贵州某磷尾矿再选试验研究

贵州某磷矿石浮选尾矿中主要矿物为白云石,其次为氟磷灰石。采用自制的高效捕收剂AB和1段磨矿、1粗1精氟磷灰石反浮选工艺对该尾矿进行分离白云石与氟磷灰石的再选试验,在磨矿细度为-75 μm占62.50%,抑制剂磷酸用量为14 kg/t,AB用量粗选为300 g/t、精选为100 g/t的条件下,获得了P₂O₅品位为22.29%、P₂O₅回收率为56.72%、MgO含量为4.23%的磷精矿和MgO品位为19.97%、MgO回收率为93.38%、P₂O₅含量为5.68%的镁精矿,为该尾矿的综合利用提供了一条经济可行的途径。     

碳化法处理巴盟菱镁矿

采用碳化法处理巴盟菱镁矿,以煅烧制得的轻烧镁为原料,经消化、碳化、浸出和煅烧后,可获得MgO品位大于99.41％的高纯活性产品,MgO回收率达61.34％。其最佳工艺条件：煅烧温度800 ℃,轻烧时间2.5 h,振动磨磨矿时间2.5 min,消化时间30 min,重镁水加温温度150 ℃,CO₂通气量8 L/min,通气时间3 min,固液比60∶1,二次碳化的pH值7.0。     

Das Auflösungsverhalten von Al2O3 und MgO*Al2O3 Partikeln mit definierter Oberfläche in hoch MgO-hältigen sekundärmetallurgischen Pfannenschlacken

The importance of enhanced knowledge concerning the dissolution behavior of non-metallic inclusions in secondary metallurgical ladle slag is rising. This is mainly caused by increasing demands on steel cleanness. To clarify this behavior, an experimental investigation campaign was carried out by In-situ Laser-Scanning-Confocal-Microscopy investigations. The dissolution kinetics of Al₂O₃ and MgO*Al₂O₃ spherical particles were studied for various CaO-Al₂O₃-SiO₂-MgO slag compositions at 1600 °C.     

BK425和HA-1对磷矿反浮选脱镁脱铝效果影响研究

某难选磷矿由于其脉石矿物与胶磷矿嵌布关系复杂,为了获得合格的磷精矿,用脱镁捕收剂BK425和脱铝捕收剂HA-1对原矿进行反浮选试验。当原矿磨矿细度为-74μm占70%时,采用反浮选脱镁(一次粗选、一次扫选)—反浮选脱铝(一次粗选、两次精选)全开路流程,可以获得P_2O_5品位31.14%,Al_2O_3含量2.60%,MgO含量0.92%,P_2O_5回收率79.54%的磷精矿。     

基于镁合金微弧氧化技术制备浅绿色陶瓷膜

在硅酸盐体系下,研究AZ91D镁合金微弧氧化着色盐种类及用量对陶瓷膜颜色、微观结构及组成的影响。制备的彩色陶瓷膜通过X-衍射、TEM和SEM分析表明陶瓷膜由Mg₂SiO₄、MgCr₂O₄和MgO尖晶石相组成;表面由许多颗粒组成,颗粒上有孔洞;膜由里向外由致密层、过渡层和疏松层组成。研究表明陶瓷膜颜色与主盐的浓度无关,K₂Cr₂O₇、KMnO₄为着色盐均可着色,以K₂Cr₂O₇为着色盐制备的陶瓷膜为浅绿色。     

水热法制备超细氢氧化镁

以水镁石为原料,通过煅烧,制得氧化镁粉末,然后将氧化镁和尿素碱溶液反应,通过氧化镁水合法制备出了超细氢氧化镁颗粒,同过利用X-射线衍射仪(XRD)和扫描电子显微镜(SEM)对所制得氢氧化镁颗粒的晶相、形貌和颗粒尺寸进行了表征。试验结果表明,溶液浓度和添加剂对氢氧化镁晶体的晶相和颗粒尺寸有显著的影响,当溶液浓度为2.5 mol/L,添加剂为PEG 6000的情况下,制备出了半径为250 nm,片厚约150 nm,晶形完整,大小均一的六方片形超细氢氧化镁颗粒,但是样品的纯度有待于进一步的提高。     

