Abstract: Distillation is the most widely used separation technology in the chemical industry, and its high energy consumption has been a major concern. Traditional distillation process control usually focuses on controlled variables, such as tower top and bottom temperature. Engineering process control (EPC) on the operating variables can maintain the control output in a given range. In real-time production, regulation of EPC might cause shifts in the mean value of the manipulation variables, and energy waste might occur when both the cold and hot utilities increase spontaneously. Under carbon peaking and carbon neutrality, it is important to seek an accurate monitoring/control strategy to realize the energy-saving operation of the distillation processes. This work proposes to combine statistical process control (SPC) and EPC, i.e., SPC charts are introduced to determine the disturbance scenario as well as EPC is adopted to control the process. According to the analysis of SPC charts, the interference source could be identified, which might assist in the control decision on EPC. To demonstrate the monitoring effect, a benzene separation column is taken as a case study where decoupling control is implemented for temperature disturbance rejection. Then, step and slope disturbances are introduced into the system to locate or predict shifts of the manipulated/control variables, afterwards, root cause analysis is implemented. The simulation results show that while EPC could maintain tower temperature within a specific range for a relatively long period, SPC might suggest abnormal working status, which would cause unnecessary consumption of energy. The results show that combining EPC and SPC could effectively enhance the understanding of the process run-away conditions, and assist reduce the unnecessary energy consumption of the distillation process.

Key words: Distillation process, Control charts, Statistical process control, Engineering process control

摘要： 在“双碳”目标背景下，寻求面向工业数据的精确监控，并实现精馏过程节能操作十分重要。本工作针对精馏过程塔顶、塔釜存在热耦合的情况，提出了统计过程控制(Statistical Process Control, SPC)和工程过程控制(Engineering Process Control, EPC)相结合的精馏过程监控策略，并以苯塔精馏的解耦控制为案例，探讨系统引入阶跃、斜坡扰动时，联合EPC与SPC对该过程控制/操作变量的均值漂移工况进行分析。仿真结果显示，针对塔顶回流阀坏导致回流量斜坡上升的情况，发现EPC在较长时间内能维持塔顶、塔釜温度稳定，但是SPC识别出塔顶、塔釜能耗均可能上升的情况。因此，精馏过程在传统EPC控制下，增加SPC可有效预报出精馏控制冷、热能耗均同时、同向漂移的情况，为提前判断并避免非必要能耗提供监测及诊断依据。

关键词: 精馏过程, 控制图, 统计过程控制, 工程过程控制