Simulation and experimental study on ultrasonic spray pyrolysis of ultrafine vanadium dioxide powder
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摘要: 针对喷雾热解过程，采用计算流体力学（CFD）方法对其装置进行了设计优化，通过对比分析，对管式炉的进出口段进行保温优化来改善管内温度和速度场分布不均的问题；设计搭建了超声喷雾热解装置，并通过试验考察了不同的前驱体溶液、前驱体浓度、热解温度对于产物粒径和形貌的影响。结果表明：草酸氧钒溶液超声热解后的产物主要为V2O3，而硫酸氧钒及二氯氧钒热解后的产物为蓝黑色VO2颗粒；随着硫酸氧钒前驱体浓度的增加，大颗粒粉体明显增多，颗粒粒径大于100 nm；二氯氧钒热解后的VO2颗粒以二次粒子和一次粒子的形式存在，随着热解温度和前驱体浓度的提高，颗粒分散性明显提高，小粒径颗粒增加，粒径基本在100 nm左右。Abstract: For the spray pyrolysis process, the device was optimized by computational fluid dynamics (CFD) method. Through comparison and analysis, the heat preservation optimization was adopted for the inlet and outlet sections of the tubular furnace to improve the uneven temperature and velocity field distributions. An ultrasonic spray pyrolysis device was designed and set up, and the influences of precursor solution, precursor concentration and pyrolysis temperature on the particle size and morphology of the products were investigated through experiments. The results show that the main products of the ultrasonic pyrolysis of vanadyl oxalate solution are V2O3, while the pyrolysis products of vanadyl sulfate and vanadyl dichloride are blue black VO2 particles. With increase of the concentration of vanadyl sulfate precursor, the amount of large particles increases significantly, and the particle size is more than 100 nm. The VO2 particles obtained via pyrolysis of vanadyl dichloride are the secondary and primary particles. With increase of the pyrolysis temperature and precursor concentration, the dispersion of the particles increases obviously, and the number of small particles increases, and the particle size is about 100 nm.
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Key words:
- superfine VO2 /
- ultrasonic spray pyrolysis /
- vanadyl oxalate /
- vanadyl sulfate /
- vanadyl dichloride /
- velocity field /
- temperature field /
- CFD
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图 2 不同进口流速下管式炉内的温度分布
Figure 2. Temperature distribution in the tubular quartz reactor with different inlet flow rates
图 3 不同进口流速下管式炉的轴面速度分布
Figure 3. Axial velocity distribution in the tubular quartz reactor with different inlet flow rates
图 4 进口流速0.5 m/s下管式炉的轴面速度矢量
Figure 4. Axial velocity vector distribution in the tubular quartz reactor with inlet flow rate of 0.5 m/s
图 5 改进后进口流速0.5 m/s条件下管式炉的轴面云图
Figure 5. Axial velocity distribution in the improved tubular quartz reactor with inlet flow rate of 0.5 m/s
图 8 不同前驱体热解产物的XRD谱
Figure 8. XRD patterns of pyrolysis products of different precursor solutions
图 10 硫酸氧钒前驱体浓度对于产物形貌的影响
Figure 10. Effect of concentration of vanadyl sulfate precursor on product morphology
图 11 热解温度对于二氯氧钒热解产物形貌的影响
Figure 11. Effect of pyrolysis temperature on the morphology of pyrolytic products of vanadyl dichloride
图 12 前驱体浓度对于二氯氧钒热解产物形貌的影响
Figure 12. Effect of precursor concentration on the morphology of pyrolysis products of vanadyl dichloride
表 1 固体硫酸氧钒中主要化学成分
Table 1. The main compositions of solid vanadyl sulfate
% K Na Fe Cr Si Al Ca Mg Mn P 0.0033 <0.002 0.0037 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 <0.002 
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表 2 超声喷雾热解法制备VO2粉体的试验参数
Table 2. The experimental parameters for preparation of VO2 powder by ultrasonic spray pyrolysis
试验编号 前驱体溶液 浓度/(mol·L−1) 反应温度/℃ EX1 VOSO4 0.1 750 EX2 VOSO4 0.01 750 EX3 VOC2O4 0.1 380 EX4 VOCl2 0.1 500 EX5 VOCl2 0.1 700 EX6 VOCl2 0.2 700
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