(226b) High Purity Benzene Production from FCC Gasoline Using a Top Dividing Wall Column

An increasing global trend among refiners to transition into refinery petrochemicals is attributed to a projected higher profitability of petrochemicals compared to refinery fuels. Aromatics are important building blocks in the petrochemical value chain, and most aromatics are derived from reformate or pygas. In addition, RFCC/FCC-based refiners have shown a disposition towards aromatics extraction from FCC gasoline. Benzene extraction, as opposed to saturation, not only gives value upgrade but also aids the refiner in MOGAS benzene content management.

As compared to reformate or pygas feedstocks, FCC gasoline has a higher quantity cyclic olefins and naphthenes. In traditional solvent-based extraction processes, these compounds are relatively difficult to separate from aromatics, imposing challenges on the extraction unit design. GT-BTX PluS^® can circumvent this situation by employing a proprietary solvent blend with a strong aversion towards cyclic and normal olefins and high affinity towards aromatic species. The solvent’s behavior, coupled with unique design features in the downstream hydro-desulfurization (HDS) unit, enables GT- BTX PluS^® to achieve a benzene purity in excess of 99.8%. The benzene product obtained qualifies as petrochemical grade and requires no further processing such as re-extraction. A commercial unit with this technology, is operating in South Korea with the benzene product meeting all petrochemical grade requirements.

Leveraging on the success of the above-mentioned unit and operational knowledge gained, Sulzer GTC Technology has further improved the process by converting the stabilizer downstream of the HDS unit into a Top Dividing Wall Column (TDWC). Any aromatic saturation across the HDS unit coupled with slippage of cyclic compounds will directly affect the benzene purity. If not properly accounted for, this results in the requirement of a re-extraction unit to recover benzene purity. This presentation will show the benefits of using proper VLE along with a TDWC approach for azeotropic recycle back to upstream extraction section. This failsafe can be built into the unit to recover benzene purity to account for unwanted impurities in the benzene product.