Research on wall flow and backmixing in semi-circular packing layer of dividing wall column

doi:10.11949/0438-1157.20190881

Abstract

Abstract:

Based on the three-parameter wall flow model of the packed tower, a wall flow model applied to the semi-circular filler layer of the dividing wall tower is proposed. Refer to experimental data, the model parameters were estimated. The results agree well with the theoretical value. A set of semicircular cold test system with a diameter of 580 mm and a height of 2800 mm was built, and the effect of gas and liquid rate change on the wall flow was analyzed. The residence time distribution(RTD) curves were obtained by pulse injection stimulus-response technique. It is found that the RTD is affected by the change of gas and liquid rate. The influence of wall flow effect is quantified by the average residence time comparison between wall section and bulk section, the results show that the average residence time of wall section was smaller than that of bulk section at the wall flow full development stage. Such data are essential for design and optimization of dividing wall column distillation processes. Correlation of Pe_d is calculated by liner regression. This experiment has reference significance for the development of new packings, inner parts and the improvement of the design method of DWC to achieve safe, reliable and effective amplification.

Key words: dividing wall column, random packing, wall flow, residence time, backmixing

摘要：

在填料塔三参数壁流模型的基础上，提出了应用于隔壁塔半圆型填料层的壁流模型。通过实验对模型参数进行了估计。模型计算值与实验值吻合较好。在内径为580 mm、高2800 mm的半圆冷模塔内，常温常压下以空气-水为介质，测取了散堆填料的壁流曲线，分析了气液速率变化对壁流的影响。以氯化钠溶液为示踪剂，通过脉冲注入扰动响应技术获得停留时间分布曲线。发现气液速率变化均对停留时间分布产生不同程度影响。同时比较了同一填料层高度塔壁区和整体区的平均停留时间，在壁流充分发展阶段，塔壁区的平均停留时间明显小于整体区。从另一方面量化了壁流效应的影响。应用线性回归得到单相流和气液逆流时计算Pe_d的关联式。对于新型填料及塔内件的开发、改进隔壁塔的设计方法，从而实现安全有效放大具有参考意义。

关键词: 隔壁塔, 散堆填料, 壁流, 停留时间, 返混

CLC Number:

TQ 028.8

Chunli LI, Jingyu LI, Mingxia ZHANG. Research on wall flow and backmixing in semi-circular packing layer of dividing wall column[J]. CIESC Journal, 2020, 71(4): 1460-1468.

李春利, 李景玉, 张明霞. 隔壁塔内半圆填料层中壁流与返混特性研究[J]. 化工学报, 2020, 71(4): 1460-1468.

Figures/Tables 8

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