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Sharipov Khasan T., Tashkent State Technical University, Professor, Doctor of Chemical Sciences, Deputy Chairman of the SUE «Fan va tarakkiet" Sharafutdinov Ulugbek Z., Navoi Mining and Metallurgical Combinate, Chief of the technical control service of the MA. of the NMMC
E-mail: [email protected] Saparov Anvarjon B., Navoi Mining and Metallurgical Combinate, NMMCs chief of the process engineering department
Current state of the uranium extraction at the NMMC
Abstract: Currently of the uranium mined in NMMC is obtained by means of underground leaching in the Kyzyl-Kum open pits. This method allows to reduce the cost of uranium mining and ensure the environmentally clean production.
Keywords: uranium, underground leaching, sorption, extraction, rhenium, environmental protection.
The Basic proven, estimated and expected reserves logical-radiometric searches. of the uranium are concentrated at Kyzyl-Kum Province As a result of such exploration works there has been
of the Uzbekistan. From 1940s there were intensified re- found out more than 70 uranium ore occurrences, this dis-
search works on the natural recourses at the territory of coveries was the beginning of the development of Kyzyl-
the Uzbekistan: have been carried out complex geologic Kum region from the Uchkuduk deposits at 1952 years.
surveying at Kyzyl-Kum and special exploration works Just from the base of this deposit at 1958 there has
on uranium, as well as aeroradiometric and surface geo- been started the construction of the Navoi Mining and
Current state of the uranium extraction at the NMMC
Metallurgical Combinate (NMMC) and then in 1962 for the first time in mining industry by specialists of the NMMC was discovered the innovative technology of the uranium extraction by the underground leaching method.
Determined that the uranium extraction by underground leaching method have a number of advantages in comparison with traditional method:
- Smaller power consumption;
- Lower capital and operational costs;
- Possibility of the profitable execution of the poor sandstone uranium ores;
- Insignificantly radiation influence on environment.
Today the uranium extraction at NMMC is executed
only by underground leaching method. NMMC's uranium extraction structure consists of three uranium production enterprises there are.
- Northern Mining Administration: Uchkuduck, Kendik-Tube, Meylisay mined deposits;
- Mining Administration № 5: Shimoliy Bukinoy, Janubiy Bukinoy, Aulbek, Kuhnur, Istiklol, Northern Kanimex, Beshkok, Loyliken, Sugrali, Ketmonchi, Yo-gdu mined deposits;
- South Mining Administration: Sabirsoy, Jarkuduck mined deposits;
- and Gydrometallurgical Plant № 1 for output of the uranium oxide concentrate after sulfuric salts processing.
Uranium extraction by underground leaching at NMMC's structures executed of three differ methods using various leaching chemical agents and their combinations: acid, acid-carbonate, nonchemical treatment.
Both traditional and underground leaching methods initially accessed ore body. Uranium ore deposits have been accessed by injection and extraction wells system. Depending on filtration properties and rock ore homogeneity there are used various drilling patterns: rectilinear, hexagonal with different distance between rows and holes. Usually at NMMC's sites the holes constructed by rectilinear circuit which clasped ore shoots fully, although in comparison with hexagonal way this way is less effective. The hexagonal layout does not become common use by reason of disadvantage costs on consumables. There are developed deposits with ore depth formation up to 500 meters and more with combined mining and geological conditions due to uranium reserves depletion superposed on shallow depth. Provision of the holes qualitative constructions become much actual from which work depends extraction efficiency considering the fact that geotechnologi-cal holes are compound construction.
Well tube filters are integrant parts of the holes, which are made at the NMMC's Machinery Plant, its
provides for maximal porosity with high stabile production rate of the holes. The rising of the solution from borehole on underground leaching areas has been made by electro-submersible pumping units, replaced air-lift solution rising units starting from 2000 year. Usage of the electro-submersible pumping unit s had achieved the uranium production considerably at a reduced power supply of the production process and to omit the usage of the expensive compressor units.
Implementation attempts of the electro-submersible pumping units as units lifting solution has been used in the 80-s, but due to short working life of such units and unavailability of the standard size ranges this works was stopped. Today by the NMMC's subdivisions have been gained wide experience on qualitative maintenance of the submersible pumping units, this increase interval between failures of the pumping units up to 12000 hours, by comparison in 2000-2002 years the interval between failures was 2500 hours. Currently at NMMC' subdivisions are used the submersible pumping units of the following companies: Oddesse (Germany), Grundfos (Denmark, Germany), Wilo (Germany), Impo (Turkey).
