INTERNATIONAL ATOMIC ENERGY AGENCYINTERNATIONAL ATOMIC ENERGY AGENCYTechnical Meeting on Low Grade Uranium OreTechnical Meeting on Low Grade Uranium Ore

29 29 –– 31 March 2010, Vienna, Austria31 March 2010, Vienna, Austria

Pa Pa LuaLua low grade uranium ore leaching low grade uranium ore leaching by mixing and curing with sulfuric acidby mixing and curing with sulfuric acid

Than Van Lien, Le Than Van Lien, Le QuangQuang Thai, Le Thai, Le ThiThi Kim Dung, Doan Kim Dung, Doan ThiThi Mo, Tran The Mo, Tran The DinhDinh, et al., et al.

Institute for Technology of Radioactive and Rare Elements. Institute for Technology of Radioactive and Rare Elements. 48, 48, LanghaLangha –– DongDaDongDa -- Hanoi Hanoi -- Vietnam.Vietnam.

Email: tvlien59Email: tvlien59@yahoo.com.vn@yahoo.com.vn

Contents to IntroduceContents to Introduce1.1. Introduction;Introduction;

2.2. Experimental Procedure; Experimental Procedure;

3.3. Results and discussion;Results and discussion;

4. Conclusions;4. Conclusions;

IntroductionIntroduction�� Uranium Uranium exploratonexploraton in selected areas of Vietnam began in in selected areas of Vietnam began in

1955. Since 1978, a systematic regional 1955. Since 1978, a systematic regional exlorationexloration programmeprogrammehave been underway throughout the entire country. From 1997 have been underway throughout the entire country. From 1997 up to now exploration activities are concentrated on project: up to now exploration activities are concentrated on project: exploration of sandstone terrain in exploration of sandstone terrain in PaluaPalua, , TabhingTabhing and Ben and Ben GiangGiang areas, in the western of areas, in the western of NongNong Son basin, Son basin, QuangQuang Nam Nam province province –– the middle of Vietnamthe middle of Vietnam

�� Vietnam uranium speculative resources are estimated at Vietnam uranium speculative resources are estimated at �� 230 000 230 000 tUtU, of which 100 000 , of which 100 000 tUtU from sandstone ores in from sandstone ores in NongNong

Son basinSon basin. .

�� The uranium ore The uranium ore proccessingproccessing are conducted only in Institute are conducted only in Institute for Technology of Radioactive and Rare elements for Technology of Radioactive and Rare elements ..

IntroductionIntroduction�� Vietnam economic growth has lead to raising energy Vietnam economic growth has lead to raising energy

demand, so development of nuclear powder is one of priorities. demand, so development of nuclear powder is one of priorities. In this context, Vietnam government had planed to build the In this context, Vietnam government had planed to build the first nuclear powder plant in order to put it into generation infirst nuclear powder plant in order to put it into generation inthe year of 2020the year of 2020. .

�� In this context, continuing research for completion and In this context, continuing research for completion and selection of the most appropriate technology for uranium ore selection of the most appropriate technology for uranium ore processing in Vietnam is extremely necessary and crucial. processing in Vietnam is extremely necessary and crucial.

�� This is in line with the development trend in the world andThis is in line with the development trend in the world and at at the same time helps gradually produce locally fuel for nuclear the same time helps gradually produce locally fuel for nuclear power plants.power plants.

Introduction (cont)Introduction (cont)�� The project entitled: The project entitled: ““Pa Pa LuaLua low grade uranium ore low grade uranium ore leaching by mixing and curing with sulfuric acidleaching by mixing and curing with sulfuric acid””, was set , was set up to conduct additional researches on several technical up to conduct additional researches on several technical issues of mixing and curing with acid and washing to issues of mixing and curing with acid and washing to recover uranium from sandstone ores in Pa recover uranium from sandstone ores in Pa LuaLua area, area, QuangQuang Nam province Nam province -- Vietnam to complete a set of data Vietnam to complete a set of data in ore processing procedure, to develop an appropriate in ore processing procedure, to develop an appropriate technological procedure for ore processing, calculating technological procedure for ore processing, calculating and designing several main equipments based on the and designing several main equipments based on the data obtained from the project and previous ones. data obtained from the project and previous ones.

Concerned oresConcerned ores�� Sandstone ores used in the research have different weatheriSandstone ores used in the research have different weathering ng

degrees. Sizes of nondegrees. Sizes of non--weathered and semiweathered and semi--weathered ores are pretty weathered ores are pretty large, mostly over 20 cm. Weathered ore is under the powder formlarge, mostly over 20 cm. Weathered ore is under the powder forms.s.

