预热器换热管内粉体物料轴向浓度分布的试验研究

An Experimental Investigation into Axial Distribution of Powder in the Heat-exchange Pipe of a Suspension Preheater

采用光纤探头针对7个不同高度的预热器换热管截面做粉料轴向相对浓度分布测试。研究发现,沿换热管下料点断面向上,同一径向位置的颗粒浓度总是不断减小。换热管边壁区颗粒浓度沿轴向位置升高而减小远比中心区域迅速,当表观气速较小或物料负荷率较高时此现象尤为明显。随换热管截面高度的增高,气固两相流场发展逐步充分而趋于稳定,两者的相对运动速度逐渐变小。气流沿轴向的湍动逐步减弱,中心区和边壁区的颗粒浓度的差异逐渐缓和。改变操作条件对同一轴向断面边壁区颗粒浓度的影响较大,对中心区颗粒浓度的影响较小。增大系统的固气比,轴向不均匀性增大,物料下冲高度增大。

Particle concentrations at 7 levels along the axial direction of a heat-exchange pipe were measured by a optical fiber probe with the superficial gas velocity ranging from 12 to 21 m/s and different solids loading. The results indicated that the particle concentrations decreased upwards, for a given radial position, from the level of the feeding port. As the axial altitude increased, the solids concentration in the near wall region decreased, more rapidly in comparing with that determined in the central region of the pipe. The phenomenon was more obvious when the observation was performed at lower superficial velocity or heavier solids loading. Observing at successively higher positions along the axis, the gas-solid two- phase flow field become more and more stably and the relative velocity between particle and gas decreased step by step. Meanwhile, the turbulence strength of the gas flow extenuated evenly, the particle concentration difference between central and near wall region decreased gradually. Alternating operation conditions resulted in variation in solids concentration in the near wall region more significant than that in the central region. With inereasifig solids loading , the dispersion distance of the powder increased and the axial un-uniformity of particle concentration became more appreciable.