• 专利附录
  • 专利说明
  • 权利要求
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    • 专利摘要:
    Abstract A method of recovering uranium wherein a siliceous pulp is leached with sulphuric acid at a pH <2, the pH of the resulting pulp is increased to pH 3,5, and uranium is then extracted using ion exchange techniques. SILICEOUS ORE -10 H2SO LEACH - 12 PLS -16 INCREASE -18 pH>3.0 RIP CIRCUIT - 20 WASTE U,30a
    公开号:AU2013200762A1
    申请号:U2013200762
    申请日:2013-02-13
    公开日:2013-08-29
    发明作者:Martha H. Kotze；Volha Yahorava
    申请人:Mintek；
    IPC主号:C22B3-20
    专利说明:
    - I OPERATION OF URANIUM RECOVER RIP CIRCUITS AT ELEVATED pH VALUE BACKGROUND OF THE INVENTION [0001] This invention relates to the recovery of uranium from siliceous low-grade uranium pulp leached with sulphuric acid. [0002] A typical process applied for uranium recovery from a low-grade ore includes atmospheric leaching of the ore with sulphuric acid generally to a pH value of 1,0 to 2,0. The uranium is extracted from a resultant pregnant leach solution (PLS) using an anion exchange (IX) resin or circuit, or a solvent extraction circuit (SX) . In one approach the solids are separated from the unclarified PLS and the uranium is recovered via a fluidized bed IX system. Alternatively the PLS is clarified and the uranium is then recovered using a fixed bed IX or SX system. [0003] A problem associated with the use of IX technology for uranium recovery from a PLS produced via sulphuric acid leaching, is silica fouling. [0004] Silica fouling causes: (a) a decrease in the rate of adsorption and elution factors which must be taken account of during the design of the recovery plant; (b) an increased resin loss. This is due to the fact that the resin becomes brittle when the amount of silica on the resin increases above a certain level; (c) a need for caustic regeneration which results in weakening of the resin due to osmotic shock; and (d) an increase in capital and operating costs associated with the poorer equilibrium performance of the resin when fouled with silica over a certain level. 407s23S_1 (CHMatters) P92683.AU 13/02/13 - 2 [0005] An object of the present invention is to address, at least to some extent, the aforementioned fouling problem. SUMMARY OF THE INVENTION [00061 The invention provides a method of recovering uranium from siliceous pulp which includes the steps of: (a) leaching the pulp with sulphuric acid generally to a pH value of 1,0 to 2,0 to produce a pregnant leach solution (PLS) or pulp, (b) after step (a) increasing the pH of the PLS or pulp to a value of at least 2,5-4,5 and (c) after step (b) recovering uranium from the unclarified PLS or pulp using ion exchange. [0007] Preferably, in step (b), the pH is increased to a value of about 4,5. BRIEF DESCRIPTION OF THE DRAWINGS [0008] The invention is further described by way of example with reference to the accompanying drawings in which : Figure 1 graphically depicts a relationship between the gelling (polymerizing) time of silica (on a log scale) as a function of pH, Figure 2 shows uranium adsorption equilibrium isotherms at different pH values, and Figure 3 is a block diagram representation of a method according to the invention. DESCRIPTION OF PREFERRED EMBODIMENT [0009] Freshly leached silica is present as mono silicic acid in an acidic solution. When a super 4075235_1 (GHMatters) P92683.AU 13/02/13 - 3 saturated solution containing mono-silicic acid ages, the silica polymerises or gels and precipitates. [0010] Figure 1 depicts on a log scale a gelling or polymerisation time of silica as a function of pH. The silica is most stable in an acidic solution when the pH is of the order of 2,0 to 2,5 for it then takes the longest time to polymerise. As noted in the preamble hereof uranium typically is leached at a pH value of 1, 0 to 2, 0. In this pH region the silica is less stable and tends to polymerise and precipitate out of the acidic solution quicker. [0011] When an ion exchange circuit is used to recover uranium from the PLS or pulp, the silica polymerisation continues to take place and the silica tends to precipitate on the IX polymer. Thus silica fouling of the ion exchange resin becomes more severe when the uranium recovery operation is done at pH values which are outside of the optimum silica stability region. [0012] Once the uranium has been recovered, barren liquors or pulps are generally neutralised. Thus an increase of pH prior to uranium adsorption does not require any additional reagent consumption. This factor has given rise to the method of the present invention which method is illustrated in block diagram form in Figure 3. [0013] Referring to Figure 3 a siliceous low-grade uranium ore 10 is leached in a step 12 with sulphuric acid 14 at a final pH of 1,0 to 2,0 to produce a pregnant leach solution (PLS) or pulp 16. [00141 In a subsequent step 18 the pH of the PLS is increased by the addition of lime, limestone or any other neutralising agent to a pH value which is in the range of greater than 2,5 to 4, 5 and which, preferably, is at the upper end of this range. 