【作者】 刘牡丹；

【导师】 邱冠周； 姜涛；

【作者基本信息】 中南大学 ， 钢铁冶金， 2010， 博士

【摘要】 本研究为国家自然科学基金委国家杰出青年科学基金“矿物工程与物质分离科学”项目(批准号：50725416)资助课题。高铝铁矿是一类典型的难处理矿石,采用常规选矿工艺难以有效实现铝铁分离。为实现高铝铁矿资源的综合利用,本文以印尼某铁矿石为对象,系统研究了其物理化学特性及工艺矿物学特征；在探索试验基础上,针对该资源铁铝嵌布紧密的特点,研究了钠化还原焙烧过程中铁、铝、硅氧化物的热力学行为及条件；采用纯物质为原料进一步研究了钠化还原过程中铁、铝、硅氧化物的反应历程,建立了铁、铝、硅组分分离行为基础；通过深入研究焙烧球团的微观结构、还原气氛下钠盐的熔融特性及在钠盐存在条件下铁氧化物还原动力学,揭示了钠化还原焙烧过程中铁、铝、硅矿物分离的微观机制,阐明了不同钠盐对铝铁分离的作用机理,在此基础上开发了基于还原法的铝铁分离新工艺,形成高铝铁矿石铝铁分离技术原型。1、原料物化性能研究试验所用原料铁品位为48.92%,Al2O3和Si02含量分别为8.16%、4.24%。铁矿物以赤铁矿和针铁矿为主；脉石矿物主要是三水铝石、石英及硅酸盐类粘土矿物。原矿中占总铝含量40.44%的铝以类质同像形式存在于铁矿物中,硅酸盐矿物与铁矿物交生镶嵌,形成矿石内部铁、铝、硅矿物复杂的嵌布关系,采用常规选矿方法难以有效脱除铁矿中的Al2O3和Si02。2、热力学研究(1)固体碳还原铁氧化物,当T>968K,CO%>59.1％时,铁氧化物可被还原为金属铁。还原过程中FeO、SiO2、Al2O3三者之间将发生固相反应,生成铁橄榄石、FeO·Al203及Al2O3·Si02。固体碳还原FeO·Al203的开始温度为1190K,添加硫酸钠后开始还原温度为1010K,添加碳酸钠后开始还原温度为1080K。(2)氧化气氛下Al2O3、8iO2很难与硫酸钠自发反应,还原气氛下Al2O3、Si02均优先与钠盐反应生成铝硅酸钠,Al2O3和Si02与Na2CO3开始反应的最低温度为275K,与Na2SO4开始反应的最低温度为500K。同时,添加硫酸钠还原时,FeS及Na2S能自发生成,Na2SO4被还原为S的最低温度为690K。(3)根据各反应△G大小可知,当1000K<T<1500K时,碳酸钠存在的还原体系各物质生成的优先顺序为：Na2O·Al203·6 Si02>Na2O·Al2O3·4Si02>Na2O·2Si02>Na2O·SiO2>NaAlO2>2Na2O·Si02；硫酸钠存在的还原体系各物质生成的优先顺序为：Na20·Al203·6SiO2>Na20·Al2O3·4SiO2>Na20·2SiO2>Na2O·Si02>2Na2O·Si02>NaAlO2。3、纯物质体系还原焙烧过程中各组分物相变化研究(1)在Fe2O3-Al2O3-SiO2-Na2SO4体系,600℃-700℃时,铁的物相为Fe3C、Fe1-xS和NaFeS2；800℃-1000℃时,铁的物相为Fe和NaFeS2；1150℃时铁的物相为FeO、Fe、NaFeS2和NaFe3Si2O6；1250℃时铁的物相为FeO、Fe、NaFeS2和(Fe0.88Al0.12)(Al1.88Fe0.12)O4。SiO2、Al2O3在700℃与硫酸钠反应生成铝硅酸钠。(2)在Fe2O3-Al2O3-SiO2-Na2CO3体系,400℃-700℃时,铁的物相为Fe3C、FeO和Fe3O4；800℃-1100℃时,铁的物相为Fe。SiO2与Al2O3在550℃时反应生成Al2O3·SiO2,同时铝硅酸钠开始大量生成。(3)在Fe2O3-SiO2-Na2SO4体系,600℃时,铁的物相有Fe3C、FeO、FeS、NaFeS2；740℃时铁的物相有FeO、Fe和FeS；800℃时铁的物相为FeO、Fe、FeS和NaFeO2.35Si0.175；900℃-1000℃时铁的物相是FeO和Fe；1100℃铁的物相为FeO、Fe、FeO·SiO2和Fe2SiO4。SiO2在800℃时与铁、钠反应生成NaFeO2.35Si0.175,900℃时与硫酸钠反应生成Na2Si2O5,1100℃时与FeO反应生成硅酸铁。(4)在Fe2O3-Al2O3-Na2SO4体系,600℃-700℃时,铁的物相以Fe3C、Fe3O4和NaFeS2为主,800℃-1100℃时,铁的物相以Fe和NaFeS2为主。Al2O3与硫酸钠在740℃时开始反应生成铝酸钠。4、还原焙烧过程中铁、铝、硅矿物分离的微观机制研究(1)物相研究表明,高铝铁矿石不添加钠盐还原焙烧,铁氧化物部分被还原成无磁性的γ-Fe,难以通过磁选回收；添加钠盐后,铁氧化物的还原得到改善,脉石矿物Al2O3、SiO2与钠盐发生反应生成铝硅酸钠。(2)还原球团显微结构研究表明,不添加钠盐还原,大部分铁矿物与铝、硅矿物结合紧密；碳酸钠能促进铁氧化物的还原,但是铁晶粒数目多、粒度小,与脉石矿物铝硅酸钠结合较紧密；添加硫酸钠还原,铁晶粒与脉石矿物界限分明；硼砂能促进铁晶粒沿边界析出连接长大,使得铁晶粒间相互连接成一个整体。(3)还原气氛钠盐熔融性质研究表明,硫酸钠存在的还原体系将新生成S、Na2S、FeS等物质,在局部形成液相,为铁离子的扩散提供通道。而碳酸钠存在的还原体系,铁离子的迁移只能通过固相扩散进行,迁移阻力较大,因此铁晶粒与脉石矿物的界限不及添加硫酸钠时分明。(4)硫酸钠和碳酸钠均能显著提高铁矿石的还原速率,在还原初期,添加碳酸钠还原速率较硫酸钠要慢。因此,碳酸钠存在的还原体系,在还原初期,一方面,铁氧化物的还原速度较硫酸钠慢,另一方面,碳酸钠与铝、硅矿物反应温度低,速度快,铝硅酸钠的快速生成成为铁离子迁移的壁垒,铁离子扩散的势垒增大,不利于铁晶粒长大及其与脉石矿物的分离。5、高铝铁矿石钠化还原铝铁分离新工艺研究(1)钠化还原-磨矿磁选工艺能有效实现铝铁分离,在硫酸钠用量12%,硼砂用量2.5%,焙烧温度1050℃,焙烧时间60min,磨矿细度-0.074mm粒级占98%,磨矿浓度50%,磁场强度675mT的条件下,可获得铁品位91.00%,Al2O3含量1.36%的金属铁粉,铁的回收率为91.58%,铝的脱除率为90.47%。(2)在钠化还原焙烧过程中,铁氧化物被还原成金属铁,大部分铝、硅矿物与硫酸钠反应生成不溶于水的铝硅酸钠,经磁选后进入非磁性物中,从而实现了铝铁的高效分离。(3)钠化还原法所得金属铁粉经过进一步处理后可用于电炉炼钢,非磁性物可综合回收铝、硅、钠、铬等有价元素,从而实现资源的综合利用。更多还原

