Abstract:

Particle velocity distributions were investigated in draft tube and annulus region of a φ600 mm CSVQS cold-state setup under conditions of gas velocities at 0.2 and 0.3 m·s^-1 in the draft tube, at 0.03 and 0.07 m·s^-1 in the annulus region and 0 and 0.13 m·s^-1 in the stripper. Mean residence time distribution of particles in the pre-tripper section was also calculated by the method proposed here. Experimental results demonstrated that gas flowed as center-airlifting circulation in the pre-stripper section and most of the gas went into the draft tube under the above-stated operating conditions. Under constant gas velocity in the draft tube and increased gas velocity in the annulus region, the radial velocity distribution of particles changed from steep to smooth without stripper wind whereas that distribution changed slightly with stripper wind. Under the same gas velocity in the annulus region and increased velocity in the draft tube, the radial velocity distribution of particles changed from smooth to steep without stripper wind whereas distribution remained quite steep with stripper wind under the two different velocities in the draft tube. Compared to that in the draft tube, the radial velocity distribution of particles in annulus region kept almost no change with varied operating conditions. When the gas velocity was increased in the draft tube or was decreased in the annulus section, the average residence time distribution of particles was narrowed and the mass fraction of particles was decreased. When the circulation strength of particles in the pre-stripper section was increased, the average residence time distribution of particles was narrowed but the mass fraction of particles was changed irregularly.

Key words: riser, air-lift loop pre-stripper, particle velocity, residence time distribution, optical fiber probe, particle

摘要：

在一套φ600 mm CSVQS的环流预汽提段冷态实验床装置上，在导流筒区气速为0.2 m·s^-1和0.3 m·s^-1，环隙区气速为0.03 m·s^-1和0.07 m·s^-1，汽提段气速为0和0.13 m·s^-1时，考察了预汽提导流筒区和环隙区的颗粒速度分布，同时在上述条件下，根据提出的计算方法，考察了由提升管引入环流预汽提段颗粒的平均停留时间分布。结果表明，在上述几种操作条件下，预汽提段均为中心气升式环流，汽提段气体大部分进入导流筒区。在导流筒区气速相同时，在无汽提风时，导流筒区颗粒速度随环隙区气速的增加沿径向由陡峭分布转变为平缓分布；在有汽提风时，导流筒区颗粒速度径向分布随环隙区气速的变化很小。在环隙区气速相同时，在有汽提风时，导流筒区颗粒速度随其气速的增加由平缓分布转变为陡峭分布；在无汽提风时，两种导流筒区气速下的颗粒速度径向分布均比较陡峭。与导流筒区相比，环隙区颗粒速度径向分布几乎不随操作条件的不同而变化。随着导流筒气速的增加或环隙气速的降低，颗粒平均停留时间分布变窄，质量分数降低；随着颗粒循环强度的增加，颗粒平均停留时间分布变窄；质量分数变化不一。

关键词: 提升管, 环流预汽提器, 颗粒速度, 停留时间分布, 光纤探头, 颗粒