After lifting on daylight the productive solutions using pumps on the lines of process pipelines are going to sorption treatment. Uranium sorption from productive solutions is made by ion exchange resin Purolite A-606 (England), BD-706, B0-020 (China) at the ionexchange columns. Uranium poor solution (mother solution) passed the sorption treatment has been reinforced by reagent and returned back on production sites for injection wells feed for further uranium leaching. Enriched ion exchange resin is sent to desorption column, executed by sulfuronitrate solutions. Uranium extractions from industrial reclaim is carried out by ammonia water by cascade precipitation on pH defined value. For separation from solution precipitated uranium is passed through filter-press. After filtration the yellow cake is dissolved at sulphuric acid solution until the formation of the sulphuric salts, which are intermediate product of the underground leaching process. Further sulfuric salts from subdivisions have been delivered to Hydrometal-lurgical Plant #1, where dissolved uranium has got extraction concentrating using organic extractant. Uranium rich organic phase is passed re-extraction by carbonate and ammonium bicarbonate mix. Obtained pulp from crystals of the ammonium-uranyl-three-carbonate after decontamination has been delivered to filtration. Further filtered crystals will be roasted until the end product formation in the form of uranium oxide concentrate. Uranium oxide concentrate, produced at NMMC is exporting
to foreign countries fully, that consistently provides NMMC for foreign currencies. In order to provide the scale-up uranium production outputs, NMMC specialists works hard on exploration and continually going into operation of the new deposits. New deposits are characterized by bigger depth of the ore formation, as was mentioned previously and higher rock carbonate content of the ore-hosting deposits. The carbonate content indicator of the old deposits is not exceed 0,6-1,0%, and at new sites carbonate content indicator is more than 2%, ran up at some sites 10-12%. In this case using of the sulphuric acid as leaching reagent is not technically and economically reasonable, whereas the communication the carbonates with sulphuric acid results in reduction of the filtration properties of the waterbearing ore-hosting bed and impossibility of the uranium extraction in future.
Today we are monitoring the reserves classified as off-balance, whereas there are available positive results of the ore development with increased carbonate content on the Aulbek deposit.
There are carried out development works on the Maylisay, Northern Kanimeh and Yogdu deposits. At the same time planned uranium extraction ratio is unchanged. Increasing of the ore body formation depth from 110 to 550 meters and mean effective power of the ore-hosting water bearing beds from 12 to 20 meters as well as reduction of the value per surface unit of the open ore bodies adversely affected on ore deposits development. The main cause is the uranium impoverishment at product solutions, as well as actual power increase of the ore-hosting water-bearing beds caused on high reagents consumption used for uranium extraction. Currently the specialists of the NMMC and Research Institutes of the Republic of Uzbekistan carried out the works on identification the most effective technical procedure for the processing of above mentioned deposits. Development of the infiltration uranium deposits by the underground leaching method had been considered as monogene at the initial period. Later has been ascertained that single elements accumulated in process solutions of the underground leaching and can be extracted as by-product. Based on market data rhenium, molybdenum and other rare-earth elements are one of the perspective by-products. At the NMMC's Mining Administration № 5 and Northern Mining Administrations is extracted rhenium as by-product from tail solutions of the geo-technologi-cal sites of the underground leaching. Special attention is given to environmental protection questions. During development by underground leaching method the key source ofpollution are process solution spillages on loss-
of-piping integrity, hole washing leakages, solution spillage on submersible pumping, slime and core on making holes, residual solutions in production sections as well as their spreading into water-bearing grounds and others. Herewith the main polluted objects are atmospheric air, ground, surface and mostly underground waters. Simultaneous operations monitoring for environmental conditions is the environment-related activity of the NMMC management.
This makes it possible to establish influence on atmospheric air, water reservoirs, soil covering and flora, as well as to determine qualitative and quantity characteristics of the contaminants and to monitor the compliance of the adjusted standards of the maximum permissible emissions and discharges the hazardous substances.
