微孔曝气对环己烷液相氧化过程的强化作用

Enhancement Effect of Microporous Sparger on the Liquid-phase Oxidation of Cyclohexane

采用照相法分别对平均孔径为40μm的微孔曝气头和孔径为1mm的单孔曝气头在纯氧-环己烷体系中,表观气速在0.629×10-3～3.15×10-3m·s-1范围内的曝气特性进行了实验研究。研究发现在实验条件下单孔曝气产生的气泡的Sauter平均直径(d32)不小于4.0mm,而微孔曝气产生的气泡的d32不大于1.3mm。相同的表观气速下微孔曝气的气含率高于单孔曝气的气含率,但其传质面积是单孔曝气传质面积的5倍以上。对微孔曝气产生的气泡的直径分布及其沿塔高的变化进行考察发现,塔内气泡的直径分布服从对数正态分布,气泡直径沿塔高方向的聚并作用小。在1.15×10-3m·s-1的表观气速下,利用纯氧进行环己烷液相催化氧化,微孔曝气时环己烷的反应速率为0.62mol·m-3·s-1比单孔曝气时的氧化速率提高约1倍。

The bubbles produced by a microporous sparger （Dp = 40μ m） and a single orifice sparger （Dp = 1 mm） at superficial gas velocities ranging from 0.629 × 10^-3 m · s^-lto 3.15 × 10^-3m · s^-1 were compared in the oxygen-cyclohexane system . The results showed that the Sauter mean diameter d32 of the bubbles produced by the microporous sparger were below 1.3 mm, and those by the single orifice sparger were larger than 4.0 mm. The diameters of the bubbles produced by the microporous sparger met the logarithmic normal distribution, and the coalescence of the bubbles was negligible. The gas hold-up of the microporous sparger bubbling was relatively higher in the examined superficial gas velocity range . By using the microporous sparger , an cyclohexane oxidation rate of 0.62 mol · m^-3· s^-lat a superficial gas velocity of 1.15 × 10^-3 m. s^-1 was achieved, which was about 1 fold higher than that performed by using the single orifice sparger.