�� MainMain mineralsminerals ofof thisthis sandstonesandstone ore are ore are quartzquartz ((SiOSiO22), ), albitealbite((NaAlSiNaAlSi33OO88), ), glauconiteglauconite ((((K,NaK,Na)(Fe)(Fe+3+3,,Al,MgAl,Mg))22((Si,AlSi,Al))44OO1010(OH)(OH)22), ), calcitecalcite((CaCOCaCO33), ), kaolinitekaolinite ((AlAl22SiSi22OO55(OH)(OH)44), ), sericitesericite (K(K22O.O.3Al3Al22OO33..6SiO6SiO22.2H.2H22O), O), illiteillite ((KH((KH33O)O)AlAl22SiSi33AlOAlO1010(OH)(OH)22), ), sideritesiderite ((FeCOFeCO33), ), sphenesphene((CaO.SiOCaO.SiO22..TiOTiO22). ). Mineral containing uranium is mainly Mineral containing uranium is mainly NasturanNasturan((U,Th)O((U,Th)O22.(O.(O0,50,5--33)UO)UO33.xPbO)..xPbO).

�� Uranium content in the ore is about 0.053 Uranium content in the ore is about 0.053 –– 0.058%. The most 0.058%. The most abundant impurities are silica (average 75%), aluminum (>5%), irabundant impurities are silica (average 75%), aluminum (>5%), iron on (1%), potassium, sodium and alkaline metals (calcium in the non(1%), potassium, sodium and alkaline metals (calcium in the non--weathered ores even reaches >0.9%) and many other impurities. weathered ores even reaches >0.9%) and many other impurities. Distribution of uranium based on particle sizes is relatively unDistribution of uranium based on particle sizes is relatively uniform.iform.

�� NonNon--weathered and semiweathered and semi--weathered ores need to be crushed into weathered ores need to be crushed into particle sizes appropriate for chemical treatment.particle sizes appropriate for chemical treatment.

Experimental ProcedureExperimental ProcedureFrom investigated results have built experimental From investigated results have built experimental procedure for leaching of mixing and curing on a procedure for leaching of mixing and curing on a scale of 3 scale of 3 tonnestonnes ores /batch:ores /batch:�� Ores:3 Ores:3 tonnestonnes / batch/ batch

�� Chemical: HChemical: H22SOSO44, 96%, MnO, 96%, MnO22, 75%, Water,, 75%, Water,……

�� Equipments: Mixer, pump, ..Equipments: Mixer, pump, ..

Experimental Procedure (cont)Experimental Procedure (cont)

Mixing – curing: 3 days

Ore H2SO4 40% (solution)MnO2 4kg/ton ore

Washing H2SO4 solution pH=2

Tailings Urani sulfate solution

Experimental Procedure (cont)Experimental Procedure (cont)

WaterH2SO4 concentrated

MnO2

Crushed ore and powder

WaterH2SO4 concentrated

MixingCuring and Washing

Ponds containing leaching solution

ModelizationModelization for mixingfor mixing--curing leaching equipmentcuring leaching equipment

Results and discussionResults and discussion2.1. Crushing ores and calculating energy for 2.1. Crushing ores and calculating energy for crushing;crushing;

2.2. Recreating fine ores;2.2. Recreating fine ores;

2.3. Mixing and curing;2.3. Mixing and curing;

2.4. Washing for uranium recovery.2.4. Washing for uranium recovery.

Crushing ores and calculating Crushing ores and calculating energy for crushingenergy for crushing

�� For crude pieces of ores (>10 cm), it is needed to crush For crude pieces of ores (>10 cm), it is needed to crush according to two levels (using crusher). In the first level, sizaccording to two levels (using crusher). In the first level, size is e is decreased to <10 cm, then in the second level, the size is decreased to <10 cm, then in the second level, the size is decreased to appropriate size for mixing and curing stage. decreased to appropriate size for mixing and curing stage.

�� When comparing grinding features of nonWhen comparing grinding features of non--weathered and semiweathered and semi--weathered ores, it is shown that porosity of nonweathered ores, it is shown that porosity of non--weathered ore is weathered ore is larger than that of semilarger than that of semi--weathered one. In addition, nonweathered one. In addition, non--weathered weathered ores have less hardness. Most ore particles after crushing have ores have less hardness. Most ore particles after crushing have their their size bigger than 0.6 mm. Portion of fine particles that can caussize bigger than 0.6 mm. Portion of fine particles that can cause clog e clog in the ore column accounts for relatively low, less than 10%. in the ore column accounts for relatively low, less than 10%.

