【作者】 曾绍洪；

【导师】 殷素红； 吴焕勋；

【作者基本信息】 华南理工大学 ， 材料工程（专业学位）， 2022， 硕士

【摘要】 硫铁矿尾矿是硫铁矿（FeS₂）浮选过程中被舍弃的低硫连生体。云浮硫铁矿床作为亚洲已探明储量最大的矿床,年开采硫铁矿300万吨,产生约120万吨的尾矿,开采近30年以来尾矿一直未获得有效高消纳量利用,多年堆积使尾矿库不堪重负,浪费资源且严重危害生态环境。故本课题开展云浮硫铁矿尾矿用于辅助性胶凝材料的研究,基于尾矿的理化特性分析和用于辅助性胶凝材料的性能,提出煅烧法和碱激发提高尾矿活性并弱化有害杂质影响的技术路线,以期为云浮硫铁矿尾矿的资源化利用提供理论依据和新途径。论文首先研究了硫铁矿尾矿的理化特性,重点分析了硫和铁的赋存状态及含量。结果表明,云浮硫铁矿尾矿化学成分以Si O₂、Fe₂O₃、Ca O、Al₂O₃和SO₃为主,普通尾矿（CT）和压滤尾矿（FT）中总SO₃含量分别为15.89%、18.27%,属高硫型硫铁矿尾矿。尾矿中的硫（S）以黄铁矿、磁黄铁矿(Fe_1-xS)、石膏三种矿物形态存在;尾矿中的铁（Fe）主要以黄铁矿、磁黄铁矿和云母类矿物形态存在,部分以风化后的低结晶度矿物形式存在。普通尾矿中总硫含量及石膏含量更少,黄铁矿和磁黄铁矿含量更高;压滤尾矿中则相反。尾矿中黄铁矿和石膏含量较高,可能对水泥基材料产生不利影响。其次,研究了硫铁矿尾矿用于辅助性胶凝材料的性能及及硫赋存状态变化。结果表明,普通尾矿的水化活性高于压滤尾矿;掺30%硫铁矿尾矿的水泥胶砂7d和28d活性指数均高于65%,但28d活性指数不增长甚至下降,180d抗压强度倒缩,用作矿物掺合料会对混凝土或水泥制品体积稳定性和耐久性能产生不利影响,在使用时需加以限制。由于尾矿中含有石膏,可延缓水泥凝结时间,因此将尾矿同时用作水泥混合材和调凝剂,可能是一种更好的利用方式。在硬化水泥浆体中,尾矿中的石膏在28d龄期时大部分已反应生成钙矾石（AFt相）;FeS₂氧化较为缓慢,至180d龄期时氧化程度仍很低。故掺尾矿的水泥胶砂28d活性指数不增长甚至下降及180d抗压强度倒缩主要是由于尾矿中石膏反应生成AFt晶体产生膨胀所致而非FeS₂氧化所致。当尾矿中FeS₂掺量高于8.5%时,才会产生由于其氧化导致的水泥胶砂180d抗压强度降低。基于尾矿胶凝活性不高和FeS₂可能氧化,采用煅烧法去除其中FeS₂并提高胶凝活性。结果表明,尾矿在800℃下保温0.5 h的煅烧效果最佳,FeS₂和Ca CO₃已完全分解,以FeS₂和Fe_1-xS赋存的硫（以SO₃计）约2/3转化为SO₂逸出,1/3转化为Ca SO₄残留,煅烧后主要矿物为石英,赤铁矿和硬石膏;煅烧普通尾矿和压滤尾矿（CCT/CFT）中SO₃含量分别为8.27%、15.51%。煅烧后尾矿活性提高,但由于硬石膏含量多生成更多AFt,导致水泥胶砂的抗压强度比未煅烧的更低,不宜直接用作矿物掺合料,更适宜同时用作水泥混合材和调凝剂,其中硬石膏能达到与等SO₃含量的石膏类似的缓凝效果;水泥熟料胶砂7d和28d强度满足国家标准规定标号为425普通硅酸盐水泥的强度指标,7d和28d活性指数分别为62%、81%。进一步采用碱激发提高尾矿胶凝活性。结果表明,采用碱激发尾矿能减少硬化浆体中生成的AFt数量,弱化尾矿中石膏（硬石膏）的负面影响。复掺3%水玻璃和5%矿渣碱激发煅烧普通尾矿的效果最好,其用作矿物掺合料,水泥胶砂抗压强度比煅烧普通尾矿更高,7d和28d活性指数均≥70%;同时用作水泥混合材和调凝剂,水泥熟料胶砂7d和28d强度满足国家标准规定标号为425普通硅酸盐水泥的强度指标,活性指数分别为80%、83%,虽延缓水泥熟料凝结时间的程度比未碱激发的减弱,但仍与等SO₃含量的石膏缓凝效果相近。更多还原

