上行气固两相流充分发展段颗粒浓度关联及预测

Correlation and Prediction of Solids Holdups of Gas-Solid Two-Phase Flow in Fully Developed Region of CFB Risers

在高度分别为15.1m和10.5m的两套实验装置上,对快速流态化到稀相气力输送流型下提升管内的轴向压力梯度进行了系统测试,以研究提升管充分发展段内不同颗粒的浓度变化及其与操作参数的关系.实验在其中175组操作条件下展现出明显的充分发展段(> 2.8 m).结果表明,表观气速在3～8 m·s-1之间变化时,对充分发展段颗粒浓度随终端颗粒浓度的变化关系影响显著,但当表观气速>8 m·s-1或< 3 m·s-1时,其对充分发展段颗粒浓度随终端颗粒浓度线性增加的关系影响极弱;在此基础上提出的预测关联式更明确地反映了操作条件等因素对充分发展段颗粒浓度的定量影响关系,其计算结果与本实验和相关文献的实验数据吻合良好.

To investigate the solids holdups in fully developed region of CFB risers, experiments were carried out in two CFB risers with the heights of 15.1m and 10.5m, respectively. FCC particles （Geldart A） and sand particles （Geldart B） were used in the experiments and the solids holdups were calculated by using measured pressure gradients. The experimental results obtained from 175 sets of operation conditions, under which the lengths of fully developed section are longer than 2.8 m, show that when the superficial gas velocity is between 3 m·s^-1 and 8 m·s^-1, it has a significant effect on the variations of the average solids holdups in fully developed region with the terminal solids holdups, but when it is less than 3 m·s^-1 or greater than 8 m·s^-1, the effect becomes inapprecible and the average solids holdups vary linearly with the terminal solids holdups. By taking into account the effects of superficial gas velocity, particle properties and riser geometry, a new empirical correlation for the average solids holdups in fully developed region of CFB riser were developed, which is in good agreement with the experimental data of this work and accords with the correlations reported in literatures.