�� Therefore this portion needs to be aggregated into bigger size Therefore this portion needs to be aggregated into bigger size depends on their impacts to the further treatment stages. The depends on their impacts to the further treatment stages. The smaller width of the voids, the higher fine portion. It is possismaller width of the voids, the higher fine portion. It is possible to ble to reduce the amount of fine ore by selecting an appropriate crushireduce the amount of fine ore by selecting an appropriate crushing ng condition that is without adjustment of the width of crushing gacondition that is without adjustment of the width of crushing gap to a p to a certain value and with circulation of crude ore portion. Howevercertain value and with circulation of crude ore portion. However, it is , it is also needed to pay attention to energy consumption and any raisealso needed to pay attention to energy consumption and any raised d issue. issue.

Crushing ores and calculating Crushing ores and calculating energy for crushing (cont)energy for crushing (cont)

�� For nonFor non--weathered and semiweathered and semi--weathered ores, to produce ore weathered ores, to produce ore particles appropriate to heap leaching, using jaw crushing is thparticles appropriate to heap leaching, using jaw crushing is the e most appropriate. In order to get the ore with appropriate size most appropriate. In order to get the ore with appropriate size for for mixing and washing, appropriate width of the gaps between mixing and washing, appropriate width of the gaps between crushing bars in the second level is 20 mm.crushing bars in the second level is 20 mm.

�� For sandstone ore with average hardness, energy consumption for For sandstone ore with average hardness, energy consumption for crushing 1 tone of ore with sizes reduced from 20 cm to 2cm is crushing 1 tone of ore with sizes reduced from 20 cm to 2cm is 0.46KW. 0.46KW.

�� However, in reality, depending on productivity of the equipHowever, in reality, depending on productivity of the equipment ment and operation, the real energy consumption may increase in and operation, the real energy consumption may increase in comparison to the above calculated values. Results of calculatiocomparison to the above calculated values. Results of calculation of n of consumed crushing energy will be used as basis for calculating consumed crushing energy will be used as basis for calculating capacity and productivity of crusher.capacity and productivity of crusher.

��

Recreating fine oresRecreating fine ores�� The purpose of this process is to make ore portion of fine pThe purpose of this process is to make ore portion of fine particles articles

become particles with size large enough to ensure that washing become particles with size large enough to ensure that washing process is not disturbed due to clogging or blocking the flow ofprocess is not disturbed due to clogging or blocking the flow ofsolution. solution.

�� In addition, particles need to remain stable in leaching meIn addition, particles need to remain stable in leaching medium of dium of acid. Efficiency of leaching uranium needs to be at an acceptablacid. Efficiency of leaching uranium needs to be at an acceptable e degree without considerable impacts to the total efficiency of degree without considerable impacts to the total efficiency of uranium recovery from the ores. uranium recovery from the ores.

�� When investigating factors impacting to the process of recrWhen investigating factors impacting to the process of recreation eation of particles, it is shown that necessary moisture content is 15 of particles, it is shown that necessary moisture content is 15 -- 16% 16% and duration of 14 and duration of 14 -- 16 minutes is needed. 16 minutes is needed.

�� For the ore with size of For the ore with size of --300 300 µµm, the amount of liquid glass as m, the amount of liquid glass as adhesive appropriate for each type of nonadhesive appropriate for each type of non--weathered, semiweathered, semi--weathered and weathered ores are 6.9%; 6% and 4% weathered and weathered ores are 6.9%; 6% and 4% correspondingly. correspondingly.

Recreating fine oresRecreating fine ores (cont)(cont)�� To strengthen ability of solidifying of the obtained pellets, NaTo strengthen ability of solidifying of the obtained pellets, Na22SiFSiF66 is is

added with the rate of 1%. Mixing of these agents is selected foadded with the rate of 1%. Mixing of these agents is selected for r research because they create pellets with certain stability afteresearch because they create pellets with certain stability after r mixing and curing with strong acid while other agents do not havmixing and curing with strong acid while other agents do not have e these characteristics. As results of trial of immersing in acid,these characteristics. As results of trial of immersing in acid, ore ore pellets obtained in appropriate condition are as follows.pellets obtained in appropriate condition are as follows.

