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首页> 外文会议>Beneficiation of phosphates VIII >RARE EARTHS OCCURRENCE IN FLORIDA PHOSPHATE ORE AND THEIR FATE DURING MINING AND CHEMICAL PROCESSING
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RARE EARTHS OCCURRENCE IN FLORIDA PHOSPHATE ORE AND THEIR FATE DURING MINING AND CHEMICAL PROCESSING

机译：采矿和化学加工过程中佛罗里达磷酸盐矿中罕见的稀土元素及其赋存状态

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Phosphate minerals have been identified as significant unconventional rare earths resources. World's identified phosphate resources total about 300 billion tons, representing 90 million tons of rare earth elements (REE), assuming an average REE content of 300 ppm Under a project funded by the Critical Materials Institute (CMI), the Florida Industrial and Phosphate Research Institute (FIPR Institute) conducted detailed chemical and mineralogical characterization of REE in different phosphate mining and processing streams. The research project include three major parts. Part Ⅰ covers chemical analysis and some basic properties of different samples. Part Ⅱ is a detailed process mineralogy study of the amine flotation tails. The third part focuses on isolation and characterization of REE mineral particles in three samples using two advanced techniques, dual energy (DE) rapid scan radiography and high resolution X-ray microtomography (HRXMT).Five samples were collected from a central Florida phosphate operation, including amine flotation tails, waste clay, phosphate rock, phosphoric acid, wet phosphogypsum (PG), and phosphoric acid sludge. These samples were analyzed for rare earth elements, uranium, thorium, routine chemical compositions, and radioactivity. Results show total REE of 70-500 ppm in the samples with uranium ranging from 25-120 ppm. Radium-226 analyzed about 20 pCi/g in phosphogypsum, 28 in phosphate rock, and 0.2 in phosphoric acid, and the corresponding uranium-238 numbers are 2.8, 20 and 36 pCi/g. Simple sizing and chemical analysis of phosphogypsum revealed an extremely encouraging piece of information on REE in PG. About 65% of the REE in PG is concentrated in the minus 500 mesh (approximately 30 microns) fraction that represents less than 10% of the total PG mass. Another fact is that the finest fraction also contains most of the thorium but little uranium.A detailed process mineralogy study was conducted on the amine flotation tails sample using a Mineral Liberation Analyzer, the most advanced instrument for this type of study. Two major rare earth minerals were detected in the amine tails including monazite and xenotime. The monazite monomers average 1.27% CaO, 13.73% La_2O_3, 29.28% Ce_2O_3, 12.26% Nd_2O_3, 0.63% UO_2, 6.2% ThO_2, 3.55% Pr_2O_3, 0.46% Al_2O_3, 1.69% SiO_2, and 30.92% P_2O_5. Xenotime is composed of the following chemicals: 46.44% Y_2O_3, 2.29% Gd_2O_3, 5.24% Dy_2O_3, 3.93% Yb_2O_3, 0.31% Nd_2O_3, 4.61% Er_2O_3, 0.66% Sm_2O_3, 1.06% UO_2, 0.19% CaO, and 35.26 P_2O_5. Other major minerals in the amine tails include quartz, fluoapatite, feldspar, rutile, pseudorutile and zircon.In Part Ⅲ, dual energy (DE) rapid scan radiography was used to first identify potential RE particles, followed by a more detailed quantified liberation analysis by high resolution X-ray microtomography (HRXMT). Three sample