(148g) Furnace Revamps in Low Budget Times

With the current economical down tide the number of prospects for investments in new grass-root crackers has been substantially gone down as compared to only a few years ago. This makes it even more worthwhile for olefin producers to identify if improvements can be made in existing operations with relatively small investments.

The heart of the steam cracker are the cracking furnaces, where the pyrolysis reactions take place that largely determine the cracker overall material balance. As the furnace needs by nature periodic replacement of the radiant coil (typically after 4-8 years), a revamp strategy aiming at a new radiant coil with improved performance often pays back, considering that the budget for one-to-one replacement is normally already available.

Main drivers for revamp are increase of selectivity, capacity, run length or a combination of these. Other benefits could be increase of overall thermal efficiency, additional flexibility for alternate feedstocks, extension of the furnace life cycle or reduction of NOx emissions.

A furnace revamp project is preferably preceded by a study where various options for new radiant coils are scouted, taking into consideration current operational feedback. A recommended approach is to reconcile the existing operating data by rigorous modeling, in order to thoroughly understand the current furnace limitations. The scouting needs to include adequacy checks of remaining furnace parts under the new operating conditions. Finally, scope, downtime and required investment are determined in order to assess the overall project feasibility.

In this paper case studies are presented that show the economical benefits for various revamp examples. Special emphasis will be given to the recent recoiling project of LyondellBasell Industries for their OM4 cracker in Germany.