Stability of calcium silicate in basic solution

1　INTRODUCTIONInaluminaproductionbysinteringprocess ,themoleratioofCaO/SiO2 isabout 2inordertoform β 2CaO·SiO2 .The β 2CaO·SiO2 existsrelativelystablyintheleachingprocess ,andthendischargestogetherwiththeredmud .Butsomeβ 2CaO·SiO2 istobede composed ,andthenconvertsintohydrategarnetorsodiumhydratealumino silicate .Thisprocessisoftencalledasthesecondaryreaction .Therearetwodiffer entopinionsinthecauseofdecompositionofβ 2CaO·SiO2 ,thefirstisthatβ 2CaO·SiO2 isdecompo…     

高苛性比铝酸钠溶液中氧化铝的回收

对加入石灰后的高苛性比铝酸钠溶液中氧化铝的回收进行了研究。热力学计算结果表明,氧化钙较氢氧化钙更容易使铝酸钠溶液中的铝酸根离子转化为水合铝酸钙,使铝酸钠溶液的平衡苛性比能达到很高的值;水合铝酸钙随着温度的升高,稳定性降低,因而能在拜尔法高温溶出过程中分解以代替石灰,并回收其中的氧化铝。实验结果表明,影响水合铝酸钙形成因素的大小顺序为：温度≈碱浓度＞ＣａＯ／Ａｌ２Ｏ３＞时间。     

Behavior of calcium silicate in leaching process

1　ＩＮＴＲＯＤＵＣＴＩＯＮＩｎｇｅｎｅｒａｌ ,ａｌｕｍｉｎａｃａｎ ｔｂｅｐｒｏｄｕｃｅｄｅｃｏｎｏｍｉｃａｌｌｙｂｙＢａｙｅｒｐｒｏｃｅｓｓｉｎＣｈｉｎａｂｅｃａｕｓｅｔｈｅｂａｕｘｉｔｅｃｈａｒａｃｔｅｒ ｉｚｅｓｉｎｄｉａｓｐｏｒｅａｎｄａｂｏｕｔ 80 %ｂａｕｘｉｔｅｅｘｉｓｔｉｎｌｏｗｄｅ ｇｒｅｅｏｆｔｈｅｍａｓｓｒａｔｉｏｏｆａｌｕｍｉｎａｔｏｓｉｌｉｃａ(Ａ/Ｓ)ｗｈｉｃｈｖａｒｉｅｓｆｒｏｍ 4ｔｏ 9[1] .Ａｎｄａｂｏｕｔ 4 0 %ｏｆａｌｕｍｉｎａｉｓｐｒｏ ｄｕｃｅｄｂｙｓｉｎｔｅｒｉｎｇ…     

拜耳法溶出过程降低赤泥碱耗

拜耳法生产氧化铝的过程中,碱耗的主要原因是因为有钠硅渣的生成,碱耗可以用赤泥钠硅比(N/S)表征。通过对钠硅渣和水化石榴石反应行为的热力学分析,发现高饱和系数(x>1)的水化石榴石不易被苛性碱分解,低饱和系数的水化石榴石易被分解而转化为钠硅渣,且钠硅渣也可以转化为水化石榴石,而在Na2CO3溶液中,任何形式的水化石榴石均能被分解生成钠硅渣。实验研究结果表明,不同矿区的铝土矿对赤泥N/S影响不明显,母液中Na2CO3浓度升高、石灰加入量降低、母液中碱浓度降低均会导致赤泥N/S升高,引起碱耗增大。因此,降低母液中Na2CO3浓度、提高石灰添加量将明显有利于赤泥N/S的降低。     

氧化钙或氢氧化钙与浓碱铝酸钠溶液的反应特性

研究了氧化钙、氢氧化钙与浓碱铝酸钠溶液的反应特性,在相同条件下,氧化钙的反应活性高于氢氧化钙,这归结于氧化钙在水化放出大量热量的同时,固相颗凿细化,比表面积增大。较多量的氧化钙加入反应体系后,体系主要因固相颗粒团聚容易发生膨胀。玎的扫描电镜分析表明：加入表面活性剂后,表面活必有因吸附“挤占”了新生因相表面吸附的小分子,破坏或削弱了体系的团聚,从而消除和体系的膨胀;同时,表面活性剂的会降低了固液界面     

Reaction behavior and mechanism of anatase in digestion process of diasporic bauxite

