Appraisal study on processing low-grade molybdenite concentrates

This paper investigates how the low-temperature roasting of low-grade molybdenite concentrates ([Mo] < 20%) produced at different deposits and the posterior leaching of stubs with soda and alkali affect Mo recovery in a solution. Based on the results obtained, it has been revealed that there do seem to be sufficient reasons for using soda as a selective chemical for leaching stubs; the roasting and leaching modes have been optimized and a processing flowchart of the above concentrates has been proposed. Such a flowchart ensures molybdenum recovery in a solution at 87–97%, depending on the concentrate’s phase composition.     

Chemistry and Mechanism of Interaction Between Molybdenite Concentrate and Sodium Chloride When Heated in the Presence of Oxygen

Roasting of molybdenum concentrates with sodium chloride has high potential and can be an alternative to oxidizing roasting and autoclave leaching; however, the chemistry and mechanism are poorly known. The chemical mechanism of the roasting process between molybdenite concentrate and sodium chloride in the presence of atmospheric oxygen is proposed. It is demonstrated that the process occurs through molybdenite oxidation, up to molybdenum trioxide, with subsequent formation of sodium polymolybdates and molybdenum dioxydichloride from molybdenum trioxide. It is found that the formation of water-soluble sodium polymolybdates from molybdenum trioxide stops over time due to passivation of sodium chloride surface by polymolybdates. It is proved experimentally that preliminary grinding of the mixture in a furnace charge leads to an increase in the polymolybdate fraction of the roasting products, which constitutes approximately 65 pct of molybdenum initially in the roasted mixture against 20 to 22 pct in a nonground mixture (or 75 to 77 pct against 30 to 33 pct of molybdenum in calcine). For the first time, the presence of the Na₂S₂O₇ phase in the calcine was confirmed experimentally. The suggested mechanism gives possible explanations for the sharp increase of MoO₂Cl₂ formation within the temperature range of 673 K to 723 K (400 °C to 450 °C) that is based on the catalytic reaction of molybdenum dioxydichloride from the Na₂S₂O₇ liquid phase as it runs in a melt.     

Characteristics of electrochemical reactions accompanying chlorinating annealing of copper sulfide concentrates

The mechanism for reactions accompanying the low-temperature roasting of a copper sulfide concentrate with potassium and sodium chlorides without the formation of sulfurous gases and their evolution into the atmosphere is suggested. The obtained cake is leached with water under pH correction in the vicinity of 6. Water-soluble sulfates transfer into the solution, while copper and iron hydroxides remain in the cake. The further leaching of the cake by an aqueous sulfuric acid at the final pH 2.5–3.0 makes it possible to completely transfer copper into the solution, while iron completely remains in the solid phase. The recovery of copper into the solution under the optimal annealing conditions (t = 450°C, τ = 1 h) and the above conditions of double leaching is no lower than 95%. Chlorinating annealing at temperatures below and above 450°C results in a decrease in the recovery of copper into the final product of copper sulfate. The found maximum is explained.     

Variants of processing molybdenite concentrates involving the use of preliminary mechanical activation

A review of possible ways to process molybdenite concentrates of various grades by both pyrometallurgical and hydrometallurgical methods is given and the most rational are noted. Prospects for processing low-grade molybdenum raw materials by nitric acid autoclave-less leaching with the complete transfer of molybdenum into the solution in the composition of sulfate complexes is shown. The variant that intensifies the nitric acid leaching of low-grade (6–17% Mo) concentrates obtained by the flotation of ores of the Bugdainskoe deposit via their preliminary dry mechanical activation is suggested.     