【Abstract】 High-aluminium content iron ore is a typical refractory ore, traditional processes are found invalid to separate aluminium and iron. To utilize such resources, a high-aluminium content iron ore, taken from Indonesia, is used in the thesis. The physicochemical properties and mineralogy characters are systematically studied. Considering the close distribution relationship between iron and aluminium, the thermodynamic behaviours and conditions of ferreous, aluminiferous and silaceous oxides in the process of reduction roasting with addition of sodium salts are analysed. The reaction processes of ferreous, aluminiferous and silaceous oxides are studied by using pure materials, and the fundamental of separation behaviour is set up. The micromechanism of ferreous, aluminiferous and silaceous minerals in the process of reduction roasting with addition of sodium salts is revealed, and the action mechanism of different sodium salts on the Al-Fe separation is also illuminated, based on the studies of the microstructure of roasted pellets, smelting characters of sodium salts in reduction atmosphere and reduction dynamics of iron oxides with addition of sodium salts. On this basis, the new process of reduction roasting is developed, and the Al-Fe separation technological prototype for hig-aluminium content iron ore is formed.1. Research on the physicochemical properties of materialsIt is indicated that major iron minerals in the ore, with 48.92% TFe, 8.16% Al2O3 and 4.24% SiO2, are hematite and goethite, and gangue minerals are gibbsite, quartz and silicate-clay. There are 40.44% aluminium of total Al2O3 content exist in iron minerals in the form of isomorphism, and silicate minerals also form complex relationship with iron minerals. It is shown that the existential relationship among ferreous, aluminiferous and silaceous minerals is very complex, resulting in the difficult removal of aluminiferous and silaceous minerals from ferreous minerals by using normal physical beneficiation methods.2. Thermodynamics investigation(1) When iron oxide is reduced by carbon, iron oxide is reduced to metallic iron when temperature exceeds 968K and CO concentration exceeds 59.1%. FeO, SiO2 and Al2O3 will react with each other and form FeO·SiO2, FeO·Al2O3 and Al2O3·SiO2 in the reduction process. The lowest reduction temperature of FeO·Al2O3 is found to be 1190K by carbon reduction, while the lowest temperature is 1010K when sodium sulfate added, and the temperature is 1080K when sodium carbonate added in the reduction process.