【Abstract】 Pyrite tailings are low sulfur intergrowth abandoned in the flotation process of pyrite（FeS₂）.Yunfu pyrite deposit,with the largest proven reserves in Asia,mines 3 million tons of pyrite and generates about 1.2 million tons of tailings every year.Since mining for nearly 30years,the tailings have not been effectively utilized with high absorption capacity.Years of accumulation has overwhelmed the tailings reservoir,wasted resources and seriously harmed the ecological environment.Therefore,this subject carries out the research on the use of Yunfu Pyrite Tailings as auxiliary cementitious materials.Based on the physical and chemical properties of the tailings and the performance of the tailings used for auxiliary cementitious material,this paper puts forward the technical route of calcination and alkali-activated to improve the activity of tailings and weaken the influence of harmful impurities,so as to provide theoretical foundation and new ways for the resource utilization of Yunfu pyrite tailings.Firstly,the physical and chemical properties of pyrite tailings were studied,and with emphasis on the occurrence and content of sulfur and iron.The results show that the chemical composition of Yunfu pyrite tailings is mainly Si O₂,Fe₂O₃,Ca O,Al₂O₃ and SO₃.The total SO₃ content of ordinary tailings（CT）and filter-press tailings（FT）is 15.89%and 18.27%respectively,belonging to high sulfur pyrite tailings.Sulfur（S）in tailings exists in the form of pyrite,pyrrhotite(Fe_1-XS)and gypsum.Iron（Fe）in tailings mainly exists in the form of pyrite,pyrrhotite and mica minerals,and some exists in the form of low crystallinity minerals after weathering.The contents of total sulfur and gypsum in ordinary tailings are less,but the contents of pyrite and pyrrhotite are higher.The opposite is true in filter-press tailings.The high content of pyrite and gypsum in tailings may have adverse effects on cement-based materials.Secondly,the properties of pyrite tailings used as auxiliary cementitious materials and the change of sulfur occurrence state are studied.The results show that the hydration activity of common tailings is higher than that of filter-press tailings.The activity index of cement mortar mixed with 30%pyrite tailings is higher than 65%at 7 and 28 days,but the activity index of 28 days does not increase or even decrease,and the compressive strength of 180 days shrinks.As a mineral admixture,the volume stability and durability of concrete or cement products will be adversely affected,so it needs to be restricted in use.Since tailings contain gypsum,which can delay cement setting time,it may be a better way to use tailings as both cement mixture and setting agent.In hardened cement paste,most of the gypsum in tailings has reacted to ettringite（AFt phase）at the age of 28 days.The oxidation of FeS₂ is relatively slow,and the oxidation degree is still low at the age of 180 days.Therefore,the fact that the28 days activity index of cement mortar mixed with tailings does not increase or even decrease and its compressive strength shrinks at 180 days is mainly caused by the expansion of AFt crystal generated by gypsum reaction in tailings,rather than the oxidation of FeS₂.When the content of FeS₂ in tailings was higher than 8.5%,the 180 days compressive strength of cement mortar decreased due to its oxidation.Based on the low cementification activity of tailings and the possible oxidation of FeS2,calcination method was adopted to remove FeS₂ and improve the cementification activity.The results show that the calcination effect of tailings is the best when the tailings are held at800℃for 0.5 h.FeS₂ and Ca CO₃ have been completely decomposed.About 2/3 of the sulfur（calculated by SO₃）stored in FeS₂ and Fe_1-XS is converted to SO₂ and escapes,while 1/3 is converted to Residual Ca SO₄.After calcination,the main minerals are quartz,hematite and anhydrite.The content of SO₃ in calcined common tailings and filter-press tailings（CCT/CFT）is 8.27%and 15.51%,respectively.After calcination,the activity of tailings is improved.But due to the high content of anhydrite,more AFt was generated.The compressive strength of cement mortar is lower than that of uncalcined cement mortar.So calcined common tailings is not suitable to be directly used as mineral admixture,but more suitable to be used as cement mixture and setting agent at the same time.Anhydrite can achieve the retarding effect similar to that of gypsum with equal SO₃ content.The 7 and 28 days strength of cement clinker mortar meets the strength index of 425 ordinary Portland cement stipulated in the national standard,and the activity index of 7 and 28 days is 62%and 81%respectively.Alkali-activated and activation is further used to improve the cementitious activity of tailings.The results show that alkali-activated tailings can reduce AFt generated in hardened paste and weaken the negative effect of gypsum（anhydrite）in tailings.The performance of 3%sodium silicate and 5%slag alkali-activated calcined common tailings is the best.As a mineral admixture,the compressive strength of cement mortar is higher than that of common tailings calcined,and the activity index of 7 and 28 days are both≥70%.At the same time,used as cement mixed material and the admixture,cement paste intensity of 7 and 28 days meet grade of national standard is 425 ordinary Portland cement strength index,and the activity index is 80%and 83%,respectively.Although the degree of delaying the setting time of cement clinker is weaker than that of non alkali excitation,3%sodium silicate and 5%slag alkali-activated calcined common tailings is still similar to that of gypsum with equal SO₃content.更多还原