多层双锥液固逆流浸洗塔颗粒停留时间分布研究

Investigation on the Particle Residence Time Distribution in a Multistage Double Cones Liquid-Solid Countercurrent Extraction Column

针对石油钻井钻屑污染物治理的需要,开发了具有新颖结构的多层双锥液固逆流浸洗塔,整体上具有液固两相多级逆流传质浓度分布特征,级内呈现液固流态化良好的混合传递特性.采用脉冲示踪法进行了颗粒停留时间分布实验研究,结果显示多釜串联模型符合其结构与流动混合特征,以理论级数N作为模型参数可以很好地表达颗粒物性及操作参数对过程的影响.在研究范围内,内径100 mm的24层双锥塔理论级数在6.11～11.0,随液固比增大而增大、随颗粒粒径增大而减小的趋势.该塔在理论级数6.93的操作条件下连续逆流浸洗,钻屑平均停留时间4.23 min、残留COD浓度77 mg·L-1,与6级间歇逆流平衡浸洗钻屑残留COD浓度56 mg·L-1的实验结果相近,为多釜串联模型用于多层双锥塔浸洗传质模型研究与过程放大提供了实验依据.

Focusing on removing pollutants from oil drilling cuttings, a multistage double cones column （MDCC） was developed with a novel configuration for countercurrent liquid-solid extraction, maintaining favorable overall concentration distributions for the liquid and solid two phases counter-current mass transfer as well as good performances of mixing and transferring within a stage. According to the characteristics of particle residence time distribution （RTD） curves, which were obtained experimentally through pulse tracer method, the model of tanks-in-series matches the configuration properties and the process hydrodynamics. As the characteristic model parameter, the theoretic stage number N can response sensitively to the effect of particle properties and operation conditions in the process. Within the experimental range of this investigation carried out in the MDCC of 100 mm inner diameter with 24 units of double cones in-series, the theoretic stage number N is between 6.11-11.0, increasing when the ratio of flow rate of liquid/solid is increased and decreasing when the particle diameter is increased. Compared with the residual COD concentration of 56 mg.L-1 in the oil drilling cuttings after six stages batch counter-current equilibrium extraction, the corresponding concentration is 77 mg.L-1 after continuous counter-current extraction by the MDCC operated with a theoretic stage number N of 6.93 and an average residence time tav=4.23 rain. It provides an experimental evidence for the application of the tanks-in-series in the investigation of mass transfer and the scale-up of processes in the MDCC.