Based on the study of influence of temperature, digestion time, amount of CaO added and composition of aluminate solution on reaction behavior of pure anatase in high-pressure digestion process of bauxite, reaction mechanism of anatase was preliminarily determined. Anatase first reacts with caustic soda to produce Na2TiO3, then the resultant Na2TiO3 reacts with 3CaO·Al2O3·6H2O resulting from the reaction of CaO with sodium aluminate solution to produce CaO·2TiO2·H2O which eventually converts into CaTiO3. Higher temperature, concentration of free Na2Ok (the caustic soda uncombined with aluminate anions in the form of Na2O) and molar ratio of CaO to TiO2 are favorable to the conversion of CaO·2TiO2·H2O to CaTiO3. And Al(OH)4- shows the function of a catalyzer in the reaction of anatase with caustic soda with or without CaO added during the digestion process of diasporic bauxite.     

Removing Al and regenerating caustic soda from the spent washing liquor of Al etching

Spent liquor from washing of aluminum section materials after etching with caustic soda (NaOH) has been treated. Aluminum was removed from the liquor and caustic soda was regenerated by adding precipitating agents to hydrolyze sodium aluminate (Na₂AlO₂), separating the aluminumprecipitate, and concentrating free NaOH in the resulting solution for reuse in the etching process. Four systems were investigated: hydrated lime [Ca(OH)₂], hydrogen peroxide (H₂O₂), H₂O₂/Ca(OH)₂ mixture, and dry lime (CaO). Results revealed that CaO was more efficient in the removal of aluminum from the spent liquor with a higher hydrolyzing rate of Na₂AlO₂ than Ca(OH)₂, H₂O₂, or their mixture. For more information, contact M.A. Barakat, Central Metallurgical R&D Institute, P.O. Box 87 Helwan 11421, Cairo, Egypt; fax: +20-2-501-0639; e-mail: mabarakat@gmail.com.     

种分制备超细氢氧化铝中碱含量的变化(英文)

种分氢氧化铝中碱含量变化规律关系到氢氧化铝的质量和碱耗,通过测定溶液浓度和电导率、氢氧化铝中碱含量和粒度分布以及分析粒子形貌,研究种分氢氧化铝中碱含量的变化规律。结果表明,溶液组分浓度高、球磨晶种循环、种分温度低、初始分解速率快或产品比表面积大都会导致氢氧化铝中碱含量升高;在低硅铝酸钠溶液种分过程中,粒子的附聚得到抑制,超细氢氧化铝中碱主要以晶格碱形式存在,以钠硅渣形式存在的碱含量极低;同时,升高初始分解温度,晶种老化,降低分解速率,延长种分时间,都有利于产品中碱含量的降低。结果还表明:种分过程中,Na+Al(OH)4离子可能对产品中碱含量有很大的影响。     

SiO2-Al2O3-CaO-Fe2O3系微晶玻璃的晶化过程

利用差热分析（ＤＴＡ）、红外吸收光谱（ＩＲ）、Ｘ射线衍射（ＸＲＤ）和扫描电镜（ＳＥＭ）等手段研究了ＳｉＯ２－Ａｌ２Ｏ３－ＣａＯ－Ｆｅ２Ｏ３系微晶玻璃晶化过程及其结晶化过程及其结晶动力学。结果表明：ＳｉＯ２－Ａｌ２Ｏ３－ＣａＯ－Ｆｅ２Ｏ３系微晶玻璃晶化过程中,初晶相是钙铁透辉石,钙铝黄长石是中间过渡相且随晶化温度的提高而消失,最终晶相只有钙铁透辉石;晶体生长指数为２．９,属三维生长。玻璃网络中主要有     

Technology and mechanism of desilication from roasted diasporic bauxite in atmosphere

The leaching desilication technology of roasted diasporic bauxite in atmosphere by caustic soda solution was investigated. The optimum parameters were: the grinding fineness of the roasted bauxite -0. 076 mm and 80 % -85 %,leaching time 2h, Na2Ok100-150g/L, L/S 4-5, leaching temperature 90-95℃. The desilication rate 55.20% and concentrate A/S (mass ratio of A12O3 to SiO2) 9.90, as good as those obtained at pressure, were obtained respectivdy.Investigation of two-stage leaching shows that it can both improve desilication rate of roasted ore and reduce leaching time.When time of the first stage and the second stage is 30 min and 30 min respectively, desilication rate can reach 59.65 %.X-ray diffraction analysis of the concentrate has proved that desilication procedure is accompanied with the formation of sodium aluminosilicate hydrate. X-ray spectra also show that silica removed during leaching is amorphous silica. SiO2 occurrina as ouartz in raw ore or mullite formed during roasting can not dissolve in alkali solution.     

