变径提升管反应器扩径段内固含率分布研究

Study on solids concentration distribution in the diameter - enlarged section of a novel riser reactor

以催化裂化平衡催化剂为固体介质,空气为流化介质,在变径提升管流态化实验装置上,考察了扩径段内固含率的轴径向分布情况及操作条件的影响,并对瞬时固含率信号进行了概率密度分析。结果表明,变径提升管内截面平均固含率沿轴向大致呈S形分布,扩径段固含率高于等径提升管底部;扩径段径向固含率呈中心稀、边壁浓的不均匀分布,相对于等径提升管底部,径向不均匀程度得到有效改善;截面平均固含率及各径向位置固含率均随颗粒循环速率的提高和表观气速的降低而增大。扩径段各径向位置瞬时固含率信号波动强度大,频率高,概率密度分布均匀,有利于强化气固混合并改善两相间接触情况。

In a circulating fluidized bed system, axial and radial solids concentration distributions in- side a novel riser and the effect of operating condi- tions were investigated, moreover, probability density analysis of transient solids concentration signals was also conducted. The results showed that the cross - sectional averaged solids concentration along this no- vel riser presented as S - type,with much higher sol- ids concentration in the diameter - enlarged section than that of the bottom region of conventional riser. Compared with the bottom region of conventional riser, more uniform radial flow structure with higher solids concentration in the central region and almost saturated solids concentration near the wall was observed in the diameter - enlarged section. In addi- tion,cross- sectional averaged solids concentration and local solids concentration at all radial positions increased with increasing solids circulation rate and decreasing superficial gas velocity. Analysis of transi- ent concentration signals in diameter- enlarged sec- tion demonstrated that both fluctuation amplitude and frequency were very high, and the corresponding probability density distributions were uniform, which would further enhance the gas - solids mixing and in-tensify the interaction between gas and solids phases.