unknownunknown202018-05-25T04:35:00Z2018-05-25T04:35:00Z23481985Sky123.Org164232914.00CleanCleanfalse7.8 磅02falsefalsefalseEN-USZH-CNX-NONE/* Style Definitions */ table.MsoNormalTable {mso-style-name:普通表格; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.5pt; mso-bidi-font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi; mso-font-kerning:1.0pt;}钛、钒、铬是世界各国公认的重大特色战略资源，广泛用于钢铁工业、冶金工业、化学工业、航空航天以及国防军事等领域，对国民经济发展和国家安全保障具有十分重要的作用。我国绝大多数的铬资源储藏于四川攀西红格矿区的高铬型钒钛磁铁矿中，在国内铬资源紧缺的大环境下，对高铬型钒钛磁铁矿进行综合利用就成为了亟需解决的问题。目前，对于高铬型钒钛磁铁矿的利用方法与普通钒钛磁铁矿无异，主要是高炉法和直接还原-电炉熔分都存在着工艺流程长、资源利用率低、能耗高、环境负荷重等问题。本论文针对上述问题，提出了一种高铬型钒钛磁铁矿综合利用新工艺，该工艺主要包含一步高温过程和一步水浸出过程，之后，铁铬、钒、钛分别被富集在块状生铁、含钒浸出液和含钛浸出渣中。高铬型钒钛磁铁矿在高温过程中先后发生了一系列反应，包括铁氧化物向金属铁的还原、钒氧化物钠化氧化为水溶性钒酸钠、铬氧化物的还原碳化并溶解于铁水中、熔融渣铁相的分离。因此将该新工艺流程称之为“还原钠化熔分耦合新工艺”。该工艺流程具有流程短、能耗低、资源综合利用率高、环境污染小等优点，为高铬型钒钛磁铁矿的高效综合利用提供了一种创新性的思路。论文取得的创新性成果如下：（1）对还原钠化耦合过程进行热力学可行性分析，发现在耦合过程中理论上可以同时实现铁氧化物向金属铁的还原和钒氧化物向水溶性钒酸钠的氧化钠化；（2）在钒钛磁铁精矿、还原剂和钠盐的混合物中，当碳铁摩尔比在2.0-3.2的范围内，碳酸钠的添加量在40 wt%-100 wt%的范围内，且焙烧温度在1150-1200℃的范围内时，可以在焙烧过程中同时实现铁氧化物的还原、钒氧化物的氧化钠化和渣铁熔化分离，即实现了直接还原-氧化钠化-渣铁熔分耦合过程，焙烧过程后，铁铬富集在块状铁相中用于后续特种钢的制备，钒钛富集在焙烧渣中用于后续钒钛的分离提取和利用。（3）对渣铁熔分过程的影响因素进行了系统地研究，发现多种因素会对渣铁熔分过程产生影响，包括还原剂类型、钠盐类型、焙烧温度、焙烧时间、碳铁摩尔比、碳酸钠添加量、料层厚度等；综合考虑渣铁熔分的效果和钒铬在渣铁相之间的分配情况，得到最优的焙烧条件，还原剂为无烟煤、钠盐为碳酸钠、焙烧温度1200℃、焙烧时间2 h、碳铁摩尔比2.6、碳酸钠添加量70%、料层厚度42.5 mm。在最优焙烧条件下，铁的回收率为98.15%，铁相中的铁品位为95.44%，96.19%的铬赋存在铁相中，84.9%的钒赋存在渣相中。（4）铁相的钒品位会随着焙烧条件的变化而变化，铁相中的铬品位则不随焙烧条件的变化而变化，始终保持在0.925%左右；钒在渣铁相之间的迁移与钒的铁相中的含量和铁的回收率及渣铁分离效果有关；铬在渣铁相之间的迁移仅与铁的回收率即渣铁分离效果有关。（5）对焙烧渣中钒的浸出工艺进行优化，得到钒的最佳浸出条件为粒度-0.035 mm、浸出温度90℃、液固比4:1、搅拌速度400 r/min、浸出时间30 min，此时钒的浸出率为85.62%；焙烧渣中钒浸出过程的活化能为19.27 kJ/mol，浸出过程受内扩散控制。（6）对浸出渣和浸出液进行分析发现，浸出渣中Fe、Ti、V、Cr的含量分别为7.27%、13.22%、0.078%、0.006%，物相组成为硅铝酸钠盐和少量钛酸钙，可以作为生产钛白粉的原料，浸出渣主要由硅铝酸钠盐和少量钛酸钙组成，浸出液中含有3.68 g/L V2O5、50.39 g/L NaOH、0.3 g/L SiO2和1.5 g/L Al(OH)3。（7）对还原钠化耦合过程中铁氧化物的还原过程进行研究，发现焙烧产物中主要包含三种物相，金属铁相、富钛相和硅酸盐相；随着焙烧时间的延长，铁钛硅元素逐渐迁移和聚集形成铁相、富钛相和硅酸盐相，且彼此相之间的界限逐渐清晰；在相同的焙烧时间下，升高焙烧温度、升高碳铁摩尔比、升高碳酸钠的添加量均有利于铁钛硅在各自富集相中的聚集和各个物相之间的相互分离；随着焙烧时间的延长，钒铬逐渐向硅酸盐相和铁相中迁移；并且升高焙烧温度、升高碳铁摩尔比、升高碳酸钠的添加量均有助于钒铬向硅酸盐相和铁相中的富集。（8） 对还原钠化耦合过程中铁钒铬钛氧化物的反应机理进行研究，发现在Cr2O3-C-Na2CO3三元体系中，当Na2CO3与C的摩尔比大于0.5:3.33时，Cr2O3仅能被氧化钠化为Na2CrO4，当Na2CO3与C的摩尔比小于0.5:3.33时，Cr2O3优先被钠化为NaCrO2，其余的Cr2O3被C还原为碳化铬，且碳化铬的种类随着C的增加逐渐由Cr7C3向Cr3C2转变；在V2O3-C-Na2CO3三元体系中，V2O3可以被氧化钠化为水溶性的钒酸盐，且钒酸盐的种类随着Na2CO3的增加逐渐按照NaVO3 → Na4V2O7 → Na3VO4的顺序发生转变，但在转变的过程中会有非水溶性钒青铜的出现，另外C的加入会消耗一部分Na2CO3，且这种相互作用优先于V2O3的氧化钠化从而使得相同量的V2O3需要更多的Na2CO3才能达到相同的反应程度；在Fe2O3-C-Na2CO3三元体系中，当Na2CO3与C的摩尔比大于0.52:1.68时，过量Na2CO3的存在会对Fe2O3的还原产生影响，Fe2O3会与Na2CO3发生反应，且随着Na2CO3含量的增加，反应产物会发生Na2.4Fe10.99O16.03→ NaFeO2→ Na4Fe2O5的转变；在TiO2-C-Na2CO3三元体系中，随着Na2CO3的增加，生成钛酸盐的顺序为Na2TiO3→Na16Ti10O28→Na4TiO4，Na2CO3过量时，反应产物中仅有Na4TiO4存在。;unknownunknown202018-05-25T04:42:00Z2018-05-25T04:42:00Z412527139Sky123.Org5916837514.00CleanCleanfalse7.8 磅02falsefalsefalseEN-USZH-CNX-NONE/* Style Definitions */ table.MsoNormalTable {mso-style-name:普通表格; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.5pt; mso-bidi-font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi; mso-font-kerning:1.0pt;}Titanium, vanadium and chromium are recognized as major strategic resources in various countries all over the world. They are widely used in fields of iron and steel industry, metallurgical industry, chemical industry, aerospace, and other fields, which are very important to national economic development and national security. The vast majority of China's chromium resources are stored in the high chromium vanadium-bearing titanomagnetite in the hongge mining area in Sichuan Province. Under the environment of the shortage of domestic chromium resources, the comprehensive utilization of the high-chromium vanadium-bearing titanomagnetiteneeds to be solved urgently. At present, the utilization methods of high chromium vanadium-bearing titanomagnetite are the