水合碳铝酸钙深度脱硅的工业实践

详细地论述了水合碳铝酸钙合成的机理,利用水合碳铝酸钙深度脱硅的机理以及在工业生产中的应用,使烧结法精制铝酸钠溶液的硅量指数由400－480提高到600以上,同时产品氧化铝的质量有了明显的提高。     

合成水合铝酸钙的性质研究

通过研究工业拜耳法种分母液与石灰反应生成的水合铝酸钙的物理及化学性质粒度细(10μm左右),比表面积大(5.0m2/g以上),主要物相为3CaO·Al2O3·6H2O,加热脱水分解为12CaO·7Al2O3和CaO等(差热分析吸热峰为270～320 ℃和800～830 ℃),发现它适于作有机高分子材料的阻燃填充剂和铝酸钙水泥等化工及耐火材料的原料.     

六方水合铝酸钙的性质研究

叙述了六方水合铝酸钙的合成条件和方法,并通过化学分析,TG－DTA分析和XRD分析对所合成的六方水合铝酸钙进行了表征,实验结果表明,在本实验条件下所合成的样品中除六方水合铝酸钙外,还含有少量的立方水合铝酸钙和氢氧化钙,在90℃下添加六方水合铝酸钙进行深度脱硅,脱硅2h后的铝酸钠溶液中SiO2含量可降低到0．009g/l,硅量指数可达11111。     

超细脱硅剂的制备与应用

采用液相沉淀法制备了超细水合铝酸钙(C3AHx),在单因素实验的基础上通过正交实验确定了合成超细水合铝酸钙的最佳工艺条件。采用XRD、SEM对脱硅剂进行物相和粒度形貌分析,探讨其脱硅机理。在最佳条件下添加超细水合铝酸钙进行深度脱硅,脱硅后的铝酸钠溶液中SiO2含量可降低到0.008g/L,硅量指数可达12500。     

纳米六方水合铝酸钙的制备与应用

采用液相沉淀法制备了纳米六方水合铝酸钙(C4AHx),在单因素实验的基础上,通过正交实验确定了合成纳米六方水合铝酸钙的最佳工艺条件。采用XRD、SEM对脱硅剂进行物相和粒度形貌分析,探讨其脱硅机理。在最佳条件下添加纳米六方水合铝酸钙进行深度脱硅,脱硅后的铝酸钠溶液中SiO2含量可降低到0.007 g/L,硅量指数可达14000。     

铝酸钠溶液预脱硅晶种活化技术

在烧结法氧化铝生产工艺中,为了保证产品质量,必须对粗液进行脱硅,而基于形成水合铝硅酸钠的脱硅路线,由于渣中硅含量高、铝损失少,是进行粗液第一步脱硅的必要步骤。烧结法氧化铝生产,采用粗液常压预脱硅—中压压煮脱硅—加石灰常压深度脱硅的三段脱硅工艺,对粗液一段常压预脱     

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。     

烧结法生产一级品Al2O3

烧结法生产Ａｌ２Ｏ３在我国已有４０余年的历史，在技术进步上有多方面的重大成就，生产冶金级Ａｌ２Ｏ３以三级品为主，兼有部分二级品，与拜耳法种分产品相比，产品级别和Ｎａ２Ｏ的含量仍有差别，并反映到价格上的差别，开发和应用新的脱硅与分解技术，生产与种分质量相当的碳分产品，有利于低钠化学制品的生产，提高冶金级产品在市场的竞争力，提高企业的经济效益。     

铝酸钙代替石灰——拜耳法溶出的提案

针对一水硬铝石型铝土矿采用联合法生产氧化铝、添加石灰脱硅和石灰法回收镓的国情，提出用烧结法系统产出的铝酸钙替代石灰去拜耳法溶出方案，试验表明，不仅回收了铝酸钙中Ａｌ２Ｏ３，对拜耳法溶出率也无不利影响。故可作为降低联合法生产氧化铝成本的途径。     

NaAl（OH）4溶液脱硅动力学研究现状

系统地概述了铝酸钠溶液中脱硅动力学的研究现状,对于进一步研究脱硅动力学,更好地服务于工业生产有一定的参考价值。     

铝酸钠溶液深度脱硅

叙述了硅在铝酸钠溶液中的存在状态,指出了在烧结法生产氧化铝过程中铝酸钠溶液深度脱硅的重要性.介绍了铝酸钠溶液深度脱硅研究现状,讨论了Ca(OH)2、C3 AH6(立方水合铝酸钙)、C4 AHn(六方水合铝酸钙)、HCAC(水合碳铝酸钙)、HSAC(水合硫铝酸钙)、C4 FHn(六方水合铁酸钙)等含钙化合物深度脱硅机理及脱硅效果.     