高铜非标钼精矿处理研究进展

高铜非标钼精矿不适合采用传统冶炼工艺处理。目前处理高铜非标钼精矿主要有加压浸出、焙烧-酸浸、电化学浸出和生物浸出等工艺方法,本文着重阐述高铜非标钼精矿的研究进展情况。     

Factors influencing the selective leaching of molybdenum with sodium hypochlorite from copper/molybdenum sulphide minerals

The leaching of molybdenite and copper sulphides with solutions of hypochlorite has been studied. The roles of pH and additions of carbonate ion in controlling molybdenum extraction and hypochlorite decomposition are described. The presence of carbonate ions during leaching prevents loss of molybdenum through precipitation as calcium molybdate. Carbonate ions while increasing copper extraction appear to act as stabilizers for the hypochlorite by delaying the onset of precipitation of catalytically active copper compounds. The leaching of molybdenite-containing copper sulphide rougher concentrates, it is concluded, is best performed at pH 9 with a carbonate-containing hypochlorite solution. Theoretical consideration is given to the possible influence of cadmium, zinc and lead ions on molybdenum extraction during the leach.     

Co-extraction of tungsten and molybdenum from refractory scheelite–powellite blend concentrates by roasting with Na2CO3 and SiO2 and leaching with water

Studies on the recovery of tungsten and molybdenum from refractory scheelite–powellite blend concentrates – mainly composed of scheelite, powellite, and fluorite – were performed using soda-silicon roasting and water leaching processes. However, significant amounts of scheelite and powellite ore are present in an intergrowth state and the application of mineral dressing is not suitable for the separation and extraction of tungsten and molybdenum from this refractory ore. The effects of roasting parameters including sodium carbonate addition, roasting temperature, roasting time, and mass ratio of SiO₂/concentrate (w_SiO2/w_conc.) and the effects of leaching parameters including leaching temperature, leaching time, and liquid-to-solid ratio on the leaching efficiency of tungsten and molybdenum were investigated. The results demonstrated the efficiency of this process for the extraction of tungsten and molybdenum from the ore. Under the optimum experimental conditions where soda-silicon roasting is performed for 2?h at 850°C with three times, the stoichiometric ratio of Na₂CO₃ (Na₂CO₃:WO₃ and Na₂CO₃:MoO₃) and w_SiO2/w_conc of 12%, and water leaching is subsequently performed for 1?h at 70°C with a liquid-to-solid ratio of 3:1, the leaching ratios of W and Mo are 98.89% and 99.41%, respectively.     

用化学处理法从低品位辉钼矿精矿中回收钼

本文报导的研究成果涉及两种工艺:(1)苏打灰焙烧法;(2)石灰强化碳热还原法。将它们用于从低品位辉钼矿精矿中提取钼产品的试验已经获得成功。用上述两种工艺已分别产出MoO_3和钼金属半成品,所得半成品再分别用炭吸附—解吸法和熔盐电解精炼法进一步提纯,最终产品的纯度分别达到99．9%和99．8%。此外,这些工艺还提供了包括环境污染和废气治理等的有效解决办法。而它们在处理高品位MoS_2矿石(或精矿)的传统工艺中,正是两个尚未解决的主要问题。     

从火法冶炼硅酸钙渣中回收钨钼的试验研究

以某厂火法冶炼硅酸钙渣为原料,在前期探索试验中,采用常压高温碱煮和高温高压碱煮、碱性条件下磷酸盐浸出取得浸出效果不好的情况下,通过采用加碱焙烧-球磨浸出工艺综合回收钨钼,成功实现钨钼高回收率。由于焙烧方法需要采用高温,能耗较高,因此主要进行加碱焙烧条件试验以及探索降低焙烧温度试验研究。经过试验,找到最佳工艺为:原料与Na2CO3和Na2O2的重量之比为10∶5∶1,在800℃下联合焙烧1 h,加水球磨,钨钼的回收率能达到92%以上。     

工业氧化钼提纯研究

近几年,我国每年约生产15万t工业氧化钼,绝大部分由氧化焙烧钼精矿制得,其中约30%用于生产钼酸铵,进而生产钼化学品及钼金属制品。这种方法生产的工业氧化钼用于钼酸铵生产存在以下实际问题：1）氨浸后产生含钼高达10%～20%的氨浸渣,损失大量的钼。2）氨浸后的钼酸铵溶液需要净化再结晶,加大了企业生产成本。针对第一项问题,我国的钼酸铵生产企业通常采用以下解决办法：1）低价出售氨浸渣;2）将氨浸渣与工业氧化钼混合后炼制钼铁;3）将氨浸渣加Na2CO3焙烧,再提纯后制成钼酸钠。上述各种都是企业为提高钼资源利用而被动采用的办法。本文通过研究加压氧化法提纯工业氧化钼的工艺,不仅解决钼酸铵生产中面临的氨浸渣处理问题,而且氨溶后的钼酸铵纯度高,不需要再净化。所获氧化钼经化学检测和X-射线衍射检测,其中的金属杂质和MoO2显著降低。试验中,试剂BM的加入显著增加了固体三氧化钼比率,从而提高了纯三氧化钼的产率。     

