Abstract

The classical routes for residue conversion are coking and hydrotreating / hydrocracking technologies. There are other options, however, to use crude oil residues efficiently and economically.

OMV has chosen to install Shell's Deep Thermal Gasoil Unit (DTGU) in the Schwechat refinery which has looked best to fit to the existing units and infrastructure. Vacuum residue should be converted well above 40%, the produced vacuum distillate is thermally cracked to mainly middle distillates which can be further hydrotreated in conventional diesel hydrotreaters eliminating the need of an expensive hydrocracking unit. The thermal tar, the residue of the deep thermal conversion unit, is used hot in existing power stations in the refinery to produce electricity and steam for the refinery. A new flue gas treating unit based on Haldor Topsoe's SNOX process was installed in order to achieve the most stringent emission specifications for SO2 and NOx.

The operation of the DTGU, however, has turned out difficulties to achieve conversion and run time simultaneously. A substantial reconstruction of the furnace helps but does not solve the problem completely requesting more creative ideas of all parties involved. The unit has also proved to be very sensitive to the crude quality.

In addition to that, the SNOX unit has also turned out to have some unexpected design shortcomings which will be corrected.

OMV will present the pros and cons with these technologies as well as the lessons learned.

Summary

The classical routes for residue conversion are coking and hydrotreating / hydrocracking technologies. However, there are other means of using crude oil residues efficiently and economically.

OMV chose to install a Shell deep thermal gasoil unit (DTGU) at its Schwechat refinery, because it looked the best fit with existing plant and infrastructure. Design vacuum residue conversion is well over 40%, and the produced vacuum distillate is thermally cracked, mainly yielding middle distillates which can be further hydrotreated in conventional diesel hydrotreaters, eliminating the need for an expensive hydrocracking unit. The thermal tar, the residue of the deep thermal conversion unit, is used hot by existing power stations at the refinery to generate electricity and steam for the refinery. A new flue gas treating unit based on Haldor Topsoe's SNOx process was installed in order to comply with the most stringent emission limits for SO2 and NOx.

Unfortunately, in operation the DTGU has encountered difficulties in simultaneously achieving adequate conversion rates and run times. A major reconstruction of the furnace has helped, but has not completely solved the problem. The unit has also proved to be highly sensitive to crude quality.

This content is only available via PDF.
You can access this article if you purchase or spend a download.