�� Table 1: Table 1: Efficiency of uranium leaching and degree of particle Efficiency of uranium leaching and degree of particle broken down when creating particle in appropriate conditions:broken down when creating particle in appropriate conditions:

Recreating fine oresRecreating fine ores (cont)(cont)�� Thus, after pelletizing, efficiency of uranium recovery partThus, after pelletizing, efficiency of uranium recovery partly ly

reduces while acid consumption considerably increases (e.g. reduces while acid consumption considerably increases (e.g. ordinary nonordinary non--weathered ore when mixed and cured just consumes weathered ore when mixed and cured just consumes 50 kg acid/ ton of ore, but after pelletizing, this figure incre50 kg acid/ ton of ore, but after pelletizing, this figure increases to ases to 95 kg/ton of ore to reach uranium recovery over 75%. 95 kg/ton of ore to reach uranium recovery over 75%. Correspondingly, for semiCorrespondingly, for semi--weathered ores weathered ores -- 35 kg/ton of ore 35 kg/ton of ore -- 80 80 kg/ton of ore kg/ton of ore -- 66%). Degree of complete breaking down of pellets is 66%). Degree of complete breaking down of pellets is in the acceptable range. The bigger initial ore particles, the min the acceptable range. The bigger initial ore particles, the more ore cost of agents and the more difficult pelletizing. cost of agents and the more difficult pelletizing.

�� Based on the above research results, in case it is necessaryBased on the above research results, in case it is necessary to to pelletize, only portion of ore with particle sizes less than 0,3pelletize, only portion of ore with particle sizes less than 0,3 mm mm needs to be pelletized. In that case, it is acceptable that acidneeds to be pelletized. In that case, it is acceptable that acidconsumption increase not much while efficiency of uranium consumption increase not much while efficiency of uranium decreases a bit. decreases a bit.

�� If the ore contains a large portion of fine particles, the uIf the ore contains a large portion of fine particles, the use of this se of this method needs to be reconsidered because the efficiency of uraniumethod needs to be reconsidered because the efficiency of uranium m recovery is impacted considerably. Moreover, high acid consumptirecovery is impacted considerably. Moreover, high acid consumption on and high operational cost can cause the increase of production and high operational cost can cause the increase of production price. price.

Mixing and curingMixing and curing�� Several parameters related to ore mixing, curing and washinSeveral parameters related to ore mixing, curing and washing g

processes such as capability of water retention, void volume of processes such as capability of water retention, void volume of the the heap etc. are paid attention to. In the ore body, water can be heap etc. are paid attention to. In the ore body, water can be in the in the capillaries of ore particles, in the gap among ore particles andcapillaries of ore particles, in the gap among ore particles and stick stick on the surface of particles and the wall of columns. For each oron the surface of particles and the wall of columns. For each ore e particle size, the following parameters are determined (Table 2)particle size, the following parameters are determined (Table 2). . According to the results, the larger ore particles, the less watAccording to the results, the larger ore particles, the less water er retention; therefore, it is very difficult to carry out mixing aretention; therefore, it is very difficult to carry out mixing and curing nd curing process. process.

�� Table 2.Table 2. Capability of remaining water and void volume of all types Capability of remaining water and void volume of all types of ores according to sizes of ore particlesof ores according to sizes of ore particles

Mixing and curingMixing and curing (cont)(cont)�� However, if ore body consists of many degrees of particle siHowever, if ore body consists of many degrees of particle size ze

with a certain ratio ( for example, ore with distribution as menwith a certain ratio ( for example, ore with distribution as mentioned tioned in the Table 3 used in the research), due to the mixing of diffein the Table 3 used in the research), due to the mixing of different rent ore sizes, degree of water retention and bulk density change (Taore sizes, degree of water retention and bulk density change (Table ble 4), creating a favorable condition for reaction. 4), creating a favorable condition for reaction.

�� Table 3.Table 3. Distribution of particle size is usedDistribution of particle size is used

Mixing and curingMixing and curing (cont)(cont)�� Determining water retention of ores allows us to calculate Determining water retention of ores allows us to calculate

necessary amount of water during mixing and curing with strong necessary amount of water during mixing and curing with strong acids. acids.

