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。     

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.     

非均相法制备斜方水合碳铁酸钙用于高浓碱溶液脱硅的研究

针对亚熔盐反应体系处理一水硬铝石型铝土矿后的高浓碱溶出液难以脱硅的问题,提出采用碳铁酸钙作为高浓碱溶液深度脱硅的脱硅剂。采用非均相方法合成了斜方晶型的水合碳铁酸钙(3CaO.Fe2O3.CaCO3.12H2O),并对影响合成过程的主要因素进行了考察。结果表明,反应温度和反应时间对水合碳铁酸钙的合成具有交互影响,合成过程中适当提高温度、缩短合成时间可以提高水合碳铁酸钙的含量。合成水合碳铁酸钙脱硅剂最优的工艺条件为:反应温度303K,反应时间16h,反应液固比25,搅拌速率500r/min;氧化钙粒度在0.104mm～0.120mm范围内。在高浓碱溶液脱硅过程中,水合碳铁酸钙产生了物质结构改变,斜方晶系的水合碳铁酸钙转变为立方晶型的钙铁石榴石,在此过程中二氧化硅和少量氧化铝进入晶体结构,形成钙铁硅石榴石和钙铁铝硅石榴石。脱硅产物中氧化铝含量低于1%,氧化钠含量低于2%,SiO2含量高于2%,脱硅产物的铝硅比小于0.5;通过加入水合碳铁酸钙进行高浓碱介质下的溶液深度脱硅,可使溶液中二氧化硅浓度低于0.1g/L。     

水合硫铝酸钙的合成

通过正交实验对水合硫铝酸钙的合成温度、合成时间、合成体系中CaO与A12O3的摩尔比、合成体系中SO4^2-高于的浓度等因素对其脱硅效果的影响进行了研究，并给出了水合流铝酸钙的最佳合成条件。结合XRD分析和IR光谱分析讨论了水合硫铝酸钙合成机理和脱硅机理，提出水合流铝酸钙是一种高水合、高度分散的含钙化合物，其脱硅活性高。在最佳条件下添加水合硫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8mg／L，硅量指数可达12500。     

非均相法制备高浓碱溶液脱硅剂斜方水合碳铁酸钙的研究

提出以斜方水合碳铁酸钙为脱硅剂解决亚熔盐法处理一水硬铝石型铝土矿所得高浓碱溶出液的深度脱硅问题.采用非均相方法合成了碳铁酸钙(3CaO·Fe2O3·CaCO3·12H2O)脱硅剂,对影响合成过程的主要因素进行了考察.结果表明,适当提高合成温度、缩短合成时间可以提高水合碳铁酸钙的含量.最优合成工艺条件为:反应温度313 K,反应时间16 h,反应液固比25,搅拌速率500 r/min,氧化钙粒度0.104mm～0.120mm.脱硅过程中,斜方晶系的水合碳铁酸钙转变为立方晶型的钙铁石榴石,在此过程中二氧化硅和少量氧化铝进入晶体结构,形成钙铁硅石榴石和钙铁铝硅石榴石,脱硅产物的铝硅比小于0.5.     

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。     

煤系硫铁矿浮选尾矿热化学活化脱硅制备铝精矿

提出热活化脱硅技术处理某煤系硫铁矿浮选尾矿制备铝精矿,对制备氧化铝精矿的工艺制度及脱硅机理进行研究。结果表明:该尾矿适宜的热化学活化脱硅制度为活化焙烧温度1 150℃、焙烧时间15～20 min、碱浸溶硅温度125～140℃、溶出时间30 min、NaOH浓度140 g/L。在此条件下,对Al2O3和SiO2含量分别为46.22%和28.33%(质量分数)的硫铁矿浮选尾矿,焙砂SiO2溶出率达到71.91%,所得铝精矿中Al2O3含量达69.29%,铝硅比5.59。XRD结果表明:硫铁矿尾矿中伊利蒙脱石、高岭石和叶腊石等铝硅酸矿物在焙烧过程中活化分解生成无定形SiO2和少量莫来石,与此同时,一水硬铝石转变成α-Al2O3。在焙砂的碱浸过程中,无定形SiO2溶解于NaOH溶液被脱除,而α-Al2O3和莫来石不能溶解,同时生成的水合铝硅酸钠(Na8Al6Si6O24(OH)2(H2O)2)将导致SiO2溶出率降低。焙烧过程中尾矿中的黄铁矿转化为赤铁矿、锐钛矿部分转化成金红石,在碱浸过程中它们均不会溶解而进入铝精矿中。     

碱法对粉煤灰的预脱硅处理

在NaOH溶液中,常压下采用加热、搅拌的溶出方式,对某电厂粉煤灰进行预脱硅处理。通过分光光度法和EDTA置换滴定法分别测出溶渣中SiO2和Al2O3的量,计算得出渣中的铝硅比。考察液固比、溶出温度、溶出时间、碱浓度等因素对粉煤灰溶出后渣中铝硅比的影响。结果表明,在液固比为30∶1、温度90℃、溶出时间2h、30%碱浓度(质量分数)条件下,粉煤灰的脱硅率可达58%以上,预脱硅后渣中铝硅比由0.97提高到2.71。     

碱石灰烧结法从脱硅粉煤灰中提取氧化铝

采用碱石灰烧结法,对脱硅粉煤灰中提取氧化铝过程进行了研究,系统探讨了熟料烧成条件对氧化铝溶出率的影响.实验结果表明:烧结过程中,在生料配比CaO/SiO2值为2.0、Na20/Al2O3值为1.0,烧结温度为1200℃,保温时间60分钟的烧结条件下烧成熟料,在规定的溶出条件下,熟料中A1203的溶出率可达90%以上.     

