Abstract: The running condition of refrigeration system is the key factor to ensure the ethylene recovery of ethylene plant. When the load of ethylene plant was high, the problems of unreasonable refrigerant distribution and poor system operation stability of the ternary refrigeration system were easy to exist, which led to excessive temperature at the top of demethanation column and serious ethylene loss. A ternary refrigeration system model was established by process simulation software, and the influence of pyrolysis gas volume and its composition on the operation of ternary refrigeration system was analyzed by steady-state simulation and dynamic simulation. The key parameters affecting the stable operation of the system were found, and some optimization suggestions were put forward, such as the adjustment methods for ternary cold box and demethanation column for various working conditions, the three-stage outlet temperature modification scheme of ternary refrigeration compressor, and the top-span line the adjustment strategy of demethanation column, it was of theoretical significance for the optimal operation of ternary refrigeration system in ethylene plant.

Key words: ternary refrigeration system, cold box, demethanation tower, dynamic simulation, ethylene plant