(2) It is difficult for the reaction of Al2O3 and SiO2 with Na2SO4 in air atmosphere, while sodium aluminosilicate will be formed preferentially in reducing atmosphere among Al2O3, SiO2 and sodium salts. The lowest temperature for reaction of Al2O3 and SiO2 with Na2CO3 is found to be 275K, and for Al2O3 and SiO2 with Na2SO4, the temperature is 500K. On the other hand, FeS and Na2S will be formed spontaneously in the reduction system with sodium sulfate exited, and the lowest temperature for formation of S is 690K.(3) It is known that, according to the values ofΔG, when 1000K<T < 1500K, the formation order of sodium-salts in the reduction system with sodium carbonate exited is as the following:Na2O·Al2O3·6 SiO2>Na2O·Al2O3·4SiO2>Na2O·2 SiO2> Na2O·SiO2>NaAlO2>2Na2O·SiO2.And in reduction system with sodium sulfate exited is as the following:Na2O·Al2O3·6SiO2>Na2O·Al2O3·4SiO2>Na2O·2SiO2>Na2O·SiO2>2N a2O·SiO2>NaAlO2.3. Research on the phase transformation of components in the reduction roasting process in the pure materials system(1) For Fe2O3-Al203-SiO2-Na2SO4 system, Fe3C, Fe1-xS and NaFeS2 are found as main iron phases in the temperatures of 600℃-700℃, and Fe and NaFeS2 will be formed when temperature is between 800℃-1000℃. Iron phases are FeO, Fe, NaFeS2 and NaFe3Si2O6 at 1150℃, and when temperature is 1250℃, iron phases are FeO, Fe, NaFeS2 and (Fe0.88Al0.12)(Al1.88Fe0.12)O4. SiO2 and Al2O3 react with Na2SO4 at 700℃and form sodium aluminosilicate.(2) For Fe2O3-Al2O3-SiO2-Na2CO3 system, iron phases are Fe3C, FeO and Fe3O4 in the temperatures of 400℃-700℃, and when temperature is between 800℃-1100℃, iron phase is metallic Fe mainly. SiO2 and Al2O3 react with each other at 550℃and forms Al2O3·SiO2, then sodium aluminosilicate will be formed simultaneously.(3) For Fe2O3-SiO2-Na2SO4 system, iron phases are Fe3C, Fe, FeS and NaFeS2 at 600℃, FeO, Fe and FeS at 740℃, and FeO, Fe, FeS and NaFeO2.35Si0.175 at 800℃. FeO and Fe are main iron phases in roasted ore when temperature is between 900℃-1000℃. FeO, Fe, FeO·SiO2 and Fe2Si04 are main iron phases at 1100℃. SiO2 reacts with FeO and Na2O at 800℃and forms NaFeO2.35Si0.175, and Na2Si205 is formed at 900℃, and iron silicate is formed at 1100℃.(4) For Fe2O3-Al2O3-Na2SO4 system, iron phases are Fe3C, Fe3O4 and NaFeS2 when temperature is between 600℃-700℃, and iron phases are Fe and NaFeS2 when temperature is between 800℃-1100℃. Al2O3 reacts with Na2SO4 at 740℃and forms sodium aluminate.4. The micromechanism of separation of ferreous, aluminiferous and silaceous minerals in the reduction roasting process(1) Some iron oxides are reduced to non-magnetic ironγ-Fe, which is unable to be recovered through magnetic separation, when high-aluminium content iron ore is reduced without sodium salts. The reduction of iron oxides gets improvement when sodium salts are added, and SiO2, Al2O3 will react with Na2CO3 or Na2SO4 to produce sodium aluminosilicate.