Published December 2008
One of the major sources of BTX aromatics is the pyrolysis gasoline by-product from steam cracking of naphtha for olefins production. A variety of process schemes are available to recover the aromatics as well as other value-added products from the feedstock. One such process is the subject of a recent US patent assigned to the SK Corporation. The process is named Advanced Pygas Upgrading or APU™ and is exclusively licensed by Axens. It involves the use of a catalytic hydrodealkylation step that produces a BTX mixture with low ethylbenzene content, LPG and fuel gas from the C6+ fraction derived from stabilized pygas. Simple distillation is used to recover the pure aromatics fractions and the LPG.
This review compares the relative economics of the APU process with that of an alternative conventional scheme that incorporates C7/C8 splitting, extractive distillation to separate the aromatics and nonaromatics from the C7 fraction and thermal hydrodealkylation to convert the C8+ fraction to additional benzene and toluene. Products are benzene, toluene, C6- raffinate and fuel gas. Conceptual process designs, capital estimates and production cost estimates are developed for both processes for plants processing ~22,000 bbls/day of pygas.
The estimated CAPEX and OPEX for both processes are roughly the same. The relative economics hinge on the value of the product slates. Based on 3rd quarter 2008 Gulf Coast prices the APU process has very favorable economics (B/T ROI > 25%) and has a distinct advantage over the conventional route (B/T ROI<25%).
