【作者】 胡小莲；

【导师】 陈文汩；

【作者基本信息】 中南大学 ， 有色金属冶金， 2011， 博士

【摘要】 我国铝土矿资源的保障程度差,为了保证我国氧化铝工业的可持续发展,对我国的一些中高品位的高硫铝土矿进行脱硫工艺的研究,将缓解我国的供矿危机,同时由于硫在氧化铝生产中造成极大的危害,也需要在氧化铝生产过程中进行经济合理高效的脱硫方法的研究。本论文包括三个方面的内容：首先是关于高硫铝土矿硫的物相研究；其次是高硫铝土矿硫在溶出过程中的行为研究；第三是采用氧化焙烧、氧化钙焙烧对高硫铝土矿进行脱硫工艺的研究,最后采用湿式氧气氧化法对铝酸钠溶液进行脱除二价硫离子工艺的研究。首先,采用X射线衍射定性分析和硫的化学物相定量分析两种研究方法对高硫铝土矿硫的物相进行研究,结果表明：高硫铝土矿中的硫有的以硫化物型硫为主(主要是黄铁矿),有的以硫酸盐型硫为主,不同产地的铝土矿硫的主要存在形态是不同的；采用Na2CO3溶液洗涤工艺能有效地脱除铝土矿石中的硫酸盐,通过Na2CO3溶液洗涤后,原矿全硫含量下降到0.2%以下,从而符合生产中对硫含量的要求；确定高硫铝土矿中硫的主要存在形态对除硫方法的选择具有理论指导意义。其次,研究硫在溶出过程中的行为。采用广西高硫矿和低硫矿两种矿混合以获得不同硫含量的混合矿进行高压釜溶出试验,详细研究了在溶出过程中铝土矿中硫含量对硫转化率的影响、对铝酸钠溶液中二价硫离子浓度和铁含量的影响,通过在高压釜内对高硫铝土矿及自制的含不同硫离子的铝酸钠溶液进行溶出试验,研究了拜耳法溶出液中硫的形态、硫的转化规律及拜耳液中硫的去向。研究结果表明,铝土矿中硫含量越高,硫的溶出率越大、铝酸钠溶液中铁含量越大、二价硫离子的浓度越高,而且产品中的硫可以使氢氧化铝带色。高硫铝土矿溶出时,其溶出液的硫是各种形式的硫离子的混合物,各种形式的硫离子可以进行相互转换,溶液中的不同形式的硫离子一部分会留在溶液中,一部分会随着溶出产生的脱硅产物而随着赤泥带走,其中硫酸根离子最终以一元型含水硫铝酸钙和硫酸钙的形式随赤泥排出。针对一水硬铝石高硫型铝土矿,以河南矿石为原料,在马弗炉进行焙烧除硫及氧化钙焙烧除硫的研究,重点研究了氧化钙在焙烧过程中的作用。研究表明,矿石中硫的物相不同,其硫的脱除率不同,矿石经焙烧后,硫化物型硫含量降低,加CaO焙烧效果更好；同时CaO起到固硫的作用而降低焙烧过程SO2在空气中的排放,原矿在600℃,45min条件下焙烧时,排放到空气中的硫含量为0.51%,而加了1%的CaO后,则下降为0.31%；矿石经焙烧后,黄铁矿发生反应生成了赤铁矿Fe2O3,加氧化钙焙烧后,氧化钙起到固硫的作用,固硫主产物为CaSO4。焙烧后的矿石溶出液中S2-的含量显著降低,矿石的溶出性能更好。对于以黄铁矿为硫的主要物相的河南A铝土矿,在600℃、60min焙烧的矿石,与原矿同时在240℃,60min的条件下进行溶出试验,焙烧矿溶出液中S2-的含量由原矿的1.78g/L下降到0.15g/L,同时矿石的相对溶出率由85.27%提高到91.21%。鉴于铝酸钠溶液中二价硫离子使得铁的含量增加而影响氧化铝的品位,进行了往高压釜内通入氧气的湿式氧化法脱除拜耳液中的二价硫离子的工艺研究,首先探索各种因素对硫化物去除率的影响,后对湿式氧化法转化硫化物的规律和机理进行了初步探讨,结果表明：湿式氧气氧化法除硫率受釜内氧气起始平衡压力、反应温度、反应时间的影响；较适宜的操作条件为反应温度200℃,氧气起始平衡压力3.0MPa, S2的浓度为1g/L,此时S2-的去除率为99%。在高温高压下,铝酸钠溶液中的S2-大部分被氧化为SO42-,进行的是深度氧化,只有少部分S2-被氧化为硫代硫酸根、亚硫酸根及硫的其它形态；影响S2-氧化为SO42-主要是反应温度和氧气起始平衡压力,当温度高达260℃,氧气起始平衡压力达到1.0MPa,就有98%以上的S2-被氧化为SO42-。更多还原