(2) It is indicated by the results of microstructure of reduced pellets that, most ferrous minerals combine with aluminiferous and silaceous minerals tightly without addition of sodium salts in the roasting process. Sodium carbonate can be able to promote the reduction of iron oxides, and many iron grains with small size are found in the pellet, which combine with sodium aluminosilicate closely. While the boundary between iron grains and gangue minerals is clear as sodium sulfate is added. Addition of borax promotes iron grains to separate out along borderline of gangue minerals and grow big, making iron grains join together.(3) The smelting properties of sodium salts show that, S, Na2S and FeS will be formed spontaneously in reduction system with addition of sodium sulfate, which become liquid phase in local area, providing migrating passage for iron ions. While in reduction system with sodium carbonate existed, iron ions only diffuse in solid phase, and the migrating resistance is relatively big, so the boundary between iron grains and gangue minerals is not clear as sodium sulfate exited.(4) Sodium sulfate and sodium carbonate can both accelerate the reduction of high-aluminium content iron ore. While the reduction rate is slow in reduction system with sodium carbonate exited compared with sodium sulfate exited during early stage. On the other hand, sodium carbonate reacts with aluminium and silicon oxide quickly, and the formation of sodium aluminosilicate becomes move holdback of iron ions, and the diffusion barrier of iron ions increases, which goes against the separation iron grains and gangue minerals.5. New process of sodium-added reduction for Al-Fe separation of high-aluminium content iron ore(1) The process of sodium-added reduction followed by grinding-magnetic separation has been developed to separate iron and aluminium effectively. A metallic iron powder with total iron grade of 91.00% and Al2O3 content of 1.36% is obtained at the sodium sulfate dosage of 12%, the roasting temperature of 1050℃and time of 60min, the grinding fineness of 98% less than 0.074mm and the magnetic field intensity of 675mT, then the iron recovery is 91.58%, and the removal of Al2O3 is 90.35%.(2) In the sodium-added reduction process, iron oxides are transformed into metallic iron, and most aluminiferous and silaceous minerals react with sodium sulfate and form no-nmagnetic sodium aluminosilicates, which enter into non-magnetic materials during magnetic separation, then Al-Fe separation is realized successfully.(3) The metallic iron powder obtained from the sodium-added reduction process can be used for steel-making in electric furnace by further treatment. Some valuable elements such as alimiunium, silicon, sodium and chrome can be recovered from non-magnetic materials, then the utilization of the resources is realized.更多还原