Studies on Processing of Low Grade Indian Molybdenum Sulphide Concentrate

In India, a low grade molybdenum sulphide concentrate containing 25–30% molybdenum is recovered as a by-product of uranium operations at Jaduguda. This concentrate contains a high association of copper and nickel. If it is processed by the conventional route, both copper and nickel would decrease molybdenum recovery. Such concentrates need a different processing route. Various processes such as soda ash roasting, lime roasting, oxychlorination, and electro-oxidation have been studied. The processes aimed at converting molybdenum into a soluble form, then purified by chemical processing as well as by carbon adsorption-desorption route to yield pure molybdic oxide. The oxide was then reduced to metal with hydrogen. In an alternate scheme, molybdenum values in solution have been converted into molybdenum intermediates such as calcium molybdate/ferrimolybdate. This paper presents the result of these investigations.     

Salt roasting of suncor oil sands fly ash

Fly ash samples from 25 years of Suncor’s oil sands upgrading operations were tested to determine the effects of time, temperature, and salt addition on vanadium recovery by salt roasting and water leaching. The optimum roasting conditions for “carbon-free” ash were determined to be 2 to 3 hours roasting at 850 °C to 900 °C with NaCl additions of 20 to 30 pct that resulted in vanadium extractions of 75 to 85 pct for all samples tested. Leach solutions contained less than 150 mg/L Al, Fe, Ni, Si, and Ti and typically analyzed 12–20 g/L V, 0.3 to 0.6 g/L Mo, 3.2 g/L K, and 10 g/L Na. Sodium carbonate (100 g/L) was also a selective lixiviant for vanadium and produced 2 to 7 pct higher extractions than water leaching. Characterization tests showed that most of the mineral matter in the Suncor fly ash is initially present as a poorly crystalline aluminosilicate glass, but crystallizes on heating with NaCl to form distinct aluminosilicate (albite and hauyne) and iron-titanium (pseudobrookite and hematite) phases. Water-soluble vanadium and molybdenum compounds are likely formed by reacting with NaCl during this crystallization. These tests indicate that insoluble vanadium and molybdenum are associated with the aluminosilicates and that nickel is associated with the iron-titanium minerals.     

含铼钼精矿的焙烧及烟灰中铼的回收工艺研究

于低温450℃和高温550℃焙烧钼精矿各9 h,>95%的铼进入烟灰中;过氧化氢∶水∶烟灰=0.4 L∶4 L∶1 kg、60℃和2 h时,铼浸出率73.15%~74.00%;沉淀液含铼浓度20 g/L、氯化钾∶铼酸钾=2∶1、≤80℃、恒温搅拌1 h、重结晶2次和80℃烘干,粗铼酸钾中铼含量,铼的浸出率、回收率和总回收率分别为45.92%~56.30%、73.15%~74.00%、57.68%~58.25%和69.00%~69.10%。工艺简便、经济,已应用于生产实践中。     

从火法冶炼硅酸钙固溶体渣中提钨钼探索性试验

针对钨钼品位低的火法冶炼硅酸钙固溶体废渣的特点,进行了碱煮、焙烧、酸洗等提钨钼探索性试验。试验表明:高浓度碱煮钨的回收率可达68%,钼的回收率达21%,但随分解碱液循环次数的增加,钨钼回收率越来越低,浸出过程同时受渣粒度的影响;在试验条件下,KMnO4作氧化剂,略有利于钼的浸出;掺入磷酸钠,在相对低浓度碱条件下,没有改善试验效果。苛性钠焙烧温度低,钨的收率可达74%,钼的收率可达53%;苏打焙烧温度虽高,但钨钼回收率均达到90%以上,苏打用量的增加有利于提高钨钼回收率,苏打的回收技术有待于进一步研究。     