�� During mixing and curing process, only a small part of acid During mixing and curing process, only a small part of acid is is used to dissolve minerals containing uranium while most part of used to dissolve minerals containing uranium while most part of the the acid is consumed by other minerals present in the ore, especiallacid is consumed by other minerals present in the ore, especially y carbonate (as in the case of noncarbonate (as in the case of non--weathered ore). Specific acid weathered ore). Specific acid consumptions for each type of ores are as follows: nonconsumptions for each type of ores are as follows: non--weathered weathered ––50 kg/ton, semi50 kg/ton, semi--weathered weathered –– 35 kg/ton and weathered ore 35 kg/ton and weathered ore –– 30 30 kg/ton. kg/ton.

�� If ore contains different minerals, acid consumption will beIf ore contains different minerals, acid consumption will be higher higher than the average value that is calculated according to the certathan the average value that is calculated according to the certain in ratio. ratio.

�� For example, acid consumption of 46 kg/ton is needed for thFor example, acid consumption of 46 kg/ton is needed for the ore e ore containing noncontaining non--weathered and semiweathered and semi--weathered parts with a ratio of weathered parts with a ratio of 1/1. 1/1.

Mixing and curingMixing and curing (cont)(cont)�� After mixing and curing with strong acid, initial ore partiAfter mixing and curing with strong acid, initial ore particles are cles are

broken down into smaller sizes, especially for nonbroken down into smaller sizes, especially for non--weathered ore. weathered ore. Degree of breaking down depends on initial level of particle sizDegree of breaking down depends on initial level of particle size, e, acid concentration, duration of curing and degree of weathering.acid concentration, duration of curing and degree of weathering.Therefore, degree of water retention as well as other parametersTherefore, degree of water retention as well as other parameters of of ore residues changes a lot. ore residues changes a lot.

�� Now, different levels of particle size stick together leadiNow, different levels of particle size stick together leading to the ng to the increase of water retention and the decrease void volume (see increase of water retention and the decrease void volume (see Table 5). Table 5).

�� However, the ratio of fine particles (<0.3 mm) almost does However, the ratio of fine particles (<0.3 mm) almost does not not increase. Obviously, when reacting with strong acid during mixinincrease. Obviously, when reacting with strong acid during mixing g and curing, some products from reaction under the form of and curing, some products from reaction under the form of precipitant such as calcium sulfate. SiOprecipitant such as calcium sulfate. SiO22 etc... aggregate fine etc... aggregate fine particles together or with larger particles. particles together or with larger particles.

�� This is an advantage for washing uranium in the next stage. This is an advantage for washing uranium in the next stage. ��

Mixing and curingMixing and curing (cont)(cont)�� Table 4.Table 4. Degree of water retention and void volume of ores with Degree of water retention and void volume of ores with

many degrees of particle sizesmany degrees of particle sizes

�� Table 5.Table 5. Some features of ore tailingsSome features of ore tailings

Mixing and curingMixing and curing (cont)(cont)�� When investigating affect of oxidants to the efficiency of uraniWhen investigating affect of oxidants to the efficiency of uranium um

dissolution, it is found that in nondissolution, it is found that in non--weathered and semiweathered and semi--weathered weathered ores, a part of uranium existing under the form of U (IV) cannotores, a part of uranium existing under the form of U (IV) cannotdissolve in acid solution. dissolve in acid solution.

�� Therefore, it is needed to have an amount of oxidant to mainTherefore, it is needed to have an amount of oxidant to maintain tain iron concentration (Fe III) to supply for oxidizing reaction of iron concentration (Fe III) to supply for oxidizing reaction of U (IV). U (IV). The appropriate amount of oxidant is around 3 kg/ton. The appropriate amount of oxidant is around 3 kg/ton.

�� After being mixed with acid, the mixture is cured for 3 daysAfter being mixed with acid, the mixture is cured for 3 days. It is . It is important that only after curing process is completed, the wholeimportant that only after curing process is completed, the whole ore ore body is moved to columns or heaps to rinse for uranium recovery.body is moved to columns or heaps to rinse for uranium recovery.

�� If the ore is placed into the column right after completion If the ore is placed into the column right after completion of curing, of curing, the ore body. the ore body.

Washing for uranium recoveryWashing for uranium recovery�� After trials of options for washing ores that are mixed and cureAfter trials of options for washing ores that are mixed and cured with d with

acid, it is found that the technique using batch washing should acid, it is found that the technique using batch washing should be be used in combination with leaching. Based on this technique, at used in combination with leaching. Based on this technique, at several initial washing times, the solution has pH value of 1. several initial washing times, the solution has pH value of 1.

