Abstract: Demethanizer system is the key of cryogenic separation in ethylene plant, which can influence the loss of ethylene products. The loss of ethylene is often related to the design and operation of demethanizer system. Taking a demethane tower system in the former depropane process of ethylene plant as an example, the influencing factors, such as methane/hydrogen mole ratio of feed and feed temperature, setting of ethylene scrubber, reflux of demethanizer and overhead temperature, as well as heat load of reboiler/condenser were studied. And the solutions were proposed to reduce ethylene loss in the demethanizer top and provided reference for the design and operation of demethane tower system in ethylene plant.

Key words: ethylene plant, demethanizer, cryogenic separation, reflux, reboiler, condenser