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.     

Effect of refractory agent on ash fusibility temperatures of briquette

To solve the problem of the low ash fusion point of briquette, this paper reported that the ash fusibility temperatures can be elevated by changing ash ingredients through blending refractory agents in briquette ash, which will create favorable conditions for moving bed continuous gasification of briquette with oxygen-rich air. The effects of Al₂O₃, SiO₂, kaolin, dry powder and bentonite on ash fusibility temperatures were studied, based upon the relationship between briquette ash components and ash fusibility. The results show that the increasing of ash fusibility temperatures by adding the same amount (11%, w) of refractory agents follows the sequence of SiO₂, bentonite, dry powder, kaolin, Al₂O₃, with the softening temperatures being elevated by 37.2, 57.6, 60.4, 82.6 and 104.4 °. With the same ratio of SiO₂/Al₂O₃ in briquette, adding the Al₂O₃ component is more effective than SiO₂ for raising ash fusibility temperatures. In this paper, inexpensive kaolin and bentonite rich in Al₂O₃ are found to be better refractory agents, and the suitable adding quantities are 9% and 11%, respectively.     

高硅铝土矿正浮选两段脱硅试验研究

本文以云南鲁甸高硅低铝硅比型铝土矿为研究对象,通过正浮选阶段磨矿阶段选别、两段脱硅工艺流程获得了较好的铝土矿精矿,浮选指标良好。原矿含Al2O360.78%、Si O220.84%,铝硅比(A/S)为2.92,主要脉石矿物为白云母、石英等。通过在粗磨条件下进行一段浮选脱硅,粗精矿再磨再选后进行二段浮选脱硅,产出合格精矿。粗精矿再磨后进行五次精选,闭路试验获得精矿产率为64.74%、Al2O370.83%,Si O28.40%、A/S为8.43、Al2O3回收率为75.83%的良好指标。     

Research on the recycling of valuable metals in spent Al2O3-based catalyst

A new technology was developed to recover multiple valuable elements in the spent Al₂O₃-based catalyst by X-ray phase analysis and exploratory experiments. The experiment results showed: In the condition of roasting temperature of 750 °C and roasting time of 30 min, mol ratio of Na₂O: Al₂O₃ 1.2, the leaching rate of alumina, vanadium and molybdenum in the spent catalyst is 97.2%, 95.8% and 98.9%, respectively. Vanadium and molybdenum in sodium aluminate solution can be recovered by barium hydroxide and barium aluminate, the precipitation rate of vanadium and molybdenum is 94.8% and 92.6%. Al(OH)₃ is prepared from sodium aluminate solution with carbonation decomposition process, and the purity of Al₂O₃ is 99.9% after calcinations, the recovery of alumina can reach 90.6% in the whole process. The Ni–Co concentrate was leached by sulfuric acid, a nickel recovery of 98.2% and over 98.5% cobalt recovery was obtained respectively under the experimental condition of 30% (w/w) H₂SO₄, 80 °C, reaction time 4 h, liquid:solid ratio (8:1) by weight, stirring rate of 800 rpm.     

新载体及活性组分对瓦斯传感器抗毒性能的改善

针对瓦斯传感器在含硫气氛中容易中毒导致灵敏度下降问题,在载体中加入氧化铈,用纳米制备工艺制成CeO2-AL2O3纳米载体,利用共沉淀法制备Pt-Pd双金属纳米催化剂。通过对催化元件制成电桥的灵敏度和稳定性进行测试和分析,证明大大改善了瓦斯传感器的灵敏度和长期运行的稳定性。     

Experimental study on performance that carbon dioxide inhibits coal oxidation and spontaneous combustion

Adopting oil-bath temperature programming experiment and gas chromatography, CO₂’s inhibitory performance on spontaneous combustion of Tingnan Coal Mine sample was analyzed. Through temperature rise rate test experiment, the accuracy, stability and reliability of the improved oil-bath temperature programming system applied in this experiment was proved to be superior to the traditional system. Spontaneous combustion characters parameters test of coal sample in pure air was carried out with this system and offered comparison standard for research in next stage. Temperature programming to coal sample was further conducted in oil-bath with different concentration of CO₂. Testing results are compared with parameters of concentration of CO, O₂, temperature, CO generation rate and O₂ consumption rate tested and calculated in previous experiment in pure air. Methods of proportioning between concentration of CO and O₂, CO concentration and temperature, CO generation rate and O₂ consumption rate were applied to eliminate obstructions from certain external factors such as inlet of CO₂; meanwhile influences of CO₂ of different concentrations to coal oxidation and spontaneous combustion were investigated. Also CO₂ inhibition technique was used in spontaneous combustion prevention in workface No.106 of Tingnan Coal Mine, data collected from which indicate that CO₂ performs well in inhibiting coal oxidation and spontaneous combustion.     

