大型下行式循环流化床反应器颗粒浓度分布研究

采用双光路光纤密度探头研究了内径418mm,高18米大型下行式循环流化床（其中下行床部分长度6．5m)反应器中的颗粒浓度分布，结果表明大直径下行床中颗粒浓度沿径向呈现中心均匀，近壁处存在高浓环形区的分布，这类似于小直径反应器中的结果，随着反应器直径的增加，颗粒浓度分布最大值的径向位置向边壁方向移动，即：当下行床放大时，中心颗粒浓度均匀分布区的面积占整个床层截面积的比例增大，在一种特殊设计的下行床边壁结构中测量了颗粒浓度沿径向的分布，实验结果说明边壁效应对下行床近壁区颗粒浓环的形成起到了重要作用，研究结果将有助于了解下行床反应的放大特性。

Study on Radial Solid-Fraction Profiles in Large-Scale Downer Reactor

Radial profiles of local solid fraction under different operating conditions were obtained through a dual-optical density probe in a 0.418m I.D. and 18m high large-scale circulating fluidized-bed (CFB) apparatus with 6.5m length downer reactor. Radial distribution of local solid fraction in large-scale downer is uniform in the central region and a relatively high concentration ring exists near the wall, as that in the downer with small diameter. The radial position of the maximum solid fraction moves more closely to the wall while the diameter of the downer increases. It indicates that the proportion of the area of the core region, where solids distributed uniformly, to that of the whole cross-section increases with the scale-up of the downer. Experiments were also carried out in a specially designed downer wall structure, and results show that the existence of the near wall dense ring is related with the wall of downer. These experiment results are beneficial to understand the scale-up feature of this kind of excellent gas-solid CFB reactor.