same as ordinary vanadium-bearing titanomagnetite, including blast furnace method and direct reduction-electric furnace melting method, but all of them have long process flow, low resource utilization rate, high energy consumption, environmental load and other issues.In order to solve the above problems, a new technology of comprehensive utilization of high chromium vanadium-bearing titanomagnetite is proposed in this paper. The process mainly includes one-step high temperature process and one-step water leaching process. After that, iron and chromium, vanadium, titaniumare enriched in pig iron, vanadium-bearing leaching solution and titanium-bearing leaching residue, respectively. A series of reactions occurred during the high temperature process for high chromium vanadium-bearing titanomagnetite, including the reduction of iron oxide to metal iron, sodium oxidation of vanadium oxide into water-soluble sodium vanadate, the reduction, carbonation and dissolved in molten iron of chromium, the separation of molten slag and iron phase. Therefore, the new process is called "reduction-sodium oxidation-smelting separation coupled technology." The technological process has the advantages of short process, low energy consumption, high comprehensive utilization of resources and small environmental pollution, and provides an innovative idea for efficient comprehensive utilization of high chromium vanadium-bearing titanomagnetite. The dissertation's innovative achievements are as follows:(1) The feasibility of thermodynamic analysis of reduction and sodium oxidation coupling process was studied, and it is found that the reduction of iron oxide to metal iron and the sodium oxidation of vanadium oxide to water-soluble sodium vanadate can theoretically be achieved simultaneously in the coupling process;(2) In the mixture of the vanadium-bearing titanomagnetite concentrate, the reduction agent and the sodium salt, when the molar ratio of carbon to iron is in the range of 2.0 to 3.2, the added amount of sodium carbonate is in the range of 40wt% to 100 wt%, and when the roasting temperature is in the range of 1150-1200℃, the reduction of iron oxide, the sodium oxidation of vanadium oxide and the separation of molten slag and iron can be achieved simultaneously during the calcination, that is, after the direct reduction-sodium oxidation-smelting separation process, the iron and chromium are enriched in the massive iron phase for the subsequent special steel preparation. The vanadium and titanium are enriched in the roasted slag for the subsequent extraction and utilization of vanadium and titanium.(3) A systematic study on the influencing factors of slag-iron melting process found that many factors have an impact on the slag-iron melting process, including the type of reduction agent, type of sodium salt, calcination temperature, calcination time, the amount of sodium carbonate, the thickness of the material layer; comprehensively considering the effect of slag-iron smelting separation and the distribution of vanadium and chromium in the iron and slag phase, the best roasting conditions are obtained and showed as follows, reduction agent anthracite, additive sodium carbonate, roasting temperature 1200 °C, roasting time 2 h, molar ratio of carbon to iron 2.6, 70% addition of sodium carbonate, layer thickness 42.5 mm. Under optimal roasting conditions, the recovery rate of iron was 98.15%, the iron grade in the iron phase was 95.44%, 96.19% of the chromium was in the iron phase and 84.9% of the vanadium was in the slag phase.