Targeting the toughest feedstocks

Hyundai Oil Bank is one of four refinery operators in South Korea. When the company was looking to develop a new gas oil hydrotreater at the Daesan refinery to process difficult feedstocks to high specifications, it worked with Shell Global Solutions to develop an innovative solution.

Now on-stream, the new gas oil hydrotreater deals with the most severe feedstocks the company has ever processed and overcomes high aromatic and low cetane contents to deliver products that meet the stringent domestic ultra-low-sulphur-diesel (ULSD) specification, equivalent to Euro 4 or 5. In addition to producing diesel with an ultra-low sulphur content, the new unit helps to lower the total aromatic content of the product to less than 30 wt%, a specification unique to South Korea in Asia Pacific.

The selection process focused on technical and commercial factors, as Gurminder Singh, Hydroprocessing Licensing Technology Manager, Shell Global Solutions, explains: “The key issues for Hyundai Oil Bank were the effectiveness of the reactor system for dearomatisation and cetane boosting, minimised investment costs and outstanding operational reliability. Design factors such as operating pressure and temperature, and catalyst volume were also assessed.”

Shell Global Solutions drew on experience gained in processing heavy feedstocks in North America to establish an international process design team. The most innovative aspect of the proposal was the liquid quench solution in the hydrotreater. This differed from conventional recycling or a gas quench method, which would cause a pressure drop in the unit and require a larger and more powerful compressor. 

Hyundai Oil Bank wanted the new gas oil hydrotreater to treat gas oil from a residue hydrotreater (hydrodesulphurisation) and light cycle oil from a new residue catalytic cracking unit. The product would be mainly for export diesel or blending in the ULSD pool. The unit was designed for 50% cracked feed, but has processed more demanding feeds since start-up.

To date, the unit has achieved or surpassed its operational design targets. The normalised weighted-average bed temperature has been stable. The hydrodearomatisation section is delivering a polyaromatic content in the product of less than 3 wt% and the overall dearomatisation rate is about 85%, which is significantly higher than the design value of 72%.

Furthermore, with a sulphur content of about 5 wppm, despite the low hydrodesulphurisation reactor temperature, the product is suitable for ULSD blending. The low cetane content of the feedstock has also been addressed: after start-up, cetane boosting of 7–9 was achieved. This has enabled the refinery operator to maintain the cetane index above 50. 

Hyundai Oil Bank has commissioned Shell Global Solutions to conduct a study into processing even harsher feedstocks to even tighter specifications. C. W. Lee, Process Engineer, Hyundai Oil Bank, stated, “We are happy with the process performance so far and would like to discuss the possibility of debottlenecking the unit to achieve a total aromatic specification of less than 20 wt%.”

For more information, contact Gurminder Singh.