【作者】 高峰；

【导师】 张懿； 杜浩；

【作者基本信息】 东北大学 ， 冶金物理化学， 2023， 博士

【摘要】 钒是重要的战略金属,在钢铁、新能源、材料、化工等领域均有广泛应用。钒钛磁铁矿是重要的提钒原料,传统的钠盐焙烧提钒工艺不仅产生氨氮废水、有害窑气,而且尾渣含有钠无法进入高炉流程回收其中的铁,导致铁资源的浪费,是传统钠化焙烧提钒工艺亟需解决的行业共性问题。本文针对钠盐焙烧工艺的不足,提出了一种钒钛磁铁矿钙化焙烧-铵盐强化浸出清洁提钒的新工艺。新工艺钒回收率高,焙烧过程不产生有害窑气,铵盐介质循环利用避免废水产生,而且尾渣不含钠,为提钒尾渣的资源化利用提供了有利条件。本文得到的创新性成果如下:(1)比较了钙化焙烧和钠化焙烧过程物相变化规律。对两种不同焙烧工艺进行对比发现,在钠盐焙烧工艺中,800℃下已有钒酸钠生成,但在钙化焙烧工艺中,钒酸钙的生成温度要大于800℃。钙化焙烧过程的最优条件为CaCO3加入量为矿物质量的5%,焙烧时间1 h,焙烧温度1150℃,矿物中钒的氧化率可以达到89.72%。对比钠盐焙烧工艺,由于CaCO3分解后的CaO熔点高,以固相形式在矿物中扩散速率慢,需要更高的温度来促进钒酸盐的转化和矿物结构的破坏。(2)研究了钙化焙烧工艺钒的浸出动力学,研究发现在钙化焙烧工艺中,当浸出条件为浸出温度80℃,浸出时间为1 h,浸出液中(NH4)2C2O4浓度为120 g/L,此时钒的浸出率为64%,而钠盐焙烧-水浸工艺的浸出率可以达到84%。对浸出尾渣进行SEM分析发现,在钙化焙烧熟料浸出过程中有不溶性钙盐在矿物颗粒表面和孔隙中富集,阻碍了钒的浸出。浸出过程的表观活化能为19.502 kJ/mol,限制性环节为跨越固态产物层的扩散。(3)开发了机械活化法强化提钒工艺,研究发现在转速为360 r/min,机械活化浸出时间为20 min的条件下,钒的浸出率达到81%,达到了钠盐焙烧-水浸提钒方法的钒浸出率水平。对机械活化浸出工艺的浸出动力学研究发现,在机械活化浸出过程中,钒的浸出过程的限制性环节仍为跨越产物层的扩散,CaC2O4层的生成依然对钒的浸出产生影响,表观活化能为8.924 kJ/mol。机械活化浸出促进矿物颗粒比表面积从0.296 m2/g增加至1.486 m2/g,说明机械活化过程主要破坏矿物结构,创造新的反应界面,从而促进钒的浸出。(4)开发了 H2C2O4强化提钒工艺,研究发现在浸出时间为1 h,浸出温度为70℃,固液质量比为0.8:1,机械活化浸出时间为15 min,(NH4)2C2O4浓度为90 g/L,H2C2O4浓度为40 g/L,钒浸出率为90%,优于现有的钠盐焙烧-水浸提钒方法的钒浸出率。经过3次循环,循环液中钒达到29.62 g/L,循环过程浸出率可以保持在89%～90%。对H2C2O4强化浸出机理研究发现在H2C2O4的作用下,V(V)首先与NH4+形成NH4V3O8,NH4V3O8随后溶解形成HV10O285-,HV10O285-最终被C2O42-还原并形成VO(C2O4)22-。NH4+与HV10O285-的相互作用、HV10O285-的还原以及C2O42-与VO2+的络合是浸出率提高的主要原因。(5)开发了铵盐介质中偏钒酸铵的纯化分离方法。研究发现在(NH4)2C2O4体系中,含钒液中主要杂质为Fe和Al,并且溶解度随着pH升高逐渐降低。在(NH4)2C2O4 体系中 Fe、Al 与 C2O42-结合为 Fe(C2O4)33-和 Al(C2O4)33-,并且改变了 Fe、Al元素水解沉淀的pH。当溶液的pH升高至9后,经过60 min的除杂,Fe和Al的去除率可以达到63.16%和41.17%,液相中Fe、Al的浓度降低至0.42 g/L和0.30 g/L。随后对含钒液中钒的冷却结晶进行了研究。研究发现在结晶终点温度为40℃时,结晶率为69.84%,此时液相中V2O5的浓度为3.64 g/L。结晶后液经过补充(NH4)2C2O4可以返回体系进行浸出,经过4次循环后,液相中V2O5浓度达到13.17 g/L,钒的浸出率始终保持在80%,浸出介质可以循环利用。(6)对H2C2O4-(NH4)2C2O4体系中的含钒液的处理进行研究发现,含钒液的处理除需要对钒进行氧化外,其余操作与(NH4)2C2O4体系相同。在含钒液pH为9,用氧气为氧化剂,氧化5 min后钒的氧化率可达99%,同时可以有效控制液相中的Fe、Al杂质,除杂过程与(NH4)2C2O4体系相同。含钒液经过氧化除杂后可以采用结晶来分离液相中的偏钒酸铵,其结晶率可以达到86.85%。更多还原

