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钒渣钾系亚熔盐反应的基础和应用研究
其他题名Fundamental Research on Recovering Vanadium and Chromium from Vanadium Slag by KOH Sub-molten Salt and Its Applications
刘挥彬
学位类型硕士
导师张懿 ;    郑诗礼 ;    杜浩
2012-05-22
学位授予单位中国科学院研究生院
学位专业化学工艺
关键词钒渣 氢氧化钾 亚熔盐 碳糊电极 清洁工艺
摘要针对传统钠化焙烧钒铬提取率低、能耗高、环境污染严重等问题,本文提出应用KOH亚熔盐法高效提取钒铬的清洁生产新技术。相比传统工艺,新工艺可使反应温度从850 oC降低到180-250 oC,能耗降低,钒铬转化率分别大于95%和90%,过程无含氯、硫废气产生,并可实现尾渣的综合利用,过程清洁,具有良好的工业前景。本文基于前人在钒渣处理和本课题组在亚熔盐新工艺方面的研究积累,重点开展了钒渣在KOH亚熔盐介质中宏观动力学和微观机理方面的基础研究,主要创新结果如下: (1) 得到了钒渣在KOH亚熔盐体系中的化学反应热力学数据。计算结果表明,在KOH亚熔盐体系中,钒渣中的铁橄榄石、石英相会发生氧化或分解,然后在KOH和氧气的协同作用下钒铬尖晶石逐渐发生氧化分解,生成可溶性钒酸钾、铬酸钾; (2) 揭示了三价铬在碱性介质中电化学氧化机制。通过电化学的方法研究了Cr2O3在KOH溶液中的循环伏安行为,证明了三价铬的氧化本质上是E-C偶合过程,即先发生直接电化学氧化,少量的三价铬被氧化,然后发生间接电化学氧化,相对较多的三价铬被氧化,后者作用更为关键; (3) 获得了钒渣在KOH亚熔盐中高效氧化浸出的最优工艺条件。研究结果表明,较高的反应温度、碱矿比、氧气流量、搅拌转速和相对较小的钒渣粒径更有利于钒铬的高效氧化溶出。在反应温度为180-250 oC,碱矿比4:1,KOH碱浓度75%,反应时间300 min,常压通氧气流量为1 L/min的反应条件下,最终钒铬的转化率分别达到了95%和90%。钒渣在KOH亚熔盐介质中氧化分解遵循缩核模型,主要受内扩散控制,通过拟合其各自动力学方程得到钒铬溶出的活化能分别为40.57 kJ/mol、50.27 kJ/mol; (4) 掌握了碱性介质脱硅的最优操作参数。通过工艺条件实验的方法,证明了在80 oC,250 g/L碱浓度条件下,加入1.5倍煅烧后的氧化钙可以在2 h内有效地将硅浓度降低到2 g/L以下,从而避免了对后续结晶、过滤的负面影响。
其他摘要Sodium salt roasting is currently the most popular process to extract vanadium from vanadium slag. However, in this process the yields of vanadium and chromium are very low. Further, high reaction temperature (850 oC) causes high energy consumption. Meanwhile, chlorine and sulfur exhaustion gases produced are hazardous to the environment. In order to solve these problems mentioned above, a novel method called KOH sub-molten salt technology has been proposed to treat vanadium slag by the IPE. Compared with the traditional process, the operation temperature in the new process can be reduced to 180-250 oC, significantly decreasing the energy consumption. Chemical conversion ratios of vanadium and chromium can reach up to 95% and 90% without any harmful gases being released. This clean process has been proven to be feasible and attractive. This paper focused on experimental investigation of reaction kinetics and microcosmic mechanism of vanadium slag oxidation dissolution in KOH sub-molten salt. The innovative results are summarized as follows: (1) Thermodynamics study shows: Firstly, FeSiO4 and SiO2 will form more complex potassium silicate when react with KOH. Then vanadium and chromium spinels react with O2 in KOH medium. Finally, water-soluble K3VO4 and K2CrO4 are produced. (2) Electrochemical study shows: The oxidation of Cr2O3 in KOH solution is controlled by a electrochemical reaction coupled with a chemical reaction. Firstly, direct electrochemical oxidation of Cr2O3 occurs at low potential, however, the oxidation rate is low. Further, indirect oxidation of Cr2O3 can be achieved with the help of reactive oxygen species produced due to the hydrolysis of H2O/OH- at high potential, and this indirect oxidation process plays a bigger role than that of the direct oxidation process. (3) Conditional experiments show: Increase of temperature, KOH-to-ore ratio, gas flow, agitator speed and decrease of vanadium slag particle size are beneficial for the leaching of vanadium and chromium. Under the conditions of temperature of 180-250 oC, initial KOH-to-ore ratio of 4:1, stirring speed 700 rpm, and gas flow 1 L/min, vanadium and chromium conversion ratios obtained are 95% and 90% with reaction time around 300 min, respectively. The results show that decomposing process of vanadium slag in KOH sub-molten salt is well interpreted with the shrinking core model under internal diffusions control. The apparent activation energy of vanadium and chromium is 40.57 kJ/mol and 50.27 kJ/mol, separately. (4) Desilication experiments show: Under the conditions of temperature of 80 oC and KOH concentration of 250 g/L, the silicon compound (in terms of SiO2) concentration can be controlled to be under 2 g/L with the reaction time of around 120 min after addition of 1.5 times of CaO (nCaO:nSiO2=1.5 by weight).
语种中文
文献类型学位论文
条目标识符http://ir.ipe.ac.cn/handle/122111/1847
专题研究所(批量导入)
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刘挥彬. 钒渣钾系亚熔盐反应的基础和应用研究[D]. 中国科学院研究生院,2012.
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