then a solution of barium chloride in the amount of 1.5-3 g of BaCl 2 / dm 3 is introduced into the pulp, the hydrate-sulphate pulp is treated with a solution containing 0.8 to 16 g of Fe3 + / dm of the initial solution and / or pulp , Treated with a high molecular weight flocculant and kept without stirring for 0.5-2 hours, the radioactive precipitate is separated from the mother liquor, washed first with 0.5-2 volumes of water per 1 volume of the precipitate, then with a solution and / or suspension containing magnesium chloride in an amount of 1 -2 volume per 1 volume of sediment, the radioactive sediment from the filter is discharged and mixed with magnesium-containing oxide mineral materials taken in an amount of 0.5-0.8 kg of MgO per kg of sludge, the resulting paste-like composite mixture is placed in molds and / or molds and Pressed at a simultaneous heating to 80-120 ° C.
2. A method according to claim 1, characterized in that a suspension prepared on the basis of magnesium-containing oxide mineral materials, for example asbestos waste, is used as the magnesia milk.
3. A method according to claim 1, characterized in that magnesium-containing oxide mineral materials use pre-heat treated natural mineral materials, industrial products and / or asbestos waste products with a particle size of less than 100 μm.
4. The process of claim 1, wherein a sulfate-containing inorganic compound is a solution of Na 2 SO 4 at a concentration of 50-200 g / dm 3 .
5. A process according to claim 1, characterized in that a solution with a concentration of 50-200 g of BaCl 2 / dm 3 is used as a solution of barium chloride.
6. A process according to claim 1, characterized in that a slurry obtained by the interaction of magnesium-containing oxide mineral materials, for example asbestos production waste, with a solution of hydrochloric acid is used as a solution and / or suspension of magnesium chloride.
7. A process according to claim 1, characterized in that a slurry formed in the purification of off-gas from Cl 2 and / or HCl by magnesia milk is used as a solution and / or suspension of magnesium chloride.
8. A method according to claim 1, characterized in that a solution with a concentration of 10-100 g of FeCl 3 / dm 3 is used as the ferric chloride solution.
9. A method according to claim 1, characterized in that as a solution of iron chloride, the shop sewage generated by washing the production sites and equipment with an iron content of 5-2 g / dm 3 is used .
10. The method of claim 1, wherein a solution of a high molecular weight flocculant is a solution of polyacrylamide with a concentration of 0.01-0.2%.
print version
Published on February 19, 2007
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