氟盐对炼镁还原渣中氧化铝浸出率的影响研究

以白云石和菱镁石为原料以铝粉为还原剂真空热还原炼镁过程中添加氟化钙可使镁还原率提高5%以上,还原温度降低50℃,还原后还原渣的主要物相为CaO.2Al2O3,加入的氟化钙在还原过程会参与反应生成氟铝酸钙。在实验室以氢氧化钠和碳酸钠的混合碱液对该含氟盐还原渣中氧化铝的浸出进行了研究,研究结果表明:经碱液浸出后还原渣中的CaO.2Al2O3全部被分解,还原渣中的氧化铝浸出率在70%以上,浸出渣的主要物相为CaCO3。含氟盐炼镁还原中氧化铝的浸出率比不含氟盐的氧化铝浸出率低10%以上,在还原过程中生成的氟铝酸钙和浸出过程中生成的水合铝酸钙是导致氧化铝损失增加的主要原因。     

熟料烧结过程中氧化铁反应行为的热力学分析

通过对Fe2O3与碳酸钠、氧化钙以及硅酸钙反应的热力学分析,明确Fe2O3在铝土矿炉料烧结过程中的热力学反应规律。热力学计算、分析结果表明:Fe2O3在正常烧结温度范围内能与Na2CO3或CaO发生反应,但更易与CaO反应形成2CaO.Fe2O3或CaO.Fe2O3,Fe2O3和Na2O.Fe2O3能使2CaO.SiO2和3CaO.2SiO2转变为CaO.SiO2,CaO.SiO2进一步与Na2O.Al2O3或Na2O.Fe2O3反应生成不溶的三元化合物而造成烧结法生产氧化铝过程中Na2O和Al2O3的损失。4CaO.Al2O3.Fe2O3不能由铁酸钙和铝酸钠相互反应产生,而可能是CaO、Al2O3和Fe2O3三者直接反应的产物,且在烧结条件下Na2O.Fe2O3可分解4CaO.Al2O3.Fe2O3。     

Behavior of calcium oxalate in sodium aluminate solutions

The stability of calcium oxalate is critical for the removal of sodium oxalate from sodium aluminate solutions. This study investigated the behavior of calcium oxalate in sodium aluminate solution containing sodium carbonate. Results show that calcium oxalate can be converted to tricalcium aluminate hydrate (TCA) and calcium carbonate in sodium aluminate solution and sodium carbonate solution, respectively. Elevating temperature, extending residence time, or increasing caustic soda concentration enhances the conversion ratio of calcium oxalate in sodium aluminate solution; as a consequence, anti-causticisation occurs. Stability of calcium-containing compounds in sodium aluminate solution containing sodium carbonate differs from that in sodium aluminate solution or sodium carbonate solution. Na₂CO₃ in aluminate solution accelerates the transformation of calcium oxalate; thus, alumina is lost because of 4CaO·Al₂O₃·CO₂·11H₂O and TCA formation. Calcium carbonate, 4CaO·Al₂O₃·CO₂·11H₂O and calcium oxalate can change into TCA in sodium aluminate solution at elevated temperature. Calcium oxalate remains relatively stable in dilute aluminate solution within a short residence time at low temperature. Thus, a novel process for removal of sodium oxalate by lime causticisation was presented and employed in an alumina refinery in China.     

六方水合铁酸钙的合成及其脱硅

通过正交实验对六方水合铁酸钙的合成温度、合成时间和合成体系中CaO与Fe2O3的摩尔比及合成体系的搅拌强度等因素对其脱硅效果的影响进行研究,并给出六方水合铁酸钙的最佳合成条件。结合X射线衍射分析讨论水合铁酸钙的脱硅机理,提出水合铁酸钙是一种高度分散的含钙化合物,其晶面间距较大,脱硅活性较高,并可大幅度降低铝损。在最佳条件下添加水合铁酸钙进行深度脱硅时,脱硅后铝酸钠溶液中的SiO2含量可降低到7 mg/L,硅量指数可达14 000,且脱硅产物中SiO2的饱和系数可达0.46。     

CaO/SiO_2和Fe/SiO_2比对空气中PbO-ZnO-CaO-SiO_2-“Fe_2O_3”系相平衡的影响(英文)