Iron redox-equilibria and sulphide capacity of PGM melter-type slags

New measurements have been made on the ferric to ferrous ratio as well as the sulphide capacity for platinum group metals (PGM) melter-type slags. In South Africa, these slags are produced from the smelting of low-grade copper–nickel sulphide ores, Nell [Nell, J., 2004. Melting of platinum group metal concentrates in South Africa. The South African institute of Mining and Metallurgy 104 (7), 423–428]. The typical mass compositions are 5–10% Al₂O₃, 2–15% CaO, 5–30% FeO_x, 15–25% MgO and 40–60% SiO₂ with a molar basicity defined as (CaO + MgO)/SiO₂ of 0.6–1. The industrial furnaces operate at temperatures ranging from 1450 to 1600 °C under fairly reducing conditions (typically a pO₂ close to 10⁻⁸ atm at 1500 °C). The gas–slag equilibrium was studied by subjecting a synthetic slag to controlled atmospheres in a vertical tube-furnace using Ar–CO–CO₂ (–SO₂) gas mixtures. The ratio of ferric to ferrous was determined at 1450 °C for oxygen activities, defined as pCO₂/pCO, ranging from 0.11 to 1.75 by analysing the quenched slags using the standard titration and XRF techniques. The measured Fe³⁺/Fe²⁺ ratio increased from 0.029 to 0.110 with the increasing oxygen activity. Slight non-ideal iron redox behaviour was observed, as has been reported for low alumina and low iron-containing slags. The present results are in good agreement with the trends found in the literature for similar multi-component slag systems (mostly iron bath smelting slags). Sulphide capacity was measured at partial pressures of oxygen and sulphur of approximately 10⁻⁹ and 10⁻³ atm respectively, with total-iron contents of 8.2 and 15.6 wt%, and temperature ranging from 1450 to 1525 °C. The present sulphide capacity data ranged from 10^−4.43 to 10^−3.71. The expected increase in sulphide capacity with increasing temperature was observed, and at a given temperature, the sulphide capacity increased with an increase in iron oxide content.     

贵州某难选硅质胶磷矿正-反浮选试验研究

对贵州某难选硅质胶磷矿进行正-反浮选试验研究,以GC-4为捕收剂,经过一粗二精一扫正浮选脱硅和一段反浮选脱镁工艺流程,最终获得磷精矿P₂O₅品位34.65%、回收率92.39%,MER值7.18%的良好指标,该磷精矿可直接用于湿法磷酸的生产,同时获得了P₂O₅品位19.80%、SiO₂含量29.23%、MgO含量1.23%,倍半氧化物含量12.52%的中精矿,该部分可直接用于生产中低端磷复肥。试验结果表明,GC-4是一种多功能捕收剂,泡沫稳定性可控,流动性好,最终指标较好,可以作为单一捕收剂参与正-反浮选,同时避免了因pH不同造成多种捕收剂相互影响的局面,也有利于正-反浮选回水的混合再利用;WFS是磷化工酸性废水,在磷矿反浮选中取得较好效果,可以代替H₂SO₄作为反浮选的抑制剂,同时节约生产成本,提高社会效益。GC-4和WFS在本试验的成功应用为该类复杂难处理胶磷矿规模化利用提供技术参考。     

Nickel and cobalt precipitation from sulphate leach liquor using MgO pulp as neutralizing agent

