Knowledge Management System Of Institute of process engineering,CAS
|Thesis Advisor||张红玲, 江军生|
石煤钒矿是我国特有的钒资源，储量丰富，但因钒品位较低，生产每吨五氧化二钒产品通常产生120至150吨提钒尾渣，我国石煤提钒行业每年产生的提钒尾渣总量高达数百万吨。硫酸浸出工艺是当前我国石煤提钒行业的主流生产工艺之一，该工艺产生的提钒尾渣主要成分为二氧化硅，但硫酸盐含量较高，行业现行的堆存或填埋处理方式不仅造成一定程度的资源浪费，而且还存在较高的环境风险，亟待开发石煤钒矿酸浸提钒尾渣资源化利用的新方法。目前已有部分研究表明该提钒尾渣可与一定配比的含铝辅料高温烧结制备陶粒，但在含铝辅料遴选、工艺系统优化等方面研究较少，对于提钒尾渣中硫酸盐的分解与含硫组份的释放规律未做关注。为此，本论文以我国西北、西南地区石煤钒矿经硫酸熟化浸出提钒处理后产生的提钒尾渣为原料，根据区域资源特点遴选了合适的含铝辅料，分析了工艺过程机理与主要影响因素，确定了优化的工艺参数，调控制备出了性能较好的陶粒产品。本论文主要取得了如下进展：（1）结合区域资源特色遴选了多种含铝辅料，通过理论分析和探索性实验确定了提钒尾渣为主要原料制备陶粒时的辅料种类和配比。结合Riley相图中指出的烧制陶粒合理原料的成分范围和原辅料易烧系数的计算结果，遴选确定赤泥作为辅料进行陶粒的制备实验研究。根据不同质量比提钒尾渣-赤泥组合制备烧胀陶粒的探索性实验结果，确定提钒尾渣与赤泥的较佳质量比为70:30。（2）根据选择的物料配比，开展了陶粒制备工艺研究，确定了较适宜的工艺参数。以提钒尾渣:赤泥质量比为70:30的混合料为原料时，制备陶粒的较佳工艺参数为：无需预热，直接以8℃/min的升温速率升温至1080℃，焙烧30 min，然后随炉冷却至室温。在此工艺条件下制备得到的陶粒样品的堆积密度为809.3 kg/m3，吸水率为1.9%，抗压强度为9.1 MPa，满足《轻集料及其试验方法 第1部分：轻集料》（GB/T 17431.1-2010）的要求。（3）根据不同焙烧温度下陶粒样品形貌和物相的表征结果，分析了以提钒尾渣为主要原料制备陶粒的膨胀机理。在制备过程中，陶粒体积随焙烧温度升高呈现先收缩后膨胀的规律。陶粒收缩和膨胀的过程与升温过程中产生的玻璃相和碳、硫释放产生的气体密切相关。当焙烧温度高于1060℃时，玻璃相的产生量和粘度足够大，释放的SO2气体被玻璃相包裹，陶粒内部出现封闭气孔，发生膨胀，堆积密度逐渐减小并在1085℃时出现极小值。（4）研究了以提钒尾渣为主要原料制备陶粒过程中硫的释放规律，可为以提钒尾渣为主要原料制备得到满足轻集料硫含量要求的陶粒提供基础数据和理论依据。借助热重-红外联用分析了以提钒尾渣为原料制备陶粒过程中的质量、热量变化以及气体释放规律，测试了不同温度焙烧所得样品的硫含量，表征了其物相，并结合热力学计算，讨论了提钒尾渣中硫的释放机理，发现：1200℃下样品的硫含量可降低至0.44 wt%，满足轻集料硫含量要求；提钒尾渣中含有的SiO2、Fe2O3、Al2O3等组分可促进硫的释放。;In China, vanadium-bearing stone coal minerals is a unique vanadium resource, which is rich in reserves. However, due to the low vanadium grade, 120-150 tons of vanadium extraction tailings were usually discharged in the production of per ton vanadium pentoxide products. The total amount of vanadium extraction tailings produced by the industry of extracting vanadium from stone coal in China is up to several million tons per year. Sulfuric acid leaching process is one of the main production processes in the current vanadium extraction industry from stone coal in China. The main component of vanadium extraction tailings produced by this process is silicon dioxide, but the sulfate content is relatively high. The industry's current storage or landfill treatment methods not only cause a certain degree of waste of resources, but also have high environmental risks. It is urgent to develop a new method for resource utilization of acid-leaching tailings of vanadium-bearing stone coal minerals. At present, some studies have shown that the vanadium extraction tailings can be sintered with a certain proportion of aluminum containing auxiliary materials to prepare ceramsite. However, researches on the selection of aluminum containing auxiliary materials and the optimization of process systems are relatively few, and no attention has been paid to the decomposition of sulfates and the release of sulfur-containing components in the vanadium extraction tailings. Therefore, in this thesis, vanadium extraction tailings produced by sulfuric acid baking and leaching of vanadium-bearing stone coal minerals in Northwest and Southwest China were used as raw materials. According to the characteristics of regional resources, suitable aluminum containing auxiliary materials were selected, the process mechanism and main influencing factors were analyzed, the optimized process parameters were determined, and ceramsite products with excellent performance were prepared.The main innovative progress can be summarized as follows:(1) Based on the characteristics of regional resources, a variety of aluminum containing auxiliary materials were selected. Through theoretical analysis and exploratory experiments, one suitable aluminum source was selected as the auxiliary material for vanadium extraction tailings to prepare ceramsite. The optimal proportion between vanadium extraction tailings and the selected