实验测定了CaO/SiO2和Fe/SiO2质量比分别为1～1.6和1.3～1.7、含40%PbO和8%ZnO的PbO-ZnO-CaO-SiO2-"Fe2O3"渣系的相平衡和液相线温度。将该渣系在1273～1573K达到平衡,然后快速淬火冷却。XRD和SEM-EDS分析结果表明,该渣的成分位于锌铁尖晶石相的初始成相区,在1273～1473K生成硅酸钙/铅,部分硅酸钙/铅和磁铁铅矿相是通过转熔反应生成的。实验结果和热力学计算结果表明,液相线温度随着渣中CaO/SiO2比的增加和Fe/SiO2比的降低而增加。     

玻璃净化剂组分对Cu50Ni50合金熔体过冷度稳定性的影响

在高真空下,研究了净化剂Ｂ２Ｏ３,８９％ＳｉＯ２＋１２．５％Ｂ２Ｏ３＋２．２％Ａｌ２Ｏ３＋０．６％ＣａＯ＋５．７％Ｎａ２Ｏ（简写为Ｎａ－Ｃａ－Ａｌ－Ｂ－Ｓｉ）和５０％Ｎａ－Ｃａ－Ａｌ－Ｂ－Ｓｉ＋５０％ｎａ２Ｂ８Ｏ４对Ｃｕ５０Ｎｉ５０ｘ合金溶体在循环过热过程中的过冷度及其稳定Ｃａ－Ａｌ－Ｂ－Ｓｉ玻璃的净化过程为物理－化学复合净化,但由于该净化剂粘度大,在循环过热的冷却过程中因发生合金溶体与净化剂分离     

加碳条件下钼精矿真空冶炼过程中主要杂质元素的行为分析

采用在钼精矿真空冶炼过程中添加碳粉的方法,进一步降低钼精矿真空冶炼过程中主要杂质SiO2、MgO、Al2O3和CaO的含量。热力学计算结果表明:SiO2、MgO、Al2O3和CaO均有可能与碳发生反应,生成气态物质被去除。试验研究结果表明,在钼精矿真空冶炼过程中加入碳粉可以明显降低其中Si、Mg、Al和Ca的含量,其中Si的脱除率约达到100%,Mg的脱除率约达到99.7%,Al的脱除率约达到78.44%,Ca的脱除率最高约为9.8%。采用品位为48%的低品位钼精矿为原料,经过真空冶炼过程,得到的金属钼产品中钼含量达到92%,S含量降至0.69%,主要杂质元素SiO2含量降至0.0021%,Cu含量小于0.005%,P含量小于0.005%,Mg含量降至0.001%,Al含量降至0.64%,Ca含量为0.51%。     

Preparation of Al(OH)3 by ion membrane electrolysis and precipitation of sodium aluminate solution with seeds

The preparation of Al(OH)3 by the ion exchange membrane electrolysis followed by the precipitation of sodium aluminate solution with seeds was made. During the process of ion membrane electrolysis, the sodium aluminate solution is rapidly acidified and the caustic ratio (aK) is decreased due to oxygen evolution in the anodic region. And the causticity of solution is increased due to hydrogen evolution in the cathode region, producing the high concentration of caustic soda solution. Regulating the acidity of the anodic solution by controlling the electric quantity in the electrolysis and subsequent decomposing the solution, Al(OH)3 could yield with very large rate and high efficiency. The experiments also indicate that the quality of aluminum hydroxide product is greatly affected by the impurity silicon.     

水化石榴石渣湿法处理的研究

研究了水化石榴石被含碳酸钠溶液分解的热力学规律,实验结果也表明,升高反应温度,提高液固比,增大溶液中碳酸钠的浓度都有利于水化石榴石的分解,水化石榴石中二氧化碳饱和系数的增大不利于氧化铝的溶出;在一定条件下,延长反应时间对水化石榴石的分解影响不大。     

Preparation of chain copper oxide nanoparticles by microwave

Cu（OH）2 nano-fibers were prepared by chemical precipitation with CuSO4·5H2O and NaOH as raw materials. The Cu（OH）2 nano-fibers have a diameter of 10-30 nm and a length of 1-6 μm. The reaction conditions were as follows： the concentration of CuSO4 solution was 0.1 mol·L^-1,NaOH solution 4 mol·L^-1,the dropping rate of the NaOH solution 50 mL·min^-1,the reaction temperature 20℃the pH value of the reaction terminal 13,and the stirring rate 1200 r·min^-1. The chain nano-CuO grains were obtained through the microwave radiation of the Cu（OH）2 nano-fibers.