铼的生产与应用研究进展

铼是难熔金属，主要赋存于斑岩铜钼矿床的辉钼矿和黄铜矿中，铼含量在20～2000g／t之间。从钼精矿焙烧产出的烟尘和淋洗液中回收铼及从钼精矿氧压氧化浸出液中回收铼多采用溶剂萃取法和离子交换法。铼用作制取各种催化剂，如汽油重整、烯烃复分解等。铼也用于生产钼铼合金、钨铼合金、镍基超合金和铌铼合金等。铼的某些配合物用作抗癌药物。     

钼焙烧烟气铼回收工艺中的几个关键问题

铼是典型的稀散金属,自然界没有固定的矿物,主要从铜、钼加工“三废”——烟气、烟道灰及浸出废液中回收和提取。本文总结了十余年铼回收工作实践中对钼焙烧铼回收工艺中逸出、吸收、净化、提取等几个关键问题的认知和解决方法,以促进钼焙烧烟气铼回收的推广和钼焙烧清洁生产工艺的进步。     

废弃电路板冶炼烟灰脱溴工艺研究

针对废弃电路板冶炼烟灰的特性,提出了碱性焙烧—水浸—熔炼综合回收工艺,通过添加碱性剂将烟灰中的金属溴氯化物转化为氧化物,实现了有价金属与溴的高效分离。探索了焙烧温度、加碱量、碱性剂类型对浸出渣组成及脱溴率的影响。在焙烧温度650~800℃,碱性剂氢氧化钠加入量为烟灰质量25%的优化工艺条件下,溴脱除率达到90%以上。滤渣主要组成为PbO、ZnO、CuO等金属氧化物和碳,结晶盐中的主要杂质为F、Al、S和K,NaCl和NaBr的含量达到90%以上。     

Solubility of vanadium from manganese vanadates in aqueous solutions of soda ash

It is shown that, in the course of developing the technology of pure vanadium pentoxide preparation from manganic vanadium-containing metallurgical slags, their oxidative roasting and cinder formation without alkaline additives are accompanied by the decomposition of spinelides with the formation of manganese meta- and pyrovanadates. Concentrated aqueous solutions of soda ash with an Na₂CO₃ concentration of 120–150 g/dm³ are accepted as a selective leaching reagent for vanadium from a cinder. Manganese metaand pyrovanadates are synthesized, and the procedure of their preparation is presented. The solubility of vanadium from manganese vanadates in aqueous solutions of soda ash at \(C_{Na_2 CO_3 } = 150 g/dm^3 \) is studied at 20–95°C for pyrovanadate and at 85–95°C for metavanadate. It is shown that vanadium should be leached from converter manganic slags roasted without alkaline metal additives at a leaching solution temperature higher than 95°C. There is a possibility to increase the vanadium content in a leaching solution to 60–80 g/dm³. The results obtained are used in the development of the technology of vanadium leaching.     

辉钼矿焙烧工艺研究进展及现状

对辉钼矿的回转窑焙烧。反射炉焙烧、多膛炉焙烧、流化床焙烧、闪速炉焙烧、添加助剂焙烧等焙烧工艺及直接热解工艺进行了评述。并对辉钼矿焙烧工艺的发展提出了建议。     

Extraction of rhenium from calcines of the oxidation roasting of low-grade molybdenite concentrate in a rotating tubular furnace

Consideration is given to the effect of various oxidizers used in the process of leaching on the extent of extraction of rhenium remained in the calcine as a result of incomplete sublimation upon the oxidation roasting of molybdenite concentrate in a tubular furnace. Its maximum extraction α_Re = 88%) is reached when using manganese concentrate. It has been established that for the Almalyk Metallurgical Integrated Works the most suitable oxidizer is a mixture of nitric and sulfuric acids (α_Re = 71–73%); in this case, a virtually complete purification of the calcine from copper takes place (≤0.05–0.07% Cu is retained in it). It is shown that molybdenum and rhenium that passed into solution can be separated by precipitation and ion-exchange methods.