铝土矿反浮选新型捕收剂QAS224的应用研究

应用自行研制的新型捕收剂QAS224,对Al₂O₃品位为64%左右、铝硅比为6.1左右的河南某铝土矿矿石进行反浮选脱硅试验,结果在磨矿细度为-0.074 mm占81.24%,矿浆pH为11的条件下,通过1次粗选、2次精选、2次扫选,获得了精矿Al₂O₃品位为67.79%,Al₂O₃回收率为81.72%,铝硅比为9.67的较好指标。试验结果证明QAS224是铝土矿反浮选脱硅的有效捕收剂。     

山西古县某低品位铝土矿浮选脱硅试验研究

以山西古县某低品位铝土矿为研究对象,开展了原矿性质研究分析及浮选脱硅性能研究。考察了磨矿细度及药剂用量对浮选指标的影响,确定出合适的工艺参数,原矿Al₂O₃含量为58.47%,SiO₂含量为19.75%,A/S为2.96的低品位铝土矿,通过“一粗二精一扫”浮选脱硅闭路试验可得铝精矿产率60.64%,A/S为6.11,Al₂O₃回收率为69.52%；尾矿A/S为1.41。     

Technological characterization of kaolin tailing from small-scale mining in RN and PB states – Brazil

In small-scale mining in north-eastern Brazil, the exploitation of industrial minerals, where kaolin bearing pegmatites are mined, is common. The mineral processing of kaolin is based in mixer and classification by screen and cyclone. The overflow of cyclone is thickened and filtered by pressure filter. The product is dried for market. This work presents the results of tailings characterization. Mass balance was realized and recuperation of kaolin about 56% was identified. The feed grade of Al₂O₃ in the plant is 21.20%. The kaolin product for market sold by the company presents 37.19% Al₂O₃ and whiteness of 81.9%. The average Al₂O₃ content of the tailing is 15.55%. Minerals identified are feldspar, muscovite, tourmaline, illite and kaolinite. The −325# fraction of the tailings present Al₂O₃ grades with characteristics for market (Al₂O₃-35%) and whiteness of 79.7%. Values from 7 to 34 wt% of this −325# fraction were determined in the tailing samples analyzed; these results validate the feasibility of reprocessing the tailings for using in the ceramic industry.     

Effect of incorporation manner of Zr promoter on precipitated iron-based catalysts for Fischer-Tropsch synthesis

The promotional effects of Zr on the structure, reduction, carburization and catalytic behavior of precipitated iron-based Fischer-Tropsch synthesis (FTS) catalysts were investigated. The catalysts were characterized by N₂ physisorption, temperature-programmed reduction (TPR), and M?ssbauer effect spectroscopy (MES) techniques. As revealed by N₂ physisorption, Zr decreased the BET surface area and pore volume of the catalyst. The results of TPR and MES show that Zr suppresses the reduction and carburization of Fe catalysts because of the interaction between Fe and Zr. The FTS reaction results indicate that Zr decreases the FTS activity of Fe catalysts but improves the catalysts?? stability. In addition, Zr promoter restraines the formation of light hydrocarbons (methane and C₂??C₄) and shifts the production distribution to the heavy hydrocarbons.     

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.     

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.     

某铝土矿新型组合捕收剂试验研究

采用自行研制的新型ZF组合捕收剂,对主要成分为高岭石和一水硬铝石,Al₂O₃品位为63.16%,铝硅比为5.32的一种山西铝土矿进行正浮选脱硅试验。在磨矿细度-0.074 mm占84.51%,碳酸钠用量3 500 g/t,硅酸钠用量113 g/t,ZF捕收剂用量800 g/t的条件下,通过1次粗选,1次精选,2次扫选,获得了精矿Al₂O₃品位68.92%,Al₂O₃回收率81.05%,铝硅比9.16的较好指标。     

Effects of sodium tripolyphosphate and sodium carbonate on the selective flocculation of diasporic-bauxite in the presence of calcium and magnesium ions

