基于TOUGHREACT模拟分析黄铁矿对酸法地浸采铀的影响

酸法地浸采铀过程中,铀矿的伴生矿黄铁矿作为非目标矿物会消耗氧化剂和酸。为探明酸法浸铀过程中因黄铁矿溶解产生的变化规律,本文以巴彦乌拉铀矿采铀过程为例,采用六注二抽的“网格式”井型构建二维酸法地浸采铀模型进行模拟研究,在抽注平衡的条件下,模型中只考虑黄铁矿(FeS₂),沥青铀矿(UO₂),与石英(SiO₂)。结果表明：1)模拟结束后(1000 d),在抽注单元控制的地下水流场作用下,边界处注液井的黄铁矿溶解范围呈两极分化,最远处抵达抽液孔,为30 m,最近仅距注液井8.4 m,而中间处注液井的黄铁矿溶解范围最远达27.8 m,最近达8 m;2)地浸采铀中的关键因素Fe^₃₊在氧化还原次序中排名靠后,黄铁矿未完全溶解之时,在缺少Fe^₃₊的情况下,铀矿的溶解速率极低,直至黄铁矿完全溶解时,铀矿溶解速率才迅速增加,模拟结束后(1000 d),边界处注液井铀矿完全溶解范围为距注液井7.2 m-12.8 m,中间处注液井铀矿完全溶解范围为距注液井7 m-11 m,此时溶浸液中的六价铀(UO_2²⁺)迁移前端距离抽液孔仅8.4 m;3)铀矿的浸出经过溶解(液相)-沉淀(固相)-再溶解(液相)的多次旋回,根据铀矿的溶解-沉淀量将其划分为完全溶解区,有效溶解区和沉淀区,模拟结束后(1000 d),注液孔1完全溶解区范围为7.2m-12.8 m,此时沉淀区已形成一个锥形区域,范围为18.6 m-21.6 m,同样在抽注作用的影响下,在靠近抽液孔方向上,锥形沉淀区的尖端铀矿沉淀量最多;4)在抽注单元控制的地下水流场作用下,黄铁矿与铀矿的溶解区域,均出现靠近抽液孔方向的溶解范围大于远离抽液孔方向的溶解范围。

TOUGHREACT simulation was used to analyze the effect of pyrite on uranium extraction by acid leaching

In the in-situ leaching of uranium, pyrite, the associated ore of uranium ore, as a non-target mineral, will consume oxidants and acids. Therefore, in order to explore the change rule of the dissolution of pyrite in the process of acid leaching of uranium, this paper takes the uranium mining process of Bayanwu la uranium mine as an example, and uses the "grid pattern" well type of six injection and two pumping to construct the two-dimensional in-situ leaching of uranium for simulation study. Under the condition of pumping equilibrium, only pyrite (FeS₂), pitchblende (UO₂) and quartz (SiO₂) are considered in the model. Results show that: 1) after the simulation (1000 d), in the pumping unit control injection under the action of groundwater flow field, the border range of pyrite dissolution are polarized liquid injection Wells, the farthest reached draining hole, to 30 m, recently from the liquid injection Wells, only 8.4 m, and dissolution of pyrite fluid injection wells at the centre of the range of 27.8 m, as far as recent up to 8 m;2) the key factors in uranium Fe^{_{3 +}} in REDOX order low-ranking, pyrite is not completely dissolved, in the case of lack of Fe^₃₊, uranium dissolution rate is extremely low, until completely dissolved pyrite, uranium dissolution rate was increased rapidly, after the simulation (1000 d), border completely dissolved uranium range for liquid injection Wells, from 7.2 m to 12.8 m, liquid injection Wells, fluid injection Wells at the centre of the scope of completely dissolved uranium from 7 m to 11 m, liquid injection wells, the leaching liquid of hexavalent uranium (UO_2²⁺) pump fluid migration front distance hole is only 8.4 m; 3)Uranium leaching after dissolving precipitation (liquid) - (solid) - to dissolve (liquid) cycle for many times, according to the dissolved uranium - precipitation amount will be divided into completely dissolved, effectively dissolve and precipitation area, after the simulation (1000 d), liquid injection hole 1 completely dissolved the range of 7.2 m to 12.8 m, the precipitation area has formed a conical area, range of 18.6 m to 21.6 m, under the influence of smoke injection effect, also near the infusion hole direction, to precipitate the tip of the tapered area biggest uranium deposit ;4) Under the action of the underground water flow field controlled by the pumping unit, the dissolution range of pyrite and uranium ore close to the direction of the pumping hole is greater than that far away from the direction of the pumping hole.