|Thesis Advisor||崔丽杰, 许光文|
|Keyword||流化床 石煤 焙烧 钒浸出|
钒是珍贵的稀有金属，以其优良的理化和机械性能，广泛应用于钢铁、化工、国防和电池等领域。钒的主要来源有钒钛磁铁矿和含钒石煤。我国含钒石煤储量丰富，其V2O5储量是我国钒钛磁铁矿中V2O5储量的6-7倍。目前，国内的石煤提钒技术仍然以先火法焙烧再湿法浸出工艺为主。在此工艺中，焙烧效果直接影响钒浸出率，进而决定了全流程的钒总回收率。现有的焙烧工艺仍然存在着资源利用率低、生产规模小、环境污染严重等问题。随着钒及钒制品需求量的剧增，开发新的石煤提钒焙烧工艺，对实现石煤资源高效综合利用、促进我国钒制品加工和应用等相关行业的发展均具有重要意义。 针对现有石煤提钒技术存在的弊端，中科院过程所提出了一种新型的流化床两段复合盐法焙烧石煤提钒工艺。该工艺充分整合了流化床和输送床反应器各自的优势，联合复合添加剂焙烧工艺，具有处理量大、焙烧转浸率高、污染物可控等特点和优势。 为配合新型流化床两段石煤焙烧工艺的设计和开发，本文利用实验室流化床小试装置系统地研究了流化床焙烧特性、添加剂与石煤的混合方式、添加剂用量、焙烧时间等因素对钒转浸率的影响，优化了焙烧工艺条件，与固定床焙烧工艺进行了对比，并对添加剂与石煤的作用机理和钙氧化物固氯可行性进行了考察，在此基础上提出了石煤焙烧提钒的工艺路线，为新型流化床两段石煤焙烧工艺的设计和运行提供基础数据。 本论文的主要研究内容和结果如下： 1. 研究了石煤焙烧条件对提钒转浸率的影响特性，并对钙氧化物的固氯效果进行了考察。实验结果显示，对比固定床焙烧，流态化焙烧缩短了焙烧时间，降低了达到最大钒浸出率所需的反应温度；对比石煤和添加剂不同的混合方式发现，与简单的物理混合法相比，浸渍法不仅能提高钒的浸出率、缩短焙烧时间，而且能降低添加剂的使用量；在焙烧过程中加入CaO明显减少了生成气体中的Cl含量，并能进一步提高钒的浸出率。 2. 确定了流化床复合添加剂提钒技术的最佳工艺参数。流化床焙烧石煤提钒的最佳工艺条件是：采用浸渍法混合石煤与添加剂，焙烧温度800℃，焙烧时间45 min，添加剂用量6 wt.%，CaO用量6 wt.%。此时，V2O5浸出率达到85.2%，氯的吸收率也可以达到73.6%。 3. 从热力学上对石煤在复合添加剂焙烧过程中可能发生的主要化学反应进行了可行性分析，绘制了有机质、黄铁矿、钒、复合添加剂和氧化钙等参与反应的吉布斯自由能-温度图。结果表明，有机质、黄铁矿的氧化反应在热力学上比三价钒氧化反应更易进行，即石煤中有机质和黄铁矿的存在对钒氧化具有抑制作用。TG、XRD、SEM-EDS等的分析结果表明，复合添加剂在焙烧过程中能破坏云母矿物的晶格结构；钒浸出率的高低，不仅与钒是否被氧化有关，而且与钒是否被“包裹”有关。
Vanadium, as one of the important rare elements, is widely used in the steel industry, chemical industry, national defense technology and battery production because of its good and unique physical, chemical and mechanical properties. In China, apart from the vanadium-titanium magnetite, stone coal is another important vanadium-bearing resource. In terms of V2O5 amount, vanadium in stone coal accounts for more than 87% of the domestic reserves of vanadium in China. At present, the extracting process of acid leaching after roasting for vanadium from stone coal is widely adopted. In this process, stone coal roasting plays the critical role in oxidizing V(Ⅲ) to V(Ⅳ) and V (Ⅴ), which is determinative to the available total vanadium recovery ratio and is thus the rate-limiting step. However, the existing roasting technologies still have some limitations, such as low vanadium leaching rate, small-scale production, serious environmental pollution and so on. Thus, for meeting the increasing demand for vanadium and its products, improving the efficiency of resource utilization for stone coal and promoting the development of vanadium and its related industry, a high efficient and environmental friendly extracting technology for vanadium from stone coal is becoming more and more necessary and essential. To solve these problems, a novel fluidized bed two-stage roasting process for extracting vanadium from stone coal has been proposed by Institute of Process Engineering, Chinese Academy of Sciences. By combining the advantages of fluidized bed and transport bed reactor, and adopting advanced composite additives, this process ensures fully the roasting time for small and large stone coal particles and also has the advantages of large treating capacity, high leaching rate and lower environmental pollution. For designing this new fluidized bed two-stage roasting process, this article firstly compared the roasting property of fluidized bed and fixed bed, and then investigated the effect of experimental conditions on leaching rate of V2O5, including roasting temperature, roasting time, quality and kinds of additive, mixing methods between stone coal and additive, and method of removal of chlorine-containing gas and so on. On this basis, the experimental conditions were optimized and a complete process route was proposed. The main conclusions are as follows: 1. Examining experimental conditions of fluidized bed roasting for vanadium leaching and the method of removing chlorine-containing gas. The results showed that fluidized roasting is more favorable to V2O5 leaching than static fixed bed roasting, which greatly shortened the roasting time and increased the leaching rate of V2O5. Comparing to the physical mixing, the impregnation of additive onto stone coal not only increased the vanadium leaching rate and shortened the roasting time for the maximum leaching rate but also reduced the necessarily required amount of additive. Adding CaO in roasting process sharply decreased the content of Cl-containing gas in the effluent gas of roasting to alleviate thus the environmental pollution. 2. Optimizing experimental conditions of fluidized bed roasting with composite additive. It was shown that the optimal fluidized roasting conditions were found to be impregnating 6 wt.% additive on coal, adding 3 wt.% CaO and roasting at 800 °C for 0.75 h. Under these conditions the available maximal vanadium leaching rate reached 85.2%, and Cl removal was about 73.6% against the formed Cl gaseous components in the roasting-generated flue gas. 3. Mechanism of extracting vanadium from stone coal by additive. Thermodynamic analysis of composite additive roasting process was carried out. From the result, it can be seen that oxidation reactions of organic matter and pyrite are easier to happen than that of oxidation reaction of vanadium, and the presence of organic matter and pyrite in stone coal can restrain the oxidation of V(Ⅲ). The analysis results of TG, XRD, SEM-EDS also showed the lattice structure of mica minerals can be broken easily by composite additive in the roasting process, and with the increasing of roasting temperature, particles sintering was intensified. And leaching rate of vanadium from stone coal is not only related to the state of oxidation, but also to the case of package with other composite.
|MOST Discipline Catalogue||化学工程|
|张会丰. 流化床焙烧石煤提钒工艺与机理研究[D]. 中国科学院大学,2014.|
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|流化床焙烧石煤提钒工艺与机理研究.pdf（20820KB）||学位论文||限制开放||CC BY-NC-SA||Application Full Text|
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