(4) The grade of vanadium in the iron phase will change with the roasting conditions. The grade of chromium in the iron phase will not change with the roasting conditions, and will always be kept at about 0.925%. The migration of vanadium in the slag and iron phase is related to the recovery rate of iron and the separation effect of slag and iron. The migration of chromium in the slag and iron phase is only related to the recovery rate of iron, that is, the separation effect of slag and iron.(5) The leaching process of vanadium in roasted slag was optimized. The optimal leaching conditions of vanadium were particle size -0.035 mm, leaching temperature 90 ℃, liquid-solid ratio 4: 1, stirring speed 400 r/min and leaching time 30 min. The leaching rate of vanadium was 85.62%, the activation energy of vanadium leaching process was 19.27 kJ/mol. The leaching process was controlled by internal diffusion.(6) The results of leaching residue and leachate analysis showed that the content of Fe, Ti, V and Cr in leaching residue were 7.27%, 13.22%, 0.078% and 0.006% respectively. Leaching residue mainly consists of sodium aluminosilicate and a small amount of calcium titanate which can be used as raw material for the production of titanium dioxide.The leachate contains 3.68 g/L V2O5, 50.39 g/L NaOH, 0.3 g/L SiO2 and 1.5 g /L Al(OH)3.(7) The reduction process of iron oxide in the reduction-sodium oxidation coupling process was studied. It is found that the roasted product mainly contains three phases, including metallic iron phase, titanium-rich phase and silicate phase. With the prolongation of roasting time, iron, titanium and silicon elements gradually migrate and aggregate to form an iron phase, a titanium-rich phase and a silicate phase, and the boundaries between them gradually become clear; at the same roasting time, the increasing roasting temperature, the increasing molar ratio of carbon to iron, the increasing addition amount of sodium carbonate are favorable for the aggregation of iron, titanium, and silicon in the respective enrichment phase and the separation of the phases from each other. With the prolongation of roasting time, vanadium and chromium gradually migrate into the silicate phase and the iron phase, respectively. And the increasing roasting temperature, the increasing molar ratio of carbon to iron, and the increasing addition of sodium carbonate all contribute to the enrichment of vanadium and chromium into the silicate and iron phases.(8) The reaction mechanism of iron-vanadium-chromium-titanium oxides during reduction-sodium oxidation was studied. It was found that when the molar ratio of Na2CO3to C is greater than 0.5:3.33 in Cr2O3-C-Na2CO3ternary system, the Cr2O3 is sodiumizedand oxidized to Na2CrO4, when the molar ratio of Na2CO3to C is less than 0.5:3.33, the Cr2O3 is preferentially sodiumized to NaCrO2, and the rest of the Cr2O3is reduced to chromium carbide by C, and the type of chromium carbide gradually changes from Cr7C3 to Cr3C2 with the increase of C. V2O3 can be oxidized into water-soluble vanadate in V2O3-C-Na2CO3ternary system, and the types of vanadate gradually follow the order of NaVO3→ Na4V2O7 → Na3VO4 with the increase of Na2CO3. But in the process of transformation there will be the emergence of water-insoluble vanadium bronze. In addition, the addition of C will consume a part of Na2CO3, and this interaction takes precedence over that of V2O3so that the same amount of V2O3 needs more Na2CO3. In the Fe2O3-C-Na2CO3 ternary system, when the molar ratio of Na2CO3 to C is greater than 0.52:1.68, the presence of excess Na2CO3 will affect the reduction of Fe2O3, Fe2O3 will react with Na2CO3. And with the increase of Na2CO3content, the reaction product will transform following the order of Na2.4Fe10.99O16.03→ NaFeO2 → Na4Fe2O5. In TiO2-C-Na2CO3ternary system, with the increase of Na2CO3, the transformation order of titanate is Na2TiO3→Na16Ti10O28→Na4TiO4and when Na2CO3 are in excess, only Na4TiO4exists in the reaction product.