In this study, sedimentation tests for individual minerals and artificially mixed minerals and bauxite ores were carried out to understand the effects of sodium tripolyphosphate (STPP) on the selective flocculation of diasporic-bauxite in the presence of Ca²⁺ and Mg²⁺ ions. It was found that STPP can mitigate the detrimental effects of Ca²⁺ and Mg²⁺ ions on the dispersion of diaspore and kaolinite. When separating bauxite from the mixtures of minerals and in the presence of Ca²⁺ ions, STPP can serve as better dispersant than sodium carbonate. By jointly using STPP as a dispersant and PAAS as a flocculant, a flocculation concentrate with the mass ratio of Al₂O₃/SiO₂ (Al/Si) of 7.14 and Al₂O₃ recovery of 89.97% was produced from the feed (Al₂O₃/SiO₂ = 5.64) in the presence of Ca²⁺ ions. In contrast, with using sodium carbonate as the dispersant and PAAS as the flocculant, selectivity of the flocculation separation of diasporic-bauxite was deteriorated. These experimental data were satisfactorily interpreted by some chemical reactions occurring in the pulp, which were deduced from measured zeta potentials of the reaction resultant products and residual Ca²⁺ concentrations of the pulp.     

Role of silicate phases during comminution of titania slag

Titania slag is the primary product of ilmenite smelting, and serves as a feedstock to the TiO₂ pigment industry. The fine material (smaller than 106 μm in diameter) which is produced during milling of titania slag is enriched in some impurities, notably SiO₂, Al₂O₃, K₂O and CaO. Investigation of microstructures of solidified slags confirmed that these oxides partition to the silicate phases which form during final solidification. The presence of silicates on the surfaces of particles in milled slag supports the suggestion that the silicates contribute to fracture during crushing and milling. No significant macro-segregation was found in the slag ingots.     

天然膨润土对Cr(VI)的吸附动力学及等温线研究

研究所用膨润土的主要成分为SiO₂和Al₂O₃,属于钙基膨润土,BET表面积为47.98 m₂/g。在恒温及恒定pH条件下,用动态吸附法研究了膨润土对Cr(VI)的吸附特性,结果表明其较好符合Lagergren二级吸附速率方程。利用Langmuir等温线方程和Freundlich等温线方程对动态吸附过程进行拟合,发现其吸附等温反应与Langmuir等温线更适合,属于表面单分子吸附。     

Effects of aluminosilicate minerals on copper-molybdenum flotation from Sarcheshmeh porphyry ores

The presence of aluminosilicate minerals adversely affects the floatability of copper during processing of Sarcheshmeh porphyry ores. In this work, ores containing different types and quantities of aluminosilicate minerals, as well as copper sulfides (i.e., chalcopyrite and chalcocite), were examined in the laboratory to determine how aluminosilicate minerals affect the floatability of copper and to find ways to decrease their unwanted effects. It was shown that ore types that contain muscovite and vermiculite have the greatest effect on the floatability of copper sulfides. To overcome this problem, two reagent strategies were used: (a) dextrin at 100, 200, and 600 g/ton and (b) a mixture of dextrin, sodium silicate, and sodium hexametaphosphate (20%, 40%, and 40% by weight, respectively) at 200 and 300 g/ton. The reagent mixture (case b) at a dosage of 200 g/ton improved the copper recovery and decreased the grade and the recovery of Al₂O₃ and SiO₂ in the flotation concentrate. As an alternative solution, flotation at reduced pulp density (24%) improved the grade and the recovery of copper and molybdenum and decreased the grade and recovery of Al₂O₃ and SiO₂ in comparison to the currently used pulp density (29%) in the Sarcheshmeh flotation plant.     

Mineralogical Characterization of Dilband Iron Ore Deposits of Balochistan, Pakistan

Summary  Dilband iron ore deposits, recently discovered in 1997 by Geological Survey of Pakistan (GSP) in Kalat Division Balochistan, Pakistan, is of major importance from a socio-economical point of view among the indigenous iron ore deposits discovered so far in Pakistan. In order to meet the requirements of Pakistan Steel Mills ore specification (i.e. 57–60 % Fe (min), 8.5 % SiO₂ (max), 0.5 % Al₂O₃ (max), 0.1 %P (max), and 0.05 % S), the ore requires an adequate concentration method. This calls for detailed characterization of process relevant minerals and their intergrowth. For this reason mineralogical, petrographic, and elemental analysis were performed using XRD, thin section and SEM with EDS, and XRF and Atomic Absorption Spectrometer techniques, respectively. Mineralogical study revealed that Dilband iron ore is mainly composed of 46.27 % hematite, 17.41 % quartz 14.47 % calcite, 9.24 % chlinochlore, 10.5 % kaolinite, and 1.75 % fluorapatite minerals. Atomic absorption analysis of different size fractions ranging from −600 μm down to −38 μm indicated that Dilband iron ore contains on average of 40.18 % Fe, 18.34 % SiO₂, 5.32 % Ca, and 2.262 % Al. Whereas average analysis of different size fractions on XRF indicated 44.3 % Fe, 20.4 % SiO₂, 8.8 % CaO, 6.35 % Al₂O₃, 1.08 % P₂O₅, and 0.065 % SO₃. Three types of iron stones namely hematiteooides, hematite-peloids, and hematite biosparite were identified from petrographic study. From the mineralogical and elemental analysis data finely dissemination of impurities specially quartz, alumina and phosphorous in hematite phase is conceived, suggesting that Dilband iron ore is not amenable to upgrade with conventional techniques.

