Chemical plant startup is a plant-wide dynamic operation that usually involves discontinuous and/or parallel operating procedures, as well as the wide change of controllers' set points. During the plant startup, the operation for multi-stage compression system (MSCS) especially needs sufficient care. This is not only because the compression equipments are the most valuable facilities in the plant, but also its failure operation will cause dangerous situations to the whole process and thereby cause tremendous raw material and energy loss. Thus, the startup procedure for MSCS must be virtually evaluated prior to the real implementation.

This paper employs rigorous dynamic simulation to test both safety and economic performance for MSCS startup operation. For safety consideration, anti-surge process design and control strategies are dynamically evaluated along with startup procedures. Operating point trajectory for each compressor and their potential surge risks will be identified. For economic consideration, on the other hand, feasible and energy-efficient operating (economic) zone for each compressor will also be identified. The difference between the operating trajectory and the economic zone is thus available, which will be utilized to guide the performance optimization for MSCS design and control.

The rigorous dynamic simulation is a cost-effective and general way for MSCS system performance evaluation. The best-performance oriented rigorous dynamic simulation can be extended in future to any critical chemical process systems to improve their turnaround or routine operations. A case study for performance improvement of an MSCS during an ethylene plant startup will be demonstrated in this paper.