分壁精馏塔分离芳烃的温差控制

Temperature Difference Control of Divided-Wall Column for Separating Aromatics

与传统精馏塔相比,分壁精馏塔（DWC）具有明显的节能和节约设备投资的优势,但是其控制方法较复杂,主要原因在于DWC多个控制回路的相互耦合,且多元物系的塔板温度与塔板组成也非一一对应。在组分控制的基础上,采用Aspen Dynamic模拟DWC分离苯、甲苯、二甲苯和均三甲苯四组分体系动态过程,提出了温度控制和温差控制方法,并考察了这两种控制方法的控制效果。结果表明,当进料流量和组成发生±10%波动后,利用温度控制,各产品纯度的最大波动范围为0.985-0.995,而温差控制的各产品纯度最大波动范围为0.988-0.992;当塔压发生波动时,温差控制和温度控制的各产品纯度最大波动范围分别为0.9885-0.9915和0.980-0.996。温差控制效果明显优于温度控制。

As the strong interaction of control loops of divided-wall column （DWC）, it is more difficult to control a DWC than a conventional column. More, the stage temperature of DWC is not strongly connected with the stage composition in DWC. So some control failures often happen by only using temperature control for DWC. The temperature control structure （TC） and the temperature difference control structure （DTC） of a DWC were proposed, and their control results were compared for separating benzene, toluene, o-xylene and 1, 3, 5-trimethylbenzene mixture. The dynamic simulation showed that in facing of ±10% feed flow and composition disturbances, the product purities could be maintained between 0. 985 and 0. 995 by TC structure, but between 0. 988 and 0. 992 by DTC structure. Besides, in facing of pressure change the products purities could be kept between 0. 9885 and 0. 9915 by DTC structure while only between 0. 980 and 0. 996 by TC structure. The performance of DTC structure was better than that of TC structure.