Emission Constrained Cyclic Scheduling of Ethylene Cracking Furnace Systems

Cracking furnace system is the starting and the most critical sector of an ethylene plant where heavier components are cracked into lighter products, such as ethylene, propylene, and etc. During the production, coking can adversely affect the manufacturing performance, such that furnaces have to be decoked for some controlled time. The cracking and decoking processes both influence the plant profit, as well as the emissions from the furnace operations. Nowadays, the profit enhancement is never the sole target for an ethylene plant; emission reduction is becoming a hot concern. How to schedule the decoking operation among multiple cracking furnaces with emission reduction consideration presents a new optimization problem. In this paper, an MINLP (mixed-integer nonlinear programming) model has been developed to optimize the cyclic operation of cracking furnace system with consideration of various emissions. The efficacy of the proposed methodology is demonstrated by a case study with in-depth analysis.