【Abstract】 Vanadium is an important strategic metal and is widely used in steel,new energy,materials,chemical industry and other fields.Traditional sodium salt roasting process produces ammonia nitrogen wastewater,harmful kiln gas,resulting in the waste of iron resources,causing significant environmental burden.The tailings contain sodium cannot enter the blast furnace process to recover the iron,resulting in the waste of iron resource.In view of the shortcomings of sodium salt roasting process,we proposed a new process to extract vanadium from vanadium titano-magnetite using(NH4)2C2O4 solutions.The new process can realize high recovery rate of vanadium,does not produce harmful kiln gas,and avoids the generation of wastewater via the recycling of ammonium salt.Further,the tailings do not contain sodium,which provides favorable conditions for the resource utilization of vanadium tailings.The innovative results obtained in this paper are as follows:(1)The phase change rules of calcification roasting and sodium slat roasting were compared.Comparing the two different roasting processes,it was found that sodium vanadate was formed at 800℃ in sodium salt roasting process,but the formation temperature of calcium vanadate was higher than 800℃ in calcification roasting process.The optimum conditions for the calcification roasting process were the amount of CaCO3 5%of the mineral mass,roasting time 1 h,roasting temperature 1150℃,and the oxidation rate of vanadium in the mineral could reach 89.72%.In comparison with the sodium salt roasting process,due to the high melting point of CaO after CaCO3 decomposition,the diffusion rate of solid phase CaO was slow,and higher temperature was needed to promote the transformation of vanadate and the destruction of mineral structure.(2)The leaching kinetics of vanadium from calcification roasting was investigated.It was found that when the leaching temperature was 80℃,the leaching time was 1 h,and the concentration of(NH4)2C2O4 in the leaching solution was 120 g/L,the leaching rate of vanadium was 64%.SEM analysis of the leaching tailings showed that insoluble calcium salts were enriched on the surface of mineral particles and in the pores of the calcified roasting calcine,which hindered the leaching of vanadium.It was found that in(NH4)2C2O4 solution,the apparent activation energy of the leaching process was 19.502 kJ/mol,and the controlling step was the diffusion across the solid product layer.(3)The mechanical activation method was developed to enhance the vanadium leaching process.It was found that under the conditions of rotation speed of 360 r/min and mechanical activation leaching time of 20 min,the leaching rate of vanadium reached 81%,which was similar to the results obtained from sodium salt roasting-water leaching process.The leaching kinetics of mechanical activation leaching process was studied.It was found that the controlling step was the diffusion across the product layer,and the formation of CaC2O4 layer still affected the leaching of vanadium.The apparent activation energy was 8.924 kJ/mol.Mechanical activation leaching promoted the specific surface area of mineral particles to increase from 0.296 m2/g to 1.486 m2/g,indicating that the mechanical activation process mainly destroyed the mineral structure and created a new reaction interface,thereby promoting the leaching of vanadium.(4)The H2C2O4 enhanced vanadium extraction process was developed.It was found that under the conditions of the leaching time 1h,the leaching temperature 70℃,the solid-liquid mass ratio 0.8:1,the mechanical activation leaching time 15 min,the concentration of(NH4)2C2O4 90 g/L,and the concentration of H2C2O440 g/L,the vanadium leaching rate could reach 90%.After three cycles,the vanadium in the circulating solution reached 29.62 g/L,and the leaching rate could be maintained at 89%～90%.Mechanism analysis suggested that under the action of H2C2O4,V(V)first formed NH4V3O8 with NH4+,NH4V3O8 then was dissolved to form HV10O285-,which was finally reduced by C2O42-to form VO(C2O4)22-.The interaction between NH4+and HV10O285-as well as the reduction of HV10O285-and the complexation between C2O42-and VO2+ were the main reasons for the increase of leaching rate.(5)The purification and separation method of ammonium metavanadate in ammonium salt medium was developed.It was found that in the(NH4)2C2O4 solution,the main impurities were Fe and Al in the form Fe(C2O4)33-and Al(C2O4)33-,and their solubility gradually decreased with the increase of pH due to hydrolysis precipitation.When the pH of the solution increased to 9,the removal rates of Fe and Al could reach 63.16%and 41.17%after 60 min,and the concentrations of Fe and Al in the liquid phase decreased to 0.42 g/L and 0.30 g/L,respectively.Subsequently,the cooling crystallization of vanadium in vanadium-containing liquid was studied.It was found that when the crystallization end temperature was 40℃,the crystallization rate was 69.84%,and the concentration of V2O5 in the liquid phase was 3.64 g/L.After crystallization,the liquid can be returned to the system for leaching after adding(NH4)2C2O4.After 4 cycles,the concentration of V2O5 in the liquid phase reached 13.17 g/L,the leaching rate of vanadium was maintained at 80%,and the leaching medium can be recycled.(6)The treatment of vanadium-containing H2C2O4-(NH4)2C2O4 solution was studied.It was found that the treatment of vanadium-containing liquid was the same as that of the(NH4)2C2O4 system except for the oxidation of vanadium.When solution pH was contained at 9,the oxidation rate of vanadium could reach 99%after 5 min oxidation with oxygen.At the same time,the impurities of Fe and Al in the liquid phase could be effectively controlled,and the impurity removal effect was the same as that of the(NH4)2C2O4 system.Ammonium metavanadate could be separated by crystallization after oxidation and impurity removal,and the crystallization rate could reach 86.85%.更多还原