streams, Shaking Table Concentrate, Acid Plant Feed, and Phosphogypsm, were separated into three size classes: >106 μm, 75-106 μm, and 53-75 μm. DE radiographs were taken at two energy levels and the ratio calculated. The images were thresholded to show only potential rare earth particles and then those particles were removed to prepare HRXMT samples. The samples were digitally reconstructed and the concentration of rare earth particles found using digital processing software. Based on the degree of liberation, the best particle size to find fully liberated monazite particles is 75-106 μm, although other sizes can reasonably be considered for Acid Plant Feed and Phosphogypsm.Based on chemical analyses and minerals characterization, the following conclusions may be made about the occurrence and fate of REE in phosphate mining and processing: 1) REE in the flotation tails exist primarily in monazite with some in xenotime and heavy minerals such as zircon; 2) In the phosphoric acid manufacturing process over 70% of the REE in phosphate rock is dissolved, but a majority (about 70%) of which is either re-precipitated with PG or get absorbed onto PG; 3) the REE in phosphoric acid is mostly precipitated as the acid is concentrated from about 30% P2O5 to 54%; 4) REE in the waste clay occur in two major forms, xenotime and calcium substitution in phosphate crystals.
机译：磷酸盐矿物已被确认为重要的非常规稀土资源。在关键材料研究所（CMI），佛罗里达州工业和磷酸盐研究所资助的项目下，世界平均已查明的磷酸盐资源总量约为3000亿吨，代表9000万吨稀土元素（REE） （FIPR研究所）对不同磷酸盐开采和加工流中的REE进行了详细的化学和矿物学表征。该研究项目包括三个主要部分。第一部分介绍了化学分析和不同样品的一些基本特性。第二部分是胺浮选尾矿的详细工艺矿物学研究。第三部分着重介绍了使用两种先进技术（双能（DE）快速扫描射线照相和高分辨率X射线显微断层照相术（HRXMT））对三个样品中的REE矿物颗粒进行分离和表征。\ r \ n从佛罗里达州中部收集了五个样品磷酸盐操作，包括胺浮选尾料，废粘土，磷酸盐岩，磷酸，湿式磷石膏（PG）和磷酸污泥。分析了这些样品的稀土元素，铀，or，常规化学成分和放射性。结果显示，铀的总稀土元素含量为70-500 ppm，铀的含量为25-120 ppm。镭226在磷石膏中的含量约为20 pCi / g，在磷矿石中的含量约为28 pCi / g，在磷酸中的含量约为0.2，而铀238的相应数量分别为2.8、20和36 pCi / g。对磷石膏进行简单的尺寸测定和化学分析后，发现了有关PG中REE的极为令人鼓舞的信息。 PG中约65％的REE集中在负值500目（约30微米）的部分中，该部分占PG总质量的不到10％。另一个事实是，最细的级分还包含大部分most，但几乎没有铀。\ r \ n使用矿物解放分析仪（一种用于此类研究的最先进的仪器）对胺浮选尾矿样品进行了详细的工艺矿物学研究。在胺尾矿中检测到两种主要的稀土矿物质，包括独居石和xenotime。独居石单体的平均含量为1.27％CaO，13.73％La_2O_3、29.28％Ce_2O_3、12.26％Nd_2O_3、0.63％UO_2、6.2％ThO_2、3.55％Pr_2O_3、0.46％Al_2O_3、1.69％SiO_2和30.92％P_2O_5。 Xenotime由以下化学物质组成：46.44％Y_2O_3、2.29％Gd_2O_3、5.24％Dy_2O_3、3.93％Yb_2O_3、0.31％Nd_2O_3、4.61％Er_2O_3、0.66％Sm_2O_3、1.06％UO_2、0.19％CaO和35.26 P_2O_胺尾矿中的其他主要矿物包括石英，氟磷灰石，长石，金红石，假金红石和锆石。\ r \ n在第Ⅲ部分中，使用双能（DE）快速扫描射线照相法首先鉴定了潜在的RE颗粒，然后进行了更详细的定量高分辨率X射线显微照相术（HRXMT）进行游离分析。三种样品流（振动台浓缩液，酸厂进料和磷石膏）分为三个尺寸级别：> 106μm，75-106μm和53-75μm。在两个能级上拍摄了DE射线照片，并计算了比率。将图像阈值化以仅显示潜在的稀土粒子，然后将这些粒子去除以制备HRXMT样品。对样品进行数字重建，并使用数字处理软件找到稀土颗粒的浓度。根据自由度，找到完全释放的独居石颗粒的最佳粒径为75-106μm，尽管对于酸性植物饲料和磷石膏，可以合理考虑其他尺寸。\ r \ n根据化学分析和矿物表征，以下关于磷酸盐开采和加工过程中稀土元素的发生和结局可以得出以下结论：1）浮选尾矿中的稀土元素主要存在于独居石中，有些还存在于异种时代和重矿物如锆石中。 2）在磷酸生产过程中，磷酸盐岩中超过70％的稀土元素被溶解，但其中的大部分（约70％）要么被PG重新沉淀，要么被PG吸收； 3）当磷酸从大约30％的P2O5浓缩至54％时，磷酸中的REE大部分沉淀。 4）废粘土中的稀土元素以两种主要形式存在，即异磷酸盐和磷酸盐晶体中的钙取代。

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    Patrick Zhang; Jan Miller; David DePaoli; Mei Yang;

  • 作者单位

    FIPR Institute, Florida Polytechnic University, Bartow, FL, USA.;

    University of Utah, Salt Lake City, UT, USA;

    Oak Ridge National Laboratory, Oak Ridge, TN, USA;

    China University of Geoscience, Wuhan, China;

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