Soil covering protection: at desert and semiarid climate zone on blown and semi-blown sands on wind ward are build the countershafts from native soil and covered by restraining material. All process wells equipped by hatchways those excepts their leaking on overflow. Solutions flushing on cleaning and hole washing is made in special reservoirs for settling and subsequent return in holes.
Surface water protection: For protection of the water bodies there provided relevant engineering constructions as crown ditches, by-pass canals, barrages, transfers and others), excludes their pollution and providing allocation water recourses as well as safety process equipment and communication lines. In the presence of water zones at the underground leaching areas there are formed the water quality monitoring stations, which placed at three zones: internal (within the balance emplacement), peripheral (on 20 meters from internal), and regional (side with peripheral zone). Data observed on perimeter inspection holes, placed on productive waterbearing horizons, suggests that on all underground leaching zones independently of applied process layout out of 200-300 meters from ore deposit circuit the natural background edge waters remains unchanged. Radiation control is conducted by working conditions supervisory services and environment protection services, as well as sanitary-industrial laboratories, territorial and central organization of the State Committee for Health Supervision, State Committee for Ecology, State Inspection «Sanoatkontechnazorat». NMMC's many years' experience on underground leaching method confirms its high performance and environmental safety, which expands implementation area. Market conditions demand considerable relations for technical excellence of all uranium production components and their cost re-
Development of Algorithm of process management of ore enrichment in fluidizated layer
duction. In this regard by NMMC specialists has been developed economic uranium extraction development program until 2020 year and have been implemented some measures:
- Bridging into service of the new perspective deposits;
- Modernization of the existing sulfate plant and construction of the new one;
- Construction and start-up in 2013-2016 new underground leaching deposits under North Kanimeh and Sugrali deposits;
- Reconstruction of the shop # 3 of the Hydrometal-lurgical plant # 1;
- Development of the program shall guarantee stable growth of the uranium production output at NMMC until 2020.
Yunusov Bokhodir, senior teacher
chair «Informatics, automation and managements», Tashkent chemical institute of technology, Tashkent, Uzbekistan E-mail: [email protected]
Development of Algorithm of process management of ore enrichment in fluidizated layer
Abstract: The automated installation with the device of multicell separation of loose material is developed, with algorithm of intellectual management air separation process in a fluidizated layer of the crushed particles of the different limiting sizes and offered a function chart of an automated control system by process of an air separation of loose materials in a fluidizated layer. For this purpose using Archimedes, Lyashchenko and Reynolds's criteria, algorithmization of calculation of speeds the beginning of a fluidization and an ablation ofparticles of different density and is carried out the sizes, the formalized equations allowed creation of computer model of process of an air separation of firm particles in a fluidizated layer with use of a package applied the MATLAB programs. Nomograms of change of speed of gas depending on density and the sizes of particles of separated loose material are received.
Keywords: mathematical model, air separation, beginning of speed fluidization, speed of ablation, algorithm of management, automated control system.
Application of methods of an air separation at enrichment of ores of rare and precious metals is caused by that use of traditional methods are accompanied by big power consumption and water.
Technological installation of an air separation offered by us in a fluidizated layer analyzed by use of the multistage system analysis [1].
For the bottom hierarchical level process of moving of particles is defined. For this purpose, considering the forces influencing a particle, possible movings of certain particles are defined. Thus, it is possible to find equilibrium speed of a stream, at which particles of a certain weight will be is in a scaled condition [2-5].
For particles of the identical size ablation from the device depends on weight (specific weight) of particles.
Calculations defined speed of an air stream for a conclusion of a particle of easy weight. The maximum
limit of this speed should not reach the speed deducing particles with heavy weight.
By fluidizated consideration with use of the criterion equations, is defined possibilities of creation of a fluidizated layer and questions of determination of speed of ablation of particles.
Considering disorder of the sizes of particles, defined equivalent diameter of a particle. Knowing equivalent diameter, it is possible to define speed of the beginning of a fluidizated and to pass to definition of criterion of Archimedes. Then, it is possible to define Reynolds's criterion for a fluidizated layer.
Reynolds's criterion for a particle is defined by the classical equation according to which it is possible to define speed of a fluidizated or speed of a ablation of particles.
If speed is known, it is possible to define a consumption of gas.