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Mineralogische Beschreibung der Dilband-Eisenerzlagerst?tten in Balochistan, Pakistan

Zusammenfassung  Die Dilband-Eisenerzlagerst?tten, die erst 1997 vom geologischen Dienst Pakistans in Kalat, Distrikt Balochistan, Pakistan, entdeckt wurden, sind im Vergleich zu den bisher in Pakistan entdeckten Eisenerzlagerst?tten aus gesellschaftlicher und wirtschaftlicher Sicht von besonderer Bedeutung. Um die Qualit?tsanforderungen des nationalen pakistanischen Stahlherstellers Pakistan Steel Mills (PSM) (i.e. 57–60 % Fe(min), 8,5 % SiO₂ (max), 0,5 % Al₂O₃ (max), 0,1 %P (max) and 0,05 %S) zu erreichen, muss das Erz mit geeigneter Aufbereitungstechnik angereichert werden. Dies macht die Beurteilung des prozessrelevanten Mineralbestandes und der Verwachsung notwendig. Mineralogisch-petrographische sowie Elementanalysen wurden mittels R?ntgendiffraktometrie, Mikroskopie, Rasterelektronenmikroskop mit energiedispersivem Spektrometer sowie R?ntgenfluoreszenzanalytik und Atomabsorptionsspektroskopie durchgeführt. Mineralogische Untersuchungen ergaben, dass die untersuchten Proben haupts?chlich aus H?matit (46 %), Quarz (17 %), Kalzit (14,5 %), Klinochlor (9,2 %), Kaolinit (10,5 %) und Flurapatit (1,75 %) aufgebaut sind. AAS in Kornklassen des Zerkleinerungsproduktes <600 μm lieferte einen durchschnittlichen Eisengehalt von 40,2 % bei 18,3 % SiO₂, 5,3 % Ca und 2,62 % Al. Demgegenüber stehen 44,3 % Fe, 20,4 % SiO₂, 8,8 % CaO, 6,35 % Al₂O₃ und 1,08 % P₂O₅ aus der R?ntgenfluoreszenzanalyse. Drei Typen von Eisensteinvariet?ten, n?mlich H?matit-Ooide, H?matit-Peloide und H?matit-Biosparit, konnten identifiziert werden. Aus den mineralogischen Untersuchungen, kombiniert mit jenen der Elementanalyse, lassen sich feinste Verteilung von Quarz-, Aluminium- und Phosphorverunreinigungen in den H?matit-Aggregaten ableiten, was zu dem Schluss führt, dass die Dilband-Eisenerze für konventionelle Aufbereitungstechnik nicht geeignet sind.

     

滇池地区磷块岩中倍半氧化物的赋存特征

磷矿中的倍半氧化物会导致后续湿法磷酸过滤困难,降低设备生产能力。为降低磷矿中的倍半氧化物含量,利用荧光光谱仪(XRF)、偏光显微镜、扫描电镜(SEM)、矿物参数自动定量分析系统(MLA)等分析手段,查明了磷矿矿物组成特征、倍半氧化物的赋存特征、磨矿分异特征、赋存矿物单体解离特征等。结果表明：Fe₂O₃主要赋存在褐铁矿中,主要呈集合体形式集中分布、星点状分散分布、侵染状分布、脉状分布;Al₂O₃主要赋存在白云母、水云母中,呈碎片状,为层状硅酸盐矿物;磨矿后,Fe₂O₃、Al₂O₃均有向细粒级富集的分异特征,且单体解离情况较好,为选矿脱除提供了基础条件。褐铁矿和层状硅酸盐矿物表面具亲水性,磷矿反浮选工艺难以脱除,建议采用正浮选工艺脱除。     

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。