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.     

Preparation of SO2-4/TiO2-WO3 solid superacid and its catalytic activity in acetalation and ketalation

SO2-4/TiO2-WO3 was prepared and its catalytic activity under different synthetic conditions was discussed with esterification of n-butanoic acid and n-butyl alcohol as probing reaction. The optimum conditions are found that the mass fraction of H2WO4 used in the compound is 12.5%, the calcination temperature is 580℃, the calcination time is 3 h, and the soaked consistency of H2SO4 is 1.0 mol.L-1. Then SO2-4 /TiO2-WO3 was applied as the catalyst in the catalytic synthesis of eight similar important ketals and acetals under the optimum conditions and revealed high catalytic activity. On condition that the molar ratio of aldehyde/ketone to glycol is 1:1.5, the mass fraction of the catalyst used in the reactants is 0.5%, and the reaction time is 1.0 h, the yields of ketals and acetals can reach 64.2%-95.1%. Moreover, it can be easily recovered and reused.     

添加晶种低温脱硅及其动力学

研究了晶种容量表面积的低温脱硅动力学，建立了低温脱硅动力学的经验公式及溶液中ＳｉＯ２ 含量与脱硅时间的曲线方程，探索了晶种的选择及晶种的循环利用。晶种容量表面积的作用是随溶液中ＳｉＯ２介稳浓度的升高而增强，又随介稳浓度的降低而减弱。增大晶种容量表面积能加快脱硅速度。     

Catalytic synthesis of cyclohexanone 1,2-propanediol ketal with H_4SiW_(12)O_(40)/PAn

A new environmental friendly catalyst, H4SiW12O40/PAn was prepared and identified by means of FT-IR, XRD and TG/DTA. Cyclohexanone 1,2-propanediol ketal was synthesized from cyclohexanone and 1,2-propanediol in the presence of H4SiW12O40/PAn. The factors influencing the synthesis were discussed and the best conditions were found out. The optimum conditions are: molar ratio of cyclohexanone to 1,2-propanediol is 1:1.4, the quantity of catalyst is equal to 1.0% of feed stocks, and the reaction time is 40 min. H4SiW12O40/PAn is an excellent catalyst for synthesizing cyclohexanone 1,2-propanediol ketal and its yield can reach over 96.5%.     

钒钛渣碱浸脱硅

研究一种选择性脱除钒钛渣中二氧化硅的工艺。利用XRD、SEM和EDS对钒钛渣和碱浸出后的样品进行表征。结果表明：钒钛渣的主要组分是黑钛石、辉石和金属铁。黑钛石为板状和颗粒状,分布于辉石中;金属铁为球型,呈蠕虫状被包裹于辉石和黑钛石中,边缘被氧化;硅主要分布在辉石中;钛和钒主要分布在黑钛石中。对搅拌速度、浸出温度、浸出时间、NaOH浓度和液固比对浸出的影响进行研究。结果表明：浸出温度和液固比对Si02的浸出率有较大的影响,在最佳实验条件下,Si、A1、Mn和v的浸出率分别为88．2％、66．3％、27．3％和1．2％。钒钛渣碱浸脱硅动力学过程受化学反应控制,其表观活化能为46．3kJ／mol。     

Intensifying digestion of diaspore and separation of alumina and silica

1　INTRODUCTIONDespitetheabundantdepositofbauxitesinChi na ,ofthosepredominantisthediasporictypewithhighalumina ,highsilicaandlowferricoxides .Thebauxitedeposit,withthemassratioofaluminatosil ica(A/S)between 4and 8,accountsfor 80 %ofallthebauxitedeposit.Thenatureofhighsilicacontentdeterminesthatthemainlyadoptedtechniquetopro ducealuminainChinashouldbeBayer sinteringcom binationprocessorevenpuresinteringprocess .Althoughadramaticadvancementinaluminaproductionhasbeenachievedandthetechnolo…     

加热界面温度对一水硬铝石型铝土矿浆加热面结疤过程的影响机理

通过研究矿浆预热温度对矿浆液相中SiO2浓度以及Mg(OH)2的平衡浓度等的影响，揭示了矿浆加热界面温度对结疤过程的影响规律。矿浆加热界面温度越高。界面处矿浆液相中SiO2浓度越高，SiO2的过饱和程度也越高；同时．脱硅反应速度常数越大，则脱硅反应速度越快。矿浆加热界面温度越高．界面处Mg(OH)2的平衡浓度越低．则Mg(OH)2的过饱和程度越高．Mg(OH)2的析出速度越快。矿浆加热界面温度越高，含钛矿物的结疤速度也越快。所以．矿浆加热界面温度越高．总体结疤速度越快。在保证预热温度的前提下，尽可能地降低矿浆间接加热界面的温度，例如．采用蒸汽而不是熔盐作为加热介质。可以在一定程度上达到减缓结疤的目的。     

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.