New Process Flowsheet for CO2 Compression and Purification Unit; Dynamic Investigation and Control

The present study provides a novel process flowsheet for CO2 compression and purification unit (CPU) in order to improve its product quality and control performance. Unlike the previous process flowsheet, the number of cold-boxes has been reduced to one, which in turn decreases investment costs and improves energy integration. The performance of the proposed flowsheet was compared with two recently suggested ones for a given feed. The results showed that, compared with the other process flowsheet, the new one not only can operate at lower operating pressure but also needs a significantly smaller heat-transfer area. Also the dynamic behavior and controllability of the proposed process flowsheet are analyzed to ensure the proper functioning. The control loops used in the new flowsheet were simpler than those used in the previous flowsheet, and controllability was achieved using proportional (P) and proportional-integral (PI) controllers, which offers a performance advantage over the other process flowsheet. Using step changes, the effects of disturbances in feed temperature, flow rate, and composition on the final product specifications were also investigated. The proposed flowsheet process proved to be robust against the disturbances and the control structure was able to handle them appropriately. The proposed process flowsheet was also able to maintain purity and recovery rates of 96.74% and 90.08%, respectively, in the face of disturbance.