�� When each washing time is completed, the solution appears at theWhen each washing time is completed, the solution appears at thebottom of the column. When the solution mostly doesnbottom of the column. When the solution mostly doesn’’t flow, it is the t flow, it is the time to continue washing. Solutions with higher pH or clean watetime to continue washing. Solutions with higher pH or clean water r are used for washing residues. are used for washing residues.

�� In the first washing times, total amount of solution released frIn the first washing times, total amount of solution released from the om the column will be smaller than the total amount of solution providecolumn will be smaller than the total amount of solution provided to d to the column because a part of solution is remained to maintain the column because a part of solution is remained to maintain moisture content (the moisture content of residues increases) anmoisture content (the moisture content of residues increases) and d time for the solution to break through the column will be longertime for the solution to break through the column will be longer than than that of the further times of washing. that of the further times of washing.

Washing for uranium recoveryWashing for uranium recovery (cont)(cont)�� This technique allows saving retention time of solution in tThis technique allows saving retention time of solution in the ore he ore

body so that reaction continues and amount of water needed is body so that reaction continues and amount of water needed is reduced. reduced.

�� Efficiency of uranium increases. For example, for nonEfficiency of uranium increases. For example, for non--weathered weathered ore and semiore and semi--weathered ore, efficiency of uranium recovery can be weathered ore, efficiency of uranium recovery can be 78% and 84.3% respectively while if solution with pH=2, is 78% and 84.3% respectively while if solution with pH=2, is continuously rinsed, corresponding efficiencies can be 73.1% andcontinuously rinsed, corresponding efficiencies can be 73.1% and81.6%. The rate of washing is controllable.81.6%. The rate of washing is controllable.

�� Although after mixing and curing, all levels of particle siAlthough after mixing and curing, all levels of particle sizes are zes are more even than that of direct leaching on the column, it is more even than that of direct leaching on the column, it is unavoidable that there is a phenomenon in which residues of crudunavoidable that there is a phenomenon in which residues of crude e ore stick together in one place and fine particles stick togetheore stick together in one place and fine particles stick together in r in another place causing inconsistence. another place causing inconsistence.

�� In the primary study, if the flow rate of washing is gettinIn the primary study, if the flow rate of washing is getting higher, g higher, solution is getting more priority to go through ore body with lasolution is getting more priority to go through ore body with large rge size and vice verse. Only when the flow rate is in a certain ransize and vice verse. Only when the flow rate is in a certain range, ge, flow of solution will be likely consistent in the ore body flow of solution will be likely consistent in the ore body

Washing for uranium recoveryWashing for uranium recovery (cont)(cont)

Ficgure 1. Effect of washing flow rate on uraium recovering efficiency (non-weathered ore)

01020304050607080

0,00E+00 2,00E-05 4,00E-05 6,00E-05 8,00E-05 1,00E-04Flow rate of solution (m/s)

Recov

ering

effic

iency

U (%)

Washing for uranium recoveryWashing for uranium recovery (cont)(cont)

Ficgure 2. Washing curve for uranium recovery

0,00,51,01,52,02,53,03,54,0

0 0,2 0,4 0,6 0,8 1 1,2 1,4Volume (L/S ratio)

U con

centra

tion (

g/l)

Non-weatheredSemi-weathered

Washing for uranium recoveryWashing for uranium recovery (cont)(cont)�� Therefore, the flow rate of washing is the most affecting fTherefore, the flow rate of washing is the most affecting factor to actor to

washing process. washing process.

�� When trying with nonWhen trying with non--weathered ore which is mixed and cured as weathered ore which is mixed and cured as well as continuous rinsed with the total volume of solution reacwell as continuous rinsed with the total volume of solution reaches a hes a ratio of L/R = 1/1v (L/R = liquid/solid).ratio of L/R = 1/1v (L/R = liquid/solid).

�� Diagram in the Figure 1 shows that only in a certain appropDiagram in the Figure 1 shows that only in a certain appropriate riate flow rates (around 6.00Eflow rates (around 6.00E--05 05 m/sm/s); efficiency of uranium recovery ); efficiency of uranium recovery reaches the highest value at 73.1%. reaches the highest value at 73.1%.

Washing for uranium recoveryWashing for uranium recovery (cont)(cont)�� Flow rate depends on particle size. The finer ore particles, theFlow rate depends on particle size. The finer ore particles, the

lower flow rate. lower flow rate.