auxiliary material was determined, too. In consideration of the composition range of ingredients for firing expandable ceramsite indicated in the Riley phase diagram, as well as the calculation results of the firing coefficients of vanadium extraction tailings and several auxiliary materials, red mud was selected as the auxiliary material for the experimental research of ceramsite preparation. According to the exploratory experiment of preparing expandable ceramsite using mixture of vanadium extraction tailings and red mud with different mass ratios, an optimal mass ratio of vanadium extraction tailings and red mud was determined to be 70:30.(2) The preparation process of ceramsite was carried out using the selected materials, and the appropriate process parameters were determined. When the mixture of vanadium extraction tailings and red mud with a mass ratio of 70:30 was used as raw material, the preferred parameters for preparing ceramsite were determined as follows: ramp rate ~ 8 ℃/min, dwell temperature ~1080 ℃, dwell time ~30 min, and then naturally cooled to room temperature. Ceramsite with a bulk density of 809.3 kg/m3, a water absorption rate of 1.9% and a compressive strength of 9.1 MPa was obtained under this process condition, which can meet the requirements of "Lightweight Aggregate and its Test Methods Part 1: Lightweight Aggregate" (GB/T 17431.1-2010).(3) The expansion mechanism of ceramsite was analyzed according to the morphologies and the crystal phases of ceramsite samples roasted at different temperatures. In the process of preparing ceramsite, the volume of ceramsite shows a rule of firstly shrinking and then expanding with the roasting temperature increases. This phenomenon (the shrinking and expanding) is closely related to the glassy phase produced during the heating process and the gas produced by the release of carbon and sulfur. When the roasting temperature was higher than 1060 ℃, the amount and viscosity of the glassy phase were large enough. So the SO2 gas released could be encapsulated by the glass phase, and interior pores were formed inside the ceramsite. Consequently, the ceramsite expanded, and its bulk density began to decrease and yielded a minimum value at 1085 ℃. (4) The release law of sulfur during the preparation of ceramsite using vanadium extraction tailings as raw materials was studied, which can provide some basic data and theoretical basis for using vanadium extraction tailings as one main material to preparing ceramsite with a sulfur content lower than the requirements of lightweight aggregates. Simultaneous thermogravimetric / Fourier transform infrared spectrometry analysis were used to investigate the weight loss, the exothermic/endothermic phenomenon, and the releasing of gases in the process of roasting the vanadium extraction tailings as the raw material for preparing ceramsite. The sulfur contents of samples prepared by roasting vanadium extraction tailings at different temperatures were tested, their crystal phases were characterized, the Gibbs free energies of several reactions were obtained by thermodynamic calculation, and the mechanism of sulfur releasing from vanadium extraction tailings was discussed accordingly. The results showed that the sulfur content (0.44 wt%) of samples obtained at 1200 ℃ can meet the requirements of lightweight aggregate. Intermediated phases such as Wollastonite (CaSiO3) might be formed by the reaction of Anhydrite and Quartz in the vanadium extraction tailings, accompanied with the releasing of SO2. SiO2, Fe2O3 and Al2O3 in vanadium extraction tailings might be helpful for the releasing of sulfur.
|宋春光. 石煤钒矿酸浸提钒尾渣制备陶粒工艺应用基础研究[D]. 中国科学院大学,2020.|
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