流化床射流区域细粉浓度分布的实验研究

EXPERIMENTAL STUDY ON FINE PARTICLE CONCENTRATION DISTRIBUTING IN THE JET REGION OF A JETTING FLUIDIZED BED

在直径1 m,高8 m的半圆冷模射流流化床上,利用PC-4颗粒浓度测定仪和局部取样的方法,考察了细粉通过密相输送的方式进入中心射流区时,射流区域的颗粒浓度分布.实验所用细粉粒径为-80+160目(均粒径为138μm)的聚氯乙烯细粉颗粒,粗颗粒为均粒径为1.1 mm的聚苯乙烯颗粒.研究结果表明,在流化床射流区域存在一细粉高浓度区.在径向上,细粉颗粒浓度呈先增高后降低的趋势,在轴向上,当达到一定射流高度的床截面时细粉浓度逐渐降低.在两种不同细粉进料量时,射流区域细粉浓度的增大幅度与进料量的增加成正比.在较低进料量时,细粉高浓度区较不明显且靠近分布板区域细粉浓度较高.较高细粉进料量时,细粉高浓度区域更为显著.

Experiments were carried out to study the concentration distributing of fine particles in the jet region of a 1 m dia and 8 m high semicircular jetting fluidized bed with a conical distributor. The particle concentration was measured with PC-4 optical fiber probe system and local-sampling. The average size of large particle is 1.2 mm. Fines, -80＋160 mesh with an average size of 138 μm, were injected coaxially to simulate fines recycle back to the jet region in an actual operating unit at different fines feed in quantity. It was found that there is a high fines concentration region existing in the jet region of fluidized bed. The fine particle concentration increases along the radial direction firstly, and then decreases. When reaching certain bed height, the absolute volume fraction of fines begins to decrease along the axial direction. Two kinds of fines with different feed in quantity, fines concentration in jet region increases proportionally with fines feed in quantity. When the feed-in quantity of fines is low, its high concentration zone is not obvious and the fines concentration near distributor is higher. Otherwise, high fines concentration in jet region is more significant.