�� For instance, for mixed ores consisting of 3 types of nonFor instance, for mixed ores consisting of 3 types of non--weathered, semiweathered, semi--weathered and weathered ores with a ratio of weathered and weathered ores with a ratio of 1/1/1, in the first washing time, flow rate from outlet of the c1/1/1, in the first washing time, flow rate from outlet of the column olumn just reaches 1.9Ejust reaches 1.9E--05 05 m/sm/s, and then increases more and more in the , and then increases more and more in the next washing times. For such fine ores like the above ones, flownext washing times. For such fine ores like the above ones, flow rate rate also depends on the height of ore layer. also depends on the height of ore layer.

�� The higher height, the more pressed the ore. Because void spThe higher height, the more pressed the ore. Because void space ace is very small, the flow of solution is also blocked. Therefore, is very small, the flow of solution is also blocked. Therefore, flow flow rate also is much decreased (for the height of 5 meters, the florate also is much decreased (for the height of 5 meters, the flow rate w rate of the first washing time only reaches 7.78Eof the first washing time only reaches 7.78E--06 06 m/sm/s). Time for ). Time for washing also increases considerably when the height of ore layerwashing also increases considerably when the height of ore layerincreases.increases.

��

Washing for uranium recoveryWashing for uranium recovery (cont)(cont)�� During washing process, uranium and dissolved substances arDuring washing process, uranium and dissolved substances are e

rinsed right in the first time (see Figure 2. 3 and 4). Results rinsed right in the first time (see Figure 2. 3 and 4). Results show show that the change of concentration and amount of dissolved that the change of concentration and amount of dissolved substances almost takes place with a total volume of solution atsubstances almost takes place with a total volume of solution at the the L/R ratio of 1/3. L/R ratio of 1/3.

�� After that, though more amount of solution is needed, the amAfter that, though more amount of solution is needed, the amount ount of dissolved uranium obtained is only some percentages. Thereforof dissolved uranium obtained is only some percentages. Therefore, e, to decrease solution consumption and increase uranium to decrease solution consumption and increase uranium concentration, the part of dilute solution needs to be circulateconcentration, the part of dilute solution needs to be circulated in the d in the next columns. next columns.

�� The part of high concentration is moved to the next treatment stThe part of high concentration is moved to the next treatment stage age as ion exchange and consequently, precipitation to get technicalas ion exchange and consequently, precipitation to get technicaluranium products.uranium products.

Washing for uranium recoveryWashing for uranium recovery (cont)(cont)

Ficgure 3. Iron washing curve

05

1015202530

0 0,2 0,4 0,6 0,8 1 1,2 1,4Volume (L/S ratio)

Fe co

ncentr

ation (

g/l)

Non-weatheredSemi-weathered

Washing for uranium recoveryWashing for uranium recovery (cont)(cont)

Ficgure 4. Accumulative percentage of recovered uranium with solution volume

0102030405060708090

100

0 0,2 0,4 0,6 0,8 1 1,2 1,4Volume (L/S ratio)

Accum

ulative

perce

ntage

of rec

overed

U (%

)

Non-weatheredSemi-weathered

Washing for uranium recoveryWashing for uranium recovery (cont)(cont)�� Trial of processing ore on a scale of 500 kg/batch with mixtTrial of processing ore on a scale of 500 kg/batch with mixture of ure of

nonnon--weathered, semiweathered, semi--weathered and weathered ores at the ratio of weathered and weathered ores at the ratio of 1/1/1 (height of ore layers in the washing column is up to 500 1/1/1 (height of ore layers in the washing column is up to 500 kg/batch) took place in a completely favorable condition. kg/batch) took place in a completely favorable condition.

�� Washing is carried out with two stages, 6 times of washing Washing is carried out with two stages, 6 times of washing without clogs of the column. Consumption of water when washing iwithout clogs of the column. Consumption of water when washing is s just 1/3 of the weight of treated ores. Efficiency of uranium rejust 1/3 of the weight of treated ores. Efficiency of uranium recovery covery reaches 85reaches 85--90 %. Obtained solution contains around 1.2 g U/L.90 %. Obtained solution contains around 1.2 g U/L.

�� After processing, the result obtained by using After processing, the result obtained by using AmberlteAmberlte IRAIRA--420 420 resin in static column system, then followed by precipitation byresin in static column system, then followed by precipitation byagents Hagents H22OO22 and NHand NH44OH, technical uranium with high quality (80% OH, technical uranium with high quality (80% UU33OO88 and low contents of other metal impurities). and low contents of other metal impurities).