40752351 (GHMatters) P92683.AU 13/02/13 - 4 [0015] The resulting solution is then subjected to a resin in pulp (RIP) process in a step 20 to produce uranium 22 and waste 24. In the step 20 use could be made of a fluidized bed IX system or, as noted, the PLS could be clarified whereafter uranium is recovered via a fixed bed IX system. [0016] An anticipated drawback of the method of the invention is the potential loss of uranium during pH adjustment or when the pH is increased above the targeted value. It has been found though that if the co precipitated uranium is allowed to be contacted with the resin in a fluidized bed system or in a pulp medium, the co-loaded uranium is recovered onto the resin. For a fixed bed system the co-precipitated uranium can be filtered out and the solids are then recycled to the uranium leach. [0017) The benefits of the invention were confirmed by means of comparative tests done on the same uranium pulp at pH values of 1,7 and 3,5 respectively. The advantages of operating at an elevated pH level, as described, include the following. 1. Uranium adsorption improvement 1.1 The number of adsorption stages could be reduced significantly, as the rate of silica fouling of the resin becomes significantly lower and hence the adsorption could be operated with resin fouled to relatively low silica levels. This results in a more favourable operating equilibrium isotherm. 1.2 As the speciation of the uranium sulphate complex changes, higher resin loadings are achievable. Hence the resin flow rate is lower, the resin inventory required on the plant is also lower, and downstream elution, solvent extraction, and precipitation circuits can be smaller. 4075235_1 (GHMatters) PS2683.AU 13/02/13 - 5 1.3 There is a significant reduction of CAPEX and OPEX due to the improved adsorption performance and hence lower resin inventory and flowrate. 2. A decrease in the rate of silica buildup 2.1 As is shown in the attached Figure 2 at a pH value of 1.7 the silica build-up in the resin took place at a rate of about 0,5 g/l/h. However, at a pH value of 3.5 the rate of silica build-up was significantly lower i.e. of the order of 0,05 g/l/h for the specific pulp and operating conditions being evaluated. 2.2 A decrease in the silica build-up rate reduces or eliminates the resin regeneration requirements and consequently minimizes resin breakage due to osmotic shock. This lowers operating costs. 3. Decrease in impurities deportment 3.1 There is a decrease in the co-loading of impurities such as ferric and zirconium onto the resin as these impurities generally precipitate efficiently at pH values greater than 3,0. This offers an opportunity to produce a purer eluant for uranium production. This reduces purification requirements. [0018] In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention. [0019] It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part 4075235 1 (GHMatters) P92683.AU 13/02/13 - 6 of the common general knowledge in the art, in Australia or any other country. 4075235_1 (GHMatters) P92683.AU 13/02/13
    权利要求:
    Claims (2)
    [1] 1. A method of recovering uranium from siliceous pulp which includes the steps of: (a) leaching the pulp with sulphuric acid at a final pH value of 1,0 to 2,0 to produce a pregnant leach solution (PLS) or pulp, (b) after step (a) increasing the pH of the PLS or pulp to a value in the range of 2,5 to 4,5 and (c) after step (b) recovering uranium from the unclarified PLS or pulp using ion exchange.
    [2] 2. A method according to claim 1 wherein, in step (b), the pH is increased to a value of 4,5. 4075235_1 (GHMatters) P92683.AU 13/02/13
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    同族专利:
    公开号 | 公开日
    RU2608862C2|2017-01-25|
    AP2013006722A0|2013-02-28|
    AU2013200762B2|2018-02-15|
    ZA201301132B|2013-09-25|
    AP3785A|2016-08-31|
    RU2013105789A|2014-08-20|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US9896744B2|2015-06-01|2018-02-20|Her Majesty The Queen In Right Of Canada As Represented By The Minister Of Natural Resources Canada|Process for metals leaching and recovery from radioactive wastes|US4560538A|1979-12-19|1985-12-24|Exxon Research And Engineering Co.|Curing and leaching process for metal ores|
    CA1156047A|1980-08-22|1983-11-01|Donald R. Weir|Recovery of uranium from material containingiron, arsenic and siliceous matter|
    US4430308A|1982-12-13|1984-02-07|Mobil Oil Corporation|Heated ion exchange process for the recovery of uranium|
    DE19737794C1|1997-08-29|1999-01-21|Wismut Gmbh|Uranium mixed oxide separation|
    RU2217380C2|2001-10-15|2003-11-27|Государственное унитарное предприятие "Всероссийский научно-исследовательский институт химической технологии"|Method for sorption extraction of uranium from silicon-containing solutions and pulps|
    RU2226177C2|2002-05-23|2004-03-27|Государственное унитарное предприятие "Всероссийский научно-исследовательский институт химической технологии"|Method of sorption recovery of uranium from solutions and pulps|
    JP3677013B2|2002-06-20|2005-07-27|財団法人産業創造研究所|Method for separating and recovering elements from radioactive liquid waste|
    RU2364642C1|2008-01-30|2009-08-20|Российская Федерация, от имени которой выступает государственный заказчик-Федеральное агентство по атомной энергии|Method of uranium sorption extraction from sulphuric acid solutions and pulps|
    AU2011243991B2|2010-04-19|2013-10-10|Areva Mines|Industrial extraction of uranium using ammonium carbonate and membrane separation|
    法律状态:
    2018-06-14| FGA| Letters patent sealed or granted (standard patent)|
    优先权:
    申请号 | 申请日 | 专利标题
    ZA2012/01010||2012-02-13||
    ZA201201010||2012-02-13||
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