旋转填料床间歇精馏不稳态开工过程

为了深入了解三角形螺旋填料旋转床间歇精馏不稳态开工过程的影响因素及规律,以乙醇-水为实验物系进行实验和模型研究。改变料液浓度、再沸器加热功率和转速的开工实验结果表明,旋转填料床中强大的离心力和高效填料的协同作用使得间歇精馏不稳态开工过程得到极大强化、开工时间很短(30min左右),节能;在最佳转速下开工可使馏出液浓度最大,馏出液浓度随料液浓度和再沸器加热功率的增加而增大。旋转填料床间歇精馏过程在最佳转速和较大的再沸器加热功率下开工,效果最好;以平衡级理论为基础建立的数学模型能较好地描述该过程的不稳态开工规律,模拟值与实验值吻合良好,平均相对误差在2%以内。旋转填料床是强化间歇精馏过程的有效途径。

Transient startup process of batch distillation in rotating packed bed

The purpose of the study is to deeply understand the influence factors and laws of transient startup process of batch distillation in rotating packed bed(RPB) which is packed with triangular spiral packing. The batch distillation experiments were done with ethanol-water system at atmospheric pressure and under the total reflux conditions. The rotational speed ranged 450 rpm from 1050 rpm, which provided centrifugal forces a great many times than the Earth’s gravity. By means of changing the feed concentration, rotational speed and heating power, experimental results indicate that the transient startup process is greatly enhanced in terms of shortening time and saving energy. The startup process in our study only needs about 30 minutes and the concentration of distillate is high(nearly the azeotropic mixture of the ethanol-water system). Comparing with the conventional column in the gravitational field, the startup process in RPB is not a time-consuming process. Consequently, the concentration of distillate which increases with the feed composition and the heating power of reboiler comes up to maximum under the optimal rotational speed. An unusual result is also noted that the startup process of batch distillation in RPB with different feed composition should operate under the higher heating power of reboiler and the corresponding optimal rotational speed conditions in practical production process. Therefore, the batch distillation transient startup process in RPB has the best effect under the optimal rotational speed and higher heating power. The results indicate that the startup process of batch distillation in RPB is greatly intensified, which places an important role in the process of product removal in terms of shortening period of operation, enhancing produce capacity and saving energy, etc. Moreover, the mathematical model based on the equilibrium stage theory was built to describe the laws of transient startup of batch distillation in RPB. The average relative error between simulative value and experimental data of the mass fraction of ethanol in distillate and the temperature of overhead vapor are only 0.4% and 0.08%, respectively. The comparison results prove the accuracy and commonality of the model. So the rotating packed bed is an effective way to strengthen the batch distillation process, which is flexible and convenient to manipulate and is expected to apply in industrial process. Fundamental performance characterizations and more generalized theoretical expressions for parameters of batch distillation in RPB that accurately predict batch distillation performance in RPB will be needed to confidently scale-up this application.