In-situ measurement of mineral phase transition and kinetics in roasting process of Bayan Obo mixed rare earth concentrate by sodium carbonate

In this study, the Bayan Obo rare earth concentrates mixed with Na₂CO₃ were used for roasting research. The phase change process of each firing stage was analyzed. The kinetic mechanism model of the continuous heating process was calculated. This study aims to recover valuable elements and optimize the production process to provide a certain theoretical basis. Using X-ray diffraction (XRD), Fourier infrared spectroscopy, scanning electron microscopy with energy dispersive spectrometry, the reaction process and the existence of mineral phases were analyzed. The variable temperature XRD and thermogravimetric method were used to calculate the roasting kinetics. The phase transition results show that carbonate-like substances first decompose into fine mineral particles, and CaO, MgO, and SiO₂ react to form silicates, causing hardening. Further, REPO₄ and NaF can directly generate CeF₃ and CeF₄ at high temperatures, and a part of CeF₄ and NaF forms a solid solution substance Na₃CeF₇. Rare earth oxides calcined at a high temperature of 750 °C were separated to produce Ce_0.6Nd_0.4O_1.8, Ce₄O₇, and LaPrO_3+x. Then, BaSO₄, Na₂CO₃, and Fe₂O₃ react to form barium ferrite BaFe₁₂O₁₉; the kinetic calculation results show that during the continuous heating process, the apparent activation energy E reaches the minimum in the entire reaction stage in the temperature range of 440–524 °C, and the reaction order n reaches the maximum, which indicates that the decomposition product REFO significantly impacts the reaction system and reduces the activation energy. The mechanism function is F(α) = [?ln (1?α)]^1/3. The reaction order n reaches the minimum in the temperature range of 680–757 °C, and the apparent activation energy E is large. The difficulty of the reaction increases during the final stage. The reaction mechanism function is F(α) = [1?(1?α)^1/3]². Observing the entire reaction stage, the step of controlling the reaction rate changes from random nucleation to three-dimensional diffusion (spherical symmetry).     

细粒磁铁精矿球团孔隙结构的优化研究

针对-10 μm粒级含量32.63%、比表面积2 980 cm²/g的细粒磁铁精矿,通过有机粘结剂取代部分膨润土优化细粒磁铁精矿球团的孔隙结构,从而改善了生球及成品球质量。相比单独添加1.75%的膨润土球团,配加0.05%的有机粘结剂使膨润土用量降低至0.8%,由于有机粘结剂使小颗粒团聚成较大的颗粒,使得生球的孔隙率从16.68%提高到23.15%,球团爆裂温度从370 ℃提高到500 ℃;且预热过程球团的氧化率从67.48%提高到79.08%,球团均匀氧化避免了球团焙烧时形成双层结构;同时焙烧球孔隙率从12.33%提高到16.83%,使得球团还原度从56.8%提高到69.7%。有机粘结剂部分取代膨润土成功解决了细粒磁铁精矿球团孔隙率低导致的爆裂温度低、氧化速度慢、还原性能差等问题。     

某含铅金精矿中回收铅的试验研究

针对某金精矿中伴生铅含量高(含铅7.83%)的特点,为综合回收其中有价金属铅,详细查明金精矿中的组成成分以及铅的赋存状态,提出采用"抑硫浮铅"工艺。试验结果表明,采用该工艺处理此类含铅金精矿,可获得含铅61.94%、金75.40 g/t、银3 481.0 g/t、铅回收率88.10%的铅精矿以及含金30.85 g/t、银682.6 g/t、铅1.08%的金精矿,实现了伴生金属铅的高效回收。     

介孔分子硅剂改善茶浓缩膜结构特性应用研究

为有效提高功能性茶浓缩反渗透膜的回收效率和抗污性能,探究了3种介孔分子硅材料(MCM-41、SBA-15和MCFs)对浓缩膜面聚酰胺层聚合形成过程的结构影响。结果表明,添加质量分数0.02%经磺化预处理的MCM-41于间苯二胺水相可接枝酰氯基团,形成的聚酰胺结构层峰谷粗糙跨度仅为220 nm且交联紧致,膜抗拉伸强度增加37.8%;SBA-15和MCFs相膜面峰谷跨度达500~780 nm,横向褶皱和团聚,结构存在孔道塌陷;改性膜在3 h内对茶多酚、茶多糖、茶蛋白即可达到最大浓缩度,减少50%浓缩时间;MCM-41和SBA-15膜长时间运行的浓缩降率仅为2.8%~6.1%,48 h下降率比显示改性膜达标使用时长增加112.5%~137.5%,亲水性和抗污堵能力均大幅提升,可有效满足功能化茶浓缩精度。     