The research work presented in this paper determined the conditions at which nickel and cobalt can be recovered, as easily filterable precipitates, from leach liquors, which are produced by sulphuric acid leaching of nickel oxide ores, at atmospheric pressure. More specifically, nickel and cobalt were precipitated as hydroxides at pH = 9, using MgO pulp as a neutralizing agent, by 99.9% and 99.0%, respectively. At this pH value, manganese, which was contained in the leach liquor, was precipitated having a concentration of about 3% in the final mixed precipitate. Statistical design and analysis of experiments were used in order to determine the main effects and interactions of the precipitation factors, which were the pH at equilibrium and the addition of seed material. The characterization of the produced mixed precipitate was carried out by X-ray diffraction, TG–DTA, scanning electron and optical microscopy and particle size distribution analyzer. The main mineralogical phases in the precipitate were theophrastite (Ni(OH)₂) and brucite (Mg(OH)₂). The microscopic observation revealed that the presence of brucite was, mainly, due to the un-reacted MgO pulp, during the precipitation process. This brucite content acted as seed material for nickel precipitation.     

Combined application of different collectors in the floatation concentration of Turkish feldspars

The application of different cation collectors in the floatation concentration of feldspar has been investigated. Raw material (Kaltun Mining Co.) from Cine, Aydin in Turkey was used. The results showed that for floatation of feldspars, combined application of AERO 3030C and AERO 801 + AERO 825, performed better than the application of these collectors alone. They were more selective, and with their application a higher mass recovery of feldspar was obtained. However, the chemical compositions of the feldspar concentrates were not significantly different no matter which of these reagents was used. A higher quality of feldspar concentrate: 67.06% SiO₂; 19.49% Al₂O₃; 0.018% Fe₂O₃; 0.135% TiO₂; 0.98% CaO; 0.02% MgO; 11.02% Na₂O; 0.22% K₂O; 0.02% P₂O₅ was obtained when a combination of these collectors was applied.     

云南某低品位细粒硅质胶磷矿浮选试验研究

介绍云南某低品位硅质胶磷矿的矿石性质,针对此矿石嵌布粒度细,且含硅、镁高的特性,采用"正—反浮选"流程,最终获得磷精矿品位30.05%,回收率78.18%,磷精矿含MgO 0.79%、SiO_2 16.97%的指标。     

Chemical and mineralogical characterization of a South African bituminous coal and its ash,and effect on pH of ash transport water

Sasol utilizes a low-rank bituminous coal for steam and synthetic gas production. The ash produced is transported by water for further processing. Understanding the chemistry of coal and the resulting ash properties would allow a better understanding of the origin of high pH of water used during ash handling or transport. A main objective of this study was to identify the species responsible for high pH values of the ash transport water, when burning coal from the Sasolburg Mooikraal mine. The coal contained proportions of extraneous carbonates, i.e. CaMg(CO₃)₂ and CaCO₃, that decompose at elevated temperatures to form CaO and MgO. The ash samples in this work contained free CaO, as verified by X-ray diffraction and ethylene glycol leaching. ICP-OES analysis of water leachates of the ash showed calcium dissolution into the water. The high pH values of the leachates were consistent with the expected pH of a saturated water solution of calcium hydroxide. Contact of the ash with water produced Ca(OH)₂. For combustion of this coal, the high pH of the water used for ash transport can be attributed to the free CaO in the ash. The methodological approach to this study could be directly applicable to other coals and their ashes, even of different composition than the specific coal and ash used in this study.     

Removal of cyanide in aqueous solution by oxidation with hydrogen peroxide in presence of copper-impregnated activated carbon

