Olefin Co-product Links – Extraction, Hydrogenation, Isomerization

Integration of crackers with other process plants such as refinery and natural gas plants has been the topic of interest over many years driven by motivation to improve overall economics. Cracker integrations have taken on added importance due to wide swings in cracker feed and product prices occurring in today's world. Integrated crackers are better able to survive bottom of the cycle prices.

The menu of cracker integration technologies can be expanded to other processes. In this presentation we have chosen three processes namely aromatics extraction, propane dehydrogenation and isomerization. Our objective in choosing these technologies was to evaluate efficiency of feed usage and their economics. As we move forward we must be mindful of “conserving hydrocarbon resources” and employ synergies which maximize cracker feed potential to produce desired olefin products.

About 50% of world ethylene capacity is based on naphtha. For world size naphtha crackers with dedicated aromatics extraction unit, naphtha feed can be de-aromatized in the aromatics extraction unit (economy of scale) which can result in improved feed efficiency. Detailed process and economic evaluation is presented which shows that this integration is economical. Other benefits of naphtha de-aromatization are also presented.

A few crackers are being planned with E/P (ethane/propane) mix as the feedstock. In this case E/P cracker is compared to ethane cracker integrated with propane dehydrogenation unit. E/P cracker has the design propylene to ethylene ratio of 0.225 while integrated ethane cracker with propane dehydrogenation unit results in propylene to ethylene ratio of about 0.97 and about 8% increase in total ethylene + propylene production.

Application of isomerization is presented for mixed butane feeds. Many crackers receive mixed butane feeds which have increasingly large content of iso-butane. We have presented one case study of separating iso-butane from feed and isomerizing it to normal butane.

Obviously important consideration in these integrations is to maintain proper independent operational flexibility which needs good process understanding and careful strategic planning.

We as ethylene cracker owners will need to take charge of feed at some point in time just to improve our economics and survive in difficult periods. We hope this presentation encourages examination of other technologies for cracker integrations.