ConclusionsConclusions�� Using option of crushing at 2 levels in which the width of crushUsing option of crushing at 2 levels in which the width of crushing ing

gap at the second level of 20 mm is appropriate, can reduce the gap at the second level of 20 mm is appropriate, can reduce the amount of fine ores. Energy consumption for this stage is 0.46 amount of fine ores. Energy consumption for this stage is 0.46 KW/ton of ore.KW/ton of ore.

�� Regenerating particles in the portion of fine sizes which createRegenerating particles in the portion of fine sizes which creates s relatively stable particles in acid medium will have an ability relatively stable particles in acid medium will have an ability to avoid to avoid clogging in the column when washing. However, this will cause thclogging in the column when washing. However, this will cause the e increase of acid consumption and partly decrease efficiency of increase of acid consumption and partly decrease efficiency of uranium recovery, especially for semiuranium recovery, especially for semi--weathered and weathered weathered and weathered ores. The larger initial size of ore particles, the higher degreores. The larger initial size of ore particles, the higher degree of this e of this change. This stage should only be applied for weathered ores witchange. This stage should only be applied for weathered ores with h fine particles less than 0.3 mm on a scale in which the column ifine particles less than 0.3 mm on a scale in which the column is s high. high.

ConclusionsConclusions (cont)(cont)�� During mixing and curing, ore is broken down too much, especiallDuring mixing and curing, ore is broken down too much, especially y

nonnon--weathered ore. However, the portion of fine residues (less thanweathered ore. However, the portion of fine residues (less than0.3 mm) mostly doesn0.3 mm) mostly doesn’’t increase considerable, not causing any t increase considerable, not causing any difficulty for the further process like washing to recover uranidifficulty for the further process like washing to recover uranium. An um. An appropriate mechanism for the stage is acid consumption of 30appropriate mechanism for the stage is acid consumption of 30--55 55 kg/ton of ore; moisture content of 10 kg/ton of ore; moisture content of 10 --13%, oxidant 213%, oxidant 2--3 kg/ton of ore 3 kg/ton of ore and curing duration of 3 days. After curing for 3 days, the ore and curing duration of 3 days. After curing for 3 days, the ore needs needs to be cured before being placed in the washing column.to be cured before being placed in the washing column.

�� In the stage of washing, it is recommended that batch washing beIn the stage of washing, it is recommended that batch washing beapplied and several initial washing times be used with pH 1 so tapplied and several initial washing times be used with pH 1 so that hat efficiency of uranium recovery can increase and the amount of efficiency of uranium recovery can increase and the amount of washing water can be reduced.washing water can be reduced.

ConclusionsConclusions (cont)(cont)�� After mixing and curing process, flow rate of washing solution iAfter mixing and curing process, flow rate of washing solution in n

washing stage can be controllable and stable in the whole washing stage can be controllable and stable in the whole process, avoiding column from being clogged. Appropriate flow process, avoiding column from being clogged. Appropriate flow rate of washing is around 6.0Erate of washing is around 6.0E--0.5 0.5 m/sm/s. However, for weathered . However, for weathered ores, the flow rate decreases considerably. Circulation of washiores, the flow rate decreases considerably. Circulation of washing ng solution (2 stages) leads to the increase of concentration of solution (2 stages) leads to the increase of concentration of uranium in the solution and reduction of water used. uranium in the solution and reduction of water used.

�� When trying processing ores by mixing and curing, then washing When trying processing ores by mixing and curing, then washing on a scale of 500 kg/batch of ores, a solution containing 1.2 on a scale of 500 kg/batch of ores, a solution containing 1.2 gU/lgU/lwas obtained. Amount of water consumed is equal to 1/3 ore was obtained. Amount of water consumed is equal to 1/3 ore weight. Duration for ore processing needs only 12 days. Efficienweight. Duration for ore processing needs only 12 days. Efficiency cy of uranium recovery can reach up to 85of uranium recovery can reach up to 85--90%. Treatment of 90%. Treatment of leaching solution by ionleaching solution by ion--exchange with exchange with amberliteamberlite IRAIRA--420 resin is 420 resin is conducted and followed by precipitation to obtain product with conducted and followed by precipitation to obtain product with concentration higher than 80%Uconcentration higher than 80%U33OO88..

Thank you for your attention!Thank you for your attention!