Effect of precursor, ambient pressure, and temperature on the morphology, crystallinity, and decomposition of powders prepared by spray pyrolysis and drying

The effect of reactor pressure and temperature on the morphology, crystallinity, and decomposition behavior of various powders produced by spray pyrolysis or drying is investigated. Zirconia, magnesium sulphate, and sodium chloride powders are produced at the reactor pressures of 760, 400, 250, and 120 Torr, and at the reactor temperatures of 100 °C, 200 °C, and 400 °C. Zirconia and magnesium sulphate powders are spherical, whereas the sodium chloride powders are cubic. Regardless of the pressure, the powders produced at 100 °C and 200 °C appear solid, and powders produced at 400 °C are hollow and disrupted. The experimental data and the calculations indicate that the evaporation rate, which is a function of pressure and temperature, controls the solute distribution within the droplet and as such determines the morphology of the powders. In addition, the shape and morphology of the powders are strong functions of the precursor type. The decomposition and crystallinity of the powders are determined using XEDS and XRD analyses, respectively. The crystallinity and decomposition of the powders are weak functions of pressure and strong functions of temperature.     

高温高压喷雾闪蒸的蒸发特性

基于新型高温高压喷雾闪蒸实验台,以水为工质,研究初始条件和运行条件对闪蒸蒸发特性的影响。首次将液体初始温度提高至100℃以上,将闪蒸罐运行压力保持为正压,并使用具有独特双S形叶片的涡旋实心锥喷嘴,将液体向上或向下喷入闪蒸罐。实验过程中液体初始温度为135～150℃,闪蒸压力分别为121、126、131、136、141、146 kPa,液体过热度为30～46℃。实验结果表明,闪蒸蒸汽流量随初始温度的提高而增大,随闪蒸压力的提高而减小。液体向下喷射比向上喷射产汽量更高,蒸汽带水更少。闪蒸效率随过热度呈线性增长,在大量实验数据基础上拟合出二者之间的经验公式。实验结果为高温高压喷雾闪蒸的工业应用提供借鉴。