This work is devoted to the removal of free cyanide from aqueous solution by oxidation with hydrogen peroxide H₂O₂ catalyzed by copper-impregnated activated carbon. Effects of initial molar ratio [H₂O₂]₀/[CN⁻]₀, copper-impregnated activated carbon amount, pH and the temperature on cyanide removal have been investigated.The presence of copper-impregnated activated carbon has increased the reaction rate showing thus a catalytic activity. The rate of cyanides removal increases with the raise of the initial molar ratio [H₂O₂]₀/[CN⁻]0 and decreases with the increase in the pH from 8 to 12. The increase in the copper-impregnated activated carbon amount from 1.5 to 10 g/L in reaction solution has a beneficial effect. Beyond this value, the impact of activated carbon amount is not anymore significant. The temperature does not have a significant effect between 20 and 35 °C. The four successive times re-use of catalyst shows a good stability. The kinetics of cyanide removal has been found to be of pseudo-second-order with respect to cyanide and the rate constants have been determined. This process seems very interesting because the rate of cyanides removal is very fast, the reaction does not use soluble metal catalyst and it consumes only hydrogen peroxide as chemical product.     

Understanding the influence of acidic components (Si,Al, and Ti) on ash flow temperature of South African coal sources

Ash flow temperature is one property that specifically gives more information on the suitability of a coal source for combustion or gasification purposes. Therefore the chemistry and mineral interaction have to be understood in order to determine the suitability for fixed bed gasification purposes with regards to ash flow properties. Various authors ([Seggiani, M., 1999. Empirical correlations of the ash flow temperatures and temperature of critical viscosity for coal and biomass ashes. Fuel 78, 1121; Alpern, B., Nahuys, J., Martinez, L., 1984. Mineral matter in ashy and non-washable coals—its influence on chemical properties. Commun. Serv. Geol. Portugal 70 (2), 299]) have expressed the fusibility of coal ash as a function of the content of the principal oxides frequently found in coal ash, i.e. SiO₂, Al₂O₃, TiO₂, Fe₂O₃, CaO, MgO, Na₂O and K₂O. However, coal ash fusibility characteristics are difficult to determine precisely, partly because coal ash contains many components with different chemical behaviours, and may very from coal source to coal source.The purpose of this study is primarily to understand the effect and chemistry of the acidic components (Si, Al and Ti) of South African coal sources, as well as the manipulation or addition of these components to the coal sources, with the view to understand their effect on the ash flow properties.A representative coal blend as it is currently used for gasification purposes, as well as coal mixtures with the addition of pure SiO₂, Al₂O₃ and TiO₂, respectively, were prepared. The variation of the acidic components SiO₂, Al₂O₃ and TiO₂ varied from 1 mass% to 50 mass% to the coal blend. The particle size of the samples were representatively prepared to <1 mm and analyzed for ash flow temperature and ash composition as dependant variables according to ASTM D1857-87 and ASTM D2795-95, respectively. The raw data was then statistically evaluated by means of regression models.Results of the statistical evaluation of ash flow temperature and the ash elemental composition indicated that based on the 95% confidence interval Al₂O₃, Fe₂O₃, CaO, MgO, P₂O₅, as well as the SiO₂–Al₂O₃ ratio have a statistical significant effect on ash flow temperature. Regression trends of the coal and Al₂O₃, SiO₂ and TiO₂ mixtures indicated that Al₂O₃ has the biggest effect on the ash flow temperature. A shift towards increasing the Al₂O₃ concentration has a significant increasing effect on the ash flow temperature in the three-component system Al₂O₃–SiO₂–TiO₂ phase diagram. The ash flow temperature is the highest at the point where the Al₂O₃ concentration is maximized. The shifts in frequency of the absorption band associated with the 6s–6p electron transaction which relates to the basicity of a glass or slag also relates to the different effect of the individual acidic components on ash flow temperature. The shift can be considered as a measure of the electron donor power and is usually expressed in terms of the optical (Λ) basicity. The ion–oxygen attraction and the stronger (more positive) value obtained for Al₂O₃ in comparison with TiO₂ and SiO₂ could be seen; and possibly explain why Al₂O₃ has a bigger influence and effect on increasing the ash flow temperature.It can be concluded from this experimental work with the emphasis on flow properties, that the acidic components Al₂O₃, SiO₂ and TiO₂ all have an increasing effect on ash flow temperature when added to the coal blends currently used for gasification. In addition to this general conclusion, it has also been confirmed that Al₂O₃ addition to the coal blend has the most significant effect towards increasing the ash flow temperature when compared to SiO₂ and TiO₂.     

