A large explosion at an oil refinery in South Korea

A large explosion rocked the S-oil refinery in Ulsan, southeast Of South Korea, Thursday evening, killing one person and injuring nine others, Yonhap news agency reported.  The flames rose tens of meters into the air and were felt as far away as 15 kilometers.  Nearby people said the incident heard a "rumble" sound, thought there was an earthquake.  

As of 9 a.m. local time on Saturday, 12 hours after the explosion, the fire has not been completely extinguished.  The refinery's chief executive planned to issue an apology that morning after the fire was extinguished.  

The plant operates three CDU units -- units 1 (90,000 b/d), 2 (240,000 b/d) and 3 (250,000 b/d) -- as well as a condensate fractionation unit with a capacity of 89,000 b/d, giving it a total refining capacity of 669,000 b/d.  

In addition, the plant operates two RFCC at the Onsan complex -- Unit 1 (73,000 b/d) and Unit 2 (76,000 b/d).  S-oil also operates three RHDS or residue hydrodesulfurization units with a total production capacity of 166,000 b/d.  The plant also has a capacity of 545,000 tons for pure benzene, 1.79 million tons for PX, 660,000 tons for toluene and 200,000 tons for ethylene.  

Local officials said police and firefighters would investigate the exact cause of the explosion once the fire was completely extinguished.  According to an initial investigation, the fire department believes the explosion occurred during maintenance of equipment used in the refinery's alkylation process, an additive that uses butane to boost the octane number of gasoline.  

S-oil is one of the largest petrochemical companies in Asia, covering petroleum, chemicals, petroleum products, lubricating base oils, lubricants and so on.  Founded in 1976, the company was listed on the Korea Stock Exchange in 1987 and is headquartered in Seoul.