(194c) Expanding the Capacity of Ethylene Plant Distillation Towers

Incremental expansions of existing olefins plants often show very attractive net present value (NPV) for invested capital. Improved furnace designs, or the addition of a furnace, can provide the incremental capacity at the front end of the plant, but then the downstream equipment also needs to be capable of receiving the increased product flow. The fractionation towers are a very important part of the downstream equipment that need to be carefully reviewed when considering such a plant expansion. Another area where the fractionation equipment is likely to be implicated is in changes to the plant feed, for example switching from cracking naphtha to ethane, which can significantly alter the hydraulic loading of the fractionation equipment. This presentation will review the current state of the art in revamps of fraction internals, focussing on the high pressure, cold section of the fractionation train, including deethanizers and ethylene splitters with some examples to increase capacity

Such tower revamps typically take place during scheduled plant outages and are therefore often time sensitive, which adds another constraint. We will also describe some of the special mechanical design techniques that have been developed to simplify the installation of the improved fractionation internals, allowing complex revamps to be completed safely and on schedule.