Bifurcation characteristics of coal spontaneous combustion and analysis of critical state of gaseous reaction in a packed bed

The numerical model was presented for the coal combustion in the packed bed. The bifurcation characteristic of the ignition-extinction of solid-phase smoldering and transition to flaming was studied for the packed bed of coal. One of the Frank-Kamenetskii parameter β ₁ was selected as the control parameter. The computed results show that the bifurcation curve is obviously divided into two zones of solid-phase reaction and gasphase reaction, and the total process of ignition-extinction presents twice bifurcation characteristic. Moreover, the vanishing of critical state of ignition-extinction is studied. One of the transition points, ɛ ₂=0.05, is numerically solved for the vanishing of critical state. The larger the value of ɛ ₂ is, the easier the gas-phase can react. However, the combustion temperature will decrease with increasing ɛ ₂. The other transition point α ₂=0.53 is also obtained. With increasing the value of α ₂, the combustion temperature of gas-phase reaction is close to the smoldering temperature of coal. When α ₂ is infinite, the only reaction occurring is the smoldering combustion of solid-phase, and the gas-phase cannot react. Supported by the National Natural Science Foundation(50574049); National Key Technology R&D Pogram of China(2006BAK03B05)     

Beneficiation of diasporic-bauxite ore by selective flocculation with a polyacrylate flocculant

Beneficiation of a diasporic-bauxite ore by selective flocculation with sodium polyacrylate (PAS) was studied. Flocculation behaviors of diaspore, kaolinite, illite and pyrophyllite in the presence of PAS were also investigated by sedimentation tests. PAS shows good selectivity for the flocculation separation of diaspore from silicates in the range of pH 8–12. A concentrate with Al₂O₃/SiO₂ ratio 8.9 and the recovery of Al₂O₃ 87.0% was obtained from a diasporic-bauxite ore with Al₂O₃/SiO₂ ratio 5.7 with the addition of sodium carbonate 5 kg/t and PAS 7 g/t. Micro-photogram, zeta potential and FTIR measurements were then performed to study the mechanisms. It was observed that the zeta potentials of diaspore shifted to negative value strongly and the isoelectric point (IEP) of diaspore was also changed from about pH 6–4, and the flocs of diaspore were larger and denser than that of kaolinite in the presence of PAS. A new band at 1640 cm⁻¹ was found in the infrared spectrum of the diaspore after interaction with PAS, and this new band matched the characteristic peak at 1624 cm⁻¹ in the infrared spectrum of the reaction products of PAS and AlCl₃. The adsorption of PAS on diaspore is concluded to be chemisorption caused by the chemical reaction between carboxylate group and the exposed Al sites on diaspore surface.     

Alkaline digestion of dunite for Mg(OH)2 production: An investigation for indirect CO2 sequestration

The sequestration of CO₂ by carbonating natural minerals has a great potential for secure reduction of net CO₂ emissions. Feedstock Mg–silicate minerals are usually converted into Mg rich solutions or Mg(OH)₂ before the carbonation process, due to the slow reaction kinetic of direct carbonation. The present work studied the alkaline digestion of Mg–silicate minerals into Mg(OH)₂ for CO₂ sequestration. Powdered dunite containing ∼73 ± 2 wt% of forsterite (Mg₂SiO₄) was dissolved using highly concentrated NaOH aqueous systems at 90 and 180 °C with varied NaOH concentration and duration of reaction. Thermal analysis and Rietveld Refinement Quantitative Phase Analysis (QPA) confirmed that an effective digestion of dunite was possible at 180 °C achieving 80 wt% of Mg(OH)₂. It was found that NaOH concentration in solution, temperature and duration of reaction significantly influence the progress of digestion.     

