筛板结构与分布对脉冲萃取塔传质性能的影响

Effect of Sieve Plate Arrangement on Mass Transfer Performance of Pulsed-Sieve-Plate Extraction Column

为了考察萃取柱内液滴的分散与聚集对于传质性能的影响,比较了3种不同筛板结构与分布的脉冲萃取塔的传质性能,即通过在标准柱内加入聚集板加强液滴的聚集,并通过改变板间距来调整塔内分散相的聚集、分散行为。结果表明,板间距为50mm,每隔3块标准板放置1块被分散相浸润的聚集板,可以有效地利用分散相液滴在塔内周期性的表面更新效应强化传质,传质效率较标准脉冲筛板萃取塔高30%以上。降低分散-聚集筛板分布的板间距后,连续相的轴向返混系数会明显降低,但分散性能降低,从而造成全塔的传质效率较低。因此优化塔内分散、聚集频率是设计高效萃取设备的关键因素之一。

To investigate the effect of dispersion and coalescence on mass transfer performance in extraction columns,three types of sieve arrangement in a pulsed-sieve-plate extraction column (PSEC) were designed by inserting different number of dispersion and coalescence plates into the column.Characteristics of mass transfer and axial mixing were evaluated and compared using a working system of 30% tributylphosphate(TBP,in kerosene)/ nitric acid / water.Thus,the mass transfer efficiency of dispersion-coalescence pulsed-sieve-plate extraction column (DCPSEC) could increase by more than 30% as compared with standard PSEC,due to the influence of an interface renewal through an arrangement of 50 mm in plate spacing and one coalescence plate every four plates.Mass transfer efficiency of another type of DCPSEC with 25 mm in plate spacing was lower than standard PSEC because lowering plate spacing would lead to bad dispersibility and lower interface area,despite the lowering of axial mixing was greater than the other two types of PSEC.Therefore,a very important aspect is to optimize dispersion and coalescence conditions for better performance of columns.