Abstract: Gas holdup (eg) was studied in a bubble column operated at elevated temperature. The column is 300 mm in diameter and 1.2 m in height, and the distributor has four nozzles with large diameter. The adjusted mixture of acetic acid (the solvent of the reaction) and p-, m-, o-xylene (homologous compound mixture of the reactant) was employed as the liquid phase, considering the oxidation of p-xylene. The experiments were conducted systematically to investigate the influences of superficial gas velocity (Ug), temperature, composition of the organic solutions on eg. The research ranges of superficial gas velocity and temperature were 0.009~0.224 m/s and 11~99℃ respectively. The effect of superficial gas velocity was summed up by eg-Ugn, the value of n varied with temperature, that is, n=0.6 at ambient temperature, n=0.4~0.5 at elevated temperature and 0.2 at the nearing boiling point. There was a transition point at eg-T curve, so the effect of temperature on eg can be classified into two stages, one far from the boiling point and another near to the boiling point. eg was nearly a constant at the first stage and increased significantly at the second. The critical temperature was varied with the superficial gas velocity, it was 90℃ in the range of 0.009~0.045 m/s and 70℃ from 0.072 to 0.18 m/s. As to the effect of the composition of organic liquid solutions, eg increased at first, and decreased when the mass concentration of acetic acid was higher than 80% in tap water-acetic acid system, eg in the acetic acid-xylene solution was lower than that of the water-acetic acid, while solutions had the same acetic acid content, eg in partly soluble water-acetic acid-xylene system was lower than that of the completely soluble system. A gas holdup correlation implicating the effects of various factors was given.

Key words: elevated temperature bubble column, gas holdup, far from the boiling point, near to the boiling point, organic liquid solutions

摘要： 以对二甲苯氧化为背景，在直径300 mm、高1.2 m、大直径多管式分布器升温鼓泡塔内，采用压缩空气为气相，自来水、醋酸、二甲苯(邻、间、对二甲苯混合物)为液相，在表观气速0.009~0.224 m/s、温度11~99℃范围内，系统地考察了气速、温度、溶液组成对气含率的影响. 结果表明，不同温度范围表观气速对气含率的影响程度不同，气速幂律指数n在常温下约为0.6，升温情况下减小为0.4~0.5，接近沸腾时n值仅为0.2. 温度对气含率的影响可分为远沸点与近沸点两个阶段，在前一阶段气含率随温度上升而缓慢升高，在后一阶段则迅速上升. 不同气速范围内临界温度不同，在0.009~0.045 m/s范围内临界温度为90℃，在0.072~0.18 m/s范围内临界温度为70℃. 水-醋酸体系的气含率随醋酸浓度的增大先升高后降低，最大值出现在浓度80%(w)左右；醋酸-二甲苯体系气含率低于相同浓度的醋酸-水体系；部分互溶水-醋酸-二甲苯三元体系气含率低于完全互溶体系. 综合考虑各因素对气含率的影响，给出了气含率关联式.

关键词: 升温鼓泡塔, 气含率, 远沸点, 近沸点, 有机溶液