铋精矿加压氧化氨浸高效分离铜、硫和铋

针对湖南柿竹园铋精矿火法冶炼过程中存在的成本高、低浓度SO₂和散烟排放污染环境、有价金属综合回收率低等问题, 以柿竹园铋精矿为原料, 提出了加压氧化氨浸分离铋与铜、硫的新工艺, 研究了氨水加入量、浸出温度、浸出时间、浸出压力及浸出液固比等因素对铜、硫、铋浸出率的影响。在氨水用量1.8 mL/g_铋精矿、液固比4∶1、釜压2.8 MPa、浸出温度160 ℃、浸出时间5 h、搅拌速度600 r/min的优化工艺条件下, 铜、硫浸出率分别达93.57%和92.87%, 铋不浸出并以氧化铋形态全部入渣, 实现了铜、硫与铋的高效分离。     

内蒙古某磁选铁精矿浮选脱硫试验研究

对内蒙古某磁选铁精矿进行了浮选脱硫试验研究。以FS为活化剂、碳酸钠为pH调整剂、黄药和双黄药为混合捕收剂、2^#油为起泡剂, 经过一粗一精一扫闭路反浮选, 获得了产率94.54%、铁品位67.88%、铁回收率95.04%、含硫0.26%的铁精矿。     

Effect of different fibres on texture,rheological and sensory properties of acid casein processed cheese sauces

The objective of this study was the evaluation of different fibres (bamboo, acacia, potato or citrus) addition on texture, rheological and sensory properties of acid casein processed cheese sauces. Fibres used in production of sauces had an impact on the texture, viscosity, viscoelastic and sensory properties. The largest increase in viscosity was observed in products with addition of potato fibre, which have good water holding and adsorption capacity. Processed cheese sauce with the addition of citrus fibre was characterised by the highest values in general, and the increase of this feature in the tested samples was regular. Adhesiveness was the highest in products with 1% addition of every fibre. The lowest values of viscosity single shear, G′ and G″ moduli, among all tested, had sauces with acacia fibre. Moreover, they had the most thin liquid consistency, which was different from preferred one.     

四川冕宁稀土精矿中钍的赋存状态及分布规律研究

利用扫描电镜背散射电子成像技术,微区能谱分析,自动矿物分析软件,对四川冕宁稀土精矿中钍的赋存状态及其分布规律进行了研究。结果发现稀土精矿中存在钍的独立矿物(钍石、铀钍石、铅钍石等),且27.28%的ThO_2存在于钍的独立矿物中,52.46%的ThO_2主要以类质同象形式赋存于稀土矿物(氟碳酸盐矿物、硅酸盐矿物、磷酸盐矿物)中,氟碳酸盐矿物主要为氟碳铈矿、氟碳钙铈矿,硅酸盐矿物主要为硅钛铈矿,二者矿物中ThO_2的平均含量相对较低,磷酸盐矿物主要为独居石,其ThO_2的平均含量明显高于氟碳酸盐矿物和硅酸盐矿物,个别独居石中ThO_2含量高达5.91%;此次研究可为今后充分合理回收稀土精矿中的钍资源提供一定的依据。     

Chemical reaction kinetics dataset of Cs-I-B-Mo-O-H system for evaluation of fission product chemistry under LWR severe accident conditions

In order to improve LWR source term under severe accident conditions, the first version of a fission product chemistry database named ‘ECUME’ was developed. The ECUME is intended to include several datasets of major chemical reactions and their effective kinetic constants for representative severe accident sequences. It is expected that the ECUME can serve as a fundamental basis from which fission product chemical models can be elaborated for use in the severe accident analysis codes. The implemented chemical reactions in the first version were those for representative gas species in Cs-I-B-Mo-O-H system from 300 to 3000 K. The chemical reaction kinetic constants were evaluated from either literature data or calculated values using ab-initio calculations. The sample chemical reaction calculation using the presently constructed dataset showed meaningful kinetics effects at 1000 K. Comparison of the chemical equilibrium compositions by using the dataset with those by chemical equilibrium calculations has shown rather good consistency for the representative Cs-I-B-Mo-O-H species. From these results, it was concluded that the present dataset should be useful to evaluate fission product chemistry in Cs-I-B-Mo-O-H system under LWR severe accident conditions, where kinetics effects should be considered.