【Abstract】 At present, China’s alumina industry has a very limited supply of high-grade bauxite resources. In order to bridge the gap between the natural shortage and the high industrial demand for high quality bauxite, an alternative solution to solve the shortage of high-grade bauxite is to develop a process of desulfurization for high sulfur containing bauxite. Moreover, sulfur can affect the production of alumina, so it is necessary to develop an economical and practical method for the removal of the sulfur in high sulfur-containing bauxite. This thesis is composed of three parts. The first part is the study on sulfur phase in high sulfur-containing bauxite; the second part is related to the behavior of sulfur in aluminate solution after digestion process by Bayer process; the third part is concerned with desulfuration of high sulfur bauxite by oxidation roasting, and the tretment of Bayer liquor containing divalent sulfur ions via wet oxidation process.Firstly, I investigated sulfur-presence phases of the ore by means of both the XRD and a chemistry quantitative analysis.The results show that high sulfur-containing bauxite is in the main form of sulfide sulfur (pyrite) and sulfate sulfur, and the main sulfur form of bauxites from different regions is not the same. Using sodium carbonate solution washing technology to wash bauxite can effectively remove sulfate sulfur. After washing process, the content of the total sulfur in ore is lowered to below0.2%and can meet the production requirements as to the sulfur content. Identification of the main sulfur form of high sulfur-containing bauxite can provide theoretical instruction for choosing methods for the removal of sulfur from bauxite.Secondly, the behavior of sulfur during digestion process was studied. Guangxi bauxite containing low amount of sulfur was mixed with Guangxi high sulfur-containing bauxite and was then digested, influence of content of sulfur on conversion of sulfur, on the concentration of S2-and on concentration of iron in aluminate solution was researched. Through digestion experiment using high sulfur-containing bauxite and aluminate solution containing various forms of sulfur in autoclave, the forms and the conversion mechanism of sulfur and the path of sulfur in Bayer liquor were investigated. The results show high amount of sulfur in bauxite would lead to more sulfur entering solution, and with the increase of sulfur in bauxite, iron and S2-concentration in aluminate solution rise significantly. In addition, the sulfur of aluminum hydroxide can make aluminum hydroxide colored. After high sulfur-containing bauxite is digested, the sulfur of aluminate solution is a mixture with various forms of sulfur, and various forms of sulfur can be mutually transformed; some of sulfur in bauxite remains in solution, some is discharged along with desiliconization substance of the red mud, but SO42-is finally discharged with the red mud in the form of3CaO·Al2O3·CaSO4·12H2O and CaSO4.In the third part, using the ore from Henan province, the oxidation roasting process of the desulfuration from the diasporic high sulfur-containing bauxite was studied in the muffle roaster and the action of CaO was emphasized. The results show that the roasting results of bauxite from the different main sulfur phase is not the same, and the content of sulfide (mainly pyrite) reduce with the addition of CaO after being roasted; CaO played the role of fixing sulfur and reduce the release of sulfur in the air. When the raw ore is roasted in the condition of600℃and45min, the release of sulfur in the air (S%) is0.51%, but lowers to0.31%when1%CaO is added to the ores; when CaO is added to the ores during roasting, pyrite reacts and hematite forms, CaO plays the role of fixing sulfur, and the main product of reaction of sulfur fixation is CaSO4. It can dramatically lower S2-concentration in aluminate solution and improve digestibility by roasting; Using Henan bauxite with mainly sulfide sulfur (pyrite), the S2" concentration in aluminates solution is0.15g/L after being roasted under the conditions of600℃,which is about10%of S2-concentration (1.78g/L) in the solution of digested raw ore under the same digesting conditions of240℃,60min60min,,and the extraction rate of aluminum increases to91.21%from85.27%.Because the iron content in alumina products was associated with bivalent sulfur ions in aluminate solution, the wet oxidation had been used to remove the bivalent sulfur ions in high pressure autoclave. The influence of various conditions on the removal of S2-and the oxidation mechanism was investigated in this thesis. The results show it can effectively remove the bivalent sulfur ions in high pressure autoclave with oxygen as the oxidizer by wet oxidation, the removal efficiency of bivalent sulfur ions is affected by the oxygen pressure inside the reactor, reaction temperature, reaction time. The optimum conditions for wet oxidation is the reaction temperature200℃, the oxygen pressure3.0MPa, S2-concentration of1g/L, under these conditions, the removal rate of S2-is99%. At high temperature and pressure, the majority of S2-in aluminate solution is oxidized to SO42-, only a small part of S2-is oxidized to thiosulfate, sulfite and other forms of sulfur; Conversion Of S2-to SO42-is mainly affected by the oxygen pressure and reaction temperature. When the temperature is up to260℃, the oxygen pressure reaches1.OMPa, more than98%of S2-is oxidized to SO42-.更多还原