Study on Cu2S mineral surface modification by low temperature Ar/O2 plasmas

The oxidation of mineral and synthetic chalcocite (Cu₂S), using low temperature plasmas, has been investigated and compared to thermodynamic calculations. The main aim of this work is to understand the fundamental interaction between mineral surfaces and low temperature plasmas, with a view to improving froth flotation by mineral pretreatments. Capacitive radio frequency (RF) discharge Ar/O₂ plasmas, operating at different external parameters, have been used to treat powder samples, which resulted in surface modifications. These were analyzed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). In situ mass spectrometry (MS) was used to determine oxidation reaction rates. The energy flux density from the plasma on the sample surface was determined by active thermal probe measurements, and the density of atomic oxygen produced within the plasma zone was obtained by optical emission spectroscopy (OES). Sulfur dioxide (SO₂), one reaction product of mineral Cu₂S plasma oxidation, was emitted with a certain delay, which depends on energy flux density and atomic oxygen density. In contrast, no delay was found as synthetic Cu₂S was treated. This indicates that the contamination by pyrite (FeS₂), found in mineral samples, plays an important role, significantly influencing the mechanisms of plasma surface interaction. Comparisons of mass spectrometry (MS)-, XPS- and XRD-measurement results with thermodynamic calculations give evidence for a stepwise plasma processing, whereas the transition of sulfur atoms from FeS₂ to Cu₂S could be identified as a first step in forming cupric sulfate ( CuSO₄). This effect might be used to develop selective plasma surface pretreatments for mineral mixtures in order to improve their separation efficiency of froth flotation.     

Preparation of hydrolyzate of hogwash oil (HHO) and its application in separating diaspore from kaolinite

Hydrolyzate of hogwash oil (HHO) was prepared at ambient pressure using hogwash oil that was collected from the dietary industry as a raw material by means of non-pressurized multistage hydrolyzation. Before hydrolyzation, the collected hogwash oil was subject to pre-treatment that included deposition edulcoration, acidification degumming and deodorization by digestion as well as vacuum dewatering. Components of the synthesized products were detected by gas chromatography and the results indicated that unsaturated fatty acids are the major components.Using HHO as a collector, the flotation behavior of diaspore and kaolinite was investigated. The reaction mechanisms of diaspore and kaolinite with HHO are discussed based on a zeta potential test. The results showed that a concentrate with a mass ratio of Al₂O₃ to SiO₂ of 14.42 and an Al₂O₃ recovery of 81.80% can be obtained at a feed mass ratio of Al₂O₃ to SiO₂ of 5. This indicated that the HHO is a potential collector for separating diaspore from aluminosilicate minerals in bauxite. The results also suggested a possible way to reuse discarded hogwash oil to avoid environmental pollution.     

熔盐法制备氧化镁粉体及其反应机理研究

以MgCl₂、CaCO₃、NaNO₃和KNO₃为原料, 采用熔盐法制备了MgO粉体。通过X射线衍射仪(XRD)、场发射扫描电子显微镜(SEM)对产物的组成与形貌进行了表征, 借助热重-差示扫描热量计(TG-DSC)、X射线衍射仪(XRD)对制备氧化镁粉体的反应机理进行了探讨。结果表明, 在熔盐反应过程中, Mg²⁺与Ca²⁺发生置换反应, 生成白云石和碳酸镁等中间产物, 随着反应的不断进行, 白云石最终转变为碳酸镁; 550 ℃热处理碳酸镁分解为氧化镁, 经水浸泡后氧化镁水解生成氢氧化镁, 氢氧化镁前驱物为不规整的层状形貌, 厚度介于0.03～0.05 μm, 直径介于0.2～1.0 μm之间; 600 ℃热处理氢氧化镁分解为氧化镁, 产品氧化镁为颗粒状形貌, 粒径介于0.2～0.5 μm之间。