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.     

Mineral transition of desilication products precipitated in synthetic sodium aluminate solution under atmospheric pressure

The liquor concentration, mineral proportion, crystal parameters and micro morphology of various desilication products (DSPs) precipitated in silica-supersaturated sodium aluminate solution at 95 °C under different reaction conditions were systematically researched. The DSPs formed under atmospheric pressure comprise amorphous phase, zeolite A, zeolite and sodalite, and the DSPs concentration and crystallinity increase with the increase of initial silica concentration, initial molar ratio of caustic Na₂O to Al₂O₃ (α_K) and desilication duration. Decreasing the initial silica concentration, initial α_K and increasing the desilication duration can reduce the proportion of zeolite A. The zeolite and sodalite are the stable DSPs, while the precipitation of zeolite A occurs at a high silica-supersaturated state in sodium aluminate solution. The DSPs are precipitated in the form of agglomerates, but the morphologies of various DSPs are quite different. Both the molar ratios of Na₂O to Al₂O₃ and SiO₂ to Al₂O₃ in DSPs increase with the increasing desilication duration, resulting in the increase of the cell volumes of various DSPs. The precipitation sequence of DSPs under atmospheric pressure is: amorphous phase→zeolite A→zeolite→sodalite.     

铝酸钠溶液添加硫酸钙脱硅过程的研究

以硫酸钙作为脱硅剂,对铝酸钠溶液脱硅条件和结果进行了研究。实验中考察了脱硅温度、脱硅时间、脱硅剂的用量、搅拌速度对脱硅效果的影响,确定了最佳脱硅工艺条件:在95℃的温度下添加硫酸钙30g/L深度脱硅90min,精制液的硅量指数达3681。对硫酸钙脱硅后所形成的硅渣进行XRD测定,并且对硫酸钙的脱硅机理进行了分析。     

氧化镁在铝酸钠溶液脱硅中的反应行为

通过分析含硅铝酸钠溶液脱硅过程二氧化硅浓度、脱硅渣成分和物相,研究氧化镁在铝酸钠溶液中的反应行为。结果表明,在95~100 ℃的常压脱硅条件下,氧化镁在铝酸钠溶液中易形成水合碳铝酸镁,对溶液基本无脱硅效果,氧化铝损失较多,但氧化镁能显著促进石灰的脱硅作用,且在石灰用量一定时随氧化镁添加量的增加,溶液的脱硅率显著升高;在190 ℃的高压脱硅条件下,氧化镁对铝酸钠溶液石灰脱硅作用的促进不明显,但它可使脱硅渣的钠硅比(质量比)显著降低;无论是单独采用石灰(CaO),还是采用石灰和氧化镁混和物脱硅,含硅铝酸钠溶液高温脱硅渣中均含有钠硅渣相,这与热力学分析结果一致。     

常压混合脱硅工艺生产种分精液

本文介绍了碳分、种分工艺对精液硅量指数A/S的不同要求,认为种分精液单独生产是很有必要的.本文从理论上分析了目前所应用的脱硅工艺,提出了一种常压生产种分精液的方法-常压混合脱硅工艺,并对某厂采用此工艺进行种分精液生产的情况进行了简单的介绍.     

Combined effect of amino and carboxyl group in α-alanine on seeded precipitation of sodium aluminate solution

α-alanine was adopted as a new additive to elucidate the seeded precipitation mechanism of sodium aluminate solution. α-alanine has the inhibitory effect at the initial period of reaction, but the favorable effect in subsequent reaction. The combined effect of amino and carboxyl group in α-alanine was confirmed by investigating the effect of propionic acid, ethamine and the mixture of propionic acid and ethamine (mole ratio 1:1) on the precipitation of sodium aluminate solution, respectively. The inhibitory effect derives from the adsorption of amino or carboxyl group in α-alanine on the active surface sites of gibbsite, which was confirmed by the alleviating inhibitory effects of propionic acid, ethamine and α-alanine due to the double crystal seed mass. The semi-quantitative IR spectrum analysis of the relative concentrations of Al2O(OH)62- with the band at about 550 cm-1 and polynuclear aluminate ion with the bands at about 880 cm-1 and 635 cm-1, indicates that the dynamic balance among some aluminate species present in sodium aluminate solution is broken due to the addition of α-alanine, thus resulting in the change of the seeded precipitation ratio of sodium aluminate solution.